material 12% chrome steel for shafts

[adula29]

Hello, I added my question on another group (API pumps), but I did no recive an answer.
Maybe someone here will be able to help me.

I have a question. API610 table H.2 for materials recommended for 12%Cr, do not use on hardened shafts (above 302 HB). (material groups 1.4021, 1.4005, 1.4005)
In many applications we have seen this type of material used for the shaft, why doesn't API allow it?

 

[MagBen]

To prevent HIC cracking under sour environment, NACE places a max hardness of 22HRC, which might not make lots of sense in some perspectives.
you will need to temp material to knock down hardness to comply with some specs.

 

[adula29]

Do You think that is the main reason (HIC)?
similar issue i saw in nuclear specification
302HB corresponding with 32HRC so that is no NACE requirement 22HRC.

 

[adula29]

Can someone address the hardness requirement of maximum 302HB for API pump shafts?

 

[MagBen]

Check with NACE MR0175, there is a big range on max hardness. PH grades have pretty high hardness max. i think 17-4 is 32-33HRC if remember correctly.