JP2013144843A - Method for adjusting components in molten steel - Google Patents
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 142
- 239000010959 steel Substances 0.000 title claims abstract description 142
- 238000000034 method Methods 0.000 title claims abstract description 44
- 239000000956 alloy Substances 0.000 claims abstract description 13
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 13
- 229910052751 metal Inorganic materials 0.000 claims abstract description 11
- 239000002184 metal Substances 0.000 claims abstract description 11
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 116
- 229910052742 iron Inorganic materials 0.000 claims description 46
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 44
- 229910052760 oxygen Inorganic materials 0.000 claims description 17
- 229910052782 aluminium Inorganic materials 0.000 claims description 14
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 14
- 238000004090 dissolution Methods 0.000 claims description 13
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 10
- 239000001301 oxygen Substances 0.000 claims description 10
- 239000000203 mixture Substances 0.000 claims description 9
- 238000004364 calculation method Methods 0.000 claims description 8
- 230000014509 gene expression Effects 0.000 claims description 8
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- 238000004458 analytical method Methods 0.000 description 27
- 238000012360 testing method Methods 0.000 description 8
- 238000007670 refining Methods 0.000 description 7
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 5
- 238000011088 calibration curve Methods 0.000 description 5
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- 239000000155 melt Substances 0.000 description 5
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- 238000005336 cracking Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 229910004709 CaSi Inorganic materials 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
- 238000009838 combustion analysis Methods 0.000 description 3
- 238000009841 combustion method Methods 0.000 description 3
- 238000009749 continuous casting Methods 0.000 description 3
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- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 230000001174 ascending effect Effects 0.000 description 2
- 238000001636 atomic emission spectroscopy Methods 0.000 description 2
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- 238000009864 tensile test Methods 0.000 description 2
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- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
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- 150000002739 metals Chemical class 0.000 description 1
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- 239000002436 steel type Substances 0.000 description 1
- 239000013077 target material Substances 0.000 description 1
- 238000009849 vacuum degassing Methods 0.000 description 1
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Abstract
Description
本発明は容器内に収容された溶鋼へCaまたはMgを添加して溶鋼の成分を調整する溶鋼の成分調整方法に関する。 The present invention relates to a molten steel component adjusting method for adjusting molten metal components by adding Ca or Mg to molten steel contained in a container.
例えば、ラインパイプや電縫鋼管(ERW鋼管)に使用する鋼のような、脱硫や鋼中の介在物の組成制御が必要な鋼には、CaやMgのような溶鋼温度では蒸発してしまうような金属又はこれらの合金(以下、「Ca等」という)を溶鋼に精錬剤として使用している。
Ca等の溶鋼へ添加方法として、他の合金で行われるように取鍋精錬炉等を用いて溶鋼湯面上に添加する方法では、Ca等が溶鋼と反応する前に蒸発してしまう。そのため、Ca等の溶鋼への添加方法としては、Ca等をワイヤとして添加する方法が用いられている。
For example, steels that require desulfurization and composition control of inclusions in steel, such as steel used in line pipes and ERW steel pipes, will evaporate at molten steel temperatures such as Ca and Mg. Such metals or their alloys (hereinafter referred to as “Ca etc.”) are used as refining agents in molten steel.
As a method of addition to molten steel such as Ca, when adding to the molten steel surface using a ladle smelting furnace or the like as in other alloys, Ca or the like evaporates before reacting with the molten steel. Therefore, as a method for adding Ca or the like to molten steel, a method of adding Ca or the like as a wire is used.
このようなCa等の溶鋼への添加方法としては、例えば、特許文献1ではCaを30kg/分以上で添加する方法が開示されている。
また、他の方法として、特許文献2では取鍋精錬においてCaSiワイヤを80〜100m/minで投入する方法が開示されている。
As such a method for adding Ca or the like to molten steel, for example, Patent Document 1 discloses a method of adding Ca at 30 kg / min or more.
As another method, Patent Document 2 discloses a method in which a CaSi wire is thrown at 80 to 100 m / min in ladle refining.
溶鋼へCaを添加するためのワイヤは、鉄シース内に合金を充填したものが一般的である。そのため、Ca等と溶鋼が反応するためには、まず、鉄シースが溶解しなければならない。
しかし、鉄シースが溶鋼への投入直後に溶解してしまったり、投入速度が大きすぎて、鉄シース溶解前に鉄シースが取鍋底まで到達し、さらに上方へ戻ってくる途中で溶解するような場合、鉄シースが溶解してCa等が気化しても溶鋼とCa等との反応時間が短く、Ca等の歩留まりが悪化してしまうとともに、Ca等が溶鋼の界面で空気と反応して、Ca等の酸化物が生成し、有効に作用しない。
A wire for adding Ca to molten steel is generally an iron sheath filled with an alloy. Therefore, in order for Ca etc. and molten steel to react, an iron sheath must first melt | dissolve.
However, the iron sheath melts immediately after charging into the molten steel, or the charging speed is too high so that the iron sheath reaches the bottom of the ladle before melting the iron sheath and melts while returning further upward. If the iron sheath is dissolved and Ca etc. is vaporized, the reaction time between the molten steel and Ca etc. is short, the yield of Ca etc. deteriorates, and Ca etc. reacts with air at the interface of the molten steel, Ca and other oxides are formed and do not work effectively.
鉄シースの溶解速度は、シースの厚み、溶鋼温度、投入速度で変化すると考えられる。
しかしながら、特許文献1に記載の方法では、Ca純分のみでの添加速度の規定であり、ワイヤのシースの溶解速度までは考慮されていない。
また、特許文献2に記載の方法では、ワイヤ投入速度を規定しているが、前述したシースの厚み、溶鋼温度、投入速度といった投入時の条件が考慮されてない。
このため、特許文献1,2の方法では、Ca等を歩留まりよく効果的に溶鋼に添加することが難しい。
It is considered that the melting rate of the iron sheath varies depending on the thickness of the sheath, the molten steel temperature, and the charging rate.
However, in the method described in Patent Document 1, the addition rate is defined only for pure Ca, and the dissolution rate of the sheath of the wire is not considered.
Further, in the method described in Patent Document 2, the wire feeding speed is specified, but the above-described conditions such as the sheath thickness, molten steel temperature, and feeding speed are not considered.
For this reason, in the methods of Patent Documents 1 and 2, it is difficult to effectively add Ca or the like to molten steel with a high yield.
本発明はかかる課題を解決するためになされたものであり、容器内に収容された溶鋼へCa等を歩留まりよく効果的に添加することができる溶鋼の成分調整方法を提供することを目的としている。 The present invention has been made to solve such a problem, and an object of the present invention is to provide a method for adjusting the composition of molten steel that can effectively add Ca and the like to the molten steel accommodated in the container with a good yield. .
本発明者らは鉄シースのワイヤを溶鋼へ添加するにあたり、鉄シースが溶解するまでの時間が鉄シース厚み、溶鋼温度に関係すると考え、熱電対を挿入した鉄シース(シース厚み0.04cm、0.05cm、0.06cm)を、温度を測定済の溶鋼の入った取鍋内に投入して、熱電対の温度変化を測定することによって鉄シースの溶解時間を求める実験を行った。
実験の結果を表1に示す。
The inventors considered that the time until the iron sheath melts when adding the iron sheath wire to the molten steel is related to the iron sheath thickness and the molten steel temperature, and the iron sheath (sheath thickness 0.04 cm, 0.05 mm) into which the thermocouple was inserted. cm, 0.06 cm) was put into a ladle containing molten steel whose temperature had been measured, and an experiment was conducted to determine the melting time of the iron sheath by measuring the temperature change of the thermocouple.
The results of the experiment are shown in Table 1.
表1の結果に基づいて、鉄シース溶解時間t(s)と、鉄シース厚みd(cm)及び溶鋼温度T(K)の関係を式によって整理したのが下記の式(2)である。
t=600・d・exp(-1.6×10-3・T) ・・・(2)
ここで、t:鉄シース溶解時間(s)
d:鉄シース厚み(cm)
T:溶鋼温度(K)
Based on the results in Table 1, the relationship between the iron sheath melting time t (s), the iron sheath thickness d (cm), and the molten steel temperature T (K) is organized by the following equation (2).
t = 600 ・ d ・ exp (-1.6 × 10 -3・ T) (2)
Where t: Iron sheath dissolution time (s)
d: Iron sheath thickness (cm)
T: Molten steel temperature (K)
式(2)によって求まる鉄シース溶解時間t(s)が表1に示した実験結果の「シース溶解時間(s)」とよく一致していることは、下記の表2及び表2をグラフ表示した図1からわかる。図1においては、縦軸が(2)式右辺であり、横軸が表1における「シース溶解時間(s)」である。 The fact that the iron sheath dissolution time t (s) obtained by the equation (2) is in good agreement with the “sheath dissolution time (s)” of the experimental results shown in Table 1 is shown in the graphs of Table 2 and Table 2 below. It can be seen from FIG. In FIG. 1, the vertical axis represents the right side of equation (2), and the horizontal axis represents “sheath dissolution time (s)” in Table 1.
次に、本発明者らは、鉄シースが溶解した後、CaやMgのような溶鋼温度で気化する金属と溶鋼が接触すると、気化した金属は溶鋼内を溶鋼と反応しながら上昇するため、鉄シースが溶解する溶鋼の深さによって該金属と溶鋼の反応時間が変化し、該金属の歩留まりが変化すると考えた。
そこで、CaSi合金を充填したワイヤを用いて、投入速度を変えて溶鋼へ添加し、鉄シースが溶解する溶鋼の深さとCaの歩留まりとの関係を求めた。
その結果を、図2のグラフに示す。図2において、縦軸がCa歩留(%)、横軸がワイヤ鉄シース溶解深さ/取鍋内溶鋼深さ(%)を示している。なお、ワイヤ鉄シース溶解深さは、(2)式で求まる鉄シース溶解時間t(s)を用いて、「ワイヤ投入速度(m/s)×鉄シース溶解時間t(s)」によって求めた。また、取鍋内溶鋼深さは溶鋼湯面から取鍋底部までの距離である。
なお、Ca歩留(%)の定義は以下の通りである。
T.[Ca]/(投入Ca純分量/溶鋼量x1000)x100(%)
上式の単位は、次の通りである。T.[Ca](ppm)、投入Ca純分量(kg)、溶鋼量(ton)
Next, the present inventors, after the iron sheath is dissolved, when the metal and the molten steel contact at the molten steel temperature such as Ca and Mg, the vaporized metal rises while reacting with the molten steel in the molten steel, It was considered that the reaction time of the metal and the molten steel changes depending on the depth of the molten steel in which the iron sheath melts, and the yield of the metal changes.
Therefore, using a wire filled with a CaSi alloy, the addition rate was changed to the molten steel, and the relationship between the molten steel depth at which the iron sheath melted and the Ca yield was determined.
The result is shown in the graph of FIG. In FIG. 2, the vertical axis represents Ca yield (%), and the horizontal axis represents wire iron sheath melting depth / ladder molten steel depth (%). The wire iron sheath dissolution depth was determined by “wire injection speed (m / s) × iron sheath dissolution time t (s)” using the iron sheath dissolution time t (s) obtained by equation (2). . The ladle depth in the ladle is the distance from the molten steel surface to the bottom of the ladle.
The definition of Ca yield (%) is as follows.
T. [Ca] / (Pure amount of Ca input / Amount of molten steel x1000) x100 (%)
The unit of the above formula is as follows. T. [Ca] (ppm), input Ca pure amount (kg), molten steel amount (ton)
図2に示されるように、鉄シースが溶鋼湯面から深さ80%以上の深さで到達したと計算される領域にある時にCaの歩留まりが最も高くなることが分かる。
したがって、Caの歩留まりを高くするためには、鉄シースが溶鋼湯面から深さ80%以上の深さで溶解するようにワイヤ投入速度(m/s)を設定すればよい。具体的には、ワイヤ投入速度(m/s)Vを下記の(1)式を満たすように設定すればよい。
0.8・H/t≦V≦1.2・H/t・・・(1)
ここで、V:ワイヤ投入速度(m/s)
H:取鍋内溶鋼深さ(m)
t:鉄シース溶解時間(s)(上記の(2)式参照)
As shown in FIG. 2, it can be seen that the yield of Ca is the highest when the iron sheath is in a region where it is calculated that the iron sheath has reached a depth of 80% or more from the molten steel surface.
Therefore, in order to increase the Ca yield, the wire feeding speed (m / s) may be set so that the iron sheath melts at a depth of 80% or more from the molten steel surface. Specifically, the wire feeding speed (m / s) V may be set so as to satisfy the following expression (1).
0.8 ・ H / t ≦ V ≦ 1.2 ・ H / t (1)
Where V: Wire input speed (m / s)
H: Molten steel depth in ladle (m)
t: Iron sheath dissolution time (s) (see equation (2) above)
また、発明者らは、ラインパイプ材での硫化物制御のためのCa添加量についても検討した。
ラインパイプ材での硫化物制御のためのCa添加に本方法を適用した際に、溶鋼中の介在物組成を分析したところ、溶鋼中の全Ca濃度(T.[Ca])のうち、酸化物であるCaの濃度Ca,oが以下の式(4)で表されることを見出した。
Ca,o=1.23×T.[O]-3.65・・・(4)
ここで、Ca,o:酸化物分Ca濃度(ppm)
T.[O]:鋼中全酸素濃度(ppm)
The inventors also examined the amount of Ca added for sulfide control in the line pipe material.
When this method was applied to the addition of Ca for sulfide control in line pipe materials, the inclusion composition in the molten steel was analyzed. Of the total Ca concentration (T. [Ca]) in the molten steel, oxidation It was found that the concentration Ca, o of the product Ca is expressed by the following formula (4).
Ca, o = 1.23 × T. [O] -3.65 (4)
Where Ca, o: oxide Ca concentration (ppm)
T. [O]: Total oxygen concentration in steel (ppm)
(4)式の導出方法は以下の通りである。
鋼サンプルを採取し、サンプル中酸化物の組成分析により、酸化物中CaO,Al2O3濃度測定を行う。酸化物中Ca濃度(%Ca)は、(%Ca)=(%CaO)×40/56として求まる。また、酸化物中のO濃度(%O)はCaO中O濃度(%O・CaO)とAl2O3中O濃度(%O・Al2O3)の合計であるから、(%O)=(%O・CaO)×16/56+(%O・Al2O3)×48/102として求まる。鋼中T.[O]は酸化物中のOによるものとすると、酸化物中のCaによる鋼中Ca濃度Ca,oは、Ca,o=T.[O]/(%O)×(%Ca)により算出できる。
The method for deriving equation (4) is as follows.
A steel sample is taken, and the CaO and Al 2 O 3 concentration in the oxide is measured by composition analysis of the oxide in the sample. The Ca concentration (% Ca) in the oxide is obtained as (% Ca) = (% CaO) × 40/56. In addition, O concentration (% O) in oxide is the sum of O concentration in CaO (% O · CaO) and O concentration in Al 2 O 3 (% O · Al 2 O 3 ), so (% O) = (% O · CaO) × 16/56 + (% O · Al 2 O 3 ) × 48/102 Assuming that T. [O] in steel is due to O in oxide, Ca concentration in steel due to Ca in oxide Ca, o is Ca, o = T. [O] / (% O) × (% Ca).
具体的な分析結果と、計算結果を表3に示す Specific analysis results and calculation results are shown in Table 3.
表3に示した、Ca,oと、T.[O]の関係を一次式で近似すると(4)式が得られる。
表3には、分析によるCa,oの算出値と、(4)式から求めたCa,oを記載している。また、(4)式の右辺の値を縦軸とし、算出値を横軸としたグラフが図3である。表3及び図3のグラフを見ると、(4)式の値が算出値を近似していることがわかる。
When the relationship between Ca, o and T. [O] shown in Table 3 is approximated by a linear expression, Expression (4) is obtained.
Table 3 shows the calculated value of Ca, o by analysis and Ca, o obtained from the equation (4). FIG. 3 is a graph in which the value on the right side of equation (4) is the vertical axis and the calculated value is the horizontal axis. When the graph of Table 3 and FIG. 3 is seen, it turns out that the value of (4) Formula approximates the calculated value.
発明者は、溶鋼中T.[Ca]のうち、上記(4)式から得られる酸化物分のCa(Ca,o)以外の余剰Ca(T.[Ca]-Ca,o)が溶鋼中Sと反応してCaSになると考え、Caによる硫化物制御のためには、余剰CaとSが原子量比で1.0:1.0以上が必要であることを見出した。 The inventor has found that excess Ca (T. [Ca] -Ca, o) other than Ca (Ca, o) of the oxide obtained from the above formula (4) in T. [Ca] in the molten steel is in the molten steel. We considered that it reacts with S to become CaS, and in order to control sulfide by Ca, it was found that the excess Ca and S need an atomic weight ratio of 1.0: 1.0 or more.
また、Caが過剰となると、Caを歩留まり高く添加しても、気化したCaにより取鍋内溶鋼湯面が乱れて空気とCaが反応してしまって発生するCaO量が増大し、それが鋼中に残留して鋳造されることで、HIC感受性の高い鋼板となってしまう。
そこで、Ca量の上限を調査するため、余剰CaとSの比を変えた試験片を用いて、NACE規格TM0284の規格に準拠してHIC(Hydrogen
Induced Cracking、水素誘起割れ)試験を行って耐HIC性を評価した。
なお、試験液は、規定のA溶液とし、試験片を該試験液に浸漬したのち、割れ発生有無を超音波探傷で調査した。
その結果、余剰CaとSの原子量比で4.0:1.0以下であれば、NACE溶液によるHIC試験により割れが発生しないことがわかった。
以上の検討をまとめると、Caによる硫化物制御を行いかつHIC感受性を抑制するには下記の式(3)を満たせばよいことになる。
In addition, when Ca is excessive, even if Ca is added at a high yield, the amount of CaO generated due to the reaction of air and Ca due to disturbance of the molten steel surface in the ladle due to vaporized Ca increases, It remains in the cast and becomes a steel sheet with high HIC sensitivity.
Therefore, in order to investigate the upper limit of the Ca content, HIC (Hydrogen) is used in accordance with the standard of NACE standard TM0284, using a test piece in which the ratio of excess Ca and S is changed.
Induced Cracking (hydrogen induced cracking) tests were conducted to evaluate the HIC resistance.
The test solution was a prescribed A solution, and after the test piece was immersed in the test solution, the presence or absence of cracking was investigated by ultrasonic flaw detection.
As a result, it was found that when the atomic weight ratio of surplus Ca and S was 4.0: 1.0 or less, the HIC test with NACE solution did not cause cracking.
In summary, the following equation (3) should be satisfied to control sulfide with Ca and suppress HIC sensitivity.
1.0≦{T.[Ca]-(1.23×T.[O]-3.65)}/1.25×S≦4.0・・・(3)
ここで、T.[Ca]:鋼中全Ca濃度(ppm)
T.[O]:鋼中全酸素濃度(ppm)
S:鋼中S濃度(ppm)
1.0 ≦ {T. [Ca]-(1.23 × T. [O] -3.65)} / 1.25 × S ≦ 4.0 (3)
Where T. [Ca]: Total Ca concentration in steel (ppm)
T. [O]: Total oxygen concentration in steel (ppm)
S: S concentration in steel (ppm)
本発明は上記の知見に基づくものであり、具体的には以下の構成からなるものである。 The present invention is based on the above findings, and specifically comprises the following configuration.
1)本発明に係る溶鋼の成分調整方法は、容器内に保持された溶鋼へCaまたはMgを添加するに際し、該金属あるいはその合金を鉄シース内に充填してワイヤ状とし、(1)、(2)式を満たす速度で溶鋼中へ投入することを特徴とするものである。
0.8・H/t≦V≦1.2・H/t ・・・(1)
t=600・d・exp(-1.6×10-3・T) ・・・(2)
ここで、V:ワイヤ投入速度(m/s)
H:取鍋内溶鋼深さ(m)
t:鉄シース溶解時間(s)
d:鉄シース厚み(cm)
T:溶鋼温度(K)
1) In the method for adjusting the composition of molten steel according to the present invention, when adding Ca or Mg to molten steel held in a container, the metal or its alloy is filled into an iron sheath to form a wire, (1) (2) It introduce | transduces in molten steel at the speed | rate which satisfy | fills Formula.
0.8 ・ H / t ≦ V ≦ 1.2 ・ H / t (1)
t = 600 ・ d ・ exp (-1.6 × 10 -3・ T) (2)
Where V: Wire input speed (m / s)
H: Molten steel depth in ladle (m)
t: Iron sheath dissolution time (s)
d: Iron sheath thickness (cm)
T: Molten steel temperature (K)
2)また本発明の、溶鋼の成分調整方法は、上記1)に記載の溶鋼成分調整方法によって(3)式を満たす範囲となるようにCaまたはCa含有合金を添加することを特徴とする。
1.0≦{T.[Ca]-(1.23×T.[O]-3.65)}/1.25×S≦4.0・・・(3)
ここで、T.[Ca]:鋼中全Ca濃度(ppm)
T.[O]:鋼中全酸素濃度(ppm)
S:鋼中S濃度(ppm)
2) Further, the molten steel component adjusting method of the present invention is characterized in that Ca or a Ca-containing alloy is added so as to satisfy the formula (3) by the molten steel component adjusting method described in 1) above.
1.0 ≦ {T. [Ca]-(1.23 × T. [O] -3.65)} / 1.25 × S ≦ 4.0 (3)
Where T. [Ca]: Total Ca concentration in steel (ppm)
T. [O]: Total oxygen concentration in steel (ppm)
S: S concentration in steel (ppm)
3)また、上記2)に記載のものにおいて、前記(3)式におけるT.[O]濃度の分析方法が、スパーク放電発光分光法を用いる方法であって、以下のステップを有することを特徴とするものである。
ア)多数回の放電パルスによるアルミニウムと鉄の発光強度比を放電パルス毎に求める強度比計算ステップ
イ)下記式にて求められるアルミナ分率を算出するステップ。
アルミナ分率=前記発光強度比が閾値αより大きいパルス数/全パルス数
ここで、閾値αは、放電パルス毎の前記発光強度比を横軸、頻度を縦軸とした度数分布図から求められた発光強度比の最頻値のf1(1.5≦f1≦2.5)倍
ウ)前記強度比計算ステップにより得られた放電パルス毎の前記発光強度比を小さい方から配列し、小さい方から全パルス数の30%以内の一定位置の前記発光強度比を代表アルミ強度比とし、次いで、前記アルミナ分率算出ステップで得られたアルミナ分率と代表アルミ強度比の積からアルミナ強度比(=アルミナ分率×代表アルミ強度比)を算出するステップ
エ)前記アルミナ強度比とT.[O]との関係式を用いてT.[O]を算出する定量ステップ
3) In addition, in the method described in 2) above, the T. [O] concentration analysis method in the equation (3) is a method using spark discharge emission spectroscopy, and has the following steps. It is what.
A) Intensity ratio calculation step for obtaining the emission intensity ratio of aluminum and iron for each discharge pulse by a number of discharge pulses a) Step for calculating the alumina fraction obtained by the following formula.
Alumina fraction = number of pulses where the emission intensity ratio is greater than the threshold α / total number of pulses
Here, the threshold value α is the mode f 1 (1.5 ≦ f 1 ≦ 2.5) of the light emission intensity ratio obtained from the frequency distribution diagram with the light emission intensity ratio for each discharge pulse as the horizontal axis and the frequency as the vertical axis. X) Arrange the emission intensity ratio for each discharge pulse obtained by the intensity ratio calculation step from the smaller one, and the emission intensity ratio at a fixed position within 30% of the total number of pulses from the smaller one. And then calculating the alumina strength ratio (= alumina fraction × representative aluminum strength ratio) from the product of the alumina fraction obtained in the alumina fraction calculating step and the representative aluminum strength ratio d) the alumina strength ratio and T Quantification step to calculate T. [O] using the relational expression with. [O]
本発明によれば、Ca、Mgまたはその合金を歩留まりよく効果的に溶鋼に添加することができる。 According to the present invention, Ca, Mg, or an alloy thereof can be effectively added to molten steel with a high yield.
本実施の形態に係る溶鋼の成分調整方法は、容器内に収容された溶鋼へCaまたはMgを添加するに際し、該金属あるいはその合金を鉄シース内に充填してワイヤ状とし、(1)、(2)式を満たす速度で溶鋼中へ投入することを特徴とするものである。
0.8・H/t≦V≦1.2・H/t ・・・(1)
t=600・d・exp(-1.6×10-3・T) ・・・(2)
ここで、V:ワイヤ投入速度(m/s)
H:取鍋内溶鋼深さ(m)
t:鉄シース溶解時間(s)
d:鉄シース厚み(cm)
T:溶鋼温度(K)cm)
The component adjustment method for molten steel according to the present embodiment is such that when adding Ca or Mg to molten steel contained in a container, the metal or its alloy is filled into an iron sheath to form a wire, (1), (2) It introduce | transduces in molten steel at the speed | rate which satisfy | fills Formula.
0.8 ・ H / t ≦ V ≦ 1.2 ・ H / t (1)
t = 600 ・ d ・ exp (-1.6 × 10 -3・ T) (2)
Where V: Wire input speed (m / s)
H: Molten steel depth in ladle (m)
t: Iron sheath dissolution time (s)
d: Iron sheath thickness (cm)
T: Molten steel temperature (K) cm)
転炉あるいは電気炉等の精錬炉から取鍋へ出鋼された溶鋼は、取鍋精錬炉等で処理され、その後、連続鋳造までの間に、溶鋼は容器に収容される。この容器とは、例えば、取鍋、タンディッシュなどであり、このような容器に収容された溶鋼に鉄シース厚みが既知のワイヤを投入する。
ワイヤの投入は、溶鋼の温度を測定した後であり、鋳造を開始する前であれば、いつ行ってもよい。溶鋼の温度の測定は、ワイヤ投入直前に行うのが好ましいが、温度測定をする装置と、ワイヤ投入を行う設備間が離れているような場合には、予め、温度変化の挙動を測定等して把握しておき、ワイヤ投入時の溶鋼温度を推定するようにしてもよい。
容器内の溶鋼深さは、溶鋼湯面から容器底部までに距離をいう。
以上の測定値、計算値から、取鍋において上記(1)、(2)式を満たすような投入速度でCa、Mgあるいはそれらの合金を溶鋼に添加することで該金属の歩留まりを最大限に高めることが可能となる。
Molten steel discharged from a refining furnace such as a converter or an electric furnace to a ladle is processed in a ladle refining furnace or the like, and thereafter, the molten steel is accommodated in a container until continuous casting. This container is, for example, a ladle, a tundish, etc., and a wire having a known iron sheath thickness is put into molten steel accommodated in such a container.
The introduction of the wire may be performed any time after the temperature of the molten steel is measured and before the casting is started. It is preferable to measure the temperature of the molten steel immediately before the wire is thrown in. However, if the temperature measuring device and the equipment that throws in the wire are separated from each other, the temperature change behavior is measured in advance. It is also possible to estimate the molten steel temperature when the wire is thrown in.
The depth of molten steel in the container refers to the distance from the molten steel surface to the bottom of the container.
From the above measured and calculated values, the yield of the metal can be maximized by adding Ca, Mg or their alloys to the molten steel at a charging rate that satisfies the above formulas (1) and (2) in the ladle. It becomes possible to raise.
また、上記(1)、(2)式を満たす方法でCaを添加する場合には、ラインパイプ材等の耐水素誘起割れ性を向上させるために、歩留まりを考慮して、下記(3)式を満足するように添加量を決めればよい。
1.0≦{T.[Ca]-(1.23×T.[O]-3.65)}/1.25×S≦4.0・・・(3)
ここで、T.[Ca]:鋼中全Ca濃度(ppm)
T.[O]:鋼中全酸素濃度(ppm)
S:鋼中S濃度(ppm)
Further, when Ca is added by a method that satisfies the above formulas (1) and (2), the following formula (3) is considered in consideration of the yield in order to improve the hydrogen-induced crack resistance of line pipe materials and the like. The addition amount may be determined so as to satisfy the above.
1.0 ≦ {T. [Ca]-(1.23 × T. [O] -3.65)} / 1.25 × S ≦ 4.0 (3)
Where T. [Ca]: Total Ca concentration in steel (ppm)
T. [O]: Total oxygen concentration in steel (ppm)
S: S concentration in steel (ppm)
その際、T.[O],Sの値についてはCa添加前に予め溶鋼サンプルから分析しておいても良いし、同じ鋼種のデータを蓄積しておき、そこから処理条件から予測した値を用い、バラツキを考慮して上記(3)式の中央値を狙う等などしておき、Ca添加後、タンディッシュ、あるいは連鋳機鋳型内からの溶鋼のサンプルを分析して確認し、上記(3)式の範囲を外れていれば、圧延前に材料変更等の対応をとるようにすればよい。
なお、Ca添加前のT.[O]の定量方法としては燃焼分析法や、スパーク放電発光分光法で直接的にT.[O]を求める方法があるが、より好ましいT.[O]の分析方法について以下に説明する。
At that time, the values of T. [O] and S may be analyzed from the molten steel sample in advance before adding Ca, or the data of the same steel type is accumulated, and the value predicted from the processing conditions from that is accumulated. In consideration of dispersion, aim at the median of the above formula (3), etc., and after adding Ca, analyze and confirm a sample of molten steel from the tundish or continuous caster mold. If it falls outside the range of 3), it is sufficient to take measures such as changing the material before rolling.
In addition, as a method for quantifying T. [O] before Ca addition, there are a combustion analysis method and a method for directly obtaining T. [O] by spark discharge emission spectroscopy, but a more preferable T. [O] The analysis method will be described below.
対象とする材料では、タンディッシュ注入前の溶鋼中の酸素濃度(T.[O])はほぼ全てAl2O3(以下、アルミナと称す)に起因するものであると考えられる。
したがって、アルミナの濃度を分析することでT.[O]を分析することができる。
In the target material, the oxygen concentration (T. [O]) in the molten steel before the tundish injection is considered to be due to Al 2 O 3 (hereinafter referred to as alumina).
Therefore, T. [O] can be analyzed by analyzing the concentration of alumina.
ところで、製鋼精錬工程で溶鋼に添加されたアルミニウム(以下、Alと称す)は、その一部は鋼中の酸素と反応しアルミナとなって徐々に表面に浮上して溶鋼から取り除かれる。
一方、残りの未反応のAlは鋼中に溶解したまま凝固する。
鋼の凝固後、浮上除去されなかったアルミナはそのままの状態で鋼中に残り、一方、未反応のAlは主として固溶Alとして鋼中に存在する。固溶Alは鋼試料を酸で溶解する際に一緒に溶解するが、アルミナは溶解しないので、酸溶解により互いに分離され、前者は酸可溶性Al(以下、sol.Alと称す)と呼ばれ、後者は酸不溶性Al(以下、insol.Alと称す)と呼ばれる。
By the way, a part of aluminum (hereinafter referred to as “Al”) added to the molten steel in the steel refining process reacts with oxygen in the steel to become alumina and gradually floats on the surface and is removed from the molten steel.
On the other hand, the remaining unreacted Al solidifies while being dissolved in the steel.
After the solidification of the steel, the alumina that has not been lifted and removed remains in the steel as it is, while the unreacted Al is mainly present in the steel as solute Al. Solid solution Al dissolves together when the steel sample is dissolved with acid, but alumina does not dissolve, so they are separated from each other by acid dissolution, the former is called acid-soluble Al (hereinafter referred to as sol.Al), The latter is called acid-insoluble Al (hereinafter referred to as insol.Al).
鉄鋼製造工程においては、鋼組成を制御するための迅速分析法としてスパーク放電発光分光分析法が広く利用され、成分分析のみならず、鋼中における酸化物量の定量法としても様々な取り組みがなされてきた。
しかしながら従来の解析手法では、鋼中50ppm以下の微量なアルミナ量を精度良く分析することは難しかった。
In the steel manufacturing process, spark discharge emission spectrometry is widely used as a rapid analysis method for controlling steel composition, and various efforts have been made not only for component analysis but also for quantitative determination of the amount of oxide in steel. It was.
However, with the conventional analysis method, it was difficult to accurately analyze a small amount of alumina in steel at 50 ppm or less.
これに対し、発明者らはスパーク放電発光現象におけるパルスごとの発光強度、および発光強度分布状態の示す物理化学的な意味を見直すことにより、アルミナ量の定量方法を見出した。
sol.Al濃度が等しくinsol.Al濃度の異なる鋼試料(sol.Al=66ppm、insol.Al=10ppm未満の試料、sol.Al=66ppm 、insol.Al=32ppmの試料)をそれぞれスパーク放電により発光させ、放電パルス毎にAlの発光強度と鉄の発光強度の比(Alの発光強度を鉄の発光強度で除した値であり、以下、Al/Fe強度比と称す)を経時的に観察した。
その結果、insol.Alの多い試料では、スパイク状の点が不規則に数多く確認され、スパイク状の点は、鋼中に不均一に存在するinsol.Alを含んだ放電によって生成されたものと推察される。スパーク放電では介在物(insol.Al)に放電が集中しやすいとされ、観察されるAl強度は、地鉄中のsol.Alからの光と、介在物(insol.Al)からの光から構成されるが、それぞれの割合は放電パルスごとに異なっている。
放電パルスを、Al/Fe強度比の小さい順(昇順)に配列し、縦軸をAl/Fe強度比とし、横軸をAl/Fe強度比が小さいものから順に並び変えた位置を%表示したグラフを図4に示す。
図4に示されるように、Al/Fe強度比の大きい側はinsol.Alが支配的で、小さい側はsol.Alが支配的となっている。
sol.Alは地鉄中に均一に存在しているので、放電時に蒸発する地鉄の量が変動しても、sol.Al由来のAl強度はFeとの相対値(Al/Fe強度比)とする限り一定値を示すはずである。
つまり、Al/Fe強度比は、一定のsol.Al強度比と不確定なinsol.Al強度比の和であって、その大きさは不確定なinsol.Al強度比の大小で決定されるため、よりAl/Fe強度比の小さいパルスほどsol.Al強度比に近づき、Al/Fe強度比全体の積算値からsol.Alの寄与する強度積算値を差し引くことにより、アルミナ量を定量することができる。
具体的には以下のようにする。
In contrast, the inventors have found a method for quantifying the amount of alumina by reviewing the luminescence intensity for each pulse in the spark discharge luminescence phenomenon and the physicochemical meaning of the luminescence intensity distribution state.
Each steel sample with the same sol.Al concentration but different insol.Al concentration (sol.Al = 66ppm, insol.Al = less than 10ppm, sol.Al = 66ppm, insol.Al = 32ppm) is emitted by spark discharge. The ratio of the emission intensity of Al to the emission intensity of iron for each discharge pulse (a value obtained by dividing the emission intensity of Al by the emission intensity of iron, hereinafter referred to as the Al / Fe intensity ratio) was observed over time. .
As a result, in the sample with a lot of insol.Al, a lot of spike-like points were confirmed irregularly, and the spike-like points were generated by the discharge containing insol.Al that existed unevenly in the steel. Inferred. In spark discharge, the discharge is likely to concentrate on inclusions (insol.Al), and the observed Al intensity consists of light from sol.Al in the ground iron and light from inclusions (insol.Al). However, each ratio is different for each discharge pulse.
Discharge pulses are arranged in ascending order of Al / Fe intensity ratio (ascending order), the vertical axis is the Al / Fe intensity ratio, and the horizontal axis is the percentage displayed in order from the smallest Al / Fe intensity ratio. A graph is shown in FIG.
As shown in FIG. 4, insol.Al is dominant on the side where the Al / Fe strength ratio is large, and sol.Al is dominant on the side where the Al / Fe strength ratio is small.
Since sol.Al is present uniformly in the steel, even if the amount of steel that evaporates during discharge fluctuates, the Al strength derived from sol.Al is relative to Fe (Al / Fe strength ratio). It should show a constant value as long as
In other words, the Al / Fe strength ratio is the sum of a constant sol.Al strength ratio and an uncertain insol.Al strength ratio, and its magnitude is determined by the magnitude of the uncertain insol.Al strength ratio. The smaller the Al / Fe intensity ratio, the closer to the sol.Al intensity ratio, and the amount of alumina can be quantified by subtracting the integrated intensity value contributed by sol.Al from the integrated value of the entire Al / Fe intensity ratio. it can.
Specifically:
多数回(例えば、2000回)の放電パルスによるアルミニウムと鉄のAl/Fe強度比を放電パルス毎に求める(強度比計算ステップ)。 An Al / Fe intensity ratio between aluminum and iron by a number of discharge pulses (for example, 2000 times) is determined for each discharge pulse (intensity ratio calculation step).
下記式にて求められるアルミナ分率を算出する(アルミナ分率を算出ステップ)。
アルミナ分率=Al/Fe強度比が閾値αより大きいパルス数/全パルス数
「閾値α」は、図5に示すように、放電パルス毎のAl/Fe強度比を横軸、頻度を縦軸とした度数分布図を作図した後、該度数分布図から求められたAl/Fe強度比の最頻値のf1倍として特定する。ここで、f1の値は、1.5≦f1≦2.5とするのが好ましい。
同様の手法で処理した試料を同様の測定条件で測定する限り、固溶Alに由来する発光強度比の頻度分布は、同様のバラツキ幅を持つと考えられることから、Al/Fe強度比の最頻値の1より大きい定数倍の値を閾値とすることで、固溶Alの影響度を一定の比率に保って、アルミナ由来の信号成分を分離できると考えられる。
従って、放電パルス毎のAl/Fe強度比が最頻値のf1倍より大きいパルス数を求め、求めたパルス数を全パルス数で除したものをアルミナ分率とする。ここで、f1の値は、1.5〜2.5の範囲、より好ましくは1.7〜2.0の範囲とする。f1の値が1.5より小さい場合、固溶アルミに由来するデータが多くなるため、アルミナ量との相関が悪くなる。一方、f1の値が2.5より大きい場合、抽出されるアルミナ由来の信号を含むパルス数が少なくなりすぎるため、分析ばらつきが大きくなる。
The alumina fraction obtained by the following formula is calculated (calculating alumina fraction).
Alumina fraction = number of pulses with Al / Fe intensity ratio greater than threshold α / total number of pulses As shown in FIG. 5, “threshold α” indicates the Al / Fe intensity ratio for each discharge pulse on the horizontal axis and the frequency on the vertical axis. Then, the frequency distribution chart is specified as f 1 times the mode value of the Al / Fe intensity ratio obtained from the frequency distribution chart. Here, the value of f 1 is preferably set to 1.5 ≦ f 1 ≦ 2.5.
As long as a sample treated by the same method is measured under the same measurement conditions, the frequency distribution of the emission intensity ratio derived from solute Al is considered to have the same variation width. It is considered that the signal component derived from alumina can be separated by keeping the influence degree of the solid solution Al at a constant ratio by setting the value of a constant multiple larger than 1 as the threshold value.
Therefore, Al / Fe intensity ratio of each discharge pulse is determined the number of pulses greater than 1 times f the mode, what the number of determined pulses divided by the total number of pulses and the alumina fraction. Here, the value of f 1 is in the range of 1.5 to 2.5, more preferably in the range of 1.7 to 2.0. When the value of f 1 is smaller than 1.5, data derived from solute aluminum increases, and thus the correlation with the amount of alumina is deteriorated. On the other hand, when the value of f 1 is larger than 2.5, the number of pulses including the signal derived from alumina to be extracted becomes too small, and the analysis variation becomes large.
ここで、アルミナ分率を算出する際のf1値の影響を確認するために、f1値を1.4〜2.6の範囲において0.05ステップで変えてアルミナ強度比(insol.Al強度比)を計算した。各f1値におけるアルミナ強度比と化学分析値との相関係数および繰り返し分析時の変動係数を図6および図7にそれぞれ示す。
図6より、f1が1.5以下となるとアルミナ強度比と化学分析値の相関係数が急激に低下することがわかる。これは、固溶アルミ由来の発光の影響によるものと考えられる。また、図7より、f1の値が大きくなるほど、繰り返し分析時のバラツキが大きくなっていることがわかる。これは、抽出されるパルス数が少なくなりすぎるためである。
しかし、f1値が1.5および2.5の場合でも、分析正確さ(σd)は、それぞれ、2.4ppm、1.9ppmであり、従来法よりも高精度に分析が可能である。
f1値が2.0の場合の、本発明に係るアルミナ定量法により求めたアルミナ濃度と化学分析値との相関を図8に示す。このときの分析正確さは1.8ppmであった。
Here, in order to confirm the influence of the f 1 value in calculating the alumina fraction, the alumina strength ratio (insol.Al strength ratio) was calculated by changing the f 1 value in the range of 1.4 to 2.6 in 0.05 steps. . FIG. 6 and FIG. 7 show the correlation coefficient between the alumina strength ratio and the chemical analysis value at each f 1 value and the coefficient of variation during repeated analysis, respectively.
FIG. 6 shows that when f 1 is 1.5 or less, the correlation coefficient between the alumina strength ratio and the chemical analysis value rapidly decreases. This is considered to be due to the influence of light emission derived from solid solution aluminum. Moreover, FIG. 7 shows that the variation at the time of repeated analysis increases as the value of f 1 increases. This is because the number of extracted pulses is too small.
However, even when the f 1 value is 1.5 and 2.5, the analysis accuracy (σd) is 2.4 ppm and 1.9 ppm, respectively, which can be analyzed with higher accuracy than the conventional method.
FIG. 8 shows the correlation between the alumina concentration obtained by the alumina quantification method according to the present invention and the chemical analysis value when the f 1 value is 2.0. The analysis accuracy at this time was 1.8 ppm.
強度比計算ステップにより得られた放電パルス毎のAl/Fe強度比を小さい方から配列し、一定位置のAl/Fe強度比を代表アルミ強度比とする。
ここで、「代表アルミ強度比」は、放電パルス毎のAl/Fe強度比を小さい方から配列した際に(図4参照)、Al/Fe強度比の小さい方から全パルス数の30%以内のいずれかの位置となるような強度比とするのが好ましい。この理由は以下の通りである。
30%よりも大きい位置を代表アルミ強度比とした場合には、試料中に存在するアルミナ量の影響が大きくなりすぎ、酸可溶性Al(sol.Al)とアルミナを精度よく分配するための代表値とならずに分析精度が劣化するからである。
次に、アルミナ分率算出ステップで得られたアルミナ分率と代表アルミ強度比の積からアルミナ強度比を算出する。
The Al / Fe intensity ratio for each discharge pulse obtained by the intensity ratio calculation step is arranged from the smaller one, and the Al / Fe intensity ratio at a fixed position is set as the representative aluminum intensity ratio.
Here, the “representative aluminum intensity ratio” is within 30% of the total number of pulses from the smaller Al / Fe intensity ratio when the Al / Fe intensity ratio for each discharge pulse is arranged from the smaller one (see FIG. 4). It is preferable to set the intensity ratio so as to be any one of the positions. The reason is as follows.
When the position greater than 30% is used as the representative aluminum strength ratio, the influence of the amount of alumina present in the sample becomes too great, and the typical value for accurately distributing acid-soluble Al (sol.Al) and alumina. This is because the analysis accuracy deteriorates.
Next, the alumina strength ratio is calculated from the product of the alumina fraction obtained in the alumina fraction calculation step and the representative aluminum strength ratio.
スパーク放電発光分光法における特性値とT.[O]の関係を調査して予め作成した検量線を用いて、目的とするT.[O]を求める。
検量線試料には同じCa添加鋼を用い、各試料について予めスパーク放電発光分光分析法で得られるAl/Fe強度比から必要な各係数を設定した後、算出された特性値と燃焼分析法から求められるT.[O]の相関線を検量線とする。検量線の一例を図9に示す。
The target T. [O] is obtained using a calibration curve prepared in advance by investigating the relationship between the characteristic value and T. [O] in spark discharge emission spectroscopy.
The same Ca-added steel is used for the calibration curve sample, and after setting each necessary coefficient from the Al / Fe intensity ratio obtained by spark discharge optical emission spectrometry for each sample, the calculated characteristic value and combustion analysis method are used. The calculated correlation line of T. [O] is used as a calibration curve. An example of a calibration curve is shown in FIG.
なお、溶鋼中の酸素量は継時変化しやすいことから、スパーク放電発光分光分析装置は極力、製造現場に近いことが望ましく、可能であれば機側でのオンサイト分析が最も好適である。 Since the amount of oxygen in the molten steel is likely to change over time, it is desirable that the spark discharge optical emission spectrometer is as close as possible to the production site, and if possible, on-site analysis on the machine side is most suitable.
鋼中Ca量についてはもともとスパーク放電発光分光分析法による分析感度・精度が良好であるため、通常の手段で定量した結果を用いることが可能である。
また、鋼中S量については、AP(アークプロセス)処理以降の工程ではほとんど変化しないことが調査の結果分かった。すなわち、AP処理終了後からCa添加までの間に分析を行なえば問題なく、高精度な鋼中Sの分析法である、燃焼法などの適用が十分に可能である。
As for the Ca content in steel, the analysis sensitivity and accuracy by the spark discharge optical emission spectrometry are originally good, so that the result quantified by the usual means can be used.
As a result of the investigation, it was found that the amount of S in steel hardly changed in the processes after the AP (arc process) treatment. That is, there is no problem if the analysis is performed after the AP treatment is completed and before the addition of Ca, and the combustion method, which is a highly accurate analysis method for S in steel, can be sufficiently applied.
本発明の効果を確認する実験を行ったので、以下これについて説明する。
転炉で約250トンの溶鋼を酸素吹錬した後、取鍋に出鋼し、取鍋精錬炉、RH真空脱ガス装置で必要に応じた精錬を施した。その後、取鍋をワイヤ投入設備へ搬送した。
ワイヤ投入開始前に溶鋼の温度、深さの測定を行った。ワイヤは厚み0.04,0.05cmの鉄シース内にCaSi合金を充填したものを使用した。
ワイヤを(1)、(2)式を満たす速度で投入した。また、比較例として、(1)、(2)式の範囲外の速度で投入した実験も行った。
実験結果を表4に示す。
An experiment for confirming the effect of the present invention was conducted, and this will be described below.
About 250 tons of molten steel was blown with oxygen in a converter, and then steel was taken out into a ladle and subjected to refining as needed in a ladle refining furnace and RH vacuum degassing equipment. Then, the ladle was conveyed to the wire charging equipment.
The temperature and depth of the molten steel were measured before starting the wire charging. The wire used was a 0.04, 0.05 cm thick iron sheath filled with CaSi alloy.
The wire was thrown in at a speed satisfying equations (1) and (2). In addition, as a comparative example, an experiment was performed in which the input was performed at a speed outside the range of the formulas (1) and (2).
The experimental results are shown in Table 4.
表4に示すように、ワイヤ投入速度が(1)、(2)式の範囲にある本発明例1〜6と、ワイヤ投入速度が(1)、(2)式の範囲外の比較例1〜4を比較すると、本発明例1〜6の方が比較例1〜4よりもCaの歩留まりが高くなっていた。
このことから、ワイヤ投入速度が(1)、(2)式の範囲内にすることで、Caの歩留を向上させることができることが確認された。
As shown in Table 4, Invention Examples 1 to 6 in which the wire throwing speed is in the range of the formulas (1) and (2), and Comparative Example 1 in which the wire throwing speed is outside the range of the formulas (1) and (2). -4, the inventive examples 1-6 were higher in Ca yield than the comparative examples 1-4.
From this, it was confirmed that the yield of Ca can be improved by setting the wire throwing speed within the range of the formulas (1) and (2).
上記の実験の続きとして、ワイヤ投入後、取鍋を連続鋳造機上に設置されたタンディッシュ上へ搬送し、タンディッシュへ溶鋼を注入した。取鍋内溶鋼の約50%を注入した時点で、タンディッシュ内から溶鋼サンプルを採取し、機側に設置したスパーク放電発光分光分析装置によりT.[Ca],T.[O]濃度を分析した。
Caについては通常の分析手段にて定量し、T.[O]については前述した方法によって定量値を算出した。なお、検量線は、図9に示したものを用いた。
一方、Sについてはスパーク放電発光分光分析装置による分析精度が充分ではないと判断されたことから、AP終了後の燃焼法による分析結果をそのまま用いた。念の為、T.[Ca],T.[O]分析用のサンプルを保管し、後日、採取した切り粉を用いて燃焼法による定量を行なったが、ほとんど1ppm以内の範囲で一致しており、AP処理終了後の分析値を用いて問題の無いことを確認した。
ここで(3)式を満たすものを本発明例1〜6とし、満たさなかった場合を比較例1〜8とした。
As a continuation of the above experiment, the ladle was transported onto the tundish installed on the continuous casting machine after the wire was introduced, and molten steel was injected into the tundish. When about 50% of the molten steel in the ladle is injected, a molten steel sample is taken from the tundish and analyzed for T. [Ca] and T. [O] concentrations using a spark discharge emission spectrometer installed on the machine side. did.
Ca was quantified by ordinary analytical means, and T. [O] was quantified by the method described above. The calibration curve shown in FIG. 9 was used.
On the other hand, for S, it was determined that the analysis accuracy by the spark discharge optical emission spectrometer was not sufficient, so the analysis result by the combustion method after the end of AP was used as it was. As a precaution, samples for T. [Ca], T. [O] analysis were stored and quantified by the combustion method using the collected chips at a later date. Therefore, it was confirmed that there was no problem using the analysis value after the AP processing was completed.
What satisfy | filled (3) Formula here was set as Examples 1-6 of this invention, and the case where it was not satisfied was set as Comparative Examples 1-8.
これら溶鋼を連続鋳造法によりスラブとし、これを用いて板厚25.4mm及び33mmの厚鋼板を製造した。
加熱したスラブを熱間圧延により圧延し、その後、加速冷却を施して所定の強度とした。この時のスラブ加熱温度は1050℃、圧延終了温度は800〜840℃、加速冷却開始温度は760〜800℃、加速冷却停止温度は450〜550℃とした。
These molten steels were made into slabs by a continuous casting method, and thick steel plates having thicknesses of 25.4 mm and 33 mm were manufactured using the slabs.
The heated slab was rolled by hot rolling and then subjected to accelerated cooling to a predetermined strength. The slab heating temperature at this time was 1050 ° C., the rolling end temperature was 800-840 ° C., the accelerated cooling start temperature was 760-800 ° C., and the accelerated cooling stop temperature was 450-550 ° C.
得られた鋼板の強度はいずれもAPIX65を満足するものであり、引張強度は570〜630MPaであった。鋼板の引張特性については、圧延垂直方向の全厚試験片を引張試験片として引張試験を行い、引張強度を測定した。
これらの鋼板について、複数の位置から各10〜15個のHIC試験片を採取し、耐HIC特性を調べた。耐HIC特性は、pHが約3の硫化水素を飽和させた5%NaCl+0.5%CH3COOH水溶液(通常のNACE溶液)中に試験片を96時間浸漬した後、超音波探傷により試験片全面の割れの有無を調査し、割れ面積率(CAR)で評価した。ここで、それぞれの試験片の割れ面積率3%以下を合格とした。
表5に処理条件及び結果を示す。
All the strengths of the obtained steel plates satisfied APIX65, and the tensile strength was 570 to 630 MPa. Regarding the tensile properties of the steel sheet, a tensile test was performed using a full thickness test piece in the rolling vertical direction as a tensile test piece, and the tensile strength was measured.
About these steel plates, 10-15 HIC test pieces were sampled from a plurality of positions, and the anti-HIC properties were examined. The HIC resistance is that the specimen is immersed in a 5% NaCl + 0.5% CH3COOH aqueous solution (normal NACE solution) saturated with hydrogen sulfide with a pH of about 3 for 96 hours, and then the entire specimen is cracked by ultrasonic flaw detection. The crack area ratio (CAR) was evaluated. Here, a crack area ratio of 3% or less for each test piece was regarded as acceptable.
Table 5 shows the processing conditions and results.
表5に示すように、成分が(3)式を満たす範囲にある本発明例1〜6ではHIC試験不合格率が7.1%以下であり、耐HIC性能がきわめて良好であった。これに対して、成分が(3)式の範囲外の比較例1〜8では、ワイヤ投入速度が(1)、(2)式の範囲内にあるかどうかに関わりなく耐HIC性能がきわめて悪かった。
このことから、成分が(3)式を満たす範囲にあることで耐HIC性能を良好にすることができることが確認された。
As shown in Table 5, in Examples 1 to 6 of the present invention where the components satisfy the formula (3), the HIC test rejection rate was 7.1% or less, and the HIC resistance performance was extremely good. On the other hand, in Comparative Examples 1 to 8 whose components are out of the range of the formula (3), the anti-HIC performance is extremely bad regardless of whether the wire feeding speed is in the range of the formulas (1) and (2). It was.
From this, it was confirmed that the HIC resistance can be improved when the component is in a range satisfying the expression (3).
Claims (3)
0.8・H/t≦V≦1.2・H/t ・・・(1)
t=600・d・exp(-1.6×10-3・T)・・・(2)
ここで、V:ワイヤ投入速度(m/s)
H:取鍋内溶鋼深さ(m)
t:鉄シース溶解時間(s)
d:鉄シース厚み(cm)
T:溶鋼温度(K) When adding Ca or Mg to the molten steel accommodated in the container, the metal or its alloy is filled into an iron sheath to form a wire, and is poured into the molten steel at a speed satisfying the expressions (1) and (2). A method for adjusting the composition of molten steel.
0.8 ・ H / t ≦ V ≦ 1.2 ・ H / t (1)
t = 600 ・ d ・ exp (-1.6 × 10 -3・ T) ・ ・ ・ (2)
Where V: Wire input speed (m / s)
H: Molten steel depth in ladle (m)
t: Iron sheath dissolution time (s)
d: Iron sheath thickness (cm)
T: Molten steel temperature (K)
1.0≦{T.[Ca]-(1.23×T.[O]-3.65)}/1.25×S≦4.0・・・(3)
ここで、T.[Ca]:鋼中全Ca濃度(ppm)
T.[O]:鋼中全酸素濃度(ppm)
S:鋼中S濃度(ppm) The molten steel component adjusting method according to claim 1, wherein Ca or Ca-containing alloy is added so as to be in a range satisfying the expression (3).
1.0 ≦ {T. [Ca]-(1.23 × T. [O] -3.65)} / 1.25 × S ≦ 4.0 (3)
Where T. [Ca]: Total Ca concentration in steel (ppm)
T. [O]: Total oxygen concentration in steel (ppm)
S: S concentration in steel (ppm)
ア)多数回の放電パルスによるアルミニウムと鉄の発光強度比を放電パルス毎に求める強度比計算ステップ
イ)下記式にて求められるアルミナ分率を算出するステップ。
アルミナ分率=前記発光強度比が閾値αより大きいパルス数/全パルス数
ここで、閾値αは、放電パルス毎の前記発光強度比を横軸、頻度を縦軸とした度数分布図から求められた発光強度比の最頻値のf1(1.5≦f1≦2.5)倍
ウ)前記強度比計算ステップにより得られた放電パルス毎の前記発光強度比を小さい方から配列し、小さい方から全パルス数の30%以内の一定位置の前記発光強度比を代表アルミ強度比とし、次いで、前記アルミナ分率算出ステップで得られたアルミナ分率と代表アルミ強度比の積からアルミナ強度比(=アルミナ分率×代表アルミ強度比)を算出するステップ
エ)前記アルミナ強度比とT.[O]との関係式を用いてT.[O]を算出する定量ステップ 3. The method for adjusting the composition of molten steel according to claim 2, wherein the method for analyzing T. [O] in the formula (3) is a method using spark discharge emission spectroscopy, which comprises the following steps.
A) Intensity ratio calculation step for obtaining the emission intensity ratio of aluminum and iron for each discharge pulse by a number of discharge pulses a) Step for calculating the alumina fraction obtained by the following formula.
Alumina fraction = number of pulses where the emission intensity ratio is greater than the threshold α / total number of pulses
Here, the threshold value α is the mode f 1 (1.5 ≦ f 1 ≦ 2.5) of the light emission intensity ratio obtained from the frequency distribution diagram with the light emission intensity ratio for each discharge pulse as the horizontal axis and the frequency as the vertical axis. X) Arrange the emission intensity ratio for each discharge pulse obtained by the intensity ratio calculation step from the smaller one, and the emission intensity ratio at a fixed position within 30% of the total number of pulses from the smaller one. And then calculating the alumina strength ratio (= alumina fraction × representative aluminum strength ratio) from the product of the alumina fraction obtained in the alumina fraction calculating step and the representative aluminum strength ratio d) the alumina strength ratio and T Quantification step to calculate T. [O] using the relational expression with. [O]
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WO2020255917A1 (en) * | 2019-06-17 | 2020-12-24 | Jfeスチール株式会社 | METHOD FOR ADDING Ca TO MOLTEN STEEL |
CN114309494A (en) * | 2021-12-30 | 2022-04-12 | 苏州石川制铁有限公司 | Casting method for dynamically controlling wire feeding speed of vermiculizer and nodulizer cored wire |
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JP2014005534A (en) * | 2012-05-28 | 2014-01-16 | Jfe Steel Corp | Steel material having excellent hic resistance and its production method |
WO2020255917A1 (en) * | 2019-06-17 | 2020-12-24 | Jfeスチール株式会社 | METHOD FOR ADDING Ca TO MOLTEN STEEL |
JPWO2020255917A1 (en) * | 2019-06-17 | 2021-09-13 | Jfeスチール株式会社 | Method of adding Ca to molten steel |
JP7060113B2 (en) | 2019-06-17 | 2022-04-26 | Jfeスチール株式会社 | Method of adding Ca to molten steel |
CN114309494A (en) * | 2021-12-30 | 2022-04-12 | 苏州石川制铁有限公司 | Casting method for dynamically controlling wire feeding speed of vermiculizer and nodulizer cored wire |
CN114309494B (en) * | 2021-12-30 | 2024-05-10 | 苏州石川制铁有限公司 | Casting method for dynamically controlling feeding speed of vermiculizer and nodulizer cored wire |
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