JPH05214493A - Fe-cr-al alloy for strain gage and its manufacture as well as sensor device - Google Patents

Abstract

PURPOSE:To develop an alloy for a strain gage having a high gage rate and a relatively low resistance temp. coefficient by meling an Fe-Cr-Al alloy having a specified compsn., casting the ingot at a specified temp. and thereafter finishing it into a disk shape or a fine wire. CONSTITUTION:The raw material metal of an Fe-Cr-Al alloy essentially consisting of, by weight, 65 to 85% Fe, 13 to 23% Cr and 2 to 15% Al and furthermore contg., as accesory components, total <=5.0% of one or >= two kinds among Ni, Cu, Co, Mo, W, Nb, Ta, V, Zr, Mn, Ti, Si, Mg, Ca and rare earth elements is heated to a one directly below the m.p. in vacuum to release the contained gas. After that, it is heated and melted in an atmosphere of an inert gas such as Ar to remove oxide slag and is cast. The obtd. ingot is cast at 1000 to 1200 deg.C and is worked into a disk shape or wire rod. This stock is cooled by air cooling or at 10 to 150 deg.C/min cooling rate to manufacture the objective alloy for a strain gage having 2 to 4 rage rate and +500 to -250X10<-6>/ deg.C resistance temp. coefficient.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Fe-Cr-Al based strain gauge alloy. More specifically, the present invention contains iron (Fe), chromium (Cr) and aluminum (Al) as main components, and nickel (Ni), copper (Cu), cobalt (Co), molybdenum (Mo) and tungsten as sub-components. (W), niobium (Nb), tantalum (Ta), vanadium (V), zirconium (Z
r), manganese (Mn), titanium (Ti), silicon (Si), magnesium (Mg), calcium (Ca)
And an alloy for a Fe-Cr-Al-based strain gauge consisting of one or more rare earth elements and 5% or less in total, and a method for producing the same, the object of which is a high gauge ratio of 2 to 4, +500 ~ -250 x 10 ^-6
Fe-Cr-Al for strain gauges, which has a relatively small temperature coefficient of resistance of / 100 ℃, preferably +100 to -100 × 10 ^-6 / ℃, and has excellent stability of gauge characteristics and high-temperature workability.
To provide base alloys.

The present invention also provides a high-sensitivity strain gauge, a resistance element, various sensors and the like using the alloy.

[0003]

2. Description of the Related Art Strain gauges generally use the phenomenon that the electrical resistance of a gauge wire or gauge foil changes due to elastic strain, and conversely measure the amount of strain or stress by measuring the change in resistance. Used for stress conversion equipment. For example, strain sensors in the production industry, weight measurement, accelerometers and various mechanical quantity-electricity conversion devices, earth pressure gauges in the civil engineering industry, pressure gauges and deflection measurement in the construction and energy related industries, aviation, space, railroads and ships. It is widely used not only for various stress / strain measurement in Japan, but also for commercial scales and various security devices for consumer use.

The conditions imposed on the strain gauge material are: 1. Large gauge factor and low temperature dependence 2. Large specific electric resistance 3. Small resistance temperature coefficient 4. Small thermoelectromotive force against copper 5. Good workability and good mechanical properties 6. Inexpensive, etc.

By the way, the structure of the strain gauge has a thin metal wire (13 to 25 μm) or a metal foil (3 to 5 μm).
Are arranged in a grid or rosette, and as a method of using them, the gauge is attached to the object to be measured with an adhesive, and the strain generated in the object to be measured is indirectly measured from the resistance change of the gauge. Is.

The sensitivity of the strain gauge is determined by the gauge factor K, and the value of K (20 ° C.) is generally expressed by the following equation.

[Equation 1]

Here, R is the total resistance of the gauge thin wire, σ is the Poisson's ratio of the gauge thin wire, ρ is the specific electric resistance of the gauge thin wire, and L is the total length of the gauge thin wire. In this formula, σ is approximately 0.3 for general metals and alloys, so the sum of the first term and the second term on the right-hand side is about 1.6, which is a constant value. Therefore, in order to increase the gauge factor, it is an essential condition that (Δρ / ρ) / (ΔL / L) of the third term on the right side of the above equation is large. That is, when the material is subjected to tensile deformation, the electronic structure in the lengthwise direction of the material changes significantly, and the amount of change in electric resistance Δρ / ρ increases.

The temperature dependence of the gauge factor is evaluated by the gauge factor difference ΔK in the following equation.

## EQU00002 ## .DELTA.K = K (60.degree. C.)-K (20.degree. C.) (2) Table 1 shows the gage characteristics (gauge factor K, specific electric resistance .rho., The temperature coefficient of resistance C _f and the thermoelectromotive force with respect to copper Em _f ) are shown.

[0009]

[Table 1]

The most frequently used material in Table 1 is Cu-Ni alloy. This alloy has a characteristic that the temperature coefficient of resistance C _f is extremely small, but on the other hand, it has a small gauge factor K and a small specific electric resistance ρ, and has a large thermoelectromotive force Emf to copper, so it cannot be used as a material for a high-sensitivity strain gauge. .. Moreover, K of pure nickel is -12 to -20, and its absolute value is 6 to 10 times that of Cu-Ni alloy, which is very large.
It cannot be used as a strain gauge element material because it has a very small specific electric resistance, a large thermoelectromotive force with respect to copper and a large temperature coefficient of resistance, and also has complicated strain-resistance characteristics. Moreover, the material cost of pure platinum is high.

In addition to these materials, semiconductors such as carbon (C), silicon (Si) and germanium (Ge) are known as materials having a high gauge factor [Naoji Nakamura: Nondestructive Inspection, Volume 40]. , No. 8 (1991), p. 546-551].

However, in the case of these semiconductors, the gauge factor is several.
Although it has a very large value of 10 to 170, it has drawbacks such as large anisotropy of gauge factor, positive and negative values, lack of stability, and poor mechanical strength.
It is only applied to special small pressure transducers.

Further, Fe-Cr- which the present inventor has previously discovered
Co-based and Fe-Cr-Co- (Mo, W, Nb, Ta)
Multi-component alloys also have excellent features [Japanese Patent Publication No. 45-13
229; Japanese Patent Laid-Open No. 61-15914; Naoji Nakamura: Nondestructive Inspection, Volume 40, No. 8 (1991), p. 546-551]. When these alloys are heat-treated at high temperature, they have a large gauge factor of 10 or more, but the only drawback is that the temperature coefficient of resistance is 1000.
It is a very big thing at ~ 2500 × 10 ^-6 / ° C. When a material having such a large temperature coefficient of resistance is used for a strain gauge, an apparent strain occurs due to a change in temperature around the strain gauge. Usually, a temperature compensating resistor incorporated in the bridge circuit is required so that an output corresponding to apparent distortion is not output. Therefore, application to dynamic strain gauges, strain sensors, etc. is being sought.

[0014]

[Problems to be Solved by the Invention] Strain gages have been expanding their application fields with the advancement of microcomputers in recent years, toward ultra-precision, miniaturization and high performance. In addition to pressure transducers and load cells that require stability, there are increasing demands for tactile sensors and slip sensors for robots.

By the way, R. Bertodo [Proc. Instrn. Me
chanical Engineers, Vol.178, No.34, (1964) p.907〜9
26], the Fe-Cr-Al ternary alloy has a specific electric resistance of 120 μΩ · cm or more and a temperature coefficient of resistance of + 164-
Since it is -205 × 10 ^-6 / ° C, it has been proposed as a promising high-temperature resistance strain gauge. This alloy has a small gauge factor of 1.88 to 2.37, changes greatly due to heat treatment and is not only unstable, but also has the drawback that it is significantly oxidized in the manufacturing process and causes work cracks at high temperatures. Processing into lines is a difficult task.

1, FIG. 2, FIG. 3 and FIG. 4 show the gauge factor K, the specific electric resistance ρ (room temperature) and the temperature coefficient of resistance C _f (0 to 50) of the Fe-Cr-Al ternary alloy, respectively. C) and the copper electromotive force Emf with respect to Emf. Moreover, FIG.
2 shows the range in which cold and hot working of a --Cr--Al ternary alloy is possible.

That is, as can be seen from these figures,
In order to obtain a large gauge factor, the temperature coefficient of resistance becomes large and it cannot be used for a high-sensitivity strain gauge. On the other hand, an alloy having a small temperature coefficient of resistance not only has a small gauge factor but also has difficulty in cold working after high temperature working, and therefore cannot be used for a high-sensitivity strain gauge. It should be noted that, even in the alloy in the hot workable region in FIG. 5, as the Al amount and Cr amount increase, the oxidation becomes remarkable, and embrittlement occurs due to the precipitation of the σ phase. In some cases, it becomes difficult to process.

In order to apply the above Fe-Cr-Al ternary alloy to a strain gauge, the gauge ratio should be made as large as possible and it should be stable even after heat treatment. It is important to improve workability and cold workability. In particular, since the oxidation concentrates a lot between crystal grains and structural defects, it is important that the crystals are fine and cracks during high temperature processing be eliminated.

The present invention has been made in earnest to overcome these problems, and has a specific electric resistance of 120 μΩ · cm or more, a temperature coefficient of resistance of + 500 × 10 ⁻⁶ / ° C. or less, and a gauge factor of 2 to 2. 4. A Fe-Cr-Al-based alloy having stable gauge characteristics and good workability at high temperature, and a high-sensitivity strain gauge, a resistance element and various sensor devices using the same.

[0020]

The present invention has been made in view of these points, and has made extensive efforts to carry out many experiments and detailed studies to improve the Fe-Cr-Al ternary alloy. As a result, the findings of the present invention have been obtained.

The features of the present invention are as follows. 1st invention 65 to 85% iron and 13 to 23% chromium as main components by weight ratio
And aluminum 2 to 15%, and nickel 5% or less, copper 5% or less, cobalt 5% or less, molybdenum 2% or less, tungsten 4% or less, niobium 2% or less, tantalum 4% or less, vanadium 2% or less as auxiliary components. , Zirconium 2
% Or less, manganese 5.0% or less, titanium 2.0% or less, silicon 0.5% or less, magnesium 0.5% or less, calcium
It consists of 0.5% or less and one or more rare earth elements of 0.1% or less, or 5.0% or less in total.
4 and a temperature coefficient of resistance of +500 to −250 × 10 ⁻⁶ / ° C. Fe-Cr- for strain gauges
Al-based alloy.

Second invention In the weight ratio, iron as a main component is 69 to 80% and chromium is 13 to 23%
And aluminum 4 to 8%, and nickel 5% or less, copper 5% or less, cobalt 5% or less, molybdenum 2% or less, tungsten 4% or less, niobium 2% or less, tantalum 4% or less, vanadium 2% or less as auxiliary components. , Zirconium 2
% Or less, manganese 5.0% or less, titanium 2.0% or less, silicon 0.5% or less, magnesium 0.5% or less, calcium
It consists of 0.5% or less and one or more rare earth elements of 0.1% or less, or 5.0% or less in total.
3 and a temperature coefficient of resistance of +100 to −100 × 10 ⁻⁶ / ° C. and an excellent high-temperature workability, and an Fe—Cr—Al based alloy for strain gauges.

Third invention In the weight ratio, the main components are iron 65 to 85%, chromium 13 to 23%
And aluminum 2 to 15%, and nickel 5% or less, copper 5% or less, cobalt 5% or less, molybdenum 2% or less, tungsten 4% or less, niobium 2% or less, tantalum 4% or less, vanadium 2% or less as auxiliary components. , Zirconium 2
% Or less, manganese 5.0% or less, titanium 2.0% or less, silicon 0.5% or less, magnesium 0.5% or less, calcium
A raw material consisting of 0.5% or less and one or more of rare earth elements of 0.1% or less and a total of 5.0% or less is heated in a vacuum to just below the melting point to exhaust the contained gas and dissolve it in an inert gas. A step of casting ingot after removing oxides and the like, and a step of forging the ingot at 1000 to 1200 ° C, and then air cooling or cooling at 10 to 150 ° C / min to obtain a plate or wire rod of an appropriate size. Fe-Cr-A for strain gauges, which is characterized by further performing a finishing process from these materials into an arbitrary shape such as a disc or a thin wire.
Method for producing l-based alloy.

Fourth invention In the weight ratio, as main components iron 65-85%, chromium 13-23%
And aluminum 2 to 15%, and nickel 5% or less, copper 5% or less, cobalt 5% or less, molybdenum 2% or less, tungsten 4% or less, niobium 2% or less, tantalum 4% or less, vanadium 2% or less as auxiliary components. , Zirconium 2
% Or less, manganese 5.0% or less, titanium 2.0% or less, silicon 0.5% or less, magnesium 0.5% or less, calcium
Fe-Cr-Al consisting of 0.5% or less and one or more of rare earth elements of 0.1% or less and a total of 5.0% or less.
Melting, casting, forging to form a base alloy composition, forming into a plate or wire, and forming a thin film by a suitable method such as sputtering, vapor deposition or ion plating,
A method for producing an Fe-Cr-Al based alloy for strain gauges, which comprises patterning in a grid pattern.

Fifth invention Iron 65 to 85% and chromium 13 to 23% as main components by weight ratio
And aluminum 2 to 15%, and nickel 5% or less, copper 5% or less, cobalt 5% or less, molybdenum 2% or less, tungsten 4% or less, niobium 2% or less, tantalum 4% or less, vanadium 2% or less as auxiliary components. , Zirconium 2
% Or less, manganese 5.0% or less, titanium 2.0% or less, silicon 0.5% or less, magnesium 0.5% or less, calcium
Fe-Cr-Al consisting of 0.5% or less and one or more of rare earth elements of 0.1% or less and a total of 5.0% or less.
A high-sensitivity strain gauge, a resistance element and various sensors characterized by being melted, cast and forged using a base alloy.

[0026]

The operation of the Fe-Cr-Al based alloy for strain gauge will be described below. In order to produce the alloy of the present invention, the main component of Fe65-
85%, Cr 13 to 23% and Al 2 to 15% as raw materials, and as additional elements, additional elements of Ni 5% or less, C
u5% or less, Co5% or less, Mo2% or less, W4% or less, Nb2% or less, Ta4% or less, V2% or less, Zr2
% Or less, Mn 5.0% or less, Ti 2.0% or less, Si 0.5%
In the following, one or two or more kinds of Mg 0.5% or less, Ca 0.5% or less and rare earth element 0.1% or less and a total of 5.0% or less of each raw material is heated to a temperature just below the melting point in a vacuum to exhaust the contained gas, It is melted in an inert gas and sufficiently stirred to form a compositionally uniform molten alloy.

Next, oxides such as Al ₂ O ₃ and Cr ₂ O ₃ are removed and then cast in a mold of an appropriate shape and size to obtain a sound ingot. Then the ingot is 1000-1200
After forging at ℃, preferably 1050-1100 ℃, air-cooling, preferably 10-150 ℃ / min to form a plate or wire of appropriate size, and the desired shape, for example from the plate thickness 0.02 mm thick foil material, 2 mm thick x 105 mm diameter sputter target material, and wire diameters of 0.15 and 0.06
Alternatively, a 0.02 mm thin wire is subjected to finishing processing and molded to obtain a target sample. In the middle of the above process, the softening treatment performed in vacuum at the same time as the removal of the oxidizing gas by the getter method is a very effective means for improving the subsequent workability and the stability of the gauge characteristics.

Here, the alloy of the present invention will be described in the following four groups. 1. Group A: Main components (Fe, Cr, Al) + subcomponents (Ni, Cu, Co) 2. Group B: Main components (Fe, Cr, Al) + subcomponents (Mo, W, Nb, Ta,) V, Zr) 3. Group C: Main component (Fe, Cr, Al) + Subcomponent (Mn, Ti, Si, Mg, Ca, rare earth element) 4. Group D: Main component (Fe, Cr, Al) + Subcomponents (Ni, Cu, Co, Mo, W, Nb, Ta, V, Z
r, Mn, Ti, Si, Mg, Ca, rare earth element)

Next, as a result of measuring the gage characteristics of the ultrafine wire (wire diameter 0.06 mm, processing rate 75%) produced from the alloy of the present invention by the above method, Table 2 (Group A), Table 3 (Group B), The characteristics shown in Table 4 (Group C) and Table 5 (Group D) were obtained.

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

[Table 4]

[0033]

[Table 5]

From these results, the gauge factor K: 2 to 4,
Thermoelectromotive force for copper Emf: ± 5 μV / ° C or less, specific electrical resistance ρ:
80 μΩ · cm and temperature coefficient of resistance C _f : +500 to −250 ×
An Fe-Cr-Al-based alloy for strain gauges is obtained which has characteristics of 10 ^-6 / ° C, stability of gauge factor K with very little temperature stability, and high temperature workability. I understand.

In the present invention, the reasons for limiting the numerical values of the alloy composition and heat treatment in the manufacturing process will be described below.

[0036]

[Table 6]

Table 6 shows the main components Al, Cr and F.
The evaluation of the gauge characteristics and the high temperature workability for each composition range of e is shown. Here, the symbol ◎ is very good, ○ is good, △
Somewhat good, x not possible and-no change. The evaluation method of the high temperature workability was performed by the method shown in FIG.
That is, an ingot with a diameter of 35 mm is formed into a disc with a thickness of 5 mm, three discs are stacked, and upset forging is performed at 1050 ° C. It was decided by observing the occurrence of surface cracks. Further, FIG. 7 is a sketch diagram in which the disc after forging is observed, and each evaluation is indicated by the above symbols.

Here, FIG. 8 shows the evaluation results in the case of the above-mentioned group C as an example of the high temperature workability of the alloy of the present invention. In FIG. 8, Mn 0.1% and S as auxiliary components
It contains i0.1%, Ti0.05% and Ce0.0015%. Comparing the results of FIG. 8 with FIG. 5, it was revealed that not only the composition range in which cold working and hot working are possible is expanded, but also cold workability after hot working becomes extremely good.

In FIG. 7, (a) is a sound disk having no flaws or cracks, which is a very good material <Judgment criteria: strong cold workable (⊚)>. In (b), there are wrinkles and some small cracks around the disk, but there is no problem in use. <Judgment criteria: cold work possible, hot work partially acceptable (○)
>. In (c), the disk is slightly deformed and the surrounding work cracks are inside, but it can be solved by lowering the work rate <Judgment criteria: Hot work possible (△)>. In addition, (d) cannot be used as a material because the entire disk becomes brittle and processing cracks occur on the entire surface and the shape cannot be maintained. <Judgment criteria: processing difficulty (x)>. Judging from the evaluation of Table 6, A
The composition ranges of 1, Cr and Fe are 2 to 15%,
When the content is 13 to 23% and 65 to 85%, the gauge characteristics and the high temperature workability are good, but if the composition is out of these compositions, the requirements of the present invention are not satisfied.

That is, when the amount of Al is 2 to 15%, the gauge characteristics and the high temperature workability are very good, and it is preferable as the material for the strain gauge which is the object of the present invention. However, if the amount of Al is less than 2%, the temperature coefficient of resistance becomes very large, and the thermoelectromotive force with respect to copper is also considerably large, which is outside the scope of the present invention. On the other hand, when the Al content exceeds 15%, the specific electric resistance is remarkably increased, the temperature coefficient of resistance and the thermoelectromotive force with respect to copper are considerably small, but the high temperature workability becomes difficult, which is outside the object of the present invention.

When the Cr content is 13 to 23%, the temperature coefficient of resistance becomes very small, other gauge characteristics do not change significantly, and the high temperature workability is good, so the strain gauge of the present invention is desired. It is preferable as a material. However, when the amount of Cr is less than 13%, the high temperature workability is good,
The temperature coefficient of resistance becomes large and deviates from the object of the present invention.
On the other hand, if the amount of Cr exceeds 23%, the temperature coefficient of resistance becomes large, making high temperature processing difficult and deviating from the object of the present invention.

Further, when the amount of Fe is 65 to 85%, the specific electric resistance is large, the temperature coefficient of resistance and the thermoelectromotive force for copper are small, and the high temperature workability is relatively good. It is preferable as a strain gauge material. However, when the Fe content is less than 65%, the specific electric resistance is very large and other gauge characteristics are suitable, but it is difficult to perform high temperature processing, which is outside the scope of the present invention. Also Fe
When the amount exceeds 85%, the high temperature workability is very good,
The large temperature coefficient of resistance deviates from the object of the present invention.

Next, the reasons for limiting the numerical values of the types and compositions of the sub-components will be described. Ni, Cu and C as subcomponents
As you can see from Table 2, we chose o.
In particular, temperature change of gauge ratio (difference in gauge ratio) is improved, stability against heat treatment is improved, and σ
This is because the precipitation of phases is suppressed and the workability is improved.

Further, Mo, W, Nb, Ta, V and Zr were selected as the sub-components, as shown in Table 3, not only the gauge characteristics, especially the electrical characteristics were improved but also the crystal was refined. This is because it has an effect of preventing oxidation.

Furthermore, Mn, Ti, Si, Mg, and
Ca and rare earth elements are selected because these elements have a remarkable deoxidizing effect in the melting process and further reduce defects inside the alloy to prevent work cracking during high temperature working, so that the subsequent cold workability is improved. This is because it will be greatly improved.

Next, the reason why the total amount of subcomponents is set to 5% or less is that the effect of the addition of the above-mentioned respective elements is remarkable within this range, but if it exceeds 5%, various characteristics are deteriorated or excessive. This is because the addition deteriorates the hot workability and deviates from the object of the present invention.

In the manufacturing process of the alloy of the present invention, the reason for limiting the forging temperature to 1000 to 1200 ° C. is that the workability at high temperature is very good and no work cracking occurs during forging. However, if the temperature is lower than 1000 ° C., the material is very hard, and if it is forcibly processed with strength without ductility, it will be out of the object of the present invention. Vice versa
This is because if forging is performed at a temperature higher than 00 ° C., the oxide film on the surface of the material peels off, the cracked portion inside is oxidized, loses ductility and becomes brittle, and the desired shape cannot be obtained, which is outside the object of the present invention.

The cooling rate after forging is air-cooling because the growth of recrystallized grains is not promoted and the subsequent cold working is good. Especially, the cooling rate of 10 to 150 ° C./min suppresses the generation of the σ phase and improves the cold workability. However, at a cooling rate other than these, the oxidation proceeds and the ductility is lost, so that it is out of the object of the present invention.

[0049]

EXAMPLES Examples of the present invention will be described below. Examples 1 to 8

The purity of the main component raw material is 99.99% for electrolytic Fe.
%, Thermite Cr 99.9% or more and electrolytic Al 99.9%
9%. Further, although other raw materials had a purity of 99.99%, FeCe (1% Ce) master alloy was used as Ce.

The method for producing the sample is as follows. First, the raw materials weighed so as to have a predetermined composition are put in an alumina crucible and sufficiently degassed to a temperature below the melting point, and then the amount of argon is maintained at 1/10 atmospheric pressure and high frequency melting is performed. Melted in a furnace. The molten alloy is thoroughly stirred to remove the residue, and then cast to obtain an ingot having a diameter of 10 mm and a length of 150 mm. Next, after removing oxides and flaws on the surface of the ingot, forging was performed at 1050 ° C. After further heating at 1050 ° C for 30 minutes, it is rapidly cooled at a rate of 100 ° C / minute to form a round bar having a diameter of 5 mm. Then, after polishing the surface of the round bar, the wire diameter is 0.5 by cold swaging and cold drawing.
Make it with a thin line of mm. The thin wire is heated by applying red heat to remove the oxide film by utilizing the shrinkage during cooling, and finally cold drawing is performed to produce an ultrafine wire with a working rate of 50 to 97% and a wire diameter of 0.1 to 0.06 mm. About this ultra-thin wire at 300-800 ℃ for 30 minutes to 5
Heat for a sample to make a sample. Table 7 shows a part of the evaluation of the gauge characteristics of the obtained sample corresponding to the heat treatment conditions.

[0052]

[Table 7]

Examples 9 to 11 The purity of the raw materials used was the same as in Examples 1 to 8. The method of sample preparation is based on the raw material consisting of a prescribed composition.
Put 800 g in a high-purity alumina crucible, use a high-frequency melting furnace, degas at a high temperature in a vacuum of 10 ^-5 Torr, melt in high-purity argon gas, cast after slag removal to obtain an ingot. .. This ingot was forged at 1150 ° C and had a diameter of 105
mm into a disk shape with a thickness of 3 mm. Next, a lathe is used for precision processing to produce a disc having a diameter of 105 mm and a thickness of 2 mm. Finally, the copper electrode is bonded to form a sputtering target.

A thin film having a thickness of 1 μm is produced from these targets. Next, masking is performed to form a gauge pattern by etching, electrodes are attached, and a gauge is manufactured. The gauge is heated in an Ar atmosphere at 200 to 500 ° C. for 30 minutes to 5 hours to prepare a sample. Table 8 shows a part of the characteristics of these samples corresponding to the heat treatment conditions.

[0055]

[Table 8]

[0056]

As shown in the above experimental results, the present invention has improved gauge characteristics and hot workability, and has a specific electric resistance of
Fe-Cr-Al based alloy for strain gauge with 120 μΩ · cm or more, resistance temperature coefficient of +500 × 10 ^-6 / ° C or less, gage factor of 2 to 4 and extremely low temperature dependency and excellent stability can be obtained. Therefore, it was found that not only a high-sensitivity strain gauge can be provided, but also the resistance element, various sensor devices, and the like can exhibit various excellent characteristics of the alloy of the present invention.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing an equivalent curve of a gauge factor K of an Fe—Cr—Al ternary alloy.

FIG. 2 is a characteristic diagram showing an isoelectric curve of a specific electric resistance ρ of a Fe—Cr—Al ternary alloy.

FIG. 3 is a characteristic diagram showing an iso-value curve of a temperature coefficient of resistance C _f of a Fe—Cr—Al ternary alloy.

FIG. 4 is a characteristic diagram showing an iso-value curve of a thermoelectromotive force Emf with respect to copper of an Fe—Cr—Al ternary alloy.

FIG. 5 is a characteristic diagram showing a relationship between cold and hot working and composition of a Fe—Cr—Al ternary alloy.

FIG. 6 is a schematic view showing an evaluation method of hot workability by upsetting forging according to the present invention.

FIG. 7 is an observation sketch diagram of the disc-shaped sample of the present invention.

FIG. 8 is a characteristic diagram showing the relationship between cold and hot working and composition of the Fe—Cr—Al alloy according to the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication H01C 7/00 D 9069-5E // G01B 7/00 M 9106-2F

Claims (5)

[Claims] 1. Iron 65 to 85% as a main component in a weight ratio,
Chromium 13-23% and aluminum 2-15%, with nickel 5% or less, copper 5% or less, cobalt 5% or less, molybdenum 2% or less, tungsten 4% or less, niobium 2% or less, tantalum 4% or less as auxiliary components. , Vanadium 2% or less,
Zirconium 2% or less, manganese 5.0% or less, titanium 2.0
% Or less, 0.5% or less of silicon, 0.5% or less of magnesium, 0.5% or less of calcium and 0.1% or less of a rare earth element, or 5.0% or less in total.
Gauge factor is 2 to 4 and resistance temperature coefficient is +500 to -250
An Fe-Cr-Al-based alloy for strain gauges, which has ^{x10 -6} / ° C. 2. Iron as a main component in a weight ratio of 69 to 80%,
Chromium 13 to 23% and aluminum 4 to 8%, and nickel 5% or less, copper 5% or less, cobalt 5% or less, molybdenum 2% or less, tungsten 4% or less, niobium 2% or less, tantalum 4% or less as auxiliary components. , Vanadium 2% or less,
Zirconium 2% or less, manganese 5.0% or less, titanium 2.0
% Or less, 0.5% or less of silicon, 0.5% or less of magnesium, 0.5% or less of calcium and 0.1% or less of a rare earth element, or 5.0% or less in total.
Gauge factor is 2 to 3 and temperature coefficient of resistance is +100 to -100
Fe-Cr-Al based alloy for strain gauges, which has ^{x10 -6} / ° C and is excellent in hot workability. 3. Iron as a main component in a weight ratio of 65 to 85%,
Chromium 13-23% and aluminum 2-15%, with nickel 5% or less, copper 5% or less, cobalt 5% or less, molybdenum 2% or less, tungsten 4% or less, niobium 2% or less, tantalum 4% or less as auxiliary components. , Vanadium 2% or less,
Zirconium 2% or less, manganese 5.0% or less, titanium 2.0
% Or less, 0.5% or less of silicon, 0.5% or less of magnesium, 0.5% or less of calcium, and 0.1% or less of a rare earth element, or a total of 5.0% or less of two or more kinds, and heated to a temperature just below the melting point in a vacuum. Evacuating the contained gas, dissolving it in an inert gas, removing oxides etc. and then casting to obtain an ingot, and the ingot is 1000-1200
After forging at ℃, air-cooling or cooling at 10 ~ 150 ℃ / min to make a plate or wire of appropriate size, and the step of finishing from these materials into any shape such as a disk or fine wire F for strain gauges characterized by
Method for producing e-Cr-Al based alloy. 4. Iron 65 to 85% as a main component in a weight ratio,
Chromium 13-23% and aluminum 2-15%, with nickel 5% or less, copper 5% or less, cobalt 5% or less, molybdenum 2% or less, tungsten 4% or less, niobium 2% or less, tantalum 4% or less as auxiliary components. , Vanadium 2% or less,
Zirconium 2% or less, manganese 5.0% or less, titanium 2.0
% Or less, 0.5% or less of silicon, 0.5% or less of magnesium, 0.5% or less of calcium and 0.1% or less of a rare earth element, or a total of 5.0% or less of F or less.
Melt, cast, and forge into a composition of an e-Cr-Al-based alloy to form a plate or wire, which is then formed into a thin film by a suitable method such as sputtering, vapor deposition, or ion plating, and formed into a grid. A method for producing a Fe-Cr-Al based alloy for strain gauge, which comprises patterning. 5. Iron as a main component in a weight ratio of 65 to 85%,
Chromium 13-23% and aluminum 2-15%, with nickel 5% or less, copper 5% or less, cobalt 5% or less, molybdenum 2% or less, tungsten 4% or less, niobium 2% or less, tantalum 4% or less as auxiliary components. , Vanadium 2% or less,
Zirconium 2% or less, manganese 5.0% or less, titanium 2.0
% Or less, 0.5% or less of silicon, 0.5% or less of magnesium, 0.5% or less of calcium and 0.1% or less of a rare earth element, or a total of 5.0% or less of F or less.
A high-sensitivity strain gauge, a resistance element, and various sensors, which are obtained by melting, casting, and forging using an e-Cr-Al-based alloy.