Hardness Test Methods
Hardness is a surface properties where indentation, scratching or wear is resisted. The higher the hardness the more resistant the surface and the more difficult surface operations such as cutting and machining are. Testing the hardness of steel can be used an indication of how they can be manipulated (formed, machined etc.) and how they will perform mechanically.
Hardness Test Methods
Common tests for hardness in metals involve measuring the resistance to indentation by a hardened steel or diamond ball, cone or pyramid.
The common test methods include:
The hardness figures do not have units. They are an index, based on either the cross-section of the indentation made, measured after the test, or the depth of indentor travel into the metal surface. The hardness figure is followed by a code indicating the test method.
The Brinell and Vickers methods have been used historically in the UK, the Brinell method for softened steel and Vickers method for either softened or hardened steel.
In these tests the 'diameter' of the impression is measured.
The Rockwell method was first introduced in the US.
These methods assess the hardness by measuring the depth of indentor penetration.
The B scale is used for softened steel and the C scale for hardened steels.
Other scales are also available. These include scales A, D, E, F, G H, K, as well as 'superficial test' scales HR15N, HR30N, HR45N (cone indentor) and HR15T, HR30T, HR45T (ball indentor).
Normally the B and C scales are used on stainless steel, B for softened steel and C for hardened steel.
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