Lining of the cone of a converter

Abstract

A lining at the restriction part of a converter capable of more suppressing the falling of bricks than before even if the bricks at the restriction part are stack aslant and increasing a workability at the time of installation, wherein the shell of the converter at the restriction part is lined with firebricks by tilt stacking to protect the restriction part against melting by hot molten steel and slag, a projectedly bent locking part is provided on the upper and lower surfaces of the firebricks, and the locking part on the lower surface of the firebrick stacked on an upper side is overlapped with the locking part on the upper surface of the firebrick stacked on a lower side.

Description

TECHNICAL FIELD

[0001] The present invention relates to the lining of a converter and, specifically, to a brick structure for lining a converter used for the smelting of molten steel, particularly the brick lining structure of the cone of a throat.

BACKGROUND ART

[0002] A converter is one of metallurgical vessels used to smelt molten steel. As for the entire structure of the converter, as shown in FIG. 6, the converter comprises a throat 1 used for the charge of raw material and the discharge of slag generated by the refining, a barrel portion 2 and a bottom portion 3 for holding molten steel and slag and refining, and a cone 4 interposed between the barrel portion 2 having a large diameter and the throat 1 and gradually tapered off toward the upper end. The outer surface portion of the converter 5 is composed of a shell 6 and the inner surface portion in contact with high-temperature molten steel and slag thereof is lined with a refractory material such as a firebrick 7 to protect it.

[0003] The above cone 4 is generally lined by a “horizontal lining” of firebricks 7 (to be simply referred to as “bricks” hereinafter) that the bricks 7 are lined(heaped up) in such a manner that the surfaces of the bricks become horizontal as shown in FIG. 4 or an “inclined lining” of the bricks 7 that the bricks 7 are lined up in such a manner that the surfaces of the bricks are inclined from the horizontal plane as shown in FIG. 5. Besides these, the following special technologies are used to heap up bricks.

[0004] For example, it is proposed that bricks are heaped up in such a manner that the surfaces of the bricks become perpendicular to the shell of the cone (refer to patent document 1). There is disclosed a technology for preventing the bricks of the cone from falling by providing the bricks of the cone with a metallic connecting device and interconnecting the connecting devices (refer to patent documents 2 and 3). There is further disclosed a technology for preventing the bricks from falling by grooving the bricks and combining them together (refer to patent documents 4 and 5).

[0005] According to experience in the past, in order to extend the service life of the cone 4, “inclined lining” is better than “horizontal lining”. Erosion by molten steel and slag generally proceeds from the barrel portion 2 to the cone 4. In the case of “horizontal lining”, bricks underlying a portion damaged by melting are easily broken by downward force applied to bricks above the portion damaged by melting. If part of a brick is missing by breakage, hustling force of the bricks laid on the full arc of the cone will be lost and all the bricks will fall off, thereby interfering with the operation of the converter.

[0006] In contrast to this, since downward force is divided and reduced in the case of “inclined lining”, “inclined lining” has the effect of avoiding breakage of the bricks as compared with “horizontal lining”. To develop this effect to the maximum, as disclosed by the above patent document 1, bricks are heaped up in such a manner that the surfaces of the bricks become perpendicular to the wall surface of the converter.

[0007] However, in the technology of the patent document 1, if the inclination of the wall of the converter is steep, the bricks may slip off during lining bricks in the converter, thereby making it impossible to carry out such lining work smoothly. Particularly when the converter is used for the first time (start-up), after coke is charged into the converter to be heated so as to dry the lining, the converter is turned upside down to discharge the coke. At this point, the bricks of the cone heaped up obliquely may fall off. To prevent the bricks of the cone from falling, there is the technology for providing the bricks with a connecting device as disclosed by the above patent documents 2 and 3, which boosts materials cost. Further, when the bricks of the cone are grooved and combined together as disclosed in the above patent documents 4 and 5, the grooving step is additionally needed, thereby increasing the number of steps and boosting cost. When a depression or projection is formed in a mold used to press a brick in accordance with the groove as disclosed by the above patent documents 4 and 5, cracking easily occurs from the corner of the groove when the brick is heated. Therefore, grooving must be carried out separately after the production of a brick.

[0008] In view of the above situation, it is an object of the present invention to provide a lining for a converter which can further suppress the fall of bricks even when the bricks of the cone are heaped up obliquely compared with the prior art and has high construction work efficiency.

[0009] [Patent Document 1]

[0010] Japanese Laid-open Utility Patent Application No. 3-67050

[0011] [Patent Document 2]

[0012] Japanese Laid-open Patent Application No. 1-309915

[0013] [Patent Document 3]

[0014] Japanese Laid-open Utility Patent Application No. 5-37950

[0015] [Patent Document 4]

[0016] Examined Japanese Patent No. 58-32311

[0017] [Patent Document 5]

[0018] Japanese Laid-open Patent Application No. 5-279719

DISCLOSURE OF THE INVENTION

[0019] The inventor of the present invention has conducted intensive studies to attain the above object and has embodied the results in the present invention.

[0020] That is, the present invention is a lining for the cone of a converter, which is composed of firebricks lined(heaped up) obliquely on the shell of the cone of a converter and prevents melting damage by high-temperature molten steel and slag, wherein a projecting bent engagement portion is formed on the top and bottom surfaces of the above firebricks so that the engagement portion on the bottom surface of an overlying firebrick and the engagement portion on the top surface of an underlying firebrick are engaged with each other.

[0021] In the present invention, preferably, the top surface and the bottom surface of each firebrick are made perpendicular to the surface of the shell, the height of the projecting bent engagement portion is set to 5 to 20 mm, or the position of the projecting bent engagement portion is {fraction (1/15)} to ⅓ the total length of the firebrick from the shell-side end of the firebrick.

[0022] According to the present invention, since bricks adjacent to each other in a vertical direction are engaged with each other by newly providing projecting bent engagement portions, even if the melting damage of the barrel portion of the converter proceeds, the brick will hardly fall off. The bricks can be prevented from falling when they are lined or when they are turned upside down. That is, according to the present invention, the bricks of the cone can be prevented from falling more than in the prior art even when they are lined obliquely and a lining for a converter which has excellent construction work efficiency can be provided at a low cost.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 is an entire cross sectional view of the cone of a converter according to the present invention;

[0024] FIG. 2 is a cross sectional view of the details of the cone of the converter according to the present invention;

[0025] FIG. 3 is a diagram showing the service lives of the cones of a converter having a cone of the present invention and a converter having a cone of the prior art;

[0026] FIG. 4 is a cross sectional view of the cone of the converter constructed by lining bricks horizontally in the prior art;

[0027] FIG. 5 is a cross sectional view of the cone of a converter constructed by lining bricks obliquely in the prior art;

[0028] FIG. 6 is a cross sectional view showing the structure of a general top-blowing converter; and

[0029] FIG. 7 are diagrams showing the size and shape of a brick according to the present invention, wherein FIG. 7(A) is a side view and FIG. 7(B) is a plan view.

BEST MODE FOR CARRYING OUT THE INVENTION

[0030] Embodiments of the present invention will be described with reference to the accompanying drawings.

[0031] FIG. 1 is a whole view of the lining of the cone of a converter according to the present invention. As shown in FIG. 1, bricks 7 used for this lining are heaped up obliquely on the bricks 8 which are lined(heaped up) horizontally of the barrel portion of the converter. The important point is not to use bricks having flat surfaces like an ordinary brick but to use bricks having projecting bent engagement portions 9 on part of the surface as shown in the cross sectional view of FIG. 2. That is, an engagement portion 9a on the bottom surface of an overlying brick and an engagement portion 9b on the top surface of an underlying brick are fit in with each other. Since bricks adjacent to each other in a vertical direction are engaged with each other, even if the melting damage of a brick 8 of the barrel portion or a brick 7 of the cone 4 proceeds to some extent and an underlying brick is lost, an overlying brick will hardly fall off. The reason that the engagement portion 9 projects upward is that if a sinking engagement portion is formed, when bricks are placed one upon the other, they will easily slip off and when extraneous force is applied, both of them will fall off together.

[0032] To construct this lining, an operator who has entered the converter simply pushes a brick 7 from his side toward the shell until that the engagement portion 9a of an overlying brick falls in the engagement portion 9b of an underlying brick to line bricks, thereby preventing an increased load on the converter construction work. Further, the manufacture of bricks only requires the production of a mold for obtaining the above shape without any additional cost. Further, as bricks for lining a converter are laid on the annular shell, there may be a case where the bricks are not rectangular and opposed two faces of adjacent bricks are not parallel to each other. In the present invention, projecting bent portions are formed on a brick to make it into a polyhedral shape, thereby preventing a problem with construction.

[0033] In a technical field different from the field of converters, firebricks having engagement portions have already been used in the inner wall, especially the ceiling portion of a hot stove or the like to prevent the fall of the bricks. A typical example of the firebrick used for a hot stove or the like has the above engagement portion (corresponding to 9a in FIG. 2) near the center in the thickness portion of the lining, the engagement portion has a difference in a level with its height of about 25 mm, and an inclined portion (corresponding to 9c) having the above level difference has an angle (corresponding to &thgr;1) of about 30° from the horizontal plane of the brick. However, it has been difficult to apply this shape to the lining of a converter under the following situations.

[0034] Firstly, in general, the firebricks of the hot stove are rarely damaged and have a service life of 10 years or more before exchange. On the other hand, since the inner wall of the converter is always subject to erosion by molten steel or the like, it has a service life of about 1 year at maximum. In addition, when the erosion of the lining reaches the above engagement portion, the engagement effect is lost, thereby increasing the risk of losing a brick. Therefore, when the engagement portion is existent near the center portion in the thickness direction of the lining as used in a hot stove and a brick is half eroded, the risk of losing a brick sharply grows, thereby increasing the frequency of exchanging the bricks.

[0035] Secondly, since the inside temperature of the converter exceeds 1,700° C. at maximum while the inside temperature of the hot stove is about 1,200° C., the environment of the converter has a greater heat load than the hot stove. Further, as a MgO—C (magnesia•carbon) brick used in the converter has higher heat conductivity than a silica brick used in the hot stove or the like, in the case of the lining of the converter, force concentrated on a deformed portion such as the engagement portion is greater than in the hot stove.

[0036] To solve the above first problem, the engagement portion must be formed as close to the shell in the thickness direction of the lining as possible. On the other hand, the second problem makes it difficult to increase engagement force by arranging the engagement portion close to the end of the brick or by enlarging the projection of the engagement portion. To satisfy these contradictory requirements, the inventors of the present invention have tried various shapes and sizes and have found that the following shape can overcome the above problems to attain the above object.

[0037] Firstly, in the present invention, the shape of the projecting bent engagement portion may be a key-like shape, a right-angled level difference like a step or inclined level difference, or hiragana(Japanese syllabary character) “he”-like or letter S-like shape if it has an engagement effect. A gentle S-like shape as shown in FIG. 2 is the most preferred from the viewpoint of balance between engagement force and the strength of the engagement portion. A projecting portion 9a preferably is not angular but curved and preferably has an angle larger than 90°. This can suppress cracking starting from the bent corner caused by the concentration of stress.

[0038] Further, an inclined portion 9c has an inclination angle (&thgr;1) from the horizontal plane of the brick of preferably about 30° or more and less than 90°, preferably about 45 to 75°. That is, when the angle is too small, engagement force becomes insufficient. When the bricks are lined perpendicular to the wall of the converter, this tendency becomes marked. When the angle is too large, the engagement portion is easily broken.

[0039] In addition, in the present invention, the height of the projecting bent engagement portion 9 is preferably 5 to 20 mm. The reason for this is that when the height is smaller than 5 mm, engagement between bricks is unstable and a brick may fall off even with small extraneous force and when the height is larger than 20 mm, an engagement effect may be saturated and the engagement portion may become weak.

[0040] Besides, in the present invention, the position of the projecting bent engagement portion 9 is preferably set to {fraction (1/15)} to ⅓ the total length in the thickness direction of the lining from the shell-side end of the brick. When the position of the engagement portion is shorter than {fraction (1/15)} the total length from the shell-side end of the brick, if the brick is broken, the shell cannot be protected by the remaining bricks. When the position is longer than ⅓ the total length, erosion proceeds or a brick easily falls off if downward force is applied. Particularly preferably, the position is set to about {fraction (1/15)} to {fraction (1/10)} the total length of the brick. Since the above bent engagement portion is simple in shape, it can be easily manufactured by forming a depression or projection corresponding to the bent engagement portion in a mold for the production of the brick. Any type of the brick is used, but magnesia•carbon is preferably used as described above. As for the inclination angle (&thgr;2 in FIG. 1) at which the bricks 7 are lined, the bricks may be inclined from the horizontal plane at a certain angle (for example, about 10°), preferably 15° or more, the most preferably such that the surface of the brick becomes perpendicular to the shell surface. This is because the effect of dividing downward force applied to the brick 7 is large.

EXAMPLES

[0041] Bricks shown in FIG. 2 were manufactured for the cone of a converter and lined(heap up) on the cone 4 of a converter 5 in such a manner that bricks 7 became perpendicular to the shell (Examples of the present invention) in order to smelt molten steel with the converter. The operation of a converter which was constructed using bricks having ordinary flat surfaces was also carried out (Comparative Examples). The bricks 7 were made from MgO—C (magnesia•carbon-based) and so-called “unburned bricks” manufactured by charging a mixed powder of MgO and C into a mold, pressing and drying it. The brick of the present invention had a height of 150 mm, a length (in the thickness direction of the lining) of 810 mm and a width of 75 mm as shown in FIG. 7 and a projecting bent engagement portion 9 on the top and bottom surfaces. An inclined level difference as shown in FIG. 2 was formed as the projecting bent engagement portion 9 at a position 75 mm from the shell side end and had a height of 15 mm. In portions other than the cone 4 of the converter 5, bricks are lined in a commonly used manner. The inclination angle (&thgr;1: see FIG. 2) of the inclined portion 9c having the above level difference was 60°. Referring to the lining of bricks for the above cone, Comparative Example 1 shows “horizontal lining” (&thgr;2=0°) of the prior art, Comparative Example 2 indicates “inclined lining” having an inclination angle (&thgr;2=12°), and Examples of the present invention show “inclined lining” in which the surfaces of the bricks became perpendicular to the shell surface. It was difficult to further increase the inclination angle with the conventional flat bricks. The inclination (&thgr;2: see FIG. 1) of the brick from the horizontal plane when it was heaped up perpendicular to the shell surface (wall surface) was about 30°. Although the effect of the present invention becomes maximum by lining bricks perpendicular to the shell of the cone of the converter (&thgr;3=90°, see FIG. 1), it was confirmed that the same effect was obtained even when &thgr;3 (see FIG. 1) was 95 to 105° (see FIG. 3). Although various kinds of steel including normal carbon steel were produced during operation, efforts were made to obtain almost the same type of steel (composition) on average in Comparative Examples and Examples of the present invention.

[0042] The operation results of these converters were evaluated by the serve life index of the cone of the converter (based on the service life when bricks were heaped up horizontally) and shown in FIG. 3. It is obvious from FIG. 3 that the service life of the cone of the converter can be extended to about 2 times longer than that of the prior art by the present invention. The consumption of bricks is caused by multiple effects of cracking and damage(erosion) when bricks are heaped up horizontally or obliquely in the prior art. When bricks are heaped up perpendicular to the shell, force applied to the bricks is dispersed, thereby making it possible to suppress the cracking of the bricks. When the lining of the converter according to the present invention is constructed, the number of steps for constructing the converter does not increase and the production cost of the brick does not rise as compared with the prior art because only a new mold is manufactured.

Claims

1. A lining for the cone of a converter, which is composed of firebricks lined on the shell of the cone of a converter obliquely and prevents erosion by high-temperature molten steel and slag, wherein

a projecting bent engagement portion is formed on the top and bottom surfaces of the above firebricks so that the engagement portion on the bottom surface of an overlying firebrick and the engagement portion on the top surface of an underlying firebrick are engaged with each other.

2. The lining for the cone of a converter according to claim 1, wherein the top surface and the bottom surface of the firebrick are perpendicular to the surface of the shell.

3. The lining for the cone of a converter according to claim 1 or 2, wherein the height of the projecting bent engagement portion is 5 to 20 mm.

4. The lining for the cone of a converter according to any one of claims 1 to 3, wherein the position of the projecting bent engagement portion is {fraction (1/15)} to ⅓ the total length of the brick from the shell-side end of the firebrick.

5. A magnesia•carbon firebrick which is an almost rectangular parallelepiped brick comprising MgO and C as main components and has a projecting bent engagement portion on the top surface and the bottom surface of the brick at a position {fraction (1/15)} to ⅓ the total length from the end portion in the longitudinal direction of the brick.