Study of the Effect of Composition and Thermal Deformation Treatment on Properties of Ferritic Steels Microalloyed with Titanium and Niobium. Part 1. Microstructure Characteristics

Abstract

The effect of composition and thermal deformation processing (finishing temperature of rolling and coiling, cooling rate after rolling) parameters on the mechanical properties and structure of advanced Ti, Mo micro-alloyed structural (automobile sheet) ferritic steels is studied. It is established that the strength characteristics of steel increase regularly with increasing Ti content within appropriate limits and additional microalloying with molybdenum. The resultant structural state is primarily determined by the cooling rate after steel hot rolling. At relatively low values of 10–15 °C/sec polygonal ferrite is formed, and on increasing up to 30 °C/sec formation of a high dislocation acicular ferrite is observed. The expediency of reducing carbon content to 0.04–0.06 wt.% is demonstrated.