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Definition of steel: Steel is a material which is processed into various shapes, sizes and properties by pressure. Iron and steel nonferrous metals, also known as nonferrous metals, refer to metals and alloys other than ferrous metals, such as copper, tin, lead, zinc, aluminum, brass, bronze, aluminum alloy and bearing alloy. , IKO bearing. In addition, chromium, nickel, manganese, molybdenum, cobalt steel, vanadium, tungsten and titanium are also used in industry. These metals are mainly used as alloy additives to improve the properties of metals, among which tungsten, steel, titanium and molybdenum are mostly used to produce cemented carbide for cutting tools. These nonferrous metals are called industrial metals, and steel products also include precious metals: platinum, gold, silver and rare metals, including radioactive steel products such as uranium and radium. Steel is an indispensable and important material for national construction and the realization of the four modernizations. Wide application range and many varieties. According to the different cross-sectional shapes, steel products are generally divided into four categories: profiles, plates, pipes and metal products. In order to facilitate the organization of steel production, order supply and good management, it is also divided into heavy rail, light rail, large steel, medium steel, small steel, cold-formed steel, high-quality steel, wire rod, medium-thick steel and thin steel. [Edit this paragraph] Classification of steel 1. Before introducing the classification of steel, briefly introduce the basic concepts of ferrous metal, steel and nonferrous metal. 1, ferrous metal refers to the alloy of iron and carbon. Such as steel, pig iron, ferroalloy, cast iron, etc. Both steel and pig iron are alloys based on iron and with carbon as the main additive element, which are collectively called iron-carbon alloys. Pig iron refers to the products made of iron ore smelted by blast furnace, which is mainly used for steelmaking and casting. Pig iron is melted in a melting furnace to get cast iron (liquid), and liquid cast iron is cast into castings, SKF, which is called cast iron. Ferroalloy is an alloy composed of iron, silicon, manganese, chromium, titanium and other elements. Ferroalloy is one of the raw materials for steelmaking, which is used as deoxidizer and alloying element additive for steel. 2. Put pig iron for steelmaking into a steelmaking furnace and smelt it according to a certain process to obtain steel. Iron and steel products include direct casting of steel ingots, continuous casting billets and various steel castings. Generally speaking, steel refers to steel rolled into various kinds of steel. Steel belongs to ferrous metal, but steel is not completely equal to ferrous metal. 3. Non-ferrous metals, also known as non-ferrous metals, refer to metals and alloys other than ferrous metals, such as copper, tin, lead, zinc, aluminum, brass, bronze, aluminum alloy and Timken bearing alloy. In addition, chromium, nickel, manganese, molybdenum, cobalt, vanadium, tungsten and titanium are also used in industry. These metals are mainly used as alloy additives to improve the properties of metals, among which tungsten, titanium and molybdenum are mostly used to produce cemented carbide for cutting tools. These nonferrous metals are called industrial metals, in addition to precious metals: platinum, gold, silver and rare metals, including radioactive uranium and radium. Second, the classification of steel is iron-carbon alloy with carbon content between 0.04% and 2.3%. In order to ensure its toughness and plasticity, the carbon content of Timken bearing generally does not exceed 1.7%. Besides iron and carbon, the main elements of steel are silicon, manganese, sulfur and phosphorus. There are various classification methods of steel, including 1, classification by quality (1), ordinary steel (P0.045%, S 0.050%), high-quality steel (both P and S are 0.035%) and advanced high-quality steel (P0.035%). B. medium carbon steel (c 0.25 ~ 0.60%); C. high carbon steel (C0.60%). (2) Alloy steel: a. Low alloy steel (the total content of alloy elements is 5%); B medium alloy steel (total content of alloying elements > 5 ~10%); C. high alloy steel (total content of alloying elements > 10%). 3. Classification according to forming mode: (1) forged steel; (2) cast steel; (3) hot rolled steel; (4) cold-drawn steel bars. 4. According to the classification of metallographic structure, the annealing state is (1): a. Submerged arc welding steel (ferrite+pearlite); B.*** steel precipitation (pearlite); * * * steel after precipitation (pearlite+cementite); D ledeburite steel (pearlite+cementite). (2) normalizing: a. pearlite steel; B. bainite steel; C. martensitic steel; Austenite steel. (3) No phase change or partial phase change 5. Classification by use (1) steel for building and engineering: a. ordinary carbon structural steel, SKF；; ; B. low alloy structural steel; C. steel bars. (2) Structural steel A. Steel for machinery manufacturing: (a) quenched and tempered structural steel; (b) Case-hardened structural steel: including carburized steel, ammoniated steel and case-hardened steel; (c) free-cutting structural steel; (d) Steel for cold plastic forming: including steel for cold stamping and steel for cold heading. B. Spring steel C. Bearing steel (3) Tool steel: A. Carbon tool steel; B. alloy tool steel; C. high-speed tool steel. (4) Special performance steel: a. Stainless and acid-resistant steel; B. Heat-resistant steel: including oxidation-resistant steel, heat-resistant steel and valve steel; C. electrothermal alloy steel; D. wear-resistant steel; E. low temperature steel; Electrical steel. (5) Professional steels such as steel for bridges, ships, boilers, pressure vessels and agricultural machinery. 6. Comprehensive classification (1) Ordinary steel A. Carbon structural steel: (a) Q195; (b) Q2 15(A、B)； (c) Q235(A、B、C)； Q255(A、B)； Question 275.b. Low-alloy structural steel C. General structural steel for specific purposes (2) High-quality steel (including high-quality steel) A. Structural steel: (a) High-quality carbon structural steel; (b) alloy structural steel; Spring steel; Free cutting steel; Timken bearing steel; (f) Special-purpose high-quality structural steel. B. Tool steel: (a) carbon tool steel; (b) alloy tool steel; (c) high-speed tool steel. C. Special performance steel: (a) stainless steel and acid-resistant steel; Heat-resistant steel; Electrothermal alloy steel; (d) electrical steel; (e) High manganese wear-resistant steel. 7. Classification by smelting method (1) and classification by furnace type A. Open hearth steel: (a) acid open hearth steel; Alkaline open hearth steel. B converter steel: (a) acidic converter steel; Alkaline converter steel. Or (a) bottom-blown converter steel; (b) Side-blown converter steel; (c) Top blown converter steel. C. electric furnace steel: (a) electric furnace steel; Electroslag furnace steel; Induction furnace steel; (d) Vacuum consumable furnace steel; (e) electron beam furnace steel. (2) According to the deoxidation degree and gating system, a. Boiling steel (f); B. semi-killed steel (b); Killed steel (z); D. special killed steel (TZ). [Edit this paragraph] The serial number name of iron and steel products means 1 carbon steel, also known as carbon steel, which 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. Carbon steel can be divided into carbon structural steel, carbon tool steel and free-cutting structural steel according to its use. Carbon structural steel can be divided into building structural steel and machine-made structural steel. Carbon steel can be divided into low carbon steel (WC 0.25%), medium carbon steel (WC 0.25%-0.6%) and high carbon steel (wc > O.6%%) according to carbon content, and ordinary carbon steel (high phosphorus and sulfur content), high quality carbon steel (low phosphorus and sulfur content) and high quality steel (low phosphorus and sulfur content) according to phosphorus and sulfur content. Generally, the higher the carbon content in carbon steel, the higher the hardness and strength, but the lower the plasticity. Carbon structural steel mainly guarantees mechanical properties, NSK bearings, so its brand reflects its mechanical properties. If the brand is marked with letters A, B, C and D, it means that the steel quality grades are different, the content of S and P decreases in turn, and the steel quality increases in turn. If the brand is marked with the letter F, it is boiling steel; If B is semi-killed steel, if F is not, or B is killed steel. For example, Q235-AF stands for Grade A boiling steel with a yield point of 235MPa, and Q235-c stands for Grade C killed steel carbon structural steel with a yield point of 235MPa. Generally, it can be used directly in the supply state without heat treatment. Generally, Q 195, Q2 15 and Q235 steels have low carbon content, good weldability, good plasticity and toughness, and certain strength. They are usually rolled into thin plates, steel bars, welded steel pipes, etc. , used in bridges, buildings and other structures, as well as manufacturing ordinary rivets, screws, nuts and other parts. Q255 and Q275 steels have high carbon content, high strength, good plasticity and toughness, and can be welded. It is usually rolled into steel, bar and steel plate as structural parts, and high-quality structural steel is used to manufacture simple mechanical parts such as connecting rods, gears, couplings and pins. These steels must ensure chemical composition and mechanical properties. Its brand number is ten thousand parts of the average carbon content in steel (wс 10000), which is expressed by two digits. For example, 45 steel means that the average carbon content in steel is 0.45%; 08 steel means that the average carbon content in steel is 0.08%. High quality carbon structural steel is mainly used to manufacture machine parts. Generally speaking, heat treatment is needed to improve mechanical properties. According to the different mass fraction of carbon, it has different uses. 08,08f, 10, 10F steel has high plasticity and toughness, excellent cold formability and weldability, and is often cold-rolled into thin sheets, which are used to manufacture cold-stamped parts on instrument housings, automobiles and tractors, such as automobile bodies and tractor cabs. 15, 20 and 25 steels are used to manufacture carburized parts with small size, light load, wear-resistant surface and low central strength, such as piston pins and templates. 30, 35, 40, 45 and 50 steels have good comprehensive mechanical properties after heat treatment (quenching+high temperature tempering), that is, they have high strength, high plasticity and toughness. They are used to manufacture shaft parts, such as 40 and 45 steels, and are often used to manufacture crankshaft, connecting rod of automobiles and tractors, spindle of general machine tools, gear of machine tools and other shaft parts with less stress. Steel 55, 60 and 65 have high elastic limit after heat treatment (quenching+medium temperature tempering), and are often used to make springs with small load and small size (cross section size less than 12 ~ 15 mm). For example, four kinds of carbon tool steels, such as pressure regulating and speed regulating spring, plunger spring and cold coil spring, are all high carbon steels, which basically contain no alloying elements and have a carbon content of 0. Its production cost is low, raw materials are easily available and machinability is good, and high hardness and wear resistance can be obtained after treatment. Therefore, it is a kind of steel widely used in manufacturing various tools, molds and measuring tools. However, the red hardness of this steel is poor, that is, when the working temperature is greater than 250℃, the hardness and wear resistance of the steel will drop sharply and the working ability will be lost. In addition, if carbon tool steel is made into larger parts, it is not easy to harden, and it is easy to produce deformation and cracks. 5 Free-cutting structural steel Free-cutting structural steel is to add some elements that make steel brittle, so that chips are easy to break into chips when cutting steel, which is conducive to improving cutting speed and prolonging tool life. The element that makes steel brittle is mainly sulfur. Lead, tellurium, bismuth and other elements are used in ordinary low-alloy free-cutting structural steel. The sulfur content of this steel is in the range of 0.08%-0.30%, and the manganese content wMn is in the range of 0.60%- 1.55%. Sulfur and manganese in steel exist in the form of manganese sulfide, which is brittle and has lubricating effect, making chips easy to break and improving the quality of machined surfaces. In addition to iron, carbon and a small amount of inevitable silicon, manganese, phosphorus and sulfur, alloy steel also contains a certain amount of alloying elements, including silicon, manganese, molybdenum, nickel, chromium, vanadium, titanium, niobium and niobium. This kind of steel is called alloy steel, and the alloy steel system varies with their respective resources, production and use conditions. In the past, Ni-Cr steel series was developed abroad, but in China, it was found that the alloy steel series dominated by silicon, manganese, vanadium, titanium, niobium, boron and rare earth accounted for about 10% of the total steel production. Generally speaking, alloy steel smelted by electric furnace can be divided into 8 categories according to their uses. They are: alloy structural steel, spring steel, bearing steel, alloy tool steel, high-speed tool steel, stainless steel and heat-resistant skinless steel. Silicon steel for electrical purposes 7 ordinary low-alloy steel is an ordinary alloy steel containing a small amount of alloying elements (in most cases, its total W does not exceed 3%). This kind of steel has high strength, good comprehensive properties, corrosion resistance, wear resistance, low temperature resistance, good cutting performance and welding performance. Under the condition of saving a lot of scarce alloy elements (such as nickel and chromium), lt ordinary low-alloy steel can usually be used against 1.2 1.3t carbon steel, and its service life and application range far exceed that of carbon steel. Ordinary low alloy steel can be smelted in open hearth and converter by ordinary smelting method, and the cost is close to that of carbon steel. 8. Alloy steel for engineering structures refers to alloy steel for engineering and building structures, including weldable high-strength alloy structural steel, alloy steel for steel bars, alloy steel for railways, alloy steel for geological and petroleum drilling, alloy steel for pressure vessels and high-manganese wear-resistant steel. This kind of steel is used as a structural component in engineering and building. Among alloy steels, the total alloy content of this kind of steel is low, but it is produced and used in large quantities. 9. Alloy steel for mechanical structure refers to alloy steel suitable for manufacturing machines and mechanical parts. It is based on high-quality carbon turbulent steel, and one or several alloying elements are appropriately added to improve the strength, toughness and hardenability of the steel. This kind of steel is generally used after heat treatment (such as quenching and tempering treatment and surface hardening treatment). It mainly includes alloy structural steel and alloy spring steel, including quenched and tempered alloy steel, surface hardened alloy steel (carburized steel, nitrided steel, surface high frequency hardened steel, etc.). ) and alloy steel used for cold plastic forming (cold heading 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, Nj series steel and B series steel. The carbon content wc of alloy structural steel is lower than that of carbon structural steel, which is generally in the range of O.15%-O. 50%. In addition to carbon, alloy structural steel also contains one or more alloying elements, such as silicon, manganese, vanadium, titanium, boron, nickel, chromium, molybdenum and so on. It is easy to harden, not easy to deform or crack, and convenient for heat treatment to improve the properties of steel. Alloy structural steel is widely used to manufacture various transmission parts and fasteners for 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. 1 1 alloy tool steel is a medium-high carbon steel, which contains many alloying elements such as silicon, chromium, tungsten, molybdenum and vanadium. Alloy tool steel is easy to harden, and it is not easy to produce deformation and cracks. Suitable for manufacturing tools, molds and measuring tools with large size and complex shape. The carbon content of alloy tool steel varies with different uses. The carbon content of most alloy tool steels is 0.5% ~ 1.5%. The carbon content of hot deformation die steel is low, and the wc is in the range of 0.3% ~ 0.6%. General steel for cutting tools contains about WC 1% carbon; Cold working die steel has high carbon content, such as graphite die steel with carbon content of 1.5% and high carbon and high chromium cold working die steel with carbon content of more than 2%. 12 high-speed tool steel is a kind of high-carbon and high-alloy tool steel, with carbon content of 0.7%- 1.4% and alloy elements capable of forming high-hardness carbides. Such as tungsten, molybdenum, chromium and vanadium high-speed tool steels, have high red hardness, and under the condition of high-speed cutting, even if the temperature is as high as 500-600c, the hardness will not decrease, thus ensuring good cutting performance. Spring steel 13 is used under impact, vibration or long-term alternating stress, and is used in bearings, so spring steel is required to have high tensile strength, elastic limit and high fatigue strength. Technically, spring steel is required to have certain hardenability, not easy to decarburize and good surface quality, that is, high-quality carbon structural steel with carbon content of 0.6% ~ 0.9% (including normal and high manganese content). Alloy spring steel is mainly Si-Mn series steel, with slightly lower carbon content. The properties are improved mainly by increasing the silicon content WSI (1.3% ~ 2.8%). In addition, there are alloy spring steels of chromium, tungsten and vanadium. In recent years, according to the requirements of new technology for automobile and tractor design, a new steel with boron, niobium and molybdenum added is developed on the basis of silicon manganese steel, which prolongs the service life of the spring and improves its quality. Bearing steel 14 is used to manufacture ball, roller and Timken bearing rings. Bearing bears great pressure and friction when working, so bearing steel is required to have high and uniform hardness, wear resistance and high elastic limit, NSK. Skf bearing steel has strict requirements on the uniformity of chemical composition, the content and distribution of nonmetallic inclusions and the distribution of carbides. Bearing steel is also called high carbon chromium steel, with carbon content of about L% and chromium content of 0.5%- 1.65%. Bearing steels are divided into six categories: high carbon chromium bearing steel, chromium-free bearing steel, carburized bearing steel, stainless bearing steel, medium and high temperature bearing steel and diamagnetic bearing steel. 15 electrical silicon steel is mainly used to manufacture electrical silicon steel sheets. Silicon steel sheet is a large number of steel used to manufacture motors and transformers. Silicon steel can be divided into low silicon steel and high silicon steel according to its chemical composition. The silicon content of low silicon steel WSI 1.0% ~ 2.5% is mainly used to manufacture motors. The silicon content of high silicon steel is WSi3. O% ~ 4.5%, generally used to manufacture transformers. Their carbon content WCO. 06% ~ 0.08% 16 rail mainly bears the pressure and impact load of rolling stock, so it is required to have sufficient strength, hardness and certain toughness. The commonly used rail steel is carbon killed steel smelted in open hearth and converter, containing 0.6% WC. 0.8%, belonging to medium carbon steel and high carbon steel, but the content of manganese in steel is high, ranging from 0.6%- 1. 1%. In recent years, commonly used low alloy steel rails, such as high silicon rails, medium manganese rails, copper rails and titanium rails, have been widely used. Compared with carbon rail, ordinary low alloy steel rail is more wear-resistant and corrosion-resistant, and its service life is greatly improved. Shipbuilding steel 17 refers to the steel used to manufacture the hull structure of seagoing ships and large inland rivers. Because the hull structure is generally made by welding, it is required that the shipbuilding steel has good welding performance. In addition, it also requires certain strength, toughness, low temperature resistance 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 manganese ship, 16 manganese ship and 15 manganese vanadium ship. These steels have comprehensive characteristics such as high strength, good toughness, easy processing and welding, and seawater corrosion resistance. It can be successfully used to manufacture 10,000-ton ocean-going ship 18 bridge steel, railway or highway bridge to bear the impact load of vehicles. Bridge steel requires certain strength, toughness and good fatigue resistance, and requires high surface quality of steel. Alkaline open hearth killed steel is often used as bridge steel. Recently, common low alloy steels such as 16 Mn, 15 Mn, v, n and so on 19 boiler steels have been successfully adopted. Boiler steel mainly refers to the materials used to manufacture superheater, main steam pipe and heating surface of boiler furnace. The performance requirements of boiler steel are mainly good weldability, certain high temperature strength, alkali corrosion resistance and oxidation resistance. Commonly used boiler steels include low-carbon killed steel smelted in open hearth furnace or low-carbon steel smelted in electric furnace, and the carbon content wc ranges from 0.16% to 0.26%. When manufacturing high-pressure boilers, pearlite heat-resistant steel or austenitic heat-resistant steel is used. In recent years, ordinary low-alloy steels have also been used to build boilers, such as 12 Mn, 15 Mn-V, 18 Mn-Mo-Nb and other 20 kinds of covered electrode steels. These steels are specially used to manufacture covered electrode steel wire for arc welding and gas welding. The composition of steel varies with the welding material. According to the needs, it can be roughly divided into three categories: carbon steel, alloy structural steel and stainless steel. The sulfur and phosphorus contents ws and wP of these steels are less than 0.03%, which is stricter than that of ordinary steels. These steels do not need mechanical properties, Timken bearings, only chemical composition inspection. 2 1 stainless steel is called stainless steel for short and consists of stainless steel and acid-resistant steel. In short, steel that can resist atmospheric corrosion is called stainless steel, and steel that can resist chemical media (such as acid) is called acid-resistant steel. Generally speaking, steel with chromium content greater than 12% has the characteristics of stainless steel. According to the microstructure after heat treatment, stainless steel can be divided into five categories: ferritic stainless steel, martensitic stainless steel, austenitic stainless steel, austenitic-ferritic stainless steel and precipitation hardening stainless steel. At high temperature, steel with oxidation resistance, sufficient high temperature strength and good heat resistance is called heat-resistant steel, FAG. Heat-resistant steel includes oxidation-resistant steel and heat-resistant steel. Oxidation resistant steel is also called skinless steel. Heat-resistant steel refers to steel with good oxidation resistance and high high temperature strength at high temperature. Heat-resistant steel is mainly used as a part for long-term use at high temperature. 23 Superalloy Superalloy refers to a heat-resistant material with sufficient endurance strength, creep strength, thermal fatigue strength, high-temperature toughness and sufficient high-temperature chemical stability. According to their basic chemical composition, thermal power components used at high temperature of about 1000℃ can be divided into nickel-based superalloy, iron-nickel-based superalloy and cobalt-based superalloy. Precision alloys refer to alloys with special physical properties. It is an indispensable material in electrical industry, electronic industry, precision instrument industry and automatic control system. Precision alloys can be divided into seven categories according to their physical properties, namely: soft magnetic alloys, deformed permanent magnetic alloys, elastic alloys, expansion alloys, thermal bimetals, resistance alloys and thermocouple alloys. Most precision alloys are based on ferrous metals, and only a few are based on nonferrous metals. Note: Wc, Ws, Wmn and Wp represent the mass fractions of C, S, mn and P respectively. Table 2 terminology of steel defects.