GB/T 3074.4-2016 English PDF (GBT3074.4-2016)

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GB/T 3074.4-2016: Method for the determination of the coefficient of thermal expansion of graphite electrodes
GB/T 3074.4-2016
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 29.050
Q 51
Replacing GB/T 3074.4-2003
Method for the determination of the coefficient of
thermal expansion of graphite electrodes
ISSUED ON: AUGUST 29, 2016
IMPLEMENTED ON: JULY 01, 2017
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3 
1 Scope ... 5 
2 Normative references ... 5 
3 Definitions and principles ... 5 
4 Instruments and equipment ... 6 
5 Specimen preparation ... 7 
6 Test steps ... 7 
7 Results calculation ... 8 
8 Test error ... 8 
9 Test report ... 8 
Foreword
GB/T 3074 consists of four parts:
- GB/T 3074.1, Method for the determination of the flexure strength of
graphite electrodes;
- GB/T 3074.2, Method for the determination of the elastic modulus of
graphite electrodes;
- GB/T 3074.3, Method for the determination of the oxidation resistance of
graphite electrodes;
- GB/T 3074.4, Method for the determination of the coefficient of thermal
expansion of graphite electrodes.
This Part is Part 4 of GB/T 3074.
This Part was drafted in accordance with the rules given in GB/T 1.1-2009.
This Part replaces GB/T 3074.4-2003 “Method for the determination of the
coefficient of thermal expansion of graphite electrodes”. Compared with GB/T
3074.4-2003, main changes in this Part are as follows:
-- deleted the formula derivation process (see 3.2 of Edition 2003);
-- modified the extensometer in Figure 1 to the displacement measuring
device (see Figure 1 of this Edition);
-- added “can be accessed to protective gas” in the part of thermal
dilatometer (see 4.1 of this Edition);
-- modified the device for measuring expansion on thermal dilatometer from
dial indicator to displacement measuring device (see 4.3 of this Edition);
-- modified thermometer to temperature measuring device (see 4.4 of this
Edition);
-- deleted the processing requirements for temperature measuring hole from
the part of test size (see 5.1 of Edition 2003);
-- modified the specimen size from length to “shall not be less than 50mm”;
deleted the requirements for length deviation (see 5.3 of this Edition);
-- deleted the zeroing operation of dial indicator, modified as “record the initial
reading of the displacement measuring device or reset the device to zero”
(see 6.1 of this Edition);
Method for the determination of the coefficient of
thermal expansion of graphite electrodes
1 Scope
This Part of GB/T 3074 specifies determination principles, instruments and
equipment, specimen preparation, test steps and results calculation for the
coefficient of thermal expansion of graphite electrodes.
This Part is applicable to the coefficient of other solid carbon materials of which
the ordinary power, high power, ultra-high-power graphite electrode and total
expansion at 600°C does not exceed 1mm, of which the temperature range is
room temperature ~ 600°C. If it needs to test the coefficient of thermal
expansion in other temperature ranges, it may refer to this method.
2 Normative references
The following referenced documents are indispensable for the application of
this document. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any
amendments) applies.
GB/T 1427, Sampling method for carbon material
GB/T 8170, Rules of rounding off for numerical values and expression and
judgement of limiting values
3 Definitions and principles
3.1 Definitions
The coefficient of thermal expansion refers to the variable of thermal expansion
of material, that is, when the temperature rises by 1°C, the amount of expansion
in a certain direction caused by the solid material per unit length is called the
coefficient of linear expansion of the material in that direction.
3.2 Principles
As shown in the schematic diagram (see Figure 1), the specimen and the quartz
reference are installed on the same base and the other end of the specimen is
5 Specimen preparation
5.1 Sampling
In accordance with GB/T 1427.
5.2 Sampling quantity
Take 2 parallel specimen for each lot.
5.3 Specimen size
For cylindrical or rectangular specimen, its diameter or side length at least is
twice maximum aggregate diameter. For cylinder or cuboid, the specimen
diameter or side length shall not be less than 5mm, the length is not less than
50mm.
5.4 Specimen requirements
Both end faces shall be perpendicular to the specimen axis. Its parallelism is
not greater than 0.1mm/100mm. There are no visible cracks or defects on the
surface of the specimen.
6 Test steps
6.1 Turn on the thermal dilatometer heating furnace. Put the specimen into the
quartz tube in the furnace. Use quartz gaskets to cushion both ends of the
specimen. The specimen, quartz dilatometer, and quartz gasket shall be on a
central axis. Then place the temperature measuring end of the temperature
measuring device close to the side surface of 1/2 of the specimen. Close the
furnace lid. Record the initial reading of the displacement measuring device or
reset the device to zero.
NOTE: If the device does not have a quartz gasket, there shall be no operation procedure
about the gasket.
6.2 Start the power switch of the heating furnace. Adjust the voltage and current.
Record the time, temperature and expansion. Control the heating rate within
6°C/min. When the temperature rises to 400°C, the protective gas is supplied
to the heating furnace. The flow is 5L/min.
6.3 When the temperature rises to 600°C, record the amount of expansion after
insulating (600°C±5°C) for 5min. Adjust the voltage back to zero. When the
furnace temperature drops to about 400°C, stop the protective gas and turn off
the power switch.