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Extrusion process of graphite electrode

Release time:2019-12-09 From: Zhengnai Industry in China

Factors that determine the fluidity of the paste

The flow characteristics of the paste during extrusion depend on the type of paste, the temperature of the extrusion process, the shape of the nozzle and the surface finish, and the extrusion ratio.

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The ideal state of the paste through the extruded nozzle

The ideal movement of the paste through the extrusion nozzle is that all flow cross sections are subjected to shear forces, and there is no slip layer in the layer, which is practically difficult to achieve.

Extrusion process of graphite electrode

The paste which is loaded into the extruder chamber during the extrusion molding process discharges the gas trapped in the paste agglomerate under the pressure of the pressurized plunger, and tends to become dense, and plastically deforms when passing through the extruded nozzle, and then passes through The straight line segment is finally extruded.

Determinants of extrusion product size

The cross-sectional shape and size of the extruded product is determined by the shape and size of the inner cross section at the exit of the extruded nozzle.

Factors affecting the friction of the paste

1. The magnitude of the external friction depends mainly on the temperature of the friction surface.
2. The internal friction of the paste is mainly determined by the particle size composition of the ingredients, the softening point and amount of the binder, the paste temperature and the extrusion pressure.

The benefits of adding a small amount of minerals during kneading

Adding a small amount of mineral, stearic acid or paraffin during kneading helps to improve the plasticity and lubricity of the paste, lower the external friction coefficient and the internal friction coefficient, thereby improving the yield of extrusion molding.

Principle of extrusion equipment

The principle of the extrusion molding equipment is to push the plunger to pressurize the paste in the material chamber by means of the high-pressure liquid medium. The paste is extruded from the extrusion nozzle, the cross-sectional shape and size of the green body and the outlet of the extruded nozzle. The cross-sectional shape and size are the same.

There are 2 kinds of extrusion equipment

There are two types of extrusion equipment: hydraulic press and hydraulic press. The construction and operation principle of the two devices are basically the same.

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

Our factory uses more hydraulic presses

Because the water press has strict requirements on water quality and the operation is not as convenient as the hydraulic system, the hydraulic presses in our factory are gradually reduced, and the use of hydraulic presses is increasing.

Extrusion machine tonnage selection

The tonnage of the extruder is mainly selected according to the specifications, size and process requirements of the product. Firstly, the diameter of the chamber is selected according to the diameter and extrusion ratio of the product, and then the maximum pressure required for extrusion is determined.