I don't understand what you mean by "cold stretching" of a cryogenic equipment.
Let's talk of piping, that's easier to envision. When a piping subject to high temperature service is fabricated at room temperature, a previously calculated gap is left in one or two, rarely three, points. The welding ends where the gap is located must be pulled until the weld can be executed. In this manner, one or two straight runs of piping are shorter than they should be. When the pipe is heated up by the fluid it carries, it expands, and so its length, when in service, is exactly (more or less) its correct length.
Cryogenic service works the opposite way. The piping should be left a little longer than its final length, so when it shrinks due to the cold fluid, its length in service will be exactly (more or less) the correct one.
What I've said of piping applies also to vessels. So, I don't understand why your tanks must be stretched before welding. Their diameter should be a little longer than the design one. Contraction at cryogenic temperature will reduce them to their final value.
Giovanni S. Crisi
Sao Paulo - Brazil
Way back when in the 1960's the company I worked for made stretched tanks. We used a modified 301 alloy and then pumped in liquid nitrogen. With about 15 % elongation we got between 275,ooo and 290,000 tensile strength at room
temperature due to the retained martensite at room temperature. The stainless was a "tweaked" version of 301.
Are you folks using a T 304 deritive ?