2010 年 51 巻 588 号 p. 28-32
The endless hot rolling concept was introduced to meet the demand for diverse hot-rolled steel sheet products produced by a process that is cost-effective compared with the conventional batch-type process. Endless rolling involves joining the head and tail ends of two bars after rough rolling. A new solid-state joining technology was proposed to instantaneously obtain a joint with high integrity using relatively simple equipment. The process requires no external heating since the bar temperature on the line is sufficiently high for joining. In this report, we present the super deformation joining (hereinafter referred to as “SDJ”), specifically, the introduction of the developed process and the effects of joining conditions on the characteristics of joints. The new model, the type II SDJ device, improved joint shape and performance compared with the type I SDJ device, mentioned in a previous paper. In laboratory tests, the joint strength of carbon steel was within 70 - 85 % of the base metal strength, which is from 394 to 440 MPa, and the grain size across the joint interface was very fine. Elucidating the SDJ mechanism and evaluating the characteristics of joints to rolling remain to be performed.