Application area of gray cast iron
Gray cast iron is an alloy of iron and carbon, which, when the metal cools, forms in the form of flake-like or plate-like inclusions. carbon in the alloy exceeds 2.14%, which is higher than normal solubility. This is what distinguishes the alloy from steel, in which carbon is completely dissolved and is absent in the form of separate inclusions, the structure of which defines them as graphite.
Main characteristics
Gray cast iron is the basis of ferrous metallurgy, as it is obtained from the reduction of iron ores using carbon fuel (coke). As a result, in addition to the chemical reaction of reduction of iron oxides, the alloy is additionally saturated with free carbon.
The high free carbon content determines the mechanical properties of gray cast iron. One of the main qualities that allow gray cast iron to be used not only as a pigment metal is its high casting qualities and low shrinkage during solidification. Molten metal has high fluidity, so it can be used to make castings of complex shapes.
Gray cast iron plates
The restriction on the use of products made of gray cast iron is due to the fact that it has low bending strength and high fragility. At the same time, the compressive strength of gray cast iron is very high.
https://www.youtube.com/watch?v=Wj3yX7R9dE4
Despite its high fragility, such a characteristic as the wear resistance of cast iron allows it to be used in products operating under friction conditions. Under these conditions, the antifriction properties of the alloy have a strong influence.
The presence of a large amount of carbon reduces the density of gray cast iron compared to most types of steel and ranges from 6.8 to 7.3 tons per m 3.
Due to the presence of carbon inclusions, welding gray cast iron is practically impossible. There are welding technologies under certain conditions. This is preheating of parts, the use of special high-carbon electrodes, but still, the structure of the weld metal is very different from the base material. The parts to be welded must be cooled slowly to eliminate stress in the weld area.
Chemical composition and structure
The chemical composition of the alloy, in addition to iron and carbon, also includes some silicon content. The properties of the alloy depend on the cooling conditions, since the time of temperature change affects the formation of the internal structure of the material.
Source: https://MyTooling.ru/instrumenty/oblast-primenenija-serogo-chuguna
Gray and white cast iron: conditions of formation
Cast irons are ternary alloys of iron-carbon-silicon. There are four main types of cast iron: – gray cast iron; – white cast iron; – malleable cast iron;
– nodular cast iron.
The chemical composition of these four types of cast irons is presented in the table below.
Table - Four main types of cast iron
Gray cast iron – graphite, white cast iron – cementite
In gray cast iron, a graphitic eutectic is formed - the carbon is mainly in the form of graphite, while in white cast iron a cementite eutectic is formed and the carbon is mainly in the form of cementite Fe3C.
The influence of silicon on the type of eutectic in cast irons
The addition of silicon allows graphite to form more easily, especially when formed directly from the liquid phase. It might even be more correct to say that the addition of silicon makes it more difficult for Fe3C to form cementite.
Figure 1 shows how silicon reduces the temperature of the austenite-cementite eutectic and at the same time raises the temperature of the austenite-graphite eutectic.
Figure 1 – Change in eutectic temperatures of graphite and cementite Fe3C
with increasing silicon content in cast iron from 0 to 2%
According to Figure 1, for an iron-carbon alloy with a silicon content of 2%, there are two eutectic temperatures: 1163 ºC for the formation of graphite and 1120 ºC for the formation of cementite. As the alloy cools, the liquid between the dendrites continues to become enriched in carbon until the temperature rises until one of these eutectics is formed.
Competition between graphite and cementite
There is a kind of competition between the two types of eutectics over which one is formed first. This competition involves three important factors:
1) Both types of eutectics require some undercooling below their eutectic temperatures, which are shown in Figure 1.2, before the formation of the eutectic begins. 2) The amount of undercooling increases with increasing cooling rate.
3) The amount of supercooling for the formation of austenite-cementite eutectic is less than that required for the formation of austenite-graphite eutectic.
Slow cooling - gray cast iron
Let us assume that the interdendritic liquid is cooled to 1130 ºС and that none of the eutectics have formed. Then the liquid is cooled by another 33 ºС – from 1163 to 1130 ºС. This supercooling is sufficient for the formation of graphite eutectic.
This cooling is not sufficient for the formation of cementite eutectic, since the temperature of the liquid has not dropped below 1120 ºС. Therefore, under these conditions, cementite eutectic cannot form.
Theoretically, supercooling of 33 ºС is sufficient for the formation of graphite eutectic and as a result, gray cast iron is obtained.
Fast cooling - white cast iron
Let's imagine that the same iron-carbon alloy with 2% silicon is cooled faster, so that the required amount of supercooling for the formation of graphite eutectic increases from 33 to 53 ºС.
This means that graphitic eutectic will not form until the interdendritic fluid reaches 1110 ºC. However, at a temperature of 1110 ºС, the liquid is supercooled by 10 ºС, the temperature of the cementite eutectic is 1120 ºС.
Since a slight supercooling of less than 10 ºС is sufficient for the formation of cementite eutectic, this alloy will harden like white cast iron.
Cast iron production practice
These “theoretical” calculations confirm practical recommendations for the production of gray and white cast iron: 1) With the same chemical composition of cast iron, it will be white cast iron with rapid cooling or gray cast iron with slow cooling. 2) An increased silicon content in cast iron promotes the formation of gray cast iron . The difference between the graphite and cementite eutectic temperatures decreases from 43 ºC for a silicon content of 2% to only 6 ºC in cast iron without any silicon.
3) In cast iron without silicon, as a rule, white cast iron is formed. This occurs because the interdendritic fluid reaches supercooling earlier for the “white eutectic” than for the “gray eutectic”.
Source: https://steel-guide.ru/chuguny/chugun-seryj-i-belyj-usloviya-obrazovaniya.html
Gray cast iron
Gray cast iron is an alloy of iron and carbon, the graphite in which has the form of flake-like, plate-like or fibrous inclusions. This alloy received this name due to the type of fracture, which has a characteristic gray color. Gray cast iron owes its color to the amount of free graphite - it is this, and not the form of graphite inclusions in the alloy, that is color-forming.
There are different types of gray cast iron, which have an alphanumeric designation, where the numbers are an indicator of the tensile strength in kg/mm2. Among them there are the main ones: SCh 10, SCh 15, SCh 20, SCh 25, SCh 30, SCh 35, and additional grades of gray cast iron: SCh 18 and SCh 21. The latter are used for the production of castings at the request of the consumer.
A separate group of grades includes gray high-strength cast iron, which contains graphite, which has a globular shape as a result of its modification with magnesium, tsarium, and other elements. This type of cast iron has the letter marking HF, after which the strength is indicated in numbers, and the relative elongation as a percentage is indicated through a hyphen.
For example, HF 60 -2.
The production of gray cast iron is carried out through reduction processes using carbon fuel (coke). The main and only material for this process is iron ore. In the process of producing gray cast iron, not only the reduction of iron oxides occurs, but also the filling of the alloy with free carbon.
Gray cast iron. Properties
Depending on the percentage of free carbon in the alloy, gray cast iron may have certain mechanical properties. Among them, the most important qualities can be identified, which are its castability (or fluidity), as well as low shrinkage during solidification.
The indicated properties of the alloy make it possible to produce castings of complex shapes from it. It is also worth saying that parts made of gray cast iron have a fairly high resistance to the effects of external stress concentrators on them under cyclic loads, and also have a high vibration absorption coefficient when vibrations of parts occur.
Gray cast iron has high strength properties.
The thickness of the casting walls affects the tensile strength (or tensile strength) of gray cast iron. Due to the fact that this alloy contains plate-like forms of graphite inclusions, it is brittle.
This is due to the fact that the characteristic lamellar graphite inclusions act as multiple cuts in cast iron. Gray cast iron has the following strength: 100 MPa for SCh 10 and 350 MPa for SCh 35.
Despite the fact that this alloy has a fairly low bending strength and high fragility, it has a fairly high compressive strength.
Due to its wear resistance, cast iron is the main material for the manufacture of parts that operate under high friction. Due to its properties, processing of gray cast iron is not possible in all ways. For example, the high carbon content in the alloy, which is the main condition for the production of cast iron, does not allow welding work to be done with this alloy. They are practically impossible.
However, taking into account technological progress and modern methods, certain conditions still make it possible to perform such manipulations with gray cast iron. Special conditions include: preliminary and high-quality heating of workers, the use of special electrodes with a high carbon content. But even with all the correctly created conditions and welding, the structure of the weld metal has significant differences from the original material.
In order to avoid stress in the weld area, welded cast iron parts are cooled quite slowly.
Structure of gray cast iron
The main components of cast iron are iron and carbon, which is necessarily contained in the alloy in quantities greater than 2.4%. Often the carbon content ranges from 2.9 to 3.7%.
Despite the fact that carbon is the main component, it is not the only one, and gray cast iron necessarily contains other components, in particular silicon, without which the formation of graphite is not possible. The cooling conditions after solidification and the cooling time itself play a major role in the formation of the internal structure of the alloy.
Depending on this, cast iron may have a ferritic, ferritic-pearlitic or purely pearlitic metal base. The faster cast iron is cooled, the greater the proportion of pearlite in its composition, which, in turn, is reflected in its strength - it increases, however, at the same time its ductility decreases significantly.
Each specific grade of cast iron, which has an optimal combination of properties for a particular case, is used in a very specific area. The structural components of gray cast iron are designated conventionally according to GOST 3443-87. For example, the designation of ductile graphite contained in gray cast iron according to GOST will be marked PG. Graphite in the structure of gray cast iron can take various forms:
- rectilinear lamellar, designated PG f1;
- plate vortex, which is designated PG f2;
- needle-shaped - PG f3;
- nest-shaped - PG f4.
The structure of cast iron is very important so that the necessary casting properties can be obtained in the future. In this regard, all technological modes of melting and pouring when working with gray cast iron are very important.
Application of gray cast iron
Gray cast iron, due to its unique properties combined with a fairly low cost, is a material that has found wide application, primarily for the manufacture of parts that are subject to minor mechanical loads.
Thus, this type of material is very popular and in demand in such areas of human activity as mechanical engineering, construction, plumbing work and much more.
It is also used in the manufacture of various everyday items, kitchen utensils, etc.
Source: http://mining-prom.ru/rud/zhelez/seryy-chugun/
Difference between gray and white cast iron
The most common types of cast iron are gray and white. What does each one represent?
articles
The corresponding type of cast iron is one of the most common in the field of mechanical engineering. This metal is characterized by the presence of plate-shaped graphite in the thin section. Its content in gray cast iron may vary. The larger it is, the darker the metal becomes at the fracture, and also the softer the cast iron. Castings from the type of metal in question can be produced in any thickness.
Main features of gray cast iron:
- minimum relative elongation - as a rule, not exceeding 0.5%;
- low impact strength;
- low plasticity.
Gray cast iron contains a small percentage of fixed carbon - no more than 0.5%. The remaining part of the carbon is presented in the form of graphite - that is, in a free state. Gray cast iron can be produced on a pearlitic, ferritic, or mixed ferrite-pearlite base. The metal in question usually contains a significant percentage of silicon.
Gray cast iron is quite easy to process using cutting tools. This metal is used for casting products that are optimal in terms of compression resistance. For example, various supporting elements, batteries, water pipes. The use of gray cast iron is also widespread in mechanical engineering - most often in the manufacture of parts that are not characterized by shock loads. For example, housings for machine tools.
What is white cast iron?
This type of cast iron is characterized by the presence of carbon, which is almost completely represented in the metal structure in a bound state. The metal in question is hard and at the same time quite fragile. It is resistant to corrosion, wear, and temperature effects. White cast iron is quite difficult to work with hand tools. When broken, this metal has a light tint and a radiant structure.
The main area of application of white cast iron is subsequent processing. As a rule, it is converted into steel, and in many cases into gray cast iron. In industry, its use is not very common due to its fragility and difficulty in processing.
The percentage of silicon in white cast iron is significantly less than in gray cast iron. The metal in question may also have a higher concentration of manganese and phosphorus (note that their presence is largely determined by the chemical composition of the ore from which the cast iron is smelted). Actually, an increase in the amount of silicon in a metal is accompanied by a decrease in the volume of bound carbon in its structure.
Comparison
The main difference between gray cast iron and white is that the former contains a small percentage of fixed carbon, while the latter, on the contrary, contains mainly fixed carbon. This feature determines the difference between the metals under consideration in terms of:
- hardness;
- colors on the break;
- wear resistance;
- fragility;
- machinability with hand tools;
- scope of application;
- percentage of fixed and free carbon;
- percentage of silicon, manganese, phosphorus.
To more clearly study the difference between gray and white cast iron in these aspects, a small table will help us.
Table
| Gray cast iron | White cast iron |
| Less hard | More solid |
| Darker at the break | Lighter on the break |
| Less resistant to wear | More resistant to wear |
| Less fragile | More fragile |
| Easy to process with hand tools | Not very easy to work with hand tools |
| Actively used in various industries | Mainly used for the purpose of making steel, gray cast iron |
| Has a large percentage of free carbon - in the form of graphite | Includes mostly fixed carbon |
| Characterized by a large percentage of silicon, a smaller percentage of manganese and phosphorus | Characterized by a lower percentage of silicon, a higher percentage of manganese and phosphorus |
Source: https://TheDifference.ru/chem-otlichaetsya-seryj-chugun-ot-belogo/
Gray cast iron: application, composition and marking
Cast iron is an alloy of iron and carbon. One of the most widespread types is gray cast iron. The volume of carbon in its composition exceeds 2.14% and is contained in the range from 2.4 to 4.2%.
The material got its name from the color of the fracture, which is gray.
Essentially, it is cast iron interspersed with flake graphite. But, nevertheless, they continue to call him gray. By the way, the same color can be seen on the fracture of malleable cast iron. Metallurgists established a relationship between the volume of free carbon, but not on its form.
In gray cast iron, carbon takes the form of flake-like or plate-like inclusions as it cools. The difference between cast iron and steel is the volume of carbon. Carbon is absolutely completely dissolved in steel and is not contained in the form of inclusions; gray cast iron contains inclusions of carbon called graphite.
Marking
Metallurgical plants produce several grades of this material. Its marking is carried out as follows. The two letters at the beginning of the abbreviation indicate the type of cast iron, the marking of gray cast iron begins with SCH, the numbers located after the letters indicate the tensile strength
The following classification of gray cast iron is accepted:
- SCh10 - ferritic;
- SCh15, SCh18, SCh20 - ferrite-pearlite cast iron;
- starting from SCh25 - pearlitic cast iron.
Composition of gray cast iron and its structure
The parameters and properties of the alloy directly depend on the cooling mode; the fact is that it is during cooling that the structure of the material is formed.
During the process of slow cooling, considerable iron crystals are formed, and the combination of metal and carbon becomes pearlitic. During such cooling, not only the size of metal crystals increases, but also carbon inclusions. This combination leads to the fact that pearlite material has not only high strength, but also increased fragility.
Assessment of the structure of the MF determines:
- the size of graphite inclusions, measured in micrometers (μM), their distribution, quantity (in%), the type of structure of the metal base and, if pearlite is present, its dispersion.
According to the structure of the metal base, gray cast irons are divided into:
- pearlite - the structure contains pearlite and graphite;
- ferrite-pearlite - ferrite, pearlite and graphite;
- ferritic - the structure consists of ferrite and graphite.
Which base will be depends on the cooling rate after hardening.
To designate parts of the microstructure of cast iron of this type, the terminology defined in GOST 3443-87 is used, for example, flake graphite is designated by the letters PG. Carbon is included in the material in the following forms.
- lamellar rectilinear, it is designated PGF1;
- plate vortex - PGF2;
- needle-shaped - PGF3;
- nest-shaped -PGF4.
Of primary importance for acquiring the required parameters of an iron casting is its structure, which is why when making blanks, careful implementation of the technology of melting and pouring raw materials is required. To obtain the required parameters of gray cast iron and eliminate defects, a modification operation is used.
The composition of SP, depending on its brand, may include the following substances:
The base is Fe (iron), the rest:
- C (carbon) - 2.9-3.7%;
- Si (silicon) -1.2-2.6%;
- Mn (manganese) - 0.5-1.1;
- P (phosphorus) no more than 0.2-0.3%;
- S (sulfur) no more than 0.12-0.15%.
It is permissible to alloy gray cast iron using substances such as Cr, Ni, Cu, and some other elements.
Silicon in the composition increases the graphitization of carbon. Manganese, although it makes graphitization difficult, improves its mechanical properties.
The chemical composition of SP is defined in GOST 1412-85. Gray cast iron is produced in many countries around the world; in the USA, A48-30B is considered an analogue of this material, in Britain BS 200 or 220, in China GB HT 20, in the European Union EN-JL1030 FG20.
Application
Gray cast iron has found its use in the production of castings of various shapes, which require high compressive strength. This characteristic is important mainly in the production of cast frames intended for the manufacture of machine tools. The use of this material is limited by the high fragility of finished products. This is especially true in the presence of severe bending loads.
Not so long ago, the casting characteristics of gray cast iron were used in the manufacture of kitchen utensils and other household utensils, in particular, cast iron pots, frying pans, etc. The products produced using casting were distinguished by ease of production and low cost.
Nowadays, casting is used to produce loaded machine components that operate without bending loads, for example, parts of the piston group that are installed in the internal combustion engine.
High-strength parts cast from this material have low cost and long service life. We can safely say that cast frames and housings of machine tool equipment are eternal components of machine tool equipment, in comparison with other equipment units.
Cast iron grades SCh15, SCh18, SCh20 are used for lightly loaded parts. These are: flanges, covers, flywheel, gear housing.
Grades SCh20 and SCh25 are used where increased load on parts is required. These are: cylinder pistons, engine cylinder blocks, machine bed.
I use grades of increased strength and wear resistance SCh30, SCh35, SCh40, SCh45 in gears, engine liners, camshafts, spindles, and for parts of steam boilers. These brands have high heat resistance.
Source: https://prompriem.ru/chugun/seryj.html
Plumbing pipes for sewerage: types and installation features
What materials are modern sewer pipes made from? Are there any features of their installation that a potential owner should know? What solutions are preferable for an apartment or a private house? Let's figure it out.
Meet polymer sewer pipes and fittings.
Scroll
First, let's list all the solutions on the market.
- Cast iron is a time-tested classic . Gray cast iron differs favorably from steel in its corrosion resistance, which, in fact, earned it popularity in times of cheap metallurgical products and a shortage of plastics. Now it has been forced to make room for ubiquitous polymers.
- Polyvinyl chloride is the current leader in sales volumes . Its main advantage is the minimum price with more than passable performance characteristics and exceptional durability.
- Polypropylene is slightly more expensive and less common . Its main advantage compared to the previous material is its greater heat resistance: if PVC plumbing pipes for sewerage are limited to a long-term operating temperature of 65 C, then polypropylene pipes serve well at 90 C.
Material: polypropylene.
In addition: polypropylene is the lightest (0.91 g/cm3) and one of the hardest plastics.
It is practically not subject to wear even when transporting wastewater with a large amount of abrasive.
- Polyethylene is in rather low demand due to its very low heat resistance: sewage systems made from polyethylene pipes are designed for a wastewater temperature of no higher than 40 C. However, pressure pipes made from it are fully compatible with PVC fittings of the appropriate diameter (50, 110 and 150 mm) and can be very successfully used as risers: thick walls and elasticity make the movement of drains in an apartment building almost inaudible.
Dimensions
What sections and slopes should be followed when designing a wastewater system?
| Pipe diameter, mm | Application |
| 50 | Connection of one or two plumbing fixtures, except for the toilet (showers, bathtubs, washbasins, sinks, etc.) |
| 110 | Toilet connection; connecting three or more simultaneously used devices of other types; riser in an apartment building |
| 150 | Connecting two or more toilets with the possibility of simultaneous use; release to a well in an apartment building |
| 200 — 300 | Areas between wells |
As a rule, pipes with a cross-section of up to 110 mm are used within an apartment or private house.
What should the pipe slope be?
| Pipe diameter, mm | Slope, cm/linear meter |
| 50 | 3,5 |
| 110 | 2 |
| 150 | 1 |
| 200 | 0,8 |
Now let's take a closer look at the properties and installation of various types of sewage systems.
Peculiarities
Its main advantage is its excellent acoustic properties. The drain in the toilet of the neighbors above will not disturb your sleep if the sewer riser is made of cast iron: the thickness and weight of the walls will allow the pipe to completely absorb sound.
Alas, all other properties of cast iron can be safely attributed to disadvantages.
- The retail cost of pipes and fittings is several times higher than that of any type of polymer.
- The weight makes loading, transportation and installation extremely inconvenient. If plumbing plastic sewer pipes and hardware used as fasteners can be easily and effortlessly installed by one person, then replacing a cast iron riser will require the participation of at least two people with good physical development.
- Cutting a pipe in place or cutting it when dismantling it near a wall is a non-trivial task. You will need a grinder with a metal circle; Moreover, cutting a pipe with a cross-section of 110 mm from the side of the wall will be problematic for her, to put it mildly.
Useful: experienced plumbers make a notch on a cast iron pipe with a chisel, and then break it along the notch line.
However, without proper practice, you are likely to simply ruin expensive material.
A simpler method: the pipe is cut with a grinder from the front side, after which a chisel is driven into the cut.
- Installation of the connection requires caulking and subsequent sealing with cement mortar. Each joint takes an experienced plumbing installer at least fifteen minutes.
We will dwell on installation in a little more detail.
Installation
How is the connection of cast iron socket sewer pipes sealed?
All stages of embossing and sealing the socket.
How to dismantle an old cast iron sewer?
Useful: in houses built about half a century ago, melted sulfur was often used as a sealant. The simplest way to disassemble such a compound with your own hands is to heat it to the melting point of the sulfur.
The instructions for performing this work are to remember to wear a gas mask: the fumes are so caustic that they can easily cause respiratory paralysis.
Dismantling a bell filled with sulfur.
Plastics
Many properties and, most importantly, methods of installing plastic sewerage are common to all polymers used, so we will combine them in one subsection.
Conclusion
Of course, telling everything about sewer pipes in a short article is quite problematic; We limited ourselves to a short overview of frequently used solutions. This article will offer the reader some additional information. Good luck!
Source: https://remstroymast.ru/santehnicheskie-tryby-dlia-kanalizacii-vidy-i-osobennosti-montaja.html
Application of gray cast iron: industrial and household products
The use of metal alloys is influenced by two main factors: operational parameters and economic feasibility.
The second criterion becomes decisive when engineering and technical characteristics are not significant, and the manufacturer is guided by considerations of maximizing the cost of manufactured products.
In industry, in particular, for the manufacture of products that are subject to requirements for resistance to fracture, tension, and compression, the metal is selected with priority attention to the calculated values of strength, reliability, flexibility, resistance to static loads and vibration vibrations.
Black metal gray
Steel alloys are more expensive than cast iron alloys, which is due to more complex and expensive production specifics. Therefore, cast iron is used where it is possible to save on the financial component. Depending on the metal structure, there are five main types of this material: white, gray, malleable, high-strength, half-section. The determining factor for classification is the form of graphite in the crystal lattice.
The most brittle cast iron is white, containing ladeburite instead of graphite particles. Cast iron alloys, called “gray”, also include malleable varieties in their group, which introduces some confusion in understanding the issue. To simplify, generalized standards are used, where gray cast iron is an iron-based metal material with graphite (which gives a characteristic color at the fracture) and other additives that are used for alloying and forming the necessary properties.
Advantages and disadvantages
Gray cast iron has the following features that justify its use in industrial production:
- resistance to compressive forces;
- absorption of vibration vibrations (an order of magnitude higher than that of steel);
- does not accumulate stress under cyclic loads (“metal fatigue”);
- Due to its fluidity in the melt and low shrinkage during solidification, it is well suited for casting.
Along with its advantages, the material also has disadvantages that limit its scope of practical use. The main one is fragility, which is associated with graphite inclusions, which create peculiar “cuts” in the metal structure.
Essentially, these are vulnerabilities that make the metal less dense and solid (compared to steel alloys).
Therefore, gray cast iron cannot be used where shock loads are applied (for example, a cast-iron samurai sword will shatter into pieces no worse than a glass one at the first strong blow).
The main advantage of steel is its tensile strength and the ability to maintain a given shape under breaking forces, including returning to its original form after deflection. If you add alloying additives to gray cast iron, you can bring its physicochemical parameters closer to those of a steel alloy.
The resulting materials are rare and little used. For industrial purposes and for the manufacture of useful products, cast iron compositions with a “classical” formula are used, where the carbon content is on average three percent, silicon - one or two, manganese - about one percent.
Their distinctive feature is their exceptional resistance to compression, vibration and micro-oscillations that accumulate as metal fatigue.
Where is it in demand?
A significant portion of parts in mechanical engineering are made from gray cast iron. For example, in an agricultural tractor the number of cast iron elements of the total mass reaches twenty percent.
These are, first of all, those mechanisms and fragments of mechanical components that are subject to microvibrations in the engine and bearings, with the main load being compression. In industrial machines, heavy bases, beds, and bushings are made of a metal alloy containing graphite inclusions.
In such an application, functional validity, although combined with an economic factor, is more significant than the desire to save money.
Gray cast iron will cost more in the case of some household and decorative products:
- An ordinary steel bathtub is cheaper than a cast iron one, but you won’t be able to soak in such a vessel for a long time, since the thin walls quickly say goodbye to the heat.
- Welded iron fences, even if they have a complex design, are more affordable for money than cast iron fragments.
- “Outdated” cast iron heating radiators cost approximately the same as “high-tech” radiators in the budget segment, but the former can withstand sudden pressure changes, and the latter leak after a strong water hammer.
Thanks to the graphite content, iron becomes resistant to oxidation, which makes the material resistant to destruction from corrosion. Pipes and fittings with a body made of gray cast iron are used for laying main and local communications. Cast iron fittings, valves, bends, and adapters are used not only in water pipelines, but also in natural gas supply systems, as well as for pipeline transportation of chemically aggressive liquid and gaseous compounds.
September 16, 2017
Source: https://tdspecstal.ru/articles/seryy-chugun-osobennosti-i-sfera-primeneniya.html
How to distinguish cast iron from steel, iron and aluminum at home
Cast iron is an alloy of iron with a sufficient carbon content (from 2.14 to 6.67%). The concentration of the added substance affects the ductility, ductility and hardness of the metal, so steel is made from an alloy of iron and less than 2.14% carbon. Cast iron alloy is very hard and brittle and difficult to cast and process with cutting tools. Therefore, it is quite simple to distinguish cast iron from steel by properties, appearance and characteristics.
The high carbon content gives the high-carbon iron alloy a dark, almost black color. You can visually distinguish cast iron from steel by the lack of shine. Also, spel is formed on its surface - large inclusions of lamellar graphite, which are visible to the naked eye at the fracture. They appear as a result of crystallization of high-carbon alloys.
Types of alloys
Main varieties:
- white - a metal with a light gray hue that is difficult to process, but has high hardness;
- gray - a material with a high carbon content in the form of graphite, which has good casting properties, is easy to process and is suitable for the production of machine elements, beds, covers, pulleys and presses;
- malleable - metal obtained as a result of heat treatment of a white alloy with the formation of flake-like granite (in demand in automotive production, in the manufacture of agricultural machinery and spare parts for it);
- half - material for the production of wear-resistant friction parts;
- high-strength – an alloy with spherical graphite in the composition for the production of pipes and machine elements.
To understand how to distinguish cast iron, it is important to study the characteristic features and areas of application of its varieties.
Metals that are often confused
A high-carbon iron alloy is often confused with other metals used for the production of plumbing fixtures, fittings, shut-off valves, machine tool parts, and radiators. People think about how to identify cast iron when trying to hand over scrap metal to a collection point. Scrap of this metal is one of the cheapest, since it is difficult to process, fragile, and harmful impurities (phosphorus and sulfur) are difficult to remove from it.
Therefore, before traveling to the collection point, it is important to determine whether it is cast iron or steel. It is also often confused with pure iron, aluminum and silumin - an alloy of aluminum and silicon used for the production of frying pans, pots, mixers, taps, etc. You can distinguish cast iron from iron and other metals at home: by color, magnetic properties, strength and even the sound!
Differences from iron
Pure iron is a material that can only be seen in the laboratory. It practically does not occur in nature, and is also not applicable for mass production of spare parts, plumbing products and household items. You can determine whether the material in front of you is cast iron or cast iron by its appearance: iron has a light silver color, is very soft and ductile, and is also highly susceptible to corrosion.
It is important not to confuse iron and its derivative, steel. These concepts are not interchangeable. Steel is an alloy of iron, small amounts of carbon, manganese, silicon, sulfur and phosphorus. This iron-carbon alloy is elastic, deformable, and malleable. It can also be difficult to distinguish steel from cast iron by eye: a similar composition gives them similar shades, but completely different properties and characteristics. Steel is easier to process, stronger, and resistant to shock and mechanical stress.
How to distinguish cast iron from steel?
Steel is a high-strength material with a melting point of approximately 1300–1500 °C. From it they produce:
- plumbing tools (hammers, chisels, screwdrivers, scythes, saws, scissors, etc.);
- machine parts (pushers, gears);
- springs and leaf springs;
- blacksmith tools;
- products for stone and wood processing;
- pipes and radiators;
- surgical equipment;
- building materials;
- dishes, cutlery and household items.
It is widely believed that cast iron can be distinguished from steel using a magnet. The statement is partly true, since the magnetic properties of a metal depend on its composition. Ausetnitic and austenitic-ferritic alloys with a high content of chromium (up to 20%) and nickel (up to 15%) are not magnetic. The inclusion of titanium, molybdenum, and niobium also reduces the magnetic properties of the metal.
Differences between steel and cast iron
A high-carbon alloy is always magnetic, while steel depends on its composition. Cast iron is also determined by the color and condition of the surface: products made from it have a dark, almost matte black color, and when broken, the metal is dark gray. Also, cast iron objects are more massive and weigh more compared to their steel counterparts, although the density of steel is much higher - up to 7900 kg / cubic meter. m.
Steel is easier to process, so items made from it are produced by stamping. Weak, non-ductile cast iron is suitable for the manufacture of cast products. It does not withstand strong impacts and can crack, so a strong blow with a hammer will help to distinguish it. At the same time, it is porous and retains heat longer, and therefore another test option is strong heating. Cast iron products heat up slowly but evenly, and cool down for at least 10 minutes.
Differences from aluminum
A magnet can be used to distinguish cast iron not only from steel, but also from aluminum - a silvery-white light metal. This substance is paramagnetic, therefore it has external magnetic susceptibility (in the absence of an external magnetic field, the magnetic moments of atoms are non-zero).
The relative magnetic permeability of the metal is slightly greater than unity, and the magnetic field in it increases insignificantly. Accordingly, aluminum is magnetic, but very weakly. This is not visible visually, so it is generally accepted that it is not magnetic.
In addition to magnetic properties, metals have other differences: color, mass, density, hardness and flexibility. Therefore, you can distinguish them from each other in other ways.
How to distinguish aluminum from cast iron?
1 cubic meter of aluminum weighs 2,700 kg, and cast iron - more than 7,000 kg. The first is less dense, and therefore products made from it should be much lighter compared to cast iron. But it should be taken into account that aluminum is less durable, so objects made from it are made thick-walled, which affects the weight.
Aluminum products are lighter and have a slightly shiny surface. Under atmospheric conditions, the metal is immediately covered with a transparent, gas-permeable oxide film. Aluminum is smooth and even, while cast iron is dark, porous and rough. A significant difference between metals is hardness: aluminum is easy to bend, and impacts form dents on its surface. Cast iron cannot be bent: under heavy loads it will crack, but will not deform.
Features of the delivery of cast iron scrap
This type of ferrous scrap metal is the most in demand, and it is classified as metal waste. It is recycled, melted down in smelters, and even recycled into steel by reducing its carbon concentration. Most of the cast iron scrap is of industrial origin.
Outdated machines, equipment, and dismantled metal structures are sold for scrap metal. The cost of such scrap is relatively low, but due to the large mass, these items can fetch good money.
You can distinguish cast iron from aluminum, steel, and iron by color, weight, and even sound (cast iron products are the most resonant, so when struck they make loud, sharp sounds). But the most reliable way is to send a metal sample to our laboratory equipped with a spectrometer. We will accurately determine the composition of the alloy and offer the best price for scrap metal!
Source: https://blog.blizkolom.ru/kak-otlichit-chugun
