... , heat penetration, quenching, brazing, siphon, sintering steel pipe seam annealing furnace transfers a work frequency 50Hz AC power supply to DC ... seam annealing, fusion, heat penetration, quenching, brazing, siphon, sintering etc.Power grade: 50 kW~1500kWFrequency range: 500Hz~8kHz steel pipe seam annealing furnace