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gengi (Mechanical) (OP)
16 Mar 08 4:21
Dear all,

could someone let me know about a requirement of Dual Certified Stainless Steel 304/304H with 0.04% minimum carbon content?

Which allowable stress is correct to use in this case?
Is that of 304 or 304H?

Do you have some information about the reasons of such requirement?

many thanks in advance

Helpful Member!  metengr (Materials)
16 Mar 08 13:43
What is the material specification and product form, pipe, tube, plate? For example, for tube SA 213 TP 304, the maximum carbon is 0.08%, for TP 304H, the minimum is 0.04% and the maximum is 0.10%. However, you need to carefully review the material test report for the solution treatment temperature and grain size for dual certification.

Regarding allowable stress for this dual certification, you can use the TP304H allowable stress values.
Helpful Member!  jte (Mechanical)
17 Mar 08 1:35

As metengr noted, a bit more info from you would be better.

To answer your second question, the reason I as a pressure vessel engineer might specify a dual certified material is that I want the higher allowable stresses of one while keeping my materials engineer happy with the qualities of the other. Happens often enough, though I wouldn't say that it is common.

If this is for a pressure vessel, you'll reach a more focused audience at forum794: Boiler and Pressure Vessel engineering.

gengi (Mechanical) (OP)
18 Mar 08 2:26
Dear Metengr and jte,

first of all many thanks for your reply.

The material specification and product are for exchanger tubes- SA 213 or SA 249, plate/sheet SA 240, pipe-SA 312 and forgings SA 965 , designed at temperature greater than 343°C.

My approach was to design the parts using the allowable stress of SS 304H even if I am noting that per ASME II Part.D - Table 1A the allowable stresses of 304 and 304H are the same.

Anyway as you both suggested, in case the allowable stresses were different I would use the higher stresses of those.

In cese you think it would be better to give me some instruction please do it.

thanks again for your precious support.

have a nice day.
moltenmetal (Chemical)
18 Mar 08 7:19
What qualities of plain 304 grade are you interested in which are not also offered by 304H?

Clearly you can't have dual-certified 304L/304H!

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