Aluminum alloy refining treatment is mainly to reduce the content of hydrogen and Al2O3 in the alloy liquid through chemical reaction, adsorption and filtration, so as to improve the quality of die-castings. The amount of hydrogen and inclusions in aluminum alloy liquid depends on the refining agent and refining method.
Casting aluminum alloy needs refining treatment before pouring to purify alloy liquid, but it has not been paid enough attention. The main reason for neglecting the refining treatment of die casting aluminum alloy is the particularity of die casting production mode. As the alloy liquid is formed under high pressure and chilling conditions, the porosity defect caused by air wrapping is the main reason. Therefore, the sensitivity of aluminum alloy to refining treatment is weaker than that of other casting methods. For die casting, it is necessary to eliminate the air in the mold cavity as much as possible, such as opening an overflow groove on the die.
Other factors can easily make people ignore the necessity of refining die-casting aluminum alloy, such as:
- The quality requirements of die casting are not high.
- The climate of the factory is dry, and the oxide content of aluminum ingot is small.
- The proportion of waste recycled from normal mass production is small, the recovery rate is low, and the quality of new ingot is better.
- The melting capacity of melting equipment does not match the production capacity of die casting machine (i.e. the melting capacity is in short supply).
- Based on the consideration of the production cost of die casting parts, the influence of traditional customs.
With the increasing requirements for the internal and external quality of die castings, many castings have the requirements of air tightness and machinability. Therefore, the refining treatment of die casting aluminum alloy can not be ignored to improve the quality of die castings.
Under the condition that alloy brand, ingot quality, allowable impurity type and content, smelting (remelting) equipment and other processes except refining treatment have been determined, the key to obtaining high-quality alloy liquid is to use ideal and efficient “refining agent” to refine alloy liquid to remove gas and various inclusions in alloy liquid to the maximum extent, and purify the alloy liquid.
