Mould

It has good matching of tensile strength, yield strength, reduction of area, elongation, impact toughness and hardness within the range of mold service temperature (room temperature to maximum working temperature). 1) Different types of molds with tensile strength and yield strength focus on the specific mechanical properties required by forging die materials. At the same time, the room temperature mechanical properties should not only be considered and the more important actual working temperature performance indicators should not be ignored; do not pursue blindly A comprehensive high index that is out of reality. For example: in cold forging hard-to-deform alloy forgings with extremely high deformation resistance, when the stress of the die exceeds the tensile strength of the forging die material at the service temperature, the die will be cracked and scrapped; if the stress of the die exceeds the forging die material When the yield strength at the service temperature is used, it will cause permanent deformation such as die collapse, resulting in excessive forgings. Under this condition, it is necessary to choose forging die materials with high tensile strength and yield strength. Generally, the tensile strength of forging die materials should be greater than 30% of the stress that should be withstood. 2) Impact toughness, reduction of area and elongation. Since the choice of impact toughness index of forging die materials is closely related to the properties of forging load, for the die used in impact load equipment such as forging hammers and screw presses, if the forging die material is used The impact toughness is low, and the die may crack and be scrapped; under this condition, it is necessary to choose a forging die material with high impact toughness. For forging die materials with high shrinkage of area and elongation, they can be used in the presence of micro cracks without breaking quickly. Therefore, as far as possible under the conditions of tensile strength, yield strength and hardness index permitting Ground increase its reduction of area and elongation. 3) Hardness In view of the fact that hardness has a corresponding relationship with the strength index, it is also closely related to the wear resistance of the mold. Under the conditions of impact toughness, reduction of area and elongation, the hardness (or wear resistance) Sex). Forging die hardness and red hardness are important properties of forging die materials, and the die should be able to keep its shape and size unchanged when working at high temperatures. As we all know, there are contradictory relationships among the tensile strength, yield strength, hardness, reduction of area, elongation, and impact toughness of the same forging die material. If the former is increased, the latter must be sacrificed. This requires specific The actual working environment of the mold to choose the corresponding performance matching. It must be pointed out that the hardness of a material can not only reflect the level of strength to a certain extent, but also has a sweet correspondence between hardness and wear PET preform mould resistance. Generally, materials with high hardness have good wear resistance. Therefore, many forging die materials usually simply Specify the requirements for hardness.　　2. Fatigue performance 　　The fatigue performance of forging die materials includes mechanical fatigue and thermal fatigue. The hot work mold has been cycled alternately between high mechanical load to zero mechanical load and temperature range of 200℃～600℃ for a long time. The superposition of stress caused by the loading and unloading of these two pulses will cause microcracks to grow on the surface of the mold cavity over time; Further development will accelerate mold wear and produce fragments, which will lead to mold failure. Therefore, forging mold materials are required to have good resistance to mechanical fatigue and resistance to cold and heat fatigue. 3. Organizational stability Generally, the working temperature of hot work die is 200℃～600℃ or even higher.