GB/T 4339-2008 PDF English
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Test methods for thermal expansion characteristic parameters of metallic materials
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GB/T 4339-2008: PDF in English (GBT 4339-2008) GB/T 4339-2008
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.040.99
H 21
Replacing GB/T 4339-1999, GB/T 10562-1989
Test Methods for Thermal Expansion Characteristic
Parameters of Metallic Materials
ISSUED ON: OCTOBER 10, 2008
IMPLEMENTED ON: MAY 1, 2009
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine of the People’s Republic of China;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative References ... 5
3 Terms and Definitions ... 5
4 Symbols and Descriptions ... 6
5 Method Overview ... 7
6 Test Devices and Requirements ... 7
7 Specimen Preparation ... 10
8 Device Calibration ... 11
9 Test Procedures ... 14
10 Calculation ... 16
11 Accuracy and Deviation ... 17
12 Test Report ... 18
Appendix A (informative) A Comparison of Chapter No. of This Standard and ASTM
E 228-06 ... 20
Appendix B (informative) Technical Differences between This Standard and ASTM E
228-06 and the Causes ... 23
Appendix C (normative) Supplementary Provisions of Thermal Expansion Test ... 25
Appendix D (informative) Measurement Method for Extra-low Expansion Coefficient
of Metallic Materials - Light Interferometer Method ... 27
Test Methods for Thermal Expansion Characteristic
Parameters of Metallic Materials
1 Scope
This Standard specifies the definitions and symbols, principles, test devices and requirements,
specimen preparation, device calibration, measurement procedures, calculation of measurement
results, test report, accuracy and deviation, etc. of the thermal expansion characteristic
parameter measurement methods of metallic materials and other related solid materials.
This Standard specifies the use of a push-rod dilatometer to test the linear thermal expansion of
rigid solid materials. This is applicable to the testing of the linear thermal expansion of metallic
material specimens within the temperature range of 180 C ~ 900 C with the help of a
component composed of the same fused quartz carrier and push rod. It is also applicable to the
testing of the linear thermal expansion of specimens with rigid solid characteristics, such as:
ceramics, refractory materials, glass and rocks, etc. If components of high-purity alumina are
used instead, the testing temperature range can be expanded to 1,600 C; if isotropic graphite
is used, then, it can be expanded to 2,500 C.
2 Normative References
The clauses in the following documents become clauses of this Standard through reference in
this Standard. In terms of references with a specified date, all subsequent amendments
(excluding corrigenda) or revisions do not apply to this Standard. However, parties to an
agreement based on this Standard are encouraged to explore the possibility of adopting the latest
versions of these documents. In terms of references without a specified date, the latest version
applies to this Standard.
GB/T 8170 Rules of Rounding off for Numerical Values & Expression and Judgement of
Limiting Values
JJG 141 Working Noble Metal Thermocouples
JJG 229 Verification Regulation of Industry Platinum Copper Resistance Thermometers
JJG 351 Verification Regulation of Working Base Metal Thermocouple
3 Terms and Definitions
3.1 linear thermal expansion
L/L0
(L)---the specimen length change shown by the displacement sensor, expressed in (m);
m---the average linear expansion coefficient, commonly expressed as 106 C1, in units of
(C1);
t---the thermal expansion rate at the temperature t, commonly expressed as 106 C1, in units
of (C1);
t0---the temperature corresponding to the original length L0, expressed in (C);
t1, t2---the two temperatures (t1 < t2) selected during the measurement, expressed in (C);
t---the temperature difference (t1 < t2) between t2 and t1, expressed in (C).
5 Method Overview
5.1 Adopt a stepwise temperature change mode or a slow constant speed temperature change
mode for temperature control. Use a push rod fused quartz dilatometer to detect the length
change of a solid material specimen relative to its carrier as a function of temperature.
5.2 Distinguished by the basic configuration, there are often various variants, including test
devices called “differential dilatometers” that use simulated temperature measurement. The
basic requirements for these devices are the same as those specified in this Standard.
5.3 Most thermomechanical analyzers (TMA) have the function of a dilatometer, which has the
advantages of high degree of automation and relatively small specimen size. However, if a
small-sized specimen is used, considering the measurement accuracy, it can generally only
detect high expansion materials, for example, polymers, etc.
6 Test Devices and Requirements
6.1 Specimen Carrier and Push Rod or Pipe
6.1.1 The carrier of the specimen and the push rod or pipe are composed of annealed fused
quartz, which transmit changes in the length of the specimen to the sensor. The shape and size
of the push rod shall ensure that the load is applied to the specimen without causing indentation
on the specimen within the required temperature range. Figure 1 shows a typical shape of the
pipe and rod.
specimen and its carrier into electrical and optical signals suitable for input to the data
processer–recorder. There can be various types, such as: digital encoders, differential or pointer-
type conversion devices, etc. The accuracy shall satisfy the performance testing requirements.
For example, within the temperature interval of 20 C ~ 100 C, it shall be ensured that the
testing accuracy of the specimen with a length of 25 mm and an average linear expansion
coefficient of 1.0 106/C is better than 0.1 106/C. The measurement uncertainty of the
displacement sensor used shall be better than 85 nm (see 11.3).
The displacement sensor shall be protected, so as to ensure that the maximum temperature
change in the sensor caused by the test has no obvious effect on its indication value.
6.3.2 The shape and size of the push rod shall ensure that the load is applied to the specimen
without causing indentation on the specimen within the required temperature range. The
diameter of the straight circular cross-section push rod used in this method is 2 mm ~ 5 mm.
6.3.3 The expansion displacement measurement system consisting of a displacement sensor, a
data processer-recorder, a specimen carrier and a push rod shall have a stable zero indication.
Within the temperature range used by the system, the absolute value of the apparent average
linear expansion coefficient measured for a reference specimen that is homogeneous with the
specimen carrier shall not be greater than 0.3 106/C.
6.4 Temperature Measurement System
This system consists of a calibrated temperature sensing device or device group and a manual,
electronic or other equivalent read-out device. The uncertainty of the tested temperature
indication is required to be better than 0.5 C or not greater than 1% of the entire temperature
range.
6.4.1 Since this test method involves a wide temperature range, different types of sensing
devices can be used depending on the temperature range. Generally, wire-shaped (0.5 mm or
finer wire) and foil-shaped thermocouples calibrated by the verification regulation of JJG 141
and JJG 351, as well as wire-shaped resistance thermometers calibrated by the verification
regulation of JJG 229 are used.
6.4.2 Within the range of 190 C ~ 350 C, it is recommended to use E-type or T-type
thermocouples. Within the range of 0 C ~ 900 C, it is recommended to use K-type, S-type
and N-type thermocouples. Thermocouples shall be regularly calibrated and inspected, so as to
ensure that they are not contaminated during use or eliminate phase changes caused by the
migration of alloy components at the joints.
6.4.3 When a thermocouple is used, an ice tank or an equivalent electronic reference device that
is not affected by ambient temperature changes shall be used to ensure that its reference end is
0 C.
6.4.4 For additional precautions for temperature detection during precision measurement, see
C.4 in Appendix C.
9.3.1 Fused quartz heated above 500 C will crystallize due to contamination by alkaline
compounds. In order to prevent this phenomenon from happening, before each test, it is
recommended to clean the fused quartz component with the following process: soak it in 10%
hydrofluoric acid aqueous solution for 1 minute, then, use distilled water to thoroughly rinse it.
9.3.2 In order to prevent further contamination by alkaline compounds, the cleaned fused quartz
component must not be touched with hands until the measurement is completed.
9.4 Preparation before Test
9.4.1 At room temperature, measure the original length L0 of the specimen in the direction of
thermal expansion detection.
9.4.2 On the premise of confirming that the surface of the specimen is not contaminated by
other substances, place it into the dilatometer and ensure that its position is stable.
9.4.3 Place the temperature sensor in the middle of the specimen, so that it is as close to the
specimen as possible without affecting the movement of the sample in the carrier.
9.4.4 Ensure reliable contact between the displacement sensor, the push rod and the specimen.
9.4.5 Place the assembled expansion measurement system into a furnace, thermostat or a
combination thereof to allow the specimen temperature to equilibrate with its ambient
temperature.
9.4.6 An appropriate minimal load shall be applied to the push rod to ensure contact between it
and the specimen. Depending on the compressibility of the specimen and the temperature range,
this force shall generally be between 0.1 N ~ 1 N; if it is possible to reduce it, it is recommended
to take 30 mN ~ 50 mN. To indicate zero load, a precision and gradual increase in load shall be
used and the applied force shall be indicated in the report.
9.4.7 Record the initial reading t0 of the temperature sensor and the initial reading of the
displacement sensor corresponding to L0.
9.5 Automatic Measurement
9.5.1 Measure the expansion (shrinkage) values of the specimen over the entire required
temperature range, until reaching the maximum temperature.
9.5.2 A measurement procedure with a constant heating or cooling rate of no more than 5
C/min can be used. In high-precision tests, the upper limit of this rate shall be 3 C/min. During
variable-temperature measurement, the average temperature in the specimen is generally
different from the measured temperature (lower when heated, and higher when cooled), but if
the system has been correctly calibrated with reference materials, the measured expansion value
of the specimen is still accurate. Temperature and length change values shall be continuously
recorded.
9.6 Precision Measurement
can be determined from the plot in accordance with the graphing method, or can be calculated
from the fitting equation of the data [see Formula (2)]:
10.4 In the calculation of relevant quantities, the number of digits of all parameters involved in
the calculation shall be maintained. The accuracy level of the measurement is reflected in the
final result, which is generally reported with 3 significant figures.
11 Accuracy and Deviation
11.1 The measurement method specified in this Standard is a comparative method, and its
measurement accuracy is lower than the light interferometer method (see Appendix D), which
is an absolute method. It is usually used to detect materials with a linear expansion coefficient
of not less than 0.5 106/C. If the accuracy of the sensor and the stability of the device satisfy
the requirements, this method can also be used to detect low-expansion materials.
11.2 The measurement accuracy and deviation of thermal expansion and average linear
expansion coefficient are related to the measurement simultaneity corresponding to temperature
and length.
11.2.1 Measurement uncertainty generally consists of accuracy and deviation in repeated
measurements of length and temperature, but may also involve other factors that can interfere
with the measurement, such as: changes in the reproducibility of the specimen position, and
fluctuations in the voltage applied to the sensor, etc.
11.2.2 The system deviation is relatively large and derives from many sources, including the
accuracy of length and temperature measurement, the deviation between the average
temperature of the specimen and the temperature indicated by the temperature sensor, the
deviation caused by the non-linearity of the displacement sensor, the temperature differences
between the specimen carrier and the push rod and between the specimen carrier and the
specimen, the deviation between the assumed value of fused quartz expansion and the actual
measured value, and the impact of additional surface contact between the specimen and the
push rod, etc. For the selected displacement sensors and temperature sensors, the influence of
random factors can be reduced by improving operating quality, while system deviations can
only be eliminated or reduced through careful correction of each independent component and
the entire system.
11.3 The estimated value of the average linear expansion coefficient testing accuracy can be
obtained from Formula (7):
Where,
m/m---the average linear expansion coefficient testing accuracy within the measurement
temperature range, expressed in (%);
(L/L0)---the thermal expansion measurement uncertainty, dimensionless;
L/L0---the thermal expansion value, dimensionless;
t---the testing uncertainty of the temperature sensor, expressed in (C);
t---the measurement temperature range, expressed in (C).
11.4 By using a carefully calibrated fused quartz expansion test device that complies with the
provisions of this Standard, within the temperature range of 25 C ~ 400 C, the accuracy of
the 95% confidence level testing of linear expansion of borosilicate glass, copper and tungsten
is up to 4%.
11.5 Based on the technical points stipulated in this Standard, by using a high-temperature
dilatometer with alumina or graphite as the push rod and carrier, at below 2,000 C, similar
accuracy and deviation can be obtained.
11.6 To determine the accuracy of thermal expansion measurement values, the dilatometer must
be calibrated with reproducible reference materials with known thermal expansion values.
12 Test Report
If necessary, the test report shall include the following content:
a) A description of the manufacturer, chemical composition of the material, heating and
processing history;
b) Details of the method of specimen preparation, the axial direction of anisotropy and
the thermal, mechanical, humidity or other treatments, to which, the specimen has
been subjected;
c) The shape and size of the specimen, including the original length and reference
temperature;
d) A concise description of the device used, including expansion displacement and
temperature measurement systems, accuracy estimates, heating and cooling rates,
temperature control and atmosphere;
e) A list of the reference materials used and the calibration method for the entire
expansion testing system, including expansion displacement sensors and temperature
sensors;
f) A data table demonstrating linear thermal expansion, measurement temperatures and
average linear expansion coefficient within a specified temperature range;
Appendix C
(normative)
Supplementary Provisions of Thermal Expansion Test
C.1 Reference Temperature
C.1.1 Generally, 20 C is used as the reference temperature t0, and the specimen length at 20
C is taken as the reference length L0. In actual measurements, the length L1 at the initial
temperature t1 is often used instead of L0, if the average linear expansion coefficient obtained
from this is m, then, the relation between the two is as follows:
Where,
t1, t0---the average linear expansion coefficient of the specimen between the temperatures t1
and t0.
C.1.2 During production inspection, the impact of room temperature changes on the specimen
length value can be ignored.
C.2 Specimens
C.2.1 In order to ensure the reproducibility of the measurement results, general testing of the
specimen shall be carried out after thermal or mechanical processing or treatment; for some
materials, especially composite materials, before testing, the specimen shall be stabilized (pre-
treated) first to eliminate stress or distortion. When the original state of the specimen is not
known, after the specimen is installed, it can be heated to the highest measurement temperature,
kept for 1 hour, then, cooled to room temperature in the furnace. Then, the thermal expansion
measurement can be carried out.
C.2.2 When measuring temperature with a thermocouple, if there is any doubt about the
measurement results obtained by performing 8.4 or for the purpose of improving the accuracy
of temperature measurement, a hole with a diameter of 1.0 mm ~ 1.5 mm can be drilled at the
midpoint of the specimen. Its depth shall be no less than the specimen radius, so as to facilitate
the insertion of the thermocouple.
C.3 Displacement Sensor
The measurement range, minimum division and magnification of the displacement sensor shall
be selected in accordance with the measurement requirements. The greater the magnification,
the higher the measurement sensitivity, but at the same time, the reproducibility of the data will
decrease.
C.4 Thermocouples for Temperature Measurement
C.4.1 When measuring temperature, even if the temperature sensor is not in direct contact with
the specimen, deviation due to heat exchange shall be prevented. This deviation is caused by
the heat flow out of or into the specimen and the thermocouple contacts. This heat flow can be
minimized by reducing the temperature gradient across the thermocouple wire near the contacts.
For example, the thermocouple wire can be wound once or twice in a space close to the
temperature of the specimen; at this moment, the temperature gradient will move to between
the midpoint of the thermocouple wire in this interval and the edge of the furnace.
C.4.2 When the thermocouple contact is not in direct contact with the specimen, the temperature
measurement during the heating or cooling process will be inaccurate; the size of the
temperature sensor generally has little effect on the lead or lag of the temperature. This
temperature deviation depends on the distance between the sensor and the specimen, the
specimen size, the emissivity and thermal diffusivity of the specimen material, and the heating
or cooling rate used.
C.4.3 Nickel-chromium - nickel aluminum galvanic couples shall not be used above 800 C. It
is recommended to use heat-resistant glass to weld and seal their contacts, so as to prevent
contamination.
C.5 Protective Atmosphere
C.5.1 For general metallic materials, when measuring above 400 C, argon or nitrogen shall be
introduced into the heating furnace; unless careful calibration work is performed in advance,
measurements shall not be performed in vacuum.
C.5.2 When measuring with a TMA type device, inert gases, for example, nitrogen or helium,
must be used as a tool to purify the specimen environment.
C.6 Report
C.6.1 The measurement results are reported to 107 (unit: C1); the rounding-off of numerical
values shall comply with the relevant provisions in GB/T 8170.
C.6.2 In accordance with the requirements of product use, the report content can be
appropriately simplified.
Appendix D
(informative)
Measurement Method for Extra-low Expansion Coefficient of Metallic Materials - Light
Interferometer Method
D.1 Scope
This method specifies the application of Fizeau light interferometer method to determine the
thermal expansion characteristic parameters of metallic materials between 195 C and +100
C. The temperature range of this method is determined by equipment conditions and the
characteristics of the reference specimen used for calibration, and it may be expanded or
narrowed down.
The specific provisions of this method are mainly applicable to the measurement of the average
linear expansion coefficient of metallic materials with low expansion characteristics. As an
absolute measurement method of thermal expansion characteristic parameters, its measurement
accuracy is significantly higher than comparative measurement methods, such as: push-rod
dilatometers and thermomechanical analyzers, etc. The determination of thermal expansion
characteristic parameters of reference materials used for calibration is one of the main purposes
of this method.
D.2 Method Overview
D.2.1 By observing the change of interferometric fringes corresponding to the expansion
(shrinkage) of the specimen, complete the measurement with the aid of the change of the
wavelength of light, which is an absolute measurement method.
D.2.2 Adopt the Fizeau light interferometer method to complete the measurement: respectively
place two optical flat plates, which are known as “interference plates” at the top and bottom of
the cylindrical specimen; there is a certain angle between the upper and lower interference
plates, and the projected laser beam interferes after being reflected by them, forming
interferometric fringes; the expansion or shrinkage of the specimen causes changes in the
optical path difference, causing the fringes to move. Detect the change in the fringes and restore
it into the length change, thus, completing the measurement, as shown in Figure D.1.
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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