Surface processing method

Abstract

To provide a surface processing method of efficiently smoothing a surface of a metal laminate shaped article.SOLUTION: A surface processing method includes the steps of preparing a metal laminate shaped article, and performing blast processing on a surface of the metal laminate shaped article using a projection material. The projection material includes a first projection material of a first particle size having a grit shape and a second projection material of a second particle size having a grit shape. The first particle size is larger than the second particle size.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Patent document 1 discloses a method for treating the surface of an additively manufactured layered article, in which the surface of the layered article is smoothed by blasting with a grit-shaped projectile. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2019-525858 Summary of the Invention [Problem to be solved by the invention]

[0004] The surface of an additive manufacturing product manufactured by melting metal powder has an average roughness Ra of about 5 to 50 μm, which is very rough. For this reason, the method described in Patent Document 1 may require a long processing time to obtain a sufficiently smooth surface. The present disclosure provides a technique for efficiently smoothing the surface of a metal additive manufacturing product. [Means for solving the problem]

[0005] A surface processing method according to one aspect of the present disclosure includes the following steps. (1) The process of preparing a metal additive manufacturing product (2) A process of blasting the surface of the metal additive manufacturing product using a projectile. Here, the projection material includes a first projection material having a grit shape and a first particle size, and a second projection material having a grit shape and a second particle size, the first particle size being larger than the second particle size.

[0006] The surface of an additive manufacturing product manufactured by melting metal powder has roughness formed due to stacking (roughness due to stacking marks) and roughness formed by powder material solidifying without melting (roughness due to melting and solidifying). Roughness due to stacking marks tends to be larger than roughness due to melting and solidifying. Therefore, the surface of the metal additive manufacturing product has a shape in which different roughnesses are mixed. In the surface processing method according to the present disclosure, a projection material containing a first projection material of a first particle size and a second projection material of a second particle size smaller than the first particle size is used. As a result, the large roughness due to stacking marks is efficiently removed by the first projection material contained in the projection material. Furthermore, the fine roughness due to melting and solidifying and the processing marks of the first projection material are removed by the second projection material contained in the projection material. In this way, the surface processing method according to the present disclosure can efficiently smooth the surface of the metal additive manufacturing product compared to blast processing using only the first projection material or the second projection material.

[0007] In one embodiment, the Vickers hardness of each of the first and second shot materials may be 1.6 times or more the Vickers hardness of the metal additive manufacturing product. The first and second shot materials may be made of the same material. The metal additive manufacturing product may be made of powder of pure titanium and titanium alloy. According to these methods, the surface of the metal additive manufacturing product can be smoothed more efficiently. Effect of the Invention

[0008] According to the surface processing method according to one aspect of the present disclosure, the surface of a metal additive manufacturing product can be efficiently smoothed. [Brief description of the drawings]

[0009] [Figure 1] 2 is a flowchart of a surface processing method according to an embodiment. [Diagram 2] 1 is an example of a blast processing device used in a surface processing method. [Diagram 3]Graphs showing the relationship between the number of passes of the surface processing method according to the comparative example and the average roughness of the metal additive manufacturing product (A) and (B) show the relationship between the number of passes of the surface processing method according to the example and the average roughness of the metal additive manufacturing product (B). [Figure 4] Graphs showing the relationship between the number of passes of the surface processing method according to the comparative example and the average roughness change of the metal additive manufacturing product (A) and (B) show the relationship between the number of passes of the surface processing method according to the example and the average roughness change of the metal additive manufacturing product (B). [Diagram 5] 1A and 1B are graphs showing the relationship between the number of passes of the surface processing method and the average roughness of the metal additive manufacturing product, respectively. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Various embodiments will now be described in detail with reference to the drawings, in which the same or corresponding parts are designated by the same reference numerals.

[0011] (Blast processing method) Fig. 1 is a flowchart of a surface processing method according to an embodiment. The surface processing method M1 shown in Fig. 1 is a method of blasting a metal additive manufacturing product. A metal additive manufacturing product is obtained by melting metal powder with a laser or the like and forming it layer by layer.

[0012] Examples of the material of the metal powder include pure titanium and titanium alloy. The material of the metal powder may be pure iron and iron alloy. The iron alloy may include stainless steel and maraging. The material of the metal powder may be pure aluminum and aluminum alloy. The material of the metal powder may be pure copper and copper alloy. The material of the metal powder may be pure nickel and nickel alloy. The nickel alloy may include nickel-based superalloy. The material of the metal powder may be cobalt alloy. The material of the metal powder may be pure titanium and titanium alloy. The material of the metal powder may be pure magnesium and magnesium alloy. The material of the metal powder may be cemented carbide. The cemented carbide may include tungsten carbide.

[0013] The surface processing method M1 is realized by a blast processing device. FIG. 2 shows an example of a blast processing device used in the surface processing method. The blast processing device 1 includes a stage 10, a driving device 11, and a nozzle 12. The stage 10 supports a metal additive manufacturing product OB. The driving device 11 is connected to the stage 10 and moves the stage 10 along a direction S. The driving device 11 is, for example, a servo cylinder. The nozzle 12 is fixedly disposed facing the stage 10. The nozzle 12 sprays a blasting material together with air onto the surface of the metal additive manufacturing product OB on the stage 10. The nozzle 12 is, for example, a direct pressure air nozzle. The blast processing device 1 includes a control unit (not shown) that controls the drive amount of the driving device 11 and the spray amount of the nozzle 12. The control unit controls the drive amount of the driving device 11 and the spray amount of the nozzle 12, thereby blasting a predetermined position on the surface of the metal additive manufacturing product OB for a predetermined time.

[0014] The blast processing device used in the surface processing method M1 is not limited to the blast processing device 1 shown in Fig. 2. For example, the nozzle 12 may be configured to move relatively to the stage 10. In this case, the blast processing device 1 does not need to include the drive device 11. The nozzle 12 may be a suction type air nozzle. The drive device 11 may be a hydraulic cylinder or an air cylinder.

[0015] Returning to Fig. 1, the surface processing method M1 includes a preparation step (step S10) and a blast processing step (step S12). In the preparation step (step S10), the metal additive manufacturing product OB is placed on a stage 10 of a blast processing device 1. Then, in the blast processing step (step S12), a blasting material is sprayed onto the metal additive manufacturing product OB together with air by the nozzle 12. This causes the surface of the metal additive manufacturing product OB to be blast processed.

[0016] The blasting material used in the blasting process (step S12) includes a first blasting material and a second blasting material. The blasting material is obtained by mixing the first blasting material and the second blasting material, for example. The first blasting material and the second blasting material have a grit shape. The grit shape means a polygonal shape. The first blasting material and the second blasting material are formed by crushing shot. For example, the first blasting material and the second blasting material are steel grids and brown alundum grids. The first blasting material and the second blasting material may be formed of the same material or different materials. In this case, the quality of the blasting material is easier to maintain and easier to handle than when different materials are mixed.

[0017] The particle size of the first shot material (first particle size) is larger than the particle size of the second shot material (second particle size). The Vickers hardness of each of the first shot material and the second shot material may be 1.6 times or more the Vickers hardness of the metal additive manufacturing product OB. If the Vickers hardness of each of the first shot material and the second shot material is less than 1.6 times the Vickers hardness of the metal additive manufacturing product OB, the cutting ability is low and sufficient smoothing cannot be achieved.

[0018] (Summary of the embodiment) In the surface processing method M1, a shot material containing a first shot material of a first particle size and a second shot material of a second particle size smaller than the first particle size is used. As a result, large roughness on the surface of the metal additive manufacturing product OB resulting from lamination marks is efficiently removed by the first shot material contained in the shot material. Furthermore, fine roughness on the surface of the metal additive manufacturing product OB resulting from melting and solidification and processing marks of the first shot material are removed by the second shot material contained in the shot material. In this way, the surface processing method according to the present disclosure can efficiently smooth the surface of the metal additive manufacturing product OB compared to blast processing using only the first shot material or the second shot material. EXAMPLES

[0019] [Evaluation of smoothing efficiency] To evaluate the effectiveness of the mixed blast material, a metal additive manufacturing product was blasted.

[0020] (Preparation of metal additive manufacturing products) First, a metal additive manufacturing product was manufactured as the workpiece. The manufacturing equipment was a machine (Arcam: A2X) that irradiates an electron beam to melt metal powder and perform additive manufacturing. The metal powder was titanium alloy powder (Arcam Ti6Al-4V ELI powder). The size of the metal additive manufacturing product was a rectangular parallelepiped with one side measuring 50 mm. The Vickers hardness was 382 HV.

[0021] (Blast conditions) The blasting process was performed using a blasting device 1 shown in Fig. 2. The air pressure from the nozzle 12 was 0.3 MPa, and the amount of air sprayed was 13.5 kg / min. The blasting process was performed while moving the stage 10 along the direction S at 3000 mm / min.

[0022] (projection material) [Example 1] Mixture of first and second projection materials First shot material: steel grid, shot material hardness: 620HV, particle size: 0.7mm, hardness ratio (shot material / workpiece): 1.62 Secondary projectile: steel grid, projectile hardness: 620HV, particle size: 0.3mm, hardness ratio (projectile / workpiece): 1.62 [Example 2] Mixture of first and second projection materials First shot material: steel grid, shot material hardness: 620HV, particle size: 0.7mm, hardness ratio (shot material / workpiece): 1.62 Secondary projectile: steel grid, projectile hardness: 800HV, particle size: 0.3mm, hardness ratio (projectile / workpiece): 2.09 [Example 3] Mixture of first and second projection materials First shot material: steel grid, shot material hardness: 800HV, particle size: 0.7mm, hardness ratio (shot material / workpiece): 2.09 Secondary projectile: steel grid, projectile hardness: 800HV, particle size: 0.3mm, hardness ratio (projectile / workpiece): 2.09

[0023] [Comparative Example 1] Mixture of first and second projection materials First shot material: steel grid, shot material hardness: 620HV, particle size: 0.7mm, hardness ratio (shot material / workpiece): 1.62 Secondary projectile: steel grid, projectile hardness: 450HV, particle size: 0.3mm, hardness ratio (projectile / workpiece): 1.18 [Comparative Example 2] Mixture of first and second projection materials First shot material: steel grid, shot material hardness: 450HV, particle size: 0.7mm, hardness ratio (shot material / workpiece): 1.18 Secondary projectile: steel grid, projectile hardness: 620HV, particle size: 0.3mm, hardness ratio (projectile / workpiece): 1.62 [Comparative Example 3] Mixture of first and second projection materials First projection material: cut wire, projection material hardness: 700HV, particle size: 0.6mm, hardness ratio (projection material / workpiece): 1.83 Secondary projectile: steel grid, projectile hardness: 620HV, particle size: 0.3mm, hardness ratio (projectile / workpiece): 1.62 [Comparative Example 4] Shot material: steel grid, shot material hardness: 620HV, particle size: 0.7mm, hardness ratio (shot material / workpiece) 1.62 [Comparative Example 5] Shot material: steel grid, shot material hardness: 800HV, particle size: 0.3mm, hardness ratio (shot material / workpiece) 2.09 [Comparative Example 6] Shot material: cut wire, shot material hardness: 700HV, particle size: 0.6mm, hardness ratio (shot material / workpiece) 1.83

[0024] (surface roughness measurement) When the metal additive manufacturing product passed directly under the nozzle 12, the pass number count was incremented by one, and the surface of the metal additive manufacturing product at that time was measured with a roughness measuring device. The results are shown in FIG. 3. FIG. 3(A) is a graph showing the relationship between the pass number of the surface processing method according to the comparative example and the surface roughness of the metal additive manufacturing product (arithmetic mean roughness Ra defined in JIS B0601). FIG. 3(B) is a graph showing the relationship between the pass number of the surface processing method according to the embodiment and the average roughness of the metal additive manufacturing product. As shown in FIG. 3(A), the relationship between the pass number and the average roughness for the mixed projection material (Comparative Examples 1 to 3) was almost the same as that for the unmixed general projection material (Comparative Examples 4 to 6). In contrast, as shown in FIG. 3(B), it was confirmed that the mixed projection material (Examples 1 to 3) could reduce the average roughness compared to the unmixed general projection material (Comparative Examples 4 to 6).

[0025] FIG. 4 shows the results of converting the vertical axis of FIG. 3 into the average roughness change amount. The average roughness change amount was calculated by subtracting the average roughness after processing from the average roughness before processing. FIG. 4(A) is a graph showing the relationship between the number of passes of the surface processing method according to the comparative example and the average roughness change amount of the metal additive manufacturing product. FIG. 4(B) is a graph showing the relationship between the number of passes of the surface processing method according to the example and the average roughness change amount of the metal additive manufacturing product. As shown in FIG. 4(A), the average roughness change amount of the mixed projection material (Comparative Examples 1 to 3) was almost the same as or slightly inferior to that of the unmixed general projection material (Comparative Examples 4 to 6). In contrast, as shown in FIG. 4(B), it was confirmed that the mixed projection material (Examples 1 to 3) had a larger average roughness change amount than the unmixed general projection material (Comparative Examples 4 to 6). In particular, it was confirmed that the mixed projection material (Examples 1 to 3) could achieve a large average roughness change amount at a stage where the number of passes was small.

[0026] Based on the measurement results in Figures 3 and 4, it was confirmed that blasting can be made more efficient when grid-shaped blasting materials with different particle sizes are mixed and the Vickers hardness of each blasting material is 1.6 times or more the Vickers hardness of the metal additive manufacturing product.

[0027] (Other materials for projection material) Next, we investigated other materials for the projection material. The metal additive manufacturing products were manufactured using the same method and conditions as the metal additive manufacturing products evaluated in Figures 3 and 4.

[0028] (Blast conditions) The blasting process was performed using a blasting device 1 shown in Fig. 2. The air pressure from the nozzle 12 was 0.2 MPa, and the amount of air sprayed was 3.0 kg / min. The blasting process was performed while moving the stage 10 along the direction S at 3000 mm / min.

[0029] (projection material) [Example 4] Mixture of first and second projection materials First shot material: brown alundum grid, shot material hardness: 2100HV, particle size: 0.500mm, hardness ratio (shot material / workpiece): 5.50 Secondary projectile: brown alundum grid, projectile hardness: 2100HV, particle size: 0.125mm, hardness ratio (projectile / workpiece): 5.50 [Comparative Example 7] Brown alundum grid, projection material hardness: 2100HV, grain size: 0.500mm, hardness ratio (projection material / workpiece): 5.50 [Comparative Example 8] Brown alundum grid, projection material hardness: 2100HV, grain size: 0.125mm, hardness ratio (projection material / workpiece): 5.50

[0030] (surface roughness measurement) When the metal additive manufacturing product passed directly under the nozzle 12, the pass count was incremented by one, and the surface of the metal additive manufacturing product at that time was measured with a roughness measuring instrument. The results are shown in FIG. 5. FIG. 5(A) is a graph showing the relationship between the pass count of the surface processing method and the average roughness of the metal additive manufacturing product. As shown in FIG. 5(A), it was confirmed that the mixed projection material (Example 4) can reduce the average roughness compared to the unmixed projection material (Comparative Example 8). On the other hand, the mixed projection material (Example 4) showed the same results as the unmixed projection material (Comparative Example 7). This may be due to the variation in the surface roughness of the metal additive manufacturing product. On the other hand, FIG. 5(B) shows the result of converting the vertical axis of FIG. 5(A) into the average roughness change amount. The average roughness change amount was calculated by subtracting the average roughness after processing from the average roughness before processing. As shown in FIG. 5B, it was confirmed that the mixed shot material (Example 4) had a larger average roughness change amount than the unmixed general shot material (Comparative Examples 7 and 8). In particular, it was confirmed that the mixed shot material (Example 4) could achieve a large average roughness change amount at a stage where the number of passes was small. In this way, it was confirmed that the same effect was achieved when brown alundum grid was used as the shot material as when steel grid was used as the shot material. [Explanation of symbols]

[0031] M1...surface processing method, OB...metal additive manufacturing product, 1...blast processing device, 10...stage, 11...driving device, 12...nozzle.

Claims

1. A step of preparing a metal additive manufacturing product having roughness due to lamination marks and roughness due to melting and solidification; A step of blasting a surface of the metal additive manufacturing product using a projection material; Including, The blasting process includes removing roughness resulting from the stacking marks and roughness resulting from the melting and solidification, The projection material includes a first projection material having a first particle size in the form of grit and a second projection material having a second particle size in the form of grit, the first particle size being larger than the second particle size; Surface treatment method.

2. The surface processing method according to claim 1 , wherein the Vickers hardness of each of the first and second blast materials is 1.6 times or more the Vickers hardness of the metal additive manufacturing product.

3. The surface processing method according to claim 1 or 2, wherein the first projection material and the second projection material are formed from the same material.

4. The surface processing method according to any one of claims 1 to 3, wherein the metal additive manufacturing product is formed from powder of pure titanium and titanium alloy.

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