A Comprehensive Guide to MIG Welding Wire Types

When it comes to welding projects, selecting the right MIG wire is vital. MIG welding wires serve as consumable materials in the welding process. This plays a key role in creating strong and durable welds. This article will give you a detailed exploration of various MIG wire types, shedding light on their benefits, drawbacks, and how to make informed decisions for your welding projects.

Understanding MIG Welding Wires:

MIG welding wires consist of metal—commonly steel or aluminium—often coated with copper, and are spooled on drums or coils. Fed through a welding gun, these wires are heated and melted by an electrical arc to fuse metal pieces together when. The semi-automated feeding of MIG welding wire distinguishes this method, making it a popular choice among welders for its efficiency and ease of use.

Is MIG Solid Wire the Same as Flux Cored Wire?

While both MIG Solid Wire and Flux Cored Wires are welding filler materials, they differ significantly. Solid MIG welding wire requires a shielding gas to protect the weld puddle. Meanwhile gasless flux core wire operates without external shielding gas, thanks to a flux-filled core. This distinction gave rise to Flux-cored arc welding, a process similar to MIG welding but with unique characteristics.

MIG Welding Wire Types:

To ensure global standardisation, the American Welding Society (AWS) provides classifications for solid wires based on mechanical and chemical properties. A widely used example is AWS ER70S-6, where each element in the nomenclature signifies specific features, such as tensile strength and composition.

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).

MIG Wires for Mild Steel:

The MIG welding wires for mild steel- 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. This means that 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. Plus, using pure CO2 will reduce the amount of manganese present in the weldment and therefore will reduce the strength of the weld metal.

• ER70S-4

  Is a great filler rod for the low to 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. Generally applications include high tensile strength steels for automobiles, rolling stock, electrical appliances, machinery, air conditioners, and more.

 Aluminum MIG Wire:

When welding aluminium, specialised wires like ER4043 and ER5356 are commonly used. 

ER4043 Aluminum Wire

ER4043 is an aluminium MIG welding wire with a 5% Silicon Aluminium. Alloying with silicon provides high wetting during welding and reduces the weld cracking sensitivity. This makes ER4043 a good aluminium welding filler wire rod for general purpose welding applications.

Generally this wire 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.

However, the ER4043 aluminium MIG wire has its own sets of drawbacks. This filler alloy will typically turn dark grey after the anodizing process. As a result, you should not use it if you are considering the best colour match after post-weld anodizing. In addition, this wire is softer than ER5356, which can cause feeding issues such as clogging, tangling, or birdnesting.

ER5356 Aluminum Wire

ER5356 aluminium wire contains 5% magnesium. The addition of magnesium improves the weldability of the metal. This wire can be used to weld a variety of aluminium alloys, including those with high silicon content.However, welders commonly chose it for aluminium 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 colour 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:

For stainless steel welding, wires like ER308/308L, ER309, and ER316 are chosen based on the specific grade and application requirements.

• ER308/308L is most frequently used for base metals of similar composition. 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 grey 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 grey 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 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 at different grades, alloying elements, and specific applications.

Filler Wire for Nickel Alloys:

MIG welding wires for nickel alloys-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. 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

  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 minimised. It also has high molybdenum content and resists stress, pitting, and crevice corrosion.

MIG Welding Wire for Low Alloy Steel:

While essentially, ER70s-6 carbon steel wire can be used in MIG welding certain low alloy steel. 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. 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. 

• 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 sulphur or carbon. This wire is commonly used for welding construction equipment, pipe, and trailers.

Final Thoughts:

MIG welding wires, with their diverse benefits and applications, play a key role in achieving quality welds. Understanding the properties of various wire types is essential for selecting the right one for specific welding needs. This comprehensive guide aims to equip welders with the knowledge to make informed decisions for successful welding projects.