Module 1: Steelmaking Fundamentals
  Lecture 4: Slag in Steelmaking
 

The number of vertices destroyed depends on the fraction of basic oxide, i.e. the ratio of   O/Si as shown in the table

O:Si

Formula

Structure

Equivalent silicate ions

2:1

SiO2

All corners of tetrahedron are shared

(Si6O15)6− or (Si8O20)8−

5:2

MO.2SiO2

One broken link per tetrahedron

(Si3O9)6− or (Si4O12)8−

3:2

MO.SiO2

Two broken link
per tetrahedron

(Si3O9)6−

7:2

3MO.2SiO2

Three broken link per tetrahedron

(Si2O7)6−

4:1

2MO.SiO2

All link are broken

(SiO4)4−

All the four vertices will be broken when 2 moles of CaO are added for each mole of silica. The resulting slag would consist of  and  ions

References :

L.Coudurier, D.W.Hopkins and I.wilkomirsky: Fundamentals of metallurgical processes