Heat Treatment of Die-Cast Mold Parts
The production of die-cast parts requires careful heat treatment and subsequent cooling and holding. The heat treatment of the mold can significantly improve the mechanical properties of the parts, and the nature of the heat treatment and the microstructure of the parts are closely related.
1. Heat treatment process
The heat treatment process of die casting mold parts is generally composed of preheating, stress relief annealing, homogenization annealing and tempering. The hardness and strength requirements of the die casting mold parts depend on the specific conditions of use, and therefore the application conditions have a direct influence on the selection of the heat treatment process.
(1) Preheating
Preheating is the first step of heat treatment, which is to heat the parts to the temperature required for the subsequent process. It removes internal and external stress, reduces the fragility at the next temperature, and can facilitate the assembly and machining of the mold. Preheating is generally heated at 830~880℃ for 1~2h.
(2) Stress relieving annealing
Stress Released Annealing is a process of heating parts to a certain temperature and holding for a certain time to eliminate internal and external stress. The stress released annealing temperature of die-casting mold parts depends on the inherent heat resistance of the steel, and generally needs to be heated to 830~880℃ and maintained for 1~2h. Stress annealing should be carried out after preheating and before any further heat treatment.
(3) Homogenization annealing
Homogenization annealing is the process of heating a steel with a large size of ingots or a multi-composite steel to a certain temperature and holding for a certain time to improve the uniformity of the internal composition of the steel and the stability of the structure. The homogenization annealing temperature of die casting mold parts varies greatly depending on the steel grade, and generally needs to be heated to 1050~1150℃ and maintained for 2~6h. Homogenization annealing is usually used after stress relieving annealing and before tempering.
(4) Tempering
Tempering is to heat the parts to a certain temperature, so that the martensite in the hardened state becomes tempered martensite, so as to obtain required mechanical properties. The tempering temperature of die-casting mold parts is related to the tempering medium, tempering time and the mechanical properties of the parts. Generally, the tempering temperature is 400~700℃, and the tempering time is 0.5h~4h. Tempering is usually used after homogenization annealing or quenching.
2. Pay attention to reason
(1) Pay attention to the quenching medium. The quenching medium should be determined according to the type of steel and the requirements of the quenching and the cooling rate.
(2) Pay special attention to the effects of different cooling means on the structure of the heat treatment system.
(3) The hardness of the workpiece should not exceed the HRC55 specified by the state.
(4) The size of the die-casting parts should not be changed when heat-treated
(5) The best temperature range is 450 degrees Celsius, and the time range is 8-10 minutes.
(6) After heat treatment, the parts should be sprayed with lubricant.
In Summary
Heat treatment of die-casting mold parts is an important step in the processing of die-casting parts. The heat treatment process determines the strength, wear resistance and deformation of the parts. The quality of the heat treatment directly affects the mechanical properties and service life of the parts, so the process should be selected according to the processing requirements, and the heat treatment should be strictly carried out according to the requirements. Pay attention to process, temperature, holding time and cooling conditions, so as to ensure the quality, performance and service life of the parts.
