MIG Welding Stainless Steel Flux Cored Can You?

By Bill Byers / March 23, 2019
MIG Welding Stainless Steel Flux Cored Title Image

You have a MIG welder and some stainless steel and maybe someone told you about this great gas shielded flux core wire for stainless steel.

And now you wonder if MIG welding stainless steel flux cored is a thing.

The question is ...

Can You MIG Weld Stainless Steel With Flux Core Wire?

Yes.

Using dual shielded also known as double shielded stainless steel flux core wire. The MIG (Metal Inert Gas) also referred to as GMAW (Gas Metal Arc Welding) process, as its name implies, uses shielding gas to protect the weld puddle.

Dual shielded flux cored stainless steel wire requires shielding with gas from a tank or cylinder.

And typically 100% Carbon Dioxide is used as the shielding gas but some forms of high Argon with Carbon Dioxide mixes may be supported by the stainless steel flux core wire. Check what the welding wire manufacturer supports.

As MIG welding stainless steel is a MIG process it is generally a good idea to prepare the surface of your stainless steel well before welding.

What MIG Welding Stainless Steel Flux Cored is NOT

Any flux cored stainless steel wires that does not need shielding with gas. They are also known as gasless flux core wires. These wires are welded with the FCAW (Flux Core Arc Welding) process.

It is not strictly speaking MIG wire, as the Metal Inert Gas welding process uses gas for shielding. Although sometimes gasless flux core wire is called MIG wire which can be confusing to a newcomer.

If you want to know about gasless stainless steel flux core wire then head over to my document to find out what it is all about. ​

What this Article is About

This blog post is all about MIG welding stainless steel flux cored but before we get into the meat of the post I just want to clarify what that means for those who are new to the subject. Those who know this already can just fly past.

The MIG Welding Part of Welding Stainless Steel

MIG welding is also known by the more modern term of Gas Metal Arc Welding. Metal Inert Gas welding is done by a MIG welder. A machine that feeds welding wire continuously into the weld as you weld.

The MIG welder uses electricity to create an electrical arc. The aim of this arc is to heat the metals to be welded to a high enough temperature so that they become molten and fuse together. Then when the metals cool a weld is formed.

There are a few things missing from the picture I've just painted for you. The inert and gas part of the MIG term.

Hot molten metal exposed to the air we breathe pick up contaminants from the air.

These contaminants affect the weld so that it is made poor and fails. To prevent this happening a protective atmosphere is needed around the molten metal. This atmosphere around the hot metal is made using something called shielding gas. The gas shields the hot metal from the air giving the weld the best environment to form in.

A MIG welder not only feeds welding wire continuously, the electrical arc is formed at the tip of that welding wire, and shielding gas is fed from a gas cylinder to the point of the weld to protect it.

This is a very brief overview of the MIG welding process and I have articles on the site that explain in much more detail about ​MIG welding and MIG welders ​do go over and take a look at them if you're unsure and would like to know more about both terms.

Close Up of Mig Welding Flux Core

​Close Up of MIG welding Flux Core

Flux Cored Stainless Steel MIG Wire - Three types Of

There are three types of welding wire used to weld stainless steel.

1. The first is solid MIG wire.

And as its name suggests the wire is made of solid stainless steel. Stainless steel is produced in different grades depending on the properties desired. And so solid stainless steel MIG welding wire is available in different types depending on the type of wire needed.

This wire needs shielding gas to protect the weld. It is true MIG welding process using solid stainless steel MIG welding wire. And you can find out more about is here. ​

2. The second is Flux core Gasless Wire

The name gives the game away, that the welding wire needs no separate shielding gas to weld.

Flux core welding wire in contrast to solid wire is manufactured like a tiny tube. The stainless steel metal is around the outside and chemical compounds call flux are in the center.

Inside Flux Core Wire

​Do take a look at my document that goes into much more detail on flux core wire to find out more. ​

There are two types of flux core wire, one type that is called gasless. The flux inside the wire forms the protective shield as the wire is heated to melting point by the arc. It's not quite a true MIG process as there is no separate cylinder of gas involved. This method of welding is called FCAW (Flux Core Arc Welding). ​

3. The third type of stainless steel MIG wire is called gas shielded or double shielded. The welding process is called FACW-G (Flux Core Arc Welding Gas), and that is the type of welding this post is all about.

Not only does the flux inside the wire help form the shielding gas to protect the molten metal, gas is fed from a cylinder to protect the weld further.

Flux Core Wire Shielded with Gas

​When you are MIG welding stainless steel flux cored, this is the wire that is used. MIG welding uses a MIG welder feeding shielding gas to protect the stainless steel welding wire that is flux cored - welding wire that has flux compounds in the center of it.

Flux Core Stainless Steel MIG Welding Advantages

1. It is a fast welding process. Welding with stainless steel flux core MIG welding wire deposits the wire quickly into the welded joint. Which is why it is loved by the construction industry.

2. MIG welding stainless steel with flux core produces good looking welds with minimum weld spatter. Particularly helpful as the reason stainless steel is often chosen is because it is important the item looks good. Spatter all over your lovely stainless steel isn't desirable.

3. The separate shielding gas helps the flux move to the surface of the weld pool producing a cleaner weld with flux that should just peel off with the right welding settings.

4. Typically the shielding gas used is 100% Carbon Dioxide which is a cheaper shielding gas to buy compared to the Argon, Carbon Dioxide gas mixes, or a Helium based Tri Mix typically used when MIG welding stainless steel with solid welding wire.

5. It produces greater penetration of the welded metal. Particularly useful when welding thicker metal gauges and a reason why MIG welding stainless steel with flux core welding wire is most often seen in commercial welding.

Flux Core Stainless Steel MIG Welding Disadvantages

1. For the home workshop the consumables are expensive compared to MIG welding stainless steel with solid MIG wire. The double shielded flux core wire is more expensive per pound of welding wire compared to solid wire or even gasless flux core wire.

2, You still need shielding gas, which is an expense.

3. The flux core stainless steel dual shielded wire tends to come in larger diameter sizes - 0.035, 0.045 inch diameter and above which means home use MIG welders that can only use 0.030 inch diameter wires are not able to use.

4. Stainless steel flux core dual shielded tends to be supplied in large spools 11 lb. and 33 lb. spools plus. Not great if you only want a small spool for a quick welding job.

5. The larger diameter and spool sizes tend to push this wire toward 230 volt MIG welders. Those MIG welders have the power available to melt the dual shielded stainless steel flux core wire, can feed the larger diameter wire as well as hold the larger spool sizes.

If you have a 115 volt or 120 volt MIG welder you will struggle to find 0.030 or 0.035 inch diameter wire you can feed.

6. Is an Indoor process. More on that later.

Types of Stainless Steel

Before choosing your stainless steel flux core MIG wire it is worth understanding that there are different types of stainless steel. And that it is best to match your wire to the steel that you're planning on welding.

The most common type of stainless steel is type 300 series stainless steels. These types of stainless steels are not magnetic which means that if a magnet sticks to the steel it is not a 300 type stainless steel you're dealing with.

Type 308L stainless steel welding wire is used to weld types 321 and 347 as well as type 308 stainless steel.

Type 309L stainless steel welding wire is the most flexible and is a good go to wire when you're not sure of the type of stainless steel you have. It is the wire of choice to weld dissimilar stainless steels such as mild steel to stainless steel, if you have to do that.

Type 316L stainless steel MIG welding wire is food grade stainless steel. It is used in the food and beverages industry where food hygiene is of utmost importance.

And the ability of the steel to take sterilization and be resistant to acids is key. It is also seen in the chemical industries and is used for pipes where the steels properties are prized. Type 316L dual shielded flux core stainless steel welding wire is particularly corrosion resistant and is used for steels with Molybdenum in them.

Three Flux Core Stainless Steel MIG Wires To Consider  

I have searched for and found some stainless steel flux core MIG wires that are available in 0.035 sizes and list them for you here.

Blue Demon 308LT1/4

Wire diameter sizes 0.035, 0.045 and 0.063 inch

Reasons to Buy this Wire:

If your MIG welder will take a 10 lb. spool the odds are this spool should fit in fine.

It is available in 11lb spool and a 33 lb. spool sizes.

Can weld type 321 and 347 stainless steel and of course type 308 stainless steel.

The Blue Demon 308LTI/4 is an all positions wire, so you can weld on the flat, horizontal, overhead and vertical down

The shielding gas recommended to use: 100% Carbon Dioxide

Welding Amps needed: 150 - 165 Amp for diameter size 0.035 or 26-27 volts

The Blue Demon 308L is a well liked wire.

Blue Demon 309LT1/4

​Wire diameter sizes 0.035, 0.045 and 0.063 inch diameter wire.

Reasons to Buy this Wire:

If your MIG welder will take a 10 lb. spool this spool should fit in.

It is available in an 11 lb. and 33 lb. spool sizes.

The Blue Demon 309LT1/4 wire used for welding dissimilar stainless steels. This makes it very useful when you're not sure what kind of stainless steel you are dealing with. Or welding stainless to mild steel.

The 309LT1/4 is an all positions wire and is fine for welding flat, horizontal, overhead and vertical down.

The shielding gas recommended: 100% Carbon Dioxide

Welding Amps needed: 150 - 165 Amp for size 0.035 or 26-27 volts

Blue Demon 316LT1/4

​​Wire Diameter sizes 0.035, 0.045 and 0.063 inch.

Reasons to Buy this Wire:

If your MIG welder will take a 10 lb. spool then this spool should go in.

The Blue Demon 316LT1/4 is available in 11 lb. and 33 lb. spool sizes.

The 316LT1/4 is used for welding type 316 stainless steel.

It is a wire suitable for flat, horizontal, overhead and vertical down welding

The shielding gas recommended: 100% Carbon Dioxide

Welding Amps needed: 150 - 165 Amp for size 0.035 or 26-27 volts

​Types of Shielding Gas Used for MIG Welding Stainless Steel

The reason why industrial fabrication companies love flux cored stainless steel MIG wire is because is usually shielded with 100% Carbon Dioxide.

A gas that is relatively cheap to purchase in cylinders and tanks. Certainly cheaper to purchase than the alternatives such as high Argon (75% - 98%) and Carbon Dioxide (25% - 2%) gas mixes.

And most certainly cheaper than Tri Mix (90% Helium, 7.5% Argon, 2.5% Carbon Dioxide) that is commonly used with solid MIG stainless steel wire.

But wait, I can hear you say,

Carbon Dioxide isn't an inert gas. And yes that is true, the name of the MIG process was changed to GMAW, gas metal arc welding when it was discovered that Carbon Dioxide could also be an effective shielding gas for some wires and types of arc welding.

Most still call the process MIG welding.

Flux Core Stainless Steel MIG Welding is an Indoor Process

Because flux core stainless steel MIG welding wire needs to be used with shielding gas this means as with any MIG welding the gas needs to cover the weld pool to be effective. And welding in the outdoors where the wind can blow your shielding gas away from your weld is not recommended. 

Not unless you set up wind shields and wind breaks to protect your MIG gun from the wind as you weld. 

This means extra equipment to carry out to the welding site and as often stainless steel is used because of its rust resistant properties often the part to be welded lives outside.

If the part cannot be brought in then this may well be a situation where gasless flux core stainless steel welding wire should be used as there are no such concerns with flux core welding with that wire outdoors. ​

Flux Core Stainless Steel MIG Wire Welding Polarity

As MIG welding dual shielded stainless steel flux core wire is a MIG process there are certain electrical characteristics the welding wire needs.

FCAW-G (Flux Core Arc Welding Gas) wire needs your MIG welder set to DCEP (Direct Current Electrode Positive).

Flux Core Gas Shielded Polarity

​Stainless Steel Flux Core MIG Wire Polarity

​This means that your MIG gun is connected to the positive terminal in your MIG welder and your welding clamp connected to the negative terminal. That way you'll have the electrical features your stainless steel flux core wire needs weld.

Welding Stickout

As you weld Stainless steel flux core MIG wire needs a longer wire stickout compared to the wire stickout when welding with solid wire.

Even though you're MIG welding it cannot be treated like solid MIG wire.

A wire stickout of 1/2 inch to 5/8th needs to be maintained when MIG welding stainless steel flux cored wire.

Welding Wire Stickout

Welding Wire Stickout

​Last Words

I hope I have successfully answered your question: MIG welding stainless steel flux cored can you? And shown you that you most certainly can.

As an alternative way of arc welding stainless steel, using dual shielded stainless steel flux core wire produces fine welds with welding slag that just peels off.

Though you do need a MIG welder that can use the wire and produce the levels of amperage needed to weld well.

Resources

Welding parameters chart for the Blue Demon 308LTI14

Welding parameters chart for the Blue Demon 309LT1/4

Welding parameters chart for the Blue Demon 316LT1/4


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