Powder coat comes off between 250 – 350 degrees. To draw the temper from fully hardened 4130 you go to 600 degrees, up to that temp your frame is ok. To make it fully annealed you need to heat it red hot until it’s non-magnetic which is about 900 degrees.
It’s academic anyway, nobody can stand the smell of burning powder coat.
FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience