There are many reasons for the deformation and cracking […]
There are many reasons for the deformation and cracking of the stamping die, which are mainly related to the original structure, the chemical composition of the steel, the structural shape and cross-sectional dimension of the part, and the heat treatment process. Cracking is often preventable, but heat treatment deformation is always difficult to avoid.
In practice, the difference in cross-sectional dimensions, the structural shape of the stamping die parts, and the rate of heating and cooling during heat treatment (heating-insulation-cooling) are different under the combined effects of thermal stress, tissue stress and phase change volume. Causes the volume of the part to expand or contract, which causes the size and shape to deviate, deform, and even cause cracking.
For stamping die forgings of eutectoid steel, normalizing treatment should be carried out first, followed by spheroidizing annealing to eliminate the net secondary cementite in the forging, refine the grains, eliminate the internal stress, and organize the subsequent heat treatment. ready. Before quenching the stamped die parts, low temperature tempering (stabilization) should be performed. For some concave moulds with complex shapes and high precision requirements, before finalizing after rough machining, the quenching and tempering treatment should be carried out to reduce the quenching deformation, avoid the tendency of cracking as much as possible, and prepare for the subsequent heat treatment.
After the mould parts are taken out from the coolant, it is not suitable to stay in the air for a long time. It should be placed in the tempering furnace for tempering. When tempering, low temperature temper brittleness and high temperature temper brittleness should be avoided. For some mould parts with precision requirements, multiple tempering treatments are used after quenching to eliminate internal stress, reduce deformation and avoid cracking tendency.