What alloy is called cast iron

Cast iron alloy composition: difference from steel, melting point of cast iron and steel

Cast iron is an alloy of iron and carbon. The percentage of iron contained is more than 90%. The amount of carbon ranges from 2.14-6.67%. Thanks to this element, the material has high hardness, but becomes brittle. This entails a deterioration in ductility and ductility. In some types, alloying elements are added to improve characteristics: aluminum, chromium, vanadium, nickel.

Characteristics of types of carbon metal

The iron-carbon diagram shows what cast iron is made of. In addition to iron, carbon is present in the form of graphite and cementite.

The composition of the cast iron alloy has varieties:

White. The carbon present here is in a chemically bound state. The metal is strong, but brittle and therefore difficult to machine. In industry it is used in the form of castings. The properties of the material allow it to be processed with an abrasive wheel. The welding process causes difficulty, since there is a possibility of cracks due to the heterogeneity of the structure. Found application in areas related to dry friction. Has increased heat resistance and wear resistance.
Half-hearted. It has increased fragility, so it is not widely used.
Grey. GOST 1412–85 indicates what percentage of impurities this metal contains: 3.5% carbon, 0.8% manganese, 0.3% phosphorus, 0.12% sulfur and up to 2.5% silicon. The carbon present in the platelet form creates low impact strength. The characteristics of the type indicate that the material works better in compression than in tension. When heated sufficiently, it has good weldability.
Malleable. A ferrite base of this type provides it with high ductility. When broken, it has a black, velvety color. It is obtained from white, which languishes for a long time at a temperature of 800-950 degrees.
Highly durable. The difference from other types is the presence of spherical graphite. It is obtained from gray after adding magnesium to it.

Individual properties of metal

The material is characterized by certain characteristics. These include:

Physical. Values such as specific gravity or expansion coefficient depend on the carbon content of the metal. The material is heavy, so cast iron bathtubs can be made from it.
Thermal. Thermal conductivity allows you to accumulate heat and retain it, distributing it evenly in all directions. This is used in the manufacture of frying pans or radiators for heating.
Mechanical. These characteristics vary depending on the graphite base. The most durable is gray cast iron with a perlite base. A material with a ferrite component is more malleable.

Depending on the presence of impurities, a difference in the properties of the material appears.

These elements include sulfur, phosphorus, silicon, manganese:

Sulfur reduces the fluidity of the metal.
Phosphorus reduces strength, but makes it possible to manufacture products of complex shapes.
Silicon increases the fluidity of the material, lowering its melting point.
Manganese gives strength, but reduces fluidity.

Differences between cast iron and steel

To understand the difference between steel and cast iron, you need to consider their characteristics. A distinctive feature of cast iron is the amount of carbon. Its minimum content is 2.14%. This is the main indicator by which this material can be distinguished from steel.

iron in steel is 45%, and the percentage of carbon is up to 2. To determine the differences by eye, you need to pay attention to the color. Steel is light in color and cast iron is dark.

Only chemical analysis can determine the percentage of impurities. If we compare the melting point of cast iron and steel, then for cast iron it is lower and amounts to 1150-1250 degrees. For steel - around 1500.

To distinguish the material, you need to do the following:

The product is lowered into water and the volume of displaced water is determined. Cast iron has a lower density. It is 7.2 g/cm3. For steel - 7.7−7.9 g/cm3.
A magnet is applied to the surface, which attracts the steel better.
The chips are rubbed using a grinder or file. Then it is collected in paper and wiped on it. Steel will not leave marks.

Pros and cons of the material

Like any material, cast iron has positive and negative sides. Positive qualities include:

a wide variety of conditions.
some types are highly durable;
the ability to maintain temperature for a long time;
environmentally friendly, which allows you to make dishes from it;
resistance to acid-base environment;
high hygiene;
long service life and durability;
harmlessness of the material.

However, there are also disadvantages. These include:

when kept in water for a long time, the surface becomes covered with rust;
high cost of material;
low ductility of gray cast iron;
fragility.

Cast iron is a metal characterized by a high carbon content. Thanks to this, it has qualities that are necessary for industrial and domestic purposes.

Source: https://obrabotkametalla.info/stal/sostava-splava-chuguna-i-otlichie

At what temperature 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. Cast iron casting. DIY melting furnace from A to Z “Cupola furnace”.

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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.

At what temperature does cast iron melt? Link to main publication

Source: https://metalloy.ru/stal/plavlenie-chuguna

What is stronger, steel or cast iron?

Ferrous metallurgy products are widely used in many sectors of the national economy, and ferrous metal is always in demand in construction and mechanical engineering. Metallurgy has been successfully developing for a long time, thanks to its high technical potential. Cast iron and steel products are most often used in production and in everyday life.

Cast iron and steel both belong to the group of ferrous metals; these materials are alloys of iron and carbon that are unique in their properties. What are the differences between steel and cast iron, their main properties and characteristics?

Steel and its main characteristics

Steel is a deformed alloy of iron with carbon , which is always up to a maximum of 2%, as well as other elements.

Carbon is an important component because it gives strength to iron alloys, as well as hardness, thereby reducing softness and ductility.

Alloying elements are often added to the alloy, which ultimately results in alloyed and high-alloy steel, when the composition contains at least 45% iron and no more than 2% carbon, the remaining 53% being additives.

Steel is the most important material in many industries; it is used in construction, and as the technical and economic level of the country grows, the scale of steel production also increases. In ancient times, craftsmen used crucible melting to produce cast steel, and this process was low-productivity and labor-intensive, but the steel was of high quality.

Over time, the processes for producing steel changed; the crucible method was replaced by the Bessemer and open-hearth methods of producing steel, which made it possible to establish mass production of cast steel. Then they began to smelt steel in electric furnaces, after which the oxygen-converter process was introduced, which made it possible to obtain especially pure metal. Depending on the number and types of connecting components, steel can be:

Low alloy
Medium alloyed
High alloy

Depending on the carbon content, it is:

Low carbon
Medium carbon
High carbon.

The composition of the metal often includes non-metallic compounds - oxides, phosphides, sulfides; their content differs depending on the quality of the steel; there is a certain classification of quality.

The density of steel is 7700-7900 kg/m3 , and the general characteristics of steel consist of such indicators as strength, hardness, wear resistance and suitability for various types of processing.

Compared to cast iron, steel has greater ductility, strength and hardness.

Due to its ductility, it is easy to process; steel has a higher thermal conductivity, and its quality is improved by hardening.

Elements such as nickel, chromium and molybdenum are alloying components, each of which gives steel its own characteristics. Thanks to chromium, steel becomes stronger and harder, and its wear resistance increases. Nickel also imparts strength, as well as toughness and hardness, and increases its anti-corrosion properties and hardenability. Silicon reduces viscosity, and manganese improves weldability and hardening properties.

All existing types of steel have a melting point from 1450 to 1520°C and are strong, wear-resistant and deformation-resistant metal alloys.

Cast iron and its main characteristics

The basis for the production of cast iron is also iron and carbon, but unlike steel, it contains more carbon, as well as other impurities in the form of alloying metals. It is fragile and breaks without visible deformation. Carbon here acts as graphite or cementite and, due to the content of other elements, cast iron is divided into the following varieties:

White - where cementite is in the lead in the majority, this material is white at the fracture. This component is fragile and at the same time hard. It is easy to work, which imparts malleability to cast iron.
Gray - in this variety, a large proportion is graphite, due to which the cast iron is ductile. Ready cast iron has a low melting point, is soft, and is easier to cut.
Malleable - achieved by firing white cast iron, it is simmered in special heating furnaces at a temperature of 950-1000 ° C. The inherent hardness and brittleness of white cast iron are reduced; it is not forged, but only becomes more ductile.
High-strength cast iron alloy - it contains nodular graphite, which is formed during crystallization.

The melting point of cast iron depends on the carbon content in it; the more of it there is in the alloy, the lower the temperature, and also its fluidity when heated increases. This makes the metal non-plastic, fluid, and also brittle and difficult to process. Its melting point ranges from 1160 to 1250°C .

Cast iron has higher anti-corrosion properties because it undergoes dry rust during use, this is called chemical corrosion. Wet corrosion also attacks cast iron more slowly than steel. These qualities led to a discovery in metallurgy - steel with a high chromium content began to be smelted. This is where stainless steel came from.

We draw a conclusion

Based on their numerous characteristics, we can say the following about cast iron and steel, what is their difference:

Steel is stronger and harder than cast iron.
Steel has a higher melting point and is heavier.
The lower percentage of carbon in steel makes it easier to work with, easier to cut, forge and weld.
For this reason, cast iron products can be cast, while steel products can be welded or forged.
Steel products are less porous than cast iron, so they have greater thermal conductivity.
They also differ in color: steel is light and shiny, while cast iron is darker with a matte surface.
The cost of steel is always higher than cast iron materials.

We can conclude that steel and cast iron are united by the content of carbon and iron in them, but their characteristics are different and each of the alloys has its own characteristics.

Nikolay Ivanovich Matveev

Source: https://varimtutru.com/chto-krepche-stal-ili-chugun/

Materials Science

Cast iron is an alloy of iron with carbon and other elements containing more than 2.14% carbon.

Classification of cast irons

A characteristic feature of cast iron is that the carbon in the alloy can be found not only in a dissolved and bound state (in the form of a chemical compound - cementite (Fe3C), but also in a free state - in the form of graphite. At the same time, the shape of the graphite deposits and the structure of the metal base ( matrices) determine the main types of cast irons and their properties.

Classification of cast iron with different forms of graphite is carried out according to GOST 3443-77. according to the following characteristics:

according to the state of carbon - free or bound;
according to the shape of graphite inclusions - lamellar, vermicular, spherical, flake-like (Figure 1);
according to the type of structure of the metal base (matrix) – ferritic, pearlitic; There are also cast irons with a mixed structure: for example, ferrite-pearlite;
by chemical composition - non-alloyed cast iron (general purpose) and alloyed cast iron (special purpose).

Depending on the form of carbon release in cast iron, there are:

white cast iron, in which all carbon is in a bound state in the form of cementite Fe3C;
half cast iron, in which the main amount of carbon (more than 0.8%) is in the form of cementite;
gray cast iron, in which all or most of the carbon is in a free state in the form of flake graphite;
bleached cast iron, in which the bulk of the metal has the structure of gray cast iron, and the surface layer is white;
high-strength cast iron, in which the graphite has a spherical shape;
malleable cast iron, obtained from white cast iron by annealing, in which the carbon passes into a free state in the form of flakes of graphite.

Gray cast iron is an alloy of the Fe-C-Si system containing manganese, phosphorus, and sulfur as impurities. Carbon in gray cast iron is predominantly in the form of plate-shaped graphite.

The structure of castings is determined by the chemical composition of cast iron and the technological features of its heat treatment.
The mechanical properties of gray cast iron depend on the properties of the metal matrix, the shape and size of the graphite inclusions. The properties of the metal matrix of cast iron are close to the properties of steel. Graphite, which has low strength, reduces the strength of cast iron.

The fewer graphite inclusions and the higher their dispersion, the greater the strength of cast iron.

Graphite inclusions cause a decrease in the tensile strength of cast iron. Graphite particles have virtually no effect on the compressive strength and hardness of cast iron. The property of graphite to form lubricating films causes a decrease in the coefficient of friction and an increase in the wear resistance of gray cast iron products. Graphite improves machinability.

According to GOST 1412-85, gray cast iron is marked with the letters “S” - gray and “Ch” - cast iron. The number after the letter indicates the average tensile strength of cast iron. For example, SCh 20 is gray cast iron, tensile strength 200 MPa.

According to their properties, gray cast irons can be divided into the following groups:

ferritic and ferritic-pearlite cast irons (grades SCh10, SCh15) are used for the manufacture of low-critical, unloaded machine parts;
pearlitic cast iron (grades SCh20, SCh25, SCh30) is used for the manufacture of wear-resistant parts operated under heavy loads: pistons, cylinders, engine blocks;
modified cast irons (grades SCh35, SCh40, SCh45) are obtained by adding ferrosilicon additives before casting into liquid gray cast iron. Such cast irons have a pearlitic metal matrix with a small amount of isolated graphite platelets.

Cast iron with vermicular graphite differs from gray cast iron in its higher strength and increased thermal conductivity.
This material is promising for the manufacture of critical castings operating at elevated temperatures (engine blocks, piston rings). Vermicular graphite is produced by treating molten gray cast iron with alloys containing rare earth metals and silicobarium.

Modification of gray cast iron with magnesium and then ferrosilicon makes it possible to obtain magnesium cast iron (MCI), which has the strength of cast steel and the high casting properties of gray cast iron. It is used to make parts subject to shock, alternating stresses and intense wear, for example, crankshafts of passenger cars.

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Ductile iron

A distinctive feature of high-strength cast iron is its high mechanical properties, due to the presence of spheroidal graphite in the structure. Nodular cast iron has not only high strength, but also ductility.

The production of spheroidal graphite in cast iron is achieved by modifying the melt with additives containing Mg, Ca, Ce and other rare earth metals.

The chemical composition and properties of high-strength cast iron are regulated by GOST 7293-85 and are marked with the letters “B” - high-strength, “C” - cast iron and a number indicating the average tensile strength of cast iron. For example, HF100 is high-strength cast iron, tensile strength 1000 MPa.

High-strength nodular cast iron is the most promising casting alloy, with which you can successfully solve the problem of reducing the weight of structures while maintaining their high reliability and durability. High-strength cast iron is used for the manufacture of critical parts in the automotive industry (crankshafts, gears, cylinders, etc.).

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White cast irons are characterized by the fact that all their carbon is in a chemically bound state - in the form of cementite. The fracture of such cast iron has a matte white color.

The presence of a large amount of cementite gives white cast iron high hardness, brittleness and very poor machinability with cutting tools.

The high hardness of white cast iron ensures its high wear resistance, including when exposed to abrasive environments. This property of white cast iron is taken into account in the manufacture of piston rings.

https://www.youtube.com/watch?v=Wj3yX7R9dE4

However, white cast iron is used mainly for casting parts with subsequent annealing to malleable cast iron. Malleable cast iron is produced by annealing white cast iron of a certain chemical composition, characterized by a reduced content of graphitizing elements (2.42.9% C and 1.01.6% Si), since in the cast state it is necessary to obtain completely bleached cast iron over the entire cross-section of the casting, which ensures the formation of flake-like graphite during the annealing process.

The mechanical properties and recommended chemical composition of malleable cast iron are regulated by GOST 1215-79. Malleable cast iron is marked with the letters “K” - malleable, “C” - cast iron and numbers. The first group of numbers shows the tensile strength of cast iron, the second - its relative elongation at break. For example, KCh33-8 means: malleable cast iron with a tensile strength of 330 MPa and an elongation at break of 8%.

Malleable cast iron is used for the manufacture of small and medium-sized thin-walled castings for critical purposes, operating under conditions of dynamic alternating loads (parts of drive mechanisms, gearboxes, brake pads, gears, hubs, etc.). However, malleable cast iron is an unpromising material due to the complex production technology and the length of the production cycle for making parts from it.

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Alloy cast irons

Depending on the purpose, wear-resistant, anti-friction, heat-resistant and corrosion-resistant alloy cast irons are distinguished.

The chemical composition, mechanical properties at normal temperatures and recommended types of heat treatment of alloy cast iron are regulated by GOST 7769-82. In the designation of alloyed cast iron grades, the letters and numbers corresponding to the content of alloying elements are the same as in the steel grades.

Wear-resistant cast irons alloyed with nickel (up to 5%) and chromium (0.8%) are used for the manufacture of parts operating in abrasive environments. Cast irons (up to 0.6% Cr and 2.5% Ni) with the addition of titanium, copper, vanadium, and molybdenum have increased wear resistance under friction conditions without lubricant. They are used to make automobile brake drums, clutch discs, cylinder liners, etc.

Heat-resistant alloy cast irons ChKh2, ChKhZ are used for the manufacture of parts for contact devices of chemical equipment, turbocompressors operated at temperatures of 600°C (ChKh2) and 700°C (ChKh3).

Heat-resistant alloy cast irons ChNMSh, ChNIG7Kh2Sh with spheroidal graphite are operational at temperatures of 500-600°C and are used for the manufacture of diesel engine parts, compressors, etc.

Corrosion-resistant alloy cast irons of the ChKh1, ChNKhT, ChNKhMD ChN2Kh (low-alloy) grades have increased corrosion resistance in gas, air and alkaline environments. They are used for the manufacture of parts of friction units operating at elevated temperatures (piston rings, blocks and cylinder heads of internal combustion engines, diesel parts, compressors, etc.).

Antifriction cast irons are used as bearing alloys capable of operating under friction conditions as plain bearings.

To alloy antifriction cast irons, chromium, copper, nickel, and titanium are used.

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Steels, their classification, properties and markings

Olympics and tests

Source: http://kat.ru/materialovedenie/6-1_thuguny/

Iron-carbon alloys - steel and cast iron

The most widely used in modern mechanical engineering are iron-carbon alloys - steel and cast iron .

Steel is an alloy of iron and carbon; The carbon content in steel does not exceed 2%.

Steels include:

technical hardware,
structural and
tool steel.

Cast iron is an alloy of iron and carbon in which the carbon content exceeds 2%. The average carbon content in cast iron is 2.5-3.5%.

In addition to iron and carbon, steels and cast iron contain impurities:

silicon and manganese in tenths of a percent (0.15-0.60%)
sulfur and phosphorus in hundredths of a percent (0.05-0.03%) of each element.

Steel

Steel with a carbon content of up to 0.7% is used for the manufacture of:

sheets,
ribbons,
wires,
rails,
T-iron and angle iron,
various shaped profiles,
as well as for numerous parts in mechanical engineering : gears, axles, shafts, connecting rods, bolts, hammers, sledgehammers, etc.

Steel with a carbon content of over 0.7% is used for the manufacture of various cutting tools :

incisors,
drill,
taps,
beards,
chisels, etc.

The properties of steel depend on the carbon content. The more carbon, the stronger and harder the steel.

Cast iron

Machine-building cast iron is used for the production of castings of all kinds of machine parts.

Based on their composition and structure, cast irons are divided into:

Malleable iron

Malleable cast iron is obtained by special processing of white cast iron. In white cast iron, all carbon is in a chemically bonded state with iron (Fe 3 C - cementite), which gives this cast iron greater hardness and brittleness and poor machinability.

White cast iron

In mechanical engineering, white cast iron is used to make castings that are annealed into the so-called malleable cast iron.

During annealing, cementite decomposes into iron and free carbon, and the castings acquire low hardness and good machinability.

Gray cast iron

The most widely used in technology is gray cast iron , in which most of the carbon is in a free state, in the form of graphite. This is facilitated by the high silicon content .

This cast iron has good casting qualities and is used for the production of iron castings. Parts made from this cast iron are obtained by casting into earthen or metal molds (frames, gears, cylinders, blocks, etc.).

Due to the presence of free carbon (graphite), gray cast iron has low hardness and is easy to cut.

Source: http://www.Conatem.ru/tehnologiya_metallov/zhelezouglerodistye-splavy-stal-i-chugun.html

Many people know about such a material as cast iron and its strength characteristics. Today we will deepen this knowledge and find out what cast iron is, what it consists of, what types it comes in and how it is produced.

Compound

What is cast iron? It is an alloy of iron, carbon and various impurities, thanks to which it acquires the necessary properties. The material must contain at least 2.14% carbon. Otherwise, it will be steel, not cast iron. It is thanks to carbon that cast iron has increased hardness. At the same time, this element reduces the ductility and malleability of the material, making it brittle.

In addition to carbon, cast iron necessarily includes: manganese, silicon, phosphorus and sulfur. Some brands also contain additional additives to give the material specific properties. Commonly used alloying elements include chromium, vanadium, nickel and aluminum.

Properties of cast iron

The material has a density of 7.2 g/cm 3 . For metals and their alloys this is a fairly high figure. Cast iron is well suited for the production of all kinds of products by casting. In this regard, it is superior to all iron alloys except some grades of steel.

The melting point of cast iron is 1200 degrees. For steel, this figure is 250-300 degrees higher. The reason for this lies in the increased carbon content in cast iron, which causes less close bonds between iron atoms.

During the smelting of cast iron and its subsequent crystallization, carbon does not have time to fully penetrate into the structure of the iron. Therefore, the material turns out to be brittle. The structure of cast iron does not allow it to be used for the production of products that are constantly subject to dynamic loads.

But what cast iron is ideal for is for parts that must have increased strength.

Receipt

Producing cast iron is a very costly and material-intensive process. To obtain one ton of alloy, 550 kg of coke and 900 liters of water are needed. As for ore, its quantity depends on the iron content in it. As a rule, ore with a mass fraction of iron of at least 70% is used. Processing less rich ores is not economically feasible.

Before being melted down, the material is enriched. Pig iron production in 98% of cases occurs in blast furnaces.

The technological process includes several stages. First, ore is loaded into the blast furnace, which includes magnetic iron ore (a compound of di- and trivalent iron oxide). Ores that contain hydrous oxide of iron or its salts can also be used. In addition to raw materials, coking coals are placed in the furnace, which are necessary to create and maintain high temperatures. Coal combustion products, as iron reducers, also participate in chemical reactions.

Additionally, flux is supplied to the furnace, which plays the role of a catalyst. It accelerates the process of melting rocks and releasing iron. It is important to note that before entering the furnace, the ore must undergo special processing.

Since small parts melt better, it is pre-crushed in a crushing plant. The ore is then washed to remove non-metal impurities. Then the raw materials are dried and fired in ovens.

Thanks to firing, sulfur and other foreign elements are removed from it.

After the furnace is fully loaded, the second stage of production begins. When the burners are started, the coke gradually heats the raw material. This releases carbon, which reacts with oxygen to form an oxide. The latter takes an active part in the reduction of iron from compounds in the ore. The more gas accumulates in the furnace, the slower the reaction proceeds.

When the required proportion is reached, the reaction stops altogether. The excess gases subsequently serve as fuel to maintain the required temperature in the furnace. This method has several strengths. Firstly, it allows you to reduce fuel costs, which reduces the cost of the production process.

And, secondly, combustion products do not enter the atmosphere, polluting it, but continue to participate in production.

Excess carbon is mixed with the melt and absorbed by iron. This is how cast iron is made. Impurities that have not melted float to the surface of the mixture and are removed. They are called slag. Slag is used in the production of certain materials. When all excess particles are removed from the melt, special additives are added to it.

Varieties

We have already found out what cast iron is and how it is obtained, now we will understand the classification of this material. Pipe and foundry cast iron is produced using the method described above.

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Pig iron is used in steel production via the oxygen converter route. This type is characterized by a low content of silicon and manganese in the alloy. Foundry cast iron is used in the production of all kinds of products. It is divided into five types, each of which will be considered separately.

White

This alloy is characterized by the content of excess carbon in the form of carbide or cementite. The name of this species was given for the white color at the fracture site. carbon in such cast iron usually exceeds 3%. White cast iron is highly brittle and brittle, so its use is limited. This type is used for the production of parts of a simple configuration that perform static functions and do not bear heavy loads.

By adding alloying additives to white cast iron, it is possible to increase the technical parameters of the material. For this purpose, chromium or nickel is most often used, less often vanadium or aluminum. A brand with this kind of additives is called “sormite”.

It is used in various devices as a heating element. “Sormite” has a high resistivity and works well at temperatures no higher than 900 degrees. The most common use of white cast iron is in the production of household bathtubs.

Grey

This is the most common type of cast iron. It has found application in various areas of the national economy. In gray cast iron, carbon is present in the form of pearlite, graphite or ferrite-perlite.

In such an alloy the carbon content is about 2.5%. Like cast iron, this material has high strength, so it is used in the production of parts that receive cyclic loads.

Gray cast iron is used to make bushings, brackets, gears and housings for industrial equipment.

Thanks to graphite, gray cast iron reduces friction and improves the effect of lubricants. Therefore, parts made of gray cast iron are highly resistant to this type of wear. When operating in particularly aggressive environments, additional additives are introduced into the material to neutralize the negative impact.

These include: molybdenum, nickel, chromium, boron, copper and antimony. These elements protect gray cast iron from corrosion. In addition, some of them increase the graphitization of free carbon in the alloy.

Thanks to this, a protective barrier is created that prevents destructive elements from reaching the surface of the cast iron.

Half-hearted

An intermediate material between the first two varieties is half-cast iron. The carbon it contains is presented in the form of graphite and carbide in approximately equal proportions. In addition, such an alloy may contain small amounts of lideburite (no more than 3%) and cementite (no more than 1%).

The total carbon content of half cast iron ranges from 3.5 to 4.2%. This variety is used for the production of parts that are operated under conditions of constant friction. These include automobile brake pads, as well as rolls for grinding machines.

To further increase wear resistance, all sorts of additives are added to the alloy.

Malleable

This alloy is a type of white cast iron, which is subjected to special firing in order to graphitize free carbon. Compared to steel, such cast iron has improved damping properties. In addition, it is not as sensitive to cuts and performs well in low temperature conditions.

In such cast iron, the mass fraction of carbon is no more than 3.5%. In the alloy it is presented in the form of ferrite, granular pearlite containing inclusions of graphite or ferrite-pearlite. Malleable cast iron, like half-cast iron, is used mainly in the production of parts operating under conditions of continuous friction.

To improve the performance characteristics of the material, magnesium, tellurium and boron are added to the alloy.

Source: http://schemy.ru/info/kakoj-splav-nazyvaetsja-chugunom/

What alloy is called cast iron? — Metals, equipment, instructions

What alloy is called steel

Many people know that steel is a product obtained by melting other elements. But which ones? What does steel contain? Today, this substance is a deformable alloy of iron and carbon (its amount is 2.14%), as well as a small proportion of other elements.

General information

It is worth noting that steel is an alloy that contains up to 2.14% carbon in its composition. An alloy containing more than 2.14% carbon is already called cast iron.

It is known that the composition of carbon steel and ordinary steel is not the same. If a conventional substrate contains carbon and other alloying (improving) components, then the carbon product does not contain alloying elements. If we talk about alloy steel, then its composition is much richer.

In order to improve the performance characteristics of this material, elements such as Cr, Ni, Mo, Wo, V, Al, B, Ti, etc. are added to its composition.

It is important to note that the best properties of this substance are ensured precisely by adding doped complexes, and not just one or two substances.

The material we are considering can be classified according to several indicators:

The first indicator is the chemical composition of the steel.
The second is the microstructure, which is also very important.
Of course, steel differs in its quality and method of production.
Also, each type of steel has its own application.

The composition can be considered in more detail using the example of chemical composition. Based on this feature, two more types are distinguished - alloy and carbon steels.

Among carbon steels, there are three varieties, the main difference of which is the quantitative carbon content. If the substance contains less than 0.3% carbon, then it is classified as low-carbon. of this substance in the region of 0.3% to 0.7% transfers the final product to the category of medium-carbon steels. If the alloy contains more than 0.7% carbon, then the steel belongs to the high-carbon category.

With alloy steels the situation is approximately the same. If the material contains less than 2.5% of alloying elements, then it is considered low-alloyed, from 2.5% to 10% - medium-alloyed, and from 10% and above - highly alloyed.

Microstructure

The microstructure of steel differs depending on its condition. If the alloy is annealed, then its structure will be divided into carbide, ferritic, austenitic, and so on. With a normalized microstructure of the substance, the product can be pearlitic, martensitic or austenitic.

The composition and properties of steel determine whether a product belongs to one of these three classes. The least alloyed and carbon steels are the pearlitic class, the middle ones are martensitic, and the high content of alloying elements or carbon transfers them to the category of austenitic steels.

Production and quality

It is important to note that an alloy such as steel may also include some negative elements, a high content of which worsens the performance of the product. These substances include sulfur and phosphorus. Depending on the content of these two elements, the composition and types of steel are divided into the following four categories:

The rank and file became. This is an alloy of ordinary quality, containing up to 0.06% sulfur and up to 0.07% phosphorus.
High quality. of the above substances in these steels is reduced to 0.04% sulfur and 0.035% phosphorus.
High quality. They contain only up to 0.025% of both sulfur and phosphorus.
The highest quality alloy is assigned if the percentage of sulfur content is no more than 0.015, and phosphorus is no more than 0.025%.

If we talk about the process of producing an ordinary alloy, then most often it is produced in open-hearth furnaces or in Bessmer, Thomas converters. This product is bottled into large ingots. It is important to understand that the composition of steel, its structure, as well as quality characteristics and properties are determined precisely by the method of its manufacture.

Open hearth furnaces are also used to produce high-quality steel, but more stringent requirements are imposed on the smelting process in order to obtain a high-quality product.

Melting of high-quality steels is carried out only in electric furnaces. This is explained by the fact that the use of this type of industrial equipment guarantees an almost minimal content of non-metallic additives, that is, it reduces the percentage of sulfur and phosphorus.

In order to obtain an alloy of particularly high quality, they resort to the method of electroslag remelting. The production of this product is possible only in electric furnaces. After completing the manufacturing process, these steels are always only alloyed.

Types of alloys by application

Naturally, a change in the composition of steel greatly affects the performance characteristics of this material, which means that the scope of its use also changes. There are structural steels that can be used in construction, cold forming, and can also be case-hardened, tempered, high-strength, and so on.

If we talk about construction steels, they most often include medium-carbon and low-alloy alloys. Since they are mainly used for the construction of buildings, the most important characteristic for them is good weldability. Various parts are most often made from case-hardened steel, the main purpose of which is to work under conditions of surface wear and dynamic loading.

Other steels

Other types of steel include improveable steel. This type of alloy is used only after heat treatment. The alloy is exposed to high temperatures to harden it and then tempered in some environment.

The type of high-strength steels includes those in which, after selecting the chemical composition, as well as after undergoing heat treatment, the strength reaches almost a maximum, that is, approximately twice as much as that of the usual type of this product.

Spring steels can also be distinguished. This is an alloy that, as a result of its production, has received the best qualities in terms of elastic limit, load resistance, and fatigue.

Stainless steel composition

Stainless steel is an alloy type. Its main property is high corrosion resistance, which is achieved by adding an element such as chromium to the alloy composition. In some situations, nickel, vanadium or manganese may be used instead of chromium. It is worth noting that by melting the material and adding the necessary elements to it, it can obtain the properties of one of three grades of stainless steel.

The composition of these types of alloy is, of course, different. The simplest are considered to be ordinary alloys with increased resistance to corrosion 08 X 13 and 12 X 13. The next two types of this corrosion-resistant alloy must have high resistance not only at normal, but also at elevated temperatures.

Source: https://respect-kovka.com/kakoy-splav-nazyvaetsya-stalyu/