When the annealed iron and steel material is tempered, the cracking caused by rapid cooling, rapid heating or microstructure changes is called tempering cracking. Common tempered hardened steels such as high speed steel and SKD11 die steel can also be cooled after tempering at high temperatures. This kind of steel has a primary deformation of machan bulk during the primary quenching and a secondary deformation of machan bulk during the tempering due to quenching (residual machan bulk deformation), resulting in cracks. Therefore, to prevent tempering cracks, it is necessary to cool the self-tempering temperature slowly, and at the same time, in the quenching and tempering operation, it is also necessary to avoid putting forward tempering and quenching heat treatment way in advance.
Produces tempering tempering was the main cause of deformation of the annealing furnace of residual hard force or change of organization, i.e. by tempering the tensile stress eliminating shrinkage, elimination of compressive stress and expansion, including early tempering carbide precipitation e there will be some shrinkage, xue Ming carbon iron coagulation process will be a large number of shrinkage, residual voss Tian Tie forms of martensitic iron swells, residual voss Tian Tie change formed ductile iron will swell, lead to deformation of the workpiece after tempering. Prevention methods include:
(1) Implement pressurized tempering treatment;
(2) Use hot bath or air quenching to reduce residual stress;
(3) Correction and correction by means of mechanical processing
(4) Reserved deformation amount, etc.
On 2018-08-08 11:45:46
