JPH0776474B2 - Anti-corrosion unbonding method for PC stranded wire - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rust-preventing unbonding method for a PC steel stranded wire for the post-tensioning method used for introducing prestress in the production of prestressed concrete.

[0002]

2. Description of the Related Art After pouring concrete, wait for its solidification.
As a PC steel stranded wire used in the post-tensioning method for tensioning the C steel stranded wire and introducing prestress,
It is necessary that the PC steel wire and the concrete do not adhere to each other when the prestressing is introduced, and the PC steel wire can move in the axial direction with respect to the concrete.

As a method for producing the PC steel stranded wire, there are fourteenth methods.
As shown in the figure, a method of applying an oil-and-fat rust preventive lubricant 11 on the surface of the PC steel stranded wire 10 and covering the outside thereof with a synthetic resin cylinder 12 by an extruder (US Pat. No. 3646).
748, and Japanese Patent Publication No. 53-47609). In this method, when the rust preventive lubricant 11 applied on the surface of the PC steel wire is deteriorated with time, the applied state is likely to be incomplete, and further, the synthetic resin cylinder 12 is cracked. Has a problem that the anticorrosion effect is significantly reduced.

In order to solve such a problem, in recent years,
As shown in FIG. 15, a coating layer 14 is formed on the surface of the PC stranded wire 10 by a powder coating method using a synthetic resin material such as polyethylene or epoxy having excellent adhesion to iron, and the outside thereof is further formed. By extrusion molding synthetic resin cylinder 1
A method of overcoating 5 has been developed. However, this method also solves the problem that water or the like permeates from the cut end face or the pinhole or the damaged portion of the coating layer 14 because there is a gap 13 between the core wire and the side wire constituting the PC steel wire. Absent.

Furthermore, as shown in FIG. 16, a coating layer 17 made of synthetic resin is applied to the side wire 10a and the core wire 10b of the PC steel stranded wire before twisting, and then twisted together to form a stranded wire. None, a method has been proposed in which grease 16 is applied to the surface and a synthetic resin cylinder 18 is provided on the outside thereof (Japanese Utility Model Laid-Open No. 61-144121).

According to this method, the core wire and the side wires constituting the PC steel stranded wire are coated with a synthetic resin to achieve more complete rust prevention. A coating layer is formed on each of the core wire and the side wire and twisted together to form a twisted wire. Since there is a synthetic resin coating layer, heat treatment (blueing) to remove residual stress after twisting ) Cannot be applied.

[0007] That is, a normal PC steel stranded wire is heated to about 400 ° C after the twisting process to remove residual stress after the process and thereby stabilizes the twisted state. In the case of a line, since twisting is almost only elastically deformed, there is a problem in that, unless blueing is performed, the wire will come apart from the end of it every time it is cut. Further, if processing is performed such that the twisting is maintained even without blueing, there is a problem that the synthetic resin coating layer is damaged during the processing and the rust preventive effect cannot be maintained.

Further, as shown in FIG. 17, in order to form a grease coating on the inner surface and the outer surface of the PC steel strand 10, the twisting was gradually relaxed in the cold, and the grease was loosened. There is a method (Japanese Patent Publication No. 1-54142) in which after applying grease 11 to a part, the twisted wire is restored based on the twist and the outer surface of the PC stranded wire is covered with a synthetic resin cylinder by an extrusion forming method or the like. .

In this method, the grease 11 is applied to the inner and outer surfaces of the core wire 10b and the side wire 10a constituting the PC steel wire, which is more rustproof than the method of Japanese Patent Publication No. 53-47609. Although excellent, the problem that the rust preventive effect is remarkably reduced when the synthetic resin cylinder 12 is cracked due to the deterioration of the grease 11 over time and the synthetic resin cylinder 12 is cracked has not been solved. Further, in this method, since all the working steps such as loosening the PC steel wire and applying grease and then restoring it based on the twisting are performed in the cold, plastic working strain is caused by the working and There is a risk that the twisted state will not completely return to the state before loosening due to variation in the elongation of the steel, which will lead to a decrease in tensile load, which is also a fatal defect of the PC steel wire, and that relaxation will also greatly increase. is there.

[0010]

Therefore, according to the present invention, P
C steel stranded wire is made blue in the manufacturing process, and while maintaining a stable state, PC steel stranded wire for the post-tensioning method that has excellent properties such as complete rust prevention can be easily processed without damaging the coating layer. It was proposed for the purpose of doing.

[0011]

The constitution of the rust preventive unbonding method for PC strands of the present invention is as follows. While twisting a plurality of side wires around the core wire and performing a predetermined bluing on the PC steel stranded wire to a temperature at which plastic deformation strain does not occur due to the relaxation, the twisting is gradually and gradually relaxed. Utilizing the heating temperature, the synthetic resin powder coating material is melted and adhered to the outer circumferences of the core wire and the side wires to form the synthetic resin powder molten coating inner layers 21 and 23, and the twisted state is restored. Then, a lubricant is applied to the surface, and the surface is covered with a synthetic resin-coated outer layer cylinder 27 by an extrusion molding method.
Mating and covering.

[0012]

Function: Since the loosening is carried out sequentially and temporarily while the required heating is carried out, plastic working strain does not occur.
Therefore, the synthetic resin powder melt-coated inner layers 21, 23 are formed around the entire circumference of each of the side wires and the core wires without causing variations in the elongation between the side wires or in the fact that the twisting restoration does not completely return to the state before remission. Further, the synthetic resin-coated outer layer cylinder 27 can be formed in the desired state by an extrusion molding method on the surface thereof via a lubricant.

[0013]

EXAMPLES Examples of the present invention will now be described in detail with reference to FIGS.

FIG. 1 shows the arrangement of an apparatus used in the method for rust-proofing and unbonding PC strands of the present invention. Reference numeral 31 denotes a rewinding device. The rewinding device 31 has a reel 32 in which the side wires 10a are twisted around the core wire 10b as shown in the cross section of FIG. Is rotatably supported. Reference numeral 33 denotes an entrance-side feeding device, which presses a pair of drive endless belts 33a and 33b into pressure contact with each other, holds the PC steel wire 10 pulled out from the rewinding device 31 between them, and forces them by driving both belts 33a and 33b. I try to send it to you. Reference numeral 34 is a deposit removing device, which uses shot blasting in this embodiment.
Spraying minute steel balls, steel pieces, etc. on the surface of the C steel stranded wire 10,
It is designed to remove deposits such as oil.

Reference numeral 35 is a heating device. This heating device 35
As for the high frequency induction heating device,
The temperature at which plastic working strain does not occur by loosening the twist of the steel stranded wire, for example, 300 to 350 ° C.
It is designed to be heated. 36 is a side wire 10a ...
It is a relieving device for expanding the space between b. As shown in FIG. 2, in the loosening device 36, a loosening guide plate 39 is fixed to a rotating cylinder 38 rotatably supported by a frame 37, and the loosening guide plate 39 is rotated by a motor 41 via a chain 40. I am trying. As shown in FIGS. 3 and 4, the loosening guide plate 39 has a core wire guide tube 42 at the center thereof.
Are provided, side line guide holes 43, 43 ... Are provided on the same circumference with a required space therebetween, and a chain wheel 44 is integrally formed.

Reference numeral 45 is a powder paint supply device, which is shown in FIG.
As shown in FIG.
Of the spray gun 47, 47, 4 from the three directions toward the loosened portion 10c.
7, the synthetic resin powder paint such as polyethylene and epoxy is blown together with the air, and it is heated at the heating temperature of 300.
The synthetic resin powder melt-coated inner layers 21 and 23 are formed by melt-adhering to the entire circumference of the side wires 10a ... And the core wire 10b at ˜350 ° C.

Reference numeral 48 denotes a post-heating device, which is an infrared lamp. Reference numeral 49 is a cooling device, which allows water or cold air to flow to cool the rust-proof treated PC steel wire 10A or 10B to room temperature. Reference numeral 55 denotes a lubricant applying device, which applies a lubricant such as grease to the surface of the rust-proof treated PC steel wire 10A or 10B.
Reference numeral 56 denotes an extruder, which is an apparatus for fitting and coating a synthetic resin-coated outer layer cylinder on the outside of the rustproof PC steel strand 10A or 10B coated with the above-mentioned lubricant.

Reference numeral 60 denotes a cooling device which allows water or cold air to flow therethrough to form an unbonded PC steel strand 10.
C or 10D is cooled to room temperature. Fifty
Is an exit-side drawing device, which has a pair of endless belts 50a and 50b that are driven in pressure contact with each other, and forcibly pulling out the unbonded PC steel wire 10C or 10D by sandwiching it. . Reference numeral 51 is a winding device which drives the reel 52 to rotate and winds the wire 10C or 10D from the unbonded PC. Reference numeral 53 is a leading wire winding device for preparatory work.

Next, the unbonding process performed by using the apparatus having the above structure will be described. Preparatory work is performed prior to continuous operation of this device. First, the tip of the PC steel wire 10 is pulled out from the rewinding device 31, and the feeding device 33
The endless belts 33a and 33b are fed to the loosening device 36 through the adhering substance removing device 34 and the heating device 35.

Then, the ends are manually loosened as shown in FIG. 6, and the side wires 10a are inserted into the side wire guide holes 43 of the loosening guide plate 39 and the core wires 10b are inserted into the core wire guide tube 42. Then, as shown in FIG. 7, a loosened portion 10c is formed by a certain length L, and the tip side is manually twisted again. This twisting can be performed without requiring a particularly large labor because each side wire 10a is permanently deformed into a more bent state. Then, the leading wire 54 is fixed to the twisted tip portion as shown in FIG. 7. The leading wire 54 is wound around the leading wire winding device 53 through the powder coating material supplying device 45, the post-heating device 48, the cooling device 49, the lubricant applying device 55, the extrusion molding machine 56, the cooling device 57 and the drawing device 50. .

In this state, continuous operation of all devices is started. As a result, the PC steel stranded wire 10 is continuously drawn out from the rewinding device 31 to the feeding device 33, passes through each device, undergoes an unbonding process, and is drawn out by the drawing device 50. When the completely unbonded part is drawn out of the drawing device 50, the imperfect part is cut and the unbonded PC strands 10C or 10D that are successively drawn out are taken up by the winding device 5
It is wound around the reel 52 of 1.

Next, especially the rustproofing process of this unbonding process will be described. The PC steel stranded wire 10 is prevented from rotating in the circumferential direction by the feeding device 33 and the drawing device 50, and is moved only in the axial direction. First, the heating device 3
In No. 5, in the relieving device 36 of the next step, the PC steel strand 1
Although the twisting of 0 is temporarily relieved, the temperature at which plastic deformation does not occur due to the loosening, for example, 300 to 350 ° C.
Then, the wire 10 is heated from the PC steel just before the remission. The PC steel strand 10 is sent to the relaxation device 36 while being heated.

There, the loosening guide plate 39 is rotated by a motor 41 in the twisting direction in accordance with the twisting pitch of the PC steel stranded wire 10, whereby the PC steel stranded wire 10 is rotated.
Is always unraveled by the fixed length L unraveled in the preparatory work, and is automatically retwisted after the movement of L. This constant length L is maintained in a state of being unraveled for a certain period of time until the curing is started after the synthetic resin powder paint described later is sprayed and melted and adhered by the heating temperature for preventing plastic deformation strain due to the relaxation. The length to be set is preset. Since the heating performed by the heating device 35 is to loosen the PC steel wire 10 in a warm state, unlike the conventional case in which cold wire is loosened, the side wires 10a ... Because the effect of bluing is maintained,
It will be completely restored when the twist is returned.

The above heating also serves to form the synthetic resin powder melt-coated inner layers 21 and 23 by melting and closely adhering the synthetic resin powder paint to the side wires and the entire circumference of the core wire.

The PC steel stranded wire 10 thus unraveled is the spray booth 4 of the powder coating supply device 45.
6, the spray gun 47 sprays the synthetic resin powder paint to which a negative charge has been applied, which is applied with a positive charge by the loosening device 36.
0a and the core wire 10b are melted by adhering to the surface of FIG.
As shown in, the synthetic resin paint coating layer 9 is formed on the surface of each wire 10a, 10b to a uniform thickness. And the remission part 10
After passing through c and twisting again, as shown in FIG. 10, the space between the wires 10a and 10b is closely filled 19, and the outer surface is covered with the synthetic resin powder melt coating inner layer 21 to prevent rust. The treated PC steel wire 10A becomes the wire 10A, is heated again in the post-heating device 48 to adjust the surface of the coating layer, and is cooled by the cooling device 49 to completely cure the applied synthetic resin paint.

Depending on the length of the loosened portion 10c, FIG.
As shown in FIG. 5, the synthetic resin paint coating layer 9 of each of the wires 10a and 10b may be an independent synthetic resin powder melt coating inner layer 23 to form a rustproof PC steel stranded wire 10B.

The post-heating device 4 in the above-mentioned embodiment is used.
8 is not always necessary depending on the type of synthetic resin powder paint. Further, in the above-mentioned embodiment, the powder coating method by the electrostatic method in which the PC steel wire is attached by applying positive and negative charges to the powder coating is used. However, the PC steel wire is preheated. It is also possible to use a powder coating method by a so-called fluidized dipping method, in which a fluidized powder coating material is sprayed and adhered to this.

As described above, the anticorrosion treated PC steel stranded wire 10A or 10B in which the synthetic resin powder melt coating inner layer 21 or 23 is formed on the surface of each wire 10a, 10b is next applied to the surface by the lubricant applying device 55. After the lubricant 26 such as grease has been applied, the synthetic resin-coated outer layer cylinder 2 is extruded by the extruder 56.
7 is fitted and coated with unbonded PC stranded wire 10C or 10D as shown in FIGS. 12 and 13, respectively.
Becomes

[0029]

As is apparent from the above detailed description, according to the rust preventive unbonding method for PC stranded wire of the present invention, the following effects can be obtained.

While twisting a plurality of side wires around the core wire and performing a predetermined bluing on a PC steel stranded wire, the twisting is gradually and gradually relaxed while heating the temperature to a temperature at which plastic deformation strain does not occur due to the relaxation. Therefore, plastic working strain does not occur. Therefore, there is no variation in the elongation between the lateral lines or the twisting does not completely return to the state before the loosening. Therefore, the synthetic resin powder melt-coated inner layer can be formed on the entire circumference of each of the side wire and the core wire, and the synthetic resin-coated outer layer cylinder formed by the extrusion molding method can be formed on the surface of the inner layer through the lubricant.

In other words, the PC stranded wire obtained by the processing method of the present invention has a predetermined bluing despite the fact that the side wire and the core wire are covered with the synthetic resin powder melting inner layer and the synthetic resin coating outer layer cylinder. Because it is made, it maintains a stable and better condition. Further, since the side wire and the core wire are entirely covered with the synthetic resin powder melting inner layer and the synthetic resin coating outer layer cylinder, the rust prevention effect is remarkably high. That is, when a 200 mm test piece obtained by cutting a PC steel wire obtained by the processing method of the present invention was immersed in a salt spray for 2000 hours, it was observed that rust was generated on the cut surface without coating. There was nothing else in it, only it was accepted. Further, since the PC steel stranded wire obtained by the processing method of the present invention is fitted and covered with the synthetic resin-coated outer layer cylinder through the lubricant, the anticorrosion effect is remarkably improved, and the friction resistance at the time of introducing the prestress is small. Therefore, it is particularly excellent as a wire than PC steel for the post-tensioning method.

[Brief description of drawings]

FIG. 1 is a block diagram showing an arrangement of devices used in an embodiment of a processing method of the present invention.

FIG. 2 is a sectional view of a loosening device.

FIG. 3 is a front view of a loosening guide plate.

FIG. 4 is a sectional view of the same.

FIG. 5 is a partial cross-sectional view of the powder coating material supply device.

FIG. 6 is a side view of a PC steel stranded wire in a srating in a state of unraveling the tip end thereof.

FIG. 7 is a side view of the state where the tip end portion is similarly attached to the loosening guide plate.

FIG. 8 is a cross-sectional view of a PC steel strand before unbonding treatment.

FIG. 9 is a cross-sectional view showing a state in which a synthetic resin coating material is applied to a loosened portion.

FIG. 10 is a cross-sectional view of a PC steel strand after coating with a synthetic resin paint.

FIG. 11 is a sectional view of a PC steel strand similarly coated with a synthetic resin paint.

FIG. 12 is a sectional view of a PC steel strand obtained by the processing method of the present invention.

FIG. 13 is a sectional view of a PC steel strand similarly obtained by the processing method of the present invention.

FIG. 14 is a sectional view of a conventional example.

FIG. 15 is a cross-sectional view of another conventional example.

FIG. 16 is a sectional view of still another conventional example.

FIG. 17 is a sectional view of still another conventional example.

[Explanation of symbols]

10 PC stranded wire 10a Side wire 10b Core wire 10c Relief part 10A, 10B Synthetic resin paint-coated PC steel stranded wire 10C, 10D PC steel stranded wire obtained by the method of the present invention 21,23 Synthetic resin powder melt coating Inner layer 27 Synthetic resin coating Outer layer cylinder

Claims (1)

[Claims] 1. A twisted PC steel wire in which a plurality of side wires are twisted around a core wire and subjected to predetermined bluing is heated to a temperature at which plastic deformation does not occur due to relaxation, and the twisting is sequentially performed. The synthetic resin powder coating material is melted and adhered to the outer circumferences of the core wire and the side wires by using the heating temperature to form the synthetic resin powder melt coating inner layer (21, 23), After restoration, a lubricant is applied to the surface, and a synthetic resin-coated outer layer cylinder (27) is fitted and coated on the surface by an extrusion molding method.