Thin film material composed of resistor alloy and method for producing same

Abstract

Disclosed is a resistor of a thin film material which is composed of an amorphous structure and a martensite structure that is mixed in the amorphous structure. According to the present invention, a sintering agent that contains a carbon source is applied to one surface or both surfaces of a thin film material of austenitic stainless steel having a thickness of 50 µm or less. Subsequently, the thin film material to which the sintering agent has been applied is heated to 800-1,000°C. The heated thin film material is rapidly cooled. As a result, a thin film in which an amorphous structure and a martensitic structure are mixed can be formed. The sintering agent is in the form of a viscous liquid that contains a carbon source in sodium silicate. As a result, a thin film material which is composed of a resistor alloy that has high resistivity, low temperature dependence of resistivity, and low specific heat is obtained.

Description

Thin film material made of resistive alloy and method for manufacturing the same

[0001] The present invention relates to a thin film material made of a resistive alloy, and more particularly to a thin film material made of a resistive alloy using a thin film material of austenitic stainless steel as a starting material, and to a method for producing the same.

[0002] Stainless steel, being an iron-based material, is widely used not only as a structural material but also as a heater material due to its excellent corrosion resistance and heat resistance. As a heater material, it is used as a sheath material, where a heating element is inserted inside a stainless steel tube to protect it, and it is also used as the heater itself because its resistivity is 40 times that of copper.

[0003] Furthermore, martensitic steels (including stainless steel) with a body-centered cubic structure can be sintered (quenched) using the carbon they contain to enhance their corrosion resistance and heat resistance. Steels with such enhanced corrosion and heat resistance can then be used as high-temperature heaters.

[0004] On the other hand, amorphous alloys are increasingly being used as heaters due to their excellent corrosion resistance, heat resistance, and higher resistivity compared to alloys of the same composition. Furthermore, iron-based amorphous alloys exhibit soft magnetism and have been used as magnetic materials, for example, in the magnetic heads of tape recorders.

[0005] One method for producing amorphous alloys is to rapidly cool molten metal. For example, Japanese Patent Publication No. 2020-146714 and Japanese Patent Publication No. 2018-151172 disclose a method in which a container containing metal raw materials is heated by electromagnetic induction to melt them, and the molten metal is applied in a film-like manner to a cooling roll and rapidly cooled. Furthermore, Japanese Patent Publication No. 51-73920 discloses a composition for amorphousizing iron-based materials.

[0006] Furthermore, there is a method of implanting ions of elements such as carbon, phosphorus, and boron into the target object using an ion implantation device.

[0007] Japanese Patent Publication No. 2020-146714, Japanese Patent Publication No. 2018-151172, Japanese Patent Publication No. 51-73920

[0008] If the heater material is made into a strip material to increase the heat radiation area, it is predicted that high thermal efficiency can be obtained. As strip-shaped heater materials, stainless steel, iron, chromium, and aluminum alloy (trade name Kanthal (registered trademark)) can be cited as materials that can currently be seen on the Internet.

[0009] Since the melting temperature of stainless steel is 1400 to 1500 °C, it can be used at a temperature of about 1000 °C. Therefore, let's consider a heater using a stainless steel strip with a thickness of 30 μm.

[0010] Regarding the resistivity (SUS316L) as 7.7×10 -７ Ωm in the literature, if we want to obtain a stainless steel heater with a width of 5 mm, a thickness of 30 μm, and a power of 1 kw (10 Ω) at a voltage of 100 V, a material with a length of slightly less than 2 m is required. Considering the temperature dependence of resistance, it is considered that it will be shortened by 30%, but there is no alternative to the requirement for a long length.

[0011] Since the resistivity of the iron, chromium, and aluminum alloy is 14.5×10 -７ Ωm, if the above thickness is 30 μm, it will only require about half the length. However, considering that currently only materials with a thickness of 80 μm or more have been commercialized (from the catalog published by Tokyo Resistance Wire Co., Ltd.), it is considered that it cannot be made thinner, or even if it is made thinner, there will be problems in use.

[0012] Also, focusing on the specific heat of various heater materials in relation to the present invention, although there are various types of stainless steel, all have a specific heat of 500 J / kg·K. Nichrome has a relatively high resistivity of 10.8×10 -７ Ωm but also has a high temperature dependence, and its specific heat is 460 J / kg·K, which is not much lower than that of stainless steel.

[0013] Also, the iron, chromium, and aluminum alloy has a high resistivity of 14.5×10 -７ Ωm, and its temperature dependence is low and its heat resistance is high, so it is beneficial as a heater. However, its specific heat is 420 J / kg·K, which cannot be said to be significantly lower than that of stainless steel or nichrome.

[0014] Based on the above, the requirements for a heater material are high resistivity, low temperature dependence of resistivity, and low specific heat, but it is believed that no heater material currently meets all three of these conditions.

[0015] The methods for producing amorphous alloys described in the above patent documents involve melting the material, then rapidly cooling it by extruding it through a rotating cooling drum to form a strip. The temperature drop rate for this "rapid cooling" is described in the literature as 10 ２ ℃ / s ~ 10 ６ The description shows a wide range of °C / s, which is likely to vary depending on the substance, but 10 ２ It can be said with certainty that the temperature is not below °C / s. The amorphous metal obtained by this method is characterized by high resistivity and soft magnetism, but it requires appropriate equipment and is costly.

[0016] Another method for obtaining amorphous powder is by sputtering, but in this case, the obtained amorphous powder needs to be re-solidified, making it technically difficult to obtain long strips of material.

[0017] Furthermore, there is a method of implanting ions of elements such as carbon, phosphorus, and boron into the target object using an ion implanter, but this method is limited to producing products of a size that is constrained by the size of the ion implanter.

[0018] This invention was proposed in view of the above-mentioned conventional circumstances, and aims to provide a strip-shaped or linear heater material with high resistivity, low temperature dependence of resistivity, low specific heat, high durability and heat resistance, and length suitable for the situation.

[0019] The present invention relates to a thin film material of austenitic stainless steel with a thickness of 50 μm or less, comprising a resistive alloy having an amorphous structure and a crystalline structure that is mixed with the amorphous structure and has an XRD waveform where 2θ is only around 65° and 82°.

[0020] The thin film material described above is manufactured using the following procedure.

[0021] Austenitic stainless steel inevitably contains impurities (C, Si, S, P). Focusing on carbon, the process involves removing impurities from the molten austenitic stainless steel so that the carbon concentration is 1 / 10 or less of the upper limit of the JIS standard (impurity treatment process). Steel of a predetermined thickness is obtained from the molten metal from which the carbon has been removed (steelmaking process). A thin film material is obtained by cold-rolling the obtained steel to a thickness of 50 μm or less (cold rolling process). A sintering agent containing a carbon source is applied to one surface of the thin film material (coating process). The thin film material coated with the sintering agent is heated to 800 to 1000°C (heating process). The heated thin film material is rapidly cooled with water (cooling process).

[0022] The sintering agent is a viscous liquid mixture of sodium silicate and a carbon source. The carbon source can be carbon powder. The type of austenitic stainless steel is not limited, but SUS316, SUS316L, SUS304, and SUS304L are more preferred, with SUS316 and SUS316L being particularly preferred.

[0023] This invention provides a thin film material of an amorphous resistive alloy by processing steel obtained from molten metal that has been reduced in impurity concentration (carbon concentration) through a normal manufacturing process. This thin film material of the resistive alloy has high resistivity, corrosion resistance, and heat resistance, and because its specific heat is low, it can be used as a heater material that can achieve high temperatures with low energy input.

[0024] This is the X-ray diffraction pattern of Sample 1 (13 μm). This is the XPS image of Sample 1 (13 μm). This is the X-ray diffraction pattern of Sample 2 (28 μm). This is the X-ray diffraction pattern of Sample 3 (12 μm). This is the reference pattern for the X-ray diffraction pattern of stainless steel 316 and 316L. This is the reference pattern for the X-ray diffraction pattern of stainless steel 304. This is a diagram showing the temperature measurement process.

[0025] In the present invention, austenitic stainless steel SUS316L (or 316) is used as the starting material. Its metal composition, in weight percent, is Cr: 16.00 to 18.00, Ni: 10.00 to 15.00, Mo: 2.00 to 3.00, Mn: ≤2.00, with the remainder being Fe.

[0026] The metallic composition of SUS316L (or 316), specifically Ni, is 10.00–14.00 mass% for SUS316 and 12.00–15.00 mass% for SUS316L; therefore, 10.00–15.00 mass% was used above.

[0027] Alternatively, SUS304 (or 304L) can be used. Its metal composition is, in weight percent, Cr: 18.00–20.00, Ni: 8.00–10.50 (SUS304L: 9.00–13.00), Mn: ≤2.00, with the remainder being Fe.

[0028] Austenitic stainless steel inevitably contains impurities (C, Si, S, P). While the JIS standard specifies an upper limit of 0.03% by weight for carbon in SUS316L (SUS304L) (the upper limit for SUS316 and 304 is 0.08% by weight), here, steel with carbon removed to a value even lower than 1 / 10, or technically as low as possible, is used in the following examples.

[0029] To produce steel with the above composition, the molten metal of austenitic stainless steel is treated for impurities. This impurity treatment is a technique commonly used in steelmaking, and is performed by blowing oxygen into the molten metal container (tundish). This causes carbon to turn into carbon dioxide and other substances to turn into oxides, which are removed from the molten metal as slag. This low-carbonization makes it easier for the carbon that will be applied to the surface in the subsequent sintering process to penetrate, facilitating amorphous formation.

[0030] Next, a steel sheet with a thickness of about 1 mm is obtained from the molten metal, which has been treated for impurities (low-carbonization), using a conventional method. After curing this steel sheet in a vacuum at a temperature of about 1000°C for about an hour, it is cold-rolled to obtain a thin film material with a thickness of 50 μm or less. Cold rolling allows the material to be formed to a uniform thickness, so uniformity of properties can be ensured even for long products.

[0031] To remove oxides and impurities adhering to the surface of the stainless steel thin film material obtained as described above, it is polished with an abrasive roller. Here, polishing means removing a very thin layer of surface deposits and does not mean achieving a mirror finish. Therefore, the important point is that the abrasive roller creates microscopic scratches on both surfaces. Alternatively, microscopic scratches can also be created on both surfaces by using abrasive powder, or by using a manual abrasive scouring pad or abrasive paper.

[0032] A sintering agent, which is sodium silicate (or sodium silicate containing potassium silicate) mixed with carbon powder as a carbon source, is applied to one side of the polished thin film material of a predetermined thickness obtained in this way. After applying the sintering agent, the sodium silicate is wiped off with a rubber blade, so that as a result, the sodium silicate containing carbon powder adheres to the surface of the stainless steel thin film in an extremely thin layer (estimated to be 1 μm or less).

[0033] At this time, as mentioned above, the surface of the thin film material has scratches from polishing, so when wiped with the blade, the carbon powder and the like get embedded in the scratches and become fixed to the surface of the stainless steel.

[0034] As described above, the stainless steel thin film material coated with sintering agent is heated at 800°C to 1000°C for approximately 15 to 25 seconds, and then rapidly cooled with water.

[0035] The thickness of the thin film material described above is preferably 50 μm or less, provided that the sintering agent is applied to only one side of the thin film material. If the thickness exceeds this, the conversion to amorphous material by sintering, as described below, will not extend to the entire thickness of the object.

[0036] In addition, although boric acid is mixed into the sintering agent in the present invention, this boric acid is added for the purpose of preventing high-temperature cracking of the workpiece and is considered to contribute little to amorphous formation, as will be explained later.

[0037] As the sodium silicate, a commercially available product is used, and carbon powder and boric acid are added to the sodium silicate at a weight ratio of 8:1:1 to 4:3:3. However, the penetration amount of carbon into the thin film material is a correlation with the heating temperature, heating time, and carbon concentration, and the above weight ratio cannot be determined uniformly.

[0038] In Japanese Patent Laid-Open No. 51-73920, the material conditions for changing an iron-based material into an amorphous state are any one or two or more of carbon, phosphorus, and boron. However, it is considered that carbon penetrates into the thin film material by heat after once becoming steel as in the present application.

[0039] In fact, when the applicant measured the concentrations of carbon and boron in the following examples, almost no penetration of boron into the thin film material was observed, and it is considered that carbon contributes to the amorphization. Boron is considered to have a function of preventing high-temperature cracking, similar to a welding agent.

[0040] Further, the sintering agent may be applied to one side or both sides of the thin film material.

[0041] The temperature during sintering is generally 800°C to 1000°C used in the quenching treatment of iron. This temperature is maintained for 15 to 25 seconds, and then it is immersed in water and rapidly cooled.

[0042] As a result, carbon rapidly penetrates into the thin film material, and an amorphous structure is formed by rapid cooling, but a martensite crystal structure is partially formed, and a thin film in which both are mixed is formed.

[0043] Generally, when trying to obtain an amorphous metal by rapidly cooling molten metal, a temperature drop rate of 10 ２ °C / s to 10 ６ °C / s is required. In the present invention, as a starting material, a thin film of steel is used instead of molten metal. This thin film is considered to progress in amorphization due to the synergistic effect that the carbon concentration is significantly reduced in the process before becoming steel, and the thickness is 50 μm or less, and a temperature drop rate inversely proportional to the thickness can be obtained.

[0044] The following examples, Samples 1 to 3, describe a case where a sintering agent, prepared by mixing the above-mentioned carbon powder and boric acid with sodium silicate (weight ratio of sodium silicate 6, carbon powder 2, boric acid 2), was applied to one side, the sintering temperature was set to 900°C, and the holding time at the sintering temperature was 20 seconds.

[0045] <Sample 1 (Invention of the present application: Thickness 13 μm)> First, impurity treatment is performed at the molten metal stage until the carbon content of SUS316L is reduced to about 1 / 100 of the JIS standard upper limit (0.03 w%), and steel with a thickness of about 1 mm is obtained from the molten metal. This steel is cold-rolled after the curing process in a vacuum to obtain an unpolished thin film material with a thickness of 13 μm. After this, the unpolished thin film material is polished to obtain a polished thin film material (the thickness before and after polishing is approximately the same as the thickness after polishing). The 13 μm represents the limit of the applicant's equipment, and it may be thinner.

[0046] Separately, a sintering agent is prepared by mixing commercially available sodium silicate with carbon powder and boric acid in the above proportions. When the sintering agent is applied to the surface of the material and wiped off with a blade, a very thin layer of sodium silicate mixed with carbon powder and boric acid adheres to the surface of the stainless steel thin film, and in particular, the carbon powder and boric acid become embedded in the very fine scratches formed during polishing.

[0047] Therefore, it is preferable that the particle size of the carbon powder be as small as possible, for example, nano-order particles.

[0048] The thin film material in this state is heated to 900°C as described above and held at that temperature for 20 seconds. Then, it is rapidly cooled by immersion in water to complete the sintering process. As a result, as explained below, a portion of the austenite structure transforms into an amorphous structure, and the remainder transforms into a martensite crystalline structure.

[0049] Figure 1(a) shows the X-ray diffraction pattern of the side (front) of sample 1 coated with the sintering agent after sintering, and Figure 1(b) shows the X-ray diffraction pattern of the opposite side (back). There are two points to note here. The reference pattern of X-ray diffraction of SUS316L before processing is shown in the top row of Figure 5(b), which will be described later.

[0050] First, as a result of the sintering of the invention of the present application, on both the front and back surfaces, the curve broadens at a shallow angle with 2θ being 40° or less. This broad curve is presumably likely to be an amorphous structure (on the other hand, there is also a possibility of a baseline). As characteristics of an amorphous material, (1) an increase in resistivity and (2) an increase in magnetic permeability can be cited.

[0051] In the literature, the resistivity of SUS316L is 7.7×10 -７ Ωm, while in Sample 1 it is 14.4×10 -７ Ωm (calculated from the value at the time of applying 0.5 V in Table 2 to be described later), thus satisfying the requirement of (1) above. The applicant does not have equipment for calculating the magnetic permeability as a numerical value, but when a permanent magnet is brought close, SUS316L before processing shows no reaction, while Sample 1 is attracted. Therefore, it also satisfies the requirement of (2) above.

[0052] However, as described below, as an effect of the sintering, a part of the austenite structure (non-magnetic) of the target stainless steel has transformed into a martensite structure (magnetic) (refer to the peaks around 65° and around 82° in FIGS. 1(a) and (b)). Therefore, the cause of the high magnetic permeability cannot be attributed only to amorphization.

[0053] Next, peaks are observed around 65° and around 82° in FIGS. 1(a) and (b) above. On the other hand, FIG. 5(a) is an X-ray diffraction pattern that appears according to the degree of cold rolling of SUS316, and FIG. 5(b) is an X-ray diffraction pattern that appears according to the degree of cold rolling of SUS316L (https: / / tt-tech.jimdo.com / 4-%E3%82%B9%E3%83%86%E3%83%B3%E3%83%A9%E3%82%B9-sus-%E9%92%A2%E3%81%AE%E4%BA%8B%E6%95%85%E4%BE%8B-1 / 4-1-%E3%82%B9%E3%83%86%E3%83%B3%E3%83%A9%E3%82%B9%E9%92%A2%E3%81%AE%E6%A6%82%E8%A6%81-2 / 4-1-2-%E3%82%AA%E3%83%BC%E3%82%B9%E3%83%86%E3%83%B3%E3%82%A4%E3%82%B9us%E9%92%A2%E3%81%AE%E5%8A%A0%E5%B7%A5%E8%AF%B1%E8%B0%B8%E3%83%9E%E3%83%AB%E3%83%86%E3%83%B3%E3%82%BF%E3%83%83%E3%83%88 / , from "Dr. TT's Metal and Material Technology Problem Consultation"). In FIGS. 5(a) and 5(b), the peak of martensite is represented by the symbol M, and the peak of austenite is represented by the symbol A.

[0054] From Figure 5(b), a slight transformation to martensite, which occurs during the 90% rolling process of SUS316L, is visible around 82°. From this, it can be seen that the peaks appearing around 82° in Figures 1(a) and (b) are martensite peaks. From Figure 5(b), the identity of the peaks appearing around 65° in Figures 1(a) and (b) remains unknown.

[0055] Therefore, referring to Figure 5(a), which shows the processing transformation of SUS316, a martensite peak appears around 65°, and it can be understood that the peaks around 65° in Figures 1(a) and 1(b) are also martensite peaks.

[0056] Next, comparing Figures 1(a) and 1(b) above, the peaks around 65° and 82° on the front side where the sintering agent was applied (Figure 1(a)) are higher than on the back side where the sintering agent was not applied. In other words, the effect of sintering is more pronounced on the front side and decreases as you move towards the back side.

[0057] Figures 2(a) and 2(b) are XPS images of the front and back of sample 1, which has a thickness of 13 μm. The fact that the carbon peak indicated by the arrow on the front side (Figure 2(a)) is higher than that on the back side (Figure 2(b)) supports the above. It is thought that this carbon penetration greatly contributes to the formation of the amorphous material shown in Figures 1(a) and 1(b). In other words, if the carbon content is reduced to less than 1 / 10 of the specified amount at the molten metal stage, it becomes easier for carbon to penetrate the thin film material in the subsequent sintering process, and in combination with the presence of chromium, amorphous material is formed.

[0058] To rapidly cool the molten metal and form an amorphous substance, 10 ２ Rapid cooling at a rate of decrease of °C / s or higher is necessary. Although the present invention starts from a thin film of steel rather than from molten metal, the thinness of the material and the low initial concentration of carbon (conversely, the ease with which carbon in the sintering agent penetrates) are thought to produce an effect equivalent to rapid cooling from molten metal as described above.

[0059] Here, considering that the carbon concentration of sample 1 was measured at 0.013 w% and the boron concentration at 0.0002 w%, it can be understood that carbon is the one contributing to amorphous formation. Since no boron peaks appear in Figures 2(a) and (b), this is consistent with the low measured concentration, and it is thought that boron hardly contributes to amorphous formation. Rather, it is thought to have a function similar to that of general welding agents, preventing high-temperature cracking.

[0060] Furthermore, since the material in Figures 2(a) and (b) is stainless steel that originally contains Ni and Mo, the peaks for Ni and Mo should be visible, but they are hidden.

[0061] At what point did the above transformation to martensite occur? Considering that the degree of transformation around 82° in Figure 5(b) is smaller than in Figures 1(a) and (b), and that no transformation to martensite is observed around 65°, it appears that some transformation occurs during the rolling process, but the main transformation to martensite is thought to occur during the sintering process, not the rolling process.

[0062] Furthermore, since no transformation to amorphous material can be observed at all in Figures 5(a) and (b), which show the X-ray diffraction patterns at different degrees of rolling, it can be said that the transformation to amorphous material occurs only during the sintering process.

[0063] From Figure 5(a), it can be seen that stainless steel 316 undergoes some transformation to martensite around 65° and 82° by rolling alone, but the clear transformation seen in Figure 1 is not observed. On the other hand, in the present invention, impurities are treated at the molten metal stage, so the carbon concentration of SUS316 and SUS316L, which have almost the same metal composition, can be made the same at the molten metal stage, and the present invention is applicable not only to SUS316L but also to SUS316.

[0064] <Sample 2 (Product of the present invention: 28 μm)> Figures 3(a) and 3(b) show the X-ray diffraction patterns of the front and back surfaces of SUS316L, which was rolled to a thickness of 28 μm and polished after undergoing the same sintering process as described above, similar to Sample 1, which had gone through the impurity treatment process, steelmaking process, and curing process in a vacuum. While the overall surface is weakly broad, peaks of martensite structure can be seen around 65° and 82°.

[0065] Figure 3(a) is the X-ray diffraction pattern of the side (front) of sample 2 coated with the sintering agent, and Figure 3(b) is the X-ray diffraction pattern of the side (back) not coated with the sintering agent. On both sides, a low, broad curve is observed, with martensite peaks around 65° and 82°. In this case as well, the peaks on the front side are higher. It is unclear from this figure whether the broad curve represents the amorphous phase or the baseline.

[0066] However, as explained below, the resistivity of sample 2 is 14.4 × 10 -７ Considering the extremely high Ωm value, it is thought to represent amorphous material. Furthermore, the peaks around 65° and 82° are larger on the front side than on the back side, indicating that the penetration of the sintering agent is more pronounced on the front side.

[0067] <Sample 3 (Product of the present invention: SUS304, 12 μm)> Figure 4 is an X-ray diffraction pattern of the side of a sample (Sample 3) on which the sintering agent was applied. This sample was obtained by treating molten metal with the composition of stainless steel 304 for impurities, going through a steelmaking process and a curing process in a vacuum, cold rolling it to 12 μm, and then performing the above-mentioned sintering. Similar to Figure 1, peaks appear around 65° and 82° of 2θ, and the surface is broadly raised in the area where 2θ is low.

[0068] Compared to the reference pattern of SUS304 at 90% rolling shown in Figure 6, the peaks around 2θ of 65° and 82° in Figure 4 are considered to be martensite peaks. In addition, in Figure 4, broad elevations indicating amorphous material can be observed in the region where 2θ is lower than 40° (though considerably lower than in Figure 1).

[0069] This is also reflected in the experimental results, which will be explained later, and the exothermic effect is not as large as that shown by 316L. Even if this part is not considered to represent amorphous material, the crystal would only show the two peaks mentioned above.

[0070] <Measurement> (Apparatus) As shown in Figure 7, a strip heater 11 (each of the comparative products below, or each of the samples of the present invention) was wound spirally around a quartz tube 10, minimizing the gaps as much as possible. The probe 21 of the thermometer 20 was inserted into the quartz tube 10, and the apparatus was assembled so that its tip was located in the center of the winding width y.

[0071] Using the above apparatus, voltages were applied at 0.5V intervals between the electrodes (90 mm) of each comparative product and the present invention, and the voltage, current, and temperature were measured, and the resistance and power were calculated.

[0072] <Measurement Results 1> Table 1(a) shows the measured voltage, current, and temperature when an unprocessed SUS316L with a thickness of 9 μm was cut to a width of 5 mm to form comparison sample 1a, with an electrode distance of 90 mm, and the resistance and power calculated based on these measured values. Table 2 shows the measured voltage, current, and temperature when the sintered sample 1 (thickness 13 μm) was cut to a width of 5 mm to form sample 1s, with an electrode distance of 90 mm, and the calculated values ​​of resistance and power.

[0073] Table 1(b) is presented based on the data in Table 1(a), converted to the same value as sample 1s with a thickness of 13 μm, and designated as comparative product 1b. The conversion from the data of comparative product 1a with a thickness of 9 μm (Table 1(a)) to comparative product 1b with a thickness of 13 μm is calculated as: Current Ia of comparative product 1a × 13 / 9 = Current Ib of comparative product 1b.

[0074] Furthermore, although the thickness increases from 9 μm to 13 μm, and the current increases accordingly, the increased current is responsible for the temperature corresponding to the increased thickness, so the temperature at each voltage remains unchanged between comparative samples 1a and 1b.

[0075] <Sample 1s and comparative samples 1a and 1b> Using the resistance value of comparative sample 1b at 0.5V (resistance value at a temperature close to room temperature) of 1.07Ω, the resistivity is 7.7 × 10⁻⁶ -７The calculated value is Ωm, which closely matches the value in the literature.

[0076] In contrast, the resistance of sample 1s is 2.00Ω (resistivity 14.4 × 10) when using the current value at a voltage of 0.5V. -７ It shows a value of Ωm, which is slightly less than double the value in the literature at near room temperature.

[0077] Next, the resistance values ​​of the unprocessed samples (comparison sample 1a, comparison sample 1b) and sample 1s show only a small temperature dependence. As will be explained later, the resistance of unprocessed SUS304 has a large temperature dependence, but for SUS316L, both processed and unprocessed samples show little temperature dependence of resistance. This is presumed to be due to the addition of Mo.

[0078] Although there is a difference in thickness between 9 μm and 13 μm, we will compare the raw data of comparison product 1a and sample 1s.

[0079] In Table 2, sample 1s achieves 900°C with an input energy of 70W (13V) (more precisely, the input energy per second, where 1W = 1J / s, and the same applies hereafter). In comparison product 1a in Table 1a, an input energy very close to this is obtained with an applied voltage of 12-12.5V, but only around 850°C is achieved. Also, in Table 2, sample 1s achieves 882°C with an input energy of 60W (12V), but in comparison product 1a in Table 1a, an input energy close to this is obtained with an applied voltage between 11.0-11.5V, but only around 800°C is achieved.

[0080] Generally, the relationship between the input energy Q and the temperature K is determined by the heat capacity and specific heat of the substance and is given by the following equation (1).

[0081] Q = mcΔK ... (1) m: mass, c: specific heat, ΔK: temperature change. The following description assumes that the specific gravity is the same before and after the sintering process.

[0082] Since sample 1s, with a thickness of 13 μm, has a mass m that is more than 40% greater than that of comparative sample 1a, with a thickness of 9 μm, it can be inferred that the specific heat of sample 1s is more than 40% less than that of comparative sample 1a.

[0083] Next, compare the value of comparative product 1b in Table 1(b) with the value of sample 1s in Table 2.

[0084] Sample 1s achieves 900°C with an input energy of 70W (13V). Comparative sample 1b achieves a similar input energy with a voltage between 10.0 and 10.5V, but only achieves around 750°C. Furthermore, while sample 1s achieves 882°C with an input energy of 60W (12V), comparative sample 1b achieves a similar input energy with a voltage of 9.5V, but only achieves a temperature of around 700°C.

[0085] From the above, it can be understood that when sintering is performed as in the present invention, the material transforms into an amorphous structure, improving heat resistance and reducing specific heat compared to the material before processing. Therefore, when the same amount of heat is applied to comparative product 1b and sample 1s, sample 1s will reach a higher temperature.

[0086] <Considerations regarding specific heat> Here, the specific heat is known to be c ０ We will attempt to calculate the specific heat of sample 1s (target substance) based on comparative sample 1b (reference substance) which has a specific heat of 500 J / kg·s.

[0087] Focusing on the energy input per second and the temperature change at that time, the power W (watts) shown in each table can be used as the input energy Q in equation (1).

[0088] W ０ : Energy input to the reference substance, m ０ : Mass of the reference substance, c ０ Specific heat of the reference substance, ΔT ０ : Temperature change of the reference substance. W １ : Energy input to the target substance, m １ : Mass of the target substance, c １ : Specific heat of the substance, ΔT １ The temperature change of the target substance is as follows:

[0089] W ０ = m ０ c ０ ΔT ０ ... (2) W １ = m １ c １ ΔT １ ... (3) Here, m０ = m １ Assuming the temperature change per second is the same ΔT ０ = ΔT １ If so, then the specific heat c ０ , c １ The difference is the energy W given per second. ０ , W １ This appears as a difference. Conversely, W ０ = W １ If so, then the specific heat c ０ , c １ The difference is ΔT ０ ΔT １ This appears as a difference, but here ΔT ０ ΔT １ Since measurement is not possible, we will consider the former case.

[0090] However, the above temperature ΔT ０ and ΔT １ The temperature before (and after) the change must be the same. From equations (2) and (3) above, m ０ = m １ ΔT ０ = ΔT １ Then we obtain the following equation (4).

[0091] W ０ / W １ = c ０ / c １ c １ = c ０ W １ / W ０ ... (4) That is, the specific heat c of the substance in question １ The specific heat c of the reference substance ０ The ratio of energy W to the energy supplied to both in order to maintain a specific temperature. １ / W ０ It can be obtained by multiplying by [a certain factor].

[0092] For sample 1s (the target substance), an input energy of 60 W (12 V) results in a temperature of 882°C. For the corresponding comparative sample 1b (the reference substance), the input energy was calculated to be 112 W, and the specific heat was calculated as 500 × 60 / 112, yielding 267 J / kg·s. Calculating the specific heat for each temperature range from 50°C to 882°C in this manner yielded roughly similar values ​​across the entire range, with an average of 269 J / kg·s.

[0093] In other words, the specific heat of sample 1s was found to be more than 40% lower than that of the unprocessed product (comparison product 1b), which is in good agreement with the inferences made from comparing the mass m of comparison product 1a and sample 1s.

[0094] <Measurement Results 2> Table 3 shows the measured values ​​of voltage, current, resistance, and temperature, as well as the calculated values ​​of resistance and power, for comparison sample 2, which was cut from unprocessed SUS316L with a thickness of 28 μm to a width of 5 mm, with an electrode spacing of 90 mm. Table 4 shows the measured values ​​of voltage, current, temperature, resistance, and power, as well as the calculated values ​​of resistance and power, for sample 2s, which was cut from sample 2, which was processed from SUS316L with a thickness of 28 μm to a width of 5 mm, with an electrode distance of 90 mm.

[0095] In this case as well, the resistance of comparative product 2 does not change much regardless of the temperature rise, similar to comparative product 1a.

[0096] Table 4 shows that when 68.32W (12V) was applied to sample 2s, the temperature was 898°C. For comparative product 2, the corresponding applied energy was between 6.5V and 7.0V, and only about 729°C was obtained. Also, in Table 4, when 52.43W was applied to sample 2s, the temperature was 802°C. For comparative product 2, the corresponding applied energy was between 5.5V and 6.0V, and only about 644°C was obtained.

[0097] Following the procedure used to determine the specific heat of sample 1s, the specific heat of sample 2s was determined to be 310 J / kg·T, which is slightly higher than that of sample 1s. However, the effect of the present invention, which is to reduce the specific heat, can also be observed in sample 2s.

[0098] <Measurement Results 3> Table 5a shows the measured values ​​of current, temperature, resistance, and power associated with the change in applied voltage when comparing a 5 mm wide sample of unprocessed SUS304 with a thickness of 9 μm, with an electrode spacing of 90 mm. Table 6 shows the measured values ​​of resistance and power when comparing a 5 mm wide sample of sample 3s, which was sintered using the same method as above, with an electrode spacing of 90 mm, with current, temperature, resistance, and power associated with the change in applied voltage.

[0099] Table 5b shows the values ​​obtained by converting the data of the 9 μm comparative sample 3a to the 12 μm sample. The conversion from comparative sample 3a to 3b was performed by setting the current of comparative sample 3b = current of comparative sample 3a × 12 / 9, and assuming that the temperatures of comparative sample 3a and comparative sample 3b remained unchanged at each voltage.

[0100] From the data at 0.5V applied in Table 5a, the resistivity of comparative product 3a (3b) is 7.15 × 10⁻⁶. -７ It was calculated as Ωm, and the literature value is 7.2 × 10⁻⁶. -７ The value is close to Ωm. Also, perhaps because comparative product 3a (3b) does not contain Mo, the resistance value, unlike comparative product 1a (1b), exhibits the temperature resistance characteristics of a metal.

[0101] In contrast, the resistivity of sample 3s, as shown in Table 6 when 0.5V is applied, is 18.5 × 10⁻⁶. -７ The calculated resistance is Ωm, which is very high. Furthermore, in sample 3s, the resistance value does not change with increasing temperature, or even decreases.

[0102] Sample 3s (Table 6) obtained 882°C when 84.24W (12V) was applied. When comparative sample 3b was given a similar input energy temperature, only a temperature of about 786°C was obtained, as shown in Table 5(b). Also, in Table 6, 819°C was obtained when 71.4W (11V) was applied. When comparative sample 3b was given a similar input energy temperature, only a temperature of about 738°C was obtained, as shown in Table 5(b). Therefore, a certain degree of specific heat reduction effect is observed even with SUS304, but not to the same extent as with SUS316L (Sample 1, Sample 2).

[0103] Using the same procedure as for calculating the specific heat of sample 1s, the specific heat of sample 3 is calculated to be 390 J / kg·K. This value is larger than (and therefore less effective than) the value for sample 1s, but smaller than that of nichrome, iron, and chromium-aluminum alloys. It can also be easily estimated that similar results would be obtained for SUS304L.

[0104] <Metallic Crystals> In Figures 1, 3, and 4, peaks of metallic crystals are observed only around 65° and 82° of 2θ. The peak around 65° is thought to correspond to the 200-face peak of ferrite, and the peak around 82° is thought to correspond to the 211-face peak of ferrite. Since the subject is stainless steel and not iron, these are thought to be martensite peaks.

[0105] Furthermore, the fact that only two peaks appear here means that the crystals of each sample (1s, 2s, and 3s) are aligned in two directions, and that their intensity is higher than that of the starting material (austenite).

[0106] Furthermore, if the raw material is rapidly cooled from a molten state, the entire material changes to an amorphous state, and the peaks shown in Figures 1 and 3 do not appear. Therefore, the martensite peaks in Figures 1, 3, and 4 indicate that a thin film was formed before morphogenesis, regardless of whether it occurred during the rolling or sintering process. Conversely, if morphogenesis is performed using the ion implantation method, the material will be in a state where amorphous austenite crystals are mixed in, as shown in Figure 5, etc.

[0107] <Recrystallization> Generally, amorphous alloys recrystallize in high-temperature environments for extended periods (for example, Journal of the Japan Institute of Metals, No. 51 (1987), pp. 95-101). However, when samples 1s, 2s, and 3s of the present invention were maintained at 800°C for 10 hours, there was no change in their resistance values, confirming that they had not recrystallized.

[0108] <Thickness and Wire Material> From Figures 3(a) and 3(b) above, it can be inferred that a considerable effect can be obtained even with a thickness of around 30 μm, and that as long as the sintering agent is applied to one side during manufacturing, an effective effect can be obtained even for thin films with a thickness of about 50 μm.

[0109] When sintering agent is applied to both sides, the effect can be expected up to about 100 μm, but considering that the cooling rate slows down as the thickness increases, it is questionable whether the expected results will be obtained.

[0110] Furthermore, as shown in equation (1), the energy required to bring the heater to a specific temperature depends not only on the specific heat c but also on the mass m. Therefore, discussing the magnitude of the specific heat is not very meaningful when the mass can be freely adjusted.

[0111] On the other hand, stainless steel possesses heat resistance and durability to temperatures above 1000°C even at a thickness of around 10 μm, and as mentioned above, not only its specific heat c but also its mass m can be reduced. Moreover, at this thickness range, the types of alloys that can be realized are limited. In reality, as described in the section on conventional technology, the thinnest commercially available iron, chromium, and aluminum alloys are strip materials with a thickness of 80 μm, and the smallest wire materials have a diameter of 1 mm.

[0112] Considering the above, the most important aspect of the present invention is a method (amorphization) for obtaining an alloy that has strength and heat resistance even when its thickness is reduced (diameter is reduced), and also has high resistivity and low specific heat, and the alloy obtained as a result.

[0113] To produce wire, it is sufficient to cut the processed product obtained as a thin film as described above into a wire shape. Alternatively, a wire-shaped processed product can be obtained by applying the sintering agent around an unprocessed wire and sintering it using the procedure described above. Conversely, a block can also be created by stacking multiple thin films after sintering or by winding them in a spiral shape.

[0114] As explained above, the amorphous alloy according to the present invention has high resistivity, low temperature dependence of resistance, and low specific heat. Therefore, when used as a heater, it can achieve a higher temperature than conventional products even when the same mass and the same power are applied.

[0115] Furthermore, the carbon source contained in the sintering agent may be carbon powder or an organic material containing carbon. Although only carbon has been described, phosphorus may be used instead of carbon as a material contained in the sintering agent. While both SUS316 and SUS304 stainless steels are permitted to contain phosphorus up to an upper limit of 0.045 w%, in this invention, the concentration is reduced to 1 / 10 or less during the impurity treatment process. Since phosphorus is an unavoidable substance in iron, lowering its concentration before it becomes steel makes it easier for it to penetrate the thin film material during the sintering process, similar to carbon. In this case, phosphoric acid is used as the phosphorus source for the sintering agent. This phosphorus source can be used in addition to or in place of the carbon source.

[0116] Furthermore, as mentioned above, in addition to C and P, Si is also present as an impurity in iron. However, despite the sintering agent containing sodium silicate, which is a silicon source, Si does not appear in the XPS diagram in Figure 2. This is likely because Si is difficult to incorporate into thin film materials.

[0117] Furthermore, the XRD angles described above are somewhat vague, being stated as being "around 65°" and "around 82°". By referring to multiple data, it can be estimated that "around 65°" is between 64° and 65°, and "around 82°" is between 81° and 82°.

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[0124] 10 Quartz tube 11 Heater 20 Thermometer 21 Probe

Claims

1. A thin film material having a thickness of 50 μm or less and having a metallic composition of austenitic stainless steel, characterized in that it comprises an amorphous structure and a metallic crystalline structure which is mixed with the amorphous structure and whose surface waveform on XRD shows 2θ only around 65° and 82°.

2. A thin film material made of a resistor alloy according to claim 1, wherein the austenitic stainless steel is any of SUS316, SUS316L, SUS304, or SUS304L.

3. A method for producing a thin film material made of a resistor alloy, comprising: an impurity treatment step of removing carbon from a molten austenitic stainless steel to a concentration of 1 / 10 or less of the upper limit of the JIS standard; a cold rolling step of obtaining a thin film material by cold rolling a steel of a predetermined thickness obtained from the molten metal from which the impurities have been removed to a thickness of 50 μm or less; a coating step of applying a sintering agent, which is a viscous liquid containing a carbon source in sodium silicate, to one surface of the thin film material; a heating step of heating the thin film material coated with the sintering agent to 800 to 1000°C; and a cooling step of rapidly cooling the heated thin film material with water.

4. A method for producing a thin film material made of a resistor alloy according to claim 3, wherein the carbon source is carbon powder.

5. A method for producing a thin film material made of a resistor alloy according to claim 3, wherein the austenitic stainless steel is any of SUS316, SUS316L, SUS304, or SUS304L.

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