Despite its challenging aspects, welding dissimilar metals is a commonly used process in the construction, oil & gas, automotive, and aerospace industries, to name a few. That is because it helps bring together different metal properties, thus lowering material cost and improving performance. However, in order to have a good weld, it is critical to understand what materials are involved, what your desired welding result is, which welding process is available to you, and what filler metal is required. Otherwise, you might have undesired problems, like poor bonding, cracking, or material failure. Here, we will guide you into the selection of filler metals, or consumables, for your welding process.

What is a filler metal?

A filler metal is a material that melts upon heating to flow in between two adjacent metal workpieces and create a weld joint. It is, generally, an alloyed material with specific melting and flow properties, which can produce a joint that meets service requirements, such as corrosion resistance and mechanical strength. It is basically used or consumed until it becomes part of the created weld.

Not all welding processes require a filler metal, but for the ones that do, filler metals are a fundamental element. These processes are typically under the umbrella of fusion welding. Fusion welding is all welding practices that involve melting of materials to join multiple workpieces together at distinct points. Arc welding, for example, is a type of fusion welding, and it includes a variety of welding techniques that make use of an intermediate filler metal.

When selecting a filler metal, you have to consider the following factors:

• Base materials: what materials do you intend to weld? Check if their chemistry and mechanical properties are equivalent. If their strengths are different, match your filler metal’s strength to that of the weaker material.
• Welding position: the position of your welding can restrict your operation and undermine the welding efficiency. Make sure to select a filler metal versatile enough in terms of type and size.
• Shielding gas: be careful in selecting filler metals compatible with the available shielding gas, especially active gases like CO2 mixtures.
• Design requirements: specify your design requirements before selecting the filler metal. This helps you select a filler metal with the right penetration characteristics and properties.
• Environment: make sure to follow specifications and codes that indicate what filler metal meets the conditions of your end product. This is crucial so that the weld does not corrode or deteriorate, which could lead to weld failure.
• Welding equipment and power: electric current and filler metal should be carefully chosen to avoid undesirable weld spatter and poor weld quality.
• Heat-treatment compatibility: understand your pre-and post-weld heat treatments in order to select a filler metal that responds appropriately to that heat.

How filler metals are used in welding dissimilar metals

Welding dissimilar metals is a solution that answers the need for efficiently compiling good material properties while maintaining reliability and cost-effectiveness. But in order to do that, you have to take into account several considerations, primarily the types of materials involved.

Arc welding processes are useful techniques for welding dissimilar metals, but they require suitable filler metals to create a weld with sufficient bonding strength and corrosion resistance. These processes include gas metal arc welding (GMAW), gas tungsten arc welding (GTAW), shielded metal arc welding (SMAW), and flux-cored arc welding (FCAW). The following sections provide an insight into those welding processes and how the filler metals are employed in each. To see examples of filler metals, check Table 1 below.

Filler metals for GMAW

Gas metal arc welding (GMAW) is a process that makes use of a shielding gas protecting the weld pool from contamination and external factors, such as oxygen. GMAW processes can be classified based on the nature of the shielding gas. If the gas is an inert gas, like argon or helium, the process is more commonly referred to as metal inert gas (MIG) welding. If the gas is a reactive gas, such as carbon dioxide, the process is called metal active gas (MAG) welding.

Both MIG welding and MAG welding utilize a consumable electrode that is initially in the form of a solid wire. This continuous metal wire is passed through the welding gun and brought to contact with the workpiece. Once an electric current is applied, a welding arc is generated, which heats up the metal, causing it to melt and fuse with the base metals. The material that makes up this continuous electrode is the filler metal. Some of the commonly used filler materials are aluminium bronze and copper alloys. They can be used to weld various kinds of metals, including ferrous, non-ferrous, and copper-based materials.

Filler metals for GTAW

Gas tungsten arc welding (GATW) is another arc welding process that uses a shielding gas. In fact, it is also referred to as tungsten inert gas (TIG) welding, where just like MIG welding, it uses a noble gas as the shielding gas. However, it employs a non-consumable electrode made of pure tungsten or tungsten alloy. This electrode comes in the form of a solid wire or rod and, thanks to its high melting point, does not melt under the generated heat. This allows the generated electric arc to burn freely as the welding gun is moved over the workpiece.

For that reason, TIG welding requires a separate filler metal to be held in close proximity to the electric arc so it can heat up, melt, and coalesce with the base metals to create the weld joint. TIG welding is compatible with similar filler metals like those of MIG welding and MAG welding, mainly aluminium bronze.

Filler metals for SMAW

Another commonly used technique for welding dissimilar metals is shielded metal arc welding (SMAW). Also referred to as flux shielded arc welding – or more practically, stick welding – SMAW is a manual welding process. It utilises a consumable electrode without the need for a shielding gas. That is because the electrode is coated with a flux material that can do the shielding job. This basically happens during the welding process, where the flux disintegrates and forms inert gases and a slag that help protect the melt from oxygen.

The filler metal is the material that makes up the consumable electrode, and it can be different grades of aluminium bronze, as well. In fact, some of these filler metals can be overlay filler metals, which act as layers that enhance the properties of corrosion resistance, hardness, and wear resistance. 

Filler metals for FCAW

Flux-cored arc welding (FCAW) is a similar technique to SMAW but is distinct in terms of how weld shielding is done. In fact, FCAW was developed specifically to replace SMAW with its automatic/semi-automatic functionalities and its continuous supply of a consumable tubular electrode – comparable to MAG welding.

FCAW uses two types of shielding:

• Self-shielding, where the flux material coating the electrode disintegrates upon heating and generates protective gases and slag.
• Dual-shield welding, where in addition to the flux material’s shielding job, an additional shielding gas is supplied, usually a gas mixture of carbon dioxide and argon.

Such protection allows its use in outside settings, where the risk of contamination and oxidation is higher, such as in maritime applications.

Similarly, filler metals constitute the consumable electrode, and they are usually overlay filler metals as they can provide the necessary oxidation and corrosion resistance to the base materials.

Filler metals and how to find them

Evidently, filler metals have an extensive range of use in terms of welding processes, compatible base materials, and application areas. The table below shows a list of filler metals provided by AMPCO METAL, a leading supplier of engineering metal products. Explore the different materials and their applications.

Table 1. Filler metals for different arc welding processes

Filler metal	Compatible welding processes	Materials that can be welded	Application areas
AMPCO-TRODE® 10 (aluminium bronze)	MIG welding MAG welding TIG welding SMAW	Ferrous metals, non-ferrous metals, high-carbon steel, low-carbon steel, copper, bronze, copper-nickel alloys, steel to bronze, cast iron to steel, cast iron to bronze, copper to steel	Bearings, bushings, pump housings, condenser boxes, hydraulic pistons, brake drums, tractor gear housings, motor bases, tin plate mill rolls, gears, valve seats, press rams, ship propellers
AMPCO-TRODE® 46 (nickel-aluminium bronze spooled wire)	MIG welding MAG welding TIG welding SMAW	Cast nickel-aluminium bronze, wrought nickel-aluminium bronze	Ship fittings, propeller gear housings, power plant valves, marine propulsion systems, oil recovery pumps, piping systems, ship propellers
AMPCO-TRODE® 150 (aluminium bronze)	MIG welding MAG welding TIG welding SMAW	Copper bronze alloys	Hydraulic pistons, bearings overlays, impellers, turbine runners, press rams, valve seats, breaker blocks, steel mill rolls
AMPCO-TRODE® 940 (aluminium bronze, good alternative to beryllium copper)	MIG welding MAG welding TIG welding	Wrought copper alloys	Mould cores, mould pins, repair of blow moulds, injection moulds
COPR-TRODE® (deoxidised copper alloy)	MIG welding MAG welding	Deoxidised copper, copper castings, galvanised steel	Billet moulds, conductor rolls, heater elements, copper sculptures, copper connectors, bus bars
AMPCO-CORE® 200 (aluminium bronze flux core wire)	MIG welding MAG welding SMAW FCAW	Copper bronze alloys	Gear teeth Friction plates Pump shafts Bearings high-speed bearings Stripper columns Sliders Wear plates
AMPCO-CORE® 250 (aluminium bronze flux core wire)	MIG welding MAG welding SMAW FCAW	Copper bronze alloys	Friction plates Bearings, high-speed bearings Sliders Forming dies
AMPCO-CORE® 250s (nickel-aluminium bronze metal core wire)	MIG welding MAG welding FCAW	Aluminium bronze Ferrous metals	Shafts Guide grooves Marine applications Overlaying steel parts without a buffer layer
AMPCO-CORE® 300 (aluminium bronze flux core wire)	MIG welding MAG welding SMAW FCAW	Ferrous metals, stainless steel, low-carbon steel, medium-carbon steel, titanium	Ferrous dies, forming or drawing titanium, fabricating new rebuilding of worn parts

 

AMPCO METAL has long been providing engineers and customers with suitable materials, and they continue to do that here through Matmatch. You can further your search options by exploring AMPCO METAL’s wide range of materials listed on our platform.

You can also get in direct contact with them for more information by visiting the AMPCO METAL supplier page.