iii)  Selection for model slag phase

It is in fact very difficult to find a low temperature model slag which is similar to actual slag. Density of slag in prototype is around 0.4 times that of molten steel. Slag floats on steel.

Transitory and permanent contact of slag phase with molten steel are the principle refining mechanisms. In transitory contact, the refining occurs by rising molten slag droplets. Due to large difference in the density of molten slag and steel, transitory contact mode is difficult to model. Permanent contact mode can be modeled. Several organic oils like paraffin, mineral oil can be used as a model slag to study the physics of slag/ metal interface.

iv)  Selection of model velocity of gas

In steelmaking processes, gas is used to stirr the molten phases
Dynamic similarity must be observed between model and prototype, that

Substituting the quantitative value of the dimensionless numbers, we get.

(12)

From equations 12  we get for Reynold’s number similarity

(13)

For Froude number similarity

(13)

(14)

  
For Weber number similarity

(15)

The Weber number similarity can be neglected since the inertial forces in the prototype are very large as compared to surface tension forces.

Froude and Reynold’s number similarity can be obtained in a aqueous model only when . This lecture highlights some of the important aspects of physical modeling of steelmaking processes. In the past several years physical modeling or more precisely water modeling has become a very important tool to investigate the physical effects in steelmaking caused by either impinging or submerged gas jets. The references are given at the end of the lecture 39.