What Is the Difference Between Filler Metal and Weld Metal?

What Is the Difference Between Filler Metal and Weld Metal?

An Informative Guide to Filler Metal and Weld Metal

It is not unusual for new welders to get confused between the filler metal and weld metal. The present content walks you through the differences between the filler metal and weld metal.

Filler Metal

Filler metals are used to fill the space between two close-fitting materials in welding, soldering, or brazing. These alloys or unalloyed metals when heated, melt to flow into the gaps between two close-fitting materials to create a weld, soldered or brazed joint. Filler metals have a suitable melting point and flow properties to allow distribution by capillary action in prepared joints.

Joints produced from filler metals meet service requirements such as corrosion, strength and resistance. They also meet nearly all specifications of the American Society for Testing Materials (ASTM), the American Welding Society (AWS) and ISO standards.

Standard filler metals include silver, tin, lead-free, lead, cadmium-free, nickel, copper, aluminium and gold. Filler metals can be found in paste form and solid form (such as slugs, powder, washers, wire and rings). Fusion filler metals are first atomised into powder form and then mixed with flux into a paste composition.

How Is Filler Metal Added

During the welding process, a filler metal is added from an electrode to the joint to be weld. The filler metal is consumed in the welding process (Gas Metal Arc welding (GMAW)) or Flux Cored, Shielded Metal Arc welding (SMAW), Flux-Cored/Metal Cored welding (FC/MCAW) or Shielded Metal Arc welding (SMAW). Filler metal can also be added to the joint as a simple filler wire that is not connected electrically in Plasma Welding (PAW) and Gas Tungsten Arc welding (GTAW).

During the welding process, the heat generated by the electric arc melts the filler metal and surface of the base metal. The melted materials combine forming a weld pool which upon cooling and solidification forms a weld joint. So, the chemical composition of the filler metal changes in the final joint by the addition of melted metal from the base material.

Note: The metal or alloy being welded, soldered, brazed or cut is known as the base metal.

Weld Metal

Weld metal is the material in the welded joint which has been melted in the welding process and then resolidified. It is usually a mixture of the parent metal and filler metal is used, as well as any additions from the flux in consumables.

In some welding procedures (laser welding, autogenous arc welding, resistance welding and electron beam welding), where no filler metal is added to the weld pool, the weld metal has the same composition and characteristics as the base/parent metal.

During the welding process, when no filler metal is added (laser welding, autogenous arc welding, resistance welding and electron beam welding) then the weld metal has the same chemical composition and characteristics as the base/parent metal. However, when a filler metal is added to the weld pool, then the weld metal has different composition and characteristics than the base/parent metal. In such cases, usually, the weld pool has the characteristics of both the filler metal and base/parent metal.

The solidified weld metal possesses mechanical and chemical properties from the base metal and filler metal (electrode).

The composition of the final weld metal depends on:

  • the composition of the base metal
  • the composition of the filler metal
  • the chemical reaction between the weld metal, shielding gas or flux

ESAB offers a wide range of filler metals that you can choose from based on your application and type of welding.