Baja Karbon(Steel)
Mar 19, 2016
Baja Karbon(Steel)
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?
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.
Produk2 baja dan harga:AVERAGE IMPORT CUSTOMS VALUE
PER NET TON*
Product August200
3
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 1998.* Includes Carbon, Alloy and Stainless
Source: U. S. Dept. of Commerce, Bureau of the Census
Negara importir baja ke US?U.S. IMPORTS OF FINISHED STEEL MILL PRODUCTSBY COUNTRY OF ORIGIN (thousands of net tons)
Prelim8 Mos2003
8 Mos2002
2003Annualized
Prelim
AnnualAverage
1994-1997*
% change2002 Annualizedvs 94-97 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 254 189 381 150 154.00%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%
Kandungan karbon C pada baja :
Type baja: Fe + ... Aplikasi:
Low-C .04-.3% C Kontruksi umum,low applications.
Medium-C .3-.7% C machinery parts, nuts, bolts, shafts, gears, medium
High-C .7-1.7% C springs, cutting tools, dies, high uses.
Cast Iron 1.8 - 4% C engine blocks, drain pipes,machine cabinets
Diagram Fasa :
T
L
A B
L L
Diagram besi-karbon
Fe-Fe3C Phase Diagram, Materials Science and Metallurgy, 4th ed., Pollack, Prentice-Hall, 1988
http://www.sv.vt.edu/classes/MSE2094_NoteBook/96ClassProj/examples/kimcon.html
Iron - carbon phases
Iron - carbon transformations
http://www-g.eng.cam.ac.uk/mmg/teaching/typd/addenda/microstructures1.html
Fe murni berubah fasa :
Reaksi Eutectoid :
Lever rule :
T
A Bx1 x x2
c d% is d c + d
% is c c + d
x
Baja Hypoeuctictoid :
Baja Hypereutectoid :
Transformations :
Equilibrium transformations (slow cooling)
-> “ferrite”
-> Fe3C “iron carbide”
-> + Fe3C “pearlite”
Nonequlibrium (fast cooling / quenching)
-> ’ “martensite”
Pearlite :
Two phases ( + Fe3C)
Martensite :
Quenched in distortions :
Fe
C+ C
Martensite mechanical prop. :
Keras/very hard
dan Getas/very brittle (too brittle !!!)
Transformations :
Equilibrium transformations (slow cooling)
-> “ferrite”
-> Fe3C “iron carbide”
-> + Fe3C “pearlite”
Nonequlibrium (fast cooling / quenching)
-> ’ “martensite”
Pearlite :
Two phases ( + Fe3C)
Normalized (slow cooled) steels;mechanical properties :
Stre
ngth
(MP
a)
w/o Carbon0 1%
2,500
500
UTS
YS
Duc
tility
(%
)
0
50
f
Martensite :
Quenched in distortions :
Fe
C+ C
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 .
Quenched and tempered :S
treng
th (M
Pa)
w/o Carbon0 1%
2,500
500
UTS
YS
Duc
tility
(%
)0
50
f
UTS
YSf
normalized
tempered
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
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 - 0.2-.6%C + 2-7% (Mo, Mn, Cr, Ni)• CCR < 1 C/sec
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)
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.
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 inhundredths of a percent
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