冷却速率对LY225低屈服点钢组织和性能的影响

Effect of cooling rate on microstructure and properties of LY225 low yield point steel

利用热轧试验研究了不同冷却速率对LY225低屈服点钢显微组织、拉伸性能、冲击性能和疲劳性能的影响。结果表明,慢冷却速率(1℃/s)工艺所得组织粗大,珠光体片层间距较大,晶界游离渗碳体含量较高且沿晶界连续分布,低温韧性和疲劳性能均较差;中等冷却速率(10℃/s)和快冷却速率(20℃/s)工艺所得组织较慢冷却速率工艺所得组织明显细化,珠光体片层间距减小,晶界游离渗碳体含量减少且分布离散,强度、低温韧性和疲劳性能均得到较大提升;快冷却速率(20℃/s)较中等冷却速率(10℃/s)所得组织更加细化,但塑性有所降低,疲劳寿命也相应缩短。

Effect of different cooling rate on microstructure,tensile property,impact property and fatigue performance of the LY225 low yield point steel was studied by hot rolling trials.The results show that,at the low cooling rate(1℃/s),the grain size is coarse and the pearlite lamellar spacing is larger with a large amount of free cementite continuously distributed along the grain boundary,leading to poor toughness and fatigue performance.At the medium cooling rate(10℃/s)and high cooling rate(20℃/s),the grains are refined and the pearlite lamellar spacing is decreased with much less dispersedly distributed free cementite,showing much improved strength,toughness and fatigue performance.Compared to the medium cooling rate(10℃/s),the high cooling rate(20℃/s)offers a more refined microstructure,but with lower plasticity and fatigue performance.