Methods of Preheat (Sections III and IX)

[newweldeng09]

Situation: I am welding a P8 production part using PTA process. A min. temperature for welding has been specified on the WPS. The configuration of the part has two different diameters. The larger diameter has already been hardfaced during a prior welding operation. The smaller diameter has a weld preparation that extends for approx. 7". Preheat is applied to the larger diameter and welding is intiated at a spot closest to the larger diameter and progresses down the shaft. Section III allows preheating to be applied by any method which does not harm the base material or any weld metal...(NB-4612). Can preheat be applied by PTA torch while welding to bring the shaft end (at end of 7", opposite larger diameter) up to min. temperature for welding performed on that end?

 

[metengr]

Yes, one can take advantage of preheat in this manner. The material does not differentiate on how preheat is applied or the source, only if preheat is needed.

 

[stanweld]

As metengr stated, yes, flame preheat may be applied. Whether it should be is another matter. Hard surface chemistry and expansion characteristics need to be addressed in your preheat method selection. Dimensional requirements must also be considered. The cheapest method may not be the best choice.