JP2001316129A - Frit composition for enamel and enamel ware - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a frit composition for enamel having excellent acid resistance, alkali resistance and cohesion with a substrate, and to provide an enamel ware obtained by coating the composition onto the substrate having high brightness, high gloss and excellent bending processability. SOLUTION: This frit composition for enamel comprises SiO2, TiO2, Na2O, Li2O, K2O, B2O3 and Al2O3, wherein a mass ratio of SiO2/B2O3 is 1.5 to 5, and the content of halogens is minimized. This enamel ware is made by glazing the composition onto a steel plate or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an enamel frit composition having excellent chemical resistance (acid resistance and alkali resistance) and excellent adhesion to a substrate. The present invention relates to a manufactured enamel product having high brightness, high gloss, and excellent bending workability.

[0002]

2. Description of the Related Art Enamel products are provided with a glassy (glaze) enamel on the surface of a base material such as a metal substrate to impart corrosion resistance, weather resistance and chemical resistance. Enamel products often require a design, so high brightness, that is, high gloss is required, in addition to excellent barrier properties such that the enamel layer is sufficiently colored and the base material of the base material cannot be seen through. Often done. In addition, even when bending, there is a case where a processability is required in which the enamel is not cracked or peeled and the appearance is not impaired.

[0003] It is known that lightness (concealing properties and blocking properties) is generally satisfied by adding a color pigment to the enamel and increasing the thickness thereof. However, the present inventor, when adding a large amount of pigment to the transparent glaze to the extent that the metal substrate is not transparent, the brightness becomes high, but the enamel surface has severe irregularities and high gloss cannot be obtained.
It has been found that the contaminants that have entered the recesses are difficult to remove with a detergent or the like, and further reduce the gloss.

Since the higher the thickness of the enamel layer, the higher the brightness can be obtained, the thickness of the enamel layer is generally up to about 100 μm. However, when bending an enamel product containing a large amount of pigment, it is necessary to suppress the film thickness to about 70 μm from the viewpoint of preventing cracking.

When an enamel layer is formed on an aluminum-plated steel sheet using only a transparent frit of glaze mainly composed of P ₂ O ₅ , the enamel layer thickness is set to 10 to 50 μm to improve bending workability. An excellent enamel product can be obtained (Japanese Patent Publication 6-432)
No. 57), but the brightness is not high. Even with the usual pigments, the gloss remains poor. Furthermore, in the transparent frit of glaze mainly composed of P ₂ O ₅ ,
Due to the water resistance derived from P ₂ O ₅ , the weather resistance and chemical resistance of the enamel product may not be sufficient.

On the other hand, an enamel product using an opaque frit made of a titanium glaze has sufficient weather resistance and chemical resistance (Japanese Patent Publication No. 6-43256). Then, there is a problem that cracks occur during bending. Titanium glaze also had problems such as difficulty in adjusting the color and unclear color. As described above, an enamel product that satisfies all of chemical resistance, lightness, gloss, and workability has not yet been obtained.

Conventionally, castings and ordinary steels have been mainly used as the base material. However, when higher heat resistance and corrosion resistance are required, stainless steel is used as the base material. However, unlike the case of castings and ordinary steel, the surface of stainless steel has a passivation film of about several nm mainly composed of Cr ₂ O ₃ , so that the enamel may not adhere sufficiently to stainless steel. Was.

[0008] In order to improve the adhesion between the enamel and the stainless steel, a technique for forming an oxide film on the surface of the stainless steel has been proposed. For example, JP-A-7-233483
Japanese Patent Application Laid-Open No. 9-26 discloses a hexagonal corundum oxide.
Japanese Patent Publication No. 3901 proposes a technique for forming a cubic spinel oxide. However, even if such an oxide layer is provided, the adhesion of all enamels is not necessarily improved.

[0009]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to improve the disadvantages of the prior art, and to provide an enamel product which satisfies all of brightness, gloss, chemical resistance and workability. Enamel frit composition suitable for manufacturing, and manufactured using the composition, high brightness, high gloss,
It is an object of the present invention to provide an enameled product having excellent chemical resistance and also excellent bending workability.

[0010]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted intensive studies on the composition of the frit composition. As a result, the composition having the following composition was found to have lightness, gloss, chemical resistance and workability. Thus, they have found that they are suitable for producing an enamel product that satisfies both conditions, and have completed the first invention.

The present invention relates to the following oxides,
Contained in the ratio shown by_Two/ B _TwoO_Three(Mass ratio)
A frit composition for an enamel characterized by being 1.5 to 5.
Things. Note SiO_Two: 35-60%, TiO_Two: 5-30%, Na_TwoO: 5-25%, Li_TwoO: 1-10%, Na_TwoO + Li_TwoO + K_TwoO: 10-30%, B_TwoO_Three: 10-25%, Al_TwoO_Three: 0.1 to 5% and halogen: less than 0.05%.

[0012] A preferred present invention is the frit composition for enamel as described above, wherein the pigment is contained in an amount of 10 to 45 parts by mass based on 100 parts by mass of the composition.

[0013] A second aspect of the present invention is an enamel product comprising an enamel layer made of the composition on at least one surface of a substrate.

A preferred second invention is an enamel product wherein the base material is stainless steel.

[0015] A second preferred present invention is an enamel product characterized in that the composition is coated on stainless steel via an iron-chromium composite oxide layer.

A second preferred present invention is an enamel product characterized in that the complex oxide constituting the complex oxide layer has a tetragonal and / or hexagonal crystal structure.

In a further preferred second invention, the enamel layer has a thickness of 20 to 50 μm.

A further preferred second invention is the case where the substrate is a ferritic stainless steel.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The present invention provides a frit composition for enamel suitable for producing an enamel product satisfying all of brightness, gloss, chemical resistance, and processability (first invention), and a frit composition coated with the composition. An enamel product with high brightness, high gloss, excellent chemical resistance, and excellent bending workability (second invention). Further, the composition is a stainless steel enamel product coated with a specific composite oxide layer.

The first frit composition for enamel of the present invention comprises:
SiO ₂ , TiO ₂ , Na ₂ O, Li ₂ O, K ₂ O, B
Contains ₂ O ₃ , Al ₂ O ₃ and halogen. The reason why the amount (% by mass) of each component is limited will be described below.
SiO ₂ is 35% to 60%. If it is less than 35%, the gloss is inferior, and if it exceeds 60%, the softening temperature of the frit becomes too high, and the workability deteriorates. SiO ₂ 40 to 55
%.

TiO ₂ is 5 to 30%. If it is less than 5%, the chemical resistance is inferior, and if it exceeds 30%, the gloss decreases. TiO ₂ is preferably 10 to 30%, preferably 1 to 30%.
Particularly preferred is 5 to 25%.

Na ₂ O is 5 to 25%. If it is less than 5%, the softening temperature of the frit becomes too high and the workability deteriorates, and if it exceeds 25%, the chemical resistance decreases. Na ₂ O
Is preferably 5 to 20%, and particularly preferably 7 to 15%. Li ₂ O is from 1 to 10%. If it is less than 1%, the softening temperature of the frit becomes too high and the workability deteriorates. If it exceeds 10%, the chemical resistance decreases. Li
₂ O is preferably from ₂ to 9.5%, particularly preferably from 3 to 7%. Further, (Na ₂ O + Li ₂ O + K ₂
The alkali metal component represented by O) is 10 to 30%. If it is less than 10%, the softening temperature of the frit becomes too high and the workability deteriorates, and if it exceeds 30%, the chemical resistance decreases. The alkali metal component is preferably from 15 to 25%, particularly preferably from 15 to 20%.

B ₂ O ₃ is 10 to 25%. If it is less than 10%, the gloss is poor, and if it exceeds 25%, the chemical resistance decreases. B ₂ O ₃ is preferably from 10 to 20%, particularly preferably from 12 to 17%.

Al ₂ O ₃ is 0.1 to 5%. 0.1
% Or less than 5%, the adhesion between the enamel layer and the substrate is reduced. Al ₂ O ₃ is preferably from 0.1 to 4%, particularly preferably from 0.2 to 2%.

The frit composition for enamel may further comprise SiO ₂
It is important that / B ₂ O ₃ (mass ratio) is 1.5 to 5. When the mass ratio is less than 1.5, the gloss is poor and 5
If it exceeds, the chemical resistance decreases. The ratio is preferably from 2 to 4.5, particularly preferably from 2.5 to 4.

It is important that the frit composition for enamel has a halogen content of less than 0.05%. Halogen such as fluorine may be mixed as an impurity, and if mixed, corrodes the base metal or lowers the corrosion resistance of the enamel product. Therefore, it is necessary to regulate such adverse effects. It is preferably less than 0.04%, but more preferably less.

It is difficult to avoid mixing ZrO ₂ as an impurity in the frit composition for enamel of the present invention. However, when ZrO ₂ is contained, the softening point of the frit becomes too high, and the workability tends to deteriorate.
Preferably, rO ₂ is not substantially contained.

When an enamel product is produced using the frit composition of the present invention obtained by blending the above components in the above proportions, there are no problems such as peeling and cracking of the enamel, chemical resistance,
Matching of the coefficient of thermal expansion with the steel sheet and excellent mechanical properties can be obtained.

The raw material of the frit composition for enamel is not particularly limited as long as it produces the above-mentioned various oxides or a mixture of oxides upon firing. For example, silicic anhydride, silica sand, silica stone powder, titanium oxide, sodium carbonate, sodium silicate, lithium carbonate, potassium carbonate, boric anhydride,
Examples include borax, sodium borate, and aluminum oxide.

The frit composition for enamel of the present invention is produced, for example, by the following method. (1) Select, weigh, pulverize and mix the raw materials. However, pulverization can be omitted. (2) The mixture is heated and fired in a furnace to be melted. (3) In the final stage of melting, 900 to 1300 ° C for 30 minutes to 4 hours, preferably 1100 to 1250 ° C for 30 minutes to
Melts in 2 hours.

(4) The molten material is poured into water or poured onto a thick iron plate and rapidly cooled at once. The quenching results in a pulverized glass frit, which facilitates pulverization in the next step. (5) The obtained frit is ball mill, pot mill,
Finely pulverize using a vibrating mill or a lepter.

(6) At the time of melting, pre-firing may be performed if necessary. Pre-baking, for example, when using a carbonate, first sufficiently mix the carbonate at room temperature, then 150 to
The reaction is performed at 500 ° C. for 30 minutes to 3 hours to degas carbon dioxide gas. The obtained solid is pulverized, and the above (2) is melted. Since pre-firing hardly causes degassing at the time of melting, the work can be performed safely without the raw material blowing out of the crucible. In the case where a water-containing powder or an ammonium salt other than a carbonate is used, it is preferable to similarly perform pre-calcination.

Next, a method for preparing the frit composition as a glaze will be described. A dispersant and water are added to the frit composition and mixed and pulverized using a ball mill, a mortar, a crusher, or the like to produce a slurry. Dispersants include frog eyes (gairome) clay, borax, bentonite, magnesium oxide, magnesium carbonate, potassium carbonate, ammonium alginate, sodium nitrite, potassium nitrite, sodium hexametaphosphate, sodium tripolyphosphate, sodium pyrophosphate, phosphorus Tripotassium acid, disodium hydrogen phosphate, gum arabic and the like. Preferred are gallome clay, potassium carbonate and potassium nitrite.

Further, a pigment which does not melt at the firing temperature is blended. Examples of the shape of the pigment include a granular shape, a spherical shape, and a scale shape, but are not particularly limited. Specific examples of the pigment include white pigments such as titanium oxide, zinc oxide and antimony oxide, various pigments such as iron oxide, chromium oxide, cobalt oxide, manganese oxide and nickel oxide, and other pigments. It is preferable to use a white pigment excellent in concealing property of the base material, and particularly preferable is titanium oxide. More preferred are rutile-type titanium oxides having a high ability to absorb and block wavelengths in the visible region.

The amount of the pigment is 10 to 45 parts by mass, preferably 20 parts by mass, per 100 parts by mass of the frit composition.
４０40 parts by mass. If the amount is less than 10 parts by mass, the lightness is insufficient, and if it exceeds 45 parts by mass, the unevenness of the surface becomes large,
Insufficient gloss. The frit composition for enamel may also contain other additives that are usually added. The glaze thus prepared is glazed on a metal substrate or a plate-like base material made of a material that can withstand the enamel firing temperature.

When the prepared glaze is applied to, for example, a metal substrate, it is preferable that the metal substrate is degreased, washed, and if necessary, plated. Glazing is performed by a coating method using a brush or a roller, a spray method, a spray method using an electrostatic device, a dipping method, a flow coating method, a roll coater method, a transfer paper method, or the like. One side or both sides of the glaze may be selected as necessary.

The thickness of the enamel layer of the enamel product is 20 to 50 μm.
It is. If it is less than 20 μm, gloss and lightness are insufficient.
If it exceeds 50 μm, the appearance of the processed portion tends to be impaired. Preferred is 25-40 μm.

The glazed metal substrate is used in an electric furnace, a gas furnace,
It is held at a high temperature in a tunnel furnace, a batch furnace, or the like, and the glaze on the substrate is fired to form an enamel layer. The firing temperature is a temperature at which the frit composition for enamel melts, but at which the pigment does not melt. Preferred is 700-1000
° C, more preferably 750-900 ° C. A drying step may be interposed between the glaze and the firing.

The metal substrate to be glazed may be an uncoated metal plate such as a normal steel plate, a stainless steel plate, an aluminum plate, etc.
Examples of the metal sheet include a surface treatment such as a plating treatment, a chemical conversion treatment, and a chromate treatment of an aluminum-plated steel sheet, an aluminum-zinc alloy-plated steel sheet, a zinc-iron alloy-plated steel sheet, and the like. Stainless steel sheets are preferable because they have excellent corrosion resistance and weather resistance as compared with other cold-rolled steel sheets and plated steel sheets. In particular, since the ferrite stainless steel sheet has a linear thermal expansion coefficient similar to the linear thermal expansion coefficient of the enamel layer of the present invention, thermal distortion due to thermal expansion mismatch is small, adhesion between the steel sheet and the enamel, design of the enamel product. This is preferable because it becomes easier. The metal plate is not limited to a flat plate, but may be a bent plate. The same applies to the case of glazing a substrate other than a metal substrate. Further, the base material is not limited to a flat plate, and may have a three-dimensional shape.

Although stainless steel is excellent in corrosion resistance and weather resistance, there is a case where the adhesion to the enamel is not sufficient. Therefore, if an iron-chromium composite oxide layer is formed on the surface of the stainless steel, the adhesion to the enamel can be improved. Is improved. The composite oxide layer is formed, for example, by performing the following pretreatment on stainless steel.

When stainless steel (18Cr steel) is heated in the air, as shown in FIG.
₂ O ₃ (in the formula Fe _2X Cr _{2 (1-X)} O ₃ , when X = 1) starts to appear on the surface, and from about 900 ° C., hexagonal Fe _2X C
r _{2 (1-X)} O ₃ (X is a number greater than 0 and less than 1) appears. Then, from about 1000 ° C., tetragonal FeOCr ₂ O
₃ appears.

If a glaze is glazed and fired on the composite oxide layer obtained by such a heat treatment, an enamel product whose enamel is sufficiently adhered to stainless steel can be obtained. When the nickel-plated stainless steel is heat-treated in the same manner as above, cubic Fe ₃ O ₄ , cubic FeCr
₂ O ₄ appears on the surface. The thickness of the composite oxide layer is not particularly limited, but is preferably 0.01 to 10 μm.
m, more preferably 0.1 to 3 μm.

Further, after the passivation film on the surface is removed by shot blasting the stainless steel, the frit composition of the present invention is glazed and fired, so that the interface between the enamel layer and the stainless steel becomes hexagonal Fe _2X. A layer containing a composite oxide such as Cr _{2 (1-X)} O ₃ (X is a number greater than 0 and less than 1) and tetragonal FeOCr ₂ O ₃ is generated. In the case of shot blast, the crystal structure of the composite oxide changes according to the composition of the frit composition.

The crystal structure is preferably a tetragonal system or a hexagonal system from the viewpoint of adhesion, and tetragonal FeOCr ₂ O ₃ , hexagonal Fe _2X Cr _{2 (1-X)} O ₃ (X is larger than 0 ₎ Is more preferable. Hexagonal Fe _2X
The case where _{X of} Cr _{2 (1-X)} O ₃ is 0.3 to 0.6 is particularly preferable because the strength of the composite oxide layer itself is sufficient and the effect of improving adhesion is further improved.

[0045]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. [Inventive Example 1] 100 parts by mass of a frit composition for enamel prepared to have the composition shown in Table 1, 20 parts by mass of titanium oxide (pigment), 25 parts by mass of water, and 2 parts by mass of clay (dispersant) The mixture was put into a ball mill, pulverized and mixed to produce a slurry (glaze).

The obtained slurry was glazed on the surface of a degreased ferritic stainless steel plate by spraying,
By baking at 0 ° C. for 3 minutes, an enamel layer having an average film thickness of 30 μm was formed to obtain an enameled steel plate. The glossiness, lightness, chemical resistance (acid resistance and alkali resistance) of the obtained enameled steel sheet and the appearance of the bent product were evaluated. The results are shown in Table 2.

The test method and measurement method are described below. (Enamel Thickness) The cross section of the enamel layer was observed and measured with a scanning electron microscope (S-800, manufactured by Hitachi, Ltd.). (Glossiness) The enamel layer surface was opened at an opening angle of 45 ° using a photometer (VG-2000 type, manufactured by Nippon Denshoku Industries Co., Ltd.).
Was used to measure the glossiness. When the glossiness was 70% or more, it was determined to be high glossiness. (Lightness) A color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd .: SQ-2000) according to JIS Z8729 "Display method of object color".
), The lightness (L value) of the enamel layer was measured. The L value is an index indicating the concealability of the substrate. If the L value is 86 or more, the base steel sheet cannot be seen through.

(Acid resistance test) JIS R4301 (19
78) Based on the normal temperature spot test (10% citric acid, 15 minute spot) with citric acid specified in the “Enamel Product Quality Standard”, the surface erosion degree of the enamel layer was AA class, A specified in the test method. Grades, B class, C class, and D class were evaluated in five stages. If it was AA class or A class, it was judged that the acid resistance was good.

(Alkali resistance test) JIS R4301
(1978) Based on the alkali resistance test (10% sodium carbonate, 15 minute spot) specified in the “Enamel Product Quality Standard”, the surface erosion degree of the enamel layer was classified into AA class, A class, Classification was made in five grades of B class, C class and D class. If the class was AA or A, the alkali resistance was determined to be good.

(Appearance after Bending) The enameled steel sheet was subjected to 90 ° bending, and the appearance of the bent portion was visually observed to check for peeling of the enamel and cracks on the surface. Enamel peeling, ◎ when there is no surface cracks, cracks, but there is no enamel peeling ○, cracks, enamel peeling with both ×,
◎ and ○ were accepted.

Inventive Examples 2 to 23 and Comparative Examples 1 to 15 Inventive Examples 1 to 23 except that the composition of the frit composition for enamel, the pigment type and the content thereof were changed as shown in Table 1 or Table 2. Similarly, a frit composition for enamel was prepared. Using the obtained composition, an enameled steel sheet was manufactured in the same manner as in Invention Example 1, except that the type of the steel sheet and the thickness of the enamel layer were changed as shown in Table 3 or Table 4. Tables 3 and 4 show the properties of the enameled steel sheet.

Invention Example 24 A frit composition for enamel was prepared in the same manner as in Invention Example 1, except that 100 parts by mass of the frit composition for enamel was prepared so as to have the composition shown in Table 5 (No. A). did. Using the obtained composition, an enamel layer was formed on the surface of a ferritic stainless steel sheet shown in Table 6 in the same manner as in Inventive Example 1. Enamel film thickness, glossiness, brightness, chemical resistance (acid resistance and alkali resistance) of the obtained enameled steel sheet, amount of enamel peeling of the bent steel sheet, crystal form of the mineral phase formed on the stainless steel surface and its mineral phase Was evaluated for film thickness. The results are shown in Table 6.

(Enamel Peeling Amount after Bending) After enameled steel plate was bent at 90 ° of 2.0 mmR, a cellophane tape was attached to the bent portion, and a peeling test was performed to measure the amount of enamel peeling. (Mineral phase formed on the surface of stainless steel) An enameled steel sheet is immersed in an 80% aqueous sodium hydroxide solution at 80 ° C. for 7 days, and the enamel on the steel sheet surface is peeled off. ) Rigaku: RU300 type), and the crystal form of the mineral phase formed on the stainless steel surface was identified.

Note that the X value of hexagonal Fe _{2 X} Cr _{2 (1-X)} O ₃ (X is a number greater than 0 and less than 1) is determined by the Miller index (hkl) of the measured phase, d-spacing of (104). / Nm, Miller index (hk) of hexagonal Cr ₂ O ₃ where X = 0
l) = interplanar spacing d of (104) d = 0.26553 / nm
And the Miller index of the hexagonal Cr ₂ O ₃ where X = 1 (hk
1) The X value was calculated by the proportional distribution of (104) with the interplanar spacing d = 0.27000 / nm.

(Thickness of Mineral Phase Generated on Stainless Steel Surface) The cross section of the mineral phase was observed and measured by a scanning electron microscope (S-800, manufactured by Hitachi, Ltd.).

[Inventive Examples 25-35, Comparative Examples 16-28]
An enamel frit composition was prepared in the same manner as in Inventive Example 1, except that the composition of the enamel frit composition, the pigment type and the content thereof were changed as shown in Table 5. Using the obtained composition, an enameled steel sheet was produced in the same manner as in Invention Example 1, except that the steel sheet type and the thickness of the enamel layer were changed as shown in Table 6 or Table 7. The properties of the enameled steel sheet are shown in Table 6 or Table 7.

[0057]

[Table 1]

[0058]

[Table 2]

[0059]

[Table 3]

[0060]

[Table 4]

[0061]

[Table 5]

[0062]

[Table 6]

[0063]

[Table 7]

[0064]

According to the present invention, an enamel frit composition suitable for producing an enamel product satisfying all of brightness, gloss, chemical resistance and processability, and a frit composition produced using the composition, It is possible to provide an enamel product having high brightness, high gloss, excellent chemical resistance, and excellent bending workability. Further, the frit composition for enamel and the enamel product of the present invention do not contain harmful substances such as heavy metals, so that there is no problem in terms of hygiene and recycling. Further, the present invention provides an enamel product having excellent adhesion to stainless steel, which is not always good in adhesion to the enamel layer. Since the enamel product of the present invention has the above-mentioned characteristics, it can be suitably used for a wider range of uses than conventional enamel products.

[Brief description of the drawings]

FIG. 1 is a reference diagram showing the relationship between the temperature and the amount of iron-chromium composite oxide formed on the surface when stainless steel is heated.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masato Kumagai 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel Co., Ltd. (72) Naoki Nishiyama 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Inside Steel Technology Co., Ltd. (72) Inventor Hiroshi Nagaishi 2--18-13 Higashi Narashino, Narashino City, Chiba Prefecture Kawasaki Iron & Steel Materials Co., Ltd. Narashino Plant (72) Inventor Masao Taguchi 2-18-13 Higashi Narashino, Narashino City, Chiba Prefecture 4G062 AA08 AA09 AA15 BB05 DA05 DA06 DB02 DB03 DC04 DD01 DE01 DF01 EA03 EB03 EB04 EC01 EC02 EC03 EC04 ED01 EE01 EF01 EG01 FA01 FB03 FB01 FC01 GA01 F01 FF01 GB01 GC01 GD01 GE01 GE02 HH01 HH03 HH05 HH07 HH09 HH11 HH13 HH15 HH17 HH20 JJ01 JJ03 JJ05 JJ07 JJ10 KK01 KK03 KK0 5 KK07 KK10 MM06 MM12 NN05 NN34 PP04

Claims (6)

[Claims] (1) The following oxides are contained at the following percentages by mass, and the SiO ₂ / B ₂ O ₃ (mass ratio) is 1.5 to 5
A frit composition for an enamel. SiO ₂ : 35 to 60%, TiO ₂ : 5 to 30%, Na ₂ O: 5 to 25%, Li ₂ O: 1 to 10%, Na ₂ O + Li ₂ O + K ₂ O: 10 to 30%, B ₂ O ₃ : 10 to 25%, Al ₂ O ₃ : 0.1 to 5% and halogen: less than 0.05%. 2. A pigment is added to 100 parts by mass of the composition.
The frit composition for an enamel according to claim 1, wherein the composition comprises 0 to 45 parts by mass. 3. The method according to claim 1, wherein at least one surface of the substrate is provided.
Or an enamel product comprising an enamel layer comprising the composition according to 2. 4. The enamel product according to claim 3, wherein said substrate is stainless steel. 5. The enamel product according to claim 4, wherein said composition is coated on stainless steel via an iron-chromium composite oxide layer. 6. The enamel product according to claim 5, wherein the crystal structure of the composite oxide constituting the composite oxide layer is tetragonal and / or hexagonal.