Weld Build Up on SA-216 WCB 1

[Fizza453]

We have to do weld build up on SA-216 WCB valve body.Valve is of 600 Rating and size is NPS 8.Maximum depth of the build up is 5 mm.
What are the special precautions to take like preheating or post heating (PWHT is not a Code requirement in this case).Code of construction is ASME B31.1. We shall use GTAW with ER 70S-3
Would you please suggest better wire than ER 70S-3?
We have done without preheating with ER 70S-3 but welding is found cracking.

Nasir
Welding Engineer
DESCON ENGINEERING LIMITED
PAKISTAN

 

[metengr]

The wire is not the problem, preheat should be used. Preheat 200 deg F, maintain the interpass temperature below 650 deg F. Stringer bead sequence and after welding, blend grind and perform a surface NDT (Liquid Penetrant or wet fluorescent MT).

 

[Fizza453]

Metengr,

Thank you for nice recommendations.I shall follow it.
Would you please explain how preheating and interpass temperature in this case play the role for better welding?


Nasir
Welding Engineer
DESCON ENGINEERING LIMITED
PAKISTAN

 

[metengr]

Fizza453;
Preheat for welding slows the rate of cooling in the base material which reduces the formation of harmful martensite in the base metal heat affected zone. Martensite can increase the risk of cracking after welding.

Interpass temperature is specified to help control heat input into the base material. Excessive heat input can result in increased grain size, distortion and lower notch toughness.

 

[Vinch]

Preheat is also important to remove humidity from the base metal that could bring hydrogen in welded areas. Slow cooling rate also allows for dissolved hydrogen to get out of the weld. Hydrogen in welds causes cold cracking.