Steel Terms Glossary

Used to deoxidize steel and control grain size with additions up to around 0.05 wt. percent. Grain size control is accomplished by the formation of a fine dispersion of aluminum nitride precipitates, which restricts austenite grain growth. Aluminum can be added at higher levels as an effective nitride former in nitriding steels.

A treatment consisting of heating uniformly to a temperature, within or above the critical range, and cooling at a controlled rate to a temperature under the critical range. This treatment is used to produce a definite microstructure, usually one designed for best machinability, and/or to remove stresses, induce softness, and alter ductility, toughness or other mechanical properties.

A solid semifinished round or square that has been hot worked and is usually smaller than a bloom. Also, a general term for wrought starting stock for forgings or extrusions.

As-cast or wrought semifinished long steel products destined for further hot working processing into final form. Blooms are generally rectangular in cross-section and are larger than billets, which are usually square or round. The size differentiation is somewhat arbitrary.

A semifinished hot rolled rectangular product. The width of the bloom is no more than twice the thickness and the cross-sectional area is usually not less than 36 square inches.

Usually added between 0.0005-0.003 wt. percent to significantly increase the hardenability, especially for low carbon alloys. It does not affect the strength of ferrite, and therefore has little effect on ductility, formability or machinability in the annealed or soft state.

Used in certain steels to control the composition, type, shape, size and distribution of oxide and/or sulfide inclusions. Benefits may include improved ductility, impact strength and/or machinability. Calcium can also be added to improve castability.

A type of steel similar to rimmed steel, usually cast in a bottle top ingot, in which the application of a mechanical or chemical cap renders the rimming action incomplete by causing the top metal to solidify.

The most important alloying element, which is essential for the formation of cementite, graphite, pearlite, spheriodite, bainite, and iron-carbon martensite. Strength, hardness, hardenability, and ductile-to-brittle transition temperature are increased with increasing carbon content up to approximately 0.60 percent. Toughness and ductility of steels are decreased with increasing carbon content. The maximum achievable hardness level of a martensitic steel is a function of carbon content only, with hardness level increasing with carbon content.

Used in alloy steels to increase 1) resistance to corrosion and oxidation, 2) high temperature strength, 3) hardenability, and 4) abrasion resistance in high carbon alloys. Straight chromium steels are susceptible to temper embrittlement and can be brittle.

A solidification process in which refined liquid steel is continuously fed through a bottomless water-cooled copper mold. A solidified shell forms, supporting the remaining liquid steel within. Heat extraction and continued solidification of the steel strand proceeds below the mold via water cooling and radiation, until the entire strand cross-section is fully solidified, at which point sections of the steel strand are cut to desired lengths.

Detrimental to hot workability and subsequent surface quality, and is normally restricted to residual levels. It is used in certain steels to improve resistance to atmospheric corrosion.

The diameter of a round steel bar that will harden at the center to a given percent of martensite when subjected to an ideal quench (i.e., Grossman quench severity H=infinity).

In tensile testing, the increase in gauge length, measured after the fracture of a specimen within the gauge length, usually expressed as a percentage of the original gauge length.

A laboratory procedure for determining the hardenability of a steel or other ferrous alloy. Hardenability is determined by heating a standard specimen above the upper critical temperature, placing the hot specimen in a fixture so that a stream of cold water impinges on one end, and, after cooling to room temperature is completed, measuring the hardness near the surface of the specimen at regularly spaced intervals along its length. The data are normally plotted as hardness versus distance from the quenched end.

Resistance of a metal to plastic deformation, usually by indentation. However, this may also refer to stiffness or temper, or to resistance to scratching, abrasion, or cutting.

This is the standard process of air-cooling the steel immediately following the rolling operation. We transfer the steel to a special table or hot bed that continuously advances the product across the bed. Steel that is hot-bed cooled may require additional thermal treatment to obtain optimum machinability or required mechanical properties.

A test to determine the behavior of materials when subjected to high rates of loading, usually in bending, tension, or torsion. The quantity measured is the energy absorbed in breaking the specimen by a single blow, as in the Charpy or Izod tests.

A casting of a simple shape that can be used for hot working or remelting.

A surface imperfection that appears as a seam. It is caused by the folding over of hot metal, fins, or sharp corners and then rolling or forging them into the surface but not welding them. Laps on tubes can form from seams on piercing mill billets.

Can be added to improve machinability. It does not dissolve in the steel matrix but remains as secondary particles. Environmental concerns are resulting in a decreased usage of lead in the steel industry.

This is a generic term for describing the ability of a material to be machined. To be meaningful, machinability must be qualified in terms of tool wear, tool life, chip control, and/or surface finish and integrity. Overall machining performance is affected by a myriad of variables relating to the machining operation and the workpiece. An overall review is provided in the ASM Metals Handbook: Machinability, Ninth Edition, Volume 16, 1989.

A common alloying element used in most steels because it deoxidizes the melt, facilitates hot working of the steel by reducing the susceptibility to hot shortness due to sulfur content, and adds to hardenability. Mn also partially combines with sulfur to form MnS inclusions, which are commonly used to increase machinability. Mn also improves pearlitic strength in the non-hardened state, and is a major element used in micro-alloy steels.

 This is a controlled cooling of the steel immediately following rolling. In some low and medium carbon alloy grades, this method produces the optimum hardness and microstructure for machinability.

Increases hardenability of steels and helps maintain a specified hardenability. It increases high temperature tensile and creep strengths. Molybdenum-hardened steels require higher tempering temperatures for softening purposes.