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H

Half Hard Temper
(A) In low carbon cold-rolled strip steel, produced by cold rolling to a hardness next to but somewhat softer than full hard temper. (B) In brass mill terminology, half hard is two B&S numbers hard or 20.70% thickness reduction. (C) In Stainless Steel Strip, Tempers are based on minimum tensile or yield strength. For Chromium-Nickel grades Half-Hard Temper 150,000 T.S., 110,000 Y.S.Min.

Hammer Forging
Forging in which the work is deformed by repeated blows. Compare with press forging.

Hard Chromium
Chromium deposited for engineering purposes, such as increasing the wear resistance of sliding metal surfaces, rather than as a decorative coating. It is usually applied directly to basis metal and is customarily thicker than a decorative deposit.

Hard Drawing
Drawing metal wire through a die to reduce cross section and increase tensile strength.

Hard Drawn
Wire or tubing drawn to high tensile strength by a high degree of cold work.

Hard Drawn Spring Steel Wire
A medium high carbon cold drawn spring steel wire. Used principally for cold wound springs.

Hard Temper
(A) (For steel see Full Hard Temper) (B) In brass mill terminology. Hard Temper is four B&S numbers hard or 37.1% reduction.

Hardenability
In a ferrous alloy, the property that determines the depth and distribution of hardness induced by quenching.

Hardenability
The ability of a metal, usually steel, to harden in depth as distinguished from the terms hardness.

Hardenability
In ferrous alloys, the property that determines the depth and distribution of hardness induced by quenching.

Hardened and Tempered Spring Steel Strip
A medium or high carbon quality steel strip which has been subjected to the sequence of heating, quenching and tempering.

Hardening
Increasing hardness by suitable treatment, usually involving heating and cooling. When applicable, the following more specific terms should be used: age hardening, case hardening, flame hardening, induction hardening, precipitation hardening, quench hardening.

(2) Increasing the hardness by suitable treatment, usually involving heating and cooling.

(3) Any process which increases the hardness of a metal. Usually heating and quenching certain iron base alloys from a temperature either within or above the critical temperature range.

Hardness
Degree to which a metal will resist cutting, abrasion, penetration, bending and stetching. The indicated hardness of metals will differ somewhat with the specific apparatus and technique of measuring. For details concerning the various types of apparatus used in measuring hardness, See Brinell Hardness, Rockwell Hardness, Vickers Hardness, Scleroscope Hardness. Tensile Strength also is an indication of hardness.

Hardness (indentation)
Resistance of a metal to plastic deformation by indentation. Various hardness tests such as Brinell, Rockwell and Vickers may be used. In the Vickers test, a diamond pyramid with an included face angle of 136 is used as the indenter.

Heat of Steel
The product of a single melting operation in a furnace, starting with the charging of raw materials and ending with the tapping of molten metal and consequently identical in its characteristics.

Heat Tinting
Colouration of a metal surface through oxidation by heating to reveal details of structure.

Heat Treatment
Heating and cooling a solid metal or alloy in such a way that desired structures, conditions or properties are attained. Heating for the sole purpose of hot working is excluded from the meaning of this term.

(2) Altering the properties of a metal by subjecting it to a sequence of termperature changes, time of retention at specific temperature and rate of coolingtherfrom being as important as the temperature itself. Heat treatment usually markedly affects strength, hardness, ductility, malleability, and similar properties of both metals and their alloys.

Heat-Affected Zone
That portion of the base metal which was not melted during brazing, cutting, or welding, but whose microstructure and physical peoperties were altered by the heat.

Hematite
The oxide of iron of highest valency which has a composition close to the stoichiometric composition Fe2O3.

High Brass
65% A copper-zinc alloy containing 35% zinc. Possesses high tensile strength. Used for springs, screws, rivets, etc.

Homogenizing
Holding at high temperature to eliminate or decrease chemical segregation by diffusion.

Homogenizing Annealing
An annealing treatment carried out at a high temperature, approaching the solidus temperature, for a sufficiently long time that inhomogeneous distributions of alloying elements are reduced by diffusional processes.

Honing
Removing stock generally on the internal cylindrical surface of a workpiece with an abrasive stick mounted in a holder.

Hooke's Law
Stress is proportional to strain in the elastic range. The value of the stress at which a material ceases to obey Hooke's law is known as the elastic limit.

Hot Dip
In steel mill practice, a process wherby ferrous alloy base metals are dipped into molten metal, usually zinc, tin, or terne, for the purpose of fizing a rust resistant coating.

Hot Short
Brittleness in hot metal.

Hot Shortness
Brittleness in metal in the hot forming range.

Hot Top
(1) A reservoir, thermally insulated or heated, to hold molten metal on top of a mold to feed the ingot or casting as it contracts on solidifying to avoid having pipe or voids.

Hot Working
Deformation under conditions that result in recrystallization.

(2) Plastic deformation of metal at a temperature sufficiently high not to create strain hardening. The lower limit of temperature for this process is the recrystallization temperature.

Hydrogen Embrittlement
A condition low ductility in metals resulting from the absorbtion of hydrogen.

(2) Brittleness of metal, resulting from the occlusion of hydrogen (usually as a by-product of pickling or by co-deposition in electroplating).

(3) A condition of low ductility resulting from hydrogen absorption and internal pressure developed subsequently. Electrolytic copper exhibits similar results when exposed to reducing atmosphere at elevated temperatures.

Hypereutectoid Alloy
In a eutectoid system, any alloy containing more than the eutectoid concentration of solute.

Hypereutectoid Steel
A steel having more than the eutectoid percentage of carbon.