Soldering B razing and Braze Welding
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Transcript of Soldering B razing and Braze Welding
SOLDERINGBRAZING
AND BRAZE WELDING
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
INTRODUCTIONSoldering 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
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.
SOLDERING/BRAZING APPLICATIONS
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
BRAZE WELDING
Figure 31-2 Capillary action pulls water into a thin tube.
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!!!!!!!!!!!!!!!!!
MECHANICAL PROPERTIES
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
TENSILE AND SHEAR STRENGTH
DUCTILITYDuctility 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
Fatigue resistance is the ability to be bent repeatedly without exceeding the elastic limit
Elastic LimitPlastic 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.
FATIGUE RESISTANCE
FLUXESFluxes 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
SOLDERING AND BRAZING METHODSGrouped according to method of applying heat:
• Torch (TB)• Furnace• Induction• Dip
TORCH SOLDERING AND TORCH BRAZINGAdvantages of using a torch:
• Versatility• Portability• Speed
Disadvantages of using a torch:
• Overheating• Skill• Fires
FURNACE SOLDERING AND BRAZINGAdvantages 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
Figure 31-20 Furnace brazing permits the rapid joining of parts on a production basis.
INDUCTION SOLDERING AND BRAZINGInduction 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
DIP SOLDERING AND BRAZINGThe 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
FILLER METALSShould be selected by considering as many of the criteria as possible
Welders decide most important criteria
Soldering and brazing metals are alloys
Figure 31-27 Solder being shaped as it cools to its paste range.
SOLDERING ALLOYSUsually identified by their major alloying elements
Base metal can be joined by more than one solder alloy
TIN-LEADMost popular solder
Least expensive
Most commonly used on electrical connections
Never used for water piping
BRAZING ALLOYSThe 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
COPPER-ZINCMost 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
COPPER-ZINC AND COPPER-PHOSPHORUS A5.8Known 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
JOINT DESIGNSpacing 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
Figure 31-28 The joining area should be three times the thickness of the thinnest joint member.
BUILDING UP SURFACES AND FILLING HOLESSurfaces 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
Figure 31-51 When building up a surface, alternate the direction of each layer.
SILVER BRAZINGMelting 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
SOLDERINGPractices 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
SUMMARYBrazing 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