When welding on thinner metals, such as sheet metal, it is very common for people to complain about warped welds. After the weld cools, the metal around it is warped or bent out of shape ruining the project. To avoid this disappointment, you first need to know why it happens, and then how to minimize its effects. The following picture shows a typical cause of distortion cause by the metals cooling.
When you are welding, the welding rod leaves behind a filler metal at very high temperatures, hotter than the melting point of the base metal. Because of this, the bead tries to shrink as it cools. However, the base metal prevents this because it is not molten. This results in large amounts of stress that can warp sheet metal, or other thinner pieces of metal.
All metal has these properties, however stainless steel is more likely to warp because when it is heated it has a relatively large amount of thermal expansion and low level of heat dissipation, compared to other metals.
Now that you know what is causing your welds to warp, there are a few things that you can do to minimize the amount of distortion or use it to your advantage. Keep in mind, no matter what you do, some warping will always happen. This is simply of property of cooling metals at dissimilar temperatures.
The most effective way you can avoid this problem is to make sure you don’t over weld. This is because the more filler metal in the bead, the more it is going to shrink. Not over welding will also result in cleaner looking, stronger welds. It can also save your time and money by using less welding electrodes to complete the same number of welds.
Another strategy is to do the bead in sections, waiting for the weld to cool between. This lets lets some of the stress in the metal be dissipated, resulting in straighter welds.
By completing your weld using fewer weld passes you can get more desirable welds, since shrinkage increases from each weld pass
You can also apply welds bordering on the neutral axis, or the midpoint of the piece. This will diminish warping by way of providing less leverage for the shrinking forces to bend the plates out of adjustment. You can additionally cancel out the warping with another weld on the opposing edge.
You can also adjust for the warping, by placing your parts to be welded a little off orientation from the planned location. After wards although they warp, they will warp into the correct place.
A well-planned welding arrangement encompasses placing weld metal at contrasting facets of the fabrication so that, as the arrangement contracts in one place, it counterbalances the shrinkage powers of welds already made. An example of this is welding alternately on both sides of the neutral axis in making a complete joint penetration groove weld in a butt joint.
If you are welding on thin enough metal, using strong clamps that lock the pieces into the desired position and hold them until welding is finished will work for you. While there is some movement or distortion after the welded part is removed from the jig or clamps, it will be lower compared to the amount of movement that would occur did not use them.
You can also control the heating and cooling of the piece, using sand or a propane torch. This will even out the cooling, resulting in less stress in the metal.
No matter which method you decide to use to make your welds not warp, there is always going to be some distortion. However if you plan ahead and know how the metals will warp, you can avoid ruining your welding project.
