JP7526575B2 - Water-cooling spray nozzles, spray nozzle tip components - Google Patents

Description

The present invention relates to a water-cooling spray nozzle used in the production of cast slabs, steel plates, steel pipes, etc.

For example, cooling of materials during the manufacturing process of slabs, steel billets, steel plates, steel pipes, etc. is important from the viewpoint of obtaining appropriate surface properties and structure, as well as ensuring homogenization and stable operation.

To achieve this cooling, a water-cooling spray nozzle is used as a means of supplying cooling water to the material. Water-cooling spray nozzles spray cooling water toward the material from a thin nozzle outlet, so the nozzle outlet is particularly susceptible to clogging. If clogging occurs, the material cannot be cooled, which affects the quality mentioned above.

Patent document 1 describes the application of a metal surface coating to the tip of a spray nozzle, specifically disclosing a surface coating made of Cr and Ni. This is said to prevent clogging of the spray nozzle.

JP 2008-114244 A

However, it cannot be said that conventional coatings are sufficient to prevent clogging.

The present invention aims to provide a water-cooling spray nozzle that can more reliably prevent clogging. It also provides a tip member for this purpose.

One aspect of the present invention is a water-cooling spray nozzle or a tip member therefor, in which at least a portion of the inner surface of the nozzle discharge hole is coated with Au or an Au alloy.

The Au alloy may contain, by mass%, at least one selected from K 0.01% to 1.0%, C 0.01% to 0.5%, H 0.01% to 1.0%, O 0.01% to 1.0%, N 0.01% to 1.0%, Co 0.1% to 8.0%, Ni 0.1% to 8.0%, Cu 0.001% to 8.0%, and Fe 0.001% to 8.0%, with the remainder being Au and unavoidable impurities.

The surface roughness of the coating may be 0.01 μm or more and 10 μm or less in maximum height Rz.

The present invention makes it possible to more reliably prevent clogging of the spray nozzle.

1 is a diagram showing a configuration of a water-cooling spray nozzle 10. FIG. FIG. 2 is a diagram focusing on the vicinity of the nozzle tip 13 in FIG. 1 . 1A is a diagram showing the appearance of a nozzle tip 13, and FIG. 1B is a cross-sectional view of the nozzle tip 13. FIG. 3B, focusing on the vicinity of the nozzle discharge hole 14. FIG.

Figure 1 shows the structure of one embodiment of a water-cooling spray nozzle 10. This water-cooling spray nozzle 10 is a spray nozzle for secondary cooling of a cast piece in a continuous casting process. However, this is an example, and the same can be said for water-cooling spray nozzles used for cooling in other processes. Examples of other processes include blooming of cast pieces, a steel section rolling process, and a hot rolling process.

The water-cooling spray nozzle 10 is configured to include a mixer 11 having a hollow portion therein, a conduit 12, and a nozzle tip 13 serving as a tip member.
As can be seen from Fig. 1, an air pipe 1, which is an air passage, and a water pipe 2, which is a cooling water passage, are connected to a mixer 11, and the air and the cooling water are mixed in the hollow portion. In addition, one end of a conduit 12 is connected to the mixer 11, and a nozzle tip 13 is disposed at the other end of the conduit 12.
Therefore, the air supplied through the air pipe 1 and the cooling water supplied through the water pipe 2 are mixed in the hollow part of the mixer 11, flow through the conduit 12 to reach the nozzle tip 13, and are sprayed toward the material (the object to be cooled) from the nozzle discharge hole 14 provided in the nozzle tip 13.

Fig. 2 shows an enlarged view of the nozzle tip 13 in Fig. 1. Fig. 3(a) shows an external view of the nozzle tip 13, including a plan view and a right side view, Fig. 3(b) shows a cross-sectional view taken along line A-A, and Fig. 4 shows an enlarged view of the nozzle discharge hole 14 in Fig. 3(b).
2 to 4, the nozzle tip 13 functions as a tip member for a spray nozzle, has a hexagonal cylindrical outer shape, has a bottom 13a at one end, and is open at the other end. A slit-shaped hole is provided in the bottom 13a so as to penetrate the bottom 13a, and this hole serves as the nozzle discharge hole 14. In this embodiment, the nozzle discharge hole 14 is a slit-shaped hole, but is not limited to this and may have any necessary shape.
On the other hand, the nozzle tip 13 is attached to the conduit 12 by inserting the end of the conduit 12 into the nozzle tip 13 from the other open end and fixing it therein.
In this embodiment, the conduit 12 and the nozzle tip 13 are fixed by different members, but the present invention is not limited to this and the conduit and the nozzle tip may be integral and indistinguishable. In this case, a nozzle discharge hole is provided at the tip of the conduit.

4, the nozzle tip 13 is at least partially covered with a 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 discharge hole 14, the outer surface 13b and inner surface 13c of the bottom 13a of the nozzle tip 13, and particularly on the peripheral portion of the nozzle discharge hole 14.
Since clogging of the spray nozzle is often caused by clogging of the nozzle discharge hole 14, the clogging can be suppressed by forming the coating 15 on the inner surface of the nozzle discharge hole 14 and around it.
However, this does not prevent the coating from being formed on the entire nozzle tip 13 or on parts other than the above. For example, from the viewpoint of film formation, it may be more efficient to form a coating on the entire nozzle tip 13.

The coating 15 is made of Au or an Au alloy, which can more reliably prevent clogging of the spray nozzle. The reason for this is not entirely clear, but it can be considered as follows.
That is, the coating with Au or Au alloy suppresses the corrosion of the coated portion and suppresses the surface from becoming rough (roughened) due to corrosion. When the surface becomes significantly rough, foreign matter in the cooling water becomes more likely to be caught on the surface and accumulate. In addition, when calcium components in the cooling water precipitate on the roughened surface, the precipitated calcium components are more difficult to peel off due to the anchor effect compared to a smooth surface. Furthermore, since the precipitated calcium components are more hydrophilic than metal surfaces, once precipitated, they tend to capture foreign matter at an accelerated rate.
In this way, regardless of the type of cause, surface roughening promotes the accumulation of foreign matter on the surface, which leads to clogging of the spray nozzle. In contrast, a coating of Au or an Au alloy prevents such surface roughening and prevents the accumulation of foreign matter, thereby preventing clogging.

When the coating is made of an Au alloy, it can contain at least one of the following components other than Au and unavoidable impurities:

The K content may be 0.01% by mass or more and 1.0% by mass or less. By making the content 0.01% by mass or more, the strength of the coating can be improved. On the other hand, if the content exceeds 1.0% by mass, there is a risk that the coating may crack.
The C content may be 0.01% by mass or more and 0.5% by mass or less. By making the C content 0.01% by mass or more, the abrasion resistance of the coating can be improved. On the other hand, if the C content exceeds 0.5% by mass, there is a risk that the coating may crack.
The H content may be 0.01% by mass or more and 1.0% by mass or less. By making the H content 0.01% by mass or more, the strength of the coating can be improved. On the other hand, if the H content exceeds 1.0% by mass, the coating tends to become brittle, which may cause cracking of the coating.
The O content may be 0.01% by mass or more and 1.0% by mass or less. By making the O content 0.01% by mass or more, the strength of the coating can be improved. On the other hand, if the O content exceeds 1.0% by mass, there is a risk that the coating may crack.
The N content may be 0.01% by mass or more and 1.0% by mass or less. By making the N content 0.01% by mass or more, the abrasion resistance of the coating can be improved. On the other hand, if the N content exceeds 1.0% by mass, there is a risk that the coating may crack.
The Co content may be 0.1% by mass or more and 8.0% by mass or less. By making the Co content 0.1% by mass or more, the hardness of the coating can be improved. On the other hand, if the Co content exceeds 8.0% by mass, there is a risk that the coating may crack.
The Ni content may be 0.1% by mass or more and 8.0% by mass or less. By making the Ni content 0.1% by mass or more, the hardness of the coating can be improved. On the other hand, if the Ni content exceeds 8.0% by mass, there is a risk that the coating may crack.
The Cu content may be 0.001% by mass or more and 8.0% by mass or less. If the Cu content is 0.001% by mass or more, the hardness of the coating can be improved. On the other hand, if the Cu content exceeds 8.0% by mass, the coating may crack.
The Fe content may be 0.001% by mass or more and 8.0% by mass or less. If the Fe content is 0.001% by mass or more, the hardness of the coating can be improved. On the other hand, if the Fe content exceeds 8.0% by mass, the coating may crack.

The surface roughness of the coating is preferably 0.01 μm or more and 10 μm or less in maximum height Rz (JIS B 0601-2001). By keeping the surface roughness within this range, clogging of the spray nozzle can be more effectively suppressed.

There are no particular limitations on the thickness of the coating, but if the coating is too thick, there is a high possibility of cracks occurring in the coating during film formation, so the thickness is preferably 50 μm or less. Also, if the coating is too thin, the expected effects of the coating will be lost and the lifespan of the coating will be shortened due to wear, so a thickness of 10 μm or more is preferable in view of the need for a thickness that can guarantee this.

The base material of the nozzle tip 13 is not particularly limited, but is preferably stainless steel from the viewpoint of corrosion resistance, and more preferably has high machinability.
When the surface roughness Rz of the coating 15 is set in the above-mentioned preferred range, it is preferable to set the surface roughness Rz of the base material at the portion where the coating 15 is to be disposed smaller than the desired surface roughness of the coating, which makes it easier to adjust the surface roughness of the coating to the desired value.

The nozzle tip may be an integral structure, or may be made up of multiple separate components that are later assembled. The latter is preferred from the viewpoint of forming the coating 15.

The components of the water-cooling spray nozzle 10 other than the coating 15 can be produced by a conventionally known method. The method for forming (depositing) the coating 15 is also not particularly limited, and examples of the method include electrolytic plating and electroless plating.
"Electrolytic plating" refers to a method in which an electric current is applied from the outside, and metal cations are reacted with electrons by electrolysis to form a metal, which is then deposited on the surface of the plated body that forms the cathode, forming a coating. On the other hand, "electroless plating" refers to a method in which metal ions in a solution are reduced and deposited using a chemical reducing agent, without applying an electric current from the outside, to form a coating on the surface of the plated body.

[Test pieces]
A nozzle tip for testing was made according to the shape shown in FIG. 3. The base material was stainless steel (SUS303). A nozzle tip was made by coating a base material having a nozzle tip shape by electroless plating (Example 1, Reference Example 2, Example 3). More specifically, a plating solution was prepared at 70° C., containing 8 g/L of KAu(CN)2 as a gold salt, 200 g/L of sodium citrate as a buffer salt, and adjusted to a pH range of 6 to 7. The plating solution was stirred using a magnetic stirrer while the base material having a nozzle tip shape was placed in the plating solution, and plating was performed. In Example 1 and Reference Example 2, the thickness of the coating was adjusted by changing the immersion time in the plating solution. For Example 3, a plating solution containing cobalt citrate was used. Therefore, the coating in Example 3 is an Au alloy containing Co.
As Comparative Example 1, a nozzle tip without any coating was prepared.
Furthermore, a nozzle tip having a coating of Ni alloy was prepared as Comparative Example 2. This nozzle tip was obtained by forming a film of Ni-P alloy by electroless plating on a base material having the same shape and material as the Example. Specifically, the base material having the nozzle tip shape was immersed in a plating solution containing 0.2 mol/L of nickel sulfate, 0.2 mol/L of citric acid, 0.5 mol/L of ammonium sulfate, and 0.15 mol/L of sodium hypophosphite. The pH of the plating solution was adjusted to 10.0 with NaOH.

[test]
An accelerated test was carried out by repeated wet-dry cycles. Specifically, a beaker with a lid was placed in a dryer adjusted to a temperature range of 200° C. to 500° C., and 3 L of cooling water with a calcium hardness range of 60 mg/L to 120 mg/L was poured into the beaker. The nozzle tip of each example was immersed in the cooling water for a certain period of time, then taken out for a certain period of time and completely dried. This cycle was repeated 150 times.

[Evaluation item]
<Surface roughness>
The surface roughness was evaluated by measuring the maximum height Rz (JIS B 0601-2001) before and after the test. The maximum height Rz was expressed as the sum of the maximum peak height and the maximum valley depth in a reference length of 50 μm in the horizontal direction in the cross section. The roughness curve was obtained by observing a cross section of a part of the nozzle tip using a SEM. The position for observing the cross section was an arbitrary position in the central part between the nozzle discharge hole and the opening on the opposite side of the inner surface of the nozzle tip.

<Thickness of Adherent Material>
The thickness of the deposits was evaluated. It is believed that the smaller the thickness of the deposits, the less likely the spray nozzle will become clogged.
The thickness of the deposit was measured by measuring the film thickness by image analysis. The surface on the outermost surface of the nozzle tip where O (oxygen) was detected by EDS (energy dispersive X-ray spectrometry) analysis was defined as scale (deposit). The thickness was obtained by averaging the thickness in a field of view of 50 μm at 270 data points using image analysis software (WinROOF ver. 7.4, manufactured by Mitani Shoji Co., Ltd.). The measurement position was the same as the surface roughness measurement position.

[result]
Table 1 shows the type of coating, the thickness, and the evaluation results.

As can be seen from a comparison of Examples 1, 2, and 3 with Comparative Examples 1 and 2 in Table 1, it is understood that the presence of the Au coating can suppress the thickness of the deposits.
It is also clear that smaller surface roughness of an Au coating results in thinner deposits, and that an Au alloy coating can produce less deposits than an Au coating.

10 Water-cooling spray nozzle 11 Mixer 12 Conduit 13 Nozzle tip (tip member)
14 Nozzle discharge hole 15 Coating

Claims (4)

A water-cooling spray nozzle that ejects cooling water to cool steel ,
a coating of Au or an Au alloy is formed on at least a part of the inner surface of the nozzle ejection hole ;
The surface roughness of the coating is 0.01 μm or more and 0.68 μm or less in terms of maximum height Rz.
Water cooling spray nozzle. The water-cooled spray nozzle according to claim 1, wherein the Au alloy contains, in mass%, at least one selected from K of 0.01 mass% to 1.0 mass%, C of 0.01 mass% to 0.5 mass%, H of 0.01 mass% to 1.0 mass%, O of 0.01 mass% to 1.0 mass%, N of 0.01 mass% to 1.0 mass%, Co of 0.1 mass% to 8.0 mass%, Ni of 0.1 mass% to 8.0 mass%, Cu of 0.001 mass% to 8.0 mass%, and Fe of 0.001 mass% to 8.0 mass%, with the remainder being Au and unavoidable impurities. A tip member for a water-cooling spray nozzle that ejects cooling water for cooling steel , comprising:
a coating of Au or an Au alloy is formed on at least a part of the inner surface of the nozzle ejection hole;
The surface roughness of the coating is 0.01 μm or more and 0.68 μm or less in terms of maximum height Rz.
Tip component for spray nozzles. 4. The spray nozzle tip member according to claim 3, wherein the Au alloy contains, in mass%, at least one selected from K of 0.01 mass% to 1.0 mass%, C of 0.01 mass% to 0.5 mass%, H of 0.01 mass% to 1.0 mass%, O of 0.01 mass% to 1.0 mass%, N of 0.01 mass% to 1.0 mass%, Co of 0.1 mass% to 8.0 mass%, Ni of 0.1 mass% to 8.0 mass%, Cu of 0.001 mass% to 8.0 mass%, and Fe of 0.001 mass% to 8.0 mass%, with the remainder being Au and unavoidable impurities.

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