Burgmann-Consulting, Strasbourg, France:

Burgmann W., Dr/Eng., Consultant Vacuum Technology, wburgmann@burgmann-net.de

Profratec, St. Etienne, France:

Davené J., Engineer, Technical Consulting Steelmaking

The cost for the conversion of steel in secondary steelmaking including a ladle furnace and various vacuum treatment processes have been investigated for a large heat range comparing two commonly used vacuum pump systems. Dry operating mechanical vacuum pumps offer substantial savings over the whole melt weight range up to 360 t. Such savings differ for the various processes and depend upon the availability of energy as well as upon plant productivity. The shor tening of the treatment cycle time by a rapid pump down limits melt overheating and thus leads to savings in production cost, increased productivity and quality improvement. Dry operating mechanical va cuum pumps made a significant progress in the past ten years for heats up to 230 t. There are no limits in suction capacity or process applicability, while the savings are still substantial for highest melt weights. Comparative figures for savings as offered by dry operating mechanical vacuum pumps for a 85-t heat for different processes are given. Since varying local conditions may considerably affect operating cost for a vacuum treatment the steelmakers are invited to make an individual cost study taking into account the local availability of various energy forms, purchasing possibilities, plant productivity and environmental requirements. Recently a profitability study was made for Chinese conditions and the local currency for melts ranging from 12 to 150 t. Similar investigations taking into account the special local conditions could be made in cooperation with an independent engineering office.

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