WO2013015085A1 - 高周波焼入れ用鋼及びそれを用いて製造されるクランクシャフト - Google Patents
高周波焼入れ用鋼及びそれを用いて製造されるクランクシャフト Download PDFInfo
- Publication number
- WO2013015085A1 WO2013015085A1 PCT/JP2012/067102 JP2012067102W WO2013015085A1 WO 2013015085 A1 WO2013015085 A1 WO 2013015085A1 JP 2012067102 W JP2012067102 W JP 2012067102W WO 2013015085 A1 WO2013015085 A1 WO 2013015085A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- steel
- induction hardening
- content
- less
- sample
- Prior art date
Links
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
-
- 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
- C21D1/18—Hardening; Quenching with or without subsequent tempering
-
- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
-
- 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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/30—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for crankshafts; for camshafts
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C3/00—Shafts; Axles; Cranks; Eccentrics
- F16C3/04—Crankshafts, eccentric-shafts; Cranks, eccentrics
- F16C3/06—Crankshafts
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C2204/00—Metallic materials; Alloys
- F16C2204/60—Ferrous alloys, e.g. steel alloys
- F16C2204/64—Medium carbon steel, i.e. carbon content from 0.4 to 0,8 wt%
-
- 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
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T74/00—Machine element or mechanism
- Y10T74/21—Elements
- Y10T74/2173—Cranks and wrist pins
Definitions
- the present invention relates to steel for induction hardening and a crankshaft manufactured using the same.
- Induction hardening steel is used for engine parts. Induction hardening steels are disclosed in, for example, JP 2009-41046 A, JP 2010-144226 A, and JP 9-235654 A.
- induction hardening there may be a case where quenching cracks are generated due to residual stress. Therefore, induction hardening steel is required to have quench cracking resistance.
- Japanese Patent Application Laid-Open No. 5-25546 describes a method for manufacturing a part that prevents burning cracking and has excellent torsional strength. Specifically, the ratio t / r between the effective hardening depth t and the component radius r by induction hardening and tempering is set to 0.4 to 0.8, and the cross-sectional average hardness HVa is set to 550 or more. Are listed.
- Japanese Patent Application Laid-Open No. 2004-76086 describes a high-strength steel part that can reliably improve delayed fracture characteristics even with a wide range of component compositions. Specifically, the content of fine TiC having a particle size of 0.1 ⁇ m or less is 0.01%, and the ratio of the fine TiC content to the total Ti content is TiC / Ti ⁇ 0.4. It is described that there is.
- Japanese Patent Application Laid-Open No. 2005-256134 describes a steel material for induction hardening that does not cause grinding cracks even after grinding after induction hardening or low temperature tempering, and a crankshaft using the same.
- the steel for induction hardening in which the number of MnS in the steel in the longitudinal cross section after rolling is 300 pieces / mm 2 or less and the shrinkage ratio in the longitudinal direction in the differential thermal expansion test is 15 ⁇ m or less. Etc. are described.
- Japanese Patent Application Laid-Open No. 5-25546 describes that the ratio t / r between the effective hardening depth t and the component radius r by induction hardening and tempering is 0.8 or less in order to prevent burning cracks. Yes. However, it is preferable that the crack resistance can be improved without limiting the ratio between the effective hardened layer depth t and the partial radius r.
- Japanese Patent Application Laid-Open No. 2004-76086 is premised on the use of TiC produced by tempering at a high temperature. Therefore, it cannot be applied to general induction-hardened parts that are tempered at a low temperature.
- the steel material described in JP-A-2005-256134 is intended to improve grinding cracks. Specifically, after induction hardening and tempering, the heat generated by grinding is taken into account, and the shrinkage rate in that temperature range is reduced. Grinding cracks and fire cracks are fracture forms in different stress states. Therefore, it is unclear whether the steel material described in JP-A-2005-256134 has excellent fire cracking resistance.
- crankshafts large crankshafts used for trucks and the like require higher wear resistance and higher fatigue strength than ordinary crankshafts such as passenger cars. Accordingly, the hardened hardened layer of the large crankshaft is formed deeper than a normal size crankshaft of a passenger car or the like. In order to deepen the hardened hardening layer, the large crankshaft is heated for a long time at a higher output than usual.
- induction hardening steel when used for such a large crankshaft, it is preferable to suppress the occurrence of quench cracking even if induction hardening is performed with high output and long-time heating.
- An object of the present invention is to provide a steel for induction hardening excellent in resistance to quench cracking and a crankshaft manufactured using the same.
- the steel for induction hardening according to an embodiment of the present invention is, in mass%, C: 0.35 to 0.6%, Si: 0.01% or more and less than 0.40%, Mn: 1.0 to 2. 0%, S: more than 0.010% and 0.05% or less, Cr: 0.01 to 0.5%, Al: 0.001 to 0.05%, N: Ti / 3.4 to 0.02 %, Ti: 0.005 to 0.05%, with the balance being Fe and impurities, satisfying the formula (1). 2S-3Ti ⁇ 0.040 (1) Here, the content (mass%) of the corresponding element is substituted for each element symbol in the formula (1).
- Ca 0.005% or less may be contained instead of a part of the Fe.
- a crankshaft according to an embodiment of the present invention is manufactured by induction-quenching the above-mentioned induction hardening steel.
- a steel for induction hardening excellent in fire cracking resistance and a crankshaft manufactured using the steel are obtained.
- FIG. 1 is a graph showing the relationship between the value of the parameter 2S-3Ti defined in the embodiment of the present invention and the crack limit stress defined in the embodiment of the present invention.
- FIG. 2 is a schematic diagram showing test conditions for measuring the crack limit stress.
- % related to elements means mass%.
- the present inventors investigated and examined in order to improve the quench cracking resistance of the steel for induction hardening. As a result, the present inventors obtained the following knowledge.
- A High machinability is required for induction hardening steel.
- Such induction hardening steel has a high sulfur (S) content in order to improve machinability.
- S increases the machinability of steel by forming sulfide inclusions typified by MnS.
- sulfide inclusions are softer than the base material (matrix). Therefore, sulfide-based inclusions are likely to be the starting point of fire cracking. Therefore, the fire cracking resistance is improved by reducing the S content.
- Titanium (Ti) is effective for suppressing the coarsening of crystal grains. Ti forms nitrides and / or carbonitrides, and suppresses coarsening of crystal grains due to the pinning effect. Ti nitride and / or Ti carbonitride remain in the steel even at high temperatures. Therefore, the pinning effect can be obtained even at a high induction hardening temperature.
- V vanadium
- Ti nitride and / or Ti carbonitride does not dissolve in steel and maintains the pinning effect even when the induction hardening temperature is 1000 ° C. or higher.
- Induction hardening steel used for large crankshafts has a high induction hardening temperature and is easily overheated. Therefore, Ti is easier to maintain the pinning effect than V, and is effective in enhancing the resistance to fire cracking.
- N nitrogen
- TiC lowers the fire cracking resistance of steel. Therefore, it is preferable that N of the same amount or more of Ti is contained. Specifically, the N content is preferably Ti / 3.4 or more.
- FIG. 1 is a graph showing the relationship between the value of 2S-3Ti on the left side of Equation (1) and the crack limit stress defined below.
- FIG. 1 was obtained by the following method.
- test piece was 10.0 mm ⁇ 2.0 mm ⁇ 75.0 mm.
- the longitudinal direction of the test piece was parallel to the longitudinal direction of the round bar.
- Induction hardening was performed on each test piece. Specifically, high frequency heating was performed on the test piece at an output of 40 kW and a frequency of 200 kHz. The quenching temperature was 1000 ° C. The heating time was about 30 seconds. After the heating time, the test piece was rapidly cooled.
- the induction-quenched test piece was supported at four points, and bending stress was applied.
- the distance s1 between the two fulcrums on the upper surface of the test piece was 10 mm, and the distance s2 between the two fulcrums on the lower surface was 60 mm.
- a strain gauge was attached to the center of the test piece, the stress was measured, and a load was applied until a predetermined stress was obtained.
- the test piece to which bending stress was applied was immersed in a 0.3 mol / liter hydrochloric acid aqueous solution for 24 hours. Then, the test piece was taken out from the hydrochloric acid aqueous solution, and the presence or absence of crack generation was confirmed.
- FIG. 1 was created based on the obtained crack limit stress and 2S-3Ti.
- the lower the 2S-3Ti value the greater the crack limit stress.
- the crack limit stress increases rapidly.
- the value of 2S-3Ti is 0.040 or more, even if the value of 2S-3Ti decreases, the crack limit stress does not increase so much.
- the crack limit stress is a monotonically decreasing function with respect to the variable 2S-3Ti, and the value of 2S-3Ti has an inflection point in the vicinity of 0.040.
- the present inventors have completed the steel for induction hardening according to the present embodiment.
- the induction hardening steel according to the present embodiment will be described in detail.
- the steel for induction hardening according to the present embodiment has the following chemical composition.
- C 0.35-0.6% Carbon (C) martensites the surface layer of steel by induction hardening and increases the hardness of the surface layer.
- C carbon
- the steel is excessively hardened and the machinability of the steel is lowered. Therefore, the C content is 0.35 to 0.6%.
- the lower limit of the preferable C content is higher than 0.35%.
- the upper limit of the preferable C content is less than 0.6%, more preferably 0.5% or less.
- Si 0.01% or more and less than 0.40%
- Silicon (Si) deoxidizes steel. Si further strengthens the ferrite. On the other hand, if Si is contained excessively, the machinability of steel is lowered. Therefore, the Si content is 0.01% or more and less than 0.40%.
- the minimum of preferable Si content is higher than 0.01%, More preferably, it is 0.05% or more.
- the upper limit of the preferable Si content is 0.30% or less.
- Mn 1.0 to 2.0%
- Manganese (Mn) increases hardenability and increases the strength and hardness of the steel.
- austenite tends to remain during quenching.
- the presence of residual austenite reduces the mechanical properties of the steel. Therefore, the Mn content is 1.0 to 2.0%.
- the minimum of preferable Mn content is higher than 1.0%, More preferably, it is 1.2% or more.
- the upper limit of the preferable Mn content is less than 2.0%, more preferably 1.7% or less.
- S More than 0.010% and 0.05% or less Sulfur (S) forms sulfide inclusions represented by MnS and improves the machinability of steel. On the other hand, if S is contained excessively, a large number of coarse sulfide inclusions are formed. Coarse sulfide inclusions serve as the starting point for burning cracks. Therefore, the S content is more than 0.010% and 0.05% or less. The upper limit of the preferable S content is less than 0.05%.
- Chromium (Cr) increases the hardness of the steel. Cr further enhances the hardenability of the steel. On the other hand, if Cr is excessively contained, bainite is generated. When bainite is generated, the steel machinability decreases. Therefore, the Cr content is 0.01 to 0.5%.
- the minimum of preferable Cr content is higher than 0.01%, More preferably, it is 0.05% or more.
- the upper limit of the preferable Cr content is less than 0.5%, more preferably 0.35% or less.
- Titanium (Ti) deoxidizes steel. Ti further combines with N to produce Ti nitride and / or Ti carbonitride. Ti nitrides and / or Ti carbonitrides refine crystal grains by a pinning effect. If the crystal grains are refined, the ductility and toughness of the steel increase. Therefore, the fire cracking resistance is increased. On the other hand, if Ti is contained excessively, coarse Ti nitride, Ti carbonitride, and Ti carbide are generated, and the machinability of the steel is lowered. Therefore, the Ti content is 0.005 to 0.05%. The minimum of preferable Ti content is higher than 0.005%, More preferably, it is 0.008% or more. The upper limit of the preferable Ti content is less than 0.05%, more preferably 0.04% or less.
- Al 0.001 to 0.05%
- Aluminum (Al) deoxidizes steel. On the other hand, if Al is contained excessively, alumina inclusions are generated. Alumina-based inclusions reduce the machinability of steel. Therefore, the Al content is 0.001 to 0.05%.
- the lower limit of the preferred Al content is higher than 0.001%.
- the upper limit of the preferable Al content is less than 0.05%, more preferably 0.04% or less.
- N Ti / 3.4 to 0.02% Nitrogen (N) combines with Ti to produce Ti nitride and / or Ti carbonitride. As described above, Ti nitrides and Ti carbonitrides refine crystal grains due to the pinning effect and increase the resistance to fire cracking of steel. If the nitrogen (N) content is deficient relative to the Ti content, excess Ti combines with carbon to form TiC. TiC reduces the machinability of steel. Therefore, it is preferable that N of the same amount or more of Ti is contained. On the other hand, if N is contained excessively, defects such as voids are likely to occur in the steel. Therefore, the N content is Ti / 3.4 to 0.02%. Ti content is substituted for “Ti” in “Ti / 3.4”. 3.4 is the mass ratio of Ti and N. The lower limit of the preferable N content is higher than Ti / 3.4. The upper limit of preferable N content is less than 0.02%.
- the balance of the chemical composition of the induction hardening steel according to the present embodiment is composed of Fe and impurities.
- the impurities referred to here are ores and scraps used as raw materials for steel, or elements mixed in from the environment of the manufacturing process.
- V vanadium
- V is an impurity.
- V combines with C to form VC.
- VC has a pinning effect.
- V dissolves in steel. Therefore, the pinning effect by VC cannot be obtained.
- V reduces the machinability of the steel. Therefore, in the steel for induction hardening according to the present embodiment, V is an impurity.
- boron (B) is an impurity.
- B combines with N to form B nitride.
- B nitride reduces the cold workability of steel. Therefore, in the steel for induction hardening according to the present embodiment, B is an impurity.
- the steel for induction hardening according to the present embodiment contains Ti and N described above. Therefore, coarsening of crystal grains is suppressed, and excellent fire cracking resistance is obtained.
- the preferred crystal grain size of the induction hardening steel is 5.5 or more.
- the grain size is defined as follows. Take a specimen from induction hardening steel. Select any five views of the surface of the collected specimen. The austenite grain size in five selected fields of view is determined using the standard grain size chart of JISG0551. The average value of the five austenite grain sizes determined in each field is defined as the crystal grain size of the test piece.
- the induction hardening steel according to the present embodiment may contain Ca instead of a part of Fe.
- Ca 0.005% or less Calcium (Ca) deoxidizes steel. Moreover, Ca spheroidizes inclusions. If the inclusions are spheroidized, stress concentration due to the notch effect is alleviated. Therefore, the fire cracking resistance of steel increases. On the other hand, if Ca is contained excessively, coarse inclusions are formed, and the fire cracking resistance of the steel is lowered. Therefore, the Ca content is 0.005% or less. The upper limit of preferable Ca content is less than 0.005%.
- the molten steel is made into a slab by a continuous casting method. You may make molten steel into an ingot (steel ingot) by the ingot-making method. The slab or ingot may be hot worked to form a billet (steel piece) or a steel bar.
- the steel for induction hardening according to the present embodiment can be used for a large crankshaft.
- a hardened hardening layer is formed deeply.
- the thickness of the hardened hardening layer is 1 mm or more.
- a large crankshaft has a quenching temperature as high as 950 ° C. or higher as compared with a normal crankshaft of a general passenger car.
- the steel for induction hardening according to the present embodiment is less susceptible to quench cracking even if induction hardening is performed under such quenching conditions (quenching temperature).
- Tempering the intermediate product after induction hardening may be omitted.
- the preferable hardness of the surface layer (quenched hardened layer) of the intermediate product is 600 HV or more in terms of Vickers hardness.
- the intermediate product after induction hardening (and tempering) is ground into a predetermined shape by machining.
- a crankshaft is manufactured by the above process.
- Steel bars for induction hardening with various chemical compositions were hot forged to produce steel bars.
- Cutting resistance was measured using a steel bar to evaluate the machinability of the steel for induction hardening.
- a test piece was collected from the steel bar and subjected to induction hardening. Using the test piece, the crack limit stress, hardness and crystal grain size were measured, and the quench cracking resistance, hardness and machinability of the induction hardening steel were evaluated.
- Samples 1 to 5 and samples a to i each having 50 kg of the chemical composition shown in Table 1 were melted in a vacuum induction heating furnace. An ingot having a diameter of 100 mm was manufactured from the melted steel.
- Each element (C, Si, Mn, S, Cr, Ca, V, Ti, Al, N) in Table 1 describes the content (% by mass) of the corresponding element in the chemical composition of each sample. ing. The balance other than the above elements in the chemical composition of each sample is Fe and impurities. “-” In Table 1 indicates that the content of the corresponding element is at the impurity level.
- Ti / 3.4 a value obtained by dividing the Ti content by 3.4 is described.
- 2S-3Ti the value on the left side of the formula (1) is described.
- the chemical compositions of the steels of Samples 1 to 5 are within the range of the chemical composition of the steel for induction hardening according to the present embodiment and satisfy the formula (1).
- Each ingot was heated to 1250 ° C. and then hot forged to produce a round bar having a diameter of 60 mm.
- the forging finishing temperature was 1000 ° C.
- the round bar after hot forging was allowed to cool in air to room temperature.
- test pieces were collected from an intermediate position (R / 2 position) of the distance R between the central axis of each round bar and the surface.
- the shape of the test piece was 10.0 mm ⁇ 2.0 mm ⁇ 75.0 mm.
- the longitudinal direction of the test piece was parallel to the longitudinal direction of the round bar.
- a plurality of test pieces were prepared from the steel of each sample.
- Induction hardening was performed on each test piece. Specifically, high frequency heating was performed on the test piece at an output of 40 kW and a frequency of 200 kHz. The quenching temperature was 1000 ° C. The heating time was about 30 seconds. After the heating time, the test piece was rapidly cooled.
- Cutting resistance was measured using a round bar before induction hardening. A multi-component cutting dynamometer was used to measure the cutting resistance. Using a cemented carbide drill with a diameter of 6 mm, cutting was performed perpendicular to the axial direction of the round bar. The peripheral speed was 65 m / min, and the feed speed was 0.22 mm / rev.
- crack limit stress The crack limit stress (MPa) was calculated
- Hardness was measured using an induction-quenched test piece. Specifically, the test piece was cut perpendicular to the major axis direction. The cut surface was mirror-polished. Vickers hardness (HV) based on JISZ2244 was measured at any three points 1 mm from the surface of the cut surface after polishing, that is, 2 mm in the center. The test force was 98N. The average value of the three obtained Vickers hardnesses was defined as the hardness (HV) of each test piece.
- the induction-hardened specimen was cut perpendicular to the long axis at the center. In the cut plane, arbitrary 5 fields of view at the center of 1 mm from the surface, that is, 2 mm in thickness were selected. The austenite grain size in five selected fields of view was determined using the standard grain size chart of JISG0551. A region surrounded by a prior austenite grain boundary that appeared to corrode with a saturated aqueous solution of picric acid was identified as one austenite crystal grain. The average value of the five austenite grain sizes determined in each field was defined as the crystal grain size of the test piece.
- the test results are shown in Table 2.
- the “crack limit stress” column in Table 2 shows the crack limit stress (MPa). A crack limit stress of 250 MPa or less is indicated by “#”.
- Hardness In the “Hardness” column, hardness (HV) is shown.
- the “crystal grain size” column indicates the crystal grain size.
- the “cutting resistance” column shows the cutting resistance (N). Those with cutting resistance of 990 N or more are indicated by “#”.
- Samples 1 to 5 had a chemical composition within the range of the present embodiment and satisfied the formula (1). Therefore, the crack limit stress exceeded 250 MPa, and excellent fire cracking resistance was shown. Further, the crystal grain sizes of Samples 1 to 5 were 5.5 or more. The coarsening of crystal grains is suppressed by Ti nitride and / or Ti carbonitride, and the formula (1) is satisfied, so it is considered that excellent fire cracking resistance was exhibited. Furthermore, the cutting resistance of Samples 1 to 5 was less than 990 N, indicating excellent machinability.
- Sample 4 contains Ca, it showed a higher crack limit stress than Sample 2 having a similar chemical composition.
- the chemical composition and / or formula (1) did not satisfy the chemical composition and formula (1) of the steel for induction hardening according to this embodiment, so that the resistance to quench cracking or machinability was low. Specifically, the S content of sample a was too high and the Ti content was too low. Furthermore, the sample a did not satisfy the formula (1). Therefore, the crack limit stress was 250 MPa or less. Furthermore, the crystal grain size was less than 5.5. This is probably because the Ti content was too low.
- sample b The S content of sample b was too high and the Ti content was too low. Furthermore, the sample b did not satisfy the formula (1). Therefore, the crack limit stress was 250 MPa or less, and the crystal grain size was less than 5.5. In addition, sample b contained V. Therefore, cutting resistance was 990N or more.
- sample c The S content of sample c was too high. Further, the sample c did not satisfy the formula (1). Therefore, the crack limit stress was 250 MPa or less. Furthermore, since the sample c contained V, the cutting resistance was 990 N or more.
- the Ti content of sample e was too low. Furthermore, the sample e did not satisfy the formula (1). Therefore, the crack limit stress was 250 MPa or less, and the crystal grain size was less than 5.5.
- the S content of sample f was too high. Further, the sample f did not satisfy the formula (1). Therefore, the crack limit stress was 250 MPa or less.
- the chemical composition of the sample g was within the range of the chemical composition of the steel for induction hardening according to the present embodiment. However, sample g did not satisfy equation (1). Therefore, the crack limit stress was 250 MPa or less.
- the N content of sample i was too low. Therefore, the crack limit stress was 250 MPa or less.
- the crystal grain size of sample i was less than 5.5. This is probably because the N content was too low and sufficient TiN was not formed.
- the steel for induction hardening according to the present embodiment can be widely used for steel materials to be induction hardened. Specifically, it can be used for engine parts of automobiles. In particular, it can be used for large crankshafts such as trucks.
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Crystallography & Structural Chemistry (AREA)
- Thermal Sciences (AREA)
- Physics & Mathematics (AREA)
- General Engineering & Computer Science (AREA)
- Ocean & Marine Engineering (AREA)
- Heat Treatment Of Articles (AREA)
- Shafts, Cranks, Connecting Bars, And Related Bearings (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
Description
2S-3Ti<0.040 (1)
ここで、式(1)中の各元素記号には、対応する元素の含有量(質量%)が代入される。
2S-3Ti<0.040 (1)
ここで、式(1)中の各元素記号には、対応する元素の含有量(質量%)が代入される。
本実施の形態による高周波焼入れ用鋼は、以下の化学組成からなる。
炭素(C)は、高周波焼入れにより鋼の表層をマルテンサイト化し、表層の硬度を高める。一方、Cが過剰に含有されれば、鋼が過剰に硬化して鋼の被削性が低下する。したがって、C含有量は、0.35~0.6%である。好ましいC含有量の下限は、0.35%よりも高い。好ましいC含有量の上限は、0.6%未満であり、さらに好ましくは0.5%以下である。
シリコン(Si)は、鋼を脱酸する。Siはさらに、フェライトを強化する。一方、Siが過剰に含有されれば、鋼の被削性が低下する。したがって、Si含有量は、0.01%以上0.40%未満である。好ましいSi含有量の下限は、0.01%よりも高く、さらに好ましくは0.05%以上である。好ましいSi含有量の上限は、0.30%以下である。
マンガン(Mn)は、焼入れ性を高め、鋼の強度及び硬さを高める。一方、Mnが過剰に含有されれば、焼入れ時にオーステナイトが残留しやすくなる。残留オーステナイトが存在すると、鋼の機械的性質が低下する。したがって、Mn含有量は、1.0~2.0%である。好ましいMn含有量の下限は、1.0%よりも高く、さらに好ましくは1.2%以上である。好ましいMn含有量の上限は、2.0%未満であり、さらに好ましくは1.7%以下である。
硫黄(S)は、MnSに代表される硫化物系介在物を形成し、鋼の被削性を高める。一方、Sが過剰に含有されれば、粗大な硫化物系介在物が多数形成される。粗大な硫化物系介在物は、焼割れの起点となる。したがって、S含有量は、0.010%を超えて0.05%以下である。好ましいS含有量の上限は、0.05%未満である。
クロム(Cr)は、鋼の硬さを高める。Crはさらに、鋼の焼入れ性を高める。一方、Crが過剰に含有されれば、ベイナイトが生成される。ベイナイトが生成されると、鋼被削性が低下する。したがって、Cr含有量は、0.01~0.5%である。好ましいCr含有量の下限は、0.01%よりも高く、さらに好ましくは0.05%以上である。好ましいCr含有量の上限は、0.5%未満であり、さらに好ましくは0.35%以下である。
チタン(Ti)は、鋼を脱酸する。Tiはさらに、Nと結合してTi窒化物及び/又はTi炭窒化物を生成する。Ti窒化物及び/又はTi炭窒化物は、ピン止め効果により結晶粒を微細化する。結晶粒が微細化されれば、鋼の延性及び靭性が高まる。そのため、耐焼割れ性が高まる。一方、Tiが過剰に含有されれば、粗大なTi窒化物、Ti炭窒化物及びTi炭化物が生成され、鋼の被削性が低下する。したがって、Ti含有量は、0.005~0.05%である。好ましいTi含有量の下限は、0.005%よりも高く、さらに好ましくは0.008%以上である。好ましいTi含有量の上限は、0.05%未満であり、さらに好ましくは0.04%以下である。
アルミニウム(Al)は、鋼を脱酸する。一方、Alが過剰に含有されれば、アルミナ系介在物が生成される。アルミナ系介在物は、鋼の被削性を低下する。したがって、Al含有量は、0.001~0.05%である。好ましいAl含有量の下限は、0.001%よりも高い。好ましいAl含有量の上限は、0.05%未満であり、さらに好ましくは0.04%以下である。
窒素(N)は、Tiと結合してTi窒化物及び/又はTi炭窒化物を生成する。上述のとおり、Ti窒化物及びTi炭窒化物は、ピン止め効果により結晶粒を微細化し、鋼の耐焼割れ性を高める。窒素(N)含有量がTi含有量に対して不足すると、過剰なTiは炭素と結合してTiCを形成する。TiCは、鋼の被削性を低下する。したがって、Tiと同数以上の物質量のNが含有されていることが好ましい。一方、Nが過剰に含有されれば、鋼中にボイド等の欠陥が発生しやすくなる。したがって、N含有量は、Ti/3.4~0.02%である。「Ti/3.4」中の「Ti」にはTi含有量が代入される。3.4はTiとNとの質量比である。好ましいN含有量の下限は、Ti/3.4よりも高い。好ましいN含有量の上限は、0.02%未満である。
本実施形態による高周波焼入れ用鋼の化学組成はさらに、下記の式(1)を満たす。
2S-3Ti<0.040 (1)
ここで、式(1)中の各元素記号には、対応する元素の含有量(質量%)が代入される。
本実施形態による高周波焼入れ用鋼は、上述のTi及びNを含有する。そのため、結晶粒の粗大化は抑制され、優れた耐焼割れ性が得られる。高周波焼入れ用鋼の好ましい結晶粒度は5.5以上である。結晶粒度は次のとおり定義される。高周波焼入れ用鋼から試験片を採取する。採取された試験片の表面のうち任意の5視野を選択する。JISG0551の結晶粒度標準図を用いて、選択された5視野でのオーステナイト結晶粒度を求める。各視野で求めたオーステナイト結晶粒度の5視野の平均値を、その試験片の結晶粒度と定義する。
カルシウム(Ca)は、鋼を脱酸する。また、Caは介在物を球状化する。介在物が球状化すれば、切欠き効果による応力集中が緩和される。そのため、鋼の耐焼割れ性が高まる。一方、Caが過剰に含有されれば、粗大な介在物が形成され、鋼の耐焼割れ性が低下する。したがって、Ca含有量は0.005%以下である。好ましいCa含有量の上限は、0.005%未満である。
本実施の形態による高周波焼入れ用鋼、及び高周波焼入れ用鋼を用いたクランクシャフトの製造方法の一例を説明する。
表1に示す化学組成を有する試料1~5及び試料a~iの鋼各50kgを、真空誘導加熱炉で溶製した。溶製された鋼から、直径100mmのインゴットを製造した。
高周波焼入れ前の丸棒を用いて切削抵抗(N)を測定した。切削抵抗の測定には、多成分切削動力計を使用した。直径6mmの超硬コーティングドリルを使用し、丸棒の軸方向と垂直に切削を行った。周速は65m/min、送り速度は0.22mm/revであった。
高周波焼入れされた試験片を用いて割れ限界応力(MPa)を求めた。具体的には、各試料の試験片に対して、図1を作成した場合と同じ条件の試験を実施した。
高周波焼入れされた試験片を用いて硬度を測定した。具体的には、試験片を長軸方向に対して垂直に切断した。切断面を鏡面研磨した。研磨後の切断面の表面から1mm、すなわち厚み2mmの中心部の任意の3点でJISZ2244に基づくビッカース硬度(HV)を測定した。試験力は98Nであった。得られた3つのビッカース硬度の平均値を、各試験片の硬度(HV)と定義した。
高周波焼入れされた試験片を中央部で長軸に対して垂直に切断した。切断面内において表面から1mm、すなわち厚み2mmの中心部の任意の5視野を選択した。JISG0551の結晶粒度標準図を用いて、選択された5視野でのオーステナイト結晶粒度を求めた。ピクリン酸飽和水溶液で腐食現出した旧オーステナイト粒界に囲まれた領域を1つのオーステナイト結晶粒と認定した。各視野で求めたオーステナイト結晶粒度の5視野の平均値を、その試験片の結晶粒度と定義した。
試験結果を表2に示す。表2中の「割れ限界応力」欄には、割れ限界応力(MPa)を示す。割れ限界応力が250MPa以下のものに「#」を付して示した。「硬度」欄には、硬度(HV)を示す。「結晶粒度」欄には、結晶粒度を示す。「切削抵抗」欄には、切削抵抗(N)を示す。切削抵抗が990N以上のものに「#」を付して示した。
Claims (3)
- 質量%で、C:0.35~0.6%、Si:0.01%以上0.40%未満、Mn:1.0~2.0%、S:0.010%を超え0.05%以下、Cr:0.01~0.5%、Al:0.001~0.05%、N:Ti/3.4~0.02%、Ti:0.005~0.05%を含有し、残部はFe及び不純物からなり、下記の式(1)を満たす、高周波焼入れ用鋼。
2S-3Ti<0.040 (1)
ここで、式(1)中の各元素記号には、各元素の含有量(質量%)が代入される。 - 前記Feの一部に代えて、Ca:0.005%以下を含有する、請求項1に記載の高周波焼入れ用鋼。
- 請求項1又は2に記載の高周波焼入れ用鋼を高周波焼入れして製造されるクランクシャフト。
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CN201280037202.2A CN103717768A (zh) | 2011-07-28 | 2012-07-04 | 高频淬火用钢及使用其制造的曲柄轴 |
US14/235,105 US20140182414A1 (en) | 2011-07-28 | 2012-07-04 | Steel for induction hardening and crankshaft manufactured by using the same |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2011-165899 | 2011-07-28 | ||
JP2011165899A JP5678833B2 (ja) | 2011-07-28 | 2011-07-28 | 高周波焼入れ用鋼及びそれを用いて製造されるクランクシャフト |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2013015085A1 true WO2013015085A1 (ja) | 2013-01-31 |
Family
ID=47600940
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2012/067102 WO2013015085A1 (ja) | 2011-07-28 | 2012-07-04 | 高周波焼入れ用鋼及びそれを用いて製造されるクランクシャフト |
Country Status (4)
Country | Link |
---|---|
US (1) | US20140182414A1 (ja) |
JP (1) | JP5678833B2 (ja) |
CN (1) | CN103717768A (ja) |
WO (1) | WO2013015085A1 (ja) |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20140283960A1 (en) * | 2013-03-22 | 2014-09-25 | Caterpillar Inc. | Air-hardenable bainitic steel with enhanced material characteristics |
CN103966518B (zh) * | 2014-04-17 | 2016-05-18 | 李露青 | 一种传动轴用含Nd球笼 |
JP6477904B2 (ja) * | 2015-10-01 | 2019-03-06 | 新日鐵住金株式会社 | クランク軸粗形材、窒化クランク軸及びその製造方法 |
JP7119697B2 (ja) * | 2018-07-24 | 2022-08-17 | 日本製鉄株式会社 | 表面焼入れ用鋼材および表面焼入れ部品 |
JP7124545B2 (ja) * | 2018-08-09 | 2022-08-24 | 日本製鉄株式会社 | 機械構造部品 |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS6436779A (en) * | 1987-07-30 | 1989-02-07 | Nippon Steel Corp | Production of case-hardened product having high-fatigue strength |
JPH04141521A (ja) * | 1990-10-03 | 1992-05-15 | Nippon Steel Corp | 軸形状を有する高周波焼入れ部品の製造方法 |
JP2010013729A (ja) * | 2008-06-06 | 2010-01-21 | Sumitomo Metal Ind Ltd | 軟窒化用鋼、軟窒化用鋼材およびクランクシャフト |
JP2010285677A (ja) * | 2009-06-15 | 2010-12-24 | Sumitomo Metal Ind Ltd | 高周波焼入用鋼 |
JP2011026641A (ja) * | 2009-07-23 | 2011-02-10 | Sumitomo Metal Ind Ltd | 高周波焼入れ用非調質鋼 |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP4281441B2 (ja) * | 2003-08-08 | 2009-06-17 | Jfeスチール株式会社 | 曲げ疲労寿命に優れるクランクシャフトの製造方法 |
-
2011
- 2011-07-28 JP JP2011165899A patent/JP5678833B2/ja active Active
-
2012
- 2012-07-04 US US14/235,105 patent/US20140182414A1/en not_active Abandoned
- 2012-07-04 CN CN201280037202.2A patent/CN103717768A/zh active Pending
- 2012-07-04 WO PCT/JP2012/067102 patent/WO2013015085A1/ja active Application Filing
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS6436779A (en) * | 1987-07-30 | 1989-02-07 | Nippon Steel Corp | Production of case-hardened product having high-fatigue strength |
JPH04141521A (ja) * | 1990-10-03 | 1992-05-15 | Nippon Steel Corp | 軸形状を有する高周波焼入れ部品の製造方法 |
JP2010013729A (ja) * | 2008-06-06 | 2010-01-21 | Sumitomo Metal Ind Ltd | 軟窒化用鋼、軟窒化用鋼材およびクランクシャフト |
JP2010285677A (ja) * | 2009-06-15 | 2010-12-24 | Sumitomo Metal Ind Ltd | 高周波焼入用鋼 |
JP2011026641A (ja) * | 2009-07-23 | 2011-02-10 | Sumitomo Metal Ind Ltd | 高周波焼入れ用非調質鋼 |
Also Published As
Publication number | Publication date |
---|---|
US20140182414A1 (en) | 2014-07-03 |
CN103717768A (zh) | 2014-04-09 |
JP5678833B2 (ja) | 2015-03-04 |
JP2013028840A (ja) | 2013-02-07 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
JP5927868B2 (ja) | 冷間鍛造性に優れた浸炭用鋼およびその製造方法 | |
JP5332646B2 (ja) | 冷間鍛造性に優れた浸炭用鋼の製造方法 | |
KR100939462B1 (ko) | 피로 강도가 우수한 열간 단조품 및 그 제조 방법 그리고기계 구조 부품 | |
KR101726251B1 (ko) | 연질화용 강 및 연질화 부품 그리고 이들의 제조 방법 | |
JP2007131907A (ja) | 冷間加工性に優れる高周波焼入れ用鋼及びその製造方法 | |
JP5678833B2 (ja) | 高周波焼入れ用鋼及びそれを用いて製造されるクランクシャフト | |
EP3272896B1 (en) | Age-hardenable steel, and method for manufacturing components using age-hardenable steel | |
JP2003055714A (ja) | 非調質鋼鍛造加工品及びその製法、並びにそれを用いた内燃機関用コンロッド部品 | |
JP6217859B2 (ja) | 機械構造用圧延棒鋼及びその製造方法 | |
WO2012029395A1 (ja) | 高周波焼入れ用鋼及びそれを用いて製造されるクランクシャフト | |
JP2007231337A (ja) | 熱延鋼板および鋼部品 | |
KR101657792B1 (ko) | 흑연화 열처리용 강재 및 피삭성이 우수한 흑연강 | |
JP2009167505A (ja) | 調質型軟窒化クランク軸用粗形品および調質型軟窒化クランク軸 | |
JP2005336553A (ja) | 熱間工具鋼 | |
JP2007107029A (ja) | 鋼材及びその製造方法 | |
JP4605695B2 (ja) | ダイカスト金型用プリハードン鋼 | |
JP6390685B2 (ja) | 非調質鋼およびその製造方法 | |
KR101007417B1 (ko) | 다이 캐스트용 열간 공구 강철 | |
JP4170294B2 (ja) | 転造性、耐焼割れ性およびねじり特性に優れた機械構造用鋼材およびドライブシャフト | |
JP5476766B2 (ja) | 冷間鍛造性に優れた機械構造用鋼およびその製造方法 | |
JP6249100B2 (ja) | 機械構造用圧延棒鋼及びその製造方法 | |
JP2009221497A (ja) | 黒皮外周旋削性とねじり強度に優れた鋼材 | |
JP2006249504A (ja) | ブローチ加工性に優れた窒化部品用素材及びその製造方法 | |
JP5310095B2 (ja) | 黒皮外周旋削性とねじり疲労強度に優れた鋼材の製造方法 | |
JP3748696B2 (ja) | 自動車用コネクティングロッドの製造方法 |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 12817676 Country of ref document: EP Kind code of ref document: A1 |
|
WWE | Wipo information: entry into national phase |
Ref document number: 14235105 Country of ref document: US Ref document number: IDP00201400478 Country of ref document: ID |
|
NENP | Non-entry into the national phase |
Ref country code: DE |
|
122 | Ep: pct application non-entry in european phase |
Ref document number: 12817676 Country of ref document: EP Kind code of ref document: A1 |