The choice of the material to weld is very important in welding projects, both for DIY projects and for small repairs. That is why we have written an article on how to weld stainless steel: to give you all the information you need to get the WOW effect!
Welding steel… Sure, but which one?
To be as clear as possible, in this article we will only explain how to weld stainless steel. There are many types of steel and there are also many types of stainless steel, so it is important not to mix up materials.
Stainless steel is an alloy composed of iron with a chromium content of at least 12% to 30%. In this alloy, carbon is present in very small quantities or not at all. Because it is the chromium that makes stainless steel stainless! The chromium contained in the alloy oxidises and creates a very dense surface patina that makes stainless steel resistant to external agents.
As we said, there are different types of stainless steel, some can be welded and some cannot. That’s why you should be careful when choosing the material for your projects!
The most common welding stainless steels on the market are: AISI 304 and AISI 316.
How to recognise them at first glance? Easy: if a magnet sticks to a steel that looks stainless from the outside, it is almost certainly a 400-grade steel, such as AISI 430.
If the magnet does not stick, then it is probably 300-grade steel.
When to use stainless steel in welding projects?
Stainless steel is a cool but very expensive material, so you usually choose it for projects where its antibacterial and durability properties are crucial. But these properties remain so only if it is handled with due care. That’s why it is important to know how to weld stainless steel!
And if you’re still not sure about the material to choose, have a look at the article on how to weld iron.
How to stick-weld stainless steel
With a stick welding machine, you have to pay attention to the filler material you choose, that is the electrodes to weld stainless steel.
If you are welding 304 steel, you can use 308 alloy electrodes, whereas for 316 steel you absolutely have to use electrodes of the same alloy: 316.
How to wire-weld stainless steel
Also with a wire welding machine, you have to choose the right filler material. The wire roll for 304 steel must have 308 alloy, while the wire roll for 316 steel must always have 316 alloy.
In addition, you should use a 3 m (maximum) torch with Teflon or graphite liner.
Finally, you also need to have the cylinder because you will be using MAG (Metal Active Gas). The cylinder mixture must contain a maximum of 2% CO2 – not to contaminate the weld – and 98% argon.
How to TIG-weld stainless steel
If you use a TIG welding machine, it means that you are already rather familiar with welding. So, you already know that you need a welding rod specific for stainless steel: let’s see which ones.
If you are welding 304 steel, you can use 308 alloy rods, whereas for 316 steel you absolutely have to use rods of the same alloy: 316.
Mistakes not to make when welding stainless steel for DIY projects or small repairs
When welding, be careful not to alter or ruin the stainless steel because if heated too much, it loses its main characteristic, the one that makes it so cool: stainlessness.
Without giving you a chemistry lesson, let’s briefly explain what happens: at high temperatures, chromium has a high affinity for carbon. These two elements together create ‘chromium carbide precipitates’ when heated to high temperatures for a long time. Put simply: you lose the chromium in the alloy and, where this happens, rust can form, eventually breaking what you have created. So, in addition to ruining the project, you will also have wasted the money to buy stainless steel.
Another thing you have to watch out for is stainless steel’s aversion to iron. Basically, the two don’t really get along, like two enemies!
Iron pollutes stainless steel and makes it rust. It is called the ‘pitting effect’ (an expression you can amaze your friends with, talking like an expert). The problem is not only aesthetic: in the long run, rust passes through and breaks what you have created.
How can these mistakes be avoided?
First of all, use stainless steel brushes and grinding discs specially designed for this material.
Also, if you want to be even more sure, you can have the stainless steel workpiece pickled after welding. Basically, acids are used to restore the surface chromium oxides. We recommend that you have this done by a professional. Be careful with these substances, especially when disposing of them: although they are soluble in water, they should never be released into the environment!
Now you know how to weld stainless steel and make something really WOW! All you have to do is decide what kind of welding to do and buy the right materials.
Don’t have a welding machine? Well, you can choose one of helviLITE’s DIY welding machines specifically designed to make welding easy for hobby welders.