装配式建筑用耐候钢的焊接热模拟

Study on the welding thermal stimulation of weathering steel for fabricated building

对新开发的一种屈服强度Q390级别的装配式建筑用高强耐候钢进行焊接热模拟研究。结果表明,粗晶区硬度最高,冲击功最低,为焊接接头薄弱区域。随着热输入的增加,粗晶区组织由板条贝氏体向粒状贝氏体转变,硬度随之下降,冲击功呈现先升高后下降的趋势,在热输入为15 kJ/cm时冲击功达到最大236 J。进一步观察断面形貌及断口截面金相发现,热输入过小时,淬硬组织多,断裂过程微塑性变形小,冲击性能差;热输入超过20 kJ/cm时,随着热输入增加,阻止裂纹扩展能力下降,冲击功下降。

The performance of weathering steel for fabricated building was studied by thermal stimulation technology. The results show that coarse-grain heat affect zone(CGHAZ),which gets the highest hardness and the poorest impact toughness,is most possible to became the weak areas of welded joint. With increasing of heat input,the microstructure of CGHAZ changes from lath bainite to granular bainite,and the hardness decreases. The impact energy increases at the beginning and then decreases. The maximum impact energy reaches 236 J when heat input is 15 kJ/cm.The fracture behavior of those specimens are further analyzed by observing fracture morphology and section microstructure of those impact specimens. When heat input is too low,more quenchinghardening structure,which get little small plastic deformation during fracture process,is formed,and impact toughness is poor.When heat input was over 20 kJ/cm,the ability of preventing crack propagation decreases and impacttoughness decreases.