Cold forming of hot-finished tubes: ASME Sec-I (2019)

[sakthi06.dec]

Hi experts,

In the 2019 edition of ASME Sec-I, requirements concerning Cold forming of 'C' and 'c-Mo' steels are added. In PG 20.1.1, the defining conditions for PFHT are given. I am confused with ref to hot-finished tubes. PG-20.1.1(c)has the following text:

"Alternately, when strain developed in the cold-formed areas exceeds 5% when the straight tube or pipe starting material to be formed is in the unheat treated condition as defined below."

And in the kast line of the last paragraph, the text states,

"Allowable cold strain for this starting material is restricted to the smaller 5% strain before postforming heat treatment."

I am unable to interpret this last line in conjunction with the previous text quoted above.
Can anyone clarify? Also, please clarify the meaning of "smaller 5% strain" in the current context. Thanks in advance.

 

[r6155]

1) Can you tell us the dimensions and material of the tube you are using?

2) I take the opportunity to comment:
Formula for forming strain of pipes & tubes in ASME 1 PG-19 (b)(3) is equal in ASME VIII -1 Table UG-79-1 but different with ASME VIII-2 Table 6.1.
I understand that ASME VIII-2 is right because it considers thickness.
Please, can someone explain it? -Thanks

Regards