Common Defects And Treatment Schemes Of Aluminum Alloy Die Castings

Common defects and treatment schemes of aluminum alloy die castings
1. Pore problems and solutions
In the actual production process of aluminum alloy die castings, the casting porosity problem is the most typical defect, which is specifically manifested as porosity and bubbles. Porosity mainly refers to the smooth cavity that appears in aluminum alloy castings, usually appearing in the center of the part or in the thick-walled position, mainly due to poor exhaust or entrained gas in the solution. Bubbles are cavities created by the concentration of gas below the surface of the casting.
In order to prevent the formation of pores in aluminum alloy die castings, the equipment should be carefully cleaned before production to ensure that the charge is clean and dry, and adding a degasser is also a good choice. In the production process, we should always pay attention to exhaust, choose scientific and reasonable die-casting process indicators and well-designed molds. Secondly, expand the gate in the mold to control the flow rate of the solution, reduce the filling speed while ensuring the integrity of the molding, and prevent the turbulence of the solution. If necessary, the casting temperature, speed and pressure can be reduced to prevent air bubbles in aluminum die castings.
2. Surface crack problem and solution of aluminum alloy die casting
The surface cracks of aluminum alloy die castings are caused by flow marks, marks, strains and other phenomena caused by improper operation in the production process. Flow marks mainly refer to the stripes under the concave surface of the casting. In general, the direction of the flow mark is consistent with the flow direction of the liquid metal. Indentations are scratches, slag inclusions or seams produced during the production of liquid metal. Strain refers to the strain, pull marks or sticky die marks generated by aluminum die castings during the demolding process.
In order to avoid the above problems in aluminum alloy die castings, attention should be paid to controlling the mold temperature and rationally using the mold release agent, controlling the solution flow, using the mold scientifically, ensuring the cleanliness of the mold, and standardizing the opening and closing of the mold. Tooling to extend the retention time of the mold while waiting for production.
3. Aluminum alloy die-casting hemp surface problem and solution
The hemp surface (shrinkage hole) mainly refers to the uneven and rough holes on the surface of the aluminum alloy casting, and the general shrinkage hole will also produce pores.
The cause of shrinkage is that the casting is not sufficiently compensated when condensing. If the wall of the part is too thick, the casting temperature is too high, the die-casting process is not scientific, the specific pressure is too low, the capacity of the overflow tank is not enough, and the filling degree of the pressure chamber is not high. Not enough, the rest compensation effect is not good, or the inner gate is too small, it will cause shrinkage. Hole.
In order to prevent shrinkage defects in aluminum alloy die castings, the structure of the parts should be improved in time to ensure that the thickness of the parts is as consistent as possible, and the parts with large thickness are cooled in a planned manner. According to the strict die-casting index, prevent the temperature drop, appropriately increase the specific pressure, increase the capacity of the overflow tank, and improve the casting system. For molds with higher temperatures, the necessary cooling means should be used. 0.15%~0.2% grain refiner such as metal iron is added to the alloy liquid to improve the shrinkage tendency of the alloy; Switch to an alloy type with lower volume shrinkage and line shrinkage, or adjust the alloy fluid to reduce its shrinkage. Modification of alloy: increase the pouring cross-sectional area, ensure that the casting is under pressure, and prevent premature hardening of pouring from affecting pressure transmission.