JP2016182601A - Coating film peeling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable reduction of a physical burden of a worker and proper heat control in a method for peeling a coating film on a steel surface by induction heat.MEANS: An induction generator 12 has an induction head 18 including an induction coil therein, and an electric winch 28 for moving up or down the induction generator 12 is provided. The electric winch 28 is provided at a balance arm 22. The induction generator 12 is suspended by a cable 42 of the electric winch 28. A sensor for detecting a surface temperature of a steel plate or a surface temperature of a coating film is provided in the induction generator 12. A moving speed of the induction head 18 moved by the electric winch 28 is controlled so that the surface temperature of the steel plate or the coating film is in a predetermined range.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an improvement in a method for peeling a coating film on a steel material surface by induction heat.

A method of peeling the coating film on the steel material surface by induction heat is known. In this method, an induction head having an induction coil is provided, and an eddy current is generated in the steel material by an electromagnetic field induced by an alternating current energized to the induction coil, and the steel material is heated by electric resistance heat generation under the generation of the eddy current. The coating film on the steel material surface can be peeled off. Coating film peeling by induction heat enables clean and silent film peeling without generating noise and splashing as in shot blasting, and is relatively low-cost with little environmental impact. This is a useful technology in terms of points. See, for example, Cited Document 1 and Cited Document 2 for this type of coating film peeling method.
Japanese Patent No. 4014409 Japanese Patent Publication No. 63-0667100

  In the method of removing the coating film by induction heat, the coating generator is removed while moving the induction generator by hand along the coating surface of the steel material. The induction generator is integrated with the induction head equipped with the induction coil. Including a holding body with built-in accessories such as energization and cooling, it cannot be said that the weight is about 10 kg. Especially in the case of a bridge, etc., it takes a long time to work at a high place. It was a big and hard work, and there was a demand for reducing the physical burden on workers.

  In addition, when the induction generator is moved manually, large fluctuations in the movement speed of the induction head (induction coil) are unavoidable, and if the movement speed is slow (especially when the steel plate is not too thick), heat conduction There is concern about adverse effects on the coating film on the opposite side below, and conversely, when the moving speed is high, the coating film cannot be peeled off due to insufficient heating of the steel material. The need was sought. In other words, coating peeling by induction heat has been used mainly for large ships, and in the case of large ships, the thickness of the steel material is large, so there is little influence of heat conduction on the opposite side, and there was no importance of heat management. In the case of a bridge, the plate thickness is considerably thinner than that of a ship, so there was a great concern about the adverse effects on the steel plate base metal and the opposite side surface due to heat conduction.

  The present invention has been made in view of such problems, and can reduce the physical burden on the worker without losing the advantage of the peeling method by induction heat that the load on the environment is small. The purpose of this invention is to enable thermal management so as to generate induction heat without excess or deficiency due to the peeling of the coating film even in a steel material whose thickness is not so large.

  According to the present invention, in the paint peeling method in which the induction generator is moved along the object on which the coating film is formed on the steel surface and the coating film is peeled off from the steel surface by induction heat, the movement of the induction generator is induced. A coating film peeling method is provided which is performed by suspending a vessel with a wire and applying a load which is a reaction force of the weight of the induction generator to the wire.

  A winch can be used to apply the reaction force of the weight of the induction generator to the wire, and the winch can be electric. The control of the electric winch can detect the surface temperature of the steel material or the coating film, and can control the temperature of the steel material so that the surface temperature falls within a predetermined range.

  A coating film peeling apparatus for carrying out this method includes a support means for supporting the induction generator and the electric winch while the induction generator is suspended and held by a wire, a surface temperature detection means for an object during film peeling, Means for controlling the electric winch in accordance with the surface temperature detected by the surface temperature detecting means.

  The support means includes a two-joint balance arm and a swivel base, the lower arm of the balance arm is attached to the swivel base, a winch is attached to the upper arm of the balance arm, and the wire fed out of the winch is from the tip of the upper arm Suspend the induction generator in any direction.

  The induction head can be equipped with scrapers (peeling means) for peeling the coating film (exposing the metal surface) before and after the moving direction of the induction head, and the temperature sensor is a non-contact type, and is applied to the steel surface or coating film surface. It can be positioned before and after the guide head moving direction so as to be close to each other.

  According to this invention, the load which becomes the reaction force of the weight of an induction generator is applied to the wire which suspends an induction generator. Therefore, it is possible to reduce the load on the worker and perform long-time work without physical exhaustion.

  In addition, it is possible to perform appropriate temperature management of steel materials by controlling the movement of the induction head according to the surface temperature of the object, enabling induction heating without excess or deficiency for peeling the coating film on the surface. In addition, it is possible to prevent the temperature of the steel material from being excessive, to prevent the adverse effect on the coating film on the opposite side, and to eliminate the concern of the thermal effect on the steel material itself (base material).

FIG. 1 is a schematic perspective view of a coating film peeling apparatus according to the present invention. FIG. 2 is a schematic plan view of the electric winch and the induction head of the apparatus of FIG. 1, and shows a schematic electrical system connection diagram of both. FIG. 3 is a schematic side view of the induction head. FIG. 4 is a schematic side view of the balance arm in the apparatus of FIG. FIG. 5 is a graph showing the relationship between the moving speed of the induction head and the steel sheet surface temperature. (A) shows the measurement result immediately below the induction head (temperature peak), and (b) shows 2 after passing the induction head. The measurement result after 2 seconds is shown. FIG. 6 is a graph showing the relationship between the moving speed of the induction head and the coating film surface temperature. (A) shows the measurement result immediately below the induction head (temperature peak), and (b) shows the result after passing the induction head. The measurement result after 2 seconds is shown. FIG. 7 is a graph showing the relationship between the steel plate surface temperature and the coating film surface temperature, (A) shows the measurement result directly under the induction head, and (B) shows the measurement result 2 seconds after passing through the induction head. Indicates. FIG. 8 is a schematic operation diagram of the apparatus shown in FIGS.

[Specific configuration]
FIG. 1 schematically shows a coating peeling method according to the present invention, wherein 10 is an I-digit (I-shaped cross section) as an object of peeling work in which a coating film is formed on the surface of a steel material, and 12 is induction heat. The induction generator 12 includes a holding body 13, a cable 14 for energization and cooling water is connected to the holding body 13, and a bracket 16 extends from the holding body 13. An induction head 18 having an induction coil (not shown) is provided at the tip of the bracket 16, and wheels 20 are attached to both ends of the induction head 18. The coating film peeling by the induction generator 12 is performed by moving the guidance head 18 along the peeling required surface while the operator holds the holding body 13. At that time, the wheel 20 is intended to smoothly move the guide head 18 along the surface of the steel plate 10 by rolling. The induction head 18 is moved up and down along the surface of the steel plate 10 arranged upright (the downward direction is indicated by an arrow a in FIG. 1 and the upward direction is indicated by an arrow b), and the coating film on the surface of the steel plate 10 is induced by induction heat. The peeling of 10A (see FIG. 3) is performed. By applying an alternating voltage to the induction coil, an eddy current is generated in a portion of the steel plate 10 facing the induction coil, and the steel plate 10 is heated at the eddy current generation site by an electric resistance when the eddy current flows in the steel material. Thus, the coating film 10A on the surface of the steel plate 10 is peeled off. As an example of such a coating film peeling apparatus using induction heat, there is a product of RPR Technologies A / S of Norway. In the conventional film peeling by this kind of induction heating, an operator holds the induction generator 12 at the site of the main body 13 or the bracket 16 and moves the induction head 18 along the surface of the steel plate 10 under the guide of the wheel 20. However, since the total weight of the induction generator 12 is about 10 kg, work such as work on an upright surface at a high place such as a bridge continues to support the weight for a long time. The physical burden was heavy and it was a difficult task for the workers. In addition, it is necessary to apply appropriate heat to the steel material when the coating film is peeled off by induction heat. However, a large fluctuation in the speed of the induction head (induction coil) is unavoidable in the moving operation based on the conventional manual operation, and the speed is high. If it is too large, the coating cannot be peeled off due to insufficient heating, and if the speed is too low, excessive induction heat will be generated, and in the case of bridges, the steel sheet may be thin. This heat is transferred to the opposite side of the steel plate 10 under heat conduction (inner side in the case of a box girder (box-shaped cross section)), adversely affecting the coating applied to the opposite side (deterioration of the coating), and There was concern about overheating of the steel plate 10 even if it adversely affects the steel itself (strength and the like).

  In order to reduce the burden on the operator due to the weight of the induction generator 12, the present invention supports the induction generator 12 with a winch so that the operator can work without substantially experiencing the weight. The moving speed of the induction head 18 is controlled so that the induction heat generated in the steel sheet is appropriate, and this will be described below. The support device (support means) for the induction generator 12 according to an embodiment of the present invention is generally designated by reference numeral 22. The support device 22 includes a balance arm 24, a swivel base 26, and an electric winch 28 as basic components. The balance arm 24 is configured as a two-joint arm including an upper arm 30 and a lower arm 32, and the upper arm 30 and the lower arm 32 are pivotally connected by a pivot 34. The swivel base 26 includes a turntable 36, and the lower end of the lower arm 32 of the balance arm 24 is rotatably connected to the turntable 36 by a pivot 38. The rotary table 36 can freely rotate around the upright axis with respect to the swivel base 26. Further, in this embodiment, the swivel base 26 is placed on the slide type pedestal 40, and the slide type pedestal 40 accommodates the flange portion 10-1 of the steel plate 10 with the extending portion toward the steel plate 10 being an I-digit. Thus, the channel shape is formed, so that the slide base 40 can be freely slid along the flange portion 10-1 of the steel plate 10 in the longitudinal direction of the steel plate 10. If necessary, a lock means such as a lock bolt for temporarily fixing the slide base 40 to an arbitrary portion of the flange portion 10-1 can be provided. A wire 42 extends from the winch 28, and the wire 42 suspends the induction generator 12 via a guide roller 44 at the tip of the upper arm 30. The tip of the wire 42 is connected to a metal connecting ring 46, and the connecting ring 46 is passed through a U-shaped metal fitting on the outer wall surface of the holding body 13. Therefore, the induction generator 12 suspended from the wire 42 can be pressed against the steel plate 10 by manual operation.

  The winch 28 is an electric type, and as shown in FIG. 2, the winch 28 includes an electric motor 48 and a gear type reduction gear 50, and a winding wire 42 is wound around a winding drum 51 connected to the reduction gear 50. The winding and feeding of the winding wire 42 can be switched by forward and reverse rotation of the electric motor 48. The electric motor 48 is provided with an electromagnetic brake in a known inside, and is automatically braked when the electric motor 48 is stopped. The reduction gear 50 is configured to have a large reduction ratio of 40 to 1 with large and small meshing gears, and the rotation of the electric motor 48 is reduced and transmitted to the winding drum 51. The electric motor 48 is fixed to the upper arm 30 by a mounting portion 49 (FIGS. 1 and 4), and further includes a control unit 54 described later, and can control the speed of the induction head 18 according to the surface temperature of the steel material as described later. It has become.

  The balance arm 24 configured as a two-joint arm in FIG. 1 can maintain the posture while receiving the load of the induction generator 12 and the winch 28 by the spring. The structure itself provided is well known. The coil spring provided on the pivot 34 is schematically represented by a compression spring 52 disposed between the upper arm 30 and the lower arm 32 in FIG. 4, and the coil spring provided on the pivot 38 is represented by the lower arm 32. And a compression spring 53 between the tables 36. When these weights are applied to the natural state of the compression springs 52 and 53 where the induction generator 12 and the winch 28 are not weighted on the winding wire 42, the compression springs 52 and 53 generate a spring force in the direction of the arrow and contract. It will be. The support arm 24 is not limited to the balance arm 24 for supporting the induction generator 12 and the winch 28, and an alternative means can be adopted as the support means. For example, the induction generator 12 can be suspended simply by a columnar body. Is possible. In addition, as an embodiment of the present invention, an electric winch is not necessarily used. The induction generator 12 is suspended by a wire, and a reaction force in a direction to reduce the weight is generated on the wire, thereby reducing the load on the worker who performs coating film peeling. Mitigating is also encompassed.

  FIG. 3 schematically shows the induction generator 12 from the side. A mounting bracket 56 is provided on the top surface of the induction head 18, and the mounting bracket 56 moves in the direction of movement of the induction generator 12 (the horizontal direction in FIG. 3). Temperature sensors 58a and 58b are provided at both ends thereof (upper and lower ends in FIG. 1). The temperature sensors 58a and 58b are well-known non-contact type (infrared camera type or the like), and are arranged close to the surface of the steel plate 10. The mounting bracket 56 is provided with upper and lower scrapers 59a, 59b (partial coating film peeling means of the present invention) for scraping the coating film on the surface of the steel material, with the tip thereof facing the wheel 20 slightly downward. The scrapers 59a and 59b have sharp tip surfaces extending in the width direction (perpendicular to the paper surface of FIG. 3), and can scrape the coating film for the width of the scrapers 59a and 59b. The temperature signals from the temperature sensors 58a and 58b are sent to the control unit 54 through the signal line 60 as shown in FIG. The holding body 13 has an operation unit 62 on its upper surface. The operation unit 62 includes switches 63a and 63b. The switch 63a is used for lowering the induction generator 12, and the switch 63b is used for raising the induction generator 12. is there. Further, a green lamp 64-1 for displaying normality of the winch raising / lowering operation and a red lamp 64-2 for displaying abnormality are provided. A signal line from the switch and operation display unit 62 to the control unit 54 is indicated by 66. When neither of the switches 63a and 63b is pressed, the control unit 54 stops the electric motor 48, brakes the electromagnetic brake inside the electric motor 48, and winds (raises) the wire 42 of the electric winch 28. The induction generator 12 is designed to remain in a fixed position by being braked by a brake without being fed out or lowered (lowered). Reference numeral 68 denotes a limit switch for preventing overwinding. As shown in FIG. 4, when the induction generator 12 is wound up to the upper limit, the feeler 68-1 of the limit switch 68 generates induction. The electric motor 48 is stopped by the control unit 54 via the signal line 70 (FIG. 2) and the electric motor 48 is stopped (the brake is also applied by the electromagnetic brake) to prevent the wire 42 from being overwound. .

  In the present invention, the entire load of the induction generator 12 is supported by the support device 22, and the upper and lower sides of the induction generator 12 are performed by winding and unwinding the wire 42 of the electric winch 28. The worker places the induction head 18 close to the required peeling site of the coating film 10A (see FIG. 3) on the steel surface, bites the scrapers 59a and 59b into the coating film 10A, and operates the switches 63a and 63b to operate the coating film. 10A can be peeled off. The worker does not need to support the weight of 10 kg of the induction generator 12 during the work, and can reduce the labor of the worker. That is, in the vertical direction, the induction generator 12 is raised by rotating the winch 28 by pressing the switch 63b, and the induction generator 12 is lowered by reversing the winch by pressing the switch 63a. Thereby, coating-film peeling of the surface of the steel plate 10 can be implemented in the whole area of an up-down direction. And about the longitudinal direction of the steel plate 10, the coating film peeling by induction heat can be performed about the whole area of a longitudinal direction, moving the support apparatus 22 of the induction head little by little with the slide type base 40. FIG. Since the balance arm 24 is installed on the swivel base 26, the position of the guide head 18 with respect to the steel plate 10 in the longitudinal direction can be finely adjusted by turning the balance arm 24 on the swivel base 26.

  In the above-described example, the scrapers 59a and 59b also have a coating film peeling function, but the coating film peeling can be manually performed by a worker with a tool such as a spatula as usual. In this case, the scrapers 59a and 59b (peeling means) are provided with needle-like portions slightly bent toward the wheel 20 at the front and rear of the wheel 20, and the rear side in the moving direction of the induction generator 12 prior to coating film peeling. The needle-like body is punctured, and the coating film is peeled linearly under the continuous movement of the induction generator 12, thereby exposing the metal surface after passing the needle-like body to a linear shape. The temperature of the metal surface may be detected by the temperature sensor 58a or 58b located on the side.

[Temperature measurement results with thermocouple]
For an upright steel plate (SS400) with a thickness of 12 mm coated with a typical phthalic acid resin paint (used for bridges, etc.) (average film thickness of about 30 μm), the induction head of RPR Technologies A / S ( The thermocouple was fixedly installed so that the temperature of the steel plate surface and the coating film surface could be measured on the heating side and the back side at each of nine locations (No. 1 to No. 9). The temperature was measured by moving the induction generator 12 (moving from top to bottom or from bottom to top) as shown in FIG. The moving speed of the induction head 18 was calculated from the time required for moving between fixed points. When the induction head 18 (induction coil) in the induction generator 12 faces the thermocouple (position directly above) (when the temperature reaches a peak), the steel sheet surface temperature and the coating film surface temperature on the heating surface side and the back surface side Measurement was performed. The thermocouple measurement was sampled every 2 seconds. Table 1 shows the measurement results on the heating surface side (induction generator 12 side) and the back surface side (opposite side of the induction generator 12) when the induction head 18 is directly opposite the thermocouple and the measured value reaches a peak. It is.

Table 1 (Measured value at peak)
Heating side temperature (° C) Backside temperature (° C)
No Steel sheet surface Paint film surface Steel sheet surface Paint film surface Speed (m / min) Movement direction
1 220 87 70 72 3.3 Top → Bottom
2 259 91 78 67 3.9 〃
3 289 85 72 65 3.3 〃
4 135 57 47 49 4.7 Bottom → Top
5 211 65 55 58 5.4 〃
6 114 60 57 55 3.8 〃
7 171 66 57 54 4.9 〃
8 178 52 54 64 4.3 〃
9 144 84 59 62 4.2 〃

  Table 2 shows the measurement results of the temperature of the steel plate surface and the coating film surface on the heating surface side measured by the thermocouple at the time of sampling 2 seconds after the induction head 18 is directly facing the thermocouple.

Table 2 (Measured value after 2 seconds)
Heating surface side temperature (℃)
No Steel sheet surface Paint film surface Speed (m / min) Movement direction
1 197 86 3.3 Top → Bottom
2 221 73 3.9 〃
3 168 84 3.3 〃
4 114 57 4.7 Bottom → Top
5 89 61 5.4 〃
6 79 59 3.8 〃
7 85 65 4.9 〃
8 110 51 4.3 〃
9 86 84 4.2 〃

  From the results of Tables 1 and 2, when examining the relationship between the steel plate or coating film temperature on the heating surface side (the induction generator 12 installation side) and the moving speed of the induction head 18, FIG. The relationship between the moving speed of the induction head 18 at the peak time (when the induction head 18 is directly facing the thermocouple) and the steel sheet surface temperature is shown. (B) is the same when 2 seconds have elapsed from the peak position on the heating surface side. Showing the relationship. Although the fluctuation of the data is large, it can be seen that there is an inversely proportional relationship between the moving speed and the steel plate surface temperature at both the peak time and the time when 2 seconds elapse in the speed range of about 3-6 m / min of the induction head 18. .

  FIG. 6 (a) shows the relationship between the moving speed of the induction head 18 and the coating film surface temperature at the peak time on the heating surface side (when the induction head 18 is directly facing the thermocouple), and (b) is the heating surface. A similar relationship is shown when 2 seconds have elapsed from the peak position on the side. In this case as well, the data fluctuation is large, but it can be seen that there is an inversely proportional relationship between the moving speed and the coating film surface temperature even after 2 seconds in the speed range of about 3-6 m / min of the induction head.

  From the above, it can be seen that it is possible to use either the steel plate surface temperature or the coating film surface temperature on the heating surface side in order to manage induction heat applied to the steel plate. In addition, the detection position of the steel plate surface temperature or the coating film surface temperature is not necessarily the time when it is directly facing (peak) with the induction head. It can be seen that this can be reflected in the control of induction heat (deceleration of the induction head 18 when heating is insufficient and acceleration of the induction head 18 due to excessive heating).

  Next, when the influence of the induction heat generated by the induction generator 12 on the back side of the steel sheet is examined from the results of Table 1 in which the temperature on the back side is also measured, in the case of a phthalate resin-based paint, the steel material temperature is approximately It is said that the coating film can be peeled off from around 120 ° C. From Table 1, in the speed range of the induction head 12 of approximately 3-6 m / min, the surface temperature of the steel sheet generally reaches this value on the heating surface side. On the other hand, although it is the temperature on the back surface side, the surface temperature of the steel plate does not exceed 80 ° C. on the back surface side even if the surface temperature of the steel plate reaches the maximum around 290 ° C. on the heating surface side, and heating is performed in the above speed range. It was found that the induction heat on the surface side does not affect the coating film on the back surface side. Moreover, it can be said that the influence of the heating of the steel sheet by induction heat eliminates the concern about the strength characteristics of the steel material in view of the maximum temperature around 290 ° C. on the surface side.

[Operation example for temperature control]
Considering the above experimental results, an example of operation in which the steel sheet surface temperature range is set to 140 ° C. to 240 ° C. and control is performed from 160 ° C. to 220 ° C. with allowances in the vertical direction will be described. A schematic diagram of this operation is shown in FIG. Regarding the temperature measurement, the specific apparatus shown in FIGS. 1 to 4 uses a non-contact type sensor 58a, 58b such as an infrared camera type instead of a thermocouple for measuring the surface temperature during movement. .

In starting from a cold temperature state, the temperature of the coating film to be peeled off from the steel plate surface as well as the steel plate 10 is also low. When the induction generator 12 is brought close to the surface of the coating film in order to start the peeling operation, the temperature of the steel material facing the induction head 18 is heated by the induction heat, and the coating film on the surface is heated by the temperature increase of the steel material. Temperature rises. Assuming that the operation starts after the coating film is peeled downward, the direction in which the guide head 18 should move in FIG. 3 is an arrow a (the right direction in FIG. 3). In this direction, the scraper 59a located on the left side (upper side in FIG. 1) scrapes off the coating film 10A. In this case, the steel surface temperature is detected by the sensor 58a on the upper side (rear side in the movement direction a), and the surface temperature of the coating film 10A is detected by the sensor 58b on the lower side (front side in the movement direction a). When the coating film 10A is not peeled off, the non-contact sensor 58a cannot detect the temperature of the surface of the steel plate 10. On the other hand, the temperature of the coating film surface increases due to the heating temperature rise of the steel material by induction heating by the induction head body 13, and the sensor 58b detects the temperature of the coating film surface (the sensor 58b is located slightly off the induction head 18). However, the approximate temperature of the coating can be determined by heat conduction). In this state, the motor 48 of the electric winch 28 does not rotate and the induction generator 12 remains in that position. Temperature of the coated surface by induction heat rises like a line L _P of FIG. When induction heating of the steel material progresses from the cold temperature and the temperature of the coating film rises to about 120 ° C., the surface temperature of the steel sheet 10 also rises to a temperature at which the coating film can be peeled off, such as 200 ° C. At this time t _0, the start of coating film peeling is indicated by the movement of the induction generator 12 (lowering of the induction generator 12), the rotation of the motor 48 of the electric winch 28 is started, and the wire 42 is fed out. 12 starts descending (arrow a). At this time, the feeding speed (guide head moving speed) of the wire 42 is an initial set value such as 4 m / min. The upper scraper 59a starts peeling of the coating film 10A that has floated on the metal surface when lowered (or the scraper 59a is responsible only for the exposure of the steel surface for detecting the steel surface temperature, and the coating film peeling is performed manually with a spatula or the like. Can be done). In FIG. 3, the part of the coating film where the upper scraper 59a has started to bite is indicated by 10A ′, and FIG. 3 shows that the coating film has peeled somewhat and the upper temperature sensor 58a is opposed to the metal surface. Detection of the surface temperature of the steel material by the sensor 58a is started, and movement control of the induction generator 12 is performed so that the lower threshold value is 160 ° C. and the upper threshold value is 220 ° C. That is, in this control example, the temperature sensor 58a detects the steel sheet surface temperature at a position slightly below the induction head 18 (a position slightly beyond the position facing the induction coil). In FIG. 8, the detection interval of the metal surface temperature by the temperature sensor is δ (for example, 0.5 seconds), that is, when the temperature is lowered (arrow a), the temperature detection by the temperature sensor 58a is performed every 0.5 seconds. In a situation where the metal surface temperature detected by the upper temperature sensor 58a is lowered along the line L _S1 , if the lower temperature falls below 160 ° C., the first speed drop is commanded (this time is represented by t ₁₎ . ), the moving speed of the induction head 18 by feeding the wire 42 (lowering speed) is one paragraph 4m / min 3.8 m / min, fall change resulting temperatures are loosened like a line _{L S2.} If the steel sheet surface temperature remains below the lower threshold of 160 ° C., a second speed drop of 3.6 m / min is commanded (this time is represented by t ₂ ). In this way, temperature detection is performed at regular time intervals, stepwise (by 0.2 m / min) speed control is performed, and finally, the temperature is switched to a temperature rise as shown by line L _S3 . It exceeds the threshold value 160 ° C. (representing the time at _{t 3).} Conversely, when the steel surface temperature exceeds the upper threshold 220 ° C. (indicated by the line L _S4 ), a first-stage speed increase is commanded (this time is indicated by t ₄ ). When the state exceeding the upper threshold value 220 ° C. is continued, the second stage speed increase is commanded, and the stepwise speed increase is performed every δ seconds in this way. As a result, the steel surface temperature falls below the upper threshold value 220 ° C. as indicated by line L _S5 .

  When raising, the raising switch 63b (FIG. 2) is pushed, and the induction generator 12 is raised (in the direction of arrow b in FIG. 1 and leftward in FIG. 3), and the coating film 10A is scraped off by the lower scraper 59b ( Alternatively, the coating film is manually scraped off with a spatula or the like), and the lower temperature sensor 58b (FIG. 3), which is now positioned behind the moving direction b, faces the scraped surface of the steel plate 10. Thus, the steel plate surface temperature is measured, and the control of the upward movement speed of the induction head 18 according to the steel plate surface temperature detected by the temperature sensor 58b is performed in the same manner as the control of the downward speed of the induction head 18 described with reference to FIG. It is. That is, the temperature detection by the temperature sensor 58b is performed every time interval δ, and if the steel surface temperature detected by the temperature sensor 58b falls below the lower threshold 160 ° C., the temperature of the induction head 18 is increased due to the temperature rise of the steel plate. If the steel surface temperature detected by the temperature sensor 58b exceeds the upper threshold value 220 ° C. by stepwise deceleration (by 0.2 m / min), the temperature of the steel plate is lowered to increase the rising speed of the induction head 18 stepwise. The speed (0.2 m / min) is performed, and the steel surface temperature is controlled to a predetermined range even when the induction generator 12 is raised by such control.

  By the above control, as shown in FIG. 8, the steel surface temperature is controlled between 140 ° C. which is appropriately lower than the lower threshold value 160 ° C. and 240 ° C. which is appropriately higher than the upper threshold value 220 ° C. If so, the green lamp 64-1 (FIG. 2) is lit. If the steel surface temperature falls below 140 ° C. or exceeds 240 ° C., it is determined that the coating film has not been removed normally, and the red lamp 64-2 is turned on. The operation display of the lamps 64-1, 64-2 is performed in conjunction with the operation of the electric winch 28, and the lamp display is terminated when the electric winch stops (the wire 42 is applied by braking the brake built in the electric winch). Also stop).

  In the explanation of the operation related to FIG. 8, the speed control of the induction head 18 is performed according to the steel plate surface temperature. However, as shown in FIG. 7, the steel plate surface temperature also has a corresponding relationship with the coating film surface temperature. The speed of the induction head 18 can be controlled according to the above. That is, in this case, the front sensor in the direction of movement of the induction generator 12 (sensor 58b when the induction generator 12 moves in the direction of arrow a in FIG. 3, and the induction generator 12 moves in the direction opposite to arrow a. When the sensor 58a) detects the temperature of the coating film 10A, the movement of the induction generator 12, that is, the control of the winch 28 is controlled so that the temperature of the coating film 10A falls within a predetermined range.

  In the above description, the coating film is peeled off both when the induction generator 12 is raised and lowered. However, the movement of the induction generator 12 at the time of peeling the coating film can be performed only during one of the raising and lowering. It is. In this case, the temperature sensation does not have to be on both sides and may be installed on one side. In the case of speed control based on the steel surface temperature, the back side in the direction of movement after peeling the coating (after passing through the induction head), the speed depending on the coating surface temperature In the case of control, it may be installed only on the front side (before passing through the induction head) in the moving direction after coating film peeling.

10 ... I-type steel plate (object of peeling work)
DESCRIPTION OF SYMBOLS 12 ... Induction generator 13 ... Holding body 18 ... Induction head 20 ... Wheel 22 ... Induction generator support apparatus (support means)
24 ... balance arm 26 ... swivel 28 ... electric winch
34, 38 ... pivot 36 ... rotary table 40 ... slide base 42 ... wire 48 ... electric motor 50 ... speed reducer
58a, 58b… Temperature sensor
59a, 59b ... scraper (partial coating film peeling means of the present invention)
62. Operation unit
63a, 63b ... switch 68 ... limit switch

Claims (2)

The induction generator is moved up and down while moving along the steel sheet with the coating film formed on the surface of the existing bridge, which is the work object, and the coating film is heated by induction heat. In the longitudinal direction of the steel sheet, the induction generator is moved laterally, and the temperature rise of the coating film by the vertical movement of the induction generator and the peeling of the coating film by the scraper are repeated. The speed of the vertical movement of the induction generator for peeling the coating film is detected on the heating surface side in order to prevent adverse effects on the base material strength due to overheating. The coating film peeling method is controlled such that the steel sheet surface temperature to be within a predetermined range and the steel sheet surface temperature detected on the side opposite to the heating surface does not exceed a predetermined value . In the first aspect of the invention, the predetermined range of the steel sheet surface temperature detected on the heating surface side is 140 ° C. to 240 ° C., and the predetermined value of the steel sheet surface temperature detected on the side opposite to the heating surface is 80 Coating film peeling method which is ° C.

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