1. The pinhole

Measures to prevent pinhole formation in precision castings: it is strictly prohibited to use contaminated cast aluminum alloy materials, organic compounds and severely oxidized materials. Control smelting process and strengthen degassing refining. Control the thickness of metal coating, too thick easy to produce pinholes. Mold temperature should not be too high, casting thick wall parts to use cooling measures, such as copper or watering. When using sand mold, water should be strictly controlled and dry core should be used as far as possible.

2. The air holes

Measures to prevent the formation of air holes: improve the pouring and vertical pipe system, so that the liquid flow is stable, avoid air entrainment. Molds and cores should be preheated, then coated, and must be baked before use. Adequate exhaust measures shall be considered in die and core design.

3. Oxidation slag inclusion

Measures to prevent slag inclusion by oxidation: strict control of smelting process, rapid smelting, reduction of oxidation, complete slag removal. Aluminum - magnesium alloys must be melted under a coating. The furnace body and tools should be clean and free from oxides. The paint should be preheated and dried after use. The designed casting system must have stable flow, buffering and skimming capabilities. Inclined pouring system is adopted to make the liquid flow stable without secondary oxidation. The selected coating has strong adhesion and slag is formed in the casting during pouring without spalling.

Cracking of 4.

Measures to prevent thermal cracking: avoid local overheating and reduce internal stress in the actual casting system. Mold and core must ensure that the above 5 ° slope, poured riser in solidification can core-pulling molding, sand core may, when necessary, to replace the metal core. Control coating thickness to ensure consistent cooling speed of casting. Select proper die temperature according to casting thickness. Refine the alloy structure, improve the ability of hot cracking. Improve casting structure, eliminate sharp Angle and wall thickness mutation, reduce hot crack tendency.

5. Loose

Precautions against loose production: proper riser setting ensures solidification and shrinkage. Reduce the working temperature of metal mould. Control coating thickness, thick wall thinning. Adjust the cooling speed of each part of the metal mold, so that the thick wall of the casting has greater cooling capacity. Reduce metal casting temperature appropriately.