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Steel. General classification

Steel.

An iron-based alloy, after casting it is malleable at certain temperature ranges;

contains manganese, carbon and often other alloying elements.

In carbon and low-alloy steels, the maximum carbon content is up to 2.0%;

in high-alloy steel up to approximately 2.5%.

The dividing line between low-alloy and high-alloy steels is usually considered to be approximately 5% metal alloying elements.

Alloying element.

An element added and retained in a metal that changes its structure and chemical composition.

Alloy steels.

High strength low alloy steels.

Steel engineered to provide the best mechanical properties and higher resistance to atmospheric corrosion than carbon steel. This steel should not be classified as an alloy steel, since it was manufactured for special mechanical properties rather than a special chemical composition (HSLA steels have a yield strength of more than 275 MPa or 40 ksi). The chemical composition of HSLA steels can vary depending on the required thickness and mechanical properties. These steels have a low carbon content (0.05–0.25%) in order to obtain adequate deformability and weldability, and have a manganese content of up to 2.0%. Small amounts of chromium, nickel, molybdenum, copper, nitrogen, vanadium, niobium, titanium, zirconium are used in various combinations.

Low alloy steels.

A class of ferrous metals that exhibit strength properties greater than those of simple carbon steels as a result of the addition of alloying elements such as nickel, chromium and molybdenum. The total alloy content can range from 2.07% to just below stainless steels, which contain a minimum of 10% Cr.

Malleable cast iron.

Cast iron obtained by long-term annealing of white cast iron, during which decarburization and graphitization processes occur, eliminating partially or completely cementite. Graphite is in the form of annealed carbon. If the decarburization reaction predominates, then the product has a light fracture surface - malleable white-core cast iron. If the fracture surface is dark - dark-hearted malleable cast iron. Only dark-hearted malleable iron is produced in the United States. Ductile iron has a predominantly ferritic matrix; pearlitic ductile iron may contain nodular pearlite or tempered martensite, depending on heat treatment and desired hardness.

Gray cast iron.

A broad class of cast iron alloys (cast irons), typically characterized by a microstructure of flake graphite in an iron matrix. Gray cast iron typically contains 2.5 to 4% C, 1 to 3% silicon and manganese additives, depending on the desired microstructure (from 0.1% Mn in ferritic gray cast iron to 1.2% in pearlitic). Sulfur and phosphorus are also found in small quantities as residual impurities.

Cast iron.

A generic term for a large collection of cast iron alloys in which the carbon content exceeds the solubility of carbon in austenite at the eutectic temperature. Most cast irons contain at least 2% carbon, plus silicon and sulfur, and may contain other alloying elements. See also ductile iron, ductile iron, gray cast iron, ductile iron, and white cast iron.

Cast iron with vermicular graphite.

Cast iron having graphite in a shape intermediate between the plate shape typical of gray cast iron and the spherical shape of ductile cast iron. The structure is free of flake graphite and is composed of 20% spheroidal graphite and 80% vermicular graphite (ASTM A247 Type IV). Also known as CG-cast iron. Vermicular graphite cast iron is similar to cast ductile iron, but uses a technique that suppresses the formation of spheroidal graphite. Typical nominal CG iron compositions contain 3.1 to 4.0% C, 1.7 to 3.0% silicon, and 0.1 to 0.6% manganese.

Semi-quiet steel.

The surface condition of a semi-quiet steel ingot is close to the surface of boiling steel. The remaining characteristics are intermediate between boiling and calm steels.

Calm steel.

Steel treated with a strong deoxidizer such as silicon or aluminum to reduce the oxygen content to such a level that no reaction occurs between carbon and oxygen during crystallization.

Carbon steel.

Steel containing no more than the standard concentrations of 1.65% manganese, 0.60% silicon and 0.60% copper - and only an insignificant amount of any other elements other than carbon, silicon, manganese, copper, sulfur and phosphorus. Low-carbon steels contain up to 0.30% carbon, medium-carbon steels contain from 0.30 to 0.60% carbon and high-carbon steels contain from 0.60 to 1.00% carbon.

Alloy cast irons.

Cast irons containing more than 3% alloying elements. There are alloyed white cast irons, gray cast iron, malleable cast iron.

Alloy alloy.

An alloy enriched with one or more desired alloying elements that are added to the molten metal to obtain the required concentration.

Bearing steels.

Alloy steels used for the production of rolling bearings. Typically made from high carbon (1.00%) and low carbon (0.20%) steels. High carbon steels are used after induction surface hardening. Low-carbon steels are cemented to provide the necessary surface hardness while maintaining basic properties.

Tool steel.

Any of a class of carbon and alloy steels commonly used for making tools. Tool steels are characterized by high hardness and abrasion resistance, maintaining high hardness at elevated temperatures. These characteristics are usually achieved high content carbon and alloying.

Metal.

1) An opaque, lustrous elemental substance that is a good conductor of heat and electricity and, when polished, is characterized by good light reflection. Most metals are malleable and ductile and are denser than other elemental substances.

2) In their structure, metals differ from non-metals in their interatomic bonding and electronic potential. Metal atoms tend to lose electrons from their orbits. The positive ions formed in this way are held together by the electron gas. The ability of these "free electrons" to transfer electric charges and the fact that these powers decrease with increasing temperature establish the chief differences between metallic solids.

3) From a chemical point of view, an elemental substance whose hydroxide is alkaline.

Rental

Any technical product of a rolling mill.

The main differences between cast iron and steel:
Cast iron is lighter than steel
Cast iron has more low temperature melting.
Steel lends itself better to processing (welding, cutting, rolling, forging).
Products made of cast iron are more porous and their thermal conductivity is much lower.
Cast iron has low thermal conductivity, while steel has higher thermal conductivity.
Cast iron is the primary product of ferrous metallurgy, and steel is the final product.
Cast iron is not hardened, but some types of steel must be subjected to a hardening procedure.
Products made of cast iron are only cast, and products made of steel are forged and welded.

Iron and steel products are widely used in many industries 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 have unique properties. What are the differences between steel and cast iron, their main properties and characteristics?

Steel and its main characteristics

Steel represents deformed alloy of iron and 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 grows. 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 process was replaced by the Bessemer and open hearth method obtaining 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 carbon content it happens:

  • 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 quality classification.

The density of steel is 7700-7900 kg/m3, and the general characteristics of steel consist of indicators such as strength, hardness, wear resistance and machinability various types. 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 species steel have melting temperature from 1450 to 1520 o 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 types:

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 is from 1160 to 1250 o C.

Cast iron and steel products from the metallurgical industry are used both in everyday life and in production. Both materials are unique alloys of iron and carbon. Everyone knows that iron is mined from the depths of the earth in huge quantities. But it is impossible to use it in its pure form; this element is too soft and therefore unsuitable for the manufacture of high-strength products. Therefore, for industrial, construction and household purposes, it is not iron in its pure form that is used, but its derivatives - cast iron and steel. What is the difference between steel and cast iron?

Cast iron and steel are alloys of iron and carbon.

Their difference is manifested in many qualities, and the commonality of elements during production does not give the material identical characteristics.

Gradation of steel and cast iron

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Steel

To produce steel, iron is alloyed with carbon and various impurities. Required condition is the carbon content is no more than 2% (it increases strength), and the iron content is no less than 45%. The remainder consists of alloying binding components (chromium, molybdenum, nickel, etc.). Chromium increases the strength of steel, its hardness and wear resistance. Nickel increases strength, toughness and hardness, improves its anti-corrosion qualities and hardenability. Silicon adds strength, hardness and elasticity to steel and reduces its toughness. Manganese improves weldability and hardenability. Metallurgists distinguish different types steel. They are classified depending on the volume of the remaining elements. For example, a content of more than 11% alloy metals produces high-alloy steel. There is also:

  1. Low alloy steel - up to 4%.
  2. Medium alloy steel - up to 11%.

Based on the amount of carbon, steel is classified into:

  • low-carbon metal - up to 0.25% C;
  • medium carbon metal - up to 0.55% C;
  • high-carbon metal - up to 2% C.

The composition of non-metallic elements (phosphides, sulfides) classifies the metal into:

  • regular;
  • quality;
  • high quality;
  • especially high quality steel.

As a result, all types of steel are a strong, wear-resistant and deformation-resistant alloy with a melting point from 1450 to 1520 °C.

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Cast iron

Iron production also involves the fusion of iron and carbon. The main difference between cast iron and steel is the content of the latter in the mixture. It should be more than 2%. In addition, the mixture contains impurities: silicon, manganese, phosphorus, sulfur and alloying metals. Cast iron is more brittle than steel and breaks without visible deformation. Carbon in the metal is represented by graphite or cementite, while the volume and shape of the element determine the types of alloy:

  1. White cast iron, in which all the carbon is represented by cementite. At the fracture, this material has white, very hard, but at the same time fragile. It is easy to process and is used to produce the malleable variety.
  2. Gray - carbon is represented by graphite, which gives the material plasticity. Soft, easy to cut, with a low melting point.
  3. Malleable, which is obtained from white cast iron by special annealing (simmering) in special heating furnaces at a temperature of 950-1000 ° C. At the same time, the excessive brittleness and hardness characteristic of white cast iron are greatly reduced. Malleable cast iron cannot be forged, and the name only indicates its ductility.
  4. Ductile iron containing nodular graphite formed during the process of crystallization.

The amount of carbon in the alloy determines its melting point (than more content element, the lower the temperature and the higher the fluidity when heated). Therefore, cast iron is a fluid, non-plastic, brittle and difficult to process material with a melting point of 1150 to 1250 °C.

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Corrosion resistance

Both alloys are susceptible to corrosion, and improper use will accelerate this process.

Cast iron becomes covered with dry rust during use. This is the so-called chemical corrosion. Wet (electrochemical) corrosion affects cast iron more slowly than steel. Initially, the conclusion suggests itself that the anti-corrosion characteristics of cast iron are much higher. In fact, both of these alloys are susceptible to corrosion equally, it’s just that for cast iron products the process takes longer due to thick walls. This, for example, can explain the difference in the service life of boilers: steel - from 5 to 15 years, cast iron - from 30 years.

In 1913, Harry Brearley made a discovery in the field of metallurgy. He discovered that steel with a high chromium content had good resistance to acid corrosion. This is how stainless steel was born. It also has its own gradation:

  1. Corrosion-resistant steel is resistant to corrosion in basic industrial and domestic conditions (oil and gas, light industry, engineering industry, surgical instruments, household stainless steel utensils).
  2. Heat-resistant steel is resistant to high temperatures and aggressive environments (chemical industry).
  3. Heat-resistant steel has increased mechanical strength at high temperatures.

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Thermal shock and shock resistance

Cast iron and steel are often used in the manufacture of heating boilers. In this case, the issue of resistance to thermal shocks becomes especially important. If a cast iron boiler gets into an uncooled cold water, it may crack. Thermal shock is not dangerous for steel products. Steel is more elastic and tolerates temperature differences well. But large and frequent temperature changes in steel contribute to the appearance of “tired” zones and, as a result, cracks in places that are weakened by welding.

Good ductility makes steel products resistant to mechanical damage. The fragility of cast iron inevitably leads to the formation of cracks due to impacts or distortions.

Gray cast iron has a more uniform structure, increased ductility and anti-corrosion properties, and is able to withstand large temperature changes.

  1. Cast iron is less durable and hard than steel.
  2. Steel is heavier and has more high temperature melting.
  3. The lower carbon content in steel, unlike cast iron, makes it easier to process (cook, cut, forge).
  4. For a similar reason, cast iron products are produced only by casting, while steel products can be forged and welded.
  5. Products made of steel are less porous than those made of cast iron, and therefore their thermal conductivity is much higher.
  6. Products made of cast iron are usually black in color and have a matte surface, while those made of steel are light-colored with a shiny surface.

Modernity is iron. Anyone who understands it knows that the word “iron” means iron-carbon alloys - steel and cast iron. It would seem that two are absolutely different materials and they are very easy to distinguish. However, given the wide range of their types and brands, fine line differences in chemical composition some of them are difficult to identify. It is important to have additional skills in order to know the answer to the question: what is the difference between cast iron and steel?

Cast iron

Specifications:

  1. Rough, matte gray in color.
  2. Melting at 1000-1600˚С depending on the composition (for industrial ones on average - 1000-1200˚С, white and pig iron melt at higher temperatures).
  3. Density: 7200-7600 kg/m3.
  4. 540 J/(kg˚С).
  5. High hardness: 400-650HB.
  6. Low ductility, very crumbles when exposed to pressure; highest values ductile high-strength cast iron has a relative elongation of δ=6-12%.
  7. Low strength: 100-200 MPa, for malleable its value reaches 300-370 MPa, for some brands of high-strength - 600-800 MPa.
  8. It is modeled using heat treatment, but rarely and with great care, since it is characterized by a cracking process.
  9. It is alloyed with the help of auxiliary chemical elements, but a significant degree of alloying further complicates the processing processes.
  10. It is characterized by satisfactory weldability, good machinability, and excellent casting properties. Cannot be forged or stamped.
  11. Good wear resistance and corrosion resistance.

Cast iron is a material for body parts, blocks, and machine components made by casting. Is the main charge component for

Steel

An iron-carbon alloy containing carbon in an amount of not more than 2.14% and iron - not less than 45% is called steel. Its main characteristics:

  1. Smooth, has a silvery color with a characteristic reflection.
  2. Melting within 1450˚С.
  3. Density ranges from 7700 to 7900 kg/m3.
  4. Heat capacity at room temperature: 462 J/(kg˚C).
  5. Low hardness, on average 120-250 HB.
  6. Excellent ductility: the relative elongation coefficient δ for different brands ranges from 5-35%, for most - δ≥20-40%.
  7. Average tensile strength values ​​for construction materials- 300-450 MPa; for especially strong alloyed ones - 600-800 MPa.
  8. It lends itself well to correction of properties using thermal and chemical-thermal treatment.
  9. Actively doped with various chemical elements for the purpose of changing properties and purpose.
  10. Qualitatively high performance weldability, machinability and machinability.
  11. Characterized by low performance corrosion resistance.

Steel is the main structural alloy in modern metallurgy, mechanical engineering, instrument making and technology.

Determining origin by type of part

Having considered detailed characteristics these alloys, you can confidently use the knowledge of how cast iron differs from steel. Having a metal object in front of you, doubting its origin, it is rational to immediately remember the main distinctive technological properties. So, cast iron is a casting material. It is used to produce simple dishes, massive pipes, housings of machine tools, engines, and large objects of simple configuration. Parts of all sizes and complexity are made from steel, as forging, stamping, drawing, rolling and other methods are used for this. Thus, if there is a question about the origin of the reinforcement, there can be no doubt - it is steel. If you are interested in the origin of a massive cauldron, it is cast iron. If you need to find out what the engine housing or crankshaft is made of, you should resort to other recognition options, since both options are possible.

Color features and fragility analysis

In order to know how to distinguish cast iron from steel by eye, you need to remember the main visual differences. Cast iron is characterized by a matte finish gray and a rougher outer texture. Steel is characterized by its special silvery shiny hue and minimal roughness.

Also important knowledge How to distinguish cast iron from steel visually is information about the ductility of these materials. If the workpieces or metal objects being examined do not have serious value, you can test them for strength and ductility by applying impact force. Brittle cast iron will crumble into pieces, while steel will only deform. With more serious crushing loads, cast iron crumbs will turn out to be of small, varied shapes, and pieces of steel will be large, with the correct configuration.

Cut and drill

How to distinguish cast iron from steel at home? It is necessary to obtain fine dust or shavings from it. Since steel has high ductility, its chips also have a tortuous character. Cast iron crumbles, and when drilling, small chips are formed along with dust.

To obtain dust, you can use a file or rasp and slightly sharpen the edge of the part of interest. Examine the resulting fine shavings on your hand or a white sheet of paper. Cast iron contains carbon in large quantities in the form of graphite inclusions. Therefore, when rubbing its dust, a black graphite “trace” remains. In steels, carbon is in a bound state, so mechanical influence on dust does not give any visible results.

Heat and sparkle

How to distinguish cast iron from steel? Need to operate necessary equipment and a little patience.

In the first case, you can resort to heating, for example, using a blowtorch, initially wearing special protective clothing and following safety rules at work. The temperature must be increased before the metal begins to melt. It has already been said that the melting point of cast iron is higher than that of steel. However, this applies mainly to white and for all industrial grades - they contain carbon in an amount of no more than 4.3% and melt at 1000-1200˚C. Thus, it can be melted much faster.

An educational method for obtaining information about how cast iron differs from steel is to use an experimental sample on a grinding machine or under a sharp wheel of a grinding machine. The analysis is carried out according to the characteristics of the sparks. Cast iron is characterized by dim red sparks, while steel is characterized by bright, blinding short rays with a white-yellow tint.

What does it sound like

An interesting feature is how to distinguish cast iron from steel by sound. The two alloys sound different. It is not at all necessary to produce musical accompaniment using existing experimental facilities. But it is necessary to have both samples or have an experienced ear in this matter. Steel is characterized by a higher density, which is reflected in its sound. When you hit it with a metal object, the sound is much louder than in the same situation with cast iron.

In order to know how cast iron differs from steel, you need to have a little knowledge about these materials and some experience. After all, an experienced professional in the field of forging, grinding, milling, drilling, turning, heat treatment or welding, a metallurgist or technician can easily distinguish them from each other, assessing them only visually or by touch.

The difference between cast iron scrap and steel scrap is not only in the chemical composition, but also visual. To test the difference you will need a grinding wheel, a piece of metal, a blowtorch, a face mask and gloves

Physical properties of cast iron and cast steel

You can distinguish metals by their appearance. Cast iron is rough and matte gray in color, while cast steel is smooth and silvery gray in color.

Spark test

You will need two small pieces of each metal. Press the sanding wheel against the edge of each metal and note the color of the sparks that form. Steel will create shiny white sparks, while cast iron will generate dull red sparks.

Crushing test

Take a small piece from each metal and try to crush it. You will find that cast iron will break randomly, while cast steel will break into long, smooth, thin pieces with little or no effort.

Melting test

For this test you will need a small piece of each metal to melt. Put on your safety gear and use a blow torch to melt the metal. The more carbon in a metal, the harder the metal becomes. You will see that the cast iron melts faster and turns red. Cast steel takes longer to melt and turns white when melted.

Fragility test

Drop a thin slab of each metal and drop it onto the ground with some force. Cast iron will break into many pieces, while steel will not break, or will break into two pieces. This is because cast iron is more brittle than steel.