| This study was undertaken to observe the effect of melt rate on the microstructure of ingot in the electroslag remelting process. The structural low alloy steel, SCM 4, was remelted in the 80㎜ diameter cylindrical mold at nearly definite power of 30㎾. The melt rate was varied between 288 and 434g/min by changing the electrode mold diameter ratio and the amount of slag. It was found that the secondary dendrite arm spacing was decreased as the melt rate was increased, that is, the secondary dendrite arm spacing was almost inversely proportional to the melt rate. The moan secondary dendrite arm spacing was the greatest at the ingot mid-radius part in comparing with those of the surface and center parts of ingot. It can be explained from the fact that the local solidification rate is the least at the mid-radius part of ingot. Dendritic segregation of chromium was measured by electron probe microanalyzer. No correlation between the melt rate and the microsegregation of chromium was observed. The microstructure became inferior when the molten metal pool was deepened by increasing the melt rate, whereas the higher the melt rate, the finer the microstructure. Therefore the optimum melt rate have to be determined in remelting practice for the purpose of obtaining the sound macrostructure as well as the fine microstructure. |
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