CN108516685A - Heat and corrosion resistant enamel coating and preparation method thereof - Google Patents

Abstract

The invention belongs to enamel material technical fields, and in particular to a kind of heat and corrosion resistant enamel coating and preparation method thereof.For it is easy to fall off, heat resistance is bad under existing enamel coating high temperature the problems such as, the present invention provides a kind of heat and corrosion resistant enamel coating and preparation method thereof.The present invention prepares heat and corrosion resistant enamel coating and first burns out base enamel layer in metal base surface, cover-coat enamel slurry is sprayed to the enamel coating surface baked again, through 130~150 DEG C of dryings, heat and corrosion resistant enamel coating is made in 900~950 DEG C of 12~15min of enamel firing.The heat and corrosion resistant enamel coating of the present invention belongs to indifferent oxide system, with good, the extremely low oxygen migration rate of richness, has good thermal stability and inoxidizability, acid and alkali-resistance, anticorrosion effect are good.

Description

Heat-resistant corrosion enamel coating and preparation method thereof

technical field

The invention belongs to the technical field of enamel materials, and in particular relates to a heat-resistant corrosion enamel coating and a preparation method thereof.

Background technique

The hot-end components of thermal components in coal-fired and oil-fired devices such as turbines, steam turbines, gas turbines, and thermal power plant boilers generally work in harsh environments. These harsh environments can cause damage such as erosion, high temperature oxidation, and thermal corrosion.

When high-temperature metal parts are in the working environment of 600 ℃ ~ 1200 ℃, usually due to the impurities contained in the fuel, such as sulfur, potassium, sodium, etc., gases such as SO ₂ , SO ₃ , and H ₂ S are formed during combustion and the impurities in the air Oxygen, NaCl and other reactions accelerate the corrosion of materials, and sometimes even cause catastrophic accidents. When hot corrosion occurs, a layer of salt film will be deposited on the metal surface. After the salt film is formed, the degree of hot corrosion is related to the adhesion and wettability of the molten salt (NaCl, Na ₂ SO ₄ ) to the metal surface. Many sulphate or mixed salt films deposited on surfaces are liquid at high temperatures, thus accelerating the corrosion of metallic materials. At present, the main method to prevent salt corrosion on metal surfaces is to apply heat-resistant corrosion-resistant coatings.

Traditional protective coatings mainly include thermal diffusion coatings and alloy coatings such as TiAlCr. Although the TiAlCr coating can significantly improve the oxidation resistance, during long-term service, the interdiffusion of the coating/substrate will cause the loss of Al in the coating, which cannot maintain the growth of Al ₂ O ₃ on the surface. Poor performance. The thermal diffusion coating uses chromizing and aluminizing, and then pre-oxidizes to form chromium oxide and aluminum oxide on the surface of the alloy. Although it plays the role of a protective film, it is also in the hot molten salt environment of NaCl and Na ₂ SO ₄ . The lower sulfate or mixed salt film is in a liquid state, adheres to the surface of the thermal diffusion coating and undergoes hot corrosion with aluminum oxide to form AlCl ₃ or Al ₂ (SO ₄ ) ₃ corrosion products.

In recent years, enamel coatings have attracted great interest because of their excellent resistance to high-temperature oxidation and hot corrosion. Enamel coatings are inert oxide coatings with extremely low oxygen migration rates, which can not only significantly improve the oxidation resistance , can also significantly improve the thermal corrosion resistance.

The enamel coating is an inorganic enamel layer coated and fired on the surface of the metal base. Enamel coating does not require expensive equipment such as thermal spraying and electron beam physical vapor deposition, and has good economy. The general preparation method of enamel coating is to first burn the raw materials into enamel blocks, then grind them into fine powder, spray them on the surface of parts, and finally carry out high-temperature enamel firing to form a coating on the surface of parts, which has the functions of preventing metal corrosion and wear resistance. , heat resistance, non-toxic and other properties. Enamel has high acid corrosion resistance, smooth surface, not easy to stain, high hardness, wear resistance, and has good heat transfer coefficient and heat capacity.

The traditional enamel process is mainly based on low carbon steel research:

Patent CN201310419123.4 provides a surface alloy heat-resistant coating composite material, which is composed of metal alloy powder and enamel powder with a face-centered cubic structure. Quartz, ZrO ₂ , Cr ₂ O ₃ , AlN, Si ₃ N ₄ and metal alloy powder NiCrAlX, NiCrX and NiCoCrAlX mixed rare earth two or more rare earth elements are used at the same time, or rare earth elements are mixed with Na, K, Ca, Sr, One or more of Ba is used in combination, and then mixed with enamel and alumina particles to form a ternary composite coating, the mixed powder slurry is sprayed on the surface of high-temperature material parts, and the sprayed parts are subjected to high-temperature treatment. Forms a thermal protective coating for hardfacing alloy coating composites.

The enamel glaze in this patent is added with AlN and metal alloy powder NiCrAlX. In the hot corrosion environment, Al reacts with Cl-hot molten salt ions at high temperature to produce Cl ₂ , and Cl ₂ will micro-crack and sputter the coating along the coating surface The columnar crystal diffusion channel penetrates into the coating and reacts with metal atoms such as Al and Fe in the coating to generate AlCl ₃ or FeCl ₃ which is volatile at high temperature. Especially when the enamel coating is directly mixed with metal aluminum or aluminum alloy, in a high-temperature hot corrosion environment, ^Cl- is more likely to undergo excessive interfacial reaction with the Al matrix, resulting in continuous dissolution of the alloy matrix, and the content of low melting point components in traditional enamel coatings is too high , The ability to resist diffusion and penetration of hot corrosive media and the comprehensive performance of thermal cycle spalling are poor.

Patent CN200610047216.9 mixes metal powder and enamel powder evenly, sprays the mixed powder on the surface of the sample, and sinters the metal powder at high temperature to disperse and distribute on the enamel substrate to form a metal alloy-enamel coating, a metal alloy-enamel-hard reinforcement phase coating Layers or metal alloy-enamel coatings and metal alloy-enamel-hard reinforcement coatings are prepared as thermal anti-corrosion coatings.

The firing temperature of the mixed coating of metal powder and enamel formed in this patent is 600-900°C, which only belongs to the enamel firing process of the enamel coating. The metal powder is simply mixed in the softened enamel coating, and does not really form into the enamel. In the network oxide structure of the coating, when the metal powder has a high thermal expansion coefficient in a hot corrosion environment, it will be separated from the network structure in the enamel layer after repeated thermal expansion, and tiny cracks will appear, thus losing Protection against thermal corrosion of the glaze layer.

Patent CN201410653315.6 provides a composite enamel coating consisting of an enamel matrix and ceramic particles, wherein the ceramic particles are corundum with a particle size of less than 5 μm, and the amount added is 15 to 30 wt% of the weight of the composite enamel coating. Using absolute ethanol as a dispersant, a uniformly dispersed composite enamel suspension is obtained through magnetic stirring and ultrasonic oscillation for 15 to 30 minutes. The composite enamel suspension is uniformly sprayed on the high-temperature alloy parts with an air compressor, and dried at 200-300°C to obtain a composite enamel coating. The composition ratio of the enamel matrix is: silicon dioxide 58-62wt%, zirconium dioxide 10-13wt%, aluminum oxide 5-8wt%, calcium oxide 5-7wt%, diboron trioxide 4-6wt%, strontium oxide 2-4wt%, titanium dioxide 2-4wt%, sodium oxide and/or potassium oxide 2-6wt%, nickel oxide 0-2wt%.

The oxide of Co in this patented adhesive agent is hot-corroded at a high temperature of 650-750°C, and the hot-corrosion speed is relatively fast. During the corrosion process, the oxide of Co undergoes instantaneous sulfidation, and then forms CoSO ₄ -Na ₂ SO ₄ liquid eutectic Salt delays the formation of protective Cr ₂ O ₃ oxide film, which will accelerate the speed of hot corrosion. As the depth of hot corrosion progresses, the composite enamel coating will fall off directly, causing catastrophic corrosion of the metal substrate directly.

Therefore, the existing enamel coatings generally have the defects of being easy to fall off at high temperatures and having poor heat resistance.

Contents of the invention

The technical problem to be solved by the invention is that the existing enamel coating is easy to fall off under high temperature, poor heat resistance and the like.

The technical solution of the present invention to solve the above technical problems is to provide a heat-resistant corrosion enamel coating and a preparation method thereof.

The first technical problem to be solved by the present invention is to provide a kind of enamel bottom glaze. The composition of the enamel bottom glaze includes: 30-33 parts by weight of SiO ₂ , NaB ₄ O ₇ .4H ₂ O 44 ～48 parts, NaNO ₃ 16～18 parts, Na ₂ CO ₃ 13～15 parts, Li ₂ CO ₃ 1.5～3.5 parts, fluorite 8～11 parts, Na ₂ SiF ₆ 1～3 parts, Na ₃ AlF ₆ 6 ~8 parts, Na ₄ P ₂ O ₇ .10H ₂ O 3~5 parts, Co(NO ₃ ) ₂ 6~8 parts, and Ni(NO ₃ ) ₂ 2~4 parts.

The second technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned enamel bottom glaze material, which includes the following steps: after weighing the raw materials according to parts by weight and mixing them evenly, heating to 1300-1350° C. for 2-3 hours, turning to Quenched in cold water, dried at 100-130°C for 20-30 minutes to obtain enamel bottom glaze.

Wherein, in the preparation method of the above-mentioned enamel bottom glaze, the heating adopts an electric furnace.

The third technical problem to be solved by the present invention is to provide a kind of enamel bottom glaze slurry, which is composed of 100 parts of the above enamel bottom glaze, 15 to 19 parts of clay, 2 to 3 parts of bentonite, and 1 to 2 parts of magnesium sulfate. , crushed to a particle size of -200 mesh ≥ 98%, add 20 to 22 parts of water and mix evenly.

The fourth technical problem to be solved by the present invention is to provide an enamel surface glaze, the composition of which includes: 35-42 parts by weight of SiO ₂ , 26-28 parts of NaB ₄ O ₇ .4H ₂ O, 26-28 parts of NaB 4 O 7 .4H 2 O, ₂ CO ₃ 8.5-10 parts, Li ₂ CO ₃ 3-5 parts, NiO 0.5-1 part, Na ₃ AlF ₆ 5-7 parts, Na ₂ CrO ₄ 3.5-4 parts, NaSbO ₃ 1-2 parts, SrSO ₄ 1 to 2 parts and 0.5 to 1 part of Na ₂ MO ₃ .

The fifth technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned enamel surface glaze, which includes the following steps: after weighing the raw materials according to parts by weight and mixing them, heating to 1200-1250 ° C for 2-3 hours, turning to Quenched in cold water, dried at 100-130°C for 20-30 minutes to obtain enamel surface glaze.

The sixth technical problem to be solved in the present invention is to provide a kind of enamel surface glaze slurry, which consists of 100 parts of enamel surface glaze, 11 to 13 parts of clay, 5 to 7 parts of bentonite, 4 to 5 parts of zirconium quartz, C- Mix 25-30 parts of BN, 1-2 parts of LiF, crush until particle size -200 mesh ≥ 98%, add 25-30 parts of glass powder, 22-25 parts of water and mix evenly.

Wherein, the zircon quartz is zircon quartz with ZrO ₂ content>65%.

Wherein, the glass powder is a fine powder that passes through a 400-mesh sieve and is ground from ordinary waste glass.

The seventh technical problem to be solved by the present invention is to provide a method for preparing a heat-resistant corrosion enamel coating, which includes the following steps:

a. Spray the enamel bottom glaze slurry on the surface of the treated metal substrate to form a slurry coating of 0.3-0.5mm, dry it at 130-150°C for 30-45min, transfer it to an electric furnace at 900-950°C for 12- 15min, cooling, the bottom glaze layer of enamel is obtained;

b. Spray the enamel surface glaze slurry on the surface of the enamel bottom glaze layer obtained in step a to form a 0.2-0.4mm slurry coating, dry it at 130-150°C for 30-45min, and then transfer it to an electric furnace for 850-900°C Enameling at ℃ for 10-12 minutes, cooling to obtain a heat-resistant corrosion enamel coating.

Wherein, the metal base includes at least one of low carbon steel Q235, enamel steel BTC245R or cold rolled carbon steel SPCC.

Wherein, the treatment is cleaning with detergent, drying, and sandblasting.

The beneficial effects of the present invention are:

The invention adds B ₂ O ₃ to the enamel bottom glaze, so that the enamel bottom glaze has better metal wetting ability; in addition, it is also an excellent flux, which makes the enamel easy to melt, melt and borosilicate-free The salt melt can dissolve FeO strongly, so that the enamel coating has good thermal stability and oxidation resistance; the enamel surface glaze of the present invention is a fluorine-free surface glaze containing Cr ₂ O ₃ , NiO and ZrO, and can Slow down the corrosion of metal and play an anti-corrosion effect; and, adding cubic boron nitride (C-BN) to the enamel surface glaze makes the surface glaze better thermal stability and greater thermal shock resistance; after specific Spraying method Spray enamel base glaze and enamel surface glaze on the surface of the metal substrate to form a heat-resistant corrosion enamel coating. Glass powder is added to make the enamel surface glaze chemically stable and resistant to acid and alkali corrosion and thermal corrosion.

The heat-resistant corrosion-resistant enamel coating prepared by the present invention can be oxidized and thermally corroded 100 times in a 75wt% Na ₂ SO ₄ + 25wt% NaCl corrosion medium with a salt content of 850°C for 100 times, and the glaze surface of the coating has no peeling phenomenon, no vulcanization or internal oxidation phenomenon , the heat corrosion increment is 0.08～0.64mg/cm ² , which is less than the heat corrosion-resistant enamel coating performance test increment of 7.5mg/cm ² . Compared with the existing metal coatings, the enamel coating of the present invention has good corrosion resistance Ability to corrode at high temperatures.

Detailed ways

The invention provides an enamel bottom glaze. The composition of the enamel bottom glaze includes: in parts by weight, 30-33 parts of SiO ₂ , 44-48 parts of NaB ₄ O ₇ .4H ₂ O, 16-48 parts of NaNO ₃ 18 parts, Na ₂ CO ₃ 13-15 parts, Li ₂ CO ₃ 1.5-3.5 parts, fluorite 8-11 parts, Na ₂ SiF ₆ 1-3 parts, Na ₃ AlF ₆ 6-8 parts, Na ₄ P ₂ 3-5 parts of O ₇ .10H ₂ O, 6-8 parts of Co(NO ₃ ) ₂ and 2-4 parts of Ni(NO ₃ ) ₂ .

In the enamel bottom glaze of the present invention, NaB ₄ O ₇ .4H ₂ O is added, which is decomposed to form B ₂ O ₃ in the firing process of the enamel bottom glaze. It can improve the metal wetting ability of the enamel bottom glaze, and can also be used as a flux to make the enamel bottom glaze easy to melt, and the melt and borosilicate-free melt can strongly dissolve FeO, thus ensuring the oxidation resistance of the metal at high temperature. Na ₄ P ₂ O ₇ .10H ₂ O decomposes to form P ₂ O ₅ during the firing process of the bottom glaze, which replaces some of the positions of B ³⁺ and Si ⁴⁺ atoms in the random network structure of the bottom glaze, interlacing with each other to form The tetrahedral structure is beneficial to the strength of the underglaze layer of enamel and improves the adhesion between the underglaze and the metal substrate.

The preparation method of the above enamel bottom glaze includes the following steps: after weighing the raw materials according to the weight part, mixing them evenly, heating to 1300-1350° C. for 2-3 hours, melting in cold water, and drying at 100-130° C. for 20-30 minutes , to prepare the enamel bottom glaze.

In order to spray more evenly, when the present invention uses the above-mentioned enamel bottom glaze, the bottom glaze is prepared as an enamel bottom glaze slurry, which consists of 100 parts of the above-mentioned enamel bottom glaze, 15-19 parts of clay, and 2-2 parts of bentonite. 3 parts, 1 to 2 parts of magnesium sulfate are mixed, crushed to a particle size of -200 mesh ≥ 98%, and 20 to 22 parts are added and mixed evenly.

After adding 1-2 parts of magnesium sulfate when the slurry is prepared in the present invention, charged colloidal particles of Mg ²⁺ are formed in the slurry, and the suspoemulsion and fluidity of the slurry are increased.

Furthermore, the present invention also provides an enamel surface glaze, the composition of which includes: 35-42 parts by weight of SiO ₂ , 26-28 parts of NaB ₄ O ₇ .4H ₂ O, 8.5 parts of Na ₂ CO ₃ ～10 parts, Li ₂ CO ₃ 3～5 parts, NiO 0.5～1 parts, Na ₃ AlF ₆ 5～7 parts, Na ₂ CrO ₄ 3.5～4 parts, NaSbO ₃ 1～2 parts, SrSO ₄ 1～2 parts and Na ₂ MO ₃ 0.5 to 1 part.

In the surface glaze of the present invention, NiO is specially added, which is the main element that forms austenite and has high-temperature strength, and can improve the high-temperature resistance of the surface glaze; in addition, SiO ₂ is added to further improve the enamel surface glaze. Oxidation resistance, lowering the firing temperature can also reduce the oxidation and diffusion rate of Ni; in addition, Na ₂ CrO ₄ is added to decompose into CrO ₃ at high temperature, which is the main element to improve oxidation resistance. When corrosion occurs, the enamel The dense Cr ₂ O ₃ oxide film formed in the surface glaze can prevent the strong melting and destruction of hot molten salt Cl ^- and SO ₄ ^2- ions. As the corrosion progresses, the Cr ₂ O ₃ oxide layer continues to thicken, and the oxide film is alkaline The loose honeycomb shape produced by melting is filled with NiO, ZrO and C-BN, which blocks the diffusion channels of the metal matrix and oxygen and sulfur, slows down the corrosion of the metal, and plays an anti-corrosion role. Therefore, the enamel surface glaze of the present invention can improve the high temperature resistance and corrosion resistance of the metal substrate.

The preparation method of the above-mentioned enamel surface glaze comprises the following steps: after weighing the raw materials according to parts by weight and mixing them evenly, heating to 1200-1250° C. to melt for 2-3 hours, quenching in cold water, and drying at 100-130° C. for 20-3 hours. 30min to prepare the enamel surface glaze.

Similarly, when using the above-mentioned enamel surface glaze for spraying, it can also be prepared into enamel surface glaze slurry, and the slurry is composed of 100 parts of enamel surface glaze, 11-13 parts of clay, 5-7 parts of bentonite, zirconium Quartz (ZrO ₂ content > 65%) 4-5 parts, C-BN 25-30 parts, LiF 1-2 parts mixed, crushed to particle size -200 mesh ≥ 98%, add 400 mesh glass powder 25-30 parts, water Prepared by mixing 22-25 parts evenly.

The present invention adds C-BN and glass powder when preparing the slurry. C-BN material has good thermal stability and can be used in an oxidizing atmosphere around 1000°C and an inert atmosphere near 3000°C. It is a refractory material with higher refractoriness than mullite, alumina and silicon carbide. At the same time, it has high thermal shock resistance, and it does not crack when repeated rapid cooling and rapid heating at 1500 °C. And does not react with iron group metals. In addition to excellent wear resistance, C-BN has excellent heat resistance. Refractory materials and anti-oxidation additives are especially suitable for the use of anti-corrosion molten metal, heat-enhancing additives, and high-temperature-resistant insulating materials.

Glass powder is formed into amorphous hard particles after high-speed crushing. It is an easy-to-grind, anti-scratch, high-transparency powder with good affinity and strong steric resistance, which can be well dispersed in coatings. , small particle size, good dispersibility, high transparency, good anti-sedimentation effect. The glass raw material contains a certain amount of PbO, SiO ₂ , TiO ₂ , doped into the enamel glaze, and undergoes a high-temperature solid-state reaction to form a homogeneous enamel glass with a disordered structure, which can increase the fullness of the enamel layer. Stable chemical properties, good acid and alkali corrosion resistance, hot corrosion effect.

Further, the present invention provides a method for preparing a heat-resistant corrosion enamel coating, comprising the following steps:

a. Spray the enamel bottom glaze slurry on the surface of the treated metal substrate to form a slurry coating of 0.3-0.5mm, dry it at 130-150°C for 30-45min, transfer it to an electric furnace at 900-950°C for 12- 15min, cooling, the bottom glaze layer of enamel is obtained;

b. Spray the enamel surface glaze slurry on the surface of the enamel bottom glaze layer obtained in step a to form a 0.2-0.4mm slurry coating, dry it at 130-150°C for 30-45min, and then transfer it to an electric furnace for 850-900°C Enameling at ℃ for 10-12 minutes, cooling to obtain a heat-resistant corrosion enamel coating.

The bottom glaze in the present invention is sprayed with 0.3-0.5mm, which can improve the adhesion effect between the bottom glaze and the metal substrate, and is more conducive to protecting the metal substrate in a hot-rot environment; the surface glaze is sprayed with 0.2-0.4mm, and the surface glaze should not be sprayed. If the surface glaze is sprayed too thick, the thickness of the bottom glaze and the entire enamel coating will exceed 0.8 ~ 0.9mm, and it is easy to devitrify and crack under high temperature environment.

In the present invention, unless otherwise specified, the parts appearing are all parts by weight.

The following will further explain the specific implementation of the present invention through examples, but it does not mean that the protection scope of the present invention is limited to the scope described in the examples.

In embodiment and comparative example, described raw material is common commercially available product.

Embodiment 1 prepares enamel coating with the inventive method

In parts by weight, SiO ₂ 30 parts, NaB ₄ O ₇ .4H ₂ O 44 parts, NaNO ₃ 16 parts, Na ₂ CO ₃ 15 parts, Li ₂ CO ₃ 3.5 parts, fluorite 10 parts, Na ₂ SiF ₆ 2.5 parts, 6 parts of Na ₃ AlF ₆ , 3.5 parts of Na ₄ P ₂ O ₇ .10H ₂ O, 8 parts of Co(NO ₃ ) ₂ and 3 parts of Ni(NO ₃ ) ₂ are mixed evenly, heated to 1300°C and melted 2h, quenched in cold water, and dried at 105°C for 20min to obtain enamel bottom glaze. Mix 100 parts of bottom glaze, 16 parts of clay, 3 parts of bentonite and 1.5 parts of magnesium sulfate, pulverize to a particle size of -200, add 20 parts of water and mix evenly to prepare enamel bottom glaze slurry.

Sandblast the surface of the enamel steel BTC245R sample, clean and decontaminate, and after drying, spray the enamel bottom glaze slurry on the surface with a thickness of 0.3-0.5mm. ;

Parts by mass: SiO ₂ 40 parts, NaB ₄ O ₇ .4H ₂ O 28 parts, Na ₂ CO ₃ 8.5 parts, Li ₂ CO ₃ 3.5 parts, NiO 0.5 parts, Na ₃ AlF ₆ 5.5 parts, Na ₂ CrO ₄ 3.5 parts 1.5 parts of NaSbO ₃ , 1 part of SrSO ₄ and 0.5 parts of Na ₂ MO ₃ are mixed, melted at 1200°C for 3 hours, quenched in water, and dried to obtain enamel surface glaze. According to 100 parts of enamel surface glaze, 11 parts of clay, 6.5 parts of bentonite, 4.5 parts of zirconium quartz, 25 parts of C-BN, 1.5 parts of LiF, pulverize to a particle size of -200 mesh ≥ 98%, add 25 parts of 400 mesh glass powder, and 22 parts of water Mix parts evenly to get enamel surface glaze slurry, spray it on the 0.2-0.4mm bottom enamel layer, after drying, sinter at 900°C for 12min to obtain a heat-resistant corrosion enamel coating.

The enamel coating surface is coated with 75wt% Na ₂ SO ₄ + 25wt% NaCl corrosion medium salt, and cyclic oxidation and thermal corrosion at 850°C for 100 times in a tube furnace. It was observed that the glazed surface of the enamel coating did not peel off, and the weight gain after thermal corrosion was weighed to be 0.081 mg/cm ² .

Embodiment 2 prepares enamel coating with the inventive method

In parts by weight, SiO ₂ 30 parts, NaB ₄ O ₇ .4H ₂ O 44 parts, NaNO ₃ 16 parts, Na ₂ CO ₃ 15 parts, Li ₂ CO ₃ 3.5 parts, fluorite 10 parts, Na ₂ SiF ₆ 2.5 parts, 6 parts of Na ₃ AlF ₆ , 3.5 parts of Na ₄ P ₂ O ₇ .10H ₂ O, 8 parts of Co(NO ₃ ) ₂ and 3 parts of Ni(NO ₃ ) ₂ are mixed evenly, heated to 1300°C and melted 2h, quenched in cold water, and dried at 105°C for 20min to obtain enamel bottom glaze. Mix 100 parts of bottom glaze, 16 parts of clay, 3 parts of bentonite and 1.5 parts of magnesium sulfate, pulverize to a particle size of -200, add 20 parts of water and mix evenly to prepare enamel bottom glaze slurry.

The surface of the low-carbon steel Q235 sample is sandblasted, cleaned and decontaminated, and after drying, it is sprayed on the surface with the enamel bottom glaze slurry, with a thickness of 0.3-0.5mm. After drying, it is fired at 900°C for 12 minutes to obtain enamel bottom glaze layer;

Preparation of enamel surface glaze: parts by mass: SiO ₂ 40 parts, NaB ₄ O ₇ .4H ₂ O 28 parts, Na ₂ CO ₃ 8.5 parts, Li ₂ CO ₃ 3.5 parts, NiO 0.5 parts, Na ₃ AlF ₆ 5.5 parts , 1.5 parts of NaSbO ₃ , and 1 part of SrSO ₄ are mixed, melted at 1200°C for 3 hours, quenched in water, and dried to obtain enamel blocks. 100 parts of enamel block, 11 parts of clay, 6.5 parts of bentonite, 4.5 parts of zirconium quartz, 25 parts of C-BN, 1.5 parts of LiF, crushed to a particle size of -200 mesh ≥ 98%, add 25 parts of 400 mesh glass powder, 22 parts of water Mix uniformly the porcelain surface glaze slurry and spray it on the 0.2-0.4mm surface of the enamel bottom glaze layer. After drying, sinter at 900°C for 12 minutes to obtain a heat-resistant corrosion enamel coating.

Coat the enamel coating surface with 75wt% Na ₂ SO ₄ +25wt% NaCl corrosion medium salt, and cycle oxidation thermal corrosion in a tube furnace at 850°C for 100 times. Observe that the enamel coating glaze does not peel off, and the surface has thermal corrosion , the glaze surface is uneven. It is black gray, and the weight gain after weighing and heat corrosion is 0.45mg/cm ² .

Embodiment 3 prepares enamel coating with the inventive method

In parts by weight, SiO ₂ 30 parts, NaB ₄ O ₇ .4H ₂ O 44 parts, NaNO ₃ 16 parts, Na ₂ CO ₃ 15 parts, Li ₂ CO ₃ 3.5 parts, fluorite 10 parts, Na ₂ SiF ₆ 2.5 parts, 6 parts of Na ₃ AlF ₆ , 3.5 parts of Na ₄ P ₂ O ₇ .10H ₂ O, 8 parts of Co(NO ₃ ) ₂ and 3 parts of Ni(NO ₃ ) ₂ are mixed evenly, heated to 1300°C and melted 2h, quenched in cold water, and dried at 105°C for 20min to obtain enamel bottom glaze. Mix 100 parts of bottom glaze, 16 parts of clay, 3 parts of bentonite and 1.5 parts of magnesium sulfate, pulverize to a particle size of -200, add 20 parts of water and mix evenly to prepare enamel bottom glaze slurry.

The surface of the cold-rolled carbon steel SPCC sample is sandblasted, cleaned and decontaminated, and after drying, it is sprayed on the surface with the enamel bottom glaze slurry, with a thickness of 0.3-0.5mm. After drying, it is fired at 900 ° C for 12 minutes to obtain Enamel underglaze layer.

Preparation of enamel surface glaze: parts by mass: SiO ₂ 42 parts, NaB ₄ O ₇ .4H ₂ O 28 parts, Na ₂ CO ₃ 8.5 parts, Li ₂ CO ₃ 5 parts, NiO 1 part, Na ₃ AlF ₆ 5.5 parts , 4 parts of Na ₂ CrO ₄ , 1.5 parts of NaSbO ₃ , 1 part of SrSO ₄ and 0.5 part of Na ₂ MO ₃ were mixed, melted at 1200°C for 3 hours, quenched in water, and dried to obtain enamel blocks. Press 100 parts of enamel block, 11 parts of clay, 6.5 parts of bentonite, 5 parts of zirconium quartz, 15 parts of C-BN, 1.5 parts of LiF, grind to particle size -200 mesh ≥ 98%, add 10 parts of 400 mesh glass powder, and mix with 22 parts of water Spray the evenly obtained porcelain glaze slurry on the surface of the enamel bottom glaze of 0.2-0.4 mm, and after drying, sinter at 900 ° C for 12 minutes to obtain a heat-resistant and corrosion-resistant enamel coating.

The surface of the enamel coating was coated with 75wt% Na ₂ SO ₄ +25wt% NaCl corrosion medium salt, and it was oxidized and thermally corroded 100 times in a tube furnace at 850°C. It was observed that the enamel coating did not peel off, but the enamel surface was not. It is smooth, with sulfidation corrosion channels appearing, and the weight increases obviously by 3.21mg/cm ² after hot corrosion.

Embodiment 4 prepares enamel coating with the inventive method

In parts by weight, SiO ₂ 30 parts, NaB ₄ O ₇ .4H ₂ O 44 parts, NaNO ₃ 16 parts, Na ₂ CO ₃ 15 parts, Li ₂ CO ₃ 3.5 parts, fluorite 10 parts, Na ₂ SiF ₆ 2.5 parts, 6 parts of Na ₃ AlF ₆ , 3.5 parts of Na ₄ P ₂ O ₇ .10H ₂ O, 8 parts of Co(NO ₃ ) ₂ and 3 parts of Ni(NO ₃ ) ₂ are mixed evenly, heated to 1300°C and melted 2h, quenched in cold water, and dried at 105°C for 20min to obtain enamel bottom glaze. Mix 100 parts of bottom glaze, 16 parts of clay, 3 parts of bentonite and 1.5 parts of magnesium sulfate, pulverize to a particle size of -200, add 20 parts of water and mix evenly to prepare enamel bottom glaze slurry.

Sandblast the surface of the enamel steel BTC245R sample, clean and decontaminate, and after drying, spray the enamel bottom glaze slurry on the surface with a thickness of 0.3-0.5mm. glaze layer.

Preparation of enamel surface glaze: parts by mass: SiO ₂ 42 parts, NaB ₄ O ₇ .4H ₂ O 26 parts, Li ₂ CO ₃ 3.5 parts, NiO 1 part, Na ₂ CrO ₄ 3.5 parts, NaSbO ₃ 1 part, SrSO ₄ 1 parts were mixed and melted at 1200°C for 3 hours, water quenched and dried to obtain enamel blocks. Press 100 parts of enamel block, 11 parts of clay, 6.5 parts of bentonite, 4 parts of zirconium quartz, 25 parts of C-BN, 1.5 parts of LiF, grind to particle size -200 mesh ≥ 98%, add 25 parts of 400 mesh glass powder, 22 parts of water Mix uniformly the porcelain surface glaze slurry and spray it on the 0.2-0.4mm surface of the enamel bottom glaze layer. After drying, sinter at 900°C for 12 minutes to obtain a heat-resistant corrosion enamel coating.

The surface of the enamel coating was coated with 75wt% Na ₂ SO ₄ +25wt% NaCl corrosion medium salt, and it was oxidized and thermally corroded 100 times in a tube furnace at 850°C. It was observed that the glaze surface of the enamel coating did not peel off, and there was no internal vulcanization or Internal oxidation phenomenon, but the enamel surface is uneven, a small amount of cracks appear, and the weight gain after weighing is 0.64mg/cm ² .

Comparative example 1 does not adopt bottom glaze material of the present invention to prepare enamel coating

In parts by weight, SiO ₂ 30 parts, NaNO ₃ 16 parts, Na ₂ CO ₃ 15 parts, Li ₂ CO ₃ 3.5 parts, fluorite 10 parts, Na ₂ SiF ₆ 2.5 parts, Na ₃ AlF ₆ 6 parts, Co Mix 8 parts of (NO ₃ ) ₂ and 3 parts of Ni(NO ₃ ) ₂ evenly, heat to 1300°C and melt for 2 hours, quench in cold water, and dry at 105°C for 20 minutes to obtain the enamel bottom glaze. Mix 100 parts of bottom glaze, 16 parts of clay, 3 parts of bentonite and 1.5 parts of magnesium sulfate, pulverize to a particle size of -200, add 20 parts of water and mix evenly to prepare enamel bottom glaze slurry.

Sandblast the surface of the enamel steel BTC245R sample, clean and decontaminate, and after drying, spray the enamel bottom glaze slurry on its surface with a thickness of 0.3-0.5mm. glaze layer;

Preparation of enamel surface glaze: parts by mass: SiO ₂ 40 parts, NaB ₄ O ₇ .4H ₂ O 28 parts, Na ₂ CO ₃ 8.5 parts, Li ₂ CO ₃ 3.5 parts, NiO 0.5 parts, Na ₃ AlF ₆ 5.5 parts , 3.5 parts of Na ₂ CrO ₄ , 1.5 parts of NaSbO ₃ , 1 part of SrSO ₄ and 0.5 part of Na ₂ MO ₃ were mixed, melted at 1200°C for 3 hours, quenched in water, and dried to obtain enamel blocks. Press 100 parts of enamel block, 11 parts of clay, 6.5 parts of bentonite, and 1.5 parts of LiF, grind to a particle size of -200 mesh ≥ 98%, add 22 parts of water and mix evenly to get porcelain surface glaze slurry and spray it on the enamel bottom glaze layer 0.2-0.4mm , after drying, 900 ℃ enamelling 12min, made of heat-resistant corrosion enamel coating.

The surface of the enamel coating is coated with 75wt% Na ₂ SO ₄ +25wt% NaCl corrosion medium salt, cyclic oxidation and thermal corrosion at 850°C for 100 times in a tube furnace, and the glazed surface of the enamel coating is observed. The enamel surface is loose and porous, black-gray, and the enamel coating is completely corroded.

Comparative example 2 does not adopt surface glaze material of the present invention to prepare enamel coating

In parts by weight, SiO ₂ 30 parts, NaB ₄ O ₇ .4H ₂ O 44 parts, NaNO ₃ 16 parts, Na ₂ CO ₃ 15 parts, Li ₂ CO ₃ 3.5 parts, fluorite 10 parts, Na ₂ SiF ₆ 2.5 parts, 6 parts of Na ₃ AlF ₆ , 3.5 parts of Na ₄ P ₂ O ₇ .10H ₂ O, 8 parts of Co(NO ₃ ) ₂ and 3 parts of Ni(NO ₃ ) ₂ are mixed evenly, heated to 1300°C and melted 2h, quenched in cold water, and dried at 105°C for 20min to obtain enamel bottom glaze. Mix 100 parts of bottom glaze, 16 parts of clay, 3 parts of bentonite and 1.5 parts of magnesium sulfate, pulverize to a particle size of -200, add 20 parts of water and mix evenly to prepare enamel bottom glaze slurry.

Sandblast the surface of the enamel steel BTC245R sample, clean and decontaminate, and after drying, spray the enamel bottom glaze slurry on its surface with a thickness of 0.3-0.5mm. glaze layer;

Preparation of enamel surface glaze: parts by mass: 38 parts of SiO ₂ , 14 parts of NaB ₄ O ₇ .4H ₂ O, 8.5 parts of Na ₂ CO ₃ , 3.5 parts of Li ₂ CO ₃ , 0.5 parts of NiO, 6.5 parts of Na ₃ AlF ₆ , 3.5 parts of Na ₂ CrO ₄ , 1.5 parts of NaSbO ₃ , and 1 part of SrSO ₄ are mixed, melted at 1200°C for 3 hours, quenched in water, and dried to obtain enamel blocks. Press 100 parts of enamel blocks, 11 parts of clay, and 6.5 parts of bentonite, grind to a particle size of -200 mesh ≥ 98%, add 22 parts of water and mix evenly to obtain a porcelain glaze slurry that is sprayed on the 0.2-0.4mm surface of the enamel bottom glaze, and after drying, 900 ℃ enamelling for 12 minutes to obtain a heat-resistant corrosion enamel coating.

The surface of the enamel coating is coated with 75wt% Na ₂ SO ₄ +25wt% NaCl corrosion medium salt, cyclic oxidation and thermal corrosion at 850°C for 100 times in a tube furnace, and the glazed surface of the enamel coating is observed. Thermal corrosion occurs on the enamel surface, the enamel surface is uneven, a small amount of cracks appear, and a small amount of internal vulcanization and internal oxidation occurs inside the enamel. The mass gain after thermal corrosion is 11.56mg/cm ² .

As can be seen from the results of the examples and comparative examples: the enamel coating of the present invention is used in conjunction with the enamel surface glaze, and the prepared enamel coating is firmly bonded to the metal substrate, and the structure of the enamel surface is complete in a hot corrosion environment. There is no phenomenon of internal vulcanization and internal oxidation, and the weight gain of hot corrosion is less, indicating that it has better heat resistance and corrosion resistance.

Claims (10)

1. base enamel material, which is characterized in that composition includes：It counts in parts by weight, SiO₂30~33 parts, NaB₄O₇.4H₂O 44 ~48 parts, NaNO₃16~18 parts, Na₂CO₃13~15 parts, Li₂CO₃1.5~3.5 parts, 8~11 parts of fluorite, Na₂SiF₆1~3 Part, Na₃AlF₆6~8 parts, Na₄P₂O₇.10H₂3~5 parts of O, Co (NO₃)₂6~8 parts and Ni (NO₃)₂2~4 parts.

2. the preparation method of base enamel material described in claim 1, which is characterized in that include the following steps：Claim by weight After taking raw material mixing, be heated to melting 2~3h at 1300~1350 DEG C, be transferred in cold water quench it is broken, in 100~130 DEG C dry 20 Base enamel material is made in~30min.

3. base enamel material slurry, it is characterised in that：By 100 parts of ground-coat enamel material described in claim 1,15~19 parts of clay is swollen 2~3 parts of profit soil is crushed to -200 mesh >=98% of granularity after the mixing of 1~2 part of magnesium sulfate, add 20~22 parts of water be uniformly mixed and At.

4. cover-coat enamel material, which is characterized in that composition includes：It counts in parts by weight, SiO₂35~42 parts, NaB₄O₇.4H₂O 26 ~28 parts, Na₂CO₃8.5~10 parts, Li₂CO₃3~5 parts, 0.5~1 part of NiO, Na₃AlF₆5~7 parts, Na₂CrO₄3.5~4 Part, NaSbO₃1~2 part, SrSO₄1~2 part and Na₂MO₃0.5~1 part.

5. the preparation method of the cover-coat enamel material described in claim 4, which is characterized in that include the following steps：Claim by weight After taking raw material mixing, be heated to melting 2~3h at 1200~1250 DEG C, be transferred in cold water quench it is broken, in 100~130 DEG C dry 20 Cover-coat enamel material is made in~30min.

6. cover-coat enamel material slurry, it is characterised in that：By 100 parts of cover-coat enamel material described in claim 4, clay 11~13 Part, 5~7 parts of bentonite, 4~5 parts of zircon English, 1~2 part of 25~30 parts of C-BN, LiF mixing, be crushed to -200 mesh of granularity >= 98%, 25~30 parts of glass powder is added, 22~25 parts of water, which is uniformly mixed, to be formed.

7. cover-coat enamel material slurry according to claim 6, it is characterised in that：The zircon English is ZrO₂Content>65% Zircon English.

8. the preparation method of heat and corrosion resistant enamel coating, which is characterized in that include the following steps：

A, the base enamel material slurry described in metal base surface spraying claim 3 after treatment, forms 0.3~0.5mm Slurry coating, dry 30~45min, is transferred to 900~950 DEG C of 12~15min of enamel firing of electric furnace at 130~150 DEG C, cooling, Base enamel layer is made；

B, the cover-coat enamel material slurry described in the base enamel layer surface spraying claim 6 made from step a, formation 0.2~ The slurry coating of 0.4mm is transferred to enamel firing 10 at a temperature of 850~900 DEG C of electric furnace at 130~150 DEG C after dry 30~45min ~12min, it is cooling, heat and corrosion resistant enamel coating is made.

9. the preparation method of heat and corrosion resistant enamel coating according to claim 8, it is characterised in that：The metallic matrix Including at least one of mild steel Q235, glassed steel BTC245R or cold-rolled carbon steel SPCC.

10. the heat and corrosion resistant enamel coating that claim 8 or 9 is prepared.