JP2006288727A - Inner pot for cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inner pot for a cooker which keeps good appearance for a period longer than before without changing its original appearance when it is manufactured by avoiding discoloration of the outer side face of an inner pot body due to heating by an induction coil or due to erroneous placement of the pot directly over fire. <P>SOLUTION: A base metal layer containing at least Cu or Ni so as to cover the outer side face of the inner pot body heated by electromagnetic induction action using an induction coil of an electromagnetic induction heating cooker, and a surface metal layer formed of an alloy containing at least one of two kinds of metals Co and Sn, two kinds of metals Sn and Ni or three kinds of metals Sn, Ni and Cu is laminated on the base metal layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inner pot for a cooker used in combination with an electromagnetic induction heating cooker (so-called IH cooker) for cooking a cooked food by heating by an electromagnetic induction action using an induction coil.

  In recent years, electromagnetic induction heating cooking, in which cooking is performed by heating a cooked item by electromagnetic induction using an induction coil instead of heating by an electric heater, has been widely spread, particularly in the field of rice cookers. It's getting on.

  In this electromagnetic induction cooking device such as a rice cooker using electromagnetic induction heating cooking, Ni, Fe on the outer surface of the inner pan body made of a metal material having high thermal conductivity such as Al or its alloy. For example, an inner pot for a cooker (Patent Document 1) having a laminated structure provided with a heat generation layer made of a magnetic material such as a metal such as an alloy thereof, or the inner pot body itself, for example, a magnetic material such as magnetic stainless steel An inner pot for a cooker that is formed by the above process and omits the heat generating layer is used.

Moreover, it is common to coat a fluororesin or the like on the inner surface of the inner pot for cooking utensils in order to prevent the cooked food from being stuck or burnt. In addition, by forming a low resistance layer made of a metal having a lower electrical resistivity than the heat generation layer, such as Cu or Ni, on the outer surface of the inner pot body, the eddy current loss is increased by lowering the resistivity of the heat generation layer. It is also done. Thereby, the amount of heat generation can be increased with the thickness of the heat generation layer as it is, or the thickness of the heat generation layer can be reduced with the same amount of heat generation, thereby reducing the weight of the cooking pot.
JP-A-9-224819 (Claims 1 and 4, columns 0016 to 0017, columns 0030 to 0034) JP 2000-228279 A (claims 1 to 5, columns 0010 to 0011, columns 0012 and 0018)

  However, the inner pot for the rice cooker is exposed to hot water or heated steam while being heated by the induction coil of the rice cooker at the time of rice cooking, so that the metal surface of the inner pot body was exposed. The outer surface is easy to discolor. Moreover, discoloration is likely to occur locally in the area of the outer surface of the inner pot body facing the induction coil, and when such local discoloration occurs, uneven color unevenness occurs and the appearance is significantly worsened. There's a problem.

  Also, the discoloration can be any of Al and its alloys that form the inner pot body, magnetic stainless steel, a magnetic material that forms the heat generating layer formed on the outer surface of the inner pot body, and Cu that forms the low resistance layer. It also occurs on the metal surface. In particular, Cu forming the low resistance layer is easily discolored and discoloration is more conspicuous than other metals. Ni also changes color, although not as much as Cu.

  Therefore, in order to prevent discoloration, the outermost layer of the outer surface of the inner pot body is covered with an organic paint such as an epoxy resin, and is shielded from hot water and heated steam. Since the organic coating layer has low strength, for example, it easily peels off when the inner pot for a cooker is struck against something, and the exposed metal surface is discolored and the appearance becomes poor. There is a problem.

  In addition, for example, if the inner pot for a cooker having an organic coating layer is accidentally exposed to direct fire with a gas stove or the like, the coating layer will burn and the appearance will deteriorate further, and if the burning is bad, it will be used for cooking. There is also a problem that it cannot be used. Moreover, even if it does not have an organic coating layer, if the inner pot for a cooker is accidentally exposed to an open flame, the various metal surfaces are discolored and the appearance is remarkably deteriorated.

  The object of the present invention is that the outer surface of the inner pot body does not change color when heated by an induction coil, or does not change color when it is accidentally exposed to direct fire. An object of the present invention is to provide an inner pot for a cooker that can maintain a good appearance that does not change.

  The invention of claim 1 is an inner pot body heated by electromagnetic induction using an induction coil of an electromagnetic induction heating cooker, and at least Cu or Ni formed to cover the outer surface of the inner pot body. And a surface metal layer laminated on the base metal layer, the surface metal layer being made of two metals of Co and Sn, two metals of Sn and Ni, or Sn An inner pot for a cooker, characterized in that it is formed of an alloy containing at least one of three kinds of metals, Ni and Cu.

  The invention according to claim 2 is the inner pot for a cooker according to claim 1, wherein the surface metal layer is a Co—Sn alloy plating layer, a Sn—Ni alloy plating layer, or a Sn—Ni—Cu alloy plating layer.

  Invention of Claim 3 is an inner pot for cookers of Claim 1 whose average thickness of a surface metal layer is 0.01-10 micrometers.

  The invention according to claim 4 is the inner pot for a cooking appliance according to claim 1, wherein the base metal layer is a Cu plating layer or a Ni plating layer.

  Invention of Claim 5 is an inner pot for cookers of Claim 1 whose average thickness of a base metal layer is 0.5-50 micrometers.

  In invention of Claim 1, the surface metal layer formed in the outermost surface so that the outer surface of an inner pot main body may be covered is two types of metals, Co and Sn, two types of metals of Sn and Ni, Alternatively, it is formed of an alloy containing at least one of three kinds of metals, Sn, Ni, and Cu.

  Alloys composed of these two or three kinds of metals, that is, a Co—Sn alloy, a Sn—Ni alloy, and a Sn—Ni—Cu alloy (hereinafter, these three types of alloys may be collectively referred to as “black alloys”). ) Are known to be excellent in corrosion resistance, heat resistance, etc., as well as exhibiting black or a dark color that is hardly noticeable even when discolored, or a dark color close to it, as its inherent characteristics. . Therefore, the surface metal layer in the invention according to claim 1, which contains the two or three kinds of metals constituting these black alloys as an essential component, has characteristics as the black alloys, and electromagnetic induction. Even if it is heated by an induction coil of a cooking device or subjected to an open flame, it does not easily discolor, and since it is an alloy, there is no risk of scorching like an organic coating layer.

  And the said surface metal layer is firmly laminated | stacked on the outer surface of the inner pot main body through the base metal layer which contains the at least Cu or Ni which functions to relieve the internal stress of the said surface metal layer. Therefore, coupled with the fact that the surface metal layer itself contains an alloy that is harder than the organic material forming the organic coating layer, the inner pot for a cooker is struck against something, or repeatedly heated for cooking. However, it is also possible to prevent the surface metal layer from being cracked as a starting point of corrosion or from easily peeling off the surface metal layer. Therefore, according to invention of Claim 1, it becomes possible to provide the inner pot for cookers which can maintain the favorable appearance which is not different from the beginning of manufacture over a longer period than before.

  According to invention of Claim 2, the said surface metal layer does not contain other metals substantially other than said metals, such as said Sn which forms a black alloy, Co-Sn alloy plating layer, Sn-Ni alloy plating Or a Sn—Ni—Cu alloy plating layer. Therefore, these alloy plating layers further have the characteristics inherent to the black alloy, such as black color, which is difficult to be discolored as described above, or a dark color close to it, and good corrosion resistance, heat resistance, etc. It is excellent, and the inner pot for a cooker can be maintained for a longer period of time and in a good appearance that is the same as the original production. Moreover, each said plating layer can be formed in predetermined thickness using a simpler manufacturing equipment compared with the metal layer formed, for example by a vacuum evaporation method etc., and for a short time. Therefore, the cooking pot can be manufactured at a lower cost.

  According to the third aspect of the present invention, the average thickness of the surface metal layer is set to 0.01 μm or more to prevent the occurrence of pinholes as a starting point of corrosion in the surface metal layer, thereby improving its corrosion resistance. be able to. In addition, when the average thickness of the surface metal layer is set to 10 μm or less, the internal stress generated in the surface metal layer is suppressed, and when it is repeatedly heated for cooking, cracks that become the starting point of corrosion are generated. It can be prevented and its corrosion resistance can be improved.

  According to the invention described in claim 4, the base metal layer is formed of a Cu plating layer or a Ni plating layer, and the Cu plating layer or the Ni plating layer has an electrical resistivity higher than that of the heat generating layer as described above. For example, when the inner pot body is made of a metal material having a high thermal conductivity such as Al or an alloy thereof, and a heat generating layer made of a magnetic material is provided on the outer surface thereof. In addition, it is possible to increase the amount of heat generation while maintaining the thickness of the heat generation layer, or to reduce the thickness of the heat generation layer with the same heat generation amount, thereby reducing the weight of the inner pot for a cooker.

  In addition, since the Cu plating layer and the Ni plating layer also have better thermal conductivity than a magnetic material such as magnetic stainless steel, for example, the inner pot body is made of a magnetic material such as magnetic stainless steel. Moreover, the thermal conductivity of the entire inner pot for a cooker can be improved. Further, the Cu plating layer and the Ni plating layer can be formed to a predetermined thickness in a shorter time using a simpler manufacturing facility than a metal layer formed by a vacuum deposition method or the like. . Therefore, the cooking pot can be manufactured at a lower cost.

  According to the fifth aspect of the invention, the average thickness of the base metal layer is set to 0.5 μm or more, and the effect of relaxing the internal stress of the surface metal layer by the base metal layer is improved. It can laminate more firmly on the outer surface of the pan body. Therefore, it is possible to prevent the surface metal layer from being cracked as a starting point of corrosion, thereby reducing the corrosion resistance and preventing the surface metal layer from being easily peeled off. In addition, when the average thickness is set to 50 μm or less, the internal stress generated in the base metal layer itself is suppressed, and when repeatedly heated for cooking, the base metal layer and the surface metal layer thereon are corroded. It is possible to improve the corrosion resistance of both layers by preventing the occurrence of cracks as starting points.

  In this specification, the average thickness of each metal layer formed on the outer surface of the inner pot body, such as the surface metal layer, the base metal layer, and the heat generation layer, is represented by the value measured by the following procedure. To do. That is, as shown in FIG. 2, on a predetermined layer 7 formed on the outer surface 11 of the inner pot body 1, a line L intersecting a plane P including a central axis A passing through the center point C of the flat bottom 1 c. Is set on the line L, and points are set at regular intervals from the center point C, including the center point C, and the thickness of the layer 7 is measured for each point to obtain the average value. The average thickness.

  The inner pot for a cooker according to the present invention has a base metal layer containing at least Cu or Ni, which is formed so as to cover the outer surface of the inner pot body, and a surface metal layer laminated on the base metal layer. The surface metal layer is formed of an alloy containing at least one of two kinds of metals, Co and Sn, two kinds of metals, Sn and Ni, or three kinds of metals, Sn, Ni and Cu. And

  In addition, the surface metal layer was further excellent in the characteristics unique to the black alloy, such as the black color that is not easily noticeable, or a dark color close to it, and good corrosion resistance, heat resistance, etc. In order to achieve this, the surface metal layer is a black metal layer substantially free of other metals, that is, a Co—Sn alloy, Sn—Ni alloy, or Sn—Ni—Cu alloy layer. Is most preferred. Also, if other metals are included, the content ratio is 1% by weight or less, particularly 0.1% by weight or less of the total amount of the alloy forming the surface metal layer in order not to impair the above characteristics. It is preferable to do this.

  As the surface metal layer, those formed by various methods such as a vacuum deposition method can be adopted, all of which are formed by electroplating, Co—Sn alloy plating layer, Sn—Ni alloy. A plating layer or a Sn—Ni—Cu alloy plating layer is particularly preferred. These alloy plating layers substantially do not contain any other metal other than the above-mentioned two or three kinds of metals, or contain only a very small amount, if any, so that the color change is not noticeable, or a dark color close to it. In addition, it has excellent properties inherent to black alloys, such as good corrosion resistance and heat resistance. Moreover, since these alloy plating layers can be formed by electroplating using the inner pot body in which the base metal layer is previously formed as a cathode, compared to the base metal layer formed by vacuum evaporation or the like, There is also an advantage that it can be formed to a predetermined thickness in a shorter time using a simple manufacturing facility, and the cooking pot can be manufactured at low cost.

  Of the three types of alloy plating layers described above, the Co—Sn alloy plating layer is, for example, a Co using a stannate bath (alkaline Sn plating bath) containing a Co compound such as Co chloride and an Sn compound such as sodium Snate. -It can form by Sn alloy plating. The composition of the Co—Sn alloy plating layer is preferably such that Co is in the range of 15 to 40% by weight, particularly 25 to 35% by weight, and Sn is in the range of 60 to 85% by weight, particularly 65 to 75% by weight. . If the composition of the Co-Sn alloy plating layer is out of this range, it is inherent to the black alloy, such as black that is not easily discolored or a dark color close to it, or that has good corrosion resistance, heat resistance, etc. There is a possibility that a good surface metal layer having characteristics and glossy color tone cannot be formed.

  The Sn—Ni alloy plating layer is made of Sn—Ni alloy plating (stainless plating) using a fluoride bath or a pyrophosphate bath containing a Sn compound such as first Sn chloride and a Ni compound such as Ni sulfate. ). The composition of the Sn—Ni alloy plating layer is preferably such that Sn is in the range of 28 to 61 wt%, particularly 40 to 55 wt%, and Ni is 39 to 72 wt%, particularly 45 to 60 wt%. . When the composition of the Sn—Ni alloy plating layer is out of this range, it is inherent to the black alloy, such as black that is difficult to discolor, or a dark color close to it, or that has good corrosion resistance, heat resistance, etc. There is a possibility that a good surface metal layer having characteristics and glossy color tone cannot be formed.

  Furthermore, the Sn—Ni—Cu alloy plating layer can be formed by Sn—Ni—Cu alloy plating (black ternary alloy plating) using a pyrophosphate bath. The composition of the Sn—Ni—Cu alloy plating layer is as follows: Sn is 60 to 75% by weight, particularly 68 to 72% by weight, Ni is 24 to 30% by weight, particularly 26 to 28% by weight, and Cu is It is preferably in the range of 1 to 10% by weight, in particular 3 to 7% by weight. When the composition of the Sn—Ni—Cu alloy plating layer is out of this range, the black alloy is not easily discolored or has a dark color close to it, or has good corrosion resistance, heat resistance, etc. There is a possibility that a good surface metal layer having unique characteristics and having a glossy color tone cannot be formed.

  The average thickness of the surface metal layer is preferably 0.01 to 10 μm. When the average thickness of the surface metal layer is less than this range, a number of pinholes that are the starting points of corrosion are generated in the surface metal layer, which may reduce the corrosion resistance. In addition, when the average thickness of the surface metal layer exceeds the above range, the internal stress of the surface metal layer becomes large, and when it is repeatedly heated for cooking, cracks that become the starting point of corrosion are generated. May occur and corrosion resistance may be reduced.

  On the other hand, when the average thickness of the surface metal layer is within the above range, the occurrence of pinholes and cracks can be suppressed and the corrosion resistance can be improved. In consideration of further effectively suppressing the occurrence of pinholes and cracks and further improving the corrosion resistance of the surface metal layer, the average thickness is 0.1 to 5 μm even within the above range. In particular, the thickness is more preferably 0.5 to 2 μm.

  The base metal layer formed under the surface metal layer may contain at least Cu or Ni, and may be formed of an alloy of Cu or Ni and one or more of other metals. However, a Cu plating layer or a Ni plating layer which is substantially composed only of Cu or Ni and does not contain other metals is preferable. Since the Cu plating layer and the Ni plating layer are more flexible than the surface metal layer made of the black alloy or the like, the Cu plating layer and the Ni plating layer are excellent in the function of relaxing the internal stress of the surface metal layer.

  Further, as described above, the Cu plating layer and the Ni plating layer function as a low-resistance layer, and thus are made of a metal material having high thermal conductivity such as Al or an alloy thereof, By forming the Cu plating layer and the Ni plating layer so as to cover the outer surface of the inner pot main body including the region where the heat generating layer is formed of the inner pot main body having the heat generating layer made of the material, the thickness of the heat generating layer remains as it is. The heating value can be increased, or the heating value can be the same, and the thickness of the heating layer can be reduced to reduce the weight of the inner pot for a cooker.

  In addition, since the Cu plating layer and the Ni plating layer also have better thermal conductivity than a magnetic material such as magnetic stainless steel, when the inner pot body is made of a magnetic material such as the magnetic stainless steel, By forming the Cu plating layer or the Ni plating layer so as to cover the outer surface of the inner pot body, it is possible to improve the thermal conductivity of the entire inner pot for a cooker. In addition, since the Cu plating layer and the Ni plating layer are formed by electroplating using the inner pot body as a cathode, compared to a metal layer formed by a vacuum evaporation method or the like, using a simpler manufacturing facility, Moreover, it can be formed in a predetermined thickness in a shorter time. Therefore, the cooking pot can be manufactured at a lower cost.

  In addition, when the base metal layer contains a metal other than Cu or Ni, the ratio of the other metal is the ratio of the metal forming the base metal layer so as not to impair the effects of Cu and Ni described above. The total amount is preferably 5% by weight or less, particularly preferably 1% by weight or less.

  The average thickness of the base metal layer is preferably 0.5 to 50 μm. If the average thickness of the base metal layer is less than this range, the effect of relaxing the internal stress of the surface metal layer by the base metal layer cannot be sufficiently obtained. It cannot be firmly laminated, and the surface metal layer may be cracked as a starting point of corrosion, resulting in a decrease in corrosion resistance, or the surface metal layer may be easily peeled off. In addition, when the average thickness exceeds the above range, the internal stress of the base metal layer itself increases, so when repeatedly heated for cooking, the base metal layer and the surface metal layer thereon In addition, cracks that become the starting point of corrosion may occur, and the corrosion resistance of both layers may be reduced.

  On the other hand, if the average thickness of the base metal layer is within the above range, the internal stress of the surface metal layer can be well relaxed while suppressing the internal stress of the base metal layer itself. This problem can be prevented and the surface metal layer can be more firmly laminated on the outer surface of the inner pot body through the base metal layer. In addition, considering the fact that the stress of the surface metal layer is relaxed well and the surface metal layer is further strongly laminated on the outer surface of the inner pot body, the average thickness of the base metal layer is as described above. Even within the range, it is more preferably 1 to 30 μm, particularly 3 to 25 μm.

As the inner pot body whose outer surface is covered with the base metal layer and the surface metal layer in this order,
(1) Made of a metal material having high thermal conductivity, such as Al or an alloy thereof, and provided with a heat generating layer made of a magnetic material on the outer surface thereof;
(2) Any of magnetic materials such as magnetic stainless steel, in which the heat generating layer is omitted, can be used.

  Among these, the inner pot body of (1) is formed by drawing the plate material of the metal material. Although the thickness of the inner pot main body can be appropriately set in consideration of strength, thermal conductivity, etc., it is usually preferably about 0.5 to 5 mm. In particular, since the inner pan body made of Al or an alloy thereof is covered with an oxide film, the surface of the inner pot is oxidized prior to the formation of the heat generation layer, the base metal layer, and the surface metal layer on the outer surface. After removing the film and performing a zincate (zinc substitution) treatment to form an intermediate layer (zinc substitution plating treatment layer) made of Zn or an alloy thereof (alloy with Fe, Ni, Co, etc.), the above layers are laminated. It is preferable to do this.

  The heat generating layer formed on the outer surface of the inner pot body of (1) can be formed of an alloy that functions as a magnetic material. As an alloy for forming the heat generation layer, for example, various kinds that can function as a magnetic material containing two or more of Ni, Fe, and Co and having P, C, B, etc. added thereto as required In particular, a Ni—Fe alloy (Permalloy) is preferably used. The heat generating layer made of these alloys can be formed by electroplating using the inner pot body as a cathode, similarly to the alloy plating layer as the surface metal layer and the Cu plating layer as the base metal layer. The composition of the Ni-Fe alloy is preferably such that Ni is in the range of 40 to 90% by weight, particularly 70 to 85% by weight, and Fe is in the range of 10 to 60% by weight, particularly 15 to 30% by weight.

  The average thickness of the heat generation layer can be appropriately set in consideration of obtaining a sufficient amount of heat generation and strength, but is usually 10 to 200 μm, preferably 30 to 180 μm, and particularly preferably 40 to 160 μm. . In addition, when a Cu plating layer is formed on the heat generation layer as a base metal layer, as described above, the average thickness of the heat generation layer is set to be larger within the above range to increase the heat generation amount. It is possible to reduce the average thickness of the heat generation layer even within the above range and to reduce the weight of the inner pot for a cooking device. Moreover, as described in Patent Document 1, the heating layer can be formed only in a region of the inner pot body facing the induction coil to reduce the weight of the cooking pot.

  The heat generating layer formed by electroplating or the like is preferably heat treated to remove internal strain. That is, the heat generation layer formed by electroplating or the like on the outer surface of the inner pot body inevitably has internal strain, and the heat generation layer in the state where this internal strain exists is more than the state without internal strain. However, the permeability, which is a parameter that defines the eddy current loss and thus the amount of heat generation, is low, and the resistivity tends to be high. Therefore, the heat generating layer may not obtain a predetermined heat generation amount.

  In addition, the internal distortion is gradually alleviated by repeatedly generating heat using the inner pan body for cooking. However, the eddy current loss of the heat generation layer gradually increases, so that the eddy current loss of the heat generation layer increases. If the output to the induction coil of the electromagnetic induction heating cooker is set according to the initial value of, stable heating performance can be obtained due to aging current loss when using the electromagnetic induction heating cooker. There is also a risk of disappearing. Therefore, it is preferable to heat-treat the formed heat generating layer in advance prior to the use of the cooking pan for removing internal distortion.

  In addition, it is preferable to remove the internal strain from the base metal layer and the surface metal layer by heat treatment after the formation in order to prevent the occurrence of cracks and the like described above. The heat treatment may be performed separately every time the heat generation layer, the base metal layer, and the surface metal layer are formed. However, after forming all the layers, heat treatment is performed at once to simplify the manufacturing process. Is preferable. The heat treatment conditions are not particularly limited, but the heat treatment temperature is preferably 200 ° C. or higher, particularly 300 to 400 ° C. The heat treatment time is preferably 5 minutes or more, particularly 10 to 60 minutes.

  As the magnetic material forming the inner pan body of (2), for example, magnetic stainless steel such as SUS447J1 or YUS180 is preferably used in consideration of its strength, heat resistance, corrosion resistance, and the like. The thickness of the inner pan body made of such magnetic stainless steel can be appropriately set in consideration of its strength, thermal conductivity and the like, but is usually preferably about 0.5 to 5 mm.

  Since a strong passive film is present on the outer surface of the inner pan body made of magnetic stainless steel, good adhesion cannot be obtained even if a base metal layer and a surface metal layer are laminated thereon. Therefore, prior to the formation of the base metal layer, a strike nickel plating process accompanied by a large amount of hydrogen gas generation is performed, and nickel is electrodeposited while reducing and removing the passive film by the generated hydrogen gas, and then on it. It is preferable to laminate a base metal layer and a surface metal layer. Moreover, it is preferable to perform an electrolytic degreasing process, an acid activation process, etc. to the outer surface of the inner pot main body which consists of magnetic stainless steel before performing strike nickel plating. In addition, after laminating the base metal layer and the surface metal layer on the outer surface of the inner pan body made of magnetic stainless steel, heat treatment is performed under the same conditions as before to remove the internal strain of these layers. Is preferred.

  (1) The inner surface of the inner pot main body of (2) that accommodates the cooked food has a tetrafluoroethylene resin (PTFE), a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), a tetra A fluororesin such as fluoroethylene-hexafluoropropylene copolymer (FEP) may be coated. Other modifications can be made as appropriate without departing from the scope of the present invention.

Example 1:
<Preparation of the inner pot body>
As shown in FIG. 1 (a), the bottomed cylindrical shape and the cylindrical portion 1a gradually decrease in outer diameter from the upper opening 1b side toward the flat bottom portion 1c side, and the opening 1b. The inner pan body 1 having an outer diameter D of 150 mm, a height H of 150 mm, and a thickness T of 1.2 mm is used as a Japanese Industrial Standard JIS3004 Al alloy (MG-110, 0. 0 manufactured by Sumitomo Light Metal Co., Ltd.). 6 to 0.8 wt% Mg and 0.9 to 1.1 wt% Mn).

Specifically, the surface of the plate made of the Al alloy is electrolytically etched in an aqueous NaCl solution with an electric quantity of 20 coulomb / cm ² to form fine irregularities on the surface, and then PTFE dispersed on one side After the liquid is applied and baked to form a PTFE coating layer (thickness 20 μm), it is press-molded with the coating layer on the inside, and has the above dimensions and shape, and is attached to a commercially available IH rice cooker. The inner pot main body 1 which can be formed was formed.

  Next, the outer surface 11 of the inner pot body 1 was immersed in a 120 g / L sodium hydroxide aqueous solution kept at 80 ° C. for degreasing treatment, and then an alkaline etchant kept at 60 ° C. [Uemura Kogyo Co., Ltd. AZ-102] manufactured by AZ-102] was removed by immersing it in an aqueous solution of 50 g / L, washed with water, and then washed with a smut remover [trade name JISMatter AZ manufactured by Uemura Kogyo Co., Ltd.] at room temperature (23 ± 1 ° C.). -201] and nitric acid in an aqueous solution [concentration of smut remover 100 g / L, concentration of nitric acid 800 mL / L] to remove smut. Next, the plate material from which the smut was removed was immersed in a 3-fold diluted aqueous solution of a zincate treating agent [AZ-401 × 3, concentration: 300 to 360 mL / L manufactured by Uemura Kogyo Co., Ltd.], and zincated. A 1 μm zincate layer was formed.

  Next, the inner pot body 1 is mounted on the jig 2 as shown in FIG. 1 (b), and the jig 2 is rotated about its central axis 21 as shown by the arrow in the figure. Then, the Ni anode 3 and the Fe anode 4 are immersed in the following Ni—Fe plating bath 5 and electroplated under the condition of a bath temperature of 45 ° C., and the entire surface of the outer surface 11 is made of Ni—Fe alloy. Layer 7 was formed.

(Ni-Fe alloy plating bath composition)
Nickel sulfate hexahydrate: 105 g / L
Nickel chloride hexahydrate: 60 g / L
Boric acid: 45 g / L
Ferrous sulfate heptahydrate: 10 g / L
Additive FA-C: 20 g / L
Brightener FA-3: 25 mL / L
Brightener FA-RA: 2 mL / L
Brightener FA-4: 20 mL / L
Lubricant # 84: 2 mL / L
[Additives, brighteners, and lubricants are all manufactured by Ebara Eugene Corporation.]

  The average thickness of the formed heat generation layer was determined by the following procedure. That is, as shown in FIG. 2, on the heat generating layer 7 formed on the outer surface 11 of the inner pot body 1, a line L that intersects the plane P including the central axis A that passes through the center point C of the flat bottom 1 c. In addition to setting, on this line L, a point every 1 cm from the center point C including the center point C is set, and the thickness of the heat generating layer 7 is measured for each point, and the average value is obtained. Average thickness. The average thickness of the heat generating layer was 100 μm.

<Formation of base metal layer>
The inner pot body 1 on which the heat generating layer 7 is formed is rotated again around the central axis 21 of the jig 2 as shown by the arrows in the drawing, and instead of the Ni anode 3 and the Fe anode 4, they are not shown. Along with the Cu anode, the substrate was immersed in the following Cu plating bath 5 and electroplated under the condition of a bath temperature of 45 ° C., and a base metal layer made of Cu was laminated on the entire surface of the heat generating layer 7.

(Cu plating bath composition)
Copper sulfate pentahydrate: 210 g / L
Sulfuric acid: 55 g / L
Hydrochloric acid: 0.15 mL / L
Brightener (Makecap Kaparaside 210): 7mL / L
Brightening agent (caparaside 210A): 0.5 mL / L
Brightening agent (caparaside 210B): 0.5 mL / L
[Brighteners are manufactured by Atotech Chapan Co., Ltd., and Kaparaside is a registered trademark]

  The average thickness of the laminated base metal layer was determined by the following procedure. That is, for each point on the line L shown in FIG. 2 where the thickness of the heat generating layer was measured, the total thickness of the heat generating layer and the base metal layer was measured, and from the measured value, the thickness of the heat generating layer previously measured was measured. Subtraction was performed to determine the thickness of the base metal layer for each point, and the average value was determined as the average thickness. The average thickness of the base metal layer was 5 μm.

<Formation of surface metal layer>
The inner pot body 1 on which the base metal layer is formed is rotated again around the central axis 21 of the jig 2 as shown by the arrows in the drawing, and is not shown in place of the Ni anode 3 and the Fe anode 4. Along with the Sn anode, Ni anode, and Cu anode, it is immersed in a Sn—Ni—Cu alloy plating bath [trade name Nobroy SNC manufactured by Shimizu Corporation] 5 and electroplated at a bath temperature of 40 ° C., A surface metal layer made of a Sn—Ni—Cu alloy was laminated on the entire surface of the base metal layer.

  The average thickness of the laminated surface metal layers was determined by the following procedure. That is, for each point where the thickness of the heat generation layer and the base metal layer on the line L shown in FIG. 2 was measured, the total thickness of the heat generation layer, the base metal layer, and the surface metal layer was measured. The thicknesses of the heat generation layer and the base metal layer measured previously were subtracted to obtain the thickness of the surface metal layer at each point, and the average value was obtained as the average thickness. The average thickness of the surface metal layer was 0.5 μm.

<Finish>
The inner pot body 1 in which the above layers were laminated was heat-treated at 300 ° C. for 30 minutes in the air to produce an inner pot for a cooker.

<Cooking rice test>
The inner pot for a cooker manufactured in Example 1 was attached to a commercially available IH rice cooker, and while measuring the input power using a wattmeter, it took 2 rice to cook in an automatic rice setting. Time was measured. As a result, the input power was 1100 W, and the time until cooking was 48 minutes. For comparison, when a similar rice cooking test was conducted using Comparative Example 1 as an inner pot for a cooker, which was formed in the same manner as in Example 1 except that the surface metal layer was not laminated on the base metal layer, The input power was 1100 W and the time until cooking was 48 minutes. And from this, it was confirmed that the surface metal layer does not affect the rice cooking performance.

<Discoloration test 1>
Using the inner pot for the cooker of Example 1 and Comparative Example 1 above, cooking and washing with water, heating to 50 ° C. in the air and drying for 1 hour as one cycle was repeated, and the outer surface As a result of examining the discoloration state, it was confirmed that the copper color of the base metal layer was changed to a dull color when the two cycles were completed in the inner pot for the cooker of Comparative Example 1. On the other hand, the inner pot for a cooker of Example 1 showed no discoloration in the surface metal layer even after repeating 50 cycles.

<Discoloration test 2>
When the inner pot for a cooker of Example 1 and Comparative Example 1 was put in a furnace heated to 250 ° C. in the atmosphere for 3 hours and then heated, it was taken out and the discoloration state of the outer surface was examined. In the cooking pot, it was confirmed that the base metal layer had turned dark brown. On the other hand, almost no discoloration was seen in the surface metal layer of the inner pot for cooking appliances of Example 1.

<Corrosion resistance test>
About the inner pot for cooking appliances of Example 1, the salt spray test for 24 hours was implemented, and when the rating number (full scale of 10 points) which shows the degree of corrosion was calculated by the ratio of the corrosion area and the effective area, it was 9.8. It was confirmed that it had good corrosion resistance. Moreover, when the inner pot for a cooker after the salt spray test was put in a furnace heated to 250 ° C. in the atmosphere for 1 hour and then heated, it was taken out and the discoloration state of the outer surface was examined. There wasn't.

Fig. (A) is a half-sectional view of the inner pot body used in the embodiment of the present invention, and Fig. (B) is a heat generating layer, a base metal layer and a surface metal layer formed on the outer surface of the inner pot body by electroplating. It is sectional drawing which shows an example of the apparatus which forms. It is a perspective view explaining the procedure which measures distribution of thickness of the heat-generating layer, base metal layer, and surface metal layer which were formed in the said Example.

Explanation of symbols

1 inner pan body 11 outer surface

Claims (5)

  An inner pot body heated by electromagnetic induction using an induction coil of an electromagnetic induction heating cooker, a base metal layer containing at least Cu or Ni formed to cover the outer surface of the inner pot body, and A surface metal layer laminated on the base metal layer. The surface metal layer is composed of two kinds of metals, Co and Sn, two kinds of metals, Sn and Ni, or three kinds of Sn, Ni, and Cu. An inner pot for a cooking appliance, which is formed of an alloy containing at least one of metals.   The inner pot for a cooker according to claim 1, wherein the surface metal layer is a Co-Sn alloy plating layer, a Sn-Ni alloy plating layer, or a Sn-Ni-Cu alloy plating layer.   The inner pot for a cooker according to claim 1, wherein the average thickness of the surface metal layer is 0.01 to 10 µm.   The inner pot for a cooker according to claim 1, wherein the base metal layer is a Cu plating layer or a Ni plating layer. The inner pot for a cooking appliance according to claim 1, wherein the average thickness of the base metal layer is 0.5 to 50 µm.

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