Higgins R.A. Engineering Metallurgy: Applied Physical Metallurgy
Подождите немного. Документ загружается.
limit corrosion in a ship's hull since the EMF so provided can be monitored
to suit prevailing conditions which will vary with salinity and temperature
of the ocean, conditions of paintwork on the hull (area of metal exposed)
and the area of the hull in contact with the water (which, in turn, depends
upon the load the ship is carrying).
In some cases buried pipe lines can be cathodically protected by using
impressed EMF supplied by small windmill-driven dynamos. A similar
method is sometimes used in the cathodic protection of off-shore oil or gas
rigs,
but because frequent inspection is necessary to check for corrosion of
electrical contacts the sacrificial anode system is usually preferred. 300 kg
anodes of Al-Zn-In alloy are generally distributed uniformly around the
structure. A large structure with up to twenty-five years of design life may
require up to 500 tonnes of such anode material.
Exercises
1.
Explain why:
(i) a
penknife blade dipped into copper sulphate solution becomes
quickly coated with copper;
(ii)
zinc will dissolve
in
dilute sulphuric acid whilst
silver will
not.
(Table
21.1)
2.
A
plate
of
silver
and a
plate
of
cadmium
are
placed
in
dilute sulphuric acid.
Make
a
diagram
to
show
the
chemical reactions which take place within
the
simple cell which
is set up
when
the
plates
are
connected electrically, externally
to
the
electrolyte.
(Fig. 21.2;
Table
21.1)
3.
A
piece
of
mild steel
has
been copper plated. Show
to
what extent this coating
will protect
the
steel from rain water
if the
coating becomes scratched. (Table
21.1;
21.33)
4.
Outline
the
principles involved
in the
electrolytic corrosion
of
alloys. Explain
the meaning
of the
term sacrificial corrosion
and
illustrate this principle
in the
protection
of
steels
by
metal coatings. (21.33)
5.
Discuss
the
phenomena which
are
responsible
for the
high corrosion-resistance
of stainless steels. (21.70)
6.
Why
does
a 0.5%
carbon steel rust more quickly
in the
normalised condition
than
in the
water-quenched state? (21.36)
7.
What
are the
advantages
of
electro-galvanising over hot-dip galvanising? Give
a brief outline
of the
latter process. What other methods
are
available
for
applying
a
coating
of
zinc
to a
steel? (21.82)
8.
A
broad elastic band
is
stretched over
a
flat piece
of
stainless steel plate.
The
assembly
is
then immersed
in an
acid ferric chloride solution
for
about
two
months. Describe
the
appearance
of the
steel plate after this treatment
and
explain what
has
happened. (21.73)
9.
We get the
rotten motor cars
we
deserve! Discuss this statement with respect
to corrosion. (13.35; 21.40; 21.52)
10.
A
mild-steel nail
has a
cold-forged head. Show
how
this nail
is
likely
to
rust
when immersed
in
rain water. (21.40)
11.
Explain
how a
study
of the
relevant Pourbaix diagram
can
help
in
overcoming
some corrosion problems. (21.38)
Bibliography
Ahmed, N. A. G., Ion Plating Technology, John Wiley, 1987.
Carter, V. E., Metallic Coatings for Corrosion Control, Newnes-Butterworths,
1977.
Dennis, J. K. and Such, T. E., Nickel and Chromium Plating, Butterworths, 1972.
Evans, U. R., The Corrosion and Oxidation of Metals, Edward Arnold, 1960
(Supplements 1968, 1976.)
Fontana, M. G., Corrosion Engineering, McGraw-Hill, 1988.
Friend, W. Z., Corrosion of Nickel and Nickel-base Alloys, John Wiley, 1979.
Proskurkin, E. V. and Gorbunov, N. S., Galvanising, Sherardising and Other
Diffusion Coatings, Technicopy Ltd., 1975.
Ross,
T. K., Metal Corrosion {Engineering Design Guide), Oxford University
Press,
1978.
Scully, J. C, The Fundamentals of Corrosion, Commonwealth and International
Library, 1975.
Stewart, D. and Tullock, D. S.,
Principles
of
Corrosion
and
Protection,
Macmillan,
1968.
Trethewey, K. R. and Chamberlain, J., Corrosion for Students of Science and
Engineering, Longman, 1989.
West, J. M., Basic Corrosion and Oxidation, Ellis Horwood, 1980.
BS 729: 1986 Hot-dip Galvanized Coatings on Iron and Steel Articles.
BS 2920: 1973 Cold-reduced Tinplate and Cold-reduced Blackplate.
BS 1872: 1984 Electroplated Coatings of Tin.
BS 1615: 1987 Anodic Oxidation Coatings on Aluminium.
BS 5599: 1978
Specification
for Hard Anodic Oxide Coatings on Aluminium for
Engineering Purposes.
BS
5493:
1977 Code of
Practice
for Protective Coating of Iron and Steel Structures
against Corrosion.
BS 5466: 1979/1988 Methods for Corrosion Testing of
Metallic
Coatings.
BS 3189: 1973 Phosphate Treatment of Iron and Steel.
ANSWERS TO NUMERICAL PROBLEMS
CHAPTER 1
(1) Al
2
O
3
; (2) 3.98 g; (3) 4.9 t; (6) 2HNO
3
+ MgO - Mg(NO
3
)
2
+ H
2
O;
(7) 28°C; (11) 65.
CHAPTER 2
(2) 849 N/mm
2
; (3) (iii); (4) 208.3 kN/mm
2
; (5) 1264 N/mm
2
;
(6) (i) 95.5 kN/mm
2
; (ii) 507 N/mm
2
; (iii) 691.5 N/mm
2
; (iv) 5.4%;
(7) (a) 1944 N; (b) 22 mm.
CHAPTER 3
(4) 112
CHAPTER 4
(2) 27.1 N/mm
2
; (7) 450
0
C (approx.).
CHAPTER 8
(6)(a) (i) 7/4; (ii) 3/2; (iii)
21/13;
(iv) 3/2.
CHAPTER 9
(l)(i) Mg
2
Si; (iii) Liq., Si and Mg
2
Si; (iv) Si and Mg
2
Si are dissolved;
(v) Solid Si + Liq. (64.5 Si-35.5 Mg); (vi) Liq./Si = 1.29/1;
(viii) Mg
2
Si and Si; (ix) Mg
2
Si/Si =
3.73/1
(3)(a) Bi and Sb are close together in Group V of the Periodic Table;
(b) (i) 577°C; (ii) 96Sb-4Bi; (iii) Liq.: 44Sb-56Bi; solid:
88.5Sb-Il.5Bi; (iv) Liq./solid = 1.4/1; (v) 20Sb-80Bi; (vi) 405
0
C.
(4) 415°C; Liq.: 22.5Sb-77.5Bi, solid: 72.5Sb-27.5Bi.
(5) (i) 437°C; (iii) Equal amounts at 300
0
C; at 0
0
C: |3/cc = 9/8.
(7) (i) 15.5% (at 450
0
C); (ii) 328°-550°C;
(iii) 580
0
C; (iv) a: 90.8Al-9.2Mg; Liq.: 72Al-28Mg; (v)
a/Liq.
=
1.76/1; (vi) From 1.5% to 8.3%; (viii) (b)—because all Mg will be
in solid solution.
(8) (i) 771°C; (ii) 89.6Ag-10.4Sn; (iii) 685°C; (iv) 76Ag-24Sn; (v) Solid
solution (3: 83.6Ag-16.4Sn; Liq.: 77.7Ag-22.3Sn; (vi) (3/Liq.
=
2.7/1.
(9) Approximately 24.5% at 127
0
C.
(11) (i) XiAuSn
4
; YiAuSn
2
; Z:AuSn.
CHAPTER 11
(1) Ferrite/Cemenite = 7.42/1
(4) (i) 783°C; (ii) Pearlite/Ferrite = 1.27/1; (iii) 930
0
C^ 723°C; (iv) Pro-
duces brittleness due to networks of primary cementite.
(5) (i) Austenite (0.15%C) only; (ii) Austenite (0.37%C) + Ferrite
(0.01%C) Austenite/Ferrite = 1.57/1: (iii) Ferrite (0.02%C) +
Cementite (6.69%C), Ferrite/Cementite = 50.3/1 (or Ferrite/Pearlite
= 5/1).
CHAPTER 13
(1) 0.65%C; 660°C.
(2) 0.26%C, 1145°C.
(3) 552 N/mm
2
(4) Approx. 50% ferrite and 50% austenite.
CHAPTER 16
(1) 800
0
C; a = 63.5Cu-36.5Zn; (3:54Cu-46Zn; (3/a - 1.71/1.
(2) 6/a = 1.04/1.
(3) (i) P' (martensitic); (ii) a + |3\
(4) 1390
0
C to 1355°C.
CHAPTER 17
(1) a/eutectic = 1.29/1.
(2) (i) a; 99.8Al-0.2Cu; CuAl
2
:45.9Al-54.1Cu.
(ii) a/CuAl
2
=
3.57/1.
(iii) Between 487°C and 573°C.
(iv) 530
0
C, ie mid-way between above temperatures.
(vi) Very weak and brittle.
CHAPTER 18
(1) (i) 470
0
C; 410
0
C; (ii) 480
0
C; 300
0
C; (iii) 600°; 560
0
C.
(2) Al/eutectic = 3.975/1
(3) (i) and (ii) can be hardened by precipitation treatment; (iv) by marten-
site formation.
CHAPTER 19
(1) 1.97 mm.
CHAPTER 20
(7) Martensitic structure—hence brittle.
(10) A:a/p = 1.67/1; G:p/a = 1.67/1; W:p/a =
7.72/1.
541
This page has been reformatted by Knovel to provide easier navigation.
Index
Index terms Links
A
Absolute temperature scale 93 96
Acicular bainite 273
Acid/basic reactions 11
Acid open-hearth process 146
Acid steels 146
Acids 11
‘Admiralty’ brass 384 386
‘Admiralty’ gunmetal 389 391
Age-hardening 324 417
Aglommeration 143
Air-hardening steels 275 291 303
‘Alclad’ 526
‘Alcomax’ 347 348
Allotropy (of iron) see polymorphism of iron
Alloying elements, characteristics of 285
Alloy steels 285
‘Alni’ 347
‘Alnico’ 347 348
Alpha-brass 378
Alpha-particles 452
rays 452
Aluminium 4 406
in brass 386
in steel 316 324 325 472 473
542
Index terms Links
This page has been reformatted by Knovel to provide easier navigation.
Aluminium (Continued)
properties of 407
Aluminium alloys 408
Aluminium bronze 392
cold-working alloys 395 396
effects of additions 396
equilibrium diagram for 393
hot-working and casting alloys 395 396
Aluminium-copper alloys 414 415
Aluminium-copper-zinc alloys 42 423
Aluminium-magnesium alloys 410 412
Aluminium-magnesium-manganese alloys 414 415
Aluminium-manganese alloys 410
Aluminium-nickel alloys 191
Aluminium-silicon alloys 410 413
Aluminium-tin alloys 444
Amorphous state 59 219
Anhydride 11
Anisotropy 347
Annealing: after cold-work 90 252
of aluminium alloys 412
of brass 381
of high-speed steel 334
of steel 252
of steel castings 254
process- 252
solution- 200
spheroidising- 253
Annealing twins 89 377
Anodising 407 531
Antimony 4
in bearing metals 443 445
543
Index terms Links
This page has been reformatted by Knovel to provide easier navigation.
Antimony (Continued)
in copper 378
in solder 484
Argon-arc welding 491
‘Armco’ iron 244
Arsenic 4
in brass 386
in copper 92 376
Artificial age-hardening 417
ASTM specifications 2
Atom, definition 2
Atomic Mass 3
Atomic size factor 163
Atomic structure 12
Atomic Weight see Atomic Mass
Ausforming 276
Austempering 278 364
Austenite 153 240 260 270 286
292
Austenitic cast iron 368 371 372
Austenitic manganese steel 318 319 321
Austenitic stainless steel 293 303 304 308
Axles, steel for 158 296 298 300
B
Babbitt metals 443
Bainite 262 275
Bakelite (for mounting specimens) 220
Ball-bearing steels 158 298 300
Barium 4 343 349
-carbonate (in case-hardening) 465
Baryon 14
544
Index terms Links
This page has been reformatted by Knovel to provide easier navigation.
Base metals 11
Bases 11
Basic open-hearth process 146
Basic oxygen steelmaking (BOS) 147
Basic slag 146
Basic steel 146
Bearing bronzes 388 391 442
-metals 441
Bearings of sintered alloys 134 442 446
Beer barrels, steel for 299
Beryllium 4 456
-bronze 399
in aluminium alloys 532
-oxide coatings 531
Beryllium-copper alloys 399
Bessemer process 146
Beta-brass 378
Beta-particles 452
Bismuth 4 189
in copper 378
Bismuth-cadmium alloys 189
Blackheart malleable iron 364
Black plague 509
Blast furnace 141
‘Bloch walls’ 344
Blow-holes, in castings 69 71 123
Body-centred: -cubic 62
-tetragonal 261
Boron 4
in steel 326 327
Boundary, crystals 60 61 73
545
Index terms Links
This page has been reformatted by Knovel to provide easier navigation.
Brass 378
annealing of 381
cold-working of 380
effects of alloying elements on 386
effects of impurities on 381
effects of zinc content on 378
equilibrium diagram for 379
free-cutting- 137 138 385 386
high-tensile- 385 386
hot-working of 380
welding of 502
Brazing 486
-fluxes 487
-solders 488
Bright-drawn steels 134 137
Brightray 437
Brinell test 43
errors arising in 43
British Standards Specifications 2
for: alloy steels 137 296 300 301 305
306 310 314 319 322
328
aluminium alloys 408 410 414 422 426
aluminium bronzes 395
brasses 384
brazing solders 488
bronzes 391
carbon steels 137 281
case-hardening steels 471
cast irons 362 364 367 368 370
copper-nickel alloys 400
high-temperature ‘super alloys’ 438
magnesium-base alloys 432 434