Weld Burn-Mark Prevention 2

[steris]

I was hoping that someone here may have some experience on preventing weld burns. We are welding two .25"x36"x60" 316L plates, that are each bent into a U, together to form a box with open ends. We then tack on support bars around the outside surface. However when these bars are tacked on, the heat produces weld burns on the inside surface of the box. Since there are approximately 50 tacks per box, cleaning up all these burn marks becomes costly. I have looked into using those electrochemical wand type cleaners as well as conventional abrasive polishing but what would really help is preventing the weld burns in the first place. The size of the box makes backing material cumbersome. I have heard that with titanium, application of argon to the other side prevents burn marks. Does anyone have any suggestions? Are these marks caused by oxidation or something else? Any help is greatly appreciated!

 

[metengr]

The "burn marks" are formed from surface oxidation caused by exposure of hot metal to air. I presume by your question you are using SMAW (stick) welding for tack welds. I would consider using GTAW (TIG). The heat is more localized with the GTAW process and it might result in less heat reaching the other side of the wall thickness reducing oxidation.

 

[MikeHalloran]

You could purge the inside with inert gas, or do the whole operation in a glove box, also so purged.



Mike Halloran
Pembroke Pines, FL, USA

 

[SJones]

What is your concern about these 'burn marks': corrosion performance or aesthetics? A dip in a pickling bath will restore both fairly easily.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdoweb/

 

[steris]

First off - Thank you all for your help. I greatly appreciate it. We will try the inert gas purge and I will report back with the results. Currently the process we are using is a TIG weld and the burn mark removal is mainly aesthetic. If anyone has any other suggestions I would love to explore them. Thanks again!

Best,
AJ

 

[stanweld]

For economic reasons, I recommend using Nitrogen for your backside purge.

 

[unclesyd]

You might also want to look using a welding backup flux such as the Solar Flux, checkout the link below. We use this product on a routine basis. We have also used the products by Superior.
You can get Solar Flux at most welding supply houses.

http://www.solarflux.com/Pages/Whyuse.html

http://www.superiorflux.com/welding.html