Some problems needing attention in copper alloy smelting

(1) Copper alloy in the melting time should be controlled, from the beginning of the melting to the end of the melting time is called the melting time. The length of melting time will not only affect the productivity, but also significantly affect the quality of castings. As the melting time increases, the element loss rate of the alloy will increase, and the chance of inspiration will increase. Therefore, the melting should be completed in a short time. As far as possible, increase the preheating temperature of the charge, the operation should be compact and the action should be rapid.

(2) The stirring rod used in smelting should be carbon rod. Some elements in copper alloy, such as iron and lead, exist in the form of mechanical mixture when melting. Some elements have a tendency to produce specific gravity segregation stratification due to different densities. Practice has proved that these elements in the process of smelting and pouring, easy to cause chemical composition unqualified, resulting in mechanical properties unqualified. To overcome this phenomenon, we must rely on stirring, which is an indispensable link of melting pouring. But in the temperature measurement and cooling period, generally do not need stirring. And the mixing material composition, generally appropriate to use graphite. This is because if other agitators such as iron rods are used, the iron rods will melt during the process and the chemical composition of the alloy will be affected. At the same time, if the iron bar in the furnace preheating temperature is relatively high or stirring for a long time, the oxide on the iron bar to enter the alloy liquid as impurities; If the bar is preheated at a low temperature, the alloy will stick to the bar during agitation, which can be observed in production.

(3) the use of covering agent in copper alloy smelting, for smelting copper alloy, the amount of covering agent is generally: 0.8%-1.2% of the burden weight with glass and borax, because to maintain the thickness of the covering layer is 10-15cm; When using charcoal, the dosage is about 0.5-0.7% of the burden weight, and the thickness of the covering layer should be kept at 25-35 cm. The stripping time of coating agent is generally carried out before pouring, too early will increase the oxidation and suction of copper alloy. If charcoal is used as a covering agent, and the slag retaining effect is good, you can also not remove the covering agent, so that it also plays a slag retaining role in the casting process, the effect is more ideal.