When it comes to welding projects, selecting the right MIG welding wire is essential. Each type of MIG wire offers its own unique advantages, from required speed and size to strength.
Knowing what to look for can mean the difference between a successful project and a failed one. Understanding the different types of MIG wires can be the key to creating a quality weld.
This article will explain the various MIG wire types, including their benefits and drawbacks, so you can make an informed decision for your next welding project.
Photo by @mig_stick_welder (TikTok)
What Are MIG Welding Wires?
MIG welding wires are a crucial component of MIG welding and are the consumable materials used in the welding process. These wires are made of metal, typically steel or aluminum, or they can have a copper coating and are spooled on a drum or coil. The wire is fed through a welding gun and then heated and melted by an electrical arc to join two pieces of metal together.
So instead of manually feeding the rod in TIG welding or the electrode in Stick welding, the MIG solid wire feeds automatically at the given welding speed rate. As a result, the wire fuses the two pieces of metal, enabling them to form a strong bond. In addition, the semi-automated feeding of MIG welding wire allowed welders to complete projects much faster and with ease, which is the reason MIG welding became one of the most popular processes among hobbyists, new welders, and DIY enthusiasts.
MIG solid wire feeds automatically at the given welding speed rate.
By selecting the right type and size of wire, you can ensure that the weld is strong and free from defects. The wire also helps to protect the welder from burns by absorbing a large portion of the heat generated during the welding process. All of these factors combine to make MIG welding wires an essential part of the welding process.
Is MIG Solid Wire The Same As Flux Cored Wire?
MIG (Metal Inert Gas) Solid Wire and Flux Cored Wires are both types of welding filler material used in welding. They have similar properties: they are both made from steel, they both conduct electricity, and they are both used with a MIG welder. However, they are different in several ways.
Solid MIG welding wire, as its name states, is uniform, and it is usually called bare ware. As a result, you need a shielding gas to protect solid MIG welding wires and weld puddle from contamination.
Gasless flux core wire, on the other hand, combined the ease of use of MIG welding wires and the ability to weld without shielding gas, like with Stick welding. This is achieved by a specific hollow structure that contains a flux in its core. As the wire melts, the flux forms a layer of slag that shields the molten weld pool from contamination, so you don't need an external shielding gas.
Flux Core Arc Welding
Due to the introduction of these wires, a form of MIG welding, known as Flux-cored arc welding, was perfected. Today, we see it as similar, yet another welding process that shares the fundamentals and welding machine with MIG welding, but we cannot call flux cored wire a type of solid MIG wire.
Instead, when we talk about MIG welding wire types, we will use the AWS classification, which distinguishes MIG wires for carbon steel, aluminum, steel, and other metals.
MIG Welding Wire Types
To make sure welders around the globe get the MIG wire with the same properties, the American Welding Society (AWS) provides multiple classifications for solid wire based on mechanical and chemical properties. The wires carry a set of numbers and letters, and each letter and number in its nomenclature signifies a specific feature.
To help you understand the classification, we will take a commonly used solid wire — AWS ER70S-6.
- The “ER” indicates that the Electrode Rod, or filler metal;
- The “70” signifies that it has a tensile strength of 70,000 pounds per square inch (psi);
- The “S” means that it is a solid wire.
- The “6” denotes the chemical composition and shielding gas requirements (Ar, Ar/CO2, 100% CO2).
Now that you understand the basics, let's talk about each type of MIG wire based on the weld metal it is dedicated to.
MIG Wires For Mild Steel
The MIG welding wires for mild steel are classified by the AWS A5.18/A5.18M document - Specification for Carbon Steel Electrodes and Rods for Gas Shielded Arc Welding. This specification shows the requirements for the classification of carbon steel electrodes (solid, composite stranded, and composite metal cored) and rods (solid) for gas metal arc (GMAW), gas tungsten arc (GTAW), and plasma arc (PAW) arc welding processes. In there, you will find some of the most widely used wires, including:
- ER70S-2 is a solid MIG welding wire with added deoxidants that is primarily used for single-pass applications on killed, semi-killed, and rimmed still. The addition of deoxidants allows you to work with dirty or rusted surfaces, but it is not as effective as some stick electrodes or flux-cored wires, so there is always a risk of slight contamination. Normal applications include MIG welding structural steel, carbon steel plate, pipe, fittings, castings, and forgings. The number 2 denotes that wire requires pure argon shielding gas.
- ER70S-3 is a general-purpose MIG wire suitable for many carbon steel welding applications. It has silicon and manganese deoxidants, which make it excellent for general fabrication. This wire should be used with an argon/CO2 gas mixture as welding using pure CO2 will reduce the amount of manganese present in the weldment and hence will reduce the strength of the weld metal.
- ER70S-4 is a great filler rod for low to the medium presence of surface contaminants such as rust or mill scale. S4 wire has all of the advantages of S2, with slightly higher levels of manganese and silicon. It has higher cleaning levels and produces a more fluid weld puddle and flatter bead profile.
- ER70S-6 is an all-around solid and quality MIG wire that is widely used solid MIG wires among welders. It is suited for single-pass and multi-pass welding, it shows excellent results and uniform weld appearance on thin metal and structural plates with a moderate amount of mill scale or rust. This wire can be successfully used with pure argon and argon/co2 mixtures, but it can withstand the heat of pure CO2, which is another reason many welders prefer it.
- ER70S-7 is a general-purpose MIG wire suitable for many carbon steel welding applications but with substantially greater manganese content than ER70S-3 welding alloy. The higher manganese provides a slightly better wetting and weld appearance with slightly higher tensile and yield strengths as well. Typical applications include high tensile strength steels for automobiles, rolling stock, electrical appliances, machinery, air conditioners, and more.
There are also more specialized MIG wires for carbon steel, such as ER70-G or ER70C-G, but they are used only when specific mechanical properties are specified. Therefore, you are less likely to encounter them in your everyday applications.
Aluminum MIG Wire
When MIG welding aluminum, you will need a specialized aluminum MIG wire. The required properties of these wires are stated in AWS Specification A5.10 - Specification for bare aluminum and aluminum alloy welding electrodes and rods. Unlike the previous specification for carbon steel, where the single wire can handle multiple types of MIG welding mild steel, there are wires specialized for each grade of aluminum, from 1XXX to 7XXX.
Luckily, when choosing a MIG wire for aluminum, welders usually turn to two aluminum wire types: ER4043 and ER5356.
Mig welding aluminum with YesWelder YWM-200.
ER4043 Aluminum Wire
ER4043 is an aluminum MIG welding wire with a 5% Silicon Aluminum that is used primarily for welding Aluminum Alloys 3003, 3004, 5052, 6061, 6063 and Casting Alloys 43, 355, 356, and 214. Alloying with silicon provides high wetting during welding and reduces the weld cracking sensitivity. This makes ER4043 a good aluminum welding filler wire rod for general purpose welding applications.
This wire generally tends to produce welds with improved cosmetic appearance, smoother surfaces, less spatter, and less smut. The ER4043 has a lower melting point, which can be suitable for brazing applications, but it can be used in higher-temperature applications compared to ER5356.
The ER4043 aluminum MIG wire has its own sets of drawbacks. This filler alloy will typically turn dark gray after the anodizing process. As a result, you should not use it if you are considering the best color match after post-weld anodizing. In addition, this wire is softer than ER5356, which can cause feeding issues such as clogging, tangling, or birdnesting.
Double pulse with 4043 1.2mm wire.
Photo by @shanfiredup (TikTok)
ER5356 Aluminum Wire
ER5356 aluminum wire contains 5% magnesium. The addition of magnesium improves the weldability of the metal. This wire can be used to weld a variety of aluminum alloys, including those with high silicon content, such as the 1XXX series, 5XXX series, 6XXX series, and 7XXX series. However, welders commonly chose it for 5050, 5052, 5083, 5356, 5454, and 5456 aluminum grades.
ER5356 has a low melting point and strong weld penetration. This makes it ideal for welding thick materials or materials that are difficult to weld. Additionally, it offers better corrosion resistance when exposed to saltwater and higher shear strength. ER5356 will provide a much closer color match after anodizing.
However, its 5% magnesium content is not suitable for elevated-temperature applications. Appearance-wise, 5356 does not produce uniform or aesthetically pleasing welds like 4043, even though it has more advantages than drawbacks.
Stainless Steel MIG Wire Types
Like with aluminum, each stainless steel wire can be dedicated to a specific grade of stainless steel, and yes, there are a lot of them. The entire classification can be found in AWS A5.9/A5 document - Welding Consumables—Wire Electrodes, Strip Electrodes, Wires, and Rods for Arc Welding of Stainless and Heat Resisting Steels— Classification.
As a hobbyist or occasional welder, you are likely to use ER308/308L, ER309, or ER316 stainless steel MIG wires.
- ER308/308L is most frequently used for base metals of similar composition. It is used for welding metals of similar composition, such as 201,202, 301, 302, 304, 305, and 308 (and L Series). ER308L has the same analysis as type 308, except the carbon content has been held to a maximum of .03% to reduce the possibility of intergranular carbide precipitation. ER308L is ideal for welding Types 304L, 321, and 347 stainless steels. This wire is well suited for welding chemical, food processing, brewery, and pharmaceutical equipment.
- ER309/309L is used for the welding of similar alloys in wrought or cast form. It is mostly used for welding dissimilar materials, such as mild steel to stainless steel, as well as for a barrier layer in stainless overlays. For some applications, welding of straight chromium steels can be accomplished with this consumable.
- ER316 is recommended for welding AISI 316 stainless steel applications when high creep strength at elevated temperatures where resistance to pitting by corrosive liquids is needed.
MIG Welding Wire For Cast Iron
Welding cast iron can be a daunting task with a 50/50% success rate, and in most cases, you can fail due to its brittle nature, even if you do everything right. To MIG weld cast iron, there are not too many filler metal options. The right choice is limited to nickel-iron MIG wires, such as ERNi55 or ErNi-Fe-CI.
- ERNi55 is a solid welding wire that contains 55% of nickel and 45% iron. This is an affordable option when welding ductile (nodular) cast iron, malleable cast iron, or gray cast iron to themselves or to carbon and low alloy steel. Common applications include repair of thick and highly restrained weldments, worn or broken parts and for salvaging defective castings that require the higher tensile strength of steel.
- ErNi-Fe-CI is a high-end cast iron filler that contains 99% nickel. It is aimed at welding ductile, malleable, or gray cast iron to itself or dissimilar metals such as low alloy and carbon steel, stainless steel, iron, copper Monel, etc. It is used in critical applications in the buildup of worn parts, repairing machining errors, or detective castings.
Mig welding cast iron using cast iron nickel wire.
MIG Welding Wire For Copper
Even though copper is usually joined by soldering or brazing due to its properties and characteristics, you can weld it using popular fusion methods such as Metal inert gas (MIG) or TIG welding. The filler materials for copper and copper alloys are specified by the AWS A5.21 document, and there are a lot of them aimed at different grades, alloying elements, and specific applications.
As a beginner, to MIG weld copper, you can use ERCu or silicon-bronze wires.
- ERCu is used primarily to fabricate deoxidized copper and repair weld copper castings with the Gas Metal Arc and Gas Tungsten Arc processes. It may also be used to weld galvanized steel and deoxidized copper to mild steel where high-strength joints are not required. The wire is also used to overlay surfaces to resist corrosion, billet molds, conductor rolls, heater elements, copper sculptures, steel mill electrode holders, bus bars, and copper connectors.
- ERSiCu is a silicon-bronze wire used for welding brass (copper-silicon alloys) to cast iron or steel, bronze (copper-zinc alloys) to cast iron or steel, and copper to cast iron or steel. It is also used for joining plain or galvanized sheet steel to metals or coated steel. This wire provides high corrosion resistance. It is commonly used for welding automotive components and surfacing areas that may be prone to erosion.
Filler Wire For Nickel Alloys
MIG welding wires for nickel alloys are specified by AWS A5.14 A5.14M - Specification for Nickel and Nickel-Alloy Bare Welding Electrodes and Rods. As with other types, there are a lot of MIG wires that can match the properties of each nickel alloy grade. As a hobbyist, you are likely to use these two wires:
- ERNiCr-3 Nickel Alloy 82 is a welding wire that is used for welding nickel-chromium (NiCr) alloys to themselves or to carbon steel or stainless steel. It is one of the most used nickel alloys whose applications range from cryogenic to high temperatures. It can also be used for overlay applications.
- ERNiCrMo-3 is also known as Inconel 625 or Alloy 625 wire, and it is used to weld Ni-Cr-Mo alloy steels such as ASTM B443, ASTM B444 & B 446 types. It can be used to weld these alloys as well as their dissimilar welding to steel and other alloys. This wire has low iron content, making it suitable for welding applications where the dilution of iron must be minimized. It also has high molybdenum content and resists stress, pitting, and crevice corrosion.
MIG pulse inconel 625.
Photo by @albertobonamigoviviani2106 (YouTube)
MIG Welding Wire For Low Alloy Steel
While essentially, ER70s-6 carbon steel wire can be used in MIG welding certain low alloy steel. There is an entire specification listed in the AWS 5.28/5.28M document. Like with other materials, there are specific solid wire electrodes that suit each alloying element. However, you are likely to encounter the following:
ER100S-1 is suitable for welding nickel-molybdenum (NiMo) steel alloys, such as HY80 steel and ASTM A514 steel. It produces welds that have high tensile strength and high impact resistance and retain their toughness in low-temperature applications. This wire is commonly used for welding petrochemical equipment, structural equipment, cranes, tanks, and other industrial equipment. Minimum tensile strength, yield strength, elongation, and low-temperature impact test requirements as specified by AWS 5.28.
ER80S-D2 is used for welding manganese-molybdenum (MnMo) steel alloys with carbon dioxide shielding. It is suitable for welding rusty or dirty metals. It can also work in applications where there is a risk of porosity or the base metal being welded contains high levels of sulfur or carbon. This wire is commonly used for welding construction equipment, pipe, and trailers.
Mig welding by using ER80S-D2.
MIG welding wires offer a wide variety of benefits to welders, such as providing a consistent quality weld, improving weld properties, and reducing welding production costs. They are suitable for a range of applications and are available in a variety of materials and metal thicknesses.
With their high strength and excellent corrosion resistance, MIG welding wires are the ideal choice for any welding job. Understanding their properties is crucial in selecting the right wire for your application, and we hope our article did just that.