WO2017022328A1 - 鋼材製品の表面特性検査方法及び表面特性検査装置 - Google Patents
鋼材製品の表面特性検査方法及び表面特性検査装置 Download PDFInfo
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- WO2017022328A1 WO2017022328A1 PCT/JP2016/066920 JP2016066920W WO2017022328A1 WO 2017022328 A1 WO2017022328 A1 WO 2017022328A1 JP 2016066920 W JP2016066920 W JP 2016066920W WO 2017022328 A1 WO2017022328 A1 WO 2017022328A1
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- steel product
- output signal
- heat treatment
- inspection
- detector
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
- G01N27/82—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws
- G01N27/90—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws using eddy currents
- G01N27/9046—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws using eddy currents by analysing electrical signals
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D7/00—Modifying the physical properties of iron or steel by deformation
- C21D7/02—Modifying the physical properties of iron or steel by deformation by cold working
- C21D7/04—Modifying the physical properties of iron or steel by deformation by cold working of the surface
- C21D7/06—Modifying the physical properties of iron or steel by deformation by cold working of the surface by shot-peening or the like
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
- G01N27/82—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws
- G01N27/90—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws using eddy currents
- G01N27/9006—Details, e.g. in the structure or functioning of sensors
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D11/00—Process control or regulation for heat treatments
Definitions
- the present invention relates to a surface property inspection method and a surface property inspection method for inspecting the surface state of a steel product subjected to surface treatment.
- Patent Document 2 as a surface property inspection apparatus capable of inspecting a surface treatment state of a treatment material such as a steel material subjected to a surface treatment.
- the surface property inspection method is a surface property inspection method for evaluating the degree of heat treatment of a steel product subjected to surface treatment including heat treatment.
- This surface property inspection method includes an AC bridge circuit, an AC power source that supplies AC power to the AC bridge circuit, and a degree of heat treatment of the steel product that has been subjected to surface treatment including heat treatment based on an output signal from the AC bridge circuit.
- a surface property inspection device including an evaluation device for evaluating the above.
- An AC bridge circuit includes a variable resistor having a variable distribution ratio between a first resistor and a second resistor, a reference detector including a coil capable of exciting AC magnetism, and a coil capable of exciting AC magnetism.
- a test detector provided with a bridge circuit.
- This surface characteristic inspection method includes the following steps 1 to 5. These steps may be performed separately or two or more may be performed simultaneously.
- Preparation step a step of preparing at least a heat-treated steel product, a reference specimen having the same structure as the steel product, and a surface property inspection device.
- Arrangement step A step of arranging a coil of a reference detector so that an eddy current is excited in the reference specimen, and a coil of a test detector so that the eddy current is excited in the steel product.
- AC supply step a step of supplying AC power to the AC bridge circuit.
- Detection step Exciting AC magnetism to the reference detector coil and the inspection detector coil respectively to excite eddy currents to the reference specimen and the steel product, respectively, and the reference detector detects the reference state Detecting the electromagnetic characteristics of the steel product in a state of being performed as a first output signal.
- Heat treatment evaluation step A step of evaluating the degree of heat treatment applied to the steel product by comparing the value calculated from the first output signal with a first threshold value by an evaluation device. Then, the excitation frequency of each coil of the reference detector and the inspection detector is set to 500 Hz to 10 ⁇ 10 3 Hz.
- the depth at which the eddy current generated from the coil penetrates the subject can be set in the influence layer of the heat treatment. It can be set according to the depth. Then, the degree of heat treatment can be accurately evaluated by detecting the electromagnetic characteristics of the steel product and calculating based on the result.
- surface characteristics refers to the characteristics from the outermost surface of the subject to the affected layer on the inner surface.
- the “same structure” means that the material and shape are the same, and the presence or absence of surface treatment does not matter. Therefore, a steel product having the same material and shape can be used as a reference specimen regardless of the presence or absence of surface treatment.
- the detection step may be performed on a steel product that has been subjected to shot peening after heat treatment.
- the first output signal may be an electromagnetic characteristic of a steel product that has been subjected to shot peening after heat treatment.
- the heat treatment is performed by batch processing, the specimens are likely to vary.
- the influence layer is deep in the surface treatment, and it is difficult to accurately evaluate the degree of heat treatment in a non-destructive manner.
- SP processing can be performed relatively stably by controlling SP processing conditions.
- the present inventor can evaluate the degree of heat treatment with higher accuracy by evaluating the electromagnetic properties of the steel product after heat treatment and SP compared to the case of measuring immediately after the heat treatment. I found it.
- the evaluation result can be fed back to the heat treatment process. Therefore, it is possible to suppress a decrease in product yield due to heat treatment failure.
- the steel product prepared in the preparation step may be a steel product that has been heat-treated and not subjected to shot peening. Further, it further includes a preliminary detection step of detecting the electromagnetic characteristics of the steel product subjected to the heat treatment by the surface characteristic inspection apparatus, and a shot peening step of performing a shot peening process on the steel product after the preliminary detection step. But it ’s okay.
- the preliminary detection step an alternating voltage is supplied to the coils of the reference detector and the inspection detector, and eddy currents are respectively supplied to the reference specimen and the subject arranged in the reference detector and the inspection detector, respectively.
- the evaluation apparatus includes the step of The degree of heat treatment of the subject can also be evaluated based on the first output signal and the second output signal. Then, the heat treatment evaluation step in the surface property inspection method of one embodiment of the present invention calculates a ratio between the first output signal and the second output signal, and compares this value with the first threshold value. May include a step of evaluating the degree of heat treatment of the steel product. Because the second output signal can reduce variations in the first output signal due to individual differences in steel products, the measurement accuracy can be further improved.
- Both the first output signal and the second output signal in the surface property inspection method according to the embodiment of the present invention may be a potential difference between the reference detector and the inspection detector. It is possible to reduce the influence of the surrounding environment (temperature, humidity, noise, etc.) at the time of setting the threshold or at the time of inspection. Further, by providing a differential amplifier downstream of the AC bridge circuit, the potential difference can be amplified. Thereby, a highly accurate inspection can be performed.
- the first threshold value in the surface property inspection method is an untreated steel product not subjected to heat treatment and SP treatment, that is, not subjected to any surface treatment (hereinafter referred to as “untreated product”). It is good also as a value calculated based on the electromagnetic characteristic of this, and the electromagnetic characteristic of the steel material product (henceforth "heat-treatment reference
- the first output signal is calculated, the value is compared with a second threshold value, and the SP processing is appropriate for the subject. It may further include evaluating whether or not it is performed. Since the evaluation result for the SP process can be fed back to the SP process, a stable SP process can be performed and the accuracy of evaluating the degree of the heat treatment is improved. That is, it is possible to further suppress a decrease in product yield due to heat treatment failure.
- the second threshold value E th2 in the surface property inspection method includes the output signal E A when an unprocessed object that has not been subjected to heat treatment and shot peening is placed in the inspection detector, and the heat treatment And a value calculated by the following equation based on the output signal E C when the subject that has been appropriately subjected to the shot peening process is placed in the inspection detector, and using the second threshold as an initial value,
- the evaluation apparatus may repeatedly execute the heat treatment evaluation step.
- E Aav average value of the output signal E A
- E Cav average value of the output signal E C
- ⁇ A standard deviation of the output signal E A
- ⁇ C standard deviation of the output signal E C
- This formula makes it possible to set an appropriate initial threshold value with high accuracy even with a small number of measurements.
- the surface property inspection apparatus includes an AC bridge circuit including a variable resistor, a reference detector, and an inspection detector, an AC power supply that supplies AC power to the AC bridge circuit, and an output signal from the AC bridge circuit.
- the variable resistor is configured such that the distribution ratio is variable between the first resistor and the second resistor.
- the reference detector includes a coil capable of exciting AC magnetism.
- the inspection detector includes a coil capable of exciting AC magnetism. The excitation frequency of each coil of the reference detector and the inspection detector is set to 500 Hz to 10 ⁇ 10 3 Hz.
- the depth at which the eddy current generated from the coil penetrates the subject is set in accordance with the depth of the influence layer of the heat treatment. be able to. Then, the degree of heat treatment can be accurately evaluated by detecting the electromagnetic characteristics of the steel product and calculating based on the result.
- the surface property inspection apparatus used for this surface property inspection method uses a reference sample having the same structure as the sample when outputting as a detection signal, the surrounding environment (temperature and humidity) due to the difference in measurement time It is hard to be affected by. Therefore, measurement accuracy can be increased.
- the steel product subjected to the surface treatment may be a steel product subjected to a shot peening treatment after the heat treatment.
- a surface property inspection method capable of accurately inspecting whether or not a surface treatment for performing at least heat treatment on a steel product has been satisfactorily performed.
- the surface treatment applied to the steel product to be inspected for surface characteristics is performed by subjecting the steel product to heat treatment (quenching, tempering, annealing, nitriding treatment, austempering treatment, etc.) and then SP treatment. ing.
- heat treatment quenching, tempering, annealing, nitriding treatment, austempering treatment, etc.
- SP treatment nitriding treatment, austempering treatment, etc.
- a surface property inspection apparatus 1 includes an AC power supply 10, an AC bridge circuit 20, and an evaluation apparatus 30.
- the AC power supply 10 is configured to be able to supply AC power having a variable frequency to the AC bridge circuit 20.
- the AC bridge circuit 20 includes a variable resistor 21, a reference detector 22, and an inspection detector 23.
- the inspection detector 23 is formed so that a coil can be arranged so as to excite an eddy current in the subject M.
- the reference detector 22 is formed so that a reference sample S having the same structure as the subject M can be arranged.
- the same structure as the subject M means that the material and the shape are the same, regardless of whether or not the surface treatment is performed.
- the variable resistor 21 is configured so that the resistor R A can be distributed to the resistors R 1 and R 2 with a distribution ratio ⁇ .
- the distribution ratio ⁇ can be set arbitrarily.
- the resistors R1 and R2 form a bridge circuit together with the reference detector 22 and the inspection detector 23.
- a point B between the resistors R1 and R2 and the A and reference detector 22 that distributes the inspection detector 23 are connected to the AC power supply 10 of the surface characteristic test apparatus 1
- a resistor R 1 A point C between the reference detector 22 and a point D between the resistor R 2 and the inspection detector 23 are connected to the amplifier circuit 31 of the evaluation device 30.
- the connection point B between the reference detector 22 and the inspection detector 23 is grounded to reduce noise. Details of the reference detector 22 and the inspection detector 23 will be described later.
- the evaluation device 30 includes an amplification circuit 31, an absolute value circuit 32, a low-pass filter (LPF) 33, a phase comparator 34, a frequency adjuster 35, a determination unit 36, a display unit 37, and a temperature measurement unit 38. Further, a storage means is provided in the determination means 36 or in an area not shown.
- LPF low-pass filter
- the amplifying circuit 31 is connected to the point C and the point D, and receives a potential difference between the point C and the point D, that is, a potential difference between the reference detector 22 and the inspection detector 23, and amplifies this voltage signal. .
- the signal output from the amplifier circuit 31 is input to an absolute value circuit 32 that performs full-wave rectification on this signal, and the signal output from the absolute value circuit 32 is determined via an LPF 33 that converts this signal into direct current. Connected to means 36.
- the phase comparator 34 is connected to the AC power supply 10, the amplifier circuit 31, and the determination unit 36, compares the phase of the AC voltage supplied from the AC power supply 10 and the voltage output from the amplifier circuit 31, and compares the result. It outputs to the judgment means 36.
- the frequency adjuster 35 is connected to the output side of the AC power supply 10 and the LPF 33 and has a function of adjusting the frequency of the AC voltage supplied from the AC power supply 10 based on the output of the LPF 33.
- the judging means 36 is configured to change the position of the point A of the AC bridge circuit 20, that is, the distribution ratio ⁇ between the resistors R 1 and R 2 by outputting a control signal. Thereby, the non-equilibrium adjustment (the variable resistance setting process described later) for optimizing the distribution of R 1 and R 2 can be performed. Further, the quality of the surface state of the subject M is determined based on the output from the LPF 33.
- the display unit 37 displays or warns the determination result by the determination unit 36.
- the temperature measuring unit 38 detects the temperature at the evaluation position, that is, the surface temperature of the subject M, and outputs the temperature signal to the determining unit 36.
- the temperature measuring means 38 a non-contact type infrared sensor or a thermocouple can be used.
- the judging means 36 judges whether the surface treatment state of the subject M is good or not when the temperature of the subject M detected by the temperature measuring means 38 is within a predetermined range. Further, when the temperature detected by the temperature measuring means 38 is outside the predetermined range, the quality of the surface treatment state of the subject M is not judged. In the latter case, when the temperature of the subject M affects the accuracy of the examination, it is possible not to judge whether the surface treatment state of the subject is good or not, so that a highly accurate examination can be performed.
- the reference detector 22 and the test detector 23 have the same configuration, and are formed by winding a coil on the outer periphery of a core that can be inserted through the evaluation unit of the subject M, with the coil facing the surface of the subject M.
- the detector was configured to be close to the subject M so as to excite eddy currents. That is, this coil is wound so as to face the surface property inspection region of the subject.
- surrounding the surface property inspection region of the subject includes energizing eddy currents in the surface property inspection region by surrounding at least a part of the surface property inspection region. is doing.
- the inspection detector 23 used for inspecting the surface characteristics of the gear G having the gear portion as the subject M will be described.
- the inspection detector 23 includes a cylindrical core 23a formed so as to cover the gear portion of the gear G, and a coil 23b wound around the outer peripheral surface of the core 23a.
- the core 23a is made of a nonmagnetic material (for example, resin).
- the shape of the core 23a is not limited to a cylindrical shape as long as the gear G can be disposed inside. Note that at the time of inspection of the surface characteristics, the object M is not disposed on the reference detector 22, and the inspection can be performed by disposing the reference sample S for outputting the reference output.
- the inspection detector 23 of the present embodiment is preferably arranged with respect to the subject M so that an eddy current flows in a region where surface characteristics are desired to be inspected. That is, it is preferable to arrange the coil 23b so that the winding direction is the same as the direction in which the eddy current flows. With this configuration, the surface characteristics can be evaluated by accurately detecting the reaction of the eddy current.
- the gear G has a residual stress layer formed on the gear portion by SP treatment.
- the coil 23b may be arranged so that the winding direction of the coil 23b is substantially perpendicular to the rotation axis of the gear G.
- a magnetic field loop is generated in the direction of the rotation axis, an eddy current can be excited in the rotation direction of the gear G. it can.
- the conventional contact type detector it is necessary to prepare several types of detectors according to the shape of the teeth, and only the surface characteristics near the contact portion can be inspected.
- the surface property inspection apparatus 1 of the present embodiment can inspect a wide range of surface properties at once with a single detector.
- the inspection detector 23 may not include the core 23a as long as the coil 23b can maintain the shape.
- a coil 23b is formed, for example, by bonding an enameled copper wire wound around an air core with a curable epoxy resin or the like, or a fusion enameled copper wire having an effect of being cured by heat. It may be formed by being wound with an air core and then cured with heat from a hot air or a drying furnace.
- test detector 23 When the test detector 23 is disposed so that the coil 23b faces the test object surface of the subject M and AC power having a predetermined frequency is supplied from the AC power source 10 to the coil 23b, an AC magnetic field is generated. An eddy current flowing in the direction crossing the alternating magnetic field is excited on the surface of the substrate. The eddy current varies depending on the surface characteristics of the subject M. Therefore, it is possible to detect the electromagnetic characteristics based on a change in the potential difference between CD output from the amplifier circuit 31, and to perform an inspection regarding the degree of heat treatment.
- phase and amplitude (impedance) of the output waveform (voltage waveform) output from the amplifier circuit 31 change depending on the characteristics (surface treatment state) of the residual stress layer after SP treatment.
- the inspection detector 23 may be provided with a magnetic shield 23c.
- the magnetic shield 23 c is disposed outside the test detector 23 so as to surround the subject M. Since the external magnetism can be shielded by the magnetic shield 23c, erroneous detection can be prevented.
- the output from the AC bridge circuit 20 adjusted to a non-equilibrium state will be described with reference to the equivalent circuit of FIG.
- a reference sample S for outputting a reference output is arranged close to the reference detector 22, and an object M to be judged whether the surface treatment state is good is arranged close to the test detector 23. Yes.
- the reference specimen S has the same structure as the specimen M, and preferably an untreated product that has not been surface-treated.
- the resistor R 1 is R A / (1 + ⁇ )
- the resistor R 2 is R A ⁇ / (1 + ⁇ ).
- the impedance of the reference detector 22 is R S + j ⁇ L S
- the impedance of the inspection detector 23 is R ⁇ + j ⁇ L T.
- the potential of the point A is set to E, and the excitation current flowing in each side of the bridge when the respective specimens (reference specimen S and specimen M) are not brought close to the reference detector 22 and the test detector 23 is i 1.
- the voltage output to the amplifier circuit 31 is the difference between E 1 and E 2 and is expressed by the following equation.
- the component A is constituted by detector components: (R S + j ⁇ L S ), (R ⁇ + j ⁇ L T ), and current amounts that change when each specimen approaches the detectors: i ⁇ , i ⁇ .
- the magnitudes of i ⁇ and i ⁇ vary depending on the amount of magnetism passing through the specimen due to electromagnetic characteristics such as magnetic permeability and conductivity of each specimen. Therefore, the magnitudes of i ⁇ and i ⁇ can be changed by changing the excitation currents i 1 and i 2 that influence the amount of magnetism generated from each detector. Further, from the expressions (3) and (4), the excitation currents i 1 and i 2 change depending on the distribution ratio ⁇ of the variable resistance. Therefore, the magnitude of the component A is changed by adjusting the distribution ratio ⁇ of the variable resistance. be able to.
- the component B is composed of each detector component: (R S + j ⁇ L S ), (R ⁇ + j ⁇ L T ), and resistance parameters divided by the variable resistance distribution ratio ⁇ . For this reason, similarly to the component A, the size of the component B can be changed by adjusting the distribution ratio ⁇ of the variable resistor.
- the signal output from the amplifier circuit 31 of the bridge is a signal obtained by extracting the difference area between the voltage waveforms of the reference detector 22 and the inspection detector 23, and has a circuit configuration that makes the current (excitation current) flowing through the detector constant. It has become.
- the extracted voltage signal can be considered as a power signal. Further, the power supplied to the detector is always constant. Thereby, the magnetic energy supplied to the subject M can also be made constant.
- ⁇ S01 Preparation process> A surface property inspection apparatus 1, a reference specimen S, an untreated product, and a steel product (hereinafter referred to as “heat treated product”) subjected to only heat treatment are prepared.
- ⁇ S02 Variable resistance setting step> First, AC power is supplied from the AC power supply 10 to the AC bridge circuit 20. In this state, the distribution ratio ⁇ of the variable resistor 21 is adjusted so that the detection sensitivity of the specimen by the surface characteristic inspection apparatus 1 is increased. That is, the distribution ratio ⁇ of the variable resistor 21 is adjusted so that the output signal of the AC bridge circuit 20 becomes small without bringing the reference sample S and the subject M close to the reference detector 22 and the test detector 23, respectively. .
- the surface treatment product the surface treatment state of the steel product subjected to the surface treatment close to the inspection detector 23 is defective.
- the difference in output signal becomes large, and the detection accuracy can be increased.
- the voltage amplitude of the output signal from the AC bridge circuit 20 or the voltage output from the LPF 33 is monitored and output by a display device having a waveform display function such as an oscilloscope (for example, provided in the determination unit 36).
- the distribution ratio ⁇ is adjusted so that becomes smaller.
- the distribution ratio ⁇ of the variable resistor 21 is adjusted and set so that the output takes the minimum value or the minimum value (local equilibrium point).
- Adjustment of the distribution ratio ⁇ of the variable resistor 21 is performed in order to increase the output difference according to the difference in the surface state by reducing the output voltage (E 2 ⁇ E 1 ) of the amplifier circuit 31 and to improve the inspection accuracy. Is called.
- the components A and B change by adjusting the distribution ratio ⁇ , the components A and B are variable according to the impedance (R S + j ⁇ L S ) and (R ⁇ + j ⁇ L T ) of the reference detector 22 and the test detector 23.
- the output voltage (E 2 ⁇ E 1 ) of the amplifier circuit 31 that is the differential output from the AC bridge circuit 20 can be reduced.
- the difference in characteristics between the reference detector 22 and the test detector 23 can be reduced and the original characteristics of the subject M can be extracted as much as possible, so that the test accuracy can be improved.
- ⁇ S03 Frequency setting process>
- AC power is supplied from the AC power supply 10 to the AC bridge circuit 20, and the frequency of the AC power supplied to the AC bridge circuit 20 is changed by the frequency adjuster 35.
- the voltage amplitude output from the AC bridge circuit 20 or the voltage output from the LPF 33 is monitored.
- the frequency adjuster 35 outputs a control signal to the AC power supply 10 so that the initial frequency f 1 set in the frequency adjuster 35 is obtained, and the output voltage E f1 from the amplifier circuit 31 at the frequency f 1 is the frequency adjuster 35. Is input and stored. Subsequently, a control signal is output to the AC power supply 10 so that the frequency f 2 is a predetermined value, for example, 100 Hz higher than the frequency f 1 , and the output voltage E f2 from the amplifier circuit 31 at the frequency f 2 is the frequency regulator 35. Is input and stored.
- E f1 and E f2 are compared, and if E f2 > E f1 , a control signal is output so that the frequency f 3 is higher than the frequency f 2 by a predetermined value, and the frequency f 3
- the output voltage E f3 from the amplifier circuit 31 is input to the frequency adjuster 35 and stored.
- E f2 and E f3 are compared. Repeat this to set the frequency f n of when it becomes E fn +1 ⁇ E fn, i.e. the frequency f n that output is maximized, as the frequency used by the threshold setting step S04 and the AC supply step S05.
- the frequency at which the output from the AC bridge circuit 20 is increased corresponding to the subject M having different surface treatment state, shape, etc. and different impedance can be set by a single operation.
- the optimum frequency varies depending on the material, shape, and surface treatment state of the subject. If this is known in advance, it is not necessary to set the frequency. Thereby, an output respond
- the frequency setting step S03 can be performed before the variable resistance setting step S02.
- ⁇ S04 First Threshold Setting Step> A threshold value used for determining the quality of the surface condition of the surface-treated product is set.
- first initial threshold value a threshold value set in advance for use at the start of evaluation of a surface-treated product.
- the reference sample S is brought close to the reference detector 22, and the AC power having the frequency set in the frequency setting step S ⁇ b> 03 is supplied from the AC power supply 10 to the AC bridge circuit 20.
- the voltage output output from the AC bridge circuit 20 is amplified by the amplifier circuit 31, is subjected to full-wave rectification in the absolute value circuit 32, is subjected to DC conversion in the LPF 33, and is output to the determination means 36.
- This initial threshold value E th1 is set as a threshold value and stored in the storage means.
- the output value E A of the unprocessed product and its standard deviation ⁇ A , the output value E B of the heat treatment reference product appropriately and its standard deviation ⁇ B can be determined by the following equation.
- the first initial threshold value is determined by this equation, it is possible to judge pass / fail by comparing the voltage value, which is the second output signal, with the first initial threshold value in an evaluation step described later.
- the value can be set as the first threshold value E th1 .
- the output signal when the subject M is not in proximity to the test detector 23 is stored in the storage means as the first initial offset value E i1 .
- ⁇ S05 AC supply process>
- the AC power having the frequency set in the frequency setting step S03 is supplied from the AC power supply 10 to the AC bridge circuit 20.
- the reference sample S is close to the reference detector 22.
- ⁇ S06 Heat treatment product placement / preliminary detection process> A heat-treated product (steel product subjected to only heat treatment) is placed close to the inspection detector 23 as the subject M, and arranged so that eddy current is excited in the subject M. At the same time, the signal of the potential difference between C and D of the AC bridge circuit 20 is output in a state where the reference sample S is brought close to the reference detector 22. This signal is amplified by the amplifier circuit 31, is full-wave rectified in the absolute value circuit 32, and is subjected to DC conversion in the LPF 33, so that a potential difference signal is preliminarily detected as a second output signal.
- the reference state refers to a state serving as a reference for comparison with the output from the inspection detector 23.
- the temperature measuring unit 38 measures the temperature of the surface of the subject M before the subject M approaches the test detector 23 or after the subject M is arranged, and outputs a signal of the temperature to the judging unit 36. To do.
- the quality of the examination state of the subject M is determined.
- the phase comparator 34 compares the waveform of AC power supplied from the AC power supply 10 with the AC voltage waveform output from the AC bridge circuit 20, and detects the phase difference between them. By monitoring this phase difference, it can be determined whether or not the examination state is good (for example, there is no phase shift between the examination detector 23 and the subject M). Even if the output from the AC bridge circuit 20 is the same, if the phase difference changes greatly, it can be determined that there is a change in the inspection state and there is a possibility that the inspection is not performed properly.
- the determination unit 36 determines whether the surface treatment state of the subject M is good or not when the temperature of the subject M detected by the temperature measurement unit 38 is within a predetermined range, and is detected by the temperature measurement unit 38. When the temperature is outside the predetermined range, the quality of the surface treatment state of the subject M is not judged.
- the predetermined temperature range is a temperature range in which the temperature change of the subject M does not substantially affect the examination, and can be set to 0 to 60 ° C., for example.
- the subject M waits until the subject M is within the predetermined temperature range, air is blown to the subject M, and the subject M is inspected. It is possible to move to another line.
- ⁇ S08 Potential difference signal storage step of heat-treated product>
- the potential difference signal DC-converted by the LPF 33 in the heat treatment product arrangement / preliminary detection step S06 is stored as a second output signal by the storage means.
- ⁇ S09 SP treatment process>
- the SP treatment is performed on the heat-treated product whose potential difference E h is measured.
- the SP treatment is performed by causing a shot with a high hardness (for example, a Vickers hardness Hv of 500 to 850) (substantially spherical or a rounded cut wire) to collide with the workpiece at a high speed.
- a high hardness for example, a Vickers hardness Hv of 500 to 850
- the numerical value of the above-mentioned Vickers hardness is measured by the test method described by JISZ2244 (2009).
- the projection material can be appropriately selected from a range of particle diameters of 0.5 to 4.0 mm. Further, as a projection condition, for example, when a direct pressure type shot peening apparatus is used, a high intensity condition such that the projection pressure is 0.05 to 0.7 MPa and the projection amount is 20 kg / min at the maximum can be adopted.
- SP treatment can be performed using a steel shot having a particle diameter of 0.6 mm and a Vickers hardness of Hv700, an injection pressure of 0.3 MPa, an injection amount of 13 kg / min, and a projection time of 10 seconds.
- ⁇ S10 Surface treatment product arrangement / detection process>
- the surface treatment product (steel product after the SP process) is used as the object M, and the same process as the heat treatment product arrangement / preliminary detection process S06 is performed, and the signal of the potential difference converted into DC by the LPF 33 is detected as the first output signal.
- ⁇ S12 Potential difference signal storage step of surface treated product>
- the potential difference signal DC-converted by the LPF 33 in the surface treatment product arrangement / detection step S10 is stored as a first output signal.
- ⁇ S13 Evaluation process of heat treatment> This is a step of determining whether or not the steel product is appropriately heat-treated.
- the ratio of the output voltage value E S that is the first output signal to the output voltage value E H that is the second output signal (output voltage ratio: E S / E H ) is calculated by the determination means 36.
- the output voltage ratio is compared with the first threshold value E th1, and it is determined by the determination means 36 whether or not the heat treatment is properly performed. For example, in the example described later, if the output voltage ratio is lower than the first threshold value E th1 , it is determined that “the heat treatment has been properly performed (non-defective product)”, and the output voltage ratio is the first threshold value E th1.
- the excitation frequency of each coil of the reference detector 22 and the inspection detector 23 when the eddy current is excited in the subject M in the heat treatment product placement step S06 and the surface treatment product placement step S10 is set to 500 Hz to 10 ⁇ 10 3 Hz. can do. Since the depth at which the eddy current generated from the coil penetrates the subject M can be set in accordance with the depth of the heat treatment-affected layer, appropriate evaluation can be performed according to the heat treatment conditions.
- a system when the system is constructed as an automatable system, a system is configured to feed back the result of the determination that “the heat treatment is not properly performed (defective product)” in the heat treatment evaluation step S13 described above to the heat treatment step. You can also. Since the heat treatment conditions can be corrected according to the inspection result, the defective product occurrence rate of the steel product due to the heat treatment failure can be reduced.
- a gear G (non-defective product) made of chromium molybdenum steel and subjected to gas carburizing and quenching under appropriate conditions and a gear G (defective product) subjected to heat treatment under inappropriate conditions are prepared.
- “inappropriate conditions” were gas carburizing and quenching twice under appropriate conditions.
- the SP treatment was performed on an iron-based shot (manufactured by Shinto Kogyo Co., Ltd.) having a particle diameter of 600 ⁇ m using an air-type shot peening apparatus (manufactured by Shinto Kogyo Co., Ltd.) at an injection pressure of 0.3 MPa.
- FIG. 4 shows the calculation result of the ratio of the output value E S when the surface-treated product is measured with respect to the output value E H when the heat-treated product is measured (output voltage ratio: E S / E H ). There is a difference in the output voltage ratio depending on whether the heat treatment is properly performed.
- E S / E H output voltage ratio
- both the determination as to whether the heat treatment has been performed properly and the determination as to whether the SP process has been performed properly are performed using the same surface property inspection apparatus as in the first embodiment. Do.
- FIG. 5 shows a flowchart of the surface property inspection method of the second embodiment.
- Preparation step S101, variable resistance setting step S102, frequency setting step S103, first threshold setting step S104 are the same as S01 to S04 in the first embodiment in order.
- ⁇ S105 Second Threshold Setting Step> A threshold value used to determine whether the surface condition of the surface-treated product is good or not when performing an inspection regarding the degree of the entire surface treatment by the heat treatment and the SP treatment is set.
- second initial threshold value a threshold value set in advance for use at the start of evaluation of a surface-treated product.
- the voltage output output from the AC bridge circuit 20 is amplified by the amplifier circuit 31, is subjected to full-wave rectification in the absolute value circuit 32, is subjected to DC conversion in the LPF 33, and is output to the determination means 36.
- About 10 to several tens of untreated products and those judged to be non-defective products that have been properly surface-treated (heat treatment and SP treatment) are prepared, and the judgment is made when each test object is brought close to the inspection detector 23.
- Output value distribution data is acquired from the output value output to the means 36. This is schematically shown in FIG.
- Second initial threshold E th2 is when you place the patient M after the surface treatment is a non-defective to the output signal E A and the inspection detector 23 when placing the subject M unprocessed test detector 23 Based on the output signal E C , it is determined by the following equation in consideration of the variation of each output signal.
- FIG. 6 schematically shows the distribution of the output signal E A of the unprocessed subject and the output signal E C of the subject after the surface treatment.
- the second initial threshold value E th2 is set as a threshold value and stored in the determination unit 36.
- the second initial threshold E th2 is between the maximum value E Amax of the output signal E A and the minimum value E Cmin of the output signal E C. Have a relationship.
- an appropriate second initial threshold value E is considered in consideration of variations in the output signal E A and the output signal E C , whether there is a specific measurement value greatly deviating from the distribution, and the like.
- th2 can be set. For example, there is a method in which a plurality of untreated and surface treated states of the same subject are measured, and the initial threshold value E th2 is calculated again using these.
- the value can be set as the second threshold value E th2 .
- the output signal when the subject M is not in proximity to the test detector 23 is stored in the storage means as the second initial offset value E i2 .
- AC supply process S106 is the same as S05 in the first embodiment.
- ⁇ S109 Potential difference signal storing step of unprocessed product>
- the potential difference signal DC-converted by the LPF 33 in the unprocessed product placement step S107 is stored in the storage unit.
- the potential difference signal storage step S116 and the heat treatment evaluation step S117 are sequentially the same as S06 to S13 in the first embodiment.
- ⁇ S118 Evaluation process of the entire surface treatment> This is a step of determining whether or not the surface-treated product has been appropriately surface-treated.
- the output voltage value E s which is the first output signal is compared with the second threshold value E th2 , and if the output voltage value E s is lower than the second threshold value E th2 , “the surface treatment has been properly performed ( a good product) ", when the output voltage value E s is the second threshold value E th2 or” surface treatment is not applied properly (defective) ", is determined by the determination means 36.
- the determination result by the determination unit 36 is displayed by the display unit 37, and a warning is issued when it is determined that “the surface treatment is not properly performed”.
- the SP Since there is a possibility that the processing is not properly performed, a warning to that effect can be given and this can be fed back to the SP processing.
- the first initial threshold E th1 is good surface state in the output signal E A and the inspection detector 23 when placing the subject M unprocessed test detector 23 the example, when the difference between the output signal E B when placing the patient M after the surface treatment is large, approaching the average value E Aav of the output signal E a, the width of the output is determined to be good It can grow.
- the second initial threshold value E th2 is determined based on a large number of inspection data accumulated by performing repeated measurement using the first initial threshold E th1 and the second initial threshold E th2. Can be reset.
- the first initial offset value E i1 and the second initial offset value E i2 , the first inspection offset value E ik1, and the second inspection offset value E ik2 described above are used.
- the measured value can be calibrated.
- the first or second threshold value is corrected by using the detection signal acquired in the unprocessed product arrangement / preliminary detection step S107 and stored in the potential difference signal storage step S109 of the unprocessed product, or heat treatment evaluation It is also possible to evaluate the reliability of the surface treatment evaluation.
- FIG. 7A and 7B are graphs obtained by editing the measurement results of the gear G of the above-described embodiment.
- FIG. 7A shows measured voltages of the gear G (good product) and the gear G (defective product) before and after the SP processing.
- ⁇ E1 between the measured values of the gear G (good product) and the gear G (defective product) before SP
- ⁇ E2 between the measured values of the gear G (good product) and gear G (defective product) after the SP
- FIG. 7B shows a ratio of measured voltages of the gear G (good product) and the gear G (defective product) before and after the SP processing (1 ⁇ (gear G (good product) / gear G (defective product)) ⁇ 100). Since the value after SP is clearly larger, it is suggested that measuring the gear G after SP processing can make a more accurate determination as in FIG. 7A.
- the determination of the surface treatment for the gear has been described, but it can be widely used for the determination of the surface treatment of steel products such as springs, shafts, bearings, and the like.
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Abstract
Description
(1)準備工程:少なくとも熱処理を施した鋼材製品、及び該鋼材製品と同一構造の基準検体、及び表面特性検査装置、を準備する工程。
(2)配置工程:基準検出器のコイルを前記基準検体に渦電流が励起するように配置すると共に、検査検出器のコイルを前記鋼材製品に渦電流が励起するように配置する工程。
(3)交流供給工程:交流ブリッジ回路に交流電力を供給する工程。
(4)検出工程:基準検出器のコイル及び前記検査検出器のコイルにそれぞれ交流磁気を励磁して、基準検体及び前記鋼材製品にそれぞれ渦電流を励起させると共に、基準検出器が基準状態を検出している状態における前記鋼材製品の電磁気特性を第1の出力信号として検出する工程。
(5)熱処理評価工程:評価装置によって、第1の出力信号より演算した値を第1の閾値と比較して前記鋼材製品に施されている熱処理の程度を評価する工程。
そして、前記基準検出器及び前記検査検出器の各コイルの励磁周波数を500Hz~10×103Hzに設定する。
そして、本発明の一実施形態の表面特性検査方法における前記熱処理評価工程は、第1の出力信号と第2の出力信号との比を演算し、この値と前記第1の閾値と比較することにより前記鋼材製品の熱処理の程度を評価する工程を含んでもよい。第2の出力信号によって、鋼材製品の個体差による第1の出力信号のバラツキを少なくすることができるので、測定精度をさらに向上させることができる。
また、この表面特性検査方法に用いる表面特性検査装置は、検出信号として出力する際に被検体と同一構造の基準検体を用いていることから、測定時期の違いによる周囲の環境(温度や湿度)の影響を受けにくい。その為、測定精度を高くすることができる。
本発明において表面特性を検査される鋼材製品に施されている表面処理は、鋼材製品に熱処理(焼き入れ、焼き戻し、焼き鈍し、窒化処理、オーステンパー処理等)を施した後、SP処理を施している。この表面処理を施した鋼材製品の表面特性検査方法の一側面の実施形態を第1実施形態として、図を参照して説明する。なお、以下の説明における上下左右方向は、特に断りのない限り図における方向を指す。
図1Aに示すように、本発明の実施形態による表面特性検査装置1は、交流電源10、交流ブリッジ回路20及び評価装置30を備えている。
判断手段36は、温度測定手段38で検出された被検体Mの温度が所定範囲内である場合に、被検体Mの表面処理状態の良否を判断する。また、温度測定手段38で検出された温度が所定範囲外である場合に、被検体Mの表面処理状態の良否の判断を行わない。後者では、被検体Mの温度が検査の精度に影響を及ぼすような場合に被検体の表面処理状態の良否の判断を行わないようにすることができるので、精度の高い検査を行うことができる。ここで、熱電対などで評価位置の温度を測定し、被検体Mの表面の温度を代表する温度として被検体Mの表面処理状態の良否を判断するか否かの判断を行う構成を採用することもできる。
次に、表面処理特性検査装置1による鋼材製品の表面特性検査方法について、さらに図3を参照して説明する。
表面特性検査装置1、基準検体S、未処理品、熱処理のみを施した鋼材製品(以降、「熱処理品」と記す)、を用意する。
まず、交流電源10から交流ブリッジ回路20に交流電力を供給する。この状態で、表面特性検査装置1による検体の検出感度が高くなるように、可変抵抗21の分配比γを調整する。即ち、基準検出器22及び検査検出器23に、基準検体S、被検体Mを夫々近接させずに、交流ブリッジ回路20の出力信号が小さくなるように、可変抵抗21の分配比γを調整する。このように可変抵抗21を設定しておくことにより、検査検出器23に近接した表面処理を施した鋼材製品(以降、「表面処理品」と記す)の表面処理状態が不良である場合と、表面処理状態が良好である場合の出力信号の差異が大きくなり、検出精度を高くすることができる。具体的には、オシロスコープなど波形表示機能を持つ表示装置(例えば、判断手段36が備えている)にて交流ブリッジ回路20からの出力信号の電圧振幅、またはLPF33からの電圧出力をモニターし、出力が小さくなるように分配比γを調整する。好ましくは、出力が最小値又は極小値(局所平衡点)をとるように、可変抵抗21の分配比γを調整して、設定する。
基準検体Sを基準検出器22に近接させた状態で、交流電源10から交流ブリッジ回路20に交流電力を供給し、周波数調整器35により交流ブリッジ回路20に供給する交流電力の周波数を変化させて交流ブリッジ回路20から電圧振幅出力またはLPF33からの電圧出力をモニターする。
表面処理品の表面状態の良否を判断するために用いる閾値を設定する。ここでは、表面処理品の評価開始時に用いるために予め設定しておく閾値(以下、「第1の初期閾値」と記す)の設定方法について説明する。まず、基準検体Sを基準検出器22に近接させ、周波数設定工程S03において設定された周波数の交流電力を交流電源10から交流ブリッジ回路20に供給する。交流ブリッジ回路20から出力された電圧出力は、増幅回路31で増幅され、絶対値回路32において全波整流を行い、LPF33において直流変換を行い、判断手段36へ出力される。被検体Mとして未処理品(熱処理又はSP処理のいずれも施されていない鋼材製品)及び熱処理基準品(熱処理のみを適正に施した鋼材製品)をそれぞれ10~数10個程度用意し、まず、各未処理品を検査検出器23に近接させて、全ての未処理品の出力値EAを計測し、その平均値EAavを算出する。次いで、各熱処理基準品を検査検出器23に近接させて出力値EBを計測し、未処理品の出力値の平均値に対する熱処理基準品の比EB/EAavを算出する。これより得られた値の最小値が第1の初期閾値Eth1となる。
周波数設定工程S03において設定された周波数の交流電力を交流電源10から交流ブリッジ回路20に供給する。ここで、基準検体Sは基準検出器22に近接している。
熱処理品(熱処理のみを施した鋼材製品)を被検体Mとして検査検出器23に近接させ、被検体Mに渦電流が励起されるように配置する。同時に、基準検体Sを基準検出器22に近接させている状態で、交流ブリッジ回路20のC-D間の電位差の信号を出力させる。この信号は、増幅回路31で増幅され、絶対値回路32において全波整流され、LPF33において直流変換された電位差の信号が第2の出力信号として予備的に検出される。ここで、基準状態とは検査検出器23からの出力と比較する為の基準となる状態のことを指す。
被検体Mの検査状態の良否を判定する。位相比較器34により交流電源10から供給される交流電力の波形と交流ブリッジ回路20から出力される交流電圧波形を比較し、それらの位相差を検出する。この位相差をモニターすることにより、検査状態が良好である(例えば、検査検出器23と被検体Mの位相ずれがない)か否かを判断することができる。交流ブリッジ回路20からの出力が同じであっても、位相差が大きく変化した場合には、検査状態に変化があり、検査が適正に行われていない可能性があると判断することができる。
検査状態判断工程S07で被検体Mの検査状態が「良」と判定された場合、熱処理品配置・予備検出工程S06においてLPF33で直流変換された電位差の信号を第2の出力信号として記憶手段で記憶する。
電位差Ehを測定した熱処理品に対して、SP処理を施す。SP処理は、高硬度(例えば、ビッカース硬さHvが500~850)のショット(略球形若しくは切断された線材を丸め加工したもの)などを高速度で被処理材に衝突させて行う。なお、上述のビッカース硬さの数値はJIS Z2244(2009)により記載された試験方法で測定されたものである。
表面処理品(SP工程後の鋼材製品)を被検体Mとして、熱処理品配置・予備検出工程S06と同様の工程を行い、LPF33において直流変換された電位差の信号が第1の出力信号として検出される。
被検体Mの検査状態の良否を判定する。この工程は、検査状態判断工程S07と同様の工程である。
検査状態判断工程S11で被検体Mの検査状態が「良」と判定された場合、表面処理品配置・検出工程S10においてLPF33で直流変換された電位差の信号を第1の出力信号として記憶手段で記憶する。
鋼材製品に適正に熱処理が施されているか否かを判定する工程である。まず、第2の出力信号である出力電圧値EHに対する第1の出力信号である出力電圧値ESの比(出力電圧比:ES/EH)を判断手段36にて演算する。この出力電圧比を第1の閾値Eth1とを比較し、熱処理が適正に施されているか否かを判断手段36によって判定する。例えば、後述の実施例の場合、出力電圧比が第1の閾値Eth1を下回っていたら「熱処理が適正に施されていた(良品)」と判断し、出力電圧比が第1の閾値Eth1以上の場合は「熱処理が適正に施されていない(不良品)」と判断する(図4参照)。判断手段36による判断結果は、表示手段37により表示され、「熱処理が適正に施されていない」と判定した場合には警告を発する。
一実施形態の表面特性検査方法を用いて、ギヤGの表面特性を検査した結果について説明する。クロムモリブデン鋼材で構成され、適正な条件にてガス浸炭焼き入れを行ったギヤG(良品)と、不適正な条件で熱処理を行ったギヤG(不良品)をそれぞれ用意する。ここでの、「不適正な条件」とは、適正な条件で2度ガス浸炭焼き入れを行った。SP処理は、粒子径600μmの鉄系ショット(新東工業株式会社製)をエア式のショットピーニング装置(新東工業株式会社製)を用いて、0.3MPaの噴射圧力にて行った。
熱処理及びSP処理による表面処理全体の程度に関する検査を行う際の、表面処理品の表面状態の良否を判断するために用いる閾値を設定する。ここでは、表面処理品の評価開始時に用いるため、あらかじめ設定しておく閾値(以下、「第2の初期閾値」と記す)の設定方法について説明する。まず、基準検体Sを基準検出器22に近接させ、周波数設定工程S103において設定された周波数の交流電力を交流電源10から交流ブリッジ回路20に供給する。交流ブリッジ回路20から出力された電圧出力は、増幅回路31で増幅され、絶対値回路32において全波整流を行い、LPF33において直流変換を行い、判断手段36へ出力される。未処理品と適正に表面処理(熱処理及びSP処理)された良品と判断されるものとをそれぞれ10~数10個程度用意し、検査検出器23にそれぞれの被検体を近接させたときに判断手段36へ出力された出力値から、出力値の分布データを取得する。図6に模式的に示す。
の関係を持つ。
未処理品を被検体Mとして、第1実施形態における熱処理品配置工程S06と同様の工程を行う。
被検体Mの検査状態の良否を判定する。この工程は、第1実施形態における検査状態判断工程S07と同様の工程である。
検査状態判断工程S108で被検体Mの検査状態が「良」と判定された場合、未処理品配置工程S107においてLPF33で直流変換された電位差の信号を記憶手段で記憶する。
表面処理品が適正に表面処理が施されているか否かを判定する工程である。第1の出力信号である出力電圧値Esと第2の閾値Eth2を比較し、出力電圧値Esが第2の閾値Eth2を下回っていたら「表面処理が適正に施されていた(良品)」と、出力電圧値Esが第2の閾値Eth2以上の場合は「表面処理が適正に施されていない(不良品)」と、判断手段36によって判断する。判断手段36による判断結果は、表示手段37により表示され、「表面処理が適正に施されていない」と判定した場合には警告を発する。
また、熱処理の評価工程S117において「熱処理が適正に施されている」と判定され、表面処理全体の評価工程S118において「表面処理が適正に施されていない」と判定された場合には、SP処理が適正に施されていない可能性があるため、その旨を警告すると共に、このとこをSP処理にフィードバックすることもできる。
第1実施形態及び第2実施形態において、第1の初期閾値Eth1は、検査検出器23に未処理の被検体Mを配置したときの出力信号EA及び検査検出器23に表面状態が良好である表面処理後の被検体Mを配置したときの出力信号EBの差が大きい場合などには、出力信号EAの平均値EAav側に近づいて、良品と判定される出力の幅が大きくなる可能性がある。第2の初期閾値Eth2も同様である。そのため、更に精度の高い閾値を設定したい場合には、第1の初期閾値Eth1及び第2の初期閾値Eth2を用いて繰り返し測定を行うことにより蓄積された数多くの検査データに基づいて、閾値を設定し直すことができる。
第1実施形態及び第2実施形態において、前述した第1の初期オフセット値Ei1及び第2の初期オフセット値Ei2と、第1の検査オフセット値Eik1及び第2の検査オフセット値Eik2と、を用いて測定値の校正を行うことができる。
また、未処理品配置・予備検出工程S107において取得され、未処理品の電位差信号記憶工程S109において記憶された検出信号を利用して、第1又は第2の閾値を修正し、又は、熱処理評価及び/又は表面処理評価の信頼度を評価することもできる。
以上のように、表面処理として熱処理及びSP処理を行った鋼材製品に対する、表面処理が適正に行われたか否かの評価は、SP処理後の鋼材製品の測定を行うことで、良好に評価できる。この事項について図7A及び図7Bを用いて説明を加える。
10 交流電源
20 交流ブリッジ回路
21 可変抵抗
22 基準検出器
23 検査検出器
23a コア
23b コイル
23c 磁気シールド
30 評価装置
31 増幅回路
32 絶対値回路
33 LPF
34 位相比較器
35 周波数調整器
36 判断手段
37 表示手段
38 温度測定手段
G ギヤ
M 被検体
S 基準検体
Claims (10)
- 第1の抵抗と第2の抵抗とに分配比が可変に構成された可変抵抗、及び交流磁気を励磁可能なコイルを備えた基準検出器、及び交流磁気を励磁可能なコイルを備えた検査検出器、を備える交流ブリッジ回路と、前記交流ブリッジ回路に交流電力を供給する交流電源と、前記交流ブリッジ回路からの出力信号に基づいて熱処理を含む表面処理を施した鋼材製品の表面特性を評価する評価装置と、を備える表面特性検査装置を用いて、前記鋼材製品の熱処理の程度を検査する表面特性検査方法であって、
前記表面処理を施した鋼材製品、及び該鋼材製品と同一構造の基準検体、及び前記表面特性検査装置を準備する準備工程と、
前記基準検出器のコイルを前記基準検体に渦電流が励起するように配置すると共に、前記検査検出器のコイルを前記鋼材製品に渦電流が励起するように配置する配置工程と、
前記交流ブリッジ回路に交流電力を供給する交流供給工程と、
前記基準検出器のコイル及び前記検査検出器のコイルにそれぞれ交流磁気を励磁して、前記基準検体及び前記鋼材製品にそれぞれ渦電流を励起させると共に、前記基準検出器が基準状態を検出している状態における前記鋼材製品の電磁気特性を第1の出力信号として検出する検出工程と、
前記第1の出力信号に基づいて前記評価装置により演算した値を、第1の閾値と比較して前記鋼材製品に施されている熱処理の程度を評価する熱処理評価工程と、
を含み、
前記基準検出器及び前記検査検出器の各コイルの励磁周波数を500Hz~10×103Hzに設定することを特徴とする表面特性検査方法。 - 前記検出工程は、熱処理後にショットピーニング処理が施された鋼材製品に対して実行され、
前記第1の出力信号は、熱処理後にショットピーニング処理を施された鋼材製品の電磁気特性であることを特徴とする請求項1に記載の表面特性検査方法。 - 前記準備工程で準備する鋼材製品は熱処理が施され、ショットピーニング処理が施されていない鋼材製品であり、
前記準備工程後、前記配置工程の前に、熱処理が施され、ショットピーニング処理が施されていない鋼材製品の電磁気特性を前記表面特性検査装置によって検出する予備検出工程と、該予備検出工程の後に該鋼材製品にショットピーニング処理を施すショットピーニング工程と、を更に含み、
前記予備検出工程は、前記基準検出器及び前記検査検出器のコイルに交流電圧を供給して、前記基準検出器及び前記検査検出器のそれぞれに配置された前記基準検体及び熱処理が施された鋼材製品にそれぞれ渦電流を励起させると共に、前記基準検出器が基準状態を検出している状態における該鋼材製品の電磁気特性を第2の出力信号として取得するものであり、
前記評価装置は、前記熱処理評価工程において、前記第1の出力信号及び前記第2の出力信号に基づいて前記鋼材製品の熱処理の程度を評価することを特徴とする請求項2に記載の表面特性検査方法。 - 前記第1の閾値は、前記表面処理を施していない未処理の鋼材製品の電磁気特性と、該未処理の鋼材製品に熱処理のみを適正に施した鋼材製品の電磁気特性と、に基づいて算出された値であり、
前記評価装置は、前記熱処理評価工程において、前記第1の出力信号及び前記第2の出力信号に基づいて算出された値を当該第1の閾値と比較することにより前記鋼材製品の熱処理の程度を評価することを特徴とする請求項3に記載の表面特性検査方法。 - 前記評価装置は、前記熱処理評価工程において、前記第1の出力信号と前記第2の出力信号との比を演算し、この値と前記第1の閾値と比較することにより前記鋼材製品の熱処理の程度を評価することを特徴とする請求項3または4に記載の表面特性検査方法。
- 前記第1の出力信号及び前記第2の出力信号は、共に前記基準検出器及び前記検査検出器間の電位差であることを特徴とする請求項3乃至5のいずれか1つに記載の表面特性検査方法。
- 前記評価装置は、前記熱処理評価工程において、更に、前記第1の出力信号を第2の閾値と比較して、前記ショットピーニング工程においてショットピーニング処理が適正に行われていたか否かを評価することを特徴とする請求項2乃至請求項6のいずれか1つに記載の表面特性検査方法。
- 少なくとも熱処理を含む表面処理を施した鋼材製品における熱処理の程度を評価する表面特性検査装置であって、
前記表面特性検査装置は、第1の抵抗と第2の抵抗とに分配比が可変に構成された可変抵抗、及び交流磁気を励磁可能なコイルを備えた基準検出器、及び交流磁気を励磁可能なコイルを備えた検査検出器、を備える交流ブリッジ回路と、
前記交流ブリッジ回路に交流電力を供給する交流電源と、
前記交流ブリッジ回路からの出力信号に基づいて前記鋼材製品の熱処理の程度を評価する評価装置と、を備え
前記基準検出器及び前記検査検出器の各コイルの励磁周波数は500Hz~10×103Hzに設定されることを特徴とする表面特性検査装置。 - 前記表面処理を施した鋼材製品は、熱処理後にショットピーニング処理を施した鋼材施品であることを特徴とする請求項9に記載の表面特性検査装置。
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