Abstract

The conventional mill operators are faced with challenges of producing reinforcing steel bars of adequate strength characteristics. This stems from the inability to effectively control and monitor process variables such as temperature, strain-rate and cooling. These parameters collectively determine the microstructure and invariably the mechanical properties of the rolled bars. However, the finishing temperature appears to be more important than the temperature at the roughing stand. Often, the type and extent of in-process cooling method and duration of each rolling cycle largely determine the finishing temperature. Thus, installation of temperature monitoring devices along the rolling line will furnish prompt thermal information necessary for both process conditions and product properties optimization respectively. Detailed temperature tracking of a conventional rolling operation was carried out with a view to establish the range of finishing temperature that give rise to improved strength characteristics of steel bars produced, taking cognizance of the rolling stock chemistry. Improvement in the bars mechanical properties was achieved within 840 to 860ËšC finishing temperature and rolling stock chemistry in the range of 0.21 to 0.23% C, 0.20 to 0.25% Si and 0.50 to 0.60% Mn.

Key words: Rolling, temperature, microstructure, steel, strength.