PWHT for a P-No. 11A Steel Casting (with a little Vanadium)

[tc7]

Hello all,
I am trying to prepare for a new WPS for repairs of steel castings and need advice on appropriate PWHT. The material is ASTM A487 Gr4 Cl B. It is also listed as an ASME P-No. 11A Group 3. My application is not for pressure vessel service, but I went to Sect VIII for PWHT guidance and am finding some conflicts amongst my other references.

Section VIII Table UHT-56 suggests PWHT of 1000-1050 deg F for SA487 Class 4Q (this seems to be an old designation for A487 Gr 4 Cl B).

The ASTM A487 (and the SA487) material specification (as seen in Table 4) suggests a PWHT of "1100 deg Minimum". The "Minimum" stipulation confuses me.

Adding to a little confusion and concern is the ASTM A487 spec does not list Vanadium for Gr 4 Cl B as an allowable, but my ASM metals handbook mentions an allowable V content of .03% and also an SAE handbook cites that the UNS J13047 allows up to .03% max V-content. We did an actual spark test and are showing a spread of .028% to .033% V exists in our parts.

Are Vanadium related cracking problems that sensitive to a ~100 deg difference (or more)in heat treat temp? Or am I needlessly worrying about this?

So then what PWHT temp and time is recommended? By the way our task is to repair cracks and indications from some inservice machinery requireing grindouts of 3/16" to 1/2" deep.

Any other advice on handling this alloy would be interesting to see and appreciated.

Thanks in advance.
tc

 

[stanweld]

The .03 V maximum requirement of SA-487 Grade 4 (Table 2) assures that any Vanadium additions will principally be used for grain refinement. SA-487 Table 1 Heat Treat Requirement requires an 1100 F minimum Tempering temoperature - not to be confused with PWHT. The PWHT per Section VIII assures that you do not exceed the tempering temperature and thus will not adversely affect the Q&T properties of the base metal after PWHT.

 

[metengr]

tc7;
Per your reported chemistry with 0.030% V, I would say the material you have is closer to a Grade 7 Class A versus a Grade 4, per my review of ASME SA 487. I would perform a chemcial analysis to accurately type the material.