混晶对低成本Q355D钢低温冲击韧性的影响

Effect of Mixed Grain on the Low Temperature Impact Toughness of Low Cost Q355D Steel

为了改善含Ti低成本Q355D钢的低温冲击韧性,研究了粗轧、精轧和冷却过程对钢板组织和性能的影响,从而达到获得良好低温冲击韧性的目的。结果表明,粗轧末三道次压下率低,有效累积应变不足,粗轧未能渗透坯料芯部,难于细化坯料芯部奥氏体晶粒,同时粗轧温度高,促进晶粒快速长大,钢板易出现混晶和粗大的芯部晶粒。精轧总累积应变不足,相变细化晶粒减弱,同时冷却返红温度较高,钢板更易出现晶粒粗大。混晶会导致低温冲击功较差,并降低低温韧性的稳定性。

In order to improve the low temperature impact toughness of low cost Q355D steel containing Ti,the effects of rough rolling,finish rolling and cooling process on the microstructure and properties of steel plates were studied.The results show that the reduction rate of final three passes of rough rolling is low,the effective accumulated strain is insufficient,and rough rolling fails to penetrate the slab core,so it is difficult to refine the austenite grains in the core.At the same time,the high rough rolling temperature promotes rapid grain growth,and the steel plate is prone to appear mixed grain and the coarse core grain.The total accumulated strain of finish rolling is insufficient,then the grain refinement during phase transformation is weakened.Meanwhile,the selftempering temperature after cooling is very high,hence the steel plate is more likely to appear coarse grain.Mixed grain leads to poor impact energy at low temperature and reduces the stability of low temperature toughness.