Product Description
523H15 alloy structural steel is introduced
This kind of steel, with appropriate hardenability, by appropriate metal heat treatment, microstructure uniformity of sorbite, bainite or very fine pearlite, and therefore have a higher tensile strength and yield strength ratio ( in general about 0.85), higher toughness and fatigue strength, and more low ductile - brittle transition temperature, can be used in the manufacture of large cross - section dimension of machine parts.
The alloy elements in the steel structure in rats
There are three aspects: 1increasing the hardenability of steel. Hardenability refers to steel quenching, quenching from the surface into the martensite layer depth, good comprehensive properties of main parameters. In addition to Co, almost all alloy elements such as Mn, Mo, Cr, Ni, Si and C, N, B can increase the hardenability of steel, where Mn, Mo, Cr, B has the strongest effect, followed by Ni, Si, Cu. And strong carbide forming elements such as V, Ti, Nb, only the solution in the austenite can increase the hardenability of steel. The effect of tempering process. As a result of the alloy elements in the steel during tempering can hinder the diffusion of various atoms, and at the same temperature and carbon steel, generally to delay of decomposition of martensite and carbide agglomeration effect, thereby improving the tempering stability, improve the resistance of steel tempering softening capacity, V, W, Ti, Cr, Mo, Si effect is more distinct, Al, Mn, Ni does not play a significant role. Contain higher content of carbide forming elements such as V, W, Mo steel, in 500～ 600℃ tempering, precipitation of fine dispersed special carbide particles such as V4C3, Mo2C, W2C, instead of part of the coarse alloy cementite, the strength of the steel is no longer decreased but increased, appear namely two hardening (see tempering ). Mo on the temper brittleness of steel has prevented or diminished role. The effect of strengthening and toughening of steel. Ni to solid solution strengthening reinforced ferrite; Mo, V, Nb carbide forming elements, both with diffusion hardening and solid solution strengthening methods to improve the yield strength of steel; carbon reinforcement is the most significant. In addition, joining these alloy elements, generally refine the austenite grain, increase grain boundary strengthening effect. Impact toughness of steel Ni more complicated factors, improve the toughness of steel; Mn is easy to make the austenite grain coarsening, on temper embrittlement sensitive; lower P, S content, to improve the purity of steel, to improve the toughness of steel has important role ( see metal reinforcement).
Alloy steel classification
Alloy structural steel is generally divided into the quenching and tempering steel and surface hardening of steel.
Quenched and tempered steel of structure of this kind of steel carbon content is about 0.25%～ 0.55%, for a given size of structure, the quenching and tempering treatment ( quenching and tempering ), if the section along a quenching, quenching, mechanical property is good, if not through the microstructure, the appearance of free ferrite, the toughness drop. On the temper brittleness of steel such as manganese, chromium, nickel chromium steel, tempering after rapid cooling. This kind of steel quenching critical diameter, with grain size and alloy element content increasing, for example,40Cr and 35SiMn steel is about 30～ 40mm, while 40CrNiMo and30CrNi2MoV steel is about 60～ 100mm, commonly used in the manufacture of bears larger load shaft, connecting rod structure.
The surface hardening of steel used in the manufacture of hard surface wear resistance and heart of flexible components, such as gears, shafts and other. To make the parts of high toughness, carbon content in steels should be low, generally 0.12 to0.25%, while the amount of alloy elements, in order to ensure appropriate hardenability. Nitriding steel still need to add to the formation of nitride alloy elements ( such as Al, Cr, Mo etc.). Carburizing or carbonitriding steel, by 850～ 950 ℃carburizing or carbonitriding, quenching and tempering at low temperature (about 200 ℃) conditions using. Nitriding nitriding treatment (480～ 580 ℃), direct use, no longer after quenching and tempering treatment.
Alloy steel production process
According to the quality requirements of steel and steel, alloy structural steel, can be used for oxygen top blowing converter, open-hearth furnace, electric arc furnace; or with ESR, vacuum degassing. Ingot by continuous casting or casting. Ingot should slow cooling or hot forging, rolling. Ingot heating, should strive to uniform temperature and enough holding time, to improve the segregation and avoid forging, rolling, uneven deformation; forging rolled steel, small size, especially about 0.2% carbon steel, in600 ℃should rapid cooling, as to avoid heavy banded structure large forgings; section, measures should be taken to eliminate stress and white. Quenched and tempered steel should be as much as possible into martensite quenching and tempering, into sorbite; carburizing steel during carburizing, carbonitriding layer concentration gradient should not be too large, in order to avoid infiltration layer continuous carbide grain boundaries; nitriding steel must be heat treated to obtain the required performance, and finally finishing ability nitride. Nitriding process in addition to brittle" white layer" grind away, no longer processing.
Other information
Can be divided into common alloy structure steel and special alloy structural steel. The former consists of low alloy high strength steel, low temperature steel, high strength steel, carburizing steel, Quenched and tempered steel and non quenched and tempered steel; the latter includes spring steel, bearing steel, free cutting steel, cold stamping steel.
High yield strength, tensile strength and fatigue strength, and enough plasticity and toughness.
The general use of electric arc furnace and oxygen top blown converter smelting, high requirements of the refining outside the furnace, electric slag remelting or vacuum processing, vacuum induction smelting furnace or a pair of vacuum smelting, proper heat treatment.
This kind of steel alloy element content is high, mainly steel, heat-resistant steel, wear-resistant steel, steel and other special physical and chemical properties of special steel.
Alloy structure steels are widely used in ships, vehicles, aircraft, missiles, weapons, bridge, pressure vessel, such as machine tool structure.
Alloy structural steel than carbon steel has better mechanical properties, especially heat treatment performance.
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