NITRONIC 50 (XM-19) MAX ACCEPTABLE HARDNESS 2

[GabrieleB]

I need to approve a WPS for UNS S20910 Hot Rolled Material (also named Nitronic 50/XM-19). I found maximum hardness values in the base material zone up to 363 HV.

NACE said "However, S20910 is acceptable in the annealed or hot-rolled (hot/cold-worked) condition at a maximum hardness of 35 HRC"

NACE also said "Individual HRC readings exceeding the value
permitted by this part of ISO 15156 may be considered acceptable if the average of several readings taken
within close proximity does not exceed the value permitted by this part of ISO 15156 and no individual reading
is greater than 2 HRC above the specified value"

37 HRC corrospond exactly to 363 HV10, but my problem is that 5 hardness point exceed 35 HRC.

Is this WPS technically acceptable or we need to requalified the procedure.

 

[SJones]

If 5 points exceed 35 HRC then is the average value not greater than 35 HRC and thus unacceptable?

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[GabrieleB]

If you consider the NACE requirements, seems to be acceptable, but if you use a Cathodic Protection system there are some limitations to the hardness in order to avoid the HISC as specified in the DNV DNV RP B401 Para. 5.5.4 - 5.5.5 - 5.5.6.

According to this, anybody knows which is the good practicse maximum acceptable hardness values for this kind of material?
Thanks in advance for your suggestions.

 

[SJones]

Does RP-B401, 5.5.4 not state:

For all practical applications, austenitic stainless steels.......are generally considered immune to HISC...The same applies for welding

and is S20910 not an austenitic stainless steel?

Which specific standard is designating the hardness requirements for the weld that you are attempting to qualify, or are you hardness testing simply because you think it is a good idea?

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[GabrieleB]

That is the problem.

We need to follow the M-601 standard where the hardness test is explicitly required, but no indication are given about the maximum allowable hardness.

So I need a common standard or a good practice as reference where I can find a reasonable values of hardness to refer to. I read the above values in the WPS but I don't know if I have to accept or not.

Is possible to take as reference the NACE standard also if I haven't a Sour Service condition? At the moment is the only standard which I found, that speaks directly about this particular material.

 

[SJones]

NORSOK M-601 defers to ISO 15614-1 which states that Group 8 materials (austenitic stainless steels) are not required to be hardness tested.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[GabrieleB]

I'm agree with you. For group 8 material is clearly stated that no hardness survey is necessary.
So no maximum hardness limit shall be applicable.
I really appreciated your answer.