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Porosity And Mechanical Strength

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

Porosity definition

Porosity refers to the percentage of the pore volume in the test block to the total volume of the test piece. From the perspective of macroscopic structure, various carbonaceous raw materials, charcoal products and graphite products are composed of a solid skeleton and pores.

Porosity of graphite electrode

There are 3 types of pores
The pores in the test block can be divided into three types: closed hole (not connected to the outside world), open hole and through hole.


Impregnation has a significant effect on reducing porosity

The porosity of either carbonaceous materials or graphite electrodes is related to their true density and density. Impregnation has a significant effect on increasing density and also has a significant effect on reducing porosity.

5 precautions when using graphite electrodes

Select the appropriate electrode type and diameter according to the capacity of the furnace and the capacity of the transformer.
Take care to prevent damage and moisture during loading and unloading of graphite electrodes and storage.
When connecting the electrodes, blow off the dust in the nipple hole with compressed air, and clamp the holder above or below the bottom of the electrode nipple.
When loading the furnace into the furnace, the bulk material should be installed close to the bottom of the furnace.
During the melting period, the steelworker should be sensitive and raise the electrode in time.


Factors affecting the propertie.

The physicochemical properties of carbonaceous raw material and charcoal products are different from those of carbon. The physical and chemical properties of carbonaceous raw materials or charcoal products are closely related to their macroscopic structure and microstructure. The physicochemical properties of carbon products are not only affected by the nature of the raw materials, but also by the production process conditions.

5 factors that increase mechanical strength

The particle strength coefficient of the raw material is large.
The ingredients are composed of finer particle size.
The asphalt with higher softening point is used as the binder.
The degree of calcination of the raw materials affects the mechanical strength.
The impregnated electrode has a high mechanical strength.

Parameter of RP / HP / UHP Graphite electrode

Item Unit RP HP UHP
300-500mm 300-500mm 300-500mm
Electric resistivity Electrode μΩm 7.5-8.6 5.5-6.8 4.6-6.2
Nipple 4.5-6.0 4.0-5.5 3.5-5.0
Bending strength Electrode Mpa ≥7.5 ≥10.0 ≥10.5
Nipple ≥16.0 ≥18.0 ≥20.0
Elastic modulus Electrode Gpa ≤9.0 ≤13.0 ≤14.0
Nipple ≤13.0 ≤15.0 ≤20.0
Bulk density Electrode g/cm3 1.54-1.62 1.62-1.70 1.66-1.73
Nipple 1.70-1.78 1.72-1.80 1.75-1.82
CTE(100-600℃) Electrode 10-6/℃ 2.20-2.60 1.80-2.20 1.20-1.50
Nipple 1.50-1.90 1.50-1.80 1.10-1.40
Ash % ≤0.3 ≤0.3 ≤0.3


2 reasons why mechanical strength increases with increasing temperature

Graphite products do not produce local plastic deformation at low temperatures. When the temperature rises to a certain extent, the stress is dispersed due to the occurrence of plasticity.
When it is cooled from high temperature, it will generate large stress inside the pellet. Because the external stress superimposes the internal stress, the strength of graphite is low at low temperature, but the stress gradually decreases when heated to a certain temperature.

Definition of compressive strength

When the external force is pressure, the ultimate resistance of the object being crushed for a moment is called compressive strength (or compressive strength).

Definition of bending strength

When the external force is perpendicular to the axis of the object, the ultimate resistance of the object to the moment of bending to the moment of breaking is called bending strength (also called flexural strength).


Tensile strength definition

When the external force is the tensile force, the ultimate resistance of the object being broken is called the tensile strength.

Different force directions affect measurement data

The data measured by different force directions of the same test piece has a certain difference. For extruded products, the strength along the test block parallel to the extrusion direction is larger than perpendicular to the extrusion direction. For molded products, along the molded product The strength in the direction of the pressurization is larger than the direction perpendicular to the pressurization direction.

There are 5 external causes of damage

The external causes of damage to objects are mainly impact, shear, compressive strength, flexural strength and tensile strength.