JP3000031B2 - Coating agent for belt of belt type continuous casting machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thin cast slab by a belt type continuous casting machine, which is intended to prevent a metal belt supporting a long side surface of a slab from being thermally damaged and to extend a life of the belt. It relates to a coating agent.

[0002]

2. Description of the Related Art As an apparatus for continuously casting thin cast pieces having a rectangular cross section, there is a belt type continuous casting machine. According to this method, the conventional rolling process is simplified, and an energy-saving effect is expected, and attention has been paid. In this apparatus, molten steel is supplied from a tundish through a nozzle to a belt mold in a pool. The belt mold is stretched over pulleys, and is configured by partitioning opposing portions of a pair of belts running endlessly and both side surfaces with short side molds.

When a metal having a melting point higher than that of a metal belt to be used is injected into a belt-type continuous casting machine, the thermal load on the belt increases, and permanent thermal deformation and thermal damage of the belt become significant. As a countermeasure, it is customary to coat the belt with a refractory material. This coating agent is disclosed as to the material of the base material, but there is no mention of the adhesive strength for realizing the function. As a result, there is no report on an appropriate content of a binder which can develop adhesion strength and can be used without hindering operation.

[0004] With the recent demand for larger continuous casters and higher quality cast slabs, uniform cooling of the belt and a longer life have been desired. For example, Japanese Patent Application Laid-Open No. 60-216046 discloses means for reducing the frictional force between a belt and a slab to form a coating film having a fire resistance of 1200 ° C. or more and a thickness of 10 to 100 μm. However, a method of applying a coating agent on the belt surface to reduce the frictional force between the slab and the belt is a general technique widely used in other fields. Even if the fire resistance is regulated, it can be said that it is an incidental technology. Solid lubrication suitable for severe use conditions such as a belt mold has not yet been reported. In addition, there has been no study on the binder component of the coating agent and the proper content thereof so as to maximize the frictional force reducing effect.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art by improving the operability of continuous casting when applied to a belt and enhancing the protection of the belt. Achieving stable production of cast slabs with uniform quality, especially by preventing the occurrence of boiling phenomenon in the casting mold by the coating agent and suppressing the occurrence of splash even if it does not lead to the boiling phenomenon It is intended to be. Therefore, the present inventors have studied the binder content of a coating agent used for protecting a belt, which can satisfy the protective function and can be used without hindering operation. When the solidified shell is disturbed due to uneven cooling, a tensile force is generated at a thin part of the solidified shell when a restraining force (frictional force) exists between the solidified shell and an object in contact with the solidified shell in the process of thermal contraction. Leads to the occurrence of

However, even when the shell is not uniform, cracking cannot occur unless the binding force is ideally completely absent. The present invention examines means for reducing the frictional force applied to the belt of a belt-type continuous casting machine as means for reducing the binding force, and provides a coating agent that improves operability.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and its gist is to provide a belt coating for forming a belt mold for continuous casting of steel. And one or two or more inorganic binders: 2 to 10% by weight and organic binders: 0.01 to 3% by weight in order to develop adhesion strength in a slurry containing water as a solvent and a main raw material of a carbon material. A coating agent for a belt of a belt-type continuous casting machine characterized by being added.

Further, in a belt coating agent for a belt type continuous casting machine, the graphite concentration in the base material of the slurry is at least 20% by weight, preferably at least 30% by weight, and the base material with respect to the solvent (water) in the slurry. The solid content concentration C (% by weight) expressed as% by weight is C ≦ 75─0.
4x [the graphite concentration (% by weight) in the base material] is satisfied, the slurry solids concentration C (% by weight) is 20% or more, preferably 30% by weight or more. It is characterized in that one or more binders are added in combination of 2 to 10% by weight and organic binders: 0.01 to 3% by weight.

Further, the base material of the slurry is made of crystalline graphite having a concentration of 20% by weight or more, preferably 30% by weight or more, of crystalline graphite for the purpose of reducing friction between the belt and the slab. 70% by weight or less, and the crystalline graphite particles have an average particle size of 50 to 500 μm, preferably 1 to 500 μm.
It is characterized by having one or two or more kinds of inorganic binders: 2 to 10% by weight and organic binders: 0.01 to 3% by weight in order to have a property of not more than 00 μm and to exhibit adhesive strength.

[0010] Generally, as severe as belt-type continuous casting,
As a method of obtaining sufficient lubrication for a belt or the like used at a high temperature, coating lubrication using a solid such as a layered substance is employed instead of lubricating oil. The present inventors have conducted various studies on the improvement of the lubricity of a belt of a belt-type continuous casting machine, particularly on its coating agent. As a result, it has been found that the state of the binder and graphite in the slurry and the average particle diameter are important for improving the lubricity of the coating agent and improving the operability of continuous casting. At this time, the coating on the belt surface is performed uniformly by a method of spraying the coating agent in a slurry form from a powder mist nozzle.

However, as the amount of the base material in the slurry was increased, it was found that there was a problem in this atomized state. That is, as the amount of the base material increases, the cohesiveness of the slurry increases, and the stability (preservability) of the slurry tends to decrease. This point will be described in more detail based on the findings confirmed by the inventors' experiments.

First, as a base material (main raw material), a refractory substance,
One or more kinds of carbon material fine powders are mixed. For example, zircon, zirconia, graphite, coke, carbon black, magnesia, alumina, and compounds thereof are selected as the base material. Furthermore, in the case of graphite powder alone, a crystalline and appropriate average particle size is selected. The relationship with the particle size of the base material will be described below.

The smaller the particle size, the more uniform the coating agent slurry and the better the state of atomization by the nozzle. However, as the particle size decreases, the aggregation of the raw material particles at the time of pulverization progresses, so that the pulverization becomes difficult and the pulverization cost increases. When the particle diameter is 0.1 μm or less, when the particle surface is activated to form a slurry, the stability of the slurry is deteriorated, and aggregation and sedimentation occur. For this reason, the average particle size is desirably 0.1 μm or more. On the other hand, when the particle size increases, it becomes difficult to control the thickness of the coating agent, which causes uneven coating and increases the variation in coating thickness. For this reason, the upper limit of the average particle diameter is 50 for a coating thickness of 10 to 50 μm.
μm is desirable.

When crystalline graphite powder is used, if the upper limit is an average particle diameter of 500 μm or less, preferably 100 μm or less, the surface of the crystalline graphite may be fine even if the coating has fine irregularities due to graphite particles. The slip of the crystal cracks (see FIG. 2) is caused by the static pressure of the molten steel, and the slip during the solidification shrinkage of the slab is facilitated. The graphite crystal shown in FIG. 2 (a) has a very weak crystal force in one direction. Therefore, when a force as shown by an arrow in FIG. 2 (a) acts, the crystal is cleaved and FIG. ). In this way, the constraint point on the slab surface disappears while sliding on the surface of the coating agent, and high lubricity can be obtained. The optimal particle size of the crystalline graphite powder is 50 to 500 μm,
Preferably, it is 50 to 100 μm.

Next, a description will be given of the amount of the base material expressed as the slurry solid content concentration. According to the findings of the present inventors,
When the slurry solid content concentration (% by weight) is 20% or more,
Good coating stability. If the slurry solids concentration is low, the time required for drying is prolonged. On the other hand, if the slurry solids concentration is high, the drying property of the coating agent is improved, but the slurry viscosity is increased, so that the coating property due to fine powder is reduced. For this reason, the viscosity of the coating agent depends on the type of base material, the particle size, the type of binder and anti-settling agent used,
Although it depends on the addition amount, it is necessary to set the solid content concentration so that the viscosity of the coating agent can be atomized. In the present invention, the viscosity of the coating agent is 0.5 to 10 pois
Is a desirable range.

Next, the reason for limiting the binder in the present invention will be described in detail. In the present invention, one or more of an inorganic binder and an organic binder are used in combination based on an inorganic binder, and the requirement is to increase the adhesion strength of the coating agent to the belt. Examples of the kind of the binder include sodium silicate (water glass), silica gel, sodium aluminate, and the like as the inorganic binder, and these exhibit a hot bond strength. on the other hand,
Organic binders include CMC (carboxymethylcellulose), MC (methylcellulose), dextrin,
Resins such as starch, epoxy, acrylic and polyester can be used.

FIG. 1 shows the relationship between the amount of the inorganic binder and the residual ratio of the coating agent (adhesion strength). This was obtained by measuring the residual amount of the coating agent in a molten steel flow direct hit test after coating and drying the test piece. At this time, the residual ratio is a value obtained by measuring the thickness of the coating before and after the test and expressing the ratio. FIG.
According to the report, in order to secure the coating residual ratio (adhesion strength) of 0.7 or more required for protecting the belt, the inorganic binder is 2% by weight or more and the organic binder is 0.01% by weight.
It turns out that the above is necessary.

That is, in the present invention, the addition amount of the inorganic binder is 2 to 10% by weight based on the coating agent slurry. In this case, the amount of splash generated at the time of casting becomes large due to moisture absorption after drying. The content of the organic binder is set to 0.01 to 3% by weight with respect to the coating agent slurry. When the content is 0.01% by weight or less, the bonding strength is small, and when the content is 3% by weight or more, the organic binder is boiled by burning and decomposition at the time of casting. It is limited to this value because this causes a splash.

As another additive, in the present invention, in order to spray the slurry as a slurry on the belt, to stably store the coating agent in a slurry state, to prevent the base material of the coating agent from settling, Is added to the slurry in an appropriate amount. In the present invention, in addition to the above requirements, In the relationship between the concentration of the base material and the slurry solids concentration, the improvement in lubricity and the stability of the slurry are simultaneously satisfied, and in order to prevent vertical cracks of the slab, the slurry solids concentration is regulated to the above condition. I have. That is, the slurry solids concentration C (% by weight) ≦ 75−0.4 × [the graphite concentration (% by weight) in the base material] is set.

2. The upper limit is 50 for crystalline graphite powder.
0 μm, preferably 100 μm or less, in terms of the relationship between the base material and the solid content of the slurry, to simultaneously improve the lubricity and stability of the slurry, and to prevent vertical cracks in the slab. Is 20% by weight or more. It is necessary to increase the amount of base material from lubricity,
As the amount of base material increases, the cohesiveness of the slurry increases,
It has been found from experiments by the present inventors that the case where the above relational expression is satisfied because the stability (preservability) of the slurry is lowered is within a range in which lubricity and preservability can be simultaneously secured.
The operation and effect of the present invention will be described in detail based on examples.

[0021]

EXAMPLES Example 1 The results of actual casting using a low-carbon aluminum-killed steel and a medium-carbon aluminum-silicon-killed steel using a coating agent of the present invention using a twin-belt continuous casting machine are described. I do. Table 1 shows the composition of the coating agent used in the present invention, and Table 2 shows the results of continuous casting. The results show that the coating agents B, D, F, G, J, M and N have good casting operability. That is, splash,
No boiling phenomenon and no thermal damage to the belt.
The proper addition amount of the binder of the present invention is 2 to 10% by weight for the inorganic binder and 0.01 to 3% by weight for the organic binder.

[0022]

[Table 1]

[0023]

[Table 2]

Example 2 As an example in which the coating agent of the present invention was applied to an actual belt type continuous casting machine, Table 3 shows the results of evaluating the composition of the coating agent and the slurry stability and coating stability as coating agent characteristics. Is shown. Table 4 shows the occurrence of surface flaws in the slabs continuously cast with the coating agent of the present invention, using the incidence rate of slab vertical cracks. When the inorganic binder and the organic binder of the present invention were added, the coating agent characteristics and the rate of occurrence of surface flaws on the slab were reduced, and good results were shown. That is, it is understood that the present invention improves the lubricity and durability of the belt of the belt type continuous casting machine.

[0025]

[Table 3]

[0026]

[Table 4]

[0027]

By using the coating agent for a belt of a belt type continuous casting machine according to the present invention, the effect of reducing the frictional force between the slab and the belt is improved, and thermal deformation and heat, which are the causes of thermal damage, are improved. The industrial significance of improving the durability against shrinkage, extending the life of the belt, improving the quality of the slab, and improving the working efficiency of continuous casting is significant.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the amount of an inorganic binder and the adhesive strength of a coating agent in Examples of the present invention.

FIG. 2 is a view showing the cleavage properties of graphite crystals, and (a)
(B) The occurrence of slip due to cleavage due to stress.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C10M 107: 36 103: 06) C10N 10:04 10:06 10:08 20:06 40:00 (72) Inventor Hideyuki Misumi Oita No. 1, Nishinosu, Oita, Nippon Steel Co., Ltd. (72) Inventor Noriyoshi Masuo, 1808-3, Hachiya, Buzen-shi, Fukuoka (72) Inventor Shigeki Kashio, No. 1, Nishinosu, Oita, Oita City, Oita Prefecture Examiner, Nippon Steel Corporation Oita Works Kimihiko Kim (56) References JP-A-64-99755 (JP, A) JP-A-1-197048 (JP, A) JP-A 60-180647 (JP, A) JP-A-4-238655 (JP, A) JP-A-1-210155 (JP, A) JP-A-6-226408 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) ) B22D 11/06 340 B22D 11/07

Claims (3)

(57) [Claims] 1. A surface coating agent for a belt for continuously casting steel by forming a belt mold, wherein an inorganic binder is used to exhibit adhesion strength to a slurry containing water, which is a main raw material of a refractory substance and a carbon substance, as a solvent. : 2-1
0% by weight and organic binder: 0.01 to 3% by weight of one or two or more kinds are combined and added. A belt coating agent for a belt-type continuous casting machine. 2. A belt coating agent for a belt type continuous casting machine, wherein the graphite concentration in the base material of the slurry is 2%.
0% by weight or more, preferably 30% by weight or more, and the solid content concentration C (% by weight) expressed as% by weight of the base material with respect to the solvent (water) in the slurry is C ≦ 75─0.4x
An inorganic binder that satisfies the [graphite concentration in the base material (% by weight)] and has a slurry solids concentration C (% by weight) of 20% or more, preferably 30% by weight or more, and further exhibits adhesive strength. : 2 to 10% by weight and 0.01 to 3% by weight of an organic binder are added in combination of one or more of them. 3. The solid content of a slurry containing water as a solvent in a coating agent for a belt of a belt-type continuous casting machine,
For the purpose of reducing the friction between the belt and the slab, the concentration of the slurry of crystalline graphite is 20% by weight or more, preferably 30% by weight.
% By weight and not more than 70% by weight, and the crystalline graphite particles have an average particle size of 50 to 500 μm, preferably 1 to 500 μm.
It has a characteristic of not more than 00 μm, and is characterized by adding one or more of inorganic binder: 2 to 10% by weight and organic binder: 0.01 to 3% by weight in order to further develop the adhesive strength. Coating agent for belt of belt type continuous casting machine.