低合金耐热钢焊接接头再热裂纹研究进展

Review of reheat crack in welded joint of low alloy heat-resistant steels

综述了低合金耐热钢焊接接头再热裂纹的研究现状,概括了近几年工程中发现的新情况,并提出了需要进一步研究的问题。再热裂纹产生于接头焊后热处理(Postweld Heat Treatment,PWHT)过程中或高温运行中,其形成机理主要有四种:晶界杂质偏析弱化、晶内沉淀强化、蠕变断裂和无析出区弱化。影响再热裂纹产生的主要因素有材料成分、接头组织形态和壁厚、填充材料、预热和后热、焊接热输入、焊后热处理工艺、应力和应变等。为了评价再热裂纹敏感性,研究人员提出了理论计算方法、断面收缩率评定准则和几种试验方法。针对目前工程中出现的新问题,认为需要在新型耐热钢、厚壁耐热钢和长时运行耐热钢再热裂纹的机理与影响因素预防等方面继续进行研究。

The current research status of reheat crack in welded joint of low alloy heat-resistant steels are outlined. Some new phenomena discovered in engineering in recent years are summarized,and related problems that remain to be studied are also presented. Reheat crack in welded joint is occurred frequently during postweld heat treatment( PWHT) or its service at elevated temperature. Mainly four mechanisms,namely,impurity segregation grain boundary weakening,precipitation hardening,creep rupture and no-precipitation zone weakening,can lead to reheat crack. Several essential factors,which are consist of parent material chemical composition,microstructure and thickness of welded joint,filler material,preheat and postheat,welding energy input,PWHT parameter,stress and strain and so on,affect reheat crack. Theoretical calculation methods,evaluation criterion of ROA( Reduction of Area) and several experimental methods are put forward to evaluate reheat crack susceptibility. Based on new issues emerged in in welding of new heat-resistant steels,increasing wall thickness eat-resistant steels,and long term service conventional low alloy heat-resistant steels,problems of the formation mechanism of reheat crack in welded joint and its influencing factors are necessary to be researched.