Oxygen blowing lance and lance tips in converter steel making Apr12

Oxygen blowing lance and lance tips in converter steel making...

Oxygen blowing lance and lance tips in converter steel making Oxygen is blown on the hot metal in the converter during steel making for removal of impurities such as carbon, silicon, manganese and phosphorus etc.  In the 1950s when the top blown converter size was limited to 50t maximum then a single hole lance was being used for the oxygen blowing. With the passage of time the converter size went on increasing. This has necessitated increase of number of holes in the lance for better distribution of oxygen over a larger surface of the bath in the converter. Today 5-6 holes lances are very common. Even 8 holes lances are under use. The axes of ach of the nozzles in a multi hole lance are typically inclined at around 10 deg with respect to the lance axes. Fig 1 shows schematically the increase in jet impact area on the bath for a three holes lance when compared with a single hole lance.                        Fig 1 Comparison of jet impact area between single hole lance and 3 hole lance Oxygen is blown in the converter through a water cooled lance with a convergent-divergent (CD) nozzle at high pressure (Around 11-14 bar) and at supersonic velocity (Mach >1). Supersonic jet of oxygen from the nozzle helps higher oxygen entrainment in the melt. During the blow, a three phase dispersion consisting of slag/metal droplets/gas bubbles is formed. The most important part of the lance is the nozzle. The functions of the nozzle are i)                 Supply and distribution of oxygen ii)                To produce a gaseous jet iii)               To induce bath agitation, iv)               To produce metal droplets Oxygen lance is made up of two cylindrical pipes. The outer layer...