4130 Weld Overlay/Clad PWHT time for WPS based on ASME Section 8 Div 1 UW-40 (f)(5)(h)

[Weldeng13]

Hello,

I have a qualified a stainless steel 309L/316L corrosion resistant overlay that is 9/32 inch thick on 4130 to NACE MR0175 and API 6A and 16A (ASME IX) with the appropriate chemistry, sub 250 HV10 hardness and base metal tensile/CVN testing to prove the base still met acceptable values. The test plate is 1.5 inches thick, time was 3.5 hours at 1175F. API 6A and 16A states to follow a PWHT procedure and using ASME Section 8 Div 1 UW-40 provides sound guidance and most PWHT contractors are familiar with it. My question is about how to handle time for the WPS.

UW-40 (f)(5)(h) states the thickness of the weld metal overlay when weld metal overlay is the only welding applied.

In (f) and (5) it defines this as the nominal thickness for PWHT

My current plan is to have all overlays that are 9/32" thick and less PWHT to a minimum of 3.5 hours for all base metals above 1 inch. Below 1 inch is not covered by this procedure.

For overlay thicknesses greater than 9/32" my idea is to divide thickness by minutes to provide a minute per thickness which can then be multiplied by the maximum time allowed which is 125% of what was qualified.

3.5 hours = 210 minutes
9/32 = 0.2813 inches
0.2813 inches/210 minutes = 0.0013 inches per minute
125% of 210 minutes = 263 minutes
263 minutes x 0.0014 inches = a maximum thickness of 0.351 inches of weld overlay can be applied.

This would result in a WPS with the time dependent on clad thickness not base metal thickness.

Does this seem like a reasonable approach?

Thanks,

Peter





Peter

 

[DVWE]

A couple of questions:

What welding process are you using?

Why 1.5" thick plate? You stated that it has been subjected to tensile and cvn, so was this two plates welded together, and then will be weld overlayed?

Where was the 3.5 hours derived from?

The devil is in the details; she also wears prada.

 

[Weldeng13]

Overlay only, tensile and CVNs are base metal.

3.5 hours is the PWHT time of qualification, based on my experience.



Peter

 

[DVWE]

Welding process?

The devil is in the details; she also wears prada.

 

[CWEng]

You are over-thinking the time requirements. What you are normally after for NACE in overlay is tempering the HAZ. the HAZ thickness will not change with increased overlay thickness. Just using the time you qualified would most likely be adequate for most overlay situations on similar parts/alloys. Where are you getting that 125% is the maximum time allowed?

As for code requirements, unless you are CVN testing the weld &/or HAZ, ASME Section IX doesn't care how long you PWHT. ASME Section VIII Div 1 bases the PWHT time on the cladding thickness, but it is also specified by P-number. Are you using Section VIII for reference since 4130 doesn't have a P-number (unless it's made to some other specification you haven't mentioned). What you also have to mind if you really have to comply with all of Section VII is UCS-85 where you have to simulate the length of PWHT on non-P1 base meatls. So your PWHT time does affect the base metal requirements for the vessel material in question provided it isn't one of the exempt material forms.

 

[Weldeng13]

CWEng, you are correct it is all about tempering the HAZ, but where it can be a bit different in thickness is in a ring groove if you fill it up vs. profiling.

The 125% is from Section IX QW-407.9 (a) which is invoked from Table QW-254.1 QW-407.9.

The use of Section VIII Div 1 is self invoked and not required, it lays out PWHT well and as I said before most heat treaters are familiar with it.

As you stated 4130 is not listed and I don't know if you could get it cross referenced with any of the listed materials with its level carbon content.

With 4130 Q&T strength grades, I think it is best to keep a maximum of time regardless of a lack of CVN requirements. Normally I always do a short and long coupon and don't have this issue, which would be complying with UCS-85 by default. I have ran groove weld qualifications with much longer times on the same heat of base metal and I can use that base metal testing information as back up for valid time. Thanks for reminding me of UCS-85 and the 80%.

Peter