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Upper surface contact specific pressure selection

Release time:2019-12-11 From: Zhengnai Industry in China

Upper surface contact specific pressure selection

The upper surface contact specific pressure also has an effect on increasing the green density and shortening the vibration time.When standing upright, the green contact pressure of the large cross section is not too high, and the specific pressure should be larger for the slender green contact.

The relationship between the amount of binder and vibration molding

The vibration molding is used to overcome the internal friction of the paste and the force of the paste on the external friction of the molding die is much smaller than that during the extrusion molding, so the plasticity of the paste can be lower than that during the extrusion molding, and the same specification product can be produced. The amount of binder can be reduced by 1% to 2% compared to extrusion.

The temperature of the paste used for vibration molding can be slightly higher

The paste used for vibration molding also needs to be cooled for a short time before charging, but it does not have to be cooled for a long time like extrusion molding. It can be loaded into the molding die with a little cooling because the paste temperature is higher. The internal friction of the paste is small when vibrating

The difference between standing vibration and lying vibration

  • 1. Vertical vibration is to fix the mold vertically on the vibration table, and it is beneficial to produce short, thick and fat products for vertical vibration.
  • 2. The horizontal vibration is to lie on the mold and fix it on the vibration table. The product with large length/diameter ratio is better for lying vibration. When using the horizontal vibration method, the density of the green body along the length direction is relatively uniform.

Comparison of extrusion molding and vibration molding products

  • 1. The anisotropy of some physical and mechanical indexes of extrusion molding products is large, and the anisotropy of vibration molding products is small.
  • 2. The same graphitization high temperature treatment, the vibration forming electrode and the extruded electrode are not significantly different in axial resistivity, and the radial thermal conductivity is superior to extrusion.
  • 3. From the index of elastic modulus, the vibration molding products are small.
  • 4. The vibration molding product has a low binder content, which is beneficial to increase the density of the finished product.


Plastic deformation process of paste in extruded nozzle

The paste in the chamber must be plastically deformed through the extruded nozzle to obtain a green body of a prescribed size (diameter or cross section). The plastic deformation of the paste during extrusion mainly occurs in the deformation zone of the extrusion nozzle, and the plastic deformation process of the paste in the extrusion nozzle is more complicated.

Single arc curve deformation is simpler

The design of the single arc curve deformation is relatively simple, because the inlet diameter of the deformation zone is equal to the inner diameter of the material, and the diameter of the outlet of the deformation zone is equal to the diameter of the desired green body.

Size of 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

Propose the cause of multi-arc curve deformation

Because the diameter of the green body is very different, the single arc curve deformation is difficult to meet the extrusion requirements of various specifications of the green body, so the design method of multi-arc curve deformation is proposed.In order to overcome the adverse effects of the single arc curve deformation due to improper selection of the length of the deformation zone

Extruded nozzle deformation zone can be linearly deformed

The deformation of the extruded nozzle can be linearly deformed. As long as the linear deformation zone has sufficient length, the extrusion effect is also good. The extrusion nozzle whose deformation zone is linearly deformed is also relatively easy to manufacture.