Steel Degassing

Hardly any material has influenced world economic development to such an extent as steel. It not only plays an important role in industry but also in our everyday life. Steel is used in the manufacture of machinery, plants, bridges, buildings, ships, cars and household appliances. The economic growth of emerging markets makes it the most important metallic material of the 21st century. For producing high quality steels, the use of vacuum is essential for reducing certain amounts of interfering elements from the molten mass.

Application requirements

Dry pumps with high resistance to dust
High suction speed in first stage of pumping unit (up to 1 million m3/h)
Fast pump down of the chamber
High differential pressure operation & ATEX compliance for VOD process

Functional Principle of the Pfeiffer OktaLine Roots pump

How does it work?

For each type of element, different processes are required:

VD/RH: Vacuum Degassing (VD) and Ruhrstahl-Heraeus (RH) processes are mainly used for reducing the amount of hydrogen in the molten mass. The system needs to get pumped down to 0.67 mbar in a few minutes. During the process, a suction speed of up to 1 million m3/h is needed to evacuate the process gases and the arising dust of the slag and to perform a leak rate of the system.

VOD: Vacuum Oxygen Decarburisation (VOD) process is used to reduce the amount of carbon in the molten mass. In this process higher pressures are required so the use of explosion proofed pumps are essential. In the process Oxygen is blown into the ladle. Together with the carbon from the molten steel, CO and CO2 are produced and discharged. Typical operating pressure is in the range of 10-120 mbar, and required pumping capacity between 20,000 to 120,000 m3/h.

Often these process steps are done on the same ladle with the same pumping unit, which makes it necessary to have a customized pumping unit and broad working range. Typical chamber size for VD and VOD processes including piping and bag filter is in the range of 50 to 500 m3.

VIM: Vacuum Induction Melting (VIM) is used to melt and treat high quality steel under vacuum. Complete process runs in multiple chambers of different sizes, such as melting chambers, casting chambers or charging chambers. The melting process runs under high vacuum at about 1E-3 to 1E-4 mbar operating pressure, while other processes run in the 1E-2 mbar pressure range.

VAR: Vacuum Arc Remelting (VAR) is used to create super alloys, by using a consumable electrode by means of an arc under vacuum. The electrode melts the steel and is part of the alloy after the process at the same time. Pollution from the former steel gets into the slag. Process runs under high vacuum (1E-4 mbar range) to refine the structure and remove the smallest air pocket inside the final material. Chamber size for such process is in the range of 5 m3.

Product portfolio

Pfeiffer offers a complete solution for steel degassing applications, from vacuum pumping units to RGAs including pressure gauges. Through the calculation of the suction speed required and through the definition of customized pumping units, Pfeiffer supports you with vacuum technology that perfectly matches the requirements of each production process step. Depending on the pressure range and size of the pumping unit, several concepts can be proposed based on two, three, or even four stages Roots pumping units along with rotary vane pumps or dry screw pumps as backing pumps. Multiple stages concepts have the benefits of providing lower power consumption and lower base pressure. Our unique OktaLine G Series have the advantage to handle high inlet pressure and high differential pressure thanks to the gas cooled working principle. Such design is particularly adapted to VOD process requirements. Turbopumps can be used on VIM and VAR processes for creating high vacuum without any oil pollution into the melting chambers, thanks to an oil free working principle. For better process control, it is necessary to monitor the composition of the process gases. For such a requirement we provide a wide range of gas analysis systems, working on the Quadrupole technology.