热处理对极寒服役条件下弯管用X70钢焊接接头组织和性能的影响

doi:10.13251/j.issn.0254-6051.2022.10.029

摘要/Abstract

摘要： 采用手工焊条电弧焊焊接X70管线钢,模拟弯管热煨工艺,对焊接接头进行调质处理,采用950 ℃淬火,分别采用500、550和600 ℃回火,研究回火温度对X70管线钢焊接接头组织形貌和力学性能的影响。结果表明,经过调质处理后,焊缝中心和热影响区组织为回火索氏体,-45 ℃低温冲击吸收能量明显下降。随着回火温度的升高,焊缝组织中碳化物析出增加,分布逐渐均匀,针状铁素体增加,冲击吸收能量增加。在550 ℃回火时,热影响区-45 ℃低温冲击吸收能量最高,在600 ℃回火时,热影响区组织粗大,析出碳化物粗大,低温冲击吸收能量降低。调质处理后,焊缝中心硬度最高,拉伸时从母材处断裂,强度满足要求。由此可知,焊接接头在550 ℃回火时可以获得最佳强韧匹配性能。

关键词: X70管线钢, 焊接接头, 热处理, 低温冲击韧性

Abstract: X70 pipeline steel was welded through SMAW and then by simulating the induction pipe bending process, the welded joint was quenched at 950 ℃ and tempered at 500, 550 and 600 ℃. Effect of different tempering temperatures on the microstructure and properties of the welded joints were studied. The results show that the microstructure of the weld and the heat affected zone are tempered sorbite, and the low temperature impact absorbed energy at -45 ℃ of the weld and the heat affected zone reduces significantly after quenching and tempering. With the increase of the tempering temperature, the low temperature impact absorbed energy increases gradually, which is attribute to the increase of the content of carbide precipitates and acicular ferrite(AF) in the weld structure, and the carbide distribution gradually becomes uniform. The heat affected zone has the highest impact absorbed energy when tempered at 550 ℃, but it decreases obviously when tempered at 600 ℃, which is attribute to the coarsening of both the microstructure and the carbide precipitates. After quenching and tempering, the hardness of the weld is the highest, and the pipe during tensile test fractures in the base metal, the strength of the welded joint meets the requirements. Thus, the optimal matching of the impact toughness and tensile properties of the welded joint can be obtained when tempered at 550 ℃.

Key words: X70 pipeline steel, welded joint, heat treatment, low temperature impact toughness

中图分类号:

TG441.8

张侠洲, 陈延清, 赵英建, 董现春. 热处理对极寒服役条件下弯管用X70钢焊接接头组织和性能的影响[J]. 金属热处理, 2022, 47(10): 173-178.

Zhang Xiazhou, Chen Yanqing, Zhao Yingjian, Dong Xianchun. Effect of heat treatment on microstructure and properties of welded joint of X70 steel used for bent pipe under extremely cold service condition[J]. Heat Treatment of Metals, 2022, 47(10): 173-178.

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