WPS A335-P22 to HPNB Modified (35% Cr, 25% Ni)

[ak1965]

1. I am in search of a WPS for welding 11 mm thick pipe of A335 P22 with a pipe of HP Nb Modified material (35% Cr & 25% Ni) in the convection zone of ethylene furnace with zone service temperature at approx.900 Deg C.

2. Do I need to go for PWHT in this case?

This is urgent. Please help.

 

[metengr]

ak1965;
According to Section I, no PWHT is required for Grade P22 pipe that is 16mm or less at the weld region. I would use a preheat of 400 deg F with Inco Weld A filler metal. Perform a Liquid PT after the completion of the weld.

Here is an interesting paper on the subject of repairability of the heat resistant stainless steel castings.

http://www.aws.org/wj/supplement/WJ102010_210.pdf

 

[ak1965]

Metengr


Thanks... In our case.. the thickness is approx. 11 mm and at the weld it would be around 13 mm. which is the threshold limit of carryinbg out PWHT for CR Mo steel ( P22) as per ASEM b31.3 table 331.3.2.

since it is dissimlar metal joint with HP Nb mod. material, shoud we condier PWHT in thsi case.

Please comment.

 

[metengr]

ak1965;
If you are following minimum code requirements, you do not need to PWHT the P22 base material in the weld region. The dissimilar material does not require PWHT because it is a heat resistant stainless steel.

Now, if the P22 material was cold formed or strained with no post-forming thermal treatment near the weld region, I would PWHT. Otherwise, if the material has not been cold worked or cold strained, no I would not perform PWHT.

 

[ak1965]

P22 material is already in service at around 900 DegC.since last 15 years and the lower HP Nb modified material (35% Ni 25% Cr) is new component to be welded.

 

[ak1965]

metengr,


Waiting for your response for PWHT on the above information gievn by me regarding service temp of F 22 material that i sto be welded with HP Nb Mod.


Plz. comment.

 

[stanweld]

You need not PWHT.

 

[metengr]

ak1965
I would not PWHT.

 

[AndyVictor]

As far as I know, for welding with Inco welding rods, PWHT is not rquired. Further, heat treatment for HP Nb mod is solution annealing (app 1100 deg C with quenching) and for P22 it is PWHT at app. 720 deg C with controlled cooling. My doubt is usability of A335P22 at 900 deg C . I think at convection zone, the temperature will be around 500 deg C max.

 

[ak1965]

Temp. may not be 900 Deg C at this weld joint, It is backed with refractory and temp should be in the range of 700 Deg C.

We got some WPS from elsewhere that suggests PWHT on this dissimilar metal joint. Pl. Note that F22 (aged 15 yrs.) to be welded with HP Nb mod 35% Ni & 25% Cr (New).

Wall Thickness of weld portion is 11 mm.

 

[stanweld]

We have made these joints many times without PWHT.

 

[davefitz]

It is my understanding that it is recommended to make this DMW as a machine weld, and not a manual weld- to ensure adequate weld penetration, weld spatter would be expected, and most manual welders would tend to avoid the spatter and turn down the amps, which would prevent adequate penetration.