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Kalpakjian SchmidManufacturing Engineering and Technology 2001 Prentice-Hall Page 30-1
CHAPTER 30
Brazing, Soldering, Adhesive-Bonding,and Mechanical-Fastening Processes
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Brazing
Figure 30.1 (a) Brazing and (b) braze welding operations.
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Typical Filler Metals for Brazing VariousMetals and Alloys
TABLE 30.1
Base metal Filler metal
Brazing temperature,
(C)
Aluminum and its alloys Aluminum-silicon 570620
Magnesium alloys Magnesium-aluminum 580625
Copper and its alloys Copper-phosphorus 700925Ferrous and nonferrous (except aluminum and
magnesium)
Silver and copper alloys,
copper- phosphorus
6201150
Iron-, nickel-, and cobalt-base alloys Gold 9001100
Stainless steels, nickel- and cobalt-base alloys Nickel-silver 9251200
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Furnace Brazing
Figure 30.2 An example of furnace brazing: (a) before, (b) after. Note that the filler
metal is a shaped wire.
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Induction Brazing
Figure 30.3 Schematic illustration of
a continuous induction-brazing setup,
for increased productivity. Source:ASM International.
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Joint Designs Used in Brazing
Figure 30.4 Joint designs commonly used in brazing operations. The clearance between
the two parts being brazed is an important factor in joint strength. If the clearance is too
small, the molten braze metal will not fully penetrate the interface. If it is too large, there
will be insufficient capillary action for the molten metal to fill the interface.
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Brazing DesignFigure 30.5 Examples
of good and poor design
for brazing.
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Stenciling
Figure 30.6
(a) Screeningor stenciling
paste onto a
printed circuit
board: 1.
Schematic
illustration ofthe stenciling
process; 2. A
section of a
typical stencil
pattern.(continued)
(a)
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WaveSoldering
Figure 30.6 (continued) (b)Schematic illustration of the
wave soldering process. (c)
SEM image of wave-soldered
joint on surface-mount device.
(b)
(c)
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Types of Solders and their Applications
TABLE 30.2Tin-lead General purposeTin-zincLead-silverCadmium-silverZinc-aluminum
Tin-silverTin-bismuth
AluminumStrength at higher than room temperatureStrength at high temperaturesAluminum; corrosion resistance
ElectronicsElectronics
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Joint DesignsUsed in
Soldering
Figure 30.7 Joint designs commonly used for soldering. Note that
examples (e), (g), (i), and (j) are mechanically joined prior to being
soldered, for improved strength. Source: American Welding Society.
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Typical Properties and Characteristics of
Chemically Reactive Structural AdhesivesTABLE 30.3
Epoxy Polyurethane
Modified
acrylic Cyanoacrylate AnaerobicImpact resistance Poor Excellent Good Poor Fair
Tension-shear
strength, MPa (103
psi) 15.4 (2.2) 15.4 (2.2) 25.9 (3.7) 18.9 (2.7) 17.5 (2.5)
Peel strength, N/m
(lbf/in.) < 525 (3) 14,000 (80) 5250 (30) < 525 (3) 1750 (10)
Substrates bonded Most
materials
Most
smooth,
nonporous
Most
smooth,
nonporous
Most nonporous
metals or plastics
Metals, glass,
thermosets
Service temperature
range, C (F)
55 to 120
(-70 to 250)
160 to 80
(-250 to 175)
70 to 120
(-100 to 250)
55 to 80
(-70 to 175)
55 to 150
(-70 to 300)
Heat cure or mixing
required Yes Yes No No No
Solvent resistance Excellent Good Good Good Excellent
Moisture resistance Excellent Fair Good Poor Good
Gap limitation, mm(in.) None None 0.75 (0.03) 0.25 (0.01) 0.60 (0.025)
Odor Mild Mild Strong Moderate Mild
Toxicity Moderate Moderate Moderate Low Low
Flammability Low Low High Low Low
Source: Advanced Materials & Processes, July 1990, ASM International.
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General Properties of AdhesivesTABLE 30.4
Type Comments ApplicationsAcrylic Thermoplastic; quick setting; tough bond at room
temperature; two component; good solvent chemicaland impact resistance; short work life; odorous;
ventilation required
Fiberglass and steel sandwich bonds,tennis racquets, metal parts,
plastics.
Anaearobic Thermoset; easy to use; slow curing; bonds at roomtemperature; curing occurs in absence of air, will notcure where air contacts adherents; one component; notgood on permeable surfaces
Close fitting machine parts such asshafts and pulleys, nuts and bolts,
bushings and pins.
Epoxy Thermoset; one or two component; tough bond;strongest of engineering adhesives; high tensile and low
peel strengths; resists moisture and high temperature;difficult to use
Metal, ceramic and rigid plastic parts.
Cyanoacrylate Thermoplastic; quick setting; tough bond at roomtemperature; easy to use; colorless.
Crazy glue.
Hot melt Thermoplastic; quick setting; rigid or flexible bonds;
easy to apply; brittle at low temperatures; based on
ethylene vinyl acetate, polyolefins, polyamides andpolyesters
Bonds most materials. Packaging,
book binding, metal can joints.
Pressure sensitive Thermoplastic; variable strength bonds. Primer anchorsadhesive to roll tape backing material, a release agenton the back of web permits unwinding. Made of
polyacrylate esters and various natural and syntheticrubber
Tapes, labels, stickers.
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General Properties of Adhesives (cont.)
TABLE 30.4 (continued)
Type Comments Applications
Phenolic Thermoset; oven cured, strong bond; High tensile and
low impact strength; brittle, easy to use; cures bysolvent evaporation.
Acoustical padding, brake lining and
clutch pads, abrasive grain bonding,honeycomb structures.
Silicone Thermoset; slow curing, flexible; bonds at room
temperature; high impact and peel strength; rubber like
Gaskets, sealants.
Formaldehyde:
-urea
-melamine-phenol
-resorcinol
Thermoset; strong with wood bonds; urea is
inexpensive, available as powder or liquid and requires
a catalyst; melamine is more expensive, cures with heat,bond is waterproof; resorcinol forms waterproof bond
at room temperature. Types can be combined
Wood joints, plywood, bonding.
Urethane Thermoset; bonds at room temperature or oven cure;
good gap filling qualities
Fiberglass body parts, rubber, fabric.
Water-base
-animal-vegetable
-rubbers
Inexpensive, nontoxic, nonflammable. Wood, paper, fabric, leather, dry seal
envelopes.
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Adhesive Peeling Test
Figure 30.8 Characteristic behavior of (a) brittle and (b) tough adhesives in a peeling test. This test is
similar to the peeling of adhesive tape from a solid surface.
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Joint Designs in Adhesive Bonding
Figure 30.9 Various joint designs
in adhesive bonding. Note that
good designs require large contact
areas between the members to be
joined.
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Configurations of Adhesively Bonded Joints
Figure 30.10 Various
configurations for
adhesively bonded
joints: (a) single lap,
(b) double lap, (c)scarf, (d) strap.
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Rivets
Figure 30.11 Examples of rivets: (a) solid, (b) tubular, (c) split (or bifurcated), (d) compression.
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Design Guidelines for Riveting
Figure 30.12 Design guidelines for riveting. (a) Exposed shank is too long; the result is buckling
instead of upsetting. (b) Rivets should be placed sufficiently far from edges to avoid stress
concentrations. (c) Joined sections should allow ample clearance for the riveting tools. (d) Section
curvature should not interfere with the riveting process. Source: J. G. Bralla.
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Metal Stitching and a Double-Lock Seam
Figure 30.13 Various examples of metal stitching.
Figure 30.14 Stages in forming a double-lock seam.
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Crimping
Figure 30.15 Two examples
of mechanical joining by
crimping.
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Spring and Snap-In Fasteners
Figure 30.16 Examples of
spring and snap-in fasteners
used to facilitate assembly.