Glossary of terms


Active Fluxes Active fluxes produce changes in weld metal chemistry when welding in changed.
AISI American Iron and Steel Institute.
Ampere Unit of electrode rate of flow. Amperage in commonly referred to as the “current” in an electrical circuit.
ASME American Society of Mechanical Engineers.
Austenite High temperature crystal structure of carbon steel or the room temperature structure of chrome-nickel steel.
ASTM American Society of Testing and Materials.
Cellulose A chemical of carbon, hydrogen and oxygen. As used in mild steel electrode coatings, it consists of wood pulp or flour.
Current Density The amperes per square inch of cross-sectional area of an electrode. High current density result in high electrode melt-off rate and a concentrated, deep penetrating arc.
Carbon Steel Sometime referred to as mild steel. An alloy of iron and carbon. Carbon content is usually below 0.3%.
Conductor A material which has a relatively large number of loosely bonded electrons which may move freely when voltage (electrical pressure) is applied. Metals are good conductors.
Carbide Precipitation The formations of chromium carbide in austenitic stainless steel that allow inter granular corrosion in corrosive service.
Direct Current An electrical current which flows in only one direction in a conductor. Direction of current is dependent upon the electrical connections to the battery or other DC power source. Terminals on all DC devices are usually marked (+) or (-). Reversing the leads will reverse the direction of current flow.
Electron Negatively charged particles that revolve around the positively charged nucleus in an atom.
Electrode Core Wire The wire about which the coating is applied. The electrode size is determined by the diameter of the core wire.
Electrode Coating The mixture of chemicals, minerals and metallic alloy applied to the core wire. The coating controls the welding current, the welding position, and provides as shielding atmosphere, deoxidizers to clean the weld metal. It also helps shape the weld bead and becomes an insulating blanket over the weld bead.
Ferrous Containing iron. Example; carbon steel, low alloy steels stainless steel.
Ferrite The normal crystal structure of low carbon steel at room temperature.
Ferrite Number Ferrite Numbers (FN) are the current industry accepted figures for specifying ferrite content in austenitic stainless steel weld metal, as approved by the Welding Research Council (WRC), American Welding Society (AWS) and other organizations. Adopted during the 1970’s, “ferrite number” is not to be confused with “Percent Ferrite” that is still used in some cases.
Hertz (Hz) is the symbol which has replaced the term “cycles per second”. Today, rather than saying 60 cycles per second or simply 60 cycles, we say 60 Hertz or 60 Hz.
High Alloy Steel Steels containing in excess of 10% alloy content. Stainless steel is considered a high alloy because it contains in excess of 10% chromium.
Heat Affected Zone The area of the base metal that did not become molten in the welding process, but did undergo a microstructure change as a result of the head induced into the area. If the HAZ in hardenabie steels is cooled rapidly, the area becomes excessively brittle.
Insulator A material which has a tight electron bond, that is, relatively few electrons which will move when voltage (electrical pressure) is applied. Wood, glass, ceramics and most plastic are good insulators.
Interpass Temperature The lowest temperature at which the part being welded is held during welding.
Low Hydrogen Electrodes Stick electrodes that have coating ingredients that are very low in hydrogen content. The low hydrogen level is achieved primarily by keeping the moisture content of the coating to a bare minimum.
Low Alloy Steels Steel containing small amounts of alloying elements (usually 1-1/2% to 5% total alloy content) which drastically improves their properties.
Metallurgically Similar Steels Multiple steel compositions that have essentially the same crystal structure, such as austenite or ferrite.
Mild Steel An alloy of mostly iron with low content of alloying elements such as carbon and manganese.
Martensite The hard phase that develops on rapid cooling of carbon and low alloy steels.
Manual Arc Welding Welding with a coated electrode where the operator’s hand controls travel speed and the rate of electrode is fed into the arc.
Non-Ferrous Containing no iron. Example; Aluminum, copper, copper alloys.
Neutral Fluxes Neutral fluxes produce little change to mechanical properties when adjusting the voltage. Best utilized when welding on plate thickness of one inch or more.
Proton Positively charged particles which are part of the nucleus of atoms.
Preheat The heating of the parts of a structure to be welded before welding is started.
Quench The rapid cooling of steel from a temperature above the transformation temperature. This result in hardening of the steel.
Reverse Polarity Welding condition when the electrode is connected to the positive terminal and the work is connected to the negative terminal of the welding power source.
SAE Society of Automotive Engineers.
Spalling The loss of particles of pieces from a surface due to cracking.
Stainless Steel The magnetic finely dispersed crystal structure in austenitic steels that causes the austenite grains to become smaller and crack resistant.
Straight Polarity Welding condition when the electrode is connected to the negative terminal and the work is connected to the positive terminal of the welding power source.
Slag The brittle mass that forms over the weld bead on welds made with coated electrodes, flux cored electrodes, submerged arc welding and other slag producing welding processes. Welds made with the gas metal arc and the gas tungsten arc welding processes are slag free.
Volt Unit of electromotive force, or electrical pressure which causes current to flow in an electrical circuit.
Watt A unit of electrical power. Watts = Volts x Amperes.