JP5956704B1 - Test piece manufacturing method - Google Patents

Abstract

A method of manufacturing a test piece for a metal detector, which can perform a performance evaluation with high accuracy regardless of the detection method, can be obtained at low cost. In a test piece manufacturing method used for performance evaluation or adjustment of a metal detector, a plurality of particles made of austenitic stainless steel are repeatedly collided with a projection target as a shot blasting material, whereby each particle All of the outer peripheral surface of the sphere is uniformly stressed by collision, and all of the surface layer portion extending from the outer peripheral surface to a predetermined depth is made into a spherical material weakened by martensite transformation. . [Selection] Figure 2

Description

  The present invention relates to a test piece manufacturing method, and in particular, a metal test piece used for evaluating and adjusting the detection performance of a metal detector that detects the contamination of a metal foreign substance into a product in the manufacturing process of food or the like. It relates to the manufacturing method.

  In the manufacturing process of foods and pharmaceuticals, blades and sieves provided on manufacturing equipment such as conveyors, cutting machines, stirrers, packaging machines, kneaders, and stir-fries are broken, peeled off and scraped due to metal fatigue. Since the metal foreign matter may be mixed into the product due to curling or chipping, the metal foreign matter mixed at a predetermined stage of the process is detected by a detector and eliminated.

  As such a metal detector, a search coil type and a magnetic field type are known. As described in Japanese Patent Application Laid-Open No. 2005-188985, the search coil method radiates a high-frequency magnetic field to a product being transported to generate an eddy current in a conductive metallic foreign object, and the phase of the eddy current magnetic field. In this method, foreign matter is detected by detecting a shift in the coil. On the other hand, in the magnetic field method, as described in Japanese Patent Application Laid-Open No. 2004-85439, the metal foreign matter mixed in the product being transported is exposed to a high magnetic field environment and magnetized to pass through the magnetic sensor. This is a method of detecting while capturing as a change in magnetic flux.

  In order to evaluate and adjust the detection performance of such a metal detector, an iron ball or a stainless steel ball having a diameter of 0.5 mm to 2.5 mm is generally used as a test piece assuming a mixed foreign substance. In this way, the metal ball is used for evaluating the performance of the metal detector because it is easily available and low in cost because it can be used as a bearing ball, etc. This is because the flowing surface area also increases, and it is easy to perform effective evaluation regardless of the sensitivity directionality of the search coil. These are also used in the X-ray inspection, and can be evaluated without considering the directionality in the transmission image.

  However, as metal foreign matter mixed in the manufacturing process of foods and pharmaceuticals, metal balls such as test pieces cannot be assumed unless they are intentionally mixed, and variability due to needles, shavings, wear, etc. Most of them are irregular foreign objects whose shapes cannot be predicted, such as cracks and cracks due to metal fatigue. For this reason, when the detection performance is set by using a metal ball test piece with a search coil type metal detector, there may be a situation where an actual irregular foreign object cannot be detected. For example, even if a metal sphere having a diameter of 2 mm can be detected, a wire rod having a diameter of 0.5 mm and a length of 3 mm and a spring washer having a diameter of 3 mm often cannot be detected because the surface area through which eddy current flows is smaller than that of a sphere.

  On the other hand, in the magnetic field type metal detector, since the whole foreign matter is magnetized, the variation in detection accuracy due to the shape of the foreign matter is relatively small. In addition, there is an advantage that it is possible to detect a metal foreign object in an aluminum package which is difficult to detect by the above-described search coil method with high accuracy. However, 95% or more of austenitic stainless steel (mostly SUS304) is used for metal parts used in the parts close to the product in the food manufacturing process from the viewpoint of corrosion resistance, easy cleaning, and manufacturing cost. In many cases, the same kind of stainless steel sphere is also used for the test piece. However, since austenitic stainless steel is essentially a non-magnetic metal, there is a problem that it is not magnetized even in a high magnetic field environment.

  Actually, foreign matter due to austenitic metal mixed in the manufacturing process causes weak martensite transformation due to plastic deformation when partially falling off, so the detection performance itself of the metal detector by the magnetic field method itself Is not inferior to a search coil type metal detector. However, when austenitic stainless steel spheres are used as test pieces for magnetic field type metal detectors, there are many cases where martensite is formed by applying some stress when manufacturing spherical test pieces. Since the relative permeability varies depending on the degree of application and the manufacturer, there is a problem that the detection results are likely to vary.

  In order to solve this problem, the inventors of the present application previously disclosed in Japanese Patent Application Laid-Open No. 2007-47086 that the austenitic stainless steel is made into a regular cubic shape, and stress is applied uniformly to all of its sides to make martensite. We have proposed a test piece made weakly magnetic by site transformation and its manufacturing method, and it is possible to perform performance evaluation assuming the state of metal foreign matter actually mixed even in magnetic field type metal detector did.

  However, in order to obtain a test piece of this regular cube having a minute size corresponding to the assumed size of the metal foreign material, there is a problem that much labor and cost are required even if only one piece is manufactured. In addition, it is technically difficult to uniformly transform martensite while applying the same stress to all the faces of the regular cube, and because of its shape, the side faces with respect to the metal detector transport direction. Since the length in the conveyance direction differs by 1.4 times or more between the matching and the matching of the diagonal lines, there is a problem that the detection accuracy is likely to vary depending on the orientation of the test piece.

Japanese Patent Laid-Open No. 2005-188985 JP 2004-85439 A JP 2007-47086 A

  The present invention is intended to solve the above-described problems, and a test piece manufacturing method for a metal detector can be obtained at a low cost so that a highly accurate performance evaluation can be performed regardless of the detection method. The challenge is to do so.

  Therefore, the present invention, in the test piece manufacturing method used for performance evaluation or adjustment of the metal detector, by repeatedly colliding a plurality of particles of austenitic stainless steel as a shot blasting projection material to the projection target, It is characterized in that all the outer peripheral surface of the granule is uniformly stressed by collision, and all of the surface layer part extending from the outer peripheral surface to a predetermined depth is made into a spherical material weakened by martensite transformation. It was.

  As is well known, by applying stress to austenitic stainless steel and transforming it into martensite, it becomes possible to evaluate the performance with high accuracy even with magnetic field type metal detectors. As a manufacturing method in which stress is applied evenly with repeated collisions, a spherical test piece whose surface layer is uniformly weakly magnetized can be obtained without excessive labor and cost. Therefore, it is possible to accurately evaluate the performance of the metal detector without questioning.

  Further, in this test piece manufacturing method, the granular material is a cylindrical shape obtained by cutting an austenitic stainless steel wire to a length equivalent to its diameter, and plastic deformation is caused by repeated collisions by shot blasting. If it becomes spherical, it becomes easy to manufacture in large quantities at low cost.

  Further, in the test piece manufacturing method described above, if the austenitic stainless steel is SUS304, it is easy to match the material of the metal foreign substance actually mixed in the food production line or the like. Therefore, highly accurate performance evaluation and setting are possible.

  Furthermore, in the test piece manufacturing method described above, if the surface is completely scratched by a polishing process using a barrel after the shot blasting process, the test piece is closer to a true sphere. In addition to being finished in a state, the surface is evenly scratched, so that the uniformity among a plurality of test pieces is excellent.

  According to the present invention, austenitic stainless steel particles are repeatedly collided as a shot blasting projection material to uniformly apply stress to the outer peripheral surface to uniformly weaken the magnetic material. A test piece that can be evaluated can be obtained at low cost.

It is a drawing substitute photograph of the test piece of the embodiment of the present invention. It is a graph of the output waveform of the performance evaluation test by a magnetic field type metal detector, the upper part is the waveform of the test piece not martensitic, and the lower part is the waveform of the martensitic test piece according to the present invention. This is a graph of the output waveform of the performance evaluation test using a magnetic field type metal detector, where the top is a waveform with the front of the martensitic cube test piece parallel to the transport direction, and the bottom is the diagonal of the martensitic cube test piece Is a waveform in parallel with the conveying direction hole. It is a graph of the output waveform of the performance evaluation test by a magnetic field type metal detector, and the upper stage, the middle stage, and the lower stage are the waveforms of three randomly selected test pieces according to the present invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the present invention, the spherical shape is not limited to a true sphere, and the variation in the radius difference between the minimum circumscribed sphere and the maximum inscribed sphere centered on the center of the least mean square sphere of the sphere surface is within ± 15%. It should be included.

  FIG. 1 is a photograph showing a test piece actually produced by the manufacturing method according to the embodiment of the present invention. The test piece according to the present invention is for use in performance evaluation or adjustment of a metal detector, but can be used for all of the search coil method and the magnetic field method, and further the X-ray method, and particularly the magnetic field method. In the metal detector, the feature is remarkably exhibited.

  As shown in the photograph, the test piece according to the present embodiment is formed in a spherical shape, and the outer peripheral surface of the austenitic stainless steel particle is repeatedly collided with a projection target such as a workpiece as a shot blasting projection material. Magnetic field metal detectors are characterized by the fact that all of the surface layer from the outer peripheral surface to a predetermined depth is made weak magnetic by martensitic transformation by applying all of the stress due to collision all over. When the performance evaluation is performed, even if austenitic stainless steel is used, it is magnetized by the magnetic field environment and can be detected.

  The manufacturing method is a granular material (cylindrical cut wire) obtained by cutting a wire made of austenitic stainless steel such as SUS304 (having the same diameter or slightly smaller diameter as the target test piece) into a length equivalent to the diameter. ), And a plurality of them are formed into a spherical shape by repeatedly colliding with a projection target (workpiece) as a shot blasting projection material. Projection continues until the body is plastically deformed.

  By this shot blasting process, the entire surface layer part extending from the outer peripheral surface to a predetermined depth in the process of plastic deformation from a granular body (cylindrical body) to a spherical body undergoes martensitic transformation, and the outer peripheral surface side is uniformly weakly magnetic. Will be. A test piece as shown in the photograph of FIG. 1 is obtained by aligning a plurality of the spherical bodies with a diameter within a target range by a sorting process using a filter or the like as a sieving means.

  In this way, stress is applied evenly to the outer peripheral surface of the austenitic stainless steel wire by simply colliding repeatedly into spherical shapes while using it as a shot blasting projection material. Compared to the one that is precisely molded one by one while applying stress to all sides like the regular cubic test piece described in Patent Document 3, because it can be made martensite uniformly. Thus, a large number of test pieces can be easily manufactured at low cost.

  If the surface is scratched evenly by adding a barrel polishing process after the shot blasting process, the test piece will be finished in a more nearly spherical state, and the uniformity among many manufactured test pieces will be uniform. It will be excellent. In addition, as a projection target for colliding the particles in the above-described shot blasting process, the same kind of metal as the test piece is used from the viewpoint of sufficiently plastic deformation while avoiding adhesion of components different from the particles to the surface of the particles. Those having equivalent hardness are suitable.

  In addition, as long as the test piece can be molded by plastic deformation and the component to be projected does not adhere to the surface, the austenitic stainless steel particles used as the projecting material in the shot blasting process for ordinary workpieces are made spherical. It is also possible to use the test piece of the present invention after repeating the projection. Furthermore, the granular material used for the projection material is not limited to the cylindrical shape as described above, and even if it has various shapes such as a spherical shape or a cubic shape, it is formed into a spherical shape and uniform weak magnetism. As long as it can be embodied, it can be used in the same manner as described above.

  The characteristics of the test piece according to the present invention were confirmed by conducting the following tests. As a test piece of the present invention, a SUS304 spherical test piece having a diameter of 1.0 mm (invention 1) and a diameter of 1.5 mm (invention 2) made into martensite by the above-described method was prepared. A diameter of 1.0 mm of a commercially available SUS304 spherical test piece not subjected to the site conversion step (Control Example 1) and a side of 1.5 mm of a martensitic SUS304 regular cubic test piece described in Patent Document 3 (Control Example) 2) was used.

  Each test piece was held at the same height in the recesses provided in the resin holder, and the output waveform was recorded on a magnetic field type metal detector. The test pieces according to the present invention 1 and 2 are both made to collide with the SUS304 plate material 200 times in the shot blasting process, and then the sizes are made uniform using a filter.

(Test 1) In order to verify whether or not the test piece (SUS304) according to the present invention has been martensified to a level that can be used as a test piece for a magnetic field type metal detector, the present invention 1 and the control example 1 are each The output waveform was compared with a magnetic metal detector. The result is the graph of FIG. 2, wherein the upper stage is the output waveform of the control example 1 that is not martensite, and the lower stage is the output waveform of the present invention 1. In the vicinity of 4000 μs in the graph, the invention 1 has a remarkable waveform as compared with the control example 1, and it has been verified that a sufficient function as a test piece is exhibited.

(Test 2) The directionality of Control Example 2 of a martensitic regular cube was verified using a magnetic field type metal detector. The result is the graph of FIG. 3, where the upper stage is an output waveform with its front face parallel to the transport direction, and the lower stage is an output waveform with its diagonal line parallel to the transport direction. In the waveform at the detection position, the lower row records a vertical width that is three times or more that of the upper row, and it has been verified that the detection accuracy of a regular cubic test piece varies greatly depending on the direction of placement on the conveyor.

(Test 3) With regard to the test piece of the present invention 2, regarding the functional variation of a plurality of test pieces manufactured, three test pieces randomly selected from a large number of test pieces manufactured at the same time under the same conditions It verified with the magnetic metal detector. The result is the graph of FIG. The upper, middle, and lower stages have almost common waveforms at the detection positions, and it has been verified that there is almost no functional variation in at least these three test pieces. Moreover, it is guessed from these three results that the test piece of the second aspect of the present invention does not matter in the directionality.

  From the above test results, the test piece according to the present invention can be detected by a magnetic metal detector even though austenitic stainless steel is used as the material, and there is almost no functional variation. It was found to be suitable as a test piece for performance evaluation and adjustment in metal detectors. In addition, the test piece according to the present invention is not only advantageous in terms of manufacturing cost but also advantageous in terms of directionality compared to a regular cubic test piece obtained by martensitic austenitic stainless steel. It was.

  As described above, regarding the test piece for a metal detector, according to the present invention, the performance of the metal detector can be evaluated with high accuracy at low cost regardless of the detection method.

Claims (4)

  In the test piece manufacturing method used for the performance evaluation or adjustment of the metal detector, a plurality of austenitic stainless steel particles are repeatedly collided with the projection object as a shot blasting projection material, whereby the outer peripheral surface of each of the particles A test piece manufacturing method, characterized in that all of the surface layer portion extending from the outer peripheral surface to a predetermined depth is made spherical with weak magnetic material by martensitic transformation, all of which stress due to collision is applied evenly.   The granular material is a cylindrical shape formed by cutting an austenitic stainless steel wire to a length equivalent to the diameter, and is plastically deformed into a spherical shape by repeating the collision by the shot blasting. The test piece manufacturing method according to claim 1.   The method for producing a test piece according to claim 1, wherein the austenitic stainless steel is SUS304. The test piece manufacturing method according to claim 1, 2, or 3, wherein the surface is uniformly scratched by a polishing process using a barrel after the shot blasting process.