What is carbon steel, its production, marking and methods of application
Due to its strength characteristics and affordable price, carbon steel is a very common alloy. Its main elements are iron and carbon with a minimum of drops. Carbon steel is used to produce various engineering products, pipeline and boiler parts, and tools. Alloys are also widely used in construction.
Depending on their main purpose, carbon steels are divided into instrumental and structural; there are practically no alloying elements in their composition.
They also differ from ordinary steel alloys in that they contain significantly fewer basic impurities: manganese, magnesium, silicon. the main element - carbon - varies over a fairly wide range .
High-carbon steel contains 0.6-2% C, medium-carbon steel - 0.3-0.6%, low-carbon steel - up to 0.25%.
The main element determines the properties and structure. In the internal structure of alloys with less than 0.8% C (hypoeutectoid steel) there is predominantly pearlite and ferrite, and with an increase in the concentration of the main element, secondary cementite is formed.
The presented steels with a predominant ferritic structure are highly ductile and have low strength. If the structure is dominated by cementite , the metal is characterized by high strength, but also great fragility. When the C content increases to 0.8−1%, strength and hardness increase, but viscosity and ductility greatly deteriorate.
The quantitative carbon content affects the technological characteristics, in particular, weldability, ease of cutting and pressure.
- Low-carbon steels are used to make parts and structures that are not intended for significant loads.
- The characteristics of medium-carbon steels make them the main structural material used in the production of structures and parts for transport and general engineering.
- High-carbon alloys are optimal for the manufacture of parts that must have increased wear resistance in the production of measuring and impact tools.
The metal, like other steel alloys, contains impurities:
- silicon;
- phosphorus;
- manganese;
- nitrogen;
- sulfur;
- hydrogen;
- oxygen.
Silicon and manganese are useful impurities that are introduced into the composition at the smelting stage for deoxidation. Phosphorus and sulfur are harmful impurities that impair the quality characteristics of the alloy.
It is believed that alloying and carbonaceous species are incompatible, however, in order to improve their technological and physical-mechanical characteristics, microalloying can be performed by adding various additives:
- boron;
- titanium;
- zirconium;
- rare earth elements.
With their help, it will not be possible to turn metal into stainless steel, but it will significantly improve the properties.
Classification by degree of deoxidation
The division into types is influenced, in particular, by the degree of deoxidation. Depending on this parameter, our alloys are divided into semi-calm, calm and boiling.
Quiet steels have a more uniform internal structure, whose deoxidation is achieved by adding aluminum, ferrosilicon and ferromanganese to the molten metal . Due to the fact that the alloys of our category are completely deoxidized in the furnace, they do not contain ferrous oxide.
Residual aluminum, which inhibits grain growth, provides a fine-grained structure. This and the almost absolute absence of dissolved gases makes it possible to obtain high-quality metal for the manufacture of the most critical parts and structures.
Along with the advantages, quiet alloys have a big disadvantage - rather expensive smelting.
There are cheaper, although lower quality, carbon alloys, the smelting of which uses a minimum of special additives.
In the structure of such a metal, due to the fact that the deoxidation process in the furnace was not completed , there are dissolved gases that negatively affect the characteristics. Nitrogen, for example, has a bad effect on weldability and provokes the formation of cracks in the weld area.
Developed segregation in the structure of alloys leads to the fact that rolled metal products made from them are characterized by heterogeneity in structure and mechanical characteristics.
Semi-quiet steels have an intermediate position in properties and degree of deoxidation. Before pouring into the molds, a small amount of deoxidizing agents are introduced into their composition, due to which the metal solidifies practically without boiling , but the release of gases in it continues. The result is a casting whose structure contains fewer gas bubbles than boiling steels. These internal pores are welded almost completely during subsequent rolling of the metal.
Most semi-mild carbon steels are used as structural materials.
Carbon steels are produced using different technologies. There are:
- high-quality carbon steels;
- high quality steel alloys;
- carbon steel alloys of ordinary quality.
Alloys of ordinary quality are obtained in open-hearth furnaces, and large ingots are formed from them. Melting equipment used to produce such steels includes, in particular, oxygen converters. Compared to high-quality steel alloys, the metal may contain many harmful impurities, which affects the characteristics and cost of production.
Formed and solidified ingots are rolled hot or cold. Hot rolling produces long and shaped products, thin and thick sheet metal, and wide metal strips. Cold rolling produces thin sheet metal.
To produce high-quality and high-quality steel, open hearth furnaces and converters are used, as well as melting furnaces that run on electricity.
GOST imposes strict requirements on the composition, namely the presence of harmful and non-metallic impurities in the structure. High-quality steels should contain no more than 0.04% sulfur and no more than 0.035% phosphorus . High-quality and high-quality steel alloys, due to strict requirements for the smelting method and characteristics, have increased structural purity.
Application and labeling
Tool alloys containing 0.65−1.32% C are used to make various tools. To improve the mechanical properties of tools, the manufacturing material is hardened.
Structural alloys are used to make parts for various equipment, structural elements for construction and engineering purposes, fasteners, etc.
is made from structural steel , which is used in everyday life , in the production of fasteners, in construction, and for the manufacture of springs.
After carburization, structural alloys are successfully used in the production of parts that are subject to severe surface wear during operation and experience high dynamic loads.
The marking indicates the chemical composition of the alloy and its category. In the designation of carbon steel of ordinary quality there are the letters “st”. GOST stipulates seven conventional brand numbers (0−6), also indicated in the designation. The degree of deoxidation is indicated by the letters “kp”, “ps”, “sp”, placed at the end of the marking. Grades of high-quality and high-quality steels are designated by numbers that indicate the C content in the alloy in hundredths of a percent.
The fact that the alloy is instrumental can be understood by the letter “U” at the beginning of the marking. The number following this letter indicates the C content in tenths of a percent. The letter “A”, if present in the designation of tool steel, indicates improved quality characteristics of the alloy.
Steels with a higher carbon content may be less prone to forming low-ductility structures. When exposed to structural and welding stresses, a metal of low ductility can collapse. This is facilitated by the presence of diffusion hydrogen in it and its welding seam. To prevent the appearance of cold cracks, methods are used to eliminate the factors that contribute to the appearance of such defects.
Source: https://tokar.guru/metally/stal/uglerodnaya-uglerodistaya-stal-vidy-proizvodstvo-i-primenenie.html
Classification of carbon steels by structure
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.
How to distinguish steel from iron?
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://varimtutru.com/klassifikatsiya-uglerodistyh-staley-po-strukture/
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.
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
Products – Tekhmashholding – group of companies, official website
- 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. Calibrated carbon steel wheels are most often used in shipbuilding and mechanical engineering
- 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.
- 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.
- 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.
- 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%.
- Construction materials, their main property is good weldability; these are low-alloy alloys of ordinary quality.
- For cold stamping, rolled products from low-carbon alloys of ordinary quality are used.
- Cementable, used in the manufacture of parts with surface abrasion.
- High-strength ones are characterized by a double strength threshold relative to other structural types.
- Spring steels with the addition of vanadium, bromine, silicon, chromium and manganese are designed to maintain elasticity for a long time.
- Ball bearing steels with a large proportion of carbon and the addition of chromium, which are characterized by special wear resistance, strength and endurance.
- 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
- Stainless steel, these include alloys with a high content of chromium and nickel. The carbon concentration in such alloys is minimal.
- 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.
- 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.
- 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.
- 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.
- manganese – 0.4-0.65%;
- silicon – 0.15-0.17%;
- nickel and chromium – 0.3% each;
- arsenic – 0.08%;
- copper – up to 0.3%;
- sulfur – 0.05%;
- phosphorus – 0.04%;
- nitrogen – up to 0.008%.
- the first two letters indicate carbon steel of ordinary quality;
- the number “3” means the serial number of the brand according to this GOST;
- the sign “G” indicates a modification with a high manganese content;
- “sp”, “kp”, “ps” – degrees of deoxidation.
- C245, according to GOST 27772-88;
- C285;
- VSt3Sp.
- A57036, K01804 – USA;
- 40B, 722M24, HFS4 – UK;
- 1.0038, DC03 – Germany;
- E24-2, E24-4 – France;
- SS330, SS400 – Japan;
- Fe360B, Fe360C – Italy;
- G235C – China;
- RSt360B – Austria;
- Fe235D – Hungary.
- long and shaped steel according to GOST 2591-2006;
- sheets of various thicknesses and stampings;
- pipes and fittings, according to GOST 10705-80;
- tapes and strips that are produced in accordance with GOST 14918-80;
- wire of different sections.
- density – 7850 kg/m3, the indicator may vary within certain limits;
- elastic modulus – 200 GPa;
- thermal conductivity coefficient – 55 W/m*K;
- a value characterizing the ratio of relative transverse compression to tension – 0.3.
- 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.
- St0;
- St1ps, St1sp, St1kp;
- St2ps, St2sp, St2kp;
- St3ps, St3sp, St3kp, St3Gsp, St3Gps;
- St4ps, St4sp, St4kp;
- St5ps, St5sp, St5Gps;
- St6ps, St6sp.
- 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.
- The first indicator is the chemical composition of the steel.
- The second is the microstructure, which is also very important.
- Of course, steel differs in its quality and method of production.
- Also, each type of steel has its own application.
- The 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%.
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:
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:
Unfortunately, there are also some disadvantages:
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:
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:
Types of tool steel
Tool steels come in several varieties:
Special-purpose steels include steel grades that are used in specific production areas:
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:
Annealed steels are divided into:
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)
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Carbon Steel Specifications 3
Steel 3 belongs to the category of structural carbon alloys of ordinary quality, the characteristics of which have ensured its use in many areas of the national economy. One of the factors contributing to the wide distribution of the material is its low cost.
Chemical composition
Decoding the steel grade St3 indicates the main components in its composition - iron (97%) and carbon (0.14-0.22%). The main quality of the alloy—its hardness—depends on the carbon concentration. The steel also contains small amounts of:
A feature of the St3 alloy is the strict regulation of the content of harmful impurities - sulfur and phosphorus. Phosphorus reduces the plasticity of the metal when exposed to high temperatures, and sulfur, when interacting with iron, forms sulfides, causing the phenomenon of red brittleness. It should be noted that there is an increased concentration of nitrogen, which accounts for almost 0.1%. In accordance with GOST 380-2005, the alloy is marked with accompanying indices that indicate the degree of deoxidation, for example, St3Gsp:
Substitutes for steel grade St3 can be:
Foreign analogues are labeled according to different rules:
The product range includes:
Alloy properties
Basic physical properties of steel 3:
Source: https://svarkaipayka.ru/material/stal/tehnicheskie-harakteristiki-uglerodistoy-stali-3.html
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:
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:
Alphanumeric marking of this group of alloys:
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
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.
Classification
The material we are considering can be classified according to several indicators:
The composition can be considered in more detail using the example of chemical composition. Based on this feature, two more types are distinguished - alloy and carbon steels.
Among carbon steels, there are three varieties, the main difference of which is the quantitative carbon content. If the substance contains less than 0.3% carbon, then it is classified as low-carbon. of this substance in the region of 0.3% to 0.7% transfers the final product to the category of medium-carbon steels. If the alloy contains more than 0.7% carbon, then the steel belongs to the high-carbon category.
With alloy steels the situation is approximately the same. If the material contains less than 2.5% of alloying elements, then it is considered low-alloyed, from 2.5% to 10% - medium-alloyed, and from 10% and above - highly alloyed.
Microstructure
The microstructure of steel differs depending on its condition. If the alloy is annealed, then its structure will be divided into carbide, ferritic, austenitic, and so on. With a normalized microstructure of the substance, the product can be pearlitic, martensitic or austenitic.
The composition and properties of steel determine whether a product belongs to one of these three classes. The least alloyed and carbon steels are the pearlitic class, the middle ones are martensitic, and the high content of alloying elements or carbon transfers them to the category of austenitic steels.
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:
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.
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