JPS59114749A - Tungsten wire for filament - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a tungsten wire of a tube filament;
More specifically, it relates to tungsten wire with excellent vibration resistance and droop resistance.

[Technical background of the invention and its problems]

Thin tungsten wire is used in the filament of various light bulbs. Such tungsten 1v11 is often used at a high temperature near or above the recrystallization temperature, and its crystal structure changes during use. The mode of this change has a great influence on the filament's strength, brittleness, and sagging resistance, but especially at high temperatures, the sagging resistance (
Non-sag property) is an important characteristic.

In order to improve this non-sag property, the recrystallized grains must be long and thin.
Moreover, it is necessary to form a structure in which these recrystallized grains penetrate each other in the axial direction in a wedge shape and overlap. That is, when the length of the recrystallized grain is L1 and the width is W, the important necessary characteristics are that -LAN is large and that the recrystallized grains interpenetrate each other in a complicated manner.

However, when the wire diameter of the tungsten wire is made thinner, even if the L4/W is large, the recrystallized grains do not penetrate into each other in a wedge shape, and in extreme cases, only one grain is formed. The recrystallized grains are connected one after another in the wire axis direction to form one wire rod as a whole.

・Under such conditions, V Fi is large and has excellent non-sag properties, but on the other hand, the filament of automobile light bulbs,
When used in applications where vibrations are severe, such as filaments for copying machine lamps, the vibrations may cause the recrystallized grains to be cut from the grain boundaries (simple grain boundaries). In other words, there is a problem with vibration resistance.

[Purpose of the invention]

An object of the present invention is to provide a tungsten wire for filament that has not only non-sag properties but also excellent vibration resistance.

[Summary of the invention]

The present inventor has discovered that even if the Llw of the recrystallized grains is large, when the cross section of the wire is observed, the number of recrystallized grains (what is observed is the cross-sectional shape) that exists in the cross section of the wire is the same as the vibration resistance of the wire. Based on this discovery, we developed the tungsten wire of the present invention.

That is, the tungsten wire of the present invention has recrystallized grains with a length of 7
It is characterized by a structure in which the width ratio (Llw) is 7 or more and the number of recrystallized grains included in the cross section of an arbitrary portion is 4 or more.

The recrystallized grains according to the present invention have a wire diameter of 0.25 to 0.5
This refers to recrystallized grains that are precipitated when an RTM tungsten wire is heated with a fusing current of 70 to 90 inches. In such recrystallized grains, when the diameter W is smaller than 7, the non-sag property decreases. Usually, the length is 0.2 to 0.5 ran
The O wire diameter is preferably about 12 to 25.

Furthermore, if the number of recrystallized grains contained in the wire is less than four in its cross section, the recrystallized grains do not penetrate through the grain boundaries of each other, resulting in a decrease in vibration resistance as a whole. Normally, in a wire diameter of 0.2 to 0.5 mm, 6
It is preferable that the value is about 10 to 10.

Such a wire can be easily manufactured by appropriately selecting the tungsten powder used as a raw material, its forming conditions, sintering conditions, and processing conditions such as rolling and wire drawing.

The tungsten wire of the present invention has a wire diameter of the applied filament (e.g. *0.1 rrrrn e O, 05 m
+) and put into practical use.

[Embodiments of the invention]

LA averaged 14.0. A tungsten wire (example) with an average number of circular recrystallized grains in cross section of 6 and a wire diameter of 0.39 m, and W is 1
8.0. The average number of cross-sectional circular recrystallized grains is 3 and the wire diameter is 0.39.
A □- tungsten wire (comparative example) was prepared.

After drawing these two wires using 43MGK4, they were made into coiled filaments for incandescent light bulbs.

The non-sag properties and vibration resistance of two types of coil filaments were measured. Non-sag properties were investigated by measuring the drooping value when a current was passed through the filament and the temperature was raised to 2500 C and held for 100 hours.

Also: Vibration resistance is 70% of the filament's fusing current, 8
0%, 90% current for 3 seconds, then 2700C
The coil was reheated for 60 seconds, then cooled to room temperature, pulled at 40 MG at room temperature, and the elongation of the coil was measured, and the elongation value was expressed as a percentage of the original length of the coil. The larger the value, the better the vibration resistance.

There was almost no difference in non-sag properties between the two wires. However, in terms of vibration resistance, the leg material of the present invention exhibited very excellent characteristics as shown in the figure.

〔Effect of the invention〕

As is clear from the above description, the tungsten wire of the present invention has excellent non-sag properties as well as excellent vibration resistance, and is useful as a filament for light bulbs used in locations subject to severe vibration.

[Brief explanation of the drawing]

The figure is a diagram showing the vibration resistance of coil filaments manufactured from wire rods of Examples and wire rods of Comparative Examples.

Claims (1)

[Claims] 1. A filament characterized in that the recrystallized grains have a length-to-width ratio of 7 or more, and the number of recrystallized grains included in the cross section of any part is 4 or more. tungsten wire. 2 The diameter of the tungsten wire is 0.25 to 0.5++
The tungsten wire for filament according to claim 1, which is IIm.