According to the surface defect occurred at lower part of ESR ingot of 521 steel (/% : 0. 37 ~ 0. 45C

0. 80 ~ 1. 15Si

4. 50 ~5. 30Cr

1. 20 ~ 1. 40Mo

0. 85 ~ 1. 10V) and GCr15 steel (/% : 0. 97C

1. 57Cr) melted by ESR furnace with double electrode

the effect of binary slag amount

lower part remelting voltage and current as well as remelting time on surface quality of 2. 5 ~ 5 t ESR ingot has been statistically analyzed. Results show that control remelting time (remelting rate) has obvious effect on surface quality of ESR ingot: for 5 1521 steel remelting ingot

with slag amount 200 kg

voltage 55 V and current 15 500 ~ 16 800 A in melting at ingot lower part

as total remelting time is 434 ~489 min

the ingot surface is smooth

while the total remelting time is 500 min

there is 15 mm depth slag scar at ESR ingot lower part； for 2. 5 t GCr15 steel remelting ingot

with slag amount 120 kg

voltage 43 ~44 V and current 13 500 ~ 14 000 A in melting at ingot lower part

as the total remelting time is 316 ~ 359min

the surface of ingot is smooth while the total remelting time is 380 min

the ESR ingot lower part has 7 mm depth slag runner and slag inclusion.