WO2005003400A1

WO2005003400A1 - Method of continuous vacuum carburization of metal wire, metal band or metal pipe and apparatus therefor

Info

Publication number: WO2005003400A1
Application number: PCT/JP2004/009181
Authority: WO
Inventors: Kiyohito Ishida; Hirokuni Amano; Yasushi Hara; Tetsushi Machi
Original assignee: Nachi-Fujikoshi Corp.
Priority date: 2003-07-04
Filing date: 2004-06-30
Publication date: 2005-01-13
Also published as: JP4381381B2; US20060124203A1; JPWO2005003400A1

Abstract

A method of continuous vacuum carburization in which a material of desirable carbon content or less carbon content, such as steel wire (7), is continuously passed through carburization atmosphere (5) of given pressure and gas composition in vacuum to thereby effect carburization. The continuous vacuum carburization apparatus for carrying out this method comprises vacuum vessel (1) and, disposed therein, at least one furnace core pipe (1, 11, 12) and steel wire (7) delivery and winding means (13, 14). Carburization source gas is charged into and discharged from the furnace core pipe (1) through pipes (2, 4) to thereby form carburization atmosphere (5). The furnace core pipe (1) is heated by heater (10) to thereby activate carbon contained in the carburization source gas. Thus, carburization with reduced carburization quantity variation and free of surface oxidation and sooting can be carried out on a material of thickness as small as, for example, 0.02 to 3 mm.

Description

Specification

Method and apparatus for continuous vacuum carburization of metal wires, metal strips or metal pipes

The present invention generally relates to a method and an apparatus for producing a metal material having excellent toughness and wear resistance.

In particular, the invention relates to a method for continuous vacuum carburization of metal wires, strips or pipes and to an apparatus for performing the method.

Background art

[0002] Most steels used as wear-resistant materials have relatively high carbon contents and poor cold workability. Therefore, for example, in the cold drawing process of a steel wire, it is necessary to frequently perform strain relief annealing on the work-hardened wire to reduce the hardness. Such frequent strain relief annealing increases the process lead time.

Furthermore, in the case of ingots, huge primary carbides are formed in the material during the solidification process. This giant carbide remains without being completely destroyed in the subsequent hot working and cold working. Therefore, when this material is used as a wire rod, the giant carbide acts as a stress concentration source for fracture, causing chipping or breakage.

[0003] In response to such a problem, Japanese Patent No. 3053605 discloses a technique of processing a low-carbon steel material having a limited component balance into a thin plate or a thin wire shape, and thereafter carburizing the steel to the center. are doing. This technology provides a metal material having excellent toughness and abrasion resistance with high production efficiency, in which hard carbides are finely and uniformly distributed. However, there is no mention in this patent of the problems of carburizing wire and strip.

[0004] JP-A-6-192814 and JP-A-7-126829 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 the above patents indicate.

[0005] Regarding the carburizing depth when carburizing steel, when carburizing an object having a size of a semi-infinite depth in practical use, gas carburizing by adjusting the carbon potential of the carburizing gas, Vacuum carburization, in which carburization is performed under pressure, is a known technique.

However, in the case of a small diameter material such as a steel wire, since the material radius and the carburizing depth are the same, as shown in the above-mentioned Japanese Patent No. 3053605, the carburized material is put into a furnace and then carburized. Even if the carburizing 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.

[0006] In addition, particularly in the case of gas carburization, soot adheres to the surface of the material, so that the amount of carburization increases and coarse carbides are generated, or surface defects occur due to surface oxidation, or the amount of carbon is insufficient. As a result, a problem that a predetermined heat treatment hardness cannot be obtained easily occurs.

Particularly when the wire diameter is small and the material is subjected to batch processing, a predetermined amount of carburizing is reached in the initial stage of introduction of the carburizing atmosphere gas into the furnace, and the control thereof is extremely difficult. Furthermore, because of the large specific surface area, the effect of surface defects cannot be ignored.

Disclosure of the invention

Problems to be solved by the invention

[0007] In view of the above-mentioned problems, the present invention provides a method of carburizing a metal wire, a metal strip, or a metal pipe in which the amount of carburization in the material is extremely small and there is no surface oxidation coating. The purpose is to:

Another object of the present invention is to provide a carburizing apparatus that effectively performs the above method. Means for solving the problem

[0008] To achieve the first object, according to the present invention, one of a chain saturated hydrocarbon, a chain unsaturated hydrocarbon gas, and a cyclic hydrocarbon is carburized under a reduced pressure of 5 kPa or less. Forming at least one carburizing atmosphere of constant pressure and gas composition as a source, activating the carbon in this carburizing atmosphere, and the desired or lower carbon content A continuous vacuum carburizing method comprising continuously carburizing one material of one of the following metal wires, metal strips and metal pipes through the carburizing atmosphere.

[0009] In order to effectively carry out the above method, a continuous vacuum carburizing apparatus according to another aspect of the present invention encloses a certain space and continuously cuts one material of a metal wire, a metal strip, and a metal pipe. A core formed so as to pass through a certain space, and a cup with constant pressure and gas composition At least one of chain-type saturated hydrocarbon, chain-type unsaturated hydrocarbon gas and cyclic hydrocarbon is supplied as a carburizing source into the core under reduced pressure of 5 kPa or less so as to form at least one carburizing atmosphere. And a means for activating carbon in the carburizing source in the core.

[0010] According to the above configuration, the carburizing atmosphere is in a reduced pressure state in which an oxide layer is not formed on the surface of the material and the carburizing source does not generate soot on the surface of the material. The composition is constant. By passing the material to be carburized into such an atmosphere, good carburization with little variation in the amount of permeation is possible. The material can be continuously carburized, and large amounts of material can be processed efficiently.

[0011] The continuous vacuum carburizing method further heats a certain region where one material passes following the carburizing atmosphere and where there is no carburizing source, and diffuses the carburized carbon into this one material into the inside of the cross section. Preferably, including including letting.

A carrier gas atmosphere may be formed in this fixed region by supplying and exhausting a carrier gas.

Therefore, the continuous vacuum carburizing apparatus supplies the carrier gas to the core so as to form at least one carrier gas atmosphere having no carburizing source downstream of the carburizing atmosphere in the moving direction of one material. It is preferable to have a means for exhausting gas. By providing such a region, a desired amount of carbon can be surely diffused into the material.

[0012] The activation of the carbon 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.

The activation of the carbon may be performed by turning the carbon into plasma in addition to heating the carburizing atmosphere. Therefore, the continuous vacuum carburizing apparatus preferably includes an electric heater for heating the core to 400 ° C. and 1050 ° C., and a discharger for performing glow discharge. By accelerating the carbon ions, carburizing of the material can be performed more efficiently. [0013] The method may further include reducing the pressure around the carburizing atmosphere to a lower pressure than the carburizing atmosphere.

The above apparatus has a feeding and winding mechanism for passing one material through a core portion, and a vacuum container for storing the core portion, a supply / exhaust means, and a heating means. It is preferable to keep the pressure lower than the inside of the section.

By reducing the pressure in the surroundings, the gas that has degraded by the reaction can be quickly taken out of the carburizing atmosphere, and the external pollutant gas can be prevented from flowing into the carburizing atmosphere. Thus, the gas composition in the carburizing atmosphere can be stably maintained at a desired state.

[0014] In the above-mentioned method, passing one material into a carburizing atmosphere in the next step without a carburizing source or passing through a certain region may be repeated a plurality of times.

In order to carry out such a method, in the continuous vacuum carburizing apparatus, it is preferable that the core portion and the supply / exhaust means form a plurality of carburizing atmospheres in the core portion. Depending on the steel material, if the amount of carbon necessary for carburizing the central portion is carburized at once, coarse reticulated carbide may be precipitated on the surface. In this case, pulse carburization in which carburization and diffusion are gradually repeated several times is effective. Such pulse carburizing can be performed by forming a plurality of carburizing atmospheres in the core.

[0015] Carburization is preferably performed until one material has a desired or higher carbon content.

According to such a method, a material having a low carbon content is used, and the material is formed into a desired shape by cold working and then subjected to a good carburizing treatment, thereby facilitating the working of the material and providing a desired strength. be able to.

[0016] The material to be carburized has a diameter of 0.02 mm to 3 mm for a metal wire, a thickness or width of 0.02 mm to 3 mm for a metal band, and a thickness of 0 for a metal pipe. It can be from 02mm to 3mm.

In the continuous vacuum carburizing method of the present invention, the material is continuously fed into a constant carburizing atmosphere, so that even if the material has a small thickness and the thickness and the carburizing depth are almost the same level, the carburizing variation is extremely small. is there.

The carburization may be performed up to the center of the cross section of the material or may be performed only on the surface layer. [0017] The material 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 to be carburized is one of a nickel and cobalt alloy containing at least one element of boron, titanium, vanadium, chromium, zirconium, niob, molybdenum, hafnium, tantalum, and tungsten carbide forming elements. I'm sorry.

Alternatively, the material to be carburized may be a metal or alloy based on one of the carbide-forming elements boron, titanium, vanadium, chromium, zirconium, niob, molybdenum, hafnium, tantalum, and tungsten. .

The invention's effect

[0018] As described above, according to the continuous vacuum carburizing method and apparatus of the present invention, by passing a material through a constant carburizing atmosphere, it is possible to perform good carburization with extremely little variation in the amount of permeation. . In particular, in the case of a material having a small diameter and thickness, conventionally, there has been a problem that a predetermined hardness cannot be obtained after heat treatment or a problem that coarse carbides are generated. However, according to the method and apparatus of the present invention, these problems are solved. Can be prevented.

BEST MODE FOR CARRYING OUT THE INVENTION

[0019] The continuous vacuum carburizing method and apparatus of the present invention will be described in detail based on embodiments shown in the accompanying drawings.

FIG. 1 schematically shows a process of manufacturing a tool steel wire employing a continuous vacuum carburizing apparatus according to an embodiment of the present invention. This process includes a continuous drawing step, a continuous strain relief annealing step, a carbide dispersion carburizing step, and a quenching and tempering step using a low carbon alloy steel wire as a raw material.

[0020] In the continuous drawing step, the wire is continuously fed from the supply side to the winding side, and is drawn with high efficiency through a plurality of dies. A wire with a diameter of 5-8 mm is passed through the die about 5 to 20 times, and the cross-sectional area is reduced to 1/5 or less.

The wire hardened by this processing is then transferred to a continuous strain relief annealing stage, where it is heated to a predetermined temperature in a continuous strain relief furnace to reduce its hardness. After that, the wire is returned to the continuous drawing stage and drawn again until it becomes thinner than the cross-sectional area force. Drawing and continuous straightening are repeated until the wire reaches a predetermined wire diameter. When the wire is completely drawn to a predetermined wire diameter, the wire is moved to a carbide dispersed carburizing stage. At this stage, the continuous vacuum carburizing apparatus of the present invention performs carburizing treatment on the wire to the inside of the cross section. The carburized wire is transferred to a quenching and tempering stage. At this stage, the wire is continuously quenched and tempered in a continuous quenching and tempering furnace, and thus a wire having a predetermined hardness is obtained.

FIG. 2 shows the continuous vacuum carburizing apparatus or furnace of the present embodiment in detail.

This continuous vacuum carburizing furnace comprises an elongated vacuum vessel 9, a plurality of (three in the illustrated example) furnace core tubes 1, 11, 12 arranged along the longitudinal direction of the vessel, and a steel wire drawn to a predetermined diameter. It has a payout winding mechanism for passing the wire 7 through a core portion composed of these core tubes.

Each furnace 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, 4. Furthermore, each furnace tube is provided with an electric heater 10 along its longitudinal direction.

These introduction pipes 2 and 3 and exhaust pipes 4 and 4 are connected to the furnace tube through the vacuum vessel 9. Carburizing gas and carrier gas are introduced into the furnace tube from outside the vacuum vessel and discharged outside the vacuum vessel. It is supposed to.

[0024] The exhaust pipes 4, 4 are arranged on both sides of the carburizing gas introduction pipe 2 in the longitudinal direction of the furnace core pipe, and the inside of the furnace core pipe between these exhaust pipes becomes a carburizing portion 5 occupied by the carburizing gas. The carrier gas introduction pipe 3 is disposed downstream of the introduction pipe 2 and the exhaust pipes 4, 4 with respect to the moving direction of the steel wire 7, and the inside of the core pipe on the downstream side becomes a diffusion section 6 filled with carrier gas.

In FIG. 2, power core tubes 11 and 12 in which reference numerals 2 to 6 and 10 are assigned only to core tube 1 have the same structure.

The vacuum container 9 has an exhaust pipe 8 provided with a vacuum exhaust valve (not shown), and the inside of the container can be exhausted.

The unwinding mechanism includes an unwinding bobbin 13 and a unwinding bobbin 14 disposed on both sides of the core tubes 1, 11, and 12 in the vacuum vessel. These bobbins 13 and 14 are driven to rotate, pay out the steel wire 7 wound on the bobbin 13, and wind up the bobbin 14 through the core tubes 1, 11 and 12.

Note that the feeding and winding mechanism may be provided outside the vacuum vessel. In this case, the differential It is desirable to provide a pneumatic mechanism so that the air does not enter the vacuum vessel as the steel wire 7 moves.

[0026] This continuous vacuum carburizing furnace is operated as follows according to an embodiment of the method of the present invention.

First, the steel wire 7 is passed from the unwinding bobbin 13 to the core tubes 1, 11, 12 and connected to the winding 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 equal to or less than lOPa, an electric current is supplied to the heater 10, and the core tubes 1, 11, and 12 are 850. C force, et al 1050. Heat the calo to a predetermined temperature of C.

Thereafter, a carburizing source gas such as ethylene and a carrier gas such as nitrogen or argon are introduced into the furnace core tubes 1, 11 and 12 from the carburizing gas introducing pipe 2 and the carrier gas introducing pipe 3. 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 furnace tubes 1, 11, and 12 is restored to 5 kPa or less, preferably to 13 kPa. After adjusting the atmosphere, the pay-out winding mechanism is operated, and the steel wire 7 is passed through the core tubes 1, 11, and 12 and wound on the bobbin 14. When the required amount of steel wire has been obtained, cool the furnace, break the vacuum vessel in vacuum, and remove the steel wire 7 from the furnace together with the bobbin. Thus, a steel wire processed to a predetermined diameter and carburized can be obtained.

[0028] The carburizing source gas can be vacuum carburized by being continuously introduced into and exhausted from each of the core tubes heated to 850 ° C to 1050 ° C from the introduction tube 2 and the exhaust tubes 4, 4. It functions as a constant carburizing atmosphere of pressure and composition gas. This atmosphere carburizes the steel wire 7 passing through it. The carburized steel wire 7 subsequently passes through the heated diffusion 6 of each core tube. Carburized carbon diffuses into the alloy cross section from the surface of the steel wire 7 where there is no carburizing gas in the diffusion part.

The carburized portion may be limited to the vicinity of the surface or may be entirely carburized to the center.

[0029] In the continuous vacuum carburizing method of the present invention, a chain saturated hydrocarbon, a chain unsaturated hydrocarbon gas, or a cyclic hydrocarbon is used as a carburizing source under a reduced pressure of 5 kPa or less. The reason is that if the pressure exceeds 5 kPa, soot is generated on the surface of the material to be treated, and normal carburization cannot be performed. The reason why the carburizing atmosphere is reduced pressure is that the gas carburizing performed at normal pressure generates an oxide layer of 5-10 zm on the surface of the material to be treated. In particular, in the case of small-diameter wire rods having a large specific surface area, the effect of defects caused by the small diameter wire rods is large. [0030] The heating temperature condition of the above-mentioned carburizing atmosphere is such that at 850 ° C or lower, except for a specific gas such as acetylene, the gas to be a carburizing source does not start the reaction to form cementite on the surface of the material. As a result, the material is not carburized. At 850 ° C or lower, the diffusion rate of carbon in steel is low, 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 if the temperature exceeds 1050 ° C, the mechanical properties which are remarkable due to the grain growth of the steel wire are deteriorated.

[0031] The material to be treated by the continuous vacuum carburizing method of the present invention is preferably, for example, a wire having a diameter of 0.02 mm 3 mm. If it is less than 0.02 mm, it is difficult to control the carburizing depth. If the diameter exceeds 3 mm, the carburizing time required for carburizing to the center is long, and the influence of the variation in the gas introduction time is small, so there is no need to use the method of the present invention for carburizing.

It is needless to say that the method of the present invention is effective when only the surface layer is carburized at a constant concentration regardless of the size of the material.

[0032] In the above embodiment, the force for heating the furnace tubes 1, 11, 12 to activate the carbon in the carburizing source gas may be used in combination with the plasma.

FIG. 3 shows a main part of a continuous vacuum carburizing apparatus according to another embodiment of the present invention, which performs such vacuum plasma carburizing. This device has the same configuration as that of the embodiment of FIG. 2 except for the portion 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. Discharger 15 is electrically connected to furnace tube 1 and steel wire 7 via bobbin 13. During operation of the apparatus, the discharger 15 pumps the voltage using the furnace tube 1 as an anode and the steel wire 7 as a cathode. As a result, a glow discharge occurs in the furnace tube 1 and the introduced carburizing source gas is turned into plasma. In addition, the electric heater 10 core furnace tube 1 is heated to 400 ° C-1050 ° C.

The carbon in the plasma carburizing source gas is ionized, and the carbon ions adhere to the surface of the steel wire 7 effectively. The apparatus of this embodiment further promotes carburizing of the steel wire 7 by turning the carburizing source gas into plasma.

FIG. 4A is 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. Is shown.

The pipe arrangement in FIG. 4A is such that only the hatched portion of each core tube is the carburizing source gas atmosphere, that is, the carburizing portion 5, and the adjacent region on the right side of the drawing is the diffusion portion 6 where no carburizing source gas is present. In other words, the carburizing gas and the carrier gas are simultaneously introduced into the furnace tube, and try to mix inside. By arranging the exhaust pipe 4 between the inlet pipes 2 and 3 and evacuating independently from the furnace tube at the intermediate portion of both gases, it is possible to prevent carburizing gas from entering the right side of the furnace tube.

[0035] The introduction and exhaust of the carburizing source into the furnace tube is performed in order to maintain the carburizing source inside the furnace tube at an appropriate pressure and atmosphere. Gas exists. In order to prevent this gas from leaking to the diffusion part, a carrier gas introduction pipe for blocking may be installed near the boundary with the diffusion part.

Alternatively, the furnace tube portion of the carburizing section and the furnace tube section of the diffusing section are cut off to allow the carburizing source gas introduced into the carburizing section to escape into the vacuum vessel, thereby preventing the carburizing gas from leaking to the diffusing section. Good. In any case, it is important to keep the carburized part and the diffused part in the carburizing source gas atmosphere and the carburizing source free atmosphere, respectively.

FIGS. 4B and 4C show modified examples of the arrangement in FIG. 4A, respectively, to prevent carburizing gas from leaking to the diffusion section.

In the example of FIG. 4B, the carrier gas introduction pipes 31-33 and the exhaust pipes 41, 42 to the furnace core pipe are increased in order to more reliably prevent the carburizing gas from entering the furnace core pipe right side area.

In the example of Fig. 4C, the furnace tube for the carburizing region and the furnace tube for the diffusion region are completely separated from each other. In this case, the carburizing gas and the carrier gas escape from the respective furnace tubes into the vacuum vessel, so there is no need to exhaust them directly from the furnace tubes.

Table 1 shows the results of trial production of carbon steel for machine structures, alloy steel for machine structures, tool steel, spring steel, or stainless steel wire by the above-described manufacturing process. Table 1 shows the carbon content after carburizing at 6 places of the samples made by drawing the rolled coils of various steel materials and carburizing according to the present invention and carburizing by the conventional batch processing. The variability examined is shown.

Prototype No. 1 No. 9 in Table 1 is a tool steel wire, prototype No. 10 No. 15 is stainless steel No. 16-No. 17 is a carbon steel wire, No. 18-19 is an alloy steel wire, and No. 20-21 is a spring steel wire.

[table 1]

[0039] According to Table 1, when the diameter is 0.1 mm, the carburization variation is about 2.0% in the conventional carburizing method, and 0.01% in the method of the present invention. In addition, when the diameter is 0.2 mm, the carburization variation is about 1.5% in the conventional carburizing method, and about 0.02% in the method of the present invention. Thus, in the continuous vacuum carburizing method of the present invention, good results were obtained.

[0040] Of the tool steel wire rods, a probe pin was formed from a 0.1 mm diameter SKH5 :! equivalent steel wire made in prototype No. 13 and a 3 mm diameter SKH51 equivalent steel wire made in prototype No. 46. Drill pins were manufactured, and dot pins were manufactured from 0.2 mm diameter Co-containing high-speed tool steel wires made in Prototype Nos. 7-9. The results of the performance evaluation are shown in FIGS. 5, 6, and 7.

[0041] The graph of Fig. 5 shows the bending strength of the prototyped probe pin in comparison.

Prototype No. 1 was prepared by drawing a 5.5 mm diameter rolled coil having a carbon content smaller than desired to a diameter of 0.1 mm and then obtaining the desired carbon content by the continuous vacuum carburizing method of the present invention. . Prototype No. 2 measures the same rolled coil as prototype No. 1 and draws the same carbon content by the conventional method. The amount of the sample within a predetermined range is selected and allocated to the probe pin. In prototype No. 3, a 5.5 mm diameter rolled coil already containing the desired carbon content was drawn to a diameter of 0.1 mm.

[0042] The graph of Fig. 6 shows a comparison between the lifespans of the trial drills used for cutting under the conditions shown.

Prototype No. 4 is obtained by drawing a 5.5 mm-diameter rolled coil having a carbon content smaller than the desired amount to a diameter of 3 mm, and then carburizing to a desired carbon content by the continuous vacuum carburizing method of the present invention. In prototype No. 5, the same rolled coil as in No. 4 was similarly drawn and then carburized to the desired carbon content by the conventional method. In prototype No. 6, a 5.5 mm diameter rolled coil already containing the desired amount of carbon was drawn to a diameter of 3 mm.

The graph of FIG. 7 shows a comparison between the bending strengths of the prototype dot pins.

Prototype No. 7 is obtained by drawing a 5.5 mm-diameter rolled coil having a carbon content smaller than desired to a diameter of 0.2 mm, and then obtaining the desired carbon content by the continuous vacuum carburizing method of the present invention. . Prototype No. 8 measures the same carbon content as the prototype No. 7 after drawing the same rolled coil and then using the conventional method to obtain a predetermined carbon content. Samples having a carbon content within a predetermined range are selected and allocated to dot pins. Trial production

In No. 9, a 5.5 mm diameter rolled coil already containing the desired amount of carbon was drawn to a diameter of 0.2 mm.

[0044] Of the tool steel wire rods shown in the graphs of Fig. 5 to Fig. 7, trial production Nos. 1, 2, 4, 5, 7 and 8 use steel wire having a lower carbon content than the desired carbon content. A steel wire having a desired carbon content was obtained by carburizing after drawing with efficiency.

[0045] The bending stress of the probe pin and the dot pin and the cutting life of the drill shown in Figs. 5 to 7 were determined by carburizing after drawing a sample manufactured from a rolled coil containing a desired amount of carbon shown as a comparative example. The samples obtained exceeded the results of the conventional method and the method of the present invention. Among them, the method of the present invention has obtained even better results. This is an effect due to the fact that the method of the present invention is an excellent carburizing method in which coarse carbides and the like are less likely to be generated.

Table 2 shows the results of applying the continuous vacuum carburizing method of the present invention to a nitinol wire composed of nickel and titanium. Table 2 shows the variation in the carbon content measured and measured at six force points for the ditinol wire rod carburized by the method of the present invention and the conventional method. From Table 2, it can be seen that, similarly to the results for the steel materials in Table 1, the carburization by the method of the present invention has much less variation in carbon content than the conventional method.

[Table 2]

,

Supply chemical composition; ash diffusion diffusion

(w t%)

Wire diameter JD time Time Time After carburizing c%

No C Ti Ni Carbon adjustment Adjusted ash car method mm. c minutes. c min 1 2 3 4 5 6

1 2.20 2.21 2.20 2.20 2.20 2.20

0.01 45.0 The method of the present invention

55.0 1.00 950 3.0

2 Carburizing of supply line 0.5 950

Conventional method 0.50 0.25 0.99 3.20 2.45 1.91

[0048] Although the present invention has been described based on the embodiments, the present invention is not limited to only these specific forms, and various changes may be made to the specific forms described within the definitions described in the appended claims. Alternatively, the present invention may take other forms.

For example, in the above-described embodiment, the steel wire is carburized. However, the present invention is not limited to a wire having a circular cross-section, but a material having a small cross-section even if it has a different shape such as a pipe or a band. If so, it is as effective as a line.

[0049] Further, instead of the carburizing source, for example, nitrogen gas is introduced into the second half of the first core tube or the second and third core tubes, and when the metal wire after carburizing passes through these core tubes, A functionally graded material can be produced by forming a nitrided phase on the surface.

Industrial applicability

[0050] By performing the carburization of the present invention using a tool steel having a carbon content less than a desired amount, a tool steel thin wire can be manufactured with high manufacturing efficiency, and a tool used for a dot printer pin, a probe pin, a drinole, and the like. The production lead time of steel wire can be greatly reduced.

In addition, by applying the carburizing of the present invention to stainless steel, a carburized layer can be uniformly obtained near the surface with a depth accuracy that cannot be obtained by the conventional carburizing method. As a result, the inside of the cross section has flexibility, and the surface force is carburized to an arbitrary constant depth to obtain an ultra-fine stainless steel wire with appropriate rigidity, making it suitable for machine parts that require corrosion resistance and wear resistance. The range of applications for is expanded.

Alternatively, by carburizing Nitinol, an example of a nickel alloy, fine carbides precipitate on the surface or inside the cross section. When this is applied to a guide wire for a catheter, a guide wire excellent in operability having flexibility and appropriate rigidity can be obtained.

Brief Description of Drawings

FIG. 1 is a schematic view showing a process for manufacturing a tool steel wire employing a continuous vacuum carburizing apparatus according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of the continuous vacuum carburizing apparatus of FIG. 1.

FIG. 3 is a cross-sectional view showing a main part of a continuous vacuum carburizing apparatus according to another embodiment of the present invention.

FIG. 4A is a view showing an arrangement of a gas introduction pipe and an exhaust pipe of the apparatus of FIG. 2.

FIG. 4B is a view showing a modified example of the pipe arrangement of FIG. 4A. 4C] is a view showing another modification of the pipe arrangement in FIG. 4A.

Garden 5] is a graph showing a comparison between the bending strengths of the probe pins prototyped by the method of the present invention and the conventional method.

Garden 6] is a graph showing a comparison of the processing performance of a drill material prototyped by the method of the present invention and a conventional method.

FIG. 7 is a graph showing a comparison between the bending strengths of the dot pins prototyped by the method of the present invention and the conventional method.

Claims

The scope of the claims

[1] At least one carburizing atmosphere with a constant pressure and gas composition using one of a chain saturated hydrocarbon, a chain unsaturated hydrocarbon gas, and a cyclic hydrocarbon under a reduced pressure of 5 kPa or less under a reduced pressure. And activating the carbon in the carburizing atmosphere, and the material of one of the desired carbon content or less, a carbon wire, a metal strip, a metal strip and a metal pipe. A continuous carburizing method comprising continuously carburizing the one material through the carburizing atmosphere.

[2] The method according to claim 1, further comprising: heating a certain area where the one material passes following the carburizing atmosphere and where the carburizing source is not present, to remove the carburized carbon in the one material. A continuous vacuum carburizing method comprising diffusing into the interior of the cross section.

[3] The method according to claim 1, wherein activating the carbon comprises heating the carburizing atmosphere to 850 ° C to 1050 ° C.

[4] The method according to claim 1, wherein activating the carbon comprises plasmaticizing the carbon and heating the carburizing atmosphere to 400 ° C-1050 ° C. Method.

[5] The method according to claim 1, further comprising reducing the pressure around the carburizing atmosphere to a lower pressure than the carburizing atmosphere.

[6] The method according to claim 2, further comprising supplying and exhausting a carrier gas to the certain area to form a carrier gas atmosphere.

7. The continuous vacuum carburizing method according to claim 2, wherein passing the one material through the carburizing atmosphere and then through the certain area is repeated a plurality of times.

[8] The continuous vacuum carburizing method according to claim 1, wherein the carburizing is performed until the one material has a desired carbon content or higher.

[9] The method according to claim 1, wherein the one material has a diameter of 0.0 in the case of a metal wire.

2 mm to 3 mm, thickness or width of 0.02 mm to 3 mm for metal strip, 0.02 mm to 3 mm for metal pipe, carburized to the center of the cross section of the one material Is a continuous vacuum carburizing method.

[10] The method according to claim 1, wherein the one material is carburized only on its surface. Continuous vacuum carburizing method.

[11] The method according to claim 1, wherein the one material comprises one of carbon steel for machine structure, alloy steel for machine structure, tool steel, spring steel and stainless steel.

12. The method according to claim 1, wherein said one material comprises one or more of the following carbide forming elements: boron, titanium, vanadium, chromium, zirconium, niobium, molybdenum, hafnium, tantalum, and tungsten. A continuous vacuum carburizing method that produces one of these.

[13] The method according to claim 1, wherein the one material is mainly composed of one of boron carbide forming elements of boron, titanium, vanadium, chromium, zirconium, niobium, molybdenum, hafnium, tantalum, and tungsten. Continuous vacuum carburization method consisting of one of the following metals and alloys:

[14] a core portion surrounding a certain space and formed by continuously passing one material of a metal wire, a metal strip and a metal pipe through the certain space;

One of a chain saturated hydrocarbon, a chain unsaturated hydrocarbon gas and a cyclic hydrocarbon under reduced pressure of 5 kPa or less so as to form at least one carburizing atmosphere with a constant pressure and gas composition. Means for supplying and exhausting into the core part as a carburizing source, and means for activating carbon in the carburizing source in the core part

And a continuous vacuum carburizing device.

[15] The apparatus according to claim 14, wherein the means for activating the carbon comprises:

Continuous vacuum carburizing equipment including an electric heater that heats to 1050 ° C.

[16] The apparatus according to claim 14, wherein the means for activating the carbon comprises: a discharge device for performing glow discharge in the core portion; and an electric heater for heating the core portion to 400 ° C to 1050 ° C. Including, continuous vacuum carburizing equipment.

[17] The apparatus according to claim 14, further comprising a feeding and winding mechanism for passing the one material through the core portion, and a vacuum container accommodating the core portion, supply / exhaust means and heating means. A continuous vacuum carburizing apparatus for maintaining the inside of the vacuum vessel at a lower pressure than the inside of the core.

[18] The apparatus according to claim 14, further comprising at least one carrier gas atmosphere free of the carburizing source downstream of the carburizing atmosphere with respect to the moving direction of the one material. A continuous vacuum carburizing apparatus, comprising: means for supplying and exhausting a carrier gas to the core.

19. The continuous vacuum carburizing apparatus according to claim 14, wherein the core portion and the supply / exhaust means form a plurality of carburizing atmospheres in the core portion.