ASTM C1025 - 15 (2020)

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Designation: C1025 −15 (Reapproved 2020) An American National Standard
Standard Test Method for
Modulus of Rupture in Bending of Electrode Graphite
1
This standard is issued under the ﬁxed designation C1025; 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
1.1 This test method covers determination of the modulus of
rupture in bending of specimens cut from graphite electrodes
using a simple square cross section beam in four-point loading
at room temperature.
1.2 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
standard.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accor-
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
2
C651 Test Method for Flexural Strength of Manufactured
Carbon and Graphite Articles Using Four-Point Loading at
Room Temperature
C783 Practice for Core Sampling of Graphite Electrodes
E4 Practices for Force Veriﬁcation of Testing Machines
E691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
3. Terminology
3.1 Deﬁnitions:
3.1.1 electrode graphite, n—a type of manufactured graph-
ite with less restrictive controls on homogeneity and purity,
commonly produced to carry current in electric arc furnaces, as
a consumable item in electrical discharge machining, and as a
structural material in plastic-injection molds.
3.1.2 ﬂexural strength, n—property of solid material that
indicates its ability to withstand a ﬂexural or transverse load,
obtained through a measurement of the ultimate load-carrying
capacity of a speciﬁed beam in bending.
3.1.3 modulus of rupture in bending, n—the value of maxi-
mum stress in the extreme ﬁber of a speciﬁed beam loaded to
failure in bending.
4. Signiﬁcance and Use
4.1 This test method provides a means for determining the
modulus of rupture of a square cross section graphite specimen
machined from the electrode core sample obtained according to
Practice C783, with a minimum core diameter of 57 mm. This
test method is recommended for quality control or quality
assurance purposes, but should not be relied upon to compare
materials of radically different particle sizes or orientational
characteristics. For these reasons as well as those discussed in
4.2 an absolute value of ﬂexural strength may not be obtained.
4.2 Specimen Size—The maximum particle size and maxi-
mum pore size vary greatly for manufactured graphite
electrodes, generally increasing with electrode diameter. The
test is on a rather short stubby beam, therefore the shear stress
is not insigniﬁcant compared to the ﬂexural stress, and the test
results may not agree when a different ratio or specimen size is
used.
5. Apparatus
5.1 The testing machine shall conform to the requirements
of Sections 14 and 17 of Practices E4.
5.2 The four-point loading ﬁxture shall consist of bearing
blocks or roller assemblies which ensure that forces applied to
the beam are normal only and without eccentricity. (See Test
Method C651.) The directions of loads and reactions may be
maintained parallel by judicious use of linkages, rocker
bearings, and ﬂexure plates. Eccentricity of loading can be
avoided by the use of spherical or cylindrical bearings.
Provision must be made in ﬁxture design for relief of torsional
loading to less than 5 % of the nominal specimen strength.
Refer to Fig. 1 for a suggested four-point ﬁxture with a
semi-articulating roller conﬁguration.
1
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.F0 on Manufactured Carbon and Graphite Products.
Current edition approved May 1, 2020. Published June 2020. Originally
approved in 1984. Last previous edition approved in 2015 as C1025 – 15. DOI:
10.1520/C1025-15R20.
2
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
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

5.3 The bearing block diameter shall be between

⁄

and

⁄

of the specimen support span, 12 mm to 6 mm. A hardened

steel bearing block, roller assembly, or its equivalent is

necessary to prevent distortion of the loading member.

6. Test Specimen

6.1 Sampling—A core sample (minimum of 57 mm diam-

eter and 165 mm long) shall be obtained from the electrode in

accordance with Practice C783.

6.2 Preparation—A test specimen shall be prepared from

the core to yield a parallelepiped of square cross section. The

faces shall be parallel and ﬂat within 0.002 mm ⁄mm of length.

Specimen edges shall be free from visible ﬂaws and chips. All

surfaces shall be smooth with a surface texture equivalent to

that obtained from a precision band saw or better.

6.3 The square cross section specimen shall be 38 mm by

38 mm and at least 153 mm long.

6.4 Measurements—All dimensions shall be measured to at

least 0.03 mm.

6.5 Drying—Each specimen must be dried in an oven at

greater than 110 °C for 2 h. The specimen must then be cooled

to room temperature and stored in a desiccator or dry environ-

ment and held there prior to testing.

NOTE 1—Water, either in the form of liquid or as humidity in air, can

have an effect on ﬂexural mechanical behavior. Excessive adsorbed water

can result in a reduced failure stress due to a decrease in fracture surface

energy.

7. Procedure

7.1 Center the specimen in the test ﬁxture. Make sure that

no extraneous torsional loads are being introduced to the

specimen.

7.2 The support span shall be equal to three times the

specimen thickness, 114 mm. The load span shall be one third

the support span, 38 mm. Refer to Fig. 1.

7.3 Apply the breaking load at a maximum rate of

0.02 mm ⁄s.

8. Test Data Record

8.1 Measurements to 0.03 mm shall be made to determine

the average width and thickness of the specimen at the section

of failure.

8.2 The load at failure shall be recorded to 61%.

9. Calculation

9.1 If the fracture occurs within the load span, calculate the

modulus of rupture, the maximum bending moment, the

distance from the neutral axis to the location where the ﬁber

failed, and the moment of inertia of the original cross section

as follows:

9.1.1 Modulus of rupture:

MOR 5Mc/I

MOR 5

PL/bt

1000

9.1.2 Maximum bending moment:

P/2

L/3

9.1.3 Distance from the neutral axis to the location where

the ﬁber failed:

t/2

9.1.4 Moment of inertia of the original cross-section:

/12

where:

MOR = modulus of rupture, kPa,

M= maximum bending moment, N · mm,

c= distance from the neutral axis to the location where

the ﬁber failed, mm,

I= moment of inertia of the original cross-section, mm,

P= maximum applied load indicated by the testing

machine, N,

L= support span length, mm,

b= average width of the specimen, mm, and

t= average thickness of the specimen, mm.

9.2 If the fracture occurs outside of the load span, this

observation shall be reported.

FIG. 1 Beam with Four-Point Loading (Not to Scale)

C1025 − 15 (2020)

10. Report

10.1 The report of each test shall include the following:

10.1.1 Sample identiﬁcation,

10.1.2 Average width to the nearest 0.03 mm,

10.1.3 Average thickness to nearest 0.03 mm,

10.1.4 Support span length, mm,

10.1.5 Rate of loading, mm/min. or N/min.

10.1.6 Maximum applied load, N,

10.1.7 Modulus of rupture calculated to the nearest 70 kPa,

10.1.8 Defects in specimen,

10.1.9 Orientation and location of specimen within the

parent electrode, and

10.1.10 Failure location.

11. Precision and Bias

11.1 The precision of this test method (see Practice E691)

was determined from an ASTM round robin test on 38 mm

square cross section specimens which were cut from a 153 mm

thick slab from a 610 mm diameter premium grade electrode

having a maximum particle size less than 6 mm. Since this

round robin was a destructive test, each participating labora-

tory tested only their samples. The samples sent to each

laboratory were selected so as to represent the slab of graphite;

that is, samples from different radial locations within the

610 mm diameter slab. Hence the stated precision not only

represents the variations within the test itself but also the

variations within the sampled electrode.

11.2 The referenced ASTM round robin test was a multi-

purpose test and only that portion of the test data accumulated

on four-point bending tests on square cross section specimens

was analyzed to arrive at the stated precision. Six laboratories

participated in the test to the extent that their methodology and

test ﬁxtures conform to, but may not be identical to, this

method and the ﬁxture shown in Fig. 1.

11.3 The six sets of data contained all of the specimens of

the stated test geometry, and form a homogeneous population.

The data also exhibited a correlation between strength and

density. Their mean strength, corrected by regression to the

mean density, was 225.4 kPa with a standard deviation of

4.3 kPa. Plotted on probability paper, their distribution ap-

peared normal with no signiﬁcant skewness or kurtosis. Tested

by analysis of variation with degrees of freedom 5 (between

groups) and 24 (within groups against the null hypothesis and

the random effects hypothesis), a difference between labs was

barely discernible. The null hypothesis was satisﬁed at 90 %

conﬁdence level. The conﬁdence band on the ratio of variances

(between labs to within labs) included zero at the two-sided

80 % conﬁdence level. Best estimates for the standard devia-

tions are:

11.3.1 Between Laboratories:

56.76 kPa

with 5 degrees of freedom.

11.3.2 Within Laboratories:

514.6 kPa

with 24 degrees of freedom.

11.3.3 Mean Value:

5225.4 kPa

11.3.4 It can also be safely concluded that the within-lab

variability is largely due to materials variability for which no

data was available for correlation. Known effects include

orientation and disparate ﬂaws.

11.4 The stated precision of this test will probably worsen if

electrodes having a maximum particle size larger than 6 mm

are tested using this test method.

11.5 Bias—Bias cannot be determined as this is a destruc-

tive test and no standard specimens are available.

12. Keywords

12.1 carbon; electrode graphite; ﬂexural strength; graphite;

modulus of rupture

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in this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk

of infringement of such rights, are entirely their own responsibility.

This standard is subject to revision at any time by the responsible technical committee and must be reviewed every ﬁve years and

if not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standards

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C1025 − 15 (2020)

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ASTM C1025 - 15 (2020) 标准规范详细规定了使用量热计法测定耐火材料热导率的试验方法，适用于高温条件下耐火砖、耐火浇注料等材料的导热性能评估。该标准通过测量试样在稳态热流下的温度梯度与热流量，计算出材料的热导率，为耐火材料在钢铁、玻璃、陶瓷等高温工业领域的应用提供关键性能数据。标准明确了试样制备、试验设备要求、校准步骤及数据处理方法，确保测试结果的准确性与可重复性。更新于2020年的版本维持了2015年的技术内容，并延续了其在全球耐火材料行业中的权威参考地位。本标准的有效应用

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