The bearing steel G13Cr4Ni4Mo4VA (/% ： 0. 13C

4.13Cr

3. 52Ni

4.39Mo

1. 19V) is melted by 6 t vacuum induction furnace +1. 3 t (Φ406 mm) vacuum arc remelting furnace

and forged to Φ120 mm bar with heating at 1 160 °C

beginning forging at ≥1 140 ℃ and end forging at ≥900 ℃. The specimen for mechanical properties examination is quenched at 1 100 ℃ for 80 min (N

2

gas cooling)

cold treated at -73℃ for 2 h and 3 times tempering treated at 550 ℃ for 2 h

air cooling. The impact value a

ku

is 27. 1 ~ 39. 5 J/cm

2

lower than that of requirement of standard i. e. 87. 5 J/cm

2

. It is obtained by test that due to higher forging temperature

led to δ ferrite precipitating at grain boundaries

the impact value of bar decreases

. With optimizing forging process

decreasing ingot heating temperature to 1 110 ℃ from original 1 160 ℃

to avoid the δ ferrite precipitation

the average impact value a

ku

of bar increases to 113. 6 J/cm

2

.