阅读说明：本技术 残余应力测量方法 (Residual stress measuring method ) 是由 松田真理子 兜森达彦 高松弘行 于 2018-11-30 设计创作，主要内容包括：本发明是使用X射线的铸锻钢件的残余应力测量方法,其具备：对于铸锻钢件照射X射线的工序；二维检测来自上述X射线的衍射X射线的强度的工序；基于由上述检测工序检测到的上述衍射X射线的强度分布所形成的衍射环,计算残余应力的工序,上述照射工序具有变更对于上述铸锻钢件的上述X射线的照射条件的工序,上述照射工序是每一次对于上述铸锻钢件照射上述X射线都实行上述变更工序的工序,上述算出工序,是每一次对于上述铸锻钢件照射上述X射线都计算残余应力的工序,还具备平均化工序,即按顺序多次实行上述照射工序、上述检测工序和上述计算工序后,将经由上述算出工序计算出的多个上述残余应力平均化。(The present invention is a method for measuring residual stress of a cast and forged steel product using X-rays, comprising: a step of irradiating the forged steel piece with X-rays; a step of two-dimensionally detecting the intensity of the diffracted X-rays from the X-rays; a step of calculating a residual stress based on a diffraction ring formed by the intensity distribution of the diffracted X-rays detected in the detection step, wherein the irradiation step includes a step of changing the irradiation conditions of the X-rays with respect to the forged steel, the irradiation step is a step of performing the changing step every time the X-rays are irradiated to the forged steel, and the calculation step is a step of calculating a residual stress every time the X-rays are irradiated to the forged steel, and further includes an averaging step of averaging a plurality of residual stresses calculated in the calculation step after the irradiation step, the detection step, and the calculation step are performed a plurality of times in this order.)

1. A residual stress measuring method for a forged steel piece using X-rays, comprising:

an irradiation step of irradiating the forged steel piece with X-rays;

a detection step of two-dimensionally detecting the intensity of the diffracted X-rays from the X-rays;

a calculation step of calculating a residual stress based on a diffraction ring formed by the intensity distribution of the diffracted X-rays detected in the detection step,

the irradiation step includes a step of changing the irradiation conditions of the X-rays with respect to the forged steel piece,

the irradiation step is a step of performing the changing step every time the forged steel piece is irradiated with the X-rays,

the calculating step is a step of calculating the residual stress every time the forged steel piece is irradiated with the X-rays,

the residual stress measuring method further includes an averaging step of averaging the plurality of residual stresses calculated in the calculating step after the irradiating step, the detecting step, and the calculating step are sequentially performed a plurality of times.

2. A residual stress measuring method for a forged steel piece using X-rays, comprising:

an irradiation step of irradiating the forged steel piece with X-rays;

a detection step of two-dimensionally detecting the intensity of the diffracted X-rays from the X-rays;

a calculation step of calculating a residual stress based on a diffraction ring formed by the intensity distribution of the diffracted X-rays detected in the detection step,

the irradiation step includes a step of changing the irradiation conditions of the X-rays with respect to the forged steel piece,

the irradiation step is a step of performing the changing step every time the forged steel piece is irradiated with the X-rays,

after the irradiation step and the detection step are alternately performed a plurality of times, in the calculation step, the residual stress is calculated based on a diffraction ring formed by an intensity distribution in which the intensities of the plurality of diffracted X-rays are averaged.

3. A residual stress measuring method for a forged steel piece using X-rays, comprising:

an irradiation step of irradiating the forged steel piece with X-rays;

a detection step of two-dimensionally detecting the intensity of the diffracted X-rays from the X-rays;

a calculation step of calculating a residual stress based on a diffraction ring formed by the intensity distribution of the diffracted X-rays detected in the detection step,

the irradiation step includes a step of changing the irradiation conditions of the X-rays with respect to the forged steel piece,

the irradiation step is a step of continuously irradiating the X-ray by performing the changing step,

in the calculation step, the residual stress is calculated based on a diffraction ring formed by the intensity distribution of the diffracted X-rays averaged by the continuous irradiation of the X-rays.

4. The residual stress measuring method according to claim 1, claim 2, or claim 3, wherein in the changing step, the total of the X-ray irradiation areas is 20mm²The irradiation conditions of the X-ray with respect to the forged steel piece are changed in the above manner.

Technical Field

The invention relates to a residual stress measuring method.

Background

In recent years, a residual stress measurement technique using X-rays has been widespread. This technique measures lattice distortion occurring inside an object having a crystal structure by using X-rays, and converts the measurement result into a residual stress.

As a residual stress measuring method using X-rays, a cos α method is known. The cos α method is as follows: an X-ray is irradiated to a subject at a specific irradiation angle, the intensity of a diffracted X-ray generated by the reflection of the X-ray on the subject is two-dimensionally detected, and a residual stress is calculated based on a diffraction ring formed by the intensity distribution of the detected diffracted X-ray. For example, patent document 1 describes a specific procedure for calculating the residual stress by the cos α method.

In the X-ray diffraction system described in patent document 1, the X-ray diffraction device is stopped at an arbitrary measurement position of the orbit, and X-rays are irradiated, and the diffracted X-rays are detected by the imaging plate, and the residual stress is evaluated based on the diffraction ring formed by the diffracted X-rays (paragraph 0025). The X-ray diffraction system of patent document 1 can monitor the deterioration over time of each portion of a track by accumulating measurement data for each measurement point of the track and evaluating the average value of the measurement data for each measurement point while moving a vehicle on which an X-ray diffraction apparatus is mounted (paragraphs 0057 and 0059).

However, the forged steel may have local chemical composition variations therein due to different manufacturing conditions such as the kind of the contained element, the concentration of the contained element, and the cooling rate when the molten steel is solidified. In this case, the structure and hardness of the forged steel piece cannot be completely homogeneous, and the residual stress generated in the forged steel piece tends to change locally. This tendency is particularly pronounced in large forged steel parts.

When residual stress is measured using X-rays with a forged steel piece as an object to be measured, if a non-homogeneous portion of the forged steel piece is selected as a measurement position, a measurement result of the residual stress may include a significant error. Therefore, a residual stress measuring method capable of appropriately evaluating the residual stress generated in the interior of the forged steel piece is required.

[ Prior Art document ]

[ patent document ]

[ patent document 1 ] Japanese patent laid-open No. 2005-241308

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a residual stress measuring method capable of appropriately evaluating a residual stress generated in a forged steel piece.

One aspect of the present invention devised to solve the problem is a method for measuring residual stress of a forged steel piece using X-rays, the method including: a step of irradiating the forged steel piece with X-rays; a step of two-dimensionally detecting the intensity of the diffracted X-rays from the X-rays; a step of calculating a residual stress based on a diffraction ring formed by the intensity distribution of the diffracted X-rays detected in the detection step, wherein the irradiation step includes a step of changing the irradiation conditions of the X-rays with respect to the forged steel, the irradiation step is a step of performing the changing step every time the X-rays are irradiated to the forged steel, and the calculation step is a step of calculating a residual stress every time the X-rays are irradiated to the forged steel, and further includes an averaging step of averaging a plurality of residual stresses calculated in the calculation step after the irradiation step, the detection step, and the calculation step are performed in sequence a plurality of times.

In this residual stress measuring method, the irradiation conditions of the X-rays with respect to the forged steel piece are changed, and the residual stress averaged in accordance with the change in the irradiation conditions of the X-rays is calculated, so that even when the X-rays are irradiated to the region of the forged steel piece containing the inhomogeneous portion, the influence of the inhomogeneous portion on the calculation result of the residual stress can be suppressed. Therefore, the residual stress measuring method can appropriately evaluate the residual stress of the forged steel piece. In particular, in this residual stress measuring method, the residual stress is calculated every time the X-ray is irradiated, and the plurality of calculated residual stresses are averaged, so that the residual stress can be grasped every time the X-ray is irradiated, and the averaged residual stress can be appropriately calculated.

Another aspect of the present invention devised to solve the problem described above is a method for measuring residual stress of a forged steel piece using X-rays, the method including: a step of irradiating the forged steel piece with X-rays; a step of two-dimensionally detecting the intensity of the diffracted X-rays from the X-rays; and a step of calculating a residual stress based on a diffraction ring formed by the intensity distribution of the diffracted X-rays detected in the detection step, wherein the irradiation step includes a step of changing the irradiation conditions of the X-rays with respect to the forged steel piece, and the irradiation step is a step of performing the changing step for each irradiation of the X-rays with respect to the forged steel piece, and after the irradiation step and the detection step are alternately performed a plurality of times, the residual stress is calculated based on a diffraction ring formed by an intensity distribution in which the intensities of the plurality of diffracted X-rays are averaged in the calculation step.

In this residual stress measuring method, the irradiation conditions of the X-rays with respect to the forged steel piece are changed, and the residual stress averaged in accordance with the change in the irradiation conditions of the X-rays is calculated, so that even when the X-rays are irradiated to the region of the forged steel piece containing the inhomogeneous portion, the influence of the inhomogeneous portion on the calculation result of the residual stress can be suppressed. Therefore, the residual stress measuring method can appropriately evaluate the residual stress of the forged steel piece. In particular, in this residual stress measuring method, the intensities of the diffracted X-rays obtained by the plurality of times of X-ray irradiation are averaged, and the residual stress is calculated based on the diffraction ring formed by the averaged intensity distribution, so that the residual stress can be evaluated in a shorter time than in the case where the residual stress is calculated for each diffraction ring.

In order to solve the above problems, another aspect of the present invention is a method for measuring residual stress of a forged steel product using X-rays, including: a step of irradiating the forged steel piece with X-rays; a step of two-dimensionally detecting the intensity of the diffracted X-rays from the X-rays; and a step of calculating a residual stress based on a diffraction ring formed by the intensity distribution of the diffracted X-rays detected in the detection step, wherein the irradiation step includes a step of changing the irradiation conditions of the X-rays with respect to the forged steel piece, the irradiation step is a step of continuously irradiating the X-rays while performing the change step, and the residual stress is calculated based on a diffraction ring formed by the intensity distribution of the diffracted X-rays averaged by the continuous irradiation of the X-rays in the calculation step.

In this residual stress measuring method, the irradiation conditions of the X-rays with respect to the forged steel piece are changed, and the residual stress averaged in response to the change in the irradiation conditions of the X-rays is calculated, so that even when the X-rays are irradiated to the region of the forged steel piece containing the inhomogeneous portion, the influence of the inhomogeneous portion on the calculation result of the residual stress can be suppressed. Therefore, the residual stress measuring method can appropriately evaluate the residual stress of the forged steel piece. In particular, in this residual stress measuring method, since the X-ray is continuously irradiated while changing the irradiation condition of the X-ray, the residual stress can be evaluated in a shorter time than in the case where the irradiation condition of the X-ray is changed every time the X-ray is irradiated.

In the residual stress measuring method, the total of the X-ray irradiation areas in the changing step is 20mm²In the above manner, the conditions for the irradiation of the X-ray to the forged steel piece may be changed. Thus, the residual stress measuring method can more appropriately evaluate the residual stress of the forged steel piece.

The residual stress measuring method of the present invention can properly evaluate the residual stress of a forged steel piece.

Drawings

Fig. 1 is a flowchart illustrating a residual stress measuring method according to a first embodiment of the present invention.

Fig. 2 is a flowchart showing a residual stress measuring method according to a second embodiment of the present invention.

Fig. 3 is a flowchart showing a residual stress measuring method according to a third embodiment of the present invention.

Fig. 4 is a graph showing the relationship between the measured X-ray stress and the nominal stress using a test piece with a large segregation.

Fig. 5 is a graph showing the relationship between the measured X-ray stress and the nominal stress using a test piece with less segregation.

Fig. 6 is a diagram showing a relationship between an X-ray irradiation area and a measurement error of X-ray stress after changing an X-ray irradiation position.

Fig. 7 is a diagram showing a relationship between an X-ray irradiation area and a measurement error of X-ray stress after changing an X-ray irradiation angle.

Fig. 8 is a diagram showing a relationship between the X-ray irradiation area and the maximum error of the X-ray stress after changing the irradiation position while irradiating X-rays.

Detailed Description

Hereinafter, embodiments of the residual stress measuring method according to the present invention will be described in detail with reference to the drawings.

[ first embodiment ]

The residual stress measuring method shown in fig. 1 is a residual stress measuring method of a forged steel piece using X-rays, and includes: an irradiation step of irradiating the forged steel piece with X-rays; a detection step of two-dimensionally detecting the intensity of the diffracted X-rays from the X-rays; and a calculation step of calculating the residual stress based on a diffraction ring formed by the intensity distribution of the diffracted X-rays detected in the detection step. The irradiation step includes a changing step of changing an irradiation condition of the cast steel member with respect to the X-rays, and the changing step is performed every time the cast steel member is irradiated with the X-rays. In the calculation step, the residual stress is calculated every time the forged steel piece is irradiated with X-rays. The residual stress measuring method further includes an averaging step of averaging the plurality of residual stresses calculated in the calculating step after the irradiating step, the detecting step, and the calculating step are sequentially performed a plurality of times.

In this residual stress measuring method, an X-ray stress measuring apparatus including an X-ray irradiation apparatus and a two-dimensional detector is used. In the residual stress measuring method, the irradiation conditions of the X-rays to the forged steel are changed for each irradiation of the X-rays to the forged steel, and the residual stress is calculated for each irradiation of the X-rays to the forged steel. In this residual stress measuring method, when the total of the number of times of irradiation with X-rays or the irradiation area with X-rays reaches a certain value, the residual stress that averages the residual stresses is calculated. In short, in this residual stress measuring method, the forged steel piece is irradiated with X-rays under various irradiation conditions, and the residual stresses calculated under each irradiation condition are averaged.

< irradiation step >

The irradiation step is a step of irradiating the forged steel with X-rays from the X-ray irradiation apparatus, and includes a changing step of changing an irradiation condition of the X-rays with respect to the forged steel. In the irradiation step, the forged steel piece is irradiated with X-rays without changing the irradiation conditions in one X-ray irradiation, and the irradiation conditions of the X-rays are changed when the changing step is performed.

(Change step)

The changing step is a step of changing the irradiation conditions of the X-rays by changing the irradiation position, irradiation angle, or irradiation area of the X-rays with respect to the forged steel piece. And a changing step of performing each X-ray irradiation under the condition that the number of X-ray irradiations or the X-ray irradiation area in the plurality of X-ray irradiations does not reach a predetermined value. In addition, although not particularly limited, if there is a possibility that the residual stress generated in the interior of the forged steel piece may vary greatly from one portion to another, the distance of change in the irradiation position of the X-ray performed for each X-ray irradiation is preferably within 5 times the irradiation diameter of the X-ray, for example.

The irradiation angle of the X-ray is an incident angle of the X-ray to the steel casting, and is changed by relatively rotating the nozzle of the X-ray irradiation device and the steel casting in a state where the irradiation position of the X-ray is fixed. The irradiation position of the X-ray is changed by relatively moving the nozzle of the X-ray irradiation device and the forged steel piece in a state where the irradiation angle of the X-ray is fixed. The X-ray irradiation area is the area of the X-ray irradiation region on the surface of the cast steel, and is changed by, for example, changing the irradiation angle, changing the distance between the irradiation port of the X-ray irradiation device and the cast steel, changing the collimator diameter of the X-ray irradiation device, and the like.

< detection Process >

The detection step is a step of detecting the intensity of the diffracted X-rays from the X-rays irradiated to the forged steel piece by a two-dimensional detector. Since the forged steel is polycrystalline, the X-rays irradiated to the forged steel are diffracted at angles satisfying the bragg diffraction condition in a large number of crystals. The X-rays diffracted by the plurality of crystals are detected as diffracted X-rays by a two-dimensional detector. The intensity of the diffracted X-rays is detected by a two-dimensional detector, but the intensity distribution of the diffracted X-rays forms a diffraction ring.

< calculation Process >

The calculation step is a step of calculating the residual stress based on a diffraction ring formed by the intensity distribution of the diffracted X-rays detected by the two-dimensional detector for each irradiation of the cast steel with X-rays. As a method of calculating the residual stress based on the diffraction ring, a calculation method based on the cos α method can be used, but a method of calculating the direct stress from the distortion of the X-ray can also be used.

< averaging Process >

The averaging step is a step of averaging the plurality of residual stresses calculated in the calculating step, and is performed after the plurality of times of irradiation with the X-rays is completed.

The steps of the residual stress measuring method are carried out as follows. First, in the residual stress measuring method, the irradiation step and the detection step are performed, and after the irradiation and the detection of the X-ray are stopped, the calculation step is performed. When the residual stress is calculated based on the diffraction ring in the calculation step, X-ray diffraction information on the intensity of the diffracted X-rays of the two-dimensional detector is initialized. After the calculation step, if the total number of times of irradiation of the X-rays or the irradiation area of the X-rays does not reach a predetermined value, the changing step is performed. When the changing step is performed, the irradiation step and the detection step are performed after the change of the irradiation conditions of the X-rays in the changing step is stopped. On the other hand, when the total of the number of times of irradiation with X-rays or the irradiation area with X-rays reaches a predetermined value, the calculated plurality of residual stresses are averaged in the averaging step.

(advantages)

In this residual stress measuring method, the irradiation conditions of the cast steel member with the X-rays are changed, and the residual stress averaged in response to the change in the irradiation conditions of the X-rays is calculated, so that even when the region including the inhomogeneous portion of the cast steel member is irradiated with the X-rays, the influence of the inhomogeneous portion on the calculation result of the residual stress can be suppressed. In particular, in this residual stress measuring method, the residual stress is calculated every time the X-ray is irradiated, and the plurality of calculated residual stresses are averaged, so that the residual stress corresponding to the change in the irradiation condition of the X-ray can be grasped, and the averaged residual stress can be appropriately calculated.

In the residual stress measuring method, the irradiation position, the irradiation angle, or the irradiation area of the X-ray with respect to the forged steel piece is changed in the changing step, thereby changing the irradiation condition of the X-ray. The residual stress of various portions of the cast steel can be evaluated by changing the X-ray irradiation position or the irradiation area, and the residual stress can be evaluated by changing the direction of the crystal contributing to diffraction by changing the X-ray irradiation angle. Therefore, the residual stress measuring method can appropriately evaluate the residual stress of the forged steel by irradiating the forged steel with X-rays under various irradiation conditions.

[ second embodiment ]

The residual stress measuring method shown in fig. 2 is different from the residual stress measuring method according to the first embodiment in that the intensity distribution of the diffracted X-rays obtained by the irradiation of X-rays a plurality of times is averaged, and the residual stress is calculated based on the diffraction ring formed by the averaged intensity distribution. In this residual stress measuring method, the irradiation step and the detection step are different from those of the first embodiment in the calculation step and the averaging step, as in the residual stress measuring method of the first embodiment.

The residual stress measuring method is a residual stress measuring method of a cast and forged steel piece using X-rays, and comprises the following steps: an irradiation step of irradiating the forged steel piece with X-rays; a detection step of two-dimensionally detecting the intensity of the diffracted X-rays from the X-rays; and a calculation step of calculating the residual stress based on a diffraction ring formed by the intensity distribution of the diffracted X-rays detected in the detection step. The irradiation step includes a changing step of changing an irradiation condition of the forged steel with the X-ray, and the changing step is performed every time the forged steel is irradiated with the X-ray. The residual stress measuring method further includes an averaging step of averaging intensities of the plurality of diffracted X-rays detected in the detection step after the irradiation step and the detection step are sequentially performed a plurality of times. Then, in the residual stress measuring method, the residual stress is calculated based on a diffraction ring formed by an intensity distribution in which the intensities of the multiple diffraction X-rays are averaged, through a calculation step.

In the residual stress measuring method, the irradiation conditions of the X-rays on the forged steel are changed every time the forged steel is irradiated with the X-rays, and the intensity of the diffracted X-rays is detected every time the forged steel is irradiated with the X-rays. In the residual stress measuring method, when the total of the number of times of irradiation with X-rays or the irradiation area with X-rays reaches a certain value, the intensities of a plurality of detected diffracted X-rays are averaged. Then, the residual stress measuring method calculates the residual stress based on the diffraction ring formed by the averaged intensity distribution. In short, in this residual stress measuring method, the forged steel piece is irradiated with X-rays under various irradiation conditions, and the intensities of the diffracted X-rays detected under each irradiation condition are averaged to average the residual stress.

< averaging Process >

The averaging step is a step of averaging the intensities of the plurality of diffracted X-rays detected in the detecting step, and is performed after the plurality of times of irradiation with the X-rays.

< calculation Process >

The calculation step is a step of calculating the residual stress based on the diffraction ring formed by the intensity distribution of the diffracted X-rays averaged in the averaging step. As a method of calculating the residual stress based on the diffraction ring, cos α method may be used, but a method of calculating the direct stress from the distortion of the X-ray may be used.

The steps of the residual stress measuring method are carried out as follows. First, in the residual stress measuring method, the irradiation step and the detection step are performed, and the irradiation and the detection of the X-ray are stopped. The changing step is performed when the total number of times of irradiation of the X-rays or the area of irradiation of the X-rays does not reach a predetermined value. When the changing step is performed, the irradiation step and the detection step are performed after the change of the irradiation conditions of the X-rays in the changing step is stopped. The X-ray diffraction information on the intensity of the diffracted X-rays of the two-dimensional detector is taken out from the two-dimensional detector for each X-ray irradiation and is held therein. When the X-ray diffraction information is extracted from the two-dimensional detector, the X-ray diffraction information of the two-dimensional detector is initialized. On the other hand, when the total of the number of times of irradiation with X-rays or the irradiation area with X-rays reaches a predetermined value, the intensities of a plurality of diffracted X-rays are averaged based on a plurality of pieces of X-ray diffraction information held in the averaging step, and then the residual stress is calculated in the calculating step.

In the residual stress measuring method, the intensity distribution of the plurality of diffracted X-rays may be averaged by a step of overlapping the X-ray diffraction information of the two-dimensional detector without initializing the X-ray diffraction information per one X-ray irradiation. In this case, in the residual stress measuring method, since averaged X-ray diffraction information can be obtained from the two-dimensional detector at the time when the X-ray irradiation is completed a plurality of times, the averaging step can be omitted.

(advantages)

In this residual stress measuring method, the irradiation conditions of the cast steel member with the X-rays are changed, and the averaged residual stress is calculated based on the change in the irradiation conditions of the X-rays, so that even when the X-rays are irradiated to a region including an inhomogeneous portion of the cast steel member, the influence of the inhomogeneous portion on the calculation result of the residual stress can be suppressed. In particular, in this residual stress measuring method, since the intensities of the diffracted X-rays obtained by the irradiation of the X-rays are averaged a plurality of times and the residual stress is calculated based on the diffraction ring formed by the averaged intensity distribution, the residual stress can be evaluated in a shorter time than in the residual stress measuring method of the first embodiment in which the residual stress is calculated for each irradiation of the X-rays.

[ third embodiment ]

The residual stress measuring method shown in fig. 3 is different from the residual stress measuring method according to the second embodiment in that X-rays are continuously irradiated while changing the irradiation conditions of the X-rays. In this residual stress measuring method, the detection step and the calculation step are different from those of the second embodiment in the irradiation step, as in the residual stress measuring method of the second embodiment. This residual stress measuring method is also different from the residual stress measuring method according to the second embodiment in that the averaging step is not provided.

The residual stress measuring method is a residual stress measuring method of a cast and forged steel piece using X-rays, and comprises the following steps: an irradiation step of irradiating the forged steel piece with X-rays; a detection step of two-dimensionally detecting the intensity of the diffracted X-rays from the X-rays; and a calculation step of calculating the residual stress based on a diffraction ring formed by the intensity distribution of the diffracted X-rays detected in the detection step. The irradiation step includes a changing step of changing the irradiation conditions of the X-rays with respect to the forged steel piece, and the X-rays are continuously irradiated while the changing step is performed. Then, in the residual stress measuring method, the residual stress is calculated by the calculating step based on the diffraction ring formed by the intensity distribution of the diffracted X-rays averaged by the continuous irradiation of the X-rays.

The residual stress measuring method continuously irradiates X-rays to a forged steel piece while changing the irradiation conditions of the X-rays, and detects the intensity of diffracted X-rays. That is, this residual stress measuring method detects the intensity of the diffracted X-ray averaged in accordance with the change in the irradiation condition of the X-ray. In this residual stress measuring method, when the total of the X-ray irradiation areas reaches a certain value, the residual stress is calculated based on the diffraction ring formed by the averaged intensity distribution. In short, this residual stress measuring method continuously irradiates the forged steel with X-rays while changing the irradiation conditions, averages the intensities of the detected diffracted X-rays, and averages the residual stress.

< irradiation step >

The irradiation step is a step of irradiating the forged steel with X-rays from the X-ray irradiation apparatus, and includes a changing step of changing an irradiation condition of the X-rays with respect to the forged steel. In the irradiation step, the forged steel piece is continuously irradiated with X-rays while changing the irradiation conditions. In short, the irradiation step irradiates X-rays while performing the changing step. The changing step changes the irradiation position, irradiation angle, or irradiation area of the cast steel product with the X-ray, as in the changing step of the residual stress measuring method according to the first embodiment.

The steps of the residual stress measuring method are carried out as follows. First, in the residual stress measuring method, an irradiation step of irradiating X-rays is performed while performing the changing step. The detection step is performed in conjunction with the irradiation step. When the total of the X-ray irradiation areas does not reach a predetermined value, the irradiation step and the detection step are continued. Meanwhile, the X-ray diffraction information on the intensity of the diffracted X-rays of the two-dimensional detector is not initialized but is superimposed. On the other hand, when the total of the X-ray irradiation areas reaches a predetermined value, the calculation step calculates the residual stress.

(advantages)

In this residual stress measuring method, the irradiation conditions of the X-rays with respect to the cast steel product are changed, and the residual stress averaged in response to the change in the irradiation conditions of the X-rays is calculated, so that even when the X-rays are irradiated to a region including an inhomogeneous portion of the cast steel product, the influence of the inhomogeneous portion on the calculation result of the residual stress can be suppressed. In particular, in this residual stress measuring method, since the X-ray is continuously irradiated while changing the irradiation condition of the X-ray, the residual stress can be evaluated in a shorter time than in the residual stress measuring method of the second embodiment in which the irradiation condition of the X-ray is changed every time the X-ray is irradiated.

< other embodiments >

The residual stress measuring method of the present invention is not limited to the above embodiment.

In the first and second embodiments, the averaged residual stress is calculated when the total number of X-ray irradiations or the total X-ray irradiation area reaches a predetermined value, and in the third embodiment, the averaged residual stress is calculated when the total X-ray irradiation area reaches a predetermined value. In short, the irradiation conditions of the X-rays with respect to the forged steel piece may be changed in such a manner that the total of the irradiation areas of the X-rays is averaged to a sufficient area. In this case, the lower limit of the total X-ray irradiation area is preferably 20mm²More preferably 23mm²More preferably 26mm². If the total of the X-ray irradiation areas is less than the lower limit, the influence of the inhomogeneous portion of the forged steel piece may not be suppressed.

In the above embodiment, the changing step of changing the irradiation conditions of the X-rays by changing the irradiation position, irradiation angle, or irradiation area of the X-rays with respect to the forged steel material has been described, but the changing step may change at least one of the irradiation position, irradiation angle, and irradiation area, or may change both the irradiation position and irradiation angle.