Please take 'micrographs of microstructures' of sample of both material. Then re-heat a sample piece, tempered at 620 Deg C, to 740 Deg C. Take 'micrographs of microstructures' of the re-heat treated sample. Compare the 'micrographs of microstructures' to determine if it compares faithfully with ASTM A182 F11 Class 1 material.

I referred to an ASME version of the same standard i.e., SA 182 F11. There is a provision made for retreatment. So re-heat treating the material is permissible. The mechanical properties will change. Whether the change will be favourable, you may determine experimentally. With the new properties the existing material test certificate will need to be amended.

I will be happy to know what you finally decide upon and the consequent results.

Thanks for the information. I shall refer to the standard. However, our requirement is F11 Class 1 which got the lowest value of hardness among the Classes 1,2 & 3. I doubt on limiting the hardness value within range on re-heating.

Moreover any dimensional variation happen?

Have you no access to the designer to ascertain his/her purpose?

We are the procurement department of an EPC contractor. The designer has clearly specified their requirements as Tempering at 740 Deg C.