Do you believe that you can weld any material on earth?
You know that welding is only done on metals and even plastics. But what you probably don’t know is that this is easier said than done. Welding may seem all the same to you but it actually has different types, with each type more suitable for specific materials than others.
This is also the case when it comes to welding metals. Contrary to popular belief, you cannot simply weld any metal using any type you want. Each metal has unique properties that allow it to either be easy or difficult to weld.
Among the many metals around, stainless steel is one of the most notorious materials to weld. In fact, many don’t even know if this is possible. But can you actually weld stainless steel? And if so, how do you do it?
All those questions will be answered if you continue reading. Not only that, but you will also discover if the most popular welding types around, namely MIG and TIG, are suitable for it.
Can You Weld Stainless Steel?
Yes, you can weld stainless steel.
In fact, doing so is not really that different compared to welding other metals. But admittedly, its unique characteristics make it a little complicated to do so. This is because stainless steel has certain requirements when it comes to heating and cooling that other metals do not need. Not only that, the filler material must always be appropriate to the type of stainless steel being welded.
And because there are also different types of stainless steel, you need to weld them differently. Each stainless steel type has characteristics that you need to take note of if you want a quality weld.
Welding stainless steel is doable but it is not as straightforward as welding other metals.
Is it Difficult to Weld Stainless Steel?
Are you now wondering how difficult it is to weld stainless steel?
For most beginners, it can be a challenge especially because of its heat-retention properties. If too much welding heat is applied, this metal had the tendency to warp or become distorted as it cools down. To avoid this, controlling the heat is important. And if you have yet to master heat control when welding, don’t be surprised to see warping on your workpiece.
Stainless steel is renowned for its finish, which can be a nightmare for those who want a flawless finish when welding. This material gets scratches easily and any scratch or physical flaw present will be immediately visible. So if you want a smooth finish, you need to observe proper welding practices at all times, from preparation to finishing.
Not only that, stainless steel is more difficult to weld than other metals because of its higher electrical resistance and heat expansion and lower heat conductivity and melting temperature. You need to keep all of these in mind when welding, but sadly, this is easier said than done.
How to Weld Stainless Steel
Because of their physical characteristics, not all welding types can be used for stainless steel. Only those that involve an electric arc are can be used, namely stick or shielded metal arc welding, MIG or gas metal arc welding, and TIG or gas tungsten arc welding.
Despite having three options to choose from, how you can weld stainless steel will depend on its type. Stainless steel is classified into three distinct types, as well as combinations of these types, and each of them have their own unique characteristics that will affect their ability to be welded easily:
- Austenitic Stainless Steel – preheating and post-heating are not necessary but it has a maximum interpass temperature, which means you must pause welding when the base metal reaches this temperature and allow it to cool down first before you continue welding. Also, fast welding at high travel is needed to avoid any distortions on the material. Low welding current is often sufficient for this type.
- Martensitic Stainless Steel – the chromium and carbon content present in this type are balanced, and this affects its hardening capacity. Because of this, most of the stainless steel under this category require preheating and post-heating before letting it slowly cool. The heat applied must be consistent as you weld and must meet the minimum interpass temperature.
- Ferritic Stainless Steel – welding in a single pass is sufficient, but the welding process negatively affects the resulting weld. To improve its quality, you need to quench it with either water or air after welding. Also, thicker materials only need low heat to avoid grain coarsening that leads to cracks in the joints.
A duplex type, which is a combination of austenitic and ferritic stainless steel, also exists. While it has the characteristics of both ferrite and austenite, you only need to ensure that the heat applied is within its heat input range when welding.
In general, you need to observe the following when it comes to welding stainless steel:
- Wear personal protective equipment (PPE). This not only applies when you start welding; you also need to wear them even while preparing the material for welding and as you do any necessary post-heating. Toxic fumes and sparks are produced when welding and you need to be protected against them. You must also ensure that you work in an area without any flammable items nearby.
- Prepare – because stainless steel is a delicate material to weld, there should be no room for error if you want a flaw-free finish. You need to prepare not just the material itself but also your workspace. Plan ahead, especially in terms of what kind of joint you will be using and how you will do the actual welding.
- Practice on other pieces first – there is no way to undo your work, so any mistakes you make on stainless steel will be glaringly obvious. Practice on spare pieces of material first to get the feel of it. The more you practice, the less the chances of committing errors as you weld.
- Follow proper welding practices – make sure that you follow the right procedures of your chosen welding method. Not only that, keep the material in place to prevent scratching it as you weld. If you need to, use a clamp or any other mechanism. Always keep a close eye on your work because it is easy to damage or discolor this metal when welding.
Welding stainless steel may be a bit more complicated, but it doesn’t mean you can’t do it. Even if you are just a novice welder right now, you can work on stainless steel; you just need to learn and understand how to properly do it.
MIG Welding Stainless Steel
If welding stainless steel involves thick materials, MIG welding is most suitable. This is the preferred method for those who prioritize cost-effectiveness over the neatness of the weld.
This type allows you to weld quickly but the specific settings required to weld will depend on the MIG welder you are using. This is because different machines have different recommendations when welding stainless steel, specifically in terms of the wire to be used and the feed rate, the power supply, shielding gas, size of electrode, and so much more. This information is usually found on the chart that MIG welding machines come with.
There are different modes of metal transfer in MIG welding that can be used for stainless steel, which are:
- Spray Transfer – the electrode metal is transferred via a voltage electric arc to create a weld line with a clean finish. This method also includes pulse spray transfer wherein the electrode is melted by the pulsing current and the molten material falls onto the workpiece.
- Globular Metal Transfer – a large blob or molten globule forms at the electrode tip and eventually drops to the workpiece.
- Short-Circuit Transfer – the gap present between the workpiece and the electrode is filled up with filler material. This happens when there is a slow feed rate that results in a short circuit that momentarily extinguishes the arc.
Aside from that, you also need to choose the proper shielding gas to use. Different manufacturers are in consensus that pure inert gases are not recommended, that is why the shielding gas used is typically a mix of different gases, with the tri-mix gas being used most often.
Due to the nature of the material, you also need to ensure that a brace is present to hold the material in place and you must evenly spread out the heat when welding. These two are vital to avoid joint distortions on stainless steel as you weld, which is a common issue with MIG welding.
MIG welding on stainless steel is commonly used for repair and maintenance works.
TIG Welding Stainless Steel
TIG welding is the most popular type when it comes to working with stainless steel. Ideal for thin materials, this is preferred by many welders because it results in a neater finish compared to MIG welding. Unfortunately, this method may not be suitable for inexperienced welders that have yet to master it.
Do note that the clean weld it produces is because of the slower welding involved, which also requires proper techniques to achieve. Fortunately, distortions are more easily preventable with this type because of the careful welding involved. But no matter which TIG welder you use, what is important is to have the right speed, shielding gas, and heat applied when welding. Just like in welding other metals, you also need to make sure that your chosen tungsten electrode is sharp.
Discoloration is also common when using TIG welding on stainless steel, especially when too much heat is applied. To avoid it, not only should you use only the right amount of heat but you also need to keep an eye out on the color of the metal when welding. Once it starts changing color, it means it is too hot and must be cooled down first before you continue with the welding.
Experienced welders suggest using the DCEN or DC electrode negative setting and to have a welding current with a ratio of 1 amp for every 1/1000-inch thickness of the metal. Argon is the most ideal shielding gas for this because it prevents a reaction between the molten material and air. But if you are automating the work, you can use a mix of argon and other gases.
Welding Stainless Steel to Mild Steel
Welding dissimilar metals is a common practice in various industries, as it helps them not only to save money but also to meet certain requirements that only welding such metals will meet. This is also the case when it comes to welding stainless steel particularly to mild steel.
Both MIG and TIG welding can be used to join these two metals through welding. You can follow the usual procedures with any of these two methods, but what matters more is that you use the right filler material. In this case, the 309L filler material is the most suitable.
Some welders do frown upon welding stainless steel to mild steel or even completely discourage it. This is because the resulting weld is often inferior compared to the one produced when welding the same metals. Not only that, but you also need to prepare them separately before welding. Heat also affects them differently, and this makes the entire welding process much more complicated. This combination of metals can also affect the overall corrosion resistance of both metals.
Simply put, welding stainless steel to metal is doable but it is a complicated process and the resulting weld is often brittle compared to the weld joint between the same metals.
Always keep in mind that when welding stainless steel to the same or different metal and using whatever method you choose, prep work is vital. This means ensuring that the surface of the metal is free from any contaminants, you have practiced welding on other workpieces, and that you have a clear plan on how you should weld.
There is no room for error if you want the clean finish when welding stainless steel.