A filler wire is a welding product that is used to lay material in a weld joint to fill up the gaps or to improve the load bearing capacity of the joint between two pieces of metal. It is used in MIG, TIG, and stick welding, among other welding processes, by being fed into the weld pool. There are different kinds of filler wires available on the market, including stainless steel, aluminium, and carbon steel filler wires, based on the type of base metal to be welded. They offer reinforcement, stiffness and other improved properties to the weld that has been done.
Types of Filler Wire
Filler wires come in various types, each designed to suit specific welding processes and applications:
- Solid Filler Wire: An uncoated, smooth and solid wire utilized in the MIG welding that is an acronym for Metal Inert Gas welding. The filler wires are in the form of solid wires and they are made from carbon steel, stainless steel or aluminium to give a clean weld.
- Flux-Cored Filler Wire: This type has a flux core through which the shielding gas and deoxidisers are fed once the flux core is heated and therefore does not require an external supply of the gases. It is used in gas-shielded FCAW-G and self-shielded FCAW-S flux-cored arc welding processes appropriate for high-duty and outdoor welding conditions.
- Seamless Filler Wire: Seamless filler wires are less permeable to moisture as compared to the conventional filler wires which are made in segments and then joined and therefore, the chances of hydrogen induced cracking in the weld are less. They are mainly applied where strength of the welds are needed in service conditions.
- Welded Filler Wire: These are produced by joining the ends of a strip and they are normally employed where a specific filler material and narrow tolerance level is required.
- Metal-Cored Filler Wire: Similar to the solid and the flux cored wires, this wire also contains a tubular core packed with metallic powders and alloys to improve the weld characteristics. High deposition rate is achieved by metal cored wires and offer smooth arc and low spatter.
- TIG Filler Rods: These rods are used in TIG welding and are fed to the weld pool by the operator in the process. They are available in different materials such as aluminium, stainless steel and mild steel and these are very flexible when it comes to welding.
These filler wires are available to meet the various welding processes and base metal needs to produce the best weld.
Different Filler Wire Materials
Filler wires are available in a variety of metal materials to match the base metals being welded and to achieve the desired weld properties:
- Carbon Steel: Carbon steel filler wires are usually used for welding carbon and low alloy steel. It has moderate mechanical characteristics and is used in various types of welding processes for general use.
- Stainless Steel: They are particularly constructed from stainless steel material and are very immune to corrosion and possess high strength which makes them suitable for use in welding of stainless steel parts.
- Aluminium: Aluminum filler wires are relatively lighter in weight and possess a good corrosion resistance. They are used in welding of aluminum and it’s alloys.
- Nickel Alloys: Nickel alloy filler wires of Inconel and Monel are used in welding of nickel based alloys and dissimilar joints. They provide high temperature as well as corrosion resistance.
- Copper and Copper Alloys: Copper filler wires are employed for welding copper and copper alloys for having high electrical conductivity and good corrosion resistance.
- Titanium: It is well established that titanium filler wires are characterized by high strength to weight ratio especially when used under harsh environment. They are used in sectors that demand strength and compatibility of the material with human body.
- Bronze and Brass: Copper and copper alloy filler wires are employed in welding copper and copper alloys and in welding cast iron. It has good wear resistance and can be used in applications where parts are required to have good wear resistance.
- Cobalt Alloys: Cobalt alloy filler wires are used in the regions where components are subjected to high stress, high temperature and corrosion.
This is why such materials offer a number of characteristics that meet specific welding needs.
Features of Filler Wire
Filler wires have several key features that make them suitable for different welding applications:
- Composition: The filler wires are made of the base metals to be welded or similar materials to achieve the best weld properties.
- Diameter: It is available in several sizes to meet the various welding processes and uses in the market. The diameter influences the deposition rate, weld bead profile and heat input when welding.
- Coating and Flux: Some filler wires have some coatings or flux cores which help in supplying shielding gas, deoxidisers and other materials that help in the protection of the weld pool and enhancement of the weld quality. This is particularly the case with flux-cored and metal-cored wires in which the core wire is usually an electrically conducting metal.
- Strength and Ductility: These wires are intended to give strength and flexibility in the weld joint. The mechanical properties of the filler wire are selected in such a manner that they are better than or equal to the base metals to be welded.
- Corrosion Resistance: Therefore, the level of corrosion protection provided by the filler wires depends on the type of material used.
- Conductivity: In MIG welding, the conductor of the filler wire is very crucial because MIG welding is an electrically operated process.
- Cleanliness and Purity: The filler wires are manufactured without any contaminants and impurities which are essential in making a clean weld without any defects such as porosity and inclusions.
- Melting Point: The filler wire’s melting point is adjusted to match the welding process and the base metals to be joined. This is crucial in welding so that the right metallurgical bonding and affinity between the two metals are achieved.
- Flexibility: These filler wires can be rigid or flexible, depending upon the type of welding process and the nature of the job to be done. Manual welding of the wire into the weld pool is possible in TIG welding, and hence, flexibility is an important factor.
Such characteristics make the filler wire suitable for different welding conditions and uses.
Applications of Filler Wire
Filler wires are used in a wide range of applications across various industries, which include:
- Construction: Welding of construction elements, structural steel, beams and other similar materials is done through filler wire. It also offers a good and sound link between the members, thus increasing the stability of structures.
- Automotive: In the automotive industry, filler wire is employed to weld various parts of automobiles, such as frames, bodies, and chassis, as well as exhaust systems. Depending on the material of the component and the automobile's performance characteristics, different types of filler wire are used.
- Aerospace: Filler wire welds aircraft and spacecraft parts because it gives strong, light and resistant joints to severe conditions.
- Shipbuilding: In ship construction, filler wire is utilized to join parts of ships and submarines, such as hulls, decks and piping. The marine environment is also another factor that defines the filler wire, and thus, corrosion-resistant filler wire is used.
- Oil and Gas: Welding of pipelines, pressure vessels, and drilling equipment that is used in the oil and gas industry necessitates the use of filler wire. It has to be able to withstand pressure and resist the corrosive environment that exists during the extraction and processing of the resources.
- Manufacturing: Filler wire is used to manufacture machinery, equipment, and industrial tools. The material to be joined and the application in which the final products will be used are considered.
- Medical Devices: In medical device manufacturing, filler wire is used in welding of surgical instruments, implants and other equipment. It has to be sterile and non-toxic to the human body or at least it should not be hazardous to the human body.
From these applications we can deduce that filler wires are helpful in providing good, sound and clean welds in various working sectors and zones.
