JPS5836076B2 - Manufacturing method of anodized electric wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an alumite electric wire in which the electrical insulation properties of an anodic oxide film of aluminum or aluminum alloy are improved.

The anodized film produced by anodizing aluminum or aluminum alloy consists of a dense non-porous film called a barrier layer and a porous γ film formed on top of this.
- The barrier layer has a thickness of 1 μm or less and has very high electrical insulation properties.

The porous film has a thickness of 5 to 100 μm and an outer diameter of 100 io
There are approximately 1011 micropores/d.

Therefore, the anodic oxide film has electrical insulation properties.

The electrical insulation property of this anodic oxide film increases in proportion to the thickness of the anodic oxide film, for example when looking at dielectric breakdown voltage as an indicator. It decreases due to the influence of residual electrolytes, moisture, air, etc.

Furthermore, when the anodic oxide film is subjected to processing such as bending, the cracks and defects described above increase and the dielectric breakdown voltage decreases.

By the way, the expansion coefficient of the anodic oxide film is about 5XI O-'17G, and for aluminum or aluminum alloy it is approximately 25X10-'1/℃, which is about 5 times larger for aluminum or aluminum alloy, and once the anodic oxide film is heated. Due to the difference in expansion coefficient, cracks occur in the barrier layer and the porous layer in the coating, resulting in a significant decrease in electrical insulation.

The electrical insulation properties of the anodic oxide film vary widely depending on the handling conditions and are unstable, so various measures have been taken to improve this and obtain stable and high electrical insulation properties. Ta.

For example, attempts have been made to seal the micropores by impregnating them with various substances, thickening the oxide film, devising electrolytes, and sealing the pores by two-stage electrolysis, but the effects are insufficient. When aluminum or aluminum alloys with anodic oxide coatings are used for heat-resistant wires, which is an important use thereof, it is impossible to avoid the occurrence of cracks due to the above-mentioned difference in thermal expansion.

This invention was made in view of the above circumstances, and its purpose is to provide a method for manufacturing an alumite electric wire that is stable against heating and processing and has high electrical insulation properties, and is made of aluminum or aluminum alloy. The anodized film produced by anodizing the wire is subjected to secondary electrolysis as an anode in an electrolytic bath containing an ammonium salt of a metal thioacid, and then subjected to a sealing treatment, or the anodized film is heat-treated and honed. Cracks are actively generated through treatment, and then this film is subjected to secondary electrolysis in an electrolytic bath containing a metal thioate as a main component to impregnate the fine pores with metal sulfide, followed by sealing treatment. It is characterized by this.

This invention will be explained in detail below.

The anodic oxide film of aluminum or aluminum alloy wire of this invention can be obtained by immersing aluminum or aluminum alloy wire in an acid bath, alkaline bath, or non-aqueous bath, using this as an anode, and electrolyzing it with direct current, alternating current, orthogonal superimposed current, etc. It consists of a dense barrier layer and a porous film made of γ-alumina with a thickness of 5 to 100 μm formed thereon.

The anodic oxide film thus obtained is then subjected to secondary electrolysis in an electrolytic bath containing a metal thioate as a main component, using the bed film as an anode.

At least one of the ammonium salts of thiomolybdic acid, thiotungstic acid, thiostannic acid, and thioantimonic acid is used as the thioate salt of this metal, and these thioate salts are added to demineralized water at a concentration of 0.01 to 30 wtφ. It is dissolved and the pH is adjusted to 4 to 12 to form a secondary electrolytic bath.

Next, the anodic oxide film is connected to a power source in this electrolytic bath so as to become an anode, whether continuously or intermittently.
electrolyzed.

The counter electrode uses a suitable non-eluting conductive material.

As the electrolytic current, periodic waveform currents such as direct current, imperfectly rectified waveform current, AC/DC superimposed current, AC/DC combined current, AC current pulse waveform current, rectangular wave current, triangular wave current, etc. are used.

The temperature of the electrolytic bath ranges from 08C to 100C.

In DC electrolysis, the current density is 10rrIA/dm2 to IA/
Preferred electrolysis conditions are dm2 and electrolysis time of 1 minute to 1 hour.

In this way, metal sulfides are formed or impregnated into the pores and fine cracks in the anodic oxide film.

The reason why this metal sulfide is produced is thought to be as follows.

The thioate salt dissociates in the electrolytic bath to produce negatively charged thioate ions.

When the anodic oxide film acts as an anode during electrolysis, metal thioate ions penetrate into minute cracks and pores by electrophoresis.

On the other hand, at the bottom of the pores and cracks, an anodic oxidation reaction of barrier single-layer aluminum and an electrode reaction of OH-1--i02+H +2e occur, and H is released.

The inside of the pore becomes acidic due to this H+, and the metal thioate ion is decomposed to become metal sulfide, which is deposited in the microcrack and inside the pore.

This metal sulfide deposition begins at the bottom of the pore, which is the source of H+ release, and progresses toward the opening.

The anodic oxide film subjected to the secondary electrolytic treatment as described above is further subjected to a sealing treatment in order to improve its electrical insulation properties.

This sealing treatment is mainly preferably a boiling water sealing treatment, which is carried out in demineralized water for about 30 minutes to 2 hours.

In addition, nickel acetate sealing has a similar effect.

In addition, after generating fine cracks in the anodized film through heat treatment or honing treatment,
Secondary electrolytic treatment and sealing treatment using the above-mentioned metal thioate salts can also be performed.

The heat treatment is performed in a heating furnace or the like at 15.0 to 300° C. for about 10 to 20 minutes.

The honing process is performed using a #200 to 4P400 horn at a pressure of 3 to 100 kg/i.

In addition, there are methods such as low-temperature hard alumite that generate fine cracks during anodic oxide film formation.

The anodic oxide film in which fine cracks have been generated is then subjected to the above-mentioned secondary electrolytic treatment and sealing treatment using a metal thioate salt.

The secondary electrolytic anodized film thus formed has a structure in which the barrier layer is thickened and strengthened, and the metal sulfide is impregnated and filled into the fine cracks and pores, and the pores are sealed.

Therefore, when this alumite electric wire is heated or processed, the stress acting on the anodic oxide film is randomly dispersed, and the oxide acts as a cushioning material, so that the occurrence of cracks is extremely reduced.

Furthermore, since the fine cracks and pores are filled with electrically insulating metal sulfide, the electrical insulation will not deteriorate due to the influence of moisture or residual electrolyte.

Furthermore, since the film is smoothed, protrusion discharges are eliminated.

The present invention will be specifically described below based on Reference Examples and Examples.

Reference example: On the semi-rigid aluminum plate between IXIOOXIOO,
An anodic oxide film having a thickness of 15 μm was formed at 20° C. in two types of electrolytic baths: 15 vol % sulfuric acid and 5 W t % oxalic acid.

Some of the aluminum plates that have been chemically anodized are 20
Fine cracks were generated by heating for 10 minutes in a heating furnace at 0°C.

Next, direct current electrolysis was performed as an anode at 50 mA7' dm2 in a 0.5 wt% aqueous solution of ammonium thiomolybdate, ammonium thiotungstate, and ammonium thiostannate.
Time-sealed.

The obtained test piece was subjected to an AC dielectric breakdown test and an insulation resistance measurement under conditions of 25°C and 60φRH, and at the same time, the occurrence of cracks on the surface was observed.

The results are shown in Table 1. The dielectric breakdown voltage was measured using AC breakdown of the anodic oxide film using mercury as an electrode.

The insulation resistance was measured by using a super insulation resistance meter to measure the volume resistivity value when charged at a voltage of 50 V for 1 minute.

The cracks were observed by measuring the number and type of cracks within a 10 inch length using a 20x magnifying glass.

Example diameter: 0. 8 mm electrical soft aluminum wire at 15v
Anodized at 20°C in an ol% sulfuric acid bath to a thickness of 1
A 0 μm anodic oxide film was chemically formed, and a portion of this aluminum wire was heat-treated in a heating furnace at 250° C. for 5 minutes to generate fine cracks in the anodic oxide film.

Next, in a 1 wt % ammonium thiomolybdate aqueous solution, direct current electrolysis (secondary electrolysis) was performed for 5 minutes using the aluminum wire as an anode, and then a portion of these was sealed in boiling water for 1 hour.

A reciprocating abrasion test, AC breakdown voltage measurement, and insulation resistance measurement at an applied voltage of 50 V were performed on these test pieces of alumite electric wire.

For comparison, similar tests and measurements were also conducted on a sample that was not subjected to secondary electrolysis using ammonium thiomolybdate.

The results are shown in Table 2.

The reciprocating abrasion test was performed by sliding a bead needle orthogonally over the sample alumite wire reciprocatingly under a load of 250 g, and evaluating the number of times the bead needle was slid until the insulation was broken.

AC breakdown voltage measurement was performed by twisting two sample alumite wires together.

As described above, the present invention applies thioacid to a porous anodic oxide film produced by anodizing aluminum or aluminum alloy wire, or to an anodized film in which fine cracks have been generated by heat treatment, etc. Metal sulfide is deposited and impregnated into the pores and fine cracks of the film through secondary electrolysis in an electrolytic bath containing ammonium salt as the main ingredient, and the pores are further sealed. It has high properties, is stable without being affected by heating or processing, and is not affected by humidity.

Furthermore, the mechanical strength of the film itself is improved and the surface of the film becomes smooth, eliminating protrusion discharges.

Furthermore, it has advantages such as a simple processing method and no special equipment required, and is particularly suitable for alumite electric wires.

Claims (1)

[Scope of Claims] 1 An anodized film of aluminum or aluminum alloy wire is subjected to secondary electrolysis as an anode in an electrolytic bath containing at least one of ammonium salts of thiomolybdic acid, thiotungstic acid, thiostannic acid, and thioantimonic acid. . A method for manufacturing an alumite electric wire, characterized in that the film is made into an electrically insulating film by subsequently performing a sealing treatment. 2. Fine cracks are generated in the anodic oxide film of aluminum or aluminum alloy wire by heat treatment, honing treatment, etc., and then the film is treated with at least one ammonium salt of thiomolybdic acid, thiotungstic acid, thiostannic acid, and thioantimonic acid. 1. A method for producing an alumite electric wire, which comprises performing secondary electrolysis as an anode in an electrolytic bath containing alumite, and then performing a sealing treatment to form the coating into an electrically insulating coating.