JPS6248741B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a low-temperature high-permeability alloy having an initial magnetic permeability of 20,000 or more in the low-temperature range from extremely low temperatures to room temperature, and a method for producing the same. Recently, there has been active research into cryoelectronics using superconductors, especially applied research on Josephson devices that operate in liquid helium (4.2〓 or less), and some of them have been put into practical use. Generally, a superconductor is a perfect antiferromagnetic material (Meissner effect) that completely excludes magnetic flux in a weak magnetic field below a critical magnetic field specific to the material. However, in reality, various physical and
The magnetic flux remains trapped in the chemical defect. On the other hand, the Josephson device operates by inputting a minute magnetic field. Therefore, in order to operate the Josephson device without malfunction, it is necessary to completely shield the external magnetic field (residual magnetic field of 1 μG or less). Two methods have been considered for magnetic shielding: one is to shield the Josephson element itself, and the other is to insert the Josephson element into the cryostat and shield the cryostat. In the latter case, a cylindrical case of high permeability material (e.g. permalloy) is used to surround the cryostat as completely as possible with ferromagnetic material and to form a magnetic circuit with high permeability to external magnetic fields. ,
It must be installed on the outer periphery of the cryostat.
Furthermore, in order to provide sufficient shielding, a large-scale case having a multilayer structure (with gaps between layers) is required, so the latter method is not practical. On the other hand, in the former case, a Josephson element shielded with permalloy or the like is inserted into the cryostat.
The former is structurally more advantageous than the latter. However, since the temperature in the cryostat is below 4.2〓, the curve a in Figure 1 for normal permalloy
The magnetic permeability decreases as shown in , and the initial permeability is 10000.
Therefore, sufficient magnetic shielding cannot be expected. Further, some low-temperature permalloys having high magnetic permeability in liquid helium (having the characteristics shown by curve b in FIG. 1) have been put into practical use, but this low-temperature permalloy has the following drawbacks. (1) The temperature range in which high magnetic permeability can be obtained is narrow. In other words, it has high magnetic permeability at 4.2〓, but the initial magnetic permeability at room temperature is less than 10,000. When a shield case is made using this material and put into practical use,
4.2〓The shielding effect increases in the vicinity, but
Above this temperature, for example, around room temperature, the shielding effect deteriorates significantly, and the usable temperature range as a shield case is narrow, which is disadvantageous in practice. (2) Difficulty in heat treatment to obtain high magnetic permeability In other words, in this conventional low-temperature permalloy, two-stage heat treatment is performed to adjust the temperature at which the initial magnetic permeability reaches a maximum to around 4.2〓. If the temperature of this two-stage treatment changes from the predetermined temperature by ±5° C. or more, the maximum temperature of the initial magnetic permeability changes greatly, which is industrially disadvantageous. Therefore, an object of the present invention is to provide a high magnetic permeability alloy for low temperature use that is easy to heat treat and has an initial magnetic permeability of 20,000 or more in the low temperature range from extremely low temperatures to room temperature. That is, this invention has Ni70~84 in weight%.
%, Mo0.5~2.5%, Cu0.5~6.5%, Mn2% or less,
Consisting of less than 1% Si, the balance being Fe and a small amount of impurities,
Initial permeability is 20,000 in the low temperature range from extremely low temperatures to room temperature.
This is a high magnetic permeability alloy for low temperature use having the above characteristics. This high magnetic permeability alloy is produced by preparing an alloy with the above composition, heating the alloy at a high temperature of 1000°C or higher and lower than the melting point in a non-oxidizing atmosphere or in a vacuum for 10 minutes or more and 100 hours or less to fully recrystallize it. , 1000℃/min~0.1
Cool to room temperature at a rate of 1000°C/min to room temperature, or further heat at a temperature of 300 to 700°C for 10 minutes to 100 hours, and then cool to room temperature at a rate of 1000°C/min to 0.1°C/min. It is obtained by The reason for limiting the composition of each component of this invention alloy as described above will be described below. This is because when Ni is outside the range of 70 to 84%, the magnetic permeability decreases not only near room temperature but also in a low temperature region below room temperature. When Mo and Cu are less than about 10%, they have high magnetic permeability near room temperature, but below room temperature, especially below 100〓, the initial permeability becomes a small value of 20,000 or less, and high magnetic permeability occurs in the low temperature region below room temperature. The upper limit for Mo to obtain is 2.5% and the upper limit for Cu is 6.5%. The lower limit of Mo and Cu is set to 0.5% because if it is less than this, the initial magnetic permeability will not exceed 20,000 in a low temperature region below room temperature. Mn and Si are added to improve workability, and sufficient improvements can be made with Mn at 2% or less and Si at 1% or less. Furthermore, in the method for manufacturing the alloy of the present invention, high-temperature heat treatment is carried out for solution treatment and removal of processing strain, and the heating temperature is set at 1000°C or higher and below the melting point because the temperature is higher than the recrystallization temperature (approximately 500°C). If the heating temperature is high, recrystallization will start, but recrystallization will be insufficient.
1000℃ or higher, especially 1100℃, more preferably 1200℃
This is because it is suitable for sufficiently recrystallizing and obtaining high magnetic permeability at temperatures above .degree. The upper limit of the heating temperature is set below the melting point (approximately 1500° C.) because this heat treatment is performed after the molding process and cannot be heated above the melting point. Further, the atmosphere during this heat treatment must be a non-oxidizing atmosphere or a vacuum in order to avoid the formation of oxides on the material surface. The reason why the heating time in this case is 10 minutes or more and less than 100 hours is because the heating time is related to the temperature.
At 1400°C or higher, recrystallization can be achieved in a short time of about 10 minutes, but if the heating temperature is lower than 1000°C, more than 100 hours are required, which is not industrially practical. The reason why the rate of cooling from the above recrystallized state to room temperature was set at a rate of 1000℃/min to 0.1℃/min is as follows.
At temperatures above 1000℃/min, thermal distortion occurs due to cooling.
At 0.1℃/min or less, high magnetic permeability can be obtained near room temperature, but in the low temperature region below room temperature (especially below 100〓), the initial magnetic permeability decreases to 20,000.
This is because the following is true. Note that an appropriate cooling rate may be determined within this range depending on the alloy composition.
Figure 3 shows the relationship between cooling rate and alloy composition. This represents the relationship between the amount of (Mo + Cu) on the cooling rate, and the inner range surrounded by the line is
This is an area to which the present invention can be applied. Furthermore, when performing low temperature heat treatment following the above-mentioned high temperature heat treatment, a heating temperature of 300 to 700°C is appropriate; outside this temperature range, the initial magnetic permeability will be 20,000 or less in the low temperature range below room temperature. In addition, the heating time and cooling rate at this time were set to 10 minutes to 100 hours and 1000℃/min to 0.1℃/min, respectively, because even outside these ranges, the initial magnetic permeability at around room temperature is
This is because although a value of 20,000 or more can be obtained, it becomes 20,000 or less in a low temperature region below room temperature. Figure 4 shows the relationship between the low temperature heat treatment temperature and the amount of (Mo+Cu). The inner range surrounded by the line is the range of the present invention. Also,
Regarding the cooling rate at this time, FIG. 3 is applied. In addition, the reason why we set the initial magnetic permeability to 20,000 or more in the low temperature region below room temperature is because the shielding effect when making a shield case with this alloy is related to the dimensions and shape of the shield case, but if the initial magnetic permeability is 20,000 or more, Preferably, if it is 40,000 or more, a practically sufficient shielding effect can be obtained. Next, embodiments of this invention will be described. Note that this example does not limit the present invention. Example 1 77%Ni-2.4%Mo-4.7%Cu-0.6%Mn-0.3%
Si-Fe alloy. Using raw materials with a nominal purity of 99% or more, a total weight of 3 kg mixed to have the above composition was placed in an alumina crucible and melted in a high frequency induction furnace in a vacuum.
A small amount (1% or less) of deoxidizing agents and desulfurizing agents such as Ca, Mg, and Al were added, and the molten metal was poured into a mold of an appropriate shape to obtain a sound ingot. Further, this ingot was hot forged at 1100°C and hot rolled into a 4 mm thick plate, which was then cold rolled to a 1.5 mm thick plate. Next, it was heated to 900℃ to soften it, and then cold rolled to a thickness of 1mm, with an outer diameter of 10mm and an inner diameter of 6mm.
A ring-shaped sample was punched out. This sample was subjected to various heat treatments shown in Table 1 in hydrogen, and the properties shown in Table 1 were obtained. The measurement temperature is liquid helium (4.2〓), liquid nitrogen (77〓), room temperature (293〓),
〓), and some samples were also measured using dry ice + acetone (196〓). Curve 1 in FIG. 2 shows the relationship between the measured temperature and initial magnetic permeability of the sample treated under the heat treatment conditions (a) in Table 1.

[Table] Example 2 76%Ni-2.0%Mo-4.3%Cu-0.4%Mn-0.2%
Si-Fe alloy. This alloy sample was produced in the same manner as in Example 1, and subjected to various heat treatments as shown in Table 2, to obtain the properties shown in Table 2. Heat treatment conditions in Table 2
The relationship between the measured temperature and initial permeability of the sample treated in (a) is shown by curve 2 in Figure 2. It can be seen from Examples 1 and 2 that an initial magnetic permeability of 40,000 or more was obtained in a low temperature region below room temperature.

【table】

[Table] Example 3 Alloys having the compositions shown in Table 3 were produced and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[Table] As can be seen from the above examples, the Ni-
Mo-Cu-Mn-Si alloy is heated at a high temperature of 1000℃ or higher and below the melting point in a non-oxidizing atmosphere or in vacuum for at least 10 minutes and 100 hours or less.
Cool to room temperature at a rate of 1000°C/min to 0.1°C/min, or further heat at a temperature of 300 to 700°C for 10 minutes to 100 hours, and then cool to a rate of 1000°C/min to 0.1°C/min. It is easy to heat treat and has an initial permeability of 20,000 in the low temperature range from room temperature to extremely low temperatures.
A high permeability alloy for low temperature use having the above properties is obtained. Therefore, this alloy exhibits a good shielding effect when used in shield cases used below room temperature.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the initial magnetic permeability and temperature of conventional permalloy, and FIG. 2 is a graph showing the relationship between the initial magnetic permeability and temperature of different embodiments of the present invention.
FIG. 3 is a graph showing the relationship between cooling rate and alloy composition, and FIG. 4 is a graph showing the relationship between low temperature heat treatment temperature and alloy composition. 1...Characteristics of the alloy treated under the condition (a) of Example 1 2...Characteristics of the alloy treated under the condition (b) of Example 2.

Claims (1)

[Claims] 1. Ni 70-84%, Mo 0.5-2.5%,
Cu0.5~6.5%, Mn2% or less, Si1% or less, balance Fe
and a small amount of impurities, and has an initial magnetic permeability of 20,000 or more in the low temperature range from extremely low temperatures to room temperature. 2.Ni70-84%, Mn0.5-2.5% by weight,
Cu0.5~6.5%, Mn2% or less, Si1% or less, balance Fe
and a small amount of impurities.
A pole characterized by being heated at a temperature of 1000°C or more and below the melting point in a non-oxidizing atmosphere or vacuum for 10 minutes or more and 100 hours or less, and then cooled to room temperature at a rate of 1000°C/min to 0.1°C/min. A method for producing a high magnetic permeability alloy for low temperature use that has an initial magnetic permeability of 20,000 or more in the low temperature range from low temperature to room temperature. 3 Ni70-84%, Mo0.5-2.5%, by weight%
Cu0.5~6.5%, Mn2% or less, Si1% or less, balance Fe
and a small amount of impurities.
After heating for at least 10 minutes to 100 hours in a non-oxidizing atmosphere or vacuum at a temperature of 1000°C to 700°C and below the melting point, cool to room temperature and further heat in a non-oxidizing atmosphere or vacuum at a temperature of 300°C to 700°C. The initial magnetic permeability is 20,000 in the low temperature range from extremely low temperatures to room temperature, which is characterized by heating in a vacuum for 10 minutes to 100 hours and then cooling to room temperature at a rate of 1,000℃/min to 0.1℃/min. A method for producing a high magnetic permeability alloy for low temperature use having the above.