冷却速度对贝氏体焊缝金属硬度及冲击韧性的影响

Influence of cooling rate on microhardness and impact toughness of bainite weld metal

随着高强高韧板条贝氏体钢的快速发展,研发与其匹配的高强高韧焊缝金属及其强韧性机理的研究具有重要的科学意义和实用价值。通过Gleeble-3800热模拟试验机,采用热膨胀法测得不同焊接热循环条件下贝氏体焊缝金属的相变温度和时间,分析不同模拟焊接冷却速度下贝氏体焊缝金属的微观组织、显微硬度和冲击韧性的变化规律。在此基础上,绘制得到贝氏体焊缝金属的CCT曲线,进而为制定贝氏体钢焊接工艺提供了非常有力的技术支持。试验结果表明,当焊接冷却速度处于0.5-5℃/s范围内,形成更多的板条贝氏体组织,可以达到提高冲击韧性的目的。

With rapid development of high strength and high toughness lath bainite steel,it is very important to develop high strength and high toughness weld metal which is matched with high strength high toughness lath bainite steel and study strengthening-toughening mechanisms of high strength and high toughness weld metal. The temperatures and time of phase transformation with different welding thermal cycles were measured by thermal expansion method in Gleeble- 3800 thermo-mechanical simulator. The microstructure,microhardness and impact toughness were analyzed and tested,and the continuous cooling transformation( CCT) curve of bainite weld metal was established,which provides technical support for determining the welding parameters of bainite steel. The experimental results show that while welding cooling rates are in the range of 0. 5 ~ 5 ℃ / s,the microstructures with more lath bainite form,so that microhardness decreased and impact toughness improved.