Thin-slab casting - New possibilities

Changes in the IT industry are known to proceed at a scorching pace. Tn sha rp contrast, the rate of development in the steel industry is generally slo w. Nonetheless, the impact of recent technical developments on the steel in dustry has been quite significant. The production chain from iron ore to fi nal rolled steel is a long one and the shortening of this length has long b een the endeavour of scientists and engineers. The initial development came in the form of speeding up the process of steelmaking by reducing the slow open-hearth process (8 h tap-to-tap time) with the 45 min tap-to-tap time of the Basic Oxygen Furnace (BOF) process. Significant developments thereaf ter have been in the process of continuous production of billets and blooms from liquid steel thereby doing away with the large blooming mills needed for rolling ingots. For a fairly long time after the stabilisation of continuous casting, hot r olling involved reheating thick (200-250 mm) slabs and reducing them in a h ot-strip mill. The advent of thin-slab casters has made even these large ho t-strip mills redundant. The new installations produce thin slabs (50-70 mm ) that are directly rolled into strips without the need of an intermediate furnace for raising the stock temperature; the so-called tunnel furnace pri or to the rolling stands serving only to equalise stock temperatures. Addit ionally, what started as a step for reducing investment in hot rolling has, in fact, given new opportunity for direct hot rolling of thicknesses that were: for long, considered to be feasible only through the cold-rolling rou te. This article discusses the slow but steady encroachment of hot-rolled sheet s into the domain of strip thicknesses hitherto produced by cold rolling an d tries to show how the development of thin-slab casters has allowed this p rocess to be accelerated. A techno-economic analysis of thin-slab casting h as been presented along with the benefits that arise when a thin-slab easte r is linked to the blast furnace and basic oxygen route of steelmaking.