Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


304 vs 304L vs Dual rated 304/L as it applies to ASME code

304 vs 304L vs Dual rated 304/L as it applies to ASME code

304 vs 304L vs Dual rated 304/L as it applies to ASME code

I have recently performed an ASME code calculation (using software) on a pressure vessel.  I thought that it was odd that the vessel would pass for 304 but not for 304L.  This of course raised the question of what the difference is between the two at say 1150 degrees F.  My question isn't really what the difference between them is, rather what are the properties of the dual rated version, and if there is such a clear dividing line of 0.03% carbon content, how can the material perform the function of both?  Also, my purchasing manager has stated that he cannot find pure 304 anywhere, that we must use 304/L or go to a different # stainless, is this true?

RE: 304 vs 304L vs Dual rated 304/L as it applies to ASME code

Hi There jcmech,
                304/304L dual certified material is readily available if you go to the right stockists/manufacturers. 304 is stronger than 304L. The dual certified material meets the requirements of both material specifications.We have used dual certified plate and pipe material on a recent Project. We did not have much problem sourcing.

RE: 304 vs 304L vs Dual rated 304/L as it applies to ASME code

Dual certified stainless has to be carefully evaluated for service. At low to moderate temperature service, no problem because corrosion resistance is the controlling factor in design application. Once you get above 1000 deg F, there are noticeable differences in creep strength that you must consider in your design (the maximum service temperature permitted for 304L is 1200 deg F, while for 304 is 1500 deg F).  

If you have access to ASME B&PV Code, review Section II, Part D. Evaluate the differences in allowable stress values between 304 and 304L.

RE: 304 vs 304L vs Dual rated 304/L as it applies to ASME code

Remember that 304 has no minimum carbon level.  Any 304L that has enough room temp strength will be able to be dual certified.
The real issue is creep resistance.  The original creep limits for 304 were based on material with some C in it.  Even if you have high strength 304L with nitrogen it will not have as high of creep strength.
You need to look at the limitation on your design very carefully.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

RE: 304 vs 304L vs Dual rated 304/L as it applies to ASME code

We don't allow dual certified 304/304L other than some specific applications on our site due to inherent corrosion problems with our process. We specifically call out the allowable Carbon, Sulphur, and Phosphorous on all 304L material used in site, none of the dual certifiable material can meet our chemistry requirements.

We also take into account both the High and Low allowable for design with both 304 and 304L, noting that the Low values for 304 and the High values for 304L overlap at the lower temperatures. I'm not sure how this is handled at the present with the dual certified materials.

RE: 304 vs 304L vs Dual rated 304/L as it applies to ASME code

Since you are operating at temperatures in the creep range there is the possibility of dual certified 304/304H (UNS 30400/30409).  This would ensure a minimum carbon content and a minimum grain size to provide adequate creep strength.  It is available in plate form.  Other product forms could have availability issues.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close