In the production of aluminum alloy casting, the aluminum alloy should be smelted, and the quality of the smelting process control directly affects the quality of the aluminum alloy liquid, further affects the quality of aluminum alloy casting products, and reduces the product qualification rate.
1.Pay attention to the control of raw materials.
The raw materials used for smelting generally include electrolytic aluminum ingots, recycled aluminum materials, and return materials such as pouring risers produced by casting production. Electrolytic aluminum is produced and tested according to specifications, mineral materials with less impurity content are selected, and the production process strictly implements the relevant standards, and the impurity content is controlled according to the relevant national standards; Recycled material or recycled material is different, and it is easy to have water, oil or other metal impurities mixed in it. The production process should be strictly managed, and clean, water-free and oil-free return materials can be used. Other metal debris contained in it must be sorted clean before use.
2.Strict feeding ratio of new and old materials.
Strict control of the feeding ratio of new materials (electrolytic aluminum) and old materials (return materials), the feeding ratio of new and old materials must be controlled, the degree of oxidation of new materials is low, the moisture contained is less, and the gas impurities produced are also less. The old material contains many impurities, the degree of oxidation is heavier, the moisture and oil pollution contained in it will be higher, and the polluted procedure is high, resulting in a high proportion of gas impurities contained in the molten aluminum, and the density index (DI) value will be higher, sometimes far greater than 5%, if the refining and degassing time is short, the amount of refining agent is improper, and the parameters of the degassing equipment are not properly selected, it is difficult to remove the gas impurities.
3.Temperature is an important process parameter.
In the case of the metal in the liquid state, due to the partial pressure of the gas, the gas will be inhaled, and the higher the temperature, the more gas in the molten metal will be inhaled, resulting in a high proportion of metal oxidation, a high oxidation ratio, a high metal fever loss rate, a large loss, and a higher production cost. If the inhaled gas is more, the density of the aluminum alloy liquid will be reduced, and it cannot meet the technical requirements of production.
4.The process management of slag removal and degassing should be in place.
The aluminum alloy liquid should be refined, and it would be better if the refining and degassing time was appropriately longer, but too long time would cause the temperature of the molten metal to drop too much, which could not meet the temperature requirements of the next process production; Sometimes the temperature is low and the temperature needs to be raised, resulting in downtime and waiting. The graphite rod for stirring should be as long as possible, and the distance from the bottom of the transfer bag should be as small as possible, as long as it can ensure that it does not touch the bottom, and the safety distance (50mm) is around the right, it should be safe enough. The scum should be removed, so that there is no aluminum slag visible visually, and then transferred to the holding furnace for production after 3-5 minutes. The nitrogen pressure and flow rate during degassing are controlled within the specified range to ensure that the nitrogen pressure and flow rate in the whole process are stable, without excessive fluctuations, and always within the specified range.