Co-precipitation of copper-manganese sulphide in Fe-3%Si steel

In Fe-3%Si grain-oriented steel, there are two prerequisites for development of the sharp {110}〈001〉 Goss texture during secondary recrystallization: the presence, in the primary recrystallized matrix, of (i) a {110}〈001〉 texture component, and (ii) a dispersion of second-phase particles of appropriate number and size to inhibit normal grain growth. The nature of the dispersion is dependent on the prior processing history, particularly slab reheating and hot rolling practice. The present paper gives, in the first part, a breif review of the role of manganese sulphide as an inhibitor of normal grain growth in Fe-3%Si. The second part of the paper deals with novel information obtained on the precipitation of manganese sulphide, and the co-precipitation of copper-manganese sulphide, in hot-rolled strips of commercially produced grain-oriented silicon steel. It was observed, using transmission electron microscope energydispersive analysis of X-rays (TEM-EDAX), that an increase in copper concentration in the sulphide particles was associated with (i) a change in shape from spherical to parallelopipedal to cuboidal, and (ii) a simultaneous decrease in size.