JP2018053344A - Surface treatment metallic component, and heating tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface treatment metallic component capable of preventing not only a color change due to oxidization even under a high temperature circumstance of 700°C or higher but also an appearance abnormality other than a color change due to an oxidation such as the cracking or whitening of a coated film, or the reduction of corrosion resistance of the base material.SOLUTION: A surface treatment metallic component having a coating layer 12 on the surface of a metallic layer 11 is characterized in that the metallic layer 11 is a stainless steel material containing aluminium, and in that the coating layer 12 includes a first layer 21 containing a silica-base compound, and a second layer 22 laminated over the first layer 21 and containing an aluminum compound.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a metal member used for an appliance that is exposed to a direct fire during heating, such as a gas stove, a grill, and five virtues, and a metal member used in a high-temperature environment such as a heater part, a drying and firing furnace, and boiler piping. The present invention relates to a surface-treated metal member capable of effectively preventing discoloration by preventing metal oxidation due to high temperature, and a heating apparatus in which the surface-treated metal member is used.

  Stainless steel has a very thin passive film having a very thin thickness of about several nm to several tens of nm, and exhibits excellent corrosion resistance and heat resistance while maintaining a beautiful metallic luster. For this reason, it has traditionally consisted of heating appliances that are exposed to direct flames during heating, such as gas stoves, grills, virtues, gas burners, etc., and equipment used in high-temperature environments such as heater parts, drying firing furnaces, boiler piping, etc. It is used as a material.

  However, this stainless steel may generate a so-called temper color in which the surface is discolored and colored in an environment where the above-mentioned direct flame is touched or in a high temperature environment. Such discoloration of stainless steel is based on oxidation of the stainless steel due to high temperature to form an oxide layer. When the thickness of the 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 the design are rapidly deteriorated. In particular, heaters such as Gotoku, gas stove, gas burner, etc. may appear such discoloration just by touching an open fire, even though not many days have passed since purchase. It gives the impression that it has become aged rapidly.

  For this reason, the technique which can prevent the discoloration based on the 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 the surface. Through this reaction layer, it is expected that the diffusion of atoms to the alkali silicate film covering the steel material surface will be suppressed, the formation of Cr-Fe-O-based oxide layer that causes temper color will be prevented, and discoloration will be prevented. It is a thing.

  Patent Document 2 discloses a technique in which a surface of stainless steel is coated with an oxide layer made of a silica-based compound with a thickness of 1 μm or less. Since this silica-based compound is an oxide with a slow diffusion of oxygen, it is expected to prevent discoloration 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 similarly occurring in the vicinity of the surface of stainless steel. Is.

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

  Patent Document 4 discloses a technical idea of using an alumina thin film as an oxidation-inhibiting film. Alumina thin film has excellent film formability, denseness, 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. However, the stainless steel used in this method cannot sufficiently prevent discoloration due to oxidation, and cannot improve the corrosion resistance.

JP 2008-231551A JP 2006-63427 A JP2015-44300A JP 2013-216760 A

  Therefore, the present invention has been devised in view of the above-described problems, and the object of the present invention is to prevent discoloration due to oxidation even in a high temperature environment of 700 ° C. or higher. An object of the present invention is to provide a surface-treated metal member capable of preventing appearance abnormality other than discoloration due to oxidation such as cracking or whitening and deterioration of corrosion resistance of a substrate, and a heating apparatus in which the surface-treated metal member is used.

  In order to solve the above-mentioned problems, the present inventors provide a surface-treated metal member in which a coating layer is formed on the surface of a stainless steel material containing aluminum, wherein the coating layer contains a silica-based compound. Invented a surface-treated metal member having a layer and a second layer laminated on the first layer and containing an aluminum compound, and a heating apparatus in which the surface-treated metal member 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, wherein the metal layer is a stainless steel material containing aluminum, and the coating layer is a silica-based compound. And a second layer that is laminated on the first layer and contains an aluminum-based compound.

In the surface-treated metal member according to the second invention, in the first invention, the first layer contains SiO ₂ as the silica-based compound, and the second layer contains Al ₂ O ₃ as the aluminum-based compound. It is characterized by that.

  The surface-treated metal member according to a third aspect of the present invention is characterized in that, in the second aspect of the present invention, the first layer has a coating material that is a precursor thereof as a crystal particle dispersion.

  The surface-treated metal member according to a fourth invention is characterized in that, in any one of the first invention to the third invention, the first layer and the second layer exhibit transparency.

  A heating instrument according to a fifth aspect has a metal member to be heated, and the surface-treated metal member according to any one of the first to fourth aspects is used for the metal member.

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

  Further, according to the present invention, the stainless steel constituting the metal layer contains aluminum, so that the first layer and the second layer of the present invention are applied to stainless steel not containing aluminum, When exposed to a high temperature environment exceeding 700 ° C. for a long time, the time until the discoloration due to oxidation can be detected with the naked eye is significantly longer than that of the heat-resistant stainless steel containing no coating. 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 with which the surface treatment metal member to which this invention is applied is applied. It is a figure for demonstrating each layer which comprises the surface treatment 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 in the upper layer of the metal member which comprises the surface of a gas burner.

  Hereinafter, a 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 Gotoku 3 or the like as a heating instrument that is touched by a direct fire during cooking as shown in FIG. Gotoku 3 is used for the gas stove 2 in the system kitchen. Gotoku 3 is often configured in a shape like a claw extending from the periphery of the gas stove 2 toward the center, and a heating container such as a kettle or a pan is placed thereon. Gotoku 3 is located in the vicinity of a direct fire ignited from a gas stove, so it is often used in a high temperature environment of 700 ° C or higher. When touching a direct fire, it is used in a high temperature environment of 1000 ° C or higher. There are many cases.

  FIG. 1B shows a cross-sectional view taken along the line BB ′ of the surface-treated metal member constituting such virtues 3. The surface-treated metal member constituting the virtues 3 includes a metal layer 11 as a base material and a coating layer 12 that is 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. The metal layer 11 must contain aluminum among the stainless steel. Stainless steel forms a very thin passive protective film having a thickness of about several nanometers to several tens of nanometers by adding added Cr to oxygen in the air. This passive film exhibits excellent corrosion resistance and heat resistance. That is, Gotoku 3 can prevent the occurrence of rust by the metal layer 11 on which the passive film is formed.

  Incidentally, as an example of the stainless steel constituting the metal layer 11, a stainless steel containing at least aluminum 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 4% by weight, for example.

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

The first layer 21 is composed of a layer containing a silica compound. Examples of the silica-based compound constituting the first layer 21 are all concepts including any compound having a bond of Si and O, such as dehydrated and condensed silicon tetraethoxide, SiO ₂ , (polysilazane). Siloxane, silicate) and the like. However, this silica compound is not limited to these examples. Since the first layer 21 is made of a material exhibiting transparency, the metal color of the metal layer 11 covered by the first layer 21 can actively appear on the surface. However, it goes without saying that the first layer 21 may be made of a material other than a material exhibiting transparency.

  The first layer 21 can suppress the movement of the Fe element in the metal layer 11 mainly diffusing 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 more than 1000 ° C. And it can prevent that the black spot by the oxidation of this Fe element arises.

The coating amount of the first layer 21 is preferably greater than 300 mg / m ^{2 and} less than 3000 mg / m ² in terms of the total SiO ₂ conversion value. However, the first layer 21 is not limited to the case where the first layer 21 is constituted by 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, since the film thickness is too thin, an interference color is generated and a stable appearance cannot be maintained. Further, when it is brought into contact with a flame reaching a temperature of 1200 °, the color changes and black spots are generated. On the other hand, when the coating amount of the first layer 21 is laminated over 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 exhausted, and this appears as a cloudy pattern, which causes a decrease in appearance and design.

  The silica-based compound of the first layer 21 may be a precursor of a coating material that is a crystal particle dispersion or may be obtained from an amorphous coating material. When the coating material that is a precursor of the silica-based compound is a crystal particle dispersion, the Fe element in the metal layer 11 must move around the crystal, so that the barrier layer This increases the amount of movement of the first element 21 when passing through the first layer 21, thereby preventing the Fe element from diffusing into the second layer 22. 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 to suppress the diffusion of Fe element.

  Note that another layer may be interposed between the first layer 21 and the metal layer 11.

The second layer 22 is composed of a layer containing an aluminum compound. Examples of the aluminum-based compound constituting the second layer 22 include Al ₂ O ₃ , (aluminum nitride, mullite, spinel) and the like. As the aluminum-based compound, crystalline Al ₂ O ₃ may be desirably used. However, this aluminum compound is not limited to these examples. Since the second layer 22 is made of a material exhibiting transparency, the metal color of the metal layer 11 covered by the second layer 22 can be positively exhibited on the surface. However, it is needless to say that the second layer 22 may be composed 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 thus exceeds 1000 ° C., and hardly causes poor appearance in such a high temperature range. That is, the second layer 22 hardly causes an appearance abnormality in a high temperature environment due to being positioned in the vicinity of an open fire. In addition, in the second layer 22, the first layer 21 functions as a barrier layer for the diffusion of Fe element, so that it can be prevented from diffusing inside. For this reason, in the aluminum-based compound, oxidation itself due to oxidation of Fe cannot occur, and it is possible to prevent occurrence of temper color due to so-called oxidation discoloration.

The coating amount of the second layer 22 is desirably less than 2500 mg / m ^{2 in} total in terms of Al ₂ O ₃ , particularly in the case of an aluminum compound. However, the second layer 22 is not limited to the case where the second layer 22 is constituted by such a coating amount, and may be any coating amount.

If the coating amount of the second layer 22 is laminated over 2500 mg / m ² or more, the film thickness is too thick, and the line between the metal layer 11 and the second layer 22 in the high temperature environment described above. Due to the difference in the expansion coefficient, the second layer 22 may be peeled off and the coating film may be cracked.

  The operation of Gotoku 3 having the surface-treated metal member having the above-described configuration will be described below. When the cooking container placed on Gotoku 3 is heated by direct fire from gas stove 2, Gotoku 3 is located in the vicinity of the direct fire, and in some cases, the direct fire is directly touched. As a result, Gotoku 3 is placed in a high temperature environment exceeding 1000 ° C. Even in the case where the direct fire is not touched, it is placed in a high temperature environment of 700 ° C. or more in the vicinity of the direct fire.

  In such a case, the 2nd layer 22 can suppress the appearance defect with respect to this high temperature environment exceeding 700 degreeC through an aluminum-type compound. Further, the Fe element in the metal layer 11 tends to diffuse under 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 diffusing Fe element passing through the first layer 21 and entering the second layer 22. As a result, since the Fe element does not enter the second layer 22, it can be prevented from being oxidized in a high temperature environment, and discoloration can be prevented. In particular, when aluminum is contained in the stainless steel constituting the metal layer 11, the first layer and the second layer of the present invention are applied to the stainless steel not containing aluminum, or the heat-resistant stainless steel containing aluminum. When exposed to a high temperature environment exceeding 700 ° C. for a long time, the time until the discoloration due to oxidation can be detected with the naked eye is significantly longer than that without the coating. In this way, the effect of significantly improving the durability of preventing discoloration due to oxidation is produced.

  In addition, this invention is not limited to the case where it applies to heating appliances, such as Gotoku 3 and a grill, It is applied to what is a metal member used in a high temperature environment, Also good. For example, it goes without saying that the present invention may be applied to a gas burner 5, a heater component, boiler piping, and the like 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, and the second layer 22 is further formed on the upper layer. The metal layer 11 is made of a stainless steel material containing aluminum.

  Moreover, this invention is not limited to these, You may apply to any instrument which has a metallic member heated to high temperature. In such a case, the first layer 21 is formed on the upper layer of the metal member made of a stainless steel material containing aluminum, and the second layer 22 is further formed on the upper layer.

  Hereinafter, the experimental verification performed in order to confirm the effect of the surface treatment metal member to which this invention is applied is demonstrated in detail.

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

  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 stacked on the surface, and the first layer 21 and the second layer 22 on the metal layer 11. It consists of the comparative example 3 laminated | stacked over 2 layers, and the example of this invention.

  Among these, the comparative example 1 and the comparative example 3 use the stainless steel (19Cr-0.4Cu-0.4Nb-LC, N) which does not contain aluminum as the metal layer 11, and the comparative example 2 and this invention example. Uses a 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 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 a dispersion of aluminum hydroxide nanoparticles having a concentration of 3% and an average diameter of 200 nm or more.

  Each material described above was assigned to the single layer, the first layer 21, and the second layer 22 for experimental verification.

  As for the evaluation method of each item, the appearance after painting is first evaluated visually after paint baking, in accordance with JIS K5600-4-3 (LED only uses light source (Ohm Electric LEDPL48W)). When there is no, it is marked with ◯, and when an appearance abnormality is found, it is marked with ×. The appearance evaluation after painting was conducted in an environment where the floor wall surface was all neutral gray (SCI value 47.69) and the illuminance at the observation position was about 1100 Lux, and the floor wall surface was all white (SCI value was 90.61) was performed in both of the environments where the illuminance at the observation position was about 2300 Lux.

  Regarding coating film cracking, magnified observation is performed at 450 times with a microscope after painting and baking. When there is no coating film cracking, it is indicated as “◯”, and when coating film cracking is found, it is indicated as “X”.

  The degree of corrosion was evaluated by JIS K5621 7.12 combined cycle anti-corrosion resistance test for 2 cycles.

  For whitening, each sample after heating by direct flame is visually observed in accordance with JIS K5600-4-3 (LEDs are used only for the light source (Ohm Electric LEDPL48W)). When it does not occur, it is marked as “◯”. In this visual observation, the floor wall surface was all in a neutral gray (SCI value 47.69) room, and the illuminance at the observation position was about 1100 Lux.

  For the water pot discoloration test, 2 liters of water was put into a pot (diameter 24 cm) having a metal layer 11 made of stainless steel, and heated continuously with a 4.4 kW high-calorie burner for 1 hour, and JIS K5600- The discoloration was visually evaluated according to 4-3 (LED only light source (ohmic LEDPL48W) is used). This water pan discoloration test was performed in a room whose floor wall surface was all white (SCI value 90.61), and the illuminance at the observation position was about 2300 Lux.

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

  In addition, about the coating amount, the quantitative analysis by the fluorescent X ray analyzer is performed. As the apparatus, Rigaku Co., Ltd. wavelength-dispersed tabletop fluorescent X-ray analyzer (Supermini200) was used.

  In Comparative Examples 1 and 2, the appearance after coating, coating film cracking, and whitening test are not evaluated because there is no coating film in the first place. Moreover, in the corrosion test, the comparative example 1 was x and the comparative example 2 was x.

  On the other hand, Comparative Example 3 and Example of the present invention were both good in appearance after coating and cracks in the coating film, and good in both the corrosion test and the whitening test.

  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 results, Comparative Example 1 was Δ 1 minute after the start of heating, and Comparative Example 2 was Δ 1.5 minutes after the start of heating. 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, only 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 above the metal layer 11 can satisfy various test conditions. I understood.

2 Gas stove 3 Gotoku 5 Gas burner 11 Metal layer 12 Coating layer 21 First layer 22 Second layer

Claims (5)

In the surface-treated metal member in which the 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,
A surface-treated metal member having a second layer laminated on the first layer and containing an aluminum-based compound. The first layer contains SiO ₂ as the silica compound,
The surface-treated metal member according to claim 1, wherein the second layer contains Al ₂ O ₃ as the aluminum-based compound. The surface-treated metal member according to claim 2, wherein the first layer includes a crystal particle dispersion liquid as a precursor. The surface-treated metal member according to any one of claims 1 to 3, wherein the first layer and the second layer exhibit transparency. Having a metal member to be heated,
A surface-treated metal member according to any one of claims 1 to 4 is used for the metal member.

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