Magnetic conductive material for cookware, preparation method for magnetic conductive material, and cookware

Abstract

A magnetic conductive material for cookware, a preparation method thereof, and a cookware containing said magnetic conductive material. The magnetic conductive material is composed of a high-entropy alloy and a rare earth oxide, wherein the high-entropy alloy comprises at least four of Mg, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W, Pb, Si and B and at least comprises one or more of Fe, Co and Ni. The rare earth oxide comprises an oxide of at least one of lanthanides, Sc and Y.

Description

[0001] Magnetic conductive material for cookware, preparation method thereof, and cookware TECHNICAL FIELD The present invention relates to the field of cookware, and more specifically, to a magnetic conductive material for cookware, a method for preparing the magnetic conductive material, and a cookware comprising the magnetic conductive material. BACKGROUND ART Existing induction cookware products (except iron pots) generally achieve the purpose of induction cookware universality by attaching magnetic conductive material to the outer surface. Specifically, the following technical solutions can be adopted: (1) attaching a cold-key stainless steel composite sheet to the outer surface of the universal cookware product; (2) preparing the pot body of the universal cookware product by using an iron or stainless steel composite material; and (3) hot-spraying the iron or stainless steel composite material onto the outer bottom surface of the universal cookware product. The advantages of the above method are fast, convenient, and clean heating; the disadvantage is that the bottom conducts heat unevenly, resulting in high local temperature, easy to burn the bottom, and even dry burning, causing the bottom of the pot to deform and become scrapped. SUMMARY OF THE INVENTION: The present invention aims to provide a magnetic conductive material that utilizes a high-temperature alloy and rare earth oxides to lower its Curie temperature. This allows the material to operate at low power when heated to the Curie temperature, thereby preventing problems such as dry-burning and burning the bottom of magnetic flux products (such as induction cookware or pots) caused by continued temperature increases during use. Another object of the present invention is to provide a method for preparing a magnetic conductive material with adjustable Curie temperature. Yet another object of the present invention is to provide a pot (hereinafter referred to as a pot) that operates at low power when heated to the Curie temperature, thereby preventing problems such as dry-burning and burning the bottom of magnetic flux products caused by continued temperature increases during use. According to one aspect of the present invention, a magnetic conductive material is provided. The magnetic conductive material is composed of a high-voltage alloy and rare earth oxides. The high-voltage alloy includes at least four of Mg, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W, Pb, Si, and B, and at least one or more of Fe, Co, and Ni. The rare earth oxides include oxides of copper-based elements and at least one of Sc and Y. The high-voltage alloy significantly lowers the Curie temperature of the alloy, and the rare earth oxides further adjust the Curie temperature of the high-voltage alloy.When the heating temperature reaches the Curie temperature, the magnetic permeable material operates at low power, thereby preventing problems such as dry-burning and burnt bottoms in magnetic flux products (such as induction cookware) containing this magnetic permeable material due to continued temperature increases during use. In an embodiment of the present invention, based on the total amount of the high-yong alloy and rare earth oxide being 100%, the high-yong alloy can account for 80%-95% of the material, with the balance being rare earth oxide. A magnetic permeable material comprising the high-yong alloy and rare earth oxide within the aforementioned content range can significantly lower its Curie temperature. In an embodiment of the present invention, based on the total atomic number of the high-yong alloy, the atomic number percentage of each element in the high-yong alloy can be between 5 at% and 35 at%, and the total atomic number percentage of Fe, Co, and Ni can be between 35 at% and 95 at%. This high-yong alloy significantly lowers the alloy's Curie temperature. When the temperature reaches the Curie point, the high-yong alloy material changes from ferromagnetic to paramagnetic and stops heating on an induction cooker, thus preventing overheating and causing dry cooking that could damage the cookware. In an embodiment of the present invention, the high-yong alloy may include at least one of AlCrFeCoNi, AlCrFeTiNi, AlCrFeCoNiCu, Al2CrFe3CoNiCu, AlCrFeMnNi, AlCr1.5Fe3MnNi, FeNiAlCr, and FeNiAl2Cr. These high-yong alloys have a reduced Curie temperature. According to another aspect of the present invention, a method for preparing a magnetic conductive material is provided, comprising: ball milling a high-yong alloy and a rare earth oxide; solid-phase sintering the milled powder; and mechanically crushing the magnetic conductive material blocks obtained by solid-phase sintering. The magnetic conductive material prepared by the above method has a reduced Curie temperature, so that when the heating temperature reaches the Curie temperature, the magnetic conductive material operates at low power, thereby preventing problems such as dry burning and burnt bottoms in magnetic flux products (such as induction cookware or pots) caused by continued temperature increases during use. In an embodiment of the present invention, during the ball milling step, ball milling can be performed in a ball mill to obtain a powder with a particle size greater than 300 mesh. The powder is then dried by maintaining it at 80°C to 200°C for 2-4 hours. Ball milling can ensure that the particle size of the high-yong alloy and rare earth oxide is reduced and that the high-yong alloy and rare earth oxide are thoroughly mixed.In an embodiment of the present invention, during the ball milling step, the parameters can be set as follows: a rotation speed of 100-500 rpm, a ball-to-material ratio of 2:1-20:1, anhydrous ethanol or polyvinyl alcohol as the ball milling medium, a vacuum or 99.999% chlorine atmosphere, and a ball milling time of 20-50 hours. Anhydrous ethanol or polyvinyl alcohol does not dissolve the raw materials, and using anhydrous ethanol or polyvinyl alcohol for ball milling can increase grinding efficiency and facilitate powder refinement. In an embodiment of the present invention, during the solid-phase sintering step, liquid paraffin can be added to the ball-milled powder, thoroughly mixed, and pressed into a compact, which is then sintered at 800-1200°C for 5-8 hours. The mass ratio of powder to liquid paraffin can be 5%-10%. Solid-phase sintering can gradually transform microscopically discrete powder particles into a continuous solid structure, reducing the overall free energy of the sample and thereby improving its strength. In an embodiment of the present invention, during the mechanical crushing step, the crushed magnetic conductive material powder can be sieved to obtain magnetic conductive material with a particle size of 200-800 mesh. Mechanical crushing can produce magnetic conductive material of a desired particle size. According to another aspect of the present invention, a cookware is provided. The cookware includes a cookware body and a magnetic conductive layer formed on the outer bottom surface of the cookware body, wherein the magnetic conductive layer comprises a magnetic conductive material. When the heating temperature reaches the Curie temperature, the cookware operates at low power, thereby preventing problems such as dry-burning and burning the bottom caused by continued temperature increases during use. The magnetic conductive material of the present invention utilizes a high-temperature alloy and rare earth oxides to lower its Curie temperature. When the heating temperature reaches the Curie temperature, the magnetic conductive material operates at low power, thereby preventing problems such as dry-burning and burning the bottom caused by continued temperature increases during use in magnetic flux products (such as induction cookware). BRIEF DESCRIPTION OF THE DRAWINGS The above and / or other features and aspects of the present invention will become clear and easily understood through the description of the embodiments in conjunction with the accompanying drawings. FIG1 is a diagram illustrating a cookware including magnetic conductive material according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described more fully below with reference to exemplary embodiments. However, the present invention can be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. These embodiments are provided so that the disclosure of the present invention will be thorough and complete and will fully convey the scope of the present invention to those skilled in the art.The present invention provides a magnetic material for magnetic flux products (e.g., cookware). This magnetic material is composed of a high-temperature alloy and rare earth oxides to lower the Curie temperature of the material. This allows the material to operate at low power when heated to the Curie temperature, thereby preventing problems such as dry-burning and burnt bottoms in magnetic flux products such as induction cookware or cookware for induction cookers, which can occur during use due to continued temperature increases. Ferromagnetic materials possess strong magnetism after magnetization, but this strong magnetism is temperature-dependent. As the temperature of the ferromagnetic material increases, the thermal motion of the metal lattice intensifies, affecting the orderly arrangement of the magnetic domains. Before the ferromagnetic material reaches a certain temperature, the thermal motion is insufficient to disrupt the parallel arrangement of the magnetic domains. At this point, the average magnetic moment of any macroscopic region remains non-zero, and the ferromagnetic material still possesses magnetism, though the average magnetic moment decreases with increasing temperature. However, when the ferromagnetic material is heated to a certain temperature, the intense thermal motion of the molecules causes the magnetic domains to disintegrate, the average magnetic moment drops to zero, and the ferromagnetic material loses its magnetism, transforming into a paramagnetic material. A series of ferromagnetic properties associated with magnetic domains (such as high magnetic permeability and magnetostriction) disappear, the hysteresis loop disappears and becomes a straight line, and the corresponding ferromagnetic material's magnetic permeability transforms into that of a paramagnetic material. The temperature corresponding to the temperature at which ferromagnetism disappears is the Curie temperature. The magnetic material for cookware according to the present invention includes a high-yong alloy that can significantly reduce the alloy's Curie temperature. The BCC and FCC phases of the high-yong alloy can significantly lower the alloy's Curie temperature. When the magnetic material including the high-yong alloy is heated to the Curie point, the material changes from ferromagnetic to paramagnetic, and then stops generating heat on the induction cooker or generates extremely low heat, preventing the temperature of the cookware containing the magnetic material from rising further. When the temperature of the cookware drops due to the paramagnetic nature of the magnetic material, the material transitions from paramagnetism to ferromagnetism, allowing the induction cooker to continue heating the cookware. Eventually, the cookware temperature reaches a dynamic equilibrium near the Curie point, thus preventing excessive temperatures from causing dry cooking and damaging the cookware (for example, deformation and discoloration of the cookware, or damage to the non-stick coating). According to embodiments of the present invention, the magnetic material used in the cookware may also include rare earth oxides. These rare earth oxides can further adjust the Curie point of the high-temperature alloy.Rare earth oxides are introduced into high-voltage alloys. These oxides can replace matrix atoms, creating surface defects and lowering the Curie temperature of the high-voltage alloy. Rare earth oxides are significantly less expensive than rare earth metals. During solid-phase sintering, the oxygen in the rare earth oxides is displaced by the more active high-voltage alloying elements. This displaces the rare earth elements, creating surface defects and lowering the Curie temperature. Oxide components are non-conductive. When mixed with magnetically conductive materials, they further increase electrical resistance, rapidly disabling magnetic conductivity once the temperature reaches the Curie point, resulting in a more sensitive reaction. According to embodiments of the present invention, the high-voltage alloy may include Mg, Al, Ti, V, Cr, and Mg.

[0002] Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W, Pb,

[0003] At least four of Si and B may be present. The rare earth oxide may include oxides of at least one of copper-based elements and sulphur (Sc) and palladium (Y), which have similar chemical properties to copper-based elements. The high-yong alloy may include at least one or more of Fe, Co, and Ni. According to exemplary embodiments of the present invention, examples of high-yong alloys may include AlCrFeCoNi, AlCrFeTiNi, AlCrFeCoNiCu, AlCrFeMnNi, FeNiAlCr, Al2CrFe3CoNiCu, AlCr1.5Fe3MnNi, and FeNiAhCr. The high-yong alloys may be used alone or in combination in any proportion. According to an embodiment of the present invention, the copper-based elements may include 15 elements with atomic numbers 57 to 71 in the periodic table, namely, copper (La), cadmium (Ce), prism (Pr), nephrite (Nd), vanadium (Pm), sulphur (Sm), uranium (Eu), galvanneal (Gd), titanium (Td), dynamite (Dy), horn (Hg), uranium (Er), ytterbium (Yb), and radium (Lu). According to an exemplary embodiment of the present invention, examples of rare earth oxides may include palladium oxide, copper oxide, thorium oxide, and ytterbium oxide. Rare earth oxides may be used alone or in combination in any proportion. According to an embodiment of the present invention, based on the total amount of the high-yong alloy and the rare earth oxides being 100%, the high-yong alloy may account for 80%-95%, for example, 80%-90%, 80%-95%, and preferably 80% or 90%, with the remainder being rare earth oxides. Excessive rare earth oxide content increases the resistance of the magnetic material, weakening the conductivity of the magnetic layer and ultimately rendering it incapable of sensing or conducting magnets. Excessive high-Yong alloy content prevents the rare earth oxide from fully exerting its Curie temperature-lowering effect.According to an embodiment of the present invention, in a high-wall alloy, the atomic fraction of each element in the high-wall alloy can be between 5 at% (atomic fraction) and 35 at%, for example, between 5 at% and 30 at%, between 5 at% and 25 at%, between 5 at% and 20 at%, between 5 at% and 15 at%, or between 5 at% and 10 at%. Furthermore, the total atomic fraction of Fe, Co, and Ni can be between 35 at% and 95 at%, for example, between 40 at% and 80 at%, between 45 at% and 75 at%, between 50 at% and 70 at%, between 55 at% and 65 at%, or between 60 at% and 65 at%. A method for preparing a magnetic conductive material for cookware according to the present invention will be described below. The method for preparing the magnetic conductive material can include high-energy ball milling, solid-phase sintering, and mechanical crushing. Specifically, the method for preparing a magnetic conductive material may include: ball milling a high-yong alloy and rare earth oxide; solid-phase sintering the milled powder; and mechanically crushing the resulting mixture to obtain a magnetic conductive material of a desired particle size. During the ball milling step, the high-yong alloy and rare earth oxide particles can be placed in a ball mill in the desired proportions, then milled with high-speed stirring to obtain a powder with a particle size greater than 300 mesh. The milled powder is then dried by maintaining it at 80°C to 200°C for 2-4 hours. Ball milling ensures that the particle size of the high-yong alloy and rare earth oxide is reduced and that the high-yong alloy and rare earth oxide are thoroughly mixed. The ball mill parameters can be set as follows: a rotation speed of 100-500 rpm, a ball-to-material ratio of 2:1-20:1, anhydrous ethanol or polyvinyl alcohol as the milling medium, a vacuum or inert atmosphere (for example, a 99.999% chlorine atmosphere), and a milling time of 20-50 hours. Anhydrous ethanol or polyvinyl alcohol does not dissolve the raw materials, so using anhydrous ethanol or polyvinyl alcohol for ball milling can increase grinding efficiency and facilitate powder refinement. During the solid-phase sintering step, liquid paraffin can be added to the milled powder, thoroughly mixed, and compacted. The resulting pellets are then sintered at 800-1200°C for 5-8 hours. The mass ratio of powder to liquid paraffin can be 5%-10%. , Preferably, 6%-9% or 7%-8%, more preferably 5%o Through solid-phase sintering, microscopically discrete powder particles can gradually form a continuous solid structure, reducing the overall free energy of the sample and thereby increasing its strength. During the mechanical crushing step, the crushed magnetic conductive material powder can be sieved to obtain magnetic conductive material with a mesh size of 200-800. Mechanical crushing can produce magnetic conductive material of the desired particle size. Below, cookware according to an embodiment of the present invention will be described with reference to the accompanying drawings. Figure 1 shows a cookware including magnetic conductive material according to an embodiment of the present invention. Referring to Figure 1, the cookware may include a pot body and a magnetic conductive layer formed on the outer bottom surface of the pot body. The magnetic conductive layer may include the magnetic conductive material described above. The magnetic conductive material may be sprayed onto the outer bottom surface of the pot body to form the magnetic conductive layer. When the cookware is heated to the Curie temperature, it can operate at low power, thereby preventing problems such as dry-burning and burning the bottom due to the continuous increase in temperature during use. The magnetic conductive material of the present invention utilizes high-temperature alloys and rare earth oxides to lower its Curie temperature. This allows the material to operate at low power when heated to the Curie temperature. This prevents problems such as dry-burning and burnt bottoms that can occur in magnetic flux products (such as induction cookware) during use due to continuously rising temperatures. The following describes the method for preparing the magnetic conductive material of the present invention in detail with reference to examples. Example 1: The cookware of Example 1 was prepared using the following steps.

[0004] 1. Preparation of magnetic conductive material. Two raw materials, a high-wall alloy AlCrFeCoNi and copper oxide, were ball milled at a molar ratio of 4:1 in a 99.999% chlorine atmosphere. The resulting powder had a particle size of 500 mesh and was then held at 120°C for 2 hours to dry the milled powder. Ball mill parameters were as follows: anhydrous ethanol as the milling medium; a speed of 300 r / min, a ball-to-material ratio of 12:1, and a milling time of 30 hours. Liquid paraffin was added to the milled powder at a mass ratio of 5% by weight, thoroughly mixed, and pressed into a compact. The mixture was then solid-phase sintered at 1100°C for 6 hours. The resulting magnetic conductive material blocks were mechanically crushed and sieved to obtain a magnetic conductive material with a particle size of 200-800 mesh.

[0005] 2. Prepare the cookware. Select a pretreated cookware substrate (made of aluminum). Select a magnetic conductive material with an average particle size of 400 mesh and load the magnetic conductive material into a powder feeder. Spray the magnetic conductive material onto the outer bottom surface of the cookware substrate to complete the cookware of Example 1. The spraying process parameters are set as follows: spray power of 25 kW, powder feed rate of 20 g / min, spray distance of 100 mm, arc current of 400 A, hydrogen pressure of 0.3 MPa, hydrogen flow rate of 9 L / min, chlorine pressure of 3 MPa, and chlorine flow rate of 1500 L / min. Example 2: The cookware of Example 2 was manufactured using the same method as Example 1, except that the molar ratio of the two raw materials, the high-wall alloy AlCrFeCoNi and copper oxide, was 9:1. Example 3: The cookware of Example 3 was manufactured using the same method as Example 1, except that FeNiAhCr was used instead of AlCrFeCoNi. Example 4: The cookware of Example 4 was manufactured using the same method as Example 1, except that palladium oxide was used instead of copper oxide. Example 5: The cookware of Example 5 was manufactured using the same method as Example 1, except that a mixture of copper oxide and palladium oxide (the molar ratio of copper oxide to palladium oxide being 1:1) was used instead of copper oxide. [Comparative Example] The cookware of Comparative Example 1 was manufactured using the same method as Example 1, except that only AlCrFeCoNi powder was used as the magnetic conductive material. Comparative Example 2: A conventional cold-key stainless steel magnetic conductive sheet was attached to the outer lower surface of the cookware substrate to obtain the cookware of Comparative Example 2. Comparative Example 3: The cookware of Comparative Example 3 was manufactured using the same method as Example 1, except that copper was used instead of palladium oxide. Comparative Example 4: The cookware of Comparative Example 4 was manufactured using the same method as Example 4, except that palladium was used instead of palladium oxide. Performance Index Tests The cookware obtained above was subjected to performance tests, and the test results are recorded in Table 1 below. The specific performance test methods are as follows: Magnetic Permeability Test Method: Tested using a standard induction cooker in accordance with GB T 32147-2015, applicable to pots for household induction cookers. Curie Temperature Test: Dry-heated on a household induction cooker at 2100W, measuring the highest temperature of the inner surface when the induction cooker stops heating.Initial power is the maximum output power a new product can achieve when it is used for the first time. Table 1. Comparisons of Examples 1-5 of the present invention with Comparative Examples 1-4 show that cookware including a magnetic conductive layer formed from a magnetic conductive material according to the present invention exhibits a low maximum inner surface temperature when the induction cooker stops heating, effectively preventing the cookware from drying out due to user negligence during use. While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, those skilled in the art will appreciate that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the claims and their equivalents. The embodiments should be considered in a descriptive sense only and not for purposes of limitation. The scope of the invention is therefore defined not by the specific embodiments thereof but by the claims, and all differences within the scope are to be construed as being encompassed within the present invention.

Claims

Claims 1. A magnetic conductive material for cookware, characterized in that: The magnetic conductive material is composed of a high-voltage alloy and rare earth oxides, wherein the high-voltage alloy includes at least four of Mg, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W, Pb, Si and B, and at least one or more of Fe, Co and Ni, and the rare earth oxides include oxides of copper series elements and at least one of Sc and Y.

2. The magnetic conductive material according to claim 1, characterized in that: Based on the total amount of Gaoyong alloy and rare earth oxide being 100%, the amount of Gaoyong alloy accounts for 80%-95%, and the balance is rare earth oxide.

3. The magnetic conductive material according to claim 1, characterized in that: Based on the total atomic number of the Gaoyong alloy, the atomic number of each element in the Gaoyong alloy accounts for 5 at % to 35 at %, and the total atomic number of Fe, Co and Ni accounts for 35 at % to 95 at %.

4. The magnetic conductive material according to claim 1, characterized in that: Gaoyong alloys include AlCrFeCoNi, AlCrFeTiNi, AlCrFeCoNiCu, Al2CrFe3CoNiCu, At least one of AlCrFeMnNi > AlCn.5Fe3MnNi > FeNiAlCr and FeNiAkCr.

5. A method for preparing a magnetic conductive material, characterized in that: The method comprises the following steps: - Ball milling of high-pressure alloys and rare earth oxides; - Solid phase sintering of the ball milled powder; as well as - Mechanically crushing the magnetic conductive material blocks obtained by solid phase sintering to obtain the magnetic conductive material according to claim 1.

6. The method according to claim 5, characterized in that In the ball milling step, ball milling is performed in a ball mill to obtain a powder with a particle size greater than 300 mesh, and then the ball milled powder is dried by maintaining it at 80° C. to 200° C. for 2 h to 4 h.

7. The method according to claim 6, characterized in that In the ball milling step, the parameters are set as follows: rotation speed of 100r / min-500r / min, ball-to-material ratio of 2:1-20:1, ball milling medium of anhydrous ethanol or polyvinyl alcohol, ball milling atmosphere of vacuum or 99.999% chlorine atmosphere, and ball milling time of 20h-50h.

8. The method according to claim 5, characterized in that In the solid phase sintering step, liquid paraffin is added to the ball-milled powder, and the mixture is fully mixed and pressed into a green sheet. The green sheet is then sintered at 800°C-1200°C for 5-8 hours. The mass ratio of the powder to the liquid paraffin is 5%-10%.

9. The method according to claim 5, characterized in that In the mechanical crushing step, the crushed magnetic conductive material powder is sieved to obtain a magnetic conductive material with a mesh size of 200-800.

10. A cookware, characterized in that: The cookware includes a cookware body and a magnetic conductive layer formed on an outer bottom surface of the cookware body, wherein the magnetic conductive layer includes the magnetic conductive material according to any one of claims 1 to 4.

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