JPH0299857A - Ultrasonic flaw detector for weld part of seam welded steel pipe - Google Patents

Abstract

PURPOSE:To enable detection of flaws even with a small diameter size immediately after a welding by providing an array contact under a seam welded steel pipe at the right angle to the direction of carrying the seam welded steel pipe. CONSTITUTION:A water tank 11 for storing an acoustic coupling water 5 is provided along a pass line of a tube 1 to be inspected on the outgoing side of a welding machine and an array probe 4 comprising a plurality of vibrators at the right angle to the pass line in the center of the bottom surface thereof. First, a deviation position DELTAl1 is determined from a vertical line CO to an outer diameter D of the tube 1 to be inspected using a specified formula to set a position of two horizontally symmetrical sets of vibrator groups 4i of a probe 4 on a controller 20. A copying mechanism 12 is operated to position the water tank 11 so that the underside of the tube 1 immerses. With such an arrangement, as the tube 1 is transported, the tube 1 is mutually excited horizontally with the vibrator groups 4i selected to the probe 4 through the coupling water 5 and any defect at a weld part causes a peak echo. The peak echo is received separately with the two sets of vibrator groups to determine the presence of a defect with the controller 20.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an ultrasonic flaw detection device for welded parts of ERW steel pipes, and is particularly suitable for detecting defects in the pipe axis direction of welded parts of ERW steel pipes. The present invention relates to a suitable ultrasonic flaw detection device for welded parts of ERW steel pipes.

<Prior Art> Generally, an ultrasonic angle flaw detection method is used to detect defects in the pipe axis direction in a welded portion of an electric resistance welded steel pipe. In this method, ultrasonic waves are applied obliquely to the inspection surface of the tube to be inspected, which is an ERW steel tube, and defects on the inner and outer surfaces of the tube to be inspected and internal defects are detected from the reflected waves that are reflected by the defects. .

In addition, in order to detect defects over the entire length of the welded part of the ERW steel pipe, an ultrasonic probe (hereinafter simply referred to as a probe) is scanned parallel to the welded part of the pipe to be inspected. On the other hand, means for propagating the ultrasonic beam at right angles is used.

However, in this type of ultrasonic angle flaw detection method, as the distance from the point where the ultrasonic beam is incident to the defect position changes, that is, the distance from the probe to the defect position changes, the echo from the defect increases. It is known that the height varies greatly, as shown in FIG. This is disclosed in, for example, FIG. 2 of Japanese Unexamined Patent Publication No. 55140148. Therefore, it is difficult to determine the reference echo height, and if the distance from the probe to the defect position changes, there is a problem that accurate flaw detection becomes difficult.

As a means to solve such problems, for example,
As disclosed in Japanese Patent No. 7-8420, the twist amount of the welded portion and the length of the pipe to be inspected are preset,
Thereafter, the length of the current position is sequentially detected, the amount of deviation of the probe from the welded part is calculated, and the welded part is followed. , multiple transmitter/receiver coils are attached to the probe along the circumferential direction of the tube to be inspected, and the received signal levels of these transmitter/receiver coils are determined in chronological order to determine the relative position of the weld and the probe. A method has been proposed in which the weld is followed by maintaining a constant relationship.

<Problems to be Solved by the Invention> However, the above-mentioned conventional examples have the following problems.

■ If the distance between the probe and the defect location changes, the echo height as described above will change significantly, so it is necessary to accurately follow the weld.

■ Also, the appearance position of the beak echo differs depending on the outer diameter and thickness of the tube to be inspected.

That is, as shown in FIG. 6, the probe 2 is mounted, for example, at a point P on the outer surface of the pipe I to be inspected with an outer diameter and a pipe thickness t, facing the center point O, and detects defects in the weld W. Assuming that the ultrasonic beam 3 is incident on 1a at a refraction angle θ, η·1−U, the appearance position I7 of the peak echo is expressed by the following equation (1).

L=N- to -t-j, an θ, ----------
(1) Here, N is a coefficient (N-3
10,5), k is a correction coefficient determined by the refraction angle θ and L/D.

As can be seen from this equation, the appearance position of the beak echo of the ultrasonic wave 3 varies depending on the outer diameter and tube thickness of the tube to be inspected 1. The distance between the feeler 2 and the weld W must be adjusted each time.

■ Furthermore, when placing the probe on the inspection surface of the tube to be inspected, acoustic coupling water such as water or water containing Soriple oil is required. When inspecting a test tube, the acoustic coupling water cools the welded area, which has an adverse effect on the quality of the welded area.

■Furthermore, in the case of small-diameter test tubes, when installing the probe on the test surface of the test tube, the adjustment of the physical positional relationship between them is extremely delicate. it takes time.

The present invention has been made to solve the above-mentioned problems, and uses ultrasonic waves to detect flaws in welded parts of ERW steel pipes, which can detect flaws even immediately after welding and even in small diameter pipes. The purpose is to provide flaw detection equipment.

Means for Solving the Problems> The gist of the present invention is to provide a water tank for storing acoustic coupling water provided at the bottom of the pass line of an ERW steel pipe conveyed in the longitudinal direction, and a water tank for storing acoustic coupling water. and an array probe consisting of a plurality of vibrators provided on the bottom of the water tank in a direction perpendicular to the conveying direction of the electric resistance welded steel pipe. This is an ultrasonic flaw detection device for welded steel pipes.

<Operation> The principle of the present invention will be explained below using FIG. 4.

As shown in FIG. 4(a), an array probe 4 consisting of a plurality of transducers is installed at the bottom of the pipe 1 to be inspected, which is transported with the weld W in the top position, and an acoustic coupling water 5, select any two symmetrical transducer groups 4m and 4n to be excited according to their outer diameters, and oscillate the ultrasonic beams 3m and 3n. Propagate alternately into walls IA and IB.

Now, as shown in FIG. 4(b), a vibrator 41 is selected that corresponds to a position I that is deviated by Δft from a vertical line C8 passing through the center point O of the tube 1 to be inspected, which has a large outer diameter and a thick wall. Assuming that the ultrasonic beam 31 is oscillated parallel to the vertical line C6, the angle of the ultrasonic beam 31 with respect to the center line C+ passing through one point of the tube 1 to be inspected, that is, the incident angle θ1 is expressed by the following equation. Given.

sin θ, -2・ΔI! ,, /D -11---
−・−−−−−(2) Also, the ultrasonic beam 3 at this time
The refraction angle θ of 1 into the tube 1 to be inspected is determined by the following equation (3).

sin θr = (cr/C+) sin
θ, -111-(3) Here, c8 is the incident sound velocity, and cr is the refracted sound velocity, both of which are constant depending on the material of the tube 1 to be inspected and the acoustic coupling water 5.

From these equations (2) and (3), the outer diameter of the pipe to be inspected 1,
If the refraction angle θ is constant depending on the wall thickness, the incident angle θ,
is uniquely determined, and therefore, the deviation position Δ! from the perpendicular line C0 to the outer diameter. 1, it is possible to select any two bilaterally symmetrical vibrator groups 4m and 4n to be excited.

Therefore, by using an array probe 4 in which a large number of small transducers arranged at the bottom of the tube to be inspected 1 is used, the tube to be inspected can be
By selecting arbitrary 241 left-right symmetrical vibrator groups 4m and 4n to be excited according to the outer diameter and wall thickness t of Furthermore, it is possible to detect flaws even in small diameter sizes.

The array probe used here is capable of ultra-high performance by controlling the phase of the oscillation timing of each vibrator, as described in, for example, Document 1, Nondestructive Testing (Vol. 35, No. 9, p. 667). Any device that can scan a sound wave beam over a wide range may be used.

<Example> Below, an example of the present invention will be described in detail with reference to drawing C1.

FIG. 1 is a side view showing an embodiment of an ultrasonic flaw detection apparatus according to the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a sectional view taken along the line A-A.

In the figure, 11 is a water tank that stores acoustic coupling water 5, for example, a pipe 1 to be inspected on the outlet side of a welding machine (not shown).
An array probe 4 made up of a plurality of transducers is disposed along the pass line PL of the transducer, and is arranged approximately at the center of the bottom surface in a direction perpendicular to the pass line I'L.

Reference numeral 12 denotes a tracing mechanism that allows the water tank 11 to be moved vertically and horizontally, and the water tank 1 is moved vertically and horizontally.
1 for positioning. This tracing mechanism 12 is
One end of a shaft 15 that penetrates and is slidably supported by a support member 14 that is fixedly attached to the pedestal 13 is connected to the water tank 11 .
coupled to one support member 16a fixed to the bottom of the
The other end passes through the other support member 16b and is connected to the cylinder 17, and a cylinder 18 that supports the water tank 11 and the pedestal 13 is removed from the bottom of the pedestal 13. .

As a result, by operating the cylinder 17, the water tank 11 can be traced from side to side, and by operating the cylinder 18, it can be traced up and down.

Note that this tracing mechanism 12 is not limited to the configuration described above, and may be of any type as long as it has a structure that allows the water tank 11 to be moved up and down and left and right. This is a guide roller for the tube 1 to be inspected.

20 is a controller that selects two symmetrical transducer groups to be excited in the array probe 4, oscillates the ultrasonic beam 3, and detects the welded portion of the pipe to be inspected l from its beak echo. It has a function of determining whether there is a defect 1a in W.

The operation of the ultrasonic flaw detection apparatus configured in this way will be explained.

■ First, using equation (2) and (31) above, determine the deviation position Δ!5 from the vertical line C0 with respect to the outer diameter of the ERW steel pipe that is the pipe to be inspected l, and then The positions of the 2ill symmetric transducer groups of the probe 4 are set in the controller 20.

■ Next, operate the tracing mechanism 12 to adjust the water iff 1.
Position 1 (7) so that the lower surface of the tube to be inspected 1 is submerged in water.

(2) When the tube 1 to be inspected is conveyed, the tube 1 to be inspected is alternately excited left and right by the two selected sets of transducers of the array probe 4 via the acoustic coupling water 5.

(2) If there is a defect 1a in the welded portion W of the tube to be inspected 1, a beak echo will be generated, so it is received by two sets of transducers and input to the controller 20, and it is determined that there is a defect.

<Effects of the Invention> As explained above, according to the zero-fiber 1914, the array probe is installed perpendicular to the direction of conveyance of the ERW steel pipe and located below it, so that the welding It is possible to reliably detect flaws even immediately after use, and therefore, action can be taken quickly, contributing to improving the quality of ERW steel pipes.

Further, even if the size of the electric resistance welded steel pipes is different, there is no need to adjust the distance between the welded part and the ultrasonic probe, so it is possible to save labor and contribute to improved productivity.

[Brief explanation of the drawing]

FIG. 1 is a side view showing an embodiment of the ultrasonic flaw detection device according to the present invention, FIG. 2 is a plan view of FIG. 1, and FIG. 3 is a sectional view taken along the line A-A in FIG. Fig. 4 is a schematic diagram showing the principle of the present invention, Fig. 5 is a diagram showing an example of distance amplitude characteristics in the conventional ultrasonic angle flaw detection method, and Fig. 6 shows the measurement principle of the conventional example. It is a schematic diagram. 11...Aquarium. 17, 18... shillings. 20...controller. I2... Tracing mechanism. 19...Guide roller. 1... Pipe to be inspected (ERW steel pipe). 3... Ultrasonic beam, 4... Array probe. 5...Acoustic coupling water.

Claims (1)

[Claims] A water tank is provided below the pass line of the ERW steel pipe that is conveyed in the longitudinal direction to store acoustic coupling water, a tracing mechanism that allows the water tank to be moved vertically and horizontally, and the bottom of the water tank is provided with the ERW steel pipe. 1. An ultrasonic flaw detection device for a welded part of an ERW steel pipe, comprising: an array probe consisting of a plurality of transducers arranged perpendicular to a conveying direction.