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# EN 13445 allowable bolt stress

## EN 13445 allowable bolt stress

(OP)
Suppose one has to calculate with A2-70, or more specific with 1.4404 +C700 acc. EN 10269.

For the allowable bolt stress the EN 13445-3 §6.1.1 clearly excludes bolts, and refers to clause 11 and 12 of EN 13445-3.

In §11.4.3.1 for austenitic material it states fB = Rm,t/4. This means tensile strength at designtemperature. Now where do I find this? Not in EN 10269 (yes, for 1.4404 +AT it does, but that is the A2-50 equivalent). I have checked EN ISO 3506-1, AD Merkblatt W7, DIN 267-13.

It also appears that this tensile strength does not remain the same, otherwise the tensile strength of 1.4404 +AT and +C700 should be the same.

Is there anyone who has experience on how to cope with this? A2-70 is a widely used material, and I can not believe it is impossible to use it with regard to EN 13445.

Is it allowed to extrapolate the tensile strength? For example: at 200ºC => Rm,t = 390 * (700/500) = 546 N/mm² ?

Kind regards,

Kelly

### RE: EN 13445 allowable bolt stress

I cant help you, but Im curious to see the outcome. Ive came accross similar problems in several 'pressure codes', like 13480, 15001, 13445, and all the codes/standard(s) that are (sub)referenced in them.

When it comes to pressure codes, EN is by far a mature code to be seriously considered, at times.

### RE: EN 13445 allowable bolt stress

A2-70 can be used up to temperatures of 400 C according to EN 1515-4. I could not find elevated temperature properties for A2-70 in any of the Euronorms either. I did find one document that showed the following:

200 C --> 81% of 25C Rm
300 C --> 77%
400 C --> 74%

### RE: EN 13445 allowable bolt stress

(OP)
Carefull there. These percentages are related to the yield stress, not the tensile stress.

### RE: EN 13445 allowable bolt stress

OSIRIS7,

Since this thread did not receive many replies, I suggest that you submit a new thread to the forum Metal and Metallurgy engineering. There will be other experts that frequently contribute there (Metengr is one) that are very familiar with pressure vessel codes. It may be ASME instead of EN, but they will likely provide additional information related to strain hardened stainless steel fasteners (ASTM A193 Grade B8 Class 2).

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