Abstract

A ferrite-pearlite type microalloyed steel has been developed for use in the crankshafts of small multipurpose engines. Although the thermal refining process after hot forging has been eliminated, this steel possesses equivalent strength and toughness to thermally refined steel, and can also be induction hardened. The design of the alloy sought to ensure toughness by increasing the ratio of ferrite in the structure of the steel and refining the structure through the use of intragranular ferrite and, at the same time, to ensure strength by strengthening of solid solution and precipitation strengthening and increasing hardenability while still employing a carbon content within the range enabling induction hardening. In addition, conditions for the temperature of heating during hot forging and for cooling after hot forging were established to control coarsening of the structure and optimize the characteristics of the alloy. At the same time, the design ensured that while no lead was added, a level of machinability equivalent to that conventional free-cutting steel with added lead was achieved. This has reduced the cost of crankshaft manufacture by eliminating the thermal refining process and done away with the necessity of adding lead, an environmentally harmful substance.

References

1. (1) Nomura, I.: Metallurgical Technology in Microalloyed Steels for Automotive Parts, Materia Japan, Vol. 34, No. 6, p. 705 (1995)
2. (2) Hosono, A., Fujita, K.: Current Status of Microalloyed Steel, Isuzu Technical Journal, Vol. 90, p. 90
3. (3) Ikeda, M., Anan, G.: High Strength Microalloyed Steels, R&D Kobe Steel Engineering Reports, Vol.52, No. 3, p. 47 (2002)
4. (4) Takada, H., Koyasu, Y.: The Present and the Future of Forging Steel Free of Quenching and Tempering, Shinnittetsu Giho, Vol. 354, p. 6 (1994)
5. (5) Satoh, T., Kurita, M.: Saikin no Hityoushitsukou ni Tsuite, Tanzou Gihou, Vol. 83, p. 16 (2000) (in Japanese)
6. (6) Inoue, K., Nakamura, S.: High Strength and High Toughness Microalloyed Steels, Denki-Seiko (Electric Furnace Steel), Vol. 67, No. 1, p. 56 (1996)
7. (7) Ochi, T., Takahashi, T., Takada, H.：Improvement of the Toughness of Hot Forged Products Through Intragranular Ferrite Formation，Iron & Steel Maker, 16-2, p. 21-28 (1989)
8. (8) Katsumata, M., Matsushima, Y., Yamamoto, Y.: Newly Developed Low Carbon Martensite-Bainite Type High Strength High Toughness Steel Used in As-Hot Forged Condition, Bulletin of The Japan Institute of Metals, Vol. 31, No. 6, p. 547 (1992)
9. (9) Okatsu, M., Hayashi, T., Amano, K.: Weldability of Advanced Extremely-low Carbon Bainitic Steels for Thick Plate of 570 MPa Grade through As-rolled Process, Kawasaki Steel Giho, Vol. 30, No. 3, p. 131 (1998)
10. (10) Inoue, K., Nakamura, S.: Influence of Alloying Elements on Mechanical Properties and Fatigue Strength in Notched Specimens of Bainitic Microalloyed Steels, Denki-Seiko (Electric Furnace Steel), Vol. 69, No. 1, p. 27 (1998)
11. (11) Fukuzumi, T.: Development of Microalloyed Steels with Bainitic Microstructure for Hot-Forgings, Mitsubishi Steel Technical Review, Vol. 19, No. 1, 2, p. 33 (1985)
12. (12) Satoh, T.: Micro-alloyed High-strength Steel, Sumitomo Metals, Vol. 45, No. 4, p. 120 (1993)
13. (13) Ono, T.: A Review of Recent Studies for Machinability of Steel, Sumitomo Metals, Vol. 48, No. 1, p. 4 (1996)
14. (14) Hashimura, M., et al.: Development of Lead Free Micro Alloyed Steel for Crank Shafts, Shinnittetsu Giho, Vol. 378, p. 68 (2003)
15. (15) Tsunekage, N., et al.: Effect of Mg and Ca Addition on Toughness and Machinability of Resulfurized Freecutting Steel (Development of New Resulfurized Freecutting Steel – 1), CAMP-ISIJ, Vol. 14, No. 6, p. 1233 (2001)
16. (16) Sato, K., et al.: Effect of S Content and Mg and Ca Addition on the Machinability and Strength of Steels (Development of New Resulfurized Free-cutting Steel – 2), CAMP-ISIJ, Vol. 14, No. 6, p. 1234 (2001)

Author (organization or company)

• Yuzuru TAHARA（Honda Motor Co.,Ltd.）
• Shingo SHIMIZU（Asakahigashi R&D Center）

Publication Information

Article of Honda R&D Technical Review Vol.16 No.2 (191 - 196)

PDF

Citation Information