SPHEROIDIZING. Any process of heating and cooling steel that produces a rounded or globular form of carbide. The
spheroidizing methods generally used are:
a. Prolonged heating at a temperature just below the lower critical temperature, usually followed by relatively slow
b. In the case of small objects of high carbon steels, the spheroidizing result is achieved more rapidly by prolonged
heating to temperatures alternately within and slightly below the critical temperature range.
c. Tool steel is generally spheroidized by heating to a temperature of 749°-804C (1380° 1480F) for carbon steels and
higher for many alloy tool steels, holding at heat from 1 to 4 hours, and cooling slowly in the furnace.
STRAIN. The elongation per unit length.
STRESS. The internal load per unit area.
STRESS-RELIEF. This is annealing process which removes or reduces residual stresses retained after forming, heat
treating, welding or machining. The anneal is accomplished at rather low temperatures for the primary purposes of
reducing residual stresses, without material affecting other properties.
TEMPERING (ALSO TERMED DRAWING). Reheating hardened steel to some temperature below the lower critical
temperature, followed by any desired rate of cooling. Although the terms "tempering" and "drawing" are practically
synonymous as used in commercial practice, the term "tempering" is preferred.
TENSILE STRENGTH. The tensile strength is the maximum load per unit area which a material is capable of
withstanding before failure. It is computed from the maximum load carried during a tension test and the original cross-
sectional area of the specimen.
TENSION. That force tending to increase the dimension of a body in the direction of the force.
THERMOCOUPLE. Thermocouple consists of a pair of wires of dissimilar metals connected at both ends. When the
two junctions are subjected to different temperatures an electric potential is set up between them. This voltage is almost
in direct proportion to the temperature difference, and hence, a voltage measuring instrument inserted in the circuit will
measure temperature. The voltage measuring instrument is usually calibrated in °C or F.
TOLERANCES. Slight deviations in dimensions or weight or both, allowable in the various products.
VISCOSITY. Viscosity is the resistance offered by a fluid to relative motion of its parts.
WIRE. The product obtained by drawing rods through a series of dies.
WORK HARDNESS. Hardness developed in metal resulting from mechanical working, particularly cold working.
YIELD POINT. The load per unit of original cross section at which a marked increase in deformation occurs without
increase in load..
YIELD STRENGTH. Stress arbitrarily defined as the stress at which the material has a specified permanent set (the
value of 0.2% is widely accepted).
YOUNG'S MODULUS. See Modulus of Elasticity.