JP2004043975A - Method for rustproofing processing of pc steel material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for rustproofing processing of a PC steel material by which coated materials are not damaged by readily following elongation and bending of the PC steel material and are not easily impaired during handling at a site of civil engineering and construction and the relaxation in rustproofing coating treatment is not increased. <P>SOLUTION: The PC steel material 1 composed of a PC steel rod or PC steel stranded wire is preheated, passed through a synthetic resin molding machine 5 for first coating, the surface of the PC steel material 1 is subjected to primary coating with a soft thermoplastic resin containing an adhesion promoter. Then the coated PC steel material is passed through a synthetic resin molding machine 7 for second coating and the surface of the first coating is subjected to second coating by fusing a rigid thermoplastic resin to the surface of the first coating. <P>COPYRIGHT: (C)2004,JPO

Description

(4) The present invention relates to a method for rust-proofing PC steel used as a stress-introducing material for prestressed concrete or a suspension material for bridges.

Conventionally, a technology for rust prevention by coating a PC steel material with a synthetic resin has been developed, and in the case of a PC steel stranded wire (PC strand), an outer peripheral surface of each single strand constituting the stranded wire is used. In addition, a rustproofing method for rustproofing has been developed.

従 来 Conventional rust-proofing methods of this kind include those using a thermosetting epoxy resin and those using a thermoplastic polyethylene resin.

In addition, the resin coating method is a method in which a thermoplastic resin is passed through a crosshead type synthetic resin molding machine, and the outer surface is coated while filling the rust-preventive filler up to the internal space of the stranded PC steel by applying pressure, After untwisting the PC strands (PC strands), applying an epoxy resin to each single strand by electrostatic coating, returning the twists to the original state, heating the steel material to a high temperature on the outer surface, and applying the epoxy resin Is a typical method.

The above-mentioned conventional method of applying a thermosetting epoxy resin to the inner surface by electrostatic coating is a method of electrostatic coating, so that the resin thickness to be coated is limited, and a thick coating layer is formed. In addition, the surface rust-preventive coating hardens the steel material because it is heated and solidified at a high temperature. In addition, since the material is hard, it does not easily elongate, and when the PC steel material after the rust-proof coating treatment is bent or stretched by tension, the coating layer is easily cracked and the rust-preventive effect is easily impaired. Was.

On the other hand, using a conventional thermoplastic polyethylene-based resin, in the method of applying the coating, it is easy to increase the thickness of the resin coating layer as necessary, and because it is relatively soft Although cracks are not easily formed by following bending or elongation, there is a problem that the rust preventive coating is easily scraped off due to abrasion or the like when handling as a steel material for building civil engineering due to its softness.

(4) Further, in the conventional method, the PC steel material is heated at a high temperature prior to the resin coating, so that there is a problem that relaxation is increased.

In particular, since the epoxy resin is used for the rust-preventive coating on the PC steel rod, the thickness of the coating must be at least 600 microns (0.6 mm) or more to prevent pinholes. In addition, since the steel rod is heated to a high temperature to solidify the epoxy resin, there is a problem that relaxation is increased.

In view of such conventional problems, the present invention does not easily break following the elongation or bending of the PC steel material, and is not easily damaged at the time of handling at the site of civil engineering construction. It is an object of the present invention to provide a rust-proofing method for PC steel that can be treated without affecting relaxation at the time of rust-proof coating.

The feature of the method for rust-proofing PC steel according to the present invention for solving the conventional problems as described above and achieving the intended object is that the surface of PC steel made of PC steel rod or PC steel stranded wire is synthesized. In a rust-preventing method for a PC steel material coated with a resin rust preventive agent, the PC steel material is preheated, passed through a synthetic resin molding machine for primary coating, and a surface of the PC steel material such as a polyethylene-based thermoplastic resin is applied. Applying a primary coating with a soft thermoplastic resin, then passing through a synthetic resin molding machine for secondary coating, and fusing a hard thermoplastic resin such as a saturated polyester or nylon resin to the surface of the primary coating to perform secondary coating. It is in.

The PC steel material consisting of the stranded PC steel was preheated and passed through a synthetic resin pressure molding machine for injecting resin. Immediately after the rust-preventive filler is pressure-filled, it is preferable to pass through a synthetic resin molding machine for primary coating to apply primary coating with a soft thermoplastic resin on the surface of the PC steel material. The preheating is preferably performed by medium frequency induction heating of about 10 kHz to 15 kHz to heat the PC steel material to a single element wire and the surface thereof so that the temperature does not exceed 200 ° C. In the preheating, it is preferable to heat the PC steel from the inside to the surface by low frequency induction heating of about 1 kHz so that the temperature does not exceed 200 ° C.

As described above, in the method for rust-proofing PC steel according to the present invention, when coating the surface of PC steel made of PC steel rods or PC steel stranded wires with a synthetic resin rust preventive, the PC steel is preheated. Then, this is passed through a synthetic resin molding machine for primary coating, the surface of the PC steel material is subjected to primary coating with a soft thermoplastic resin, and then passed through a synthetic resin molding machine for secondary coating, and the surface of the primary coating is hard-heated. By fusing the plastic resin and performing the secondary coating, the primary coating is a soft thermoplastic resin containing an adhesion promoter, so that the adhesiveness to the steel material is high, so that a hard thermoplastic resin is fused to this. Hard thermoplastic resin, which is difficult to adhere to PC steel, can be firmly integrated, and the outer surface of the rust-proof coating can be made of synthetic resin with high hardness and high abrasion resistance. Rich, following large bending and elongation Became possible anti-rust coating that can Rukoto.

In addition, the PC steel material consisting of the PC steel stranded wire is pre-heated and passed through a synthetic resin pressure molding machine for injecting a resin, so that the inside of the internal gap is removed from the gap between the single strands constituting the PC steel stranded wire. Immediately after pressure-filling the rust-preventive agent, it is passed through a synthetic resin molding machine for primary coating, and the surface of the PC steel is subjected to primary coating with a soft thermoplastic resin, thereby providing a PC steel having more excellent rust prevention. .

Furthermore, in the case of a pre-heated PC steel wire, the PC steel material is heated to a surface of a single element wire by a medium frequency induction heating of about 10 kHz to 15 kHz so that the temperature does not exceed 200 ° C. In the case of a PC steel rod, the reduction in relaxation can be reduced by heating the PC steel material from the inside to the surface by a low frequency induction heating of about 1 kHz so that the temperature does not exceed 200 ° C.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration of an apparatus for carrying out an example of the method of the present invention. In the drawing, 1 is a PC steel material, 2 is a preheating machine for a rust-preventive filling material, and 3 is a rust-proof filling for a resin injection. A material press molding machine, 5 is a synthetic resin coating molding machine for primary coating, and 7 is a synthetic resin coating molding machine for secondary coating.

As the PC steel material 1, as an example, a stranded PC steel wire (PC strand) composed of seven single strands 1a as shown in FIG. 2 is used. In addition, as shown in FIG. 11, a multi-strand wire rod or a single-wire steel rod of 19 or more can be used.

A medium frequency induction heater is used for the preheating machine 2 for injecting the rust-preventive filler when the PC steel stranded wire is preheated, and heat is applied to the inside of the stranded wire in a relatively low frequency region of about 10 kHz to 15 kHz. And heat so that the whole does not exceed 200 ° C. In addition, a low frequency induction heater 21 of about 1 kHz is used as a preheater for preheating the PC steel bar.

The rust-preventive filler press molding machine 3 for injecting the rust-preventive filler material has an auxiliary pressurized tank 32 continuously arranged at the outlet side of a cross-head type rust-preventive filler press-molding machine body 31 as shown in FIG. It has a structure in which a molding die 33 adapted to the outer shape of the PC steel material 1 is rotatably attached to the end thereof. In the figure, reference numeral 35 denotes a heater.

In this rust-preventive filler press molding machine 3, the rust-preventive filling material 34, which is a rust-preventive material, is melted and extruded into the crosshead portion, and while passing through the auxiliary pressurizing tank 32, as shown in FIG. The rust-preventing filler material 34 is injected under pressure from the gap between the single wires on the outer periphery of the PC steel material, and the interior space 1b (shown in FIG. 2) of the stranded PC steel wire is filled with resin.

錆 The rust-preventive filling material adhering to the outer peripheral surface is scraped off with a molding die 33 except for a part.

合成 As the synthetic resin coating molding machine 5 for primary coating, a crosshead type synthetic resin coating molding machine shown in FIG. 8 is used, and a molding die 52 is rotatably installed at an outlet of the crosshead section 51. As shown in FIG. 6, the molding die 52 is formed in a shape that is larger than the outer shape of the PC steel material 1 by the thickness of the resin coating.

In the synthetic resin coating molding machine 5 for the primary coating, the outer peripheral surface of the PC steel material 1 immediately after the rust-preventive filler material 34 has been filled into the above-mentioned internal space at the crosshead part of the rust-preventive filler press molding machine 3. Then, a primary coating synthetic resin 53 made of a polyethylene-based thermoplastic resin in a molten state is extruded, and as shown in FIG.

The synthetic resin material to be used should be one with an adhesion promoter added.

As the synthetic resin coating molding machine 7 for secondary coating, a crosshead type synthetic resin molding machine shown in FIG. 9 is used, and the outer peripheral surface of a PC steel material primarily coated with the above-described synthetic resin material 53 at the crosshead portion is provided. The secondary coating synthetic resin 71 composed of a saturated polyester-based or nylon-based hard thermoplastic resin in a molten state is extruded, and the outer surface of the primary coating synthetic resin 53 covering the outer peripheral surface of the PC steel material 1 as shown in FIG. Then, a synthetic resin secondary coating layer having a predetermined thickness is fused.

に よ り Thereby, the secondary coating synthetic resin 71 is integrated with the outer peripheral surface of the primary coating synthetic resin 53 in a fused state.

(4) The PC steel material thus completed with the secondary coating is passed through a cooling device (not shown) to be cooled, thereby completing the rust-preventive processing.

In the embodiment described above, the secondary coating is performed after the primary coating, but the primary coating and the secondary coating may be performed by the same device.

In this case, as shown in FIG. 10, the above-mentioned synthetic resin coating molding machine for primary coating 5 is omitted, and the primary coating and the secondary coating are performed by the synthetic resin coating molding machine for secondary coating 7.

In addition, when the PC steel material is a single-line PC steel rod 1A as shown in FIGS. 12 and 13, it is not necessary to fill the internal voids. In this case, as shown in FIG. In the apparatus shown in FIG. 1, instead of the pre-heating machine 2 for resin injection and the rust-preventive filler press molding machine 3 for rust-preventive filling material injection, a device provided with a low-frequency induction heating machine 21 is also used for the primary, Secondary coating is performed in order.

It is a diagram showing the outline of the device used for one embodiment of the present invention. FIG. 2 is a cross-sectional view of a stranded PC steel wire to be rust-proof coated by the above device. It is sectional drawing of the PC steel stranded wire which shows the state after resin filling in the internal space by the same apparatus. It is sectional drawing of the PC steel stranded wire which shows the state after the primary coating by the same device. It is sectional drawing of the PC steel stranded wire which shows the state after the secondary coating by the same device. It is sectional drawing which shows the shaping | molding dice | dies of the crosshead part of the rust preventive filler press-forming machine in an apparatus same as the above. It is sectional drawing which shows the crosshead part of the rust preventive filler press molding machine in an apparatus same as the above. It is sectional drawing which shows the crosshead part of the synthetic resin coating molding machine for primary coatings in an apparatus same as the above. It is sectional drawing which shows the crosshead part of the synthetic resin coating molding machine for secondary coatings in an apparatus same as the above. It is a diagram showing the outline of the device used for other embodiments of the present invention. 1 is a cross-sectional view showing a 19-strand PC steel stranded wire to be rust-proof coated by the device according to the present invention. It is sectional drawing which shows an example which applied this invention to the PC steel bar. It is sectional drawing which shows another example which implemented this invention to the PC steel bar. FIG. 2 is a diagram schematically illustrating an apparatus used in the above case.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 PC steel material 1a Single strand 1b Internal space 2 Preheating machine for resin injection 3 Synthetic resin pressure molding machine 31 Synthetic resin molding machine main body 32 Auxiliary pressurized tank 33 Molding die 34 Void filling synthetic resin material 5 Synthetic resin for primary coating Coating molding machine 51 Crosshead 52 Molding die 53 Primary coating synthetic resin 7 Synthetic resin coating molding machine for secondary coating 71 Secondary coating synthetic resin

Claims (4)

In a rust-proofing method for PC steel material, which comprises coating the surface of a PC steel material consisting of a PC steel rod or a PC steel stranded wire with a synthetic resin rust inhibitor,
The PC steel material is pre-heated, passed through a synthetic resin molding machine for primary coating, subjected to a primary coating with a soft thermoplastic resin such as a polyethylene thermoplastic resin on the surface of the PC steel material, and then to a synthetic resin for secondary coating. A rust-proofing method for a PC steel material, characterized in that a hardened thermoplastic resin such as a saturated polyester-based or nylon-based resin is fused to the surface of the primary coating through a molding machine to perform secondary coating. A pre-heated PC steel material consisting of a PC steel stranded wire is passed through a synthetic resin pressure molding machine for injecting a resin to prevent a gap between the single wires constituting the PC steel stranded wire into an internal space. The rust-proofing method for PC steel according to claim 1, wherein the PC steel is first coated with a soft thermoplastic resin on a surface of the PC steel by passing through a synthetic resin molding machine for primary coating immediately after pressure-filling the rust filler. The preheating is performed by medium frequency induction heating of about 10 kHz to 15 kHz to heat the PC steel to a single element wire and the surface thereof so that the temperature does not exceed 200 ° C. Rust prevention processing method. (4) The method for rust-proofing PC steel according to claim 1, wherein the preheating is performed by heating the PC steel from the inside to the surface by a low frequency induction heating of about 1 kHz so that the temperature does not exceed 200 ° C.

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