In addition to the reasonable cooperation of the mold with sufficient strength and toughness, the surface properties of the mold are crucial to the working performance and service life of the mold. These surface properties are: abrasion resistance, corrosion resistance, friction coefficient, fatigue properties, and the like. These performance improvements, which rely solely on the improvement and improvement of the matrix material, are very limited and uneconomical, and surface treatment techniques can often achieve twice the result with half the effort, which is why surface treatment technology has developed rapidly. Compared with other methods, if the method of establishing a heat treatment center is adopted, the cost of coating the cured film will be greatly reduced, and if more molds adopt this technology, the overall mold manufacturing level in China can be improved. What is the common heat treatment method? I. Annealing: A heat treatment process in which the steel is heated to a certain temperature and then cooled for a period of time with the furnace slowly cooled (or buried in sand or lime) to high speed injection molding below 500 degrees in air.
These include: 1, complete annealing and isothermal annealing 2, spheroidizing annealing 3. The purpose of stress relief annealing is to: 1. reduce hardness, improve plasticity, improve cutting and pressure processing properties; 2. refine grains and improve mechanical properties , to prepare for the next step; 3. Eliminate the internal stress generated by cold and hot processing. Second, normalizing: Operation method: The steel is heated to 30~50 degrees above Ac3 or Accm, and then cooled to a little more than the cooling rate of annealing. Objective: 1. Reduce hardness, improve plasticity, improve cutting and pressure processing performance; 2. Refine grain, improve mechanical properties, prepare for the next step; Third, quenching: operation method: heating steel to phase change The temperature is above Ac3 or Ac1, kept for a while, and then rapidly cooled in water, nitrate, oil, or air.
Purpose: Quenching is generally used to obtain high-hardness martensite structure. Sometimes, when quenching some high-alloy steels (such as stainless steel and wear-resistant steel), it is to obtain a single uniform austenite structure to improve wear resistance. And corrosion resistance. Fourth, quenching and tempering: operation method: high temperature tempering after quenching is called quenching and tempering, that is, the steel piece is heated to a temperature 10 to 20 degrees higher than quenching, quenching after heat preservation, and then tempering at a temperature of 400 to 720 degrees. . Objective: 1. Improve the cutting performance and improve the smoothness of the machined surface; 2. Reduce the deformation and cracking during quenching; 3. Obtain good comprehensive mechanical properties. V. Tempering: Operation method: reheat the quenched steel to a temperature below Ac1, and after cooling, cool in air or oil, hot water and water. Objective: 1. Reduce or eliminate the internal stress after quenching, reduce the deformation and cracking of the workpiece; 2. Adjust the hardness, improve the plasticity and toughness, and obtain the mechanical properties required for the work; 3. Stabilize the workpiece size.
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