Single-pass full-penetration welding for thick stainless steel using high-current GMAW

ABSTRACT

This paper describes a high-current Gas Metal Arc Welding (GMAW) process using a constant voltage power source developed for high-efficiency welding of thick stainless steel plates. A short arc length as a welding condition is preferable to concentrate the arc and obtain a deep penetration for thick plate welding. However, it is easily found that an unstable arc derived from a short circuit happens irregularly by using a general purpose GMAW with constant voltage characteristics. A ‘low-frequency modulated voltage control’ was applied for stabilizing a high-current arc that can maintain a short arc length without short circuiting. The welded joint using the developed welding process showed the similar corrosion resistance as that using the submerged arc welding; however, porosity was observed in the welded joints using the developed welding process in the current region of 400 A or above. Consequently, a new current waveform control that changes the welding current dynamically and periodically has been developed, which realized reducing porosity and single-pass full-penetration welding of 9-mm-thickness type 304 stainless steel plates with square groove.

KEYWORDS:

• High-current
• GMAW
• thick stainless steel
• porosity
• current waveform control