Influence of Welding Repair Times on the Microstructure and Properties of Q450NQR1 Atmospheric Corrosion Resistant Steel MAG Welded Joints

DAI Zhongchen; FU Ningning; WANG Pengfei; DING Yaping; LI Lintong; MENG Weifeng; LIU Fanjie; DING Chengguo

doi:10.7512/j.issn.1001-2303.2025.04.08

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Influence of Welding Repair Times on the Microstructure and Properties of Q450NQR1 Atmospheric Corrosion Resistant Steel MAG Welded Joints
Vol. 55, Issue 4, Pages: 56-63(2025)
Received：24 February 2025，

Published：20 April 2025
DOI： 10.7512/j.issn.1001-2303.2025.04.08
稿件说明：

移动端阅览

戴忠晨，付宁宁，王鹏飞，等.焊修次数对Q450NQR1耐候钢MAG焊对接接头组织和性能的影响［J］.电焊机，2025，55（4）：56-63. DOI： 10.7512/j.issn.1001-2303.2025.04.08.

DAI Zhongchen, FU Ningning, WANG Pengfei, et al.Influence of Welding Repair Times on the Microstructure and Properties of Q450NQR1 Atmospheric Corrosion Resistant Steel MAG Welded Joints[J].Electric Welding Machine, 2025, 55(4): 56-63. DOI： 10.7512/j.issn.1001-2303.2025.04.08.

摘要

针对轨道交通装备制造与运维中Q450NQR1耐候钢焊接接头的焊修需求，探究了MAG焊修工艺（1~4次）对接头微观组织演变及力学性能的影响。结果表明：经1~4次焊修后，接头组织类型保持一致，焊缝区和熔合区主要由先共析铁素体、针状铁素体构成，同时包含少量珠光体和粒状贝氏体。然而，过热区晶粒尺寸随焊修次数增加而显著增大。4次焊修后，盖面粗晶区晶粒平均等效直径增加了约20%，而打底层晶粒平均等效直径增加了约8%。焊接接头拉伸试验和弯曲试验结果表明，焊缝具有良好的塑性和韧性。随着焊修次数的增加，接头的冲击韧性和疲劳强度均有所下降。4次焊修后，焊缝区冲击功值降低了约4.2%，而热影响区降低了约40.1%；疲劳中值强度降低了约29.0%。焊修过程中叠加的热输入导致过热区晶粒长大，降低了接头韧性。同时，焊接热循环对热影响区的反复作用导致晶粒粗化，进一步降低了接头的冲击韧性和疲劳强度。本研究揭示了焊修次数对Q450NQR1耐候钢焊接接头组织和性能的影响规律，为优化焊修工艺、提升焊接接头可靠性提供了重要的理论依据。

Abstract

In response to the welding repair needs of Q450NQR1 atmospheric corrosion resistant steel welded joints in rail transit equipment manufacturing and maintenance

this study investigates the effects of MAG welding repair processes (1~4 times) on the evolution of microstructure and mechanical properties of the joints. The results show that after 1~4 times of welding repair

the types of joint microstructure remain consistent

with the weld zone and fusion zone mainly consisting of pro-eutectoid ferrite and acicular ferrite

and a small amount of pearlite and granular bainite. However

the grain size in the overheated zone increases significantly with the increase in the number of welding repairs. After 4 times of welding repair

the average equivalent diameter of grains in the cover coarse grain zone increased by about 20%

while that in the underbead zone increased by about 8%. Tensile and bend tests of the welded joints indicate that the welds have good plasticity and toughness. With the increase in the number of welding repairs

both the impact toughness and fatigue strength of the joints decrease. After 4 times of welding repair

the impact energy value in the weld zone decreased by about 4.2%

while in the heat affected zone it decreased by about 40.1%; the median fatigue strength decreased by about 29.0%. The accumulated thermal input during the welding repair process leads to grain growth in the overheated zone

reducing the toughness of the joints. At the same time

the repeated action of welding thermal cycles on the heat-affected zone causes grain refinement

further reducing the impact toughness and fatigue strength of the joints. This study reveals the influence pattern of the number of welding repairs on the microstructure and properties of Q450NQR1 atmospheric corrosion resistant steel welded joints

providing an important theoretical basis for optimizing welding repair processes and enhancing the reliability of welded joints.

关键词

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references

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