Tips for FCAW Welding Stainless Steel

Table of Contents > 1. Can You Flux Core Weld Stainless Steel?     1.1 Is Stainless Steel Hard to Weld?     1.2 When Should You FCAW Weld Stainless Steel?     1.3 Pros & Cons of FCAW Welding Stainless Steel 2. FCAW Welding Stainless Steel Basics     2.1 Stainless Steel Flux Core Wires     2.2 Welding Parameters for Stainless Steel 3. Flux-core Welding Stainless Steel Tips and Tricks     3.1 Check the Polarity Before Starting     3.2 "If There is Slag, You Drag"     3.3 Run 10-15% Hotter Than You Would with Mild Steel     3.4 Be Careful with Heat     3.5 Ignore the Ball on Tip of Wire     3.6 Carefully Clean Slag and Stainless Steel 4. Final Thoughts 5. 🧐Tips for FCAW Welding Stainless Steel FAQ

Stainless steel is a fantastic metal that is resistant to corrosion. Its unique composition makes it highly valuable in various applications, but it also presents different welding challenges compared to mild steel.

In general, stainless steel is weldable, but heat control is necessary to prevent distortion or burn-through. FCAW and SMAW are two methods that are not renowned for their control of heat input, especially when working with thin pieces.

That's why Flux-core welding stainless steel raises many questions. Nonetheless, in this article, we will cover the basics of FCAW welding stainless steel and provide some tips to make your tasks easier.

FCAW Welding Stainless Steel
Source: https://www.youtube.com/watch?v=yx6weJurINc

Can You Flux Core Weld Stainless Steel?

Yes, you can FCAW-weld stainless steel, although it is not often the preferred choice. Most seasoned welders will recommend MIG or TIG welding when dealing with stainless steel.

TIG is perfect for delicate, thin stainless steel components and pipes. MIG works great for medium-thickness pieces, and it is easy to perform. But what about Flux-cored Arc Welding?

MIG Welding Stainless Steel 316
Source: https://www.youtube.com/shorts/dxbvyyDUDH8

Flux-cored Arc Welding (FCAW) is undoubtedly capable of welding stainless steel, and dedicated flux-core wires are available for this purpose. However, keep in mind that stainless steel is different from mild steel.

FCAW is a self-shielded process, which means it does not require external shielding gas for welding. Instead, it produces a layer of slag that protects the molten puddle from contamination. After welding, you must remove the slag. However, while chipping it, you can damage the protective surface layer of the stainless steel.

Keep in mind that Flux core welding naturally produces some spatter. Overall, the produced welds are less visually appealing compared to GMAW and, especially, TIG welds.

Spatter During Flux-Cored Arc Welding
Source: https://www.youtube.com/watch?v=tD49lWotEjY&t=1318s

Is Stainless Steel Hard to Weld?

Stainless steel is generally weldable; however, it exhibits poor thermal conductivity and high thermal expansion. Poor thermal conductivity means it doesn't transfer heat well. Instead, it concentrates the heat in HAZ, which can lead to overheating.

Meanwhile, high thermal expansion means it highly expands and contracts when affected by heat. Combined with heat retention, stainless steel can easily oxidize, warp, or distort during welding.

Therefore, you'll need to be extra careful and avoid distortion or burn-through when welding stainless steel. To produce sound welds, you will need precise heat control, good cleaning, and clamping methods.

If you are familiar with Flux-cored welding, you know it is not a low-heat method. It lacks heat control and works best with medium- to thick pieces. That's why FCAW is not the preferred choice for welding stainless steel, but it is still capable of doing so. 

FCAW Welding Stainless Steel with SS Wire
Source: https://www.youtube.com/watch?v=rFkcQnklIOI

When Should You FCAW Weld Stainless Steel?

Flux cored welding is a quite versatile method that combines the ease of use of MIG welding with the gasless (self-shielded) approach of Stick welding. When it comes to stainless steel welding, you should use it in the following cases:

How Flux-cored Arc Welding Works
Source: https://www.lincolntech.edu/

• You need to weld outside: Since you don't need a shielding gas, you can use FCAW for quick outdoor repairs. If looks are not essential, you can repair the stainless steel pieces without worrying about wind or draft blowing away shielding gas and contaminating the pieces.

• You rarely weld stainless steel: MIG welding stainless steel requires a tri-gas mixture of Argon, Helium, and CO2, or Argon-rich blends. If you don't have these gases readily available or don't want to change cylinders, you can always use a smaller roll of flux-cored wire to finish the job. It is a more cost-effective option for occasional stainless steel repairs than building a dedicated setup you will rarely use.

• You don't have any other options available: You can use FCAW to weld stainless steel if you don't have a TIG welder or any other machine, except a flux-core welder. Today, most MIG welders also support FCAW welding. All you need to do is change the wire, and you are set for FCAW welding stainless steel. If you need a versatile option for stainless steel, mild steel, and aluminum, we recommend checking out the YesWelder DP200 Dual-pulse Welder.

Firstess DP200 Multi-Process MIG Welder

Pros & Cons of FCAW Welding Stainless Steel

Pros:

• You don't need a shielding gas, meaning you can weld outdoors.

• Can produce sound, structural stainless steel welds.

• You don't need to move cylinders around.

• More cost-efficient compared to MIG or TIG setups, especially for welders who don’t have dedicated gear.

• FCAW welders are often inexpensive or integrated into MIG welding machines or multi-process welders.
  

• Great for hobbyists who occasionally weld stainless steel.

• Much easier than TIG welding.

TIG Welding Stainless Steel
Photo by @snapterz2 (TikTok)

Cons:

• It produces slag that you must clean after the weld.

• Cleaning the slag can damage the protective layer that gives stainless steel its resistance to corrosion.

• FCAW lacks heat control, which can cause warping or distortion on thin stainless steel pieces.

• Overheating can cause oxidation.

• It produces more spatter and yields less visually appealing stainless steel welds.

• Stainless steel flux core wire is more expensive than TIG rods and MIG wire.

• All-position stainless steel gasless wires are scarce.

Gasless FCAW Welds on Stainless Steel
Source: https://www.youtube.com/watch?v=ZAXbRqYZkxw

FCAW Welding Stainless Steel Basics

If you decide to flux-core weld stainless steel, you will need the correct wire and parameters for the job. Getting these right will significantly increase your chances of successfully welding stainless steel.

Flux core welding uses hollow, self-shielded wire, filled with flux. The base has the same composition as the base metal, in this case, the stainless steel. The flux is inside the wire, and it moves to the surface once the wire melts, creating a protective layer.

Since the FCAW uses the same base as MIG welding, you need the same parameters, including the voltage and wire feed speed (amperage). Let's take a closer look at the basics.

Stainless Steel Welding with Gasless FCAW 
Source: https://www.youtube.com/watch?v=l9gAYiMyIRY

Stainless Steel Flux Core Wires

Stainless steel comes in dozens of grades, which can pose a unique challenge when choosing the right filler. The goal is to match the composition of the metal with the flux core wire.

Issues arise if you don't know the grade of the base metal. The American Welding Society classifies stainless steel flux core wires in accordance with AWS A5.22/A5.22M standard: Specification for Stainless Steel Flux-Cored and Metal-Cored Welding Electrodes.

AWS A5.22/A5.22M Standard

Since there are various grades, there are dozens of flux-cored stainless steel wire types. But, in your everyday applications, you are likely to use the following wires:

• E308LFC: Versatile choice, mainly used for 300 to 308 series stainless steel, sometimes 430.

• E309LFC: Works great with 300 to 309 series stainless steel. Welders also use it to weld stainless steel to mild steel.

• E312LFC: Designed strictly for 312 series stainless steel used in high-temperature applications.

• E316LFC: Used for 316 series stainless steel (food-grade stainless steel).

Main Types of FCAW Stainless Steel Wires and Their Applications

As you can notice, manufacturers often use the letters "FC" to indicate that the wire is flux-cored. Since FCAW typically works with thicker fillers, most stainless steel wires are .035-.045" thick, but you can also find .030, 1/16-3/32 wires on the market.

Keep in mind that many flux-cored stainless steel wires on the market are designed for use in flat and horizontal positions (F, H) only. Also, since they are scarce, gasless stainless steel wires can be pricy.

Welding positions: Most flux-cored stainless wires are limited to Flat (F) and Horizontal (H).
Source: https://www.theengineeringchoice.com/

Welding Parameters for Stainless Steel

FCAW uses two primary parameters: voltage (V) and wire feed speed (IPM). Overall, you should match the parameters according to the thickness of the stainless steel and the wire diameters.

FCAW uses voltage (V) and wire feed speed (IPM) as key parameters.

Wire feed speed directly affects amperage. A low wire feed speed can cause excessive spatter and inadequate penetration. High feed speed can cause overheating, which is common with stainless steel, and leads to oxidation, distortion, or burn-through. Incorrect voltage can cause undercutting or excessive reinforcement.

Besides base welding parameters, don't forget about welding speed and wire stickout. If you go fast, stainless steel won't heat up enough, and you'll end up with a lack of fusion. If you move your torch too slowly, stainless steel will retain excessive heat, causing discoloration (oxidation), distortion, or burn-through.

Stickout refers to the length of the wire sticking out of your nozzle. It affects the tip-to-work distance (stickout + arc length). Welding too close to the stainless steel joint will cause poor flux coverage, as it does not preheat sufficiently. You'll end up with dark surfaces (oxidation) and porosity. Welding too far from the joint will make controlling the puddle challenging.

Stickout in FCAW Stainless Steel Welding
Source: https://www.youtube.com/watch?v=yx6weJurINc

Here are some parameters manufacturers recommend when using different Flux-cored stainless steel wires:

*Note: This is a general guideline only. Recommendations may vary among different flux-cored stainless steel wires and manufacturers.

FCAW Welding Stainless Steel Process
Source: https://www.youtube.com/watch?v=avSAH4XQRV0

Flux-core Welding Stainless Steel Tips and Tricks

If you have previously MIG-welded stainless steel, you should be familiar with the basics of the process. However, Flux-cored welding can be specific, especially when working with stainless steel.

Therefore, we'll present some tips and tricks that will help you successfully FCAW-weld stainless steel. Let's see what you should do differently.

Welding Stainless Steel Using Gasless FCAW
Source: https://www.youtube.com/watch?v=8K2V4GtiYvQ

Check the Polarity Before Starting

Flux-cored Arc Welding (FCAW) works at DCEN polarity due to the physics of attraction and repulsion. So, if you are switching from MIG to Flux-core, pay attention to the polarity to avoid getting excessive spatter and a highly unstable arc.

FCAW typically uses DCEN polarity for stable arc performance.
Source: https://www.youtube.com/shorts/vvNPWCvm_10

But that's not the case with stainless steel flux wires. Most stainless steel wire manufacturers, such as ESAB, Harris, or Blue Demon, recommend using DCEP polarity with their Flux-cored stainless steel wires. 

Therefore, before making any changes, check the box for the manufacturer's recommendation. Most flux-cored stainless steel wires on the market will work with DCEP, so you shouldn't switch from the original MIG welding polarity.

Flux-core welding is often a part of MIG welding machines, as they share many of the same elements. However, Gas Metal Arc Welding works at DCEP (Direct Current Electrode Positive), or reverse polarity. DC+ in MIG focuses the heat onto the wire, allowing it to melt and create a stable arc. Interestingly, DCEP will also apply this to flux-cored stainless steel wires.

DCEP (Direct Current Electrode Positive)

"If There is Slag, You Drag"

This is a common saying among older welders that can greatly aid you in mastering welding technique. Like Shielded Metal Arc Welding (Stick) or Submerged Arc Welding (SAW), FCAW is a slag welding method.

To avoid the risk of slag inclusions, always drag or pull the torch when FCAW welding stainless steel. When dragging, you minimize the risk of trapping the slag inside the weld.

Always drag (pull) the torch when welding with self-shielded FCAW.
Photo by @arclabsweldingschool (TikTok)

 

The slag forms once the flux from the core of the wire moves to the surface and solidifies. Flux protects the molten puddle from atmospheric contamination, but its composition differs from the base metal. If it gets trapped inside the weld, it creates weak zones or porosity that affects the structural integrity.

On rare occasions, you can push when FCAW welding stainless steel. Nevertheless, it takes a lot of skill to keep the wire on the leading edge of the puddle.

So, unless you are sure you can keep the slag out of the weld, stick to dragging when FCAW welding stainless steel. For FCAW stainless steel welding, a 10-degree drag angle should work fine.

FCAW Stainless Steel Welding with a 10° Drag Angle
Source: http://www.halversoncts.com/ 

Run 10-15% Hotter Than You Would with Mild Steel

As noted, stainless steel exhibits different properties from mild steel, which also affects welding. Since FCAW welding stainless steel is not a typical application, you'll rarely find a dedicated chart on your welder or in the instruction manual.

If there are no other recommendations, you can use the given mild steel charts as a starting point, and add 10-15% more heat for stainless steel. However, considering the thermal properties of stainless steel, you should exercise caution. We recommend running a few practice beads on a scrap metal to make sure you are not running too hot.

Run practice beads on scrap when FCAW stainless steel.
Source: https://www.youtube.com/watch?v=rFkcQnklIOI

Another alternative is to check the manufacturer's recommendation for parameters. Most flux-cored stainless steel wire manufacturers will also include a reference chart. Use it as a starting point until you find a sweet spot that matches your welding technique and preferences.

Be Careful with Heat

The thermal properties of stainless steel can make FCAW welding a nightmare if you are not careful enough. The truth is, Flux core welding is not renowned for being a low-heat process or for its heat control.

The primary issue with stainless steel is that it retains heat in the HAZ. If you overheat the joint, it can cause burn-through or oxidation. Oxidation renders stainless steel welds less effective, as they lose their primary advantage: resistance to corrosion.

Heat-affected Zone (HAZ) in Welding
Source: https://www.cwbgroup.org/

Overheating on thinner pieces will also cause excessive distortion. Stainless steel expands and contracts significantly when exposed to heat, resulting in excessive warping.

The nature of the process (FCAW) and the metal itself (stainless steel) require great care during welding. Yes, stainless steel requires a bit more heat than mild steel, but overheating it can cause various defects and faulty welds.

Overheating in FCAW Stainless Steel
Source: https://www.youtube.com/watch?v=8K2V4GtiYvQ

Ignore the Ball on Tip of Wire

DCEP polarity on stainless steel flux-cored wires can create a unique occurrence. From time to time, you will notice a small ball at the tip of the wire, and in most cases, it is not dangerous for flux core welds.

A ball can indicate you are running a bit slow, but it usually won't cause any severe welding defects. Nevertheless, if you are not careful enough, the ball can burn back and fuse with the nozzle. It can also be a sign of poor ground or excessive wire speed. But do not panic, as it won’t affect the structural integrity of the weld.

Ball on the Wire Tip in Stainless Steel FCAW
Source: https://www.youtube.com/watch?v=yx6weJurINc

Carefully Clean Slag and Stainless Steel

Once the FCAW welds solidify, clean the slag from the surface, but be cautious when doing so. Although stainless steel is durable and resistant to scratches, damaging the protective layer can affect its corrosion resistance.

When cleaning stainless steel and slag on top of it, use stainless steel-specific tools. Stainless steel brushes and discs are carbon-free, meaning you won't compromise base material corrosion resistance.

Stainless Steel-specific Tools
Source: https://www.youtube.com/watch?v=UdOY9qdZOq4

Having a set of tools specifically designed for welding stainless steel is a must-have if you work with it frequently. However, do not make the mistake of using a mild steel brush, thinking you can get away with it for minor errors.

In general, stainless steel dislikes contamination, as it can affect its corrosion resistance. Therefore, ensure that you thoroughly clean the pieces before welding, including Flux core welding. Remember that FCAW naturally produces more spatter, and you should clean it along with the slag after the welding.

Remove Slag after Flux-Cored Welding
Source: https://www.youtube.com/watch?v=yx6weJurINc

Final Thoughts

Flux core welding stainless steel is not a go-to choice for most welders, but it is possible. You can use the FCAW if you don't have any other options or need to complete quick outdoor projects without investing too much time or equipment.

However, keep in mind that stainless steel is different from mild steel. It retains heat and distorts when overheated, so it requires effective heat control. Flux-cored welding is not known for heat control or low amp performances, so you'll need to be careful.

Therefore, make sure you understand the basics and follow our tips for successful stainless steel welding with Flux-cored Arc Welding.