ASME BPVC 8-2 & 4340 steel

[TerryR1]

I have a customer that wants to use 4340 for an asme vessel. Can anyone point me somewhere that explains why 4340 isn't listed in IId? I'm thinking there must be a good reason.

The other threads here mention things about it having too a high carbon content, but I can't find a reference supporting this. Rather, I find references saying it is a popular material for pressure vessels.

http://www.google.com/#hl=en&sugexp=bvie&cp=20&gs_id=5&xhr=t&q=4340+pressure+vessel

Thanks!

 

[TGS4]

As long as a material is listed in Section II, Part D, with an ASME material specification and an allowable stress, it's OK to use in pressure vessels (with some caveats, of course).

As far as why - well, you should write an inquiry to the Code Committee and ask. Then, come to the meetings and present your question to the committee. Nothing like hearing it from the horse's mouth (no offense intended to II-D committee members).

 

[Duwe6]

4340 mechanical properties are very dependant on the Heat Treatment -- it is Quenched & Tempered material. Thus there is no single "Allowable Stress" value.

And how does your customer propose to deal with the issue of the HAZ being tempered to Dead Soft during the welding of nozzles.

 

[blacksmith37]

There is not total agreement on the use of 4340 where H may enter the steel- causing hydrogen stress cracking. My opinion is that some volumes have a low, lower critical temp, preventing use of a very high tempering temperature. The Cr:Mo which have excellent H resistance are tempered at relatively high temperatures. Dr B. Craig did a lot of work for NiDi (nickel development)(20+ yr ago) tring to get 4340 accepted into various codes, without sucess (is my memory).

 

[TerryR1]

Thanks guys. I wrote a humble letter to ASME.

TGS4 - it is only approved for bolts as used in part 4.16 (not part 5 for some reason, and I'm not sure how to draw the line)

Duwe6 - very true. We aren't welding this vessel.

 

[metengr]

Simply writing a letter to ASME B&PV Code is not going to provide the answer you want because it could be construed as consulting. Either material is permitted or excluded, no reasons are given.
If you want to use this material, it will be necessary to develop a code case. Typically, 0.35% carbon content is the maximum for ASME B&PV Code materials, unless exemptions are given via code cases. You can try a code case for use in a vessel. However, this will require test data to be submitted at moderate and high temperature, along with weldability and formability demonstrations.

 

[Duwe6]

And the data will have to include tensiles & yields at the normal Sect II-D temp's: 100°F, 200, 300, 400, 500, 600, 650, etc. up to your proposed MAWT.

Gonna make for a pretty expensive vessel.