JP2015141075A - Method for forming standard test piece for ultrasonic flaw detection of weld zone of laser welded steel tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a standard test piece for sampling test data required for evaluating the weld zone of a laser welded steel tube, such as adjustment of a measuring range and flaw detection sensitivity in an ultrasonic flaw detection test targeting the weld zone, especially, a method for forming a standard test piece suitable for the detection of a porosity-like defect.SOLUTION: When a standard test piece used for an ultrasonic flaw detection test of the weld zone of a laser welded steel tube is subjected to bead-on plate welding by a laser or a carbon dioxide gas laser used for the weld zone of the laser welded steel tube on a surface of a tabular member consisting of the same material as the laser welded steel tube, the bead-on plate welding is performed by changing only a shielding gas flow rate 2.5-5 times out of laser welding conditions of the weld zone without changing the other laser welding conditions.

Description

  The present invention relates to a method for producing a standard test piece for collecting test data necessary for evaluation of a welded part such as adjustment of a measurement range and adjustment of flaw detection sensitivity in an ultrasonic flaw detection test for a welded part of a laser welded steel pipe. In particular, the present invention relates to a material suitable for detecting porosity defects.

  Laser welded steel pipes that weld the edge of open pipes by laser welding can concentrate heat energy at a higher density than ERW welded steel pipes, where alloying elements easily segregate in the molten metal. In many cases, it is excellent in prevention of formation, low temperature toughness of welded parts, and corrosion resistance, and its application range is expanded.

  Various proposals have been made regarding a method for manufacturing a laser welded steel pipe from the viewpoint of improving the quality of a welded portion. For example, in Patent Document 1, in the production of a laser welded steel pipe, in order to obtain a welded part of good quality without reducing the welding efficiency, the steel pipe is formed into an open pipe, and two laser beams are placed on the right side of the edge part. On the left side, it is described that the irradiation is performed so that the distance between the laser beam center points on the surface of the steel pipe becomes a specific value.

  In Patent Document 2, in laser welding in which undercut and underfill are likely to occur, two laser beams having a spot diameter of just over 0.3 mm in front and rear are arranged along the edge portion in the welding progress direction. In such a case, it is described that the incident angle and the center point interval of the preceding laser beam and the succeeding laser beam are defined as specific values.

  In Patent Document 3, two or more laser beams having a spot diameter exceeding 0.3 mm are classified into a preceding laser beam and a following laser beam, and the preceding laser beam is welded in a direction of the welding line more than the following laser beam. And the laser welding is performed by arranging the preceding laser beam and the succeeding laser beam in the direction of the welding line with a center line interval of 1 mm or more in the steel plate.

JP 2012-187590 A JP 2012-213798 A JP2011-224655A

  However, the laser welded steel pipe generally has a width of about several mm to several tens mm when the coil as a raw material has a total length of about 100 to 400 m, and the welded portion becomes a groove (edge) during pipe making. On the other hand, since the position is shifted and a weld defect is likely to occur, all the manufactured parts are shipped after an ultrasonic flaw detection test of the welded part.

However, in the ultrasonic flaw detection test, the echo height of the obtained defect echo is proportional to the sound pressure of the ultrasonic wave reflected by the defective portion, and the larger the defect, the higher the echo height, but the flaw detection sensitivity and the like are different. In order to improve detection accuracy, such as the difference in echo height even if flaws with the same dimensions as flaws are detected,
Requires skill.

  Although the performance evaluation of the ultrasonic flaw detector is JISZ3060, it is stipulated that the reference defect having a predetermined size and shape is irradiated with ultrasonic waves and is performed by the echo height of the reflected echo from the reference defect. If the relationship between the echo height of the defect echo and the defect size is not clarified, it cannot be judged whether the product is acceptable for the allowable defect size defined for each product standard.

  In particular, in the case of laser welded steel pipes made of stainless steel, porosity-like defects degrade the corrosion resistance of the weld, so it is necessary to accurately determine the defect dimensions from the echo height of the defect echo. The relationship has not been fully understood, and conventionally it has been processed to be on the safe side.

  Therefore, the present invention is a standard test piece used in the ultrasonic flaw detection test, and the porosity of various dimensions can be estimated from the echo height of the defect echo in the ultrasonic flaw detection test of the welded portion of the laser welded steel pipe. The purpose of this study is to propose a method for producing a standard test piece having a defect.

The solution of the problem of the present invention can be achieved by the following means.
1. A method for producing a standard test piece used in an ultrasonic flaw detection test of a laser welded steel pipe weld,
On the surface of the plate-like member made of the same material as the laser welded steel pipe, only the shield gas flow rate is changed to 2.5 to 5 times out of the laser welding conditions of the welded portion, and other laser welding conditions are not changed. A method for producing a standard test piece for ultrasonic flaw detection in a welded part of a laser welded steel pipe, characterized by bead-on-plate welding.
2. A method for producing a standard test piece used in an ultrasonic flaw detection test of a laser welded steel pipe weld,
When bead-on-plate welding is performed with a carbon dioxide laser on the surface of a plate-like member made of the same material as the laser-welded steel pipe, the bead-on-plate welding is performed with a shield gas flow rate of 2.5 to 2.5 of the laser welding conditions of the weld. A method for producing a standard test piece for ultrasonic flaw detection of a welded portion of a laser welded steel pipe, characterized in that it is changed to 5 times and other laser welding conditions are not changed.
3. The standard test piece for ultrasonic flaw detection of a laser welded steel pipe welded portion according to 1 or 2, wherein the welding speed is adjusted under the laser welding conditions so that the bead-on-plate welding does not result in welding penetrating the steel plate. Manufacturing method.
4). The method for producing a standard test piece for ultrasonic flaw detection of a laser welded steel pipe welded portion according to any one of claims 1 to 3, wherein the material is stainless steel.

  According to the present invention, it is possible to generate a porosity defect having a diameter of about 50 to 400 μm with an excellent reproducibility at an arbitrary location on a standard test piece, setting of a flaw detection sensitivity when detecting a porosity-like defect, and a defect echo The relationship between the echo height and the porosity-like defect size can be easily grasped, which is extremely useful in industry.

The figure which shows typically the X-ray-penetration test result of the plate-shaped member which performed bead-on-plate welding. The figure which shows typically the macro cross section of the bead on-plate welding part of the plate-shaped member shown in FIG.

  In the present invention, the plate-like member is laser welded so that standard test pieces (JISZ2345: 2000) having porosity-like defects of various dimensions as reference defects can be obtained. Laser welding is performed by bead-on-plate welding while changing the flow rate of the shielding gas and the type of laser among the laser welding conditions of the laser welded steel pipe to be subjected to the ultrasonic flaw detection test. The plate-like member is made of the same material as the laser welded steel pipe, and has a dimension that allows a standard test piece (JISZ2345: 2000) to be collected.

  When performing bead-on-plate welding on a plate-shaped member by adjusting the shield gas flow rate, the shield gas flow rate is changed to 2.5 to 5 times of the laser welding conditions of the laser welded steel pipe to be subjected to the ultrasonic flaw detection test. .

  In laser welding, it is considered that porosity defects are generated as bubbles when the shielding gas entrained in the molten pool solidifies the molten pool. When the flow rate of the shield gas is increased from that which can obtain a sound weld, the interaction between the weld pool of the laser welding and the shield gas is increased, and porosity defects are continuously generated.

  In the present invention, the shield gas flow rate is changed to 2.5 to 5 times the laser welding condition of the laser welded steel pipe targeted in the ultrasonic flaw detection test, and bead-on-plate welding is performed on the plate-like member. If the flow rate is less than 2.5 times, porosity defects do not occur, and if it exceeds 5 times, the shielding gas flow is disturbed and defects other than porosity defects due to air entrainment occur. ~ 5 times.

  Also, the carbon dioxide laser has a larger amount of plasma generated during welding and has a larger interaction with the shielding gas than the general industrial laser devices such as YAG laser and fiber laser, and easily generates porosity defects. Therefore, it is desirable to perform bead-on-plate welding in combination with an increase in the shielding gas flow rate as appropriate.

  The laser welding conditions for performing bead-on-plate welding are the laser welding conditions used for a laser welded steel pipe that performs an ultrasonic flaw detection test, except for the type of laser used and the shielding gas flow rate.

  However, laser welding of laser welded steel pipe is keyhole welding in which the keyhole penetrates in the plate thickness direction, but it is disadvantageous for the occurrence of porosity defects so that the keyhole depth is less than the plate thickness. Adjustment of the welding speed is desirable because it facilitates adjustment of the state of occurrence of porosity defects. When the depth of the keyhole is less than the plate thickness, the gas entrained in the keyhole is retained and porosity defects are likely to occur.

  In FIG. 1, among the conditions shown in Table 1, X of the plate-like member 1 subjected to bead-on-plate welding by continuously changing the welding speed to 2.0 m / min and the shield gas flow rate from 50 to 100 L / min. FIG. 2 shows a schematic diagram of a macroscopic cross section of the bead-on-plate welded portion 2 of the plate-like member 1 in the direction perpendicular to the weld line. The material of the plate member 1 is stainless steel. The shield gas flow rate was changed from 50 to 100 L / min from the left end to the right end in FIG. The schematic views of FIGS. 1 and 2 show a case where the bead-on-plate welding is performed so as not to penetrate the plate-like member 1.

  As schematically shown, porosity defects 3 having various dimensions are generated. According to the X-ray transmission test, the defect size of borocity is 50-400 μm, and the standard test piece produced according to the present invention has a flaw detection sensitivity setting when detecting the porosity-like defect 3 and the echo height of the defect echo. In order to understand the relationship between the porosity-like defect dimensions, the porosity-like defects 3 having various dimensions are provided.

1 Plate-like member 2 Bead-on-plate weld 3 Porosity-like defect

Claims (4)

A method for producing a standard test piece used in an ultrasonic flaw detection test of a laser welded steel pipe weld,
On the surface of the plate-like member made of the same material as the laser welded steel pipe, only the shield gas flow rate is changed to 2.5 to 5 times out of the laser welding conditions of the welded portion, and other laser welding conditions are not changed. A method for producing a standard test piece for ultrasonic flaw detection in a welded part of a laser welded steel pipe, characterized by bead-on-plate welding. A method for producing a standard test piece used in an ultrasonic flaw detection test of a laser welded steel pipe weld,
When bead-on-plate welding is performed with a carbon dioxide laser on the surface of a plate-like member made of the same material as the laser-welded steel pipe, the bead-on-plate welding is performed with a shield gas flow rate of 2.5 to 2.5 of the laser welding conditions of the weld. A method for producing a standard test piece for ultrasonic flaw detection of a welded portion of a laser welded steel pipe, characterized in that it is changed to 5 times and other laser welding conditions are not changed.   3. The ultrasonic flaw detection of a laser welded steel pipe welded portion according to claim 1, wherein the welding speed is adjusted under the laser welding conditions so that the bead-on-plate welding is not welding that penetrates a plate-like member. Standard test piece production method.   4. The method for producing a standard test piece for ultrasonic flaw detection of a laser welded steel pipe welded portion according to claim 1, wherein the material is stainless steel. 5.

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