graphite electrode news

Pubdate: 07-12 2021

Graphite electrode news and the choice and use of adhesives in the production of graphite products

The purpose of producing graphite electrode news and graphite products with a binder is to bond various particles as aggregates, and to make the kneaded hot paste have good plasticity for molding. In the roasting process of the formed raw product, the pitch coke produced by the coking of the binder itself firmly connects the aggregate particles into a whole.

graphite electrode news

The quality and physical and mechanical properties of various graphite electrode news and graphite products depend to a large extent on the nature of the binder and the infiltration, penetration and bonding force of the binder to the carbon material particles. The graphite electrode news and the binder used in graphite products are made of thermoplastic materials. Thermoplastic material is solid at room temperature, it melts into liquid when it is slightly heated, and can be adsorbed by carbon material particles to bond to each other into a paste. After the paste is press-formed, it can be hardened and fixed in shape after a little cooling, so it is easy to stack and Handling. The binder should have a higher carbon content and residual carbon ratio (that is, the percentage of coking residual carbon after roasting).

graphite electrode news

In addition, the adhesive must be a material that is relatively inexpensive and can be supplied in large quantities. At present, only coal pitch can better meet the above requirements. Coal pitch can be divided into soft pitch (softening point below 65℃, measured by mercury method), medium pitch (softening point 6575℃) and hard pitch (softening point above 75℃) according to its softening point. For coal pitch without special treatment, the higher the softening point, the higher the free carbon content, the lower the volatile content, and the greater the residual carbon rate after roasting. At present, most carbon plants use medium pitch as a binder, and only a few plants use hard pitch. Using hard asphalt can improve the quality of products, such as density and mechanical strength. However, the use of hard asphalt must increase the melting temperature of the asphalt and the temperature of the kneading type. For some products (such as all electrode pastes in enclosed calcium carbide furnaces or ferroalloy furnaces), in order to appropriately speed up the sintering speed of electrode pastes, it is necessary to add a small amount of coal tar or anthracene oil to the medium pitch to reduce the softening point of the binder to about 50°C . When producing fine seam pastes for building blast furnace carbon blocks, more anthracene oil or coal tar is required to be added.

The amount of binder also has a great influence on the quality of graphite electrode news. If the amount of binder is too small, the plasticity of the paste after kneading will be poor, the pressure of extrusion molding or compression molding needs to be increased correspondingly, and the possibility of cracking waste is much greater; if the amount of binder is too much, the production The product is easy to bend and deform after firing, the porosity increases and the mechanical strength decreases. The amount of binder used in graphite electrode news and graphite products is generally determined as follows: ①The product particle size composition is relatively coarse, that is, the number of powdery small particles is small, and the size of large particles is larger. The amount of binder should be cut back. On the contrary, the particle size composition is relatively fine (fewer large particles, more powdery small particles), and the amount of binder must be increased. Therefore, the amount of bonding agent for graphite electrode news with small diameter is less, and the amount of bonding agent for graphite electrode news with larger diameter is more. ②The amount of binder has a great relationship with the surface properties of raw material particles (such as porosity and adsorption to asphalt). The surface of anthracite particles is smoother, has fewer pores, and has poorer asphalt adsorption. Therefore, the amount of binder used in products such as carbon blocks and electrode pastes with anthracite as the main component is less.

The surface of the particles of petroleum coke and pitch coke is a honeycomb structure, and the specific surface area is large, and the adsorption of pitch is good. Therefore, graphite electrode news and graphite products using petroleum coke and pitch coke as raw materials need more binders. Graphitized crushed and graphitized metallurgical coke have better adsorption of pitch. Therefore, when graphitized crushed or graphitized metallurgical coke is added to the ingredients, the amount of binder should be appropriately increased. ③The molding method of the product is directly related to the amount of adhesive. For example, extrusion molding requires the paste to have better plasticity, so the amount of binder should be more; on the contrary, the amount of binder for compression molding can be less. Coal pitch is generally used after melting. This is because the coal pitch entering the plant contains a lot of moisture and some mechanical inclusions. The coal tar pitch is unloaded in the melting tank, melted and stood for 3-7 days at a temperature of 120-150℃, so that the moisture in the pitch is reduced to less than 0.2%. Anthracene oil or coal tar should also be heated and dehydrated in the melting tank to less than 0.5%. While melting, the mechanical inclusions also settle to the bottom of the tank.

The temperature of the molten asphalt should not be too high, so as to prevent the volatiles in the asphalt from decomposing and volatilizing in advance and reducing the cohesiveness of the asphalt. In some cases, if the asphalt has little moisture, solid asphalt can also be used directly. Before use, the solid asphalt is broken into smaller particles. As a graphite electrode news manufacturer, CGM new material uses domestic high-quality pitch coke to ensure that each batch of products can meet the qualified factory requirements.


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