JP4051778B2 - Steel plate for cans suitable for 3-piece cans with good surface properties - Google Patents

Description

【００４９】
一方、比較のために、転炉出鋼後、300 ton の溶鋼をRH真空脱ガス装置にて脱炭処理し、Ｃ＝0.014 wt％、Si＝0.01wt％、Mn＝0.25wt％、Ｐ＝0.010 wt％、Ｓ＝0.002wt ％に調整するとともに、溶鋼温度を1590℃に調整した。この溶鋼中に、Alを1.2 〜1.6kg/ton 添加し脱酸処理を行った。脱酸処理後の溶鋼中のAl濃度は0.041 wt％であった（Alキルド鋼）。その後、FeTiを添加するとともに、成分調整を行った。この処理の後のTi濃度は0.040 wt％であった。
【００５０】
次に、この溶鋼を２ストランドスラブ連続鋳造装置にて鋳造し連鋳スラブを製造した。なお、このときの、タンディッシュ内溶鋼の介在物の平均的な組成は、95〜98wt％Al₂O₃, 5％以下のTi₂O₃ のクラスター状の介在物が主体であった。
【００５１】
鋳造時にタンディッシュならびに浸漬ノズル内にArガスを吹き込まなかった場合には、著しくノズルにAl₂O₃ が付着し、３チャージ目にスライディングノズルの開度が著しく増加し、ノズル詰まりにより鋳込みを中止した。また、Arガスを吹いた場合にも、ノズル内にはAl₂O₃ が大量に付着しており、８チャージ目にはモールド内の湯面の変動が大きくなり鋳込みを中止した。
【００５２】
次に、上記連鋳スラブはスラブ加熱温度：1150℃、仕上圧延温度：890 ℃、巻取り温度：680 ℃で1.8 mmまで熱間圧延したのち、酸洗・冷延して板厚0.18mmの冷延板とした。その後、750 ℃で20 s均熱の連続焼鈍型の短時間焼鈍を行い、介在物の調査、成形性調査試験（伸びフランジ割れ発生試験）及び錆発生の調査を行った。この冷延鋼板にはヘゲ、スリーバー、スケールなどの非金属介在物性の欠陥は0.45個/1000m−コイル認められた。
【００５３】
得られた冷延板のフランジ割れ試験の結果を、Ｓ− 5×（(32/40) Ca＋(32/140) REM) との関係で表１に示す。ここで、比較例１〜６は、Ｓ、Ca、REM の関係以外はこの発明に従う方法で製造した鋼であり、比較例７は比較用に溶製したAlキルド鋼である。
【００５４】
表１より、この発明の方法で溶製し、Ｓ− 5×（(32/40) Ca＋(32/140) REM) が0.0014wt％以下の鋼板は、優れた伸びフランジ特性を示した。なお、鋼板の錆発生率（０℃、湿度95％中に10時間放置後）については、発明鋼、比較鋼とも問題のない値であった。
【００５５】
（実施例２）
表２に示す成分組成を含み、残部は実質的に鉄からなる鋼を転炉で溶製し、この鋼スラブを表３に示す条件で熱間圧延、冷間圧延、連続焼鈍、そして二次冷延を行い、最終仕上板厚を0.16mmとした。そして、ハロゲンタイプの電気めっきラインにて25番相当の錫メッキを連続的に施してぶりきに仕上げた。比較として、同じ板厚に仕上げた従来鋼に対して同様の錫めっきを施し、以降の各種評価に供した。
【００５６】
【表２】

【００５７】
【表３】

【００５８】
このようにして得られた錫めっき鋼板の硬さHR30T 、耐食性試験そして製缶後の評価としてネックしわ発生率、フランジ割れ発生率の調査を行い、それを表４に示した。なお、耐食性試験は５％NaCl水溶液を用い、塩水噴霧試験機で溶接補修塗装部に塩水を連続噴霧し、20日後の錆発生面積を計測し、比較として従来鋼の数値に対して±20％以内を○、20％を超えるものを×、−20％より少ないものを◎と評価し、表４に示した。また、ネックしわ発生率の調査は、製缶機によりノーマルグレーン法（圧延方向が缶の円周方向となるように円筒成形する板取り方法）及びリバースグレーン法（圧延方向と直角の方向が缶の円周方向となるように円筒成形する板取り方法）により、市販の190 g 缶と同径の缶胴部を成形した後に、実験室の（口絞り加工機）により１段ネックを行った際のネックしわ発生の目視検査により評価し、また、フランジ割れ発生率の調査は、開口端部をトリム後、円錐台状のパンチを開口端に挿入しながら実缶のフランジ加工と同程度の加工率に至るまで開口端の径を広げる試験を行い、その際の割れの発生率で評価した。
【００５９】
表４から分かるように、発明鋼は従来鋼に比して、ノーマルグレーン法、リバースグレーン法のいずれを問わずフランジ割れは全く発生していなかった。また、ネックしわも全く発生しなかった。耐食性も従来鋼に比べて優れていた。
なお、表４中の酸化物系介在物組成は粒径１〜50μm の介在物を調査し、平均値（介在物サイズによる重み付けはせず）をとった。本発明の成分組成範囲になる試料は、介在物の個数の50％以上がTi酸化物：20wt％以上90wt％以下、CaO ，REM 酸化物の１種又は２種の合計：10wt％以上40wt％以下、Al₂O₃ ：40％以下の範囲内になることを確認している。
【００６０】
【表４】

【００６１】
【発明の効果】
この発明の鋼板は、その製造にあたり、連続鋳造時に浸漬ノズルの閉塞を引き起こすことがなく、極めて安定した連続鋳造が可能であり、また、錆が少なく、介在物や析出物による変形能の劣化がほとんどなく、かつ、クラスター状介在物による表面欠陥のない、表明性状が良好な溶接部の成形性に優れており、３ピース缶用鋼板として極めて優れている。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steel plate for cans (including those coated with a surface coating such as plating) particularly suitable for use in a three-piece can having good surface properties and being hard to rust.
[0002]
[Prior art]
A steel plate for a three-piece can is required to be soft and easy to make at the time of can making. On the other hand, as a can after making a can, sufficient can strength is required for various external force loads. In addition, it is important that the three-piece can has good flange formability of the welded portion. If the components and the manufacturing method are inappropriate, winding failure may occur due to a failure in flange forming. It is important as a characteristic of the steel plate used for 3 piece cans to improve the stretch flangeability of such a weld.
[0003]
  Regarding improvement of formability of a steel sheet including a welded portion, JP-A-63-192849IssueA method for lowering the melting point of inclusions by controlling the composition of inclusions as shown in the report, and adjusting the dissolved oxygen in steel as disclosed in JP-A-2-220735 to precipitate TiN and MnS A control method has been proposed. However, local deformability deteriorates due to the presence of MnS and steel oxides that extend long in the rolling process, and it has been difficult to obtain sufficient deformability.
  In the method disclosed in JP-A-5-9549, inclusions are CaO-Al.₂O_Three There was a problem that the system became a starting point of rust and the corrosion resistance deteriorated.
[0004]
[Problems to be solved by the invention]
  This invention was developed as a result of adding experiments, investigations, and studies to solve the above-mentioned problems of the prior art, has little rust, and there is almost no deterioration of deformability due to inclusions and precipitates. And there are no surface defects due to cluster inclusions.surfaceIt aims at proposing the steel plate for cans suitable for 3 piece which is excellent in the formability of the weld part with a good property.
[0005]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above-mentioned object, the inventors have controlled the composition of oxides and sulfides remaining in the steel, which is an important factor for solving these problems. I thought of it. That is, by controlling the composition of these inclusions within an appropriate range, and more preferably by optimizing the manufacturing process of these steel sheets, it is difficult to rust as a final product, has good surface properties, and is welded. It was found that a steel plate for cans suitable for a three-piece can having good formability of the part can be obtained.
[0006]
In other words, the oxide inclusions in the steel are controlled, the formation of giant cluster inclusions is suppressed, the fine dispersion is achieved in inclusions of 50 μm or less, and the amount of MnS in the steel is reduced. By making all oxides and sulfides in steel finer and non-ductile, the can-making characteristics required as a three-piece can and the ultra-thin ( It was found that a steel sheet having a thickness of 0.3 mm or less) can be obtained.
The present invention is based on the above findings.
[0007]
  That is, this invention
C: more than 0.005wt% and 0.10wt% or less,
Si: 0.2 wt% or less,
Mn: 0.05 to 1.0 wt%,
P: 0.04 wt% or less,
Ti: 0.015-0.10wt%,
Al: 0.001 to 0.01 wt%,
N: 0.02 wt% or less and
0.0005 ~ 0.01wt% of one or two of Ca and REM in total
In addition,
The content of one or two of S, Ca and REM is
S-5 × ((32/40) Ca + (32/140) REM) ≦ 0.0014wt%
The balance is Fe and the inevitable impurities composition, and oxide inclusions with a particle size of 1-50 μm are Ti oxide: 20 wt% or more90wt %Less thanOne or two of CaO and REM oxides: 10wt% or more40wt %Less than, Al₂O_Three: 40wt% or less, SiO ₂ : 30wt % And other oxides: 3 wt % Or less (however, Ti Oxide, CaO , REM Oxide 1 Seeds or two, Al ₂ O _Three , SiO ₂ And other totals 100wt %)A surface having a tensile strength of less than 540 MPa and at least one r value of 1.0 or less in the rolling direction and the direction perpendicular to the rolling direction (the direction forming 90 ° with the rolling direction on the plate surface), It is a steel plate for cans suitable for a three-piece can with good properties.
  In addition, this invention
C: more than 0.005wt% and 0.10wt% or less,
Si: 0.2 wt% or less,
Mn: 0.05 to 1.0 wt%,
P: 0.04 wt% or less,
Ti: 0.015-0.10wt%,
Al: 0.001 to 0.01 wt%,
N: 0.02 wt% or less and
0.0005 ~ 0.01wt% in total of one or two of Ca and REM
Including, and
Ni: 0.005 to 1.0 wt%,
Cr: 0.005 to 1.0 wt%,
Nb: 0.002 to 0.04 wt%,
B: 0.0002-0.005wt%
1 type or 2 types or more, and
The content of one or two of S, Ca and REM is
S-5 × ((32/40) Ca + (32/140) REM) ≦ 0.0014wt%
The balance is Fe and the inevitable impurities composition, and oxide inclusions with a particle size of 1-50 μm are Ti oxide: 20 wt% or more90wt %Less thanOne or two of CaO and REM oxides: 10wt% or more40wt %Less than, Al₂O_Three: 40wt% or less, SiO ₂ : 30wt % And other oxides: 3 wt % Or less (however, Ti Oxide, CaO , REM Oxide 1 Seeds or two, Al ₂ O _Three , SiO ₂ And the total of other oxides is 100wt %)A steel plate for cans suitable for a three-piece can with good surface properties, characterized in that the tensile strength is less than 540 MPa and the r value of at least one of the rolling direction and the direction perpendicular to the rolling direction is 1.0 or less. is there.
  In this invention,grainIt is more desirable to be composed of uniform and fine crystal grains having a diameter of 15 μm or less.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, the present invention will be described more specifically.
  In the present invention, a steel sheet with less rust is obtained by satisfying the conditions that Al is 0.001 wt% or more and 0.01 wt% or less, Ti is 0.015 wt% or more, and Ca and / or REM is 0.0005 wt% or more and 0.01 wt% or less. And At this time, the inclusion is Ti₂O_Three-CaO (and / or REM Oxide) -Al₂O_Three -SiO₂If the Ca concentration in the inclusions is 40 wt% or less, the starting point of rust does not occur. When the amount of Al exceeds 0.01 wt%, inclusions are Al₂O_Three-CaO system (and / or REM Therefore, the Ca concentration in the inclusions is about 50%, which becomes a starting point of rust and deteriorates the corrosion resistance.
  In order to improve the plastic deformability of steel sheets including welds,
1) Do not coarsen the oxides in the steel,
2) Do not coarsen the sulfides in the steel,
3) Refinement of crystal structure
is important.
[0009]
Regarding the prevention of coarsening of the oxide of 1) above, the Al content is 0.001 wt% or more and 0.01 wt% or less, the Ti content is 0.015 wt% or more, and the Ca and / or REM content is 0.0005 wt% or more and 0.01 wt%. % Or less.
In addition, to prevent the coarsening of the sulfide of 2), it is important to suppress MnS precipitated during solidification. This is because the presence of MnS extends during hot rolling and promotes cracking during final product can manufacturing. For this solution, it is necessary to fix (detoxify) S in the steel by Ca and / or REM which forms a more stable sulfide. Specifically, for the content of one or two of S, Ca, and REM,
S-5 × ((32/40) Ca + (32/140) REM) ≦ 0.0014wt%
(In the formula, S represents the amount of S (wt%), Ca represents the amount of Ca (wt%), and REM represents the amount of REM (wt%).)
It came to the idea that it was necessary to satisfy this relationship. That is, in order to fix S by the formation of CaS and REM sulfide, it is better that the addition amount of Ca and REM is larger, but the lower limit is 0.0014 wt% or less as the amount of S that is not fixed as shown by the above inequality. The experimental result that it was necessary to have been obtained.
[0010]
With regard to the refinement of the crystal structure in 3) above, by using fine crystal grains of 15 μm or less, a remarkable effect of improving stretch flangeability was confirmed in both the welded portion and the non-welded portion.
In addition, it is important not to increase the crystal grain size of the welded portion, and for that purpose, inclusions must be fine, that is, as described in 1) and 2) above, to prevent the inclusions from becoming coarse. is important.
As a result of various studies based on the above experimental results, the inventors have obtained the present invention.
[0011]
Next, the reason for limiting the component composition range in the steel sheet for cans of the present invention will be described.
C: more than 0.005 wt% and 0.10 wt% or less;
C is one of the important additive components in the present invention. By increasing the amount of C, the strength of the steel sheet as annealed can be determined. If the amount of C is 0.005 wt% or less, the crystal grains become too coarse, resulting in an increased risk of rough skin when applied for cans. However, when the amount of C is increased and the amount added exceeds 0.10 wt%, the amount of pearlite in the ferrite / pearlite structure increases and both hot rollability and cold rollability deteriorate, The corrosion resistance is also significantly lowered, which is not preferable for use as a steel plate for cans. Therefore, the amount of C exceeds 0.005 wt% and is 0.10 wt% or less. The amount of C has a direct effect on the hardness increase of the welded portion. The higher the amount, the higher the hardness of the welded portion. As a result, the formability of the welded portion is reduced. For this purpose, it is more preferable that the content be 0.07 wt% or less. Also, the lower limit is preferably 0.010 wt% or more from the viewpoint of ensuring the stability of the product material.
[0012]
Si: 0.2 wt% or less (excluding 0);
Si is a component necessary for deoxidation at the time of melting, but as the addition amount increases, the steel is solid-solution strengthened, resulting in hot deformation resistance, cold deformation resistance, and deformation resistance in secondary cold rolling after annealing. Any increase is not preferable. Moreover, although a detailed mechanism is unknown, when using as a steel plate for cans, a fall of corrosion resistance becomes remarkable. From the above, the upper limit of the amount of Si added was set to 0.2 wt%. A preferable lower limit value is not particularly limited, but is 0.002 wt% in view of an increase in cost required for de-Si.
[0013]
Mn: 0.05 to 1.0 wt%;
Mn, like Si, is effective for deoxidation during melting. It also has the effect of suppressing hot brittleness of steel. In order to exert these desirable effects, addition of 0.05 wt% or more is generally desirable. On the other hand, the present invention relates to a steel sheet that is subjected to cylindrical forming, flange forming, etc. for a three-piece can, and in particular, improvement of stretch flange workability is desired. Here, if the amount of Mn is 1.0 wt% or less, the amount of decrease in stretch flangeability due to its inclusion is small. Therefore, the upper limit of Mn is 1.0 wt%. If it is 0.7 wt% or less, it is more desirable.
[0014]
P: 0.04 wt% or less;
P has the effect of strengthening steel, and is a desirable component to be added when trying to obtain a high-strength steel sheet. However, P has a strong tendency to segregate, and the corrosion resistance of the surface tends to decrease. There are specific problems such as lowering the strength of the bonding interface. If the amount of P added is 0.04 wt% or less, such a problem does not occur. The lower limit is not specified, but about 0.005 wt% is considered to be a level that can be reduced without a significant increase in production cost.
[0015]
Ti: 0.015-0.10 wt%;
Ti is an important component in the present invention, and by deoxidizing Ti, fine oxide inclusions with a size of 50 μm or less are formed, and grain growth during cold rolling and annealing is controlled to refine crystal grains. And improve the strength-elongation balance. Furthermore, the fine oxide of Ti can improve the formability of the welded portion by suppressing the coarsening of the structure of the welded portion (particularly the heat affected zone). If the addition amount of Ti is less than 0.015 wt%, the addition effect, that is, the amount of fine oxide is too small, so that a desired effect cannot be obtained. However, if the amount of Ti exceeds 0.10 wt%, the hot rollability, the cold rollability, and the secondary cold rollability after annealing are significantly lowered, and the properties of the product surface are also markedly lowered. Therefore, Ti is set to a range of 0.015 to 0.10 wt%. In order to secure a more excellent surface property, the content is more preferably 0.05 wt% or less. Ti addition is also an important element in the control of the r value of the steel sheet described later.
[0016]
Al: 0.001 to 0.01 wt%;
Al is an important component in the present invention, and if it exceeds 0.01 wt%, deoxidation becomes Al deoxidation and a huge Al₂O_ThreeThere is a risk that defects such as rough skin at the time of canning become a problem because a large amount of clusters are generated, surface properties are deteriorated, and fine oxides of 50 μm or less that can control grain growth during cold rolling and annealing are reduced. Increase. Moreover, the effect of improving the surface properties is not exhibited. Therefore, it was limited to 0.01 wt% or less. More importantly, if the amount of Al is large, the inclusion composition is Al.₂O_Three-CaO and / or Al₂O_ThreeSince it is a REM oxide type, such inclusions are the starting point of rust and deteriorate the corrosion resistance, and the corrosion resistance, which is important for steel plates for cans, tends to decrease. Also from this point, the upper limit of Al was set to 0.01 wt%. On the other hand, the lower limit of Al is set to 0.001 wt% from the viewpoint of degassing and stabilizing the operation of continuous casting.
[0017]
N: 0.02 wt% or less (excluding 0);
Since N contributes as a solid solution strengthening component, when applied to extremely severe plastic working as in the present invention, it leads to a decrease in ductility, so it is desirable to reduce it as much as possible. In consideration of the amount of ductility deterioration accompanying the increase in N content, the upper limit was set to 0.02 wt%. A preferable lower limit value is not particularly limited, but is 0.001 wt% in consideration of an increase in manufacturing cost for preventing nitriding and a change in mechanical characteristics. Moreover, a preferable upper limit is 0.005 wt%, and if it is 0.003 wt% or less, it is more preferable.
[0018]
0.0005 to 0.01wt% of one or two of Ca and REM in total;
  Ca and metal REM (referring to rare earth elements such as La and Ce) are important components in the present invention, and one or two of Ca and REM must be added in an amount of 0.0005 wt% or more. That is, after deoxidizing Ti, one or two of Ca and REM are added so that the content becomes 0.0005 wt% or more, and the oxide composition in the molten steel is changed to Ti oxide: 20 wt% or more and 90 wt%. Or less, preferably 85 wt% or less, CaO and / or REM oxide:Tenwt% to 40wt%, Al₂O_ThreeIs a low-melting oxide oxide inclusion with a content of 40 wt% or less. If it does so, the adhesion to the nozzle of the Ti oxide containing a base metal can be prevented effectively at the time of continuous casting, and clogging of a nozzle can be prevented. Furthermore, CaO and / or REM oxide can contribute to the suppression of grain growth after cold rolling and annealing and the prevention of coarsening of the welded portion (particularly the heat affected zone). For these reasons, one or two of Ca and REM are added in a total amount of 0.0005 wt% or more. On the other hand, if the total amount of Ca and REM exceeds 0.01 wt%, the risk of surface defects increases, and the disadvantage of reduced corrosion resistance, which is important for steel sheets for cans, becomes obvious. The upper limit was limited to 0.01 wt%.
[0019]
(S-5 x ((32/40) Ca + (32/140) REM) ≤ 0.0014 wt%)
Since S is a harmful component to the workability of steel, it is desirable to reduce it as much as possible. However, excessive desulfurization treatment increases costs, so the upper limit is set to 0.01 wt% in consideration of the cost required for desulfurization treatment and the effect of improving the mechanical properties by desulfurization. A more preferred upper limit is 0.005 wt%.
In addition, S can exist as various sulfides in steel, but when it exists as MnS inclusions, it significantly extends in the rolling direction during hot rolling, and can be used during the can manufacturing of the final product. Helps crack.
In this respect, by adding Ca and REM, the form and non-ductility of the sulfide are improved, and the improvement of the formability of the processed part including the welded part, which is the main object of the present invention, becomes remarkable. According to the investigation by the inventors, the addition of Ca and REM is not clear for reasons, but it is considered that harmless sulfides up to about 5 times S of these elements by atomic ratio become harmless sulfides. Therefore, if the harmful amount of S, that is, the value of S-5 × ((32/40) Ca + (32/140) REM) is sufficiently small, the workability due to sulfide does not deteriorate. According to the investigation, it was found that there is no problem if the harmful amount of S is 0.0014 wt% or less.
[0020]
(O: 0.010 wt% or less)
O is a necessary component from the viewpoint of forming fine oxides, but if added over 0.010 wt%, coarse Al₂O_ThreeIs produced in large quantities, and the ductility during processing and the deep drawability deteriorate, so 0.010 wt% was made the upper limit. Moreover, a preferable upper limit is 0.007 wt%, and if it is 0.005 wt% or less, it is more desirable.
[0021]
Ni: 0.005 to 1.0 wt%: Cr: 0.005 to 1.0 wt%;
  Ni and Cr can be refined without strengthening the steel sheet, or can be easily deformed in a low temperature / high strain rate environment. The characteristics can be improved. Moreover, since any component has the effect of reducing the transformation point of steel, it is also effective in relaxing the conditions for regulating the hot finishing temperature. Therefore, in the present invention, if necessary, Ni andCrOne or two of these can be added. Both Ni and Cr exert a remarkable effect when added in an amount of 0.005 wt% or more, and this effect is not offset even when they are added in combination. However, even if added over 1.0 wt%, the effect tends to saturate, so the upper limit was set to 1.0 wt% in all cases. From the viewpoint of stabilizing the material, the range of 0.01 to 0.5 wt% is more preferable.
[0022]
Nb: 0.002 to 0.04 wt%;
Nb is extremely effective for refining the crystal grains of the steel sheet. Therefore, in this invention, Nb can be added as needed. By refining the crystal grains, the steel sheet for a three-piece can, which is the object of the present invention, exerts a remarkable effect on preventing the surface roughness after forming and improving the ductility in connection therewith. Nb exhibits a remarkable effect when added in excess of 0.002 wt%. However, even if Nb is added in excess of 0.04 wt%, the effect tends to saturate, and conversely, there is a possibility that the hot and cold deformation resistance of the steel is remarkably increased. The range was -0.04 wt%. From the viewpoint of stabilizing the material, 0.01 to 0.025 wt% is more preferable.
[0023]
B: 0.0002 to 0.005 wt%;
Addition of B contributes effectively to refinement of the structure of the steel sheet, as with Nb. In order to exhibit this desirable effect, it is generally necessary to add 0.0002 wt% or more. However, even if added over 0.005 wt%, the effect is saturated and the hot deformation resistance of the steel is remarkably increased. Based on the above, the range was 0.0002 to 0.005 wt%.
[0024]
In the steel satisfying the above component composition range, the oxide inclusions having a particle size of 1 to 50 μm are inclusions containing one or two of Ti oxide, CaO and REM oxide. Then it is particularly important. The inclusion as such a deoxidation product contains one or two of Ti oxide and CaO, REM oxide, more specifically, Ti oxide-CaO and / or REM oxide-Al.₂O_Three-SiO₂Ti-based oxide inclusions cause little rust, almost no deterioration of deformability due to inclusions and precipitates, and no surface defects due to cluster-like inclusions. The steel plate for cans as expected in the present invention has no adhesion of oxide to the nozzle.
[0025]
The reason why the oxide inclusions defined in the present invention are limited to those having a particle diameter of 1 to 50 μm is because inclusions in such a range can be regarded as inclusions generated by deoxidation, Inclusions with particle sizes greater than 50 μm are generally due to extraneous inclusions such as slag or mold powder. Al₂O_ThreeSome clusters are larger than this, but if the oxide composition of inclusions with a particle size of 50 μm or less satisfies the above requirements, a huge Al₂O_ThreeIt can be considered that the system cluster is also sufficiently reduced.
Such inclusions should be 80 wt% or more. The reason for this is that if it is less than 80 wt%, the inclusions are not sufficiently controlled, which may cause coil surface defects and nozzle clogging.
[0026]
  The composition of the oxide inclusions having a particle diameter of 1 to 50 μm is as follows: Ti oxide: 20 wt% or more and 90 wt% or less, CaO or REM oxide, one or two total: 10 wt% or more and 40 wt% or less, Al₂O_Three: 40wt% or less, SiO ₂ : 30wt % And other oxides: 3 wt % Or less (however, Ti Oxide, CaO , REM Oxide 1 Seeds or two, Al ₂ O _Three , SiO ₂ And the total of other oxides is 100wt %).
[0027]
  When the inclusion Ti oxide is less than 20wt%, it is not Ti deoxidized steel but Al deoxidized steel.₂O_ThreeNozzle clogging occurs due to increased concentration. In addition, as the CaO and REM oxide concentration increases, the rusting property becomes remarkable.20wt %more thanAnd On the other hand, when the Ti oxide concentration exceeds 90 wt%, the ratio of CaO and REM oxide decreases and nozzle clogging occurs. Therefore, the Ti oxide concentration is set to 20 wt% or more and 90 wt% or less. More preferably, it is 30 wt% or more and 80 wt% or less.
[0028]
Further, if the total of one or two of CaO and REM oxides in the inclusion is less than 10 wt%, the inclusion does not have a low melting point and causes the nozzle to be blocked as described above. On the other hand, if it exceeds 40 wt%, the inclusions will subsequently absorb S and change to water-solubility, which becomes the starting point of rust, thus reducing the corrosion resistance. A more preferable range is 20 to 40 wt%.
[0029]
In addition, Al in the inclusion₂O_ThreeWhen the content exceeds 40 wt%, not only the nozzle clogging occurs due to the high melting point composition, but also the inclusions are clustered, increasing non-metallic inclusion physical defects in the product plate. In addition, when Al is hardly contained in steel, Al in inclusions₂O_ThreeIs almost negligible.
[0030]
  furtherThe oxide inclusions may contain oxides other than those listed above, and the amount of oxides other than those listed in that caseageThe, SiO₂About 30wt% or less(However, 0 wt %including),Other oxides (MnOetc)about,3wt% or less(However, 0 wt %including)To controlTheThe reason for this is that if these amounts exceed the respective amounts, it cannot be said that the titanium killed steel is an object of the present invention, and under such a composition, there is no nozzle clogging even without adding Ca, and there is also a problem of rusting. This is because it disappears. Moreover, SiO in the inclusions₂In order to contain MnO, it is preferable to set the Si and Mn concentrations of molten steel to Mn / Ti> 100 and Si / Ti> 50 in consideration of the oxide formation tendency. Cause deterioration of surface properties.
[0031]
The steel sheet of the present invention has a tensile strength of less than 540 MPa. When the tensile strength (TS) is 540 MPa or more, the difference in strength between the base metal and the welded part (heat affected zone) increases, resulting in concentrated processing deformation in the welded part, leading to defects during processing. This is because the shape freezing property also deteriorates due to the increase in yield strength accompanying the increase in strength. From the viewpoint of can body strength, it is desirable that the pressure be 400 MPa or more. TS is controlled to the target value mainly by controlling the content of strengthening elements (Mn, Si, P, etc.) and the skin pass rolling performed after annealing or the rolling reduction of secondary cold rolling.
[0032]
Moreover, the control of the texture of the steel sheet is also important as a three-piece can material. When the can is made, the neck-in after making the can has a texture where the r value of the material corresponding to the circumferential direction of the can body (the state where the secondary rolling is not performed after recrystallization annealing) is 1.0 or less. This is important for preventing the occurrence of defects such as wrinkles during molding.
Therefore, in a normal so-called normal grain can (can where the circumferential direction of the can body corresponds to the L direction of the steel plate), the L direction (rolling direction) of the steel plate and the reverse grain can (the circumferential direction of the can body is the C direction of the steel plate). In the C direction (the direction perpendicular to the rolling direction) of the steel sheet is important. As a result of various can manufacturing experiments, it is clear that if the r value of the material in the direction corresponding to the circumferential direction of the can body exceeds 1.0, wrinkle defects and shape defects are likely to occur during neck-in molding. Based on that.
It has also become clear that the Ti—Ca-added steel of the present invention is suitable for producing such a steel sheet having a reduced r value in the L or C direction.
The r value is measured by a so-called tensile method. However, in the case where the secondary cold rolling is performed after annealing in the production stage of the product, since the ductility is lowered, it is easy to cause necking. A strain of 20% cannot be applied in a uniform elongation range. As a result of various investigations, if the r value measured in the as-annealed state or with a light skin pass of several percent does not exceed 1.0, the secondary cold-rolled material similarly has problems during neck-in forming. I knew it was n’t there. In other words, it is important for preventing the occurrence of defects during neck-in forming that the r value does not exceed 1.0 when the recrystallized texture is sufficiently maintained (as-annealed or in a light skin pass state).
In addition, in order to obtain a texture corresponding to an r value of 1.0% or less with the raw material, in addition to Ti-Ca addition, primary cold rolling is performed under high pressure, annealing is performed at low temperature, and the like in the L and C directions. In both cases, it is preferable to decrease the r value (although Δr slightly increases on the negative side).
The thickness of the steel sheet according to the present invention is desirably 0.3 mm or less so that the merit of thinning can be obtained.
[0033]
When the steel sheet of the present invention has a structure composed of uniform and fine crystal grains having a crystal grain size of 15 μm or less, even in an ultrathin steel sheet, such as a poor appearance due to surface roughness after forming, a decrease in elongation caused by this, etc. Problems can be avoided. Accordingly, it is preferable to have a structure composed of uniform and fine crystal grains having a crystal grain size of 15 μm or less, and it is more preferable that the grain size be 12 μm or less. Uniform means that it is not a so-called mixed grain structure containing coarse grains, and the uniform and fine structure is to adjust the steel composition and hot rolling conditions (slab heating temperature, finishing temperature, etc. described later). Can be obtained.
[0034]
Next, the manufacturing method of the steel of this invention is demonstrated.
In this invention, the reason why Ti as an adjustment component is Ti: 0.015 wt% or more is that if the Ti content is less than 0.015 wt%, the oxygen removal capacity is weak, the total oxygen concentration in the molten steel becomes high, elongation, drawing, etc. This is because the material characteristics deteriorate. In this case, it is conceivable to increase the concentration of Si and Mn to increase the deoxidizing power, but if Ti is less than 0.015 wt%, SiO₂Or a large amount of inclusions containing MnO causes hardening of the steel material and deterioration of plating properties. In order to prevent this, it is necessary to contain Ti so that (wt% Mn) / (wt% Ti) <100. In that case, the Ti oxide concentration in the inclusions is 20% or more.
[0035]
In producing the titanium killed steel sheet according to the present invention, first, the molten steel is deoxidized with a Ti-containing alloy such as FeTi, and oxide inclusions mainly composed of Ti oxide are generated in the steel. The inclusions are not in the form of large clusters as in the case of deoxidation with Al, but are mostly granular and ruptured with a size of about 1 to 50 μm. However, if the Al concentration exceeds 0.010 wt% at this time, huge Al₂O_ThreeA cluster is generated. Such Al₂O_ThreeEven if the Ti alloy is added to increase the Ti concentration, the cluster cannot be reduced and remains in the steel as cluster-like inclusions. Therefore, with respect to the steel sheet according to the present invention, it is preferable to first produce Ti oxide in the molten steel at the stage of production.
[0036]
Under the present invention, the yield of the Ti alloy is poor compared to the conventional method of deoxidizing with Al, and the inclusion composition adjusting alloy is expensive because it contains Ca and REM. For this reason, it is economically preferable to add such an alloy into the molten steel so that the amount of the alloy is as small as possible within the range in which the composition of inclusions can be controlled. In this sense, prior to the addition of a deoxidizing agent such as a Ti-containing alloy, it is desirable to perform preliminary deoxidation in order to reduce dissolved oxygen in the molten steel and FeO and MnO in the slab. This preliminary deoxidation is preferably performed by deoxidation with a small amount of Al so that Al in the molten steel after deoxidation is 0.010 wt% or less, and addition of Si, FeSi, Mn, and FeMn.
[0037]
As mentioned above, Ti produced by Ti deoxidation₂O_ThreeA steel plate in which 70% or more of the Ti oxide inclusions are produced is free from surface defects due to cluster inclusions because the inclusions are dispersed in the steel in a size of about 2 to 20 μm. However, Ti oxide is in a solid state in molten steel, and ultra-low carbon steel has a high solidification temperature, so it grows on the inner surface of the tundish nozzle in the form of taking in the metal, and clogs the nozzle. There is a risk of triggering.
[0038]
Therefore, in the steel sheet according to the present invention, after deoxidizing with a Ti alloy, either one or two of Ca and REM are further added so as to be 0.0005 wt% or more, and the grain size in the molten steel is 1 to 50 μm. Ti oxide: 20 wt% or more and 90 wt% or less, preferably 85 wt% or less, CaO and / or REM oxide: 5 wt% or more and 40 wt% or less, Al₂O_ThreeIs a low-melting oxide oxide inclusion with a content of 40 wt% or less. If it does so, it will become possible to prevent effectively adhesion to the nozzle of Ti oxide containing bullion. More preferable inclusions are Ti oxide: 30 wt% to 80 wt%, CaO 2 REM oxide (La₂O_Three, Ce₂O_ThreeEtc.): 10wt% or more and 40wt% or less, Al₂O_Three : 20wt% or less, other (SiO₂, MnO, etc.): 10 wt% or less.
The composition of such oxide inclusions is measured by performing quantitative analysis on each inclusion using EPMA or a scanning electron microscope having an EDX function. Although it is most desirable that all the inclusions in the steel analyzed in this way satisfy the above composition, in practice, the number of inclusions having a size of 1 to 50 μm is 50% or more. Is within the above composition range, the various properties of the hot-rolled steel sheet as the object of the present invention are achieved. In addition, the largest diameter in each grain shall be used for a particle size.
[0039]
In this invention, when the composition of the inclusions to be generated is controlled as described above, it is possible to completely prevent oxides and the like from adhering to the inner surface of the tundish nozzle and the immersion nozzle of the mold during continuous casting. Therefore, Ar and N are used to prevent adhesion of oxides in tundish and immersion nozzles.₂It is no longer necessary to blow in gas. As a result, it is possible to prevent the occurrence of powder defects in the slab due to powder entrainment during continuous casting and bubble defects due to the blown gas in the slab.
[0040]
Regarding the hot rolling process after continuous casting, the slab heating temperature is preferably 900 to 1300 ° C. At slab heating temperatures below 900 ° C, the load load during rolling becomes too high, causing operational problems. On the other hand, at a high temperature exceeding 1300 ° C., the crystal grain size before rolling becomes too large, so that the hot-rolled mother plate is not refined. Therefore, the slab heating temperature is preferably 900 to 1300 ° C. Of these, a slab heating temperature of 1200 ° C. or lower is preferable from the viewpoint of deep drawability. Further, continuous casting-direct rolling (CC-DR) and DHCR (direct hot charge rolling) in which a continuously cast slab is inserted into a heating furnace with a hot piece are preferable from the viewpoint of energy saving.
[0041]
The hot rolling end temperature is preferably 650 to 960 ° C. At temperatures lower than 650 ° C, in addition to a significant increase in the rolling load of the steel sheet, the structure becomes non-uniform in any of the thickness direction, width direction, and longitudinal direction, which causes the material at each of these positions to become uneven. Variations are also noticeable. When the temperature is higher than 960 ° C, the risk of generating scale flaws on the steel sheet surface becomes extremely high, and the crystal grain size increases. The hot rolling end temperature is also important for controlling the texture of the steel sheet, and is preferably within the above temperature range.
In addition, the coil winding temperature after hot rolling is more advantageous for coarsening of precipitates as the temperature is higher, but if it is too high, the scale becomes too thick, and problems such as an increase in crystal grain size occur. 400 to 750 ° C is preferred.
[0042]
After hot rolling, pickling and cold rolling are performed before annealing.
In pickling, the scale layer on the surface is removed with normal hydrochloric acid or sulfuric acid. In particular, in the case of a steel plate having a thin scale phase, the pickling process can be omitted.
In the cold rolling, in order to obtain a uniform material, it is preferable that the reduction ratio of the (primary) cold rolling is 80% or more in the ultrathin steel plate targeted by the steel plate of the present invention. In order to obtain a texture corresponding to an r value of 1.0 or less, the preferred cold rolling reduction ratio is 90% or more.
[0043]
Although annealing can be applied to either continuous annealing or batch annealing, continuous annealing is recommended from the viewpoint of the efficiency of annealing work and the uniformity of the material. Annealing needs to be performed at the recrystallization temperature or higher. At a temperature lower than the recrystallization temperature, partial recrystallization occurs, and it is extremely difficult to obtain a shape of a steel sheet that can satisfy the standard after secondary cold rolling after annealing.
In order to obtain desired fine grains and recrystallized texture, the annealing temperature is particularly preferably in the range of 680 to 780 ° C.
[0044]
In the secondary cold rolling after annealing, the rolling reduction is adjusted to obtain a target hardness. 40% or less is recommended from the viewpoint of material stability. When secondary cold rolling is applied exceeding 40%, the heat-affected zone of the welded part is particularly softened, and the risk of cracking when the welded part is flanged is significantly increased. Absent. A preferable secondary cold rolling reduction ratio is about 1% to 15%.
[0045]
【Example】
Example 1
After converter steelmaking, 300 ton molten steel was decarburized with RH degassing equipment, C = 0.014 wt%, Si = 0.01 wt%, Mn = 0.25 wt%, P = 0.010 wt%, S = 0.005 〜 While adjusting to 0.009 wt%, the molten steel temperature was adjusted to 1585-1615 degreeC. In this molten steel, Al was added in an amount of 0.2 to 0.8 kg / ton, and preliminary deoxidation was performed for 3 to 4 minutes to reduce the dissolved oxygen concentration in the molten steel to 55 to 260 ppm. The Al concentration in the molten steel at this time was 0.001 to 0.005 wt%. And 70 wt% Ti-Fe alloy was added to this molten steel 0.8-1.8kg / ton, and Ti deoxidation was carried out over 8-9 minutes. Then, after adjusting the components, the molten steel contains 30wt% Ca-60wt% Si alloy, an additive mixed with metal Ca, Fe, 5-15wt% REM, or 90wt% Ca-5wt% Processing was performed by adding 0.05 to 0.5 kg / ton of Fe-coated wire of Ca alloy such as Ni alloy and REM alloy. After this treatment, the Ti concentration is 0.026 to 0.058 wt%, the Al concentration is 0.001 to 0.005 wt%, the Ca concentration is 0.0000 to 0.0036 wt%, the REM concentration is 0.0000 to 0.0021 wt%, and the sum of the Ca and REM concentrations is It was 0.0005-0.0043 wt%.
[0046]
Next, this steel was cast with a two-strand slab continuous casting apparatus to produce a continuous cast slab. Ar gas was not blown into the tundish and immersion nozzle during casting. As observed after continuous casting, there was almost no deposit in the tundish and the immersion nozzle.
[0047]
Next, the continuous cast slab was hot-rolled to a thickness of 1.8 mm. The hot rolling conditions were slab heating temperature: 1130 ° C, finish rolling temperature: 890 ° C, and hot rolling coiling temperature: 620 ° C. The hot-rolled steel sheet was pickled and cold-rolled to obtain a cold-rolled sheet having a thickness of 0.18 mm. After that, a short-time annealing of a 20 s soaked continuous annealing type at 740 ° C. was performed, and a flange cracking evaluation test and an investigation of rust generation were performed. Table 1 shows the results of the investigation on the steel composition and flange crackability. At this time, most of the oxide inclusions had a width of 50 μm or less. The breakdown of oxide is Ti₂O_Three: 60-70%, CaO + REM oxide: 20-30%, Al₂O_Three: 15% or less. In this cold-rolled sheet, defects of non-metallic inclusion physical properties such as heges, slivers, and scales were found to be 0.00 to 0.02 pieces / 1000 m-coil or less.
[0048]
[Table 1]

[0049]
On the other hand, for comparison, 300 ton of molten steel was decarburized by RH vacuum degassing equipment after the converter steel, C = 0.014 wt%, Si = 0.01 wt%, Mn = 0.25 wt%, P = The molten steel temperature was adjusted to 1590 ° C. while adjusting 0.010 wt% and S = 0.002 wt%. The molten steel was deoxidized by adding 1.2 to 1.6 kg / ton of Al. The Al concentration in the molten steel after deoxidation was 0.041 wt% (Al killed steel). Thereafter, FeTi was added and the components were adjusted. The Ti concentration after this treatment was 0.040 wt%.
[0050]
Next, this molten steel was cast with a two-strand slab continuous casting apparatus to produce a continuous cast slab. At this time, the average composition of inclusions in the molten steel in the tundish is 95 to 98 wt% Al.₂O_Three, Ti below 5%₂O_ThreeThe cluster-like inclusions were mainly.
[0051]
If Ar gas is not blown into the tundish and immersion nozzle during casting, the nozzle₂O_ThreeAttached, the opening of the sliding nozzle increased significantly at the third charge, and casting was stopped due to nozzle clogging. In addition, even when Ar gas is blown,₂O_ThreeA large amount of was attached, and the fluctuation of the molten metal surface in the mold increased at the 8th charge, and casting was stopped.
[0052]
Next, the continuous cast slab was hot-rolled to 1.8 mm at a slab heating temperature of 1150 ° C, a finish rolling temperature of 890 ° C and a winding temperature of 680 ° C, and then pickled and cold-rolled to a thickness of 0.18 mm. Cold-rolled sheet was used. After that, short-time annealing was performed in a continuous annealing mold of 20 s soaking at 750 ° C., and the inclusions were investigated, the formability investigation test (elongation flange crack generation test), and the rust generation investigation. This cold-rolled steel sheet was found to have defects of non-metallic inclusions such as heges, three bars and scales of 0.45 / 1000 m-coil.
[0053]
The results of the flange cracking test of the obtained cold-rolled sheet are shown in Table 1 in relation to S-5 × ((32/40) Ca + (32/140) REM). Here, Comparative Examples 1 to 6 are steels manufactured by the method according to the present invention except for the relationship of S, Ca and REM, and Comparative Example 7 is Al killed steel melted for comparison.
[0054]
From Table 1, the steel sheet melted by the method of the present invention and having S-5 × ((32/40) Ca + (32/140) REM) of 0.0014 wt% or less showed excellent stretch flange characteristics. Incidentally, the rust generation rate of the steel sheet (after standing for 10 hours in 0 ° C. and 95% humidity) was a value with no problem in both the inventive steel and the comparative steel.
[0055]
(Example 2)
Including the component composition shown in Table 2, the remainder is made of steel substantially made of iron in a converter, and this steel slab is hot-rolled, cold-rolled, continuously annealed, and secondary under the conditions shown in Table 3 Cold-rolled to a final finished thickness of 0.16 mm. Then, tin plating equivalent to No. 25 was continuously applied on a halogen type electroplating line to finish it with a tinplate. As a comparison, the same tin plating was applied to the conventional steel finished to the same plate thickness and used for various subsequent evaluations.
[0056]
[Table 2]

[0057]
[Table 3]

[0058]
The hardness HR30T of the tin-plated steel sheet thus obtained, the corrosion resistance test, and the evaluation after the can making were investigated for the occurrence rate of neck wrinkles and the rate of occurrence of flange cracking. In addition, the corrosion resistance test uses a 5% NaCl aqueous solution, and salt water is continuously sprayed on the weld repair coating part with a salt spray tester, and the rust generation area after 20 days is measured. The results are shown in Table 4. The results were evaluated as ○, less than -20%, and ◎. In addition, the neck wrinkle occurrence rate was investigated by using the normal grain method (a plate cutting method in which the rolling direction is the circumferential direction of the can) and the reverse grain method (the direction perpendicular to the rolling direction is a can). After forming a can body of the same diameter as a commercially available 190 g can by a cylindrical capping method so that it is in the circumferential direction, a one-stage neck was made by a laboratory (mouth drawing machine). In addition, it was evaluated by visual inspection of the occurrence of neck wrinkles at the same time, and the investigation of the rate of occurrence of flange cracking was similar to the flange processing of actual cans while trimming the opening end and inserting a truncated cone punch into the opening end. A test was conducted to increase the diameter of the open end until the processing rate was reached, and the crack generation rate at that time was evaluated.
[0059]
As can be seen from Table 4, the inventive steel had no flange cracks at all compared to the conventional steel regardless of the normal grain method or the reverse grain method. Neck wrinkles were not generated at all. Corrosion resistance was also superior to conventional steel.
The oxide inclusions in Table 4 were investigated for inclusions having a particle size of 1 to 50 μm and averaged (not weighted by inclusion size). In the sample having the component composition range of the present invention, 50% or more of the number of inclusions is Ti oxide: 20 wt% or more and 90 wt% or less, and the total of one or two of CaO and REM oxide: 10 wt% or more and 40 wt% Hereafter, Al₂O_Three : Confirmed to be within the range of 40% or less.
[0060]
[Table 4]

[0061]
【The invention's effect】
The steel sheet according to the present invention does not cause the clogging of the immersion nozzle during the continuous casting, enables extremely stable continuous casting, has little rust, and deteriorates deformability due to inclusions and precipitates. There is almost no surface defect due to cluster-like inclusions, and the formability of the welded portion with good manifestation properties is excellent, and it is extremely excellent as a steel plate for a three-piece can.

Claims (3)

C: more than 0.005wt% and 0.10wt% or less,
Si: 0.2 wt% or less,
Mn: 0.05 to 1.0 wt%,
P: 0.04 wt% or less,
Ti: 0.015-0.10wt%,
Al: 0.001 to 0.01 wt%,
N: 0.02 wt% or less and
0.0005 ~ 0.01wt% in total of one or two of Ca and REM
In addition,
The content of one or two of S, Ca, and REM is the following formula S-5 × ((32/40) Ca + (32/140) REM) ≦ 0.0014 wt%
And the balance is Fe and inevitable impurities, and the oxide inclusions having a particle size of 1 to 50 μm are Ti oxide: 20 wt % or more and 90 wt % or less , one kind of CaO, REM oxide or two: more 10 wt% 40 wt% or less, Al ₂ O _3: 40wt% or less, SiO _2: 30 wt% or less, and other oxides: 3 wt% or less (, Ti oxide, CaO, 1 kind of REM oxides Or the total of Al ₂ O ₃ , SiO ₂ and other oxides is 100 wt %) , the tensile strength is less than 540 MPa, and the r value of at least one of the rolling direction and the perpendicular direction of rolling is 1.0. A steel plate for cans suitable for a three-piece can with good surface properties, characterized by the following: C: more than 0.005wt% and 0.10wt% or less,
Si: 0.2 wt% or less,
Mn: 0.05 to 1.0 wt%,
P: 0.04 wt% or less,
Ti: 0.015-0.10wt%,
Al: 0.001 to 0.01 wt%,
N: 0.02 wt% or less and
0.0005 ~ 0.01wt% in total of one or two of Ca and REM
Including, and
Ni: 0.005 to 1.0 wt%,
Cr: 0.005 to 1.0 wt%,
Nb: 0.002 to 0.04 wt%,
B: 0.0002-0.005wt%
1 type or 2 types or more, and
The content of one or two of S, Ca, and REM is the following formula S-5 × ((32/40) Ca + (32/140) REM) ≦ 0.0014 wt%
And the balance is Fe and inevitable impurities, and the oxide inclusions having a particle size of 1 to 50 μm are Ti oxide: 20 wt % or more and 90 wt % or less , one kind of CaO, REM oxide or two: more 10 wt% 40 wt% or less, Al ₂ O _3: 40wt% or less, SiO _2: 30 wt% or less, and other oxides: 3 wt% or less (, Ti oxide, CaO, 1 kind of REM oxides Or the total of Al ₂ O ₃ , SiO ₂ and other oxides is 100 wt %) , the tensile strength is less than 540 MPa, and the r value of at least one of the rolling direction and the perpendicular direction of rolling is 1.0. A steel plate for cans suitable for a three-piece can with good surface properties, characterized by the following: The steel plate for cans suitable for a three-piece can having good surface properties according to claim 1 or 2 , comprising crystal grains having a particle size of 15 µm or less.