JP4427602B1 - PC steel strand anticorrosive film forming method and PC steel strand - Google Patents

Abstract

A rust preventive film formed on a wire than conventional PC steel has a problem that it is inferior in a weather-resistant environment, and therefore improves corrosion resistance and weather resistance as a wire than PC steel.
A PC steel wire 1 is returned and a side wire is loosened from the core wire, and a synthetic resin powder coating is applied to the outer peripheral surfaces of the core wire and the side wire in a loosened state, and heated and uniformly adhered. A method for forming a rust-preventive coating of PC steel strand 1 in which a rust-preventive coating is formed by cooling, and then the side wires are aligned with the core wire in the original state. After the coating film is melt-bonded and integrated, after curing, the side wires are aligned with the core wires in the original state to obtain PC steel with improved corrosion resistance and weather resistance.
[Selection] Figure 1

Description

  The present invention relates to a post-tensioning method or a pretensioning type tension material or tensioning material for prestressed concrete methods in building structures and civil engineering structures, etc. The present invention relates to a method of forming a rust-preventing film with a synthetic resin powder coating on the core and side wires of a PC steel wire used as a cable for a cable or a cable for a cable, and a PC steel wire obtained by the method.

  In general, the structure of the PC steel stranded wire is a structure in which a plurality of side wires are joined together around the core wire. The reason for this is to give flexibility to the strands of PC steel and to obtain adhesion strength to the concrete with spiral grooves formed by twisting side wires. Therefore, a method that does not hinder the above characteristics is also desired as a rust-proofing method for stranded wires of PC steel. At present, several methods are known as rust-proofing methods for PC steel strands.

  As a first prior art according to the public knowledge, there is a PC stranded wire having a cross-sectional shape shown in FIG. This rust prevention method for the PC steel wire is to first heat the wire from the PC steel, and temporarily return the side wire 1b from the periphery of the core wire 1a by the strand opener, and the portion where the side wire 1b is returned is electrostatic powder. The side wire 1b that has been returned from 15 inches to 18 inches in the body coating machine is reconstructed into the original twisted state, and the resin that is adhering to the core wire 1a and the side wire 1b and dissolving (during gel time) In order to prevent pinholes generated in the spiral groove due to the twisting of the side lines 1b, the thick coating 50 (500 ˜600 μm) to form a composite by integrating the inside and outside, and this is a rust prevention method for PC steel wires (Japanese Patent No. 2597795).

  By the way, the formed thick film is not individually formed on the core wire 1a and the side wire 1b, but is a continuous film covering the entire outer peripheral surface of the wire from the PC steel. Although the rust prevention property is improved as compared with the wire, the flexibility of the wire is lost compared with the PC steel.

  On the other hand, the rust prevention method which concerns on a 2nd prior art is known. This rust prevention method is to temporarily return the twisted portion of the strands of PC steel one after another, maintain the returned portion by the expansion maintaining means and adjust the excess core wire, A synthetic resin powder coating film is formed on the entire outer peripheral surface of each of the core wire and the side line, and these coated films are heat-welded to form a film on the entire outer peripheral surface of each of the core wire and the side line. This is a method for forming a rust-preventing film on a PC steel wire, wherein the core wire and the side wire are aligned again after cooling (Patent Publication No. 2691113).

  The PC steel strands formed in this way are required as PC steel strands because the coatings are formed one by one over the entire outer peripheral surface of each of the core wires and the side wires. Properties such as flexibility and bond strength with concrete are not disturbed at all, and the rust prevention function is sufficient, and this rust prevention method is evaluated as the ultimate rust prevention method for PC steel wires. It is what has been.

  This kind of film thickness is defined as follows in the industry. In other words, according to many research results in order to satisfy the corrosion resistance and mechanical performance (impact resistance, bending characteristics, adhesion of concrete), the film thickness is 200 ± A film thickness of 50 μm is reported to be reasonable, and an experimental result of FHWA (United States Federal Highway Administration) in the United States reports that a range of about 170 ± 50 μm is preferable.

Patent Publication No. 2597795 Japanese Patent No. 2691113

  In the first prior art, an epoxy resin powder is used as the film to be formed, and it is not individually formed on the core wire 1a and the side wire 1b, but continuously covers the entire outer peripheral surface of the PC steel wire. Because it is a coated film, it has excellent corrosion resistance, but not only does it lose the flexibility required as a wire from PC steel, but it does not mention the problem of weather resistance at all. .

  Also in the second prior art, an epoxy resin powder is used as the film to be formed, and unlike the first prior art, the film is formed on the core wire 1a and the side wire 1b, respectively. Therefore, it is excellent in corrosion resistance and excellent in flexibility required as a strand of PC steel, but does not mention the problem of weather resistance at all.

The corrosion resistance and weather resistance of the epoxy resin powder coating and other resin powder coatings were tested. The test methods and test results were as shown in Tables 1 and 2.

  Therefore, in any of the conventional techniques, the formed anticorrosive film has a problem that it is excellent in a corrosion-resistant environment but inferior in a weather-resistant environment. There is a problem to be solved in improving the weather resistance.

The present invention is a specific means for solving the problems of the above-described conventional example. The first invention is that the PC steel wire is returned and the side wire is loosened from the core wire to expand, and the core wire in the expanded state Synthetic resin powder coating is applied to each outer peripheral surface of the side wires by electrostatic powder coating, and heated to uniformly adhere, then cooled to form a rust-proof coating, and then the side wires are restored to the core wires. A method for forming a rust-proof coating of PC steel wire that is adapted to the state, and first as the synthetic resin powder coating, a synthetic resin powder coating excellent in adhesion to metal and corrosion resistance is used as a primary coating. After coating, the coating film is heated and melted with a heating device , and while the primary coating film is in a molten state, a synthetic resin powder coating having excellent corrosion resistance and weather resistance is applied to the surface as a secondary coating film. the coating film heated and melted by the heating device from the one in the molten state That is a coating film and secondary coating matched by the original state lateral line with respect to the core wire after curing is cooled by becomes the resin film cooling device integrated without boundary melt bonded mingled with each other at the boundary A feature of the present invention is to provide a method for forming an anticorrosive film on a PC steel strand.

  In this invention, it is included as an additional requirement that the primary coating is an epoxy resin and the secondary coating is an acrylic resin.

  Moreover, as 2nd invention, the rust prevention film obtained by the method which concerns on the said 1st invention is formed, The PC steel strand characterized by the above-mentioned is provided.

According to the method of forming a rust-proof coating for PC steel strands according to the present invention, the coating formed on the core wire and the side wire is integrated by mixing the primary coating and the secondary coating having different properties at the boundary portion. Because the inner primary coating film is made of a resin having adhesion and corrosion resistance to metal, and the outer secondary coating film is made of a resin having corrosion resistance and weather resistance. In addition to excellent adhesion to metal, corrosion resistance and tensile fatigue properties, the outer surface of the coating is formed of a resin with excellent weather resistance, and it can withstand even in harsh weather resistant environments. Play.

It is the side view which showed the outline of the processing line which enforces the processing method which concerns on embodiment of this invention. It is sectional drawing which shows a strand from PC steel processed by the embodiment. It is a schematic front view which shows the slow release apparatus (slow closure apparatus) used in the same embodiment. It is a schematic front view which shows the expansion apparatus used in the embodiment. It is the side view which showed schematically the core wire adjusting device of an example used in the embodiment. It is the expanded sectional view which showed the strand from PC steel in the state where a rust prevention film is formed by the method of the present invention, and the side line is not loosely closed with respect to the core wire. It is the expanded sectional view which showed the strand from PC steel of the state which formed the antirust coating by the method of this invention, and match | combined the side line with the original state with respect to the core wire. It is an expanded sectional view of a strand from PC steel of a prior art (patent documents 1).

  The present invention will be described in detail based on the illustrated embodiment. FIG. 1 is a schematic view of a processing line for carrying out a method for forming a rust-preventing film of a PC steel wire according to the present invention. And, as shown in FIG. 2, the PC steel stranded wire 1 of the example used has a core wire 1a at the center, and a plurality of (six) side wires 1b are spirally joined to the outer periphery thereof. PC steel strand.

  In general, this type of PC steel strand 1 has a long coil wound in a coiled state, and the wound PC steel wire 1 remains in a coiled state as in the prior art. The rust preventive film is formed while being set on the start end side and being sequentially fed out from the start end side.

  An outline of the process of the processing line according to the present invention is that a gantry 2 on which a PC steel wire 1 wound in a coiled state is set is provided, and the PC stranded wire 1 set on the gantry 2 is formed with a rust-proof coating. Sequentially sent to each process for processing. That is, it consists of a winding process C in which the pre-processed process A and the coating process B are returned to the original stranded state, and then the coated PC steel wire is wound in a coil shape on the terminal end side of the processing line. . Hereinafter, each step will be described.

  First, at the start of continuous operation, the same kind of dummy PC steel strand is used as a preparatory work, and it is inserted in a state according to the category or method of each process in advance from the start to the end of the processing line by hand. The end of core wire 1a and side wire 1b of PC steel strand 1 newly set to cradle 2 to be rust-proofed and the corresponding core wire and end of side wire of dummy PC steel strand are brought into contact with each other. After the preparation work is completed by welding, continuous operation is started.

  When the operation of the apparatus is started, the wire 1 from the PC steel moves at a constant speed from the start end side to the end end side, and a uniform coating film is formed on each outer peripheral surface of the core wire 1a and each side wire 1b. It is formed and wound in the original twisted state.

  The PC steel strand 1 set on the gantry 2 first passes through the pretreatment step A through the core wire adjusting device 5. In this case, the side wire 1b is returned from the core wire 1a and expanded by the relieving device 3 shown in FIG. 3, and the expanded state is maintained by the expansion maintaining devices 4a to 4d shown in FIG. The wire 1 passes through the PC steel at a speed set up to the coating process B in which the coating film is formed in a state where the coating film is maintained in the expanded state.

  In the loosening device 3, a rotating ring 18 is rotatably arranged via a bearing 17, and a core wire passage hole 19 through which the core wire 1a of the PC steel strand 1 is inserted is provided in the rotating ring 18. In addition, side line passage holes 20 through which six side lines 1b are inserted radially from the core wire passage hole 19 with a required interval are provided.

  The expansion maintaining devices 4 a to 4 d are substantially the same in configuration as the loosening device 3 and have a large diameter, and maintain the expanded state of the wire 1 from the loosened PC steel, and rotate via a bearing 27. A ring 28 is rotatably arranged, and a core wire passage hole 29 through which the core wire 1a of the PC steel strand 1 is inserted is provided at the center of the rotation ring 28, and a required interval from the core wire passage hole 29 is provided. The side line passage holes 30 through which the six side lines 1b are inserted radially are provided, and the difference from the relaxation device 3 is that the interval between the core wire passage hole 29 and the side line passage hole 30 is wide. Yes, the size of each hole is substantially the same.

  In the shot blasting device 6 according to the pretreatment step A, a polishing material (steel ball of about 0.3 mm) is projected by a high-speed rotating blade on the entire outer peripheral surface of the core wire 1a and the side wire 1b in the expanded state. In addition to removing foreign substances such as oil and rust adhering to the outer peripheral surface, the surface of the entire outer peripheral surface is adjusted, for example, it is made into a satin-like substrate state to improve the adhesion to the coating film (coating film).

  The core wire adjusting device 5 shown in FIG. 5 is disposed between the gantry 2 and the pretreatment step A and between the expansion maintaining devices 4a and 4b. A pulley arm 23 that maintains the outer ring 21 at a predetermined interval, a movable pulley 24 that moves along the pulley arm and is pulled by the tension adjusting spring 22 toward the relieving device 3 with a constant tension, and a pulley arm 23. It is composed of a fixed pulley 25 attached, and the core wire 1a through the core wire passage hole 29 of the expansion maintaining device 4a is first hung on the fixed pulley 25 and then U-turned, and then spread on the movable pulley 24. By adjusting to the maintenance device 4b side, adjustment is made by pulling back the excess core wire 1a by returning the rust preventive film formation and the side wire 1b to the original alignment state.

  Note that the moving distance of the movable pulley 24 or the number of grooves in the pulley is determined according to the length of the excess core wire to be absorbed or recovered. For example, if the number of pulley grooves is set to two, the excess core wire integrated absorption amount Becomes 4 times. Since the movable pulley 24 is pulled to the relieving device 3 side with a constant tension by the tension adjusting spring 22 that is always in a tension state, the side wire 1b is aligned with the core wire 1a in the original state on the terminal end side, so that the surplus is achieved. The core wire 1a is automatically absorbed or collected. The core wire adjusting device is not limited to the pulley system.

  The core wire 1a and the side wire 1b processed in the pretreatment process A maintain the expanded state by the expansion maintaining devices 4c and 4d, and are expanded to a necessary interval, and the coating process B is performed during the expanded interval. Is provided. In this coating process B, a primary coating film coating device 7a, a heating device 8, a secondary coating film coating device 7b, a heating device 9, and a cooling device 10 are sequentially provided adjacent to each other. In the coating apparatus 7a and the secondary coating apparatus 7b, resin powder coatings having different properties are supplied, and the primary coating 26a and the secondary coating 26b are integrated as shown in FIG. The anticorrosive coating 26 is formed. Then, the rust preventive coating 26 is sufficiently cooled by the cooling device 10 to increase the surface hardness.

For the anticorrosive coating 26 made of the resin powder coating having different properties, the primary coating device 7a forms the primary coating 26a by supplying an epoxy resin powder coating excellent in adhesion to metal and corrosion resistance. After that, when the primary coating film 26a is heated and melted by the heating device 8 and the coating film is in a heated and melted state, an acrylic resin excellent in corrosion resistance and weather resistance is applied from the coating device 7b for the secondary coating film thereon. After the powder coating material is supplied to form the secondary coating film 26 b, the secondary coating film 26 b is heated and melted by the heating device 9.

Thus, while the primary coating film 26a is in the molten state, the secondary coating film 26b is formed thereon, and the coating film is heated and melted by another heating device 9, whereby the primary coating film 26a in the molten state is formed. And the secondary coating film 26b are partially mixed with each other at the boundary portion indicated by the phantom line, and there is substantially no boundary between the primary coating film 26a and the secondary coating film 26b. Thus, an integrated resin film 26 is formed.

  For the heating devices 8 and 9, for example, a high frequency induction heating method that can easily adjust the temperature in the range of 120 to 230 ° C. is desirable. The powder coating method may be either a gun spraying method or a fluidized dipping method. In short, it is desirable to use an electrostatic powder coating method. Furthermore, the state of formation of the resin coating film, that is, the thickness and quality, can be determined by the heating method and temperature, the type and number of electrostatic guns, the position of the arrangement, the air condition, and the particle size of the powder coating. It is.

  The cooling device 10 may be cooled by sprinkling cold water in a shower shape over a certain length. In this case, as a shower-like water droplet, it is sprinkled in a state where small-diameter water droplets are densely packed, and by reducing the contact pressure of the water droplets, the coating film surface as a whole is finished almost uniformly and smoothly.

  The thickness of the anticorrosion film 26 formed in the painting process B is, for example, about 200 ± 50 μm. After the anticorrosion film 26 is formed in the painting process B and cooled by the cooling device 10, the side line 1b is The loose closing device 11 is fitted to the core wire 1a in the original state. In this case, the slow closing device 11 uses the slow release device 3 shown in FIG. 3 in the reverse direction, and has substantially the same configuration, so that the description thereof is omitted and the slow closing device 11 The device 11 is given a reference numeral. And since the wrinkle remains more as it is by the gentle closure apparatus 11, it can match | combine with the core wire 1a quickly by the original state, and the cross section of the PC steel strand 12 matched by the original state The shape is as shown in FIG. 7, and a rust-proof coating 26 having a uniform thickness is formed on the entire circumference of the core wire 1a and the side wire 1b.

  The PC steel strands that have been fitted in the original state after the formation of the rust preventive coating 26, the surface thickness is measured by the thickness measuring device 13 as a coating inspection device, and the thickness is other than the set tolerance value. An alarm for notifying that is issued, and a signal indicating whether the allowable value is not reached or the allowable value is exceeded is issued. Further, the state of the coating is inspected by the pinhole detector 14. In the inspection method, when a pinhole is detected using, for example, an optical detection means so as not to damage the coating, marking is applied to the detection position and an alarm signal is generated.

  The PC strand 12 thus inspected is taken up by a take-up device 15 in which endless rubber belts are arranged on the upper and lower sides and taken up by a take-up device 16. The take-up device 15 has a structure that does not damage the anticorrosion film, and the tension device 15 is a speed setting device for this processing line, so an inverter motor is used to freely convert the line speed. It has a possible structure. The film thickness to be formed differs depending on the line speed, and a film having an arbitrary thickness can be formed by selecting the line speed.

  When the continuous operation proceeds and the wire 1 from the PC steel set on the gantry 2 disappears, the drive of the processing line is stopped, the coating film formation is temporarily stopped, and the new PC steel wire is set on the gantry 2 Then, the operation is resumed by butt welding the end side rear end of the previous PC steel wire 1 and the newly set PC steel wire 1 by butt welding, and the coating film forming work is efficiently performed. It becomes possible continuously.

  The PC steel strand 12 formed in this manner is required for this kind of PC steel wire because the anticorrosive coating 26 is formed on the surface of the core wire 1a and the side wire 1b independently or independently. In addition to not losing the flexibility, the corrosion resistance and tensile fatigue resistance can be improved, and in particular, the jacket portion has excellent weather resistance.

  The method for forming a rust-preventive coating for PC steel strands according to the present invention is to apply resin powder paints with different properties on appropriate parts, and in particular, apply an epoxy resin powder paint with excellent adhesion and corrosion resistance on the inside. Then, the adhesiveness between the core wire 1a and the side wire 1b is sufficient, and an acrylic resin powder coating having excellent corrosion resistance and weather resistance is applied thereon, and the previously applied epoxy resin coating is heated and melted. Acrylic resin powder paint is applied and melted by heating, and both paints are melted and the boundary part is mixed with each other so that there is no substantial boundary. Thus, an ideal rust preventive film that takes advantage of each characteristic is formed. It should be noted that any resin other than an epoxy resin that has excellent adhesion and corrosion resistance can be used instead, and any resin other than an acrylic resin that has excellent corrosion resistance and weather resistance can be used instead. It is included in the category of the present invention.

As described above, the method for forming a rust-proof coating for PC steel strands according to the present invention uses resin powder coatings of different properties in the right place, but the primary coating and the secondary coating are merely used. After forming the primary coating instead of the layered coating, it is heated to a molten state, and after the secondary coating is formed in the molten state, the secondary coating is heated and melted. Each film has a uniform thickness , and its boundary part is mixed with each other in the molten state , forming an integrated resin film with no substantial boundary. In other words, it is possible to make use of the respective characteristics without forming any film, and furthermore, it is possible to form a coating film of another synthetic resin paint having different characteristics by the same method. It can be widely used for anti-rust processing technology.

1 PC Steel Stranded Wire 1a PC Steel Stranded Wire 1b PC Steel Stranded Wire 2 Mounting System 3 Relaxation Device 4a, 4b, 4c, 4d Expansion Maintaining Device 5 Core Wire Adjusting Device 6 Shot Blasting Device 7a Primary Coating Device 7b Coating device for secondary coating film 8, 9 Heating device 10 Cooling device 11 Slowly closing device 12 PC steel strand with resin coating 13 Film thickness measuring device 14 Pinhole detector 15 Take-up device 16 Winding device 17, 27 Belling 18, 28 Rotating ring 19, 29 Core wire passage hole 20, 30 Side wire passage hole 21 Outer ring 22 Tension adjusting spring 23 Pulley arm 24 Movable pulley 25 Fixed pulley 26 Anticorrosion coating 26a Primary coating 26b Secondary coating A Pre-treatment process B Painting process C Winding process

Claims (2)

PC wire is returned and the side wire is loosened from the core wire and expanded , and then the synthetic resin powder coating is applied to each outer peripheral surface of the expanded core wire and side wire by electrostatic powder coating and heated. A method for forming a rust-preventive coating on a PC steel wire, which is cooled after forming a uniform coating to form a rust-preventive coating, and then the side wires are matched to the core wire in the original state,
First, a synthetic resin powder coating excellent in adhesion and corrosion resistance to metal as the synthetic resin powder coating is applied as a primary coating, and then the coating is heated and melted by a heating device .
While the primary coating is in a molten state, a synthetic resin powder coating excellent in corrosion resistance and weather resistance is applied as a secondary coating on the surface, and then the coating is heated and melted with a heating device .
The primary and secondary coatings in the molten state are mixed with each other at the boundary and melt-bonded to form an integrated resin coating without any boundary . A method for forming an anticorrosive film on a PC steel wire, characterized by matching according to the state. The method for forming a rust-proof coating for PC steel strands according to claim 1, wherein the primary coating is an epoxy resin and the secondary coating is an acrylic resin.

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