JPS6174723A - Tungsten wire rod and its production - Google Patents

Abstract

PURPOSE:To improve a wear resistance and break resistance by forming the fiber organizations more than the specified number on the unit length which is at right angles with the longitudinal direction of a wire rod. CONSTITUTION:The wear resistance and break resistance of a tungsten wire rod are much concerned with the hardness and bend fatigue strength of a wire rod. The tungsten blank material having the prescribed wire diameter is subjected to a wire drawing work at >=99.6% work rate, after performing forging and medium heat treatment. The hardness of >=650 Vickers is obtd. due to the forging being reduced while wire drawing work being increased. With said wire drawing work the fiber organizations in the 100mum unit length which is at right angles with the longitudinal direction can be formed in numbers of >=10<5>. By the achievement in the number of said fiber organizations, the break resistance is improved to at least >=five times. Consequently with >=99.6% wire drawing work, the prescribed hardness is obtd. and wear resistance and break resistance are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tungsten wire and a method for manufacturing the same, and particularly to a tungsten wire used as a wire for a dot printer and a method for manufacturing the same.

[Prior art]

Generally, tungsten wire is often used as wire for dot printers. By the way, dot printer wires wear out due to repeated printing.

Mechanical strength above a certain value is required to prevent breakage.

The wear resistance and breakage resistance of tungsten wire are as follows:
Regarding the former, it is the hardness of the tungsten wire.

The latter concerns the bending fatigue strength and internal defects of the tungsten wire.

The hardness of the tungsten wire mentioned above is measured using a Havickers hardness tester, and the Vickers hardness (Hv) is used for wear resistance.
650 or more is required. Regarding the bending fatigue strength, as shown in Fig. 1, the tungsten wire is held in a jig 2 with a pair of corners formed by the radius (-!-R) of the tungsten wire 1. The product is sandwiched and bent 90 degrees from side to side repeatedly.For breakage resistance, the bending strength must be able to withstand 5 or more times according to the test method shown in Figure 1.

In the conventional manufacturing method of tungsten wire.

After rolling and intermediate heat treatment, rolling is continued until the crystals recrystallized by the intermediate heat treatment reach a crystalline state that can withstand wire drawing. The wire diameter after rolling is 2.0 to 3.
It will be about 0 order. Thereafter, wire is drawn using a carbide die while being heated with gas, and the wire is finished to a predetermined diameter.

However, in general, for tungsten wires, when Hv=600 or more, the processing strain reaches a saturated state and the wire ((cracks)
There are problems in that cracks are likely to occur and the bending strength is reduced, resulting in a significant decrease in yield.

[Purpose of the invention]

An object of the present invention is to provide a tungsten wire that has sufficient hardness and bending fatigue strength and does not cause cracks.

Another object of the present invention is to provide a method for manufacturing a tungsten wire that provides sufficient hardness and bending fatigue strength and does not generate cracks.

[Structure of the invention]

According to the present invention, the number of fiber structures extending in the length direction of the tungsten wire is as follows in a cross section parallel to the length direction.
Unit length perpendicular to the length direction of the fiber structure: 100 μm
A tungsten wire characterized by the presence of IO or more in the wire is obtained, and this tungsten wire is obtained by increasing the processing rate by drawing to 99.6% or more.

[Embodiments of the invention]

The present invention will be explained below with reference to Examples.

Prepare a tungsten material with a predetermined wire diameter.

As mentioned above, it was subjected to rolling processing and intermediate heat treatment.

A tungsten material with a wire diameter (φ) of 6 mm and a wire diameter of 3 was used.

These 6- and 3-year tungsten materials are drawn into wire using a carbide die, and each is finally made into a wire with a wire diameter of 0.
35 tm. Also, in the middle of the above line drawing, the wire diameter is 1,
Tungsten wires of 0.8, 0.6, and 0.4 were also produced.

The wire diameter after drawing as described above is 1 mn, 0.8 x
, Processing rate of 0.6 tone, 0.1 m and 0.35 m+++ tungsten wire (referring to the cross-sectional area reduction rate of tungsten wire before and after drawing), Pickus hardness (load was 500 I), fiber Tests were conducted on the degree of bending (the number of fiber structures in a unit length of 100 μm perpendicular to the length direction in a cross section parallel to the length direction of the tungsten wire) and the number of bends. The results are shown in FIG. In this test, 10 tungsten wires of each diameter were prepared, and FIG. 2 shows the average value of the 10 tungsten wires.

As shown in FIG. 2, it can be seen that as the wire drawing rate increases, the Vickers hardness, fiber content, and number of bends increase. As mentioned above, the tungsten wire used as the wire for dot printers needs to have a Vickers hardness of 650 or higher in order to have good wear resistance. As is clear from FIG. 2, in order to obtain a Vickers hardness of 650 or more, the wire drawing rate should be 99.6% or more.

3 to 5 show the relationships between the number of bends and fiber content, the wire diameter and the number of bends, and the wire diameter and Vickers hardness using the numerical values shown in FIG. 2, respectively. Incidentally, the dashed-dotted line shown in FIG. 3 represents a tungsten wire drawn from a tungsten material having a diameter of 6 and 3 after rolling and intermediate heat treatment. The solid lines and broken lines shown in FIGS. 4 and 5 represent tungsten wire rods obtained by drawing tungsten materials having wire diameters of 6III+ and 3 mm after rolling and intermediate heat treatment, respectively.

As is clear from FIG. 3, the fiber content increases rapidly as the number of folds increases. As mentioned above, the tungsten wire used in the wire for dot printers must have a bending strength of 5 times or more from the viewpoint of breakage resistance. It can be seen that this bending strength can be obtained if the thickness is 100 μm or more. Also, Figures 11 and 5
It can be seen from the figure that as the wire diameter decreases, that is, as the wire drawing rate increases, both the number of bends and the Vickers hardness increase. In particular, for the tungsten wire (solid line) drawn from a tungsten material with a wire diameter of 6, the tungsten wire after the final drawing (wire diameter 0.35 m).

At a wire-drawing rate of 99.6%, the wire showed a bending strength of 10 times, and the Vickers strength at that time was Hv=692. In addition, no internal cracks were found in the tungsten wires drawn from tungsten wires with wire diameters of 6 and 3.

As described above, in the present invention, the ratio of the rolling process after the intermediate heat treatment is reduced and the ratio of the rolling process is increased.

In other words, the processing rate in the wire drawing process is increased.

Rolling is a forging process at high temperatures.

If the ratio of rolling processing is high, the development of the fiber structure will be delayed.

Furthermore, the fiber structure tends to be irregular and non-uniform residual strain is likely to occur.On the other hand, in the case of wire drawing, uniform strain is applied, and the fiber structure becomes extremely elongated and fine grained.

〔Effect of the invention〕

As explained above, according to the present invention, a tungsten wire with high wear resistance and folding resistance and a method for manufacturing the same can be obtained.

In addition, in the method for manufacturing tungsten wire according to the present invention, the processing rate in the rolling process is reduced, and the force (
Since the wire drawing rate is increased, it is easy to put it into practical use without requiring new equipment, and the area reduction rate for one pass in wire drawing is approximately 3() ~ . Since it is possible to increase the amount by 10%, it is also an advantageous manufacturing method in terms of cost.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the method for testing the bending strength of tungsten wire 1. Figure 2 is a diagram showing the tungsten wire after drawing, the loading rate of the Gesten wire, the Vickers hardness, the fiber degree, and the number of folds. FIG. 3 is a diagram showing the relationship between the number of bends and the steel strength, and FIG. 4 is a diagram showing the relationship between the wire diameter and the bending rate. FIG. 5 is a diagram showing the relationship between wire diameter and Vickers hardness. Figure 3 Folding concave number C times) Line + (mm) Gland length (mm)

Claims (1)

[Claims] 1. The number of fiber structures extending in the length direction of the tungsten wire is such that the number of fiber structures extending in the length direction of the tungsten wire is within a unit length of 100 μm perpendicular to the length direction of the fiber structures in a cross section parallel to the length direction. 10^
A tungsten wire material characterized by the presence of 5 or more tungsten wires. 2. A method for producing a tungsten wire, characterized in that the processing rate by drawing is 99.6% or more.