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设计了一种9MnCr低合金磨球用钢,绘制了9MnCr钢的连续冷却转变曲线,并对其组织和硬度进行了分析。结果表明,当冷却速度小于2℃/s时,转变产物为片层状珠光体和沿晶界分布的二次碳化物;当冷却速度为2～5℃/s时,转变产物为片层状珠光体、马氏体和少量贝氏体;当冷却速度大于5℃/s时,转变产物为马氏体组织。硬度随冷却速度的增加而增加,当冷却速度大于5℃/s时,基本保持不变,为61 HRC。220℃等温30 min后,转变产物基本为马氏体组织,随着等温温度的升高,逐渐出现贝氏体,硬度呈下降趋势;在420℃等温过程中,初期贝氏体的转变速率较快,但转变一段时间后,贝氏体的转变速率减慢。
A 9MnCr low alloy ball steel was designed and the continuous cooling transformation curve of 9MnCr steel was drawn. The microstructure and hardness of 9MnCr steel were also analyzed. The results show that when the cooling rate is less than 2 ℃ / s, the transformation products are lamellar pearlite and secondary carbides distributed along grain boundaries. When the cooling rate is 2 ~ 5 ℃ / s, the transformation products are lamellar Pearlite, martensite and a small amount of bainite; when the cooling rate is greater than 5 ℃ / s, the transformation product is martensite. The hardness increases with the increase of the cooling rate. When the cooling rate is more than 5 ℃ / s, the hardness remains unchanged at 61 HRC. After isothermal at 220 ℃ for 30 min, the transformation product was basically martensite. With the increase of isothermal temperature, the bainite gradually appeared and the hardness decreased. During the isothermal temperature of 420 ℃, the transformation rate of initial bainite Fast, but after a period of change, the rate of bainite transformation slows down.