Surface treatment method and surface treatment system

Abstract

To provide a technique which can effectively smooth a work-piece with irradiation of an electron beam.SOLUTION: A surface treatment method includes a blast processing step of applying blast processing on a surface of a work-piece, and an electron beam irradiation step of irradiating the surface of the work-piece, to which the blast processing is applied, with an electron beam.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a surface treatment method and a surface treatment device. [Background technology]

[0002] Patent Document 1 discloses a surface treatment method for smoothing the surface of a mold by irradiating it with an electron beam. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-1086 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the method of Patent Document 1, it is believed that the surface of the workpiece is smoothed by melting the surface of the workpiece with an electron beam. Therefore, if the surface condition of the workpiece can be controlled to a shape that is easily melted by an electron beam, it may be possible to efficiently remove the roughness of the workpiece. The present disclosure provides a technology that can efficiently smooth a workpiece by irradiating it with an electron beam. [Means for solving the problem]

[0005] The inventors focused on the fact that blasting can control the surface condition using a different principle than melting, and discovered that performing blasting before irradiating with an electron beam results in a greater reduction in the surface roughness of the workpiece (the percentage of reduction in the roughness of the workpiece before and after electron beam irradiation) compared to when only electron beam irradiation is performed.

[0006] That is, a surface treatment method according to one aspect of the present disclosure includes a blasting process for performing blasting on a surface of a workpiece, and an electron beam irradiation process for irradiating an electron beam onto the blasted surface of the workpiece. According to this surface treatment method, the reduction rate of the surface roughness of the workpiece is greater than that in the case where only the electron beam is irradiated, and therefore the workpiece can be efficiently smoothed by the electron beam irradiation.

[0007] In one embodiment, the workpiece may be a sintered product of metal powder. In one embodiment, the workpiece may be an additive manufacturing product. The surface of a sintered product or an additive manufacturing product tends to have a relatively large roughness. This surface treatment method can efficiently flatten even the surface of a sintered product or an additive manufacturing product.

[0008] In one embodiment, the blasted surface of the workpiece may have an average length of roughness curve elements of less than 770.80 μm. In this case, the surface treatment method can reduce the surface roughness of the workpiece by 20% or more.

[0009] A surface treatment system according to another aspect of this embodiment includes a blasting device that performs blasting on a workpiece, an electron beam irradiation device that irradiates the workpiece with an electron beam, and a control unit that controls the blasting device and the electron beam irradiation device. The control unit controls the blasting device to perform blasting on the surface of the workpiece, and controls the electron beam irradiation device to irradiate the electron beam on the surface of the workpiece that has already been blasted. This surface treatment system, like the above-mentioned surface treatment device, can efficiently smooth the workpiece by irradiating it with the electron beam, compared to the case where only the electron beam is irradiated. Effect of the Invention

[0010] According to the present disclosure, a workpiece can be efficiently smoothed by irradiating it with an electron beam. [Brief description of the drawings]

[0011] [Figure 1]2 is a flowchart showing an example of a surface treatment method according to the embodiment. [Diagram 2] FIG. 1 is a schematic diagram showing an example of a blast processing device. [Diagram 3] FIG. 1 is a schematic diagram illustrating an example of an electron beam irradiation device. [Figure 4] 1 is a block diagram showing an example of a surface treatment system according to an embodiment; [Diagram 5] 1 is an example of irradiation of a workpiece with an electron beam. [Figure 6] 1 is a table showing evaluation results of surface roughness. [Figure 7] FIG. 1 is a scatter diagram showing the correlation between RSm (average length of roughness curve element) and Rz (maximum height roughness) reduction rate. [Figure 8] 4 shows the cross-sectional observation results of a workpiece before and after electron beam irradiation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In the following description, the same or equivalent elements are given the same reference numerals, and redundant description will not be repeated. The dimensional ratios of the drawings do not necessarily match those in the description. The terms "upper", "lower", "left" and "right" are based on the illustrated state and are for convenience.

[0013] [Surface treatment method] FIG. 1 is a flow chart showing an example of a surface treatment method according to an embodiment. The surface treatment method shown in FIG. 1 is a method for smoothing the surface of a workpiece. The workpiece is an object to be surface-treated. The workpiece is made of a metal such as iron, aluminum, titanium, stainless steel, copper alloy, or carbon steel. The workpiece may be a sintered product of metal powder. The sintered product is manufactured by sintering metal powder by powder metallurgy. The workpiece may be an additive manufacturing product. The additive manufacturing product is manufactured by repeatedly irradiating metal powder with laser light. The workpiece may be a cast product. The workpiece may be a machined product. The workpiece may be a forged product.

[0014] As shown in Fig. 1, the surface treatment method includes a blasting process (step S10) and an electron beam irradiation process (step S20). The blasting process is performed by a blasting device. The electron beam irradiation process is performed by an electron beam irradiation device. First, an overview of an example of the device used in each process will be described.

[0015] [Blast processing equipment] FIG. 2 is a schematic diagram showing an example of a blasting device. Blasting is a processing method for grinding the surface of a workpiece by projecting an abrasive. The material of the abrasive is selected from various materials such as metal (e.g., iron, zinc, stainless steel), ceramic (e.g., alumina, silicon carbide, zircon), glass, resin (e.g., nylon resin, melamine resin, urea resin), and plant-derived materials (e.g., walnut, peach). The shape of the abrasive is selected from various shapes such as spherical, polygonal, and cylindrical. For example, in the case of metal particles, spherical particles called shot, polygonal particles with acute angles called grid, and cylindrical particles or cylindrical particles with rounded corners called cut wire can be selected.

[0016] The blast processing device 10 shown in FIG. 2 is a direct pressure type (pressurized type) blast processing device 10. As shown in FIG. 2, the blast processing device 10 includes a storage container 20 and a nozzle 30. The storage container 20 defines a space for storing the abrasive therein and stores the abrasive. The abrasive is supplied to the storage container 20 from the outside. For example, an operator may supply the abrasive to the storage container 20. The storage container 20 may reuse a part of the abrasive used in the blast processing. In this case, the storage container 20 is supplied with the abrasive used in the blast processing from a classification mechanism 14 described later. The storage container 20 is connected to the nozzle 30 via a fixed-volume supply unit 21 and a pipe 13. The fixed-volume supply unit 21 is a device that sends the abrasive stored in the storage container 20 to the pipe 13, and is, for example, a screw feeder.

[0017] A gas supply source 12 that supplies gas is connected to the piping 13. The gas supply source 12 may be, for example, a compressor or a gas cylinder that supplies gas at a medium pressure (for example, 0.1 MPa to 0.6 MPa), or a blower such as a fan or a blower that supplies gas at a low pressure (for example, 0.01 MPa to 0.1 MPa). In this embodiment, compressed air is supplied by a compressor. The gas supplied from the gas supply source 12 to the piping 13 transports the abrasive sent out by the constant-volume supply unit 21 to the nozzle 30.

[0018] The nozzle 30 sprays the abrasive supplied from the storage container 20 together with the gas. The nozzle 30 is housed in a processing chamber 31, and a gas-solid two-phase flow in which the abrasive supplied from the storage container 20 and the gas are mixed is supplied to the nozzle 30 via piping 13. The nozzle 30 sprays the abrasive together with the gas toward the workpiece W placed in the processing chamber 31. This performs blast processing on the workpiece W. The workpiece W is supported on a table (not shown), and the position may be adjusted by a table driving mechanism.

[0019] The lower part of the processing chamber 31 is connected to the storage container 20 via the classification mechanism 14. The abrasive and chips of the workpiece W that have fallen to the lower part of the processing chamber 31 are sucked into a dust collector (not shown) and pass through the classification mechanism 14. The classification mechanism 14 classifies the abrasive into reusable abrasive and other fine powders (such as crushed abrasive and chips of the workpiece W). The other fine powders are collected in the dust collector. The lower part of the classification mechanism 14 is connected to the upper part of the storage container 20. The reusable abrasive is supplied from the classification mechanism 14 to the storage container 20. If the abrasive is not reused, the blast processing device 10 does not need to be equipped with the classification mechanism 14.

[0020] The blasting apparatus 10 is controlled by a control device 11. The control device 11 is configured as, for example, a PLC (Programmable Logic Controller). The control device 11 may be configured as a computer system including a processor such as a CPU (Central Processing Unit), memories such as a RAM (Random Access Memory) and a ROM (Read Only Memory), input / output devices such as a touch panel, a mouse, a keyboard, and a display, and a communication device such as a network card. The control device 11 realizes the functions of the control device 11 by operating each piece of hardware under the control of the processor based on a computer program stored in the memory.

[0021] [Configuration of electron beam irradiation device] Fig. 3 is a schematic diagram showing an example of an electron beam irradiation device. The electron beam irradiation device 40 shown in Fig. 3 is a device that irradiates an electron beam EB onto a workpiece W to perform surface treatment of the workpiece W. As shown in Fig. 3, the electron beam irradiation device 40 includes a vacuum chamber 41, a cathode 50, an anode 51, a pair of solenoids 60, and a stage 70.

[0022] The vacuum chamber 41 houses therein a workpiece W to be irradiated with the electron beam EB and a source of the electron beam EB. The workpiece W to be irradiated with the electron beam is placed on a stage 70 in the vacuum chamber 41. A cathode 50, which is a source of the electron beam EB, is disposed inside the vacuum chamber 41 so as to face the stage 70. An annular anode 51 is disposed between the stage 70 and the cathode 50. The stage 70, the cathode 50, and the anode 51 are disposed inside the vacuum chamber 41 so as to be aligned on one axis. Each of the pair of solenoids 60 is an annular member. The first solenoid is disposed outside the vacuum chamber 41 so as to surround the cathode 50, and the second solenoid is disposed outside the vacuum chamber 41 so as to surround the anode 51.

[0023] A vacuum pump (not shown), such as a rotary pump or a turbo pump, is connected to the vacuum chamber 41. The vacuum chamber 41 is evacuated in advance when irradiating the electron beam EB. An inert gas, such as Ar (argon) gas, is introduced from the outside into the evacuated vacuum chamber 41, and the inside of the vacuum chamber 41 is filled with a gas of 5 to 15×10 -2 The atmosphere is kept at about Pa inert gas.

[0024] A power supply (not shown) that applies a pulse voltage is connected to the cathode 50 and the anode 51 housed in the vacuum chamber 41. A power supply (not shown) separate from the power supply connected to the cathode 50 and the anode 51 is connected to the solenoid 60.

[0025] When a voltage is applied to the solenoid 60, the solenoid 60 generates a magnetic field near the anode 51 inside the vacuum chamber 41. When the magnetic field generated near the anode 51 reaches a maximum, a pulse voltage is applied to the anode 51. Electrons in the vacuum chamber 41 move toward the anode 51 to which the voltage is applied. At this time, since a magnetic field is generated near the anode 51 by the solenoid 60, the electrons move while drawing a spiral due to the Lorentz force. These electrons repeatedly collide with gas molecules, and the gas molecules that collide with the electrons are ionized into positive ions and electrons. The positive ions and electrons further repeatedly collide with the gas, and plasma is formed near the cathode 50 and the anode 51, respectively.

[0026] When the plasma formed near the anode 51 reaches a maximum, a pulse voltage is applied to the cathode 50. At this time, the potential difference between the cathode 50 and the plasma near the cathode 50 reaches a maximum. As a result, electrons emitted from the cathode 50 are accelerated toward the anode 51 by the electric field generated by the cathode 50 and the plasma near the cathode 50, generating an electron beam EB. The electron beam EB passes through the annular anode 51 and is irradiated onto the workpiece W placed on the stage 70.

[0027] The surface treatment method will be described below with reference to Fig. 1 again. First, in a blasting process (step S10), a blasting process is performed on the surface of the workpiece by a blasting device 10. As a result, the workpiece surface is physically cut.

[0028] Next, in the electron beam irradiation step (step S20), an electron beam is irradiated onto the blasted surface of the workpiece by the electron beam irradiation device 40. The minute irregularities on the workpiece surface are melted and smoothed by the irradiation of the electron beam. Specifically, the minute protrusions are melted by the electron beam, and the molten metal flows into the minute recesses, smoothing the surface of the workpiece.

[0029] [Surface treatment system] The surface treatment method shown in FIG. 1 may be performed by a surface treatment system. FIG. 4 is a block diagram showing an example of a surface treatment system according to an embodiment. As shown in FIG. 4, the surface treatment system 90 includes a blasting device 10, an electron beam irradiation device 40, and a control unit 80. The control unit 80 is configured as a PLC as an example, and is communicably connected to the blasting device 10 and the electron beam irradiation device 40. The control unit 80 may be configured as the above-mentioned computer system. The control unit 80 controls the blasting device 10 and the electron beam irradiation device 40. The blasting device 10 performs blasting on the workpiece W under the control of the control unit 80, and the electron beam irradiation device 40 irradiates the workpiece W on which the blasting has been performed with an electron beam under the control of the control unit 80. In this way, the surface treatment system 90 controls the blasting device 10 and the electron beam irradiation device 40, respectively, and can perform the surface treatment method shown in FIG. 1.

[0030] [Summary of the embodiment] In the surface treatment method according to the present embodiment, the blasted surface of the workpiece W is irradiated with an electron beam. The blasted surface of the workpiece W is physically cut to remove irregularities of 100 μm or more. The melting speed of irregularities of 100 μm or more by irradiation with an electron beam tends to be slower than that of irregularities less than 100 μm. Therefore, it can be said that the blasted surface of the workpiece W has a shape that is easily melted by an electron beam. In other words, the surface treatment method according to the present embodiment can control the surface of the workpiece W to a shape that is easily melted by an electron beam by performing blasting. As a result, the reduction rate of the surface roughness of the workpiece is greater than when only irradiation with an electron beam is performed. Therefore, the surface treatment method according to the present embodiment can efficiently smooth the workpiece by irradiating it with an electron beam.

[0031] Furthermore, the surface treatment method according to this embodiment can shorten the time of the electron beam irradiation step compared to the case where only electron beam irradiation is performed, even when the workpiece W is a sintered product or an additive manufacturing product with a relatively high surface roughness. Furthermore, the surface treatment method according to this embodiment can also remove defects formed on the surface of the workpiece W by blasting using the electron beam.

[0032] Although various exemplary embodiments have been described above, various omissions, substitutions, and modifications may be made without being limited to the above exemplary embodiments. For example, the blast processing device 10 is not limited to a direct pressure type (pressure type) blast processing device, and may be a gravity type (suction type) air blast device or a centrifugal type blast device. EXAMPLES

[0033] In the following, examples carried out by the present inventors will be described in order to explain the above-mentioned effects, but the present disclosure is not limited to these examples.

[0034] [Workpiece creation] A roughly cubic additive manufacturing product with a side length of 50 mm was prepared as the workpiece W. The workpiece W was obtained by additive manufacturing of metal powder Ti6Al4V ELI powder manufactured by Arcam. The additive manufacturing was performed using an additive manufacturing device, Arcam A2X, manufactured by Arcam. Sixteen identical workpieces W were prepared.

[0035] Next, 15 of the 16 workpieces W were subjected to blasting processing using a blasting processing device 10 shown in Fig. 2 under blasting conditions that were set for each workpiece. The blasting conditions were as follows: the type of blasting material was steel grid or steel shot, the lower limit of the hardness of the blasting material was 450HV to 800HV, and the grain size was 0.2mm to 2.5mm. As a result, 15 blasted workpieces W and one unblasted workpiece were obtained.

[0036] Next, the surfaces of all 16 workpieces W were irradiated with an electron beam EB using an electron beam irradiation device 40 shown in FIG. 3. FIG. 5 shows an example of electron beam irradiation performed on a workpiece. As shown in FIG. 5, a mask material M was used to compare the surface state before and after irradiation with the electron beam EB. The mask material M was a copper mask having an opening of 25 mm square. The workpieces W covered with the mask material M were irradiated with an electron beam EB. The irradiation conditions for the electron beam EB were a pulse width of 2 μs, a pulse frequency of 0.125 Hz, and an energy density of 15 J / cm. 2 The number of pulse irradiations was set to 50.

[0037] [Confirmation of surface roughness] The surface roughness of 15 blasted workpieces W (Examples) and unblasted workpieces W (Comparative Examples) was confirmed before and after electron beam irradiation. The surface roughness was evaluated using the maximum height roughness Rz (μm) and the average length RSm (μm) of the roughness curve element, as specified in JIS B0601:2001. The maximum height roughness Rz (μm) is the difference between the highest point and the lowest point on the roughness curve of the surface of the workpiece W. The average length RSm (μm) of the roughness curve element is the average value of the length of the contour curve element in the reference length of the roughness curve of the surface of the workpiece W. Furthermore, the maximum height roughness Rz reduction rate (%) was calculated using the maximum height roughness Rz (μm) before and after irradiation with the electron beam EB. The maximum height roughness Rz reduction rate (%) is the rate at which the irradiation with the electron beam EB smoothes the surface of the workpiece W, and was calculated using the following formula. Maximum height roughness Rz reduction rate (%) = (1 - maximum height roughness Rz after electron beam irradiation / maximum height roughness Rz before electron beam irradiation) x 100

[0038] The evaluation results of the surface roughness are shown in Fig. 6. Fig. 6 is a table showing the evaluation results of the surface roughness. Blasting condition "1" shown in Fig. 6 is the evaluation result of the surface roughness of a workpiece W that was not blasted (Comparative Example). Blasting conditions "2" to "16" shown in Fig. 6 are the evaluation results of the surface roughness of a workpiece W that was blasted (Examples).

[0039] As shown in blast condition "1", the Rz of the unblasted workpiece W was 174.51 μm before irradiation with the electron beam EB, and was reduced to 139.75 μm after irradiation with the electron beam EB (Rz reduction rate: 20%). The RSm was 367.35 μm before irradiation with the electron beam EB, and increased to 752.66 μm after irradiation with the electron beam EB.

[0040] In blasting condition "2", the workpiece W was blasted with steel grids having a Vickers hardness of 450HV and a grain size of 1.4mm. The Rz of the blasted workpiece W was 53.19μm before irradiation with the electron beam EB, and reduced to 45.68μm after irradiation with the electron beam EB (Rz reduction rate: 14%). On the other hand, the RSm was 1091.55μm before irradiation with the electron beam EB, and increased to 1322.48μm after irradiation with the electron beam EB.

[0041] In blasting condition "3", the workpiece W was blasted with steel grids having a Vickers hardness of more than 800HV and a grain size of 0.7mm. The Rz of the blasted workpiece W was 54.66μm before irradiation with the electron beam EB, and reduced to 24.65μm after irradiation with the electron beam EB (Rz reduction rate: 55%). On the other hand, the RSm was 391.86μm before irradiation with the electron beam EB, and increased to 1291.25μm after irradiation with the electron beam EB.

[0042] In blasting condition "4", the workpiece W was blasted with steel grids having a Vickers hardness of more than 800HV and a grain size of 0.7mm. The Rz of the blasted workpiece W was 65.99μm before irradiation with the electron beam EB, and reduced to 27.98μm after irradiation with the electron beam EB (Rz reduction rate: 58%). On the other hand, the RSm was 433.89μm before irradiation with the electron beam EB, and increased to 1098.82μm after irradiation with the electron beam EB.

[0043] In blasting condition "5", the workpiece W was blasted with steel shot having a Vickers hardness of 450HV and a grain size of 1.0mm. The Rz of the blasted workpiece W was 45.43μm before irradiation with the electron beam EB, and reduced to 34.36μm after irradiation with the electron beam EB (Rz reduction rate: 24%). On the other hand, the RSm was 860.99μm before irradiation with the electron beam EB, and increased to 1180.18μm after irradiation with the electron beam EB.

[0044] In blasting condition "6", the workpiece W was blasted with steel shot having a Vickers hardness of 450HV and a grain size of 2.5mm. The Rz of the blasted workpiece W was 45.36μm before irradiation with the electron beam EB, and reduced to 32.19μm after irradiation with the electron beam EB (Rz reduction rate: 29%). On the other hand, the RSm was 922.88μm before irradiation with the electron beam EB, and increased to 937.18μm after irradiation with the electron beam EB.

[0045] In blasting condition "7", the workpiece W was blasted with steel shot having a Vickers hardness of 450HV and a grain size of 1.4mm. The Rz of the blasted workpiece W was 45.45μm before irradiation with the electron beam EB, and reduced to 35.67μm after irradiation with the electron beam EB (Rz reduction rate: 22%). Meanwhile, the RSm was 1009.34μm before irradiation with the electron beam EB, and reduced to 956.43μm after irradiation with the electron beam EB.

[0046] In blasting condition "8", the workpiece W was blasted with steel shot having a Vickers hardness of 450HV and a grain size of 0.6mm. The Rz of the blasted workpiece W was 47.04μm before irradiation with the electron beam EB, and reduced to 38.62μm after irradiation with the electron beam EB (Rz reduction rate: 18%). On the other hand, the RSm was 959.69μm before irradiation with the electron beam EB, and increased to 1234.12μm after irradiation with the electron beam EB.

[0047] In blasting condition "9", the workpiece W was blasted with steel shot having a Vickers hardness of 450HV and a grain size of 2.5mm. The Rz of the blasted workpiece W was 39.45μm before irradiation with the electron beam EB, and reduced to 35.29μm after irradiation with the electron beam EB (Rz reduction rate: 11%). On the other hand, the RSm was 1024.41μm before irradiation with the electron beam EB, and increased to 1400.89μm after irradiation with the electron beam EB.

[0048] In blasting condition "10", the workpiece W was blasted with steel grids having a Vickers hardness of more than 800HV and a grain size of 0.3mm. The Rz of the blasted workpiece W was 44.08μm before irradiation with the electron beam EB, and reduced to 27.91μm after irradiation with the electron beam EB (Rz reduction rate: 37%). On the other hand, the RSm was 582.93μm before irradiation with the electron beam EB, and increased to 1298.67μm after irradiation with the electron beam EB.

[0049] In blasting condition "11", the workpiece W was blasted with steel grids having a Vickers hardness of 450HV and a grain size of 0.7mm. The Rz of the blasted workpiece W was 53.04μm before irradiation with the electron beam EB, and reduced to 28.44μm after irradiation with the electron beam EB (Rz reduction rate: 46%). On the other hand, the RSm was 610.62μm before irradiation with the electron beam EB, and increased to 1114.42μm after irradiation with the electron beam EB.

[0050] In blasting condition "12", the workpiece W was blasted with steel grids having a Vickers hardness of 600HV and a grain size of 0.7mm. The Rz of the blasted workpiece W was 53.98μm before irradiation with the electron beam EB, and reduced to 37.35μm after irradiation with the electron beam EB (Rz reduction rate: 31%). On the other hand, the RSm was 770.80μm before irradiation with the electron beam EB, and increased to 1154.21μm after irradiation with the electron beam EB.

[0051] In blasting condition "13", the workpiece W was blasted with steel grids having a Vickers hardness of more than 800HV and a grain size of 0.2mm. The Rz of the blasted workpiece W was 63.02μm before irradiation with the electron beam EB, and reduced to 51.61μm after irradiation with the electron beam EB (Rz reduction rate: 18%). On the other hand, the RSm was 781.94μm before irradiation with the electron beam EB, and increased to 1136.86μm after irradiation with the electron beam EB.

[0052] In blasting condition "14", the workpiece W was blasted with steel grids having a Vickers hardness of more than 800HV and a grain size of 0.2mm. The Rz of the blasted workpiece W was 38.16μm before irradiation with the electron beam EB, and reduced to 24.31μm after irradiation with the electron beam EB (Rz reduction rate: 36%). On the other hand, the RSm was 496.27μm before irradiation with the electron beam EB, and increased to 1311.28μm after irradiation with the electron beam EB.

[0053] In blasting condition "15", the workpiece W was blasted with steel grids having a Vickers hardness of more than 800HV and a grain size of 0.2mm. The Rz of the blasted workpiece W was 49.53μm before irradiation with the electron beam EB, and reduced to 38.95μm after irradiation with the electron beam EB (Rz reduction rate: 21%). Meanwhile, the RSm was 852.99μm before irradiation with the electron beam EB, and increased to 1195.85μm after irradiation with the electron beam EB.

[0054] In blasting condition "16", the workpiece W was blasted with steel grids having a Vickers hardness of more than 800HV and a grain size of 0.2mm. The Rz of the blasted workpiece W was 32.90μm before irradiation with the electron beam EB, and reduced to 16.18μm after irradiation with the electron beam EB (Rz reduction rate: 51%). On the other hand, the RSm was 299.65μm before irradiation with the electron beam EB, and increased to 1248.80μm after irradiation with the electron beam EB.

[0055] As shown in Fig. 6, the workpiece W that has been blasted under blast conditions "2" to "16" has an Rz in the range of 16.18 µm to 51.61 µm after irradiation with the electron beam EB. In contrast, the workpiece W that has only been irradiated with the electron beam EB (not blasted) has an Rz of 139.75 µm after irradiation with the electron beam EB. Therefore, it was confirmed that the surface of the workpiece W that has been blasted can be made smoother by irradiating the surface with the electron beam EB.

[0056] Furthermore, based on the results of Fig. 6, the correlation between RSm before irradiation with the electron beam EB and the reduction rate of Rz due to irradiation with the electron beam EB was confirmed. Fig. 7 is a scatter plot showing the correlation between RSm and the reduction rate of Rz. The horizontal axis is RSm before irradiation with the electron beam EB, and the vertical axis is the reduction rate of Rz. In Figure 7, the data is divided into six categories according to the blasting conditions: no blasting (blasting condition "1"), blasting with steel shots (blasting conditions "5" to "9"), Rz less than 40 μm after blasting with steel grids (blasting conditions "9" and "16"), Rz 40 μm to 50 μm after blasting with steel grids (blasting conditions "10" and "15"), Rz 50 μm to 60 μm after blasting with steel grids (blasting conditions "2", "3", "11", and "12"), and Rz 60 μm or more after blasting with steel grids.

[0057] As shown in Fig. 7, a correlation was confirmed in which the smaller the RSm, the higher the reduction rate of Rz. It was also confirmed that in order to achieve a reduction rate of Rz of 20% or more, it is necessary to satisfy the conditions that the workpiece has been blasted and that the Rsm is less than 770.80 μm. In addition, the blasted workpieces W (blast conditions "3", "4", and "16") having RSm similar to that of the unblasted workpiece W all had an Rz reduction rate more than twice that of the unblasted workpiece W. From this, it is inferred that the blasted surface is controlled to a shape that is easily melted by the electron beam in parameters other than RSm evaluated this time.

[0058] [Cross-sectional observation of surface] FIG. 8 shows the cross-sectional observation results of the workpiece before and after the electron beam irradiation. (A) to (E) of FIG. 8 show the cross-sectional observation results of the workpiece W before the irradiation of the electron beam EB. (A) of FIG. 8 shows the observation result of the workpiece W not yet blasted (blast condition "1"); (B) and (D) of FIG. 8 show the observation result of the workpiece W after the blasting process (blast condition "12"); and (C) and (E) of FIG. 8 show the observation result of the workpiece W after the blasting process (blast condition "16"). As shown in (A) of FIG. 8, minute irregularities of 100 μm or less and irregularities larger than 100 μm were confirmed in the workpiece W before the blasting process. In contrast, as shown in (B) to (E) of FIG. 8, there are no irregularities larger than 100 μm in the workpiece W after the blasting process. Therefore, it was confirmed that the irregularities larger than 100 μm were removed and flattened by the blasting process. Furthermore, as shown in (D) and (E) of FIG. 8, cracks of about 20 μm were confirmed on the surface of the workpiece W that had been blasted.

[0059] (F) to (H) in FIG. 8 are cross-sectional observation results after irradiation with the electron beam EB. (F) in FIG. 8 is an observation result after the workpiece W according to (A) in FIG. 8 is irradiated with the electron beam EB, (G) in FIG. 8 is an observation result after the workpiece W according to (B) and (D) in FIG. 8 is irradiated with the electron beam EB, and (H) in FIG. 8 is an observation result after the workpiece W according to (C) and (E) in FIG. 8 is irradiated with the electron beam EB. As shown in (F) in FIG. 8, the minute irregularities of 100 μm or less confirmed before the electron beam EB irradiation were removed by the electron beam EB irradiation. On the other hand, even if the electron beam EB was irradiated, the irregularities larger than 100 μm were not completely removed and remained. This confirmed that the irradiation with the electron beam EB cannot efficiently remove the irregularities larger than 100 μm. In contrast, as shown in (G) and (H) in FIG. 8, the workpiece W that had been blasted was extremely flattened by the electron beam irradiation. It was confirmed that the blasted surfaces shown in Figures 8(B) to (E) have no irregularities larger than 100 µm, and therefore have a shape that is easily melted by an electron beam.

[0060] From the above, it was confirmed that blasting can remove irregularities larger than 100 μm that cannot be removed by irradiation with an electron beam EB (in other words, it can control the surface to a shape that is easily melted by an electron beam). Therefore, it was confirmed that the surface treatment method of irradiating the electron beam EB after blasting can efficiently smooth the surface of the workpiece W. It was also confirmed that irradiation with the electron beam EB can remove cracks caused by blasting. [Explanation of symbols]

[0061] 10...blast processing device, 40...electron beam irradiation device, 80...control unit, 90...surface treatment system, EB...electron beam, W...workpiece.

Claims

1. a blasting process for performing blasting on the surface of the workpiece; an electron beam irradiation step of irradiating the blasted surface of the workpiece with an electron beam; Equipped with The workpiece is a sintered product of metal powder and an additive manufacturing product; The blasted surface of the workpiece has unevenness of 100 μm or more physically removed, and the average length of the roughness curve element is less than 770.80 μm. Surface treatment method.

2. In the electron beam irradiation step, The minute convex portions are melted by the electron beam, and the molten metal flows into the minute concave portions, so that the surface of the workpiece that has been physically cut by the blasting process is smoothed. The defects formed on the surface of the workpiece by the blasting process are removed by the electron beam. The surface treatment method according to claim 1 .

3. A blast processing device that performs blast processing on a workpiece; an electron beam irradiation device that irradiates the workpiece with an electron beam; A control unit that controls the blast processing device and the electron beam irradiation device; Equipped with The workpiece is a sintered product of metal powder and an additive manufacturing product; The control unit is The blast processing device is controlled to perform blast processing on the surface of the workpiece, and the blast-processed surface of the workpiece is physically cut to remove irregularities of 100 μm or more, and the average length of the roughness curve element is less than 770.80 μm; Also, the electron beam irradiation device is controlled to irradiate the electron beam onto the surface of the workpiece that has been blasted. Surface treatment systems.

4. The control unit controls the electron beam irradiation device, The minute convex portions are melted by the electron beam, and the molten metal flows into the minute concave portions, smoothing the surface of the workpiece that has been physically cut by the blast processing device; The electron beam is used to remove defects formed on the surface of the workpiece by the blast processing device. The surface treatment system according to claim 3 .

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