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SA234 WPB 1

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dahar

dahar

Mechanical
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Oct 16, 2003
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ASME BOILER & PRESSURE VESSLE CODE II PART A - FERROUS MATERIAL SPECIFICATIONS, SA-234, Para 7.5 states: Liquid quenching followed by tempering shall be permitted for all grades when approved by the purchaser.

I have a recieved a request to accept some material that has been manufactured this way. I checked the mill test report and all data meets the requirements of SA-234. I'm inclined to accept the fittings, but I'm cautiously curious why does the spec require that this be approved by the purchaser? Am I missing something? Any problem with liquid quenching fittings?
 
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No, you are not missing anything. Liquid quenching may be required to allow for thicker parts or components, which have limited hardenability, to be tempered after quenching to achieve minimum mechanical properties for the specification. The reason Purchaser approval is required is more for cautionary purposes related to distortion concerns for certain grades of steel, and because liquid quenching costs more as part of the heat treatment cycle.
 
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It's also a two stage process with more to go wrong plus it may have knock on effects for welding if PWHT is involved.

Steve Jones
Materials & Corrosion Engineer
 
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SJones,
I don't believe there would be welding issues with PWHT unless impact testing is required.
 
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It's true that it is standard to specify a PWHT temp lower than the tempering temp, but, it seems that in the case of this material, it would be more of an issue if impacts are required.
 
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It has not been uncommon for manufacturers to "sweeten" the mechanial properties through Q&T as well as use it for thicker parts to meet the mechanical properties as stated by metengr. Unfortunatly, that "sweetening" may not prove so useful to the Purchaser when the fitting is welded and placed into service.

 
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