Welding Alloys – Choosing the Right Materials for the Job

In the metal fabrication world, alloys can mean several things. However, welders most often use the term welding alloys when talking about filler metals in processes such as MIG, TIG, Stick, or Flux-Cored Arc welding. Welding alloys come as solid wire, hollow wire, electrode, paste, or powder.

In this article, we will discuss welding alloys and choosing the right materials for the job. Each job and welding project requires a different filler metal, so we will ensure you understand everything to help you make an informed choice.

What Are Welding Alloys?

Welding alloys is a term many welders use to refer to a filler metal. Filler metal, filler rod, wire, or electrode is a consumable that welders use to fill the gap between the two pieces they are about to join.

The AWS definition states that a filler metal is "the metal to be added in making a welded, brazed, or soldered joint." Simply put, whenever a larger joint or gap between two pieces exists, you must fill it with a consumable to produce a uniform and strong bond between them.

A filler metal is the metal added to form a welded, brazed, or soldered joint.
Source: https://yeschefcatering.ie/

But many are wondering why the name is welding alloys. In the past, the first filler metals had a pure composition. Unalloyed fillers showed a good composition match but had poor weldability and performance, so the experts introduced additives or alloying elements.

Adding nonmetallic materials or alloys such as flux, silicon, or manganese stabilized an arc and provided better weld pool fluidity or protection. Although alloying elements can only take up to 5 percent of the filler metal composition, they can significantly boost its weldability or welding performance. That’s why alloyed fillers became the essential part of each filler metal, ergo the name welding alloy.

Don't get confused: Metal and welding alloys sound similar, but they are two different terms. Metal alloys are a type of metal consisting of a base metal and alloying elements. Welding alloys are filler metals used to fill the joint in welding.

Stick welding uses the rod as filler metal.
Photo by @weldspecialist (TikTok)

Types of Welding Alloys

At their core, welding alloys contain roughly 95% of the base metal and 5% alloying elements. Depending on the base element of the filler metal, we see several different types. The most widespread base metals of welding alloys are steel, aluminum, manganese, bronze, cobalt, titanium, zirconium, etc.

Source: https://www.mechdaily.com/what-is-alloy-metal/

Manufacturers use different combinations of these materials to create welding alloys. The most commonly used welding alloys are:

• Steel filler metals

• Aluminum filler metals

• Stainless steel filler metals

• Bronze filler metals

• Magnesium filler metals

• Nickel filler metals

• Titanium filler metals

For example, steel welding alloys contain vast portions of steel but with added silicon and manganese to increase weld pool fluidity and welding performance. Aluminum wires, such as ER4043, contain aluminum in their base, with added 4.5-6% silicon and small additions of manganese, zinc, titanium, and magnesium. Aluminum-bronze fillers contain both aluminum and bronze, with other additives, etc.

Several similar filler metals under one category exist based on the type of alloying elements and the number of alloys. For example, dozens of electrodes, such as ER6010, ER6011, ER6013, ER7018, and ER7024 are designed for steel. However, each electrode shows different welding results regarding penetration, arc stability, spatter, or slag. Therefore, the composition plays a crucial role in the welding performance of a single welding alloy.

Steel Welding Electrodes Comparison
Source: https://www.kingsofwelding.com/guides/6010-vs-6011-vs-6013-vs-7018-vs-7024-welding-rod-comparison/

Forms of Welding Alloys

Besides the composition, the welding alloys also come in different forms. The most common welding alloy forms are:

• Solid wire (a solid, non-shielded wire often used in MIG welding, or as a TIG rod)

• Tubular wire (hollow wire filled in flux, used in Flux-cored arc welding)

• Powder (additions of powder to coated electrodes can contribute to improved welding characteristics)

• Composite (fillers made up of several parts or elements)

• Paste (Alloy or unalloyed metal which, when heated, liquefies and melts to flow into the space between two close fittings)

• Foil (Amorphous brazing filler metal in the form of thin foil)

• Thermite mix (Used in thermite welding to give off an enormous amount of heat)

As a beginner or new welder, you will likely use welding alloys in the form of wire (solid or tubular), electrodes, or rods. If you occasionally braze or solder the pieces, you may eventually see other types.

Welding vs. Brazing vs. Soldering
Source: https://www.cruxweld.com/blog/the-difference-between-soldering-and-brazing/

How to Identify Welding Alloy

Choosing the right filler metal can be challenging since a single welding alloy can have different variations based on its composition and alloying elements. To solve these issues, renowned organizations introduced codes and standards.

TIG Welding Stainless Steel with Filler Rod
Photo by @_cody_lally_ (TikTok)

As a welder, you will have to work with several different standards, including the following:

• AWS Standards (American Welding Society)

• ASME Standards (American Society of Mechanical Engineers)

• ISO Standards (International Organization for Standards)

• ASTM International Standards

• DIN Standards (Deutsches Institut für Normung)

Each of these organizations has a list of standards concerning the composition and quality of electrodes and consumables in welding. However, as a new welder, you will likely use AWS (American Welding Society) standards to identify a welding alloy.

The AWS has a long list of Filler Metal Specifications by Material and Welding Process. You can find a filler metal based on each process (MIG/Flux Core, TIG, or Stick welding), or according to base metal composition (Filler metal for steel, aluminum, stainless steel, nickel, magnesium, or titanium).

If you need help looking for welding alloys for different types of metals, consult the AWS filler metal specifications. Here are some document references you can use to find a perfect match.

The sole purpose of adding standards to filler metals is to protect the welders. The codes state minimal and maximal amounts and required additives. So you can buy the same welding alloy from different manufacturers, and it will have the same composition.

Stick Welding Cast Iron
Source: https://www.youtube.com/watch?v=Lonih-h-cEI&t=214s

Choosing The Right Materials For The Job

Choosing suitable welding alloys for the job can be a complex task due to various factors. Some common factors that can affect the choice and make or break a project are tensile strength, yield strength, welding process, base metal properties, and the type of metal you are welding.

Therefore, when choosing the right filler metal for the job, you should consider the following:

• Welding process

• Welding alloy properties

• Base metal properties

• Welding applications

MIG Welding Stainless Steel
Source: https://www.youtube.com/watch?v=TQkSGtqJNh4&t=602s

Welding Process and Welding Alloys

As noted above, welding alloys come in different forms and shapes. Each welding process uses a different form of welding alloy, and this is the first step in choosing the right one for your applications. Although there are dozens of welding processes today, we will focus on the four most popular ones: MIG welding, Flux Cored Arc welding, Stick welding, and TIG welding.

MIG Welding (Gas Metal Arc Welding) uses a solid wire welding alloy, arranged in spools. You mount the spool on the side of your welder, and it automatically feeds it through a wire feed mechanism, liner, and into your gun. The MIG wire is a solid filler that requires external shielding gas protection from contamination.

ER70S-6/10LB-0.8 .030" 10LB Spool Carbon Steel Solid MIG Welding Wire

Flux-Cored Arc Welding (FCAW) is a wire welding process and a variant of MIG Welding. This welding method also uses an automatically fed wire, but it is tubular. The flux-cored wire is hollow and filled with flux that melts and forms a layer of slag. The slag protects the molten metal from atmospheric contamination, so you don't need a shielding gas.

E71T-GS/2LB-0.9 2LB Spool .035" Gasless Flux Core MIG Welding Wire

Stick Welding (Shielded Metal Arc Welding) uses a welding alloy in the form of self-shielded electrodes. These electrodes have a core with base metal composition, and flux shielding that melts and creates the slag. Unlike wire, the electrodes are shorter and clamped directly into an electrode holder.

TIG welding (Gas Tungsten Arc Welding) uses a welding alloy known as TIG rod. TIG rods are similar to wire but not arranged in spools. The rods are shorter than wires and straight, but have the same diameter as wires. You feed the rod manually, with one hand, while holding the torch with your dominant hand.

Welding Alloy Properties

Welding alloys have various properties that can affect their weldability and welding performance in different situations or applications. Some fillers are incompatible with specific metals, while some work great, but there are two important mechanical properties you should first consider.

Two essential mechanical properties of welding alloys are:

• Yield strength
• Tensile strength

Tensile Strength vs. Yield Strength
Source: https://www.basilius.com/blog/tensile-strength-vs-yield-strength-understanding-the-fundamentals/

Tensile strength measures the breaking point of an alloy. This characteristic measures the maximum stress material can withstand while being stretched or pulled before breaking. Meanwhile, yield strength measures the maximum stress that can be applied before permanent shape change. Once the stress surpasses a certain point, a transition from elastic to plastic occurs and causes a weld failure.

When choosing the right welding alloy for the job, you should match the strength of filler metal and base metal. The created weld and base metal will resist the external stresses without failing. A weld alloy with lower or much higher strength can cause cracking or deformities.

Other important properties include hardness, brittleness, and ductility. Each property can also affect the structural integrity of the weld, so choosing the right filler for the job is essential.

Ductility vs. Brittleness
Source: https://blog.goldsupplier.com/ductility-vs-brittleness/

Base Metal Properties

When choosing welding alloys, don't forget the base metal. Beginners and new welders often fuse incompatible metals, creating a failure. Always try to match the base metal to the filler metal to avoid this mistake. The base metal and welding alloy should have compatible properties.

Failing to do so can create a brittle structure prone to cracking and failure. In addition, some metals are more flexible, harder, or softer than others. Using a hard alloy for soft, flexible metal can create an unwanted stress point, causing the base metal to crack along the edges.

Be careful when welding dissimilar metals. Dissimilar metals can have different thermal conductivity and expansion, magnetic properties, metallurgical structure, and corrosion resistance. Choosing the right filler can be challenging, so check out our article on How to weld dissimilar metals to learn more.

Welding Dissimilar Metals
Source: https://www.youtube.com/watch?v=J4Cxk1nZyaY

Weld Applications and Welding Alloys

Another consideration when choosing welding alloys comes from the weld applications. For example, you can build projects that are in contact with water, need to look beautiful, or are often subjected to stress.

Different alloys are more resistant to corrosion than others. For example, naval-bronze, aluminium-bronze, nickel-aluminium-bronze, and copper-nickel fillers show excellent corrosion resistance, making them suitable for welds exposed to water.

Welding aesthetics can also be crucial. For example, two popular aluminum fillers, ER4043 and ER5356, have different final appearances. ER5356 provides a color match after anodizing, making it more suitable for visually appealing welds.

Two Popular Aluminum Filler Wires: ER4043 (Silicon-Based) and ER5356 (Magnesium-Based)

Can You Weld Without Filler Metal?

As a home, hobby, or DIY welder or metal fabricator, 95% of your welding applications will require welding alloys. Welders use filler metal in most applications that involve welding two pieces with a gap between them. The most common applications are metal pieces thicker than 20 ga., and common metal joining processes such as MIG, TIG, or Stick welding.

However, there are specific cases in which you won't need welding alloys. For example, when welding thin sheets of 20-22 ga, welders often decide to leave no gap at all. Then, the pieces are welded without a filler metal, in a process known as fusion welding, or Autogenous welding.

Autogenous TIG Welding
Source: https://www.youtube.com/watch?v=x98C922CLf0

Welding thin metal sheets without filler metal reduces the overall heat impact and the risk of burn-through or distortion. The most common technique is fusion TIG welding, which provides the optimal heat control.

Other examples of welding without welding alloys include specific welding methods such as resistance welding, laser welding or forge welding. Resistance welding methods, such as spot welding, involve joining thin sheets by applying pressure and heat. Traditional laser beam welding involves joining pieces by the heat of the laser, without adding additional filler.

As you can see, these are specific applications or methods that don't require filler metal. In most other cases, you will want to use a welding alloy to fill the gap between the two pieces.

Some Examples of Welding Without Welding Alloys

Final Thoughts

Welding alloys are an essential part of most welding applications. You will need a filler metal to fill the gap and provide a strong and everlasting bond between the two pieces.

However, the bond will be everlasting and solid as long as you make the right choice in selecting the suitable alloy for the job. With the many options available, choosing the right welding alloy can be challenging, but understanding the basics can drastically help you make an informed choice.