EP-3623096-B1 - LASER-ARC HYBRID WELDING METHOD

Inventors

• IWATA, Shohei
• OKITA, YASUAKI
• KITANI, Yasushi

Dates

Publication Date

20260506

Application Date

20180918

Claims (1)

1. A laser-arc hybrid welding method of performing welding by combining leading laser welding and trailing gas-shielded arc welding, wherein: a minimum diameter D MIN (mm) of droplets that are transferred from a steel welding wire to a molten pool generated by the gas-shielded arc welding satisfies expression (1) relative to a power P (kW) of a laser beam generated by the laser welding; and a maximum diameter D MAX (mm) of the droplets satisfies expression (2) relative to a length M (mm) of an arc generated by the gas-shielded arc welding; D MIN ≥ P / 15 + 1 / 2 M ≥ 4 D MAX / 3 and in the laser welding, the same shielding gas as for the gas-shielded arc welding is used, wherein in the gas-shielded arc welding, a shielding gas containing 60 volume% or more of Ar is used; the steel welding wire formed of a steel wire containing 0.015 to 0.100 mass% of a rare earth element or elements is used; and welding is performed with electrode negative polarity.

Description

Technical Field The present invention relates to a laser-arc hybrid welding method of performing welding by combining laser welding and gas-shielded arc welding. Specifically, the present invention relates to a laser-arc hybrid welding method that suppresses spatter formation by controlling the diameter of droplets that are transferred from a steel welding wire to a molten pool generated by the gas-shielded arc welding as well as by controlling the length of an arc (hereinafter, referred to as "arc length"). Background Art Laser welding can increase a welding speed and a penetration depth due to the use of a laser beam with high energy density as a heat source and can reduce thermal effects and/or thermal deformation associated with welding due to its narrow melt width. As a result, laser welding has an advantage that a high-quality weld is obtained. Meanwhile, laser welding uses an expensive apparatus and also requires accurate processing in groove formation. Accordingly, laser welding is disadvantageous in terms of costs of performing welding, compared with conventional welding techniques. In contrast, gas-shielded arc welding is inferior in welding speed and penetration depth to laser welding and is subjected to larger thermal effects and/or thermal deformation associated with welding than laser welding. Meanwhile, gas-shielded arc welding can lower costs of performing welding. In addition, there are advantages that the composition of weld metal can be controlled by adjusting the components of a steel welding wire to be used (see Patent Literature 1) and further, accuracy required for groove processing is not as high as laser welding. A welding technique that utilizes both advantages of such laser welding and gas-shielded arc welding is laser-arc hybrid welding in which the surfaces of works being welded (steel sheets, for example) are simultaneously irradiated with a gas-shielded arc and a laser beam. Since it is possible to enhance welding gap tolerance and increase a welding speed, laser-arc hybrid welding is a welding technique that can enhance welding efficiency. In general, an important factor that affects spatter formation in gas-shielded arc welding is the transfer mode of droplets. The mode of droplets transferred from a steel welding wire to a molten pool varies depending on various welding conditions, such as the components of a steel welding wire, the type of a shielding gas, and a welding current for generating an arc. In other words, when an arc is solely used as a heat source as in gas-shielded arc welding, spatter is formed, for example, by discontinuance of a short-circuiting between droplets and a molten pool or by detachment of droplets outside a molten pool. Accordingly, the amount of formed spatter largely depends on the transfer mode of droplets (i.e., the mode in which droplets are detached from a steel welding wire). Meanwhile, in laser-arc hybrid welding in which welding is performed by combining laser welding and gas-shielded arc welding, it is known that a lot of spatter is formed since droplet transfer becomes unstable due to interactions between a laser beam and an arc as heat sources. However, the effects of droplet transfer modes on spatter formation have not yet been clearly explained. When a lot of spatter is formed during performing laser-arc hybrid welding, such spatter is attached to a welding machine body and peripheral optical devices, thereby causing malfunction of facilities and low welding efficiency. Accordingly, it is necessary to suppress spatter formation as much as possible. For this reason, the present inventors closely investigated droplet transfer modes when laser-arc hybrid welding is performed with leading laser welding and trailing MAG welding as gas-shielded arc welding. As a result, it was found that spatter formation is caused by small and lightweight droplets transferred from the sharp leading end of a steel welding wire to a molten pool and found that such droplets are scattered upward due to laser irradiation-induced evaporation pressure of works being welded and then cooled to form spatter. Next, the present inventors performed the laser-arc hybrid welding method disclosed in Patent Literature 1 and closely investigated the transfer mode of droplets. Specifically, in the laser-arc hybrid welding method, laser welding was combined with electrode negative gas-shielded arc welding in which a steel welding wire formed of a steel wire added with a rare earth element (hereinafter, referred to as REM) was used as a negative electrode in a shielding gas containing 60 volume% or more of CO2. As a result, in the laser-arc hybrid welding disclosed in Patent Literature 1, scattering of droplets due to laser irradiation was not observed, but spatter was formed due to the short arc length and resulting short-circuiting between droplets and a molten pool. Further, in this laser-arc hybrid welding, globular transfer occurred under low current value conditions (w