Non-stick pan without coating and preparation process

Abstract

The invention discloses an uncoated non-stick pan and a preparation process, and relates to the technical field of metal substrate surface treatment. According to the preparation process, the pot body is processed through multi-pass shot blasting treatment by adopting tungsten alloy shot blasting of a specific specification, and a uniform and compact residual compressive stress layer and a micro-nano-scale pit structure are formed on the surface layer of the pot body by utilizing kinetic energy of shot blasting, so that the oil storage and locking effect is realized; and an oil mist air cushion is formed in the heating process, so that the adhesive force between food and the pan surface is effectively reduced, and a good non-stick effect is achieved. In addition, according to the preparation technology, the pan body is subjected to surface treatment only through the mode of shot blasting treatment and heat treatment, and compared with an existing surface treatment technology, the cost is lower, and the prepared non-stick pan is harmless to human health.

Description

Technical Field

[0001] This invention relates to the field of metal substrate surface treatment technology, and in particular to an uncoated non-stick pan and its preparation process. Background Technology

[0002] The main manufacturing methods for non-stick pans on the market include physical non-stick coatings, metal ceramic oxide coatings, or non-stick coatings. Among these, coatings and spray coatings have a relatively short lifespan. Furthermore, coated non-stick pans are prone to scratches and peeling, generally requiring replacement after 1-2 years of use. The coating debris that falls off during use can also pose a health risk. Therefore, uncoated non-stick pans relying solely on physical non-stick properties are favored. Existing physical non-stick processes include molding, rolling, etching, and shot blasting. However, these technologies have drawbacks such as food easily getting trapped and sticking within the embossed patterns, resulting in poor non-stick performance and higher costs. Summary of the Invention

[0003] The main objective of this invention is to develop a non-stick pan without coating that has minimal impact on the pan's substrate, provides good anti-stick properties, and has a low manufacturing cost.

[0004] To achieve the above objectives, the present invention proposes a manufacturing process for an uncoated non-stick pan, the manufacturing process of which includes the following steps:

[0005] S1. The metal substrate is successively blanked, stretched and trimmed to obtain the pot body;

[0006] S2. The inner surface of the pot body obtained in step S1 is subjected to shot peening to strengthen it, and a number of micro-nano-level pit structures are formed on the inner surface of the pot body. The inner surface of the pot body is cleaned until there are no residues.

[0007] S3. Heat treat the pot body after step S2 to complete the preparation of the uncoated non-stick pot.

[0008] In one embodiment, the metal substrate is selected from any one of alloy steel, titanium alloy, and aluminum alloy; wherein the alloy steel includes any one of 304 stainless steel, 306L stainless steel, and Q235 steel.

[0009] In one embodiment, the thickness of the pot body is 1mm to 2.5mm.

[0010] In one embodiment, in step S2, the inner surface of the pot body after shot peening is formed with a plurality of continuous or staggered micro-nano-scale pit structures.

[0011] In one embodiment, the depth of the micro-nano-scale pit structure is 0.1 μm to 10 μm, and the diameter of the micro-nano-scale pit structure is 0.5 μm to 10 μm.

[0012] In one embodiment, in step S2, during the shot peening process, shot is used to blast the inner surface of the pot body, and the blasting speed of the shot is 10m / s to 450m / s.

[0013] In one embodiment, during step S2, the shot peening process involves using shot peening to spray the inner surface of the pot body, with the spray gun positioned 5mm to 500mm away from the pot body.

[0014] In one embodiment, the shot peening particle size is 0.03 mm to 0.8 mm.

[0015] In one embodiment, the hardness of the shot peening is not less than 1000 HV.

[0016] In one embodiment, the density of the shot peening is not less than 14.5 g / cm³. 3 .

[0017] In one embodiment, the sphericity of the shot peening is not less than 95%.

[0018] In one embodiment, the shot peening is a tungsten alloy shot peening, which comprises the following components by mass percentage: tungsten: 59wt% to 83wt%; Ni: 8wt% to 31wt%; Co: 5.9wt% to 32.9wt%; and unavoidable impurities.

[0019] In one embodiment, the tungsten alloy shot comprises the following components by mass percentage:

[0020] Tungsten or tungsten carbide: 79wt%–93wt%; Co: 21wt%–7wt%; and unavoidable impurities.

[0021] In one embodiment, the tungsten alloy shot comprises the following components by mass percentage:

[0022] Tungsten or tungsten carbide: 79wt%–93wt%; Ni: 21wt%–7wt%; and unavoidable impurities.

[0023] In one embodiment, step S2 specifically includes the following steps:

[0024] S21. Perform a first shot peening treatment on the inner surface of the pot body using shot with a particle size distribution of 20 mesh to 100 mesh; or, perform a first shot peening treatment on the inner surface of the pot body using shot with a particle size distribution of 100 mesh to 200 mesh; or, perform a first shot peening treatment on the inner surface of the pot body using shot with a particle size distribution of 300 mesh to 500 mesh.

[0025] In one embodiment, step S2 specifically includes the following steps:

[0026] S21. The inner surface of the pot body is subjected to a first shot peening treatment using shot with a particle size distribution of 20 mesh to 100 mesh.

[0027] S22. The inner surface of the pot body is subjected to a second shot peening treatment using shot with a particle size distribution of 100 mesh to 200 mesh.

[0028] In one embodiment, step S2 specifically includes the following steps:

[0029] S21. The inner surface of the pot body is subjected to a first shot peening treatment using shot with a particle size distribution of 100 mesh to 200 mesh.

[0030] S22. Perform a second shot peening treatment on the inner surface of the pot body using shot with a particle size distribution of 300 mesh to 500 mesh, thus completing the shot peening treatment of the pot body.

[0031] In one embodiment, step S2 specifically includes the following steps:

[0032] S21. The inner surface of the pot body is subjected to a first shot peening treatment using shot with a particle size distribution of 20 mesh to 100 mesh.

[0033] S22. Use shot peening with any particle size distribution of 300 mesh to 500 mesh to perform a second shot peening treatment on the inner surface of the pot body, thus completing the shot peening treatment of the pot body.

[0034] In one embodiment, step S2, following step S22, further includes the following steps:

[0035] S21. The inner surface of the pot body is subjected to a first shot peening treatment using shot with a particle size distribution of 20 mesh to 100 mesh.

[0036] S22. The inner surface of the pot body is subjected to a second shot peening treatment using shot with a particle size distribution of 100 mesh to 200 mesh.

[0037] S23. Use shot peening with any particle size distribution of 300 mesh to 500 mesh to perform a third shot peening treatment on the inner surface of the pot body, and complete the shot peening treatment of the pot body.

[0038] In one embodiment, during step S21, when performing the first spraying process, the spraying pressure is 0.1 MPa to 1.6 MPa and the spraying time is 0.5 min to 10 min.

[0039] In one embodiment, during step S22, when performing the second spraying process, the spraying pressure is 0.1 MPa to 1.6 MPa and the spraying time is 0.5 min to 10 min.

[0040] In one embodiment, during step S23, when performing the third spraying process, the spraying pressure is 0.1 MPa to 1.6 MPa and the spraying time is 0.5 min to 10 min.

[0041] In one embodiment, step S3 includes the following heat treatment: performing a high-temperature bluing treatment on the pot body after shot peening, with a treatment temperature of 280℃~300℃ and a treatment time of 25min~35min.

[0042] The present invention also proposes an uncoated non-stick pan, which is prepared by the above-mentioned method for preparing an uncoated non-stick pan.

[0043] The technical solution of this invention designs a manufacturing process for a non-stick pan without coating. It employs a multi-pass shot peening process with tungsten alloy shot of specific specifications to process the pan body. The kinetic energy of the shot peening forms a uniform and dense residual compressive stress layer and micro-nano-scale pit structure on the surface of the pan body. This effectively inhibits crack initiation and propagation, improving the fatigue resistance of the pan body, while optimizing the shot peening process to effectively control the deformation of the pan body. Furthermore, the uniformly distributed continuous or staggered pit structure formed on the inner surface of the pan after shot peening facilitates the diffusion of oil molecules on the inner surface, achieving an oil-absorbing and locking effect. During heating, an oil mist cushion is formed, effectively reducing the adhesion between food and the pan surface, resulting in a better non-stick effect. This is especially effective for metal materials with low thermal conductivity, such as stainless steel and titanium alloys, truly achieving non-stick properties without coating. In addition, the manufacturing process of this application only involves shot peening followed by heat treatment to treat the surface of the pan body. Compared with existing surface treatment processes, this is lower in cost and poses no health risks to the prepared non-stick pan. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0045] Figure 1 This is a surface pit morphology diagram and a schematic diagram of the anti-stick principle of an uncoated non-stick pan according to an embodiment of the present invention;

[0046] Figure 2 Comparison of the metallographic structure of the pot body surface before and after shot peening according to an embodiment of the present invention;

[0047] Figure 3 Metallographic images of different shot peening passes for an embodiment of the present invention;

[0048] Figure 4 This is a test diagram of an oil coating experiment according to an embodiment of the present invention;

[0049] Figure 5 This is a metallographic image of the surface of the pot body in Comparative Example 1 of the present invention.

[0050] Figure label:

[0051] 1. Food; 2. Oil film; 3. Pot body;

[0052] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0053] 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 a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0054] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0055] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0056] The technical problem addressed by this application is that current non-stick pan manufacturing methods mainly include physical non-stick coatings, metal ceramic oxide coatings, or non-stick coatings. Among these, coatings and spray coatings have relatively short lifespans. Furthermore, coated non-stick pans are prone to scratches and peeling, generally requiring replacement after 1-2 years of use. The peeling coating debris can also pose a health risk. Therefore, uncoated non-stick pans relying solely on physical non-stick properties are favored. Existing physical non-stick processes include molding, rolling, etching, and shot blasting. However, these technologies suffer from issues such as food easily entering and sticking within the embossed patterns, resulting in poor non-stick performance and higher costs.

[0057] It should be noted that although shot peening technology is also used in related technologies, traditional shot peening processes can easily cause stress concentration during the processing of the pot body, thereby altering the workpiece dimensions or reducing the strengthening effect of shot peening in other areas. In another related technology, the pot needs to be placed in a sand bucket before shot peening to prevent macroscopic deformation of the pot body, which is too cumbersome and not conducive to automated production.

[0058] It should also be noted that in related technologies, nitriding and carburizing are often followed by other surface treatments after shot peening to enhance surface hardness and corrosion resistance. However, these processes involve certain chemical treatments, which may introduce substances harmful to human health into the pot, raising concerns about consumer health and safety. Furthermore, nitriding and carburizing are time-consuming and costly; laser equipment is expensive; and acid-base etching presents challenges in controlling etching depth, all of which limit the large-scale application of these technologies.

[0059] To address the aforementioned technical problems, this application proposes a manufacturing process for an uncoated non-stick pan, which includes the following steps:

[0060] S1. The metal substrate is successively blanked, stretched and trimmed to obtain the pot body;

[0061] S2. The inner surface of the pot body obtained in step S1 is subjected to shot peening to strengthen it, and a number of micro-nano-level pit structures are formed on the inner surface of the pot body. The inner surface of the pot body is cleaned until there are no residues.

[0062] S3. Heat treat the pot body after step S2 to complete the preparation of the uncoated non-stick pot.

[0063] Understandably, in step S1, the pot body is produced by sequentially processing the metal substrate through machining processes such as blanking, stretching, and trimming. In step S2, the pot body is shot-peened, utilizing the kinetic energy of the shot peening to induce plastic deformation and phase transformation of the metal structure on the inner surface of the pot body, forming a compressive stress layer of a certain thickness on the inner surface of the pot body. This compressive stress layer has numerous micro-nano-scale pit structures distributed on its surface, thereby increasing the contact area between the oil film and the pot surface. Due to the small volume and high density of the pit structures, the oil film stored in the pits can form molecular-level van der Waals adsorption forces, thus achieving an oil-storing and oil-locking effect on the coating surface. During daily use, due to the increased specific surface area of ​​the oil film, the heat conduction area absorbing heat from the bottom of the pot and transferring it to the pot surface during heating is large, making it very easy for the oil film to heat up. The volume expansion of oil molecules and even the boiling time are faster, making it easier to form an oil mist cushion between the pot surface and the food. This effectively reduces the contact between the food and the pot surface, reducing the adhesion of the food to the pot surface and providing a better non-stick effect.

[0064] It should also be noted that the heat treatment in step S3, by heating to a certain temperature and holding it at that temperature, makes the severe uneven internal stress generated by shot peening more uniform, thereby making the stress distribution more stable. Most of the beneficial compressive stress will be retained, making the shot peening effect more durable. In addition, during the heat treatment process, the metal surface will react with oxygen to form a dense oxide film, such as iron tetroxide or aluminum oxide, which has good rust prevention properties.

[0065] It should also be noted that after shot peening in step S2, a uniform and dense compressive stress layer is formed on the surface of the pot, and the surface of this compressive stress layer has several micro-nano-scale pit structures distributed thereon, such as... Figure 2 As shown, the left image is the metallographic structure of the metal substrate without shot peening, while the right image is the metallographic structure of the metal substrate obtained after shot peening in step S2 of this application. It can be clearly observed that the metallographic structure of the surface layer of the left pot is loose and contains microcracks, while the compressive stress layer on the surface of the right pot has a significantly higher density. The shot peening process is essentially a micro-cold forging process on the surface of the iron-based pot, inducing martensitization and grain refinement of the metallographic structure on the iron-based material surface, forming a compressive stress layer with higher hardness. Therefore, the surface wear resistance and fatigue resistance of the pitted structure are significantly increased, with an increase of approximately 3–8 HRC.

[0066] It should also be noted that the roughness of the inner surface of the pot is further reduced compared to the untreated inner surface; in one embodiment, the roughness of the inner surface of the pot corresponding to the compressive stress layer is 0.8 μm; in a preferred embodiment, the roughness of the inner surface of the pot corresponding to the compressive stress layer is 0.6 μm.

[0067] In one embodiment, a surface pretreatment step for the inner surface of the pot is further included between steps S1 and S2: polishing, cleaning and drying the machined pot surface to maintain a sufficiently high gloss level on the inner surface of the pot.

[0068] In one embodiment, the metal substrate is selected from any one of alloy steel, titanium alloy, and aluminum alloy; wherein, the alloy steel includes any one of 304 stainless steel, 306L stainless steel, and Q235 steel. It should be noted that the above-mentioned metal substrate has good ductility and toughness, possesses good plastic deformation capability, and can well adapt to shot peening and heat treatment processes.

[0069] In one embodiment, the thickness of the pot body is 1mm to 2.5mm.

[0070] It should be noted that limiting the thickness of the pot body ensures its inherent strength. If the pot body is too thin, it will vibrate and shake when impacted by shot peening, affecting the shot's impact point and preventing the formation of uniform and effective micro-indentations. In severe cases, the pot body may undergo macroscopic deformation, and the compressive stress layer generated by shot peening may even penetrate the entire thickness, thus reducing the overall mechanical properties. If the pot body is too thick, higher shot peening energy is required to create the desired indented surface, resulting in higher production costs.

[0071] In one embodiment, in step S2, the inner surface of the pot body after shot peening is formed with a plurality of continuous or staggered micro-nano-scale pit structures. Specifically, through shot peening, the inner surface of the pot body forms a plurality of continuous or staggered micro-nano-scale pit structures.

[0072] In a preferred embodiment, the depth of the micro / nano-scale pit structure is 0.1 μm to 10 μm, and the diameter of the micro / nano-scale pit structure is 0.5 μm to 10 μm. In a preferred embodiment, Figure 2 The two images above are surface pit morphology images of the pot body after shot peening. The pit diameter ranges from 3μm to 10μm, and the depth is no more than 2μm.

[0073] In one embodiment, during step S2, the inner surface of the pot is blasted with shot peening at a velocity of 10 m / s to 450 m / s. It is understood that the blasting velocity can be any of 10 m / s, 100 m / s, 110 m / s, 150 m / s, 200 m / s, or 450 m / s, and any velocity within this range is acceptable; no specific limitation is made in this application.

[0074] In one embodiment, in step S2, during the shot peening process, shot peening is used to spray the inner surface of the pot body, and the spray gun is 5mm to 500mm away from the pot body.

[0075] In one embodiment, the shot peening particle size is 0.03 mm to 0.8 mm.

[0076] In a preferred embodiment, in step S2, during the shot peening process, spherical projectiles with a particle size of 0.03 mm to 0.8 mm are shot at a high speed of 10 m / s to 450 m / s to impact the metal surface. The kinetic energy of the shot peening induces plastic deformation on the inner surface of the pot, thereby forming a uniform and dense residual compressive stress layer and a micro-nano-scale pit structure.

[0077] It should be noted that traditional shot peening processes typically use shot with a particle size of 0.5mm to 2mm impacting the metal surface at a speed of 30m / s to 80m / s. Due to the relatively large particle size, excessively high speeds of individual shot particles can lead to excessively high kinetic energy, easily altering the macroscopic dimensions of the pot. Furthermore, since the pot is spherical, stress concentration is easily caused, preventing shot peening from achieving a good strengthening effect. In contrast, this application uses shot with a smaller particle size impacting the pot surface at a higher speed to perform a micro-cold forging effect, providing more uniform and comprehensive coverage and producing a finer surface strengthening effect.

[0078] In one embodiment, the hardness of the shot peening is not less than 1000 HV.

[0079] It is understandable that the hardness of shot peening is relative to the hardness of the pot body substrate, such as various alloy steels, titanium alloys, and aluminum alloys, including 304 stainless steel, 306L stainless steel, and Q235 steel. However, this application requires the shot peening hardness to be at least 300 HV higher than that of the pot body substrate. This ensures that the vast majority of the kinetic energy is used to induce plastic flow in the substrate, forming ideal, smooth micro-pits, while also minimizing shot wear and breakage.

[0080] In one embodiment, the density of the shot peening agent is not less than 14.5 g / cm³. 3 In a preferred embodiment, the density of the shot peening is not less than 15 g / cm³. 3 It should be noted that the density of shot peening, once the shot particle size is limited, directly affects the mass of a single shot. According to the mass-energy equivalence equation, with a fixed shot peening machine speed, the density of the shot directly determines its mass, and thus its kinetic energy. Current technology typically uses a density of approximately 5.9 g / cm³. 3 The surface hardness of the zirconia shot peening is 3 to 5 HRC lower than that of the present application. This shows that the shot peening with an appropriate density can play a certain micro-forging effect on the surface of the pot.

[0081] In one embodiment, the sphericity of the shot peening is not less than 95%. It is understood that by limiting the sphericity of the shot peening, the morphology of the pit can be controlled, ensuring that each impact produces an ideal micro-pit, ultimately forming a uniform, smooth surface without sharp edges, ensuring the formation of smooth pits rather than sharp scratches, thereby obtaining better anti-sticking effect and fatigue resistance.

[0082] In one embodiment, the shot peening is tungsten alloy shot peening, which comprises the following components in weight percentage: tungsten: 59wt% to 83wt%; Ni: 8wt% to 31wt%; Co: 5.9wt% to 32.9wt%; and unavoidable impurities.

[0083] In one embodiment, the shot peening is a tungsten alloy shot peening, which comprises the following components by mass percentage: tungsten or tungsten carbide: 79wt% to 93wt%; Co: 21wt% to 7wt%; and unavoidable impurities.

[0084] In one embodiment, the shot peening is a tungsten alloy shot peening, which comprises the following components by mass percentage: tungsten or tungsten carbide: 79wt% to 93wt%; Ni: 21wt% to 7wt%; and unavoidable impurities.

[0085] In a preferred embodiment, the tungsten alloy shot peening comprises the following components by weight percentage: tungsten: 81 wt%; Ni: 11 wt%; Co: 7.9 wt%; and unavoidable impurities.

[0086] It should be noted that the aforementioned tungsten alloy shot peening was independently developed by the applicant, and it possesses the properties of a shot peening hardness of not less than 1000 HV and a density of not less than 14.5 g / cm³. 3 With a sphericity of not less than 95%, it possesses the characteristics of high hardness, high density, high sphericity, high toughness, and high wear resistance. Its cycle life in shot peening can reach more than 10,000 times. In comparison, the density of conventional high-hardness steel shot peening is only half that, and its cycle life in shot peening is only 1,500 times.

[0087] In one embodiment, step S2, the shot peening process specifically includes the following steps:

[0088] S21. Perform a first shot peening treatment on the inner surface of the pot body using shot with a particle size distribution of 20 mesh to 100 mesh; or, perform a first shot peening treatment on the inner surface of the pot body using shot with a particle size distribution of 100 mesh to 200 mesh; or, perform a first shot peening treatment on the inner surface of the pot body using shot with a particle size distribution of 300 mesh to 500 mesh.

[0089] In one embodiment, step S2, the shot peening process specifically includes the following steps:

[0090] S21. The inner surface of the pot body is subjected to a first shot peening treatment using shot with a particle size distribution of 20 mesh to 100 mesh.

[0091] S22. The inner surface of the pot body is subjected to a second shot peening treatment using shot with a particle size distribution of 100 mesh to 200 mesh.

[0092] In one embodiment, step S2 specifically includes the following steps:

[0093] S21. The inner surface of the pot body is subjected to a first shot peening treatment using shot with a particle size distribution of 100 mesh to 200 mesh.

[0094] S22. Use shot peening with any particle size distribution of 300 mesh to 500 mesh to perform a second shot peening treatment on the inner surface of the pot body, thus completing the shot peening treatment of the pot body.

[0095] In one embodiment, step S2 specifically includes the following steps:

[0096] S21. The inner surface of the pot body is subjected to a first shot peening treatment using shot with a particle size distribution of 20 mesh to 100 mesh.

[0097] S22. Use shot peening with any particle size distribution of 300 mesh to 500 mesh to perform a second shot peening treatment on the inner surface of the pot body, thus completing the shot peening treatment of the pot body.

[0098] In a preferred embodiment, step S2, the shot peening treatment specifically includes the following steps:

[0099] S21. The inner surface of the pot body is subjected to a first shot peening treatment using shot with a particle size distribution of 20 mesh to 100 mesh.

[0100] S22. The inner surface of the pot body is subjected to a second shot peening treatment using shot with a particle size distribution of 100 mesh to 200 mesh.

[0101] S23. Use shot peening with any particle size distribution of 300 mesh to 500 mesh to perform a third shot peening treatment on the inner surface of the pot body, and complete the shot peening treatment of the pot body.

[0102] It should be noted that step S2 employs a three-stage progressive shot peening sequence to sequentially bombard the pot surface. First, large-diameter, high-kinetic-energy tungsten alloy shot is used to create a deep macroscopic residual compressive stress field on the substrate surface with high impact force, constructing the framework of a micron-level pit structure. Second, medium-diameter shot is used to further forge and refine the structure formed in the first stage, making the pit edges smoother and preventing stress concentration. Finally, extremely fine shot is used for a precision treatment similar to sandblasting, greatly reducing surface roughness and forming a smooth, pebble-like microstructure. This maximizes the stability of the oil film or gas film, achieving optimal physical non-stick properties, while maintaining a relatively smooth surface that is less prone to dirt accumulation.

[0103] In a preferred embodiment, in step S21, when performing the first shot peening treatment, the blasting pressure is 0.1 MPa to 1.6 MPa and the blasting time is 0.5 min to 10 min.

[0104] In a preferred embodiment, during step S22, when performing the second shot peening treatment, the blasting pressure is 0.1 MPa to 1.6 MPa and the blasting time is 0.5 min to 10 min.

[0105] In a preferred embodiment, in step S23, when performing the third shot peening treatment, the blasting pressure is 0.1 MPa to 1.6 MPa and the blasting time is 0.5 min to 10 min.

[0106] Understandably, during multi-pass shot peening, higher blasting pressure and shorter blasting time allow for a sufficient "forging-finishing" process, resulting in a smooth, uniform microstructure free of sharp stress concentrations. Too short a time will leave burrs on the surface; too long a time will lead to over-hardening or even material delamination. Sufficient impact cycles and energy input are needed to achieve the desired depth and strength of the stress layer, thereby significantly improving the cookware's resistance to thermal fatigue.

[0107] In a preferred embodiment, step S2, the shot peening treatment specifically includes the following steps:

[0108] S21. The inner surface of the pot body is subjected to the first shot peening treatment using shot with a particle size of 50-100 mesh, the peening pressure is 0.4 MPa and the peening time is 10 minutes.

[0109] S22. The inner surface of the pot body is subjected to a second shot peening treatment using shot with a particle size of 100-200 mesh, with a peening pressure of 0.4 MPa and a peening time of 10 minutes.

[0110] S23. Use shot peening with a particle size of 300-500 mesh to perform a third shot peening treatment on the inner surface of the pot body, with a peening pressure of 0.4 MPa and a peening time of 10 minutes; the shot peening treatment of the pot body is completed.

[0111] In one embodiment, step S3 includes heat treatment including: performing high-temperature bluing treatment on the pot body after shot peening, with a treatment temperature of 280°C to 300°C and a treatment time of 25 min to 35 min.

[0112] In a preferred embodiment, step S3 includes heat treatment of the pot body after shot peening, with a high-temperature bluing treatment at a temperature of 280°C and a treatment time of 30 minutes.

[0113] It should be noted that the heat treatment process in step S3 of this invention is not the traditional normalizing or tempering process, but rather a high-temperature bluing treatment for the pot body after shot peening. High-temperature bluing treatment stabilizes stress in the pot body by heating it, preventing the restoration of pitted structures caused by stress release under natural conditions; it also delays oxidation and corrosion of the pot body by generating a dense oxide film on the metal surface. In this application, shot peening only exerts compressive stress on the metallographic structure of the metal substrate surface, without altering its overall microstructure. Normalizing or tempering, on the other hand, is typically used to adjust the overall microstructure of the material and optimize its comprehensive performance, and is not applicable to the subsequent heat treatment in this application.

[0114] The present invention also proposes an uncoated non-stick pan, which is prepared using the above-described preparation process.

[0115] Figure 1 In the two images below, the left image shows a schematic diagram of food on the inner surface of the uncoated non-stick pan. The right image is a magnified view of point A in the left image, specifically showing that point A is the contact point between the pan surface and the food, including the food 1, the oil film 2, and the pan body 3 in sequence.

[0116] The present invention will be further illustrated below through specific embodiments:

[0117] All raw materials used in the embodiments of this invention are commercially available, and this invention does not impose any restrictions on the source of raw materials.

[0118] Example 1

[0119] The tungsten alloy shot peening used in Example 1 comprises the following components by mass percentage: tungsten: 81 wt%; Ni: 11 wt%; Co: 7.9 wt%; and unavoidable impurities, and was produced by Shenzhen Hangke New Materials Co., Ltd.

[0120] Measurements showed that the hardness of the tungsten alloy shot peening particles used in Example 1 was 1400 HV, and the density of the shot peening particles was 15.2 g / cm³. 3 The sphericity of the shot peening is approximately 96%.

[0121] The preparation process of the uncoated non-stick pan in Example 1 includes the following steps:

[0122] S1. The 304 stainless steel sheet is sequentially blanked, stretched, and trimmed to obtain a pot body with an average thickness of 2.1mm. The surface of the pot body is as shown. Figure 3 As shown in a;

[0123] S21. The first shot peening treatment uses tungsten alloy shot with a particle size of 20-100 mesh. The distance between the spray gun and the pot body is controlled at approximately 90 mm, the shot peening speed is controlled at approximately 200 m / s, the spraying pressure is 0.4 MPa, and the spraying time is 10 minutes. After completing the first shot peening treatment, the surface of the pot body is as shown. Figure 3 As shown in b;

[0124] S22. The second shot peening process uses tungsten alloy shot with a particle size of 100-200 mesh. The distance between the shot blasting gun and the pot body is controlled at approximately 90 mm, the shot blasting speed is controlled at approximately 200 m / s, the blasting pressure is 0.4 MPa, and the blasting time is 10 minutes. This completes the second shot peening treatment, and the surface of the pot body is as shown in the image. Figure 3 As shown in c;

[0125] S23. The third shot peening process uses tungsten alloy shot with a particle size of 300-500 mesh. The distance between the shot blasting gun and the pot body is controlled at approximately 90 mm, the shot blasting speed is controlled at approximately 200 m / s, the blasting pressure is 0.4 MPa, and the blasting time is 10 minutes. This completes the third shot peening treatment, and the surface of the pot body is as shown in the image. Figure 3 As shown in d;

[0126] S3. Perform high-temperature bluing treatment on the shot-peened pot body, baking the pot body at 280℃ for about 30 minutes to complete the preparation of the uncoated non-stick pot.

[0127] The surface roughness Ra of the inner surface of the pot after processing in steps S1, S21, S22 and S23 was measured and found to be 1.5 μm, 1.2 μm, 0.8 μm and 0.5 μm, respectively.

[0128] Through the Figure 3 a~ Figure 3 Analysis of the pit morphology in section d shows that with each shot peening pass, the pits on the surface of the 304 stainless steel gradually become finer and smoother, especially in contrast. Figure 4 and Figure 5 We can obtain, Figure 4 The pits on the surface of the 304 stainless steel were relatively large and unevenly distributed. The effect of the third shot peening treatment was significantly better. Figure 3 The absence of significantly larger light spots in d indicates that the pits on the surface of 304 stainless steel have become finer and more uniform.

[0129] The non-stick performance of the uncoated non-stick pan prepared in Example 1 was tested for frying eggs in accordance with the provisions of Section 4.2.1 of standard GB / T 32095.2-2015. The test results showed that it had good non-stick performance.

[0130] Oil adhesion tests were conducted on the uncoated non-stick pan prepared in Example 1 and the stainless steel pan body obtained in step S1, respectively. The results are as follows: Figure 4 As shown in the analysis results, a thin and uniform oil film can be formed on the surface of the stainless steel pot after shot peening. The oil diffuses well in the pot body and the surface of the pot body can easily retain and lock in the oil. On the other hand, the oil droplets on the surface of the stainless steel pot that has not been shot peened are aggregated and have poor diffusion.

[0131] Example 2

[0132] The tungsten alloy shot peening used in Example 2 is the same as that in Example 1.

[0133] The preparation process of the uncoated non-stick pan in Example 2 includes the following steps:

[0134] S1. The Q235 steel plate is successively blanked, stretched and trimmed to obtain a pot body with an average thickness of 2.1mm.

[0135] S21. The first shot peening treatment is carried out using tungsten alloy shot with a particle size of 20-100 mesh. The distance between the spray gun and the pot body is controlled at about 90 mm, the shot peening speed is controlled at about 200 m / s, the spraying pressure is 0.2 MPa, and the spraying time is 7 minutes to complete the first shot peening treatment.

[0136] S22. The second shot peening process uses tungsten alloy shot with a particle size of 100-200 mesh. The distance between the spray gun and the pot body is controlled at about 90 mm, the shot peening speed is controlled at about 200 m / s, the spraying pressure is 0.2 MPa, and the spraying time is 7 minutes to complete the second shot peening process.

[0137] S23. The third shot peening process uses tungsten alloy shot with a particle size of 300-500 mesh. The distance between the spray gun and the pot body is controlled at about 90 mm, the shot peening speed is controlled at about 200 m / s, the spraying pressure is 0.2 MPa, and the spraying time is 7 minutes to complete the third shot peening process.

[0138] S3. Perform high-temperature bluing treatment on the shot-peened pot body, baking the pot body at 280℃ for about 30 minutes to complete the preparation of the uncoated non-stick pot.

[0139] The non-stick performance of the uncoated non-stick pan prepared in Example 2 was tested for frying eggs in accordance with the provisions of Section 4.2.1 of standard GB / T 32095.2-2015. The test results showed that it had good non-stick performance.

[0140] Example 3

[0141] The tungsten alloy shot peening used in Example 3 is the same as that in Example 1.

[0142] The preparation process of the uncoated non-stick pan in Example 3 includes the following steps:

[0143] S1. The Q235 steel plate is successively blanked, stretched and trimmed to obtain a pot body with an average thickness of 2.1mm.

[0144] S21. The first shot peening treatment is carried out using tungsten alloy shot with a particle size of 20-100 mesh. The distance between the spray gun and the pot body is controlled at about 90 mm, the shot peening speed is controlled at about 200 m / s, the spraying pressure is 0.6 MPa, and the spraying time is 5 minutes to complete the first shot peening treatment.

[0145] S22. The second shot peening process uses tungsten alloy shot with a particle size of 100-200 mesh. The distance between the spray gun and the pot body is controlled at about 90 mm, the shot peening speed is controlled at about 200 m / s, the spraying pressure is 0.6 MPa, and the spraying time is 5 minutes to complete the second shot peening process.

[0146] S23. The third shot peening process uses tungsten alloy shot with a particle size of 300-500 mesh. The distance between the spray gun and the pot body is controlled at about 90 mm, the shot peening speed is controlled at about 200 m / s, the spraying pressure is 0.6 MPa, and the spraying time is 5 minutes to complete the third shot peening process.

[0147] S3. Perform high-temperature bluing treatment on the shot-peened pot body, baking the pot body at 280℃ for about 30 minutes to complete the preparation of the uncoated non-stick pot.

[0148] The non-stick performance of the uncoated non-stick pan prepared in Example 3 was tested for frying eggs in accordance with the provisions of Section 4.2.1 of standard GB / T 32095.2-2015. The test results showed that it had good non-stick performance.

[0149] Comparative Example 1

[0150] Comparative Example 1 is based on Example 1, except that tungsten alloy shot peening is replaced with zirconium oxide shot peening, wherein the hardness of the zirconium oxide shot is 1200HV~1300HV and the density of the zirconium oxide shot peening is 6.0g / cm³. 3 The sphericity of the zirconium oxide pellets is approximately 96%.

[0151] The surface of the pot after treatment in Comparative Example 1 is as follows: Figure 5 As shown, the surface pit structure is relatively large, and the surface roughness Ra is approximately 1.5 μm; Figure 5 and Figure 3 By comparison, it can be seen that the pot surface prepared by the process in this application has better morphology and smoothness of pits, basically no fatigue cracks, and significantly lower surface roughness.

[0152] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A manufacturing process for an uncoated non-stick pan, characterized in that, The preparation process of the uncoated non-stick pan includes the following steps: S1. The metal substrate is successively blanked, stretched and trimmed to obtain the pot body; S2. The inner surface of the pot body obtained in step S1 is shot blasted to form a number of micro-nano-level pit structures on the inner surface of the pot body, and the inner surface of the pot body is cleaned until there are no residues. S3. Heat treat the pot body after step S2 to complete the preparation of the uncoated non-stick pot.

2. The preparation process of the uncoated non-stick pan as described in claim 1, characterized in that, The metal substrate is selected from any one of alloy steel, titanium alloy, and aluminum alloy; wherein the alloy steel includes any one of 304 stainless steel, 306L stainless steel, and Q235 steel. And / or, the thickness of the pot body is 1mm to 2.5mm.

3. The preparation process of the uncoated non-stick pan as described in claim 1, characterized in that, In step S2, the inner surface of the pot body after shot peening is formed with a number of continuous or staggered micro-nano-scale pit structures. And / or, the depth of the micro-nano-scale pit structure is 0.1 μm to 10 μm, and the diameter of the micro-nano-scale pit structure is 0.5 μm to 10 μm; And / or, in step S2, during the shot peening process, shot peening is used to spray the inner surface of the pot body, and the shot peening speed is 10m / s to 450m / s; And / or, during the shot peening process, the distance between the spray gun and the pot body is 5mm to 500mm.

4. The preparation process of the uncoated non-stick pan as described in claim 1, characterized in that, In step S2, during the shot peening process, The shot peening has a particle size of 0.03 mm to 0.8 mm; and / or, the shot peening has a hardness of not less than 1000 HV; and / or, the shot peening has a density of not less than 14.5 g / cm³. 3 ; and / or, the sphericity of the shot peening is not less than 95%.

5. The preparation process of the uncoated non-stick pan as described in claim 4, characterized in that, The shot peening is a tungsten alloy shot peening; The tungsten alloy shot comprises the following components by mass percentage: Tungsten or tungsten carbide: 59wt%–83wt%; Ni: 8wt%–31wt%; Co: 5.9wt%~32.9wt%; and unavoidable impurities; or, The tungsten alloy shot comprises the following components by mass percentage: Tungsten or tungsten carbide: 79wt%–93wt%; Co: 21wt% to 7wt%; and unavoidable impurities; or, The tungsten alloy shot comprises the following components by mass percentage: Tungsten or tungsten carbide: 79wt%–93wt%; Ni: 21wt%–7wt%; and unavoidable impurities.

6. The preparation process of the uncoated non-stick pan as described in claim 1, characterized in that, In step S2, the shot peening treatment specifically includes the following steps: S21. Perform a first shot peening treatment on the inner surface of the pot body using shot with a particle size distribution of 20 mesh to 100 mesh; or, perform a first shot peening treatment on the inner surface of the pot body using shot with a particle size distribution of 100 mesh to 200 mesh; or, perform a first shot peening treatment on the inner surface of the pot body using shot with a particle size distribution of 300 mesh to 500 mesh.

7. The preparation process of the uncoated non-stick pan as described in claim 1, characterized in that, In step S2, the shot peening treatment specifically includes the following steps: S21. The inner surface of the pot body is subjected to a first shot peening treatment using shot with a particle size distribution of 20 mesh to 100 mesh. S22. The inner surface of the pot body is subjected to a second shot peening treatment using shot with a particle size distribution of 100 mesh to 200 mesh. Alternatively, in step S2, the shot peening process specifically includes the following steps: S21. The inner surface of the pot body is subjected to a first shot peening treatment using shot with a particle size distribution of 100 mesh to 200 mesh. S22. Use shot peening with any particle size distribution of 300 mesh to 500 mesh to perform a second shot peening treatment on the inner surface of the pot body, and complete the shot peening treatment of the pot body. Alternatively, in step S2, the shot peening process specifically includes the following steps: S21. The inner surface of the pot body is subjected to a first shot peening treatment using shot with a particle size distribution of 20 mesh to 100 mesh. S22. Use shot peening with any particle size distribution of 300 mesh to 500 mesh to perform a second shot peening treatment on the inner surface of the pot body, and complete the shot peening treatment of the pot body. Alternatively, in step S2, the shot peening process specifically includes the following steps: S21. The inner surface of the pot body is subjected to a first shot peening treatment using shot with a particle size distribution of 20 mesh to 100 mesh. S22. The inner surface of the pot body is subjected to a second shot peening treatment using shot with a particle size distribution of 100 mesh to 200 mesh. S23. Use shot peening with any particle size distribution of 300 mesh to 500 mesh to perform a third shot peening treatment on the inner surface of the pot body, and complete the shot peening treatment of the pot body.

8. The preparation process of the uncoated non-stick pan as described in claim 7, characterized in that, During the first spray treatment, the spray pressure is 0.1MPa to 1.6MPa, and the spray time is 0.5min to 10min. And / or, during the second spray treatment, the spray pressure is 0.1MPa to 1.6MPa, and the spray time is 0.5min to 10min; And / or, during the third spray treatment, the spray pressure is 0.1MPa to 1.6MPa, and the spray time is 0.5min to 10min.

9. The preparation process of the uncoated non-stick pan as described in claim 1, characterized in that, In step S3, the heat treatment includes: performing high-temperature bluing treatment on the pot body after shot peening, with a treatment temperature of 280℃~300℃ and a treatment time of 25min~35min.

10. A non-stick pan without coating, characterized in that, The uncoated non-stick pan is prepared using the uncoated non-stick pan preparation process described in any one of claims 1 to 9.

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