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 80mm diameter cylindrical mold at nearly definite power of 30 kw. The melt rate was varied between 288 and 434 g/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 mean secondary dendrite arm spacing was the greatest at the ingot mid-radius part in comparing with those of the surface and center part of the 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 macrostructure 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 should be determined in order to obtain the sound macrostructure as well as the fine microstructure.
ESR에서 용해속도가 잉고트의 미세조직에 미치는 영향에 대하여 조사하였다. 구조용 저합금강인 $SCM_4$를 직경 80mm의 원통형 mold에서 용해하였으며, 사용한 전력은 약 30KW 이다. 전극의 크기와 스랙양을 바꾸어 용해속도를 288 에서 434g/min. 까지 변화시켰다.
잉고트의 secondary dendrite arm spacing은 용해속도가 커짐에 따라 용해속도에 거의 반비례하여 작아졌다. 또한 이것은 잉고트의 표면 및 중심부에 비해서 mid-radius부에서 가장 컸다.
Cr의 미세편석을 EPMA로 측정하였으며 용해속도는 Cr의 미세편석에 큰 영향을 주지 않았다.
용해속도를 크게 하면 용융금속pool이 깊어져 매크로 조직이 나빠지나 반면에 미세조직은 좋아졌다. 따라서 매크로 조직과 미 세조직을 동시에 좋게 하기 위해서는 적당한 용해속도를 택하여야 한다.
