Glaze of environment-friendly lead-free cadmium-free colored enamel steel and colored enamel steel firing method

Abstract

The invention belongs to the technical field of enamel steel preparation, and particularly relates to glaze of environment-friendly lead-free cadmium-free colored enamel steel and a colored enamel steel firing method. Al2O3: 10%-15%; 15% to 20% of B2O3; 8%-12% of Na2O or 3%-6% of K2O; 0.2%-2% of a coloring agent; 8%-12% of an opacifier; and 1%-3% of an additive. The invention has the advantages that: the glaze completely abandons the use of heavy metals such as lead, cadmium and the like, and the components of the glaze are completely environment-friendly. Through detection, the content of lead and the content of cadmium in the finished product are respectively lower than the detection limit of 0.01 mg / kg and 0.005 mg / kg and are far lower than the limit values of European Union REACH and other international strict laws and regulations, and potential hazards to the health of production personnel and consumers and the environment are thoroughly eliminated.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of enamel steel preparation, and particularly relates to an environmentally-friendly lead-free and cadmium-free colored enamel steel glaze and a colored enamel steel firing method. BACKGROUND

[0002] Traditional enamel steel often uses heavy metal compounds containing lead and cadmium in the glaze formula. Lead has good fluxing performance, which can reduce the melting temperature of the glaze, so that the glaze can be uniformly coated on the surface of the steel substrate at a lower temperature, and can improve the gloss and texture of the glaze. Cadmium plays an important role in color development in colored enamel, which can make the enamel present bright and stable colors. However, lead is a heavy metal that can seriously damage the nervous system, blood system and kidneys of the human body. Long-term contact with lead-containing enamel products can cause lead to accumulate in the human body, leading to children's delayed mental development, high blood pressure in adults, and other health problems such as kidney failure. Cadmium is also a strong carcinogen, which can enter the human body through the respiratory tract and digestive tract, causing irreversible damage to the liver and kidneys, and causing bone diseases such as itai-itai disease. In the production process, waste gas and waste water containing lead and cadmium are discharged into the environment, which pollutes the soil and water sources and causes long-term and difficult-to-repair damage to the ecological environment.

[0003] At present, the research on some lead-free and cadmium-free enamel steel mainly focuses on the realization of basic performance, such as only meeting the basic requirements of corrosion resistance and adhesion. In terms of color presentation, the color types are limited, which is difficult to meet the market demand for diversification and bright colors. Some so-called environmentally-friendly colored enamel steels remove lead and cadmium, but introduce other relatively complex and expensive elements or compounds to develop color in the glaze formula, which not only greatly increases the production cost, but also may bring new environmental problems in the production process, such as high energy consumption and serious pollution in the refining process of some rare metals. In the firing process, the existing lead-free and cadmium-free enamel steel firing process often fails to fully consider the characteristics of the glaze in the lead-free and cadmium-free system, resulting in high firing temperature and long firing time, which not only increases energy consumption, but also easily causes quality problems such as deformation and glaze bubbles of the enamel steel, limiting its application and promotion in actual production.

[0004] The existing lead-free and cadmium-free colored enamel steel adopts a "base glaze + surface glaze" double-firing process, which requires two times of enameling and two times of high-temperature firing (the base glaze enhances the adhesion, and the surface glaze realizes color), and has three defects: first, the production cycle is long and the energy consumption is high; second, the base glaze and the surface glaze layer are prone to peeling due to the difference in thermal expansion coefficient; third, part of the one-time firing attempt is difficult to be industrialized due to the unbalance of "adhesion-color-environmental protection", such as the influence of colorants on the adhesion of the glaze and the steel substrate, and the reduction of corrosion resistance by fluxing agents.

[0005] The prior art patent application No. CN200910062667.3 discloses a high-strength enamel steel and its production and firing process, mainly using electrostatic spraying enamel dry powder or wet immersion coating enamel, and the adaptability to different coloring agents is insufficient, which cannot meet the production needs of diversified color enamel steel, limits the application range of the product, and the characteristics of glaze in a lead-free cadmium system, such as the melting performance of the glaze in the lead-free cadmium system, the adhesion performance with the steel matrix, etc., are not fully considered, which easily causes quality problems of the enamel steel, such as deformation, glaze bubbles, low adhesion strength, and glaze falling off. The patent application No. CN201210548932.0 discloses an enamel glaze applied to a subway inner wall enamel steel plate, the technical formula does not actively exclude harmful substances, there is a potential environmental and health risk (such as lead flux residue), and only the basic performance (adhesion, wear resistance, corrosion resistance) of the subway inner wall is involved, without involving color development design, which cannot realize multi-color effects such as red, blue, and green, the application scene is limited to single-color or light-color decoration, and cannot meet the market demand for diversified color enamel.

[0006] Therefore, it is urgent to develop an environmentally-friendly lead-free and cadmium-free color enamel steel glaze formula and firing process to solve the above problems. SUMMARY

[0007] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide an environmentally-friendly lead-free and cadmium-free color enamel steel glaze and a color enamel steel firing method, which realizes rich and diverse and bright and stable color effects under an environmentally-friendly lead-free and cadmium-free system, optimizes the firing process, reduces energy consumption, improves the production quality and efficiency of the enamel steel, meets the market demand for beauty and performance while meeting the environmental protection standard.

[0008] In order to achieve the above purpose, the present application realizes the following technical scheme: An environmentally-friendly lead-free and cadmium-free color enamel steel glaze comprises the following components in terms of weight percentage: SiO2: 35%~45%; Al2O3: 10%~15%; B2O3: 15%~20%; Na2O: 8%~12% or K2O: 3%~6%; coloring agent: 0.2%~2%; opacifier: 8%~12%; additive: 1%~3%.

[0009] The opacifier is TiO2.

[0010] The additive is ZnO.

[0011] The coloring agent is one or more of Fe2O3, CoO, CuO, Sb2O3. When Fe2O3 is selected as the coloring agent, the addition amount is 0.5% to 2%; when CoO is selected, the addition amount is 0.2% to 1%; when CuO is selected, the addition amount is 0.3% to 1.5%; and when Sb2O3 is selected, the addition amount is 0.5% to 2%.

[0012] The main roles of the components in the glaze are as follows: 1. Silicon dioxide (SiO2): as a base agent. SiO2 has good chemical stability and high-temperature resistance, and can build the basic framework structure of the glaze, determining the hardness and chemical stability of the glaze surface. Too high a content of SiO2 will result in too high a melting point of the glaze, which is not conducive to the melting and uniform spreading of the glaze during the firing process; too low a content of SiO2 will result in a decrease in the hardness and chemical stability of the glaze surface.

[0013] 2. Aluminum oxide (Al2O3): can improve the chemical stability, mechanical strength and thermal stability of the glaze, and enhance the wear resistance of the glaze surface. In the glaze, Al2O3 can form stable chemical bonds with other components, improve the structure of the glaze, and make it more stable during high-temperature firing and use. If the content of Al2O3 exceeds 15%, it will result in an increase in the melting temperature of the glaze and a decrease in the fluidity of the glaze, and defects such as poor glaze leveling and pinholes are likely to occur.

[0014] 3. Boron oxide (B2O3): a high-efficiency fluxing agent that can significantly reduce the melting temperature of the glaze, improve the fluidity of the glaze, and make the glaze more easily spread evenly on the steel substrate surface during the firing process, while also increasing the gloss of the glaze surface. However, too high a content of B2O3 will reduce the chemical stability of the glaze surface.

[0015] 4. Sodium oxide (Na2O) and potassium oxide (K2O): both of which act as fluxing agents, further reducing the melting temperature of the glaze, producing a "mixed alkali effect", optimizing the melting properties of the glaze, and improving the process performance and physical and chemical properties of the glaze. However, too high a content of alkali metal oxides will reduce the water resistance and chemical stability of the glaze surface. B2O3, Na2O and K2O form a "mixed alkali effect", and the mechanism of action is as follows: the network-forming effect of B2O3, B2O3 joins the SiO2 network structure in the form of [BO3] triangle or [BO4] tetrahedron, reducing the network bond strength (Si-O bond energy 460 kJ / mol → B-O bond energy 380 kJ / mol), so that the glaze can be melted at 850-900℃ (100-150℃ lower than the traditional process). Network-breaking effect of Na⁺ / K⁺: Na + , K + as network external ions, destroying the three-dimensional network structure of SiO2 and reducing the melting viscosity. When Na2O and K2O are compounded in a ratio of 2:1, the radius difference between the two ions (Na +0.095 nm, K + 0.133 nm) causes lattice distortion, further weakening the network structure. This effect enables the enamel to rapidly melt during the rapid heating stage (15-20°C / min) and form Fe-O-Si chemical bonds with the steel substrate, reducing the loss of volatile components (such as B2O3) and improving the adhesion strength to 0.8-1.2 J.

[0016] 5. Opacifier: Titanium oxide is used as an opacifier. TiO2 can form tiny crystal particles in the enamel, which scatter light, giving the enamel steel good hiding power and making the enamel steel surface appear uniform and opaque, improving the decorative properties of the product. The opacifying mechanism of TiO2: TiO2 precipitates rutile-type crystal particles with a particle size of 0.5-2 μm during the cooling process of the enamel. The refractive index (2.76) is significantly different from that of the glass phase (1.5-1.6), causing Miescattering and making the incident light diffuse and reflect, giving the enamel surface uniform hiding power.

[0017] 6. Colorants: Single-color coloration: Stable color is achieved by controlling the addition amount and valence state of common oxide colorants; Red colorant: Iron oxide (Fe2O3) is selected. Fe 3+ absorbs blue-green light through electronic transition; During high-temperature firing, the valence state of iron ions in the crystal structure of Fe2O3 changes, absorbing and reflecting specific wavelengths of light, thereby presenting red. By precisely controlling the addition amount of Fe2O3, the depth of red can be adjusted.

[0018] Blue colorant: Cobalt oxide (CoO) is used. Co 2+ forms an octahedral coordination structure in the enamel, selectively reflecting blue light; The cobalt ions in CoO form a specific coordination structure in the enamel system, which has selectivity in absorbing and emitting light, thereby making the enamel steel appear blue. Small changes in its content will cause significant differences in blue tone.

[0019] Green colorant: Copper oxide (CuO) is used as a colorant. CuO presents green by absorbing specific wavelengths of light through copper ion electronic transition in the enamel. Different addition amounts correspond to different saturation degrees of green.

[0020] Yellow colorant: Antimony oxide (Sb2O3) is selected. Sb2O3 presents yellow by changing the absorption and scattering properties of light in the enamel through interaction with other components. The control of its addition amount determines the brightness and depth of yellow.

[0021] Complex color development: such as Fe2O3 and CoO complex to form purple, using red and blue light superposition effect, high color saturation and good uniformity.

[0022] 7. Additives: The introduction of a small amount of zinc oxide (ZnO) can improve the chemical stability and thermal stability of the glaze, enhance the adhesion of the glaze to the steel substrate, and improve the adhesion strength to 0.8~1.2J. It can also improve the melting performance of the glaze to a certain extent, reduce defects such as bubbles and pinholes, and make the glaze surface smoother. ZnO reacts with the FeO layer on the surface of the steel substrate at high temperature to form a ZnFe2O4 spinel transition layer. The lattice constant (a=0.839nm) of this layer is highly matched with the steel substrate (a=0.833nm), and the glaze layer and the steel substrate are firmly connected through chemical bonding (Zn-O-Fe).

[0023] An environmentally friendly lead-free and cadmium-free colored enamel steel firing method, comprising the following steps: 1) Steel substrate pretreatment: immerse the steel substrate in an alkaline degreaser at a temperature of 60~70℃ for 10~15 minutes; then immerse the steel substrate in a dilute hydrochloric acid solution with a mass fraction of 10%~15% for 5~8 minutes; rinse with water and dry in an oven at 80~90℃ for 15~20 minutes; 2) Glaze preparation: weigh the raw materials according to the glaze composition ratio, mix them evenly, then add water, the amount of water added being 30%~40% of the total mass of the raw materials, and wet grind to obtain a glaze slurry; 3) Coating glaze slurry: evenly coat the prepared glaze slurry on the surface of the steel substrate pretreated in step 1) by electrostatic spraying, so that the glaze slurry forms a uniform coating with a thickness of 0.1~0.2mm on the surface of the steel substrate; 4) Firing process: place the steel substrate coated with glaze slurry into a high-temperature furnace, first preheat at a low temperature, raise the furnace temperature to 300~350℃ at a rate of 5~8℃ / min, and keep it at this temperature for 10~15 minutes to ensure that the water in the glaze slurry is fully volatilized (weight loss rate <0.5%), and at the same time promote the TiO2 crystal type conversion to prepare for melting.

[0024] Then raise the temperature rapidly at a rate of 15~20℃ / min to 850~900℃, and keep it at this temperature for 5~8 minutes to make the glaze surface flat and dense. The firing temperature of 850~900℃ is 100~150℃ lower than the traditional process, which shortens the heating time, reduces the loss of volatile components, and at the same time promotes the formation of Fe-O-Si chemical bonds between the glaze and the steel substrate.

[0025] After that, cool the furnace to room temperature naturally, control the cooling rate at 10~15℃ / min, optimize the glaze crystallinity, reduce thermal stress, and avoid cracking.

[0026] Step 2) The mixing is performed by mixing in a high-speed mixer at a speed of 1000~1500 rpm for 20~30 minutes.

[0027] Step 2) refers to wet grinding in a ball mill at a speed of 200-300 rpm for 8-12 hours until the particle size of the glaze reaches 200-300 mesh, forming a uniform and fine glaze slurry.

[0028] Step 3) Electrostatic spraying: The distance between the spray gun and the steel substrate is maintained at 15~20 cm, the spraying voltage is 60~80 kV, and the spraying air pressure is 0.3~0.5 MPa.

[0029] Compared with the prior art, the beneficial effects of the present invention are: The glaze of this invention completely eliminates the use of heavy metals such as lead and cadmium, and its composition is entirely environmentally friendly. Testing shows that the lead and cadmium content in the finished product is below the detection limits of 0.01 mg / kg and 0.005 mg / kg, respectively, far below the limits set by stringent international regulations such as the EU REACH, thus completely eliminating potential hazards to the health of production personnel, consumers, and the environment.

[0030] This invention offers rich and stable colors. Through the scientific formulation of non-toxic colorants such as Fe2O3, CoO, and CuO, a variety of vibrant colors can be obtained. Its color stability is particularly outstanding; after 1000 hours of accelerated aging testing, the color difference ΔE*ab < 3, making the change imperceptible to the naked eye, and its performance superior to traditional lead- and cadmium-containing products. This invention also boasts high adhesion and strong corrosion resistance: the synergistic effect of optimized base glaze (SiO2-Al2O3-B2O3-Na2O / K2O system) and ZnO additives significantly improves the bonding force between the glaze and the steel substrate. Drop ball impact testing shows an adhesion strength of 0.8~1.2J, exceeding industry standards and effectively preventing glaze peeling during use. The glaze achieves low melting point melting and good fluidity under lead- and cadmium-free conditions. Furthermore, the product withstands 24 hours of 5% hydrochloric acid immersion and 240 hours of salt spray testing without corrosion or rust spots, demonstrating excellent durability. The overall performance of the product, including corrosion resistance and wear resistance, is significantly improved, extending its service life. The glaze of this invention has excellent quality: the fine glaze preparation (particle size controlled to 200~300 mesh) and the controlled firing process ensure a smooth and even glaze surface, effectively reducing defects such as bubbles and pinholes, and resulting in a dense and uniform microstructure.

[0031] This invention reduces production costs by eliminating expensive rare elements and primarily using common metal oxides such as iron oxide and copper oxide as colorants, significantly lowering raw material costs compared to similar environmentally friendly products. The firing process reduces the peak temperature to 850-900℃ and shortens the holding time, reducing energy consumption and achieving cost reduction and efficiency improvement.

[0032] The invention realizes strong bonding force (0.8-1.2 J), stable color (1000h aging ΔE*ab<3), lead-free and cadmium-free (lead≤0.01 mg / kg, cadmium≤0.005 mg / kg) by formula synergistic design, without secondary firing, shortens production cycle, reduces unit energy consumption, and is more suitable for industrial large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is the finished product of Example 2 Figure One .

[0034] Figure 2 is the finished product of Example 2 Figure Two . DETAILED DESCRIPTION

[0035] The invention will be described in detail below, but it should be pointed out that the implementation of the invention is not limited to the following embodiments.

[0036] Example 1: The glaze of the environmentally friendly lead-free and cadmium-free color enamel steel includes the following components according to weight percentage: Base glaze: SiO2: 40%, Al2O3: 12%, B2O3: 18%, Na2O: 10%, K2O: 5%.

[0037] Opacifier: TiO2: 10%.

[0038] Coloring agent: Fe2O3 is selected as the red coloring agent, and the addition amount is 1%.

[0039] Additive: ZnO accounts for 3%.

[0040] The balance is unavoidable impurities.

[0041] The firing method of the environmentally friendly lead-free and cadmium-free color enamel steel: Steel substrate pretreatment: The enamel steel substrate is subjected to oil removal treatment, an alkaline oil removal agent is used, and the steel substrate is soaked at a temperature of 65℃ for 12 minutes to remove oil stains and impurities on the surface of the steel substrate, so that the subsequent glaze can be well attached. Then perform pickling treatment, immerse the steel substrate in a 12% dilute hydrochloric acid solution, and soak for 6 minutes to remove rust and oxide layers on the surface of the steel substrate, so that the surface of the steel substrate presents a clean and active metal surface. After pickling, rinse with clean water and dry in an oven at 85℃ for 18 minutes.

[0042] Glaze preparation: The raw materials are weighed according to the above glaze composition, and stirred in a high-speed mixer at 1000-1500 rpm for 20-30 minutes. Then add water, the amount of water added is 30%-40% of the total mass of the raw materials, wet grinding, wet grinding in a ball mill at a speed of 200-300 rpm, grinding time is 8-12 hours, until the particle size of the glaze reaches 200-300 mesh, to get the glaze slurry.

[0043] Coating glaze slurry: electrostatic spraying is used to form a uniform coating with a thickness of 0.15 mm on the surface of the steel substrate.

[0044] Firing process: preheating temperature 320℃, holding for 12 minutes; rapid heating to 880℃, holding for 6 minutes; natural cooling in the furnace, cooling rate 12℃ / min.

[0045] Product performance: The product presents bright red color, good color stability, glaze surface light reflectance reaches 85%, adhesion strength is 0.95J, after 1000 hours of accelerated aging test, color change ΔE*ab is 2.5, good corrosion resistance, no obvious corrosion phenomenon on the glaze surface after soaking in 5% hydrochloric acid solution for 24 hours.

[0046] Example 2: The glaze of the environmentally friendly lead-free and cadmium-free color enamel steel includes the following components according to weight percentage: Base glaze: SiO2: 43.6%, Al2O3: 13%, B2O3: 17%, Na2O: 10%, K2O: 4%.

[0047] Opacifier: TiO2: 9%.

[0048] Coloring agent: CoO is used as blue coloring agent, the addition amount is 0.6%.

[0049] Additive: ZnO: 2%.

[0050] The rest is unavoidable impurities.

[0051] Firing method of environmentally friendly lead-free and cadmium-free color enamel steel: The same as example 1, the steel substrate pretreatment and glaze preparation process. The glaze slurry is coated by electrostatic spraying, and the coating thickness is 0.13 mm. Firing process: preheating temperature 330℃, holding for 13 minutes, stabilizing CoO lattice structure, avoiding color deviation; rapid heating to 870℃, holding for 7 minutes; natural cooling in the furnace, cooling rate 13℃ / min.

[0052] Product performance: See Figure 1 , Figure 2The product presents deep blue color, uniform color, adhesion strength of 1.02 J, color change ΔE*ab of 2.8 after accelerated aging test, and abrasion loss of 0.05 g / cm in abrasion resistance test (using grinding wheel friction test) 2 , showing good abrasion resistance.

[0053] Example 3: The glaze of the environment-friendly lead-free and cadmium-free colored enamel steel includes the following components according to weight percentage: Basic glaze: SiO2: 42%, Al2O3: 11%, B2O3: 19%, Na2O: 9%, K2O: 5%.

[0054] Opacifier: TiO2: 10%.

[0055] Coloring agent: CuO is used as green coloring agent, and the addition amount is 0.8%.

[0056] Additive: ZnO: 3%.

[0057] The balance is inevitable impurities.

[0058] The firing method of the environment-friendly lead-free and cadmium-free colored enamel steel: The steel substrate pretreatment and glaze preparation are the same as in Example 1. The glaze slurry is electrostatically sprayed, and the coating thickness is 0.18 mm. Firing: preheating temperature 310℃, holding for 14 minutes; rapid heating to 890℃, holding for 5 minutes to prevent CuO from being reduced to metallic copper at high temperature, leading to discoloration; natural cooling in the furnace, cooling rate 11℃ / min.

[0059] Product performance: The product is fresh green, good gloss, adhesion strength reaches 1.1 J, after salt spray corrosion test (240 hours test according to relevant standards), the glaze surface is free of rust spots and shedding, and the corrosion resistance is excellent.

[0060] Example 4: The glaze of the environment-friendly lead-free and cadmium-free colored enamel steel includes the following components according to weight percentage: Basic glaze: SiO2: 41.2%, Al2O3: 14%, B2O3: 16%, Na2O: 12%, K2O: 3%.

[0061] Opacifier: TiO2: 10%.

[0062] Coloring agent: Sb2O3 is used as yellow coloring agent, and the addition amount is 1.2%.

[0063] Additive: ZnO: 2%.

[0064] The balance is inevitable impurities.

[0065] Firing method of environment-friendly lead-free and cadmium-free colored enamel steel: The steel substrate is pretreated according to the standard process, and the enamel is prepared and electrostatically sprayed, with a coating thickness of 0.12 mm. The firing process is as follows: preheating temperature 340℃, holding for 10 minutes; rapid heating to 860℃, holding for 7 minutes; natural cooling in the furnace, cooling rate 14℃ / min, which is suitable for its low thermal expansion coefficient and reduces stress cracking.

[0066] Product performance: The product presents a bright yellow color with high color uniformity, and the adhesion strength is 0.88J. After 1000 hours of ultraviolet irradiation test, the color change ΔE*ab is 2.6, and there is no discoloration or peeling phenomenon on the glaze surface after being placed in a humid environment for 30 days, showing good weather resistance.

[0067] Example 5: The enamel of the environment-friendly lead-free and cadmium-free colored enamel steel includes the following components by weight percentage: Base enamel: SiO2: 44%, Al2O3: 12%, B2O3: 17%, Na2O: 10%, K2O: 6%.

[0068] Opacifier: TiO2: 8%.

[0069] Coloring agent: Fe2O3 and CoO are compounded as purple coloring agent, with Fe2O3 added in an amount of 0.8% and CoO added in an amount of 0.3%.

[0070] Additive: ZnO: 1%.

[0071] The balance is unavoidable impurities.

[0072] Firing method of environment-friendly lead-free and cadmium-free colored enamel steel: The pretreatment of the steel substrate and the preparation of the enamel remain unchanged, and the electrostatic spraying makes the coating thickness reach 0.16 mm. Firing: preheating at a low temperature of 330℃, holding for 13 minutes; then rapid heating to 875℃, holding for 6 minutes; then natural cooling, with a cooling rate controlled at 12℃ / min.

[0073] Product performance: The product presents an elegant purple color with high color uniformity, and the adhesion strength is 1.05J. After acid-alkali alternating corrosion test (alternately immersed in 10% sulfuric acid solution and 10% sodium hydroxide solution for 2 hours each, for 10 cycles), the glaze surface only has slight corrosion marks, showing excellent corrosion resistance, and after 1000 hours of accelerated aging test, the color change ΔE*ab is 2.7.

[0074] The firing process temperature-time data of each example is shown in Table 1, and the key process parameter explanations are shown in Table 2.

[0075] Table 1 Firing Process Temperature-Time Data Table Process stage Time range (min) Temperature range (°C) Heating / cooling rate Initial state 025 (room temperature) Low temperature preheating phase Ramp: 0→ 12-14 Hold: 12-14→ 24-27 Temperature increase: 25 -> 310-340 Hold: 310-340 5-8°C / min (ramp) fast ramping phase ramp: 24-27→ 36-41 ramp: 310-340→ 860-890 15-20°C / min (ramp) high temperature holding phase hold: 36-41→ 41-48 hold: 860-890 natural cooling phase cool: 41-48→ 86-93 cool: 860-890→ 25 10-15°C / min (cool) Table 2 Key process parameters explanation Process stage Key process parameter Description Example Key parameter difference Initial state Steel substrate Ambient temperature before entering the furnace as the starting point of the process All examples start from this point Low temperature preheating phase ① Remove the moisture of glaze slurry, avoid high temperature bubble; ② Promote the preliminary decomposition of ingredients in glaze (such as TiO2 crystal type conversion), prepare for melting - Example 1 : 320°C x 12 min - Example 2: 330°C x 13 min (CoO needs higher preheat to stabilize structure) - Example 3: 310°C x 14 min (CuO preheat to prevent agglomeration) - Example 4: 340°C x 10 min (Sb2O3 fast dehydration) - Example 5: 330°C x 13 min (complexing colorant balanced preheat) rapid temperature ramping phase ①The glaze melts and has oxidation-reduction reaction with the steel matrix to form Fe-O-Si chemical bond; ②Fast heating reduces the loss of volatile components - Example 1 : 880°C x 12 min (Fe203high temperature stable valence state) - Example 2: 870°C x 12 min (CoO low temperature coordination) - Example 3: 890°C x 14 min (CuO high temperature chromophore) - Example 4: 860°C x 10 min (Sb203low temperature melting) - Example 5: 875°C x 10 min (complexing temperature taken as intermediate value) high temperature holding stage ①Glaze surface leveling densification, eliminate bubbles and pinholes; ②Colorant ions diffuse uniformly, ensure color uniformity - Example 1 : 880°C x 6 min - Example 2: 870°C x 7 min (CoO prolonged coordination time) - Example 3: 890°C x 5 min (CuO reduction prevention) - Example 4: 860°C x 7 min (Sb2O3 homogeneous dispersion) - Example 5: 875°C x 6 min (complexing and heat soaking color balance) The furnace natural cooling stage has the following effects: ①controlling thermal stress between glaze layer and steel base body to avoid cracking; and ②promoting glaze crystallinity optimization to improve wear resistance and corrosion resistance - Example 1 : 12°C / min - Example 2: 13°C / min (blue glaze thermal match fast cool) - Example 3: 11°C / min (green glaze slow cool crack prevention) - Example 4: 14°C / min (yellow glaze low thermal expansion coefficient fast cool) - Example 5: 12°C / min (compounded glaze balanced cooling) The above examples fully verify the feasibility and superiority of the glaze formula and firing process of the environmentally friendly lead-free and cadmium-free color enamel steel according to the present application. Under the environmentally friendly lead-free and cadmium-free system, the present application realizes rich and diverse and stable and bright color presentation; the optimized firing process precisely controls the temperature, time and rate at each stage, effectively improves the adhesion performance of the glaze and the steel substrate, reduces product defects and improves product quality.

[0076] Under different light conditions and use environments, after 1000 hours of accelerated aging test (simulating actual use environment, testing under high temperature and high humidity, ultraviolet radiation and other conditions), the color change ΔE*ab (color difference standard specified by the International Commission on Illumination) is less than 3, and the naked eye can hardly detect the color change, which is significantly improved compared with the color stability of traditional lead and cadmium containing color enamel steel. The color stability, adhesion strength, corrosion resistance, wear resistance and weather resistance of the present application all meet or exceed the industry standards, meeting the market demand for high-quality enamel steel.

Claims

1. An environmentally friendly lead-free and cadmium-free colored enamel steel glaze, characterized in that, The following ingredients are included in the percentage by weight: ​ SiO2: 35%~45%; Al2O3: 10%~15%; B2O3: 15%~20%; Na2O: 8%~12%; K2O: 3%~6%; Coloring agent: 0.2%~2%; Opacifier: 8%~12%; Additive: 1%~3%.

2. The environment-friendly lead-free and cadmium-free colored enamel steel glaze according to claim 1, characterized in that, The opacifier is TiO2.

3. The environment-friendly lead-free and cadmium-free colored enamel steel glaze according to claim 1, characterized in that, The additive is ZnO.

4. The environment-friendly lead-free and cadmium-free colored enamel steel glaze according to claim 1, characterized in that, The coloring agent is one or more of Fe2O3, CoO, CuO, and Sb2O3.

5. The method according to any one of claims 1 to 4, wherein the enamel is fired to produce an environmentally friendly lead-free and cadmium-free colored enamel steel. The following steps are included: 1) Steel substrate pretreatment: immerse the steel substrate in an alkaline degreaser at a temperature of 60~70℃ for 10~15 minutes; then immerse the steel substrate in a dilute hydrochloric acid solution with a mass fraction of 10%~15% for 5~8 minutes; rinse with water and dry in an oven at 80~90℃ for 15~20 minutes; 2) Glaze preparation: weigh the raw materials according to the glaze ingredient ratio, mix well, then add water, the amount of water added is 30%~40% of the total mass of the raw materials, wet grind to obtain glaze slurry; 3) Apply glaze slurry: evenly apply the prepared glaze slurry to the surface of the steel substrate pretreated in step 1) using electrostatic spraying, so that the glaze slurry forms a uniform coating with a thickness of 0.1~0.2 millimeters on the surface of the steel substrate; 4) Firing process: place the steel substrate coated with glaze slurry into a high-temperature furnace, first preheat at a low temperature, increase the furnace temperature to 300~350℃ at a rate of 5~8℃ / minute and maintain for 10~15 minutes; then rapidly increase the temperature at a rate of 15~20℃ / minute to 850~900℃, maintain for 5~8 minutes, then naturally cool in the furnace to room temperature, the cooling rate is controlled at 10~15℃ / minute.

6. The method for firing an environmentally friendly lead-free and cadmium-free colored enamel steel according to claim 5, characterized in that, Step 2) The mixing is dry mixing in a high-speed mixer at a speed of 1000~1500 revolutions / minute for 20~30 minutes.

7. The method according to claim 5, wherein the method is characterized by: Step 2) The wet grinding is wet grinding in a ball mill at a speed of 200~300 revolutions / minute, the grinding time is 8~12 hours, until the particle size of the glaze reaches 200~300 mesh, forming a uniform and delicate glaze slurry.

8. The method for firing an environmentally friendly lead-free and cadmium-free colored enamel steel according to claim 5, characterized in that, Step 3) The electrostatic spraying: the distance between the spray gun and the steel substrate is maintained at 15~20 centimeters, the spraying voltage is 60~80 kilovolts, and the spraying air pressure is 0.3~0.5 megapascals.

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