IS 15839: Determination of Ferrite Content in Austenitic Stainless Steel Castings

2009·5.5 MB·English

by  Bureau of Indian Standards

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IS 15839 (2009): Determination of Ferrite Content in
Austenitic Stainless Steel Castings [MTD 22: Metallography
and Heat Treatment]
“!ान $ एक न’ भारत का +नम-ण”
Satyanarayan Gangaram Pitroda
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!S 15839 : 2009
(SO 13520 : 2002
~~~~ .~~
qS{!~20 etl ~ ~G
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Indian Standard
DETERM~NAT!ON OF FERR~TE CONTENT ~N
AUSTEN~T~C STA~NlESS STEEL CAST~NGS
res
77.140.80
© BIS 2009

BUR IE A U 0 F ~ N D tA N· STA N ID A R D S
MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG
NEWDELHI110002
" , .
February 2009 Price Group5
is
1"5839: 2009
ISO 13520: 2002
Indian Standard
DETERM~NAT~ON OF FERRtTE CONTENT IN
AUSTEN~T~C STA~NLESS STEEl·CASTINGS
- 1 Scope
Procedures are covered for estimating ferrite content in certain grades of austenitic iron-chromlum-nickel alloy
castings that have compositions balanced to create the formation of ferrite as a second phase in amounts
controlled within specified limits. Methods are described for estimating ferrite content by chemical, magnetic and
metallographicmeans. ,---._
2 Normative references
_The following normativedocumentscontain provisions which, through reference in thistext,constituteprovisionsof
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based onthis International Standard areencouragedto
investigate the possibility of applying the most recent editions of the normative documents indicated below, For
undated references, the latest edition of the normative document referred to applies. Members.of ISO and IEC
maintain registers ofcurrently valid lnternationalStandards.
4990:~1i.
ISO Steel castings- Generaltec1]nicaldeliveryrequirements
ISO9042:1988, Steels - Manual point counting method for statistically estimating the volume fraction of a
constituentwithapointgrid
ASTM A799,StandardPractice forSteelCastings, Stainless;InstrumentCalibration, forEstimatingFerriteConte'.!t
BNIF345, Evaluation ite la teneurenferrite danslesaciersinoxydables moulesaustenitiques
3 Terms and dlefinntnons
Forthepurposes of,thisInternationalStandard, .thefolloWing terms anddefinitionsapply.
3.1
ferrite .
ferromagnetic,.body-centered cubic microstructural constituent of variable chemical composltion iniron-chromium
nickel alloys .
NOTE Ferriteincludesbothdeltaandalphaspecies.
3.2
ferrite content • ..
proportion oftotalvolume ofanlron-chrornlum-nlckel alloypresent astheferrite phase
of
1) Tobepublished.(Revision ISO4990:1986)
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IS 15839: 2009
ISO 13520: 2002
3.3
ferrite percentage
ferritecontentexpressed as avolume percent
4 Significance effects offerrite content
The tensile and impact properties, the weldability, and the corrosion resistance of iron-chromium-nickel alloy
castings may be influenced beneficially or detrimentally by the ratio of the amount of ferrite to the amount of
austenite inthe microstructure. Theferrite content may belimited bypurchase order requirements or bythedesign
constructioncodes governing the equipment inwhich castings will beused. The quantity offerrite inthe structureis
fundamentally a function of the chemical composition of thealloy and its thermal history. Because of segregation.
the chemical composition and, therefore, the ferrite content, may differ from point to point on a casting.
Determination of the ferrite content by any ofthe procedures described In clause 5is subject tovarying degrees of
imprecision which shall be recognized in settingreahsticlimits on the range offerrite content specified. Sources of
erroraredescribed In 5.1to 5.3.
5 Methods of determination offerrite content
5.1 Chemical composition method
Deviatrons from the actual quantity of each element present in an alloy because of chemical analysts variance,
although possibly minor in each case. can result In substantial difference in the ratio of total fernte-promoting to
total austenite-promoting elements Therefore the precision of the ferrite content estimated from chemical
compositiondepends on the accuracy ofthechemical analysis procedure.
The estimation of ferrite percent by means of the chemical composition offers the most useful and most common
methodofferritecontrol during melting ofthemetal
5,2 Magnetic response method
Phases other than ferrrte and austenite may beformed at certain temperatures and persist at room temperature.
Contamination from other ferromagnetic materials may also occur. These may so alter the magnetic response of
tile alloy that the indicated ferrite content is quite different from that of the same chemical composition that has
nnderqone different thermal treatment. Also, because the magnets or probes ofthevarious measuring instruments
are small, different degrees 01 surface roughness or surface curvature will vary the magnetic linkage with the
materialbeingmeasured,
5.3 Metallographic examination
Metallographic point count estimates of ferrite percentage may vary with the etching technique used for the
identificationofthe ferrite phase andwith the numberofgridpointschosen forexamination, seeA2,
Formostaccurate local estimate offerrite percent,aquantitative metallographicmethod shall beused.
6 Ordering information
Orders formaterial to this practice shall include thefollowing asrequired.
a) Applicable ISOproduct specification orotherdocument covering product requirements.
b) Alloygrade.
c) Requiredferrite range, in volume percent, ofthecasting afterfinal heattreatment.

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~S 15839: 2009
ISO 13520: 2002
, d) Supplementaryrequirements, ifany,desired.
e) Themethod to be used for the determination ofthe ferrite content andthe locationofmeasurements;whether
ontestblocksoronthecastings shallbeagreedbetweenthecustomer andsupplier.
f) If measurements are to be carried out on the castings, the location of the measurementsshall be agreed
betweenthe purchaser andthe supplier. Intheabsenceof specification bythe purchaser,thelocat'on maybe
chosenbythesupplier.
7 Gen~ ~f cautlon
7.1 In specifying ferrite content as required in 6c) the purchaser shall not set limits that are in conflict with
materialspecification requirements.
7.2 When setting ferrite content limits the purchaser shall ensure that the limits are compatible with the
measurementmethodbeing used.
8 IEstimc:nt~oll1 offerrlte
8.1 The ferrite content of the base metal of the casting can be estimated from the chemical composition in
accordancewiththe Schoefer diagram (Figure8.1).Forfurtherinformation seeannex8.
If agreed at the time of ordering the estimation can be carried out using an equivalent diagram as described in
8NIF 3452)whichallowsferrite evaluation (from0%to30%) inausteniticsteelcastings.
8.1.1 The chemical analysis of the heat from whichthecastings are poured shall includethe followingelements
whether or not required by the chemical requirements of the product specification:carbon, manganese, silicon,
chromium,nickel,molybdenum, niobium ~nd nitrogen.
8.1.2 Theferrite contentof thecasting shall beestimatedfrom thecentral lineof thediagram atthecomposition
ratioof"chromiumequivalent" (Cre)to"nickelequivalent"(Nie)determinedfromthefollowingformula:
J
Cre [Cr(%)+1,5Si(%)+1,~Mo(%)+Nb(%)- 4,99
Nie = =Ni(%)+30C (%)+0,5Mn(%)+26(N%- 0,02%)+2,77]
8.1.3 When a product analysis is made by the purchaser, it shall include the elements listed in 8.1.1. If a
comparison is made of ferrite estimated from a product analysis performed by the purchaser,with that estimated
fromtheheatanalysis(see 8.1.1),referenceshallbemadetocheckanalysesinISO4990.
8.2 Estimation of ferrite content in heat or product may be made by the maghetic response (see A.1) or
metallographic(seeA.2) methods ontest blocksorcastingsrespectively,ifagreedby.purchaserandsupplier.
9 Acceptance standards
Conformancewith the requiredferrite rangespecified in 6 c) asindicated by the estimationprocedureof8.1shall
bethebasisfor acceptance ofmaterial supplied underthispracticeunlessothermethodsofestimationareordered
assupplementaryrequirements, in.which casethesupplementaryrequirement shallbethebasisofacceptance.

2) PublishedbyEditionsTechniquesdes IndustriesdelaFonderie,44avenue delaDivision Leclerc,92310sevrss, Frar.ce.
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ISO 13520: 2002
10 Certification
10.1 The manufacturer's certification shall be furnished to the purchaser stating that the material was sampled
andtestedinaccordancewiththespecification (inciudmgyear date)andwasfoundtomeetthe requirements
10.2 Theinspectiondocumentshallcontain theresultsofthe actualchemicalanalyses required by8 1.1.andthe
indicatedferritecontentrangerequired.Theestimatesofferritecontentcalculatedin accordance with8.1.2.and/or
from magnetic measurements (A.1) and/or from point counts (A.2), if ordered by the purchaser, shall also be
reported.
10.3 TheInspectiondocumentshallbesignedbyanauthorizedagent ofthemanufacturer.

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IS 15839: 2009
ISO 13520: 2002
Annex A
(normative)
Determination offerrite content by magnetic or rnetatloqraphic means
A.1 Estimation offerrite content by measurement of magnetic response
A.1.1 Genera!
The ferrite content ofthe heat from which the castings are poured shall be esnmated from measurements made by
primary or secondary instruments, which have been properly calibrated for ferrite in castings. See ASTM A799 or
BNIF 345. All measurements shall be made on matenal after the solution heat treatment required bythe applicable
product specification or, if any subsequent solution heat treatment IS employed, then after the final solution heat
treatment
A.i.1.1 Measurements shall be made onthe unstrainec ends oftension test specimens trom thesame heat as
the castings represented. Measurements may be made either before or after performance of the tension test If a
tension test IS not required bythe applicable product specification, measurements may be made on aspecimen cut
trorn atest block as described InISO4990
A.1.1.2 Alternatively when specified. measurements shall be made on the base metal of the castings, or a
specified sample of castings (not on weid deposits), in locations designated on the design drawing or as otherwise
agreed inwriting between the purchaserand the manufacturer.
A.i.2 Surface condition
A.1.2.1 The instrument magnet or probe and the surface to be measured shall be dry and cleaned prior to
testing inorder to remove any scale, grease, lintor dirt that could affect the accuracy ofthe measurement.
A.1.2.2 Measurements shall be made more than 5mm from the edge of a surface. When measurements are
made onacurved surfacethe radius ofcurvature shall begreaterthan 10mm.
A.;.3 Acceptance criteria
A.1.3.1 The average of the ferrite contents estimated from measurements ineach designated location shall be
within the limits stated in the order, and not more than 20 % of the individual measurements shall indicate femte
contents lessthan or inexcess ofthese limits.
A.1.3.2 Should the requirements of A1.3.1 not be met, an estimation of ferrite content may be made by the
metailographicmethod described In A2 and shall take precedenceover the magnetic method,
A.2 Estimation offerrite content by metalloqraphic examination
A.2.1 Thelocations ofspecimens tobeexamined shall beagreed between the purchaserand supplier.
A.2.2 Unless otherwise agreed the volume fraction of ferrite shall be estimated from the specimens by using the
pomtcount methoddescribed in ISO 9042.

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US 1!S83S : 2009
~SO 13520: 2002
AlJ1lll1e){ B
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Volume percentferrite
c-.: . [cr(%)+1.5Si(%)+1,4Mo.(%)+Nb(%)-4.99]
Nie - [Ni(%)+30C(%)+0,5Mn(%)+26(N- 0,02%)+2.77]
Figure8.1- Schaefer.diagramforestimatingtheaverageferrite content in austeniticiron-chromium-
. nic kel alloycastings .
6