Method for manufacturing metal material

Abstract

To provide a method for manufacturing a metal material which can significantly improve the tool life of a removal processing tool.SOLUTION: A method for manufacturing a metal material includes: a process (#5) for preparing a metal base material the main component of which is Fe, containing, by mass%, 0.05% or more of S, 0.20% or less, 0.10% or more of Mn, 2.00% or less; a process (#10) for preparing a processing liquid containing fine bubbles; and a removal process (#15) for executing a removal processing by bringing a removal processing tool into contact with the metal base material to manufacture a metal material. The removal process executes removal processing while supplying the processing liquid to the metal base material and the removal processing tool.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a metal material, and more particularly to a method for manufacturing a metal material by performing removal processing on a metal raw material. [Background technology]

[0002] There are known methods for manufacturing metal materials such as intermediate or final parts by performing removal processes on metal raw materials. Removal processes can be broadly divided into (1) cutting, (2) grinding, and (3) polishing.

[0003] Cutting uses a cutting tool as a removal tool, and presses the cutting edge of the cutting tool against the metal material to cut it. Examples of cutting processes include threading, milling, turning, and drilling (boring). Grinding uses a grinding wheel as a removal tool, and presses the grinding wheel, rotating at high speed, against the metal material to grind it. Examples of grinding processes include surface grinding, cylindrical grinding, and internal grinding. Polishing uses a grinding wheel as a removal tool, and polishes the metal part by bringing the grinding wheel into contact with the metal material to give it a smooth surface. Examples of polishing processes include grinding wheel polishing, abrasive cloth processing, lapping polishing, tape polishing, buffing, and barrel polishing.

[0004] In these removal processes, the removal tool comes into contact with the metal material during removal, which causes the removal tool to wear out or be damaged. Therefore, there is a demand for an improvement in the lifespan of the removal tool in removal processes.

[0005] Japanese Patent Laid-Open Publication No. 2007-331088 (Patent Document 1) describes a machining device. This machining device performs cutting by spraying cutting fluid containing microbubbles onto a cutting tool and a workpiece. Patent Document 1 claims that this reduces tool wear. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-331088 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the technology described in Patent Document 1 does not necessarily improve the tool life sufficiently.

[0008] An object of the present disclosure is to provide a method for manufacturing a metal material that can significantly improve the tool life of a removal tool. [Means for solving the problem]

[0009] The method for manufacturing a metal material according to the present disclosure includes the steps of preparing a metal material containing Fe as a main component and, by mass%, 0.05% to 0.20% or less of S and 0.10% to 2.00% or less of Mn, preparing a working fluid containing fine bubbles, and producing the metal material by bringing a removal tool into contact with the metal material to perform removal processing. In the removal processing step, removal processing is performed while supplying the working fluid to the metal material and the removal tool. [Effects of the Invention]

[0010] According to the method for manufacturing a metal material according to the present disclosure, the tool life of the removal tool can be significantly improved. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing the correlation between the number of drilled holes and the amount of wear on the tool in drilling. [Figure 2] FIG. 2 is a schematic diagram showing an example of a removal processing device used in the method for producing a metal material according to the first embodiment. [Figure 3] FIG. 3 is a flow diagram showing the method for manufacturing a metal material according to the first embodiment. [Figure 4]FIG. 4 is a schematic diagram showing an example of a removal processing device in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] In this specification, the portion of the removal tool that is in contact with the metal material (workpiece) during removal processing, and the portion of the metal material (workpiece) that is in contact with the removal tool, may be referred to as the processing point. During removal processing, a portion of the metal is removed from the metal material at the processing point by the removal tool. The metal portion thus removed from the metal material during removal processing is referred to as a chip.

[0013] During removal processing, the processing point becomes hot due to processing heat. As a result, chips tend to adhere to the removal processing tool. If chips adhere to the removal processing tool, the part of the removal processing tool to which the chips adhere is likely to break or wear during the removal processing. Therefore, adhesion of chips reduces the tool life of the removal processing tool. Furthermore, if removal processing is continued using a removal processing tool with chips adhered to it, the dimensional accuracy of the metal material will also decrease.

[0014] In order to improve tool life, focusing on the metal material to be processed, it is sufficient to use a steel material intentionally containing sulfur (S), i.e., sulfur-containing free-cutting steel, as the metal material. In steel materials containing S, inclusions of iron-sulfur compounds and manganese sulfide (MnS) are dispersed throughout the steel. In cutting, i.e., removal processing, MnS inclusions in the metal material, in particular, shorten the chips generated, making it easier to cut (remove) the metal material. In this specification, MnS inclusions may be simply referred to as MnS.

[0015] However, when removal processing is performed on a metal material made of steel containing S, MnS is likely to adhere to the surface of the removal processing tool. When MnS adheres to the surface of the removal processing tool, stress concentrates on the part of the removal processing tool where the MnS adheres. This stress concentration may cause chipping of the cutting edge of the removal processing tool. Therefore, simply using steel containing S as the metal material cannot be said to achieve a significant improvement in tool life.

[0016] To significantly improve tool life, it is necessary to reduce the adhesion of MnS to the removal tool. To achieve this, it is conceivable to supply a machining fluid (coolant) containing fine bubbles to the machining point during removal processing. In this specification, a machining fluid containing fine bubbles may be referred to as an "FB machining fluid," and a machining fluid that does not contain fine bubbles may be referred to as an "FB-free machining fluid."

[0017] Therefore, the inventors conducted the following test. Several soluble water-soluble machining fluids were prepared, and fine bubbles were introduced into some of the machining fluids. Specifically, microbubbles with a relatively large average diameter were introduced into some of the machining fluids, and ultrafine bubbles with an average diameter smaller than that of microbubbles were introduced into other machining fluids. Then, using each machining fluid, removal processing was performed on several metal materials. The metal material used was medium-carbon steel, mainly composed of Fe (iron), containing 0.05 mass% S (sulfur), and 1.50 mass% Mn (manganese). The removal processing was cutting, specifically drilling. The test results revealed the following.

[0018] Fig. 1 shows the correlation between the number of drilled holes and the amount of tool wear in drilling. As shown in Fig. 1, when using the FB-free machining fluid, the FB machining fluid containing microbubbles, and the FB machining fluid containing ultrafine bubbles, the amount of tool wear tends to increase as the number of drilled holes increases.

[0019] However, as is clear from Figure 1, when an FB machining fluid containing fine bubbles (microbubbles, ultrafine bubbles) is used, the amount of tool wear is reduced compared to when an FB machining fluid without fine bubbles is used. In particular, when an FB machining fluid containing ultrafine bubbles is used, the amount of tool wear is significantly reduced. Therefore, from Figure 1, it can be said that if an FB machining fluid is used to perform removal processing on a metal material that is mainly composed of Fe and also contains moderate amounts of S and Mn, the amount of tool wear can be significantly reduced.

[0020] In the aqueous machining fluid containing fine bubbles, the fine bubbles are negatively charged. On the other hand, the chips removed from the metal material by the removal process tend to be positively charged, and the MnS present in the chips and the MnS that has fallen off from the chips also tend to be positively charged. Therefore, when the FB machining fluid is supplied to the machining point, the negatively charged fine bubbles in the machining fluid adsorb the positively charged chips and MnS.

[0021] When the FB machining fluid is supplied by flowing it over the machining point, the chips and MnS adsorbed by the fine bubbles move away from the machining point as the machining fluid moves away from the machining point. In other words, the chips and MnS are quickly removed from the high-temperature machining point. This suppresses the adhesion of the chips and MnS to the removal tool. By using the FB machining fluid in this way, the adhesion of MnS to the removal tool is suppressed, significantly reducing the amount of tool wear as shown in Figure 1. As a result, the tool life of the removal tool can be significantly improved. To achieve this effect, a metallic material containing Fe as the main component and, by mass%, 0.05% to 0.20% or less of S and 0.10% to 2.00% or less of Mn can be used.

[0022] The method for manufacturing a metal material according to an embodiment of the present disclosure has been completed based on the above findings.

[0023] The method for manufacturing a metal material according to this embodiment includes the steps of preparing a metal material containing Fe as a main component and, by mass%, 0.05% to 0.20% or less of S and 0.10% to 2.00% or less of Mn, preparing a working fluid containing fine bubbles, and manufacturing a metal material by bringing a removal tool into contact with the metal material to perform removal processing. The removal processing step is performed while supplying the working fluid to the metal material and the removal tool (first configuration).

[0024] In the manufacturing method according to the first aspect, the metal material to be processed contains Fe as the main component and moderate amounts of S and Mn at the above-mentioned contents. This metal material is subjected to a removal process using an FB processing fluid. In this case, fine bubbles in the FB processing fluid adsorb chips and MnS during the removal process, removing them from the removal tool. This suppresses adhesion of MnS to the removal tool, thereby significantly improving the tool life of the removal tool.

[0025] The method for producing the metal material preferably includes determining the area ratio S (%) of MnS contained in the metal material and the total surface area SFB (m ) of fine bubbles having a diameter of 0.01 μm or more and 50.00 μm or less among the fine bubbles contained in 1 cubic meter of the processing liquid. 2 ) satisfies formula (1) (second configuration). 0.4≦SFB / S≦400 (1)

[0026] In formula (1), as mentioned above, "S" is the area ratio (%) of MnS contained in the metal material being processed, and "SFB" is the total surface area (m ) of fine bubbles with a diameter of 0.01 μm or more and 50.00 μm or less among the fine bubbles contained in 1 cubic meter of the processing fluid. 2) where the area fraction S of MnS is obtained in advance from a test steel material of the same lot as the metal material to be processed. Specifically, the test steel material is cut and the cut surface is polished. The polished surface is photographed using an optical microscope, and an image of the polished surface is obtained in black and white. In the acquired image, the areas where MnS is present appear black. Therefore, in an arbitrary field of view (50 mm x 50 mm) of the acquired image, the total area (mm 2 ) is calculated. Then, the calculated total area is divided by the area of ​​the field of view. The percentage of this value is taken as the area ratio S (%) of MnS.

[0027] "SFB / S" in formula (1) essentially corresponds to the number of fine bubbles corresponding to each MnS dispersed in the metal material to be processed. If "SFB / S" is 0.4 or higher, the number of fine bubbles corresponding to each MnS is large, and the MnS removal performance by fine bubbles is high. However, if "SFB / S" is greater than 400, the number of fine bubbles corresponding to each MnS is too large, and the fine bubbles will stick together to form large bubbles. In this case, equipment trouble may occur, and the expected effect may not be achieved. Therefore, as in formula (1), it is preferable that "SFB / S" is 0.4 or more and 400 or less.

[0028] In the above-mentioned method for manufacturing a metal material, preferably, the average circle equivalent diameter d (μm) of MnS contained in the metal material and the average diameter dFB (μm) of the fine bubbles in the processing fluid satisfy the formula (2) (third configuration). dFB <d (2)

[0029] In equation (2), as described above, "d" is the average equivalent circle diameter (μm) of MnS contained in the metal material being processed, and "dFB" is the average diameter (μm) of fine bubbles in the processing fluid. Here, the average equivalent circle diameter d of MnS, like the above-mentioned MnS area fraction S, is obtained in advance from a test steel material from the same lot as the metal material being processed. Specifically, the test steel material is cut and the cut surface is polished. The polished surface is photographed using an optical microscope, and a binary image of the polished surface is obtained in black and white. In the acquired image, the areas where MnS is present appear black. Therefore, the number of black agglomerates is counted by image analysis within an arbitrary field of view (50 mm × 50 mm) of the acquired image, and the equivalent circle diameter (μm) of each black agglomerate is calculated. The equivalent circle diameter is the diameter of a circle with an area equal to the area of ​​the agglomerate. The sum of the calculated equivalent circle diameters is then divided by the number of black agglomerates. The value thus obtained is defined as the average equivalent circle diameter d (μm) of MnS.

[0030] As shown in formula (2), the condition that "dFB" is smaller than "d" indicates that the size of the fine bubbles is substantially smaller than the size of each MnS dispersed in the metal material to be processed. If the condition of formula (2) is met, fine bubbles smaller than MnS can easily enter the gap between the removal tool and the MnS, and the MnS removal performance by fine bubbles is high.

[0031] In the above-mentioned method for manufacturing a metal material, preferably, the average circle-equivalent diameter d (μm) of MnS contained in the metal material, the average aspect ratio L / W (dimensionless) of MnS, and the average diameter dFB (μm) of fine bubbles in the processing liquid satisfy formula (3) (fourth configuration). dFB <d / (L / W) (3)

[0032] In formula (3), as described above, "d" is the average circle-equivalent diameter (μm) of MnS, "L / W" is the average aspect ratio (dimensionless) of MnS, and "dFB" is the average diameter (μm) of the fine bubbles. MnS dispersed in a metal material usually has an elongated shape. This is because, for example, in the hot plastic processing in the previous process, MnS is elongated in the direction of the plastic processing. The size of MnS with an elongated shape can be expressed by the major axis diameter L and the minor axis diameter W.

[0033] The average aspect ratio L / W of MnS, like the area fraction S and average equivalent circle diameter d of MnS, is obtained in advance from a test steel material from the same lot as the metal material to be processed. Specifically, the test steel material is cut and the cut surface is polished. The polished surface is photographed using an optical microscope, and a binary image of the polished surface is obtained in black and white. In the acquired image, the areas where MnS is present appear black. Therefore, the number of black agglomerates is counted by image analysis within an arbitrary field of view (50 mm × 50 mm) of the acquired image, and the major axis diameter L (μm) and minor axis diameter W (μm) of each black agglomerate are calculated. The aspect ratio is the ratio of the major axis diameter L to the minor axis diameter W. The sum of the calculated aspect ratios is then divided by the number of black agglomerates. The value obtained is the average aspect ratio L / W (dimensionless) of MnS.

[0034] In formula (3), "d / (L / W)" is the ratio of the average circle-equivalent diameter of MnS to the average aspect ratio of MnS, and essentially corresponds to the approximate minor axis diameter of each MnS dispersed in the metal material to be processed. Therefore, the condition that "dFB" is smaller than "d / (L / W)" as shown in formula (3) indicates that, assuming that the MnS has an elongated shape, the size of the fine bubbles is essentially smaller than the minor axis diameter of each MnS dispersed in the metal material to be processed. If the condition of formula (3) is satisfied, fine bubbles smaller than the minor axis diameter of the MnS can easily enter the gap between the removal tool and the MnS, and the MnS removal performance by the fine bubbles is high.

[0035] In the above-described method for producing a metal material, for example, the removal processing is drilling (fifth configuration). In this case, in the removal processing, i.e., drilling, it is possible to improve the removability of chips and MnS generated in the removal processing, and it is possible to significantly improve the life of the drill, which is the removal processing tool.

[0036] Hereinafter, the method for manufacturing a metal material according to this embodiment will be described with reference to the drawings. In each drawing, the same or equivalent components are designated by the same reference numerals, and redundant description will not be repeated.

[0037] [First embodiment] The method for manufacturing a metal material according to this embodiment includes a material preparation step of preparing a metal material, a processing fluid preparation step of preparing a processing fluid containing fine bubbles, and a removal processing step of bringing a removal tool into contact with the metal material to perform removal processing and manufacture the metal material. As described above, removal processing can be broadly divided into (1) cutting processing, (2) grinding processing, and (3) polishing processing. In this embodiment, the method for manufacturing a metal material according to this embodiment will be described using cutting processing as an example, but the method can also be applied to grinding processing and polishing processing in the same way as cutting processing.

[0038] [About the removal processing equipment] 2 is a schematic diagram showing an example of a removal processing device used in the manufacturing method of a metal material according to the present embodiment. Referring to FIG. 2, the removal processing device 100 includes a removal processing tool 1, a fixing jig 2 for fixing a metal material W, and a fine bubble generator 3.

[0039] The removal processing tool 1 is a tool for removing the metal material W. When the removal processing is cutting processing, the removal processing tool 1 is, for example, a cutting tool such as a turning tool, a milling cutter, an end mill, or a drill. When the removal processing is grinding processing, the removal processing tool 1 is, for example, a grinding tool such as a grinding wheel or a brush. When the removal processing tool 1 is an abrasive tool, the abrasive tool is, for example, a grinder, a sander, or a polisher. The fixing jig 2 fixes the metal material W. The fixing jig 2 is, for example, a chuck. When the removal processing is lathe processing, the fixing jig 2 fixes the metal material W so that it can rotate around its axis. When the removal processing is drilling processing (hole boring), the metal material W is completely fixed by the fixing jig 2, and the removal processing tool 1, which is a drill, moves toward the metal material W while rotating around its axis.

[0040] The fine bubble generator 3 generates fine bubbles in the machining fluid PF. The fine bubble generator 3 includes, for example, a machining fluid storage container 31, a fine bubble generator 32, a supply pipe 33, a discharge pipe 34, and a machining fluid discharge mechanism 35.

[0041] Machining fluid storage container 31 is a container capable of storing machining fluid PF. Machining fluid storage container 31 is, for example, a tank or a bathtub. Fine bubble generator 32 generates fine bubbles in machining fluid PF.

[0042] The supply pipe 33 is disposed between the machining fluid storage container 31 and the fine bubble generator 32, and connects the machining fluid storage container 31 and the fine bubble generator 32. The supply pipe 33 supplies the machining fluid PF stored in the machining fluid storage container 31 to the fine bubble generator 32.

[0043] The discharge pipe 34 is disposed between the machining liquid storage container 31 and the fine bubble generator 32, and connects the machining liquid storage container 31 to the fine bubble generator 32. The discharge pipe 34 discharges the machining liquid PF, in which fine bubbles have been generated by the fine bubble generator 32, from the fine bubble generator 32 to the machining liquid storage container 31.

[0044] There are no particular limitations on the method of generating fine bubbles using the fine bubble generator 32. Fine bubble generators are divided into two types: one that takes in external air and introduces it into the processing liquid as fine bubbles (external gas introduction type), and one that generates fine bubbles using dissolved oxygen in the processing liquid (dissolved oxygen utilization type).

[0045] External gas introduction types include impeller and venturi type fine bubble generators. The impeller type uses an impeller that rotates at high speed in the machining liquid, entraining air introduced from the outside and generating fine bubbles through centrifugal force. The venturi type uses a venturi tube to draw in external air using the pressure difference and introduce fine bubbles into the machining liquid.

[0046] Examples of dissolved oxygen utilization types include pressure change type, electrolysis type, and membrane type fine bubble generators. Pressure change type generates fine bubbles from dissolved oxygen by reducing the pressure of high-pressure machining fluid. Electrolysis type performs electrolysis in the machining fluid and uses the generated gas as fine bubbles. Membrane type generates fine bubbles from dissolved oxygen through a membrane with fine pores.

[0047] The fine bubble generator 32 used in this embodiment may be an external gas introduction type or a dissolved oxygen utilization type.

[0048] The working fluid PF is a water-soluble working fluid (coolant). The working fluid PF may be a water-insoluble working fluid. The water-soluble working fluid is, for example, one selected from the group consisting of emulsion type, soluble type, and solution type. The water-insoluble working fluid is, for example, cutting oil.

[0049] Preferably, the machining fluid PF is a soluble water-soluble machining fluid. The soluble water-soluble machining fluid contains, for example, water and a surfactant. The surfactant may be a well-known surfactant. For example, the surfactant is one or more selected from the group consisting of a nonionic surfactant, an anionic surfactant, an amphoteric surfactant, and a cationic surfactant.

[0050] Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyalkylene alkylphenyl ethers, polyoxy(ethylene and / or propylene) alkylphenyl ethers, polyoxyethylene alkyl esters composed of polyethylene glycol or ethylene oxide and higher fatty acids (e.g., having 12 to 18 carbon atoms), and polyoxyethylene sorbitan alkyl esters composed of sorbitan, polyethylene glycol, and higher fatty acids (e.g., having 12 to 18 carbon atoms).

[0051] Examples of anionic surfactants include fatty acid salts, sulfate ester salts, sulfonate salts, phosphate ester salts, dithiophosphate ester salts, etc. Examples of amphoteric surfactants include amino acid and betaine carboxylate salts, sulfate ester salts, sulfonate salts, phosphate ester salts, etc. Examples of cationic surfactants include aliphatic amine salts, quaternary ammonium salts, etc.

[0052] When the working fluid PF is a soluble water-soluble working fluid, the water-soluble working fluid may contain components other than water and surfactants, such as extreme pressure additives, rust inhibitors, preservatives, friction reducers, etc.

[0053] In this specification, fine bubbles refer to fine bubbles with an average diameter of less than 100.00 μm as defined in JIS B 8741-1:2019. Microbubbles refer to fine bubbles with an average diameter of 1.00 μm or more and less than 100.00 μm. Ultrafine bubbles refer to fine bubbles with an average diameter of 0.01 μm or more and less than 1.00 μm.

[0054] The machining fluid discharge mechanism 35 includes a drive source 351, a pipe 352, and a nozzle 353. One end of the pipe 352 is immersed in the FB machining fluid PF stored in the machining fluid storage container 31. The other end of the pipe 352 is connected to the nozzle 353. The drive source 351 supplies the FB machining fluid PF in the machining fluid storage container 31 to the nozzle 353 via the pipe 352. The drive source 351 is, for example, a pump.

[0055] During removal processing, the nozzle 353 sprays the FB processing fluid PF and supplies the sprayed FB processing fluid PF to the metal material W and the removal processing tool 1. Specifically, the nozzle 353 sprays and flows the FB processing fluid PF onto a portion of the removal processing tool 1 that is in contact with the metal material W and / or onto a portion of the metal material W that is in contact with the removal processing tool 1. In other words, when removal processing is being performed, the nozzle 353 sprays and flows the FB processing fluid PF to the processing point P0.

[0056] The removal processing apparatus 100 may further include a machining fluid recovery device 4. The machining fluid recovery device 4 includes a recovery pan 41 and a recovery pipe 42. The recovery pan 41 functions as a tray for recovering the FB machining fluid PF that is discharged from the nozzle 353, poured onto the machining point P0, and dropped there. The recovery pipe 42 is disposed between the recovery pan 41 and the machining fluid storage container 31, and connects the recovery pan 41 and the machining fluid storage container 31. The recovery pipe 42 discharges the FB machining fluid PF stored in the recovery pan 41 into the machining fluid storage container 31. The machining fluid recovery device 4 allows the FB machining fluid PF to be circulated and reused. Note that the removal processing apparatus 100 does not necessarily have to include the machining fluid recovery device 4.

[0057] [Metal manufacturing methods] The method for manufacturing a metal material according to this embodiment will be described below with reference to Figures 2 and 3. Figure 3 is a flow diagram showing the method for manufacturing a metal material according to this embodiment. As described above, the method for manufacturing a metal material according to this embodiment includes the material preparation step (#5), the machining liquid preparation step (#10), and the removal processing step (#15).

[0058] In the material preparation step (#5), a metal material W is prepared. The metal material W is primarily composed of iron (Fe) and contains, by mass, 0.05% to 0.20% S and 0.10% to 2.00% Mn. Here, "primarily composed" means that the Fe content is 50% or more by mass. The metal material W, which is primarily composed of Fe and contains the above-mentioned appropriate amounts of S and Mn, is made of, for example, low-carbon steel or medium-carbon steel. Specifically, examples of the material for the metal material W include sulfur and sulfur-complex free-cutting steels (SUM21, SUM22, SUM22L, SUM23, SUM23L, SUM24L, SUM25, SUM31, SUM31L, SUM32, SUM41, SUM42, and SUM43) as specified in JIS G 4804:2021. The prepared metal material W is fixed to a fixing jig 2 of a removal processing device.

[0059] In the machining fluid preparation step (#10), fine bubbles are generated in the machining fluid PF by the fine bubble generator 3. In this way, an FB machining fluid PF containing fine bubbles is prepared.

[0060] In the removal processing step (#15), the removal processing tool 1 is brought into contact with the metal material W to perform removal processing, thereby producing a metal material. The metal material produced is an intermediate part or a final part. If the removal processing is a cutting processing, the cutting tool 1 is brought into contact with the metal material W to perform the cutting processing. If the removal processing is a grinding processing, the grinding tool 1 is brought into contact with the metal material W to perform the grinding processing. If the removal processing is a polishing processing, the polishing tool 1 is brought into contact with the metal material W to perform the polishing processing.

[0061] When the removal process is being performed, the FB machining fluid PF is sprayed from the nozzle 353, and the sprayed FB machining fluid PF is supplied by flowing it toward the processing point P0. In this way, the removal process is performed while the FB machining fluid PF is being supplied to the processing point P0. During the removal process, chips are removed from the metal material W. Specifically, chips are successively generated and discharged from the processing point P0 of the metal material W.

[0062] In the method for manufacturing a metal material according to this embodiment, the workpiece, that is, the metal material W, is primarily composed of Fe and contains moderate amounts of S and Mn at the above-mentioned contents. The metal material W is subjected to a removal process using the FB processing fluid PF. In this case, chips are sequentially generated at the processing point P0 of the metal material W during the removal process. At this time, fine bubbles in the FB processing fluid PF adsorb the chips and remove them and MnS present in the chips from the removal processing tool 1. Even if MnS falls off from the chips, the fine bubbles in the FB processing fluid PF adsorb the MnS and remove it from the removal processing tool 1. This suppresses adhesion of MnS to the removal processing tool 1. As a result, the tool life of the removal processing tool 1 can be significantly improved.

[0063] [Favorable conditions] Hereinafter, preferred conditions for the method for producing a metal material according to this embodiment will be described.

[0064] [Average diameter of fine bubbles in FB processing fluid] In the FB processing fluid PF, the average diameter (μm) of the fine bubbles is preferably 50.00 μm or less. More preferably, the average diameter of the fine bubbles is 1.00 μm. In this case, the fine bubbles are ultrafine bubbles. Here, the average diameter (μm) of the fine bubbles is the median diameter D50.

[0065] The average diameter of fine bubbles is determined using a laser diffraction particle size distribution measurement method. Specifically, 1 L (liter) of the FB processing fluid PF sprayed from the nozzle 353 is sampled. The sampled FB processing fluid PF is allowed to stand for 60 seconds. After 60 seconds of standing, the median diameter D50 of the fine bubbles in the FB processing fluid PF is measured using a laser diffraction / scattering particle size distribution analyzer in accordance with JIS Z 8825:2022 using the laser diffraction scattering method. The diameter of the fine bubbles when their cumulative volume is 50% of the volume of all fine bubbles (volume average diameter measured by the laser diffraction scattering method) is defined as the average diameter (median diameter D50) of the fine bubbles.

[0066] When the average diameter of the fine bubbles is 50.00 μm or less, their size is extremely small. Therefore, the fine bubbles contained in the FB machining fluid PF have high adsorption performance for chips and MnS. If the adsorption performance for chips and MnS is high, the chips and MnS are quickly removed from the removal machining tool 1, including the high-temperature machining point. This further suppresses adhesion of MnS to the removal machining tool, and significantly improves the tool life of the removal machining tool 1.

[0067] When the average diameter of the fine bubbles is 50.00 μm or less, the number density of the fine bubbles in the FB processing fluid PF is preferably 5,000 bubbles / mL or more, and more preferably 10,000 bubbles / mL or more.

[0068] [Area ratio S (%) of MnS in the metal material, and total surface area SFB (m 2 ) relationship] As mentioned above, the area ratio S (%) of MnS in the metal material W and the total surface area SFB (m 2 ) preferably satisfy the relationship of formula (1). 0.4≦SFB / S≦400 (1)

[0069] As mentioned above, "S" is the area ratio (%) of MnS contained in the metal material W, and "SFB" is the total surface area (m ) of fine bubbles with a diameter of 0.01 μm or more and 50.00 μm or less among the fine bubbles contained in 1 cubic meter of the FB processing fluid PF. 2 "S" (area ratio of MnS contained in the metallic material W) is obtained in advance from a test steel material of the same lot as the metallic material W to be processed, by the method described above.

[0070] In addition, "SFB" (the total surface area of ​​fine bubbles with a diameter of 0.01 μm or more and 50.00 μm or less among the fine bubbles contained in 1 cubic meter of FB processing fluid PF) is determined by a laser diffraction particle size distribution measurement method. Specifically, the shape of the fine bubbles is measured using a laser diffraction particle size distribution measurement device (product name: SALD-2200, manufactured by Shimadzu Corporation).

[0071] "SFB / S" essentially corresponds to the number of fine bubbles corresponding to each MnS dispersed in the metal material W. If "SFB / S" is 0.4 or greater, the number of fine bubbles corresponding to each MnS is large, resulting in high MnS removal performance by the fine bubbles. However, if "SFB / S" is greater than 400, the number of fine bubbles corresponding to each MnS is too large, causing the fine bubbles to stick together and form large bubbles. In this case, equipment trouble may occur and the expected results may not be achieved. Therefore, as shown in formula (1), "SFB / S" is preferably 0.4 or greater and 400 or less. More preferably, "SFB / S" is 4.0 or greater. If removal processing is performed using an FB processing fluid PF that satisfies the conditions of formula (1), the MnS removal performance by the fine bubbles is high, thereby significantly improving the tool life of the removal processing tool 1.

[0072] [Relationship between the average circle equivalent diameter d (μm) of MnS in the metal material and the average diameter dFB (μm) of the fine bubbles in the FB machining fluid] As described above, it is preferable that the average circle-equivalent diameter d (μm) of MnS in the metal material W and the average diameter dFB (μm) of the fine bubbles in the FB machining fluid PF satisfy the relationship of formula (2). dFB <d (2)

[0073] As described above, "d" is the average circle-equivalent diameter (μm) of MnS contained in the metal material W, and "dFB" is the average diameter (μm) of fine bubbles in the FB processing fluid PF. "d" (the average circle-equivalent diameter of MnS contained in the metal material W) is obtained in advance from the same lot of test steel as the metal material to be processed by the method described above. Furthermore, "dFB" (the average diameter of fine bubbles in the FB processing fluid PF) is the median diameter D50 of the fine bubbles in the FB processing fluid PF, and is determined by the laser diffraction particle size distribution measurement method described above.

[0074] As shown in formula (2), the condition that "dFB" is smaller than "d" indicates that the size of the fine bubbles is substantially smaller than the size of each MnS dispersed in the metal material W to be processed. If the condition of formula (2) is satisfied, fine bubbles smaller than MnS can easily enter the gaps between the removal processing tool 1 and the MnS, and the removal performance of the MnS by the fine bubbles is high. Therefore, if removal processing is performed using an FB processing fluid PF that satisfies the condition of formula (2), the removal performance of the MnS by the fine bubbles is high, and the tool life of the removal processing tool 1 can be significantly improved.

[0075] [Relationship between the average circle-equivalent diameter d (μm) and average aspect ratio L / W (dimensionless) of MnS in metal materials, and the average diameter dFB (μm) of fine bubbles in FB machining fluid] As described above, it is preferable that the average circle-equivalent diameter d (μm) of MnS in the metal material W, the average aspect ratio L / W (dimensionless) of MnS in the metal material W, and the average diameter dFB (μm) of the fine bubbles in the FB processing fluid PF satisfy the relationship of formula (3). dFB <d / (L / W) (3)

[0076] As described above, "d" is the average circle-equivalent diameter (μm) of MnS contained in the metal material W, "L / W" is the average aspect ratio (dimensionless) of the MnS, and "dFB" is the average diameter (μm) of the fine bubbles in the FB processing fluid PF. "L / W" (the average aspect ratio of MnS contained in the metal material W) is obtained in advance by the above-mentioned method from a test steel material of the same lot as the metal material to be processed.

[0077] "d / (L / W)" is the ratio of the average circle-equivalent diameter of MnS to the average aspect ratio of MnS, and essentially corresponds to the minor axis diameter of each MnS dispersed in the metal material W. Therefore, as shown in formula (3), the condition that "dFB" is smaller than "d / (L / W)" indicates that, assuming that the MnS has an elongated shape, the size of the fine bubbles is substantially smaller than the minor axis diameter of each MnS dispersed in the metal material W to be processed. If the condition of formula (3) is satisfied, fine bubbles smaller than the minor axis diameter of the MnS can easily enter the gap between the removal tool and the MnS, and the fine bubbles can effectively remove MnS. Therefore, if removal processing is performed using a FB processing fluid PF that satisfies the condition of formula (3), the fine bubbles can effectively remove MnS, thereby significantly improving the tool life of the removal tool 1.

[0078] [Second embodiment] The removal processing apparatus used in the manufacturing method of the metal material of this embodiment is not limited to the removal processing apparatus 100 shown in Fig. 2. Fig. 4 is a schematic diagram showing a removal processing apparatus 100A in the second embodiment. The removal processing apparatus 100A differs from the removal processing apparatus 100 of the first embodiment in that the fine bubble generator 32 of the fine bubble generator 3 is arranged midway through the piping 352.

[0079] 4, in the case of the removal processing apparatus 100A, the fine bubble generator 32 introduces fine bubbles into the processing fluid PF supplied from the processing fluid storage container 31 to the piping 352. Even if the fine bubble generator 3 has the configuration shown in FIG. 4, fine bubbles can be introduced into the processing fluid PF.

[0080] Preferably, the fine bubble generator 3 has the configuration shown in Fig. 2. In this case, the fine bubble generator 32 can introduce fine bubbles into the machining fluid PF while circulating the machining fluid PF in the machining fluid storage container 31. This can reduce the variation in diameter of the fine bubbles in the FB machining fluid PF. [Example]

[0081] The method for producing a metal material according to the present disclosure will be described in more detail below with reference to examples, although the method for producing a metal material according to the present disclosure is not limited to the following examples.

[0082] Removal processing (cutting) was performed using the removal processing device shown in Figure 4. However, the removal processing was drilling (hole drilling). For each test number, the metal material used was sulfur and sulfur-composite free-cutting steel specified in JIS G 4804 (2021), which is primarily composed of Fe and contains S and Mn. The removal processing tool (drill) was a high-speed steel EX-SUS-GDS6.0 manufactured by OSG Corporation. Furthermore, an external gas introduction type fine bubble generator was used as the fine bubble generator. The machining fluid for each test number contained water and a surfactant. The surfactant used was polyoxyethylene alkyl ether (3% by mass). The surfactant concentration in the machining fluid was the same for all test numbers.

[0083] [Table 1]

[0084] For each test number, the S content, Mn content, and MnS in the metal material, "d" (average circle equivalent diameter of MnS contained in metal material W), "L / W" (average aspect ratio of MnS contained in metal material W), "dFB" (average diameter of fine bubbles in FB machining fluid PF), "d / (L / W)", and "SFB / S" were as shown in Table 1. In Table 1, "SFB / S" is related to the above formula (1). "d" and "dFB" are related to the above formula (2). "dFB" and "d / (L / W)" are related to the above formula (3).

[0085] [Evaluation method] For each test number, drilling was performed at a constant speed, and the number of holes drilled was counted when the drill, which was the removal tool, wore out and became unable to drill. As shown in Table 1, among test numbers 1 to 29 and 101 to 108, in test numbers 1 to 29, the S content and Mn content in the metal material both satisfied the above-mentioned prescribed contents (in mass%, S: 0.05% to 0.20%, Mn: 0.10% to 2.00%). Therefore, test numbers 1 to 29 were designated as examples of the present invention. In test numbers 101 to 108, either the S content or the Mn content in the metal material did not satisfy the above-mentioned prescribed contents. Therefore, test numbers 101 to 108 were designated as comparative examples.

[0086] The number of holes drilled when drilling was performed using no FB machining fluid was used as the standard. As shown in Table 1, the ratio of the number of holes drilled for each test number to the standard number of holes drilled was called the tool life ratio, and tool life was evaluated based on this tool life ratio.

[0087] If the tool life ratio was 1.2 or more, it was determined that an excellent tool life was obtained, whereas if the tool life ratio was less than 1.2, it was determined that an insufficient tool life was obtained.

[0088] [Evaluation results] Referring to Table 1, test numbers 1 to 29, which are examples of the present invention, had a tool life ratio of 1.2 or more, and thus achieved excellent tool life. In particular, among test numbers 1 to 29, test numbers 11 to 14 and 16 to 29 satisfied at least one of the conditions of formula (1), formula (2), and formula (3). Therefore, the tool life ratio was 4.0 or more, and an even better tool life was achieved.

[0089] On the other hand, the comparative examples, test numbers 101 to 108, had a tool life ratio of less than 1.2, which was merely the same as that when drilling was performed using an FB-free machining fluid.

[0090] The embodiments of the present disclosure have been described above. However, the above-described embodiments are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiments, and can be implemented by appropriately modifying the above-described embodiments within the scope of the present disclosure. [Explanation of symbols]

[0091] 100,100A: Removal processing equipment 1: Removal processing tool 2: Fixture 3: Fine bubble generator 4: Machining fluid recovery device

Claims

1. A method for manufacturing a metal material, comprising: A step of preparing a metal material containing Fe as a main component and containing, by mass%, 0.05% or more and 0.20% or less of S and 0.10% or more and 2.00% or less of Mn; A step of preparing a processing liquid containing fine bubbles; A method for manufacturing a metal material, comprising: a removal processing step in which a removal processing tool is brought into contact with the metal material to perform removal processing and manufacture the metal material, and the removal processing is performed while the processing liquid is supplied to the metal material and the removal processing tool.

2. The method for manufacturing a metal material according to claim 1, The area ratio S (%) of MnS contained in the metal material and the total surface area SFB (m ) of the fine bubbles having a diameter of 0.01 μm or more and 50.00 μm or less among the fine bubbles contained in 1 cubic meter of the machining fluid are ２ ) satisfies formula (1). 0.4≦SFB / S≦400 (1)

3. The method for manufacturing a metal material according to claim 1, a mean circle-equivalent diameter d (μm) of MnS contained in the metal material and a mean diameter dFB (μm) of the fine bubbles in the processing liquid satisfy formula (2). dFB<d (2)

4. The method for manufacturing a metal material according to claim 1, A method for producing a metal material, wherein an average circular equivalent diameter d (μm) of MnS contained in the metal material, an average aspect ratio L / W (dimensionless) of the MnS, and an average diameter dFB (μm) of the fine bubbles in the processing liquid satisfy formula (3). dFB<d / (L / W) (3)

5. The method for producing a metal material according to any one of claims 1 to 4, The method for manufacturing a metal material, wherein the removal processing is drilling.

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