In the production and processing of die-casting die parts, due to its complex shape and structure, there are obvious differences in the section size of each part, so the heating and cooling rates of each part are not the same during the heat treatment. This situation may lead to different thermal stress, microstructure stress and phase transformation volume in each part of the part. It causes the abnormal expansion or contraction of the volume of the parts, resulting in large deviation between the size and shape, and even cracking. The following is a brief introduction from the mold processing factory:
1. There are many reasons for heat treatment deformation and cracking of die casting die, including chemical composition and original structure of steel, structural shape and section size of parts, heat treatment process and other factors. In the actual production, deformation is often unable to completely eliminate, only to minimize the extent of its occurrence, but as long as appropriate measures are taken, the cracking can be completely avoided.
2. Pre heat treatment is relative to heat treatment, that is, adding a heat treatment step to play a preparatory role before heat treatment, which can provide a good machining performance or microstructure for heat treatment. Common preparation heat treatment processes include annealing, normalizing, quenching and tempering.
3. Quenching and tempering are easy to cause deformation and cracking of parts. For some small die-casting dies, slender cylindrical parts or high alloy steel die parts, the direct heating quenching method should be avoided. Instead, they should be preheated to 520-580 ℃, and then put into the medium temperature salt bath furnace for heating to the quenching temperature. The practice shows that the deformation of the parts with this heating method is obviously smaller than that of the parts quenched directly in the electric furnace or reverberatory furnace, and the cracking can be basically avoided.
4. When the die-casting die parts are heated, they should not be directly put into the coolant after they are taken out from the furnace, which will easily cause excessive local temperature difference and lead to deformation and cracking. The correct method is to put the parts into air for precooling, and then put them into the coolant for quenching.
5. Die casting die parts should not stay in the air too long after quenching in the coolant, but should be put into the tempering furnace for tempering treatment in time, so as to eliminate the internal stress of parts and reduce the tendency of deformation and cracking. Especially for some die-casting die parts that need to be processed by WEDM, the hierarchical quenching and multiple tempering heat treatment before WEDM can effectively improve the hardenability of the parts, make the internal stress distribution uniform, and prevent deformation and cracking. In the process of tempering, it is necessary to avoid the occurrence of low temperature temper brittleness and high temperature temper brittleness.
The above is a small die-casting mold processing plant to explain to you to prevent die-casting mold deformation cracking tips, I hope to help you!