1、 The surface of stainless steel castings may sometimes have depressions: the hot spot area of stainless steel castings is filled (with voids inside), and during shrinkage, although the skin layer has a certain strength, it is still affected by internal shrinkage without rupture, resulting in surface depressions, which is called shrinkage.

2、 Common precision casting defects include bubbles, which refer to individual locations of sand hole defects in precision castings. Bubbles are usually only discovered after machining.

Reason for formation: 1. In most cases, the appearance of bubbles is mainly due to insufficient roasting of the fine cast outer shell, which generates a large amount of gas in the shell during pouring steel and cannot be smoothly discharged, thereby invading the metal liquid to form bubbles; 2. Due to the shell making process or shell type data, the air permeability of the shell is too poor, and the gas in the mold cavity is difficult to discharge, forming bubbles in the metal liquid; 3. The air trapped in the molten steel during pouring cannot be discharged, resulting in casting bubbles.

Preventive measures: 1. If precision casting conditions permit, set exhaust bubbles at the top of complex castings; When designing the pouring system, it is important to fully consider the exhaust requirements of the mold shell; 3. The roasting temperature and time of the shell should be reasonable, and the insulation time should also be sufficient; 4. When dewaxing, the wax material should be completely swept away; 5. Properly reduce the interval between the ladle nozzle and the pouring cup, and the pouring speed should be average to ensure that the steel level is stable and fills the mold cavity, and to minimize the involvement of air in the molten steel, so that the gas in the mold cavity and molten steel can be smoothly discharged.