Plate refractory for slide valve

Abstract

To provide a plate refractory for a slide valve capable of suppressing wear at an outer peripheral edge of a sliding surface by preventing oxidation of the plate refractory in a low temperature region.SOLUTION: A plate refractory for a slide valve mainly composed of at least one of magnesia and spinel contains metal zinc, a carbon raw material, and an additive containing at least one of a metal raw material other than the metal zinc and a non-oxide, in which a content of the carbon raw material is more than 0% by weight and less than 10% by weight, a content of the additive is more than 0% by weight and less than 10% by weight, and the plate refractory is fired at 825 °C or more and less than 1300 °C in a non-oxidizing atmosphere.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a refractory plate for a slide valve. [Background technology]

[0002] A slide valve device is widely used as an outlet for discharging molten metal from a vessel such as a ladle or a tundish. The slide valve device includes a plurality of slide valve refractory plates (hereinafter also referred to as plate refractories) that are slidable relative to one another, and the flow rate of the molten metal is controlled by adjusting the relative positions of the through-holes formed in each of the plate refractories.

[0003] Plate refractories are subjected to physical effects such as sudden thermal shock and abrasion caused by molten metal, as well as chemical erosion caused by molten metal and molten slag, etc. Therefore, plate refractories are required to have various properties such as spalling resistance, abrasion resistance, corrosion resistance, and oxidation resistance, and various efforts are being made to improve the durability of plate refractories.

[0004] Patent Document 1 describes a carbon-containing refractory containing a refractory raw material such as alumina or magnesia, a carbon raw material, a metal raw material, and lanthanum boride. When the lanthanum boride oxidizes on the surface of the refractory, the surface of the refractory is covered with B2O3, improving the oxidation resistance.

[0005] Patent Document 2 describes a basic plate refractory that has improved durability by improving the spalling resistance of the plate refractory. The plate refractory contains a metal raw material to improve the strength of the refractory structure, and boron carbide to improve the oxidation resistance.

[0006] Patent Document 3 describes a plate refractory material that contains a refractory material raw material such as alumina or magnesia or a carbon raw material, a low-melting-point metal raw material, and an organic binder, and is fired at 800°C or less. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 7-172908 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-82653 [Patent Document 3] Japanese Patent Application Publication No. 56-140064 Summary of the Invention [Problem to be solved by the invention]

[0008] In recent years, the use of basic refractory plates for flow control of calcium-treated steels and special steels has been increasing, and high durability is required for these refractory plates. However, when refractory plates are used multiple times, oxidation of the carbon raw material occurs in the low-temperature range at the outer edge of the sliding surface, which is away from the high-temperature through-hole portion, causing the refractory structure to become embrittled. As a result, wear at the outer edge limits the durability of the refractory plates.

[0009] The carbon-containing refractory described in Patent Document 1 uses lanthanum boride to prevent oxidation, but there is a risk of increasing raw material costs. Furthermore, although Al, Si, Mg, Zn, etc. are exemplified as metal raw materials, the contribution of metal raw materials other than Al to oxidation resistance is not disclosed.

[0010] The plate refractory material described in Patent Document 2 lists Al, Si, Mg, etc. as examples of metal raw materials, but is not intended to prevent oxidation of carbon raw materials in low temperature ranges.

[0011] Furthermore, the plate refractory described in Patent Document 3 discloses test results for a basic plate refractory when Al is added as a metal raw material, but does not disclose any metal raw materials other than Al.

[0012] Therefore, there is a need to develop a plate refractory for a slide valve that can suppress oxidation of the plate refractory in a low temperature range and reduce wear on the outer periphery of the sliding surface. [Means for solving the problem]

[0013] The refractory plate for a slide valve according to the present invention is a refractory plate for a slide valve mainly composed of at least one of magnesia and spinel, and comprises metallic zinc, a carbon raw material, and an additive containing at least one of a metallic raw material other than metallic zinc and a non-oxide, wherein the carbon raw material content is more than 0% by weight and less than 10% by weight, and the additive content is more than 0% by weight and less than 10% by weight, and the refractory plate for a slide valve is fired at 825°C or more and less than 1300°C in a non-oxidizing atmosphere.

[0014] According to this configuration, metallic zinc, a low-melting-point metal, melted during firing is diffused into the refractory structure, strengthening the bonds of the refractory structure and sealing pores with the metallic zinc. Furthermore, the molten metallic zinc unevenly distributed in the structure forms a protective layer on the surface of the plate refractory, thereby suppressing oxidation of the carbon raw material in the plate refractory at low temperatures.

[0015] In one aspect of the refractory plate material for a slide valve according to the present invention, the content of the metal zinc is preferably 1% by weight or more and 5% by weight or less.

[0016] This configuration makes it possible to improve the oxidation resistance of the plate refractory without increasing the porosity of the plate refractory, thereby providing a plate refractory that has oxidation resistance while maintaining its corrosion resistance.

[0017] In one embodiment, the refractory plate for a slide valve according to the present invention preferably contains 30% by weight or less of refractory raw materials excluding the magnesia and the spinel.

[0018] This configuration makes it possible to impart other properties to the refractory plate for the slide valve, such as increasing the strength.

[0019] In one aspect of the refractory plate for a slide valve according to the present invention, the additive preferably includes at least one selected from the group consisting of metallic aluminum, an aluminum-silicon alloy, metallic silicon, silicon carbide, and silicon nitride.

[0020] According to this configuration, the additives can strengthen the bonding of the refractory structure, and can prevent oxidation of the plate refractory in the intermediate to high temperature range, making it possible to use the plate refractory for various steel types.

[0021] Further features and advantages of the present invention will become more apparent from the following description of illustrative and non-limiting embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0022] An embodiment of a plate refractory for a slide valve according to the present invention will be described. An example in which the plate refractory according to the present invention is applied to a plate refractory used in a slide valve device will be described below. However, the present invention is not limited to the following embodiment, and various modifications are possible within the scope of the gist thereof.

[0023] The plate refractory according to the present invention is mainly composed of at least one of magnesia and spinel. "Mainly composed" means that the content of magnesia and / or spinel in the plate refractory is 50% by weight or more, preferably 60% by weight or more, and more preferably 70% by weight or more. Only one of magnesia and spinel may be contained, and the ratio of magnesia to spinel may be set arbitrarily between 0-10:10-0. By mainly comprising at least one of magnesia and spinel in the plate refractory, it is possible to improve the corrosion resistance of steel types such as Ca-treated steel and high-oxygen steel. Magnesia and spinel having any particle size can be used.

[0024] The plate refractory according to the present invention may contain 30% by weight or less of refractory raw materials other than magnesia and spinel (for example, alumina, mullite, zirconia, composite raw materials thereof, etc.). Various known refractory raw materials can be used for magnesia, spinel, and other refractory raw materials.

[0025] Furthermore, the plate refractory according to the present invention contains more than 0% by weight and less than 10% by weight of carbon raw material. When the carbon raw material content exceeds 0% by weight, wettability and spalling resistance to molten metal are ensured. When the carbon raw material content is less than 10% by weight, it is easy to achieve the strength required for use as a plate refractory for a slide valve. Therefore, the carbon raw material content is preferably more than 0% by weight and less than 10% by weight, and more preferably 1% by weight or more and less than 10% by weight.

[0026] Examples of carbon raw materials that can be used include expanded graphite, pitch, and carbon black. The carbon raw material may be a single type or a mixture of multiple types. Such carbon raw materials are easily oxidized in the environment in which the plate refractory is used. A plate refractory has through-holes through which molten metal flows and a sliding surface that slides against other plate refractories. There is a temperature difference between the periphery of the through-holes that contact the molten metal and the outer periphery of the sliding surface. Therefore, the outer periphery of the sliding surface of the plate refractory reaches a temperature of, for example, about 400°C to 600°C, making the carbon raw material susceptible to oxidation in the low-temperature range (400°C to 600°C). Oxidation of the carbon raw material embrittles the refractory structure and causes wear on the sliding surface, limiting the number of times the plate refractory can be used.

[0027] Therefore, the plate refractory according to the present invention contains metallic zinc to suppress oxidation of the carbon raw material in the low-temperature range. Because metallic zinc has a lower melting point than the additives described below, it melts during firing of the plate refractory and forms new bonds in the structure during use. It may also react with other metals to form alloys. This improves the strength of the plate refractory, seals the pores in the plate refractory, and forms a protective layer on the surface of the refractory, thereby suppressing oxidation of the carbon raw material.

[0028] The content of metallic zinc is preferably 1% by weight or more and 5% by weight or less. If the content of metallic zinc is 1% by weight or more, oxidation of the plate refractory can be efficiently suppressed. Furthermore, if the content of metallic zinc is 5% by weight or less, the porosity of the plate refractory is less likely to increase. The particle diameter of the metallic zinc is preferably 0.3 mm or less. This is because if the particle diameter of the metallic zinc exceeds 0.3 mm, the metallic zinc is likely to segregate within the structure.

[0029] The plate refractory according to the present invention also contains a metal raw material other than metallic zinc and an additive containing at least one non-oxide. Examples of the metal raw material other than metallic zinc include metallic aluminum, aluminum-silicon alloys, and metallic silicon, and examples of the non-oxide include silicon carbide and silicon nitride. The inclusion of the additive in the plate refractory improves the strength of the refractory structure. These additives also act as antioxidants in the intermediate temperature range (600°C to 1000°C) to high temperature range (1000°C or higher).

[0030] The content of the additive is preferably more than 0 wt % and less than 10 wt %. When the content of the additive is more than 0 wt %, the refractory structure is strengthened, making the oxidation of the carbide structure less likely to occur, and when the content of the additive is less than 10 wt %, the corrosion resistance, hydration resistance, and strength can be maintained at the same level as when no additive is added.

[0031] The plate refractory is formed by kneading the above-mentioned raw materials with a binder such as a phenolic resin in the predetermined mixing ratio, forming the mixture, and drying it. The forming of the plate refractory may be performed by a known method such as a friction press method or a hydraulic press method.

[0032] After being formed, the plate refractory is fired in a non-oxidizing atmosphere at 825°C or higher and lower than 1300°C. At a firing temperature of 825°C or higher, the metallic zinc and additives are sufficiently melted, strengthening the bonds in the refractory structure. At a firing temperature lower than 1300°C, the temperature in the refractory structure does not exceed the melting point or boiling point of the metallic zinc, preventing the loss of the metallic zinc. Therefore, by setting the firing temperature at 825°C or higher and lower than 1300°C, it is possible to melt the metallic zinc while maintaining the strength of the plate refractory.

[0033] When metallic aluminum is used as an additive, the molten metallic zinc and metallic aluminum may react with each other during use to form an alloy. This alloying strengthens the bonding of the refractory structure in the low temperature range, thereby suppressing oxidation of the carbon raw material and wear of the sliding surfaces.

[0034] The above-mentioned plate refractory material can be applied to the entire plate refractory material for a slide valve, but can also be applied to only a part of the plate, for example, only the vicinity of the outer periphery of the sliding surface.

[0035] The present invention will be further described below with reference to examples, but the present invention is not limited to these examples.

[0036] Plate refractory molded bodies were prepared using the blending ratios shown in Tables 1 to 4 below, and fired in a reducing atmosphere, which is a non-oxidizing atmosphere, at the firing temperatures shown in Tables 1 to 4. One or more of metallic aluminum (Al), metallic silicon (Si), silicon carbide (SiC), and silicon nitride (Si3N4) were used as additives. Furthermore, where applicable, alumina (Al2O3) was added as an additional refractory raw material excluding magnesia and spinel. The obtained specimens were evaluated for oxidation resistance and corrosion resistance. When preparing the plate refractory molded bodies, 3% by weight of phenolic resin was used as a binder, and a hydraulic press was used for molding.

[0037] Oxidation resistance was evaluated by heating a 35mm wide x 35mm high x 35mm thick specimen in an air atmosphere in an electric furnace to 600°C, then holding it for three hours. The oxidized specimen was then cut and the thickness of the oxide layer measured. The oxide layer was identified by visually inspecting the white discoloration of the specimen caused by oxidation of the carbon raw material. Oxidation resistance was evaluated by assigning an "A" grade if the oxide layer thickness was 3.0mm or less, a "B" grade if the oxide layer thickness was greater than 3.0mm and less than 3.5mm, a "C" grade if the oxide layer thickness was greater than 3.5mm and less than 4.0mm, and a "D" grade if the oxide layer thickness was greater than 4mm.

[0038] Corrosion resistance evaluation was performed using the rotating crucible method with specimens measuring 80 mm wide, 60 mm high, and 35 mm thick. Using an erosion agent with a CaO / SiO2 weight ratio of 2, the specimens were heated with an acetylene burner at 1650°C for 5 hours. The specimens were then cut and the average thickness of the corrosion loss measured after the test was recorded as the corrosion loss. Corrosion resistance was evaluated as follows: a corrosion loss of 2.0 mm or less was assigned an "A," a corrosion loss of more than 2.0 mm but not more than 2.5 mm was assigned a "B," a corrosion loss of more than 2.5 mm but not more than 3.0 mm was assigned a "C," and a corrosion loss of more than 3.0 mm was assigned a "D." The results are shown in Tables 1 to 4.

[0039] Examples of the present invention will be described with reference to Tables 1 to 4. Tables 1 to 3 show the preparation conditions and test results of specimens for examples according to the present invention, and Table 4 shows the preparation conditions and test results of specimens for comparative examples. As shown in Table 1, Examples 1 to 3 are specimens relating to plate refractories with a metallic zinc content of 1 wt %. In all cases, the firing temperature, carbon raw material content, and additive content are within the ranges of the present invention. Compared with Comparative Examples 1 to 3 (see Table 4), which do not contain metallic zinc, both oxidation resistance and corrosion resistance were improved. [Table 1]

[0040] As shown in Table 2, Examples 4 to 8 are specimens related to plate refractories with a metal zinc content of 3% by weight. In all cases, the firing temperature, carbon raw material content, and additive content were within the ranges of the present invention, and oxidation resistance and corrosion resistance were improved compared to the comparative examples.

[0041] [Table 2]

[0042] As shown in Table 3, Examples 10 to 12 are specimens related to plate refractories with a metallic zinc content of 5 wt %. In all cases, the firing temperature, carbon raw material content, and additive content were within the ranges of the present invention, and compared to the comparative examples, the oxidation resistance and corrosion resistance were improved. All of Examples 10 to 12 were evaluated as A for oxidation resistance, indicating that they have particularly high oxidation resistance. Furthermore, Examples 10 and 12 were also evaluated as A for corrosion resistance, indicating that the addition of metallic zinc makes it possible to produce plate refractories with high corrosion resistance and high oxidation resistance.

[0043] [Table 3]

[0044] As shown in Table 4, in Comparative Examples 1 to 5, any one of the metallic zinc content, firing temperature, or carbon raw material content is outside the range of the present invention. In Comparative Examples 1 and 2, the metallic zinc content is outside the range of the present invention, so the oxidation resistance and corrosion resistance ratings are D, indicating poor oxidation resistance and corrosion resistance. In Comparative Example 3, the carbon raw material content is outside the range of the present invention, so the oxidation resistance rating is D, indicating poor oxidation resistance. In Comparative Examples 4 and 5, the firing temperature is outside the range of the present invention, so the corrosion resistance is poor. In particular, Comparative Example 4 was fired at 300°C, which does not cause the metallic zinc to melt, so the oxidation resistance was also poor.

[0045] [Table 4] [Industrial Applicability]

[0046] The present invention can be used for a refractory plate for a slide valve, which is mainly composed of at least one of magnesia and spinel.

Claims

1. A refractory plate for a slide valve mainly composed of at least one of magnesia and spinel, The method comprises: a zinc metal; a carbon raw material; and an additive containing at least one of a metal raw material other than the zinc metal and a non-oxide; The content of the carbon raw material is more than 0 wt% and less than 10 wt%, The content of the additive is more than 0 wt% and less than 10 wt%, A refractory plate for a slide valve, fired at 825°C or higher and lower than 1300°C in a non-oxidizing atmosphere.

2. 2. The refractory plate for a slide valve according to claim 1, wherein the content of said metallic zinc is 1% by weight or more and 5% by weight or less.

3. 3. The refractory plate for a slide valve according to claim 1, wherein the refractory raw materials other than the magnesia and the spinel are contained in an amount of 30% by weight or less.

4. 3. The refractory plate for a slide valve according to claim 1, wherein the additive comprises at least one selected from the group consisting of metallic aluminum, an aluminum-silicon alloy, metallic silicon, silicon carbide, and silicon nitride.

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