WO2018180342A1 - Élément d'arbre - Google Patents

Élément d'arbre Download PDF

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Publication number
WO2018180342A1
WO2018180342A1 PCT/JP2018/009027 JP2018009027W WO2018180342A1 WO 2018180342 A1 WO2018180342 A1 WO 2018180342A1 JP 2018009027 W JP2018009027 W JP 2018009027W WO 2018180342 A1 WO2018180342 A1 WO 2018180342A1
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WIPO (PCT)
Prior art keywords
hardness
shaft member
hardened layer
layer
depth
Prior art date
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PCT/JP2018/009027
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English (en)
Japanese (ja)
Inventor
健 宇佐美
浩行 水野
康弘 福田
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愛知製鋼株式会社
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Priority to JP2018531677A priority Critical patent/JP6394844B1/ja
Publication of WO2018180342A1 publication Critical patent/WO2018180342A1/fr

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    • 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
    • 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
    • F16C3/02—Shafts; Axles
    • 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
    • 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
    • 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
    • C21D9/28—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for plain shafts
    • 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

  • the present invention relates to a shaft member used for a transmission, for example.
  • the torsional stress generated when the torsional torque is applied becomes higher as the distance from the axial center increases, becomes highest on the surface, and becomes lower as the position is closer to the axial center. Therefore, in order to achieve high strength, it is important that the necessary strength of each part is appropriately taken into account in consideration of the distance from the axis.
  • the part directly under the carburized layer cannot withstand the stress and becomes the weakest part, causing a problem that plastic deformation first occurs and the proportional limit is exceeded.
  • the latter shaft member has a problem that the surface has a higher hardness than the carburizing treatment and cannot withstand a high stress load on the surface.
  • the conventional shaft member has a problem that the expected performance cannot be obtained, it is difficult to increase the torsional strength, and it is difficult to reduce the diameter.
  • the shaft member often has to be provided with oil holes for the purpose of lubrication or the like.
  • there is a portion where stress is concentrated in the case of a shaft component having a hole or the like, it is necessary to consider that it is easy to break from a stress concentration site, and there is a problem that it is more difficult to reduce the diameter than a solid case.
  • Patent Document 2 discloses a manufacturing method in which after induction hardening is performed at least once after gas carburizing and quenching, this is tempered, and thereafter an abnormal carburizing layer is removed. According to this manufacturing method, it is supposed that it has excellent impact strength and bending strength by the effect of refining crystal grains by repeatedly performing induction hardening and the effect by removing the carburized abnormal layer.
  • Patent Document 2 requires that the abnormal carburizing layer be removed, and ideally repeats induction hardening, which takes time for processing and is disadvantageous in manufacturing cost. Can be said. Further, in Patent Document 2, the strength of the carburized layer is increased by refining the crystal grains of the carburized layer, but the internal characteristics of the carburized layer are not particularly mentioned and are unknown. Yes, it remains unclear whether a higher proportional limit and excellent fatigue strength can be obtained when the internal state from the surface to the shaft center is adjusted.
  • the present invention has been made in view of such a background, and an object of the present invention is to provide a shaft member that can increase the proportional limit more reliably than ever and can be reduced in diameter.
  • the first aspect of the present invention is, in mass%, C: 0.20 to 0.45%, Si: 0.03 to 1.50%, S: more than 0% and 0.070% or less, Mn: 0 50 to 2.00%, Cr: 0.30 to 2.50%, Al: 0.010 to 0.100%, N: 0.0070 to 0.0200%, V: 0 to 0.30%, Mo: 0 to 0.50% contained, with the balance being Fe and inevitable impurities, Satisfying the following formula 1, Formula 1: 19 [C] +2.3 [Mn] +1.4 [Cr] +13 [Mo] +25 [V]> 11 (However, [C], [Mn], [Cr], [Mo] and [V] in the formulas indicate the contents (mass%) of C, Mn, Cr, Mo and V, respectively).
  • the thickness of the first hardened layer is 0.20 mm or more,
  • the inner end of the second hardened layer is at a depth position of 0.1 times or more the diameter of the shaft member from the outermost surface. Located on the shaft member.
  • the second aspect of the present invention is, in mass%, C: 0.20 to 0.45%, Si: 0.03 to 1.50%, S: more than 0% and 0.070% or less, Mn: 0 50 to 2.00%, Cr: 0.30 to 2.50%, Al: 0.010 to 0.100%, N: more than 0% and 0.0200% or less, V: 0 to 0.30%, Mo: 0 to 0.50%, B: 0% to 0.0050% or less, Ti: 0% to 0.10% or less, with the balance being Fe and inevitable impurities, Satisfying the following formula 1, Formula 1: 19 [C] +2.3 [Mn] +1.4 [Cr] +13 [Mo] +25 [V]> 11 (However, [C], [Mn], [Cr], [Mo] and [V] in the formulas indicate the contents (mass%) of C, Mn, Cr, Mo and V, respectively).
  • the thickness of the first hardened layer is 0.20 mm or more,
  • the inner end of the second hardened layer is at a depth position of 0.1 times or more the diameter of the shaft member from the outermost surface. Located on the shaft member.
  • the shaft member has a chemical component composition such that the content range of each element is in the specific range and further satisfies Formula 1, and the first cured layer and the second cured layer are sequentially formed from the outer surface. And the inner layer. And while the thickness of the said 1st hardening layer is 0.20 mm or more, the said 2nd hardening layer located under it exists to the depth of 0.1 times or more of the diameter of the said shaft member, and also under it In addition, there is an inner layer cured to a predetermined hardness or higher. By having all these requirements, the shaft member can withstand the load stress applied to each part from the shaft center to the surface, such as the hardness profile extending from the outermost surface to the inner part where there is no sudden hardness reduction part.
  • the shaft member can greatly increase the proportional limit when torsional stress is applied compared to the conventional case, and can improve torsional strength.
  • a stress concentration part such as a corner such as an oil hole exists. it can.
  • FIG. 2 is a cross-sectional view taken along line AA in FIG. 1.
  • Explanatory drawing which shows the hardness profile of Example 1 and the prior art example 1.
  • FIG. Explanatory drawing which shows the relationship between the 2nd hardened layer depth and proportional limit in Embodiment Example 2.
  • FIG. Explanatory drawing which shows the relationship between the distance from the surface and hardness in Example 3 of an embodiment.
  • Explanatory drawing which shows the relationship between the presence or absence of V addition and the temper softening resistance in Embodiment Example 4.
  • C 0.20 to 0.45%
  • C (carbon) is an element necessary for securing internal hardness, and is contained in an amount of 0.20% or more.
  • the upper limit of the C content is set to 0.45%.
  • Si 0.03-1.50%
  • Si silicon
  • Si is an indispensable element for deoxidation, and is contained by 0.03% or more.
  • the toughness and hot workability are reduced, so the upper limit of the Si content is 1.50%.
  • S more than 0% and 0.070% or less
  • S (sulfur) is an element inevitably contained, and is contained in an amount exceeding 0%.
  • the upper limit of the S content is set to 0.070%.
  • Mn 0.50 to 2.00%
  • Mn manganese
  • Mn manganese
  • Mn is an important element for securing internal hardness. Therefore, Mn is contained at 0.50% or more.
  • the upper limit of the Mn content is 2.00%.
  • Cr 0.30 to 2.50%
  • Cr chromium
  • Al 0.010 to 0.100%
  • Al (aluminum) is an effective element for suppressing coarsening of crystal grains after carburization, and is contained in an amount of 0.010% or more in order to obtain the effect.
  • the upper limit of Al content is set to 0.100%. .
  • N 0.0070 to 0.0200%
  • N (nitrogen) is also an effective element for obtaining the effect of suppressing the coarsening of crystal grains after carburization in the same manner as Al, and 0.0070% or more is contained for obtaining the effect.
  • the upper limit of the N content is set to 0.0200%.
  • V 0 to 0.30% (including 0%)
  • V (vanadium) is an optional additive element, but it can be expected to have a crystal grain refining effect and a temper softening resistance improving effect. Therefore, V (vanadium) is preferably added when it is desired to enhance these effects.
  • V greatly increases the hardness of the tempered zone by increasing the temper softening resistance by precipitation strengthening, that is, the position slightly inside the maximum depth where the temperature rises above the transformation point during high-frequency heating. it can.
  • the structure obtained by carburizing and quenching will be tempered by high-frequency heating and the hardness will be reduced, but if V is added, precipitation strengthening Since the hardness after high-frequency heating is greatly improved, the fatigue strength can be greatly improved.
  • V it is preferable to set it as 0.20% or more, and, thereby, the above-mentioned effect can be acquired reliably. On the other hand, even if V is added excessively, the above effect is saturated and the cost may be increased. Therefore, the upper limit when V is contained is 0.30%.
  • Mo 0 to 0.50% (including 0%)
  • Mo mobdenum
  • Mo mobdenum
  • Mo mobdenum
  • the cost may increase and the workability may decrease, so the upper limit of the Mo content is set to 0.50%.
  • V and Mo are inevitably contained as impurities when scrap is used as a raw material and manufactured in an electric furnace, and there are trace amounts of detection in actual analysis results.
  • V may be inevitably contained as an impurity even if not actively added up to 0.01% and Mo up to about 0.06%.
  • Formula 1 19 [C] +2.3 [Mn] +1.4 [Cr] +13 [Mo] +25 [V]> 11 (where [C], [Mn], [Cr] in the formula, [Mo] and [V] indicate the contents (mass%) of C, Mn, Cr, Mo, and V, respectively, on the premise of the above-mentioned chemical components, and in the inner layer, 300 HV or more. It is necessary to ensure hardness and has been derived from many experiments. Therefore, it is important for the improvement of the torsional strength of the shaft member to further satisfy the formula 1 in consideration of the basic chemical component range described above. If this formula 1 is not satisfied at least, it is difficult to ensure sufficient hardness in the inner layer.
  • N more than 0% and 0.0200% or less
  • N ensures 0.0070% or more as an essential element in order to obtain the effect of suppressing grain coarsening after carburizing.
  • the effect of improving fatigue strength by improving grain boundary strength by using Ti and B as essential elements exceeds the effect of improving strength by crystal grain refinement by containing N
  • the lower limit of the N content rate is not particularly set.
  • the lower limit is set to exceed 0%.
  • the upper limit is as described above.
  • B (boron): more than 0% and 0.0050% or less
  • B is an element contributing to the improvement of the grain boundary strength in the metal structure, and the fatigue strength is further improved by the effect.
  • 0.0005% or more of content is necessary, but even if it is contained in a very small amount, it is possible to obtain the same or higher characteristics as compared with Ti and B non-added steel. So, no lower limit is set.
  • the upper limit of the B content is set to 0.0050%.
  • Ti titanium: more than 0% and 0.10% or less
  • the upper limit of the Ti content is set to 0.10%.
  • the fatigue strength of the shaft member is further improved by improving the grain boundary strength, while the lower limit value of N is relaxed. ing.
  • the shaft member includes the first hardened layer, the second hardened layer, and the inner layer sequentially from the outermost surface.
  • the shaft member is prepared by performing induction hardening after carburizing and quenching immediately thereafter, and the first hardened layer is a layer cured by carburizing and induction hardening.
  • a C concentration of 0.50% or more and a hardness of 700 HV or more can be defined as a layer located on the outermost surface.
  • the thickness can be grasped by grasping a profile of C concentration and hardness, and specifying a range where the C concentration is 0.50% or more and the hardness is 700 HV or more.
  • This part has a thickness that is necessary to obtain a hard martensite structure by quenching after the required amount of C has penetrated and diffused into the surface by carburization, and then is again quenched by induction quenching and then rapidly cooled.
  • the securing can be substantially realized by securing a range where the C concentration is 0.50% or more from the surface by 0.20 mm or more during the carburizing process. Note that if the thickness of the first hardened layer, that is, the effective hardening depth by C diffusion by carburizing treatment is increased, the strength of the surface layer can be further increased, but the carburizing treatment time required for that purpose becomes longer.
  • the thickness is preferably 0.80 mm or less, which is a realistic thickness considering that point.
  • the upper limit value of the C concentration of the first hardened layer is preferably 0.95% because it is necessary to prevent cementite precipitation and suppress embrittlement of the surface layer.
  • the carburizing process may be a plurality of processing methods such as gas carburizing, vacuum carburizing, etc., but in the present invention, as long as carbon can penetrate into the surface, the necessary performance can be obtained, The method is not particularly limited.
  • the second hardened layer is provided inside the first hardened layer.
  • a 2nd hardened layer is a layer which is located inside the 1st hardened layer in which the effect of carburizing has reached, was hardened by induction hardening, and is a layer whose hardness is 450HV or more. Since the part heated during induction hardening is heated for a short time, the crystal grains are clearly finer compared to the part where the effect of induction heating inside is not exerted. can do. Specifically, since it can be confirmed by structure observation that the level of crystal grains is clearly different from the inner layer described later, those skilled in the art can easily determine the boundary between the second hardened layer and the inner layer described later. You can grasp the position.
  • the condition of being the second hardened layer does not include the C concentration.
  • the C concentration is 0.
  • the range is less than 50%.
  • this 2nd hardened layer needs to ensure thickness so that the deepest inner edge part may be located in the depth of 0.1 times or more of the diameter of a shaft member.
  • induction hardening in order to heat up to austenitizing temperature from the surface in the depth direction up to 0.1 times the diameter of the shaft member to the austenitizing temperature, It is necessary to adjust the frequency, the current value or voltage value flowing through the heating coil, the moving speed of the heat-treated material relative to the heating coil, and the like.
  • the second hardened layer cannot secure a thickness that exists to a depth of 0.1 or more times the diameter of the shaft member, it may be difficult to obtain a sufficient proportional limit improvement. Therefore, for example, if the diameter of the shaft member is 20 mm ⁇ , it is necessary to provide the second hardened layer to a depth of at least 2.0 mm from the surface.
  • the depth of the second hardened layer means not the thickness of only the second hardened layer but the depth from the surface to the boundary with the internal layer. And since the depth of a 2nd hardened layer has large influence on a proportional limit improvement, it is more preferable to set it as the depth of 2.0 mm or more from the surface irrespective of the diameter of a shaft member.
  • the inner layer is provided inside the second hardened layer.
  • the inner layer is a layer having a hardness of 300 HV or more, and after being hardened by quenching after carburizing, the inner layer does not have a hardening effect by induction hardening. That is, since heating during induction hardening is performed only to a specific distance range from the surface, the region serving as the inner layer is not heated to a temperature higher than the transformation point by heating during induction hardening. Therefore, the inner layer is cured by quenching after heating at the time of carburizing, which is the entire heating. And as above-mentioned, since the part heated by the high frequency heating can be specified by structure
  • the said inner layer can ensure the hardness of 300HV or more by making it into the component which satisfies the said Formula 1.
  • the maximum thickness of the inner layer is the range up to the shaft center of the shaft member or the inner peripheral surface in the case of being hollow, but at least from the outer peripheral surface to a position of 1/4 of the diameter.
  • the hardness is preferably 300 HV or more.
  • torsion is applied, a greater stress is applied closer to the outer periphery, and a higher stress load is not applied near the shaft center. Therefore, if a hardness of 300 HV or more is secured from the outer peripheral surface to a quarter of the diameter, This is because a high proportional limit and fatigue strength can be obtained without necessarily limiting the hardness to the axis.
  • the raise of the hardness of an inner layer contributes to the improvement of a proportional limit, it is good to set it as 350 HV or more preferably.
  • molten steel adjusted to a desired chemical composition manufactured in an electric furnace is cast to produce an ingot.
  • the ingot is subjected to hot working such as rolling and forging to form a bar material before roughing.
  • the bar material is subjected to an annealing process for improving the machinability as necessary, and then roughing is performed to cut a shaft member that is substantially close to a desired shape.
  • tempering is performed as necessary.
  • the purpose of this tempering process is to prevent delayed fracture before induction hardening, which is a subsequent process, and therefore is not necessarily required when induction hardening is performed immediately.
  • tempering is performed after subjecting the outer peripheral surface of the shaft member to induction hardening.
  • finish processing such as chamfering is performed to obtain a desired shape.
  • the carburizing conditions and the like are adjusted so that the thickness of the carburized layer with the C content of 0.50% or more is 0.20 mm or more. Further, in the subsequent induction hardening process, the heating condition is adjusted so that a sufficient quenching effect can be obtained up to a depth of 0.1 times the diameter or more.
  • the shaft member may have an inner hole along the central axis and a lateral hole provided in the radial direction so as to communicate with the inner hole from the outer surface.
  • the inner hole and the lateral hole are preferably provided during the roughing process.
  • Example 1 Examples of the shaft member will be described together with comparative examples.
  • a plurality of steel types E1 to E32, C1 to C6, conventional materials 1 and 2) having chemical components shown in Tables 1 and 2 were prepared.
  • “-” in the column of V means that the analysis result is less than 0.005%
  • “-” in the columns of B and Ti in Table 2 is positive during production. It means the case where it did not add.
  • the inner surface 2 has an inner hole 2 along the central axis and the outer surface 11.
  • a shaft member 1 having a lateral hole 3 penetrating in the radial direction so as to communicate with the inner hole 2 was prepared and evaluated.
  • the outer diameter D1 is 20 mm
  • the inner diameter D2 is 7 mm
  • the inner diameter D3 of the lateral hole 3 is 4 mm.
  • the shaft member 1 is cut to the final shape by the above-described pre-heat treatment.
  • Example 1 the carburizing and quenching of Examples 1 to 32, Comparative Examples 1 to 6, 8 to 10, and Conventional Example 1 is a gas carburizing process using RX gas and enriched gas based on propane gas, and the holding temperature : 950 ° C., carburizing period: 75 minutes, diffusion period: 75 minutes, treated at a temperature of 850 ° C., then quenched into 130 ° C. oil.
  • This condition is a condition aimed at the depth of the carburized layer where the C concentration is 0.6% or more being 0.30 mm or more.
  • tempering after carburizing and quenching in these examples was performed under the condition of 150 ° C. ⁇ 1 hr.
  • induction hardening was performed using a workpiece moving induction hardening apparatus under the condition that induction hardening was performed on the outer peripheral surface in all axial directions at a frequency of 200 kHz.
  • the cooling was water cooling.
  • the hardened layer depth was adjusted by the coil voltage and the moving speed of the test material relative to the coil. Tempering after induction hardening was performed under the condition of holding at 180 ° C. for 1 hour.
  • the hardened layer depth depth at which austenite is formed by high frequency heating was set to 3.0 mm.
  • Comparative Example 10 was intentionally adjusted to be less than 2.0 mm, which does not satisfy the conditions of the present invention, in order to confirm the influence of the cured layer depth. Comparative Example 6 was evaluated without performing induction hardening in order to confirm the effect of not performing induction hardening.
  • Conventional Example 1 is an example of a shaft material reinforced by a conventional carburizing process, and therefore, induction hardening is not performed.
  • induction hardening was performed without performing a carburizing process, the conditions are mentioned later.
  • ⁇ C concentration measurement> As shown in FIG. 2, in the cross section at the position where the horizontal hole 3 was provided, the C concentration was measured at a measurement point pitch of 1 ⁇ m using EPMA from the outer peripheral end toward the inside in the cross section along the measurement line L. Table 5 shows the C concentration at the outer peripheral edge as the surface C concentration. Further, the depth of the innermost measurement point having a C concentration of 0.50% or more was measured, and it was determined whether or not the point was 0.20 mm or more. The values are shown in Table 5 when it is 0.20 mm or more, and the values are shown in Table 5 when it is less than 0.20 mm. In addition, all the values in the circles were numerical values within the range of 0.30 to 0.45 mm.
  • ⁇ Hardness measurement> The Vickers hardness at the outermost surface position on the measurement line L shown in FIG. 2, a depth of 0.20 mm position, a position of 2.0 mm, and a position of 5.0 mm (corresponding to a depth of 1 ⁇ 4 of the diameter) Measurement was performed with a measurement load of 300 gf.
  • test materials that were not induction hardened were entered in Table 5 as not yet implemented.
  • induction hardening is adjusted so that the curing depth is 3.0 mm, except for some test materials, and the cross-sectional structure of the test materials adjusted to 3.0 mm is used.
  • the comparative material 10 which was intentionally adjusted so that the curing depth was shallower had a quenching depth of 1.8 mm as shown in Table 5. here.
  • the boundary between the second hardened layer and the inner layer was determined by observing the difference in crystal grain size. From this observation result, it was confirmed whether the thickness of the 2nd hardened layer was more than predetermined thickness.
  • the comparison material 10 has a hardening depth of 1.8 mm by induction hardening, since it had a hardness of 450 HV or more even at a position 2.0 mm from the surface, it was added to the column of the hardness of the comparison material 10. Evaluation was described as ⁇ .
  • ⁇ Proportional limit> A static torsion test was performed on each shaft member, and the proportional limit was measured. Specifically, a strain gauge is attached to the surface side of the position on the cross section L in FIG. 2 of each sample, a torsion torque is applied, and a strain-torque diagram is obtained from the output from the strain gauge and the applied torsion torque. I asked for each. Then, the torsional torque at the time when the linear relationship in the elastic deformation region was removed was obtained as the value of the proportional limit.
  • the proportional limit is determined as a ratio with respect to the case of Conventional Example 2 as 100%, x when less than 100%, ⁇ when 100% or more and less than 110%, ⁇ when 110% or more and less than 120%, Table 5 shows the case of 120% or more as ⁇ .
  • ⁇ Fatigue strength> A fatigue torsion test was performed on each shaft member, and the strength was measured 100,000 times. Specifically, when the fatigue life is 100,000 times while repeatedly varying the torque within the range of torque that the same maximum torque is applied to the right twist side and the left twist side as viewed from one axial direction, The maximum torsion torque was evaluated based on the value. The strength at 100,000 times is determined as a ratio with respect to the value in the case of Conventional Example 1 as 100%, x when less than 100%, ⁇ when 100% or more and less than 110%, and 110% or more and less than 130%. The results are shown in Tables 5 to 7 with ⁇ as the case, ⁇ as the case of 130% or more, ⁇ as the case of 140% or more, and ⁇ as the case of 150% or more.
  • the “marginal zone” means a position where the hardness is lowest in the vicinity of the depth that is slightly inside the limit depth that is heated to a temperature equal to or higher than the transformation point temperature during high-frequency heating. In other words, it is a position closer to the shaft core than the maximum depth position that is heated above the transformation point during high-frequency heating and less than the transformation point during high-frequency heating, but is heated to a considerably high temperature, so that the hardness is improved by the tempering effect. Means the position where the drop occurs.
  • Example 1 the hardness profiles of Example 1 and Conventional Example 1 are shown.
  • the horizontal axis represents the distance (mm) from the surface
  • the vertical axis represents the hardness (HV)
  • the hardness is plotted with Example 1 as a and Conventional Example 1 as b.
  • the conventional example 1 has not been induction-hardened, and thus has a carburized layer of 700 HV or more on the surface, but suddenly drops to 400 HV or less at a depth of about 0.5 to 1.0 mm. It has a hardness profile that reduces the hardness.
  • Example 1 since carburizing quenching and induction hardening are performed so that the hardening depth is suitable for obtaining strength with excellent strength, it is 700 HV or more and is cured by carburization and induction hardening.
  • the first cured layer is provided with at least 0.2 mm or more
  • the second cured layer which is 450 HV or more and hardened by induction hardening, has a depth corresponding to 0.1 or more times the diameter.
  • 1.0 mm or more (in this embodiment, adjusted to be aimed at 3.0 mm), and a hardness profile having an inner layer hardened to a hardness sufficiently exceeding 300 HV by quenching after carburizing inside You can see that it has.
  • Examples 1 to 32 have the specific chemical composition described above, and all the values of Formula 1 exceed 11. Then, by performing an appropriate heat treatment, as shown in FIG. 3, the second carbon was hardened by carburization and induction hardening so that the C concentration is 0.50% or more and the hardness is 700 HV or more.
  • the 1st hardening layer has the thickness of 0.20 mm or more, and the 2nd hardening layer hardened by induction hardening so that hardness may become 450HV or more, the inner end is 0.1 of the diameter of a shaft member from the outermost surface. It has an inner layer that has a depth more than doubled and is hardened by quenching after carburizing so that the hardness is 300 HV or more.
  • Examples 1 to 32 have a significantly improved proportional limit and superior fatigue strength as compared with Conventional Examples 1 and 2. Particularly, in Examples 1, 3 to 7, 9, 11, 13, 14, 16, 17, 19, 22 to 24, and 26 in which the hardness of the inner layer is 350 HV or more, the proportional limit is larger than that of Conventional Example 2. Improved by more than 20%.
  • Examples 11 to 24 which are examples in which Ti and B are added in a preferable range, are clearly superior in fatigue strength compared to Examples 1 to 10 which are examples of steels to which Ti and B are not added.
  • Examples 25 and 26 show examples in which Ti and B were added but the addition was not sufficient, but even in this case, the effects of addition of Ti and B were not sufficient, It was confirmed that the Ti and B non-added steels shown in Examples 1 to 10 showed almost the same performance.
  • steel types E27 to 29 and E30 to 32 contain components other than Ti, B, and V in order to clarify the difference between the effects of addition of Ti and B and the effect of the presence or absence of V addition.
  • Steel types E27 and E30 are Ti, B non-added steel, steel types E28 and E31 are Ti and B added steel, V non-added steel, steel types E29 and E32 are all added with Ti, B and V
  • Table 7 shows the evaluation results. From the results shown in Table 7, it was confirmed that the addition of Ti and B greatly improved the strength of the oil hole corners by improving the grain boundary strength, and the fracture starting point moved from the oil hole corners to the burned area. It was confirmed that when V was further added, the hardness of the fired zone was improved by about 50 to 60 HV, and the fatigue strength was further improved.
  • the hardness and quenching depth are indicated by ⁇ and ⁇ in the sense that the conditions of the present invention are satisfied.
  • Specific measured values are the hardness of the outermost layer of the carburized layer.
  • 0.2 mm position hardness was 702 to 788 HV
  • the second hardened layer hardness was 453 to 700 HV.
  • the inner layer hardness ⁇ was 352 to 446 HV
  • ⁇ was 303 to 346 HV (including the comparative example and the conventional example ⁇ ).
  • Comparative Example 1 the chemical component did not satisfy Formula 1, and thus the hardness of the inner layer was insufficient. As a result, the proportional limit was lowered.
  • Comparative Example 6 was not induction hardened, the second hardened layer satisfying the conditions of the present invention was not formed as in Conventional Example 1 above, and the hardness profile suddenly decreased in hardness directly under the carburized layer. As a result, the proportional limit became lower.
  • Comparative Example 7 the first hardened layer was not formed because carburizing and quenching was not performed.
  • the surface hardness was lower (550 HV) than when carburizing and quenching, the fatigue strength was lower than that of Conventional Example 1, and the proportional limit was not improved as expected.
  • Comparative Example 8 is C.I. P. This is a comparative example for grasping the effect of terminating the process before sufficient carbon diffuses and penetrates by carburization by adjusting the carburizing process time. For this reason, the formation of the hardened carburized layer is incomplete, the fatigue strength improving effect cannot be obtained sufficiently, and the proportional limit improving effect is also insufficient.
  • Comparative Example 9 is an example in which the carburized layer depth is intentionally adjusted to be shallow by adjusting the carburizing time, and as a result, the depth of the first hardened layer is less than 0.2 mm. The improvement effect of both the proportional limit and fatigue strength is insufficient.
  • Comparative Example 10 the hardening depth by the induction hardening treatment is shallow, and the second hardened layer that satisfies the conditions of the present invention was not formed, so that the effect of improving the proportional limit was insufficient.
  • Comparative Example 10 since the heating depth at the time of induction hardening was shallow, the hardness at the depth of 2.0 mm position was assured to be 450 HV or more, but from that position, the hardness was directed toward the inner layer. It was confirmed that the level dropped rapidly to the HV level of 350 to 360.
  • Conventional Example 1 is a gas carburized treatment using JIS SCM420, which has been used as a conventional high-strength shaft material, and is a standard for fatigue strength evaluation for grasping the fatigue strength level of a conventional shaft material. The test results are shown. This test material is not subjected to induction hardening, and the second hardened layer that satisfies the conditions of the present invention is not formed. Therefore, the proportional limit is greatly inferior.
  • Example 2 was also subjected to induction hardening using JIS SCr440 that has been used as a conventional high-strength shaft material, in order to grasp the proportional limit level of the conventional shaft material.
  • the standard of proportional limit evaluation and the test result are shown.
  • the high frequency heating conditions were adjusted so that the depth of the second hardened layer was 2.0 mm in consideration of the specifications of many conventional shaft materials.
  • the results are shown in Table 5. This test material was not carburized and quenched, and the first hardened layer having a high hardness was not formed. Therefore, it was found that the fatigue strength was greatly inferior.
  • Embodiment 2 In this example, an experiment was conducted to examine the relationship between the depth of the second hardened layer and the proportional limit in more detail.
  • the chemical composition is fixed to the steel type E1 in Example 1, the carburizing quenching and the subsequent tempering conditions are the same as in Example 1, the heating coil voltage during induction quenching, and the moving speed of the test material during heating are set.
  • a plurality of shaft members in which the depth of the second hardened layer was changed by adjustment or the like were prepared.
  • the hardness of all the inner layers was adjusted to about 400 HV due to the hardness improvement effect by quenching after carburizing, so the influence on the proportional limit due to the difference in hardness of the inner layers is I can judge that there is nothing.
  • Other conditions are the same as in the first embodiment.
  • the proportional limit was obtained as a ratio with respect to the case of Conventional Example 2 described above as 100%, and the numerical values are shown in Table 8.
  • the second hardened layer depth (mm) is plotted on the horizontal axis
  • the proportional strength ratio (based on Conventional Example 2) is plotted on the vertical axis
  • the data in Table 8 is plotted.
  • Carburizing quenching and subsequent tempering, induction quenching and subsequent tempering conditions were the same as in Example 1.
  • the induction heating conditions were adjusted so that the induction hardening depth was 3.0 mm, as in Example 1.
  • Other conditions are the same as in the first embodiment.
  • the static torsion test similar to Example 1 was implemented, and the proportional limit was calculated
  • the proportional limit was obtained as a ratio with respect to the case of the conventional example 2 as 100%, and the numerical values are shown in Table 10.
  • the hardness of the inner layer (HV) is plotted on the horizontal axis
  • the strength ratio at the proportional limit is plotted on the vertical axis
  • the data in Table 10 is plotted.
  • the proportional limit can be improved more than 10% more reliably than in the past.
  • the inner layer is closer to the axial center than the second hardened layer changed in FIG. 4, and the influence on the proportional limit due to the hardness change in the low stress region is, of course, the change in the hardness of the second hardened layer.
  • the effect of increasing the hardness is not small, even if it is the hardness of the inner layer, but it is effective to increase the proportional limit by increasing the hardness. It became clear.
  • Investigative materials 41 to 44 were machined after forging a material melted in an electric furnace and processed into a test piece having a diameter of 26 mm and a length of 40 mm.
  • the test piece was subjected to a soaking treatment at 850 ° C. for 1 hour as a pretreatment, followed by a quenching treatment in which it was quenched into 130 ° C. oil. Then, it inserted in the tubular furnace heated up to each temperature (tempering temperature), and soaked for 1 hour, and then air-cooled and tempered.
  • tempering temperatures four types of temperatures of 500 ° C., 550 ° C., 600 ° C., and 650 ° C. were used.
  • the survey materials 41 and 43 that are V-added steels exhibit higher hardness at any tempering temperature than the survey materials 42 and 44 that are V-free steels. There was little decrease in hardness after tempering. This indicates that the positive addition of V brings about the effect of improving the temper softening resistance by the effect of precipitation strengthening.
  • the induction hardening a certain depth is heated, and a deeper position is not heated more than the transformation point. Phenomenon that the structure obtained by heating at the time of carburizing and quenching before induction hardening is tempered because it is heated only below the transformation point at a position slightly inside the depth that is heated above the transformation point. happenss.

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Abstract

La présente invention concerne un élément d'arbre qui comprend de 0,20 à 0,45 % de C, de 0,03 à 1,50 % de Si, de 0,070 % ou moins de S, de 0,50 à 2,00 % de Mn, de 0,30 à 2,50 % de Cr, de 0,010 à 0,100 % d'Al, de 0,0070 à 0,0200 % de N, de 0 à 0,30 % de V, de 0 à 0,50 % de Mo, le reste étant formé de Fe et d'impuretés inévitables et répond à la formule 1 : 19[C] + 2,3[Mn] + 1,4[Cr] + 13[Mo] + 25[V] > 11. L'élément d'arbre comporte une première couche durcie pour laquelle la concentration de C est supérieure ou égale à 0,50 % et la dureté est supérieure ou égale à 700 HV, une seconde couche durcie pour laquelle la dureté est supérieure ou égale à 450 HV et une couche interne pour laquelle la dureté est supérieure ou égale à 300 HV. L'épaisseur de la première couche durcie est supérieure ou égale à 0,20 mm et le bord intérieur de la seconde couche durcie est positionné à une profondeur supérieure ou égale à 0,1 partie du diamètre de l'élément d'arbre à partir de la surface la plus extérieure. L'élément d'arbre peut comprendre de plus de 0 % à moins de 0,10 % de Ti et de plus de 0 % à moins de 0,0050 % de B si nécessaire, ce qui permet d'améliorer la résistance à la fatigue.
PCT/JP2018/009027 2017-03-30 2018-03-08 Élément d'arbre WO2018180342A1 (fr)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2020100861A (ja) * 2018-12-20 2020-07-02 山陽特殊製鋼株式会社 静捩り強度ならびに捩り疲労強度に優れた高周波焼入れ用鋼材による自動車用機械部品
WO2022158569A1 (fr) * 2021-01-22 2022-07-28 愛知製鋼株式会社 Matériau de barre d'acier ronde à cémenter

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Publication number Priority date Publication date Assignee Title
US4173501A (en) * 1978-06-01 1979-11-06 Clark Equipment Company Steel torsional element and method for making
JPS6436779A (en) * 1987-07-30 1989-02-07 Nippon Steel Corp Production of case-hardened product having high-fatigue strength
JP2015042766A (ja) * 2013-08-26 2015-03-05 新日鐵住金株式会社 肌焼鋼鋼材
JP2016125133A (ja) * 2015-01-08 2016-07-11 日産自動車株式会社 耐焼付性に優れた浸炭部材
JP2016204697A (ja) * 2015-04-20 2016-12-08 新日鐵住金株式会社 高周波焼入れ部品の素形材、高周波焼入れ部品、及びそれらの製造方法

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4173501A (en) * 1978-06-01 1979-11-06 Clark Equipment Company Steel torsional element and method for making
JPS6436779A (en) * 1987-07-30 1989-02-07 Nippon Steel Corp Production of case-hardened product having high-fatigue strength
JP2015042766A (ja) * 2013-08-26 2015-03-05 新日鐵住金株式会社 肌焼鋼鋼材
JP2016125133A (ja) * 2015-01-08 2016-07-11 日産自動車株式会社 耐焼付性に優れた浸炭部材
JP2016204697A (ja) * 2015-04-20 2016-12-08 新日鐵住金株式会社 高周波焼入れ部品の素形材、高周波焼入れ部品、及びそれらの製造方法

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2020100861A (ja) * 2018-12-20 2020-07-02 山陽特殊製鋼株式会社 静捩り強度ならびに捩り疲労強度に優れた高周波焼入れ用鋼材による自動車用機械部品
JP7149179B2 (ja) 2018-12-20 2022-10-06 山陽特殊製鋼株式会社 静捩り強度ならびに捩り疲労強度に優れた高周波焼入れ用鋼材による自動車用機械部品
WO2022158569A1 (fr) * 2021-01-22 2022-07-28 愛知製鋼株式会社 Matériau de barre d'acier ronde à cémenter

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