TWI Industrial Member Report Summary 258/1985
S A Westgate and P N Hone
Magnetically impelled arc butt welding has become increasingly employed for the butt welding of hollow section steel components up to a maximum of 5mm wall thickness. It is used mainly for automotive applications and is complementary to the other forge welding processes, flash and friction welding.
The current work involves a study of the MIAB welding of thicker wall, low carbon (~0.2%C) steel tubing (6 and 9.5mm wall by 50mm diameter) using a conventional welding sequence. A comparison has also been made of the weldability of the above carbon steel with medium carbon (0.4%C) and low alloy steel tubing. This work has demonstrated the potential for welding thicker wall tube in production using conventional techniques. Weld quality depends on steel type but low carbon steel tubing is weldable by the MIAB technique in wall thicknesses up to 9.5mm
When welding the low carbon steel, welds of acceptable quality (<5% defects exposed after 90° bend testing) could be obtained over a wide range of welding conditions for the 6mm wall thickness tubing (±20% first stage current value, ±30% second stage current value and -50% forge pressure). Weld times and material losses compared well with the other processes. The 9.5mm wall tubing was more difficult to weld and a consistency series gave a borderline level of 5% defects after bend testing.
Consistently good weld quality was achieved with the 6mm wall medium carbon steel tubing with up to ±20% tolerance to variation of welding parameters, but only moderate quality, (~10% defects after bend testing) could be achieved in the low alloy steel.