Sparks are flying in the steel sector. Metal sheets are now joined within seconds in both the shipbuilding and the automotive industries. However, the sheets sometimes become distorted after welding, requiring expensive reworking. Technologists at The Linde Group’s UK subsidiary, BOC, are part of a consortium of companies that have developed an innovative method to prevent this. It involves cooling the welding joint with CO2. This has the potential to enhance production efficiency.
Every car starts out as meter-long steel sheets. These are punched, moulded, and pressed in steel fabs, and gradually converted into various automotive body parts. Dozens of robotic welders with high-precision arms then set to work, producing a stable metal skeleton for the car. In their unprocessed state, as they leave the metal press, the steel panels are completely flat—placed on a level surface, they don’t even wobble. This changes abruptly after welding, however. The welding head instantly heats the metal to 1,500 degrees Celsius, releasing energy that has built up in the sheet during rolling. When the welding joint cools down, significant tension often remains, with the material even contracting by around half a percent along the seam. As a result, the panel sometimes buckles to such an extent that it could be used as a seesaw.
Cold Companion for Hot Welding Head
Car manufacturers are particularly affected by this issue, waging a never-ending war on welding stress. Some try to resist or counteract the distortion with additional material. However, this makes the part heavier, ultimately increasing fuel consumption of the car.
Other alternatives may include laborious reworking of the component: optimized heat management or fixturing and clamping to remain within the stipulated tolerance band, but both options are expensive. Given the limitations of current approaches, the industry warmly welcomes workable solutions to this challenge.
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