Since arc melting system has the copper hearth in which we melt other alloy but I want to know about melting of Cu based alloy, both copper hearth and Cu-based alloy has the same melting temperature. So please guide me how can it be possible?
Generally, yes, it is possible to melt a Cu-based alloy in a copper hearth. You are worried whether you melt your hearth into the alloy, and obviously you are right. Fortunately, a copper base (hearth) is usually water cooled, so melting it is possible, but difficult. The procedure we usually follow in our lab, is that the ingredients are stacked in the hearth, and delicately molten with arc acting from the top. What's important, is that we do not melt everything in one operation. It is enough that the pieces of elements lying above melt and "cover" the ones below, it takes just a few seconds. Then, the whole batch of elements is turned upside down. The partially molten pieces are on the bottom, and the not-molten pieces are heated with arc in the 2nd pass. In the 2nd melting round, the liquid touches (and partially fuses with) the bottom part. Now, we have an inhomogeneous mixture in one ugly piece. What is now necessary, is turning it upside down and melting again to homogenise the whole batch. And again, and again... This is done to obtain good homogeneity. Usually, we do 4-6 meltings. Every time care is taken to avoid complete melting of the alloy to the very bottom, because this brings the risk of melting hearth which results in contamination of the alloy. The key issue is avoiding heavy power input. It is much safer to melt the alloy step by step, with turning it upside down. My advice is: take your time during alloy preparation. If anything goes wrong at this stage, and you may not know about it, the rest of the experiment is useless.
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