Use of Dual Certified Materials 1

[rjw57]

Can anyone shed some light on the use of dual certified materials (i.e 316/316L) and what requirements must be met to use a dual certified material as (for instance) a UNS31600 vs a UNS31603. Obviously, the allowable temperature limits and stresses are significantly different. After some preliminary investigation, I believe that some light on the subject is shed in Section 2 Part A of the code, but unfortunately, I don't have this portion of the code book. Thanks for any help...

 

[spt]

I believe the confusion comes from failing to ID material by specification, in the field material at times will be identified by type or grade only.

Spec for Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater and Heat-Exchanger Tubes
Spec No, Type/Grade UNS Alloy No. P-No
SA-213 316 S31600 8
SA-213 316H S31603 8

SA-213 Type 316: The nominal composition (wt.%) of this classification is 19 Cr, 12.5
Ni and 2.5 Mo. It has been used successfully in certain applications involving high-temperature service. The presence of molybdenum provides creep resistance at elevated temperatures and pitting resistance.

SA-213 Type 316L This classification is the same as 316, except for the carbon content. Low carbon (0.03 percent max.) this reduces the possibility of intergranular chromium carbide precipitation and thereby increases the resistance to intergranular corrosion without the use of stabilizers such as columbium (niobium) or titanium.

 

[reichertc]

It is possible to create a metal that meets both the requirements for two different grades of material. For the 316/316L example, odering a dual certified grade gives you the low carbon content of the 316L material, for increased weldability, while still allowing you to use the higher allowable stresses of 316 that are given in the code (eg. B31.3)

You get the best of both worlds, but you pay for it. If you don't need the higher allowable stresses, or the incresed weldability, consider ordering straight grade materials. It will cost you less.