110
Practical exercise- 4
Topic: Mode for determining the hardness of metals.
Purpose of the work:
To determine the hardness of steels by carbon content.
Learning to determine metal hardness by Brinnell and Rockwell methods
Theoretical information
The property of being able to resist the immersion of a body harder than this
material on the surface of any material is called its hardness.
There are several ways to determine the hardness of metals. Among these
methods, Brinell and Rockwell methods are common.
The Brinell method is used to determine
the hardness of base metals, non-
ferrous metals and alloys based on them. 2.5 diameter depending on the thickness of
the metals whose hardness should be determined; 5 and 10 mm rolled steel ball 1.875
per test sample; 2.5; 5.0; 7.5; With a force of 10 and 30 kN, it is slowly immersed
for a certain time (10, 30 and 60 sec), as a result, a trace of a steel ball remains on
the surface of the tested metal, the hardness of the metal is determined depending on
the diameter of this trace.
The scheme for determining metal hardness according to the Brinell method
is presented.
Brinell hardness of the metal "NV"* force "R" pressing the ball on the
tested
metal (N) on the surface of the ball trace formed on the surface of the tested metal
due to this force F( m ∙ m
2
) is determined by the ratio:
If we express the surface of the trace left by the
ball on the metal by the
diameter of the ball "D" and the depth of the trace "h", then the surface of the trace
will be as follows:
