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Crushing and milling

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

The difference between crushing and milling graphite electrode

The crushing is to change the larger block material into smaller pieces or granular materials, and the grinding is to grind small pieces or granular materials into powdery materials.

5 levels of smash

The crushing can be divided into several grades such as coarse crushing, medium crushing, fine crushing, coarse grinding, fine grinding and ultrafine grinding, but there is no strict distinction between them.

Mainly use three crush graphite electrode material levels

  • 1. Crushed or pre-crushed, which refers to the crushing of large raw materials before entering the calcining furnace. Generally, the raw materials with a degree of 50~200mm are broken into small pieces of 50mm or less.
  • 2. Generally speaking, the calcined raw material is further crushed into several granules of 1~20mm required for the batching.
  • 3. grinding, and a part of the calcined raw material is ground into a powdery small particle size of less than 0.15 mm or less than 0.075 mm by a mill. Particles.

Fine particle charcoal requires smaller particles

The production of certain fine-grained carbon products sometimes requires the use of ultra-fine grinding machines (such as jet mills) to grind the material into smaller particles.

Crush ratio definition

The pulverization ratio indicates the extent to which the particle size of the material is reduced during the pulverization process.

Specifications of graphite electrode

Item Unit RP
Electric resistivity Electrode μΩm 7.8-8.8
Nipple 5.0-6.5
Flexural strength Electrode Mpa 7.0-12.0
Nipple 15.0-20.0
Elastic modulus Electrode Gpa 7.1-9.3
Nipple 12.0-14.0
Bulk density Electrode ≥g/cm3 1.53-1.56
Nipple 1.70-1.74
CTE(100-600℃) Electrode x10-6/℃ 2.2-2.6
Nipple 2.0-2.5
Ash   0.5

Mineral hardness is arranged from small to large

The mineral hardness sequence is divided into ten grades, from small to large:
  • (1) talc,
  • (2) gypsum,
  • (3) calcite,
  • (4) fluorite,
  • (5) apatite,
  • (6) feldspar,
  • (7) Quartz,
  • (8) Topaz,
  • (9) corundum,
  • (10) diamond.

Most carbonaceous materials are medium hard minerals

Most carbonaceous materials or charcoal products have hardness equivalent to medium hard minerals, while natural graphite is a soft mineral.

Definition of material mechanical strength

The mechanical strength of a material is the ability to resist chipping and anti-wear under mechanical or thermal stress.

The cause of the graphite electrode damage process is affected

Various cokes are bulk porous bodies which are structurally uneven and contain cracks and internal defects, so their failure process is affected by the crushing resistance of the coke pore walls (strength and thickness of the pore walls) and coke structural defects.