H

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

Hardness, Brinell:  The relative hardness value of a metal tested by measuring the diameter of the impression made by a ball of given diameter applied
under a known load. Values are expressed in Brinell Hardness numbers.

Hardness, Rockwell:  The relative hardness value of a metal determined by measuring the depth of penetration of a steel ball (1/16 in. dia. for B Scale) or a
diamond point (C Scale) with controlled loading, the Rockwell number being the difference between the depth obtained with a minor and a major loading.

Head Metal: The reservoir of metal in the feeder or riser of a mold.

Heat:  A stated tonnage of metal obtained from a period of continuous melting in a cupola or furnace; or the melting period required to handle this tonnage.

High Pressure Mold:  A strong high-density mold, made by air, hydraulic or other squeeze process.

Hollow Drill Testing (Trepanning):  Removing a cylindrical sample from a metal section or structure to determine soundness of the section.

Homogenizing:  A process of heat treatment at high temperature intended to eliminate or decrease chemical segregation by diffusion.

Hot Box Process:  A furan resin based process similar to shell coremaking; cores produced with it are solid unless mandrelled out.

Hot Strength (Sand): Tenacity (Compressive, shear or. transverse) of a sand mixture determined at any temperature above room temperature.

Hydrogen Embrittlement: A condition of low ductility resulting from the absorption of hydrogen.

Hypereutectoid Steel:  A steel containing more than the eutectoid percentage of carbon (0.83%).

Hypoeutectaid Steel: A steel containing less than the eutectoid percentage of carbon (0.83%).

Hysteresis (Cooling Lag): Difference between the critical points on heating and cooling due to tendency of physical changes to lag behind
temperature changes.