JPH0428782B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention is applicable to molten metals such as hot metal and molten steel,
Or, it relates to a method of forming a coating layer on the surface of a member such as a slag scraper that comes into direct contact with slag during production and smelting, so that the molten metal and slag will not be fused. <Conventional technology> Not only in the manufacturing and refining of steel, but also in the manufacturing and refining of all metals, the slag produced there is scraped out,
Alternatively, methods of removing it by other means are often adopted. If we take the steel industry as an example and explain it in more detail, for example, JP-A-59-13009, JP-A-61-17895, JP-A-58-192959, or JP-A-58-
As disclosed in Japanese Patent No. 155600, it is a well-known method to remove slag generated during hot metal pretreatment by scraping or blowing. In such a slag removal device, the parts that come into direct contact with slag and hot metal repeatedly come into contact with the slag and slag, which causes the pig iron and slag to fuse and accumulate, making it difficult to scrape out the slag. For this reason, it was necessary to remove this fused/deposited material using a pneumatic hammer or the like after each charge. In addition, the contact parts were damaged by melting due to the fusion of hot metal and slag, and the lifespan of the scraper plate was only a few charges.
This work of removing deposits and replacing the scraping plate for each charge involved a lot of labor and cost. <Problems to be Solved by the Invention> The purpose of the present invention is to provide a method for forming a coating layer on the surface of a steel member that comes into contact with molten metal or slag so that the metal or slag does not adhere to the surface. be. <Means for solving the problems> The above object of the present invention can be achieved by adopting the following means. In other words, Cr17 is applied to the surface of steel members that come into contact with molten metal or slag.
~80 wt%, Al2~10 wt%, balance essentially Fe
A method for forming a coating layer for preventing adhesion of metal and slag, characterized by forming a _sprayed layer of an _alloy consisting of: In this case, if the surface roughness of the sprayed layer is made below 20S before oxidation,
The peelability of the Al ₂ O ₃ film can be obtained even more effectively. <Function> The present invention will be described in detail below. In Fe-Cr-Al alloys, Cr is
It works to reduce the oxidation rate of this type of alloy by producing Cr ₂ O ₃ , and its effect becomes noticeable at 17% by weight or more. However, when the amount of Cr exceeds 80% by weight, the difference in coefficient of thermal expansion between the sprayed coating layer and the steel member becomes large, and the thermal sprayed coating layer begins to peel off during thermal oxidation treatment. Therefore, the Cr amount is 17 to 80 by weight.
limited to %. Al has a greater affinity for oxygen than Cr, and is selectively oxidized to produce Al ₂ O _3. However, if it is less than 2% by weight, it exists as an internal oxide, so an Al ₂ O ₃ based film is not formed on the surface of the coating layer. cannot be formed. If the amount of Al is 2% by weight or more, a uniform Al ₂ O ₃ film will be formed, but if it exceeds 10% by weight, the coating layer will become brittle and cracks or peels will occur in the coating layer during heating and oxidation treatment. Therefore, the amount of Al is limited to 2 to 10% by weight. The Al ₂ O ₃ film that forms on Fe-Cr-Al alloys with the above-mentioned composition range plays the role of an oxidation-resistant protective film, and has low reactivity (wettability) to molten metal and slag, making it difficult to fuse. It's difficult. Also, even if it is fused or mechanically attached,
If the thickness of the Al ₂ O ₃ based film is 1 μm or more, this
The Al ₂ O ₃ based film is weak against thermal shock and mechanical shock and easily peels off, so it can be easily removed along with deposits of fused or attached metal and slag. If thermal spraying is carried out in the atmosphere, an Al ₂ O ₃ based film will exist on the surface of the coating layer, but the thickness of this film is less than 1 μm, which is insufficient to achieve the above-mentioned effect. Therefore
In order to form an Al ₂ O ₃ film with a thickness of 1 μm or more, a thermal oxidation treatment (held at a temperature of 500° C. or higher for 1 minute in an atmosphere containing oxygen) is essential. In addition, in order to prevent metal and slag from fusion, it is effective to reduce the surface roughness of the coating layer as much as possible to reduce the contact area with the metal and slag. The above by doing the following
The peeling action of the Al ₂ O ₃ based film is further enhanced. Furthermore, it was confirmed that the thickness of the thermal spray coating layer is preferably 100 μm or more in order to continuously exhibit the effects shown in the table. However, although it is also influenced by the shape of the object to be thermally sprayed, making it too thick will deteriorate the peeling resistance of the thermal spray coating layer itself, so it is better to make it 1000 μm or less. As mentioned above, the steel parts on which the Al ₂ O ₃ film is formed on the surface by the method of the present invention are difficult to react with molten metal and slag, and even if they are attached, the Al ₂ O ₃ film itself is free from the deposits of those deposits. It peels off with
The flaking is not all of the Al ₂ O ₃ film.
The part of the Al ₂ O ₃ film that is close to the base remains, which maintains its reactivity with molten metal and slag, and with subsequent use, the surface is oxidized again and a new Al ₂ O ₃ film is formed. , which is repeated as long as the sprayed layer exists, so the above-mentioned effect continues for a long time. <Example> Examples will be described below. The table shows that hot metal transported from the pig iron manufacturing process at a steel manufacturing plant is desiliconized, then transferred to a hot metal ladle, and in order to remove P and S, the desiliconization slag in the hot metal ladle is removed. Cold Nos. 5 to 8 to which the present invention was applied to cold slag scrapers (made of SS material) and Comparative Examples Nos. 1 to 4,
Nos. 9 to 11 are shown.

【table】

[Table] Next, the embodiment shown in Fig. 1a and b shows the normal lifespan of 30 charges [340 tons-] in hot metal pretreatment equipment.
This is an example of application to a mild steel internal air-cooled slag scraping board 7 with pig/charge and slag amount: 12 tons/charge.
The front wall 7a, rear wall 7b, and side wall 7d of this slag scraping board 7
% by weight on the lower half of each surface, including the slag contact surface.
After forming a coating layer C with a thickness of 300 μm by flame spraying an alloy consisting of 26% Cr, 6% Al, and the remainder Fe, the coating layer C was processed to have a surface roughness of 20S or less, and When the coating layer C of plate 7 was heated and oxidized at 1200°C for 1 minute to form a 4 μm Al ₂ O ₃ based film, it showed a lifespan of 85 charges, and the base metal
The natural fall rate of slag deposits was 70%. Figures 1a and 1b are a front view and a side view of the slag scraping board 7. The slag scraping board 7 consists of a front wall 7a, a rear wall 7b, both side walls 7c, 7d, and an upper wall 7e, both of which have flat surfaces, and the reinforcing member 4 is attached to each of the walls to prevent contact with the slag. It is provided inside the formed V-shaped cooling chamber. Also, the air for internal cooling is
The joint arm 5 with the slag remover is designed to cool the slag efficiently.
The air passes through the supply hole 6, cools the internal reinforcing member 4 and the slag scraping plate 7, and is discharged from the exhaust hole 8. In the figure, 9 indicates a hot metal ladle, and 10 indicates a slag. <Effects of the Invention> As described above, the method of the present invention is a simple method of thermal spraying → oxidation treatment, and the product obtained by this method has Al ₂ which is difficult to react with molten metal and slag. Since it has an O ₃ film, it will not be corroded by those metals or slags, and even if those metals or slags were to adhere, the Al ₂ O ₃ film itself would easily peel off. It peels off with deposits attached, and as a result, the deposits disappear, which leads to a reduction in the work of removing deposits from this type of steel member and a longer life.

[Brief explanation of drawings]

FIG. 1 is a front view a and a side view b showing a slag scraping plate of a slag scraper for a hot metal ladle to which an embodiment of the present invention is applied.

Claims (1)

[Claims] 1. Forming a sprayed layer of an alloy consisting of 17 to 80% by weight of Cr, 2 to 10% by weight of Al, and the remainder substantially Fe on the surface of a steel member that comes into contact with molten metal or slag, A heating oxidation treatment is applied to the surface of the sprayed layer,
A method for forming a coating layer for preventing adhesion of metal and slag, characterized by forming an Al ₂ O ₃ based coating. 2. The method of forming a metal and slag adhesion prevention coating layer according to claim 1, characterized in that the steel member that comes into contact with the molten metal or slag is a slag scraper for removing slag. 3. A sprayed layer of an alloy consisting of 17 to 80% by weight of Cr, 2 to 10% by weight of Al, and the remainder substantially Fe is formed on the surface of a steel member that comes into contact with molten metal or slag, and the surface roughness of the sprayed layer is improved. A coating layer for preventing adhesion of metal and slag, characterized in that the coating layer is processed to have a degree of oxidation of 20S or less, and then a thermal oxidation treatment is applied to the surface of the sprayed layer after the processing to form an Al ₂ O ₃ based coating. Formation method. 4. The method of forming a metal and slag adhesion prevention coating layer according to claim 3, wherein the steel member that comes into contact with the molten metal or slag is a slag scraper for removing slag.