Centuries ago, sailors would tell stories of dastardly sirens. At first, they’d appear as beautiful, charming women floating in the water. The sailors would be mesmerized and duped into believing that all their problems would melt away if they could reach the sirens. But as they got closer and closer, the beautiful women would turn into horrifying monsters.
For too many welders, stainless steel has become a siren. It sounds like the world’s greatest weld metal, but the more and more you weld it, the more and more it quickly becomes a living nightmare. While many welders can weld stainless steel, they often end up destroying its stainless characteristics. But it doesn't have to be this way. Stainless steel can be as easy to weld as mild steel if you know the right tricks and utilize the proper welding technology for your job.
Why Stainless Steel?
Stainless steel gets rid of one of metal’s main weaknesses: rust. By adding chromium to the mix, we create material that doesn’t stain or rust and is actually stronger than plain steel. Unlike galvanized steel, which is coated in a protective layer, stainless steel keeps its rust-preventing properties even if its surface becomes scratched.
These properties give stainless steel a huge advantage for any application you want to keep rust-free. Whether you’re crafting furniture, food processing equipment, or kitchen sinks, they all heavily rely on stainless steel.
Identifying Stainless Steel
A brand-new piece of mild steel can be as shiny as stainless, making it difficult to know which is which. Before beginning the welding process with stainless steel, you’ll need to be sure you’ve actually got stainless steel.
There are endless ways to identify what type of material you're working with, such as a spark test. However, when trying to determine if a material is stainless or not, the easiest solution is to simply place a magnet on the material. Most types of stainless will not stick to the magnet.
WELDING STAINLESS STEEL TIPS AND TRICKS
We often treat stainless steel as one type of steel. However, stainless steel is really made up of four main types.
THE FOUR MAIN TYPES OF STAINLESS STEEL INCLUDE:
- Austenitic: The most popular type of stainless steel, austenitic also tends to be the most expensive. Compared to other types of stainless steel, austenitic stainless steel is high in nickel content, in addition to chromium, nitrogen, and molybdenum. This type of steel is well-known for its malleability and is commonly used for kitchen cutlery and storage components.
- Ferritic: This type of stainless steel is primarily made of chromium with low amounts of carbon. Ferritic stainless steel is magnetic and is renowned for its resistance to stress corrosion cracking. It’s commonly used for car components, kitchen cookware, and industrial jobs.
- Duplex: This stainless steel consists of combinations of ferritic and austenitic steel. It tends to be less expensive than pure austenitic steel and is often used in the underwater oil and drilling industry because it stands up well against the potential corrosion caused by saltwater.
- Martensitic: At a structural level, this steel is very similar to ferritic stainless steel, just with a higher percentage of carbon. This difference in carbon levels allows for martensitic steel to be hardened to great extents. This steel is often used in valves or pumps.
The majority of stainless steel used for welding is austenitic because it tends to be the easiest for welders to work with.
Despite its popularity, by no means is austenitic stainless steel the perfect solution for everything. Ferritic stainless steel can often be cheaper, making it a tempting choice when already considering the cost of stainless vs. mild steel. Martensitic stainless steel can also be welded, though it’s a little trickier to work with.
HOW TO CHOOSE THE RIGHT WELDING MACHINE AND FILLER MATERIAL FOR STAINLESS STEEL
Upwards of 90% of the problems with welding stainless steel start with the wrong setup. Trying to use the same settings you’d normally do for mild steel will often get you into trouble. If your machine has an auto-set feature like the Millermatic 211, it’s as simple as turning the knob to stainless.
If you don’t have an auto-set welder, you’ll want to use the reference guide that came with your machine. This will dictate not only your amperage and wire speed but also the filler material you’ll want to use.
For most welders, getting a good fusion between stainless pieces isn’t necessarily the hardest part. It’s doing so without ruining the material’s stainless properties. This is because heat can mess with the structure of stainless steel. Each of the types of stainless steel reacts differently to heat, with different methods of how to prevent heat-affected zones (HAZ) when welding stainless steel.
With ferritic stainless, heat will cause the affected areas to become brittle. For martensitic stainless steels, it’ll develop cracking. Austenitic is the most forgiving, but too much heat can still cause your material to lose some of its stainless properties.
Regardless of the type of stainless steel, the principle is generally the same. You want to manage your heat. For most situations, this means doing everything you can to keep the temperature of your stainless steel as low as possible. There are a million ways to do this, but we’ll cover a few of our favorites.
The first heat management tip is to avoid welding in the same area for too long. If you’re MIG welding, this usually means using as fast of a travel speed as you can while still staying in control of your weld puddle. The slower you move, the more heat that’ll build up, creating a larger HAZ. Creating HAZ is a common mistake to avoid when welding stainless steel. If you’re still learning to control your travel speed, it’s recommended you ease into stainless. Since stainless can often be five (or more) times the price of mild steel, mistakes are quite a bit more costly.
Chill bars are another common solution for managing heat. This usually means using some kind of aluminum or copper backing clamped to your workpiece. You’ll want your backing close enough to your weld spot to suck out the heat but not so close that you’ll accidentally weld your chill bar to your base metal. Aluminum and copper have significantly higher thermal conductivity properties compared to stainless steel, allowing them to pull heat from your weld spot and keep the stainless at a lower temperature.
I don’t think we’ve ever met a welder who likes purging. Many people will avoid purging if they think they can get away without it. But stainless steel is one of those materials that really benefits from careful consideration about how your protective gas is covering every angle of your weld. But what is purging, and why is it important for welding stainless steel?
Weld purging is a common process where oxygen is evacuated from a pipe, tank, or chamber using a noble gas such as argon or nitrogen. The oxygen in the atmosphere will try to attack the chromium in stainless steel when it’s heated. Since chromium is what strengthens stainless steel and makes it actually stainless, protecting chromium from the atmosphere while it’s heated is key.
However, purging can be a pain to go through, especially if proper safety protocols are followed (which they should). Nevertheless, purging is essential for those looking how to weld stainless steel without losing its properties.
Depending on your material thickness, you might be able to get away with not purging or even using a chillbar as backing for your protective gas. However, if you’re welding thinner plates or pipes, purging is the best solution.
If you don’t purge when it’s needed, the front of your weld might look great, but the backside won’t hold up. For food-grade applications, purging is almost always required. For other applications, a non-purge weld might pass, but the overall strength and life of your weld won’t be nearly as good.
If you’re unsure how to purge, check out our in-depth article here.
With the right steps, welding stainless steel can be as easy as welding regular steel. Most problems that welders face usually come from using the wrong parameters. If you’ve lost your machine’s reference guide, you might be able to find it online. For your next machine, you owe it to yourself to look at an auto-set machine (like the Millermatic 211). This feature avoids so many problems when choosing the right parameters.
WELD STAINLESS STEEL LIKE A PRO WITH WELDING SUPPLIES FROM IOC
While stainless steel certainly comes with its unique challenges, this doesn’t mean you should shy away from this amazing metal. Whether you’re utilizing MIG welding or TIG welding, there are quite a few benefits to working with stainless steel. As one of the most durable and rust-resistant metals out there, stainless steel can do amazing things and has practically countless applications.
But to effectively wield stainless steel, you need the right welding tools and supplies. That’s where we come in. At Welding Supplies from IOC, we have the widest selection of welding machines, supplies, and accessories to help you tackle any job. Whether you’re a professional welder or a weekend warrior, our selection, competitive pricing, and knowledgeable support team can help you get the job done.
Using these best practices for welding stainless steel, we are confident that, with the right tools, you can perfect your welding technique. For more on the best machines and articles, check us out Welding Supplies from IOC and learn more about the art of welding.