What is lowest MDMT of SA-266 Gr.2 & SA-106 Gr.B?

[Vessel7]

Dear Sir,

Two questions:

1. SA-106 Gr.B has been requested (by client) for an MDMT of -28°C. And it got charpy tested at -28°C and failed. Is SA-106 Gr.B not suitable at -28°C?

2. Can SA-266 Gr.2 be used at -29°C? What's the lowest temperature it can pass during charpy V-notch testing?

Please share if anyone has experience.

Thanks.

 

[metengr]

Vessel7;

1. SA-106 Gr.B has been requested (by client) for an MDMT of -28°C. And it got charpy tested at -28°C and failed. Is SA-106 Gr.B not suitable at -28°C?

SA-106 Grade B material is most suitable for elevated temperature service (review the material specification scope). Hot finished pipe material could be supplied with no supplemental heat treatment but rest assured will have a coarse grain size that translates to much lower notch toughness. Notch toughness is not a requirement for this material.

If a normalize and temper heat treatment were specified, the material should be acceptable at -28 deg C. However, why not select an alternate pipe material?

 

[metengr]

Question 2

2. Can SA-266 Gr.2 be used at -29°C? What's the lowest temperature it can pass during charpy V-notch testing?

Yes, despite the higher carbon content this material can be acceptable for use at -29 deg C MDMT because it can be specified as normalized and tempered or quenched and tempered.

 

[Vessel7]

Thanks metengr.

Re SA-106 Gr.B, this material has been selected and procured based on client's material selection report (which allows SA-106 Gr.B above -29°C). But it failed during impact testing (reported at 10J avg against 27J min.).

Now we've decided to go with SA-333 Gr.6 which we normally specify for temp. below -29°C.

Again, thanks your advice.