US3652346A - Method of induction hardening for improving fatigue strength of boundary of heated zone - Google Patents
Method of induction hardening for improving fatigue strength of boundary of heated zone Download PDFInfo
- Publication number
- US3652346A US3652346A US858812A US3652346DA US3652346A US 3652346 A US3652346 A US 3652346A US 858812 A US858812 A US 858812A US 3652346D A US3652346D A US 3652346DA US 3652346 A US3652346 A US 3652346A
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- United States
- Prior art keywords
- boundary
- fatigue strength
- hardened
- zone
- induction hardening
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/06—Surface hardening
- C21D1/09—Surface hardening by direct application of electrical or wave energy; by particle radiation
- C21D1/10—Surface hardening by direct application of electrical or wave energy; by particle radiation by electric induction
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
Definitions
- a steel object is induction-hardened to improve its resistance to fatigue and wear.
- steel objects are locally induction-hardened, a reduction in the fatigue strength of the object will occur at the boundary areas adjacent the hardened zone and the tendency of the steel object to break at such areas will be increased.
- An object of the present invention is to provide a method for preventing the reduction of the fatigue strength at such boundary areas by reducing the residual tensile stresses developed in the areas bounding a hardened zone.
- a feature of the method of the present invention is the improvement of the distribution of residual stresses generated areas bounding a hardened zone by cooling such areas during induction heating so that the thermal effect may be minimized.
- FIG. 1 is a graph illustrating the relationship between the position of a conventional induction coil and the distribution of residual tensile stresses on the surface of a steel object which has been locally case-hardened by a conventional induction-hardening method.
- FIG. 2 is an elevational, longitudinal view partly in cross section showing an embodiment of the method of the present invention.
- FIG. 3 is a graph comparing the distribution of residual stresses on the surface of a shaft hardened by the conventional method and residual stresses on the surface of a shaft hardened by the method of the present invention.
- FIG. 1 wherein the line Y in the graph illustrates the distribution of residual stresses in a longitudinal direction along the surface of a conventionally hardened straight cylindrical steel shaft.
- X refers to an induction coil
- Z refers to a hardened zone on the surface of the steel object (shown in dashed lines).
- the reference letters X, Yand Z in FIG. 1 are all shown as being disposed at corresponding axial positions.
- a large residual compressive stress will be developed.
- the residual stress is reversed to develop a residual tensile stress which quickly reduces after passing a maximum.
- a shaft l illustrated in FIG. 2, is constructedof a carbon steel (AISI 1038) containing 0.38 percent C and has a diameter of 190 millimeters.
- a hollow copper induction coil 2 having an inside diameter of 225 millimeters and six windings in series is disposed around the outer periphery of shaft 1.
- a cooling ring 4 having cooling water jetting orifices 3 is provided at each end of induction coil 2. The cooling water jetting orifices 3 are disposed on the inner periphery of cooling ring 4 so that jetted cooling water is directed onto areas b extending outwardly on shaft 1 from the boundaries of a zone a being hardened.
- zone and said area are generally cylindrical in shape, said coolant stream comprising a plurality of radially directed jets arranged around the object.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Articles (AREA)
Abstract
Residual tensile stresses are reduced in a locally casehardened steel object by cooling the boundary zone adjacent the area to be hardened during induction heating.
Description
United States Patent Tomita et al.
[ 51 Mar. 28, 1972 [54] METHOD OF INDUCTION HARDENING FOR IMPROVING FATIGUE STRENGTH OF BOUNDARY OF HEATED ZONE [5]] lnt.Cl. ..C2ld l/l0, C2ld 1/66 [58] Field oisearch ..l48/l45,146,148,149,150, 148/154 References Cited UNITED STATES PATENTS 2,958,524 11/1960 Delapenaetal ..148/145 2,275,402 3/1942 Crowe ..148/l49 Primary Examiner-L. Dewayne Rutledge Assistant Examiner-W. W. Stallard AttorneyWatson, Cole, Grindle and Watson [5 7] ABSTRACT 4 Claims, 3 Drawing Figures inventors: Katsunobu Tomita; Kentaro Ishii, both of Tokyo; Yoshito Tanaka, Nara; Takao Saito, Nishinomiya, all of Japan 173] Assignees: Japam National Railways, Tokyo, Japan; Sumitomo Metal Industries, Limited, Osaka, Japan [22] Filed: Sept. 17, 1969 [21] Appl.No.: 858,812
[30] Foreign Application Priority Data Sept. 18, 1968 Japan ..43/67742 [52] U.S.Cl ..148/154 5 1 v5 2 id RES/DUAL PATENTinmzs 1972 SHEET 1 BF 2 EELS/004A STRESS QQRMMQQEQU mvmrozz U ATTORNEY PATENTEmmza 1912 3.652 346 sum 2 OF 2 ATTORNEY METHOD OF INDUCTION IIARDENING FOR IMPROVING FATIGUE STRENGTH F BOUNDARY 0F HEATED ZONE This invention relates to a method for improving the fatigue strength at the boundaries of an induction-hardened zone on a steel object, such as, for example, a straight or curved shaft for a railway car axle, an armature shaft, a mill roll or a crank shaft.
Generally, a steel object is induction-hardened to improve its resistance to fatigue and wear. However, it is known that when steel objects are locally induction-hardened, a reduction in the fatigue strength of the object will occur at the boundary areas adjacent the hardened zone and the tendency of the steel object to break at such areas will be increased.
An object of the present invention is to provide a method for preventing the reduction of the fatigue strength at such boundary areas by reducing the residual tensile stresses developed in the areas bounding a hardened zone.
A feature of the method of the present invention is the improvement of the distribution of residual stresses generated areas bounding a hardened zone by cooling such areas during induction heating so that the thermal effect may be minimized.
In the accompanying drawings:
FIG. 1 is a graph illustrating the relationship between the position of a conventional induction coil and the distribution of residual tensile stresses on the surface of a steel object which has been locally case-hardened by a conventional induction-hardening method.
FIG. 2 is an elevational, longitudinal view partly in cross section showing an embodiment of the method of the present invention.
FIG. 3 is a graph comparing the distribution of residual stresses on the surface of a shaft hardened by the conventional method and residual stresses on the surface of a shaft hardened by the method of the present invention.
Before explaining the present invention, a conventional method shall be described with reference to FIG. 1 wherein the line Y in the graph illustrates the distribution of residual stresses in a longitudinal direction along the surface of a conventionally hardened straight cylindrical steel shaft. In FIG. 1, X refers to an induction coil and Z refers to a hardened zone on the surface of the steel object (shown in dashed lines). The reference letters X, Yand Z in FIG. 1 are all shown as being disposed at corresponding axial positions. As understood from FIG. 1, at locations within the hardened zone Z, a large residual compressive stress will be developed. However, at the areas adjacent the boundaries of the hardened zone, the residual stress is reversed to develop a residual tensile stress which quickly reduces after passing a maximum. Thus, in the case of conventionally locally case-hardened steel objects, a residual compressive stress will be generated in the hardened zone itself; however, at areas adjacent the boundaries of the hardened zone, a residual tensile stress will be generated to reduce the fatigue strength of the object and increase its susceptibility to fatigue-breakage at such locations.
The method of the present invention will be explained with reference to the drawings. A shaft l, illustrated in FIG. 2, is constructedof a carbon steel (AISI 1038) containing 0.38 percent C and has a diameter of 190 millimeters. A hollow copper induction coil 2 having an inside diameter of 225 millimeters and six windings in series is disposed around the outer periphery of shaft 1. A cooling ring 4 having cooling water jetting orifices 3 is provided at each end of induction coil 2. The cooling water jetting orifices 3 are disposed on the inner periphery of cooling ring 4 so that jetted cooling water is directed onto areas b extending outwardly on shaft 1 from the boundaries of a zone a being hardened. Electric current is passed through induction coil 2 for seconds while 10 tons/hour of cooling water are jetted through jetting orifices 3. When the surface temperature of zone a has been raised to 830 C., the entire zone is quenched. The residual stresses at various positions along the surface of the hardened shaft '1 were measured with X-rays and the results are shown in FIG. 3 where the line B is a plot of residual stress against distance along the axis of the shaft. The line A in FIG. 3 is a similar plot of a case where conventional methods were used. Except for .the fact that cooling rings were not used, the conditions were accordance with the present invention have an approximately uniform value. Accordingly, the method of the present invention is very effective in improving the fatigue strength at areas adjacent the boundary of hardened zones on locally casehardened objects.
What is claimed is:
1. A method for producing a locally case-hardening steel object having improved fatigue strength characteristics comprising:
locally case-hardening a steel object by induction heating of the same at a zone thereon constituting less than the entirety of its outer surface to produce a hardened zone bounded by at least one intentionally unhardened boundary area; and
preventing the development of excessive residual tensile stresses at said boundary area by cooling the same during said case-hardening operation.
2. A method as set forth in claim 1 wherein said cooling is accomplished by directly contacting said area with a coolant fluid stream.
3. A method as set forth in claim 2 wherein said fluid is water.
4. A method as set forth in claim 2 wherein said zone and said area are generally cylindrical in shape, said coolant stream comprising a plurality of radially directed jets arranged around the object.
Claims (3)
- 2. A method as set forth in claim 1 wherein said cooling is accomplished by directly contacting said area with a coolant fluid stream.
- 3. A method as set forth in claim 2 wherein said fluid is water.
- 4. A method as set forth in claim 2 wherein said zone and said area are generally cylindrical in shape, said coolant stream comprising a plurality of radially directed jets arranged around the object.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP6774268 | 1968-09-18 |
Publications (1)
Publication Number | Publication Date |
---|---|
US3652346A true US3652346A (en) | 1972-03-28 |
Family
ID=13353688
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US858812A Expired - Lifetime US3652346A (en) | 1968-09-18 | 1969-09-17 | Method of induction hardening for improving fatigue strength of boundary of heated zone |
Country Status (3)
Country | Link |
---|---|
US (1) | US3652346A (en) |
DE (1) | DE1947274B2 (en) |
FR (1) | FR2018371A1 (en) |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4071933A (en) * | 1976-03-03 | 1978-02-07 | Mceowen Victor R | Method of forming pivot joint housing |
US4885831A (en) * | 1988-09-26 | 1989-12-12 | Dana Corporation | Method for forming a contour hardened gear |
WO1997034326A1 (en) * | 1996-03-11 | 1997-09-18 | Temple University-Of The Commonwealth System Of Higher Education | Amorphous-crystalline thermocouple and methods of its manufacture |
US5841033A (en) * | 1996-12-18 | 1998-11-24 | Caterpillar Inc. | Process for improving fatigue resistance of a component by tailoring compressive residual stress profile, and article |
US20110315281A1 (en) * | 2010-06-24 | 2011-12-29 | Magna International Inc. | Tailored Properties By Post Hot Forming Processing |
US20120217235A1 (en) * | 2011-02-24 | 2012-08-30 | General Electric Company | Surface treatment system, a surface treatment process and a system treated component |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2275402A (en) * | 1936-05-22 | 1942-03-03 | Air Reduction | Flame hardening of shafts |
US2958524A (en) * | 1956-06-21 | 1960-11-01 | Delapena & Son Ltd | Means for hardening a surface of an article by electrical induction heating and quenching |
-
1969
- 1969-09-17 US US858812A patent/US3652346A/en not_active Expired - Lifetime
- 1969-09-18 FR FR6931837A patent/FR2018371A1/fr not_active Withdrawn
- 1969-09-18 DE DE19691947274 patent/DE1947274B2/en active Pending
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2275402A (en) * | 1936-05-22 | 1942-03-03 | Air Reduction | Flame hardening of shafts |
US2958524A (en) * | 1956-06-21 | 1960-11-01 | Delapena & Son Ltd | Means for hardening a surface of an article by electrical induction heating and quenching |
Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4071933A (en) * | 1976-03-03 | 1978-02-07 | Mceowen Victor R | Method of forming pivot joint housing |
US4144626A (en) * | 1976-03-03 | 1979-03-20 | Mceowen Victor R | Method of fabricating flexible joints |
US4885831A (en) * | 1988-09-26 | 1989-12-12 | Dana Corporation | Method for forming a contour hardened gear |
WO1997034326A1 (en) * | 1996-03-11 | 1997-09-18 | Temple University-Of The Commonwealth System Of Higher Education | Amorphous-crystalline thermocouple and methods of its manufacture |
US5808233A (en) * | 1996-03-11 | 1998-09-15 | Temple University-Of The Commonwealth System Of Higher Education | Amorphous-crystalline thermocouple and methods of its manufacture |
US5841033A (en) * | 1996-12-18 | 1998-11-24 | Caterpillar Inc. | Process for improving fatigue resistance of a component by tailoring compressive residual stress profile, and article |
US20110315281A1 (en) * | 2010-06-24 | 2011-12-29 | Magna International Inc. | Tailored Properties By Post Hot Forming Processing |
US20120217235A1 (en) * | 2011-02-24 | 2012-08-30 | General Electric Company | Surface treatment system, a surface treatment process and a system treated component |
JP2012176484A (en) * | 2011-02-24 | 2012-09-13 | General Electric Co <Ge> | Surface treatment system, surface treatment process and system treated component |
US9062354B2 (en) * | 2011-02-24 | 2015-06-23 | General Electric Company | Surface treatment system, a surface treatment process and a system treated component |
Also Published As
Publication number | Publication date |
---|---|
DE1947274A1 (en) | 1970-04-16 |
FR2018371A1 (en) | 1970-05-29 |
DE1947274B2 (en) | 1971-09-30 |
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