Updated on 19 October, 2021
The Rockwell hardness test is a metric measurement of material hardness based upon indentation hardness. The Rockwell scale, also called the Handyman scale, is a specification scale for measuring hardness. The Rockwell scale measures the depth of embedding hardness of an indentation at a load compared to the hardness produced by a similar preload. There are other scales, designated by a single letter, which use different indents or loads.
The need for a reliable and specific evaluation of material properties in applications ranging from household building components to automotive and aircraft products has prompted the development of this easy to use scale. It can be used as a tool for measuring thickness of metallic materials, to identify moisture resistance, to evaluate tensile strength, hardness, and hardness stability, and to quantify the amount of austenite, changeable carbon, and other alloy properties. It is widely accepted that materials must be tested for hardness against a standard/reliable test criteria in order to comply with requirements in the supply chain. Standard performance measurements provide a framework for material testing applications that can be implemented in many applications.
Materials such as steel, iron, titanium, aluminum, and glass are among the most commonly subjected to rockwell hardness testing. These are subjected to a variety of loading forces and indentions, such as stress-relief, bending, and penetrating, and are subjected to diverse conditions, including heating and cold treatment. Rockwell hardness testing is a comprehensive method that allows for the determination of appropriate hardness and the determination of suitability for a given application.
A diamond cone shaped hardness tester, also referred to as the diamond-tipped test material, is one of the most widely used diamond hardness testers on the market. The diamond cone allows the tester to gently apply the load, which is typically in the hundreds of pounds, over an area that includes the surface, the interior layer, and the bottom layer of any type of material, including steel or fiberglass. It can be used in a number of different applications, including in the aerospace, transportation, military, and industrial markets.
Rockwell hardness test methods for welding, sheet metal bending, and other applications include the use of various forms of indentation. Indented edges can either be flat or have a convex curve. Flat edges are the most flexible, while convex curves produce a steeper and more gradual indentation. The diamond-tipped indenter is one of the best known diamond-tipped test methods. The diamond-tipped indenter is not only used to determine the hardness of metals, but also other nonmetal alloys and plastics.
The hardness testing process produces a tensile strength value, as well as an indentation strength and softness reading. The first step of the process uses an electronic device called a hardness conversion table. This device measures the difference between the highest and lowest points on the material being tested. The hardness conversion reading is then compared to a hardness test standard to determine the hardness level of the material.
There are several types of indentation available for hardness testing metallic materials. The type of indentation is primarily based upon whether the material being tested is austenitic, alloyed, or polyaminated. Some other types of indentations include honeycomb indentations, which are produced when the hardness testing sample is subject to compression. Diamond-tipped indentations are the most common type of indentation. In addition to these types of indentations, the Rockwell hardness test-piece can also be subjected to stresses as it is pulled, compressed, or bent.
A third type of indentation, which is called the cone diffuser, is used by the Rockwell hardness tester. The cone diffuser emits a stream of infrared rays, which travels through the test-piece while concurrently measuring its surface tension and temperature. The tester then receives data that reveals the stresses that the material is subjected to, as well as the hardness level of the surface. By comparing the data from the cone diffuser with the data from the hardness tester, the engineer is able to determine the appropriate pressure and other parameters necessary to manufacture a reinforced part.