I can not do heat treatment without deformation, just reduce the deformation!
In the actual production, heat treatment deformation increase a lot of difficulties for the follow-up process, especially mechanical processing, which affect the production efficiency, the part will be waste due to too large deformation. Deformation is more difficult to solve the problem of heat treatment, it is impossible to completely eliminate deformation, the deformation is generally controlled in a certain range.
First, the reasons for heat treatment deformation
The heating and cooling process of steel bar heat treatment may produce deformation or even crack, the reason is due to the existence of quenching stress. Quenching stress is divided into thermal stress and tissue stress. Due to the functions of thermal stress and tissue stress, the parts will has different residual stress after heat treatment, which may cause deformation. When the stress is greater than the yield strength of the material, deformation will occur, therefore, quenching deformation is also related to the yield strength of steel, the greater the Plasticity deformation resistance is, the smaller the degree of deformation is.
In the heating and cooling process, due to the existence of temperature difference between parts surface and core, the thermal expansion and contraction will cause thermal stress.The surface heat will quickly lose, so the temperature is lower than the core.
2. Organizational stress
Tissue stress produce is due to different specific volume for austenite and its transformation products. Due to the smallest specific volume of austenite, its volume will surely increase during quenching cooling process.When quenching, the surface will transfer into martensite first, the volume will become big. But the core austenite volume haven’t change. Then the core will produces tensile stress.
Second, the ways to reduce and control the heat treatment deformation
1. Reasonable selection and improvement of hardness requirements.
For the parts which have complex shape, larger cross-sectional size but requires less deformation, user should choose the material with better hardenability in order to use more moderate quenching cooling medium quenching. For thin plate-like precision parts, user should choose both sides rolling plate.
2. Design the parts correctly
Parts shape should be as simple as possible, uniform, symmetrical structure, so as to avoid increasing deformation tendency due to uneven cooling. Try to avoid sudden changes in section size, reduce the groove and thin edge, do not have sharp edges and corners.
3. Reasonable arrangements for production lines, coordination the relationship of hot & cold processing and heat treatment
For the parts with complex shape and high precision parts, user should be do pre-heat treatment between rough and finishing, such as the elimination of stress, annealing and so on.
Contact person: Hailee Ma
Phone: 0086-18932783253(whatsapp, wechat)
Specialist of induction heating system in China; Glad to be your business partner in induction heating field.
Post time: 09-25-2017