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The basic task of metal alloy smelting is to put a certain proportion of metal charge into the furnace, and the melt is obtained by heating and melting. Then the composition of the molten melt is adjusted to obtain the desired alloy liquid. And in the smelting process to take appropriate measures to control the content of gas and oxide inclusions, in line with the provisions of the composition (including the main component or impurity element content), to ensure that the castings are properly organized (grain refinement) high-quality alloy liquid.
Due to the characteristics of aluminum, aluminum alloys have a strong tendency to produce pores and are also prone to oxide inclusions. Therefore, preventing and removing gas and oxidizing inclusions are the most prominent problems in the smelting process of aluminum alloys. In order to obtain a high-quality aluminum alloy liquid, the smelting process must be strictly controlled and measures must be taken to control it from all aspects.
2, melting process
The aluminum alloy smelting process is as follows:
Furnace → melting (adding copper, zinc, silicon, etc.) → slag → magnesium, yttrium, etc. → stirring → sampling → adjusting components → mixing → refining → slag → converter → refining and standing still → casting.
Furnace
The correct method of loading is very important to reduce metal burnout and shorten melting time. For the reverberatory furnace, an aluminum ingot is placed on the bottom of the furnace, placed in a burnable material, and then pressed onto the aluminum ingot. The lower melting point of the reflow material is installed on the upper layer to make it melt the earliest and flow down to cover the following burnable material, thereby reducing burn-in. All kinds of charge should be evenly distributed.
melt
The melting process and smelting speed have an important influence on the quality of the aluminum ingot. When the charge is heated to soften the bed, the flux should be properly covered. During the melting process, care should be taken to prevent overheating. After the charge liquid surface of the charge is leveled, the melt should be properly agitated to make the temperature uniform, and at the same time it is also conducive to accelerated melting. The long smelting time not only reduces the production efficiency of the furnace, but also increases the gas content of the melt. Therefore, the secondary refining of the melt should be performed when the smelting time is long.
Slag
When the charge is completely melted to the smelting temperature, the residue can be removed. Before the slag dross should be sprinkled with powdered flux (sodium-free flux should be sprinkled on high-magnesium alloys). The slag should be as thorough as possible because of the presence of scum when it can easily contaminate the metal and increase the gas content of the melt.
Magnesium plus twisting
After the slag is removed, the magnesium ingot can be added to the melt, and at the same time flux should be added to cover it. For high-magnesium alloys, 0.002% to 0.02% niobium should be added to prevent magnesium burning. Niobium can be obtained from sodium hypofluorite by a metal reduction method, and sodium hypofluorite is added by mixing with a flux.
Stirring
There should be sufficient time for stirring before sampling and after adjusting the ingredients. The stirring should be stable without destroying the oxide surface oxide film.
sampling
After the melt is fully stirred, it should be sampled immediately for pre-furnace analysis.
Adjustment component
When the composition does not meet the standard requirements, it should be fed or diluted.
Melt Converter
After the composition is adjusted, when the melt temperature meets the requirements, the surface scum is pumped out.
Melt refining
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