BAJA PADUAN DAN SUPER ALLOY. Dr.-Ing. Bambang Suharno Dr. Ir. Sri Harjanto 1. ALASAN PENGGUNAAN 2. KLASIFIKASI 3. PENGGUNAAN

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1 BAJA PADUAN DAN SUPER ALLOY Dr.-Ing. Bambang Suharno Dr. Ir. Sri Harjanto 1. ALASAN PENGGUNAAN 2. KLASIFIKASI 3. PENGGUNAAN Department of Metallurgy and Materials 2008 Silabus Tujuan : Memahami berbagai jenis material baja paduan dan super Alloy serta penggunaannya dalam bidang rekayasa Evaluasi: UTS = 35 % UAS = 45 % Tugas = 20 % Lain-lain = 5 %

2 Silabus Penggunaan Baja Paduan dan Super Alloy Pengaruh Unsur Paduan Stainless Steel (Baja Tahan Karat) Heat Resistant Steel Wear/ Abrassion Resistant Steel Tool Steel Super Alloy Ni based, Co based BAJA KARBON Low-carbon < 0.30% C. Flat-rolled products (sheet or strip), usually in the coldrolled and annealed condition. The carbon content for these high-formability steels is very low, less than 0.10% C Typical uses are in automobile body panels, tin plate, and wire products. For rolled steel structural plates and sections, the carbon content may be increased to approximately 0.30%, with higher manganese content up to 1.5%. These materials may be used for stampings, forgings, seamless tubes, and boiler plate.

3 Steel Making Flowlines Steel Making Flowlines

4 BAJA KARBON Medium-carbon steels carbon ranges from 0.30 to 0.60% and the manganese from 0.60 to 1.65%. Medium carbon steels to be used in the quenched and tempered condition. The uses of medium carbon-manganese steels include shafts, axles, gears, crankshafts, couplings and forgings. Steels in the 0.40 to 0.60% C range are also used for rails, railway wheels and rail axles. High-carbon steels 0.60 to 1.00% C with manganese from 0.30 to 0.90%. used for spring materials and high-strength wires. Pengaruh Karbon Pada Baja

5 Fe-Fe3C 0.5% C ferrite + pearlite 1.5% C ferrite + cementite 0.5%C 0.8%C 1.5%C WHY WE NEED ALLOYS? Keterbatasan Baja Karbon: a) A high critical cooling rate which leads to cracking when quenching hardening. b) Poor Hardenability. c) Ultimate Tensile Strength rendah Jika di Heat Treatment Elongasi Rendah Toughness Rendah d) Ketahahan Korosi (Corrosion Resistant) Rendah Ketahanan Aus (Wear Resistant) Rendah Ketahanan Panas (Heat Resistant) Rendah

6 KLASIFIKASI BAJA Definisi Baja : Material berbahan dasar Fe, dengan C maks : 2% Kadar C boleh 2% Tetapi harus ada unsur lain (paduan) Serta mengandung unsur pengikut seperti Si, P, S, Mn dan unsur paduan seperti Cr,Ni, Mo, V, W dll. KLASIFIKASI BAJA Klasifikasi Baja dapat berdasarkan: The composition, such as carbon, low-alloy or stainless steel. The manufacturing methods, such as open hearth, basic oxygen process, or electric furnace methods. The finishing method, such as hot rolling or cold rolling The product form, such as bar plate, sheet, strip, tubing or structural shape The deoxidation practice, such as killed, semi-killed, capped or rimmed steel The microstructure, such as ferritic, pearlitic and martensitic The required strength level, as specified in ASTM standards The heat treatment, such as annealing, quenching and tempering, and thermomechanical processing Quality descriptors, such as forging quality and commercial quality.

7 Penggunaan Baja Paduan Industry Minyak, Gas dan Petrokimia : Corrosion Resistant and Heat Resistant Steel SS 304, 316, 309, 310 Industri Semen dan Pertambangan: Wear Resistant Steel (Keras dan Tangguh) Ni Hard, High C-Chrom Steel, Baja Mn Industri Manufacture Tool Steel (H13 = SKD61, P20)

8 Super Alloys Adalah paduan yang dikembangkan untuk penggunaan material pada temperatur tinggi, tahan hot corrosion and errosion Semula dikembangkan untuk aircraft turbine engine Umumnya mengandung Fe, Ni, Co, Cr dan sejumlah W, Mo, Ta,Nb, Ti dan Al. Contoh Hastealloy, Inconel Elemen Paduan Terdiri atas : Carbide Former. Austenite Stabilizer. Ferrite Stabilizer. Graphitizer. Secara Umum 1. Penstabil γ memperlebar daerah γ 2. Penstabil α memperlebar daerah α Seluruh paduan, kecuali Co : 1. Menurunkan M s dan M f 2. Mendorong kurva TTT ke kanan memperlambat pembentukan Perlit / Bainit

9 Pengaruh Elemen Paduan Terhadap Diagram Time Temp Transformation Carbide Former (Pembentuk Karbida) Beberapa elemen paduan membentuk karbida stabil yang lebih keras dari iron carbides (Fe 3 C) Dapat meningkatkan kekerasan (hardness) cocok untuk keperluan tool (perkakas), tahan panas Cr, Mn, Nb, Mo, Ti, W, V.

10 Austenite Stabilisers C, Co, Cu, Ni, Mn, N meningkatkan A4 Temp (austenine-delta) menurunkan A3 Temp Jika elemen tersebut ditambahkan pada C-Steel akan menstabilkan fasa γ. Elemen paduan ini tidak membentuk carbida, C tetap tinggal dalam solid solution dalam γ. Bahkan jika paduan jumlahnya banyak pada temperatur kamar tetap berfasa γ (non magnetis) misal : Austenitik Stainless Steel Mn Sebagai Austenite Stabilizer

11 Fe-C Diagram Ferrite Stabilisers Al, Cr, Si, Mo, Nb, Ta, Ti, W, V, Zr Jika ditambahkan dalam baja menstabilkan fasa Ferit (alpha) Pada Temperatur kamar, berfasa Ferit Struktur kristasl BCC (Body Centered Cubic) Contoh: Ferritic Stainless Steel

12 Cr Sebagai Ferrite Stabilizer Mo Sebagai Ferrite Stabilizer

13 Graphitisers Tak semua elemen paduan berkombinasi dengan C (Ni, Al, Si), sehingga C cenderung sebagai free graphite. Jika unsur tersebut harus ada, maka: Perlu adanya elemen paduan pembentuk karbida, atau kandungan C dibuat very low. Karenanya tak mungkin membuat high C-high Ni alloy steel.