How to improve the level of processing technology in die casting manufacturing?
- Date：2022-07-10
- Read：679
The comprehensive physical properties of wool embryo were significantly improved. In other words, how can the manufacturing of die castings improve the level of processing technology?
1. Single liquid heat treatment of die steel
When the die steel or parts are heated to martensitization, they are quenched into water, oil or other refrigeration substances, and then cooled for a certain time (cooled to less than the ferrite type change temperature area or austenite change temperature area) to remove the die steel for air cooling. Because the whole refrigeration process of die steel is carried out in a single refrigeration material, it is called single liquid heat treatment.
2. Double liquid heat treatment of die steel
To put it bluntly, the whole process of heat treatment and refrigeration of die steel is realized by the cooperation of two refrigeration substances (water and oil are common). The whole process of refrigeration is ideal, i.e. rapid refrigeration in the area of ferrite change and slow refrigeration in the area of austenite change.
The specific method is to quench the die steel or parts heated to the martensitization temperature into a substance (usually water or salt solution) that is rapidly cooled at high temperature to suppress the ferrite change of low-temperature martensite. When it is cooled to within 100 ℃, it is quickly removed and transferred to another substance (usually oil) that is slowly cooled at ultra-low temperature. Because austenite change is carried out under the relatively mitigated refrigeration standard, deformation and cracking can be reasonably reduced or avoided, which is also called water quenching and oil cooling.
This method must be a higher operation method, which can sometimes be interpreted as three substances, namely, water, oil, and then gas.
3. Mold steel spray heat treatment method
For large and medium-sized miscellaneous zinc alloy die castings and die steels, especially those with large thickness difference, in order to make the temperature drop symmetrical, prevent excessive internal stress of heat treatment, and control the cooling speed of different links and different body parts in the whole process of refrigeration. This method includes spray (water or solution), spray (air compression and water will spray to different positions of parts), gas quenching and other methods. Its characteristics are: different substances or different total flow and working pressure can be manipulated to manipulate and adjust the cooling speed in various temperature areas; Or change the total number and position of different nozzles; It can make the temperature drop symmetrical. At this stage, vacuum pump high pressure quenching is more popular in the heat treatment process of die castings.
4. Graded quenching method of die steel
The quenching temperature of the die steel or product workpiece heated to the martensitization temperature is kept in the refrigeration material (usually salt bath) around the austenite change temperature for a period of time, so that the surface layer and core temperature of the product workpiece gradually tend to be the same, and then the air cooling is removed to change the austenite at a lower heat dissipation rate. This method can significantly reduce deformation and improve the toughness of die steel. It is one of the common heat treatment methods for die-casting parts.
There are two kinds of temperature selection for graded quenching of die steel. One is to take the martensitic change temperature (MS point) of the steel grade of the workpiece of the product to be solved to be 10~30 ℃ above; The other is to choose 80~100 ℃ below MS point. The residence time of grade classification also needs to be grasped. If it is too short, the temperature is not symmetrical enough to achieve the goal of grade quenching; If it is too long, it is likely to produce non austenitic changes and reduce the strength.
5. Isothermal process heat treatment of die steel
The mold steel product workpiece heated to the martensitization temperature is retained in the isothermal process in the hot bath with the quenching temperature slightly higher than the MS point of the quenched steel grade, and is changed to obtain the lower martensite mechanism or the lower martensite and austenite mixing mechanism. This method has the advantages of reducing deformation and cracking, low internal stress in heat treatment, and similar strength and toughness to quenched austenite.
To prevent the deformation and cracking of die steel in the whole process of application, it is also certain to aim at the refrigeration of die steel after heat treatment process, which will make die steel not easy to deform.
1. Single liquid heat treatment of die steel
When the die steel or parts are heated to martensitization, they are quenched into water, oil or other refrigeration substances, and then cooled for a certain time (cooled to less than the ferrite type change temperature area or austenite change temperature area) to remove the die steel for air cooling. Because the whole refrigeration process of die steel is carried out in a single refrigeration material, it is called single liquid heat treatment.
2. Double liquid heat treatment of die steel
To put it bluntly, the whole process of heat treatment and refrigeration of die steel is realized by the cooperation of two refrigeration substances (water and oil are common). The whole process of refrigeration is ideal, i.e. rapid refrigeration in the area of ferrite change and slow refrigeration in the area of austenite change.
The specific method is to quench the die steel or parts heated to the martensitization temperature into a substance (usually water or salt solution) that is rapidly cooled at high temperature to suppress the ferrite change of low-temperature martensite. When it is cooled to within 100 ℃, it is quickly removed and transferred to another substance (usually oil) that is slowly cooled at ultra-low temperature. Because austenite change is carried out under the relatively mitigated refrigeration standard, deformation and cracking can be reasonably reduced or avoided, which is also called water quenching and oil cooling.
This method must be a higher operation method, which can sometimes be interpreted as three substances, namely, water, oil, and then gas.
3. Mold steel spray heat treatment method
For large and medium-sized miscellaneous zinc alloy die castings and die steels, especially those with large thickness difference, in order to make the temperature drop symmetrical, prevent excessive internal stress of heat treatment, and control the cooling speed of different links and different body parts in the whole process of refrigeration. This method includes spray (water or solution), spray (air compression and water will spray to different positions of parts), gas quenching and other methods. Its characteristics are: different substances or different total flow and working pressure can be manipulated to manipulate and adjust the cooling speed in various temperature areas; Or change the total number and position of different nozzles; It can make the temperature drop symmetrical. At this stage, vacuum pump high pressure quenching is more popular in the heat treatment process of die castings.
4. Graded quenching method of die steel
The quenching temperature of the die steel or product workpiece heated to the martensitization temperature is kept in the refrigeration material (usually salt bath) around the austenite change temperature for a period of time, so that the surface layer and core temperature of the product workpiece gradually tend to be the same, and then the air cooling is removed to change the austenite at a lower heat dissipation rate. This method can significantly reduce deformation and improve the toughness of die steel. It is one of the common heat treatment methods for die-casting parts.
There are two kinds of temperature selection for graded quenching of die steel. One is to take the martensitic change temperature (MS point) of the steel grade of the workpiece of the product to be solved to be 10~30 ℃ above; The other is to choose 80~100 ℃ below MS point. The residence time of grade classification also needs to be grasped. If it is too short, the temperature is not symmetrical enough to achieve the goal of grade quenching; If it is too long, it is likely to produce non austenitic changes and reduce the strength.
5. Isothermal process heat treatment of die steel
The mold steel product workpiece heated to the martensitization temperature is retained in the isothermal process in the hot bath with the quenching temperature slightly higher than the MS point of the quenched steel grade, and is changed to obtain the lower martensite mechanism or the lower martensite and austenite mixing mechanism. This method has the advantages of reducing deformation and cracking, low internal stress in heat treatment, and similar strength and toughness to quenched austenite.
To prevent the deformation and cracking of die steel in the whole process of application, it is also certain to aim at the refrigeration of die steel after heat treatment process, which will make die steel not easy to deform.