Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
8th Edition
ISBN: 9781305387102
Author: Kreith, Frank; Manglik, Raj M.
Publisher: Cengage Learning
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Chapter 3, Problem 3.2P
High-strength steel is required for use in building structures and equipment (e.g., cranes). It is produced by heat treating quench-hardened steel in a process called tempering that reduces brittleness and imparts toughness. In a production facility, alloy steel plates (
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5
Temperature (°C)
800
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0
10-1
M (start)
M (50%)
M (90%)
1
10
Eutectoid temperature
M+A
10²
Time (s)
10⁰ 10⁰
T
1400
1200
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Temperature (°F)
Determine the microstructure for the steel with the isothermal transformation regimes shown
on the TTT diagram (1) after proper austenitizing. *
Needle ball bearings, D=5-mm, H=26-mm, are heated up to 1200 K in a
heat treatment furnace where the micro-structure is transformed from
pearlite to austenite. As soon as taken out of the furnace, they are quenched
in water having T=286 K and h=174 W/m2K to transform the micro-
structure from austenite to martensite. Find the time required for cooling the
bearings to T=326 K. Assume the bearings are perfectly cylindrical and
made of AISI 347 Steel.
H
The cooling rate (in °C/s) at the center of a shaft with diameter d (in mm) is given by the
following formula
log 10(CR)
-1.8024 log 10(d) + 4.0565
%3D
and the critical cooling rate (CCR in °C/s) of low alloys steels is given as a function of amount of
alloying element (in wt%6) as follow.
log 10(CCR)= 4.3-3.27×C-
(Mn + Cr+Mo+ Ni)
1.6
Find the maximum diameter (in mm) of a shaft to be made of alloy A (such that 100%
martensite will be produced after quenching) from the following table is given below:
Alloy Weight Percentage (wr%)
Mn Cr
Mo Ni
A
03 08 05 02 055
0.4 0.6 1.2
0.3 5
0 36 0.7 15 255
0.4 06 12
0.15 5
0 41 0 85o 5 o 25 o s5
04 0.65 0 75 0 25 p.85
Chapter 3 Solutions
Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
Ch. 3 - Consider a flat plate or a plane wall with a...Ch. 3 - 3.2 High-strength steel is required for use in...Ch. 3 - Prob. 3.3PCh. 3 - 3.5 In a ball-bearing production facility, steel...Ch. 3 - A 0.6-cm diameter mild steel rod at 38C is...Ch. 3 - Prob. 3.7PCh. 3 - Prob. 3.8PCh. 3 - 3.9 The heat transfer coefficients for the flow of...Ch. 3 - 3.10 A spherical shell satellite (3-m-OD,...Ch. 3 - Prob. 3.11P
Ch. 3 - Prob. 3.12PCh. 3 - Prob. 3.13PCh. 3 - 3.14 A thin-wall cylindrical vessel (1 m in...Ch. 3 - A thin-wall jacketed tank heated by condensing...Ch. 3 - 3.16 A large, 2.54-cm.-thick copper plate is...Ch. 3 - 3.17 A 1.4-kg aluminum household iron has a 500-W...Ch. 3 -
3.28 A long wooden rod at with a 2.5-cm-OD is...Ch. 3 - A mild-steel cylindrical billet 25 cm in diameter...Ch. 3 - Prob. 3.37PCh. 3 -
3.38 An egg, which for the purposes of this...
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