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Handling Mark |
- For rolled products, an area of
broken surface that is introduced after processing. The mark
usually has no relationship to the rolling direction.
- For extrusions, damage that can be
imparted to the surface during handling operations.
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Hair, Slitter |
Minute hair-like sliver along edge(s)
due to shearing or slitting operation. |
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Hard Alloys |
A term used to denote the higher
strength alloys. |
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Hardener |
An alloy containing at least some
aluminum and one or more added elements for use in making alloying
additions to molten aluminum. Also referred to as "Master
Alloy" or "Rich Alloy". |
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Hardening |
Increasing hardness by suitable
treatment, usually involving heating and cooling. When
applicable, the following more specific terms should be used:
age hardening and precipitation hardening.
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Hardness |
Degree to which a metal will resist
cutting, abrasion, penetration, bending and stretching. The
indicated hardness of metals will differ somewhat with the specific
apparatus and technique of measuring. For details concerning the
various types of apparatus used in measuring hardness, See Brinell
Hardness, Rockwell Hardness, Vickers Hardness, Scleroscope Hardness.
Tensile Strength also is an indication of hardness.
Brinell Hardness: Brinell
hardness of aluminum alloys is obtained by measuring the permanent
impression in the material made by a ball indenter 10 millimetres in
diameter after loading with a 500 kilogram force for 15 seconds and
dividing the applied load by the area of the impression. |
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Hardness (indentation) |
Resistance of a metal to plastic
deformation by indentation. Various hardness tests such as Brinell,
Rockwell and Vickers may be used. In the Vickers test, a diamond
pyramid with an included face angle of 136 is used as the indenter. |
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Heat Streak |
Milky colored band(s) parallel to the
rolling direction which vary in both width and exact location along
the length. |
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Heat Treat Lot |
Material of the same mill form,
alloy, temper, section and size traceable to one heat-treat furnace
load (or extrusion charge or billet in the case of press
heat-treated extrusions) or, if heat treated in a continuous
furnace, charged consecutively during an 8-hour period. |
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Heat Treat Stain |
A discoloration due to non-uniform
oxidation of the metal surface during solution heat treatment. |
|
Heat Treating |
Normally used to describe a process
where metal is heated at a high enough temperature to put soluble
elements into solid solution. This is followed by cooling the metal
rapidly enough to retain the elements in solid solution. Often a
separate heating operation (artificial aging) will be used
subsequently to further strengthen the material. |
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Heat-Treatable Alloys |
Alloys in the 2XXX, 6XXX and 7XXX
series that achieve their maximum strength either through heat
treating alone or through a combination of heat treating and cold
work. |
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Heat-Treat Stain |
A discoloration due to oxidation of
the metal surface during thermal treatment. |
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Heat-Affected Zone |
That portion of the base metal which was not melted during
brazing, cutting, or welding, but whose microstructure and physical properties were
altered. |
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Herringbone Streaks |
Elongated alternate bright and dull
markings at an angle to the rolling direction and having the
appearance of a herringbone pattern. |
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Hole |
Void in rolled product. Typical cause
is a non-metallic inclusion during rolling. |
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Holiday |
Region where film is absent due to
non-wetting of the metal surface by the coating. |
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Homogenizing |
Holding at high temperature to
eliminate or decrease chemical segregation by diffusion. |
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Hooke's Law |
Stress is proportional to strain in
the elastic range. The value of the stress at which a material
ceases to obey Hooke's law is known as the elastic limit. |
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Hot Line Pickup |
Small particles of aluminum and
aluminum oxide generated in the roll bite which subsequently
transfer to the rolled product. It may be distributed uniformly
and/or in streaks. |
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Hot Shortness |
Brittleness in metal in the hot
forming range. |
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Hot Working |
- Deformation under conditions that
result in recrystallization.
- Plastic deformation of metal at a
temperature sufficiently high not to create strain hardening.
The lower limit of temperature for this process is the
recrystallization temperature.
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