Laser welding related questions

Date 04-30-2009 14:18

Have 2 questions regarding laser welding. What shielding gas is normally used for welding thin gauge (.010) berryllium copper. Also have an application where I'm sealing 17-4 ph to 420 S.S. It is a butt joint on a .124 dia. Tensile strength is very important. Is it possible to achieve without using filler. Looking for min. of 400 lbs. done via destructive pull test.

By OBEWAN

Date 04-30-2009 14:25

We use argon on everything - hastelloy, stainless, inconel, kovar, ....But, that is because argon is our main bulk gas for all our arc processes. Not sure what the impact of gas selection is on the weld geometry since it is not an arc process. The cloud chemistry over a laser weld can be significant in terms of reflection, but that is mainly an issue related to metal alloys vaporized above the weld puddle. Most of the laser welding I have heard about uses argon, but maybe helium or co2 are options. Someone else might be able to give more input on this...

By Tommyjoking (****)

Date 05-01-2009 07:50

Same here ....the laser welding I have been involved with utilized Argon with a Co2 type laser. The Alloys being joined were various SS and treatable steels. I have used Argon before when joining various coppers but with different processes. Someone here more then likely has more definitive info....but if nothing else running some test joints might be a good idea.

By Weldconsultant (*)

Date 05-05-2009 23:35

The ideal shielding gas is Helium since it has good thermal conductivity, does not ionize, and is inert. You will get the deepest penetration welds with Helium. Since it is expensive, it is often only used with CW CO2 laser welding where the likelihood of ionization is very high. If you are using a YAG laser, Argon is a fine choice. You may also try Nitrogen for Be-Cu welds since it will be even cheaper than Argon.

The shielding gas flow (direction and flow rate) should be controlled to make sure that any products of ionization (gas, metal vapors, etc.) are quickly washed away. Gas flow should be optimized; if it is too high and coming out of a small nozzle, it can acutually drag oxygen into the weld. A diffuser would be a good idea.

Filler materials are not typically used in laser welding. If you do need to use a filler for metallurgical reasons, you can place it in the joint in the form of a washer.

Girish

http://www.welding-consultant.com/