1. Soldering Brazing and Braze Welding

2. 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

3. 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

4. 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.

5. 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

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 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!!!!!!!!!!!!!!!!!

8. Mechanical Properties

9. 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

10. 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

11. 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.

12. 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

13. Soldering and Brazing Methods
Grouped according to method of applying heat:
Torch (TB)
Furnace
Induction
Dip

14. Torch Soldering and Torch Brazing
Advantages of using a torch:
Versatility
Portability
Speed
Disadvantages of using a torch:
Overheating
Skill
Fires

15. 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

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 speed
Disadvantages of the induction method:
Distortion
Lack of temperature control
Incomplete 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 production
Corrosion protection
Distortion minimized
Disadvantages of dip processing:
Steam explosions
Corrosion
Size
Quantity

19. 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

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

21. Soldering Alloys
Usually identified by their major alloying elements Base metal can be joined by more than one solder alloy

22. Tin-lead
Most popular solder Least expensive Most commonly used on electrical connections Never used for water piping

23. 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

24. 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

25. 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

26. 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

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 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

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

30. 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

31. 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

32. 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