ZHENGSHAN TECHNOLOGY

Electrode paste, also known as self-baking electrode, is an important conductive material in mineral heat furnaces.It completes the roasting through the heat in the ore heat furnace, and the quality of its sintering process directly affects the mechanical strength and electrical conductivity of the electrode, as well as the safe and smooth operation of the calcium carbide furnace.In the sintering process of electrode paste, pressure control is a key factor. It not only affects the density and mechanical strength of the electrode paste, but also the sintering quality of the electrode paste and the service life of the electrode.This article will discuss how to correctly control the pressure in the sintering process of electrode paste from the aspects of the forming method of electrode paste, the pressure control in the sintering process, and the management of the height of the electrode paste column.

1. The forming method of electrode paste

In the production process of electrode paste, there are many molding methods, including molding, extrusion molding, vibration molding and isostatic compression molding.These methods have their own characteristics and are suitable for electrode paste products of different shapes and sizes.

Molding: Using a vertical press, the kneaded paste is pressed into a block or rod-like object through a mold.The molding method can be divided into one-way pressing, two-way pressing, hot pressing and cold pressing according to the process and equipment conditions.It is suitable for pressing products with small size in the three directions and little difference in size in the three directions, uniform density, dense structure and high strength.

Extrusion molding: A horizontal extruder is used to squeeze the paste out through the nozzle to form the electrode paste of the desired shape.The extrusion method is suitable for bars, pipes or other special-shaped products with relatively large L/D. It has high production efficiency and simple operation, but the bulk density and mechanical strength of the product are relatively low.

Vibration forming: The paste is loaded into a mold placed on the vibrating table of the vibration forming machine, and the high-speed vibration of the vibrating table is used to make the paste dense and formed.The vibration forming machine has a simple structure and is suitable for the production of large-size and special-shaped products.

Isostatic compression molding: It is completed in an isostatic pressure vessel, and the pressed powder is pressed by an ultra-high pressure liquid medium to form.Isostatic compression molding can produce isotropic products and special-shaped products. The structure of the products is uniform, and the density and strength are particularly high.

2. Pressure control in the sintering process

In the sintering process of electrode paste, pressure control is essential.The appropriate pressure can ensure that the electrode paste reaches the ideal density and mechanical strength during the sintering process, while avoiding the electrode paste from swelling the electrode cylinder due to excessive pressure or poor filling due to too small pressure, making it difficult to obtain dense electrodes.

Pressure control in molding: In the molding process, the pressure and time of the press need to be reasonably adjusted according to the physical properties of the electrode paste, the softening point of the binder, the amount of binder added, and the molding temperature.The choice of one-way pressing and two-way pressing, hot pressing and cold pressing also needs to be determined according to specific circumstances.
Pressure control in extrusion molding: During extrusion molding, the plunger pressure of the press needs to be reasonably controlled to ensure that the paste can pass through the nozzle smoothly during the pre-pressing and formal extrusion process to form the electrode paste of the desired shape.At the same time, the position of the cutter and the timing of cutting also need to be precisely controlled to ensure that the length of the electrode paste meets the requirements.

Pressure control in vibration molding: During vibration molding, the amplitude and frequency of the shaker, as well as the weight and position of the hammer, need to be reasonably adjusted to make the paste reach a dense state during the vibration process.At the same time, it is also necessary to control the size and shape of the mold to ensure the molding quality of the electrode paste.

Pressure control in isostatic compression molding: When isostatic compression molding, the pressure of the ultra-high pressure pump and the type of liquid medium (oil or water), as well as the material and shape of the mold, need to be reasonably set.By precisely controlling these factors, it is possible to ensure that the electrode paste is evenly pressed in a high-pressure environment, forming a dense structure and high-strength product.

3. Management of the height of the electrode paste column

The height of the electrode paste column refers to the height from the upper end of the electrode clip to the top of the electrode paste.The height of the suitable electrode paste column is conducive to improving the quality of electrode roasting and reducing consumption.If the electrode paste column is too high, the thickness of the particles in the electrode paste is prone to stratification, or the electrode cylinder is swollen due to the pressure of the paste column is too high; if the electrode paste column is too low, it is difficult to obtain a dense electrode due to the pressure of the paste column is too small and the filling is poor.

Control of the height of the ideal paste column: The height control range of the ideal paste column of the calcium carbide furnace is in the range of 3.5m to 4.5m from the upper end of the conductive element.Within this range, the pressure carried by the electrode paste per unit area is generally 0.35kg~0.45kg, which can ensure that the electrode paste obtains good compactness and mechanical strength during the sintering process.
Adjustment of the height of the electrode paste column: During the use of the electrode paste, the height of the electrode paste column needs to be adjusted according to the consumption speed and roasting speed of the electrode.If the electrode consumption is too fast, the electrode paste needs to be added in time; if the electrode consumption is too slow, the amount of electrode paste added needs to be appropriately reduced.At the same time, it is also necessary to pay attention to the particle size control of the electrode paste to avoid the failure of the electrode paste suspension or spraying phenomenon caused by the particle size being too large or too small.

4. The conclusion

Pressure control in the sintering process of electrode paste is a complex and important process.By selecting the appropriate molding method, reasonably adjusting the pressure and time, accurately controlling the height of the electrode paste column, and paying attention to the particle size control of the electrode paste, etc. Measures can ensure that the electrode paste obtains good compactness and mechanical strength during the sintering process, thereby improving the service life of the electrode and the production efficiency of the calcium carbide furnace.At the same time, it is also necessary to strengthen the quality management of the electrode paste to ensure that the ash, volatile and other quality indicators of the electrode paste meet the requirements, in order to reduce the occurrence of electrode accidents and improve the safe and smooth operation level of the calcium carbide furnace.