ASTM A956-06 pdf free download.Standard Test Method for Leeb Hardness Testing of Steel Products.
1.1 This test method covers the determination of the Leeb hardness of steel, cast steel, and cast iron (Part A), including the methods for the verification of Leeb hardness testing instruments (Part B), and the calibration of standardized test blocks (Part C).
5.2 Impact Devices—There are six types of impact devices used in Leeb hardness testing. These are the D, DC, D+15, G, C, and the E impact units. Brief descriptions of the types of devices and their common applications are given in Appendix XI.
5.3 Summary of Test Method—During a hardness test, an impact body with a spherically shaped tungsten carbide or diamond tip impacts under spring ftrce, the test surface from which it rebounds. The impact and rebound velocities are measured when the impact body is approximately 1 mm from the test surface. This is accomplished by means of a permanent magnet mounted in the impact body which, during the test, moves through a coil in the impact device and induces an electric voltage on both the impact and rebound movements. These induced voltages are proportional to the respective impact and rebound velocities. The quotient of these measured voltage values derived from the impact and rebound velocities, multiplied by the factor 1000 produces a number which constitutes the Leeb hardness value.
5.4 See 7.1.1 when using replacement machine components.
6. Test Piece
6.1 Form—The Leeb hardness test is acceptable for steel, cast steel, and cast iron with varying shapes and sizes.
6.2 Thickness and Weight—The thickness and weight of the test piece shall be considered when selecting the impact device to be employed. The following guidelines are offered as minimum weights and sizes of test pieces for selecting the proper test equipment. Test pieces of weights less than the minimum or pieces of any weight with sections less than the minimum thickness require rigid support and coupling to a thick, heavier non-yielding surface to resist the impact of the device. Failure to provide adequate support and coupling will produce test results lower than the true hardness value.ASTM A956 pdf download.