Alloy steel is divided into high-quality alloy steel and special-quality alloy steel. The quality and performance of high-quality alloy steel must be specially controlled during the production process; quality and performance must be strictly controlled during the production of special-quality alloy steel.
Alloy steel for general engineering structure
Alloy steel for general engineering structure belongs to high-quality alloy steel commonly known as composite steel. Mainly used to manufacture mechanical structural parts, mostly used after heat treatment. Due to the effect of alloying elements, increase hardenability (Mn, Mo, Cr), refine grains (V, Ti…) to improve quenching stability. After the low-carbon alloy structural steel is carburized, nitrogen-quenched and low-temperature tempered, the surface of the component is wear-resistant and the core toughness is good. It is also called surface hardened steel; the medium-carbon alloy structural steel can obtain good comprehensive performance after quenching and tempering. , Called regulator steel.
Composite steel grades are represented by two Arabic numerals and alloy element symbols and numbers. The numbers indicate the average carbon content in ten thousand. When the average alloy content is less than 1.5%, only the element symbol is indicated in the steel number, and the content is not indicated, and the content is greater than 1.5% When, use numbers to indicate.
In addition to alloy steel, high-quality alloy steel also includes alloy steel, alloy steel for geological and petroleum drilling, electrical silicon steel, and alloy steel for railway.
Spring steel is used to produce various leaf springs and coil springs or similar parts (such as rolls, etc.). A spring is a structural part that can produce a large amount of elastic deformation. Through the elastic deformation of the spring, it can absorb impact energy, alleviate the impact and vibration. Therefore, the requirements for spring steel must have high strength, especially high yield strength and Fatigue strength; it must not be easy to decarburize, have good surface quality, have certain hardenability and good process performance. Some springs also require heat resistance and corrosion resistance. Therefore, the carbon content of spring steel is relatively high, spring steel has alloy and non-alloy,
Carbon spring steels such as 65, 70, 75, and 80 have poor hardenability, and are mostly used for springs with a diameter or thickness of less than 12 mm; 65Mn has good hardenability and can be used to make springs with a cross-sectional size of 15-20 mm. widely. Larger size, most of the springs manufactured by hot rolling are 55Si2Mn, 60Si2Mn, such as leaf springs and coil springs on railway cars, automobiles, tractors, etc.; springs with large cross-sections and heavy loads usually use 50CrVa, 60Si2CrVa, 50CrMn, 65Si2MnWa, etc. manufacture.
Rolling bearing steel
Rolling bearing steel is also called bearing steel. It is mainly used to make rolling bearing inner and outer rings, balls, balls, cages, etc., but it is also widely used in measuring tools, cold work molds, low-alloy tools, diesel engine high-pressure oil pump parts, etc. There are many types of bearing steels with more high-carbon chromium, carburizing, stainless, high temperature, non-magnetic bearing steels. The grades of carburized bearing steel use “G” as the prefix in Chinese Pinyin, and the last number indicates the percentage of carbon. The number after the Cr element indicates the nominal percentage of the chromium content. The symbol of the element and its nominal content are expressed as a percentage.
High-carbon chromium stainless steel is represented by numbers (nominal thousand fractions of carbon), chromium element symbols and content percentages, and symbols containing other elements. The grades and chemical compositions are shown in the table
Alloy tool steel
In order to overcome the weakness of low hardenability of carbon tool steel and improve wear resistance, while maintaining a higher carbon content, Si, Mn, Cr, W, Mo, V, etc. are added to the steel to improve the hardenability of composite steel. Permeability, widely used in carbon steel tools with performance that can meet the requirements. The grades of Hegong Steel are composed of numerical chemical element symbols. When the carbon content in the steel is less than 1.00%, the number before the grade indicates the nominal carbon content per thousand, and the original number before the grade indicates that the carbon content is not less than 1.00% The number after the element symbol indicates the nominal percentage of the gold element, and the content is less than 1.5%.
Alloy tool steel is divided into measuring tool steel, impact-resistant tool steel, cold iron die steel, hot work die steel, magnetic die steel and plastic die steel according to its purpose.
Measuring tool steel contains 0.08-1.45% carbon, and alloy elements such as Cr, Mn, Si, W are added. Cr, Si, Mn improve the hardenability of steel; at the same time, Cr, Si, can also improve tempering stability; Mn also reduces quenching deformation; W improves wear resistance and refines the structure. This type of steel is mainly used to manufacture cutting tools such as turning tools, planers, reamers, broaches, and gauges, templates, micrometers, plug gauges and other measuring tools. Impact-resistant tool steels include 4Cr2Si, 5CrW2Si, and 6CrW2Si, which belong to medium-carbon tungsten steel. By reducing the carbon content to increase toughness, tungsten improves the wear resistance of steel, and is used to make tools subject to large impact loads, such as cold work dies, upsetting dies, and wind chisels.
Mold steel is used to manufacture forming molds, including cold work mold steel, hot work mold steel, hot work mold steel, non-magnetic mold steel and plastic mold steel.
High-speed tool steel
In order to meet the requirements of cutting tool linear speed up to 80m/min, cutting edge temperature up to 60ºC, and tool hardness HRC>60, high-speed steel is obtained by adding a large amount of W, Mo, Cr, V and other alloy elements to high-carbon steel. And Mn can improve the thermal hardness of steel. At the tempering temperature of 500ºC-600ºC, W and Mo precipitate and generate Mo2C and W2C, and secondary hardening occurs (the hardness of steel will not decrease when the temperature is 500ºC-600ºC, but will increase instead.
Phenomenon of secondary hardening of leaves). Among the high-speed tool steels, W18Cr4V is the world’s earliest produced and most commonly used high-tech steel, which is used to manufacture various tools, such as turning tools, gear shapers, reamers, drills, etc. However, due to severe segregation of carbides and low thermoplasticity, further use is restricted. CW6MoCr4V2 is a Mo-based high-speed steel that replaces W with Mo. It has uniform carbide distribution, good thermoplasticity, and low price (my country’s molybdenum reserves and production are high), but it has a slightly lower thermal hardness and is still the main rigidity of high-speed steel.