The wall thickness of copper castings (commonly referred to as wall thickness) is a significant factor in the die casting process. Wall thickness is closely related to the entire process specification, such as the calculation of filling time, the selection of inner gate speed, the calculation of solidification time, the analysis of mold temperature gradient, the effect of pressure (final specific pressure), the length of mold retention time, the level of casting ejection temperature, and the operating rate.
The quality of copper castings includes appearance quality, internal quality, and usage quality. Appearance quality refers to the surface roughness, surface quality, dimensional tolerance, geometric tolerance, and quality deviation of castings; Internal quality refers to the chemical composition, physical and mechanical properties, metallographic structure, and the presence of pores, inclusions, and cracks inside the casting; The quality of use refers to the ability of castings to meet various usage requirements and work performance, such as resistance to corrosion, machinability, weldability, etc.
Prevention methods for defects in copper castings
1. Correctly control the pouring speed, avoid getting involved in gas, do not mix impurities in the molding sand to reduce the gas generation of the molding material, improve the exhaust capacity of the sand, correctly select and handle cold iron, and improve the design of the pouring system.
2. Improve the structural design of castings, avoid sharp corners, strive for uniform wall thickness, and smooth transitions. Take measures to increase the yield of sand molds, solidify all parts of the castings simultaneously or sequentially, and improve the design of the pouring system.
3. Add molten metal from the riser, improve the design of the riser, ensure that the furnace material is clean and corrosion-free, set a riser at the shrinkage area of the casting, place cold iron or cold iron in combination with the riser, control the moisture content of the molding sand, and dry the sand core. Take measures to refine the grain size, improve the position of the casting in the mold, and reduce the pouring temperature and speed.
4. The furnace material should be blown with sand, and the amount of recycled material should be appropriately reduced. The design of the pouring system should be improved to enhance its slag blocking ability. Proper flux should be used to remove slag, and the pouring should be smooth and attention should be paid to slag blocking.
Copper castings are closely related to daily life. For example, commonly used doorknobs, door locks, radiators, plumbing pipes, iron pots, gas stoves, irons, etc. are all castings.
The cleaning of each process of copper casting electroplating should be carried out to prevent the residual solution in the pores from affecting the next process; The actual surface area of copper castings is many times larger than the calculated surface area, and the impact current density during electroplating is about three times higher than that of ordinary parts. The pre plating time is also longer than that of ordinary parts; When pre plating copper, the parts and hanging tools should be frequently shaken together to ensure uniform and consistent coating color, and to prevent the occurrence of spots during silver plating that may affect the appearance quality of the coating.
Copper castings should have the correct casting process. According to the structure, weight, and size of the casting, the characteristics of the casting alloy, and production conditions, appropriate parting surfaces, shapes, and core making methods are selected, and casting ribs, cold iron, risers, and gating systems are correctly set. The improvement of the quality of bed castings, the development of machine tool equipment manufacturing, and the overall level of improvement are beyond discussion, ultimately affecting the competitiveness of China’s machine tool equipment manufacturing industry in the market. Continuously improving the quality of machine tool castings, thereby improving the overall level of machine tool manufacturing.
Copper castings are mainly used as blanks for machine parts, and some castings can also be directly used as machine parts. Castings account for a large proportion in mechanical products, such as tractors, where the weight of castings accounts for about 50-70% of the total weight of the machine, agricultural machinery accounts for 40-70%, and machine tools, internal combustion engines, etc. account for 70-90%. Among various types of castings, there are many types of castings used for machinery, with complex shapes and large amounts, accounting for about 60% of the total production of castings. Next are steel ingot molds for metallurgy and pipelines for engineering.
Copper castings account for a large proportion of the weight, and many structural components and major components are made of castings as raw materials, which are closely related to the quality and accuracy of machine tools. The quality of machine tool castings has a significant impact on the overall quality, lifespan, and accuracy retention of the machine tool.
Post time: Aug-30-2023