Taking into account the integration of various elements, the welding position of precision castings should be as close as possible or welding and symmetrical welding should be selected, followed by the overall welding method. This can prevent stress from causing cracks in precision castings, thereby enhancing their welding quality.

When carrying out internal lap welding on precision castings, if the joint is relatively small, it is recommended to use 3.2 welding wire. It is not until the second layer is welded that 4.0 welding wire is selected. Because most precision castings are very large, segmented welding can be carried out in 1/6 turns.

Clean stainless steel precision castings using the following methods:

1. Dry cleaning: Dry cleaning includes friction cleaning and shot blasting for rust removal, but the efficiency of friction cleaning is low and the actual effect is not very good. Also known as Gan Fa Lian Ying, it refers to shot blasting for rust removal and cleaning. Shot blasting cleaning is the use of compressed gas as the driving force to spray steel balls at a faster speed onto the surface of the product workpiece, cleaning the dirt on the surface of the workpiece. Shot blasting is a relatively flexible and reliable shot blasting method for rust removal and filling. Shot blasting cleaning machines are used to spray steel balls and clean impurities on the surface of workpieces.

2. Wet cleaning: Electrohydraulic sand cleaning is the process of cleaning the casing under the pressure of electrical equipment. Its principle is the electric hydraulic impact effect, which uses high-pressure pulse deflation to charge and discharge the casing according to special electrodes, causing a lot of fluid dynamics. During the entire process of precision casting, the purpose of sand cleaning was achieved due to the different vibration frequencies of surface dirt and metal.

During the entire pouring process, the stress caused by pouring is mainly thermal stress, change stress, and mechanical obstruction stress. If the pressure value is greater than the strength of the metal at this temperature, casting will cause cracks. During the entire casting process, mechanical hindrance stress usually disappears after sand drop and belongs to temporary stress. The stress is mostly thermal stress and changing stress. The influencing factors of stress are as follows.

1. The issue of metal properties.

The larger the metal elastic mold, the greater its stress; The stress of steel castings, white cast iron, and ductile iron is greater than that of gray cast iron, one of the reasons being related to the elastic mold of the metal. The casting stress is positively correlated with the free line expansion coefficient of aluminum alloy. Under the same other standards, the stress of martensitic stainless steel is 50% higher than that of metallographic stainless steel, because α Value is high. The thermal conductivity value of aluminum alloy can affect the temperature difference between the thick and thin parts of the workpiece. Under the same conditions, the thermal conductivity of aluminum alloy is lower than that of carbon steel, so alloy steel has significant stress when other standards are the same.

2. Characteristics of the mold.

The higher the heat storage rate of the mold, the faster the cooling speed, and the greater the temperature difference between the inside and outside, resulting in greater stress. During sand casting, metal molds are more prone to significant stress than sand.

3. Casting standards.

Increasing the pouring temperature is equivalent to raising the mold temperature, delaying the cooling speed, and making the temperature of each part of the workpiece tend to be the same, thereby reducing stress.

4. Casting structure.

The larger the difference in wall thickness, the greater the temperature difference between thick walls, and the greater the heat energy generated.