Equipment operating speed The higher the operating spee […]
Equipment operating speed
The higher the operating speed, the greater the impact force the mold will receive per unit time, and the shorter the time, the less time the impact energy will be transmitted and released, it will tend to be concentrated locally, causing local stress to exceed the yield strength or fracture toughness of the mold material, making the mold Failure by breaking or forming plastic deformation.
Lubrication and cooling lubrication
Lubricating the die working surface (relatively moving or contacting the workpiece) can reduce the direct contact between the die and the workpiece, reduce wear, reduce forming force, and reduce the degree of temperature rise. The lubricant can also hinder the heat transfer of the blank to the mold to a certain extent, avoid thermal adhesion between the mold and the workpiece, and is beneficial to improve the life of the mold. For example, lubricating the contact surface of the blank and the die during the drawing process; lubricating the die cavity during the die forging process is beneficial to the smooth progress of the process and the improvement of the die life. At the same time, the effect of lubrication varies greatly with the type of lubricant and the method of lubrication. However, during the working process of the mold, lubricating the inappropriate parts is harmful to the process and the life of the mold. For example, the contact surface of the workpiece and the punch is lubricated during stretching; during die forging, the parts such as burrs, bridges, grooves, etc. Lubrication can make the process difficult. In addition, if the lubricant is improperly selected, it may also cause the lubricant to burn, generate high-pressure gas, and cause cavitation wear on the surface of the mold. A hot working die that works at a certain temperature (above room temperature) will heat up due to the heat of the workpiece (or forming material), and the strength of the die will decrease. After stopping for a few minutes, the heat of the cold water should be adjusted to reduce the mold cooling rate. It is forbidden to chill the mold with cold water. , Mold material The selection of mold material should comprehensively consider the basic performance, process characteristics and production cost of the mold material.
The wear resistance largely depends on the hardness of the material
For cold work molds that are subject to large impact loads, mold toughness is very important. It depends on the metallurgical composition, grain size, purity of the die steel, the number, morphology and distribution of carbides, and the heat treatment process of the die (material). Under the action of high stress, the mold must have sufficient hardness at room temperature and high temperature to keep its shape and size unchanged. The process performance of the mold material is one of the main factors that affect the mold production cost and manufacturing difficulty. Hot workability refers to forgeability (thermoplasticity, processing temperature range), weldability, heat treatment process performance (including hardenability, hardenability, quenching temperature range, heat treatment deformation rate, oxidation, decarburization sensitivity, etc.). Cold working performance refers to its cutting, grinding, polishing and grinding, cold drawing, cold extrusion and surface finishing performance. The forging die materials of the die manufacturing process module are mostly high-carbon and high-alloy steels, which have different degrees of component segregation, structure segregation, carbide segregation and other defects. They cannot be directly used for mold making. At the same time, the shape and size of the raw materials used are very high. It is difficult to match the module. Forging is an indispensable means to obtain the required internal structure and performance of the module and to approach the shape and size. 2 Correct forging can also reduce the heat treatment and quenching deformation rate of the material. Die steel generally has high carbon content and alloy elements, poor thermal conductivity, and the heating rate must be slow and uniform. Large forgings are generally heated by preheating or stepped heating to control the heating rate. The position of the steel in the furnace must be appropriate, sometimes It must be turned over repeatedly to make the heating as even as possible. In order to break up and uniform carbides to the maximum extent, a deformation process of upsetting 3 stretching and repeated multiple times is required. The compression ratio of upsetting is preferably greater than that. Finally, like kneading the dough, turn up and down, back and forth, left and right, and knead six sides. Forging.