Hello. We are a steel structure fabricator and have a question regarding preheating.

We prepared a prequalified WPS and for the preheat we have included the below minimum preheat temperature according to table 3.3 (AWS D1.1-15).
Process: FCAW, 1/8~3/4 (32), 3/4~1-1/2 (50), 1-1/2~2-1/2 (150), Over 2-1/2 (225)

Now, our client has experienced cracking with another vendor and for prevention, they showed us Annex-H of the AWS D1.1-15.
They advised us to include the minimum preheat temperature for high restraint level in the WPS.

Using the hydrogen control method, the susceptibility index grouping was "C" and for 3/8–3/4 thickness, the minimum preheat temperature calculated as 65 degrees (the basis of the thickness was 0.47 inch (12mm).

Our question is does "high restraint level" (H6.2.5 Annex H) apply to ASTM A36 material due to the flexibility of the material because generally, due to the room temperature, we would like to proceed without an additional procedure for preheating. Therefore we would like to propose to our client that it would be satisfactory to classify only low restraint and medium restraint.

Thank you