JP6642085B2 - RH tank bottom refractory thickness estimation method - Google Patents
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Description
本発明は、ＲＨ真空脱ガス装置の真空槽（以下、「ＲＨ真空槽」または「ＲＨ槽」とも称する。）における槽底耐火物の厚みを推定する方法に関する。 The present invention relates to a method for estimating the thickness of a refractory at the bottom of a vacuum chamber (hereinafter, also referred to as “RH vacuum chamber” or “RH chamber”) of an RH vacuum degassing apparatus.
従来より、転炉等で脱炭処理がなされた溶鋼は二次精錬工程へと搬送され、二次精錬工程にてさらにＲＨ式脱ガス法（以下、単に「ＲＨ」とも称する。）等を用いた真空脱ガス処理（精錬処理）が行われている。 Conventionally, molten steel that has been decarburized in a converter or the like is conveyed to a secondary refining process, and in the secondary refining process, an RH degassing method (hereinafter, also simply referred to as “RH”) is used. Vacuum degassing process (refining process) is performed.
ＲＨについて、以下に説明する。
ＲＨで用いられるＲＨ真空脱ガス装置は、溶鋼が装入される取鍋と、真空状態となって溶鋼内の脱ガスを行うＲＨ真空槽とを有している。取鍋は、転炉の出鋼時に用いられた取鍋と同一のものであって、ＲＨ真空槽の直下に配置されるようになっている。ＲＨ真空槽の下部には、取鍋内の溶鋼に浸漬させる２本の浸漬管が設けられており、この浸漬管の一方にはＡｒガス等の不活性ガスを吹き込む吹き込み口が設けられている。ＲＨ真空槽の上部には、当該ＲＨ真空槽のガスを排気する排気口が設けられている。より詳しくは、ＲＨ真空槽は、上下分離可能に構成された筒状であり、環流管（２本の浸漬管）が設けられた下部槽と、排気口が設けられた上部槽とを有している。
The RH will be described below.
The RH vacuum degassing device used in the RH has a ladle into which molten steel is charged, and an RH vacuum tank which is in a vacuum state and degasses the molten steel. The ladle is the same as the ladle used when tapping the converter, and is arranged directly below the RH vacuum tank. At the lower part of the RH vacuum tank, two immersion pipes for immersing in molten steel in a ladle are provided, and one of the immersion pipes is provided with a blowing port for blowing an inert gas such as Ar gas. . An exhaust port for exhausting gas from the RH vacuum chamber is provided at an upper portion of the RH vacuum chamber. More specifically, the RH vacuum tank is a tubular shape configured to be vertically separable, and has a lower tank provided with a reflux pipe (two immersion pipes) and an upper tank provided with an exhaust port. ing.
ＲＨ真空脱ガス装置を用いて精錬するにあたっては、まず取鍋を上昇もしくはＲＨ真空槽を下降させることにより、下部槽の下端に設けられた浸漬管を取鍋内の溶鋼に浸漬する。そして、吹き込み口から不活性ガスを吹き込むと共に、排気口からＲＨ真空槽のガスを排気することによりＲＨ真空槽内を略真空状態したうえで、溶鋼をＲＨ真空槽と取鍋との間で循環させ、溶鋼内に存在する水素等のガス成分を除去する精錬処理を行う。 In refining using the RH vacuum degassing apparatus, first, the ladle is raised or the RH vacuum tank is lowered, so that the dip tube provided at the lower end of the lower tank is dipped in molten steel in the ladle. Then, the inert gas is blown from the blowing port, and the gas in the RH vacuum chamber is exhausted from the exhaust port to substantially evacuate the RH vacuum chamber. Then, the molten steel is circulated between the RH vacuum chamber and the ladle. Then, a refining process for removing gas components such as hydrogen existing in the molten steel is performed.
ＲＨでは、脱ガスのほかにも溶鋼の昇熱等を目的として、ＲＨ真空槽内で、酸素上吹きが行われることもある。ＲＨで処理を繰り返すと、ＲＨ真空槽内に施工された耐火物の溶損が進み、残厚が少なくなる。ＲＨ真空槽の耐火物において、溶損が問題となるのは側壁耐火物と槽底耐火物に大別される。 In RH, in addition to degassing, oxygen is sometimes blown in an RH vacuum chamber for the purpose of raising the temperature of molten steel. When the treatment is repeated at RH, the refractory applied in the RH vacuum tank is eroded and the residual thickness is reduced. In the refractories of the RH vacuum tank, what causes a problem of melting is roughly classified into refractories on the side wall and refractories on the bottom of the tank.
例えば、上述の酸素上吹きによる温度調整は、最適な鋳造条件確保のために有効な技術である。さらに、ＲＨ処理効率化のためには酸素上吹き速度の増加が有効であるが、酸素上吹き速度の増加はＲＨ真空槽の槽底耐火物（以下、単に「槽底耐火物」または「ＲＨ槽底耐火物」とも称する。）に悪影響を与えることが知られている。この悪影響を抑制することを目的とした技術として、例えば特許文献１には、槽底耐火物の損傷を抑制する方法が記載されている。 For example, the above-described temperature adjustment by oxygen overblowing is an effective technique for securing optimum casting conditions. Further, it is effective to increase the top blowing speed of oxygen to increase the efficiency of RH treatment. It is also known to have an adverse effect on tank bottom refractories.) As a technique aimed at suppressing this adverse effect, for example, Patent Literature 1 discloses a method of suppressing damage to a tank bottom refractory.
このように、ＲＨ真空槽の耐火物の損傷を抑制する方法は、これまでに提案されている。しかしながら、これまでに提案されている技術を用いてもＲＨ真空槽を永続して使用することはできないので、耐火物の整備が行われる。ＲＨでは、耐火物を出来るだけ使い切ったタイミングで、当該ＲＨの整備（炉修）を行うことが望まれているため、精錬処理の終了等のタイミングで耐火物の残厚を予測し、予測した耐火物の残厚が小さい場合に、ＲＨに終点（炉修を実施する時期）が来たと判断している。真空脱ガス装置の終点判定方法に関する技術として、例えば、特許文献２に示すものがある。 As described above, a method of suppressing damage to the refractory of the RH vacuum chamber has been proposed. However, since the RH vacuum tank cannot be used permanently even by using the technology proposed so far, refractory maintenance is performed. In the RH, it is desired to perform maintenance (furnace repair) of the RH at the timing when the refractory is used up as much as possible. Therefore, the remaining thickness of the refractory is predicted and predicted at a timing such as the end of the refining process. When the remaining thickness of the refractory is small, it is determined that the end point (time to perform the furnace repair) has come to the RH. As a technique relating to a method for determining an end point of a vacuum degassing apparatus, for example, there is one disclosed in Patent Document 2.
特許文献２に開示された技術では、煉瓦外側に断熱シートを設けた真空脱ガス装置で、精錬処理終了後の２０〜２５分を経過するまでに、真空槽の槽底から８５０〜１４５０ｍｍの範囲であり、かつ、円周方向の４５〜１３５度又は２２５〜３１５度の範囲の鉄皮の温度が４００℃以上となったときに終点であると判断している。 In the technology disclosed in Patent Document 2, a vacuum degassing device provided with a heat insulating sheet on the outside of a brick, a range of 850 to 1450 mm from the bottom of the vacuum tank until 20 to 25 minutes after the end of the refining process. It is determined that the end point is reached when the temperature of the steel shell in the range of 45 to 135 degrees or 225 to 315 degrees in the circumferential direction becomes 400 ° C. or higher.
また、耐火物残厚のバランスに応じて、ＲＨ操業を変化させることも可能である。ＲＨ真空槽の側壁耐火物の終点判断で炉修が予定されている場合であって、かつ、槽底耐火物厚には余裕があることが分かっている場合には、炉修までの間に槽底耐火物には余裕があるので、側壁耐火物の耐用限度範囲内で酸素上吹き速度を増加させた有効なＲＨ操業ができ、かつ側壁耐火物も槽底耐火物も耐火物を出来るだけ使い切って炉修を迎えることができる。ＲＨ真空槽内の耐火物の残厚を予測するような技術として、例えば、特許文献３に示すものがある。 Further, the RH operation can be changed according to the balance of the refractory residue thickness. If the furnace repair is scheduled by judging the end point of the refractory on the side wall of the RH vacuum tank, and it is known that there is room in the thickness of the refractory at the bottom of the tank, Since there is room for refractory at the bottom of the tank, effective RH operation with an increased oxygen blowing rate within the service limit of the refractory on the side wall can be performed. We can use up and can reach furnace repair. As a technique for estimating the remaining thickness of a refractory in an RH vacuum chamber, for example, there is a technique disclosed in Patent Document 3.
特許文献３に開示された技術では、ウェア耐火物におけるパーマネント耐火物側の面又はウェア耐火物の内部に温度計を設置し、温度計の設置位置を同じとした複数の炉代について、炉代ごとに温度計により測定した窯炉設備の任意の精錬処理回数の精錬処理終了時における測定温度とウェア耐火物の残厚の実測値のデータをデータベースとして求め、測定温度と残厚の実測値との関係を表す温度残厚関係データを予め構築することによって、耐火物の残厚を正確に求めることができるようにしている。 According to the technology disclosed in Patent Document 3, a thermometer is installed on a surface of a wear refractory on a permanent refractory side or inside a wear refractory, and a plurality of furnace charges in which a thermometer is installed at the same position are used. The data of the measured temperature and the measured value of the residual thickness of the ware refractory at the end of the smelting process of the arbitrary number of refining processes of the kiln equipment measured by the thermometer for each time were obtained as a database. By constructing the temperature remaining thickness relationship data representing the relationship in advance, the remaining thickness of the refractory can be accurately obtained.
特許文献１には、槽底耐火物の損傷を抑制する操業条件が記載されているに留まり、槽底耐火物の厚み推定や終点判定については記載されていない。操業を重ねると、槽底耐火物は少しずつ損傷することがあるほか、操業方針に依っては、耐火物の損傷抑制とは相反する条件が採用されることがある。そのため、ＲＨの終点を適切に把握するために、ＲＨ槽底耐火物の厚みを推定することが望まれる。また、特許文献２に開示された真空脱ガス装置の終点判定方法や、特許文献３に開示された耐火物残厚推定方法は、いずれも側壁耐火物が対象であり、ＲＨ槽底耐火物の厚みを推定する方法（熱間測定方法）は、これまでに確立されていない。さらに、特許文献１〜３に開示された技術は、いずれも耐火物もしくは鉄皮温度の測定に基づいた方法であるため、これらをＲＨ槽底耐火物の残厚予測に適用しようとしても、至近にある浸漬管による外乱影響が大きいため、正確な測定が非常に困難である。 Patent Literature 1 only describes operating conditions for suppressing damage to the tank bottom refractory, but does not describe thickness estimation or end point determination of the tank bottom refractory. When the operation is repeated, the tank bottom refractory may be damaged little by little, and depending on the operation policy, a condition that is contrary to the control of the refractory damage may be adopted. Therefore, in order to appropriately grasp the end point of the RH, it is desired to estimate the thickness of the refractory at the bottom of the RH tank. Further, the end point determination method of the vacuum degassing device disclosed in Patent Document 2 and the refractory residual thickness estimation method disclosed in Patent Document 3 are all directed to the side wall refractories, and A method for estimating the thickness (hot measuring method) has not been established so far. Further, since the techniques disclosed in Patent Documents 1 to 3 are all based on the measurement of refractory or steel shell temperature, even if they are applied to the prediction of the residual thickness of the refractory at the bottom of the RH tank, However, accurate measurement is very difficult because of the large influence of the disturbance caused by the immersion tube.
上記問題点に鑑み、本発明は、ＲＨ槽底耐火物の厚み推定方法を提供することを課題としている。 In view of the above problems, an object of the present invention is to provide a method for estimating the thickness of a refractory in an RH tank bottom.
本発明者らは、上述の課題を解決するために、ＲＨ槽の耐火物厚みと操業条件との相関を検討・調査し、下記の（ａ）〜（ｅ）の知見を得た。なお、本発明の実施においては、溶鋼を保持した取鍋の質量（以下、「取鍋重量」と称する。）を計量する装置を有することが前提である。以下に詳述するように、「取鍋重量」は、ＲＨ操業上の制約に依って、溶鋼および取鍋の合計質量のみを常に正確に測定しているわけではない。計量により得られた測定値を「みかけの取鍋重量」と称する。 The present inventors have studied and investigated the correlation between the refractory thickness of the RH tank and the operating conditions in order to solve the above-mentioned problems, and obtained the following findings (a) to (e). In the practice of the present invention, it is assumed that a device for measuring the mass of a ladle holding molten steel (hereinafter, referred to as “ladle weight”) is provided. As described in detail below, "Ladle weight" does not always accurately measure only the total mass of molten steel and the ladle due to RH operation constraints. The measured value obtained by the weighing is called "apparent ladle weight".
（ａ）図１に概略を示すように、ある処理操業におけるＲＨ槽内圧力とみかけの取鍋重量とをプロットすると、
（ｉ）図１内の右側の上向き黒矢印で示したように、はじめは浸漬管を溶鋼に浸漬することでみかけの取鍋重量が増加する。
（ｉｉ）次に、真空脱ガス処理のためにＲＨ槽内の排気が行われて圧力を低下させていくと、図１内の左向き黒矢印で示したように、みかけの取鍋重量はある傾き（傾きＡ）で低下し、
（ｉｉｉ）ある圧力以下になると別の傾き（傾きＢ）で低下する。
(A) As schematically shown in FIG. 1, when the pressure in the RH tank and the apparent ladle weight in a certain processing operation are plotted,
(I) As indicated by the upward black arrow on the right side in FIG. 1, initially, the apparent ladle weight increases by immersing the immersion tube in molten steel.
(Ii) Next, when the pressure in the RH tank is reduced by evacuating the RH tank for vacuum degassing, the apparent ladle weight is present, as indicated by the black arrow pointing left in FIG. Decreases at a slope (slope A),
(Iii) When the pressure falls below a certain pressure, the pressure decreases with another slope (slope B).
（ｂ）（ａ）の理由を考察すると、まず、（ｉ）浸漬管を溶鋼に浸漬することによるみかけ取鍋重量の増加は、浸漬管にかかる浮力の影響であり、（ｉｉ）槽内圧力低下によるみかけの取鍋重量低下の理由は、図２に概略を示したように、槽内圧力低下によってＲＨ槽内へ溶鋼が吸い込まれ、取鍋にかかる溶鋼重量が減少することであると考えられた。（ｉｉｉ）その傾きが傾きＡから傾きＢへと変化する理由は、槽内断面積の変化による槽内圧力低下量当たりの吸い込み増加量の変化であり、傾きＡがあらわれている間はＲＨ槽内の鋼浴面は浸漬管内にあり（図２（２））、傾きＢがあらわれている間はＲＨ槽内の鋼浴面は下部槽内にあると考えられた（図２（４））。さらに傾きの変化点においては、ＲＨ槽内の鋼浴面と槽底耐火物上面とが一致していると考えられた（図２（３））。 Considering the reasons for (b) and (a), first, (i) the increase in apparent ladle weight by immersing the immersion tube in molten steel is the effect of buoyancy applied to the immersion tube, and (ii) the pressure in the tank. The reason for the apparent decrease in the ladle weight due to the drop is thought to be that the molten steel is sucked into the RH tank due to the reduced pressure in the tank and the weight of the molten steel applied to the ladle is reduced, as schematically shown in FIG. Was done. (Iii) The reason why the slope changes from the slope A to the slope B is a change in the suction increase per tank pressure drop due to a change in the tank cross-sectional area, and while the slope A appears, the RH tank. The steel bath surface inside was in the dip tube (FIG. 2 (2)), and it was considered that the steel bath surface in the RH bath was in the lower bath while the slope B appeared (FIG. 2 (4)). . Further, at the change point of the inclination, it was considered that the steel bath surface in the RH tank coincided with the tank bottom refractory upper surface (FIG. 2 (3)).
（ｃ）（ｂ）より、溶鋼密度ρＦｅが変化しないと仮定すると、槽内圧力変化時の圧力のつりあいの式である式（１）と、ＲＨ槽内外の溶鋼量のつりあいの式である式（２）、みかけの取鍋重量のつりあいの式である式（３）、取鍋−ＲＨ槽間の距離が変化した時の鋼浴面高さのつりあいの式である式（４）、みかけの取鍋重量のつりあいの式である式（５）、断面積のつりあいの式である式（６）、および、変化量の合成の式である式（７）〜（８）を用いて、ΔＸ内について解き、変化のタイミングとして、取鍋鋼浴面と浸漬管下端とが一致したタイミングから、槽内鋼浴面と槽底耐火物上面とが一致したタイミングまでを考えると、槽底耐火物厚みＴ（ｍｍ）を用いてΔＸ内はΔＸ内＝Ｔ＋ｈと表されるので、Ｔは以下の式（α）で表すことができる。
△Ｐ×ρＨｇ／ρＦｅ＝−△Ｘ内・Ｐ＋△Ｘ外・Ｐ …（１）
−△Ｘ内・Ｐ×Ｓ内＝△Ｘ外・Ｐ×Ｓ外 …（２）
△ＷＰ＝△Ｘ外・Ｐ×Ｓ浸×ρＦｅ＋（−△Ｘ内・Ｐ＋△Ｘ外・Ｐ）×Ｓ内×ρＦｅ …（３）
△Ｈ×Ｓ鍋＝△Ｘ内・Ｈ×（Ｓ内・Ｈ＋Ｓ外・Ｈ） …（４）
△ＷＨ＝△Ｘ内・Ｈ×Ｓ浸×ρＦｅ …（５）
Ｓ鍋＝Ｓ内＋Ｓ外＋Ｓ浸 …（６）
△Ｗ＝△ＷＰ＋△ＷＨ …（７）
△Ｘ内＝△Ｘ内・Ｐ＋△Ｘ内・Ｈ …（８）
(C) From equation (b), assuming that the molten steel density ρ Fe does not change, the equation (1), which is the equation for the pressure balance when the pressure in the tank changes, and the equation for the amount of molten steel inside and outside the RH tank. Equation (2), Equation (3), which is an equation for the apparent ladle weight, Equation (4), which is an equation for the steel bath surface height when the distance between the ladle and the RH tank changes. Using equation (5), which is an equation for balancing the apparent ladle weight, equation (6), which is an equation for balancing the cross-sectional area, and equations (7) to (8), which are equations for combining the amount of change. , ΔX , and from the timing when the ladle steel bath surface coincides with the lower end of the immersion pipe to the timing when the steel bath surface in the tank coincides with the upper surface of the refractory tank, since the ΔX with refractory thickness T (mm) is expressed as ΔX in = T + h, T is expressed by the following equation (alpha) Door can be.
ΔP × ρ Hg / ρ Fe = − △ X inside · P + △ X outside · P (1)
- △ in · P × within the S X = △ X outside · P × S outside ... (2)
ΔW P = ΔX outside · P × S immersion × ρ Fe + (− △ X inside · P + ΔX outside · P ) × S inside × ρ Fe (3)
△ H × S pot = △ X inside ・ H × (S inside ・ H + S outside ・ H )… (4)
ΔW H = ΔX × H × S immersion × ρ Fe (5)
S pot = S inside + S outside + S soak ... (6)
ΔW = ΔW P + ΔW H (7)
△ X in = △ X in the · P + △ X in · H ... (8)
ここで、Ｘ内：浸漬管内側での鋼浴面高さ（ｍｍ）、Ｘ外：浸漬管外側での鋼浴面高さ（ｍｍ）、Ｓ鍋：取鍋内側断面積（ｍ ２ ）、Ｓ内：浸漬管内側断面積（ｍｍ２）、Ｓ外：浸漬管外側かつ取鍋内側断面積（ｍｍ２）、Ｓ浸：浸漬管耐火物断面積（ｍｍ２）であり、各断面積はいずれも水平方向である。
Ｈ：取鍋とＲＨ槽との距離（ｍｍ）、Ｐ：ＲＨ槽内圧力（ｔｏｒｒ）、Ｗ：みかけの取鍋重量（ｔ）、ｈ：浸漬管下端とＲＨ槽底鉄皮内面との距離（ｍｍ）、ρＨｇ：水銀密度（ｔ／ｍ ３ ）、ρＦｅ：溶鉄密度（ｔ／ｍ ３ ）である。Ｈおよびｈについてはいずれも垂直方向の距離であり、また、Ｈについては変化量が分かればよく、基準点の取り方は特に規定されない。
また、添え字Ｐ、Ｈはその変化の原因を表し、添え字Ｐ：圧力変化による変化、添え字Ｈ：取鍋とＲＨ槽との距離変化による変化を表す。添え字底、０はタイミングを表し、添え字底：槽内鋼浴面と槽底耐火物上面とが一致したタイミング（傾きの変化点）、添え字０：取鍋鋼浴面と浸漬管下端とが一致したタイミング（よって、Ｐ０＝大気圧となる。）である。
Here, the X: Steel bath surface height in the immersion tube side (mm), X: outside the steel bath surface height in the immersion tube outer (mm), S pot: ladle inner cross-sectional area (m 2), Inside S: Inside cross section of immersion tube (mm 2 ) Outside S: Outside cross section of immersion tube and inside ladle (mm 2 ), S immersion : Cross section of immersion tube refractory (mm 2 ) Both are in the horizontal direction.
H: distance between ladle and RH tank (mm), P: pressure in RH tank (torr), W: apparent ladle weight (t), h: distance between lower end of immersion pipe and inner skin of RH tank bottom (Mm), ρ Hg : mercury density (t / m 3 ), ρ Fe : molten iron density (t / m 3 ). H and h are both distances in the vertical direction, and the change amount of H only needs to be known, and the way of setting the reference point is not particularly defined.
The suffixes P and H indicate the cause of the change, and the suffix P: change due to a change in pressure, and the suffix H: change due to a change in the distance between the ladle and the RH tank. Subscript bottom, 0 indicates timing, subscript bottom: timing when the steel bath surface in the tank matches the upper surface of the refractory at the tank bottom (change point of inclination), subscript 0: ladle steel bath surface and the lower end of the immersion pipe Are coincident with each other (thus, P 0 = atmospheric pressure).
（ｄ）実操業においては、ＲＨでは環流ガスを吹き込むので、その影響によってみかけ溶鋼密度が変化する。ここで、みかけ溶鋼密度とは、溶鋼が装置内で占有する体積を基準とした密度であり、環流ガスによる気泡を含む。 (D) In the actual operation, since the reflux gas is blown in the RH, the apparent molten steel density changes due to the influence. Here, the apparent molten steel density is a density based on the volume occupied by the molten steel in the apparatus, and includes air bubbles due to reflux gas.
（ｅ）厳密に溶鋼密度変化を考慮すると式が煩雑化するが、一方でみかけ溶鋼密度変化が操業ごとに大きく変動することは考えにくい。そこで、式（α）に補正項（定数Ａ）を加えることにより、槽底耐火物厚みは以下の式（β）で表すことが可能であり、後述の結果からもわかるように、実用的である。 (E) Although the equation becomes complicated when the molten steel density change is strictly considered, it is hard to imagine that the apparent molten steel density change greatly fluctuates for each operation. Therefore, by adding a correction term (constant A) to equation (α), the tank bottom refractory thickness can be expressed by the following equation (β). is there.
本発明は、上記の知見に基づいて完成されたものであり、その要旨は、下記のＲＨ槽底耐火物厚み推定方法にある。 The present invention has been completed based on the above findings, and the gist of the present invention resides in the following RH tank bottom refractory thickness estimation method.
本発明は、計量により得られる、溶鋼を保持した取鍋の質量の測定値Ｗを用いて、ＲＨ槽底耐火物厚みＴを下記式（α）により推定することを特徴とする、ＲＨ槽底耐火物厚み推定方法である。 The present invention uses the measured value W of the ladle holding molten steel obtained by measurement to estimate the RH tank bottom refractory thickness T by the following equation (α). This is a refractory thickness estimation method.
また、上記本発明において、ＲＨ槽底耐火物厚みＴを、下記式（γ）で表わされる定数Ａを含む下記式（β）を用いて、補正することを特徴とすることが好ましい。 In the present invention, it is preferable that the thickness T of the refractory at the bottom of the RH tank is corrected by using the following equation (β) including a constant A represented by the following equation (γ).
本発明の方法によれば、特別な測定方法を採用せずに、操業ロスなくＲＨ槽底耐火物の厚み変化を細かく知ることが可能になる。その結果、安全性を損なわずにＲＨ槽底耐火物を使い切ることが可能になるので、経済性の向上を図ることが可能になる。 ADVANTAGE OF THE INVENTION According to the method of this invention, it becomes possible to know the change of thickness of the refractory at the bottom of the RH tank finely without operating loss without adopting a special measuring method. As a result, it is possible to use up the refractory at the bottom of the RH tank without impairing the safety, and it is possible to improve the economic efficiency.
図面を適宜参照しつつ、本発明を実施するための形態を以下に説明する。なお、以下に説明する形態は本発明の例であり、本発明は以下に説明する形態に限定されない。 Embodiments for carrying out the present invention will be described below with reference to the drawings as appropriate. The embodiments described below are examples of the present invention, and the present invention is not limited to the embodiments described below.
一般的に、製鋼工程では、転炉等で脱炭処理した溶鋼を二次精錬工程へ搬送して、二次精錬工程にてさらに精錬を行っている。本発明は、ＲＨを用いた二次精錬工程で行われる溶鋼の真空脱ガス処理において、当該真空脱ガス処理を行うＲＨ槽底耐火物の厚みを推定するものであり、本発明では、ＲＨ真空槽内の圧力変化中にみかけの取鍋重量の変化を測定することが必要である。本発明において、この測定方法は特に限定されず、例えば、取鍋をハンガーで吊った状態でハンガー架台をシリンダーにより上昇させてＲＨ処理を行うという構成をとっている場合には、ハンガー架台の下にロードセルを設置することで、みかけの取鍋重量の変化を測定することが可能となる。またこの重量測定は、本発明のみに用いられるものである必要はない。例えば溶鋼重量は、二次精錬および鋳造において重要な情報である。あらかじめ把握しておいた、取鍋内に溶鋼が無い状態での重量と、取鍋に溶鋼を装入した後に測定した重量とを比較することで、溶鋼重量の把握が可能となる。 Generally, in a steelmaking process, molten steel decarburized in a converter or the like is transported to a secondary refining process, and further refined in the secondary refining process. The present invention estimates the thickness of the RH tank bottom refractory for performing the vacuum degassing process in the vacuum degassing process of molten steel performed in the secondary refining process using RH. It is necessary to measure the change in apparent ladle weight during pressure changes in the vessel. In the present invention, this measuring method is not particularly limited. For example, when a configuration is adopted in which the hanger rack is raised by a cylinder while the ladle is hung on the hanger to perform the RH treatment, the measurement may be performed under the hanger rack. By installing a load cell in the ladle, it is possible to measure the change in apparent ladle weight. Also, this weight measurement need not be used only for the present invention. For example, molten steel weight is important information in secondary refining and casting. The weight of the molten steel in a state where there is no molten steel in the ladle and the weight measured after charging the molten steel in the ladle, which has been grasped in advance, can be compared to determine the weight of the molten steel.
さて、ＲＨ真空槽（ＲＨ槽）内に溶鋼を吸い込む際には、図１に示したように、まず浸漬管を溶鋼に浸漬することで、装入された溶鋼と取鍋との合計でのみかけの重量（みかけの取鍋重量）が増加する。そしてＲＨ槽内を真空排気することで吸い込まれた溶鋼の重量に応じて、みかけの取鍋重量が減少する。吸い込まれる溶鋼の重量はＲＨ槽内の圧力変化のほかに、ＲＨ槽内の形状によって決定される。つまり、ＲＨ槽内の鋼浴面が浸漬管内にある場合は、ＲＨ槽内の圧力変化による吸い込み量変化は小さく、鋼浴面が下部槽内にある場合は吸い込み量変化が大きくなる。よって、ＲＨ槽底耐火物上面とＲＨ槽内鋼浴面とが一致した点が、吸い込み量の変化点であるとみなすことができる。 Now, when the molten steel is sucked into the RH vacuum tank (RH tank), as shown in FIG. 1, the immersion pipe is first immersed in the molten steel, so that the total of the charged molten steel and the ladle is taken. The apparent weight (apparent ladle weight) increases. Then, the apparent ladle weight is reduced according to the weight of the molten steel sucked by evacuating the RH tank. The weight of the molten steel to be sucked is determined by the shape of the RH tank in addition to the pressure change in the RH tank. That is, when the steel bath surface in the RH tank is in the immersion tube, the suction amount change due to the pressure change in the RH bath is small, and when the steel bath surface is in the lower bath, the suction amount change is large. Therefore, a point where the upper surface of the RH tank bottom refractory and the steel bath surface in the RH tank match can be regarded as a change point of the suction amount.
ここで、あらかじめ求めておいた、下部槽および浸漬管の耐火物が新品の状態であるときのＲＨ槽内の圧力とみかけの取鍋重量変化との関係から、ＲＨ槽内の鋼浴面とＲＨ槽底耐火物上面とが一致したタイミングを推定する。そして、そのときのみかけの取鍋重量Ｗ底、ＲＨ槽内圧力Ｐ底、および、取鍋とＲＨ槽との距離Ｈ底を用いてそれぞれ算出した、みかけの取鍋重量変化（Ｗ底−Ｗ０）、ＲＨ槽内圧力変化（Ｐ底−Ｐ０）、および、取鍋とＲＨ槽との距離（Ｈ底−Ｈ０）の実績と、水銀密度（ρＨｇ）、溶鉄密度（ρＦｅ）、取鍋内側断面積（Ｓ鍋）、および、ＲＨ槽に備えられる浸漬管下端とＲＨ槽底の鉄皮内面との距離（ｈ）とを上述の式（α）へ代入することにより、ＲＨ槽底耐火物厚みＴを計算する。その後、このようにして計算されたＲＨ槽底耐火物厚みＴと設計時の槽底耐火物厚みとを比較することにより、上述の式（β）で用いる補正項Ａを求めておく。次に、毎回のＲＨ処理において、ＲＨ槽内圧力とみかけの取鍋重量変化との関係からＲＨ槽内の鋼浴面とＲＨ槽底耐火物上面とが一致したタイミングを推定する。そして、そのときのみかけの取鍋重量Ｗ底、ＲＨ槽内圧力Ｐ底、および、取鍋とＲＨ槽との距離Ｈ底を用いてそれぞれ算出した、みかけの取鍋重量変化（Ｗ底−Ｗ０）、ＲＨ槽内圧力変化（Ｐ底−Ｐ０）、および、取鍋とＲＨ槽との距離（Ｈ底−Ｈ０）の実績と、水銀密度（ρＨｇ）、溶鉄密度（ρＦｅ）、取鍋内側断面積（Ｓ鍋）、ＲＨ槽に備えられる浸漬管下端とＲＨ槽底の鉄皮内面との距離（ｈ）、および、求めておいた補正項Ａとを上述の式（β）へと代入することにより、毎回のＲＨ処理におけるＲＨ槽底耐火物厚みＴを推定することができる。なお、終点と判断するＲＨ槽底耐火物厚みＴは、実際の損傷速度等に応じて決定されればよく、本発明では特に限定されない。 Here, from the relationship between the pressure in the RH tank and the apparent change in the ladle weight when the refractory of the lower tank and the immersion pipe is in a new state, determined in advance, the steel bath surface in the RH tank is The timing at which the upper surface of the refractory of the RH tank coincides with the upper surface is estimated. Then, the apparent ladle weight change (W bottom− W) calculated using the apparent ladle weight W bottom at that time, the pressure P bottom in the RH tank, and the distance H bottom between the ladle and the RH tank. 0 ), the pressure change in the RH tank (P bottom- P 0 ), the distance between the ladle and the RH tank (H bottom- H 0 ), the mercury density (ρ Hg ), and the molten iron density (ρ Fe ) , The ladle inner cross-sectional area (S pan ), and the distance (h) between the lower end of the dip tube provided in the RH tank and the inner surface of the steel skin at the bottom of the RH tank are substituted into the above-described equation (α) to obtain RH. The tank bottom refractory thickness T is calculated. Thereafter, by comparing the RH bottom refractory thickness T calculated in this way with the bottom thickness of the bottom refractory at the time of design, the correction term A used in the above equation (β) is obtained. Next, in each RH treatment, the timing at which the steel bath surface in the RH tank coincides with the upper surface of the refractory bottom of the RH tank is estimated from the relationship between the pressure in the RH tank and the apparent change in ladle weight. Then, the apparent ladle weight change (W bottom− W) calculated using the apparent ladle weight W bottom at that time, the pressure P bottom in the RH tank, and the distance H bottom between the ladle and the RH tank. 0 ), the pressure change in the RH tank (P bottom- P 0 ), the distance between the ladle and the RH tank (H bottom- H 0 ), the mercury density (ρ Hg ), and the molten iron density (ρ Fe ) , The ladle inner cross-sectional area (S pan ), the distance (h) between the lower end of the immersion pipe provided in the RH tank and the inner surface of the steel skin at the bottom of the RH tank, and the obtained correction term A are expressed by the above-mentioned equation (β). ), It is possible to estimate the RH tank bottom refractory thickness T in each RH treatment. The thickness T of the RH tank bottom refractory to be determined as the end point may be determined according to the actual damage speed and the like, and is not particularly limited in the present invention.
本発明によれば、みかけの取鍋重量変化の測定による時間ロスは皆無であり、かつＲＨ処理１回ごとにみかけの取鍋重量変化の測定を行うことが可能であるので、ＲＨ処理１回ごとのＲＨ槽底耐火物の厚み変化を把握することにより、ＲＨ槽底耐火物の残厚を非常に細かく管理することが可能となる。その結果、ＲＨの終点を適切に判断することが可能になる。 According to the present invention, there is no time loss due to the measurement of the apparent ladle weight change, and the apparent ladle weight change can be measured every time the RH processing is performed. By grasping the thickness change of the RH tank bottom refractory for each case, it becomes possible to control the remaining thickness of the RH tank bottom refractory very finely. As a result, it is possible to appropriately determine the end point of the RH.
実施例を参照しつつ、本発明についてさらに説明を続ける。 The present invention will be further described with reference to examples.
本実施例では、ＲＨについて、取鍋をハンガーで吊った状態でハンガー架台をシリンダーにより上昇させてＲＨ処理を行うという構成をとっていた。そのため、ハンガー架台の下にロードセルを設置することで、みかけの取鍋重量の変化量を測定した。また、上記シリンダーのストロークを計測することで、取鍋とＲＨ槽との距離の変化量を測定した。ＲＨ槽内圧力については、圧力測定器（ＥＪＸ３１０Ｊ、横河電機株式会社製）を上部槽の排気口近傍に設置し、測定した。
上記構成のＲＨ装置、および、内側断面積が１３．８５ｍ２である取鍋を用いて、２６０〜２８０ｔ／ｃｈの溶鋼をＲＨ処理し、その際の処理データをＲＨ槽底耐火物厚みの推定に用いた。
In the present embodiment, the RH processing is performed by raising the hanger gantry with the cylinder while the ladle is hung by the hanger. Therefore, by installing a load cell under the hanger base, the apparent change in the ladle weight was measured. In addition, the amount of change in the distance between the ladle and the RH tank was measured by measuring the stroke of the cylinder. The pressure in the RH tank was measured by installing a pressure gauge (EJX310J, manufactured by Yokogawa Electric Corporation) near the exhaust port of the upper tank.
Using the RH apparatus having the above configuration and a ladle having an inner cross-sectional area of 13.85 m 2 , RH processing is performed on molten steel of 260 to 280 t / ch, and the processing data at that time is used to estimate the refractory thickness of the RH tank bottom. It was used for.
処理データの一例を、図３に示す。ここでは、取鍋とＲＨ槽との距離として、取鍋上端とＲＨ槽底との垂直距離を採用している。図３に示した処理データにおける０．３〜０．６分では、浸漬管が溶鋼に浸漬されることによって、浸漬管に浮力が、溶鋼に浮力の反力がかかり、その結果、みかけの取鍋重量が増加している。０．７分以降は、ＲＨ槽内を排気することで溶鋼がＲＨ槽へと吸い込まれ、みかけの取鍋重量が低下している。 FIG. 3 shows an example of the processing data. Here, the vertical distance between the upper end of the ladle and the bottom of the RH tank is adopted as the distance between the ladle and the RH tank. At 0.3 to 0.6 minutes in the processing data shown in FIG. 3, the immersion tube is immersed in the molten steel, so that buoyancy is applied to the immersion tube and buoyancy reaction force is applied to the molten steel. Pot weight is increasing. After 0.7 minutes, the molten steel is sucked into the RH tank by exhausting the RH tank, and the apparent ladle weight is reduced.
ＲＨ槽下部槽の５炉代にわたる、ＲＨ槽底耐火物厚みの推定値と実測値との比較を、図４に示す。また、これらの推定値および実測値を算出する際に用いた、上記（α）式右辺の数値を表１に示す。ここで、各炉代初期においては、当該下部槽の１回目の処理のデータを用いて計算したＲＨ槽底耐火物厚み推定値（Ｔ推定値）と、設計時のＲＨ槽底耐火物厚み（Ｔ実測値）とを比較している。これに対し、各炉代最終においては、炉修直前の処理データを用いて計算したＲＨ槽底耐火物厚み推定値（Ｔ推定値）と、炉修時に解体したＲＨ槽底耐火物を採取して冷間で実測したＲＨ槽底耐火物厚み（Ｔ実測値）との比較を示している。なお、表１において、α１は−（Ｈ底−Ｈ０）であり、同α２は−（Ｐ底−Ｐ０）×ρＨｇ／ρＦｅであり、同α３は１０００×（Ｗ底−Ｗ０）／（Ｓ鍋・ρＦｅ）である。 FIG. 4 shows a comparison between the estimated value and the actually measured value of the thickness of the refractory at the bottom of the RH tank over the five furnace charges of the lower tank of the RH tank. Table 1 shows the numerical values on the right side of the above equation (α) used when calculating these estimated values and actual measured values. Here, at the beginning of each furnace allowance, the estimated value of the RH tank bottom refractory (T estimated value) calculated using the data of the first processing of the lower tank and the RH tank bottom refractory thickness at the time of design ( T measured value). On the other hand, at the end of each furnace cost, the RH bottom refractory thickness estimated value (T estimated value) calculated using the processing data immediately before the furnace repair and the RH bottom refractory dismantled during the furnace repair were collected. 3 shows a comparison with the refractory thickness (measured value of T) at the bottom of the RH tank measured cold and cold. In Table 1, α1 is-(H bottom -H 0 ), α2 is-(P bottom -P 0 ) × ρ Hg / ρ Fe , and α3 is 1000 × (W bottom -W 0). ) / (S pot · ρ Fe ).
図４および表１に示したように、すべての炉代において、Ｔ推定値とＴ実測値との差（誤差）は４０ｍｍ未満であった。安全性を損なわずに耐火物の厚みを使い切るには、耐火物厚みの予測精度の誤差を５０ｍｍ以内にする必要があることを考慮すると、本発明によれば、ＲＨ槽底耐火物の厚みを精度よく推定できていることが分かる。 As shown in FIG. 4 and Table 1, the difference (error) between the estimated T value and the measured T value was less than 40 mm in all the furnace charges. Considering that it is necessary to make the error of the prediction accuracy of the refractory thickness within 50 mm in order to use up the thickness of the refractory without deteriorating safety, according to the present invention, the thickness of the refractory at the bottom of the RH tank is reduced. It can be seen that the estimation was accurate.
Claims (2)
前記式（α）において、ＴはＲＨ槽底耐火物厚み（ｍｍ）、Ｈは取鍋とＲＨ槽との距離（ｍｍ）、ＰはＲＨ槽内圧力（ｔｏｒｒ）、ρＨｇは水銀密度（ｔ／ｍ ３ ）、ρＦｅは溶鉄密度（ｔ／ｍ ３ ）、Ｗは溶鋼を保持した取鍋の質量の測定値（ｔ）、Ｓ鍋は取鍋内側断面積（ｍ ２ ）、ｈはＲＨ槽に備えられる浸漬管下端とＲＨ槽底の鉄皮内面との距離（ｍｍ）であり、添え字の底はＲＨ槽内の鋼浴面とＲＨ槽底耐火物の上面とが一致したタイミングを表し、添え字の０は取鍋の鋼浴面と前記浸漬管下端とが一致したタイミングを表す。 Using the measured value of the mass of the ladle holding the molten steel obtained by weighing, the RH tank bottom refractory thickness T is estimated by the following equation (α), and the RH tank bottom refractory thickness estimation is characterized. Method.
In the formula (α), T is the thickness of the refractory at the bottom of the RH tank (mm), H is the distance between the ladle and the RH tank (mm), P is the pressure in the RH tank (torr), and ρ Hg is the mercury density (t). / m 3), ρ Fe is molten iron density (t / m 3), W is the mass of the measurements of the ladle which holds molten steel (t), S pot ladle inner cross-sectional area (m 2), h is RH The distance (mm) between the lower end of the immersion pipe provided in the tank and the inner surface of the steel skin at the bottom of the RH tank, and the bottom of the suffix indicates the timing at which the steel bath surface in the RH tank coincides with the top surface of the RH tank bottom refractory. The subscript 0 represents the timing at which the steel bath surface of the ladle coincides with the lower end of the immersion pipe.
前記式（β）において、Ａは前記式（γ）で表わされる定数であり、前記式（γ）におけるＴ実は予め冷間で測定したＲＨ槽底耐火物厚みの測定値（ｍｍ）である。 The RH tank bottom refractory according to claim 1, wherein the RH tank bottom refractory thickness T is corrected using the following equation (β) including a constant A represented by the following equation (γ). Thickness estimation method.
In the formula (beta), A is a constant represented by the formula (gamma), T real in the formula (gamma) is the previously measured value of RH tank bottom refractory thickness was measured with cold (mm) .
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