1979 Volume 65 Issue 12 Pages 1673-1682
The softening behavior under load was investigated using cold bonded pellets with cement binders, made from iron ores of several types.
In the case of cold bonded pellets, both the swelling and softening by reduction at elevating temperatures resulted in a big pressure drop in the softening test.
The prevention of the swelling was effective when iron-silicate of low melting point was made from wustite and gangue minerals in a pellet particle in the temperature range from 900 to 1 100°C at which swelling usually took place to form slag net works.
For the prevention of the softening, it was essential that the melting point of gangue minerals was transformed to higher levels.
To satisfy both the requirements, iron-silicate of low melting point, bearing CaO, must be made in the temperature range from 900 to 1 100°C and transformed to Ca-silicate of high melting points by reduction above 1100°C.
As the suitable composition of the cold bonded pellet including binders to meet the restriction, its gangue amount must be higher than 220 kg/t-Fe and its basicity (CaO/SiO) more than 1.2.