graphite manufacturing process workflow
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1. Raw Material Storage

Raw coke materials are typically stored in large storage silos before being inserted into the production process.


2. Crushing

The first step in graphite manufacturing involves crushing and pulverizing the raw coke materials, such as coal and petroleum, into a micro-fine powder. This is typically done using crushers and mills that break down the raw materials into smaller particles.


3. Milling

After the raw coke materials are crushed and pulverized into a micro-fine powder, the next step in the graphite manufacturing process is to mill the powder in a centrifuge system. This is typically the first stage of the particle size separation and selection process.


4. Vibration and Sieving

After the powder is milled in the centrifuge system and the larger and heavier particles are separated, the next step in the graphite manufacturing process is to subject the powder to a vibration and sieving operation. This is typically the second stage of the particle size separation and selection process.


5. Storage & Pitch Binder = Kneading & Mixing

After the powder has been separated by size and selected for further processing, the next step is to mix the powder with a pitch binder and then kneaded and mixed to make a blended paste.


6. 2nd Stage Milling

The paste passes through a 2nd stage milling process to break down any large lumps or agglomerates of paste that may have formed during the mixing process. This helps to ensure that the paste is a uniform consistency and texture.


7. ISO-Static Pressing

After the paste has been milled to the desired consistency, it is typically used to fill rubber molds of various shapes and lengths.

The molds are designed to create green-formed blocks, which are pre-graphitized blocks formed into a specific shape but have yet to be fully graphitized. The molds are typically made of rubber because rubber is flexible and can be easily removed from the green-formed block after it has been pressed.


8. Baking

The baking process typically involves heating the green-formed blocks in a high-temperature furnace to remove any remaining volatile materials and improve their strength and density. This process is sometimes referred to as “carburizing” because it involves converting the carbon material into a more pure and stable form.

The carbon blocks are baked in a heavy oil-fueled furnace at temperatures greater than 1,000°C to remove liquids and impurities.


9. Graphitizing

After baking, the carburized blocks are cooled down to room temperature and then placed in an electric-powered furnace. This furnace heats the blocks to temperatures greater than 2,000°C degrees, which causes the carbon atoms to rearrange themselves into graphite’s highly ordered, crystalline structure.

The graphitization process can take up to 2 months, depending on the desired properties in the final product. During this time, the blocks are carefully monitored and controlled to ensure they are heated to the correct temperature and duration.


10. Inspection

After graphitization, the blocks are carefully inspected for internal and external defects, such as cracks or voids. This is typically done using visual inspection, ultrasonic testing, and X-ray inspection techniques.

In addition to defect inspection, samples are taken from each block to determine its properties and ensure that it meets the specifications for its intended use. The specific properties tested will depend on the grade of graphite being produced, but commonly measured properties include:

  • Density
  • Specific resistance
  • Flexural strength
  • Shore hardness
  • Average grain size
  • Coefficient of thermal expansion (CTE)
  • Total ash content
  • Gas permeability

Tokai Carbon has a rigorous quality system to ensure that every block produced meets the required standards. Testing properties help ensure that the graphite blocks are of the highest quality and meet the requirements of their intended applications.

The traceability of the blocks through lot and case number identification is also an essential aspect of the quality control process, as it allows any issues or defects to be identified and addressed quickly and efficiently.

Overall, the manufacturing process of graphite is complex and involves multiple steps. Nevertheless, it is a versatile and valuable material widely used in many industries.