Stainless metal pipe welding is gravy work. Always has been. Always will be.
If you can do it and do it well, you are the man and you will by no means go hungry. However it takes some consideration to detail to do it right.
The main thing that separates the boys from the boys or should I say, the real welders from the rod burners is the willingness to follow procedures for welding stainless steel. Procedures like waiting for the pipe to chill in between passes, keeping the hot tip of the rod shielded with argon, snipping the tip of the tig welding rod when it gets crapped up, keeping your tungsten sharp.
One of the main procedures I am talking about is PURGE. Stainless metal absolutely needs to be purged with argon gas with a view to forestall sugaring. Sugaring can be called granulation however it is severe oxidation no matter what you call it.
You cant even get away with tack welding without an argon purge that shield the back side or inside of the pipe. So how do you do it? How do you protect the back side with argon?
Often it is completed with aluminum duct tape. The ends of a stainless metal pipe are taped shut and the whole inside is purged with argon gas. Even the opening in the pipe joint itself is taped in order that argon can fill the whole pipe and push out any oxygen. The tape is peeled back just sufficient to get a tack as soon as the pipe is purge enough.
What is enough? The only way to tell for sure is with an oxygen analyzer. A bic lighter will not do the trick. Even 2% oxygen content material will blow out a bic lighter. And a couple of% oxygen will end in a black root pass.
There are some other down and dirty ways to check the purge but an oxygen analyzer is the certain way.
Listed below are just a few ideas that will allow you to get a very good purge on the stainless metal pipe you weld.
Make positive there isn’t a water inside the pipe…not even a drop. One single drop of water will throw a monkey wrench in your purging till it evaporates. Keep in mind what is in water? Hydrogen and oxygen.
Poke a vent gap in the uppermost place you may find. Think of argon as if it was water. Because it is heavier than air, it will fill up any area like water, displacing the air as it fills each nook and cranny.
More purge gas flow is not always better. A high and turbulent flow of argon will not essentially purge a pipe quicker than a lower flow rate. And a diffuser on the top of the top of your argon hose often lets you use a higher flow rate. A homemade diffuser might be made with some stainless metal wool , some perforated stainless sheet, and a bit of sheet metal.
Once you verify a very good purge, you might be ready to tack. Peel the tape back just sufficient to tack and let cool a bit and re tape. Then tack once more one hundred eighty degrees apart. Continue until all tacks are in place.
More tips for welding stainless pipe…
Laying an 1/eight inch wire within the root works higher than dipping a 3/32 inch rod.
Use a feather edge bevel. No land wanted
You may fix areas that don’t penetrate by re welding
Use only stainless steel wire brushes and only use files which have only been used on stainless steel.
Use just sufficient amperage. Using too much amperage will overheat the stainless steel and make things go south quick.
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