Steel Heat Treatment - Metallurgy and Technologies 2nd ed - G. Totten (CRC_ 2007) 7 potx

For medium-alloy steels up to 6308C 11668F, with a cooling rate of 15–20 K/h furnace cooling For high-alloy steels up to 6008C 11128F, with a cooling rate of 10–15 K/h furnace cooling Fu

For medium-alloy steels up to 6308C (11668F), with a cooling rate of 15–20 K/h (furnace cooling)

For high-alloy steels up to 6008C (11128F), with a cooling rate of 10–15 K/h (furnace cooling) Further cooling below the temperatures indicated is usually performed in air

6.2.5 RECRYSTALLIZATIONANNEALING

Recrystallization annealing is an annealing process at temperatures above the recrystalliza-tion temperature of the cold-worked material, without phase transformarecrystalliza-tion, that aims at regeneration of properties and changes in the structure that exists after a cold-forming process

600 C 90

70

Time, h

650 C

675 C

700 C

FIGURE 6.78 Hardness of an unalloyed steel with 0.89% C after soft annealing, depending on the spheroidization time and temperature (From H.J Eckstein (Ed.), Technologie der Wa¨rmebehandlung von Stahl, 2nd ed., VEB Deutscher Verlag fu¨r Grundstoffindustrie, Leipzig, 1987.)

a b 200

v60

Tensile strength Rm, N/mm2

150

100

50

c

FIGURE 6.79 Influence of the ultimate tensile strength and degree of spheroidization on machinability

of steels for carburizing and structural steels for hardening and tempering, expressed as 1 h turning

and 60%; (c) spheroidization degree greater than 70% (From G Spur and T Sto¨ferle (Eds.), Handbuch der Fertigungstechnik, Vol 4/2, Wa¨rmebehandeln, Carl Hanser, Munich, 1987.)

For medium-alloy steels up to 6308C (11668F), with a cooling rate of 15–20 K/h (furnace cooling)

For high-alloy steels up to 6008C (11128F), with a cooling rate of 10–15 K/h (furnace cooling) Further cooling below the temperatures indicated is usually performed in air

6.2.5 RECRYSTALLIZATIONANNEALING

Recrystallization annealing is an annealing process at temperatures above the recrystalliza-tion temperature of the cold-worked material, without phase transformarecrystalliza-tion, that aims at regeneration of properties and changes in the structure that exists after a cold-forming process

600 C 90

70

Time, h

650 C

675 C

700 C

FIGURE 6.78 Hardness of an unalloyed steel with 0.89% C after soft annealing, depending on the spheroidization time and temperature (From H.J Eckstein (Ed.), Technologie der Wa¨rmebehandlung von Stahl, 2nd ed., VEB Deutscher Verlag fu¨r Grundstoffindustrie, Leipzig, 1987.)

a b 200

v60

Tensile strength Rm, N/mm2

150

100

50

c

FIGURE 6.79 Influence of the ultimate tensile strength and degree of spheroidization on machinability

of steels for carburizing and structural steels for hardening and tempering, expressed as 1 h turning

and 60%; (c) spheroidization degree greater than 70% (From G Spur and T Sto¨ferle (Eds.), Handbuch der Fertigungstechnik, Vol 4/2, Wa¨rmebehandeln, Carl Hanser, Munich, 1987.)

100 0 (a)

200 300 400

Time, s10 100 1000

100 0 (b)

200 300 400 500 600 700 800 900

Time, s10 100 1000

FIGURE 6.117 Comparison of measured (- - -) and calculated (—) cooling curves for the center of a 50-mm diameter bar quenched in (a) mineral oil at 208C, without agitation and (b) 25% PAG polymer solution, 408C bath temperature, and 0.8 m/s agitation rate

1 100 200 300 400 500 600 700 800 900

1000 AISI 4140

Chemical composition

Austenitizing temp 850 C

Time, s 10

C 0.38 0.23 0.64 0.019 0.013 0.99 0.17 0.16 0.08 <0.01

58

2 3

85 75 B

A

M

S 3/4 R

30

40

60 40

C

10 5 12

75

53 52 34 28 27 230 220

200

FIGURE 6.118 CCT diagram of AISI 4140 steel with superimposed calculated cooling curves for surface (S), three-quarter radius (3/4R) and center (C) of a round bar of 50-mm diameter

− 50

−100

Yield strength Rp, N /mm2

1000 1200 1400

ASTM 7

ISO-V longitudinal M

FIGURE 6.133 Transition temperature as a function of yield strength and microstructure F, Ferrite;

G Spur and T Sto¨ferle (Eds.), Handbuch der Fertigungstechnik, Vol 4/2, Wa¨rmebehandeln, Carl Hanser, Munich, 1987.)

M

M (a)

(b)

(c)

25 20 15

70

50 60

40 30 20 10 0 250 200 150 100 50 0

300 500 700

Yield strength Rp, N/mm 2

900 1100 1300

10 5

0

B

B

F + P

F + P

M

B

F + P

FIGURE 6.134 (a) Elongation; (b) reduction of area; and (c) impact toughness of hardened and tempered steels having about 0.4% C, as a function of structure constituents and yield strength F, Ferrite; P, pearlite; B, bainite; M, martensite Grain size: ASTM 6–7 Impact toughness: ISO notch specimens Testing direction: longitudinal (From G Spur and T Sto¨ferle (Eds.), Handbuch der Ferti-gungstechnik, Vol 4/2, Wa¨rmebehandeln, Carl Hanser, Munich, 1987.)