Metal treatment – Stock – Ferrous
Patent
1994-11-10
1996-08-13
Yee, Deborah
Metal treatment
Stock
Ferrous
148334, 148904, 420105, C22C 3822
Patent
active
055452671
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a steel product for an induction-hardened shaft component and a shaft component using the steel product. More particularly, the present invention relates to a steel product suitable for a shaft component, constituting a power train system in an automobile, such as a shaft provided with splines, a shaft provided with a flange and a shaft provided with a casing as shown in FIGS. 1(a) to 1(c), and an induction-hardened shaft component having excellent torsional strength. In FIGS. 1(a) to 1(c), numeral 10 designates a shaft, numerals 11, 12 designate serrations, numerals 20, 21 designate shafts, numeral 22 designates a flange, numerals 30, 31, 32 designates shafts and numeral 33 designates a casing.
PRIOR ART
Shaft components constituting a power train systems in automobiles have been generally been produced by forming a medium carbon steel into a desired component and then subjecting the components to induction hardening and tempering. In recent years, however, there has been a strong demand for an increase in strength (an improvement in torsional strength) due to the increase in engine output of automobile engines and to cope with environmental regulations.
Japanese Examined Patent Publication (Kokoku) No. 63-62571 discloses a process for producing a drive shaft comprising the steps of: forming a steel comprising C: 0.30 to 0.38%, Mn: 0.6 to 1.5%, B: 0.0005 to 0.0030%, Ti: 0.01 to 0.04% and Al: 0.01 to 0.04% into a drive shaft and subjecting the drive shaft to induction hardening in such a manner that the ratio of the induction hardening depth to the radius of the steel member is not less than 0.4. As can be seen from FIG. 1 of the same publication, the maximum attainable torsional strength is about 160 kgf/mm.sup.2.
Japanese Unexamined Patent Publication (Kokai) No. 4-218641 discloses that the use of a steel product for a high-strength shaft component produced using a particular composition system characterized by low Si and high Mn contents, i.e., comprising Si: not more than 0.05% and Mn: between 0.65% and 1.7%, enables a torsional strength of 140 to 160 kgf/mm.sup.2 to be obtained in a component provided with a spline.
Thus, the maximum torsional strength attainable in the art is about 160 kgf/mm.sup.2.
However, the above torsional strength level of 160 kgf/mm.sup.2 cannot be said to be satisfactory for shaft components in power train systems for automobiles. Further, the prevention of quench crack in the course of the production of the components has become important.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a steel product, for induction-hardened shaft components, which has a torsional strength of not less than 160 kgf/mm.sup.2 and does not cause quench crack, and a shaft component using the steel product.
The subject matter of the present invention is as follows.
(1) A steel product for an induction-hardened shaft component, characterized by having a chemical composition comprising by weight
(2) A steel product for an induction-hardened shaft component according to the above item (1), which further comprises one or more members selected from
(3) A steel product for an induction-hardened shaft component, characterized by having a chemical composition comprising by weight
(4) A steel product for an induction-hardened shaft component according to the above item (3), which further comprises one or both of
(5) A steel product for an induction-hardened shaft component according to any one of the above items (1) to (4), which further comprises
(6) A steel product for an induction-hardened shaft component according to any one of the above items (1) to (5), which further comprises one or both of
(7) An induction-hardened shaft component according to any one of the above items (1) to (6), characterized in that the average in-section hardness HVa, defined by the following formula (1), is not less than 560: ##EQU1## wherein, when a section having a radius of a is concentrically divided in a radial direction into N rings, H
REFERENCES:
patent: 3044872 (1962-07-01), Hayes et al.
patent: 4634573 (1987-01-01), Yanagiya et al.
patent: 5168768 (1993-02-01), Nonoto et al.
patent: 5279688 (1994-01-01), Isokawa et al.
Koyasu Yoshiro
Ochi Tatsuro
Nippon Steel Corporation
Yee Deborah
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