ISO 16835:2014

INTERNATIONAL ISO
STANDARD 16835
First edition
2014-04-01
Refractory products — Determination
of thermal expansion
Produits réfractaires — Dosage de la dilatation thermique
Reference number
©
ISO 2014
© ISO 2014
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ii © ISO 2014 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Contact method with cylindrical test piece . 3
4.1 Principle . 3
4.2 Apparatus . 3
4.3 Test piece . 8
4.4 Procedure .10
4.5 Calculation and drawing .10
5 Contact method with rod test piece .14
5.1 Principle .14
5.2 Apparatus, implement and reference sample .14
5.3 Test piece .17
5.4 Procedure .18
5.5 Calculation and drawing .19
6 Non-contact method.22
6.1 Principle .22
6.2 Procedure .23
6.3 Calculation and drawing a figure .23
7 Test report .25
Annex A (informative) Characteristics of the test methods .27
Annex B (informative) Recommended values of linear thermal expansion rate and coefficient of
linear thermal expansion of reference sample .28
Annex C (informative) Example of apparatus and test piece for non contact method .30
Bibliography .37
Foreword
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to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 33, Refractories.
iv © ISO 2014 – All rights reserved

INTERNATIONAL STANDARD ISO 16835:2014(E)
Refractory products — Determination of thermal
expansion
1 Scope
This International Standard specifies test methods for the thermal expansion of refractory products.
It describes a method for determining the linear thermal expansion percentage, the linear thermal
expansion curve, and the linear thermal expansion coefficient.
This International Standard includes the following three test methods for the thermal expansion of
refractory products:
a) a contact method with a cylindrical test piece;
b) a contact method with a rod test piece;
c) a non-contact method.
The characteristics of these methods are shown in Annex A.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 836, Terminology for refractories
IEC 60584-1, Thermocouples — Part 1: Reference tables
IEC 60584-2, Thermocouples — Part 2: Tolerances
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 836 and the following apply.
3.1
starting point temperature
T
starting point temperature for collecting thermal expansion results, (record ambient temperature)
3.2
reference material
materials with a known linear thermal expansion (percentage) and coefficient
3.3
lowest limit temperature
T
lowest temperature in the measurement range for linear thermal expansion
3.4
highest limit temperature
T
highest temperature in the measurement range for linear thermal expansion
3.5
linear thermal expansion
ε
i
ratio of length L at a starting point temperature T versus length change ΔL (= L − L ) between length
0 0 i i 0
L at a certain temperature T and length L
i i 0
Note 1 to entry: ε = ΔL /L
i i 0
3.6
linear thermal expansion percentage
E
i
linear thermal expansion expressed as a percentage
Note 1 to entry: E = ε × 100 ; E = ΔL /L multiplied by 100
i i i i 0
3.7
linear thermal expansion curve
curve(s) between the temperature on the abscissa and the linear thermal expansion percentage on the
ordinate
Note 1 to entry: There are two types of curves, a rising temperature curve and a declining temperature curve.
3.8
rising temperature curve
curve concerning linear thermal expansion changes caused by rising temperature, which is normally
called the linear thermal expansion curve
3.9
declining temperature curve
curve concerning linear thermal expansion changes caused by declining temperature, which is used for
the examination of the size change of sample after heating
3.10
average linear thermal expansion coefficient
α
TT−
ratio of length change ΔL(= L − L ) of a specimen within a temperature interval to that temperature
2 1
interval ΔT(= T − T ), related to the length L at the starting point temperature
2 1 0
Note 1 to entry: That means α =ΔΔLL/ T . The sample lengths L and L are at the temperatures T and
()
1 2 1
TT− 0
−1
T , respectively. The unit of this value is °C .
3.11
linear thermal expansion coefficient
α
T
i
value of average linear thermal expansion coefficient, ΔL/(L ΔT ) when ΔT(=T − T ) approaches zero
0 i 2 1
Note 1 to entry: This means the slope of the tangent line on the relational line between linear thermal expansion
−1
ε = ΔL /L at a certain temperature T and the temperature T . The unit of this value is °C .
i i 0 i i
3.12
reference sample
substance of which the linear thermal expansion rate and coefficient of linear thermal expansion are
known
Note 1 to entry: The shape of the reference sample should be the same as that of test piece.
3.13
difference of elongation
difference in length between the test piece and the reference sample of the same length as that of test
piece when heated from the lower limit temperature to the upper limit temperature
2 © ISO 2014 – All rights reserved

4 Contact method with cylindrical test piece
4.1 Principle
The amount of dimensional change of the cylinder test piece is continuously measured by using a contact
type measurement instrument while heating at the specified rate in a heating furnace, and the linear
thermal expansion rate, curve of linear thermal expansion rate, average coefficient of linear thermal
expansion, and coefficient of linear thermal expansion are obtained.
4.2 Apparatus
4.2.1 Thermal expansion test apparatus
4.2.1.1 General
The circular pressure rod (1), test piece (5), and supporting rod (9) of the thermal expansion test
apparatus shall be set in a heating furnace and all central axes aligned vertically. This alignment shall be
maintained throughout the test as shown in Figure 1 and Figure 2. The structure of the apparatus shall
be such that the thermal expansion of the test piece produced when a pressure of 0,01 MPa is applied
to the direction of this central axis and the temperature is raised can be calculated from the relative
change amount of the length of detecting tubes (7) and (8) contacted with the spacers (2) and (6) of the
upper surface and the lower surface of the test piece. The contact force shall not change more than ±1 N.
Key
1 pressure rod
2 upper disk-type spacer
3 thermocouple for measuring temperature of test piece
4 thermocouple for controlling temperature of heating furnace
5 test piece
6 lower disk-type spacer
7 tube for detecting the upper position of test piece
8 tube for detecting the lower position of test piece
9 supporting rod
10 measurement instrument
Figure 1 — Schematic drawing of the thermal expansion test apparatus (in case of measuring
the change rate of test piece at the lower part of apparatus)
4 © ISO 2014 – All rights reserved

Key
1 pressure rod (outside diameter: 45 mm or over)
2 upper disk-type spacer (outside diameter: 50,5 mm)
3 thermocouple for measuring temperature of test piece
4 test piece (outside diameter: 50 mm ± 2 mm, inside diameter: 12 mm ± 1 mm, length 50 mm ± 0,5 mm)
5 lower disk-type spacer (outside diameter: 50,5 mm, inside diameter: 10 mm)
6 tube for detecting the upper position of test piece (outside diameter: 8 mm, inside diameter: 5 mm)
7 tube for detecting the lower position of test piece (outside diameter: 15 mm, inside diameter 10 mm)
8 supporting rod (outside diameter: 45 mm, inside diameter: 20 mm)
9 platinum or platinum rhodium foil (outside diameter: 50,5 mm, inside diameter: 10 mm)
Figure 2 — Detail drawing of thermal expansion test (in case of measuring the change rate of
test piece at the lower part of apparatus)
Key
1 pressure rod
2 upper disk-type spacer
3 thermocouple for measuring temperature of test piece
4 thermocouple for controlling temperature of heating furnace
5 test piece
6 lower disk-type spacer
7 tube for detecting the upper position of test piece
8 tube for detecting the lower position of test piece
9 supporting rod
Figure 3 — Schematic drawing of thermal expansion test apparatus (in case of measuring the
change rate of test piece at the upper part of apparatus)
4.2.1.2 Constitution of thermal expansion test apparatus
The apparatus shall be comprised of the following.
a) Fixed pressure rod (1): The fixed pressure rod (1) shall be a cylindrical refractory material of at
least 45 mm outside diameter. In the apparatus in Figure 3, the hole of concentric circle for passing
through the tubes for detecting the upper and lower positions shall be provided.
Care shall be taken so as not to contact with the hole of the upper lid of the heating furnace.
6 © ISO 2014 – All rights reserved

b) Supporting rod (9): The supporting rod (9) shall be a cylindrical refractory material of at least
45 mm outside diameter. In the apparatus in Figure 1 and Figure 2, the hole of concentric circle for
passing through the tubes for detecting the upper and lower positions shall be provided.
c) Disk-type spacers (2) and (6): The disk-type spacers (2) and (6) shall be the refractory material
inserted for preventing the test piece from adhering to (1) and (9) by fusion due to chemical reaction,
for example a disk of at least 50 mm outside diameter and 5 mm to 10 mm thickness of the alumino-
silicate refractory such as high temperature sintered mullite or alumina, or the basic refractory
such as magnesia or spinel. The hole of concentric circle passing through (7) shall be provided at (6)
in the apparatus shown in Figure 1 and Figure 2, and at (2) in the apparatus shown in Figure 3. Both
ends of (1) and (9) shall be processed so as to be flat and in parallel position, and the spacers (2) and
(6) contacted with it shall be processed to make them vertical to the central axis.
When the test piece ready to react with other refractory material, such as silica especially, is
measured, the foil of platinum or platinum rhodium alloy (9) of approximately 0,2 mm in thickness
may be placed between the test piece and both spacers as shown in Figure 2.
d) Tube for detecting the lower position of test piece (8): The tube for detecting the lower position of test
piece (8) shall be the alumina tube of which the tip penetrates the supporting rod (9) in apparatus in
Figure 1 and Figure 2 or the pressure rod (1) in the apparatus in Figure 3 and is contacted with the
lower disk-type spacer adhering closely to the lower surface of the test piece, and shall be capable of
moving freely so as not to make contact with the supporting rod.
e) Tube for detecting the upper position of test piece (7): The tube detecting the upper position of test
piece (7) shall be the alumina tube of which the tip penetrates the supporting rod (9), the lower disk
type spacer (6), and test piece (5) in the apparatus in Figure 1 and Figure 2 and is contacted with
the upper disk-type spacer adhering closely to the upper surface of test piece, and shall be capable
of moving freely so as not to be contacted with those. In the apparatus in Figure 3, the structures of
these d) and e) are reversed.
f) Material and preparation of jigs: For the jigs, the material capable of enduring the load without
deformation and reaction up to the final (highest) test temperature shall be selected.
The material from which the jigs are made should have a T value greater than or equal to the temperature
at which the test material has a T value. T and T are obtained according to ISO 1893:2007.
5 1 5
4.2.2 Heating furnace
The heating furnace shall be the tubular furnace of which the central axis conforms to the measurement
system. It shall be capable of heating the test piece up to the final (highest) test temperature at the
specified rate of rising temperature [see c) in 4.4.1] in the atmosphere and of heating uniformly 12,5 mm
of the upper and lower sides of test piece at 500 °C or higher within ± 20 °C of the specified temperature.
The uniform heating zone around the test piece shall be measured beforehand.
The up-and-down moving type or opening-closing type is recommended because they do not hinder the
setting of measurement system.
4.2.3 Detector for amount of deformation of test piece
The dial gauge or differential transformer transducer connected to an automatic recorder shall be used.
These are fixed to the tip of (8), the gauge head at the tip of spindle in the case of dial gauge, or the
core in case of differential transformer transducer. These then contact the tip of (7) and the relative
deformation amount produced by the deformation of test piece is measured. The measuring instrument
shall have the sensitivity which enables the measurement to the nearest of 0,005 mm.
4.2.4 Temperature measurement apparatus
4.2.4.1 Thermocouple for measuring the temperature of test piece
The thermocouple for measuring the temperature of the test piece shall be inserted into the alumina
tube (7) which penetrates the test piece so as to be capable of measuring the temperature at the centre
of the test piece and shall be arranged so that the hot contact point comes to the centre of the test piece.
4.2.4.2 Thermocouple for controlling the temperature of heating furnace
For thermocouple for controlling the temperature of heating furnace, the thermocouple with protecting
tube shall be used and be arranged so that the hot contact comes adjacent to the test piece (see Figure 1).
It may be arranged adjacent to the heating unit depending on the structure of the furnace.
4.2.4.3 Type and precision of thermocouple
The thermocouple shall be a platinum-platinum rhodium system and the type capable of using up to the
final (highest) test temperature shall be selected. The precision of thermocouple shall be verified.
4.2.5 Callipers
The callipers of 0,05 mm minimum scale reading shall be used.
4.2.6 Reference sample
For the reference sample, the high purity sintered alumina object of the same shape as that of the test
piece specified in 4.3 shall be used. The recommended values of linear thermal expansion rate and
coefficient of linear thermal expansion for reference sample are shown in Annex B.
4.3 Test piece
4.3.1 Shape of test piece
The shape of test piece shall be as follows.
a) The test piece shall be concentrically cylindrical having a 50 mm ± 2 mm outside diameter,
12 mm ± 1 mm inside diameter, and 50 mm ± 0,5 mm length.
b) The test piece shall be taken so that the upper and lower surfaces are parallel and right-angled to
the central axis, and both surfaces shall be ground and polished so that the difference of length
measured at any two points by using callipers does not exceed 0,2 mm. The end surface of test
piece shall be placed on a flat surface plate and when a square is applied to the generating line of
cylindrical test piece, the deviation, d, between the square and the generating line shall be 0,5 mm
or below (see Figure 4).
8 © ISO 2014 – All rights reserved

d
d
Key
1 square
2 sample
The dimension d is measured by using a feeler gauge.
Figure 4 — Measuring method for verticality
c) For the purpose of confirming that the upper and lower surfaces of the test piece are smooth
throughout the whole surface, the filter paper of 0,15 mm thickness, upon which a carbon paper
is placed, shall be placed on a surface plate and each surface shall be pressed to adhere. Both
surfaces of the test piece may be coloured by using a stamp ink stand instead of carbon paper. When
uncoloured part is found on the surface by this operation, it shall be polished again.
Moreover, the smoothness of the surface may be confirmed by using a square.
4.3.2 Preparation of test piece
4.3.2.1 Shaped refractory
Unless otherwise specified, take the test sample so that the longitudinal direction of the test piece is
parallel to the pressurizing direction of the sample for testing at the time of forming.
Moreover, the direction of taking the test piece may be decided according to the agreement between the
parties concerned with the delivery by conforming to the purpose of using the thermal expansion result.
In the case of unsintered refractory, the test piece taken from the sample after sintering at a definite
temperature or the processed test piece sintered under a definite condition may be used.
4.3.2.2 Unshaped refractory
The test piece shall be either formed into the shape specified in 4.3.1 or cut off to form a definite shape.
The necessity of sintering and the sintering temperature shall be subjected to the agreement between
the parties concerned with the delivery. The preparation, forming, sintering condition of test piece, and
the dimension of test piece shall be mentioned in the test report.
4.4 Procedure
4.4.1 Measurement of test piece
The test piece shall be measured according to the following procedure.
a) Measure the inside diameter, outside diameter, and length (to the nearest 0,1 mm) of the test piece
at room temperature. Place the test piece between the supporting rod and the pressure rod with
spacers in between, aligning each of their central axes.
b) Add 0,01 MPa of compression stress including the mass of pressure rod to the test piece. The change
of the contact load shall not exceed ± 1 N.
For special purposes, the load can be modified to the actual calculated load in the application field,
according the agreement between the parties concerned with the delivery. In such a case, the applied
compression stress should be reported.
c) Then, raise the temperature of the furnace up to the object temperature of measurement at a
constant rate of 2,5 °C/min ± 0,5 °C/min.
Moreover, in the case of the materials accompanied by volume phase transition (for example, silica
and zirconia), the very slow rate of rising temperature may be used for measuring the behaviour
throughout the phase transition region.
d) Measure the central temperature of the test piece by using the thermocouple (3), and record the
amount of change in the direction of height of test piece at intervals within 5 min. When an abrupt
change appears, record the amount of change in the direction of the height of the test piece at each
temperature at intervals of 15 s.
e) If necessary, measure the relation between the temperature and length of the test piece in the
cooling process.
4.4.2 Measurement of reference sample
Measure the reference sample according to 4.4.1. The reference sample shall be measured as a minimum
whenever jigs are changed.
4.5 Calculation and drawing
The calculation and drawing shall be as follows.
a) The linear thermal expansion rate shall be calculated as follows.
10 © ISO 2014 – All rights reserved

The following steps 1) to 5) are the conceptual instructions for the correction of measured values
and the calculation of linear thermal expansion rate. The actual operation should be carried out by
using a computer.
1) Plot the change in the length of the test piece, without the correcting the change in the length of
alumina tube for detecting position, against the temperature by using the measurement result
obtained in 4.4 (curve C in Figure 5).
Y
C
A
C
C
X
B
C
D
Key
X temperature (°C)
Y change of length
Figure 5 — Correction of measurement curve
2) Measure the temperature change of length of the reference sample of the same material as that
of the tube for detecting position and of the same dimension as that of the initial test piece
(curve C in Figure 5). Table B.2 may be used.
3) Plot the curve C ( = C + C ) in which curve C is corrected by the curve of deformation C in 2).
3 1 2 1 2
Namely, it is AB = CD in Figure 5 at any temperature during measurement.
4) Obtain the amount of change in length of the test piece (ΔL ) at each temperature by correcting
i
C in 3).
5) Calculate the linear thermal expansion rate according to the following formula based on the
result in 4) and round off the result to two decimal places.
ΔL
i
E =×100 (1)
i
L
where
E is the linear thermal expansion rate (%);
i
L is the length of test pieces at starting temperature (mm);
ΔL is the amount of change in length (L − L ) of test piece at temperature T (°C) (mm).
i i 0 i
When the measured temperature is lower than the starting temperature, calculate the linear
thermal expansion rate by using the value of change in length from the starting temperature.
Furthermore, when the measured temperature is higher than the starting temperature, calculate
the linear thermal expansion rate from the starting temperature by using the coefficient of linear
thermal expansion in b) according to extrapolation method.
The starting temperature may be altered according to the agreement between the parties concerned
with the delivery.
b) Obtain the curve of linear thermal expansion rate by drawing the relation between each temperature
obtained in a) and its linear thermal expansion rate. An example is shown in Figure 6.
Y
1,00
0,80
0,60
0,40
0,20
0,00
0,20
0,40
0 200 400 600 800 1 000 1 200 1 400 1 600
X
Key
X temperature (°C)
Y linear thermal expansion rate (%)
1 rising temperature curve
2 declining temperature curve
Figure 6 — Example of curve of linear thermal expansion of clayey refractory
c) Calculate the average coefficient of linear thermal expansion according to the following formula,
−8 −6 −1
and round off the significant figure to the place of 10 . Express the result in the unit of 10 · °C .
12 © ISO 2014 – All rights reserved

ΔL
α = (2)
TT−
LT×Δ
where
−1
is the average coefficient of linear thermal expansion of test piece (°C );
α
TT−
L is the length of test piece at starting temperature (mm);
ΔT is the difference between lower limit temperature (T ,) and upper limit temperature
(T ) (°C);
ΔL is the difference of elongation of test piece corresponding to temperature difference ΔT
(mm).
When the relation curve between the linear thermal expansion rate and the temperature is straight
throughout the whole temperature region, the upper limit temperature (T ) can be taken as the
highest temperature of measurement by taking the lower limit temperature (T ) as the starting
point. If the relation curve between the linear thermal expansion rate and the temperature is
distorted, the average linear thermal expansion rate may be obtained in any temperature range as
corresponding to the purpose, provided that, for indication, the average temperature range such as
“α ” is expressed.
800-200
d) Calculate the coefficient of linear thermal expansion according to the following formula, and round
−6 −1
off the result to two significant figures to express in the unit of 10 · °C .
()LL−
TT
iA+−iA
α = (3)
T
i
LT()−T
0 iA+−iA
where
−1
is the coefficient of linear thermal expansion of test piece at temperature T (°C) (°C );
α i
T
i
L is the length of test piece at starting temperature (mm);
T is the temperature (A °C) higher than temperature T (°C);
i+A i
T is the temperature (A °C) lower than temperature T (°C);
i−A i
L is the length of test piece at temperature T (mm);
i+A
T
iA+
L is the length of test piece at temperature T (mm).
i−A
T
iA−
The recommended value of A °C is 25 °C. In case A °C cannot be taken as 25 °C, it should be taken as close
to 25 °C as possible.
The relation curve between the measured linear thermal expansion and the temperature does not
always become a smooth curve. Therefore, the length of test piece at (A °C) plus and minus the specified
temperature T is obtained and taken as the coefficient of linear thermal expansion. Alternatively, the
i
coefficient of linear thermal expansion may be determined by making the curve of the measured linear
thermal expansion rate to be a function by curve fitting, and obtaining the differential value (the slope
of tangent) at temperature T to be divided by 100.
i
5 Contact method with rod test piece
5.1 Principle
The rod test piece is set in a heating furnace with one of the ends fixed. The amount of dimensional
change of the test piece is measured through the detecting rod while heating at a definite rate and
the linear thermal expansion rate, curve of linear thermal expansion rate, average coefficient of linear
thermal expansion and coefficient of linear thermal expansion at the measurement temperature, from
the starting temperature, are obtained.
5.2 Apparatus, implement and reference sample
5.2.1 Thermal expansion test apparatus
5.2.1.1 General
The thermal expansion test apparatus is constituted by the linear thermal expansion measurement
system composed of sample supporting tube, detecting rod (hereafter referred to as “supporting tube”
and “detecting rod”, respectively), electric furnace (thermostatic bath), temperature control system,
temperature measurement system, and recorder. The test piece may be set in either lengthwise or
traverse direction. Examples of constitution of vertical type and horizontal type apparatus are shown
in Figure 7 and Figure 8, respectively.
NOTE A computer can be connected to the apparatus for easier recording and processing of the results.
14 © ISO 2014 – All rights reserved

Key
1 electric furnace heater
2 thermostatic bath
3 supporting tube
4 test piece
5 detecting rod
6 micrometer head
7 outlet and inlet of coolant
8 linear expansion measurement system (differential transducer)
9 balance
10 thermocouple
11 temperature control system
12 recorder
13 temperature measurement system
14 weight
Figure 7 — Example of vertical type thermal expansion apparatus
1 23 4
56 78
Key
1 displacement measuring device
2 measuring thermocouple
3 furnace
4 specimen
5 load controlling device
6 push-rod
7 specimen holder
8 control thermocouple
Figure 8 — Example of horizontal type thermal expansion apparatus
5.2.1.2 Component of thermal expansion test apparatus
The thermal expansion test apparatus shall be comprised of the following.
a) Supporting tube and detecting rod: The supporting tube and detecting rod shall be all made of the
same material of high purity alumina sintered object, quartz glass, or high purity graphite sintered
object, and shall be the type in which the difference of coefficient of linear thermal expansion
between the test piece and supporting tube, i. e. the difference of elongation due to the temperature
rise between test piece and reference sample, is measured. New supporting tube and detecting
rod, in order to stabilize the thermal expansion characteristic, shall be pre-sintered and cooled
gradually prior to use.
Moreover, the high purity alumina and high purity graphite shall be pre-sintered at the highest
temperature to be used for approximately 7 h and then cooled gradually at the rate of 1 °C /min as a
standard. The quartz glass shall be pre-sintered at 1 100 °C, for approximately 7 h and then cooled
gradually down to 900 °C at the rate of 0,2 °C/min.
b) Thermal expansion measurement system: The thermal expansion measurement system, of which the
−4
measurement error is corrected to ± 5 × 10 % of the length of test piece (L ) (for example, ± 0,1 μm
to 20 mm in length of test piece) by using the block gauge (for example, when the length of test
piece is 20 mm, 20,0 mm or 20,5 mm in approximate nominal dimension), shall be used. For the
measurement of length, a differential transformer shall be used.
c) Electric furnace (thermostatic bath): The electric furnace shall be constructed so as to be capable of
controlling heat at a definite rate and maintaining the temperature distribution of the whole heated
test piece at ± 0,5 °C. For the heating unit, any one of silicon carbide heating unit, molybdenum
disilicide heating unit, metal heating unit, or graphite heating unit shall be used. At least, in the
electric furnace for measuring the refractory containing carbon and/or silicon carbide, the
mechanism which allows an inert gas (nitrogen or argon) of a definite flow rate shall be provided.
16 © ISO 2014 – All rights reserved

The muffle type furnace in which the test piece is not directly subjected to the radiation heat from
heating unit should be used.
For test pieces where hydrocarbon vapour is generated during heating, the apparatus should have
a mechanism capable of exhausting this gas.
d) Temperature control system: The temperature control system shall be capable of control at ± 0,5 °C
to the set value of temperature to be targeted.
e) Temperature measurement system: The temperature measurement system shall be capable
of measuring the thermo electro motive force due to the platinum-platinum rhodium based
thermocouple in the precision of ± 0,5 °C by using the electrical method of temperature measurement.
f) Recorder: The recorder, which is capable of recording simultaneously the difference in temperature
and elongation, shall be used.
5.2.2 Micrometer or callipers
The outside micrometer or the callipers with 0,01 mm minimum graduation in scale reading shall be
used.
5.2.3 Reference sample
For the reference sample, the high purity alumina sintered object or quartz glass shall be used for the
measurement in atmosphere. In the atmosphere of inert gas, the high purity alumina sintered object or
high purity graphite sintered object shall be used. For the supporting stand and detecting rod, the same
material shall be used. The recommended values of linear thermal expansion rate and coefficient of
linear thermal expansion of the reference sample are shown in Annex B.
5.3 Test piece
5.3.1 Dimension and shape of test piece
The test piece shall be either a square rod 5 mm to 12 mm in each side and 15 mm to 100 mm in length
or a round rod 5 mm to 15 mm in diameter and 15 mm to 100 mm in length, processed vertically to the
axial direction so that both end surfaces become parallel to each other. The dimension of each side or
diameter of the section of the test piece shall be at least two times the maximum particle used in test
sample and the length of test piece shall be at least four times the maximum particle. The test piece size
and shape should be in agreement between the parties concerned.
Moreover, when the particle diameter used in test sample is large, it shall be measured either in non-
contact method or contact method with cylindrical test piece.
5.3.2 Preparation of test piece
5.3.2.1 Shaped refractory
The test piece shall be taken, unless otherwise specified, such that the longitudinal direction of the test
piece is parallel to the direction in which the test sample was pressurized in forming.
Moreover, the direction of sampling, depending on the purpose of use of the thermal expansion result,
may be as agreed between the parties concerned with the delivery. In the unsintered refractory, the
test piece can be either taken from the sample after sintered at a definite temperature or be supplied by
sintering the processed test piece under a definite condition.
5.3.2.2 Unshaped refractory
The test piece shall be either formed into the shape specified in 5.3.1 or cut off to form a definite shape.
The necessity of sintering and temperature of sintering shall be subjected to the agreement between the
parties concerned with the delivery. The conditions of preparation, forming, sintering of test piece, and
the dimensions of test piece shall be mentioned in the test report.
5.4 Procedure
5.4.1 Measurement of correction factor of difference of elongation
The correction factor of difference of elongation shall be calculated according to the following equation.
Measure the difference of elongation by using the test piece of the same material as that of the reference
sample as the standard material according to 5.4.2 and measure the change of base line (L ).
b
Measure the difference of elongation by using the high purity platinum and silicon as the standard
sample according to 5.4.2 and calculate the correction factor of the difference of elongation to the high
purity of platinum and silicon to two decimal places according to the following formula.
LT××Δ ()αα−
0 refcomp
k= (4)
L
ref
where
k is the correction factor of difference of elongation of standard sample;
L is the length of standard sample at starting temperature (mm);
ΔT is the difference between the lower limit temperature (T ) and the upper limit tempera-
ture (T ) (°C);
α is the average coefficient of linear thermal expansion of standard sample in the range
ref
−1
between the lower limit temperature (T ) and the upper limit temperature (T ) (°C );
1 2
α is the average coefficient of linear thermal expansion of reference sample in the range
comp
−1
between the lower limit temperature (T ) and the upper limit temperature (T ) (°C );
1 2
L is the difference of elongation measured about standard sample (mm).
ref
For the average coefficient of linear thermal expansion of standard sample and reference sample, use the
values in Table 1, Table B.1, and Table B.2. Average the correction factor of the difference of elongation
calculated about the high purity platinum and silicon and round off the result to two decimal places. Use
this value in 5.5 as the correction factor of difference of elongation.
Table 1 — Linear thermal expansion ε and coefficient of linear thermal expansion α
Platinum Silicon
Temperature °C Temperature °C
−4 −6 −1 −4 −6 −1
ε (l0 ) α (10 · °C ) ε (10 ) α (10 · °C )
20 0,000 0 8,9 20 0,000 0 2,5
77 0,051 3 9,1 77 0,015 6 2,9
127 0,097 2 9,2 127 0,031 0 3,2
227 0,190 9 9,5 227 0,064 0 3,5
327 0,287 1 9,7 327 0,101 0 3,8
427 0,385 6 10,0 427 0,140 0 4,0
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5.4.2 Measurement of difference of elongation of test piece
The measurement of the difference of elongation shall be carried out according to the following
procedure.
a) Measure the length of the test piece at room temperature using the outside micrometer or the
callipers and round off the result to two decimal places.
b) Set the test piece so as not to make clearance between the supporting tube and the detecting rod
and so as to stabilize and add force of 98 mN (corresponding to 10 g of weight) to the end surface of
test piece.
c) Mount the thermocouple for measuring temperature such that it is near the central part of the test
piece.
d) Carry out the measurement from room temperature to the specified temperature.
Moreover, unless otherwise specified, carry out the measurement to 1 500 °C.
e) The rate of rising temperature of the test piece shall be a constant rate of 4 °C /min. ± 1 °C /min.
f) Record the difference in temperature and elongation in definite intervals of 10 °C or lower. Carry
out recording on a recording paper by using a recorder or by using a computer.
When the reading of a thermometer and a direct reading type detector is carried out by computer,
the data processing is easy. In such a case, the amount of dimensional change should be recorded in
the unit of 1 °C.
g) If necessary, measure the relation between the temperature and length of test piece in cooling
process, and record it.
5.5 Calculation and drawing
The calculation and drawing shall be as follows.
a) Calculate the linear thermal expansion rate according to the following formula based on the
measurement results in 5.4 and round off the resultant value to two decimal places.
ΔL
i
E =×100 (5)
i
L
where
E is the linear thermal expansion rate (%);
i
L is the length of test piece at starting temperature (mm);
ΔL is the amount of change in length of test piece at temperature T (°C) (L -L ) (mm);
i i i 0
ΔL is the expressed by the following formula.
i
ΔL = L − L + L (6)
i i.act b ref
where
L is the measured value of displacement in length at temperature T in 5.4.2 f) (including the
i.act i
expansion of reference sample) (mm);
L is the base line value in 5.4.1 a) (mm);
b
L is the displacement of length of reference sample at temperature T (values in Table B.1 and
ref i
Table B.2) (mm).
Moreover, when the measured temperature is lower than the starting temperature, calculate the
linear thermal expansion rate by using the v
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