Soldering Brazing and Braze Welding

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SolderingBrazingand Braze Welding
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Objectives

• Define the terms soldering, brazing, and braze
  welding
• Advantages and disadvantages of liquid-solid
  phase bonding
• Properly clean, assemble, and perform required
  practice joints
• Functions of fluxes in making proper liquid-solid
  phase bonded joints

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Introduction

• Soldering and brazing are classified by the AWS
  as liquid-solid phase bonding processes
• Base material stays solid and filler material is
  liquid
• Hot Gluing
• Phase is the temperature at which bonding takes
  place
• Soldering and brazing differ
• Soldering takes place below 840 Fahrenheit
• FAA says its 800F?????????????????????
• Capillary action is the force that pulls water up
  into a paper towel
• Braze welding does not need capillary action

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Soldering/Brazing Applications

• Steps in Sweat Soldering
• 1) Copper pipe is cleaned
• 2) Flux is applied
• 3) Heat is applied
• 4) Solder is added
• 5) Solder is drawn into fitting via heat
  (capillary Action)
• 6) Pipe is wiped cleaned
• 7) Brazing steps are the same except for Brazing
  filler metal s added instead of solder.

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Braze Welding

• Steps in Braze Welding
• 1) Base material is cleaned
• 2) Flux is applied
• 3) Heat is applied
• 4) Braze is added
• 5) Braze material is added into a joint.
  Capillary Action is not used.
• 6) Post Braze weld is cleaned

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Figure 31-2 Capillary action pulls water into a
thin tube.
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Advantages of Soldering and Brazing

• Some advantages of soldering and brazing
• Low temperature
• Permanently or temporarily joined
• Dissimilar materials can be joined
• Speed of joining
• Less chance of damaging parts
• Slow rate of heating and cooling
• Parts of varying thicknesses can be joined
• Easy realignment
• Disadvantage
• Service Temp!!!!!!!!!!!!!!!!!

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Mechanical Properties
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Tensile and Shear Strength

• Tensile strength of a joint is its ability to
  withstand being pulled apart
• Brazed joints have a tensile strength 4-5 times
  higher than the filler metal itself
• As joint spacing decreases, surface tension
  increases the tensile strength
• Shear strength is ability of a joint to withstand
  a force parallel to the joint
• For a solder or braze joint, the shear strength
  depends upon the amount of overlapping area
• The greater the area overlapped, the greater the
  strength

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Ductility

• Ductility is the ability of a metal to
  plastically deform without breaking or
  fracturing, with the cohesion between the
  molecules remaining sufficient to hold them
  together to bend without failing.
• Most soldering and brazing alloys are ductile
  metals

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Fatigue Resistance

• Fatigue resistance is the ability to be bent
  repeatedly without exceeding the elastic limit
• Elastic Limit
• Plastic Limit
• For most soldering or brazing joints, fatigue
  resistance is low
• Fatigue failures may occur as a result of
  vibration and/or cycles of load.

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Fluxes

• Fluxes used in soldering and brazing have three
  major functions
• Remove oxides that result from heating parts
• Promote wetting
• Aid in capillary action (if soldering or brazing)
• Flux must be thin, when heated to its reacting
  temperature
• Fluxes are available in many forms
• Paste
• Liquid
• Powder

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Soldering and Brazing Methods

• Grouped according to method of applying heat
• Torch (TB)
• Furnace
• Induction
• Dip

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Torch Soldering and Torch Brazing

• Advantages of using a torch
• Versatility
• Portability
• Speed
• Disadvantages of using a torch
• Overheating
• Skill
• Fires

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Furnace Soldering and Brazing

• Advantages of using a furnace
• Furnace brazing is a semi-automatic process
• Temperature control
• Controlled atmosphere (Common atmospheres used
  include inert, reducing or vacuum atmospheres
  all of which protect the part from oxidation)
• Uniform heating
• Mass production
• Disadvantages of using a furnace
• Size
• Heat damage

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Figure 31-20 Furnace brazing permits the rapid
joining of parts on a production basis.
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Induction Soldering and Brazing

• Induction heating is the process of heating an
  electrically conducting object (usually a metal)
  by electromagnetic induction, where eddy currents
  (also called Foucault currents) are generated
  within the metal and resistance leads to Joule
  heating of the metal.
• Advantage of the induction method is speed
• Disadvantages of the induction method
• Distortion
• Lack of temperature control
• Incomplete penetration

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Dip Soldering and Brazing

• The parts to be joined are fixtured and the
  brazing compound applied to the mating surfaces,
  typically in slurry form. Then the assemblies are
  dipped into a bath of molten salt (typically
  NaCl, KCl and other compounds) which functions
  both as heat transfer medium and flux.
• Advantages of dip processing
• Mass production
• Corrosion protection
• Distortion minimized
• Disadvantages of dip processing
• Steam explosions
• Corrosion
• Size
• Quantity

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Filler Metals

• Should be selected by considering as many of the
  criteria as possible
• Welders decide most important criteria
• Soldering and brazing metals are alloys

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Figure 31-27 Solder being shaped as it cools to
its paste range.
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Soldering Alloys

• Usually identified by their major alloying
  elements
• Base metal can be joined by more than one solder
  alloy

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Tin-lead

• Most popular solder
• Least expensive
• Most commonly used on electrical connections
• Never used for water piping

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Brazing Alloys

• The AWS 's classification system for brazing
  alloys uses the letter B
• Next series of letters indicate the atomic symbol
  of metals used
• Not all available brazing alloys have an AWS
  classification
• Some special alloys are known by their trade names

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Copper-zinc

• Most popular brazing alloys
• Available as regular and low-fuming alloys
• Tendency to burn out when overheated
• If breathed in, it can cause zinc poisoning
• If you think you have zinc poisoning, get medical
  treatment immediately

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Copper-zinc and Copper-phosphorus A5.8

• Known as brazing rods
• Referred to as phos-copper
• Vast differences among the five classifications
• Five classifications of copper-zinc filler rods
• BRCuZn
• BRCuZn-A
• BRCuZn-B
• BRCuZn-C
• BRCuZn-D
• If overheated will cause zinc fumes

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Joint Design

• Spacing between parts being joined greatly
  affects tensile strength
• Strongest joints are obtained when parts use lap
  or scarf joints
• Some joints can be designed so that the flux and
  filler metal may be preplaced
• Joint preparation is very important

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Figure 31-28 The joining area should be three
times the thickness of the thinnest joint member.
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Building up Surfaces and Filling Holes

• Surfaces on worn parts are built up again with
  braze metal
• Ideal for parts that receive limited abrasive
  wear
• Braze buildup has no hard spots
• Good for flat and round stock
• Holes in light-gauge metal can be filled using
  braze metal

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Figure 31-51 When building up a surface,
alternate the direction of each layer.
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Silver Brazing

• Melting temperature for alloys is around 1400
  Fahrenheit
• Copper pipe glows a dull red
• Best types of flame to use
• Air acetylene
• Air MAPP
• Air propane
• Any air fuel-gas mixture

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Soldering

• Practices use tin-lead or tin-antimony solders
• Both have low melting temperature
• Best type of flame
• Air acetylene
• Air MAPP
• Air propane
• Any fuel-gas mixture

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Summary

• Brazing and soldering have many advantages
• Very versatile
• Ability to join many different materials with a
  limited variety of fluxes and filler metals
• Soldering can be permanent or temporary
• Be creative in the way you apply these processes