Penutup - PERANCANGAN DAN PEMBUATAN TABUNG TUNDA REAKTOR SAMOP DENGAN BAHAN STAINLESS STEEL 304

BAB V KESIMPULAN

5.2. Penutup

Dalam penulisan Tugas Akhir Perancangan dan Pembuatan Tabung Tunda Pada Reaktor SAMOP ini penulis mengucapkan banyak terima kasih kepada semua pihak yang telah banyak membantu sehingga dapat terselesaikan tugas ini. Semoga dengan terselesainya penyusunan tugas akhir ini dapat membantu dan bermanfaat bagi pembaca khususnya mahasiswa Teknik Mesin sebagai pengetahuan dalam teknologi perancangan khususnya pada perancangan tabung-tabung reaktor.

Penulis menyadari dalam penyusunan tugas akhir ini masih jauh dari kesempurnaan, untuk itu penulis mengharapkan saran dan kritik dari pembaca, agar penyusunan tugas akhir ini dapat lebih sempurna.

Akhir kata penulis mengucapkan banyak terima kasih kapada Bapak Pembimbing dan Dosen-dosen Penguji Tugas Akhir ini, semoga penulis dapat lebih mendalami tentang perhitungan dari tabung reaktor sehingga dapat berguna bagi penulis nantinya di dalam dunia kerja.

American Society for Testing and Materials. 1999, G1 Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens, ASTM Standards Vol.03.02, ASTM Society

American Society for Testing and Materials. 1999, B 117 Practice for Operating Salt Spray (Fog) Apparatus, ASTM Standards Vol.03.02, ASTM Society

Bryson, James. 1999, Corrosion of Carbon Steels, ASM Handbook Vol.13, ASM International

Callister. W, Material Science and Engineering, Third Edition

Chamberlain. 1988, Corrosion for Students of Science and Engineering, Longman Group, UK

Fontana. 1978, Corrosion Engineering. McGraw-Hill International, New York Fontana and Greene. 1978, Corrosion Engineering. McGraw-Hill. Inc,

Jaffre Dick. 2003, Effect of The Elements on Steel Properties (summary), VP Raw Material, Texas

Shreir and Jarman, Corrosion Vol.1 Metal/Environment Reactions, Butterworth-Heinemann, 2000, page 40

Widharto, Sri. 2001, Karat dan Pencegahannya, Pradnya Paramita, Jakarta http://gadang-e-bookformaterialscience.blogspot.com/2006/11/artikelperingkat-ketahanan-logamterhadap-korosi.html (Sabtu, 26 Januari 2008)

http://gadang-e-bookformaterialscience.blogspot.com/2007/4/infodaftar-pengujian-korosi-standar-astm-secara-umum.html (Sabtu, 26 Januari 2008) http://gadang-e-bookformaterialscience.blogspot.com/2005/25/infomengenal-singkat-apa-itu-stainless-steel.html (Sabtu, 26 Januari 2008)

http://gadang-e-bookformaterialscience.blogspot.com/2007/15/sekilasapakah-makna-dari-korosi-secara-umum.html (Sabtu, 26 Januari 2008)

http://gadang-e-bookformaterialscience.blogspot.com/2006/7/artikelmakalah-ilmiah-ku-korosi-material-baja-karbon-dan-stainless-steel.html (Sabtu, 26 Januari 2008)

LAMPIRAN I

Perhitungan Tebal Tabung Berdasarkan Ld

Berikut perhitungan tebal tabung berdasar rumusan Introduction to PIPE

STRESS ANALYSIS dalam usia penggunaan tabung 10, 25, 50 tahun. Ukuran

dimensi yang sudah ditentukan antara lain, diketahui laju korosi A = 0,1 mm/tahun. Diameter dalam Di = 220 mm, tekanan di dalam tabung P = 1 atm, Eq

= 0,625. Bahan yang digunakan adalah tabung berbahan 18 Cr - 8 Ni. Tabung digunakan selama Ld = 10, 25, 50 tahun dan suhu di dalam tabung T = 50°C. Hitung tebal minimum tabung (t), tebal minimum tabung akibat laju korosi (t_m) dan tebal nominal (nominal thickness).

P = 14,696 psi ; D_o = 8,701 inchi ; E_q = 0,625 dari jenis tabung

S = Sh = tegangan yang diijinkan pada temperatur bahan dari 18 Cr - 8 Ni

tubes A269 grade A = 20000 psi, lihat Tabel 4.1 dan 4.2

Allowance Stresses in Tension for Metals, SE, KSI (sumber dari :

Introduction to PIPE STREES ANALYSIS Appendix A3, hal. 220)

Y = 0,4 (karena temperaturnya dibawah 900°F atau 482,2°C)

dimana:

tm = tebal minimum dinding yang diperlukan, inchi t = tebal akibat tekanan, inchi

D_o = diameter luar tabung, inchi

S = tegangan elastis, tegangan yang diijinkan pada temperatur bahan, psi (lihat Table 4.1 dan Table 4.2)

A = korosi yang diijinkan, ketebalan tambahan untuk material yang terbuang dalam penguliran, karat, atau erosi yang diijinkan; toleransi pabrikasi mill tolerance (MT) juga perlu dipertimbangkan, inchi

Y = koefisien yang diijinkan berdasarkan material atau bahan yang digunakan. Untuk nilai Y dalam rumusan diatas didapat karena temperaturnya dibawah 900°F, (lihat Tabel 3.3) maka nilai Y yang diasumsikan adalah 0,4.

o D d d Y + = jika, 6 d t ≥ dimana: d = diameter dalam = Do – 2 t

E_q = faktor kualitas yang menjadi faktor produk kualitas tuang

Ec, faktor kualitas gabung Ej dan nilai mutu ketika digunakan E_s. Nilai E_c dari 0,85 sampai 1,00 tergantung dari metode yang digunakan untuk menguji mutu tuangan (lihat Tabel 3.4). Sedangkan nilai Ej dari 0,60 sampai 1,00 (lihat Tabel 3.5) yang tergantung pada jenis materi sambungan. Nilai Es dapat diasumsikan menjadi 0,92.

s j c q E E E E = dengan: Eq = 0,85 . 0,80 . 0,92 = 0,626

Diketahui L_d = 10 tahun, maka

) ( 2 SE PY D P t q o + = dengan:

(

20000.0,626 14,696.0,4

)

2 8,721 . 696 , 14 + = t 757 , 25051 164 , 128 = =0,005116 inchi =0,13 mm A t t_m = + dengan: t_m =0,005116+0,030 =0,035116inchi =0,89 mm Tebal nominal

(

)

t_m − = 1

( )

dengan: Tebal nominal 125 , 0 1− =⁰^,⁰³⁵¹¹⁶ =0,040133inchi 1,02= mm

Diketahui Ld = 25 tahun, maka

) ( 2 SE PY D P t q o + = dengan:

(

20000.0,626 14,696.0,4

)

2 8,811 . 696 , 14 + = t 757 , 25051 486 , 129 = =0,005169 inchi =0,13 mm A t t_m = + dengan: t_m =0,005169+0,075 =0,080169inchi =2,04mm

Tebal nominal

(

)

t_m − = 1 dengan: Tebal nominal

(

1 0,125

)

080169 , 0 − = =0,091622inchi 2,33= mm

Diketahui Ld = 50 tahun, maka

) ( 2 SE PY D P t q o + = dengan:

(

20000.0,625 14,696.0,4

)

2 8,961 . 696 , 14 + = t 757 , 25051 691 , 131 = =0,005257 inchi =0,13 mm A t t_m = + dengan: t_m =0,005257+0,150 =0,155257inchi =3,94mm

Tebal nominal

(

)

t_m − = 1 dengan: Tebal nominal

(

1 0,125

)

155257 , 0 − = =0,177437inchi 4,51= mm

LAMPIRAN II

Daftar ASTM Pengujian Korosi Secara Umum

A 143 - Practice for Safeguarding Against Embrittlement of Hot-Dip Galvanized Structural Steel Products and Procedure for Detecting Embrittlement

A 262 - Practices for Detecting Susceptibility to lntergranular Attack in Austenitic Stainless Steels

A 380 - Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment and Systems

A 763 - Practices for Detecting Susceptibility to Intergranular Attack in Ferritic Stainless Steels

***

B 76 - Test Method for Accelerated Life of Chromium and Nickel-Chromium-Iron Alloys for Electrical Heating

B 78 - Test Method for Accelerated Life of Iron-Chromium-Aluminum Alloys for Electrical Heating

B 117 - Practice for Operating Salt Spray (Fog) Apparatus

B 154 - Test Method for Mercurous Nitrate Test for Copper and Copper Alloys

B 368 - Method for Copper-Accelerated Acetic Acid-Salt Spray (Fog) Testing (Cass Test)

B 380 - Method of Corrosion Testing of Decorative Electrodeposited Coatings by the Corrodkote Procedure

B 457 - Test Method for Measurement of Impedance of Anodic Coatings on Aluminum

B 537 - Practice for Rating of Electroplated Panels Subjected to Atmospheric Exposure

B 545 - Specification for Electrodeposited Coatings of Tin

B 577 - Test Methods for Detection of Cuprous Oxide (Hydrogen Embrittlement Susceptibility) in Copper

B 605 - Specification for Electrodeposited Coatings of Tin-Nickel Alloy

B 627 - Test Method for Electrolytic Corrosion Testing (EC Test)

B 650 - Specification for Electrodeposited Engineering Chromium Coatings on Ferrous Substrates

B 651 - Method for Measurement of Corrosion Sites in Nickel Plus Chromium or Copper Plus Nickel Plus Chromium Electroplated Surfaces With the Double-Beam Interference Microscope

B 680 - Test Method for Seal Quality of Anodic Coatings on Aluminum by Acid Dissolution

B 689 - Specification for Electroplated Engineering Nickel Coatings

B 732 - Test Method for Evaluating the Corrosivity of Solder Fluxes for Copper Tubing Systems

B 733 - Specification for Autocatalytic Nickel-Phosphorus Coatings on Metals

B 734 - Specification for Electrodeposited Copper for Engineering Uses

B 735 - Test Method for Porosity in Gold Coatings on Metal Substrates by Nitric Acid Vapor

B 741 - Test Method for Porosity in Gold Coatings on Metal Substrates by Paper Electrography

B 765 - Guide for Selection of Porosity Tests for Electrodeposits and Related Metallic Coatings

B 809 - Test Method for Porosity in Metallic Coatings by Humid Sulfur Vapor "Flowers of Sulfur"

***

C 692 - Test Method for Evaluating the Influence of Thermal Insulations on the External Stress Corrosion Cracking Tendency of Austenitic Stainless Steel

C 739 - Specification for Cellulosic Fiber (Wood-Base) Loose-Fill Thermal Insulation

C 876 - Test Method for Half-Cell Potentials of Uncoated Reinforcing Steel in Concrete

D 130 - Test Method for Detection of Copper Corrosion From Petroleum Products by the Copper Strip Tarnish Test

D 610 - Test Method for Evaluating Degree 9f Rusting on Painted Steel Surfaces

D 665 - Test Method for Rust-Preventing Characteristics of inhibited Mineral Oil in the Presence of Water

D 849 - Test Method for Copper Strip Corrosion by Industrial Aromatic Hydrocarbons

D 876 - Test Methods for Nonrigid Vinyl Chloride Polymer Tubing Used for Electrical Insulation

D 930 - Test Method of Total Immersion Corrosion Test of Water-Soluble Aluminum Cleaners

D 1141 - Specification for Substitute Ocean Water

D 1193 - Specification for Reagent Water

D 1280 - Test Method of Total Immersion Corrosion Test for Soak Tank Metal Cleaners

D 1384 - Test Method for Corrosion Test for Engine Coolants in Glassware

D 1414 - Test Method for Rubber O-Rings

D 1611 - Test Method for Corrosion Produced by Leather in Contact with Metal

D 1654 - Test Method for Evaluation of Painted or Coated Specimens Subjected to Corrosive Environments

D 1734 - Test Method for Corrosion Preventive Properties of Lubricating Greases

D 1838 - Test Method for Copper Strip Corrosion by Liquefied Petroleum (LP) Gases

D 2059 - Test Method for Resistance of Zippers to Salt Spray (Fog)

D 2251 - Test Method for Metal Corrosion by Halogenated Organic Solvents and Their Admixtures

D 2570 - Test Method for Simulated Service Corrosion Testing of Engine Coolants

D 2649 - Test Method for Corrosion Characteristics of Solid Film Lubricants

D 2671 - Test Methods for Heat-Shrinkable Tubing for Electrical Use

D 2758 - Test Method for Engine Coolants by Engine Dynamometer

D 2803 - Guide for Testing Filiform Corrosion Resistance of Organic Coatings on Metal

D 2809 - Test Method for Cavitation Corrosion and Erosion-Corrosion Characteristics of Aluminum Pumps with Engine Coolants

D 2847 - Practice for Testing Engine Coolants in Car and Light Truck Service

D 2933 - Test Method for Corrosion Resistance of Coated Steel Specimens (Cyclic Method)

D 3263 - Test Methods for Corrosivity of Solvent Systems for Removing Water-Formed Deposits

D 3310 - Test Method for Determining Corrosivity of Adhesive Materials

D 3316 - Test Method for Stability of Perchloroethylene with Copper

D 3482 - Test Method for Determining Electrolytic Corrosion of Copper by Adhesives

D 3603 - Test Method for Rust-Preventing Characteristics of Steam Turbine Oil in the Presence of Water (Horizontal Disk Method)

D 4048 - Test Method for Detection of Copper Corrosion from Lubricating Grease

D 4340 - Test Method for Corrosion of Cast Aluminum Alloys in Engine Coolants under Heat-Rejecting Conditions

D 4585 - Practice for Testing Water Resistance of Coatings Using Controlled Condensation

D 4627 - Test Method for Iron Chip Corrosion for Water-Dilutable Metalworking Fluids

***

E 712 - Practice for Laboratory Screening of Metallic Containment Materials for Use with Liquids in Solar Heating and Cooling Systems

E 745 - Practices for Simulated Service Testing for Corrosion of Metallic Containment Materials for Use with Heat-Transfer Fluids in Solar Heating and Cooling Systems

E 937 - Test Method for Corrosion of Steel by Sprayed Fire-Resistive Material (SFRM) Applied to Structural Members

***

F 326 - Test Method for Electronic Hydrogen Embrittlement Test for Cadmium Electroplating Processes

F 359 - Practice for Static Immersion Testing of Unstressed Materials in Nitrogen Tetroxide (N2O4)

F 482 - Test Method for Corrosion of Aircraft Metals by Total Immersion in Maintenance Chemicals

F 483 - Test Method for Total Immersion Corrosion Test for Aircraft Maintenance Chemicals

F 519 - Test Method for Mechanical Hydrogen Embrittlement Testing of Plating Processes and Aircraft Maintenance Chemicals

F 746 - Test Method for Pitting or Crevice Corrosion of Metallic Surgical Implant Materials

F 897 - Test Method for Measuring Fretting Corrosion of Osteosynthesis Plates and Screws

F 945 - Test Method for Stress-Corrosion of Titanium Alloys by Aircraft Engine Cleaning Materials

F 1089 - Test Method for Corrosion of Surgical Instruments

F 1110 - Test Method for Sandwich Corrosion Test

***

G 1 - Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens

G 2 - Test Method for Corrosion Testing of Products of Zirconium, Hafnium and Their Alloys in Water at 680F or in Steam at 750F

G 2M - Test Method for Corrosion Testing of Products of Zirconium, Hafnium, and Their Alloys in Water at 633K or in Steam at 673K (Metric)

G 3 - Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing

G 4 - Guide for Conducting Corrosion Coupon Tests in Field Applications

G 5 - Reference Test Method for Making Potentiostatic and Potentiodynamic Anodic Polarization Measurement

G 15 - Terminology Relating to Corrosion and Corrosion Testing

G 16 - Guide for Applying Statistics to Analysis of Corrosion Data

G 28 - Test Methods of Detecting Susceptibility to Intergranular Attack in Wrought, Nickel-Rich, Chromium Bearing Alloys

G 30 - Practice for Making and Using U-Bend Stress-Corrosion Test Specimens

G 31 - Practice for Laboratory Immersion Corrosion Testing of Metals

G 32 - Test Method for Cavitations Erosion Using Vibratory Apparatus

G 33 - Practice for Recording Data from Atmospheric Corrosion Tests of Metallic-Coated Steel Specimens

G 34 - Test Method for Exfoliation Corrosion Susceptibility in 2XXX and 7XXX Series Aluminum Alloys (EXCO Test)

G 35 - Practice for Determining the Susceptibility of Stainless Steels and Related Nickel-Chromium-Iron Alloys to Stress-Corrosion Cracking in Polythionic Acids

G 36 - Practice for Evaluating Stress-Corrosion-Cracking Resistance of Metals and Alloys in a Boiling Magnesium Chloride Solution

G 37 - Practice for Use of Mattsson’s Solution of pH 7.2 to Evaluate the Stress-Corrosion Cracking Susceptibility of Copper-Zinc Alloys

G 39 - Practice for Preparation and Use of Bent-Beam Stress-Corrosion Test Specimens

G 40 - Terminology Relating to Wear and Erosion

G 41 - Practice for Determining Cracking Susceptibility of Metals Exposed Under Stress to a Hot Salt Environment

G 44 - Practice for Evaluating Stress Corrosion Cracking Resistance of Metals and Alloys by Alternate Immersion in 3.5 % Sodium Chloride Solution

G 46 - Guide for Examination and Evaluation of Pitting Corrosion

G 47 - Test Method for Determining Susceptibility to Stress-Corrosion Cracking of High-Strength Aluminum Alloy Products

G 48 - Test Methods for Pitting and Crevice Corrosion Resistance of Stainless Steels and Related Alloys by Ferric Chloride Solution

G 49 - Practice for Preparation and Use of Direct Tension Stress-Corrosion Test Specimens

G 50 - Practice for Conducting Atmospheric Corrosion Tests on Metals

G 51 - Test Method for Measuring pH of Soil for Use in Corrosion Testing

G 52 - Practice for Exposing and Evaluating Metals and Alloys in Surface Seawater

G 54 - Practice for Simple Static Oxidation Testing

G 56 - Test Method for Abrasiveness of Ink-Impregnated Fabric Printer Ribbons

G 57 - Test Method for Field Measurement of Soil Resistivity Using the Wenner Four-Electrode Method

G 58 - Practice for Preparation of Stress-Corrosion Test Specimens for Weldments

G 59 - Practice for Conducting Potentiodynamic Polarization Resistance Measurements

G 60 - Test Method for Conducting Cyclic Humidity Tests

G 61 - Test Method for Conducting Cyclic Potentiodynamic Polarization Measurements for Localized Corrosion Susceptibility of Iron, Nickel, or Cobalt Based Alloys

G 64 - Classification of Resistance to Stress-Corrosion Cracking of Heat-Treatable Aluminum Alloys

G 65 - Test Method for Measuring Abrasion Using the Dry Sand/Rubber Wheel Apparatus

G 66 - Test Method for Visual Assessment of Exfoliation Corrosion Susceptibility of 5XXX Series Aluminum Alloys (ASSET Test)

G 67 - Test Method for Determining the Susceptibility to Intergranular

Corrosion of 5XXX Series Aluminum Alloys by Mass loss Alter Exposure to Nitric Acid (NAMLT Test)

G 69 - Practice for Measurement of Corrosion Potentials of Aluminum Alloys

G 71 - Guide for Conducting and Evaluating Galvanic Corrosion Tests in Electrolytes

G 73 - Practice for Liquid Impingement Erosion Testing

G 75 - Test Method for Determination of Slurry Abrasivity (Miller Number) and Slurry Abrasion Response of Materials (SAR Number)

G 76 - Test Method for Conducting Erosion Tests by Solid Particle Impingement Using Gas Jets

G 77 - Test Method for Ranking Resistance of Materials to Sliding Wear Using Block-on-Ring Wear Test

G 78 - Guide for Crevice Corrosion Testing of Iron-Base and Nickel-Base Stainless Alloys in Seawater and Other Chloride-Containing Aqueous Environments

G 79 - Practice for Evaluation of Metals Exposed to Carbuzization Environments

G 81 - Test Method for Jaw Crusher Gouging Abrasion Test

G 82 - Guide for Development and Use of a Galvanic Series for Predicting Galvanic Corrosion Performance

G 83 - Test Method for Wear Testing with a Crossed-Cylinder Apparatus

G 84 - Practice for Measurement of Time-of-Wetness on Surfaces Exposed to Wetting Conditions as in Atmospheric Corrosion Testing

G 85 - Practice for Modified Salt Spray (Fog) Testing

G 87 - Practice for Conducting Moist SO2 Tests

G 91 - Practice for Monitoring Atmospheric SO2 Using the Sulfation Plate Technique

G 92 - Practice for Characterization of Atmospheric Test Sites

G 96 - Guide for On-Line Monitoring of Corrosion in Plant Equipment (Electrical and Electrochemical Methods)

G 97 - Test Method for laboratory Evaluation of Magnesium Sacrificial Anode Test Specimens for Underground Applications

G 98 - Test Method for Galling Resistance of Materials

G 99 - Test Method for Wear Testing with a Pin-on-Disk Apparatus

G 100 - Test Method for Conducting Cyclic Galvanostaircase Polarization

G 101 - Guide for Estimating the Atmospheric Corrosion Resistance of low-Alloy Steels

G 102 - Practice for Calculation of Corrosion Rates and Related Information from Electrochemical Measurements

G 103 - Test Method for Performing a Stress-Corrosion Cracking Test of low Copper Containing Al-Zn-Mg Alloys in Boiling 6 % Sodium Chloride Solution

G 104 - Test Method for Assessing Galvanic Corrosion Caused by the Atmosphere

G 105 - Test Method for Conducting Wet Sand/Rubber Wheel Abrasion Tests

G 106 - Practice for Verification of Algorithm and Equipment for Electrochemical Impedance Measurements

G 107 - Guide for Formats for Collection and Compilation of Corrosion Data for Metals for Computerized Database Input

G 108 - Test Method for Electrochemical Reactivation (EPR) for Detecting Sensitization of AISI Type 304 and 304L Stainless Steels

G 109 - Test Method for Determining the Effects of Chemical Admixtures on the Corrosion of Embed Steel Reinforcement in Concrete Exposed to Chloride Environments

G 110 - Practice for Evaluating Inter-granular Corrosion Resistance of Heat-Treatable Aluminum Alloys by Immersion in Sodium Chloride + Hydrogen Peroxide Solution

G 111 - Guide for Corrosion Tests in High-Temperature or High-Pressure Environment or Both

G 112 - Guide for Conducting Exfoliation Corrosion Tests in Aluminum Alloys

G 115 - Guide for Measuring and Reporting Friction Coefficients

G 116 - Practice for Conducting Wire-on-Bolt Test for Atmospheric Galvanic Corrosion

G 117 - Guide for Calculating and Reporting Measures of Precision Using Data from Inter-laboratory Wear or Erosion Tests

G 118 - Guide for Recommended Format of Wear Test Data Suitable for Databases

G 119 - Guide for Determining Synergism between Wear and Corrosion

G 123 - Test Method for Evaluating Stress-Corrosion Cracking of Stainless Alloys with Different Nickel Content in Boiling Acidified Sodium Chloride Solution

G 129 - Practice for Slow Strain Rate Testing to Evaluate the Susceptibility of Metallic Materials to Environmentally Assisted Cracking

G 132 - Test Method for Pin Abrasion Testing

G 133 - Test Method for Linearly Reciprocating Ball-on-Flat Sliding Wear

G 134 - Test Method for Erosion of Solid Materials by a Cavitating Liquid Jet

G 137 - Test Method for Ranking Resistance of Plastic Materials to Sliding Wear Using a Block-on-Ring Configuration

G 139 - Test Method for Determining Stress-Corrosion Cracking Resistance of Heat-Treatable Aluminum Alloy Products Using Breaking load Method

G 140 - Test Method for Determining Atmospheric Chloride Deposition Rate by Wet Candle Method

G 142 - Test Method for Determination of Susceptibility of Metals to

Embrittlement in Hydrogen Containing Environments at High Pressure, High Temperature, or Both

G 143 - Test Method for Measurement of Web/Roller Friction Characteristics

G 146 - Practice for Evaluation of Disbonding of Bimetallic Stainless Alloy/Steel Plate for Use in High-Pressure, High-Temperature Refinery Hydrogen Service

G 148 - Practice for Evaluation of Hydrogen Uptake, Permeation, and Transport in Metals by an Electrochemical Technique

G 149 - Practice for Conducting the Washer Test for Atmospheric Galvanic Corrosion

G 150 - Test Method for Electrochemical Critical Pitting Temperature Testing of Stainless Steels

LAMPIRAN III

Apakah stainless steel 304 dan 316 itu pasti mempunyai sifat amagnetis?

Umumnya stainless steel 304 dan 316 bersifat tidak magnetik, oleh karena itu pemesan 304 dan 316 selalu membawa magnet untuk mengecek hasilnya. Kenyataanya, dilapangan saat pembuatan autenitik stainless steel murni itu sulit. Contoh, hasil pemeriksaan spectrometer sedikit kelebihan unsur C, untuk mencapai target komposisi C tersebut caranya di-holding, sedangkan temperatur pembuatan sekitar 1650°C, jika di-holding lama ada unsur lain masuk dari lining. Atau kandungan nikel banyak losses-nya pada saat peleburan maka austenitik

stainless steel yang bersifat non-magnetik tidak terjadi. Oleh karena itu pengendalian komposisi, temperatur, atmosfir tungku peleburan, proses, SDM dan peralatan sangat menentukan keberhasilan pembuatan stainless steel.

Stainless steel 304 dan 316 termasuk jenis austenitik stainless steel yang tidak bersifat magnetis karena pengaruh kandungan unsur nikel antara 8% - 13%. Mekanisme austenitik stainless steel tidak bersifat megnetik yaitu unsur nikel yang berkisi fcc mempromote terbentuknya fasa austenit dengan cara merubah fasa feritik bcc menjadi fasa gama fcc austenit.

Batas minimum kestabilan fasa austenit untuk karbon 0,03%, krom 17 - 21% dan

molybdenum 2% - 3% untuk austenitik stainless steel, yaitu minimum kandungan nikel 8%. Semakin banyak unsur nikel maka semakin luas fasa austenit atau semakin stabil fasa austenit, oleh karena itu stainless steel tersebut semakin semakin ulet dan tahan magnit. Semakin sedikit kandungan nikel di stainless steel

atau kurang dari 8% maka semakin mempromote terbentuknya fasa ferit yang bersifat magnetis. Unsur unsur yang mempromote terbentuknya fasa ferit yaitu C, Cr, Mo dan unsur-unsur pembentuk karbida lainnya.

LAMPIRAN IV

Apakah sifat amagnetis dari stainless steel ini bisa berganti menjadi sifat magnetis-nya bila material ini di gabungkan atau di sambung dengan mild-steel biasa melalui proses pengelasan (electric welding)?

Untuk dasarnya metal stainless steel yang mempunyai sifat non-magnetik, diposisi yang jauh dari efek las sifatnya akan tetap non-magnetik. Tetapi di daerah las-an karena ada penambahan logam tambah (filler metal) komposisi logam las-an aklas-an mempengaruhi sifat meklas-anik, sifat fisik termasuk struktur. Apabila pengelasan komposisinya tidak sama dengan dasar metal stainless steel

kecenderungannya non-magnetik berubah menjadi magnetik di daerah las-an, sangat mungkin terjadi karena C, Si, Cr dan unsur pembentuk karbida yang terkandung di filler metal akan mempromote fasa ferit yang bersifat magnetik.

Tipe austenitik non-magnetik perlu diketahui juga bahwa semua jenis

pengelasan. Faktor utama yang perlu diperhatikan adalah ketahanan korosi di daerah las (weld) dan Heat Affected Zone (HAZ). Perlu diingat juga austenitik pada umumnya memiliki struktur fasa tunggal dengan adanya fasa tunggal inilah

Dalam dokumen PERANCANGAN DAN PEMBUATAN TABUNG TUNDA REAKTOR SAMOP DENGAN BAHAN STAINLESS STEEL 304 TUGAS AKHIR - Perancangan dan pembuatan tabung tunda reaktor samop dengan bahan stainless steel 304 - USD Repository (Halaman 72-98)