JPH11201949A - Ultrasonic inspection method for bonded material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ultrasonic inspection method in which bonding characteristic such as strength, toughness or the like of a bonded material to be measured can be estimated nondestructively, by measuring attenuation amount of ultrasonic waves at a time when the ultrasonic waves are transmitted through the bonding interface of the bonded material to be measured. SOLUTION: In a bonded material 1 to be measure, e.g. steel pipes 2, 3 are bonded at their pipe end faces. An ultrasonic oscillating probe 5 and a receiving probe 6 are arranged so as to sandwich a bonding interface 4. The attenuation amount of ultrasonic waves at a time when the ultrasonic waves which are oscillated by the ultrasonic oscillating probe 5 are transmitted through the bonding interface 4 so as to be received by the receiving probe 6 is measured. On the basis of its measured value, bonding characteristic of the bonded material 1 to be measured is inspected by the correlation between the attenuation amount of ultrasonic waves in a standard bonded material bonded by a known bonding condition measured in advance and the bonding characteristic. As a result, the bonding characteristic such as the bonding temperature, the bonding strength or the like of the bonded material 1 to be measured can be estimated with high accuracy. When this method is applied to the inspection of an oil well pipe, a chemical plantpipe or the like, the reliability of a bonding process can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic inspection method for a joining material, and more particularly, to a joining characteristic such as a joining temperature and strength of a joining material from an attenuation amount of an ultrasonic wave transmitted through a joining interface of the joining material. The present invention relates to an ultrasonic inspection method for a bonding material for non-destructively inspecting a bonding material.

[0002]

2. Description of the Related Art A metal joining method is a processing method in which one member is added to another member, and a metallurgical joining method in which energy is locally applied to bond a separate object to each other, It is roughly divided into mechanical joining methods such as bolt joining.

[0003] Metallurgical joining methods are further classified into a fusion welding method, a pressure welding method, a brazing method, a diffusion joining method, and the like. The fusion welding method
This is a joining method in which a joined portion of a base material is heated to a molten state, and a filler material is added and fused as needed. The pressure welding method is a method of joining by applying a large mechanical pressure to the material to be joined,
In addition to room temperature welding, friction welding, explosion welding, ultrasonic welding, etc., resistance welding is also included in this category. The brazing method is a method in which a brazing material having a melting point lower than that of a material to be joined is caused to flow into a gap of a joining portion in a molten state and solidified for joining.

In the diffusion bonding method, the materials to be joined are brought into close contact with each other, pressurized at a temperature equal to or lower than the melting point of the materials to be joined so as not to cause plastic deformation, and utilizing the diffusion of atoms generated at the joining interface. It is a method of joining the materials, the solid-state diffusion bonding method that directly adheres the materials to be joined and diffuses elements while maintaining the solid state, and inserting a low melting point insert material between the materials to be joined, There is a liquid phase diffusion bonding method in which an insert material is temporarily melted, and a specific element in a liquid phase is diffused and disappeared into a material to be bonded, and is solidified isothermally to perform bonding.

The metallurgical joining method such as the diffusion joining method, unlike the mechanical joining method, can save materials and reduce man-hours, and is excellent in joining strength, airtightness, pressure resistance and the like. There is an advantage that an improved joint can be obtained. On the other hand,
The joining operation is irreversible, and it is difficult to separate and rejoin after joining. Further, there is a defect that bonding characteristics such as strength and toughness greatly vary due to various defects generated at the bonding interface, and that the causes of the defects are various.

For this reason, in a metallurgical bonding method such as a diffusion bonding method, when high reliability is required, a radiation transmission test, an ultrasonic wave test, and an ultrasonic Various non-destructive inspections such as a flaw detection test, a magnetic particle flaw detection test, and a penetrant flaw detection test are performed on bonding materials. When the same type of bonding material is mass-produced, a part of the mass-produced bonding material is extracted, a test piece including a bonding interface is cut out from the bonding material, and a destructive inspection such as a tensile test is performed. ing.

[0007]

However, a metallurgical joining method such as a diffusion joining method involves local heating and cooling of a metal material to be joined, so that a structure or a mechanical property near a joint is required. In some cases, a heat-affected zone in which the temperature has changed may occur. Therefore, cracks, pores,
Even when no defect such as poor bonding is found, bonding characteristics such as bonding strength and toughness may be reduced.

In this case, when the joining material is mass-produced, a destructive inspection by a sampling inspection is possible.
For example, in the case of small-volume production such as plant manufacturing, a destructive test by sampling inspection is impossible, and there is a problem that there is no means for inspecting the joining characteristics of actually joined joining materials.

[0009] In order to solve this problem, for example, a means for manualizing the joining operation can be considered. However, in addition to the fact that the joining characteristics depend on many joining conditions such as joint design, accuracy, cleanliness, joining temperature, holding time, pressure, etc., when joining work must be performed outdoors In addition, it is affected by weather such as temperature, temperature, etc., and further greatly depends on the skill of the joining operator. Therefore, especially for bonding materials used in areas where high reliability is required,
It is not enough to just manage the joining operation.

An object of the present invention is to provide a metallurgical bonding method such as a diffusion bonding method, which is capable of non-destructively estimating bonding characteristics such as strength and toughness of a bonding material. An object of the present invention is to provide an inspection method.

[0011]

In order to solve the above-mentioned problems, an ultrasonic inspection method for a bonding material according to the present invention uses an ultrasonic oscillation probe on both sides of a bonding interface of a bonding material whose bonding conditions are unknown. The probe and the receiving probe are placed, and the ultrasonic wave oscillated from the ultrasonic oscillation probe transmits through the bonding interface, and measures the attenuation of the ultrasonic wave when the ultrasonic wave is received by the receiving probe. From the correlation between the ultrasonic attenuation and the bonding characteristics of the standard bonded body bonded under known bonding conditions measured in advance based on the measured values, the bonding characteristics of the bonding material to be measured are inspected. The gist is that.

The term "joining characteristics" as used herein refers to any characteristics that affect the mechanical properties of the joining material, and include defects other than defects such as cracks, pores, and poor joining formed at the joining interface. Specific examples include joining conditions such as joining temperature, cooling rate, and heat treatment temperature, mechanical properties such as joining strength, yield stress, hardness, and toughness, and material properties such as composition and crystal grain size. In particular, in structures where stress is applied, the bonding strength is the most important evaluation item, and since the bonding temperature has the greatest effect on the bonding strength, the bonding characteristics include the bonding temperature or the bonding strength. It is desirable to choose.

[0013] Ultrasonic waves incident on the material are longitudinal waves,
It propagates in various modes such as a shear wave, a surface wave, and a plate wave, but it is preferable to use a longitudinal wave or a shear wave to obtain information inside the joined body. In particular, although the details of the longitudinal wave mode ultrasonic wave are unknown, the attenuation of the ultrasonic wave transmitted through the bonding interface greatly fluctuates with the change in the bonding characteristics, thereby improving the reliability of the bonding characteristics inspection results. This is preferable because it becomes possible.

However, in the case of using a longitudinal wave mode ultrasonic wave, it is necessary to make it incident on the bonding material so that the refraction angle is 17 ° to 30 °. If the angle of refraction is less than 17 °, noise increases and the S / N ratio decreases. If the angle of refraction exceeds 30 °, the rate of mixing of the transverse wave increases, and the sensitivity decreases. Absent.

The frequency of the ultrasonic wave used for the inspection is 4
It is preferable that the frequency is not less than 10 MHz and not more than 10 MHz. If the frequency is less than 4 MHz, the wavelength of the ultrasonic wave becomes longer, and accordingly, the directional angle becomes larger and the directivity decreases. The higher the frequency is, the shorter the wavelength of the ultrasonic wave is, the more the directivity is improved and the measurement sensitivity is improved.
If it exceeds Hz, the amount of attenuation of the ultrasonic wave inside the joined body becomes too large, and the measurement sensitivity is undesirably lowered.

The probe used for inspection is 8 m on a side.
It is preferable to use a square probe having a length of not less than m and not more than 15 mm. This is because, when compared with the same area, the square probe has better directivity and the measurement sensitivity is better than the round probe. On the other hand, if the length of one side of the probe is less than 8 mm, the directivity angle is increased and the directivity is reduced, which is not preferable. The larger the probe, the smaller the directivity angle and the better the directivity.However, if the length of one side exceeds 15 mm, the limit distance of the short-range sound field increases and a strong interference phenomenon occurs in the short-range sound field. This is not preferable because noise increases.

Further, the joining material to be subjected to the inspection is not particularly limited, but the joining material is preferably made of a duplex stainless steel containing two or more phases. When duplex stainless steel is used as the material to be joined, the distribution of phases near the joint interface may change due to changes in joining conditions, but the phase boundary is a cause of scattering and attenuation of transmitted ultrasonic waves. That is, the ratio at which the ultrasonic waves are scattered changes according to the distribution state of the phase.

Therefore, if the present invention is applied to such a bonding material, a change in bonding characteristics due to a change in bonding conditions will be conspicuously expressed as a change in attenuation of ultrasonic waves, and a highly reliable inspection will be performed. It becomes possible. Specific examples of the duplex stainless steel containing two or more phases include duplex stainless steel having a structure in which austenite having a large amount of ultrasonic attenuation is dispersed in a ferrite ground at a ratio of 1: 1. One example is a precipitation hardening stainless steel based on stainless steel.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail. The joining material 1 shown in FIG. 1 is formed by joining steel pipes 2 and 3 at the pipe end faces. An ultrasonic oscillation probe 5 and a receiving probe 6 are arranged with a joining interface 4 interposed therebetween.

As shown in FIG. 2, the ultrasonic oscillation probe 5 has a vibrator 11 attached to a wedge 10 made of synthetic resin such as acrylic.
The vibrator 11 has a structure in which electrodes are attached to both surfaces of a thin plate made of a piezoelectric material such as quartz, lead niobate, or lead zircon titanate. In addition, wedge 1
At 0, a sound absorbing material 12 is attached so that the ultrasonic wave reflected on the contact surface between the ultrasonic oscillation probe 5 and the bonding material 1 can be absorbed.

The shape of the bottom surface of the ultrasonic oscillation probe 5 is desirably flat when inspecting a plate-like joining material. However, as shown in FIG. When inspecting the material 1, it is preferable that the shape of the bottom surface of the ultrasonic oscillation probe 5 be a curved surface in accordance with the curvature of the bonding material 1.
Although not shown, the receiving probe 6 has the same structure as the ultrasonic oscillation probe 5.

In addition, it is necessary to interpose a couplant in the gap between the ultrasonic oscillation probe 5 and the reception probe 6 and the bonding material 1. This is because if there is a gap between the ultrasonic oscillation probe 5 or the reception probe 6 and the bonding material 1, transmission and reception of ultrasonic waves are not performed efficiently. The couplant may be any one that can efficiently transmit ultrasonic waves, and various couplants may be used as needed. As the couplant, for example,
There are water, fat, glycerin and the like.

Further, from the ultrasonic oscillation probe 5 to the bonding material 1
In order to catch the ultrasonic wave incident on the receiving probe 6,
It is necessary to accurately set the relative positions of the ultrasonic oscillation probe 5 and the reception probe 6. The ultrasonic wave incident on the bonding material 1 from the ultrasonic oscillation probe 5 propagates while repeating total reflection on the outer peripheral surface and the inner peripheral surface of the bonding material 1. It is necessary to place the ultrasonic wave totally reflected on the inner peripheral surface of the bonding material 1 at the position where the ultrasonic wave totally reflected on the outer peripheral surface of the bonding material 1 reaches the inner peripheral surface of the bonding material 1. There is.

Ultrasonic waves incident on the bonding material 1 from the ultrasonic oscillation probe 5 arranged on the outer circumference of the bonding material 1 are totally reflected on the inner circumference of the bonding material 1 and reach the outer circumference of the bonding material 1. Assuming that the horizontal distance up to one step is one skip, the skip position at which the receiving probe 6 is arranged may be appropriately selected according to the shape of the bonding material 1 to be inspected and the measurement conditions. In the case of FIG. 1, the receiving probe 6 is arranged at the fourth skip position from the ultrasonic oscillation probe 5.

Next, a method for measuring the attenuation of the ultrasonic wave transmitted through the bonding interface of the bonding material will be described. First, a high-frequency pulse is generated in a synchronization control unit (not shown), and the high-frequency pulse is sent to the ultrasonic oscillation probe 5 via a high-frequency cable. The high-frequency pulse sent to the ultrasonic oscillation probe 5 is applied to electrodes attached to both surfaces of the vibrator 11, whereby the vibrator 11 expands and contracts in the thickness direction, and generates ultrasonic waves.

The generated ultrasonic wave enters the steel pipe 3 through the wedge 10 and propagates toward the steel pipe 2 while repeating total reflection on the inner and outer peripheral surfaces of the steel pipe 3. In the process, the ultrasonic waves pass through the bonding interface 4. After the predetermined number of reflections have been performed, the receiving probe 6 arranged on the steel pipe 2 receives the ultrasonic wave.

The received ultrasonic wave is transmitted to the transducer provided on the receiving probe 6, and expands and contracts the transducer in the thickness direction. The mechanical vibration is converted into an electric signal by the vibrator and sent to a receiving unit of an inspection device (not shown) via a high-frequency cable. Then, the attenuation amount of the ultrasonic wave is obtained from the ratio of the electric energy received by the receiving probe 6 to the electric energy input to the ultrasonic oscillation probe 5.

At this time, if the scanning is performed back and forth and left and right while keeping the distance between the ultrasonic oscillation probe 5 and the reception probe 6 at a fixed distance (for example, a distance corresponding to 4 skips), the ultrasonic wave is transmitted. Since the position to be changed is changed, two-dimensional information on the entire surface of the bonding interface 4 can be obtained. Normally, as an attenuation amount of the ultrasonic wave transmitted through the bonding interface 4, an average value of the attenuation amounts measured at each position of the bonding interface 4 is used.

The scanning method includes various methods such as zigzag scanning, forward / backward scanning, left / right scanning, and is not particularly limited, and may be appropriately selected according to the shape of the bonding material 1 or the like. The scanning distance only needs to cover the entire surface of the bonding interface 4, and therefore, in the direction perpendicular to the bonding interface 4, the scanning may be performed by a distance corresponding to at least 0.5 skips. The direction parallel to the joining interface 4 is at least a distance corresponding to the width of the joining interface 4 in the case of a plate-like joining material, and at least the pipe circumference in the case of a tubular joining material as shown in FIG. What is necessary is just to scan by a corresponding distance.

In FIG. 1, one ultrasonic oscillation probe 5 and one reception probe 6 are arranged with the bonding interface 4 interposed therebetween, but two or more reception probes 6 are provided. It may be arranged. When two or more receiving probes 6 are arranged, the amount of attenuation of the ultrasonic waves from one receiving probe 6 to another receiving probe 6 can be measured, so that the ultrasonic waves transmitted through the bonding interface 4 can be measured. In addition to the above attenuation, it is also possible to measure the attenuation of the ultrasonic wave transmitted through the heat-affected zone that spreads right and left across the bonding interface 4.

Further, two or more ultrasonic oscillation probes 5 and two or more reception probes 6 may be arranged. Since ultrasonic waves have good directivity, if the interval between the ultrasonic oscillation probes 5 is appropriate,
Ultrasonic waves incident from each ultrasonic oscillation probe 5 do not interfere with each other. Therefore, in the case of inspecting a bonding material having a large area of the bonding interface 4, if two or more probes are arranged, the scanning distance is shortened and the inspection time can be shortened.

Next, how to estimate the bonding characteristics by the ultrasonic inspection method of the bonding material according to the present invention will be described. The attenuation of the ultrasonic waves is caused by a part of the ultrasonic waves propagating in the joined body being scattered during the propagation. It is known that scattering of ultrasonic waves is caused by various causes, for example, crystal grain boundaries, internal friction, dislocation motion, phase boundaries having different acoustic impedances, and the like.

Since the metallurgical joining method involves heating in the joining process, the heating causes diffusion of elements, phase transformation, grain growth, etc. in the material to be joined, and the properties near the joining interface change before and after joining. There are cases. In particular, when the properties near the bonding interface are sensitive to the thermal history, the properties near the bonding interface greatly change due to slight fluctuations in the bonding conditions, and the attenuation of the ultrasonic wave transmitted through the bonding interface changes significantly. Will appear.

If the properties of the joining material near the joining interface are sensitive to the thermal history and the mechanical properties of the joining material are also sensitive to the thermal history, the joining conditions A slight change causes a large change in the mechanical properties of the bonding material. Therefore, in such a system, the change in the amount of ultrasonic attenuation and the change in the joining conditions or mechanical properties correspond one-to-one, and the joining conditions,
It is possible to estimate a change in the joining characteristics such as mechanical properties.

From the above-mentioned point, the ultrasonic inspection method of the bonding material according to the present invention can be applied to any system in which the attenuation and mechanical properties of the ultrasonic wave fluctuate due to the fluctuation of the bonding conditions. The larger the system, the higher the inspection accuracy. For example, from the viewpoint of the joining method, the diffusion joining method is particularly preferable. In the diffusion bonding method, bonding is performed at a temperature of about 90% of the melting point of a material to be bonded, and fluctuations in ultrasonic attenuation due to fluctuations in bonding conditions in order to actively diffuse elements at the bonding interface. This is because remarkably appears.

In terms of the material of the material to be joined, the iron-based materials include, for example, a duplex stainless steel having a structure in which austenite is dispersed at a ratio of 1: 1 in a ferrite ground, and the duplex stainless steel. Particularly preferred are precipitation hardening stainless steels based on. Austenitic crystal grains tend to be coarsened during the bonding process, and the scattering of ultrasonic waves at the crystal grain boundaries is large, so if the properties of austenite near the bonding interface change due to fluctuations in bonding conditions, the attenuation of ultrasonic waves will change. This is because it appears remarkably.

The ultrasonic inspection of the bonding material is specifically performed according to the following procedure. First, a standard joined body for examining in advance the correspondence between the joining characteristics and the attenuation of the ultrasonic wave transmitted through the joining interface is prepared. The material to be used for the production of the standard bonded body must be at least the same material as the material to be used for the actual bonding material, but the shape must be the same in order to increase the estimation accuracy of the bonding characteristics. It is desirable to do.

Next, a standard bonded body is bonded under various conditions while intentionally changing the bonding characteristics to be evaluated. For example, in the case of a joining material used for a structure on which a stress acts, the joining strength is the most important evaluation item, and the joining strength is most affected by the joining temperature. Therefore, in such a case, the bonding temperature may be selected as the bonding characteristic, and standard bonded bodies may be manufactured at various bonding temperatures around the recommended bonding temperature.

Further, for example, in the case of a system in which the strength, toughness, etc. near the bonding interface fluctuates greatly due to the heat treatment performed after the bonding, heat treatment conditions that are expected to fluctuate in the actual bonding operation, for example, the heat treatment temperature, A standard bonded body may be produced by intentionally changing the time, cooling rate, and the like.

Next, as shown in FIG. 1, the ultrasonic oscillating probe 5 and the receiving probe 6 are disposed on the standard bonded body thus manufactured with the bonding interface therebetween, and While maintaining the state where the distance between the probe 5 and the receiving probe 6 is kept constant, scanning is performed back and forth and left and right, the attenuation of the ultrasonic wave transmitted through each position of the bonding interface 4 is sequentially measured, and the average is measured. Calculate the value.

When the bonding characteristics to be evaluated are the bonding conditions such as the bonding temperature, the obtained attenuation amount of the ultrasonic wave is compared with the bonding conditions, and the correlation between the two may be obtained. Normally, one of the joining conditions such as the amount of attenuation and the joining temperature is plotted on the horizontal axis and the other is plotted on the vertical axis, and the measured data is plotted to perform a regression analysis. If one changes linearly with respect to one change, simple regression may be performed, and if the other changes linearly with one change, polynomial regression may be performed.

If the bonding characteristics to be evaluated are mechanical characteristics such as tensile strength, a test piece is cut out from each standard bonded body after the ultrasonic inspection of the standard bonded body is completed, and a fracture test such as a tensile test is performed. A test may be performed. Then, from the obtained attenuation and the data of the destructive test, a correlation between the two is obtained by regression analysis or the like according to the same procedure as described above.

Then, based on the correlation between the obtained ultrasonic attenuation of the standard joined body and the joining characteristics, a judgment criterion for pass / fail judgment is created in consideration of the variation of each measurement data. The criterion may be appropriately determined in consideration of the reliability required for the bonding material, the required characteristics, the variation in the measured ultrasonic attenuation, and the like.

Next, the attenuation of the ultrasonic wave was measured under the same conditions as the standard bonded body for the bonding material (bonded material to be measured) for which the bonding characteristics were actually unknown, and were obtained by regression analysis or the like. From the correlation between the ultrasonic attenuation of the standard joined body and the joining characteristics, the joining characteristics of the joining material to be measured are estimated.

For example, when the simple regression is performed and the correlation coefficient is close to 1, the regression line of the ultrasonic attenuation with respect to the joint characteristics substantially coincides with the regression line of the ultrasonic characteristics with respect to the ultrasonic attenuation. Therefore, the ultrasonic attenuation measured with the material to be measured is substituted into the regression line obtained for the standard bonded body, and the joining characteristics of the material to be measured are calculated backward. And
If the back calculated joining characteristic is within a predetermined criterion, it may be judged as pass, and if it is outside the criterion, it may be judged as fail.

Alternatively, when the regression coefficient of the regression line obtained for the standard joint is sufficiently large, the section of the joining characteristics at a predetermined rejection rate using the measured ultrasonic attenuation of the joint material to be measured. Estimation is performed, and if the estimated joining characteristics are within a predetermined criterion, it is determined to be acceptable, and if it is outside the criterion, it is determined to be unacceptable. The rejection rate may be appropriately selected according to the reliability required for the joining material.

When the actually joined materials to be measured are joined according to the operation manual, the properties of the joining interface of the measured materials satisfy the required joining characteristics. Since there is a high possibility that it has almost the same properties as the bonding interface of the standard bonded body, the measured attenuation of the ultrasonic wave is also likely to fall within the above-described criteria.

On the other hand, if the joining operation is not performed according to the operation manual due to the force majeure and the joining conditions are fluctuating, the joining characteristics are changed. Outside values will be detected and a reject decision will be made. In addition, for the bonding material for which rejection has been made, measures such as reheating the bonding portion to the bonding temperature or performing other non-destructive inspection such as a radiation transmission test method are taken as necessary. Will be.

(Example 1) An example in which the ultrasonic inspection method for a joining material according to the present invention is applied to a joining material joined by a liquid phase diffusion joining method using a duplex stainless steel pipe as a material to be joined. Will be described.

First, a standard joined body was prepared according to the following procedure. That is, the material to be joined is a duplex stainless steel SU.
Outer diameter 150mm, inner diameter 120mm made of S329J1
And the joint interface has a surface roughness of Rmax 30 μm
Finished as follows. The insert material used was a Ni-based alloy foil having a melting point of 1040 ° C. and a thickness of 40 μm.

An insert material is interposed between the two duplex stainless steel pipes, a pressure of 4 MPa is applied to the joint interface, and the temperature is maintained at 1150 ° C. to 1300 ° C. for 60 seconds in an Ar gas atmosphere. And liquid phase diffusion bonding of a duplex stainless steel tube. As shown in FIG. 1, an ultrasonic oscillation probe 5 and a receiving probe 6 are arranged on the obtained bonding material with the bonding interface 4 interposed therebetween, and the attenuation amount of the ultrasonic wave transmitted through the bonding interface 4 ( Ultrasonic relative specific intensity) was measured. The distance between the ultrasonic oscillation probe 5 and the reception probe 6 was set to 4 skips, and a longitudinal wave was used for the inspection.

First, changes in the relative intensity of ultrasonic waves when longitudinal waves were incident at various refraction angles on a bonding material having a bonding temperature of 1290 ° C. were examined. The probe used was a square probe with a side of 10 mm, and the frequency of the ultrasonic wave was 5 MHz.
z. In FIG. 3, when the refraction angle is set to 20 °, the relative intensity of the ultrasonic wave is the highest, showing −19 dB. As the angle of refraction became smaller, the relative intensity of the ultrasonic wave sharply decreased, and when the angle of refraction was set to 16 °, the intensity decreased to -34 dB.

When the refraction angle exceeds 20 °, the relative intensity of the ultrasonic wave decreases as the refraction angle increases, and becomes −29 dB at the refraction angle of 25 °. When the refraction angle was set to 30 °, the relative intensity of the ultrasonic wave was −30 dB, which was almost the same as when the refraction angle was set to 25 °, but the noise due to the mixing of the transverse wave increased. Furthermore, the refraction angle is 3
When the angle exceeds 0 °, the measurement becomes difficult due to the mixing of a transverse wave.

Next, the joining temperature was set to 1150 ° C. and 1290 ° C.
The change in the relative intensity of ultrasonic waves when longitudinal waves having different frequencies were incident on the joining material set to ° C was examined. The transducer is
A rectangular probe having one side of 10 mm was used, and the refraction angle was 20 °. In FIG. 4, when a longitudinal wave having a frequency of 2 MHz is used, the difference between the ultrasonic relative specific intensity of the bonding material at a bonding temperature of 1150 ° C. and the ultrasonic relative specific intensity of the bonding material at a bonding temperature of 1290 ° C. Was about 6 dB.

As the frequency increases, the difference between the relative intensities of the ultrasonic waves increases, and reaches about 11 dB when a longitudinal wave having a frequency of 5 MHz is used. Further, when a longitudinal wave having a frequency of 10 MHz is used, the difference between the ultrasonic relative specific intensities is 1
Although it was enlarged to 4 dB, the value of the ultrasonic relative specific intensity itself was -3.
It was around 0 dB, and the measurement sensitivity was reduced. When a longitudinal wave having a frequency of 12 MHz or more was used, the measurement was difficult due to increased noise.

Next, the joining temperature is increased from 1150 ° C. to 1300 ° C.
A change in the relative intensity of the ultrasonic wave when a longitudinal wave was applied to each of the bonding materials changed to ° C while changing the size of the vibrator was examined. The frequency of the used ultrasonic wave was 5 MHz, and the refraction angle was 20 °. In FIG. 5, when a rectangular oscillator having a side of 5 mm is used, the joining temperature is set to 1150 ° C.
The average value of the difference in the relative intensity of ultrasonic waves between the bonding material having the bonding temperature of 1300 ° C. and the bonding material having the bonding temperature of 1300 ° C. was 10 dB or less.

On the other hand, when a rectangular vibrator having a side of 10 mm is used, the difference in the relative intensity of the ultrasonic waves between the joining material at a joining temperature of 1150 ° C. and the joining material at a joining temperature of 1300 ° C. The average value is about 20 dB and one side is 5 m
The amount of change in the relative intensity of the ultrasonic wave was larger than that in the case where the square vibrator m was used.

From the above results, if the refraction angle, frequency, and transducer dimensions of the ultrasonic wave used for the inspection are within appropriate ranges,
It was found that a change in the bonding temperature can be detected as a change in the attenuation (ultrasonic relative specific intensity) of the ultrasonic wave transmitted through the bonding interface while maintaining the detection sensitivity of the ultrasonic wave transmitted through the bonding material high.

As shown by a white circle in FIG. 5, one side is 10 m.
A simple regression was performed on a case where a longitudinal wave having a frequency of 5 MHz was incident at a refraction angle of 20 ° using a square probe of m, and the following regression equation was obtained. Ultrasonic relative specific strength = −0.083 × (joining temperature) +91 (1)

Further, a tensile test piece (JIS Z 31214 test piece) was cut out from each of the standard joined bodies after the ultrasonic inspection, and a tensile test was performed at a crosshead speed of 1 mm / min. FIG. 6 shows the relationship between the obtained tensile strength and the joining temperature. FIG. 6 shows that the higher the bonding temperature, the higher the tensile strength, and the bonding temperature and the tensile strength correspond to 1: 1. As shown in FIG. 7, when the ultrasonic relative specific strength of the standard joined body was plotted against the tensile strength and simple regression was performed, the following regression equation was obtained. Tensile strength = −40 × (ultrasonic relative specific strength) +150 (2)

Next, using the regression formulas (1) and (2), a test was conducted to confirm whether or not bonding materials having different bonding characteristics could be actually selected. According to the same procedure as described above, ten bonding materials having a bonding temperature of 1300 ° C. and ten bonding materials having a bonding temperature of 1150 ° C. were prepared, and a penetrant test and an X-ray transmission test were performed on each bonding material. crack,
It was previously confirmed that there was no defect such as an unbonded portion.

Next, with the history of each joining material turned down,
Using a square probe with one side of 10mm, frequency is 5MHz
By injecting the longitudinal wave at a refraction angle of 20 °, a total inspection of the bonding material was performed. As a criterion, based on the regression equation of (1), an ultrasonic relative specific strength of -10 dB or more (corresponding to a joining temperature of 1200 ° C. or less) was rejected. As a result, it was possible to detect and sort all the joining materials having the joining temperature of 1300 ° C.

The tensile strength calculated back from the measured ultrasonic attenuation using the regression equation (2) was 826 MPa for a joining material with a joining temperature of 1300 ° C., and the joining temperature was 1150 ° C. It was 328 MPa for the bonding material. On the other hand, the selected steel pipe joined at 1300 ° C. and 115
A test piece was actually cut out from each of the steel pipes joined at 0 ° C., and the tensile strength was measured.
Pa and 360 MPa were in good agreement with the results estimated from the regression equation of (2).

(Example 2) According to the same procedure as in Example 1, the joining of the duplex stainless steel pipe was performed while changing the joining temperature. Next, the attenuation of the ultrasonic wave transmitted through the bonding interface was measured using the transverse wave. The probe was a square probe having one side of 10 mm.

First, the frequency of the ultrasonic wave is set to 5 MHz,
When a transverse wave is incident at various refraction angles, as shown in FIG. 8, when the refraction angle is set to 60 °, the bonding temperature is set to 11 °.
The average value of the difference between the ultrasonic relative specific strength of the bonding material at 50 ° C. and the ultrasonic relative specific strength of the bonded body at 1300 ° C. was about 10 dB. On the other hand, when the refraction angle is 70 °, the average value of the difference between the ultrasonic relative specific intensities is about 15 dB.
Expanded to.

When the relative angle of ultrasonic wave of each bonding material was measured using a transverse wave having a different refraction angle of 70 ° and a different frequency, as shown in FIG. When the transverse wave having a frequency of 5 MPa is used while the change in the relative intensity of the ultrasonic waves is small, the joining material with the joining temperature of 1150 ° C. and the joining temperature of 1300 are used.
The average value of the difference between the ultrasonic relative specific intensities of the joining materials set to ° C. was expanded to about 15 dB.

When comparing the white circle in FIG. 5 with the white circle in FIG. 9, the variation in the relative intensity of ultrasonic waves at 1150 ° C. and 1200 ° C. is smaller when the longitudinal wave is used.
The difference between the lower limit value of the ultrasonic relative specific intensity at 150 ° C. or 1200 ° C. and the upper limit value of the ultrasonic relative specific intensity at around 1290 ° C. is large. Although details are unknown, it can be understood from FIGS. 5 and 9 that a more reliable inspection can be performed by inspecting the bonding material using the longitudinal wave.

From the above results, even when a transverse wave is used, if the inspection conditions are appropriate, a change in the bonding characteristics can be detected as a change in the attenuation of the ultrasonic wave transmitted through the bonding interface. It was found that the joining characteristics of joining materials whose histories were unknown could be estimated.

Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention. . For example, in the above-described embodiment, the present invention is applied to a joining material of steel pipes. However, the present invention is not limited to steel pipes, but may be applied to a plate-like joining material.

In the above embodiment, the present invention is applied to a joining material obtained by joining a duplex stainless steel by a liquid phase diffusion joining method using a Ni-based alloy as an insert material. The present invention can be applied to a joining material joined by a solid-phase diffusion joining method, a fusion welding method, a pressure welding method or the like, and the same effects as those of the above embodiment can be obtained.

Further, the material to be joined is not limited to the duplex stainless steel or the precipitation hardening stainless steel based on the duplex stainless steel, but the ultrasonic attenuation greatly varies depending on the variation of the joining conditions and the like. The present invention can be applied to any joining material as long as the joining material is a material having properties.

For example, since pearlite has a layered structure of ferrite and cementite, the attenuation of ultrasonic waves increases, but the attenuation of ultrasonic waves tends to decrease in martensite or an intermediate structure. Therefore, when joining steel materials containing pearlite and rapidly cooling the joint to generate martensite, or when joining steel materials containing martensite or an intermediate structure and gradually cooling the joint to produce pearlite In this case, it is possible to detect the change in the amount of attenuation of the ultrasonic wave transmitted through the bonding interface, and it is possible to estimate the bonding characteristics from the amount of ultrasonic attenuation.

[0073]

As described above, according to the present invention, the correlation between the amount of attenuation of the ultrasonic wave transmitted through the bonding interface of the standard bonded body bonded under known conditions and the bonding characteristics is determined in advance, and the measured bond bonded under unknown conditions is determined. Since the joining characteristics of the material are estimated from the attenuation of the ultrasonic wave passing through the interface of the joining material to be measured, the effect that the joining characteristics such as the joining temperature and the joining strength can be estimated in a non-destructive manner. There is.

When the longitudinal wave is used for the inspection and the angle of refraction of the ultrasonic wave, the frequency, and the size of the probe are optimized, the ultrasonic measurement sensitivity is maintained at a high level, and the ultrasonic wave caused by the change in the joining characteristics is maintained. Since the change in the amount of attenuation of the sound wave can be largely recognized, there is an effect that the inspection accuracy can be improved.

Further, when a dual-phase steel containing two or more types of phases, for example, a duplex stainless steel, is used as an object to be inspected, a change in the joining characteristics appears remarkably as a change in the ultrasonic attenuation. This has the effect that non-destructive inspection of bonding characteristics can be performed with high accuracy.

As described above, according to the bonding material ultrasonic inspection method according to the present invention, the bonding characteristics such as bonding temperature and bonding strength can be estimated with high accuracy even if the bonding material cannot be sampled and inspected. Therefore, if this is applied to, for example, inspection of oil well pipes and pipes of chemical plants, it is possible to increase the reliability of the joining process. is there.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating an ultrasonic inspection method according to the present invention.

FIG. 2 is a cross-sectional view of a probe used in the ultrasonic inspection method according to the present invention.

FIG. 3 is a diagram showing the relationship between the angle of refraction of longitudinal waves and the relative intensity of ultrasonic waves.

FIG. 4 is a diagram showing the relationship between the frequency of longitudinal waves and the relative intensity of ultrasonic waves.

FIG. 5 is a diagram showing a relationship between a transducer size and an ultrasonic relative specific strength when a longitudinal wave is used.

FIG. 6 is a diagram showing a relationship between a joining temperature and a tensile strength of a duplex stainless steel pipe.

FIG. 7 is a diagram showing a relationship between an ultrasonic relative specific strength of a longitudinal wave and a tensile strength.

FIG. 8 is a diagram illustrating a relationship between a refraction angle of a transverse wave and an ultrasonic relative specific strength.

FIG. 9 is a diagram showing a relationship between the frequency of a shear wave and the relative intensity of ultrasonic waves.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Joining material 2, 3 Steel pipe 4 Joining interface 5 Ultrasonic oscillation probe 6 Receiving probe

Claims (7)

[Claims] 1. An ultrasonic oscillation probe and a reception probe are placed on both sides of a joining interface of a joining material to be measured whose joining conditions are unknown, and the ultrasonic waves oscillated from the ultrasonic oscillation probe generate the ultrasonic waves. The attenuation of the ultrasonic wave transmitted through the bonding interface and received by the receiving probe is measured, and the ultrasonic wave of the standard bonded body bonded under known bonding conditions measured in advance based on the measured value An ultrasonic inspection method for a bonding material, wherein a bonding characteristic of the bonding material to be measured is inspected based on a correlation between an attenuation amount and a bonding characteristic. 2. The ultrasonic inspection method for a bonding material according to claim 1, wherein the bonding characteristic is a bonding temperature. 3. The ultrasonic inspection method for a bonding material according to claim 1, wherein the bonding characteristic is a bonding strength. 4. The ultrasonic wave according to claim 1, wherein a longitudinal wave mode is used, and the ultrasonic wave is incident on the bonding material so as to have a refraction angle of 17 ° to 30 °. 3. The ultrasonic inspection method for a bonding material according to item 3. 5. The ultrasonic wave according to claim 1, wherein the frequency is 4 MHz or more and 10 MHz or less.
The ultrasonic inspection method for a bonding material according to 2, 3, or 4. 6. The probe has a side of 8 mm or more and 15 m in length.
The ultrasonic inspection method for a bonding material according to claim 1, 2, 3, 4, or 5, wherein a square probe of m or less is used. 7. The ultrasonic inspection method for a bonding material according to claim 1, wherein the material to be bonded is made of a duplex stainless steel.