RECENT DEVELOPMENT IN ROLLING OF BARS AND SECTION IN JAPAN

Abstract

At the end of Pacific War, Japan had 8 units of blooming mills. During ten years since then new establishment of 4 mills and renovation of 1 plant were performed. Besides, bulk amount of fund was invested to the established blooming mills to improve the soaking pits and other accessories. Above all, the Chiba plant of Kawasaki Iron Mfg. Co. constructed a latest and largest blooming mill, in which majority of mechanical equipments had been imported from the United States. On the cotrary, the plant of Nippon Steel Tube Co. shows the most modern mill made of Japanese equipments. Majority of soaking pits had been improved_in Japan following instructions of Messrs. Fred N. Hays and James T. Macleod (Carnegie-Illinois Steel Co. ). As for the bloom-rolling stands, renovation of the millmotors and the motor-generator sets was performed by turns in respective plants. The quality of cast or forged rolls still remained an unsolved problem. No continuous mill for billets, however, had been constructed anew. Nevertheless, some improvements had been made in the ways of rolling such as utilization of diamond-squared calibers and roller guides. As for the finishing of billets, Yawata Iron & Steel Works had used since July 1952 a. hot-scarfing equipment (Lindé Co. ) with heat-resisting nozzles made in Japan.
Moreover, in the field of bar sections rolling efforts had been made for recovery of devastated equipments, improvement in the quality, of products, reduction of consumption-unit of fuels and power and enhancement of the labor-productivity. In the continuous reheating furnaces, rationalization of the structure, amelioration of refractories and control-automation were performed. Heavy oil and high-pressure gas began to be utilized rationally instead of the traditional coal-combustion. As for the main motor, the chartacteristics were increase of output and magnification in the number of rotation and widening of the range of velocitychange. To meet recent demands in multiformed sections, some equipment was devised for a speediest resetting of rolls especially for the sake of heavy sections. In the new wire-rod mill at Hikari (Yawata Iron & Steel Co.). all-continuous equipment had been projected so that increase in the unit-weight of billets, increase in the finish-rolling speed, independent driving of each stand and utilization of vertical rolling stands were prospected for an enhanced production of products homogenous in quality and shape. In conclusion, the stress was laid on further improvement in the bar and section mills in Japan, although majority of the rationalization fund in the postwar Japan had been invested to amelioration of the plate or sheet mills.