JP3792224B2 - Ultrasonic flaw detection method for rebar welded joints - Google Patents

Description

  The present invention relates to a method for flaw-detecting a welding defect in a reinforcing bar weld joint with ultrasonic waves.

The ultrasonic flaw detection test for welded joints of deformed steel bars for reinforced concrete (hereinafter simply referred to as “rebars”) is performed in accordance with “Ultrasonic flaw detection test method for gas pressure welds of reinforcing bars” stipulated in JIS Z 3062 Has been.
This ultrasonic flaw detection test is performed by K-scanning using the bevel two-probe method.
As shown in FIG. 7 and FIG. 8, the K-scan of the oblique angle two probe method means that two ribs (11) formed over the entire length of the reinforcing bar at the symmetrical position of the outer surface of the reinforcing bar (1). (12) A pair of probes (4) and (4a) are arranged on the top.
One probe (4a) is placed on one fixed point P1 among a plurality of fixed points set on the rib (12), and the other probe (4) is placed on the other rib (11). Slide.

As shown in FIG. 9, the probe (4) (4a) is covered with a synthetic resin shoe (41) at a portion in contact with the rib (11) (12). ) To form a groove (43). The probe (4) can be slid straight along the rib (11) by placing the groove bottom of the shoe (41) against the rib (11) and using the groove (43) as a guide.
When there is a defect in the weld joint (2), the ultrasonic wave emitted from one probe is reflected by the defect and received by the other probe.
The probe (4a) on the fixed point side is sequentially moved to the other fixed points P2 and P3, and the flaw detection inspection is performed at each fixed point in the same manner as described above.
JIS Handbook (JIS Z 3062)

As described above, when the probe (4) is slid straight along the rib (11), the flaw detection area (22) of the weld joint (2) indicated by the two- dot chain line in FIG. as centered virtual plane F1 passing through the top of the axis and two ribs (11) (12), limited to the region of the ultrasonic transmitting and receiving width of the probe (4) (4a) at its opposite sides.
The width of ultrasonic transmission / reception of the probes (4) and (4a) used in this type of flaw detection is as narrow as about 5 mm. In addition, the backing metal (30) that prevents the weld metal from being burned out is formed by bending a rectangular iron plate having a length of about 50 mm and a width of about 45 mm in a semicircular shape in the width direction. (30) was in the way, and the probe (4a) at a fixed position could only be approached by about 20 mm from the weld joint (4).
From the above, as indicated by a two-dot chain line in FIG. 8, there is a problem that the flaw detection possible area of the welded joint portion (2) has a substantially rectangular shape, and the outside of the area is a flaw detection dead angle.
The present invention clarifies a flaw detection method for a reinforced welded joint that can solve the above problems.

In the present invention, one of the reinforcing bars (1) on one side of the welded joint (2) between the reinforcing bars (1) and (1a) having ribs (11) and (12) formed over the entire length at opposite positions on the diameter line . One ultrasonic probe (4) is placed on the rib (11), the other ultrasonic probe (4a) is placed on the other rib (12), and one probe (4) is placed on the rib. The welded joint part (2) is slid in the direction of (11) while the ultrasonic wave transmitted from one probe is reflected by the defect of the welded joint part (2) and received by the other probe. In the flaw detection method for performing the flaw detection, one probe (4) is slid on the rib (11) while the other probe (4a) is in a fixed position, and both probes (4) (4a ) Is swung in the same direction within the plane F2 orthogonal to the virtual plane F1 passing through the center of the reinforcing bar (1) and the tops of the two ribs (11) and (12), thereby expanding the flaw detection area. Ultrasonic flaw detection method for rebar welded joints.

The two probes (4) and (4a) are necked in the same direction in the two planes F2 and F2 perpendicular to the virtual plane F1 passing through the center of the reinforcing bar (1) and the tops of the two ribs (11) and (12). While swinging , one probe (4) slides on the rib (11). By swinging both the probes (4) and (4a), it is possible to widen the transmission / reception area width of the ultrasonic wave, and the flaw detection in the wide section of the weld joint (2) becomes possible.

Reinforcing bar, welded joint and backing metal FIG. 1 shows the vicinity of the welded joint (2) of the reinforcing bar (1).
Reinforcing bars form ribs (11) and (12) over the entire length at opposite positions on the diameter line, and nodes (13) and (13) are arranged at substantially equal intervals in the axial direction across the ribs (11) and (12). Is protruding. The node (13) has a substantially triangular cross section.
An arc-shaped backing metal (3) is applied to the welded joint (2) so as to straddle between the ends of both reinforcing bars (1) and (1a), and to enclose approximately half the circumference of the weld groove (21). In this state, the groove (21) is formed by gas shield arc welding.
The backing metal (3) prevents the weld metal from dripping, and the groove (21) is filled with the weld metal and solidified.
The width of the backing metal (3) needs to be larger than the groove width in order to prevent the weld metal from being burned out, but in order to eliminate the flaw detection blind spot, the probe (4) (4a) needs to be close to the weld joint (2) to about 5 mm, and for this purpose, the backing metal (3) is preferably as narrow as possible.

Backing strip of Example (3), as shown in FIG. 2 and a half arcuate narrow backing strip body (31), arm piece integrally from both side edges of the body (32) (32) Protrusively formed.
As shown in FIG. 6, the arm piece (32) rides on the nodes (13) and (13) of the reinforcing bars (1) and (1a) so as to be parallel to the axis of the reinforcing bars (1) and (1a). In order to prevent the backing metal main body (31) from being inclined with respect to the groove (21). The end of the backing metal body (31) is temporarily attached to the reinforcing bars (1) (1a) by welding.
The backing metal body (31) of the embodiment has a width length obtained by adding about 9 mm to the groove (21) width of the reinforcing bar (1). The arm piece (32) of the backing metal (3) can apply the probe (4) (4a) to the edge of the backing metal body (31) on the reinforcing bar rib (11) (12). In the same manner, the probe is set at a position out of the transition path of the probes (4) and (4a) on the reinforcing bar ribs (11) and (12).
The width center of the backing metal body (31) is almost coincident with the center of the groove (21) width, and if the backing metal (3) is temporarily attached to the reinforcing bar (1), the rib (11) (12) The probe (4) (4a) can be brought close to 4.5 mm from the groove by sliding up.

Probe FIG. 1 shows a state in which a pair of probes (4) and (4a) are arranged on a reinforcing bar (1) on one side from a weld joint (2).
The probes (4) and (4a) are capable of transmitting and receiving ultrasonic waves, respectively, and, as will be described later, a plurality of fixed points P1, with one probe (4a) set on the rib (12), It is placed on one fixed point of P2 and P3. The other probe (4) is placed on the other rib (11).
The probe (4) (4a) is 5Z5 × 5A70, and the performance is in accordance with Appendix 3 of JIS Z 3062. The contactor has a function of transmitting and receiving ultrasonic waves in a range of 5 mm × 5 mm square with a refraction angle of 70 ° with respect to a plane perpendicular to the axis of the reinforcing bar (1).
As shown in FIG. 9, the conventional probe used for ultrasonic flaw detection of the welded joint portion (2) of the reinforcing bar includes a shoe (41) made of synthetic resin in contact with the reinforcing bar ribs (11) and (12) as described above. The grooves (43) into which the ribs (11) and (12) are fitted are formed. In the present invention, as shown in FIG. 3, the contact surface (42) of the shoe (41) with the reinforcing bar ribs (11) and (12) is formed. ) Is a flat surface.

  Among a plurality of fixed points P1, P2, P3 on the reinforcing bar rib (12), the first fixed point P1 is a position where the probe (4a) is in contact with the edge of the backing metal body (31), the second fixed point P2 or less. Is a position moving away from the first fixed point P1 by 10 mm in order. The last fixed point is a position 2.5D away from the end of the backing metal body (31), where D is the distance between the tops of the ribs (11) and (12) of the reinforcing bar (1).

The two probes (4) and (4a) are connected to a flaw detector (not shown).
Flaw detector, ultrasonic were found emanating from one probe is welded joint portion when there is a defect (2), the echoes received and reflected on the defect in the other probe pulse It is a well-known device that determines whether or not the welded joint portion is acceptable based on the level and warns with a sound or the like if the level is not acceptable.

Flaw detection procedure The flaw detection procedure is:
i) Setting the reference level by transmission scanning
ii) 2 probe K scan + flaw detection by swinging
iii) There are three pass / fail judgments.

(1) Setting the reference level
1) In FIG. 6, the distance Y between the probes (4) and (4a) is derived from Y≈D · tan θ1.
θ1 is a refraction angle of 70 ° ± 2 °.
2) Place the two probes on the reinforcing bar ribs (11) and (12) with a distance Y between the probes obtained in 1). A contact medium (not shown) is applied to the reinforcing bar ribs 11 and 12 in the vicinity of the probes 4 and 4a. The contact medium prevents a gap from being generated between the probe (4) (4a) and the reinforcing bar ribs (11) (12). The contact medium of the embodiment has a concentration of 75% or more. A glycerin aqueous solution.
3) Scan the probes (11) and (12) slightly back and forth to find the point where the transmitted pulse is maximum. The maximum value of the transmitted pulse is the reference level.

(2) 2 probes (4) (4a) K scanning + flaw detection by swinging
1) On the ribs (11) and (12) on both sides of the welded joint (2), remove rust and other similar contact media over a range of about 2.5D from the welded joint (2). Apply.
2) Place the probe (4a) held in one hand on the first fixed point P1 on the reinforcing bar rib (12). This probe (4a) is called a fixed position probe (4a). The probe (4) held in the other hand is placed on the other rib (11) at a position 2.5D away from the backing metal body (31). This probe (4) is called a slide probe.
3) An ultrasonic wave is emitted from the fixed position probe (4a). The slide probe (4) is on the ultrasonic wave receiving side.
Slide the slide probe (4) toward the weld joint (2). At this time, while sliding the probe (4) is slid, position feeler element (4a) remains in place, the two probes a (4) (4a), the center and 2 rebar (1) With respect to the virtual plane F1 passing through the tops of the two ribs (11) and (12), the necks are simultaneously oriented in the same direction in the two planes F2 and F2 perpendicular to the virtual plane F2 and including the ribs (4) and (4a), respectively. Swing ( also expressed as rotation ). The swing angle may be such that the ultrasonic transmission / reception region can cover a cross section orthogonal to the axis of the weld joint (2).
Since the contact surfaces of the probes (4) and (4a) with the reinforcing bar ribs (11) and (12) are flat surfaces, as described above, the probes (4) and (4) ( 4a) can be swung smoothly, and even if it is swung , there is no gap between the shoe (41) and the reinforcing ribs (11) and (12).
When the groove (43) corresponding to the reinforcing bar ridge (11) (12) is formed in the shoe (41) as in the conventional probe (4) (4a) shown in FIG. In addition, even if the probe (4) (4a) is swung on the reinforcing bar ridge (11) (12), the ridge is caught in the groove (43) and cannot be swung smoothly. . Further, when the head is swung , a gap is formed between the shoe (41) and the protrusion by the groove (43), and the ultrasonic wave is reflected at that portion, so that correct flaw detection cannot be performed.
As shown in FIG. 5, if the reinforcing bar has a general thickness for reinforced concrete, the swing angle θ2 of the probes (4) and (4a) passes through the tops of the two ribs (11) and (12). One side is within 30 ° with respect to the virtual plane F1. If it exceeds 30 °, the ultrasonic wave may be reflected on the slope of the reinforcing bar node (13) and recognized as a defect.
The forward / backward scanning speed should not be too fast. A value of 60 mm or less per second is appropriate.
If there is no defect in the welded joint (2), the ultrasonic wave passes through the welded joint (2) and the receiving probe (4) (4a) does not react.
When there is a defect in the weld joint (2), the ultrasonic wave is reflected by the defect and the receiving probe catches it (the reflected ultrasonic wave is called “echo”). Find where the echo pulse height is maximum.
4) When the inspection for the first fixed point P1 is completed, the fixed position probe (4a) is moved onto the second fixed point P2, and the inspection is performed in the same manner as described above. The inspection similar to the above is sequentially performed for the third fixed point P3 and thereafter.
If there is a defect in the weld joint (2), the ultrasonic wave can be reflected by the defect and received by the receiving probe (4) .
5) The above operations 2) to 3) are also performed on the ribs (11) and (12) of the opposite reinforcing bar (1) of the welded joint (2).

(3) Pass / fail judgment If the pulse height of the echo reflected by the defect of the weld joint (2) obtained in (2) above is less than a predetermined pass / fail judgment level, the test is passed. If so, it will be rejected. If a pulse height equal to or higher than a failure determination level on at least one of the reinforcing bars (1) is detected with respect to the welded joint, the welded joint part (2) is rejected. When the pulse height of the echo on the reinforcing bar (1) on both sides of the welded joint (2) is less than the acceptance judgment level, the joint is accepted.
As described above, the flaw detection apparatus according to the embodiment warns with a sound or the like if it is above the reject level.

  The above description of the embodiments is for explaining the present invention, and should not be construed as limiting the invention described in the claims or reducing the scope thereof. In addition, the configuration of each part of the present invention is not limited to the above embodiment, and various modifications can be made within the technical scope described in the claims.

  For example, an ultrasonic wave can be emitted from the slide probe (4) and an echo can be caught by the fixed position probe (4a).

It is explanatory drawing which shows the position of the probe at the time of a flaw detection start. It is a slope view of the backing metal used in the present invention. It is a slope view of the probe used in the present invention. It is sectional drawing which follows FIG. 1A-A line. It is explanatory drawing of the swing of a probe. It is explanatory drawing which measures the maximum value of the transmitted pulse of an ultrasonic wave. It is explanatory drawing of the conventional 2 probe K scanning method. It is sectional drawing which follows FIG. 7A-A line. It is a slope view of the conventional probe.

Explanation of symbols

1 Rebar
11 Ribs
12 Rib 2 Welded joint 4 Probe
4a transducer

Claims (5)

A position facing diameter line, the ribs over the entire length (11) (12) rebar (1) forming a (1a) How to the welded joint portion (2) from one side of one of the ribs of the reinforcing bar (1) (11) One ultrasonic probe (4) of the pair of ultrasonic probes (4) and (4a) is placed on the other, and the other ultrasonic probe (4a) is placed on the other rib (12) . While sliding one probe (4) in the direction of the rib (11), the ultrasonic wave transmitted from one probe is reflected by a defect in the welded joint (2), and the other probe In the flaw detection method for flaw detection of the welded joint (2) by receiving, one probe (4) slides on the rib (11) while the other probe (4a) is in place. Both probes (4) and (4a) are swung in the same direction in a plane F2 orthogonal to a virtual plane F1 passing through the center of the reinforcing bar (1) and the tops of the two ribs (11) and (12). Ultrasonic flaw detection method for rebar welded joints characterized by expanding the flaw detection area . A plurality of points at different distances from the welded joint (2) are fixed points. One probe (4a) slides on the fixed point and the other probe (4) slides on the rib (11). probe (4) (4a) is swinging performs flaw detection for one fixed point, the ultrasonic testing method of reinforcing bars welded joint portion according to claim 1 for successively testing in the same manner for the remaining fixed point. To the welded joint (2), a backing metal (3) applied to the groove (21) of the reinforcing bar to prevent the weld metal from being melted is fixed, and the backing metal (3) The narrow arcuate backing metal body (31) along the arc of the weld joint (2), and the arm pieces (32) (32) extending in the longitudinal direction of the reinforcing bar from both side edges of the backing metal body (31) ), The arm pieces (32) and (32) are located away from the rebar ribs (11) and (12), and the ultrasonic probes (4) and (4a) are on the backing metal body (31) side. The ultrasonic flaw detection method for a reinforcing bar welded joint according to claim 1 or 2, wherein the ultrasonic flaw detection method is fixed so as to be able to come into contact with an edge . The surface (42) in contact with the reinforcing bar ribs (11) (12) of the probe (4) (4a) is a flat surface parallel to the virtual surface F2 for swinging the probe (4) (4a). Item 4. The ultrasonic flaw detection method for a reinforcing bar welded joint according to any one of Items 1 to 3. The reinforcing bar according to any one of claims 1 to 4, wherein after the ultrasonic flaw detection is performed on the reinforcing bar (1) on one side from the weld joint (2), the ultrasonic flaw detection is similarly performed on the other reinforcing bar (1a). Ultrasonic flaw detection method for welded joints.

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