How to repair the defects of precision casting

1, In the machine tool casting structure formed at the thick and hot joints, the implementation of rapid solidification, artificially cause the basic balance of the temperature field of the machine tool casting everywhere. Precision casting parts with internal and external cold iron, local use of heat storage large zircon sand, chromite sand or special paint. It is very important to select the molding material with high heat storage for the production of anti-wear products with lost die. Chromite sand instead of quartz sand and other small heat storage sand species, will achieve good results, pouring microseismic better.

 

2. Reasonable process design. The inner runner is located at the relatively thin wall of the machine tool casting, and the number of hours is large and scattered. The liquid metal that Z enters the thick wall early solidifies first, and the thin wall solidifies later, so that the equilibrium solidification is basically reached everywhere. For machine tool castings with uniform wall thickness, multiple inner runner and vent are used. The inner runner is many, dispersing and uniform, so that the overall heat balance. The air hole is thin and many, that is, the exhaust is unobstructed and plays the role of heat dissipation.

 

3, Low temperature quick firing, open pouring system. The liquid metal fills the mold quickly, smoothly and evenly. This should be tailored according to the circumstances; Ductile iron machine tool mold strength, surface hardness ≧90, sand box rigidity is large, it is beneficial to eliminate shrinkage; When the riser is needed, the first hot riser is migrated, and the hot joint is left. If the riser is placed on the hot joint, the riser size will be increased to form a "hot on heating". If not, not only the shrinkage is difficult to remove, but also the concentrated shrinkage hole will be produced, and the production rate of the process is reduced.

 

4, Casting tilt placement and alloying, benefit. Eliminating shrinkage defect of machine tool casting is a complex process of understanding and implementation. Based on the basic principle of "heat balance", scientific analysis should be made on the casting of the JU body, reasonable technological plan should be formulated, appropriate molding materials and tooling should be selected, and correct operation should be standardized.