Metal Terminology (G)金属术语G

GAGES
(Metal) - Mfrs. standard numbering systems indicating decimal thickness or diameters.

GALLING
The damaging of one or both metallic surfaces by removal of particles from localized areas due to seizure curing sliding friction.

GALVANIZING
Coating steel with zinc and tin (principally zinc) for rust proofing purposes. Formerly for the purpose of galvanizing, cut length steel sheets were passed singly through a bath of the molten metal. Today’s galvanizing processing method consists of uncoiling and passing the continuous length of successive coils either through a molten bath of the metal termed Hot Dipped Galvanizing or by continuously zinc coating the uncoiled sheet electrolytically - termed Electro-Galvanizing.

GAMMA IRON
The form of iron stable between 1670癋., and characterized by a face-centered cubic crystal structure.

GILDING METAL
A copper-zinc alloy containing 95% copper and 5% zinc. While similar to deoxidized copper in physical properties, it is somewhat stronger and very ductile. It has thermal and electrical conductivity slightly better than half that of electrolytic copper and corrosion resistance comparable to copper.

GRAIN
A solid polyhedral (or many sided crystal) consisting of groups of atoms bound together in a regular geometric pattern. In mill practice grains are usually studied only as they appear in one plane. (1) Direction of: Refers to grain fiber following the direction of rolling and parallel to edges of strip or sheets. (2) To bend across the grain is to bend at right angles to the direction of rolling. (3) To bend with the grain is to bend parallel to the direction of rolling. In steel, the ductility in the direction of rolling is almost twice that at right angles to the direction of rolling.

GRAIN BOUNDARY
Bounding surface between crystals. When alloys yield new phases (as in cooling), grain boundaries are the preferred location for the appearance of the new phase. Certain deteriorations, such as season cracking and caustic embrittlement, occur almost exclusively at grain boundaries.

GRAIN GROWTH
An increase in metallic crystal size as annealing temperature is raised; growth occurs by invasion of crystal areas by other crystals.

GRAINS
Individual crystals in metals.

GRAIN SIZE
Average diameter of grains in the metal under consideration, or alternatively, the number of grains per unit area. Since increase in grain size is paralleled by lower ductility and impact resistance, the question of general grain size is of great significance. The addition of certain metals affects grain size, for example vanadium and aluminum tend to give steel a fine grain. The ASTM has set up a grain size standard for steels, and the McQuaid-Ehn Test has been developed as a method of measurement.

GRANULATED
A coarse grain or pebbly surface condition which becomes evident during drawing. (See Orange Peel)

GRANULATION
The formation of grains immediately upon solidification.

GRAPHITIZING
A heating and cooling process by which the combined carbon in cast iron or steel is transformed, wholly or partly, to graphitic or free carbon.

GROUND FLAT STOCK
Annealed and preground (to close tolerances) tool steel flats in standard sizes ready for tool room use. These are three common grades; water hardening, oil hardening and air hardening quality.

GUIDE
Device for holding the metal in the proper position, during rolling, or slitting.

GUIDE SCRATCH
(Defect) - Scratches or marks appearing parallel to edges of cold rolled strip caused by scale or other articles which have become imbedded in or have adhered to the rolling mill guide. Also applies to similar scratches appearing as a result of slitting.

Metal Terminology (H)金属术语H

HALF HARD TEMPER
(A) No. 2 Temper. In low carbon cold-rolled strip steel, produced by cold rolling to a hardness next to but somewhat softer than full hard temper. (B) In brass Stainless Steel Strip, tempers are based on minimum tensile or yield strength. For Chromium-Nickel grades Half-Hard Temper 150,000 TS., 110,000 YS. Min.

HARD DRAWING
Drawing metal wire through a die to reduce cross section and increase tensile strength.

HARD DRAWN
Wire or tubing drawn to high tensile strength by a high degree of cold work.

HARD DRAWN SPRING STEEL WIRE
A medium high carbon cold drawn spring steel wire. Used principally for cold springs.

HARDENABILITY
The ability of a metal, usually steel, to harden in depth as distinguished from the terms “hardness.”

HARDENED AND TEMPERED SPRING STEEL STRIP
A medium or high carbon quality steel strip which has been subjected to the sequence of heating, quenching and tempering.

HARDENING
Any process which increases the hardness of a metal. Usually heating and quenching certain iron base alloys from a temperature either within or above the critical temperature range.

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 measuring hardness. (See Brinell Hardness, Rockwell Hardness, Vickers Hardness, Scleroscope Hardness) Tensile Strength also is an indication of hardness.

HARD TEMPER
(A) For Steel see Full Hard Temper. (B) In brass mill terminology. Hard Temper is four B & S numbers hard or 37.1 % reduction.

HEAT OF STEEL
The product of a single melting operation in a furnace, starting with the charging of raw materials and ending with the tapping of molten metal and consequently identical in its characteristics.

HEAT TREATMENT
Altering the properties of a metal by subjecting it to a sequence of temperature changes, time of retention at specific temperature and rate of cooling therefore being as important as the temperature itself. Heat treatment usually markedly affects strength, hardness, ductility, malleability, and similar properties of both metals and their alloys.

HIGH BRASS
65% - A copper-zinc alloy containing 35% zinc. Possesses high tensile strength and is used for springs, screws, rivets, etc.

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.

HOT DIP
In steel mill practice, a process whereby ferrous alloy base metals are dipped into molten metal, usually zinc, tin or terne, for the purpose of fixing a rust resistant coating.

HOT SHORT
Brittleness in hot metal.

HOT TOP
(See Sinkhead)

HOT WORKING
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.

HYDROGEN EMBRITTLEMENT
(1) Brittleness of metal, resulting from the occlusion of hydrogen (usually as a by-product of pickling or by co-deposition in electroplating). (2) A condition of low ductility resulting from hydrogen absorption and internal pressure developed subsequently. Electrolytic copper exhibits similar results when exposed to reducing atmosphere at elevated temperature.

HYPEREUTECTOID STEEL
A steel having more than the eutectoid percentage of carbon. (See Eutectoid Steel)

HYPOEUTECTOID STEEL
Steel with less than eutectoid percentage of carbon. (See Eutectoid Steel)