2 ObjectivesDefine 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
3 IntroductionSoldering and brazing are classified by the AWS as liquid-solid phase bonding processesBase material stays solid and filler material is liquidHot GluingPhase is the temperature at which bonding takes placeSoldering and brazing differSoldering takes place below 840° FahrenheitFAA says its 800F?????????????????????Capillary action is the force that pulls water up into a paper towelBraze welding does not need capillary action
4 Soldering/Brazing Applications Steps in Sweat Soldering1) Copper pipe is cleaned2) Flux is applied3) Heat is applied4) Solder is added5) Solder is drawn into fitting via heat (capillary Action)6) Pipe is wiped cleaned7) Brazing steps are the same except for Brazing filler metal s added instead of solder.
5 Braze Welding Steps in Braze Welding 1) Base material is cleaned 2) Flux is applied3) Heat is applied4) Braze is added5) Braze material is added into a joint. Capillary Action is not used.6) Post Braze weld is cleaned
6 Figure 31-2 Capillary action pulls water into a thin tube.
7 Advantages of Soldering and Brazing Some advantages of soldering and brazing:Low temperaturePermanently or temporarily joinedDissimilar materials can be joinedSpeed of joiningLess chance of damaging partsSlow rate of heating and coolingParts of varying thicknesses can be joinedEasy realignmentDisadvantageService Temp!!!!!!!!!!!!!!!!!
9 Tensile and Shear Strength Tensile strength of a joint is its ability to withstand being pulled apartBrazed joints have a tensile strength 4-5 times higher than the filler metal itselfAs joint spacing decreases, surface tension increases the tensile strengthShear strength is ability of a joint to withstand a force parallel to the jointFor a solder or braze joint, the shear strength depends upon the amount of overlapping areaThe greater the area overlapped, the greater the strength
10 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
11 Fatigue ResistanceFatigue resistance is the ability to be bent repeatedly without exceeding the elastic limitElastic LimitPlastic LimitFor most soldering or brazing joints, fatigue resistance is lowFatigue failures may occur as a result of vibration and/or cycles of load.
12 FluxesFluxes used in soldering and brazing have three major functions:Remove oxides that result from heating partsPromote wettingAid in capillary action (if soldering or brazing)Flux must be thin, when heated to its reacting temperatureFluxes are available in many formsPasteLiquidPowder
13 Soldering and Brazing Methods Grouped according to method of applying heat:Torch (TB)FurnaceInductionDip
14 Torch Soldering and Torch Brazing Advantages of using a torch:VersatilityPortabilitySpeedDisadvantages of using a torch:OverheatingSkillFires
15 Furnace Soldering and Brazing Advantages of using a furnace:Furnace brazing is a semi-automatic processTemperature controlControlled atmosphere (Common atmospheres used include: inert, reducing or vacuum atmospheres all of which protect the part from oxidation)Uniform heatingMass productionDisadvantages of using a furnace:SizeHeat damage
16 Figure 31-20 Furnace brazing permits the rapid joining of parts on a production basis.
17 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 speedDisadvantages of the induction method:DistortionLack of temperature controlIncomplete penetration
18 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 productionCorrosion protectionDistortion minimizedDisadvantages of dip processing:Steam explosionsCorrosionSizeQuantity
19 Filler MetalsShould be selected by considering as many of the criteria as possible Welders decide most important criteria Soldering and brazing metals are alloys
20 Figure 31-27 Solder being shaped as it cools to its paste range.
21 Soldering AlloysUsually identified by their major alloying elements Base metal can be joined by more than one solder alloy
22 Tin-leadMost popular solder Least expensive Most commonly used on electrical connections Never used for water piping
23 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
24 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
25 Copper-zinc and Copper-phosphorus A5.8 Known as brazing rodsReferred to as phos-copperVast differences among the five classificationsFive classifications of copper-zinc filler rods:BRCuZnBRCuZn-ABRCuZn-BBRCuZn-CBRCuZn-DIf overheated will cause zinc fumes
26 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
27 Figure 31-28 The joining area should be three times the thickness of the thinnest joint member.
28 Building up Surfaces and Filling Holes Surfaces on worn parts are built up again with braze metalIdeal for parts that receive limited abrasive wearBraze buildup has no hard spotsGood for flat and round stockHoles in light-gauge metal can be filled using braze metal
29 Figure 31-51 When building up a surface, alternate the direction of each layer.
30 Silver BrazingMelting temperature for alloys is around 1400° FahrenheitCopper pipe glows a dull redBest types of flame to use:Air acetyleneAir MAPPAir propaneAny air fuel-gas mixture
31 Soldering Practices use tin-lead or tin-antimony solders Both have low melting temperatureBest type of flame:Air acetyleneAir MAPPAir propaneAny fuel-gas mixture
32 Summary Brazing and soldering have many advantages Very versatile Ability to join many different materials with a limited variety of fluxes and filler metalsSoldering can be permanent or temporaryBe creative in the way you apply these processes