Welding guidelines

[MW2011]

We are in the process to fabricate several equipments including a conical tank (atmospheric). the service is water + slurry + bitumen + rocks and are internally protected with a liner welded-overlay (WO) Chrome Carbide (the WO CrC is deposited on a carbon steel plate and pluged weld to tank shell ) this protection is due to erosion process because of the service, however, it was proposed to use dual-phase stainless steel (ferritic-martensitic) with low percentage of carbon at some point over the liner of WO CrC as at this level problems will be more associated with corrosion than erosion (after visual inspectiopn done in the existents tanks) due to water temperature 70 ˚ C, and 400-1300 ppm Cl. Manufacturers of these stainless steel recommend welding (among them dissimilar) with 309L, however and based in current service conditions, I would like to recommend the use of ERCrNiMo-3 for many reasons and among key is the environment in which the material will be facing. With 309L/309LMo the amount of nickel may be in the range of 3% -12%, which according to the Copson curve , this weld should crack by Chlorides in hours, however with ERCrNiMo-3, % Ni would be greater than 50, thus obtaining a great resistance to weld crack susceptible to chloride.



Now, once stainless steel is welded, it Should not be recommended to make a pickling (pickling)? so as to ensure that Tint after the welding have not generated prone areas? or a simply a mechanical cleaning will be enough?

 

[metengr]

MW2011:
For this application mechanical cleaning of the stainless liner would be sufficient.

Getting back to your original concept of using the plug welded chromium carbide coating on CS plate, I believe this will be the better performing selection than the low carbon duplex stainless steel. Based on your process fluid, you really need abrasion resistance over corrosion resistance, and frankly, I don't believe this stainless steel liner will hold up in this environment.

 

[TVP]

I agree with metengr, the CrC coating on CS is a better option than duplex stainless in this environment. I don't think the duplex stainless steel will have sufficient wear resistance, and itncould be questionable in terms of corrosion resistance.