In mechanical manufacturing, the quenching deformation of the heat treatment is absolute, and the deformation is not relative. In other words, it's just a matter of deformed size. This is mainly due to the surface embossing effect of the martensitic transformation during heat treatment. Preventing heat treatment deformation (dimensional changes and shape changes) is a very difficult task and in many cases has to rely on experience to solve. This is because not only the shape of the steel and the shape of the mold have an effect on the heat treatment deformation, but also the improper carbide distribution state and the forging and heat treatment methods can also cause or aggravate, and in many conditions of heat treatment, as long as a certain condition changes, the deformation of the steel member The degree will vary greatly. Although the heat treatment deformation problem is mainly solved by experience and heuristic method for a long time, the relationship between raw material forging, module orientation, mold shape, heat treatment method and heat treatment deformation is correctly grasped, and the heat treatment deformation law is grasped from the actual data accumulated. It is a very meaningful job to establish archives on heat treatment deformation. Fourth, decarbonization Decarburization is a phenomenon and reaction in which all or part of the carbon in the surface layer is lost due to the action of the surrounding atmosphere during heating or holding of the steel. Decarburization of steel parts not only causes insufficient hardness, quenching and heat treatment deformation and chemical heat treatment defects, but also has a great influence on fatigue strength, wear resistance and mold performance. 5. Cracks caused by electrical discharge machining In the mold manufacturing, the use of electrical discharge machining (electric pulse and wire cutting) is an increasingly common processing method, but with the widespread application of electrical discharge machining, the defects caused by it are correspondingly increased. Since the electric discharge machining is a processing method for melting the surface of the mold by the high temperature generated by the discharge, a white electric discharge machining deterioration layer is formed on the machined surface, and a tensile stress of about 800 MPa is generated, so that the electric machining process of the mold is performed. Deformations such as deformation or cracks often occur. Therefore, the use of EDM molds must fully understand the impact of EDM on mold materials, and take appropriate precautions in advance. Prevent overheating and decarburization during heat treatment, and perform sufficient tempering to reduce or eliminate residual stress; in order to fully eliminate the internal stress generated during quenching, high temperature tempering is required, so steels capable of withstanding high temperature tempering should be used (eg Crl2 type, ASP-23, high speed steel, etc.), processing under stable discharge conditions; after discharge machining, for stable relaxation treatment; setting reasonable process holes and grooves; fully eliminating re-solidified layer, so as to be in a sound state Under the use of the vector translation principle, the part of the internal stress that has been concentrated in the cutting outpost is arbitrarily diverted and discharged. Sixth, insufficient toughness The reason for the insufficient toughness may be that the quenching temperature is too high, and the holding time is too long to cause coarsening of the grains, or tempering due to avoiding the temper brittle zone. Seven, grinding crack When there is a large amount of retained austenite in the workpiece, tempering transformation occurs under the action of grinding heat, thereby generating tissue stress and causing cracking of the workpiece. The precautions are: cryogenic treatment after quenching or repeated tempering (mold tempering is usually 2 to 3 times, even for low-alloy tool steels for cold working), minimizing the amount of retained austenite. Previous page PVC Tape,Adhesive Tape,PVC Adhesive Tape Fenghua Jade Motor Co., Ltd. , http://www.flagtapes.com
Third, the deformation is out of tolerance