JP2005264363A - Resin-coated pc steel strand and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin-coated PC steel strand capable of being formed with a resin coat having high adhesion, and to provide a method for producing the strand. <P>SOLUTION: The resin-coated PC steel strand comprises a PC steel strand of twisted plural drawn wires and a resin coat formed at least on the periphery of the PC steel strand. The wires are covered with a zinc phosphate coat as the pretreatment of wire drawing and are drawn by using a lubricant comprising a metal soap in wire drawing. On the surface of the PC strand, the zinc phosphate coat remains and the lubricant is practically removed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a resin-coated PC steel stranded wire and a method for producing the same. In particular, the present invention relates to a PC steel stranded wire having a resin coating with high adhesion.

  Conventionally, a resin-coated PC steel stranded wire in which a resin coating such as an epoxy resin is formed on the surface of a PC steel stranded wire is known for the purpose of improving corrosion resistance.

  This resin-coated PC steel stranded wire is generally manufactured as follows. First, a wire constituting a PC steel stranded wire is manufactured by drawing a rod as a base material. At that time, a zinc phosphate coating is often formed on the surface of the base material as a pretreatment for drawing for the purpose of improving lubricity during drawing. In addition, metal soap is also applied as a lubricant between the die and the base material during wire drawing. Next, the strands obtained by drawing in this way are twisted to form a PC steel stranded wire. Then, a resin coating is formed on the outer periphery of the PC steel stranded wire by powder coating or extrusion.

  Such resin-coated PC steel stranded wire is a cable that twists two or more resin-coated PC steel stranded wires when (1) it is cut to the specified length after the resin coating is formed at the factory. There is a possibility of contact with transport equipment, floor or construction equipment under various conditions such as during processing, (3) during transport, and (4) during construction. At this time, if the adhesion between the PC steel stranded wire and the resin coating is insufficient, the resin coating partially peels from the PC steel stranded wire, from which partial corrosion of the PC steel stranded wire begins, You may not be able to get a lifetime.

  Therefore, in order to improve the adhesion between the PC steel strand and the resin coating, as a pretreatment of the resin coating, the PC steel strand is degreased with a degreasing agent or blast, or the surface of the degreased PC steel strand is phosphoric acid. For example, a zinc coating is formed (for example, Patent Document 1).

Japanese Patent Laid-Open No. 5-195602

  However, with respect to improving the adhesion between the PC steel stranded wire and the resin coating, there has been a demand for a technique that can realize a further improvement in adhesion with a cheaper and simpler means.

  In particular, in the technique of Patent Document 1, it is described that the surface of the PC steel wire is degreased with a degreasing agent or blasting, and the zinc phosphate film is recoated after the wire drawing. There is no clear disclosure as to how much the zinc phosphate coating formed by the treatment and the lubricant at the time of drawing are removed before the resin coating, and the latter is a separate process treatment, which increases the manufacturing cost. Furthermore, there is no suggestion as to how the lubricant remaining level is related to the adhesion of the resin coating.

  Accordingly, a main object of the present invention is to provide a resin-coated PC steel stranded wire capable of forming a resin coating having high adhesion and a method for producing the same.

  In order to clarify the factors governing the adhesion between the resin coating and the PC steel stranded wire, the inventors of the present invention have a zinc phosphate coating formed by the wire drawing pretreatment and the remaining level of lubricant used during wire drawing. The relationship between the adhesive strength and the resin coating was investigated in detail. As a result, the inventors obtained the knowledge that the lubricant during wire drawing should be substantially removed to leave the zinc phosphate coating, and the present invention has been completed.

  That is, the resin-coated PC steel stranded wire of the present invention has a PC steel stranded wire obtained by twisting a plurality of drawn strands, and a resin coating formed on at least the outer periphery of the PC steel stranded wire. The wire is formed with a zinc phosphate coating as a pre-drawing treatment, and drawn with a lubricant made of a metal soap at the time of drawing. The surface of the PC steel stranded wire is characterized in that the zinc phosphate coating remains and the lubricant is substantially removed.

  To what extent can the adhesive strength of the resin coating be obtained when the zinc phosphate coating before wire drawing and the lubricant during wire drawing remain on the surface of the PC steel stranded wire before the resin coating? As a result of various studies, it was found that the lubricant reduces the adhesion of the resin coating, and the zinc phosphate coating improves the adhesion of the resin coating. Accordingly, if the zinc phosphate coating is left and the lubricant is substantially removed before the resin coating, a resin coating with high adhesion can be formed on the surface of the PC steel stranded wire.

Moreover, the manufacturing method of this invention resin coating PC steel strand wire has the following processes, It is characterized by the above-mentioned.
A pretreatment step of forming a zinc phosphate coating on the surface of a base material to be drawn as a drawing pretreatment.
A wire drawing process in which this base material is drawn using a lubricant.
A twisting process in which a plurality of the drawn wire materials are twisted to obtain a PC steel twisted wire.
A cleaning process in which the lubricant remaining on the surface of the PC steel strand is substantially removed, but the zinc phosphate coating remains.
A resin coating process for forming a resin coating on at least the outer periphery of the washed PC steel stranded wire.

  According to the method including the above steps, the zinc phosphate coating can be left while removing the lubricant, and the resin-coated PC steel stranded wire of the present invention can be easily manufactured.

  Hereinafter, the present invention will be described in more detail.

<Resin-coated PC steel stranded wire>
The PC steel stranded wire is formed by twisting a plurality of strands. For example, a PC steel stranded wire defined by JIS G 3536 can be used. Usually, PC steel stranded wire has a structure in which one or more side wires are combined in a spiral shape on the outer periphery of the center line, and there are 7 strands and 19 strands. In particular, the PC steel stranded wire used in the present invention has (1) a zinc phosphate coating formed on a rod such as a rolled material as a drawing pretreatment, and (2) a lubricant between the die and the rod during wire drawing. On the condition that the wire is drawn by applying. In the PC steel stranded wire obtained by twisting the strands obtained through these processes, the resin coating with high adhesion is twisted by PC steel by removing only the lubricant and leaving the zinc phosphate coating. It can be formed on a line.

  Substantially removing only the lubricant preferably means satisfying the following condition. In other words, when the composition analysis of the surface of the PC steel strand wire was performed by Auger electron spectroscopy, the ratio between the peak value of the metal component of the residual lubricant and the peak value of P of the zinc phosphate coating in the analysis result profile was 0.05 or less Remove the lubricant so that If this ratio condition is satisfied, it is considered that the lubricant on the surface of the PC steel stranded wire can be sufficiently removed, and the zinc phosphate coating remains, and the adhesion of the resin coating is improved by a very small amount of residual lubricant. There is no hindrance.

  Epoxy, polyethylene, polycarbonate, polyester, etc. can be used for the resin coating. In addition to the case where the resin coating is formed only on the outer periphery of the PC steel stranded wire, the resin coating may be further filled between the strands. In addition, a structure in which a resin coating is formed for each element wire and the resin-coated element wires are twisted together may be employed. The space surrounded by the center line and the side line is filled with the resin, or the resin coating is formed for each element wire.

<Manufacturing method>
The resin-coated PC steel stranded wire of the present invention can be obtained, for example, by preparing a strand, twisting the strand, washing the strand (removing the lubricant), and forming a resin coating on the surface of the strand. After the strands are washed (removal of lubricant), the strands may be twisted together.

  By forming a zinc phosphate coating on the surface of the rod before drawing, and then supplying a lubricant such as metal soap between the die and the rod during drawing, can get. Metal soap is a general term for non-alkali metal salts of organic acids such as fatty acids. For example, calcium stearate, sodium stearate, lithium stearate and the like can be mentioned.

  When a zinc phosphate coating is formed as a pretreatment for wire drawing and metal soap is used as a lubricant during wire drawing, the zinc phosphate coating or metal soap remains on the surface of the PC steel stranded wire before resin coating. Of these remaining coating and remaining lubricant, a cleaning process is performed to remove the latter and leave the former.

  This cleaning process is performed by immersing a PC steel strand in a cleaning agent. In other words, it is necessary to immerse the PC steel stranded wire in the cleaning treatment agent for a time that can remove the metal soap but not the zinc phosphate coating. Examples of the cleaning treatment agent include acids and alkalis. When phosphoric acid is used as the cleaning treatment agent, the immersion time is 2 seconds or less. If this upper limit is exceeded, not only the lubricant but also the zinc phosphate coating may be removed. The lower limit of the dipping time is sufficient if the metal soap can be removed. For example, about 1.0 second is sufficient. The immersion time of the PC steel stranded wire in the cleaning treatment agent can be adjusted by changing the wire speed of the PC steel stranded wire and the immersion tank length in the production line.

  The temperature of the cleaning agent during immersion is preferably from room temperature to 50 ° C. In this temperature range, the evaporation of moisture is small and concentration control is easy, and no excessive equipment is required for heating the cleaning treatment agent, and it is suitable for removing metal soap.

  For forming the resin coating, a known coating method such as powder coating or extrusion can be used. In particular, by attaching the resin powder in an open state to the PC steel stranded wire, returning the twist to the closed state and then curing the resin, not only the outer periphery of the PC steel stranded wire, but also between the strands Also, a coating filled with resin can be formed.

  According to the resin-coated PC steel stranded wire of the present invention, the adhesion force of the resin coating to the PC steel stranded wire can be dramatically improved. Further, according to the method for producing a resin-coated PC steel stranded wire of the present invention, it is possible to perform a cleaning process for improving the adhesion of the resin coating by a simple method.

(Example 1)
An example of producing the resin-coated PC steel stranded wire of the present invention is shown below.

  First, a PC steel stranded wire is prepared. A steel rod with a diameter of 13 mm is pickled in a batch system to remove the iron oxide coating on the rod surface. A zinc phosphate coating treatment is performed on the rod surface in a batch manner to form a zinc phosphate coating that becomes a lubricating film in the next wire drawing step. These pretreated rods are drawn with a die. At that time, metal soap is added as a lubricant between the die and the rod. The obtained wire is twisted with a twisting machine to obtain a PC steel stranded wire.

  Next, the obtained PC steel stranded wire is subjected to a cleaning treatment. This cleaning process is performed by immersing a PC steel strand in a cleaning agent. By soaking in the cleaning agent, the metal soap remaining on the surface of the PC steel stranded wire is removed, and the zinc phosphate coating remains. The immersion time can be adjusted by changing the conveying speed of the PC steel strand.

  Subsequently, a resin coating is formed on the washed PC steel strand. In this resin coating, the PC steel stranded wire after the washing treatment is washed with water and heated to adhere the resin to the surface of the PC steel stranded wire by powder coating or the like. When the resin to be used is a thermosetting resin, the attached resin is cured by performing a heat treatment later. If the resin coating is formed, it is cooled and the obtained resin-coated PC steel stranded wire is wound up.

(Test Example 1)
First, the influence of the metal soap used at the time of wire drawing on the adhesion of the resin coating layer due to the residual surface of the PC steel strand was investigated. As samples, the following three types of PC steel stranded wires were prepared. PC steel stranded wire is a JIS G 3536 SWPR7BN 7-strand (1 center wire + 6 side wires), 15.2 mm diameter PC steel stranded wire. Na-type metal soap (sodium stearate) was adopted as the metal soap used for wire drawing.

Sample 1: PC steel stranded wire with zinc phosphate coating and metal soap attached (no cleaning treatment).
Sample 2: The twisted wire of Sample 1 was opened and disassembled, each metal wire was completely wiped away with metal soap using an organic solvent, and then returned to the twisted wire state again.
Sample 3: The twisted wire of Sample 1 was untwisted and disassembled, each wire was polished with sandpaper until a metallic luster was obtained, and both the metal soap and the zinc phosphate coating were completely removed, and then the twisted wire was again removed. What was returned to the state.

  An epoxy resin coating having a thickness of about 0.8 mm was formed on samples 1 to 3 to form resin-coated PC steel stranded wires. Then, a tensile test was performed on the resin-coated PC steel stranded wire to evaluate the adhesion of the resin coating. The tensile test is performed in accordance with JIS Z 2241. Break the resin-coated PC steel stranded wire in a tensile test. And a fracture | rupture part is investigated visually and the adhesion | attachment condition of the resin coating of the fracture | rupture part vicinity is confirmed. If the resin coating remains on the entire circumference of the PC steel stranded wire, “No peeling” is determined, and if any part is peeled or broken, it is judged as defective, and the peeling state is recorded. As a result, the following was found.

  The resin-coated PC steel stranded wire using Sample 1 in which the metal soap remained had low adhesion of the resin coating, and peeling occurred. In the resin-coated PC steel stranded wire using Sample 2 from which only metal soap was completely removed, it was found that the resin coating adhered firmly. Further, the resin-coated PC steel stranded wire using Sample 3 from which the zinc phosphate coating was also removed and the metal surface was exposed had low adhesion of the resin coating, and the resin coating peeled off at the time of tensile fracture.

  From the above test results, it is considered necessary to remove the metal soap to ensure the adhesion of the resin coating.

(Test Example 2)
According to Test Example 1, it was found that if the metal soap was completely removed regardless of the practicality of the cleaning treatment, it was effective for improving the adhesion of the resin coating. It is considered difficult to completely remove the metal soap inside (several seconds to several tens of seconds). Therefore, in order to confirm how much metal soap should be removed, samples with different degrees of removal of metal soap were prepared by changing the type and immersion time of the cleaning treatment agent, composition analysis and resin coating on the surface of each sample The adhesion strength was evaluated.

  The sample was produced as follows. First, the base material on which the zinc phosphate coating is formed is drawn with a die using a Ca-based lubricant (calcium stearate) to obtain a strand. Next, the obtained strands are twisted to form PC steel stranded wires. This PC steel stranded wire is also a JIS G 3536 SWPR7BN 7 strand (1 center wire + 6 side wires), 15.2 mm diameter PC steel strand.

  Subsequently, by using this stranded wire, PC steel stranded wires having various surface states are produced on an actual production line by changing the phosphoric acid cleaning time (immersion time) as shown in Table 1. The phosphoric acid used for the cleaning treatment is 15% by mass phosphoric acid. In order to quantitatively express the surface state after the cleaning treatment, composition analysis of the surface of the PC steel stranded wire was performed by Auger Electron Spectroscopy (AES).

The analysis conditions are as follows.
Analysis method: Surface analysis by AES and composition analysis in the depth direction by combined use of argon (Ar) sputtering Analyzer name: Scanning Auger Electron Spectrometer PSAM SAM4300
Electron beam acceleration voltage: 5 kV Sample current: 300 nA
Sample inclination angle: 30 ° Analysis area: Area x 5000 times Ion gun voltage: 4 kV Sputtering time: 120 minutes Sputtering rate: 23 nm / min (SiO ₂ conversion)

  AES analysis was performed on the side surface of the stranded wire. The reason for this is that the film peeling due to insufficient adhesion is mainly due to the side surface portion of the steel wire in contact with the outside.

  The profile of AES analysis is shown in Fig. 1 for No. 2-1 in Table 1, Fig. 2 for No. 2-2, Fig. 3 for No. 2-3, and Fig. 4 for No. 2-4. .2-5 is shown in Figure 5. The peak height of each element in this profile indicates the composition distribution on the surface of the PC steel stranded wire. That is, if the peak of Ca, which is a metal element of the metal soap, is low, the metal soap is sufficiently removed, and if the peak of P constituting the zinc phosphate coating is high, the zinc phosphate coating remains. I understand. “AES analysis result” in Table 1 indicates the peak height of P or Ca in the profile, and “Ca / P ratio” indicates the ratio of the peak height of each element.

  Then, the surface of the PC steel stranded wire was covered with an epoxy resin having a thickness of about 0.8 mm, and the adhesion was evaluated by a tensile test. The tensile test is performed in accordance with JIS Z 2241. A resin-coated PC steel stranded wire is broken by a tensile test. And a fracture | rupture part is investigated visually and the adhesion | attachment condition of the resin coating of the fracture | rupture part vicinity is confirmed. If the resin coating remains on the entire circumference of the PC steel stranded wire, “No peeling” is determined, and if any part is peeled or broken, it is judged as defective, and the peeling state is recorded.

  Table 1 summarizes the cleaning treatment conditions, AES analysis results, and resin coating adhesion evaluation results.

  From this result, it was found that the adhesion of the resin coating was good when the Ca / P ratio was 0.050 or less. In addition, when the phosphoric acid washing time exceeded 2 seconds, a portion where the color tone of the surface of the PC steel stranded wire changed partially occurred. This is presumably because the zinc phosphate coating on the surface of the PC steel strand was peeled off and removed.

(Test Example 3)
Next, a PC steel stranded wire is composed of a wire drawn using a Na-based lubricant (sodium stearate). Similar to Test Example 2, composition analysis on the surface of each sample and evaluation of adhesion strength of the resin coating Went. This test example is performed under the same conditions as in Test Example 2 except that the lubricant during wire drawing is a Na-based lubricant and the resin coating is polycarbonate. Table 2 summarizes the results of the AES analysis and the evaluation results of the resin coating adhesion. Although the profile of AES analysis is not shown in this test example, the evaluation method of “AES analysis result” in Table 2 is the same as test example 2.

  This result also showed that the adhesion of the resin coating was good when the Na / P ratio was 0.049 or less.

  The resin-coated PC steel stranded wire of the present invention has a high adhesion resin coating and is expected to be used in various PC buildings that require corrosion resistance.

It is the AES profile of No. 2-1 in Table 1. It is the AES profile of No. 2-2 in Table 1. It is the AES profile of No.2-3 in Table 1. It is the AES profile of No.2-4 in Table 1. It is the AES profile of No.2-5 in Table 1.

Claims (4)

A resin-coated PC steel stranded wire having a PC steel stranded wire obtained by twisting a plurality of drawn wires and a resin coating formed on at least the outer periphery of the PC steel stranded wire,
The element wire is formed with a zinc phosphate coating as a pre-drawing treatment, and drawn with a lubricant made of metal soap at the time of drawing,
A resin-coated PC steel stranded wire, wherein a zinc phosphate coating remains on the surface of the PC steel stranded wire, and a lubricant is substantially removed.   When the composition analysis of the surface of the PC steel stranded wire is performed by Auger electron spectroscopy, the ratio between the peak value of the metal component of the residual lubricant and the peak value of P of the zinc phosphate coating in the analysis result profile is 0.05 or less. 2. The resin-coated PC steel stranded wire according to claim 1, wherein A pretreatment step of forming a zinc phosphate coating on the surface of the base material to be drawn as a drawing pretreatment;
A wire drawing step of drawing this base material with a lubricant;
A twisting step of twisting a plurality of the drawn wire materials to obtain a PC steel stranded wire,
A cleaning process that substantially removes the lubricant remaining on the surface of the PC steel stranded wire, but leaves the zinc phosphate coating,
And a resin coating step of forming a resin coating on at least the outer periphery of the washed PC steel stranded wire. A method for producing a resin-coated PC steel stranded wire.   The method for producing a resin-coated PC steel stranded wire according to claim 3, wherein the cleaning treatment step comprises immersing the PC steel stranded wire in phosphoric acid for 2 seconds or less.

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