Ultrasonic cleaning apparatus and ultrasonic cleaning method for metal materials

Abstract

The present invention provides an ultrasonic cleaning device for metal materials that can thoroughly clean the entire surface of the metal material to be cleaned. [Solution] The ultrasonic cleaning apparatus (100) comprises a cleaning tank (1) and an ultrasonic emission mechanism (2). The cleaning tank (1) is capable of storing a cleaning solution (4) containing a plurality of metal compound particles, and a metal material (WP) is capable of being immersed in the cleaning solution (4) containing the metal material (WP). The ultrasonic emission mechanism (2) emits ultrasonic waves of the fundamental frequency into the cleaning solution (4) in the cleaning tank (1). At a position 10 cm away from the surface of the metal material (WP) in the cleaning tank (1), the frequency of the propagating ultrasonic waves in the cleaning solution (4) includes the fundamental frequency and specific fractional harmonics that have frequencies of 0.5 or 1.5 times the fundamental frequency. The intensity of the fundamental frequency fref and the intensity of the specific fractional harmonics fsub satisfy equation (1). fsub / fref>0.0030 (1)

Description

[Technical Field]

[0001] This disclosure relates to an ultrasonic cleaning apparatus and an ultrasonic cleaning method for metal materials. [Background technology]

[0002] In the manufacturing process of metal materials such as wires, steel pipes, and hot-rolled coils, if scale forms on the surface of the metal material, pickling is performed to remove the scale. After pickling, the metal material is washed with a cleaning solution (e.g., water). Ultrasonics may be used for this cleaning.

[0003] Conventional ultrasonic cleaning devices are described, for example, in Japanese Patent Publication No. 3429761 (Patent Document 1). The device described in Patent Document 1 is configured to immerse the object to be cleaned in a liquid (cleaning solution) in a cleaning tank and irradiate it with ultrasonic waves of the fundamental frequency and ultrasonic waves of twice that frequency from an ultrasonic transducer. Patent Document 1 states that a high cleaning effect can be obtained with this device. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 3429761 [Overview of the project] [Problems that the invention aims to solve]

[0005] Even with the apparatus described in Patent Document 1, it is uncertain whether the object to be cleaned can be thoroughly cleaned over its entire surface.

[0006] The purpose of this disclosure is to provide an ultrasonic cleaning apparatus and ultrasonic cleaning method for metal materials that can thoroughly clean the entire surface of the metal material to be cleaned. [Means for solving the problem]

[0007] The ultrasonic cleaning apparatus for metal materials according to this disclosure comprises a cleaning tank and an ultrasonic emission mechanism. The cleaning tank is capable of storing a cleaning solution containing a plurality of metal compound particles, and the metal material can be immersed in the cleaning solution. The ultrasonic emission mechanism emits ultrasonic waves of a fundamental frequency into the cleaning solution in the cleaning tank. At a distance of 10 cm from the surface of the metal material in the cleaning tank, the frequency of the propagating ultrasonic waves in the cleaning solution includes a fundamental frequency and specific fractional harmonics with frequencies of 0.5 or 1.5 times the fundamental frequency. The intensity of the fundamental frequency fref and the intensity of the specific fractional harmonic fsub satisfy equation (1). fsub / fref>0.0030 (1)

[0008] The ultrasonic cleaning method for metal materials according to this disclosure comprises an immersion step and a cleaning step. The immersion step involves immersing the metal material in a cleaning solution. The cleaning step involves emitting ultrasonic waves of a fundamental frequency into a cleaning solution containing a plurality of metal compound particles to clean the metal material. In the cleaning step, at a distance of 10 cm from the surface of the metal material, the frequency of the propagating ultrasonic waves in the cleaning solution includes a fundamental frequency and specific fractional harmonics with frequencies of 0.5 or 1.5 times the fundamental frequency. The intensity fref of the fundamental frequency and the intensity fsub of the specific fractional harmonics satisfy equation (1). fsub / fref>0.0030 (1) [Effects of the Invention]

[0009] According to this disclosure, the metal material to be cleaned can be thoroughly cleaned over its entire surface. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram showing an example of an ultrasonic cleaning apparatus for metal materials according to this embodiment. [Figure 2] Figure 2 shows an example of the intensity spectrum of propagated ultrasound in a cleaning solution. [Figure 3] Figure 3 shows an example of the intensity spectrum of propagated ultrasound in a cleaning solution. [Modes for carrying out the invention]

[0011] The inventors diligently studied methods that can thoroughly clean a metal material, which is the object to be cleaned, over its entire surface using ultrasound. As a result, they obtained the following findings.

[0012] The metal material to be cleaned is immersed in a cleaning solution, and ultrasonic waves of the fundamental frequency are emitted into the cleaning solution from an ultrasonic emission mechanism. Because the cleaning solution contains metal compound particles, the emitted ultrasonic waves collide with these particles and undergo diffuse reflection as they propagate through the solution. This diffuse reflection causes the propagating ultrasonic waves in the cleaning solution to include specific fractional harmonics, which are 0.5 or 1.5 times the fundamental frequency, in addition to the fundamental frequency. At a distance of 10 cm from the surface of the metal material, the amount of these specific fractional harmonics increases. These propagating ultrasonic waves, containing both the fundamental frequency and specific fractional harmonics, reach the entire surface of the object being cleaned (metal material). If the ratio of the intensity of the specific fractional harmonics (fsub) to the intensity of the fundamental frequency (fref), "fsub / fref," exceeds 0.0030, cavitation occurs throughout the entire surface of the object being cleaned due to both the fundamental frequency and the sufficiently intense specific fractional harmonics. This ensures a sufficient cleaning effect throughout the entire surface of the object being cleaned.

[0013] The ultrasonic cleaning apparatus and ultrasonic cleaning method for metal materials according to the embodiments of this disclosure were completed based on the above findings.

[0014] The ultrasonic cleaning apparatus for metal materials according to this embodiment comprises a cleaning tank and an ultrasonic emission mechanism. The cleaning tank is capable of storing a cleaning solution containing a plurality of metal compound particles, and the metal material can be immersed in the cleaning solution. The ultrasonic emission mechanism emits ultrasonic waves of a fundamental frequency into the cleaning solution in the cleaning tank. At a distance of 10 cm from the surface of the metal material in the cleaning tank, the frequency of the propagating ultrasonic waves in the cleaning solution includes a fundamental frequency and specific fractional harmonics with frequencies of 0.5 or 1.5 times the fundamental frequency. The intensity fref of the fundamental frequency and the intensity fsub of the specific fractional harmonics satisfy equation (1) (first configuration). fsub / fref>0.0030 (1)

[0015] In the ultrasonic cleaning device according to the first configuration, the cleaning liquid stored in the cleaning tank and immersing the metal material contains metal compound particles. Since the cleaning liquid contains metal compound particles, the ultrasonic waves emitted from the ultrasonic wave emitting mechanism into the cleaning liquid collide with the metal compound particles during the process of propagating through the cleaning liquid. The ultrasonic waves that collide with the metal compound are diffusely reflected. Due to this diffuse reflection, at a position 10 cm away from the surface of the metal material, a specific harmonic of the propagating ultrasonic waves in the cleaning liquid increases. At this time, the intensity fref of the fundamental frequency and the intensity fsub of the specific harmonic satisfy Equation (1), that is, the ratio "fsub / fref" of the intensity fsub of the specific harmonic to the intensity fref of the fundamental frequency exceeds 0.0030, and the propagating ultrasonic waves including such a fundamental frequency and a specific harmonic reach the entire area of the metal material which is the object to be cleaned. Therefore, effective cavitation occurs over the entire area of the object to be cleaned, and a sufficient cleaning effect can be obtained over the entire area of the object to be cleaned. Therefore, according to the first configuration, the metal material which is the object to be cleaned can be sufficiently cleaned over the entire area.

[0016] In the above ultrasonic cleaning device, preferably, at a position 10 cm away from the surface of the metal material in the cleaning tank, the frequency of the propagating ultrasonic waves in the cleaning liquid further includes a second harmonic which is a frequency twice that of the fundamental frequency. In this case, the intensity fref of the fundamental frequency and the intensity f2nd of the second harmonic satisfy Equation (2) (second configuration). f2nd / fref>0.05 (2)

[0017] In the ultrasonic cleaning device according to the second configuration, the ultrasonic waves propagating in the cleaning liquid are diffusely reflected by collision with metal compound particles. Due to this diffuse reflection, at a position 10 cm away from the surface of the metal material, the second harmonic of the ultrasonic waves propagating in the cleaning liquid further increases. At this time, the intensity fref of the fundamental frequency and the intensity f2nd of the second harmonic satisfy Equation (2), that is, the ratio "f2nd / fref" of the intensity f2nd of the second harmonic to the intensity fref of the fundamental frequency exceeds 0.05, and the ultrasonic waves including such a fundamental frequency, a specific fractional harmonic, and a second harmonic reach the entire area of the metal material, which is the object to be cleaned. Therefore, effective cavitation occurs over the entire area of the object to be cleaned, and a more sufficient cleaning effect can be obtained over the entire area of the object to be cleaned. Therefore, according to the second configuration, the metal material, which is the object to be cleaned, can be more sufficiently cleaned over the entire area.

[0018] In the above ultrasonic cleaning device, preferably, the concentration of metal compound particles in the cleaning liquid is 0.20 g / L or more (third configuration).

[0019] In the ultrasonic cleaning device according to the third configuration, when the concentration of metal compound particles in the cleaning liquid is 0.20 g / L (liter) or more, the diffuse reflection of the propagating ultrasonic waves is effectively manifested. For this reason, the propagating ultrasonic waves effectively include a specific fractional harmonic. The propagating ultrasonic waves further effectively include a second harmonic.

[0020] In the ultrasonic cleaning device according to the third configuration, the metal compound particles preferably include specific metal compound particles having a radius equal to or greater than the resonance radius at the fundamental frequency and equal to or less than 10 times the resonance radius. In this case, the concentration of the specific metal compound particles in the cleaning liquid may be 0.010 g / L or more (fourth configuration).

[0021] In the ultrasonic cleaning device according to the fourth configuration, when the metal compound particles include specific metal compound particles having a radius equal to or greater than the resonance radius and the concentration of the specific metal compound particles in the cleaning liquid is 0.010 g / L (liter) or more, the specific fractional harmonic is more effectively manifested. Further, the second harmonic is more effectively manifested.

[0022] In the ultrasonic cleaning apparatus described above, preferably, the concentration of dissolved oxygen in the cleaning solution is 4.5 mg / L or less (fifth configuration).

[0023] Dissolved oxygen in the cleaning solution inhibits the propagation of ultrasound. In this regard, in the ultrasonic cleaning apparatus according to the fifth configuration, the concentration of dissolved oxygen in the cleaning solution is 4.5 mg / L (liter) or less, allowing ultrasound to propagate smoothly in the cleaning solution.

[0024] The ultrasonic cleaning apparatus described above may further include a buffer member to support the metal material within the cleaning tank. In this case, the ratio of the surface area of ​​the buffer member to the volume of the cleaning liquid in the cleaning tank is 0.1 m². 2 / m 3 Above, 2.0m 2 / m 3 The following is also possible (the sixth structure).

[0025] The ultrasonic cleaning method for metal materials according to this disclosure comprises an immersion step and a cleaning step. The immersion step involves immersing the metal material in a cleaning solution. The cleaning step involves emitting ultrasonic waves of a fundamental frequency into a cleaning solution containing a plurality of metal compound particles to clean the metal material. In the cleaning step, at a distance of 10 cm from the surface of the metal material, the frequency of the propagating ultrasonic waves in the cleaning solution includes a fundamental frequency and specific fractional harmonics with frequencies of 0.5 or 1.5 times the fundamental frequency. The intensity fref of the fundamental frequency and the intensity fsub of the specific fractional harmonics satisfy equation (1) (seventh configuration). fsub / fref>0.0030 (1)

[0026] In the ultrasonic cleaning method according to the seventh configuration, the cleaning solution into which the metal material is immersed during the cleaning process contains metal compound particles. Because the cleaning solution contains metal compound particles, the ultrasonic waves emitted into the cleaning solution collide with the metal compound particles as they propagate through the cleaning solution. The ultrasonic waves that collide with the metal compounds are diffusely reflected. Due to this diffuse reflection, specific fractional harmonics in the propagating ultrasonic waves in the cleaning solution increase at a distance of 10 cm from the surface of the metal material. At this time, the intensity fref of the fundamental frequency and the intensity fsub of the specific fractional harmonic satisfy equation (1), that is, the ratio of the intensity fsub of the specific fractional harmonic to the intensity fref of the fundamental frequency "fsub / fref" is greater than 0.0030, and the propagating ultrasonic waves including such fundamental frequencies and specific fractional harmonics reach the entire surface of the metal material being cleaned. Therefore, effective cavitation occurs over the entire surface of the object being cleaned, and a sufficient cleaning effect is obtained over the entire surface of the object being cleaned. Accordingly, according to the seventh configuration, the metal material being cleaned can be thoroughly cleaned over its entire surface.

[0027] In the ultrasonic cleaning method described above, preferably, in the cleaning step, at a position 10 cm away from the surface of the metal material, the frequency of the propagating ultrasonic waves in the cleaning solution further includes a second harmonic which has twice the frequency of the fundamental frequency. In this case, the intensity fref of the fundamental frequency and the intensity f2nd of the second harmonic satisfy equation (2) (the eighth configuration). f2nd / fref>0.05 (2)

[0028] In the ultrasonic cleaning method according to the eighth configuration, during the cleaning process, the propagating ultrasonic waves in the cleaning solution are diffusely reflected by collisions with metal compound particles. Due to this diffuse reflection, the second harmonic in the propagating ultrasonic waves in the cleaning solution increases further at a position 10 cm away from the surface of the metal material. At this time, the intensity of the fundamental frequency fref and the intensity of the second harmonic f2nd satisfy equation (2), that is, the ratio of the intensity of the second harmonic f2nd to the intensity of the fundamental frequency fref, "f2nd / fref", is greater than 0.05, and the propagating ultrasonic waves, including the fundamental frequency, specific fractional harmonics, and second harmonic, reach the entire surface of the metal material being cleaned. As a result, effective cavitation occurs over the entire surface of the material being cleaned, and a more sufficient cleaning effect is obtained over the entire surface of the material being cleaned. Therefore, according to the eighth configuration, the metal material being cleaned can be cleaned more thoroughly over its entire surface.

[0029] In the ultrasonic cleaning method described above, preferably, the concentration of metal compound particles in the cleaning solution is 0.20 g / L or more (composition 9).

[0030] In the ultrasonic cleaning method relating to the ninth configuration, the concentration of metal compound particles in the cleaning solution is 0.20 g / L (liter) or higher during the cleaning process, which effectively causes diffuse reflection of propagated ultrasonic waves. As a result, the propagated ultrasonic waves effectively contain specific fractional harmonics. Furthermore, the propagated ultrasonic waves effectively contain second harmonics.

[0031] In the ultrasonic cleaning method according to the ninth configuration, it is preferable that the metal compound particles include specific metal compound particles having a radius greater than or equal to the resonance radius at the fundamental frequency and less than or equal to 10 times the resonance radius. In this case, the concentration of specific metal compound particles in the cleaning solution may be 0.010 g / L or more (tenth configuration).

[0032] In the ultrasonic cleaning method relating to the 10th configuration, in the cleaning process, the metal compound particles include specific metal compound particles having a radius greater than or equal to the resonance radius, and the concentration of specific metal compound particles in the cleaning solution is 0.010 g / L (liter) or higher, thereby enabling the specific fractional harmonics to be expressed more effectively. Furthermore, the second harmonic is expressed more effectively.

[0033] In the ultrasonic cleaning method described above, preferably, the concentration of dissolved oxygen in the cleaning solution is 4.5 mg / L or less (composition 11).

[0034] Dissolved oxygen in the cleaning solution inhibits the propagation of ultrasound. In this regard, in the ultrasonic cleaning method according to the 11th configuration, the concentration of dissolved oxygen in the cleaning solution is 4.5 mg / L (liter) or less during the cleaning process, so that ultrasound propagates smoothly in the cleaning solution.

[0035] The ultrasonic cleaning apparatus and ultrasonic cleaning method for metal materials according to this embodiment will be described below with reference to the drawings. In each figure, the same or equivalent components are denoted by the same reference numerals, and redundant explanations will not be repeated.

[0036] [Ultrasonic cleaning device] Figure 1 is a schematic diagram showing an example of an ultrasonic cleaning apparatus 100 for metal materials according to this embodiment. Referring to Figure 1, the ultrasonic cleaning apparatus 100 ultrasonically cleans the metal material WP, which is the object to be cleaned. In the example shown in Figure 1, the metal material WP is a wire. That is, the metal material WP has a long shape. The metal material WP may also be a steel pipe. However, the metal material WP is not limited to having a long shape, and may have other shapes such as a hot-rolled coil. The ultrasonic cleaning apparatus 100 can perform a water washing treatment on the metal material WP after it has been pickled.

[0037] The ultrasonic cleaning device 100 comprises a cleaning tank 1 and a plurality of ultrasonic emission mechanisms 2. The ultrasonic cleaning device 100 further comprises a plurality of buffer members 3. Note that Figure 1 shows one buffer member 3. The number of ultrasonic emission mechanisms 2 in the ultrasonic cleaning device 100 may be one.

[0038] The cleaning tank 1 is configured to accommodate metal materials WP. During ultrasonic cleaning, multiple metal materials WP are accommodated in the cleaning tank 1. In this embodiment, the cleaning tank 1 has a rectangular shape in plan view in order to accommodate metal materials WP having an elongated shape. The cleaning tank 1 has a pair of side walls 11 extending in the longitudinal direction, a pair of side walls 12 extending in the transverse direction, and a bottom wall 13, and its top surface is open. The metal materials WP are inserted into and removed from the cleaning tank 1 through the top surface of the cleaning tank 1.

[0039] The cleaning tank 1 stores a cleaning solution 4 for cleaning the metal material WP. The type of cleaning solution 4 is not particularly limited. The cleaning solution 4 is, for example, water (tap water or industrial water). The metal material WP is immersed in the cleaning solution 4 in the cleaning tank 1.

[0040] During ultrasonic cleaning, the ultrasonic emission mechanism 2 emits ultrasonic waves of a fundamental frequency into the cleaning solution 4 in the cleaning tank 1. The ultrasonic waves emitted from the ultrasonic emission mechanism 2 propagate through the cleaning solution 4 toward the metal material WP. A known ultrasonic transducer can be used as the ultrasonic emission mechanism 2. The fundamental frequency of the ultrasonic waves emitted by the ultrasonic emission mechanism 2 is, for example, 23 kHz to 300 kHz. The ultrasonic emission mechanism 2 may have a frequency sweep function.

[0041] At least one ultrasonic emission mechanism 2 is provided on the inner surface of each side wall 11, 12 of the cleaning tank 1. An ultrasonic emission mechanism may also be provided on the inner surface of the bottom wall 13 of the cleaning tank 1. The position and number of ultrasonic emission mechanisms 2 are not particularly limited. When multiple ultrasonic emission mechanisms 2 are installed in the cleaning tank 1, it is preferable to arrange the ultrasonic emission mechanisms 2 so that the propagating ultrasonic waves emitted from each ultrasonic emission mechanism 2 and propagating through the cleaning liquid 4 reach the metal material WP in the cleaning liquid 4 uniformly without interfering with each other.

[0042] The buffer member 3 is disposed in the cleaning tank 1. The buffer member 3 serves to support the metal material WP. In the present embodiment, a plurality of buffer members 3 are arranged side by side in the longitudinal direction of the cleaning tank 1. The buffer member 3 has a substantially U shape. The metal material WP in the cleaning tank 1 is placed on the buffer member 3. The inner surface of the buffer member 3 is located inside the ultrasonic emission mechanism 2 in the cleaning tank 1. Therefore, the metal material WP does not come into contact with the ultrasonic emission mechanism 2, and the ultrasonic emission mechanism 2 is protected from the metal material WP.

[0043] The buffer member 3 is an ultrasonic absorption part, and from the viewpoint of ensuring the ultrasonic cleaning ability, it is preferable that the surface area of the buffer member 3 is small with respect to the volume of the cleaning liquid 4. On the other hand, from the viewpoint of stably supporting the metal material WP without damaging it, it is preferable that the buffer member 3 has a certain size. Therefore, the value of the ratio of the surface area of the buffer member 3 to the volume of the cleaning liquid 4 in the cleaning tank 1 is 0.1 m 2 / m 3 or more and 2.0 m 2 / m 3 or less. The buffer member 3 which is an ultrasonic absorption part is an object having an acoustic impedance of 1×10 7 (kg / (m 2 ·s)) or less. The material of the buffer member 3 is, for example, plastic (resin), and in this case, the acoustic impedance of the buffer member 3 is 0.2×10 7 ~0.4×10 7 (kg / (m 2 ·s)).

[0044] In this embodiment, the cleaning solution 4 stored in the cleaning tank 1 contains a plurality of metal compound particles. The type of metal compound particles is not particularly limited. The metal compound particles are, for example, cementite particles. The metal compound particles may also be iron powder or other metal powders. The metal compound particles may also be iron oxide, for example, Fe2O3 powder. For example, the metal compound particles contained in the cleaning solution 4 originate from the metal material WP immersed in the cleaning solution 4. If the metal material WP contains cementite, cementite particles that fall from the metal material WP into the cleaning solution 4 during ultrasonic cleaning are used as metal compound particles. However, the metal compound particles contained in the cleaning solution 4 may also be added from outside the cleaning solution 4.

[0045] The concentration of metal compound particles in the cleaning solution 4 is preferably 0.20 g / L or higher. The concentration of metal compound particles can be determined from the cleaning solution 4 collected during ultrasonic cleaning. Specifically, a predetermined amount (volume) of cleaning solution 4 is collected from the central part of the cleaning tank 1 during ultrasonic cleaning. The central part of the cleaning tank 1 from which the cleaning solution 4 is collected is within a range of ±50 cm from the center in the depth direction. The amount of cleaning solution 4 collected is, for example, 1 L (liter). The collected cleaning solution 4 is filtered to separate the metal compound particles, and the mass of the separated metal compound particles is measured. Based on this mass and the volume of the collected cleaning solution 4, the concentration of metal compound particles in the cleaning solution 4 can be determined. The concentration of metal compound particles is sufficient if the average value of the concentrations obtained by collecting cleaning solution 4 from any five locations in the central part of the cleaning tank 1 is 0.20 g / L or higher.

[0046] In the cleaning solution 4, it is preferable that the metal compound particles include specific metal compound particles having a radius greater than or equal to the resonance radius at the fundamental frequency and less than or equal to 10 times the resonance radius. The fundamental frequency referred to here is the fundamental frequency of the ultrasonic waves emitted from the ultrasonic emission mechanism 2. In this case, it is preferable that the concentration of specific metal compound particles in the cleaning solution 4 is 0.010 g / L or more. The resonance radius at the fundamental frequency refers to the average diameter of bubbles generated in the cleaning solution 4 by emitting ultrasonic waves of the fundamental frequency to the cleaning solution 4, and can be calculated according to the known Minnaert formula.

[0047] Whether or not metal compound particles contain specific metal compound particles can be determined by measuring the particle size distribution of the metal compound particles. For example, in measuring the concentration of metal compound particles as described above, the particle size distribution of the metal compound particles is measured by imaging the separated metal compound particles with an optical microscope and performing image analysis. From this particle size distribution, it is possible to determine whether or not specific metal compound particles are present, and furthermore, the mass ratio of specific metal compound particles to the total metal compound particles can be obtained. Based on this mass ratio and the concentration of metal compound particles as described above, the concentration of specific metal compound particles in the washing solution 4 can be determined.

[0048] In this case, when cementite particles are used as the metal compound particles, the cementite particles can be identified by analyzing the separated metal compound particles using EPMA during the concentration measurement of the metal compound particles described above.

[0049] In this embodiment, the dissolved oxygen concentration in the cleaning solution 4 is preferably 4.5 mg / L or less. The dissolved oxygen concentration can be measured using a known dissolved oxygen concentration meter. Specifically, the cleaning solution 4 can be sampled from any five locations in the central part of the cleaning tank 1, and the average value of the concentrations obtained by the dissolved oxygen concentration meter should be 4.5 mg / L or less. For example, if the cleaning solution 4 is degassed before ultrasonic cleaning, the dissolved oxygen will be eliminated, and the dissolved oxygen concentration will be 4.5 mg / L or less.

[0050] [Ultrasonic cleaning method] The ultrasonic cleaning method for metal material WP using the ultrasonic cleaning device 100 will be described below with reference to Figures 1 to 3.

[0051] The metal material WP to be cleaned has undergone pickling. Before pickling, scale has formed on the surface of the metal material WP due to hot working or heat treatment. Pickling is performed to remove the scale. The ultrasonic cleaning method according to this embodiment is a method for cleaning metal material WP after pickling. The ultrasonic cleaning method comprises an immersion step and a cleaning step.

[0052] The immersion process involves immersing the metal material WP in the cleaning solution 4. Specifically, the metal material WP is immersed in the cleaning solution 4 stored in the cleaning tank 1. The metal material WP is supported by a buffer member 3 inside the cleaning tank 1.

[0053] The cleaning process involves emitting ultrasonic waves of a fundamental frequency into a cleaning solution 4 containing multiple metal compound particles to clean the metal material WP. Specifically, ultrasonic waves of a fundamental frequency are emitted from the ultrasonic emission mechanism 2. The emitted ultrasonic waves propagate through the cleaning solution 4 toward the metal material WP.

[0054] Figures 2 and 3 show examples of intensity spectra of propagating ultrasonic waves in the cleaning solution 4. These intensity spectra represent the intensity spectra of propagating ultrasonic waves when the fundamental frequency f of the ultrasonic waves emitted from the ultrasonic emission mechanism 2 is 37 kHz. Figure 2 shows the intensity spectrum measured at a position away from the buffer member 3, and Figure 3 shows the intensity spectrum measured at a position near the buffer member 3. Both measurement positions are 10 cm away from the surface of the metal material WP. More specifically, the intensity spectrum shown in Figure 2 is the average value obtained by selecting the part of the metal material WP furthest from the buffer member 3 and measuring at five arbitrary locations 10 cm away from the surface of that selected part. On the other hand, the intensity spectrum shown in Figure 3 is the average value obtained by selecting the part of the metal material WP directly supported by the buffer member 3 and measuring at five arbitrary locations 10 cm away from the surface of that selected part.

[0055] The intensity spectrum can be measured using a known ultrasonic measuring instrument and frequency analysis (FFT analysis). The intensity spectra shown in Figures 2 and 3 were calculated for each frequency using a fast Fourier transform with an ultrasonic tester (model SSP-2012) manufactured by Ultrasonic Systems Laboratory.

[0056] As shown in Figures 2 and 3, the intensity fref is highest at the fundamental frequency f. This intensity ref is the same at a location near the buffer member 3 and at a location far from the buffer member 3. Note that in Figures 2 and 3, the intensity is significantly higher at frequencies even higher than the second harmonic, which is twice the fundamental frequency f (2f), but this is due to the presence of the measuring instrument and is unrelated to ultrasonic cleaning.

[0057] At both the vicinity of the buffer member 3 and at a distance from the buffer member 3, a specific frequency of 0.5f, which is 0.5 times the fundamental frequency f, appears, and a specific fractional harmonic of 1.5f, which is 1.5 times the fundamental frequency f, also appears. In other words, the frequency of specific fractional harmonics among the propagating ultrasound frequencies is increasing. The intensity fsub of these specific fractional harmonics is smaller than the intensity fref of the fundamental frequency f, but the ratio of the intensity fsub of the specific fractional harmonic to the intensity fref of the fundamental frequency, "fsub / fref", is at least 0.0030 (frequency 0.5f in Figure 3). That is, the intensity fref of the fundamental frequency and the intensity fsub of the specific fractional harmonic satisfy equation (1). fsub / fref>0.0030 (1)

[0058] Furthermore, a second harmonic, with a frequency 2f (twice the fundamental frequency f), appears both near the buffer member 3 and at a distance from it. In other words, the second harmonic frequency is increasing among the frequencies of the propagating ultrasound. The intensity f2nd of this second harmonic is smaller than the intensity fref of the fundamental frequency f, but the ratio of the intensity f2nd of the second harmonic to the intensity fref of the fundamental frequency, "f2nd / fref", is at least 0.05 (frequency 2f in Figure 3). That is, the intensity fref of the fundamental frequency and the intensity f2nd of the second harmonic satisfy equation (2). f2nd / fref>0.05 (2)

[0059] Thus, the propagating ultrasound emitted from the ultrasonic emission mechanism 2 and propagating through the cleaning liquid 4 includes the fundamental frequency f. Furthermore, specific fractional harmonics, which are 0.5 times the fundamental frequency f (0.5f) and / or 1.5 times the fundamental frequency f (1.5f), increase in the propagating ultrasound. In addition, the second harmonic, which is 2 times the fundamental frequency f (2f), increases in the propagating ultrasound. This is because the cleaning liquid 4 contains metal compound particles, as shown below. Because the cleaning liquid 4 contains metal compound particles, the ultrasound with the fundamental frequency f emitted into the cleaning liquid 4 collides with the metal compound particles as it propagates through the cleaning liquid 4. The ultrasound that collides with the metal compound particles undergoes diffuse reflection. Due to this diffuse reflection, specific fractional harmonics appear in the propagating ultrasound, and furthermore, the second harmonic appears.

[0060] Then, at a distance of 10 cm from the surface of the metal material WP, the intensity of the fundamental frequency fref and the intensity of the specific fractional harmonic fsub satisfy equation (1). Furthermore, the intensity of the fundamental frequency fref and the intensity of the second harmonic f2nd satisfy equation (2). Such propagating ultrasound, which includes the fundamental frequency f and the specific fractional harmonic, and also includes the second harmonic, reaches the entire surface of the metal material WP being cleaned. In other words, propagating ultrasound, which includes not only the fundamental frequency f but also the specific fractional harmonic at an appropriate intensity level, and also includes the second harmonic at an appropriate intensity level, reaches the entire surface of the metal material WP. As a result, ultrasonic cleaning is performed on the metal material WP.

[0061] [effect] In the ultrasonic cleaning method using the ultrasonic cleaning apparatus 100 according to this embodiment, propagating ultrasound, which includes not only the fundamental frequency f but also specific fractional harmonics of an appropriate intensity level, and further includes a second harmonic of an appropriate intensity level, reaches the entire surface of the metal material WP to be cleaned. In this case, cavitation is generated throughout the entire surface of the metal material WP by the fundamental frequency f, and effective cavitation is also generated by specific fractional harmonics of a sufficient intensity level. As a result, a sufficient cleaning effect can be obtained throughout the entire surface of the metal material WP, regardless of the presence or absence of the buffer member 3 (ultrasonic absorption part) and the position and shape of the metal material WP in the cleaning tank 1. Therefore, the metal material WP to be cleaned can be thoroughly cleaned throughout its entire surface. Furthermore, effective cavitation is generated throughout the entire surface of the metal material WP by the second harmonic of a sufficient intensity level. As a result, a more sufficient cleaning effect can be obtained throughout the entire surface of the metal material WP.

[0062] The significant effects of this embodiment can be achieved with a simple configuration in which the cleaning solution 4 contains metal compound particles. The ultrasonic emission mechanism that emits ultrasonic waves into the cleaning solution 4 only needs to be configured to emit the fundamental frequency f, and does not require a mechanism to emit ultrasonic waves of a specific fractional harmonic or a second harmonic. However, an ultrasonic emission mechanism that emits ultrasonic waves of a specific fractional harmonic or a second harmonic may be added.

[0063] In this embodiment, the concentration of metal compound particles in the cleaning solution 4 is 0.20 g / L or higher. In this case, an appropriate amount of metal compound particles is dispersed in the cleaning solution 4. This allows for effective diffuse reflection of the propagating ultrasonic waves. As a result, the propagating ultrasonic waves effectively contain specific fractional harmonics, and furthermore, effectively contain second harmonics. The concentration of metal compound particles is not particularly limited. However, if a large amount of metal compound particles is dispersed in the cleaning solution 4, the propagation of ultrasonic waves may be inhibited. Therefore, the upper limit of the concentration of metal compound particles is preferably 3.0 g / L.

[0064] In this embodiment, the cleaning solution 4 contains specific metal compound particles having a radius greater than or equal to the resonance radius at the fundamental frequency f, and less than or equal to 10 times the resonance radius. In this case, the concentration of specific metal compound particles in the cleaning solution 4 is 0.010 g / L or more. The entire amount of metal compound particles may be specific metal compound particles. If the cleaning solution 4 contains 0.010 g / L or more of specific metal compound particles having a radius greater than or equal to the resonance radius, the propagated ultrasonic waves will more effectively include specific fractional harmonics, and furthermore, will effectively include the second harmonic. On the other hand, if the radius of the metal compound particles exceeds 10 times the resonance radius, the propagation of ultrasonic waves may be inhibited. Also, if a large amount of specific metal compound particles are dispersed in the cleaning solution 4, the propagation of ultrasonic waves may be inhibited. Therefore, the upper limit of the concentration of specific metal compound particles is preferably 3.0 g / L, similar to the upper limit of the concentration of metal compound particles described above. In particular, to scatter specific fractional harmonics, it is preferable that the metal compound particles include particles having a radius greater than or equal to the resonant radius at the specific fractional harmonic and less than or equal to four times the resonant radius. The resonant radius at the specific fractional harmonic refers to the average diameter of bubbles generated in the cleaning solution 4 when ultrasonic waves of the specific fractional harmonic are emitted into the cleaning solution 4, and, like the resonant radius at the fundamental frequency, can be calculated according to the known Minnaert formula.

[0065] In this embodiment, the dissolved oxygen concentration in the cleaning solution 4 is 4.5 mg / L or less. In this case, the propagation of ultrasound in the cleaning solution 4 is not easily inhibited by dissolved oxygen. Therefore, ultrasound propagates smoothly in the cleaning solution 4. The lower the dissolved oxygen concentration, the better, and there is no particular lower limit. [Examples]

[0066] The present disclosure will be further described below with reference to examples. However, the present disclosure is not limited to the following examples.

[0067] Ultrasonic cleaning was performed on metal materials after pickling using the ultrasonic cleaning apparatus 100 shown in Figure 1. In each test number of Example 1, stainless steel wire (10 mm diameter, 6 ton coil) was used as the metal material. Water was used as the cleaning solution. The metal material was immersed in the cleaning solution, and ultrasonic waves of a reference frequency were emitted into the cleaning solution. The fundamental frequency of the ultrasonic waves was set to 37 kHz. The ultrasonic cleaning time was 120 seconds.

[0068] For each test number, the intensity spectrum of the propagating ultrasound in the cleaning solution was measured. The intensity spectrum was measured at a position away from the buffer material, specifically 10 cm from the surface of the part of the metal material furthest from the buffer material. It was also measured near the buffer material, specifically 10 cm from the surface of the part of the metal material directly supported by the buffer material. An ultrasonic measuring instrument (Ultrasonic System Laboratory, ultrasonic tester, model SSP-2012) was used for intensity spectrum measurement. The concentration of metal compound particles and the concentration of specific metal compound particles in the cleaning solution were also measured. Furthermore, the metal compound particles were analyzed by EPMA to confirm that they were composed of cementite. In addition, dissolved oxygen in the cleaning solution was measured using a dissolved oxygen meter (FUSO Corporation, dissolved oxygen meter, model PDO-519).

[0069] After ultrasonic cleaning, the degree of cleanliness of the metal surface was evaluated using the L value of lightness. Specifically, the lightness of five arbitrary locations on the metal material furthest from the buffer material was measured using a colorimeter (Color Reader, model CR-10Plus, manufactured by Conical Nomita Co., Ltd.). The same method was used to measure lightness in the vicinity of the buffer material, i.e., the portion directly supported by the buffer material. The average value of the obtained L values ​​of lightness was evaluated for each portion. For the evaluation of the degree of cleanliness, cases with an L value of 70 or higher were designated as the present invention example, and cases with an L value of less than 70 were designated as the comparative example.

[0070] The test results are shown in Tables 1 and 2. Table 1 shows the measurement results of the intensity spectrum at a distance from the buffer material, and the L values ​​in the portion away from the buffer material (test numbers 1-1 to 9-1, and 101-1 to 102-1). Table 2 shows the measurement results of the intensity spectrum at a distance from the buffer material, and the L values ​​in the portion near the buffer material (test numbers 1-2 to 9-2, and 101-2 to 102-2).

[0071] [Table 1]

[0072] [Table 2]

[0073] Referring to Tables 1 and 2, test numbers 1-1 to 9-1 and 1-2 to 9-2 are examples of the present invention, and in all cases, the intensity of the fundamental frequency fref and the intensity of a specific fractional harmonic fsub in the propagating ultrasound in the cleaning solution satisfied formula (1) "fsub / fref > 0.0030". In this case, the L value of brightness in each part of the metal material (stainless steel wire coil) after ultrasonic cleaning was 70 or higher, indicating good cleaning performance. In particular, test numbers 5-1 and 5-2 further satisfied formula (2) "f2nd / fref > 0.05" for the intensity of the fundamental frequency fref and the intensity of the second harmonic f2nd in the propagating ultrasound in the cleaning solution, and had the largest L value of brightness. On the other hand, test numbers 101-1 to 102-1 and 101-2 to 102-2 are comparative examples, and in all cases, the intensity of the fundamental frequency fref and the intensity of a specific fractional harmonic fsub in the propagating ultrasound in the cleaning solution did not satisfy formula (1). In this case, the L value of brightness did not reach 70 in each part of the metal material after ultrasonic cleaning, indicating unsatisfactory cleaning performance. Therefore, it was demonstrated that sufficient cleaning effect can be obtained throughout the entire metal material when the intensity fref of the fundamental frequency and the intensity fsub of specific fractional harmonics in the propagating ultrasound in the cleaning solution satisfy equation (1) "fsub / fref > 0.0030". [Examples]

[0074] Similar to Example 1, ultrasonic cleaning was performed on metal materials after pickling. In each test number of Example 2, stainless steel pipes (30 pipes with an inner diameter of 50 mm, a length of 10 m, and a thickness of 10 mm) were used as the metal material. Other cleaning conditions were the same as in Example 1. In each test number, the intensity spectrum of the propagating ultrasound in the cleaning solution was measured, similar to Example 1, and the degree of cleaning of the metal material surface after ultrasonic cleaning was evaluated by the L value of brightness.

[0075] The test results are shown in Tables 3 and 4. Table 3 shows the measurement results of the intensity spectrum at a position away from the cushioning material, and the L values ​​in the portion away from the cushioning material (test numbers 11-1 to 19-1, and 111-1 to 112-1). Table 4 shows the measurement results of the intensity spectrum at a position near the cushioning material, and the L values ​​in the portion near the cushioning material (test numbers 11-2 to 19-2, and 111-2 to 112-2).

[0076] [Table 3]

[0077] [Table 4]

[0078] Referring to Tables 3 and 4, test numbers 11-1 to 19-1 and 11-2 to 19-2 are examples of the present invention, and in all cases, the intensity of the fundamental frequency fref and the intensity of a specific fractional harmonic fsub in the propagating ultrasound in the cleaning solution satisfied formula (1) "fsub / fref > 0.0030". In this case, the L value of brightness in each part of the metal material (stainless steel pipe) after ultrasonic cleaning was 70 or higher, indicating good cleaning performance. In particular, test numbers 15-1 and 15-2 further satisfied formula (2) "f2nd / fref > 0.05" in the propagating ultrasound in the cleaning solution, and had the largest L value of brightness. On the other hand, test numbers 111-1 to 112-1 and 111-2 to 112-2 were comparative examples, and in all cases, the intensity fref of the fundamental frequency and the intensity fsub of specific fractional harmonics in the propagating ultrasound in the cleaning solution did not satisfy equation (1). In these cases, the L value of brightness in each part of the metal material after ultrasonic cleaning did not reach 70, indicating unsatisfactory cleaning performance. Therefore, it was demonstrated that sufficient cleaning effect can be obtained throughout the entire metal material when the intensity fref of the fundamental frequency and the intensity fsub of specific fractional harmonics in the propagating ultrasound in the cleaning solution satisfy equation (1) "fsub / fref>0.0030". [Examples]

[0079] Similar to Example 1, a coil of stainless steel wire was used as the metal material, and ultrasonic cleaning was performed on the metal material after pickling. In each test number of Example 3, the fundamental frequency of the ultrasound was set to 98 kHz. Other cleaning conditions were the same as in Example 1. In each test number, the intensity spectrum of the propagating ultrasound in the cleaning solution was measured, similar to Example 1, and the degree of cleaning of the metal material surface after ultrasonic cleaning was evaluated by the L value of brightness.

[0080] The test results are shown in Tables 5 and 6. Table 5 shows the measurement results of the intensity spectrum at a position away from the cushioning material, and the L values ​​in the portion away from the cushioning material (test numbers 21-1 to 29-1, and 121-1 to 122-1). Table 6 shows the measurement results of the intensity spectrum at a position near the cushioning material, and the L values ​​in the portion near the cushioning material (test numbers 21-2 to 29-2, and 121-2 to 122-2).

[0081] [Table 5]

[0082] [Table 6]

[0083] Referring to Tables 5 and 6, test numbers 21-1 to 29-1 and 21-2 to 29-2 are examples of the present invention, and in all cases, the intensity of the fundamental frequency fref and the intensity of a specific fractional harmonic fsub in the propagating ultrasound in the cleaning solution satisfied formula (1) "fsub / fref > 0.0030". In this case, the L value of brightness in each part of the metal material (stainless steel wire coil) after ultrasonic cleaning was 70 or higher, indicating good cleaning performance. In particular, test numbers 25-1 and 25-2 further satisfied formula (2) "f2nd / fref > 0.05" in the propagating ultrasound in the cleaning solution, and had the largest L value of brightness. On the other hand, test numbers 121-1 to 122-1 and 121-2 to 122-2 were comparative examples, and in all cases, the intensity fref of the fundamental frequency and the intensity fsub of specific fractional harmonics in the propagating ultrasound in the cleaning solution did not satisfy equation (1). In these cases, the L value of brightness in each part of the metal material after ultrasonic cleaning did not reach 70, indicating unsatisfactory cleaning performance. Therefore, it was demonstrated that sufficient cleaning effect can be obtained throughout the entire metal material when the intensity fref of the fundamental frequency and the intensity fsub of specific fractional harmonics in the propagating ultrasound in the cleaning solution satisfy equation (1) "fsub / fref>0.0030". [Examples]

[0084] Similar to Example 1, a coil of stainless steel wire was used as the metal material, and ultrasonic cleaning was performed on the metal material after pickling. In Example 4, Fe2O3 powder was added to the cleaning solution as metal compound particles. Other cleaning conditions were the same as in Example 1. Similar to Example 1, the intensity spectrum of the propagating ultrasound in the cleaning solution was measured, and the degree of cleaning of the metal material surface after ultrasonic cleaning was evaluated by the L value of brightness. The results of this test were equivalent to those of each of the above-described examples.

[0085] The embodiments of this disclosure have been described above. However, the embodiments described above are merely examples for implementing this disclosure. Therefore, this disclosure is not limited to the embodiments described above, and the embodiments described above can be modified as appropriate without departing from the spirit of the disclosure. [Explanation of Symbols]

[0086] 100: Ultrasonic cleaning device 1: Washing tank 2: Ultrasonic emission mechanism 3: Cushioning material 4: Cleaning solution WP: Metal material (object to be cleaned)

Claims

1. An ultrasonic cleaning device for metal materials, A cleaning tank capable of storing a cleaning solution containing multiple metal compound particles, and into which a metal material can be immersed in the cleaning solution containing the metal material, The cleaning tank is equipped with an ultrasonic emission mechanism that emits ultrasonic waves of a fundamental frequency into the cleaning liquid, At a position 10 cm away from the surface of the metal material in the cleaning tank, the frequency of the propagating ultrasonic waves in the cleaning solution includes the fundamental frequency and specific fractional harmonics having frequencies of 0.5 or 1.5 times the fundamental frequency. The intensity fref of the fundamental frequency and the intensity fsub of the specific fractional harmonic satisfy equation (1). Ultrasonic cleaning device. fsub / fref>0.0030 (1)

2. An ultrasonic cleaning apparatus according to claim 1, At the position 10 cm away from the surface of the metal material in the cleaning tank, the frequency of the propagating ultrasonic waves in the cleaning solution further includes a second harmonic which has twice the frequency of the fundamental frequency. The intensity of the fundamental frequency fref and the intensity of the second harmonic f2nd satisfy equation (2). Ultrasonic cleaning device. f2nd / fref>0.05 (2)

3. An ultrasonic cleaning apparatus according to claim 1 or claim 2, The concentration of the metal compound particles in the cleaning solution is 0.20 g / L or more. Ultrasonic cleaning device.

4. An ultrasonic cleaning apparatus according to claim 3, The metal compound particles include specific metal compound particles having a radius greater than or equal to the resonant radius at the fundamental frequency and less than or equal to 10 times the resonant radius. The concentration of the specific metal compound particles in the cleaning solution is 0.010 g / L or higher. Ultrasonic cleaning device.

5. An ultrasonic cleaning apparatus according to claim 1 or claim 2, The concentration of dissolved oxygen in the washing solution is 4.5 mg / L or less. Ultrasonic cleaning device.

6. An ultrasonic cleaning apparatus according to claim 1 or claim 2, further, The washing tank is equipped with a buffer member that supports the metal material, The ratio of the surface area of ​​the buffer member to the volume of the cleaning liquid in the cleaning tank is 0.1 m². ２ / m ３ Above, 2.0m ２ / m ３ The following is: Ultrasonic cleaning device.

7. The process involves immersing the metal material in a cleaning solution, The system comprises a cleaning step of emitting ultrasonic waves of a fundamental frequency into a cleaning solution containing multiple metal compound particles to clean the metal material, In the cleaning step, at a position 10 cm away from the surface of the metal material, the frequency of the propagating ultrasonic waves in the cleaning solution includes the fundamental frequency and specific fractional harmonics having frequencies of 0.5 or 1.5 times the fundamental frequency. The intensity fref of the fundamental frequency and the intensity fsub of the specific fractional harmonic satisfy equation (1). Ultrasonic cleaning method. fsub / fref>0.0030 (1)

8. An ultrasonic cleaning method according to claim 7, In the cleaning step, at the position 10 cm away from the surface of the metal material, the frequency of the propagating ultrasonic waves in the cleaning solution further includes a second harmonic which has twice the frequency of the fundamental frequency. The intensity of the fundamental frequency fref and the intensity of the second harmonic f2nd satisfy equation (2). Ultrasonic cleaning method. f2nd / fref>0.05 (2)

9. An ultrasonic cleaning method according to claim 7 or claim 8, The concentration of the metal compound particles in the cleaning solution is 0.20 g / L or more. Ultrasonic cleaning method.

10. An ultrasonic cleaning method according to claim 9, The metal compound particles include specific metal compound particles having a radius greater than or equal to the resonant radius at the fundamental frequency and less than or equal to 10 times the resonant radius. The concentration of the specific metal compound particles in the cleaning solution is 0.010 g / L or higher. Ultrasonic cleaning method.

11. An ultrasonic cleaning method according to claim 7 or claim 8, The concentration of dissolved oxygen in the washing solution is 4.5 mg / L or less. Ultrasonic cleaning method.

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