JP4452564B2 - Blasting method - Google Patents

Description

  The present invention relates to a blasting method for processing a work surface by spraying a granular material.

  Blasting, which processes the surface to be processed by spraying granular material at high speed, is widely used as a pretreatment and finishing process for the surface of metal materials, etc. The surface is roughened, cleaned, activated, and further strengthened.

  For example, when it is used as a pretreatment when painting or plating on the surface of steel, a round surface such as a round steel ball is used as a granular material, and the work surface is roughened to improve the adhesion of paint and plating. The surface to be processed is removed, and foreign matters such as oxides are removed to clean the surface to be processed. In addition, when performing thermal spray coating that is widely used as a means for imparting wear resistance to various metal materials, anticorrosion, environmental shielding, etc., use a grit such as steel or alumina with a cusp as a granular material, Is roughened and cleaned, and the surface to be processed is activated by the grinding action of the grit to enhance the adhesion of the sprayed metal to these metal materials. A cut core having a cut surface may be used for the granular material.

  Many of the granular materials used for blasting are harder and more brittle than the material of the surface to be processed, so that the granular material sprayed at a high speed and its debris bite into the surface to be processed, and some of the material is covered. May remain on the machined surface. In this way, the particulate matter and fragments remaining on the surface to be processed are different materials from the material that forms the surface to be processed, and thus various problems are caused in post-processing processes and products such as paint, plating, and thermal spray coating. There are problems to bring.

  For example, in the case of a metal particulate material, the work surface may be corroded due to the difference in electrochemical characteristics from the work surface of a dissimilar metal. Further, in the case of a ceramic granular material such as alumina, the adhesion to the plating or sprayed metal is inferior to the surface of the metal to be processed, and the plating or sprayed coating may be peeled off.

  As a means for removing foreign substances such as particulate matter remaining on the processed surface after blasting and fragments thereof, a method of blowing compressed air to the processed surface and blowing the foreign material, or ultrasonically cleaning the processed surface The method is known (for example, refer nonpatent literature 1). In addition, a method has been proposed in which dry ice particles are used as the particulate material, and the particulate material is naturally sublimated and eliminated.

Nagasaka, Ishikawa, Aoki, “Blasting Technology”, Co-Tech, 1982, p. 180

  The method of spraying compressed air on the surface to be processed described above is simple, but there is a problem that the granular material and its debris that are firmly entrapped cannot be removed. Also, the ultrasonic cleaning method of the work surface is difficult to apply to large work pieces, and it is necessary to immerse the work piece in water, so it is suitable for work pieces such as steel that are easily corroded. Not.

  On the other hand, the method using dry ice grains as a granular material is not so hard and easy to crush, so if the work piece is a hard metal such as steel, the work surface may be sufficiently roughened. There is a problem that it cannot be activated and the effect of blasting cannot be obtained satisfactorily.

  Accordingly, an object of the present invention is to reduce foreign matters such as particulate matter and fragments thereof remaining on a surface to be processed after blasting, on the premise that the effect of blasting can be obtained satisfactorily.

In order to solve the above-described problems, the present invention provides a blasting method for processing a processed surface by spraying a granular material harder than a material of the processed surface, and the processed surface to be processed with a solid lubricant in advance. Cover and vaporize the solid lubricant remaining on the work surface by heating the work surface after being blown and blown with the particulate material, assuming that the solid lubricant is vaporized at a low temperature of 500 ° C. or less. The method of removing them was adopted.

Further, the present invention provides a blasting method for processing a surface to be processed by spraying a granular material harder than a material of a surface to be processed, and coating the surface of the sprayed granular material with a solid lubricant, As a method of vaporizing at a low temperature of 500 ° C. or lower, a method of heating the work surface after being blown with the particulate material and blasting to vaporize and remove the solid lubricant remaining on the work surface was also adopted. .

  In other words, the surface to be processed is coated with a solid lubricant in advance, or the surface of the granular material to be sprayed is coated with a solid lubricant, so that slippage is caused between the sprayed granular material and the surface to be processed. Reduces the amount of particulate matter that penetrates into the work surface, and forms a solid lubricant layer at the interface between the entrained particulate material and the work surface, making it easier for the particulate matter to leave the work surface. In addition, it is possible to reduce foreign matters such as particulate matter remaining on the surface to be processed after blasting and fragments thereof.

  By vaporizing the solid lubricant at a low temperature of 500 ° C. or lower, the solid lubricant remaining on the processed surface can be vaporized and removed only by heating the processed surface after blasting at a low temperature. it can. When performing a subsequent process in which the surface to be processed is heated, such as thermal spray coating, the solid lubricant can be vaporized without performing an extra heating process by using the heating in the subsequent process. it can.

  The solid lubricant can be stearic acid, a stearate salt or a mixture thereof. As the stearate, zinc stearate, calcium stearate, or the like can be used.

  In the blasting method of the present invention, the processed surface to be processed is coated with a solid lubricant in advance, or the surface of the granular material to be sprayed is coated with a solid lubricant, so that the sprayed granular material and the processed surface In order to reduce the amount of particulate matter that penetrates the surface to be machined, a solid lubricant layer is formed at the interface between the entrained particulate material and the surface to be machined. Since it is easy to detach from the processing surface, it is possible to reduce foreign matters such as particulate matter and fragments thereof remaining on the processing surface after blasting.

  By vaporizing the solid lubricant at a low temperature of 500 ° C. or lower, the solid lubricant remaining on the processed surface can be vaporized and removed only by heating the processed surface after blasting at a low temperature. it can. When performing a subsequent process in which the surface to be processed is heated, such as thermal spray coating, the solid lubricant can be vaporized without performing an extra heating process by using the heating in the subsequent process. it can.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In 1st Embodiment, as shown in FIG. 1, the to-be-processed surface 1a of the to-be-processed object 1 of carbon steel S45C for mechanical structures is previously coat | covered with the stearic acid as the solid lubricant 2, and a granular material is by an air pressure. The blasting which sprays on the to-be-processed surface 1a by injection was performed.

The stearic acid was a solution having a concentration of 15% using tetrahydrofuran as a solvent, and the surface to be processed 1a was coated by brushing in three portions. The amount of stearic acid deposited on the work surface 1a was about 20 g / m ² . Note that stearic acid has a boiling point of 360 ° C. and is vaporized by heating at a relatively low temperature. In addition, there is a characteristic that it gradually evaporates at 90 to 110 ° C.

The granular material used for the blasting process was white alumina grit, and the average particle size was changed to two types of 328 μm and 700 μm. The injection conditions for these particulate materials are as follows.
・ Injection air pressure: 0.5MPa
・ Injection distance: 150mm
・ Injection angle: 90 °
・ Injection time: 20 seconds

  As Example 1, a workpiece after the blasting process described above was prepared. As Comparative Example 1, there was also prepared a workpiece that was subjected to blasting under the same conditions as described above without coating the surface to be processed with stearic acid. The workpieces of Example 1 and Comparative Example 1 were ultrasonically cleaned in a tetrahydrofuran solution, respectively, and then immersed in a mixed solution of hydrochloric acid 3: nitric acid 3: water 8 while dissolving the workpiece surface. Further, ultrasonic cleaning was performed for 40 minutes, and the amount of grit separated from the surface to be processed by ultrasonic cleaning twice before and after was measured. The number of workpiece samples measured was 3 for both Example 1 and Comparative Example 1.

  FIG. 2 shows the measurement result of the separated grit amount. From this measurement result, in Example 1, the separated grit amount, that is, the residual amount of grit or its fragments on the work surface is significantly reduced as compared with the comparative example 1 that does not cover the work surface as in the prior art. You can see that.

  In the second embodiment, as shown in FIG. 3, the surface of grit 3 of white alumina as a particulate material is coated with stearic acid as solid lubricant 2, and this is applied to the workpiece of structural carbon steel S45C. Blasting was applied to the work surface. The injection conditions of the grid 3 are the same as those in the first embodiment.

The average particle size of the grit 3 is changed to three types of 328 μm, 700 μm, and 1080 μm, and these are heated to about 90 ° C. in hot water, and after stirring and adding stearic acid to the hot water, The surface of Grit 3 was coated with stearic acid. The coating thickness of each grit 3 was about 4 μm when the average particle size was 328 μm, about 8 μm when the average particle size was 700 μm, and about 12 μm when the average particle size was 1080 μm.
Went in the way.

  As Example 2, a workpiece after blasting using the grit coated with stearic acid described above was prepared. As Comparative Example 2, a workpiece after blasting using a grit that does not cover anything as in the prior art was also prepared. In addition, the thing of the comparative example 1 was diverted about what uses a grit with an average particle diameter of 328 micrometers and 700 micrometers. The workpieces of Example 2 and Comparative Example 2 were subjected to ultrasonic cleaning twice before and after in the same manner as in Example 1 and Comparative Example 1, and the amount of grit separated from each workpiece surface was determined. It was measured. The number of workpiece samples measured was 3 for both Example 2 and Comparative Example 2.

  FIG. 4 shows the measurement results of the separated grit amount. Also in this case, the separation grit amount, that is, the residual amount of grit or its fragments on the work surface is significantly reduced in Example 2 as compared with the comparative example 2 that does not cover the grit as in the prior art. I understand that.

  The workpiece processed by blasting the above-mentioned processed surface with stearic acid is heated to various temperatures from 20 ° C. to 250 ° C. using an electric furnace, and the stearic acid on the processed surface after heating is heated. The residual amount was measured. The residual amount of stearic acid is measured by immersing the workpiece after heating in the tetrahydrofuran solution to dissolve the stearic acid remaining on the processed surface in the solution, and changing the color tone of the tetrahydrofuran solution that changes depending on the solubility of stearic acid. Observation was performed by a method of quantifying the solubility of stearic acid in the solution based on the degree of change in color tone. The solubility of stearic acid is determined in advance by changing the solubility of stearic acid and analyzing the color tone of the tetrahydrofuran solution with an image analyzer, and the correlation between the solubility of stearic acid and the color tone of the solution created based on the analysis result. It was performed by using.

The graph of FIG. 5 shows the measurement result of the residual amount of stearic acid. The vertical axis represents the residual rate of stearic acid with 100% of the residual amount of stearic acid 80 mg / m ² at room temperature without heating. The residual amount of stearic acid on the surface to be processed has been reduced to about 1/250 of the amount of adhesion before processing due to blasting, and the residual rate of stearic acid on the surface to be processed suddenly decreases with increasing heating temperature. When the heating temperature is 150 ° C. or higher, the stearic acid residual rate is 0%. The boiling point of stearic acid is 360 ° C, but the residual thickness of stearic acid on the processed surface after blasting is very thin, so it seems that stearic acid was completely vaporized at about 150 ° C, which is considerably lower than the boiling point. It is. From this result, it can be seen that even if the surface to be processed is coated with stearic acid, if the surface to be processed after blasting is heated at a relatively low temperature, the stearic acid can be easily removed by vaporization. Similarly, when the surface of the grit is coated with stearic acid, it can be estimated that the stearic acid is easily removed by vaporization if the surface to be processed is heated at a relatively low temperature.

  In the third embodiment, a bending test piece of the general structural steel SS400 is used as a workpiece, the one surface to be processed is coated with stearic acid in advance, and blasting is performed by spraying white alumina grit. The blasted work surface was spray coated. The stearic acid coating conditions and the grit jetting conditions were the same as in the first embodiment, and the average particle size of the grit was 700 μm. Thermal spray coating of the work surface is performed by a method of spraying the cermet powder WC-12Co on the work surface by an atmospheric plasma spraying method after holding the work after blasting at about 100 ° C. for 5 minutes. The thickness was 300 μm.

  A test piece (Example 4) in which the surface to be processed is coated with stearic acid, which is a solid lubricant, and subjected to blasting and thermal spraying coating, and blasting and thermal spraying coating without coating any surface to be processed An applied test piece (Comparative Example 4) was prepared. As a reference example 4, a test piece was also prepared which was a solid lubricant and was coated with molybdenum disulfide which does not evaporate at a low temperature of 500 ° C. or lower, and was subjected to blasting and thermal spray coating. Each test piece has a length of 110 mm, a width of 10 mm, and a thickness of 1.0 mm. These test pieces were subjected to a bending test (JIS Z 2248) with a bending radius of 10 mm, and the bending angle at which the sprayed coating started to fall off was determined. The number of samples of each test piece was three.

  FIG. 6 shows the results of the bending test. The falling start bending angle of the thermal spray coating is the largest at 40 to 43 ° in Example 4, indicating that the adhesion of the thermal spray coating is very excellent. On the other hand, in Comparative Example 4, the drop-off start bending angle is about 10 ° smaller than that of Example 4 and the variation is large, the adhesion of the sprayed coating is inferior and unstable. Moreover, the thing of the reference example 4 has a fall | offset start bending angle smaller than the thing of the comparative example 4, and the adhesiveness of a sprayed coating is the most inferior.

  About the bending test piece of the said comparative example 4 and the reference example 4, the surface of the dropping part of a sprayed coating was observed with the microscope. In the case of Comparative Example 4, it was observed that grit of white alumina remained in the dropping part, and in the case of Reference Example 4, it was observed that molybdenum disulfide as a solid lubricant remained. It was. Therefore, it is confirmed that the residual grit reduces the adhesion of the thermal spray coating, and even if the surface to be processed is covered with a solid lubricant to prevent the residual grit, the solid lubricant remains on the surface to be processed. It was also confirmed that the adhesion of the sprayed coating was lowered.

  In each of the above-described embodiments, stearic acid is used as the solid lubricant for covering the surface to be processed before blasting. However, stearates such as zinc stearate and calcium stearate, and mixtures thereof can also be used. In addition, the material of the work surface to be blasted is steel, and the granular material sprayed on it is alumina grit, but the material of the work surface may be other metals or alloys, and the granular material is also alumina grit. There is no limit.

Sectional drawing which shows the to-be-processed surface of the to-be-processed object blasted in 1st Embodiment The graph which shows the measurement result of the amount of separated grit separated from the work surface in FIG. 1 after blasting Sectional drawing which shows the grit used by the blasting of 2nd Embodiment The graph which shows the measurement result of the amount of separation grit separated from the processed surface after blasting using the grit of FIG. The graph which shows the measurement result of the residual rate of the stearic acid in the to-be-processed surface heated after the blasting of 1st Embodiment The graph which shows the drop | offset start bending angle of the thermal spray coating in the bending test of the test piece which gave the thermal spray coating after the blast processing of 3rd Embodiment

Explanation of symbols

1 Workpiece 1a Workpiece Surface 2 Solid Lubricant 3 Grit

Claims (3)

In a blasting method of processing a processed surface by spraying a granular material harder than the material of the processed surface, the processed surface to be processed is previously coated with a solid lubricant, and the solid lubricant is cooled to a low temperature of 500 ° C. or lower. The blasting is characterized in that the surface to be processed after being blown and blasted with the particulate material is heated to vaporize and remove the solid lubricant remaining on the surface to be processed. Processing method. In a blasting method in which a granular material harder than the material of the surface to be processed is sprayed to process the surface to be processed, the surface of the sprayed granular material is coated with a solid lubricant, and the solid lubricant is coated at a low temperature of 500 ° C. or lower. Blasting characterized in that, as a vaporization, the processed surface after being blown and blasted with the particulate material is heated, and the solid lubricant remaining on the processed surface is vaporized and removed. Method. The blasting method according to claim 1 or 2 , wherein the solid lubricant is stearic acid, stearate or a mixture thereof.

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