冷間圧造用高級線材の製造技術の開発とその量産

抄録

The cold heading process is a working technique which has rapidly progressed recently, to make this technique possible, however, higher properties of materials are demanded because of the severe working condition.
This paper describes the aspect of developing high quality wire rod for cold heading application by improving its production techniques.
The author investigated the properties of cold headability using several testing methods which include measuring method of working load during heading.
With these testing methods, the influence of chemical composition, hardness, macro and micro structures, and surface defects were studied.
The basic researches on nonmetalic inclusions in steel were also carried out, and at the same time a number of test trials on production scale were carried out to make a good quality of steel for cold heading. In order to improve ingot moulds for making less segregated and cleaner steel, the solidification mechanism of molten steel was investigated by adding tracer elements, and several testing models in laboratories were carried out and a computer was also used to analize their results.
On the other hand, we also improved rolling technique by our long experiences. The No. 7 wire rod mill was designed and manufactured by Kobe Steel Ltd. under the above mentioned improvements, and it is one of the most modern mills in the world. The No. 7 wire rod mill can produce heavy weighted, and large diameter wire rod with close tolerance and superior surface quality much more efficiently than before.