JPH03274232A - Heat treatment for metallic wire - Google Patents

Abstract

PURPOSE:To remove the peeling of a Cu plating layer applied to the surface of a wiredrawn core wire and the slip of a wiredrawn W wire and to prevent inferior coiling by subjecting a surface-oxidized metallic wire to reduction and forming ruggedness in the above surface. CONSTITUTION:A metallic wire is heated in an oxidizing atmosphere to undergo surface oxidation, by which a rough oxide film is formed. Subsequently, this metallic wire is heated in a reducing atmosphere to undergo surface reduction, by which ruggedness is formed in the surface of the metallic wire.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a heat treatment performed as a pretreatment for processing a metal wire.

(Prior art) When processing a metal wire, the metal wire is often heat treated in a hydrogen atmosphere as a pretreatment. For example, when producing Dumet wire, an iron-nickel alloy is annealed in a hydrogen atmosphere. The wire is softened, then drawn and annealed repeatedly until it is drawn to a predetermined wire diameter, then coated with thick copper and coated with copper.The copper coated core wire is drawn to a predetermined wire diameter and placed in an oxidizing atmosphere. The wire is heated inside to oxidize the surface of the copper plating layer, then sanded, and then heated further to transform the copper oxide on the surface into a glassy tone, forming a Dumet wire.

In addition, tungsten coil filaments used in various bulbs such as light bulbs and fluorescent lamps are made by annealing tungsten wire in a hydrogen atmosphere to soften it, then repeating wire drawing and annealing to draw it to a predetermined wire diameter. The material is then wound around a mandrel to form a coil, heated in a hydrogen atmosphere to remove distortion, and then the mandrel is removed to form a filament.

(Problems to be Solved by the Invention) In manufacturing the above-mentioned Dumet wire, when the iron-nickel core wire is drawn, the wire diameter becomes thinner and the surface is smoothed, and furthermore, this core wire is work-hardened. Even when annealed in a hydrogen atmosphere, the surface of the core wire remains smooth. As described above, when copper is thickly plated on a core wire with a smooth surface, cracks are likely to occur due to distortion occurring in the copper plating layer. In addition, when drawing an iron/nickel-plated core wire with thick copper plating, it is easy to peel off, and when applying sand, if the copper surface is too smooth, it is difficult for sand to adhere to it.

In addition, when the tungsten wire is drawn, the surface becomes smooth, and when it is wound around a mandrel, the tungsten wire tends to slip, making winding defects likely to occur.

Therefore, an object of the present invention is to provide a method for forming a surface into a finely uneven surface as a pretreatment for metal wire processing.

[Structure of the invention]

(Means for Solving the Problems) The present invention involves heating the metal wire in an oxidizing atmosphere to oxidize its surface as a pretreatment for processing the metal wire, and then reducing the oxidized metal wire. In this method, the surface of the metal wire is reduced by heating in a neutral atmosphere to form a finely uneven surface.

(Function) Metals and their oxides have different densities, so when the surface of a metal wire is oxidized, a rough oxide film forms, and when this is reduced, it becomes a finely uneven surface.

(Example) The details of the present invention will be described below with reference to a pretreatment step for applying a predetermined amount of sand to a copper coating layer/nickel alloy core wire in the production of the illustrated Dumet wire. In Figure 1, (
1) is a copper coated core wire, (21).

(22) is a spool for unwinding and winding that holds this copper coated core wire (1), (3) is an oxidation furnace that oxidizes the copper coated core wire, and (4) is an oxidation furnace (3). This is a reduction furnace that is installed as close as possible to reduce the oxidized copper-coated core wire.

The above-mentioned copper-coated core wire (1) is produced by thickly coating an iron-nickel alloy wire with copper, and then repeating both annealing and wire drawing processes to obtain a core wire with a wire diameter of 0.4 to 0.5 m and then coated with copper. The layer is formed to have a size of 20 to 30 microns, and is wound onto an unwinding spool (21).

As shown in an enlarged view in FIG. 2, the oxidizing furnace (3) has a city gas burner (32) installed at the inner bottom of a metal windproof box (31), and the oxidizing furnace (33) of this burner (32) ) The positional relationship is determined so that the copper-coated core wire (1) passes through it.

As shown in an enlarged view in FIG.
), a steel introduction pipe (43) of the same inner diameter is connected to the inlet of the core tube (42), and a cooling pipe (43) with the same inner diameter cooled with cold water is installed at the outlet of the reactor core tube (42). (44) are coaxially connected, a heating wire (45) such as molybdenum wire or nichrome wire is wrapped around the core tube (42), and a heat insulating material (46) such as magnesia is placed in the heat insulating box (41). The hydrogen supply pipe (47) is connected to the heat insulation box (41).

Next, the above pretreatment step will be specifically explained. First, open the hydrogen supply pipe (47) of the reduction furnace (4), and
Supply hydrogen inside. Then, the hydrogen flowing out from the introduction pipe (43) is ignited, and the heating wire (45) is energized.

Then, the temperature inside the furnace core tube (42) is measured from time to time, and when this temperature reaches 900°C, the current is adjusted to maintain this temperature, and the burner (32) of the oxidation furnace (3) is ignited to oxidize. Adjust the temperature of the furnace (33) to 900°C. Then, the copper coating layer g (1) is pulled out from the unwinding spool (21), passed through the oxidation furnace (3) and the reduction furnace (4) in order, and then wound around the winding spool (22) at a speed of 5 m/min. Continuous winding at a speed of Then, the copper-coated core wire (1) is heated in the oxidation furnace (3) at about 900° C. for about 2 minutes to cause annealing and surface oxidation in a short period of time. Next, while this heated copper coating layer 1 (1) leaves the oxidation furnace (3) and is still at a high temperature, it is transferred to the furnace core tube (42) of the reduction furnace (4).
go inside. However, there are about 90
It is filled with hydrogen at 0° C., and is combusted in the introduction pipe (43), and a portion flows out from the cooling pipe (44) without being combusted, and the outflow pressure prevents outside air from entering. For this reason, the copper-coated core wire (1) that entered immediately
The temperature is raised to 0° C., and the copper oxide is reduced and annealed by this high temperature hydrogen.

When the copper-coated core wire (1) is oxidized in the oxidation furnace (3) and the surface of the copper-coated layer is oxidized, the outermost layer of the copper-coated layer is mainly made of copper monoxide (Cub). Some steel dioxide (
A rough copper monoxide layer mixed with CuO□) is formed,
A dense cuprous oxide (Cu, 0) layer is formed in the lower layer.

When the oxidized copper-coated core wire (1) is reduced, the cuprous oxide layer becomes a dense and smooth reduced copper layer, and -
The copper oxide layer has an uneven surface.

The surface texture of this copper coating layer after reduction is determined by the degree of previous oxidation; the thicker the copper oxide layer is, in other words, the longer it is oxidized, and the higher the proportion of second-order copper, the more the copper oxide layer is oxidized. The higher the temperature of oxidation, the rougher and more uneven the surface will be after reduction.

Therefore, the surface condition can be controlled as desired.

In this way, the copper coated core wire (1) whose surface copper layer has been formed into an appropriately uneven surface is sent to the next sanding process, where the surface is oxidized in an oxidation furnace. When the aqueous sand solution is applied, the aqueous sand solution penetrates into the pores on the surface of the copper coating layer, so the coating amount is large and the adhesion density is uniform, so that it is evenly applied. Therefore, heating after application (boration)
The sand copper layer obtained by this method has the desired thickness and roughness.

The local condition is also uniform, and a high-quality Dumet wire can be obtained.

Furthermore, in this example, the copper-coated core wire (1) is first heated in an oxidation furnace (
3) is heated to about 900°C, and before this temperature has almost dropped, it is heated again to 900°C in the reduction furnace (4), so the result is essentially the same as if the heating time was longer, and the same reduction furnace ( 4) Copper-coated core wire (1) at the same linear speed
The same result can be obtained even if the material is wound for a longer period of time. Incidentally, we examined the tensile strength and elongation of the core wire obtained by the heat treatment method of the copper-coated core wire (1) of this example, and compared this with the result of the conventional heat treatment method in which the oxidation furnace was removed and the reduction furnace was lengthened instead. It was compared with that of the core wire. The results are shown in the table below.

This table reveals that even if an oxidation furnace is provided, the same metal properties can be obtained if the total treatment time is the same.

Further, the present invention can be applied to other methods of heat treating metal wires. For example, if a tungsten wire is heat-treated in an oxidation furnace and then heat-treated again in a reduction furnace, the reduced tungsten surface becomes uneven due to the difference in specific gravity between metal tungsten and tungsten oxide, making it easier to coil the wire without slipping on the mandrel. Can be attached. Also, since the annealing time is longer, the same reduction furnace has the same effect as annealing for a longer time, or has the same effect as a longer reduction furnace.

Therefore, there is no limit to the heating time and heating time of the oxidation furnace and the reduction furnace, and there is also no limit to the temperature.
It is sufficient if an uneven surface with desired roughness is formed after reduction.

As for the annealing effect, it is not really necessary, and furthermore,
The oxidation furnace may be an electric furnace. Furthermore, reduction may be performed after the metal wire has sufficiently cooled down after oxidation.

〔Effect of the invention〕

As described above, the metal wire heat treatment method of the present invention involves heating the metal wire in an oxidizing atmosphere to oxidize the surface as a pretreatment for processing the metal wire, and then placing the metal wire in a reducing atmosphere. Since the metal wire is heated to reduce the surface again, the surface of the metal wire can be made uneven.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the method for heat treatment of metal wires of the present invention, FIG. 2 is a sectional view of an oxidation furnace, and FIG. 3 is a sectional view of a reduction furnace. (1)...Metal 11 (21), (22)...Spool (3)...Oxidation furnace (31)...Windproof box (32)
)...Burner (33)...Oxidation furnace (4)...Reduction furnace (41)...Insulation box (42)...Furnace core tube
(43)...Introduction pipe (44)...Cooling pipe (45)
... Heating wire (46) ... Heat insulation material (47) ... Hydrogen supply pipe Representative Patent attorney Norio Ogo

Claims (1)

[Claims] As a pretreatment for processing the metal wire, the metal wire is heated in an oxidizing atmosphere to oxidize the surface, and then the metal wire is heated in a reducing atmosphere to reduce the surface. Heat treatment method for metal wire.