Abstract: Test steel 508-3 (/% : 0. 19C, 0. 26Si, 1.48Mn, 0. 009P, 0. 007S, 0. 78Ni, 0. 50Mo, 0.003Al) is melted by a vacuum induction furnace and cast to 50 kg ingot, forged at 1 150 to Φ16 mm bar, end forging ≥900℃.The effect of normalizing temperature (900 ~ 1 200 °C) and multi-normalizing process (900 〜1 200℃ 1 h-900℃ 1 h-890 °C 1 h) on austenite grain size of steel 508-3 has been studied. Results show that as normalizing at 900 ~ 1 200 °C, with increasing normalizing temperature the austenite grain size of steel coarsens obviously, the rating of austenite grain coarsens from No 6. 5 to No 3 ； with subsequent secondary normalizing at 900 °C the original course austenite grains in steel are refined to rating of No 6, then with third normalizing at 890 °C the effect of refining of austenite grains is not obvious. Multistep- normalizing treatment is available to refining the coarse austenite grains of steel 508-3, but repeating normalizing at same temperature is not obvious to refining the austenite grains in steel.

Key words:  , Pre-Heat-Treatment, Austenite Grain Size, Steel 508-3

摘要： 试验用钢508-3(/%:0.19C、0.26Si、1.48Mn、0.009F、0.007S、0.78Ni、0.50Mo、0.003Al)由真空感应炉冶炼,50kg铸锭,经1150℃锻成Φ16 mm棒材,终锻≥900℃。研究了正火温度(900～1 200℃)和多次正火工艺(900～1 200℃1 h-900℃1 h-890℃1 h)对508-3钢奥氏体晶粒尺寸的影响。结果表明,在900～1 200℃正火时,随着正火温度升高,奥氏体晶粒尺寸出现明显粗化,奥氏体晶粒度级别由6.5级粗化到3级。随后经过900℃二次正火,钢中原粗大的奥氏体晶粒可以细化到6级,再进行890℃三次正火后,奥氏体晶粒细化不明显。多次阶梯正火处理可以细化508-3钢粗大的奥氏体晶粒,但在同一温度重复正火时,钢中晶粒细化效果不明显。