How to improve the processing technology level in the production and manufacturing of die-casting parts? Die casting is a specialized tool for casting metal components, which is used for die-casting processes in specialized die casting molds and forging machines. The main die-casting process of aluminum die-casting is: the metal material liquid is first filled into the concave mold of the mold shell at low speed or quickly cast. The mold shell has a moving concave mold surface, which is filled and pressed during the entire process of cooling and forging of the metal material liquid. This not only eliminates the shrinkage and loosening casting defects of the billet, but also achieves the crushing of crystals in the forged state of the internal structural mechanism of the billet.
The comprehensive physical properties of the hair embryo have been significantly improved. So, on the other hand, how to improve the processing technology level in the production and manufacturing of die-casting parts?
1. Single liquid heat treatment method for mold steel
When heating the mold steel or parts to martensitic transformation, quench them in water, oil, or other cooling substances, and cool them for a certain period of time (to a temperature lower than the ferrite transformation temperature or austenite transformation temperature) to remove the mold steel for air cooling. Because the entire cooling process of mold steel is carried out in a single refrigerant, it is called single liquid heat treatment method.
2. Double liquid heat treatment method for mold steel
To put it simply, the entire process of heat treatment and refrigeration of mold steel is achieved through the coordination of two refrigeration substances (commonly water and oil). Make the entire refrigeration process more ideal, quickly cooling in areas with ferrite changes and slowly cooling in areas with austenite changes.
The specific method is to first quench the mold steel or parts that have been heated to the martensitic temperature into a high-temperature rapid cooling substance (usually water or salt solution) to suppress the ferrite transformation of low-temperature martensite. When cooled to below 100 ℃, quickly remove it and transfer it to another substance (usually oil) that is slowly cooled in the ultra-low temperature zone. Because the austenite transformation is carried out under relatively relaxed refrigeration standards, it can reasonably reduce or avoid deformation and cracking, also known as water quenching oil cooling.
This method requires a higher level of operation, sometimes explained as three substances, namely water, oil, and then gas.
3. Spray heat treatment method for mold steel
For large and medium-sized complex zinc alloy die-casting parts and mold steel with large thickness differences, in order to achieve uniform cooling and prevent excessive internal stress during heat treatment, it is necessary to control the cooling rate of different links and body parts in the entire refrigeration process. This method has a variety of methods, such as spray (water or solution), spray (air compression and water will be atomized and sprayed to different positions of parts), air quenching, etc. Its characteristics are: it can manipulate and adjust the cooling speed in various temperature areas by manipulating different substances or different total flow rates and working pressures; Or change the total number and location of different nozzles; It can evenly reduce the temperature. At present, vacuum pump high-pressure gas quenching is more popular in the heat treatment process of die-casting parts.
4. Classification quenching method for mold steel
The mold steel or product workpiece heated to the martensitic temperature is quenched in a cooling substance (commonly a salt bath) at a temperature around the austenite change temperature, and left for a period of time to gradually bring the surface layer and core temperature of the product workpiece to the same level. Then, it is removed from the air cooling and subjected to austenite change at a lower heat dissipation rate. This method can significantly reduce deformation and improve the toughness of mold steel, making it one of the common heat treatment methods for die-casting parts.
There are two types of temperature selection for graded quenching of mold steel. One method is to take the martensitic transition temperature (Ms point) of the steel grade of the workpiece to be solved, which is above 10-30 ℃; Another option is to choose the Ms point below 80-100 ℃. The duration of stay for level classification also needs to be carefully controlled. If it is too short, the temperature will not be evenly distributed, making it impossible to achieve the goal of graded quenching; If it is too long, it is likely to undergo non austenitic changes and reduce strength.
5. Heat treatment method for isothermal process of mold steel
The mold steel product workpiece heated to the martensitic temperature is quenched in a hot bath at a temperature slightly higher than the Ms point of the quenched steel grade, and subjected to isothermal retention to obtain a lower martensitic structure or a mixed structure of lower martensite and austenite. This method has the advantages of reducing deformation and cracking, reducing internal stress during heat treatment, and possessing strength and toughness similar to quenched austenite.
To prevent deformation and cracking of mold steel during the entire application process, refrigeration after heat treatment of mold steel is also necessary, which will make the mold steel less prone to deformation.