低合金高强度钢Q345D低温冲击脆性问题研究

Study on Brittleness at Low Temperature Impact Test of Low-alloy High-strength Steel Q345D

本文研究了化学成分、TiN夹杂、加热温度和冷却速度对低合金高强度结构钢Q345D棒材低温冲击韧性的影响。结果表明：在标准范围内C≤0.13%、Mn≥1.2%、Ti≤0.06%，低温冲击吸收能量完全满足标准要求；Ti≥0.49%时，会出现大量的TiN夹杂，严重降低低温冲击吸收能量；加热温度≥950℃，晶粒明显变粗，低温冲击吸收能量急剧下降；在0.5℃/min~空冷的冷却速度范围内，随着冷却速度的增加低温冲击吸收能量逐步增加。

In this paper,the effect of chemical composition,TiN inclusion,heating temperature and cooling speed on the low temperature impact toughness of bars of low-alloy high-strength structural steel Q345D was investigated.The results showed that when C≤0.13%,Mn≥1.2%,Ti≤0.06%,the absorption energy at low temperature impact met the requirements;when Ti≥0.49%,a large amount of TiN inclusions presented,which substantially reduced the absorption energy at the low temperature impact;when the heating temperature≥950℃,the grain size became coarser,and the absorption energy at the low temperature impact decreased sharply;when the cooling speed was within the range from0.5℃/min to air cooling,the absorption energy at the low temperature impact increased gradually with the increase in the cooling speed.When the cooling speed reached10℃/min,the absorption energy reached the maximum value;when the cooling speed increased further,the B structure presented,which resulted decrease in the absorption energy at low temperature.