Method for selecting refractory for charging wall of molten metal refining vessel and molten metal refining vessel

Abstract

To provide: a method for selecting the charging wall refractories of a molten metal refining container which can select more suitable refractories by executing the evaluation of durability in a real furnace from the result of a hot bending test; and a molten metal refining container.SOLUTION: Provided is a method for selecting charging wall refractories of a molten metal refining container in which durability of refractories with respect to collision of scraps is evaluated based on size of a scrap resistance index calculated from a value of hot bending strength measured by a hot bending test and a value of breaking energy.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for selecting a refractory material for the charging wall of a molten metal refining vessel such as a converter or electric furnace, and to the molten metal refining vessel. [Background technology]

[0002] The wear pattern of refractories in molten metal refining vessels varies depending on the location where they are installed, and the rate at which they wear varies depending on the operating conditions. Therefore, it is necessary to select materials that are suited to the operating conditions for each location where they are installed. For example, in the case of sleeve bricks for tap holes, where wear is primarily caused by slag corrosion and abrasion due to the flow of molten steel, methods for predicting and selecting refractory durability are implemented based on the results of measurements of material strength and corrosion resistance tests (see Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-145754 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-47007 Summary of the Invention [Problem to be solved by the invention]

[0004] While methods for evaluating the durability of taphole sleeve bricks in advance have been proposed, no method has been proposed for evaluating the durability of refractories for charging walls in advance. For charging walls, where mechanical damage caused by scrap collisions is the main cause of wear, refractories with excellent hot strength are generally selected.

[0005] However, in actual furnaces, not only do the working surface layers suffer damage from the collision of scrap, but repeated collisions with scrap also cause cracks to develop inside the refractory, eventually causing it to peel off. For this reason, it has been difficult to evaluate durability in actual furnaces and select an appropriate refractory material solely based on hot strength.

[0006] The present invention has been made in view of the above, and aims to provide a method for selecting a refractory material for the charging wall of a molten metal refining vessel, and a molten metal refining vessel, which allows evaluation of durability in an actual furnace from the results of a hot bending test and selection of a more appropriate refractory material. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the method for selecting a refractory for a charging wall of a molten metal refining vessel according to the present invention evaluates the durability of the refractory against the collision of scrap based on the magnitude of a scrap resistance index calculated from the hot bending strength value and the fracture energy value measured by a hot bending test.

[0008] Further, in the method for selecting a refractory material for a charging wall of a molten metal refining vessel according to the present invention, the scrap resistance index is calculated by dividing the hot bending strength value σ (MPa) by the fracture energy value γ (J / m 2 ) and is calculated using the following formula (1):

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[0009] In order to solve the above-mentioned problems and achieve the object, the molten metal refining vessel of the present invention comprises a converter or an electric furnace, in which a refractory material selected by the above-mentioned method for selecting a refractory material for a charging wall of a molten metal refining vessel is installed in a portion where scrap impinges.

[0010] In order to solve the above-mentioned problems and achieve the object, the molten metal refining vessel of the present invention comprises a converter or an electric furnace, in which a refractory material having a scrap resistance index of 14 or more, calculated from the hot bending strength value and the fracture energy value measured in a hot bending test, is installed in a portion where scrap strikes.

[0011] The molten metal refining vessel according to the present invention is the vessel described above, wherein the scrap resistance index is a ratio of the hot bending strength value σ (MPa) to the fracture energy value γ (J / m 2 ) and is calculated using the following formula (1):

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[0012] The method for selecting a refractory for the charging wall of a molten metal refining vessel and the molten metal refining vessel according to the present invention takes into account not only damage to the surface of the working surface due to scrap collisions, but also the propagation of cracks into the refractory due to repeated scrap collisions. Furthermore, by using an index that takes into account the propagation of cracks into the refractory, it is possible to accurately evaluate the durability in an actual furnace in advance from the results of a hot bending test. Furthermore, the method for selecting a refractory for the charging wall of a molten metal refining vessel and the molten metal refining vessel according to the present invention allows the durability to be evaluated solely from the results of a hot bending test, thereby enabling rapid refractory selection. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 shows the results of the method for selecting a refractory material for the charging wall of a molten metal refining vessel according to the present invention, when the method was carried out using a converter. [Figure 2] FIG. 2 is a diagram showing the hot bending strength values ​​of the refractories used in the examples. [Figure 3] FIG. 3 is a diagram showing the fracture energy values ​​of the refractories used in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0014] A method for selecting a refractory material for a charging wall of a molten metal refining vessel and a molten metal refining vessel according to an embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the following embodiments, and the components in the following embodiments include those that are easily replaceable by those skilled in the art, or those that are substantially identical.

[0015] In the method for selecting a refractory material for the charging wall of a molten metal refining vessel according to the embodiment, the scrap resistance index obtained from the results of a hot bending test is used to evaluate the durability of the refractory material, as shown in the following formula (1).

[0016]

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[0017] The hot bending test can be performed using, for example, the method specified in "JIS R 2656." The test temperature for the hot bending test is preferably set to, for example, 800°C to 1500°C, in accordance with the surface temperature of the refractory when the scrap is charged.

[0018] A hot bending test is carried out under the above conditions, and the maximum bending stress at which the test piece breaks is taken as the hot bending strength σ (MPa). The higher the hot bending strength value of the refractory, the less damage to the working surface layer when scrap hits it. Adding metals such as Al and Si is known as a method for improving the hot bending strength of MgO-C bricks.

[0019] In addition, the fracture energy γ (J / m 2 ) is the energy required to generate a crack surface divided by twice the area of ​​the crack, and is defined, for example, by the following equation (2):

[0020]

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[0021] In a hot bending test, the energy (amount of work) U, which is expressed by the area of ​​the curve of load P and displacement u from when load P is 0 to when fracture ends, is divided by twice the cross-sectional area A of the test piece to obtain the fracture energy γ (J / m 2 ) can be obtained.

[0022] The higher the fracture energy of a refractory, the less cracks will propagate into the refractory. Methods known to improve the fracture energy of MgO-C bricks include adding expanded graphite and impregnating it with pitch.

[0023] As described above, in the method for selecting a refractory for a charging wall of a molten metal refining vessel according to the embodiment, the hot bending strength value σ (MPa) and the fracture energy value γ (J / m 2 ) and the scrap resistance index calculated by the above formula (1), the durability of the refractory against the collision of scrap is evaluated.

[0024] The molten metal refining vessel according to the embodiment is, for example, a converter or an electric furnace, and a refractory material selected by the above-mentioned method for selecting a refractory material for a charging wall of a molten metal refining vessel is installed in the area where scrap will collide. The molten metal refining vessel according to the embodiment is, for example, a converter or an electric furnace, and a refractory material having a scrap resistance index of 14 or more calculated by the above-mentioned formula (1) is installed in the area where scrap will collide.

[0025] The method for selecting a refractory for the charging wall of a molten metal refining vessel and the molten metal refining vessel according to the above-described embodiments take into account not only damage to the surface of the working surface due to scrap collisions, but also crack propagation into the refractory due to repeated scrap collisions. Furthermore, by using an index that takes into account crack propagation into the refractory, the durability in an actual furnace can be evaluated in advance with high accuracy from the results of a hot bending test. Furthermore, the method for selecting a refractory for the charging wall of a molten metal refining vessel and the molten metal refining vessel according to the embodiments can evaluate durability based solely on the results of a hot bending test, allowing for rapid refractory selection.

[0026] (Example) An example of a method for selecting a refractory material for a charging wall of a molten metal refining vessel according to an embodiment of the present invention will be described with reference to FIGS.

[0027] In the examples, four types of MgO-C bricks (refractories A to D) with different hot bending strength and fracture energy values ​​were installed in the charging wall of a converter, and an actual test was conducted. The results are shown in Figure 1. The vertical axis of the figure shows the wear rate index, which was calculated by estimating the wear rate (mm / ch) from the remaining brick thickness measured with a laser profile meter and indexing the wear rate of refractory A as 1. The horizontal axis of the figure shows the scrap resistance index (see formula (1) above).

[0028] FIG. 2 shows the hot bending strength values ​​of refractories A to D used in the actual furnace test. FIG. 3 shows the fracture energy values ​​(see formula (2) above) of refractories A to D. Here, there is a very strong correlation between the scrap resistance index and the wear rate. Therefore, the refractory with a higher scrap resistance index has a lower wear rate, making it possible to accurately evaluate its durability in an actual furnace. In this example, the case of the charging wall of a converter has been described, but the present invention is not limited to this and may also be applied to the charging wall of an electric furnace.

[0029] The method for selecting a refractory material for the charging wall of a molten metal refining vessel and the molten metal refining vessel according to the present invention have been specifically described above using the detailed description and examples, but the scope of the present invention is not limited to these descriptions and should be broadly interpreted based on the claims. It goes without saying that various changes and modifications based on these descriptions are also included in the scope of the present invention.

Claims

1. The durability of the refractory material against the impact of scrap is evaluated based on the magnitude of the scrap resistance index calculated from the hot bending strength value and the fracture energy value measured by the hot bending test; The scrap resistance index is calculated by the following formula (1) using the hot bending strength value σ (MPa) and the fracture energy value γ (J / m 2 ): [Equation 1]

2. 10. A molten metal refining vessel comprising a converter or an electric furnace, wherein a refractory material selected by the method for selecting a refractory material for a charging wall of a molten metal refining vessel according to claim 1 is installed at a portion where scrap impinges.

3. The converter or electric furnace is provided with a refractory material having a scrap resistance index of 14 or more, calculated from the hot bending strength value and the fracture energy value measured by a hot bending test, installed in a portion where scrap collides, The scrap resistance index is calculated by the following formula (1) using the hot bending strength value σ (MPa) and the fracture energy value γ (J / m 2 ). [Equation 2]

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