1. 1) Nakasuji, K., Kuroda, K. & Hayashi, C.:ISIJ Int., 31-6 (1991), 620-627.
2. 2) Erman, E.:J. Appl. Metalwork., 4 (1987), 331-341.
3. 3) New Tube Investments Development:Metallurgia, (1967), 51-56.
4. 4) Blazynski, T. Z. & Jubb, C.:Journal of the Institute of Metals, 97 (1969), 363-373.
5. 5) ISIJ:Iron and Steel Handbook 3rd, 2 (1980), 940.