JP2006188728A - Method for continuously vacuum-carburizing fine metallic parts, and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for carburizing fine metallic parts having high strength, high precision, and a wall thickness of several millimeters or smaller such as a micromachine, and to provide a carburizing apparatus. <P>SOLUTION: The continuous vacuum-carburizing method comprises the steps of: hooking the fine metallic parts containing a desired or less amount of carbon onto a carrier wire 7; and continuously charging the fine metallic parts and the carrier wire 7 in a carburizing atmosphere 5 having a constant reduced pressure and a constant gas composition to carburize the parts. The continuous vacuum carburization apparatus for performing the method comprises at least one of core pipes 1, 11 and 12, and mechanisms 13 and 14 for respectively supplying and winding the carrier wire, which are all accommodated in a vacuum vessel 1. A carburizing source gas is supplied into the core pipe 1 through pipes 2 and 4 to form the carburizing atmosphere 5. A heater 10 heats the core pipe 1 to activate carbon of the carburizing source gas. Thus, the apparatus carburizes a material, for instance, having a small thickness of 0.02 to 3 mm with narrow variations in a carburized amount and without oxidizing the surface and forming soot thereon. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a continuous vacuum carburizing method for minute metal parts having excellent toughness and wear resistance, and an apparatus for carrying out the method.

Most steels used as wear resistant materials have a relatively high carbon content and poor cold workability. Therefore, for example, in the cold drawing process of a steel wire, it is necessary to reduce the hardness by frequently performing strain relief annealing on the work-hardened wire. Such frequent strain relief annealing increases the lead time of the process.
Furthermore, in the case of a melted material, giant primary carbides are generated in the material during the solidification process. This giant carbide remains without being destroyed even in subsequent hot working and cold working. Therefore, when this material is used as a wire rod, giant carbides act as a stress concentration source for fracture, causing chipping and breakage.

  With respect to such problems, Patent Document 1 discloses a technique in which a low-carbon steel material with a limited component balance is processed into a thin plate or a thin wire shape and then carburized to the center. This technology provides a metal material having excellent toughness and wear resistance in which hard carbides are finely and uniformly distributed with high production efficiency. However, this patent makes no mention of problems in carburizing wires or strips.

  Patent Documents 2 and 3 disclose a method of continuously carburizing a metal strip. However, these patent publications do not disclose or suggest carburizing uniformly to the center of the material as shown in the above-mentioned patents.

Regarding carburizing depth when carburizing steel, when carburizing an object with a practically semi-infinite depth, carburizing by carburizing by adjusting the carbon potential of the carburizing gas or by carburizing under reduced pressure. The vacuum carburizing performed is a known technique.
However, in the case of a material having a small diameter such as a steel wire, the material radius and the carburizing depth are the same. Therefore, as shown in the above-mentioned Patent Document 1, carburizing is performed by adding a carburizing source after putting the workpiece into the furnace. Even if a method (hereinafter referred to as batch processing) is applied to this material, variations in carburizing conditions are directly reflected in the carbon content inside the material cross section.

In addition to this, especially in the case of gas carburizing, the amount of carburizing increases due to the adhesion of soot to the surface of the material, coarse carbides are generated, or surface defects occur due to surface oxidation, the amount of carbon is insufficient, There is a tendency that a predetermined heat treatment hardness cannot be obtained.
In particular, when batch processing a material having a small wire diameter, a predetermined carburizing amount is reached in the initial stage of introducing the carburizing atmosphere gas into the furnace, and its control is extremely difficult. Furthermore, the influence of surface defects cannot be ignored due to the large specific surface area.

On the other hand, parts having a size of several mm or less have been used in recent years for micromachines and the like. In the case of such a component, if the hardness of the material is hard, it is difficult to process and precise processing cannot be performed, and therefore, carburization or the like is not performed. Further, even if conventional carburizing is performed after machining, the carburizing depth cannot be reduced or the amount of carburizing cannot be adjusted, and the deformation is large, so there is no example of carburizing such a minute metal part.
Japanese Patent No. 3053605 JP-A-6-192814 Japanese Patent Laid-Open No. 7-126829

An object of the present invention is to provide a carburizing method for a minute metal part having high strength and high accuracy by carburizing a part having a thickness of several mm or less such as a micromachine.
Another object of the present invention is to provide a carburizing apparatus that effectively implements the above method.

  The inventors of the present invention have filed a separate application in an unpublished international application (Application No. PCT / JP2004 / 009181), and there is very little variation in the amount of carburization of the material such as the metal wire, and surface oxidation and sooting. There was no carburizing method for metal wire, metal strip or metal pipe. As a result of further research, it is possible to carburize uniformly and stably by continuously carburizing while moving the metal wire continuously. By further promoting this, it is possible to easily carburize not only the metal wire but also minute parts. I knew.

  With this knowledge, in order to achieve the first object, according to the present invention, one of chain saturated hydrocarbon, chain unsaturated hydrocarbon gas and cyclic hydrocarbon is used under a reduced pressure of 5 kPa or less. Forming at least one carburizing atmosphere with a constant pressure and gas composition, activating the carbon in the carburizing atmosphere, and a desired carbon content or less There is provided a continuous vacuum carburizing method including continuously carburizing a carrier wire, on which the minute metal parts are locked, into the minute metal parts through the carburizing atmosphere.

  In order to effectively carry out the above method, a continuous vacuum carburizing apparatus according to another aspect of the present invention is formed so as to surround a fixed space and continuously pass a carrier wire locked with a minute metal part through the fixed space. Of the chain saturated hydrocarbon, the chain unsaturated hydrocarbon gas and the cyclic hydrocarbon under a reduced pressure of 5 kPa or less so as to form at least one carburizing atmosphere with a constant pressure and gas composition. One of these is used as a carburizing source to supply and exhaust in the core, and to activate carbon in the carburizing source in the core.

  According to the above configuration, the carburizing atmosphere is a reduced pressure state in which an oxide layer is not formed on the material surface, the carburizing source does not generate soot on the material surface, and the pressure and gas composition are constant while carbon is activated. It is. By passing the carburized material through such an atmosphere, it is possible to perform good carburizing with little variation in the amount of penetration. The material can be continuously carburized and a large amount of material can be processed efficiently. A minute metal part is tied to a carrier wire with a metal wire, or a hole is made to pass through the carrier wire, or a clip or the like is used.

The continuous vacuum carburizing method further heats a certain area where the carburizing atmosphere does not exist, followed by the carburizing atmosphere, and diffuses the carburized carbon in the metal parts into the cross section. It is preferable to include.
In this fixed region, a carrier gas may be supplied and exhausted to form a carrier gas atmosphere.
Therefore, the continuous vacuum carburizing apparatus has a carrier gas in the core portion so as to form at least one carrier gas atmosphere that does not have a carburizing source on the downstream side of the carburizing atmosphere with respect to the moving direction of the minute metal parts and the carrier wire. It is preferable to have means for supplying and exhausting.
By setting such a region, a desired amount of carbon can be reliably diffused into the material.

The carbon activation is preferably performed by heating the carburizing atmosphere to 850 ° C. to 1050 ° C. The carburizing source gas is decomposed by heating to produce activated carbon. This temperature range promotes the reaction of the carburizing source gas and the diffusion of carbon that has penetrated into the material, while suppressing grain growth in the material.
For the activation of carbon, in addition to heating in a carburizing atmosphere, carbon may be converted into plasma. Therefore, it is preferable that the continuous vacuum carburizing apparatus includes an electric heater that heats the core to 400 ° C. to 1050 ° C. and a discharger that performs glow discharge. By accelerating the carbon ions, carburization of the material can be performed more efficiently.

The method may further include lowering the surroundings of the carburizing atmosphere to a lower pressure than the carburizing atmosphere.
The apparatus includes a take-up take-up mechanism for passing a minute metal part and a carrier wire through the core, and a vacuum vessel that houses the core, supply / exhaust means, and heating means. It is preferable to keep the pressure lower than that in the core.
By making the surroundings low in pressure, the reaction-deteriorated gas is quickly taken out of the carburizing atmosphere, and outside polluted gas is prevented from flowing into the carburizing atmosphere. Thus, the gas composition in the carburizing atmosphere can be stably maintained in a desired state.

The above method may be repeated a plurality of times by passing the minute metal part and the carrier wire through a carburizing atmosphere and then passing through a certain region without a carburizing source.
In order to carry out such a method, in the continuous vacuum carburizing apparatus, it is preferable that the core part and the supply / exhaust means form a plurality of carburizing atmospheres in the core part.
Depending on the steel material, if the amount of carbon necessary for carburizing to the center is carburized at one time, coarse reticulated carbide may be deposited on the surface. In this case, pulse carburizing that repeats carburizing and diffusing gradually a plurality of times is effective. Such pulse carburization can be performed by forming a plurality of carburizing atmospheres in the core.

Carburization is preferably performed until the minute metal part has a desired carbon content or higher.
According to such a method, a material having a low carbon content is used, and this material is formed into a desired shape by general processing such as cutting, pressing, and bending, and then subjected to a good carburizing process. Can be easily processed to give a desired strength.

The thickness of the thick part of the minute metal parts to be carburized is preferably 0.02 mm to 3 mm. If it is 3 mm or more, other conventional carburizing methods are sufficient. Control is difficult at 0.02 mm or less. In the continuous vacuum carburizing method of the present invention, by continuously sending minute metal parts in a constant carburizing atmosphere, even if the material is small in size and carburizing depth, there is very little variation in carburizing. .
Carburization may be performed up to the center of the cross section of the material, or only the surface layer portion thereof.

The material for the minute metal parts to be carburized may be carbon steel for machine structure, alloy steel for machine structure, tool steel, spring steel, or stainless steel.
Alternatively, the material of the minute metal parts to be carburized is one of nickel and cobalt alloys containing one or more carbide forming elements of boron, titanium, vanadium, chromium, zirconium, niobium, molybdenum, hafnium, tantalum, and tungsten. There may be.
Alternatively, the material of the minute metal parts to be carburized is a metal or an alloy containing as a main component one of carbide forming elements of boron, titanium, vanadium, chromium, zirconium, niobium, molybdenum, hafnium, tantalum, and tungsten. May be. As the carrier wire, a steel wire or the like is appropriately used. The thickness of the carrier wire may be about 0.5 to several mm in accordance with the minute metal parts. Moreover, it is a belt | band | zone etc., Comprising: You may provide the locking hole etc. which hold | maintain a minute metal.

  As described above, according to the continuous vacuum carburizing method and apparatus of the present invention, fine metal parts having a very small variation in permeation amount are satisfactorily carburized by passing the fine metal parts and the carrier wire through a constant carburizing atmosphere. It is possible. In particular, in the case of a minute metal part having a small material diameter or thickness, conventionally, there has been a problem that a predetermined hardness cannot be obtained after heat treatment, or that a coarse carbide is generated or deformed, and there is no accuracy at all. However, according to the method and apparatus of the present invention, these problems can be prevented.

The continuous vacuum carburizing method and apparatus of the present invention will be described in detail based on the embodiments shown in the accompanying drawings. FIG. 1 shows in detail the continuous vacuum carburizing apparatus or furnace of this embodiment.
This continuous vacuum carburizing furnace includes a long and narrow vacuum vessel 9, a plurality of (three in the illustrated example) core tubes 1, 11, and 12 disposed along the longitudinal direction in the vessel, and steel that has been drawn to a predetermined diameter. It has a feed and take-up mechanism for passing the wire 7 through a core part composed of these core tubes.

Each reactor core tube 1, 11 or 12 has an elongated shape with both ends open, and includes a carburizing gas introduction tube 2, a carrier gas introduction tube 3, and a pair of exhaust tubes 4 and 4. Further, each furnace core tube is provided with an electric heater 10 along its longitudinal direction.
The introduction pipes 2 and 3 and the exhaust pipes 4 and 4 are connected to the core tube through the vacuum vessel 9, and introduce carburizing gas and carrier gas from the outside of the vacuum vessel into the core tube and discharge them outside the vacuum vessel. It is like that.

The exhaust pipes 4 and 4 are arranged on both sides of the carburizing gas introduction pipe 2 with respect to the longitudinal direction of the furnace core pipe, and the inside of the furnace core pipe between these exhaust pipes is a carburized portion 5 occupied by the carburizing gas. The carrier gas introduction pipe 3 is arranged on the downstream side of the introduction pipe 2 and the exhaust pipes 4 and 4 with respect to the moving direction of the steel wire 7, and the inside of the downstream core tube becomes a diffusion portion 6 filled with carrier gas.
In FIG. 2, only the core tube 1 is provided with reference numerals 2 to 6 and 10, but the core tubes 11 and 12 have the same structure.

The vacuum container 9 has an exhaust pipe 8 provided with a vacuum exhaust valve (not shown), and can exhaust the interior of the container.
The pay-out take-up mechanism includes a pay-out side bobbin 13 and a take-up side bobbin 14 disposed on both sides of the core tubes 1, 11, 12 in the vacuum vessel. These bobbins 13 and 14 are rotationally driven to feed out the carrier wire 7 wound around the bobbin 13 and wind it around the bobbin 14 through the core tubes 1, 11 and 12. A minute metal part (not shown) is locked to the carrier wire 7.
Note that the pay-out and winding mechanism may be installed outside the vacuum vessel. In this case, it is desirable to provide a differential evacuation mechanism so that the atmosphere does not enter the vacuum vessel as the steel wire 7 moves.

This continuous vacuum carburizing furnace operates as follows according to an embodiment of the method of the present invention.
First, the carrier wire 7 to which a minute metal part is attached is passed through the core tube 1, 11, 12 from the feeding side bobbin 13 and connected to the winding side bobbin 14. Next, the entire vacuum vessel 9 is sufficiently exhausted from the exhaust pipe 8. When the inside of the vacuum vessel reaches a predetermined degree of vacuum of 10 Pa or less, a current is supplied to the heater 10 to heat the core tubes 1, 11, and 12 to a predetermined temperature of 850 ° C to 1050 ° C.

Thereafter, a carburizing source gas such as ethylene and a carrier gas such as nitrogen or argon are introduced from the carburizing gas introduction pipe 2 and the carrier gas introduction pipe 3 into the core tubes 1, 11, and 12. At the same time, by adjusting the vacuum exhaust valve of the exhaust pipe 8 to control the vacuum in the vacuum vessel 9, the pressure inside the core tube 1, 11, 12 is restored to 5 kPa or less, preferably 1 to 3 kPa.
After such an atmosphere adjustment, the take-up take-up mechanism is operated, and the carrier wire 7 to which the minute metal parts are attached is passed through the core tubes 1, 11, 12 and taken up on the bobbin 14. When the required amount of fine metal parts is obtained, the furnace is cooled, the vacuum vessel is broken in vacuum, and the fine metal parts and the carrier wire 7 together with the bobbin are taken out of the furnace. By removing the fine metal parts from the carrier wire, carburized fine metal parts can be obtained. The carrier wire can be reused for the next carburization.

The carburizing source gas is a pressure and composition gas capable of being vacuum carburized by being continuously introduced and exhausted from the introduction pipe 2 and the exhaust pipes 4 and 4 into each furnace core tube heated to 850 ° C. to 1050 ° C. Functions as a constant carburizing atmosphere. This atmosphere carburizes the minute metal parts passing therethrough. The carburized minute metal part then passes through the heated diffusion part 6 of each core tube. There is no gas that becomes a carburizing source in the diffusion portion, and carbon that has been carburized from the surface of the minute metal part diffuses into the inside of the alloy cross section.
The carburized portion may be limited to the vicinity of the surface or the entire carburized portion may be carburized.

  The continuous vacuum carburizing method of the present invention uses a chain saturated hydrocarbon, a chain unsaturated hydrocarbon gas or a cyclic hydrocarbon as a carburizing source under a reduced pressure of 5 kPa or less. The reason is that soot is generated on the surface of the material to be treated at a pressure exceeding 5 kPa, and carburization cannot be normally performed. The reason why the carburized atmosphere is set under reduced pressure is that, in gas carburizing performed under normal pressure, an oxide layer of 5 to 10 μm is formed on the surface of the material to be treated. In particular, in a thin metal part having a large specific surface area and a thick part, the effect of the defect is large.

  When the heating temperature condition of the carburizing atmosphere described above is 850 ° C. or lower, the gas to be a carburizing source does not start a reaction to form cementite on the surface of the material except for a specific gas such as acetylene. Is not carburized. Further, at 850 ° C. or lower, the diffusion rate of carbon in steel is small, and the carburizing diffusion work becomes inefficient. On the other hand, the reason why the temperature is set to 1050 ° C. or lower is that at a temperature exceeding 1050 ° C., the grain growth of the steel wire is remarkable and the mechanical properties are impaired.

It is preferable that the thickness of the material of the minute metal part processed by the continuous vacuum carburizing method of the present invention is 0.02 mm to 3 mm. If it is less than 0.02 mm, it is difficult to control the carburization depth. This is because when the thickness exceeds 3 mm, the carburizing time required for carburizing to the center is long and the influence of variations in the gas introduction time is small, so there is no need to use the method of the present invention for carburizing.
Needless to say, the method of the present invention is effective when only the surface layer portion is carburized at a constant concentration regardless of the size of the minute metal part.

In the above embodiment, the core tubes 1, 11, and 12 are heated to activate carbon in the carburizing source gas.
FIG. 2 shows a main part of a continuous vacuum carburizing apparatus according to another embodiment of the present invention that performs such vacuum plasma carburizing. This apparatus may have the same configuration as that of the embodiment of FIG. 1 except for the part that converts to plasma, and the same or similar components are denoted by the same reference numerals and description thereof is omitted.

The continuous vacuum carburizing apparatus of this embodiment includes a discharger 15 in addition to the apparatus configuration of FIG. The discharger 15 is electrically connected to the furnace core tube 1 and the carrier steel wire 7 that can conduct electricity and the fine metal parts via the bobbin 13. During the operation of the apparatus, the discharger 15 applies a voltage with the core tube 1 as an anode and the fine metal parts and the carrier steel wire 7 as a cathode. Thereby, glow discharge occurs in the furnace core tube 1 and the introduced carburizing source gas is turned into plasma. In addition, the electric heater 10 heats the core tube 1 to 400 ° C. to 1050 ° C.
Carbon in the plasma carburizing source gas is ionized, and the carbon ions effectively adhere to the surface of the minute metal part. Thus, the apparatus of the present embodiment further promotes the carburizing of the minute metal parts by converting the carburizing source gas into plasma.

FIG. 3A shows an enlarged view of the gas introduction pipes 2 and 3 and the exhaust pipes 4 and 4 of the continuous vacuum carburizing apparatus of FIG.
The tube arrangement of FIG. 3A is for making the carburized source gas atmosphere, that is, the carburized portion 5 only in the hatched portion of each core tube, and the adjacent region on the right side of the drawing as the diffusion portion 6 in which no carburized source gas exists. That is, the carburizing gas and the carrier gas are simultaneously introduced into the furnace core tube, and try to mix them inside. By disposing the exhaust pipe 4 between the introduction pipes 2 and 3 and exhausting it independently from the core tube at the middle part of both gases, it is possible to prevent the carburizing gas from entering the right side of the core tube.

The introduction and exhaust of the carburizing source into the furnace core tube is performed in order to keep the carburizing source inside the furnace core tube at an appropriate pressure and atmosphere, and the carburizing source gas is located in the range from the introduction position of the carburizing gas to the exhaust part. Exists. In order to prevent this gas from leaking into the diffusion part, a blocking carrier gas introduction pipe may be installed in the vicinity of the boundary with the diffusion part.
Alternatively, it may be possible to prevent the carburizing gas from leaking to the diffusion part by separating the core tube part of the carburizing part and the core part of the diffusion part and letting the carburizing source gas introduced into the carburizing part escape into the vacuum vessel. . In any case, it is important to keep the carburized portion and the diffusion portion in a carburizing source gas atmosphere and an atmosphere in which no carburizing source exists, respectively.

FIG. 3B and FIG. 3C each show a modification of the arrangement of FIG. 3A in order to prevent the carburizing gas from leaking into the diffusion part.
In the example of FIG. 3B, the carrier gas introduction pipes 31-33 and the exhaust pipes 41 and 42 to the furnace core tube are increased in order to more reliably prevent the carburizing gas from entering the right side region of the furnace core tube.
In the example of FIG. 3C, the core tube for the carburizing region and the core tube for the diffusion region are installed separately. In this case, since the carburizing gas and the carrier gas escape from the respective core tubes into the vacuum vessel, there is no need to exhaust directly from the core tubes.

  The fine metal part of the present invention is a fine metal mesh having a diameter (thickness) of 35 μm and a stainless steel fine wire with a width of 2 cm and a length of 10 cm. An example of carburizing through a furnace with a carrier wire will be described. This is an example tested in the unpublished Japanese Patent Application No. 2004-280095 filed by the present inventors. FIG. 4 is a table showing components of starting materials showing an embodiment of a stainless steel wire mesh according to the present invention. FIG. 5 is a partially enlarged photograph of the stainless steel wire mesh according to the present invention before carburization. FIG. FIG. 7 is a partially enlarged cross-sectional structure photograph of the stainless fine wire shown in FIG. 5 cut. The wire mesh of the stainless fine wire of this example was woven into a wire mesh by weaving austenitic stainless steel wire equivalent to SUS304 (JIS G 4308) having a diameter of 35 μm by wire drawing or the like into a lattice shape. After weaving, some of the overlapping parts are crushed and deformed into contact, and formed into a wire mesh as shown in FIG. At this time, the tensile strength of the austenitic stainless steel wire is as low as 976 MPa, while the elongation is about 29.6%, and it can be easily woven and easily crushed and easily formed as a wire mesh.

  Next, after forming a wire mesh, carburizing treatment is performed to disperse the carbide on the surface, and the dispersive solid solution is dispersed in the matrix so that the size of the carbide becomes 2 μm or less in terms of equivalent circular diameter. Adjust the carburizing amount. As shown in FIG. 6, the metal mesh after carburizing has carbide irregularities on the surface. The substrate has an austenite structure. As shown in FIG. 7, carbides are dispersed as black dots in the substrate. The size of the carbide is 0.5 μm or less, that is, the particle size represented by the equivalent circular diameter is 2 μm or less. Further, the carbide is large on the outside and decreases on the core side, and the density of the carbide gradually decreases from the outside toward the core. Further, since the portion where the stainless fine wire overlaps is less carburized from the surface, the amount of carbide in the portion where the stainless fine wire overlaps is less than the amount of carbide on the exposed surface. Moreover, it is made almost the same amount as the core side. In addition, the overlapped part is hardly heated due to high heat during carburizing treatment, the overlapped part is returned, plastic return (swells due to heat and does not collapse), shape change, etc. are hardly recognized, and the uniformity of the eyes with a stable shape is ensured. Yes. The carburizing zone temperature was 920 ° C., the diffusion zone temperature was 920 ° C., the total length of the carburizing zone and the total length of the diffusion zone were divided by the wire feed rate, that is, the carburizing and diffusion time was 30 seconds.

  Thus, high tensile strength can be obtained by the carbide carburized in the austenite structure. On the other hand, since the carbide is carburized in the austenite structure, the decrease in elongation is small, the tensile strength is high, the shape accuracy is secured, the uniformity, shape stability, strength and flexibility are good, and the metal parts are small in thickness. Even if it exists, there is little deformation | transformation and it can be set as a highly precise micro metal part with high intensity | strength, and it will be useful for long life, further size reduction, etc. of a micromachine. Further, since the amount of carbide can be increased, it is also possible to obtain a minute metal part having a smaller elongation and a higher tensile strength.

Although the present invention has been described based on the embodiments and examples, the present invention is not limited to only these specific forms, and various specific forms described can be made within the definitions described in the appended claims. Or the present invention may take other forms.
For example, nitrogen gas is introduced into the second half of the first core tube or the second and third core tubes in place of the carburizing source, and the surface of the carburized metal wire is nitrided when passing through these core tubes. A functionally graded material can also be produced by forming a phase.

It is a longitudinal cross-sectional view of the continuous vacuum carburizing apparatus of FIG. It is sectional drawing which shows the principal part of the continuous vacuum carburizing apparatus by another Example of this invention. It is a figure which shows arrangement | positioning of the gas introduction pipe | tube and exhaust pipe of the apparatus of FIG. It is a figure which shows the example of a change of the pipe | tube arrangement | positioning of FIG. 4A. It is a figure which shows another example of a change of the pipe | tube arrangement | positioning of FIG. 4A. It is a table | surface which shows the component of the starting material of the Example of the metal mesh of a stainless steel extra fine wire as a fine metal component of this invention. It is the elements on larger scale before carburizing of the Example of the metal mesh of the stainless steel extra fine wire as a minute metal part of this invention. It is the elements on larger scale after carburizing of the Example of the metal mesh of the stainless steel extra fine wire as a minute metal part of this invention. It is the partial expanded cross-section structure | tissue photograph which cut | disconnected the stainless steel extra fine wire of the wire mesh of the stainless extra fine wire as a micro metal component of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 11, 12 Core tube 2 Carburizing gas introduction pipe 3 Carrier gas introduction pipe 4 Exhaust pipe 5 Carburizing part 6 Diffusion part 7 Carrier wire 8 Vacuum vessel exhaust pipe 9 Vacuum vessel 10 Heater

Claims (19)

  Under a reduced pressure of 5 kPa or less, at least one carburizing atmosphere having a constant pressure and gas composition is formed using one of chain saturated hydrocarbon, chain unsaturated hydrocarbon gas and cyclic hydrocarbon as a carburizing source. Activating the carbon in the carburizing atmosphere, and continuously passing through the carburizing atmosphere a carrier wire on which a minute metal component having a desired carbon content or a carbon content less than that is locked. A continuous vacuum carburizing method that includes carburizing minute metal parts.   The method according to claim 1, further comprising heating a certain area where the carburizing atmosphere does not exist and passing through the carburizing atmosphere and the minute metal part and the carrier wire, thereby removing carbon carburized in the minute metal part. A continuous vacuum carburizing method comprising diffusing into the cross section.   The method according to claim 1, wherein activating the carbon includes heating the carburizing atmosphere to 850 ° C to 1050 ° C.   2. The continuous vacuum carburizing method according to claim 1, wherein activating the carbon includes plasmifying the carbon and heating the carburizing atmosphere to 400 ° C to 1050 ° C.   The continuous vacuum carburizing method according to claim 1, further comprising setting a pressure around the carburizing atmosphere to be lower than that of the carburizing atmosphere.   3. The continuous vacuum carburizing method according to claim 2, further comprising supplying and exhausting a carrier gas to the certain region to form a carrier gas atmosphere.   3. The continuous vacuum carburizing method according to claim 2, wherein the micro metal part is repeatedly passed through the carburizing atmosphere and then through the predetermined region a plurality of times.   The continuous vacuum carburizing method according to claim 1, wherein the carburizing is performed until the minute metal part has a desired carbon content or higher.   2. The method according to claim 1, wherein the minute metal part is carburized to the center of the cross section of the minute metal part with a thickness of the thick part of 0.02 mm to 3 mm.   2. The continuous vacuum carburizing method according to claim 1, wherein the minute metal part is carburized only on a surface layer portion thereof.   2. The continuous vacuum carburizing method according to claim 1, wherein the minute metal part is made of one of carbon steel for machine structure, alloy steel for machine structure, tool steel, spring steel, and stainless steel.   2. The method according to claim 1, wherein the micro metal component is one of nickel and cobalt alloys containing one or more carbide forming elements of boron, titanium, vanadium, chromium, zirconium, niobium, molybdenum, hafnium, tantalum, and tungsten. A continuous vacuum carburizing method.   2. The method according to claim 1, wherein the minute metal part is a metal or alloy containing as a main component one of carbide forming elements of boron, titanium, vanadium, chromium, zirconium, niobium, molybdenum, hafnium, tantalum, and tungsten. A continuous vacuum carburizing method comprising one of the above. A core that surrounds the fixed space and is formed so that the carrier wire locked with the minute metal parts is continuously passed through the fixed space;
Carburize one of chain saturated hydrocarbon, chain unsaturated hydrocarbon gas, and cyclic hydrocarbon under reduced pressure of 5 kPa or less so as to form at least one carburizing atmosphere with constant pressure and gas composition Means for supplying and exhausting into the core as a source;
And a means for activating carbon in a carburizing source in the core.   15. The continuous vacuum carburizing apparatus according to claim 14, wherein the means for activating the carbon includes an electric heater for heating the core to 850 ° C. to 1050 ° C.   15. The continuous vacuum carburizing apparatus according to claim 14, wherein the means for activating the carbon includes a discharge device that performs glow discharge in the core portion and an electric heater that heats the core portion to 400 ° C. to 1050 ° C. .   15. The apparatus according to claim 14, further comprising a take-up take-up mechanism for passing the carrier wire, on which the minute metal part is locked, through the core portion, and the core portion, supply exhaust means and heating means. This vacuum vessel is a continuous vacuum carburizing apparatus that keeps the inside of the vacuum vessel at a lower pressure than the inside of the core.   15. The apparatus according to claim 14, further comprising forming at least one carrier gas atmosphere in which the carburizing source does not exist at a downstream side of the carburizing atmosphere with respect to a moving direction of the carrier wire to which the minute metal part is locked. A continuous vacuum carburizing apparatus having means for supplying and exhausting a carrier gas to the core. 15. The continuous vacuum carburizing apparatus according to claim 14, wherein the core section and the supply / exhaust means form a plurality of carburizing atmospheres in the core section.