Stainless steel is rust and corrosion resistant, making it an ideal base metal for welding. Furthermore, the metal is durable for most applications. The most common welding process used to weld stainless steel is Metal Inert Gas or MIG welding.
There are many reasons why most people prefer MIG welding stainless steel. But before we take a look at these reasons, let’s first get to know what stainless steel is.
What Is Stainless Steel?
Stainless steel is an alloy of iron and chromium that is designed to be rust and corrosion-resistant. In some cases, the alloy will also contain other metals such as nickel, manganese, and Molybdenum.
This alloy is known for being aesthetically pleasing and incredibly durable. It is for this reason that it is used in many applications.
Necessary tools for MIG welding stainless steel
Before starting your welding, it’s important to gather the right equipment for completing your work perfectly. here is a shortlist of all tools and consumables you need while welding.
-Consumables: Nozzle, contact tips, wire
–Safety Gears: Welding jacket, welding safety glasses, gloves, Auto-darkening Helmet, Knee pads, and welding chaps, Respirators, Welding Shoes,
-Gun Liner
-MIG welding machine With a proper Welding Gun
-Metal cleaning brush
-Angle grinder
-Shielding gas
-Stainless steel wire
Common Methods Of Welding Stainless Steel
There are three methods you can use to weld stainless steel. These are;
Method-1: Tungsten Inert Gas (TIG) welding
This is by far the slowest method you can opt for. However, it produces the most aesthetically pleasing results. TIG welding stainless steel is done using DC.
Method-2: Metal Inert Gas (MIG) welding
This is the fastest welding stainless steel method and is used in production. While the end result might not be a work of art as that produced by TIG welding, MIG welding stainless steel is the best option for most.
Method-3: Stick welding
The easiest method of welding stainless steel, stick welding has no complications. However, you need to watch out for slag build-up. The slag tends to fly off on its own and can cause a painful injury if not wearing proper gear.
Which Welding Method Is Best For Stainless Steel
MIG welding is the best option for welding stainless steel. It is not as messy as stick welding, but at the same time, is not as slow as TIG welding. Thus it sits in between the other two welding methods.
But what makes it the best is the production rate. MIG welding is fast and easy to pick up, making it an ideal option for most.
Choosing The Right Gases For Stainless Steel Welding
One of the essential aspects of MIG welding you will need to consider is the shielding gas. The shielding gas mixture you use will have an impact on the quality of your weld. So which shielding gases should you use to weld stainless steel?
To start with, you should never use pure argon to weld stainless steel. Argon as a shielding gas results in an unproductive electrical arc. Furthermore, it leads to an atmosphere that hinders the melting of the base metal.
This results in minimal weld penetration. To get the best results, you should use a mixture of 98% argon and 2% carbon dioxide. For low amperage welding, a tri-mixture of carbon, helium, and argon is recommended.
This trimixture should have 90% argon, 7.5% helium, and 2.5% carbon dioxide. A higher carbon percentage can also work for the argon/co2 mixture. This can be anywhere from 25% co2 and 75% argon to 2% co2 and 98% argon.
Few things need to consider when you are going to select shielding gas. These things are,
-expected result You need
-Metal Transfer process
-types of Joining materials
-Cost
_Alloy Types
-Postweld Cleaning Requirement
| Shielding Gas Mix | Metal Thickness in. (mm) |
| 90% Ar, 7.5% He, and 2.5% CO2 | Up to 14 gauge (0.1) |
| 98% Ar, 2% CO2 | Over 14 gauge (0.1) |
| 98% Ar, 2% O2 | All thicknesses |
Tips for setting up your welder
- To minimize thermal expansion, keep the heat level at the lowest rate
- Always try to maintain a consistent contact tip to work distance
- The Machine should be operated on DC mode
- Use a MIG welder, Not a flux core one.
- Use a stainless MIG Wire;
- Common MIG Welding Wire Sizes you can use in welding stainless steel: .023, .030, .035, .045
MIG Welding Setting parameters for stainless steel
| Thickness | Wire Size | Travel Speed | Voltage | Amperage |
| 18 Gauge | .035 | 120-150 ipm | 20 volts | 50-60 amps |
| 16 Gauge | .035 | 180-205 ipm | 20 volts | 70-80 amps |
| 14 Gauge | .035 | 230-275 ipm | 20-21 volts | 90-110 amps |
| 12 Gauge | .035 | 300-325 ipm | 20-21 volts | 120-130 amps |
| 3/16 Inch | .035 | 350-375 ipm | 21 volts | 140-150 amps |
| 1/4 Inch | .035 | 400-425 ipm | 21 volts | 160-170 amps |
| 5/16 Inch | .035 | 450-475 ipm | 22 volts | 180-190 amps |
| 3/8 Inch | 1.6mm | 140-170 ipm | 25 volts | 250-275 amps |
| 7/16 Inch | 1.6mm | 170-200 ipm | 27 volts | 275-300 amps |
| 1/2 Inch | 1.6mm | 200-230 ipm | 32 volts | 300-325 amps |
Choosing The Right Filler Wire And Electrode For Stainless Steel
Stainless steel, as already explained, is used in a wide array of applications. For this reason, there are a couple of electrodes you can use. However, the most common are ER308L, ER309L, and ER316L.
All electrodes used in the welding of stainless steel have an “L” at the end of their designated names. This “L” stands for low carbon
- The ER308L: This electrode is used on low-grade stainless steel. Low-grade stainless steel lacks the shiny aesthetic appeal that is commonly associated with stainless steel. As such, this type of steel is mainly used in industrial applications.
- The ER309L: This electrode is used for welding stainless steel grades 304 to 310. It is also used to weld stainless steel to mild or carbon steel. When using this electrode to weld stainless steel to steel, the finished weld will have a rough appearance.
- The ER316L: This electrode is used for welding high-grade stainless steel commonly used in the food and marine industries. It can weld stainless steel grades from 304 to 328.
Both the ER309L and ER316L use a 2% co2 and 98% argon gas mixture for MIG welding.
How to MIG weld stainless steel
There are three steps you need to follow to weld stainless steel. These are;
Step One: Preparation
Preparation is essential regardless of the type of metal you are welding. With stainless steel, you need to ensure that the surface is clean. You can use a wire brush to clean the surface. The wire brush you use should only be used on stainless steel.
Stainless steel’s corrosion-resistant properties can be undermined by contaminants, in particular carbon particles. It is possible to transport contaminants from one type of metal to your stainless steel piece.
This is why it is essential to have a wire brush designated for cleaning stainless steel metal pieces. This way, you avoid contaminating the metal surfaces with contaminants from other metal surfaces.
Step Two: Position The Metals
When welding two stainless steel pieces together, they need to be clamped to prevent them from moving while welding. Also, it is essential to prevent distortions when welding. This can be done by bracing the stainless steel sheets.
One way of doing this is by placing a wooden plank between the joints. This ensures that the two metal pieces are apart.
Step Three: Choose The Right Settings
On your welding machine, you need to pick the right settings to weld stainless steel. This will depend on several things. Key among them will be the thickness of the metal and the welder’s power output being used.
To weld thin sheets of stainless steel, you need a lower power output. This is to prevent burn through or warping, which is common when welding thin sheets of stainless steel. Ideally, the output should be between 50 to 60 amps.
This works best for about 18 gauge thick stainless steel sheets. At this amperage, the wire feed speed should be set to between 120 and 150 pm.
The thicker the metal, the more power required. As such, a ½ inch thick stainless steel sheet will require between 300 and 325 amps of power output. As for the wire feed speed, it will be set at 200 to 230 pm.
Some welders come with a chart displaying the best settings for welding metals of varying thickness. It is essential to check this chart before welding.
Step Four: Start Welding
The one thing to note about stainless steel is that it heats very fast. To prevent distortion and burn through, you need to spread the heat when welding. This is done by back-stepping as you weld to allow the joint to cool down when welding.
Heat spreading will be essential when welding thin sheets of stainless steel. This distortion can cause the metal to move. In this case, a 90 degree T joint ends up distorting by up to 45 degrees.
How to Clean/prep your Stainless steel before welding?
Proper Cleaning is the best practice for getting a good weld. Automatic electric sanding belts and discs are the perfect way to remove dirt, oxidation, oil, and other substances that may be present on a wide variety of work surfaces. These machines are designed using an oscillating motion that grinds away rough surfaces as it glides across the surface of the processed material by pulling them in and pushing them out.
The first step is to power wash or use a confined spray operation with harsh chemicals like alcohol or acetone if possible. Sometimes power washing alone will be enough, though, depending on what has accumulated on your stainless steel surface in need of cleaning from welding.
Abrasive Flap Discs — which, at this Welding level, are probably more like sandpaper – it’ll wear out quickly
Angle Grinder with a Flap Disc on the side to grind down the stainless steel until it’s gleaming. You can use an Angle Grinder to clean off debris from other metals that you’re welding too. It’s unlikely you’ll need to get all the way down to bare metal before welding, though.
Conclusion
Stainless steel is a metal used in fabrication, industrial settings, and in several other applications. Its corrosion and rust-resistant properties make it a favorite of many. However, it differs significantly from different types of steel, such as carbon and mild steel.
Thus extra care should be taken when welding stainless steel. MIG welding is the best method for welding stainless steel.