JP2007118067A - Method and apparatus for manufacturing wire material for steel cord - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a wire material for steel cord, which can surely reduce tensile residual stress of the wire at low cost, without reducing productivity, in a wire drawing process of the wire to be used for a steel cord for reinforcement such as a tire cord. <P>SOLUTION: The method for manufacturing the wire material for steel cord is characterized in that tension as much as 40-90% of breaking load of the wire material is applied to the wire material f after the final wire drawing process, in the manufacturing method of a high tensile-strength wire material to be used for the steel cord such as a hard steel wire and a piano wire. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a wire used for a tire reinforcing steel cord (hereinafter simply referred to as “wire”) and a manufacturing apparatus thereof, and to reduce tensile residual stress of the wire in order to ensure fatigue strength. The present invention relates to a manufacturing method and a manufacturing apparatus thereof.

  The wire rod of the steel cord for reinforcement is formed into a thin wire having a diameter of 0.5 mm or less by cold drawing with a die (hereinafter referred to as “drawing”). Since the wire is pulled out against the frictional force with the die surface, there is a difference in the elongation rate between the surface portion and the center portion, and it is known that tensile residual stress occurs in the surface portion of the wire, It is a well-known technical matter that the fatigue strength of the wire decreases as the tensile residual stress increases.

And the following two methods are known as a method of reducing the tensile residual stress of the wire drawn by drawing.
(1) A method of reducing the die angle of the final die.
(2) A method of repeatedly bending a drawn wire with a straightening roller.

  The method (1) is a method for reducing the generated tensile residual stress, and the method (2) is a method for reducing the tensile residual stress that has already occurred by deforming the surface layer of the wire material by plastic deformation. It is. An example of the method (2) is described in JP-A-5-104181.

In the case of the above method (1), productivity is low (dies life is reduced) and other physical properties of the wire may be adversely affected.
The method according to the above (2) is the most general. However, when the drawing speed of the drawing process is high (1000 m / min or more), the durability is low due to wear of the straightening roller and wear of the bearing. Since operation is not possible, there is a problem that productivity cannot be increased.

JP-A-5-104181

  Accordingly, the present invention provides a method and a manufacturing apparatus thereof that can reliably reduce the tensile residual stress of the above-mentioned wire rod without reducing the productivity for wire drawing of the wire rod used for the tire reinforcing steel cord. It is to be an issue.

  The present invention is a method for producing a high-strength wire used for a steel cord such as a hard steel wire or a piano wire, wherein a tension of 40 to 90% of the breaking load of the wire is applied to the wire after the final wire drawing. And

  In the above invention, the tension applied to the wire is preferably 40 to 90% of the breaking load of the wire, and more preferably 70 to 90% of the breaking load.

The steel cord wire manufacturing apparatus of the present invention comprises:
(I) Between the final die of a wire drawing machine that draws a high tensile strength wire used for steel cords such as hard steel wires and piano wires and draws them to a wire diameter of 0.25 to 0.5 mm, and the take-up reel, At least a tensile residual stress reduction device with a capstan, dancer roller and turn roller is provided,
(B) The movable roller of the dancer roller is biased with a predetermined biasing force,
(C) Between the capstan and the dancer roller, tension is applied to the wire at 40 to 90% of the breaking load by the biasing force,
(D) The wire rod is drawn from the final die at a predetermined speed by the capstan and wound on a take-up reel.

  The steel cord wire manufacturing apparatus, wherein the tension applied to the wire is 70 to 90% of the breaking load of the wire.

According to the manufacturing method and the manufacturing apparatus of the present invention, the tensile residual stress of the surface portion of the wire can be reduced.
The tension applied to the wire is effective even if it is 20% or more of the breaking load, but the effect of reducing the residual stress is higher as the ratio is higher when the ratio is higher than 40%. And practically, it is desirable to make it 70 to 90%. The upper limit of the tension is 90% in order to avoid breakage of the wire.

  Further, the drawn wire is age-hardened. That is, after wire drawing, the strength of the wire increases to a certain limit with the passage of time. The present invention is more effective in reducing the tensile residual stress when the age hardening is not progressed. Therefore, it is most preferable to apply tension between the final die in the wire drawing process and the winding up to the take-up reel.

  According to the manufacturing method of this invention, the tensile residual stress of the said wire can be reduced reliably, without reducing productivity.

According to the manufacturing apparatus of the present invention, the wire is wound around the capstan, pulled by the driving force of the capstan, and pulled out from the final die of the wire drawing machine. After being pulled out from the final die, the wire is once wound into the capstan and fed out to the fixed roller of the dancer roller. Then, it is wound up on a take-up reel through a turn roller.
The movable roller of the dancer roller is urged downward with a predetermined force, tension is applied to the wire between the capstan and the fixed roller of the dancer roller, and the wire is pulled with this tension.
Since the wire is simply pulled by the above tension, it is uniformly stretched over its entire cross section.
And since the magnitude | size of the tension | tensile_strength is reliably set with the urging | biasing force of the said movable roller, the tensile residual stress of a wire is reduced uniformly and reliably in the whole cross section.

  On the other hand, the tensile residual stress reduction device using the capstan, dancer roller, and turn roller is disposed downstream of the final die of the wire drawing machine (drawing device), so that the wire drawing device is enlarged by the arrangement. It is not complicated and can be added to the existing wire drawing machine, and its cost is extremely low.

  The solving means of the present invention is as follows.

  The tension according to the present invention can be applied by the residual stress reducing device 10 shown in FIG. This residual stress reducing device 10 is composed of a capstan 11, a dancer roller 12 and a turn roller 13, and the wire f drawn from the final die 1a of the wire drawing machine 1 passes through the capstan 11, the dancer roller 12 and the turn roller 13. , Wound on a take-up reel R.

The dancer roller 12 is configured by winding a wire f around a fixed roller 12a and a movable roller 12b, and the movable roller 12b is pulled downward by an urging force F caused by a weight w, thereby being fixed to the capstan 11. A tension T is applied to the wire f between the roller 12a.
The diameter of the capstan 11 in this apparatus 10 is 240 mm, and the wire f is wound six times. The fixed roller 12a and the movable roller 12b of the dancer roller 12 have the same diameter, and the wire f is wound twice between the two rollers. The movable roller 12b is supported and guided by a guide (not shown) so as to move up and down with a stroke of 200 mm, and a weight w is attached to the shaft of the movable roller 12b. Accordingly, the movable roller 12b is urged downward by the weight w, and a tension T is applied to the wire between the capstan 11 and the fixed roller 12a. This tension T is 40 to 90% of the breaking load of the wire f, and more preferably 70 to 90% of the breaking load.

  The downward biasing means of the dancer roller 12 with respect to the movable roller 12b is not limited to the weight w, and may be a coil spring, an air spring, or the like. However, the biasing force is accurately constant regardless of the vertical position of the movable roller 12b. Is a requirement.

Although tension can be applied to the wire f by the above-described device, the above-mentioned device is wound on the take-up reel R with the tension T applied to the wire f, and the load on the take-up reel R increases. The service life of the take-up reel R is reduced. In order to avoid this, another set of capstan 14 and dancer roller 15 may be provided in front of the turn roller 13 behind the dancer roller 12 (on the take-up reel R side) as shown in FIG. In this way, the tension T of the wire f can be made zero by the capstan 14, and an appropriate tension T ′ is applied to the take-up reel by the dancer roller 15 (weight w ₂ , biasing force F ₂ ). Can be wound up.

Further, in the residual stress reducing device 10 or 10 ′ shown in FIG. 1 or 2, the movable roller of the dancer roller 12 (hereinafter referred to as dancer roller 12 ′ in FIG. 3) has a brake mechanism (not shown), and the brake rotates freely. The roller 16 may be used (FIG. 3). However, the brake roller 16 is a roller that does not move up and down. The wire rod rotates the brake roller 16 by the take-up force of the take-up reel R in the mechanism shown in FIG. 1 or the take-up force of the capstan 14 in the mechanism shown in FIG. 2, and the brake roller 16 has a brake mechanism. Therefore, the tension T is applied to the wire f.
A plurality of grooves (not shown) are provided in the fixed roller 12a and the brake roller 16 above the dancer roller 12 'so that the length of the wire f contacting the roller is increased by winding the wire f multiple times. preferable. Further, the contact length can be further increased by winding it in the shape of figure 8.

  An embodiment using the tensile residual stress reducing apparatus shown in FIG. 2 will be described below.

  A steel wire rod (JIS G3506) having a wire diameter of 2.5 mm was drawn into a wire rod having a wire diameter of 0.5 mm. The drawing speed is 1000 m / min. The weight of the weight attached to the movable roller 12b of the dancer roller 12 is 140 kg. A tension of 340 N is applied to the wire rod having a wire diameter of 0.5 mm between the capstan 11 and the fixed roller 12a by the weight. This tension corresponds to 65% of the breaking load (520 N) of the wire.

A steel wire with a wire diameter of 2.5 mm is drawn into a wire with a wire diameter of 0.20 mm, 0.30 mm, and 0.50 mm, and test pieces are made with various tensions T applied thereto. Went. The test results are shown in Table 1.
This fatigue test was conducted by a so-called rotational bending fatigue test (JISZ2272).

In Table 1 above, “BL” is the breaking load of the wire, and “T” is the tension applied to the wire f by the urging force F by the weight w.
The fatigue strength of each test piece is expressed as an index corresponding to a “conventional example” in which the tensile residual stress is not removed, with a durability of 100.
From this test result, it can be seen that when T / BL × 100 is 21, the fatigue strength is improved by about 10%, and the fatigue strength is most improved near 90%. Further, it is shown that the 0.20 mm wire was disconnected at 92%, the 0.30 mm wire was disconnected at 93%, and the 0.50 mm wire was disconnected at 92%.

The front view which shows an Example typically. FIG. 2 is a schematic diagram in which another set of capstan and dancer roller is provided in front of the turn roller behind the dancer roller (on the take-up reel side) in the embodiment of FIG. 1. FIG. 3 is a schematic diagram in which the movable roller of the dancer roller on the final die side is a brake roller that has a brake mechanism and rotates freely but does not move up and down in FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wire drawing machine 1a Final die 10,10 'Residual stress reduction device 11,14 Capstan 12,12', 15 Dancer roller 12a, 12a 'Fixed roller 12b Movable roller 13 Turn roller 16 Brake roller R Winding reel f Wire rod T, T 'tension

Claims (4)

  In a method of manufacturing a high tensile strength wire used for a steel cord such as a hard steel wire or a piano wire, a steel cord characterized by applying a tension of 40 to 90% of the breaking load of the wire to the wire after the final wire drawing. Manufacturing method for wire.   The method for producing a steel cord wire according to claim 1, wherein a tension applied to the wire is 70 to 90% of a breaking load of the wire. Tensile residual stress due to at least the capstan, dancer roller and turn roller between the final die of the wire drawing machine that draws and draws high tensile strength wire used for steel cords such as hard steel wire and piano wire A reduction device,
The movable roller of the dancer roller is biased with a predetermined biasing force,
Between the capstan and the dancer roller, tension is applied to the wire by the urging force, and the tension is 40 to 90% of the breaking load of the wire,
An apparatus for producing a wire material for a steel cord, wherein a wire rod is drawn from a final die at a predetermined speed by the capstan and wound on a take-up reel.   4. The steel cord wire manufacturing apparatus according to claim 3, wherein the tension applied to the wire is 70 to 90% of the breaking load of the wire.

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