With using the process measures including controlling mold inlet water temperature 40℃outlet water temperature 68 ℃ ； controlling model of computer auto back feeding for shrinkage ； at end auto back feeding

changing consumable electrode to graphite electrode withing 90 s and power supply with 53 V

3 000 A melting for 3 ~5 min

then again changing to consumable electrode and power supply with 50 V

4 000 A for 6 min

the depth of top shrinkage cavity defect of electroslag remelting ( ESR) ingot decreases to 30 ram from original 100 mm. Production practice shows that the process operation of back feeding for shrinkage is simple and easier to do. The forged billets of remelting 210 piece tool steel 9Cr2Mo Φ 280 mm x 1 000 mm

480 kg ESR ingot and 60 piece hot die working steel H13 420 mm x 1 400 mm

1 500 kg ESR ingot by optimized process have not been rejected due to ingot top shrinkage cavity defect

the ingot yield increases obviously.