JPH0592208A - Manufacture of invar having high strength, high toughness and low linear expansion coefficient - Google Patents

Abstract

PURPOSE:To provide an inver wire manufacturing method improved in workability, product accuracy, reliability, high strength and toughness and low linear expansion coefficient by conducting specified finishing by means of wire manufacturing technique, returning strength, linear expansion coefficient to a level before annealing and easily adjusting each property after the stress relief annealing in the manufacture of an invar wire (Fe-Ni alloy). CONSTITUTION:Wire drawing is conducted to Fe-Ni alloy (a) to obtain a wire rod a2 (or a1) of a specified diameter, and after stress relief annealing 9 (or 5), wire drawing 12 is conducted to the wire rod a2 (or a1) at a light reduction rate of area, further, a light stress relief working 13 is conducted by straightening rolls 20 and in this invar wire manufacture, wire drawing 12 is conducted to the wire rod a2 (or a1) after the stress relief annealing at the reduction rate of area, 2.0-8.0%, furthermore, stress relief working 13 is conducted by the straightening rolls 20 at roll diameter D/wire diameter (d)=9.0-16.0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an overhead power transmission line (ACS).
The present invention relates to a method for producing an Invar wire having high strength, high toughness and a low coefficient of linear expansion suitable as a core wire of R).

[0002]

2. Description of the Related Art Conventionally, a 7-strand high carbon steel wire has been used for the core wire of the overhead power transmission line. However, the high carbon steel wire expands comparatively largely due to a temperature rise and causes a large sag. There is a tendency, and recently, attempts have been made to use an Invar wire (Fe—Ni alloy) having a low coefficient of linear expansion as the core wire. However, the Fe-Ni alloy has a low coefficient of linear expansion, but its tensile strength is 90K.
gf / mm2 or less, both strength and toughness are insufficient as a core wire of an overhead power transmission line, and its high strength,
High toughness is achieved.

As a measure for increasing the strength and the toughness of the conventional Invar wire (Fe-Ni alloy), for example, F
Based on the e-Ni alloy, various elements such as Mo, Cr, Si, etc. are added in a trace amount to increase the strength while maintaining the characteristics of the low linear expansion coefficient. A high strength, high toughness and low linear expansion coefficient Invar wire manufacturing method has been developed and proposed, for example, by performing strain relief annealing to increase the toughness level in the process or the final process, or both the intermediate process and the final process. ing.

[0004]

The above-mentioned conventional Invar wire manufacturing method is based on a Fe--Ni system alloy and is based on a trace component (M
(O, Cr, Si, etc.), each characteristic of the finished product is enhanced, and is basically largely regulated, and each characteristic is easily affected by a subtle change in the composition. Strain relief annealing performed in the final step or in both the intermediate step and the final step is effective in recovering toughness, but on the contrary, the high strength and low linear expansion coefficient of the wire material returns to the values before processing. There is a tendency that adjustment of each characteristic is very difficult, and it is difficult to meet various product characteristic demands.

The present invention was developed in order to address the above-mentioned problems, and the purpose thereof is to produce an Invar wire (Fe-Ni alloy) at the time of strain relief annealing and By finishing the properties by wire-making technology, the strength and linear expansion coefficient are returned to the levels before annealing, and the toughness is recovered, and the adjustment of each property is facilitated to improve workability, product accuracy, and reliability. It is to provide an Invar wire manufacturing method with improved high strength, high toughness and low linear expansion coefficient.

[0006]

According to the present invention, an Fe-Ni alloy is wire-drawn into a wire having a predetermined diameter, strain-relieved and annealed, and then the wire is wire-drawn with a light reduction in area. By subjecting the wire material to mild strain relief processing, the strength and linear expansion coefficient of the wire are returned to the levels before annealing, the toughness is recovered, and the adjustment of each of the above characteristics is facilitated.

Further, the wire rod after the strain relief annealing is wire-drawn at a surface reduction ratio of 2.0 to 8.0%, and strain relief is performed by a straightening roll at a roll diameter / wire diameter = 9.0 to 16.0. By processing, the above-mentioned characteristics are further enhanced and adjustment of each characteristic is facilitated.

[0008]

Function: A Fe-Ni alloy is drawn into a wire having a predetermined diameter. The wire is stretched and twisted by strain relief annealing,
The toughness such as winding and unwinding is recovered, the strength is slightly reduced by the annealing, and the linear expansion coefficient is increased, but the strength and the linear expansion coefficient are not increased by the wire drawing with a light surface reduction rate after the annealing. To a level where there is practically no problem with the mild strain relief processing by the straightening rolls, and the wire drawing with the light surface reduction ratio after annealing and the straightening are performed. The mild strain relief processing by rolls is a finishing step by a mechanical wire-making technique, and the product characteristics can be easily adjusted with high precision and various product characteristics can be obtained.

Further, in the above-mentioned Invar wire manufacturing method, the area reduction ratio of the wire rod in the wire drawing process after the strain relief annealing is 2.0 to
By setting the ratio to be 8.0% and the roll diameter / wire diameter in the mild strain relief processing by the straightening roll to be in the range of 9.0 to 16.0, the above respective characteristics are further enhanced and the reliability is improved. It

[0010]

FIG. 1 is a process diagram showing an embodiment of the present invention, FIG.
Fig. 3 is a mechanism diagram of a straightening roll applied to the example, and Figs. 3 to 9 are characteristic explanatory views of the example. The alloy composition of the present invention has a weight ratio as shown in Table 1, Fe-Ni
A base alloy is used as a base, and C, Cr, Mo, Nb, etc. are added.

[0011]

[Table 1] The Invar wire of the present invention is obtained by subjecting the Fe-Ni alloy a composed of the compounding components as shown in Table 1 to each step of casting 1, forging 2, wire drawing 3, skinning 4, etc. as shown in FIG. For example, 6.
An intermediate working step in which wire rod a1 having a diameter of 5 mmφ is drawn, and the wire rod a1 is subjected to strain relief annealing 5, and the wire rod a1 is subjected to wire drawing pretreatment 6, wire drawing 7, washing 8, and wire rod a2 having a predetermined diameter. Then, the conventional final step of strain-relieving annealing 9 the wire rod a2, and further, the wire rod a2 (or a1) formed into a predetermined diameter and strain-annealing 9 (or 5) is subjected to wire drawing pretreatment 11. Then, the Invar wire manufacturing method with high strength, high toughness and low coefficient of linear expansion, in which the wire drawing process 12 (hereinafter referred to as the skin pass process) with a light surface reduction rate and the mild strain relief process 13 with the straightening roll 20 is performed. There is. Further, in the above-mentioned Invar wire manufacturing method, the area reduction rate of the wire drawing process 12 is 2.0 to
The invar wire manufacturing method has a high strength, a high toughness, and a low coefficient of linear expansion, in which the roll diameter / the wire diameter of the strain relief processing 13 by the straightening roll 20 is 9.0% to 8.0%. ..

Each of the steps of the casting 1 to the strain relief annealing 9 and the like shows an example of a conventional manufacturing method for manufacturing an invar wire, and the present invention is not limited to the above-mentioned steps, but various conventional manufacturing methods. In the final step, after the strain relief annealing 9 in the final step, or after the strain relief annealing 5 in the intermediate step as necessary, the wire rod a2 is subjected to a pre-drawing treatment 11, and a wire reduction processing 12 (skin pass processing) with a light surface reduction rate. Further, it is characterized in that a finishing process including a process of light strain relief processing 13 by the straightening roll 20 is performed.

In the Invar wire manufacturing method of the above-mentioned high strength, high toughness and low linear expansion coefficient of the present invention, as shown in the figure, before the skin pass working 12, the wire drawing pre-treatment 11 by a conventional appropriate means is performed to perform the skin pass working 12. Is performed with a very small surface reduction rate by an appropriate conventional wire drawing process, and the straightening rolls 2 formed in a plurality of stages as shown in FIG.
When 0, a sufficient effect is obtained.

More specifically, the Fe-Ni alloy is
When wire drawing is applied as shown in Fig. 3, the coefficient of linear expansion is small,
Although the strength has a property of gradually increasing, on the contrary, the toughness such as elongation, twisting, winding and unwinding tends to decrease. Therefore, in the conventional manufacturing of Invar wire, as a means for recovering the toughness, wire drawing is performed up to the step of intermediate processing or final processing, or strain relief annealing 5, 9 is performed after the step.
Then, the toughness such as elongation, twisting, winding and unwinding of the wire rod is recovered as shown by the dotted line of the arrow, but the annealing is
The decreasing linear expansion coefficient and the increasing strength tend to be reversed before processing, as indicated by the dotted line. Also,
In order to obtain a wire with high strength and a low coefficient of linear expansion, it is necessary to increase the workability (larger area reduction rate), but if the workability is increased, the degree of toughness deterioration increases and the subsequent strain relief annealing is performed. It becomes difficult to recover the toughness due to the above, and in order to recover the toughness, it is necessary to increase the degree of annealing, that is, increase the annealing temperature and lengthen the annealing time, but this is also regulated within the range of maintaining the predetermined linear expansion coefficient and strength. It

Therefore, the working degree of high strength and low linear expansion coefficient is limited to the range in which the toughness is restored by annealing and the strength and linear expansion coefficient are maintained, and the strength and linear expansion coefficient obtained by this are limited. Maximum and minimum values. As described above, conventionally, in order to achieve high strength, high toughness, and low linear expansion coefficient of Invar wire,
In order to increase the working limit by performing working such as wire drawing and strain relief annealing, various elements have been added in trace amounts and the composition has been improved. In contrast, the present invention is
High strength and high toughness are obtained by performing processing 12 such as wire drawing with a very light surface reduction rate and straightening roll processing 13 for mild strain relief on the wire rod made of the Fe-Ni alloy after annealing. And a wire rod made of a Fe-Ni alloy having a low linear expansion coefficient, that is, an Invar wire a3.

The degree of working such as wire drawing after annealing, the strength, and the coefficient of linear expansion have the relationships shown in FIGS. 4 and 5, and the strength sharply increases at the beginning of working (FIG. 4), and the coefficient of linear expansion is It drops sharply (Fig. 5). Further, the workability such as wire drawing after annealing and the toughness such as elongation, twisting, winding and unwinding have a relationship as shown in FIG. 4, and the toughness sharply decreases at the initial processing, but the toughness at the initial processing is The decrease is recovered by the straightening roll processing 13 to the extent that there is no practical problem, and this straightening roll processing causes a slight decrease in strength, but it has almost no effect on the linear expansion coefficient and is effective for recovering toughness at the initial stage of processing. It becomes a means.

Therefore, in the above embodiment of the present invention, Fe-
First, a wire rod a2 (or a1) formed by rolling a Ni-based alloy to a predetermined diameter is annealed 5 in an intermediate working step,
Alternatively, it is processed by wire drawing or the like to a predetermined diameter without being annealed to have high strength and a low linear expansion coefficient. Next, strain relief annealing 9 restores toughness such as elongation, twisting, winding and unwinding. At this time, the strength is slightly decreased and the linear expansion coefficient is slightly increased with the recovery of the toughness, but after the strain relief annealing, the processing such as wire drawing with a very light reduction in area (skin pass processing) 12
By carrying out, the strength and the coefficient of linear expansion are returned to the same level as before annealing. Although the toughness decreases again with the skin pass processing 12, the straightening roll processing 13 is further performed,
The toughness is restored to a level where there is no practical problem.

The Fe-Ni alloy having the composition shown in Table 1 was 6.5 m by the steps of casting, forging, wire drawing and peeling.
A mφ wire rod was processed in the process shown in FIG. 1 to produce 2.48 mmφ and 3.38 mmφ Invar wires. In the above processing, annealing is performed at an appropriate temperature of 500 ° C. or higher, and skin pass processing is performed with a surface reduction rate of 2.0 to
It is performed at about 8.0%, and the straightening roll processing is D /
d = 9.0 to 16.0 (diameter D of straightening roll, diameter d of Invar wire), 2.48 mmφ and 3.38 mmφ
The invar wire of FIG. 6 was manufactured, and the characteristic diagrams as shown in FIGS. 6 to 9 were obtained.

As shown in FIGS. 4 and 5, skin pass processing 12
Is preferably performed at a surface reduction rate of about 2.0 to 8.0%, and as shown in FIGS. 6 and 7, the ratio D / d of the diameter D of the straightening roll to the diameter d of the invar wire is 9. It is preferable to perform strain relief processing in the range of 0 to 16.0.
The measurement result of each wire rod characteristic of 8 mmφ is shown in FIG. 7, and the measurement result of each wire rod characteristic of Invar wire 3.38 mmφ is shown in FIG. 8. As apparent from FIGS. 7 and 8, in the present invention, the strength is about 5 Kgf / mm 2 Rises and the coefficient of linear expansion is 0.5 × 10
Decrease by ^-6 / ° C, elongation increased by 1.0% or more, torsion was equal or higher, variation was small, and remarkable good results were confirmed in terms of strength, toughness, and coefficient of linear expansion. ing.

[0020]

The present invention is constructed as described above, and the Fe-Ni alloy is drawn into a wire having a predetermined diameter by a conventional appropriate working means, and the wire is strain-relieved and annealed. ,
In addition to recovering toughness such as twisting, winding and unwinding, by drawing wire with a light reduction in area after annealing, strength and linear expansion coefficient are returned to about the level before annealing, and further mild strain relief by straightening rolls. By working, the toughness is restored to a practically problem-free level, a slight decrease in strength caused by the annealing, and an increase in the linear expansion coefficient are easily and effectively eliminated by the finishing process as described above. The wire drawing process with a light surface reduction rate after annealing and the mild strain relief process with the straightening rolls are effective finishing processes by mechanical wire-making technology, and have high strength, high toughness and a low coefficient of linear expansion. Each property can be easily obtained with high precision and finely adjusted, and the workability, product accuracy, and reliability are remarkably improved. Further, the area reduction rate of the wire rod in the wire drawing process after the strain relief annealing is 2.0 to
By setting the ratio to 8.0% and setting the roll diameter / wire diameter in the mild strain relief processing by the straightening rolls to 9.0 to 16.0, the above respective characteristics are further enhanced, and excellent product accuracy and reliability are obtained. can get.

[Brief description of drawings]

FIG. 1 is a process chart showing an embodiment of the present invention.

FIG. 2 is a side view mechanism diagram (A) and an XX view mechanism diagram (B) of the straightening roll applied to the embodiment.

[Fig. 3] Mechanical characteristic diagram of Invar wire by wire drawing

FIG. 4 is a characteristic diagram showing mechanical changes of Invar wire in the initial stage of wire drawing.

FIG. 5 is a characteristic diagram showing changes in the coefficient of linear expansion of the Invar wire in the initial stage of wire drawing.

[Fig. 6] D / d of straightening roll and elongation characteristic diagram after straightening roll processing

FIG. 7: Characteristic diagram of elongation improvement by straightening rolls

FIG. 8 is a characteristic diagram of each step of the example (2.48 mmφ)

FIG. 9 is a characteristic diagram of each process of the example (2.38 mmφ).

[Explanation of symbols]

a Fe-Ni alloy D Roll diameter (rectifying roll) d Wire diameter a1, 2 Wire material 5,9 Strain relief annealing 12 Light wire reduction wire drawing (skin pass processing) 13 Mild strain relief by straightening roll (Rectification roll processing) 20 Rectification roll

Claims (2)

[Claims] 1. An Fe-Ni alloy is drawn into a wire having a predetermined diameter, strain-annealed, and then wire-drawn with a small reduction in area, and a straightening roll is used to remove the slight strain. Invar wire manufacturing method with high strength, high toughness and low coefficient of linear expansion characterized by processing. 2. The high strength, high toughness and low linear expansion coefficient Invar wire manufacturing method according to claim 1, wherein the wire rod after strain relief annealing is wire-drawn at a surface reduction rate of 2.0 to 8.0%. , Furthermore, by the straightening roll, roll diameter / wire diameter = 9.0-1
Invar wire manufacturing method with high strength, high toughness and low linear expansion coefficient, which is characterized by performing strain relief processing at 6.0.