Glossary

RA & RMS

RMS (root mean square) is the measure of the surface texture of a material. Texture is a deviation of the actual surface profile from the nominal surface, including roughness and waviness. RA has replaced RMS as the US standard because it averages important detail needed to analyze complex engineering surface.

Ragged Edges

Edges of Sheet or Strip which are torn, split, cracked, ragged or burred or otherwise disfigured.

Range

In inspection, the difference between the highest and lowest values of given quality characteristic within a single sample.

Recovery

Removal of residual stresses from col- working as the result of annealing.

Recrystallization

Process whereby the distorted grain structure of cold worked metals or alloys is replaced by a new strain free grain structure during annealing above a specific minimum temperature (recrystallization temperature).

Refining Temperature

A temperature, usually just higher than the transformation range, employed in the heat treatment of steel to refine the structure — in particular, the grain size.

Refractory

A heat-resistant material, usually nonmetallic, which is used for furnace linings and such.

Refractory Alloy

A term applied to those alloys which due to hardness or abrasiveness present relative difficulty in maintaining close dimensional tolerances.

Residual Elements

Elements present in a metal or alloy that are not deliberately added during melting and refining; in most stainless steels for strip product, residual elements might be phosphorus, sulfur, tin, and lead.

Resulferized Steel

Steel to which sulfur has been added in controlled amounts after refining. The sulfur is added to improve machinability.

Reversing Mill

A reversing mill is used to reduce material to gauge. The steel enters the rolling mill from one side, passes through the other side and then comes back through the mill again. Normally it will go left to right through the mill a number of times being rolled a little thinner each time it goes through.

Ribbon Wound

A term applied to a common method of winding strip steel layer upon layer around an arbor or mandrel.

Riffles

Waviness at the edge of sheet or strip.

Ripple (defect)

A slight transverse wave or shadow mark appearing at intervals along

Rock Candy Fracture

A fracture that exhibits separated-grain facets, most often used to describe intergranular fractures in large grained metals.

Rockwell Hardness (HRB or HRC)

Rockwell is a method of measuring the hardness of materials. Hardness, in this sense, means resistance to penetration. The test gets its name from Stanley P. Rockwell who devised the test and original machines, later selling the rights. The test measures the hardness by pressing an indentor into the surface of the steel with a specific load and them measuring how far the indentor was able to penetrate. While there are a number of Rockwell tests, the common is Rockwell B. Rockwell C is used on hard materials. When the material is very thin, lighter loads must be used. Resulting in Rockwell 30T, 1ST, Rockwell 15-N, 30-N scales. There are conversion charts which will allow conversion from one method of hardness to another, but it must be remembered that these conversion charts cannot precisely convert from one to another. Unfortunately, most customers do not recognize that there are different Rockwell test and/or do not realize that conversion charts are not totally accurate.

Rod Mill

(1) A mill for fine grinding, somewhat similar to the ball mill, but employing long steel rods instead of balls as the grinding medium. (2) A mill for rolling metal rod.

Roll Forming

An operation used in forming sheet.

Roll Marks

Concave or convex defects introduced on the surface of the metal or alloy coil by rolls. A combination of roll pressure and the defects in the rolls or contamination on the rolls determine the severity of the roll marks. Roll marks are generally repetitive.

Rolled Edges

Finished edges, the final contours of which are produced by side or edging rolls. The edge contours most commonly used are square corners, rounded corners and rounded edges.

Roller Flattening

The process in which a series of staggered rolls of small diameter is used to remove bow and waves from sheet. While passing through the roll, the sheet is bent back and forth slightly and is delivered approximately flat.

Rusting

Corrosion mechanism of iron and steel when iron oxide is formed. Passive stainless steel does not rust, but iron or steel contamination on the surface will, which gives consumer a false impression concerning the stainless steel itself. Passivation of stainless steel parts in a nitric acid solution will remove this contamination while maintaining the passivity of the stainless steel surface.