BHW35钢埋弧焊环缝组织及高温冲击性能分析

Metallograph and high-temperature impact toughness of circumferential joint by SAW of BHW35 steel

关键词:  BHW35钢  埋弧焊接接头  金相组织及硬度  冲击吸收功  断口分析

Key words:  BHW35 steel  submerged-arc weld joint  metallograph and hardness  impact absorbing energy  fractograph

摘要:

BHW35钢匹配H08Mn2MoA+HJ350焊材,采用埋弧自动焊焊制的厚壁焊接接头,经消应力退火热处理后,对接头及母材实施了室温,100,200,350℃下缺口冲击试验,并进行冲击断口、金相组织、硬度及化学成分分析.结果表明,接头硬度为291.6HV.随着温度升高,接头韧度较室温大幅度提高,冲击吸收功均出现峰值温度,焊缝为100℃,而HAZ和母材为200℃.热影响区的韧度优于焊缝,接头冲击吸收功室温为47.33 J以上,350℃为134.67 J以上,满足韧度要求.断口分析表明,母材冲击断口均为延性韧窝,室温焊缝及HAZ冲击断口呈准解理+韧窝的混合断裂特征,而高温下均变为延性韧窝.冲击吸收功越高,断口撕裂特征越明显,韧窝越大,分布越不均匀.

Abstract:

BHW35 steel was welded by automatic submerged-arc welding(SAW) with H08Mn2MoA welding wires and flux HJ350.After stress relief annealing by the postweld heat-treatment system,impact tests on welded joint and base metal were carried out at 20,100,200 and 350℃,and the scanning electron microscopy(SEM) fractograph,metallograph,hardness and chemical compositions of welding seam were analyzed.The results indicate that the highest hardness of HAZ is 291.6 HV.The toughness increases greatly compared with that at room temperature.The temperature peak value of impact absorbing energy of welding seam occurs at weld of 100℃ and both HAZ and base metal of 200℃.The impact toughness in HAZ is better than that in welding seam.The impact absorbing energy of welded joint is over 47.33 J at room temperature and 134.67 J at 350℃,which meets the toughness demand for the welded joint and base metal.SEM fractograph indicates that all impact fractures of base metal exhibit ductile dimple,and the impact fractures in welded joint at room temperature exhibit quasi-cleavage and ductile dimple.With the temperature increasing,the fractures subjected high temperature impact all exhibit ductile dimple;the better toughness is,the more obvious tearing feature of ductile dimple is,and the larger the ductile dimple is,the more obvious non-uniform distribution is.