PURPOSE: To obtain an electric welded steel pipe having excellent low-heat toughness by conducting an open pipe to a sealed welding part and welding the pipe by the heat input in an adequate temp. range.
CONSTITUTION: An open pipe formed to approximately a circular shape is conducted into a sealed box provided internally with contact chips and squeezing rolls and is heated and subjected to shielded welding under the pressure exerted by the squeezing rolls in the stage of producing an electric welded steel pipe by a high-frequency induction or resistance electric welding method. The heat input for welding from a high-frequency power source is made within the range of the heat input for welding where cold junction and burn-through do not arise and above the central value thereof. The electric welded steel pipe which has excellent low-temp. toughness and is usable in an extremely cold area is obtd. by the supply of such heat input for welding.
KUSUKI TADASHI
NAKADE HIROSHI
INABA HIROTSUGU
Next Patent: DEVICE FOR CONTROLLING TEMPERATURE AT WHICH ELECTRIC WELDED PIPE IS FORMED