JP6326266B2 - Dry coating material - Google Patents

Description

  The present invention relates to a dry coating material suitably used as a tundish coating material.

  In the continuous casting of steel, the tundish has a role of distributing the molten steel, homogenizing the molten steel temperature, and floating the deoxidized product. The tundish lining is usually coated with a thin refractory coating material mainly composed of basic refractory raw materials such as magnesia and dolomite to prevent molten steel contamination and refractory lining protection. The construction is generally performed by adding water and spraying or troweling.

  This coating material is heat-dried after construction and before use. However, the water added to the coating material cannot be completely removed even by drying, and the quality of the steel product is lowered due to the hydrogen pickup caused by the water.

  In addition, the coating material is dismantled and newly constructed when the remaining thickness decreases due to wear, etc., but seizure to the lining refractory requires considerable labor and time to reduce the operating rate of the tundish. ing.

  Thus, in recent years, a dry coating material construction method has been proposed (for example, Patent Document 1). In this dry method, a core is provided in a tundish where a lining refractory is arranged, and a dry powder-like state in which water consisting of a refractory raw material and a binder (phenol resin) is not added between the lining refractory and the core. The coating material is charged, and after filling, the coating material is preliminarily cured by heating from the inside of the core with a gas burner, and the core is demolded and finally cured. This dry method, unlike spraying or ironing, eliminates the problems of hydrogen pickup and image sticking by not adding water to the coating material.

  When the dry powder coating material (hereinafter referred to as “dry coating material”) used in the dry method has insufficient strength after temporary curing, the dry coating material adheres to the core when the core is removed. End up. For this reason, it is necessary to improve the strength after temporary curing as a characteristic of the dry coating material.

  As a technique for improving the strength of the dry coating material, it is conceivable to increase the amount of phenol resin. However, when the amount of the phenol resin is increased, there is a problem that a bad odor is generated and a problem that requires a cost. Therefore, there has been a demand for realizing an improvement in the strength of the dry coating material without increasing the amount of phenol resin.

No. 2006-7317

  The problem to be solved by the present invention is to improve the strength of the dry coating material before demolding of the core, that is, after pre-curing, and to suppress adhesion to the core during demolding.

According to one aspect of the present invention, a dry coating material containing a magnesia material in an amount of 80% by mass to 98% by mass and a phenol resin in an amount of 2% by mass to 8% by mass , Particles having a particle size of 1 mm or more and less than 3 mm are 20% by mass or more and 40% by mass or less, particles having a particle size of 0.075 mm or more and less than 1 mm are 20% by mass or more and 40% by mass or less, and particles having a particle size of 0.075 mm or less are 20% by mass. or more and 40 mass% or less, the loose apparent specific gravity of the particles having a particle size of less than 1mm or 3mm in the dry coating material 1.5 (g / mL) above, loose apparent diameter of less than 0.075mm particles A dry coating material having a specific gravity of 0.8 (g / mL) or more is provided.
The “slack apparent specific gravity” as used in the present invention is measured by the method described later (paragraph 0024), and the unit is (g / mL), but the unit is omitted in the following description.

  In the dry coating material of the present invention, the apparent specific gravity of loose particles having a particle diameter of 1 mm or more and less than 3 mm corresponding to the aggregate is 1.5 or more. For this reason, compared with the case where the loose apparent specific gravity is less than 1.5, the aggregates have a dense structure and the gaps between the aggregates are reduced, so that the strength of the dry coating material after temporary curing is improved.

  Further, since the apparent specific gravity of loose particles having a particle diameter of 1 mm or more and less than 3 mm corresponding to the aggregate is 1.5 or more, the aggregate of the magnesia material has few pores as conceptually shown in FIG. It is dense. On the other hand, if the apparent specific gravity of particles having a particle diameter of 1 mm or more and less than 3 mm corresponding to the aggregate is less than 1.5, the aggregate of the magnesia material has many pores as conceptually shown in FIG. It is porous. Thus, if the aggregate of the magnesia material is porous, the phenol resin enters the pores of the aggregate, and the amount of the phenol resin contributing to the strength development is reduced, thereby reducing the strength of the dry coating material (FIG. 1 ( b)). On the other hand, according to the present invention, since the aggregate of the magnesia raw material is dense, the amount of phenol resin entering the pores of the aggregate is reduced, and the decrease in the amount of phenol resin contributing to strength development is suppressed. Therefore, the strength of the dry coating material is improved (FIG. 1 (a)).

  On the other hand, since the dry coating material is filled in the concavo-convex gap, if there is no fluidity, a void is formed without entering the concavo-convex gap. In this respect, according to the present invention, since the apparent specific gravity of the loose particles having a particle diameter of less than 0.075 mm is 0.8 or more, fluidity can be ensured and it becomes possible to enter the uneven gap. For this reason, the filling property of the dry coating material is improved, and as a result, the strength of the dry coating material is improved.

The mechanism of strength development of the dry coating material is conceptually shown, in which (a) is the case of the present invention and (b) is the conventional case. It is a measuring container used for measurement of loose apparent specific gravity.

  The dry coating material of the present invention contains a magnesia raw material and a phenol resin as raw material particles.

  Here, the “magnesia raw material” refers to a refractory raw material mainly composed of MgO, and includes magnesia, dolomite, olivine and the like. Examples of the “phenol resin” include novolak type phenol resins and resole type phenol resins.

  The dry coating material of the present invention contains 80 mass% or more and 98 mass% or less of magnesia material. When the magnesia raw material is less than 80% by mass, the durability is inferior and the purpose as a coating material cannot be achieved. If it exceeds 98 mass%, demolding cannot be performed due to poor curing.

  The dry coating material of the present invention contains 2% by mass or more and 8% by mass or less of phenol resin. When the phenol resin is less than 2% by mass, demolding is impossible due to poor curing. If it exceeds 8% by mass, a strange odor is generated, resulting in high costs. Furthermore, when it exceeds 8 mass%, the strength of the dry coating material can be ensured, but there is a problem that excess phenol resin is fused to the core surface.

  In addition, the dry coating material of the present invention may appropriately include one or more selected from silicates, phosphates, magnesium sulfate, glucose and the like as other binders. Furthermore, the dry coating material of the present invention may appropriately contain one or more refractory raw materials selected from clay, ultrafine silica powder, etc., in addition to the magnesia raw material and phenol resin.

  Since it is assumed that the dry coating material is in the form of a dry powder, the whole is constituted by particles (solid). The loose specific gravity of particles having a particle diameter of less than 0.075 mm is 0.8 or more. When the loose apparent specific gravity of particles having a particle diameter of 1 mm or more and less than 3 mm is less than 1.5, or when the loose apparent specific gravity of particles having a particle diameter of less than 0.075 mm is less than 0.8, the above-described effects cannot be obtained.

  The loose apparent specific gravity of particles having a particle size of 1 mm or more and less than 3 mm is preferably 1.7 or more, and more preferably 1.9 or more. The apparent specific gravity of loose particles having a particle size of less than 0.075 mm is preferably 0.9 or more, and more preferably 1.0 or more.

  Furthermore, the dry coating material of the present invention preferably has an overall loose specific gravity of 1.6 or more. If it does so, the fillability of the whole dry coating material will improve, and the intensity | strength of a dry coating material will improve as a result.

  As the particle size constitution of the dry coating material of the present invention, particles having a particle size of 1 mm or more and less than 3 mm are 20% by mass or more and 40% by mass or less, and particles having a particle size of 0.075 mm or more and less than 1 mm from the viewpoint of improving strength or fluidity. It is preferable that 20 mass% or more and 40 mass% or less and the particle size of less than 0.075 mm is 20 mass% or more and 40 mass% or less.

  The “slack apparent specific gravity” as used in the present invention refers to that measured by the following method. As shown in FIG. 2, the measurement of the loose apparent specific gravity uses a stainless steel cylindrical 100 mL measuring container having an inner diameter of 50.5 (mm) and a height of 50 (mm). In the measurement, a sample (referring to a dry coating material adjusted in particle size or the entire dry coating material) is allowed to flow into the measurement container until it overflows. When the sample flows into the measurement container until it overflows, it is scraped off from the upper surface of the measurement container. The mass (m) of the sample is measured to 0.1% by subtracting the mass of the empty measurement container that has been measured in advance. The bulk density (g / mL) is calculated by the formula m / 100, and the average value of the bulk density calculated from three measurements using three different samples is defined as the “slack apparent specific gravity”.

  In addition, said dry-coating material which adjusted the particle size is a material which adjusted the particle size by the sieve. Specifically, a 1 mm sieve was passed, and the particles remaining on the sieve were made particles having a particle size of 1 mm or more and less than 3 mm in the dry coating material. Moreover, the particle | grains which passed the 0.075mm sieve and fell under the sieve were made into the particle | grains in the dry coating material with a particle size of less than 0.075mm. Then, the apparent specific gravity of each of the particles of 1 mm or more and less than 3 mm and particles of less than 0.075 mm was measured by the above method. The loose apparent specific gravity of the entire dry coating material was also measured by the above method.

  Table 1 shows the raw material structures and evaluation results of Examples and Comparative Examples of the present invention.

  Natural magnesia, olivine and dolomite were used as the magnesia material. Natural magnesia A and natural magnesia B in Table 1 are natural magnesias with different origins. The loose apparent specific gravity of each magnesia material is “natural magnesia B> natural magnesia A ≧ dolomite> olivine”.

  As the phenolic resin, a novolac type phenolic resin was used, and as other binders, silicate and magnesium sulfate were used. The other refractory raw materials used clay and ultrafine silica powder.

  About the dry coating material of each case, while measuring the loose specific gravity and bending strength, odor was evaluated.

  The loose apparent specific gravity was measured by the method described above.

  The bending strength was measured by the following method. The inside of a 40 × 40 × 160 metal frame is placed on the vibration table, and the raw material is filled while applying 3G vibration. After filling the raw material, the material with the metal frame is dried at 200 ° C. × 3 h. After drying, the mold is removed, and the bending strength of the sample is measured in accordance with the provisions of JIS-R2553. If the bending strength is 0.5 MPa or more, it is a strength capable of demolding, and if it is 2 MPa or more, it is even better. If it is less than 0.5 MPa, it does not have sufficient strength for demolding. In Table 1, the bending strength is represented by ◯ when 2 MPa or more, Δ by 0.5 MPa or more and less than 2 MPa, and x by less than 0.5 MPa. This bending strength is an index representing the strength of the dry coating material after temporary curing.

  As the odor evaluation, the odor generated when the sample was heated at 200 ° C. was evaluated. The case where there was almost no odor was rated as ◯, the case where there was an odor but there was no trouble in the work was marked as Δ, and the case where there was an odor and work was impossible, was marked as ×. This odor evaluation is an index representing the odor generated when the dry coating material is temporarily cured.

  The overall evaluation was X when either one of bending strength and odor was x, △ when either or both of bending strength and odor was Δ, and ◯ when both bending strength and odor were ○.

  In Examples 1 to 8, the overall evaluation was Δ or more, the strength improvement of the dry coating material after the temporary curing was confirmed, and the odor was within the allowable range. Among them, Examples 4 and 5 in which the loose specific gravity of particles having a particle size of 1 mm or more and less than 3 mm is 1.7 or more and the loose specific gravity of particles having a particle size of less than 0.075 mm are 0.9 or more are comprehensively evaluated. Was ◯ and was particularly good.

  Comparative Example 1 is an example in which the loose apparent specific gravity of particles having a particle size of 1 mm or more and less than 3 mm is too small, and Comparative Example 2 is an example in which the loose apparent specific gravity of particles having a particle size of less than 0.075 mm is too small. Met.

  Comparative Example 3 was an example in which there was too little phenol resin, and this was also insufficient in strength. On the other hand, Comparative Example 4 is an example in which there is too much phenol resin, and the strength was sufficient, but the evaluation of odor was bad.

Claims (4)

A dry coating material comprising a magnesia material in an amount of 80% by mass to 98% by mass and a phenol resin in an amount of 2% by mass to 8% by mass,
The particle size composition of the dry coating material is such that particles having a particle size of 1 mm or more and less than 3 mm are 20% by mass or more and 40% by mass or less, particles having a particle size of 0.075 mm or more and less than 1 mm are 20% by mass or more and 40% by mass or less, and particle size 0 0.075 mm or less of particles are 20% by mass or more and 40% by mass or less,
The loose specific gravity of particles having a particle size of 1 mm or more and less than 3 mm in the dry coating material is 1.5 (g / mL) or more, and the loose apparent specific gravity of particles having a particle size of less than 0.075 mm is 0.8 (g / g). mL) or more dry coating material. A loose apparent specific gravity of particles having a particle size of 1 mm or more and less than 3 mm is 1.7 (g / mL) or more, and a loose apparent specific gravity of particles having a particle size of less than 0.075 mm is 0.9 (g / mL) or more. Item 2. The dry coating material according to Item 1. The loose apparent specific gravity of particles having a particle size of 1 mm or more and less than 3 mm is 1.9 (g / mL) or more, and the loose apparent specific gravity of particles having a particle size of less than 0.075 mm is 1.0 (g / mL) or more. Item 2. The dry coating material according to Item 1. The dry coating material according to any one of claims 1 to 3, wherein an overall loose specific gravity is 1.6 (g / mL) or more.