Baja Karbon(Steel)Baja Karbon(Steel)

Pertanyaan ttg Baja –> what, where, when, why?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?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:Produk2 baja dan harga:

AVERAGE IMPORT CUSTOMS VALUEPER 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?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 :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 :Diagram Fasa :

T

L

A B

L L

Diagram besi-karbonDiagram 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 phasesIron - carbon phases

Iron - carbon transformationsIron - carbon transformations

http://www-g.eng.cam.ac.uk/mmg/teaching/typd/addenda/microstructures1.html

Fe murni berubah fasa :Fe murni berubah fasa :

Reaksi Eutectoid :Reaksi Eutectoid :

Lever rule :Lever rule :

T

A Bx1 x x2

c d% is d c + d

% is c c + d

x

Baja Hypoeuctictoid :Baja Hypoeuctictoid :

Baja Hypereutectoid :Baja Hypereutectoid :

Transformations :Transformations :

Equilibrium transformations (slow cooling)

-> “ferrite”

-> Fe3C “iron carbide”

-> + Fe3C “pearlite”

Nonequlibrium (fast cooling / quenching)

-> ’ “martensite”

Pearlite :Pearlite :

Two phases ( + Fe3C)

Martensite :Martensite :

Quenched in distortions :

Fe

C+ C

Martensite mechanical prop. :Martensite mechanical prop. :

Keras/very hard

dan

Getas/very brittle (too brittle !!!)

Transformations :Transformations :

Equilibrium transformations (slow cooling)

-> “ferrite”

-> Fe3C “iron carbide”

-> + Fe3C “pearlite”

Nonequlibrium (fast cooling / quenching)

-> ’ “martensite”

Pearlite :Pearlite :

Two phases ( + Fe3C)

Normalized (slow cooled) steels;mechanical properties :Normalized (slow cooled) steels;mechanical properties :

Str

engt

h (M

Pa)

w/o Carbon0 1%

2,500

500

UTS

YS

Duc

tility

(%

)

0

50

f

Martensite :Martensite :

Quenched in distortions :

Fe

C+ C

Quench and Temper :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 :Quenched and tempered :S

tren

gth

(MP

a)

w/o Carbon0 1%

2,500

500

UTS

YS

Duc

tility

(%

)0

50

f

UTS

YSf

normalized

tempered

Heat treatments and cooling :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 :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 :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 :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) :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 :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