Atlas Specialty Metals. Technical Handbook of Stainless Steels

45 Pages·0.566 MB·English

The
Atlas Specialty Metals
Technical Handbook
of
Stainless Steels
Copyright © Atlas Specialty Metals Atlas Specialty Metals
Revised : July 2003 Technical Services Department
Editorial revision May 2008
Technical Assistance Freecall: 1800 818 599
E-mail: [email protected]
www.atlasmetals.com.au
ATLAS SPECIALTY METALS  Technical Handbook of Stainless Steels
FOREWORD
ThisTechnicalHandbookhasbeenproducedasanaidtoallpersonnelofAtlasSpecialtyMetals,theircustomersandtheengineering
community generally. It is intended to be both background reading for technical seminars conducted by Atlas Specialty Metals
TechnicalServicesDepartment,andalsoasasourceofongoingreferencedata.
Anysuggestionsforimprovements,additionsorcorrectionswouldbeverywelcome;theseshouldbedirectedto:
ManagerTechnicalServices,
AtlasSpecialtyMetals
Telephone[phone],[email protected]
CopiesofthishandbookcanbedownloadedfromtheAtlasSpecialtyMetalswebsite.
DetailsofspecificproductsaregivenintheAtlasSpecialtyMetals“SpecialtySteels,ProductReferenceManual”,theseriesofAtlas
GradeDataSheetsandinAtlasTechnotes,aslistedbelow;copiesoftheseare availableonrequestfromanyAtlasSpecialtyMetals
branch,orcanbeviewedordownloadedfromtheAtlasSpecialtyMetalsWebsite.
AtlasSpecialtyMetalsTechnotes
1. QualitativeSortingTestsforStainlessSteels
2. Pitting&CreviceCorrosionofStainlessSteels
3. StainlessSteels-Properties&EquivalentGrades
4. MachiningofStainlessSteels
5. Cleaning,Care&MaintenanceofStainlessSteels
6. LifeCycleCosting
7. GalvanicCorrosion
8. "L","H"andStandardGradesofStainlessSteels
9. StainlessSteelTubefortheFoodIndustry
AtlasSpecialtyMetalsGradeDatasheets
Concisedatasheets,coveringallthecommonstainlesssteels,includechemicalcomposition,mechanicalandphysicalproperties,
fabricationandapplicationofeachgrade. AgaintheseareavailablefromtheAtlasSpecialtyMetalsWebsite.
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OurMaterialsEngineeroffersafreeinformationservice,including:
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LIMITATIONOFLIABILITY
TheinformationcontainedinthisHandbookisnotintendedtobeanexhaustivestatementofallrelevantdataapplicabletospecial
andgeneralsteelproducts.IthasbeendesignedasaguideforcustomersofAtlasSpecialtyMetals.Noresponsibilityisimpliedor
acceptedfororinconjunctionwithqualityorstandardofanyproductoritssuitabilityforanypurposeoruse.
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Allconditions,warranties,obligationsandliabilitiesofanykindwhichareormaybeimpliedorimposedtothecontrarybyany
statute,ruleorregulationorunderthegenerallawandwhetherarisingfromthenegligenceoftheCompany,itsservantsor
otherwiseareherebyexcludedexcepttotheextentthattheCompanymaybepreventedbyanystatute,ruleorregulationfromdoing
so.
PublishedbyAtlasSpecialtyMetalsTechnicalServicesDepartment
Copyright©AtlasSpecialtyMetals
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ATLAS SPECIALTY METALS  Technical Handbook of Stainless Steels
TABLE OF CONTENTS
FOREWORD Degreasing 27
Electropolishing 27
TABLE OF CONTENTS 1 Grinding & Polishing 27
Mechanical Cleaning 27
THE FAMILY OF MATERIALS 2 Blackening 28
Steel Grade Designations 2
SURFACE CONTAMINATION IN FABRICATION 29
GRADES & FAMILIES OF STAINLESS STEELS 4 Contamination by Mild Steel 29
The Families of Stainless Steels 4 Contamination by Chlorides 29
Characteristics of Stainless Steels 5 Contamination by Carbon 29
Standard Classifications of Stainless Steels 5
Comparative Properties of Alloy Families DESIGN CONSIDERATIONS IN FABRICATION 30
8 Grade Selection for Fabrication 30
Design to Avoid Corrosion 30
CORROSION RESISTANCE 9 Specific Design Points 31
General Corrosion 9
Pitting Corrosion 9 GUIDELINES FOR GRADE SELECTION 33
Crevice Corrosion 10
Stress Corrosion Cracking 10
Sulphide Stress Corrosion Cracking 10 APPENDICES
Intergranular Corrosion 11
Galvanic Corrosion 11 1. Steel Grade Summary - Stainless Steels.
Contact Corrosion 12 2. Stainless Steel Grade Comparisons -
specification designations
HIGH TEMPERATURE RESISTANCE 13 3. Physical Properties of Stainless Steels
Scaling Resistance 13 4. Hardness Conversion Table for Stainless
Creep Strength 13 Steel
Structural Stability 14 5. Factors for Unit Conversions
Environmental Factors 14 6. Dimensional Tolerances for Bar
Thermal Expansion 14 7. Further Information
Printed references
CRYOGENIC PROPERTIES 15 Internet sites.
MAGNETIC PROPERTIES 16
Magnetically Soft Stainless Steels 16
MECHANICAL PROPERTIES 17
FABRICATION OF STAINLESS STEELS 19
Forming Operations 19
Machining 20
Welding 20
Soft Soldering 21
Brazing ("Silver Soldering") 22
HEAT TREATMENT 24
Annealing 24
Hardening 24
Stress Relieving 25
Surface Hardening 25
SURFACE FINISHING 26
Passivation 26
Pickling 26
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ATLAS SPECIALTY METALS  Technical Handbook of Stainless Steels
THE FAMILY OF MATERIALS
Materialscanbedividedintometalsandnon-metals;the
historyofcivilisationhaslargelybeencategorisedbythe Type Typical Alloy TypicalUses
abilitytoworkmetals-hence"bronzeage"and"ironage" Grade Content
- but until quite recently most large-scale construction
was still in non-metals, mostly stone or masonry and plain 1020 0.2%C bridges,
wood. carbon building
steels frames,
Todayavastnumberofmaterialscompetefortheirshare machinery
of the market, with more new materials being added shafts
every year. Someparticularlyexcitingdevelopmentsare
lowalloy 4140 0.4%C highlystressed
now occurring in the fields of ceramics, plastics and
steels 1.0%Cr shafts,forged
glassesandcompositesofthesematerials.Thedayofthe
0.2%Mo machine
ceramiccarengineisprobablynotallthatfaroff-already
components
therearesomehightemperaturecomponentsmadefrom
thenewgenerationoftougherceramics,andthemodern
stainless 304 0.05%C corrosion
motor vehicle also offers many examples of the use of
&high 18%Cr resistant
engineeringplastics.Recentdevelopmentsinmetalshave
alloy 9%Ni tanks,bolts,
re-assertedtheircompetitivepositioninautoengineering,
steels springs
inparticulartheuseofaluminiumandmagnesiumalloys.
A major revolution under way at present is the
tool H13 0.4%C toolsfor
replacementofmuchcoppertelecommunicationscabling
steels 1.05%Si castingand
withglassopticalfibre.Formetalstocompetetheymust
5.2%Cr hotforging
be able to demonstrate superior properties to their
1.3%Mo
competitors.
1.0%V
Inasimilarfashioneachofthemetalshastocompetefor
Figure1Typicalgradesineachsteelgroup
its market share, based on demonstrated superiority of
propertiesoreconomics.Itisthereforeworthidentifying
"Micro" additions of alloys are also present in some
thevariousmetalsavailableandindicatingjustwhattheir
grades.
mostimportantfeaturesare.Abasicdifferentiationisto
divide metals into "ferrous" and "non-ferrous", ie those
Atlas Specialty Metals distributes product from all four
iron-basedandalltheothers.
categories (plain carbon, low alloy, stainless and tool
steels).
Amongst the non-ferrous metals the most importantfor
engineering applications are the families of aluminium
SteelGradeDesignations
alloys(withverylowdensities,highelectricalandthermal
conductivity, good formability and good corrosion
Designation systems for metals vary widely. In the past
resistancethesefindapplicationsinaircraft,hightension
everyproducerhadtheirownnameforeachgradethey
electricity conductors, yacht masts etc) and of copper
produced-someexampleswere"Duraflex"(BHP'sname
alloys(withveryhighelectricalandthermalconductivities
for1045)and"Sixix"(AtlasSteelsCanada'snameforM2
andreadyformabilitythesefindtheirprincipalapplications
highspeedsteel).
in electrical wiring). Other important non-ferrous alloys
(an alloyissimplyamixtureof two ormoremetals) are
Thankfullythispracticeisnowreducing,withbenefitsto
thebrassesandbronzes.
all users. In some instances there is justification for the
use of a specific trade name, for instance where a
Thefamilyofferrousmetalsincorporatesavastnumber
manufacturer has made a grade significantly different
of alloys. Thosealloyscontainingaveryhighproportion
from other similar products. This is particularly
ofcarbon(overabout2%)arecalledcastirons.Virtually
appropriateinnewproductareassuchasduplexstainless
all of the remainder are termed steels and these can be
steels, where national standards lag behind commercial
found in either cast form (produced by pouring molten
alloy development, and where grades are still evolving.
metal into a mould of the shape of the finished part) or
Some producers, however, cling to the use of trade
wroughtform(castasingotsorcontinuouscastbilletsor
names for quite standard grades in the hope of
slabs, but then hot rolled or forged to produce bars,
generating sales on the basis of perceived rather than
plates or complex shapes such as rail sections and
actualproductsuperiority.
beams). They can also be formed to finished shape by
sinteringpowderedmetalathightemperature.Steelsare
Apartfromtradedesignationsavarietyofnamingsystems
categorised by their major alloying elements (carbon,
exist, supported by one or other standards body. In
manganese,chromium,nickelandmolybdenum)andby
Australiametalsdesignationstendtomoreorlessfollow
the presence or absence of minor elements (silicon,
thoseoftheUSA-principallytheAmericanIronandSteel
sulphur,phosphorus,nitrogenandtitanium),asshownin
Institute (AISI) and American Society for Testing and
thetableFigure1.
Materials (ASTM). These bodies many years ago
developed three-digit designations for stainless steels,
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ATLAS SPECIALTY METALS  Technical Handbook of Stainless Steels
four-digitdesignationsforcarbonandlowalloysteelsand encounteredsystemistheGermanWerkstoff(Workshop)
one letter plus one or two digit designations for tool Number giving all steels a single digit plus four digit
steels. All three systems have proven inadequate for designation, eg "1.4301" for Grade 304. A second
coping with an on-going series of new alloy identifier associated with each grade is the DIN
developments,soanewUnifiedNumberingSystem(UNS) designation,eg"X5CrNi189"forGrade304.
has been implemented by ASTM and the Society of
AutomotiveEngineers(SAE).TheUNSdesignationshave In addition to these national specifications there are
been allocated to all metals in commercial production, International Standards (ISO) which tend to follow
throughout the world; a single letter indicates the alloy variousEuropeansystems,andanewlydevelopingsetof
family (N = nickel base alloys, S = stainless steels, etc) "Euronorm" (EN) European specifications from the
and five digits denote the grade. This system is now European Union. We are now seeing these Euronorms
incorporated in most ASTM standards, and also some replacing national specifications from Britain, Germany
standardsfromothercountriessuchasAustralia. andothermembernations.
JapanesegradedesignationsarebasedontheAISI/ASTM Numerous cross references between grades are
designationsasfarasstainlesssteelsareconcerned,but published; the most complete is the German
followtheirownsystemforotheralloygroups. "Stahlschlüssel" (Key to Steel). This is particularly good
for German specifications but does cover all significant
BritishStandardshaveusedadesignationsystemforsteel steel specifying countries, including Australia, and lists
gradesbasedupontheAISI/ASTMsystem,butwithextra tradenamesinadditiontonationalspecifications.
digitstospecifyslightvariantsofgrades,eg316S31isa
particularvariantofGrade316stainlesssteel. A summary of these grade equivalents (or near
alternatives)isshowninAppendix2.
Europeannationalstandardsarequitedifferent,andalso
differ among themselves. The most commonly
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ATLAS SPECIALTY METALS  Technical Handbook of Stainless Steels
STAINLESS STEELS - INTRODUCTION TO THE GRADES AND FAMILIES
The group of alloys which today make up the family of
stainless steels had their beginning in 1913 in Sheffield,
England;HarryBrearleywastryinganumberofalloysas
possible gun barrel steels, and noticed that samples cut
fromoneofthesetrialHeatsdidnotrustandwereinfact
difficult to etch. When he investigated this curious
material - it contained about 13% chromium - itleadto
thedevelopmentofthestainlesscutlerysteelsforwhich
Sheffield became famous. Coincidentally development
work was also being carried out in France at about the
sametimewhichculminatedintheproductionofthefirst
austeniticstainlesssteels.
Although the consumption of stainless steels is growing
very rapidly around the world (average of 5.8% per
annum in the Western world over the period 1950 to
2001)averagepercapitaconsumptioninAustraliaisvery
low by comparison with other developed, and many
developingcountries. In1999Australianseachconsumed
about5kg,comparedwithabout8kgperheadinFrance,
13kginJapan,16kginGermany,26kginSingaporeand
38kg in Taiwan. On average each Chinese consumed
about1.3kg,butthisfigureisrapidlyrising.
THEFAMILIESOFSTAINLESSSTEELS
Figure2Familiesofstainlesssteels
Stainless steels are iron based alloys containing a
minimum of about 10.5% chromium; this forms a Additionalelementscanbeaddedsuchasmolybdenum,
protectiveself-healingoxidefilm,whichisthereasonwhy titaniumorcopper,tomodifyorimprovetheirproperties,
this group of steels have their characteristic making them suitable for many critical applications
"stainlessness"orcorrosionresistance.Theabilityofthe involvinghightemperatureaswellascorrosionresistance.
oxidelayertohealitselfmeansthatthesteeliscorrosion This group of steels is also suitable for cryogenic
resistant,nomatterhowmuchofthesurfaceisremoved; applications because the effect of the nickel content in
this is not the case when carbon or low alloy steels are making the steel austenitic avoids the problems of
protectedfromcorrosionbymetalliccoatingssuchaszinc brittlenessatlowtemperatures,whichisacharacteristic
orcadmiumorbyorganiccoatingssuchaspaint. ofothertypesofsteel.
Although all stainless steels depend on the presence of Therelationshipbetweenthevariousausteniticgradesis
chromium, other alloying elements are often added to showninFigures3.
enhancetheirproperties. Thecategorisationofstainless
steelsisunusualamongstmetalsinthatitisbasedupon FerriticStainlessSteels
thenatureoftheirmetallurgicalstructure-thetermsused
denotethearrangementoftheatomswhichmakeupthe Theseareplainchromium(10½to18%)gradessuchas
grains of the steel, and which can be observed when a Grade430and409.Theirmoderatecorrosionresistance
polishedsectionthroughapieceofthematerialisviewed andpoorfabricationpropertiesareimprovedinthehigher
at high magnification through a microscope. Depending alloyedgradessuchas434and444andintheproprietary
upon the exact chemical composition of the steel the grade3CR12.
microstructure may be made up of the stable phases
austenite or ferrite, a "duplex" mix of these two, the The relationship between the various ferritic grades is
phase martensite created when some steels are rapidly showninFigure4.
quenched from a high temperature, or a structure
MartensiticStainlessSteels
hardenedbyprecipitatedmicro-constituents.
Martensiticstainlesssteelsarealsobasedontheaddition
The relationship between the different families is as
of chromium as the major alloying element but with a
shown in Figure 2. A broad brush comparison of the
highercarbonandgenerallylowerchromiumcontent(eg
propertiesofthedifferentfamiliesisgiveninFigure5.
12% in Grades 410 and 416) than the ferritic types;
AusteniticStainlessSteels Grade431hasachromiumcontentofabout16%,butthe
microstructure is still martensite despite this high
Thisgroupcontainatleast16%chromiumand6%nickel chromium level because this grade also contains 2%
(the basic grade 304 is sometimes referred to as 18/8) nickel.
andrangethroughtothehighalloyor"superaustenitics"
suchas904Land6%molybdenumgrades. Therelationshipbetweenthevariousmartensiticgradesis
showninFigure4.
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ATLAS SPECIALTY METALS  Technical Handbook of Stainless Steels
DuplexStainlessSteels CHARACTERISTICSOFSTAINLESSSTEELS
Duplex stainless steels such as 2205 and 2507 (these Thecharacteristicsofthebroadgroupofstainlesssteels
designationsindicatecompositionsof22%chromium,5% can be viewed as compared to the more familiar plain
nickel and 25% chromium, 7% nickel but both grades carbon "mild" steels. As a generalisation the stainless
contain further minor alloying additions) have steelshave:-
microstructures comprising a mixture of austenite and  Higherworkhardeningrate
ferrite.Duplexferritic-austeniticsteelscombinesomeof  Higherductility
the features of each class: they are resistant to stress  Higherstrengthandhardness
corrosion cracking, albeit not quite as resistant as the  Higherhotstrength
ferritic steels; their toughness is superior to that of the  Highercorrosionresistance
ferritic steels but inferiorto thatof theaustenitic steels,  Highercryogenictoughness
andtheirstrength isgreaterthanthatofthe(annealed)  Lowermagneticresponse(austeniticonly)
austeniticsteels,byafactorofabouttwo.Inadditionthe
duplexsteelshavegeneralcorrosionresistancesequalto Thesepropertiesapplyparticularlytotheausteniticfamily
or better than 304 and 316, and in general their pitting andtovaryingdegreestoothergradesandfamilies.
corrosion resistances are superior to 316. They suffer
reducedtoughnessbelowabout-50oCandafterexposure Thesepropertieshaveimplicationsforthelikelyfieldsof
above 300oC, so are only used between these application for stainless steels, but also influence the
temperatures. choiceoffabricationmethodsandequipment.
The relationship between the various duplex grades is STANDARDCLASSIFICATIONS
showninFigures3.
There are many different varieties of stainless steel and
PrecipitationHardeningStainlessSteels the American Iron and Steel Institute (AISI) in the past
designated some as standard compositions, resulting in
These are chromium and nickel containing steels which the commonly used three digit numbering system. This
can develop very high tensile strengths. The most rolehasnowbeentakenoverbytheSAEandASTM,who
commongradeinthisgroupis"17-4PH";alsoknownas allocate 1-letter + 5-digit UNS numbers to new grades.
Grade630,withthecompositionof17%chromium,4% The full range of these standard stainless steels is
nickel, 4% copper and 0.3% niobium. The great contained in the Iron and Steel Society (ISS) "Steel
advantageofthesesteelsisthattheycanbesuppliedin Products Manual for Stainless Steels", and in the
the"solutiontreated"condition;inthisconditionthesteel SAE/ASTM handbook of Unified Numbering System.
isjustmachinable.Followingmachining,formingetc.the Certainothergradesdonothavestandardnumbers,but
steelcanbehardenedbyasingle,fairlylowtemperature are instead covered by other national or international
"ageing"heattreatmentwhichcausesnodistortionofthe specifications,orbyspecificationsforspecialisedproducts
component. such as standards for welding wire. The following
diagrams show most of the grades of stainless steels
distributedbyAtlasSpecialtyMetalsandalsosomeother
important grades, identified by their grade numbers or
commondesignations,illustratingsomeoftheimportant
propertiesofthevariousfamiliesofgrades.
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ATLAS SPECIALTY METALS  Technical Handbook of Stainless Steels
The Families of Austenitic and Duplex Stainless Steels
AusteniticStainlessSteel
304
BasicGrade
Increasinghightemperatureresistance>>>
253MA
310
S30815
Increasingcorrosionresistance>>>>
6Mo
316 317 904L
S31254
316L Weldstabilizedgrades
304L 321 Weldstabilizedgrades
308L 347 Weldingconsumablegrades
303 FreeMachininggrade
302HQ Lowworkhardeningrateforcoldheading
DuplexStainlessSteels
2304 2250 superduplex
S32304 S31803 grades
Figure3ThefamiliesofAusteniticandDuplexStainlessSteels
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ATLAS SPECIALTY METALS  Technical Handbook of Stainless Steels
The Families of Ferritic and Martensitic Stainless Steels
FerriticStainlessSteels
430
basicgrade
444 Highercorrosionresistingweldablegrade.
Utilitygradeswithincreasing
409 3CR12 toughness>>>
430F Freemachininggrade
MartensiticStainlessSteels
410
basicgrade
420 Higherhardnessgrade
431 Highercorrosionresistance
andhighertoughnessgrade
Increasinghardnessafterheattreatment>>>
440A 440B 440C
416 Freemachininggrade
Figure4ThefamiliesofFerriticandMartensiticStainlessSteels
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ATLAS SPECIALTY METALS  Technical Handbook of Stainless Steels
Comparative Properties of the Stainless Steel Alloy Families
Alloy Group Magnetic Work Corrosion Hardenable Ductility High Low Weldability
Response Hardening Resistance Temperature Temperature
(note 1) Rate (note2) Resistance Resistance
(note 3)
Austenitic Generally No Very High High By Cold Very High Very High Very High Very High
Work
Duplex Yes Medium Very High No Medium Low Medium High
Ferritic Yes Medium Medium No Medium High Low Low
Martensitic Yes Medium Medium Quench & Low Low Low Low
Temper
Precipitation Yes Medium Medium Age Medium Low Low High
Hardening Hardening
Notes
1. Attraction of the steel to a magnet. Note some austenitic grades can be attracted to a magnet if cold worked.
2. Varies significantly between grades within each group. e.g. free machining grades have lower corrosion resistances, those grades
higher in molybdenum have higher resistances.
3. Measured by toughness or ductility at sub-zero temperatures. Austenitic grades retain ductility to cryogenic temperatures.
Figure5Comparativeproperties
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