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 material components, which is used for die casting processes in specialized die 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, and the mold shell has a movable concave surface. It is accompanied by the cooling of the metal material liquid throughout the entire process of filling, pressing, and calcination, which not only removes the shrinkage and casting defects of the blank, but also enables the internal structural mechanism of the blank to achieve the crushing of crystals in the forged state.
The comprehensive physical properties of the wool embryo have been significantly improved. So, how can we improve the level of processing technology in the production and manufacturing of die-casting parts?
1. Single liquid heat treatment method for mold steel
Heat the mold steel or parts to martensite and quench them into water, oil, or other refrigeration substances. After a certain period of cooling (cooling to areas below the temperature of ferrite or austenite changes), remove the mold steel and air cool it. Because the entire cooling process of mold steel is carried out in a single refrigerant, it is called single liquid heat treatment method.
2. Dual liquid heat treatment method for mold steel
Simply put, the entire process of heat treatment and refrigeration of mold steel is achieved through the combination of two refrigeration substances (commonly water and oil). Make the entire refrigeration process ideal, rapidly 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 heated to the martensitic temperature into a high-temperature and rapidly cooling substance (usually water or salt solution) to suppress the ferrite transformation of low-temperature martensite. When cooled to below 100 ℃, quickly remove another substance (usually oil) that is slowly cooled in the ultra-low temperature zone. Because the transformation of austenite occurs 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: water, oil, and gas.
3. Mold steel spray heat treatment method
Large and medium-sized complex zinc alloy die-casting parts and mold steel, especially those with large thickness differences, need to control the cooling rate of different stages and body parts throughout the refrigeration process to ensure uniform cooling and prevent excessive internal stress during heat treatment. 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; Can achieve uniform cooling. At present, the most popular heat treatment process for die-casting parts is vacuum pump high-pressure quenching.
4. Grading quenching method for mold steel
Mold steel or product workpieces heated to martensitic temperature are quenched into a cooling substance (commonly a salt bath) at a temperature around the austenite transformation temperature, and retained for a period of time, so that the surface layer and core temperature of the product workpiece gradually converge. After that, they are removed from air cooling and undergo austenite transformation 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 cast parts.
There are two types of temperature selection for graded quenching of mold steel. One method is to gradually increase the temperature (Ms point) above 10-30 ℃ by taking the martensitic change of the steel grade of the workpiece being solved; Another option is to choose 80-100 ℃ below the Ms point. The duration of stay for grade classification also needs to be well controlled. If it is too short, the temperature will not be uniform enough to achieve the goal of graded quenching; If it is too long, it is very likely to cause 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 subjected to isothermal quenching in a hot bath slightly higher than the Ms point of the quenched steel grade, and changes are made to obtain a lower martensite mechanism or a lower martensite and austenite mixing mechanism. 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 during the entire application process of mold steel, the cooling process after heat treatment of mold steel is also necessary, which will make it less prone to deformation.