ESAB, the world-renowned welding and cutting specialist, has ordered an EFD Induction Minac 50/80 Twin for one of its ESAB IT-100 automatic T-beam welding machines. The machine, to be installed at a shipyard in the Ukraine, is a fully automated solution with a welding speed of more than 1m/min. The EFD Induction Minac will be used to provide in-line straightening of the welded beams.
“We’re always delighted to work with ESAB,” says Patrik Olsson, technical manager at EFD Induction Sweden, “and we’re particularly excited to contribute to the T-beam welding machine. It’s a solution that really exploits the characteristics of in-line induction heating to cut costs and lead times for customers. For example, the Minac straightens the beams during the welding phase, thereby eliminating the need for a separate post-weld straightening stage.”
Straightening of T-beams is necessary because of cambers (bow-shaped bending distortion) caused by longitudinal upwards shrinkage following heat inputs from the welding process. A typical camber for a 16m-long T-beam that has been welded without in-line straightening would be between 60mm and 100mm.
“Induction heating is ideal for this sort of automated application,” comments Olsson. “Alternative methods such as mechanical and manual flame straightening are slow, inaccurate and demand hours of work by skilled operators. There is an in-line alternative that uses propane burners mounted on the welder. But even this method has drawbacks. Heat input is difficult to predict, repeatability is poor, and distortion can be corrected in one dimension only.”
The Minac ordered by ESAB is a ‘twin’ model. That means the induction heating system has two independent power outputs and coils. The two coils simultaneously heat each side of the ‘web’, the part of the beam represented by the vertical stroke in the letter T (the horizontal stroke is known as the ‘flange’). The heat induced in the beam by the induction coils causes shrinkage that compensates for that caused by the welding heat.
“The use of induction straightening in automated T-beam welding leads to significant financial savings,” says Olsson. “The process not only eliminates an entire production phase, it is also virtually impossible to overheat the beam. And since induction is so controllable, it is possible to achieve extremely accurate repeatability.”