The development and removal mechanisms of wire rod mill scale are outlined with the aid of the Fe-0 diagram. Data obtained in field experiments and laboratory experiments show that factors such as thickness and composition of the scale, presence of cracks and rod surface roughness have large effects on the pickling property and mechanical descaling property of scale. Further, laying temperatures, cooling rates, temperatures at the end of cooling and the conditions controlling roll roughness that are necessary for obtaining a good descaling property are described.

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Synopsis An in-line direct solution heat treatment process for austenitic stainless steel wire rods has been developed. This process utilizes the rolling sensible heat of wire rods. The results of the fundamental research on the recrystallization and the growth of austenite grains after hot rolling are described. The direct solution heat treatment line designed and built on the basis of the results of this fundamental study is outlined, and the quality of wire rods treated by the line is summarized. In the direct solution heat treatment process, the wire rod finish rolled at a high speed and a high temperature is first held in a high-temperature furnace for a short time and then cooled rapidly in a water box. These treatments are continuously performed in a short time in-line with the wire rod mill. The quality of wire rods thus treated is better than that of off-line annealed wire rods, enabling the elimination of solution heat treatment prior to drawing into wire.

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