JPH10277729A - Construction method of castable refractory with two-layer lining - Google Patents

Abstract

(57) [Problem] To provide a method for constructing a castable refractory having a two-layer lining, which can prevent delamination without employing a stud support means that may lead to a steel leak accident. SOLUTION: In a method of constructing a two-layer castable refractory on a molten metal container, first, an outer-side castable construction body (outer layer) is provided with a middle frame provided with a plurality of protrusions of a predetermined size on an outer surface. It is constructed by pouring castables between the casing of the container and, after curing, is removed from the frame and the protrusions are removed.Next, the inner frame for castable construction on the inner surface side is arranged at a predetermined position, The castable is poured into a space between the inner frame and the outer castable construction body, which also includes a depression on the inner surface of the outer castable construction body formed after removing the protrusion, and the inner castable construction body (inner layer) is formed. ).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing a refractory lining of a molten metal container, and more particularly, to an inner castable construction (inner layer) and an outer castable construction (outer layer).
And a method for constructing a castable refractory having a two-layer lining.

[0002]

2. Description of the Related Art In a molten steel ladle and a tundish, which are typical in the steel industry as a molten metal container, an alumina spinel or alumina-magnesia refractory castable is poured into a refractory lining. In recent years, in order to reduce the heat dissipated from the wall surfaces of these containers, for example, as disclosed in JP-A-6-285614, a heat insulating board or the like is provided between the permanent brick on the castable back surface and the iron shell. Attempts have been made to apply insulation.

However, in such a method, when the container is heated or subjected to molten steel, the castable thermally expands,
A compressive stress acts on the heat insulating material via the permanent brick.

FIG. 3 schematically shows a temperature gradient taking the side wall of a ladle as an example. T _{1 for} molten steel temperature and T for steel shell temperature
₂ , the atmospheric temperature is T ₃ , the thermal conductivity of the refractory castable is λ ₁ , the thickness is D ₁ , the thermal conductivity of the permanent brick is λ ₂ ,
The thickness is D ₂ , the thermal conductivity of the heat insulating board is λ ₃ , the thickness is D ₃ , the thermal conductivity of the steel is λ ₄ , the thickness is D ₄ , and the heat transfer coefficient in the ladle is h ₁ , following a typical example of obtaining the dissipation heat Q ₂ from the heat transfer amount Q _1, steel shell of the ladle sidewalls by convergence calculation by the constant heat transfer. Q ₁ = (T ₁ −T ₂ ) / ｛(1 / h ₁ ) + (D ₁ /
λ ₁ ) + (D ₂ / λ ₂ ) + (D ₃ / λ ₃ ) + (D ₄ / λ
₄ )｝

Here, h ₁ = 400 kcal / m ² · hr · ° C., λ ₁ = 2.0 kcal / m · hr · ° C., D ₁ = 0.
15 mλ ₂ = 1.0 kcal / m · hr · ° C., D ₂ = 0.
065m λ ₃ = 0.05 kcal / m · hr · ° C., D ₃ = 0.
025m λ ₄ = 46 kcal / m · hr · ° C., D ₄ = 0.
05 m, molten steel temperature T ₁ = 1600 ° C., steel shell temperature T ₂ = 16
Assuming 0 ° C. and the atmospheric temperature T ₃ = 20 ° C., Q ₁ = 2237 kcal / m ² · hr.

On the other hand, the amount of heat Q ₂ dissipated from the steel shell is given by: Q ₂ = 4.88 × [｛(273 + 160) / 100｝ 4, where convection heat transfer coefficient h ₂ = 6.4 kcal / m ² · hr · ° C. − ｛(273 + 20) / 100｝ 4] + 6.4 × (160−20) = 2252 kcal / m ² · hr Since the steady state, Q ₁ = Q _2. Q ₁ = Q ₂ is calculated. Using the above assumed values, the average temperature of the castable is calculated from the above temperature gradient to be about 1510 ° C. The compressive stress acting on the heat insulating material by the thermal expansion of the castable at this temperature constrained by the steel shell on the side wall of the ladle is determined based on the following formula.

The strain ε of the castable can be expressed by the ratio of the value obtained by subtracting the theoretical expansion amount δ ₂ of the steel shell in the radial direction from the theoretical expansion amount δ ₁ of the castable and the initial length R, so that ε = ( δ ₁ −δ ₂ ) / R. Assuming that the Young's modulus of the castable is E, the generated stress σ can be expressed by the following equation. σ = E · ε

Here, assuming that the diameter of the ladle is 4 m, R =
2000 mm, the coefficient of thermal expansion of the castable α ₁ =
When the theoretical expansion amount δ ₁ of the castable in the radial direction is calculated using 6 × 10 ^-6 , δ ₁ = 2075 × 6 × 10 ^-6 × 1510 Further, the thermal expansion coefficient α ₂ of the steel shell = 10.7 × 10 ^When the theoretical expansion amount δ ₂ of the steel shell in the radial direction is obtained using ^-6 , δ ₂ = 2240 × 10.7 × 10 ⁻⁶ × 160. When the generated stress σ is calculated using the castable Young's modulus E = 4000 MPa, σ = E · (δ ₁ −δ ₂ ) / R = 30 MPa. That is, the heat insulating board receives a compressive stress of 30 MPa.

However, the compressive strength of the heat insulating board is several M
Since it is Pa, it will be crushed by this compressive stress.
If the crushing is severe, a large crack is formed in the castable in the process of repeatedly heating and cooling the ladle, and molten steel may be inserted into the castable, thereby causing a steel leak accident.

In order to solve the above-mentioned problem of the method of insulating refractories lining a molten metal container, there is a method of applying a high-strength heat insulating material to the rear surface of the refractory castable. For example, by using a hollow raw material, a fire-resistant heat-insulating castable (hereinafter, referred to as a heat-insulating castable) that achieves both heat insulation and high strength
That. ) Can be achieved on the back of the refractory castable to achieve the intended purpose.

When such a two-layer castable is applied, the heat-insulating castable on the outer surface side is applied, and the refractory castable on the inner surface is applied after hardening. There is a problem that peeling is easy to occur. To prevent this,
A method of erecting a bolt on an iron skin, constructing a castable layer on the outer surface with the tip of the bolt protruding, hardening, fixing a stud to the tip of the bolt, and forming a castable layer on the inner surface is disclosed in Tokubo Sho 60 -5876. In an atmospheric furnace, castable two-layer construction in which delamination between layers is prevented by such a stud supporting force is generally adopted.

[0012]

However, in a molten metal container such as a molten steel ladle or a tundish, if the thickness of the refractory castable becomes thin due to abrasion due to the molten metal or reaction and erosion with the molten slag, the stud is exposed. In addition, there is a problem that there is a high risk of causing a steel leak accident due to melting with molten metal.

The present invention has been made in view of these problems, and has as its object to provide a method of constructing a castable with a two-layer lining that does not cause a steel leak accident and does not cause delamination. It is.

[0014]

The gist of the present invention is as follows. In the method of constructing a castable refractory of two layers of an inner surface castable body (inner layer) and an outer surface castable body (outer layer) in a molten metal container, first,
The outer surface side castable construction body (outer layer) is constructed by pouring the castable between a middle frame provided with a plurality of projections of a predetermined size on the outer surface and a casing of the container, and after the castable is cured, While removing the middle frame, removing the protrusions, then arrange the inner frame side castable construction middle frame at a predetermined position, between the middle frame and the outer surface side castable construction body, Castable refractory of a two-layer lining, wherein the castable is poured into a space including a depression on the inner surface of the outer castable construction body formed after removing the protrusion, and the inner castable construction body (inner layer) is constructed. Construction method of the object.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention aims to achieve the prevention of peeling between layers of a castable construction having a two-layer lining by a wedge effect. The construction procedure will be described below with reference to FIGS.

First, the construction of the outer-side castable will be described with reference to FIG. Prior to the castable work on the outer surface side, a plurality of protrusions are provided on the outer surface of the middle frame 2 by means such as bonding, and then the middle frame 2 is fixed at a position where a predetermined castable work thickness can be secured. Thereafter, the castables on the outer surface side are poured into the space between the middle frame 2 and the casing 1 of the container, constructed, cured, cured, and then deframed. At this time, the protrusions 6 provided by means such as bonding are peeled off from the middle frame and are left in the outer surface side castable construction body 4 and are removed.

Next, as shown in FIG. 1, the inner frame 3 for castable construction on the inner surface side is newly set at a predetermined position, and the protrusion 6 between the middle frame 3 and the outer castable construction body 4 is formed. Castable is poured into the space including the recess 6 on the outer castable surface formed after removing the caster (inner castable construction body 5), cured, cured and then deframed to form a two-layer lining construction body. obtain.

As described above, the plurality of recesses on the outer castable surface are filled with the inner castable, so that separation between the layers can be prevented by the wedge effect of the fitting portion.

Although the size of the protrusion is not specified here, the size is such that the recess after removing the protrusion can be smoothly filled with the castable due to the fluidity at the time of casting the inner surface side castable. Is desirable.

[0020]

As described above in detail, according to the present invention, a castable construction having a stable two-layer lining which does not require support by studs which may lead to a steel leak accident in a molten metal container and does not cause delamination. Can be obtained.

[Brief description of the drawings]

FIG. 1 is a view showing a construction example of a castable with a two-layer lining according to the present invention.

FIG. 2 is a diagram showing an example of the construction of an outer surface-side castable which is one process of the present invention.

FIG. 3 is a view schematically showing a temperature gradient of a side wall of a molten steel ladle;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Container casing 2 Inner-side castable construction middle frame 3 Inner-side castable construction middle frame 4 Outer-side castable construction body 5 Inner-side castable construction body 6 Protrusion (dent on the surface of the outer-side castable construction body,
Fitting part between castable layers)

Claims (1)

[Claims] In a method for constructing a castable refractory having two layers, an inner castable construction (inner layer) and an outer castable construction (outer layer), first, the outer castable construction (outer layer) is formed. It is constructed by pouring castables between the inner frame and the casing of the container provided with protrusions of a predetermined size at a plurality of locations on the outer surface, and after the castables are cured, removing the inner frame,
Remove the protrusions, then arrange the inner frame for castable construction at the predetermined position, between the middle frame and the outer surface castable construction, formed after removing the protrusions A castable refractory having a two-layer lining, comprising: casting a castable into a space including a depression on the inner surface of an outer castable construction body, and constructing the inner castable construction body (inner layer).