JP4027749B2 - Adjustment method of refining vessel for melting high clean steel - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to adjustment of a refining vessel for melting high cleanliness steel, and more particularly to adjustment of a ladle for melting high cleanliness steel while avoiding contamination by oxides and impurity elements.
[0002]
[Prior art]
Conventionally, molten steel melted in an electric furnace or the like is put into a ladle and smelted in the ladle, and further RH vacuum degassing refining is performed to produce highly clean steel. Al ₂ O ₃ − in the vicinity of the molten steel surface in the ladle by bubbling of inert gas from the bottom of the ladle in smelting or by convection in the ladle of molten steel generated by the reflux of RH degassing smelting The SiO ₂ —CaO-based slag melt layer was rolled into the molten steel, which deteriorated the cleanliness of the molten steel. When left standing for a long time in order to float these slags, the molten steel temperature is lowered, and the inclusions that are separated from the side wall of the ladle and float are trapped in the molten steel. In addition, when left standing for a long time, the opening rate of the nozzle of the ladle becomes low, which causes a delay in opening the molten steel from the ladle to the tundish for continuous casting. For this reason, the inclusion of inclusions due to a decrease in the amount of molten steel retained in the tundish, the contamination of molten steel due to an increase in the amount of cutting oxygen used to open the ladle nozzle, and the continuous failure of continuous casting due to the loss of molten steel in the previous charge, etc. There was a risk of causing it.
[0003]
Such a problem is not limited to the ladle, but also in the case of a converter or a refining vessel such as AOD.
[0004]
Apart from this, it is desirable to reduce the mechanical properties of steel if it contains a certain amount of elements, which are usually impurities, and it is usually preferable to manage the raw materials. It has been dissolved. However, when these elements are contained in a small amount, they impart certain properties to the steel, and may be actively added in consideration of the balance with the mechanical properties. For example, Pb is added to improve machinability and is also defined in JIS. However, these steel-dissolved pans have bullion attached to the inner wall of the pan, and bullion has infiltrated the joints on the inner wall of the pan. The bullion melts and pushes up the level of impurities in the steel (hereinafter referred to as “pickup”).
[0005]
[Problems to be solved by the invention]
The problem to be solved by the present invention is that in refining with a refining vessel such as a steel ladle with a high degree of cleanness, the effect of slag on the refining vessel, adhering metal or impurity elements that have infiltrated the joints is removed for melting. Is to provide a method.
[0006]
[Means for Solving the Problems]
The inventors have previously found that, in order to melt steel with a high degree of cleanliness, steel removal at high temperatures is effective in order to eliminate the effects of slag and adhered metal from all molten steel types in the ladle. ing. By the way, newly produced pans and pans renewed by replacing the refractories (hereinafter referred to as “new pans”), and the line of online operation where refining and casting into continuous casting are performed in order. All pans (hereinafter referred to as “rest pans”) that have been removed to allow the refractory to be sprayed and repaired on the inner wall of the pan are cooled to a certain extent or sufficiently (hereinafter referred to as “rest pan”) are in a thermally unbalanced state. Therefore, it is considered that it is disadvantageous for the melting of steel with high cleanliness that usually requires heavy refining.
[0007]
However, the inventors have intensively studied, and as a first means, Pb, Ti infiltrated into the joint of the inner wall of the pan by dissolving a steel type that does not contain Pb, Ti, B impurity elements multiple times in the empty pan. The present inventors have found that steel having a high cleanliness can be melted by using a pan from which the impurity element B has been washed and removed, and have obtained means for solving the above-mentioned problems.
[0008]
The meaning of not containing the impurity elements of Pb, Ti and B described in the first means does not mean that it does not contain at all, but the content is so small that it can be said to be an inevitable impurity from the viewpoint of steelmaking technology. That means.
[0009]
Further, the melting for the cleaning purpose described in the first means may be a melting for cleaning only, or a melting also for the production of steel having a normal level of cleanliness with respect to high cleanliness steel. .
[0010]
That is, the means of the present invention for solving the above-described problems are shown below.
In the present invention of claim 1, a melting method of the steel according to the ladle other refining vessel, Pb, refining vessel the impurity element by melting a steel containing the impurity elements Ti and B are infiltrated in joints Prior to smelting, the refining vessel is repeatedly smelted more than a predetermined number of times with a wash steel type made of a steel type containing the impurity element as an unavoidable impurity, so that each impurity element of Pb, Ti and B can be dissolved. after removal from infiltrating joints, in melting methods of the impurity element by using the refining vessel to remove high steel of smelting to RuKiyoshi Kiyoshido steel, previously, containing the impurity element in the refining vessel After the steel type is melted, the above-mentioned impurity element is dissolved into the molten steel from the joint corresponding to the number of times of repeating the melting of the washing after analyzing the steel material at least once after the washing with the above-mentioned washing steel type is dissolved. By calculating the amount, which is melting method highly clean steel and determining the predetermined number of times.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings. 1 and 2 are diagrams relating to the invention according to claim 1. FIG. 1 is a view showing a ladle and other smelting containers 1 after steeling having a joint 3 to which an adherent metal 2 is adhered and Pb, Ti and B impurity elements are infiltrated. FIG. 2 is a graph showing the relationship between the number of repetitions of smelting by the type of washed steel and the relative ratio of the amounts of impurity elements Pb, Ti and B eluted from the smelting vessel into the molten steel.
[0012]
In an embodiment of the invention according to claim 1, when steel containing Pb, Ti and B impurity elements is melted and produced by a ladle or other refining vessel 1, the refining vessel 1 contains Pb, Ti and The joint 3 is infiltrated with the impurity element B. The refining vessel 1 having the joints 3 infiltrated with the impurity elements is charged with a steel type that does not contain the Pb, Ti, and B impurity elements as a steel type, melted, and discharged. The smelting and leaving steel with this wash steel type is repeated several times. These impurity elements are washed out from the joints 3 infiltrated with the impurity elements in the refining vessel 1 by repeating the smelting and steeling with this washing steel type. Next, steel with high cleanliness is melted by melting new steel using the refining vessel 1 in which the impurity elements are washed out.
[0013]
The amount of elution from the joints into the molten steel in the present invention was evaluated as follows. First, the content of each element of Pb, Ti, and B contained in the steel material after the 10th time in the case where the steel type that contains each element of Pb, Ti, and B only as an inevitable impurity is continuously dissolved 10 times or more. Analyze and use this average value as the reference value. And when the steel grade which contains 1 type or 2 types or more of each element of Pb, Ti, and B was melt | dissolved after this, the melt | dissolution of washing was performed several times, the steel material at that time was analyzed, and this and reference value and The amount of elution from the joint to the molten steel was evaluated. Further, in the case of the comparative example, after dissolving the steel type positively containing each element of Pb, Ti, and B described above, it was dissolved without dissolving the washing, and the analytical values were compared. FIG. 2 summarizes the above results. In FIG. 2, the index on the vertical axis is expressed as a relative ratio where the amount of each impurity element of Pb, Ti, and B eluting from the joint to the molten steel when using a refining vessel that has been washed and melted once is 1. Is.
[0014]
As can be seen in FIG. 2, it can be seen that the amount of elution from the joints into the molten steel is almost 0 with Pb being the number of repetitions of melting by washing steel type 2 to 4 and Ti and B being twice. Here, it is an absolute value of the pick-up amount when the washing steel type as a comparative example is not melted. However, this is a general variation because it varies greatly depending on the contents of Pb, Ti, B, etc. at the previous melting. Absent. Therefore, in FIG. 2, the outline is shown by relative values.
[0015]
【The invention's effect】
As described above, the present invention reduces the elution of these impurity elements from joints infiltrated with impurity elements that generate non-metallic inclusions by repeated melting with a ladle steel type in a ladle or other refining vessel. By doing so, in the melting of steel in ladle and other smelting containers, it is possible to melt high-cleanness steel by avoiding contamination of molten steel by oxides and impurity elements, and it has an excellent effect. .
[Brief description of the drawings]
FIG. 1 is a view showing a ladle and other smelting containers after steeling having joints to which adhered metal has adhered and infiltrated with impurity elements such as Pb, Ti and B;
FIG. 2 is a graph showing the relationship between the number of repetitions of smelting by the type of washed steel and the amounts of impurity elements Pb, Ti, and B eluted from the refining vessel into the molten steel, as a relative ratio.
[Explanation of symbols]
1 Refining vessel 2 Adhered metal 3 Joint

Claims (1)

A melting method for the steel according ladle other refining vessel, prior Pb, the melting of the steel containing the impurity element of Ti and B in the melting of the impurity element using the refining vessel infiltrating the joints Te, the purified smelting vessel by melting is repeated a predetermined number of times or more by washing steel grade made of steel species containing only as unavoidable impurities the impurity element, Pb, after removal from the joint infiltrated each impurity element Ti and B in this melting process of high steel of smelting to RuKiyoshi Kiyoshido steel using refining vessel with an impurity element has been removed, in advance, to dissolve the steel species containing the impurity element in the refining vessel, after this The dissolution of the washing with the above-mentioned washing steel type is performed at least once, the steel material at that time is analyzed, and the amount of the impurity element eluted to the molten steel from the joint corresponding to the number of times the washing is dissolved is calculated. Ri, a method of melting the high cleanliness steel and determining the predetermined number of times.

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