JPH0213023B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention uses iron (Fe), chromium (Cr), cobalt (Co), tungsten (W), molybdenum (Mo),
One or more additive elements of niobium (Nb) and tantalum (Ta) with a total content of 0.01 to 15%;
This relates to an alloy for strain gauges that contains a small amount of impurities and a method for producing the same.The purpose is to create strain gauges that have a large gauge factor, a small change in gauge factor depending on the composition, excellent other properties, and are easy to process. To provide alloys for Strain gauges generally utilize the phenomenon that the electrical resistance of a thin 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. In addition to being used for strain measurement, in recent years it has also been used as a so-called strain sensor, a mechanical quantity-to-electrical quantity converter element for industrial equipment such as balanced recorders. The conditions imposed on strain gauge materials are: 1. A large gauge factor. 2. A small thermoelectromotive force against copper. 3. A large specific electrical resistance. 4. A small temperature coefficient of specific electrical resistance. 5. Good workability and mechanical properties. Good things can be summarized as 6. It's cheap. By the way, the structure of the strain gauge is made of thin metal wire (13 to 25 μmφ) or foil (3 to 5 μm thick).
The gauge is arranged in a grid or rosette shape, and its usage is to attach the gauge to the object to be measured with adhesive and indirectly measure the strain generated in the object from the change in resistance of the gauge. It is. The sensitivity of a strain gauge is determined by the gauge factor K, and the value of K is generally expressed by the following equation. K=ΔR/R/Δl/l=1+2σ+Δρ/ρ/Δl
/l where R is the total resistance of the gauge thin wire σ is the Boisson's ratio of the gauge thin wire ρ is the specific electrical resistance of the gauge thin wire l is the total length of the gauge thin wire In the above equation, σ is approximately 0.3 for metals, so
In order to increase the gauge factor K, Δρ/ρ・(Δl/
l) ^-1 must be increased. In other words, it is necessary to have the property that when tensile deformation is applied, the electronic structure in the longitudinal direction of the material changes significantly and ρ increases. Now, with the advancement of microcomputers in recent years, the field of application of strain gauges is expanding more and more, and they are increasingly being used in highly sensitive pressure transducers and load cells. In particular, load cells are used not only for consumer use but also for industrial scales such as hopper scales and tank scale force meters, pressure gauges for rolling and extrusion processing machines, constant feeders, vehicle weight scales, and crane load meters. In addition to detecting and giving instructions on the number of parts, weight, pressure, etc., along with a microcomputer, it also serves the purpose of not only stabilizing the high quality of products and improving yields in factory management through automatic control, but also saving labor and energy. There is. However, in automatic control technology, the characteristics of strain gauge elements used in load cells are important determining factors in order to obtain high precision and high reliability of measuring instruments. Table 1 shows the gauge factor K, thermoelectromotive force Emf relative to copper, specific electrical resistance ρ, and temperature coefficient C _f of ρ for the main strain gauge element materials currently known.

[Table] Among the alloys in Table 1, Cu-Ni alloys are the most commonly used. Although this alloy has a small temperature coefficient C _f of specific electrical resistance ρ, the values of gauge factor K and specific electrical resistance ρ are also too small, and the thermoelectromotive force Emf against copper is large, making it difficult to use as a material for strain gauges. It cannot be said that the characteristics are sufficient. In addition, the variation in performance within the same lot or between lots is 5.
It reaches ~10% and is extremely unstable. The properties of other alloys also have advantages and disadvantages, and it is difficult to say that their properties are sufficient as substitutes for conventionally used materials for strain gauges. The present inventors have previously developed a material for strain gauges that has a large gauge factor K and is excellent in other properties.
We have proposed that Fe-Cr-Co alloys are very promising (Special Publication No. 13229/1983). However, the above alloy system has the disadvantage that its gauge factor K varies greatly depending on the composition.
As the variation could reach as high as 20%, it was extremely difficult to manufacture stable products with little variation. Therefore, in order to solve the above-mentioned drawbacks, the present inventors continued research and found that the large variation in the composition of the gauge factor K in the Fe-Cr-Co alloy was found to be
It has been shown that the addition of this material improves the results. This alloy not only has a stable gauge factor within a very narrow range of Ni content, but also has a gauge factor K of Fe.
-There is a drawback that it is smaller than the Cr-Co ternary alloy. Therefore, the present inventors have developed an alloy for strain gauges that has a large gauge factor K, has little change in gauge factor with respect to composition, has excellent other properties, and has good workability such as forging, rolling, and drawing. Continuing research with the aim of obtaining the above-mentioned
As a result of trying to improve Fe-Cr-Co alloy, Cr3～
Contains a small amount of impurities, the remainder being substantially We have found an alloy for strain gauges consisting of Fe that has a large gauge factor K, a very small change in gauge factor K with respect to composition, excellent other properties, and is easy to process. Hereinafter, the present invention will be explained in detail with reference to the drawings. In order to produce the alloy of the present invention, one or more of 3 to 35% Cr, 17 to 70% Co, and 9% or less of W, 10% or less of Mo, 7% or less of Nb, and 10% or less of Ta are used to obtain the above alloy composition. Total 0.01~15% and balance Fe
After melting an appropriate amount of in air, preferably in a non-oxidizing atmosphere or in vacuum using a suitable melting furnace, add a small amount (1% or less) of calcium alloy, magnesium alloy or other deoxidizing agent or desulfurizing agent.
The mixture is added to remove as many impurities as possible, and thoroughly stirred to obtain a compositionally uniform molten alloy. Next, this is poured into a mold of an appropriate shape and size to obtain a sound casting soul, and then this casting soul is subjected to forging, rolling, drawing, etc. at high temperature or room temperature to achieve a processing rate of 1% or more. Cold-work the desired shape, such as a wire rod with a diameter of 0.06 mm or a foil material with a thickness of 0.02 mm.The wire rod or foil material can be used as is after the above processing, or heated in hydrogen or other suitable non-oxidizing solution. in a gas or vacuum
The desired sample is obtained by heat treatment at a temperature of 400°C or less for 1 minute or more and 100 hours or less. And for the alloy sample obtained by the above method, the gauge factor K,
When the thermoelectromotive force Emf, specific electrical resistance ρ, and temperature coefficient C _f of specific electrical resistance against copper were measured, K: 2 to 5.7,
Emf: ±3μV/℃ or less, maximum value of ρ: 90μΩ−cm
and C _f :+7×10 ⁻⁴ /° C. or less, and an alloy for strain gauges having the characteristics that the composition dependence of the gauge factor K is extremely small can be obtained. FIG. 1 shows an investigation of the effect of cold working rate on the gauge factor K of four types of alloy samples. As can be seen from the figure, the gauge factor K before processing is small, 2 or less, for all alloy samples, but as the processing rate increases, the gauge factor K rapidly increases and becomes a nearly constant value. It is clear that the machining rate at which the gauge factor K is 2 or more is 1% or more for any alloy sample. Therefore, the above-mentioned cold working has the effect of obtaining a high gauge factor K by forming a dense working composition, but this is particularly noticeable when the working rate is about 20% or more. Further, the heat treatment (at a temperature and time below the recrystallization temperature) performed subsequent to the above-mentioned cold working has the effect of removing part of the internal strain caused by the working and stabilizing the gauge factor and other various properties. In this case, the higher the heating temperature or the longer the heating time, the more remarkable the effect. It goes without saying that the higher the heating temperature, the shorter the heating time, and conversely, the lower the heating temperature, the longer the heating time. Next, examples of the present invention will be described. Example 1 Alloy number 111 (composition Fe = 52.3%, Cr = 14.3%,
Production of alloy with Co=28.6%, W=4.8%) 99.97% pure electrolytic iron, 99.44% pure chromium metal, 99.59% pure electrolytic cobalt, and 99.9% pure tungsten metal were used as raw materials. To make the sample, raw materials were placed in an alumina crucible with a total weight of 100 g, and melted in air using a high-frequency induction electric furnace while blowing argon gas onto the surface to prevent oxidation. Thereafter, the mixture was thoroughly stirred to obtain a homogeneous molten alloy. Next, add the molten alloy to a height of 10 mm in inner diameter and
It was cast into a 120 mm iron mold, and the resulting ingot was forged at 1000°C to form a round bar with an outer diameter of 5 mm. After further intermediate annealing at 1000℃, swaging and cold drawing were performed to obtain a diameter of 0.5mm, intermediate annealing was again performed at 1000℃, and cold drawing was performed to obtain a thin wire with a diameter of 0.06mm, which was then cut to a length of 70cm to form a sample. did. The final processing rate (area reduction rate) in this case is 98%. These various types of processing could be easily performed both at high temperatures and at room temperature. Table 2 shows the characteristics corresponding to the processing and heat treatment conditions of this sample.

[Table] Example 2 Alloy number 222 (composition Fe = 51.5%, Cr = 14.0%,
Production of alloy with Co=28.0%, Mo=6.5%) The raw materials used were iron, chromium, and cobalt of the same purity as in Example 1, and molybdenum of 99.9% purity. The method for manufacturing the sample was the same as in Example 1. The samples were subjected to various processing and heat treatments to obtain the properties shown in Table 3.

[Table] Example 3 Alloy number 333 (composition Fe = 53.4%, Cr = 14.6%,
Production of alloy with Co=29.1%, Nb=2.9%) The raw materials used were iron, chromium, and cobalt of the same purity as in Example 1 and Example 2, and metallic niobium of 99.95% purity. The method for manufacturing the sample was the same as in Example 1. The samples were subjected to various processing and heat treatments to obtain the properties shown in Table 4.

[Table] Example 4 Alloy number 444 (composition Fe = 50.4%, Cr = 13.8%,
Production of alloy (Co = 27.5%, Ta = 8.3%) The raw materials are iron of the same purity as in Examples 1 to 3,
Uses chromium, cobalt and 99.9% pure tantalum metal. The method of manufacturing the sample was the same as in Example 1. The fifth sample was subjected to various processing and heat treatments.
The characteristics shown in the table were obtained.

[Table] Example 5 Alloy number 555 (composition Fe = 36.9%, Cr = 13.9%,
Production of alloy with Co = 41.7%, W = 6.5%, Nb = 1.0%) The raw materials are iron of the same purity as in Examples 1 to 4.
Chromium, cobalt, tungsten with the same purity as in Example 1, and niobium with the same purity as in Example 3 were used. The method for manufacturing the sample was the same as in Example 1. The samples were subjected to various processing and heat treatments to obtain the properties shown in Table 6.

[Table] The characteristic values of typical alloys belonging to the alloy area of the present invention are shown for the Fe-Cr-Co ternary alloy and the Fe-Cr-Co ternary alloy.
Table 7 shows the comparison with -Ni quaternary alloy.

【table】

[Table] Figures 2 to 5 show 5% W, 5% Mo, 3% Nb, or 9% Ta in Fe-Cr-Co ternary alloys.
FIG. 3 is a curve diagram showing the relationship between the gauge factor K and the amount of Co in the case of a constant amount of Cr and a processing rate of 98% for various samples to which Co is added. These figures show curves for a Fe-15%Cr-Co ternary alloy and a Fe-15%Cr-Co+20%Ni quaternary alloy as comparative alloys for reference. As you can see from both figures,
The gauge modulus K of the alloy of the present invention decreases as the amount of Co increases, but the decrease is smaller than that of the Fe-Cr-Co alloy, which is a comparative alloy, and shows a gentle curve. It can be seen from these curves that W, Mo, Nb, and Ta elements have the effect of increasing the gauge factor K. In addition, the gauge factor K of the alloy of the present invention is the comparative alloy Fe-Cr-Co-
It is larger than that of the Ni type, and shows a value of 3 or more at 70% Co in all cases of Figs. 2 to 5. In other words, the gauge factor K of the alloy of the present invention not only changes very little with respect to the composition, but also has a value of
In the range of 20 to 40% Co, it has features such as being about twice as large as that of practical materials. Figure 6 was obtained by cold drawing at a processing rate of 20% or more.
Fe-Cr-Co-W alloy, Fe-Cr-Co-Mo alloy, Fe-Cr-Co-Nb alloy and Fe-Cr-
Co-Ta alloy samples (all Cr15%,
FIG. 3 is a curve diagram showing the relationship between the gauge factor K and the amounts of W, Mo, Nb, and Ta added for a steel sheet containing a fixed amount of 30% Co. Gauge factor K of all alloys is 4
Shows values within the range of ±0.2, W, Mo, Nb
Or there is very little change in Ta content. Particularly in the case of W addition, K shows a constant value of 4.1 up to 9% W. The alloy having the composition indicated by the broken line in the figure was difficult to form into a fine wire and to roll. As described above, the gauge properties of the alloy of the present invention are excellent over a wide range of compositions. That is, Examples 1 to 5, Table 7, and Figures 2 to 6
As you can see from the figure, Cr3~35%, Co17~70%
and W9% or less, Mo10% or less, Nb7% or less,
Total of one or more of Ta10% or less
In a multicomponent alloy consisting of 0.01 to 15% and the balance Fe, the gauge factor K is 2 to 5.7, and the thermoelectromotive force Emf against copper is ±
3 μV/℃ or less, specific electrical resistance ρ 60 to 90 μΩ-cm,
A characteristic in which the temperature coefficient C _f of ρ is 7×10 ^-4 /°C or less can be obtained. These gauge properties are the values of the practical Cu-Ni alloy shown in Table 1 above, K = 2.04 to 2.12, Emf
= −43 μV/°C, ρ = 45 to 49 μΩ-cm and C _f = ±
Comprehensive evaluation compared to 0.2×10 ^-4 /°C shows that there is no subtraction at all and it is extremely excellent. The alloy of the present invention has a particularly large gauge factor K and a K
It has a previously unparalleled feature of almost no composition dependence, and is therefore very suitable as a material for strain gauges for load cells, which require high sensitivity and high stability. The alloy of the present invention is used in a processed state or after being heat treated at a low temperature of about 400°C or less;
Below, the gauge characteristics show only slight changes.
However, the characteristics change rapidly above 400℃. Further, the alloy of the present invention can be easily processed by forging, rolling, drawing, swaging, etc. both at room temperature and at high temperature, and has great industrial advantages. Figure 7 shows the gauge properties (K , ρ, Cf and Emf) and the amount of Cr. Figure 8 shows the gauge properties (K, ρ, Cf and Emf) and the amount of C. FIG. Figures 9 to 12 show Fe-15%Cr- heated at 250℃ for 12 hours after 80% cold working.
Co amount and W amount, Mo amount, Nb amount or Ta for Co + (W, Mo, Nb or Ta) alloy respectively.
It is a characteristic diagram showing K, ρ, Cf and processing range with respect to quantity. Next, in the alloy of the present invention, the composition of the alloy is changed from Cr3 to
35%, Co17~70%, W9% or less, Mo10% or less,
The reason for limiting the content to a total of 0.01 to 15% of one or more of Nb 7% or less, Ta 10% or less, and the balance Fe is as follows. (1) Chromium (Cr) 8-35%; In Figure 7, when the composition is 8% or less of Cr, the workability is excellent, but the gauge factor K decreases significantly to a small value of 2 or less, and the specific electricity Not only does the resistance ρ suddenly decrease, but also the temperature coefficient Cf of specific electrical resistance has a large value of 10×10 ⁻⁴ /° C. or more, making it unsuitable for use as the alloy of the present invention.
In addition, for compositions with Cr35% or more, the specific electrical resistance ρ is
It becomes extremely large at 90μΩ・cm or more, and both the temperature coefficient of specific electric resistance Cf and the thermoelectromotive force against copper Emf become small, so it is preferable as an alloy for strain gauges, but when the gauge factor K is 2 or less, it is small and has poor workability. It is therefore unsuitable for use as the alloy of the present invention. (2) Cobalt (Co) 17-70%; In Figure 8, when the composition is less than 17% Co, the gauge factor K shows a large value at 4 or more, which is preferable as an alloy for strain gauges, but as the amount of Co decreases, the ratio The electrical resistance ρ decreases rapidly, and the temperature coefficient of specific electrical resistance Cf and the thermoelectromotive force against copper Emf increase, making this alloy unsuitable as the alloy of the present invention. Also Co70%
With the above composition, the thermoelectromotive force Emf against copper is extremely small, but not only does the gauge factor K rapidly decrease, but the temperature coefficient of specific electrical resistance Cf shows a large value of 10×10 ^-4 /°C or more. As shown in FIGS. 9 to 12, the workability deteriorates, so that the alloy is unsuitable as the alloy of the present invention. (3) Tungsten (W) 9% or less; The workability of alloys containing W varies depending on the amount of Cr and Co, but as shown in Figure 9, Fe-Cr-Co-W with a constant Cr of 15% In the case of steel, cold working is possible in the range of 0 to 9% W, and the gauge factor K
is approximately 3 or more and specific electrical resistance ρ is 50 to 90μΩ・cm
Since these alloys have large values such as , they are suitable as alloys for strain gauges. However, in the case of an alloy that does not contain W (W=0%), the temperature coefficient of specific electrical resistance Cf becomes a large value of 10×10 ⁻⁴ /° C. or more, making it unsuitable as an alloy of the present invention. Furthermore, if W exceeds 9%, processing becomes extremely difficult, making it unsuitable for the alloy of the present invention. (4) Molybdenum (Mo) 10% or less; The workability of alloys containing Mo varies depending on the Cr content, Co content, etc., but as shown in Figure 10, Cr15%
0 to 10Mo for certain Fe-Cr-Co-Mo systems
Cold working is possible in the range of , gauge factor K is approximately 3 or more, and specific electrical resistance ρ is 50 to 90 μΩ・
Since these alloys have large values of cm, they are suitable as alloys for strain gauges. However, in the case of an alloy that does not contain Mo (Mo=0%), the temperature coefficient of specific electrical resistance Cf becomes a large value of 10×10 ^-4 /°C or more, making it unsuitable as an alloy of the present invention. Furthermore, if the Mo content exceeds 10%, processing becomes extremely difficult, making it unsuitable as an alloy of the present invention. (5) Niobium (Nb) 7% or less; The workability of alloys containing Nb varies depending on the Cr content, Co content, etc., but as shown in Figure 11, Cr15% or less
0-7% for certain Fe-Cr-Co-Nb systems
Cold working is possible in the range of Nb, the gauge factor K is about 3 or more, and the specific electrical resistance ρ is 50~50.
Since it has a large value of 90 μΩ cm, it is suitable as an alloy for strain gauges. However, in the case of an alloy that does not contain Nb (Nb = 0%),
Since the temperature coefficient Cf of specific electrical resistance becomes a large value of 10×10 ^-4 /°C or more, it is unsuitable as an alloy of the present invention. Furthermore, if the Nb content exceeds 7%, processing becomes extremely difficult, making it unsuitable for the alloy of the present invention. (6) Tantalum (Ta) 10% or less; The workability of alloys containing Ta varies depending on the Cr layer and Co content, but as shown in Figure 12, Cr15% or less
0 to 10Ta for certain Fe-Cr-Co-Ta systems
Cold working is possible in the range of , gauge factor K is approximately 3 or more, and specific electrical resistance ρ is 50 to 90 μΩ・
Since these alloys have large values of cm, they are suitable as alloys for strain gauges. However, in the case of an alloy that does not contain Ta (Ta=0%), the temperature coefficient of specific electrical resistance Cf becomes a large value of 10×10 ⁻⁴ /° C. or more, making it unsuitable as an alloy of the present invention.
Furthermore, if the Ta content exceeds 10%, processing becomes extremely difficult, making it unsuitable for the alloy of the present invention. As is clear from Figures 2 to 6, Figures 7 to 12, each example, and Table 7, the gauge factor K of the composition range is 2 or more, other gauge properties are excellent, and the processability is excellent. However, if the composition falls outside this range, the gauge properties will deteriorate and the initial required properties will not be obtained, and the alloy will be difficult to process, making it unsuitable as an alloy for strain gauges. was limited as above. In addition, in the alloy of the present invention, the cold working rate (area reduction rate)
The reason why is limited to 1% or more and 98% or less is as shown in Figure 1. At a machining rate of 1% or more, the gauge factor K shows a high value of 2 or more, but at a machining rate below this, the gauge factor K is small. Not only that, but it becomes difficult to control the processing rate in the manufacturing process, making it inappropriate as a method for manufacturing strain gauge alloys. Furthermore, if the processing rate exceeds 98%, the processing becomes extremely poor and desired shapes such as ultra-fine wires and foil materials cannot be obtained, so this is not suitable as a method for producing alloys for strain gauges. For the above reasons, the cold working rate was limited to 1% or more and 98% or less. Furthermore, the reason why the heating temperature after cold working of the alloy of the present invention was limited to 120°C or more and 400°C or less is that, as is clear from Tables 2 to 8, the gauge properties change only slightly below 400°C. However, when heating is performed at a temperature of 400℃, the temperature coefficient of specific electrical resistance Cf becomes
This is because the value exceeds 10×10 ^-4 /°C or more, which deviates from the required characteristics of strain gauges, making it inappropriate as a method for producing alloys for strain gauges. Also, if the heating temperature is below 120℃,
When the alloy of the present invention is applied to strain gauge elements as ultra-fine wire or foil material, not only will the electrical insulating material coated on the surface of the ultra-fine wire or foil material dry for more than 100 hours, but the alloy This method is inappropriate as a manufacturing method for strain gauge alloys because the internal stress causes apparent strain in the insulating material and the alloy, making the value of the gauge factor K unstable. Table 8 shows the relationship between the composition and various conditions.

[Table] ○: Improved -: No change ×: Worsened In addition, the reason why the cold working rate (area reduction rate) was limited to 1% or more in the alloy of the present invention is as shown in Figure 1, the working rate is 1%. The above gauge factor K shows a high value of 2 or more, but if the working rate is less than this, the gauge factor K is not only small but also makes it difficult to control the working rate in the manufacturing process. This is because it would be inappropriate as a. In addition, the reason why the heating temperature after cold working of the present alloy was limited to 400°C or less is as shown in Tables 2 to 6.
As is clear from the table, the gauge characteristics change only slightly below 400°C, but when heated at 400°C, the temperature coefficient of specific electrical resistance C _f exceeds a value of 10×10 ^-4 or higher. This is because the method deviates from the required characteristics of strain gauges, making it inappropriate as a method for producing alloys for strain gauges. Finally, when the alloy of the present invention is further heated at a temperature of 400°C or less after cold working, the reason for limiting the heating time to 1 minute or more and 100 hours or less is the second reason.
As is clear from Tables 6 to 6, when heat treatment is performed within the above time range, the gauge characteristics not only do not change much, but also stabilize because some of the processing strain is removed. It is possible to provide an alloy for strain gauges that exhibits little deterioration over time. However, if the heating time is less than 1 minute, the stability of the gauge properties will be poor, and if it exceeds 100 hours, the gauge properties will rapidly deteriorate, making it unsuitable as a manufacturing method for strain gauge alloys. be. As described above, according to the present invention, Ni-
Cu alloy or known Fe-Cr-Co alloy or Fe
- An alloy that not only makes it possible to obtain a material with no variation in composition of gauge factor K compared to Cr-Co-Ni alloys, etc., but also has excellent gauge properties and good workability, and its manufacturing method can be provided.

[Brief explanation of drawings]

FIG. 1 is a curve diagram showing the relationship between gauge factor K and cold working rate of typical alloys of the present invention, and FIGS.
The figure shows 98% cold worked Fe-15%Cr-Co+
(5%W, 5%Mo, 3%Nb or 9%Ta) alloy, Fe-15%Cr-Co comparison alloy and Fe-15
%Cr-Co+20%Ni A curve diagram showing the relationship between the gauge factor K and the amount of Co for the comparative alloy and Figure 6 shows the Fe-15%Cr-30%Co+(W,
Gauge factor K and W of Mo, Nb or Ta) alloy,
A curve diagram showing the relationship with the amount of Mo, Nb or Ta,
Figure 7 shows 80% cold working and then heating at 250℃ for 12 hours.
Characteristics showing the relationship between the gauge properties (K, ρ, Cf and Emf) and Cr content of the present invention alloy with the composition of Fe-Cr-30%Co + 5%W + 5%Mo and the comparative alloy consisting of Fe-Cr-30%Co Figure 8 is after 80% cold working.
Fe-15%Cr-Co+5% heated at 250℃ for 12 hours
Invention alloy consisting of W+5%Mo and Fe-15%Cr-
Gauge properties of Co comparative alloys (K, ρ, Cf and
Characteristic diagram showing the relationship between Emf) and Co amount and 9th
Figures 12 to 12 show the amount of Co and amount of W, respectively, for the Fe-15%Cr-Co+(W, Mo, Nb or Ta) alloy heated at 250℃ for 12 hours after 80% cold working.
K, ρ, Cf for Mo amount, Nb amount or Ta amount
and a characteristic diagram showing a processing range.

Claims (1)

[Claims] 1. Chromium 3-35%, cobalt 17-70% by weight
% and W9% or less, Mo10% or less, Nb7% or less,
Total of one or more of Ta10% or less
An alloy for strain gauges, which contains a small amount of impurities of 0.01 to 15%, the remainder substantially consists of iron, and has a gauge factor of 2 or more. 2 Chromium 3-35%, cobalt 17-70% by weight
% and W9% or less, Mo10% or less, Nb7% or less,
Total of one or more of Ta10% or less
The alloy contains a small amount of impurities (0.01 to 15%) and the remainder is essentially iron, and is cold-worked at a processing rate of 1% to 98%, and further processed at a temperature of 120°C to 400°C. A method for producing an alloy for strain gauges, characterized in that an alloy having stable gauge properties and a gauge factor of 2 or more is obtained by heating for at least 1 minute and at most 100 hours.