Control of common defects in lost foam casting of aluminum alloy

Aiming at the common defects in the process of aluminum alloy lost foam casting, the following measures have been widely used to eliminate these defects in actual production. Several typical processes will be introduced here.

1. Refined aluminum alloy

The physical and chemical reactions and energy transfer of aluminum alloy liquid in the mold filling process require the aluminum alloy liquid to be cleaner. After refining, aluminum alloy liquid can achieve the purpose of degassing and slag removal, and can effectively reduce the defects of lost foam castings.

2. Properly increase the pouring temperature

The casting temperature of lost foam casting has a great relationship with the fluidity of liquid metal. Increasing the casting temperature can greatly increase the fluidity of liquid metal and reduce some defects, but too high temperature can not be used. On the one hand, with the increase of temperature, the gas generated by the decomposition of the foam model is more and the back pressure increases. On the other hand, too high temperature will cause the aluminum alloy liquid to absorb more gas and increase the probability of defects such as pores and oxidation slag inclusion in lost foam casting parts.

3. Control the coating

Lost foam casting coating is one of the important raw materials in production. The quality of coating and coating proportion have a great impact on the quality of lost foam casting parts. In order to ensure the basic quality of parts, the coating shall be of excellent quality, and it shall be evenly and densely applied on the die surface to ensure good performance.

4. Reasonably set the foam pattern.

Reasonable foam patterns mainly include pattern density, bead fusion and geometric structure. The high-density pattern will absorb more heat in the mold filling process, have more obvious cooling effect on the front of the liquid metal, and produce more gas and increase the back pressure. With low degree of fusion, the pore volume between particles is large, which improves the porosity of the whole pattern and makes the flow of molten metal more smooth. The more complex the geometric structure, the thinner the wall and the more turns, the more likely it is to produce insufficient pouring cold insulation.

5. Pressurization

The pressure also has a certain influence on the quality of lost foam casting. If the pressure on the parts is increased, there will be many benefits, such as improving the molding ability of metal liquid, increasing the compactness of lost foam casting parts, effectively reducing the problem of surface roughness, so as to greatly improve the product quality.

6. Application of mechanical vibration

In addition to the above methods, the method of increasing vibration can also be used to reduce lost foam casting defects. The vibration is mainly increased during model solidification. The advantage is that it can increase the core condensation of the casting, refine its quality and make its microstructure more superior. This method is easy to operate, low cost and high environmental friendliness, so it is widely used.

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