Before beginning I do want to say there are not many places that will give you the chance to learn how to TIG weld thin wall stainless steel pipe. I was lucky enough to have Fluor train me and am very thankful for being able to attend their training program! Fluor is the only reason I got to learn this skill!
What I can share is that TIG welding stainless steel pipe is not much harder than carbon steel pipe. There are a few rules to follow and you should be able to pick it up quickly! The rules are as follows:
- Purge your pipe well.
- Everything must be clean.
- Keep your tungsten moving at all times.
- Allow the pipe to cool before the next weld.
Stainless steel pipe must always be purged. The result from a less than perfect purge will cause the root to get contaminated. The slang term used in the field for root contamination or oxidization is “sugar”. Sugar is caused from the weld being exposed to oxygen in the atmosphere. The weld joint must be taped off and only untapped when you are ready to weld that part if the pipe.
In general TIG welding requires a very clean weld joint but with stainless steel this is an absolute must! The tungsten must be clean. That means cleaning it after every restart and pass. The weld joint must be filed before every pass except the root pass. Even the bevel needs to be filed on the hot pass and all color changes need to be filed to pure metal at all times. Failure to file all heat affected areas will result in the filler wire not being able to flow into the joint smoothly.
Moving your tungsten quickly is very important when TIG welding stainless steel pipe. The trick to avoid melt through and overheating the pipe is to move quickly. From the moment you strike the arc that tungsten needs to be moving. Don’t start and wait for the metal to heat up before moving. Ideally you want to start 3/4 of an inch before the area you will start adding filler wire too. This will allow enough preheat for the filler wire to flow properly. Ideally when the weld is finished it should have a copper color to it. If it is gray or dark in nature you are using too much heat or moving too slow!
When it comes to stainless steel the heat this metal absorbs and holds is unbelievable. Now add thin wall pipe to the picture and you have a radiator that is always ready to overheat! You need to allow the pipe to cool enough that you are able to touch it with your bare hand. TIG welding stainless steel pipe requires a lot of waiting for the pipe to cool. It only takes an extra inch of weld too soon to ruin the weld joint!