kalpakjian schmid manufacturing engineering and technology © 2001 prentice-hall page 30-1 chapter...

Kalpakjian • SchmidManufacturing Engineering and Technology © 2001 Prentice-Hall Page 30-1

CHAPTER 30

Brazing, Soldering, Adhesive-Bonding, and Mechanical-Fastening Processes


Brazing

Figure 30.1 (a) Brazing and (b) braze welding operations.

Kalpakjian • SchmidManufacturing Engineering and Technology © 2001 Prentice-Hall 0-3

Typical Filler Metals for Brazing Various Metals and Alloys

TABLE 30.1

Base metal Filler metalBrazing temperature,

(°C)Aluminum and its alloys Aluminum-silicon 570–620Magnesium alloys Magnesium-aluminum 580–625Copper and its alloys Copper-phosphorus 700–925Ferrous and nonferrous (except aluminum and

magnesium)Silver and copper alloys,

copper- phosphorus620–1150

Iron-, nickel-, and cobalt-base alloys Gold 900–1100Stainless steels, nickel- and cobalt-base alloys Nickel-silver 925–1200


Furnace Brazing

Figure 30.2 An example of furnace brazing: (a) before, (b) after. Note that the filler metal is a shaped wire.


Induction Brazing

Figure 30.3 Schematic illustration of a continuous induction-brazing setup, for increased productivity. Source: ASM International.


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.


Brazing Design

Figure 30.5 Examples of good and poor design for brazing.


Stenciling

Figure 30.6 (a) Screening or stenciling paste onto a printed circuit board: 1. Schematic illustration of the stenciling process; 2. A section of a typical stencil pattern. (continued)

(a)


Wave Soldering

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)


Types of Solders and their Applications

TABLE 30.2Tin-lead General purposeTin-zincLead-silverCadmium-silverZinc-aluminumTin-silverTin-bismuth

AluminumStrength at higher than room temperatureStrength at high temperaturesAluminum; corrosion resistanceElectronicsElectronics


Joint Designs Used 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.


Typical Properties and Characteristics of Chemically Reactive Structural Adhesives

TABLE 30.3

Epoxy PolyurethaneModified

acrylic Cyanoacrylate AnaerobicImpact resistance Poor Excellent Good Poor FairTension-shearstrength, MPa (10

3 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

materialsMost

smooth,nonporous

Mostsmooth,

nonporous

Most nonporousmetals or plastics

Metals, glass,thermosets

Service temperaturerange, °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 mixingrequired Yes Yes No No NoSolvent resistance Excellent Good Good Good ExcellentMoisture resistance Excellent Fair Good Poor GoodGap limitation, mm(in.) None None 0.75 (0.03) 0.25 (0.01) 0.60 (0.025)Odor Mild Mild Strong Moderate MildToxicity Moderate Moderate Moderate Low LowFlammability Low Low High Low LowSource: Advanced Materials & Processes, July 1990, ASM International.


General Properties of Adhesives

TABLE 30.4Type 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 lowpeel 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 onethylene 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 ofpolyacrylate esters and various natural and syntheticrubber

Tapes, labels, stickers.


General Properties of Adhesives (cont.)

TABLE 30.4 (continued)Type Comments ApplicationsPhenolic Thermoset; oven cured, strong bond; High tensile and

low impact strength; brittle, easy to use; cures bysolvent evaporation.

Acoustical padding, brake lining andclutch pads, abrasive grain bonding,honeycomb structures.

Silicone Thermoset; slow curing, flexible; bonds at roomtemperature; high impact and peel strength; rubber like

Gaskets, sealants.

Formaldehyde: -urea -melamine -phenol -resorcinol

Thermoset; strong with wood bonds; urea isinexpensive, available as powder or liquid and requiresa catalyst; melamine is more expensive, cures with heat,bond is waterproof; resorcinol forms waterproof bondat 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 sealenvelopes.


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.


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.


Configurations of Adhesively Bonded Joints

Figure 30.10 Various configurations for adhesively bonded joints: (a) single lap, (b) double lap, (c) scarf, (d) strap.


Rivets

Figure 30.11 Examples of rivets: (a) solid, (b) tubular, (c) split (or bifurcated), (d) compression.


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.


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.


Crimping

Figure 30.15 Two examples of mechanical joining by crimping.


Spring and Snap-In Fasteners

Figure 30.16 Examples of spring and snap-in fasteners used to facilitate assembly.

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