JP2009102733A - Method for producing rolling member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a rolling member of a high-frequency induction hardening gear, etc., at a low cost for various kinds of materials having high surface pressure resistance of ≥50 HRC in tempered hardness at 300°C. <P>SOLUTION: The method for producing the rolling member is performed as the followings, that a steel material composed of 0.5-1.5 wt.% C, 0.3-1.5 wt.% Cr and 0.2-2.0 wt.% one or more kinds selected from group of V, Ti, Zr, Nb, Ta, Hf and dispersing 0.4-4.0 vol% one or more kinds of carbide, nitride and carbonnitride having 0.2-5 μm average particle diameter composed of the elements, and 7.5-20 vol% cementite, is used. In such a rolling member, the solid solution carbon concentration in a martensite parent phase of rolling-contact surface layer, is adjusted to 0.3-0.8 wt.% by induction-hardening and tempering at low temperature, and in this parent phase, 0.4-4.0 vol% of one or more kinds of the carbide, nitride and carbonnitride, and 2-15 vol% of cementite, are dispersed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a rolling member such as a gear manufactured by quenching and hardening a rolling surface layer by induction hardening, carburizing and quenching, carburizing and nitriding and quenching, or nitrocarburizing and quenching.

Traditionally, construction and in civil engineering machinery of the reduction gear, from the viewpoint of high resistance to surface-pressure (200 kgf / mm ² or more) is important, SCr, SCM, carburized or carbonitriding窒焼insertion process SNCM based low carbon steel In general, some ring gears used under relatively low surface pressure (˜150 kgf / mm ² ) conditions are medium carbon steel and medium carbon low alloy steel (0.45). Gears that have been subjected to heat treatment such as induction quenching to .about.0.6 wt% C) are used.

  As a gear reducer used in the construction / civil engineering machine, there is a demand for a gear having higher strength and lower cost as well as withstanding higher surface pressure from the viewpoint of higher output and compactness. .

  In addition, the construction and civil engineering machines often climb over obstacles such as rocks and structures during driving or excavate these obstacles while turning. Due to the impact load, the carburizing and quenching gear is damaged.

On the other hand, induction hardening and hardened gears have higher toughness than carburized and hardened gears. However, as described above, when used under a high surface pressure of 150 kgf / mm ² or more, surface pressure resistance such as pitching, scuffing, and early wear. There is a problem that defects in strength are likely to occur. In addition, the carburized and hardened gear has a problem that it does not have sufficient durability for use under a high surface pressure of 230 kgf / mm ² or more, and the surface pressure strength for compactness is not sufficient.

  The present invention has been made to solve the above-described problems. In a gear used in a rolling condition with slip, the surface pressure resistance strength is localized adhesion due to slip under boundary lubrication. Focusing on the tooth surface temperature rising to 300 ° C. due to heat generation due to heat generation, and one or more carbides of V, Ti, Zr, Nb, Ta, Hf that hardly dissolve in austenite by induction hardening of the rolling surface, Low cost for various high surface pressure resistance that improves seizure resistance of tooth surface by pre-dispersing nitride and / or carbonitride on tooth surface and tempering hardness at 300 ° C. is HRC50 or more It aims at providing the manufacturing method of rolling members, such as an induction hardening gear.

For SNCM815, SCM420, SCr420, and SMnB420 steel (carburized case-hardened steel) that have undergone carburizing and quenching treatment, preliminary investigation of rolling surface pressure strength (pitting strength) with their sliding in the range of surface pressure of 375 to 220 kgf / mm ² As a result, 10 ⁷ surface pressure pitching starts to occur at a rotation is 210 kgf / mm ^2, X-ray half width of the martensite phase of the rolling contact surface outermost layer generated pitching in each surface pressure 4-4 It decreases to 2 ° and remarkable softening is observed in the outermost surface of the rolling contact surface.

Further, the carbon steel was adjusted to HRC61~62 the S55C carbon steel by quenching and tempering treatment, as a result of rolling contact fatigue strength at a surface pressure of 250 kgf / mm ² were preliminary study, pitching at ¹⁰⁷ rotation begins to occur surface pressure approximately 180kgf a / mm ^2, X-ray half width of the rolling surface of the martensite phase occurring pitching at a surface pressure of 250 kgf / mm ² is substantially similar to that of the carburized hardened steel 3.6 to 4. It has decreased to 2 °.

Furthermore, eutectoid Motoko (1) (0.77 wt% C) is also a result of the preliminary study the rolling contact fatigue strength on, 10 ⁷ surface pressure pitching starts to occur at a rotational almost 230~240kgf / mm ² It is almost the same as the rolling surface pressure strength of the carburized case-hardened steel consisting of substantially the same carbon amount, and the carburized case-hardened steel has a grain boundary oxide layer and an incompletely hardened layer on the rolling surface. It was found that there was a decrease due to variations in the rolling contact pressure strength due to.

Furthermore, as a result of preliminary investigation on the rolling contact surface pressure strength of the eutectoid carbon steel (2) subjected to spheroidizing treatment (2) (0.85 wt% C, 0.43 wt% Cr) subjected to induction hardening. The surface pressure at which pitching starts to occur at 10 ⁷ rotations is approximately 260 to 270 kgf / mm ^2, which is higher than the rolling surface pressure strength of the eutectoid carbon steel (1) (0.77 wt% C). It has been found that this is due to the fact that about 2% by volume of fine cementite particles are dispersed in the rolling surface martensite phase.

Furthermore, from the viewpoint of increasing the martensite hardness while dispersing the fine cementite particles (about 2% by volume), SUJ2 containing about 1.0% by weight carbon and 1.5% by weight Cr is increased from 840 ° C. result of rolling contact fatigue strength despite tempered so that HRC62.5 after quenching and preliminary study, 10 ⁷ are substantially at 270 kgf / mm ² is the surface pressure which pitting begins to occur at rotation therewith of the eutectoid steel The X-ray half-value width of the martensite phase of the rolling contact surface, which showed almost the same strength and generated pitching at a surface pressure of 250 kgf / mm ² , was 4.2-4.5 °, almost the same as that of the carburized case-hardened steel. It turns out that it is decreasing. Further, in order to disperse more fine cementite particles, SUJ2 subjected to spheroidizing treatment was induction-quenched at a heating temperature of 950 to 980 ° C., but the rolling contact pressure strength was higher than that obtained from quenching from the previous 840 ° C. 300 kgf / mm ² , and this is due to the fact that fine cementite particles are dispersed by about 10% by volume in the rolling surface martensite phase with a solid solution carbon concentration of 0.35% by weight. Further, it was found that the lower limit dispersion amount of at least fine cementite particles was 2% by volume, preferably 5% by volume, and the upper limit dispersion amount was 10% by volume or more.

  Further, the hardness when carbon steel containing 0.46, 0.55, 0.66, 0.77, 0.85 wt% of carbon is quenched from 820 ° C. and tempered at 100 to 350 ° C. for 3 hours each. As a result of investigating the X-ray half width, and further examining the data related to these already published (for example, “Materials”, Vol. 26, No. 26, P26), the X-ray half width of the martensite phase Is equivalent to a state of tempering to approximately HRC 51 to 53, for example, the surface carbon concentration of carburized case-hardened steel is adjusted to approximately 0.7 to 0.9% by weight. As a result, it was found that the tempering temperature corresponds to approximately 300 ° C.

  From the above preliminary test results, in the present invention, it is clarified that the tooth surface outermost surface portion is tempered by the heat generated when the gears mesh with each other under high surface pressure, and softens, thereby generating pitching. It was clarified that the tempering hardness at 300 ° C. should be HRC53 or higher as an index for obtaining a pitching strength similar to that of a carburized and quenched gear.

  In addition, in the comparison of the 300 ° C. tempered hardness of the carburized hardened layer obtained by carburizing and quenching SCM420 steel and the 300 ° C. tempered hardness of the eutectoid carbon steel simply subjected to the quenching treatment, Cr and Mo with respect to temper softening resistance were compared. Since almost no improvement has been confirmed, a new alloy design is required to increase the temper softening resistance in low temperature tempering at approximately 300 ° C. in order to impart pitching strength higher than that of carburized and quenched gears by induction hardening. In addition, the cementite carbon steel (2) (0.85 wt% C), fine cementite particles having a particle size of 0.1 to 1.5 μm, such as the effect of improving the rolling contact pressure strength of SUJ2, are martensified. It has been clarified that dispersion in the site phase effectively improves the surface pressure strength, and the cementite particles have an average particle diameter of 1.5 μm or less. It was clarified that it is preferable.

  In addition, the mechanism by which the dispersion of the cementite particles improves the surface pressure resistance is that the seizure resistance on the rolling surface during sliding in the boundary lubrication state is remarkably improved by the dispersion of the hard cementite. It is clear that the outermost surface temperature is reduced and the wear resistance is improved (called hard particle dispersion effect). In order to improve the seizure resistance more effectively, as described later, steel is used as the hard particles. It is preferable to use MC type carbides, M (C, N) type carbonitrides, and MN type nitrides formed by V, Ti, Zr, Nb, Ta, Hf, etc., which have a very low adhesion property. Revealed.

The induction-hardened gear design that can withstand the above-mentioned pitching strength by carburizing and quenching (surface pressure Pmax = 230 kgf / mm ² or more) is 0.3 times the surface pressure value based on the theoretical analysis of Hertz surface pressure. The hardness to withstand the fatigue strength of the cantilever shear stress (R = 0) is set, but the calculated value is approximately HRC 53.4, and the martensitic phase of the rolling surface where pitting occurred in the above-described preliminary test The hardness obtained from the X-ray half width (HRC = 53) agrees very well, and the hardness of the outermost surface of the rolling surface is approximately 300 ° C. due to frictional heat generated by rolling accompanied by slip. since the pitching occurs at the time of heating to, to 300 ° C. temper hardness is set to be at least Pmax = 230kgf / mm ² to endure for HRC53 or more Carburized gear equal to or greater than that of the high surface 圧歯 car was found to be developed me.

Furthermore, as will be described later in Example 2, the hardness of the 300 ° C. tempered martensite phase of carbon steel containing 0.1 to 1.0% by weight of carbon is HRC = 36 × √C (% by weight) +20. 9
As a result of investigating the influence of various alloy elements on the hardness of the 300 ° C. tempered martensite phase based on this hardness, the hardness of the 300 ° C. tempered martensite phase is HRC = (36 × √C (weight %) + 20.9) + 4.33 × Si (wt%) + 7.3 × Al (wt%) + 3.1 × V (wt%) + 1.5 × Mo (wt%) + 1.2 × Cr (wt%) ) × (0.45 ÷ C (% by weight))
It was clarified that it can be described in.

  In the present invention, based on the gear material / heat treatment design described above, the content (% by weight) of each alloy component in the steel is limited as follows.

  In short, at least 0.5 to 1.5% by weight of carbon and one or more alloy elements of V, Ti, Zr, Nb, Ta, Hf are contained in an amount of 0.2 to 2.0% by weight and alloys thereof. Induction heating is performed in the rolling contact surface layer using a steel material in which one or more of carbides, nitrides, and carbonitrides having an average particle size of 0.2 to 5 μm are dispersed in an amount of 0.4 to 4.0% by volume. The solid solution carbon concentration of the quenched and tempered martensite matrix is adjusted to 0.3 to 0.8% by weight, and at least one of the carbides, nitrides, and carbonitrides in the matrix is 0.00. A rolling member characterized by being dispersed in an amount of 4 to 4.0% by volume has been developed.

  The hard particle dispersion effect usually starts to act at 0.1% by volume or more, and when it exceeds 5.0% by volume, seizure resistance decreases due to an increase in the coefficient of friction and the other party. Since it is known that the attack property to the material is also remarkable, in the present invention, for one or more of carbides, nitrides and carbonitrides, the lower limit of 0.4 volume% at which the dispersion effect appears more clearly The value is 4.0% by volume and the upper limit is set. However, it is clear that the attack property is more preferably 2.0% by volume from the viewpoint of economy.

Incidentally, the hard particles, for example, _TiC, since the case of the V 4 _{C 3} is, _TiC, V 4 _C specific gravity of ₃ are each approximately 4.9gr ^/ cm 3, a 5.65gr / cm ^3, Addition of 0.2 wt% Ti (0.25 wt% TiC is formed) and almost 0.4 vol% TiC is formed, and V ₄ C ₃ can be introduced into austenite depending on high-frequency heating conditions. Considering that the solid solution of V is not negligible (maximum 0.3 wt% V), the addition of 2.0 wt% of V forms almost 2 vol% of V ₄ C _3. The addition amount of alloy elements forming nitrides and / or carbonitrides was set to 0.2 to 2.0% by weight.

  Furthermore, in steel materials in which these carbides are dispersed in advance, the amount of carbon consumed for the formation of these carbides and the amount of solid solution carbon (0) for obtaining a hardened and tough martensitic matrix by the above various quenching. .3 to 0.9% by weight), and the carbon amount in the rolling contact layer of the present invention is set to 0.5 to 1.5% by weight. In the rolling member that quenches and hardens the rolling contact surface layer by induction hardening and nitriding, carburizing, or carburizing and nitrocarburizing induction hardening process, the carbon content of the steel to be used is 0.5. -1.5% by weight, but for rolling members that quench and harden the rolling contact surface layer by oil quenching after nitriding, carburizing or carburizing, adjust to 0.2-0.8% by weight. Obviously, it is preferable to keep it.

Further, in order to efficiently improve the seizure resistance and wear resistance on the rolling surface, carbides, nitrides and / or carbonitrides that are precipitated and dispersed in the melting stage of the steel must be relatively large. The average particle size is preferably 0.2 μm or more from the dispersed particle size (0.2 to 1.5 μm) of cementite in the above-mentioned SUJ2, and the average particle size to the counterpart material during sliding is In consideration of the attack property, it is desirable that the thickness be 5 μm or less. (Although it is refined depending on the forging conditions after melting, it is understood that the dispersion is adjusted almost uniformly with a size of 5 μm or less for TiC described later and 2 μm or less for V ₄ C _3. )

In addition, when the rolling member is applied as a gear, since there is a concern that a reduction in tooth root bending fatigue strength is caused by an internal notch action due to the carbide, nitride and / or carbonitride or the cementite, the rolling By compressing the face layer (quenched hardened layer) after high-frequency heating for a short time, the rolling austenite grain size of the rolling austenite is refined to ASTM No. 10 or more, and the amount of retained austenite remains 10 to 50% by volume, and compression A sufficient measure was taken by adding residual stress. Furthermore, a compressive residual stress of 50 kgf / mm ² or more is reliably applied to the outermost surface portion of the rolling surface layer by performing shot peening treatment on the tooth surface and the tooth base.

As described later, the hard particle dispersing effect is that the induction hardening gear in which TiC, V ₄ C ₃ (No. P7, No. P2) is dispersed in carbon steel (S55C) has the same surface pressure strength as the SCM420 carburized gear. From the fact that it was confirmed, the improvement effect is due to improving the seizure resistance when sliding under high surface pressure on the tooth surface, and suppressing the occurrence of scoring and the increase in tooth surface temperature. It is clear that it is preferable to manufacture an inexpensive induction-hardened gear. Furthermore, in the present invention, in order to further improve the surface pressure strength and make a compact high-strength gear, as described above, induction hardening is applied in which quenching is performed after short-time high-frequency heating (900 to 1050 ° C.). By adding a fine cementite particle of 1 μm or less in the martensite matrix in the rolling surface layer and dispersing it by 10% by volume or less, and containing Si and / or Al for improving the low temperature temper softening resistance Developed a rolling member using steel material.

  The cementite has a hardness of approximately Hv 850 to 1000, and is not significantly different from the martensite matrix hardness. Therefore, the cementite has little attack on the counterpart material, and the hard particle dispersion effect is small. 10 volume% is effective in consideration of the cementite dispersion amount (about 10 volume%) of the SUJ2 induction hardening rolling surface layer, but from the viewpoint of further improving the surface pressure strength, the upper limit of the cementite dispersion amount is 15 volume%. It is clear that it is preferable to do so.

  Since the heating temperature at the time of induction hardening is as extremely high as 900 to 1050 ° C. compared to the quenching temperature such as carburizing and quenching mainly including furnace heating, for example, the surface of a rolling member using carbon steel often used as induction hardening steel. It is difficult to form a hardened hardened layer in which cementite is dispersed in the layer, and in the case of using low alloy steel, a hardened hardened layer in which cementite is dispersed in the martensite phase that dissolves the target carbon concentration is used. It cannot be formed. In order to solve this problem, in the state where a ferrite phase (αFe phase) and cementite coexist, an alloying element Cr, which is most remarkably concentrated in cementite, is added to the steel material in a range of 0.3 to 1.5% by weight. Furthermore, Cr is concentrated in the cementite in the range of 2.5 to 10.0% by weight (second invention), and the solid solution of cementite in austenite is delayed by rapid induction heating to the quenching temperature; By delaying the solid solution of cementite, the concentration of carbon dissolved in austenite was adjusted.

  The Cr concentration in cementite in the steel subjected to induction hardening is determined by the concentration of Cr in cementite in the two-phase structure (ferrite + cementite), which is the previous structure. It is known that when the phase structure is sufficiently heated, the Cr concentration in cementite is concentrated to about 28 times the Cr concentration in ferrite (about 35 times when heated at 600 ° C.). The cementite enriched with Cr is dissolved in the austenite during heating, and the solid solution mechanism (speed) of the cementite at that time is the Fe-C-M (alloy element) ternary state at the heating temperature shown in FIG. This can be explained from the relationship between the figure and the carbon isoactivity diagram (isocarbon activity diagram) shown in the figure.

  FIG. 1 is an isothermal sectional view at a quenching temperature of induction heating of an Fe-C-M ternary phase diagram in which an alloy element similar to Cr having a strong affinity with carbon is added as a main component of a steel material used in the present invention. The carbon activity equal to the carbon activity in the steel having the composition indicated by point A in the figure is schematically shown, and the carbon activity is increased by the addition of M element as shown by a thin line passing through the point A in the figure. The isocarbon activity curve rises to the right as it decreases, intersects with the solid solubility line of cementite, and is linear with the cementite composition point (point C) contained by the M element that balances with the intersection (point B). It is tied to.

  Other isocarbon activity lines (thin lines) are calculated according to each carbon activity, and the carbon activity increases as the carbon concentration increases, but the Fe-C axis (Fe-C binary system). ) Is defined as the carbon activity Ac = 1.

  In the steel composition A point used in FIG. 1, the composition of ferrite and cementite in the pre-quenching structure is given by E point and F point. When rapidly heated to the quenching temperature, Cementite leaves the alloy element M in place, and only extremely diffusible carbon rapidly dissolves in austenite. In this case, the austenite interface composition that is locally equilibrated with cementite is given by the G point. Is larger than the carbon activity at point A of the steel composition, carbon diffuses rapidly due to the gradient of the chemical potential of the carbon, and the cementite disappears in a very short time, but after the cementite disappears, the cementite Is homogenized toward the point A composition on the isocarbon activity line in FIG. ← → indicated by) with for, it can be seen that the homogenization of the carbon (example solid solution in cementite readily austenite by rapid induction heating).

  However, when more alloying element is added to the steel (H point) and more alloying elements are concentrated in the cementite (J point), the cementite will leave the alloying element M in place and carbon. The carbon activity in austenite that equilibrates with cementite when only the solid solution is dissolved (K point) is lower than the carbon activity of the original A point composition, so along the isocarbon activity line passing through the K point Carbon diffuses in an extremely short time, but further solid solution progresses, and in order for cementite to completely dissolve, alloy element M moves from point K to point B along the solid solubility line of cementite. It can be seen that the cementite cannot be dissolved unless it diffuses, and the solid solution of cementite is slowed down while being controlled by the diffusion of the alloy element M. In addition, the time for complete dissolution of cementite is such that the difference in alloy element concentration between the intersection of the isocarbon activity line passing through the original C point composition and the cementite solid solubility line and the B point in the cementite increases. It is clear that it becomes slow, and it can be seen that the cementite is easily dispersed by high-frequency heating and quenching. In addition, it is possible to adjust the solid solution carbon concentration in the martensite matrix by the carbon concentration at the M concentration in the original ferrite on the isocarbon activity line passing through the K point position determined by the CM concentration in the cementite. it is obvious. The distance that the alloy element diffuses when heated and held at 1000 ° C. for 2 seconds is about 0.03 μm with respect to the distance that carbon diffuses under the same condition, about 0.03 μm, and 0.5 μm diameter cementite particles Because the diffusion distance is about 12% of the radius, cementite remains according to the above mechanism, carbon diffuses sufficiently in the austenite matrix, and a hard martensite matrix is formed after quenching. I understand.

  Furthermore, by performing induction heating in which the solid solution time of cementite in the austenite (γ phase) from A1 temperature to induction heating to 900 to 1050 ° C. is controlled within 10 seconds and subsequent quenching treatment, cementite As described above, the carbon concentration in the martensite matrix in which the carbon is dispersed in an undissolved state is equal to the carbon concentration corresponding to the equivalent carbon activity passing through the K point governed by carbon diffusion, and accordingly, However, the hardenability of the γ phase, which is the parent phase, is almost determined by the alloy element concentration in the original ferrite and the carbon concentration in the γ phase. By applying this principle to the gear, it becomes easy to form a hardened hardened layer along the tooth profile shape. Thereby preventing quench cracking by generating compressive residual stress along the shape, developed tooth root, a more elevated gear member fatigue strength bending of the tooth bottom. It is also clear that the rate of decrease in hardenability increases as the alloy element concentrates in the cementite in the pre-quenching structure, and the decrease is more noticeable as the element is more easily concentrated in the cementite of Cr, Mn, and Mo. .

  In order to be more specific, induction hardening is performed by rapidly heating to 1000 ° C. using the Fe—C—Cr ternary phase diagram and the isocarbon activity diagram (at 1000 ° C.) shown in FIG. The case is considered below.

(1) When cementite rapidly dissolves (when Cr concentration in cementite is low)
When the steel indicated by point A (0.8 wt% C, 0.4 wt% Cr) in Fig. 2 is sufficiently heated at 700 ° C in the coexistence region of (cementite + ferrite), point B (cementite, 2.6 wt% Cr) ) And C point (ferrite, 0.09 wt% Cr), and in this state, when rapidly heated to 1000 ° C. where it becomes an austenite state by high frequency heating, the B point and C point are homogenized toward the A point. As mentioned above, while the alloy element in the cementite at point B hardly diffuses in the austenite, the arrow passes through the point D to the austenite (point C) in which the carbon had a ferrite composition. After rapidly diffusing and dissolving cementite as indicated by (↑ ↓), equilibration with the carbon isoactivity curve (isocarbon activity curve) passing through the point A, the Cr element is converted to the point A by the subsequent heating. For By homogenizing, it is possible to achieve a faster solid solution of cementite, and the carbon concentration of the martensite matrix is almost the same as that of point A, so that martensite with higher hardness can be obtained. I understand that.

(2) When the cementite solid solution is greatly delayed 1
When steel indicated by point E (0.8 wt% C, 1 wt% Cr) in Fig. 2 is sufficiently heated at 700 ° C in the coexistence region of ferrite and cementite, point G (ferrite, 0.24 wt% Cr) and point F (Cementite, 6.61 wt% Cr). In this state, when rapidly heated to 1000 ° C., which becomes an austenite state by high-frequency heating, the F point becomes a solid solution toward the H point as described above. However, the carbon activity at the H point (the austenite interface having the same carbon activity as cementite when the cementite is dissolved) is lower than the carbon activity at the original E point. First, after cementite quickly dissolves to the H point by the diffusion-controlled mechanism of carbon, the γ-phase composition (H point) that equilibrates with cementite by further heating for a long time is the solid solubility curve of cementite. Along with this, the cementite is dissolved at the point I on the solid solubility line of the cementite, which is in the relationship with the E point and the isocarbon activity, with the diffusion of Cr, and when the austenite (γ) composition reaches the point I, the cementite It turns out that it dissolves completely. Therefore, the carbon concentration in the martensitic matrix after heating and quenching for a short time is about 0 at the same Cr concentration (0.24 wt%) as the G point on the isocarbon activity line passing through the H point. It can be seen that about 3% by volume of cementite is dispersed in an undissolved state in very hard martensite.

(3) When the dissolution of cementite is greatly delayed 2
In the case of (2), the H ₇ point is that Cr ₇ C ₃ carbide different from cementite and austenite (γ phase) are in equilibrium, and the two-phase equilibrium of non-equilibrium cementite and austenite (γ phase) is in the solution process of cementite. In this solid solution process of cementite, up to the isocarbon activity line (about 0.2) passing through point J on the solid solubility line of Cr ₇ C ₃ carbide, the cementite is controlled by carbon diffusion rate. However, the subsequent cementite solid solution does not require the formation of Cr ₇ C ₃ carbide before the disappearance of cementite, so that the austenite (γ phase) interface composition is at least Cr ₇ C ₃ carbide. There does not need to be deposited (the austenite (gamma phase) + cementite + Cr 7 _{C 3)} of the cementite to constraints reaching the K point of the three-phase coexisting region is applied It can be seen that the solvent is more delay. In this case, the carbon concentration in the martensite matrix obtained by the induction heating and quenching is about 0.45% by weight, and about 5% by volume of cementite is not solidified in the hard (HRC 57-61) martensite matrix. It turns out that it disperses in a molten state.

From the above-mentioned examination results, it is clear that the limit point at which a significant delay of cementite occurs is when the Cr concentration in cementite is concentrated to about 3% by weight (point J) under heating conditions of 1000 ° C. When heated at 900 ° C., about 2.5% by weight, for example, [Cr in cementite in the case where steel containing C: 0.55% by weight and Cr: 0.3% by weight is heated at 700 ° C. Concentration] = αKCr × Cr concentration in steel / (1- (carbon concentration in steel / 6.67) × (1-αKCr)) is calculated as 2.6% by weight, so the lower limit addition amount of Cr Is about 0.3 wt%, preferably 0.4 wt% or more. Here, αKCr is a distribution coefficient representing the concentration of Cr between the ferrite phase and cementite, and is defined as distribution coefficient αKM = M element concentration in cementite (wt%) ÷ M element concentration in ferrite (wt%). The distribution coefficient (at 700 ° C.) of each alloy element is
It is known that αKCr = 28, αKMn = 10.5, αKv = 9.0, αKMo = 7.5, αKW = 2.0, αKNi = 0.34, αKSi, Al≈0, and Cr is It turns out that it concentrates most to cementite in various alloys.

  Furthermore, in order to apply the high-frequency heating / quenching method to the rolling member at 900 to 1050 ° C., it is necessary to increase the martensitic matrix hardness after tempering at 140 ° C. or higher to at least HRC 55 or higher after the quenching. In order to increase the carbon concentration in the martensite matrix to 0.3 wt%, more preferably 0.4 wt% or more, it is necessary to adjust the Cr concentration in cementite to 10 wt% or less. I know that there is. Therefore, in this invention, it turns out that it is preferable to adjust Cr density | concentration in cementite in the range of 2.5 to 10 weight%.

  Further, when the carbon concentration in the martensite matrix when diffusing at the carbon diffusion rate is about 0.9 wt% or more, the carbon cracking property at the time of induction heating and quenching is likely to increase, so the carbon concentration Is preferably adjusted so as to be 0.3 to 0.8% by weight, and the amount of steel carbon is 0.5 to 1.5% by weight when the amount of undissolved cementite is 2 to 15% by volume. It turns out that it is applicable.

  Therefore, the Cr amount when adding 0.5 to 1.5 wt% carbon is preferably 1.8 wt% or less, but is adjusted to 1.5 wt% or less from an economical viewpoint. It is preferable. Furthermore, when applied to gear steel as will be described later, it is preferably used at 1.0% by weight or less in order to suppress hardenability.

Furthermore, V, Cr, Mo, and W, which have a large affinity with carbon and have a large partition coefficient αKM between ferrite and cementite, are not only highly concentrated to cementite, but also described in the relationship (3) above. Similar to the presence of such Cr ₇ C ₃ carbides, Fe ₂₁ Mo ₂ C ₆ , V ₄ C ₃ , and WC special carbides are present, so the same examination as Cr ₇ C ₃ is conducted, and V in the cementite, It is understood that the Mo and W concentrations need to be adjusted to 0.3 wt% V, 1 wt% Mo, 1 wt% W or more, respectively. As a result, V: 0.1 wt% or more, Mo: 0.3 Addition of not less than wt% and W: 0.5 wt% or more causes a solid solution delay of the cementite, so in the present invention, at least Cr is 0.3 wt% or more and / or V is 0.1 wt% Add more Shall be, Mo, W is assumed is preferably added in combination as needed.

When V exceeds 0.3% by weight as described above, V ₄ C ₃ carbides remain in the martensite matrix after induction hardening, and V ₄ C ₃ is remarkable. Since the particle dispersion effect is exhibited, it is understood that 0.1 to 2.0% by weight is preferable as the V addition amount range.

  It is known that Mo, V, and W can be dissolved in cementite up to Mo: about 2% by weight, V: about 0.6% by weight, and W: about 1.5% by weight. % Or less, V: 0.3% by weight or less, and W: 1% by weight or less, because it relates to the solid solution delaying action of cementite in the relationship of (2), the relationship of (2) above. It is clear that it is added to the action of Cr, and it is clear that the (Cr + V + Mo + W) concentration in cementite is more preferably adjusted to 2.5 to 10% by weight.

  Further, Mn has a larger αKMn than V and Mo, and is an element that is remarkably concentrated in cementite. However, there is no special carbide in the austenite state, and the steel composition range that is usually added (˜1.5). Weight%) (˜8.5 wt% Mn in cementite), it is clear that there is no solid solution delaying action of the cementite due to the relationship (2) above, so Mn should be 1.5 wt% or less. Obviously we can do it.

  The distribution coefficient αKM between the cementite and the ferrite is that when sufficiently heated at 700 ° C. as described above. For example, when the heating temperature is lowered to 600 ° C., the distribution coefficient becomes larger, Cr, Although Mn, V, and Mo are more concentrated to cementite, it is clear that it is preferable to heat-treat in advance below the eutectoid temperature of the steel because it is not sufficiently concentrated when the heating is too short. is there.

  Furthermore, it is clear that it is not preferable in terms of strength to disperse pearlite-structured plate-like cementite or coarse cementite particles in the martensite matrix of the rolling surface layer, and as a pretreatment for induction hardening, cementite is granular. It is clear that it is more preferable to reduce the size to an average particle size of 1 μm or less. However, it is necessary to add an element having a large αKM, and the concentration tendency to cementite is the most. Clearly, it is preferable to add large Cr.

  Concentration of the alloy to cementite is a heat treatment in a (ferrite + cementite) two-phase structure, but the alloy element is also concentrated in the cementite by heating in the two-phase structure at (Austenite + cementite) above the A1 temperature. For example, at 800 ° C., the concentration of alloy element M in cementite / the concentration of alloy element M in austenite = the concentration of alloy element M in austenite = γKM (partition coefficient of alloy element M between cementite / austenite. For example, γKCr. : 8.5, γKV: 13, γKMo: 4.2, γKMn: 2.4), it is apparent that the alloying element concentration in cementite can be adjusted.

  Further, as described above, in the vicinity of the position of dissolved cementite and the vicinity of undissolved cementite when heated rapidly and for a short time, as understood from the relationship of the isocarbon activity lines in FIGS. 1 and 2 above. Cs, Mn, Cr, and Mo that remarkably lower the Ms temperature are concentrated, and the residual austenite phase is likely to be formed in the vicinity thereof. In particular, the above-mentioned special carbides, nitrides, and charcoals that are prone to internal notches It is clear that it is preferable to recover toughness in the rolling contact layer in which nitride and cementite are dispersed and to improve the surface pressure strength, and in the present invention, the residual austenite phase is adjusted in the range of 10 to 50% by volume. It was decided to be done.

  The lower limit value of the retained austenite is referred to the amount of retained austenite phase by conventional carburizing and quenching, and it is well known that the upper limit retained austenite phase amount is 50 volume% or more, so that the wear resistance is significantly reduced. %.

  In addition, in the case where the structure before induction hardening is a cementite spheroidized structure as described above, a deep martensite layer needs to be formed once when spheroidizing is performed by material refining (quenching and tempering heat treatment). In addition, it is inevitably necessary to use a steel having high hardenability, but in the present invention, it is preferably carried out by spheroidizing annealing, and in particular, a large amount of Si and Al that significantly increase the eutectoid temperature is added. Steel has a feature that its heat treatment time can be greatly shortened.

The rolling member used by performing the induction hardening often has a heating homogenization time within a few seconds. As described above, Cr, Mo, V, Mn, etc. are concentrated in the cementite and induction-quenched. In this case, since the homogenization of the alloy elements in the martensite matrix hardly progresses, the particle dispersion effect due to cementite on the rolling contact surface strength is not sufficiently exhibited due to the decrease in temper softening resistance. Because there is a concern that the surface pressure strength is not improved compared to carburized and quenched rolling members, it hardly concentrates in cementite and remains efficiently in the martensite matrix, temper softening of the martensite matrix Si or Al for improving resistance is added to at least the steel material, either Si: 0.5 to 3.0 wt% or Al: 0.20 to 1.5 wt%. (Si + Al): 0.5 to 3.0% by weight, and more than one of V, Ti, Zr, Nb, Ta, Hf, Mn, Ni, Cr, Mo, Cu, W, B, and Ca An alloy element and unavoidable impurity elements such as P, S, N, and O are contained, and the balance is substantially made of Fe. Furthermore, the rolling surface layer made of the steel material is subjected to tempering treatment at 300 ° C. or lower after quenching treatment or induction quenching treatment, and the hardened hardened layer becomes HRC50 or more by tempering at 300 ° C.
5 ≦ 4.3 × Si (wt%) + 7.3 × Al (wt%) + 3.1 × V (wt%) + 1.5 × Mo (wt%) + 1.2 × Cr (wt%) × (0 .45 ÷ C (wt%))
It is more preferable to use a steel material adjusted so as to satisfy the above relationship.

  In addition, the 300 ° C. tempering hardness of the S55C carbon steel described above is HRC47, and considering that when the hard particles are dispersed in this martensite matrix, it almost matches the surface pressure strength of the carburized and quenched gear. In the present invention, the hardness of the martensite matrix is set to HRC50 or higher even by tempering at 300 ° C., but as a rolling member with higher surface pressure strength, the hardness is HRC53 or higher. It is more preferable.

  In the present invention, since a large amount of ferrite stabilizing elements such as Si and Al is added, it is necessary to first examine the risk that the ferrite phase remains in the hardened hardened layer during induction hardening. As shown, in the steel added with 3 wt% Si, the heating temperature during induction hardening (900 to 1050 ° C.) by adding the carbon amount to 0.35 wt% or more, more preferably 0.45 wt% or more. It can be seen that the austenite is sufficiently formed. In addition, when Al is added instead of Si, since Al has a ferrite stabilizing ability that is twice or more that of Si, in the present invention, it is preferable that 1.5% by weight is the Al upper limit addition amount. It is clear.

  Even if it is a (ferrite + pearlite) structure as a structure prior to induction hardening, it is difficult to homogenize by high-frequency heating for a short time when coarse ferrite is present. Contains carbides, carbonitrides of V, Zr, Nb, Ta, and Hf, refines the structure of (ferrite + pearlite), suppresses the generation of coarse ferrite, and adjusts the amount of carbon in steel to 0.6 weight or more It is clear that it is preferable to do so.

  Note that Cr, Mn, and Mo significantly increase the hardenability of the steel, and in steels containing high concentrations of carbon, the cracking properties during induction hardening and quenching increase. It is preferable that the hardenability of austenite is significantly reduced by concentrating in cementite sufficiently in a heated state at a temperature of 550 ° C. and induction hardening so as to leave the cementite, and in particular, Mn is a hardened steel. It is an element that enhances the properties most. Concentration of Mn in the residual cementite by adding Cr as described above has the effect of reducing the hardenability of austenite by induction hardening. It is convenient for contour quenching in which the gear is hardened by hardening along the tooth profile, but more preferably, Mn addition in the steel material is performed. It is clear that it is preferable to limit the amount to 0.2 to 0.5% by weight, and in the present invention, at least Cr: 0.3 to 1.5% by weight and steel used for the rolling member / Or V: 0.1 to 0.3 wt%, Mn: 0.2 to 0.5 wt%, Mo: 0.5 wt% or less, W: 0.5 wt% or less It is clear that it is preferable to contain the above.

  Further, carbides, nitrides and / or carbonitrides having an average particle size of 0.2 to 5 μm, and an average particle size of 1.5 μm or less, composed of one or more alloy elements of V, Ti, Zr, Nb, Ta, and Hf. The average particle diameter of one or more alloy elements of V, Ti, Zr, Nb, Ta, and Hf is 0.2 μm by carburizing, carburizing, or nitriding treatment on the rolling surface layer in which the cementite particles are dispersed. The following nitrides and / or carbonitrides are newly deposited and dispersed, and the rolling surface layer has a carbon content of C: 0.65 to 1.5% by weight and / or a nitrogen content of N: 0.1 to 0. Developed a rolling member with excellent surface pressure strength, characterized by being adjusted to 0.7% by weight.

  As described above, steel in which carbides, nitrides and / or carbonitrides having an average particle diameter of 0.2 to 5 μm made of one or more alloy elements of V, Ti, Zr, Nb, Ta, and Hf are dispersed in advance. In addition, when carburizing, carburizing, nitriding, or nitriding treatment is performed, V, Ti, Zr, Nb, Ta, Hf dissolved in the matrix may precipitate as finer nitrides or carbonitrides. V, Ti, Zr, Nb, Ta, and Hf dissolved in the matrix are carbonitrides having a lower solid solubility, and the previously dispersed carbides are changed to carbonitrides and partially re-solidified once. It melts and precipitates as fine as 0.2 μm or less as a more stable carbonitride, and the seizure resistance of the rolling surface layer is remarkably improved and the surface pressure strength is improved at the same time. It revealed that.

  In addition, the layer depth at which extremely fine carbides, nitrides and / or carbonitrides are newly dispersed in the carburizing, carburizing and nitriding treatments, and the dispersion action improves seizure resistance on the sliding surface. Since the temper softening of the rolling surface layer concentrates on the outermost surface layer portion and the rolling surface wear life of the gear member or the like is determined in the range of up to 100 μm, it may be set to 100 μm or less from an economical viewpoint. It is clear that it is preferable.

  The rolling surface layer is hardened by induction hardening on the premise of induction hardening. However, an average grain composed of one or more alloy elements of V, Ti, Zr, Nb, Ta, and Hf is used. Carbide, carburizing or nitrocarburizing treatment is performed on a rolling surface layer in which cementite particles having a diameter of 1 μm or less are dispersed by previously dispersing carbide, nitride and / or carbonitride having a diameter of 0.2 to 5 μm. Rolling by newly depositing and dispersing carbide, nitride and / or carbonitride having an average particle size of 0.2 μm or less composed of one or more alloy elements of V, Ti, Zr, Nb, Ta, and Hf It is clear that the method of improving the surface pressure resistance of the surface layer can be applied by carburizing and carburizing and nitrocarburizing methods, but by applying the above-mentioned induction hardening treatment after carburizing and carburizing and nitriding. It is clear that it is more preferable to improve the dispersion of fine cementite particles, application of large compressive residual stress, refinement of prior austenite crystal grains, and toughening by adjusting the solid solution carbon concentration of the martensite matrix. .

  Furthermore, in the case of applying a method of strengthening the rolling surface layer by induction hardening after carburizing, carburizing or nitriding treatment, at least C: 0.2 to 0.8% by weight And containing either Si: 0.5 to 3.0 wt% or Al: 0.2 to 1.5 wt% or (Si + Al): 0.5 to 3.0 wt%, Further, one or more alloy elements of Mn, Ni, Cr, Mo, V, Cu, W, Ti, Nb, B, Zr, Ta, Hf, and Ca, and inevitable impurity elements such as P, S, N, and O are included. It is contained that the steel material is substantially composed of Fe, and the economical efficiency of machining, formation of a hardened hardening layer along the tooth profile after induction hardening, more effective generation of the large compressive residual stress, the fine Dispersion of cementite particles, former austenite Such finer Akiratsubu, it is clear and more preferable for the gear member.

  In the steel material used for the rolling member subjected to the carburizing or nitrocarburizing treatment, the remaining carbon amount excluding the carbon amount necessary to disperse V, Ti, Zr, Nb, Ta, and Hf in advance as a carbide is obtained. It is adjusted to be 0.1 to 0.3% by weight, and when adding a large amount of Si, the ferrite phase tends to remain in the inner position than the carburized or carburized nitrogen layer during induction hardening. Since there is a concern that martensite having sufficient strength is not formed, Mn and Ni for stabilizing the austenite phase are set to (Mn + Ni): 1.0 to 2.5% by weight, and the quenching temperature is kept low. Cr for dispersing cementite: 0.5 to 1.5% by weight, Mo for enhancing hardenability: 0.35% by weight or less, B: 0.0005 to 0.005 It was it preferably contains an amount%.

  Furthermore, it has already been reported in Japanese Patent Application No. 2002-135274 that a remarkable toughness effect is exhibited by coexistence of the added amounts of Al and Ni: 0.3 to 1.5% by weight, The excellent Charpy impact properties even in a hard martensite structure containing 0.6% by weight and 1.2% by weight carbon are effective as gear materials that can dramatically improve the impact load resistance of gears. It is clear that there is. In the present invention, the addition of Ni is made 1.5% by weight or less in order to make the steel material more expensive.

Even when the rolling member is a gear member that is induction-hardened after carburizing and quenching, carburizing and nitriding, or carburizing or carburizing and nitriding, the carbide, nitride and / or carbonitride, and cementite, etc. A gear using physical processing means such as shot peening so that compressive residual stress of at least 50 kgf / mm ² or more remains in the root portion in order to suppress deterioration of the root bending strength due to the internal notch action. Clearly, the member is preferred.

  The function of each alloy element that leads to each of the above inventions will be described below.

V, Ti, Zr, Nb, Ta, Hf: 0.2 to 2.0% by weight
The alloy element reacts with carbon and nitrogen in steel to form MC type carbide, nitride and M (CN) type carbonitride, and since the solid solubility in steel is extremely small, These materials easily disperse and precipitate finely in steel, but these materials are extremely hard (Vickers hardness of 1500 or more) and have excellent thermal and chemical stability compared to the hardened and hardened layer of steel. For example, carbide and cermet, such as tools exposed to extremely high temperatures, show excellent wear resistance and seizure resistance. However, when it is dispersed in a large amount, there is a problem that the friction coefficient at the time of sliding becomes large, and the seizure resistance is deteriorated and the attack property against the counterpart material becomes remarkable. Therefore, in the present invention, the amount of dispersion is limited to the range of 0.4 to 4% by volume, and the improvement of seizure resistance is optimized.

Among the alloy elements, V ₄ C ₃ carbide has a relatively large solid solubility with respect to austenite, and depending on the high-frequency heating conditions, 0.3 wt% V equivalent is solid solution. It is preferable to be 2 wt%, but further, the addition of 0.1 wt% or more of V delays the solid solution of cementite by high frequency heating, and the cementite particles effectively remain in the rolling surface layer. The lower limit of the V addition amount was 0.1% by weight. Further, as described above, V enhances the softening resistance at low temperature tempering, and at the higher temperature tempering softening resistance, the softening resistance is more remarkable than Si and Al. It is preferable to actively add at least wt%.

  Furthermore, it is very preferable that the austenite crystal grains can be prevented from becoming coarse by dispersing the carbide, nitride and / or carbonitride in the austenite even when it is overheated during induction hardening.

Si: 0.5 to 3.0% by weight
Si is an element that remarkably enhances the temper softening resistance in the low temperature tempering temperature range of 350 ° C. or lower. As a mechanism for improving the temper softening resistance, ε carbide precipitated at a low temperature is further stabilized, and cementite is precipitated. It has been shown that softening is prevented by pulling to higher temperatures.

  The lower limit addition amount of Si is that the softening resistance ΔHRC at 300 ° C. tempering of Si per 1 wt% is 4.3 and the base hardness of 300 ° C. tempering obtained from 0.55 wt% carbon is HRC47. Therefore, the Si addition amount for securing the 300 ° C. tempering hardness HRC50 is about 0.5 wt%, and the Al addition amount when 0.15 wt% Si coexists is softened. Since the resistance ΔHRC was 7.3, the lower limit amount of Si and Al was set because the resistance ΔHRC was about 0.25% by weight.

  The upper limit of Si is such that the Ac3 transformation temperature does not exceed 900 ° C. within the range of 0.3 to 0.8% by weight of solid solution carbon in the martensite matrix, and the induction hardening temperature is unnecessarily high. However, in the case of oil quenching after carburizing and carburizing and nitriding, the carbon content of the steel material must be 0.2 to 0.8% by weight. Therefore, it is clear that the upper limit value is preferably suppressed to 2% by weight so that the quenching temperature does not become excessively high.

Al: 0.25 to 1.5% by weight
Al has a strong deoxidizing action and is effective in purifying steel materials because it has a strong action of rejecting P and S, which are impurity elements contained in steel, from grain boundaries, Furthermore, in the present invention, it is confirmed that Al is an element that enhances the low-temperature temper softening resistance than Si (ΔHRC = 7.3), and the addition amount when adding Al alone is 0.25 to 1. 5% by weight, and when Si is partially replaced with 0.15 to 1.5% by weight of Al (Si + Al): 0.5 to 3.0% by weight, As mentioned above, Al is a ferrite stabilizing element that is stronger than Si, and has the effect of raising the Ac3 temperature by about 1.6 times compared to Si, so its maximum addition amount is 1.5 wt%. The following was set (2.5% by weight / 1.6). In addition, when oil quenching or induction quenching after carburizing and carburizing and nitriding treatment, the carbon content of the steel material needs to be 0.2 to 0.8 wt%, so the quenching temperature becomes excessively high. Obviously, it is preferable to keep the upper limit to 1% by weight.

Ni:
It has already been reported in Japanese Patent Application No. 2002-240967 that when the added amounts of Al and Ni: 0.3 to 2.5% by weight coexist, a remarkable toughness action is exhibited. The fact that a high hardness martensite structure containing 6 wt% and 1.2 wt% carbon exhibits excellent Charpy impact characteristics is that it is effective as a gear material that the impact load of a gear can be dramatically improved. it is obvious. In the present invention, the addition of Ni is made 1.5% by weight or less in order to make the steel material more expensive. Ni is an element that stabilizes austenite, and its addition reduces the quenching temperature when coexisting with Si and Al. Therefore, the rolling surface layer that hardens the rolling surface layer by carburizing and carburizing and nitrocarburizing quenching is applied. The moving member is preferably used together with the amount of Mn added, and the guideline is preferably (Mn + Ni): 2.5% by weight when, for example, a maximum of 3% by weight Si is added.

Cr:
Cr is an element that remarkably enhances hardenability. However, when the gear tooth surface is hardened by induction hardening, only the surface layer heated to the Ac3 transformation temperature or higher by high-frequency heating is rapidly cooled. Therefore, the hardenability (DI value) as a gear material does not need to exceed the hardenability DI value of ordinary carbon steel level: 2.0 inch or more, so that cementite is not dispersed as described above. As a gear material, Cr is often adjusted to 0.5% by weight or less in order to reduce its cracking property. However, in the case where cementite is dispersed by induction hardening as described above, cementite should be added. In order to reduce the size, it is preferable to add 0.3 to 1.5% by weight of Cr. In this case, the cementite is spheroidized to sufficiently concentrate Cr in the cementite and suppress the solid solution of the alloy elements in the austenite that occurs during high-frequency heating, thereby substantially quenching the austenite phase. It is clear that it is preferable to suppress the cracking property by suppressing the property, but it is also preferable to disperse the cementite by V which hardly affects the hardenability and to keep the Cr addition amount to 0.5% by weight or less. It is. Moreover, in the rolling member which carries out oil hardening after the above-mentioned carburizing and carburizing and nitriding, Cr is preferably 1.5% by weight or less from the viewpoint of ensuring hardenability.

Mn:
Mn is not only a remarkable desulfurization action, but also an element that stabilizes austenite as described above. Furthermore, since Mn is an effective element that improves the hardenability of steel, an appropriate amount is added depending on the purpose. However, in a rolling member containing 0.3 to 0.8% by weight of solid solution carbon in the martensite matrix, considering that austenite is sufficiently stabilized by carbon, The limiting amount is 0.2% by weight. In addition, in a rolling member that performs carburizing and carburizing and nitrocarburizing treatment and induction-quenching the rolling surface layer, the amount of carbon that sufficiently stabilizes austenite is small. When adding up to 3% by weight of stabilizing Si, add up to about 2% by weight of inexpensive Mn, or (Mn + Ni): 2.5% by weight together with the amount of Ni added Preferred.

Mo:
Mo is an effective element that improves the hardenability of the steel and is an element that suppresses temper brittleness. Therefore, in the present invention, it is usually added in the range of 0.35% by weight or less, which is the same level as the case-hardened SCM steel. In rolling members to which the above-described induction hardening method is applied, the addition of 0.3% by weight or more delays the solid solution of cementite in austenite during induction heating, but its role It is clear that it is not an indispensable additive element in consideration of the economic viewpoint, and W is almost the same.

Next, about the manufacturing method of a rolling member, the manufacturing method of the rolling member by 1st invention is the following.
0.5 to 1.5% by weight of carbon, 0.3 to 1.5% by weight of Cr, and one or more alloy elements selected from the group consisting of V, Ti, Zr, Nb, Ta, and Hf are added in an amount of 0. One to one or more of carbides, nitrides and carbonitrides having an average particle size of 0.2 to 5 μm, containing 2 to 2.0% by weight of those alloy elements, 0.4 to 4.0% by volume, and cementite Using a steel material dispersed by 7.5 to 20% by volume, the solid solution carbon concentration of the matrix phase martensitic structure of the rolling contact surface layer that has been induction-hardened and tempered at a low temperature is 0.3 to 0.8% by weight. In the matrix, one or more of the carbide, nitride and carbonitride are dispersed in an amount of 0.4 to 4.0% by volume, and cementite is dispersed in an amount of 2 to 15% by volume. .

Moreover, the manufacturing method of the rolling member by 2nd invention is as follows.
0.5 to 1.5% by weight of carbon, 0.3 to 1.5% by weight of Cr, and one or more alloy elements selected from the group consisting of V, Ti, Zr, Nb, Ta, and Hf are added in an amount of 0. One to one or more of carbides, nitrides and carbonitrides having an average particle size of 0.2 to 5 μm, containing 2 to 2.0% by weight of those alloy elements, 0.4 to 4.0% by volume, and cementite Using a steel material dispersed in an amount of 7.5 to 20% by volume, induction heating quenching and rapid tempering rolling surface layer which are rapidly heated within 10 seconds from A1 temperature to a quenching temperature of 900 to 1050 ° C. The solid solution carbon concentration of the martensite structure matrix is adjusted to 0.35 to 0.8% by weight, and 2 to 15% by volume of particulate cementite having an average particle size of 1.5 μm or less is dispersed in the matrix. Furthermore, 10 to 50% by volume of residual austenite remains. One or more of the retained carbide, nitride and carbonitride are dispersed in an amount of 0.4 to 4.0% by volume, and cementite is dispersed in an amount of 2 to 15% by volume.

Moreover, the manufacturing method of the rolling member by 3rd invention is as follows.
One or more alloy elements selected from the group consisting of 0.2 to 0.8% by weight of carbon and 0.5 to 1.5% by weight of Cr and V, Ti, Zr, Nb, Ta, and Hf One to one or more of carbides, nitrides, and carbonitrides containing 2 to 2.0% by weight and having an average particle size of 0.2 to 5 μm composed of those alloy elements are dispersed in an amount of 0.4 to 4.0% by volume. An average grain composed of one or more alloy elements selected from the group consisting of V, Ti, Zr, Nb, Ta, and Hf by using a steel material, carburizing, carburizing, or nitriding the rolling surface layer. Nitride and / or carbonitride having a diameter of 0.2 μm or less is newly precipitated and dispersed, and the amount of carbon on the rolling surface is 0.65 to 1.5% by weight and / or the amount of nitrogen is 0.1 to 0. 0.7% by weight and cementite is dispersed by 7.5 to 20% by volume, Furthermore, the solid solution carbon concentration of the martensitic matrix of the rolling surface layer of the rolling surface layer that has been induction-heated and quenched by low-temperature tempering is adjusted to 0.35 to 0.8% by weight. One or more of carbides, nitrides and carbonitrides are dispersed in an amount of 0.4 to 4.0% by volume, and cementite is dispersed in an amount of 2 to 15% by volume.

  In each of the above inventions, it is preferable to perform physical processing of shot peening in order to increase the compressive residual stress in the rolling contact surface layer (fourth invention).

  In addition, when quenching and hardening the gear tooth surface portion using the induction hardening method, it is sufficient that only the surface layer portion heated to the Ac3 transformation temperature or higher by high-frequency heating is hardened and hardened. (DI value) is not required to exceed the hardenability of ordinary carbon steel level of 2.0 inch or more, and has the feature that inexpensive steel can be used. Therefore, in the present invention, the addition amount of Mn and Cr is adjusted to be lower. It is clear that it is more preferable to adjust alloy elements such as Si, Al, Ni, Mo, and V so that the DI value of the steel material is 2.0 inches or less.

  As the induction hardening method using the above steel material, induction hardening is performed after rapid heating within 10 seconds by induction heating from a preheated state at room temperature or below A1 temperature to a hardening temperature of 850 to 1100 ° C. exceeding A1 temperature. At least the rolling contact surface layer was quenched and hardened by the work. Quenching hardening when SUJ2 (1.01 wt% C-1.5 wt% Cr, Hv200) sufficiently spheroidized as described later is heated to each quenching temperature at a heating rate of 6 ° C / sec and then rapidly cooled. As a result of investigating the layer hardness, the cementite residual amount, and the solid solution carbon content of the martensite phase, a structure in which 5% by volume or more of cementite is dispersed at a high density in a sufficiently hard martensite matrix is sufficiently formed. Although it is clear that the proper heating temperature in this case is 900 to 1000 ° C., when the Cr concentration is lowered from SUJ2, the Cr concentration in cementite is lowered, and the proper heating lower limit temperature is 1100. It is clear that the temperature is about ° C. In addition, when estimated from a heating rate of at least 6 ° C./sec, it is difficult to generate a large compressive residual stress and to form a hardened hardened layer along the tooth profile in the gear member of the present invention. It is clear that the high-frequency heating time is preferably 10 seconds or less in terms of a high-frequency heating rate using a high-frequency (induction) heating method suitable for rapid heating by internal heat generation of the face layer.

  Furthermore, the rolling contact surface layer of the rolling member is preheated to a temperature of 300 ° C. to A1 and rapidly heated to a quenching temperature of 900 to 1100 ° C. at a frequency of 60 kHz or less and a heating rate of 150 ° C./sec or more. More preferred is a rolling member that is rapidly cooled and formed with a hardened hardened layer along the tooth profile with a lower strain. From the economic point of view of production, the upper limit of the heating rate is 2500 ° C./sec. Clearly, a quenching method is preferred.

  Next, specific examples of the method for manufacturing a rolling member according to the present invention will be described with reference to the drawings.

[Example 1: Pitting strength of quenched and tempered carbon steel and carburized and quenched case-hardened steel (preliminary test)]
In this example, in order to investigate the rolling fatigue strength accompanied by slipping on the tooth surface of the gear, a roller pitching test was performed using the test piece shown in FIG. 4, and various quenched and tempered carbon steels and carburized and quenched skins were used. The pitching strength of the baked steel was examined. Table 1 shows the chemical components of various carbon steels and case-hardened steels used in this example. After the various steel materials were processed into the small roller shape shown in FIG. 1, 2, and 4 were heated at 820 ° C. for 30 minutes and then quenched with water, tempered at 160 ° C. for 3 hours, and subjected to the test. No. In No. 3, the rolling surface was quenched and hardened using a 40 kHz high frequency power source after the material tempering treatment, and the same tempering treatment as described above was performed. Furthermore, no. 5 was carburized at 930 ° C. for 5 hours (carbon potential 0.8), cooled to 850 ° C., held at 850 ° C. for 30 minutes, quenched into 60 ° C. quenching oil, and then tempered in the same manner as described above. gave.

The large roller is No. 4 SUJ2 material was heated at 820 ° C for 30 minutes and then water-quenched and tempered at 160 ° C for 3 hours. The roller pitching test was lubricated with # 30 engine oil at 70 ° C, with a small roller at 1050 rpm and a large roller. (Load roller) was set at 292 rpm to give a slip rate of 40%, and surface pressure was applied under various conditions of 375 to 220 kgf / mm ² .

FIG. 5 summarizes the number of repetitions in which pitching occurred at various surface pressures. The life line connecting the minimum number of repetitions at each surface pressure in the case-hardened case-hardened steel is shown by the solid line in the figure. but if the pitting number of repetitions was defined as the rolling surface fatigue strength the surface pressure at which the 10 ⁷ times, the pitting strength was found to be approximately 210 kgf / mm ^2. In addition, when the same arrangement is considered, no. 1: 175 kgf / mm ² , No. 1 2: 240 kgf / mm ² , No. 3 (Induction hardening): 260 kgf / mm ² , No. 3 4: 270 kgf / mm ² and no. 4 (induction hardening): 290 kgf / mm ² , No. 4 in which about 2% by volume and about 10% by volume of cementite particles were dispersed by induction hardening. 3, no. It can be seen that the rolling contact surface fatigue strength of No. 4 is remarkably improved. In addition, carburized case-hardened steel has some variation, which is due to grain boundary oxidation during carburizing on the rolling surface, the presence of an incompletely hardened layer, and a large amount of retained austenite. When compared by the number of times, No. It can be seen that the pitching strength of 2 is not different.

  Further, as a result of investigating the X-ray half width of the martensitic phase of the rolling contact surface where pitching occurred, 1: 3.6-4.0 °, No. 2: 4 to 4.2 °, no. 3: 4.2-4.4 °, no. 4: 4.3-4.6 °, no. 5: 4 to 4.2 °.

  Further, No. 1 subjected to the heat treatment. As a result of investigating the X-ray half width when the test pieces of 1 to 5 were tempered at 250 to 350 ° C. for 3 hours each, the half width of the pitching generation rolling surface was tempered at about 300 ° C. In addition, it can be seen that the relationship between the tempering hardness and the half-value width of carbon steel having various carbon concentrations reported in "Materials, Vol. 26, No. 280, P26" is almost matched.

[Example 2: Confirmation of resistance to temper softening]
Table 2 shows the alloy composition used in this example. Heat treatment was performed at 810 to 870 ° C. for 30 minutes, then water cooled, and the Rockwell hardness HRC of the test pieces tempered at 300 ° C. and 350 ° C. for 3 hours was investigated. Further, the influence of each alloy element addition amount on these hardnesses Was analyzed.

As a preliminary experiment, carbon steel containing 0.1 to 1.0% by weight of carbon and 0.3 to 0.9% by weight of Mn was also investigated, and base data for analyzing the influence of the alloy elements It was. as a result,
At 250 ° C., HRC = 34 × √C (weight%) + 26.5
At 300 ° C., HRC = 36 × √C (weight%) + 20.9
At 350 ° C., HRC = 38 × √C (wt%) + 15.3
It was found that

Further, as a result of analyzing the influence of the alloy element based on the hardness of these carbon steels, it was found that the temper softening resistance ΔHRC can be described by the following equation at 300 ° C., for example.
ΔHRC = 4.3 × Si (wt%) + 7.3 × Al (wt%) + 1.2 × Cr (wt%) × (0.45 ÷ C (wt%)) + 1.5 × Mo (wt%) + 3.1 × V (% by weight)

  From this result, it was found that Al exhibited 1.7 times the temper softening resistance of Si and was found to be extremely effective as an element for improving the rolling contact pressure strength.

  FIG. 6 shows the consistency between the tempering hardness obtained from the analysis result and the actually measured tempering hardness, and it can be seen that the variation width can be accurately predicted within the range of HRC ± 1. Further, the 300 ° C. tempering hardness of the carburized layer (0.8 wt% carbon) of SCM420 (No. 5) of Example 1 is also indicated by ☆ in FIG. 6 and is in good agreement with the calculated value. I understand.

[Example 3: Improvement 1 of pitching strength by a steel material excellent in temper softening resistance]
Table 3 shows the alloy components of the steel materials used in this example. No. P1-No. P3 was quenched from 850 to 920 ° C. and then tempered at 160 ° C. for 3 hours. P4-No. P9 is the one subjected to induction hardening under the same induction heating conditions as in Example 1 and subjected to a roller pitching test.

  The pitching strength test was performed under substantially the same conditions as in Example 1, and the results are shown in FIG. Further, the solid line in the figure shows the pitching generation line obtained in Example 1 by the solid line in FIG. 7, and the pitching generation line obtained in this example is shown by the broken line.

  From these results, it was found that Al, Si was added alone or in combination, and further, no. From the comparison of P4-9, it was found that the addition of V and Ti markedly improved the anti-pitching strength of the rolling surface. No. 1 in which cementite was dispersed. 4, no. 9 and No. 5, no. From the comparison of 6, it can be seen that the pitting resistance is remarkably improved by the dispersion of cementite.

FIG. 8 shows No. 1 with 1.94 wt% V added. The V ₄ C ₃ carbide dispersed in the P6 alloy is shown, and it can be seen that the particle size is approximately 1.5 μm or less and is uniformly dispersed.

[Example 4: Improvement of pitching strength 2 by steel material excellent in temper softening resistance]
Table 4 shows the alloy components of the steel materials used in this example. No. G1-No. As shown in FIG. 9, G5 is 850 ° C. after performing a carburizing treatment at 950 ° C. consisting of a 2 hr carburizing period at a carbon potential (CP) of 1.2 wt% C and a 4 hr diffusion period at CP = 0.8. Then, it was quenched into a quenching oil at 60 ° C., and further subjected to a tempering treatment at 180 ° C. for 3 hours (carburizing quenching tempering treatment). In addition, a constant temperature period of 850 ° C. in FIG. 9 is set to 2 hours, and a carburizing / nitrogen quenching / tempering process in which ammonia gas is added to the constant temperature period and subjected to a nitriding process is also prepared, which is the same as the previous example. A roller pitching test was performed under the conditions.

  FIG. 10 shows the result of the roller pitching test. As a result, in the carburized quenching and tempering test specimen, it was confirmed that the rolling surface strength was significantly improved by adding Ti and V, but the level of the carburizing and quenching quenching and tempering treatment was further enhanced. I understand that.

  FIG. The distribution state of Ti was examined by X-ray microanalyzer of the rolling surface layer obtained by carburizing and nitriding G3, and FIG. 12 shows an electron micrograph of the rolling surface layer. In addition to TiC, it can be seen that new TiCN is very finely dispersed and precipitated by the diffusion permeation treatment of C and N into the rolling surface layer.

[Example 5: Improvement of sliding characteristics by dispersion of carbide, nitride, and carbonitride 1]
In this example, the same steel material as in Examples 3 and 4 was used, and a peripheral speed was 10 m while being lubricated with engine oil # 30 at 80 ° C. using a constant speed friction wear sliding test piece as shown in FIG. / Sec, and the other material was subjected to carburizing, quenching and tempering treatment on SCM420, and the surface hardness was adjusted to HRC60, the same pressing pressure was maintained for 5 minutes, and the pressing pressure was 25 kgf / cm ² The pressing pressure (kgf / cm ² ) at the time when the coefficient of friction suddenly increases (burn-in state) was increased every time.

  The sliding test pieces in Table 3 of the present invention were quenched from 870 ° C. and tempered at 160 ° C. for 3 hours, and the sliding test pieces in Table 4 were subjected to the heat treatment of Example 4 and were compared materials. SCM420 carburized, quenched and tempered (SCM420 + GCQT), SCM44040 (SCM440 + QT), S55C (S55C + QT), and SUJ2 (SUJ2 + QT) were used.

  The results are shown in Tables 3 and 4, but clearly no. P4-9, no. In G1-5, the seizure resistance is remarkably improved by the dispersion effect of the hard particles. In particular, it can be seen that the improvement in seizure resistance due to the addition of Ti is significant.

[Example 6: Confirmation of dispersion conditions and wear resistance of cementite particles]
In this example, in order to verify that cementite is dispersed at a high density in the martensite matrix and the wear resistance of the rolling member accompanied by slip is remarkably improved, the steel materials shown in Table 1 are used. The induction hardening was performed under various conditions while adjusting the structure before induction hardening, and the quenched structure was observed and the wear resistance was investigated.

  14 (a), 14 (b), and 14 (c) are Nos. Four steel materials (SUJ2-equivalent materials) were heated to 810 ° C. for 2 hours, subjected to cementite spheroidization treatment (slow cooling method) to gradually cool to 600 ° C., and then heated at 800 to 1000 ° C. at a heating rate of 6 ° C./sec by high-frequency heating. It shows the result of investigating the relationship between the carbon concentration in martensite and the amount of undissolved cementite from the hardness of the quenched layer after heating to each temperature. Clearly, the concentration of Cr to cementite (about 9 wt% Cr) delays solid solution of cementite in austenite during heating, and martensite with sufficient hardness required for rolling members. In order to obtain, it is necessary to set the heating temperature to at least 900 ° C., the carbon concentration in the martensite at that time is about 0.3% by weight, and 12% by volume of hard cementite particles From the fact that it is dispersed, it can be seen that the gear member has excellent seizure resistance (scoring resistance), pitting resistance, and wear resistance.

  In addition, even when the high-frequency heating temperature is set to 1000 ° C., it can be seen that an extremely hard quench hardened layer in which about 6% by volume of cementite is dispersed in a 0.7% by weight C martensite matrix can be obtained. Since the retained austenite phase increases and the hardness of the hardened hardened layer is saturated, the rolling member has an induction hardening temperature of 1050 ° C. or less in consideration of quenching cracking properties, and the amount of carbon in martensite. It can be seen that it is necessary to satisfy one of the conditions of 0.7% by weight or less and the cementite dispersion amount of 2% by volume or more.

  Further, Fe-0.98 wt% C-0.55 wt% Si-1.11 wt% Mn-1.08 wt% Cr (Table 5, No. W3 described later) and the above spheroidizing treatment , Kept at 820 ° C. for 1.5 hours and then air-cooled to prepare a dispersion of pearlite-like cementite and granular cementite, and each of 900 to 1100 ° C. at a heating rate of 1000 ° C./sec which is extremely higher than the normal high-frequency heating rate. The structure of the sliding surface quenched after heating to temperature was investigated.

  FIG. 15 shows the structure of the spheroidizing treatment (slow cooling method) that was quenched from a heating temperature of 1000 ° C., and the granular cementite was dispersed at a high density. Further, as shown in FIG. As for the hardness in the hardened layer, it can be seen that even though the retained austenite contains 30 to 45% by volume, it is markedly hardened to the maximum Hv830, and the amount of retained austenite is contained up to 50% by volume. It can also be seen that it can be used without any problem in wear resistance. In addition, it is clear that a remarkable increase in SUJ3 is recognized as compared with the retained austenite in the oil quenching heat treatment from 830 ° C. in the conventional furnace heating.

  FIG. 17 shows the structure of a sliding surface obtained by heating the pearlite cementite and granular cementite dispersed at 1000 ° C. at a heating rate of 1000 ° C./sec. It was found that pearlite-structured plate-like cementite was dispersed in the martensite matrix, and it was hardened (Hv940) more significantly than the structure hardness (Hv880) in FIG.

  Furthermore, as a result of investigating the relationship between the heating rate at which the pearlite-like cementite is dispersed and the heating temperature using the present steel material containing the pearlite-pre-textured structure, the pearlite-like cementite is also obtained in a quenched structure at a heating rate of 150 ° C / sec and a heating temperature of 900 ° C It was found that the hardness of the quenched and hardened layer at that time was significantly hardened to Hv945, and at least 100 ° C / sec when 850 ° C was set as the lower limit of the heating temperature in order to stably disperse cementite. Although it is clear that the heating rate is necessary, it is clear that the heating rate is preferably 150 ° C./sec or more. It can also be seen that the time for rapid heating beyond the A1 temperature to a quenching temperature of 1050 ° C. is preferably within 3 seconds.

  FIGS. 15 and 17 show the Cr concentration in cementite analyzed by EDAX (Energy Dispersive Analysis of X-ray) inside the electron microscope, but significant Cr concentration is also observed in pearlite cementite. As can be seen, since the Cr concentration is lower than that of granular cementite, the result is that pearlitic cementite is likely to be in solid solution, and heat treatment is performed to concentrate Cr in the pearlite cementite in the pre-quenched structure. Thus, it is clear that the pearlite cementite can be dispersed more stably.

  Furthermore, rapid heating and hardening No. The carbon concentration in martensite obtained from the measurement of the lattice constant of the martensite phase of steel No. 1 was 0.5% by weight. Compared with the result of 1 (0.7% by weight), the solid solution carbon concentration is reduced by rapid high-frequency heating, and the cementite dispersion is increased in order to improve the surface pressure strength and wear resistance of the rolling member. Is clearly the preferred method.

  Further, in No. 5 containing 0.53% by weight carbon in Table 5 described later. FIG. 18 shows a structure obtained by quenching a spheroidizing material of W2 (equivalent to SCM453) at 1000 ° C. at an induction heating rate of 1000 ° C./sec. The structure of a rolling member (gear member) using a low-carbon steel material is shown in FIG. It can be seen that fine cementite having an average particle size of about 0.2 μm remains sufficiently to improve the surface pressure strength, seizure resistance, and wear resistance.

Table 5 shows the surface pressure using the roller pitching test method in which the above-mentioned slip was applied using steel materials in which various cementites were dispersed after being heated to 1000 ° C. at a heating temperature of 1000 ° C./sec in the same manner as described above. 240 kgf / mm ² , 2 × 10 ⁶ shows the result of evaluating the wear resistance of the rolling surface layer by the wear depth (μm) of the small roller after ⁶ tests. It can be seen that the abrasion resistance is improved by the dispersion of cementite. However, when compared with the wear resistance of a conventional carburized and quenched rolling surface (SCM420 + carburized and quenched in Table 5), 2% by volume or more of cementite is present. Clearly, it is more preferable to disperse.

  It can also be seen that the structure in which cementite is dispersed in a pearlite form in the martensite matrix is superior in wear resistance as compared with that in which granular cementite is dispersed.

Solid solution mechanism diagram in γ phase using Fe-CM system phase diagram and carbon isocarbon activity diagram Fe-C-Cr isocarbon activity diagram (at 1000 ° C) Phase diagram showing the effect of alloying elements on Fe-3 wt% Si It is a figure which shows the test piece for roller pitching tests, (a) is a small roller test piece, (b) is a large roller test piece. Graph showing the preliminary test results of roller pitching strength Graph showing comparison of measured value and calculated value of tempering hardness (at 300 ° C) Graph (1) showing the pitching strength of the rolling member of the present invention No. Photo showing the metal structure of the P6 rolling surface layer The figure which shows the heat treatment pattern of carburizing quenching tempering processing Graph (2) showing the pitching strength of the rolling member of the present invention No. Photo showing the distribution of Ti by X-ray microanalyzer analysis of the rolling surface layer of carburizing and nitriding quenching of G3 No. Photograph showing the metallographic structure of the rolling contact layer after carburizing and nitriding treatment of G3 Diagram showing the shape of a constant speed frictional wear test piece The graph (a) showing the relationship between the high-frequency heating temperature and the quenching hardness, the graph (b) showing the relationship between the high-frequency heating temperature and the martensite C concentration (6 ° C./sec), and the high-frequency heating temperature and the θ phase volume%. Graph showing relationship (c) Photo showing hardened and hardened structure with dispersed granular cementite Graph showing the relationship between heating temperature, quenching hardness and residual γ amount Photograph showing a hardened and hardened structure in which pearlite-structured cementite is dispersed A cementite spheroidized by quenching and tempering. Photograph showing the hardened structure of W2 alloy

Claims (4)

  0.5 to 1.5% by weight of carbon, 0.3 to 1.5% by weight of Cr, and one or more alloy elements selected from the group consisting of V, Ti, Zr, Nb, Ta, and Hf are added in an amount of 0. One to one or more of carbides, nitrides and carbonitrides having an average particle size of 0.2 to 5 μm, containing 2 to 2.0% by weight of those alloy elements, 0.4 to 4.0% by volume, and cementite Using a steel material dispersed by 7.5 to 20% by volume, the solid solution carbon concentration of the matrix phase martensitic structure of the rolling contact surface layer that has been induction-hardened and tempered at a low temperature is 0.3 to 0.8% by weight. One or more of the carbides, nitrides, and carbonitrides are dispersed in the parent phase in an amount of 0.4 to 4.0% by volume and cementite is dispersed in a volume of 2 to 15% by volume. Manufacturing method.   0.5 to 1.5% by weight of carbon, 0.3 to 1.5% by weight of Cr, and one or more alloy elements selected from the group consisting of V, Ti, Zr, Nb, Ta, and Hf are added in an amount of 0. One to one or more of carbides, nitrides and carbonitrides having an average particle size of 0.2 to 5 μm, containing 2 to 2.0% by weight of those alloy elements, 0.4 to 4.0% by volume, and cementite Using a steel material dispersed in an amount of 7.5 to 20% by volume, induction heating quenching and rapid tempering rolling surface layer which are rapidly heated within 10 seconds from A1 temperature to a quenching temperature of 900 to 1050 ° C. The solid solution carbon concentration of the martensite structure matrix is adjusted to 0.35 to 0.8% by weight, and 2 to 15% by volume of particulate cementite having an average particle size of 1.5 μm or less is dispersed in the matrix. Furthermore, 10 to 50% by volume of residual austenite remains. One or more of the retained carbides, nitrides and carbonitrides are dispersed in an amount of 0.4 to 4.0% by volume, and cementite is dispersed in an amount of 2 to 15% by volume.   One or more alloy elements selected from the group consisting of 0.2 to 0.8% by weight of carbon and 0.5 to 1.5% by weight of Cr and V, Ti, Zr, Nb, Ta, and Hf One to one or more of carbides, nitrides, and carbonitrides containing 2 to 2.0% by weight and having an average particle size of 0.2 to 5 μm composed of those alloy elements are dispersed in an amount of 0.4 to 4.0% by volume. An average grain composed of one or more alloy elements selected from the group consisting of V, Ti, Zr, Nb, Ta, and Hf by using a steel material and subjecting the rolling surface layer to carburizing, carburizing, or nitriding. Nitride and / or carbonitride having a diameter of 0.2 μm or less is newly precipitated and dispersed, and the amount of carbon on the rolling surface is 0.65 to 1.5% by weight and / or the amount of nitrogen is 0.1 to 0. 0.7% by weight and cementite is dispersed by 7.5 to 20% by volume, Furthermore, the solid solution carbon concentration of the martensitic matrix of the rolling surface layer of the rolling surface layer that has been induction-heated and quenched by low-temperature tempering is adjusted to 0.35 to 0.8% by weight. One or more of carbide, nitride and carbonitride are dispersed in an amount of 0.4 to 4.0% by volume, and cementite is dispersed in an amount of 2 to 15% by volume.   The method for manufacturing a rolling member according to claim 1, wherein physical processing of shot peening is performed in order to increase compressive residual stress in the rolling surface layer.

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