低碳高强贝氏体钢焊接粗晶热影响区的组织与性能

摘要

研究了一种低碳高强贝氏体钢焊接热影响区粗晶区在不同热输入条件下的组织与性能。结果表明,该钢热影响区粗晶区的低温冲击吸收功随t8/5的增加先增大后减小。当t8/5为30 s时,少量细小粒状贝氏体分割板条贝氏体,使板条贝氏体更细,方向性减弱,低温韧性最佳。当t8/5大于或小于30 s时,钢的组织形态发生变化,均使低温冲击韧性降低。随着冷却速度的降低及t8/5的增大,热影响区硬度呈逐渐减小的趋势;当t8/5超过30 s后,热影响区的硬度低于基材,此时热影响区粗晶区将发生软化。所以,对焊接热输入进行控制、减少热影响区软化是保证焊接接头强度的重要措施。%Microstructural evolution and mechanical properties of coarse-grained heat-affected zone（CGHAZ） in a kind of low carbon bainitic steel were investigated at different heat inputs by means of welding thermal simulation on an MMS-300 thermo-mechanical simulator.The results show that the impact toughness of CGHAZ is first increased and then decreased with increasing t8/5.When t8/5 is equal to 30 s,lath bainite can be split by a small amount of fine granular bainite such that lath bainite is finer and has weak directionality.In this case,the steel has the best low temperature impact toughness.The impact toughness is decreased when t8/5 is greater than or less than 30 s owing to the change of microstructure.With the decrease of cooling rate and the increase of t8/5,the hardness of heat-affected zone is gradually decreased.When t8/5 is greater than 30 s,the hardness of heat-affected zone is lower than that of base metal and the softening of CGHAZ will occur.Therefore,an important way to ensure the strength of welded joints is to control the heat input in order to reduce the softening of heat-affected zone.