Water-cooled spray nozzle, spray nozzle tip component

Abstract

To suppress reduction in wall thickness of a coating in a water-cooling spray nozzle.SOLUTION: A water-cooling spray nozzle includes a coating which is made of Ni-P alloy and formed at least part of an inner surface of a nozzle ejection hole, where the coating has a Vickers hardness of 500Hv or more and 1300Hv or less.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a cooling spray nozzle for water cooling used in the manufacture of slabs, steel plates, steel pipes, etc.

Background Art

[0002] For example, the cooling of these materials in the manufacturing process of slabs, steel pieces, steel plates or steel pipes is important from the viewpoints of obtaining appropriate surface properties and structures, and ensuring homogenization and stable operation.

[0003] As a means for supplying cooling water to the material for this cooling, a water-cooling spray nozzle is used. Since the water-cooling spray nozzle injects cooling water toward the material from a thin nozzle discharge hole, clogging is particularly likely to occur in the nozzle discharge hole. And when clogging occurs, the material cannot be cooled, which affects the quality of the object to be cooled.

[0004] Patent Document 1 describes applying a metal surface coating to the tip portion (tip member) of a spray nozzle, and specifically discloses surface coatings made of Cr, Ni-P, and Ni-W. It is said that this can prevent clogging of the spray nozzle.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, conventional coatings have a problem in that the use of spray nozzles tends to cause thinning of the coating. Thinning of the coating causes changes in the dimensional of the nozzle discharge hole, either by enlarging the opening of the nozzle discharge hole or by narrowing the opening due to deposits on the coating surface, thereby hindering the planned supply of cooling water. In addition, thinning of the coating necessitates the replacement of the spray nozzle and the tip component of the spray nozzle, and frequent replacement of these components leads to a decrease in manufacturing efficiency and an increase in manufacturing costs, so it is desirable to minimize them as much as possible.

[0007] Therefore, the object of the present invention is to provide a water-cooling spray nozzle that can suppress thinning of the coating. Furthermore, the present invention provides a tip component for this purpose. [Means for solving the problem]

[0008] One aspect of the present invention is a water-cooled spray nozzle or a tip member for a spray nozzle, wherein a coating made of Ni-P alloy is formed on at least a part of the inner surface of the nozzle discharge hole, and the Vickers hardness of the coating is 500 Hv or more and 1300 Hv or less. [Effects of the Invention]

[0009] According to the present invention, it is possible to more reliably suppress the thinning of the coating on the spray nozzle. [Brief explanation of the drawing]

[0010] [Figure 1] This diagram shows the configuration of the water-cooling spray nozzle 10. [Figure 2] This figure focuses on the vicinity of the nozzle tip 13 in Figure 1. [Figure 3] (a) is a diagram showing the external appearance of the nozzle tip 13, and (b) is a cross-sectional view of the nozzle tip 13. [Figure 4] This is a view of Figure 3(b), focusing on the vicinity of the nozzle discharge hole 14. [Modes for carrying out the invention]

[0011] Figure 1 shows the structure of a water-cooling spray nozzle 10 in one configuration. This water-cooling spray nozzle 10 is a spray nozzle for secondary cooling of a cast slab in a continuous casting process. However, this is merely an example, and the same considerations can be applied to water-cooling spray nozzles used for cooling in other processes. Other processes include, for example, slab bloc rolling, structural steel rolling, and hot rolling processes.

[0012] The water-cooled spray nozzle 10 is composed of a mixer 11 having a hollow section inside, a conduit 12, and a nozzle tip 13 as a tip component. As can be seen in Figure 1, the air pipe 1, which is the air passage, and the water pipe 2, which is the cooling water passage, are connected to the mixer 11, and the air and cooling water are mixed in the hollow section of the mixer. In addition, one end of the conduit 12 is connected to the mixer 11, and a nozzle tip 13 is positioned at the other end of the conduit 12. Accordingly, the air supplied by the air pipe 1 and the cooling water supplied by the water pipe 2 are mixed in the hollow section of the mixer 11, flow through the conduit 12 to the nozzle tip 13, and are sprayed from the nozzle discharge hole 14 provided in the nozzle tip 13 toward the material (to be cooled).

[0013] Figure 2 shows a magnified view of the nozzle tip 13 from Figure 1. Figure 3(a) shows an external view of the nozzle tip 13, including a plan view and a right side view, Figure 3(b) shows a cross-sectional view AA, and Figure 4 shows a magnified view of the nozzle discharge hole 14 from Figure 3(b). As can be seen in Figures 2 to 4, the nozzle tip 13 functions as the tip component for the spray nozzle. It has a hexagonal cylindrical shape, with a bottom 13a at one end and an open end at the other. A slit-shaped hole is provided in the bottom 13a, penetrating through it, and this is the nozzle discharge hole 14. In this embodiment, the nozzle discharge hole 14 is a slit-shaped hole, but it is not limited to this shape; any necessary shape is acceptable. On the other hand, the nozzle tip 13 is attached to the conduit 12 by inserting and fixing the end of the conduit 12 inside the nozzle tip 13 from the other end that opens. In this embodiment, the conduit 12 and the nozzle tip 13 are fixed by different components, but the invention is not limited to this configuration. The conduit and the nozzle tip may be integrated and indistinguishable. In this case, a nozzle discharge hole is provided at the tip of the conduit.

[0014] As can be seen from Figure 4, the nozzle tip 13 is covered at least partially by the coating 15. Specifically, the coating 15 is provided on at least a portion of the inner surface of the nozzle discharge hole 14. In this embodiment, the coating 15 is provided on the entire inner surface of the nozzle discharge hole 14, the outer surface 13b of the bottom 13a of the nozzle tip 13, and the inner surface 13c, and in particular the portion surrounding the nozzle discharge hole 14. However, this does not prevent the coating from being formed on all of the nozzle tip 13, or on parts other than those mentioned above. For example, from a film formation standpoint, it may be more efficient to form the coating on all of the nozzle tip 13.

[0015] The coating 15 is composed of a Ni-P alloy (nickel-phosphorus alloy) among Ni alloys (nickel alloys), and its Vickers hardness (at a load of 10 gf) is set to be between 500 Hv and 1300 Hv. More preferably, it is between 500 Hv and 1100 Hv. This suppresses the thinning of the coating due to wear and corrosion even with prolonged injection of coolant. Furthermore, by suppressing the thinning of the coating, the opening of the nozzle discharge hole is prevented from becoming larger, and the formation of deposits on the coating surface that conversely narrows the nozzle discharge hole opening is also prevented. As a result, the dimensional change of the nozzle discharge hole remains stable over the long term, enabling the planned supply of coolant. In addition, the frequency of replacement of spray nozzles and nozzle tips due to coating thinning is reduced, leading to improved manufacturing efficiency and reduced manufacturing costs. If the Vickers hardness is less than 500 Hv, this effect will not occur, and if it is greater than 1300 Hv, the coating will become brittle and prone to cracking.

[0016] Particularly when film thinning occurs due to film wear or corrosion, the generation of deposits becomes prominent, and the dimensions of the nozzle discharge holes may become narrow or clogged. However, according to the present invention, such problems can be suppressed. The reason is not necessarily clear, but it can be considered as follows. That is, when the coating with Ni-P alloy is heat-treated so that the Vickers hardness (load 10 gf) is in the range of 500 Hv or more and 1300 Hv or less, at that time, when the P content is relatively low (4 mass% or less), P segregates at the grain boundaries and grain boundary strengthening is achieved. When the P content is more than that, Ni3P is further precipitated, and it becomes possible to resist wear and corrosion, and roughening of the surface due to wear and corrosion (roughening) is suppressed. When the roughening of the surface becomes prominent, foreign substances in the cooling water are likely to be caught on the surface and accumulate. In addition, when calcium components in the cooling water are deposited on the roughened surface, the deposited calcium components are more difficult to peel off due to the anchor effect compared to a smooth surface. Furthermore, since the deposited calcium components are more hydrophilic than the metal surface, once deposited, they are more likely to capture foreign substances acceleratively. In this way, roughening promotes the deposition of foreign substances on the surface regardless of the type of cause, and causes narrowing and clogging of the nozzle discharge holes. On the other hand, if a Ni-P alloy coating is applied and its Vickers hardness (load 10 gf) is 500 Hv or more and 1300 Hv or less, such roughening is suppressed and such deposition of foreign substances can be suppressed.

[0017] The component constituting the film may be a Ni alloy containing P in the range of 0.001 mass% or more and 12 mass% or less, and at least one of the following components can be included as other components. That is, in addition to Ni (nickel), P (phosphorus), and inevitable impurities, the following components may be included.

[0018] K (potassium) can be contained in the range of 0.001 mass% or more and 1.0 mass% or less. By setting it to 0.001 mass% or more, the strength of the film can be improved. On the other hand, if it exceeds 1.0 mass%, there is a risk of causing cracks in the film. C (carbon) can be contained in an amount of 0.001% by mass or more and 0.5% by mass or less. By setting it to 0.001% by mass or more, the wear resistance of the film can be improved. On the other hand, if it exceeds 0.5% by mass, there is a risk of causing cracks in the film. H (hydrogen) can be contained in an amount of 0.001% by mass or more and 1.0% by mass or less. By setting it to 0.001% by mass or more, the strength of the film can be improved. On the other hand, if it exceeds 1.0% by mass, the film tends to become brittle and there is a risk of causing cracks in the film. O (oxygen) can be contained in an amount of 0.001% by mass or more and 1.0% by mass or less. By setting it to 0.001% by mass or more, the strength of the film can be improved. On the other hand, if it exceeds 1.0% by mass, there is a risk of causing cracks in the film. N (nitrogen) can be contained in an amount of 0.001% by mass or more and 1.0% by mass or less. By setting it to 0.001% by mass or more, the wear resistance of the film can be improved. On the other hand, if it exceeds 1.0% by mass, there is a risk of causing cracks in the film. S (sulfur) can be contained in an amount of 0.001% by mass or more and 1.0% by mass or less. By setting it to 0.001% by mass or more, the hardness of the film can be improved. On the other hand, if it exceeds 1.0% by mass, there is a risk of causing cracks in the film. Co (cobalt) can be contained in an amount of 0.001% by mass or more and 8.0% by mass or less. By setting it to 0.001% by mass or more, the hardness of the film can be improved. On the other hand, if it exceeds 8.0% by mass, there is a risk of causing cracks in the film. Cu (copper) can be contained in an amount of 0.001% by mass or more and 8.0% by mass or less. By setting it to 0.001% by mass or more, the hardness of the film can be improved. On the other hand, if it exceeds 8.0% by mass, there is a risk of causing cracks in the film. Fe (iron) can be contained in an amount of 0.001% by mass or more and 8.0% by mass or less. By setting it to 0.001% by mass or more, the hardness of the film can be improved. On the other hand, if it exceeds 8.0% by mass, there is a risk of causing cracks in the film. The coating may contain chromium (Cr) in an amount of 0.001% by mass or more and 8.0% by mass or less. A concentration of 0.001% by mass or more improves the corrosion resistance of the coating. Conversely, exceeding 8.0% by mass may cause cracking of the coating. The coating may contain tin (Sn) in an amount of 0.001% by mass or more and 1.0% by mass or less. A concentration of 0.001% by mass or more improves corrosion resistance. However, exceeding 1.0% by mass may cause cracking of the coating. The coating may contain palladium (Pd) in an amount of 0.001% by mass or more and 1.0% by mass or less. A concentration of 0.001% by mass or more improves corrosion resistance. Conversely, a concentration exceeding 1.0% by mass may cause cracking of the coating.

[0019] While there are no particular limitations on the thickness of the coating, it is preferable that the thickness be 50 μm or less, as excessive thickness increases the likelihood of cracking within the coating during film formation. Conversely, if the coating is too thin, the expected effects of the coating may not be achieved, so it is preferable that the thickness be 10 μm or more to ensure these effects.

[0020] The base material of the nozzle tip 13 is not particularly limited, but it is preferably stainless steel from the viewpoint of corrosion resistance, and even more preferably has high machinability.

[0021] Furthermore, the nozzle tip may be an entire integrated structure, or it may be made of multiple divided components that are later assembled. From the viewpoint of forming the coating 15, the latter is preferred.

[0022] Aside from the coating 15 on the water-cooling spray nozzle 10 as described above, the other parts can be manufactured by conventionally known methods. Furthermore, the method for forming (depositing) the coating 15 is not particularly limited, and examples include electroplating and electroless plating. "Electroplating" refers to a method of forming a coating by applying an electric current from an external source, causing metal cations to react with electrons through electrolysis to form a metal, and then depositing it on the surface of the object to be plated, which forms the cathode. On the other hand, "electroless plating" refers to a method of forming a coating on the surface of the object to be plated by reducing and depositing metal ions in a solution using a chemical reducing agent, without applying an external electric current. Then, in order to make the Vickers hardness of the coating 15 between 500 Hz and 1300 Hz, heat treatment is performed after film formation. The heat treatment can be carried out, for example, by heating in a vacuum furnace at 400°C for about one hour. [Examples]

[0023] [Test piece] A nozzle tip for testing was fabricated following the shape shown in Figure 3. The base material was stainless steel (SUS303). A Ni-P alloy film was formed on the nozzle tip-shaped base material by electroless plating (Example 1, Comparative Example 2). Specifically, the nozzle tip-shaped base material was plated by immersing it in the plating bath shown below. That is, the plating bath consisted of 0.2 mol / L nickel sulfate, 0.2 mol / L citric acid, 0.5 mol / L ammonium sulfate, and 0.15 mol / L sodium hypophosphite. The pH of the plating bath was adjusted to 9.0 with NaOH. This resulted in a film with a P content of 9% by mass. The nozzle tip of Example 1 was further heat-treated in a vacuum furnace at 400°C for 1 hour. No heat treatment was performed on the nozzle tip of Comparative Example 2. For the nozzle tip of Comparative Example 3, plating was performed by immersing the base material in the following plating bath. Specifically, the plating bath consisted of 0.2 mol / L nickel sulfate, 0.2 mol / L citric acid, 0.5 mol / L ammonium sulfate, and 0.20 mol / L sodium hypophosphite. The pH of the plating bath was adjusted to 10.0 with NaOH. This resulted in a coating with a phosphorus content of 5% by mass. After this, heat treatment was performed in a vacuum furnace at 400°C for 1 hour. In addition, a nozzle tip without a coating was prepared as Comparative Example 1.

[0024] [Hardness measurement] The Vickers hardness of the nozzle tip was measured using a micro-Vickers hardness tester (HM-210A, manufactured by Mitutoyo Corporation). The pressing load was set to 10 gf, and the average of three measurements was taken as the hardness. The measurement position was any point in the central part of the inner surface of the nozzle tip, between the nozzle discharge hole and the opening on the opposite side.

[0025] [Measuring the amount of meat loss] To measure the amount of wall thickness loss, an accelerated test was conducted using a wet-dry cycle, and the amount of wall thickness loss was determined by the difference in coating thickness before and after the test. The accelerated testing using repeated wet-dry cycles was conducted as follows: Specifically, a lidded beaker was placed inside a drying oven adjusted to a temperature between 200°C and 500°C. 3 liters of cooling water containing a calcium hardness between 60 mg / L and 120 mg / L, and an iron oxide concentration between 0.1 mg / L and 40.0 mg / L, were placed inside the beaker. The cooling water in the beaker was continuously stirred at 500 rpm using a stirrer throughout the test. After immersing each nozzle tip in this cooling water for a certain period of time, it was removed at a lifting speed of 1.0 m / sec and allowed to dry completely outside the beaker for a certain period of time. This constituted one cycle, and this was repeated 150 times. The amount of material loss was evaluated by observing the nozzle tip cross-section with a scanning electron microscope (SEM). For Example 1, Comparative Example 2, and Comparative Example 3, the evaluation was based on the difference in average coating thickness before and after the accelerated testing. For Comparative Example 1, the thickness of the base material lost before and after the accelerated testing was measured. Similar to the hardness measurement, the measurement position was selected from any point in the central part of the inner surface of the nozzle tip, between the nozzle discharge hole and the opening on the opposite side. Ten measurements were taken randomly within a 200 μm × 200 μm field of view, and the average value was used.

[0026] [result] Table 1 shows the type of coating, hardness, and amount of wall thickness reduction.

[0027] [Table 1] [Explanation of symbols]

[0028] 10 Water-cooling spray nozzles 11 Mixer 12 Conduit 13. Nozzle tip (tip component) 14 Nozzle discharge holes 15 Coating

Claims

1. A spray nozzle for water cooling, A water-cooled spray nozzle, wherein at least a portion of the inner surface of the nozzle discharge hole is coated with a Ni-P alloy to a thickness of 22.48 μm to 50 μm, and the Vickers hardness of the coating is 1089 Hv to 1300 Hv.

2. A tip component for a spray nozzle, A tip component for a spray nozzle, wherein at least a portion of the inner surface of the nozzle discharge hole is coated with a Ni-P alloy to a thickness of 22.48 μm to 50 μm, and the Vickers hardness of the coating is 1089 Hv to 1300 Hv.

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