1. Baja Karbon(Steel)

2. Pertanyaan ttg Baja –> what, where, when, why?
Apa itu baja?
Berapa ton/tahun baja dibuat di dunia?
Berapa ton/tahun di Amerika?
Berapa ton/tahun digunakan/konsumsi di Amerika?
Pengguna utama siapa?
Jenis Baja?

3. Steel – what, where, when, why?
Apa itu baja? Fe + C (Mo, Mn, Cr, Ni, Si, etc.)
Berapa ton/tahun baja dibuat di dunia? 100,000,000
Berapa ton/tahun di Amerika? 13,000,000
Berapa ton/tahun digunakan/konsumsi di Amerika? 31,000,000
Pengguna utama siapa? automotive, construction, oil & gas, appliances, containers,
Jenis Baja? low C, high C, alloy, stainless, martensitic, etc.

4. AVERAGE IMPORT CUSTOMS VALUE PER NET TON*
Produk2 baja dan harga:
AVERAGE IMPORT CUSTOMS VALUE PER NET TON*
Product
August 2003
21 Year Ave
% Change
Wire Rods
$302
$349
-13.60%
Bars - Hot Rolled
$429
$455
-5.90%
Bars - Cold Finished
$903
$927
-2.60%
Standard Pipe
$462
$468
-1.10%
Oil Country Goods
$598
$685
-12.70%
Mechanical Tubing
$677
$775
-12.60%
Structural Pipe & Tubing
$446
$452
-1.30%
Wire-Drawn and/or Rolled
$767
$811
-5.40%
Tin Plate
$557
$574
-3.00%
Sheet & Strip Galv. (Electrolytic)
$479
$555
-13.80%
Electrical Sheet & Strip
$715
$923
-22.50%
Strip - Hot Rolled
$379
$445
14.90%
Note: record import surge began in the first quarter of * Includes Carbon, Alloy and Stainless Source: U. S. Dept. of Commerce, Bureau of the Census

5. Negara importir baja ke US?
U.S. IMPORTS OF FINISHED STEEL MILL PRODUCTS BY COUNTRY OF ORIGIN (thousands of net tons)
Prelim 8 Mos 2003
8 Mos 2002
2003 Annualized Prelim
Annual Average *
% change 2002 Annualized vs Avg.*
Canada
3,315
3,847
4,973 -
European Union
2,256
2,954
3,384
6,111
-44.60%
Mexico
988
1,136
1,482
Korea
812
1,148
1,218
1,432
-14.90%
Turkey
685
694
1,028
460
123.50%
Japan
650
1,184
975
2,200
-55.70%
China
435
313
653
362
80.40%
Brazil
350
344
525
850
-38.20%
India
318
299
477
138
245.70%
Australia
254
217
381 56
580.40%
Argentina
189
150
154.00%
Egypt
247
204
371 51
627.50%
South Africa
218
180
327
321
1.90%
Romania
190
140
285 92
209.80%
Others
1,411
1,993
2,117
4,375
-51.60%
Total
12,383
14,842
18,575
22,192
-16.30%

6. Kandungan karbon C pada baja :
Type baja: Fe Aplikasi:
Low-C % C Kontruksi umum, low  applications.
Medium-C % C machinery parts, nuts, bolts, shafts, gears, medium 
High-C % C springs, cutting tools, dies, high uses.
Cast Iron % C engine blocks, drain pipes,
machine cabinets

7. Diagram Fasa : T  L A B b
+b
+L
b+L

8. Diagram besi-karbon
Fe-Fe3C Phase Diagram, Materials Science and Metallurgy, 4th ed., Pollack, Prentice-Hall, 1988

9. Iron - carbon phases

10. Iron - carbon transformations

11. Fe murni berubah fasa :

12. Reaksi Eutectoid :

13. Lever rule : 
%  is d
c + d
%  is c x
c d T  A
x1 x x2 B

14. Baja Hypoeuctictoid :

15. Baja Hypereutectoid :

16. Transformations :
Equilibrium transformations (slow cooling)  ->  “ferrite”  -> Fe3C “iron carbide”  ->  + Fe3C “pearlite”
Nonequlibrium (fast cooling / quenching)  -> ’ “martensite”

17. Pearlite :
Two phases ( + Fe3C)

18. Martensite :
Quenched in distortions :
+ C C Fe

19. Martensite mechanical prop. :
Keras/very hard dan
Getas/very brittle (too brittle !!!)

20. Transformations :
Equilibrium transformations (slow cooling)  ->  “ferrite”  -> Fe3C “iron carbide”  ->  + Fe3C “pearlite”
Nonequlibrium (fast cooling / quenching)  -> ’ “martensite”

21. Pearlite :
Two phases ( + Fe3C)

22. Normalized (slow cooled) steels; mechanical properties :
2,500 50
Strength (MPa)
Ductility (%) f
UTS
500 YS
0 1%
w/o Carbon

23. Martensite :
Quenched in distortions :
+ C C Fe

24. Quench and Temper : Temper : heat treat at intermediate T (300-600 C)
Mechanical properties:
Toughness meningkat (critical) namun kekerasan sedikit turun
Strukturmikro :
C membentuk presipitates Fe3C, dan penurunan distorsi dengan turunnya kandungan C yang terlarut.
Hilangnya distorsi membentuk struktur bcc yang ductility.
Fe3C precipitates - precipitation strengthen the .

25. Quenched and tempered :
2,500 50
normalized
UTS f YS
Strength (MPa)
Ductility (%) f
UTS
tempered
500 YS
0 1%
w/o Carbon

26. Heat treatments and cooling :
Normalizing (heating to form )
T ~ 1,000 C
much easier to roll / forge / form at this temperature
Quench - or - Slow cooling
martensite • pearlite
Tempering (heating to “soften” martensite)
carbides form, distortions relax

27. Quench rates : To form martensite in pure Fe
Critical Cooling Rate (CCR) ~ 100,000 C/sec
To form martensite in mild steel : Fe - 0.8% C
CCR ~ 200 C/sec
To form martensite in alloy steels : Fe %C + 2-7% (Mo, Mn, Cr, Ni)
CCR < 1 C/sec

28. Alloying elements are added to :
improve hardenability of the steel
aides nucleation of martensite
solution strengthen and precipitation hardening
MxCy carbides form
give corrosion resistance
especially Cr which forms Cr203
stabilize FCC austenite at RT
especially Ni
tougher, more ductile and easier to form
non-magnetic and creep resistant (diffusion is slower in FCC)

29. Alloying of steels : Type of steel: Fe + ... Typical uses:
Low-alloy .2%C + pressure vessels, aircraft .8Mn,1Cr,2Ni parts, high  applications.
High-alloy .1% C High T and anti-corrosion,
Stainless-steels .5Mn,18Cr,8Ni silverware, medical, etc.

30. Steel terminology (SAE-AISI) :
Plain carbon
10xx
Manganese steels
13xx
Nickel steels
23xx
Ni-Cr-Mo steels
43xx
HSLA
9xx
Note: xx indicates
carbon content in
hundredths of a percent

31. Other steel standards :
SAE-AISI
Society of Automotive Engineers ; American Iron and Steel Institute
ASTM
American Standards for Testing and Materials
AMS
Aerospace Materials Specifications
DIN
Deutsches Institut fur Normung
JIS
Japanese Industrial Standards Committee
UNS
Unified Numbering System