By chemical composition distinguish carbonistic and alloyed become

Carbon steel are iron alloys with carbon containing up to 2.14% carbon (C) with a small content of other elements. They have high plasticity and well deformed. Carbon strongly affects the properties of steel even with a minor change in its content. Carbon steel can be classified by several parameters:

• By quality

According to the method of deoxidation

By quality

Ordinary quality steel

Made according to GOST 380-71. Denote by letters of art and conventional numbers from 0 to 6, for example: Art 0, Article 1, ..., Article 6. The degree of deoxidation is denoted by the letters of the joint venture (calm steel), PS (semi-calm), KP (boiling) that put At the end of the mark mark.

Depending on the purpose, three groups of steel of ordinary quality distinguish: A, B and V. in the brands indicate only groups B and B, group, and do not indicate.

• Group A is supplied only by mechanical properties, the chemical composition of the steels of this group is not regulated, it is only indicated in the certificates of the manufacturer. The steel of this group is commonly used in products in the state of supply without pressure and welding. The greater the digit of the conditional number of steel, the higher its strength and less placot.
• The group B is supplied only with a guaranteed chemical composition. The greater the digit of the conditional number of steel, the higher the carbon content. These steel may further undergo deformation (forging, stamping, etc.), and in some cases and thermal processing. At the same time, their initial structure and mechanical properties are not saved. Knowledge of the chemical composition of steel allows you to determine the temperature of hot pressure and heat treatment.
• The group in may be welding. They are supplied with guaranteed chemical composition and guaranteed properties. The steel of this group are marked with the letter in and digit, for example - in the STZPS. This steel has mechanical properties corresponding to its number A group A, and the chemical composition - the number of group B with a correction by the method of deoxidation.

High-quality carbon steel

This class of carbon steels is manufactured according to GOST 1050-74. Qualitative steel supply both chemical composition and mechanical properties .. These are presented to more stringent requirements for the content of harmful impurities (sulfur no more than 0.04%, phosphorus not more than 0.035%), non-metallic inclination and gases, macro- and microstructure.

High-quality carbon-dystone steel is marked with double digits 08, 10, 15, ..., 85, indicating the average carbon content in hundredths of the pro-cents indicating the degree of dedication (KP, PS).

Quality steel is divided into two groups: with the usual content of manganese (up to 0.8%) and with high content (up to 1.2%). In the designation of the latter at the end of the brand, the letter G is put, for example, 60 g. The manganese increases the calcination and strength properties, but slightly reduces the plasticity and viscosity of steel.

With the designation of boiling or semi-luminous steel at the end of the brand, the degree of dedication is indicated: KP, PS. In the case of calm, the deck of deoxidices is not specified.

By carbon content High-quality carbonaceous steel are divided:

• low carbon (up to 0.25% C),
• medium carbon (0.3-0.55% C)
• high carbon (0.6-0.85% C).

For responsible purposes, high-quality steel with even lower sulfur and phosphosis content are used. The low content of harmful impurities in high-quality steels further increases the costs and complicates their production. Therefore, usually high-quality steel are not carbon, but alloyed steel. With the designation of high-quality steels at the end of the brand, the letter A is added, for example Steel U10A.

Carbon steel, containing 0.7-1.3% C, are used for the manufacture of a shock and cutting tool. Their brands are y7, y13, where u means carbon steel, and the digit is the carbon content in the tenths of the percentage.

According to the method of deoxidation

Boiling
It contains up to 0.05% of silicon, are torn by manganese. Have sharply pronounced chemical heterogeneity in the ingot. Their advantages are a high yield of a suitable product (more than 95%), good ability to stamping in cold condition. The disadvantages of the self-well threshold of the cooler and the impossibility of widespread use for the cold climate territories.

Semidious
It contains 0.05-0.15% of silicon, are deoxidized by manganese and aluminum, the yield of the suitable product is 90-95%.

Calm
Contains 0.15-0.35% silicon, is deoxidized with silicon, manganese and aluminum. The yield of suitable is about 85%, however, the metal has more dense structures and a homogeneous chemical composition.

By Method of smelting Steel divide on Marten, converters, electrostals and steel obtained by special methods of smelting.

By Structure Steel is divided into pearlit, austenitic, ferritic and carbide.

By Appointment Distinguished steel structural, instrumental and steel with special properties. From structural steels, columns, farms, bridges, machine parts, etc., from instrumental - various tools: cutting (cutters, drills, cutters, chisel, etc.), stamped (stamps for cold and hot stamping) and measuring ( Schunciters, micrometers, rules, caliber, etc.). Steel with special properties include heat-resistant, loan, stainless (corrosion-resistant) and steel with special physical properties: magnetic (magnetically solid and magnetic), with high electrical resistance, with special thermal and elastic properties.

By Quality Steels are divided into ordinary quality, high-quality, high-quality and high-quality. The quality of the steel is determined by the content of harmful impurities (sulfur and phosphorus), non-metallic inclusions, etc. For example, the sulfur content is allowed in the steel of ordinary quality. 0,05 , phosphorus 0,04 , high-quality - respectively 0,03 and 0,035 and high quality - 0,02 and 0,03 %.

By degree of deoxidation Steel are made boiling, calm and semidal.

In accordance with the GROST, the following main types of carbon steels are paid: low carbon (less than 0.3% C), medium carbon (0.3-0.7% C) and high carbon (more than 0.7% C); By appointment: on structural ordinary quality and high-quality (including cement, improved, high-strength and spring-spring), instrumental for cutting and measuring instrument, as well as cold stamps (less than 200 ° C) and hot pressing.

Steel carbon-free common quality structural is smelted according to GOST 380-85 and is supplied to the consumer in the form of rods, sheets and other rental profiles. Depending on the purpose and the characteristics guaranteed by the metallurgical plant, the steel is divided into three groups: a, b, in, which, in turn, are divided into categories.

Steel group A comes on mechanical properties and the following brands are manufactured: St0, St1 KP (SP), ST2 KP (PS and SP), ST3 KP (PS, GPS, GSP), ST4 KP (PS), ST5 PS, ST6SP (PS ).

Steel group B is supplied according to the guaranteed chemical composition and manufactures the following marks: BST0, BST1, BST2, BST3, BST4, BST5, BST6.

The steel of the group B is supplied according to the guaranteed mechanical properties and chemical composition and is manufactured by the following marks: Easy, Esset, Escap, Install, Escint.

Knowledge of the chemical composition is necessary in the case when the steel from the consumer is subjected to hot stamping, and the parts made from it are thermal processing, since the heating temperature is selected depending on the carbon content in steel.

According to the degree of deoxidation, steel of all groups with numbers 1, 2, 3, 4 is made boiling, calm and semi-luminous, and with numbers 5 and 6 - only calm and semi-luminous. Steel CT0 and BST0 according to the degree of deoxidation are not separated. Steel Marks Es1, Esset, Esk3 of all decks of deoxidation comes with a welding guarantee.

Decoding brands:

a) the letters b and in in front of the letters of the ST - steel group; Group A does not indicate, for example, ST3, BST3, EST3;

b) the letters of st - steel, numbers, from 0 to 6 - the conditional number of the brand; With an increase in the room grows the carbon content in steel and its strength. For example, in Steel St3 and St5, the carbon content is respectively: 0.14-0.22 and 0.23-0.37%; The temporal resistance σ in: 380-490 (38-49) and 560-640 (56-64) MPa (kgf / mm 2);

c) letters added after the brand number - degree of deoxidation: KP - boiling, ps - semi-luminous, sp - calm, such as ST3KP;

d) letter G is an increased maintenance of manganese (ST3GPS, ESTA3GSP);

Steel quality construction The chemical composition and the mechanical properties of the following brands are supplied: 08, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60. Mark means the average content ( mass share) Carbon in hundredths of interest. In addition to the specified, steel grades are supplied 05 and 58 (55 PP - steel decreased calcination).

By deadscence Steel are smelted: boiling (KP) - 05 kp, 08 kp, 10 kp, 15 kp, 20 kp; semi-grams (PS) - 08 ps, 10 ps, \u200b\u200b15 ps, 20 ps (sheet steel for cold stamping); Calm (SP) - 08, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60 (the joint venture in the brand is not placed).

By state Steel is manufactured without heat treatment, thermally treated T (annealed, high-pressure or normalized) and garting H (calibrated, silver).

By appointment The subgroups of steel are distinguished: a - for hot pressure processing; b - for cold machining (sharpening, milling, rigs, etc.); B - for cold drawing.

Sproughts and springs are made of steels smelted according to GOST 14959-79 (steel spring-spring carbon and alloy). Carbonaceous spring-spring steel is supplied in the form of rods of round, square and profile, strips and sweating of the following marks: 65, 70, 75, 80 and 85.

Steel Tool carbongOST 1435-90 is smelted, it is supplied for chemical composition and mechanical properties (hardness). For chemical composition, steel is divided into high-quality and high quality. Qualitative steel contains harmful sulfur impurities no more than 0.03 and phosphorus 0.035%. In high-quality steels - sulfur no more than 0.02% and phosphorus 0.03%, less than in high-quality steels of non-metallic inclusions, as well as the limits of content, silicon and manganese are more narrowed. Steel comes in annealed state hardness NV. 187-217. Hardness after quenching HRC. 62.

Stami brands: high-quality - U7, U8, U9, U10, U11, U12, U13; High quality - u7a, u8a, u9a, u10a, u11a, u12a, u13a. We also produced steel with an increased content of manganese grades U8g and U8Ga, in which the content of manganese is in the range of 0.35-0.60%.

In the designation of the brand of the letter, it means carbonaceous instrumental steel, the numbers are the average massage of carbon in the tenths of the percentage, the letter A is steel high quality, the letter G is an increased manganese content.

Chisel, hammers, screwdrivers, lathe centers (U7, U7a);

Punches, matrices, scissors, saws (U8, U8A);

Cores, woodworking tools (U9, U9a);

Cutters, taps, sweep, cutters (U10, U10A);

Stamps cutting down, saws, molds (U11, U11A);

Cutters, drills, cutters, taps (U12, U13, U13A).

Steel automatic GOST 1414-75 of the following marks: A11, A12, A20, A30, A35E, A40G. Steel contain harmful additives of sulfur 0.08-0.25 and phosphorus 0.06-0.15%. Lead (up to 0.3%), manganese (up to 1.5%) and selenium (up to 0.1%) (AC14, AC35G and A35E) are injected into the steel to improve the machinability.

Application area:

Fasteners (bolts, nuts);

Sleeves, rollers, engine parts.

Foundry steel GOST 977-79 The following marks: 15l, 20l, ..., 55l.

Alloy steel, their types and brands

Alloy steel differ from carbon steels:

Increased heat resistance, corrosion resistance;

Significant shock viscosity;

High values \u200b\u200bof σ t and γ;

High electrical resistivity;

Possess the best calcination;

Increase the amount of residual austenite.

In the FE state diagram, the doping element Ni and Mn - expand the region of the existence of the γ-phase; MO, TI - narrow the region of the existence of the γ-phase; Si, Al, W, Sn, Mo and Ti are expanding the region of the α-phase. The main alloying elements in steel are CR, Ni, Si, Mn. Nickel - increases the plasticity and viscosity of steel; Reduces the temperature of the threshold of the coolant; Reduces steel sensitivity to voltage concentration. Chrome increases heat resistance and corrosion resistance of steel; increases electrical resistance; reduces linear expansion coefficient; increases the calcination of steel; slows down the collapse of Martensita. Silicon increases the heat resistance of steel; makes it difficult for the formation and growth of cement particles; Used as a deoxidizer when weaving steel.

W, Mo, V, Ti, B - additionally improve steel properties. Mo and W - increase the calcination of steel (+ ni); promote grain chopping; Suppress the selling fragility of steel.

V, Ti, Ni, Zr - form the carbides employed in austenite; (up to 0.15%) grind grains; Reduce the threshold of colder.

AT - increases the strength and calcination of steel (0.001-0.005%).

The efficiency of alloyed elements is achieved with their optimal content in steel.

Alloy steel classified:

By the type of equilibrium structure;

Structure after normalization;

Chemical composition;

Appointment.

Alloy steel belongs: to dashtectoid (ferrite + doped perlite); zaletetoid (doped perlite + carbides); euteteidoid.

Separed steel for 3 main classes:

Pearlit (sorbitol, cane and bainite);

Martensitic (in alloyed);

Austenitic (in high-alloyed).

Alloyed steel are divided:

By chemical composition: on chromium; manganese; chromonicel; chromonicelmolybdenum, etc.;

By the total number of alloying elements in them: on low alloyed (up to 2.5%); alloyed (2.5-10%); high-alloyed (over 10%);

By appointment: on structural (cement, improved); instrumental; with special properties ("automatic" spring, ball bearings, wear-resistant, corrosion-resistant, heat-resistant, heat-resistant, electrical and other steel).

Marking of alloyed steels: A - Nitrogen, B - Niobium, Volfram, Mr. - Marganese, D - Copper, E - Selen, T - Titan, K - Cobalt, N - Nickel, M - Molybdenum, P - Phosphorus, R - Bor, C - Silicon, F - Vanadium, X - Chrome, C - Zirconia, Ch - Rare-earth, Yu - Aluminum.

Machine-building cemented Improved steel contain 0.1-0.3% carbon and 0.2 - 4.4% of alloying elements. After saturation by carbon, quenching and low vacation, the part of these steels have a high surface hardness (up to 58-63 HRC.) When viscating central part. 15khf, 15x, 20x (with the yield strength up to 700 MPa) are used to manufacture small loaded parts experiencing the average largest alternate and shock loads.

Steel 12HNZA, 20HNZ, 20HN4A (with the yield strength of more than 700 MPa) are used to make parts of medium and large sizes operating under intensive wear conditions, with elevated loads. Particularly responsible details, for example, gear wheels of aviation and ship engines, are made from steel 18x2n4m, 18x2n4w. Economically doped steel 18HGT, 30HG, 25HGT have a hereditary fine-grained structure, which reduces the technological cycle of the processing of the part. Such steel is used to manufacture responsible parts of large-scale and mass production.

Machine-building improvements Alloy steel contains 0.3-0.5% of carbon and up to 5% of alloying elements. Used primarily after improvement (hardening and high vacation at a temperature of 500 - 600 ° C for sorbitals). Basic use - Responsible parts of machines operated when exposed to cyclic or shock loads. For the manufacture of medium-wide small parts of machines and mechanisms without significant dynamic loads, chromium steel 30x, 38x, 40x, 50x are used.

With increasing carbon content, the strength of these steels is increasing, but their viscosity and plasticity decreases somewhat. From chromonichel steels 40HN, 50HN, as well as from chromocremmerganic steels of 30xgs, 35xgss, which have high strength and viscous properties, make responsible parts operating when exposed to dynamic loads.

Chromonicelmolybdenum steel 40HNMA, 38xmmism has increased mechanical properties at temperatures up to 450 ° C.

Martensit-solid high-strength steel (With a strength of 1800-2000 MPa) - carbon black (no more than 0.03% c) iron alloys with nickel doped with cobalt, molybdenum, titanium and other elements. High mechanical properties of Hi8K9M5T steels, H12KI5M10 are achieved by combining martensitic G ® A-transform, aging of martensite and doping of a solid solution. These steel retain high mechanical characteristics at low temperatures up to the temperatures of liquefied gases. Such steel heat resistant to temperatures 500 - 700 ° C. Find application for responsible parts in aviation, shipbuilding.

Wear-resistant structural steel They have high resistance of contact fatigue and abrasion due to high hardness, homogeneity of the structure, the minimum content of non-metallic inclusions and metallurgical defects. Heat processing (hardening and low vacation) Steel Shx15GS provides their hardness HRC. 60-66. For parts operating in aggressive media (seawater, weak solutions of acids, alkalis), apply corrosion-resistant high carbon steel 95x18.

Details operated when exposed to shock loads causing their surface slope, and consequently, a decrease in the wear resistance of conventional steels, made from austenitic high-headed steel G13l. For the manufacture of parts operated under gliding friction conditions, a graphitized steel, having a structure of ferrithic cement mixture and graphite, is used. The latter plays the role of lubricant, preventing the capture of contacting parts.

Corrosion-resistant steel and alloys Resistant to corrosion in air, in water (incl. marine), in a number of acids, salts and alkalis. From chromium steels x25t, x28, having a ferritic structure, made parts operated in highly aggressive media, for example in boiling nitric acid. Chromonichel steel 04х18Н10, 08Х18Н10, 12х12Н10Т, having austenitic structure, are used in aviation and shipbuilding.

Heat resistant steel and alloys ensure the operation of parts at a temperature of over 500 ° C. For parts operated in an environment with a temperature of 500 - 580 ° C, low carbon steel, having a structure of a plate perlite, doped with cobalt, molybdenum, vanadium, in particular 16m, 25xm, 12x1mf. Loaded parts operated in a temperature with a temperature of up to 450-470 ° C are made from high-chromium steels 15x11nmf, 1xcvnmf, depending on the tempering temperature of sorbitol or trotostite.

Carbon steel due to accessible cost and high strength characteristics refers to widespread alloys. Of these steels consisting of iron and carbon and a minimum of other impurities, various engineering products are manufactured, the parts of the cocov and pipelines, tools. Wide use these alloys are found in the construction sector.

What is carbon steel

Carbon steel, which, depending on the main scope of use, are divided into structural and instrumental, practically do not contain alloying additives. These steel from ordinary steel alloys also distinguishes the fact that they contain a significantly smaller number of such basic impurities such as manganese, magnesium and silicon.

The content of the main element - carbon - in the stories of this category may vary in fairly wide limits. Thus, high carbon steel contains in its composition 0.6-2% of carbon, medium carbon steel - 0.3-0.6%, low carbon - 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% of carbon containing in its composition consists mainly of ferrite and perlite, with an increase in carbon concentration begins to form secondary cementitis.

Carbon steel with a predominant ferrite structure are distinguished by high plasticity and low strength. If cementitis prevails in the structure, it is characterized by high strength, but at the same time it is very fragile. With an increase in the amount of carbon to 0.8-1%, the strength characteristics and hardness of carbon steel increase, but its plasticity and viscosity deteriorate significantly.

The quantitative carbon content also has a serious effect on the technological characteristics of the metal, in particular on its weldability, ease of pressure and cutting processing. From steels related to the category of low carbon, make parts and structures that will not be subjected to significant loads during operation. The characteristics with which the average carbon steel possess them make them the main structural material used in the production of structures and parts for the needs of the general and transport engineering. Thanks to its characteristics, it is optimally suitable for the manufacture of parts to which increased wear resistance requirements are presented, for the production of shock-stamp and measuring instruments.

Carbon steel, as well as a steel alloy of any other category, contains in its composition 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 steel at the stage of its smelting in order to ensure its deoxidation. Sulfur and phosphorus are harmful impurities that worsen the qualitative characteristics of the steel alloy.

Although it is believed to be incompatible to improve their physicomechanical and technological characteristics, microlation can be performed. To do this, various additives are introduced into the carbon steel: boron, titanium, zirconium, rare earth elements. Of course, with the help of such additives it will not be possible to make a carbon steel with a carbon steel, but it can be noticeably improved by the properties of the metal.

Classification for degree of dedication

The separation of carbon steels on various types has an influence, including such a parameter as a degree of deoxidation. Depending on this parameter, carbon steel alloys are divided into calm, semi-luminous and boiling.

A more uniform internal structure is distinguished by calm steel, the deoxidation of which is carried out by adding to the molten metal of ferrosilica, ferromargana and aluminum. Due to the fact that alloys of this category were completely deoxidized in the furnace, they do not contain iron zaksi. Residual aluminum, which prevents grain growth, emphasizes such a fine-grained structure. The combination of fine-grained structure and almost complete absence of dissolved gases allows the formation of high-quality metal from which the most responsible parts and structures can be made. Along with all its advantages, carbon steel alloys of a calm category have one significant drawback - their milking is quite expensive.

Cheapening, but less qualitative are boiling carbon alloys, when smelting, which uses the minimum number of special additives. In the internal structure, this was due to the fact that the process of its deoxidation in the furnace was not communicated to the end, there are dissolved gases that are negatively reflected on the characteristics of the metal. Thus, the nitrogen contained in the composition of these steels does not affect their weldability, provoking cracking in the weld area. Developed liquor in the structure of these steel alloys leads to the fact that the metal rolling, which is manufactured from them, has inhomogeneity of both its structure and mechanically characteristics.

Intermediate position and in its properties, and in the degree of deoxidation occupy semi-luminous steel. In front of the fill in the mold, there is a small amount of deoxidial in their composition, thanks to which the metal solidifies almost without boiling, but the gas selection process in it continues. As a result, casting is formed, in the structure of which contains fewer gas bubbles than in boiling steels. Such internal pores in the process of subsequent metal rolling are almost completely brewed. Most of the semi-deval carbon steels are used as structural materials.

You can familiarize yourself with all the requirements of GOST to carbon steel by downloading this document in PDF format on the link below.

Methods of production and separation in quality

For the production of carbon steels, various technologies are used, which affects their separation not only by the method of production, but also by quality characteristics. So, distinguish:

• high quality steel alloys;
• carbon steel alloys of ordinary quality.

Steel alloys possessing ordinary quality are paid in the Marten furnaces, after which the ingots of large sizes are formed. Melting equipment, which is used to obtain such steels, also includes oxygen converters. Compared to high-quality steel alloys, the steels considered may have a greater content of harmful impurities, which affects the cost of their production, as well as on their characteristics.

The formed and fully frozen metal ingots are subjected to further rolling, which can be performed in hot or cold condition. The hot rolling method is made of shaped and variety products, thick and thin metal metal, metal strips of a large width. Using rolling performed in a cold condition, a thin-sheet metal is obtained.

For high-quality and high-quality categories, both converters and marten furnaces can be used and more modern equipment - melting furnaces operating on electricity. To the chemical composition of such steels, the presence in their structure of harmful and non-metallic impurities the corresponding GOST presents very stringent requirements. For example, in steels, which relate to the category of high-quality, must contain no more than 0.04% sulfur and not more than 0.035% phosphorus. High-quality and high-quality steel alloys due to the strict requirements for the method of their production and characteristics are distinguished by the increased cleanliness of the structure.

Application area

As mentioned above, carbon steel alloys in the main purpose divide into two large categories: instrumental and structural. containing 0.65-1.32% of carbon are used in full compliance with their name - for the production of a tool for various purposes. In order to improve the mechanical properties of the tools, refer to such a technological operation, as which is performed without special difficulties.

Structural steel alloys are used in the modern industry very wide. Of these, they make parts for equipment for various purposes, elements of engineering and construction designs, fasteners and much more. In particular, such a popular product, as a carbon wire, is made precisely from steel structural type.

A carbon wire is used not only for domestic purposes, for the production of fasteners and in the construction sphere, but also for the manufacture of such responsible parts as springs. After completion of cementation, structural carbon alloys can be successfully used for the production of parts, which during operation are subjected to serious surface wear and test significant dynamic loads.

Of course, carbon steel alloys do not possess many properties of alloyed steels (in particular, the same stainless steel), but their characteristics are quite enough to ensure the quality and reliability of parts and structures that are manufactured from them.

Marking features

The rules for the compilation of which are strictly stipulated by paragraphs of the corresponding GOST, makes it possible to learn not only the chemical composition of the alloy represented, but also what category it refers. In the designation of carbon steel, possessing ordinary quality, there are letters "Art". GOST points are stipulated by seven conventional marks of stamps of such steels (from 0 to 6), which are also indicated in their designation. To learn what degree of deoxidation corresponds to the same brand, it is possible by the letters "KP", "PS", "SP", which are affixed at the very end of the labeling.

Contains a small amount of manganese (Mn), silicon (Si), sulfur (S) and phosphorus (P).

Steel divided:

• in purpose - on structural and instrumental;
• according to the method of production - on the Martenovskiy, paid in Marten furnaces; Bessemer, obtained in converters having a lining of acidic materials; Thomasovskaya, obtained in converters with a lining of the main materials, and the electric power plant paid in arc or induction high-frequency furnaces;
• by chemical composition - on carbon and alloyed.

Alloyed steel In addition to carbon, there is an increased amount of manganese (Mn), silicon (Si), chrome (CR), nickel (Ni), molybdenum (MO), tungsten (W), Vanadium (V) and other elements that give these steels special properties, For example, increased strength and hardness, corrosion resistance.

For the manufacture of welded structures, a carbon steel of ordinary quality, supplied according to GOST 380, was obtained by carbon-free solid quality, depending on the destination, is divided into three groups:

• group A - supplied by mechanical properties;
• group B - supplied by chemical composition;
• group B - supplied by mechanical properties and chemical composition.

Depending on the normalized indicators:

• steel groups A are divided into three categories - Al, A2, A3;
• steel groups B - into two categories - B1 and B2;
• steel groups in six categories - BL, B2, VZ, B4, B5, B6.

For steel groups, the stamps of St0, ST1, ST2, ST4, ST5, ST6 are installed. For steel bands B - brand BST0, BST1, BST2, BSTZ, BST4, BST5, BST6. Steel group in manufactured by Marten and converter ways. For her, Installation Marks are installed, Escap, Escap, Escint. The letters of ST denotes steel, numbers from 0 to 6 - the conditional range of the steel grade depending on the chemical composition and mechanical properties. The letters B and in before the designation of the brand indicate the group of steel, the group A in the designation is not specified. If the steel refers to boiling, the index "KP" is set, if to a semide-"PS" and calm - "SP".

By types of rolled steel, steel is leaf, broadband, varietal (strip, round, etc.), shaped (channel, corner, 2-way). The reinforcement steel, depending on the manufacturing technology, is divided into rod and wire fittings, and depending on the profile - on the smooth and periodic profile. High-quality carbonistic structural steel are used for the manufacture of responsible welded structures.

Qualitative Steel According to GOST 1050-88, label two-digit numbers denoting the average carbon content in hundredths of interest. For example, grade 10, 15, 20, etc. mean that steel contains an average of 0.10, 0.15, 0.20% carbon.

Steel according to GOST 1050-88 produce two groups:

• group I-with normal content Mn (0.25-0.80%);
• group II - with an increased content of Mn (0.70-1.2%). With an elevated manganese content (Mn), the letter r was additionally introduced into the designation, indicating that the steel has an increased content of Mn.

Alloyed steel In addition to conventional impurities, it is elements specifically entered in certain quantities to provide the required properties. These elements are called alloying. Alloyed steel are divided depending on the content of alloying elements on low-alloyed (up to 2.5% of alloying elements), single-deregulated (from 2.5 to 10%) and high-alloyed (over 10%). Alloyed steel marked with numbers and letters indicating the approximate composition of steel. The letter shows what is included in the steel, and the numbers standing behind it are the average content of the element in percent. If the item is contained less than 1%, then the figures are not set per letter. The first two digits indicate the average carbon content in hundredths of interest.

The effect of the main elements on the properties of carbon steels

• low carbon containing from 0.05 to 0.25% C;
• medium carbon - from 0.25 to 0.6% C and
• high carbon - Over 0.6% C.

With an increase in carbon content, the tensile strength, hardness and fragility increases while reducing relative elongation and shock viscosity. The carbon content in conventional structural steels within up to 0.25% does not worsens the weldability of steel. At a higher carbon content, steel is deteriorated, since in the heat influence zones, quenching structures are formed, leading to cracks. Increased carbon content in the additive metal causes the porosity of the seam.

Manganese It is contained in steel in the range of 0.3-0.8%, in the specified limits of the manganese (Mn) does not complicate the welding process. In welding of middle-average steel with a content of 1.8-2.5% Mn, there is a risk of appearance due to the fact that the manganese (Mn) promotes steel hardening.

Silicon It is contained in low and medium carbon steel in the range of 0.02-0.35%, in the specified limits it does not cause difficulties during welding. With a silicon content (Si) in special steels from 0.8 to 1.5%, it is difficult due to the high liquid process of silicon steel and the formation of refractory silicon oxides (Si).

Sulfur It is harmful impurity in steel. It forms a chemical iron called sulfur iron. Steel with an admixture S gives a heated state, that is, it becomes a rug. The content of S in steel should not exceed 0.055%. The weldability of steel with an increase in the content of S is deteriorating sharply.

Phosphorus Also harmful impurity in steel. The p in steel should not exceed 0.05%, it forms a chemical compound with iron - phosphorous iron. Phosphorus increases the hardness and fragility of steel, causes a coolness, i.e. the appearance of cracks in the cold state.

Vanadium In alloyed steel, it is contained in the range of 0.2-0.8%. It contributes to the hardening of steel, which makes it difficult for welding. In the process of welding V actively oxidized and burns out.

Tungsten In alloyed steel, it is from 0.8 to 18%. W increases the hardness of steel and makes it difficult to make the welding process, as it is strongly oxidized.

Nickel In low carbon steel, it is contained in the range of 0.2-0.3%, in construction - from 1 to 5% and alloyed - from 8 to 35%. In steel nickel (Ni) increases plastic and strength properties, weldability does not worsen.

Molybdenum It is limited to the content in steel from 0.15 to 0.8%. When welding molybdenum (MO) contributes to the formation of cracks, is actively oxidized and fuses.

Chromium In low carbon steel, it is contained within up to 0.3% of the structural - 0.7-3.5%, alloyed chromium steels - 12-18% and chromonichel - 9-35%. CR makes it difficult for welding, as in the process of welding, refractory chromium forms.

Titanium and Niobi In high-alloy chromium and chromonichel steels during welding, connected with C, preventing the formation of chromium carbides. This titanium (TI) and Niobium (NB) improves the weldability.

Copper in steels contained in the range of 0.3-0.8%; C improves weldability, increases the strength, plastic properties and corrosion resistance of steel.

Oxygen It is contained in stools in the form of iron oxide, which dissolves in pure molten gland in an amount of up to 0.5, which corresponds to the content of 0.22% O 2. The solubility of iron oxide in steel is reduced with an increase in the content of C. worsens the weldability of steel, reduces its strength and plastic properties.

Nitrogen dissolves in molten metal, falling into an ambient air welding bath. When cooling the welding bath, N 2 forms chemical compounds with iron (nitrides), which increase the strength and hardness and significantly reduce steel.

Hydrogen - harmful impurity in steel, accumulates in separate places of the welding seam, when welding causes the appearance of small cracks.

Carbon steel - illegal structural or tool steel containing less than 2, 14% carbon. Carbonaceous steel is classified according to the structure, the method of production and deoxidation, in quality. According to the structure, carbon steel can be deetectoid (contains up to 0, 8% carbon, the structure consists of ferrite and perlite), eutectoid (contains about 0, 8% carbon, the structure consists only of pearlitis), the extender, (contains 0, 8-2 , 14% carbon, structure consists of pearlitis grains, bounded cementite grid). According to the method of production, carbon steel is distinguished by carbon steel, melted in electric hinges, Marten furnaces and an oxygen converter method. By the method of deoxidation distinguish boiling, semi-luminous, calm steel. In prescription, carbonaceous steel is divided into structural steel and instrumental steel; There is also a group of carbon steels of special purpose. In the content of carbon, carbonaceous steel is divided into low carbon, with a carbon content to 0, 25%; medium carbon, with a carbon content of 0, 3-0, 6%; High carbon, with carbon content above 0, 6%. Also, ordinary carbonaceous steel and high-quality carbon steel are distinguished.

The carbon content in steel determines its structure and properties, since with an increase in the concentration of carbon in steel, the number of cementitis increases in its structure. The structure of steel with a carbon content of less than 0, 8% consists of ferrite and perlite, with a higher carbon content in the steel structure, except perlite, the structurally free secondary cementite appears. Steel with the structure of ferrite is quite plastic, but has low strength; Steel with the structure of cementite fragile, but has a high hardness. With increasing carbon content (up to 0, 8-1, 0%), the hardness and strength of unallowned steels increase, but their viscosity and plasticity decreases. The carbon content affects such technological properties of steel as weldability, pressureability of pressure and cutting. Low carbon steel are used for the manufacture of low-loaded parts and structures, medium carbon steel - the main construction material in general and transport engineering, high carbon steel are used to make parts with high wear resistance, as well as for the manufacture of measuring, cutting, shock-stamp tools.

The properties of steel affect the content of constant (manganese, silicon, sulfur, phosphorus) and hidden (oxygen, nitrogen, hydrogen) impurities. Useful impurities are manganese and silicon, which are introduced into steel in the process of smelting for deoxidation. Harmful impurities in carbon steel are sulfur and phosphorus. To improve physico-chemical and technological properties, micro-linking of carbon steel titanium, zirconium, boron, rare earth elements are used.

A characteristic feature of boiling steel is the incomplete process of its deoxidation. This steel has high plasticity, well stamped and welded. It is cheaper, since when it is smelting, the minimum number of special additives is consumed and the maximum yield of the suitable product is ensured. The disadvantage of boiling steel is a developed liquor, as a result of which the rental from its is non-uniform under the structure and mechanical properties.

Calm steel is deoxidized by ferromargangane, ferrosilicide, aluminum and more homogeneous in composition. Residual aluminum reduces the tendency to grow grain, so the strength and cold-resistance of rolled products from calm and fine-grained steel is higher than that of boiling steel rolled steel. The semi-deval steel is characteristic of an intermediate degree of deoxidation. Unlike boiling steel, it is treated with a small amount of deoxidizers. According to the properties, it occupies an intermediate position between boiling and calm steels.

In carbon steels of ordinary quality, a higher content of harmful impurities is allowed than in high-quality carbon stools. They are paid in large Marten sorrows and oxygen converters, denoted by the letters of art and numbers from 0 to 6. The numbers indicate the conditional number of the steel grade depending on its chemical composition. The letters of the KP, PS, the joint venture at the end of the brand indicate the method of deoxidation: KP - boiling, PS - semi-luminous, SP - calm. A carbon steel of ordinary quality includes hot-rolled steel (varietary, shaped, thick, thin-column, broadband) and cold-rolled steel (thin-poly).

A high-quality carbonaceous steel is presented with strict requirements for the content of harmful impurities (the sulfur content should not exceed 0, 04%, phosphorus - 0, 035%). They are paid in electric hollows, oxygen converters, Martensian furnaces. High-quality carbonaceous steel is marked with double digits (05, 10, 15), indicating the average carbon content in hundredths of percent. Letter A at the end of the brand indicates improved metallurgical quality. With the designation of boiling or semi-luminous steel, the degree of stretchability is indicated: KP, PS. In calm, the deck of deoxidices is not specified.

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