Preparation for a butt weld in 304 SS 3

[kellnerp]

What is the appropriate preparation for a vertical butt weld in 304 SS that can be accessed from one side. The material is .187" thick and full penetration is necessary for strength.

TIA

 

[metengr]

Where you intend to butt weld the ends of the sheet, introduce a single bevel on one side (the accessible side for welding) to provide for a full penetration weld. For additional information regarding welding fabrication, see the Nickel Development reference below. There are some excellent publications that are free regarding welding of stainless steels and the necessary precautions – a must read;

http://www.stainlessarchitecture.org/index.cfm/ci_id/11476/la_id/1.htm

 

[kellnerp]

Metengr,

Thanks for the URL.

 

[Goahead]

Please note that 304 stainless steel is prone to precipitation of chromium carbides upon welding.
A strip of material on both sides and parallel to the joint will thus be subject to intergranular attack because of chromium depletion.
In principle this condition could be cured by undertaking high temperature solution treatment and rapid cooling of the welded construction, if the resulting deformations can be tolerated.
Better material selections not developing carbide precipitation and not requiring heat treatment after welding, would be 304L (low carbon) or 321 (titanium stabilized).

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

 

[kellnerp]

Goahead,

Thanks. I was aware of that and specified a 308L wire. Heat treatment is not an option as the weldment is done in place in a structure. Preparation and welding technique are the big issues I am faced with.

 

[Goahead]

Your selection of filler metal is correct, the other option being 347, but this would not change the basic weakness of welded 304. Why selecting a stainless steel and then destroying its corrosion resistance properties, at least locally? My previous recommendation is still valid.

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

 

[Jon22]

A typical weld prep would be 30 degree per side 60 degree overall, with a open root of .062 to .125. Remember this will pull with out bridging. The root is up to the comfort of your welder. Remember to use a purge gas for back of root
if using GTAW process.

 

[stanweld]

This is not a difficult weld to make provided your welder is capable and qualified to make single side full penetration welds. The joint design described by Jon22 or a square edge on the downside pipe and a 45 degree bevel on the top side can be used. For these thin wall joints, I would advise qualifying your welder on stainless steel to assure his capability.

With regard to goahead's concerns, there is almost nothing that you can do to avoid HAZ sensitization if the material is actually 304 SS and not dual certified 304/304L but there are some methods that have proven effective for me. After the depositing the root pass, run cool water through the pipe to rapidly cool the weld and HAZ during second pass thru final weld passes; flow cool water on the weld immediately after depositing (risky due to potential for contamination)and have used copper chills within 1/8" of the weld bevel to provide rapid cooling.

 

[kellnerp]

This is not a difficult weld to make provided your welder is capable and qualified to make single side full penetration welds. The joint design described by Jon22 or a square edge on the downside pipe and a 45 degree bevel on the top side can be used. For these thin wall joints, I would advise qualifying your welder on stainless steel to assure his capability.

We ended up using TIG. We qualified the welder before proceeding. This was not pipe, but sheet. The weld was done from both sides with a gap filler because the gap was wider than recommended by Jon22.

Thanks.

http://www.engtran.com

http://www.niswug.org