Does ASME VIII Div. 1 have requirements for normalization/annealing after cold forming?

[julian89]

Good day ladies and gentlemen.

I recently stumbled upon a case where a part (low carbon steel) was cold formed from plates with a resultant strain of more than 5%. The part was therefore subject to heat treatment, but in ASME VIII Div. 1 I cannot find anywhere that normalization/annealing is required, only post-weld heat treatment (PWHT). In the Eurocode equivalent, EN 13445-4, it is stated that "Heat treatments after cold or hot forming, shall be carried out in accordance with the appropriate standards or data sheets or other specifications and shall include normalising, normalising plus tempering, quenching plus tempering, annealing, solution annealing." Have I missed something, or is this correct? For clarity: I am concerned with the base material, not welds.

 

[metengr]

You have the option of either re-heat treatment (simulated with a coupon) or subcritical thermal treatment (aka PWHT) to remove previous forming strains.

 

[TomBarsh]

Yes. See UG-79 and UCS-79 (etc) in this Code.

 

[julian89]

Thank you so much for replying!

From what I can gather, there is no requirement for annealing/normalizing. UCS-79 refers to UCS-56 which gives specifications for PWHT. These holding temperatures are in the area of ~600°C depending on material, however not full annealing/normalizing. I cannot see that the Eurocode and ASME have the same requirements in this regard.

This raises a couple of interesting questions. The European Pressure Directive (PED) states that materials used shall have at least 14% fracture elongation to be considered sufficiently ductile. I have stumbled upon a case where a conical section had calculated strains in the area of ~20%, and thus heat treatment was necessary. However, will PWHT at ~600°C sufficiently restore ductility to be able to satisfy this PED requirement? For clarity, I am here referring to base materials and not weldments.

 

[metengr]

However, will PWHT at ~600°C sufficiently restore ductility to be able to satisfy this PED requirement?

Yes. The reason is that weld coupons are subjected to tensile and bend testing and the fiber elongation for bend testing is a minimum of 20%.

 

[r6155]

julian89
".........was cold formed from plates with a resultant strain of more than 5%"

How did you get this value?

Regards
r6155

 

[metengr]

UCS-79 FORMING PRESSURE PARTS

(d) Except when made of P-No. 1, Group Nos. 1 and 2;
and P-No. 15E materials, all vessel shell sections, heads,
and other pressure parts fabricated by cold forming shall
be heat treated subsequently (see UCS-56) when the resulting
extreme fiber elongation exceeds 5% from the
supplied condition. For P-No. 1, Group Nos. 1 and 2, this
subsequent heat treatment is required when the extreme
fiber elongation exceeds 40%, or if the extreme fiber elongation
exceeds 5% and any of the following conditions

 

[r6155]

I know UCS-79
My questions is how did Julian89 to “measure real” strain after cold forming, “resulting” extreme fiber elongation UCS -79 (d), not previous calculation with table UG-79.1 of part being forming.
The resulting extreme fiber elongation, real value measure in situ is 6%, 8% ???? How much?

Regards
r6155

 

[julian89]

Thank you for replying guys!

The strains have not been measured - they were calculated with Table UG-79-1. Please also be aware that I am concerned with the base material and not weldments. So for the 14% PED requrierement, the question is if there is at least 14% elongation to fracture in the base material after cold-forming and PWHT.

Please forgive me metengr - I am not all that familiar with testing of weld coupons. However, I cannot see the practical relevance. Would you mind giving some more details to a newbie? How would small scale tests verify the ductility of large scale, cold-formed shells or cones, for example? Again - I am concerned with the base material, and not welds. I'm afraid I may not have been clear enough about this.

Thanks for your help guys - I have gotten the answer I originally posted to get.

Wish you all a nice day!

 

[metengr]

You asked if a subcritical post weld thermal treatment will restore ductility in carbon steel. My reply is yes. I cited the example of a weld joined to carbon steel base material where the base material can be locally hardened from the heat of welding.

 

[julian89]

Thank you for chiming in sir! Much appreciated. So, in a practical sense, PWHT mya sufficient to restore ductility. My take is that the Eurocodes are simply more conservative in this respect, and therefore full annealing is required after excessive cold forming to meet the PED requirement.

 

[212197]

As per Engineers India Limited standard, when cold formed part is having thickness more than 16 mm, the formed part shall be normalized.

As per Engineers India Limited standard, when cold formed part is having thickness equal to or less than 16 mm, the formed part shall be stress relieved.

Experts are requested to comment on the rationale of these 2 requirements.

 

[metengr]

The rationale for the above needs to be specified from the Engineers India Limited. It is a different approach and could be based on local practice and/or conservatism. Just a different way to do things.

 

[r6155]

I feel that people use table UG-79-1 to calculate forming strains, but nobody do strain measurement in situ. ¿Why?
Equation in table UG-79-1 for tube a pipe bends is wrong: thickness is not included. See ASME VIII Div.2 Table 6.1

Regards
r6155