Heat treating and inspection of metals Page: 38
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41-42 AIR CORPS
(4) A release mechanism to relieve the hydraulic pressure after
the test has been made. .,
(5) A microscope with micrometer eyepiece for calculating the
area of the impression.
c. The test is performed as follows:
(1) Prepare the sample by filing, grinding, polishing, etc., to
remove all scratches and variations that may effect the reading.
(2) Place the sample on the anvil of the machine and elevate until
hardened ball contacts surface to be tested.
(3) Apply the load by pumping handle shown at (3), figure 5.
(a) A load of 3,000 kilograms is required for steel, while 500
kilograms is used when testing the softer metals, such as brass,
(b) Normally, the load should be applied for 30 seconds although
this period may be increased to 1 minute for extremely; hard steels,
in order to produce equilibrium.
(4) Release the pressure, and measure area of impression with
(5) Calculate the Brinell number, completing the test.
(a) After obtaining a Brinell number for a metal, its correspond-
ing tensile strength may be determined by referring to table VII.
(b) Reference may also be made to table VIII to identify the
metal and determine its heat treatment.
42. Rockwell hardness test.-a. The Rockwell hardness test
consists of the measurement of the difference between a minor and
major load applied to a diamond penetrator or hardened steel ball.
In all tests, a minor load of 10 kilograms is first applied, in order
to seat the penetrator in the surface of the specimen. The actual
penetration is then produced by applying a major load. When using
the diamond cone penetrator, this major load is 150 kilograms but
when a 1/6-inch steel ball is used the load is reduced to 100 kilo-
grams. An indication of the application of the major load may be
observed by watching the dial indicator; after the pointer comes
to rest this major load is released, leaving the minor load still
applied. As Rockwell hardness numbers are based on the difference
between the depths of penetration at major and minor load, it will
be evident that the greater this difference, the less the hardness
number and the softer the material. This difference is automatically
registered when the major load is released by a reversed scale on the
indicator dial, which thus reads directly the Rockwell hardness
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United States. War Department. Heat treating and inspection of metals, book, September 10, 1941; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc96657/m1/40/: accessed August 18, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.