AWS Brazing Handbook Errata Reprint 2011 · 256 CHAPTER 13—INDUCTION BRAZING AWS BRAZING HANDBOOK...
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INDUCTION BRAZING Prepared by: S. Skewes Induction Atmospheres K. Krause Pillar Industries Contents Introduction 256 Process Fundamentals 256 Equipment 259 Materials and Consumables 265 Process Considerations 267 Applications 271 Safe Practices 271 Bibliography 274 Suggested Reading List 274 CHAPTER 13 Photograph courtesy of Induction Atmospheres AWS BRAZING HANDBOOK 255
Transcript of AWS Brazing Handbook Errata Reprint 2011 · 256 CHAPTER 13—INDUCTION BRAZING AWS BRAZING HANDBOOK...
INDUCTIONBRAZING
Prepared by:
S. SkewesInduction Atmospheres
K. KrausePillar Industries
Contents
Introduction 256
ProcessFundamentals 256
Equipment 259
Materials andConsumables 265
ProcessConsiderations 267
Applications 271
Safe Practices 271
Bibliography 274
SuggestedReading List 274
CHAPTER 13
Photograph courtesy of Induction Atmospheres
AWS BRAZING HANDBOOK 255
INTRODUCTION
256 CHAPTER 13—INDUCTION BRAZING AWS BRAZING HANDBOOK
Many designs specify that metal components bejoined by induction brazing to fabricate weldments.In the induction brazing process, the components atthe joint area, including the surfaces of the compo-nents to be joined and the brazing filler metal, areheated selectively to the brazing temperature. This isaccomplished by means of induced electrical energyin the joint using an induction coil or inductor. Byheating only the joint area, significant energy savingsresult. Induction brazing can be implemented inmanual, mechanized, semiautomated, and automatedproduction modes.
Induction brazing is particularly well suited tomass production applications that require selectivejoint heating. In automated induction brazing opera-tions involving large production runs, the processingtime amounts to a matter of seconds. This brazingprocess finds extensive use in the aerospace, auto-motive, electronic, and electrical industries, amongothers, for the fabrication of industrial and consumerproducts.
This chapter describes the induction brazing pro-cess, its fundamentals, required equipment, materialsand consumables, process considerations, applica-tions, uses, and safety considerations.
PROCESS FUNDAMENTALS
The heat required for induction brazing is gener-ated primarily as result of resistance to the flow ofthe induced current (referred to as I2R losses), asshown in Figure 13.1. Resistance occurs in each sub-assembly, provided it is an electrical conductor, whenit is placed in an electromagnetic field established byrapid alternating-current (ac) flow in the inductioncoil. The response to the electromagnetic fielddepends on various factors, including the frequencyof the current, the type of materials being heated,
the shape of the subassemblies, and the design ofthe coil.
Magnetic materials with high electrical resistivity(e.g., steel) are heated more efficiently than nonmag-netic materials with a low electrical resistance (e.g.,copper and brass). This is due to the magnetic dipolehysteris heating that occurs below the Curie point ofthe material. This heating is directly proportional tothe frequency of the induction power supply. Thehigher the frequency is, the faster the heating ofmagnetic materials.
The induced current is greatest at the surface ofthe assembly, decreasing exponentially toward theinterior, as shown in Figure 13.2. Therefore, surfaceheat is possible with a high power density (kilowatts
INDUCTION BRAZINGCHAPTER 13
KeyIC = Coil current, amps (A)II = Induced current in the assembly, A
Figure 13.1—Induced Current, IIProduced by an Electromagnetic Field
in a Conducting Assembly
IcIc
II II
