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

GTBL042-14 GTBL042-Callister-v3 October 2, 2007 13:45

2nd Revised Pages

580 • Chapter 14 / Synthesis, Fabrication, and Processing of Materials

Time (s)

Temperature (

°C)

Temperature (

°F)

0.1 1 10 102 103

0

200

400

600

800

1000

1200

1400

0

200

400

600

800

70 End-quench hardenability

Hardness, HRC

0 0.5 1.0 1.5

M (start)

Austenite Martensite

Martensite

A

Cooling transformation diagram

Cooling curves

Transformation during cooling

Martensite and

pearlite

Fine

pearlite

Pearlite

2.0 2.5 3.0

B C D

A B C D

60

50

40

30

20

Distance from quenched end (in.)

Pearlite

Austenite

Figure 14.7

Correlation of

hardenability and

continuous cooling

information for an

iron–carbon alloy of

eutectoid

composition.

[Adapted from H.

Boyer (Editor),Atlas

of Isothermal

Transformation and

Cooling

Transformation

Diagrams, American

Society for Metals,

1977, p. 376.]

1040

5140

8640

4140

4340

Hardness, HRC

Percent martensite

0 10 20 30 40 50 mm

20

40

50

60

170 70 31 18 9 5.6 3.9 2.8 2

305 125 56 33 16.3 10

Cooling rate at 700°C (1300°F)

7 5.1 3.5

°C/s

°F/s

100

80

50

30

Distance from quenched end

490

270

0 14 12 34 1 14 12 111 34 2 in.

Figure 14.8

Hardenability curves

for five different steel

alloys, each

containing 0.4 wt%

C. Approximate

alloy compositions

(wt%) are as follows:

4340–1.85 Ni, 0.80

Cr, and 0.25 Mo;

4140–1.0 Cr and 0.20

Mo; 8640–0.55 Ni,

0.50 Cr, and 0.20 Mo;

5140–0.85 Cr; and

1040 is an unalloyed

steel. (Adapted from

figure furnished

courtesy Republic

Steel Corporation.)