ASTM A956-00

Designation: A 956 – 00 An American National Standard
Standard Test Method for
1
Leeb Hardness Testing of Steel Products
This standard is issued under the fixed designation A 956; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope average roughness value, AA 5 arithmetic average).
3.1.5 verification—checking or testing the instrument to
1.1 This test method covers the determination of the Leeb
ensure conformance with this test method.
hardness of steel, cast steel, and cast iron (Part A), including
the methods for the verification of Leeb hardness testing
4. Significance and Use
instruments (Part B), and the calibration of standardized test
4.1 Hardness of a material is a poorly defined term that may
blocks (Part C).
have many meanings depending on the type of test performed
1.2 The values stated in inch-pound units are to be regarded
and the expectations of the person involved. The Leeb hardness
as the standard. The values given in parentheses are for
test is of the dynamic or rebound type, which primarily
information only.
depends both on the plastic and on the elastic properties of the
2. Referenced Documents material being tested. The results obtained are indicative of the
strength and dependent on the heat treatment of the material
2.1 ASTM Standards:
tested.
E 691 Practice for Conducting an Interlaboratory Study to
2
4.2 The Leeb hardness test is a superficial determination
Determine the Precision of a Test Method
only measuring the condition of the surface contacted. The
3. Terminology
results generated at that location do not represent the part at
any other surface location and yield no information about the
3.1 Definitions:
material at subsurface locations.
3.1.1 calibration—determination of the values of the sig-
nificant operating parameters of the instrument by comparison
A. GENERAL DESCRIPTION OF INSTRUMENTS
with values indicated by a reference instrument or by a set of
AND TEST PROCEDURE FOR LEEB HARDNESS
reference standards.
TEST
3.1.2 Leeb hardness number—a number equal to the ratio of
the rebound velocity to the impact velocity of a 3-mm or 5-mm
5. Apparatus
(based on the type of impact device) diameter tungsten carbide
5.1 The instrument used for Leeb hardness testing consists
ball or diamond tipped impact body, multiplied by 1000.
of (1) an impact device that is equipped with a tungsten carbide
Rebound Velocity
ball or synthetic diamond tipped impact body, an induction coil
L 5 3 1000
Impact Velocity
velocity measuring assembly, and a support ring, and ( 2)an
electronic digital display hardness indicating device.
The Leeb hardness number is followed by the symbol HL
with one or more suffix characters representing the type of 5.2 Impact Devices—There are six types of impact devices
used in Leeb hardness testing. These are the D, DC, D+15, G,
impact device.
C, and the E impact units. Brief descriptions of the types of
3.1.3 Leeb hardness test—a dynamic hardness test method
devices and their common applications are given in Table X1.1
using a calibrated instrument that impacts a spherically shaped
in Appendix X1.
carbide ball or diamond tipped body with a fixed velocity
5.3 Summary of Test Method—During a hardness test, an
(generated by a spring force) onto a surface of the material
impact body with a spherically shaped tungsten carbide or
under test. The ratio of the rebound velocity to the impact
diamond tip impacts under spring force, the test surface from
velocity of the impact body is a measure of the hardness of the
which it rebounds. The impact and rebound velocities are
material under test.
measured when the impact body is approximately 1 mm from
3.1.4 surface finish—all references to surface finish in this
the test surface. This is accomplished by means of a permanent
test method are defined as surface roughness (that is, Ra 5
magnet mounted in the impact body which, during the test,
moves through a coil in the impact device and induces an
1
This test method is under the jurisdiction of ASTM Committee A-1 on Steel,
electric voltage on both the impact and rebound movements.
Stainless Steel, and Related Alloys and is the direct responsibility of Subcommittee
A01.06 on Steel Forgings and Billets.
These induced voltages are proportional to the respective
Current edition approved Jan. 10, 2000. Published February 2000. Originally
impact and rebound velocities. The quotient of these measured
published as A 956–97. Last previous edition A 956–97.
2 voltage values derived from the impact and rebound velocities,
Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
1

---------------------- Page: 1 ----------------------
A 956
multiplied by the factor 1000 produces a
...