Dureza

E 18 – 05e1

B 370 Specification for Copper Sheet and Strip for Building
Construction
E4 Practices for Force Verification of Testing Machines
E 29 Practice for Using Significant Digits in Test Data to
Determine Conformance with Specifications
E 140 Hardness Conversion Tables for Metals
E 691 Practice for Conducting an Interlaboratory Study to
Determinethe Precision of a Test Method

3. Terminology
3.1 Definitions:
3.1.1 calibration—determination of the values of the sig- nificant parameters by comparison with values indicated by a reference instrument or by a set of reference standards.
3.1.2 Rockwell hardness number, HR—a number derived from the net increase in the depth of indentation as the force on an indenter isincreased from a specified preliminary test force to a specified total test force and then returned to the prelimi- nary test force.
3.1.2.1 Discussion—Indenters—Indenters for the Rockwell hardness test include a diamond spheroconical indenter and ball indenters of specified diameters. The tungsten carbide ball
is considered to be the standard type of Rockwell indenter ball for allRockwell ball scale hardness testing. Steel indenter balls may be used only if specified in a product specification or by special agreement.
3.1.2.2 Discussion—Rockwell hardness numbers are al- ways quoted with a scale symbol representing the indenter and forces used. The hardness number is followed by the symbol HR and the scale designation. When a ball indenter is used, the scaledesignation is followed by the letter 9W9 to indicate the use of a tungsten carbide ball or the letter 9S9 to indicate the use of a steel ball.
3.1.2.3 Examples—64 HRC = Rockwell hardness number of 64 on Rockwell C scale. 81 HR30N = Rockwell superficial
hardness number of 81 on Rockwell 30N scale. 72 HRBW =
Rockwell hardness number of 72 on the Rockwell B scale measured using a tungstencarbide ball indenter.
3.1.3 Rockwell hardness test—an indentation hardness test using a verified machine to force a diamond spheroconical indenter (diamond indenter), or a ball indenter under specified conditions, into the surface of the material under test in two operations, and to measure the difference in depth of the indentation under the specified conditions ofpreliminary and total test forces (minor and major loads, respectively).
3.1.4 Rockwell superficial hardness test—same as the Rock- well hardness test except that smaller preliminary and total test forces are used.
3.1.5 verification—checking or testing to assure conform- ance with the specification.

4. Significance and Use
4.1 The Rockwell hardness test is an empiricalindentation hardness test. Rockwell hardness tests provide useful informa- tion about metallic materials. This information may correlate to tensile strength, wear resistance, ductility, and other physical characteristics of metallic materials, and may be useful in quality control and selection of materials.
4.2 Rockwell hardness testing at a specific location on a part may not representthe physical characteristics of the whole part or end product.
4.3 Rockwell hardness tests are considered satisfactory for acceptance testing of commercial shipments, and have been used extensively in industry for this purpose.
4.4 Performance verifications of Rockwell hardness indent- ers and hardness machines shall be made using test blocks calibrated traceable to theRockwell standards maintained by NIST when primary reference test blocks are available from NIST for the specific Rockwell scale.



A. GENERAL DESCRIPTION AND TEST PROCEDURE FOR ROCKWELL HARDNESS AND ROCKWELL
SUPERFICIAL HARDNESS TESTS

5. Principles of Test and Apparatus

5.1 General Principles—The general principles of the Rockwell...