At what temperature does a metal turn red - Metals and their processing

At what temperature does metal turn red?

Already in ancient times, people mined and smelted copper. This metal was widely used in everyday life and served as a material for the manufacture of various objects. They learned to make bronze about 3 thousand years ago. This alloy was used to make good weapons. The popularity of bronze quickly spread, as the metal was distinguished by its beautiful appearance and durability. Jewelry, hunting and labor tools, and dishes were made from it. Thanks to the low melting point of copper, people quickly mastered its production.

The metal received its Latin name Cuprum from the name of the island of Cyprus, where they learned to mine it in the third millennium BC. e. In the periodic system, Cu received number 29, and is located in the 11th group of the fourth period.

In the earth's crust, the element is in 23rd place in distribution and is most often found in the form of sulfide ores. The most common are copper luster and pyrite. Today, copper is extracted from ore in several ways, but any technology requires a step-by-step approach to achieve results.

At the dawn of the development of civilization, people were already obtaining and using copper and its alloys.
At that time, it was not sulfide ore that was mined, but malachite ore, which did not require pre-roasting.
A mixture of ore and coals was placed in a clay vessel, which was lowered into a small pit.
The mixture was ignited, and carbon monoxide helped the malachite to be restored to the state of free Cu.
There is native copper in nature, and the richest deposits are in Chile.
Copper sulfides often form in medium-temperature geothermal veins.
Often the deposits are in the form of sedimentary rocks.
Copper sandstones and shales are found in Kazakhstan and the Chita region.

Physical properties

The metal is ductile and in the open air it becomes covered with an oxide film in a short time. Thanks to this film, copper has its yellowish-red tint; in the lumen of the film, the color can be greenish-blue. In terms of thermal and electrical conductivity, Cuprum is in second place after silver.

Density - 8.94×103 kg/m3.
Specific heat capacity at T=20 ° C - 390 J/kg x K.
Electrical specific at 20−100 ° C - 1.78×10−8 Ohm/m.
Boiling point - 2595 ° C.
Specific electrical conductivity at 20 ° C is 55.5−58 MS/m.

At what temperature does copper melt?

Melting occurs when a metal changes from a solid state to a liquid state. Each element has its own melting point. Much depends on the impurities in the metal . The normal melting point of copper is 1083 ° C. When tin is added, the temperature drops to 930-1140 ° C. The melting point here depends on the tin content of the alloy. In an alloy of cuprum and zinc, melting occurs at 900-1050 ° C.

When any metal is heated, its crystal lattice is destroyed. As it heats up, the melting point increases, but then levels off once a certain temperature limit is reached. At this moment the metal melts. It melts completely and the temperature rises again.

When the metal cools, the temperature decreases, at a certain point it remains at the same level until the metal hardens completely. After complete hardening, the temperature drops again.

This is demonstrated by the phase diagram, which shows the temperature process from the beginning of melting to solidification. When heated, heated copper at 2560 ° C begins to boil. Boiling is similar to the boiling of liquid substances, when gas is released and bubbles appear on the surface.

At the moment of boiling at the highest possible temperatures, the release of carbon formed during oxidation begins.

Melting at home

Due to its low melting point, ancient people could melt cuprum over a fire and use the metal to make various products.

To melt copper at home you will need:

charcoal;
crucible and special tongs for it;
muffle furnace;
household vacuum cleaner;
bugle;
steel hook;
melting mold.

The process proceeds in stages, the metal is placed in a crucible and then placed in a muffle furnace. The desired temperature is set, and the process is monitored through a glass window. During the process, an oxide film will appear in the container with Cu, which needs to be removed - open the window and move it to the side with a steel hook.

What metal are the rails made of?

In the absence of a muffle furnace, copper can be melted using an autogenous furnace. Melting will occur if there is normal air access. A blowtorch melts brass and fusible bronze. The flame should cover the entire crucible.

If you don’t have any of the above products at hand, you can use a forge set on a layer of charcoal. To increase T, you can use a vacuum cleaner turned on in the blowing mode, but the hose must have a metal tip, it’s good if it has a narrowed end, so the air stream will be thinner.

The melting point of bronze and brass, like the melting point of copper and aluminum, is low.

Today, Cu is not used in its pure form in industrial settings. It contains many impurities: nickel, iron, arsenic, antimony, and other elements. The quality of the product is determined by the percentage of impurities in the alloy (no more than 1%). Important indicators are thermal and electrical conductivity. Due to its ductility, low melting temperature and flexibility, copper is widely used in many industries.

Source: http://ooo-asteko.ru/pri-kakoy-temperature-metall-krasneet/

At what temperature does iron melt, the melting point of ferrous, non-ferrous metals and some alloys

In the metallurgical industry, one of the main areas is the casting of metals and their alloys due to the low cost and relative simplicity of the process. Molds with any shape and various dimensions can be cast, from small to large; It is suitable for both mass and customized production.

Casting is one of the oldest areas of working with metals, and begins around the Bronze Age: 7-3 millennium BC. e. Since then, many materials have been discovered, leading to advancements in technology and increased demands on the foundry industry.

Nowadays, there are many directions and types of casting, differing in technological process. One thing remains unchanged - the physical property of metals to pass from a solid to a liquid state, and it is important to know at what temperature the melting of different types of metals and their alloys begins.

Metal melting process

This process refers to the transition of a substance from a solid to a liquid state. When the melting point is reached, the metal can be in either a solid or liquid state; further increase will lead to the complete transition of the material into a liquid.

The same thing happens during solidification - when the melting point is reached, the substance will begin to transition from a liquid to a solid state, and the temperature will not change until complete crystallization.

It should be remembered that this rule applies only to pure metal. Alloys do not have a clear temperature boundary and undergo state transitions in a certain range:

Solidus is the temperature line at which the most fusible component of the alloy begins to melt.
Liquidus is the final melting point of all components, below which the first alloy crystals begin to appear.

It is impossible to accurately measure the melting point of such substances; the point of transition of states is indicated by a numerical interval.

Depending on the temperature at which metals begin to melt, they are usually divided into:

Low-melting, up to 600 °C. These include tin, zinc, lead and others.
Medium melting, up to 1600 °C. Most common alloys, and metals such as gold, silver, copper, iron, aluminum.
Refractory, over 1600 °C. Titanium, molybdenum, tungsten, chromium.

There is also a boiling point - the point at which the molten metal begins to transition into a gaseous state. This is a very high temperature, typically 2 times the melting point.

Effect of pressure

The melting temperature and the equal solidification temperature depend on pressure, increasing with its increase. This is due to the fact that with increasing pressure the atoms come closer to each other, and in order to destroy the crystal lattice they need to be moved away. At increased pressure, greater thermal energy is required and the corresponding melting temperature increases.

There are exceptions when the temperature required to transform into a liquid state decreases with increased pressure. Such substances include ice, bismuth, germanium and antimony.

Melting point table

It is important for anyone involved in the metallurgical industry, whether a welder, foundry worker, smelter or jeweler, to know the temperatures at which the materials they work with melt. The table below shows the melting points of the most common substances.

Table of melting temperatures of metals and alloys

NameT pl, °CAluminum Copper Tin Zinc Tungsten Nickel Silver Gold Platinum Titanium Duralumin Carbon steel Cast Iron Mercury Cupronickel Zirconium Silicon Nichrome Bismuth Germanium Tin Bronze Cobalt Potassium Sodium Brass Magnesium Manganese Chrome Molybdenum Lead Beryllium Fechral Antimony titanium carbide zirconium carbide Gallium

660,4
1084,5
231,9
419,5
3420
1455
960
1064,4
1768
1668
650
1100−1500
1110−1400
1539
-38,9
1170
3530
1414
1400
271,4
938,2
1300−1500
930−1140
1494
63
93,8
1000
650
1246
2130
2890
327,4
1287
3150
1460
630,6
3150
3530
29,76

In addition to the melting table, there are many other supporting materials. For example, the answer to the question what is the boiling point of iron lies in the table of boiling substances. In addition to boiling, metals have a number of other physical properties, such as strength.

Strength of metals

In addition to the ability to transition from a solid to a liquid state, one of the important properties of a material is its strength - the ability of a solid body to resist destruction and irreversible changes in shape. The main indicator of strength is the resistance that occurs when a pre-annealed workpiece breaks. The concept of strength does not apply to mercury because it is in a liquid state. The designation of strength is accepted in MPa - Mega Pascals.

There are the following strength groups of metals:

Fragile. Their resistance does not exceed 50MPa. These include tin, lead, soft-alkaline metals
Durable, 50−500 MPa. Copper, aluminum, iron, titanium. Materials of this group are the basis of many structural alloys.
High strength, over 500 MPa. For example, molybdenum and tungsten.

Metal strength table

MetalResistance, MPaCopper Silver Tin Gold Lead Zinc Magnesium Iron Aluminum Titanium

200−250
150
27
120
18
120−140
120−200
200−300
120
580

The most common alloys in everyday life

As can be seen from the table, the melting points of elements vary greatly even among materials commonly found in everyday life.

Thus, the minimum melting point of mercury is -38.9 °C, so at room temperature it is already in a liquid state. This explains why household thermometers have a lower mark of -39 degrees Celsius: below this indicator, mercury turns into a solid state.

The most common solders in household use contain a significant percentage of tin, which has a melting point of 231.9 °C, so most solders melt at the operating temperature of the soldering iron 250−400 °C.

In addition, there are low-melting solders with a lower melt limit, up to 30 °C, and are used when overheating of the materials being soldered is dangerous. For these purposes, there are solders with bismuth, and the melting of these materials lies in the range from 29.7 - 120 °C.

Melting of high-carbon materials, depending on alloying components, ranges from 1100 to 1500 °C.

The melting points of metals and their alloys are in a very wide temperature range, from very low temperatures (mercury) to several thousand degrees. Knowledge of these indicators, as well as other physical properties, is very important for people who work in the metallurgical field. For example, knowledge of the temperature at which gold and other metals melt will be useful to jewelers, foundries and smelters.

Source: https://obrabotkametalla.info/splavy/temperatura-plavleniya-cvetnyx-i-chernyx-metallov

What are tarnish colors

Tarnish colors are oxide films on the surface of iron alloys of varying thickness and density. They are formed without the participation of water molecules when heated to certain temperatures. The simplest idea of thin films can be obtained from the example of soap bubbles or films of petroleum products on the surface of water. For iron, tarnish colors are formed when heated, and the thickness of the film is commensurate with the size of the molecules.

From a physical point of view, this phenomenon is explained by the theory of “thin films” and is caused by the optical interference of oxide films depending on their thickness.

Tarnish color scale

The thickness of the oxide films is determined by the temperature and heating time, and the existing scales of tarnish colors are rather arbitrary.

First, visual evaluation is a highly subjective process, with results determined by lighting conditions and practical experience.
Secondly, the density of the oxide film is also determined by the chemical composition of the alloy.

Therefore, the correspondence tables differ (scales for carbon, heat-resistant, stainless steels), and we can only talk about approximate compliance. But the average table of tarnish colors looks like this:

Colors	Heating temperature, °C
pale yellow	220
pale straw yellow	230
golden yellow	246
brown-yellow to brown	256
purple-red	265
purple	275
lilac	280
blue	290
cornflower	295
indigo	300
light blue	310
sea water color	320

For example, prolonged heating at 220 °C can cause steel to turn blue. Or the desired color is obtained by briefly heating to a temperature higher than that indicated in the table. But for each tarnish color there is a temperature minimum, below which the desired color will not work.

Tarnish colors for surface finishing

When preparing regulations, one should prefer lower temperatures and longer holding times, since in this case the films are more durable and the creation of additional thermal stresses, which can lead to warping of products, is eliminated.

Tarnish colors are used to finish the surface of products made of steel, cast iron and non-ferrous metals: buckles, forgings, solar collectors, edged weapons and processing tools. This is the well-known bluing process.

For both hardened and non-hardened steel, the formation of oxide films will occur differently. The rate of formation of oxide films is significantly influenced by:

structure. Hardened steels oxidize more slowly
surface contamination. Oil films are charred to soot, so the films will be loose and loose,
surface roughness. On a polished surface, the film will be thinner than on a rough surface under the same conditions.

To obtain a dense, uniform oxide film, heating furnaces are required that can maintain a stable temperature for a long time.

At home, this is either a forge, or a blowtorch, or a high-quality stove with oven. And in this case, the blackening mode is selected individually for each product. It must be remembered that the transition from one color to another occurs quickly, so the process requires the closest attention.

Irina Faydyuk

Source: https://engitime.ru/metallicheske-materiali/chto-takoe-cveta-pobezhalosti.html

Measuring metal temperatures

To measure temperatures during heat treatment, special devices are used - pyrometers.

The most widespread are thermoelectric and optical pyrometers.

The diagram of a thermoelectric pyrometer is shown in the figure:

It is a thermocouple with a galvanometer . A thermocouple is two wires made of dissimilar metals or alloys welded together.

If the junction of the wires is placed in molten metal, the temperature of which we want to determine, then a thermoelectromotive force will arise the CC , the greater the greater the temperature difference between the “hot junction” - the junction immersed in the metal, and the free ends - the “cold junction” " .

The deflection of the needle of a galvanometer connected to the free ends of the thermocouple at a constant ambient temperature will be proportional to the temperature of the metal being tested.

For ease of use, the galvanometer has a temperature scale.

Various metals and alloys are used for thermocouples.

For example, to measure temperatures of 1000–1300° a thermocouple is made of platinum and an alloy of platinum and rhodium.

For temperatures of 700–950°, a thermocouple is used - chromel (chromium-nickel alloy) and alumel (aluminum-nickel alloy); at even lower temperatures, iron-constantan (copper-nickel alloy) and copper-constantan thermocouples are used.

The temperature of a hot metal can be determined with an optical pyrometer - by comparing the brightness of its glow with the filament of an electric light bulb.

In Fig. 63, and an optical pyrometer is shown . The pyrometer lens is pointed at a hot object. A light bulb glows inside the pyrometer. In the field of view of the eyepiece, both the filament and the red-hot metal are visible.

the strength of the electric direct current feeding the electric lamp using a rheostat

Depending on the magnitude of the current, the needle of the device will deviate on the scale at a different angle. For convenience, the scale is graduated in degrees Celsius.

Approximate methods for determining the metal temperature value

In addition to the listed methods, in the practice of heat treatment, approximate methods are used that give only approximate values of the metal temperature. Such methods include determining the temperature of the metal by the colors of heat when heated for hardening or annealing and determining the temperature of the metal during tempering by the colors of tarnish that appear on the light surface of the parts (Fig. 64).

Source: http://www.Conatem.ru/tehnologiya_metallov/izmerenie-temperatur-metalla.html

Metal tarnish colors

Greetings, colleagues and gentlemen craftsmen. I will talk about an ancient method of measuring the temperature of steel objects by external signs. Nowadays, there are plenty of instruments for accurately measuring the temperature of various objects. Thermometers are used to measure temperatures by contact method. And to control heating at a distance, that is, without contact, pyrometers with various designs and technical characteristics are used.

And yet, those involved in metalworking must be able to determine the temperature of steel products. Let it be approximately, but quickly and without instruments.

Tarnish colors

When some metal alloys are heated to certain temperatures, oxide films on their surfaces can acquire different colors.

Such colors and their shades, characteristic of the temperatures that caused their appearance, are called tarnish colors.

The colors of tarnish appear more expressively on steels: carbon, alloy and stainless steel. We will observe the appearance of tarnish colors when a sheet of low-carbon steel is heated with a gas flame. I will call the designated place on the surface of the sheet, under which the heating source is located, the heating point. It is noticeable that the natural color of the steel at the heating point has changed to light yellow.

This means that the temperature of the material in this place has reached approximately 205 C. As the temperature increases further, the light yellow area appears to move away from the heating point. And its place has acquired a dark yellow color, with an inherent temperature of 240 C. The spot of general heating is expanding.

The tarnish colors are arranged around the heating point in a characteristic order, indicating to what temperature the material was heated in the area occupied by each of them. With smoother heating, the color temperature areas will be expanded. As in this sample of medium carbon steel, on which we will continue to examine them.

If we do not take into account the color shades observed in a very narrow arrangement, there are nine clearly defined color temperature regions, of which the region with the natural color of steel is not included.

Next, one by one, a template will be applied to each of the nine color-temperature areas, the color and shade of which is most similar to the color of this area.

The template shows the temperature range and average value that is inherent in a given color of tarnish on the surface of carbon steel.

Once developed, tarnish colors do not disappear after cooling. Based on their presence, it is possible, for example, to determine that a part or tool was operated with certain violations, which led to its overheating. The colors of tarnish on alloy, stainless and heat-resistant steels are the same. However, they appear at higher temperatures, the values of which depend on the content of alloying elements.

Heat colors

As heating continues, the tarnished colors are replaced by incandescent colors.

Since heat is the glow of a material, an objective assessment of its darkest colors is possible only in the dark. And lighter ones, at least when darkened. The first color of heat visible to the eye is reddish-brown, meaning that the temperature of heat in the area of its manifestation is in the range of 530 – 580 degrees Celsius. Unlike tarnished colors, incandescent colors are not preserved when cooled, but change in the opposite order.

If scale has formed on the surface, its color returns to a light gray shade. When magnetic, iron-carbon alloys are heated above 768 C, their magnetic properties disappear. And they appear again after cooling below this temperature.

This phenomenon can be used as an additional means of temperature control. Heat colors reflect the heating temperature of not only metal bodies, but also non-metal ones. For example, products made of ceramics, graphite and others.

Method for measuring temperatures by tarnish and heat colors

The method of measuring temperatures by the colors of tarnish and heat has been successfully used since ancient times by metallurgists, blacksmiths, thermal experts, as well as representatives of other professions, including machine operators. To measure temperature using this method, tables are used that contain patterns of tarnish and heat colors with a description of their shades and an indication of the temperatures that lead to the appearance of each of them.

Craftsmen and specialists who have regular practice usually do not use tables. Because they know all the color shades and temperature values associated with their manifestations by heart.

When there is no constant practice in this area, it is probably not worth relying on memory, especially color memory. By visual comparison from one table or another, a template is selected whose color is more similar to the color of the controlled area of the object.

I would like to draw your attention to the fact that when comparing the colors of a template and an object, you should not expect them to be completely identical.

The similarity of their color shades is enough. And then we can assume that the temperature of a uniformly heated object is in the range of values indicated on the color template.

Often two adjacent colors appear on the surface of an object at once. It is not difficult to guess that the temperature of this object is between the average temperatures indicated on both templates. Compared to instrumental measurements, the accuracy of this method is, of course, lower.

And yet, in many applications, for example, when performing not particularly important hardening or tempering, the accuracy of the color method is quite sufficient. As for cutting, when the distance of the cutting edge is controlled by the colors of tarnish on the moving chips, and at different points, there is probably no replacement for this old method.

Enough tables with the colors of tarnish and heat have been published in the literature and on the Internet. Their interpretations differ in form and content, unfortunately, too. Unlike most of them, the colors used in this template video tutorial are computer matched to real heat colors and the tarnish colors of carbon steels.

The names of color shades indicated on the templates are conditional. And their exact identification is possible using the so-called html color code indicated below.

Using this code entered into the search, the color of any of their templates can be easily found on the Internet. Ready-made tables with color templates for downloading to a mobile device or for printing can be downloaded from the project website.

Possible causes of errors when measuring temperatures It must be taken into account that color perception is affected by the general illumination of the room, as well as its color, which can be natural, white or yellowish, coming from incandescent lamps. This applies to cases when trying to evaluate colors relying on memory.

When measuring temperatures by tarnish colors, you need to understand that they reflect the temperature on the controlled surface. And this does not always correspond to the temperature of the entire mass of the heated object. If the task is to heat an object to a certain temperature, controlled by the color of the tarnish, it must be heated not through one point or surface, but evenly, from all sides.

The uniformity of heating is also controlled by the colors of the heat. The same glow color at different points in any area of the object indicates its uniform heating. And vice versa. The scale that peels off from the hot base cools and heats up faster than the base mass, which distorts the actual color of the surface. This must be taken into account.

Source: https://kovkapro.com/metalloobrabotka-obschie-svedeniya/cveta-pobezhalosti-metalla/

What temperature can paints for exterior work withstand?

The answer to the question at what temperature you can paint metal outdoors depends on the primer used. Previously, in weather colder than +5 ° C, painting became impossible, but some new compositions can be used even at low temperatures.

Features of paintwork in winter

It is better to refrain from painting at temperatures of -5+5 °C, since this range is considered unfavorable due to the formation of condensation. Moisture changes the properties of paintwork materials - the coating becomes of poor quality and does not last long.

Facade paints will take 2-3 times longer to dry in the cool season. You can improve the quality of the coating using a thermal gun. You can also attach film to scaffolding.

When choosing paintwork materials, you need to make sure that the composition is suitable for painting in frost. If the dye is not suitable for winter use, it will freeze. The quality of the paint also matters.

The temperature of the paint and varnish material must exceed 0 °C. If the composition cools more, the container containing it must be placed in a basin with preheated liquid.

Maximum temperature limits for paints

Before carrying out work, you need to make sure that the established temperature regime is suitable for the purchased paint.

Previously, the minimum temperature at which it was allowed to paint the walls of residential and commercial buildings was +5 ° C. Now, however, dyes are being produced that can be used at zero temperatures and even in severe frost, down to -30 ° C. The upper limit at which painting can be done is considered to be +40 °C.

Recommendations for better drying

To make frost-resistant metal paints dry faster, you can use devices that heat the air over a short distance. Not only special devices are suitable, but also household appliances (for example, a hair dryer).

It is necessary to pre-prepare the surface. You will have to remove the previous coating from it. Then the metal product is processed with special devices.

Suitable:

sandblasting machine;
sandpaper.

If there are irregularities, use putty.

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It will not work in rainy or snowy weather. Precipitation will prevent winter metal paint from drying.

You only need to work with dry and clean material. Dust, dirt and mold are removed with a brush.

If the work is carried out in an unheated room, you can speed up the drying process using a portable heater; the paint dries faster when exposed to heat.

Frost-resistant paints for rust

Infrazim-Antikor is suitable for painting rusted structures. This paint is used in the range of -20+30 °C. Humidity should not exceed 80%.

The composition is simultaneously a rust converter, a corrosion-preventing primer and an environmentally resistant decorative enamel. You can purchase glossy or matte paint.

As for the palette, paintwork materials are available in white, gray, beige, cream, red, green, light green, light blue, blue, ocher, brown, yellow, orange, black and red-brown.

Primer enamel XB-0278 can be used for outdoor work at a temperature range of -10+25 °C. This product is applied to metal with rust and traces of scale that cannot be removed.

Primer-enamel for rust “Spetsnaz” is used to treat rusted steel and cast iron products in order to prevent the occurrence of corrosion. The composition will also protect the metal from aggressive gases and fumes during production. "Spetsnaz" can be used for repair painting of car parts. They work with paintwork materials at sub-zero temperatures (down to -10 °C).

The best winter coatings for metal

KO-870 enamel is used even in severe frost – down to -30 °C. It is used to paint metal structures exposed to temperatures in the range of +60+600 °C. The dye is resistant to a number of aggressive substances (oil, saline solutions).

Primer enamel "SpetsKor" is resistant to moisture, ultraviolet rays and temperatures down to -60 °C. Does not allow air or steam to pass through. Has a hammer effect (hides defects in products that are being painted).

Organosilicate composition OS-12-03 will prevent corrosion that occurs due to the unfavorable influence of the surrounding atmosphere. Used at -30+40 °C.

Facade enamel KO-174 is used not only for protecting metal products, but also for painting facades. Suitable for painting concrete, brick products, plastered walls, floors, ceilings. Well protects metal from moisture and air. The composition must be applied at a temperature of -30+40 °C.

HB-785 enamel is used in multi-layer painting. It is used to treat plastered structures. Paintwork protects products from the adverse effects of gaseous substances, acid, salt and alkaline solutions, if the temperature does not rise above +60 °C. The composition can be applied at +35-10 °C.

Source: https://vmirekraski.ru/rabota-s-kraskami/temperatura-pri-pokraske-metalla

At what temperature does copper melt: necessary process conditions in production and at home

At the dawn of the development of civilization, people were already obtaining and using copper and its alloys.
At that time, it was not sulfide ore that was mined, but malachite ore, which did not require pre-roasting.
A mixture of ore and coals was placed in a clay vessel, which was lowered into a small pit.
The mixture was ignited, and carbon monoxide helped the malachite to be restored to the state of free Cu.
There is native copper in nature, and the richest deposits are in Chile.
Copper sulfides often form in medium-temperature geothermal veins.
Often the deposits are in the form of sedimentary rocks.
Copper sandstones and shales are found in Kazakhstan and the Chita region.

Why does the snow turn red in the mountains?

The phenomenon, called “snow bloom,” can actually be found in the mountains of the Northern Urals, as well as in the Caucasus, Antarctica and Siberia, that is, where it is quite cold. And this feature is connected with the heat sensitivity of plants, which cause “snow blooming”.

Plants with heat sensitivity

According to Vladimir Pasechnik, author of the publication “Biology. Bacteria, fungi, plants,” a phenomenon called “snow blooming,” occurs in many parts of the planet. In our country, it can be observed in the Caucasus, the Northern Urals, in some areas of Siberia and Antarctica. This feature is due to the fact that for the successful development of lower plants, which cause “snow blooming”, both a large amount of light and sufficiently cold weather are required.

And in fact, as Boris Sergeev writes in his book “Entertaining Physiology”, the species of single-celled green algae Chlamydomonas nivalis, thanks to which the snow turns red, dies already at a temperature of +4°C, and literally "from the heat." Sergeev suggests that organisms with a stronger heat phobia than Chlamydomonas most likely do not exist.

What causes snow to be colored?

The short duration of the “snow bloom” is also due to heat fear. Valeria Kuchmenko, Irina Ponomareva and Olga Kornilova report on the pages of their publication “Biology” that “blooming” is observed exclusively when the upper layers of snow cover thaw. Under the influence of sunlight, Chlamydomonas snowy, whose cells contain red pigment, begins to actively multiply, forming a color spot.

According to Professor Vladimir Pasechnik, the size of such a color spot formed by Chlamydomonas can reach several square kilometers. And the color of the snow varies depending on the amount of algae: from pale pink to dark burgundy. However, red is far from the only color that snow in the mountains and Antarctica is “capable” of coloring.

Other colors

Source: https://123ru.net/pics/231530229/

At what temperature does steel turn red - Metalworker's Handbook

Cast iron consists of carbon, iron and some impurities. It is one of the main materials of ferrous metallurgy. Cast iron is used in the manufacture of household and utility items, machine parts and in other industries. It is used in production, focusing and taking into account its properties and characteristics.

This article is precisely intended to tell you about the density of high-strength, liquid, white and gray cast iron, its melting points and specific heat capacity will also be considered separately.

Cast iron, like any metal, has the following properties: thermal, physical, mechanical, hydrodynamic, electrical, technological, chemical. Let's look at each properties in more detail.

This video talks about the structure and composition of cast iron alloys and the dependence of their properties on a specific composition:

Heat capacity

The thermal capacity of cast iron is determined using the displacement rule. When the heat capacity of cast iron reaches a temperature period, the beginning of which begins at a temperature whose value is greater than phase transformations and ends at a level equal to the melting temperature, then the heat capacity of cast iron takes on a value of 0.18 cal/Ho C.

If the value of the melting temperature exceeds the absolute value, then the heat capacity is equal to 0.23 ± 0.03 cal/Ho C. If the solidification process occurs, then the thermal effect is equal to 55 ± 5 cal. The thermal effect depends on the amount of pearlite when pearlite transformation occurs. Typically it takes a value of 21.5 ± 1.5 cal/G.

The volumetric heat capacity is taken to be the product of the specific gravity and the specific heat capacity. For solid cast iron this value is 1 cal/cm3*ºС, for liquid cast iron – 1.5 cal/cm3*ºС.

The specific heat capacity of cast iron is 540 J/kg C.

Specific heat capacity of cast iron and other metals in table form

Thermal conductivity

Unlike heat capacity, thermal conductivity is not determined by the displacement rule. Only if the amount of graphitization changes, the composition of the cast iron will affect the thermal conductivity.

Thermal diffusivity

The thermal diffusivity value of solid cast iron (for large calculations) can be taken equal to its thermal conductivity, and that of liquid cast iron – 0.03 cm2*/sec.

Read below about the melting point of cast iron.

Melting temperature

Cast iron melts at a temperature of 1200ºС. This temperature value is 300 degrees lower than the melting point of steel. With an increased carbon content, this chemical element has a close connection at the molecular level with iron atoms.

During the process of melting cast iron and its crystallization, the carbon component cannot completely penetrate the structural lattice of iron. As a result, the material cast iron takes on the property of brittleness. Cast iron is used for parts that require increased strength. However, cast iron is not used in the manufacture of objects that will be subject to constant dynamic loads.

The table below shows the melting point of cast iron in comparison with other metals.

Melting point of cast iron and other metals

Weight

The weight of the material varies depending on the amount of fixed carbon and the presence of a certain percentage of porosity. The specific gravity of cast iron at the melting point can be significantly reduced depending on the presence of impurities in the cast iron.

In addition, the linear expansion of the metal and the structure of cast iron changes depending on the state of each indicator. That is, these are dependent quantities.

The specific gravity of each cast iron differs depending on the type of material. Gray cast iron has a specific gravity of 7.1±0.2 g/cm3, white cast iron has a specific gravity of 7.5±0.2 g/cm3, and malleable cast iron has a specific gravity of 7.3±0.2 g/cm3.

The video below will tell you about some of the physical properties of cast iron:

The volume of cast iron, passing through the temperature of phase transformations, reaches an increase of 30%. However, when heated to 500ºC, the volume increases by 3%. Growth is aided by graphite-forming elements. Carbide-forming components inhibit volume growth. The same growth is prevented by applying galvanic coatings to the surface.

carbon is usually at least 2.14%. Thanks to the carbon content, cast iron has excellent hardness. However, the plasticity and malleability of the material suffers against this background.

We will talk about the density of cast iron below.

Density

The density of the described material, cast iron, is 7.2 g/cm3. If we compare other metals and alloys with cast iron, this density value is quite high.

Due to its good density, cast iron is widely used for casting various parts in industry. In terms of this property, cast iron is only slightly inferior to some steels.

Tensile strength

The compressive strength of cast iron depends on the structure of the material itself. The components of the structure gain their strength along with an increase in the level of dispersion. The tensile strength is strongly influenced by the number, size, distribution and formagraphite inclusions. The tensile strength decreases by a noticeable amount if the graphite inclusions are arranged in the form of a chain. This arrangement reduces the cohesion of the metal mass.

The tensile strength reaches its maximum value when the graphite takes on a spheroidal shape. This form is obtained without the influence of temperature, but when cerium and magnesium are included in the cast iron mass.

When the melting temperature increases to 400ºС, the tensile strength does not change.
If the temperature rises above this value, the tensile strength decreases.
Note that at temperatures from 100 to 200ºС, the tensile strength can decrease by 10-15%.

Cold-worked steel is

Plastic

The ductility of cast iron largely depends on the shape of the graphite, and also depends on the structure of the metal mass. If graphite inclusions have a spheroidal shape, then the percentage of elongation can reach 30.

In ordinary gray cast iron, the elongation reaches only a tenth.
In annealed gray cast iron, the elongation is 1.5%.

Elasticity

Elasticity depends on the shape of the graphite. If the graphite inclusions did not change, and the temperature increased, then the elasticity remains at the same value.

The elastic modulus is considered a conditional value, since it has a relative value and directly depends on the presence of graphite inclusions. The elastic modulus decreases if the number of graphite inclusions increases. Also, the elastic modulus increases if the shape of the inclusions is distant from the globular shape.

Impact strength

This indicator reflects the dynamic properties of the material. The impact strength of cast iron increases:

when the shape of graphite inclusions is close to spherical;
when the ferrite content increases;
when the graphite content decreases.

Endurance limit

The endurance limit of cast iron becomes greater when the frequency of loading increases and the tensile strength becomes greater.

Dynamic viscosity

Viscosity becomes less if the amount of manganese in cast iron increases. A decrease in viscosity was also noticed with a decrease in the content of sulfur impurities and other non-metallic components.

The process is affected by the temperature value. Thus, the viscosity becomes less when the ratio of two temperatures is directly proportional (the temperature of the experiment and the start of solidification).

Surface tension

This figure is 900±100 dynes/cm2. The value increases as the amount of carbon decreases and undergoes significant changes in the presence of non-metallic components.

Toxicity

Cookware is often made from cast iron. The fact is that cast iron as a material is non-toxic and tolerates temperature changes well.

Electrical characteristics

The electrical conductivity of cast iron is assessed using Kurnakov's law. The electrical resistance of some types is given below:

white cast iron - 70±20 Mk·oi·cm.
gray cast iron - 80±40 Mk·oi·cm.
malleable cast iron - 50±20 Mk·oi·cm.

According to the weakening effect on electrical resistance, the elements of solid cast iron can be arranged as follows: first - silicon, second - manganese, third - chromium, fourth - nickel, fifth - cobalt.

Technological features

Fluidity can be determined by various methods. This indicator depends on the shape and properties of cast iron.

Fluidity becomes greater when:

overheating increases;
viscosity decreases;
hardening becomes less.

Fluidity also depends on the heat of fusion and heat capacity.

Chemical properties

The corrosion resistance of a material depends on the external environment and its structure. If we consider cast iron from the side of decreasing electrode potential, then its components have the following arrangement: graphite-cementite, phosphide eutectic-ferrite.

It should be noted that the potential difference between graphite and ferrite is 0.56 V. If the dispersion increases, the corrosion resistance becomes less. With a strong decrease in dispersion, the opposite effect occurs, and corrosion resistance decreases. Alloying elements also affect the resistance of cast iron.

Industrial cast iron contains impurities. These impurities greatly affect the properties, characteristics and structure of cast iron.

Thus, manganese inhibits the graphitization process. The release of graphite is stopped, as a result, cast iron acquires the ability to bleach.
Sulfur degrades casting and mechanical properties.
Sulfides are mainly formed in gray cast iron.
Phosphorus improves casting properties, increases wear resistance and increases hardness. However, against this background, cast iron still remains fragile.
Silicon has the greatest influence on the structure of the material. Depending on the amount of flint, white and ferritic cast iron are obtained.

To obtain certain characteristics, special impurities are often introduced into cast iron during its manufacture. Such materials are called alloy cast iron. Depending on the added element, cast iron can be called aluminum, chromium, or sulfur. Basically, elements are introduced with the aim of obtaining a wear-resistant, heat-resistant, non-magnetic and corrosion-resistant material.

This video will compare the properties of cast iron and steel:

Source: https://ssk2121.com/pri-kakoy-temperature-stal-krasneet/

How to get rid of an abscess without getting blood poisoning

The word abscess is translated from Latin simply as an abscess. Doctors use this Latin term to describe an active inflammatory process in which a cavity filled with pus forms in living tissue.

Tavarius/Shutterstock

An abscess can occur in any part of the human body, including internal organs. But most often it affects the skin in the armpits, groin, area around the anus, base of the spine and gums near the teeth.

Inflammation around the hair follicle can also lead to the formation of an abscess - this type of abscess is commonly called a boil.

How to tell if you have an abscess

Symptoms of an external abscess developing inside the skin are usually obvious:

it looks like a dense swelling, a “bump” that has grown under the skin;
touching him is painful;
the skin on the affected area turns red and feels hot to the touch;
not always, but quite often you can see an accumulation of white or yellow pus under the stretched skin.

Extensive subcutaneous abscesses may also be accompanied by fever.

Abscesses that arise on internal organs or in the tissues between them are more difficult to recognize. Signs of an abscess in this case are vague and may vary depending on which organ is affected. For example, a liver abscess is often accompanied by jaundice, a yellowing of the skin of the body and the whites of the eyes. A lung abscess causes coughing and shortness of breath.

If we talk about the general and most common symptoms of an internal abscess, here they are:

discomfort and pain in the area of the organ on which the abscess occurred;
temperature increase;
loss of appetite up to complete reluctance to eat;
active sweating;
distinct weakness.

Small abscesses often resolve on their own. However, much more negative scenarios are also possible.

When to Seek Help Quickly

Consult your physician or surgeon immediately if:

the diameter of the subcutaneous abscess exceeds 1 cm;
the abscess continues to grow and becomes more and more painful;
inflammation occurs in the groin or anus;
the abscess is accompanied by an increase in temperature.

Go to the emergency room or call 911 if:

An abscess with a diameter of more than a centimeter appeared on the face.
The temperature rose to 38.8 °C and above.
You notice red streaks under the skin that spread outward from the abscess.
In the area between the abscess and the breast, the lymph nodes were enlarged. For example, an abscess on the leg can cause enlarged lymph nodes in the groin area.

Such symptoms indicate that there is a high risk of blood poisoning. And this is a deadly condition.

What to do if you have an abscess

Ideally, any abscess, even if it looks small and relatively harmless, should be shown to a doctor - a therapist, surgeon or dermatologist. The specialist will examine the abscess, assess its location and size, and analyze your health condition. And after that he will give recommendations on how and with what to treat the abscess in your particular case. Please note: antibiotics or surgical removal of the abscess may be required.

Until you see a doctor, you can try to alleviate the condition with home methods.

Apply warm compresses

They will help reduce pain and accelerate the maturation of the abscess. Apply gauze soaked in warm water to the affected area 3-4 times a day for 15 minutes.

Use ointments

Apply antiseptic ointments with a pulling effect to the abscess. To find out which is better and safer to use in your case, consult your doctor.

Don't forget about antiseptic

If the abscess opens on its own, wash the wound with antibacterial soap and treat with any antiseptic, possibly alcohol-based. Then apply an antibacterial ointment (for example, levomekol or tetracycline) and apply a bandage. Wash the wound with warm water 2-3 times a day and apply warm compresses until it heals.

Trying to squeeze out the pus

Pressure can drive it deeper, which means the abscess will only increase in size.

Piercing an abscess with a needle

You can accidentally damage a blood vessel, which means pus will enter the bloodstream - with the expected consequences of sepsis.

Rely only on home methods

Do not continue home treatment if the abscess does not decrease in size (much less if it continues to grow) within a couple of days. Consult a physician as soon as possible.

Ignore general health

Do not take risks, but consult a doctor immediately if an abscess develops against the background of problems with the cardiovascular system, iron deficiency anemia, diabetes, any problems in the immune system, or taking drugs that suppress the immune system. In this case, the body's defenses may not be enough to defeat the infection on its own.

Table of melting temperatures of various metals, and at how many degrees they melt

Each metal and alloy has its own unique set of physical and chemical properties, not least of which is the melting point. The process itself means the transition of a body from one state of aggregation to another, in this case, from a solid crystalline state to a liquid one.

To melt a metal, it is necessary to apply heat to it until the melting temperature is reached. With it, it can still remain in a solid state, but with further exposure and increased heat, the metal begins to melt. If the temperature is lowered, that is, some of the heat is removed, the element will harden.

The highest melting point among metals belongs to tungsten : it is 3422Co, the lowest is mercury: the element melts at - 39Co. As a rule, it is not possible to determine the exact value for alloys: it can vary significantly depending on the percentage of components. They are usually written as a number interval.

How it happens

Will there be a quarantine in schools in 2020, what is the epidemic threshold?

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Doctors urge to act in advance to prevent mass diseases. Parents are already wondering whether schools should be closed for quarantine this year.

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What determines the color of tarnish?

Many people who have heated metal to high temperatures have observed a change in the color of the surface. Moreover, it can be of different shades and does not capture the entire metal object. Places that change color are called discoloration. People who work with metals need to know what it is and how it manifests itself under different types of heating. It is also advisable to distinguish the colors of tarnish.

What caused

At what temperature does metal turn red?

At the dawn of the development of civilization, people were already obtaining and using copper and its alloys.
At that time, it was not sulfide ore that was mined, but malachite ore, which did not require pre-roasting.
A mixture of ore and coals was placed in a clay vessel, which was lowered into a small pit.
The mixture was ignited, and carbon monoxide helped the malachite to be restored to the state of free Cu.
There is native copper in nature, and the richest deposits are in Chile.
Copper sulfides often form in medium-temperature geothermal veins.
Often the deposits are in the form of sedimentary rocks.
Copper sandstones and shales are found in Kazakhstan and the Chita region.

Physical properties

Density - 8.94×103 kg/m3.
Specific heat capacity at T=20 ° C - 390 J/kg x K.
Electrical specific at 20−100 ° C - 1.78×10−8 Ohm/m.
Boiling point - 2595 ° C.
Specific electrical conductivity at 20 ° C is 55.5−58 MS/m.

At what temperature does copper melt?

When the metal cools, the temperature decreases, at a certain point it remains at the same level until the metal hardens completely. After complete hardening, the temperature drops again.

At the moment of boiling at the highest possible temperatures, the release of carbon formed during oxidation begins.

Melting at home

Due to its low melting point, ancient people could melt cuprum over a fire and use the metal to make various products.

To melt copper at home you will need:

charcoal;
crucible and special tongs for it;
muffle furnace;
household vacuum cleaner;
bugle;
steel hook;
melting mold.

THIS IS INTERESTING: What types of metals are there?

What metal are the rails made of?

The melting point of bronze and brass, like the melting point of copper and aluminum, is low.

Today, Cu is not used in its pure form in industrial settings. It contains many impurities: nickel, iron, arsenic, antimony, and other elements. The quality of the product is determined by the percentage of impurities in the alloy (no more than 1%). Important indicators are thermal and electrical conductivity. Due to its ductility, low melting temperature and flexibility, copper is widely used in many industries.

Source: http://ooo-asteko.ru/pri-kakoy-temperature-metall-krasneet/

At what temperature does iron melt, the melting point of ferrous, non-ferrous metals and some alloys

Metal melting process

It should be remembered that this rule applies only to pure metal. Alloys do not have a clear temperature boundary and undergo state transitions in a certain range:

Solidus is the temperature line at which the most fusible component of the alloy begins to melt.
Liquidus is the final melting point of all components, below which the first alloy crystals begin to appear.

It is impossible to accurately measure the melting point of such substances; the point of transition of states is indicated by a numerical interval.

Depending on the temperature at which metals begin to melt, they are usually divided into:

Low-melting, up to 600 °C. These include tin, zinc, lead and others.
Medium melting, up to 1600 °C. Most common alloys, and metals such as gold, silver, copper, iron, aluminum.
Refractory, over 1600 °C. Titanium, molybdenum, tungsten, chromium.

There is also a boiling point - the point at which the molten metal begins to transition into a gaseous state. This is a very high temperature, typically 2 times the melting point.

Effect of pressure

There are exceptions when the temperature required to transform into a liquid state decreases with increased pressure. Such substances include ice, bismuth, germanium and antimony.

Melting point table

Table of melting temperatures of metals and alloys

660,4
1084,5
231,9
419,5
3420
1455
960
1064,4
1768
1668
650
1100−1500
1110−1400
1539
-38,9
1170
3530
1414
1400
271,4
938,2
1300−1500
930−1140
1494
63
93,8
1000
650
1246
2130
2890
327,4
1287
3150
1460
630,6
3150
3530
29,76

Strength of metals

There are the following strength groups of metals:

Fragile. Their resistance does not exceed 50MPa. These include tin, lead, soft-alkaline metals
Durable, 50−500 MPa. Copper, aluminum, iron, titanium. Materials of this group are the basis of many structural alloys.
High strength, over 500 MPa. For example, molybdenum and tungsten.

Metal strength table

MetalResistance, MPaCopper Silver Tin Gold Lead Zinc Magnesium Iron Aluminum Titanium

200−250
150
27
120
18
120−140
120−200
200−300
120
580

The most common alloys in everyday life

As can be seen from the table, the melting points of elements vary greatly even among materials commonly found in everyday life.

In addition, there are low-melting solders with a lower melt limit, up to 30 °C, and are used when overheating of the materials being soldered is dangerous. For these purposes, there are solders with bismuth, and the melting of these materials lies in the range from 29.7 - 120 °C.

Melting of high-carbon materials, depending on alloying components, ranges from 1100 to 1500 °C.

Source: https://obrabotkametalla.info/splavy/temperatura-plavleniya-cvetnyx-i-chernyx-metallov

What are tarnish colors

From a physical point of view, this phenomenon is explained by the theory of “thin films” and is caused by the optical interference of oxide films depending on their thickness.

Tarnish color scale

The thickness of the oxide films is determined by the temperature and heating time, and the existing scales of tarnish colors are rather arbitrary.

First, visual evaluation is a highly subjective process, with results determined by lighting conditions and practical experience.
Secondly, the density of the oxide film is also determined by the chemical composition of the alloy.

Colors	Heating temperature, °C
pale yellow	220
pale straw yellow	230
golden yellow	246
brown-yellow to brown	256
purple-red	265
purple	275
lilac	280
blue	290
cornflower	295
indigo	300
light blue	310
sea water color	320

Tarnish colors for surface finishing

For both hardened and non-hardened steel, the formation of oxide films will occur differently. The rate of formation of oxide films is significantly influenced by:

structure. Hardened steels oxidize more slowly
surface contamination. Oil films are charred to soot, so the films will be loose and loose,
surface roughness. On a polished surface, the film will be thinner than on a rough surface under the same conditions.

To obtain a dense, uniform oxide film, heating furnaces are required that can maintain a stable temperature for a long time.

Irina Faydyuk

Source: https://engitime.ru/metallicheske-materiali/chto-takoe-cveta-pobezhalosti.html

Measuring metal temperatures

To measure temperatures during heat treatment, special devices are used - pyrometers.

The most widespread are thermoelectric and optical pyrometers.

The diagram of a thermoelectric pyrometer is shown in the figure:

It is a thermocouple with a galvanometer . A thermocouple is two wires made of dissimilar metals or alloys welded together.

The deflection of the needle of a galvanometer connected to the free ends of the thermocouple at a constant ambient temperature will be proportional to the temperature of the metal being tested.

For ease of use, the galvanometer has a temperature scale.

Various metals and alloys are used for thermocouples.

For example, to measure temperatures of 1000–1300° a thermocouple is made of platinum and an alloy of platinum and rhodium.

The temperature of a hot metal can be determined with an optical pyrometer - by comparing the brightness of its glow with the filament of an electric light bulb.

the strength of the electric direct current feeding the electric lamp using a rheostat

Depending on the magnitude of the current, the needle of the device will deviate on the scale at a different angle. For convenience, the scale is graduated in degrees Celsius.

Approximate methods for determining the metal temperature value

Source: http://www.Conatem.ru/tehnologiya_metallov/izmerenie-temperatur-metalla.html

Metal tarnish colors

And yet, those involved in metalworking must be able to determine the temperature of steel products. Let it be approximately, but quickly and without instruments.

Tarnish colors

When some metal alloys are heated to certain temperatures, oxide films on their surfaces can acquire different colors.

Such colors and their shades, characteristic of the temperatures that caused their appearance, are called tarnish colors.

If we do not take into account the color shades observed in a very narrow arrangement, there are nine clearly defined color temperature regions, of which the region with the natural color of steel is not included.

Next, one by one, a template will be applied to each of the nine color-temperature areas, the color and shade of which is most similar to the color of this area.

The template shows the temperature range and average value that is inherent in a given color of tarnish on the surface of carbon steel.

Heat colors

As heating continues, the tarnished colors are replaced by incandescent colors.

Method for measuring temperatures by tarnish and heat colors

Craftsmen and specialists who have regular practice usually do not use tables. Because they know all the color shades and temperature values associated with their manifestations by heart.

I would like to draw your attention to the fact that when comparing the colors of a template and an object, you should not expect them to be completely identical.

The similarity of their color shades is enough. And then we can assume that the temperature of a uniformly heated object is in the range of values indicated on the color template.

Enough tables with the colors of tarnish and heat have been published in the literature and on the Internet. Their interpretations differ in form and content, unfortunately, too. Unlike most of them, the colors used in this template video tutorial are computer matched to real heat colors and the tarnish colors of carbon steels.

The names of color shades indicated on the templates are conditional. And their exact identification is possible using the so-called html color code indicated below.

When measuring temperatures by tarnish colors, you need to understand that they reflect the temperature on the controlled surface. And this does not always correspond to the temperature of the entire mass of the heated object. If the task is to heat an object to a certain temperature, controlled by the color of the tarnish, it must be heated not through one point or surface, but evenly, from all sides.

Source: https://kovkapro.com/metalloobrabotka-obschie-svedeniya/cveta-pobezhalosti-metalla/

What temperature can paints for exterior work withstand?

Features of paintwork in winter

Facade paints will take 2-3 times longer to dry in the cool season. You can improve the quality of the coating using a thermal gun. You can also attach film to scaffolding.

The temperature of the paint and varnish material must exceed 0 °C. If the composition cools more, the container containing it must be placed in a basin with preheated liquid.

Maximum temperature limits for paints

Before carrying out work, you need to make sure that the established temperature regime is suitable for the purchased paint.

Recommendations for better drying

It is necessary to pre-prepare the surface. You will have to remove the previous coating from it. Then the metal product is processed with special devices.

Suitable:

sandblasting machine;
sandpaper.

If there are irregularities, use putty.

It will not work in rainy or snowy weather. Precipitation will prevent winter metal paint from drying.

You only need to work with dry and clean material. Dust, dirt and mold are removed with a brush.

If the work is carried out in an unheated room, you can speed up the drying process using a portable heater; the paint dries faster when exposed to heat.

Frost-resistant paints for rust

Infrazim-Antikor is suitable for painting rusted structures. This paint is used in the range of -20+30 °C. Humidity should not exceed 80%.

The composition is simultaneously a rust converter, a corrosion-preventing primer and an environmentally resistant decorative enamel. You can purchase glossy or matte paint.

As for the palette, paintwork materials are available in white, gray, beige, cream, red, green, light green, light blue, blue, ocher, brown, yellow, orange, black and red-brown.

Primer enamel XB-0278 can be used for outdoor work at a temperature range of -10+25 °C. This product is applied to metal with rust and traces of scale that cannot be removed.

The best winter coatings for metal

Organosilicate composition OS-12-03 will prevent corrosion that occurs due to the unfavorable influence of the surrounding atmosphere. Used at -30+40 °C.

Facade enamel KO-174 is used not only for protecting metal products, but also for painting facades. Suitable for painting concrete, brick products, plastered walls, floors, ceilings. Well protects metal from moisture and air. The composition must be applied at a temperature of -30+40 °C.

Source: https://vmirekraski.ru/rabota-s-kraskami/temperatura-pri-pokraske-metalla

At what temperature does copper melt: necessary process conditions in production and at home

At the dawn of the development of civilization, people were already obtaining and using copper and its alloys.
At that time, it was not sulfide ore that was mined, but malachite ore, which did not require pre-roasting.
A mixture of ore and coals was placed in a clay vessel, which was lowered into a small pit.
The mixture was ignited, and carbon monoxide helped the malachite to be restored to the state of free Cu.
There is native copper in nature, and the richest deposits are in Chile.
Copper sulfides often form in medium-temperature geothermal veins.
Often the deposits are in the form of sedimentary rocks.
Copper sandstones and shales are found in Kazakhstan and the Chita region.

THIS IS INTERESTING: What are refractory metals?

Why does the snow turn red in the mountains?

Plants with heat sensitivity

What causes snow to be colored?

Other colors

Source: https://123ru.net/pics/231530229/

At what temperature does steel turn red - Metalworker's Handbook

This article is precisely intended to tell you about the density of high-strength, liquid, white and gray cast iron, its melting points and specific heat capacity will also be considered separately.

Cast iron, like any metal, has the following properties: thermal, physical, mechanical, hydrodynamic, electrical, technological, chemical. Let's look at each properties in more detail.

This video talks about the structure and composition of cast iron alloys and the dependence of their properties on a specific composition:

Heat capacity

The specific heat capacity of cast iron is 540 J/kg C.

Specific heat capacity of cast iron and other metals in table form

Thermal conductivity

Thermal diffusivity

The thermal diffusivity value of solid cast iron (for large calculations) can be taken equal to its thermal conductivity, and that of liquid cast iron – 0.03 cm2*/sec.

Read below about the melting point of cast iron.

Melting temperature

The table below shows the melting point of cast iron in comparison with other metals.

Melting point of cast iron and other metals

Weight

In addition, the linear expansion of the metal and the structure of cast iron changes depending on the state of each indicator. That is, these are dependent quantities.

The video below will tell you about some of the physical properties of cast iron:

carbon is usually at least 2.14%. Thanks to the carbon content, cast iron has excellent hardness. However, the plasticity and malleability of the material suffers against this background.

We will talk about the density of cast iron below.

Density

The density of the described material, cast iron, is 7.2 g/cm3. If we compare other metals and alloys with cast iron, this density value is quite high.

Due to its good density, cast iron is widely used for casting various parts in industry. In terms of this property, cast iron is only slightly inferior to some steels.

Tensile strength

When the melting temperature increases to 400ºС, the tensile strength does not change.
If the temperature rises above this value, the tensile strength decreases.
Note that at temperatures from 100 to 200ºС, the tensile strength can decrease by 10-15%.

Cold-worked steel is

Plastic

In ordinary gray cast iron, the elongation reaches only a tenth.
In annealed gray cast iron, the elongation is 1.5%.

Elasticity

Elasticity depends on the shape of the graphite. If the graphite inclusions did not change, and the temperature increased, then the elasticity remains at the same value.

Impact strength

This indicator reflects the dynamic properties of the material. The impact strength of cast iron increases:

when the shape of graphite inclusions is close to spherical;
when the ferrite content increases;
when the graphite content decreases.

Endurance limit

The endurance limit of cast iron becomes greater when the frequency of loading increases and the tensile strength becomes greater.

Dynamic viscosity

Surface tension

This figure is 900±100 dynes/cm2. The value increases as the amount of carbon decreases and undergoes significant changes in the presence of non-metallic components.

Toxicity

Cookware is often made from cast iron. The fact is that cast iron as a material is non-toxic and tolerates temperature changes well.

Electrical characteristics

The electrical conductivity of cast iron is assessed using Kurnakov's law. The electrical resistance of some types is given below:

white cast iron - 70±20 Mk·oi·cm.
gray cast iron - 80±40 Mk·oi·cm.
malleable cast iron - 50±20 Mk·oi·cm.

Technological features

Fluidity can be determined by various methods. This indicator depends on the shape and properties of cast iron.

Fluidity becomes greater when:

overheating increases;
viscosity decreases;
hardening becomes less.

Fluidity also depends on the heat of fusion and heat capacity.

Chemical properties

Industrial cast iron contains impurities. These impurities greatly affect the properties, characteristics and structure of cast iron.

Thus, manganese inhibits the graphitization process. The release of graphite is stopped, as a result, cast iron acquires the ability to bleach.
Sulfur degrades casting and mechanical properties.
Sulfides are mainly formed in gray cast iron.
Phosphorus improves casting properties, increases wear resistance and increases hardness. However, against this background, cast iron still remains fragile.
Silicon has the greatest influence on the structure of the material. Depending on the amount of flint, white and ferritic cast iron are obtained.

This video will compare the properties of cast iron and steel:

Source: https://ssk2121.com/pri-kakoy-temperature-stal-krasneet/

How to get rid of an abscess without getting blood poisoning

The word abscess is translated from Latin simply as an abscess. Doctors use this Latin term to describe an active inflammatory process in which a cavity filled with pus forms in living tissue.

Tavarius/Shutterstock

Inflammation around the hair follicle can also lead to the formation of an abscess - this type of abscess is commonly called a boil.

How to tell if you have an abscess

Symptoms of an external abscess developing inside the skin are usually obvious:

it looks like a dense swelling, a “bump” that has grown under the skin;
touching him is painful;
the skin on the affected area turns red and feels hot to the touch;
not always, but quite often you can see an accumulation of white or yellow pus under the stretched skin.

Extensive subcutaneous abscesses may also be accompanied by fever.

If we talk about the general and most common symptoms of an internal abscess, here they are:

discomfort and pain in the area of the organ on which the abscess occurred;
temperature increase;
loss of appetite up to complete reluctance to eat;
active sweating;
distinct weakness.

Small abscesses often resolve on their own. However, much more negative scenarios are also possible.

When to Seek Help Quickly

Consult your physician or surgeon immediately if:

the diameter of the subcutaneous abscess exceeds 1 cm;
the abscess continues to grow and becomes more and more painful;
inflammation occurs in the groin or anus;
the abscess is accompanied by an increase in temperature.

Go to the emergency room or call 911 if:

An abscess with a diameter of more than a centimeter appeared on the face.
The temperature rose to 38.8 °C and above.
You notice red streaks under the skin that spread outward from the abscess.
In the area between the abscess and the breast, the lymph nodes were enlarged. For example, an abscess on the leg can cause enlarged lymph nodes in the groin area.

Such symptoms indicate that there is a high risk of blood poisoning. And this is a deadly condition.

What to do if you have an abscess

Until you see a doctor, you can try to alleviate the condition with home methods.

Apply warm compresses

They will help reduce pain and accelerate the maturation of the abscess. Apply gauze soaked in warm water to the affected area 3-4 times a day for 15 minutes.

Use ointments

Apply antiseptic ointments with a pulling effect to the abscess. To find out which is better and safer to use in your case, consult your doctor.

Don't forget about antiseptic

What you should never do if you have an abscess

Trying to squeeze out the pus

Pressure can drive it deeper, which means the abscess will only increase in size.

Piercing an abscess with a needle

You can accidentally damage a blood vessel, which means pus will enter the bloodstream - with the expected consequences of sepsis.

Rely only on home methods

Do not continue home treatment if the abscess does not decrease in size (much less if it continues to grow) within a couple of days. Consult a physician as soon as possible.

Ignore general health

Source: `https://lifehacker.ru/abscess/`

Table of melting temperatures of various metals, and at how many degrees they melt

How it happens

Melting of all metals occurs approximately the same way - using external or internal heating. The first is carried out in a thermal furnace; for the second, resistive heating is used by passing an electric current or induction heating in a high-frequency electromagnetic field. Both options affect the metal approximately equally.

As the temperature increases the amplitude of thermal vibrations of molecules , and structural defects in the lattice arise, expressed in the growth of dislocations, jumping of atoms and other disturbances. This is accompanied by the rupture of interatomic bonds and requires a certain amount of energy. At the same time, a quasi-liquid layer forms on the surface of the body. The period of lattice destruction and defect accumulation is called melting.

Metal separation

Depending on their melting point, metals are divided into:

Low-melting: they need no more than 600Co. This is zinc, lead, hang, tin.
Medium-melting: melting point ranges from 600Со to 1600Со. These are gold, copper, aluminum, magnesium, iron, nickel and more than half of all elements.
Refractory: requires temperatures above 1600°C to make the metal liquid. These include chromium, tungsten, molybdenum, titanium.

Depending on the melting temperature, the melting apparatus is also selected . The higher the indicator, the stronger it should be. You can find out the temperature of the element you need from the table.

Another important quantity is the boiling point. This is the value at which the process of boiling liquids begins; it corresponds to the temperature of saturated steam that forms above the flat surface of the boiling liquid. It is usually almost twice the melting point.

Both values are usually given at normal pressure. directly proportional to each other .

As the pressure increases, the amount of melting increases.
As the pressure decreases, the amount of melting decreases.

Table of low-melting metals and alloys (up to 600C o)

Table of medium-melting metals and alloys (from 600C to 1600C)

Table of refractory metals and alloys (over 1600C o)

Source: https://stanok.guru/stanki/metallorezhuschiy-stanok/temperatura-plavleniya-raznyh-metallov-v-tablice.html

Will there be a quarantine in schools in 2020, what is the epidemic threshold?

Doctors urge to act in advance to prevent mass diseases. Parents are already wondering whether schools should be closed for quarantine this year.

In which Russian cities has quarantine been declared?

The autumn-winter period, which for obvious reasons always falls during the academic year, rarely passes in Russia without quarantine. So on the eve of the New Year holidays 2020, a number of Russian schools were forced to send their students into quarantine.

In many cities of the Russian Federation, a forced quarantine was announced in December 2019 due to the illness of students. Quarantine was declared in Kurgan until further notice. In the entire region, more than 7,000 cases were recorded in less than a month. In Yekaterinburg, due to the unfavorable situation with the spread of the virus, not only schools, but also kindergartens are closed.

Students in Birobidzhan, where the epidemiological threshold was exceeded by 130%, are also on forced holidays. Schoolchildren in Khanty-Mansiysk, Ulan-Ude and Perm have been transferred to distance learning. In total, exceeding the incidence threshold was noted in 23 regions of the Russian Federation.

Quarantine in schools 2020 in Russia, will it happen or not?

Quarantine is a set of restrictive measures aimed at stopping the spread of the epidemic. Its main task is to minimize or isolate communication between infected persons and others in order to avoid worsening the situation. Quarantine may be declared due to the spread of influenza or ARVI.

If up to 30% of the total number of students in a class or group are absent from school, the class teacher is obliged to contact the students’ parents. His task is to find out the reason for the decision not to go to classes and find out whether changes will be made (they are a valid reason for the child’s absence). The issue of closing a class for quarantine will be considered if 30 percent or more of the students in the class are officially ill and contact medical institutions.

Let's look at the situation clearly. Let's imagine that there are 29 students in a class. Seven students did not come to school because they would be filing for sickness certificates. In this case, the management of the educational institution makes a decision to introduce quarantine. Often the period of temporary cessation of the educational process drags on for three days or until the end of the current week. Next, the decision is made according to the situation.

Flu epidemic in 2020

According to experts, this winter season Russia, like other European countries, will have to deal with several strains of influenza - Colorado, Brisbane, Kansas and Phuket. Each of them, except Brisbane, belongs to the group of deadly dangerous to humans. At the same time, different variants of the disease differ little from each other. All of them have ARVI symptoms.

People infected with the virus do not “sneeze.” During the course of the disease, a person may feel heaviness while breathing. The disease is accompanied by a state of weakness throughout the body. It is characterized by nasal congestion, but there will be no tickling in the nose characteristic of ARVI.

Each of us can contribute to the speedy stabilization of the situation. In addition to personal prevention, you need to think about not infecting other people. Therefore, as soon as you feel unwell, you should not go to school or work, you should go to the doctor. It will help you endure the disease without complications.

to the FTimes channel in Yandex.Zen

Source: https://ftimes.ru/306399-budet-li-karantin-v-shkolax-v-2020-godu-kakoj-epidemporog.html

What determines the color of tarnish?

What caused

A color change upon heating indicates that an oxide film several molecules thick is formed on the surface of the heated material. The color varies depending on its density and thickness. The larger the size and density of the oxides, the more significantly the color tone will differ from the original one.

Some people believe that the color tone of the tarnish can accurately indicate the degree of heating. However, this is a false statement. The appearance of different shades is affected by heating time, heating speed, the content of various impurities, and the nature of lighting. If we talk about alloy steels, then they need to be heated up more.

Tarnished colors on metal. How to make rainbow colors on steel

Origin

The color tone of tarnish belongs to interference colors. Visually, they change under different lighting and viewing angles. Also, the physical and chemical properties of the metal affect the color change of the material.

Physics of the process

After the steel surface begins to heat up, tarnish appears, which quickly changes color, ranging from yellow to gray. Depending on the temperature (more than 500 degrees), the first tones of heat appear, noticeable only in complete darkness.

If the temperature exceeds 650 degrees, the metal becomes red-hot. At high temperatures, the color of the oxide film can change from cherry to white (at 1100–1200 degrees). With further heating, the white will only become brighter, but will not change. As mentioned above, the heating color of a metal surface is not an accurate indicator of temperature.

Optical effects

The color tone directly depends on the thickness of the oxide film. When it increases, colors with a short wavelength range are extinguished. As the temperature increases, the film thickness increases. Thus, certain shades of oxides begin to disappear. First purple disappears, then yellow, then green and red disappear. This is the so-called interference of light.

Where do they appear?

A change in color occurs during oxidation, which occurs due to heating of the metal. During the heating process, color tones change in the same sequence, but at different speeds (depending on the increase in temperature and heating duration).

Due to the fact that the pattern of color changes is known, in the past blacksmiths relied on this fact to know how the temperature changes. With the development of technology, a pyrometer appeared.

Color tones for steel

If it makes sense to describe the pattern of changes in the color of tarnish for carbon steel depending on the degree of heating:

straw - after 220;
brown - up to 240–250;
raspberry - 250–270;
violet-blue - from 300;
gray - from 350.

If alloy steel is used, color changes must be expected with a further increase in heating temperature.
9-1 Measuring temperature by tarnish and heat colors - revised with corrections