CN111485173B

CN111485173B - Novel constant-temperature material and preparation method and application thereof

Info

Publication number: CN111485173B
Application number: CN202010274569.2A
Authority: CN
Inventors: 叶勤政; 陈树清
Original assignee: Guangdong Deluxe Metal Products Co ltd
Current assignee: Guangdong Deluxe Metal Products Co ltd
Priority date: 2020-04-09
Filing date: 2020-04-09
Publication date: 2020-12-08
Anticipated expiration: 2040-04-09
Also published as: CN111485173A

Abstract

The invention provides a novel constant temperature material and a preparation method and application thereof, and the novel constant temperature material contains the following elements in percentage by mass: 0.4 to 1.4 percent of Si; 0.35-0.855% of Mn and 8-30% of Ni; 0.015-0.3% of Nb; 0.3-2% of W; 0.005-0.12% of Sn; 0.001-0.003% of rare earth elements, wherein the rare earth elements comprise at least one of La, Yb, Er, Ho, Nd, Lu and Ce; iron content is not less than 55%. The Curie temperature of the novel constant-temperature material is between 150 and 225 ℃, and the Curie temperature of the material can be effectively adjusted by adjusting the types and the component contents of the raw materials of the novel constant-temperature material, so that the novel constant-temperature material can flexibly adapt to different heating requirements.

Description

Novel constant-temperature material and preparation method and application thereof

Technical Field

The invention belongs to the technical field of temperature control materials, and particularly relates to a novel constant temperature material and a preparation method and application thereof.

Background

The Curie point (Curie point) is also referred to as Curie temperature (Tc) or magnetic transition point. It is the temperature at which the spontaneous magnetization of a magnetic material drops to zero, and is the critical point at which a ferromagnetic or ferrimagnetic substance is converted into a paramagnetic substance. Below the curie point temperature the substance becomes ferromagnetic, where the magnetic field associated with the material is difficult to change. When the temperature is higher than the curie point, the substance becomes a paramagnet, and the magnetic field of the magnet is easily changed by the change of the surrounding magnetic field. The magnetic susceptibility is then about minus 6 th power of 10. The curie point is determined by the chemical composition and crystal structure of the substance.

A PTC (Positive Temperature Coefficient effect) material refers to a thermistor phenomenon or material having a Positive Temperature Coefficient in which resistance sharply increases at a certain Temperature, and can be used exclusively as a constant Temperature sensor. The temperature control principle of the PTC material is that the PTC material is heated to rise, when the temperature reaches the distance temperature of the PTC material, the resistance value of the PTC material enters a jump region, the resistance value of the PTC material greatly jumps, and the effects of power failure and heating stop are achieved.

At present, stainless steel, aluminum, iron and other conventional metal materials are frequently used in the kitchenware industry and the small household appliance industry, and particularly, the stainless steel is most widely applied, and the kitchenware has the main defects that: the conventional metal materials such as stainless steel, aluminum, iron and the like are in a rising state all the time in the heating process due to the characteristics of the materials; secondly, the temperature rises quickly and is easy to stick to the pan. Taking the use on an induction cooker as an example: the temperature of the stainless steel pot can reach 300 ℃ or above in 2-3 minutes, the temperature of the stainless steel pot can reach 400 ℃ or above in 3-4 minutes, the temperature of the pot is required to be 150-230 ℃ in general cooking, and meanwhile, most domestic edible oil commonly used by families is as follows: peanut oil, rapeseed oil, soybean oil, palm oil and the like, the smoke point temperature of the edible oil is about 230 ℃, and a large amount of dense smoke is generated when the temperature in the pot exceeds the smoke point temperature of the edible oil. The control of the smoke point of the food oil during cooking is a very important factor. The smoking of the heated edible oil is actually a process of decomposing the oil into glycerol and free fatty acid by heating, the glycerol is further decomposed into acrolein after being heated, and the acrolein has strong stimulation effect on human eyes and respiratory tracts, so the smoke point is the inflection point of the deterioration of the taste and the nutritional value of the edible oil, and the traditional stainless steel kitchen ware has no constant temperature function at present, so the temperature in the pot exceeds the temperature of the smoke point and continuously rises, and is the main reason of the generation of kitchen oil smoke. Aiming at the problem of sticking the pot, a plurality of kitchen ware manufacturers at home and abroad adopt the measure of compounding the non-stick coating on the pot. The non-stick coating mainly contains fluorine-containing resin such as polytetrafluoroethylene, and has certain requirements on the use temperature of a pan, the suitable use temperature of the non-stick coating is below 260 ℃, the coating gradually changes to an unstable state after the temperature exceeds 260 ℃, the coating is decomposed when the temperature exceeds 350 ℃, hydrogen fluoride gas is easily released, and the gas is dissolved in water, has strong corrosivity and high toxicity, so the current non-stick pan has no dry burning prevention function, and is limited in use.

With the development of cookware manufacturing, the application of PTC materials to constant temperature cookers is becoming more and more extensive, and the problems of the prior art mentioned above can be solved by using PTC materials to make PTC elements and using PTC effect to limit the maximum heating temperature of the cookers. However, the PTC materials are of various kinds, and the properties of the PTC materials, such as curie temperature, coercive force, etc., will directly determine the application of the PTC materials in manufacturing or processing cookers and temperature control effects.

Disclosure of Invention

The invention aims to provide a novel constant temperature material, a preparation method and application thereof, so as to obtain a PTC material with the Curie temperature of between 150 and 225 ℃.

According to one aspect of the invention, a novel constant temperature material is provided, which comprises the following elements in percentage by mass: 0.4 to 1.4 percent of Si; 0.35-0.855% of Mn and 8-30% of Ni; 0.015-0.3% of Nb; 0.3-2% of W; 0.005-0.12% of Sn; 0.001-0.003% of rare earth elements, wherein the rare earth elements comprise at least one of La, Yb, Er, Ho, Nd, Lu and Ce; iron content is not less than 55%.

Preferably, the composition also contains the following elements in percentage by mass: 0.1 to 0.3 percent of Ti; 0.01-0.08% of Cu; 0.03 to 3 percent of Cr.

Preferably, the alloy contains the following elements in percentage by mass: 0.6 to 0.9 percent of Si; 0.35-0.65% of Mn and 12-19% of Ni; 0.025 to 0.15 percent of Nb; 0.3-1% of W; 0.1 to 0.12 percent of Sn; 0.15 to 0.3 percent of Ti; 0.05 to 0.08 percent of Cu; 1-3% of Cr.

Preferably, the rare earth elements comprise light rare earth elements and heavy rare earth elements, the light rare earth elements are selected from at least one of La, Ce and Nd, and the heavy rare earth elements are selected from at least one of Ho, Er, Yb and Lu; according to the mass percentage, the proportion of the light rare earth elements is 0 to 0.0012 percent, and the proportion of the heavy rare earth elements is 0.0015 to 0.0025 percent.

Preferably, the light rare earth element is La and the heavy rare earth element consists of Yb and Lu.

Preferably, the light rare earth element is Ce and the heavy rare earth element consists of Yb and Ho.

Preferably, the light rare earth element is Nd and the heavy rare earth element is comprised of Lu and Er.

The Curie temperature of the novel constant-temperature material is between 150 and 225 ℃, and the Curie temperature of the material can be effectively adjusted by adjusting the types and the component contents of the raw materials of the novel constant-temperature material, so that the novel constant-temperature material can flexibly adapt to different heating requirements. The novel thermostatic material is heated and then heated, and when the temperature rises to be close to the corresponding Curie temperature, the resistance of the novel thermostatic material greatly rises to achieve the effect of cutting off a circuit.

According to another aspect of the present invention, there is provided a method for preparing the above novel thermostatic material, comprising the steps of: s1, preparing materials; s2, vacuum smelting: s2.1 refining: feeding Fe-supplying raw material and Ni-supplying raw material into a smelting zone, melting at 1320-1360 ℃ in vacuum, and adding other raw materials after completely melting the Fe-supplying raw material and the Ni-supplying raw material; s2.2, pouring: pouring at 1180-1210 deg.c; s3, annealing: annealing is carried out at 780-830 ℃ in a nitrogen atmosphere. In the process of preparing the novel constant-temperature material, the material is annealed in a nitrogen atmosphere, the resistance of the manufactured finished product has a higher resistance temperature coefficient, a circuit can be quickly cut off when the Curie temperature is reached, and the Curie temperature value of the novel constant-temperature material cannot be obviously influenced.

According to another aspect of the present invention, there is provided the use of the above-described novel thermostatic material for the preparation and/or processing of cookware.

According to another aspect of the present invention, there is provided a thermostatic pot: the pot comprises a pot main body and a PTC heating layer, wherein the PTC heating layer is compounded at the bottom of the pot main body and is made of the novel constant temperature material according to any one of claims 1 to 8.

After the temperature in the pot rises to the peak value and the highest point, the constant temperature pot starts to enter a constant temperature mode based on the PTC effect of the material, so that the average temperature in the pot is maintained in a certain temperature range near the Curie temperature of the material (the temperature requirement of common cooking is met, and meanwhile, the smoke point lower than common edible oil is met), and the edible oil cannot be decomposed in the temperature range, so that smokeless cooking is realized. Because the Curie temperature of the rare earth PTC is not more than 230 ℃, the average temperature inside the constant temperature pot is not more than 215 ℃, and is far lower than the proper use temperature (260 ℃) which is not sticky with the coating, the constant temperature pot also has the dry burning prevention function, the problem of high-temperature decomposition of the coating can not occur under any condition, and the constant temperature pot has longer service life and higher food processing safety. In addition, in the actual production process, the production flow of constant temperature pan is similar with the flow of present stainless steel kitchen utensils and appliances, can use the production line of present stainless steel kitchen utensils and appliances to produce, need not to add other special equipment. The preheating speed of the thermostatic pot is almost the same as that of the current stainless steel kitchen ware, and the use habit and the cooking speed of a user are not influenced.

Drawings

FIG. 1 shows the temperature rise test results for material 304 and the novel constant temperature material prepared in treatment 1D;

FIG. 2 shows a pot of embodiment 4;

FIG. 3 shows a cooking pot of example 4;

FIG. 4 shows a third embodiment of the cookware in example 4;

fig. 5 shows the pot temperature measuring points of embodiment 4.

Detailed Description

In order to make the technical solutions of the present invention better understood by those skilled in the art, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments.

Example 1

(I) preparing materials

Taking the component composition of the novel constant temperature material as a variable, the present embodiment sets a group 4 of treatment groups, which are respectively labeled as a treatment group 1A, a treatment group 1B, a treatment group 1C, and a treatment group 1D, and the component compositions corresponding to the treatment groups are calculated according to the weight percentage as shown in table 1. In addition to the components listed in Table 1, each treatment group produced a finished product having a carbon content of 0.005% to 0.050%, and further, each treatment group produced a finished product containing inevitable impurities derived from the raw materials, the impurities in each treatment group corresponding to the finished product satisfying: p is less than or equal to 0.035%, S is less than or equal to 0.018%.

TABLE 1 composition of each treatment group in this example

(II) preparation method

All treatment groups of this example prepared the novel thermostatic material according to the following method:

s1, material preparation: according to table 1, the required raw materials corresponding to each group were calculated and weighed according to the specific composition of the components of each treatment group.

S2, vacuum melting

S2.1 refining

Putting nickel and iron into a crucible of a vacuum smelting furnace, and putting the rest trace element materials into a hopper respectively for putting; setting the heat preservation temperature of a vacuum smelting furnace to 1330 ℃, and enabling the vacuum degree of the vacuum smelting furnace to reach 10 DEG C^-2Starting heating after the millimeter mercury column vacuum degree; after the nickel and iron were completely melted, the crucible was charged with other raw materials using a hopper and refined for 30 minutes.

S2.2 casting

After refining, calming for 10 minutes, and then carrying out charged pouring, wherein the pouring temperature is 1190 ℃, and the pouring time is 3-4 minutes; stopping heating after the pouring is finished, cooling for more than 10 minutes along with the furnace, breaking the vacuum and then discharging from the furnace.

S3, annealing

Filling the semi-finished product obtained in the step S2 into a reaction area of a tempering furnace, vacuumizing, and then filling nitrogen, so that the reaction area is filled with nitrogen atmosphere, setting the heating temperature to 800 ℃, and keeping the temperature for 60 minutes; after the heat preservation time is over, the pressure of the gas in the furnace is kept until the furnace shell is cooled to the room temperature, and then the furnace cover can be opened to discharge the furnace.

And S4, obtaining a finished product.

Example 2

(I) preparing materials

Taking the component composition of the novel constant temperature material as a variable, the present embodiment sets a group 4 of treatment groups, which are respectively labeled as a treatment group 2A, a treatment group 2B, a treatment group 2C, and a treatment group 2D, and the component compositions corresponding to the treatment groups are calculated according to the weight percentage as shown in table 2. In addition to the components listed in Table 2, each treatment group produced a finished product having a carbon content of 0.005% to 0.050%, and further, each treatment group produced a finished product containing inevitable impurities derived from the raw materials, the impurities in each treatment group corresponding to the finished product satisfying: p is less than or equal to 0.035%, S is less than or equal to 0.018%.

TABLE 2 composition of each treatment group in this example

(II) preparation method

s1, material preparation: according to table 2, the required raw materials corresponding to each group were calculated and weighed according to the specific composition of the components of each treatment group.

S2, vacuum melting

S2.1 refining

Putting nickel and iron into a crucible of a vacuum smelting furnace, and putting the rest trace element materials into a hopper respectively for putting; setting the heat preservation temperature of the vacuum melting furnace to 1320 ℃, and enabling the vacuum degree of the vacuum melting furnace to reach 10 DEG C^-2Starting heating after the millimeter mercury column vacuum degree; after the nickel and iron were completely melted, the crucible was charged with other raw materials using a hopper and refined for 30 minutes.

S2.2 casting

After refining, the mixture is calmed for 10 minutes and then is electrically cast, wherein the casting temperature is 1170 ℃, and the casting time is 3 to 4 minutes; stopping heating after the pouring is finished, cooling for more than 10 minutes along with the furnace, breaking the vacuum and then discharging from the furnace.

S3, annealing

And S4, obtaining a finished product.

Example 3

(I) preparing materials

Taking the component composition of the novel constant temperature material as a variable, the present embodiment sets a group 4 of treatment groups, which are respectively labeled as a treatment group 3A, a treatment group 3B, a treatment group 3C, and a treatment group 3D, and the component compositions corresponding to the treatment groups are calculated according to the weight percentage as shown in table 3. In addition to the components listed in Table 3, each treatment group produced a finished product having a carbon content of 0.005% to 0.050%, and further, each treatment group produced a finished product containing inevitable impurities derived from the starting materials, the impurities in each treatment group corresponding to the finished product satisfying: p is less than or equal to 0.035%, S is less than or equal to 0.018%. 0 to 0.0012 percent and the proportion of the heavy rare earth elements is 0.0015 to 0.0025 percent.

TABLE 3 composition of components corresponding to each treatment group of this example

(II) preparation method

s1, material preparation: according to table 3, the required raw materials corresponding to each group were calculated and weighed according to the specific composition of the components for each treatment group.

S2, vacuum melting

S2.1 refining

Putting nickel and iron into a crucible of a vacuum smelting furnace, and putting the rest trace element materials into a hopper respectively for putting; setting the heat preservation temperature of a vacuum smelting furnace to 1340 ℃, and ensuring the vacuum degree of the vacuum smelting furnace to 10^-2Starting heating after the millimeter mercury column vacuum degree; after the nickel and iron were completely melted, the crucible was charged with other raw materials using a hopper and refined for 30 minutes.

S2.2 casting

After refining, calming for 10 minutes, and then carrying out charged pouring, wherein the pouring temperature is 1180 ℃, and the pouring time is 3-4 minutes; stopping heating after the pouring is finished, cooling for more than 10 minutes along with the furnace, breaking the vacuum and then discharging from the furnace.

S3, annealing

And S4, obtaining a finished product.

Test example 1

In this test example, finished products obtained by treating group 1A, group 1B, group 1C, group 1D, group 2A, group 2B, group 2C, group 2D, group 3A, group 3B, group 3C and group 3D in examples 1 to 3 were used as reference objects, and the yield strength at normal temperature, the yield tensile strength at normal temperature, the curie temperature and the antioxidant effect of the material were tested, wherein the antioxidant effect of the material was characterized by the oxidation weight gain of the material at 1100 ℃, and the specific test mode was as follows: and (3) putting the material to be tested into a high-temperature furnace, introducing air from bottom to top, rapidly heating to 1100 ℃, and maintaining constant temperature for oxidation for 30 hours. The test results are shown in table 4.

TABLE 4 Material Properties for each treatment group

The alloy main phase of each treatment group is a nickel-iron-based alloy. The price of iron is relatively low and the raw materials are readily available. The nickel can improve the strength of the alloy material and maintain good plasticity and toughness. Nickel is a face centered cubic lattice, has a high melting point, is not easily oxidized in air, and has stable chemical properties. The resistivity of nickel at 20 ℃ is 6.84 mu omega cm, the linear expansion coefficient is small, the high-temperature oxidation and corrosion resistance is good, and the nickel is a good alloy matrix material.

Respectively carrying out combination comparison on a processing 1A group, a processing 1B group, a processing 1C group and a processing 1D group, carrying out combination comparison on a processing 2A group, a processing 2B group, a processing 2C group and a processing 2D group, and carrying out combination comparison on a processing 3A group, a processing 3B group, a processing 3C group and a processing 3D group:

the rare earth metal is introduced into the alloy material, and the rare earth element can replace matrix atoms, so that surface defects are formed, and the Curie temperature of the alloy material can be effectively reduced. On the other hand, the rare earth element has great affinity with sulfur, not only has a deoxidation effect in a molten pool, but also has the obvious functions of desulfurization and improvement of the size, the form and the distribution of sulfide inclusions, thereby improving various properties of the alloy material, such as toughness, magnetism and the like. In addition, the introduction of the rare earth material can reduce oxygen in the alloy, and obviously improve the oxidation resistance of the alloy below 1100 ℃.

The silicon can obviously improve the elastic limit, the yield point and the tensile strength of the nickel-iron alloy, reduce the coercive force, reduce the anisotropy tendency of crystals, make the magnetization easy and reduce the magnetic resistance, thereby improving the heat sensitivity of the novel constant temperature material. When heated, the silicon on the surface of the alloy will form a layer of SiO₂The film is distributed at the interface of the base metal, can prevent oxygen from permeating and reduce the oxidation speed of the alloy. It is worth noting that when silicon and rare earth elements exist simultaneously, an oxidation film formed by the silicon has higher compactness and can achieve more remarkable anti-oxidation effect.

The manganese can be used as a good deoxidizer and desulfurizer in the smelting process of the iron-based alloy material, and the manganese can reduce the critical cooling speed of the alloy material and improve the hardenability.

Niobium can refine crystal grains, reduce the overheating sensitivity and the tempering brittleness of the alloy, improve the strength and prevent intergranular corrosion.

The titanium has stronger deoxidation effect, can compact the internal structure of the alloy, refine the grain strength and reduce the aging sensitivity and cold brittleness. Copper has good plasticity and ductility, so that the tensile strength of the alloy material can be improved to a certain extent by introducing the copper into the alloy matrix. Chromium has good stability, and the introduction of chromium can bring a certain positive effect on the corrosion resistance of the alloy.

Comparative example 1

In this example, three control groups, which are labeled as control 1 group, control 2 group and control 3 group, were set with the annealing atmosphere during the preparation of the novel thermostatic material as a variable, to serve as comparative embodiments of the treatment 1D group of example 1, the treatment 2D group of example 2 and the treatment 3D group of example 3, respectively.

Preparation method adopted by control 1 group

S1, material preparation: according to table 1, the required raw materials for each group were calculated and weighed according to the composition of the components of treatment 1D group of example 1.

S2, vacuum melting

S2.1 refining

S2.2 casting

S3, annealing

Filling the semi-finished product obtained in the step S2 into a reaction area of a tempering furnace, vacuumizing, and then filling argon gas into the reaction area, so that the reaction area is filled with argon gas atmosphere, setting the heating temperature to 800 ℃, and keeping the temperature for 60 minutes; after the heat preservation time is over, the pressure of the gas in the furnace is kept until the furnace shell is cooled to the room temperature, and then the furnace cover can be opened to discharge the furnace.

And S4, obtaining a finished product.

(II) preparation method adopted by control group 2

S1, material preparation: according to table 2, the required raw materials for each group were calculated and weighed according to the composition of the components for treating group 2D of example 2.

S2, vacuum melting

S2.1 refining

S2.2 casting

S3, annealing

And S4, obtaining a finished product.

(III) preparation method adopted by control group 3

S1, material preparation: according to table 3, the required raw materials for each group were calculated and weighed according to the composition of the components for treating the 3D group of example 3.

S2, vacuum melting

S2.1 refining

S2.2 casting

S3, annealing

And S4, obtaining a finished product.

(IV) Performance testing

In this test example, finished products obtained from the treatment 1D group of example 1, the treatment 2D group of example 2, the treatment 3D group of example 3, and the control 1 group, the control 2 group, and the control 3 group of this example were used as reference objects, and the curie temperature, the resistance value at normal temperature (25 ℃) and the resistance value at curie temperature of the test material were measured, and the resistance temperature coefficient α of the reference product was calculated from the above data, and the calculation formula of α was:

wherein R1 represents a resistance value at normal temperature (25 ℃), R2 represents a resistance value at Curie temperature, TC represents a Curie temperature value, and T0 represents 25 ℃.

The test results are shown in table 5, the curie temperature of the material is not significantly affected by the annealing atmosphere, however, compared with the argon atmosphere, the annealing reaction is performed in the nitrogen atmosphere, the prepared material has a higher temperature coefficient of resistance, which shows that the sudden change degree of the resistance is higher along with the temperature rise, and the novel constant temperature material has higher heat sensitivity.

TABLE 5 Material Properties for each treatment group

Group of	Curie temperature (. degree. C.)	Temperature coefficient of resistance (. degree.C)^-1)
			Treatment of group 1D	220	6.96×10³
Control 1 group	219	5.34×10³
			Treatment of 2D groups	225	6.82×10³
Control 2 group	225	5.37×10³
			Processing 3D groups	187	7.74×10³
Control 3 group	185	7.20×10³

Example 4

The material properties of all the novel constant temperature materials related in the above embodiments are comprehensively considered, and the novel constant temperature material prepared by processing the group 1D is most suitable for being applied to the field of cookers to manufacture constant temperature cookers.

And (3) taking the 304 material commonly used for manufacturing the cookware as a comparison, and carrying out a temperature rise test on the 304 material and the novel constant-temperature material prepared by the processing group 1D. As shown in fig. 1, the temperature of both materials started to rise after the start of heating, and both materials tended to rise before 1 minute and 10 seconds; when the temperature of the 304 material exceeds 230 ℃ by 1 minute and 10 seconds, the temperature of the 304 material continuously rises along with the prolonging of the heating time, the temperature of the novel constant temperature material is about 220 ℃, the change of the temperature is in a moderate and reciprocating relative steady state, and finally, the temperature stays in the interval of 217 ℃ and 222 ℃.

The pan of this embodiment includes pan main part and PTC zone of heating 3, and the bottom in the pan main part is compound to PTC zone of heating 3, and the pan main part includes stainless steel's pot body 1 and compound aluminium lamination 2 in pot body 1 bottom, and pot body 1 and the integrative casting of aluminium lamination 2 form, and aluminium lamination 2 has certain thickness, at aluminium lamination 2's surface recombination one deck PTC zone of heating 3, and the material of PTC zone of heating 3 is the novel constant temperature material who handles 1D group and make. According to the difference of the shapes of the aluminum layer 2 and the PTC heating layer 3, the pot manufactured by the embodiment has three forms, which are respectively:

pan (corresponding to fig. 2), aluminium lamination 2 is the structure of falling the trapezoidal body, and PTC zone of heating 3 is the form of buckling, including smooth bottom surface and the continuous folded surface of buckling with the bottom surface, the angle that folded surface and bottom surface become is the obtuse angle, and the bottom surface complex of PTC zone of heating 3 is at the lower surface of aluminium lamination 2, and two folded surfaces of PTC zone of heating 3 complex respectively are at two sides of aluminium lamination 2.

Secondly, the bottom surface of the aluminum layer 2 is smoothly and excessively connected with the two side surfaces of the aluminum layer by round corners, the PTC heating layer 3 is of a cambered surface structure, the bottom surface and the side surfaces of the attached aluminum layer 2 are compounded, and the PTC heating layer 3 covers or partially covers the round corner of the aluminum layer 2.

No. three pan (corresponding to fig. 4), aluminium lamination 2 is the cuboid structure, and PTC zone of heating 3 is the form of buckling, including smooth bottom surface and the continuous folded surface of buckling with the bottom surface, the angle that folded surface and bottom surface become is the right angle, and the bottom surface complex of PTC zone of heating 3 is at aluminium lamination 2's lower surface, and two folded surfaces of PTC zone of heating 3 are compound respectively in two sides of aluminium lamination 2.

And respectively carrying out pot bottom temperature peak value test on the pot I, the pot II and the pot III, heating the pot, and testing the temperature of each position point according to the position shown in the figure 5 after the pot enters a constant temperature state. The test results of the pan with the first formula are shown in Table 6, wherein the highest temperature point is about 213 ℃ at the center of the pan bottom, the lowest temperature point is about 187 ℃ at the edge of the pan bottom, and the average temperature in the pan is maintained at about 200 ℃ and 203 ℃. The test results of the pan No. 7 are shown in Table 7, the highest temperature point is about 213 ℃ at the center of the pan bottom, the lowest temperature point is about 196 ℃ at the edge of the pan bottom, and the average temperature in the pan is maintained at about 203 ℃ and 204 ℃. The test results of the pot are shown in Table 8, the highest temperature point is about 219 ℃ at the center of the pot bottom, the lowest temperature point is about 198 ℃ at the edge of the pot bottom, and the average temperature in the pot is maintained at about 206-.

Table 6 temperature test results of each test point after the pan enters into the constant temperature state

TABLE 7 temperature test results of test points after the No. 7 cookware enters into a constant temperature state

Table 8 temperature test results of each test point after No. 8 pot enters constant temperature state

Table 9 lists the corresponding smoke points of several common edible oils on the market, and by comprehensively analyzing the data in tables 7-9, the first, second and third pots provided in this embodiment are all suitable for cooking scenarios using peanut oil, refined corn oil, refined soybean oil, palm kernel oil, sunflower seed oil, refined high oleic sunflower seed oil, semi-refined sunflower seed oil, olive pomace oil and ultra-light olive oil.

TABLE 9 common lampblack spot

Although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the present invention.

Claims

1. The novel constant-temperature material is characterized by comprising the following elements in percentage by mass:

0.4 to 1.4 percent of Si; 0.35-0.855% of Mn and 8-30% of Ni; 0.015-0.3% of Nb; 0.3-2% of W; 0.005-0.12% of Sn; 0.001-0.003% of rare earth elements, wherein the rare earth elements comprise at least one of La, Yb, Er, Ho, Nd, Lu and Ce; the balance being Fe and unavoidable impurities.

2. The novel thermostatic material as claimed in claim 1, further comprising the following elements in mass percent: 0.1 to 0.3 percent of Ti; 0.01-0.08% of Cu; 0.03 to 3 percent of Cr.

3. The novel thermostatic material as claimed in claim 2, characterized by comprising the following elements, calculated in mass percent:

Si，0.6–0.9％；Mn，0.35–0.65％，Ni，12–19％；Nb，0.025–0.15％；W，0.3–1％；Sn，0.1–0.12％；Ti，0.15–0.3％；Cu，0.05–0.08％；Cr，1–3％。

4. a novel thermostatic material as set forth in claim 3, wherein:

the rare earth elements comprise light rare earth elements and heavy rare earth elements, the light rare earth elements are selected from at least one of La, Ce and Nd, and the heavy rare earth elements are selected from at least one of Ho, Er, Yb and Lu;

according to the mass percentage, the proportion of the light rare earth elements is 0-0.0012%, and the proportion of the heavy rare earth elements is 0.0015-0.0025%.

5. The novel thermostatic material as set forth in claim 4, wherein: the light rare earth element is La, and the heavy rare earth element is composed of Yb and Lu.

6. The novel thermostatic material as set forth in claim 4, wherein: the light rare earth element is Ce, and the heavy rare earth element is composed of Yb and Ho.

7. The novel thermostatic material as set forth in claim 4, wherein: the light rare earth element is Nd, and the heavy rare earth element is Lu and Er.

8. A method for preparing a novel thermostatic material as claimed in any one of claims 1 to 7, which comprises the steps of:

s1, preparing materials;

s2, vacuum smelting:

s2.1 refining: feeding Fe-supplying raw materials and Ni-supplying raw materials into a smelting zone, melting the raw materials in vacuum at the temperature of 1320-1360 ℃, and adding other raw materials after the Fe-supplying raw materials and the Ni-supplying raw materials are completely melted;

s2.2, pouring: pouring at 1180-1210 deg.c;

s3, annealing: annealing is carried out at 780-830 ℃ in a nitrogen atmosphere.

9. Use of the novel thermostatic material according to any of claims 1 to 7 or the method of preparation according to claim 8 for the preparation and/or processing of cookware.

10. A constant temperature pan, its characterized in that: the pot comprises a pot body and a PTC heating layer, wherein the PTC heating layer is compounded at the bottom of the pot body, and is made of the novel constant temperature material according to any one of claims 1 to 7 or the novel constant temperature material prepared by the preparation method according to claim 8.