Steel Heat Treatment - Metallurgy and Technologies 2nd ed - G. Totten (CRC_ 2007) Episode 11 pdf

and minimal distortion. Furthermore, it has been demonstrated that the servi ce life under
cyclic loads may be increased by approximately one order of magnitude [54].
Intensive quenching requires appropriate quenching facilities and quenching media.
Quenching media include pressurized water streams, water containing various additives,
and liquid nitrogen. Figure 9.52 shows a que nching chamber for the intensive cooling of an
automobile semiaxis using pressurized water flow .
The water supply to the chamber and the charging and discharging of the axles are
controlled by two sensors. The first sensor (5 in Figure 9.52) analyzes the process of film
boiling and nucleate boiling, and the second, 6, describes the transformation of austenite into
martensite by the change of the ferromagnetic state of the material. One method of intensive
quenching has been used that achieve s maximum compressive stresses at the surface when
sensor 6 indicates a specific magnetic phase transformation. In this case, sensor 5 is used to
minimize the duration of film boiling by regulating the water flow velocity. A second method
has also been used, with sensor 5 indicating the beginning and completion of nucleate boiling,
while sensor 6 controls the water pressure and determines the end of intensive quenching, so
that no more than 30% martensite is formed.
Intensive que nching methods offer many possibilities for the successful cooling of parts
with optimized strength properties and improved service life. However, a precondition for the
use of this technology is the development of appropriate que nching equipment that enables
precise control of the quenching performance. Ref. [4c] provides an overview of intensive
quenching probes design.
9.8 PROPERTY PREDICTION METHODS
There are increasing demands on the heat treater to achieve as-quenched properties while
simultaneously reducing heat treatment costs. To achieve these goals it is becoming increas-
ingly important that experimentally or mathematically based methods to predetermine the as-
quenched strength and hardness propert ies be applied with sufficient accuracy. Currently, a
computer-based selection of steels and optimization of quenching conditions according to the
desired service properties are generally possible. Hardenability is one of the most important
properties to be predicted because it determines as-quenched microstructure formation. The
ability to predict hardenability curves from chemical composition has already been described
in Chapt er 5, Secti on 5.4. How ever, these harden ability curves pro vide only lim ited informa-

tion about the distribution of mechanical properties in the quenched part. It is necessary to
correlate steel chemical composition, cooling rates during quenching, metallurgical trans-
formation behavior, and the final physical properties. These correlations are often complex.
}
1
2
3
5
6
7
8
4
FIGURE 9.52 Quenching chamber for intensive quenching of semiaxes in a pressurized water flow: 1,
semiaxis; 2, quenching chamber; 3, water flow; 4, mechanical drive for the semiaxis; 5, sensor for
analyzing the process of film boiling and nucleate boiling; 6, sensor for analyzing the portion of formed
structures; 7, 8, amplifiers.
Quenching and Quenching Technology 589
ß 2006 by Taylor & Francis Group, LLC.
and minimal distortion. Furthermore, it has been demonstrated that the servi ce life under
cyclic loads may be increased by approximately one order of magnitude [54].
Intensive quenching requires appropriate quenching facilities and quenching media.
Quenching media include pressurized water streams, water containing various additives,
and liquid nitrogen. Figure 9.52 shows a que nching chamber for the intensive cooling of an
automobile semiaxis using pressurized water flow .
The water supply to the chamber and the charging and discharging of the axles are
controlled by two sensors. The first sensor (5 in Figure 9.52) analyzes the process of film
boiling and nucleate boiling, and the second, 6, describes the transformation of austenite into
martensite by the change of the ferromagnetic state of the material. One method of intensive
quenching has been used that achieve s maximum compressive stresses at the surface when
sensor 6 indicates a specific magnetic phase transformation. In this case, sensor 5 is used to

minimize the duration of film boiling by regulating the water flow velocity. A second method
has also been used, with sensor 5 indicating the beginning and completion of nucleate boiling,
while sensor 6 controls the water pressure and determines the end of intensive quenching, so
that no more than 30% martensite is formed.
Intensive que nching methods offer many possibilities for the successful cooling of parts
with optimized strength properties and improved service life. However, a precondition for the
use of this technology is the development of appropriate que nching equipment that enables
precise control of the quenching performance. Ref. [4c] provides an overview of intensive
quenching probes design.
9.8 PROPERTY PREDICTION METHODS
There are increasing demands on the heat treater to achieve as-quenched properties while
simultaneously reducing heat treatment costs. To achieve these goals it is becoming increas-
ingly important that experimentally or mathematically based methods to predetermine the as-
quenched strength and hardness propert ies be applied with sufficient accuracy. Currently, a
computer-based selection of steels and optimization of quenching conditions according to the
desired service properties are generally possible. Hardenability is one of the most important
properties to be predicted because it determines as-quenched microstructure formation. The
ability to predict hardenability curves from chemical composition has already been described
in Chapt er 5, Secti on 5.4. How ever, these harden ability curves pro vide only lim ited informa-
tion about the distribution of mechanical properties in the quenched part. It is necessary to
correlate steel chemical composition, cooling rates during quenching, metallurgical trans-
formation behavior, and the final physical properties. These correlations are often complex.
}
1
2
3
5
6
7
8

4
FIGURE 9.52 Quenching chamber for intensive quenching of semiaxes in a pressurized water flow: 1,
semiaxis; 2, quenching chamber; 3, water flow; 4, mechanical drive for the semiaxis; 5, sensor for
analyzing the process of film boiling and nucleate boiling; 6, sensor for analyzing the portion of formed
structures; 7, 8, amplifiers.
Quenching and Quenching Technology 589
ß 2006 by Taylor & Francis Group, LLC.

10
Distortion of Heat-Treated
Components
Michiharu Narazaki and George E. Totten
CONTENTS
10.1 Introduction 614
10.2 Basic Distortion Mechanisms 609
10.2.1 Relief of Residual Stresses 609
10.2.2 Material Movement Due to Temperature Gradients during Heating
and Cooling 610
10.2.3 Volume Changes during Phase Transformat ions 610
10.3 Residual Stresses 612
10.3.1 Residual Stress in Components 612
10.3.2 Residual Stresses Prior to Heat Treatment 612
10.3.3 Heat Treatment after Work-Hardening Process 612
10.4 Distortion during Manufacturing 613
10.4.1 Manufacturing and Design Factors Prior to Heat Treatment That
Affect Distortion 613
10.4.1.1 Material Properties 614
10.4.1.2 Homogeneity of Material 614
10.4.1.3 Distribution of Residual Stress System 614
10.4.1.4 Part Geometry 614

10.4.2 Distortion during Component Heating 615
10.4.2.1 Shape Change Due to Relief of Residual Stress 615
10.4.2.2 Shape Change Due to Thermal Stresses 615
10.4.2.3 Volume Change Due to Phase Change on Heating 615
10.4.3 Distortion during High-Temperature Processing 616
10.4.3.1 Volume Expansion during Case Diffusion 616
10.4.3.2 Distortion Caused by Metal Creep 616
10.4.4 Distortion during Quenching Process 617
10.4.4.1 Effect of Cooling Characteristics on Residual
Stress and Distortion from Quenching 617
10.4.4.2 Effect of Surface Condition of Components 624
10.4.4.3 Minimizing Quench Distort ion 625
10.4.4.4 Quench Uniformity 629
10.4.4.5 Quenching Methods 630
10.5 Distortion during Post Quench Processing 631
10.5.1 Straightening 631
10.5.2 Tempering 631
10.5.3 Stabilization with Tempering and Subzero Treatment 632
10.5.4 Metal Removal after Heat Treatment 633
ß 2006 by Taylor & Francis Group, LLC.
60
20
600
400
200
0
0
(a)
(b)
10

Still water
Spray (open) lateral
Spray (submerged) lateral
Spray (open) lateral
Spray (submerged) lateral
0.3m/s upward
0.7m/s upward
0.3m/s upward
0.7m/s upward
20 30
Distance from lower end, mm
40 50 60
010
Still water
20 30
Distance from lower end, mm
40 50 60
Residual stress, MP
a
−200
−400
−600
−800
−1000
600
400
200
0
Residual stress, MP
a

−200
−400
−600
−800
−1000
A
B
s
z
s
q
101064
FIGURE 10.11 Effect of agitation methods on residual stress after water quenching of JIS S45C steel
rod (20-mm diameter by 60 mm long). Quenchant was 308C city water. Agitation methods were still,
0.3 m/s upward flow, 0.7 m/s upward flow, and lateral submerge in immersion quenching, and lateral
open spray quenching in air. (a) Axial stress on surface, (b) tangential stress on surface. (From
M. Narazaki, G.E. Totten, and G.M. Webster, in Handbook of Residual Stress and Deformation of
Steel, G.E. Totten, M.A.H. Howes, and T. Inoue, Eds., ASM International, Materials Park, OH, 2002,
pp. 248–295.)
ß 2006 by Taylor & Francis Group, LLC.