How is carbon steel designated?

Carbon steels classification, marking and use for the manufacture of elements

Steel is a metal widely used in mechanical engineering, aircraft manufacturing, construction and other industries. The popularity of the material is due to the combination of its excellent technological and physical and mechanical properties. Steels include iron-carbon compounds, the chemical composition of which implies a carbon content of less than 2.14%, and in addition to this component there are harmful and useful impurities.

The combination of characteristic static cyclic strength and stiffness is achieved by varying the carbon content and alloying components. Different qualities of steel are obtained as a result of the use of certain chemical and thermal technologies in production.

Classification of carbon steels

Carbon alloys are divided according to the following characteristics:

• amount of carbon contained;
• purpose;
• structure in a state of equilibrium;
• degree of deoxidation.

Depending on the amount of carbon, the material is divided into categories:

• high-carbon - more than 0.7%;
• medium carbon - 0.3−0.7%;
• low carbon - up to 0.3%.

As a result of the resulting quality, steel alloys are divided into:

• high quality;
• ordinary;
• quality.

Oxygen is removed from the metal in its liquid state to reduce brittleness during hot forming, a process called deoxidation. Based on the nature of hardening and the degree of deoxidation, the material is classified as boiling, semi-calm and calm.

Depending on the resulting structure in the equilibrium state, the material is divided into:

• eutectoid, characterized by a pearlite structure;
• hypoeutectoid, containing pearlite and ferrite;
• hypereutectoid - with secondary cementite and pearlite.

According to the intended use, metal is divided into groups:

• structural (improvable, high-strength, cemented, spring-spring), used in construction, instrument making, mechanical engineering and aircraft manufacturing;
• instrumental for hot (200˚C) and cold pressing dies, measuring and cutting tools).

Structural metals

Ordinary quality steels are produced in the form of beams, rods, sheet material, channels, pipes, angles and other rolled products and are divided into categories A, B, B. The name contains the letters St and a number indicating the grade number; as the value of the number increases, the indicator increases carbon content. For materials of categories B and B, but not A, the required letter is placed before St to indicate affiliation.

The deoxidation group is designated SP, PS, KP - calm, semi-quiet and boiling, respectively. Category A is used for the production of parts obtained by cold working, Category B is used for elements manufactured by welding, forging, and heat treatment. Steel B is more expensive than the previous categories and is used for the production of critical structures and welding elements.

All three categories of ordinary carbon steels are used to make metal structures and parts in instrument making and mechanical engineering with light loads, in cases where performance is determined by the required rigidity. Metals in the form of reinforcement are placed in reinforced concrete structures. From categories B and B, welded trusses, frames and metal components are made, which are then covered with cement mortar.

Medium-carbon groups with a large margin of safety are used for rails, wheels of railway cars, pulleys, shafts and gears of mechanical devices and machines. Some materials in this group are allowed for heat treatment.

High-quality steels of the carbon group are used in lightly loaded parts; they are marked with numbers from 05 to 85, indicating the percentage concentration of carbon. Carbon materials include steels with increased manganese content, which are characterized by increased hardenability. By changing the amount of carbon, manganese and choosing the appropriate heat treatment method, various technological and mechanical qualities are obtained.

Low-carbon alloys have good ductility during cold working, but have a small margin of safety. They are produced in the form of sheets, the material is soft, easily stamped, stretched, this includes tin and metal for enameled household items. When cementing steels in production, the surface strength indicator increases, which makes it possible to produce light-loaded gear wheels, cams, etc.

Medium-carbon metals and similar compositions with an increased percentage of manganese are characterized by average strength, but their ductility and toughness are reduced. Based on the operating conditions of the spare parts, the method of strengthening steels is determined in the form of normalization, low-temper and high-frequency hardening, etc. They are used to make high-strength wire, springs, springs with increased requirements for wear resistance.

Automatic types

These materials are marked with the letter A and numbers indicating the carbon concentration in hundredths of a percent. Alloying with lead adds the letter C after A. The introduction of selenium, manganese, and tellurium makes it possible to reduce the use of cutting tools during processing. The degree of workability is also affected by the addition of phosphorus, sulfur and calcium, the latter being introduced in the form of silicalcite into the liquid alloy.

phosphorus and sulfur reduce quality indicators, sulfur reduces anti-corrosion properties, sulfides lead to a violation of the homogeneity of the metal. This class of steel is used to make parts of complex shapes and surfaces, and fasteners designed for light loads.

Alloy types

These include metals containing alloying additives in amounts up to 2.5%. The letter designations of the brand include letters indicating certain impurities, and the number after them indicates the percentage of the element. If its content is less than 1.5%, then the additive is not included in the designation.

carbon in this group of steels is normalized by the amount of 0.1−0.3%; the main properties after thermal, chemical treatment and low tempering after hardening include:

• high hardness of the material on the surface;
• reduced strength of the middle layers and increased viscosity.

Steels are used for the production of machine parts and devices designed to work with shock and variable loads under conditions of increased wear.

Cementable materials

To increase hardness, contact endurance, wear resistance, and hardenability, chromium, magnesium, and nickel are used; the latter element increases viscosity and reduces the cold brittleness limit. Cementable compounds are divided into two groups:

• average strength with a yield threshold less than 700 MPa;
• increased strength with a similar indicator in the range of 700−1100 MPa.

Based on the content of additives, the following types are distinguished:

• chromium compounds and chrome vanadium, cemented to a depth of less than 1.5 mm;
• chromium-manganese compositions include titanium 0.06%, manganese and chromium 1% each, they tend to internally oxidize during gas carburization, which leads to a decrease in strength characteristics;
• chromium-nickel-molybdenum alloys are representatives of the martensitic class and are characterized by reduced warping, which is due to air hardening and alloying with rare earth metals, which increase hardenability, static strength and impact resistance.

Spring-spring alloys

Parts operate under conditions of elastic deformation and are subject to cyclic loads, so steels are required to have high levels of fluidity, ductility and fracture resistance. Includes:

• manganese - less than 1.2%;
• silicon - less than 2.7%;
• vanadium - up to 0.26%;
• chromium - up to 1.25%;
• nickel - less than 1.75%;
• tungsten - less than 1.2%.

During processing, the grain sizes decrease and the metal resistance increases.

Silicon alloys are especially valuable for transport production; if technology does not allow them to be decarbonized in production, then the endurance of the material remains at the level of the specified parameters.

The introduction of vanadium, chromium, vanadium, and nickel helps to inhibit excessive grain growth when heated and increase hardenability. Springs and other elastic elements are also made from high-carbon cold-drawn wires, austenitic stainless steels and high-chromium martensitic steels.

To ensure reliable operation of tools, steel must have special properties, which manifest themselves differently in each group of materials depending on production and technology for introducing additives.

Ball bearing molds

During production, alloys are cleaned of non-metallic impurities; the use of vacuum-arc or electric shock remelting technology reduces the porosity of the metal.

In the production of bearings and their assemblies, chromium ball bearing steels with chromium additives are used. Additional alloying is carried out with manganese and silicon in order to increase the hardenability index.

So that parts can be produced by cold stamping and cutting, metal annealing is used for hardness.

Hardening of parts (rollers, ball bearings and rings) is carried out in an oil bath at a temperature of 850−870˚С, they are cooled to ensure stability to 25˚С before tempering. Since bearing and similar elements experience strong dynamic loads during operation, they are made of metals with further heat treatment and carburization.

Wear-resistant types

Wear resistance increases with increasing surface hardness of the material. For long-term operation, the following qualities of the alloy are important:

• resistance to destruction due to abrasive friction;
• long-term operation under conditions of high pressure and shock loads.

Wear-resistant metals are used in the manufacture of caterpillar tracks, crushing plates of stone crushing equipment, and crushing jaws. Work in such conditions is effective due to the property of steels to gain strength and hardness under conditions of plastic cold deformation, reaching 70%. Phosphorus additions greater than 0.027% lead to an increase in the cold brittleness of the raw material.

Cast steel has an austenite structure, in which excess manganese carbide precipitates at the grain boundaries, leading to a decrease in strength and toughness. To obtain an austenitic single-phase structure, the workpieces are quenched in an aqueous environment at a temperature of about 1100˚C.

Corrosion resistant

These materials are used for the manufacture of elements of devices operating under conditions of electrochemical corrosion; they are called stainless. Corrosion resistance develops after the introduction of additives leading to the formation of surface films with good adhesion to the metal. These layers reduce the direct interaction of steels with external irritating factors and increase the potential in the electrochemical environment.

Stainless metals are divided into chromium-nickel and chromium. Chromium compounds are used for plastic parts that are produced by stamping and welding. This type is divided into ferritic, martensitic-ferritic and martensitic alloys. To increase impact resistance, they are hardened in oil at a temperature of about 1000˚C under high tempering conditions with temperatures ranging from 600-800˚C.

Heat-resistant alloys

Low-alloy compositions containing up to 0.25% C and other alloying additives: chromium, tungsten, nickel are used for the manufacture of elements operating at temperatures above 500˚C. Quenching and normalization is carried out in oil at a temperature of about 890−1050˚С. Pearlitic steels are used to make parts that are subject to creep in operation under low loads, for example, steam heating pipes, fittings for steam boilers, and fasteners.

Source: https://tokar.guru/metally/stal/himicheskiy-sostav-i-klassifikaciya-staley-po-naznacheniyu.html

Designation of high-quality structural carbon steel (GOST 1050-88)

page » Designation of high-quality structural carbon steel (GOST 1050-88)

High-quality structural carbon steel is regulated by GOST 1050-88.

High-quality steels are subject to higher requirements for chemical composition:

• sulfur content <0.04%,
• phosphorus content <0.035%.

GOST 1050-88 establishes grades of structural carbon quality steel: 0.5 kp; 0.8kp; 0.8ps; 0.8; 10kp; 10ps; 10; 11kp; 15kp; 15ps; 15; 18kp; 20kp; 20ps; 20; 25; thirty; 35; 40; 45; 50; 55; 58 (55pp) and 60. The numbers indicate the average carbon content in hundredths of a percent; the word “Steel” is written before the numbers in the brand designation.

Application

Low-carbon steel grades from 0.5 kp to 11 kp have low strength and high ductility. These steels without heat treatment are used for lightly loaded parts. Thin-sheet, cold-rolled low-carbon steel is used for cold stamping of products.

Steel grades from 15 kp to 25 are used without heat treatment or in a normalized form. Steels come in the form of rolled products, forgings, pipes, sheets, strips and wires and are intended for less critical parts.

Medium carbon steel grades 30; 35; 40; 45; 50; 55; 58 (55pp); 60 is used after normalization, improvement and surface hardening for various parts in all branches of mechanical engineering.

Steel grades 4060 should be used for the manufacture of parts that do not require through hardenability.

Scope of application of high-quality carbon structural steels:

• 0.5kp; 0.8kp; 0.8ps; 0.8; 10kp; 10ps; 10; 11kp - Gaskets, mounting caps, bushings, rollers, stops, gears, friction discs.
• 10kp; 10ps; 15; 18kp; 20ps; 20 - Rollers, pins, stops, copiers, axles, gears, levers, hooks, traverses, liners, bolts, couplers.
• thirty; 35 - Axles, spindles, sprockets, rods, cross-arms, levers, disks, shafts.
• 40; 45 - Crankshafts, connecting rods, ring gears, camshafts, flywheels, gears, studs, ratchets, plungers, spindles, friction discs, axles, couplings, racks.
• 50; 55; 58 (55pp); 60 - Gears, rollers, rods, bands, shafts, eccentrics, lightly loaded springs and leaf springs.

Steel 0.8kp GOST 1050-88

This is high-quality steel, low-carbon (boiling), carbon content - 0.08%;

Steel 40 GOST 1050-88

This is high-quality steel, medium carbon, carbon content - 0.40%.

Source: https://pro-techinfo.ru/oboznachenie-stali-konstrukcionnoj-uglerodistoj-kachestvennoj-gost-1050-88/

Marking of steels. Marking of carbon steels. Marking of alloy steels. Marking of tool steels. | mtomd.info

Steels contain increased amounts of sulfur and phosphorus. Marked St.2kp., BSt.3kp, VSt.3ps, VSt.4sp.

St – index of this steel group. The numbers from 0 to 6 are the conventional number of the steel grade. As the grade number increases, the strength of the steel increases and the ductility decreases. According to guarantees upon delivery, there are three groups of steels: A, B and C. For steels of group A, mechanical properties are guaranteed upon delivery; the index of group A is not indicated in the designation. For steels of group B, the chemical composition is guaranteed. For group B steels, both mechanical properties and chemical composition are guaranteed upon delivery.

The indices kp, ps, sp indicate the degree of deoxidation of the steel: kp - boiling, ps - semi-calm, sp - calm.

Steel classification

Quality carbon steels

High-quality steels are supplied with guaranteed mechanical properties and chemical composition (group B). The degree of deoxidation is generally calm.

Structural quality carbon steels. They are marked with a two-digit number indicating the average carbon content in hundredths of a percent. The degree of deoxidation is indicated if it differs from calm.

Example: steel 08 kp, steel 10 ps, ​​steel 45. carbon, respectively, 0.08%, 0.10%, 0.45%.

High-quality tool carbon steels are marked with the letter U (carbon tool steel) and a number indicating the carbon content in tenths of a percent.

Example: U8 steel, U13 steel. carbon, respectively, 0.8% and 1.3%

Tool high-quality carbon steels. They are marked similarly to high-quality tool carbon steels, only at the end of the mark they put the letter A to indicate the high quality of the steel.

Example: U10A steel.

Effect of carbon on steel. The influence of carbon on the properties of steel.

Quality and high quality alloy steels

Designation is alphanumeric. Alloying elements have symbols, designated by letters of the Russian alphabet.

Designations of alloying elements:
X - chromium, N - nickel, M - molybdenum, B - tungsten, K - cobalt, T - titanium, A - nitrogen (indicated in the middle of the mark), G - manganese, D - copper, F - vanadium, S – silicon, P – phosphorus, P – boron, B – niobium, C – zirconium, Y – aluminum.

Influence of impurities on properties. The influence of impurities on the properties of steels. Red brittleness. Flockens.

Alloy structural steels

At the beginning of the stamp there is a two-digit number indicating the carbon content in hundredths of a percent. Alloying elements are listed below. The number following the symbol of the element shows its content as a percentage. If the number does not appear, then the content of the element does not exceed 1.5%. To designate high-quality alloy steels, the symbol A is indicated at the end of the grade.

Alloy steels. Classification of alloy steels. Classification of alloy steels by microstructure. Marking of alloy steels.

Example: steel 15Х25Н19ВС2. The specified grade of steel contains 0.15% carbon, 35% chromium, 19% nickel, up to 1.5% tungsten, up to 2% silicon.

Alloy tool steels

At the beginning of the brand there is a single-digit number indicating the carbon content in tenths of a percent. If the carbon content is more than 1%, the number is not indicated. Alloying elements are listed below, indicating their content. Some steels have non-standard designations.

Tool alloy steels. Marking of tool alloy steels. Diamond steel.

Example: steel 9ХС, steel ХВГ.

High-speed tool steels

P – index of this group of steels (from rapid – speed). carbon more than 1%. The number shows the content of the main alloying element - tungsten. If steels contain alloying elements, then their content is indicated after the designation of the corresponding element.

High speed steel. Tool high-speed steels. Grades of high-speed steels. Heat treatment of high-speed steels.

Example: P18 steel. The tungsten content in this steel is 18%.

Ball bearing steels

Ш – index of this group of steels. X - indicates the presence of chromium in the steel. The following number shows the chromium content in tenths of a percent; in the indicated steels, 0.6% and 1.5%, respectively. Alloying elements included in the steel composition are also indicated. carbon more than 1%.

Ball bearing steels. Ball bearing steel grades.

Example: steel ШХ6, steel ШХ15ГС

Source: http://www.mtomd.info/archives/1311

Classification of carbon steels by purpose

Steel is a metal alloy of iron and carbon, necessary for the production of semi-finished products and products by plastic deformation in cold and hot states. To change the properties of a material, various elements can be added to its composition. Thus, with an increase in the amount of carbon, the strength of steel increases. If it is more than 2.14% in the alloy, we get cast iron.

The main qualities of steel are strength, ductility, toughness, hardness, elasticity, and heat resistance. However, it inherited its susceptibility to corrosion from iron.

Classification of steels by chemical composition:

• carbon steel, without improving (alloying) components;
• alloy steel, to which alloying elements (manganese, chromium, nickel, tungsten, silicon, molybdenum, vanadium) are added to improve technological properties.

Through research, stainless steel and galvanized steel were also obtained.

Carbon steel

Carbon steels (CS) are low-alloy compositions consisting of 99.5% iron. Strictly dosed various additives determine the operational, mechanical and technological properties of alloys.

Carbon compositions account for up to 80% of the total amount of steel produced. There are over two thousand grades of these alloys.

According to the area of ​​use, they are divided into structural, tool, and also ordinary quality steel (for example, wire rod).

In terms of quality, the classification of carbon steel provides:

• ordinary steel, which can be cold-rolled or hot-rolled;
• high-quality structural steel in the form of forged and hot-rolled billets, silver bars (round bars), calibrated steel.

High-quality structural steel is used for the production of critical components of machines and mechanisms, stamping. The main advantages of the US include:

• optimal ratio of consumer properties and price;
• high modulus of elasticity, which allows its use in power structures, where the performance of the structure depends on the rigidity of the material;
• heat treatment of steel increases its strength, but practically does not change the elastic modulus (an important process in the heat treatment of metal is hardening of carbon steel, on which the quality of the product depends, the hardening speed is in the range of 200-600 C per second);
• Amenable to finishing by pressure and cutting, welding is excellent.

Thanks to these advantages, the control system has found wide application in the production of mass products.

Marking of carbon steels

Carbon and alloy steels are classified according to:

• structural composition;
• chemical composition;
• quality;
• purpose;
• degree of deoxidation.

The main feature that determines the name and grade of steel is its chemical composition. This marking of steels also takes into account production conditions, quality, and area of ​​application.

If the grade of steel is known, then its properties are quite easy to understand. For example, ordinary quality carbon dioxide is marked with two letters and a number, which indicates the presence of carbon in tenths of a percent (Article 1 - Article 7).

Alloy steels, in addition to markings and numbers, have letters indicating additives in the steel. For better orientation, there are marking tables.

Chemical composition of steel

Depending on the chemical composition, carbon steels are divided into three types:

• low-carbon – carbon is present in small quantities (up to 0.25%). These compositions are well deformed in both cold and hot states.
• Medium carbon - carbon present 0.3-0.6%. Such alloys are characterized by good ductility, fluidity and at the same time strength.
• High-carbon (0.6 - 1.4%) - have increased density and unique characteristics, which are determined by the peculiarities of the structure.

To reduce the number of non-metallic inclusions and refine grains, steel is deoxidized. The smaller the number of non-metallic inclusions and the more uniformly they are distributed, the lower the threshold of brittleness of the material and the higher the impact strength and strength.

Classification according to the degree of deoxidation implies: calm, semi-calm, boiling steels.

Boiling steel

Boiling steel production technology ensures minimal waste and the yield of the largest amount of usable metal. Due to the absence of silicon, steel is very ductile and is used for the manufacture of products by deep drawing.

Boiling steels are deoxidized with manganese until the presence of oxygen is 0.02-0.04% and then poured into ingots. Emitted CO bubbles create a picture of steel boiling, which explains its name. When marking, it is additionally indicated by KP.

As a result of the fact that boiling steel requires a small amount of deoxidizer, and the top part of the ingot is not scrapped, it is cheaper than semi-calm and calm steel.

Ingots from such steel are used for the production of sheets, plates, pipes, wire, and long products.

Calm steel

This type of metal belongs to structural carbon steels. It is obtained by deoxidation with aluminum, manganese and silicon. The level of oxygen in it is so reduced that no reaction occurs between carbon and oxygen during metal processing.

Calm steel is distinguished by a dense structure and has good mechanical properties. It is less prone to negative reactions to welding heat and to aging. The features of a uniform (homogeneous) microstructure give the alloy maximum corrosion resistance and ductility.

In terms of cost, this is the most expensive steel. It is used for the construction of rigid metal structures, non-load-bearing and load-bearing elements. It is made from:

• procurement of parts for pipelines;
• basic elements for railway tracks;
• sheets, shapes, etc.

 Semi-quiet steel

Semi-quiet steels have a middle position between boiling and calm types of raw materials. They contain oxygen, which gives the raw material less pronounced properties of plasticity and hardness. They harden without boiling, however, with the release of gases. The chemical composition is heterogeneous.

Semi-quiet steel is melted using boiling steel technology, but with subsequent deoxidation of the metal in a mold or ladle. As a rule, aluminum or silicon is used for deoxidation.

The following grades of steel are used to produce:

• stripes, circles, squares, hexagons, corners, embedded parts;
• pipe and sheet metal.

Steel is one of the most important metal materials

Steel is one of the main metal materials that is used in the production of tools, instruments, and machines. Its widespread use is justified by the presence of a whole complex of high mechanical, technological, physicochemical properties.

In addition, steel has a relatively low cost and can be produced in large quantities. The production process of this material is constantly being improved, as a result of which the quality and properties of steel can ensure trouble-free operation of modern devices and machines under high workloads.

Source: https://varimtutru.com/klassifikatsiya-uglerodistyh-staley-po-naznacheniyu/

Properties and composition of carbon steel, application and labeling

The scope of carbon steel is wide - it is used to create tools, load-bearing structures and elements for mechanical engineering are made from it. Currently, this is one of the most popular types of steel, as it has unique properties. Its operational and technical properties are determined by the components and their ratio in the composition.

Compound

Carbon and additional elements are used to melt steel. Depending on the future purpose, certain requirements are imposed on the material: hardness, ductility, fluidity, etc. These parameters can be adjusted by changing the % carbon content.

Its ratio to the total volume is one of the main conditions for dividing steel into types.

Their distinctive qualities and features are described in regulatory documents:

• Ordinary quality - GOST 380-85.
• Structural – GOST 380-88.
• Instrumental - GOST 1435-54 and GOST 5952-51.

carbon determines the hardness index. The more it is, the different the product will be. However, it must be taken into account that at the same time fragility increases.

Depending on this indicator, steel is divided into several types:

• Low carbon – up to 0.25%. It has good ductility and is relatively easy to deform, both in a cold state (suitable for cold forging) and under the influence of high temperatures.
• Medium carbon – from 0.3% to 0.6%. It has sufficient strength, but also has good ductility and fluidity, which is important for processing. Scope of application – structural elements whose operation implies normal conditions.
• High carbon - from 0.6% to 1.4%. High-strength tools and measuring instruments are made from it.

Each of these types of steel has a specific area of ​​application.

Ordinary quality

This is the most popular type of steel at present. It is produced in the form of rolled products - sheets, rods, channels and beams. Due to its properties, it can be used as supporting structures and mechanical engineering elements.

In order to find out the properties of a certain type of carbon steel of ordinary quality. you need to know the principle of its marking.

The designation must always comply with GOST. The name indicates the type of metal - ST. Then comes a digital number that determines the perlite and carbon content. The higher the number, the stronger the product. The numbering can vary from 0 to 6. Then the name indicates the method of deoxidation - SP - calm; PS – semi-quiet; KP – boiling.

In addition, carbon steel is divided into three subtypes.

• A – its chemical composition is not regulated. The main indicator is mechanical properties. It does not undergo a preliminary stage of pressure treatment. Not intended for welding.
• B – its chemical composition must comply with regulatory documentation. Products made from this material can be processed - stamping, forging, etc. However, it is possible to change the mechanical properties. Some varieties can be exposed to heat.
• And - the highest quality type of material. These brands are characterized by the mechanical properties of group “A” and the guaranteed chemical composition of group “B”. The structures can be welded together.

Group “A” is not indicated in the labeling. If the material grade corresponds to groups “B” or “C”, these letters are indicated at the beginning of the marking. When using manganese with a high content in the composition, the letter “G” is used in the brand name. Example: BSt3Gps – steel of group “B”, with a carbon content corresponding to the designation “6”, with the addition of manganese in a semi-quiet state.

High quality

In the manufacture of these types of steel, increased demands are placed on both the chemical composition and mechanical properties. In addition, the content of harmful components is regulated.

• Sulfur – no more than 0.04%.
• Phosphorus – no more than 0.035%.

These varieties are designated by the letter “U”. The numbers following it indicate the % carbon content (in hundredths of a percent). Such steel grades are used for the manufacture of tools, critical elements in mechanical engineering, as well as in the production of precision measuring instruments.

• U7 – used for the production of chisels, dies, forging tools, and hammers.
• U8 and U8G (containing manganese) – punches, metal knives, tools designed for stone processing.
• U9 – tools for woodworking, punches, stamps.
• U10 and U11 – taps, reamers, dies, blades for hacksaws.
• U12 and U13 – cutters for processing hard metal, drills.

What else should you pay attention to when choosing carbon steel? It is important to remember that the better the hardness index, the more fragile the product will be. Thus, high-quality tool steels are characterized by good mechanical strength, low fluidity and ductility.

Source: https://ismith.ru/metal/uglerodistaya-stal/

Carbon tool steel

1. Steel U7, U7A
2. Steel U8, U8A
3. Steel U9, U9A
4. Steel U10, U10A
5. Steel U12, U12A

Application area

Carbon tool steels are the cheapest steels in the category of tool steels (there are also alloyed, high-speed, die and roll tool steels) and do not contain specially introduced alloying elements.

In the manufacture of large-sized tools, an important characteristic is the hardenability of steels; according to this indicator, carbon tool steels belong to shallow hardenability steels. As a rule, their hardness after hardening is within HRC 63-66 and at the same time they have a soft core.

Carbon tool steels are used for the manufacture of tools that operate under conditions that do not cause heating of the working edge, operate at low processing speeds, and are not subject to heating during operation. Below is a list of tools that are manufactured using carbon tool steels:

• side cutters
• beards
• smooth calibers
• bits
• countersinks
• chisels
• measuring instrument of simple form: smooth gauges, staples
• woodworking tool
• calibers of simple shape and lower accuracy classes
• punches
• cleavers
• combination pliers
• sledgehammers
• metal cutting scissors blades
• dies for cold stamping
• small size machine taps
• hand taps
• hammers
• needle files
• knurling rollers
• screwdrivers
• rip saws and circular saws
• saws for wood processing
• dies for grains
• small-sized reamers
• rasps
• fitter's assembly tool
• chisels
• axes
• cutters

Marking

Carbon tool steels are designated by the letter “U”, and the numbers following it indicate the average carbon content in tenths of a percent. For example, steel designation U8 means that this tool steel contains 0.8% carbon. If the steel designation contains the letter A, for example U7A, then this letter indicates that the steel is high quality.

The presence of the letter G in the marking means a high content of manganese.

The grades and chemical composition of steel according to heat analysis must correspond to Tables 1 and 2.

Table 1

table 2

Source: http://enginiger.ru/materials/instrumentalnye-stali/stal-instrumentalnaya-uglerodistaya/

Carbon steel - classification, marking and application

Steel is an alloy consisting of two essential components - iron and carbon. Additional elements: silicon less than 1%, manganese less than 1%, sulfur less than 0.05%, phosphorus less than 0.06%. carbon no more than 2.14%.

Alloys with a C percentage greater than 2.14% are classified as cast iron. Based on their chemical composition, steel grades are divided into carbon and alloy, which contain additional additives that give the material the desired characteristics.

Carbon steel alloys are classified according to the degree of deoxidation, carbon content, and quality.

Calm

Such alloys have the most uniform structure. For deoxidation, aluminum, ferrosilicon and ferromanganese are used, which almost completely remove the gases present in the melt. The combination of the almost complete absence of gases with a fine-grained structure due to the presence of residual aluminum ensures good quality of the metal. These grades are suitable for the manufacture of parts, products and structures for critical purposes. The main disadvantage is the high cost.

Boiling

This is the cheapest and least quality group. Due to the use of a minimal amount of additives for deoxidation, dissolved gases are present in the material, which cause heterogeneity in the structure, chemical composition, and therefore mechanical properties. Such metals have poor weldability, since due to the presence of gases there is a high probability of cracks forming at the seams.

Semi-calm

The group occupies an intermediate position in terms of cost and characteristics. Much fewer gas bubbles form in the casting compared to boiling steels. When rolling, internal defects in the bulk are eliminated. Such materials are often used as structural alloys.

Low carbon with a C content of no more than 0.25%

Most of these products are produced in the form of cold-rolled or annealed sheets and strips. Properties, and therefore the scope of its application, depend on the percentage of components:

• Up to 0.1% C, Mn less than 0.4%. High ability to hot deformation and cold drawing. The materials are in demand in the production of wire, very thin sheets used in the manufacture of containers, and also for the manufacture of car bodies.
• C 0.1-0.25%. The ability to deform is lower than that of the group described above, but the hardness and strength are higher. Often these grades are in demand for the production of parts with a cemented surface layer. The carburization process produces a wear-resistant surface layer combined with a tough core. This is true for shafts and gears.
• C at 0.25%, Mn and Al – up to 1.5%. They have high viscosity. Aluminum is not added to metals intended for stamping, forging, the production of seamless tubes and sheets for boilers.
• C at 0.15%, Mn - up to 1.2%, Pb up to 0.3% or without it, minimum amount of Si. This group is used in mass production on automatic lines of parts not intended to withstand severe mechanical and temperature loads. For products with high requirements for ductility, toughness, and corrosion resistance, alloys are not used.

Medium carbon with C0.2-0.6%

manganese is usually in the range of 0.6-1.65%. They are used in the production of products intended for use under high loads. They are usually produced calm. They are strengthened by cold hardening or heat treatment. All steels in this group can be forged. These metal products are widely used in mechanical engineering. Grades with a high carbon content (0.4-0.6%) are in demand in the production of railway rails, wheels and car axles.

High carbon – 0.6-2.0%

Increasing the amount of carbon to 1% leads to an increase in strength and hardness with a gradual decrease in the yield strength and plasticity. When the percentage of C increases above 1%, the formation of a coarse network of secondary martensite begins, leading to a decrease in the strength of the material. Therefore, steels with a C content of more than 1.3% are practically not produced.

High-carbon grades have a high manufacturing cost, have low ductility, and are difficult to weld. The scope of application of this group is quite limited - the production of cutting tools, including those intended for earthmoving and agricultural machinery, and the production of high-strength wire.

Structural steels of ordinary quality

They are produced in accordance with GOST 380-2005 and supplied for sale in the form of sheets, sections and shaped products. GOST implies the release of the following brands:

• St0;
• St1ps, St1sp, St1kp;
• St2ps, St2sp, St2kp;
• St3ps, St3sp, St3kp, St3Gsp, St3Gps;
• St4ps, St4sp, St4kp;
• St5ps, St5sp, St5Gps;
• St6ps, St6sp.

Alphanumeric marking of this group of alloys:

• St – steel;
• numbers 0-6 indicate the brand number;
• the presence of the letter “G” in the designation indicates the presence of manganese in an amount of 0.8% or more;
• the last two letters characterize the degree of deoxidation, sp - calm, ps - semi-calm, kp - boiling.

High-quality structural steel

Manufactured in accordance with GOST 1050-2-13 of the following grades - 05, 08, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 58, 60, as well as grades 55PP, 60PP, 60PP " select” – reduced hardenability. The marking of such alloys indicates the degree of deoxidation if they are boiling or semi-quiet, for example 10 kp or 10 ps. The cn index is not indicated in the designation of quality construction grades.

Source: https://TreydMetall.ru/info/uglerodistaya-stal-klassifikikaciya

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