Straightening Technology of Round Bars Using 2-roll Rotary Straightener

Abstract In order to improve the productivity and quality of round bar products, the finishing area of the round bar mill was revamped at Kobe Works, Kobe Steel Ltd. in 2011. Various pieces of equipment were newly installed, such as a high-speed rotary straightener, a magnetic leakage flux testing system and an ultrasonic testing system. Among them, the straightener was the key device and was expected to soon be in actual operation. In addition, it was necessary for this straightener to correct the round bar shape of the product, widening its diameter from 17 to 80 mm more than the conventional one. To decide the proper setting of the roll gap, the roll skew angle and the rotation speed of the top and bottom rolls of the straightener, a simple 3-point bending model was applied, and the inside of the working straightener was observed by an infrared camera. This paper describes the synergistic effect of the above mentioned three straightening factors and the applied result of these straightening conditions in actual operation.