November 5, 2025
The vacuum degassing process begins with the suction of molten steel into a vacuum chamber. Subsequently, argon gas is introduced into the molten steel along the side walls of two risers. Under the high temperature of the molten steel and the low pressure in the upper part of the vacuum chamber, the argon gas rapidly expands. This expansion causes the density of the mixture of molten steel and gas to continuously decrease along the height of the immersion tube.
Driven by the pressure difference resulting from this density variation, the molten steel flows into the vacuum chamber. Once inside, the mixture of molten steel and gas releases gas under the influence of the high vacuum environment. Simultaneously, the molten steel transforms into small droplets, or beads, which further release the gas to be removed into the vacuum. Throughout this process, the molten steel beads are broken down into even smaller droplets, achieving an excellent degassing effect.
The degassed molten steel then returns to the ladle via a downcomer. After undergoing several such cycles, the gas content in the molten steel can be significantly reduced to a relatively low level.
During the initial phase of cyclic treatment, sampling and temperature measurements are conducted every 10 minutes. As the treatment nears completion, these measurements are taken every 5 minutes. Based on the sampling and analysis results, if alloy materials (including deoxidizers or other additives) need to be added, an automatically controlled feeding hopper can be utilized to introduce these materials into the vacuum chamber at a constant rate without disrupting the vacuum.
Enhanced Degassing Effect: The introduction of driving gas generates a large number of bubble nuclei in the riser, causing the molten steel entering the vacuum chamber to be sprayed into fine droplets. This significantly increases the surface area available for degassing, facilitating efficient gas removal.
Minimal Temperature Drop: Typically, the temperature drop during treatment is only 30-50°C. Moreover, electric heating can be applied during the degassing process, reducing the need for excessive overheating of the molten steel in the furnace.
Wide Processing Range: The same equipment can handle molten steel of varying capacities and is compatible with both electric arc furnaces and induction furnaces.
Due to these advantages, the vacuum cycle degassing method has experienced rapid development and widespread application.
According to statistics, over 100 RH devices have been put into production, with the largest equipment having a processing capacity of 350 tons. Several factories in China have also adopted RH devices. For instance, Daye Steel Plant installed a 60-100t RH device (commissioned in 1967), followed by Shanghai Heavy Machinery Plant (commissioned in 1972), Wuhan Iron and Steel Company's second steelmaking plant (1#RH in 1979, 2#RH in 1990), and Baoshan Iron and Steel General Plant's steelmaking plant (put into operation in December 1985). Practice has demonstrated the operational flexibility of this equipment.
Induction melting vacuum degassing furnaces can perform the following conventional processes:
