What is the annealing temperature at the mouth of the small steel pipe with high frequency ການໃຫ້ຄວາມຮ້ອນ induction?

The mouth of the small-diameter steel pipe is annealed in a resistance furnace with a maximum furnace temperature of 840℃; when high-frequency induction heating is used, in order to achieve the purpose of recrystallization, the actual heating temperature of the mouth of the small-diameter steel pipe is 840℃.