JP2006214647A - Water-cooled cover for ladle refining and refining treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively prevent attachment of splash generated in refining. <P>SOLUTION: This metallic furnace cover 1 of jacket structure covers an upper opening 2a of a ladle 2 in refining, and comprises at least one of lance insertion holes 1a, 1b for heating or stirring molten steel 3 and an alloy charging hole. An inner face is composed of a smooth iron plate 6, and the inside of a side wall 1c is tapered. At least two cooling systems are mounted for cooling the inside of the furnace cover 1, and these cooling systems are independently controlled. As the attachment of splash scattering during refining treatment can be effectively prevented, troubles in the refining treatment caused by the increase of attachment of splash can be prevented, and working load can be reduced as the maintenance after refining treatment is unnecessary. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a water-cooled lid used at the time of ladle refining, for example, and a method of refining treatment using the water-cooled lid.

In ladle refining, where gas is blown into the molten steel and oxygen is blown onto the molten steel surface, to prevent splash (bullion) generated during molten steel stirring during the refining process from splashing outside the ladle. Installation of a lid (hereinafter also referred to as a ladle lid) is indispensable. As this ladle lid, conventionally, for example, as described in Patent Document 1, a refractory lined inner surface of an iron skin has been used.
Japanese Patent Publication No. 7-35533

  Such ladle lids are generally used in an uncooled state without being cooled by water. Therefore, the ladle lid was deformed by radiant heat from the molten steel during the refining process. In addition, due to cracks and dropping off of the refractory during the refining process, splash was attached to the inner crack portion of the ladle lid. Once splashed, the splash grew each time the refining process was repeated, and eventually dropped with the refractory. As a result, frequent inspections and repairs are required, which is very expensive and uneconomical.

Therefore, in recent years, as a ladle lid used for ladle refining, a composite water-cooled lid combining refractory and water cooling, as described in Patent Document 2, or an interior of the lid as described in Patent Document 3 There has been proposed a water-cooled lid in which a plurality of metal tubes through which cooling water flows are wound.
JP 2000-304451 A JP-A-7-103664

  However, the composite water-cooled lid proposed in Patent Document 2 is complicated in construction because refractories and cooling water pipes are alternately arranged and both are cast and joined. In addition, there is a problem that unevenness is generated between the cooling pipe and the refractory material, which promotes the adhesion of splash during the refining process.

  In addition, since the water-cooled lid proposed in Patent Document 3 has irregularities between metal tubes, the splash during the refining process tends to adhere due to the irregularities. When the splash adheres, an operation trouble during the refining process, a maintenance after the refining process, and the like cause a work load and an operation loss, which becomes a big problem.

Therefore, in Patent Document 4, a plurality of steel pipes are wound, and the gap between the steel pipes is build-up welded or covered with metal to form a smooth surface.
JP-A-7-90350

  However, as proposed in Patent Document 4, overlay welding of the gap requires a great deal of man-hours and high costs, and the overlay welded portion has a lower cooling ability than other portions. In addition, when the steel pipe surface is coated with metal, the adhesion of splash due to the irregularities inside the water-cooled lid is reduced, but the cooling performance is worse than when it is not coated, so the adhesion of splash due to local insufficient cooling. Occurs.

  Further, in Patent Document 3 and Patent Document 4, water supply / drainage is performed from a plurality of locations, but since the coolant supply source is common control at one location, adjustment of the coolant according to each part of the water cooling lid is possible. There is also a problem that the possibility of local lack of cooling increases as a result.

  The problem to be solved by the present invention is that the conventional water-cooled lid for ladle refining cannot effectively prevent the adhesion of splash generated during refining.

The water-cooled lid for ladle refining of the present invention is
In order to effectively prevent the adhesion of splash that occurs during refining,
At the time of refining, a jacket-structured metal furnace cover that covers the upper surface opening of the ladle and has at least one of a lance insertion hole for heating and stirring the molten steel, and an alloy charging hole,
The inner surface is made of a smooth iron plate, the inside of the side wall is tapered,
Provide at least two cooling systems for internal cooling of the furnace lid,
The most important feature is that each cooling system is controlled independently.

Moreover, the refining process method of this invention performs a refining process in the state which covered the upper surface opening of the ladle with the water cooling lid | cover of the said this invention.
According to the refining treatment method of the present invention, it is possible to effectively prevent the splash generated during refining from adhering to the inner surface of the water-cooled lid.

  In the present invention, the inner surface of the water cooling lid of the jacket structure is made of a smooth iron plate, the inside of the side wall is tapered, and each cooling system is independently controlled, so that splash splashed during the refining process is attached. Can be effectively prevented. Therefore, troubles during the refining process due to an increase in the amount of splash can be prevented, and the work load can be reduced by the maintenance free after the refining process.

Hereinafter, the best mode for carrying out the present invention will be described with reference to FIG.
FIG. 1 is a schematic longitudinal sectional view for explaining a state in which the upper surface opening of the ladle is covered with the water-cooled lid of the present invention for refining treatment.

  1 is a water-cooled lid of the present invention that covers an upper surface opening 2a of a ladle 2 used for metal refining. For example, an insertion hole 1a of a heat-feeding acid lance 4 for molten steel 3 and a stirring lance 5 for molten steel 3 are inserted. A hole 1b is provided.

  In the present invention, the water-cooled structure lid is used in order to prevent the splashed splash from adhering to the inner surface of the lid at the time of the refining process so that it does not adhere continuously. is there.

  In the present invention, as the water cooling structure, a jacket structure in which the inside of the water cooling lid 1 is hollow and the inside is divided into a plurality of parts is adopted. This is because, when a type in which a plurality of steel pipes are wound as proposed in Patent Document 3 and Patent Document 4 is adopted as the water cooling structure, the adhesion of splash cannot be effectively prevented as described above.

In addition, regarding this jacket structure, in Patent Document 5, the lack of cooling due to an internal air pool is cited as a problem, and the necessity of installing an air vent valve on the cooling water outlet side for air venting inside is indicated. ing.
JP 2000-28273 A

  However, if the inventor installs the cooling water supply port 7 at a position equal to or lower than the position of the cooling water discharge port 8 as shown in FIG. The inside air was discharged together with the cooling water from the drain port 8, and it was found that air accumulation in the jacket could be prevented.

  Therefore, the water-cooled lid 1 of the present invention employs a jacket structure that is simple in structure and low in cost.

  In addition, when the cooling system has a single flow path, the flow path from the inlet side to the outlet side of the cooling water is relatively long. If the flow path becomes longer, the temperature difference on the inlet / outlet side of the cooling water becomes large and a sufficient cooling effect cannot be obtained. As a result, splash splashed and adhered to the inner surface of the water cooling lid 1 immediately comes from the water cooling lid 1. There is a high possibility that the adhesion layer gradually enlarges without peeling.

  On the other hand, if the flow rate is simply controlled at the inlet side of the cooling water only by dividing the flow path into a plurality of parts, the cooling at each part becomes non-uniform, resulting in local insufficient cooling. Therefore, in the water-cooled lid 1 of the present invention, at least two cooling system flow paths are provided (four in the example of FIG. 1), and each cooling system is controlled independently, so that the temperature gradient of the water temperature at the cooling site. Must be as small as possible.

  Moreover, in this invention, the inner surface of the water cooling lid | cover 1 is comprised with the smooth iron plate 6. FIG. This is because if the inner surface of the water-cooled lid 1 on which the splash scatters is uneven during the refining process, the adhesion of the splash is promoted. However, the iron plate 6 used may be a general structural carbon steel, and it is not particularly necessary to polish the surface of the iron plate 6 anew. In general, the iron plates 6 are joined to each other by welding, but it is desirable to grind the weld convex portion so that the weld surface does not become convex as compared with the surface of the iron plate 6.

  In the present invention, in order to make it easy to drop the splash adhering to the inside of the side wall 1c of the water-cooled lid 1, a taper is attached to the inside of the side wall 1c in a range of 70 to 90 °, for example.

  The reason why the taper angle is set to 70 to 90 ° is to promote the adhesion of splash when the taper angle exceeds 90 °. When the taper angle is less than 70 °, the diameter of the upper part of the water-cooled lid 1 is too small relative to the diameter of the lower part, making it difficult to install the lance insertion holes 1a, 1b and the like, and radiating heat from the molten steel 3 This is because the effect of the iron shell deformation is increased unless the cooling water is increased.

  If the refining process is performed in a state where the upper surface opening 2a of the ladle 2 is covered with the water cooling lid 1 of the present invention having the above-described configuration, it is possible to effectively prevent the splash generated during refining from adhering to the inner surface of the water cooling lid 1. It becomes like this. This is the refining treatment method of the present invention.

Hereinafter, the results of experiments conducted to confirm the effects of the present invention will be described.
A water-cooled lid of the present invention having a taper angle of 80 ° and four cooling system water supply / drain ports is installed in a ladle holding 250 tons of molten steel, as shown in FIG. Refining treatment was carried out.

  The ladle free board (distance from the top end of the ladle to the molten steel surface) is 400 to 800 mm, and the slag volume is 20 to 30 kg per ton of molten steel. Ascending heat treatment and argon gas bubbling using a stirring lance (immersion lance) were performed for 15 to 30 minutes.

  The cooling water was controlled by adjusting the flow rate of each cooling system between 20 to 50 tons per hour so that the cooling water temperature on the outlet side during the refining treatment was 60 ° C. or lower. Further, a non-water-cooled lid (hereinafter referred to as a conventional lid) in which a refractory is attached inside the iron skin was also tested in the same manner.

  The above-mentioned refining treatment conditions are shown in Table 1 below, and the results of comparison of splash adhesion and lid life after refining treatment are shown in Table 2 below and FIG.

  In the refining treatment using the conventional lid and the water-cooled lid of the present invention, molten steel splash was confirmed during the refining treatment from the gap between the ladle and the lid and the insertion hole of the lance. The conventional lid has been confirmed to have a splash attached to the surface of the refractory after the refining treatment, and it has been necessary to remove the adhered splash during the non-treatment once every two to three heats. As a result, the lifetime of the conventional lid was as low as about 100 times as shown in FIG.

  On the other hand, the water-cooled lid of the present invention did not show any splash adhesion after the refining treatment, and it was not necessary to remove the splash during the non-treatment. Further, it was found that the effect continued even after repeated refining treatments, and as a result, the life of the water-cooled lid of the present invention was greatly improved to 1000 heat or more as shown in FIG.

  The present invention is not limited to those shown in the above-described embodiments, and it goes without saying that the embodiments may be appropriately changed within the scope of the technical idea described in each claim. For example, the water-cooled lid 1 may be provided with only one of a lance insertion hole for heating a molten steel, a stirring lance insertion hole, or an alloy injection hole.

  The present invention is not limited to the water-cooled lid for ladle refining shown in the above example, but can also be applied to a similar water-cooled lid for refining.

It is a schematic longitudinal cross-sectional view explaining the state which covers the upper surface opening of a ladle with the water cooling lid | cover of this invention, and is refining-treating. It is the figure which compared and showed the lifetime of the water cooling lid | cover of this invention, and the conventional lid | cover.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Water-cooled cover 1a Insertion hole of heat-feeding acid lance 1b Insertion hole of stirring lance 1c Side wall 2 Ladle 2a Top surface opening 3 Molten steel 4 Heat-feeding acid lance 5 Stirring lance 6 Iron plate 7 Water supply port 8 Drainage port

Claims (4)

At the time of refining, a jacket-structured metal furnace cover that covers the upper surface opening of the ladle and has at least one of a lance insertion hole and an alloy charging hole for heating and stirring the molten steel,
The inner surface is made of a smooth iron plate, the inside of the side wall is tapered,
Provide at least two cooling systems for internal cooling of the furnace lid,
A water-cooled lid for ladle refining, wherein each cooling system is controlled independently.   2. The intake according to claim 1, wherein an inlet side position of the water supply port constituting the cooling system is equal to or lower than an outlet side position of the drain port. Water-cooled lid for pot refining.   The water cooling lid for ladle refining according to claim 1 or 2, wherein a taper angle inside the side wall is 70 to 90 °. A refining treatment method, wherein the refining treatment is carried out by covering the upper surface opening of the ladle with the water-cooled lid according to any one of claims 1 to 3.

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