Method for evaluating cross-sectional shape of welded portion, device for evaluating cross-sectional shape of welded portion, and method for welding metal material

Abstract

A device for evaluating the cross-sectional shape of a welded portion according to the present invention comprises: a transmission / reception unit that focuses ultrasonic waves near a welded portion by using a contact medium, transmits ultrasonic waves having a plurality of refraction angles at an angle inclined with respect to the thickness direction of a metal material by using a contact medium, and receives reflected ultrasonic waves for each of the plurality of refraction angles by using a contact medium; a signal processing unit that performs amplification processing and filter processing on the reflected waves having each of the plurality of refraction angles, then uses the amplification-processed and filter-processed reflected waves to extract echo amplitudes within a detection gate for each of the plurality of refraction angles, generates an image showing the distribution of the echo amplitudes within the detection gate for each ultrasonic wave refraction angle, and generates an echo amplitude map obtained by synthesizing each image by using the refraction angle corresponding thereto; and an output unit that outputs the echo amplitude map.

Description

Method for evaluating cross-sectional shape of welded joint, apparatus for evaluating cross-sectional shape of welded joint, and welding method for metal material

[0001] The present invention relates to a method for evaluating the cross-sectional shape of a welded joint, an apparatus for evaluating the cross-sectional shape of a welded joint, and a welding method for a metal material.

[0002] It is known that the cross-sectional shape of the weld metal in the welded joint of a metal material affects the mechanical properties of the welded joint. For example, Patent Document 1 describes that the cross-sectional shape of the weld metal in the welded joint of a steel pipe affects the toughness of the welded joint. Therefore, from the viewpoints of quality control and quality assurance of the welded joint, techniques for imaging and non-destructively evaluating the cross-sectional shape of the weld metal have been proposed. For example, Patent Documents 2 and 3 describe techniques for imaging the cross-sectional shape of the weld metal by receiving ultrasonic waves reflected at the boundary between the base metal part and the welded joint. Specifically, the techniques described in Patent Documents 2 and 3 receive the reflected waves of ultrasonic waves obliquely transmitted to the boundary between the base metal part and the welded joint while moving the probe or switching the vibrators of the array probe. Then, the techniques described in Patent Documents 2 and 3 image the cross-sectional shape of the weld metal by specifying the reflection points of the ultrasonic waves from the received reflected waves.

[0003] Japanese Unexamined Patent Application Publication No. 2009-233679, Japanese Unexamined Patent Application Publication No. 2009-069077, International Publication No. 2014 / 013940

[0004] The techniques described in Patent Documents 2 and 3 set the time range for detecting the reflected waves as a detection gate, and specify the cross-sectional shape of the weld metal based on the reflected waves having an intensity equal to or greater than a threshold value detected within the detection gate. Therefore, according to the techniques described in Patent Documents 2 and 3, there is a possibility that the cross-sectional shape of the weld metal may be misrecognized by specifying the cross-sectional shape of the weld metal based on the reflected waves having an intensity stronger than the intensity of the ultrasonic waves reflected at the boundary, or that the cross-sectional shape of the weld metal may not be specified.

[0005] The present invention has been made to solve the above problems, and an object thereof is to provide a method and an apparatus for evaluating the cross-sectional shape of a welded joint capable of accurately and non-destructively evaluating the cross-sectional shape of the weld metal. Another object of the present invention is to provide a welding method for a metal material capable of generating a welded joint having desired mechanical properties.

[0006] The present invention provides a method for evaluating the cross-sectional shape of a welded joint, which is a method for evaluating the cross-sectional shape of a weld metal in a welded joint of a metal material, comprising: an ultrasonic array control step of focusing ultrasonic waves near the welded joint via a coupling medium; an ultrasonic transmission step of transmitting ultrasonic waves at multiple refraction angles via the coupling medium at an angle inclined with respect to the thickness direction of the metal material; an ultrasonic reception step of receiving reflected waves of the ultrasonic waves via the coupling medium for each of the multiple refraction angles of the ultrasonic waves; an echo height extraction step of performing amplification and filtering on the reflected waves for each of the multiple refraction angles, and then using the reflected waves after amplification and filtering to extract the echo height within a detection gate for each of the multiple refraction angles; and generating an image showing the distribution of echo height within the detection gate for each of the multiple refraction angles. The ultrasonic wave extraction step includes an echo height imaging step of generating an echo height map by synthesizing the images at corresponding refraction angles and outputting the generated echo height map, and a step of evaluating the cross-sectional shape of the weld metal based on the echo height map, wherein the excitation voltage of the ultrasonic wave in the ultrasonic wave transmission step is in the range of 20 to 150 V, the interval of the refraction angle in the ultrasonic wave transmission step is 5 degrees or less when the distance between the transducer that transmits and receives ultrasonic waves and the weld is set so that 0 to 0.5 skips of ultrasonic waves coincide with the boundary between the base material and the weld metal, or 3 degrees or less when the distance between the transducer and the weld is set so that 0 to 1.0 skips of ultrasonic waves coincide with the boundary between the base material and the weld metal, and the amplification gain of the reflected wave in the echo height extraction step is in the range of 30 to 60 dB.

[0007] The echo height extraction step may include a step of removing frequency components of the reflected wave below 2 MHz.

[0008] The present invention provides a device for evaluating the cross-sectional shape of a welded joint, which evaluates the cross-sectional shape of the weld metal in a welded joint of a metal material, comprising: a transmitting and receiving unit that focuses ultrasonic waves near the welded joint via a coupling medium, transmits ultrasonic waves at multiple refraction angles via the coupling medium at an angle inclined with respect to the thickness direction of the metal material, and receives reflected waves of the ultrasonic waves via the coupling medium for each of the multiple refraction angles of the ultrasonic waves; and after applying amplification and filtering processing to the reflected waves for each of the multiple refraction angles, extracts the echo height within a detection gate for each of the multiple refraction angles using the reflected waves after amplification and filtering, generates an image showing the distribution of echo height within the detection gate for each of the refraction angles of the ultrasonic waves, and The transmitting and receiving unit comprises a signal processing unit that generates an echo height map by synthesizing the recorded images at corresponding refraction angles, and an output unit that outputs the echo height map, wherein the transmitting and receiving unit sets the excitation voltage of the ultrasonic waves within the range of 20 to 150 V, and sets the refraction angle interval to 5 degrees or less when the distance between the transducer that transmits and receives ultrasonic waves and the weld is set so that the ultrasonic wave skip of 0 to 0.5 coincides with the boundary between the base material and the weld metal, and sets the refraction angle interval to 3 degrees or less when the distance between the transducer that transmits and receives ultrasonic waves and the weld is set so that the ultrasonic wave skip of more than 0.5 to 1.0 coincides with the boundary between the base material and the weld metal, and sets the refraction angle interval to 3 degrees or less, and the amplification gain of the reflected waves within the range of 30 to 60 dB.

[0009] The welding method for metal materials according to the present invention includes the step of adjusting the welding conditions of the weld based on the evaluation result of the cross-sectional shape of the weld metal using the evaluation method for the cross-sectional shape of the weld according to the present invention.

[0010] According to the method and apparatus for evaluating the cross-sectional shape of a welded joint of the present invention, the cross-sectional shape of the weld metal can be evaluated non-destructively and accurately. Furthermore, according to the welding method for metal materials of the present invention, a welded joint having desired mechanical properties can be produced.

[0011] Figure 1 is a block diagram showing the configuration of an evaluation device for the cross-sectional shape of a welded joint, which is one embodiment of the present invention. Figure 2 is a schematic diagram showing the configuration of the transmitting and receiving unit shown in Figure 1. Figure 3 is a flowchart showing the flow of the evaluation process, which is one embodiment of the present invention. Figure 4 is a diagram showing an example of an image showing echo height and the distribution of echo height. Figure 5 is a diagram showing an example of an echo height map. Figure 6 is a diagram showing an echo height map of the inventive example. Figure 7 is a diagram showing an echo height map of the inventive example.

[0012] The configuration and operation of an evaluation device for the cross-sectional shape of a welded joint, which is one embodiment of the present invention, will be described below with reference to the drawings.

[0013] [Configuration] First, with reference to Figures 1 and 2, the configuration of an evaluation device for the cross-sectional shape of a welded joint, which is one embodiment of the present invention, will be described. Figure 1 is a block diagram showing the configuration of an evaluation device for the cross-sectional shape of a welded joint, which is one embodiment of the present invention. Figure 2 is a schematic diagram showing the configuration of the transmitting and receiving unit 1a shown in Figure 1.

[0014] As shown in Figure 1, the weld cross-sectional shape evaluation device (hereinafter abbreviated as "evaluation device") 1, which is one embodiment of the present invention, transmits ultrasonic waves to the weld of a metal material at multiple refraction angles, and generates and outputs an echo height map by synthesizing images showing the distribution of echo heights within the detection gate at angles corresponding to the refraction angles of the ultrasonic waves. According to this echo height map, the user can accurately and non-destructively evaluate the cross-sectional shape of the weld metal by confirming on the map lines of the same echo height extending in the penetration direction of the weld metal, starting from the boundary between the base material surface and the weld bead. Details of the echo height map will be described later.

[0015] The evaluation device 1 comprises a transmitting / receiving unit 1a, a control unit 1b, a signal processing unit 1c, and an output unit 1d. As shown in Figure 2, the transmitting / receiving unit 1a includes an array transducer 11 with multiple transducers and a wedge 12, and operates according to a control signal from the control unit 1b. Specifically, the transmitting / receiving unit 1a drives the array transducer 11 according to a control signal from the control unit 1b, thereby focusing transverse wave mode ultrasonic waves near the weld W of the metal material S via the wedge 12 and the coupling medium 13. Examples of coupling medium 13 include glycerin paste, a glycerin aqueous solution with a concentration of 75% (volume fraction) or higher, water, oil, etc.

[0016] Furthermore, the transmitting / receiving unit 1a drives the array transducer 11 according to a control signal from the control unit 1b, thereby transmitting ultrasonic waves at multiple refraction angles inclined with respect to the thickness direction of the metal material S via the wedge 12 and the coupling medium 13. In addition, the transmitting / receiving unit 1a drives the array transducer 11 according to a control signal from the control unit 1b, thereby receiving some or all of the reflected ultrasonic waves transmitted at multiple refraction angles via the coupling medium 13 and the wedge 12, and outputs an electrical signal indicating the received reflected wave to the signal processing unit 1c for each of the multiple refraction angles.

[0017] Returning to Figure 1, the control unit 1b is composed of an information processing device such as a computer and controls the operation of the transmitting / receiving unit 1a. Specifically, the control unit 1b controls the ultrasonic excitation voltage to 20V or more, preferably 40V or more, so that the boundary between the base material and the weld metal M (see Figure 2) can be clearly identified in the echo height map described above. On the other hand, if the ultrasonic excitation voltage is made excessively high, noise will be generated and will adversely affect the identification of the boundary between the base material and the weld metal M, so the control unit 1b controls the ultrasonic excitation voltage to 150V or less, preferably 100V or less, and more preferably 80V.

[0018] Furthermore, the control unit 1b focuses the transmitted ultrasonic waves at a position in front of the wedge 12 in the direction of propagation A (see Figure 2). However, in order to clearly identify the boundary between the base material and the weld metal M in the echo height map, it is preferable to set the ultrasonic wave focusing position at a distance of 10 mm or more from the installation position of the array probe 11 in the direction of the probe weld distance (Y distance). Also, if the refraction angle of the ultrasonic waves is less than 30 degrees, the ultrasonic waves will enter longitudinal wave mode and will become unusable. Also, if the refraction angle of the ultrasonic waves exceeds 80 degrees, surface waves will be generated and will become unusable. For this reason, it is preferable that the control unit 1b includes a range of 30 to 80 degrees as the range of ultrasonic wave refraction angles.

[0019] Furthermore, increasing the interval of the ultrasonic refraction angle reduces the resolution of the echo height map, making it difficult to identify the cross-sectional shape of the weld metal. For this reason, when the distance D between the array probe 11 and the weld W (see Figure 2) is set so that ultrasonic skips of 0 to 0.5 coincide with the boundary between the base material and the weld metal, the control unit 1b sets the ultrasonic refraction angle to an interval of 5 degrees or less, preferably 3 degrees or less. Also, when the distance D between the array probe 11 and the weld W is set so that ultrasonic skips of more than 0.5 to 1.0 coincide with the boundary between the base material and the weld metal, the control unit 1b sets the ultrasonic refraction angle to an interval of 3 degrees or less, preferably 2 degrees or less.

[0020] The signal processing unit 1c is composed of an information processing device such as a computer and uses an electrical signal indicating the reflected wave input from the transmitting / receiving unit 1a to generate an echo height map for evaluating the cross-sectional shape of the weld metal M in the welded part W of the metal material S. Specifically, the signal processing unit 1c amplifies and filters the electrical signal indicating the reflected wave input from the transmitting / receiving unit 1a, and then extracts an image showing the distribution of echo height within the detection gate for each ultrasonic refraction angle. The signal processing unit 1c then generates an echo height map by combining the images for each ultrasonic refraction angle at the corresponding ultrasonic refraction angle positions, and outputs the generated echo height map to the output unit 1d.

[0021] Furthermore, in order to clearly distinguish the boundary between the base material and the weld metal M in the echo height map, the signal processing unit 1c sets the amplification gain of the reflected wave to 30 dB or more, preferably 40 dB or more. On the other hand, if the amplification gain is made excessively large, noise will be generated, which will adversely affect the identification of the boundary between the base material and the weld metal M, so the signal processing unit 1c sets the amplification gain of the reflected wave to 60 dB or less. In addition, the frequency components of the reflected wave below 2 MHz consist only of noise and do not include signals from the boundary between the base material and the weld metal M. For this reason, the signal processing unit 1c should remove the frequency components of the reflected wave below 2 MHz in the filtering process and use only the frequency components of the reflected wave above 2 MHz.

[0022] The output unit 1d consists of a display device such as a liquid crystal display, a printing device such as a printer, a communication device, etc., and outputs a map of the echo height output from the signal processing unit 1c.

[0023] [Evaluation Process] Next, with reference to Figures 3 to 5, a method for evaluating the cross-sectional shape of a welded joint using the evaluation device 1 will be described.

[0024] Figure 3 is a flowchart showing the flow of an evaluation process according to one embodiment of the present invention. The flowchart shown in Figure 3 starts when an execution command for the evaluation process is input to the evaluation device 1, and the evaluation process proceeds to step S1.

[0025] In step S1, the control unit 1b controls the transmitting / receiving unit 1a to drive the array probe 11 and focus the transverse wave mode ultrasonic waves near the weld W via the wedge 12 and coupling medium 13 (ultrasonic array control step). With this, step S1 is completed, and the evaluation process proceeds to step S2.

[0026] In step S2, the control unit 1b controls the transmitting / receiving unit 1a to drive the array transducer 11 and transmit ultrasonic waves with multiple refraction angles at angles inclined with respect to the thickness direction of the metal material S via the wedge 12 and coupling medium 13 (ultrasonic transmission step). With this, the process of step S2 is completed, and the evaluation process proceeds to step S3.

[0027] In step S3, the control unit 1b drives the array transducer 11 by controlling the transmitting / receiving unit 1a, and receives part or all of the reflected ultrasonic waves via the coupling medium 13 and wedge 12 at each ultrasonic refraction angle (ultrasonic reception step). Then, the control unit 1b controls the transmitting / receiving unit 1a to output an electrical signal indicating the received reflected wave to the signal processing unit 1c at each ultrasonic refraction angle. With this, the process of step S3 is completed, and the evaluation process proceeds to step S4.

[0028] In step S4, the signal processing unit 1c first performs amplification and filtering on the reflected waves for each refraction angle of the ultrasound. Then, as shown in Figure 4(a), the signal processing unit 1c uses the amplified and filtered reflected waves to extract the echo height within the detection gate for each refraction angle of the transmitted ultrasound (echo height extraction step). Figure 4(a) shows the echo height within the detection gate at a certain refraction angle. With this, the processing of step S4 is completed, and the evaluation process proceeds to step S5.

[0029] In step S5, the signal processing unit 1c first generates an image showing the distribution of echo heights within the detection gate, as shown in Figure 4(b), for each refraction angle of the transmitted ultrasound. The format of the image showing the distribution of echo heights is not limited as long as it can distinguish the differences in echo heights, and examples include RGB format and grayscale format. Then, as shown in Figure 5, the signal processing unit 1c generates an echo height map as shown in Figure 5 by combining the images for each ultrasound refraction angle at the corresponding ultrasound refraction angle position (echo height imaging step). The image enclosed by the rectangular region shown in Figure 5 corresponds to the image shown in Figure 4(b), and the angle θ shown in Figure 5 corresponds to the refraction angle of the ultrasound from which the echo height shown in Figure 4(a) was obtained. The output unit 1d then outputs the generated echo height map. With this, the processing of step S5 is completed, and the series of evaluation processes is finished.

[0030] Subsequently, the user evaluates the cross-sectional shape of the weld metal by referring to the echo height map. Specifically, the user refers to the echo height map to identify where welding defects or abnormalities in penetration shape occur and investigate the cause of the abnormalities. In addition, by checking the cross-sectional shape of the weld metal immediately after welding, the user adjusts the welding conditions to improve the cross-sectional shape of the weld metal and manages mechanical performance such as weld toughness, which is affected by the cross-sectional shape of the weld metal. For example, if the penetration depth is insufficient, the welding current is increased; if undercut occurs, the welding speed is reduced or the arc voltage is increased, etc., to adjust the welding conditions. This makes it possible to produce a weld with the desired mechanical performance.

[0031] [Examples] In this example, the welded joint of a UOE steel pipe with an outer diameter of 36 inches and a thickness of 38.1 mm was used as the target, and the change in the echo height map associated with changes in the ultrasonic skip number, excitation voltage, focusing position, filter frequency, amplification gain, and refraction angle interval was evaluated to determine the preferred range of excitation voltage, amplification gain, refraction angle, and refraction angle interval in the present invention. Glycerin paste was used as the coupling medium. Furthermore, the bead width of the inner weld metal and the outer weld metal was measured at the longitudinal center of the weld bead. If the bead width value obtained from the echo height map obtained in this test was within ±2 mm of the measured bead width value for both the inner and outer weld metal, it was evaluated as a good result and marked with "○". If at least one of the inner and outer weld metals exceeded ±2 mm, it was evaluated as an unsatisfactory result and marked with "×". The evaluation results are shown in Table 1. The echo height maps obtained for the invention examples No. 21 and 22 are shown in Figures 6 and 7, respectively.

[0032] In the echo height map shown in Figure 6, the cross-sectional shape of the weld could be clearly identified by lines (dotted lines in the figure) that started from the boundary between the inner surface of the steel pipe and the weld on the inner surface of the steel pipe, represented by intermittent lines of constant density horizontally connected around 40 mm on the vertical axis, and the boundary between the outer surface of the steel pipe and the molten metal, and started from the boundary (dotted lines in the figure) that started from the boundary between the inner surface of the steel pipe and the weld metal, and the boundary between the outer surface of the steel pipe and the molten metal, and started from the boundary (dotted lines in the figure) that started from the boundary between the inner surface of the steel pipe and the weld metal, and the boundary between the outer surface of the steel pipe and the molten metal, between the inner surface of the steel pipe and the outer surface of the steel pipe, represented by intermittent lines of constant density horizontally connected around 40 mm on the vertical axis and the outer surface of the steel pipe, and the outer surface of the steel pipe.

[0033] Table 1 shows examples of the invention, Nos. 1-14, 21, and 22, which yielded favorable results. On the other hand, Nos. 15-20 are comparative examples that do not meet the conditions of the present invention, and the bead width value obtained from the echo height map obtained in this test exceeded ±2 mm from the measured bead width value in at least one of the inner weld metal and the outer weld metal. This confirms that, according to the present invention, the cross-sectional shape of the weld metal can be evaluated non-destructively and accurately.

[0034]

[0035] Although embodiments applying the invention made by the present inventors have been described above, the present invention is not limited by the descriptions and drawings that constitute part of the disclosure of the present invention in this embodiment. For example, in the above embodiment, the case of a UOE steel pipe to which submerged arc welding with one pass each for internal and external welding was applied was described, but the scope of evaluation of the present invention is not limited to this embodiment and can be applied to all metal materials to which welding is applied. That is, other embodiments, examples, and operational techniques made by those skilled in the art based on this embodiment are all included in the scope of the present invention.

[0036] According to the present invention, it is possible to provide a method and apparatus for evaluating the cross-sectional shape of a welded joint that can evaluate the cross-sectional shape of the weld metal nondestructively and with high accuracy. Furthermore, according to the present invention, it is possible to provide a welding method for metal materials that can produce a welded joint having desired mechanical performance.

[0037] 1. Apparatus for evaluating the cross-sectional shape of a welded joint 1a. Transmitter / receiver unit 1b. Control unit 1c. Signal processing unit 1d. Output unit 11. Array probe 12. Wedge 13. Coupling medium A. Direction of ultrasonic wave propagation D. Distance M. Weld metal S. Metal material W. Welded joint

Claims

1. A method for evaluating the cross-sectional shape of a weld in a metal material, comprising: an ultrasonic array control step of focusing ultrasonic waves near the weld via a coupling medium; an ultrasonic transmission step of transmitting ultrasonic waves at multiple refraction angles via the coupling medium at an angle inclined with respect to the thickness direction of the metal material; an ultrasonic reception step of receiving reflected waves of the ultrasonic waves via the coupling medium for each of the multiple refraction angles of the ultrasonic waves; an echo height extraction step of applying amplification and filtering to the reflected waves for each of the multiple refraction angles, and then using the amplified and filtered reflected waves to extract the echo height within a detection gate for each of the multiple refraction angles; an echo height imaging step of generating an image showing the distribution of echo heights within the detection gate for each of the multiple refraction angles, generating an echo height map by synthesizing the images at the corresponding refraction angles, and outputting the generated echo height map; and a step of evaluating the cross-sectional shape of the weld metal based on the echo height map, wherein the excitation voltage of the ultrasonic waves in the ultrasonic transmission step is within the range of 20 to 150 V. A method for evaluating the cross-sectional shape of a weld, wherein the interval of the refraction angle in the ultrasonic transmission step is 5 degrees or less when the distance between the ultrasonic transmitter / receiver and the weld is set so that the ultrasonic skip of 0 to 0.5 skips coincides with the boundary between the base material and the weld metal, and 3 degrees or less when the distance between the transmitter / receiver and the weld is set so that the ultrasonic skip of more than 0.5 skips and less than or equal to 1.0 skip coincides with the boundary between the base material and the weld metal, and the amplification gain of the reflected wave in the echo height extraction step is within the range of 30 to 60 dB.

2. The method for evaluating the cross-sectional shape of a welded joint according to claim 1, wherein the echo height extraction step includes a step of removing frequency components of the reflected wave below 2 MHz.

3. An apparatus for evaluating the cross-sectional shape of a weld in a welded joint of a metal material, comprising: a transmitting and receiving unit that focuses ultrasonic waves near the weld via a coupling medium, transmits ultrasonic waves at multiple refraction angles via the coupling medium at an angle inclined with respect to the thickness direction of the metal material, and receives reflected waves of the ultrasonic waves via the coupling medium for each of the multiple refraction angles of the ultrasonic waves; a signal processing unit that performs amplification and filtering on the reflected waves for each of the multiple refraction angles, extracts the echo height within a detection gate for each of the multiple refraction angles using the amplified and filtered reflected waves, generates an image showing the distribution of echo height within the detection gate for each of the refraction angles of the ultrasonic waves, and generates an echo height map by synthesizing the images at the corresponding refraction angles; and an output unit that outputs the echo height map. The transmitting and receiving unit sets the excitation voltage of the ultrasonic waves within the range of 20 to 150 V; the transmitting and receiving unit sets the refraction angle interval to 5 degrees or less when the distance between the transducer that transmits and receives ultrasonic waves and the weld is set so that the ultrasonic wave skip of 0 to 0.5 coincides with the boundary between the base material and the weld metal; the refraction angle interval to 3 degrees or less when the distance between the transducer that transmits and receives ultrasonic waves and the weld is set so that the ultrasonic wave skip of more than 0.5 and 1.0 coincides with the boundary between the base material and the weld metal; and the signal processing unit sets the amplification gain of the reflected wave within the range of 30 to 60 dB; this is an evaluation device for the cross-sectional shape of a weld.

4. A method for welding a metal material, comprising the step of adjusting the welding conditions of a weld based on the evaluation result of the cross-sectional shape of the weld metal using the method for evaluating the cross-sectional shape of a weld described in claim 1 or 2.

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