9%Ni钢焊接粗晶区的韧化因素  

Factors Influencing Notch Toughness of Coarse-grained Heat Affected Zone for 9% Ni Steel

作　　者：严春妍[1] 李午申[2] 刘欢[2] 白世武[3] 

机构地区：[1]河海大学机电工程学院,常州213022 [2]天津大学材料科学与工程学院,天津300072 [3]中国石油天然气管道科学研究院,廊坊065000

出　　处：《机械工程学报》2010年第18期96-101,共6页Journal of Mechanical Engineering

摘　　要：采用热模拟技术,利用光学显微镜、X射线衍射仪、扫描电镜等现代物理测试手段,研究晶粒尺寸、残余奥氏体和M-A组元等因素对液化天然气储罐用9%Ni钢焊接粗晶区低温韧性的影响。研究结果表明,经历焊接热循环后,焊接粗晶区的韧性与母材相比有显著的下降。在焊接粗晶区中,临界粗晶区是9%Ni钢低温下主要的局部脆性区。残余奥氏体数量的变化不是韧性变化的决定因素;晶粒尺寸增加,低温韧性显著下降;M-A组元的尺寸越大、含碳量越高、数量越多,则越不利于材料的韧性。根据分析结果得出,为改善9%Ni焊接粗晶区的低温韧性、防止焊接接头发生脆性断裂,现场焊接时应采用较小的焊接热输入配合较高的层间温度来控制晶粒尺寸和显微组织。Thermal simulation and modern physical test means like optical microscopy,X-ray diffractometry and scanning electron microscopy are used to investigate the effects of factors like grain size,retained austenite and martensite-austenite（M-A） constituents on cryogenic toughness in heat affected zone（HAZ） of 9% Ni steel for liquefied natural gas storage tanks.Results show that the cryogenic toughness of coarse-grained HAZ is much lower than that of base metal after experiencing welding heat cycles.Inter-critically reheated coarse-grained HAZ（IRCGHAZ） is a primary local brittle zone（LBZ） of 9% Ni steel at cryogenic temperature.The change in the amount of retained austenite is not the governing factor of toughness change.Cryogenic toughness is severely reduced with the increase of grain size,and the larger the size and the higher thecarbon content of M-A constituents are,the more unfavorable to the material toughness will be.Analysis results indicate that low heat input and high interpass temperature should be applied for field welding to control grain size and microstructure characteristics,in order to improve cryogenic toughness of CGHAZ of 9%Ni steel and prevent brittle failure of the welding joint.

关 键 词：9%NI钢 热模拟 低温韧性 晶粒尺寸 M-A组元 

分 类 号：TG142.79[一般工业技术—材料科学与工程]