JP4027749B2 - Adjustment method of refining vessel for melting high clean steel - Google Patents
Adjustment method of refining vessel for melting high clean steel Download PDFInfo
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- JP4027749B2 JP4027749B2 JP2002243588A JP2002243588A JP4027749B2 JP 4027749 B2 JP4027749 B2 JP 4027749B2 JP 2002243588 A JP2002243588 A JP 2002243588A JP 2002243588 A JP2002243588 A JP 2002243588A JP 4027749 B2 JP4027749 B2 JP 4027749B2
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- Prior art keywords
- steel
- melting
- refining vessel
- impurity element
- washing
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Treatment Of Steel In Its Molten State (AREA)
Description
【0001】
【発明の属する技術分野】
この発明は、高清浄度の鋼を溶製するための精錬容器の調整に関し、特に酸化物と不純物元素による汚染回避して高清浄度鋼を溶製するための取鍋の調整に関する。
【0002】
【従来の技術】
従来、電気炉などで溶製した溶鋼を取鍋に出鋼して取鍋内で取鍋精錬し、さらにRH真空脱ガス精錬をして清浄度の高い鋼を製造するが、この工程において取鍋精錬における取鍋底部からの不活性ガスのバブリングにより、あるいはRH脱ガス精錬の還流によって発生する溶鋼流の取鍋内での対流により、取鍋内の溶鋼湯面近傍のAl2O3−SiO2−CaO系スラグ溶融層を溶鋼に巻き込む形となり、溶鋼の清浄度を悪化させていた。これらの巻き込んだスラグを浮上させるために長時間静置を行うと、溶鋼温度が低下し取鍋の側壁部から剥離して浮上する介在物が溶鋼中に捕捉されることになる。また、長時間の静置では取鍋のノズルの開孔率が低くなり、連続鋳造するために取鍋からタンディッシュへ溶鋼を注入する際の開孔遅れを招くこととなる。このためタンディッシュ保持溶鋼量が減少することによる介在物の巻き込みや、取鍋ノズルの開孔に使用する切断酸素量の増加による溶鋼汚染や、前チャージの溶鋼切れによる連連鋳の継続失敗などを引き起こす恐れがあった。
【0003】
こうした問題は取鍋に限られず、転炉の場合やAODなどの精錬容器などにおいても同様であった。
【0004】
またこれとは別に、通常は不純物とされる元素はある程度の量を含むと鋼の機械的性質などを低下させるので少ない方が望ましく、通常は原材料の管理を行うなどしてある程度の量に収まるように溶解がなされている。しかしこれらの元素は少量を含有すると鋼にある性質を付与するので、機械的性質とのバランスを考慮して積極的に添加される場合がある。例えばPbは被削性を向上させることから添加され、JISにも規定されている。しかしこうした鋼を溶解した鍋は、鍋の内壁に地金が付着したり、鍋の内壁の目地に地金が浸潤していたりするため、次にこうした元素を含ませない鋼を溶解するとこれらの地金が溶解して鋼の不純物レベルを押し上げる(以下「ピックアップ」という。)ことになっている。
【0005】
【発明が解決しようとする課題】
本発明が解決しようとする課題は、清浄度の高い鋼の取鍋などの精錬容器による精錬において、精錬容器へのスラグや付着地金あるいは目地に浸潤した不純物元素の影響を取り除いて溶製する方法を提供することである。
【0006】
【課題を解決するための手段】
発明者らは、清浄度の高い鋼を溶製するためには、取鍋の全溶製鋼種のスラグや付着地金の影響を取り除くため、高温における出鋼が有効であることを以前に見出している。ところで、新たに製作された鍋や耐火物の張り替えによって更新された鍋(これらを以下、「新鍋」という。)や、精錬と連続鋳造への鋳込みとを順繰りに行っているオンライン操業のラインから鍋の内壁に耐火物の吹付け補修などを行うために外されてある程度あるいは十分に冷やされた鍋(以下、「休み鍋」という。)は、いずれも熱的に非平衡な状態にあるので、通常は負荷の大きい精錬を行う必要のある清浄度の高い鋼の溶製には不利であると考えられている。
【0007】
しかし、発明者らは鋭意考究したところ、第一の手段として空鍋に対してPb、Ti、Bの不純物元素を含有しない鋼種を複数回溶解して鍋の内壁の目地に浸潤したPb、Ti、Bの不純物元素を洗浄して除去した鍋を使用することで、清浄度の高い鋼を溶製できることを見出し、上記の課題を解決するための手段を得たものである。
【0008】
なお第一の手段で記載した、Pb、TiおよびBの不純物元素を含有しないという意味は、含有しないとは全く含まないということではなく、製鋼技術からみて不可避的不純物といえるほど含有量が少ないことをいう。
【0009】
また第一の手段で述べた洗浄目的の溶解は、洗浄のみを目的にした溶解であっても、高清浄度鋼に対する通常レベルの清浄度の鋼の生産を兼ねた溶解であっても構わない。
【0010】
すなわち、上記の課題を解決するための本発明の手段を以下に示す。
請求項1の発明では、取鍋その他の精錬容器による鋼の溶製方法であって、Pb、TiおよびBの各不純物元素を含有する鋼の溶製により該不純物元素が目地に浸潤した精錬容器を使用する溶製に先立って、該精錬容器を該不純物元素を不可避的不純物としてしか含有しない鋼種からなる洗い鋼種により繰り返し所定回数以上溶製することで、Pb、TiおよびBの各不純物元素を浸潤した目地から除去した後、この不純物元素を除去した精錬容器を使用して鋼を溶製する清浄度の高い鋼の溶製方法において、予め、上記精錬容器において上記不純物元素を含有する鋼種を溶解し、この後、上記洗い鋼種による洗いの溶解を1回以上行いその時の鋼材を分析し、該洗いの溶解を繰り返す回数に対応する目地から溶鋼へ溶出する上記不純物元素の量を算出することにより、上記所定回数を決定することを特徴とする清浄度の高い鋼の溶製方法である。
【0011】
【発明の実施の形態】
本発明の実施の形態を図面を参照して説明する。図1、図2は請求項1に係る発明に関する図である。図1は、付着地金2が付着し、Pb、TiおよびBの不純物元素が浸潤した目地3を有する出鋼後の取鍋その他の精錬容器1を示す図である。図2は、洗い鋼種による溶製の繰り返し数とその精錬容器から溶鋼に溶出される不純物元素のPb、TiおよびBの量の相対比との関係を示すグラフである。
【0012】
請求項1に係る発明の実施の形態では、取鍋その他の精錬容器1によりPb、TiおよびBの不純物元素を含有する鋼を溶製して出鋼した場合、精錬容器1はPb、TiおよびBの不純物元素が浸潤した目地3となっている。この不純物元素が浸潤した目地3を有する精錬容器1にPb、TiおよびBの不純物元素を含有しない鋼種を洗い鋼種として装入し、溶製して出鋼する。この洗い鋼種による溶製、出鋼を数回繰り返し行う。この洗い鋼種による溶製・出鋼を繰り返すことで、この精錬容器1の不純物元素を浸潤した目地3からこれらの不純物元素を洗い出す。次いで、不純物元素を洗い出した精錬容器1を使用して新たな鋼を溶製することにより清浄度の高い鋼の溶製する。
【0013】
本発明における目地から溶鋼へ溶出する量の評価は次のようにして行った。まずPb、Ti、Bの各元素を不可避的不純物としてしか含有しない鋼種を連続して10回以上溶解する場合の、10回目以降の鋼材に含まれるPb、Ti、Bの各元素の含有量を分析し、この平均値を基準値とする。そしてPb、Ti、Bの各元素の一種または二種以上を積極的含有する鋼種を溶解したときに、この後、洗いの溶解を複数回行い、その時の鋼材を分析し、これと基準値との差を求めて目地から溶鋼へ溶出する量を評価した。また比較例の場合には先述したPb、Ti、Bの各元素を積極的含有する鋼種を溶解した後に、洗いの溶解を行わず溶解し、その分析値の比較を行った。以上の結果をまとめたものが図2である。なお、図2において、縦軸の指数は洗い溶解を1回行った精錬容器を使用した時の目地から溶鋼へPb、Ti、Bの各不純物元素が溶出する量を1として相対比で示したものである。
【0014】
図2に見られるように、Pbは洗い鋼種による溶製の繰り返し数2〜4回により、TiおよびBは2回により、目地から溶鋼に溶出する量はほぼ相対比0となることがわかる。なおここで、比較例である洗い鋼種を溶解しない場合のピックアップ量の絶対値であるが、これは前の溶解のときのPb、Ti、Bの含有量などにより変動が大きいので一概にはいえない。よって図2では相対値でその概要を示した。
【0015】
【発明の効果】
以上に説明したように、本発明は、取鍋その他の精錬容器内の洗い鋼種による繰り返し溶製により非金属介在物を生成する不純物元素の浸潤した目地からこれらの不純物元素が溶出することを減少することにより、取鍋その他の精錬容器における鋼の溶製において、酸化物や不純物元素による溶鋼の汚染を回避して高清浄度鋼を溶製することができ、優れた効果を奏するものである。
【図面の簡単な説明】
【図1】 付着地金が付着し、Pb、TiおよびBなどの不純物元素が浸潤した目地を有する出鋼後の取鍋その他の精錬容器を示す図である。
【図2】 洗い鋼種による溶製の繰り返し数とその精錬容器から溶鋼に溶出される不純物元素のPb、TiおよびBの量の関係を指数化して相対比で示すグラフである。
【符号の説明】
1 精錬容器
2 付着地金
3 目地[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
[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
[0012]
In an embodiment of the invention according to
[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
[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]
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JP2002243588A JP4027749B2 (en) | 2002-08-23 | 2002-08-23 | Adjustment method of refining vessel for melting high clean steel |
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Cited By (1)
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CN100396572C (en) * | 2002-09-04 | 2008-06-25 | 石崎资材株式会社 | Compressive accommodation bag having non-return valve function |
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JP4722772B2 (en) * | 2006-06-12 | 2011-07-13 | 株式会社神戸製鋼所 | Manufacturing method of high cleanliness steel |
JP5606152B2 (en) * | 2010-05-24 | 2014-10-15 | 株式会社神戸製鋼所 | How to remove ladles from ladle |
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CN100396572C (en) * | 2002-09-04 | 2008-06-25 | 石崎资材株式会社 | Compressive accommodation bag having non-return valve function |
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