Causes of waste products produced by carbon baking and graphitization

01 What are the causes of cracks and waste products in carbon products baking process?

Generally speaking, due to process reasons, many products produce transverse cracks and internal cracks，high density and low power consumption graphite electrode products for reference. However, due to this process, most of the products will produce columns. The causes of various cracks are as follows:

• 1. During molding, the material temperature is too low, the pre pressure is insufficient, and the molding pressure is insufficient.

• 2. The paste will be pulled off during the pressing return. Although the surface is smooth after pressing, the internal structure is not good.

• 3. The calcination degree of raw materials is not enough, or the ingredients are mixed with raw blocks, resulting in secondary shrinkage during calcination.

• 4. The plunger head of the press is coated with too much oil, and the joints of the two pots can not stick, resulting in cracks after baking.

• 5. The binder content of the product is too little and the powder content is too much.

• 6. The paste is not kneaded evenly or there is water in the paste.

• 7. The heating rate is too fast.

• 8. The product is too close to the furnace wall when loading.

• 9. The furnace wall leaks locally and is heated too fast.

• 10. The upper layer is loaded with large-size and less ash products.

02 What are the causes of oxidation waste products in baking furnace?

• 1. The product upper insulation is too thin.

• 2. The furnace chamber leaks and the motor box is ventilated.

• 3. The water content of the filler is too large, the blanking is not solid, and the product shrinks and sinks during baking, so that the product is exposed and oxidized.

• 4. The temperature was too high when the furnace was discharged, and the products were not dispersed in time when the site was cleaned.

03 What are the causes of crack waste products in the graphitization process?

The cracks produced during graphitization appear on the surface and inside of the product, which is due to the thermal stress caused by the temperature difference during heating. There are three kinds of cracks observed on the product surface: longitudinal crack, transverse crack and network crack. It is generally believed that the longitudinal crack is caused by the poor quality of baked products and is related to several processes before graphitization, while the transverse crack or network crack is closely related to the graphitization process.

• 1. During charging, the products are arranged irregularly, the resistance material is filled unevenly, and even there is the phenomenon of "shed material" of resistance material. When powered on, the current distribution is uneven, resulting in an increase in the temperature difference of products during heating.

• 2. The power transmission system is unreasonable, and the selected starting power and rising power are too high, resulting in too fast heating rate. The temperature difference between the surface and inside of the product increases, and the thermal stress caused by the temperature difference leads to cracks.

• 3. When the mixture of metallurgical coke and graphitized metallurgical coke is used as resistance material, if the mixture is uneven, the furnace core current will deviate, resulting in uneven temperature at all parts of the furnace core, and it is easy to produce a large number of crack wastes.

• 4. The production of the previous processes of graphitization is unstable, such as low calcined material temperature, low calcined product temperature, unqualified weight gain rate of impregnated products, etc. the carbon blank quality fluctuation caused by it will be intensively exposed in the graphitization process, that is, during graphitization high temperature treatment, the secondary shrinkage or uneven shrinkage of the aggregate in the product is very easy to produce crack waste products.

• 5. Graphitization furnace core current deflection, sometimes will also produce transverse cracks, to read more graphite products news consult us.