JPH0882043A - Compression grip for fixing pc steel wire and manufacture thereof - Google Patents

Abstract

PURPOSE: To provide high pressure fit degree and fixing load equal to or more than those in the case of combination of an insert with a sleeve by only a single sleeve. CONSTITUTION: Chromium-molybdenum steel or nickel-chrominum-molybdenum steel of which carburization property is favorable and high hardness can be obtained and machinability for groove working and the like is good, is adopted as the material of a sleeve 1, and a recessed and projecting part such as thread ridge 3 is formed on the inner circumferential face of the through hole 2 of the sleeve. A carburization preventing agent is spread on the outer circumferential part so as to carry out carburization/quenching treatment, and a carburization layer is formed only on the inner circumferential part including the recessed and projecting part, so as to raise the hardness of the inner circumferential part over Hv700.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing tool for fixing a PC steel wire or the like by a die extrusion method, and in particular, a compression grip for fixing a PC steel wire, which is integrated by pressure-bonding to an end portion or an intermediate portion of the PC steel wire. And a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, a compression grip composed of a combination of a cylindrical sleeve and an insert has been known as a fixing tool for PC steel wire or PC steel stranded wire (hereinafter, simply referred to as PC steel wire). The conventional compression grip uses a carbon steel material for machine structure as a material, and an insert having a deformed cross-section material made of a high hardness material formed in a coil shape is fitted on the inner peripheral surface of a sleeve drilled in the material. In combination, it is inserted into a PC steel wire, and in that state, surface reduction processing is performed by swaging to crimp it to the PC steel wire (for example, Japanese Patent Publication No. 51-30373). However, this method requires two parts and is costly, and further, there is a problem that the workability is poor because the insert is inserted into the PC steel wire and further inserted into the sleeve.

On the other hand, an integral type compression grip, which inserts the sleeve directly into the PC steel wire and presses the sleeve onto the PC steel wire by pressing, is applied to the PC steel wire having a small diameter. There is. Conventionally, also in the case of an integral type compression grip, a low carbon steel similar to the carbon steel steel S09CK for machine structure having good carburizing property is used as the material of the sleeve (Japanese Utility Model Publication No. 45-32657).

[0004]

In the case of the integral type compression grip, since the insert is not required, the above problem does not occur. However, in order to obtain the crimping degree similar to that having the insert, the sleeve is required. It must be crimped with a very high degree of processing. However, the low carbon steel conventionally used as the material for the sleeve has a low strength, so that the sleeve must have a large diameter in order to withstand a high degree of processing (area reduction compression processing) and to obtain a high fixing load. On the other hand, if the sleeve has a large diameter, when it is crimped to the PC steel wire, if it is extruded with a die, deformation will occur during processing and it will not be possible to reliably extrude, so only crimping by pressing can be done, and the combination of insert and sleeve There is a problem in that a high pressure bonding force cannot be obtained as in the case of.

The present invention was devised in view of the above-mentioned circumstances, and can be constituted only by a sleeve, and it is possible to obtain a high degree of crimping and a fixing load which are equal to or higher than those in the case of the insert method, and the fixing process can be performed. An object of the present invention is to provide a compression grip for fixing a PC steel wire and a method for manufacturing the same, which can be easily manufactured by die extrusion and can be manufactured at a reduced cost.

[0006]

[Means for Solving the Problems] In order to achieve the above object, as a result of various studies, a compression grip consisting only of a sleeve without an insert has a holding force equal to or higher than that of a compression grip consisting of a combination of an insert and a sleeve. It was found that the following conditions must be satisfied in order to obtain the fixing load. In order to increase the frictional force between the sleeve and the PC steel wire, the inner peripheral surface of the sleeve and the PC steel material should bite into each other and be crimped, as in the case of providing an insert. Since the surface hardness of high-strength PC steel wire is as high as Hv = 450 to 500, unless the hardness of the inner peripheral surface of the sleeve is made higher than that, the described effect is not sufficiently exhibited and PC is applied to a high fixing load. The steel wire cannot be held securely. However, if a high hardness material having a hardness of Hv 450 to 500 or more is used for the sleeve, it is difficult to perform pressure bonding by surface reduction processing, so that the inner peripheral surface has the high hardness and the outer peripheral surface is not surface reduced. It should be as hard as possible. As for the pressure-bonding process of the sleeve to the PC steel wire, the extrusion process with a die gives the highest holding force, so the extrusion process with a die should be possible.

The present invention has solved the above conditions by the following technical means. That is, the compression grip for fixing the PC steel wire of the present invention is used as a sleeve material, which has a good carburizing property and can be made to have a high hardness, and has a good workability such as grooving. A steel material was adopted, unevenness was formed on the inner peripheral surface of the sleeve, and a carburized layer was formed only on the inner peripheral portion including the unevenness so that the hardness of the inner peripheral portion was Hv 700 or more. With the above configuration, the compression grip can be applied to a die extrusion crimping process that can be crimped to a PC steel wire by a die extrusion process. The unevenness formed on the inner peripheral surface of the sleeve can be easily formed, for example, by forming a screw thread on the inner peripheral surface.

According to the present invention, a fixing tool is manufactured from the above-mentioned fixing compression grip by the following method. (1) A desired round bar made of the above-mentioned material is cut, bored by machining, and further threaded on the inner surface to obtain a sleeve. (2) A carburizing inhibitor is applied to the surface of the sleeve to carry out carburizing and quenching treatment. (3) After the carburizing and quenching, the sleeve surface is subjected to a surface treatment such that the carburizing preventive material is peeled off by a shot or the like. As the chrome molybdenum steel material, JIS SCM
415 or SCM421 is the most suitable, and SNCM415 or SNC is used as the nickel chrome molybdenum steel material.
M420 is good.

[0009]

[Function] The chrome molybdenum steel material or nickel chrome molybdenum steel material adopted in the present invention is excellent in machinability and carburizing / hardening property in place of the low carbon steel conventionally used as the material of the sleeve. It is easy to process complicated irregularities such as thread cutting on the inner peripheral surface of the sleeve, and the carburizing treatment on the inner peripheral surface is surely performed, and the hardness of the inner peripheral surface is Hv7.
A compression grip of 00 or more is obtained. Moreover, since the outer peripheral surface is carburized / quenched with the carburizing inhibitor applied, carburization on the outer peripheral surface can be reliably prevented, and good pressure bonding can be performed without increasing surface reduction resistance during pressure bonding.

Further, since the material has higher strength and hardness as compared with the conventional low carbon steel material, the diameter (wall thickness) of the sleeve can be reduced, and the sleeve is extruded by a die. Even if it is carried out by processing, irregular deformation such as chewing does not occur, and excellent extrusion processing can be performed. Therefore, the pressure-bonding property is very good, and it is possible to obtain a fixing load and fixing efficiency that are equal to or higher than those of the conventional insert method. Since the compression grip of the present invention is composed of only a single sleeve, P
The crimping work to the C steel wire can be performed very easily.

[0011]

EXAMPLES Examples of the present invention will be described in detail below. FIG. 1 is a sectional view of a compression grip according to an embodiment of the present invention, and FIG. 2 is a side view of the compression grip fixed to a PC steel wire.

In the figure, reference numeral 1 is a sleeve constituting a compression grip, and a through hole 2 through which a PC steel wire penetrates is formed in a central shaft portion, and a friction resistance with the PC steel wire is formed on an inner peripheral surface of the through hole. Screws 3 are formed to increase. The inner peripheral surface including the screw is carburized to form a carburized layer. Reference numerals 4 and 5 are chamfered portions formed on both ends of the outer peripheral surface of the sleeve.

Example: As the steel material, SCM415 chrome molybdenum steel material, three kinds of round bars having different diameters are adopted,
7 wires for 9.3 mm diameter wire, 7 wires for 12.7 diameter
For the mm wire and for the 19 to 21.8 mm diameter wire, boring was performed on each of them and the inner peripheral surface was threaded to obtain three types of sleeves having different inner and outer diameters. Further, as a comparative material, a 7-strand wire of 9.3 mm made of S09CK material was similarly processed to obtain a sleeve.

A carburizing inhibitor was applied to the surface of each sleeve. As a carburizing inhibitor, copper powder was used as a base, and water glass and additives were added to this to form a liquid "No Cub" (trade name) diluted with water. In addition, as a carburizing preventive material, "condorsal" (trade name) based on a boron-based compound and an organic resin or the like may be diluted with a solvent and used.

The sleeves whose outer peripheral surfaces were coated with a carburizing inhibitor were carburized and quenched. For each of the sleeves manufactured as described above, the change in hardness depending on the distance from the inner peripheral surface and the change in hardness depending on the distance from the outer peripheral surface were measured. The results are shown in Tables 1 and 2.

[Table 1]

[Table 2]

As is clear from Table 1, in the sleeve of this embodiment, the hardness of the inner peripheral portion is approximately Hv800 or more in the range where the distance from the inner peripheral surface is 0.5 mm. Hardness sufficiently higher than the surface hardness Hv 450 to 550 of the stranded wire can be ensured, and the PC steel wire can be reliably held. On the other hand, in the sleeve of the comparative example, even if the same treatment is performed, the hardness on the inner surface side is high, but in the range where the distance from the inner peripheral surface surface is 0.5 mm, the Hv
The hardness is rapidly decreased to 382, and sufficient hardness is not obtained to hold the high strength PC steel wire.

Further, as shown in Table 2, the hardness of the outer peripheral surface of the sleeve is approximately Hv 300 to 330 in the range of 5.0 mm from the surface in Examples 1 to 3 as well.
In other words, carburization of the outer periphery is completely prevented,
It can be seen that there is no adverse effect such as decarburization, the effect of the carburizing inhibitor is sufficiently exerted, and the hardness of the SCM steel material is maintained. The same applies to the comparative example, but S09CK
The material has a low hardness and only has a hardness of about Hv 150 to 180.

The sleeve thus obtained was subjected to a fixing test as follows. The fixing of the sleeve was carried out by extrusion using a pressure bonding machine 10 shown in FIG. 3 and a die 12 having a processing hole 11 having a circular cross section with a squeezed central portion. That is, in a state where the PC twisted wire 6 is inserted into the sleeve 1, the sleeve 13 is pressed by the jack 13 to push the sleeve into the processing hole of the die, thereby reducing the diameter of the sleeve and the screw thread on the inner peripheral surface. Is entangled in the surface of the PC stranded wire, and is solidified and crimped to be integrated. In the drawing, 14 is a plunger of the jack 13.

In this fixing test, in addition to the sleeves obtained in the above-mentioned examples, in the same manner as in the above-mentioned examples, 7 for 12.4 mm diameter wire, 7 for 15.2 mm diameter wire, 7 Sleeves for a 17.8 mm diameter wire from this book and sleeves for a 19.3 mm diameter wire from 7 pieces were manufactured and the same fixing test was conducted. In all of the fixing tests, the extrusion process using a die was performed at a processing rate such that the diameter reduction rate of the sleeve was 20% or more. In addition, as a comparative example, the same test was conducted on the fixed sleeve of the comparative example. The results of the fixing test are shown in Table 3.

[Table 3]

As a result, for example, in the case of 9.3 mm diameter,
The fixing load is 9660 kg, which is 7,000 of the conventional one for the same diameter.
The sleeve of this embodiment is
In each case, a high fixing load could be obtained. And, in any of the examples, there is no slip, etc.
And JIS. The standard tensile load value according to G-3536 was satisfied.

Further, regarding fatigue resistance, in the fatigue test of 0.6 × tensile load value + 10 Kgf / mm ² , all of the examples of this example were more than 2 million times, and it was found that the durability was also excellent. It was

From the above test results, the compression grips according to the present invention can obtain the fixing load and the fixing efficiency which are equal to or higher than those of the conventional compression grips including the combination of the insert and the sleeve.
It was also confirmed that the durability was similarly good.

[0023]

As described above, according to the compression grip of the present invention, it is possible to obtain a high degree of crimping and a fixing load which are equal to or higher than those of the insert method, and which can be constituted by only a sleeve, and a fixing process. Can be done easily by die extrusion, and the manufacturing cost can be reduced.

Further, complicated irregular processing such as thread cutting on the inner peripheral surface of the sleeve is easy, and the inner peripheral surface is surely carburized, and a compression grip having an inner peripheral hardness of Hv 700 or more can be obtained. . Moreover, since the outer peripheral surface is carburized / quenched with the carburizing inhibitor applied, carburization on the outer peripheral surface can be reliably prevented and good crimping can be performed.

Further, even with a compression grip for a high fixing load, the diameter of the sleeve can be made small, and the sleeve can be fixed by extrusion processing with a die, so that the work of crimping to the PC steel wire is extremely difficult. It is easy to perform and very high crimping force is obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a compression grip according to an embodiment of the present invention.

FIG. 2 is a side view of a compression grip according to an embodiment of the present invention in a state of being crimped to a PC steel wire.

FIG. 3 is a plan view of a crimping machine showing a state in which a compression grip is crimped to a PC steel wire.

[Explanation of symbols]

1 Sleeve 2 Through hole 3 Thread
6 PC twisted line

Claims (4)

[Claims] 1. A sleeve made of chrome molybdenum steel or nickel chrome molybdenum steel,
PC steel wire fixing, characterized in that the inner peripheral surface of the sleeve is formed with concavities and convexities, and the carburized layer is formed only on the inner peripheral part including the concavities and convexities, and the hardness of the inner peripheral part is Hv 700 or more. Compression grip. 2. The compression grip according to claim 1, wherein the compression grip is for die extrusion crimping which is crimped to a PC steel wire by die extrusion. 3. The unevenness is a screw thread.
The listed compression grips. 4. A step of boring a round bar made of chrome molybdenum steel or nickel chrome molybdenum steel and further forming an unevenness on the inner peripheral surface to obtain a sleeve, the surface of the sleeve being coated with a carburizing inhibitor, PC comprising a carburizing / quenching process to prevent carburizing of the sleeve surface and carburizing only the inner peripheral portion, and a surface treating process of peeling the carburizing preventive material from the sleeve surface after carburizing and quenching. A compression grip for fixing a steel wire and a method for manufacturing the same.