Weld undercut on 304 stainless steel bar

[grayseal]

We have been experiencing undercut problems while fillet welding .625" diameter SA-479, type 304 stainless steel bar. We buy from several suppliers and it is only happens with bar from one of them. All bar is received with Certified Material Test Reports. What could be the cause of the undercut?

 

[apiguy]

My first guess would have to be improper electode angle or current input. Try a weldability test by running a bead in the flat position. If you still see the UC reduce current and try again. Have several different welders perform the same test and review the results

The APIGUY....

 

[grayseal]

apiguy,
Thanks for the response. Your idea of improper technique was my first thought also. I don't think it is valid since the same five welders have been welding thousands of these fittings every year and these two heats of material are the only ones that exhibit the undercut.

grayseal

 

[apiguy]

Do you have any digital pictures? I would love to see some. Now I'm just as baffled as you are. What is the specfic type and grade of material again?

The APIGUY....

 

[grayseal]

apiguy,

Just got results of the chemical analysis. High carbon (.11), low chromium (17.01), and high sulfer (.285). I'm assuming the sulfer caused the undercut.
My question now is, who checks the steel mills. This particular heat of material came from Saudi Arabia.

grayseal

 

[apiguy]

It's highly possible that someone tried to pull a fast one you at the supplier. I rejected some materials for out of spec elements a while back and sent the material back. When it came time for the shut down and we had to have the material asap, a different supplier tried to sell me the same material I had rejected three months earlier. Imagine to his suprise when I pulled my reject tag out of a joint pipe in the lot in front of him,my buyer, and plant manager.

Since then I request PMI on all alloy materials brought on to my site.

We've all heard the old phrase "one man's trash is another's treasure" I can't help but think that phrase was coined from the materials supply industry.

This is only my opinion.......

The APIGUY....

 

[grayseal]

apiguy,

That's interesting. Just bought a material analyzer and I may set up a PMI program since our supplier buys globally. What ever happened to getting what you asked for?

grayseal

 

[apiguy]

Unless you really trust your supplier, I would go ahead with the PMI.

Too bad purchasing materials has evolved to this but it's a lot like changing a baby's diaper.....You just don't know what your going to get. Might be something easy, might be crap.

The APIGUY....