Smelting is to provide ingots for plastic processing. Smelting furnaces mostly use gas-fired reverberatory furnaces or oil-fired reverberatory furnaces, with a general capacity of 20 to 40 tons or more; resistance heating reverberatory furnaces are also used, with a capacity of generally about 10 tons. In order to shorten the furnace loading time, improve melting efficiency, and reduce gas absorption and oxide film involvement, tilting top-loading circular furnaces have been adopted in industry. It is best to use rapid analysis instruments to analyze the alloy composition during smelting and make timely adjustments. In order to ensure the purity of the melt, prevent the pollution of harmful gases and control the chemical composition, in addition to shortening the smelting time as much as possible, it is advisable to cover it with powdery flux mainly composed of potassium chloride and sodium chloride. The general dosage is 0.4 to 0.4% of the weight of the charge. 2%. The melting temperature is usually controlled at 700~750℃.
The melted metal also needs to be refined and filtered to remove harmful hydrogen gas and non-metallic inclusions in the metal to improve the purity of the metal. Refining usually uses solid refining agents or gaseous refining agents. Solid refining agents are generally based on chlorine salts, and refining agents that use hexachloroethane instead of chlorine salts are also used. In the early days, highly active chlorine was used as a gas refining agent. Although the purification effect was good, it caused serious environmental pollution. Therefore, nitrogen-chlorine mixed gas, inert gas and three-gas refining agent were developed, which have better effects. In order to ensure the refining effect, the oxygen and moisture contents in the refining gas should generally be less than 0.03% and 0.3 g/m3 respectively. The dynamic vacuum degassing method also has good degassing and sodium removal effects.