1. Some of the molds produce only a few hundred pieces of the cracked grain, and the crack develops rapidly.Capable of guaranteeing the appearance size, only when is forging and steel of the dendritic crystal, mixed carbide, loose defects such as shrinkage cavity, bubbles stretched along the processing method is extended, streamline, the streamline final quenching distortion and cracking in the future, in the process of the use of effect has enormous influence on the tendency.
2. The cutting stress occurred during the final processing of cars, milling and planing, which can be eliminated by the center annealing.
3. The grinding stress occurs when the hardened steel is grinding, and the friction heat occurs during grinding. The softening layer and decarburization layer occur, which reduces the strength of the heat, which easily leads to hot crack and early cracks.Of H13 steel after fine grinding, tolerated heated to 510-570 ℃, to one hour per 25 mm insulation thickness to eliminate stress annealing.
4. Stress of electrical discharge machining.The surface of the mould has a layer of enriched electrode element and dielectric element white bright layer, hard and brittle, this layer itself will have cracks, there is stress.The high frequency should be used in the electric discharge machining to minimize the whitening layer. The polishing method must be removed and the tempering treatment is carried out, and the tempering is carried out at the three level tempering temperature.