TWI Frequently asked questions
by Steve Westgate
High frequency induction welding is used to make pipe or tube from strip which is fed into rolls which form the strip into a cylindrical shape. The faying edges are brought together between squeeze rolls to produce a V at the point of welding, with an included angle of typically 2-5° for steel.
A high frequency coil introduces current into the tube ahead of the squeeze rolls. This current is concentrated on the edges of the strip in the V and resistance heats a narrow zone at the edges to the welding temperature. The squeeze rolls consolidate the weld by expelling any melted material and contaminants and forming a small upset bead inside and outside the tube. These beads may be immediately scarfed from the tube to give a smooth surface. Thin wall steel tube may be welded at up to a few hundred m/min.
