There are many reasons for the deformation and cracking of the Dustbin Mould, 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. Cracks are usually preventable, but heat treatment deformation is always difficult to avoid.
In practice, the difference in cross-sectional dimensions, the structural shape of the dustbin mould parts, and the heating and cooling rates during heat treatment (heating-insulation-cooling) are different under the combined action of thermal stress, tissue stress and combined stress. . Phase variable. This causes the part to expand or contract in volume, resulting in deviations in size and shape, and even cracking.
For the eutectoid steel stamping die forgings, normalizing treatment should be carried out first, followed by spheroidizing annealing to eliminate the net secondary cementite in the forgings, refine the grains, eliminate the internal stress, and organize the subsequent heat treatment. ready. Low temperature tempering (stability) should be performed before quenching the parts of the waste bin. For some concave moulds with complex shapes and high precision requirements, after roughing, quenching and tempering should be carried out to reduce quenching deformation, avoid cracking as much as possible, and prepare for subsequent heat treatment. .
After removing the dustbin mould piece from the coolant, it is not suitable for staying in the air for a long time. It should be placed in a tempering furnace for tempering. When tempering, low temperature temper brittleness and high temperature temper brittleness should be avoided. For some dustbin mould parts with high precision requirements, multiple tempering treatments are used after quenching to eliminate internal stress, reduce deformation and avoid cracking tendency.
