Product Code: ICA13_1307

Effect of Shielding Gas Composition on Co2-Laser Welding Quality
Authors:
Jukka Siltanen, Rautaruukki Oyj; Hämeenlinna Finland
Ville-Matti Nurmela, Ruukki Metals Oy; Uusikaupunki Finland
Ilpo Maaranen, Ruukki Metals Oy; Uusikaupunki Finland
Sakari Tihinen, Ruukki Metals Oy; Raahe Finland
Jukka Komi, Ruukki Metals Oy; Raahe Finland
Jurgen Scholz, Linde AG; Unterschleissheim Germany
Jyrki Honkanen, Oy AGA Ab; Espoo Finland
Bo Williams, AGA Gas Ab Weldonova; Lidingo Sweden
Presented at ICALEO 2013

Shielding gas is significant cost factor for CO2-laser welding, especially if helium is used. Replacing a part of the helium with some other gases, such as argon and carbon dioxide, might reduce operation costs. The effect of such a substitutive shielding gas mixture on the total laser welding quality was studied by Ruukki Metals steel service centre of Uusikaupunki in Finland. Several shielding gas mixtures (He+Ar+CO2) were tested. The percentage quantity of helium was set at a constant of 35% and the percentage quantities of argon varied from 40% to 55% and carbon dioxide from 10% to 25%. The test material was a wear-resistant steel Raex 450 with a 4 mm of thickness. Raex is a trademark for wear-resistant steels manufactured by a Finnish steel making company Rautaruukki. The number 450 signifies the hardness of steel in Brinell units. Wear-resistant steels as well as other direct quenched steels produced on a modern hot rolling line are typically used in applications under extremely demanding conditions that require steel with very high strength and other special properties, such as excellent abrasion resistance. The manufacture of these steels is very demanding for the rolling and coiling process and the width of a ready steel coil can be insufficient for end products, such as buckets and containers. Laser welding is a suitable joining process for achieving the desired size by joining together two or more steel strip plates. A 5 kW CO2 laser was first used for the laser cutting to trim the edges of plates and finally for joining plate with a butt joint. The welding speed remained invariable and was 2300 mm/min. The total weld quality was evaluated according to the standards ISO 13919-1 and ISO 15614-11.