How do I weld or braze stainless steel tubing?

“How do I weld or braze stainless steel tubing?” is a question you may want to ask when dealing with stainless steel tubes. Although the common practice is getting your manufacturer or supplier to do this task for you, it is still possible to do it on your own. To be able to answer this question however, the first thing you need to know is the difference between welding and brazing.

Welding and brazing

Welding and brazing are two methods used to join metals together. Brazing is a soldering process that uses a filler metal that has a high melting point to join the metals. The filler metal to be used should have a higher melting point than the one being soldered. In this case, it should have a higher melting point than the stainless steel. Gas is the heat source used in soldering and various gas combinations can be used, i.e. oxygen-acetalyne, oxygen MAPP (methylacetylene-propadiene, stabilized) gas, and oxygen-propane. In welding, on the other hand, the metals are heated up to the melting point before sticking the tubes together at the joints. The heat source used in fusion welding can either be gas or electric.

For welding stainless steel tubing, it is best to use electric power. The stainless steel tubing is grounded and the electrode is brought closer to the current arcs across the gap. This is what creates high heat of up to 10,000 to 20,000 degrees Fahrenheit. The power sources that can be used include AC, DC straight polarity, DC reverse polarity, constant voltage, constant current, single, and three phase.

So how do I weld or braze stainless steel tubing exactly?

As mentioned in brazing, you have to use a filler material that has a higher melting point than the stainless steel tubing. A metal that you can be used as filler is silver, but not pure silver, ofcourse. What you need is silver that has copper and tin in it, but not cadmium.

The first thing to do is to coat the stainless steel tubing with flux to prevent the formation of oxides. Make sure that you get a cadmium-free flux as well. The stainless steel tubing and the filler are heated together until melting point. When the melting point is reached, the molten filler will flow to the joint by capillary action and this will bond the two tubes together. This process makes the joint very strong. Brazing equipment is largely available and easy to operate. You can have everything you need for under $200. The disadvantage of brazing, however, is that the heat is hard to control and, in effect, can cause annealment and brittleness. This can make the stainless steel tubing lose its corrosion resistant element.

The best way to weld stainless steel tubing is by using TIG welding method. It uses a non-consumable electrode that allows you to control the heat. The electrode is held by a torch and inert gas flows through and around it. The tubing is heated and melted to join them together and the gas shields the arc and avoids oxidation. Its main advantage is that it is a precise method and is the most recommended for stainless steel tubing. However, the equipment can be quite heavy and expensive at around $1,200 to $1,500 dollars.

If you are still asking “How do I weld or braze stainless steel tubing?” tutorials and short courses are usually available in technical colleges. You can also go to your local library and read up on the basics of brazing and welding. Also, when buying brazing and welding equipment, be sure you have an expert with you to help you buy the right equipment. Do not forget to use them properly and with safety precautions on hand. You should be able to answer the question “How do I weld or braze stainless steel tubing?” very knowledgeably first before you even attempt to do it on your own.