PROBLEMS OF INDIAN LOW ALLOY STEELS

Abstract

India has entered the age of high strength low alloy steel with SAILMA and LA grade steels produced by Steel Authority of India Limited and TISCO respectively. The problem of modifying the existing hot rolling mills to control suitably the precipitation during hot working in order to limit the austenite recrystallisation and grain growth has been a crucial problem for achieving the desired mechanical properties. In addition, the precipitate size and distribution is of importance because of its contribution to strength. The present investi-gation has been undertaken to understand the kinetics of preci-pitation as the first step. The samples have been held at 950°C and 10500C for different lengths of time and the precipitate sizes are coarser at 950°C and grows almost at the same rate initially but at an enhanced rate subsequently at 950°C. The strength of the samples treated at 103000 is higher than that observed at 950°C for the entire period of precipitation upto 10,000 seconds. The strength remains steady upto about 1000 seconds but decreases subsequently at both the temperatures. The hardness peak for 10500C occurs at 31.6 seconds but that at 9500C occurs at 100 seconds. The fracture characteristics of the samples have also been studied in detail. However, the kinetics of precipitation in presence of deformation is of more direct relevance to the problem at hand. The next step of the investigation should be directed to study the effect of deformation on the kinetics observed