Study on the Microstructure and Toughness of Welded Joint of S690QL Low-alloy High-strength Steel

WANG Yanhua; XIE Geng; ZHANG Bin; MU Weidong; CAI Yan

doi:10.7512/j.issn.1001-2303.2024.05.02

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Study on the Microstructure and Toughness of Welded Joint of S690QL Low-alloy High-strength Steel
Vol. 54, Issue 5, Pages: 17-24(2024)
Published： 25 May 2024 ，
DOI： 10.7512/j.issn.1001-2303.2024.05.02

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王艳华，谢耿，张斌，等.S690QL低合金高强钢焊接接头组织特征和低温韧性研究［J］.电焊机，2024，54（5）：17-24.

WANG Yanhua, XIE Geng, ZHANG Bin, et al.Study on the Microstructure and Toughness of Welded Joint of S690QL Low-alloy High-strength Steel[J].Electric Welding Machine, 2024, 54(5): 17-24.
王艳华，谢耿，张斌，等.S690QL低合金高强钢焊接接头组织特征和低温韧性研究［J］.电焊机，2024，54（5）：17-24. DOI： 10.7512/j.issn.1001-2303.2024.05.02.

WANG Yanhua, XIE Geng, ZHANG Bin, et al.Study on the Microstructure and Toughness of Welded Joint of S690QL Low-alloy High-strength Steel[J].Electric Welding Machine, 2024, 54(5): 17-24. DOI： 10.7512/j.issn.1001-2303.2024.05.02.

摘要

对40 mm厚S690QL高强钢进行多层多道焊接，观察焊缝金属和热影响区的显微组织特征，统计M-A组元数量和形貌，分别对母材、焊缝金属和热影响区进行了冲击韧性测试和断裂韧性测试。结果表明：多次热循环促进了碳元素的析出和偏聚，在焊缝金属和粗晶区均发现了M-A组元的存在，它们的含量分别为5.8%和12.5%，平均尺寸分别为0.157 μm和0.194 μm。粗晶区的M-A组元尺寸较大，且在原奥氏体晶界处呈链状分布。母材、焊缝金属和粗晶区的室温CTOD平均值分别为0.38 mm，0.25 mm和0.22 mm。粗晶区的力-位移曲线出现明显的局部陡降特征，表明粗大的M-A组元加速了裂纹扩展速率。焊缝金属和粗晶区的冲击吸收功均随温度下降而显著下降，表明M-A组元的脆化效应随温度下降而加剧。-40 ℃时，焊缝金属冲击吸收功急剧降低，与粗晶区接近，表明M-A组元对韧性的不利影响在低温时占主导地位。

Abstract

The study involved the multi-layer and multi-pass welding of 40 mm thick S690QL high-strength steel. The research focused on observing the microstructure characteristics of the weld metal and heat affected zone

as well as counting the number and morphology of M-A constituents. Additionally

tests were conducted to evaluate the impact toughness and fracture toughness of the base metal

weld metal

and heat affected zone. The results revealed that multiple thermal cycles facilitated the precipitation and segregation of carbon elements. M-A constituents were present in both the weld metal and coarse crystal zone

with contents of 5.8% and 12.5% respectively. The average size of the M-A constituents was measured at 0.157 μm and 0.194 μm. In the coarse-grained zone

the M-A constituents exhibited a larger size and formed a chain-like distribution along the grain boundary of the prior austenite. The average CTOD values for the base metal

weld metal

and coarse crystal area were 0.38 mm

0.25 mm

and 0.22 mm respectively. Notably

the force-displacement curve of the coarse crystal zone demonstrated a significant localized steep drop

indicating an accelerated crack growth rate due to the presence of coarse M-A constituents. Furthermore

the impact absorption energy of both the weld metal and coarse crystal zone exhibited a significant decrease with decreasing temperature

suggesting an increased embrittlement effect of the M-A constituents at lower temperatures. At -40 ℃

the impact absorption energy of the weld metal sharply decreased

close to the CGHAZ

indicating that the adverse effect of M-A constituents on toughness dominated at low temperatures.

关键词

高强钢M-A组元粗晶区冲击韧性断裂韧性

Keywords

high-strength steelM-A constituentsCGHAZimpact toughnessfracture toughness

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