by Jason Becker
We're busting out another viewer submitted request from our audience members. A few viewers have requested us to do some thin gauge stainless steel to a thicker piece of material. This process is a much easier than most people think.
Stainless steel has a relatively low thermal conductivity rate, meaning it does not dissipate heat rapidly. It takes a bit for the stainless to heat up but once it does, it will hold the heat longer than some other materials. The trick to welding the thin to thick is all about speed and your work angle. You need to make sure the the bulk of your heat is placed onto the thicker material, and the weld puddle for all intents and purposes is washed up on to the thinner material. The whole process happens pretty quick so you will have to judge your travel speed accordingly. Moving too slowly will cause a much wider puddle than needed and will erode the top edge in a lap joint, or cause sugaring on the backside of a t-joint. Moving too fast will cause a lack of fusion to both the thick and the thin material, you have to establish the size of the puddle you feel is appropriate and maintain it throughout the joint.
There are a couple other tricks that will help you to weld thick materials to thin metals, my personal favorite is to use a chill block to help pull away some of the heat on a lap joint, or placed on the backside of t-joint to prevent burn-through and/or sugaring. A chill block is pretty much a thick chunk of copper, brass, or even aluminum that will pull some of the residual heat out of the part. These materials work great due to their high rate of thermal conductivity. The are able to rapidly absorb and dissipate heat. By placing the chill block on the back side of the material oxygen cannot get to the heated material and therefore cannot react with oxygen and oxidize.
Another sound practice method to get into is to make several small tacks throughout the piece, I usually go about 1" to 1-1/2" inches apart. Stainless has a tendency to draw (pull) in the direction of the heat. This can cause warpage in the material and create a less than ideal situation for welding. As the material starts to draw, it creates voids which are harder to fill in. The tacks help to keep the piece in place so that there is no movement along the seam while you are welding. These little tacks will save you a lot of time and frustration while you are welding.
As you can see in the video, thin stainless to thick stainless isn't as difficult as most people would think. You just need to watch you work angle, travel speed and heat input. Thanks for watching the video and reading the article and until next time, Make Every Weld Better Than Your Last.