Fundamentals of Materials Science and Engineering: An Integrated Approach, 3e

GTBL042-14 GTBL042-Callister-v2 August 29, 2007 8:59

14.6 Heat Treatment of Steels • 585

EXAMPLE PROBLEM 14.1

Determination of Hardness Profile for Heat-Treated

1040 Steel

Determine the radial hardness profile for a 50 mm (2 in.) diameter cylindrical

specimen of 1040 steel that has been quenched in moderately agitated water.

Solution

First, evaluate the cooling rate (in terms of the Jominy end-quench distance)

at center, surface, mid-, and three-quarter radial positions of the cylindrical

specimen. This is accomplished using the cooling rate-versus-bar diameter plot

for the appropriate quenching medium, in this case, Figure 14.11a. Then, convert

the cooling rate at each of these radial positions into a hardness value from a

hardenability plot for the particular alloy. Finally, determine the hardness profile

by plotting the hardness as a function of radial position.

This procedure is demonstrated in Figure 14.13, for the center position.

Note that for a water-quenched cylinder of 50 mm (2 in.) diameter, the cooling

Diameter of bar (in.)

(^00)
1
2
3
4
(a)
(b)
(c)
1
4
1
2
3
4 1
Center
(^114)
Distance from quenched end (in.)
Hardness, HRC
Hardness, HRC
0
30
40
50
1040
60
20
50
40
30
20
60
1
4
1
2
3
4
1 1
4
11 1 1
2
(^32)
4
Distance from quenched end (in.)
2 in.
Figure 14.13 Use of hardenability
data in the generation of hardness
profiles. (a) The cooling rate at the
center of a water-quenched 50 mm
(2 in.) diameter specimen is
determined. (b) The cooling rate is
converted into an HRC hardness for a
1040 steel. (c) The Rockwell hardness
is plotted on the radial hardness
profile.