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| Radiography |
| A method of non-destructive inspection in which the object being inspected is exposed to a beam of X-rays or gamma rays and the resulting shadow image of the object is recorded on film or is displayed on a viewing screen or television monitor. Internal defects are then detected due to differences in absorption. |
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| Recrystallisation |
| The formation of new strain-free grains in a metal brought about either by heating a cold-worked metal, or by hot working a metal, or by heating a metal through an allotropic change. |
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| Red Hardness |
| The hardness of a steel when it is at a temperature high enough to cause it to have a dull red appearance. The term usually associated with high speed tool steels as their chemical composition is such that they are generally capable of retaining sufficient hardness and hence their cutting ability even when the tool is at a dull red heat. |
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| Reduction of Area |
| The difference between the original cross-sectional area of the gauge length of a tensile specimen and the cross-sectional area at the point of fracture. This difference is usually then expressed as a percentage of the original cross-sectional area and the result used as a measure of the ductility of the metal being tested. |
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| Residual Stress |
| The stress in a body resulting from some previous forming and/or heat treatment operation. Found for example in castings, weldments and cold formed parts. |
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| Rimming Steel |
| Rimming steel ingots are produced by adjusting the oxygen content of the liquid prior to casting so that vigorous carbon monoxide evolution occurs during solidification. This produces an ingot with an outer layer of very pure iron which gives rise to a sheet product with excellent surface and good formability. The widespread adoption of the continuous casting process has resulted in rimming steels generally being replaced by killed steels. |
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| Rockwell Hardness Testing |
| A hardness test in which an indenter, either a cone-shaped diamond or a hard steel ball, is left for a set time under constant load on the test specimen. On release of the load the Rockwell hardness of the material, which is related the depth of the indentation produced, is displayed on a dial. |
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| Roller Quenching |
| Roller quenching is a process associated with heat treatment. Components which have been taken up to the required temperature are then transported through the quenching medium on a roller table, thus rendering the process semi-continuous, and the properties of the product more consistent. |
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| Rolling |
| The reduction of the cross-sectional area of metal stock by its passage between rotating rolls. |
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| Rolling Lap |
| "See 'Lap' |
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| Ruling Section |
| The term ruling, or limited ruling section, is the maximum diameter or cross-section of a steel, of a particular chemical composition, up to which a specific set of mechanical properties apply after a given heat treatment. It is a term used particularly with respect to the mechanical properties of quenched and tempered steels. |
