The structure and properties of warm-extruded mild steel

Abstract

Mild steel billets, 73 mm dia., were preheated at 660°C and extruded using three different die sizes. The tensile and impact properties of the products were measured and compared with those of the initial stock. The structure of the materials was studied using conventional optical and electron microscopy and X-ray techniques. The microstructure of the extrudes was shown to be inhomogeneous in form, being dependent upon the strain and temperature gradients existing during extrusion. Extrusion increases the strength and toughness of the steel with no significant loss in tensile ductility. These property improvements are associated with grain refinement, pearlite spheroidization, and the production of a crystallographic fibre texture. The magnitude of these improvements is dependent upon the degree of static recrystallization.