Brazing Technology of Ti Alloy/Stainless Steel Dissimilar Metal Joint at System Integrated Modular Advanced Reactor 2001
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KR0100910 KAERI/AR-589/2001 Brazing Technology of Ti alloy/Stainless Steel Dissimilar Metal Joint at System Integrated Modular Advanced Reactor 2001. 2. o ofc II £Uflol*J ^ 7)^$] 7^ik QSft 7l#^ BC 4000V! ceramic^ Ill 3.7% 71 £7} *>7flEH -8-71-^71- ^ 511^x1x1 &-S- ^£ 014. IV 350MPa Ti-Fe V §1-^1, -8-71- BAg-19, BVAg-30 ^ Gapasil-9^- ^-§- ^«H, Ni 40% HNOs + 2% HF + 58% H2O *°^ macroetch test SUMMARY I Title Brazing Technology of Ti alloy/Stainless Steel Dissimilar Metal Joint at System Integrated Modular Advanced Reactor II The Development of Brazing Technology As a joining technology, brazing has a long history since those ancient times in about 4000 B. C, when both silver and gold brazing were carried out at Sumer which is now Iraq. Nowadays, the technology is developed even for the joint of metal/ceramics and applied to many industrial fields. In the initial times, they used blowpipes and charcoal as the heat source. Now, many kinds of heating methods including laser heating ;are being applied to brazing. And also, a great development in technologies has been made in filler metals, fluxes and so on. Because brazing can be applied to the joint where cannot be welded and mass production of it is possible, it is utilized in special fields of rockets, electronic packages and superconductor. In the nuclear fields, the technique has been applied widely to fuel assemblies, accelerators, laboratory equipments and measuring sensors. III Brazing Process Brazing processes customarily are designated according to the sources or methods of heating like as torch brazing, furnace brazing, induction brazing, resistance brazing, dip brazing, infrared brazing, etc.. Eacli process is selected according to the condition of the base metal, the filler metal, the flux, the brazing temperature and the heating rate. Whatever the process used, the filler metal has a melting point below that of the base mtital, and should have good wettability and spreadability. Fluxes are used to protect the surface of the base metal and to reduce the oxides on it. Therefore, recommended fluxes should be used in their proper temperature ranges and on the base metals for which they are designed. When gas atmosphere or vacuum is used, fluxes are not required. For the metal which forms oxides on the surface at the brazing temperature, gas atmosphere or vacuum should be used. Since surface tension forces can operate only over relatively small distances, capillary penetration will occur only if the joint gap is below a certain maximum value. But, too little clearance may lead in certain cases to incomplete joint filling due to entrapment of flux or air. When electronic packages are jointed, filler metal should be selected considering its electrical conductivity. IV Joining of Ti alloy to Stainless Steel It is well known that fusion welding between Ti alloy and stainless steel is almost impossible because of brittle intermetallic compound in its weld metal. For this reason, various methods have also been tried for joining those dissimilar metals. Until Now, diffusion welding and friction welding have been known as the candidate joining processes with the joint strength of about 350 MPa. Because the joint strength doesn't reach the strength of base metals, the designer should consider this fact and select a method to maintain a proper joint strength. At the System Integrated Modular Advanced Reactor Project, they applied a thread joint to get strength and solved the problem of leakage through brazing the joint area. During brazing process, Ti diffuses into the surface of stainless steel through the melt of filler metal and forms brittle Ti-Fe intermetallic compounds. To reduce the formation of intermetallic compounds, the selection of an optimal brazing condition is required. In addition to it, the brazed joint should be resistant to corrosive environment. Therefore, brazing technology should be developed to get both high joint strength and sound joint. V Brazing of Ti alloy to Stainless Steel The joint part is assembled with male part of Ti alloy and female part of stainless steel. A funnel is welded to the upper end of female part for containing the filler metal. Filler metal will be selected among BAg-19, BVAg-30 and Gapasil-9, after the comparison test of joint strength. To increase the wettability of stainless steel, Ni or Ni-Pd will be coated by plating or other coating methods. The filler metal and stainless steel will be - iv with 40% HNO3 + 2%HF + 58% H2O. Vacuum electric furnace and induction furnace wil be used for heating. Brazing temperature will be about 900 °C. Optimal brazing condition will be set up through comparison of joint strength according to heating rate, temperature and holding time. For the evaluation of process and performance, visual inspection, macroetch test and liquid penetrant inpection will be carried out. - v - PLEASE BE AWARE THAT ALL OF THE MISSING PAGES IN THIS DOCUMENT WERE ORIGINALLY BLANK CONTENTS Chapter 1 Introduction 1 Section 1 Definition of Brazing 1 Section 2 Development of Brazing Technology 3 1 The Ancient Orient 3 2 The Greek, Roman and Aegean Civilization 4 3 Europe, Ancient to Early Middle Age (8-11C) 5 4 Europe, Later Middle Age 5 5 The Age of Manufacture (16-17C) 5 6 Dawning of Modern Science (18C) 6 7 The Industrial Revolution (19C) 7 8 20C 8 Section 3 Procedure of Joining 10 1 Selection of Joining Method 10 2 Planning of Brazing 12 3 Preparation of Filler Metal, Flux And Others 13 4 Brazing 15 5 Test and Inspection 16 Section 4 Application of Brazing to Nuclear Industry 18 1 Fuel 19 2 Heat Exchanger 20 3 Others 21 Chapter 2 Brazing Process 21 Section 1 Brazing Methods 21 1 Torch Brazing 21 2 Furnace Brazing 21 3 Induction Brazing 22 4 Resistance Brazing 22 5 Dip Brazing 22 6 Infrared Brazing 23 7 Others 23 - vii - Section 2 Filler Metals 23 1 Characteristics 23 2 Melting and Fluidity 24 3 Liquidation 25 4 Wetting and Bonding 25 5 Filler Metal Selection 26 6 Kinds of Filler metals 27 Section 3 Fluxes and Atmospheres 30 1 Fluxes 31 2 Atmospheres 33 Section 4 Joint Design 36 1 Types of Joints 36 2 Joint Clearance 37 3 Stress Distribution 40 4 Filler Metal Placement 40 5 Electrical Conductivity 41 6 Dissimilar Metal Combination 41 Section 5 Brazing Procedures 42 1 Precleaning and Surface Preparation 42 2 Fluxing and Stop-off 43 3 Assembly 44 4 Postbraze Treatment 45 Section 6 Inspection 45 1 Nondestructive Testing Methods 46 2 Destructive Testing Methods 48 Chapteter 3 Brazing of Ti Alloy and Stainless Steel 50 Section 1 Brazing of Ti Alloys 50 1 Chemical and Metallurgical Characteristics 50 2 Surface Preparation 50 3 Fluxes and Atmospheres 51 4 Brazing Methods 51 5 Brazing Temperature 52 - vm - 6 Filler Metals 52 7 Mechanical Properties of Joints 54 Section 2 Brazing of Stainless Steels 54 1 Base Metals 54 2 Filler Metals 55 3 Interactions during Brazing 56 4 Joint Design 57 5 Processes and Equipment 57 6 Precleaning 57 7 Fluxes and Atmospheres 57 8 Postbraze Operations 58 Section 3 Brazing of Ti Alloy to Stainless Steel 59 1 Examples of Brazing 59 2 Brazing Conditions 61 3 Interface of Joint 64 4 Intermetallic Compounds 65 5 Residual Stresses 67 6 Patent 68 Section 4 Brazing Method of Dissimilar Metal Joints at SMART 69 1 Base Metals 69 2 Filler Metals 70 3 Joint Design 71 4 Brazing Process 71 5 Test and Inspection 76 Chapter 3 Conclusions 77 Chapter 4 References 79 - ix *!• 4 1 Q iie-llo]^^ jg6j i 4 2 ^ JS^IM^ 7l# £^ 3 1 Jicfl .2.5] <&;E 3 2 ^5]i, S4 ^ al|7l| £-*8 4 3 itfl-^4 ^7] (8-11471)^] 4r^ 5 4 ^4^71(12-15471)^1 -fi-^ 5 5 Manufactured tfl (16-17471) 5 6 ^ufl2f*v^ <$x$71(18471) 6 7 ^^(19471) • 7 8 20 4 7] 8 4 3 ^ JEL3H^ ^^-o] ^ejwj-rf 10 1 ^^ ^^1 ^1^ • 10 2 J±i!fl6l3J 3|3 ^H 12 3 -g-7l-j4|/-S-*f|/7lEj-*1|5. ^ ^ul ^-iL 13 4 w.511 <^1 ^ ^ ^ • 15 5 ^ 9J 34 16 4 4 =g €^>^^r^°fl^^ ti.eflo]^l 21^- 18 1 Sj^I 19 2 IHL^l 20 3 7]T% 20 2 =3- iLefloi^i ^-yg 21 4 1^ «.^°1^ Hov^ 21 1 S*l «.iSllol^ 21 2 Furnace JELS| °1 ^O1 21 3 Induction «.«fl °1 ^ 22 4 Resistance «-3l ^1 ^J 22 5 Dip H31 o] $ 22 6 Infrared a-3M^j 23 7 n 21^1 iieflo]^ HOV^ 23 4 2^ -§-7>^ 23 1 ^ 23 2 -g-§-2J- ft&q 24 3 -§--§-^re| 25 x - 4 ^-ET(wetting)^ ^ ^-(bonding) 25 5 -g-7|-7]] *i^ 26 6 -§-7^5] f^ 27 A 3 ^ -g-4^- -§-^7] 30 1 -Ml 31 2 £-$]7) 33 A4& 3^f -£31 36 1 ^ ^ *8 ^ 36 2 ^ t^- -t 37 3 -g-^5. 40 4 -g-7M uH^] 40 5 ^71 T^ILS- 41 6 *lf^-# ^^- 41 *fl 5 ^ iLefl°l^ ~4.^\ 42 1 <i)]ujAI|ajjif S^^ej 42 2 -g-^1^- stop-off 43 3 ^Sfl 44 4 *-Ao]% ^-x)5] 45 41 6 ^ 34 45 1 «1 4JI1 A] *| 46 2 4^1 A] ^ 48 3 =8- Ti-^-^-^l- At|oie||i7j2l JiefloH 50 41 1 '4. 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