Chapter 11 Part 2 Nomenclature and Applications of Metals.ppt

8/9/2019 Chapter 11 Part 2 Nomenclature and Applications of Metals.ppt

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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

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Chapter 11 Part 2 Nomenclature and Applications of Metals.ppt