Microstructure and mechanical properties of weld metal in laser and gas metal arc hybrid welding of 440-MPa-grade high-s
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ORIGINAL PAPER
Microstructure and mechanical properties of weld metal in laser and gas metal arc hybrid welding of 440-MPa-grade high-strength steel Fu-xing Yin1,2,3 • Xu-chen Li1,3 • Cui-xin Chen2,3 • Lin Zhao4
•
Yun Peng4 • Zhi-ling Tian4
Received: 6 April 2020 / Revised: 17 June 2020 / Accepted: 27 June 2020 China Iron and Steel Research Institute Group 2020
Abstract Fiber laser and gas metal arc hybrid welding of 440-MPa-grade high-strength marine steel was carried out at different welding speeds. The influence of welding speed on the microstructure and mechanical properties of weld metal was investigated. The weld-metal microstructure mainly consisted of pre-eutectoid ferrite, side-plate ferrite, acicular ferrite and lath bainite at a low welding speed. With the increase in welding speed, acicular ferrite and lath bainite were the dominant weld-metal microstructures. All samples failed at the base metal during tensile tests, which indicates that there is no soft zone in the hybrid welds. The welding speed had a significant effect on the impact toughness of the weld metal. The impact absorbed energy of the weld metal increased from 35 to 105 J with the increase in welding speed from 0.8 to 2.0 m/min. Large amounts of acicular ferrite and lath bainite were formed in the weld metal at a high welding speed, which resulted in an excellent impact toughness. Keywords Laser–arc hybrid welding High-strength steel Microstructure Mechanical property
1 Introduction The ship industry is a modern comprehensive industry that provides essential technical equipment for ocean development, water transportation and energy transportation. Welding quality and efficiency are two important factors that determine developments in the shipbuilding industry [1]. Welding accounts for 30%–40% of fabrication time and welding expenses and for 30%–50% of shipbuilding
& Lin Zhao [email protected] 1
School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China
2
Tianjin Key Laboratory of Laminating Fabrication and Interface Control Technology for Advanced Materials, Hebei University of Technology, Tianjin 300130, China
3
Research Institute for Energy Equipment Materials, Hebei University of Technology, Tianjin 300130, China
4
Central Iron and Steel Research Institute, Beijing 100081, China
cost [2]. To develop the ship industry further, the efficiency and quality of ship welding must be improved. Most shipbuilding enterprises use gas-shield and submerged-arc automatic welding [3]. Because of the slow welding speed and high heat input, serious welding deformation occurs. To correct the welding deformation, mechanical or thermal methods are required, which reduces shipbuilding efficiency and increases shipbuilding cost. A welding method is required to minimize welding deformation and heat input with full weldment penetration. Laser welding with deep penetration, low heat input and rapid welding speed can reduce welding deformation effectively [4
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