JP3835304B2 - Iron skin repair method for molten metal smelting furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for repairing an iron skin of a molten metal smelting furnace such as a converter.
[0002]
[Prior art]
In molten metal smelting furnaces such as converters, cracks and perforations in the iron skin may occur due to temperature changes during operation, melting of the refractory lining, or carburization by carbon contained in the refractory. appear.
In general, for crack repair, gouging is performed and a groove is formed, and overlay welding as shown in Fig. 3 is performed, and perforation repair is performed by cutting out the iron skin and matching the shape of the notched part. The frame is welded with an iron skin. In addition, for the problem that the repaired welded portion deteriorates again due to carburizing, JP-A-3-249113 discloses cutting and removing over the range of the carburized portion of the iron skin, cutting the cut portion, and cutting it out. It is disclosed that a new iron skin having the same shape as the part is fitted and welded.
[0003]
Regardless of the repair method, the weld heat affected zone is always formed as long as welding is performed. Such weld heat-affected zone generates residual stress and becomes the starting point for cracking again.
In a converter such as a converter that generates a large amount of gas and a combustible gas such as CO, such cracks may cause gas leakage, and if ignited, peripheral equipment may be burned out.
[0004]
[Problems to be solved by the invention]
However, depending on the conventional repair method, there is no method for suitably preventing the occurrence of cracks after repair, and it is necessary to monitor the reoccurrence of cracks by visual observation or the like and repeat the repair again if a crack is found. There was a serious inconvenience that the operation of the smelting furnace had to be stopped each time.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention is a method for repairing the iron skin of a molten metal smelting furnace, in which a low-melting-point metal is inserted into a gap before welding, and the outside is repaired by welding. We propose a method for repairing the iron skin of the molten metal smelting furnace.
[0006]
Here, it is preferable that the low melting point metal is lead and zinc or a low melting point alloy containing one or more of these.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment of a method for repairing an iron skin of a molten metal smelting furnace according to the present invention will be described below.
In the present invention, as shown in FIG. 1 (a), first, a crack generated in the iron skin 1, or a gap when a new iron skin having the same shape as that of a part cut out of the iron skin 1 is inserted. The low melting point metal 2 is inserted into. Thereafter, the outside (the front side and the back side of the iron skin 1) is repaired by welding. As shown in FIG. 1 (b), the welding repair may be performed by welding a steel material of the same type as the iron skin 1 as the metal pad 3. Alternatively, as shown in FIG. Further, as shown in FIG. 2, after repairing one surface of the iron skin 1 by welding in advance, the low melting point metal 2 may be inserted from the other side, and then the other surface side may be repaired by welding. .
[0008]
As the low melting point metal 2, lead, zinc or a low melting point alloy containing these can be preferably used. In inserting these low melting point metals 2, there are a method of flowing in a molten state, a method of pressing or striking a sheet or wedge-shaped low melting point metal 2 into a gap, a method of filling powdery low melting point metal 2, and the like. However, either method may be used.
[0009]
Since the outside is repaired by welding, even if there is a gap between the low melting point metal 2 and the iron skin 1 during insertion, the inside and outside of the furnace will not be communicated. This is because the gap is filled because it melts. The low melting point metal 2 must be melted at the temperature of the iron skin 1 at the time of operation. From this point, the melting point is preferably 600 ° C. or less, more preferably 500 ° C. or less.
[0010]
On the other hand, too low melting point metals have low boiling points, which may cause evaporation loss during welding repair. Therefore, it is preferably 200 ° C or higher, more preferably 300 ° C or higher. From this point of view, lead (melting point: 371 ° C.) and zinc (melting point: 420 ° C.) are preferable for single metals, and low melting point alloys based on these can be preferably used for alloys.
[0011]
Even in the present invention, cracks may occur in the weld heat affected zone around the repaired portion. Even in such a case, the low melting point metal 2 filled in the repaired portion fills the crack, so Gas ejection can be prevented. Although there is a concern that cracks will remarkably expand after a long period of time and the low melting point metal 2 melts and flows out, the period from furnace repair to the next furnace repair, which is the replacement work of the lining brick, It is not necessary to stop the smelting furnace in operation and repair it urgently as in the past, because it does not reach such a state of cracks. Even if repairs are required again, it is sufficient to perform the repairs in accordance with the furnace repairs, so there is no downtime in operation.
[0012]
【Example】
In a converter type smelting reduction furnace that performs smelting reduction of Cr ore, the conventional iron skin repair method and the iron skin repair method of the present invention were compared.
First, a conventional example is as follows.
The operation of the smelting reduction furnace, in which cracks were observed near the furnace body constricted part during operation, was stopped, the crack part was gouged, a groove was provided, and overlay welding was performed using the same boiler steel plate material as the furnace body. During this time, 108 hours of downtime occurred due to the cooling and repair of the furnace and preheating of the furnace. After that, when smelting reduction smelting, after cracking about 100 charges (half of the furnace cost), a crack occurred again in the part repaired last time, and it was found that the gas leaked from the crack was burning. It was. Therefore, after the furnace operation was stopped and the furnace was cooled, the iron skin 1 was repaired and smelting reduction smelting was resumed after preheating the furnace. Again, the downtime was about 108 hours.
[0013]
On the other hand, examples of the present invention are as follows.
Similarly to the above, the furnace in which the occurrence of cracks was observed was stopped, the furnace was cooled, lead powder was filled in the cracked portion, and then the iron shell 1 was covered with a metal 3 and welded. The furnace was then preheated and smelting reduction smelting was resumed. At this time, due to emergency repairs and furnace repairs in the middle of the operation, downtime of about 108 hours occurred as in the conventional case. After that, the operation was continued, but no cracks were found again during one furnace cost (200 charges). After the repair of the furnace, cracks were not regenerated at the next furnace cost, and the next furnace repair was started. When the repaired part was confirmed at the time of furnace repair, a fine crack with an interval of about 0.3 mm and a length of about 30 mm was found, so the patch 3 was removed and repairs were performed again. When the state of lead filled in the last time when the plating 3 was removed was observed, there was no molten lead out of lead, so a slight replenishment of lead powder (corresponding to the gap between the lead powder at the previous filling) Then, the repair was completed by welding the pad 3 again. Since this repair was done during the furnace repair, there was no downtime in operation.
[0014]
As described above, according to the repair method of the present invention, there was no occurrence of cracking again such that gas was ejected from the furnace in the repair portion, and the repair itself could be performed without causing downtime in operation.
[0015]
【The invention's effect】
As described above in detail, according to the present invention, in the method of repairing the iron skin of a molten metal smelting furnace such as a converter, it is preferable to prevent the occurrence of cracks after repair and to repair the furnace again. What can be done from time to time has the advantage of preventing the serious inconvenience of having to stop the operation of the smelting furnace each time for repair.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of repair by the method of the present invention.
FIG. 2 is a cross-sectional view showing an example of repair by the method of the present invention.
FIG. 3 is a cross-sectional view showing an example of repair by a conventional method.
[Explanation of symbols]
1 Iron skin 2 Low melting point metal 3 Latch 4 Welded part

Claims (2)

In the molten metal smelting furnace, the repair of the iron skin of the molten metal smelting furnace is characterized in that after the low melting point metal is inserted into the gap before welding, the outer side is welded and repaired. Method. 2. The method of repairing a molten metal smelting furnace according to claim 1, wherein the low melting point metal is lead and zinc or a low melting point alloy containing one or more of them.

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