1.Carbon steel
Carbon steel, also known as carbon steel, is an iron-carbon alloy with a carbon content of ωc less than 2%. Carbon steel in addition to carbon generally contains a small amount of silicon, manganese, sulfur, phosphorus.
According to the use of carbon steel can be divided into carbon structural steel, carbon tool steel and free cutting structural steel three categories. Carbon structural steel can be divided into two types of structural steel and machine structural steel. According to the carbon content of carbon steel can be divided into low carbon steel (ωc ≤ 0.25%), medium carbon steel (ωc = 0.25% -0.6%) and high carbon steel (ωc> 0.6%)
According to the amount of phosphorus, sulfur can be divided into ordinary carbon steel carbon steel (containing phosphorus, sulfur higher), high-quality carbon steel (containing phosphorus, sulfur lower) and high-quality steel (containing phosphorus, sulfur lower) general carbon steel in the carbon content of the higher the higher the hardness, the strength is also high, but the plasticity is reduced.
2, carbon structural steel
This type of steel is mainly to ensure mechanical properties. Therefore, its grade reflects its mechanical properties, with Q + digital representation of which 'Q' for the yield point 'yield' the word of the Hanyu Pinyin prefix.
Numbers indicate the yield point value, for example, Q275 that the yield point of 275Mpa, if the grade number marked with the letters A, B, C, D, it means that the quality of the steel grade is different, containing the amount of S, P, the amount of lower, the quality of the steel in order to improve.
If the label after the grade letter 'F' is boiling steel, marked 'b' for semi-sedated steel, not marked 'F' or 'b' for sedated steel. ' for the sedentary steel. For example, Q235-AF indicates that the yield point of 235MPa A grade boiling steel, Q235-C indicates that the yield point of 235MPa C grade sedentary steel.
Carbon structural steel is normally used directly in the state of supply without heat treatment. Usually Q195, Q215, Q235 steel carbon quality fraction is low, good welding performance, good plasticity, toughness, have a certain strength, often rolled into thin plates, reinforcing bars, welded steel tubes and so on.
Used for bridges, buildings and other structures and the manufacture of ordinary rivets, screws, nuts and other parts. Q255 and Q275 steel carbon mass fraction is slightly higher, higher strength, plasticity, toughness, can be welded, usually rolled forming steel, steel and steel plate for structural components and the manufacture of simple machinery such as connecting rods, gears, couplings, pins and other parts.
3, high-quality structural steel
This type of steel must also ensure that the chemical composition and mechanical properties. Its grade is a two-digit number indicating the average carbon mass fraction of steel in ten thousand fractions (ωс * 10,000). For example, 45 steel that steel in the average carbon mass fraction of 0.45%; 08 steel that steel in the average carbon mass fraction of 0.08%.
High-quality carbon structural steel is mainly used in the manufacture of machine parts. They are generally heat-treated to improve mechanical properties. Depending on the carbon mass fraction, there are different uses.
08, 08F, 10, 10F steel, high plasticity, toughness, with excellent cold forming properties and welding properties, often cold rolled into thin plates, used to make instrument housings, automobiles and tractors on the cold stamping parts, such as car body, tractor cabs;
15, 20, 25 steel used in the production of smaller size, lighter load, surface requirements of wear resistance, the heart of the strength requirements of the carburised parts, such as piston pins, samples and so on;
30, 35, 40, 45, 50 steel after heat treatment (quenching + high temperature tempering) has good overall mechanical properties, that is, with high strength and high plasticity, toughness, used to make shaft parts, such as 40, 45 steel is commonly used in the manufacture of automobiles, tractors, crankshafts, connecting rods, general machine tool spindles, machine tools, gears and other shafts are not much of a force parts;
55, 60, 65 steel heat treatment (quenching + medium temperature tempering) has a high elastic limit, commonly used in the production of load is not small, small size (cross-section size of less than 12 ~ 15mm) of the spring, such as regulating the pressure and speed springs, plunger springs, cold rolled springs and so on.
4、Carbon tool steel
Carbon tool steel is basically no alloying elements of high-carbon steel, carbon content in the range of 0.65% - 1.35%, its low production costs, easy access to raw materials, good cutting and machining, heat treatment can be obtained after the high hardness and high abrasion resistance, so it is a widely used steel used to make a variety of edged tools, moulds, gauges.
But the red hardness of this type of 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 lose the ability to work. In addition, carbon tool steel, such as made of larger parts is not easy to harden, and easy to produce deformation and cracks.
5, free cutting structural steel
Free cutting structural steel is in the steel to add some elements to make steel brittle, so that when cutting steel cutting easy to brittle broken into chips, thus helping to improve cutting speed and extend tool life. Elements that make steel brittle are mainly sulphur, and lead, tellurium, bismuth and other elements are used in ordinary low-alloy free-cutting structural steel.
The sulphur content of this steel is in the range of 0.08%-0.30% and the manganese content is in the range of 0.60%-1.55%. The sulphur and manganese in the steel exist in the form of manganese sulphide, which is brittle and has a lubricating effect, thus making the chips easy to break and helping to improve the quality of the machined surface.
6、Alloy steel
In addition to the steel contains iron, carbon and a small amount of unavoidable silicon, manganese, phosphorus, sulfur elements, but also contains a certain amount of alloying elements, steel alloying elements are silicon, manganese, molybdenum, nickel, chromium, vanadium, titanium, niobium, boron, lead, rare earths and so on which and one or several kinds of, this steel is called alloy steel.
Alloy steel system with their respective resources, production and use of different conditions, foreign countries used to develop nickel, chromium steel system, China's development of silicon, manganese, vanadium, titanium, niobium, boron, rare earths, mainly alloy steel system.
Alloy steel in the total output of steel accounted for about ten per cent, generally smelted in an electric furnace according to the use of alloy steel can be divided into eight categories, they are: alloy structural steel, spring steel, bearing steel, alloy tool steel, high-speed tool steel, stainless steel, heat-resistant steel, electrician with silicon steel.
7、Ordinary low alloy steel
Ordinary low alloy steel is a small amount of alloying elements (in most cases the total amount of not more than 3%) of the ordinary alloy steel. This steel is relatively high strength, good overall performance, and has corrosion resistance, wear resistance, low temperature resistance and better cutting performance, welding performance in a large number of savings in scarce alloying elements (such as nickel, chromium) under the conditions of the usual 1t ordinary low alloy steel can be top 1.2-1.3t of carbon steel to use, and its service life and the use of the scope of the carbon steel is much more than the carbon steel. Ordinary low alloy steel can be smelted with general smelting methods in the flat furnace, converter smelting, and the cost is close to carbon steel.
8, engineering structural alloy steel
This refers to engineering and construction structures with alloy steel, including weldable high-strength alloy structural steel, alloy reinforcing steel, railway alloy steel, geological and petroleum drilling alloy steel, pressure vessels with alloy steel, high manganese wear-resistant steel and so on. These steels are used as engineering and construction structural parts, in the alloy steel, the total alloy content of such steel is low, but the production and use of a larger amount.
9, mechanical structure with alloy steel
This type of steel is suitable for the manufacture of machines and mechanical parts of alloy steel. It is based on high-quality carbon steel, the appropriate addition of one or more alloying elements, used to improve the strength, toughness and hardenability of steel. This type of steel is usually used after heat treatment (such as tempering treatment, surface hardening treatment).
Mainly includes commonly used alloy structural steel and alloy spring steel two categories, including tempering treatment of alloy steel, surface hardening treatment of alloy steel (carburising steel, nitriding steel, surface high-frequency quenching of steel, etc.), cold plastic forming alloy steel (cold top forging steel, cold extrusion steel, etc.).
According to the chemical composition of the basic composition series 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 and so on.
10、Alloy structural steel
Alloy structural steel carbon content than carbon structural steel lower, generally in the range of 0.15% -0.50%. In addition to carbon, but also contains one or more alloying elements, such as silicon, manganese, vanadium, titanium, boron and nickel, chromium, molybdenum and so on. Alloy structural steel is easy to harden and not easy to deformation or cracking, easy to heat treatment to improve the performance of steel.
Alloy structural steel is widely used in the manufacture of automobiles, tractors, ships, turbines, heavy machine tools and fasteners for a variety of transmission parts. Low-carbon alloy steel is generally carburised, medium-carbon alloy steel is generally tempered.
11, alloy tool steel
Alloy tool steel is containing a variety of alloying elements, such as silicon, chromium, tungsten, molybdenum, vanadium and other medium and high carbon steel. Alloy tool steel is easy to harden, not easy to produce deformation and cracks, suitable for use in the manufacture of large size, complex shape of the cutting edge, moulds and gauges for different purposes, alloy tool steel carbon content is also different.
Most of the alloy tool steel carbon content ωc for 0.5% - 1.5%, hot deformation of mould steel carbon content is lower, ωc in the range of 0.3% -0.6%; cutting tool steel generally contain carbon ωc1% or so;
Cold working mould steel is higher carbon content, such as graphite mould steel carbon content ωc up to 1.5%, high carbon and high chromium cold working mould steel carbon content ωc up to 2% or more.
12, high-speed tool steel
High-speed tool steel is a high-carbon, high-alloy tool steel, steel carbon content ωc 0.7% - 1.4%, steel contains alloying elements that can form high hardness carbide, such as tungsten, molybdenum, chromium, vanadium.
High-speed tool steel has a high red hardness, in high-speed cutting conditions, temperatures as high as 500-600 ℃ hardness is not reduced, thus ensuring good cutting performance!
13、Spring
Spring in shock, vibration or long-term alternating stress, so the spring steel is required to have high tensile strength, elastic limit, high fatigue strength. In the process requires a certain degree of hardenability of spring steel, not easy to decarburise, good surface quality, etc.
Carbon spring steel, that is, the carbon content ωc in the range of 0.6% -0.9% of high-quality carbon structural steel (including normal and higher manganese content). Alloy spring steel is mainly silicomanganese steel, their carbon content is slightly lower, mainly by increasing the silicon content ωsi (1.3%-2.8%) to improve performance;
There are also chromium, tungsten, vanadium alloy spring steel. In recent years, combined with China's resources, and according to the automobile, tractor design new technology requirements, developed in the silicomanganese steel based on the addition of boron, niobium, molybdenum, and other elements of the new steel, to extend the service life of the spring, and improve the quality of spring steel.
14, bearing steel
Bearing steel is used to manufacture balls, rollers and bearing rings of steel. Bearings are subject to great pressure and friction when working, so bearing steel is required to have high and uniform hardness and wear resistance, as well as high elasticity limit. The uniformity of the chemical composition of the bearing steel, the content and distribution of non-metallic inclusions, the distribution of carbides and other requirements are very strict.
Bearing steel is also known as high-carbon chromium steel, containing carbon ωc is about 1%, lead content ωcr is 0.5%-1.65%. Bearing steel is divided into high carbon chromium bearing steel, chromium-free bearing steel, carburised bearing steel, stainless bearing steel, high temperature bearing steel and antimagnetic bearing steel six categories.
15、Silicon steel for electrical industry
Silicon steel for electrical appliances is mainly used to manufacture silicon steel sheet for electrical appliances. Silicon steel sheet is a large amount of steel used in the manufacture of motors and transformers. According to the chemical composition of silicon steel can be divided into low-silicon steel and high-silicon steel. Low silicon steel silicon content ωsi = 1.0% -2.5%, mainly used in the manufacture of motors; high silicon steel silicon content ωsi = 3.0% -4.5%, generally used in the manufacture of transformers. Their carbon content ωc = 0.06%-0.08%.
16、Rail steel
Steel rails are mainly subjected to rolling stock pressure and impact loads, therefore. Requirements for adequate strength and hardness and a certain degree of toughness. Usually used rails are flat furnace and converter smelting carbon sedentary steel, this steel contains carbon ωC = 0.6% -0.8%, belongs to the middle carbon steel and high carbon steel, but the steel contains manganese ωMn higher, in the range of 0.6%-1.1%. In recent years, ordinary low alloy steel rails have been widely used, such as high silicon rails, medium manganese rails, copper-containing rails, titanium-containing rails and so on. Ordinary low alloy steel rail than carbon steel rail wear-resistant, corrosion-resistant, service life has been greatly improved.
17、Shipbuilding steel
Shipbuilding steel refers to the steel used in the manufacture of sea-going vessels and large river trade vessels hull structure. As the hull structure is generally manufactured using welding methods, where the requirements of shipbuilding steel has better welding performance. In addition, it is also required to have a certain degree of strength, toughness and a certain degree of low temperature resistance and corrosion resistance. In the past, the main use of low carbon steel as shipbuilding steel. Recently, a large number of ordinary low alloy steel, there are steel such as 12 manganese ship, 16 manganese ship, 15 manganese vanadium ship and other steel. These steel grades have high strength, good toughness, easy processing and welding, seawater corrosion resistance and other comprehensive characteristics, can be successfully used to manufacture 10,000 tonnes of ocean-going giant ships.
18, bridge steel
Railway or highway bridges bear the impact load of vehicles, bridge steel requires a certain degree of strength, toughness and good fatigue resistance, and the surface quality of the steel requires high. Bridge steel is often used alkaline flat furnace quiescent steel. Recently successfully used ordinary low alloy steel such as 16 manganese, 15 manganese vanadium and nitrogen.
19, boiler steel
Boiler steel is mainly used to manufacture superheater, main steam pipe and boiler fire chamber heating surface with the material. Boiler steel performance requirements are mainly good welding properties, a certain degree of high-temperature strength and resistance to alkali corrosion, oxidation resistance. Commonly used boiler steel has a flat furnace smelting of low-carbon sedentary steel or electric furnace smelting of low carbon steel, carbon content ωc in the range of 0.16% -0.26%. Manufacture of high-pressure boilers are applied to pearlite heat-resistant steel or austenitic heat-resistant steel. In recent years, the use of ordinary low alloy steel boiler construction, such as 12 manganese, 15 manganese vanadium, 18 manganese molybdenum niobium.
20, welding rod steel
This type of steel is specifically for the manufacture of electric arc welding and gas welding rods with steel wire. Steel composition varies with the welding material. According to the needs of carbon steel, alloy structural steel and stainless steel three categories. The sulphur and phosphorus content of these steels ωs, ωp is not more than 0.03%, higher than the general steel requirements. These steels do not require mechanical properties, but only for the chemical composition of the test.
21, stainless steel
Stainless acid-resistant steel is referred to as stainless steel, which is composed of two major parts of stainless steel and acid-resistant steel. In short, can resist atmospheric corrosion of steel called stainless steel, and can resist chemical media (such as acids) corrosion of steel called acid-resistant steel. Generally speaking, the chromium content ωcr greater than 12% of the steel has the characteristics of stainless steel; in the stainless steel according to the microstructure after heat treatment can be divided into five categories: that is, ferrite stainless steel, martensitic stainless steel, austenitic stainless steel, austenitic - ferrite stainless steel and precipitation hardening stainless steel.
22、Heat-resistant steel
Under high temperature conditions, with oxidation resistance and sufficient high temperature strength and good heat-resistant steel is called heat-resistant steel. Heat-resistant steel, including oxidation-resistant steel and heat-strengthened steel two categories. Oxidation-resistant steel is also known as non-skinning steel. Heat-strengthened steel is a steel with good oxidation resistance and high high-temperature strength at high temperatures. Heat-resistant steel is mainly used for long-term use of parts at high temperatures.
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