production technology ch30

7/31/2019 Production technology Ch30

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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.

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