0. Introduction to Manufacturing
Ferrous Alloys (l.u. 10/1/10)

1. Ferrous Metals and Alloys
Contain IRON as their base metal.
second most abundant element in Earth’s crust (5%).
Relatively inexpensive.
Relative cost per unit Volume (Kalpakjian & Schmid, 2006)
Carbon Steel
Copper
Nickel
Silver
Gold 1
5-6X
35X
600X
60,000X
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2. Three materials used in Steel:
Iron ore - pelletized metal
Coke - for heat & producing carbon monoxide which reduces iron-oxide to iron (removes oxygen)
Limestone - combines with impurities which floats to surface (slag)
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3. Common Terms
Pig Iron- hot metal, molten metal used in making iron and steels Ingot- molten metal to solid form – ready for rolling/forging = Inefficient! Continuous Casting become most popular steel-making technique
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4. Three Types of Steel Ingots:
Killed Steel- steel is fully deoxidized: oxygen is removed and porosity is eliminated (consistent mechanical and chemical properties)
Semi-Killed Steel- partially deoxidized steel: contains some porosity (economical)
Rimmed Steel- low carbon content, porosity (blowholes), lower quality steel (requires inspection)
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5. Refining Removal of impurities (Trace Elements)
Tin
Hot shortness & temper embrittlement (melting)
Oxygen
Reduces toughness
Hydrogen
Causes embrittlement
Nitrogen
Decreases ductility and toughness
Antimony & Arsenic
Cause temper embrittlement
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6. Refining: Used to create higher quality steels
Improves uniformity and consistency in composition
Removing impurities, inclusions, other elements
Adding various elements
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7. Inclusions? Good or bad?
“Free-machining steels are basically carbon steels that have been modified by an addition of sulfur, lead, bismuth, selenium, tellurium, or phosphorous plus sulfur to enhance machinability. Sulfur combines with manganese to form soft manganese sulfide inclusions. These, in turn, serve as chip-breaking discontinuities within the structure. The inclusions also provide a build-in lubricant that prevents formation of a build-up edge on the cutting tool and imparts an improved geometry” (Black & Kohser, 2008, p. 130).
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8. Alloy Steels
(Black & Kohser, 2008, p. 125)
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9. Iron - Carbon Alloys  typically less than 4.5% C
Pure Iron - less than 0.008% C
Steel - up to 2.11% C
Cast Iron - up to 6.67% C*
 typically less than 4.5% C
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10. Carbon Steels Classification
Low-Carbon (mild steel): 0.30% or less
Medium-Carbon: %
High-Carbon: more than 0.60%
Bolts, nuts, sheet, tubes, plate, low strength machine components
Machinery and automotive parts, gears, axles, connecting rods, etc.
Cutting tools, cables, springs, cutlery
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11. Carbon Effects
(Black & Kohser, 2008, p. 124)
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12. Common Designations for Steel:
AISI - The American Iron and Steel Institute
SAE - Society of Automotive Engineers
ASTM - American Society for Testing Materials
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13. Carbon and Alloy Steels
AISI and SAE designate a four-digit numbering system for the classification of steels.
first two digits indicate alloying elements.
last two digits percentage of carbon.
Plain Carbon
.2% Carbon Content
1020
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14. (Black & Kohser, 2008, p. 126)
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15. (Black & Kohser, 2008, p )
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16. Sample Question What makes up a “forty-three forty” 4340 steel?
43 = Mo, Cr, Ni
40 = .40% C
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17. Sample Question
Why is aircraft landing gear made of 4140 or 4340 steel?
Mo = imparts temperature strength, toughness, hardness, dimensional stability
C = imparts hardness, wear resistance, reduces ductility
Ni/Cr = hardness and oxidation resistance
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18. Stainless Steels
Characterized by their corrosion resistance, high strength and ductility, and high chromium content.
In the presence of air (oxygen) they develop a thin and hard adherent film of chromium oxide which protects the metal from corrosion  Passivation
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19. (Black & Kohser, 2008, p. 132)
(Black & Kohser, 2008, p. 134)
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20. Stainless Steels Classifications
Austenitic
( series)
Kitchenware, fittings, welded construction,
Heat/chemical resistant environments
Nonmagnetic
Most ductile of all stainless steels
Susceptible to stress-corrosion cracking
Ferritic
(400 series)
Non-structural applications, automotive trim, kitchenware
High chromium content
Lower ductility
Not heat-treatable
Martensitic
(400 and 500 series)
Cutlery, surgical tools, springs, valves
Magnetic.
Moderate corrosion resistance.
High strength, hardness, fatigue resistance, good ductility
Precipitation Hardening (PH)
Aircraft & aerospace applications
Chromium and nickel (along with copper, aluminum, titanium, or molybdenum.
Good corrosion resistance, ductility, and high strength at elevated temperatures
Duplex Structure
Heat exchangers
Austenite and ferrite.
Higher resistance to corrosion and stress corrosion than 300 series
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21. Tool and Die Steels
Special alloys designed for high strength, impact toughness, and wear resistance at room or elevated temperatures.
For forming and machining of metals
High-Speed Steels
maintain strengths at elevated temperatures.
molybdenum (95% of all HSS) and tungsten series.
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22. Tool and Die Steels (Cont.) – (See text table)
Hot Work Steels
designed for use at elevated temperatures
high toughness, resistance to wear and cracking.
Cold Work Steels
designed for cold working operations.
Shock-resistant
designed for impact toughness.
For dies, punches, chisels
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