IMPROVEMENT IN STRENGTH CHARACTERISTICS OF CONSTRUCTION STEEL THROUGH INNOVATIVE COOLING

Abstract

The increasing adverse effects of low strength characteristics of conventional hot rolled structural steel have become a major threat to safety of life and property. Several techniques aimed at achieving improved strength property of this class of steel include among others thermo-mechanical treatment, grain size refinement, solid-solution hardening and precipitation hardening. However, the solid solution method is known to be the most suitable for improving strength properties of structural steels. Two processes, Tempcore and Thermex developed through solid solution hardening are plagued by some constraints that bother on patent restrictions, suitability for only integrated mill and a rather prohibitive cost. Most rolling plants in the third world countries are mini mills and hardly can afford the adoption of either process. In a bid to overcome some of these constraints and challenges, attempt is made in this study to develop a type of microstructure that enhances strength characteristics at a less drastic cooling rate through spray quenching. The method is cost effective, highly flexible and devoid of any need for plant re-engineering. Strength characteristics comparable international standards specifications were achieved between 47 and 118 °C/s cooling rates within 15 seconds of spray quenching compared with about 500°C/s conventional solid solution hardening practice.