JP2018135596A - Manufacturing method of metal products - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a metal product capable of reducing the surface roughness of the metal product after machining. SOLUTION: A solid solution layer in which a predetermined atom exists as an intrusion type solid solution atom is formed on at least the surface of a metal material by an atom nitriding method under the following conditions (a) and / or (b). Later, a method for manufacturing a metal product in which the solid solution layer is machined. (A) Perform the atom nitriding method at a pressure of 10 Pa or less. (B) In the atom nitriding method, the potential of the metal material based on the potential of plasma is −300 to 300V. [Selection diagram] Fig. 2

Description

  The present disclosure relates to a method of manufacturing a metal product.

  Conventionally, a technique for manufacturing a metal product by machining a metal material made of steel or the like using a tool such as a diamond tool is known. This technique has a problem that the tool wears quickly. Non-Patent Document 1 discloses a technique for reducing wear of a diamond tool by subjecting the surface of a metal material to gas nitriding treatment by a conventional method and machining using a diamond tool.

E.Brinksmeier, R.Glabe, J.Osmer, "Ultra-Precision Diamond Cutting of Steel Molds", Annals of CIRP Vol.55 / 1/2006

  In the technique described in Non-Patent Document 1, the surface roughness of the metal product after machining is increased. An object of one aspect of the present disclosure is to provide a method for manufacturing a metal product that can reduce the surface roughness of the metal product after machining.

One aspect of the present disclosure is a solid solution layer in which a predetermined atom exists as an interstitial solid solution atom on at least a surface of a metal material by an atom nitriding method under the following conditions (a) and / or (b): Is a metal product manufacturing method in which a solid solution layer is machined.
(A) An atom nitriding method is performed at a pressure of 10 Pa or less.
(B) In the atom nitriding method, the potential of the metal material with respect to the plasma potential is −300 to 300V.

According to the method for manufacturing a metal product that is one aspect of the present disclosure, the surface roughness of the metal product after machining can be reduced.
Another aspect of the present disclosure is a method for manufacturing a metal product in which a metal material is machined, wherein at least a surface of the metal material is subjected to an atom nitriding method under the following conditions (a) and / or (b): Thus, a solid solution layer in which predetermined atoms exist as interstitial solid solution atoms is formed, and this is a method for manufacturing a metal product in which the solid solution layer is machined.
(A) An atom nitriding method is performed at a pressure of 10 Pa or less.
(B) In the atom nitriding method, the potential of the metal material with respect to the plasma potential is −300 to 300V.
According to the metal product manufacturing method which is another aspect of the present disclosure, the surface roughness of the metal product after machining can be reduced.

FIG. 1A is a plan view illustrating the configuration of the workpiece 101, and FIG. 1B is a cross-sectional view taken along the line IB-IB in FIG. 1A. 2 is an explanatory diagram illustrating a configuration of a nitriding apparatus 1. FIG. It is a measurement result of the three-dimensional optical profiler showing the surface shape of the workpieces 101A and 101R after processing. 4A is a measurement result of an electron beam microanalyzer representing the element distribution in the depth direction of the processed workpiece 101A, and FIG. 4B is an electron beam microanalyzer representing the element distribution in the depth direction of the processed workpiece 101R. It is a measurement result. It is a measurement result of the hardness meter showing the hardness distribution in the depth direction of the workpieces 101A and 101R after processing. It is a graph showing surface roughness Rt of metal products M1-M4. It is a measurement result of the three-dimensional optical profiler showing the surface roughness of the flank near the cutting edge of the cutting tool used in the manufacturing methods P2 and P4. 2 is an explanatory diagram illustrating a configuration of a nitriding apparatus 201. FIG. It is sectional drawing showing the structure of the metal material 301 provided with the solid solution layer 303 on the surface.

An embodiment of the present disclosure will be described.
1. Metal material Examples of the metal material include iron and stainless steel. An example of iron is steel. The metal material may be made of a metal other than iron or stainless steel. Examples of metals other than iron include tungsten, cobalt, and nickel. The metal material may be an alloy of two or more metals.

2. Solid solution layer A solid solution layer is a layer in which predetermined atoms exist as interstitial solid solution atoms in a metal material. A solid solution layer can be formed on at least the surface of the metal material. Examples of the predetermined atom include a carbon atom, a hydrogen atom, a boron atom, a nitrogen atom, and an oxygen atom. The predetermined atom is preferably a nitrogen atom. When the predetermined atom is a nitrogen atom, the surface roughness of the metal product after machining can be further reduced. For example, as shown in FIG. 9, the metal material 301 includes a solid solution layer 303 on the surface.

The solid solution layer can be formed, for example, by a method in which a metal material is placed in a dilute gas containing predetermined atoms, and the dilute gas is irradiated with an electron beam to be excited.
It is preferable that the solid solution layer does not substantially contain a compound having a predetermined atom (hereinafter referred to as a specific compound). This specific compound is a compound of a predetermined atom and a metal contained in a metal material. Specific examples of the specific compound include iron nitride. When the compound of a predetermined atom is not substantially contained, the surface roughness of the metal product after machining can be further reduced.

  When the surface on which the solid solution layer is formed is analyzed by XRD, the amount of the specific compound of the metal that is the main component of the metal product and a predetermined atom is less than the detection limit. It means that there is. It is particularly preferable that the solid solution layer does not contain a specific compound.

  When the predetermined atom is nitrogen, for example, a solid solution layer can be formed by nitriding. An example of the nitriding method is an atom nitriding method. The atom nitriding method is a method of invading and diffusing nitrogen atoms from the surface of a metal material using plasma containing nitrogen atoms. When the atom nitriding method is used, the solid solution layer can be prevented from containing a specific compound of nitrogen and metal.

As a method for generating plasma containing nitrogen atoms, for example, an electron beam excited plasma method or a microwave excited plasma method can be given. The electron beam excitation plasma method is a method of generating plasma by irradiating a gas containing nitrogen with an electron beam. The microwave excitation plasma method is a method of generating plasma by irradiating a gas containing nitrogen with microwaves. Examples of the gas containing nitrogen include a gas composed only of nitrogen, a gas mainly containing nitrogen and further containing hydrogen and the like. According to the electron beam excited plasma method or the microwave excited plasma method,
A high concentration of nitrogen atoms can be generated in the plasma.

In the atom nitriding method, the potential of the metal material is preferably lower than the potential of the plasma, and the potential difference between them is preferably 50 V or less. In this case, it is difficult to form one compound layer on the surface of the metal material. The potential of the metal material based on the plasma potential is defined as a bias voltage. The bias voltage is preferably −300 to 300V. The condition (b) below is that the bias voltage is −300 to 300V.
The bias voltage is more preferably −200 V or more, further preferably −100 V or more, and particularly preferably −50 V or more. The bias voltage is more preferably 200 V or less, still more preferably 100 V or less, and particularly preferably 50 V or less. When the atom nitriding method is performed under the condition (b), the amount of the specific compound contained in the solid solution layer can be suppressed.
The bias voltage is more preferably in the range of −5 to −10V. By being in this range, it is possible to suppress the electrons contained in the plasma from flowing into the metal material.
The pressure when performing the atom nitriding method is preferably 10 Pa or less, and more preferably 1 Pa or less. In the following, it is assumed that the pressure when performing the atom nitriding method is 10 Pa or less (a). When the atom nitriding method is performed under the condition (a), the amount of the specific compound contained in the solid solution layer can be suppressed. When the atom nitriding method is performed under the conditions (a) and (b), the amount of the specific compound contained in the solid solution layer can be further suppressed.

  In the nitriding treatment, for example, electrons contained in the plasma can be prevented from flowing into the metal material. As a method for suppressing the electrons contained in the plasma from flowing into the metal material, for example, there is a method of applying a magnetic field in the vicinity of the metal material. The direction of the magnetic field is preferably a direction parallel to the surface of the metal material.

When the metal material is iron or an alloy containing iron as a main component, the surface hardness of the metal material forming the solid solution layer is, for example, preferably 700 Hv or more, and more preferably 1200 to 1500 Hv. When the metal material is iron or an alloy containing iron as a main component, the surface hardness of the metal material including the solid solution layer is, for example, preferably 700 Hv or more, and more preferably 1200 to 1500 Hv. For example, by using an atom nitriding method, when the metal material is iron or an alloy containing iron as a main component, the surface hardness of the metal material can be 700 Hv or more, and can be 1200 to 1500 Hv. The surface hardness of the metal material is a value measured using a micro hardness meter (Vickers hardness meter). When the surface hardness is 700 Hv or more, it is difficult to be damaged when the metal material is made into a mold or the like.
When the metal material is a tungsten alloy, the surface hardness of the metal material on which the solid solution layer is formed is, for example, preferably 580 Hv or more, and more preferably 600 Hv or more. When the surface hardness is 580 Hv or more, it is difficult to be damaged when the metal material is made into a mold or the like.

3. Machining In machining, for example, a tool with high hardness can be used. An example of a high hardness tool is a diamond tool. An example of machining is cutting.

  According to the metal product manufacturing method of the present disclosure, the service life of the diamond tool used in machining can be extended. The reason can be estimated as follows. The metal material has a solid solution layer. Therefore, the carbon in the diamond tool is difficult to diffuse into the metal material and hardly react with the metal. As a result, wear of the diamond tool used in machining is suppressed, and the service life of the tool is extended.

  The solid solution layer containing nitrogen atoms as interstitial solid solution atoms formed under the conditions (a) and / or (b) by the atom nitriding method is unlikely to contain a specific compound. For this reason, even when the tool has a sharp cutting edge, the cutting edge is not easily damaged. As a result, the service life of the tool can be extended.

In addition, it is difficult for the phenomenon of generating scratches (scratches in the cutting direction) on the finished surface because the particles of the specific compound move together with the cutting edge. As a result, the finished surface roughness is unlikely to deteriorate.
The generation of the scratch is a phenomenon often seen when a hard material such as particles of a specific compound is deposited and hardened. For example, the above-mentioned scratch generation is disclosed in Kobe Steel Technical Report Vol.39, No.4 (1989) p.39.

  On the other hand, when nitriding is performed by a gas soft nitriding method, a specific compound is easily generated. This specific compound may cause defects in the sharp cutting edge of the tool. As a result, the service life of the tool is shortened. Moreover, it is easy to produce | generate a scratch on a finishing surface because the particle | grains of a specific compound move with a cutting edge. As a result, the finished surface roughness tends to deteriorate.

4). Metal Product Examples of the metal product manufactured by the method for manufacturing a metal product according to the present disclosure include a mold. The metal product may be other than a mold. The surface roughness of the metal product manufactured by the metal product manufacturing method of the present disclosure is small. In addition, a rainbow is unlikely to form on the surface of the metal product. The reason is presumed as follows. According to the method for manufacturing a metal product of the present disclosure, streaky wear or breakage is unlikely to occur on a cutting tool. In addition, the phenomenon that the specific compound moves with the cutting edge hardly generates a scratch on the finished surface. For this reason, it is possible to suppress streak-like wear and loss in the cutting edge of the tool, and rainbow surfaces caused by scratches.

5. Example 1
(5-1) Workpiece Workpiece 101 shown in FIG. 1 was prepared. The material of the workpiece 101 is SUS420J2. The workpiece 101 corresponds to a metal material. The workpiece 101 has a disk-like basic form having a diameter of 50 mm and having a hole 102 in the center.

  The workpiece 101 includes a protrusion 105 on one surface 103 thereof. The protruding portion 105 is a portion protruding in the thickness direction of the workpiece 101 by 1 mm from the other portion of the surface 103. The protruding portion 105 is formed on the outer peripheral portion of the surface 103. However, the protruding portion 105 is not formed in a fan-shaped region of the surface 103 having a central angle of 50 ° with the hole 102 as the center. The width of the protrusion 105 in the radial direction of the surface 103 is 10 mm.

(5-2) Configuration of Nitriding Apparatus 1 The configuration of the nitriding apparatus 1 will be described with reference to FIG. The nitriding apparatus 1 includes a cathode 5, a preliminary anode 7, an anode 9, and an acceleration electrode 11 in a chamber 3. The chamber 3 is provided with an argon inlet 13, a nitrogen inlet 15, and a vacuum exhaust 17. In the chamber 3, a region sandwiched between the cathode 5 and the auxiliary anode 7 and facing the argon inlet 13 is an initial discharge formation region 19. In the chamber 3, a portion on the right side of the acceleration electrode 11 and facing the nitrogen inlet 15 and the vacuum exhaust port 17 is a reaction chamber 21.

(5-3) Nitriding Method Using Nitriding Apparatus 1 A nitriding method performed on the workpiece 101 using the nitriding apparatus 1 will be described. In this nitriding method, an electron beam excited plasma method is used. First, the workpiece 101 is installed in the reaction chamber 21. Then, after the inside of the nitriding apparatus 1 is evacuated to a sufficient vacuum, nitrogen gas is introduced into the reaction chamber 21 from the nitrogen inlet 15.

  Next, argon gas is introduced from the argon inlet 13 into the initial discharge formation region 19 to generate a discharge between the cathode 5 and the auxiliary anode 7. Thereafter, discharge is transferred between the cathode 5 and the anode 9 to generate a stable argon plasma 27. From the argon plasma 27, only the electrons are accelerated by the acceleration electrode 11 to generate an electron beam 29, and the electron beam 29 is extracted to the reaction chamber 21.

  In the reaction chamber 21, the nitrogen gas is irradiated with the electron beam 29, and the nitrogen gas is efficiently dissociated and ionized to generate a plasma 31 having a high nitrogen atom density. The workpiece 101 is included in the plasma 31. The surface of the workpiece 101 is nitrided by the plasma 31 to form a solid solution layer in which nitrogen atoms exist as interstitial solid solution atoms.

  The temperature of the reaction chamber 21 is controlled to an appropriate temperature by a heater (not shown) provided in the nitriding apparatus 1. The energy of the electron beam 29 can be arbitrarily set by the voltage applied to the acceleration electrode 11.

The operating conditions for nitriding were as follows.
Pressure in reaction chamber 21: 0.2 Pa
Electron beam 29 acceleration voltage: 80V
Current of electron beam 29: 8A
Temperature in reaction chamber 21: 500 ° C
Time for nitriding treatment: 5 hours Bias voltage (potential of workpiece 101 based on plasma 31 potential): -50V
After the nitriding process, the workpiece 101 was taken out from the nitriding apparatus 1. The surface hardness of the surface 103 was measured using a micro hardness meter (Vickers hardness meter). As a result of the measurement, the surface hardness was 1120 Hv. This surface hardness was remarkably improved as compared with 205 Hv which was a value before nitriding. In addition, the workpiece 101 after performing the nitriding treatment as described above is hereinafter referred to as a post-treatment workpiece 101A. The post-treatment workpiece 101A has a solid solution layer on the surface. (5-4) Gas Soft Nitriding Method A gas soft nitriding method performed on the workpiece 101 will be described. The workpiece 101 is placed in an atmosphere containing ammonia and carbon dioxide and treated at 580 ° C. for 100 minutes. Thereafter, the workpiece 101 is cooled using liquid nitrogen. In addition, the workpiece 101 after performing the gas soft nitriding as described above is hereinafter referred to as a post-treatment workpiece 101R. A compound layer made of iron nitride is formed on the surface of the processed workpiece 101R.

(5-5) Analysis of post-treatment workpieces 101A and 101R The surfaces of the post-treatment workpieces 101A and 101R were observed. A three-dimensional optical profiler (product name: Zygo, NewView 7300) was used for observation. The surface shapes of the processed workpieces 101A and 101R are shown in FIG. The surface shape shown in FIG. 3 is a cross-sectional profile in one scanning line. The surface shape of the post-treatment workpiece 101A was flat compared to the surface shape of the post-treatment workpiece 101R.

  The element distribution in the depth direction of the workpieces 101A and 101R after the treatment was measured. An electron beam microanalyzer (Shimadzu Corporation, EPMA-1610) was used for the measurement. The measurement result of the processed workpiece 101A is shown in FIG. 4A, and the measurement result of the processed workpiece 101R is shown in FIG. 4B. In both the treated workpieces 101A and 101R, the concentration of nitrogen was high near the surface.

The hardness distribution in the depth direction of the workpieces 101A and 101R after processing was measured. For the measurement, a hardness meter manufactured by Mitutoyo Corporation was used. The measurement results are shown in FIG. Post-processing workpiece 101A, 10
In any of 1R, the hardness near the surface was high. The hardness in the vicinity of the surface of the processed workpiece 101A was 700 Hv or more.

  Further, X-ray diffraction was performed on the processed workpiece 101A. No peak of iron and nitrogen compound was observed in the workpiece 101A after the treatment. That is, the presence of a compound layer made of iron nitride was not recognized in the processed workpiece 101A.

(5-6) Machining Machined workpieces 101A and 101R were processed. The machining is a process of cutting the protruding portion 105 to a predetermined depth. Table 1 shows combinations of types of workpieces after processing and machining conditions. Hereinafter, the combination of the type of workpiece after processing and the machining conditions will be referred to as a manufacturing method. The manufacturing method includes P1 to P4 shown in Table 1. Note that the depth of cut at P4 is 2 μm in the final pass and 5 μm in the other passes.

The cutting tools used are common to all, and are single crystal diamond cutting tools. The nose radius of this cutting tool is 1 mm.
The “first device” in Table 1 is an ultra-precision micromachining machine (trade name: N2C-53US4N4) manufactured by Nagase Integrex Co., Ltd. The “second device” is an ultra-precision 5-axis machine (trade name: ASP01UPX) manufactured by Fujikoshi Co., Ltd.

The oil mist used is common to all manufacturing methods, and is Bluebe LB10 (trade name) manufactured by Fuji BC Giken Co., Ltd.
(5-7) Evaluation of metal product and tool The work after implementing manufacturing method P1-P4 is set as metal product M1-M4 below, respectively. The workpiece after performing the manufacturing methods P1 to P4 corresponds to a workpiece or a work material. The surface roughness Rt at the protrusions 105 of the metal products M1 to M4 was measured. For the measurement, a three-dimensional optical profiler (product name: Zygo, NewView7300) was used. The measurement results are shown in FIG. The surface roughness Rt in the metal products M1 to M3 was smaller than the surface roughness Rt in the metal product M4.

The rainbow surface did not occur in the metal products M1 to M3. On the other hand, a rainbow surface occurred in the metal product M4.
The surface roughness of the flank near the cutting edge of the cutting tool used in the manufacturing methods P2 and P4 was measured. For the measurement, a three-dimensional optical profiler (product name: Zygo, NewView7300) was used.
The measurement results are shown in FIG. FIG. 7 shows the surface roughness of the flank.

  The surface roughness of the cutting tool used in the manufacturing method P2 was flat. On the other hand, streak-like wear occurred on the surface of the cutting tool used in the manufacturing method P4. This streak-like wear is presumed to be the cause of the rainbow surface produced in the metal product M4.

6). Example 2
(6-1) Difference from Example 1 In Example 1 described above, plasma is generated by an electron beam excitation plasma method. In contrast, the second embodiment is different from the first embodiment in that plasma is generated by the microwave excitation plasma method.

(6-2) Configuration of Nitriding Apparatus 201 The configuration of the nitriding apparatus 201 will be described with reference to FIG. The nitriding apparatus 201 includes a quartz glass window 205 and a processing object holder 207 in a chamber 203. The processing object holder 207 can hold the workpiece 101 on its upper surface. Further, the processing object holder 207 incorporates a heater (not shown) and can heat the workpiece 101. Further, the chamber 203 is provided with a waveguide 209 for sending microwaves, a nitrogen inlet 211, and a vacuum exhaust 213. Inside the chamber 203 is a reaction chamber 215.

(6-3) Nitriding Method Using Nitriding Apparatus 201 A nitriding method using the nitriding apparatus 201 will be described. First, the workpiece 101 is attached to the processing object holder 207 and installed in the reaction chamber 215. The workpiece 101 is heated to 500 ° C., and then nitrogen gas is introduced into the reaction chamber 215 from the nitrogen inlet 211. Next, a microwave is introduced from the waveguide 209. The microwave passes through the quartz glass window 205 and generates surface wave plasma on its lower surface. The surface wave plasma acts on the nitrogen gas in the reaction chamber 215 to generate a plasma containing a high concentration of nitrogen atoms in the reaction chamber 215. The surface of the workpiece 101 is nitrided by the plasma containing high-concentration nitrogen atoms.

  Also by the nitriding method using the nitriding apparatus 201, a solid solution layer in which nitrogen atoms exist as interstitial solid solution atoms can be formed on the surface of the workpiece 101, and the hardness near the surface can be increased. Also in the nitriding method using the nitriding apparatus 201, the formation of a nitrogen compound layer such as iron is suppressed, and the surface roughness is not increased.

(6-4) Machining The machined workpiece after nitriding can be machined in the same manner as in Example 1 to produce a metal product. The manufactured metal product has a small surface roughness Rt. Further, no rainbow surface is formed on the surface of the metal product.

7). Other Embodiments Although the embodiment of the present disclosure has been described above, the present disclosure is not limited to the above-described embodiment, and various modifications can be made.

(7-1) A function of one constituent element in each of the above embodiments may be shared by a plurality of constituent elements, or a function of a plurality of constituent elements may be exhibited by one constituent element. Moreover, you may abbreviate | omit a part of structure of each said embodiment. In addition, at least a part of the configuration of each of the above embodiments may be added to or replaced with the configuration of the other above embodiments. In addition, all the aspects included in the technical idea specified from the wording described in the claims are embodiments of the present disclosure.
(7-2) In Examples 1 and 2, the place where nitriding is performed and the place where machining is performed may be different. In the first and second embodiments, the main body that performs nitriding and the main body that performs machining may be different. In Examples 1 and 2, machining may be performed after a lapse of time after completion of the nitriding treatment.

  (7-3) In addition to the above-described method for manufacturing a metal product, the present disclosure can also be realized in various forms such as a metal product and a processing method for a metal material.

DESCRIPTION OF SYMBOLS 1 ... Nitriding apparatus, 3 ... Chamber, 5 ... Projection part, 5 ... Cathode, 7 ... Preliminary anode, 9 ... Anode, 11 ... Accelerating electrode, 13 ... Argon inlet, 15 ... Nitrogen inlet, 17 ... Vacuum exhaust port 19 ... Initial discharge forming region, 21 ... Reaction chamber, 27 ... Argon plasma, 29 ... Electron beam, 31 ... Plasma, 101 ... Work piece, 101A ... Work piece, 101R ... Work piece, 102 ... Hole, 103 ... Surface, 105 ... Projection, 201 ... Nitriding apparatus, 203 ... Chamber, 205 ... Quartz glass window, 207 ... Object holder, 209 ... Waveguide, 211 ... Nitrogen inlet, 213 ... Vacuum exhaust, 215 ... Reaction Room

Claims (7)

After forming a solid solution layer in which predetermined atoms exist as interstitial solid solution atoms on at least the surface of the metal material by the atom nitriding method under the following conditions (a) and / or (b):
A metal product manufacturing method for machining the solid solution layer.
(A) An atom nitriding method is performed at a pressure of 10 Pa or less.
(B) In the atom nitriding method, the potential of the metal material based on the plasma potential is −300 to 300V. A method for producing a metal product according to claim 1,
The metal material includes iron, and the metal material on which the solid solution layer is formed has a surface hardness of 700 Hv or more. A method of manufacturing a metal product by machining a metal material,
A solid solution layer in which a predetermined atom exists as an interstitial solid solution atom is formed on at least the surface of the metal material by an atom nitriding method under the following conditions (a) and / or (b):
A metal product manufacturing method for machining the solid solution layer.
(A) An atom nitriding method is performed at a pressure of 10 Pa or less.
(B) In the atom nitriding method, the potential of the metal material based on the plasma potential is −300 to 300V. It is a manufacturing method of the metal product according to claim 3,
The metal material includes iron, and the metal material including the solid solution layer has a surface hardness of 700 Hv or more. It is a manufacturing method of the metal product according to any one of claims 1 to 4,
The said solid solution layer is a manufacturing method of the metal product which does not contain the compound of the said predetermined atom substantially. It is a manufacturing method of the metal product according to any one of claims 1 to 5,
The method for producing a metal product, wherein the predetermined atom is a nitrogen atom. It is a manufacturing method of the metal product according to any one of claims 1 to 6,
A method for producing a metal product, wherein the metal material is machined using a diamond tool.