JP2021084115A - Tundish coating material - Google Patents

Abstract

To provide a tundish coating material that is easily removed, wherein seizure with a tundish body material, the Al2O3-SiO2-based refractory, hardly occurs.SOLUTION: A tundish coating material comprises: a magnesia clinker having an MgO content of 90 mass% or more; and 0.3-2.0 mass% magnesium sulfate in terms of outer percentage to the magnesia clinker, wherein the tundish coating material does not comprise sodium silicate substantially.SELECTED DRAWING: None

Description

The present invention relates to a tundish coating material.

As the tundish body material, an Al ₂ O _3- SiO ₂ refractory is generally used. When the Al ₂ O _3- SiO ₂ refractory and the molten steel come into contact with each other, silicon in the refractory elutes into the molten steel, so that the quality of the molten steel deteriorates. Therefore, the surface of the tundish body material is sprayed with a magnesia-based tundish coating material or coated with a trowel _{to prevent the Al 2} O _3- SiO ₂ refractory from coming into direct contact with the molten steel. The method of making is general purpose. After the casting is completed, the tundish coating material is removed and a new coating material is coated in preparation for the next casting. At that time, if the tundish coating material is firmly baked on the tundish main body material, it may be difficult to remove the coating material. At this time, a large force is required to remove the coating material, and the impact of the removal may damage the main body material.

Japanese Patent Application Laid-Open No. 05-238837 (Patent Document 1) states that "binders with respect to 100 parts by weight of a natural magnesium clinker having a CaO content of 1.5% by weight or less and an MgO content of 90% by weight or more". It is composed of a formulation prepared by adding 2 to 5 parts by weight and 0.5 to 3 parts by weight of an additive, and the CaO content of the formulation is 1.5% by weight or less. "Magnesia spray material for tundish coating" is disclosed. According to the technique of Patent Document 1, a magnesia spraying material for tundish coating, which is less likely to seize _{with an Al 2} O _{3- SiO 2 refractory which is a tundish main body material, can be obtained.} Here, examples using powdered soda silicate No. 3 and sodium hexametaphosphate as binders are disclosed.

Japanese Patent Application Laid-Open No. 01-157949 (Patent Document 2) states, "By weight, 0.5 to 10 parts of powdered sodium silicate, 0.05 to 7 parts of slaked lime, and magnesium sulfate per 100 parts of basic refractory aggregate. "Tandish spray coating material consisting of 0.05 to 7 parts and a mixture containing a required amount of short fibers and a binder" is disclosed. Patent Document 2 discloses an example in which magnesia clinker is used as an aggregate and slaked lime and magnesium sulfate are used in combination as a curing agent.

Japanese Unexamined Patent Publication No. 05-238837 Japanese Unexamined Patent Publication No. 01-157749

However, even with the inventions disclosed in Patent Documents 1 and 2, seizure between the tundish coating material and the tundish main body material still poses a problem.

An object of the present invention is to provide a tundish coating material which has less seizure with _{an Al 2} O _3- SiO ₂ refractory which is a tundish main body material and is easy to remove.

Based on a detailed analysis of the tundish coating material in which seizure occurred, the present inventors have determined that the cause of seizure is the reaction product generated by the reaction between the binder component and the slag component of the main body material and the coating material. I came up with the idea. Based on this idea, the present inventors examined the binder component used for the tundish coating material, and used a specific amount of magnesium sulfate as the binder in place of the conventionally used sodium silicate to significantly burn the binder. The present invention has been completed with the knowledge that the sticking can be reduced.

The tundish coating material according to the present invention contains, substantially, a magnesia clinker having an MgO content of 90% by mass or more and magnesium sulfate having an external amount of 0.3 to 2.0% by mass based on the magnesia clinker. It is characterized by not containing sodium silicate.

According to this configuration, a _{tundish coating material with less seizure with the Al 2} O _3- SiO ₂ refractory which is the tundish base material can be obtained.

Hereinafter, preferred embodiments of the present invention will be described. However, the scope of the present invention is not limited by the preferred embodiments described below.

As one aspect, the tundish coating material according to the present invention preferably further contains 1.0% by mass or less of sodium phosphate in an external manner with respect to the magnesia clinker.

According to this configuration, the adhesiveness of the tundish coating material can be improved.

As one aspect, the tundish coating material according to the present invention preferably further contains an amorphous silica having an outer weight of 3.0% by mass or less with respect to the magnesia clinker.

According to this configuration, the strength of the tundish coating material can be improved.

As one aspect, the tundish coating material according to the present invention preferably further contains 5.0% by mass or less of clay on the outside with respect to the magnesia clinker.

According to this configuration, the shape retention of the tundish coating material can be improved.

As one aspect, the tundish coating material according to the present invention preferably further contains 3.0% by mass or less of organic fibers on the outside with respect to the magnesia clinker.

According to this configuration, the shape retention of the tundish coating material can be improved.

Further features and advantages of the present invention will be further clarified by the following illustration of exemplary and non-limiting embodiments described with reference to the drawings.

Schematic diagram of seizure property evaluation test

Hereinafter, embodiments of the tundish coating material according to the present invention will be described.

The magnesia clinker used in the tundish coating material according to the present invention contains 90% by mass or more of MgO. If the MgO content is less than 90% by mass, the corrosion resistance may be poor.

Further, the tundish coating material according to the present invention contains magnesium sulfate in an external amount of 0.3 to 2.0% by mass with respect to the magnesia clinker (that is, the mass of the magnesia clinker is 100% by mass, and magnesium sulfate is used. Includes 0.3-2.0% by mass). If the content of magnesium sulfate is less than 0.3 mass on the outside, the effect as a binder is insufficient. Further, if the content of magnesium sulfate exceeds 2.0% by mass on the outside, an odor may be generated during firing. The content of magnesium sulfate is preferably 0.5 to 1.5% by mass on the outside. Incidentally, magnesium sulfate is intended content of crystal water is different variety can be used, particularly preferably the use of trihydrate _{(MgSO 4 · 3H 2 O)} , in that higher anti-seizing effect is obtained ..

In addition, the tundish coating material according to the present invention is substantially free of sodium silicate. Here, "substantially free of sodium silicate" means at least not containing intentionally added sodium silicate.

The tundish coating material according to the present invention preferably contains 1.0% by mass or less of sodium phosphate on the outside with respect to the magnesia clinker. Sodium phosphate has the effect of improving the adhesiveness of the tundish coating material. If the content of sodium phosphate exceeds 1.0% by mass on the outside, it may easily seize on the tundish body material. The content of sodium phosphate is more preferably 0.2 to 0.5% by mass on the outside. Incidentally, sodium phosphate, can be used those proportions are different variety of P ₂ O ₅ to Na, the use of sodium hexametaphosphate, since tends to increase adhesiveness, particularly preferred.

The tundish coating material according to the present invention preferably further contains an amorphous silica having an outer weight of 3.0% by mass or less with respect to the magnesia clinker. Amorphous silica has the effect of improving the strength of the coating layer. When the content of amorphous silica exceeds 3.0% by mass on the outside, the strength of the coating layer may be inferior. The content of the amorphous silica is more preferably 1.0 to 3.0% by mass in the outer cover. As the amorphous silica, various kinds such as by-products produced during the production of metallic silicon and the production of zirconia by desiliconization of zircon can be used. From the viewpoint of the purity of the amorphous silica, the SiO ₂ content is preferably 95% by mass or more.

The tundish coating material according to the present invention preferably further contains 5.0% by mass or less of clay on the outside with respect to the magnesia clinker. Since clay has the effect of imparting shape retention, a tundish coating material containing an appropriate amount of clay does not easily run off during spraying. If the clay content exceeds 5.0% by mass, the strength of the coating layer may decrease. The content of clay is more preferably 0.5 to 3.0% by mass in the outer cover. Although various types of clay can be used, clays _{containing less impurities other than Al 2} O ₃ and SiO ₂ are preferable, and clays having _{a total content of Al 2} O ₃ and SiO ₂ of 80% by mass or more are particularly preferable.

The tundish coating material according to the present invention preferably further contains 3.0% by mass or less of organic fibers on the outside with respect to the magnesia clinker. Since organic fibers have the effect of imparting shape retention, a tundish coating material containing an appropriate amount of organic fibers does not easily run off during spraying. The content of the organic fiber is more preferably 0.5 to 2.0% by mass in the outer cover. As the organic fiber, various organic fibers mainly composed of cellulose can be used.

In addition, known dispersants and the like can be added as long as the effects of the present invention are not impaired.

The tundish coating material according to the present invention can be obtained by mixing the above-mentioned constituent components by a known method.

The tundish coating material according to the present invention can be used as a coating material for preventing contact between the surface of the tundish main body material and molten steel, similarly to the known tundish coating material. The construction method is the same as that of a known tundish coating material, and the construction can be performed by a spray treatment, a trowel coating treatment, or the like.

It should be understood that with respect to other configurations, the embodiments disclosed herein are exemplary in all respects and the scope of the invention is not limited thereto. Those skilled in the art will be able to easily understand that modifications can be made as appropriate without departing from the spirit of the present invention. Therefore, another embodiment modified without departing from the spirit of the present invention is naturally included in the scope of the present invention.

Hereinafter, the tundish coating material according to the present invention will be described in detail with reference to Examples and Comparative Examples.

[Material used]
Commercially available magnesia clinker, sodium sulfate, sodium phosphate, sodium silicate, amorphous silica, clay, and organic fibers were used in each case.

[Sample preparation]
Each material weighed according to the blending ratios shown in Tables 1 to 4 below was placed in a bag and mixed well to prepare a tundish coating material for each of Examples and Comparative Examples.

[Seizure evaluation test]
Each of the Examples and Comparative Examples shown in Table 1 was subjected to a seizure evaluation test by the crucible erosion test method. The test method will be described with reference to FIG. First, an Al ₂ O _3- MgO quality base material castable is poured into a frame of 30 mm × 80 mm × 60 mm, molded, cured at room temperature for 24 hours, then unframed, dried at 110 ° C. for 24 hours, and the test piece base material Was preformed. The dried test piece base material was fired at 1500 ° C. for 3 hours in an oxidizing atmosphere, and then the 80 mm × 60 mm surface of the fired test piece base material 1 was coated with the tundish coating material of each of Examples and Comparative Examples. 2 was applied to a thickness of 5 mm and cured at room temperature for 24 hours (S1). Subsequently, the crucible 3 formed by combining four coated test piece base materials was heated to 1550 ° C. by a burner, and the slag 4 was melted in the crucible 3 and held for 3 hours (S2). The crucible 3 was cooled to room temperature and then disassembled (S3), and the test piece base material 1 after the test was cut and the cross section was observed to evaluate the degree of seizure between the test piece base material and the coating material. The relationship between the symbols in Table 1 and the observed degree of seizure is shown below.
A: No seizure was observed B: Slightly seized but easily peeled off C: Seized and difficult to peel off

[Odor evaluation test]
In the seizure property evaluation test, the examiner determined whether or not an odor was felt when the crucible 3 was heated.

[Adhesion evaluation test]
Adhesion evaluation tests were conducted for each of the Examples and Comparative Examples shown in Table 1. An _{iron cylindrical metal frame (inner diameter 70 mm, height 20 mm) is placed on an Al 2} O _3- MgO quality base material castable test plate, and the tundish coating materials of Examples and Comparative Examples are placed in the metal frame. It was put in and dried at 150 ° C. for 24 hours. Then, the adhesive strength between the base material and the coating material was measured using a shear adhesive strength measuring machine. The relationship between the symbols in Table 1 and the adhesive strength is shown below.
A: 2.0 MPa or more B: 1.5 MPa or more and less than 2.0 MPa C: 1.0 MPa or more and less than 1.5 MPa D: less than 1.0 MPa

[Strength evaluation test]
A strength evaluation test was conducted for each of the Examples and Comparative Examples shown in Tables 2 to 4. The tundish coating materials of Examples and Comparative Examples were placed in a 40 mm × 40 mm × 160 mm mold, dried at 150 ° C. for 24 hours, removed from the mold, and fired at 1200 ° C. to obtain a test piece. The number of test pieces was 2 per case. For each test piece, the bending strength (n = 2 average value) was measured by a three-point bending test based on JIS R 2553-2005. However, Comparative Example 6 was not included in the strength evaluation test because it had a high content of amorphous silica (3.2% by mass) and was at a level where explosive fracture could occur during drying. The relationship between the symbols in Tables 2 to 4 and the bending strength is shown below.
A: 1.6 MPa or more B: 1.0 MPa or more and less than 1.6 MPa C: less than 1.0 MPa-: Strength evaluation test not performed (not applicable)

[Shape retention evaluation test]
A shape retention evaluation test was conducted for each of the Examples and Comparative Examples shown in Tables 2 to 4. After spraying the tundish coating material of each of Examples and Comparative Examples onto the plate-shaped refractory, the refractory was held for 5 minutes so that the coated surface was along the vertical direction. After that, it was visually observed whether or not the coating material was moving downward. No runoff of the coating material was observed in all of Examples 6 to 14 and Comparative Examples 6 to 8 (denoted as "A" in Tables 2 to 4).

〔Evaluation results〕
In each example shown in Table 1, the difference in seizure property, odor, and adhesiveness due to the difference in the type and content of the binder component was evaluated. In Examples 1 to 5, no seizure was observed between the test piece base material and the tundish coating material. Moreover, in Examples 1 to 5, good adhesiveness was observed. On the other hand, in Comparative Example 1 in which the content of magnesium sulfate was higher than that in Examples 1 to 5, seizure was observed. Further, in Comparative Example 2 in which the content of magnesium sulfate was lower than in Examples 1 to 5, the adhesiveness was inferior to that in Examples 1 to 5. At this time, when the content of sodium phosphate was increased without changing the content of magnesium sulfate, seizure was observed instead of improving the adhesiveness (Comparative Examples 3 and 4). In addition, Comparative Example 5 (conventional coating material) using sodium silicate was inferior in seizure property as compared with Examples 1 to 5. In Comparative Example 1, an odor was felt during firing.

In each example shown in Table 2, the difference in strength and shape retention due to the difference in the content of amorphous silica was evaluated. In Examples 6 to 8 (amorphous silica 0.8 to 2.8% by mass), both strength and shape retention were good. On the other hand, in Comparative Example 6, the content of amorphous silica (3.2% by mass) is at a level at which explosive fracture may occur during drying. In addition, all the examples showed good shape retention. Moreover, in none of the cases, seizure between the test piece base material and the coating material was not observed.

In each example shown in Table 3, the difference in strength and shape retention due to the difference in clay content was evaluated. In Examples 9 to 11 (clay 0.4 to 3.1% by mass), both strength and shape retention were good, but in Comparative Example 7 containing 5.1% by mass of clay, the strength was significantly inferior. In addition, all the examples showed good shape retention. Moreover, in none of the cases, seizure between the test piece base material and the coating material was not observed.

In each example shown in Table 4, the difference in strength and shape retention due to the difference in the content of organic fibers was evaluated. In Examples 12 to 14 (organic fibers 0.4 to 2.0% by mass), both strength and shape retention were good, but in Comparative Example 8 containing 3.2% by mass of organic fibers, the strength was significantly inferior. .. In addition, all the examples showed good shape retention. Moreover, in none of the cases, seizure between the test piece base material and the coating material was not observed.

The present invention can be used, for example, as a coating material for preventing contact between the surface of the tundish main body material and molten steel.

1: Test piece base material 2: Tandish coating material 3: Crucible 4: Slag

Claims (5)

With a magnesia clinker with an MgO content of 90% by mass or more,
Containing 0.3 to 2.0% by mass of magnesium sulfate externally to the magnesia clinker.
Tandish coating material that is virtually free of sodium silicate. The tundish coating material according to claim 1, further comprising 1.0% by mass or less of sodium phosphate on the outside with respect to the magnesia clinker. The tundish coating material according to claim 1 or 2, further comprising an amorphous silica having an outer weight of 3.0% by mass or less with respect to the magnesia clinker. The tundish coating material according to any one of claims 1 to 3, further containing 5.0% by mass or less of clay on the outside with respect to the magnesia clinker. The tundish coating material according to any one of claims 1 to 4, further comprising 3.0% by mass or less of organic fibers on the outside with respect to the magnesia clinker.

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