Ch11 - Metals

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PART T W O
CHAPTER

Metals

11

These automotive steering and suspension components are made of wrought aluminum to provide reduced weight and improved fuel economy. (Courtesy of TRW.)

(a)

(b)

Figure 11-1 Typical microstructures of (a) white iron (400 × ), eutectic carbide (light constituent) plus pearlite (dark constituent). (b) gray iron (100 × ), graphite flakes in a matrix of 20% free ferrite (light constituent) and 80% pearlite (dark constituent).

(c)

(d)

Figure 11-1 (c) ductile iron (100 × ), graphite nodules (spherulites) encased in envelopes of free ferrite, all in a matrix of pearlite. (d) malleable iron (100 × ), graphite nodules in a matrix of ferrite. (From Metals Handbook, 9th Ed., Vol. 1, American Society for Metals, Metals Park, Ohio, 1978.)

STEELMAKING From raw materials to finished mill products (excluding coated products)

Continuous casting machine Solid steel Blooms

Coal mines

Coal

Coke ovens

Coke

Limestone quarries

Crushing, Raw screening, limestone etc.

Prepared limestone

Molten pig iron Blast furnace (hot metal)

Steelmaking furnaces (open-hearth basic oxygen and electric-arc)

Molten steel

Ladle

Molten steel

Billets

High-grade Iron-bearing materials Iron-ore beneficiating plants Iron-ore mines As-mined ore Scrap Alloying elements and addition agents

Ingot molds Solid steel

Ingots

Slabs

Soaking pits

Primary rolling mills (blooming mills, slabbing mills, billet mills)

Figure 11-2 Schematic summary of the wrought process for producing various steel product shapes. (From W. T. Lankford et al., Eds., The Making, Shaping, and Treating of Steel, 10th Ed., United States Steel, Pittsburgh, Pa., 1985. Copyright 1985 by United States Steel Corporation.)

Structural mills Heating furnaces Rail mills

Structural shapes

Some product forms (not to scale)

Beams
Rails and joint bars

Angles Tees Zees Channels

Piling

Standard rails
Bars

Crane rails

Joint bars

Bar mills

Round Hexagonal Flat Half round Square Octagonal Triangular
Rods Wire Wire mills and wire products

Heating furnaces

Rod mills Seamless pipe and tube mills Skelp mills

Wire
Pipe and tubes

Wire rope Nails

Wire fabric

Skelp

Continuous butt-weld pipe mill Plates

Note: Some tubular products include electric-welded large-diameter pipe made from plates, and electric-resistance-welded (ERW) pipe made from hot-rolled and cold-rolled strip.

Heating furnaces

Plate mills

Hot-rolled sheets and strips Hot-strip mills

Hot-rolled breakdowns in coil forms

Cold Sheets reduction Cold-rolled sheets mills and strip (inc. black plate)

Coils

Figure 11-2 (Continued)

Handle Pattern assembly

Flask

Pouring basin Sprue Lug Wax pattern (1 of 4) (a) Wax sprue pattern

Wax sprue

Mold slurry

(b) Pattern assembly (wax patterns attached to wax sprue)

Wax attaching mold to base plate (c) Pattern assembly in flask after mold slurry has been poured (Precoating of pattern assembly with slurry is required for metals with pouring temperatures above 2000 F.)

Workpiece (1 of 4)

Gate stub (to be removed)

(d) Mold after pouring

(e) Solidified casting after mold has been broken away

(f) One of four castings after removal from sprue

Figure 11-3 Schematic illustration of the casting of a metal alloy form by the “investment molding” process. (From Metals Handbook, 8th ed., Vol. 5: Forging and Casting, American Society for Metals, Metals Park, Ohio, 1970.)

Figure 11-4 Microstructure of a cast alloy (354-T4 aluminum), 50× . The black spots are voids, and gray particles are a siliconrich phase. (From Metals Handbook, 9th ed., Vol. 9: Metallography and Microstructures, American Society for Metals, Metals Park, Ohio, 1985.)

Temperature

0 A

50 Composition (wt % B)

100 B

Figure 11-5 Schematic illustration of the development of a cored structure in the nonequilibrium solidification of a 50:50 alloy in a system exhibiting complete solid solution. (This case can be contrasted with the equilibrium solidification shown in Figure 9–33.) During the rapid cooling associated with casting, the liquidus curve is unaffected given the rapid diffusion in the liquid state, but solid state diffusion may be too slow to maintain uniform grain compositions upon cooling. As a result, the solidus curve is shifted downward as indicated by the dashed line.

Figure 11-6 Example of a tree-like dendritic structure in a 20 Pb–80 Sn alloy. A eutectic microstructure is seen at the base of the dendrites. (From Metals Handbook, 9th ed., Vol. 9: Casting, ASM International, Materials Park, Ohio, 1988.)

Bore section for contact Flux-covered portion Weld metal Ground clamp A Electrode

Insulated handle

Electrode holder To power supply A

To power supply

Workpiece

Electrode covering Cup formed on (flux) electrode tip Slag blanket Gaseous shield Weld puddle

Core wire

60 to 80

Depth of fusion

Heat-affected zone

Arc stream

Weld crater

Section A-A

Figure 11-7 Schematic illustration of the welding process. Specifically, “shielded metal-arc” welding is shown. (From Metals Handbook, 8th ed., Vol. 6: Welding and Brazing, American Society for Metals, Metals Park, Ohio, 1971.)

Fill shoe 4.240 1.000

Inner upper punch Outer upper punch

Loose powder

Die cell 0.300 1.440 diameter 0.960 0.190 (a) Green compact

Core rod (c) Powder leveled in cavity

(b) Die cavity filled with powder Core rod Green compact

Outer lower Intermediate punch Stationary lower punch lower punch (d) Powder forced into upper punch cavity

(e) Compact pressed (e) Compact ejected

Figure 11-8 Schematic illustration of powder metallurgy. The green, or unfired, compact is subsequently heated to a sufficiently high temperature to produce a strong piece by solid-state diffusion between the adjacent powder particles. (From Metals Handbook, 8th Ed., Vol. 4: Forming, American Society for Metals, Metals Park, Ohio, 1969.)

1

2 3

Overbore for cladding 4

Place cans and weld 5 Load powder 6

Remove can Hot outgas Hot isostatically press to compact (using inert gas)

Figure 11-9 Hot isostatic prossing (HIP) of a cladding for a complex-shaped part. (After Advanced Materials and Processes, January 1987.)

Bubble plate

Tool plate

Figure 11-10 Superplastic forming allows deep parts to be formed with a relatively uniform wall thickness. Modest air pressure (up to 10 atmospheres) stretches a heated “bubble” of metal sheet, which then collapses over a metal former pushed up through the plane of the original sheet. (After Superform USA, Inc.)

Chilling Techniques Conductive heat removal: splat cooling, planar flow casting, double roller quenching, injectin chilling, plasma spray deposition. Heat transfer coefficient, h, = 0.1–100 kW/m2K Convective heat removal: various forms of gas and water atomizers, unidirectional and centrifugal atomizers, rotating cup process, plasma spray deposition. h = 0.1– 100 kW/m2K Radiative heat romoval: electrohydrodynamic process, vacuum plasma process. h = 10 W/m2K Directed and concentrated energy techniques: conductive heat removal lasers (pulsed and continuous), electron beam. h→∞ Undercooling Techniques Metal liquid droplets Emulsion Liquid Solid Levitated liquid Heating and levitation coils Liquid Nucleant fluxing Glass P

Droplet emulsion

Eqilibrium mushy zone

Levitation (gas jet or induction current)

P P P

P P

Liquid

Rapid pressure application

P

P

Figure 11-11 Schematic summary of several techniques for the rapid solidification of metal alloys. (From Metal Progress, May 1986.

Tensile strength, MPa

400 300 200

60 50 40 0 50 Nickel, % (a) 30 100

Yield strength, MPa

40 30 20

200 100 0

10 0 50 Nickel, % (b) 0 100

120

Elongation, % in 50 mm (2 in.)

50 40 30 20 10 0 0 50 Nickel, % (d) 100

Hardness, Rf

100 80 60 40

0

50 Nickel, % (c)

100

Figure 11-12 Variation of mechanical properties of copper–nickel alloys with composition. Recall that copper and nickel form a complete solid-solution phase diagram (Figure 9–9). (From L. H. Van Vlack, Elements of Materials Science and Engineering, 4th Ed., Addison-Wesley Publishing Co., Inc., Reading, Mass., 1980.)

Yield strength, 1000 psi

70

Tensile strength, 1000 psi

500

300

Tensile strength, MPa

70 Cu–30 Zn

Hardness, RB

80 70 60 50 85 Cu–15 Zn

500

70 Cu–30 Zn

80 70

Elongation, % in 50 mm (2 in.)

Tensile strength, 1000 psi

90

600

80 60 70 Cu–30 Zn 40 20 85 Cu–15 Zn 0 0 10 20 30 40 Cold work, % (c) 50 60

400

85 Cu–15 Zn

60 50

0

10

20 30 40 Cold work, % (a)

50

60

300

0

10

20 30 40 Cold work, % (b)

50

60

Figure 11-13 Variation of mechanical properties of two brass alloys with degree of cold work. (From L. H. Van Vlack, Elements of Materials Science and Engineering, 4th Ed., Addison-Wesley Publishing Co., Inc., Reading, Mass., 1980.)

(Courtesy of the Casting Emissions Reduction Program [CERP].)

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