JPH0691323A - Manufacture of corrosion resistant heater wire rod - Google Patents

Abstract

PURPOSE:To manufacture a heater wire rod excellent in corrosion resistance at low cost by winding an Al tape around a Ni-Cu-Al alloy wire, giving pressure from the outside while heating the wire, then, heating it in the oxidizing atmosphere after it is drawn. CONSTITUTION:The alloy wire 1 of 10-50wt% Cu, 1-7wt% Al, balance: Ni is made to run continuously and the Al tape 2 is wound around the outer periphery. As the obtained wire rod 1 is made to run on electrified rollers 3a, 3b, an electric current of a prescribed value is caused to flow between the rollers 3a, 3b to resistance-heat the wire rod 1. At the same time, pressure is given by pessurizing rollers 4a-4d to the wire rod 1 to join the wire rod 1 to the Al tape 2. Then, drawing is executed by a drawing die 5 at 10-15% reduction rate of area. The Al tap 2 is heat-treated in a furnace 6 under oxidizing atmosphere to be converted into Al2O3. The heater wire rod excellent in corrosion resistance under a high temperature can be manufactured by a simple equipment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a corrosion resistant heater wire, and more particularly to a method for continuously manufacturing a heater wire having excellent corrosion resistance at high temperatures.

[0002]

2. Description of the Related Art For example, in the case of a microwave oven, in order to realize a feeling of baking similar to that of a gas oven,
Development of a heater member that can be used in a state where the heat generating portion is exposed in the range is underway. The material of the heater member used in such a manner has a high specific resistance and a large amount of resistance heat generation during energization operation, and even if oil, soy sauce or salt used for cooking adheres, it does not corrode during high temperature operation. Performance that does not progress is required.

In such a heater member, the core portion is made of Ni.
A material has been proposed which is composed of a base alloy and on which an Ni—Al intermetallic compound and an Al ₂ O ₃ layer are sequentially formed. Among the heater members proposed here, the heater wire is formed by inserting a Ni-based alloy wire into an Al tube and then wire-drawing the entire wire, or by coating the surface of the Ni-based alloy wire with Al by plating, thermal spraying, or vapor deposition. After the layers are formed, the whole is baked in an oxidizing atmosphere to be manufactured.

[0004]

However, of the above-mentioned two methods, the former method requires complicated loading of the alloy wire into the Al tube, and the workability is deteriorated especially when the wire is long. There is a problem. Further, the latter method has a problem that the formed Al layer is thin or the thickness thereof is likely to vary, and thus the quality of the obtained heater wire becomes unstable.

The present invention solves the above-mentioned problems in the production of a heater wire having a Ni-Cu-Al alloy as the core and having excellent corrosion resistance, and produces a corrosion-resistant heater wire of stable quality and easy to produce. The purpose is to provide a method.

[0006]

In order to achieve the above-mentioned object, in the present invention, Ni—Cu— which continuously runs is used.
An Al tape is wound around the outer periphery of the Al alloy wire, and a pressure is applied from the outside of the wire while electrically heating the obtained wire.
Then, a method for producing a corrosion-resistant heater wire is provided, which comprises performing wire drawing with a surface reduction rate of 10 to 15% and then heating in an oxidizing atmosphere.

The method of the present invention will be described below in detail with reference to FIG. Fig. 1 shows Al to Ni-Cu-Al alloy wire.
It is a figure which shows a series of processes of winding of a tape, heat joining of the wound Al tape and an alloy wire, wire-drawing process, and baking in an oxidizing atmosphere. First, the Ni-Cu-Al alloy wire 1
Runs continuously in the direction of arrow p in the figure, and the Al tape 2 is first wrapped, for example, by wrapping around the outer circumference thereof.

This Ni-Cu-Al alloy wire is Cu: 1.
It is preferable that the composition is 0 to 50% by weight, Al: 1 to 7% by weight, and the balance is Ni as an essential component. In this alloy composition, when the Cu content is less than 10% by weight, the specific resistance of the obtained alloy is low, and when it is more than 50% by weight, the corrosion resistance of the alloy is deteriorated.

When Al is less than 1% by weight,
As in the case of Cu, the resistivity of the alloy is lowered, and when Al is more than 7% by weight, the workability of the alloy is lowered and cracks or the like occur in the material during the production of the heater wire described later. It is easier to do. The alloy wire around which the Al tape 2 is wound is next heated by energization and simultaneously pressed from the outside.

That is, while the wire rod is running on the current-carrying rollers 3a and 3b, a current having a predetermined value is passed between the rollers 3a and 3b to cause the wire rod between the rollers 3a and 3b to generate heat by resistance. At the same time, pressure is applied to the wire from above and below by the pair of pressure contact rollers 4a and 4b, and the pair of pressure contact rollers 4c (4
In d), pressure is applied to the wire from the left and right. In this way, both the alloy wire 1 and the wound Al tape 2 are bonded to each other. At this time, the diameter of the wire rod and the energizing rollers 3a, 3
Although the resistance heating amount of the wire changes depending on the distance between b, if the temperature of the wire is too low, the joining force between the alloy wire 1 and the Al tape 2 becomes weak, and conversely if too high, the Al tape melts. Therefore, the temperature of the wire is usually 250 to 6
The energization amount is preferably controlled so as to be 00 ° C.

If the pressure applied to the wire rod by the pressure contact rollers 4a, 4b, 4c, 4d is too low, the joining force between the alloy wire 1 and the Al tape 2 will be weak, and if it is too high, it will depend on the wire temperature. However, since problems such as the local sticking of the Al tape 2 and uneven distribution of the joining force begin to occur, it is preferable that the pressure applied by these pressure rollers be 5 kg / mm ² or less.

In this way, the wire rod in which the Al tape is joined to the surface of the alloy wire 1 is next run to the wire drawing die 5, where it is wire-drawn to a predetermined wire diameter to form a clad wire material. Become. The area reduction rate at this time is set to 10 to 15%. When the area reduction rate is less than 10%, it becomes difficult to obtain a wire having a high roundness, and therefore, the amount of heat generated varies when used as a heater wire.
Further, when the surface reduction rate exceeds 15%, the roundness increases, but on the other hand, the following problem occurs.

The wire drawing process is not limited to the drawing process using a die, and may be performed by using a rolling roll, for example. The wire rod that has been drawn is then run into the oxidizing atmosphere furnace 6 where it is subjected to heat treatment. In this case, the firing temperature is preferably about 500 to 1000 ° C. The heating time is about 5 to 1200 minutes.

By this heating, the Al tape 2 wound around the outer circumference of the alloy wire 1 is oxidized from the outside, and the oxidized portion is converted into Al ₂ O ₃ . Then, mutual diffusion occurs between the alloy wire 1 and the Al tape 2 in the wire material, and a Ni—Al intermetallic compound such as Ni ₃ Al is generated outside the central alloy wire. Therefore, after firing, the outermost layer is an Al ₂ O ₃ layer having excellent corrosion resistance, a Ni-Al intermetallic compound layer having a relatively high resistance is interposed in the middle, and the core portion is made of the Ni-Cu-Al layer having the above composition. A wire made of an alloy is manufactured.

The heating conditions are the composition and diameter of the alloy wire used, the thickness of the Al tape, the oxygen concentration in the heating atmosphere,
It is determined by appropriately combining factors such as heating temperature and heating time. All of these factors regulate the thickness of the outermost Al ₂ O ₃ layer that affects the corrosion resistance and the thickness of the intermediate layer and the core that affect the specific resistance. It is determined from the relationship between the required specific resistance and corrosion resistance. For example, depending on the firing conditions, all of the Al tape in the wire is not made into Al ₂ O ₃ and a Ni-Al intermetallic compound, but a part of the Al tape is left, and the Ni-Al formed on the core part and the outside thereof. The intermetallic compound layer, the Al layer formed on the outer side thereof, and the Al ₂ O ₃ layer as the outermost layer may be used.

[0016]

Example: Cu: 15% by weight, Al: 5% by weight, balance:
An alloy consisting of Ni and inevitable impurities was melted, and the ingot was drawn to obtain an alloy wire having a wire diameter of 2.2 mm. This alloy wire 1 is continuously run in the system shown in FIG.
An Al tape 2 having a width of 30 mm and a width of 30 mm was wrapped with a wrap width of 2 mm. Electric current was applied between the electric current rollers 3a and 3b to bring the temperature of the wire material to 300 to 350 ° C., and a pressure of 5 kg / mm ² was applied from the outside of the wire material by the pressure contact rollers 4a, 4b, 4c and 4d.

Then, with a die 5, withdrawal with a surface reduction rate of 15%
After milling, inside the atmospheric atmosphere furnace 6 at 1000 ° C
Was run for about 60 minutes. The wire diameter of the obtained wire rod is 2.0 mm
And the cross-section was observed under a microscope, the composition of the core
Is Ni-15% Cu-5% Al and its diameter is 1.96 μm.
And Ni on the outside has a thickness of 19.5 μm.₃Al layer,
Furthermore, 0.5 μm thick Al is placed on the outer side.₂O ₃Layers formed
It was

The specific resistance of this wire was about 60 μΩ · cm. Next, the wire is energized to increase the surface temperature to 600,8.
The temperature is set to 00 ° C, and in each case 0.5% salt water is used.
5 ml was dropped onto the surface of the wire at a cycle of once every 2 minutes, and the number of drops until the wire was broken was measured. The number of drops until breaking was 80 and 110, respectively.

Normally, in the case of a nichrome heater wire rod, 800
Considering that the number of wire breaks under the above conditions at ℃ is about 40 times, the heater wire of the present invention has very excellent corrosion resistance.

[0020]

As is apparent from the above description, according to the method of the present invention, a heater wire having a high specific resistance and an excellent corrosion resistance at high temperature can be stably and inexpensively prepared with relatively simple equipment. Can be manufactured. Therefore, the heater wire produced by the method of the present invention is particularly useful as a heater for a microwave oven.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining the steps of the method of the present invention.

[Explanation of symbols]

 1 Ni-Cu-Al alloy wire 2 Al tape 3a, 3b Energizing roller 4a, 4b, 4c, 4d Pressure contact roller 5 Wire drawing die 6 Oxidizing atmosphere furnace

[Procedure amendment]

[Submission date] November 17, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

The wire drawing process is not limited to the drawing process using a die, and may be performed by using a rolling roll, for example. The wire rod that has been drawn is then run into the oxidizing atmosphere furnace 6 where it is subjected to heat treatment. In this case, the heating temperature is preferably about 500 to 1000 ° C. The heating time is about 5 to 1200 minutes.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

Then, the die 5 was used for drawing with a surface reduction rate of 15%, and then it was run in the atmospheric atmosphere furnace 6 at 1000 ° C. for about 60 minutes. The wire diameter of the obtained wire rod is 2.0 mm
As a result of microscopic observation of the cross section, the composition of the core portion was Ni-15% Cu-5% Al, the diameter was 1.96 mm , and the outside was a Ni ₃ Al layer having a thickness of 19.5 μm. Further, an Al ₂ O ₃ layer having a thickness of 0.5 μm was formed on the outer side.

Claims (2)

[Claims] 1. A continuous running Ni-Cu-Al alloy wire is wrapped with an Al tape, and the wire is heated while being energized and pressure is applied from the outside of the wire. % Of wire is drawn and then heated in an oxidizing atmosphere to produce a corrosion-resistant heater wire. 2. The Ni—Cu—Al alloy wire is Cu:
A method for producing a corrosion-resistant heater wire, which essentially comprises 10 to 50% by weight, Al: 1 to 7% by weight, and the balance: Ni.