JPH02270906A - Ladle bottom structure in molten iron pre-treating ladle - Google Patents

Abstract

PURPOSE:To improve durability of refractory bricks for ladle bottom by using a large size Al2O3-SiC-C quality unburnt brick to center brick in the refractory bricks at the bottom part in the pre-treating ladle for molten iron and setting and arranging along the circumference, refractory bricks having dowels. CONSTITUTION:The molten iron from a blast furnace is poured into the pre- treating ladle for desiliconizing, dephosphorizing and desulfurizing pre-refining. In this case, the refractory at the bottom part in the treating ladle is subjected to crack and spalling by the poured high temp. molten iron and the operation rate is lowered. As a countermeasure, the center brick 7 at center part of the ladle in direct contact with the molten iron is composed of the large size Al2 O3-SiC-C quality unburnt brick integrally formed to top cutting right circular cone shape, in which scaly graphite has orientated structure of almost in direction perpendicular, to the using surface. Further, the refractory bricks 9-11 having dowels 8 and dumpy shape, are set along the circumference of this center brick 7. The cracking and spalling of the refractory bricks at the center part in the pre-treating ladle are hardly developed, and the service life thereof is greatly extended.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is directed to the prevention of damage caused by the operation of the refractory lining the bottom of a hot metal pre-treatment ladle that receives hot metal from a blast furnace and pre-treats the hot metal, and particularly to It concerns the shape and organization of things.

[Prior Art] In recent years, hot metal has been subjected to preliminary treatment for desiliconization, dephosphorization, and desulfurization, and a hot metal pot is used as a reaction vessel.

The refractory lining at the bottom of the hot metal pretreatment ladle used in this case has conventionally been constructed as shown in Figures 9 and 1O, with Figure 9 being a cross-sectional view and Figure 10 being a plan view. In the figure, the soil is the bottom of the pot, 2 is the center, and 3 is the central brick located in the center of this center, with a diameter of 4.00 mm and a height of 2.
Because it is large, about 80 mm, it is difficult to press-form it, so it is made into a truncated right conical shape by combining four quarter-shaped pieces as shown in the perspective view of Fig. 11.

4, 5, and 6 are peripheral bricks that surround the outer periphery of the center brick 3, and form the center part 2 of the Sa bottom. As shown in the perspective view of FIG. 12, each of the surrounding bricks has a horizontally extending shape, and has a thickness a of 80 to 1.5 mm with respect to a height of 280 mm. OOm
m, thickness b is 40-60mm, length 210-230m
A relatively thin brick of m is used.

The bottom of the conventional hot metal pretreatment pot, especially the refractory brickwork in the center, is constructed as described above, and its material is low stone,
In recent years, high alumina-carbon type (A1.O, -C type) unfired bricks have been widely used in place of viscous, high alumina and zircon type bricks.

[The problem that the invention tries to solve! l! ] Due to the operation of the hot metal pot, when discharging the hot metal, the lining refractory is
While the blast furnace is being cooled to 00 to 400 degrees Celsius, hot metal at 1,300 to 1,400 degrees Celsius falls and flows in from the blast furnace.
Especially the center of the bottom of the pot is exposed to rapid heat and large mechanical shock. Furthermore, during the dephosphorization stage of hot metal pretreatment, lime-based and iron oxide-based powders (processing agents) are injected and stirred with nitrogen gas (carrier gas), which is harsh for lined refractories. .

In this case, since the lining refractory brick is thin in the drying contact part of the pot bottom structure of the conventional hot metal pretreatment pot as described above, there are inevitably many joints in the circumferential direction, and this part is the first to melt. As a result of damage, individual bricks become convex or pencil-shaped, increasing the area exposed to the harsh conditions mentioned above.Also, since the pig iron receiving and preliminary treatments are repeated hundreds of times, the refractory bricks may crack, peel, or peel. There was a problem in that chips were likely to fall off, and furthermore, metal was inserted into the joints, bricks were lifted up, etc., and the pots had to be repaired more frequently.

In addition, when forming refractory bricks, 4
In the split shape, the press pressure direction is perpendicular to the parallel plane of the brick, that is, the surface in which the brick is used. As shown in Figure 13 (micrograph showing internal particle composition), it is easy to arrange and stack the bricks in a direction perpendicular to the press pressure direction, that is, parallel to the use surface of the brick. For this reason, there is a drawback that repeated use of refractory bricks tends to cause peeling due to this laminated arrangement of scaly graphite.

This invention was made to solve these problems, and provides a hot metal pre-treatment ladle that does not cause cracking or peeling of the lining refractory even after multiple pig iron receiving and stirring treatments, and requires fewer repairs. The purpose is to obtain a pot bottom structure.

[Means for Solving the Problems] The pot bottom structure of the hot metal pretreatment pot according to the present invention has a central brick located at the center of the pot bottom that is integrally molded in the shape of a large truncated right cone, and this brick is made of alumina-silicon carbide. - It is a carbonaceous unfired brick with a structure in which the scaly graphite in the brick is arranged in a direction almost perpendicular to the surface in which it is used, and a refractory brick with dowels and a hollow shape is arranged around it. .

[Function] In this invention, since there are no joints in the central brick, which is exposed to the harshest usage conditions, there is no melting loss from the joints, and cracks and chips that are promoted by this melting loss are removed, and metal insertion, etc. Moreover, since the scaly graphite in the bricks is oriented almost vertically, the peeling phenomenon of the bricks is suppressed.

Furthermore, since the dowels are provided, it also prevents the floating phenomenon caused by the difference in specific gravity with the hot metal.

The alumina-silicon carbide-carbon unfired product, which is the material of the central brick, can be used for conventional fired bricks and unfired bricks made of waxite, silicon carbide-carbon, high alumina, alumina-carbon, etc. It has increased resistance to cracking caused by falling hot metal and thermal stress, as well as strong resistance to mechanical shock, thermal spalling and erosion.

[Embodiment] Fig. 1 is a sectional view showing an embodiment of the present invention at the bottom of a hot metal pretreatment ladle 250, and Fig. 2 is a plan view. It is made of bricks, and Fig. 3 is its plan view, and Fig. 4 is its side view. It has a truncated right conical shape with a diameter of 364 mm and a height of 349 mm, and is an unfired product that is molded by applying pressure from the circumferential direction using a rubber press molding method so that the scales are oriented vertically.It weighs 107 kg. The materials are as shown in Table 1, and a dowel 8 is provided at the bottom of the dowel 8, which fits into the dowel of the surrounding brick 9 and is partially buried in the permanently laid brick.

As shown in the micrograph in Figure 5, the internal grain structure in Table 1 shows that many scaly graphites are oriented almost perpendicularly to the surface in which the refractory brick is used, i.e., the lateral plane in the photograph. It is less prone to erosion, cracking, chipping, and peeling during use.

6 and 7 are a cross-sectional view and a plan view of the surrounding brick 9,
Thickness a 146mm, thickness b 75mm, length 1.68m
m, and the thicknesses a and b of the surrounding bricks 10 and 11 are respectively] 35 mm, 130 mm, and 83
mm, 95 mm.

That is, the thickness of the conventional peripheral brick 4.5.6 is a80~1
00 mm, thickness b is thicker than 40-60 mm,
It has a zigzag shape.

By making the shape of the refractory brick into a square shape, that is, by making the used surface as close as possible to a square instead of a rectangle, the stress generated inside the brick is reduced, which is effective in preventing cracking during repeated use. This is σ = α・E・Δ1 for the generated stress σ, expansion coefficient α, elastic modulus E, and temperature difference Δt inside and outside the brick.
; has been experimentally confirmed. In addition, each of the refractory bricks 7, 9, 1.0.11 in the center part 2 is fitted into each other by tabs.

The hot metal pretreatment ladle of the above example was heated to 250 ml under the same conditions as before.
Figure 8 shows the relationship between the number of pig iron charges for 10 pots subjected to pig iron receiving treatment using $ pots and the remaining residue of the lining refractory bricks in the center of the pot bottom.

In the figure, A and B are 80 to 10 in a conventional 250 $ pot.
This shows the results for 0 units, and 2 generations of pot bottoms are required for 1 generation of side walls, and the first generation of pot bottoms is 100 to 14
At 0 charge, there was almost no remaining brick, so it was repaired and replaced, and in the second generation, at 250 to 280 charge, the remaining thickness of the brick was almost 0. C shows the usage results for 10 units of the above-mentioned example, and the brick residual thickness became 0 after 350 to 400 charges, indicating an operating charge number exceeding the conventional number of charges for 2 generations.

[Effect of the invention] As explained above, this invention improves the shape and material of the lining refractory brick in the center of the bottom of the pot, and further improves the internal structure of the refractory brick, thereby making it possible to operate multiple times under harsh conditions. Cracks, peeling, and chips in the lining bricks will also fall off,
It has the effect that lifting and melting damage can be greatly suppressed, and the service life of the center part of the hot metal pretreatment pot bottom can be extended to more than twice that of the conventional method.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the bottom of a pot showing an embodiment of the present invention;
The figure is a plan view, FIGS. 3 and 4 are a plan view and a side view of the central brick in the above embodiment, FIG. 5 is a micrograph showing the internal grain structure of the refractory brick of the pot bottom of this invention, and FIG. 6 , FIG. 7 is a cross-sectional view and a plan view of the surrounding brick 9, FIG. 8 is a graph comparing the usage results of the ladle of this invention and a conventional ladle, and FIG. 9 is a cross-section of the bottom of the ladle of a conventional hot metal pretreatment ladle. Figure 10 is a plan view of the bottom of the pot, Figure 11 is a perspective view showing the center brick of the conventional pot bottom, Figure 12 is a perspective view showing the peripheral part, and Figure 15 is the lining of the conventional pot bottom. This is a mirror photograph showing the internal particle structure of a refractory brick.
- Center brick, 8...Taboo, 9, 10, 1.1... Surrounding brick. Agent Patent Attorney Kubo 1) Law Mei Figure 9, District 11, Figure 12? Figure 0

Claims (1)

[Claims] A truncated conical integral refractory brick with a dowel is placed in the center of the bottom of the pot. A pot bottom structure for a hot metal pretreatment pot characterized by having a structure oriented in a right angle direction and further having dowel-shaped refractory bricks arranged around the structure.