Sky, while there is lots of hot work done in twisters, the ideal is too twist cold, if possible.
The reason for cold twisting aside from economy of fuel and time is the consistency of temperature across the bar.
My old free from the dump Beaver pipe threader would twist 3/4" square steel bar cold.
When I tried to twist s.s. 11/16" the torque was insufficient. In the end I incorporated the uneven twisting into design elements in the rail but there were a few anxious days while I developed even that process. The idea of addition torch heating and cooling while twisting didn't work well at the speed of pipe threading. It happened too fast. Hence my impetus to build a unit to twist 1 1/4" inch cold. (Which can twist much larger hot, my biggest twist so far is 1 3/4" cold finished square.