JP2017062177A - Quality assurance method and device for machine element material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a quality assurance method and device for a machine element material capable of discriminating whether a rolling fatigue lifetime reaches a fixed level by assuring an existence probability of an interposing object which is positioned in fixed depth from a raceway surface and in which a crack may progress, at a predetermined value or less by performing an interposing object inspection in a steel material state.SOLUTION: The method includes the steps of: acquiring information relating to an interposing object of a steel material (S1); simulating casting and acquiring information about a direction of a fiber flow after the casting (S2); investigating a distribution state of the interposing object positioned in fixed depth from a surface of a rolling plane in a state where the steel material is productized into a machine element based on the information relating to the interposing object acquired in the interposing object inspection step and the information about the direction of the fiber flow acquired in the casting simulation step (S3); and calculating an existence probability of the interposing object which is positioned in fixed depth from a raceway surface and in which a crack may progress, based on stored information in a database relating to the interposing object in which a crack may progress, and the distribution state of the interposing object (S6).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a quality assurance method and apparatus for machine element material that guarantees that the rolling fatigue life of a material of a machine element that fatigues due to rolling of a bearing or the like of a rolling bearing has reached a certain level.

  It is well known that the bearing surface of the bearing and non-metallic inclusions directly under the raceway affect the rolling fatigue life of the rolling bearing. For example, in the paper “Non-Patent Document 1” “Effect of Non-Metallic Inclusion Size on Rolling Fatigue Life of Bearing Steel”, the L10 life of the same material and hardness depends on the type of inclusion. It is said that it is governed by the size of the largest inclusion existing in the dangerous volume directly below the surface. In recent years, the existence probability of huge non-metallic inclusions affecting the rolling fatigue life has been reduced by reducing the oxygen concentration in steel, but it cannot be made zero at all. There has been proposed a method for detecting the enormous non-metallic inclusions inevitable in the vicinity of the raceway surface and guaranteeing the lifetime. For example, in Patent Document 1, a stable rolling fatigue life can be guaranteed by regulating the non-metallic inclusions on the raceway surface to a length of less than 500 μm, preferably less than 100 μm, using an ultrasonic exploration method.

  It has also been reported that the direction of fiber flow introduced in steelmaking and forging processes also affects the rolling fatigue life. Patent Document 2 states that the influence of the fiber flow on the life can be removed by defining the alloy component amount in the steel, specifically, the Cu and AL amounts below the threshold value. As disclosed in Patent Document 3, a technique for correcting the influence of fiber flow by devising a forging method is also disclosed.

  According to Patent Document 4, it is possible to extend the life by regulating the non-metallic inclusions on the raceway surface to a length of less than 300 μm and the fiber flow to the raceway surface to less than 15 ° using an ultrasonic exploration method. Yes.

JP 2000-130447 A Japanese Patent No. 2969232 Japanese Patent Laid-Open No. 5-277615 JP 2003-301850 A

"Effect of nonmetallic inclusion size on rolling fatigue life of bearing steel" Sanyo Technical Report Vol.12 (2005) No.1 p38 “New Test Method for Determining Mode / Fatigue Crack Propagation Properties of Hard Steel” NTN Technical Review No.69 (2001) p53

  Although the ultrasonic flaw detection method described above has an advantage that the entire bearing raceway surface can be inspected, a dead zone is formed, so that it is difficult to detect the vicinity of the surface. Although it is possible to detect non-metallic inclusions with a size of several tens of μm by performing ultrasonic flaw detection with a high frequency, it is difficult to detect a size of less than 100 μm when considering industrial use. Non-Patent Document 2 presents the calculation result of the critical diameter of a disk-shaped crack in which the crack propagates under the JIS-SUJ2 mode / lower limit stress intensity factor ΔKth condition obtained from experiments. According to this, when the maximum surface pressure is 2.5 GPa, the critical diameter of the crack is 50 μm, and if it is less than 100 μm, which is the regulation value of Patent Document 1, it cannot be said that sufficient rolling fatigue life can be secured.

  Further, it may be difficult to control the fiber flow direction with respect to the raceway surface by forging due to the complicated shape of the product and the manufacturing process. Along with the diversification of steel materials and global procurement, steel materials with alloy component amounts that exceed the threshold may be used, so a new method for ensuring a rolling fatigue life is required.

  The object of the present invention is to perform the inclusion inspection in the state of the steel material, and to determine the existence probability of the inclusion that can be cracked and located at a certain depth from the raceway surface when it is commercialized as a machine element. It is intended to provide a quality assurance method and apparatus for a machine element material that guarantees a predetermined value or less and can determine whether or not the rolling fatigue life has reached a certain level.

According to the quality assurance method for machine element material of the present invention, when a steel material, which is a material of a machine element having a rolling surface, is commercialized into the machine element through forging, the rolling fatigue life reaches a certain level. A quality assurance method for machine element material for determining whether or not
Inclusion inspection process (step S1) for acquiring information related to inclusions in the steel material;
A forging simulation process (step S2) for obtaining information on the direction of fiber flow after the forging by performing a forging simulation for processing the steel material into the shape of the machine element;
From the information on the inclusions obtained in the inclusion inspection process and the information on the direction of the fiber flow obtained in the forging simulation process, the surface of the rolling surface in a state where the steel material is commercialized into the machine element. A distribution state simulation process (step S3) for examining the distribution state of the inclusions located at a certain depth from
Accumulated information of inclusions related to inclusions that can crack in the machine element when rolling is performed on the rolling surface, and the distribution state of inclusions obtained in the distribution state simulation (step S3) From the crack propagation inclusion existence probability estimation process (step S6) for obtaining the existence probability of an inclusion that is located at a certain depth from the raceway surface of the product and that can propagate a crack;
And a rolling fatigue life securing step (step 8) for judging whether or not the obtained existence probability is a predetermined value or less.

According to this method, first, an inclusion inspection of a steel material is performed (step 1), and a distribution state of nonmetallic inclusions in a product shape is simulated through a forging simulation (step 2) (step 3). Furthermore, for example, the existence probability of inclusions where a crack located at a fixed depth from the raceway surface can be determined by comparing with the inclusion size that can be propagated by a crack obtained by a finite element method and database (step) 6). It is assumed that the dimensional shape and the direction of fiber flow of the steel material, which is the material at the time of forging, are always determined according to how the steel material is forged into a product-shaped machine element.
In this way, by performing the inclusion inclusion inspection of the steel material, by assuring the existence probability of the nonmetallic inclusion that the crack located at a certain depth from the raceway surface of the product can propagate to a certain value or less, A stable rolling fatigue life can be secured.

  In addition, the said inclusion is a nonmetallic inclusion, for example. Further, in this specification, “constant” is a value that is arbitrarily determined, and may be arbitrarily determined based on results of design, simulation, test, and the like.

In the method of the present invention, in the distribution state simulation process (step 3), the distribution state of the inclusions located at a certain depth from the surface of the rolling surface is determined by a plurality of trials using random numbers. May be.
As a result, the existence probability of inclusions through which cracks can propagate can be determined with higher accuracy, and the accuracy of estimating the rolling fatigue life can be increased.

In the method of the present invention, regarding the construction of the database, the stress intensity factor amplitude around an arbitrary inclusion is calculated by a finite element method under an arbitrary use condition, and the calculated stress intensity factor amplitude and a known By comparison with the lower limit stress intensity factor, when the stress intensity factor amplitude is large, it is determined that the inclusion can be cracked by rolling. It is possible to construct the database of inclusions that can be implemented and cracks can propagate.
In the case of this method, the database of inclusions through which cracks can propagate can be constructed so as to be searchable according to usage conditions and specifications of the inclusions, the existence probability of inclusions through which cracks can propagate, and rolling The fatigue life can be determined with higher accuracy.

In the method of the present invention, by performing a rolling fatigue life test, a database of the relationship between the existence probability of inclusions that can propagate cracks and the rolling fatigue life is constructed, and this database and the existence of the crack propagation inclusions You may make it include the process of determining whether the rolling fatigue life has reached a fixed level by collating with the existence probability of the inclusion which the crack can progress calculated | required in the probability estimation process.
In this case, since it is possible to determine whether the rolling fatigue life has reached a certain level when an arbitrary product is processed using an arbitrary steel material, a stable rolling fatigue life can be ensured.

In the method of the present invention, the mechanical element may be a bearing ring or a rolling element of a rolling bearing.
The method of the present invention can be applied as long as it is a material of a machine element having a rolling surface, and can be applied to a joint member of a constant velocity joint in addition to a bearing component. In the case of a wheel or a rolling element, it is strongly required to estimate the rolling fatigue life, and the request can be satisfactorily met.

In the machine element material quality assurance device 20 according to the present invention, when a steel material, which is a material of a machine element having a rolling surface, is commercialized into the machine element through forging, the rolling fatigue life is maintained at a certain level. A machine element material quality assurance device for determining whether or not
Inclusion inspection information storage means 21 for storing information relating to the inclusions of the steel material;
Forging simulation means 22 for performing simulation of forging for processing the steel material into the shape of the machine element to obtain information on the direction of fiber flow after the forging;
From the information on the inclusions stored in the inclusion inspection information storage means 21 and the information on the direction of the fiber flow obtained by the forging simulation means 22, the steel material in the state of being commercialized into the machine element. A distribution state simulation means 23 for examining the distribution state of the inclusions located at a certain depth from the surface of the rolling surface;
From the accumulated information of the database 25 relating to the inclusions that can crack in the machine element when rolling is performed on the rolling surface, and the distribution state of the inclusions obtained by the distribution state simulation, Crack propagation inclusion existence probability estimation means 26 for determining the existence probability of an inclusion that can be propagated by a crack located at a certain depth from the track surface of the product;
Rolling fatigue life securing means 28 for judging whether or not the obtained existence probability is a certain value or less.

  According to the machine element material quality assurance apparatus of this configuration, as described above with respect to the machine element material quality assurance method of the present invention, the inclusion inspection is performed in the steel material state, so that the machine element material is commercialized as a machine element. In addition, it is possible to guarantee that the existence probability of inclusions, which are located at a certain depth from the raceway surface, and in which cracks can propagate, is below a predetermined value, and to determine whether the rolling fatigue life has reached a certain level.

  According to the quality assurance method for machine element material of the present invention, when a steel material, which is a material of a machine element having a rolling surface, is commercialized into the machine element through forging, the rolling fatigue life reaches a certain level. It is a quality assurance method for machine element material to determine whether or not it is an inclusion inspection process for obtaining information on inclusions in the steel material, and forging simulation for processing the steel material into the shape of the machine element Forging simulation process for obtaining information on the direction of fiber flow after forging, information on inclusions obtained in the inclusion inspection process, and information on the direction of fiber flow obtained in the forging simulation process. From the information, a distribution state simulation for examining a distribution state of the inclusions located at a certain depth from the surface of the rolling surface in a state where the steel material is commercialized into the machine element. Process, accumulated information in a database relating to inclusions that can crack in the machine element when rolling occurs on the rolling surface, and the distribution state of inclusions obtained by the distribution state simulation From the crack propagation inclusion existence probability estimation process for obtaining the existence probability of an inclusion that can be propagated by a crack located at a certain depth from the raceway surface of the product, and the obtained existence probability is less than a certain value. The rolling fatigue life ensuring process to determine whether or not there is, the inclusion is inspected in the steel material state, and when it is commercialized as a machine element, it is located at a certain depth from the raceway surface. It is possible to guarantee that the existence probability of inclusions that can develop cracks is below a predetermined value, and to determine whether the rolling fatigue life has reached a certain level.

  In the machine element material quality assurance device according to the present invention, when a steel material, which is a material of a machine element having a rolling surface, is commercialized into the machine element through forging, the rolling fatigue life reaches a certain level. A machine element material quality assurance device for determining whether or not a steel element includes inclusion inspection information storage means for storing information relating to the inclusion of the steel material, and forging that processes the steel material into the shape of the machine element. Forging simulation means for obtaining information on the direction of fiber flow after forging by performing simulation of the above, information on inclusions stored in the inclusion inspection information storage means, and fiber obtained by the forging simulation means From the information on the flow direction, the distribution state of the inclusions located at a certain depth from the surface of the rolling surface in a state where the steel material is commercialized into the machine element is examined. Distribution state simulation means, stored information in a database relating to inclusions that can crack in the machine element when rolling is performed on the rolling surface, and inclusions obtained in the distribution state simulation A crack propagation inclusion existence probability estimating means for obtaining an existence probability of an inclusion which can be propagated from a distribution state and located at a certain depth from the raceway surface of the product, and the obtained existence probability is a constant value. It is located at a certain depth from the raceway surface when it is commercialized as a machine element by conducting inclusions inspection in the steel material state, because it is provided with rolling fatigue life securing means for judging whether or not In addition, the existence probability of inclusions that can develop cracks is guaranteed to be a predetermined value or less, and it can be determined whether the rolling fatigue life has reached a certain level.

It is a flowchart which shows the quality assurance method of the machine element material which concerns on one Embodiment of this invention. It is an example of the simulation result performed by the same quality assurance method. It is a block diagram of a conceptual structure which shows the quality assurance apparatus of the machine element material which concerns on one Embodiment of this invention. It is sectional drawing of the bearing for wheels which is a machine element which has an example of the machine element made into the object of this invention. It is explanatory drawing of the fiber flow of the outer ring | wheel in the wheel bearing. It is explanatory drawing of the manufacturing process of the outer ring | wheel of a rolling bearing.

  An embodiment of the present invention will be described with reference to the drawings. This quality assurance method determines whether or not the rolling fatigue life has reached a certain level when a steel material, which is a material of a machine element having a rolling surface, is commercialized into the machine element through forging. Is a quality assurance method for machine element material in the state of a steel material, and FIG. 1 shows a flowchart of each process. The machine element having the rolling surface is, for example, a machine element that makes rolling contact with a bearing ring or rolling element of a rolling bearing, a pair of joint members of a constant velocity joint, or a torque transmission ball. In this embodiment, the rolling element is a rolling element. It is intended for bearing rings.

The process for each step in FIG. 1 will be described with FIG.
“Steel Inclusion Inspection Process” (Step S1) Acquisition of Distributed Inclusion Information This is a process of acquiring information relating to the inclusion of steel. In this process, the steel material to be inspected is cut so that the inspection surface is parallel to the steel material axial direction, that is, parallel to the fiber flow direction, to prepare a sample. Quenching is performed to ensure the hardness of the sample. The inspection surface is finished to an observable mirror surface by polishing and polishing processes. The specimen inspection surface is observed using an optical microscope or SEM-EDX (scanning electron microscope), and inclusion information such as the type, size, aspect ratio, distribution density, etc. in an arbitrary inspection area is acquired. Determination of the type of inclusions when using an optical microscope is carried out by identification based on the color of the inclusions. On the other hand, when SEM-EDX is used, elemental analysis using EDX is performed for identification.

"Forging simulation process" (step S2) Acquisition of fiber flow direction information in product shape Performs forging simulation for processing the steel material into the shape of the machine element to acquire information on the direction of fiber flow after forging It is a process.
A simulation is carried out using CAE (computer aided engineering) software such as DEFORM (Comprehensive Processing Simulation System) to see how the fiber flow in the product shape changes after forging from the steel material state. Obtain fiber flow direction information just below the raceway surface from the simulation results. FIG. 2 shows an example of the forging simulation result. The figure is an example in the case of forging the outer ring in the wheel bearing, and the part protruding in the product state is a part that becomes the outer peripheral flange of the outer ring. When forging simulation is difficult, the angle information of the inclusions obtained by carrying out the inclusion inspection of the product shape after forging rather than the steel material is adopted as alternative information.

“Simulation process of the distribution of inclusions directly under the raceway” (step S3)
Using the type, size, aspect ratio, distribution density obtained from the inclusion inspection of the steel material, and information on the fiber flow direction obtained from the forging simulation, the steel material has been commercialized into a machine element. A simulation of the distribution of inclusions located at a certain depth just below the raceway surface is performed.
Examples of inclusion distribution state simulation include random number simulation using the Monte Carlo method. In this case, the distribution state of the inclusions located at a certain depth from the surface of the rolling surface is determined by a plurality of trials using random numbers. Subsequently, by performing the inclusion inspection on the product shape of the machine element, it is also possible to confirm the accuracy of the simulation result of the inclusion distribution state obtained from the inclusion information in the steel material state.

"Examination process of crack growth from inclusions" (Steps S4 and S5)
Calculates the stress intensity factor amplitude around the inclusion of any given specification under any use condition (load, friction coefficient, etc.) by the finite element method. The presence or absence of crack growth is determined by comparing the calculated stress intensity factor amplitude with the known lower stress intensity factor reported in the paper. For example, in the case of mode II, compared with the JIS-SUJ2 mode II lower limit stress intensity factor (ΔKth = 3 MPa√m) obtained from the experiment reported in Non-Patent Document 2, the calculated stress intensity factor amplitude is When it is large, it is determined that the crack can be propagated by rolling.
This examination is carried out for each use condition and inclusion specification, and a database of inclusions in which cracks can develop is constructed for each use condition and inclusion specification. (Step S5)

“Existence probability of inclusion that can crack” (Step 6)
Deriving the probability of existence of inclusions where cracks can be developed by studying the results of simulation of the distribution of inclusions directly under the raceway and the database of inclusions where cracks can propagate can do. Therefore, it is possible to guarantee the existence probability of inclusions in which a crack located at a certain depth from the raceway surface can propagate.

"Life test result" (steps S7, S8)
A rolling fatigue life test is conducted using the test conditions such as load and the direction of the forging line as parameters, and a database of the relationship between the existence probability of inclusions that can propagate cracks and the rolling fatigue life is constructed. (Step S7)
By collating with the database, it is possible to determine whether the rolling fatigue life has reached a certain level when processing any product using any steel material, ensuring a stable rolling fatigue life can do. (Step S8)

  As described above, if the quality assurance method for machine element material according to this embodiment is used, by performing inclusion inspection in the steel material state, a crack is caused by rolling, which is located at a certain depth from the raceway surface in the product shape. The existence probability of inclusions that can progress can be obtained, and it can be determined whether or not the rolling fatigue life has reached a certain level by guaranteeing the existence probability of inclusions to a certain value or less.

FIG. 3 is a block diagram showing a conceptual configuration of a machine element material quality assurance apparatus for performing the machine element material quality assurance method according to the embodiment.
This machine element material quality assurance device 20 has a rolling fatigue life that reaches a certain level when steel material, which is a material of a machine element having a rolling surface, is commercialized into the machine element through forging. An inclusion inspection information storage means 21, forging simulation means 22, distribution state simulation means 23, database 25, crack growth inclusion existence probability estimation means 26, life test result storage means 27, and rolling fatigue life securing means 28.

The quality assurance device 20 is means for storing information relating to steel inclusions, and stores the results of the inclusion inspection performed in step S1 of FIG.
The forging simulation means 22 is means for obtaining information on the direction of fiber flow after the forging by performing a forging simulation for processing the steel material into the shape of the machine element, and the process of step S2 in FIG. I do.

  The distribution state simulation means 23 uses the information on the inclusions stored in the inclusion inspection information storage means 21 and the information on the fiber flow direction obtained by the forging simulation means 22 to make the steel material the machine element. Means for examining the distribution of the inclusions located at a certain depth from the surface of the rolling surface in the state of being commercialized. The distribution state simulation means 23 performs the process of step S3 in FIG.

  The database 25 is a means for storing information on inclusions that can develop cracks when rolling is performed on the rolling surface for each use condition of machine elements and specifications of inclusions. The information of the examination result performed in step S4 of 1 is stored.

  The crack propagation inclusion existence probability estimation means 26 is information related to inclusions in which a crack can propagate to the machine element when rolling is performed on the rolling surface, which is stored information in the database 25. And means for determining the existence probability of inclusions that are located at a certain depth from the raceway surface of the product and can propagate cracks from the distribution state of inclusions obtained by the distribution state simulation means 23. The crack growth inclusion existence probability estimation unit 26 performs the process of step S6 in FIG.

  The life test result storage means 27 is a database that stores information on the relationship between the existence probability of inclusions through which cracks can propagate and the rolling fatigue life, and is implemented using test conditions such as load and forging line direction as parameters. Information on the rolling fatigue life test performed is stored. That is, the result of the life test performed in step S7 in FIG. 1 is stored.

  The rolling fatigue life securing means 28 is means for determining whether or not the existence probability obtained by the crack propagation inclusion existence probability estimating means 26 is equal to or less than a certain value.

The machine element material quality assurance apparatus 20 includes an input processing means 29 and an output processing means 30 in addition to the above-described means. The input processing means 29 receives and stores an operator's operation input from an input device 31 such as a keyboard or a mouse, or receives an input from an external storage device or another computer. Input necessary for each means is performed through the input processing means 29. The output processing means 30 is means for outputting to an image display device such as a liquid crystal display device or an output device 32 such as a printer, and items obtained by each means are sent to the output device 32 via the output processing means 30. Is displayed.
The machine element material quality assurance device 20 may be composed of one computer such as a personal computer, or may be composed of a plurality of computers connected to each other via a network.

  According to the quality assurance device 20 for the machine element material having this configuration, cracks located at a certain depth from the raceway surface when the product is commercialized as a machine element are developed by performing the inclusion inspection in the steel material state. The existence probability of the inclusions to be obtained can be guaranteed below a predetermined value, and it can be determined whether the rolling fatigue life has reached a certain level.

  Next, specific examples of machine elements to which the machine element material quality assurance method and apparatus are applied will be described with reference to FIGS. FIG. 4 is a cross-sectional view of an inner ring rotating type wheel bearing device. This wheel bearing device includes an inner member 3 composed of an inner ring 2 fitted to the outer periphery of the hub wheel 1 and its inboard side end, and an outer member 4, and rotatably supports the wheel with respect to the vehicle body. To do. The outer member 4 is a machine element subject to quality assurance in the embodiment.

  The hub wheel 1 has a wheel mounting flange 5 at an end on the outboard side, and wheel mounting bolts 8 are press-fitted into bolt insertion holes 7 formed at a plurality of locations in the circumferential direction of the flange 5. . The hub wheel 1 is a cylindrical member through which the central hole 1a passes. A shaft portion of an outer joint member of a constant velocity universal joint (not shown) is fitted in the central hole 1a. The hub wheel 1 and the inner ring 2 are each provided with one of the double-row rolling surfaces 10 and 11. The rolling surfaces 10 and 11 may be called a raceway surface or a rolling surface. The outer member 4 is composed of a single outer ring, and has a flange 6 for attachment to the vehicle body on the outer periphery. Bolt insertion holes 9 are formed at a plurality of locations in the circumferential direction of the flange 6. The outer member 4 has double rows of rolling surfaces 12 and 13 facing the rolling surfaces 10 and 11 of the hub wheel 1 and the inner ring 2, and between the opposing rolling surfaces 10 and 12 of both rows and between the rolling surfaces. A rolling element 14 is interposed between the moving surfaces 11 and 13. The rolling element 14 is a ball such as a steel ball. These rolling elements 14 are held by a holder 29 for each row. Both ends of the bearing space between the inner member 3 and the outer member 4 are sealed by sealing devices 15 and 16.

  Both the hub wheel 1 and the outer member 4 are manufactured by turning after forging. The material of the hub wheel 1 and the outer member 4 is, for example, bearing steel, carburized steel, or carbon steel having a carbon content of 0.4 to 0.8%. In the forging process, as shown in FIG. 6, the outer member 4 cuts the bar material W, which is a steel material of the above material, into a predetermined dimension, heats it to around 1100 ° C., and places it up, rough forming, finish forming, And the inner diameter is removed. The outer member 4 is processed into the shape shown in FIG. 5 by such a forging process. In the figure, the finished shape of the outer member 4 after turning is indicated by a broken line. Moreover, the curve which shows the fiber flow F was shown in the cross section of the same figure. The locations indicated by reference signs A and B in the figure are locations that constitute the rolling surface.

  In order to examine the fiber flow F, for example, the outer member 4 may be cut along the axial direction, and the cut sample may be immersed in a heated hydrochloric acid solution to be deposited on the cut surface.

  In the above embodiment, the case where the mechanical element is an outer member of the wheel bearing device has been described.However, the present invention is not limited to the case where the mechanical element targeted for quality assurance is a bearing ring of a rolling bearing, The present invention can be applied to a machine element that performs rolling contact.

  As mentioned above, although the form for implementing this invention based on embodiment was demonstrated, embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

4 ... Outer member (machine element)
20 ... Machine element material quality assurance device 21 ... Inclusion inspection information storage means 22 ... Forging simulation means 23 ... Distribution state simulation means 25 ... Database 26 ... Crack growth inclusion existence probability estimation means 27 ... Life test result storage means 28 ... Rolling fatigue life securing means F ... Fiber flow

Claims (6)

When a steel material, which is a material of a machine element having a rolling surface, is commercialized into the machine element through forging, it is determined whether or not the rolling fatigue life has reached a certain level. A quality assurance method,
Inclusion inspection process for obtaining information on inclusions in the steel material;
A forging simulation process of obtaining information on the direction of fiber flow after the forging by performing a forging simulation for processing the steel material into the shape of the machine element;
From the information on the inclusions obtained in the inclusion inspection process and the information on the direction of the fiber flow obtained in the forging simulation process, the surface of the rolling surface in a state where the steel material is commercialized into the machine element. A distribution state simulation process for examining the distribution state of the inclusion located at a certain depth from
From the accumulated information in the database related to inclusions that can crack in the machine element when rolling is performed on the rolling surface, and the distribution state of inclusions obtained by the distribution state simulation, the product A crack propagation inclusion existence probability estimation process for determining the existence probability of an inclusion that can propagate a crack, located at a certain depth from the orbital plane of
A quality assurance method for a machine element material, comprising: a rolling fatigue life securing process for determining whether or not the obtained existence probability is a predetermined value or less.   The quality assurance method for machine element material according to claim 1, wherein, in the distribution state simulation process, the inclusions located at a certain depth from the surface of the rolling surface are subjected to a plurality of trials using random numbers. Quality assurance method for machine element material that determines distribution status.   The quality assurance method for machine element material according to claim 1 or 2, wherein the database is constructed by using a finite element method to determine the stress intensity factor amplitude around an inclusion of an arbitrary specification under an arbitrary use condition. By calculating and comparing the calculated stress intensity factor amplitude with a known lower limit stress intensity factor, it is determined that the inclusion can cause a crack to develop by rolling when the amplitude of the stress intensity factor is large. The quality assurance method for machine element materials, in which this examination is performed for each use condition and inclusion specification, and the database of inclusions in which cracks can develop is constructed.   In the quality assurance method of the machine element material according to any one of claims 1 to 3, the existence probability of inclusions that can develop cracks and the rolling fatigue life are determined by performing a rolling fatigue life test. The rolling fatigue life is constant by collating this database with the existence probability of inclusions that can be propagated by the crack, which is obtained in the crack propagation inclusion existence probability estimation process. A quality assurance method for machine element materials, including a process for determining whether the level has been reached.   The quality assurance method for machine element material according to any one of claims 1 to 4, wherein the machine element is a bearing ring or a rolling element of a rolling bearing. When a steel material, which is a material of a machine element having a rolling surface, is commercialized into the machine element through forging, it is determined whether or not the rolling fatigue life has reached a certain level. A quality assurance device,
Inclusion inspection information storage means for storing information relating to inclusions in the steel material;
Forging simulation means for obtaining information on the direction of fiber flow after the forging by performing a forging simulation for processing the steel material into the shape of the machine element;
The rolling in a state in which the steel material is commercialized into the machine element from the information related to the inclusion stored in the inclusion inspection information storage means and the information on the direction of the fiber flow obtained by the forging simulation means. A distribution state simulation means for examining the distribution state of the inclusions located at a certain depth from the surface of the surface;
From the accumulated information in the database related to inclusions that can crack in the machine element when rolling is performed on the rolling surface, and the distribution state of inclusions obtained by the distribution state simulation, the product A crack propagation inclusion existence probability estimating means for obtaining the existence probability of an inclusion that can be propagated by a crack located at a certain depth from the orbital plane of
A rolling element fatigue life securing means for judging whether or not the obtained existence probability is a predetermined value or less, and a quality assurance device for machine element material.

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