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Resistivity and Modulus of elasticity

Release time:2019-11-04 From: Zhengnai Industry in China

Relationship between elastic modulus and stress

The greater the modulus of elasticity, the greater the stress required to produce a certain degree of elastic deformation, or the less the elastic deformation produced under a certain stress.


 

5 factors affecting the elastic modulus

  • The modulus of elasticity parallel to the direction of extrusion is greater than perpendicular to the direction of extrusion.
  • The elastic modulus of the graphite electrode increases as the temperature increases. Under normal circumstances, when the temperature rises to 1500 ° C, the elastic modulus of the Regular power graphite electrode is increased by about 25% compared with room temperature.
  • The larger the porosity, the smaller the modulus of elasticity.
  • The higher the degree of graphitization, the smaller the linear expansion coefficient of the product, and the elastic modulus is affected by the plastic deformation of the graphite crystal, so the elastic modulus is lowered.
  • The extrusion speed is fast, the elastic modulus of the finished product is high, the extrusion speed is slow, and the elastic modulus of the finished product is low.
     

Artificial graphite is a brittle material

The artificial graphite material is basically a brittle material, and is susceptible to brittle fracture after being subjected to a certain stress at room temperature.
 
 

Definition of thermal conductivity

Thermal conductivity is the amount of heat transferred per unit area per unit time of a material sample under a unit temperature gradient.


 

Thermal conduction of solid materials

The thermal conduction of solid materials is dependent on the thermal vibration of the crystal lattice and the flow of free electrons. For most metals, the thermal conduction of free electron flow is dominant. For many non-metallic materials, the thermal conduction mechanism is primarily the thermal vibration of the crystal lattice.
 

3 factors affecting the conductivity

The factors affecting the conductivity of the conductor are mainly
The resistance of the conductor, the smaller the resistance of the material, the easier the current to pass.
the length of the conductor material, and the magnitude of the conductor resistance is proportional to its length.
It is inversely proportional to the size of its cross-sectional area.
 

2 methods for measuring resistivity

Determine the electrical resistivity of the powdered material, as used to determine the electrical resistivity of the raw material after calcination.
Determine the resistivity of the entire electrode of the semi-finished or finished product.

Size of UHP graphite electrode

Item Unit UHP
300-600mm 650-800mm
Electric resistivity Electrode μΩm 4.8-5.8 4.6-5.8
Nipple 3.8-4.5 3.8-4.5
Flexural strength Electrode Mpa 10.0-14.0 10.0-14.0
Nipple 20.0-26.0 22.0-26.0
Elastic modulus Electrode Gpa 9.0-13.0 10.0-14.0
Nipple 15.0-18.0 15.0-18.0
Bulk density Electrode ≥g/cm3 1.68-1.74 1.70-1.74
Nipple 1.77-1.82 1.78-1.84
CTE(100-600℃) Electrode x10-6/℃ 1.1-1.4 1.1-1.4
Nipple 0.9-1.2 0.9-1.2
Ash   0.3 0.3

 

5 factors affecting the resistivity of graphite electrodes

Raw materials.
The final heat treatment temperature of the finished product.
The density of the finished product.
Resistivity and test temperature.
Anisotropy of graphite electrode resistivity.
 

Method for reducing the resistivity of a finished product

When producing carbon products, adding a certain amount of natural graphite or graphite to the formulation is beneficial to reduce the electrical resistivity of the finished product.
The resistivity of the graphite electrode produced by petroleum coke with pitch coke is also lower.
The difference in residual oil is that the graphite electrode produced by petroleum coke produced using a residue containing a lower sulfur content is slightly lower in electrical resistivity.
Graphite electrodes produced by needle coke have lower resistivity at the same graphitization temperature.


 

Relationship between resistivity and firing temperature

The resistivity of the carbon product is the highest temperature of the calcination, and the resistivity of the graphite product is related to the highest temperature of graphitization. The higher the temperature, the lower the resistivity.
 

Effect of test temperature on resistivity

The test temperature has an effect on the electrical resistivity of the conductor. Different materials have different degrees of change in resistivity when the test temperature rises, that is, different materials have different temperature coefficients of resistance. When the test temperature rises, the resistivity of the conductor decreases, and the temperature coefficient of resistance of such materials is negative.
 

Anisotropic judgment of molding method and resistivity

The forming method of the graphite electrode can be judged by the anisotropy of the resistivity of the graphite electrode, that is, the size of the resistivity of the test piece in different test directions is used.
 
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