1. Carbon steel
Carbon steel, also known as carbon steel, is an iron carbon alloy with carbon content less than 2%. In addition to carbon, carbon steel generally contains a small amount of silicon, manganese, sulfur and phosphorus.
According to the application, carbon steel can be divided into three types: carbon structural steel, carbon tool steel and free cutting structural steel. Carbon structural steel can be divided into building structural steel and machine manufacturing structural steel. According to the carbon content, carbon steel can be divided into low carbon steel (ω C ≤ 0.25%), medium carbon steel (ω C = 0.25% - 0.6%) and high carbon steel (ω C > 0.6%)
According to the content of phosphorus and sulfur, carbon steel can be divided into ordinary carbon steel (with high phosphorus and sulfur content), high-quality carbon steel (with low phosphorus and sulfur content) and high-quality steel (with lower phosphorus and sulfur content). Generally, the higher the carbon content in carbon steel, the higher the hardness and strength, but the lower plasticity.
2. Carbon structural steel
This kind of steel mainly guarantees the mechanical properties. Therefore, its brand reflects its mechanical properties, and is represented by Q + number, in which "Q" is the initial Chinese phonetic alphabet of the word "Qu" at the yield point. The number indicates the yield point value. For example, Q275 indicates that the yield point is 275mpa. If the letters a, B, C and D are marked after the grade, it indicates that the steel quality grade is different, the content of S and P decreases in turn, and the steel quality improves in turn. If the letter "F" is marked after the brand, it is rimmed steel, the mark "B" is semi killed steel, and the one without "F" or "B" is killed steel. For example, q235-af represents A-class rimmed steel with a yield point of 235mpa, and q235-c represents a class C killed steel with a yield point of 235mpa.
In general, carbon structural steel is not heat treated, but directly used in the state of supply. Generally, Q195, Q215 and Q235 steels have low carbon content, good weldability, good plasticity and toughness, and certain strength. They are often rolled into thin plates, steel bars and welded steel pipes. It is used for bridge, building and other structures and manufacturing Ordinary rivets, screws, nuts and other parts. Q255 and Q275 steels have higher carbon content, higher strength, better plasticity and toughness, and can be welded. Generally, rolled steel, strip steel and steel plate are used as structural parts, and connecting rod, gear, coupling, pin and other parts of simple machinery are manufactured.
3. High quality structural steel
The chemical composition and mechanical properties of this kind of steel must be guaranteed at the same time. The grade of the steel is expressed by two digits of the mass fraction of the average carbon in the steel (ω с * 10000). For example, 45 steel means the average carbon content in steel is 0.45%; 08 steel means the average carbon content in steel is 0.08%.
High quality carbon structural steel is mainly used for manufacturing machine parts. Generally, the mechanical properties are improved by heat treatment. According to the carbon mass fraction, there are different uses. 08, 08F, 10, 10F steel, with high plasticity and toughness, has excellent cold forming performance and welding performance. It is often cold rolled into thin plate, which is used to make cold stamping parts on instrument shell, automobile and tractor, such as automobile body and tractor cab; 15, 20 and 25 steel are used to make carburized parts with small size, light load, wear-resistant surface and low core strength requirements, such as piston Pin, After heat treatment (quenching + high temperature tempering), 30,35,40,45,50 steel has good comprehensive mechanical properties, i.e. high strength, high plasticity and toughness, which are used to make shaft parts, such as 40,45 steel, which are often used to manufacture crankshaft, connecting rod, general machine tool spindle, machine tool gear and other shaft parts with small force; 55,60,65 Steel has high elastic limit after heat treatment (quenching + tempering at medium temperature). It is often used to make springs with small load and small size (section size less than 12 ~ 15mm), such as pressure regulating and speed regulating spring, plunger spring, cold coil spring, etc.
4. Carbon tool steel
Carbon tool steel is a kind of high carbon steel without alloy elements. The carbon content is in the range of 0.65% - 1.35%. It has low production cost, easy access to raw materials, good machinability, high hardness and high wear resistance after heat treatment. Therefore, it is widely used to manufacture various cutting tools, moulds and measuring tools. But the red hardness of this kind of steel is poor, that is, when the working temperature is higher than 250 ℃, the hardness and wear resistance of the steel will drop sharply and lose its working ability. In addition, if the carbon tool steel is made into larger parts, it is not easy to harden, and easy to produce deformation and cracks.
5. Free cutting structural steel
Free cutting structural steel is to add some elements which make the steel brittle, so that the steel can be easily brittle broken into debris when cutting, which is conducive to improving the cutting speed and prolonging the tool life. The main element that makes steel brittle is sulfur. Lead, tellurium and bismuth are used in ordinary low alloy free cutting structural steel.
The sulfur content of the steel is in the range of 0.08% - 0.30%, and the manganese content is in the range of 0.60% - 1.55%. The sulfur and manganese in the steel exist in the form of manganese sulfide. Manganese sulfide is very brittle and has lubricating effect, which makes the chip easy to break and is conducive to improve the quality of the machined surface.
6. Alloy steel
In addition to iron, carbon and a small amount of inevitable silicon, manganese, phosphorus and sulfur elements, there are also a certain amount of alloy elements in steel. The alloy elements in steel include silicon, manganese, molybdenum, nickel, chromium, vanadium, titanium, niobium, boron, lead, rare earth, etc., and one or more of them is called alloy steel. The alloy steel systems in different countries vary with their resources, production and use conditions. In the past, nickel and chromium steel systems have been developed abroad, while in China, alloy steel systems mainly composed of silicon, manganese, vanadium, titanium, niobium, boron and rare earth elements have been developed in China.
Alloy steel accounts for more than ten percent of the total output of steel, which is usually smelted in electric furnace. According to the use, alloy steel can be divided into eight categories: alloy structural steel, spring steel and bearing
7. Ordinary low alloy steel
Ordinary low alloy steel is a kind of ordinary alloy steel containing a small amount of alloying elements (the total amount of which is less than 3% in most cases). This kind of steel has high strength, good comprehensive performance, corrosion resistance, wear resistance, low temperature resistance, good cutting performance and welding performance. Under the condition of saving a lot of rare alloy elements (such as nickel and chromium), 1 t ordinary low alloy steel can be used as 1.2-1.3t carbon steel, and its service life and service range are far beyond that of carbon steel. Ordinary low alloy steel can be smelted in open hearth furnace and converter by general smelting method, and the cost is close to that of carbon steel.
8. Alloy steel for engineering structure
This refers to the alloy steels used in engineering and building structures, including weldable high-strength alloy structural steel, alloy reinforced steel, alloy steel for railway, alloy steel for geological oil drilling, alloy steel for pressure vessels, high manganese wear-resistant steel, etc. This kind of steel is used as engineering and building structural parts. In alloy steel, the total alloy content of this kind of steel is low, but the amount of production and use is large.
9. Alloy steel for mechanical structure
This kind of steel refers to the alloy steel suitable for manufacturing machine and mechanical parts. On the basis of high quality carbon steel, one or several alloy elements are properly added to improve the strength, toughness and hardenability of the steel. This kind of steel is usually used after heat treatment (such as quenching and tempering treatment, surface hardening treatment). It mainly includes alloy structural steel and alloy spring steel which are commonly used, including alloy steel with quenching and tempering treatment, alloy steel with surface hardening treatment (carburizing steel, nitriding steel, surface high frequency quenching steel, etc.), and alloy steel for cold plastic forming (cold forging steel, cold extrusion steel, etc.). According to the basic composition series of chemical composition, it can be divided into Mn series steel, SIMN series steel, CR series steel, CrMo series steel, CrNiMo series steel, Ni series steel, B series steel, etc
10. Alloy structural steel
The carbon content of alloy structural steel is lower than that of carbon structural steel, generally in the range of 0.15% - 0.50%. In addition to carbon, it also contains one or several alloy elements, such as silicon, manganese, vanadium, titanium, boron, nickel, chromium and molybdenum. The alloy structural steel is easy to harden and not easy to deform or crack, which is convenient for heat treatment to improve the properties of the steel.
Alloy structural steel is widely used in manufacturing various transmission parts and fasteners of automobiles, tractors, ships, steam turbines and heavy machine tools. Low carbon alloy steel is generally carburized, and medium carbon alloy steel is generally quenched and tempered.
11. Alloy tool steel
Alloy tool steel is a kind of medium and high carbon steel containing many kinds of alloy elements, such as silicon, chromium, tungsten, molybdenum, vanadium, etc. The alloy tool steel is easy to harden and not easy to produce deformation and crack. It is suitable for manufacturing large size and complex shape cutting tools, dies and measuring tools. The carbon content of alloy tool steel is also different due to different uses. The carbon content of most alloy tool steel is 0.5% - 1.5%, the carbon content of hot deformation die steel is low, and the range of ω C is 0.3% - 0.6%; the carbon content of cutting tool steel is about 1.5%; the carbon content of high carbon and high chromium cold working die steel is more than 2%
12. High speed tool steel
High speed tool steel is a kind of high carbon and high alloy tool steel. The carbon content of the steel is 0.7% - 1.4%. The steel contains alloying elements such as tungsten, molybdenum, chromium and vanadium which can form high hardness carbides.
High speed tool steel has high red hardness. Under the condition of high-speed cutting, the hardness does not decrease when the temperature is as high as 500-600 ℃, thus ensuring good cutting performance
Spring is used under impact, vibration or long-term alternating stress, so spring steel is required to have high tensile strength, elastic limit and high fatigue strength. In the process, it is required that the spring steel has certain hardenability, difficult decarburization and good surface quality
Carbon spring steel is a kind of high quality carbon structural steel with carbon content of 0.6% - 0.9% (including normal and high manganese content). The alloy spring steel is mainly silicon manganese series steel, their carbon content is slightly lower, and the performance is improved mainly by increasing the silicon content ω Si (1.3% - 2.8%); in addition, there are chromium, tungsten, vanadium alloy spring steel. In recent years, combined with the resources of our country and according to the requirements of new technology for automobile and tractor design, new steel grades with boron, niobium, molybdenum and other elements have been developed on the basis of silicon manganese steel, which has extended the service life of spring and improved the quality of spring steel.
14. Bearing steel
Bearing steel is the steel used to make balls, rollers and bearing rings. Bearing bears a great deal of pressure and friction when it works, so it is required that the bearing steel has high and uniform hardness, wear resistance and high elastic limit. The requirements for the uniformity of chemical composition, the content and distribution of non-metallic inclusions and the distribution of carbides of bearing steel are very strict.
Bearing steel, also known as high carbon chromium steel, contains about 1% carbon and 0.5% - 1.65% lead. Bearing steel can be divided into high carbon chromium bearing steel, chromium free bearing steel, carburized bearing steel, stainless bearing steel, medium and high temperature bearing steel and antimagnetic bearing steel.
15. Electrical silicon steel
Silicon steel for electrical industry is mainly used to manufacture silicon steel sheet for electrical industry. Silicon steel sheet is a large amount of steel used in motor and transformer manufacturing.
According to the chemical composition, silicon steel can be divided into low silicon steel and high silicon steel. The silicon content of low silicon steel is 1.0% - 2.5%, which is mainly used to make motor; the silicon content of high silicon steel is 3.0% - 4.5%, which is generally used to manufacture transformer. Their carbon content is 0.06% - 0.08%.
16. Rail steel
The rail mainly bears the pressure and impact load of rolling stock. Sufficient strength, hardness and toughness are required. The steel rail is usually made of carbon killed steel produced by open hearth furnace and converter. The carbon content of this steel is 0.6% - 0.8%, which belongs to medium carbon steel and high carbon steel. However, the manganese content in steel is relatively high, ranging from 0.6% to 1.1%. In recent years, ordinary low alloy steel rails have been widely used, such as high silicon rail, medium manganese rail, copper rail, titanium rail, etc. Compared with carbon steel rail, ordinary low alloy rail has better wear resistance, corrosion resistance and longer service life.
17. Shipbuilding Steel
Shipbuilding steel refers to the steel used for manufacturing marine ships and large inland river hull structures. Because the hull structure is usually made by welding method, the shipbuilding steel is required to have good welding performance. In addition, it also requires certain strength, toughness and certain low temperature and corrosion resistance. In the past, low carbon steel was mainly used as shipbuilding steel. Recently, a large number of ordinary low alloy steels have been used, such as 12 Mn ship, 16 Mn ship, 15 Mn V ship and so on. These steels have the comprehensive characteristics of high strength, good toughness, easy processing and welding, and seawater corrosion resistance. They can be successfully used to manufacture 10000 ton ocean going ships.
18. Bridge steel
Railway or highway bridges bear the impact load of vehicles. Bridge steel requires a certain strength, toughness and good fatigue resistance, and the surface quality of steel is required to be higher. Basic open hearth killed steel is often used for bridge steel. Recently, ordinary low alloy steels such as 16 Mn, 15 Mn, V-N have been successfully used.
19. Boiler steel
Boiler steel mainly refers to the materials used to manufacture superheater, main steam pipe and heating surface of boiler fire chamber. The main performance requirements of boiler steel are good welding performance, high temperature strength, alkali resistance and oxidation resistance. The commonly used boiler steels are low carbon killed steel produced by open hearth furnace or low carbon steel produced by electric furnace. The carbon content ω C is in the range of 0.16% - 0.26%. Pearlite Heat-resistant steel or austenitic heat-resistant steel shall be used in the manufacture of high-pressure boilers. In recent years, ordinary low alloy steel has been used to build boilers, such as 12 Mn, 15 Mn V, 18 Mn Mo Nb, etc.
20. Welding rod steel
This kind of steel is specially used for the manufacture of electrode wire for arc welding and gas welding. The composition of steel varies with the material being welded. According to the needs, it can be roughly divided into three categories: carbon steel, alloy structural steel and stainless steel. The sulfur and phosphorus content of these steels is less than 0.03%, which is higher than that of common steels. These steels do not require mechanical properties, but only chemical composition tests.
21. Stainless steel
Stainless acid resistant steel is referred to as stainless steel, which is composed of stainless steel and acid resistant steel. In short, the steel that can resist atmospheric corrosion is called stainless steel, and the steel that can resist chemical medium (such as acid) corrosion is called acid resistant steel. Generally speaking, the steel with chromium content more than 12% has the characteristics of stainless steel; according to the microstructure of stainless steel after heat treatment, it can be divided into five categories: ferritic stainless steel, martensitic stainless steel, austenitic stainless steel, austenitic ferritic stainless steel and precipitation hardening stainless steel.
22. Heat resistant steel
Under high temperature conditions, steel with oxidation resistance, sufficient high temperature strength and good heat resistance is called heat resistant steel. Heat resistant steels include oxidation resistant steels and heat-resistant steels. Oxidation resistant steel can not be called skin steel. Hot strength steel is a kind of steel with good oxidation resistance and high temperature strength at high temperature. Heat resistant steel is mainly used for long-term parts at high temperature.
Superalloy is a kind of thermal strength material with sufficient rupture strength, creep strength, thermal fatigue strength, high temperature toughness and sufficient chemical stability at high temperature. It is used for thermal power components working at about 1000 ℃.
According to their basic chemical composition, they can be divided into nickel base superalloy, iron nickel base superalloy and cobalt base superalloy.
24. Precision alloy
Precision alloy refers to the alloy with special physical properties. It is an indispensable material in electrical industry, electronic industry, precision instrument industry and automatic control system.
According to their different physical properties, precision alloys can be divided into seven categories: soft magnetic alloy, deformation permanent magnet alloy, elastic alloy, expansion alloy, thermal bimetal, resistance alloy and thermoelectric alloy. Most precision alloys are based on ferrous metals, while only a few are based on nonferrous metals.