JP2008111164A - Method of melting ultra-clean steel - Google Patents
Method of melting ultra-clean steel Download PDFInfo
- Publication number
- JP2008111164A JP2008111164A JP2006295522A JP2006295522A JP2008111164A JP 2008111164 A JP2008111164 A JP 2008111164A JP 2006295522 A JP2006295522 A JP 2006295522A JP 2006295522 A JP2006295522 A JP 2006295522A JP 2008111164 A JP2008111164 A JP 2008111164A
- Authority
- JP
- Japan
- Prior art keywords
- molten steel
- cold material
- temperature
- steel
- cooling material
- Prior art date
- 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.)
- Granted
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 128
- 239000010959 steel Substances 0.000 title claims abstract description 128
- 238000000034 method Methods 0.000 title claims description 20
- 238000002844 melting Methods 0.000 title claims description 8
- 230000008018 melting Effects 0.000 title claims description 8
- 239000000463 material Substances 0.000 claims abstract description 79
- 238000009849 vacuum degassing Methods 0.000 claims abstract description 42
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 27
- 239000001301 oxygen Substances 0.000 claims abstract description 27
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 27
- 230000003749 cleanliness Effects 0.000 claims description 11
- 238000001816 cooling Methods 0.000 abstract description 25
- 238000007670 refining Methods 0.000 abstract description 18
- 238000011282 treatment Methods 0.000 abstract description 9
- 238000007872 degassing Methods 0.000 abstract description 7
- 238000010992 reflux Methods 0.000 description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 8
- 230000007547 defect Effects 0.000 description 7
- 238000009749 continuous casting Methods 0.000 description 5
- 238000009628 steelmaking Methods 0.000 description 5
- 238000004458 analytical method Methods 0.000 description 4
- 229910052742 iron Inorganic materials 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 239000002436 steel type Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000000700 radioactive tracer Substances 0.000 description 2
- 229910000532 Deoxidized steel Inorganic materials 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 229910000655 Killed steel Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000005261 decarburization Methods 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 230000003009 desulfurizing effect Effects 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Abstract
Description
本発明は、ＲＨ真空脱ガス装置を用いて酸化物系非金属介在物の少ない高清浄度鋼を溶製する方法に関するものである。 The present invention relates to a method for melting high cleanliness steel with a small amount of non-metallic oxide inclusions using an RH vacuum degassing apparatus.
鉄鋼材料の高機能化及び高品質化への要求の高まりから、鋼中の不純物元素を極限まで低減することが望まれており、溶鋼段階における鋼の高純度化及び高清浄度化のための技術が必要とされている。鋼中の不純物元素の１つである酸素は、鋼中で酸化物として存在した場合、鋼板における欠陥の原因となる。 Due to the increasing demand for higher functionality and higher quality of steel materials, it is desired to reduce the impurity elements in steel to the utmost limit, and to increase the purity and cleanliness of steel in the molten steel stage. Technology is needed. When oxygen, which is one of the impurity elements in steel, is present as an oxide in steel, it causes defects in the steel sheet.
鋼の精錬段階において、鋼中に酸化物を生成させる要因の１つとして、溶鋼の温度調整のために添加される冷材中の酸化物が挙げられており、こうした背景から冷材からの酸化物の汚染を防止する対策が実施されている。 In the steel refining stage, one of the factors that generate oxides in steel is the oxide in the cold material added to adjust the temperature of the molten steel. Measures are taken to prevent contamination of goods.
例えば、特許文献１には、製鋼炉からの出鋼に先立ち、受鋼を予定している取鍋の内壁表面温度を測定することにより、その取鍋の放冷カーブを求め、この放冷カーブに基づいて出鋼から連続鋳造までの温度降下を予測し、それによって製鋼炉からの出鋼温度及び各プロセスの適正温度の設定を行う方法が開示されている。この方法のようにして温度設定が可能であれば、冷材の添加は不要である。 For example, in Patent Literature 1, by measuring the inner wall surface temperature of a ladle that is scheduled to receive steel prior to steeling from a steelmaking furnace, a cooling curve for the ladle is obtained, and this cooling curve is obtained. Is used to predict the temperature drop from steelmaking to continuous casting, thereby setting the steelmaking temperature from the steelmaking furnace and the appropriate temperature for each process. If the temperature can be set by this method, it is not necessary to add a cold material.
また、特許文献２には、ＲＨ真空脱ガス装置で溶鋼を精錬する際に、冷材によって持ち来される酸素量が或る一定値以下となるように、冷材の酸素含有量に応じて冷材添加量を規定して精錬する方法が開示されている。特許文献２によれば、冷材によって持ち来される酸素量が或る一定値以下となるので、清浄性に優れた溶鋼を短時間で得ることができるとしている。
しかしながら、上記従来技術には以下の問題点がある。 However, the above prior art has the following problems.
即ち、特許文献１の方法で温度を設定しても、実際の操業では、転炉や電気炉において溶鋼温度自体を精度良く制御できるとは限らず、また、ＲＨ真空脱ガス装置の真空槽の状態によっては、真空脱ガス処理中に溶鋼温度が通常よりも低下してしまう場合もあることから、転炉や電気炉からの出鋼時には或る程度の余裕を持った温度で出鋼することが一般的であり、その場合には、ＲＨ真空脱ガス装置において溶鋼に冷材が添加されることが前提になる。 That is, even if the temperature is set by the method of Patent Document 1, in actual operation, the molten steel temperature itself may not be accurately controlled in the converter or the electric furnace, and the RH vacuum degassing apparatus has a vacuum chamber. Depending on the condition, the molten steel temperature may be lower than usual during the vacuum degassing process, so the steel should be output at a certain margin when steel is output from the converter or electric furnace. In this case, it is assumed that a cold material is added to the molten steel in the RH vacuum degassing apparatus.
また、特許文献２のように、冷材投入量の上限値を定めてしまうと、それ以上には溶鋼温度を強制的に低減することができず、冷材を上限値まで添加しても溶鋼温度が目標温度よりも高い場合には、ＲＨ真空脱ガス装置で処理することによる温度降下に依存せざるを得ず、ＲＨ真空脱ガス装置における処理時間が延長し、ＲＨ真空脱ガス装置の生産性が損なわれることになる。 Further, as in Patent Document 2, if the upper limit value of the amount of cold material is determined, the molten steel temperature cannot be forcibly reduced beyond that, and even if the cold material is added to the upper limit value, the molten steel When the temperature is higher than the target temperature, it must be dependent on the temperature drop caused by processing with the RH vacuum degassing apparatus, and the processing time in the RH vacuum degassing apparatus is extended, producing the RH vacuum degassing apparatus. Sexuality will be impaired.
本発明は上記事情に鑑みてなされたもので、その目的とするところは、ＲＨ真空脱ガス装置において溶鋼を精錬するに当たり、溶鋼温度調整用の冷材の使用量を規定しなくても、最小限の脱ガス処理時間の延長により、酸化物系非金属介在物の極めて少ない高清浄度鋼を安定して溶製することのできる、高清浄度鋼の溶製方法を提供することである。 The present invention has been made in view of the above circumstances, and the object of the present invention is to minimize the amount of cold material used for adjusting the molten steel temperature when refining the molten steel in the RH vacuum degassing apparatus. An object of the present invention is to provide a method for melting high cleanliness steel, which can stably melt high cleanliness steel with very few oxide-based non-metallic inclusions by extending the degassing time limit.
本発明者等は、上記課題を解決すべく鋭意検討・研究を実施した。以下に、検討結果を説明する。 The present inventors have conducted intensive studies and studies to solve the above problems. In the following, the examination results will be described.
一般的に、ＲＨ真空脱ガス装置における溶鋼の精錬工程は鋳造工程の直前の工程であり、鋳造される溶鋼に対して溶鋼温度の調整が可能な最後の工程であることが多い。そのため、溶鋼温度が鋳造時の目標温度に対して高過ぎる場合には、ＲＨ真空脱ガス精錬中の溶鋼に冷材を添加し、溶鋼温度を強制的に低下することが行われる。これは、連続鋳造時の溶鋼温度が目標温度に比べて高くなると、鋳型内での抜熱が遅れ、凝固シェルが発達せず、ブレークアウトの危険性があるからである。 Generally, the refining process of the molten steel in the RH vacuum degassing apparatus is a process immediately before the casting process, and is often the last process capable of adjusting the molten steel temperature with respect to the molten steel to be cast. Therefore, when the molten steel temperature is too high with respect to the target temperature at the time of casting, a cold material is added to the molten steel during RH vacuum degassing and the molten steel temperature is forcibly lowered. This is because if the molten steel temperature during continuous casting becomes higher than the target temperature, heat removal in the mold is delayed, the solidified shell does not develop, and there is a risk of breakout.
冷材としては、製鉄プロセスの各工程で発生した鉄スクラップが一般的に使用されており、冷材中には脱酸生成物が酸化物系非金属介在物（以下「介在物」と記す）として存在し、また、冷材の表面が酸化している場合もある。即ち、冷材を溶鋼に添加すると、冷材が溶解することによって冷材中の介在物が溶鋼中に持ち来たされて、溶鋼中の介在物が増加する。また、冷材表面の鉄酸化物によって、溶鋼中に存在するＡｌやＳｉなどの鉄よりも酸素との親和力の強い元素が酸化され、溶鋼中に介在物が形成される。 As the cold material, iron scrap generated in each step of the iron making process is generally used, and the deoxidation product is an oxide-based non-metallic inclusion (hereinafter referred to as “inclusion”) in the cold material. In some cases, the surface of the cooling material is oxidized. That is, when the cold material is added to the molten steel, the inclusions in the cold material are brought into the molten steel due to melting of the cold material, and the inclusions in the molten steel increase. In addition, the iron oxide on the surface of the cold material oxidizes elements having a higher affinity with oxygen than iron such as Al and Si present in the molten steel, and inclusions are formed in the molten steel.
これらの介在物を溶鋼から除去するためには、冷材添加後に所定時間のＲＨ真空脱ガス精錬時間つまり環流時間を確保する必要があり、また、冷材の添加に伴う介在物の発生量は、冷材の投入量や冷材自体の介在物含有量などによってばらつくので、介在物の発生量に応じて環流時間を延長する必要のあることが分かった。尚、ＲＨ真空脱ガス装置においては、溶鋼は取鍋と真空槽との間を環流しながら精錬されているので、「ＲＨ真空脱ガス精錬時間」と「環流時間」とは同一の意味で使用されている。 In order to remove these inclusions from the molten steel, it is necessary to secure a predetermined RH vacuum degassing refining time, that is, a recirculation time after adding the cold material, and the amount of inclusions generated due to the addition of the cold material is It was found that it was necessary to extend the reflux time according to the amount of inclusions produced because it varied depending on the amount of cold material introduced and the inclusion content of the cold material itself. In the RH vacuum degassing device, the molten steel is refined while circulating between the ladle and the vacuum tank. Therefore, “RH vacuum degassing refining time” and “circulation time” are used in the same meaning. Has been.
環流時間の必要延長時間は、冷材の添加によって発生する介在物の量と、使用するＲＨ真空脱ガス装置自体の介在物除去能力とによって決まり、様々な検討の結果、必要延長時間は下記の（１）式で表されることを見出した。つまり、冷材添加後の環流時間として、少なくとも（１）式で算出される必要延長時間を確保することで、冷材添加によって発生する介在物を除去できることを見出した。但し、（１）式において、ｔは、必要延長時間（分）、ｋは、ＲＨ真空脱ガス装置の脱酸速度定数（１／分）、Ｗc は、冷材の添加量（トン）、Ｗm は、溶鋼処理量（トン）、Ｏc は、冷材の酸素濃度（ｐｐｍ）、Ｏm は、冷材添加時の溶鋼中酸素濃度（ｐｐｍ）である。 The required extension time of the reflux time is determined by the amount of inclusions generated by the addition of the cooling material and the inclusion removal capability of the RH vacuum degassing apparatus itself. As a result of various studies, the required extension time is as follows: (1) It discovered that it represented by Formula. That is, it was found that inclusions generated by the addition of the cooling material can be removed by ensuring at least the necessary extension time calculated by the equation (1) as the reflux time after the addition of the cooling material. However, in the formula (1), t is the required extension time (min), k is the deoxidation rate constant (1 / min) of the RH vacuum degassing apparatus, Wc is the amount of cooling material added (tons), Wm Is the amount of molten steel treated (tons), Oc is the oxygen concentration (ppm) of the cold material, and Om is the oxygen concentration (ppm) in the molten steel when the cold material is added.
ここで、冷材によって発生する介在物量が少ない場合、つまり、冷材の酸素濃度と冷材添加時の溶鋼中酸素濃度とが同等の場合には、（１）式で得られる必要延長時間は非常に短くなる。しかし、余りに時間が短い場合、冷材が溶解しても溶鋼が十分に混合されず、溶鋼の介在物濃度に偏りができてしまう可能性がある。このような場合には、冷材添加後の環流時間として、少なくとも下記の（２）式で算出される必要延長時間を確保することで、解消されることを見出した。但し、（２）式において、ｔは、必要延長時間（分）、Ｗm は、溶鋼処理量（トン）、Ｑは、溶鋼環流量（トン／分）である。 Here, when the amount of inclusions generated by the cold material is small, that is, when the oxygen concentration of the cold material is equal to the oxygen concentration in the molten steel at the time of adding the cold material, the necessary extension time obtained by the equation (1) is It becomes very short. However, if the time is too short, the molten steel may not be sufficiently mixed even if the cold material is melted, and the inclusion concentration of the molten steel may be biased. It has been found that such a case can be resolved by ensuring at least the necessary extension time calculated by the following equation (2) as the reflux time after the addition of the cooling material. However, in the formula (2), t is the required extension time (minutes), Wm is the molten steel throughput (tons), and Q is the molten steel ring flow rate (tons / minute).
本発明は、上記知見に基づいてなされたものであり、本発明に係る高清浄度鋼の溶製方法は、ＲＨ真空脱ガス装置で処理中の溶鋼に温度調整用の冷材を添加して溶鋼温度を調整するに際し、冷材を溶鋼に添加した後、更に、上記の（１）式及び（２）式によって算出される必要延長時間のうちでどちらか長い方の必要延長時間以上にわたって溶鋼を環流することを特徴とするものである。 The present invention has been made on the basis of the above knowledge, and the method for melting high cleanliness steel according to the present invention includes adding a cooling material for temperature adjustment to the molten steel being processed by the RH vacuum degassing apparatus. In adjusting the molten steel temperature, after adding the cold material to the molten steel, the molten steel is further applied over the longer required extension time of the required extension time calculated by the above formulas (1) and (2). It is characterized by circulating.
本発明によれば、ＲＨ真空脱ガス装置において溶鋼を精錬する際に、処理中の溶鋼に溶鋼温度調整用の冷材を添加しても、脱ガス処理時間の最小限の延長で、冷材の添加により発生した介在物を溶鋼から浮上・分離することができ、介在物の極めて少ない高清浄度鋼を安定して溶製することが可能となり、工業上有益な効果がもたらされる。 According to the present invention, when refining molten steel in the RH vacuum degassing apparatus, even if a cold material for adjusting the molten steel temperature is added to the molten steel being processed, the cold material can be extended with a minimum extension of the degassing time. Inclusions generated by the addition of can be levitated and separated from the molten steel, and high cleanliness steel with very few inclusions can be stably melted, resulting in an industrially beneficial effect.
以下、本発明を詳細に説明する。 Hereinafter, the present invention will be described in detail.
転炉または電気炉などの製鋼炉で溶製された溶鋼を取鍋に出鋼し、取鍋に収容された溶鋼をＲＨ真空脱ガス装置に搬送し、ＲＨ真空脱ガス装置で真空脱ガス精錬を実施する。真空脱ガス精錬としては、真空脱炭処理、脱硫剤を使用した脱硫処理、水素や窒素或いは酸素などのガス成分の除去処理、合金成分の調整処理、及び、これらの２以上を組み合わせた処理などがあり、どのような真空脱ガス精錬を実施する場合であっても本発明を適用することができる。但し、合金成分の調整処理（成分調整処理）は、ほぼ全ての真空脱ガス精錬で実施されている。尚、本発明は高清浄度鋼の溶製を目的としており、Ａｌ脱酸やＳｉ脱酸の施されたキルド鋼を対象とし、清浄性に劣る未脱酸鋼は対象としてない。従って、少なくとも上記成分調整処理終了の時点には、溶鋼は脱酸された状態となっている。 The molten steel melted in a steelmaking furnace such as a converter or electric furnace is taken out into a ladle, the molten steel contained in the ladle is transported to an RH vacuum degasser, and vacuum degassing refining is performed with an RH vacuum degasser. To implement. As vacuum degassing refining, vacuum decarburization treatment, desulfurization treatment using a desulfurizing agent, removal treatment of gas components such as hydrogen, nitrogen or oxygen, adjustment treatment of alloy components, and a combination of these two or more The present invention can be applied to any vacuum degassing refining. However, the alloy component adjustment processing (component adjustment processing) is performed in almost all vacuum degassing refining. In addition, this invention aims at melting of high cleanliness steel, and is intended for the killed steel in which Al deoxidation or Si deoxidation was performed, and is not objected to the non-deoxidized steel inferior in cleanliness. Accordingly, the molten steel is in a deoxidized state at least at the end of the component adjustment process.
ＲＨ真空脱ガス装置において、これらの処理を行った後、溶鋼温度を測定し、測定された温度が目標温度範囲であれば、真空脱ガス精錬を終了し、一方、測定された温度が目標温度を超える場合には、溶鋼温度調整用の冷材を真空槽内の溶鋼に添加して溶鋼温度を目標温度に調整する。冷材の添加量は、測定された温度と目標温度との差に応じて決定する。この場合の目標温度は、次工程の連続鋳造工程における待ち時間などを考慮して決められるので、一般的には同一鋼種であっても異なる場合が多い。溶鋼温度調整用の冷材としては、製鉄プロセスの各工程で発生したスクラップを粒状または中空球状に加工したものが好適である。 After performing these treatments in the RH vacuum degassing apparatus, the molten steel temperature is measured, and if the measured temperature is within the target temperature range, the vacuum degassing refining is terminated, while the measured temperature is the target temperature. In the case of exceeding, the cold steel for adjusting the molten steel temperature is added to the molten steel in the vacuum chamber to adjust the molten steel temperature to the target temperature. The amount of cold material added is determined according to the difference between the measured temperature and the target temperature. Since the target temperature in this case is determined in consideration of the waiting time in the subsequent continuous casting process, in general, it is often different even for the same steel type. As the cooling material for adjusting the temperature of the molten steel, it is preferable to process scrap generated in each step of the iron making process into a granular shape or a hollow spherical shape.
尚、冷材を添加した場合には、冷材添加によって一般的には溶鋼成分が希釈されるので、再度成分調整を実施する場合がある。また、測定した溶鋼温度が目標温度よりも低い場合には、溶鋼を加熱処理する必要があるので、加熱装置を備えた取鍋精錬炉に搬送して加熱する、或いは、ＲＨ真空脱ガス装置で酸素ガスを供給して溶鋼中のＡｌを燃焼させて加熱するなどの加熱処理を実施した後、再度、前述の真空脱ガス精錬を実施する。 In addition, when a cold material is added, since the molten steel component is generally diluted by the cold material addition, the component adjustment may be performed again. Also, when the measured molten steel temperature is lower than the target temperature, it is necessary to heat the molten steel, so it is transported to a ladle refining furnace equipped with a heating device and heated, or with an RH vacuum degassing device After carrying out heat treatment such as supplying oxygen gas to burn and heat Al in the molten steel, the above-mentioned vacuum degassing refining is carried out again.
そして、溶鋼の測温値から、冷材による溶鋼の温度調整が必要となったときには、ＲＨ真空脱ガス装置の脱酸速度定数（ｋ）、測定された溶鋼温度と目標温度との差によって定められた冷材の添加量（Ｗc ）、溶鋼処理量（Ｗm ）、冷材の酸素濃度（Ｏc ）、冷材添加時の溶鋼中酸素濃度（Ｏm ）を前述した（１）式に代入して必要延長時間（ｔ）を求める。 When the temperature of the molten steel needs to be adjusted based on the measured temperature of the molten steel, it is determined by the deoxidation rate constant (k) of the RH vacuum degassing apparatus and the difference between the measured molten steel temperature and the target temperature. The amount of cold material added (Wc), the amount of molten steel treated (Wm), the oxygen concentration of the cold material (Oc), and the oxygen concentration in the molten steel (Om) when the cold material was added were substituted into the above-described equation (1). The required extension time (t) is obtained.
ここで、ＲＨ真空脱ガス装置の脱酸速度定数（ｋ）は、脱酸速度を一次反応と仮定した場合の脱酸速度定数であり、ＲＨ真空脱ガス装置の操業条件、処理する鋼種などによって異なるので、予め各種の操業条件下で溶鋼中酸素濃度の推移を実測して脱酸速度定数（ｋ）を求めておく必要がある。冷材添加時の溶鋼中酸素濃度（Ｏm ）は冷材添加直前の実溶鋼を分析することが望ましいが、分析に時間を費やすため、ＲＨ真空脱ガス装置に搬送される前に溶鋼が脱酸されている場合には、ＲＨ真空脱ガス装置に溶鋼が到着した時点の溶鋼中酸素濃度を分析し、また、ＲＨ真空脱ガス処理中に溶鋼が脱酸された場合には、脱酸直後の溶鋼中酸素濃度を分析し、これらの分析値から、予め求めた脱酸速度定数（ｋ）を用いて冷材添加直前の酸素濃度を推定するようにしてもよい。冷材の酸素濃度（Ｏc ）はスクラップのロッド毎に予め分析しておくこととする。 Here, the deoxidation rate constant (k) of the RH vacuum degassing device is a deoxidation rate constant when the deoxidation rate is assumed to be a primary reaction, and depends on the operating conditions of the RH vacuum degassing device, the steel type to be processed, and the like. Therefore, it is necessary to obtain the deoxidation rate constant (k) in advance by actually measuring the transition of the oxygen concentration in the molten steel under various operating conditions. Although it is desirable to analyze the actual molten steel immediately before the addition of the cold material, the oxygen concentration (Om) in the molten steel at the time of adding the cold material is time-consuming, so that the molten steel is deoxidized before being transported to the RH vacuum degasser. When the molten steel arrives at the RH vacuum degassing apparatus, the oxygen concentration in the molten steel is analyzed. When the molten steel is deoxidized during the RH vacuum degassing process, The oxygen concentration in the molten steel may be analyzed, and the oxygen concentration immediately before the addition of the cooling material may be estimated from these analysis values using the deoxidation rate constant (k) determined in advance. The oxygen concentration (Oc) of the cold material is analyzed in advance for each scrap rod.
（１）式によって必要延長時間（ｔ）を求めると同時に、前述した（２）式によっても必要延長時間（ｔ）を求める。（２）式では、溶鋼環流量（Ｑ）が必要であり、溶鋼環流量（Ｑ）は、微量のトレーサー成分を脱ガス処理中の溶鋼に添加してトレーサー成分の挙動から推定してもよく、また、Ｑ＝11.4×Ｇ1/3 ×Ｄ4/3 ×［ln（P1／P2）］1/3 の実験式（但し、Ｇ：環流用Ａｒ流量（Ｌ／ｍｉｎ）、Ｄ：浸漬管内径（ｍ）、Ｐ1 ：環流用Ａｒ吹き込み管位置での溶鋼静圧（Ｐａ）、Ｐ2 ：真空槽内圧（Ｐａ））を用いて算出してもよい。 The required extension time (t) is obtained from the equation (1), and at the same time, the necessary extension time (t) is obtained from the equation (2). In formula (2), the molten steel ring flow rate (Q) is required, and the molten steel ring flow rate (Q) may be estimated from the behavior of the tracer component by adding a trace amount of tracer component to the molten steel being degassed. In addition, Q = 11.4 × G 1/3 × D 4/3 × [ln (P 1 / P 2 )] 1/3 empirical formula (where G: Ar flow rate for reflux (L / min), D: The inner diameter (m) of the dip tube, P 1 : the molten steel static pressure (Pa) at the position of the Ar blowing tube for reflux, and P 2 : the pressure in the vacuum chamber (Pa)) may be used for calculation.
そして、（１）式によって求めた必要延長時間（ｔ）と、（２）式によって求めた必要延長時間（ｔ）とを比較し、冷材添加後の環流時間として、どちらか長い方の必要処理時間（ｔ）を少なくとも確保するように、冷材を添加した後も脱ガス精錬を継続する。この環流時間の間に、冷材添加によって鋼成分が目的成分から外れる恐れがある場合には、再度成分調整を実施する。冷材添加後の環流時間が、少なくとも、どちらか長い方の必要処理時間（ｔ）を確保したならば、ＲＨ真空脱ガス装置を終了し、溶鋼を次工程の連続鋳造工程に搬送する。 Then, the required extension time (t) obtained by the equation (1) is compared with the required extension time (t) obtained by the equation (2), and the longer one is necessary as the reflux time after the addition of the cold material. The degassing refining is continued even after the cooling material is added so as to secure at least the processing time (t). If there is a risk that the steel component may deviate from the target component due to the addition of the cold material during this reflux time, the component adjustment is performed again. If the recirculation time after the addition of the cold material secures at least the required processing time (t), whichever is longer, the RH vacuum degassing apparatus is terminated and the molten steel is conveyed to the next continuous casting process.
ＲＨ真空脱ガス装置において、このようにして溶鋼の温度調整を実施することにより、脱ガス処理時間の最小限の延長で、冷材添加量の如何に拘わらず、冷材の添加により発生した介在物を溶鋼から浮上・分離することができ、介在物の極めて少ない高清浄度鋼を安定して溶製することが可能となる。 In the RH vacuum degassing apparatus, by adjusting the temperature of the molten steel in this way, with the minimum extension of the degassing processing time, the intervention generated by the addition of the cold material regardless of the amount of the cold material added. The object can be levitated and separated from the molten steel, and high cleanliness steel with very few inclusions can be stably melted.
転炉で約２００トンの溶鋼を溶製した後、得られた溶鋼を取鍋に出鋼した。出鋼時、溶鋼に金属Ａｌを添加して溶鋼を脱酸した。出鋼終了後、溶鋼を収容した取鍋をＲＨ真空脱ガス装置へ搬送し、ＲＨ真空脱ガス装置の真空槽の下部に取り付けられた一対の浸漬管を取鍋内溶鋼に浸漬させ、一方の浸漬管からＡｒガスを０．０３３Ｎｍ3 ／ｓで吹き込み、溶鋼を取鍋と真空槽との間で環流させ、ＲＨ真空脱ガス精錬を実施した。 After melting about 200 tons of molten steel in a converter, the obtained molten steel was put into a ladle. At the time of steel removal, metal Al was added to the molten steel to deoxidize the molten steel. After finishing the steel, the ladle containing the molten steel is transported to the RH vacuum degassing device, and a pair of dip tubes attached to the lower part of the vacuum tank of the RH vacuum degassing device is immersed in the molten steel in the ladle. Ar gas was blown from the dip tube at 0.033 Nm 3 / s, and the molten steel was circulated between the ladle and the vacuum chamber, and RH vacuum degassing was performed.
尚、予め冷材を添加しない条件でＲＨ真空脱ガス精錬中に測定した溶鋼酸素濃度の挙動から、この操業条件における、ＲＨ真空脱ガス装置の脱酸速度定数（ｋ）は０．０５／分であることを確認している。また、冷材の酸素濃度（Ｏc ）は予め酸素分析により求め、その冷材をＲＨ真空脱ガス装置のホッパーに装入した。 In addition, from the behavior of the molten steel oxygen concentration measured during the RH vacuum degassing refining without adding a cooling material in advance, the deoxidation rate constant (k) of the RH vacuum degassing apparatus under this operating condition is 0.05 / min. It is confirmed that. The oxygen concentration (Oc) of the cold material was obtained in advance by oxygen analysis, and the cold material was charged into the hopper of the RH vacuum degasser.
取鍋がＲＨ真空脱ガス装置に到着した時点で溶鋼サンプルを採取し、このサンプルの酸素分析を実施した。この分析値と予め求めた脱酸速度定数（ｋ）とにより、冷材添加時の溶鋼中酸素濃度（Ｏm ）を推定した。また、溶鋼環流量（Ｑ）は、前述した実験式により求めた。 When the ladle arrived at the RH vacuum degasser, a molten steel sample was taken and oxygen analysis of this sample was performed. Based on this analysis value and the deoxidation rate constant (k) determined in advance, the oxygen concentration (Om) in the molten steel at the time of adding the cold material was estimated. The molten steel ring flow rate (Q) was determined by the empirical formula described above.
脱ガス精錬によりガス成分を除去した後に脱ガス処理中の溶鋼にＳｉ、Ｍｎを添加して成分調整を行い、その後、溶鋼温度を熱電対により測定した。脱ガス処理終了時の目標温度に対して高過ぎる場合に冷材を添加して溶鋼の温度調整を行った。冷材添加後の環流時間は、（１）式及び（２）式による必要延長時間（ｔ）を把握した上で、長い方の必要延長時間（ｔ）を基準として分単位で設定した。また、この冷材添加後の還流時間の間に、成分の微量調整も実施した。ＲＨ真空脱ガス処理後の溶鋼を連続鋳造機で鋳造し、熱間圧延を経て厚板製品とし、厚板製品において介在物起因の欠陥発生率を調査した。 After removing gas components by degassing refining, Si and Mn were added to the molten steel being degassed to adjust the components, and then the molten steel temperature was measured with a thermocouple. When it was too high with respect to the target temperature at the end of the degassing treatment, a cold material was added to adjust the temperature of the molten steel. The recirculation time after the addition of the cooling material was set in units of minutes based on the longer required extension time (t) after grasping the required extension time (t) according to the equations (1) and (2). In addition, minute adjustment of the components was also performed during the reflux time after the addition of the cooling material. The molten steel after the RH vacuum degassing treatment was cast with a continuous casting machine, subjected to hot rolling to obtain a thick plate product, and the occurrence rate of defects due to inclusions in the thick plate product was investigated.
また、比較例として、冷材添加後に、（１）式及び（２）式による必要延長時間（ｔ）の長い方の必要延長時間（ｔ）よりも短い時間だけ環流した操業についても、同様の調査を行った。更に、冷材を添加しない操業についても、同様の調査を行った。表１に、各試験操業における試験条件及び試験結果を示す。 Further, as a comparative example, the same applies to an operation in which after the cooling material is added, the operation is refluxed for a shorter time than the required extension time (t) of the longer required extension time (t) according to the formulas (1) and (2). We conducted a survey. In addition, the same investigation was conducted for the operation in which no cooling material was added. Table 1 shows test conditions and test results in each test operation.
表１に示すように、本発明例１〜６では厚板製品における欠陥指数が、冷材を添加している比較例１〜５に比べて低減し、冷材を添加していない比較例６，７と同等レベルであり、冷材添加に伴って発生する介在物が本発明により大幅に低減することが確認できた。尚、表１における欠陥指数は、本発明例に使用した同じ鋼種において過去１年間で介在物起因による欠陥が最も多かったロットの欠陥発生率を１として、本発明例のロットの欠陥発生率との比より決定したものである。 As shown in Table 1, in Invention Examples 1 to 6, the defect index in the plate product is reduced as compared with Comparative Examples 1 to 5 in which the cold material is added, and Comparative Example 6 in which the cold material is not added. , 7 and the inclusions generated with the addition of the cooling material were confirmed to be greatly reduced by the present invention. The defect index in Table 1 is defined as the defect occurrence rate of the lot of the present invention example, where the defect occurrence rate of the lot with the most defects due to inclusions in the same steel type used in the present invention example in the past year is 1. It is determined from the ratio.
Claims (1)
t=0.9×Wc×(Oc-Om)/(k×Wm×Om ) …(1)
t=Wm/Q …(2)
但し、（１）式及び（２）式において、ｔは、必要延長時間（分）、ｋは、ＲＨ真空脱ガス装置の脱酸速度定数（１／分）、Ｗc は、冷材の添加量（トン）、Ｗm は、溶鋼処理量（トン）、Ｏc は、冷材の酸素濃度（ｐｐｍ）、Ｏm は、冷材添加時の溶鋼中酸素濃度（ｐｐｍ）、Ｑは、溶鋼環流量（トン／分）である。 When adjusting the molten steel temperature by adding a temperature adjusting cold material to the molten steel being processed by the RH vacuum degassing apparatus, after adding the cold material to the molten steel, the following equations (1) and (2) A method for melting high cleanliness steel, characterized in that the molten steel is circulated over the longer required extension time of the required extension time calculated by the above.
t = 0.9 × Wc × (Oc-Om) / (k × Wm × Om)… (1)
t = Wm / Q… (2)
However, in the formulas (1) and (2), t is the required extension time (min), k is the deoxidation rate constant (1 / min) of the RH vacuum degasser, and Wc is the amount of cold material added. (Tons), Wm is the molten steel throughput (tons), Oc is the oxygen concentration (ppm) of the cold material, Om is the oxygen concentration (ppm) in the molten steel when the cold material is added, and Q is the flow rate of the molten steel (tons) / Min).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2006295522A JP5239147B2 (en) | 2006-10-31 | 2006-10-31 | Method of melting high cleanliness steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2006295522A JP5239147B2 (en) | 2006-10-31 | 2006-10-31 | Method of melting high cleanliness steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2008111164A true JP2008111164A (en) | 2008-05-15 |
| JP5239147B2 JP5239147B2 (en) | 2013-07-17 |
Family
ID=39443842
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2006295522A Active JP5239147B2 (en) | 2006-10-31 | 2006-10-31 | Method of melting high cleanliness steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP5239147B2 (en) |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4819045B1 (en) * | 1969-05-21 | 1973-06-11 | ||
| JPS5773118A (en) * | 1980-10-25 | 1982-05-07 | Nippon Steel Corp | Production of clean steel |
| JPH0741829A (en) * | 1993-07-21 | 1995-02-10 | Nippon Steel Corp | Method for detoxicating oxide in high carbon chromium bearing steel |
| JPH09157728A (en) * | 1995-12-04 | 1997-06-17 | Nkk Corp | Method for smelting clean steel |
| JP2001262218A (en) * | 2000-03-21 | 2001-09-26 | Kawasaki Steel Corp | Method for producing high cleanliness steel |
| JP2003183722A (en) * | 2001-12-11 | 2003-07-03 | Jfe Steel Kk | Method for smelting high cleanliness steel |
-
2006
- 2006-10-31 JP JP2006295522A patent/JP5239147B2/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4819045B1 (en) * | 1969-05-21 | 1973-06-11 | ||
| JPS5773118A (en) * | 1980-10-25 | 1982-05-07 | Nippon Steel Corp | Production of clean steel |
| JPH0741829A (en) * | 1993-07-21 | 1995-02-10 | Nippon Steel Corp | Method for detoxicating oxide in high carbon chromium bearing steel |
| JPH09157728A (en) * | 1995-12-04 | 1997-06-17 | Nkk Corp | Method for smelting clean steel |
| JP2001262218A (en) * | 2000-03-21 | 2001-09-26 | Kawasaki Steel Corp | Method for producing high cleanliness steel |
| JP2003183722A (en) * | 2001-12-11 | 2003-07-03 | Jfe Steel Kk | Method for smelting high cleanliness steel |
Also Published As
| Publication number | Publication date |
|---|---|
| JP5239147B2 (en) | 2013-07-17 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP2008240126A (en) | Method for refining molten stainless steel | |
| JP2007319872A (en) | Method for producing high-s free cutting steel wire rod | |
| JP5904237B2 (en) | Melting method of high nitrogen steel | |
| JP7167646B2 (en) | Method of adding alloy to molten steel | |
| JP2020032442A (en) | Method for casting molten steel | |
| JP2018131651A (en) | Method for melting high-nitrogen low-oxygen steel | |
| TWI593803B (en) | Melting method of high cleanness steel | |
| JP3893770B2 (en) | Melting method of high clean ultra low carbon steel | |
| JP5239147B2 (en) | Method of melting high cleanliness steel | |
| JP2007169717A (en) | Method for judging decarburize-end point in vacuum degassing facility | |
| JP4722772B2 (en) | Manufacturing method of high cleanliness steel | |
| JP5590056B2 (en) | Manufacturing method of highly clean steel | |
| EP4066961A1 (en) | Method for casting molten steel, method for producing continuous cast slab, and method for producing steel for bearing | |
| JP2010116610A (en) | Method for manufacturing low-sulfur thick steel plate excellent in haz toughness at the time of inputting large amount of heat | |
| EP3940088B1 (en) | Method for producing ti-containing ultralow-carbon steel | |
| JP2018127680A (en) | Method for smelting clean steel | |
| JP5326201B2 (en) | Method for melting aluminum killed steel | |
| JP4882249B2 (en) | Manufacturing method of high clean steel | |
| JP4811018B2 (en) | Deoxidation method for molten steel | |
| JP3674422B2 (en) | Melting method of high cleanliness low carbon steel | |
| JP5387045B2 (en) | Manufacturing method of bearing steel | |
| JP2006233254A (en) | Method for producing high cleanliness steel | |
| TWI805460B (en) | Method for deoxidizing and refining molten steel, method for manufacturing steel and the steel | |
| JP7248153B2 (en) | Method for manufacturing slab | |
| JP2019014944A (en) | Steel refining method |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20090727 |
|
| A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20100519 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20111005 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20111018 |
|
| A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20111215 |
|
| RD03 | Notification of appointment of power of attorney |
Free format text: JAPANESE INTERMEDIATE CODE: A7423 Effective date: 20120321 |
|
| RD04 | Notification of resignation of power of attorney |
Free format text: JAPANESE INTERMEDIATE CODE: A7424 Effective date: 20120327 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20120710 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20130305 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20130318 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20160412 Year of fee payment: 3 |
|
| R150 | Certificate of patent or registration of utility model |
Free format text: JAPANESE INTERMEDIATE CODE: R150 Ref document number: 5239147 Country of ref document: JP Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |