X70钢级弯管焊缝冲击性能劣化成因分析  

Cause Analysis for Impact Resistance Deterioration of X70 Elbow Weld

作　　者：曹华勇 张志明 李周波[2] 李芳芳 汪初霞 CAO Huayong;ZHANG Zhiming;LI Zhoubo;LI Fangfang;WANG Chuxia(Nanjing Julong Steel Pipe Co.,Ltd.,Nanjing 210061,China;Baoji Petroleum Steel Pipe Co.,Ltd.,Baoji 721008,China)

机构地区：[1]南京巨龙钢管有限公司,江苏南京210061 [2]宝鸡石油钢管有限责任公司,陕西宝鸡721008

出　　处：《钢管》2023年第6期30-34,共5页Steel Pipe

摘　　要：X70钢级Φ711 mm×11 mm规格弯管弯曲段采用淬火+全管体回火工艺生产时,出现直管段焊缝回火后冲击韧性无法满足技术要求的情况。研究X70钢级弯管焊缝冲击性能劣化的原因,认为:焊态焊缝中有来源于母材的强淬透性元素Cr,而Cr有利于韧性较差的粗大板条状先共析铁素体的析出,从而造成焊态焊缝冲击韧性不高;直管段焊缝回火后,先共析铁素体明显长大,从先共析铁素体中析出的C、N形成了碳氮化物,造成焊缝冲击韧性的继续降低。During manufacturing the Φ711 mm×11 mm X70 elbow,the bended section is made with the quenching+whole pipe body tempering process,which leads to the problem that after tempering,the impact toughness of the str-aight section of the elbow fails to meet applicable technical requirement.Accordingly the causes for deterioration of the impact resistance of the X70 elbow weld are investigated.It is identified via the analysis that there exist in the as-welded weld of the said elbow chemical element Cr that possesses strong hardenability,and comes from the base metal,and is helpful for the precipitation of coarse strip proeutectoid ferrite with poor toughness,which leads to the low impact toughness of the elbow weld;as for the weld of the straight section of the elbow,after being tempered,the proeutectoid ferrite grows bigger obviously,and furthermore the C and N as precipitated from the proeutectoid ferrite turn into carbonitrides which in turn cause the further reduction of the impact toughness of the weld.

关 键 词：弯管 X70钢级 焊缝 冲击性能 淬火 回火 先共析铁素体 

分 类 号：TG142.1[一般工业技术—材料科学与工程] TG156.3[金属学及工艺—金属材料]