WO2003060507A1 - Acier pour roulements, procede d'evaluation d'inclusions de grandes dimensions dans ledit acier, et roulement - Google Patents
Acier pour roulements, procede d'evaluation d'inclusions de grandes dimensions dans ledit acier, et roulement Download PDFInfo
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- WO2003060507A1 WO2003060507A1 PCT/JP2003/000380 JP0300380W WO03060507A1 WO 2003060507 A1 WO2003060507 A1 WO 2003060507A1 JP 0300380 W JP0300380 W JP 0300380W WO 03060507 A1 WO03060507 A1 WO 03060507A1
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- bearing
- flaw detection
- inclusions
- steel
- large inclusions
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/04—Analysing solids
- G01N29/11—Analysing solids by measuring attenuation of acoustic waves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
- F16C33/02—Parts of sliding-contact bearings
- F16C33/04—Brasses; Bushes; Linings
- F16C33/06—Sliding surface mainly made of metal
- F16C33/12—Structural composition; Use of special materials or surface treatments, e.g. for rust-proofing
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
- F16C33/30—Parts of ball or roller bearings
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/24—Probes
- G01N29/2456—Focusing probes
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/26—Arrangements for orientation or scanning by relative movement of the head and the sensor
- G01N29/265—Arrangements for orientation or scanning by relative movement of the head and the sensor by moving the sensor relative to a stationary material
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/28—Details, e.g. general constructional or apparatus details providing acoustic coupling, e.g. water
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C2204/00—Metallic materials; Alloys
- F16C2204/60—Ferrous alloys, e.g. steel alloys
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/01—Indexing codes associated with the measuring variable
- G01N2291/014—Resonance or resonant frequency
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/023—Solids
- G01N2291/0234—Metals, e.g. steel
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/028—Material parameters
- G01N2291/02836—Flow rate, liquid level
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/04—Wave modes and trajectories
- G01N2291/042—Wave modes
- G01N2291/0421—Longitudinal waves
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/04—Wave modes and trajectories
- G01N2291/042—Wave modes
- G01N2291/0422—Shear waves, transverse waves, horizontally polarised waves
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/10—Number of transducers
- G01N2291/101—Number of transducers one transducer
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/26—Scanned objects
- G01N2291/269—Various geometry objects
- G01N2291/2696—Wheels, Gears, Bearings
Definitions
- the present invention relates to a bearing steel, a method for evaluating large inclusions therein, and a rolling bearing.
- large non-metallic inclusions (hereinafter referred to as “large inclusions”) that exist on the raceway surface and directly below this surface have a significant effect on the life of rolling bearings. The effect is well known.
- Recent improvements in metallurgical technology have significantly improved the cleanliness of metallic materials used as rolling bearing materials, such as steel, so that large-scale inclusions in this metallic material have been further reduced and large-scale inclusions have been reduced. The size is getting smaller.
- the most common method for evaluating the cleanliness of metallic materials is an evaluation method based on the oxygen content in steel.
- this evaluation method based on the oxygen content in steel has not been useful for judging the superiority of large inclusions because the oxygen content in metal materials has been greatly improved in recent years and is stable at a low level.
- Literature 5 and Literature 6 do not allow the test to be performed nondestructively, and may cause large inclusions to be dissolved in acid, or large inclusions to be melted or aggregated. It cannot be used to evaluate large inclusions present in metallic materials with high cleanliness.
- none of the above-described metal material cleanliness evaluation methods can perform a test in a non-destructive manner, and inspects a representative sample of a certain steel material rod, and evaluates the rolling produced in this steel material lot. This is to evaluate the life of the bearing. Therefore, it is not possible to individually evaluate the large inclusions present in the rolling bearing as a product, and it is not possible to accurately evaluate a short-lived product that occurs slightly.
- rolling bearings for steel such as roll neck bearings
- rolling equipment has been downsized, and housings in which bearings have been introduced have been downsized.
- the bearing follows the housing, and a repeated bending stress is applied to the outer ring, which may lead to the generation of short-life products and the occurrence of breakage.
- the inner ring of rolling bearings for paper machines is used in a state where fitting stress is applied.However, in an environment where the temperature is increasing in recent years, a larger hoop stress may act on the bearing. there were. For example, when hoop stress is applied to the inner ring, the surface of the inner diameter surface becomes the position where the maximum tensile stress is generated, and the tensile stress decreases as it goes inside, but defects such as large inclusions etc. If present, the stress concentration on that part will increase, resulting in breakage.
- ultrasonic inspections performed by steelmakers are generally performed by scanning in the axial direction at the product stage, such as steel pipes and round bars.
- the inspection pitch in the axial direction can be made finer, so that smaller defects can be detected.
- the inspection requires a long time.
- search The higher the frequency used for the flaw, the higher the frequency allows the detection of smaller defects in accordance with the flaw detection principle.However, the higher the frequency, the greater the attenuation of the sound wave with respect to the flaw detection distance and the smaller the flaw detection area. There's a problem.
- the inspection speed required for flaw detection exceeds several 10 m / min even at low speeds, and exceeds 100 m / mn at high speeds. Inspections are being conducted at speed.
- the frequency used for flaw detection should be selected to be a few MHz or more and less than 10 MHz with less attenuation of sound waves in the depth direction. It is desirable to do.
- the ultrasonic flaw detection method performed by a steelmaking manufacturer requires a high inspection speed required for flaw detection, and is a high-speed flaw detection performed while rotating a probe or a steel material. There is a problem when the sensitivity of the flaw detector cannot be increased very much.
- the defects that can be detected by the ultrasonic flaw detection method used in steelmaking have a detection limit of several hundreds of width; am, and several tens of millimeters in length.
- a first object of the present invention is to provide a method for evaluating large inclusions in bearing steel that can quantitatively evaluate large inclusions even with high cleanliness.
- a second object is to provide an appropriate bearing steel evaluated based on the method for evaluating large inclusions in the bearing steel.
- short life The third issue is to provide a rolling bearing that can achieve long life of the whole bearing by eliminating parts that are broken or broken. Disclosure of the invention
- the method for evaluating large inclusions employs a round bar made of steel for a bearing to be evaluated and an ultrasonic probe with an ultrasonic transmission medium. It is placed in the body, measures the size and number of large inclusions present in the inspection volume by ultrasonic inspection, and estimates the existence probability of the large inclusions in the evaluation target bearing steel. It is.
- This invention is mainly used for comparison and evaluation of different charges in steelmaking methods.
- the method for evaluating large inclusions in bearing steel according to claim 2 is a method for evaluating large inclusions in bearing steel according to claim 1,
- the flaw detection method is an oblique flaw detection method.
- an oblique flaw detection method and a vertical flaw detection method as an ultrasonic flaw detection method using a water immersion method using water as an ultrasonic transmission medium.
- the detection limit of the defect in each method is proportional to the sound speed of the wave transmitted by each.
- the oblique flaw detection method uses a shear wave
- the vertical flaw detection method uses a longitudinal wave.However, since the sound velocity of a shear wave propagating through a steel material is about 1/2 times that of a longitudinal wave, the detection limit using a shear wave is It is about 1 times 2 times. In other words, the smaller the sound velocity, the smaller the inclusions can be detected. Therefore, the oblique flaw detection method using transverse waves is smaller.
- the method for evaluating large inclusions in bearing steel according to claim 2 includes the step of detecting the oblique flaw detection method. It is characterized in that it is performed at a flaw frequency of 15 MHz or less.
- the relationship between the flaw detection frequency and the defect detection limit is set to 1/2 to 1/4 of the wavelength. Therefore, when the flaw detection frequency is increased, the detection limit is improved, but the attenuation of the propagating sound wave is increased, and the inspection depth is reduced.
- the present invention aims to detect flaws of large inclusions harmful to the life of the bearing by using the oblique flaw detection method, and to find the optimum flaw detection frequency in order to obtain an inspection volume as large as possible. Was.
- the method for evaluating large inclusions in bearing steel according to claim 1 is the same as the method for evaluating large inclusions in bearing steel, wherein And a vertical flaw detection method using a focus type polymer probe as the ultrasonic probe.
- the oblique flaw detection method can detect smaller inclusions than the vertical flaw detection method.However, since ultrasonic waves are incident on steel and then refracted in accordance with the angle of incidence, they can be detected vertically. Compared to the flaw detection method, there is a limit in specifying the exact position of the defect. In addition, the oblique flaw detection method has a disadvantage that the depth range of the flaw detection becomes shallower than the vertical flaw detection method because ultrasonic waves propagate in a tilted manner in the depth direction.
- This polymer probe has excellent damping characteristics when receiving a signal reflecting an ultrasonic wave, so it is generally used when it is necessary to perform flaw detection at high frequencies (for example, 5 MHZ or more). This is known to be effective because there is less dead zone due to resonance and the like as compared with the case where a simple ceramic vibrator is used. For this reason, about the scope of the present invention At present, it is not used in the frequency band.However, when the present inventors applied a polymer probe to the ultrasonic flaw detection of bearing steel, compared with the conventional ceramic probe, It has been found that even when the frequency is increased, the ultrasonic wave is less attenuated, and that flaw detection can be performed effectively in a deeper range.
- the flaw detection frequency can be increased, a vertical flaw detection method capable of detecting a large, large-sized inclusion and deeper can be adopted.
- ultrasonic inspection of bearing steel can be accurately performed over more cross sections. Therefore, vertical flaw detection using a polymer probe is desirable for flaw detection of small large inclusions over a wide range.
- the method for evaluating large inclusions according to claim 5 of the present invention is the method for evaluating large inclusions in bearing steel according to claim 4, wherein the vertical flaw detection method is a method for flaw detection. It is characterized in that it is performed at a frequency of 3 OMHz or less.
- An object of the present invention is to detect a large inclusion having a size harmful to the life of a bearing to a deeper depth by using a vertical flaw detection method, and to find an optimal flaw detection frequency capable of detecting a large inclusion to a smaller size.
- the bearing steel according to claim 6 of the present invention is estimated by the method for evaluating large inclusions in bearing steel according to any one of claims 1 to 5. It was among the large inclusions, in which flaw detection volume 2. 0 x 1 0 6 mm 3 square zero length present per. large inclusions than 2 mm is equal to or 1 0. is 0 or less is there. Further, in the present invention, the bearing bearing according to claim 7 is estimated by the method for evaluating large inclusions in bearing steel according to any one of claims 1 to 5. It was among the large inclusions, flaw detection volume 1. those total length of O x 1 0 6 mm 3 length present per 0. 5 mm or larger inclusions, characterized in that at 8 0 mm or less is there.
- the number of large inclusions having a square root length of 0.2 mm or more per a predetermined inspection volume is measured.
- an elongated inclusion of 5 mm and a short inclusion of 0.5 mm are evaluated as one.
- the present inventors evaluated the degree of harm due to the length of inclusions As a result, in the bearing steel according to claim 6, not only the number of large inclusions having a square root length of 0.2 mm or more per predetermined inspection volume but also the total length of the inclusions per unit volume By limiting the length, we found that the service life could be prolonged with a higher probability.
- the bearing leakage according to claim 8 of the present invention is of the estimated large inclusions, flaw detection volume 4. 0 x 1 0 5 that the square root length present per mm 3 0. 2 mm or larger inclusions, characterized in that 2. is 0 or less It is.
- the bearing steel according to claim 8 has a lower degree of cleanliness than the bearing steel according to claim 6 or claim 7, the quality of the bearing can be guaranteed with a smaller flaw detection volume.
- the inspection time can be shortened (especially when defective products are judged).
- the rolling bearing according to claim 9 of the present invention is a rolling bearing in which a plurality of rolling elements are arranged at predetermined intervals in a circumferential direction between an inner ring and an outer ring. It is characterized by being manufactured using the bearing steel evaluated by the large inclusion evaluation method described in paragraph 3 as a raw material.
- a rolling bearing according to claim 10 of the present invention is a rolling bearing in which a plurality of rolling elements are disposed at predetermined intervals in a circumferential direction between an inner ring and an outer ring. It is characterized in that it is manufactured using the bearing steel evaluated by the large inclusion evaluation method described in Section 5 as a material.
- the rolling bearing according to claim 11 of the present invention is a rolling bearing in which a plurality of rolling elements are disposed at predetermined intervals in a circumferential direction between an inner ring and an outer ring. It is characterized in that it is manufactured using the bearing steel according to any one of paragraphs 6 to 8 as a raw material.
- the rolling bearing according to claim 12 of the present invention is a rolling bearing in which a plurality of rolling elements are arranged at predetermined intervals in a circumferential direction between an inner ring and an outer ring, and It is manufactured using seamless steel pipes with a thickness of 25 mm or less and a wall thickness of 25 mm or less, and it is guaranteed that there are no defects with a length of 1 mm or more at the material stage. .
- the rolling bearing according to claim 13 of the present invention is characterized in that the inner ring and the outer ring Rolling bearings in which a plurality of rolling elements are arranged at predetermined intervals in the circumferential direction, are manufactured using round bars with a diameter of 60 mm or less, and there are no defects with a length of 1 mm or more at the material stage Is guaranteed.
- the present inventors have disclosed a method of detecting large non-metallic inclusions harmful to the bearing life as described in Document 10 (Japanese Patent Application Laid-Open No. 11-337530) and Document 11 (Japanese Patent Application Laid-Open No. No. 0 0 1 3 4 4 7) discloses a method for detecting large non-metallic inclusions directly under the raceway surface at the stage of a finished bearing product, which can guarantee the long life of the bearing A new method.
- the present inventors have proposed a method for manufacturing bearings in recent years, in which, in order to improve the yield of materials, after forming a shaped material from steel by hot forging, and then manufacturing a bearing ring by one cold opening ring and turning. And the like. Then, the present inventors have found that, for a round bar having a diameter of 6 O mm or less as a material, inclusions having a length of 1 mm or more can be detected at the material stage as inclusions harmful to the life. By conducting a 100% inspection, they have found that a long-life bearing can be provided without affecting the manufacturing cost, and the present invention has been completed.
- the rolling bearing according to claim 14 of the present invention is characterized in that the inner ring and the outer ring In a rolling bearing in which a plurality of rolling elements are disposed at predetermined intervals in a circumferential direction, a defect in a volume to be measured in a whole cross section from below an outer diameter surface of the inner ring, the outer ring, and a steel material for the rolling elements. Is not larger than the maximum length of 0.6 mm in the turning process, and the surface roughness is 5 mRa or less.
- a method for detecting a non-metallic inclusion having a size of several tens to several hundreds of meters including the entire cross section including a deep position from immediately below the bearing raceway surface as a test volume has been proposed in the above-mentioned reference 10;
- the inventors of the present invention have conducted intensive studies on improving the accuracy of defect detection, and as a result, by limiting the surface roughness of the outer diameter surface of the bearing steel material to 5 mRa or less, the inner and outer races and rolling elements are reduced.
- FIG. 1 is a longitudinal sectional view showing one embodiment of a rolling bearing made of the bearing steel of the present invention.
- FIG. 2 is a schematic configuration diagram showing one example of an ultrasonic inspection equipment used in the method for evaluating large inclusions in bearing steel according to the present invention.
- FIG. 3 is an explanatory diagram for explaining an angle adjustment method between the oblique flaw detection method and the vertical flaw detection method.
- FIG. 4 is an explanatory diagram showing the relationship between the volume of flaw detection inspection and the number of inclusions in the bearing steel of the present invention.
- Figure 5 shows the use of ceramic for the vibrator.
- FIG. 1 is a longitudinal sectional view showing one embodiment of a rolling bearing made of the bearing steel of the present invention.
- FIG. 2 is a schematic configuration diagram showing one example of an ultrasonic inspection equipment used in the method for evaluating large inclusions in bearing steel according to the present invention.
- FIG. 3 is an explanatory diagram for explaining an angle adjustment method between the oblique flaw detection method and the vertical
- FIG. 5 is an explanatory diagram showing the difference between the number of inclusions detected by the vertical flaw detection method and the number of inclusions detected by the oblique flaw detection method in the bearing steel of the present invention at ⁇ .
- FIG. 6 is a cross-sectional view showing a state in which artificial defects are formed in a round bar made of the bearing steel of the present invention.
- FIG. 7 is an explanatory diagram showing the relationship between the flaw detection frequency and the flaw detection depth in the bearing steel of the present invention.
- FIG. 8 is an explanatory diagram showing the relationship between the inspection frequency and the inspection length in the bearing steel of the present invention.
- FIG. 9 is a schematic explanatory view showing an example of a bearing life tester.
- FIG. 10 is an explanatory diagram of the bearing life for each charge in the bearing steel of the present invention.
- FIG. 11 is an explanatory diagram showing the relationship between the number of inclusions and the bearing life in the bearing steel of the present invention.
- FIG. 12 is an explanatory diagram showing the relationship between the flaw detection volume and the number of inclusions in the bearing steel of the present invention.
- FIG. 13 is an explanatory diagram of the bearing life of each charge in the bearing steel of the present invention.
- FIG. 14 is an explanatory diagram showing the relationship between the flaw detection depth and the flaw detection frequency in the bearing steel of the present invention.
- FIG. 15 is an explanatory diagram showing the relationship between the inspection frequency and the inspection length in the bearing steel of the present invention.
- FIG. 16 is an explanatory diagram of the bearing life for each charge in the bearing steel of the present invention.
- FIG. 17 is an explanatory diagram showing the relationship between the flaw detection volume and the total length of inclusions having a length of 0.5 mm or more per unit volume in the bearing steel of the present invention.
- FIG. 18 is a perspective view showing a state in which artificial defects are formed in a seamless steel pipe made of the bearing steel of the present invention.
- FIG. 19 is a graph showing the relationship between the distance (depth) from the surface of the test piece and the relative echo intensity.
- FIG. 20 is a graph showing the relationship between the relative movement range of the probe in the circumferential direction with respect to the test piece.
- FIG. 21 is a graph showing the relationship between the distance (depth) from the surface of the test piece and the relative echo intensity.
- FIG. 22 is a graph showing the relationship between the circumferential movement range of the probe with respect to the test piece and the relative echo strength.
- FIG. 23 is an explanatory view for explaining the heat treatment method, in which (a) is carburized steel and (b) is galvanized steel.
- FIG. 24 is a schematic configuration diagram showing another example of the ultrasonic inspection equipment used in the method for evaluating large inclusions in bearing steel according to the present invention.
- FIG. 25 is an explanatory diagram for explaining the inner ring splitting life tester.
- FIG. 26 is a cross-sectional view showing a test piece of a bearing steel material used for detecting an artificial defect by an ultrasonic flaw detection method.
- FIG. 27 is a graph showing the relationship between the outer diameter surface roughness of the test piece and the S / N ratio.
- FIG. 1 is a cross-sectional view of a rolling bearing made of the bearing steel of the present embodiment.
- This rolling bearing is a tapered roller bearing with an internal number of ⁇ 85 mm s, an outer diameter of ⁇ 130 mm, and a width of 29 mm, with a nominal number of HR32017XJ.
- reference numeral 1 denotes an inner ring
- reference numeral 2 denotes an outer ring
- reference numeral 3 denotes a rolling element (a tapered roller).
- Table 1 shows the oxygen content and the results evaluated by the extreme value statistical method.
- Table 1 shows the oxygen content and the results evaluated by the extreme value statistical method.
- 1 O mmx estimated by 1 0 mmx 3 0 field extremum statistical method examines in, extreme statistical method shown by the square root length of the maximum inclusion area present in 3 X 1 0 4 mm 2 No significant difference was observed in the results, and the results of the extreme value statistical method did not find the presence of large inclusions having a square root length of the order of 0.2 mm, which is the object of the present invention.
- the extreme value statistical method is described in detail in “Effects of Microdefects and Inclusions” (Takenobu Murakami, Yokendo Publishing).
- the large inclusions shown in the present embodiment are oxide inclusions and sulfide inclusions, and the same applies to the following large inclusions.
- FIG. 2 shows a schematic configuration diagram of an ultrasonic inspection equipment used in the method for evaluating large inclusions in bearing steel according to the present invention.
- Reference numeral 11 in the figure denotes a round bar made of steel for bearings to be evaluated.
- Reference numeral 12 denotes a focus type ultrasonic probe, which is immersed together with the round bar 11 in a water tank 13 storing water as an ultrasonic transmission medium. The size of the round bar 11 will be described in detail later.
- the round bar made of the steel for the bearing to be evaluated is rotated in a fixed direction by a motor 14, and the ultrasonic probe 12 is shown by motors 15, 16, and 17. Move in the Z-axis direction and detect flaws in a predetermined volume to detect large inclusions.
- Each of the motors 14 to 17 is driven by a motor controller 18, and a detection signal of the ultrasonic probe 12 is analyzed by a flaw detector 19.
- the operation of the controller 18 is controlled by an input to the personal computer 20.
- the motor controller 18 controls the position of the probe 12 and the round bar 11 by controlling the rotation; direction, rotation speed, and rotation angle of each of the motors 14 to 17. You.
- the flaw detector 19 monitors the flaw detection frequency and the reflected echo of the probe 12 and the size of the inclusion detected from the intensity of the reflected echo, and stores it in the memory of the personal computer 20. To memorize.
- the ultrasonic inspection method used in the method of the present invention includes a vertical inspection method and an oblique inspection method.
- the vertical flaw detection method sets the probe directly above the center line of the round bar.
- the oblique flaw detection method performs flaw detection by offsetting the probe from the center line of the round bar (offset).
- the angle of incidence of the ultrasonic wave in the oblique flaw detection method can be obtained by the inverse sine of the value obtained by dividing the amount of offset by the radius of the round bar, and this is input to a personal computer and controlled by a motor controller.
- the angle adjustment of the oblique flaw detection method and the vertical flaw detection method is performed by sending the ultrasonic probe 12 in the depth direction by X and setting 0 to the desired angle (bevel angle ⁇ 2 19). °).
- the above-mentioned bearing steel for each charge was subjected to ultrasonic inspection.
- the oblique flaw detection method was used as the ultrasonic flaw detection method, and the flaw detection frequency was 10 MHz and the ultrasonic wave incident angle on the bearing steel was 19. And then, flaw detection volume 3. 5 X 1 0 6 mm 3 and until in testing has identified the position and detected interposed the number.
- Figure 4 shows the relationship between the flaw detection volume and the number of inclusions in bearing steel.
- the number of inclusions is shown by the ratio between the above-mentioned charge A and other charges B to D.
- testing volume 2. 0x 1 0 6 mm It becomes almost constant in three or more regions.
- the time of flaw detection is increased, 2.
- Runode can be increased more reliable flaw detection volume of the embodiment 2. 0 X and 1 0 6 mm 3.
- Figure 5 shows the detection inclusions ratio of the number of when the vertical flaw detection method and the oblique flaw detection method, were all flaw inspection volume 2. 0X 1 0 6 mm 3 in flaw detection frequency of 1 0MH z.
- the number of entities is shown by the ratio of the above-mentioned charge A and other charges B to D.
- the angle detection method has a higher number of detections than the vertical inspection method, which indicates that the ultrasonic inspection method uses the angle inspection method to provide more reliable cleanliness. Good for guarantee.
- FIG. 6 is a cross-sectional view showing a state in which artificial defects are formed in a round bar made of the bearing steel of the present invention. .
- cylindrical holes dimensions: 00.5 x 15 mm
- a ceramic probe (5 MHz, 10 MHz, 15 MHz, 20 MHz: vibrator diameter 6 mm, focal length 25 mm in water) using a ceramic vibrator is attached to this artificially defective round bar.
- the ultrasonic flaw detector shown in Fig. 2 (USD15, manufactured by Nippon Clark Kramer), the ultrasonic wave by the oblique flaw detection method (incident angle: 19 °, water distance 1 Omm) Inspection was performed.
- FIG. 7 is an explanatory diagram showing the relationship between each flaw detection frequency and flaw detection depth.
- the effective inspection depth was defined as the depth at which the echo intensity was half of the peak echo intensity.
- the higher the inspection frequency the smaller the inspection depth. This means that when scanning the same area, a smaller flaw detection depth means a smaller flaw detection volume. For example, when testing a round rod (diameter) ⁇ 5 Omm, as flaw detection depth is small, the length reaching the required inspection volume 2. 0 X 1 0 6 mm 3 in this embodiment is longer.
- the flaw length sharply increases at flaw detection frequencies of 15 MHz and higher.
- the practical flaw detection frequency is set to 15 MHz or less.
- Figure 10 shows the results of the life test.
- Some bearings made from Charge C and Charge have a short life. This is Li. It can be seen that Charge A and Charge B have a longer life and Charge C and Charge D have a shorter life below the life (that is, shorter life). In other words, Charges A and D have extremely short lifespans compared to Charges A and B, indicating that the life reliability of the bearing steel is poor.
- the stripped portion of the short-life product is generated on each of the inner and outer rings using the evaluation material. If a large inclusion exists, regardless of the rolling member, a short-life product is generated. You can see that
- Table 2 shows the oblique flaw detection method, testing frequency 1 5MH z less, flaw detection volume 2. 0X 1 0 6 mm 3, the results of ultrasonic flaw detection under the conditions of an incident angle 1 9 °. Table 2 shows the evaluation of the number of inclusions with a square root length of 0.15 mm or more and the number of inclusions with a square root length of 0.2 mm or more.
- Figure 11 shows the number of inclusions with a square root length of 0.15 mm or more, the number of inclusions with a square root length of 0.2 mm or more, and the bearing life (Li. Life).
- inclusions with a square root length of 0.15 mm or more and inclusions with a square root length of 0.2 mm or more there is a correlation that the life decreases with the number of inclusions. ing.
- the number of inclusions with a square root length of 0.15 mm or more has a shorter life as the number of inclusions increases, so it is difficult to set a threshold for the number of inclusions.
- the number of inclusions with a square root length of 0.2 mm or more has a sharply shortened service life after the detection of 10 inclusions.
- Inclusions with a square root length of 0.15 mm or more The number is too large per flaw detection volume of 2.0 ⁇ 10 6 mm 3 , and the number detection is complicated. Therefore, in this embodiment, the size and the square root length 0. 2 mm or more in size of the inclusions, the detection inclusions number inclusions for life assurance, flaw detection volume 2. 0x 1 0 6 mm 3 It was set to 10.0 or less per hit.
- Table 3 also shows the results of the evaluation by the oxygen content and extreme value statistical methods.
- pole indicated by the square root length of the maximum inclusion area 1 Ommx l Ommx 30 examines the in-field estimated by the extreme value statistics method, may be present in 3 x 1 0 4 mm 2 for each Chiya each one di result value statistical methods, which the evaluation per 4 X 1 0 5 mm 3 by the method of ultrasonic word parity method (present invention, the square root length 0.2 mm or more inclusions showed how many there ) Also shows a difference. This is because, as described in detail below, the maximum inclusion diameter estimated by the extreme value statistical method does not indicate the presence of large inclusions that actually exist, but is based on the values estimated statistically. Because there is.
- the ultrasonic flaw detection method using a scratch method probe oblique angle flaw detection frequency was 1 0 MH z, flaw detection volume 4. flaw detection to 0 X 1 0 6 mm 3, and specifies the position and detected interposed the number.
- Figure 12 shows the relationship between the volume of flaw detection and the number of large inclusions detected per unit volume.
- testing volume in this embodiment is 4.
- 0 X 1 0 5 mm 3 shows a tendency of stabilization in the region on the following, the detection number of large charge E, the detection number number stable even at F is a flaw detection volume 4.
- a tapered roller bearing as shown in FIG. 1 was manufactured from the bearing steel of each charge described above, and a bearing life tester shown in FIG. 8 was manufactured for this tapered roller bearing in the same manner as in the first embodiment described above. Was used to perform a life test. The test conditions are the same as in the first embodiment described above.
- Figure 13 shows the results of the life test.
- the tapered roller bearings made from Charge E and Charge F generally have a short life.
- Table 3 shows the results of evaluation of ultrasonic flaw detection by the oblique flaw detection method with a flaw detection frequency of 15 MHz or less (incident angle: 19 °).
- Table 3 shows the square root inclusions number of length 0. 2 mm or more in size when the flaw detection volume 4. 0 X 1 0 5 mm 3 and ultrasonic testing.
- the number of inclusions is 2.0 or less. Therefore, in this embodiment, the size was as inclusions of the square root length 0. 2 mm or more in size, the number of detected inclusions for life assurance, the flaw detection volume 4. Ox 1 0 5 mm 3 2.0 or less per hit.
- the bearing steel of the present invention has been described in the first embodiment and the second embodiment.
- the order of assurance of cleanliness is as follows. First, as shown in the second embodiment, the flaw detection volume 4.Ox 1 0 5 mm 3 square length 0.2mm or more inclusions present per is determined whether 2. is 0 or less, is defective does not satisfy this, it is a good product for this condition is satisfied Assure the cleanliness of the charge to be guaranteed. If necessary, as shown in the first embodiment, it takes a long time, but it is desirable to make a stricter guarantee only for the bearing steel guaranteed as a good product in order to shorten the inspection time. ⁇ Third embodiment>
- a polymer probe (20 MHz, 30 MHz, 40 MHz) using the polymer oscillator according to the present invention is applied to the artificially defective round bar manufactured as shown in FIG. : Oscillator diameter 6 mm, underwater focal length 25 mm) and ceramic probe using conventional ceramic oscillator (10 MHz, 15 MHz, 2 OMHz: Oscillator diameter 6 mm, underwater focal length 25 mm) mm) and vertical flaw detection at a water distance of 15 mm.
- Fig. 4 shows the relationship between the flaw detection depth at each flaw detection frequency and the artificial defect echo intensity.
- the effective flaw detection depth was defined as the depth at which the echo intensity was half of the peak echo intensity.
- the characteristics of the ceramic probe and the polymer probe are different from each other due to the difference in the reflection intensity of the same defect at the same amplifier strength.
- the defect at the lower 2 mm position was adjusted and compared to 100% with the ceramic oscillator 2 OMHz and the polymer oscillator 3 OMHz.
- the polymer probe of the present invention when the polymer probe of the present invention is compared with the conventional ceramic probe, the polymer probe has a small sound wave attenuation even when the frequency is high, so that the flaw detection frequency is low.
- the 30 MHz polymer probe has a deeper flaw detection depth than the 15 MHz ceramic probe. Also, comparing the same probe, the higher the frequency, the smaller the flaw detection depth.
- a small flaw detection depth means a small flaw detection volume. For example, phi when testing a round bar of 50 mm, the more shallow flaw depth, necessary inspection volume shown in the first and second exemplary type J described above 2. Ox 1 0 6 a length reaching mm 3 Many Required.
- each of the flaw detection frequency to inspection round bar of ⁇ 50 Rutoki it reaches its testing frequency, the flaw detection volume required inspection volume 2.
- 0x 1 0 6 mm 3 This shows the relationship with the flaw detection length.
- the flaw detection length rapidly increases at a flaw detection frequency of 15 MHz or more.
- the flaw detection range can be widened even if the flaw detection frequency is increased, and the flaw detection length increases sharply when it exceeds 3 OMHz and becomes 4 OMHz. From this, when performing ultrasonic flaw detection using a polymer probe, The practical flaw detection frequency was 30 MHz.
- Table 4 shows the results of evaluation using the oxygen content and extreme value statistical methods.
- the five types of Charges I to V have low values of oxygen content of 9 ppm or less, while the charge VI has a high value of 13 ppm.
- the size of the inclusions evaluated by the above-mentioned extreme value statistical method is the square root length of the maximum inclusion area obtained by inspecting 1 Ommxl 0 mm X 30 visual fields for each charge. It is shown as the square root length of the largest inclusion area estimated to be present in 3 ⁇ 10 6 mm 2 using the it statistical method. As in the case of the oxygen content, this value is low for the five types of Charges I to V with a maximum square root length of 32 ⁇ m or less, whereas it is high for Charge VI of 48 ⁇ m.
- the bearing steel of each of the above-described chargers is evaluated by an ultrasonic inspection method using the ultrasonic inspection apparatus used in the first embodiment.
- the flaw detection frequency was 2 OMH ⁇ and the flaw detection volume was 1.5 ⁇ 10 7 mm 3 by a vertical flaw detection method using a focused polymer probe.
- Table 4 shows the number of inclusions with a flaw detection volume of 1.5 x 10 7 mm 3 and a square root length of 0.2 x 10 6 mm 3 or more for each charge]: ⁇ VI and it showed total length of the flaw detection volume 1. 0x10 6 mm 3 length 0. 5 mm or more inclusions in terms of per.
- a tapered roller bearing as shown in FIG. 1 was prepared in the same manner as in the first embodiment using the bearing steel of each of the above-described bearings.
- a life test was performed using the bearing life tester shown below. The test conditions are the same as in the first embodiment.
- Figure 16 shows the results of the life test.
- Figure 17 shows the relationship between each flaw detection volume and the total length of inclusions with a length of 0.5 mm or more per unit volume at that time.
- the results in the figure the total length of the inclusions in the case of each switch catcher temporary described above the flaw detection volume 4.
- the results were evaluated by the Ox 1 0 6 mm 3 and 1, of reduced flaw detection volume Ri by it It shows how it varies.
- the ratio of the total length of the inclusions fluctuates when the flaw detection volume is small, but as the flaw detection volume increases, the ratio of the total length of the inclusions stabilizes and the flaw detection volume becomes 2.0x. 1 0 substantially constant at 6 mm 3 or more regions.
- the flaw detection volume increases time to flaw detection increases, 2. Since the 0x 1 0 6 mm 3 or more in volume can be increased more Shintabapeji properties when testing, it requires inspection volume of the embodiment 2. 0x 1 and 0 6 mm 3. That is, since the required flaw detection volume is the same as the result shown in the first embodiment described above, the number of inclusions and the total length of inclusions having a length of 0.5 mm or more per unit volume are determined. In any case, in order to obtain a stable value, it is desirable to perform flaw detection with a flaw detection volume of 2.0 ⁇ 10 6 mm 3 or more.
- nonmetallic inclusions have been described as examples of defects in the steel for bearings of the present invention. It can be applied to cracks and the like.
- the square root length of these defects can be obtained as follows according to the shape of the defect.
- the square root length is the square root (LXD) 1/2 of the product of its length L and width D.
- the shape of the defect is granular, spherical or massive (non-linear defect)
- the square root of the product of the maximum diameter (long axis diameter) D1 and the minimum diameter (short axis diameter) D2 (D1 XD2) 1 / 2 is the square root length.
- a seamless steel pipe having an outer diameter of 01 80 mm and an inner diameter of 01 3 mm (wall thickness 25 mm) is cut out at a length of 300 mm, and cut from the outer peripheral surface of the seamless steel pipe.
- An artificially defective steel pipe was produced by providing each of the central axes 0, 0 so as to be parallel to the central axis 0 of the round bar 11.
- this artificially defective steel pipe was subjected to ultrasonic inspection using the same ultrasonic inspection equipment (USD15, manufactured by Nippon Clout Kramer I) similar to that shown in the first embodiment, and the detection limit was detected. Verification was conducted to determine The ultrasonic flaw detection method in the present embodiment has an incident angle of 19. (Refractive angle: 45 °), flaw detection frequency: 15 MHz, oblique flaw detection at a water distance of 10 mm using a focus type probe (vibrator diameter: 6 mm, focal length: 25 mm in water) was done. The amplifier sensitivity was set so that the defect at a position 2 mm below the surface was 100%. Fig.
- FIG. 19 shows the results of flaw detection in the depth direction of the artificially defective steel pipe by this ultrasonic flaw detection
- Fig. 20 shows the results of this flaw detection in which a flaw at a depth of 2 mm was detected in the circumferential direction. The results are shown.
- FIG. 20 shows the results of verifying the effective flaw detection pitch required to move in the axial direction while maintaining the flaw detection capability described above.
- the position of 2 to 5 mm from the surface of the artificially defective steel pipe shows a relative echo intensity of 100%. It was verified that flaw detection of the entire cross section of 25 mm in thickness was possible at the depth of 50%, which is 50% of the depth, at the 25 mm position. Therefore, the feasible range of flaw detection in the depth direction under these conditions may be up to 25 mm from the surface if the echo intensity is reduced to half (1-6 dB). As is evident from Fig. 20, the range where the echo height is half (-6 dB) is about 2.5 mm in the movement width, and about 4 mm even if the width decreases by 1/4 (-3 dB). To some extent.
- the figure shows the result of adjusting the sensitivity to 100% echo height, and further finely adjusting the pitch back and forth in the circumferential direction around that position and performing flaw detection.
- the relative echo intensity for each moving distance (rotation distance) with respect to the value (100%) is shown.
- the state where the relative echo intensity gradually increases from the point before the point where the probe reaches the peak value (point 0) and decreases after passing the point 0 is shown.
- This relative echo intensity is proportional to the length of the defect. Therefore, focusing on only the 0 point (peak value) in the moving range, the peak hold process is performed by the personal computer 20 shown in FIG. 2 described above, and the peak value is always stored in the memory. This is because, unless the movement range is specified, the relative echo intensity does not become constant, so that a defect having a length of 1.0171171 ⁇ 1.1 mm in the present invention cannot be correctly obtained.
- FIG. 19 shows the peak value obtained as described above as the relative echo intensity (100% from 2 to 5 mm as the vertical axis) and the intensity of the artificial defect echo of 0.50 mm ⁇ 20 mm on the vertical axis. It is shown as a ratio to the depth from the surface, and it can be seen that the relative strength decreases as the distance from the surface increases.
- a defect having the same defect length has a different relative echo intensity depending on the depth (attenuates as the depth increases).
- the depth of the 0.5 mm0x2 Omm defect from the surface depends on how the oscillated ultrasonic signal is reflected by the defect and returns to the probe. From the relationship between the detected time and the oscillation frequency, it can be accurately obtained by the personal computer 20.
- the relationship shown in Fig. 19 is obtained in advance using artificial defects.
- the relationship shown in FIG. 19 is stored in the personal computer 20 as a correction coefficient (for example, the reciprocal of the relative echo intensity at each depth position) as a correction coefficient of the defect echo with respect to the obtained depth. Let it be calculated.
- defect echo values peak values for the depth from the surface of the seamless steel pipe are successively loaded into the memory of the personal computer 20 and, if calculated, are found in the entire cross section (including the desired depth). Defect length can be detected.
- the defect length of the entire cross section can be detected at the stage of the material of the seamless steel pipe having a diameter of 18 Omm0 or less and a wall thickness of 25 mm or less, which has not been conventionally possible at a steelmaking manufacturer.
- all cross sections of materials suitable for bearings on the user side can be inspected. Then, in this example, it was found that there was no defect having a length of 1 mm or more in the entire cross section, which could extend the life.
- the flaw detection depth (beam diameter) is about 2.5 mm from the surface in the depth direction. It was found to have flaw detection capability.
- the flaw detection pitch was set to about 2.5 mm for a diameter of 180 mm, and the transmission / reception speed of ultrasonic waves by a general commercially available flaw detection device was also considered. Considering that, it was found that flaw detection was possible at a speed of about 7 m / min.
- the speed of hot forging for example, is as high as about 1 Om / min at the highest, so it is within the range where all 100% flaw detection is possible.
- the production capacity is not reduced. It can be seen that evaluation by ultrasonic flaw detection of all the samples and all the cross sections is possible.
- a high-quality seamless steel pipe selected by the method described in the fourth embodiment is used as a material. The prolonged service life of the manufactured rolling bearing was verified.
- a seamless steel pipe for the outer ring (outer diameter ⁇ 102 mm, wall thickness 6 mm) and a seamless steel pipe for the inner ring (outer diameter 057 mm, wall thickness 7 mm) were used as materials. Ultrasonic testing was performed at. Then, the material was selected by ultrasonic inspection, and the seamless steel pipe with high cleanliness and the seamless steel pipe with low cleanliness without ultrasonic inspection were turned and heat-treated. After grinding, 6309 deep groove ball bearings were manufactured. .
- the evaluation results of ultrasonic flaw detection of two types of materials with different cleanliness described above are obtained by dividing the number of defects with a length of 1 mm or more detected in the volume of the effective flaw detection area by the evaluation volume (weight). Represented by
- the life test conditions are as follows.
- Lubricating oil Mineral oil equivalent to VG 68
- the test was interrupted at 200 times, which is three times the calculated life under the above test conditions, which was 67 hours, and the presence or absence of peeling at that time was evaluated.
- Table 5 shows the evaluation results.
- test bearings of the present invention made of a seamless steel pipe material with no defect of 1 mm or more in length in the entire cross section (balls are quenched and tempered SUJ 2). It can be seen that all of them passed the 200-hour test.
- test bearings (No.1, No.2) using materials with poor cleanliness used ordinary materials in which the inclusions with a length of 1 mm or more were present in the entire cross section. Although it is higher than the test bearings (No. 3 and No. 4), 200 hours for test bearings (No. 2) made of selected materials without inclusions longer than 1 mm being detected. No peeling occurred even if the temperature exceeded, and a stable long life was obtained.
- test bearings (No. 1) made of materials that had not been sorted by ultrasonic flaw detection generated cracks at a high rate of 4 out of 10 during 200 hours when censoring was performed. .
- Test bearings using normal materials (No. 3) though infrequent, suffered from cracking in one out of ten bearings, and at the point where stable long life was obtained, It turns out that it is inferior to the sorted product by ultrasonic inspection.
- a round bar steel material of bearing material ⁇ 60 mm is cut out at a length of 300 mm, and a depth A from the outer peripheral surface of the round bar steel material toward the central axis toward ⁇ .
- 5mm, 10mm, 15mm, 20mm, 25mm, 30mm Insert a cylindrical hole (dimensions ⁇ 1. Ommx 20mm) into the position where it enters Provisionally round rods were prepared by setting them so as to be parallel to 0.
- ultrasonic flaw detection is performed on this artificially defective round bar using the same ultrasonic flaw detection equipment (USD15, manufactured by Nippon Craw Kramer I) as in the first embodiment described above to determine the detection limit. Verification was performed.
- the ultrasonic flaw detection method in the present embodiment uses a focus flaw detector (vibrator diameter 6 mm, underwater focal length 50 mm) under the flaw detection conditions of an incident angle of 0 ° and a flaw detection frequency of 15 MHz. Vertical flaw detection was performed at a water distance of 10 mm.
- Fig. 21 shows the results of the ultrasonic flaw detection in the depth direction of the artificial defect round bar
- Fig. 22 shows the results of the ultrasonic flaw detection in the circumferential direction of the artificial defect round bar.
- FIG. 22 shows the results of verifying the effective flaw detection pitch required to move in the axial direction while maintaining the flaw detection capability described above.
- the range where the echo height is half (1.6 dB) is about 1.6 mm in the movement width, and the range where the echo height is reduced by 1-4 (-3 dB) is about It was about 1 mm.
- the figure shows the result of adjusting the sensitivity to the echo height of 100%, and further finely adjusting the pitch back and forth in the circumferential direction around that position and performing flaw detection.
- this method uses the vertical flaw detection method, an area (dead band) where flaw detection cannot be performed from the surface of the artificial defect round bar to a depth A of about 2 to 3 mm is generated.
- the bearing is cut off by turning or the like until the bearing is completed, or even if it remains, it is the outer diameter surface of the bearing, so the life is not affected.
- the defect echo value (peak value) with respect to the depth A from the surface of the round bar material is stored in the memory of the personal computer 20 shown in FIG. 2 in the same manner as in the fourth embodiment. If you take in one after another and calculate, it will be in the whole section (including the desired depth) Defect length can be detected.
- the present embodiment can detect the defect length of the entire cross section at the stage of a round bar material having a diameter of 60 mm ⁇ or less, and is suitable for a bearing on the side of the user, which was conventionally impossible with a steel maker. All cross sections of the material can be inspected. In the present embodiment, it has been found that the absence of a defect having a length of 1 mm or more in the entire cross section can extend the life. From the above results, in the present embodiment, if the flaw detection is performed under the above-described conditions, the flaw detection capability is about 30 mm from the surface in the depth direction, and the effective flaw detection pitch (beam diameter) is about 1.5 mm. It was found to have.
- the flaw detection depth is about 3 Omm, and the diameter of the material is limited to ⁇ 6 Omm.
- the flaw detection pitch is set to about 1.5 mm, and the ultrasonic flaw is detected by a general commercially available flaw detection device.
- the transmission / reception speed it was found that flaw detection was possible at a speed of about 1 Om / min. (The smaller the diameter, the longer the measurement length per unit time. The slowest condition).
- the speed of hot forging is about 10 m / min at the highest, so it is within the range where 100% flaw detection is possible.
- the life test conditions are as follows.
- Lubricating oil VG68 equivalent mineral oil
- the test was interrupted at 200 hours, which is three times as long as the calculated life under the self-test conditions was 67 hours, and the presence or absence of peeling at that time was evaluated.
- test bearing (No. 1 s No. 2) using a material with poor cleanliness uses a normal material in which the inclusions with a length of 1 mm or more are present in the entire cross section. Test axis Although it is higher than the bearings (No. 3 and No. 4), the test bearing (No. 2) made of selected material without inclusions of 1 mm or more in length is not detected. No peeling occurred even if it exceeded, and a stable long life was obtained.
- test bearings (No. 1) made of materials that have not been sorted out by ultrasonic flaw detection generate cracks in a large proportion, 6 out of 10 during 200 hours when censoring occurs. did.
- each steel type shown in Table 7 is formed into an inner ring shape of a bearing, and carburized, quenched and tempered heat treatment is performed on the carburized steel by the heat treatment shown in FIG. 23, and quenching is performed on the sobu hardened steel.
- finish polishing was performed to produce a tapered inner ring 33 (see Fig. 25).
- the inner ring 33 was subjected to the heat treatment shown in FIG. 23 after being turned, but was not subjected to grinding.
- the surface roughness is 3.0 mRa.
- the inner rings of Examples 1, 4, and 6 of the present invention and the inner ring of Comparative Example 2, that is, the hardened steel (SUJ) have 800 to 860 as shown in FIG. After quenching for 1 hour at C, heat treatment was performed by tempering at 160 to 200 ° C.
- this ultrasonic flaw detector uses two pulleys 5 in which a test piece TP made of a ring-shaped bearing steel material (equivalent to an outer ring) is horizontally separated from each other in a water tank 50.
- a belt 54 is wound in an equilateral triangle around each pulley 51 and a pulley 53 fixed to the motor shaft of the rotary drive motor 52.
- the rotary drive motors 52 are controlled by a control device 45 via a motor drive control amplifier 53, and each of the pulleys is driven by the rotary drive motors 52.
- the test piece TP placed on 1 rotates at a predetermined speed.
- the control device 45 is configured by a personal computer or the like having a display means such as a CRT.
- the probe 40 is mounted via a probe mounting bracket 43 to an XY stage 42 of a linear guide device 41 arranged movably along the axial direction of the test piece TP. In the mounted state, it is arranged facing the inner peripheral surface of the test piece TP.
- the probe 40 transmits an ultrasonic pulse toward the inner peripheral surface of the test strip TP according to the voltage signal from the ultrasonic flaw detector 44, receives the reflected echo, and transmits the voltage signal. And transmitted to the ultrasonic flaw detector 4 4.
- the ultrasonic flaw detector 44 transmitted a command signal consisting of a voltage signal to the probe 40 based on a command from the controller 45, and was obtained based on the transmitted signal and the received signal.
- the flaw detection information is transmitted to the controller 45, and the controller 45 displays the information on the CRT.
- the linear guide device 41 is configured to move the probe 40 in the axial direction of the test piece TP via a servo motor (not shown) controlled by a linear guide controller 46.
- the linear guide controller 46 receives a command from the control device 45. Then, the servomotor is controlled to move the probe 40 by a predetermined dimension in the axial direction of the test piece TP. As a result, flaw detection of the entire cross section under the entire orbital plane of the test piece TP is performed.
- a steel material for the bearing corresponding to the outer ring is shown as the test piece TP, but if the probe 40 and the pulley 51 are configured to be reversed, a bearing equivalent to the inner ring can be obtained. Also applies to test pieces made of steel O
- the ultrasonic flaw detection conditions in this embodiment were performed at a flaw detection frequency of 15 MHz using a focus type probe (vibrator diameter 6 mm, underwater focal length 25 mm).
- the incident angle of the ultrasonic wave incident from the raceway surface of the inner ring to about 2 mm was set to 25 °
- the water distance was set to 25 mm.
- the incident angle of the ultrasonic wave incident on the inner ring was set to 5 °
- the water distance was set to 15 mm, and both were used together to achieve an arbitrary depth. A defect was detected.
- the maximum length of non-metallic inclusions is determined in advance by performing a large number of inspections on each bearing (steel type) and using the information on the intensity, length, and width of the detected defect echo to determine the detected defect.
- the grinding was performed from the raceway surface to determine the relationship between the intensity of the ultrasonic echo and the size of the defect, and the bearing inner rings shown in Table 7 were selected.
- Table 7 shows the results of the fracture life test.
- the upper surface (outer diameter surface) of a test piece made of a steel material for a bearing as shown in FIG. 26 is turned to produce one having various surface roughnesses of 1 to 12 zmRa (see FIG. 27).
- a 0. 5 mm hole (artificial defect) was machined vertically from the bottom of the specimen to a position 2 mm below the surface.
- the ratio of the echo intensity to the noise of the artificial defect was determined for specimens of various surface roughness, and the feasibility of defect detection was investigated.
- the detection of artificial defects on the test piece was performed using the ultrasonic flaw detector shown in Fig. 24 under the conditions of a focus type probe (vibrator diameter 6 mm, underwater focal length 25 mm) and a flaw detection frequency of 15 MHz. Ultrasonic flaw detection was performed. Note that the ultrasonic flaw detection in this embodiment was set so that the incident angle of the ultrasonic wave incident on the test piece was 25 ° and the water distance was 15 mm.
- FIG. 27 shows the relationship between the S / N ratio and the surface roughness of the outer diameter surface of the test piece.
- defects including aggregates of non-metallic inclusions
- the test volume of the entire section from below the outer diameter surface of the steel material in the bearing material, regardless of the cleanliness regulation by the conventional sample evaluation of the steel material
- the surface roughness of the steel outer diameter surface to 5 Aim Ra or less, it is possible to accurately detect defects with a maximum length of 0.6 mm or more in the entire cross section of the bearing material.
- the round bar and the ultrasonic probe made of the steel for the bearing to be evaluated are arranged in the ultrasonic transmission medium,
- the size and number of large inclusions in the inspection volume were measured by flaw detection, and the probability of the presence of large inclusions in the bearing steel to be evaluated was estimated.
- ultrasonic inspection it is possible to estimate the existence probability of large inclusions in a large flaw detection volume, and it is possible to evaluate large inclusions that are appropriate even for bearing steel with high cleanliness.
- the oblique flaw detection method as the flaw detection method of the ultrasonic flaw detection, it is possible to accurately detect smaller inclusions, thereby more accurately detecting the presence of large inclusions. .
- the flaw detection method of the ultrasonic flaw detection can detect a flaw of a small large inclusion in a deeper range. Thus, the presence of large inclusions can be detected more accurately.
- the vertical flaw detection method by performing the vertical flaw detection method at a flaw detection frequency of 30 MHz or less, a deeper area can be flaw-detected, thereby shortening the time required for flaw detection of large inclusions.
- the bearing steel of the present invention among the large inclusions estimated Te cowpea 'large inclusions evaluation method of steel the bearing present in flaw detection volume 2. 0X 1 0 6 mm 3 per Since the number of large inclusions with a square root length of 0.2 mm or more is 10.0 or less, it is possible to provide long-life bearing steel that quantitatively guarantees the presence of large inclusions. .
- the large inclusions caries Chi estimated by large inclusions evaluation method of steel bearings, flaw detection volume 2.
- 0x 1 0 6 mm 3 Since the total length of large inclusions with a length of 0.5 mm or more that exist in the bearing is set to 8 Omm or less, it is possible to provide a long-life bearing steel that further quantitatively assures the presence of large inclusions. The answer is g.
- the rolling bearing of the present invention it is possible to secure high reliability by eliminating a short-life product of the bearing and extending the life of the entire bearing.
- the rolling bearing of the present invention is used under high load and high surface pressure like a steel bearing, and is used under high temperature by applying a fitting stress to an inner ring like a paper machine bearing. when used in harsh environment, eliminating the concern of the occurrence of short life products and Warison products, it is possible to ensure high reliability by extending the life of the entire bearing c
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Description
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Priority Applications (5)
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DE60335172T DE60335172D1 (de) | 2002-01-17 | 2003-01-17 | Verfahren zur bewertung grosser einschlüsse in einem stahl zur verwendung in lager |
EP03701775A EP1475633B1 (en) | 2002-01-17 | 2003-01-17 | Method for evaluating large-sized inclusions in a steel for use in bearing |
AU2003203256A AU2003203256A1 (en) | 2002-01-17 | 2003-01-17 | Bearing steel, method for evaluating large-sized inclusions in the steel, and rolling bearing |
JP2003560553A JPWO2003060507A1 (ja) | 2002-01-17 | 2003-01-17 | 軸受用鋼及びその大型介在物評価方法、並びに転がり軸受 |
US10/498,876 US20060048576A1 (en) | 2002-01-17 | 2003-01-17 | Bearing steel,method for evaluating large-sized inclusions in the steel and rolling bearing |
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CN (1) | CN100390534C (ja) |
AU (1) | AU2003203256A1 (ja) |
DE (1) | DE60335172D1 (ja) |
PL (1) | PL374571A1 (ja) |
WO (1) | WO2003060507A1 (ja) |
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- 2003-01-17 US US10/498,876 patent/US20060048576A1/en not_active Abandoned
- 2003-01-17 AU AU2003203256A patent/AU2003203256A1/en not_active Abandoned
- 2003-01-17 CN CNB038024438A patent/CN100390534C/zh not_active Expired - Fee Related
- 2003-01-17 WO PCT/JP2003/000380 patent/WO2003060507A1/ja active Application Filing
- 2003-01-17 JP JP2003560553A patent/JPWO2003060507A1/ja active Pending
- 2003-01-17 EP EP03701775A patent/EP1475633B1/en not_active Expired - Fee Related
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Cited By (15)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2006030787A1 (ja) * | 2004-09-16 | 2006-03-23 | Nsk Ltd. | 転がり軸受の超音波探傷方法および欠陥検出方法 |
JP2008516211A (ja) * | 2004-10-20 | 2008-05-15 | エス・エム・エス・デマーク・アクチエンゲゼルシャフト | 圧延設備のロール表面の欠陥、例えば、ひび割れ、陥没などを検出するための方法、装置及び回路 |
JP2006234387A (ja) * | 2005-02-22 | 2006-09-07 | Sanyo Special Steel Co Ltd | 鋼材の白点性欠陥の評価方法 |
JP4559254B2 (ja) * | 2005-02-22 | 2010-10-06 | 山陽特殊製鋼株式会社 | 鋼材の白点性欠陥の評価方法 |
JP2006317192A (ja) * | 2005-05-10 | 2006-11-24 | Sanyo Special Steel Co Ltd | 鋼の信頼性評価方法 |
US7971484B2 (en) | 2005-05-10 | 2011-07-05 | Sanyo Special Steel Co., Ltd. | Method for evaluating reliability of steel and high-reliability steel obtained by the same |
KR101257687B1 (ko) | 2011-10-14 | 2013-04-24 | 국방과학연구소 | 비파괴 검사 장치 및 이를 포함하는 비파괴 검사 시스템 |
US10365253B2 (en) * | 2015-07-09 | 2019-07-30 | Ntn Corporation | Method for manufacturing outer joint member for constant velocity universal joint and ultrasonic flaw detection method for welded section |
WO2017051682A1 (ja) * | 2015-09-24 | 2017-03-30 | Ntn株式会社 | 等速自在継手の外側継手部材の製造方法および溶接部の超音波探傷検査方法 |
JP2017061987A (ja) * | 2015-09-24 | 2017-03-30 | Ntn株式会社 | 等速自在継手の外側継手部材の製造方法および溶接部の超音波探傷検査方法 |
US10365249B2 (en) | 2015-09-24 | 2019-07-30 | Ntn Corporation | Method for manufacturing outer joint member of constant velocity universal joint and ultrasonic flaw detection-inspection method for a welded portion |
WO2019034315A1 (de) | 2017-08-17 | 2019-02-21 | Robert Bosch Gmbh | Verfahren und vorrichtung zur magnetischen detektion von fehlstellen in einem ferromagnetischen bauteil |
DE102017214328A1 (de) | 2017-08-17 | 2019-02-21 | Robert Bosch Gmbh | Verfahren und Vorrichtung zur magnetischen Detektion von Fehlstellen in einem ferromagnetischen Bauteil |
JP2018036280A (ja) * | 2017-11-13 | 2018-03-08 | 東北特殊鋼株式会社 | 丸棒材の超音波探傷装置 |
CN108760882A (zh) * | 2018-05-29 | 2018-11-06 | 沈阳飞机工业(集团)有限公司 | 航空用料多功能检测平台及其使用方法 |
Also Published As
Publication number | Publication date |
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EP1475633A1 (en) | 2004-11-10 |
AU2003203256A1 (en) | 2003-07-30 |
PL374571A1 (en) | 2005-10-31 |
DE60335172D1 (de) | 2011-01-13 |
JPWO2003060507A1 (ja) | 2005-05-19 |
US20060048576A1 (en) | 2006-03-09 |
EP1475633B1 (en) | 2010-12-01 |
CN1620608A (zh) | 2005-05-25 |
EP1475633A4 (en) | 2006-10-11 |
CN100390534C (zh) | 2008-05-28 |
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