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Your search for "g" found 13 matching terms. Click here to search again.

Term	Definition
Ga	Chemical symbol for Gallium.
Galvanic Action	When iron and steel are subject to conditions of aqueous corrosion the incidence and rate at which the corrosion takes place will alter if the steel is coupled with other metals or alloys that are also exposed to the electrolyte. Copper, brass, bronze, lead and nickel are more "noble" and act as auxiliary cathodes to the steel and accelerate its anodic dissolution, that is, its corrosion. Magnesium, zinc and zinc-base alloy are nearly always less noble and tend to divert the attack from the steel to themselves. The galvanic relationship of various metals is an important factor affecting corrosion.
Gamma Iron	The allotropic form of iron existing between the temperature 910oC and 1400oC is known as Gamma Iron. It has a face centred cubic lattice and is non-magnetic. Gamma iron containing carbon or other elements in solution is known as austenite.
Gas Carburising	A heat treatment method used in the case- hardening of steel. Carbon is absorbed into the outer layers of the components by heating in a current of gas, rich in carbon compounds. The process is more versatile than some other methods as the depth of the case and the limiting carbon content of the case can be controlled by the composition of the atmosphere, the dew point and the temperature.
Gauge Length	Used in the mechanical testing of steel, it is the length marked on the parallel portion of a tensile test piece from which the elongation is measured.
Gauge Plate	An alloy tool steel supplied in flat and square section with the surfaces ground to close limits. It is also known as Ground Flat Stock and is used for the manufacturing of gauges, punches, dies, jigs, templates etc.
Ge	Chemical symbol for Germanium.
Grain Size Control	When a steel is austenitised by heating to above the critical range, time is required for the production of a homogeneous structure during which there is a tendency towards grain growth. Although subsequent hot and cold working affect the grain size, it is originally controlled at the steel making stage by the addition ofaluminium.
Grain Size Measurement	Grain size is normally quantified by a numbering system. Coarse 1-5 and fine 5-8. The number is derived from the formula N=2n-1 where n is the number of grains per square inch at a magnification of 100 diameters. Grain size has an important effect on physical properties. For service at ordinary temperatures it is generally considered that fine grained steels give a bettercombination of strength and toughness, whereas coarse grained steels have better machinability.
Graphitising	An annealing process applied to cast iron and steels with a high carbon and high silicon content by which the combined carbon is wholly or in part transformed to graphitic or free carbon.
Grey Iron	Also known as flake iron on account of all or part of the carbon content being in the form of graphite distributed through the metal as flakes.
Grinding	A machining process:- (a) to shape components that are too hard to be machined by conventional methods such as hardened tool steels and case or induction hardened components. (b) to obtain a high degree of dimensional accuracy and surface finish on a component.
Grinding Cracks	Cracks can arise from incorrect grinding and appear in the form of a network. They are caused by the generation of high heat and rapid cooling in the area of contact and they mostly occur when grinding fully hardened material such as tool steel.

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