JP3431712B2 - Stainless steel sheet for electromagnetic induction heating - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material for an inner pot used in an electromagnetic induction heating type rice cooker.

[0002]

2. Description of the Related Art As a material for an inner pot of an electromagnetic induction heating type rice cooker, pure Al and a clad material of SUS430 or SUS304 are used. In the rice cooker, a magnetic force generation coil is provided under the inner pot, and an induction current is generated inside the inner pot by magnetic force lines from this coil. SUS430 of the outer material of the inner pot
Or, since SUS304 has a larger electric resistivity than pure Al, it causes Joule heat generation due to the induced current, and the generated heat is transmitted through Al of the inner pot inner material with good thermal conductivity and enters the inner pot. Cook the rice with water. In order to prevent the cooked rice from sticking to the inner pot, it is necessary to coat the inner surface of the inner pot with a fluororesin, and Al is used for the inner material of the inner pot in terms of adhesion with the resin.

However, the pure Al used in the inner pot
The clad materials of SUS430 and SUS430 and SUS430 have extremely high manufacturing costs compared to the single materials, and the recycling system of the clad material is not socially well-established, so there is a big problem in processing scrap after disposal. is there. Further, in SUS430 or SUS304, electric resistivity is not sufficient, a large-capacity magnetic force generating coil is required, and if there is a restriction on the space for installing the coil, a heating wire must be provided as an auxiliary heating. I have to.

Therefore, there has been a strong demand for an inner pot material for electromagnetic induction heating which has good electromagnetic induction heating characteristics, high efficiency, and excellent adhesiveness with a fluororesin in a single material which can be easily scrapped. .

[0005]

DISCLOSURE OF THE INVENTION The present invention provides an inner pot material for electromagnetic induction heating which has good electromagnetic induction heating characteristics and excellent adhesion to fluororesin in a single material which can be easily scraped. The purpose is to provide.

[0006]

SUMMARY OF THE INVENTION The present invention is intended to achieve the above object, and the gist thereof is as follows. (1) In weight%, Cr: 10-35%, Al: 2.5
~ 10.0% as an impurity, C: 0.05%
Hereinafter, N: 0.05% or less, Mn: 2.0% or less, S:
The alloy composition is 0.01% or less and the balance is substantially Fe, and the electrical resistivity in the thin plate state is 110 to 110%.
200 μΩ · cm, surface roughness Ra is 0.02 to 3.0
μm, and the thickness of the Al oxide film in the surface layer is 80
Stainless steel thin plate for electromagnetic induction heating, characterized in that it is ~ 850Å.

(2) Further, Ti, Nb, Zr, V, W,
The stainless steel thin plate for electromagnetic induction heating according to item 1, which contains 1.0% or less in total of at least one of Ta, Hf, B and REM. (3) 10 or more in total of one or more of Ni, Mo, Cu and Co
% Or less, the stainless steel thin plate for electromagnetic induction heating according to item 1 or 2 above.

[0008]

The reason for limiting the present invention will be described in detail below. First, the reasons for limiting each element of the alloy of the present invention will be described. Cr is an essential element of stainless steel, and if it is less than 10%, corrosion resistance and oxidation resistance deteriorate. Also, Cr is 35
If it exceeds%, the steel becomes brittle and cannot be processed into an inner pot. Therefore, Cr is limited to 10 to 35%. A desirable range is 14 to 23%.

In the present invention, Al is a basic element for ensuring the electrothermal property, and if less than 2.5%, the desired electrical resistivity cannot be obtained. On the other hand, if the content exceeds 10.0%,
The toughness of the hot-rolled sheet is extremely lowered and the productivity is impaired. Therefore, Al is limited to 2.5 to 10.0%. A desirable range is 4.0 to 6.0%. When each of C and N is present in an amount exceeding 0.05%, the toughness of the hot rolled sheet is significantly reduced. Therefore, C and N are limited to 0.05% or less. The preferable range is 0.0 + 0.0% of the total amount of C + N.
It is 6% or less.

In the present invention, if a small amount of Mn acts as a deoxidizing agent, if it is contained in a large amount, it is concentrated particularly in the oxide film at the very early stage, which is harmful to the subsequent formation of an Al oxide film. This is a factor that causes structural defects to remain in the coating film and is therefore limited to 2.0% or less. Desirable range is 0.7
~ 2.0%. In the present invention, S is 0.01% or less in order to reduce the oxidation resistance.

Ti, Nb, Zr, V, W, Ta, Hf,
B forms nitrides or carbides to reduce solid solution C and N, and precipitates on dislocations introduced by reduction during hot rolling to refine the structure and further improve the toughness of the hot rolled sheet. Add as needed to improve. Further, REM represents a rare earth element, and Y, La, Ce, P
There are r, Nd, etc., and they are added as necessary in order to remarkably improve the oxidation resistance. When one or more of these elements are contained in a total amount of more than 1.0%, cold or hot workability is significantly deteriorated. Therefore, Ti, N
One or more of b, Zr, V, W, Ta, Hf, B, and REM were set to 1.0% or less in total.

Ni, Mo, Cu and Co are added as needed in order to remarkably improve the corrosion resistance. When one or more of these elements are contained in a total amount of more than 10%, cold or hot workability is significantly deteriorated.
Therefore, 1 or more of Ni, Mo, Cu and Co in total is 1
It was set to 0% or less. As a result of various studies on the relationship between the rice cooking condition and the electric resistivity of the inner pot material in the electromagnetic induction heating type rice cooker, the present inventors have found that the electric power of the inner pot material is set as a condition for uniformly heating the rice. Resistivity is 110-200
It was found to be μΩ · cm.

FIG. 1 shows the result of using an electromagnetic induction heating type rice cooker with a power consumption of 1300 W and putting 6 go of rice in an inner pot material having a plate thickness of 1 mm for 30 minutes. If the electric resistivity is less than 110 μΩ · cm, the cooked rice will be uneven depending on the position of the inner pot, and if it exceeds 200 μΩ · cm, the cooked rice grains tend to have a so-called core in which the surface layer is soft and the center is hard. Therefore, the electrical resistivity of the inner pot material is set to 110 to 200 μΩ · cm. A desirable range is 120 to 160 μΩ · cm.

As a result of various studies on the relationship between the adhesiveness with the fluororesin and the surface characteristics of the inner pot material, the present inventors have found that the surface roughness of the inner pot material is a condition for ensuring the adhesiveness with the fluororesin. Was 0.02 to 3.0 μm in Ra and the thickness of the Al oxide film in the surface layer was 80 to 850 Å. Fig. 2 shows the results of an examination of the relationship between the adhesion to fluororesin, the surface roughness of the material, and the thickness of the Al oxide film.
Shown in. If the surface roughness Ra of the material is less than 0.02 μm, there is no effect in securing the adhesiveness, and if it exceeds 3.0 μm, the adhesiveness deteriorates. Further, if the Al oxide film thickness is less than 80 Å, there is no effect in securing the adhesiveness, and if it exceeds 850 Å, the adhesiveness deteriorates. Therefore, the surface roughness Ra of the inner pot material was 0.02 to 3.0 μm, and the thickness of the Al oxide film in the surface layer was 80 to 850 Å. A desirable range is a surface roughness of 0.20 to 2.0 μ.
m, and the thickness of the Al oxide film is 100 to 300Å.

Although the details of the above reason are unknown,
Since the 1 atom has 3 outermost shell electrons, it has the property of receiving 4 electrons and stabilizing the electronic state, while the F atom has 7 outermost shell electrons. Donate electrons for 6
It has the property of stabilizing the electronic state of individual pieces. Therefore, it is presumed that electron affinity acts between Al atoms in the oxide film and F atoms in the fluororesin, and coating the fluororesin on the surface having the Al oxide film improves the adhesion.

In order to control the thickness of the Al oxide film on the surface, it is possible to carry out under the annealing atmosphere and annealing conditions in the finish annealing. The annealing atmosphere is preferably a mixed gas of N ₂ gas and H ₂ gas. When N ₂ gas exceeds 90% by volume, the oxidizing property becomes strong and exceeds 500Å, and when N ₂ gas is less than 10% by volume, the reducing property becomes strong. It is less than 25Å. Also, the annealing temperature exceeds 500Å above 1150 ° C,
Below ℃, it will be less than 25 Å, so 800-1150 ℃
Is desirable.

The surface roughness is preferably controlled by roll roughness in temper rolling after finish annealing.

[0018]

EXAMPLES Tables 1 and 2 (continued from Table 1) show the chemical composition of thin steel sheets of the present invention and comparative examples. Converter-VOD
Method or electric furnace-AOD method,
According to the conditions shown in (continued from Table 3), the plate thickness is 1 to 2 m.
manufactured to m. Power consumption is 13 when the rice is cooked.
Using a 00W electromagnetic induction heating type rice cooker, 6 go of rice was put in the inner pot material and cooked for 30 minutes. A is
Evenly cooked, there is no unevenness, and the surface and center of the cooked rice grains are in a soft state. B is cooked almost evenly and has no unevenness, and the cooked rice grains have a soft surface layer / center. In C, the cooked rice is slightly uneven, and the cooked rice grains have a slightly hard center. In D, the unevenness of the cooked rice is remarkable, and the center of the cooked rice grains is hard and has a core. Also,
For the evaluation of the adhesiveness with the fluororesin, the fluororesin is 20 cm.
After coating the corners, a material with ruled lines in a 2 cm square grid is used, and the temperature is 200 ° C for 12 hours (relative humidity 30
% For 6 hours, relative humidity 80% for 6 hours), and 50 ° C. × 6 hours (relative humidity 30% for 6 hours) as one cycle were subjected to a dry and wet heating test to investigate the peeling condition. ⊚ indicates no peeling at all, ◯ indicates peeling within 3 places, Δ indicates peeling within 4 to 10 places, and x indicates peeling at 11 or more places.

It can be seen that the inner pot material produced according to the present invention cooks rice evenly and evenly, and has good adhesion to the fluororesin so that the cooked rice does not stick to the inner pot.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

[Table 4]

[0024]

As is apparent from the above, according to the present invention, a single material that is easily scrap-processed has good electromagnetic induction heating characteristics and excellent adhesion to fluororesin. Can provide the inner pot material for.

[Brief description of drawings]

[Fig. 1] Using an electromagnetic induction heating type rice cooker with a power consumption of 1300W, 6 rices were put into an inner pot material with a plate thickness of 1 mm and cooked for 30 minutes, and as a result, the rice cooking condition and the inner pot material It is a figure which shows the relationship of the electrical specific resistance of.

[FIG. 2] Using a material in which a fluorocarbon resin is coated on a 20 cm square and then ruled lines are formed in a 2 cm square grid,
0 ° C x 12 hours (6 hours at 30% relative humidity, 8 hours relative humidity)
6 hours at 0%, 6 hours at 50 ° C (6 hours at 30% relative humidity)
As a result of performing a dry / wet heating test with one cycle as time, adhesion with fluororesin, surface roughness of material and Al
FIG. 3 is a diagram showing the relationship with the thickness of the oxide film of FIG.

Claims (3)

(57) [Claims] 1. Cr: 10 to 35% by weight, A
1: 2.5 to 10.0%, and as an impurity, C:
0.05% or less, N: 0.05% or less, Mn: 2.0%
Hereinafter, S: 0.01% or less, the balance is an alloy composition substantially consisting of Fe, and the electrical resistivity in the thin plate state is 110 to 200 μΩ · cm, and the surface roughness Ra is 0.0.
A stainless steel thin plate for electromagnetic induction heating, which has a thickness of 2 to 3.0 μm and an Al oxide film thickness in the surface layer of 80 to 850 Å. 2. Further, Ti, Nb, Zr, V, W, T
The stainless steel thin plate for electromagnetic induction heating according to claim 1, which contains 1.0% or less in total of at least one of a, Hf, B, and REM. 3. The stainless steel sheet for electromagnetic induction heating according to claim 1 or 2, which contains at least one kind of Ni, Mo, Cu and Co in a total amount of 10% or less.