Effect of Heat Input on Microstructure and Properties of Q420 Steel Electrogas Welding Joints

LONG Hanxin; WANG Guoping; WANG Pingxin; CAI Ruimou

doi:10.3969/j.issn.1674-6457.2026.06.004

PDF(4117 KB)

Journal of Netshape Forming Engineering ›› 2026, Vol. 18 ›› Issue (6) : 37-45. DOI: 10.3969/j.issn.1674-6457.2026.06.004

Joining of New Materials and Dissimilar Materials

Effect of Heat Input on Microstructure and Properties of Q420 Steel Electrogas Welding Joints

LONG Hanxin^1,2, WANG Guoping^1,*, WANG Pingxin^1,*, CAI Ruimou²

Author information +

History +

Abstract

The work aims to analyze the effect of heat input on microstructure and properties of electrogas welding joints of thick Q420 low-alloy high-strength steel plates, to reveal the inherent relationship between heat input, microstructure, and properties. Electrogas welding with high heat input was employed to weld 40 mm thick Q420 steel plates. The effect of heat input on the microstructure of the electrogas welding joints was analyzed by optical microscopy (OM) and scanning electron microscopy (SEM). The tensile strength, yield strength, and low-temperature impact toughness (-40 ℃) of the joints were evaluated. Electrogas welding successfully achieved sound welds without visible defects in 40 mm thick Q420 steel. With increasing heat input, the weld bead width increased, reaching a maximum of 41.2 mm. The ferrite content in the weld increased with higher heat input, transforming from acicular ferrite to coarse blocky ferrite. The coarse-grained heat-affected zone (CGHAZ) was primarily composed of ferrite, with bainite and pearlite precipitating at grain boundaries. Increased heat input enlarged the ferrite grain size, forming coarse blocky ferrite and promoting the transformation of bainite to equilibrium pearlite. Higher heat input led to a decrease in the tensile properties of the joint. The maximum tensile strength reached 546 MPa at a heat input of 205 kJ/cm. When the heat input increased to 376 kJ/cm, the impact toughness of the joint generally increased with heat input; however, the weld metal exhibited a minimum impact energy of 22.5 J at this highest heat input of 376 kJ/cm. Increased heat input results in the formation of coarse blocky ferrite and some pearlite in both the weld metal and the heat-affected zone. These coarse microstructures offer weaker resistance to crack propagation, leading to a reduction in the mechanical properties of the joint.

Key words

Q420 steel / electrogas welding (EGW) / heat input / microstructure / mechanical properties

Cite this article

EndNote

Ris (Procite)

Bibtex

Download Citations

LONG Hanxin, WANG Guoping, WANG Pingxin, CAI Ruimou. Effect of Heat Input on Microstructure and Properties of Q420 Steel Electrogas Welding Joints[J]. Journal of Netshape Forming Engineering. 2026, 18(6): 37-45 https://doi.org/10.3969/j.issn.1674-6457.2026.06.004

References

[1] 徐望辉, 贾兴华, 赵荣泽, 等. 中心通气对窄间隙TIG焊缝成形的影响[J]. 焊接学报, 2025, 46(1): 121-127.
XU W H, JIA X H, ZHAO R Z, et al.Influence of Central Ventilation on the Formation of Narrow Gap TIG Welds[J]. Transactions of the China Welding Institution, 2025, 46(1): 121-127.
[2] 李雨, 徐望辉, 谢伟峰, 等. 超声振动对304不锈钢窄间隙TIG焊接接头组织和力学性能的影响[J]. 材料热处理学报, 2023, 44(9): 188-194.
LI Y, XU W H, XIE W F, et al.Effect of Ultrasonic Vibration on Microstructure and Mechanical Properties of 304 Stainless Steel Narrow Gap TIG Welded Joint[J]. Transactions of Materials and Heat Treatment, 2023, 44(9): 188-194.
[3] 徐望辉, 杨清福, 肖逸峰. 窄间隙焊接侧壁熔合控制技术的研究现状[J]. 精密成形工程, 2020, 12(4): 47-54.
XU W H, YANG Q F, XIAO Y F.Research Status of Sidewall Fusion Control Technology in Narrow Gap Welding[J]. Journal of Netshape Forming Engineering, 2020, 12(4): 47-54.
[4] 徐望辉, 李占雷, 袁浩, 等. 线能量及轨迹夹角对304不锈钢CMT增材成形的影响[J]. 精密成形工程, 2025, 17(10): 127-134.
XU W H, LI Z L, YUAN H, et al.Effect of Line Energy and Trajectory Angle on CMT Additive Forming of 304 Stainless Steel[J]. Journal of Netshape Forming Engineering, 2025, 17(10): 127-134.
[5] 车平, 李军平, 黄会强, 等. 高性能Q420qENH耐候桥梁钢焊接试验[J]. 焊接, 2021(1): 42-50.
CHE P, LI J P, HUANG H Q, et al.Welding Tests of High Performance Q420qENH Weathering Bridge Steel[J]. Welding & Joining, 2021(1): 42-50.
[6] 黄俊, 徐望辉, 刘静, 等. 旋摆TIG-MIG复合热源堆焊焊缝成形研究[J]. 热加工工艺, 2020, 49(5): 49-52.
HUANG J, XU W H, LIU J, et al.Research of Weld Forming of Swing TIG-MIG Composite Heat Source Surfacing[J]. Hot Working Technology, 2020, 49(5): 49-52.
[7] LI Z R, ZHANG D C, WU H Y, et al.Fatigue Properties of Welded Q420 High Strength Steel at Room and Low Temperatures[J]. Construction and Building Materials, 2018, 189: 955-966.
[8] SUN X J, YAO J Z, MAO C B, et al.Numerical Simulation of 50mm Thick Q420 Steel Plate Welding with Multi-Layer and Multi-Pass Welding Process[J]. Journal of Physics: Conference Series, 2025, 2944(1): 012005.
[9] YANG L G, XING Y M.Experimental Study on Fatigue Properties of Q420C Steel Welded Joints at Room Temperature[J]. Latin American Journal of Solids and Structures, 2022, 19: e417.
[10] 陈哲, 温志刚, 田雷, 等. 海洋平台用Q420钢焊接接头裂纹扩展行为研究[J]. 焊接技术, 2020, 49(2): 9-13.
CHEN Z, WEN Z G, TIAN L, et al.Crack Propagation Behavior of Welded Joint of Q420 Steel for Offshore Platform[J]. Welding Technology, 2020, 49(2): 9-13.
[11] 李俊琛, 张亚森, 杨新龙, 等. 热输入对高钼Q420钢焊接接头组织和性能的影响[J]. 材料热处理学报, 2018, 39(7): 156-160.
LI J C, ZHANG Y S, YANG X L, et al.Effect of Heat Input on Microstructure and Properties of High Molybdenum Q420 Welded Joint[J]. Transactions of Materials and Heat Treatment, 2018, 39(7): 156-160.
[12] LI Q Y, XU C B, LUO Z C, et al.Fatigue Performance of Q420C Steel Fillet-Welded Joints at Low Temperatures[J]. Structures, 2023, 51: 1341-1353.
[13] CHENG H G, HU C, JIANG Y.Experimental Study on Fatigue Performance of Q420qD High-Performance Steel Cross Joint in Complex Environment[J]. Asian Journal of Civil Engineering, 2021, 22(5): 865-876.
[14] SHENG J, MA J J, WEI F F, et al.Study on the Mechanical Properties and Constitutive Model of Q420 Steel under Different Strain Rates[J]. Nano, 2025, 20(9): 2550023.
[15] ZHANG P Y, ZHANG J, LI B Z.Mechanical Properties and Microstructure Transformation Behavior for Welded Joints in Ship Plate Steel with High-Heat Input Welding[J]. Journal of Materials Engineering and Performance, 2022, 31(2): 944-952.
[16] CHEN H, PU T W, ZHANG H, et al.Mechanical Properties of Bridge Steel Q420qE at Elevated Temperatures[J]. Journal of Constructional Steel Research, 2025, 226: 109207.
[17] TANG H Q, YANG Q L, MI P C, et al.Precipitation Behavior and Strengthening Mechanism of Q420 Grade Hot Rolled V Microalloyed Ultra Large H-Beam[J]. Vacuum, 2025, 233: 113924.
[18] HWANG S Y, KIM Y, LEE J H.Finite Element Analysis of Residual Stress Distribution in a Thick Plate Joined Using Two-Pole Tandem Electro-Gas Welding[J]. Journal of Materials Processing Technology, 2016, 229: 349-360.
[19] BANASCHIK R, BRÄTZ O, GERICKE A, et al. Modification of Electro Gas Weld Metal Microstructure Reflecting Mechanical Property Specifications in Cruise Vessel Shipbuilding[J]. Welding in the World, 2024, 68(6): 1625-1639.
[20] SEO K, RYOO H, KIM H J, et al.Local Variation of Impact Toughness in Tandem Electro-Gas Welded Joint[J]. Welding in the World, 2020, 64(3): 457-465.
[21] XIE X, ZHAO T, ZHAO H M, et al.Heterogeneous Microstructure-Induced Mechanical Responses in Various Sub-Zones of EH420 Shipbuilding Steel Welded Joint under High Heat Input Electro-Gas Welding[J]. Acta Metallurgica Sinica (English Letters), 2021, 34(10): 1427-1433.
[22] PARK T G, KIM J M, YOON H Y, et al.Impact Toughness and Microstructure of the Weld Metal by Tandem Electro-Gas Welded EH40 Steel[J]. Korean Journal of Metals and Materials, 2010, 48(11): 1021-1027.
[23] YI J L, NIU B, GAO W W, et al.Heterogeneous Microstructure and Corrosion Resistance of the EH36 Steel Joined by Vertical Electro-Gas Welding[J]. International Journal of Electrochemical Science, 2020, 15(3): 2822-2838.
[24] 曹胜利, 张庆军, 张彩军. 焊接热输入对EH420海工钢热影响区组织和性能的影响[J]. 中国冶金, 2025, 35(4): 58-66.
CAO S L, ZHANG Q J, ZHANG C J.Influence of Welding Heat Input on Microstructure and Properties of Heat Affected Zone of EH420 Offshore Steel[J]. China Metallurgy, 2025, 35(4): 58-66.
[25] LONG H X, WANG G P, WANG P X, et al.Study on the Influence of Heat Input on Microstructure and Properties of Q420C Steel Welded Joints[J]. Coatings, 2025, 15(8): 957.
[26] 余陈, 许磊, 徐望辉, 等. 船用高强钢大线能量焊接接头组织性能研究[J]. 热加工工艺, 2021, 50(1): 20-24.
YU C, XU L, XU W H, et al.Study on Microstructure and Properties of Large Line Energy Input Welded Joints of High-Strength Marine Steel[J]. Hot Working Technology, 2021, 50(1): 20-24.
[27] ABSON D J.Acicular Ferrite and Bainite in C-Mn and Low-Alloy Steel Arc Weld Metals[J]. Science and Technology of Welding and Joining, 2018, 23(8): 635-648.