What is included in steel

Steel is the most common alloy in industry:

The durability and reliability of mechanisms depend on the material from which they were made, that is, on the totality of all its properties and features, which determine the performance characteristics. Today, most machine components and parts are made from various grades of steel. Let's look at this material in more detail.

What is steel

Steel is an alloy of two chemical elements: iron (Fe) and carbon (C), and the content of the latter should not exceed 2%. If there is more carbon, then this alloy belongs to cast iron.

But steel is not only a chemically pure compound of two elements; it contains both harmful impurities, such as sulfur and phosphorus, and special additives that impart the desired properties to the material - increase strength, improve workability, ductility, etc.

If the alloy contains less than 0.025% carbon and contains a small amount of impurities, then it is considered technical iron. This material differs from steel in all respects; it has high magnetic characteristics, and is used for the manufacture of electrical components. Pure iron does not exist in nature; it is very difficult to obtain it even in laboratory conditions.

Despite the fact that carbon is contained in a very small percentage, it has a significant impact on the mechanical and technical properties of the material.

An increase in this substance leads to an increase in hardness, strength increases, but at the same time ductility sharply decreases.

And, as a result, the technological characteristics change: with an increase in carbon, the casting properties decrease and the machinability deteriorates. At the same time, low-carbon steels are also difficult to cut.

Obtaining steel. Metallurgy

Steel is the most common alloy on the planet. It is produced industrially from cast iron, from which excess carbon and other impurities are burned off under the influence of high temperatures.

Steels are mainly produced in two ways: melting in open hearth furnaces and melting in electric furnaces. The material made in an electric furnace is called electric steel. It turns out to be cleaner in composition.

In addition, there are many special processes for producing alloys with special properties, such as vacuum arc melting or electron beam melting.

You can learn more about steels and other alloys by studying the science of metallurgy. It is considered one of the branches of physics and covers not only information about steel grades and their composition, but also contains information about the structure and properties of materials at the atomic and structural level.

Students of specialized universities take a special course “Industrial Steels”, where they examine in detail special-purpose alloys: construction, improveable, cemented, for cutting and measuring tools, magnetic, spring-spring, heat-resistant, steels for structures in cold climates, etc.

Classification of steels by quality

All steels are divided by quality into:

- ordinary quality steel;

- high quality;

— high quality steel;

- high quality.

The quality of steel directly depends on the percentage of harmful impurities (composition) and compliance with the declared mechanical and technological characteristics. All types are used in industry, but in different directions: steel of ordinary quality - for non-critical parts, steel of improved quality and high quality - in structures for which special requirements are imposed.

Steel according to GOST: classification

1. GOST 380-88. Ordinary quality carbon - St.1, St.2, St3ps, etc. Numbers from 0 to 6 indicate the grade; as the number increases, the carbon content increases. Letters ps, kp; cn – indices of the degree of deoxidation of the material: semi-calm, boiling, calm, respectively.
2. GOST1050-74. Carbon quality steel – 05; 08; 10; 20ps; 08 kp.

   Numbers up to 60 are the average C content in hundredths of a percent, letters ps, kp; sp – similar to step 1.

3. GOST 5632-72. High-alloy steels and alloys, corrosion-resistant, heat-resistant and heat-resistant – 30KhGSA, GN2; 50X; 20ХН3А. The first numbers are the carbon content: 30 – 0.3%; 40 - 0.4%; 45 - 0.45%, letters - the corresponding alloying element (X-chrome; G - manganese; T - titanium; A-nitrogen, etc.

   ), the number behind the letter is the percentage of the alloying element. If there is no number, then the proportion of the substance is 1.5%, the letter A at the end means that it is high-quality steel. This applies to both tool and alloy steels.

4. GOST1435-74. Carbon instrumental - U7, U8, U10A. Explanation: U7 – 0.7% C; U8 – 0.8% C; U – carbon; A - high quality.
5. GOST5950-73.

   Alloyed instrumental – 5ХГН; X12; 8X3, etc. The decoding of the brand is similar to point 3, but the C content is indicated in tenths of a percent. If carbon is less than 0.1%, then the numbers are not indicated - XB4; CHC; CHV, etc.

6. GOST801-78. Bearing – ШХ4; ШХ15; SHH15SG. ШХ – bearing, number – chromium content: ШХ4 – 0.4% chromium, ШХ15 – 1.5% chromium, other letters and numbers – content of additional alloying elements.
7. GOST 1414-75.

   Structural grades with increased and high cutting machinability - A12, A20, A30, A40G. Decoding of carbon content: A20 - 0.2% C, A12 - 0.12% C, A30 - 0.3% C.

Steel. Properties: tables for the most common brands with basic mechanical and technological characteristics

steel grade	Mechanical properties	Technological properties
σt, MPa	σв, MPa	δ, %	Machinability	Weldability	Plasticity during cold working
40X	786	980	10	IN	U	U
45G	372	569	15	U	N	N
25ХГТ	1080	1470	10	U	N	U
40ХС	1080	1225	12	U	N	N
30HMFA	932	1030	13	IN	N	U
ШХ15	410	715	21	U	N	U
12Х13	415	588	20	U	N	IN
A20hot rolled	510	600	15	IN	—	—

N - low;

U - satisfactory;

B – high;

σт – physical yield strength, MPa;

σв – tensile strength, MPa;

δ – relative elongation, %.

Source: https://www.syl.ru/article/205882/new_stal---eto-samyiy-rasprostranennyiy-splav-v-promyishlennosti

Steel

Steel (Polish stal, from German Stahl) is a deformable (malleable) alloy of iron with carbon and other elements, the carbon content of which does not exceed 2.14%.  

Carbon provides iron alloys with strength and hardness, while reducing ductility and toughness. Like cast iron, steel contains impurities of silicon, manganese, sulfur and phosphorus. The main difference between steel and cast iron is the reduced content of carbon and impurities.  

Steel is obtained through the process of melting scrap metal or from pig iron. To produce steel, excess carbon is removed from cast iron and the amount of impurities included in it is reduced.  

Classification

According to the chemical composition, steels are divided into carbon and alloy. 

The composition of carbon steel includes carbon and a certain amount of permanent impurities (Si, Mn, S, P) that enter it during smelting. The main element that determines the properties of carbon steel is carbon. It increases hardness, elasticity, strength, reduces ductility and resistance to impact loads.  

Silicon and manganese in small quantities do not have a special effect on the properties of steel. Sulfur and phosphorus are considered harmful impurities. Sulfur causes red brittleness, brittleness at high temperatures, and reduces corrosion resistance. Phosphorus increases the brittleness and cold brittleness of steel, i.e. brittleness at normal temperatures. However, in certain doses they are necessary to obtain the special properties of steel.  

Carbon steel, in turn, is divided according to purpose and quality. According to its purpose, it is divided into structural and instrumental.  

Structural carbon steel contains up to 0.6% carbon (as an exception, carbon content up to 0.85% is allowed). Based on quality, structural carbon steel is divided into ordinary quality steel and high-quality steel.  

Tool carbon steel contains 0.7% carbon or more. It is distinguished by its hardness and strength. Alloy steel, along with the usual impurities, contains one or more special elements that improve its properties: chromium, tungsten, molybdenum, etc., as well as silicon and manganese in relatively large quantities.  

Alloying elements have a diverse effect on the properties of steel—for example, chromium increases hardness and corrosion resistance; tungsten increases hardness and red-hardness; molybdenum increases red-hardness, strength and oxidation resistance at high temperatures; Manganese content above 1% increases hardness, wear resistance, and resistance to impact loads.  

According to their purpose, alloy steel is divided into three groups: structural, tool and steel with special physical and chemical properties. 

Steels with special physical properties include: magnetic and non-magnetic steels, steels with high electrical resistance, and steels with special thermal properties. 

Steels and alloys with special chemical properties - corrosion-resistant, stainless, heat-resistant and heat-resistant. 

Principles of steel marking in Russia

Russia has adopted an alphanumeric marking system for alloy steels. Each grade of steel contains a certain combination of letters and numbers. Alloying elements are designated by letters of the Russian alphabet:  

X - chrome, 

N - nickel, 

B - tungsten, 

M—molybdenum,  

F—vanadium, 

T—titanium, 

Yu - aluminum, 

D - copper, 

G - manganese, 

C—silicon, 

K - cobalt, 

C - zirconium, 

R - boron, 

C—niobium. 

The letter A in the middle of the steel grade indicates the nitrogen content, and at the end of the grade indicates that the steel is high quality. 

For structural grades of steel, the first two digits indicate the carbon content in hundredths of a percent. If the content of the alloying element is more than 1%, then after the letter its average value is indicated in whole percentages.  

Application

Steel is the most important structural material for mechanical engineering, transport, construction and other industries. 

Steels with high elastic properties are widely used in mechanical and instrument making. In mechanical engineering they are used for the manufacture of springs, shock absorbers, power springs for various purposes, in instrument making - for numerous elastic elements: membranes, springs, relay plates, bellows, braces, suspensions.

Steel production process

The essence of the process of processing cast iron into steel is to reduce to the required concentration the content of carbon and harmful impurities - phosphorus and sulfur, which make steel brittle and brittle. 

Depending on the method of carbon oxidation, there are various methods for processing cast iron into steel: converter, open-hearth and electrothermal. 

The open-hearth method of steel smelting is quite energy-consuming and environmentally harmful. Thus, now all over the world, the vast majority of steel products are produced using the converter method.  

Oxygen-converter method of steel production

According to this oxidation method, excess carbon and other impurities of cast iron are oxidized in the presence of oxygen from the air, which is blown through molten cast iron under pressure in special furnaces - converters. 

The converter is a pear-shaped steel furnace lined inside with refractory bricks. It can rotate around its axis (Lining is a special finish to ensure protection of surfaces from possible mechanical or physical damage).  

The capacity of the converter is 50-60 tons. Its lining material is either dinas (which consists mainly of SiO2 (silicon oxide), which has acidic properties) or dolomite mass (a mixture of CaO and MgO (heat-resistant cement)). Depending on the furnace lining material, the converter method is divided into two types: Bessemer and Thomas.

Bessemer method

The Bessemer method processes cast irons that contain little phosphorus and sulfur and are rich in silicon (at least 2%). With this method, phosphorus is completely transferred from cast iron to steel. Therefore, phosphorous cast iron cannot be processed into steel using this method.  

All processes in the converter proceed quickly - within 10-20 minutes, since air oxygen blown through the cast iron reacts with the corresponding substances immediately throughout the entire volume of the metal. 

Bessemer steel usually contains less than 0.2% carbon and is used as industrial iron for the production of wire, bolts, roofing iron, etc. 

Thomas method

The Thomas method processes cast iron with a high phosphorus content (up to 2% or more). The main difference between this method and the Bessemer method is that the converter lining is made of magnesium and calcium oxides.  

Thomas steel is also low-carbon and is used as technical iron for the production of wire, roofing iron, etc. 

Open hearth furnace

The open-hearth method differs from the converter method in that the burning of excess carbon in cast iron occurs not only due to atmospheric oxygen, but also the oxygen of iron oxides, which are added in the form of iron ore and rusty iron scrap. 

An open-hearth furnace consists of a melting bath, covered with a refractory brick arch, and special regenerator chambers for preheating air and combustible gas. The capacity of such baths reaches 500 tons of steel. Scrap iron and iron ore are loaded into the smelting bath. The oven temperature is maintained at 1600–1650 °C  

The process of converting cast iron into steel in open hearths occurs relatively slowly - within 6-7 hours. Unlike a converter, in open-hearth furnaces the chemical composition of steel can be easily adjusted by adding scrap iron and ore to the cast iron in varying proportions. Alloy steel can also be produced in open hearths. To do this, appropriate metals or alloys are added to the steel at the end of the melting process.  

Electrothermal method

The electrothermal method has a number of advantages over the open-hearth method and especially the converter method. This method makes it possible to obtain very high quality steel and precisely regulate its chemical composition. Air access to the electric furnace is insignificant, therefore significantly less iron monoxide FeO is formed, which pollutes the steel and worsens its properties.  

The temperature in the electric furnace is not lower than 2000 °C. But electric ovens consume a lot of electricity. Therefore, this method is used only for producing high-quality special steel.

world's leading steel producers 

The growth of global steel production at the end of 2012 was 1.2% compared to 2011, only a few companies increased their production volumes. 

According to SBB, the first place in the world ranking was taken by the transnational corporation ArcelorMittal, which produced 88.2 million tons of steel in 2012 (the decrease in production compared to 2011 was 4.0%, for the first time since 2009). 

The top twenty largest steel producing companies in 2012 included one Russian company - Evraz - 20th place with production of 15.9 million tons (19th position in 2011), two Japanese companies Nippon Steel and JFE Steel. The merger of Nippon Steel with Sumitomo Metal Industries gave the combined company third position in 2012; Nippon Steel itself was seventh in 2011.  

Source: https://www.lsst.ru/article/stal/

Carbon steel: composition, classification, GOST

Carbon steel, due to its affordable cost and high strength characteristics, is one of the most widely used alloys. From such steels, consisting of iron and carbon and a minimum of other impurities, various engineering products, parts of stakes and pipelines, and tools are made. These alloys are also widely used in the construction industry.

Carbon steel calibrated wheel is most often used in shipbuilding and mechanical engineering

What are carbon steels?

Carbon steels, which, depending on the main scope of application, are divided into structural and instrumental, practically do not contain alloying additives. These steels are also distinguished from conventional steel alloys by the fact that their composition contains a significantly smaller amount of such basic impurities as manganese, magnesium and silicon.

the main element - carbon - in steels of this category can vary within fairly wide limits. Thus, high-carbon steel contains 0.6–2% carbon, medium-carbon steel – 0.3–0.6%, low-carbon steel – up to 0.25%.

This element determines not only the properties of carbon steels, but also their structure.

Thus, the internal structure of steel alloys containing less than 0.8% carbon consists predominantly of ferrite and pearlite; with increasing carbon concentration, secondary cementite begins to form.

Standards for the content of chemical elements in carbon steels

Carbon steels with a predominant ferritic structure are characterized by high ductility and low strength. If cementite predominates in the steel structure, then it is characterized by high strength, but at the same time it is also very brittle. When the amount of carbon increases to 0.8–1%, the strength characteristics and hardness of carbon steel increase, but its ductility and toughness significantly deteriorate.

The quantitative carbon content also has a serious impact on the technological characteristics of the metal, in particular on its weldability, ease of processing by pressure and cutting. Low-carbon steels are used to make parts and structures that will not be subject to significant loads during operation.

 The characteristics of medium-carbon steels make them the main structural material used in the production of structures and parts for the needs of general and transport engineering.

 Due to their characteristics, high-carbon steel alloys are optimally suited for the manufacture of parts that are subject to increased wear resistance requirements, for the production of impact punches and measuring tools.

Chemical composition of carbon steels of ordinary quality

Carbon steel, like any other category of steel alloy, contains various impurities: silicon, manganese, phosphorus, sulfur, nitrogen, oxygen and hydrogen. Some of these impurities, such as manganese and silicon, are useful; they are introduced into the steel composition at the stage of its smelting in order to ensure its deoxidation. Sulfur and phosphorus are harmful impurities that impair the quality characteristics of the steel alloy.

Although it is believed that carbon and alloy steels are incompatible, microalloying can be performed to improve their physical, mechanical and technological characteristics. For this purpose, various additives are introduced into carbon steel: boron, titanium, zirconium, rare earth elements. Of course, with the help of such additives it will not be possible to make stainless steel out of carbon steel, but they can significantly improve the properties of the metal.

Classification by degree of deoxidation

The division of carbon steels into various types is influenced, among other things, by such a parameter as the degree of deoxidation. Depending on this parameter, carbon steel alloys are divided into calm, semi-calm and boiling.

Quiet steels have a more homogeneous internal structure, the deoxidation of which is carried out by adding ferrosilicon, ferromanganese and aluminum to the molten metal. Due to the fact that the alloys of this category were completely deoxidized in the furnace, their composition does not contain ferrous oxide.

Residual aluminum, which inhibits grain growth, gives such steels a fine-grained structure. The combination of a fine-grained structure and the almost complete absence of dissolved gases allows the formation of high-quality metal from which the most critical parts and structures can be made.

Along with all their advantages, carbon steel alloys of the quiet category also have one significant drawback - their smelting is quite expensive.

The structure of a steel ingot depends on the degree of deoxidation of the steel

Cheaper, but also of lower quality, are boiling carbon alloys, the smelting of which uses a minimum amount of special additives.

In the internal structure of such steel, due to the fact that the process of its deoxidation in the furnace was not completed, there are dissolved gases that negatively affect the characteristics of the metal. Thus, the nitrogen contained in such steels has a bad effect on their weldability, provoking the formation of cracks in the weld area.

The developed segregation in the structure of these steel alloys leads to the fact that the rolled metal that is made from them has heterogeneity both in its structure and in its mechanical characteristics.

Semi-quiet steels occupy an intermediate position both in their properties and in the degree of deoxidation. Before pouring into molds, a small amount of deoxidizing agents is introduced into their composition, due to which the metal hardens practically without boiling, but the process of gas evolution in it continues.

As a result, a casting is formed, the structure of which contains fewer gas bubbles than in boiling steels. Such internal pores are almost completely welded during the subsequent rolling of the metal.

Most semi-mild carbon steels are used as structural materials.

You can familiarize yourself with all GOST requirements for carbon steel by downloading this document in pdf format from the link below.
Download GOST 380-2005 Carbon steel of ordinary quality. Stamps Download

Production methods and quality division

Various technologies are used for the production of carbon steels, which affects their division not only by production method, but also by quality characteristics. So, they distinguish:

Classification of carbon steels

Steel alloys of ordinary quality are smelted in open-hearth furnaces, after which they are formed into large ingots. Melting equipment used to produce such steels also includes oxygen converters. Compared to high-quality steel alloys, the steels in question may have a higher content of harmful impurities, which affects the cost of their production, as well as their characteristics.

Formed and completely solidified metal ingots are subjected to further rolling, which can be done in a hot or cold state. The hot rolling method produces shaped and sectioned products, thick and thin sheet metal, and large-width metal strips. Cold rolling produces thin sheet metal.

Modern enterprises use electric arc furnaces to produce high-quality alloys

To produce carbon steels of high-quality and high-quality categories, both converters and open-hearth furnaces, as well as more modern equipment - melting furnaces powered by electricity, can be used.

The corresponding GOST imposes very stringent requirements on the chemical composition of such steels and the presence of harmful and non-metallic impurities in their structure. For example, steels classified as high-quality should contain no more than 0.04% sulfur and no more than 0.035% phosphorus.

Due to the strict requirements for their production method and characteristics, high-quality and high-quality steel alloys are distinguished by increased structural purity.

Application area

As mentioned above, carbon steel alloys according to their main purpose are divided into two large categories: instrumental and structural.

Tool steel alloys containing 0.65–1.32% carbon are used in full accordance with their name - for the production of tools for various purposes.

In order to improve the mechanical properties of tools, they turn to such a technological operation as hardening carbon steel, which is performed without any particular difficulties.

Areas of application of carbon tool steels

Structural steel alloys are used very widely in modern industry. They are used to make parts for equipment for various purposes, structural elements for mechanical engineering and construction purposes, fasteners and much more. In particular, such a popular product as carbon wire is made from structural steel.

Carbon wire is used not only for domestic purposes, for the production of fasteners and in the construction industry, but also for the manufacture of such critical parts as springs. After carburization, structural carbon alloys can be successfully used for the production of parts that, during operation, are subject to severe surface wear and experience significant dynamic loads.

Of course, carbon steel alloys do not have many of the properties of alloy steels (in particular, stainless steel), but their characteristics are quite sufficient to ensure the quality and reliability of the parts and structures that are made from them.

Marking features

Marking of carbon steels, the rules for compiling which are strictly stipulated by the clauses of the relevant GOST, allows you to find out not only the chemical composition of the alloy presented, but also what category it belongs to.

The designation of carbon steel of ordinary quality contains the letters “ST”. GOST clauses stipulate seven conventional numbers of grades of such steels (from 0 to 6), which are also indicated in their designation.

You can find out what degree of deoxidation a particular brand corresponds to by the letters “kp”, “ps”, “sp”, which are placed at the very end of the marking.

Color marking is applied at the request of the consumer with indelible paint

Carbon steel grades according to GOST and ISO international standards

Grades of high-quality and high-quality carbon steels are simply designated by numbers indicating the carbon content in the alloy in hundredths of a percent. At the end of the designation of some brands you can find the letter “A”. This means that the steel has improved metallurgical quality.

You can tell that this is tool steel by the letter “U” at the very beginning of its marking. The number following such a letter indicates the carbon content, but in tenths of a percent. The letter “A”, if it appears in the designation of tool steel, indicates that this alloy has improved quality characteristics.

Source: http://met-all.org/stal/stal-uglerodistaya-sostav-klassifikatsiya-gost.html

Carbon steel

Carbon steel is characterized by a carbon content of up to 2.14% without the presence of alloying elements, a small amount of impurities in the composition, and a small content of magnesium, silicon and manganese. This in turn affects the properties and features of application. It is the main product of the metallurgical industry.

Compound

Depending on the amount of carbon, carbon and alloy steel are divided. The presence of carbon gives the material strength and hardness, and also reduces viscosity and ductility. Its content in the alloy is up to 2.14%, and the minimum amount of impurities due to the manufacturing process allows the bulk to consist of iron up to 99.5%.

High strength and hardness are what characterize carbon steel.

Impurities that are constantly included in the structure of carbon steel have a small content. Manganese and silicon do not exceed 1%, and sulfur and phosphorus are within 0.1%. An increase in the amount of impurities is characteristic of another type of steel, which is called alloyed.

The lack of technical ability to completely remove impurities from the finished alloy allows the following elements to be included in carbon steel:

• hydrogen;
• nitrogen;
• oxygen;
• silicon;
• manganese;
• phosphorus;
• sulfur

The presence of these substances is determined by the steel melting method: converter, open-hearth or other. And carbon is added on purpose. If the amount of impurities is difficult to regulate, then adjusting the level of carbon in the composition of the future alloy affects the properties of the finished product. When the material is filled with carbon up to 2.4%, steel is classified as carbon.

Characteristic

The characteristics and structure of the metal are changed using heat treatment, through which the required surface hardness or other requirements for the use of the steel structure are achieved.

However, not all structural properties can be adjusted using thermal methods. Such structurally insensitive characteristics include rigidity, expressed by the elastic modulus or shear modulus.

This is taken into account when designing critical components and mechanisms in various fields of mechanical engineering.

In cases where the calculation of the strength of an assembly requires the use of small-sized parts that can withstand the required load, heat treatment is used. This effect on “raw” steel makes it possible to increase the rigidity of the material by 2-3 times. The metal that is subjected to this process is subject to requirements regarding the amount of carbon and other impurities. This steel is called high quality.

Classification of carbon steels

According to the direction of application of products, carbon steel is divided into tool and structural.

The last of them is used for the construction of various buildings and frame parts. Tools are used to make durable tools for performing any work, including metal cutting. The use of metal products in the household required the classification of steel into different categories with specific properties: heat-resistant, cryogenic and corrosion-resistant.

According to the method of production, carbon steels are divided into:

• electric steel;
• open hearth;
• oxygen converter.

Differences in the structure of the alloy are due to the presence of different impurities characteristic of a particular smelting method.

The relationship of steel to chemically active environments has made it possible to divide products into:

• boiling;
• semi-calm;
• calm.

carbon divides steel into 3 categories:

1. hypereutectoid, in which the amount of carbon exceeds 0.8%;
2. eutectoid, with a content of 0.8%;
3. hypoeutectoid – less than 0.8%.

It is the structure that is a characteristic feature in determining the state of the metal. In hypoeutectoid steels, the structure consists of pearlite and ferrite. Eutectoid ones have pure pearlite, while hypereutectoid ones are characterized by pearlite with admixtures of secondary cementite.

By increasing the amount of carbon, steel increases strength and reduces ductility. The viscosity and brittleness of the material also have a great influence. As the percentage of carbon increases, the impact strength decreases and the fragility of the material increases. It is no coincidence that when the content is more than 2.4%, metal alloys are already classified as cast iron.

According to the amount of carbon in the alloy, steel is:

1. low carbon (up to 0.29%);
2. medium carbon (from 0.3 to 0.6%);
3. high carbon (more than 0.6%).

Marking

When designating carbon steels of ordinary quality, the letters St are used, which are accompanied by numbers characterizing the carbon content. One digit shows the quantity multiplied by 10, and two digits by 100. When guaranteeing the mechanical composition of the alloy, B is added before the designation, and compliance with the chemical constituents is B.

At the end of the marking, two letters indicate the degree of deoxidation: ps - semi-quiet, kp - boiling state of the alloys. For calm metals this indicator is not indicated. An increased amount of manganese in the structure of the product is designated by the letter G.

When designating high-quality carbon steels used in the manufacture of tools, the letter U is used, next to which a number is written confirming the percentage of carbon in a 10-fold amount, regardless of whether it is two-digit or single-digit. To highlight higher quality alloys, the letter A is added to the designation of tool steels.

Examples of designation of carbon steels: U8, U12A, St4kp, VSt3, St2G, BSt5ps.

Production

The metallurgical industry produces metal alloys. The specificity of the process for producing carbon steel is the processing of cast iron billets with the reduction of suspended matter such as sulfur and phosphorus, as well as carbon, to the required concentration. The differences in the oxidation technique by which carbon is removed allows us to distinguish different types of smelting.

Oxygen converter method

The basis of the technique was the Bessemer method, which involves blowing air through liquid cast iron. During this process, carbon is oxidized and removed from the alloy, after which the iron ingots gradually turn into steel.

The productivity of this technique is high, but sulfur and phosphorus remained in the metal. In addition, carbon steel is saturated with gases, including nitrogen.

This improves strength but reduces ductility, making the steel more prone to aging and high in non-metallic elements.

Given the low quality of steel produced by the Bessemer method, it was no longer used. It was replaced by the oxygen-converter method, the difference of which is the use of pure oxygen, instead of air, when purging liquid cast iron.

The use of certain technical conditions during purging significantly reduced the amount of nitrogen and other harmful impurities.

As a result, carbon steel produced by the oxygen-converter method is close in quality to alloys melted in open-hearth furnaces.

The technical and economic indicators of the converter method confirm the feasibility of such smelting and make it possible to replace outdated methods of steel production.

Open hearth method

A feature of the method for producing carbon steel is the burning of carbon from cast iron alloys not only with the help of air, but also by adding iron ores and rusty metal products. This process usually takes place inside furnaces, to which heated air and combustible gas are supplied.

The size of such melting baths is very large; they can hold up to 500 tons of molten metal. The temperature in such containers is maintained at 1700 ºC, and carbon burning occurs in several stages. First, due to excess oxygen in flammable gases, and when slag forms above the molten metal, through iron oxides. When they interact, slags of phosphates and silicates are formed, which are subsequently removed and the steel acquires the required quality properties.

Steel melting in open hearth furnaces takes about 7 hours. This allows you to adjust the desired composition of the alloy when adding different ores or scrap. Carbon steel has long been manufactured using this method. Such stoves, in our time, can be found in the countries of the former Soviet Union, as well as in India.

Steel: composition, properties, types and applications. Stainless steel composition

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.

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.

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://FB.ru/article/341012/stal-sostav-svoystva-vidyi-i-primenenie-sostav-nerjaveyuschey-stali

Steel structure. Chemical, mechanical and physical properties

“Iron is not only the basis of the whole world, the most important metal of the nature around us,

it is the basis of culture and industry, it is an instrument of war and peaceful labor.”

 A.E.Fersman

Everyone knows that steel is the most important tool and structural material for all industries.

The metallurgical industry of Ukraine has more than 50 metallurgical plants and is strategically important for the country. Ukraine produces a wide range of rolled metal products, such as: rebar, circles, squares, rods, wires, strips, angles, beams, channels, sheets, pipes and hardware.

Steel

Considering this issue, let's start with the chemical composition.

Steel is a compound of iron (Fe) + carbon (C) + other elements dissolved in iron.

Iron in its pure form has very low strength, and carbon increases it.

Carbon improves some other indicators:

• hardness,
• elasticity,
• wear resistance,
• endurance.

 “Fe” in steel should be at least 45%, “C” - no more than 2.14% - theoretically, but in practice the % carbon concentration has the following range of values:

• Low carbon steels - 0.1-0.13%
• Carbon steels 0.14-0.5%
• High carbon – from 0.6%

The higher the percentage of carbon content in steel, the higher its strength and the lower its ductility. CARBON is a non-metallic element. Its density is 2.22 g/cm3, and melts at t -3500 °C. In nature, it is present in 2 polymorphic modifications - graphite (stable modification) and diamond (metastable modification), and in an alloy with iron:

• in free - graphite (in gray cast iron),
• when bound, it is a solid state - cementite.

Carbon in combination with iron is in the state of cementite , i.e. in a chemical bond with iron (Fe3C). The structure of cementite can be very different, and it depends on the formation process, carbon content and heat treatment methods.

Carbon is present in a free state in gray cast iron (GC), in the form of graphite. Gray cast iron has a porous metal structure and is very brittle; Cracks easily appear on it (especially during the welding process).

Chemical composition of carbon steels of ordinary quality (GOST 380-71)

Iron-carbon system

The structure of steel is studied using the state diagram of the iron-carbon system. It characterizes the structural transformations of steel and expresses the dependence of the structural state on temperature conditions and chemical composition.

State diagram of the iron-carbon system

The phase diagram contains critical points that are very important theoretically and practically for steel heat treatment processes and their analysis. Using the Fe-C diagram, you can determine the type of heat treatment, the temperature range of structure changes and predict the microstructure.

Steel structures

Iron-carbon alloys at different temperatures and different “C” contents have different structures and, accordingly, physical and chemical properties. One of these conditions is the cementite described above. And now about them:

Austenite – a solid carbon structure in gamma iron – contains “C” up to 1.7% (t > 723° C). As the temperature decreases, austenite decomposes into ferrite and cementite, and a lamellar structure—pearlite—appears.

Ferrite is a solid solution of “C” in α-iron - at t> 723-768°C, the concentration of “C” is 0.02%, and at t 20°C about 0.006% “C”. It is very plastic, not hard and has low magnetic properties.

Cementite is iron carbide Fe3C. Concentration "C" 6.63%. Cementite is brittle and its hardness is HB760-800.

Pearlite is a mechanical mixture of ferrite and cementite, formed during gradual cooling during the decomposition of austenite. Based on the size of the cementite particles, perlite has different mechanical properties. "C" -0.8%.

Ledeburite (cast iron structure) is a mixture formed from the crystallization of a liquid alloy of cementite and austenite. Ledeburite is very hard, but brittle. Concentration "C" -4.3%

Properties of steel

Of course, it is not only carbon that affects the properties of steel. The composition of additional elements and their quantity impart certain properties to steel. Impurities can be beneficial or harmful. Good impurities affect exclusively the crystals themselves, while harmful impurities negatively affect the connection of crystals with each other. Good impurities include: manganese (Mn), silicon (Si). The bad ones: phosphorus (P), sulfur (S), nitrogen, oxygen and others.

Physical and mechanical properties of steel

The main physical properties of steel are:

• heat capacity;
• thermal conductivity;
• elastic modulus.
• The concept of elastic modulus of steel (E) is the ratio of a solid to deform elastically when subjected to a force. This characteristic directly depends on stress, or more precisely, it is a derivative of the ratio of stress to elastic deformation.
•  shear modulus (shear elasticity) (G) – a value measured in Pascals (Pa), which determines the elastic properties of a body or material and their ability to resist shear deformations. It is used to calculate shear, shear, and torsion.
•  coefficient of linear and coefficient of volumetric expansion with a change in temperature is a value showing the relative change in the linear dimensions or volume of a material or body with increasing temperature at a constant pressure.

The main mechanical properties of steel are:

• strength
• hardness
• plastic
• elasticity
• endurance
• viscosity

Indicators of mechanical properties of carbon steels of ordinary quality (GOST 380-71)

The main chemical properties of steel are:

•  oxidation state
•  corrosion resistance
•  heat resistance
•  heat resistance

The quality of steel is determined by various indicators of all its properties and structure. The properties of products made from this steel are also taken into account.

According to the quality of steel, they are divided into:

• ordinary quality,
• quality steel,
• high quality steel.

In this article we consider only the structure of steel and related concepts. The quality of steel, the composition of additional impurities and their properties will be discussed in the next publication.

Source: https://vikant.com.ua/news/chto_takoe_stal

Steel: types, properties, grades, production technology

Steel: types, properties, grades, production

Steel and products made from it have become so firmly established in the life and everyday life of modern people that it is difficult to imagine existence without metal objects. When it comes to dishes, small tools, household appliances and equipment, it is not at all necessary to know the brand, classification of alloys, and their areas of application.

This information is important, rather, for those who have decided to start building their own housing and do not know which metal products are suitable for these purposes. So, what steel is, what types of steel exist, and what properties this alloy, popular today, has, will be discussed in the construction magazine samastroyka.ru.

What is steel and its difference from cast iron

Iron-carbon alloy is the well-known steel. Typically, the proportion of carbon in the alloy varies from 0.1 to 2.14%. Increasing carbon concentration makes steel brittle. In addition to the main components, the alloy also contains small amounts of magnesium, manganese and silicon, as well as harmful sulfur and phosphorus impurities.

The basic properties of steel and cast iron are very similar. Despite this, there are significant differences between them:

• steel is a stronger and harder material than cast iron;
• cast iron, despite the deceptive massiveness of cast iron products, is a lighter material;
• Since steel contains a negligible percentage of carbon, it is easier to process. For cast iron, casting is preferable;
• products made of cast iron retain heat better due to the fact that its thermal conductivity is significantly lower than that of steel;
• hardening of the metal, which increases the strength of the material, is impossible with cast iron.

Advantages and disadvantages of steel alloys

Since there are a huge number of steel brands, and even more products made from it, it is pointless to talk about the pros and cons. Moreover, the properties of the metal largely depend on manufacturing and processing technologies.

As a result, we can only highlight a few general advantageous features of steel, such as:

• strength and hardness;
• viscosity and elasticity, that is, the ability not to deform and withstand shock, static and dynamic loads;
• accessibility for different processing methods;
• durability and increased wear resistance compared to other metals;
• availability of raw materials, cost-effectiveness of production technologies.

Unfortunately, there are also some disadvantages:

• instability to corrosion, including a high level of electrochemical corrosion;
• steel is a heavy metal;
• The manufacture of steel products is carried out in several stages; violation of technology at any of them leads to a decrease in quality.

Types and classifications of steel alloys

Today it is difficult to determine the number of steel alloys produced and used. It is also not easy to classify them, since their properties depend on many parameters, such as composition, nature and amount of additives, manufacturing and processing methods, purpose and many others.

Based on quality, it is customary to distinguish between ordinary, high-quality, high-quality and especially high-quality steels. The proportion of harmful impurities is the main criterion for determining the quality of the alloy. Ordinary steels are characterized by higher values ​​of the proportion of impurities than especially high-quality alloys.

Chemical composition of steel . The production of iron alloys is based on its ability to form different structural phases at different temperatures, the so-called polymorphism. Thanks to this ability, impurities dissolved in iron form alloys of various compositions. It is customary to divide steel alloys into carbon and alloy .

Steel, by definition, is an alloy of iron and carbon, the concentration of which determines its properties: hardness, strength, ductility, toughness. Carbon steel contains practically no additional additives.

Basic impurities - manganese, magnesium, and silicon are contained in minimal quantities and do not impair its properties and qualities. Silicon and manganese have a deoxidizing effect on the alloy, increasing elasticity, wear resistance, and heat resistance. But, in case of increasing the proportion, they are alloying elements. Steels with a high manganese content lose their magnetic properties.

Sulfur and phosphorus impurities are much more harmful for both types of steel. Sulfur, when combined with iron, increases brittleness when processed at high temperatures (rolling, forging), increases fatigue, and reduces corrosion resistance.

Phosphorus, especially with a large proportion of carbon in the alloy, increases its brittleness under normal temperature conditions. In addition, there is a whole group of hidden harmful impurities that cannot be removed during smelting. These non-metallic inclusions in the form of nitrogen, hydrogen and oxygen make the metal more friable during hot processing.

Types of Carbon Steel

Carbon steels are divided into types, which are characterized by the proportion of carbon content:

• high-carbon alloys include alloys with a share of more than 0.6%;
• in medium-carbon alloys, the carbon concentration ranges from 0.25 to 0.6%;
• permissible values ​​typical for low-carbon steels - no more than 0.25%.

Alloy steels are divided into:

— low-alloy, with the share of alloying additives no more than 2.5%;

— medium alloyed, with a share of additional elements up to 10%;

- highly alloyed, in which the share of alloying elements is more than 10%.

Alloy steels are characterized by a low carbon concentration and the presence of various alloying additives.

In accordance with their purpose, steels are divided into groups of structural, tool and special purpose steels.

Each group is divided into subgroups and types, which specify the properties, features and areas of application of alloys.

Structural steels include:

1. Construction materials, their main property is good weldability; these are low-alloy alloys of ordinary quality.
2. For cold stamping, rolled products from low-carbon alloys of ordinary quality are used.
3. Cementable, used in the manufacture of parts with surface abrasion.
4. High-strength ones are characterized by a double strength threshold relative to other structural types.
5. Spring steels with the addition of vanadium, bromine, silicon, chromium and manganese are designed to maintain elasticity for a long time.
6. Ball bearing steels with a large proportion of carbon and the addition of chromium, which are characterized by special wear resistance, strength and endurance.
7. Automatic, they contain impurities of sulfur, lead, tellurium and selenium, which facilitate the processing of metal by automatic machines on which mass parts are produced
8. Stainless steel, these include alloys with a high content of chromium and nickel. The carbon concentration in such alloys is minimal.

Types of tool steel

Tool steels come in several varieties:

• Used in the production of cutting tools, these include some types of carbon, alloy and high-speed steel.
• Measuring instruments are made from fairly hard alloys that are wear-resistant and have the ability to maintain constant dimensions; most often, hardened and cemented steel is used for this.
• Die steel is characterized by hardness, heat resistance and hardenability. This type is divided into subtypes, which include roll alloys and steels for multi-temperature processing.

Special-purpose steels include steel grades that are used in specific production areas:

• electrical steels - they are used to produce magnetic wires;
• superinvars - used in the production of high-precision instruments;
• heat-resistant - operate at temperatures above 900 °C;
• heat-resistant - can operate at high temperatures in loaded conditions.

Steel structure

The carbon concentration in the alloy determines not only the properties of the metal, but also its internal structure. For example, low- and medium-carbon alloys have a structure consisting of ferrite and pearlite. As the proportion of carbon increases, the formation of secondary cementite begins. Alloying steel also changes the structure of the alloy.

The structure of steel can be:

• pearlitic - with a low content of alloying additives;
• martensitic - steels with a reduced critical hardening rate and an average level of alloying impurities;
• austenitic - high-alloy alloys used in aggressive environments.

Annealed steels are divided into:

• hypoeutectoid steel, with a carbon concentration of less than 0.8%;
• hypereutectoid steel, consisting of pearlite and cementite, is used as a tool steel;
• carbide (ledeburite) - this includes high-speed steels;
• ferritic - high-alloy steel with low carbon content.

Steel manufacturing methods and technologies

The structure of this alloy, its composition and properties depend on the steel manufacturing technology. Conventional steels are produced in open hearth furnaces or converters. As a rule, they are saturated with a significant amount of non-metallic impurities.

High-quality alloys are produced using electric furnaces. Particularly high-quality alloy steels, containing a minimum amount of harmful impurities, are produced through the process of electroslag remelting.

In the production of steel, a deoxidation process is used to remove oxygen from the alloy structure. The amount of oxygen removed determines what kind of steel is obtained: slightly deoxidized, completely deoxidized, or semi-deoxidized. They are classified as boiling, calm and semi-calm.

Steel grades

Despite the fact that steel is clearly recognized as the most popular iron alloy, a unified system for marking its types has not yet been developed. The simplest and most popular is alphanumeric marking.

High-quality carbon steels are marked using the letter “U” and a two-digit numerical value (in hundredths%) of the level of carbon in their composition (U11). In the grade of ordinary carbon steels, the letter is followed by a number indicating the amount of carbon in tenths of% - U8.

Letters are also used in marking alloy steels. They indicate the main element used for alloying. The following figure shows the concentration of this element in the steel composition. The letter is preceded by a number corresponding to the proportion of carbon in the metal in hundredths of a percent.

For example, the letter “A” at the end of a high-quality alloy mark indicates its quality. The same letter in the middle of the mark notifies the main alloying element, in this case it is nitrogen. The letter at the beginning of the stamp indicates that this is automatic steel.

The letter “Ш” at the end of the marking, written through a hyphen, indicates that this is an especially high-quality alloy. High-quality steels are not marked with the letters “A” and “W”. In addition, there are additional markings indicating the special characteristics of steels. For example, magnetic alloys are marked with the letter “E”, and electrical alloys with the letter “E”.

Alphanumeric marking is perhaps one of the simplest and most understandable for the consumer. Others, more complex, are available only to specialists.

(4 5,00 out of 5)

Source: https://samastroyka.ru/stal.html

How to decipher steel grade

Steel, cast iron and alloys of non-ferrous metals are subject to mandatory marking. There are more than 1.5 thousand different types of steels and alloys made from them in the world.

Alloyed steels , unlike unalloyed steels, have a slightly different designation, since they contain elements that are specially introduced in certain quantities to ensure the required physical or mechanical properties. Eg:

• chromium (Cr) increases hardness and strength
• Nickel (Ni) provides corrosion resistance and increases hardenability
• Cobalt (Co) improves heat resistance and increases impact resistance
• Niobium (Nb) helps improve acid resistance and reduces corrosion in welded structures.

That is why it is customary to include in the names of alloy steels the chemical elements present in the composition and their percentage content. Chemical elements in such steel grades are designated by Russian letters given in the table.

X-chrome	A-nitrogen
C-silicon	N-nickel
D-copper	M-molybdenum
T-titanium	K-cobalt
B-tungsten	B-niobium
G-manganese	E-selenium
F-vanadium	C-zirconium
R-boron	U-aluminum

There is also a marking H , which tells us that the alloy contains rare earth metals, such as cerium, lanthanum, neodymium and others. Cerium (Ce) affects the strength and ductility of steel, and neodymium (Nd) and lanthanum (La) reduce porosity and sulfur content in steel and refine the grain.

An example of decoding steel grade 12Х18Н10Т

12Х18Н10Т is a popular austenitic steel, which is used in welding machines operating in dilute acid solutions, in solutions of alkalis and salts, as well as in parts operating under high pressure and in a wide temperature range. So, what do these mysterious symbols in the name mean, and how to combine them correctly?

The two numbers at the very beginning of the alloy steel grade are the average carbon content in hundredths of a percent. In our case, the carbon content is 0.12%. Sometimes, instead of two numbers, there is only one: it shows how much carbon (C) is contained in tenths of a percent. If there are no numbers at the beginning of the steel grade, this means that there is a fairly decent amount of carbon in it - from 1% and above.

The letter X and the number 18 following it indicate that this brand contains 18% chromium. Please note: the ratio of an element in fractions of a percent expresses only the first number at the beginning of the mark, and this only applies to carbon! All other numbers present in the name express the number of specific elements as a percentage.

Combination H10 follows. As you may have guessed, this is 10% nickel.

At the very end there is the letter T without any numbers. This means that the content of the element is too small to pay attention to. As a rule, about 1% (sometimes up to 1.5%). It turns out that in this grade of alloy steel the amount of titanium does not exceed 1.5%.

If suddenly at the very end of the brand you find a modestly standing letter A, remember that it plays a very important role: this means high-quality steel, the content of phosphorus and sulfur in which is kept to a minimum.

Two letters A at the very end (AA) indicate that this grade of steel is especially pure, i.e. there is practically no sulfur and phosphorus here.

In the course of a simple analysis of combinations of letters and numbers, we found out that the steel grade 12Х18Н10Т (structural cryogenic, austenitic class) reports the following information about itself: 0.12% carbon, 18% chromium (X), 10% nickel (N) and a small content titanium (T), not exceeding 1.5%.

At the beginning of the alloy steel grade there may also be additional designations:

R - high-speed;

Ш - ball bearing;

A - automatic (do not confuse with the letter A at the end of the name, which indicates the purity of the steel!);

E - electrical.

It is also worth noting some features of these subtypes of alloy steels:

1. in ball bearing steels, the chromium content is indicated in tenths of a percent (for example, ShKh4 steel contains 0.4% chromium);
2. in grades of high-speed steel, after the letter P there is immediately a number indicating the tungsten content as a percentage. Also, all high-speed steels contain 4% chromium (X).

To show the method of steel deoxidation, there are special letter designations: 

• sp - mild steel;
• ps - semi-quiet steel;
• kp - boiling steel.

Now let's take a closer look at how to decipher the grade of unalloyed steel , which is divided into ordinary and high-quality.

Ordinary unalloyed steel (St3, St3kp) has the letters St at the very beginning. This is followed by numbers indicating the carbon content in steel in tenths of a percent.

At the end there may be special indices: for example, St3kp steel belongs to the boiling category, as indicated by the letters kp at the very end. The absence of an index means that this steel is calm.

letters sv are added at the end . For example: St3st.

High-quality unalloyed steel (St10, St30, St20, St45) contains a two-digit number in the marking, indicating the average carbon content in the steel in hundredths of a percent. Thus, steel grade St10 contains 0.1% carbon; St30 has 0.3% carbon; St20 - 0.2%; St45 contains 0.45% carbon.

Structural low-alloy steel 09G2S contains the following chemical elements: 0.09% carbon, 2% manganese and a small amount of silicon (approximately 1%).

Steels 10KhSND and 15KhSND differ only in different carbon content: 0.1% and 0.15%, respectively. There is very little chromium (X), silicon (C), nickel (H) and copper (D) here (up to 1-1.5%), so numbers are not placed after the letter.

High-quality steels are used for the production of steam boilers and high-pressure vessels. Their markings have the letter K at the end: 20K, 30K, 22K.

If the steel is structural casting , then the letter L is placed at the end of the marking. For example: 40ХЛ, 35ХЛ.

Non-alloy tool steels are designated by the letter U. This is followed by a number expressing the average carbon content in the steel: U10, U7, U8. If the steel is also high-quality, this is also noted in the marking: U8A, U10A, U12A. If it is necessary to emphasize the increased manganese content, an additional letter G is used. For example, there are U8GA and U10GA steels.

Tool alloy steels have the same designation as structural alloy steels. For example, the HVG brand indicates the presence of three main alloying elements: chromium (X), tungsten (B) and manganese (G). There is approximately 1% carbon here, and therefore the number is not written at the beginning of the stamp. Another type of steel, 9KhVG, has a lower carbon content compared to KhVG: here there is 0.9% carbon.

High-speed steels are marked with the letter P, followed by the tungsten content in %. steel R6M5F3 as an example . It is high-speed (P), contains 6% tungsten, 5% molybdenum (M) and 3% vanadium (F).

Unalloyed electrical steel (ARMCO) has a very low electrical resistivity. This is achieved due to the minimal amount of carbon in the composition (less than 0.04%). Such steel is also commonly called technically pure iron . The marking of electrical non-alloy steels consists only of numbers. For example: 10880, 21880, etc.

Each number contains important information. The very first digit shows the type of processing: 1 - forged or hot-rolled; 2 - calibrated. The second digit indicates the presence/absence of a normalized aging coefficient: 0 - without a coefficient; 1 - with a coefficient. The third digit is the group according to the main standardized characteristic.

The last two are associated with the values ​​of the main standardized characteristic.

Structural steel is marked with the letter C, followed by the minimum yield strength of the steel. Additional designations are also used: K - increased corrosion resistance (S390K, S375K); T - heat-strengthened rolled products (S345T, S390T); D - increased copper content (S345D, S375D).

Aluminum casting alloys are designated by the letters AL at the beginning of the marking. Here are some examples: AL4, AL19, AL27.

Aluminum alloys for forging and stamping contain the letters AK, and then the conditional number of this alloy: AK6, AK5.

There are also wrought alloys containing aluminum . Avial alloy: AB, aluminum-magnesium alloy: AMg; aluminum-manganese alloy: AMts.

Now you have learned how to decipher the grade of steel containing various chemical elements. This steel marking was developed back in the USSR and is still in effect not only in the Russian Federation, but also in the CIS countries.

European steel markings are subject to the EN 100 27 standard. Japan and the United States have their own standards. There is currently no single world classification of steels.

Understanding the general rules for designating grades of unalloyed and alloyed steels, as well as by correctly deciphering steel grades, you can easily determine what kind of steel a particular part is made of.

Competent employees of the UralTeploMontazh plant will help you determine the required grade of steel that can withstand the required pressure and specified temperature conditions.

We always have in stock (or on order) steel fittings for pipelines, bent elbows and other pipeline fittings made of various grades of steel.

Source: http://uraltm08.ru/stati/kak-rasshifrovat-marku-stali.html