Welding Glossary H

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.