Inter pass is max temp, so normally this will be governed by the max temperature the PQR is subjected to, however will depend on the manufactures recommendations, standard or material standard stating the max inter pass recommendation. If you run a PQR then this will result in Minimum temp (preheat) and max temp (max inter pass). This is what I go on, however the standard will dictate what is required. If you think about it, then the mechanical testing shows that between these temps then its all good, out with this (dependent on standard).
I hope this helps, but look forward to further comments!