Post Weld Normalize

[jwhit]

Every so often, the idea of welding carbon steel castings(A216 WCB/WCC) in the as cast condition and normalizing after welding is brought up. My opinion is that doing so is a fool's errand at best. Castings have CE restricted to 0.41 max, process is GTAW with ER70S-2, 100% argon. My concerns are mainly base metal cracking during welding and severe reduction of the mechanical properties of the filler by normalizing (1700-1750 Air Cool) after welding. We won't even think about toughness. The relatively low CE should help with the cracking possibilities, but may not eliminate them. A change to ER70S-3 or 6 might improve the response to a normalize. Material is supposed to be NACE compliant as well and ASME IX and VIII are involved as well. My knowledge of the subject is apparently less than I give myself credit for, which is why I'm throwing it out to the forum for opinions.

 

[metengr]

I have seen welding in the as cast condition to repair major defects followed by normalize many times with no issues using SMAW. I have not seen it with GTAW only because depth of repairs and extent of welding.

 

[jwhit]

I have run into issues in the past with both the as cast and annealed conditions, where a great deal of time was spent chasing base metal cracks that developed after welding (SMAW). These were found by magnaflux and weren't evident during the original magnaflux operation. Normalizing before welding resolved the problem. A lot of those types of problems can relate to the foundry and the issues did originate with castings made in other foundries. I am concerned about welding as cast because of those experiences.
In regards to the filler metal, I have experimented with normalizing ER70S-2 and found that the mechanicals drop into the 60-65KSI range vs the 70 ksi min. Base metal is also 70 ksi min. A change of filler metal has the possibility of resolving that issue. My preference would be to normalize, repair and perform a temper/pwht.

 

[weldstan]

The lowered tensile properties of the ER70S-2 are well known after normalizing. There are other filler metals that can be used that will meet the 70Ksi minimum after normalizing. The hardness requirements of NACE for Sour Service are readily met with mnormalizing even if your filler metal is ER80S-D2. ER70S-6 may well meet the 70Ksi requirements. Toughness should be improved for both the weld metal and the base metal with normalizing after welding.

A216 does not require normalizing after weld repair, only stress relief per 10.3 when the weld repair is of sufficient size. So why do it?

 

[jwhit]

The idea being floated around is to weld as cast and normalize after welding. The process in the past has been normalize, temper and weld repair followed by pwht. The idea some people have, which I'm not comfortable with, nor is our metallurgist, is to repair as cast, normalize and eliminate the pwht/stress relief altogether. I'm fine with doing a normalize, weld and then a temper/pwht, or with approved procedure, for minor repairs, a normalize only.

 

[weldstan]

Depending on casting thickness, changes in geometry and the nature of the defect/repair, high internal casting stresses may adversely affect weld repairs in the "as cast" condition. While elimination of a heat treatment may well be cost effective, if chasing cracks during weld repair results, it soon becomes cost ineffective. Whether to normalize or not prior to weld repair should be based on your own experiences based on the nature of the repairs required and the casting complexity and thickness.