JP2000271779A - Method and device for annealing metal wire immediately after welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an annealing method not generating a structure boundary part and improving workability with preventing wire breaking at twisting and a device therefor. SOLUTION: It is a method to anneal a metal wire W immediately after welding. After a metal wire is fixed by fixing means 7, 7 in a tension state, the welded part A of the metal wire W is held with a pair of left/right roller electrodes 6, 6 movable at a nearly same speed so as to position roughly at center between the electrodes 6, 6, and successively the electrodes are energized/ heated while moving so that electrode interval L is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for annealing as a post heat treatment performed immediately after welding of a metal wire.

[0002]

2. Description of the Related Art Upset welding has conventionally been performed for welding metal wires. This upset welding is a type of butt resistance welding, in which the ends of the metal wires to be welded are butt-bonded with a strong force, and a large-capacity welding current flows between the electrodes.
The terminal part is heated and melted by resistance heating between both metal wires,
In this state, pressure bonding is performed. In this upset welding, for example, when a hardenable metal wire such as carbon steel is welded, a fusion-bonded portion (hereinafter referred to as a welded portion)
Has a very hard and brittle martensitic structure. For this reason, an annealing process is generally performed as a post-heat treatment to soften a welded portion.

As shown in FIG. 2, a conventional annealing treatment apparatus is generally a pair of fixed left and right annealing electrodes (hereinafter simply referred to as electrodes) provided in a part of a welding machine base (not shown). ) C, C When using this device, the weld A
Is positioned substantially at the center between the electrodes C, C, and the metal wires W are held by the electrodes C, C. At this time, the electrodes C, C
Is set to be longer than the heat-affected zone B (length h) in the longitudinal direction of the metal wire received by welding (for example, a wire diameter of 2).
mm or less (about 100 to 150 mm). Then, the annealing temperature is set to 400 ° C to 5 ° C.
The temperature is set to 00 ° C., an annealing current smaller than the welding current value is passed between the electrodes, and annealing is performed by utilizing the resistance heating of the metal wire W.

[0004] However, at the above annealing temperature, the whole is softened so that the martensitized welded portion does not undergo structural transformation and remains in the martensitic structure. For this reason, it is strong in the pulling direction, and there is almost no trouble in the drawing process. However, because of poor toughness, it is vulnerable to bending and twisting.For example, such as steel cord used for reinforcing automobile tires, there is a problem that the wire breaks during stranded wire processing in which a plurality of metal wires are twisted. there were.

In order to solve the above problem,
The set annealing temperature is equal to or higher than the transformation point of the metal.
Recently, the temperature has been raised to the gasification temperature. Aussie
If you raise the temperature to the night temperature and then cool it down, it will burn
Soft and tough pearlite structure
Can be However, in the prior art, FIG.
As shown, the electrodes C, C are fixed and
The diameter D of the burr portion of A is larger than the diameter d of the metal wire W.
To heat the flash part to the austenitizing temperature.
Then, the metal wire W between the electrodes C and C ₁ Austenitic until
Temperature to the temperature of₁ Becomes a transformation part. This and
Metal wires W between the outer electrodes C, C_Two Is not heated
And the temperature difference before and after the electrode
Causes a tissue boundary. Therefore, before and after the organizational boundary
Metal wire W₁ And W_Two And the toughness of the two
And ductility difference, especially in twisted wire processing with twisting
The torsional stress concentrates at the tissue boundary, and cannot withstand this stress
There is a problem that the metal wire is broken. Disconnection in the twisting process
Then, weld or twist the broken part for restart.
Glue (a process of joining and joining wires without welding)
Must be performed, and the workability is extremely reduced.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, does not generate a tissue boundary portion, prevents breakage during stranded wire processing, and improves workability of a metal wire. An object of the present invention is to provide an annealing method and an apparatus therefor.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and a first invention is a method for annealing a metal wire immediately after welding, wherein the method comprises the steps of: With the pair of left and right electrodes made possible, the welding portion of the metal wire is positioned substantially at the center between the electrodes, and after the metal wire is clamped, the current is applied while moving so that the electrode interval changes. It is characterized by heating. The annealing temperature of the metal wire is
According to this method, the electrode moves while changing the electrode interval with the weld substantially at the center, and the current is applied at the central portion between the electrodes. It is the longest and progressively shorter on both sides. Therefore, the annealing temperature of the metal wire is highest at the welded portion, and has a temperature distribution that gradually decreases in a direction away from the welded portion, thereby preventing the occurrence of a tissue boundary portion due to a rapid temperature difference between before and after the electrode.

According to a second aspect of the present invention, in the first aspect, before the metal wire is sandwiched between the electrodes, the metal wire is fixed in a tensioned state by fixing means disposed outside the left and right electrodes. It is characterized by doing. According to this method, since the metal wire is previously fixed in a tensioned state by the fixing means, the influence of the repulsive force due to the habit of the metal wire or the like is eliminated, and the movement of the electrode is further smoothed. In the first or second aspect of the present invention, it is preferable that the electrodes move from both sides near the welded portion in directions away from each other. This is because the electrode moves in the direction of lower temperature as the metal wire is heated, so that the heat-affected zones on both sides of the weld are annealed in a single pass without forming a structural boundary, and the metal wire is heated. This is because deterioration of the electrodes due to the above is prevented. Further, the electrodes may first approach each other from the both sides toward the welded portion up to a predetermined interval, and then move in a direction in which the electrodes are turned away from each other. In this case, the annealing time becomes longer, which is advantageous in the case of a metal wire having a large wire diameter requiring time for annealing heating. Further, when the electrodes are separated from both sides in the vicinity of the welded portion, or when the electrodes are separated from each other after approaching toward the welded portion, the electrode may be temporarily stopped while energizing near the welded portion. In this case, a sufficient heating time for the welded portion can be obtained. In addition, even after the electrodes move in the separating direction and stop, the current may be supplied for a certain time.

The invention of a third device is an annealing device for a metal wire immediately after upset welding, comprising a pair of left and right electrodes, an electrode operating means for changing the interval between the electrodes during energization heating, and these electrodes and the electrodes. Electrically connected to the actuation means,
And an annealing control unit for setting and controlling annealing conditions.

[0010] In the third aspect of the invention, it is preferable that a metal wire fixing means is provided at a position outside the electrode. Further, the moving range detecting means of the electrode may be provided close to the moving locus of one electrode. As the moving range detecting means,
A laser or an optical sensor may be used, but using a limit switch is inexpensive.

The electrodes are preferably composed of a pair of upper and lower roller electrodes capable of holding a metal wire. If the upper electrode can be opened and closed using a spring or the like, the metal wire can be easily attached and detached, and the roller electrode rolls freely while contacting the metal wire, preventing wear with the metal wire. Is done.
The roller electrodes may be energized using a brush or the like.

According to the present invention, even if the metal wire immediately after welding is heated to the austenitizing temperature, no temperature boundary portion occurs at the electrode portion, and the structure difference between the deteriorated portion and the raw portion as in the prior art. Is eliminated, and disconnection in stranded wire processing involving twisting can be prevented.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numerals 1 and 1 denote ball screws arranged side by side in parallel with a machine stand (not shown). In addition to connecting the reversible motors 2 and 2, a limit switch 4 synchronized with the operation of the motors 2 and 2 is provided near the end of one of the ball screws 1. The nuts 1a, 1a of the ball screws 1, 1 are provided with a bracket 5,
5, and roller electrodes 6, 6 are attached to the brackets 5, 5 via bearings and insulators (not shown), respectively. As shown in FIG. 1 (b), the roller electrodes 6, 6 each comprise a pair of upper and lower copper rollers, which can pinch the metal wire W and are free to roll. Due to the left and right movement of the nuts 1a and 1a associated with the rotation of 1, the metal wire W is rolled to the left and right while approaching or separated from each other, sandwiching the welded portion A of the metal wire. The electrode interval L on both sides can be changed. Outside the roller electrodes 6, 6, a pair of upper and lower clamps 7, 7 capable of holding a metal wire W are attached to a part of a machine base (not shown).
2. The limit switch 4 and the roller electrodes 6 and 6 are electrically connected to an annealing control unit 8 having a built-in electric circuit or the like capable of setting annealing conditions (for example, a current value and a conduction time). An annealing apparatus according to the present invention is configured. In addition, 9 in the figure
Is a carbon brush for passing an annealing current from the annealing control unit 8 to the roller electrodes 6.

This annealing device is disposed on a part of a machine base (not shown) of a conventional welding machine or adjacent to the welding machine to perform annealing of a metal wire immediately after welding. That is, FIG.
As shown in (b), the metal wire W immediately after welding is fixed with the clamps 7, 7 so that the welded portion A is located between the ball screws 1, 1. Subsequently, the roller electrodes 6 and 6 are set in advance at positions equidistant from the terminal ends of the ball screws 1 and 1 (ie, positions equidistant from the welded portion A and including at least the heat-affected zone). After the metal wire W is clamped, an annealing current value and an energization time of the annealing control unit 8 are set, and energization is started. When energization starts, the rotation of the motors 2 and 2 and the ball screws 1 and 1 causes the nuts 1a and 1a to move toward the end portions of the ball screws 1 and 1 and, accordingly, the roller electrodes 6 and 6 move to the welding portion A. It rolls while flowing an annealing current at a constant speed in the approaching direction to the metal wire within the interval L between the two electrodes. When one of the roller electrodes 6 comes into contact with the limit switch 4 provided near the end of the ball screw 1, the motor 2,
2 reverse rotation, ball screw 1, 1 reverse rotation, nuts 1a, 1a
, The roller electrodes 6, 6 are inverted and the welding portion A
When it reaches the start position after rolling in a direction away from
When the motors 2 and 2 are stopped, the supply of the annealing current from the annealing control unit 8 is also stopped, and the annealing is completed.

Therefore, at the same time as the energization is started, the rolling distance of the roller electrode changes the electrode interval L with the welding point substantially at the midpoint, so that the time during which the annealing current flows gradually decreases around the welding point. The temperature of the metal wire between the electrodes is distributed such that the highest temperature is obtained at the welded portion and the temperature gradually decreases on both sides thereof, thereby eliminating the tissue boundary.

In this case, if the roller electrodes 6 and the fixed clamps 7 have a structure that can be opened and closed vertically, the metal wire W after welding can be easily attached and detached.
The structure is such that one is fixed and the other is opened and closed up and down, but is not limited to this. Also,
Although two motors 2 and 2 are provided as drive sources for the two ball screws 1 and 1, respectively, a known power transmission mechanism may be used or a single ball screw provided with left and right reverse screws may be used. Thus, it is possible to use one motor. further,
In this embodiment, only one limit switch 4 is provided in the vicinity of the welded portion. However, the limit switch 4 may be provided on both sides near the welded portion, or may be provided at a position where the limit switch 4 is separated and stopped.
When setting the annealing conditions by omitting the limit switch, the motors 2 and 2 may be stopped at the same time as the energization is stopped, and the roller electrodes 6 and 6 may be automatically stopped.

[0018]

EXAMPLE Next, in order to compare the performance of the annealing apparatus of the present invention with that of a conventional annealing apparatus, a metal wire was actually annealed and evaluated.

A piano wire having a wire diameter of 5.5 mm and a carbon content of 0.8% is used, and this is pickled, drawn, patented, and so forth.
After drawing, the surface was subjected to brass plating to produce a metal wire having a wire diameter of 1.5 mm. After the metal wires were butted and joined by an upset welding machine, the welds were annealed by an annealing apparatus of the present invention and a conventional annealing apparatus. The welding method is the same as the conventional method.
The annealing length was 100 mm, the annealing current and the time were the same between the annealing method of the present invention and the conventional annealing method.

Next, the metal wire obtained as described above is drawn to a wire diameter of 0.2 mm by a wet wire drawing machine, and a steel cord having a 1 × 6 structure is manufactured by a stranded wire machine. The state of disconnection during wire drawing and stranded wire processing was compared. Table 1 shows the results. However, the disconnection rates shown in Table 1 are numerical values obtained from 50 experiments, and exclude the disconnection at the welded portion.

[0021]

[Table 1]

As is clear from Table 1 above, the metal wire using the annealing device of the embodiment has no break in both the wire drawing process and the stranded wire process, and is compared with the metal wire annealed by the conventional annealing device.
It turned out to be very strong for wire drawing and twisting.

[0023]

According to the present invention, a sharp temperature difference does not occur in the metal wires on both sides of the electrode, and the tissue boundary can be eliminated, so that disconnection due to stress concentration in stranded wire processing can be prevented. It is possible to improve the productivity of the stranded wire.

[Brief description of the drawings]

FIG. 1 shows an embodiment of an annealing apparatus according to the present invention, in which (a)
FIG. 2 is a schematic front view of the configuration, and FIG. 2B is an enlarged side view of a main part.

FIG. 2 is a schematic configuration diagram showing a conventional annealing device.

[Explanation of symbols]

 Reference Signs List 1 ball screw 1a nut 2 motor 3 reduction gear 4 limit switch 5 bracket 6 roller electrode 7 clamp 8 annealing control unit 9 carbon brush A welding portion L electrode interval W metal wire

Claims (10)

[Claims] 1. A method for annealing a metal wire immediately after welding, comprising a pair of left and right electrodes movable at substantially constant speed, wherein a welded portion of the metal wire is located substantially at the center between the electrodes. A method for annealing a metal wire immediately after welding, wherein the metal wire is heated while being moved so as to change the electrode interval after the metal wire is sandwiched. 2. The metal wire immediately after welding according to claim 1, wherein before the metal wire is clamped by the electrodes, the metal wire is fixed in a tensioned state by fixing means disposed outside the left and right electrodes. Annealing method. 3. The method for annealing a metal wire immediately after welding according to claim 1, wherein the left and right electrodes move in directions away from each other from both sides near the welded portion of the metal wire. 4. The method for annealing a metal wire immediately after welding according to claim 1, wherein the left and right electrodes approach each other from both sides toward a welded portion of the metal wire, and then move in a direction in which they are turned away from each other. . 5. The method for annealing a metal wire immediately after welding according to claim 3, wherein the left and right electrodes are temporarily stopped while energizing near the welded portion of the metal wire. 6. The method for annealing a metal wire immediately after welding according to claim 3, 4 or 5, wherein the left and right electrodes are energized and energized for a predetermined time after stopping. 7. An apparatus for annealing a metal wire immediately after welding, comprising a pair of left and right electrodes, an electrode operating means for changing the interval between the electrodes during energization heating, and an electrical connection between the electrodes and the electrode operating means. And an annealing control unit for setting and controlling annealing conditions connected to the metal wires. 8. The apparatus for annealing a metal wire immediately after welding according to claim 7, wherein means for fixing the metal wire is provided outside the left and right electrodes. 9. The annealing apparatus for a metal wire immediately after welding according to claim 7, wherein the electrode movement range detecting means is provided in proximity to the movement trajectory of at least one electrode. 10. The apparatus for annealing a metal wire immediately after welding according to claim 7, 8 or 9, wherein the left and right electrodes are a pair of upper and lower roller electrodes capable of holding the metal wire.