Quenching treatment: quenching + tempering = double heat treatment and quenching and tempering, the purpose is to make the workpiece has good mechanical properties.
Heat treatment of steel, including annealing, normalizing, quenching, tempering and surface heat treatment methods. It also includes tempering treatment and aging treatment.
Steel tempering: on the basis of hardened steel under certain temperature and then heated to (350 ℃ ~ 650 ℃), the mechanical properties of carbon in the form of fine cementite precipitation distribution. With the increase of tempering temperature, carbide particles increase, yield point and tensile strength decrease, hardness and brittleness decrease, elongation and shrinkage increase. Its purpose is to eliminate the internal stress produced by quenching, in order to obtain the required mechanical properties.
Quenching treatment: quenching method is called quenching. Tempering is refers to between 500-650 ℃ tempering. The properties and materials of quenched and tempered steel can be greatly adjusted, and its strength, ductility and toughness are very good, with good mechanical properties. Soxhlet after conditioning treatment. Sorbite (tempered sorbite) is the tempered martensite formed at that time, which is distinguished by optical zoom lens for more than 500 ~ 600 times under the microscope, so that the compound grain structure of carbide ferrite matrix (including cementite) is distributed. It is also a mixture of tempered martensite, ferrite and granular carbide. In this ferrite, there is basically no oversaturation of carbon, and the stable carbides are carbides. It's an equilibrium tissue at room temperature.
Aging treatment: in order to eliminate or mould precision measurement, parts of the size, shape, change for a long time, often in the low temperature tempering (150-250 ℃ tempering temperature) completed before the workpiece and then heated to 100-150 ℃, 5-20 hours to keep the stable quality and precision parts processing, known as aging. It is particularly important to conduct low temperature aging treatment under the condition of steel component or dynamic load to eliminate residual stress, microstructure stability and size of steel.
Class: quenched and tempered steels are carbon steels and alloy quenched and tempered steels. If the carbon content is too high, the strength of the workpiece after quenching is very high, but the toughness is not enough, because the carbon content is too low, the toughness and strength is insufficient. In order to obtain a good overall quenching performance of the workpiece, the carbon content is generally controlled at 0.30% to 0.50%.
When the whole cross section of the workpiece is required for quenching hardenability, the main martensite structure of the workpiece fine needle is obtained after quenching. Uniform sorbite oriented structure was obtained by tempering. Each furnace is impossible to be engaged in small factory metallurgical analysis, generally only for hardness test, that is, after quenching must meet the hardness requirements of the material, its hardness requirements in the tempering diagram inspection.