JPH0717937B2 - Manufacturing method of high cleanliness ultra low carbon steel - Google Patents
Manufacturing method of high cleanliness ultra low carbon steelInfo
- Publication number
- JPH0717937B2 JPH0717937B2 JP1098836A JP9883689A JPH0717937B2 JP H0717937 B2 JPH0717937 B2 JP H0717937B2 JP 1098836 A JP1098836 A JP 1098836A JP 9883689 A JP9883689 A JP 9883689A JP H0717937 B2 JPH0717937 B2 JP H0717937B2
- Authority
- JP
- Japan
- Prior art keywords
- vacuum
- slag
- molten steel
- concentration
- treatment
- 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.)
- Expired - Fee Related
Links
- 229910001209 Low-carbon steel Inorganic materials 0.000 title claims description 10
- 238000004519 manufacturing process Methods 0.000 title claims description 7
- 230000003749 cleanliness Effects 0.000 title description 4
- 229910000831 Steel Inorganic materials 0.000 claims description 38
- 239000010959 steel Substances 0.000 claims description 38
- 239000002893 slag Substances 0.000 claims description 31
- 238000005261 decarburization Methods 0.000 claims description 23
- 238000011282 treatment Methods 0.000 claims description 22
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 21
- 229910052782 aluminium Inorganic materials 0.000 claims description 21
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 19
- 229910052799 carbon Inorganic materials 0.000 claims description 19
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims description 16
- 229910001882 dioxygen Inorganic materials 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 13
- 238000010079 rubber tapping Methods 0.000 claims description 10
- 238000009849 vacuum degassing Methods 0.000 claims description 6
- 238000005507 spraying Methods 0.000 claims description 5
- 238000009489 vacuum treatment Methods 0.000 claims description 4
- 238000002844 melting Methods 0.000 claims 1
- 230000008018 melting Effects 0.000 claims 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 13
- 229910052760 oxygen Inorganic materials 0.000 description 13
- 239000001301 oxygen Substances 0.000 description 13
- 238000009749 continuous casting Methods 0.000 description 7
- 239000010960 cold rolled steel Substances 0.000 description 6
- 239000007789 gas Substances 0.000 description 6
- 230000007423 decrease Effects 0.000 description 5
- 230000007547 defect Effects 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 238000007664 blowing Methods 0.000 description 4
- 238000005266 casting Methods 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- 239000007921 spray Substances 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 2
- 230000002950 deficient Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 239000000523 sample Substances 0.000 description 2
- 238000009628 steelmaking Methods 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000005262 decarbonization Methods 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 239000010955 niobium Substances 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000010405 reoxidation reaction Methods 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
Landscapes
- Treatment Of Steel In Its Molten State (AREA)
Description
【発明の詳細な説明】 〈産業上の利用分野〉 本発明は、清浄性に優れた極低炭素鋼を製造する方法に
関するものである。DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing an extremely low carbon steel having excellent cleanability.
〈従来の技術〉 極低炭素鋼スラブは、転炉を用いて経済的に脱炭し得る
限界まで転炉内で脱炭し、その後真空脱ガス装置を用い
て減圧下で目的の濃度まで脱炭し、その後脱酸材を添加
して脱酸処理を行い、連続鋳造機などの鋳造工程を経て
スラブを製造する。<Prior art> Ultra-low carbon steel slabs are decarburized in a converter to the limit where they can be economically decarburized, and then degassed to a desired concentration under reduced pressure using a vacuum degassing device. It is carbonized and then deoxidized by adding a deoxidizer, and a slab is manufactured through a casting process such as a continuous casting machine.
これらの工程において、転炉での経済的な脱炭限界は炉
の型式のもよるが0.02〜0.06重量％（以下％と略す）が
一般的である。このような低炭素まで脱炭処理を行う
と、転炉内では炭素と共に多量の鉄が酸化されてスラグ
中のFeO濃度が増大する。In these steps, the economical decarburization limit in the converter depends on the type of furnace, but is generally 0.02 to 0.06% by weight (hereinafter abbreviated as%). When decarburizing treatment is performed to such low carbon, a large amount of iron is oxidized together with carbon in the converter, and the FeO concentration in the slag increases.
このスラグは、転炉からの出鋼流と共に取鍋に流入する
ために、真空脱ガス装置での真空脱炭処理終了後にアル
ミニウムによる脱酸処理を行っても、スラグ中のFeOが
分解して溶鋼に酸素を供給するために溶鋼中の酸素が十
分に低下しないといった問題がある。また、例え真空脱
ガス装置での脱酸処理終了時には溶鋼中の酸素が低下し
たとしても、その後の鋳造工程までの時間で、あるい
は、鋳造中にスラグから溶鋼に酸素が供給され、溶鋼の
清浄度がそこなわれ、これらの溶鋼から連続鋳造と圧延
工程を経て製造される冷延鋼板には表面欠陥が発生し易
いといった問題があった。Since this slag flows into the ladle together with the steel flow from the converter, FeO in the slag will decompose even if deoxidation treatment with aluminum is performed after the completion of the vacuum decarburization treatment in the vacuum degassing device. Since oxygen is supplied to the molten steel, there is a problem that the oxygen in the molten steel does not sufficiently decrease. In addition, even if the oxygen in the molten steel decreases at the end of the deoxidation treatment with the vacuum degassing device, oxygen is supplied to the molten steel from the slag during the time until the subsequent casting process or during casting, and the cleaning of the molten steel is performed. The cold rolled steel sheet produced from these molten steels through continuous casting and rolling processes has a problem that surface defects are likely to occur.
このために、スラグ中のFeOを低下するために、転炉か
らの出鋼時に取鍋にアルミニウムなどを添加して、取鍋
浴面上のスラグ中のFeO濃度を低下させることも考えら
れるが、この方法では以下の問題があった。Therefore, in order to reduce FeO in the slag, it is possible to add aluminum or the like to the ladle at the time of tapping from the converter to reduce the FeO concentration in the slag on the ladle bath surface. , This method had the following problems.
すなわち、真空脱炭処理においては、炭素は溶鋼中の酸
素と反応してＣ＋Ｏ→COとなる反応で脱炭され、真空脱
炭中には溶鋼中の酸素濃度が欠乏すると脱炭速度が低下
する。そのため、溶鋼中の酸素濃度を上昇させるための
酸素の供給源であるスラグ中のFeOは、高くしておくこ
とが必要であると考えられており、炭素濃度が50ppm以
下といった極低炭素鋼の製造については、スラグ中のFe
Oを低下させる試みは全くなされていなかった。That is, in the vacuum decarburization treatment, carbon is decarburized by the reaction of oxygen in molten steel to change to C + O → CO, and the decarburization rate decreases when the oxygen concentration in molten steel is deficient during vacuum decarburization. . Therefore, FeO in the slag, which is the source of oxygen for increasing the oxygen concentration in the molten steel, is considered to be required to be high, and the carbon concentration of ultra-low carbon steel such as 50 ppm or less. For manufacturing, Fe in slag
No attempt was made to reduce O.
〈課題を解決するための手段〉 本発明者らは、この点に着目し、極低炭素鋼製造のため
の真空脱炭処理中の脱炭速度とスラグ中のFeO濃度との
関係がについて調査し、スラグ中のFeO濃度が低くとも
十分な脱炭速度の得られる条件を見出し、この知見にも
どづいて本発明をなすに至った。<Means for Solving the Problem> The present inventors have focused on this point and investigated the relationship between the decarburization rate during vacuum decarburization treatment and the FeO concentration in slag for the production of ultra-low carbon steel. However, the inventors have found conditions under which a sufficient decarburization rate can be obtained even when the FeO concentration in the slag is low, and based on this finding, the present invention has been completed.
本発明は、炭素濃度が、0.003重量％以下の極低炭素鋼
を溶製するにあたり、転炉から出鋼する溶鋼の炭素濃度
を0.02〜0.06重量％とし、出鋼時あるいは出鋼後に取鍋
のスラグ中にアルミニウムを添加して該スラグ中のFeO
濃度を0.2〜2.0重量％とし、その後、真空脱ガス装置で
真空脱炭処理をするに際して、該真空処理開始時の脱炭
初期に酸素ガスを溶鋼1t当たり0.14〜1.4Nm3吹き付けつ
つ炭素濃度が100から200ppmとなるように真空脱炭し、
所定量の酸素ガスの供給が終了した時点でさらに真空脱
炭処理を続け、炭素濃度が0.003重量％以下となった時
期にアルミニウムを添加して真空処理を５分間以上継続
し、この溶鋼を鋳造することを特徴とする高清浄度極低
炭素鋼の製造方法である。The present invention has a carbon concentration of 0.02 to 0.06% by weight in molten steel to be tapped from a converter in producing ultra-low carbon steel having a carbon concentration of 0.003% by weight or less, and a ladle during or after tapping. FeO in the slag by adding aluminum to the slag
The concentration is 0.2 to 2.0% by weight, and then, when performing vacuum decarburizing treatment with a vacuum degassing apparatus, the carbon concentration is 0.14 to 1.4 Nm 3 per 1 ton of molten steel while blowing oxygen gas at the initial decarburizing at the start of the vacuum treatment. Vacuum decarburize to 100 to 200ppm,
When the supply of a predetermined amount of oxygen gas is completed, vacuum decarburization is further continued, aluminum is added when the carbon concentration becomes 0.003% by weight or less, and vacuum treatment is continued for 5 minutes or longer to cast this molten steel. It is a method for producing a high-cleanliness ultra-low carbon steel.
〈作用〉 以下に本発明の構成および作用について説明する。<Operation> The configuration and operation of the present invention will be described below.
転炉にて炭素濃度を0.02〜0.06％まで脱炭した溶鋼を取
鍋に出鋼した時に、不可避的に取鍋に転炉スラグが流入
するが、このスラグ中のFeO濃度を低下するためにアル
ミニウムを添加する。アルミニウムの添加は出鋼中に行
ってもよく、また出鋼後、浴をガス攪拌などの方法で攪
拌しながら行ってもよい。アルミニウムの添加量はスラ
グの流出量やスラグ中のFeO濃度によっても異なるが、
スラグ中のFeO濃度を２％以下とするように添加する必
要があり、溶鋼1t当たり１〜3kg程度である。また、ア
ルミニウムはできるだけスラグ中に溶解するように添加
する必要がある。また過度にアルミニウムを添加し、Fe
O濃度が0.2％以下となると溶鋼中にも多量のアルミニウ
ムが含有され、これを酸化除去しないと脱炭反応が生じ
ないために、後工程での真空脱炭処理工程が長びき生産
能率が低下する。When molten steel decarburized to a carbon concentration of 0.02 to 0.06% in a converter is tapped into a ladle, converter slag inevitably flows into the ladle, but to reduce the FeO concentration in this slag. Add aluminum. Aluminum may be added during tapping, or after tapping, the bath may be stirred with a method such as gas stirring. The amount of aluminum added varies depending on the outflow amount of slag and the FeO concentration in the slag,
It is necessary to add it so that the FeO concentration in the slag is 2% or less, and it is about 1 to 3 kg per ton of molten steel. Also, aluminum must be added so that it is dissolved in the slag as much as possible. Also, excessively adding aluminum, Fe
When the O concentration is 0.2% or less, a large amount of aluminum is also contained in the molten steel, and if this is not removed by oxidation, the decarburization reaction does not occur, so the vacuum decarburization process in the post process becomes long and the production efficiency decreases. To do.
この取鍋中の溶鋼を循環式真空脱ガス装置（以下、RHと
略す）で真空脱炭する。RH処理に際しては、真空槽内に
酸素ガスを供給しつつ真空脱炭を開始する。この際の酸
素ガスの供給は、溶鋼浴面上に酸素ガスを吹き付けても
よいし、浴中に浸漬させた羽口から吹き込んでもよい
が、浴中から発生するCOガスの一部をCO2まで燃焼させ
て、その際に発生する反応熱で処理中の溶鋼の温度降下
を防止したり、積極的に溶鋼を加熱する点からは浴表面
に吹き付ける方が好都合である。The molten steel in the ladle is vacuum decarburized by a circulation type vacuum degassing device (hereinafter abbreviated as RH). At the time of RH treatment, vacuum decarburization is started while supplying oxygen gas into the vacuum chamber. The supply of oxygen gas at this time may be carried out by blowing oxygen gas onto the surface of the molten steel, or by blowing it from the tuyere immersed in the bath, but a part of the CO gas generated from the bath is CO 2 It is more convenient to burn the molten steel to the surface of the bath in order to prevent the temperature drop of the molten steel during the treatment by the reaction heat generated at that time and to positively heat the molten steel.
酸素ガスの供給量は、スラグ中のFeO濃度に因るが、ほ
ぼ0.14〜1.4Nm3/t/steelが適値である。この値よりも多
い場合には、脱炭速度の増大効果は期待できないのみな
らず、ガス吹込みによって真空度が低下して脱炭速度が
低下し、またこの値よりも少ない場合には、脱炭反応
（Ｃ＋Ｏ→CO）のための酸素ガスが欠乏して脱炭速度が
低下する。The supply amount of oxygen gas depends on the FeO concentration in the slag, but a suitable value is approximately 0.14 to 1.4 Nm 3 / t / steel. If it is more than this value, not only the effect of increasing the decarburization rate cannot be expected, but also the degree of vacuum is lowered by the gas injection and the decarburization rate is lowered. Oxygen gas for the carbon reaction (C + O → CO) is deficient and the decarburization rate decreases.
以上のようにして、酸素ガスを供給しながら真空脱炭処
理を行い、所定量の酸素ガスの供給が終了した時点では
浴中の炭素濃度は100〜200ppmとなるが、さらに炭素濃
度が30ppm以下の所定の濃度まで真空脱炭を続ける。そ
の後、アルミニウムを添加して溶鋼の脱酸処理を継続す
る。この際に、必要とあればチタンやニオブなどの合金
元素も添加する。溶鋼を十分に脱硫して清浄化するため
には10分間以上の脱酸処理が望ましい。As described above, performing vacuum decarburization while supplying oxygen gas, the carbon concentration in the bath becomes 100 to 200 ppm at the time when the supply of a predetermined amount of oxygen gas is completed, but the carbon concentration is 30 ppm or less. Vacuum decarburization is continued until the prescribed concentration of. Then, aluminum is added to continue the deoxidizing treatment of the molten steel. At this time, alloy elements such as titanium and niobium are also added if necessary. In order to sufficiently desulfurize and clean molten steel, deoxidation treatment for 10 minutes or longer is desirable.
これらの処理に引き続いて、取鍋を連続鋳造工程に移し
鋳造するが、これらの工程は従来法と同一であるのでこ
こでは説明を省略する。ただし、本発明方法によれば、
スラグ中のFeO濃度が２％以下となっているので、PH処
理終了から連続鋳造工程間でのスラグ中のFeOによる溶
鋼の再酸化が少ない。Subsequent to these treatments, the ladle is transferred to a continuous casting process for casting, but since these processes are the same as the conventional method, the description thereof is omitted here. However, according to the method of the present invention,
Since the FeO concentration in the slag is 2% or less, the reoxidation of molten steel due to FeO in the slag from the end of the PH treatment to the continuous casting process is small.
また連続鋳造工程では、２チャージ以上の溶鋼を連続し
て注入すると、取鍋内スラグがタンディッシュ内に不可
避的に流入して、タンディッシュ内でもこれらスラグに
よって溶鋼が再酸化を受け清浄性が低下する。しかし、
本発明の場合にはこのような現像も防止でき、清浄度に
優れた極低炭素の連続鋳造スラブが製造でき、これらの
スラブを圧延して得られる冷延鋼板の品質も優れたもの
となる。Further, in the continuous casting process, when molten steel of 2 charges or more is continuously injected, the slag in the ladle inevitably flows into the tundish, and the molten steel is reoxidized by these slags in the tundish to improve the cleanliness. descend. But,
In the case of the present invention, such development can also be prevented, an extremely low carbon continuous cast slab with excellent cleanliness can be produced, and the quality of the cold rolled steel sheet obtained by rolling these slabs will also be excellent. .
〈実施例〉 180tonの溶鋼23チャージを本発明方法で処理した実施例
について説明する。<Example> An example in which a 180 ton molten steel 23 charge is treated by the method of the present invention will be described.
180tonの上底吹き転炉で精錬した炭素濃度が0.04〜0.06
％約220tonの溶鋼を取鍋に出鋼した。この時の転炉内の
スラグ中のFeO濃度は16〜24％であった。出鋼時には転
炉内のスラグはできるだけ取鍋に流出しないようにし、
出鋼中に0.8〜1.5kg/t・steelのアルミニウムを添加し
た。Carbon concentration smelted in 180 ton top-bottom blow converter has a concentration of 0.04 to 0.06
% About 220 tons of molten steel was tapped in a ladle. The FeO concentration in the slag in the converter at this time was 16 to 24%. When tapping, try to prevent slag in the converter from flowing into the ladle,
During tapping, 0.8 to 1.5 kg / t · steel of aluminum was added.
出鋼完了後、取鍋底部に設置した多孔質耐火物を通じて
Arガスを200〜400l/min吹き込み、浴のガス攪拌を５分
間実施した。攪拌中にもスラグのFeO濃度を推定しつつ
必要に応じてアルミニウムを0.1〜0.6kg/t・steel添加
した。攪拌終了時のスラグ中のFeO濃度は0.4〜1.8％の
範囲であった。After tapping, through the porous refractory installed at the bottom of the ladle
Ar gas was blown at 200 to 400 l / min, and gas stirring in the bath was performed for 5 minutes. While estimating the FeO concentration in the slag, aluminum was added in an amount of 0.1 to 0.6 kg / t · steel as needed while stirring. The FeO concentration in the slag at the end of stirring was in the range of 0.4 to 1.8%.
その後、取鍋をRH処理場に搬送し、RH処理を開始した。
処理開始と同時に、真空槽内の浴面上にランスを用いて
酸素ガスを30Nm3/minの速度で吹き付けた。処理開始と
同時に１〜３分間隔で取鍋内の溶鋼中の酸素濃度を酸素
プローブで測定し、炭素濃度の1.5倍以上の濃度が保持
できるように、酸素濃度が欠乏する時にはさらに酸素ガ
スの吹付を継続し、十分な酸素濃度が保持できる時には
酸素ガスの吹付けを停止するといった操作を行い、必要
最小限の酸素ガスを吹き付けた。After that, the ladle was transported to the RH treatment site and the RH treatment was started.
Simultaneously with the start of the treatment, oxygen gas was blown onto the bath surface in the vacuum chamber at a rate of 30 Nm 3 / min using a lance. The oxygen concentration in the molten steel in the ladle is measured with an oxygen probe at intervals of 1 to 3 minutes at the same time as the treatment is started. The spraying was continued, and when a sufficient oxygen concentration could be maintained, the spraying of oxygen gas was stopped to spray the minimum required oxygen gas.
その後、酸素ガス吹付けを停止してそのまま真空脱炭処
理を続けた。酸度ガスの吹付けは継続的な場合もあった
が、吹付け量の合計は溶鋼1t当たり0.14〜1.4Nm3であ
り、最大で10分間吹き付けた。その後６〜10分間、酸素
ガスを吹き付けずに真空脱炭素処理を継続し、炭素濃度
が25ppm以下となる時点で脱酸用のアルミニウムを添加
した。アルミニウムの添加量は酸素プローブで測定した
酸素濃度に応じて添加したが、その量は目標とする製品
のアルミニウム濃度によって異なるが0.03〜0.08％の範
囲で0.8〜2.1kg/t・steelであった。アルミニウム添加
後６〜12分間のRH処理を継続して溶鋼を十分に脱酸す
る。Then, the oxygen gas spraying was stopped and the vacuum decarburization treatment was continued as it was. The spray of acidity gas was continuous in some cases, but the total spray amount was 0.14 to 1.4 Nm 3 / t of molten steel, and spraying was performed for a maximum of 10 minutes. Thereafter, the vacuum decarbonization treatment was continued for 6 to 10 minutes without blowing oxygen gas, and aluminum for deoxidation was added when the carbon concentration reached 25 ppm or less. The amount of aluminum added was according to the oxygen concentration measured by an oxygen probe, and the amount varied depending on the aluminum concentration of the target product, but was 0.8-2.1 kg / t ・ steel in the range of 0.03-0.08%. . After adding aluminum, the RH treatment is continued for 6 to 12 minutes to sufficiently deoxidize the molten steel.
その後取鍋を連続鋳造工程に移し、通常の連続鋳造を実
施した。After that, the ladle was transferred to the continuous casting process, and ordinary continuous casting was performed.
以上の実施例で得られたスラグを熱間圧延と冷間圧延と
を行い、0.8mm厚さの冷延鋼板を得た。これらの冷延鋼
板の12〜23t重量のコイル当たりで製鋼条件に起因する
表面欠陥の発生率を調べた。また、比較例として、転炉
出鋼時にアルミニウム添加をしない場合、およびアルミ
ニウムを添加したが添加量が少なくスラグ中のFeO濃度
が２％以下にしなかった場合の８チャージの例について
前述の実施例と同様にして製造した冷延鋼板の製鋼条件
に起因する欠陥発生率についても調査した。これらの結
果を第１表に示す。The slag obtained in the above examples was subjected to hot rolling and cold rolling to obtain a cold rolled steel sheet having a thickness of 0.8 mm. The occurrence rate of surface defects due to steelmaking conditions was investigated for each coil of these cold-rolled steel sheets having a weight of 12 to 23 tons. In addition, as a comparative example, an example of 8 charges when aluminum was not added at the time of tapping the converter and when aluminum was added but the FeO concentration in the slag was not set to 2% or less was described. The defect occurrence rate due to the steelmaking conditions of the cold-rolled steel sheet manufactured in the same manner as above was also investigated. The results are shown in Table 1.
本発明の表面欠陥発生率は、平均で0.078％であり、比
較例の0.23％と比べて約1/3と著しく減少した。また表
面欠陥発生率のバラツキも減少して、安定して優れた製
品を得られることが明らかである。 The surface defect occurrence rate of the present invention was 0.078% on average, which was significantly reduced to about 1/3 of 0.23% of the comparative example. Further, it is clear that the variation of the surface defect occurrence rate is reduced and a stable and excellent product can be obtained.
〈発明の効果〉 本発明方法によれば、前述のように清浄性に優れ、品質
に優れた極低炭素鋼系の冷延鋼板を真空脱炭処理の能率
の低下なしに製造することができる。<Effects of the Invention> According to the method of the present invention, as described above, it is possible to produce an extremely low carbon steel cold-rolled steel sheet having excellent cleanliness and excellent quality without lowering the efficiency of vacuum decarburization treatment. .
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 昭60−152611（ＪＰ，Ａ) 特開 昭62−240712（ＪＰ，Ａ) 特公 昭62−39205（ＪＰ，Ｂ２) ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-60-152611 (JP, A) JP-A-62-240712 (JP, A) JP-B-62-39205 (JP, B2)
Claims (1)
を溶製するにあたり、転炉から出鋼する溶鋼の炭素濃度
を0.02〜0.06重量％とし、出鋼時あるいは出鋼後に取鍋
のスラグ中にアルミニウムを添加して該スラグ中のFeO
濃度を0.2〜2.0重量％とし、その後、真空脱ガス装置で
真空脱炭処理をするに際して、 該真空処理開始時の脱炭初期に酸素ガスを溶鋼1t当たり
0.14〜1.4Nm3吹き付けつつ炭素濃度が100から200ppmと
なるように真空脱炭し、所定量の酸素ガスの供給が終了
した時点でさらに真空脱炭処理を続け、炭素濃度が0.00
3重量％以下となった時期にアルミニウムを添加して真
空処理を５分間以上継続し、この溶鋼を鋳造することを
特徴とする高清浄度極低炭素鋼の製造方法。1. When melting ultra-low carbon steel having a carbon concentration of 0.003% by weight or less, the molten steel discharged from the converter has a carbon concentration of 0.02 to 0.06% by weight, and a ladle at the time of tapping or after tapping. FeO in the slag by adding aluminum to the slag
When the concentration is set to 0.2 to 2.0% by weight and then vacuum decarburization treatment is performed by the vacuum degassing device, oxygen gas is added per 1 ton of molten steel at the initial decarburization at the start of the vacuum treatment.
Vacuum decarburization so that the carbon concentration becomes 100 to 200 ppm while spraying 0.14 to 1.4 Nm 3, and when the supply of a predetermined amount of oxygen gas is completed, the vacuum decarburization process is further continued until the carbon concentration is 0.00
A method for producing a high-cleanliness ultra-low carbon steel, which comprises adding aluminum at a time when the amount of water becomes 3% by weight or less and continuing vacuum treatment for 5 minutes or more to cast the molten steel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1098836A JPH0717937B2 (en) | 1989-04-20 | 1989-04-20 | Manufacturing method of high cleanliness ultra low carbon steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1098836A JPH0717937B2 (en) | 1989-04-20 | 1989-04-20 | Manufacturing method of high cleanliness ultra low carbon steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH02277711A JPH02277711A (en) | 1990-11-14 |
| JPH0717937B2 true JPH0717937B2 (en) | 1995-03-01 |
Family
ID=14230356
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1098836A Expired - Fee Related JPH0717937B2 (en) | 1989-04-20 | 1989-04-20 | Manufacturing method of high cleanliness ultra low carbon steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0717937B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100419656B1 (en) * | 1999-12-06 | 2004-02-25 | 주식회사 포스코 | Method for refining extra low carbon steel by double deoxidizing slag |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60152611A (en) * | 1984-01-18 | 1985-08-10 | Nippon Steel Corp | Method for modifying slag |
| US4631091A (en) * | 1985-08-13 | 1986-12-23 | English China Clays Lovering Pochin & Co. Ltd. | Method for improving the dispersibility of organoclays |
| JPH0619102B2 (en) * | 1986-04-11 | 1994-03-16 | 新日本製鐵株式会社 | Ultra low carbon steel melting method |
| JPS63190113A (en) * | 1986-09-25 | 1988-08-05 | Nippon Steel Corp | Production of dead low carbon steel |
-
1989
- 1989-04-20 JP JP1098836A patent/JPH0717937B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH02277711A (en) | 1990-11-14 |
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