Expanded graphite chip and carbon-containing brick

Abstract

To provide an expanded graphite chip capable of suppressing the bulkiness of a brick green body during molding, improving molding workability, and improving spalling resistance.SOLUTION: The expanded graphite chip is made of expanded graphite, has a density of 0.5 to 2.0 g / cm3, and has a first principal plane and a second principal plane, with at least the first principal plane having a plurality of grooves.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to expanded graphite chips and carbon-containing bricks. [Background technology]

[0002] Carbon-containing bricks are widely used as materials for high-temperature equipment in steelmaking processes, etc. Examples of materials for carbon-containing bricks include magnesia-carbonaceous, magnesia-spinel-carbonaceous, spinel-carbonaceous, alumina-magnesia-carbonaceous, and alumina-silicon carbide-carbonaceous. Conventional carbon raw materials such as scaly graphite and carbon black are usually used as the carbon, whereas Patent Document 1 discloses a carbon-containing brick containing crushed particles of expanded graphite sheets in order to reduce the bulk of the brick clay and improve the molding workability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-045575 A Summary of the Invention [Problem to be solved by the invention]

[0004] Carbon-containing bricks containing crushed particles of expanded graphite sheets reduce the bulkiness of the brick clay during molding and improve molding workability, but there remain issues with respect to spalling resistance.

[0005] The present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide expanded graphite chips and carbon-containing bricks that can reduce the bulkiness of the brick clay during molding, improve molding workability, and improve spalling resistance. [Means for solving the problem]

[0006] (1) One aspect of the present disclosure is Made of expanded graphite, Density: 0.5~2.0g / cm 3 and A first main surface and a second main surface, The present invention relates to an expanded graphite tip, wherein at least the first major surface has a plurality of grooves.

[0007] (2) Another aspect of the present disclosure is The material contains a refractory material, a carbon material, and a binder as main components, The present invention relates to a carbon-containing brick, characterized in that the carbon raw material contains the expanded graphite chips according to one embodiment of the present disclosure.

[0008] The carbon-containing brick of the present disclosure contains the expanded graphite chips of the present disclosure as a carbon raw material, which makes it possible to reduce the bulkiness of the brick clay, improve the molding workability, and improve the spalling resistance.

[0009] (3) In another aspect of the present disclosure, The content of the expanded graphite chips is preferably 1 to 50% by mass, which can further improve spalling resistance. [Brief description of the drawings]

[0010] [Figure 1] 1 shows an example of an expanded graphite tip according to the present embodiment. [Diagram 2] An example in which the cross-sectional shape of the groove is triangular is shown. [Diagram 3] An example in which the cross-sectional shape of the groove is square is shown. [Figure 4] An example of a groove having an arc-shaped cross section is shown. [Diagram 5] 1 shows an example of a conventional expanded graphite chip. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] A preferred embodiment of the present disclosure will be described in detail below. Note that the embodiment described below does not unduly limit the contents of the present disclosure described in the claims, and all of the configurations described in the embodiment are not necessarily essential as a means for solving the problems of the present disclosure.

[0012] <Expanded graphite chip> The expanded graphite chips of this embodiment are made of expanded graphite and have a density of 0.5 to 2.0 g / cm 3 and having a first major surface and a second major surface, at least the first major surface having a plurality of grooves.

[0013] The density of the expanded graphite chips is preferably 1.0 to 2.0 g / cm 3 and the loose bulk density is preferably 0.25 to 0.50 g / cm 3 In this specification, the term "loose bulk density" refers to a value obtained by gently placing a measurement object in a graduated cylinder and dividing the mass of the measurement object by its volume. The thickness of the expanded graphite chip is not particularly limited, but is preferably 0.3 to 1.0 mm, and more preferably 0.4 to 0.7 mm. The depth of the groove is not particularly limited as long as the expanded graphite chip is not cut, but for example, the ratio (d / t) of the depth (d) of the groove to the thickness (t) of the expanded graphite chip is preferably 0.5 or less, and more preferably 0.05 to 0.2. The interval between the multiple grooves is not particularly limited, but is preferably 0.5 to 2.0 mm, and more preferably 1.0 to 1.5 mm. The size of the expanded graphite chip can be appropriately selected depending on the application of the brick and the particle size of the raw material. As an example, it can be about 10 mm long x 4 mm wide x 0.5 mm thick. Examples of the expanded graphite chip of this embodiment are shown in Figs. 1 to 4. Expanded graphite chips of different sizes, densities, etc. may be mixed. The method for producing the expanded graphite chips of the present embodiment is not particularly limited, but may be, for example, the following method.

[0014] A graphite intercalation compound is formed by infiltrating sulfuric acid, nitric acid, or the like between the layers of highly crystalline graphite such as natural graphite, and when the graphite intercalation compound is heated to a high temperature in a short time, it expands rapidly to obtain expanded graphite. The expanded graphite is rolled with a roll or the like to obtain an expanded graphite sheet. In this specification, "expanded graphite" refers to expanded graphite that has been compressed after expansion. The density and thickness of the expanded graphite sheet can be adjusted by adjusting the rolling pressure and thickness, the input speed of the expanded graphite, and the like. The density of the expanded graphite sheet is 0.5 to 2.0 g / cm. 3 and preferably 1.0 to 2.0 g / cm 3 The thickness of the expanded graphite sheet is not particularly limited, but is preferably 0.3 to 1.0 mm, and more preferably 0.4 to 0.7 mm.

[0015] Next, the expanded graphite sheet is cut using, for example, a known method as shown below, to obtain the expanded graphite chip of this embodiment. Like a shredder, two cylindrical blades are arranged in parallel and rotated, and the expanded graphite sheet is cut by passing it between them. Here, a plurality of protrusions are formed on the outer peripheral surface of a part of the cylindrical blades. The shape is transferred to the first main surface of the expanded graphite sheet that contacts the outer peripheral surface on which the protrusions are formed, and an expanded graphite chip having a plurality of grooves on the first main surface can be obtained. The reverse side of the first main surface is referred to as the second main surface. The cross-sectional shape and depth of the grooves can be arbitrarily determined depending on the cross-sectional shape and height of the protrusions. For example, by making the cross-sectional shape of the protrusions triangular, square, and arc, grooves having cross-sectional shapes of triangular, square, and arc, respectively, can be formed. The depth of the groove is not particularly limited as long as the expanded graphite sheet is not cut, but for example, the ratio (d / t) of the depth (d) of the groove to the thickness (t) of the expanded graphite sheet is preferably 0.5 or less, more preferably 0.05 to 0.2. The interval between the multiple grooves is not particularly limited, but is preferably 0.5 to 2.0 mm, more preferably 1.0 to 1.5 mm. The interval between the multiple grooves can be arbitrarily determined depending on the interval between the protrusions. As another method for producing the expanded graphite chips of this embodiment, when the expanded graphite is rolled to obtain an expanded graphite sheet, multiple protrusions are formed on a part of the outer peripheral surface of the roll, and the shape of the protrusions is transferred to the first main surface of the expanded graphite sheet that contacts the outer peripheral surface on which the protrusions are formed, and then the sheet is cut. The grooves may be continuous or may have a break. Similarly to the first main surface, the second main surface may have multiple grooves.

[0016] <Carbon-containing bricks> The carbon-containing brick of this embodiment contains a refractory raw material, a carbon raw material, and a binder as main components, and the carbon raw material contains the expanded graphite chips of this embodiment. When the carbon raw material contains the expanded graphite chips of this embodiment, the bulkiness of the brick clay is reduced, and molding workability is improved, and spalling resistance can be improved. This is believed to be because the grooves on the surface of the expanded graphite chips engage with the matrix of the brick raw material, improving crack propagation resistance. The content of the expanded graphite chips is not particularly limited, but is preferably 1 to 50 mass %, and more preferably 10 to 30 mass %.

[0017] <Refractory raw materials> As the refractory raw material, for example, a magnesia raw material, a spinel raw material, an alumina raw material, a silicon carbide raw material, or other general refractory raw material can be used.

[0018] The magnesia raw material may be any one generally used for magnesia-carbonaceous refractories, such as electrofused magnesia, seawater magnesia, natural magnesia, sintered magnesia, etc. The purity of the magnesia raw material is preferably MgO: 98 mass% or more. In this case, the corrosion resistance of the magnesia-carbonaceous refractory is improved and the magnesia-carbon reaction can be suppressed.

[0019] The spinel raw material may be any material generally used for carbon-containing bricks, such as electrofused spinel and sintered spinel. The stoichiometric composition of spinel (MgAl2O4) is 71.7% by mass of Al2O3 and 28.3% by mass of MgO, but there are various other compositions. A spinel containing more Al2O3 than the stoichiometric composition is called an alumina-rich spinel, and a spinel containing more MgO than the stoichiometric composition is called a magnesia-rich spinel. Either of these may be used as the spinel raw material in this embodiment.

[0020] The alumina raw material may be any one generally used for carbon-containing bricks, such as fused alumina, sintered alumina, natural alumina, etc. The purity of Al2O3 is preferably 95 mass% or more. In this case, corrosion resistance is improved.

[0021] The silicon carbide raw material may be any one generally used for carbon-containing bricks. The purity of the SiC is preferably 95 mass% or more. In this case, the corrosion resistance is improved and the oxidation of carbon can be suppressed.

[0022] <Carbon raw materials> The carbon raw material may include, in addition to the expanded graphite chips of the present embodiment, commercially available solid carbon such as scaly graphite, amorphous graphite, carbon black, anthracite, artificial graphite, etc. These carbon raw materials may be used alone or in combination of two or more kinds.

[0023] <Binder> The binder may be any one that is generally used for carbon-containing bricks, such as thermosetting (resol type) or thermoplastic (novolac type) phenolic resins, ethylene glycol, etc. The form of the binder is not particularly limited as long as it is generally used, and may be, for example, liquid, powder, etc. Binders that have low viscosity at room temperature or binders whose viscosity has been reduced by heating to a certain temperature are particularly preferred, since they can be uniformly dispersed with the addition of a small amount. In addition, the binder does not have to be a resin, so long as it is generally used for unfired bricks, such as polysaccharide solutions such as molasses, and inorganic compounds such as silicates.

[0024] <Small additives> Small amounts of additives other than the main components may be added as long as they are generally used in carbon-containing bricks, such as antioxidants, carbon black, powdered pitch, etc. Examples of antioxidants include Al, Si, B4C, SiC, and Al-Mg alloys. EXAMPLES

[0025] Hereinafter, embodiments of the present disclosure will be described in detail.

[0026] <Preparation of test specimen> The loose bulk density due to expansion treatment is 0.01g / cm3 Expanded graphite of the above formula was obtained. Next, an expanded graphite sheet was obtained using a rolling mill. After that, the expanded graphite sheet was cut using a sheet pelletizer equipped with a cylindrical blade with multiple protrusions formed on some of its outer peripheral surfaces. The protrusions of the cylindrical blade had three types of cross-sectional shapes: triangular, square, and arc, and expanded graphite chips were obtained with multiple grooves with cross-sectional shapes of triangular, square, and arc on one surface (first main surface) (Figs. 1 to 4). For comparison, a cylindrical blade without protrusions was used to prepare conventional expanded graphite chips with a smooth surface (Fig. 5).

[0027] The refractory raw material, expanded graphite chips as the carbon raw material, and phenolic resin as the binder were mixed and kneaded, and formed into a rectangular parallelepiped shape of 900 mm in length, 180 mm in width, and 150 mm in height, and then dried at 250°C for 24 hours to obtain a carbon-containing brick. This was then processed into a specified shape according to the evaluation test to prepare a test piece. The raw material composition and the cross-sectional shape of the multiple grooves formed on the first main surface of the expanded graphite chips are shown in Table 1.

[0028] <Evaluation method> The test pieces were evaluated for spalling resistance as shown below.

[0029] Carbon-containing bricks were cut into test pieces measuring 80 mm in length, 20 mm in width, and 20 mm in thickness, and the spalling resistance of the test pieces was evaluated according to JIS Z2242:2018 (Charpy impact test method for metallic materials). The test pieces were not notched and were placed on the test machine's platform. The pendulum weight was 922 g, the swing down angle was 60°, and the Charpy impact value was calculated using the following formula. Charpy impact value = (absorbed energy / cross-sectional area)

[0030] The higher the Charpy impact value, the greater the absorbed energy and the better the spalling resistance. 3 J / cm 2 Above 80x10: Spalling resistance passed (○) 3 J / cm 2 When the spalling resistance was less than 10%, the spalling resistance was evaluated as unacceptable (×).

[0031] <Evaluation Results> The evaluation results are shown in Table 1. [Table 1]

[0032] Comparative Example 1, which used a conventional expanded graphite chip with a smooth surface, had a low Charpy impact value and was poor in spalling resistance. In contrast, Examples 1 to 8, which used an expanded graphite chip with multiple grooves on the first main surface, all had high Charpy impact values ​​and were excellent in spalling resistance. This is thought to be because the grooves on the surface of the expanded graphite chip allowed it to mesh with the matrix of the brick raw material, improving resistance to crack propagation.

[0033] In Examples 1 to 3, expanded graphite chips with different groove cross-sectional shapes, i.e., triangular, rectangular, and arc, were used. All of them had high Charpy impact values ​​and excellent spalling resistance. In particular, the Charpy impact values ​​of Examples 1 and 2, which used expanded graphite chips with triangular and rectangular groove cross-sectional shapes, were high. This is believed to be because the triangular or rectangular groove cross-sectional shape allowed the expanded graphite chips to more easily mesh with the matrix of the brick raw material, improving spalling resistance.

[0034] In Examples 4 to 5, the content of the expanded graphite chips was changed. All of the examples had high Charpy impact values ​​and excellent spalling resistance. The content of the expanded graphite chips in this embodiment is considered to be preferably 1 to 50 mass %, and more preferably 10 to 30 mass %.

[0035] In Examples 6 to 8, the content of expanded graphite chips was fixed, and the blending ratio of the refractory raw materials: magnesia raw material, spinel raw material, alumina raw material, and silicon carbide raw material was changed. All of them had high Charpy impact values ​​and excellent spalling resistance.

[0036] Although the present embodiment has been described in detail as above, it will be easily understood by those skilled in the art that many modifications are possible without substantially departing from the novel matters and effects of the present disclosure. Therefore, all such modifications are included in the scope of the present disclosure. For example, a term described at least once in the specification together with a different term having a broader meaning or the same meaning may be replaced with that different term anywhere in the specification or drawings. Furthermore, the configuration of the present embodiment is not limited to that described in the present embodiment, and various modifications are possible.

Claims

1. Made of expanded graphite, Density: 0.5 to 2.0 g / cm ３ and A first main surface and a second main surface, 1. An expanded graphite chip, wherein at least said first major surface has a plurality of grooves.

2. The material contains a refractory material, a carbon material, and a binder as main components, A carbon-containing brick, characterized in that the carbon raw material contains the expanded graphite chips according to claim 1.

3. The carbon-containing brick according to claim 2, A carbon-containing brick, characterized in that the content of the expanded graphite chips is 1 to 50 mass %.

Images