X90高强管线钢母材及焊缝的冲击韧性  

Ipmact toughness of base metal and welding seams of X90 high-strength pipeline steel

作　　者：毕宗岳 杨军[1,2] 牛辉 芦琳[1,2] 

机构地区：[1]国家石油天然气管材工程技术研究中心,陕西宝鸡721008 [2]宝鸡石油钢管有限责任公司钢管研究院,陕西宝鸡721008

出　　处：《材料热处理学报》2017年第10期72-79,共8页Transactions of Materials and Heat Treatment

基　　金：国家科技支撑计划项目(2011BAE35B01)

摘　　要：利用OM、SEM、TEM、EDS、EBSD及Charpy冲击实验对试制的X90钢级螺旋埋弧焊管母材和焊缝冲击断口形貌、近断口区微观组织特征、夹杂物成分、晶粒取向特征、大/小角度晶界占比及低温冲击韧性进行了研究。结果表明,在-10℃下,母材平均冲击功值达314 J,焊缝仅为157 J,母材冲击韧性远优于焊缝。母材试样近断口区显微组织为细小针状铁素体(FAF)+板条贝氏体(LB)+多边形铁素体(QPF)+少量M-A组元,M-A组元呈颗粒状,平均粒径约0.3μm,有效平均晶粒尺寸为2.3μm,大角度晶界比列为91.04%;焊缝试样近断口区组织为AF+QPF+M-A组元+少量先共析铁素体(PF),M-A组元弥散分布,形态多样,平均尺寸1.0~2.0μm,有效平均晶粒尺寸为3.5μm,大角度晶界比列为80.4%。晶粒尺寸粗大、大角度晶界占比偏低和大尺寸尖角型M-A组元是导致焊缝冲击韧性差的主要原因,而大尺寸密集型夹杂物分布使焊缝有更差的冲击韧性。The fracture morphology,microstructure characteristics of near fracture zones,composition of inclusions,grain orientation,percentage of large/small angle grain boundaries and impact toughness at low temperature of base metal and welding seams of X90 steel grade spiral submerged arc welded pipe were investigated by means of OM,SEM,TEM,EDS analysis,EBSD technique and Charpy impact test. The results show that the low temperature impact toughness of the base metal is better than that of the weld seams,and the average impact energy values of the base metal is up to 314 J while the welded joints is only 157 J at-10 ℃. The microstructure in near fracture zone of the base metal is composed of fine acicular ferrite（ FAF）,lath bainite（ LB）,quasi-polygonal ferrite（ QPF） and a small amount of M-A（ martenite/austenite） structure,the average size of the M-A structure is about 0. 3 μm,the average effective grain size is 2. 3 μm,and the proportion of large-angle grain boundaries is 91. 04%. The microstructure in near fracture zone of the weld seam is composed of acicular ferrite,QPF,M-A structure and a small amount of proeutectoid ferrite（ PF）,the average size of the M-A structure is 1. 0-2. 0 μm,the average effective grain size is 3. 5 μm,and the proportion of large-angle grain boundaries is 80. 4%. The coarse grain sizes and the low proportion of large-angle grain boundaries and the large size cusp type M-A structure are the main reason for the poor impact toughness of the welding seams,and the dense distribution of the large-sized inclusion leads to the worse impact toughness.

关 键 词：X90管线钢 冲击韧性 焊接接头 针状铁素体 

分 类 号：TG407[金属学及工艺—焊接]