The Rockwell scale characterizes the indentation hardness of materials through the depth of penetration of an indenter, loaded on a material sample and compared to the penetration in some reference material. It is one of several definitions of hardness in materials science. Its hardness values are noted by HR* where * is the letter for the scale used. Hardness' relation to strength is that both are measures of the pressure it take to get plastic deformation to occur in materials. As the direction of materials science continues towards studying the basis of properties on smaller and smaller length scales, different techniques are used to quantify material characteristics and tendencies. ... Look up hardness in Wiktionary, the free dictionary. ... The Materials Science Tetrahedron, which often also includes Characterization at the center Materials science is an interdisciplinary field involving the properties of matter and its applications to various areas of science and engineering. ...

Operation

The determination of the Rockwell hardness of a material involves the application of a minor load followed by a major load, and then noting the depth of penetration, vis a vis, hardness value directly from a dial, in which a harder material gives a higher number. The chief advantage of Rockwell hardness is its ability to display hardness values directly, thus obviating tedious calculations involved in other hardness measurement techniques. Also, the relatively simple and inexpensive set-up enables its installation in college laboratories.

It is typically used in engineering and metallurgy and is most common in the USA. Its commercial popularity arises from its speed, reliability, robustness, resolution and small area of indentation. Engineering is the design, analysis, and/or construction of works for practical purposes. ... Metallurgy is a domain of materials science and of materials engineering that studies the physical and chemical behavior of metallic elements, their intermetallic compounds, and their mixtures, which are called alloys. ...

Good practices

• Cleaning indenter and test-piece to be clear of dirt, grease, rust or paint
• Measuring on a perpendicular, flat surface ("round work correction factors" are invoked to adjust for test-piece curvature)
• Ensuring that the thickness of the test-piece is at least 10 times the depth of the indentation
• Maintaining an adequate spacing between multiple indentations
• Controlling the speed of the indentation

Scales and values

There are several alternative scales, the most commonly used being the "B", and "C" scales. Both express hardness as an arbitrary dimensionless number. In dimensional analysis, a dimensionless number (or more precisely, a number with the dimensions of 1) is a pure number without any physical units. ...

• The B-scale is used for softer materials (such as aluminum, brass, and softer steels). It employs a hardened steel ball as the indenter and a 100kg weight to obtain a value expressed as "HRB".
• The C-scale, for harder materials, uses a diamond cone, known as a Brale indenter and a 150kg weight to obtain a value expressed as "HRC".

Readings below HRC 20 are generally considered unreliable, as are readings much above HRB 100. The steel cable of a colliery winding tower. ... This article is about the gemstone. ... This article is about the geometric object, for other uses see Cone. ...

Common values

• Very hard steel (e.g. a good knife blade): HRC 55 - HRC 62
• Axes, chisels, etc.: HRC 40 - 45

Several other scales, including the extensive A-scale, are used for specialised applications. There are special scales for measuring case-hardened specimens. A replica Colt 1873 revolver, showing case hardening colors on the frame Case hardening or surface hardening is the process of hardening the surface of a metal, often a low carbon steel, by infusing elements into the materials surface, forming a thin layer of a harder alloy. ...

Standards

• International (ISO)

• ISO 6508-1 : Metallic materials -- Rockwell hardness test -- Part 1: Test method (scales A, B, C, D, E, F, G, H, K, N, T)

• US standard (ASTM International)

• ASTM E18 : Standard methods for rockwell hardness and rockwell superficial hardness of metallic materials

Standards are produced by many organizations, some for internal usage only, others for use by a groups of people, groups of companies, or a subsection of an industry. ... This article does not cite any references or sources. ... ASTM International is an international standards developing organization that develops and publishes voluntary technical standards for a wide range of materials, products, systems, and services. ... ASTM International is an international voluntary standards organization that develops and produces technical standards for materials, products, systems and services. ...

See also

• Vickers hardness test
• Brinell hardness test
• Knoop hardness test
• Shore durometer
• Hardness comparison

A Vickers hardness tester The Vickers hardness test was developed in the early 1920s as an alternative method to measure the hardness of materials. ... The Brinell scale characterises the indentation hardness of materials through the scale of penetration of an indenter, loaded on a material test-piece. ... The Knoop hardness test is a microhardness test - a test for mechanical hardness used particularly for very brittle materials or thin sheets, where only a small indentation may be made for testing purposes. ... Durometer is one of several ways to indicate the hardness of a material, defined as the materials resistance to permanent indentation. ... There are a large number of hardness testing methods avaiable (eg. ...

External links

• WilsonInstruments.com