X80级管线钢热影响区的局部脆化

钢铁, 2007, 42(3): 69-0.

X80级管线钢热影响区的局部脆化

张小立 , 庄传晶 , 冯耀荣 , 赵文轸 , 霍春勇

1.1. 中国石油天然气集团公司管材研究所，陕西西安 710065； 2. 西安交通大学材料科学与工程学院，陕西西安 710049

1.1. Research Institute of Tubular Goods, CNPC, Xi’an 710065, Shanxi, China

2.2. School of Material Science and Engineering, Xi’an Jiaotong University, Xi’an 710049, Shanxi, China

关键词： X80管线钢;焊接热影响区;裂纹;局部脆化

Local Brittleness of HeatAffected Zone of X80 Pipeline Steel

ZHANG Xiaoli , ZHUANG Chuanjing , FENG Yaorong , ZHAO Wenzhen , HUO Chunyong

Keywords： X80 pipeline steel;weld heataffected zone;microcrack;local brittleness

研究了国产X80级管线钢热影响区的冲击韧性和组织的局部脆化。结果表明，该钢的焊接热影响区的冲击韧性较母材降低50%以上；在所研究的20~-40 ℃温度区间内，其断口的宏观形貌特征从部分脆性特征转变为完全的脆性断口；20 ℃放射区断口呈现韧性断裂和解理断裂共存的混合型断口，并且试验温度为20 ℃和0 ℃时，分别在放射区和纤维区可观察到微观裂纹；热影响区断口表层剖面组织为粒状贝氏体，显示出粗晶区的特征。裂纹扩展方向为沿晶界扩展，粒状贝氏体中M/A岛尺寸增大，并存在裂纹穿过岛状物的现象，这是晶界严重脆化的结果。

Impact Charpy toughness and local brittleness of HAZ of X80 linepipes made in China were studied. It was shown that the impact toughness of HAZ is 50% of base metal.From 20 ℃ to -40 ℃, the fracture is changed from part brittleness to total brittleness.At 20 ℃,the radial region is a mixture of cavitation and cleavage fracture and at 20 ℃and 0 ℃ the microcracks could be observed in radial region and fibrous region, respectively.The microstructure of fracture surface of HAZ is of granular bainite,with characteristics of coarse crystal zone.The propagation of microcracks goes along grain boundaries, the size of M/A islands in granular bainite is increased, and the phenomenon of crack traversing through M/A island exists as the result of serious embrittlement of grain boundary in HAZ.

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