控轧温度对LPG船用低温钢板韧性的影响

Effects of Controlled Rolling Temperature on Toughness of Low Temperature Steel for LPG Tanker

利用冲击试验、显微组织对比等方法,研究了控轧控冷(TMCP)工艺下控轧温度对LPG船用低温钢板韧性的影响。冲击试验结果显示,试验钢在-60^-80℃冲击试验温度下都具有良好的冲击韧性,而在-80^-100℃更低的冲击试验温度下,随着控轧温度的降低,冲击韧性出现增高趋势,韧脆转变温度进一步降低。通过显微组织对比分析发现,随着控轧温度的降低,奥氏体有效晶界和内部储能增加,铁素体形核率相对较高,因此铁素体晶粒相对更加细小,随着晶粒的进一步细化,能有效抑制裂纹扩展并促使裂纹扩展改变方向,从而提高了钢板的冲击韧性。

The effects of controlled rolling temperature on toughness of low temperature steel plate for LPG tanker are studied by means of impact test and microstructure comparison.The impact test results show that the test steel possesses good impact toughness at the impact testing temperature from-60℃to-80℃.The impact toughness increases with the decrease of controlled rolling temperature at the impact testing temperature between-80℃and-100℃,but the ductile-brittle transition temperature reduces further.By microstructure comparitive analysis,it is found that,with the decrease of controlled rolling temperature,the amount of effective austenite grain boundaries and the grain boundary internal stored energy increase,the nucleation rate of ferrite is higher,as a result,the ferrite grain is relatively refined.With further refinement of the grain,the cracks propagation is effectively prohibited and turned to other directions,which improves the impact toughness of the test steel plate.