热输入对管线钢热模拟焊缝粗晶热影响区冲击韧性的影响  

Effect of Welding Heat Input on Impact Toughness of Pipeline Steel Thermal Simulated Weld Seam Coarse Grain Heat Affected Zone

作　　者：胡平[1] 郑磊[1] HU Ping ZHENG Lei(Research Institute, Baoshan Iron and Steel Co., Ltd., Shanghai 201900, China)

机构地区：[1]宝山钢铁股份有限公司研究院,上海201900

出　　处：《焊管》2017年第6期9-19,共11页Welded Pipe and Tube

摘　　要：为了研究不同热输入对管线钢焊缝粗晶热影响区冲击韧性的影响,选用40~55 kJ/cm 4种不同焊接热输入量(对应于t8/5=21~40 s)对管线钢进行了热模拟焊接试验,并对不同焊接热输入下的焊缝冲击韧性、冲击断口形貌进行了研究。研究结果显示,随着t8/5的增加,相变过程的冷速逐渐降低,导致相变形成的板条结构宽化,M-A组元的宽度逐渐变粗(即短轴、长轴之比增大),尺寸增大且粗大的M-A组元在晶界上链接成串,从而降低了冲击韧性;随着t8/5的增加,韧脆转变温度升高;热模拟峰值温度一致且较高导致混晶,也是引起冲击韧性降低和试验值分散性较大的原因;冲击断口的SEM形貌观察和能谱分析显示,材料中形成的大尺寸Ti、Nb复合碳氮化物析出相,以及形成的邻近两个或多个Al_2O_3和CaS复合夹杂物可以成为诱发脆性解理断裂的起裂源。In order to study the effect of different welding heat input on pipeline steel thermal simulated weld seam coarse grain heat affected zone, selected 40-55 kJ/cm 4 kinds of welding heat input（namely the range of t8/5 from 21 to 40 s） to conduct thermal simulation welding test, and studied weld impact toughness and fracture appearance morphology under different welding heat input. The results showed that as the ts15 increased, the cooling rate dropped gradually resulting in the coarsening of the lath structure. Moreover, the width of the M-A constitute increased（namely minor axis to major axis ratio increased） and agglomeration of coarse M-A constitutes along the grain boundaries both contribute to the decline of the impact toughness. With the t8/5 extended, the ductile to brittle transition temperature was raised. Furthermore, inhomogeneous prior-austenite grain size caused by the high peak temperature during heating also led to the decreasing of the impact toughness and a large scatter of the impact toughness testing values. By means of SEM observation on the impact fractographs and EDS analysis on inclusions and precipitations, it is shown that large size carbonitride precipitation containing Ti and Nb and two or more Al2O3 and CaS combined inclusions also can played a role as the initiation site of brittle cleavage fraeture.

关 键 词：管线钢 焊接热输入 冲击韧性 粗晶热影响区 

分 类 号：TG407[金属学及工艺—焊接]