Heating wire and manufacturing method thereof, heating coil and cooking appliance

Abstract

This invention discloses a heating wire, its manufacturing method, a heating coil, and a cooking appliance, relating to the field of electric heating technology. The heating wire includes an inner core made of copper alloy, which is composed of copper, a first alloying element A, and a second alloying element B. Each of the first alloying element A and the second alloying element B includes one of aluminum, chromium, zirconium, nickel, cobalt, iron, zinc, manganese, silicon, and titanium. When the material to be heated is magnetic, the heating wire generates an alternating magnetic field under the action of an alternating current, thus electromagnetically inducing the heating of the material. When the material to be heated is non-magnetic, the heating wire resistively heats the material under the action of an alternating current. The heating wire of this invention can achieve integrated electromagnetic induction / resistance heating, improving upon the problems of complex structure and poor heating effect in existing hybrid electric stoves.

Description

Technical Field

[0001] This invention relates to the field of electric heating technology, and in particular to a heating wire and its manufacturing method, and a heating coil cooking appliance. Background Technology

[0002] Induction cookers and ceramic cooktops are common cooking appliances in kitchens. Induction cookers use a heating coil to generate magnetic lines of force, which heats the surface of the cookware using eddy currents. They offer advantages such as fast heating and high heat output, but they are also incompatible with certain cookware types and materials. Induction cookers can only heat cookware with magnetic induction, and cannot heat non-metallic cookware such as ceramic or glass pots. Ceramic cooktops, on the other hand, use resistance heating wires to generate infrared radiation, which heats the cookware. They have no special requirements regarding the material of the cookware. However, because the infrared heat absorption rate of metal surfaces is much lower than that of ceramic, ceramic cooktops tend to heat metal cookware more slowly.

[0003] As a result, hybrid electric stoves have emerged on the market, which combine an electromagnetic coil and an infrared heating plate internally and externally to heat both metal and non-metal cookware. However, these hybrid electric stoves suffer from complex structures and poor heating performance. Summary of the Invention

[0004] The main objective of this invention is to provide a heating wire and its manufacturing method, a heating coil, and a cooking appliance, aiming to improve the problems of complex structure and poor heating effect of hybrid electric stoves.

[0005] In a first aspect, the present invention provides a heating wire comprising an inner core, the inner core being a copper alloy composed of copper, a first alloying element A, and a second alloying element B, wherein the first alloying element A and the second alloying element B each comprise one of aluminum, chromium, zirconium, nickel, cobalt, iron, zinc, manganese, silicon, and titanium; when the material of the heating carrier is a magnetic material, the heating wire generates an alternating magnetic field under the action of an alternating current, thereby electromagnetically inducing the heating carrier; when the material of the heating carrier is a non-magnetic material, the heating wire performs resistance heating on the heating carrier under the action of an alternating current.

[0006] In one embodiment, the heating wire further includes an oxide protective layer, which at least covers a portion of the surface of the inner core; the oxide protective layer includes at least one of a copper oxide layer, a copper-AB composite oxide layer, and an A / B oxide layer.

[0007] In one embodiment, the thickness of the copper oxide layer is 1 μm-10 μm; and / or, the thickness of the copper-AB composite oxide layer is 1 μm-5 μm; and / or, the thickness of the A oxide layer / B oxide layer is 0.5 μm-3 μm.

[0008] In one embodiment, the mass percentage of the first alloying element A and the second alloying element B in the copper alloy is 0.5%-8%.

[0009] In one embodiment, the first alloying element A and / or the second alloying element B are selected from aluminum, chromium, nickel, and titanium.

[0010] In one embodiment, the first alloying element A is aluminum, the second alloying element B is chromium, the mass percentage of aluminum in the copper alloy is 1%-5%, and the mass percentage of chromium in the copper alloy is 0.5%-8%; the oxide protective layer includes, from the outside to the inside, a copper oxide layer, a copper-aluminum-chromium composite oxide layer, and an aluminum oxide layer.

[0011] In one embodiment, the electrical conductivity of the copper alloy is 15% IACS-41% IACS.

[0012] In one embodiment, the hardness of the copper alloy is 35HV-180HV.

[0013] In one embodiment, the longitudinal section of the heating wire includes one of the following: rectangle, rounded rectangle, trapezoid, and parallelogram.

[0014] In one embodiment, the longitudinal section of the heating wire has a long side and a short side, and the ratio of the long side to the short side is ≥2.

[0015] In one embodiment, the length of the short side is 0.01mm-0.5mm, and the length of the long side is 1mm-10mm.

[0016] Secondly, the present invention provides a method for manufacturing a heating wire, comprising:

[0017] Copper, a first alloying material, and a second alloying material are smelted to obtain a mixed liquid material. The first alloying material and the second alloying material each include one of aluminum, chromium, zirconium, nickel, cobalt, iron, zinc, manganese, silicon, and titanium. The mixed liquid material is then vacuum-cast into a plate. After homogenization treatment, the plate is cold-rolled into a heating wire.

[0018] In one embodiment, "homogenizing the board material" includes:

[0019] The board is kept at 900℃-1000℃ for 4-12 hours in a vacuum environment, and then cooled to room temperature in air.

[0020] In one embodiment, "cold rolling to form a heating wire" includes:

[0021] The sheet material is cold rolled in multiple passes at 20℃-200℃, with a reduction of 5% in each pass, and finally rolled into a heating wire of the target thickness.

[0022] In one embodiment, the process of "cold-rolling the sheet metal into a heating wire after homogenization treatment" further includes:

[0023] Under an inert atmosphere, the heating wire is kept at 500℃-800℃ for 0.5h-12h, and then naturally cooled to room temperature.

[0024] Thirdly, the present invention provides a heating coil, which is manufactured from any of the heating wires described above or from heating wires manufactured using any of the methods described above.

[0025] In one embodiment, the heating coil is formed by winding at least one section of heating wire, and the winding shape of the heating coil includes a spiral shape; when the heating coil is formed by winding multiple sections of heating wire, adjacent heating wires are connected end to end.

[0026] In one embodiment, the heating coil includes at least an arcuate portion.

[0027] In one embodiment, the shape of the arc portion includes either a wavy shape or a zigzag shape.

[0028] Fourthly, the present invention provides a cooking appliance including the heating coil described above.

[0029] In one embodiment, the cooking appliance is an electric stove, which includes a heating plate, a support, a magnetic strip, a heat insulation layer, and a heating coil. The heating coil is embedded in the heat insulation layer, which is located on the side of the magnetic strip facing the working surface of the cooking appliance. Both the heat insulation layer and the magnetic strip are housed within the support.

[0030] The heating wire provided by the technical solution of this invention can meet the requirements of integrated electromagnetic induction / resistance heating. When the heating medium is a magnetic material, the heating wire mainly uses electromagnetic induction heating, resulting in low power loss for its own heating and a heating temperature lower than the electromagnetic induction heating temperature. When the heating medium is a non-magnetic material, the heating wire mainly uses resistance heating, resulting in low power loss for electromagnetic induction heating and a heating temperature higher than the electromagnetic induction heating temperature.

[0031] When the heating wire of the present invention is used in cooking appliances such as electric stoves, only one set of heating coils is needed to heat carriers of different materials, and the structure is simple. Since the heating coil heats evenly, the heating efficiency is also high, thereby improving the problems of complex structure and poor heating effect of existing hybrid electric stoves.

[0032] Furthermore, the core of the heating wire of this invention is a ternary copper alloy. The doping of the first alloying element A and the second alloying element B causes a dense oxide layer to form on the surface of the copper alloy when used at high temperatures. The presence of this oxide layer prevents the reaction between oxygen and copper, thus ensuring that the copper in the center of the alloy is not oxidized. When applied to high-temperature cooking appliances such as electric stoves (heating treatment at no less than 200°C), the dense oxide layer formed on the surface of the heating wire of this invention improves its resistance to high-temperature oxidation after the heating wire is formed into a heating coil, thus preventing the core and central part of the heating wire from being oxidized. This promotes the copper alloy core itself to maintain high conductivity, thereby enabling the copper alloy heating wire of this invention to not only meet the requirements of integrated electromagnetic induction / resistance heating, but also to have excellent resistance to high-temperature oxidation at 700°C. Attached Figure Description

[0033] To more clearly illustrate the embodiments of the present invention, the accompanying drawings used in the description of the embodiments 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.

[0034] Figure 1 This is a schematic diagram of the longitudinal section of the heating wire in some embodiments of the present invention;

[0035] Figure 2 This is a schematic diagram of the longitudinal cross-sectional shape of the heating wire in some embodiments of the present invention;

[0036] Figure 3 This is a schematic diagram of a heating coil in some embodiments of the present invention;

[0037] Figure 4 This is a schematic diagram (top view) of the heating coil in some embodiments of the present invention;

[0038] Figure 5 This is a schematic diagram (top view) of the heating coil in some other embodiments of the present invention;

[0039] Figure 6 This is a schematic diagram (top view) of the heating coil in some embodiments of the present invention;

[0040] Figure 7 This is a schematic diagram (top view) of the heating coil in some embodiments of the present invention;

[0041] Figure 8 This is a schematic diagram (top view) of the heating coil in some other embodiments of the present invention;

[0042] Figure 9 This is a schematic diagram of the heating plate structure in some embodiments of the present invention;

[0043] Figure 10 This is a schematic diagram of the heating plate structure in some other embodiments of the present invention;

[0044] Figure 11 This is a partial enlarged view of the heating plate in region A in the embodiment shown in Figure 10;

[0045] Figure 12 This is a top view of the structure of the heating coil in some other embodiments of the present invention;

[0046] Figure 13 This is a partial enlarged view of the heating coil in region B in the embodiment shown in Figure 12;

[0047] Figure 14 This is an exploded view of the heating plate in some embodiments of the present invention;

[0048] Figure 15 This is a SEM image of the longitudinal section of the heating wire in Embodiment 2 of the present invention;

[0049] Figure 16 This is a composition line scan of the longitudinal section of the heating wire in Embodiment 2 of the present invention;

[0050] Figure 17 This is a compositional plane scan of the longitudinal section of the heating wire in Embodiment 2 of the present invention.

[0051] Explanation of icon numbers

[0052] 100. Heating wire; 11. Inner core; 12. Oxidation protective layer; 121. Copper oxide layer; 122. Copper-AB composite oxide layer; 123. A / B oxide layer;

[0053] 200. Heating coil;

[0054] 300, bracket;

[0055] 400. Magnetic strip;

[0056] 500. Insulation layer. Detailed Implementation

[0057] It should be noted that if the embodiments of the present 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. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Furthermore, the use of "and / or" or "and / or" throughout the text implies three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied. In the embodiments of the present invention, "at least one" refers to one or more, and "more" refers to two or more.

[0058] In this invention, the "range" is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is understood that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this invention, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0059] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0060] Induction cookers work on the principle of electromagnetic induction. An alternating current passing through a heating coil generates an alternating magnetic field with constantly changing direction. Cookware placed in this magnetic field will generate eddy currents, thus heating the surface of the cookware. Induction cookers have the advantages of fast heating and strong heat, but they also have limitations. They are not very compatible with the shape and material of cookware, and can only electromagnetically heat cookware made of magnetic materials (iron or alloy steel). They cannot heat non-metallic cookware such as ceramic or glass pots.

[0061] The principle of an electric ceramic cooktop is the electric current heating effect, which uses the infrared radiation generated by the electric current flowing through a resistance heating wire to heat the cookware. Electric ceramic cooktops do not have special requirements for the material of the cookware; however, because the infrared heat absorption rate of metal surfaces is much lower than that of ceramics, electric ceramic cooktops have a slower acceleration effect on metal cookware.

[0062] As a result, hybrid electric stoves have emerged on the market, which combine an electromagnetic coil and an infrared heating plate to heat both metal and non-metal cookware. However, these hybrid electric stoves have uneven heating areas, limited power, and poor heating performance for both metal and non-metal cookware. Furthermore, the use of two heating plates results in a complex structure and higher cost.

[0063] Based on this, the present invention proposes a heating wire 100, with reference to... Figure 1 As shown, it includes an inner core 11, which is a copper alloy composed of copper, a first alloying element A, and a second alloying element B. The first alloying element A and the second alloying element B each include one of aluminum, chromium, zirconium, nickel, cobalt, iron, zinc, manganese, silicon, and titanium. When the material of the heating carrier is magnetic, the heating wire generates an alternating magnetic field under the action of alternating current to perform electromagnetic induction heating on the heating carrier. When the material of the heating carrier is non-magnetic, the heating wire performs resistance heating on the heating carrier under the action of alternating current.

[0064] Alloying elements are elements added to a copper matrix that interact with the copper matrix to alter its microstructure and properties. The first alloying element A and the second alloying element B each include one of the following: aluminum, chromium, zirconium, nickel, cobalt, iron, zinc, manganese, silicon, and titanium. Copper alloys include copper-aluminum-chromium alloys, copper-aluminum-zirconium alloys, copper-aluminum-nickel alloys, copper-aluminum-cobalt alloys, copper-aluminum-iron alloys, copper-aluminum-zinc alloys, copper-aluminum-manganese alloys, copper-aluminum-silicon alloys, copper-aluminum-titanium alloys, copper-chromium-zirconium alloys, copper-chromium-nickel alloys, copper-chromium-cobalt alloys, copper-chromium-iron alloys, copper-chromium-zinc alloys, copper-chromium-manganese alloys, copper-chromium-silicon alloys, and copper-chromium-titanium alloys. One of the following: copper-zirconium-nickel alloy, copper-zirconium-cobalt alloy, copper-zirconium-iron alloy, copper-zirconium-zinc alloy, copper-zirconium-manganese alloy, copper-zirconium-silicon alloy, copper-zirconium-titanium alloy, copper-nickel-cobalt alloy, copper-nickel-iron alloy, copper-nickel-zinc alloy, copper-nickel-manganese alloy, copper-nickel-titanium alloy, copper-nickel-titanium alloy, copper-cobalt-iron alloy, copper-cobalt-zinc alloy, copper-cobalt-manganese alloy, copper-cobalt-silicon alloy, copper-cobalt-titanium alloy, copper-iron-zinc alloy, copper-iron-manganese alloy, copper-iron-titanium alloy, copper-manganese-titanium alloy, copper-manganese-titanium alloy, and copper-silicon-titanium alloy.

[0065] According to the standard formation free energy ΔG of oxides 0(Under standard conditions (typically a temperature of 298.15 K and a pressure of 100 kPa), the change in free energy when 1 mol of the oxide is formed from the most stable element) shows that the stability of oxides of cobalt, zinc, chromium, manganese, silicon, titanium, aluminum, and zirconium increases in that order. Therefore, all of the above alloying elements can improve the oxidation resistance of copper alloys, and the oxidation resistance increases in that order. Therefore, this invention uses copper as the base material and adds two of the above alloying elements to form a copper alloy. This allows the copper alloy to resist oxidation for a long time at 700℃ while ensuring its electrical conductivity, thereby extending the service life of cooking utensils.

[0066] Magnetic materials refer to substances composed of transition elements such as iron, cobalt, and nickel, and their alloys or oxides, that can directly or indirectly generate magnetism. Generally, in the field of cooking utensils, magnetic materials are typically ferromagnetic, meaning they exhibit spontaneous magnetization under certain conditions. Specifically, these can include materials containing iron, cobalt, nickel, their alloys, or their oxides. Ferromagnetic materials can be magnetized to saturation under very small magnetic fields, exhibiting a magnetic susceptibility greater than 0 and values ​​reaching 10⁻¹⁰. 6 Order of magnitude. Non-magnetic materials refer to materials that cannot be magnetized, specifically including ceramics, glass, plastics, copper, silver, platinum, gold, etc.

[0067] When the heating medium is made of magnetic material, the heating wire generates an alternating magnetic field under the action of alternating current. The medium within this magnetic field generates eddy currents, and the Joule heating effect of these eddy currents raises the temperature of the medium. The magnetic material strengthens the magnetic field and generates even stronger eddy currents within the medium, further increasing its temperature to meet the requirements for cooking. In other words, given a fixed power, if the heating medium is magnetic, the heating wire primarily uses electromagnetic induction heating, resulting in less power loss for its own heating and a lower heating temperature.

[0068] When the material of the heating medium is non-magnetic, it cannot generate induced current. In this case, the heating wire's temperature rises continuously under the influence of the current, which is equivalent to resistance heating. The heating temperature can reach about 700℃, which can meet the temperature requirements for cooking. That is, with a certain power, if the heating medium is non-magnetic, the heating wire mainly uses resistance heating, and the power loss for electromagnetic induction heating is relatively small.

[0069] It should be noted that if the magnetic conductivity of the carrier to be heated is between that of magnetic and non-magnetic materials, the heating wire will perform both electromagnetic induction heating and infrared induction heating. That is, the power ratio of the heating wire allocated to electromagnetic induction heating and infrared radiation heating will be different depending on the change in the magnetic conductivity of the carrier to be heated.

[0070] The heating wire of the present invention can adjust the heating state according to the material of the carrier to be heated. The carrier to be heated is a container that holds the object to be heated, which can be one of the following: a plate container, a pot container, a bowl container, or a barrel container.

[0071] When the heating wire of this invention is used in cooking appliances such as electric stoves, only one set of heating coils is needed to heat carriers of different materials, resulting in a simple structure. Because the heating coils provide uniform heating, the heating efficiency is also high, thus improving the problems of complex structure and poor heating effect found in existing hybrid electric stoves. Furthermore, the inner core of the heating wire of this invention is made of ternary copper alloy, which, while meeting the requirements of integrated electromagnetic induction / resistance heating, also possesses resistance to oxidation at 700℃.

[0072] According to some embodiments of the present invention, further reference is made to Figure 1 As shown, the heating wire 100 also includes an oxide protective layer 12, which covers at least a portion of the surface of the inner core 11; the oxide protective layer 12 includes at least a copper oxide layer 121, a copper-AB composite oxide layer 122, and an A / B oxide layer 123.

[0073] The oxide protective layer 12 refers to an oxide film layer that prevents the copper alloy of the inner core 11 from continuing to oxidize at high temperatures. The oxide protective layer 12 can be formed on the surface of the inner core 11 after the heating wire 100 is heated once at a temperature of not less than 200°C.

[0074] A / B oxide layer 123 refers to either oxide A or oxide B. Whether A / B oxide layer 123 is an oxide A layer or an oxide B layer depends on the standard formation free energy ΔG of oxide A and oxide B. 0 Standard formation free energy of oxides ΔG 0 The standard free energy of formation (ΔG) refers to the change in free energy when 1 mol of oxide is formed from a stable element under standard conditions. It is an important thermodynamic parameter for measuring the spontaneous tendency of oxide formation reactions under standard conditions. 0 The standard formation free energy ΔG of oxide B is greater than that of oxide B. 0 Then, oxide layer 123 of A / B is oxide layer A, because under the same conditions, the standard formation free energy ΔG of oxide A is... 0 A larger value indicates a stronger tendency for A to form oxides, and a greater inclination to form oxides. The standard formation free energy ΔG for oxide B is... 0 The standard formation free energy ΔG of oxide A is greater than that of oxide A. 0 The same principle applies at other times.

[0075] When the oxide protective layer 12 includes a copper oxide layer 121, a copper-AB composite oxide layer 122, and an A / B oxide layer 123, the three oxide layers play a synergistic and gradient anti-oxidation role, enabling the copper alloy to resist oxidation for a long time at 700℃.

[0076] It should be noted that although an oxide protective layer will form on the surface of the inner core 11 at room temperature or low temperature (below 200°C), this oxide protective layer cannot effectively prevent the copper alloy of the inner core 11 from being further oxidized.

[0077] According to some embodiments of the present invention, the thickness of the copper oxide layer 121 is 1 μm-10 μm; and / or, the thickness of the copper-AB composite oxide layer 122 is 1 μm-5 μm; and / or, the thickness of the A / B oxide layer 123 is 0.5 μm-3 μm.

[0078] The thicknesses of the copper oxide layer 121, the copper-AB composite oxide layer 122, and the A / B oxide layer 123 change during the heating process of the heating wire 100. As the heating temperature increases, the thickness of each oxide layer tends to increase. This is because at high temperatures, oxygen atoms can more easily penetrate the already formed oxide protective layer and diffuse to the interface between the copper alloy and the oxide protective layer. When the formed oxide protective layer 12 is established, it can largely prevent oxygen from further diffusing inwards, at which point the thickness of each oxide layer remains essentially stable.

[0079] According to some embodiments of the present invention, the mass percentage of the first alloying element A and the second alloying element B in the copper alloy is 0.5%-8%.

[0080] For example, the mass percentage of the first alloying element A in the copper alloy can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, or 8%, and the mass percentage of the second alloying element B in the copper alloy can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, or 8%. When the mass percentages of the first alloying element A and the second alloying element B in the copper alloy are between 0.5% and 8%, the impact on the electrical conductivity of the copper alloy can be reduced.

[0081] According to some embodiments of the present invention, the first alloying element A and / or the second alloying element B are selected from aluminum, chromium, nickel, and titanium.

[0082] The first alloying element A and / or the second alloying element B being selected from aluminum, chromium, nickel, and titanium means that the first alloying element A is selected from aluminum, chromium, nickel, and titanium, and the second alloying element B is selected from zirconium, cobalt, iron, zinc, manganese, and silicon; or the second alloying element B is selected from aluminum, chromium, nickel, and titanium, and the first alloying element A is selected from zirconium, cobalt, iron, zinc, manganese, and silicon; or both the first alloying element A and the second alloying element B are selected from aluminum, chromium, nickel, and titanium.

[0083] Aluminum, chromium, nickel, and titanium all form a relatively dense aluminum oxide film with oxygen at high temperatures, which can prevent oxygen from entering and prevent further oxidation of the copper alloy surface, thus improving the oxidation resistance of the heating wire.

[0084] According to some embodiments of the present invention, the first alloying element A is aluminum, the second alloying element B is chromium, the mass percentage of aluminum in the copper alloy is 1%-5%, and the mass percentage of chromium in the copper alloy is 0.5%-8%; the oxide protective layer 12 includes, from the outside to the inside, a copper oxide layer, a copper-aluminum-chromium composite oxide layer, and an aluminum oxide layer.

[0085] In copper-aluminum-chromium alloys, aluminum is mainly used for resistance to high-temperature oxidation. For example, the mass percentage of aluminum in the copper alloy can be 1%, 2%, 3%, 4%, or 5%. Because aluminum can be dissolved in copper, it causes electron scattering in the copper alloy, thus affecting its electrical conductivity. When the mass percentage of aluminum in the copper alloy is between 1% and 5%, it achieves the effect of resisting high-temperature oxidation while minimizing the impact on the electrical conductivity of the copper alloy.

[0086] Chromium also plays a role in resisting high-temperature oxidation. For example, the mass percentage of chromium in copper alloys can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, or 8%. At high temperatures, chromium reacts with oxygen to form a chromium oxide passivation film, thereby preventing oxygen diffusion; on the other hand, chromium can improve the strength of copper alloys. Since chromium is not solid-soluble in copper alloys and exists in the form of a precipitated phase, it has little effect on the electrical conductivity of copper alloys. The addition of chromium helps aluminum to resist high-temperature oxidation at lower contents, with minimal impact on the electrical conductivity of copper alloys.

[0087] When the copper alloy is a copper-aluminum-chromium alloy, the standard formation free energy ΔG of alumina is... 0 The standard formation free energy ΔG of chromium oxide is greater than that of chromium oxide. 0 Therefore, the innermost layer is an aluminum oxide layer.

[0088] During the high-temperature oxidation of copper-aluminum-chromium alloys, copper first reacts with oxygen to form the outermost copper oxide layer 121. The main component of copper oxide layer 121 is copper oxide. Due to the relatively porous nature of copper oxide layer 121, oxygen atoms can penetrate it and oxidize the copper alloy. The oxygen penetrating copper oxide layer 121 reacts with copper, aluminum, and chromium to form a copper-aluminum-chromium composite oxide layer 122, which further prevents the penetration of oxygen atoms. Finally, the oxygen atoms penetrating copper oxide layer 121 and the copper-aluminum-chromium composite oxide layer 122 form an aluminum oxide layer 123 on the surface of the copper alloy, which can essentially isolate oxygen from the copper alloy, thus protecting the copper alloy from further oxidation.

[0089] According to some embodiments of the present invention, the electrical conductivity of the copper alloy is 15% IACS-41% IACS.

[0090] IACS is the percentage of electrical conductivity, which is the ratio of the resistivity (volume or mass) specified in the International Standard for Annealed Copper (IACS) to the resistivity of a sample of the same unit.

[0091] When the conductivity is greater than 41% IACS, the resistance of the heating wire is too low to generate sufficient Joule heat, resulting in poor infrared radiation and thus affecting the heating effect. When the conductivity is less than 15% IACS, the resistance of the heating wire is too high. Under a certain voltage, the current flowing into the heating alloy is low, which makes it impossible to generate a magnetic field of sufficient strength, resulting in poor electromagnetic induction heating effect.

[0092] According to some embodiments of the present invention, the hardness of the copper alloy is 35HV-180HV.

[0093] HV refers to Vickers hardness, which is determined by pressing a diamond indenter in the shape of a square pyramid with a 136° angle between its two faces into the surface of a copper alloy under a certain test force. After holding the indentation for a specified time and then removing the test force, the diagonal length of the indentation is measured, and the hardness value is calculated. A hardness of 35HV-180HV for copper alloys means that the Vickers hardness of the copper alloy is 35-180.

[0094] In some applications, heating wires may need to meet winding and bending requirements, thus limiting the wire's stiffness to ensure it can be wound into a heating coil winding, meeting the integrated needs of electric stoves and other cooking appliances that utilize electromagnetic induction / resistance heating. When the heating wire's stiffness exceeds 180 HV, it becomes difficult to bend and shape. When the heating wire is processed into a heating coil for use in heating plates, the coil needs to be inserted into insulating material (such as silica) to assemble the heating plate. When the heating wire's stiffness is less than 35 HV, it is too soft and will curl when inserted into the insulating material, making assembly impossible.

[0095] According to some embodiments of the present invention, the longitudinal section of the heating wire 100 includes one of a rectangle, a rounded rectangle, a trapezoid, and a parallelogram.

[0096] refer to Figure 2 As shown, the longitudinal sections of the heating wire 100, from left to right, are rectangle, rounded rectangle, trapezoid, and parallelogram. A rounded rectangle can be a shape formed by combining two semicircles with two parallel straight lines, or it can be a shape formed by rounding the four vertices of a rectangle. The aforementioned longitudinal sections of the heating wire facilitate bending and assembly with insulation materials.

[0097] According to some embodiments of the present invention, the longitudinal section of the heating wire 100 has a long side and a short side, and the ratio of the long side to the short side is ≥2.

[0098] The longitudinal section of the heating wire 100 has a long side and a short side. A ratio of the long side to the short side ≥ 2 indicates that the heating wire 100 is flat. (Refer to...) Figure 3 As shown, the long side of the longitudinal section of the heating wire 100 is set as 'a', and the short side as 'b', i.e., a / b ≥ 2. This satisfies both the requirements for processing into a heating coil and for inserting a heat insulation layer for fixation. Figure 2 For example, when the longitudinal section of the heating wire 100 is a rounded rectangle, the longer side refers to two parallel straight lines, and the shorter side is the diameter of the semicircle, which is the distance between the two parallel straight lines. When the longitudinal section of the heating wire 100 is a trapezoid, the longer side is the lower base of the trapezoid (the longer side of the trapezoid is the lower base), and the shorter side is the height of the trapezoid. When the longitudinal section of the heating wire 100 is a parallelogram, the longer side is the longer side of the parallelogram, and the shorter side is the height of the parallelogram.

[0099] According to some embodiments of the present invention, the length of the short side is 0.01mm-0.5mm, and the length of the long side is 1mm-10mm.

[0100] When the longitudinal section of the heating wire 100 is rectangular, rounded rectangular, trapezoidal, or parallelogram, the length of the short side is the thickness of the heating wire 100. For example, the length of the short side can be 0.01mm, 0.05mm, 0.1mm, 0.2mm, 0.3mm, 0.4mm, or 0.5mm; the length of the long side can be 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, or 10mm. A short side length of 0.01mm-0.5mm facilitates processing and insertion of the insulation layer, while a long side length of 1mm-10mm reduces the risk of the heating wire 100 collapsing and improves its insertion stability.

[0101] According to some embodiments of the present invention, the present invention also provides a method for manufacturing a heating wire, comprising: melting copper, a first alloying material, and a second alloying material to obtain a mixed liquid material, wherein the first alloying material and the second alloying material each include one of aluminum, chromium, zirconium, nickel, cobalt, iron, zinc, manganese, silicon, and titanium; casting the mixed liquid material into a plate; and homogenizing the plate material and then cold rolling it into a heating wire.

[0102] The raw materials can be smelted using a vacuum arc furnace, which has the advantages of fast heating speed and uniform heating. In other embodiments, a vacuum induction furnace, resistance furnace, or similar equipment can also be used for smelting.

[0103] Suction casting is a casting method in which a vacuum environment is created inside a mold cavity, and then molten metal is drawn into the cavity from bottom to top for solidification. Products formed by suction casting have the characteristics of low impurity content and are less prone to forming pores inside the product.

[0104] The suction casting process may include the following steps: (1) Prepare the suction casting equipment and mold. The mold should be cleaned in advance and coated with a suitable coating. For the casting, the mold should be placed in the corresponding position in the vacuum chamber to ensure that the vent holes and other structures are unobstructed. (2) Suction casting operation: Immerse the lower end of the riser pipe connected to the gating system into the mixed liquid. When the vacuum chamber reaches a suitable vacuum degree, the mixed liquid fills the mold cavity through the riser pipe under the action of pressure difference. (3) Solidification stage: After suction casting is completed, maintain the vacuum state for a period of time. After the bottom inner gate section of the mold is completely solidified, remove the vacuum. (4) Remove the casting: After solidification, close the vacuum system and remove the casting from the mold or crystallizer.

[0105] Homogenization is performed to improve the internal crystalline structure of the sheet metal and eliminate casting stress. Cold rolling refers to the rolling deformation process performed below the recrystallization temperature of the material. During cold rolling, pressure is applied to the sheet metal through rolls to cause plastic deformation, thereby changing its shape, size, and properties to obtain the finished heating wire.

[0106] According to some embodiments of the present invention, "homogenizing the board" includes: holding the board at 900°C-1000°C for 4-12 hours in a vacuum environment, and then cooling it to room temperature in air.

[0107] In a vacuum environment, the sheet material can be held at 900℃-1000℃ for 4-12 hours in a tube vacuum furnace. Residual stress is generated during the suction casting process; when held in a tube vacuum furnace at 900℃-1000℃, atoms have sufficient energy to migrate, thus relaxing the internal stress of the material. Furthermore, due to the high temperature of the homogenization process, homogenizing the sheet material in a vacuum environment can reduce the formation of easily detachable oxide layers on the surface.

[0108] According to some embodiments of the present invention, "cold rolling to form heating wire" includes: cold rolling a sheet at 20°C-200°C in multiple passes, with a reduction of 2%-7% in each pass, and finally rolling it into a heating wire of the target thickness.

[0109] The reduction in thickness per pass refers to the amount by which the rolls reduce the thickness of the sheet metal during a single rolling pass. It is an important parameter for measuring the degree of deformation in cold rolling and can be expressed as the rate of change in sheet thickness before and after rolling. For example, the reduction per pass can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, or 7%. When the reduction per pass is 2%-7%, the rate of work hardening is relatively moderate. Compared to larger reductions, this level of work hardening does not cause a sharp increase in the material's hardness and strength, thus avoiding the situation where the material becomes difficult to process further due to excessive hardening during subsequent rolling processes. Furthermore, a reduction of 2%-7% helps to achieve better dimensional accuracy. In some embodiments, the target thickness of the heating wire is no greater than 2 mm; when used to process heating coils that can be inserted into the insulation layer, the target thickness of the heating wire may be no greater than 1 mm.

[0110] Since the recrystallization temperature of copper alloys varies depending on the alloying elements, the cold rolling temperature can be adjusted between 20℃ and 200℃ depending on the different alloying elements.

[0111] According to some embodiments of the present invention, after "cold rolling the sheet metal into a heating wire after homogenization treatment", the process further includes: holding the heating wire at 500°C-800°C for 0.5h-12h in an inert atmosphere, and then naturally cooling it to room temperature.

[0112] An inert atmosphere can be one of nitrogen, argon, or helium. When the temperature is maintained between 500℃ and 800℃, the surface of the heating wire is prone to oxidation and peeling. Therefore, heat preservation treatment of the heating wire under an inert atmosphere can reduce the formation of an easily detachable oxide layer on the surface of the heating wire.

[0113] Natural cooling to room temperature refers to the heating wire cooling naturally along with the heating equipment after heating is stopped in an inert atmosphere. Holding the heating wire at 500℃-800℃ for 0.5h-12h, followed by natural cooling to room temperature, refers to annealing the heating wire. This invention uses annealing to adjust the conductivity and hardness of the heating wire and further eliminate residual stress.

[0114] According to some embodiments of the present invention, reference Figures 4 to 8As shown, the present invention also provides a heating coil 200, which is manufactured from any of the heating wires 100 described above or from heating wires 100 manufactured using any of the methods described above. Since the heating coil 200 employs all the technical solutions of all embodiments of the heating wire 100 described above, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated upon here.

[0115] According to some embodiments of the present invention, the heating coil 200 is formed by winding at least one section of heating wire 100, and the winding shape of the heating coil 200 includes a spiral shape; when the heating coil 200 is formed by winding multiple sections of heating wire 100, adjacent heating wires 100 are connected end to end.

[0116] refer to Figures 4 to 6 As shown, the heating coil 200 is formed by spirally winding a section of heating wire 100, so as to... Figure 4 and Figure 5 For example, the winding of heating coil 200 is circular, with... Figure 6 For example, the winding of the heating coil 200 is a rounded rectangle. However, the shape of the winding of the heating coil 200 is not limited to this. In some other embodiments, the winding of the heating coil 200 can also be one of elliptical, polygonal, or flower-shaped.

[0117] refer to Figure 7 and Figure 8 As shown, the heating coil 200 is formed by winding three heating wires 100. The tail end of the first heating wire located at the center is connected to the head end of the second heating wire, and the tail end of the second heating wire is connected to the head end of the third heating wire located on the outermost side. The winding density of the three heating wires 100 can be the same or different. Using multiple heating wires 100 to prepare the heating coil 200 helps to adjust parameters such as the winding density of the heating coil 200.

[0118] According to some embodiments of the present invention, the heating coil 200 includes at least an arcuate portion.

[0119] The heating coil 200 including at least an arc portion means that the heating coil 200 can be entirely arc-shaped, such as... Figure 4 and Figure 5 The heating coil 200 shown can also be composed of an arc portion and a straight portion, that is, the corners of the heating coil 200 are set as arc structures, such as... Figure 6 The heating coil 200 is shown. When the heating wire 100 is wound to form the heating coil 200, if the corner is directly bent into an angled structure, the stress at the corner will be concentrated, and it is easy for the coil to break at the corner. Therefore, the heating wire 100 and heating coil 200 of the present invention include at least an arc portion, which can reduce the problem of breakage at the corner of the heating coil 200.

[0120] According to some embodiments of the present invention, the shape of the arc portion includes one of wavy or zigzag.

[0121] refer to Figure 5 , Figure 10 and Figure 11 As shown, the winding of the heating coil 200 is circular, meaning the entire heating coil 200 is an arc. Therefore... Figure 5 and Figure 10 The heating coil 200 has an overall wavy shape, with the heating wire 100 forming a triangular shape in the area pointed to by arrow a. The peaks and troughs of the wave shape can form a triangular stable structure, which can prevent the heating coil 200 from collapsing and improve the heating stability and uniformity of the heating coil 200.

[0122] refer to Figure 6 As shown, the winding of the heating coil 200 is a rounded rectangle, meaning the heating coil 200 includes both curved and straight sections. Compared to the straight section, the curved section is more prone to deformation and collapse. Figure 6 Only the rounded corners of the heating coil 200 are set to a wavy shape.

[0123] refer to Figure 8 As shown, the heating coil 200 can be composed of multiple spiral sections. In areas of sparse or dense winding, it can be set to a wavy shape to enhance anti-collapse and adjust the length of the heating coil 200, thereby adjusting its impedance and reactance and improving the heating effect of the integrated electromagnetic induction / resistance.

[0124] Optionally, in some embodiments, reference is made to Figure 12 and Figure 13 As shown, in the direction of the center line of the heating wire 100, the distance between two adjacent peaks is the tooth pitch of the wavy line; the tooth pitch ranges from 1 mm to 15 mm.

[0125] In the direction perpendicular to the center line of the wavy line of the heating wire 100, the maximum distance between adjacent crests and troughs is the tooth height of the wavy line; the tooth height ranges from 0.5 mm to 10 mm.

[0126] In this embodiment, referring to Figure 13, the height between the crests and troughs of the wavy line of the heating wire 100 is the tooth height H, and the distance between the first crest and the second crest is the tooth pitch L. H must be greater than or equal to 0.5 mm and less than or equal to 10 mm, specifically greater than or equal to 1 mm and less than or equal to 2 mm; L must be greater than or equal to 1 mm and less than or equal to 15 mm, specifically greater than or equal to 3.5 mm and less than or equal to 6.5 mm. The values ​​of tooth height H and tooth pitch L can be equal throughout the entire heating coil 200, or they can gradually increase in size or alternate between large and small values.

[0127] Preferably, the wavy shape of the heating coil 200 is a uniform design, which is more in line with the low-cost production process of forming coil windings and has better electrical performance. The principle is that the tooth pitch and center distance of the impeller pressing the wave are fixed, which makes production more stable. The uniform wave shape results in more balanced stress after heating, which means that it is not easily deformed by heat and the heating area is uniform. The heating uniformity of the heating coil 200 is better.

[0128] According to some embodiments of the present invention, the present invention also provides a cooking appliance, including the heating coil 200 described above.

[0129] According to some embodiments of the present invention, the cooking appliance is an electric stove, which includes a heating plate, see reference. Figure 9 , Figure 10 as well as Figure 14 As shown, the heating plate includes a support 300, a magnetic strip 400, a heat insulation layer 500, and a heating coil 200; the heating coil 200 is embedded in the heat insulation layer 500, the heat insulation layer 500 is disposed on the side of the magnetic strip 400 facing the working surface of the cooking appliance, and both the heat insulation layer 500 and the magnetic strip 400 are housed within the support 300.

[0130] The magnetic strip 400 is a component made of a material with high magnetic permeability, capable of guiding and concentrating magnetic lines of force, making the magnetic field generated by the heating coil 200 more concentrated, thereby enhancing the magnetic field strength. This allows for better generation of sufficient eddy currents at the bottom of the magnetic cookware during operation, thus improving heating efficiency. The material and structure of the magnetic strip 400 are not specifically limited in this invention.

[0131] refer to Figure 14 As shown, the heat insulation layer 500 being disposed on the side of the magnetic strip 400 facing the working surface of the cooking appliance means that the heat insulation layer 500 is disposed above the magnetic strip 400. In some embodiments, the heat insulation layer 500 may be made of silica.

[0132] In practical applications, the electric furnace also includes a panel, which is fixed on the heating plate. The panel can be a microcrystalline glass panel, a ceramic panel, or a stainless steel panel.

[0133] It should be noted that cooking appliances are not limited to the electric stoves mentioned above. Alternatively, cooking appliances can also be heating products such as rice cookers, electric pressure cookers, electric frying pans, and electric hot pots.

[0134] The following description is based on specific embodiments.

[0135] Example 1

[0136] Copper, aluminum, and chromium were added to a vacuum arc furnace in a mass ratio of 90:5:5. After melting, the mixture was vacuum-cast into a sheet. The sheet was then held at 900℃ for 6 hours under vacuum, followed by air cooling to room temperature. The sheet was then subjected to multiple cold rolling passes, with a 5% reduction in pressure per pass, ultimately producing a 1mm thick heating wire sample. The heating wire sample had a flat longitudinal section with a / b = 2. Under a nitrogen atmosphere, the heating wire was held at 750℃ for 1 hour, followed by natural cooling to room temperature.

[0137] Example 2

[0138] Unlike Example 1, the mass ratio of copper, aluminum, and chromium in this example is 92:3:5. The SEM image of the longitudinal section of the heating wire after oxidation in this example is shown below. Figure 15 As shown, the composition line scan diagram of the heating wire is as follows: Figure 16 As shown, the surface scan image is as follows Figure 17 As shown, the composition analysis was performed using an energy dispersive spectroscopy (EDS) instrument.

[0139] from Figure 15 It can be seen that the inner core surface of the heating wire has three oxide layers arranged sequentially from the outside to the inside. According to... Figure 16 The compositional line scan diagram shows that the three oxide layers from the outside in are a copper oxide layer, a copper-aluminum-chromium composite oxide layer, and an aluminum oxide layer. According to... Figure 17 The compositional surface scan diagram shows that aluminum is in solid solution in copper alloys, while chromium is not in solid solution and exists as a precipitated phase.

[0140] Example 3

[0141] Unlike Example 1, the mass ratio of copper, aluminum, and chromium in this example is 94:1:5.

[0142] Example 4

[0143] Unlike Example 1, the copper alloy in this example is a copper-aluminum-nickel alloy with a copper-aluminum-nickel mass ratio of 95.5:1.5:3.

[0144] Example 5

[0145] Unlike Example 1, the copper alloy in this example is a copper-aluminum-titanium alloy, with a copper-aluminum-titanium mass ratio of 95:2:3.

[0146] Example 6

[0147] Unlike Example 1, the copper alloy in this example is a copper-chromium-nickel alloy with a copper-chromium-nickel mass ratio of 90:6:4.

[0148] Example 7

[0149] Unlike Example 1, the copper alloy in this example is a copper-chromium-titanium alloy, with a copper-chromium-titanium mass ratio of 88:8:4.

[0150] Example 8

[0151] Unlike Example 1, the copper alloy in this example is a copper-nickel-titanium alloy with a copper-nickel-titanium mass ratio of 88:6:6.

[0152] Comparative Example 1

[0153] The heating wire in Comparative Example 1 is made of pure copper.

[0154] Comparative Example 2

[0155] Unlike Example 1, the inner core of the heating wire in this comparative example is a copper-aluminum alloy with a copper-aluminum mass ratio of 95:5.

[0156] Performance testing

[0157] Conductivity: The conductivity of the heating wire was tested using an eddy current conductivity meter.

[0158] Antioxidant properties: The heating wire sample was placed in an alumina crucible and heated in a muffle furnace at a heating rate of 10℃ / min. The temperature was raised to 700℃ and held for 8 hours. Then the power to the muffle furnace was turned off, and the heating wire sample was cooled with the furnace. The surface state of the sample after oxidation was observed.

[0159] Heating performance: The heating wire is processed into a heating coil by bending and winding. The heating coil is inserted into the heat insulation layer to prepare a heating plate. It is then assembled with microcrystalline glass to form a test plate. The electromagnetic heating and infrared heating performance are tested by placing a magnetic metal pot and a glass pot on the plate.

[0160] Test Results

[0161] The test results are shown in Table 1.

[0162] Table 1 Performance test results of heating wires in Examples 1-8 and Comparative Examples 1-2

[0163]

[0164]

[0165] As can be seen from the table above, the heating wires prepared in Examples 1-8 of this invention can all meet the requirements of integrated electromagnetic induction / resistance heating. However, while the pure copper heating wire in Comparative Example 1 can meet the requirements of electromagnetic induction heating, it cannot meet the requirements of resistance heating. This is because the conductivity of pure copper is too high, resulting in insufficient heating temperature. Infrared radiation is proportional to the fourth power of temperature; an excessively low heating temperature fails to meet the temperature requirements of the heating medium during cooking.

[0166] As can be seen from Comparative Example 1, copper exhibits significant oxidation, peeling, and powdering under 700℃ oxidation conditions. This indicates that the copper oxide film cannot resist oxygen penetration at high temperatures. As peeling and powdering continue, fresh metal surfaces are constantly exposed, leading to ongoing oxidation of the material. In contrast, the copper alloy in this application exhibits oxidation resistance at 700℃, thus improving its service life.

[0167] Comparing Example 1 and Comparative Example 2, it can be seen that the binary copper-aluminum alloy is difficult to meet the requirements for long-term oxidation resistance at 700°C, and problems such as oxidation peeling and powdering will occur.

[0168] 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's 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 heating wire, characterized in that, The heating wire includes an inner core, which is a copper alloy. The copper alloy is composed of copper, a first alloying element A, and a second alloying element B. The first alloying element A and the second alloying element B each include one of aluminum, chromium, zirconium, nickel, cobalt, iron, zinc, manganese, silicon, and titanium. When the material of the carrier to be heated is a magnetic material, the heating wire generates an alternating magnetic field under the action of alternating current, and performs electromagnetic induction heating on the carrier to be heated. When the material of the carrier to be heated is a non-magnetic material, the heating wire performs resistance heating on the carrier under the action of alternating current.

2. The heating wire as described in claim 1, characterized in that, The heating wire also includes an oxidation protection layer, which at least covers a portion of the surface of the inner core. The oxide protective layer includes at least one of the following: a copper oxide layer, a copper-AB composite oxide layer, and an A / B oxide layer.

3. The heating wire as described in claim 2, characterized in that, The thickness of the copper oxide layer is 1 μm-10 μm; and / or, the thickness of the copper-AB composite oxide layer is 1 μm-5 μm; and / or, the thickness of the A / B oxide layer is 0.5 μm-3 μm.

4. The heating wire as described in any one of claims 1 to 3, characterized in that, The mass percentages of the first alloying element A and the second alloying element B in the copper alloy are both 0.5%-8%.

5. The heating wire as described in claim 4, characterized in that, The first alloying element A and / or the second alloying element B are selected from aluminum, chromium, nickel, and titanium.

6. The heating wire as described in claim 5, characterized in that, The first alloying element A is aluminum, the second alloying element B is chromium, the mass percentage of aluminum in the copper alloy is 1%-5%, and the mass percentage of chromium in the copper alloy is 0.5%-8%. At least a portion of the surface of the copper alloy is covered with an oxide protective layer, which, from the outside to the inside, comprises a copper oxide layer, a copper-aluminum-chromium composite oxide layer, and an aluminum oxide layer.

7. The heating wire according to any one of claims 1 to 6, characterized in that, The electrical conductivity of the copper alloy is 15% IACS-41% IACS.

8. The heating wire according to any one of claims 1 to 6, characterized in that, The hardness of the copper alloy is 35HV-180HV.

9. The heating wire according to any one of claims 1 to 6, characterized in that, The longitudinal section of the heating wire includes one of the following: rectangle, rounded rectangle, trapezoid, and parallelogram.

10. The heating wire as described in claim 9, characterized in that, The longitudinal section of the heating wire has a long side and a short side, and the ratio of the long side to the short side is ≥2.

11. The heating wire as described in claim 10, characterized in that, The length of the short side is 0.01mm-0.5mm, and the length of the long side is 1mm-10mm.

12. A method for manufacturing a heating wire, characterized in that, include: Copper, a first alloying material, and a second alloying material are smelted to obtain a mixed liquid. The first alloying material and the second alloying material each include one of aluminum, chromium, zirconium, nickel, cobalt, iron, zinc, manganese, silicon, and titanium. The mixed liquid material is vacuum-cast into a sheet; The sheet material is homogenized and then cold-rolled into heating wire.

13. The method for manufacturing the heating wire as described in claim 12, characterized in that, The "homogenization treatment of the board material" includes: The plate is kept at 900℃-1000℃ for 4-12 hours in a vacuum environment, and then cooled to room temperature in air.

14. The method for manufacturing the heating wire as described in claim 12, characterized in that, The "cold rolling into heating wire" includes: The sheet material is subjected to multiple cold rolling passes at 20℃-200℃, with a reduction of 5% in each pass, and is finally rolled into a heating wire of the target thickness.

15. The method for manufacturing a heating wire as described in any one of claims 12 to 14, characterized in that, The phrase "after homogenizing the sheet material, cold-roll it into heating wire" further includes: Under an inert atmosphere, the heating wire is kept at 500℃-800℃ for 0.5h-12h, and then naturally cooled to room temperature.

16. A heating coil, characterized in that, It is processed from the heating wire as described in any one of claims 1 to 11 or the manufacturing method of any one of claims 12 to 15.

17. The heating coil as claimed in claim 16, characterized in that, The heating coil is formed by winding at least one section of heating wire, and the winding shape of the heating coil includes a spiral shape; When the heating coil is made of multiple heating wires wound together, adjacent heating wires are connected end to end.

18. The heating coil as claimed in claim 17, characterized in that, The heating coil includes at least an arc portion.

19. The heating coil as claimed in claim 18, characterized in that, The shape of the arc portion includes either a wavy shape or a zigzag shape.

20. A cooking utensil, characterized in that, Includes the heating coil as described in any one of claims 16 to 19.

21. The cooking appliance as described in claim 20, characterized in that, The cooking appliance is an electric stove, which includes a heating plate, a support, a magnetic strip, a heat insulation layer, and a heating coil. The heating coil is embedded in the heat insulation layer, which is located on the side of the magnetic strip facing the working surface of the cooking appliance, and both the heat insulation layer and the magnetic strip are housed within the bracket.

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