High-speed coupling

A coupling designed to operate at a surface velocity above 3200 in./sec. For a high-speed coupling, V = D x rpm/l9, where D is the maximum outside diameter of the coupling in inches.

Horsepower

The unit of power that has been adopted for engineering work in the English system. One horsepower (1 hp) is equal to 33,000 ft-lb (of work) per minute, or 550 ft-lbhec.

Hypereutectoid Alloy

In an alloy system exhibiting a eutectoid, any alloy whose composition has an excess of alloying element compared with the eutectoid composition, and whose equilibrium microstructure contains some eutectoid structure.

Hypoeutectic Alloy

In an alloy system exhibiting a eutectic, any alloy whose composition has an excess of base metal compared with the eutectic composition, and whose equilibrium microstructure contains some eutectic structure.

Hypoeutectoid Alloy

In an alloy system exhibiting a eutectoid, any alloy whose composition has an excess of base metal compared with the eutectoid composition, and whose equilibrium microstructure contains some eutectoid structure.

Horizontal Batch Furnace

A versatile batch-type furnace that can give light or deep case depths, and because the parts are not exposed to air, horizontal batch furnaces can give surfaces almost entirely free of oxides.

Hot Quenching

An imprecise term used to cover a variety of quenching procedures in which a quenching medium is maintained at a prescribed temperature above 70 °C (160 °F).

Hot-Wire Analyzer

An electrical atmosphere analysis device that is based on the fact that the electrical resistivity of steel is a linear function of carbon content over a range from 0.05% C to saturation. The device measures the carbon potential of furnace atmospheres (typically). This term is not to be confused with the hot-wire test which measures heat extraction rates.

Hot-Wire Test

Method used to test heat extraction rates of various quenchants. Faster heat-extracting quenchants will permit more electric current to pass through a standard wire because it is cooled more quickly. Compare with hot-wire analyzer .

Hypereutectic Alloy

In an alloy system exhibiting a eutectic, any alloy whose composition has an excess of alloying element compared with the eutectic composition, and whose equilibrium microstructure contains some eutectic structure.