IRSID has been evaluating thin strip casting on a single roll caster at the 《hot model》 scale in its Maizieres pilot steel shop for two years. A water cooled copper wheel is fed from a 300 kg induction furnace to produce strip 170 mm wide and from 0.3 to almost 3 mm thick. 304 stainless has been used as a model alloy. In addition to direct experimentation on steel, a tin 《warm model》 and a water 《cold model》, built at Madylam Laboratories, have been used. Heat transfer analysis demonstrates that very high heat flux densities (from 5 to 15 MW/m~2) are extracted by the wheel and that this can be carried out without water boiling because of the transient nature of the heat transfer over one revolution of the roll. The regimes of flow, in that part of the tundish where the melt wets the wheel, have also been investigated: depending on the roll velocity, a turbulent boundary layer may form, which affects the flow in the tundish and possibly the "quality" of the top surface of the strip. Provided that proper countermeasures are taken, two forbidding defects, the 《saw tooth defect》 and the 《Tolling hills defect》 can be avoided and the resulting strip can exhibit good quality, on a par with conventional hot strip: long continuous strip is obtained and can be coiled; the sides are straight; the thickness regularity is acceptable, and bulk mechanical properties of the strip, after cold rolling and annealing, is equivalent to that of conventionally processed material.
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