Presentation on theme: "Metal – Designation & Properties R. Lindeke Engr. 2110 Introduction to Materials for Engineers."— Presentation transcript:
Metal – Designation & Properties R. Lindeke Engr Introduction to Materials for Engineers
Adapted from Fig. 9.24,Callister 7e. (Fig adapted from Binary Alloy Phase Diagrams, 2nd ed., Vol. 1, T.B. Massalski (Ed.-in-Chief), ASM International, Materials Park, OH, 1990.) Adapted from Fig. 11.1, Callister 7e. Taxonomy of Metals Metal Alloys Steels FerrousNonferrous Cast Irons CuAlMgTi <1.4wt%C3-4.5wt%C Steels <1.4 wt% C Cast Irons wt% C Fe 3 C cementite L austenite +L+L +Fe 3 C ferrite +Fe 3 C + L+Fe 3 C (Fe) C o, wt% C Eutectic: Eutectoid: °C 1148°C T(°C) microstructure: ferrite, graphite cementite
Alloy Taxonomy – (FerrousFocus!)
Based on data provided in Tables 11.1(b), 11.2(b), 11.3, and 11.4, Callister 7e. Steels Low Alloy High Alloy low carbon <0.25 wt% C Med carbon wt% C high carbon wt% C Usesauto struc. sheet bridges towers press. vessels crank shafts bolts hammers blades pistons gears wear applic. wear applic. drills saws dies high T applic. turbines furnaces V. corros. resistant Example Additionsnone Cr,V Ni, Mo none Cr, Ni Mo none Cr, V, Mo, W Cr, Ni, Mo plainHSLAplain heat treatable plaintool austenitic stainless Name Hardenability TS EL increasing strength, cost, decreasing ductility
-LOW-CARBON STEEL ~<0.25%C Unresponsive to heat treatment Consist of ferrites and pearlite Relatively soft and weak Relatively ductile and tough Weldable and machinable Economical amongst all steel -High Strength Low Alloy Steel -Alloying up to 10% -Increase corrosion properties -Higher strength SAE – Society of Automotive engineers AISI- American Iron and Steel Institute ASTM- American Society for Testing and Materials UNS- Unified Numbering System
MEDIUM CARBON STEELS – wt%C Heat treated by austenizing, quenching, and then tempering to improve their mechanical properties. Most often utilized in tempered condition with tempered martensite microsture. Low hardenability can be heat treated only in very thin sections and with rapid quenching
High Carbon steels: wt%C – hardest, strongest, least ductile Always used in hardened/tempered condition – wear and indentation resistant Tool/die steels contain high Carbon and Chromium, Vanadium, tungsten and molybdenum Carbides
Corrosion resistant Cr of at least 11 wt% Three classes -Martensitic – heat treated (Q&T), Magnetic -Ferritic – not heat treated, Magnetic -Austenitic – heat treatable (PH), Non- magnetic & most corrosion resistant Stainless Steel
CAST IRONS – Carbon > 2.14 wt. %C, usually 3-4.5wt%C Complete Melting 1150 o C-1300 o C Gray, White, Nodular, malleable Silicon > 1%, slower cooling rates during solidification
Types of Cast Iron Gray iron graphite flakes weak & brittle under tension stronger under compression excellent vibrational dampening wear resistant Ductile iron add Mg or Ce graphite in nodules not flakes matrix often pearlite - better ductility Adapted from Fig. 11.3(a) & (b), Callister 7e.
Types of Cast Iron White iron <1wt% Si so harder but brittle more cementite Malleable iron heat treat at ºC graphite in rosettes more ductile Adapted from Fig. 11.3(c) & (d), Callister 7e.
Production of Cast Iron Adapted from Fig.11.5, Callister 7e.
Based on discussion and data provided in Section 11.3, Callister 7e. Nonferrous Alloys NonFerrous Alloys Al Alloys -lower : 2.7g/cm 3 -Cu, Mg, Si, Mn, Zn additions -solid sol. or precip. strengthened (struct. aircraft parts & packaging) Mg Alloys -very low : 1.7g/cm 3 -ignites easily -aircraft, missiles Refractory metals -high melting T -Nb, Mo, W, Ta Noble metals -Ag, Au, Pt -oxid./corr. resistant Ti Alloys -lower : 4.5g/cm 3 vs 7.9 for steel -reactive at high T -space applic. Cu Alloys Brass : Zn is subst. impurity (costume jewelry, coins, corrosion resistant) Bronze: Sn, Al, Si, Ni are subst. impurity (bushings, landing gear) Cu-Be: precip. hardened for strength
Additions to Cu and Al alloy Designations Temper designation scheme for alloys: a letter and possibly a one- to three-digit number: F, H, and O represent, respectively, the as-fabricated, strain hardened, and annealed states. T3 means that the alloy was solution heat treated, cold worked, and then naturally aged (age hardened). T6 means that the alloy was solution heat treated followed by artificial aging.
Metal Fabrication How do we fabricate metals? –Blacksmith - hammer (forged) –Molding - cast Forming Operations –Rough stock formed to final shape Hot working vs. Cold working T high enough for well below T m recrystallization work hardening Larger deformations smaller deformations
FORMING roll A o A d Rolling (Hot or Cold Rolling) (I-beams, rails, sheet & plate) A o A d force die blank force Forging (Hammering; Stamping) (wrenches, crankshafts) often at elev. T Adapted from Fig. 11.8, Callister 7e. Metal Fabrication Methods - I ram billet container force die holder die A o A d extrusion Extrusion (rods, tubing) ductile metals, e.g. Cu, Al (hot) tensile force A o A d die Drawing (rods, wire, tubing) die must be well lubricated & clean CASTINGJOINING
FORMINGCASTINGJOINING Metal Fabrication Methods - II Casting- mold is filled with liquid metal –metal melted in furnace, perhaps alloying elements added. Then cast in a mold –most common, cheapest method –gives good reproduction of shapes –weaker products, internal defects –good option for brittle materials or microstructures that are cooling rate sensitive
plaster die formed around wax prototype Sand Casting (large parts, e.g., auto engine blocks) Investment Casting (low volume, complex shapes e.g., jewelry, turbine blades) Metal Fabrication Methods - II wax Die Casting (high volume, low T alloys) Continuous Casting (simple slab shapes) molten solidified FORMINGCASTINGJOINING Sand molten metal
CASTINGJOINING Metal Fabrication Methods - III Powder Metallurgy (materials w/low ductility) pressure heat point contact at low T densification by diffusion at higher T area contact densify Welding (when one large part is impractical) Heat affected zone: (region in which the microstructure has been changed). Adapted from Fig. 11.9, Callister 7e. (Fig from Iron Castings Handbook, C.F. Walton and T.J. Opar (Ed.), 1981.) piece 1piece 2 fused base metal filler metal (melted) base metal (melted) unaffected heat affected zone FORMING
Annealing: Heat to T anneal, then cool slowly. Based on discussion in Section 11.7, Callister 7e. Thermal Processing of Metals Types of Annealing Process Anneal: Negate effect of cold working by (recovery/ recrystallization) Stress Relief: Reduce stress caused by: -plastic deformation -nonuniform cooling -phase transform. Normalize (steels): Deform steel with large grains, then normalize to make grains small. Full Anneal (steels): Make soft steels for good forming by heating to get, then cool in furnace to get coarse P. Spheroidize (steels): Make very soft steels for good machining. Heat just below T E & hold for h.
a)Annealing b)Quenching Heat Treatments c) c)Tempered Martensite Adapted from Fig , Callister 7e. time (s) T(°C) Austenite (stable) 200 P B TETE 0% 100% 50% A A M + A 0% 50% 90% a) b)
Hardenability--Steels Ability to form martensite Jominy end quench test to measure hardenability. Hardness versus distance from the quenched end. Adapted from Fig , Callister 7e. (Fig adapted from A.G. Guy, Essentials of Materials Science, McGraw-Hill Book Company, New York, 1978.) Adapted from Fig , Callister 7e. 24°C water specimen (heated to phase field) flat ground Rockwell C hardness tests Hardness, HRC Distance from quenched end
The cooling rate varies with position. Adapted from Fig , Callister 7e. (Fig adapted from H. Boyer (Ed.) Atlas of Isothermal Transformation and Cooling Transformation Diagrams, American Society for Metals, 1977, p. 376.) Why Hardness Changes W/Position distance from quenched end (in) Hardness, HRC A M A P T(°C) M(start) Time (s) 0 0% 100% M(finish) Martensite Martensite + Pearlite Fine Pearlite Pearlite
Hardenability vs Alloy Composition Jominy end quench results, C = 0.4 wt% C "Alloy Steels" (4140, 4340, 5140, 8640) --contain Ni, Cr, Mo (0.2 to 2wt%) --these elements shift the "nose". --martensite is easier to form. Adapted from Fig , Callister 7e. (Fig adapted from figure furnished courtesy Republic Steel Corporation.) Cooling rate (°C/s) Hardness, HRC Distance from quenched end (mm) %M%M 4340 T(°C) Time (s) M(start) M(90%) shift from A to B due to alloying B A TETE
Effect of quenching medium: Medium air oil water Severity of Quench low moderate high Hardness low moderate high Effect of geometry: When surface-to-volume ratio increases: --cooling rate increases --hardness increases Position center surface Cooling rate low high Hardness low high Quenching Medium & Geometry
wt% Cu L +L +L (Al) T(°C) composition range needed for precipitation hardening CuAl 2 A Adapted from Fig , Callister 7e. (Fig adapted from J.L. Murray, International Metals Review 30, p.5, 1985.) Precipitation Hardening Particles impede dislocations. Ex: Al-Cu system Procedure: Adapted from Fig , Callister 7e. --Pt B: quench to room temp. --Pt C: reheat to nucleate small crystals within crystals. Other precipitation systems: Cu-Be Cu-Sn Mg-Al Temp. Time --Pt A: solution heat treat (get solid solution) Pt A (soln heat treat) B Pt B C Pt C (precipitate Consider: 17-4 PH St. Steel and Ni-Superalloys too!
Effect of time at Temperature during Precipitation Hardening