Non-stick frying pan and method of manufacture

Abstract

The application discloses a non-stick frying pan and a manufacturing method. The non-stick frying pan is a bottomed pan formed by deep drawing of a planar sheet material, which comprises a bottom and a wall raised around the bottom, and the top of the wall defines a rim; the wall has a thickness-reduced zone formed in the deep drawing process, which is arranged between the bottom and the rim and extends in the height direction of the frying pan; the outer surface of the thickness-reduced zone has a plurality of annular grooves extending in the circumferential direction of the wall, and the inner surface has a plurality of annular oil storage grooves corresponding to the annular grooves in number and position; wherein the annular grooves are wall thickness-reduced features pre-set on the outer side of the planar sheet material before the frying pan is deep drawn, and the annular oil storage grooves are recessed features formed on the inner surface of the wall in the deep drawing process based on the fact that the annular grooves are more prone to tensile deformation than other parts; compared with the prior art, the scheme can simplify the production process of the non-stick frying pan and reduce the production cost.

Description

Technical Field

[0001] This invention relates to the field of cookware technology, and in particular to a non-stick frying pan and its manufacturing method. Background Technology

[0002] As an indispensable cooking utensil in daily life, the non-stick performance of a wok directly affects the user experience and health. Currently, most non-stick woks on the market rely on a chemical non-stick coating (such as Teflon) applied to the inner surface of the wok. This type of coating achieves its non-stick effect by forming a physical barrier between the food and the wok. However, chemical coatings have significant drawbacks: First, the coating is prone to wear and peeling under prolonged use or scraping with metal spatulas, leading to a loss of non-stick performance. Furthermore, the detached coating may contaminate food, posing a health risk. Second, the coating has limited high-temperature resistance; prolonged dry heating or high-temperature stir-frying may cause the coating to decompose, releasing harmful substances. Third, coated cookware usually requires specific tools for use and cleaning, limiting its versatility.

[0003] To overcome the drawbacks of chemical coatings, the industry has developed uncoated, physically non-stick pans. The principle behind this is to create a specific oil-retaining structure on the inner surface of the pan, achieving a non-stick effect by increasing the contact angle between food and the pan surface or utilizing an oil film. However, the fabrication of this type of oil-retaining structure typically requires secondary processing after the pan body is formed, increasing the complexity and cost of the manufacturing process.

[0004] Therefore, it is necessary to propose a new technical solution to overcome the shortcomings of existing technologies. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a non-stick frying pan and its manufacturing method, wherein an annular oil storage groove is formed during the deep drawing process of the frying pan to achieve its non-stick properties, thereby simplifying the production process of the non-stick frying pan and reducing production costs.

[0006] The present invention provides a non-stick frying pan, which is a bottomed cookware formed by deep drawing a flat sheet, including a bottom and a raised wall around the bottom, the top of the wall defining a rim. The pot wall has a thickness reduction band formed during the deep drawing process. The thickness reduction band is disposed between the bottom of the pot and the edge of the pot and extends in the height direction of the pot. The outer surface of the thickness reduction band has a plurality of annular grooves extending in the circumferential direction of the pot wall, and its inner surface has annular oil storage grooves that are the same number and positional as the plurality of annular grooves. The annular groove is a wall thickness reduction feature pre-set on the outer side of the flat plate before the wok is drawn, and the annular oil storage groove is a recessed feature formed on the inner surface of the wok wall during the drawing process, based on the fact that the annular groove is more prone to tensile deformation than other parts.

[0007] Several alternative methods are provided below, but they are not intended as additional limitations on the overall solution above. They are merely further additions or optimizations. Provided there are no technical or logical contradictions, each alternative method can be combined individually with respect to the overall solution above, or multiple alternative methods can be combined with each other.

[0008] Optionally, the pot wall includes a first metal layer, a second metal layer, and a third metal layer from the inside out; The annular groove is formed in the third metal layer.

[0009] Optionally, the ductility of the second metal layer is greater than that of the first metal layer and the third metal layer.

[0010] Optionally, the first and third metal layers are iron layers, and the second metal layer is an aluminum layer.

[0011] Optionally, the thickness of the pot wall is 1.0mm-5.0mm, the depth of the annular groove is 0.005mm-0.3mm, and the width of the annular groove is 0.1mm-5mm.

[0012] Optionally, the inner wall of the annular oil storage tank has a roughly arc-shaped cross-section.

[0013] Optionally, the annular groove can be etched, laser-engraved, or machined on the outer side of the planar plate.

[0014] Optionally, the inner surface of the pot wall has a porous membrane layer, the porous membrane layer including a first part covering the annular oil storage tank and a second part covering the outside of the annular oil storage tank; The porosity of the first part is greater than that of the second part.

[0015] Optionally, the porous membrane is an iron phosphate membrane or a phosphating membrane.

[0016] Optionally, the porous membrane layer can be heated to perform a solidification treatment on the porous membrane layer.

[0017] This invention also includes a method for manufacturing a non-stick frying pan, comprising: An annular groove is machined into the flat plate to reduce the wall thickness of the flat plate. A wok is produced by deep drawing the flat sheet. During the deep drawing process, an annular oil storage groove is formed on the inner surface of the wok wall because the annular groove is more prone to tensile deformation than other parts.

[0018] Optionally, the annular groove can be etched, laser-engraved, or machined on the outer side of the planar plate.

[0019] Optionally, the flat sheet material can be drawn by hydraulic pressure or stamping to form the wok.

[0020] Optionally, the inner surface of the pot wall has a porous membrane layer.

[0021] Optionally, a porous film layer is formed on the inner surface of the pot wall by an acid oxidation process.

[0022] Optionally, the porous membrane layer can be heated to perform a solidification treatment on the porous membrane layer.

[0023] This invention discloses a non-stick frying pan and its manufacturing method. The annular oil reservoir stores edible oil, allowing a dynamic oil film to form on the inner surface of the pan during use. This effectively reduces food adhesion and enhances the non-stick performance. Since the annular oil reservoir is formed by stretching and deforming a flat sheet, the manufacturing process of the non-stick frying pan is simplified, reducing production costs. Furthermore, the annular groove disperses stress during the deep-drawing process, effectively reducing stress concentration on the pan wall and minimizing the risk of cracks or deformation during molding, further improving the reliability and durability of the frying pan. Attached Figure Description

[0024] Figure 1 A schematic diagram of the structure of a planar plate in one embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a planar plate in another embodiment of the present invention; Figure 3 A schematic diagram of the structure of a wok in one embodiment of the present invention; Figure 4 for Figure 3 A partial structural diagram of a wok; Figure 5 for Figure 3 A schematic diagram of the structure of the wok and the membrane layer.

[0025] The annotations in the figure are explained as follows: 100. Wok; 101. Flat panel; 10. Bottom of the pot; 20. Pot wall; 21. Thickness reduction zone; 22. Annular groove; 23. Annular oil storage tank; 24. First metal layer; 25. Second metal layer; 26. Third metal layer; 27. Porous membrane layer; 30. The edge of the pot. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] It should be noted that when a component is said to be "connected" to another component, it can be directly connected to the other component or it can be connected to a component in between. When a component is said to be "set on" another component, it can be directly set on the other component or it may be set to a component in between.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0029] like Figures 1 to 5 As shown, this application provides a non-stick frying pan 100, which is a bottomed cookware formed by deep drawing a flat sheet 101. It includes a bottom 10 and a wall 20 that rises around the bottom 10. The top of the wall 20 defines a rim 30. The wall 20 has a thickness reduction band 21 formed during the deep drawing process. The thickness reduction band 21 is disposed between the bottom 10 and the rim 30 and extends in the height direction of the frying pan 100. The outer surface of the thickness reduction band 21 has a plurality of annular grooves 22 extending in the circumferential direction of the wall 20. The inner surface of the wall 21 has annular oil reservoirs 23 that are the same number and corresponding in position as the plurality of annular grooves 22. The annular grooves 22 are wall thickness reduction features pre-set on the outer side of the flat sheet 101 before the frying pan 100 is deep drawn. The annular oil reservoirs 23 are recesses formed on the inner surface of the wall 20 during the deep drawing process because the annular grooves 22 are more prone to tensile deformation than other parts.

[0030] The wok 100 is manufactured by a deep drawing process using a flat sheet 101. Specifically, annular grooves 22 are first pre-formed on the outer side of the flat sheet 101, followed by deep drawing to form the wok 100. During the deep drawing process, the pre-formed annular grooves 22 are more prone to stretching deformation due to the material, and annular oil storage grooves 23, with the same number and corresponding positions as the annular grooves 22, are simultaneously formed on the inner surface of the wok wall 20.

[0031] The annular oil reservoir 23 stores cooking oil, allowing a dynamic oil film to form on the inner surface of the wok wall 20 during use. This effectively reduces food adhesion and improves non-stick performance. Since the annular oil reservoir 23 is formed by stretching and deforming the flat sheet 101, the manufacturing process of the non-stick wok 100 is simplified, reducing production costs. Furthermore, the annular groove 22 disperses stress during the deep-drawing process, effectively reducing stress concentration on the wok wall 20 and minimizing the risk of cracks or deformation during molding, further enhancing the reliability and durability of the wok 100.

[0032] In this embodiment, as Figure 3 As shown, the wok 100 has a cooking cavity, which is formed by the bottom 10 and the wall. The wall 20 has: (i) an overall shape symmetrical about the longitudinal axis, and (ii) a diameter perpendicular to the longitudinal axis, making the wok 100 more aesthetically pleasing and ensuring that it is heated evenly during the heating process, thus improving the cooking effect. The bottom can be a planar structure or a curved structure; when the bottom is curved, there is no clear boundary between the bottom and the wall, and the part below the thinning zone 21 can be considered as the bottom. The height direction of the wok 100 can be understood as: along the direction from the bottom 10 to the edge 30, or along the axial extension direction of the longitudinal axis.

[0033] In this embodiment, as Figures 1 to 5 As shown, the pot wall 20 can be a single-layer metal layer or multiple-layer metal layers; for example, the pot wall 20 includes a first metal layer 24, a second metal layer 25, and a third metal layer 26 from the inside out; the annular groove 22 is formed in the third metal layer 26. The ductility of the second metal layer 25 is greater than that of the first metal layer 24 and the third metal layer 26, so that during the deep drawing process, the pre-set annular groove 22 area is more prone to tensile deformation due to the material. The deformation is transmitted to the inner layer through the plastic deformation of the second metal layer 25, and finally annular oil storage grooves 23 are formed on the inner surface of the pot wall 20 in the same number and corresponding to the position of the annular groove 22. Among them, the first metal layer 24 and the third metal layer 26 are iron layers, and the second metal layer 25 is an aluminum layer.

[0034] In this embodiment, as Figures 3 to 5As shown, the thickness of the pot wall 20 is 1.0mm-5.0mm; preferably, the thickness of the pot wall 20 is 1.5mm-3.0mm. The thickness of the first metal layer 24 and the third metal layer 26 is 0.3mm-1.0mm, and the thickness of the second metal layer 25 is 0.4mm-3.0mm. Preferably, the thickness of the first metal layer 24 and the third metal layer 26 is 0.4mm-0.6mm, and the thickness of the second metal layer 25 is 0.8mm-1.5mm.

[0035] In this embodiment, as Figures 1 to 5 As shown, an annular groove 22 is etched, laser-engraved, or mechanically machined on the outer side of the flat plate 101; then, the flat plate 101 is drawn by hydraulic pressure or stamping to form a wok 100. During the stamping process, because the wall thickness at the annular groove 22 is less than that of the surrounding area, the material in this part exhibits higher ductility during stamping and stretching deformation, resulting in a significantly greater change in wall thickness than other areas. This differentiated deformation characteristic causes the corresponding position of the annular groove 22 to simultaneously form an annular oil storage groove 23 recess on the inner surface of the wok wall 20.

[0036] In this embodiment, as Figures 1 to 5 As shown, the depth of the annular groove 22 is 0.005mm-0.3mm. If the depth of the annular groove 22 is too shallow, the material deformation guidance effect during the deep drawing process is insufficient, making it difficult to form an effective annular oil storage groove 23 on the inner surface of the pot wall 20, resulting in weakened oil storage capacity and affecting non-stick performance. If the depth of the annular groove 22 is too deep, it may lead to excessive thinning of local materials or even cracking, reducing the structural strength and service life of the wok 100. Preferably, the depth of the annular groove 22 is 0.01mm-0.1mm. For example, the depth of the annular groove 22 is 0.03mm, 0.04mm, 0.06mm, or 0.07mm.

[0037] In this embodiment, as Figures 1 to 5 As shown, the width of the annular groove 22 is 0.1mm-5.0mm. If the width of the annular groove 22 is too narrow, the recessed feature of the annular oil storage groove 23 is not significant, and the oil storage space is limited; if the width of the annular groove 22 is too wide, it may disrupt the uniformity of the pot wall 20 thickness, causing stress concentration during deep drawing and increasing the risk of cracking of the pot wall 20. Preferably, the width of the annular groove 22 is 0.2mm-0.6mm or 1.0mm-3.0mm. For example, the width of the annular groove 22 is 0.3mm or 2mm.

[0038] In this embodiment, as Figure 1 As shown, when the width of the annular groove 22 is 1 mm-3 mm, the distance between adjacent annular grooves 22 is 4.0 mm-10.0 mm. Figure 2As shown, when the width of the annular groove 22 is in the range of 0.2mm-0.6mm; two adjacent annular grooves 22 form a group; the distance between two annular grooves 22 in the same group is 1.0mm-3.0mm; and the distance between two adjacent groups of annular grooves 22 is 4.0mm-10.0mm.

[0039] In this embodiment, as Figures 3 to 5 As shown, the inner wall of the annular oil storage tank 23 is roughly arc-shaped, which can guide the cooking oil to spread evenly and adhere stably in the tank, forming a long-lasting dynamic oil film. This effectively reduces the direct contact area between food and the pot wall 20, thereby significantly improving the non-stick performance of the wok 100. In addition, the arc-shaped inner wall has no sharp corners or irregular uneven structures. During the cleaning process after cooking, oil residues are easily peeled off naturally with the water flow, greatly reducing the difficulty and time of cleaning. At the same time, it avoids the scratch damage that may be caused by traditional rough surfaces, extending the service life of the wok 100.

[0040] In this embodiment, as Figure 5 As shown, the inner surface of the pot wall 20 has a porous membrane layer 27, which includes a first part covering the annular oil storage tank 23 and a second part covering the area outside the annular oil storage tank 23. The porosity of the first part is greater than that of the second part, which allows the porous structure of the annular oil storage tank 23 area to more efficiently adsorb and store cooking oil, forming a stable dynamic oil film. The relatively dense membrane structure in other areas of the pot wall 20 takes into account both the non-stick performance and structural strength requirements, while facilitating cleaning and maintenance after cooking, thus achieving a balanced improvement in non-stick performance and durability.

[0041] In this embodiment, as Figure 5 As shown, the pore size in the porous membrane layer 27 is 8μm-30μm. The porous membrane layer 27 is formed by acid oxidation of the inner surface of the pot wall 20, followed by polishing of the inner surface of the pot wall 20 to make the porosity of the first part greater than that of the second part. The porous membrane layer is an iron phosphate membrane or a phosphating membrane.

[0042] The wok 100 forms a porous phosphate film as a protective layer on the inner surface of the wok wall 20 through an acidic oxidation reaction in a phosphoric acid solution. The film can be quite thick, effectively preventing damage or perforation of the protective layer; for example, the thickness of the phosphate film is not less than 8 μm. The phosphate film is an insoluble phosphate conversion film formed on a metal surface through a chemical or electrochemical reaction, primarily achieved through a phosphating reaction. The phosphating reaction is the process of reacting a metal with phosphoric acid or acidic phosphate in an acidic solution containing an oxidizing agent to form a phosphate protective film.

[0043] The acidic oxidation process involves placing at least a portion of the surface of the wok 100 in a phosphoric acid solution containing phosphate anions and iron cations at a temperature above 85°C. Specifically, the pH of the phosphoric acid solution is 1-4, preferably 1.5-2.5. The wok 100 undergoes the acidic oxidation reaction in this phosphoric acid solution at a temperature above 85°C, preferably at a temperature of 90°C to boiling point. During the acidic oxidation reaction, on the one hand, the iron cations added to the phosphoric acid solution and some iron ions dissolved from the wok 100 react with phosphate ions and other ions in the phosphoric acid solution to generate iron phosphate compounds, which are deposited to form the porous phosphate film. On the other hand, the acidic solution corrodes the iron wok to dissolve iron ions, which then react with the wok 100 to generate various iron oxides, mainly iron(III) oxide (Fe3O4), which may include ferric oxide (Fe2O4) and ferrous oxide (Fe2O4). Since the reaction occurs in solution, the generated iron phosphate compounds often contain water of crystallization, forming hydrated phosphates, i.e., phosphate salts. When the cations in the solution are only iron ions, the main components of the resulting phosphating film are amorphous ferrous phosphate (Fe3(PO4)2•nH2O) and microcrystalline ferric phosphate (FePO4•2H2O). Additionally, there are some iron oxides, primarily Fe3O4, which are embedded in the phosphate matrix as microparticles. Of course, other types of compounds may also be included.

[0044] Because the acidic oxidation process corrodes the wok 100, and the reaction is carried out at a high temperature, resulting in a vigorous reaction, rapid film growth, and the release of H2 gas, the resulting phosphating film has numerous pores, forming a loose and porous structure; that is, the resulting phosphating film is a porous phosphating film. The loose and porous structure performs poorly in terms of wear resistance and corrosion resistance; therefore, acidic oxidation is generally not used as a protective layer for iron woks in the art. In this application, because the porous phosphating film has a porous structure, the acidic oxidation solution can penetrate the gaps in the film and continuously react with the iron wok, thereby continuously thickening the porous phosphating film. As the porous phosphating film thickens, the difficulty for the acidic solution to penetrate it also increases, thus slowing down the film formation rate until the reaction terminates. The resulting porous phosphating film comprises iron phosphate compounds and iron oxides, wherein the content of iron oxides decreases from the inside to the outside of the porous phosphating film. That is, the inner layer is mostly composed of iron oxides, while the outer layer is mostly composed of iron phosphate compounds. Generally, acidic oxidation processes can produce porous phosphating films with a thickness of 10μm to 200μm.

[0045] Before acid oxidation, the wok 100 requires pretreatment such as cleaning, grinding, and sandblasting to ensure it is clean, fresh, and has a certain degree of roughness to facilitate subsequent acid oxidation. After pretreatment, acid oxidation is performed using the following process: the wok 100 is placed in an acidic oxidation solution with iron as the cation and phosphate as the main anion, and a chemical reaction is carried out at a temperature above 90°C until boiling, generating a loose, porous phosphating film. After the chemical reaction, the particularly loose layer on its surface is appropriately ground with a scouring pad or similar material, thus completing the formation of the porous phosphating film. In actual production, the above process can be repeated once or multiple times as needed to form a porous phosphating film with the required thickness and porosity.

[0046] The porous phosphating film obtained using acidic iron oxide cookware with phosphoric acid solution has the following main characteristics: the film thickness can be relatively thick, exceeding 8 μm, but the film layer is loose and porous with relatively low hardness. After appropriate surface grinding to remove the surface floating film, the hardness of the film layer is approximately 120~170 HV. Because the porous phosphating film contains amorphous and microcrystalline phosphates, which contain bound water of crystallization, the structure is loose, the hardness is low, and the structural stability is poor. During long-term use, the physicochemical properties of the phosphating film will change, affecting the protective effect. To address this, the method provided in this application further includes a film-fixing treatment.

[0047] In this embodiment, the porous membrane layer 27 is heated to perform a solidification treatment, thereby improving the wear resistance of the wok 100. The wok 100 is heated to a set solidification temperature above the set temperature. At this temperature, the porous phosphating film undergoes a phase transition reaction tending towards crystallization to form a thermally stable porous phosphating film, thus achieving the solidification treatment. After the solidification treatment, the porous phosphating film transforms from an amorphous structure containing water of crystallization to a dehydrated crystalline structure.

[0048] High-temperature heating induces a phase transition reaction in porous phosphating films, causing them to crystalline. This process causes hydrated phosphates and amorphous phosphates in the porous phosphating film generated by acid oxidation to lose their water of crystallization and transform into a crystalline state, achieving a film-fixing effect. This makes the structure of the phosphating film more stable, ensuring that the physicochemical properties of the phosphating film remain unchanged during long-term use. The resulting phase transition phosphating film exhibits increased hardness and thermal stability, achieving a long-lasting and stable protective effect. Furthermore, high-temperature heating can further oxidize the low-valence iron compounds in the porous phosphating film into high-valence compounds, increasing the chemical passivation of the porous phosphating film and improving its corrosion resistance.

[0049] The set solidification temperature is between 200 and 600°C. At this temperature, the amorphous ferrous phosphate hydrate Fe3(PO4)2•nH2O and microcrystalline ferric phosphate FePO4•2H2O included in the porous phosphate film gradually lose their water of crystallization (H2O), transforming into crystalline anhydrous ferrous phosphate Fe3(PO4)2 and dense anhydrous FePO4. After the removal of the water of crystallization, the crystalline Fe3(PO4)2 and FePO4 exhibit reduced intermolecular distances and a more compact crystal structure. Furthermore, crystallization reduces disordered defects in the amorphous structure, improving the film's hardness and chemical stability.

[0050] The water of crystallization in phosphate salt hydrates is bound by molecular bonds. At lower temperatures, this water is difficult to remove or requires a longer time. Therefore, the preferred temperature for the solidification treatment is not lower than 300-360℃. However, excessively high temperatures can cause calcination of ferric phosphate, leading to particle fusion and a decrease in specific surface area, increasing the brittleness of the film and even causing fracture, resulting in surface ashing and loss of protective function. Therefore, the preferred temperature for the solidification treatment is not higher than 600℃. In some embodiments, the solidification process is carried out in a heating furnace, with the temperature preferably between 280 and 450℃. Temperatures below 280℃ may result in incomplete crystallization, insufficient hardness and density; temperatures above 450℃ may trigger matrix oxidation or uncontrolled local phase transformation. Typically, the iron pot is held at the set solidification temperature for at least 3 minutes. The solidification treatment time varies at different temperatures; generally, higher temperatures require shorter treatment times.

[0051] During the process of heating the wok 100 to a set solidification temperature or higher, the change process of the porous phosphating film may be divided into the following stages.

[0052] 1. High-Temperature Dehydration and Lattice Reconstruction Stage. In the initial heating stage, when the temperature reaches approximately 200-300℃, the water of crystallization and adsorbed water of the hydrochloride in the porous phosphate film are gradually removed. For example, the typical component of iron-based phosphate films, Fe3(PO4)2•8H2O, will lose some of its water of crystallization, forming anhydrous or low-hydrated form of iron phosphate, Fe3(PO4)2. At this time, the film volume shrinks, and the porosity temporarily increases due to the escape of water. Simultaneously, the phosphate lattice begins to transform from an amorphous state to a microcrystalline state, the amorphous phase gradually decreases, and a more stable crystal structure is formed.

[0053] 2. Oxidation and Phase Transformation Stage. When the temperature rises above 300℃, Fe... 2+ It is oxidized to Fe in a high-temperature oxidizing environment. 3 +This leads to the further conversion of iron phosphate into more stable iron phosphate FePO4 and iron oxides (such as Fe2O3 or Fe3O4). The oxidation reaction increases the valence state of iron in the film, while the generated P2O5 may form glassy complexes with other metal oxides, filling pores and enhancing compactness.

[0054] 3. Phosphate Condensation and Crystal Phase Reorganization Stage. At higher temperatures, such as 400–600 °C, phosphate undergoes a condensation reaction. FePO4 may combine with other metal oxides, such as Fe2O3, to form more complex crystal phases. At this stage, the grain size in the film increases, grain boundaries decrease, and porosity significantly decreases. Iron-based phosphating films may form a composite phase of FePO4 and Fe2O3 during this stage, and in some regions, even an Fe3O4 spinel structure may appear, further improving thermal stability.

[0055] When the temperature exceeds 600℃, the phosphating film may experience structural deterioration and changes in its protective performance. At temperatures above 600℃, phosphates may decompose, with some FePO4 decomposing into Fe2O3 and P2O5 gases, leading to cracks or peeling of the film. At this point, the film's density is compromised, and its antioxidant capacity decreases.

[0056] In some embodiments, the temperature of the solid film treatment can be controlled in a stepped manner. Specifically, in one embodiment, heating the prepared wok 100 to a set solid film temperature includes: first heating to a first stage temperature and maintaining it for a first duration, then heating to a second stage temperature and maintaining it for a second duration; wherein the first stage temperature is between 300 and 400°C, and the second stage temperature is between 400 and 500°C. At the first stage temperature, the main reaction occurring is the removal of water of crystallization, while at the second stage temperature, the main reactions occurring are oxidation, phase transformation, condensation, and crystal phase recombination. By using a stepped temperature control method, the film layer can be prevented from cracking due to a sudden temperature rise, while the removal of water of crystallization and phase transformation processes such as condensation and crystal phase recombination are carried out step by step, avoiding the potential for uncontrolled phase transformation caused by simultaneous and rapid reactions. In a specific embodiment of this application, the temperature is first maintained at 350°C to achieve sufficient dehydration, and then raised to 440°C to promote phase transformation.

[0057] Thermogravimetric analysis (TGA) showed that phosphates experienced significant weight loss at 300–350 °C, indicating that the water of crystallization (nH₂O) was removed during this process. XRD analysis revealed that after high-temperature treatment, the characteristic peaks of Fe₃(PO₄)₂ gradually disappeared, while the diffraction peaks of FePO₄ and Fe₂O₃ increased, confirming the occurrence of a phase transition.

[0058] In summary, after the solidification treatment, the porous phosphating film exhibits a more compact crystal structure, finer grains, and improved microhardness, resulting in enhanced hardness and wear resistance. Furthermore, the higher chemical inertness of anhydrous FePO4 allows for the formation of a more stable passivation film, inhibiting electrochemical corrosion of the ferrous substrate. The high temperature during the solidification process also causes the surface of Fe3O4 to oxidize, forming a thin layer of Fe2O3. This Fe2O3 surface layer exhibits high corrosion resistance, while the interior retains the magnetic protective effect of Fe3O4, with both synergistically enhancing corrosion resistance. Simultaneously, Fe3O4 and phosphate may form an Fe-PO composite interface phase at high temperatures, strengthening the adhesion between the film and the iron pot substrate and inhibiting phosphating film peeling. The pore structure of the porous phosphating film is also optimized after the solidification treatment, with partial pore closure and densification. The high temperature induces slight sintering of the film, causing the pore edges to shrink due to reduced surface energy, thus decreasing porosity. The reduction in porosity and average pore size leads to fewer stress concentration points and improved hardness and wear resistance. In the phosphating film after solidification treatment, crystalline FePO4 and Fe3(PO4)2 can release PO4³⁻ in a humid environment, which reacts with Fe²⁺. + / Fe³ + The combination forms a dense phosphate passivation film, blocking the penetration of corrosive media; the Fe2O3 surface layer and the densed phosphate together constitute a composite oxide-phosphate barrier, delaying substrate corrosion; simultaneously, when an oxidation reaction is present, Fe3O4 (mixed Fe²⁺) + / Fe³ + It can act as a sacrificial phase, preferentially oxidizing and consuming to protect the iron matrix. Based on the mechanisms of chemical passivation, physical isolation, and electrochemical protection, the corrosion resistance of cookware is significantly improved.

[0059] like Figures 1 to 5 As shown, this application also provides a method for manufacturing a non-stick frying pan 100, including the following steps: S100. An annular groove 22 is machined into the flat plate 101 to reduce the wall thickness of the flat plate 101. S200, a non-stick frying pan 100 is formed by deep drawing the flat plate 101. During the deep drawing process of the flat plate 101, an annular oil storage groove 23 is formed on the inner surface of the pan wall 20 because the annular groove 22 is more prone to tensile deformation than other parts.

[0060] The annular oil reservoir 23 stores cooking oil, allowing a dynamic oil film to form on the inner surface of the wok wall 20 during use. This effectively reduces food adhesion and improves non-stick performance. Since the annular oil reservoir 23 is formed by stretching and deforming the flat sheet 101, the manufacturing process of the non-stick wok 100 is simplified, reducing production costs. Furthermore, the annular groove 22 disperses stress during the deep-drawing process, effectively reducing stress concentration on the wok wall 20 and minimizing the risk of cracks or deformation during molding, further enhancing the reliability and durability of the wok 100.

[0061] The structure of the wok 100 can adopt the technical solutions in the aforementioned embodiments, including but not limited to: the structure of the wok wall 20, the structure of the annular groove 22, the structure of the annular oil storage tank 23, and the structure of the film layer 27.

[0062] In this embodiment, as Figures 1 to 5 As shown, an annular groove 22 is etched, laser-engraved, or mechanically machined on the outer side of the flat plate 101. Then, the flat plate 101 is drawn using hydraulic pressure or stamping to form the wok 100. During the stamping process, because the wall thickness at the annular groove 22 is less than that of the surrounding area, the material in this area is more prone to plastic deformation during stamping and stretching, resulting in a significantly greater change in wall thickness than other areas. This differentiated deformation characteristic causes the corresponding position of the annular groove 22 to simultaneously form an annular oil storage groove 23 recess on the inner surface of the wok wall 20.

[0063] In this embodiment, as Figure 5 As shown, the inner surface of the pot wall 20 has a porous membrane layer 27, which includes a first part covering the annular oil storage tank 23 and a second part covering the area outside the annular oil storage tank 23. The porosity of the first part is greater than that of the second part, which allows the porous structure of the annular oil storage tank 23 area to more efficiently adsorb and store cooking oil, forming a stable dynamic oil film. The relatively dense membrane structure in other areas of the pot wall 20 takes into account both the non-stick performance and structural strength requirements, while facilitating cleaning and maintenance after cooking, thus achieving a balanced improvement in non-stick performance and durability.

[0064] In this embodiment, as Figure 5 As shown, the pore size in the porous membrane layer 27 is 8μm-30μm. The porous membrane layer 27 is formed by acid oxidation of the inner surface of the pot wall 20, followed by polishing of the inner surface of the pot wall 20 to make the porosity of the first part greater than that of the second part. The porous membrane layer is an iron phosphate membrane or a phosphating membrane. The process for the porous membrane layer 27 is the same as the technical solutions described in the preceding embodiments.

[0065] The method provided in this application further includes heating the porous membrane layer 27 to perform a film-solidification treatment on the porous membrane layer 27, thereby improving the wear resistance of the wok 100. The film-solidification treatment employs the technical solutions described in the foregoing embodiments.

[0066] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered to be within the scope of this specification. When technical features of different embodiments are embodied in the same drawing, it can be regarded as the drawing also disclosing examples of combinations of the various embodiments involved.

[0067] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A non-stick frying pan, a bottomed cookware formed by deep drawing a flat sheet, comprising a bottom and a raised wall surrounding the bottom, the top of the wall defining a rim; characterized in that: The pot wall has a thickness reduction band formed during the deep drawing process. The thickness reduction band is disposed between the bottom of the pot and the edge of the pot and extends in the height direction of the pot. The outer surface of the thickness reduction band has a plurality of annular grooves extending in the circumferential direction of the pot wall, and its inner surface has annular oil storage grooves that are the same number and positional as the plurality of annular grooves. The thickness of the pot wall is 1.0mm-5.0mm, the depth of the annular groove is 0.005mm-0.3mm, and the width of the annular groove is 0.1mm-5mm. The annular groove is a wall thickness reduction feature pre-set on the outer side of the flat plate before the wok is drawn, and the annular oil storage groove is a recessed feature formed on the inner surface of the wok wall during the drawing process, based on the fact that the annular groove is more prone to tensile deformation than other parts.

2. A non-stick frying pan according to claim 1, characterized in that, The pot wall comprises a first metal layer, a second metal layer, and a third metal layer from the inside out; The annular groove is formed in the third metal layer.

3. A non-stick frying pan according to claim 2, characterized in that, The ductility of the second metal layer is greater than that of the first metal layer and the third metal layer.

4. A non-stick frying pan according to claim 2 or 3, characterized in that, The first and third metal layers are iron layers, and the second metal layer is an aluminum layer.

5. A non-stick frying pan according to claim 1, characterized in that, The inner wall of the annular oil storage tank has an arc-shaped cross-section.

6. A non-stick frying pan according to claim 1, characterized in that, The annular groove is etched, laser-engraved, or machined on the outer side of the flat plate.

7. A non-stick frying pan according to claim 1, characterized in that, The inner surface of the pot wall has a porous membrane layer, which includes a first part covering the annular oil storage tank and a second part covering the outside of the annular oil storage tank. The porosity of the first part is greater than that of the second part.

8. A non-stick frying pan according to claim 7, characterized in that, The porous membrane is an iron phosphate membrane or a phosphate membrane.

9. A non-stick frying pan according to claim 8, characterized in that, The porous membrane is heated to perform a solidification treatment on the porous membrane.

10. A method for manufacturing a non-stick frying pan, characterized in that, include: An annular groove is machined into the flat plate to reduce the wall thickness of the flat plate. A wok is produced by deep drawing the flat sheet. During the deep drawing process of the flat sheet, an annular oil storage groove is formed on the inner surface of the wok wall because the annular groove is more prone to tensile deformation than other parts. The thickness of the pot wall is 1.0mm-5.0mm, the depth of the annular groove is 0.005mm-0.3mm, and the width of the annular groove is 0.1mm-5mm.

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