White cast iron melting point
Cast iron is an alloy based on iron and carbon. It differs from steel in the latter content – 2% or more. Some brands contain up to 4% carbon. Most often, an alloy with a carbon content of 3-3.5% is used.
This is a casting material. For such a metal, such properties as its melting point, as well as its thermal properties - heat capacity, thermal conductivity, thermal diffusivity - come to the fore. How different chemical elements affect the quality of this metal and whether it is possible to melt it yourself - this will be discussed in the article.
Thermal properties of cast iron
An important category of physical properties of a material is its thermal properties. These include:
- Heat capacity.
- Thermal conductivity.
- Thermal diffusivity.
- Thermal expansion coefficient.
They all depend on the composition, structure, and therefore on the grade of the alloy. In addition, these properties of the metal change with changes in its temperature (the so-called displacement rule). The nature of this dependence and the main physical properties are given in the table.
Heat capacity (s)
This is the amount of heat that must be supplied to the body in order for its temperature to increase by one Kelvin (hereinafter all values are converted to degrees Celsius).
The heat capacity depends on the composition of the alloy, as well as on temperature (T). The higher T, the greater the heat capacity. If the temperature is above T for phase transformations, but below T for melting, then
at T exceeding the melting point:
c = 0.23±0.03 cal/(G˚С)
Volumetric heat capacity (the ratio of heat capacity to the volume of a substance) for approximate calculations is accepted:
- cast iron in solid state c' = 1 cal/(cm3G˚C)
- molten c' = 1.5 cal/(cm3G˚C)
Thermal conductivity (λ)
This is a quantitative characteristic of a body's ability to conduct heat. The displacement rule does not apply to thermal conductivity. The temperature of the material increases – λ decreases. It depends on the composition of the alloy, and to a greater extent on its structure. Substances that increase the degree of graphitization increase thermal conductivity, and substances that prevent the formation of graphite decrease it.
By the way, the thermal conductivity of molten cast iron is much less than that of solid cast iron. But due to convection it is greater than λ of the solid metal.
Thermal conductivity for different brands lies within:
λ =0.080.13 cal/ (cm·sec oC)
Thermal conductivity and other thermophysical properties depending on the temperature of the alloy are given at the end of the section.
Thermal diffusivity (α)
This is a physical quantity that shows how quickly body temperature changes. Equal to the ratio of thermal conductivity to volumetric heat capacity.
For approximate calculations you can take:
α=λ for solid metal (equal to its thermal conductivity);
α=0.03 cm2/sec for liquid.
Melting temperature
This alloy has good casting properties. Better than steel. The fluidity is high and the shrinkage is low (about 1%). It can be melted at a temperature 300-400 degrees lower than steel. Cast iron melting point:
What is it like?
The structure of cast iron is an iron base with graphite (carbon) inclusions. This material is distinguished not by its composition, but by the form of carbon in it:
- White cast iron (BC). Contains carbide (cementite) - this is a form of carbon, the same as in steel. It has a whitish color when scrapped. Very hard and brittle. In its pure form it is almost never used.
- Gray cast iron (GC). Contains carbon in the form of flake graphite. Such inclusions have a bad effect on the quality of the material. To change the shape of graphite grains, there are special methods of melting and further processing. Graphite in midrange can also be in the form of fibers (“worm-shaped” form) - the so-called vermicular graphite (from the Latin word vermiculus - a worm, like vermicelli).
- Highly durable. Spherical shape of graphite grains. It is obtained by introducing magnesium into the alloy.
- Malleable cast iron. To obtain it, warheads are annealed. Graphite grains in the form of flakes.
As a result, the main difference between it (apart from white) and steel is the presence of a graphite structure. And different forms of graphite determine the properties of different grades.
Conventionally, graphite grains are voids and cracks, and cast iron is steel riddled with microscopic cracks.
Accordingly, the more voids, the worse the quality of the metal. The shape and relative position of the inclusions also matters.
However, graphite grains should not be accepted as exclusively harmful. Due to the presence of graphite, this material is easier to machine and the chips become more brittle. In addition, it resists friction well also due to the graphite.
Impurities
Of course, this metal contains more than just iron and carbon. It contains the same elements as steel alloys - phosphorus, manganese, sulfur, silicon and others. These additives indirectly affect the characteristics of the alloy - they change the course of graphitization. The quality of the material depends on this parameter.
- Phosphorus. Has little effect on the formation of graphite. But it is still needed, because it improves fluidity. Solid inclusions of phosphorus provide high hardness and wear resistance of the metal.
- Manganese. It interferes with graphitization and, as it were, “bleaches” cast iron.
- Sulfur. Like silicon, it promotes bleaching of the metal, and also impairs fluidity. The amount of sulfur in the alloy is limited. For small castings no more than 0.08%, for parts more - up to 0.1-0.12%.
- Silicon. Strongly affects the properties of the material, increasing graphitization. The metal can contain from 0.3-0.5 to 3-5% silicon. By varying the amount of silicon, an alloy with different properties is obtained - from white to high-strength.
- Magnesium. Helps to obtain material with spherical grain shape. The boiling point of magnesium is low (1107˚C). For this and other reasons, introducing magnesium into the alloy is difficult. To avoid its boiling, the material is smelted using various methods of introducing magnesium.
Source: http://schemy.ru/info/belyj-chugun-temperatura-plavlenija/
Melting temperature, properties and independent melting of cast iron
Cast iron is an alloy based on iron and carbon. It differs from steel in the latter content – 2% or more. Some brands contain up to 4% carbon. Most often, an alloy with a carbon content of 3-3.5% is used.
This is a casting material. For such a metal, such properties as its melting point, as well as its thermal properties - heat capacity, thermal conductivity, thermal diffusivity - come to the fore. How different chemical elements affect the quality of this metal and whether it is possible to melt it yourself - this will be discussed in the article.
Self-smelting technology
Non-industrial smelting of cast iron is a very labor-intensive process. It is impossible to smelt factory-quality castings with your own hands in artisanal conditions.
You cannot smelt this metal at home. You need a separate ventilated room - a garage, for example. Melting is carried out in furnaces. In industry, blast furnaces, cupola furnaces and induction furnaces are used.
A blast furnace is an industrial unit capable of melting metal on a huge scale. Iron ore raw materials can be smelted in it. After launch, it works without interruption for up to 5-6, or even up to 10 years. Then it is stopped, serviced and started again. Melting of the metal takes place in the presence of gases to improve the quality of the material. Such ovens are not suitable for small and medium-sized production. Fuel - coke.
A cupola furnace is a shaft-type furnace, like a blast furnace. It differs from the latter in that it does not maintain a special composition of gases. It is not ore that is smelted in it, but scrap iron. It is more suitable for small production.
An induction furnace is a modern type of equipment. The smelting process in such a furnace can be controlled, temperature, heating time and charge composition can be adjusted.
Melting is carried out in crucibles made of refractory clay or brick. Steel ones are not suitable, although steel begins to melt at a temperature higher than cast iron. Flux is required - a substance that promotes the formation of low-melting slag. For example, limestone (CaCO3), fluorspar (CaF2). To obtain gray rather than white cast iron, ferrosilicon (an alloy of iron and silicon) is added to the charge. It improves the formation of graphite grains. Once melted, the metal is poured into a sand or metal mold.
Metal casting is an explosive and fire hazardous job. In addition, it is necessary to have certain knowledge in the field of metallurgy. To organize production, you will need to complete documentation, pass inspections, obtain permission and a license to work.
We also recommend reading:
Classification of cast iron and its types
Source: https://oxmetall.ru/metalli/chugun/temperatura-plavleniya
At what degrees does cast iron melt?
Today, cast iron is considered one of the most common metals. Parts for machinery and industrial equipment, building materials and much more are made from it. Before casting, you need to know the melting point of cast iron.
Types of cast iron
There are several types of cast iron. Various alloying impurities are added to it, which change the characteristics of the solid material. For this, aluminum, chromium, vanadium or nickel are used. In addition to them there are other impurities. The parameters of finished products directly depend on the composition of the alloy. Varieties:
- Gray cast iron. It is considered the most popular type. The composition contains 2.5% carbon, which is a particle of graphite or perlite. Has a high strength index. Gray cast iron is used to make parts that can withstand constant loads. These can be gears, housing parts, bushings.
- White cast iron. The carbon contained in the composition is carbide particles. A white mark remains on the fracture of the material, which corresponds to the name. carbon on average more than 3%. A fragile and brittle type of material, which is why it is used only in static parts.
- Half-hearted. Combines the characteristics of the two previous types of cast iron. Graphite and carbide particles saturate the metal with carbon. Its content is from 3.5 to 4.2%. Wear-resistant material used in mechanical engineering. Withstands constant friction.
- Malleable cast iron. It is obtained from the second type of material, after annealing. The alloy contains carbon in the form of ferrite particles. Its amount is about 3.5%. Like half-shaft, it is used for the manufacture of parts in mechanical engineering.
To obtain a high-strength material, graphite particles are processed so that they take on a spherical shape and fill the crystal lattice. Magnesium, calcium or cerium are added to the alloy.
Thermal properties of cast iron
The characteristics of a metal depend on its thermal properties. They change when treated with high and low temperatures. Directly depend on the composition of the alloy.
Heat capacity
Heat capacity is the processing of metal with heat. Heats up until the temperature of the workpiece rises by one Kelvin. This indicator depends on the presence of additional components in the alloy and temperature. If it is high, then the heat capacity will be greater. Average heat capacity:
- Hard metal - 1 cal/cm3G.
- Molten material - 1.5 cal/cm3G.
From these indicators the ratio of heat capacity and volume of the substance is calculated.
Thermal conductivity
This parameter determines how well a material can conduct heat energy. It depends not only on the components in the alloy, but also on the structure of the metal. The thermal conductivity for a solid material is higher than for a molten one. For different grades of steel, this indicator varies within 0.08–0.13 cal/cm sec oC.
Thermal diffusivity
This physical quantity reflects the ability of a material to change body temperature. When calculating, it is necessary to take into account the following indicators:
- Thermal conductivity range for different grades of cast iron. Applicable to solid material.
- For liquid metal - 0.03 cm2/sec.
Additionally, the heat capacity indicator is taken into account.
Melting temperature
Cast iron is considered the best metal for smelting. Its high fluidity rate and low shrinkage allow it to be used more effectively in casting. Below are the boiling points for different types of this metal in degrees Celsius:
- Gray cast iron - melting point reaches 1260 degrees. When pouring into molds it rises to 1400.
- White - melts at 1350 degrees. Poured into molds at 1450.
The melting rates of cast iron are 400 degrees lower than those of steel. This reduces energy costs when processing cast iron.
The influence of chemical elements on the properties of metal
To understand how impurities affect the characteristics and properties of cast iron, it is necessary to understand the structure of its individual types:
- White - The form of carbon in this variety is carbide. White color is visible at the break. It is considered a brittle and brittle material that is rarely used in industry without additives.
- Gray cast iron. The graphite plates in this material saturate it with carbon. To use the material in the production of parts for industrial equipment, the shape of the grains is changed by melting.
- Malleable - The graphite grains in this type of metal have the appearance of flakes.
High-strength cast iron is obtained by adding magnesium to the alloy. To improve the characteristics of this metal, impurities are used.
Impurities
Each impurity added to iron and carbon changes the properties of the finished material. The influence of additives on the quality of cast iron:
- Magnesium. Allows you to make spherical grains in the material. This increases the strength and hardness of the workpiece.
- Manganese. Slows down the graphitization process. The metal is whiter at fractures.
- Silicon. Increases graphitization of the material. The maximum amount of silicon in the workpiece is 3.5%. The strength indicator depends on its quantity.
- Sulfur. The amount of this impurity is reduced to improve fluidity.
- Phosphorus. Has virtually no effect on the graphitization process. Improves fluidity. By adding phosphorus to the alloy, wear resistance and strength are improved.
Alloy materials can be added to cast iron.
Self-smelting technology
Knowing at what temperature cast iron melts, you can carry out independent smelting. However, this is a costly and time-consuming process. It is impossible to make a high-quality casting without special equipment.
First of all, you need to equip a separate room with good ventilation. The smelting process is carried out in a furnace. The best option is a blast furnace. It can be used to process large volumes of consumables (iron ore). The fuel used is coke. However, this is industrial equipment that requires special conditions of use.
Induction furnaces are used in our own workshops. The raw materials are melted in crucibles. During the smelting process, it is necessary to use flux, which creates a low-melting slag. Once the metal is molten, the craftsman pours it into sand or metal molds.
The melting point of cast iron varies slightly depending on the type of material and the impurities it contains. It is extremely difficult to process this metal at home. It is necessary to equip the room, take care of ventilation and fire safety.
After preparation, install the furnace and other equipment for smelting.
Source: https://varimtutru.com/pri-skolki-gradusah-plavitsya-chugun/
Melting point of cast iron 1200: melting white, gray types of metal
In industry and everyday life, cast iron products are widely used. The metal is iron, which has 2 percent carbon integrated into its molecular structure. Today, many grades of metal are produced that have different fracture characteristics. About a hundred species.
Production requires a huge amount of thermal energy, since the melting point of cast iron is over one thousand degrees Celsius. Melting occurs at a temperature of 1150 - 1200 C°.
In addition to carbon, to obtain the required grade, silicon, sulfur, manganese, and phosphorus are added to the batches. Increased strength is achieved by incorporating alloying additives into the batches.
Differences from steel
According to the technological process, cast iron is the primary product obtained by casting, and steel is the final product. The molecular structure of steel contains carbon in an insignificant amount. The material is plastic and lends itself well to mechanical processing. Products are manufactured by forging, welding, and rolling in mills. Has a high melting point. According to technology, steel is subject to hardening. The quality depends on the prepared mixture and on the melting temperature of the steels.
The rate of transformation of steel into a liquid state depends on various additives. A specific answer to the question at what temperature steel melts can be conditionally given only the heating range. The transition from a solid to a liquid consistency occurs at a temperature of 1450-1600 C°. The given digital parameter indicates the difference between steel and cast iron. These are different melting temperatures.
Cast iron is not as strong as steel. Cast blanks contain pores, making them brittle. It is during the casting process that cast iron products are produced. The presence of microscopic voids reduces the thermal conductivity characteristics of the metal. It is important to set the thermal regime, to record at what temperature cast iron melts.
Ferrous metallurgy produces several types of primary products. Let's look at some of them.
Grayish cast iron
Alloys formed by iron and carbon components change structure when integrating flake, flake, and fibrous graphite. Manufacturers obtain high-strength cast iron by adding globular graphite. The presence of Mg, Ce (magnesium, cerium) in the batch motivates its modification. Depending on how quickly molten cast iron cools, it acquires new consumer characteristics. Products of the required quality are obtained from a skillful combination of specific properties.
To make it easier to find the right material in catalogs, products are marked with the abbreviation S. Ch. The numbers following the letters indicate the force load limit in kilograms/per square millimeter. High-strength metal has the letter designation V.Ch. The numbers indicate the amount of strength, and also separated by a hyphen - the increase in length as a percentage. For example, HF60−1
Gray cast iron has excellent technological characteristics during its production process:
- Crystallization does not require extreme temperatures, which has a positive effect on saving electricity and other types of energy.
- Shows unique liquid fluidity.
- When poured, it exhibits optimal shrinkage.
Due to its unique properties, metal is the base material for the production of products.
Has disadvantages in application. They manufacture units and parts that work only in compression. Machine beds, cylinders, various pistons, and so on are cast. Critical fragility indicators do not allow use for the production of products operating under conditions of bending forces. Melting point 1150 - 1260 C°
Bleached fabric colors
White cast iron contains an iron-carbon compound called cementite. It has colossal hardness, excluding plasticity. If you break a metal, the color is visible on the break. Cast iron is harder than stone and as fragile as eggshells.
Subjected to processing to obtain a malleable variety. The melting point occurs in the range of 1150 – 1350 C°. It is appropriate to note that the term malleable is used conditionally, since the metal cannot be processed plastically.
Malleable cast iron is produced by thermal firing.
Heating the material above 900 degrees Celsius affects its properties. The rapid cooling of graphite also leads to this result. Failure to comply with technological parameters leads to complications in the production of welding work and processing of workpieces.
High strength cast iron
In ferrous metallurgy, high-strength material is called cast iron, which has graphite inclusions in its molecular structure, the shape of which is spheroidal. The unique ratio of spherical graphite surface to volume ensures the formation of a metal base, that is, it affects strength. Melting the metal with the integration of spheroidal graphite does not allow cracks. New properties of the metal are formed: it becomes strong when subjected to bending force. In addition, it demonstrates:
- instantaneous impact viscosity;
- increase in turnover rate;
- slight elongation, which can be called a relative phenomenon.
- unique resistance to compression;
- wear resistance.
This type can be welded. The metal connection is carried out using fluxes used in the form of paste-like consistencies.
Heavy duty cast iron material has excellent casting properties. Excellent fluidity in the liquid state ensures exemplary filling of molds. According to some technological parameters, the material can be compared with steel.
Taking into account the excellent structural properties, factories produce parts for components and systems if they do not experience tensile loads during operation of machines and mechanisms.
Grid changes
With increasing heat (cast iron melts at a temperature of 1200 degrees Celsius), the crystal lattice transitions into the current liquid state. It is at this moment that the internal energy of the metal increases.
Having reached heating above one thousand degrees, the crystal lattice is destroyed. At this time, incoming thermal energy continues to weaken molecular bonds. There is an increase in energy reserves inside the metal.
It is several times higher than that containing crystallized material.
The cessation of heating is the beginning of cooling of the metal. A reverse crystallization process occurs, developing according to a dendritic algorithm. That is, from the points that motivate such development. They (dendrites) act as a priori stages of the process. The crystal grows, as it were, from the center of the phenomenon.
In liquid, but already cooling cast iron, crystallization occurs according to the principle of the structure of wood. The process involves dendrites of cementite, austenite and graphite. It has been established thermodynamically that it is spherical graphite that is represented by a dendrite having a sectoral layered structure.
Source: https://obrabotkametalla.info/stal/temperatura-plavleniya-chuguna
Boiling point of cast iron
Cast iron is an alloy of iron that contains more than 2% carbon. In addition to these components, the mixture contains permanent substances such as sulfur, silicon, phosphorus, manganese and alloying additives.
The material is divided into different types depending on the alloy, which is determined by the fracture structure.
Cast iron has up to a hundred different grades, among which cast iron stands out; it differs from the rest in texture, purpose and production technology.
Material classification
This material is more brittle than steel . It can collapse without noticeable deformation. Carbon in the alloy takes the form of graphite and cementite, or each substance is presented separately. Varieties of cast iron appear in connection with their shape and quantity:
- White. All carbon is in the form of cementite. This color of the material is visible at the fracture. It can be described as brittle but hard. It is processed mainly to produce the malleable variety.
- Grey. Carbon in the form of a plastic form of graphite. It is characterized as soft, easy to process using low melting temperatures.
- Malleable. This type is named conventionally, since the material is not forged. This type is obtained as a result of prolonged firing of white, after which graphite is formed. The properties of the material are negatively affected by heating above 900 degrees, as well as by the cooling rate of graphite. As a result, the welding and processing process becomes difficult.
- Highly durable. It contains spherical graphite, which is formed through crystallization.
Differences between steel and cast iron
The difference in materials is expressed as follows:
- Cast iron is less hard and durable than steel.
- Steel is heavier and has a higher melting point.
- Since steel has a lower carbon content, it is easier to process (forging, cutting, welding, rolling). For this reason, cast iron products are made by casting.
- Cast iron products are porous (due to casting), so their thermal conductivity is lower.
- Artwork made of steel has a shine and shine, while art products made of cast iron are black and matte.
- Cast iron is the primary product of ferrous metallurgy, and steel is the final product.
- Steel is usually subjected to a hardening procedure.
- Cast iron products are produced through the casting process, while steel products are forged and welded.
This material good casting properties , good fluidity, and a lower melting point compared to steel and ductile iron. These properties are taken into account when making the mold.
The gaseous flux is most often used for welding materials with brass. Copper-coated cast iron rods are also used, which improve the wettability of the edging with the deposited metal.
Rods made of eutectic cast iron are used; its melting point is in the range of 1050 - 1200 degrees . Welding also occurs thanks to fluxes, which are used in the form of a paste.
If there are no special cast iron rods or L-62 brass, then cracks in parts made of this material can be welded with wire made of electrolytic red copper.
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Significantly above the melting point, cast iron overheats, which causes these suspended particles to dissolve, perhaps not completely, and this makes the formation of graphite more difficult. In some cases, it can occur when various substances are added to cast iron, which causes additional centers of graphite crystallization to appear.
Cast iron has better casting properties when compared to steel. Ease of use, as well as good fluidity and mold fillability, are ensured by a lower melting point and the final crystallization process at a constant temperature.
The above advantages of cast iron turn the material into a valuable structural material, which is widely used in machine parts when they are not subject to significant tensile and impact loads.
Melting point of semi-synthetic material
Semi-synthetic cast iron is melted by melting the charge, and the temperature range ranges from 1400-1450 degrees .
After melting the charge, the cast iron is stored in the furnace crucible at slight overheating, not exceeding the melting point by one hundred degrees.
What needs to be done to create a slag cover? When the charge gradually begins to melt, crushed glass or calcined quartz sand should be applied to the metal surface.
Types of welding
Gas welding should be carried out by melting with a flame parts of the elements being connected and a rod of filler metal. This welding is used to connect metal parts, non-metallic elements and alloys that have different melting points, and the thickness should be no more than 30 mm . To arrange it, you do not need to resort to electricity.
Electric arc welding is widely used. Thanks to the electric arc, the melted metal, which combines various elements, interacts with the metal of the electrode, forming a strong seam.
flux or inert gases are used for this .
Electric arc welding uses various methods (manually, semi-automatically and automatically) to connect parts made of cast iron, structural steel, copper, aluminum and other alloys.
The melting point depends on the carbon contained in the material. The more it is, the lower the temperature, and the higher the fluidity when heated. From this we can conclude that the material is fluid, brittle, non-plastic and difficult to process. Its specific gravity is 6.9 G/cm3. The melting point is in the range of 1150-1250 degrees.
Source: https://steelfactoryrus.com/temperatura-kipeniya-chuguna/
Cast iron material: basic properties and important characteristics
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.
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%.
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: http://stroyres.net/metallicheskie/vidyi/chyornyie/chugun/vazhnyie-harakteristiki.html
Cast iron: melting point of the material
Cast iron is an alloy of iron that contains more than 2% carbon. In addition to these components, the mixture contains permanent substances such as sulfur, silicon, phosphorus, manganese and alloying additives. The material is divided into different types depending on the alloy, which is determined by the fracture structure. Cast iron has up to a hundred different grades, among which cast iron stands out; it differs from the rest in texture, purpose and production technology.
Melting cast iron: optimal temperature, material classification, comparison with steel - SibNovStroy
The melting temperatures of cast iron are significantly lower (by 300 - 400 C) than those of steel, which facilitates the casting process.
The melting point of cast iron is lower than the ignition temperature, and the emerging refractory silicon oxides interfere with the normal cutting process. Non-ferrous metals cannot be cut due to the high melting point of the resulting oxides and significant thermal conductivity.
The melting point of cast iron is below the temperature t - then ignition, and the emerging refractory silicon oxides interfere with the normal cutting process. Non-ferrous metals cannot be cut due to the high melting point of the resulting oxides and significant thermal conductivity.
The melting point of cast iron is lower than the combustion temperature of iron, so oxygen cutting of cast iron without the use of flux is difficult. When cutting cast iron, silicon, when burned, produces a refractory oxide film that prevents cutting. And when burned, carbon pollutes the cutting oxygen, thereby preventing the combustion of iron.
Oxygen cutting of cast iron without flux is also difficult, since the melting point of cast iron is lower than the combustion temperature of iron. The silicon contained in cast iron produces a refractory oxide film that prevents normal cutting. When the carbon in cast iron burns, it produces carbon monoxide gas, which contaminates the cutting oxygen and prevents the combustion of the iron.
Conventional welding of cast iron is carried out at a temperature of the weld pool exceeding the melting point of cast iron.
Monel has a melting point of 1260 - 1340 C, which corresponds to the melting point of cast iron. and thanks to nickel, it alloys well with cast iron.
However, this alloy exhibits significant shrinkage, which leads to the appearance of high internal stresses, which contribute to the formation of cracks.
Therefore, Monel is welded with short beads 40-50 mm long and immediately after this the seam is hammered.
Cast iron containing more than 1-7% carbon cannot be cut with oxygen, since the melting point of cast iron is lower than the temperature of its combustion in a stream of oxygen.
Cast iron, as is known, is not amenable to oxygen cutting using conventional methods due to the fact that the melting point of cast iron is lower than its ignition temperature in oxygen, and the film of silicon-containing oxides formed during cutting on the surface of the part is much more refractory than the base metal.
Welding cast iron is also hampered by the formation of various refractory oxides with a higher melting point than the melting point of cast iron.
In the molten state, cast iron quickly oxidizes and becomes covered with oxides, the melting point of which can be higher than the melting point of cast iron.
Cast iron is cast, machined and welded; when heated, it does not soften and remains brittle; The melting point of cast iron is 1150 - 1250 C.
But only if copper contains 10–15% iron, it is possible to obtain an alloy with a melting point of 1330–1370 C, close to the melting point of cast iron. In this case, the miscibility of the components of the melt itself with the cast iron is ensured.
However, after solidification, the surfacing is a soft copper base with inclusions of a very hard steel component of varying shapes and sizes. These inclusions make machining of the metal difficult.
Partially diffusing into the base metal, copper manifests itself as a graphitizer, so chill appears weakly in the area/heat-affected zone.
Cast iron is an alloy of iron and carbon. the latter in cast iron can vary within 2.0. 6.7%. In addition to carbon, it contains silicon, manganese, sulfur and phosphorus, and there is more sulfur and phosphorus in cast iron than in steel.
Cast iron classification
Cast iron is classified according to the following criteria:
- chemical composition: alloyed; unalloyed;
- strength: normal strength; high strength;
- structure: white cast iron is a very hard material that is difficult to machine and weld. As a result, it is used mainly for the production of malleable cast iron (by heating to a temperature of 800–850°C and long-term exposure); gray cast iron is soft, can be easily processed by cutting tools, and has a melting point in the range of 1100–1250°C, depending on the carbon content. The more carbon, the lower the melting point of cast iron and the higher its fluidity. It welds well; malleable cast iron - heating to temperatures above 900 ° C leads to a significant deterioration in ductility and weldability. After welding, heat treatment is required to restore the structure of the material.
The influence of chemical elements on the properties of cast iron
Depending on the content of certain alloying elements, cast iron acquires certain properties. Carbon - an increase in its content in cast iron leads to deterioration of weldability, pore formation and a decrease in the melting point. Silicon - complicates the welding process due to the formation of refractory oxides.
Manganese - with a content of more than 1.5%, it impairs the weldability of cast iron. Magnesium - increases the strength of cast iron. Chromium - increases the acid resistance of cast iron. Molybdenum - helps improve mechanical properties under dynamic loads. Sulfur is a harmful impurity; reduces strength and promotes the formation of hot cracks during welding.
Its content should not exceed 0.15%.
Phosphorus - increases the fluidity and weldability of cast iron, but at the same time leads to an increase in brittleness and hardness. Its content should not exceed 0.3%.
Symbols for cast iron
According to GOST 1412-85, gray cast iron is denoted by two capital letters SCH and two numbers are put through a hyphen, the first of which represents the value of the tensile strength of cast iron, in tens of MPa, in tension, and the second in bending. Example. SCh-15-32 - gray cast iron with a tensile strength of 150 MPa (15 kgf/mm2) and a bending strength of 320 MPa (32 kgf/mm2).
Malleable cast iron is denoted in capital letters KCH and separated by two numbers, the first of which is the value of the tensile strength, in tens of MPa, and the second is the relative elongation, expressed as a percentage.
Example. KCh-35-10 - malleable cast iron with a tensile strength of 350 MPa (35 kgf/mm2) and a relative elongation of 10%.
Source: https://sibnovostroy.ru/obrabotka/plavlenie-chuguna-optimalnaya-temperatura-klassifikatsiya-materiala-sravnenie-so-stalyu.html
Melting cast iron: optimal temperature, material classification, comparison with steel
Cast iron is an alloy of iron that contains more than 2% carbon. In addition to these components, the mixture contains permanent substances such as sulfur, silicon, phosphorus, manganese and alloying additives. The material is divided into different types depending on the alloy, which is determined by the fracture structure. Cast iron has up to a hundred different grades, among which cast iron stands out; it differs from the rest in texture, purpose and production technology.
Advantages of the material
This material good casting properties , good fluidity, and a lower melting point compared to steel and ductile iron. These properties are taken into account when making the mold.
The gaseous flux is most often used for welding materials with brass. Copper-coated cast iron rods are also used, which improve the wettability of the edging with the deposited metal.
Rods made of eutectic cast iron are used; its melting point is in the range of 1050 - 1200 degrees . Welding also occurs thanks to fluxes, which are used in the form of a paste.
If there are no special cast iron rods or L-62 brass, then cracks in parts made of this material can be welded with wire made of electrolytic red copper.
Significantly above the melting point, cast iron overheats, which causes these suspended particles to dissolve, perhaps not completely, and this makes the formation of graphite more difficult. In some cases, it can occur when various substances are added to cast iron, which causes additional centers of graphite crystallization to appear.
Cast iron has better casting properties when compared to steel. Ease of use, as well as good fluidity and mold fillability, are ensured by a lower melting point and the final crystallization process at a constant temperature.
The above advantages of cast iron turn the material into a valuable structural material, which is widely used in machine parts when they are not subject to significant tensile and impact loads.
At what temperature does cast iron melt: melting point of the alloy
Cast iron is an iron alloy whose carbon content exceeds 2%. In addition to these components, the mixture contains a number of permanent substances, such as manganese, silicon, phosphorus, sulfur, and alloying additives.
Materials are divided into types depending on the alloy, which is determined by the structure of the fractures. There are about a hundred grades of cast iron, among which foundry is especially distinguished; it is distinguished from others by its texture, purpose and production technology.
The material is more brittle compared to steel and can break even in cases where there is no significant deformation. Carbon in the composition is presented in the form of graphite or cementite; each substance can be presented separately. Cast iron is divided into types, focusing on the shape and quantity of these substances:
- White. Carbon in its entirety is in the form of cementite. The tint can be seen precisely on the fracture of the materials. It is distinguished by fragility and simultaneous hardness. It can be processed mainly in order to ensure normal forging.
- Grey. Carbon has a plastic form in the form of graphite. It is characterized by softness and is easy to process at low temperatures.
- Malleable. This designation is conditional, because the material cannot be forged. The variety is obtained by prolonged firing of white, resulting in the formation of graphite. The beneficial properties are negatively affected by heating exceeding 900 degrees Celsius, as well as a significant cooling rate of the graphite itself, which leads to difficulties in the processing and welding process.
- Highly durable. It is characterized by the content of spherical graphite, which is obtained by crystallization.
Melting cast iron
The material has excellent casting properties, has good fluidity, and its melting point is significantly lower when compared with steel and ductile iron. Such properties are taken into account when giving shape.
To connect the material to brass, in most cases, gaseous flux is used. Cast iron rods coated with copper can also be used, which has a good effect on the wettability of the edging with the deposited metal. For rods, eutectic cast iron is used, the melting point of which ranges from 1050-1200 degrees .
Welding can also take place using paste-like fluxes. When there are no special rods made of cast iron or brass L-62, then cracks in elements made of this material can be eliminated by using wire, the main component of which is electrolytic red copper.
Significantly above the melting point, the material overheats, which leads to the dissolution of suspended particles. They do not always dissolve completely, but graphite still forms with difficulty. In some cases, it occurs if additional substances are added to cast iron that affect the formation of additional graphite crystallization centers.
Cast iron has excellent casting qualities when compared to steel, which makes working with it convenient. Good fluidity and mold fillability are ensured by a lower melting point and the final crystallization process at constant temperatures.
These advantages suggest that cast iron is a valuable structural material, which is actively used in the production of machine parts (if there are no significant tensile and impact loads).
Semi-synthetic cast iron is melted by melting the charge; the temperature range is 1400−1450 degrees . After the melting of the charge is completed, the material is stored in the furnace crucible at slight overheating (the melting temperature should not be exceeded by more than one hundred degrees). What should be done to create a slag cover? When the charge gradually melts, it is necessary to apply cullet or hot quartz sand to the metal mirror.
Types of welding
Gas welding is carried out by melting particles of joined elements and rods made of filler metals with a flame.
This welding is used to join metal parts, non-metallic components and alloys with unequal melting points. Their thickness should not exceed 30 mm. The device does not require electricity.
Electric arc welding is also widely . The electric arc promotes the active interaction of the melted metal with the metal of the electrode and the formation of a durable seam. To avoid oxidation, a special protective layer is applied to the seam.
Using electric arc welding, cast iron parts, structural steels, copper, aluminum and other alloys are connected.
Source: https://tokar.guru/metally/temperatura-plavleniya/temperatura-plavleniya-chuguna-osobennosti-materiala.html
