How is a vacuum arc furnace used to smelt bearing steel
High power arc furnace initial refining
Main tasks: melting scrap steel, decarburization, dephosphorization and heating; Carbon content in the furnace can be allocated to 1.00%-1.3%, with ore, oxygen decarburization, dephosphorization, automatic slag flow, eccentric steel out, retained slag. The carbon content can be controlled at the lower limit of high carbon chromium bearing steel when steel is produced. It is required that the molten steel of the primary furnace should be low oxidized and low temperature to prevent the oxidized slag from entering the ladle.
LF ladle furnace
Purpose of LF refining: deoxidization, sulfur reduction, alloying, adjustment of ingredients, and control of proper casting temperature. The central task of bearing steel: deoxygenation; Before LF is heated, aluminum is used to precipitate and deoxygenate the steel solution, and then heat, adjust the steel solution composition, adjust the refined slag composition, and blow argon to stir. Rapid desulphurization and desulphurization of alkaline slag.
The bottom blowing argon control is too large, the steel slag reaction is too intense and the steel liquid scours the refractory seriously, the oxide and titanium compound enter the steel liquid; The temperature, composition and slag reaction of supersmall liquid steel are not uniform and sufficient. Proper bottom blowing argon system: in the early stage of refining, it is stirred with greater argon pressure. In the later stage, the titanium content is basically stable in the refining process by stirring with less argon pressure, and the activity of sulfur and oxygen content is continuously decreased.
VD vacuum degassing
The main purpose is to dehydrogenate in vacuum, continue deoxygenation in carbon deoxygenation under vacuum, stir with argon to remove inclusions, generally without obvious denitrification. Before entering the VD, remove the slag, reduce the slag alkalinity, and control the blowing argon intensity. In the early stage, argon blowing is not greater than 0.2mpa, and in the later stage, it is less than 0.1mpa, which can make the steel liquid and furnace slag fully react and the deoxidization product fully float. The deoxygenated products could not float up sufficiently during the vacuum time. The overlength refractory surface is washed and spalled into the molten steel for a long time, which is not conducive to the control of titanium content in the steel. The content of non-metallic inclusions was controlled by soft blowing argon stirring after vacuum degassing.