ASTM A897/A897M-06(2011)
(Specification)Standard Specification for Austempered Ductile Iron Castings
Standard Specification for Austempered Ductile Iron Castings
ABSTRACT
This specification covers ductile iron castings that are subsequently heat treated by an austempering process. The chemical composition requirements may be agreed upon between the manufacturer, heat treater, and the purchaser. Requirements for the microstructure constituents such as graphite, ausferrite (acicular ferrite and high carbon, stable austenite), pearlite, and martensite are prescribed. The iron shall conform to the mechanical property requirements including tensile strength, yield strength, elongation, impact energy, and Brinell hardness. Castings shall be heat treated by an austempering process detailed in this specification. The standard specimens for tension and Charpy impact tests are illustrated.
SCOPE
1.1 This specification covers ductile iron castings that are subsequently heat treated by an austempering process as defined in 10.1.
1.2 The application of the austempering heat treatment extends the range of properties achievable in ductile iron castings.
1.3 No precise quantitative relationship can be stated between the properties of the iron in various locations of the same casting or between the properties of castings and those of a test specimen cast from the same iron (see Appendix X1). However, austempering heat treatment will tend to diminish any differences in mechanical properties.
1.4 The production of castings, machining (if required), and the austempering heat treatments may be performed by different manufacturers, as covered in Section 15. The purchaser should establish by contract agreement, at the time of ordering, the responsibility of the various parties for meeting the specification requirements.
1.5 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.
1.5.1 Exception—Within the text, the SI units are shown in brackets.
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Designation: A897/A897M −06(Reapproved 2011)
Standard Specification for
Austempered Ductile Iron Castings
This standard is issued under the fixed designationA897/A897M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope A370 Test Methods and Definitions for Mechanical Testing
of Steel Products
1.1 This specification covers ductile iron castings that are
A732/A732M Specification for Castings, Investment, Car-
subsequently heat treated by an austempering process as
bon and Low Alloy Steel for General Application, and
defined in 10.1.
Cobalt Alloy for High Strength at Elevated Temperatures
1.2 The application of the austempering heat treatment
A834 Specification for Common Requirements for Iron
extends the range of properties achievable in ductile iron
Castings for General Industrial Use
castings.
E8 Test Methods for Tension Testing of Metallic Materials
1.3 No precise quantitative relationship can be stated be- E10 Test Method for Brinell Hardness of Metallic Materials
E23 Test Methods for Notched Bar Impact Testing of Me-
tweenthepropertiesoftheironinvariouslocationsofthesame
casting or between the properties of castings and those of a test tallic Materials
specimen cast from the same iron (see Appendix X1).
2.2 Military Standard:
However, austempering heat treatment will tend to diminish
MIL-STD-129 Military Marking for Shipment and Storage
any differences in mechanical properties.
1.4 The production of castings, machining (if required), and 3. Ordering Information
the austempering heat treatments may be performed by differ-
3.1 Orders for material to this specification shall include the
ent manufacturers, as covered in Section 15. The purchaser
following information:
should establish by contract agreement, at the time of ordering,
3.1.1 ASTM designation, with year of issue,
the responsibility of the various parties for meeting the
3.1.2 Grade of austempered ductile iron required (see Table
specification requirements.
1 and Sections 6 and 7),
1.5 The values stated in either SI units or inch-pound units
3.1.3 Chemical composition requirements, if any (see Sec-
are to be regarded separately as standard. The values stated in
tion 4),
each system may not be exact equivalents; therefore, each
3.1.4 Heat treated microstructure restrictions (see Section
system shall be used independently of the other. Combining
10),
values from the two systems may result in non-conformance
3.1.5 Test coupon criteria (see Section 12),
with the standard.
3.1.6 Lot size and tests per lot (see 12.6 and Section 15),
1.5.1 Exception—Within the text, the SI units are shown in
3.1.7 Special requirements, if desired, including hardness,
brackets.
radiographic soundness, magnetic particle inspection, pressure
tightness, dimensions, or surface finish (see Section 9),
2. Referenced Documents
3.1.8 Certification, if required (see Section 16),
2.1 ASTM Standards:
3.1.9 Special preparation for delivery, if required (see Sec-
A247 Test Method for Evaluating the Microstructure of
tion 17).
Graphite in Iron Castings
4. Chemical Composition
This specification is under the jurisdiction of ASTM Committee A04 on Iron
4.1 Although this specification has no specific chemical
Castings and is the direct responsibility of Subcommittee A04.02 on Malleable and
requirements, such requirements may be agreed upon between
Ductile Iron Castings.
the manufacturer, heat treater, and the purchaser.
Current edition approved Nov. 1, 2011. Published April 2012. Originally
approved in 1990. Last previous edition approved in 2006 as A897/A897M - 06.
DOI: 10.1520/A0897_A0897M-06R11.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,
Standards volume information, refer to the standard’s Document Summary page on Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098, http://
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A897/A897M − 06 (2011)
TABLE 1 Mechanical Property Requirements of Grades
Inch-pound units Grade Grade Grade Grade Grade Grade
110/70/11 130/90/09 150/110/07 175/125/04 200/155/02 230/185/01
Tensile strength, min, ksi 110 130 150 175 200 230
Yield strength, min, ksi 70 90 110 125 155 185
Elongation in 2 in., min, % 11 9 7 4 2 1
A
Impact energy, ft-lb 80 75 60 45 25 15
2B
Typical hardness, HBW, kg/mm 241–302 269–341 302–375 341–444 388–477 402–512
A
Unnotched charpy bars tested at 72 ± 7°F. The values in the table are a minimum for the average of the highest three test values of the four tested samples.
B
Hardness is not mandatory and is shown for information only.
SI units Grade Grade Grade Grade Grade Grade
750/500/11 900/650/09 1050/750/07 1200/850/04 1400/1100/02 1600/1300/01
Tensile strength, min, MPa 750 900 1050 1200 1400 1600
Yield strength, min, MPa 500 650 750 850 1100 1300
Elongation in 50 mm, min, % 11 9 7 4 2 1
A
Impact energy, J 110 100 80 60 35 20
2B
Typical hardness, HBW, kg/mm 241–302 269–341 302–375 341–444 388–477 402–512
A
Unnotched charpy bars tested at 22 ± 4°C. The values in the table are a minimum for the average of the highest three test values of the four tested samples.
B
Hardness is not mandatory and is shown for information only.
5. Microstructure 7. Impact Requirements
5.1 The graphite component of the microstructure shall 7.1 The iron represented by the test specimens shall con-
consist of a minimum 80 % spheroidal graphite conforming to form to the impact properties presented in Table 1.
Types I and II per Test Method A247.
7.2 Impact energy requirements apply only after test mate-
5.2 The matrix microstructure shall substantially consist of rial has been austempered. The impact test specimens must be
ausferrite (acicular ferrite and high carbon, stable austenite). finish ground to required dimensions after heat treatment.
Proeutectoid ferrite will also be present in Grade 110/70/11
8. Hardness
[750/500/11].
8.1 The area or areas on the castings where hardness is to be
5.3 The cooling rate within some sections may not be
checked shall be established by agreement between the manu-
sufficient to avoid the formation of pearlite or other high
facturer and purchaser, or the manufacturer and the end user.
temperature transformation products. In some cases, the maxi-
mum acceptable quantities of these microconstituents and the
8.2 Brinell hardness shall be determined according to Test
location(s) within the casting may be established by agreement
Method E10 after sufficient material has been removed from
between the manufacturer, heat treater, and the purchaser.
the casting surface to insure representative hardness readings.
The 10 mm ball and 3000 kg load shall be used unless
5.4 Martensite may be present in minor amounts in the
otherwise specified and agreed upon.
microstructures of Grades 200/155/02 [1400/1100/02] and
230/185/01 [1600/1300/01]. Acceptable quantities of marten-
9. Special Requirements
site may be established by agreement between the
manufacturer, heat treater, and the purchaser. 9.1 When specified in the contract or purchase order,
castings shall meet special requirements as to hardness, chemi-
5.5 The microstructure shall be substantially free of unde-
cal composition, microstructure, pressure tightness, radio-
sirable microconstituents, the details of which shall be agreed
graphic soundness, magnetic particle inspection, dimensions,
upon by the manufacturer, heat treater, and the purchaser.
and surface finish. Refer to Specification A834 for a list of
5.6 The manufacturer, heat treater, and the purchaser may
common requirements for iron castings not specifically refer-
agree upon special chemical compositions or processing re-
enced elsewhere in this specification.
quirements to limit the microconstituents described in 5.3, 5.4,
9.2 When specified in the contract or purchase order,
and 5.5.
castings shall meet special requirements prior to the austem-
pering heat treatment operation.
6. Mechanical Properties
6.1 Tensile property requirements include tensile strength,
10. Heat Treatment
yield strength, and elongation and apply only after austemper-
10.1 Castings produced in accordance with this specifica-
ing heat treatment.
tionshallbeheattreatedbyanaustemperingprocessconsisting
6.2 The iron represented by the test specimens shall con-
of heating the castings to a fully austenitic, homogeneous
form to the requirements as presented in Table 1.
condition or an austenite/ferrite condition for Grade 110/70/11
6.3 The yield strength shall be determined by the 0.2 % [750/500/11], cooling (at a rate usually sufficient to avoid the
offset method (see Test Methods E8). formation of pearlite) to a temperature above the martensite
A897/A897M − 06 (2011)
start temperature, and isothermally transforming the matrix
structure for a time sufficient to produce the desired properties.
Thisprocessshallproduceamicrostructurethatissubstantially
ausferrite or ausferrite/proeutectoid ferrite for Grade 110/70/11
[750/500/11].
10.2 Upon agreement between the manufacturer and the
purchaser, tension test specimens described in Section 13 may
be machined prior to the austempering heat treatment. In this
case, heat treatment shall be performed in an inert or carbon
controlled environment so as to prevent carburization,
decarburization, or scaling. Handling and fixturing must be
“Y” Block Size
such as to prevent test bar distortion (see X1.4).
For Castings of For Castings of For Castings of
10.3 Re-austempering of castings or any deviation from the 1 1
Thickness Less Thickness ⁄2 Thickness of 1 ⁄2
Dimensions
1 1
Than ⁄2 in. to 1 ⁄2 in. [13 to 38 in. [38 mm]
established heat treating process is only permissable with the
[13 mm] mm] and Over
approval of the casting purchaser.
in. [mm] in. [mm] in. [mm]
A ⁄2 [13] 1 [25] 3 [75]
11. Workmanship, Finish, and Appearance
5 1
B1 ⁄8 [40] 2 ⁄8 [55] 5 [125]
11.1 The surfaces of castings shall be clean and free of
C 2 [50] 3 [75] 4 [100]
D 4 [100] 6 [150] 8 [200]
adhering molding material, heat treatment oils or salts, cracks,
E 7 [175] 7 [175] 7 [175]
hot tears, or other injurious defects such as slag and surface
approx approx approx
9 1 1
porosity. Dimensions shall conform to drawings or patterns F ⁄16 [14] 1 ⁄16 [27] 3 ⁄16 [78]
1 1 1
G7 ⁄8 [180] 7 ⁄8 [180] 7 ⁄8 [180]
supplied by the purchaser.
approx approx approx
11.2 Castingsshallnothavechilledcornersorcenterchillin
FIG. 2 Y-Blocks for Test Coupons
areas to be machined.
11.3 Welding repair is not acceptable on austempered cast-
ings.
core sand having a minimum wall thickness of 1 ⁄2 in. [38-mm]
for the ⁄2 -in. [13-mm] and 1-in. [25-mm] sizes and 3 in.
12. Test Coupons
[76-mm] for the 3-in. [76-mm] size. The coupons shall be left
12.1 Separately cast test coupons from which the tension
in the mold until they have cooled to a black color (900°F
test and Charpy test specimens are machined shall be cast to
[480°C] or less). The size and type of coupon cast to represent
the size and shape shown in Fig. 1 or Fig. 2. A modified keel
the casting shall be at the option of the purchaser. In case no
block cast from the mold shown in Fig. 3 may be substituted
option is expressed, the manufacturer shall make the choice.
for the 1-in. [25-mm]Y-block or the 1-in. [25-mm] keel block.
12.2 Wheninvestmentcastingsaremadeinaccordancewith
The test coupons shall be cast in open molds made of suitable
this specification, the manufacturer may use cast-to-size test
specimens that are either incorporated in the mold with the
castings or separately cast using the same type of mold and the
same thermal conditions that are used to produce the castings.
The test specimens shall be made to the dimensions shown in
Fig. 1 of Specification A732/A732M or Fig. 5 of Test Methods
and Definitions A370. The exact procedure to be used for
producing test specimens shall be agreed upon by the manu-
facturer and the purchaser.
12.3 When castings made in accordance with this specifi-
cation are produced by nodularization directly in the mold, the
manufacturermayuseeitherseparatelycasttestcouponsortest
specimens cut from castings. If test bars are to be cut from
castings,testbarlocationshallbeagreeduponbythepurchaser
and the manufacturer and indicated on the casting drawing.
When separately cast test coupons are used, selection shall be
as outlined in 12.1 and shown in Figs. 1-6. Appendix X2
provides guidelines for selection of coupons with mold cooling
rates representative of various casting sections.
12.4 Test coupons shall be poured from the same ladle or
heat as the castings they represent and, unless otherwise agreed
upon by the manufacturer and the purchaser, shall be subject to
FIG. 1 Keel Block for Test Coupons the same post inoculation and alloying practice.
A897/A897M − 06 (2011)
FIG. 3 Mold for Modified Keel Block
12.5 Test coupons shall be heat treated with the castings Positions A (preferred) or B in Fig. 4. The test bars may be
they represent. machined before or after heat treatment in accordance with
10.2.
12.6 The number of test coupons and the number of tests
required per order or lot size shall be established at the time of
14. Impact Test Specimens
ordering.Thisagreementshouldincludeadefinitionoflotsize.
14.1 The unnotched Charpy impact strength shall be deter-
Lot size can be defined to include the entire order, a specified
mined according to Test Methods E23 with the following
portion of that order, a specified manufacturing production
variations: Specimens are to be prepared unnotched to dimen-
period,oraspecifiedquantityofpartsshippedtothepurchaser.
sions in Fig. 9 of Test Methods E23. Blanks from which test
12.7 If any test specimen shows obvious defects, another
specimens are machined shall be cut only from Positions A or
may be cut from the same test block or from another test block
Bin Fig. 4. Test temperature shall be 72 6 7°F [22 6 4°C].
representingthesamemetal.Positionsotherthan“A”or“B”in
Four specimens shall be tested, with the lowest impact energy
Fig. 4 shall not be used. In those cases where removal of test
value discarded and the remaining three values averaged. The
bars from actual castings has been agreed upon (see 12.2 and
average impact energy shall meet the requirement of Table 1.
12.3), a second test bar may be o
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