Filler Materials and Flux
The metals added during the welding process are known as filler materials or filler metals. Filler materials used in welding processes include welding rods and electrodes.
In welding processes in which space is left between the parts to be joined, filler metals provide the intimacy of contact necessary for coalescence.
Welding Rods
The term welding rod refers to a filler metal, in wire or rod form, used in gas welding and brazing processes and in certain electric welding processes (tungsten inert gas) in which the filler metal is not a part of the electric circuit. A welding rod serves only one purpose - it supplies filler metal to the joint.
As a rule, rods are uncoated except for a thin film resulting from the manufacturing process. Welding rods for steel are often copper-coated to protect them from corrosion during storage. Most rods are furnished in 36-inch lengths and a wide variety of diameters, ranging from 1/32 to 3/8 inch. Rods for welding cast iron vary from 12 to 24 inches in length and are frequently square rather than round in cross section. The rod diameter selected for a given job is governed by the thickness of the metals being joined.
Electrodes
In electric welding, electrodes form a part of the electrical circuit. In gas tungsten arc welding, electrodes melt off and are a source of the filler metal supply.
- Solid Electrodes - These electrodes are consumable (composed of steel, copper, aluminum, various alloys, and other metals) or non-consumable (primarily tungsten). They produce less fumes, compared with flux-cored wire or coated electrodes.
- Covered and Coated Electrodes - These are the largest group of electrodes used in welding. The covering provides the flux from the weld. Major metals from the coatings include fluoride, nickel, iron, chromium, manganese, copper, and molybdenum
Fluxes
Welding or brazing certain materials requires the use of flux to produce a sound joint. Fluxes are available as liquids, pastes, and powders.
They have a melting point below that of the base and filler metals, and they are not incorporated into the weld. Their primary purpose is to prevent the formation of oxides on the weld joint before and during welding operations. Fluxes should never be used as a substitute for proper cleaning.
Observe the following precautions when you are working with fluxes.
- Unless the base metal is properly cleaned and the correct flux applied to the joint, fluxing will hinder rather than aid in making the joint.
- Flux should not be overheated, or it will fail to serve its purpose.
- Fluxes will also deteriorate if they are kept at brazing temperatures for too long.
- Fluxes should always be used in a well-ventilated space.
Knowledge Check Choose the best answer for the question.
1-3. What is the only purpose of a welding rod?
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