chapter 11 part 2 nomenclature and applications of metals.ppt
TRANSCRIPT
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Chapter 11
Part 2
Metals and Alloys
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Nomenclature of Steels
Historically, many methods for identifying alloysby their composition ha e been de eloped
!he commonly used schemes in this country arethose de eloped by A"S"#SA$ and AS!M
% !he American "ron and Steel "nstitute &A"S"' and theSociety of Automoti e $ngineers &SA$'
% American Society for !esting and Materials &AS!M'
$uropean countries, (apan, )ussia etc*de eloped their o+n schemes
"n order to a oid confusion, the ni ersal# nifiedNumbering System & NS' +as de eloped
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A"S"#SA$ Classification of Steels
A four digit description
% -irst t+o digits identify the alloy type % .ast t+o digits indicate the carbon content % -or e/ample
A"S"#SA$ 1020 steel is a plain carbon steel &10//' +hich has 0*20+t* carbon &//20'
Plain carbon steel &10//' are ine/pensi e, but ha e se eral limitationsincluding % Poor hardenability because the critical cooling rate is ery high % )apid cooling leads to distortion and crac3ing % Poor corrosion resistance % Poor impact resistance at lo+ temperature
Alloy steels +ere de eloped to address these issues % Alloying changes the eutectoid composition, the eutectoid carbon
content and the critical cooling rate % !hese alloys are more e/pensi e, but a better combination of properties
is obtained
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A"S"#SA$ Classification of Steels
NS uses the A"S"#SA$ designation +ith a letter before and a 405 after the 6 digits!he letter identifies the alloy group
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7 er ie+ of NS
Axxxxx 8 Aluminum Alloys Cxxxxx 8 Copper Alloys, including 9rass and 9ron:e Fxxxxx 8 "ron, including ;uctile "rons and Cast "rons Gxxxxx 8 Carbon and Alloy Steels Hxxxxx 8 Steels 8 A"S" H Steels Jxxxxx 8 Steels 8 Cast Kxxxxx 8 Steels, including Maraging, Stainless, HS.A, "ron89ase Superalloys L5xxxx 8 .ead Alloys, including 9abbit Alloys and Solders
M1xxxx 8 Magnesium Alloys Nxxxxx 8 Nic3el Alloys Rxxxxx 8 )efractory Alloys
% R03xxx 8 Molybdenum Alloys % R04xxx 8 Niobium &Columbium' Alloys % R05xxx 8 !antalum Alloys % R3xxxx 8 Cobalt Alloys
% R5xxxx 8 !itanium Alloys % R6xxxx 8
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A"S"#SA$, AS!M, NS
AS!M de eloped a parallel classification, starting +itha letter A follo+ed by numbers and other descriptors
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!ool Steels
A"S" designation has a letter and a number*!he letter describes the application
% M &high speed machine tool', H &hot +or3ing'!he letter describes the heat treatment
% A &air hardening', 7 &oil =uenching', > &+ater =uenching'
NS designation % all tool steels start +ith a 4!5
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Stainless Steels
$/cellent corrosion resistance Contain 12 to ?0 Chromium
% Cr o/idi:es easily and forms a thin continuous layer of o/ide thatpre ents further o/idation of the metal
Cr is a ferrite stabili:er
Austenite is restricted to a smallregion of the phase diagram
Ferritic Stainless Steels areessentially -e8Cr Alloys -errite phase &bcc structure'"ne/pensi e, high strength
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Stainless Steels
Austenitic Stainless Steels % Nic3el is an austenite stabili:er* !he addition of both
Cr and Ni results in the austenite & , fcc' phase beingretained to room temperature
% !he austenite phase is ery formable &fcc structure'
% Ni ma3es these alloys e/pensi e Martensitic Stainless Steels
% Ha e both Cr and C % !here is more Cr than in ferritic SS since Cr tends to
form Cr 2? C @, +hich remo es a ailable Cr for corrosionprotection
% Can be heat treated to high strength
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NS letter S indicates stainless steel
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Cast "ron
-e8C alloys +ith 286 C
18? Si is added to impro ecastability Phase diagram sho+s
graphite rather than -e ? Csince C may be present in theform of both graphite and
cementite !emperatures andcompositions are differentfrom the -e8-e ? C diagram
-eatures % .o+ melting temperature
&11 ?BC to 1600BC' % .o+ shrin3age % $asily machinable % .o+ impact resistance % .o+ ductility
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Cast "rons
!ypes % ray cast iron
Carbon in the form of graphite fla3es 2* % 6 C and 1 % ? Si &Promotes formation of graphite'
% Nodular cast iron Carbon in the form of spherical graphite nodules
?86 C and 1*D % 2*D Si E Mg or Ce, and lo+ impurities
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Cast "rons
!ypes % >hite cast iron
Carbon in the form of cementite
% Malleable cast iron Carbon in the form of irregular graphite nodules
7btained by heat treating +hite cast iron
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Cast "rons
!he microstructure ofthe iron rich matri/ canbe modified by heattreatment % Pearlite
% -errite ray cast iron
% -racture surfaceappears gray becauseof graphite fla3es
>hite cast iron % -racture surface
appears +hite &shiny'
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Cast "rons
>hite cast iron hasno other use that tobe starting materialfor malleable cast iron
"n the other forms ofcast iron, carbon is inthe form of graphite % !he graphite fla3es
absorb ibration % .ubricate during
machining % -racture initiation sites
Cast iron Steel
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AS!M % specification by strength and ductilityNS % .etter - indicates cast iron
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Copper Alloys
eneral properties of Copper
% ood electrical and thermal conduction % ease of fabrication % corrosion resistance % medium strength
NS Classification
% C follo+ed by digits % Numbers C10100 to CFGG00 designate +rought alloys % Numbers CD0000 to CGGG00 designate casting alloys
$lectrolytic tough pitch copper &C11000' is the least e/pensi e andused in production of +ire, rod, and strip* % Has 0*06 o/ygen % Cu 2 7 E H 2 2Cu E H 2 7 at 600BC causing blisters
Copper cast in controlled reducing atmosphere to form 7-HCcopper &C10200'
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NS Classification of Copper Alloys
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Copper Alloys
Cu8
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Aluminum Alloys
rouped into >rought and Cast Alloys >rought Alloys % mechanically +or3ed to final shape
% 6 digits based on ma or alloying elements* % -irst digit ma or group of alloying elements % Second digit impurity limits % .ast t+o digits identify specific alloy
Cast Alloys % cast to final shape % 6 digits +ith a period bet+een the third and fourth digit % Compositions optimi:ed for casting and mechanical properties
Alloy designations sometimes preceded +ith AI or AA Also classified into heat8treatable and non8heat treatable
alloys % Heat treatable alloys are strengthened by precipitation hardening % Non8heat treatable alloys are used in the as8cast condition or
can be +or3 hardened
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Classification of +rought aluminum alloys
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Non8heat treatable aluminum alloys
1/// alloys GG Al E -e E Si E 0*12 Cu % !ensile strength J G0 MPa % sed for sheet metals
?/// alloys Mn principle alloying element
% AA?00? J AA1100 E 1*2 Mn % !ensile strength J 110 MPa % eneral purpose alloy
/// alloys Al E up to Mg % AA 0 2 J Al E 2* Mg E 0*2 Cr % !ensile strength J 1G? MPa % sed in bus, truc3 and marine sheet metals*
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Heat treatable aluminum alloys
2/// alloys Al E Cu E Mg % AA2026 J Al E 6* Cu E 1* Mg E0*@ Mn % Strength J 662 MPa % sed for aircraft structures*
@/// alloys Al E Mg E Si % AA@0@1 J Al E 1 Mg E 0*@ Si E 0*? Cu E 0*2 Cr % Strength J 2G0 MPa % sed for general purpose structures*
F/// alloys Al E
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Cast Aluminum Alloys
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!emper ;esignations
H designations
% H1/ % Strain hardened % H2/ % Strain hardened and partially annealed % H?/ % Strain hardened follo+ed by a lo+ temperature thermal treatment
to impro e ductility "n the abo e 4/5 indicates amount of strain hardening &/JD means
!S that is achie ed by F cold +or3K /J0 means fully annealedK/J6 means !S half8+ay bet+een /J0 and /JD'
! designations % !1 % cooled from shaping temperature and naturally aged % !2 % cooled from shaping temperature, cold +or3ed and naturally aged % !? % Solution treated, cold +or3ed and naturally aged % !6 % Solution treated and naturally aged %
! % Cooled from shaping temperature and artificially aged % !@ % Solution treated and artificially aged % !F % Solution treated and o eraged % impro es resistance to stress
corrosion crac3ing % !D % Solution treated, cold +or3ed and artificially aged
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NS % AG used to identify +rought aluminum alloys
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NS % A0 used to identify cast aluminum alloys
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Magnesium Alloys
;ensity L1*F6 g#cm ? , less than that of Al &2*F g#cm ? '
More e/pensi e than aluminum because % HCP structure ma3es Mg difficult to cold +or3 % hot +or3 only % Molten Mg can burn in air % difficult to cast
Classification % !+o letters follo+ed by t+o numbers
A % Aluminum
%
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NS % .etter M indicates magnesium alloys
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!itanium Alloys
!itanium is the 6 th most common metal on the earthOs crust* % Chemically ery reacti e and is difficult to e/tract % .i3e Cr and Al, it forms a protecti e o/ide layer, ma3ing it corrosion resistant % ;ensity L6* g#cm ? % lo+er density than -e or Ni, higher use temperature than Al % $/hibits polymorphism % At lo+ temperatures Alpha % hcp % At high temperatures 9eta % bcc
Alloying elements are either % Alpha stabili:ers % Al, 7 ma3e the alpha phase stable at higher temperatures % 9eta stabili:ers % , Mo, -e and Cr cause a eutectoid reaction in the alloys and
ma3e the beta phase to be stable at lo+er temperatures, e en do+n to )! Alloys classified as , or + depending on the composition Ne+ alloys are still being de eloped, and NS designations ha e not been
standardi:ed for all alloys
Properties depend upon composition and thermomechanical processing thatcan change the microstructure of the alloys Processing of titanium alloys is ery difficult because of the structure $/pensi e aerospace alloy that is no+ seeing more commercial applications
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NS % .etter ) indicates refractory metal &high melting point'
) //// % !itanium alloys
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Materials Selection
Mechanical properties %Stiffness, strength, ductility, fatigue, creep
Manufacturability %Machining, Mechanical +or3ing, Casting,
>elding
Physical properties %;ensity, Melting point, !hermal conducti ity
Cost % A ailability, ease of processing