ANNEALING – A heating and cooling operation, usually slow cooling, performed on steels in the solid state.
Annealing is a comprehensive term, the purpose of which may be:
(1) To remove stresses.
(2) To induce softness.
(3) To alter ductility, toughness, electrical, magnetic or other physical properties.
(4) To refine the crystalline structure.
(5) To remove gases.
(6) To produce a definite microstructure
CARBURIZING – A case hardening process by which carbon alone is added to a limited or specified penetration by heating steel below its melting point in contact with carbonaceous solids, liquids, or gases.
CASE – The surface area of an iron-base alloy whose carbon content has been increased substantially by case hardening.
CASE HARDENING – A process of carbonizing or cyaniding followed by quenching, or of nitriding, which is used to substantially increase the surface hardness of an iron-base alloy.
CORE – The interior portion of an iron-base alloy whose chemical composition has not been substantially changed as the result of case hardening.
ELASTIC LIMIT – The greatest stress a material is capable of developing without a measurable change remaining after complete release of the stress. To determine the elastic limit, a load is applied to a specimen at a uniform rate, and the stress at which the specimen suddenly elongates is recorded on an “extensometer”, reading to 0.0002 inch, which is attached to the specimen to indicate distance between gauge marks.
HARDENING – A Heat Treating Process that implies heating steel to a temperature above the critical range, and cooling it rapidly enough through the critical range to harden it appreciably.
HARDNESS TESTS –
COLD SHORTNESS – The characteristic of metals that are brittle at ordinary or low temperatures.
EFFECT OF CARBON ON STEEL – Increasing the carbon content increases the tensile strength and hardness.
EFFECT OF SULPHUR ON STEEL – When sulphur is over .06 there is a tendency to red shortness. Free cutting steel, for threading and screw machine work, is obtained by increasing sulphur content to about .075 to .10.
EFFECT OF PHOSPHOROUS ON STEEL – Produces brittleness and general cold shortness. Strengthens low carbon steel, increases resistance to corrosion, and improves machinability.
EFFECT OF MANGANESE ON STEEL – Manganese is added in the making of steel to prevent red shortness and increase hardenability.
EFFECT OF SILICON ON STEEL – Used as a general purpose deoxidizes. Strengthens low alloy steels and increases hardenability. Used as alloying element for electrical and magnetic steels.
EFFECT OF COPPER ON STEEL – Used to increase atmospheric corrosion resistance, and sensitivity to both cold and hot short.
EFFECT OF NICKEL ON STEEL – Strengthens and toughens ferrite and pearlitic steels, and renders high chromium alloy steels austenitic (stainless steels).
EFFECT OF CHROMIUM ON STEEL – Increases hardenability, resistance to corrosion and oxidation, abrasion and high temperature strength.
EFFECT OF MOLYBDENUM ON STEEL – Increases hardenability and coarsening temperature. Raises the creep strength and red hardness, and enhances corrosion resistance of stainless steel.
EFFECT OF VANADIUM ON STEEL – Elevates coarsening temperatures, increases harden ability, and is a strong deoxidizes.
EFFECT OF BORON ON STEEL – Increases hardenability of lower carbon steels up to 0.008% maximum boron content. Has improved machinability, as well as hot and cold working characteristics over standard alloy steels.
|A & P – Annealed and Pickled
Av. AverageB & O – Blued and Oiled
|Ex. – Extra
F.C. – Free Cutting
F.T. – Free Turning
H.D. – Hard Drawn
Hex. – Hexagon
H.F. – Hot Finished
H.H. – Half Hard
H.R. – Hot Rolled
Hvy. – Heavy
HEAT TREATMENT – Steel is heat treated to improve it for the service intended or to prepare it for operations such as cold rolling, cold drawing or machining. This process is broadly defined as an operation or combination of operations involving the heating and cooling of steel in the solid state to obtain a certain desired condition or set of properties.
MECHANICAL WORKING – Changing the former structure of a metal by subjecting it to pressure by rolling, pressing, or forging. The crystalline structure is refined and the quality of the metal is improved as the particles are forced into intimate contact. The strength is always increased by working and the hardness and ductility may be affected depending upon the amount of work done and by the temperature at which the working is carried on.
NITRIDING – A process by which nitrogen alone is added to a limited or specified penetration by heating certain alloy steels, which have a properly conditioned surface, in contact with ammonia gas or other substance from which the steel may absorb nitrogen. This produces an extremely hard, wear-resistant surface.
NORMALIZING – The normalizing process is applied to steel to restore its normal condition after hot working, cold working, or non-uniform cooling, or to efface the effects of a previous heat treatment. Normalizing is accomplished by heating to a temperature about 100° F above the critical range and then cooling in still air at room temperature.
PERCENTAGE OF ELONGATION – The percentage of increase in length of a tension test specimen after rupture.
PICKLING – Removing scale by immersion in a dilute acid bath.
QUENCHING – Cooling by immersion in some medium, which may be any liquid or gas, or even a solid in suitable form, to absorb heat rapidly from the article to be quenched.
REDUCTION OF AREA – The difference between the original cross sectional area and that of the smallest area at point of rupture. It is usually stated as a percentage of the original area.
SPHERODIZING – A heat-treating process which is generally applied to high carbon steel to improve machinability. It consists of prolonged heating at a temperature just below or within the critical temperature range, followed usually by slow cooling.
TEMPERING OR DRAWING – This process is applied to relieve stresses due to hardening and to adjust the hardness to the value desired. The hardened steel is reheated to a temperature below the lower critical range and is then permitted to cool.
TENSILE STRENGTH – The maximum load, per unit of original cross-sectional area, a material in tension is capable of withstanding before complete failure or rupture.
YIELD POINT – The load per unit of original cross-sectional area at which a marked increase in the deformation of a specimen occurs without increase of load. It is usually determined by the sudden drop of the beam of the testing machine or by use of dividers or by means of an extensometer.
RED SHORTNESS – Brittleness in steel when it is red hot.