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

Abstract

To obtain a resistive alloy with high resistivity, low temperature dependence of resistivity, and low specific heat. [Solution] The resistor is a thin film material consisting of an amorphous structure and a martensitic structure mixed in with the amorphous structure. A sintering agent containing a carbon source is applied to one or both sides of a thin film material of austenitic stainless steel with a thickness of 50 μm or less. Next, the thin film material to which the sintering agent has been applied is heated to 800 to 1000°C. The heated thin film material is rapidly cooled. This makes it possible to form a thin film in which an amorphous structure and a martensitic structure are mixed. The sintering agent is a viscous liquid containing a carbon source in sodium silicate.

Description

[Technical Field]

[0001] The present invention relates to a resistor alloy, and more particularly to a resistor alloy using a thin film material of austenitic stainless steel as a starting material. [Background technology]

[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 so-called 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. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2020-146714 [Patent Document 2] Japanese Patent Publication No. 2018-151172 [Patent Document 3] Japanese Patent Application Publication No. 51-73920 [Overview of the project] [Problems that the invention aims to solve]

[0008] It is predicted that high thermal efficiency can be obtained by using a strip-shaped heater material to increase the heat dissipation area. Currently, the materials that can be seen on the internet for strip-shaped heater materials include stainless steel, iron, chromium, and aluminum alloy (trade name Kanthal®).

[0009] Since the melting point of stainless steel is 1400-1500°C, it can be used at temperatures of around 1000°C. Therefore, we will consider a heater using a 30μm thick stainless steel strip.

[0010] The resistivity (SUS316L) is 7.7 × 10⁻⁶ as stated in the literature. ?7 To obtain a stainless steel heater with a resistance of Ωm, a width of 5 mm, a thickness of 30 μm, and a power output of 1 kW (10 Ω) at a voltage of 100 V, a length of material slightly less than 2 m would be required. Considering the temperature dependence of the resistance, the required length could be reduced by 30%, but the need for a long piece of material remains.

[0011] The resistivity of the aforementioned iron, chromium, and aluminum alloy is 14.5 × 10⁻⁶. ?7 Since it is Ωm, if the thickness is 30 μm, then about half the length mentioned above would suffice, but currently only materials with a thickness of 80 μm or more are commercially available. 1729129614476_0.html Considering the information in the catalog, it is likely that it cannot be made any thinner, or that even if it were made thinner, it would cause problems with its use.

[0012] Furthermore, considering the specific heat of various heater materials in relation to the present invention, there are various types of stainless steel, but all have a specific heat of 500 J / kg·K. Nichrome has a resistivity of 10.8 × 10 ?7 Its Ωm is relatively high, but it is also highly temperature-dependent, and its specific heat is 460 J / kg·K, which is not significantly lower than that of stainless steel.

[0013] Furthermore, the resistivity of the aforementioned iron, chromium, and aluminum alloy is 14.5 × 10 ?7 Its high Ωm density, low temperature dependence, and high heat resistance make it useful as a heater, but its specific heat of 420 J / kg·K is not 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 injecting ions of elements such as carbon, phosphorus, and boron into an object using an ion implantation apparatus. However, with this method, only products of a size limited by the size of the ion implantation apparatus can be obtained.

[0018] The present invention has been proposed in view of the above-mentioned conventional circumstances, and aims to obtain a strip-shaped or linear heater material with high resistivity, low temperature dependence of resistivity, low specific heat, high durability and heat resistance, and a length according to the situation.

Means for Solving the Problems

[0019] The invention of the present application is a thin film material with a thickness of 50 μm or less of the metal composition of austenitic stainless steel, and is a resistor alloy having an amorphous structure and a crystal structure that is mixed with the amorphous structure and has 2θ only in the vicinity of 65° and 82° in the XRD waveform.

[0020] The above resistor alloy is manufactured by the following procedure.

[0021] Inevitable impurities (C, Si, S, P) are contained in austenitic stainless steel. Here, attention is paid to carbon, and impurities are removed from the molten metal of the metal composition of austenitic stainless steel so that the carbon concentration becomes 1 / 10 or less of the upper limit value of the JIS standard (impurity treatment step). Steel of a predetermined thickness is obtained from the molten metal from which the carbon has been removed (steelmaking step). A thin film material obtained by cold rolling the obtained steel to 50 μm or less is obtained (cold rolling step). A sintering agent containing a carbon source is applied to one surface of the thin film material (coating step). The thin film material coated with the sintering agent is heated to 800 to 1000 °C (heating step). The heated thin film material is quenched with water (cooling step).

[0022] The sintering agent is a mucous substance in which a carbon source is mixed with sodium silicate. The carbon source can employ carbon powder. Also, although the type of the austenitic stainless steel is not limited, any of SUS316, SUS316L, and 304 is more preferable, and particularly SUS316 and SUS316L are preferable.

Effects of the Invention

[0023] This invention allows for the production of an amorphous resistive alloy by processing steel obtained from molten metal that has been reduced in impurity concentration (carbon concentration) through a conventional manufacturing process. This resistive alloy possesses high resistivity, corrosion resistance, and heat resistance, and because of its low specific heat, it can be used as a heater material to achieve high temperatures with minimal energy input. [Brief explanation of the drawing]

[0024] [Figure 1] This is the X-ray diffraction pattern of sample 1 (13 μm). [Figure 2] This is an XPS image of sample 1 (13 μm). [Figure 3] This is the X-ray diffraction pattern of sample 2 (28 μm). [Figure 4] This is the X-ray diffraction pattern of sample 3 (12 μm). [Figure 5] This is the reference pattern for the X-ray diffraction pattern of stainless steel 316 and 316L. [Figure 6] This is the standard pattern for the X-ray diffraction pattern of stainless steel 304. [Figure 7] This diagram shows the temperature measurement process. [Modes for carrying out the invention]

[0025] The present invention uses austenitic stainless steel SUS316L (or 316) as a starting material. Its metal composition, in weight percent, is Cr: 16.00~18.00, Ni: 10.00~15.00, Mo: 2.00~3.00, 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 can be used. Its metal composition, in weight percent, is Cr: 18.00-20.00, Ni: 8.00-10.50, 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 (compared to 0.08% by weight for SUS316 and 304), here, steel with carbon removed to a technically feasible level—less than 1 / 10—is used. In the examples below, the carbon content is reduced to approximately 1 / 100.

[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 approximately 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 approximately 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, thus ensuring uniformity of properties even in 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 invisible scratches on both surfaces. In addition, invisible scratches can 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 less than 1 μm).

[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 should preferably be 50 μm or less, as long as 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] Commercially available sodium silicate is used as the above-mentioned sodium silicate, and carbon powder and boric acid are added to the sodium silicate in a weight ratio of 8:1:1 to 4:3:3. However, the amount of carbon penetration into the thin film material is correlated with the heating temperature, heating time, and carbon concentration, and the above weight ratio cannot be uniformly determined.

[0038] In Japanese Patent Application Laid-Open No. Sho 51-73920, the material conditions for changing iron-based materials into amorphous state include any one or two or more of carbon, phosphorus, and boron. However, it is considered that carbon is the one that penetrates into the thin-film material by heat after it has once become 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] Also, the sintering agent may be applied to one side or both sides of the thin-film material.

[0041] The temperature during sintering is generally from 800°C to 1000°C, which is 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. However, a martensite crystal structure is formed in part, 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 invention of the present application, as a starting material, a thin film of steel is used instead of molten metal. This thin film has a significantly reduced carbon concentration in the process before becoming steel, and a thickness of 50 μm or less. It is considered that amorphization progresses due to the synergistic effect that a temperature drop rate inversely proportional to the thickness can be obtained.

[0044] Hereinafter, Samples 1 to 3 will be described by taking an example where a sintering agent in which the above carbon powder and boric acid are mixed into sodium silicate (weight ratio of sodium silicate 6, carbon powder 2, and boric acid 2) is applied to one side, the sintering temperature is 900°C, and the holding time of the sintering temperature is 20 seconds.

[0045] <Sample 1 (Invention in this application: Thickness 13 μm)> First, impurity treatment is performed on the molten metal 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 this molten metal. This steel is then 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). 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. 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.

[0048] Figure 1(a) shows the X-ray diffraction pattern of the side (front) of sample 1 where the sintering agent was applied, 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.

[0049] 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 (while 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.

[0050] 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 0.5 V applied in Table 2 described later), satisfying the requirement of (1) above. Although the applicant does not have equipment for calculating the magnetic permeability as a numerical value, when a permanent magnet is brought close, the pre-processed SUS316L does not react at all, but Sample 1 is attracted. Therefore, it also meets the requirement of (2) above. However, as described below, as an effect of the sintering, a part of the austenite structure (non-magnetic) of the stainless steel target 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. 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%B1%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 Consultation on Metal and Material Technology Problems"). In FIGS. 5(a) and 5(b), the peak of martensite is represented by symbol M, and the peak of austenite is represented by symbol A.

[0051] 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.

[0052] 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 (b) are also martensite peaks.

[0053] 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.

[0054] Figures 2(a) and (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 (b). In other words, if the carbon content is reduced to less than 1 / 10 of the specified amount at the molten 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.

[0055] 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 required. 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.

[0056] 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 concentrations mentioned above, and it is thought that boron contributes very little to amorphous formation. Rather, it is thought to have a function similar to that of general welding materials, preventing high-temperature cracking.

[0057] Furthermore, since the subjects in Figures 2(a) and (b) are stainless steel that originally contains Ni and Mo, the peaks for Ni and Mo should be visible, but they are hidden.

[0058] 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.

[0059] 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.

[0060] From Figure 5(a), it can be seen that stainless steel 316 undergoes some transformation to martensite around 65° and 82° during 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.

[0061] <Sample 2 (Invention of this application: 28 μm)> Figures 3(a) and (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, following the impurity treatment, steelmaking, and vacuum curing processes as in Sample 1. While the overall surface is weakly broad, peaks of martensitic structure can be seen around 65° and 82°.

[0062] 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.

[0063] However, as explained below, the resistivity of sample 2 is 14.4 × 10⁻⁶ ?7 Given its 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.

[0064] <Sample 3 (Product of the present invention: SUS304, 12μm)> Figure 4 shows the 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 stainless steel 304 with impurities, going through the steelmaking process and curing process in a vacuum, cold rolling it to 12 μm, and then sintering it as described above. Similar to Figure 1, peaks appear around 2θ 65° and 82°, and there is a broad elevation in the lower 2θ range, but not as pronounced as in Figure 1. In addition, high peaks are also observed at 2θ below 20°.

[0065] Comparing this to the reference pattern of SUS304 at 90% rolling shown in Figure 6, the peaks around 65° and 82° 2θ are thought to be martensite peaks, but the peaks appearing below 20° have not yet been identified. These are likely substances derived from sodium silicate or boric acid used as sintering agents, but based on estimations from Figures 5 and 6, they are not thought to be peaks of metal crystals. In any case, it does not exhibit a clean amorphous curve like 316L.

[0066] This is also reflected in the experimental results, which will be explained later, and the heat generation effect is not as large as that shown by 316L.

[0067] <Measurement> (Device) As shown in Figure 7, a strip heater 11 (each of the comparative products below, or each of the samples of the present invention) is wound spirally around a quartz tube 10 with the gaps as small as possible, and the probe 21 of the thermometer 20 is inserted into the quartz tube 10, and the device is assembled so that the tip of the probe is located in the center of the winding width y.

[0068] Using the above apparatus, voltages were applied at 0.5V intervals between the electrodes (90mm) of each comparative product and the present invention, and the voltage, current, and temperature were measured, and the resistance and power were calculated.

[0069] <Measurement result 1> Table 1(a) shows the measured voltage, current, and temperature, as well as the calculated resistance and power, for comparison sample 1a, which was cut from an unprocessed SUS316L with a thickness of 9 μm to a width of 5 mm, with an electrode distance of 90 mm. Table 2 shows the measured voltage, current, and temperature, as well as the calculated resistance and power, for sample 1s, which was cut from the sintered sample 1 (thickness of 13 μm) to a width of 5 mm, with an electrode distance of 90 mm.

[0070] 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 for 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.

[0071] 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.

[0072] <Sample 1s and comparative products 1a and 1b> Using the resistance value of comparison product 1b at 0.5V (resistance value at a temperature close to room temperature) of 1.07Ω, the resistivity is 7.7 × 10⁻⁶. ?7 The result is calculated as Ωm, which closely matches the value in the literature.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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, a similar input energy 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, a similar input energy is obtained with an applied voltage between 11.0-11.5V, but only around 800°C is achieved.

[0077] 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 equation (1) below.

[0078] 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.

[0079] 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, which has 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.

[0080] Next, we compare the value of comparison product 1b in Table 1(b) with the value of sample 1s in Table 2.

[0081] Sample 1s achieves 900°C with an input energy of 70W (13V). For comparison product 1b, a nearly equivalent input energy is between 10.0 and 10.5V, but only around 750°C is achieved. Furthermore, while Sample 1s achieves 882°C with an input energy of 60W (12V), comparison product 1b, with a similar input energy of 9.5V, only achieves a temperature of around 700°C.

[0082] 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.

[0083] <Considerations regarding specific heat> Here, we attempt to calculate the specific heat of sample 1s (target substance) based on comparative sample 1b (reference substance) whose specific heat c0 (= 500 J / kg·s) is known.

[0084] 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).

[0085] If W0 is the energy input to the reference substance, m0 is the mass of the reference substance, c0 is the specific heat of the reference substance, and ΔT0 is the temperature change of the reference substance, then W1 is the energy input to the target substance, m1 is the mass of the target substance, c1 is the specific heat of the target substance, and ΔT1 is the temperature change of the target substance, then the following applies.

[0086] W0 = m0c0ΔT0···(2) W1 = m1c1ΔT1···(3) Here, assuming m0 = m1 and the temperature change per second is the same ΔT0 = ΔT1, the difference in specific heats c0 and c1 manifests as a difference in the energy W0 and W1 supplied per second. Conversely, if W0 = W1, the difference in specific heats c0 and c1 manifests as a difference in ΔT0 and ΔT1, but since we cannot measure ΔT0 and ΔT1 here, we will consider the former case.

[0087] However, the temperatures before (and after) the change in temperature ΔT0 and ΔT1 must be the same. From equations (2) and (3) above, if we set m0 = m1 and ΔT0 = ΔT1, we obtain the following equation (4).

[0088] W0 / W1=c0 / c1 c1 = c0W1 / W0··(4) In other words, the specific heat c1 of the target substance is obtained by multiplying the specific heat c0 of the reference substance by the ratio W1 / W0 of the energy required to maintain a specific temperature for both substances.

[0089] For sample 1s (target substance), an input energy of 60W (12V) results in a temperature of 882°C. The corresponding input energy for comparative sample 1b (reference substance) is calculated to be 112W, and the specific heat is 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.

[0090] 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.

[0091] <Measurement result 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.

[0092] In this case as well, the resistance of comparison product 2 does not change much regardless of the temperature rise, similar to comparison product 1a.

[0093] Table 4 shows that when 68.32W (12V) was applied to sample 2s, the temperature was 898°C. For comparison product 2, the corresponding applied energy was between 6.5V and 7.0V, resulting in a temperature of only about 729°C. Also, in Table 4, when 52.43W was applied to sample 2s, the temperature was 802°C. For comparison product 2, the corresponding applied energy was between 5.5V and 6.0V, resulting in a temperature of only about 644°C.

[0094] 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 a decrease in specific heat, can also be observed in sample 2s.

[0095] <Measurement result 3> Table 5a shows the measured values ​​of current, temperature, resistance, and power in response to changes in applied voltage when comparing a 5mm wide sample of unprocessed SUS304 with a thickness of 9μm, designated as comparative sample 3a, with an electrode spacing of 90mm. Table 6 shows the measured values ​​of resistance and power when comparing a 5mm wide sample of sample 3s, which was sintered using the same method as above, with an electrode spacing of 90mm, and the current, temperature, and resistance in response to changes in applied voltage.

[0096] 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 assuming that the current of comparative sample 3b = the current of comparative sample 3a × 12 / 9, and that the temperatures of comparative sample 3a and comparative sample 3b remained constant at each voltage.

[0097] From the data at 0.5V applied in Table 5a, the resistivity of comparative product 3a (3b) is 7.15 Ωm × 10⁻¹⁵ ?7 It was calculated as follows, and the literature value is 7.2 Ωm × 10 ?7 The value is close to that. Also, perhaps because comparative product 3a (3b) does not contain Mo, the resistance value, unlike comparative product 1a (1b), shows the temperature resistance characteristics of a metal.

[0098] In contrast, the resistivity of sample 3s, as shown in Table 6 when 0.5V is applied, is 18.5Ωm × 10 ?7 The calculated value is very high. Furthermore, in sample 3s, the resistance value does not change with increasing temperature, or even decreases.

[0099] 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 approximately 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 approximately 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).

[0100] Using the same procedure as for calculating the specific heat of sample 1s, the specific heat of sample 3 can be calculated as follows: 1729129614476_1 The value obtained is kg·K. This value is greater than the value obtained for sample 1s (indicating a weaker effect), but smaller than that obtained for nichrome, iron, and chromium-aluminum alloys.

[0101] <Metal crystals> In Figures 1, 3, and 4, peaks of metallic crystals are observed only around 2θ of 65° and 82° (peaks at angles lower than 20° in Figure 4 are not considered to be metallic crystals). The peak around 65° appears to correspond to the 200-face peak of ferrite, and the peak around 82° appears 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.

[0102] Furthermore, the fact that only two peaks are present here means that the crystals of each sample (1s, 2s, and 3s) are aligned in two directions, indicating that the intensity is higher than that of the starting material (austenite).

[0103] 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.

[0104] <Recrystallization> Generally, amorphous alloys recrystallize under prolonged high-temperature conditions (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.

[0105] <Thickness and wire weight> 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 only one side during manufacturing, an effective effect can be obtained even for thin films with a thickness of about 50 μm.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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 it is permitted that both SUS316 and SUS304 stainless steels 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.

[0113] 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 image in Figure 2. This is likely because Si is difficult to incorporate into thin film materials.

[0114] 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 approximately 65°, and "around 82°" is somewhere between 82° and 83°.

[0115] [Table 1]

[0116] [Table 2]

[0117] [Table 3]

[0118] [Table 4]

[0119] [Table 5]

[0120] [Table 6] [Explanation of symbols]

[0121] 10 Quartz tube 11 Heater 20 thermometer 21 probes

Claims

1. A thin film material with a metal composition of austenitic stainless steel and a thickness of 50 μm or less, Amorphous tissue and, The amorphous structure is mixed with a metallic crystal structure where the surface waveform on XRD shows that 2θ is only around 65° and 82°. A resistor alloy characterized by having the following properties.

2. The resistor alloy according to claim 1, wherein the austenitic stainless steel is SUS316 or SUS316L.

3. For molten austenitic stainless steel, an impurity treatment process is performed to remove carbon so that the concentration becomes 1 / 10 or less of the upper limit value according to JIS standards. A cold rolling process to obtain a thin film material by cold rolling a steel of a predetermined thickness to 50 μm or less, obtained from molten metal from which the above impurities have been removed, A coating step of applying a sintering agent containing a carbon source to one surface of the thin film material, A heating step of heating the thin film material to which the sintering agent has been applied to 800 to 1000°C, A cooling step is performed in which the heated thin film material is rapidly cooled with water. A method for manufacturing a resistor alloy, characterized by comprising the following features.

4. The method for producing a resistor alloy according to claim 3, wherein the sintering agent is a viscous liquid containing a carbon source in sodium silicate.

5. The method for producing a resistor alloy according to claim 3, wherein the carbon source is carbon powder.

6. The method for manufacturing a resistor alloy according to claim 3, wherein the austenitic stainless steel is SUS316 or SUS316L.

7. The method for producing a resistor alloy according to claim 4, wherein the sodium silicate is in a viscous state containing a phosphorus source in addition to, or instead of, a carbon source.

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