Baja Karbon(Steel)

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 VALUEPER NET TON* August2003 Product 21 Year Ave %Change Wire Rods $302 $349 -13.60% Bars - Hot Rolled $429 $455 -5.90% Bars - Cold Finished $903 $927 -2.60% 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 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% Produk2 baja dan harga:

5. U.S. IMPORTS OF FINISHED STEEL MILL PRODUCTSBY COUNTRY OF ORIGIN (thousands of net tons) Prelim8 Mos2003 8 Mos2002 2003AnnualizedPrelim AnnualAverage1994-1997* % 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% Negara importir baja ke US?

6. 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

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

8. 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

9. Iron - carbon phases

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

11. Fe murni berubah fasa :

12. Reaksi Eutectoid :

13. Lever rule :  %  is d c + d %  is c c + d x c d T  x1 x x2 A 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 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 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 - 0.2-.6%C + 2-7% (Mo, Mn, Cr, Ni) • CCR < 1 C/sec

28. Alloying elements are added to : • improvehardenabilityof 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