JP2003172728A - Ultrasonic detector and ultrasonic inspection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the deterioration of flaw detection accuracy, detect the existence of a minute flaw when detecting a flaw in a deep part in the axial direction in a scanning manner, and improve an S/N ratio of a signal when detecting a flaw whose existence can be detected conventionally. <P>SOLUTION: An ultrasonic detector is composed of an ultrasonic transmitter 11 having an ultrasonic wave effective outgoing point P and an ultrasonic receiver 12 having an ultrasonic wave effective incident point Q. The shortest line segment connecting either P among the ultrasonic wave effective outgoing point P and the ultrasonic wave effective incident point Q with one arbitrary point R of a metal melting body 3 crosses a join face 9 on one side among opposite faces on which a body to be welded 2 and the metal melting body 3 join mutually. Since an incident path for ultrasonic waves crosses the join face 9 and enters a flaw detection point R, a length of an ultrasonic wave path in which the ultrasonic waves pass in the metal melting body 3 is shorter than a conventional ultrasonic wave path in which ultrasonic waves enter the metal melting body directly from an outer face of the metal melting body and reaches the flaw detection point R, if the flow detection point is at a deep position. Shortening of the ultrasonic wave path in the metal melting body receiving thermal denaturation improves an S/N ratio of a detection signal. Consequently, a minute flaw which cannot be detected in a conventional method can be detected by this ultrasonic detector, and a flaw which can be detected conventionally can be detected with further high accuracy. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an ultrasonic flaw detector,
The present invention also relates to an ultrasonic flaw detection method, and more particularly, to an ultrasonic flaw detection apparatus and an ultrasonic flaw detection method for highly accurately detecting flaws in an axial defect of a welded portion where a pipe and a cylindrical container are circumferentially welded.

[0002]

2. Description of the Related Art A pipe such as a boiler pipe or a cylindrical container, when it has a large diameter, is integrally manufactured by butt-welding annular butting portions in the circumferential direction. The material of such a welded portion or safe end portion changes under the influence of welding heat. The presence / absence of defects in the welded part is one of the inspection targets of the nondestructive inspection. Ultrasonic flaw detection technology is used for nondestructive inspection. Due to the material change, abnormal ultrasonic waves propagate inside the welding site. Noise is generated in the weld site due to the propagation of abnormal ultrasonic waves. The generation of such noise deteriorates the flaw detection accuracy. Such deterioration is prominent at welded portions where weld metals such as austenitic stainless steel and Inconel alloy are used. The flaw detection of the welded part of the pipe after welding must be performed from the outer side surface. Therefore, highly accurate flaw detection of the deep inside portion is required.

In the circumferential flaw detection of an axial defect target of a circumferential welded portion or a safe end portion, ultrasonic waves penetrate deeply and transparently into the welded portion, are reflected by the defective portion, and return along the ultrasonic path. It is affected by the remarkable deterioration of flaw detection accuracy. The circumferential flaw detection is more strongly affected by the flaw detection accuracy deterioration than the axial flaw detection. Ultrasonic flaw detection that passes through the joint surface is known.

It is required to suppress deterioration of flaw detection accuracy. In particular, when scanning a deep axial defect in the circumferential direction in a scanning manner, it is possible to detect the presence of a minute defect, and the S / N ratio of the signal at the time of defect detection, which has been possible to detect the presence, can be improved. Improvement is desired.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ultrasonic flaw detection apparatus and an ultrasonic flaw detection method capable of suppressing deterioration of flaw detection accuracy. Another object of the present invention is to enable detection of the presence of a microdefect when scanningly detecting a deep axial defect in the circumferential direction, and to detect the presence of a signal that was previously possible for the detection of a defect. An ultrasonic flaw detection apparatus and an ultrasonic flaw detection method capable of improving the S / N ratio of

[0006]

Means for solving the problem Means for solving the problem are expressed as follows. The technical matters appearing in the expression are accompanied by parentheses (), and numbers, symbols and the like are added. The numbers, symbols and the like are technical matters constituting at least one embodiment or a plurality of examples of the plurality of embodiments or a plurality of examples of the present invention, particularly, the embodiment or the example. It corresponds to the reference numbers, reference symbols, etc. attached to the technical matters expressed in the drawings corresponding to. Such reference numbers and reference symbols clarify correspondences and bridges between the technical matters described in the claims and the technical matters of the embodiments or examples. Such correspondence / bridge does not mean that the technical matters described in the claims are limited to the technical matters of the embodiment or the examples.

The ultrasonic flaw detector according to the present invention comprises an ultrasonic transmitter (11) having an effective ultrasonic emission point (P) and an ultrasonic receiver (12) having an effective ultrasonic incidence point (Q). It is configured. The shortest line segment that connects one (P) of the ultrasonic wave effective emission point (P) and the ultrasonic wave effective incidence point (Q) and any one point (R) of the molten metal (3) is to be welded. The body (2) and the molten metal body (3) are intersected with one of the facing surfaces (9) of the facing surfaces. Since such an ultrasonic wave incident path crosses the joint surface (9) and is incident on the flaw detection point (R), if the flaw detection point is located at a deep position, the ultrasonic wave is generated in the molten metal body (3). The length of the ultrasonic path that passes through is shorter than that of a conventional ultrasonic path that directly enters the molten metal from the outer surface of the molten metal and reaches the flaw detection point (R). The shortening of the ultrasonic path in the heat-modified metal melt improves the S / N ratio of the detection signal.

The shortest line segment connecting the other (Q) of the effective ultrasonic wave emission point (P) and the effective ultrasonic wave incident point (Q) and the arbitrary one point (R) described above is the opposite surface. It intersects with the other joint surface (8). As described above, the ultrasonic path in the molten metal of ultrasonic waves reflected at the flaw detection point (R) is shortened.

The molten metal body (3) extends in one direction, and the ultrasonic wave effective emission point (P) and the ultrasonic wave effective incidence point (Q) move in one direction. By such scanning, flaw detection can be continuously performed in a deep search area. A particularly effective search is possible when searching for the presence of a defect at a deep position from the outer surface to the inner surface, where the welded body (2) and the molten metal body (3) form a cylindrical body. If the cylindrical body is a cylindrical container or pipe for piping, the search is effectively executed. One such direction is the circumferential direction and the metal melt (3) is a ring. The ring includes a disc as its special form.

The molten metal body (3) is a metal that easily generates ultrasonic noise. Such metals are austenitic stainless steels or Inconel alloys. The inventor has found that a welded portion which is a molten metal body formed of such a metal is likely to generate noise in ultrasonic waves.

The object to be welded and the molten metal are pipes for piping. It is difficult to introduce ultrasonic wave transmitting / receiving equipment into a thin pipe, and its inner diameter is small enough to allow flaw detection only from the outside.

In the ultrasonic flaw detection method according to the present invention, a step of transmitting ultrasonic waves to the joint surface of welding, a step of receiving ultrasonic waves, and a defect in the welded portion based on the ultrasonic waves received at the step are detected. It is particularly useful when the molten metal has an annular shape.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Corresponding to the drawings, an embodiment of an ultrasonic flaw detector according to the present invention is illustrated with respect to a butt portion of a cylindrical container. As shown in FIG. 1, the cylindrical container 1 is formed of two opposed cylindrical portions 2 that are axially opposed to each other, and a gap between opposed surfaces of the opposed cylindrical portion 2 is filled with a molten metal portion 3 by butt welding. Formed. The following embodiment will be described as an axial direction being a vertical direction for convenience of expression. The opposed cylindrical portion 2 is
It is formed of a lower cylindrical portion 2-1 and an upper cylindrical portion 2-2.

The shape of the molten metal portion 3 is approximately trapezoidal on a cross section taken along a plane including the axis. The lower cylindrical portion 2-1 is
It has a lower outer cylindrical surface 4-1 and a lower inner cylindrical surface 4-2. The upper cylindrical portion 2-2 has an upper outer cylindrical surface 5-1.
And an upper inner cylindrical surface 5-2. Metal part 3
Is an outer molten metal portion surface 6 that is substantially flush with the lower outer cylindrical surface 4-1 and the upper outer cylindrical surface 5-1; the lower inner cylindrical surface 4-2 and the upper inner cylindrical surface 5-2. And an inner molten metal portion surface 7 that is substantially coplanar. The opposed cylindrical portion 2 and the molten metal portion 3 share a first joint surface 8 and a second joint surface 9 which are butt opposed surfaces. The molten metal portion 3 is used as a weld metal in a welding region formed as a substantially trapezoidal ring in cross section surrounded by an outer molten metal portion surface 6, an inner molten metal portion surface 7, a first joint surface 8 and a second joint surface 9. Match. First joint surface 8 and second
The joint surface 9 is orthogonal to the outer molten metal portion surface 6 and the inner molten metal portion surface 7, or the first joint surface 8 and the second joint surface 9 are both the outer molten metal portion surface 6 and the outer molten metal portion surface 6. It is oblique to the inner molten metal portion surface 7, or only one of them crosses the outer molten metal portion surface 6
Alternatively, the inner molten metal portion surface 7 is obliquely crossed.

The ultrasonic flaw detector comprises an ultrasonic transmitter 11 and an ultrasonic receiver 12. Ultrasonic transmitter 11
The ultrasonic receiver 12 has a physically symmetric structure similar to the relationship between the radio wave transmitting antenna and the radio wave receiving antenna.
The ultrasonic transmitter 11 and the ultrasonic receiver 12 can exchange the transmitting side and the receiving side with each other. Ultrasonic transmitter 1
The ultrasonic wave emission point region P of No. 1 does not exist on the outer molten metal portion surface 6 (upper) but exists on the upper outer cylindrical surface 5-1 (upper). The ultrasonic receiving point area Q of the ultrasonic receiver 12 is
The lower outer cylindrical surface 4 that does not exist on the outer molten metal portion surface 6 (upper)
-1 (above). The ultrasonic wave emission point-like region (ultrasonic wave effective emission point) P is axially opposed to the ultrasonic wave reception point-like region (ultrasonic wave effective incidence point) Q across the outer molten metal site 6.

In other words, the shortest line connecting the ultrasonic wave emission point area P and the ultrasonic wave reception point area Q is on the outer molten metal site surface 6. Both points of the ultrasonic emission point-like region P and the ultrasonic reception point-like region Q can be arranged on the upper inner cylindrical surface 5-2 and the lower inner cylindrical surface 4-2. In this case, the ultrasonic wave emission spot-like region P is axially opposed to the ultrasonic wave reception spot-like region (effective ultrasonic wave incident point) Q across the inner molten metal site 7.
Alternatively, the ultrasonic wave emission spot-like region P may be arranged on the upper outer cylindrical surface 5-1 and the ultrasonic wave reception spot-like region Q may be arranged on the lower inner cylindrical surface 4-2. In this case, the ultrasonic wave emission spot-like region P faces the ultrasonic wave reception spot-like region Q across the molten metal portion 3.

FIG. 1 shows a target area 13 for welding defect inspection. The welding defect inspection target area (the trapezoidal ring having the above-described cross-section) is a cross-sectional area in a region far from the outer molten metal portion surface 6 and closer to the inner molten metal portion surface 7 and deeper than the outer molten metal portion surface 6. It is assumed to be a rectangular ring area. In the present case, the ultrasonic wave emission point region P and the ultrasonic wave reception point region Q
Respectively exist on the upper outer cylindrical surface 5-1 and the lower outer cylindrical surface 4-1. Weld defect inspection target area 13
Is scanned continuously or intermittently in the Y direction by scanning movement of the ultrasonic emission point-shaped region P and the ultrasonic reception point-shaped region Q in the circumferential direction (Y direction as the circumferential direction of the cylindrical coordinate system). It

FIG. 2 shows a positional relationship in which the ultrasonic wave emitting point region P and the ultrasonic wave receiving point region Q are integrally moved in the circumferential direction and stopped or fixed at a certain circumferential position. . The positional relationship is shown by a cross-section perpendicular to the circumference cut by a plane including the axis. A point region of the welding defect inspection target region 13 is typically shown by a point R. The line segment PR is
The point S intersects the second joint surface 9. The line segment QR is the first
It intersects with the joint surface 8 at a point T. Directional line segment PR (P
→ R) coincides with the incident-side effective ultrasonic wave path. The directional line segment RQ (R → Q) coincides with the reflection-side effective ultrasonic wave path.

In the known device, a known corresponding point P'corresponding to the ultrasonic wave emitting point area P and a known corresponding point Q'corresponding to the ultrasonic wave receiving point area Q are present on the outer molten metal portion surface 6. is doing. Point P'that minimizes (segment P'R + segment Q'R)
And point Q'exists as one point M on the outer molten metal site surface 6. A point P or a point Q that is shorter than (line segment MR + line segment MR) cannot exist on the outer molten metal site 6. In the case of the illustrated example, line segment SR + line segment TR <2, line segment MR <(line segment P′R + line segment Q′R)

Particularly when austenitic stainless steel or Inconel alloy is used as the molten metal portion 3, abnormal ultrasonic noise due to material change due to the influence of welding heat is likely to occur. In the present invention, noise may occur in the in-melt metal incident-side ultrasonic path SR and the in-metal reflection-side ultrasonic path RT due to the propagation of abnormal ultrasonic waves. In the known art,
Ultrasonic path P'R on incident side in molten metal and ultrasonic path R on reflective side in molten metal
With Q ′, noise may occur due to the propagation of abnormal ultrasonic waves. The abnormal noise occurrence probability of the present invention is lower than the known art abnormal noise occurrence probability. Such reduction in noise occurrence probability can effectively suppress deterioration in flaw detection accuracy. If the probability of noise occurrence is reduced, the SN ratio of the detection signal is improved, and the microdefect detection performance for detecting microscopic defects is improved.

FIG. 3 shows another embodiment of the ultrasonic flaw detector according to the present invention. In the present embodiment, the welding target is two square pole metal rods 2-1 and 2-1 extending in a straight line.
Is. The molten metal portion 3 ′ occupies a cubic area or a rectangular area. As the flaw detection search area, a first linear search area 13'-1 and a second linear search area 13'-2 are shown. The first linear search area 13'-1 and the second linear search area 13'-2 are orthogonal to each other. First exploration point R
1 is above the first linear survey area 13'-1. First
The ultrasonic effective emission point P1 is located on the one side first scanning line 14. The first ultrasonic effective incident point Q1 is on the other side first scanning line 15. The first effective ultrasonic wave emission point P1 and the first effective ultrasonic wave incident point Q1 are on the same plane or substantially the same plane. The first scanning line 14 on one side is parallel to the first scanning line 15 on the other side.

The second search point R2 is the second linear search area 1
Above 3'-2. The second ultrasonic effective emission point P2 is located on the one side second scanning line 16. The second ultrasonic effective incident point Q2 is on the other side second scanning line 17. The second effective ultrasonic wave emission point P2 and the second effective ultrasonic wave incident point Q2 are on the same plane or substantially the same plane. The second scanning line 16 on one side is
It is parallel to the second scanning line 17 on the other side. The one side first scanning line 14 is orthogonal to the one side second scanning line 16. Line segment P
1R1 and the line segment P2R2 both intersect the one side joint surface 18, and both the line segment R1Q1 and the line segment R2Q2 intersect the other side joint surface 19. The one side joint surface 18 and the other side joint surface 19 are parallel to each other.

The welding area sandwiched between the two columnar bodies does not have a large difference between the horizontal length, the vertical length and the depth length as in the case of a cube, and the linear region to be measured is close to the surface and When measuring from the surface on the far side with higher accuracy, when measuring from the surface on the far side to the linear region to be measured,
The measuring method according to the present invention can be effectively used.

FIG. 4 shows still another embodiment of the ultrasonic flaw detector according to the present invention. In the present embodiment, the welding target is two cylindrical metal rods 2 ″ − extending in a straight line.
One and two. The molten metal portion 3 ″ occupies a cylindrical body region. An annular inspection region 13 ″ is illustrated as the flaw detection inspection region. The search point R is on the annular search region 13 ″. The ultrasonic wave effective emission point P is on the one side scanning circle 21. The ultrasonic wave effective incident point Q is on the other side scanning circle 22. The joining surfaces on both sides facing each other are circular surfaces 23 and 24. The line segment PR intersects the joining surface 23, and the line segment RQ intersects the joining surface 24.

The shortening of the ultrasonic path by the straight line connecting the output point P and the search point R penetrating the one-side joint surface and the straight line connecting the incident point Q and the search point R penetrating the other-side joint surface, Reduce the amount of noise generated. By measuring the same point R from the far side and the near side, it is possible to perform flaw detection with higher accuracy.

In the ultrasonic flaw detector according to the present invention, the pipe to be welded is difficult to introduce a measuring instrument into,
It can be applied particularly effectively when it is a solid body. Ultrasonic transmitters / receivers placed outside these pipes detect defects in the area on the inner peripheral surface side of the pipes, thereby detecting minute defects that could not be detected by conventional methods. Therefore, it becomes possible to detect a defect that could be detected in the past with higher accuracy.

FIG. 5 shows diffused propagation of ultrasonic waves when the welding target area is an open plate and an annular body.
An ultrasonic wave that does not go straight from the point P to the point Q toward the vicinity of the point R is reflected by the plane S and diffuses in the in-plane direction. The degree of diffusion is greater in the case where the point F is largely displaced in the circumferential direction and reflected in the cylindrical surface S ′ than when it is reflected in the plane S. If the deviation from the point R is increased even slightly, the degree of diffusion will be dramatically increased. When the diffusion occurs only inside the molten metal and the propagation distance is long, the noise picked up by the diffusion ultrasonic waves in the martensitic stainless molten metal becomes synergistically increased. The total amount of noise picked up is synergistically low, as a synergistic result of the large directional diffusion and the short propagation distance in the melt. The present invention is therefore particularly useful for flaw detection of an annular metal body that connects two cylindrical bodies (eg pipe, tank) in the axial direction.

[0028]

The ultrasonic flaw detector and the ultrasonic flaw detection method according to the present invention can detect minute defects which could not be detected by the conventional method, and further can detect them. It has become possible to detect defects that have occurred more accurately.

[Brief description of drawings]

FIG. 1 is an oblique-axis projection view showing an application target of an ultrasonic flaw detector according to the present invention.

FIG. 2 is a sectional view showing an embodiment of an ultrasonic flaw detector according to the present invention.

FIG. 3 is an oblique-axis projection view showing linear propagation of ultrasonic waves.

FIG. 4 is an oblique-axis projection view showing another embodiment of the ultrasonic flaw detector according to the present invention.

FIG. 5 is a cross-sectional view showing diffused propagation of ultrasonic waves.

[Explanation of symbols]

2 ... Object to be welded 3 ... Fused metal 8 ... Bonding surface 9 ... Bonding surface 11 ... Ultrasonic transmitter 12 ... Ultrasonic receiver P ... Effective output point of ultrasonic waves Q: Effective point of ultrasonic wave incidence R: flaw detection point

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor, Shoji Suyama             2-8-19 Niihama, Arai-cho, Takasago-shi, Hyogo             Takaryo Engineering Co., Ltd. F-term (reference) 2G047 AA07 AB01 AB02 AB07 BA02                       BB02 BC09 CA01 DB17 EA04                       GF34

Claims (9)

[Claims] 1. An ultrasonic transmitter having an ultrasonic effective emitting point and an ultrasonic receiver having an ultrasonic effective incident point, wherein one of the ultrasonic effective emitting point and the ultrasonic effective incident point is provided. An ultrasonic flaw detection device in which a shortest line segment connecting the point and any one point of the molten metal intersects with one of the facing surfaces where the body to be welded and the molten metal are bonded. 2. A shortest line segment connecting the other one of the ultrasonic wave effective emission point and the ultrasonic wave effective incident point and the arbitrary one point intersects with the other joint surface of the facing surfaces. The ultrasonic flaw detector according to claim 1. 3. The ultrasonic flaw detector according to claim 1, wherein the molten metal extends in one direction, and the ultrasonic effective emission point and the ultrasonic effective incident point move in the one direction. 4. The ultrasonic flaw detector according to claim 1, wherein the body to be welded and the molten metal form a cylindrical body. 5. The ultrasonic flaw detector according to claim 4, wherein the cylindrical body is a pipe for piping. 6. The name according to claim 5, wherein said one direction is a circumferential direction and said molten metal forms a closed ring. 7. The molten metal is a metal that easily generates ultrasonic noise, and the metal is selected from the group consisting of austenitic stainless steel and Inconel alloy.
The ultrasonic flaw detector according to claim 6, which is an element. 8. The molten metal is a metal that easily generates ultrasonic noise, and the metal is selected from the group consisting of austenitic stainless steel and Inconel alloy.
The ultrasonic flaw detector according to claim 1, which is an element selected from claims 1 to 5. 9. A method comprising: transmitting an ultrasonic wave to a joint surface of welding; receiving the ultrasonic wave; and detecting a defect in a welded portion based on the ultrasonic wave received in the step. The ultrasonic flaw detection method, wherein the joint surface is an annular surface closed in the circumferential direction.