Product Code: ICA13_1103

Porosity Suppression In Laser Welding of Pure Nickel and Stainless Steel
Authors:
Xudong Zhang, Hitachi Ltd.; Hitachi-shi, Ibaraki-ken Japan
Nobuaki Kobayashi, Hitachi Automative Systems, Ltd.; Isesaki, Gunma Japan
Yasuhiro Motegi, Hitachi Automotive Systems, Ltd.; Isesaki, Gunma Japan
Norihiro Yade, Hitachi Automotive Systems, Ltd.; Isesaki, Gunma
Presented at ICALEO 2013

In keyhole laser welding of pure nickel and martensite stainless steel, one of the problems is porosity formation in the weld metal. Since almost of the shielding gases, except hydrogen, can hardly be dissolved in nickel after solidification, the gas involved into the keyhole during the welding will form porosities. For hydrogen, it is no safe and may induce low temperature cracking for martensite stainless steel. Thus, the possible method for suppression of porosity is using pulse laser welding to control the stability of keyhole. In this paper, overlap laser welding of pure nickel plates with the thickness of 0.5mm and martensite stainless steel plates were conducted. The effect of pulse width and frequency of laser beam on the porosity formation was investigated. The results show that the porosity can be completely suppressed by optimizing the pulse width and welding speed. The mechanism of the porosity suppression was also discussed.