JP4863495B2 - Hermetic sealing ring and manufacturing method thereof - Google Patents

Description

  The present invention accommodates an element body provided at the tip of a lead terminal inside a sealing cap, and seals the opening of the sealing cap with a glass lid through which the lead terminal penetrates. The present invention relates to an airtight sealing ring that is fitted and fixed between a peripheral surface and an outer peripheral surface of a glass lid, and a method for manufacturing the same.

In general, an electrical element such as a crystal resonator has a structure in which an element body provided at the tip of a lead terminal is sealed in a sealing cap in order to stabilize characteristics. The hermetic sealing ring is fitted between the outer peripheral surface of the glass lid (insulating member) through which the lead terminal penetrates and the inner peripheral surface of the sealing cap, and the gap between the glass lid and the sealing cap is airtight. Used to hold on. And the conventional airtight sealing ring was the structure which shape | molded the Fe-Ni type alloy in the ring shape (for example, refer patent document 1, 2).
JP 2001-267190 A (paragraphs [0002], [0003], FIGS. 6 and 13) JP 2001-214295 A (paragraph [0007])

  By the way, Ni is more expensive than Fe, and has continued to soar in recent years. For this reason, from the viewpoint of reducing raw material costs, it has been studied to reduce the amount of Ni used in the hermetic sealing ring. However, if an airtight sealing ring is simply formed using an Fe-Ni alloy with a reduced Ni composition ratio (content), it is difficult to ensure the airtight performance between the airtight sealing ring and the glass lid. The problem of becoming.

  The present invention has been made in view of the above circumstances, and aims to provide a hermetic sealing ring capable of ensuring hermetic performance between the glass lid and reducing the cost of raw materials compared to the conventional one, and a method for manufacturing the same. To do.

  According to a first aspect of the present invention, there is provided a method of manufacturing an airtight sealing ring according to the first aspect of the present invention, in which an element body provided at the tip of a lead terminal is accommodated inside a sealing cap and the sealing cap is opened. An airtight sealing ring that is fitted and fixed between the inner peripheral surface of the sealing cap and the outer peripheral surface of the glass lid in order to seal the opening with the glass lid through which the lead terminal passes, In the manufacturing method of the hermetic sealing ring in which the inner peripheral surface of the configured ring body is covered with the Fe—Ni-based alloy layer, the entire Ni plating of the Ni plating sheet metal is heated by heat-treating the Ni plating sheet metal. A feature is that a plurality of ring main bodies are formed from the Ni-plated sheet metal after the Fe-Ni alloy layer is formed by diffusing to the iron plate substrate.

  According to a second aspect of the present invention, there is provided a method of manufacturing an airtight sealing ring in which a device body provided at the tip of a lead terminal is accommodated in a sealing cap, and the lead terminal penetrates the opening of the sealing cap. An airtight sealing ring that is fitted and fixed between the inner peripheral surface of the sealing cap and the outer peripheral surface of the glass lid in order to seal at the inner peripheral surface of the ring body made of iron In the method of manufacturing an airtight sealing ring in which a Fe—Ni alloy layer is covered, the Fe—Ni alloy plate as the Fe—Ni alloy layer is obtained by heat-treating the Fe—Ni alloy plating sheet metal. Diffusion to the inner iron plate substrate was performed, and a diffusion layer was formed at the boundary between the Fe-Ni alloy plating and the iron plate substrate, where the Fe content gradually increased toward the iron plate substrate and integrated with the iron plate substrate. Later, the Fe-Ni alloy plating sheet metal Characterized in place of forming a plurality of ring body.

  According to a third aspect of the present invention, there is provided a method for manufacturing an airtight sealing ring, wherein a device body provided at a tip of a lead terminal is accommodated in a sealing cap, and the lead terminal penetrates the opening of the sealing cap. An airtight sealing ring that is fitted and fixed between the inner peripheral surface of the sealing cap and the outer peripheral surface of the glass lid in order to seal at the inner peripheral surface of the ring body made of iron In the method for manufacturing an airtight sealing ring in which the Fe—Ni alloy layer is covered, the entire Ni plating is diffused into the ring body by heat-treating the ring body covered with the Ni plating, and the Fe—Ni alloy layer. It has the feature in generating.

  The “ring body covered with Ni plating” may be a Ni-plated sheet metal formed into a ring shape, or a sheet metal or pipe formed into a ring shape with Ni plating. Also good.

  According to a fourth aspect of the present invention, there is provided a method for producing an airtight sealing ring, comprising: a glass lid in which an element body provided at a tip of a lead terminal is housed in a sealing cap; An airtight sealing ring that is fitted and fixed between the inner peripheral surface of the sealing cap and the outer peripheral surface of the glass lid in order to seal at the inner peripheral surface of the ring body made of iron In the manufacturing method of the airtight sealing ring which covers with a Fe-Ni type alloy layer, the ring body covered with the Fe-Ni type alloy plating as a Fe-Ni type alloy layer is heat-processed, and Fe-Ni type The alloy plating is diffused in the ring body, and at the boundary between the Fe-Ni alloy plating and the ring body, the Fe content gradually increases toward the ring body to create a diffusion layer integrated with the ring body. It has a feature.

  The “ring body covered with Fe—Ni alloy plating” may be formed by forming an Fe—Ni alloy plated sheet metal into a ring shape, or forming a sheet metal or a pipe into a ring shape. What gave Fe-Ni type alloy plating may be used.

  According to a fifth aspect of the present invention, in the method for manufacturing the hermetic sealing ring according to any one of the first to fourth aspects, the composition on the surface side of the Fe—Ni-based alloy layer after the heat treatment has a Fe of 50-60. It is characterized by mass% and Ni being 40-50 mass%.

  The hermetic sealing ring according to the invention of claim 6 accommodates the element body provided at the tip of the lead terminal inside the sealing cap, and seals the opening of the sealing cap with a glass lid through which the lead terminal penetrates. An airtight sealing ring that is fitted and fixed between the inner peripheral surface of the sealing cap and the outer peripheral surface of the glass lid in order to stop, and the inner peripheral surface of the ring body made of iron material is Fe- It is characterized by being covered with a Ni-based alloy layer.

  According to a seventh aspect of the present invention, in the hermetic sealing ring according to the sixth aspect, the Fe content is gradually increased toward the ring body at the boundary portion between the Fe-Ni alloy layer and the ring body. It is characterized in that a diffusion layer integrated with the ring body is provided.

  The invention according to claim 8 is the hermetic sealing ring according to claim 6 or 7, wherein the composition on the surface side of the Fe-Ni-based alloy layer is 50-60 mass% Fe and 40-50 mass% Ni. It has the characteristics in the place.

  Since the hermetic sealing ring according to the inventions of claims 1 to 8 has a structure in which the inner peripheral surface of the ring body made of iron material is covered with the Fe—Ni-based alloy layer, Fe— It is possible to reduce the amount of Ni used for the entire hermetic sealing ring while maintaining the Ni composition ratio (content ratio) of the Ni-based alloy at the same ratio as before. In other words, the hermetic sealing ring according to the present invention can ensure the hermetic performance between the glass lid and reduce the amount of Ni used compared to the prior art, thereby reducing raw material costs.

  In order to secure the airtight performance between the airtight sealing ring and the glass lid, the composition of the Fe—Ni-based alloy layer is 50 to 60% by mass as in the inventions of claims 5 and 8. Ni is preferably 40 to 50% by mass.

  In addition to the above-described effect, in the method for manufacturing an airtight sealing ring according to claim 1, since the Ni plating sheet metal is heat-treated to diffuse the entire Ni plating to the iron plate substrate, the Fe—Ni-based alloy layer is generated. The Ni-based alloy layer and the iron plate substrate are integrated to improve their bond strength. Further, in the method of manufacturing the hermetic sealing ring according to claim 2, since the Fe—Ni-based alloy plating sheet metal is heat-treated to produce a diffusion layer in which the Fe—Ni-based alloy plating is integrated with the iron plate substrate, The bond strength between the Fe—Ni alloy plating and the iron plate substrate is improved. Furthermore, in the manufacturing method of the hermetic sealing ring of Claim 1 and 2, since the said heat processing is performed before the formation process of a some ring main body, productivity improves.

  Further, in the method of manufacturing the hermetic sealing ring according to claim 3, the ring main body covered with the Ni plating is heat-treated to diffuse the entire Ni plating into the ring main body, thereby generating the Fe—Ni alloy layer on the surface. As a result, the Fe—Ni-based alloy layer and the ring body are integrated to improve their bond strength. Moreover, according to this manufacturing method, compared with the method of punching the sheet metal covered with Ni plating and manufacturing an airtight sealing ring, the amount of Ni discarded can be suppressed, and Ni resources can be effectively used.

  In the method of manufacturing an airtight sealing ring according to claim 4, the ring body covered with the Fe-Ni alloy plating is heat-treated, so that the ring body is formed at the boundary with the ring body in the Fe-Ni alloy plating. As a result, a diffusion layer integrated with each other is produced, so that the bond strength between the Fe—Ni alloy plating and the ring body is improved. Moreover, according to this manufacturing method, compared with the method of punching a sheet metal covered with Fe—Ni-based alloy plating to manufacture an airtight sealing ring, the amount of Ni discarded can be suppressed, and Ni resources can be effectively used. .

  The hermetic sealing ring according to the invention of claim 7 is provided with a diffusion layer integrated with the ring body at the boundary between the Fe-Ni alloy layer and the ring body. The bond strength between the layer and the ring body is improved.

[First Embodiment]
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a crystal oscillator 10 as an electric element having an airtight sealing ring according to the present invention. The crystal oscillator 10 has a structure in which an element body 12 is connected to the tips of a pair of lead terminals 11 and 11 and the element body 12 is accommodated in a sealing cap 13. The opening of the sealing cap 13 is sealed with a glass lid 14 through which the lead terminals 11 and 11 pass, and the hermetic sealing ring 20 according to the present invention is used for the sealing.

  Specifically, the element body 12 has a structure in which a crystal piece (crystal blank) that is a piezoelectric body is sandwiched between two electrodes. The leading ends of the lead terminals 11 are connected to the two electrodes, respectively. Each of these lead terminals 11 is formed by cutting a wire made of an Fe—Ni alloy into a predetermined length. The glass lid 14 is made of a glass sintered material. Further, the sealing cap 13 is formed by drawing a sheet metal into a cylindrical shape with one end.

  Now, the hermetic sealing ring 20 is, for example, a molded product of an Fe—Ni alloy plated sheet metal 50 (FIG. 4), and has a cylindrical shape with both ends open (see FIG. 7C). Hereinafter, the structure of the hermetic sealing ring 20 will be described in detail together with the method for manufacturing the hermetic sealing ring 20.

  The Fe—Ni alloy plating sheet metal 50 used for manufacturing the hermetic sealing ring 20 is shown in FIG. 4, and both the front and back surfaces of the iron sheet base 53 (for example, low carbon steel) are formed on the Fe—Ni alloy plating 21. It has a covered structure. The composition of the Fe—Ni-based alloy plating 21 is, for example, 50 to 60 mass% for Fe and 40 to 50 mass% for Ni. More specifically, the composition of the Fe—Ni-based alloy plating 21 is, for example, 58% by mass of Fe and 42% by mass of Ni, which is the same as the so-called “42 alloy”. In addition, the overall thickness of the Fe—Ni alloy plating sheet metal 50 of the present embodiment is 0.1 to 0.3 [mm], and the thickness of the Fe—Ni alloy plating 21 is 1 to 0.3 mm. 3 [μm].

  In the manufacturing method of the hermetic sealing ring 20 of the present embodiment, the Fe—Ni-based alloy plating sheet 21 is heat-treated in, for example, a neutral or weakly reducing atmosphere to thereby form the Fe—Ni-based alloy plating 21. As shown in FIG. 5, the Fe content gradually increases toward the iron plate substrate 53 at the boundary between the Fe—Ni-based alloy plating 21 and the iron plate substrate 53, as shown in FIG. The integrated diffusion layer 22 is generated. At this time, the surface side in the Fe—Ni-based alloy plating 21 is, for example, 50 to 60 mass% Fe and 40 to 50 mass% Ni (more specifically, 58 mass% Fe, Ni The heating time and the heating temperature are adjusted so as to be maintained at 42% by mass).

  Next, as shown in FIG. 6, a plurality of discs 54 are punched out from the heat-treated Fe—Ni alloy plated sheet metal 50. Then, the circular plate 54 (see FIG. 7A) is squeezed to form the one-end-bottomed cylindrical body 55 shown in FIG. 7B, and the bottom wall of the cylindrical body 55 is punched out to form FIG. 7C. The hermetic sealing ring 20 shown in FIG.

  The hermetic sealing ring 20 thus manufactured has a structure in which the inner peripheral surface and the outer peripheral surface of the ring main body 23 made of iron material are covered with the Fe—Ni-based alloy plating 21. Further, the entire outer diameter of the hermetic sealing ring 20 is, for example, 3 [mm], the inner diameter is, for example, 2.6 [mm], and the thickness of the Fe—Ni alloy plating 21 is, for example, 2 [μm]. Yes. The ring body 23 is exposed at one end of the inner peripheral surface of the ring body 23 by punching the bottom wall.

  Manufacturing the crystal oscillator 10 using the hermetic sealing ring 20 is as follows. That is, a prototype of the glass lid 14 through which the lead terminals 11 and 11 pass is formed from a mixture of powdered glass and a binder, and preliminarily fired.

  Next, the glass lid 14 is fitted inside the hermetic sealing ring 20 manufactured by the above-described manufacturing method and set in a jig (not shown), and the glass constituting the glass lid 14 is melted. When the molten glass is solidified, the glass lid 14 is in close contact with the inner peripheral surface of the hermetic sealing ring 20 and the outer surface of each lead terminal 11. In this way, the hermetic sealing terminal 15 (see FIG. 2), which is a component in which the glass lid 14, the lead terminals 11 and 11, and the hermetic sealing ring 20 are integrally fixed, is completed.

  Next, the entire hermetic sealing terminal 15 is coated with, for example, a brazing material (not shown), and then the element body 12 is connected between one end of the lead terminals 11 and 11.

  Next, the hermetic sealing terminal 15 is inserted into the sealing cap 13 from the element body 12 side, and the hermetic sealing ring 20 is fitted inside the sealing cap 13 to seal the inner peripheral surface of the sealing cap 13 and the hermetic seal. The space between the outer peripheral surface of the retaining ring 20 is sealed in an airtight state. Thus, the crystal oscillator 10 is completed.

  Thus, by using the hermetic sealing ring 20 of this embodiment, the space between the sealing cap 13 and the glass lid 14 can be fixed in an airtight state. Here, the hermetic sealing ring 20 covers the ring body 23 formed of the iron material (see the iron plate base 53 in FIGS. 4, 5, and 7 (A)) with the Fe—Ni alloy plating 21 as described above. Therefore, the composition ratio (content ratio) of Ni in the Fe—Ni alloy in contact with the glass lid 14 is the same as the conventional ratio (for example, Fe is 58 mass%, Ni is 42 mass%). Thus, the amount of Ni used for the entire hermetic sealing ring 20 can be reduced. That is, the hermetic sealing ring 20 of the present embodiment can secure the hermetic performance between the glass lid 14 and can reduce the raw material cost by suppressing the amount of Ni used conventionally. Moreover, since the hermetic sealing ring 20 of the present embodiment includes the diffusion layer 22 integrated with the ring body 23 at the boundary between the Fe—Ni alloy plating 21 and the iron plate base (see FIG. 3), The bond strength between the Fe—Ni alloy plating 21 and the ring body 23 is increased. Moreover, in the manufacturing method of the hermetic sealing ring 20 of this embodiment, since the said heat processing for producing | generating the diffused layer 22 is performed to the some ring main body 23 before a formation process, productivity improves and air sealing is carried out. The manufacturing cost of the stop ring 20 can be reduced.

[Second Embodiment]
This embodiment is shown in FIGS. 8 to 11, and differs in that an air-tight sealing ring 20 </ b> V (see FIG. 10) is manufactured using a Ni-plated sheet metal 50 </ b> V (see FIGS. 8 and 9). As shown in FIG. 8, the Ni-plated sheet metal 50V has a structure in which both front and back surfaces of an iron plate base 53 (for example, low carbon steel) are covered with Ni plating 21V.

  In addition, as for the Ni plating sheet metal 50V of this embodiment, the whole board thickness is 0.1-0.3 [mm], and the thickness of the Ni plating 21 is 1-3 [micrometer]. .

  In the manufacturing method of the hermetic sealing ring 20 of the present embodiment, the Ni plating sheet metal 50V is heat-treated in, for example, a neutral or weakly reducing atmosphere to diffuse the entire Ni plating 21V to the iron plate base 53, As shown in FIG. 9, the Fe—Ni alloy layer 24 is generated. At this time, the composition of the Fe—Ni-based alloy layer 24 generated by the heat treatment has a heating time so that, for example, at least on its surface side, Fe is 50 to 60 mass% and Ni is 40 to 50 mass%. Adjust the heating temperature.

  Next, a plurality of discs 54 (see FIG. 10A) are punched out from the heat-treated Ni-plated sheet metal 50V, and each disc 54 is squeezed to form a cylindrical body 55 with one end (see FIG. 10B). Then, the bottom wall of the cylindrical body 55 is punched out to complete the hermetic sealing ring 20V (see FIGS. 10C and 11).

  Also by the manufacturing method of this embodiment, the airtight sealing ring 20V which has the same effect as the said 1st Embodiment can be manufactured.

[Third Embodiment]
In the method for manufacturing the hermetic sealing ring 20 </ b> W according to the present embodiment, the circular plate 57 shown in FIG. 12A is punched from an iron plate (for example, a steel plate) that has not been subjected to plating. Then, the ring main body 23 shown in FIG. Next, the ring body 23 is plated, and the entire ring body 23 is covered with the Fe—Ni alloy plating 21 as shown in FIG. As a result, as shown in FIG. 13, the Fe—Ni-based alloy plating 21 diffuses into the ring body 23, and the Fe content in the boundary portion between the Fe—Ni-based alloy plating 21 and the ring body 23 is reduced. A diffusion layer 22 that is gradually increased toward and integrated with the ring body 23 is generated.

According to the manufacturing method of this embodiment, compared with the method of punching a sheet metal covered with Fe—Ni-based alloy plating to manufacture an airtight sealing ring, the amount of Ni discarded can be suppressed, and Ni resources can be effectively used. It is done.
[Fourth Embodiment]

  In the manufacturing method of the hermetic sealing ring 20X according to the present embodiment, as in the third embodiment, the ring main body 23 is formed from an iron plate that has not been plated, and the entire ring main body 23 is covered with Ni plating. After performing the plating process, heat treatment is performed. As a result, as shown in FIG. 14, the entire Ni plating is diffused into the ring body 23, and an Fe—Ni-based alloy layer 24 is generated. This manufacturing method also has the same effect as the third embodiment.

[Other Embodiments]
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.

  (1) In the above embodiment, the ring body 23 is formed from sheet metal, but the pipe may be cut into a predetermined length to form a ring body.

  (2) Further, heat-treating the pipe with Fe-Ni alloy plating or Ni plating to produce the diffusion layer or the Fe-Ni alloy layer and then cut it to produce an airtight sealing ring. May be. By doing so, the amount of Ni discarded can be suppressed, and Ni resources can be effectively used.

Sectional drawing of the crystal oscillator which concerns on 1st Embodiment of this invention. Perspective view of hermetic sealing terminal FIG. 2 is a partially enlarged cross-sectional view of an airtight sealing ring taken along a line AA in FIG. Partially cutaway perspective view of Fe-Ni based plated metal sheet Partially broken perspective view after heat treatment of Fe-Ni based plated metal sheet Perspective view of a state in which a disc has been punched out of an Fe-Ni based plated metal sheet Sectional drawing showing the process of forming the ring body from a disc Partially broken perspective view of Ni plated sheet metal according to the second embodiment Partially broken perspective view after heat treatment of Ni plated sheet metal Sectional drawing showing the process of forming the ring body from a disc Partially enlarged sectional view of hermetic sealing ring Sectional drawing which showed the manufacturing process of the airtight sealing ring of 3rd Embodiment Partially enlarged sectional view of hermetic sealing ring Partially enlarged sectional view of the hermetic sealing ring of the fourth embodiment

Explanation of symbols

10 Crystal oscillator (electric element)
DESCRIPTION OF SYMBOLS 11 Lead terminal 12 Element body 13 Sealing cap 14 Glass lid 20, 20V, 20W, 20X Airtight sealing ring 21 Fe-Ni type alloy plating 21V Ni plating 22 Diffusion layer
2 3 Ring body 24 Fe-Ni alloy layer 50 Fe-Ni alloy plated sheet metal 50V Ni plated sheet metal 53 Iron sheet substrate

Claims (8)

An inner peripheral surface of the sealing cap for housing the element body provided at the tip of the lead terminal inside the sealing cap and sealing the opening of the sealing cap with a glass lid through which the lead terminal penetrates And a hermetic sealing ring that is fitted and fixed between the outer peripheral surface of the glass lid and the inner peripheral surface of the ring body made of iron is covered with a Fe-Ni alloy layer. In the manufacturing method of the stop ring,
By heat-treating the Ni-plated sheet metal, the entire Ni plating of the Ni-plated sheet metal is diffused into the inner iron plate base to generate the Fe-Ni alloy layer, and then the plurality of ring bodies are formed from the Ni-plated sheet metal. The manufacturing method of the airtight sealing ring characterized by shape | molding. An inner peripheral surface of the sealing cap for housing the element body provided at the tip of the lead terminal inside the sealing cap and sealing the opening of the sealing cap with a glass lid through which the lead terminal penetrates And a hermetic sealing ring that is fitted and fixed between the outer peripheral surface of the glass lid and the inner peripheral surface of the ring body made of iron is covered with a Fe-Ni alloy layer. In the manufacturing method of the stop ring,
By heat-treating the Fe—Ni alloy plating sheet metal, the Fe—Ni alloy plating as the Fe—Ni alloy layer is diffused into the inner iron plate substrate, and the Fe—Ni alloy plating and the iron plate substrate are diffused. And a diffusion layer integrated with the iron plate substrate is formed by gradually increasing the Fe content toward the iron plate substrate, and a plurality of the rings are formed from the Fe-Ni alloy plated sheet metal. A method for producing an airtight sealing ring, comprising molding a main body. An inner peripheral surface of the sealing cap for housing the element body provided at the tip of the lead terminal inside the sealing cap and sealing the opening of the sealing cap with a glass lid through which the lead terminal penetrates And a hermetic sealing ring that is fitted and fixed between the outer peripheral surface of the glass lid and the inner peripheral surface of the ring body made of iron is covered with a Fe-Ni alloy layer. In the manufacturing method of the stop ring,
A method of manufacturing an airtight sealing ring, wherein the ring body covered with Ni plating is heat-treated to diffuse the entire Ni plating into the ring body to produce the Fe-Ni alloy layer. An inner peripheral surface of the sealing cap for housing the element body provided at the tip of the lead terminal inside the sealing cap and sealing the opening of the sealing cap with a glass lid through which the lead terminal penetrates And a hermetic sealing ring that is fitted and fixed between the outer peripheral surface of the glass lid and the inner peripheral surface of the ring body made of iron is covered with a Fe-Ni alloy layer. In the manufacturing method of the stop ring,
The Fe—Ni alloy plating is diffused in the ring body by heat-treating the ring body covered with the Fe—Ni alloy plating as the Fe—Ni alloy layer, and the Fe—Ni alloy plating is performed. Manufacturing a hermetic sealing ring, wherein a diffusion layer integrated with the ring body is formed by gradually increasing the Fe content toward the ring body at a boundary portion between the ring body and the ring body Method.   The composition on the surface side of the Fe-Ni-based alloy layer after the heat treatment is such that Fe is 50 to 60% by mass and Ni is 40 to 50% by mass. The manufacturing method of the airtight sealing ring of description. An inner peripheral surface of the sealing cap for housing the element body provided at the tip of the lead terminal inside the sealing cap and sealing the opening of the sealing cap with a glass lid through which the lead terminal penetrates And an airtight sealing ring that is fitted and fixed between the outer peripheral surface of the glass lid,
An airtight sealing ring characterized in that an inner peripheral surface of a ring body made of an iron material is covered with an Fe-Ni alloy layer.   The boundary portion between the Fe-Ni alloy layer and the ring body is provided with a diffusion layer in which the Fe content gradually increases toward the ring body and is integrated with the ring body. The hermetic sealing ring according to claim 6.   The hermetic sealing ring according to claim 6 or 7, wherein the composition of the surface side of the Fe-Ni alloy layer is 50 to 60 mass% Fe and 40 to 50 mass% Ni.