graphite electrode hp

Pubdate: 07-09 2021

In the extrusion process, the factors affecting the quality of graphite electrode hp green body by temperature

graphite electrode hp

1. When the mixture is dry mixed in the kneading tank for a period of time, the temperature of the mixture measured when preparing to add asphalt is called the dry material temperature.

The temperature of the dry material has an important influence on the density of the green body. The temperature of the drying material is low. When the asphalt reaches the specified temperature (generally set according to the softening point of the asphalt) and enters the dry material for kneading and soaking, due to the effect of heat exchange, the temperature of the added asphalt decreases, thereby increasing the viscosity of the asphalt, resulting in a gap between the asphalt and the material The soaking angle is reduced, resulting in poor wettability of the asphalt to the material, thereby affecting the plasticity of the paste. The asphalt content on the surface of this slurry is too large, but the actual material diverges, which will mislead whether the asphalt content is appropriate or not, and will also mislead the cooler to determine the blanking temperature during the molding process. According to the principle of high oil and low oil, the blanking temperature is actually lower, resulting in an increase in waste products such as cracks, bubbles and internal cracks.

At the same time, due to the soaking of the material, the difference in the movement speed of the material during the extrusion process can easily lead to an increase in layered waste. In addition, due to uneven penetration of asphalt and low temperature, the paste in the cylinder is not tightly meshed, resulting in a low weight of the extruded billet (each factory has its own prescribed length). In addition, when vacuuming during the molding process, due to the effect of negative pressure, part of the impermeable part of the asphalt in the paste retracts to the surface, and the contact surface between the nozzle and the material is more serious, making the internal penetration of the material more uneven. When the same pressure is squeezed, it will also cause the material to squeeze unrealistically, thus affecting the individual weight. At the same time, it also increases the elastic expansion and diameter of the green body, resulting in a low density of the green body.

2. The influence of asphalt temperature on green density

The bitumen temperature refers to the bitumen temperature measured when the bitumen is melted and added to the kneading tank. Generally, industry experts believe that the temperature of asphalt is about 1.8 times the softening point of asphalt. At this temperature, the penetration angle of asphalt to the material is the best to ensure that when the dry material temperature reaches the specified value, the viscosity of the asphalt will not be affected. Only when the temperature of the paste is controlled at 1.5-1.7 times the softening point of the asphalt can it be obtained. Only better plastic paste can obtain green bodies with high bulk density and good quality.

3. The influence of blanking temperature and paste chamber temperature on the density of green body

In actual production, whether it is a plate cooler or a roller cooler, the temperature difference between the inside and outside of the material block exists in the cooling equipment. What is the temperature difference between the inside and outside of the material? In order to facilitate operation and minimize errors, some manufacturers now use the core temperature of the raw material extrusion as a control parameter as a basis for adjusting the raw material temperature. Practice has proved that the temperature (reflecting the cutting temperature) has a great influence on the density of the blank. When the cutting temperature is low (the measuring center temperature is SP+0~5~C), the cutting temperature of the slurry is low, and the same pressure extrusion density is low when the slurry is extruded in the material cavity, resulting in a higher unit weight low. The reason has been explained above, and the degree of vacuum determines the diameter. Therefore, it is only the single weight that determines the body density, and the single weight of low body density is very low, which runs counter to our desire to obtain a high-density green body.

When the cutting temperature increases slightly, the center temperature of the extruded billet is SP+Lo~L5°C, ​​because the punching temperature is reasonably matched with the temperature of the nozzle and the material chamber, and the temperature difference is less than 5~C; the green billet after extrusion is not only a net The hole is tight and the extrusion is tight, and it will not cause the second heating of the asphalt layer on the contact surface of the nozzle and the material, so that the extruded product will not only increase the weight of a single piece, but also will not have a large anti-expansion in diameter, thereby obtaining a large accumulation Density lays a solid foundation for the high bulk density of electrodes in a short process.


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