UHA-51, UG-84 - Impact testing for stainless steel

[marty007]

Hello,

We're working on a stainless vessel with an MDMT of -150°C, and I'm trying to understand the acceptance criteria for impact testing of stainless materials. (helping out my colleague that normally handles welding).

Going through the various paragraphs of UHA-51, I've determined that our base metals do not require impact testing, but that welding procedure qualifications will require impact testing per UHA-51(e).

Now I'm trying to determine specimen requirements and acceptance criteria.

Acceptance:
UHA-51(a) provides minimum values for lateral expansion on the impact specimen. Reading through UG-84, the absorbed energy requirements appear to only apply to carbon steel materials. Is lateral expansion the only acceptance criteria for stainless steel impact testing?

Specimen size:
With respect to specimen geometry, UG-84(4)(a) provides scaling methods for absorbed energy based on the ratio of the actual specimen width along the notch to the width of a full-size (10mm x 10mm) specimen.

When working with thin stainless fabrication (3/16" -> 1/4") we can't help but use specimens less than 10mm x 10mm. I am not familiar with lateral expansion from impact tests, but does this value scale at all with the size of the specimen? Or do we just make a specimen based on our nominal plate size and use the acceptance criteria of UHA-51(a) without scaling?


Thank you to anyone that has read all the way through this. Any help is appreciated.

Cheers,
Marty

 

[metengr]

The only impact testing you need to perform is on the weld metal used in fabrication, as stated in UHA-51 (e)2 (b).
Now look at
UHA-51(f) Required Impact Testing for Austenitic
Stainless Steel Welding Consumables With MDMTs Colder
Than −155°F (−104°C). For production welds at MDMTs
colder than −155°F (−104°C), all of the following conditions
shall be satisfied:

You can follow the rest.

 

[SnTMan]

marty007, per my reading:

Acceptance: Lateral expansion only

Specimen size: per UG-84(c)(4)(b) it appears lateral expansion acceptance is indepedent of specimen size. Have to admit I had not considered this aspect of UHA-51 before.

Interesting to see what other opinions you get.

Regards,

Mike

 

[marty007]

Digging around, I chose to take a quick look at how ASME VIII-2 handles this (just for reference).

Div2 actually provides an interesting chart of lateral expansion requirements (Fig 3.6 in 2011a Ed.). It's a curious looking chart with a flat requirement of 20mils from 0"-1" thk, then a slope up to 32mils at 2" thk, then flat at 32mils until chart ends at 4" thk.

At least in Div2 it appears flat in the region I'm considering.

Does anyone know the basis of this chart, theory, etc?

 

[Fizza453]

Figure 3.6 is for the carbon and low alloy steels with minimum specified tensile strength greater than or equal to 655 MPa (95 ksi), please see 3.11.2.1(b)(2).
Now please see UG-84(c)(4)(b)thar refers to UHT-6(a)(3) and UHT-6(a)(4) for those carbon steel and low alloy steels with MSTS greater than or equal to 655 MPa(95 ksi, the reffered clauses further refers to Figure UHT-6.1 that is like that Figure 3.6 in Division 2.
For lateral expansion, it should be noted that Division 2 acceptance criteria is strict if compraed with Divison 1, see Fig. 3.6 versus Fig. UHT-6.1.
For stanless steels, Division 2 almost reads out the same way as Division does.

Nasir
Welding Engineer
DESCON ENGINEERING LIMITED
PAKISTAN