JP7309468B2 - dip tube - Google Patents

Description

TECHNICAL FIELD The present invention relates to a dip tube used in a vacuum degassing apparatus for RH, DH, or the like used in secondary refining of molten steel.

An immersion pipe used in a vacuum degassing device is usually composed of a flange, a cylindrical core attached to the flange, and refractory materials placed on the inner and outer circumferences of the core. ing. This refractory wears considerably due to the action of the molten steel flow, reaction with slag floating on the molten steel, and flaking due to cracks caused by thermal cycles. there is a problem to
It is believed that one of the major reasons for this fall-off is that the lower portion of the core bar expands outward due to thermal strain. Therefore, various countermeasures have been conventionally attempted to suppress the outward expansion of the lower part of the metal core in the immersion pipe.

For example, Patent Literature 1 discloses an immersion tube in which the entire core bar has a double structure and a cooling space through which a cooling gas passes is provided inside. However, the structure of Patent Document 1 prevents air suction through the gap generated between the core metal and the refractory. The effect of suppressing cracks and falling off of the refractory by is insufficient.

Patent Literature 2 discloses a structure in which a gas passage is provided in an annular shape around the lower outer circumference of the cored bar, but there is a problem that the cooling efficiency of the cored bar is insufficient. That is, when the immersion tube is immersed in molten steel, the upper part of the outer circumference is in contact with the outside air, so the temperature of the outer circumference of the lower part of the core bar is lower than that of the inner circumference. Furthermore, in many cases, a monolithic refractory is placed around the outer circumference of the immersion tube as the refractory on the outer peripheral side, and is arranged with a smaller thickness than the refractory on the inner peripheral side. Furthermore, since the outer periphery of the immersion pipe is in contact with the slag, it is easily damaged and cracked. For this reason, when a gas passage is provided on the outer periphery of the metal core, there is also a problem that the gas passage is easily damaged and gas leaks occur.

Therefore, Patent Document 3 discloses a cooling structure for cooling the lower inner circumference of the cored bar. Specifically, a cooling passage for cooling the core metal is an immersion pipe provided along the core metal, and the cooling passage for passing the cooling gas is inside the core metal and has a crescent-shaped cross section. A cooling structure provided in the is disclosed. It is also disclosed that the cooling passage in this cooling structure is provided by cutting a cylindrical pipe so as to have a crescent-shaped cross section and fixing it by welding to a metal core.

However, in the case of the cooling structure of Patent Document 3, the thickness of the center of the cooling passage is large because the cooling passage is formed by a cut pipe. For this reason, the cooling passage becomes an obstacle and the inner brick cannot be arranged to the lower end of the core metal or the immersion pipe. In order to reduce , the cooling passage itself needs to be made small, which leads to a problem that the cooling effect becomes insufficient because the cooling area becomes small. Furthermore, if the cooling passage is arranged between the outer peripheral surface of the inner peripheral brick and the inner peripheral surface of the core bar, the thickness of the inner peripheral brick must be reduced, resulting in a problem of shortening the life of the inner peripheral brick. be.

On the other hand, in Patent Document 4, as a structure to prevent the lower end of the immersion pipe from falling off, the lower end of the inner peripheral shaped refractory layer has a long and short structure alternately in the circumferential direction of the immersion pipe, and further, the inner peripheral shaped refractory layer The lower end of the long shaped refractory constituting the lowermost end is positioned at the lowest end of the immersion tube, and the short shaped refractory constituting the inner peripheral shaped refractory layer other than the lowest end is continuous from the lower part to the outer peripheral part. A structure in which monolithic refractories are arranged is disclosed. It is said that such a structure suppresses the development of horizontal cracks in the monolithic refractory and prevents the monolithic refractory from coming off.
Although the structure of Patent Document 4 can suppress the occurrence of horizontal cracks, the monolithic refractory may still fall off, and further improvement is desired.

Microfilm of Japanese Utility Model Application No. 1-93788 (Japanese Utility Model Application No. 3-34053) JP-A-11-21617 JP 2005-226092 A JP-A-2006-104520

The problem to be solved by the present invention is an immersion tube for a vacuum degassing device in which bricks (inner bricks) are arranged on the inner circumference side of a cylindrical core metal, and the service life of the inner bricks is adversely affected. To provide an immersion pipe capable of enlarging a cooling area without imparting a heat resistance, and arranging an inner peripheral brick up to the lower end of the metal core or the immersion pipe.

According to one aspect of the present invention, the following dip tube is provided.
An immersion tube for a vacuum degassing device in which bricks (hereinafter referred to as "inner bricks") are arranged on the inner circumference side of a cylindrical core bar, wherein the outer peripheral surface of the inner brick and the inner circumference of the core bar between the surface and within a range of up to 50% of the length of the core bar upward from the lower end of the core bar, consisting of an upper wall, a lower wall, an inner wall, and a core bar An immersion pipe in which a cooling box is provided in an annular shape, the distance between the outer peripheral surface of the inner wall of the cooling box and the inner peripheral surface of the core metal is 6 mm or more and 14 mm or less, and the thickness of the inner wall of the cooling box is 8 mm or more and 15 mm or less.

According to the present invention, by providing a double cylindrical cooling box between the inner peripheral surface of the core metal and the outer peripheral surface of the inner peripheral brick, the reduction in the thickness of the inner peripheral brick can be minimized. There is no adverse effect on the service life of the inner peripheral brick. In addition, since the cooling area of the metal core can be increased, the cooling effect can be enhanced, and the life of the immersion tube can be extended. Furthermore, it is possible to arrange the inner bricks up to the core metal or the lower end of the immersion pipe. Falling-off of the refractory at the lower end can be further suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS The longitudinal cross-sectional view of the dip tube which is one Embodiment of this invention. 2 is an enlarged view of the cooling box in the embodiment of FIG. 1; FIG. FIG. 4 is a vertical cross-sectional view of an immersion tube that is another embodiment of the present invention;

FIG. 1 shows a dip tube that is one embodiment of the present invention.
The immersion pipe 1 of this embodiment includes a metal flange 2, a cylindrical metal core 3 attached to the flange 2, and two rings provided annularly on the lower inner peripheral surface of the core 3. A heavy cylindrical cooling box 4 , inner bricks 5 (upper inner brick 51 and lower inner brick 52 ) arranged on the inner circumference side of the core bar 3 , and bricks arranged on the outer circumference side of the core bar 3 . It has a shaped refractory 6.

As shown in FIG. 2, the cooling box 4 is provided between the outer peripheral surface of the lower inner peripheral brick 52 and the inner peripheral surface of the core metal 3, and the lower end surface of the cooling box 4 is the same as the lower end surface of the core metal 3. is in position. That is, the lower end of the cooling box 4 is aligned with the lower end of the cored bar 3 .

The cooling box 4 is composed of an upper wall 41, a lower wall 42, a cylindrical inner wall 43, and a metal core 3, and a space 45 is formed therein for passage of a cooling medium. Round steels are used for the upper wall 41 and the lower wall 42, respectively. These round steels are sandwiched between a cylindrical inner wall 43 and a core metal 44, and their joints are fixed by welding. there is

The thickness of the inner wall 43 of the cooling box 4 is 12 mm, the thickness of each of the upper wall 41 and the lower wall 42 is 9 mm, and the distance D between the outer peripheral surface of the inner wall 41 and the inner peripheral surface of the core bar 3 (the space 45 of the cooling box 4 is The thickness D) is 9 mm, the thickness of the cored bar 3 is 19 mm, the width W of the cooling box 4 is 200 mm, the diameter of the cored bar 3 is 800 mm, and the length of the cored bar 3 is 700 mm. Here, the length of the cored bar is the length from the lower end of the flange 2 to the lower end of the cored bar 3 . Based on the above dimensional relationship, the cooling box 4 is arranged within a range of up to 50% of the length of the core metal 3 from the lower end of the core metal 3 upward, that is, within a range of 350 mm upward from the lower end of the core metal 3. found to be set. Specifically, the cooling box 4 is provided within a range of about 29% (200/700×100) of the length of the cored bar 3 upward from the lower end of the cored bar 3 .

A metal introduction pipe 44 is connected to the cooling box 41 for introducing nitrogen as a cooling medium. One end of the lead-in pipe 44 penetrates into the inner wall 43 of the cooling box 4 and is fixed. It penetrates the core metal 3 to come out to the outer peripheral side, passes through the monolithic refractory 6, and exposes the other end under the flange 2. - 特許庁Also, although not shown, a similarly constructed exhaust pipe for exhausting nitrogen is also arranged at another location. A plurality of inlet pipes and outlet pipes may be provided to improve the cooling efficiency.

Twenty inner bricks 51 and 52 made of magnesia carbon are arranged cylindrically in two stages on the inner circumference side of the core bar 3 . A monolithic refractory 6 that is an alumina-magnesia castable is arranged. The thickness T of the lower inner brick 52 is 145 mm, which is 25 mm smaller than the thickness of the upper inner brick 51 in order to secure a gap for arranging the cooling box 4 and the introduction pipe 44 . The lower inner peripheral bricks 52 are held by brick receiving portions 46 provided on the inner wall 43 of the cooling box 4, respectively. The brick receiving portion 46 is fixed to the inner peripheral surface of the inner wall 43 by welding, and holds the lower inner peripheral brick 52 by receiving the upper part in the concave portion 53 provided on the outer peripheral surface of the lower inner peripheral brick 52 . there is The distance between the outer peripheral surface of the upper inner peripheral brick 51 and the inner peripheral surface of the cored bar 3 is 20 mm. Alumina-magnesia-based castables are arranged as monolithic refractories 6 around and under the core metal 3, but the studs provided on the core metal 3 are omitted in the drawing to prevent them from coming off.

In the immersion tube 1 of the present embodiment having the above configuration, nitrogen is introduced into the introduction pipe 44 as a cooling medium during use, passes through the cooling box 4, and is discharged from the discharge pipe. The lower inner circumference of 3 is cooled. Since the inner periphery of the lower portion of the core metal 3 is cooled, the opening of the lower portion of the core metal 3 is suppressed, cracks in the refractory at the lower end of the immersion pipe are reduced, and the refractory can be prevented from coming off.

In addition, in the immersion tube 1 of the present embodiment, the cooling box 4 has a double cylindrical structure, so that the thickness of the cooling box 41 can be reduced. Even if it is provided between the inner peripheral surface, the reduction in the thickness of the inner peripheral bricks 5 can be minimized, and the cooling area can be widened without adversely affecting the life of the inner peripheral bricks. As a result, the cooling effect of the inner circumference of the lower portion of the cored bar 3 can be enhanced, so that the opening of the lower portion of the cored bar 3 can be suppressed, and cracking of the refractory at the lower end of the immersion tube can be suppressed.

In addition, since the inner wall 43 of the cooling box 4 is cylindrical, the brick receiving portion 46 can be provided at an arbitrary position on the inner peripheral surface of the inner wall 43, so that there is no restriction when arranging the inner peripheral bricks 5. . As a result, it is possible to employ the well-known falling-off prevention structure of the lower end of the immersion pipe in which the inner brick 5 is arranged to the lower end of the core metal or the immersion pipe without any problem, so that the falling-off of the lower end of the immersion pipe is suppressed more reliably. can be used to further extend the life of the dip tube.

Here, the inner wall 43 of the cooling box 4 needs to have strength when the brick receiving portion 46 is provided, so it is better to thicken it. For example, the thickness of the inner wall 43 can be 8 mm or more and 15 mm or less, preferably 10 mm or more and 14 mm or less.

Also, if the distance D between the outer peripheral surface of the inner wall 43 of the cooling box 4 and the inner peripheral surface of the core bar 3 (the thickness D of the space 45 of the cooling box 4) is too large, the thickness of the inner peripheral brick 5 will be too small. Since the cooling effect becomes small, the size may be set appropriately according to the size of the immersion pipe and the inner brick. thickness reduction can be minimized.

Round steel can be used for the upper wall 41 and the lower wall 42 of the cooling box 4 . As for the round bar, standardized products such as JIS standard products are commercially available, and since many types of the outer diameter size are commercially available in units of 1 mm, the distance D ( The thickness D) of the space 45 of the cooling box 4 can be adjusted in millimeters according to the design conditions of the cooling box, and can be obtained at a low cost. In addition, bending to match the inner diameter of the cored bar 3 is easy. In addition to round steel, bar-shaped steel materials such as square steel and half-round steel are also standard products and can be used because there are many kinds of outer diameter dimensions.

As a method of manufacturing the cooling box 4, for example, a bar-shaped steel material such as a round steel is machined into a circular shape so that the outer diameter thereof is the same as the inner diameter of the core bar 3, and two circular rod-shaped members for the upper wall and the lower wall are manufactured. A steel material and a cylinder for the inner wall formed so that the outer diameter is the same as the inner diameter of a circular steel bar are prepared. There is a method in which two steel rods are welded and fixed, and a cylinder for the inner wall is welded and fixed inside these two steel rods. Alternatively, two circular steel rods can be welded to the outer peripheral surface of the inner wall cylinder and then welded to the inner peripheral surface of the core bar. By prefabricating the circular rod-shaped steel material and the cylinder for the inner wall in this way, the welding operation to the inner peripheral surface of the core bar can be performed accurately, simply, and in a short time.

On the other hand, the brick receiving portion 46 can be installed either before or after the inner wall cylinder is attached to the core bar. Also, the introduction pipe 44 and the discharge pipe for the cooling medium can be attached after the cooling box 4 is provided on the core bar 3, but the holes for attachment can also be provided in the inner wall cylinder in advance.

If the width W of the cooling box 4 is in the range of, for example, 50 mm or more and 350 mm or less, a sufficient cooling effect can be obtained, and an effect of suppressing dropout of the lower end of the immersion tube can be obtained.
In addition, by setting the range in which the cooling box 4 is provided within the range from the lower end of the core metal 3 upward to 50% of the length of the core metal 3, the lower inner circumference of the core metal 3 can be effectively cooled. can.

The position of the lower end of the lower wall 42 of the cooling box 4 is preferably close to the lower end of the core 3 from the viewpoint of effectively preventing the lower part of the core 3 from opening due to thermal expansion during use. 70 mm or less upward from the lower end of the core metal, more preferably 30 mm or less upward from the lower end of the core metal, more preferably 15 mm or less upward from the lower end of the core metal. Most preferably, it coincides with the lower end of 3.

In the present embodiment, one end of the cooling medium introduction pipe 44 and one end of the cooling medium discharge pipe are fixed by welding through holes provided in the inner wall 43 . It can also be fixed.

Next, another embodiment of the present invention shown in FIG. 3 will be described.
Compared to the immersion pipe of FIG. 1, the immersion pipe 1 of FIG. is different. The base end of the stud 47 is fixed to the inner peripheral surface of the inner wall 43 of the cooling box 4 by welding, and one stud 47 is arranged below each lower inner peripheral brick 52 . This stud 47 can be attached to any position on the inner wall 43 of the cooling box 4 .
As described above, according to the present invention, the stud can be arranged at any position on the inner peripheral surface of the lower part of the core bar. It is possible to further enhance the effect of preventing the lower end of the pipe from coming off.

Table 1 shows the test results of using the immersion tube shown in FIG. 3 with different dimensions at an actual RH.
In this test, the dip tube was used as an ascending tube and then as a descending tube, and the total number of uses was evaluated. The usable number of times was determined comprehensively by visually observing the state of cracks and peeling at the lower end of the immersion tube during use and the state of erosion of the refractory.

Reference Example 1, Examples 2 to 4, Reference Example 5, and Reference Example 6 have the thickness D of the space of the cooling box (the distance D between the outer peripheral surface of the inner wall 43 of the cooling box 4 and the inner peripheral surface of the core bar 3). are different, and as the thickness of this space increases, the thickness T of the lower inner peripheral brick is made smaller. The number of usable times is greater than in Comparative Example 2, which is a good result. In addition, according to the appearance observation of the immersion tube, the cracks and peeling at the lower end were smaller than those in Comparative Example 2, which was greatly improved. .

Here, in Example 4 in which the thickness D of the space in the cooling box is 14 mm, the thickness of the lower inner peripheral brick is 5 mm smaller than in Example 3 in which the thickness D of the space in the cooling box is 9 mm. has decreased slightly. Reference examples 5 and 6, in which the thickness D of the space of the cooling box is even greater, also have a reduced usable number of times.

On the other hand, Reference Example 1, in which the thickness D of the space in the cooling box is 3 mm, can be used 130 times, while Example 2, in which the thickness D of the space in the cooling box is 6 mm, can be used 152 times. There is a large difference in the number of times it can be used. It should be noted that the factor of the service life of Reference Example 1 was due to cracks and peeling at the lower end.

In Examples 7 and 8, the width W of the cooling box is different, and the ratio of the width of the cooling box to the length of the core bar is different. results.

On the other hand, in Comparative Example 1, the width W of the cooling box is as large as 500 mm, the ratio of the width of the cooling box to the length of the core metal is 71%, which is outside the scope of the present invention, and the peeling of the refractory at the lower end is large. The number of times it can be used is decreasing.

1 Immersion pipe 2 Flange 3 Core metal 4 Cooling box 41 Upper wall 42 Lower wall 43 Inner wall 44 Introductory pipe 45 Space 46 Brick receiving part 47 Stud 5 Inner brick 51 Upper inner brick 52 Lower inner brick 53 Recess 6 Monolithic refractory Item W Width of cooling box D Distance between the outer peripheral surface of the inner wall of the cooling box and the inner peripheral surface of the core metal (thickness of the space in the cooling box)
T: Thickness of the lower inner brick

Claims (5)

An immersion tube for a vacuum degassing device in which bricks (hereinafter referred to as "inner bricks") are arranged on the inner circumference side of a cylindrical core bar, wherein the outer peripheral surface of the inner brick and the inner circumference of the core bar between the surface and within a range of up to 50% of the length of the core bar upward from the lower end of the core bar, consisting of an upper wall, a lower wall, an inner wall, and a core bar An immersion pipe in which a cooling box is provided in an annular shape, the distance between the outer peripheral surface of the inner wall of the cooling box and the inner peripheral surface of the core metal is 6 mm or more and 14 mm or less, and the thickness of the inner wall of the cooling box is 8 mm or more and 15 mm or less. 2. The immersion tube according to claim 1 , wherein the lower end of the lower wall of the cooling box is positioned within a range of 70 mm or less upward from the lower end of the core bar. 3. The immersion pipe according to claim 1 or 2 , wherein the inner wall of the cooling box is provided with a brick receiving portion for holding the inner peripheral brick. 4. The cooling box according to any one of claims 1 to 3 , wherein the cooling box has a structure in which an upper wall and a lower wall are sandwiched between an inner wall and a core bar, and the upper wall and the lower wall are made of bar-shaped steel. subsection as described above. 5. The dip tube according to claim 4 , wherein the bar-shaped steel material is round steel.

Images