heating the steel sheet 7 to {HEAD ~ a temperature range} from an Ac3 transformation point to {TAIL ~ 1000° C.}; and 
to
heating the steel sheet 7 to { HEAD ~ a temperature range } from an Ac3 transformation point to { TAIL ~ 1000 ° C. } ; and
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH