Imbalance

A condition such that the mass of a shaft and its geometric centerlines do not coincide.

Intermediate-speed coupling

A coupling designed to operate at a surface velocity of 2300-3200 in./sec. For an intermediate-speed coupling, V = D x rpm/ 19, where D is the maximum outside diameter of the coupling in inches.

Isothermal Transformation

A change in phase that takes place at a constant temperature. The time required for transformation to be completed, and in some instances the time delay before transformation begins, depends on the amount of supercooling below (or superheating above) the equilibrium temperature for the same transformation

Isothermal Transformation (IT) Diagram

Set of curves drawn using logarithmic time and linear temperature as coordinates, which define for each level of temperature the beginning and end of the transformation of the initial phase under isothermal conditions.

Intense Quenching

Quenching in which the quenching medium is cooling the part at a rate at least two and a half times faster than still water. See Grossmann chart .

Intercritical Annealing

Any annealing treatment that involves heating to, and holding at, a temperature between the upper and lower critical temperatures to obtain partial austenitization, followed by either slow cooling or holding at a temperature below the lower critical temperature.

Ion Carburizing

A method of surface hardening in which carbon ions are diffused into a workpiece in a vacuum through the use of high-voltage electrical energy. Synonymous with plasma carburizing or glowdischarge carburizing.

Ion Nitriding

A method of surface hardening in which nitrogen ions are diffused into a workpiece in a vacuum through the use of high-voltage electrical energy. Synonymous with plasma nitriding or glowdischarge nitriding.

Isothermal Annealing

Austenitizing a ferrous alloy and then cooling to and holding at a temperature at which austenite transforms to a relatively soft ferrite carbide aggregate.

Immersed-Electrode Furnaces

A furnace used for liquid carburizing of parts by heating molten salt baths with the use of electrodes immersed in the liquid. See submerged-electrode furnace .