HEAT CHECK: A pattern of parallel surface cracks that are formed by alternate rapid heating and cooling of the
extreme surface metal, sometimes found on forging dies and piercing punches. There may be two sets of parallel
cracks, one set perpendicular to the other.
HEAT CHECKING: The crazing of a die surface, especially when the die is subjected to alternate heating and cooling
by molten metal; the resulting fine cracks produce corresponding veins on castings.
HEAT TINTING: Coloration of a metal surface through oxidation by heating to reveal details of the microstructure.
HEAT TREAT: Heating and cooling of a metal or alloy in the solid state for the purpose of obtaining certain desirable
conditions or properties.
HEAT TREAT CRACKS: See CRACKS, QUENCHING.
HEAT TREATMENT: Exposure of a metal to predetermined temperatures beyond the range of normal atmospheric
conditions for a specific time to obtain a specific range of mechanical properties.
HERTZ: One cycle per second; a unit for frequency. Abbreviation is Hz.
HETEROGENEOUS RADIATION (RT): Radiation consisting of particles or photons that have a broad spectrum of
HIGH-CONDUCTIVITY COPPER: Copper that, in the annealed condition, has a minimum electrical conductivity of
100% IACS as determined in accordance with ASTM methods of test.
HIGH RADIATION AREA: Means an area, accessible to individuals, in which radiation levels could result in an
individual receiving a dose equivalent in excess of 0.1 rem (1 mSv) in 1 hour at 30 centimeters from the radiation
source or from any surface that the radiation penetrates.
HOMOGENIZING: Holding at high temperature to eliminate or decrease chemical segregation by diffusion.
HOMOGENIZING TREATMENT: A heat treatment of an alloy intended to make it uniform in composition by
eliminating coring and concentration gradients.
HOODED ANODE (RT): A type of anode, in medium or high voltage X-ray tubes, in which the target is recessed in a
metal hood that intercepts electrons. The hood may also incorporate a filter to absorb unwanted radiation.
HORIZONTAL LINEARITY (UT): Constant relationship between the incremental horizontal displacement of vertical
indications on an A-scan presentation and the incremental time required for reflected waves to pass through a known
length in a uniform transmission medium.
HORSESHOE MAGNET: A bar magnet, bent into the shape of a horseshoe so that the two poles are adjacent. Usually
the term applies to a permanent magnet.
HOT-CATHODE TUBE (RT): An X-ray tube in which the cathode is electrically heated to provide electrons.
HOT CELL: A heavily shielded enclosure in which radioactive materials can be handled remotely through the use of
manipulators and viewed through shielded windows so that there is no danger to personnel.
HOT CRACKS: See CRACKS, HOT.
HOT FORMING: Working operations, such as bending, drawing, forging, piercing, pressing and heading performed
above the recrystallization temperature of the metal.