JPH1041062A - Metallic plate and container for induction heating apparatus and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration in heat generating property, formability, corrosion resistance, etc., by forming a conductive layer having a specified rupture elongation value in part of external surface of aluminum or aluminum alloy material. SOLUTION: Part of external surface of a heating metal plate is formed with an electric conductive layer serving as a heat generating layer. The conductive layer is specified to have an elongation value of 1% to 30% at rupture. On the other hand, the aluminum plate used is a soft material and exhibits elongation of 30% to 50% at rupture. Therefore, if a conductive material combined with aluminum has an elongation of less than 1%, the conductive material develops defects such as cracks. As a result, forming process is difficult, and the material has a very small impact strength. The cracks in the conductive layer may lead to gap corrosion occurring on boundary surfaces of different metals. Furthermore, although the conductive layer has to be placed in alternating magnetic field to induce an eddy current in the conductive layer, heat generating property is remarkably reduced as the eddy current is interrupted by the cracks.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal plate for electromagnetic heating, a container for electromagnetic heating, and a method of manufacturing the same, and more particularly to a vessel used for an electromagnetic heating type cooking appliance and a metal plate used for the same.

[0002]

2. Description of the Related Art Conventionally, utensils used in electromagnetic heating type cooking utensils, for example, rice cooker inner pots, are made of a composite plate material of a magnetic metal plate such as iron or stainless steel which generates heat and an aluminum or aluminum alloy plate which performs heat conduction. It is manufactured by press forming such as deep drawing with the latter plate inside. Further, a coating of a fluororesin is generally applied to the inner inner surface to prevent sticking of the cooked rice. The composite plate material as the base material is, for example, a material obtained by cladding (compositing) a magnetic metal plate and aluminum or an aluminum alloy by roll rolling described in JP-B-54-3468 and JP-B-54-9985. Had been. Further, Japanese Patent Application Laid-Open No. 155035/1984 discloses that a magnetic metal layer is formed by thermal spraying on the outer surface of the bottom of a light metal container. It also discloses that the light metal has excellent thermal conductivity, so that the heat generated in the magnetic layer is uniformly transferred to the container, and that the thermal spraying is a low-cost coating method, so that the cost is low as a whole.

[0003]

The composite plate is manufactured by a clad method using roll rolling and is suitable for mass production. However, since it is made by roll rolling, the thickness of the aluminum or aluminum alloy is compressed and joined, and the thickness varies greatly.Therefore, in the process of pressing the clad plate, cracks or wrinkles often occur. There was a big problem in processing. Furthermore, the composite plate material, which is a material that receives heat, such as a magnetic metal plate such as iron or stainless steel, and an aluminum or aluminum alloy plate that receives heat, is both highly extensible and has a function to withstand rolling and forming. Must have
There are many limiting factors in material selection.

[0004] In recent years, in the cladding method by roll rolling, in which recycling of materials is regarded as important for effective use of industrial resources, a composite plate of a magnetic metal plate and an aluminum or aluminum alloy plate is prepared and then a predetermined plate is formed. Punched into shape. At this time, a large amount of blanking is a composite plate, and is not a simple metal plate like aluminum or an aluminum alloy plate, but is difficult to recycle, leading to high cost. Further, it is also difficult to manufacture a composite plate material in which a magnetic metal plate is provided in a predetermined portion of an aluminum or aluminum alloy plate in a necessary portion in advance. When a magnetic metal layer is formed by thermal spraying, the thermal spray coating itself does not have a metal structure and is difficult to plastically deform, so it is necessary to cover the magnetic metal layer after molding. That is, it is technically difficult to carry out the molding after the formation of the magnetic metal layer.
It is not disclosed in JP-A-9-155035. Further, there is a method of forming a magnetic metal layer on a container after molding, but there is a problem that corrosion resistance, impact resistance and workability are not sufficient.

Accordingly, an object of the present invention is to provide a metal container for electromagnetic heating having the following characteristics, a plate used for the container, and a method of manufacturing the same. (A) Have appropriate heat generation characteristics. (B) Forming is easy. (C) The selection range of the magnetic metal material is large. (D) The cost is low. (E) It has excellent corrosion resistance and impact resistance.

[0006]

According to the present invention, there is provided a magnetic metal layer (hereinafter simply referred to as a "conductive layer") formed on an outer surface of an aluminum or aluminum alloy plate as a heat conducting layer by electroplating having a breaking elongation of 1% or more and 30% or less. A layer). Further, it is preferable that the elongation at break of the conductive layer has a characteristic of 1% or more and 30% or less even after being molded into a container. % Or less. The occurrence of cracks and wrinkles during molding has almost no effect on the thickness or elongation of the aluminum or aluminum alloy layer, and the elongation at break of the conductive layer functioning as a heating layer for induction heating is important. It is important to form this conductive layer by electroplating in which non-oxidizing gas bubbling is performed constantly or intermittently from the viewpoints of elongation and thickness control of the conductive layer and manufacturing costs. The non-oxidizing gas refers to a mixed gas containing no inert gas such as nitrogen, argon, and helium and no oxygen atom.

Further, in the present invention, a conductive layer having a breaking elongation of 1% or more and 30% or less is formed on the outer surface of an aluminum or aluminum alloy container. The aluminum or aluminum alloy container used as the base material for electroplating is not only preformed into a container with a casting or the like, but also subjected to press forming and / or punching,
The conductive layer may be formed on the outer surface of a molded product made of cut aluminum or aluminum alloy.

The thickness of the conductive layer must be greater than the depth of the skin effect determined by the material of the conductive layer as compared with the frequency of the alternating magnetic field applied by the high-frequency heating. In addition,
Although there is no theoretical upper limit thickness, it is not necessary to be too thick from the viewpoint of processability and cost, and it is appropriate that the upper limit thickness is within twice the penetration depth.

In the present invention, it is possible to form a plate material, and a high degree of adhesion between the conductive layer and the heat conductive layer is required for the forming process. Therefore, aluminum or aluminum alloy which originally does not have high adhesion and at least part of the outer surface, an intermediate layer made of zinc or zinc alloy is formed,
It is preferable to form a conductive layer thereon.

As a specific example of the conductive layer, a single layer or a plurality of layers made of at least one of nickel or a nickel alloy, iron or an iron alloy, cobalt or a cobalt alloy is preferable. In order to further improve the heat generation characteristics, it is conceivable to increase the electric resistance by dispersing at least one element of P, C or B in these conductive layers.

In applications where the conductive layer is particularly required to have corrosion resistance, it is preferable to form a corrosion-resistant layer made of a heat-resistant resin such as ceramics, metal, or Teflon on the outermost surface of the conductive layer. In consideration of food hygiene and corrosion resistance, the conductive layer is preferably made of nickel, a nickel alloy, iron, or an iron alloy, and a metal layer having a thickness of 0.2 μm or more and 1 μm or less outside the conductive layer. It is preferable to apply a coating having a multilayer structure of chromium and chromium oxide.

Further, when used for cooking, it is preferable to coat the surface of aluminum or aluminum alloy with a fluororesin in order to prevent scorching on the inner surface.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A conductive layer functioning as a heat generating layer is formed on a part of the outer surface of a metal container for electromagnetic heating of the present invention or a metal plate used therein. It is specified that it is 1% or more and 30% or less. The reason why this elongation is necessary is as described in the present invention.
When a composite material is formed by laminating more than one kind of metal, the elongation of the composite material often follows the composite rule. This compound rule is an arithmetic mean weighted by the cross-sectional area ratio of the elongation of each material.

Further, the aluminum used in the present invention is a soft material and exhibits an elongation at break of 30 to 50%. In the case where the elongation of the conductive material composited with aluminum does not exceed 1%, that is, in a material having almost no elongation, when the composite material is formed, defects such as cracks are generated in the conductive material, and stress is concentrated on the cracks. . For this reason, it was found that the entire composite broke at a much smaller elongation than expected by the composite rule. For example, in the case of a composite material of an iron-nickel alloy material having a breaking elongation of about 0.8% and an aluminum alloy having a breaking elongation of 30%, a breaking elongation of 0.8% was observed. Thus, one of the materials to be composited is 1
%, The elongation of the composite material does not follow the composite rule even when the layers are sufficiently adhered to each other, and the elongation at break is determined by the elongation specified for a material having a small elongation. Found them.

The necessary material elongation differs depending on the processing shape and the processing conditions even in the molding process, but it has been found that the representative value examined by the inventors elongates at a maximum of 50% in the molding process. However, the elongation at break as a material is 5
It need not be 0% or more. The reason for this is that since the deformation of the molding process is a plastic deformation under constraint conditions, it does not have an end that is the base point of fracture, and a compressive force acts in the direction perpendicular to the elongation, so the elongation at break becomes considerably large . The rate at which this elongation is increased depends on the clearance between the mold and the mold,
Although it depends on the processing speed, the pressing force of the workpiece, and the like, it often extends 10 times or more.

[0016] Even when a heat conductive material composed of aluminum is formed and then a conductive layer is formed by an electroplating method, a molten metal forging, a thermal spraying method, or various vapor deposition methods, the elongation at break of the conductive layer is low and a composite rule is required. If you do not follow, if the molding material is hit by something harder or dents,
Cracks occur on the surface with dents. That is, the conductive layer forming a composite material with aluminum as in the present invention,
Elongation of 1% or more is required for moldability and impact resistance of the molded product.

The cracks in the conductive layer cause crevice corrosion occurring at the interface between dissimilar metals, and as the corrosion progresses, the adhesion of the entire coating layer is lost. In addition, the conductive layer is placed in an alternating magnetic field, and it is necessary that the magnetic field lines penetrate into the conductive layer to excite the eddy current. I do. This impact resistance was evaluated by considering the use at home as a result of holding the molded product on a concrete floor at a height of 1 m so that the bottom face down, and letting go of the hand to drop it I did it. As a result, even when the conductive layer was formed on the surface of the molding material, it was found that a sample having a breaking elongation of less than 1% requires cracks to occur on the surface, so that elongation of 1% or more was necessary.

The cracks in the conductive layer cause a decrease in heat generation characteristics due to the division of the eddy current and a cause of crevice corrosion as described above. Therefore, in the case where the conductive layer is formed in a plate shape and then the molding process is performed, the processing distortion removal processing is required for the strongly processed portion, that is, the side surface portion. When the elongation at break of the conductive layer is reduced to 1% or less due to work hardening due to strong working and the impact resistance is lost, it is possible to recover this by a long-time heat treatment. However, it is necessary to perform the heat treatment in an inert gas because the heat treatment has a long time and the conductive layer may be oxidized.

Preferably, the elongation at break of the conductive layer is 1% or more even after the forming process, so that the processing distortion removal treatment after the forming process is unnecessary. Therefore, when the conductive layer is formed in a plate shape in consideration of the work hardening due to the forming process, it is necessary to set the elongation at break of the conductive layer to 3% or more.

The conductive layer is a material that generates heat by eddy current generated by a high-frequency magnetic flux. In the high-frequency heating method, for example, a conductor is placed in an alternating magnetic field oscillated at a frequency of about 20 kHz used for household appliances. When it is arranged, an eddy current is generated, and heat is generated by Joule heat of this current.
For this reason, dimensions such as the material of the container and the thickness of the material are limited for efficient heating.

This is because the skin effect produced when a high-frequency current flows through a conductor such as a metal is significantly affected. Whether each material is suitable for the load of the electromagnetic cooker is determined by the skin resistance at the operating frequency. The conductive layer is not limited to the metal species, but can be used by increasing the specific resistance and increasing the skin resistance by alloying mainly with nickel or iron.

Further, in the present invention, elongation at break is important.
Although elongation at break is a mechanical property due to the material, it is greatly affected by the process being formed. In the present invention, the formation is mainly performed by the electroplating method in consideration of the cost. However, it is necessary to pay attention to the fact that the growth is particularly large during the electroplating. Generally, when obtaining a film with a large elongation by the electroplating method, the metal structure is refined by electrodeposition at a relatively large current density,
There is a reduction in the amount of brightener, which is an organic additive, and a decrease in residual stress due to a high electrodeposition temperature.

In the present invention, it goes without saying that these known findings are followed, but in the present invention, it has been found that dissolved oxygen in the electrolytic bath is important as a factor for increasing the elongation. When dissolved oxygen was present in the electrolytic bath, metal ions were oxidized, and it was confirmed that a small amount of metal oxide was formed and a high stress hard film was formed by electrodeposition from ions having a high valence.

Generally, in the plating operation, stirring by air bubbling is carried out to prevent surface pits and pits of the electrodeposited film. In the present invention, bubbling with a non-oxidizing gas such as nitrogen gas is performed during or at all times because the increase in the amount of dissolved oxygen greatly affects the elongation of the electrodeposited film due to the air bubbling.

This effect is particularly significant when the electrolytic bath contains iron. As an example, in the deposition of an iron-nickel alloy from a nickel bath containing iron ions, dissolved oxygen by air bubbling increases ferric iron ions during electrolysis and coexists with ferric ions required for electrodeposition. become. Electrodeposition from ferrous ions produces an iron-nickel alloy film with large elongation, but electrodeposition from trivalent iron ions generates an intermetallic compound Ni ₃ Fe, which, in addition to the effect due to stress, causes elongation at break. descend. In this case, the elongation is significantly reduced, and 1%
The breaking elongation of less than is remarkable when the amount of ferric iron exceeds 4% of the total iron ions.

Even when a conductive layer is formed on the surface of a molded product, the importance of elongation is reduced as much as the molding process. However, the film does not crack even when subjected to an impact that produces an indentation. As described above, a manufacturing process that takes into account elongation is required. In the case of a composite material, when cracks occur in the coating, the bonding interface between different metals is exposed, and crevice corrosion from the exposed interface proceeds, thereby increasing the risk of exfoliation of the entire coating.

There is no particular upper limit for the thickness of the conductive layer. However, in the case of a material having high cost and poor thermal conductivity, it is not necessary to exceed the thickness of aluminum. However, the lower limit is important. The thickness of the conductive layer serving as a heating element for effectively consuming the alternating magnetic flux generated by the high-frequency current and generating heat needs to be formed larger than the depth of the skin effect of the generated eddy current, that is, the penetration depth. .

This penetration depth is the thickness at which the eddy current near the surface of the conductive layer becomes 1 / e, that is, the thickness required for the magnetic flux density to attenuate by about 63%, which is 90% in terms of electric power.
About. In other words, when the thickness of the conductive layer is smaller than the penetration depth, the applied magnetic flux energy is not completely consumed, and the thickness of the conductive layer needs to be at least the penetration depth specified by the material. To consume nearly 100% of the generated magnetic flux, it is preferable that the magnetic flux is somewhat thick.

With respect to the material of the conductive layer, in order to efficiently generate heat, as a means for increasing the skin resistance, one of the materials for forming the conductive layer is nickel, nickel-chromium alloy, iron such as iron, permalloy or stainless steel. Use of an alloy or the like can be mentioned. In the present application, a nickel-iron alloy (iron content: 10 to 30%) is preferred as the most suitable material from the viewpoint of heat generation characteristics and industrial viewpoint.

At the time of electroplating or chemical plating, a phosphoric acid compound is added to a bath to form phosphorus eutectoid plating, for example, N 2
Carbon eutectoid plating, such as Ni-C plating, by adding i-P plating, Fe-P plating or a carboxylic acid compound.
By adding a boron compound such as Fe-C plating or aminoborane, boron eutectoid plating, for example, Ni-B,
Although Fe-B plating can be obtained, these can increase the skin resistance while almost maintaining the original magnetic properties and mechanical properties of the metal material, and are very effective for this application.

Further, since the surface of aluminum or aluminum alloy is covered with a layer mainly composed of aluminum oxide, it is necessary to provide a new metal surface to form a conductive layer film thereon with good adhesion. . There is a method of creating a new surface by electron or ion bombardment in a vacuum device, but in the case of electroplating or chemical plating,
It is suitable to use a zincate treatment as a technique for precipitating another kind of metal while dissolving the aluminum surface. In this zincate treatment, in the case of aluminum, zinc alone may be used, but in the case of an aluminum alloy, a zinc alloy containing elements such as iron, nickel, and cobalt is used in order to effectively increase adhesion.

When the conductive layer is made of nickel, a nickel alloy, iron or an iron alloy, it is preferable to coat with an anticorrosion layer in order to prevent discoloration of the metal. Therefore, the anticorrosion layer needs to be usable for food hygiene. For this reason,
A coating having a multilayer structure of metallic chromium and chromium oxide formed by electroplating from a dilute sulfuric acid bath is used as a corrosion protection layer.

In the case of electroplating, an electrolytic bath containing chromium ions in dilute sulfuric acid is used, and a two-layer structure having a hydrated chromium oxide layer on chromium metal is used, although the structure is slightly different depending on the plating conditions. Form a film. Although this film contains sulfate as an impurity, the corrosion resistance can be slightly improved by mixing a small amount of fluorine ions into the electrolytic bath. The thickness of the film is preferably 1 μm or less in order to absorb the magnetic lines of force and sufficiently reach the conductive layer.

Further, even when the elongation at break of the conductive layer is lower than the elongation at the time of molding, the thickness of the conductive layer is limited to the frequency of the eddy current only at the portion where the elongation at the time of processing does not exceed the elongation at break of the conductive layer. In comparison with the conductive layer material, a molding process can be performed by forming the conductive layer to be thicker than the skin effect depth determined by the material of the conductive layer.
Where the conductive layer is unnecessary without application of magnetic flux, it is not necessary to cover the conductive layer at all. However, if the conductive layer is sufficiently thin according to the composite rule with aluminum, or if the aluminum is sufficiently thick, the composite elongation is large. Therefore, molding processing becomes possible.

When the conductive layer is formed only partially on the aluminum or zinc base plating, the above-described crevice corrosion at the metal interface becomes a problem. Therefore, it is preferable to further cover the conductive layer and the entire gap. In this case, if coated with a metal having good electrical conductivity, the eddy current will flow in a short-circuit manner, and the resistance will not contribute to heat generation due to the small resistance, but will also exceed the allowable current of the high-frequency transmitter due to excess current. Circuit damage. Therefore, the present invention also contributes to heat generation to some extent and the electric resistance is one-third that of copper.
It is preferred to coat some nickel. Further, regarding the thickness, since the conductive metal functions as an electromagnetic shielding layer, if the conductive metal is thick, the magnetic flux attenuates to reach the conductive layer contributing to heat generation. For this reason, a thinner one is preferable. For example, in the case of nickel, the magnetic flux density attenuates to about 80% when the thickness near the surface is 100% at a thickness of 10 μm. If the material is coated with a material having sufficient elongation and low magnetic permeability, the attenuation rate is considered to decrease, and a thickness design corresponding to the magnetic permeability of the material is required.

As described above, the present invention shows, as a conductive layer, a metal material so as to have appropriate heat-generating properties, a range of mechanical properties excellent in workability and impact resistance, and a manufacturing process. It is also possible to form the conductive layer thickness with high precision by a plating technique.However, after processing aluminum or an aluminum alloy into a desired shape, a conductive layer is formed at a necessary portion to form the conductive layer. Easy going. In addition, it is possible to produce at low cost because the process used is electroplating or electroless plating with little loss of material.

[0037]

Embodiments of the present invention will be described below. Figures 1-5
7 is a schematic longitudinal sectional view for explaining the present invention. In FIG. 1, 1 is aluminum, 2 is an iron-nickel alloy film, in FIG. 2, 3 is a fluororesin, 4 is an aluminum alloy, 5 is a zinc base plating layer, 6 is a nickel-cobalt alloy film, and in FIG. Resin, 8 is an aluminum alloy, 9 is a zinc base plating layer, 10 is an iron-nickel alloy film, 11 is a nickel layer, and FIG. 4 is a cross-sectional view of a container formed by molding the plate shown in FIG. .

FIG. 5 shows an article obtained by treating a container-shaped aluminum base material, in which 12 is a fluororesin, 13 is an aluminum alloy, 14 is a zinc base plating layer, 15 is an iron-nickel alloy film, and 16 is metallic chromium. It is a chromium oxide composite film. FIG. 6 shows the shape of the test piece used when measuring the elongation at break.
FIG. 7 shows an article in which a conductive layer is formed on a pan-shaped aluminum base material. Reference numerals 17 and 21 denote fluororesins, 18 denotes an aluminum alloy, 19 denotes a zinc base plating layer, and 20 denotes a nickel-iron alloy film.

Example 1 Aluminum 1 in FIG. 1 is made of JIS1050 pure aluminum and has a size of 2.0.
A circle plate having a thickness of 425 mm and a thickness of 425 mm was used. This aluminum alloy plate is placed in a 120 g / L aqueous sodium hydroxide solution for 8 hours.
After treatment at 0 ° C., in a room temperature aqueous solution of oxalic acid 20 g / L,
Using the base material as an anode, a process of applying a voltage of 5 V for 60 seconds was performed. Then, 320 g / L of nickel sulfate heptahydrate,
Nickel chloride 20 g / L, ferrous sulfate heptahydrate 18 g /
L, boric acid 30 g / L, and an electrolytic bath to which hydroxylamine chloride NH ₂ OH.HCl 15 g / L was added as a stabilizer of ferrous iron, at a bath temperature of 60 ° C. and a cathode current density of 5 A / dm ² .
Ni / Fe25 of about 150 μm, which is a conductive layer, is formed on the aluminum alloy plate surface by performing a nitrogen gas bubble to perform processing.
% Coating 2 was formed. For comparison, a sample in which air bubbles were used instead of nitrogen gas bubbles was also prepared. The metal plate for the electromagnetic heater was manufactured using Matsushita Electric's IH cooker KZ.
The exothermic characteristics were investigated using P1.

As a comparative material, SUS4 having a thickness of 0.5 mm was used.
When a rolled material of 30 and the above-mentioned aluminum alloy plate was used, the surface temperature of the comparative material reached 60 ° C. in 10 seconds, whereas the material according to the present example reached 95 ° C. by heating for 10 seconds. Results were obtained. In addition, when the elongation at break was examined with a JIS No. 5 test piece (FIG. 6), the composite material showed a 35% elongation at break. Further, this test piece was treated with a 120 g / L aqueous sodium hydroxide solution at 80 ° C., only aluminum was dissolved, only the coating 2 was separated, and the elongation at break was measured.
%Met. The air-bubble-plated sample prepared for comparison was examined for elongation at break with a JIS No. 5 test piece, and showed a 0.8% elongation at break for the composite material. Press the cover plate with a hydraulic press to a depth of 100m so that the conductive layer is on the outside.
When processing was attempted into a pot shape having an inner diameter of 250 mm and an inner diameter of 250 mm, processing was possible without cracking. The comparative material broke at the side of the container, called a body crack, during molding.

The impact resistance was evaluated by dropping a 1 kg iron ball and visually observing the impacted portion. The part to be dropped was the side wall of the container where the elongation at break became the smallest due to work hardening by molding. In the case of the nitrogen gas bubble, as a result of observing the impacted portion, dents were observed, but no defects such as cracks were observed in the film. Further, with respect to the sample of the portion subjected to the impact, only aluminum was dissolved and only the coating 2 was separated, and the elongation at break was 1.5%.

Example 2 Aluminum 4 in FIG. 2 is made of JIS 3004 aluminum alloy MG-110 (manufactured by Sumitomo Light Metal) (Mg 0.6-0.8%, Mn 0.9-1.
1%), a 1.5 mm thick, 425 mmφ circle plate was used. Fluororesin 3 on one side of the circle plate
Was used. This substrate was immersed for 60 seconds in a 70 ° C. solution of 80 g / L of an SZ etching agent manufactured by Kizai Co., Ltd. to dissolve and remove the natural oxide film on the aluminum alloy surface. Thereafter, the substrate was immersed in a solution of 68% nitric acid at room temperature of 700 ml / L for 30 seconds to dissolve the strong oxide remaining on the surface. Next, it was immersed in a room temperature solution of Super Zincate SZ2 manufactured by Kizai Co., Ltd. for 60 seconds to replace and deposit zinc alloy 5 on the aluminum substrate. Thereafter, using an electrolytic bath of 135 g / L of nickel sulfate heptahydrate, 15 g / L of potassium chloride, 115 g / L of cobalt sulfate heptahydrate and 30 g / L of boric acid, a bath temperature of 60 ° C. and a cathode current density of 2 A / dm ² At 100m
The electroplating process was performed under nitrogen gas bubbling at 1 / min. As a result, the conductive layer of about 1
A Ni-Co 15% coating 6 of 00 μm was formed. The metal plate for the electromagnetic heater was created using Matsushita Electric's IH cooker KZP1.
Was used to investigate the heat generation characteristics.

According to the present embodiment, 10 seconds of heating
The temperature reached 0 ° C., and good results were obtained. In addition, when the elongation at break was examined using a JIS No. 5 test piece (FIG. 6), it was found that 5% was obtained for the composite material.
Showed the breaking elongation. Further, for the purpose of examining the elongation at break of only the conductive layer, a sample in which the adhesion of the conductive layer was lowered was prepared. Since the base material of this example is not pure aluminum but aluminum alloy, the method of peeling was selected without applying the method of melting aluminum of Example 1. Material of JIS3004 series aluminum alloy MG-1 which is the base material of this embodiment
Sample No. 10 was cut into the shape of a JIS No. 5 test piece and used as a test substrate. This substrate was immersed in a 70 ° C. solution of 80 g / L of an SZ etching agent manufactured by Kizai Co., Ltd. for 60 seconds to dissolve and remove the natural oxide film on the aluminum alloy surface.

Thereafter, it was immersed in a solution of 68% nitric acid at 700 ml / L at room temperature for 30 seconds to dissolve the strong oxide remaining on the surface in the same manner as described above. Next, a zinc alloy film was not formed for the purpose of reducing the adhesion of the plating film on the aluminum surface, and an electrolytic bath of nickel sulfate heptahydrate 135 g / L was used at a bath temperature of 60 ° C. and a cathode current density. 1 at 2 A / dm ²
Electroplating was performed under nitrogen gas bubbling at 00 ml / min. As a result, a Ni—Co 15% coating 6 of about 100 μm as a conductive layer was formed on both surfaces of the aluminum alloy plate. The end face of the test piece was polished, and only the conductive layer was peeled off to obtain a test piece. When the elongation at break of this test piece was investigated, it showed an elongation at break of 1.8%.

When the coated plate was processed by a hydraulic press into a rice cooker inner pot shape having a depth of 146 mm and an inner diameter of 221 mm so that the conductive layer was on the outside, it could be processed without cracking. In this molding process, a maximum of 50
% Elongation was confirmed. In the rising part from the bottom part to the side part, the elongation was 5%. Rice cooked using a commercially available jar rice cooker. We confirmed that we could cook rice without any problems. In order to evaluate the elongation of the conductive layer after molding, a sample was prepared using the above-described peeling method. The elongation at break is 1.5% at the part that has been processed by 5%.
The elongation at break was reduced to 0.8% at the part that had been processed by 50%. When heat treatment was performed at 400 ° C. for 2 hours for recovery of elongation and impact resistance, the elongation at break of the conductive layer was about 3% at any part due to softening. When the impact resistance test was performed on the side surface of the molded product, dents were observed but no cracks were observed.

Embodiment 3 Aluminum 8 in FIG. 3 is made of JIS 3004 aluminum alloy MG-110 (manufactured by Sumitomo Light Metal) (Mg 0.6-0.8%, Mn 0.9-1.
1%), a 1.5 mm thick, 425 mmφ circle plate was used. Fluororesin 7 on one side of the circle plate
Was used. This substrate was immersed for 60 seconds in a 70 ° C. solution of 80 g / L of SZ etching agent manufactured by Kisai Co., Ltd. to dissolve and remove the natural oxide film on the surface of the aluminum alloy. Thereafter, the substrate was immersed in a solution of 68% nitric acid at room temperature of 700 ml / L for 30 seconds to dissolve the strong oxide remaining on the surface. Next, Super Zincate SZ2 manufactured by Kizai Co., Ltd.
Was immersed in the solution at room temperature for 60 seconds to replace and deposit zinc alloy 9 on an aluminum substrate. Thereafter, a shielding plate having a through-hole having a diameter of 120 mm was arranged between the base material and the anode in the electrolytic bath, and electroplating was performed mainly at the center to produce a raised conductive layer 10.

The electroplating solution used at this time was 480 g / L of nickel sulfamate tetrahydrate, 25 mg of iron sulfate heptahydrate.
g / L, boric acid 30 g / L, sodium gluconate 20
g / L, sodium saccharin 1 g / L, sodium lauryl sulfate 0.1 g / L, NH ₂ SO ₃ H sulfamate
Using 15 g / L, bath temperature 45 ° C, cathode current density 25A
/ Dm ² under a nitrogen gas bubble of 100 ml / min to form a conductive layer of about 150 μm Ni-20% Fe coating (permalloy) 10 on the aluminum alloy plate surface.
After the surface of the substrate was washed with 10% hydrochloric acid, the cathode current density was 20 A / dm in a 50 ° C. solution of 680 g / L of nickel sulfamate tetrahydrate, 20 g / L of nickel chloride hexahydrate and 40 g / L of boric acid. ^The treatment was performed in Step ² , and nickel plating 11 was formed on the surface of the nickel-iron alloy film 10 to about 10 μm. Further, for the purpose of examining the elongation at break of only the conductive layer, a test piece was prepared in the same manner as in Example 2, and the elongation at break of this test piece was examined. As a result, the elongation at break was 7%.

As shown in FIG. 4, the coated plate was processed into a rice cooker inner shape having a depth of 146 mm and an inner diameter of 221 mm so that the conductive layer was on the outside as shown in FIG. . In this molding process, a maximum elongation of 50% was confirmed in the side surface portion. In the rising part from the bottom part to the side part, the elongation was 5%. When the molded product was cooked using a commercially available jar rice cooker, it was confirmed that rice could be cooked without any problem. A test piece was prepared in the same manner as in Example 2 for the elongation at break of only the conductive layer of this container, and the elongation at break was 2% and 5% at the side where the elongation of 50% occurred. 5. Elongation at break at rising portion from bottom to side
5%. Further, when the impact resistance test was performed on the side surface portion where the breaking elongation became the smallest, dents occurred but no cracks were observed.

Example 4 Material JIS 3004 aluminum alloy MG-110 (manufactured by Sumitomo Light Metal) (Mg 0.6
(Including 0.8-1.1% and Mn 0.9-1.1%) in the shape of a pot as shown in FIG. The size of the molded product of the aluminum alloy 13 was 146 mm in depth and 221 mm in inner diameter, and the inner surface of the kettle was coated with the fluororesin 12. This molded product is called SZ
It was immersed in a solution of 80 g / L of an etching agent at 70 ° C. for 60 seconds to dissolve and remove the natural oxide film of the aluminum molded product. Then, it was immersed in a 68% nitric acid room temperature solution of 700 ml / L for 30 minutes to dissolve the strong oxide remaining on the surface. Next, it was immersed in a room temperature solution of Sparzincate SZ2 manufactured by Kizai Co., Ltd. to replace and precipitate zinc alloy 14 on the outer surface of the aluminum molded product.

Using this molded product as a base material, a nickel-sulfamate tetrahydrate 480 g /
L, 25 g / L of iron sulfate heptahydrate, 30 g / L of boric acid, 15 g / L of hydroxylamine hydrochloride NH2OH.HCl, 1 g / L of sodium saccharin, 0.1 g of sodium lauryl sulfate
g / L, using 15 g / L of sulfamic acid NH2SO3H,
100 m at a bath temperature of 45 ° C. and a cathode current density of 25 A / dm ²
1 / min under nitrogen gas bubbling, and a conductive layer of about 150 μm Ni-
An Fe 20% film 15 was formed. Aiming to improve corrosion resistance,
Using an aqueous solution of 40 g / L of chromic anhydride and 45 g / L of sulfuric acid as an electrolytic solution, plating was performed at a current density of 5 A / dm ² for 10 minutes. Then, the metal chromium / chromium oxide composite layer 16
Was formed about 1 micron.

When the processed container was cooked using a commercially available jar rice cooker, it was confirmed that rice could be cooked without any problem. Furthermore, when the corrosion resistance was evaluated based on the salt spray test method of container JISZ2371,
In a sample in which the conductive layer was exposed without performing plating treatment with an aqueous solution of chromic anhydride and sulfuric acid, discoloration to a little brown was confirmed by a treatment for about 50 hours, but in a sample prepared according to this example, 1000 No discoloration was observed even with the time treatment.

For the purpose of examining the elongation at break of only the conductive layer, a sample in which the adhesion of the conductive layer was lowered was prepared. The molded product is made of Kisai Co., Ltd. SZ etching agent 80g / L
Was immersed in a 70 ° C. solution for 60 seconds to dissolve and remove the natural oxide film on the aluminum alloy surface. After that, 700% of 68% nitric acid
It was immersed in a room temperature solution of ml / L for 30 seconds to dissolve the strong oxide remaining on the surface in the same manner as described above. Next, a zinc alloy film was not formed for the purpose of reducing the adhesion of the plating film on the aluminum surface, and nickel sulfamate tetrahydrate 480 g / L, iron sulfate heptahydrate 25 g / L, boric acid 30g / L, hydroxylamine hydrochloride NH2OH.HCl1
5 g / L, saccharin sodium 1 g / L, sodium lauryl sulfate 0.1 g / L, sulfamic acid NH2SO3H1
5 g / L, bath temperature 45 ° C, cathode current density 25A
/ Dm ² under bubbling of nitrogen gas at 100 ml / min, and a conductive layer of about 150 μm
Was formed. The molded product was cut, and only the conductive layer was peeled off. The conductive layer peeled from the bottom of the kettle was adjusted to the shape of a JIS No. 5 test piece to obtain a test piece. When the elongation at break of this test piece was examined, it showed an elongation at break of 7%.

Example 5 Aluminum Cast AC4C
(Si 6.5-7.5%, other Cu, Fe, Mn, Mg,
7 may be included as impurities), and the thickness is 5 mm in the vicinity of the handle and the center of the body, and 10 m in the lower half and the bottom of the body, as shown in FIG.
m molded product 18 was used as a substrate. This molded product had a depth of 180 mm and an inner diameter of 210 mm. The inner surface of the pot was coated with a fluororesin 17 by sandblasting and then baked. The coating of the fluororesin may be performed simultaneously on the inner and outer surfaces after the coating of the conductive layer.

The molded product was treated with 80 g / L of SZ etching agent 7
It was immersed in a 0 ° C. solution for 80 seconds to dissolve and remove the natural oxide film of the aluminum casting. Then, 700 ml / L of 68% nitric acid
Was immersed in a room temperature solution for 30 seconds to dissolve the strong oxide remaining on the surface in the same manner as described above. Next, Super Zincate SZ
2 was immersed in a room temperature solution to replace and precipitate zinc alloy 19 on the outer surface of the aluminum molded product. In order to improve the adhesion, after the substitution precipitation, immersion was performed in a room temperature solution of 68% nitric acid at 700 ml / L for 20 seconds to partially dissolve the zinc, and further immersed in a room temperature solution of Super Zincate SZ2. The zinc alloy was replaced and precipitated again on the outer surface.

Using this molded product as a base material, the Fe—Ni plating bath used was 320 g / L of nickel sulfate heptahydrate, 20 g / L of nickel chloride, 18 g / L of ferrous sulfate heptahydrate,
An electrolytic bath containing 30 g / L of boric acid and 20 g / L of sodium ascorbate as a stabilizer of divalent iron was used. The bath temperature was 60 ° C., the cathode current density was 25 A / dm ² , and the concentration was 100 ml / L.
For about 150 μm, which is a conductive layer, on the aluminum alloy surface.
% Iron-nickel alloy film 20 was formed. For comparison, a sample in which air bubbles were used instead of nitrogen gas bubbles was also prepared. The thickness of the film was set so that the bottom of the intervening portion was thicker by arranging the anode in the plating process on the side surface or the side surface of the pot. The thickness of 150 μm described in this example is the thickness of the bottom of the pot, and was about 10 μm near the center of the body. After the outer surface of the conductive layer was subjected to blasting for the purpose of improving the corrosion resistance, a baking coating of the fluororesin 21 was performed similarly to the inner surface.

When the processed container was cooked using a commercially available jar rice cooker, it was confirmed that rice could be cooked without any problem. Further, the container is JISZ2371
When the corrosion resistance was evaluated based on the salt spray test method, no discoloration was observed in the sample prepared according to the present example even after the test for 1000 hours. Further, the breaking elongation of only the conductive layer was performed by cutting the molded product in the same manner as in Example 4.
Only the conductive layer was peeled off. The conductive layer peeled from the bottom of the kettle was adjusted to the shape of a JIS No. 5 test piece to obtain a test piece. When the elongation at break of this test piece was examined, it showed an elongation at break of 7%.

The bottom surface and the side surfaces were subjected to the above-mentioned impact resistance test. As a result of observing the impacted portions, dents were observed, but no defects such as cracks were observed in the film. . Similarly, the impact resistance test was performed on the bottom and side surfaces of the container by air bubbling. As a result, in the case of the air gas bubble, as a result of observing the impacted portion, a clear crack was confirmed around the dent, and the tip of the crack reached aluminum. When the heat generated in the cracked kettle was examined using an IH cooker KZP1 manufactured by Matsushita Electric, the rise in surface temperature was small, and only a rise of about 20 ° C. in 10 seconds was confirmed.

[0058]

The container for an electromagnetic heater according to the present invention comprises a metal plate having a conductive layer having an elongation at break of 1% or more and 30% or less formed on at least a part of the outer surface of aluminum or aluminum alloy by electroplating. Even if it is molded into a vessel such as a rice cooker, it does not break, and an efficient heat generating layer can be formed.

Since the conductive layer is a metal or alloy layer that becomes a heating element when an eddy current generated by a high-frequency magnetic flux flows, an efficient heating layer can be formed. Further, since the thickness of the conductive layer is formed to be greater than the depth of the skin effect determined by the frequency of the eddy current and the material of the conductive layer, an efficient heat generating layer can be formed.

The thickness of the conductive layer is determined by the frequency of the eddy current and the material of the conductive layer after the metal plate is formed within a range in which the elongation of the conductive layer does not exceed the elongation at break. Since it is formed before molding so as to be thicker than the depth of the determined skin effect, it is possible to form the initial heat generating layer even when molded into a rice cooker jar. Since the intermediate layer made of zinc or a zinc alloy is formed between the outer surface of aluminum or an aluminum alloy and the conductive layer, the conductive layer can be in close contact with the conductive layer.

As the conductive layer, a single layer or a plurality of layers made of at least one of nickel or nickel alloy, iron or iron alloy, cobalt or cobalt alloy is subjected to electroplating by non-oxidizing gas bubbling.
Cracking does not occur in the conductive layer, and the conductive layer can be made relatively inexpensive and appropriately formed with a suitable thickness, so that efficient heat generation can be obtained. Since at least one element of phosphorus, carbon, or boron is further dispersed in the conductive layer, the heat generation efficiency of the conductive layer can be increased.

Since a corrosion-resistant layer of a chromium layer is formed outside the conductive layer, it is not corroded for a long time. Since the metal chromium and chromium oxide having a multilayer structure having a thickness of 0.2 to 1 μm are provided outside the conductive layer, they are not corroded, so that hygiene can be maintained for a long period of time. Since the outer surface of the aluminum or aluminum alloy is covered with the fluororesin, it is not corroded and hygiene is maintained. Since the container is molded so that the conductive layer is on the outside, a molded product for electromagnetic heating such as a rice cooker can be obtained relatively easily.

[Brief description of the drawings]

FIG. 1 is a schematic vertical sectional view of an aluminum plate showing an embodiment of the present invention.

FIG. 2 is a schematic longitudinal sectional view of an aluminum plate showing another embodiment of the present invention.

FIG. 3 is a schematic vertical sectional view of an aluminum plate showing another embodiment of the present invention.

FIG. 4 is a schematic vertical sectional view of a container formed by processing the aluminum plate shown in FIG. 3;

FIG. 5 is a schematic vertical sectional view of a container subjected to a process according to an embodiment of the present invention.

FIG. 6 shows the shape of a test piece used for measuring elongation at break.

FIG. 7 is a schematic longitudinal sectional view of a container subjected to a treatment according to another embodiment of the present invention.

[Explanation of symbols]

 1: Aluminum, 2, 15, 20: Iron-nickel alloy coating, 3, 7, 12, 17, 21: Fluororesin, 4, 8, 13, 18: Aluminum alloy, 5, 9, 14, 19: Zinc base plating Layers 6, 10: Nickel-cobalt alloy film, 11: Nickel layer, 16: Metallic chromium oxide composite film

 ──────────────────────────────────────────────────の Continued on front page (72) Inventor Masaya Nishi 950 Noda, Kazatori-cho, Sennan-gun, Osaka Sumitomo Electric Industries, Ltd.

Claims (10)

[Claims] 1. A metal plate for an electromagnetic heater, wherein a conductive layer having a breaking elongation of 1% or more and 30% or less is formed on at least a part of the outer surface of aluminum or an aluminum alloy by electroplating. 2. The electromagnetic heating metal plate according to claim 1, wherein the breaking elongation of the conductive layer is 3% or more. 3. The metal plate for an electromagnetic heater according to claim 1, wherein an intermediate layer made of zinc or a zinc alloy is formed between aluminum or an aluminum alloy and the conductive layer. 4. A container for an electromagnetic heater, wherein a conductive layer having a breaking elongation of 1% or more and 30% or less is formed on at least a part of an outer surface of a container made of aluminum or an aluminum alloy by electroplating. 5. The container for an electromagnetic heater according to claim 4, wherein an intermediate layer made of zinc or a zinc alloy is formed between aluminum or an aluminum alloy and the conductive layer. 6. A conductive layer having an elongation at break of 1% or more and 30% or less formed on at least a part of an outer surface of an aluminum or aluminum alloy plate is formed by an electroplating method of bubbling a non-oxidizing gas in an electrolytic bath. A method for producing a metal plate for an electromagnetic heater, comprising: 7. The elongation at break formed on at least a part of the outer surface of the aluminum or aluminum alloy container is 1%.
A method for producing a container for an electromagnetic heater, wherein the conductive layer of 30% or less is formed by an electroplating method in which a non-oxidizing gas is bubbled in an electrolytic bath. 8. An elongation at break of 1% or more on at least a part of the outer surface of the aluminum or aluminum alloy plate.
% Or less as a conductive layer, wherein a nickel-iron alloy film deposited by performing non-oxidizing gas bubbling from an electrolytic bath in which trivalent ions of iron are 4% or less of the total iron ion amount is coated with a thickness of 40 μm or more. A method for producing a metal plate for an electromagnetic heater. 9. An aluminum or aluminum alloy container having an elongation at break of at least 1%
As a conductive layer of 0% or less, a nickel iron alloy film deposited by performing non-oxidizing gas bubbling from an electrolytic bath in which trivalent ions of iron are 4% or less of the total amount of iron ions is coated with a coating of 40 μm or more. Of producing a container for an electromagnetic heater. 10. A method for producing a metal container for electromagnetic heating, wherein the metal plate for an electromagnetic heater according to claim 6 or 8 is formed into a container such that the conductive layer is on the outside.