JP6908982B2 - Surface-treated metal parts, heating appliances - Google Patents

Description

The present invention relates to metal members used for appliances that are exposed to direct fire during heating, such as gas stoves, grills, and trivets, and metal members used in high temperature environments, such as heater parts, drying and firing furnaces, and boiler piping. In the present invention, the present invention relates to a surface-treated metal member capable of effectively preventing discoloration by preventing oxidation of a metal due to high temperature, and a heating appliance in which the surface-treated metal member is used.

Stainless steel has an extremely thin, highly protective passivation film with a thickness of several nm to several tens of nm, and exhibits excellent corrosion resistance and heat resistance while maintaining a beautiful metallic luster. For this reason, conventionally, heating appliances such as gas stoves, grills, trivets, gas burners, etc. that are exposed to direct flames during heating, and equipment used in high temperature environments such as heater parts, drying and baking furnaces, boiler piping, etc. are configured. It is used as a material for grilling.

However, the surface of this stainless steel may be discolored and colored in an environment exposed to an open flame as described above or in a high temperature environment, so-called temper color may occur. Such discoloration of stainless steel is based on the fact that the stainless steel is oxidized by high temperature to form an oxide layer. When the thickness of this oxide layer matches the wavelength of light, the reflected light interferes and is recognized as a color difference. When such discoloration due to oxidation appears on the surface of stainless steel as a metal member, it gives the impression that the appearance and design are rapidly deteriorated. In particular, heating appliances such as trivets, gas stoves, and gas burners may show such discoloration just by touching an open flame, even though it has not been so many days since they were purchased. It gives the impression that it is suddenly out of date.

Therefore, a technique capable of preventing discoloration due to oxidation of stainless steel in a high temperature environment has been studied conventionally. First, Patent Document 1 discloses a technique in which a reaction layer having a thickness of 5 to 100 nm is interposed between a steel base and an alkali silicate film in a stainless steel material having an alkali silicate film on its surface. Through this reaction layer, it is expected that the diffusion of atoms into the alkali silicate film covering the surface of the steel material will be suppressed, the formation of the Cr-Fe-O oxide layer that causes the generation of temper color will be stopped, and discoloration will be prevented. It was done.

Further, Patent Document 2 discloses a technique of coating a surface of stainless steel with an oxide layer made of a silica-based compound having a thickness of 1 μm or less. Since this silica-based compound is an oxide in which oxygen diffusion is slow, it is expected that discoloration can be prevented by suppressing the progress of oxidation occurring in the vicinity of the surface of stainless steel.

Further, Patent Document 3 is expected to prevent discoloration by forming a coating film made of polysilazane on the surface of stainless steel, thereby suppressing the progress of oxidation that also occurs in the vicinity of the surface of stainless steel. It is a thing.

However, according to the disclosed technology of Patent Document 1-3, although it is possible to prevent discoloration due to oxidation of stainless steel at high temperatures, stainless steel used in an environment of 700 ° C. or higher during heating is used. There is a problem that discoloration due to oxidation cannot be sufficiently prevented, and appearance abnormalities other than discoloration due to oxidation such as cracking and whitening of the coating film cannot be suppressed.

Further, Patent Document 4 discloses a technical idea of using an alumina thin film as an oxidation-suppressing film. Alumina thin film has excellent film forming properties, compactness, thermal stability, electrical insulation, etc., and although it can certainly prevent discoloration due to oxidation of stainless steel at high temperatures, it can be used in an environment of 700 ° C or higher when heated. In the stainless steel used in the above, there is a problem that discoloration due to oxidation cannot be sufficiently prevented and corrosion resistance cannot be improved.

Japanese Unexamined Patent Publication No. 2008-231551 Japanese Unexamined Patent Publication No. 2006-63427 JP 2015-44300 Japanese Unexamined Patent Publication No. 2013-216760

Therefore, the present invention has been devised in view of the above-mentioned problems, and an object of the present invention is that it is possible to prevent discoloration due to oxidation even in a high temperature environment of 700 ° C. or higher, and the coating film is coated. It is an object of the present invention to provide a surface-treated metal member capable of preventing appearance abnormalities other than discoloration due to oxidation such as cracking and whitening, and deterioration of corrosion resistance of a base material, and a heating device in which this is used.

In order to solve the above-mentioned problems, the present inventors are surface-treated metal members in which a coating layer is formed on the surface of an aluminum-containing stainless steel material, and the coating layer is a first containing a silica-based compound. We have invented a surface-treated metal member having a layer and a second layer laminated on the first layer and containing an aluminum-based compound, and a heating device in which this is used.

The surface-treated metal member according to the first invention is a surface-treated metal member in which a coating layer is formed on the surface of the metal layer. The metal layer is a stainless steel material containing aluminum, and the coating layer is a silica-based compound. a first layer containing, laminated on the first layer, have a second layer containing an aluminum-based compound, the first layer contains SiO ₂ as the silica-based compound, The total amount of coating is 300 mg / m ² or more and 3000 mg / m ² _{or less in total in terms of SiO 2 , and the second layer contains Al 2} O ₃ as the aluminum-based compound , and the coating amount is Al. It is characterized in _{that the total of 2} O ₃ conversion values is less than 2500 mg / m ^2.

The method for producing a surface-treated metal member according to the second invention includes a step of preparing a metal layer and a step of forming a coating layer on the surface of the metal layer, and the metal layer is a stainless steel material containing aluminum. The coating layer is a first layer in which a coating material as a precursor contains a silica-based compound which is a crystal particle dispersion liquid, and a second layer in which the coating material is laminated on the first layer and contains an aluminum-based compound. And the first layer is SiO as the silica-based compound. ₂ The amount of coating is SiO ₂ 300 mg / m in total of converted values ² Above 3000 mg / m ² The second layer is Al as the aluminum compound. ₂ O ₃ Is contained, and the amount of coating is Al. ₂ O ₃ 2500 mg / m in total of converted values ² It is characterized by being less than.

The method for producing a surface-treated metal member according to the third invention is characterized in that, in the second invention, the first layer and the second layer are transparent.

Heating device according to the fourth invention has a metal member to be heated, a surface-treated metal member according to the first invention is characterized in that it is used for the metal member.

According to the present invention having the above-described configuration, it is possible to prevent an abnormality in appearance from occurring in a high temperature environment due to being located in the vicinity of an open flame due to the aluminum-based compound constituting the second layer. In addition to this, according to the present invention, the first layer functions as a barrier layer for diffusion of Fe elements, so that it can be prevented from diffusing into the inside of the second layer. For this reason, the structure is such that oxidation itself due to oxidation of Fe in the aluminum compound cannot occur, and even in a high temperature environment exceeding 700 ° C., discoloration due to oxidation can be prevented, and discoloration due to corrosion can be prevented. Can be done.

Further, according to the present invention, since aluminum is contained in the stainless steel constituting the metal layer, the stainless steel containing no aluminum is subjected to the first layer and the second layer of the present invention, or aluminum is used. Compared with the heat-resistant stainless steel contained without coating, when exposed to a high temperature environment exceeding 700 ° C. for a long time, the time until discoloration due to oxidation can be detected with the naked eye is significantly longer. In this way, the effect of significantly improving the durability of preventing discoloration due to oxidation is produced.

It is a figure which shows the heating appliance to which the surface-treated metal member to which this invention is applied is applied. It is a figure for demonstrating each layer constituting the surface-treated metal member to which this invention is applied. It is a figure which shows the example which formed the 1st layer and the 2nd layer 22 on the upper layer of the metal member which constitutes the surface of a gas burner.

Hereinafter, the surface-treated metal member to which the present invention is applied will be described in detail with reference to the drawings.

The surface-treated metal member to which the present invention is applied is used, for example, in Gotoku 3 or the like as a heating appliance that is exposed to an open flame during cooking as shown in FIG. 1 (a). The trivet 3 is used for the gas stove 2 in the system kitchen. The trivet 3 is often formed in the shape of a claw extending from the periphery of the gas stove 2 toward the center, and a heating container such as a kettle or a pot is placed therein. Since Gotoku 3 is located near an open flame that ignites from a gas stove, it is often used in a high temperature environment of 700 ° C or higher, and when it comes into contact with an open flame, it is used in a high temperature environment of 1000 ° C or higher. In many cases.

A cross-sectional view taken along the line BB'in the surface-treated metal member constituting the trivet 3 is shown in FIG. 1 (b). The surface-treated metal member constituting the trivet 3 includes a metal layer 11 as a base material thereof, and a coating layer 12 coated and laminated so as to cover the surface of the metal layer 11.

The metal layer 11 is made of a metal such as stainless steel. It is essential that the metal layer 11 contains aluminum among the stainless steels. In stainless steel, the added Cr combines with oxygen in the air to form an extremely thin, highly protective passivation film having a thickness of several nm to several tens of nm. This passivation film exhibits excellent corrosion resistance and heat resistance. That is, the trivet 3 can prevent the occurrence of rust by the metal layer 11 on which the passivation film is formed.

Incidentally, as an example of the stainless steel constituting the metal layer 11, at least stainless steel containing aluminum or the like may be used. At this time, the content of aluminum with respect to the total weight of the stainless steel is not particularly limited, but is preferably set to, for example, 4% by weight.

The coating layer 12 has a first layer 21 laminated on the surface of the metal layer 11 as shown in FIG. 2, and a second layer 22 laminated on the first layer 21 to form the outermost surface. ing.

The first layer 21 is composed of a layer containing a silica-based compound. Examples of the silica-based compound constituting the first layer 21 are all compounds having a bond between Si and O, and are, for example, dehydration-condensed silicon tetraethoxydo, SiO ₂ , (polysilazane). , Siloxane, silicate) and the like. However, this silica-based compound is not limited to these examples. Since the first layer 21 is made of a transparent material, it is possible to positively show the metal color of the metal layer 11 that it covers on the surface. However, it goes without saying that the first layer 21 may be made of a material other than the material exhibiting transparency.

The first layer 21 can mainly suppress the movement of the Fe element in the metal layer 11 to diffuse into the second layer 22. That is, the first layer 21 can act as a barrier against the movement of the Fe element, and thus the Fe element can be prevented from reaching the second layer 22. As a result, it is possible to prevent the Fe element from being oxidized in a high temperature environment of 700 ° C. or higher, and by extension, 1000 ° C. or higher. Then, it is possible to prevent black spots from being generated due to the oxidation of this Fe element.

It is desirable that the coating amount of the first layer 21 exceeds 300 mg / m ^{2 in} _{total in terms of SiO 2, and} is less than 3000 mg / m ^2. However, the first layer 21 is not limited to the case where it is composed of such a coating amount, and may be any coating amount.

If the coating amount of the first layer 21 is 300 mg / m ² or less, the film thickness is too thin, interference color is generated, and a stable appearance cannot be maintained. In addition, when it comes into contact with a flame that reaches a temperature of 1200 ° C, it discolors and black spots are generated. On the other hand, when the coating amount of the first layer 21 is 3000 mg / m ² or more, the film thickness of the first layer 21 as the barrier layer is too thick, and the inside of the metal layer 11 The contained gas cannot be completely removed, and this appears as a cloudy pattern, which causes deterioration of appearance and design.

The coating material as a precursor of the silica-based compound of the first layer 21 may be a crystalline particle dispersion liquid or may be obtained from an amorphous coating material. When the coating material which is the precursor of this silica-based compound is a crystal particle dispersion liquid, the Fe element in the metal layer 11 has to move so as to bypass the crystal, and therefore, as this barrier layer. The amount of movement of the Fe element through the first layer 21 is increased, and the diffusion of the Fe element into the second layer 22 can be prevented. However, it goes without saying that even if the silica-based compound of the first layer 21 is obtained from an amorphous paint, it can act so as to suppress the diffusion of Fe elements.

In addition, another layer may intervene between the first layer 21 and the metal layer 11.

The second layer 22 is composed of a layer containing an aluminum-based compound. Examples of the aluminum-based compound constituting the second layer 22 are Al ₂ O ₃ , (aluminum nitride, mullite, spinel) and the like. As the aluminum-based compound, preferably crystalline Al ₂ O ₃ may be used. However, this aluminum-based compound is not limited to these examples. Since the second layer 22 is made of a transparent material, it is possible to positively show the metal color of the metal layer 11 that it covers on the surface. However, it goes without saying that the second layer 22 may be made of a material other than the material exhibiting transparency.

The aluminum-based compound constituting the second layer 22 does not cause crystal transition or the like in a high temperature range of 700 ° C. or higher, and by extension, 1000 ° C. or higher, and almost no appearance defect occurs in such a high temperature range. That is, since the second layer 22 is located in the vicinity of an open flame, there is almost no abnormality in appearance in a high temperature environment. In addition to this, in the second layer 22, the first layer 21 functions as a barrier layer for diffusion of Fe elements, so that it can be prevented from diffusing inside. Therefore, the structure is such that oxidation itself due to oxidation of Fe cannot occur in the aluminum-based compound, and it is possible to prevent the occurrence of temper color due to so-called oxidative discoloration.

It is desirable that the coating amount of the second layer 22 is less than 2500 mg / m ^{2 in} _{total in terms of Al 2} O _{3 in the case of an aluminum compound.} However, the second layer 22 is not limited to the case where it is composed of such a coating amount, and may be any coating amount.

If the coating amount of the second layer 22 is 2500 mg / m ² or more, the film thickness becomes too thick, and the lines of the metal layer 11 and the second layer 22 are formed under the above-mentioned high temperature environment. Due to the difference in expansion coefficient, the second layer 22 may be peeled off and the coating film may be cracked.

The operation of the trivet 3 having the surface-treated metal member having the above-described configuration will be described below. When the cooking container placed on the trivet 3 is heated by an open flame with a gas stove 2, the trivet 3 is located in the vicinity of the open flame, and in some cases, the direct flame comes into direct contact with the cooking container. As a result, the trivet 3 is placed in a high temperature environment exceeding 1000 ° C. Even if it does not come into direct contact with an open flame, it will be placed in a high temperature environment of 700 ° C. or higher in the vicinity of the open flame.

In such a case, the second layer 22 can suppress the appearance defect in the high temperature environment exceeding 700 ° C. via the aluminum-based compound. Further, the Fe element in the metal layer 11 tries to diffuse in this high temperature environment, but the diffusion toward the first layer 21 is suppressed through the silica-based compound constituting the first layer 21. As a result, it is possible to suppress the movement of the diffused Fe element to pass through the first layer 21 and enter the second layer 22. As a result, since the Fe element does not enter the second layer 22, it is possible to prevent it from being oxidized in a high temperature environment, and it is possible to prevent it from being discolored. In particular, since aluminum is contained in the stainless steel constituting the metal layer 11, the stainless steel that does not contain aluminum is subjected to the first layer and the second layer of the present invention, and the heat-resistant stainless steel that contains aluminum. When exposed to a high temperature environment exceeding 700 ° C. for a long time, it took a significantly longer time to detect discoloration due to oxidation with the naked eye than that without coating. In this way, the effect of significantly improving the durability of preventing discoloration due to oxidation is produced.

The present invention is not limited to the case where it is applied to a heating appliance such as a trivet 3 or a grill, but is applied to any metal member used in a high temperature environment. May be good. For example, it goes without saying that the present invention may be applied to the gas burner 5, heater parts, boiler piping, etc. as shown in FIG. Even in the gas burner shown in FIG. 3, the first layer 21 is formed on the upper layer of the metal layer 11 constituting the metal member constituting the surface thereof, and the second layer 22 is formed on the upper layer thereof. The metal layer 11 is made of a stainless steel material containing aluminum.

Further, the present invention is not limited to these, and may be applied to any device having a metal member heated to a high temperature. In such a case, the first layer 21 is formed on the upper layer of the metal member made of the stainless steel material containing aluminum, and the second layer 22 is formed on the upper layer thereof.

Hereinafter, the experimental verification performed for confirming the effect of the surface-treated metal member to which the present invention is applied will be described in detail.

In the experimental verification in Example 1, first, as shown in Table 1, a plurality of types of samples were prepared, and five items were obtained: appearance after painting, coating film cracking, degree of corrosion, degree of whitening, and presence / absence of water pot discoloration test. Was verified.

The sample is composed of only the metal layer 11, and Comparative Examples 1 and 2 in which the first layer 21 and the second layer 22 are not laminated on the surface thereof, and the first layer 21 and the second layer 22 are provided on the metal layer 11. It is composed of Comparative Example 3 and the example of the present invention in which two layers are laminated.

Of these, Comparative Example 1 and Comparative Example 3 use aluminum-free stainless steel (19Cr-0.4Cu-0.4Nb-LC, N) as the metal layer 11, and Comparative Example 2 and the example of the present invention. Uses stainless steel (15Cr-4Al-LC, N) containing 4% by weight of aluminum with respect to the total weight of the stainless steel as the metal layer 11.

The first layer 21 applied in the experiment is a crystal dispersion liquid mainly composed of silica having a concentration of 10% and an average diameter of 25 nm or more.

The second layer 22 applied in the experiment is an aluminum hydroxide nanoparticle dispersion having a concentration of 3% and an average diameter of 200 nm or more.

Each of the above-mentioned materials was assigned to a single layer, a first layer 21, and a second layer 22, and experimental verification was performed.

Regarding the evaluation method of each item, first, the appearance after painting is visually evaluated according to JIS K5600-4-3 (only the light source uses LED (Ohm Electric LEDPL48W)) after painting and baking, and the appearance is abnormal. If there is no such thing, it is marked with a circle, and if an appearance abnormality is found, it is marked with a cross. The appearance evaluation after painting is as follows: In a room where the floor wall surface is all neutral gray (SCI value is 47.69), the illuminance at the observation position is about 1100 Lux, and the floor surface wall surface is all white (SCI value is 47.69). It was performed in the room of 90.61) in both environments where the illuminance at the observation position was about 2300 Lux.

The coating film cracks are magnified at 450 times with a microscope after coating and baking, and are marked with ◯ when there is no coating film cracking and x when no coating film cracking is found.

Regarding the degree of corrosion, JIS K5621 7.12 compound cycle corrosion resistance test was conducted for 2 cycles, and the case where corrosion occurred was marked with × and the case where it did not occur was marked with ○.

For whitening, visually observe each sample after heating with an open flame in accordance with JIS K5600-4-3 (only the light source uses LED (Ohm Electric LEDPL48W)), and if whitening occurs, × If it does not occur, it is marked with a circle. In this visual observation, the floor wall surface was all neutral gray (SCI value 47.69), and the illuminance at the observation position was about 1100 Lux.

For the water pot discoloration test, 2 liters of water was placed in a pot (diameter 24 cm) having a metal layer 11 made of stainless steel and repeatedly heated with a 4.4 kW high calorie burner for 1 hour, and JIS K5600- Discoloration was visually evaluated according to 4-3 (only the light source uses LED (Ohm Electric LEDPL48W)). This water pot discoloration test was conducted in a room where the floor wall surface was all white (SCI value was 90.61), and the illuminance at the observation position was about 2300 Lux.

In the water pot discoloration test, as a result of visual evaluation under the above-mentioned conditions, it is evaluated as ◯ when there is no discoloration, Δ when there is little discoloration, and × when there is large discoloration.

The amount of coating is quantitatively analyzed by a fluorescent X-ray analyzer. As the apparatus, a wavelength dispersion desktop fluorescent X-ray analyzer (Supermini200) of Rigaku Co., Ltd. was used.

In both Comparative Examples 1 and 2, the appearance after painting, the cracking of the coating film, and the whitening test are excluded from the evaluation because there is no coating film itself in the first place. Further, in the corrosion test, Comparative Example 1 was × and Comparative Example 2 was ×.

On the other hand, in Comparative Example 3 and the example of the present invention, the appearance after painting and the cracking of the coating film were both ◯, and both the corrosion test and the whitening test were ◯.

Table 2 shows the evaluation results according to the elapsed time from the start of heating in the water pot discoloration test.

In the water pot discoloration test result, Comparative Example 1 became Δ 1 minute after the start of heating, and Comparative Example 2 became Δ 1.5 minutes after the start of heating. Further, in the water pot discoloration test result, Comparative Example 3 was Δ after 310 hours of heating, but the example of the present invention was ◯ even after 1300 hours had elapsed from the start of heating.

From the above experimental results, it is possible to clear various test conditions only in the example of the present invention in which aluminum is contained as the metal layer 11 and the first layer 21 and the second layer 22 are formed on the upper layer of the metal layer 11. I found out.

2 Gas stove 3 Gotoku 5 Gas burner 11 Metal layer 12 Coating layer 21 1st layer 22 2nd layer

Claims (4)

In a surface-treated metal member in which a coating layer is formed on the surface of the metal layer,
The metal layer is a stainless steel material containing aluminum.
The coating layer includes a first layer containing a silica-based compound and
It has a second layer laminated on the first layer and containing an aluminum compound, and has.
_{The first layer contains SiO 2} as the silica-based compound, and the total coating amount thereof is 300 mg / m ² or more and 3000 mg / m ² or less in _{total in terms of SiO 2.}
The second layer is a surface-treated metal member _{containing Al 2} O ₃ as the aluminum compound, and the coating amount thereof is less than 2500 mg / m ^{2 in} _{total in terms of Al 2} O _{3 conversion value.} The process of preparing the metal layer and
It has a step of forming a coating layer on the surface of the metal layer.
The metal layer is a stainless steel material containing aluminum.
The coating layer has a first layer in which a paint as a precursor contains a silica-based compound as a crystal particle dispersion, and a second layer in which the coating material is laminated on the first layer and contains an aluminum-based compound. death,
_{The first layer contains SiO 2} as the silica-based compound, and the total coating amount thereof is 300 mg / m ² or more and 3000 mg / m ² or less in _{total in terms of SiO 2.
The second layer contains Al 2} O ₃ as the aluminum compound, and the coating amount thereof is less than 2500 mg / m ^{2 in} _{total in terms of Al 2} O ₃ of the surface-treated metal member. Production method. The method for producing a surface-treated metal member according to claim 2, wherein the first layer and the second layer are transparent. Has a metal member to be heated
Heating appliance surface treated metal member of claim 1 wherein is characterized in that it is used for the metal member.

Images