PWHT Heating and Cooling rates PNo 6 Group 4

[dieselofdog]

Hi,

Need some guidance on PWHT heating and cooling rates. An new to ASME and still finding my feet, the standards are laid out a little different from the Australian Standards I am used to.

Thanks

 

[metengr]

If you mean P-No 6, Groups 1-3, the PWHT is 1400 deg F minimum based on ASME Section VIII, Div 1, Table UHA-32-1. Requirements for PWHT can be found in UHA-32 and UW-40.

 

[denlow60]

can you tell which steel in this group you meant ?

 

[jwhit]

These materials aren't included in the tables found in ASME Section VIII, UHA32. If you are working with ASTM A487 CA6NM I would look to the base metal spec. for guidance based on the end use of the casting. I'm not as familiar with the wrought designations but suspect the same advice would apply. Typically this material is air cooled rather than furnace cooled and IMHO it normally doesn't hurt to control the heating rate to some degree.

 

[metengr]

There are three P-No 6 Group 4 materials identified in Section IX
SA 240 S41500 13Cr–4.5Ni–Mo (plate version of CA 6NM)
SA 352 CA6NM 13Cr–4Ni
SA 479 414 12.5Cr–2Ni–Si

Use of the above materials would be required by code case because they are not listed as pressure retaining materials. PWHT would need to be established using the material specification or by code case use.

 

[denlow60]

and SA 487 13Cr-4Ni

 

[dieselofdog]

Thanks, this confirms what I was thinking in regards to the Group 4 not being listed in PWHT tables. The material is SA 487 CA6NM 13Cr-4Ni . I have the ASTM Material spec which does give a guide on PWHT temps but not heating and cooling rates. After welding I was planning on heating to 10deg c below the final tempering temp of the casting, hold at 1 inch per hour.

Any suggestions on cooling rate (JWHIT - "air cooled")?

Thanks

 

[jwhit]

Most foundry practice for CA6NM that I've run across is to air cool in still air. Depending on your application the double temper (Class B) post weld works out well. This material tends to be more forgiving than CA15. Is this a pump application by any chance?

 

[denlow60]

dieselofdog,

do you have ASME BPVC SECTION II , PART A-2 2013 available to you , you would be able to look here in SA-487-CA6NM .

 

[dieselofdog]

Yes JWHIT it is a pump, hot oil. The pump is being build back to original wall thickness. In the material spec for CA6NM B it recommends an intermediate and final PWHT. I will follow the double treatment, cooling to below 200deg c before the final treatment. I will instruct that the cooling is to be in still air. Thanks.

Thanks guys, I thought I was on the right track, good to hear it from others. This forum is a wealth of knowledge and experience.

 

[jwhit]

Do you have a qualified WPS for this material? If not, that is something you should probably do before any production welding. The first stage of the PWHT cycle can fall between the criticals, so it should have a separate procedure from just an 1125F post weld.

 

[dieselofdog]

I have just sent a PQR coupon out for RT. I have not had it PHWT yet. So you suggest just one treatment at 1125F for the test coupon?

 

[metengr]

dieselofdog;
The PQR should be qualified to ASME B&PV Code, Section IX, which requires bend and tensile testing, and not RT. Unless, you are talking about welder performance qualification.

Second, I would qualify the WPS using both PWHT's as part of the PQR.

 

[dieselofdog]

Thanks metengr,

I am qualifying my procedure to Section IX, RT is being performed as a precaution before mechanical testing is carried out. The test plates have cost me big $$$ (special pour from the foundry). If there has been a operator issue I can re-weld using the same plates.

 

[jwhit]

Qualify it with both heat treatments, this material should be treated as ASME Sec.IX QW407.1(a)(5) for the first cycle and (2) for the second. By including both there should be no questions regarding PWHT. As far as RT is concerned, I spend the money to RT as well to avoid testing a plate that will fail due to a hidden defect. It is especially critical now as I am doing plates to ASME IX with added testing per EN15614.

 

[dieselofdog]

Thanks jwhit,

My test has passed RT. Heat treatment plan is sorted. Thanks

FYI NDT is also a requirement for Australian Standards (AS) before you can procedure to mechanical testing. AS is a mixture of ASME and BS.

 

[jwhit]

I probably should have worded my last post a little differently. The additional requirements mandated by EN15614 include NDE, however we have always done it as a form of preventive medicine. Isn't it fun trying to hybridize these spec's to satisfy all of the requirements?

 

[denlow60]

I think you meant EN15614-1.