Vacuum degassing guide to principle, process and parameters

Vacuum degassing furnace principle

Vacuum degassing furnace is composed of touch screen, vacuum chamber, butterfly valve, roots pump, vacuum pump and chiller.

What is vacuum degassing furnace refining method? Vacuum degassing furnace is to place the initial molten steel of electric furnace and converter in a closed tank. A vacuum treatment method of molten steel in which vacuum is evacuated inside and argon is blown at the bottom of the ladle to stir. After melting and preliminary blowing in electric furnace and converter, it is placed in a vacuum tank through bottom blowing argon stirring and vacuum degassing process to obtain pure molten steel. Vacuum degassing furnace is a widely used vacuum refining equipment with good degassing and deoxidizing effects. Vacuum degassing furnace can effectively reduce the content of hydrogen and nitrogen in steel, remove oxygen in steel through carbon and oxygen reaction, and pass Sufficient reaction of alkaline top slag and molten steel for desulfurization, in addition, the vacuum degassing furnace also has the function of uniform composition and temperature.

Vacuum refining furnace process

Vacuum degassing is carried out in the furnace body under a special vacuum environment. After a series of process operations, the product can achieve the specified effect.

First, the molten steel is sucked into the vacuum chamber, and then argon gas is blown into the molten steel through the side walls of the two riser pipes. The argon gas expands rapidly under the action of the high temperature of the molten steel and the low pressure in the upper part of the vacuum chamber, which causes the density of the mixture of molten steel and gas to continuously decrease along the height direction of the immersion tube. The molten steel enters the vacuum chamber.

The mixture of molten steel and gas entering the vacuum chamber releases gas under the action of high vacuum, and at the same time, the molten steel becomes molten steel beads, and the gas to be removed in the molten steel beads is released into the vacuum under the action of high vacuum. In the process, the molten steel droplets are turned into smaller ones, so as to achieve a very good degassing effect. The degassed molten steel is returned to the ladle along the downcomer. After several cycles of this, the gas in the molten steel can be reduced to a relatively low level.

In the early stage of the cycle treatment, sampling and temperature measurement are required every 10 minutes; at the end of the treatment, sampling and temperature measurement are required every 5 minutes. According to the results of sampling analysis, if it is necessary to add alloy materials (including deoxidizers or other additives), the automatic control feeding hopper can be operated, and the alloy material can be added to the vacuum chamber at a constant feeding rate without breaking the vacuum. .

Industrial vacuum furnace process parameters

When using a vacuum degassing furnace, reasonable selection of process parameters is of great significance to obtain a good degassing effect, increase the life of the vacuum degassing furnace lining and save operating costs.

1. The processing capacity refers to the capacity of the molten steel to be processed. If the amount of molten steel is too small, the temperature will drop too quickly and the processing purpose will not be achieved. The general capacity of the ladle is ≥30t. When the molten steel capacity is larger, the thermal stability is better, and the treatment can be carried out calmly to achieve good treatment results.

2. The cycle factor, also known as the number of cycles, refers to the ratio of the amount of molten steel passing through the vacuum chamber to the amount of molten steel in the ladle during the treatment process. The general circulation factor is 3, that is, the degassing process is completed after 3 cycles.

3. The pressure of the vacuum chamber of the vacuum degassing furnace is about 50~100Pa. After 3 cycles, the degassing treatment of molten steel is completed. Each cycle takes 3min, 3 times a total of 10min, plus 5min for alloying and other operations , a total of 20min. Therefore, the vacuum cycle degassing has the characteristics of fast processing rhythm, which can be matched with the rhythm of converter refining. The rhythm of vacuum cycle degassing equipment used in electric arc furnace workshops can be slower.

4. The circulating flow of the vacuum cycle refers to the molten steel volume (t/min) passing through the rising pipe per unit time. The factors that affect the circulation flow are the diameter of the riser or the descender; the flow rate of the lift gas; the distance of the lift gas from the molten steel surface of the vacuum chamber. Increasing the values of these parameters can improve the circulating flow of molten steel, but if the increase is too large, the density of the mixture of molten steel and gas will be too small, and the gas will block the passage of molten steel and reduce the circulating flow.

5. The vacuum pump must have sufficient capacity to ensure the vacuum level during degassing and to ensure the quality of molten steel. When designing or using a cyclic degassing device, reasonable selection of process parameters is of great significance to achieve good degassing effect, longer lining life and reduce operating costs.

Parameters such as processing capacity, circulation factor, processing time, circulation flow, vacuum degree and vacuum pump pumping capacity are the main process parameters that should be considered in the operation and design of the circulation degassing method.