Terminology of steel materials and steel specification.

Adhesive Wear – The displacement of material resulting from two materials sliding against one another while under pressure then being redeposited on the other surface leaving pits and surface projections. Also known as galling.

Alloy – A steel material contents two or more elements in a solid solution.

Annealing – Heating and cooling of steel materials for the purpose of removing stresses, softening or changing in its ductility.

Austenite – This phase is achieved by heating the steel to above its critical transformation temperature to dissolve the alloying elements into the iron matrix.

Billet – A solid semi-finished round or square ingot that has been hot-worked by forging or rolling.

Cold-work – Plastic deformation of steel at a temperature to insure strain hardening.

Compressive strength - the ability for a tool steel to resist permanent deformation when a load is applied axially. When a load is applied in compression on a tool steel, the tool will compress in the longitudnal direction and expand outward. When the load is removed the tool will return to its original shape and size. If the tool doesn't return to its original dimensions, then the load has exceeded the tool's compressive strength.

Critical Temperature - The temperature at which austenite transforms to martensite. This is the stage when steel harden actually takes place.

Decarburization – The loss of carbon from the surface of steel. It is a common surface condition of hot rolled steel and is produced during the heating and rolling operations when atmospheric oxygen reacts with the heated surface and removes the carbon.

Ductility – The ability of a steel to deform plastically without fracturing, ductility can be measured by it elongation or reduction of area in a tensile test.

Elastic Limit – The greatest amount of stress that a steel can withstand without a permanent deformation.

Elements – a pure chemical substance consisting of one type of atom. Steels are comprised of iron, carbon and other elements such as silicon, manganese,chromium and vanadium.

Elongation – The amount of permanent extension in the vicinity of the fracture in the tensile or tension test, usually expressed as a percentage of the original gauge length.

Fatigue – The progressive fracture of a steel by means of a crack which spreads under repeated cycles of stress.

Grain Size – The physical size of the austenite grains during austenizing. The actual size can vary due to thermal treatment, time and forging operations.

Hardening – The process of heating and cooling a steel to increase the steel hardness.

Hardness – How hard is the treated steel. Hardness is measured in Rockwell, Brinell or Vickers.

Heat Treatment - The heat treating the steel. The series of processes can include austenizing, quenching, annealing and tempering.

Ingot – A steel casting that was formed when molten steel solidifies in a mold. The ingot is then reheated and rolled into slabs, plates, blooms or billets for further processing into bars and sheets.

Martensite – The resulting maximum hardness microstructure acquired from the transformation of the softer austenite microstructure.

Mechanical Properties – The properties of steel such as, modulus of elasticity, tensile strength, elongation, hardness and fatigue limit.

Modulus of Elasticity – The ratio within the limit of elasticity of the stress to the corresponding strain. The stress in pounds per square inch is divided by the elongation in fractions of an inch for each inch of the orginal length of the test specimen.

Nitriding – Is a surface hardening process that adding nitrogen to an steel alloy by heating the metal in contact with ammonia gas or other suitable nitrogenous material.

Plastic Deformation – Deformation of a material that will remain after removal of the load which caused it.

Quenching – The process of rapidly cooling a steel in order to obtain the hardened martensite of the steel.

Red Hardness – A steels ability to resist softening at elevated temperatures over extended periods of time.

Residual Stress - The stresses within the steel caused by coldworking or drastic temperature differences from quenching or welding..

Strain – Deformation of a material produced by an outside force.

Stress Releiving – The heating of steel to a temperature below its transformation temperature and then slowly cooling to minimize the development of new residual stresses.

Tempering – The process of reheating steel to a suitable temperature below the transformation temperature for an appropriate amount of time. The steel is then allowed to cool to room temperature. This process changes the hardness, increases the toughness and reduces the stress in the steel.

Tensile strength – The maximum amount of pressure that a material will carry before breaking under a slowly applied, gradually increasing load.

Toughness – The ability of a metal to absorb energy and plastically deform before fracturing.

Transverse Toughness – This is the steel's ability to flex in a sideways direction while maintaining the ability to return to its original shape without breaking or cracking.

Wear Resistance – A steels ability to resist wear from contact with another material.

Yield Strength – Stress corresponding to the fixed permanent deformation such as .1 or .2% offset from the modulus or elastic slope.