Welding a thin material like sheet metal to thicker metal surfaces can be somewhat of a headache, especially without taking the right approach to welding sheet metal. Below, you'll learn why ordinary welding techniques for thick steel won't work for fusing thinner metals and how you can avoid damaging or destroying work pieces by using the proper techniques.
Those Old Welding Tricks Just Won't Work
Most welding techniques that work perfectly well for thicker metal won't work, as they focus heavily on applying a continuous bead on the work piece. These techniques are fine on thicker metal, which takes a bit longer to absorb the heat of the weld.
On thinner metals, heat transfer occurs more quickly, resulting in a number of problems. For starters, exposing the sheet metal to too much heat could cause discoloration of the back side of the thinner work piece. This could be a problem if you're concerned with the material's cosmetic appearance. Too much heat can also cause thin work pieces to warp.
The other issue is blow-through, which happens when the metal completely melts and the molten material is effectively blown out of the work piece. It's easy for thin metals to melt and create large holes or gaps where a weld should be, especially if you're not paying attention to weld temperatures and duration.
Techniques for Reducing Penetration and Heat Transfer
One of the tricks to keeping your welds cool enough to properly set involves applying the weld in short bursts. This non-continuous movement gives both the weld and the surrounding metal enough time to cool before applying another burst. Welding expert Malcolm Vardy suggests leaving less than half a second of cooling time in between bursts, although such times could be longer or shorter depending on the nature of the weld.
Another method involves focusing the majority of the welding heat on the thicker piece while allowing the pool of molten metal to overlap the thinner metal. This can be done by quickly and gently "pushing" the molten metal towards the thinner work piece, allowing it to fuse to the thicker piece without melting from the excess heat. This technique keeps the thinner metal from being subjected to temperatures during welding that could cause the work piece to melt.
Keeping the above tips in mind can keep you out of hot water when it comes to welding sheet metal and other types of thin steel onto thicker work pieces. For more advice or techniques, ask a representative from a company like Sheridan Metal Products Ltd steel welding.