JPS6125776B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for repairing an electric resistance welded part of a plated steel pipe by melting and adhering a repair metal wire to a bead cut part and applying ultrasonic vibration. Thermal spraying is a conventional method for repairing electric resistance welded parts of galvanized steel pipes, but the present inventors have proposed an improved method of applying ultrasonic vibration by supplying molten metal, and a method that replaces molten metal. We have previously proposed a method for supplying metal wires. These conventional techniques and prior art will be explained below. First, the outline of the manufacturing process for galvanized ERW steel pipe will be explained. As shown in Fig. 1, the pre-stripped steel strip is
It is formed into a U-shape by a breakdown roll, and then made into a circle by the seam guide part 1, and at the same time, while being correctly guided at both ends, it is transferred to the welding process in the form of an open pipe 2 with an open seam. Here, the welding machine 3 uses a low-frequency or high-frequency alternating current as a power source and uses the heat generated by the induced current to rapidly and intensively heat only both edges of the open pipe 2 after forming, and immediately heats the squeeze roll 4. Apply pressure from the side to join. Furthermore, when pipes are welded using the method described above, some of the softened steel is pushed out by the pressure of the squeeze rolls and remains as a bead on the outside and inside of the pipe. , among these, the outer ones are always cut and removed by the bead cutter 5.
In addition, the inner bead is cut and removed, if necessary, with a knife attached to the end of a rod inserted halfway into the molding machine. In addition, in FIG. 1, two bead cutters 5 on the outer surface are arranged in series in the line direction, but
The cutter blades are operated one at a time in turn due to the need to replace the cutting edges. This cutting simultaneously removes the pre-applied dings, so after removing the bead portion on the outer surface, a thermal spray coating is formed on the cut surface of the bead using a hot-dip metal spraying machine 6, and repair plating is performed. Furthermore, since the repaired plating surface will show unevenness of the thermal spray particles and deteriorate its appearance, the thermal spraying surface will be polished and smoothed using a polishing device 7 such as a buff or wire brush, and the plating will be removed from the areas other than the repaired area. Thermal spray particles adhering to the surface of the steel pipe are also removed by polishing. After this, the electric resistance welded pipe P is cooled, the outer diameter is corrected using a shaping machine consisting of several sets of rolls, and then cut to a predetermined length by a traveling cutting machine that moves in synchronization with the pipe, and then the finishing process is carried out. send to In this galvanized electric resistance welded steel pipe manufacturing process, the conventional plating repair of the welded portion after cutting the outer surface bead has been carried out by the thermal spraying method as described above. (i) Thermal spraying method In this thermal spraying method, galvanized metal wire such as zinc wire is melted by heat from gas and arc, and at the same time, the molten metal is atomized by high pressure gas such as compressed air. This method involves spraying these fine particles onto the cut surface of the bead at high speed to make them adhere tightly. However, the adhesion between the thermal sprayed metal and the bead cut surface steel substrate is often a mechanical or physical bond, and the metal particles are layered one after another on the substrate to form an adhesion form. There are many pores in the coating, and its bulk density is 80 to 90 times the density of solid metal.
%. For this reason, the adhesion of the sprayed coating is poor, causing problems such as the repair layer peeling off when processed. In addition, in the thermal spraying method, polishing is added to obtain a smooth surface of the sprayed coating, but this removes the sprayed coating on the surface, making the entire repair layer thinner and resulting in extremely poor corrosion resistance in the repaired area. Such problems arise. In this thermal spraying method, several thermal spraying machines are lined up in a line direction, or several thermal spraying machines are placed at the same point, and spraying is carried out in order to improve adhesion and repair plating thickness and improve rust prevention performance. Measures are being taken.
However, even in this case, the essential drawbacks of the thermal spraying method cannot be compensated for, and it seems that it is not a fundamental countermeasure. (ii) Repair by supplying molten metal In order to solve these problems, the inventor of the present invention brought the molten metal itself into contact with the repaired part using a special method, instead of using fine molten metal particles, and applied ultrasonic vibration. We have previously proposed a method to improve the adhesion between the steel base of the bead cut and the molten metal. In this method, as shown in FIG. 2, the bead portion of an electrically welded and clamped steel pipe 11 is removed with a cutting tool, and then molten zinc 14 is supplied from a molten metal supply tank 13 to the bead cut surface 12 of the welded portion. At the same time, the ultrasonic vibrator 15 is activated to apply ultrasonic vibration to the molten zinc 14, the bead cut surface 12, and the plating layer near the bead cut surface, thereby forming a plating metal layer on the bead cut surface 12. This is the way to do it. According to this method, the oxide film and other stains that have formed on the bead cut surface are removed due to the cavitation effect in the zinc bath due to the sound pressure and ultrasonic vibration of the ultrasonic waves, so an iron-zinc alloy layer is formed. It becomes easy to apply and the adhesion is good. Moreover, since the surface of the repair plating layer is smooth, polishing such as buffing is not required as in the case of thermal spraying, and a sufficient plating thickness, a uniform plating layer, and sufficient corrosion resistance can be obtained. However, it is relatively difficult to operate this method without causing molten zinc to flow out from the gap between the tip 13a of the molten metal supply layer 13 and the fitted steel pipe 11. For this reason, there is a drawback that it is difficult to maintain a constant repair plating width. (iii) Repair method by supplying metal wire To solve this problem, the present inventor previously proposed a method in which a solid plated metal wire is supplied directly to the bead cut surface and melted instead of molten metal. . In this method, as shown in FIG. 3, the ends of the steel strip are brought into close contact with each other, and after electric resistance welding, the bead portion is cut and smoothed. Next, the bead cut portion of the plated steel pipe 21 is locally heated using a burner 22 or the like. This heating is performed to a temperature at which the plated metal wire 23 melts (approximately 420° C. or higher). After that, conduit 2
4 is supplied to the bead cut part, and is melted by the amount of heat held by the bead cut part. Further, at the same time as this melting or before resolidification, ultrasonic vibrations generated by an ultrasonic vibrator 25 are applied to the molten metal layer by an ultrasonic tip 26, so that the entire surface of the bead cut portion is coated with the molten metal. Form a layer. According to this method, while melting the plated metal wire 23 according to the required amount, ultrasonic vibrations are applied by the ultrasonic chip 26 having the same width as the bead cut portion, so that the molten metal does not flow out other than the bead cut portion. This allows for stable repair work without the risk of disrupting operations. However, in this method, since the bead cut portion is heated with a burner or the like prior to supplying the plated metal wire, a large amount of oxide film is present on the surface. For this reason, if a plating metal wire is supplied and melted and adhered to this surface, the oxide film cannot be removed even if ultrasonic vibration is applied, and there is a risk that the necessary plating adhesion cannot be secured. . The present invention has been made in view of the above circumstances, and its purpose is to perform part or all of the process from bead cutting to ultrasonic vibration in a non-oxidizing atmosphere, thereby causing oxidation to occur on the steel base surface of the bead cut portion. It is an object of the present invention to provide a method for repairing an electric resistance welded part of a galvanized steel pipe, which can improve the adhesion of the repaired welded part without forming a film. That is, in the present invention, after bead-cutting and heating a plated electric resistance welded part of a plated steel pipe, a metal wire for repair is fed by a feed roll at an angle close to perpendicular to the bead cut part, and the wire is melted and adhered. This is a method in which a part or all of the steps from the bead cutting step to the step of applying ultrasonic vibration are performed in a non-oxidizing atmosphere. The method of the present invention will be explained below with reference to Examples 1 to 5 illustrating the method. 4 to 8 show a repair device for an electric resistance weld. This repair device includes, after a bead cutter 31, a bead cut part heating device 32, a bead cut surface polishing device 33 for removing an oxide film, a plating metal wire supply device 34 for repair, and an ultrasonic vibration applying device 3.
5 are arranged in series, a part or all of the ultrasonic application device 35 from the bead cutter 31 is covered with seal boxes 36 and 37, and an inert gas,
It is maintained in a non-oxidizing atmosphere such as reducing gas. The bead cut portion heating device 32 uniformly preheats the surface of the relatively narrow bead cut without affecting the plating portion of the plated electric resistance welded tube 38.
Examples include high frequency heaters, infrared heaters, gas burners, and the like. Further, some steel weaving pipe manufacturing lines can melt the zinc wire with only the residual heat during welding, so in this case there is no particular need to use the heating device 32. The bead cut surface polishing device 33 physically removes an oxide film of iron oxide formed on the surface of the bead cut in the section from the bead cut to the plating metal wire supply position. This device is also used appropriately depending on the type of heating device 32 and the range of use of the seal box. The plated metal wire supply device 34 appropriately supplies the plated metal wire 39 to the bead cut portion, and has a mechanism that can control the supply speed for various plated metal wire diameters. Furthermore, if the supply device 34 is provided with a plating metal wire preheating device 40 such as an electric heating type, the plating metal wire supplied to the bead cut portion can be easily melted, which is very effective. Further, the ultrasonic vibration applying device 35 propagates the ultrasonic vibration generated by the vibrator 41 from the ultrasonic iron part 42 to the repair plating layer 43.
directly contacts the repair plating layer 43 and applies ultrasonic sound pressure and cavitation effect to the interface between the iron oxide film and the molten metal to destroy the oxide film and improve adhesion, wettability, and width uniformity. This improves the properties and thickness uniformity. The tip of this iron part 42 is
It is preferable to heat the plating metal to a temperature higher than the melting point of the plating metal using a heating device 44 such as electric heating to prevent quality deterioration of the repaired plating portion due to solidification of the plating metal. Furthermore, the seal boxes 36 and 37 are used to prevent the formation of an oxide film from immediately after the bead cut to the plating metal wire supply position. It is shielded from the atmosphere by the atmosphere. However, as will be described later, in cases where a polishing device 33 for polishing the oxide film is used, or when a burner that generates a reducing flame is used as the bead cut heating device 32, everything from the bead cut 31 to the ultrasonic application device 35 is used. It is also possible to provide a seal box not only in a part of the seal box but also in a part of the seal box. Example 1 However, in the example shown in Fig. 4, the electric resistance welded steel pipe used has an outer diameter of 60.3 mm and a wall thickness of 3.2 mm, and is hot-dip galvanized on the inner and outer surfaces. One side is 500g/ ^m2 . This electric resistance welded steel pipe 38 is formed into a pipe by passing through a forming mill, a welding machine, and a squeeze roll at a speed of 25 m/min, and enters the seal box 36. Inside the seal box 36, the outer bead after welding is scraped off by a bead cutter 31 made of a bead cutting tool. The width of the bead cut part after bead cutting is
Approximately 5 mm, its surface is relatively smooth. At the center of this bead cut, the temperature is around 600℃ due to residual welding heat, but at both ends of the bead cut, the temperature drops to around 300℃, and the temperature distribution in the width direction is extremely big. After the bead is cut, the bead cut is uniformly heated in the width direction using a high frequency bead cut heating device 32 to raise the average temperature to about 500°C. Immediately thereafter, a zinc wire 39 having a diameter of 5 mm, which is a plating metal wire, is supplied from the tip of the plating metal wire supplying device 34 to the bead cut portion, and is heated and melted at the same time as it comes into contact. This zinc wire 39 is held in a state wound around a plated metal wire spool 45, and is continuously pulled out by a plated metal wire feed roll 46.
sent to a. Further, an electric plated metal wire preheating device 40 is installed around this tip 34a,
The zinc wire is preheated to near melting temperature before contacting the bead cut. In this embodiment, the electric power supplied to the preheating device 40 is controlled in accordance with the amount of zinc wire supplied, and the temperature of the zinc wire is set at 350 to 400°C. Immediately after the zinc wire is supplied, ultrasonic vibrations are propagated from the ultrasonic vibrator 41 to the iron part 42. The ultrasonic vibrations are propagated from the tip of the iron part 42 into the molten zinc coating.
In this embodiment, the output of the ultrasonic transducer 41
The power was 300W, the ultrasonic vibration was 19.5KHz, and the tip of the iron was kept at a constant temperature of about 450°C by an ultrasonic iron heating device 44. In this embodiment, the shape of the tip of the soldering iron part is slightly wider than the width of the bead cut part. In this way, the molten zinc coating is applied to the ERW steel pipe 3.
8, there is no plating missing between the repaired part and the pre-pitched part, and there is no difference in appearance from the plating part of the electric resistance welded pipe. , it becomes possible to perform repair fixing with the same adhesion strength. In addition, the width of the repair plating is almost the same as the width of the ultrasonic iron part 42, so by using ultrasonic irons of different widths, it is possible to easily handle electric resistance welded steel pipes with different bead cut widths. The width of the repair plating can be arbitrarily controlled by the width of the ultrasonic iron. Further, in this embodiment, the seal box is divided into a seal box 36 that encloses the bead cutter portion and a seal box 37 that encloses the heating device. This is because the bead cutter needs to be communicated with the outside air periodically in order to remove cutting waste from the bead, and the seal box here has a structure that can be easily opened and closed. The gas fed into the seal box is
Using a mixed gas of 5% H ₂ and 95% H ₂ , the flow rate is controlled so that the seal box internal pressure is 5 to 0 mmAg in terms of gauge pressure. When the oxygen concentration in the source gas to be supplied is 2 to 3 ppm, the oxygen concentration in the seal box is maintained at 30 to 50 ppm. Note that as the bead cut portion heating device, means such as infrared heating may be used instead of high frequency induction heating. Example 2 This method involves removing the seal box from the bead cutter portion of the seal box shown in Fig. 4 and surrounding only the heating device with the seal box.
The seal box used is placed close to the bead cutter. According to this method, bead cutting waste can be easily removed. The oxide film generated immediately after bead cutting can also be suppressed to a relatively small amount. Although the adhesion of the repair plating layer is slightly inferior to that of Example 1, it does not cause any practical problems. Example 3 In this method, as shown in FIG. 6, bead cutting by a bead cutter 31 and high-frequency heating by a heating device 32 are performed in an atmospheric atmosphere, and then,
A polishing device 3 in which the bead cut portion is surrounded by a seal box 37 and has an inert gas or reducing gas atmosphere.
3. Pass the metal wire through the tip 34a of the metal wire supply device and the ultrasonic iron part 42. Then, in the polishing device 33, the oxide film formed on the bead cut part during and immediately after the high-frequency heating is polished away, and then the zinc wire is supplied from the supply device tip 34a, and the ultrasonic iron part 42 applies ultrasonic waves to the repair plating layer. Gives vibration. Bead cutter 31 and high frequency heating device 32
are large and it is relatively difficult to install a seal box, but this method eliminates the need for a seal box surrounding them, makes it possible to downsize the seal box 37 after the polishing device 33, and reduces the consumption of inert gas or reducing gas. The amount can be reduced. The polishing device 33 used in this example is a polishing brush with a diameter of 300 mm and a brush width of 100 mm in the line running direction for a plated electric resistance welded pipe (outer diameter of 48.6 mm), but it is a hydraulic uniform reduction method. Then, only the width of the bead cut can be polished without damaging the plating of the steel pipe base material. Since this polishing brush can remove most of the oxide film formed during the heating section, the adhesion of the repair plating layer is higher than that of conventional methods, and does not cause any practical problems. Embodiment 4 In this method, a combustion gas burner (reducing premix gas burner) having a reducing combustion gas flame is used as the bead cut heating device 32 instead of an electric heating method. This method is the seventh
As shown in the figure, the beads are cut in a non-oxidizing atmosphere and then heated in an atmospheric atmosphere using a reducing premix gas burner. In this case the surface is not oxidized. The heated bead cut section is supplied with zinc wire from the tip 34a of the metal wire supply device, which is made into a non-oxidizing atmosphere in a sealed box, and ultrasonic waves are applied by the ultrasonic iron section 42. In this embodiment, there is no need for a seal box for the heating device, which requires a large size, so the device can be made smaller and the amount of atmosphere gas used can be reduced. Furthermore, since the reducing flame of the reducing gas burner reduces minute oxide films to a clean steel base, the seal box surrounding the bead cutter can be removed. The performance of the repair plating layer was also the same as in Example 1. Example 5 In this method, as shown in FIG. 8, the bead is cut in an atmospheric atmosphere and then directly heated in the atmospheric atmosphere by the combustion flame of an oxidizing burner. In this case, since the combustion flame is oxidizing, the bead cut portion is oxidized at the same time. Next, the heated bead cut portion was passed through a seal box 37 to polish and remove the oxide film in a non-oxidizing atmosphere, and a zinc wire was welded to the clean steel base. The adhesion strength of the repaired part obtained by this method is
Although it was slightly inferior to other examples, it was not to the extent that it would pose a practical problem. According to this method, a normal combustion burner can be used, so the combustion system mechanism is simple, and unlike reducing burners, a gas mixer or special burner nozzle is not required, making it possible to reduce equipment costs. . Next, the performance of the repair plating layer obtained in Examples 1 to 5 was evaluated using the conventional method (method without attaching a seal box).
A comparison is shown in Table 1.

[Table] Here, the adhesion test used a 10-step evaluation method.

[Table] Test method Hammer test: According to JIS regulations. Flattening test: The repaired patched part was turned right sideways, the plated pipe was flattened to 1/3 of the pipe outer diameter D, and then cellophane tape was peeled off. 90° bending: Cut out only the repaired part from the plated pipe, bend it 90°, and then peel off the sellotape. Copper sulfate test: Follow JIS regulations. As described above, according to the present invention, part or all of the repair process is performed in a non-oxidizing atmosphere, and an oxide film is not formed on the bead cut portion, or even if it is formed, it is removed, thereby forming a repair plating layer. It has a remarkable effect of improving adhesion.

[Brief explanation of the drawing]

Figures 1 to 3 are explanatory diagrams of different conventional repair methods, Figure 4 is an explanatory diagram showing an example of the repair method according to the present invention, and Figure 5 is a cross-sectional view of a galvanized electric resistance welded pipe using the same method. , and FIGS. 6 to 8 are explanatory diagrams showing other different examples of the repair method according to the present invention. 31... Bead cutter, 32... Bead cut part heating device, 33... Bead cut surface polishing device, 34... Plating metal wire supply device, 35... Ultrasonic vibration application device, 36, 37... Seal box, 38... ... Plated ERW pipe, 39 ... Plated metal wire, 40 ... Plated metal wire preheating device, 41 ... Ultrasonic vibrator, 42 ... Ultrasonic iron part, 43 ... Repair plating layer, 44...Heating device, 45...Plated metal wire spool, 46...Plated metal wire feed roll.

Claims (1)

[Claims] 1. After bead-cutting and heating the electric resistance welded part of the plated steel pipe, a metal wire for repair is supplied by a feed roll at an angle close to perpendicular to the bead-cut part, and the wire is melted and attached, and ultrasonic vibration is applied. A method for repairing an electric resistance welded part of a plated steel pipe, characterized in that part or all of the steps from the bead cutting step to the step of applying ultrasonic vibration are performed in a non-oxidizing atmosphere.