JP2017001041A - Method for determining abnormality in seam welding part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a breaking of a seam welding part during passing of a steel strip.SOLUTION: A method for determining abnormality in a seam welding part comprises: a load current measuring step for measuring a load current applied to an electric motor 25 when a weld bead 2a in a seam welding part 2 formed by seam welding of a flash butt welding at end parts of steel strips 1, is cut off by a trimmer 7 operated with a power of the electric motor 25; and an abnormality determination step for determining that the seam welding part 2 is abnormal when the load current value measured at the load current measuring step deviates from a predetermined threshold range.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a seam welded portion abnormality determining method, and more particularly, to a seam welded portion abnormality determining method for determining whether or not a seam welded portion formed by seam welding the end portions of steel strips by flash butt welding is present.

  In the steel material production line, there is a method of continuously producing by continuously welding the end portions of the steel strips as raw materials. In this method, the unrolled band steel is passed through, the rear end of the preceding band steel and the front end of the subsequent band steel are connected by seam welding, and the material is continuously supplied. Such a system is applied to a welded steel pipe production line, and is also used in a cold rolled steel sheet production line and a plated steel sheet line.

  By the way, in the joint weld part formed by seam-welding the edge part of band steel, a fracture | rupture may arise in the sheet | seat passage of band steel. When a fracture occurs in the seam welded portion, it is necessary to treat the steel strip remaining in the production line and re-pass through the production line, so that the working efficiency is remarkably lowered and the yield is also deteriorated. Therefore, in the steel material production line that continuously welds the end portions of the steel strips by flash butt welding and continuously threading, abnormalities in the seam welds are detected early and abnormal seam welds are cut. It is important to prevent the trouble caused by the breakage of the seam welded portion by performing the seam welding again to ensure a sound seam welded portion.

For example, Patent Document 1 discloses a method for improving ductility by heat-treating a seam weld as a measure for preventing breakage of the seam weld.
However, in the continuous rolling line, since a great tensile stress is applied to the seam weld during transportation of the strip steel, the measures for improving the ductility of the seam weld as in Patent Document 1 are sufficient for operation troubles due to the fracture of the seam weld. It is difficult to prevent.

JP 2011-36898 A

Therefore, the inventors of the present invention have a welded state after flash butt welding the ends of the steel strips and a cutting state when cutting the weld bead of the welded seam welded part affects the fracture of the seam welded part. The present invention was made by paying attention to the above.
The objective of this invention is providing the technique which can suppress the fracture | rupture of the seam welding part in the plate | board of a steel strip.

In order to achieve the above object, a method for determining an abnormality in a seam weld according to an aspect of the present invention includes a welding bead of a seam weld formed by seam welding the ends of steel strips by flash butt welding. When cutting with a trimmer that operates by power, when the load current measurement step for measuring the load current applied to the motor and the load current value measured in the load current measurement step are outside the predetermined threshold range, the seam is removed. An abnormality determination step for determining that there is an abnormality in the welded portion.
The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  ADVANTAGE OF THE INVENTION According to this invention, the fracture | rupture of the seam weld part in the sheet | seat passage of a strip can be suppressed.

It is a block diagram which shows the continuous rolling line of the continuous pipe making system provided with the control computer which implements the seam weld part abnormality determination method which concerns on one Embodiment of this invention. It is a schematic block diagram which shows schematic structure of a flash butt welder. It is a schematic diagram which shows the seam weld part seam-welded with the flash butt welder. It is a schematic block diagram which shows schematic structure of a trimmer. It is a flowchart which shows the seam welding part determination program which a control computer performs.

Before describing the seam weld abnormality determination method according to an embodiment of the present invention, a continuous pipe-forming continuous rolling line including a control computer that implements the seam weld abnormality determination method will be described.
As shown in FIG. 1, a continuous pipe-forming continuous rolling line 10 includes an uncoiler 3 that feeds the strip 1 onto the line, and a coil leveler 4 that feeds out the strip 1 while correcting the shape of the strip 1 immediately after passing through the plate. ing. The continuous rolling line 10 includes a flash butt welder 5 that performs cutting and seam welding of the end of the fed steel strip 1 and a coil looper 6 that stores the steel strip 1 after welding. The continuous rolling line 10 includes a trimmer 7, a control computer 8, and an output device 9.

The flash butt welder 5 is configured to cut the leading end of the preceding strip steel 1a, the leading end portion of the trailing strip steel 1b, and the end portions of the strip steels 1 after shear cutting. The rear end of the steel strip 1a and the front end of the trailing steel strip 1b are seam welded by flash butt welding.
The flash butt welder 5 includes a fixed base 11 and a movable base 15 as shown in FIG. The fixed base 11 is fixed on the floor surface. The moving table 15 is moved back and forth along the plate passing direction of the steel strip 1 by a moving mechanism constituted by a guide rail or a hydraulic cylinder (not shown). And the fixed stand 11 has the upper electrode 12 and the lower electrode 13 which can operate | move to an up-down direction with drive devices, such as a hydraulic cylinder which is not illustrated so that the preceding strip steel 1a may be pinched | interposed from an up-down direction. . Similarly, the movable table 15 also has an upper electrode 16 and a lower electrode 17 that can be moved in the vertical direction by a driving device such as a hydraulic cylinder (not shown) so as to sandwich the trailing steel 1b from the vertical direction. doing. The upper electrode 12 and the lower electrode 13, and the upper electrode 16 and the lower electrode 17 are connected to a welding power source (not shown).

  The flash butt welder 5 first sandwiches the preceding steel strip 1a from the upper and lower directions with the upper electrode 12 and the lower electrode 13 of the fixed base 11, and the trailing steel strip with the upper electrode 16 and the lower electrode 17 of the moving base 15. 1b is sandwiched from above and below. Then, in this sandwiched state, the rear end portion of the preceding strip steel 1a and the front end portion of the subsequent strip steel 1b are shear-cut. Then, after the shear cutting, the moving table 15 is moved forward to approach the fixed table 11 and lightly contacted so that the rear end of the preceding steel strip 1a and the front end of the following steel strip 1b are abutted. And by making a large electric current flow between the rear-end part of the preceding strip steel 1a and the front-end | tip part of the succeeding strip steel 1b in the state contacted lightly, the rear end part of the preceding strip steel 1a and the trailing strip steel 1b The contact portion with the tip is heated to cause a flushing that is in a molten state. Then, by further moving the moving table 15 forward, flushing is caused one after another to bring the entire contact portion into a molten state. Then, when the temperature reaches the appropriate temperature, the moving table 15 is strongly moved forward toward the fixed table 11 to apply a strong pressure between the rear end of the preceding steel strip 1a and the front end of the following steel strip 1b. To do. Thereby, the rear end part of the preceding band steel 1a and the front end part of the succeeding band steel 1b are joint-welded by flash butt welding.

  In this flash butt welding, as shown in FIG. 3, a weld bead 2a is formed in the seam welded portion 2 that has been seam welded. The weld bead 2a is formed by the molten metal rising outward when the respective ends of the molten state of the preceding strip steel 1a and the trailing strip steel 1b are pressed. Therefore, the weld bead 2 a is formed on each of the front surface side and the back surface side of the steel strip 1 and is formed over the entire plate width direction of the steel strip 1.

  As shown in FIG. 1, the trimmer 7 cuts and removes the weld bead 2 a of the seam weld 2 formed by seam welding the ends of the steel strips 1 by flash butt welding with the power of the electric motor 25. ing. Although the trimmer 7 is not limited to this, for example, as shown in FIG. 4, the cutting blade 21 is moved along the longitudinal direction (width direction of the steel strip) of the seam welded portion 2 by the power of the electric motor 25. At 21, the weld bead 2 a is removed by cutting. Further, the trimmer 7 includes cutting blades 21 on the front surface side and the back surface side of the steel strip 1, respectively, and collectively cuts and removes the respective weld beads 2 a on the front surface side and the back surface side of the steel strip 1. ing. Although the trimmer 7 is not limited to this one embodiment, as shown in FIG. 2, for example, the welding bead 2 a is cut and removed between the fixed base 11 and the movable base 15 of the flash butt welder 5. Are arranged as follows.

The control computer 8 is constituted by an information processing apparatus such as a microcomputer or a personal computer. As shown in FIG. 1, the control computer 8 includes a control unit 31 and a storage unit 32.
The storage unit 32 is configured by a nonvolatile storage device such as a ROM. The storage unit 32 stores data in a predetermined threshold range with respect to the load current applied to the electric motor 25 of the trimmer 7 when the weld bead 2a of the joint weld 2 is cut and removed by the trimmer 7. The threshold range is a threshold range indicating the soundness of the seam welded portion 2 and is a threshold range for determining whether or not the seam welded portion 2 is abnormal.

  In addition, the storage unit 32 stores a seam welded portion abnormality determination program for determining whether or not the seam welded portion 2 is abnormal. The seam welded portion abnormality determination program includes a load current measuring function (load current measuring step) that measures a load current applied to the motor 25 of the trimmer 7 when the weld bead 2a of the seam welded portion 2 is cut and removed by the trimmer 7, and measurement. If the measured load current value is outside the predetermined threshold range, the seam weld is determined as “abnormal”, and if the measured load current value is within the predetermined threshold range, the seam weld is determined as “no abnormality”. Is provided with an abnormality determination function (abnormality determination step). The seam welded portion abnormality determination program has a transmission function for transmitting data of the abnormality determination result of the seam welded portion 2 to the output device 9.

The control unit 31 is configured by an arithmetic processing device such as a CPU. The control unit 31 controls the operation of the control computer 8 according to the control program stored in the storage unit.
The output device 9 includes a display device, a printing device, a sound output device, and the like. The output device 9 is configured to output the seam welded portion abnormality determination result of the control computer 8.

  Here, the load current applied to the electric motor 25 of the trimmer 7 when the weld bead 2a of the seam weld 2 is cut and removed varies depending on the welding state of the seam weld 2 and the cutting state of the weld bead 2a. The seam weld abnormality determination method according to an embodiment of the present invention includes a load current value obtained by measuring a load current applied to the electric motor 25 of the trimmer 7 when the weld bead 2a of the seam weld 2 is cut and removed. By comparing with a predetermined threshold range, the presence or absence of abnormality of the seam welded portion 2 is determined.

Next, a seam weld abnormality determination method according to an embodiment will be described using the flowchart shown in FIG. 5 with reference to the block diagram shown in FIG. The flowchart shown in FIG. 5 is a joint weld abnormality determination program executed by the control computer 8.
After the seam welding is completed by flash butt welding of the rear end portion of the preceding steel strip 1a and the front end portion of the subsequent steel strip 1b (the end portion of the steel strips), the seam weld abnormality determination program shown in FIG. It starts at the timing when the process of cutting and removing the weld bead 2a of the joint weld 2 by the trimmer 7 is started.

  In step ST <b> 1, the control computer 8 measures the load current applied to the electric motor 25 of the trimmer 7 when the weld bead 2 a of the joint weld 2 is cut and removed by the trimmer 7. The control computer 8 proceeds to step ST2 at the timing when the cutting and removal of the weld bead 2a is completed. This step ST1 corresponds to the load current measurement step of the seam weld abnormality determination method according to the embodiment.

In step ST2, the control computer 8 reads out a predetermined threshold range from the storage unit 32, and determines whether or not the load current value measured in step ST1 is within the threshold range.
In step ST2, if the control computer 8 determines that the load current value is out of the threshold range, the control computer 8 determines that the seam weld 2 is “abnormal” (step ST3), and transmits the determination result to the output device 9. Then, the seam welded portion abnormality determination program is terminated. This step 3 corresponds to the abnormality determination step of the seam welded portion abnormality determination method according to one embodiment.

  On the other hand, if the control computer 8 determines in step ST2 that the load current value is within the threshold range, it determines that the seam weld 2 is “abnormal” (step ST4), and outputs the determination result to the output device 9. To end the joint weld abnormality determination program. That is, the method for determining an abnormality in a seam weld according to an embodiment of the present invention early detects the presence or absence of an abnormality in the seam weld 2 of the steel strip 1 in the step of cutting and removing the weld bead 2a of the seam weld 2. be able to. When the seam weld 2 is detected as “abnormal”, the seam weld 2 detected as “abnormal” is cut and removed by the flash butt welder 5, and the seam is welded again.

Here, the cause of breakage of the seam welded portion 2 during the passage of the steel strip 1 that has been seam welded is the breakage caused by the welded state of the seam welded portion 2 and the breakage caused by the cutting state of the weld bead 2a. There is.
As a break resulting from the welded state of the seam weld 2,
(A) Fracture caused by insufficient weld strength due to poor penetration of the seam weld 2
(B) a step is generated in the thickness direction when the leading end of the preceding strip steel 1a and the leading end of the trailing strip steel 1b are brought into contact with each other.
and so on.

As the breakage caused by the cutting state of the weld bead 2a,
(C) Breakage caused by a decrease in weld strength of the seam weld 2 due to overcutting of the weld bead 2a,
(D) Fracture caused by welding bead 2a as a starting point due to poor cutting of weld bead 2a,
and so on.
Therefore, in the seam weld abnormality determination method according to an embodiment of the present invention, when the load current value falls below the threshold range, the seam weld 2 is regarded as a poor penetration due to insufficient cutting or narrowing of the weld bead 2a. Judged as “abnormal”. Moreover, the seam welding part abnormality determination method which concerns on one Embodiment of this invention is the butt | matching part which faced the overcutting of the weld bead 2a or the ends of the strips 1 when the load current value exceeded the threshold range. As a misunderstanding, the joint weld 2 is determined as “abnormal”.

  As described above, the continuous pipe-making type continuous rolling line 10 includes the control computer 8 that performs the seam weld abnormality determination method according to an embodiment of the present invention. And the seam welding part abnormality determination method which concerns on this one embodiment WHEREIN: When the welding bead 2a of the seam welding part 2 is cut and removed by the trimmer 7 in the process of cutting and removing the welding bead 2a of the seam welding part 2, the trimmer 7 When the load current value obtained by measuring the load current applied to the electric motor 25 is outside a predetermined threshold range, the joint weld 2 is determined to be “abnormal”, so the joint weld of the strip 1 The presence or absence of 2 abnormalities can be detected at an early stage. As a result, in the flash butt welder 5, the seam welded part 2 determined as “abnormal” is cut and eliminated, and the seam welded part 2 can be improved in soundness by performing seam welding again. The breakage of the seam welded portion 2 in the plate of the steel strip 1 can be suppressed.

Moreover, since the breakage of the seam welded portion 2 during the passing of the steel strip 1 can be suppressed, the end portions of the steel strips 1 are continuously welded by flash butt welding to continuously pass the steel strip. Stable production can be performed in the rolling line 10.
In addition, in the continuous rolling line 10 shown in FIG. 1, when performing seam welding by flash butt welding and then cutting the weld bead 2a of the seam weld 2, the seam weld abnormality according to one embodiment of the present invention Judgment method was implemented. Thereafter, a plate sample is collected around the seam weld 2, the appearance after the weld bead cutting is confirmed, and the seam weld 2 at the fracture position by a tensile test in the 90 ° direction with respect to the longitudinal direction of the seam weld 2 is obtained. The soundness was evaluated. For plate samples, a reference threshold range is provided for the load current value, and the load current value is broadly classified as a sample within the threshold range, a sample below the threshold range, and a sample greater than the threshold range, and welding bead cutting is performed for each. The frequency at which the fracture position becomes the seam welded portion 2 was determined during the subsequent appearance evaluation and tensile test. The results are shown in Table 1. The threshold range for the load current value (A) is 80-120.

As can be seen from Table 1, when the load current value is within the threshold range, the seam weld 2 did not break, whereas the load current value was less than the threshold range and greater than the threshold range. The frequency of breakage at the seam weld 2 was high.
From the above, by measuring the load current applied to the electric motor 25 of the trimmer 7 when cutting and removing the weld bead 2a of the seam weld 2 formed by seam welding by flash butt welding, the abnormality of the seam weld 2 is measured. The presence or absence was detected, and it was confirmed that the occurrence of breakage at the seam weld 2 could be prevented.

The present invention has been specifically described based on the above-described embodiment. However, the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the scope of the invention. .
For example, in the above-described embodiment, the production line in which the trimmer 7 is disposed so as to cut and remove the weld bead 2a between the fixed base of the flash butt welder and the moving body has been described. The present invention can also be applied to a production line in which the trimmer 7 is disposed so as to cut and remove the weld bead 2a at the subsequent stage of the welder 5.

  Moreover, although the above-mentioned one embodiment demonstrated the continuous rolling line of the continuous pipe making system, this invention is applicable also to steel plate manufacturing lines, such as a cold rolled steel plate manufacturing line and a plated steel plate line. That is, the present invention can be applied to all production lines in which the end portions of the steel strips that are the raw materials are welded together for continuous production.

DESCRIPTION OF SYMBOLS 1, 1a, 1b ... Strip steel 2 ... Seam weld part, 2a ... Weld bead 3 ... Uncoiler 4 ... Coil leveler 5 ... Flash butt welder 6 ... Coil looper 7 ... Trimmer (cutting device)
8. Control computer (control device)
DESCRIPTION OF SYMBOLS 9 ... Output device 10 ... Continuous rolling line 11 ... Fixed stand, 12 ... Upper electrode, 13 ... Lower electrode 15 ... Moving stand, 16 ... Upper electrode, 17 ... Lower electrode 21 ... Cutting blade, 25 ... Electric motor 31 ... Control Part, 32 ... storage part

Claims (5)

A load that measures the load current applied to the motor when the weld bead of the seam weld formed by seam welding the ends of the steel strips by flash butt welding is removed by a trimmer that operates by the power of the motor A current measurement step;
An abnormality determination step for determining that the seam weld is abnormal when the load current value measured in the load current measurement step is outside a predetermined threshold range;
A method for determining abnormality of a seam welded portion, comprising:   2. The seam weld portion abnormality determination method according to claim 1, wherein the abnormality determination step determines that the seam weld has no abnormality if the load current value is within the predetermined threshold range.   The said abnormality determination step transmits a determination result to an output device, The seam weld part abnormality determination method of Claim 2 characterized by the above-mentioned.   In the abnormality determination step, when the load current value falls below the threshold range, it is determined that the seam weld is abnormal due to insufficient cutting of the weld bead or poor penetration due to narrowing. The method for determining an abnormality in a seam weld according to any one of claims 1 to 3.   In the abnormality determination step, when the load current value exceeds the threshold range, it is determined that the seam weld is abnormal as an overcutting of the weld bead or a misalignment of the butt portion of the steel strip. The method for determining an abnormality in a seam weld according to any one of claims 1 to 3.

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