GB/T 3074.4-2016Method for the determination of the coefficient of thermal expansion of graphite electrodes (English PDF)

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);

-- modified "room temperature ~ 600°C" to "delta T" in some calculation formulas (see Clause 7 of this Edition).

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

3 Definitions and principles

4 Instruments and equipment

4.1 Thermal dilatometer. where the temperature can reach above 600°C, protective gas (nitrogen or argon) can be introduced. The thermal dilatometer of which the error of two repeated tests during measurement is not more than ±0.1 x 10^-6°C-1 can be used.

4.2 Vernier caliper. the accuracy is 0.02mm.

5 Specimen preparation

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.

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.

7 Results calculation

The coefficient of thermal expansion of specimen, alpha (°C-1) is calculated according to formula (1).

8 Test error

The error of two repeated tests should not exceed ±0.1 x 10^-6°C-1.

9 Test report

The test report shall at least contain the following information. […]