JPH0735531B2 - Lining method for immersion pipe for vacuum degassing equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for lining a dip tube for a vacuum degassing device, which suppresses vertical joint melting damage of an inner lining brick and makes it possible to extend its service life. Is.

(Prior Art) Conventionally, the immersion pipe for a vacuum degassing device has a cylindrical cored bar with a flange on the upper end, and a brick lined in a cylindrical shape through a castable refractory to form a molten steel flow port. The lining method was to cover the outer circumference of the core metal with castable refractory. At this time, the lining brick has a general horizontal jelly shape, the width of the molten steel passage surface, the so-called operating surface, is the same in the upper and lower sides, and the width of the non-operating surface is the same in the upper and lower sides. It was made of chrome. And this horizontal jelly-shaped lining brick was constructed with magnesia mortar with vertical joints of 0.5 to 2.0 mm thickness.

(Problems to be Solved by the Invention) By the way, the conventional dipping tube for a vacuum degassing apparatus by a lining method using a horizontal jelly-shaped lining brick has the following drawbacks.

The dip tube for the vacuum degassing device uses magrochrome because the corrosion resistance of molten steel is important in its use. However, this magchromic material is also a material having a very large coefficient of thermal expansion.

Therefore, generally, the thickness of the joint mortar is designed in consideration of this thermal expansion. However, unlike a general container, this immersion tube for a vacuum degassing device has contact with molten steel both inside and outside, and there is also a thermal expansion of the cylindrical core metal and the intervening castable itself.
It is not possible to secure the bearing capacity for this compression toward the outer surface, and expansion absorption is impossible only with joint joint design. Then, the phenomenon that the lining bricks are displaced to the back side occurs, and this displacement weakens the compressive force in the vertical joints between the lining bricks,
The refractory mortar in the joint portion was not easily densified, but was easily damaged by molten steel flow or slag, leading to joint erosion and low durability in many cases.

This joint erosion phenomenon has been observed in recent years by diversification of refining steel types and ultra-low carbon steel processing. In order to reduce the CO partial pressure in the vacuum chamber, the flow rate of blown Ar gas is doubled to 3000 times the normal flow rate. ~ 4000
The operation rate of Nl / min increased, and along with this, the speed of molten steel flow tended to be further promoted.

The present invention has been made for the purpose of providing a method for lining a dipping pipe for a vacuum degassing apparatus, which solves the above-mentioned drawback of vertical joint erosion of an inner lining brick.

(Means for Solving the Problems) In order to achieve the above object, the present invention is configured as follows.

The present invention will be described below with reference to the drawings.

According to the present invention, a cylindrical cored bar 1 having a flange 2 at the upper end is laminated with a castable refractory 3 on which an inner brick 4 is lined to form a molten steel passage opening 5, and the cylindrical cored bar is formed. In the method for lining a dip tube for a vacuum degassing device, the outer periphery of which is covered with castable refractory 3
As shown in FIG. 1, when the width of one end of the so-called working surface A, the so-called working surface A, is a and the width of the other end is b, as shown in FIG. , And the width of one end of the non-operating surface B is c and the width of the other end is d, c <d
It is characterized in that it has a four-sided taper satisfying the conditions of (1), and that each of the lining bricks 4 is alternately lined up and down to form a cylindrical laminated lining.

With this lining method, as shown in FIG. 2, in the thermal stress due to the thermal expansion of each lining brick 4, the thermal stress in the horizontal direction is dispersed in the vertical direction. Therefore, non-operating surface B
Side stress is reduced, ie castable refractory 3
And, it is possible to reduce the pressing force to the cylindrical core metal 1,
It has the effect of suppressing joint opening.

(First Embodiment) A first embodiment of the present invention will be described with reference to the drawings. As shown in Fig. 3, it is a 100T vacuum degasser dip tube, the shape is a in Table 1, and the material is a magnesia chrome direct bond lining brick with MgO 59% and Cr ₂ O ₃ 19% components. The first stage is a high alumina monolithic brick, which is the same as the conventional one, and the top and bottom are alternated with magnesia mortar of MgO 95%, the longitudinal joint is 0.5 mm and the lateral joint is 1.0 mm. Lined the steps.

Then, a high alumina castable having an outer diameter of φ810 was cast-molded between the outer periphery of the core metal and between the core metal and the lining brick layer. Then, it was demolded and dried to obtain a dipping tube for a vacuum degassing device. The obtained immersion tube for vacuum degassing device was put to practical use.

For comparison, a conventional horizontal jelly brick having the shape of B shown in Table 1 is used as a vertical joint with magnesia mortar containing 95% MgO at the second and third lining bricks constructed in the first embodiment of the present invention. mm, horizontal joint 1.0 mm, and the other similarly constructed ones were used.

As a vacuum degassing device, an RH device was applied to a capacity of 100 T, the operating time was 20 minutes / ch on average, and the temperature was 1630 ° C. The results were as shown in Table 2.

Second Embodiment A second embodiment will be described with reference to the drawings. As shown in FIG. 3, as a 250T RH degasser dip tube, in Table 1,
In the shape of c, the material is a magnesia chrome direct bond lining brick containing 55% of MgO and 19.5% of Cr ₂ O ₃ , 1, 2, 3
As with the first embodiment, both stages were used, and as with the first embodiment, magnesia mortar containing 95% MgO was designed to have a vertical joint of 0.5 mm and a horizontal joint of 1.0 mm, and both were lined up and down alternately.

In addition, as the first-stage lined brick, a c-shaped product was used with a back surface being a supporting portion for the core metal. Next, a castable high alumina castable material having an outer diameter of φ1050 was formed between the outer periphery of the cored bar and between the cored bar and the lining brick layer. Then, it was obtained by demolding and drying. The obtained immersion tube for vacuum degassing apparatus was put to practical use. For comparison, the conventional horizontal jelly bricks having the shape of D shown in Table 1 were used for the first to third lining bricks constructed in the second embodiment of the present invention with magnesia mortar of MgO 95% to have vertical joints of 0.5 mm and horizontal joints. The same construction was used with a ground of 1.0 mm.

Applying these to a RH device with a capacity of 250T, operating time averages 25 minutes
/ ch, used under the condition of operating average temperature 1650 ℃, the result is the second
It was as shown in the table.

(Effects of the Invention) The present invention relates to a dip tube for a vacuum degassing device, wherein the shape of the lining brick is tapered on four sides as described above,
By alternating the upper and lower sides of the lining, the stress on the back surface of thermal expansion was suppressed, the displacement of brick joints and erosion were alleviated, and the service life was extended.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a four-sided taper lining brick used in the present invention, FIG. 2 is a partial explanatory view in which upper and lower alternate bricks are constructed by the method of the present invention, and FIG. It is a longitudinal cross-sectional view of a dip tube for a vacuum degassing device. 1 ... Cylindrical core metal, 2 ... Flange, 3 ... Castable refractory material, 4 ... Lining brick, 5 ... Molten steel passage port, A ... Operating surface, B
… Non-operating surface, a, b, c, d… Width,

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuji Matsubuchi 163-1 Shinmei, Narumi-cho, Midori-ku, Aichi Prefecture Nagoya City (72) Inventor Toshikatsu Kiuchi Chita City, Aichi Prefecture 91-1

Claims (1)

[Claims] 1. A cylindrical cored bar having a flange on the upper end thereof is covered with a castable refractory to lay bricks in a cylindrical shape to form a molten steel passage opening, and the outer periphery of the cylindrical cored bar is castable. In a method of lining a dip tube for a vacuum degassing apparatus covered with a refractory, when the width of one end of the working surface is a and the width of the other end is b, as a lining brick, a <b
When the width of one end of the non-operating surface corresponding to the back side of the width a is c and the width of the other end corresponding to the back side of the width b is d, the condition of c <d is satisfied. A method for lining a dip tube for a vacuum degassing device, comprising using bricks having a four-sided taper having the above, and lining the bricks in a cylindrical shape so that the bricks are alternately staggered up and down.