Glossary


A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Nailing
Slow heating to visible redness of refractory crucibles prior to use of
crucibles for the melting of steel.
Natural Gas
Derived from the remains of marine animal and plant life (same as
petroleum), natural gas is made up predominantly of hydrocarbons. Petroleum
rarely is free of natural gas and the same fields usually produce both
fuels. Gas found in a field is usually under pressure which diminishes with
extended use or from the presence of too many other wells.
Necking
Strip condition caused by the application of too much tension which causes
the strip to become narrower (or stretched) before fracture.
Neutral Refractory
A refractory having neither strongly acidic nor basic properties, for
example, chromite.
NDT
Non-destructive testing, mainly used in pipe mills.
Nitriding
The nitrogen case-hardening process which consists of subjecting machined
and heat-treated parts to the action of a nitrogenous medium, commonly
ammonia gas, at temperatures of about 510o to 538o. The outer layer of a
conventionally nitrided case contains a shallow (0.05mm) but very brittle
'white layer' consisting or iron and other nitrides. Quenching is not
required to produce a hard case.
Nitrocarburizing
Any of several case-hardening processes in which nitrogen and carbon are
absorbed into the surface layers of a ferrous material at temperatures
below the lower critical temperature and, by diffusion, create a
concentration gradient. Compare with carbonitriding.
No. 1 Heavy Melt
Obsolete steel scrap grade, at least one-quarter inch in thickness and in
sections no larger than five feet by two feet. Much of the metal comes from
demolished buildings, truck frames and heavy duty springs. Mini-mills are
primary consumers of No. 1 heavy scrap.
Non-Aging
Little to no change in mechanical and physical properties over time; Yield
point elongation is zero. See Aging.
Normalizing
Heating to a temperature about 100o F above the critical range, as
indicated by the iron carbon diagram, and cooling in still air. Normalizing
is used to restore the steel to its normal condition after hot working,
cold working, non-uniform cooling or overheating, or to eliminate the
effects of previous heat treatment. Other common objects of normalizing
include the development of uniformity in grain, structure and physical
properties, a slight hardening of medium carbon steels to improve
machinability and the removal of stresses, strains, or course grain prior
to hardening. The usual normalizing temperatures range from about 1500o
degrees to 1800o F depending on the steel involved.
Non-Temper Passed Bands
Hot bands.
Nozzle
The refractory lined outlet tube, generally between 25 to 50 mm in
diameter, through which molten steel is released from the ladle to fill up
moulds.
Nickel (Ni)
An alloying element used as a raw material for certain classes of stainless
steel. Nickel provides high degrees of ductility (ability to change shape
without fracture) as well as resistance to corrosion. Approximately 65% of
all nickel is used in the making of stainless steel.
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