Dissolving liquid level measuring device

Abstract

To provide a device for measuring molten metal level, which can accurately detect a molten metal level in a mold in environment having flame, smoke and heat.SOLUTION: A device for measuring molten metal level 1 includes: a detection part 2 irradiating the level of a molten metal M in a mold 10 with a radar wave through the gate 11 of the mold 10 and detecting the level of the molten metal M on the basis of a reflection wave from the level; and a diffusion member 31 arranged right above the periphery of the gate 11, receiving the radar wave from the detection part 2 and diffusing the reflection wave of the radar wave. The diffusion member 3 is arranged in the existing heat insulation structure 4 between the detection part 2 and the mold 10. The heat insulation structure 4 has the passing hole 41 of the radar wave. The diffusion member 3 has the passing hole 31 of the radar wave L. Heat resistant material 5 including high temperature fire-resistant fibers is filled into the passing hole 41 of the heat insulation structure 4.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a technique for measuring the level of molten metal. [Background technology]

[0002] Techniques for measuring the level of molten metal during casting include laser-based level measuring devices as disclosed in Patent Documents 1 and 2 and radar-based level measuring devices as disclosed in Patent Documents 3 and 4.

[0003] The laser-type liquid level measuring device can pinpoint the liquid level of the molten metal in the mold by irradiating it with laser light from a relatively small diameter sprue, but the laser light may be blocked by smoke or flames that are generated when the molten metal is poured into the mold, making it impossible to accurately measure the liquid level.

[0004] In contrast, radar waves have the ability to penetrate smoke and flames, so it is expected that radar-based liquid level measurement devices will increasingly be used in place of laser-based methods in the casting industry. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-071123 [Patent Document 2] Special Publication No. 7-16776 [Patent Document 3] Japanese Patent Application Publication No. 01-145527 [Patent Document 4] Japanese Patent Application Laid-Open No. 2024-62215 Summary of the Invention [Problem to be solved by the invention]

[0006] Although radar waves can penetrate smoke and flames generated inside the mold, their wider scattering diameter compared to laser light can capture non-measurement targets around the gate, potentially leading to false detection of the molten metal level. For example, this can lead to false detection of molten metal spilled around the gate during pouring, or false detection of waves reflected by a partition intended to insulate the heat from the molten metal inside the mold.

[0007] In order to suppress the false detection, it is necessary to place the radar wave measuring device body near the spout, taking into consideration the diffusion diameter of the radar wave. However, it is necessary to separate the spout and the device body in order to prevent damage to the device body due to heat from the molten metal passing through the spout.

[0008] However, if the gate and the main body of the radar wave measuring device are separated, there is a risk of false detection as described above.

[0009] The present invention has been made in view of the above circumstances, and aims to provide a molten metal level measuring device that can accurately detect the level of molten metal in a mold even in an environment where flames, smoke, and heat are generated inside the mold. [Means for solving the problem]

[0010] Therefore, one aspect of the present invention is a molten metal level measuring device that includes a detection unit that irradiates radar waves onto the surface of the molten metal in a mold through the mold's sprue and detects the level of the molten metal based on the waves reflected from the liquid surface, and a diffusion member that is positioned directly above the periphery of the sprue and receives the radar waves from the detection unit and diffuses the reflected waves of the radar waves.

[0011] In one aspect of the present invention, the molten metal level measuring device further comprises a heat insulating structure in which the diffusion member is disposed, and a hole for passing the radar wave is formed in the heat insulating structure.

[0012] In one aspect of the present invention, in the thermal insulation structure of the molten metal level measuring device, a diffusion member is further erected around the diffusion member to receive the radar wave from the detection unit and diffuse the reflected wave of the radar wave.

[0013] In one aspect of the present invention, in the molten metal level measuring device, the passage hole is filled with a heat-resistant material that is permeable to the radar waves.

[0014] In one aspect of the present invention, in the molten metal level measuring device, the diffusion member is made of a metal plate having projections and recesses.

[0015] In one aspect of the present invention, in the molten metal level measuring device, the heat-resistant material includes high-temperature refractory fiber.

[0016] In one aspect of the present invention, in the molten metal level measuring device, the high-temperature refractory fiber includes ceramic wool, alkaline earth silicate wool, glass wool, or ceramic board. [Effects of the Invention]

[0017] According to the present invention, the level of the molten metal in the mold can be detected with high accuracy even in an environment where flames, smoke and heat are generated inside the mold. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a longitudinal cross-sectional view showing a schematic configuration of a molten metal level measuring device according to one embodiment of the present invention. [Figure 2] (a) A longitudinal cross-sectional view showing the arrangement of a detection unit, a diffusion member, a heat insulating structure, a heat-resistant material, a mold, and a measurement object in a performance test of the present invention, and (b) a plan view of the diffusion member. [Figure 3] (a) A longitudinal cross-sectional view illustrating a performance test of Comparative Example 1, (b) a longitudinal cross-sectional view illustrating a performance test of Example 1 of the present invention, (c) a longitudinal cross-sectional view illustrating a performance test of Example 2 of the present invention, and (d) a longitudinal cross-sectional view illustrating a performance test of Example 3 of the present invention. [Figure 4] FIG. 1A is a longitudinal cross-sectional view illustrating a performance test of the diffusion member of the present invention, and FIG. 1B is a plan view of the diffusion member in which a radar wave passage hole is formed. [Figure 5] (a) A longitudinal cross-sectional view of a mold illustrating the distance between the detection part and the molten metal poured into the mold. (b) A longitudinal cross-sectional view of a mold illustrating the diffusion effect of the diffusion member on the reflected radar waves. [Figure 6] A characteristic diagram showing a comparison between the gate height detected by a laser-type liquid level measuring device that does not have a diffusion member or heat-resistant material and the gate height detected by the radar-type liquid level measuring device of the present invention that has a diffusion member 3 and heat-resistant material 5. [Figure 7] A characteristic diagram showing the relationship between the gate height detected by the molten metal level measuring device in Figure 1 and the poured molten metal weight. [Figure 8] (a) A perspective view of a mold illustrating the definition of the gate height, (b) a longitudinal cross-sectional view of the mold. [Figure 9] FIG. 2 is a perspective view showing the arrangement of a detection unit, a diffusion member, a heat insulating structure, a heat-resistant material, and a measurement object in a performance test of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0020] The molten metal level measuring device 1 according to one embodiment of the present invention shown in Figure 1 is based on a radar-based liquid level measuring method, and utilizes the fact that the reflectivity and permeability of radar waves L differ depending on the material, to diffuse the reflected waves of radar waves L in the environment surrounding the gate 11 of the mold 10. This makes it possible to detect the level of the molten metal M in the mold 10 with high accuracy.

[0021] The molten metal level measuring device 1 has a detection unit 2 , a diffusion member 3 , a heat insulating structure 4 and a heat-resistant material 5 .

[0022] The detection unit 2 irradiates radar waves L onto the surface of the molten metal M in the mold 10 through the gate 11 of the mold 10 and detects the level of the molten metal M based on the waves reflected from the liquid surface. A well-known radar-type range finder is used as the detection unit 2. The distance between the detection unit 2 and the heat-insulating structure 4 is set to an appropriate distance so as not to interfere with the measurement of the liquid level.

[0023] The diffusion member 3 is disposed immediately above the periphery of the gate 11, receives radar waves L from the detection unit 2, and diffuses the reflected waves of the radar waves L. As shown in FIGS. 1(a) and 1(b), the diffusion member 3 is made of a metal plate with irregularities, and is disposed in the existing heat-insulating structure 4 between the detection unit 2 and the mold 10. A hole 31 for passing the radar waves L is formed in the diffusion member 3 at a location corresponding to the gate 11.

[0024] The metal plate may be a well-known corrugated steel plate, such as a galvanized iron plate, a galvanized iron plate, a galvanized iron plate, a galvanized iron plate, or a galvanized thin steel plate, which is used as a building material. Note that the diffusing member 3 is not limited to a corrugated metal plate, as long as it can diffuse the reflected radar waves L.

[0025] The heat insulating structure 4 is an existing heat insulating structure installed between the detection unit 2 and the mold 10, and blocks flames and smoke generated from the gate 11 of the mold 10. A passage hole 41 for radar waves L is formed in the heat insulating structure 4 at a location corresponding to the gate 11. The diffusion member 3 having the above-mentioned passage hole 31 formed therein is arranged around this passage hole 41.

[0026] Further, a diffusion member 3 is erected around the diffusion member 3 on the thermal insulation structure 4 to receive radar waves L from the detection unit 2 and diffuse the reflected waves of the radar waves L. This diffusion member 3 is attached to an existing structural wall 6 that is perpendicular to the thermal insulation structure 4, for example.

[0027] The heat-resistant material 5 is made of a material that allows the radar wave L from the detection unit 2 to pass through, and is filled into the passage holes 41 in the heat-insulating structure 4. The heat-resistant material 5 may, for example, contain high-temperature fire-resistant fibers. Examples of the high-temperature fire-resistant fibers include ceramic wool, alkaline earth silicate wool (AES wool), glass wool, and ceramic board.

[0028] According to the above-described molten metal level measurement device 1, the heat-resistant material 5 that is permeable to radar waves L is filled in the passage hole 41 of the thermal insulation structure 4 between the detection unit 2 and the gate 11, thereby preventing overheating of the detection unit 2 and reducing the distance between the detection unit 2 and the gate 11 of the mold 10. Furthermore, the reflected waves of the radar waves L from non-measurement targets other than the molten metal in the gate 11 are diffused by the diffusing member 3, reducing the laser feedback intensity that reaches the detection unit 2 and preventing erroneous detection of non-measurement targets as the measurement target. Therefore, even in an environment where flames, smoke, and heat are generated inside the mold, the measurement target can be accurately captured, allowing the level of the molten metal in the mold to be detected with high precision. [Example]

[0029] Specific examples of the present invention will be described below.

[0030] The "gate height" mentioned in the explanation of the comparative examples and examples of the present invention corresponds to the "liquid level of the molten metal" that is the object of measurement in the present invention, and is defined as "gate height h = distance d2 from the detection part 2 to the bottom of the gate 12 - distance d1 from the detection part 2 to the liquid surface of the molten metal M" as shown in Figure 8.

[0031] [Comparative Example and Performance Tests of Examples 1 to 3, Assuming a Pouring Process] Figure 2(a) shows the arrangement of the detection unit 2, diffusion member 3, insulation structure 4, heat-resistant material 5, mold 10 and target T (object to be measured) in the performance test of the present invention, and Figure 2(b) is a plan view of the diffusion member 3.

[0032] The detection unit 2 was installed at a position with a gate distance D2 of 890 mm. A Keyence radar range finder (model number: FR-LM20) was used as the detection unit 2. The spot diameter R of the detection unit 2 was set to 100 mm. A heat insulating structure 4 was installed between the detection unit 2 and the mold 10 to block flames and smoke from the mold 10. The distance D1 between the heat insulating structure 4 and the detection unit 2 was set to 620 mm.

[0033] Commercially available firebricks were used for the thermal insulation structure 4. The thermal insulation structure 4 also has a through hole 41 formed therein, which irradiates radar waves L onto a target T made of a piece of cast iron simulating the liquid surface of the molten metal M, and acquires the reflected waves from this target T. The diameter of the through hole 41 is restricted to 70 mm in order to prevent the intrusion of smoke and flames from the mold 10, and an environment was created in which the reflected waves from the thermal insulation structure 4 reach the detection unit 2 via the existing structural wall 6. The distance D between the existing structural wall 6 and the axis of the radar wave was set to 350 mm.

[0034] The diffusion member 3 placed in the insulation structure 4 is made of commercially available corrugated galvanized sheet metal, which is used as a general-purpose building material, and has a passage hole 31 with a smaller diameter (diameter 60 mm) than the passage hole 41 of the insulation structure 4 formed to correspond to the passage hole 41 of the insulation structure 4.

[0035] The detection performance of the detector 2 for detecting reflected waves from the target T was verified by varying the gate distance D2, which is the distance between the target T and the detector 2, in six steps of 50 mm each from 890 mm.

[0036] 3(a) is a cross-sectional view illustrating a reflected wave detection performance test of Comparative Example 1, FIG. 3(b) is Example 1 of the present invention, FIG. 3(c) is Example 2 of the present invention, and FIG. 3(d) is Example 3 of the present invention.

[0037] In Comparative Example 1, the diffusion member 3 is not disposed in the heat insulating structure 4 .

[0038] In the first embodiment, the diffusion member 3 is disposed around the passage hole 41 of the heat insulating structure 4 .

[0039] In the second embodiment, a diffusion member 3 is disposed on an existing structural wall 6 in the same manner as in the first embodiment.

[0040] In the third embodiment, in the same manner as in the second embodiment, the passage holes 41 of the heat insulating structure 4 are filled with heat resistant cotton as the heat resistant material 5 .

[0041] Table 1 shows the results of the evaluation of the detection of the reflected wave of the radar wave L in Comparative Example 1 and Examples 1 to 3. In the table, × means that detection was not possible, △ means that a false detection (difference from the normal value), and ◯ means that the detected value matched (difference from the normal value), with a tolerance of ±10 mm.

[0042] [Table 1]

[0043] Comparative Example 1 does not include the diffusion member 3, so the heat insulating structure 4 and the existing structural wall 6 become obstacles to detecting the reflected waves from the target T, and the detection unit 2 cannot detect the value of the gate distance D2.

[0044] In Example 1, the gate distance D2 was correctly detected from 890 mm to 990 mm, and better results were obtained than in Comparative Example 1. However, it was confirmed that misdetection occurred when the gate distance D2 was greater than 1040 mm.

[0045] In Example 2, measurements were possible without false detection when the gate distance D2 was between 890 mm and 1140 mm. In particular, it was confirmed that the detection unit 2 can capture the target T even in an environment where unnecessary structures act as barriers if the diffusion member 3 is appropriately positioned.

[0046] In Example 3, it was verified whether the detection unit 2 could detect reflected waves from the target T without attenuation when heat-resistant cotton (blanket-like ceramic wool) was filled as the heat-resistant material 5 in the passage hole 41 of the thermal insulation structure 4. The thickness of the heat-resistant cotton was set to four levels: no heat-resistant cotton, 50 mm, 100 mm, and 150 mm, and the detection of the reflected waves was evaluated for each condition. It was confirmed that normal measurement could be performed up to 100 mm even when the distance between the detection unit 2 and the target T was blocked by the heat-resistant material 5 (heat-resistant cotton).

[0047] As is clear from the evaluation results in Table 1 above, the periphery of the passage hole 41 in the thermal insulation structure 4, which is smaller than the effective width of the radar wave of the detection unit 2, is covered with the diffusion member 3, thereby diffusing the radar reflected wave around the passage hole 41 in the thermal insulation structure 4. This prevents the reflected radar wave from the periphery from reaching the detection unit 2, making it easier to detect the reflected radar wave from the measurement object.

[0048] Furthermore, in an environment where reflected waves of radar waves L from sources other than the object to be measured reach the detection unit 2, the reflected waves can be blocked by placing a diffusion member 3 on the insulating structure 4 where the reflected waves are generated from the non-object to be measured.

[0049] Furthermore, even in an environment where flames, smoke, and heat are generated, such as in the mold 10, by filling the passage holes 41 of the thermal insulation structure 4 with the heat-resistant material 5 to an appropriate thickness, smoke and flames are not emitted from the thermal insulation structure 4, and radar waves can be transmitted to the object to be measured.

[0050] Furthermore, since an inexpensive corrugated galvanized sheet can be used as the diffusion member 3, the liquid level of the molten metal in the mold can be detected at low cost and with high accuracy.

[0051] [Performance test to prevent false detection of radar reflection waves caused by molten metal scattered around the gate 11] Figure 4(a) illustrates the performance test of the diffusion member 3, (b) is a longitudinal cross-sectional view of the gate 11 without the diffusion member 3, (c) is a longitudinal cross-sectional view of the gate with the diffusion member placed directly above the gate periphery, and (d) is a plan view of the diffusion member with a radar wave passage hole formed therein.

[0052] During the mold cooling process, the detector 2 was installed at a position with a gate distance D2 of 1500 mm. A Keyence radar range finder (model number: FR-LM20) was used as the detector 2. The intensity of the radar waves emitted from the detector 2 was set so that it could selectively detect metals that have more reflected waves of radar waves L than the mold 10. When the poured molten metal M is present within the focus range of the radar waves of the detector 2, it is expected that the measurement distance will be longer than the top surface of the gate 11.

[0053] However, if the molten metal M spilled outside the sprue 11 is within the focus range of the detection unit 2, the poured molten metal M1 and the spilled molten metal M2 are made of the same material, so the intensity of the reflected wave may be higher for molten metal M2 than for molten metal M1, and the distance of molten metal M2 may be mistakenly detected as the distance of molten metal M1.

[0054] In this performance test, a corrugated galvanized sheet for construction materials, as shown in Figure 1(b), which is available at low cost, was used as the diffusion member 3. Next, as shown in Figure 1(a), the top surface of the mold 10, on which the poured molten metal M1 and the molten metal M2 spilled from the gate 11 of the mold 10 are located, was shielded by the diffusion member 3, which had a passage hole 31 with a smaller diameter than the gate 11. Then, the effectiveness of the diffusion member 3 in preventing false detection of the reflected wave was verified. The distance between the diffusion member 3 and the mold 10 was set to 300 mm.

[0055] Table 2 shows the evaluation results of the suppression of reflected waves of radar waves L with and without the diffusion member 3. In particular, the table shows the evaluation results of the suppression of reflected waves with and without the diffusion member 3 for the distance (mm) between the detection part 2 and the molten metal M1, which was set to six levels as shown in Figure 5(a). In the table, × means that detection was not possible, △ means that a false detection (difference from the normal value), and ◯ means that the detected value matched (difference from the normal value), with a tolerance of ±10 mm.

[0056] [Table 2]

[0057] As shown in Figure 1(a), the gate 11 of the mold 10 in the test environment is tapered, and the cross-sectional area of ​​the opening becomes smaller as it gets further away from the detection unit 2. As is clear from the evaluation results in Table 2, when the diffusion member 3 is not placed on the mold 10, the intensity of the reflected radar wave from the molten metal M2 spilling from the gate 11 exceeds the intensity of the reflected radar wave from the molten metal M1 in the mold 10, resulting in a false detection.

[0058] In contrast, when a diffusion member 3 is placed on the mold 10 as shown in Fig. 1(b), even if the molten metal M1 spills from the gate 11 of the mold 10, the molten metal M2 scattered around the gate 11 is shielded by the diffusion member 3, and the reflected waves of the radar waves irradiated to the surrounding area are diffused. Therefore, false detection of the reflected waves of the radar waves caused by the molten metal M2 and the environment around the gate 11 can be prevented.

[0059] Figure 6 shows a comparison between the gate height (molten metal level) detected by a laser-type liquid level measuring device (laser range finder) that does not have the diffusion member 3 and heat-resistant material 5, and the gate height detected by the molten metal level measuring device 1 (radar range finder) of Figure 1 that has the diffusion member 3 and heat-resistant material 5. It was shown that the radar-type liquid level measuring device of the present invention can detect the gate height more stably and accurately than the laser-type liquid level measuring device.

[0060] Figure 7 shows the relationship between the gate height and poured molten metal weight detected by the molten metal level measuring device 1 in Figure 1. The correlation between the gate height and the poured molten metal weight was as expected, and it was confirmed that the gate height (molten metal level) was measured as expected.

[0061] [Radar transparency performance test of the heat-resistant material 5 according to the present invention]

[0062] FIG. 9 shows the layout of the detection unit 2, the diffusion member 3, the heat insulating structure 4, the heat-resistant material 5, and the target T (object to be measured) in this performance test.

[0063] In this test, the ceramic wool of the present invention (ceramic wool (BSSR1400 blanket, thickness 50 mm) manufactured by Isolite Kogyo) and a glass plate of a comparative example (general-purpose colorless glass plate, thickness 3 mm) were used as the heat-resistant material 5, and the radar penetration performance of these two materials was compared. Note that a commercially available corrugated galvanized sheet was used as the diffusion member 3. Commercially available firebrick was used as the heat-insulating structure 4.

[0064] A Keyence radar rangefinder (model number: FR-LM20) was used for detector 2. The sensitivity of detector 2 was adjusted to 2 (standard value) in liquid level detection mode (1: weakest to 4: strongest). The tracking function was set to OFF (0 seconds) so that the lost position would not be memorized when the signal was lost.

[0065] The target T was a general-purpose iron plate with a thickness of 5 mm, and was set so that the distance d1 and facing angle to the detection part 2 would not change even if it was repeatedly attached and detached.

[0066] In order to improve the reproducibility of the evaluation, the target T was repeatedly attached and detached to check whether the distance d1 between the detection unit 2 and the target T, which was detected when the target T was installed, could be accurately measured.

[0067] The criterion for judgment was that the detection distance was 1500 mm for ±1 mm when the detection accuracy of the detection unit 2 was 0.1 to 10 m, so a value of 1500 ±1 mm was judged to be correct. The detection results for the distance d1 for each thickness of the heat-resistant material 5 are shown in Table 3 below.

[0068] [Table 3]

[0069] From the results in Table 3, when the glass plate of the comparative example was used as the heat-resistant material 5, detection became unstable at a thickness of 3 mm, and detection was impossible at a thickness of 6 mm.

[0070] On the other hand, when the ceramic wool of the present invention was used as the heat-resistant material 5, detection was possible up to 100 mm, equivalent to that without any protective material. In particular, when comparing the transmitted weight per unit area, the glass plate was 0.8 g / cm 2 ] and was undetectable, whereas ceramic wool was 0.9 [g / cm 2 ] and it was confirmed that the transmission performance is superior to that of glass plates.

[0071] It was confirmed that if the thickness of the ceramic wool required to protect the detection part 2 from the heat of the molten metal is 50 mm or less, the ceramic wool is effective for protecting the radar range finder while maintaining its detection performance.

[0072] From the results of the above performance tests, it was found that if a glass plate was used for the heat-resistant material 5, the radar waves would be attenuated more strongly when passing through, and the radar range finder would not be able to obtain sufficient detection performance.

[0073] In contrast, if ceramic wool is used as the heat-resistant material 5 and placed between the detection part 2 and the target T, as in the present invention, the measurement accuracy of the radar range finder can be improved while protecting the detection part 2 from the radiant heat and convective heat generated from the molten metal and mold, and the flames and smoke generated from the mold.

[0074] In the above performance tests, the radar penetration performance of ceramic wool was verified as the heat-resistant material 5 according to the present invention. However, it is clear that ceramic board, glass wool, and alkaline earth silicate can also exhibit radar penetration performance similar to that of ceramic wool, as long as they are materials that are heat-resistant and have radar wave penetration properties due to gaps. [Explanation of symbols]

[0075] 1... Molten metal level measuring device 2...Detection unit 3... Diffusion member, 31... Passage hole 4...insulating structure, 41...passage hole 5...Heat-resistant material 10...Mold, 11...Spring, M, M1, M2...Molten metal

Claims

1. a detection unit that irradiates radar waves onto the surface of the molten metal in the mold through a sprue of the mold and detects the level of the molten metal based on the reflected waves from the surface of the molten metal; A diffusion member that is arranged directly above the periphery of the gate, receives the radar wave from the detection unit, and diffuses the reflected wave of the radar wave; a heat-insulating structure in which the diffusion member is disposed; and a passage hole for the radar wave is formed in the heat-insulating structure, In the heat-insulating structure, a diffusion member is further provided around the diffusion member to receive the radar wave from the detection unit and diffuse the reflected wave of the radar wave. A molten metal level measuring device characterized by the above.

2. 2. The molten metal level measuring device according to claim 1, wherein the passage hole is filled with a heat-resistant material that is permeable to the radar waves.

3. 3. The molten metal level measuring device according to claim 1, wherein the diffusion member is made of a metal plate having projections and recesses.

4. 3. The molten metal level measuring device according to claim 2, wherein the heat-resistant material includes high-temperature refractory fiber.

5. 5. The molten metal level measuring device according to claim 4, wherein the high-temperature refractory fiber includes ceramic wool, alkaline earth silicate wool, glass wool, or ceramic board.

Images