Stainless steel has a wide range of applications in different industries. The excellent corrosion resistance of this steel type makes it a superior option. However, welding this material is more difficult for several reasons. People think about using flux-cored wire to weld stainless steel. But the question is: can you weld stainless steel with flux core?
Using regular wire in welding stainless steel requires shielding gas. Less-experienced welders often use the wrong shielding gas, resulting in poor welds on stainless steel. In such a case, flux-cored wire can help create a weld on stainless steel without the need for shielding gas. In this article, I’ll discuss the use of flux core for welding stainless steel. So, let’s begin.
What is Flux Core Wire?
Welding stainless steel is a bit trickier, which I discussed in a previous article. That’s why many welders turn to flux-cored wire for a stronger weld on this steel type. But what is flux wire, and why is it so helpful?
It is a hollow wire. The external side of this wire is metal. However, the inside of the wire is hollow and filled with flux. This flux is a special powder-filled wire that can melt and produce gas during welding. In this way, you don’t need external shielding gas when using flux core wire.
As you know, welding involves heat and melting metal pieces. During welding, the FCAW wire is fed through the welding gun into the weld. Due to the intense heat, this flux-cored wire melts and fuses at the weld. However, the flux (powder) inside the wire also melts and emits special gas inside the weld.
Due to this gas,oxygen can’t get to the weld pool, resulting in a weld with no contamination. Interestingly, there are different types of flux core wires available. However, two primary types of those wires include:
- Gas-shielded flux core wire
- Self-shielded flux core wire
These two flux cores differ in one fundamental point. The gas-shielded flux core wire does not rely solely on flux for gas. Instead, it requires additional (external) gas to make it strong. On the other hand, self-shielded flux core wires rely on flux for the gas, and don’t need external shielding gas.
Are you still wondering what the wire is made of? These flux-core wires are available in various materials. Those include mild steel, stainless steel, and more. However, you should choose flux core material or the material that you’re going to weld. Suppose you’ll need stainless steel flux-cored wire for welding stainless steel.
Can You Weld Stainless Steel with Flux Core?
Yes, you can use flux-core wire to weld stainless steel. Conventional wires require shielding gas; otherwise, the weld is prone to contamination. However, using flux core wire to weld stainless steel requires no shielding gas. This wire flux provides gas, ensuring a strong, contamination-free weld with slag.
It is noteworthy that you just make sure you use a specific type of flux core wire for the material you weld. For example, you’ll need stainless-steel core flux-cored wire for welding stainless steel. The best options are E308LT-1, E309LT-1, or E316LT-1. Why? The reason is that these stainless flux-core wires contain a mixed chromium in flux.
As you know, stainless steel also contains chromium. The chromium presence in this stainless steel improves its corrosion resistance. So the chromium from flux complements the composition of stainless steel (chromium). The chromium-forming flux maintains the corrosion resistance of welded stainless steel.
Using the wrong flux-cored wire will make it less effective. Imagine using mild-steel flux-core wire while welding stainless steel. The mild steel flux-cored wire will melt and fuse during the weld. However, mild steel is less corrosion-resistant, which affects stainless steel’s performance. In short, you can use flux core to weld stainless, but the flux core wire must be stainless.
Self-Shielded vs Gas-Shielded Flux Core for Stainless Steel Welding
You’ll see both self-shielded and gas-shielded stainless steel flux core wires. Both of these options can be used to weld stainless steel. However, the confusion comes when you don’t know which of these flux cores you should use.
Remember, both of these flux-core wires differ in their gas requirements. When you use self-shielded flux core wire, you won’t need additional shielding gas. The flux will melt and produce gas to protect the weld. On the other hand, when using a gas-shielded flux core, you’ll need shielding gas.
I recommend using self-shielded flux-core when welding stainless steel in outdoor conditions. The airflow can affect how the shielding gas reaches the weld. In such a case, using a self-shielded flux core is beneficial as it produces gas inside the weld. However, there is a drawback: these wires can produce larger slags.
As a result, the appearance of welding on stainless steel may not be appealing. You should use gas-shielded flux-core wire when welding stainless steel indoors. In this case, you’ll need additional shielding gas that you usually need when using conventional wire. I recommend using 75/25 Argon-CO₂ as shielding gas in this case.
If I were to give my opinion, I would prefer a gas-shielded flux core in most cases. Why? That’s because this wire helps make a weld with small spatter or slag. Additionally, you gain greater control over shielding gas, resulting in a stronger weld. Above all, this wire also ensures a better weld with a better visual appearance. The self-shielded flux core is only helpful in welding stainless steel outdoors.
Advantages of Using Flux Core for Welding Stainless Steel
Many people prefer using flux core wire when welding, especially stainless steel. The reason is that these wires offer many advantages over conventional welding wires. In the section below, I’ll explain some of the benefits of flux core wires.
1- Better Melting & Penetration
When used in welding, flux core wire offers excellent penetration. Remember, this wire melts smoothly and hotter than conventional wires. As a result, the molten form of this wire can penetrate deeper into the weld. In this way, it creates a weld with better strength and durability. In fact, this deeper penetration is very useful when welding thicker stainless steel. The molten wire will penetrate deeply into the thicker metal, ensuring a better weld quality.
2- Works Better Outdoors Than MIG Welding
As mentioned earlier, flux-core wire offers an excellent welding experience in outdoor conditions. As you know, wind or airflow is bad when welding in an outdoor setting. Airflow can remove shielding gas from the weld. As a result, the weld becomes prone to contamination.
However, flux-core wire eliminates the need for a separate shielding gas. When this wire melts, its flux melts as well, producing gas that remains in the weld. This gas cannot be removed by wind, preventing oxygen from reaching the weld. In this way, you can make a strong weld on stainless steel even in harsh outdoor conditions.
3- Consistent Corrosion Resistance
Undoubtedly, stainless steel is excellent at resisting corrosion. Right? The main reason corrosion resistance occurs is the chromium oxide layer. This layer forms on the surface of stainless steel when its chromium reacts with oxygen. During welding, this chromium oxide layer can be damaged. This can affect the corrosion resistance of stainless steel.
However, using stainless steel flux core wire maintains this material’s corrosion resistance. The reason is that the flux of this wire contains mixed chromium. This chromium remains on the weld spot when the FCAW wire melts and fuses with the weld. This ensures that stainless steel remains corrosion-resistant even after the weld.
Frequently Asked Questions
What metals can I weld with flux core?
You can weld almost every metal with decent thickness. A metal with a thickness of over 0.9 mm can be welded using this wire. You can also use flux-cored wire to make a strong weld on stainless steel.
What kind of flux core wire for stainless steel?
You must use flux core wire made of stainless steel when welding this material. The most popular options of these wires include E308LT-1, E309LT-1, or E316LT-1.
Are flux-core welds as strong as MIG?
Yes. Flux-core welds are strong, especially when made with gas-shielded flux-core wire (FCAW-G). Even in windy outdoor conditions, you’ll still get decent weld, but their appearance may not be ideal. MIG welds look more refined and visually appealing than flux-core welds.
What are the disadvantages of flux core welding of stainless steel?
A prominent disadvantage of flux-core welding is that it produces more slag and a rougher bead. You’ll notice obvious slag on the surface of the stainless (welded spot). This slag or spatter can affect the look of your stainless steel part.
Conclusion
In short, welding stainless steel with flux-core wire is possible. In fact, many welders use this wire, especially when they weld stainless steel in outdoor conditions. The wind or airflow cannot affect weld quality when using flux core wire. Remember, this flux-core wire contains a chemical. Upon heating, flux produces gas that protects the weld and prevents oxygen from attaching to the weld. As a result, the weld remains safe from air contamination and becomes strong.