JPH0334431B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a welding status monitoring method, and in particular, to a method for bending and bending a band-shaped metal material suitable for use in manufacturing ERW pipes on a production line by high-frequency heating, electric resistance heating, or induction heating. This invention relates to an improvement in a method for monitoring welding conditions when manufacturing a welded metal pipe by continuously butt-welding opposing end surfaces.

[Conventional technology]

Generally, electric resistance welded steel pipes are manufactured by continuously forming a raw steel strip into a cylindrical shape using a group of forming rolls, and then joining the joints using electric resistance welding or electric induction welding. In order to improve the welding quality of the electric resistance welded pipe manufactured in this manner, welding conditions, particularly control of heat input, are extremely important management items. Conventionally, this heat input control has been performed by a skilled worker monitoring the color of the weld, the appearance of the weld bead, etc., and setting and adjusting various conditions empirically. However, the heat input control performed by the above-mentioned method is based on human monitoring, and since individual differences occur, there is a problem in its accuracy. Therefore, recently, various control methods using automatic control mechanisms have been attempted in place of the above-mentioned control method using human monitoring. In addition, when performing this control method, it is necessary to measure the temperature of the welded part of the ERW pipe, for example, the ERW steel pipe. Conventionally, such a measurement was carried out by measuring the temperature of the end face of the ERW pipe. It was hot. As one such method, for example, Japanese Patent Application Laid-open No.
There is a welding control method for electric resistance welded pipes disclosed in No. 165188. This welding control method detects the temperature distribution in the thickness direction of the opposite end faces to be butt welded in the process of continuously manufacturing ERW pipes, determines the minimum temperature, monitors welding, and positions the position where the minimum temperature is indicated. However, this is a method in which welding conditions are controlled so that the welding temperature at the butt point is equal to or higher than a predetermined minimum welding temperature. This method is a method that attempts to correct the fact that when electric resistance welding pipes are welded by resistance heating welding or induction heating welding, the heating distribution becomes selective heating due to the proximity effect. That is, in this method, since the electric resistance welded tube is selectively heated by high-frequency resistance heating or high-frequency induction heating, the temperature at the end face has a temperature distribution in the thickness direction, and the lowest temperature is near the center of the thickness. The minimum temperature is detected taking into account that the minimum temperature will be reached.

[Problems to be solved by the invention]

By the way, there is an appropriate range for the welding heat input to the welded part of the electric resistance welded pipe, and if the welded part is heated too much, it will overheat, and if the welded part is heated too little, it will result in a cold weld. . or,
Even within the appropriate range, there is an optimum value for welding heat input. However, the above-mentioned Japanese Patent Application Laid-Open No. 57-165188
The welding control method for electric resistance welded pipes disclosed in 2003 only guarantees that the temperature of the welded part is equal to or higher than the minimum temperature, but it is not possible to obtain the optimum temperature of the welded part, and the welding quality is constantly checked. The problem was that it was difficult to maintain it in good condition. Further, the welding control method for electric resistance welded pipes monitors the welding status by detecting the minimum temperature, and it is possible to detect that the selective heating for welding changes depending on the butt state of the end faces, and the temperature distribution in the weld plate thickness direction changes. It's not something to monitor. Furthermore, heating of the abutting surfaces by high-frequency resistance heating or high-frequency induction heating is performed by proximity effect and skin effect, and the heating distribution of the abutting surfaces largely depends on the shape of the abutting surfaces. However, the welding control method for electric resistance welded pipes evaluates the amount of heat input based on the results of the selective heating, and does not mention the butt shape. For example, as shown in FIG. 7A, the left side portion 20A and the right side portion 2 of the electric resistance welded tube 20 are butted.
The position of 0B is shifted up and down, or B in the same figure
As shown in FIG. 2, if the spacing is different between the upper and lower end surfaces of each portion 20A, 20B, asymmetry in temperature and heating will occur. When the asymmetrically heated end faces are pressed together, in the case of A in the same figure, the welding state will be as shown in C in the same figure, and before B in the same figure, the welding state will be in the welded state as shown in D in the same figure. (The welded portion is indicated by the reference numeral 22 in the figure). In any of the welding conditions, the strength during pressure welding is insufficient, and therefore, there has been a need for a method for determining the suitability of this end face butt shape. In addition, as a technique related to the present invention,
There is a temperature distribution measuring device indicated by -1697. This device receives the light emitted from the weld bead of an ERW pipe with a linear array in which multiple photoelectric conversion elements are arranged in a row, and obtains a temperature signal and furthermore a temperature distribution from the received light signal. This is what we are trying to do.
However, since this device uses a linear array, the temperature distribution on the opposing end faces to be welded cannot be made linear, and the problem is that it is not possible to measure the temperature distribution in a plane to accurately obtain the welding situation. It had

[Purpose of the invention]

The present invention has been made in view of the above-mentioned conventional problems, and the present invention improves welding quality by accurately and reliably estimating the heat input status of the butt welded portion of welded metal pipes, and accurately monitoring the welding status. The first object is to provide a welding status monitoring method that allows the user to perform the following steps. A second object of the present invention is to provide a welding condition monitoring method capable of accurately monitoring the welding condition by reliably estimating the butt condition of the opposite end surfaces of the butt welded portion from the isothermal line of the opposite end surfaces. do.

[Means to solve the problem]

As shown in FIG. 1, when manufacturing a welded metal pipe by bending a band-shaped metal material and continuously butt-welding the opposing end surfaces thereof, the present invention applies the following steps from the V-shape entrance direction, as shown in FIG. The temperature distribution at the edge portion in the plate thickness direction and the center portion in the plate thickness direction in the welded portions of both the opposing end faces is simultaneously detected as an image, and the image of the detected temperature distribution is compared with a reference temperature distribution image, or the image is The first object is achieved by estimating the state of heat input to the butt welded portion from at least one of the isothermal areas at a predetermined temperature determined from the above. Further, in an embodiment of the present invention, when estimating the heat input situation, the detected temperature distribution image is corrected based on welding conditions such as welding speed, welding V-shape angle, and thickness measurement of the metal material. This is what I did. Further, the present invention provides a method for manufacturing a welded metal tube by bending a band-shaped metal material and continuously butt-welding the opposing end surfaces thereof, from the V-shape entrance direction to the plate at the welded portion of both the opposing end surfaces. The temperature distribution at the edge in the thickness direction and the center in the thickness direction are simultaneously detected, and based on the image of the detected temperature distribution,
The isothermal line of the opposing end surface is determined, and based on the shape of the obtained isothermal line, the left-right symmetry and vertical symmetry with respect to the butt welded portion are quantified, and the butt situation of the opposing end surface is estimated. This achieved the second objective.

[Effect]

When manufacturing welded metal pipes, if butt welding is performed by inductively heating or resistance heating the opposing end surfaces of bent metal strips, if it is performed under appropriate conditions, both opposing ends of the butt The temperature distribution of the welded parts of each end face becomes equal. In order to confirm that this temperature distribution is equal, it is sufficient to simultaneously observe the welded portions of both opposing end faces and measure their temperature distribution. The present invention has been made based on the above findings, and has the following effects. In the present invention, first, the temperature distribution of the butt welded portions of both opposing end faces to be welded is detected as an image. Then, the heat input situation to the butt welded portion is estimated by comparing the detected temperature distribution image with a reference temperature distribution image, or by at least one of the isotherm area of a predetermined temperature determined from the image. ing. Therefore, the temperature distribution images at the butt welded portions of both the opposing end surfaces are compared, or the isothermal line area of the temperature distribution images is determined, and the heat input status such as the amount of heat input is estimated from the comparison result or the isothermal line area. For example, it is possible to accurately measure insufficient heating at the central portion in the thickness direction of both opposing end surfaces and overheating at the edge portion in the thickness direction of both opposing end surfaces, which occurs due to the specificity of the density of the welding current. be able to. Since the heat input situation can be obtained with high accuracy in this way, by controlling welding based on the information, it is possible to obtain the optimum welding quality for the welded metal pipe. In addition, when estimating the heat input situation, if the detected temperature distribution image is corrected based on the welding conditions, such as the welding speed, weld V-shape angle, and the plate thickness of the metal material, the temperature distribution can be further improved. The detection accuracy is improved, and the heat input situation can be reliably estimated. By the way, when butt welding the opposing end surfaces of the bent metal strips as described above by, for example, induction heating or resistance heating, the abutting surfaces generate heat due to the current flowing through the welding surfaces and the temperature rises. However, the temperature of this abutting surface increases in accordance with the density of the current. The density of this current is determined by the proximity effect and skin effect, which are characteristics of high-frequency current, and the proximity effect and skin effect are influenced by the abutting shape of the end surfaces of the band-shaped metal material. Therefore, by measuring the temperature distribution of the abutting surfaces, the distribution of the current density can be estimated, and the abutting shape of the end faces of the band-shaped metal material can be estimated. The present invention has been made based on such knowledge, and the isothermal line of the opposing end surface is determined from the image of the temperature distribution detected as described above, and the left-right symmetry with respect to the butt welded portion is determined based on the shape of the isothermal line. The symmetry and the vertical symmetry are quantified to estimate the abutting situation, for example, the abutting shape of the opposing end surfaces. Therefore, the suitability of the butt shape determined by the suitability of heating the opposing end faces and the temperature distribution of the end faces can be judged, so that, for example, welds that do not have sufficient strength during pressure welding as shown in Figures 7C and D above. can be monitored with high precision.

【Example】

Hereinafter, embodiments of a welding monitoring device employing the welding status monitoring method according to the present invention will be described in detail. As shown in FIG. 2, this embodiment is a temperature distribution measurement method in which the temperature distribution in the welded part of the electric resistance welded pipe 20 to be measured and in the vicinity thereof in the plate thickness direction and in the welding progress direction is measured as an optical image. The device 10 and the temperature distribution signal S outputted from the temperature distribution measuring device 10 are used to obtain an isothermal line, and the temperature distribution signal
Image processing device 1 for determining the welding status of the welded portion based on the reference temperature distribution set as HS
2, and a setting device 13 for setting the reference temperature distribution.
and a monitor device 1 that displays the obtained temperature distribution.
The present invention is applied to a welding monitoring device equipped with 4. In order to detect the temperature distribution of the welded part, the temperature distribution measuring device 10 includes a tip 16 arranged so that both end surfaces to be butt welded are within the same field of view, and a tip 16 that detects temperature distribution at the tip 16. Image fiber 1 that guides temperature distribution as an optical image
8 is provided. The tip portion 16 may be made of a non-inductive material, such as ceramic plastic, which can be used even in a high frequency magnetic field when the electric resistance welded tube 20 is heated by induction. Further, in the image processing device 12, an area array type photoelectric element can be used in order to create an image signal from light introduced through an image fiber. Thereby, it is possible to measure the welding conditions of both end faces. Here, FIG. 3 shows a state in which the welding monitoring device according to this embodiment is attached near the welded portion 22 of the electric resistance welded pipe 20. Note that the electric resistance welded tube 20 is conveyed in the direction of arrow A. In FIG. 3, the tip 16 is located at the weld V-shape near the welded portion 22 of the ERW tube 20, and from the V-shape opening to the welded portion 22.
The cutting tool holder 24 is disposed on an inner cutting tool holder 24 for cutting a weld bead. The inner cutting tool holder 24 includes an inner cutting tool 2 for cutting an inner bead formed on the electric resistance welded pipe 20 after welding.
6 and an image fiber 18 connected to the tip 16 are provided. Moreover, the tool holder 24
is held by an internal tool holder holding mechanism 28 which is appropriately fixed. The image fiber 18 is disposed along the tool holder 24 and the inner tool holder holding mechanism 28, and the image fiber 18 is arranged along the tool holder 24 and the inner tool holder holding mechanism 28, and
It reaches 0. The effects of the embodiment will be explained below. First, appropriate welding quality can be obtained. Welding part 2
A temperature distribution (reference temperature distribution) corresponding to the heat input amount for 2 is set in the setting device 13. Next, as shown in FIG. 3, the electric resistance welded tube 20 is
When the welding part 22 is heated by a high-frequency induction heater (not shown) and butt welded, the temperature distribution is detected by the tip 16 from the V-shape opening in the front direction of the welding part 22 to the welding part 22. do. The temperature distribution detected at the tip 16 is transmitted to the image fiber 1 as an optical image.
8 and is input to the temperature distribution measuring device 10. The temperature distribution measuring device 10 converts the temperature distribution of the input optical image into a temperature distribution signal HS, and inputs the temperature distribution signal HS to the image processing device 12. The image processing device 12 compares the input temperature distribution signal HS with a reference temperature distribution set in advance by the setting device 13,
The welding status of the welded portion 22 is determined. or,
Based on the temperature distribution signal, the monitor device 14 displays the temperature distribution of the welded part 22. An example of the measurement results of the temperature distribution obtained as described above and displayed on the monitor device 14 is shown in FIG. 4A.
The appropriate reference temperature distribution set in the setting device 13 at that time is shown in FIG. In addition, the code 2 in the figure
4 indicates an isotherm. FIG. 4A shows the temperature distribution of both opposing end surfaces 23A and 23B with respect to the welded part 22, and shows the temperature distribution of the 1500°C or higher part in the figure, the 1400°C isothermal line, and the 1300°C isothermal line.
From the temperature distribution shown by the isothermal line of °C, it can be seen that a portion of 1500 °C or higher exists asymmetrically on the opposing end surfaces 23A, 23B. Also, by observing the upper and lower temperature distribution, it can be seen that the upper part of the right facing end surface 23B is higher. On the other hand, the reference temperature distribution shown in FIG. 4B is a temperature distribution in which temperature regions of 1500° C. or higher exist symmetrically on the left and right sides, and are also symmetrical on the top and bottom. Therefore, in the measurement example shown in FIG. 4A, both opposing end surfaces 23
Appropriate temperatures relative to the standards are obtained in the central part of A and 23B and the welding part 22, but the upper part of the right opposing end face 23B is heated more, and the lower right part is less heated, and proper welding quality is not achieved. I can see that you are not getting it. By measuring the temperature distribution as described above, the amount of heat input to the welded portion 22 can be determined, and the welding quality of the joint portion of the electric resistance welded pipe 20 can be monitored with high accuracy. Here, the temperature that represents the welding quality of the ERW pipe is
FIG. 5 shows the results of a comparison between the measurement using a conventional thermometer and the measurement using the method of the present invention.
When measuring temperature with a conventional thermometer, the fifth
From Figure A, it can be seen that disturbances, particularly fluctuations in the formed shape of the ERW tube, appear as fluctuations in the external surface temperature of the welded portion, making it difficult to obtain stable measurement results. On the other hand, in the method of the present invention, as shown in Fig. 5B, when the heated area (1500°C or more), which is a typical value for the quality of the temperature distribution welded part, is monitored, it shows a stable value, as shown in Fig. 5C. This corresponds to the central heating width (heat-affected zone width) of the end face of the sampled product. Therefore, the welded portion 2
If the area of the isothermal line above 1500°C is calculated from the temperature distribution in 2, the amount of heat input to the welding part 22 can be obtained more stably than with conventional temperature measurement. Quality can be represented by the isothermal area as described above. In order to estimate the amount of heat input to the welding part 22, the temperature determined by the image processing device 12 etc. is measured by measuring the influencing factors such as welding conditions such as welding speed, welding V-shape angle, and plate thickness. The estimation accuracy can be further improved by correcting the distribution image using appropriate means. Note that the influencing factors are not limited to those described above, and can also be determined by taking into account other welding conditions, and the determined temperature distribution does not need to be corrected. Here, another example of a device for measuring the temperature distribution obtained by the image processing device 12 is shown in FIG. The figure shows a comparison of the shapes of isothermal lines (indicated by reference numeral 24 in the figure) of the left and right opposing end surfaces 23A and 23B. In this case, when the shapes of the left and right isothermal lines are completely symmetrical as shown in FIG. 6A, the opposite end surface 2
The abutment surfaces of 3A and 23B were normal. On the other hand, when the left and right abutting surfaces are vertically shifted as shown in FIG. 7A, the left and right isothermal shapes also differ accordingly. As shown in Figure A, when the position of the left side portion 20A of the electric resistance welded tube 20 that is butted is higher than the right side portion, the current is concentrated at the lower edge of the left side portion 20A and the upper edge of the right side portion 20B, and the temperature increases. do. A measurement example of the temperature distribution at this time is shown in FIG. 6B, and the isothermal line is asymmetrical. Conversely, when the right side portion 20B is placed at a higher position than the left side portion 20A, the current concentrates on the lower right edge and the upper left edge, and the temperature also rises. An example of measurement at that time is shown in Figure C.
The isotherm line becomes asymmetrical as shown in . As is clear from B and C in the figure, if there is a vertical difference between the butt end faces, the left and right isothermal lines become asymmetrical, so the vertical difference between the butt end faces can be monitored from this isothermal line shape. Also, it can be determined from the asymmetry of this isothermal line which end face is on top. In this way, the butt welded portion 22
By quantifying and detecting the left-right symmetry and vertical symmetry from the detected isothermal lines, it is possible to estimate the butting situation of the opposing end surfaces. Note that this method of examining the symmetry of the isothermal line can be realized by the image processing device 12 using a conventional image processing method. Further, as shown in FIG. 7B, if the distance between the lower edges of the opposing end surfaces is narrower than the distance between the upper edges, when they are butted and a current is applied, the left and right opposing end surfaces 23A are abutted. , 23B, the current flows in a concentrated manner at the lower edge, and the current density in this portion becomes high.
The isothermal lines 24 measured at this time are those in which the lower isothermal lines 24 are spaced apart as shown in FIG. 6D. Similarly, when the distance between the upper edges is narrow and the distance between the lower edges is wide, contrary to FIG. 7B, the measured isothermal line 24 becomes as shown in FIG. 6E. Therefore, from FIGS. D and E, each opposing end surface 23 is
It can be seen that when the intervals between the upper and lower edges of A and 23B are not equal, the vertical symmetry of the isothermal line 24 is lost. Since this symmetry is lost, it is possible to know the abutting shape of each opposing end surface 23A, 23B, and it is possible to monitor the welding situation.
Note that the vertical symmetry of this isothermal line 24 can be obtained by a conventional image processing technique.

【Effect of the invention】

As explained above, according to the present invention, the heat input situation to the welded part is accurately and reliably estimated by taking into consideration the butt type, the welding situation is accurately monitored, and the optimal heat input to the welded part is determined. can give. Moreover, the butt situation of the opposing end surfaces can be estimated with high accuracy from the isothermal line near the welding part, and the welding situation can be accurately grasped.
Therefore, it has the excellent effect of reliably improving the welding quality of the welded portion of the welded metal pipe.

[Brief explanation of drawings]

FIG. 1 is a flow chart showing the gist of the present invention, FIG. 2 is a block diagram showing an embodiment of a welding monitoring device in which the welding status monitoring method according to the present invention is adopted, and FIG.
The figure is a perspective view showing an example of the installation state of the embodiment, and Figures 4A and 4B are diagrams showing an example of the temperature distribution near the welded part of the electric resistance welded pipe for explaining the principle of the present invention. , FIGS. 5A, B, and C show temperatures measured by a conventional method for explaining the effect of the above embodiment.
Figures 6A to 6E, which are diagrams showing examples of changes in the heated area and heating width at the center of the weld measured by the method of the present invention, also show other examples of the temperature distribution and isothermal lines near the weld. The diagrams shown in FIGS. 7A to 7D are
FIG. 2 is a cross-sectional view showing an example of a butting situation of electric resistance welded pipes and an example of a welding situation. 10...Temperature distribution measuring device, 12...Image processing device, 13...Setting device, 14...Monitoring device, 1
6...Tip portion, 18...Image fiber, 20
...Electronic welded pipe, 22...Welded part, 23A, 23B
... Opposite end surface, 24 ... Isothermal line.

Claims (1)

[Scope of Claims] 1. When manufacturing a welded metal pipe by bending a band-shaped metal material and continuously butt-welding its opposing end surfaces, from the V-shape entrance direction, at the welded portions of both of the opposing end surfaces. The temperature distribution at the edge of the sheet thickness direction and at the center portion of the sheet thickness direction is simultaneously detected as an image, and the detected temperature distribution image is compared with a reference temperature distribution image, or an isotherm line of a predetermined temperature is determined from the image. A welding condition monitoring method comprising estimating a heat input condition to the butt welded portion from at least one of the areas. 2. When estimating the heat input situation, the image of the detected temperature distribution is corrected based on welding conditions such as welding speed, welding V-shape angle, and plate thickness of the metal material. Welding status monitoring method described in section. 3. When manufacturing a welded metal tube by bending a strip metal material and continuously butt welding the opposing end surfaces thereof, from the V-shape entrance direction, the edges in the plate thickness direction of the welded portions of both the opposing end surfaces and Simultaneously detect the temperature distribution in the central part in the plate thickness direction as an image, determine the isothermal line of the opposing end surface based on the image of the detected temperature distribution, and determine the temperature distribution for the butt welded portion based on the shape of the determined isothermal line. A welding condition monitoring method, comprising quantifying left-right symmetry and vertical symmetry to estimate a butting condition of the opposing end surfaces.