Mon, 06 Aug 2018 02:01:36 +0000
deformation heat treatment what is
Description of deformation heat treatment:
A metal heat treatment process that combines pressure processing with heat treatment. By using deformation heat treatment, the dual purpose of forming and improving microstructure can be achieved at the same time, so that the workpiece can obtain excellent strength and toughness, greatly improve the process performance and service performance, give full play to the potential of metal materials, and improve the quality and life of parts.
When forging tools such as chisel and axe, the forging workpiece is put into water immediately for quenching, which is an early application of deformation heat treatment. It can save energy, heating equipment and workshop area, as well as oxidation, decarbonization and distortion during reheating.
Deformation heat treatment has been applied more and more widely since the early 1950s. It can be used not only for various carbon structural steels and alloy structural steels, but also for tool steels, stainless steels, heat resistant steels, high temperature alloys, as well as non-ferrous metal alloys based on aluminum, magnesium, titanium and copper. This process can adopt various thermal deformation, temperature deformation, cold deformation forming methods, such as forging, rolling, extrusion, drawing and other integral pressure processing, spinning pressure, swing rolling pressure, powerful shot blasting and other surface or local deformation. Deformation heat treatment is mainly used for workpieces with simple shape, change of section and small machining allowance. There are many techniques of deformation heat treatment, including high temperature deformation heat treatment and low temperature deformation heat treatment.
High temperature deformation and heat treatment:
It can also be divided into high temperature deformation quenching, high temperature deformation isothermal quenching and high temperature deformation normalizing.
(1) the high temperature deformation quenching: heat the steel to the Ac3 (see above) steel microstructure (950 ~ 1250 ℃) hot forging or hot rolling, and then a sharp cooling in the water or oil, quenching. This method is applicable to low carbon and medium carbon carbon structural steel and various kinds of low alloy structural steel. It can improve the strength of steel, improve the plasticity and toughness, reduce the sensitivity of tempering brittleness, and improve the brittleness resistance at low temperature. Vacuum hot deformation isothermal quenching: steel parts after high temperature heating and deformation are placed in hot bath for enough time to make isothermal transformation. The fine lamellar pearlite structure can be obtained after isothermal transformation in the pearlite temperature region, so as to improve the strength and toughness of steel. Isothermal transformation in the bainitic region can increase the strength even more. This process can be used for steel wire, screw and other metal products and parts.
Resistance to high temperature deformation and normalizing: the steel material subjected to high temperature deformation is cooled by blow, water or spray to obtain fine ferrite and pearlite tissue, so as to reduce brittle transition temperature while improving material strength. This process is mainly used for low carbon low alloy high strength steel. This is the way to control rolling more and more widely.
Low temperature deformation and heat treatment:
It can be distinguished as cold deformation quenching, cold deformation isothermal quenching, etc.
Deformation quenching: (1) the low temperature heat the steel material to normal austenitizing temperature, and then stay between 500 ~ 600 ℃, stay inside and outside temperature uniform shape variables is 60 ~ 90% immediately after deformation, then quenched. This method is suitable for steel with high content of alloy elements and long incubation period of supercooled austenite, such as hot die steel, which can obtain high tensile strength (up to 294 mpa) with little loss of plasticity.
Potassium isothermal quenching of low-temperature deformation: can be used for steel with slightly lower alloy elements. First, the steel is heated to the austenitic temperature, then deformed in the lower bainite area, and then hardened. The workpiece can obtain moderate strength and good toughness after quenching at low temperature deformation isothermal.