Laser welding different grades of stainless steel?

Date 05-15-2008 23:55

THE question is what is the application ?

If I had an idea about what you are trying to build I could make specific recomendations -

Really , in today's AOD refined world most of your materials are 304 / 304 L or 316 / 316 L

and you get 0.03 max. C without a whole bunch of sweat -

By bschlosser Date 05-16-2008 12:03

Basically I am welding an end cap onto a 1" diameter tube. The joint is a butt joint with 0.030" wall thickness. The device will be encapsulated with epoxy so it does not have to be air tight but should be water tight. Strength is not much of an issue. I has to be strong enough not to be able to break by hand. Overall, I'm interested if different materials are weldable and relative ease of weld using a laser. My experience is with plastic welding and many materials are weldable, but there is a great difference in quality and repeatability of the weld depending on the two materials being welded.

Thanks for the reply.

Bob

By js55

Date 05-16-2008 14:15

Let me premise by saying I'm no expert on laser welding period. But the metallurgy of the material is the same. I am assuming we are talking high travel speeds which means rapid cooling rates. 304 and 316 soldify as delta ferrite, then transform to austenite, and with rapid cooling rates you will see an increase in retained delta ferrite as the transformation is inhibited. High enough ferrite and you may have sigma issues, especially with Mo containing 316.

By OBEWAN

Date 05-16-2008 16:23

We routinely weld a variety of stainlesses to make aircraft igniters and turbine sensors. They have to be hermetically sealed and stand up to vibration and hcf stresses. We weld dissimilar applications too stainless-hastelloy, stainless-inconel etc...The only problem I have heard about is porosity in welding cast 304, but it is doable. We even laser weld (despite my protests) the "unweldable" 416 (high sulfur) series. For what you are doing, it should be fairly easy.

By Weldconsultant (*)

Date 05-16-2008 23:01

Obewan,

Would you mind sharing the results of welding 416 with sulphur? Do you see any cracks or porosities?

Girish

By Weldconsultant (*)

Date 05-16-2008 16:34

Laser welding (especially pulsed welding) has propensity to form cracks in 316 SS. The main source of crack formation is the solidification mode. If the melt solidifies as primary austenite, the austenite phase has low solubility for impurities and rejects them; the impurities (sulphur and phosphorous) then form low melting phases with Fe and lead to cracking. 304 is much easier to laser weld since the melt has some ferrite content which has much greater solubility for impurities and avoids cracking.

A mixture of 304 and 316 should be free from cracking. In case your experiments do indicate some level of cracks, you can try biasing the laser spot towards 304.

Additionally, it is always good to keep the carbon content low by using the L grades.

Keep in mind that the acceptable range of 316 is right on the border line between Austenite solidfication and Austenite+Ferrite. So you may find that some batches of 316 crack and some dont. This has caused issues with one of my customers who qualified a part based on experiments on 316 but when they went into production, they found the parts were cracking.

Girish

http://www.welding-consultant.com

By bschlosser Date 05-16-2008 16:41

Thank you to all who replied to this thread. This has put my mind at ease and has been very helpful.