JP4634317B2 - Method for producing resin-coated PC steel stranded wire, and apparatus for producing resin-coated PC steel stranded wire - Google Patents

Description

  The present invention relates to a resin-coated PC steel stranded wire used for prestressed concrete structures such as bridges and circular structures, and a resin-coated PC steel stranded wire for anchors used to reinforce slopes. In particular, the present invention relates to a method for producing a resin-coated PC steel stranded wire excellent in relaxation, a resin-coated PC steel stranded wire, and a device for producing a resin-coated PC steel stranded wire.

  A PC steel stranded wire (PC strand) used as a tension material in prestressed concrete (PC) is obtained by twisting a center line arranged at the center and a plurality of side lines arranged around the center line. The PC stranded wire has a gap between the center line and the side line. Conventionally, when a PC steel stranded wire is used for an oblique cable or an external cable construction method of a cable-stayed bridge or an extradosed bridge, the PC steel stranded wire is not embedded in concrete and is exposed to a corrosive environment. Further, when a PC steel stranded wire is used for an anchor, the anchor is always in the soil in a corrosive environment even though the anchor is protected by cement mortar. For this reason, when the gap is not completely covered, moisture or gas containing a corrosive component enters and corrodes the PC steel stranded wire.

  In order to prevent corrosion of the PC steel stranded wire, for example, Japanese Patent Application Laid-Open No. 5-200825 (Patent Document 1) proposes a method of forming a synthetic resin coating on a PC steel stranded wire by coating with a synthetic resin to prevent corrosion. ing. In Patent Document 1, a PC steel stranded wire is heated to a temperature at which plastic working strain does not occur and relaxed, and a polyethylene or epoxy resin or the like is heated to 300 to 350 ° C. on a PC steel stranded wire kept at a high temperature for powder coating. To fill the gap.

  Further, for example, Japanese Patent Laid-Open No. 11-50597 (Patent Document 2) proposes a resin-coated PC steel stranded wire excellent in relaxation, in which a steel stranded wire under a predetermined condition is coated with a resin to prevent corrosion. In patent document 2, since it relieves | releases in the state which reheated PC steel strand wire at the time of formation of a resin film, it is made possible to enlarge relaxation.

Further, for example, Japanese Patent Laid-Open No. 10-226973 (Patent Document 3) discloses a low-relaxation PC strand with a rust-proof coating characterized by a resin. In Patent Document 3, an internal anticorrosion layer is formed by coating a void portion and an outer peripheral surface with a rust preventive material made of a room temperature curable liquid resin.
JP-A-5-200825 Japanese Patent Laid-Open No. 11-50597 JP-A-10-226973

  However, in the synthetic resin coating forming method for a PC steel stranded wire disclosed in Patent Document 1, since the twist is released at a high temperature, distortion or residual stress is generated when untwisting. Therefore, there is a problem that the level of relaxation value is lowered when resin coating is performed.

  Further, the resin-coated PC excellent in relaxation disclosed in the above-mentioned Patent Document 2 is a steel stranded wire, and the low-relaxation compatible steel to be used is a special compound steel and is not a general-purpose product, so there is a problem that costs are increased.

  Further, in the low-relaxation PC strand with a rust-proof coating disclosed in Patent Document 3, a liquid curable resin is used as a coating raw material. Liquid curable resins use monomers or oligomers having a low molecular weight, but many of these substances are highly harmful. For this reason, the coating step of filling the liquid curable resin has a problem of great danger and harmfulness.

  Therefore, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for producing a resin-coated PC steel stranded wire with low relaxation, a resin-coated PC steel stranded wire, and a resin. It is providing the manufacturing apparatus of a covering PC steel strand.

  As a result of earnestly studying the increase in relaxation due to the relaxation of the PC stranded wire, the inventor of the present application performs the relaxation in a heated state at a high temperature by releasing the PC stranded wire in an unheated state or a heated state of 120 ° C. or less We found that the increase in relaxation was small compared to.

  Then, the manufacturing method of the resin-coated PC steel stranded wire of the present invention includes a step of preparing a PC steel stranded wire formed by twisting together a center line and six or more side wires disposed on the outer periphery of the center line. A step of relieving the PC steel stranded wire in an unheated state or a heated state of 120 ° C. or less, a step of attaching resin powder to the outer periphery of the center line and the side line of the relieved PC steel stranded wire formed by the step of releasing The preformed PC steel stranded wire formed by the attaching step is preformed into a desired shape, and the preformed PC steel stranded wire formed by the preforming step is heated at a temperature equal to or higher than the melting point of the resin powder. Process.

  According to the method for producing a resin-coated PC steel stranded wire of the present invention, the PC steel stranded wire is released in an unheated state or a heated state of 120 ° C. or lower in the step of releasing, so that it does not increase relaxation and adheres. The resin powder can be attached to the loosened PC steel stranded wire in the step of causing. And by the process of preforming and the process of heating, the gap between the center line and the side line and the gap between the side line and the side line can be filled with resin to form a rust-proof coating layer. Therefore, a resin-coated PC steel stranded wire with low relaxation can be manufactured.

Preferably, in the method for producing the resin-coated PC steel stranded wire, the distance d between the center line of the PC steel stranded wire and the center of the side wire in the step of preparing, A step of relaxing is performed such that the distance D from the center satisfies a relationship of D / d exceeding 1 and 10 or less.

  By setting it within this range, an increase in the relaxation of the resin-coated PC steel stranded wire can be suppressed, and the gap can be sufficiently filled with the resin.

  Preferably, in the method for producing the resin-coated PC steel stranded wire, the preforming step is performed by a preforming die having a tapered shape from the inlet side to the outlet side of the attached PC steel stranded wire. .

  By using a taper-shaped preform die, it is possible to press-fit the resin powder into the gap between the center line and the side line. Therefore, the filling degree of the resin into the gap can be improved. Therefore, a resin-coated PC steel stranded wire having a greater rust prevention effect can be produced.

  The resin-coated PC steel stranded wire of the present invention is manufactured by the method for manufacturing the resin-coated PC steel stranded wire. Thereby, it becomes possible to set it as the resin-coated PC steel strand wire with low relaxation.

  The apparatus for producing a resin-coated PC steel stranded wire according to the present invention is a device for producing a resin-coated PC steel stranded wire used in the above-described method for producing a resin-coated PC steel stranded wire. An opener mechanism for relieving in a heated state at a temperature of ℃ or less, a powder filling device for attaching resin powder to the outer periphery of the center line and side line of the relieved PC steel stranded wire, and preliminarily attaching the attached PC steel stranded wire to a desired shape A preforming die for molding and a heating furnace for heating the preformed PC steel stranded wire at a temperature equal to or higher than the melting point of the resin powder are provided. Thereby, the resin film PC steel strand wire with low relaxation can be manufactured.

  Preferably, the resin-coated PC steel stranded wire manufacturing apparatus has a taper shape from the inlet side to the outlet side of the attached PC steel stranded wire. Thereby, the resin-coated PC steel stranded wire having a greater rust prevention effect can be produced.

  Thus, according to the manufacturing method of the resin-coated PC steel stranded wire of the present invention, in the step of loosening, the PC steel stranded wire is loosened in a non-heated state or a heated state of 120 ° C. or less, so that the relaxation is low. A resin-coated PC steel stranded wire can be produced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a cross-sectional view showing a resin-coated PC steel stranded wire in an embodiment of the present invention. With reference to FIG. 1, the resin-coated PC steel stranded wire in Embodiment 1 of this invention is demonstrated.

  As shown in FIG. 1, the resin-coated PC steel stranded wire 10 according to Embodiment 1 of the present invention includes a center line 11, side lines 12, and a resin 13. The resin-coated PC steel stranded wire 10 is formed by twisting the center wire 11 and the side wire 12 together. The center line 11 is disposed at a substantially central portion of the resin-coated PC steel stranded wire 10. Six or more side lines 12 are arranged on the outer periphery of the center line 11. The resin 13 is disposed in the gap between the center line 11 and the side line 12, the gap between the adjacent side lines 12, and the outer periphery of the side line 12.

Specifically, the center line 11 and the side line 12 are made of steel. The side lines 12 have substantially the same shape, and six side lines 12 are arranged so as to surround the outer periphery in the extending direction of the center line 11. For example, the center line 11 can be about 5.25 mm and the side line 12 can be about 5.05 mm.

  The resin 13 has no danger and no harm and is preferably a thermosetting resin. For example, an epoxy resin can be used. The resin 13 is not particularly limited to this, and may be a thermoplastic resin, for example. As a thermoplastic resin, it is preferable that it is what is excellent in adhesiveness with steel materials, For example, it can be set as adhesive olefin resin.

  The cross-sectional shape in the longitudinal direction of the resin-coated PC steel stranded wire 10 is, for example, a petal shape. It is preferable that the valley portion 13a, which is the outer portion to which the adjacent side lines 12 are connected, has a deeply depressed valley shape such as a petal shape. When the cross-sectional shape of the continuous side line 12 is a petal shape, the cross-sectional shape of the resin 13 covering the outer peripheral surface of the side line 12 is also a petal shape. By making the cross-sectional shape into a petal shape, it is preferable because it can have a high adhesive force between a steel material such as a high-strength steel material and concrete. In addition, if the side line 12 is arrange | positioned six or more, it will not specifically limit to a petal type | mold, For example, it can arrange | position according to uses, such as a polygonal type.

  The resin-coated PC steel stranded wire 10 according to Embodiment 1 has a relaxation value of 2.5% or less. The relaxation value is measured according to JIS G3536. The relaxation characteristic is a characteristic in which prestress decreases after a long time has elapsed when a PC steel stranded wire is placed and tensioned in a structure to give prestress. The smaller the relaxation value, the more effective prestress is secured.

  As described above, according to the resin-coated PC steel stranded wire 10 according to Embodiment 1 of the present invention, the relaxation value is low. Moreover, since general-purpose steel can be used for the center line 11 and the side line 12, manufacturing cost can be suppressed. Furthermore, the resin 13 has no danger and no harm.

(Embodiment 2)
FIG. 2 is a schematic diagram showing an apparatus for producing a resin-coated PC steel stranded wire in Embodiment 2 of the present invention. 3A and 3B show a pre-molding die according to Embodiment 2 of the present invention, where FIG. 3A is a cross-sectional view and FIG. 3B is a side view. 4A and 4B show a spare die different from the second embodiment of the present invention, in which FIG. 4A is a cross-sectional view and FIG. 4B is a side view. With reference to FIGS. 2-4, the manufacturing apparatus of the resin coating PC steel strand wire in Embodiment 2 of this invention is demonstrated.

  As shown in FIG. 2, an apparatus 20 for producing a resin-coated PC steel stranded wire according to Embodiment 2 of the present invention includes an unwinding machine 21, an opener mechanism 22, a powder filling apparatus 23, a preforming die 24, The heating furnace 25 and the winder 26 are provided. The resin-coated PC steel stranded wire 10 according to the first embodiment can be manufactured by the resin-coated PC steel stranded wire manufacturing apparatus 20 according to the second embodiment.

  Specifically, the unwinding machine 21 is a member for unwinding the PC steel stranded wire 30 formed by twisting a center line and a side line.

  The opener mechanism 22 is a member for loosening the PC steel stranded wire 30 in an unheated state or a heated state of 120 ° C. or lower. In detail, the opener mechanism 22 is arrange | positioned in the part connected with the powder filling apparatus 23 of the entrance side of the PC steel strand 30. FIG. The opener mechanism 22 is a relaxed PC steel stranded wire in which the twist is expanded (relaxed) so that the center line and the side line of the PC steel stranded wire 30 are separated from each other in a non-heated state or a heated state of 120 ° C. or less. 40. The opener mechanism 22 is provided with a hole for passing a center line or a side line in the center of the disk and in a plane so that a desired D / d is obtained, for example, and this disk is automatically or passively according to the rotation of the twist. And is fixed so as not to move back and forth. The center line and the side line of the PC steel stranded wire 30 are separated by the opener mechanism 22 in an unheated state or a heated state of 120 ° C. or lower.

  The powder filling device 23 attaches the resin powder to the outer periphery of the center line and the side line of the loose PC steel stranded wire 40. The powder filling device 23 uses the loosened PC steel stranded wire 40 as an attached PC steel stranded wire 50. The powder filling device 23 is configured to have at least one filling function of, for example, fluid immersion and powder spray in which resin powder is melted. The powder filling device 23 preferably further has a function of scraping off excess resin powder.

  The preforming die 24 preforms the adhered PC steel stranded wire 50 into a desired shape. When pre-molding is performed by the pre-molding die 24, a function of pre-molding the adhesion of the powder resin adhered to the valley portion of the attached PC twisted wire 50 and a function of returning the loosened twist to the original state are provided. ing.

  Further, the preforming die 24 is disposed at a portion connected to the powder filling device 23 on the outlet side of the PC steel stranded wire 30. As shown in FIG. 3A, the pre-molding die 24 has a petal shape in cross section. By setting it as this shape, the longitudinal section of the resin-coated PC steel stranded wire 10 according to Embodiment 1 can be formed into a petal shape.

  Further, as shown in FIG. 3 (B), the preforming die 24 has a large inner diameter on the inlet side 24a from the inlet (incoming) side 24a of the PC steel stranded wire toward the outlet (outgoing) side 24b. It is preferable to have a tapered shape with a small inner diameter. In addition, the preforming die 24 is not particularly limited to this shape. For example, as shown in FIG. 4B, the preforming die 24 may have a shape extending from the inlet side 24a to the outlet side 24b of the PC steel stranded wire.

  The heating furnace 25 heats the preformed PC steel stranded wire 60 at a temperature equal to or higher than the melting point of the resin powder. The heating furnace 25 melts and hardens the resin powder in a powder state attached to the gap between the center line and the side line, and when there are two or more side lines, the center line and the side line Integrate with side wires to make a rust-proof coating layer. In the second embodiment, the heating furnace 25 has control means that can change the temperature in accordance with the resin powder.

  As described above, according to the resin-coated PC steel stranded wire manufacturing apparatus 20 in the second embodiment of the present invention, the opener for relieving the PC steel stranded wire 30 in an unheated state or a heated state of 120 ° C. or lower. A mechanism 22, a powder filling device 23 for attaching a resin powder to the outer periphery of the center line and the side line of the loose PC steel stranded wire 40, and a pre-molding die 24 for pre-molding the attached PC steel stranded wire 50 into a desired shape; And a heating furnace 25 for heating the preformed PC steel stranded wire 60 at a temperature equal to or higher than the melting point of the resin powder. Since the opener mechanism 22 can loosen the PC steel stranded wire 30 in an unheated state or a heated state of 120 ° C. or less, the powder filling device 23 can add the resin powder 53 to the loosened PC steel stranded wire 40 without increasing the relaxation. Can be attached and filled. And by the preforming die 24 and the heating furnace 25, the gap between the center line and the side line and the gap between the side line and the side line can be filled with a resin to form a rust-proof coating layer. Therefore, the resin-coated PC steel stranded wire 10 with low relaxation can be manufactured.

  Moreover, since the manufacturing apparatus 20 of the resin-coated PC steel stranded wire can use general-purpose steel for the center line and the side line, the manufacturing cost of the resin-coated PC steel stranded wire can be suppressed. Furthermore, the resin-coated PC steel stranded wire 10 with low relaxation can be manufactured even if resin powder having no danger and no harm is used.

  Furthermore, the resin-coated PC steel stranded wire manufacturing apparatus 20 includes a highly viscous resin, a resin that was difficult to adhere to the gap between the center line and the side line by extrusion at low temperature, and a heat that was difficult to mold by extrusion. A resin such as a curable resin can be attached to and coated on the PC steel stranded wire 30 without increasing relaxation.

  In the apparatus for producing a resin-coated PC steel stranded wire, preferably, the preforming die 24 has a tapered shape from the inlet side 24a to the outlet side 24b of the attached PC steel stranded wire 50. This makes it possible to press-fit the resin powder not only into the gap between the side lines 12 but also into the gap between the center line 11 and the side line 12. Therefore, the filling degree of the resin into the gap can be improved. Therefore, the resin-coated PC steel stranded wire 10 having a greater rust prevention effect can be manufactured.

(Embodiment 3)
FIG. 5 is a flowchart showing a method for manufacturing a resin-coated PC steel stranded wire according to Embodiment 3 of the present invention. FIG. 6 is a cross-sectional view showing a PC steel stranded wire before relieving. FIG. 7 is a cross-sectional view showing a PC steel stranded wire after loosening. FIG. 8 is a cross-sectional view showing a PC steel stranded wire to which a powder resin is attached. FIG. 9 is a cross-sectional view showing a pre-formed PC steel stranded wire. With reference to FIGS. 1-9, the manufacturing method of the resin coating PC steel strand wire in Embodiment 3 of this invention is demonstrated. The manufacturing method of the resin-coated PC steel stranded wire in the third embodiment uses the resin-coated PC steel stranded wire manufacturing apparatus 20 in the second embodiment to manufacture the resin-coated PC steel stranded wire 10 in the first embodiment. ing.

  First, as shown in FIG. 5 and FIG. 6, a step of preparing a PC steel stranded wire 30 formed by twisting the center line 11 and the side wires 12 arranged on the outer periphery of the center line 11 (S10) is performed. To do.

  Next, the step (S20) of relieving the PC steel stranded wire 30 in an unheated state or a heated state of 120 ° C. or less is performed. In the step of releasing (S20), for example, an opener mechanism 22 shown in FIG. 2 is used.

In the loosening step (S20), the distance d between the center of the center line 11 of the PC steel stranded wire 30 shown in FIG. 6 and the center of the arbitrary side line 12 and the center line 11 of the loosened PC steel stranded wire 40 shown in FIG. It is preferable to carry out the relaxation so that the distance D between the center of and the center of the arbitrary side line 12 satisfies the relationship of D / d exceeding 1 and 10 or less. Note that the distance d before remission is d = ( d ₁ + d ₀ ) / 2 where the side wire diameter d ₁ and the center wire diameter d ₀ are d = ( d ₁ + d ₀ ) / 2 .

  The non-heated state means the PC steel stranded wire 30 at room temperature. Moreover, when heating, it is 120 degrees C or less, Preferably it is 100 degrees C or less from a viewpoint of suppressing the increase in relaxation more. Heating to 120 ° C. or lower is preferable because the resin powder 53 can be softened in the attaching step (S30) described later. In addition, since it becomes below melting | fusing point of the resin powder 53 by setting it as 120 degrees C or less, the effect of the relaxation similar to the case where it relieves in a non-heating state is acquired.

  The step of releasing (S20) may be performed in an unheated state or a heated state of 120 ° C. or lower, and is not particularly limited to performing the releasing by the opener mechanism 22.

  When the PC steel stranded wire 30 shown in FIG. 6 is loosened in the step of releasing (S20), the loosened PC steel stranded wire 40 shown in FIG. 7 is obtained. The loosened PC steel stranded wire 40 is in a state where the twist is expanded so that the center line 11 and the side wires 12 are separated from each other.

  Next, as shown in FIG. 8, the step (S30) of attaching the resin powder 53 to the outer periphery of the center line 11 and the side line 12 of the loosened PC steel stranded wire 40 formed by the loosening step (S20) is performed. . In the attaching step (S30), for example, the powder filling device 23 shown in FIG. 2 is used.

  In the step of attaching (S30), for example, it is performed by at least one of fluid immersion and powder spray in which resin powder is melted. For example, the resin powder 53 is uniformly attached to the loosened PC steel stranded wire 40 by continuously passing through the powder filling device 23 at a constant speed. Further, the resin powder to be adhered is not dangerous and harmful, and is preferably a thermosetting resin powder. For example, an epoxy resin powder can be used. The resin powder to be adhered is not particularly limited to this, and may be, for example, a thermoplastic resin powder. The thermoplastic resin powder is preferably excellent in adhesiveness to a steel material, for example, an adhesive olefin resin powder.

  When the resin powder 53 is attached to the loosened PC steel stranded wire 40 shown in FIG. 7 in the attaching step (S30), the resin powder 53 is applied to the center line 11 and the side wires 12 in the loosened state as shown in FIG. The attached PC steel stranded wire 50 to which is attached can be obtained.

  Next, as shown in FIG. 9, a step (S40) of preforming the attached PC steel stranded wire 50 formed in the attaching step (S30) into a desired shape is performed. In the preforming step (S40), for example, the preforming die 24 shown in FIG. 2 is used.

  The preforming step (S40) is preferably performed by a preforming die having a tapered shape from the entrance side to the exit side of the attached PC steel stranded wire 50.

  When the attached PC steel stranded wire 50 to which the loosened resin powder 53 shown in FIG. 8 is attached in the pre-molding step (S40) is preliminarily molded, as shown in FIG. The preformed PC steel strand 60 which was shape | molded can be obtained.

  In addition, after carrying out the pre-molding step (S40) and attaching the resin powder 53 to the gap between the center line 11 and the side line 12, the outer peripheral surface of the side line 12 is further coated by powder coating or extrusion coating. It may be covered with a body.

  Next, a step (S50) of heating the preformed PC steel stranded wire 60 at a temperature equal to or higher than the melting point of the resin powder 53 is performed in the step of preforming (S40).

  In the heating step (S50), the resin powder 53 is dissolved by heating at a temperature equal to or higher than the melting point of the resin powder 53. Then, by cooling or leaving in that state, the dissolved resin powder 53 is cured.

  When the preformed PC steel stranded wire 60 shown in FIG. 9 is heated in the heating step (S50), the resin-coated PC steel stranded wire in which the center line 11, the side wires 12, and the resin 13 are integrated as shown in FIG. 10 can be obtained. And the resin 13 of the resin-coated PC steel stranded wire 10 has a function of a rust prevention protective layer.

  By implementing the said process (S10-S50), the resin-coated PC steel strand wire 10 with low relaxation can be obtained.

  As described above, according to the method for manufacturing the resin-coated PC steel stranded wire in the third embodiment of the present invention, the center line 11 and the side wire 12 arranged on the outer periphery of the center line 11 are twisted together. PC steel stranded wire 30 is prepared (S10), PC steel stranded wire 30 is unheated or heated at 120 ° C. or lower (S20), and is released (S20). The step (S30) of attaching the resin powder 53 to the outer periphery of the center line 11 and the side wire 12 of the loosened PC steel stranded wire 40 and the attached PC steel stranded wire 50 formed by the attaching step (S30) into a desired shape. A step of preforming (S40) and a step of heating the preformed PC steel stranded wire 60 formed at the step of preforming (S40) at a temperature equal to or higher than the melting point of the resin powder 53 are provided (S50). In the step of relieving (S20), utilizing the fact that when the PC steel stranded wire 30 is relieved in a non-heated state or a heated state of 120 ° C. or less, the increase in relaxation is less than in the case of relieving in a heated state at a high temperature, The PC steel stranded wire 30 is loosened in a heated state or a heated state of 120 ° C. or lower. Therefore, the resin powder 53 can be filled in the loosened PC steel stranded wire 40 in the attaching step (S30) without increasing the relaxation of the loosened PC steel stranded wire 40. Then, the pre-molding step (S40) and the heating step (S50) prevent the gap between the center line and the side line, and if there are two or more side lines, the resin 13 fills the gap between the side line and the side line. It can be set as a rust coating layer. Therefore, a resin-coated PC steel stranded wire with low relaxation can be manufactured.

In the method for producing the resin-coated PC steel stranded wire, the distance d between the center of the center line 11 of the PC steel stranded wire 30 and the center of the side wire 12 in the step of preparing (S10), A step (S20) is performed in which the distance D between the center of the center line 11 and the center of the side line 12 is relaxed so that D / d exceeds 1 and satisfies a relationship of 10 or less. By setting D / d to exceed 1, the resin is sufficiently filled in the gap between the center line and the side line. On the other hand, by making D / d 10 or less, an increase in relaxation can be suppressed.

Preferably, in the method for producing a resin-coated PC steel stranded wire, the preforming step (S40) is performed by a preforming die 24 having a tapered shape from the inlet side 24a to the outlet side 24b of the attached PC steel stranded wire 50. Has been. This makes it possible to press fit into the gap. Therefore, the filling degree of the resin 13 in the gap can be improved. Therefore, a resin-coated PC steel stranded wire having a greater rust prevention effect can be produced.
[Example]
In this example, the effect of the step of relieving was examined. First, each resin-coated PC steel stranded wire of Examples and Comparative Examples was produced by the following method.

(Production of resin-coated PC steel stranded wire in Example 1)
It manufactured with the manufacturing method of the resin coating PC steel strand wire in Embodiment 3. FIG. Specifically, a PC steel stranded wire having an inner diameter of 15.2 mm was prepared as a step of preparing (S10). Then, as a step of loosening (S20), the PC steel stranded wire was loosened in an unheated state so that D / d was 10. Then, as a step of attaching the resin powder (S30), an epoxy resin powder was sprayed with a spray gun toward the center line. At this time, the powder filling device 23 having a function of scraping off excess resin powder was continuously passed at a constant speed. Then, as a pre-molding step (S40), the cross-sectional shape was pre-molded with a petal-shaped pre-molding die. And as a heating process (S50), it passed through the convection heating furnace which can be heated so that the steel material surface temperature may be 230 degreeC. Thereby, a resin-coated PC steel stranded wire in Example 1 was obtained.

(Production of resin-coated PC steel stranded wire in Comparative Example 1)
Comparative Example 1 is basically the same as Example 1, except that Comparative Example 1 differs only in that it was performed in a heated state at a high temperature in the step of releasing (S20) and D / d was set to 30. . Specifically, as the step of preparing (S10), the PC stranded wire was continuously passed through a convection heating furnace and heated so that the steel material surface temperature was 230 ° C. Then, as a step of releasing (S20), the release was performed so that D / d was 30 with an opener in a heated state.

(Production of resin-coated PC steel stranded wire in Comparative Example 2)
Comparative Example 2 is basically the same as Example 1, except that Comparative Example 2 differs only in that it was performed in a heated state at a high temperature in the step of releasing (S20). Specifically, as the step of preparing (S10), the PC stranded wire was continuously passed through a convection heating furnace and heated so that the steel material surface temperature was 230 ° C.

(Evaluation methods)
About the obtained resin-coated PC steel stranded wire, the relaxation value was measured, respectively. The relaxation value was measured under the condition of 1000 hours at room temperature by the method defined in JIS G3536. Moreover, the filling condition of the resin powder was observed about the pre-molded PC strand obtained by the pre-molding step (S40). The results are shown in Table 1.

(Evaluation results)
As shown in Table 1, the relaxation value of the resin-coated PC steel wire strands in Example 1, was 2.5% or less and a low value. On the other hand, the resin-coated PC steel stranded wire in Comparative Example 1 heated at a high temperature of 230 ° C. and having a D / d outside the scope of the present invention , and the resin-coated PC steel stranded wire in Comparative Example 2 heated at a high temperature of 230 ° C. The relaxation value of was a high value exceeding 2.5%. The filling status of the resin powder of Example 1 Contact and Comparative Example 1 were all satisfactory.

  As described above, according to the examples, it was found that a resin-coated PC steel stranded wire with low relaxation can be manufactured by performing relaxation in an unheated state.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is shown not by the above-described embodiment but by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

It is sectional drawing which shows the resin coating PC steel strand wire in embodiment of this invention. It is the schematic which shows the manufacturing apparatus of the resin coating PC steel strand wire in Embodiment 2 of this invention. The preforming die in Embodiment 2 of this invention is shown, (A) is sectional drawing, (B) is a side view. The spare dice different from Embodiment 2 of this invention are shown, (A) is sectional drawing, (B) is a side view. It is a flowchart which shows the manufacturing method of the resin coating PC steel strand wire in Embodiment 3 of this invention. It is sectional drawing which shows the PC steel strand wire before relieving. It is sectional drawing which shows the PC steel strand wire after loosening. It is sectional drawing which shows the PC steel strand wire to which powder resin was made to adhere. It is sectional drawing which shows the preformed PC steel strand.

Explanation of symbols

  10 resin-coated PC steel stranded wire, 11 center line, 12 side wire, 13 resin, 13a valley section, 20 resin-coated PC steel stranded wire manufacturing equipment, 21 unwinding machine, 22 opener mechanism, 23 powder filling equipment, 24 preliminary Molding die, 24a inlet side, 24b outlet side, 25 heating furnace, 26 winder, 30 PC steel stranded wire, 40 relieved PC steel stranded wire, 50 adhered PC steel stranded wire, 53 resin powder, 60 preformed PC steel Stranded wire.

Claims (4)

Preparing a PC steel stranded wire formed by twisting a center line and six or more side wires disposed on the outer periphery of the center line;
Relieving the PC steel stranded wire in an unheated state or a heated state of 120 ° C. or less;
Attaching resin powder to the outer periphery of the center line and the side line of the relieved PC steel stranded wire formed by the relieving step;
Pre-molding the attached PC steel strand formed by the attaching step into a desired shape;
Heating the preformed PC steel stranded wire formed by the preforming step at a temperature equal to or higher than the melting point of the resin powder,
The distance d between the center line of the PC steel stranded wire and the center of the side line in the step of preparing, and the distance D between the center line of the relieved PC steel stranded wire and the center of the side line are: A method for producing a resin-coated PC steel stranded wire, wherein the step of releasing is performed so that D / d exceeds 1 and satisfies a relationship of 10 or less.   The resin-coated PC steel twist according to claim 1, wherein the preforming step is performed by a preforming die having a taper shape from an inlet side to an outlet side of the attached PC steel stranded wire. Wire manufacturing method. An apparatus for producing a resin-coated PC steel stranded wire used in the method for producing a resin-coated PC steel stranded wire according to claim 1 or 2,
An opener mechanism for relieving the PC steel stranded wire in an unheated state or a heated state of 120 ° C. or less;
A powder filling device for adhering resin powder to the outer periphery of the center line and the side line of the loosened PC steel stranded wire;
A preforming die for preforming the adhered PC steel stranded wire into a desired shape;
An apparatus for producing a resin-coated PC steel stranded wire, comprising a heating furnace that heats the preformed PC steel stranded wire at a temperature equal to or higher than the melting point of the resin powder. The apparatus for producing a resin-coated PC steel stranded wire according to claim 3 , wherein the preformed die has a tapered shape from the inlet side to the outlet side of the attached PC steel stranded wire.

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