... gas. Thereafter, when heat with high temperature, the packing can not be taken out.After the second heat, screw up, then ... , please inject the nitrogen)when heat, the furnace pressure can not exceed 0.3-0.35Mpa, if the pressure exceeds, please ... the furnace will decrease owing to air’s contract, but it can not lower than 0.05Mpa. If the pressure is lower ...