Posted by Robert Hernandez on Sep 17th 2026
| Term | Definition |
|---|---|
| Hand truck | A two wheeled cart with a means of securing gas cylinders to it, such as with chains or straps. |
| Hard facing/surfacing | The application of a hard, wear-resistant alloy to the surface of a softer metal by an arc welding process. |
| Hardness | The ability of a metal to resist plastic deformation; the same term may refer to stiffness or temper, resistance to abrading or scratching. |
| Hardness test | A measurement of hardness made by forcing a steel ball or pointed diamond under a given force into the surface of a material. |
| Heat | Molecular energy in motion. |
| Heat conductivity | The speed and efficiency of heat energy movement through a substance. |
| Heat affected zone | That part of the base metal which has been altered by the heat from welding, but may not have actually melted. |
| Heliarc welding | A welding process that uses two tungsten electrodes to create an arc. Sometimes used incorrectly to refer to TIG (GTAW) welding. |
| Helium | An inert, colorless gas used as a shielding gas in welding. |
| Helmet | A protective hood that fits over the welder's head and includes a filter plate through which the welder can safely observe the electric arc. |
| Hertz | A unit of measurement, the number of cycles per second, for measuring alternating current. |
| High Frequency | Measurements of amperage above 50,000 hertz, used in TIG welding for arc ignition and stabilization. |
| Horizontal position | A weld performed on a horizontal seam at least partially on a vertical surface. |
| Hose | Flexible medium used to carry gases from the regulator to the welding machine. Welding hoses are typically made from rubber or vinyl and may be reinforced with fabric. |
| Hot hardness | The ability of a metal to retain its strength at high temperatures. |
| Hot pass | A second pass in a multiple-pass welding joint. |
| Hydraulic | A term that refers to a device actuated by the use of a fluid to transmit and/or multiply force. |
| Hydrogen | A gas formed of the single element hydrogen. It is considered one of the most active gases. |
