JP3565131B2 - Steel sheet for 3-piece cans with excellent roll forming properties - Google Patents

Description

【００１９】
上記で得られためっき原板を、続いて、通常のめっき、塗装、焼付けを施し供試材１〜４を作成した。また、通常より大きな内部残留応力を付与することなしに、供試材と同じアルミキルド鋼スラブから熱間圧延、冷間圧延、連続焼鈍、調質圧延を施し、さらにめっき、塗装、焼付けを行った鋼板を比較材１〜４として作製した。
【００２０】
得られた供試材及び比較材について、コイル幅方向が長辺になるように、幅１０ｍｍ、長さ１００ｍｍに剪断し、さらに片面のみにシールテープを貼り、１規定の塩酸中での電気分解により表面のめっき層を除去し、これらを残留応力測定用のサンプルとした。さらに、しゅう酸と過酸化水素水の混合液に浸すことにより、片面のみ０．００５ｍｍずつ化学研磨した。片面のみ化学研磨していくと、内部残留応力のバランスがくずれ、サンプルに反りが生じるので、その反りの曲率を測定した。この作業を供試材、比較材とも、鋼板板厚が半分以下になるまで繰り返した。得られた結果より、化学研磨厚みと反り曲率の関係を求め、その結果を計算処理（板厚ｔの鋼板の表層深さａまで化学研磨した場合の曲率をφ（ａ）とすると、深さ（ａ）の残留応力σ（ａ）は、σ（ａ）＝Ｅ／６＊［（ｔ−ａ）^２＊ｄφ（ａ）／ｄａ − ４（ｔ−ａ）＊φ（ａ） ＋ ２∫^ａ _０φ（ｘ）ｄｘ ］ で表される。）することにより、サンプルの表面からの深さ位置毎の内部残留応力を求めた。図１に深さ位置と残留応力の関係を示す。
【００２１】
図１によれば、供試材は、比較材に比べ、鋼板表面と板厚中心部との残留応力の差が大きくなっていることがわかる。
【００２２】
続いて、表１に示すアルミキルド鋼スラブＮｏ１に対して熱間圧延、冷間圧延を行った後、連続焼鈍を行い、表面と裏面での焼鈍後の降温速度を種々変化させ、さまざまな内部残留応力を付与した鋼板を得た。次いで、通常の調質圧延を行った後、ローラーレベリングにより圧延方向の内部残留応力のみを低減し、コイル幅方向にのみ通常よりも大きな内部残留応力を付与して、板厚が約０．１９ｍｍ、ＹＰが約４３０ＭＰａの、さまざまな残留応力を有するめっき原板を作製した。得られためっき原板を、続いて、通常のめっき、塗装、焼付けを施し供試材を作成した。さまざまな残留応力を付与した供試材を用い、溶接缶用のブランクの寸法に剪断し、コイル幅方向について、実際のロールフォーミング加工を行い、巻幅を測定した。ここで、残留応力が約０ＭＰａの場合に、巻幅が０ｍｍになるように、ロールフォーマーを調整して行った。図２に表面と板厚中心部との残留応力の差（Δ）と巻幅の関係を示す。ここで、巻幅は、図３に示すように、ロールフォーミング加工により丸まったブランクの一端と反対側の端の間隔を巻幅として定義した。ブランクの端同士に重なりが生じた場合は、重なり幅を巻幅として負の値で表すものとする。また、図２において、引張残留応力は正の値で、圧縮残留応力は負の値で示し、表面の残留応力から板厚中心部の残留応力を引いた差の絶対値を残留応力の差（Δ）と定義した。
【００２３】
図２より、残留応力の差が大きくなるにつれ徐々に巻幅が小さくなっていき、８０ＭＰａで約４ｍｍ巻幅が低減され、ロールフォーミング効果が得られる。また、巻幅差４ｍｍというのは、板厚差０．００５ｍｍにより生じる巻幅差にほぼ等しく、例えば、実際の製缶工程において、板厚が０．００５ｍｍ異なる２種類の鋼板をロールフォーミングする場合に、板厚の薄い方の鋼板に残留応力８０ＭＰａを付与しておけば、２種類の鋼板は同等の巻幅を示す。よって、ロールフォーマーの装置調整をすることなしに、連続してロールフォーミングすることが可能になる。一方、付与する残留応力の差が８０ＭＰａ未満の場合、巻幅低減量が４ｍｍ未満になるため、ロールフォーミング効果が少ない。以上より、鋼板表面と板厚中心部との残留応力の差を８０ ＭＰａ以上に限定する。
【００２４】
本発明において、鋼板表面から０．００５ｍｍの位置より鋼板板厚の１／４の深さの位置までの範囲での残留応力の最大値を鋼板表面の残留応力と定義する。ここで、最表層０．００５ｍｍを除いた理由は、最表層では特異点的な残留応力を示すことがあるからである。
【００２５】
また、鋼板表面から鋼板板厚の１／２の深さ位置における残留応力を鋼板中心部の残留応力と定義する。
【００２６】
次に、鋼成分限定理由について説明する。
Ｃ量が０．００１％未満になると極端に軟質化し強度の確保が困難である。また０．０８％を超えると粗大なセメンタイトが析出しフランジ加工性を低下させるので缶用鋼板としてはふさわしくない。よって、Ｃ量は０．００１〜０．０８％が好ましい。
【００２７】
Ｓｉは耐食性を劣化させるため極力少ない方が望ましいが、不可避的に混入するため、上限を０．０４％とするのが好ましい。
【００２８】
Ｍｎは熱間圧延コイルの耳割れを防ぐために必要な元素であり、その効果を発揮するために下限を０．０５％とするのが好ましい。しかし、含有量が多いと製缶時の加工性を劣化させるため、上限を０．５％とするのが好ましい。
【００２９】
Ｐは耐食性を劣化させる。０．０５％超えでその影響が顕著となるので、上限を０．０５％とする。
【００３０】
Ｓは熱間圧延コイルの耳割れの原因になり、また介在物を生じさせてフランジ加工性低下の原因にもなるので、上限を０．０３％とするのが好ましい。
【００３１】
ｓｏｌ．Ａｌは溶鋼の脱酸を目的に添加されるが、ｓｏｌ．Ａｌの状態で０．０１％未満では十分な効果が得られず、一方、０．１％を超えるとその効果が飽和し、非金属介在物を増加させる。以上より０．０１〜０．１％とするのが好ましい。
【００３２】
Ｎは鋼板強度を上昇させる効果があるが、０．０２％超では、延性の低下を引き起こしフランジ加工性の面で好ましくない。一方、０．００２未満では軟質化し必要な強度の確保が困難になるため好ましくない。よって、Ｎ量は０．００２〜０．０２％とするのが好ましい。
【００３３】
本発明では、さらに、Ｎｂ、Ｔｉ、Ｂを含んでも良い。
Ｎｂは、炭素の固着により時効性を低減させる効果があるが、０．００２％未満ではその効果が小さくなりすぎる。一方、０．０６％を超えると組織の均一性に悪影響を及ぼす。以上より、０．００２〜０．０６％とするのが好ましい。
【００３４】
Ｔｉは、Ｎｂと同様の効果があるが、０．００２％未満では効果が小さくなりすぎ、０．０６％超えでは効果が飽和するので、０．００２〜０．０６％とする。
【００３５】
Ｂは、組織均一性を向上させる効果があるが、０．０００５％未満ではその効果が不足し、０．００５％超えでは加工性の劣化につながるため、０．０００５〜０．００５％とするのが好ましい。
【００３６】
また板厚に関しては、０．３ｍｍを超えた場合にロールフォーミング性の問題が生じることは稀であり、最近の缶用鋼板のゲージダウンの傾向を考慮すると、０．３ｍｍ以下が好ましい。
【００３７】
また、本発明のロールフォーミング性に優れた３ピース缶用鋼板の製造方法は残留応力が本発明範囲内であればよく、特に限定されない。
【００３８】
なお、残留応力は表面処理を施すことによる影響を殆ど受けないため、本発明の効果は冷延鋼板に表面処理を施すかどうかに拘わらず得られるものであり、本発明の対象は冷延鋼板かめっき等を施した表面処理鋼板（めっき鋼板）かどうかは問わない。すなわち、通常行われる冷延鋼板に錫めっき等を施しためっき鋼板、めっき後に塗装やラミネートを施した表面処理鋼板も本発明に含まれる。また、めっきの種類は問わず、金属クロム、クロム酸処理等のめっきでも良い。
【００３９】
さらに、本発明では、コイル幅方向の残留応力を限定しているが、コイル長手方向の残留応力は限定されない。
【００４０】
【実施例】
表１に示したアルミキルド鋼スラブに対して熱間圧延、冷間圧延を行った後、連続焼鈍を行い、焼鈍後の降温速度を表面と裏面で差をつけることにより、通常より大きな内部残留応力を付与した。次いで、通常の調質圧延または２次冷間圧延を行った後、ローラーレベリングにより圧延方向の内部残留応力のみを低減し、コイル幅方向にのみ通常よりも大きな内部残留応力を有するＳＲとＤＲのめっき原板を得た。上記で得られためっき原板を、続いて、通常のめっき、塗装、焼付けを施し実施例１〜４を作成した。
【００４１】
また、供試材と同じアルミキルド鋼スラブを用い、熱間圧延、冷間圧延を行い、次いで、通常より大きな内部残留応力を付与することなしに、連続焼鈍、調質圧延を施し、さらにめっき、塗装、焼付けを行った鋼板を比較例１〜４として作製した。
【００４２】
ＹＰは、調質圧延後に引張試験を行い測定した。また、残留応力は調質圧延後の残留応力とし、図１と同様の方法により求めた。
【００４３】
上記により得られた鋼板を溶接缶用のブランクの寸法に剪断し、コイル幅方向について、各Ｎｏ毎に比較例の巻幅が０になるようにロールフォーマーを調整しロールフォーミング加工を行い巻幅を測定した。ここで、巻幅の測定方法は図３と同様である。
【００４４】
得られた結果を鋼板成分等と併せて表２に示す。
【００４５】
【表２】

【００４６】
表２より、実施例では残留応力の差が本発明範囲内にあるので、巻幅が小さく、ロールフォーミング性に優れていることがわかる。
【００４７】
一方、比較例では残留応力の差が本発明範囲を外れるので、実施例に比べて巻幅が大きくなっている。
【００４８】
また、板厚、強度の異なる４種類の鋼板、いずれの場合においても比較例に比べて実施例は巻幅が小さく、スプリングバックの影響を受けずにロールフォーミング性に優れていることがわかる。
【００４９】
【発明の効果】
以上本発明によれば、ロールフォーミング性に優れた３ピース缶用鋼板を得ることができる。また、ＹＰを下げることなくロールフォーミング性が向上するので、ゲージダウンによって、あるいはゲージダウンと同時に缶体強度を確保する観点から鋼板を硬質化してもロールフォーミング性に悪影響を与えることはなく、製缶コストの低減が要求される３ピース缶用鋼板として好適である。さらに、ロールフォーミング工程において装置調整・改造を不要とするので、効率良く生産することができる。
【図面の簡単な説明】
【図１】深さ位置と残留応力の関係を示す図である。
【図２】表面と板厚中心部との残留応力の差（Δ）と巻幅の関係を示す図である。
【図３】巻幅の測定方法を示す図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is related to a 3-piece can steel sheet having excellent roll forming property.
[0002]
[Prior art]
Tin-free steel in which tin plate is tin-plated, metal chromium, and chromic acid treated are used as a steel plate for cans, beverage cans, aerosol cans, and the like. This tin-free steel can has a three-piece can consisting of a lid, a torso and a bottom, and a two-piece can with an integrated torso and bottom. Reduction of can cost is required. In particular, in the case of three-piece cans, it is required to reduce the thickness gauge of steel plates for can bodies in order to reduce material costs. However, when the thickness gauge of the steel plate for the can body is reduced, the influence of springback increases, and the roll forming property is reduced.
[0003]
Further, in order to prevent a reduction in the strength of the can body due to the reduction in thickness, the steel plate is hardened simultaneously with the reduction in thickness. Even when the strength (YP) is increased due to the hardening, the influence of springback is increased, so that the roll forming property is reduced.
[0004]
Conventionally, roll forming has been performed in the longitudinal direction of the coil. However, in recent years, roll forming in the coil width direction has been increasing in order to improve the board yield. Generally, since YP is larger in the coil width direction than in the coil longitudinal direction, even when roll forming is performed in the coil width direction, the influence of springback is increased, which is disadvantageous in terms of roll forming properties.
[0005]
While there are many factors that reduce the roll formability in this way, the only way to improve the roll formability is to deal with can forming manufacturers by modifying or adjusting the roll forming equipment at present. This hinders the improvement of performance.
[0006]
On the other hand, the only means on the raw material side is to reduce YP by softening the steel sheet.
[0007]
[Problems to be solved by the invention]
By the way, assuming that a steel plate is a completely elasto-plastic body that does not work harden, the following equation is generally established between springback and YP.
Δθ / θ = 3 (YP · r) / (E · t) −4 [(YP · r) / (E · t)] ³ (1)
Here, Δθ: springback angle, θ: bending angle, YP: yield stress, r: bending radius, E: Young's modulus, t: plate thickness
As described above, according to the above equation, there is no steel plate material factor that can be controlled with respect to the improvement of the roll forming property other than YP, and the roll forming property cannot be improved without lowering the YP.
[0009]
However, in recent years, it has become necessary to secure the strength of the can body due to the progress of gauge down, and it has become substantially difficult to lower YP.
[0010]
The present invention has been made in view of the above problems, and solves the problem of roll formability reduction that becomes apparent due to gauge down without lowering YP, and provides a three-piece can steel sheet excellent in roll formability. The purpose is to provide.
[0011]
[Means for Solving the Problems]
The present inventors have conducted various studies to solve the above-mentioned problems, and have obtained the following findings. In a three-piece steel sheet for a can, by applying a residual stress larger than usual before roll forming, a stress-strain curve in that direction can be changed. That is, when a tensile stress is applied to a portion where a compressive residual stress exists, or when a compressive stress is applied to a portion where a tensile residual stress exists, the YP at that portion is the sum of the original YP of the material and the residual stress. When a tensile stress is applied to a portion where a residual tensile stress exists or a compressive stress is applied to a portion where a residual compressive stress exists, the YP at that portion is the difference between the original YP of the material and the residual stress. When different residual stresses are applied to the surface of the steel sheet and the center of the thickness, the YP on the surface and the YP at the center of the thickness are different. Then, when viewed from the YP of the entire steel sheet, the YP on the stress-strain curve apparently decreases, and as a result, the deformation stress near the boundary between the elastic region and the plastic region decreases. In the roll forming process, since there are many deformed portions near the boundary between the elastic region and the plastic region, the relational expression between the springback and the YP no longer holds, and the springback is reduced due to the effect of the deformation stress reduction. As a result, the roll forming property is improved.
[0012]
The present invention has been made based on such knowledge, and the above-mentioned problems are solved by the following inventions.
[0013]
[1] By weight%, C : 0.001 to 0.08 %, Si : 0.04 % or less, Mn : 0.05 to 0.5 %, P : 0.05 % or less, S : 0.03 % or less, sol.Al : 0.01 to 0.1 %, N : 0.002 to 0.02 %, the balance being Fe and unavoidable impurities. In the coil width direction, the difference between the tensile or compressive residual stress at the steel sheet surface and the tensile or compressive residual stress at the center of the steel sheet thickness: Δ ≧ 80 MPa A three-piece steel sheet with excellent roll forming properties, characterized in that:
[0015]
[ 2 ] The roll formability according to [ 1 ], further comprising one or two of Nb: 0.002 to 0.06% and Ti: 0.002 to 0.06% by weight. Steel plate for 3 piece cans.
[0016]
[ 3 ] The steel sheet for a three-piece can excellent in roll forming properties according to the above [ 1 ] or [ 2 ], further containing B: 0.0005 to 0.005% by weight.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described specifically.
First, the residual stress of the steel sheet will be described.
After performing hot rolling and cold rolling on the aluminum-killed steel slab shown in Table 1, continuous annealing is performed, and the temperature reduction rate after annealing is made different between the front surface and the back surface, so that the internal residual stress larger than usual can be reduced. Granted. Next, after performing normal temper rolling or secondary cold rolling, only the internal residual stress in the rolling direction is reduced by roller leveling to obtain a plating sheet having an internal residual stress larger than normal only in the coil width direction. Was. Here, the plated base plate that has been subjected to normal temper rolling is referred to as single-reduce (hereinafter abbreviated as SR), and the plated base plate that has been subjected to the secondary cold rolling is referred to as double-reduce (hereinafter abbreviated as DR).
[0018]
[Table 1]

[0019]
The plating base plate obtained above was subsequently subjected to normal plating, painting, and baking to prepare test materials 1 to 4. In addition, without applying a larger internal residual stress than usual, hot rolling, cold rolling, continuous annealing, temper rolling was performed from the same aluminum killed steel slab as the test material, and further, plating, painting, and baking were performed. Steel sheets were produced as comparative materials 1 to 4.
[0020]
The obtained test material and comparative material were sheared to a width of 10 mm and a length of 100 mm so that the coil width direction became a long side, and a seal tape was applied to only one side, and electrolysis in 1N hydrochloric acid was performed. To remove the plating layer on the surface, and these were used as samples for measuring residual stress. Furthermore, by immersing in a mixed solution of oxalic acid and hydrogen peroxide solution, only one side was chemically polished by 0.005 mm. When only one side was chemically polished, the balance of the internal residual stress was lost, and the sample was warped. The curvature of the warpage was measured. This operation was repeated for both the test material and the comparative material until the thickness of the steel plate became half or less. From the obtained results, the relationship between the chemically polished thickness and the warpage curvature is determined, and the result is subjected to a calculation process (when the curvature when chemically polished to the surface depth a of a steel plate having a thickness t is φ (a), the depth The residual stress σ (a) in (a) is given by σ (a) = E / 6 * [(ta) ² * dφ (a) / da−4 (ta) * φ (a) +2} ^a ₀ φ (x) dx]) to obtain the internal residual stress at each depth position from the surface of the sample. FIG. 1 shows the relationship between the depth position and the residual stress.
[0021]
According to FIG. 1, it can be seen that the test material has a larger difference in residual stress between the steel sheet surface and the center part of the sheet thickness than the comparative material.
[0022]
Subsequently, after hot rolling and cold rolling were performed on the aluminum killed steel slab No. 1 shown in Table 1, continuous annealing was performed, and the temperature lowering rate after annealing on the front surface and the back surface was variously changed to obtain various internal residuals. A stressed steel sheet was obtained. Next, after performing normal temper rolling, only the internal residual stress in the rolling direction is reduced by roller leveling, and an internal residual stress larger than usual is applied only in the coil width direction, and the sheet thickness is about 0.19 mm. , YP was about 430 MPa, and plated original plates having various residual stresses were produced. The obtained plating base plate was subsequently subjected to normal plating, painting, and baking to prepare a test material. Using the test materials to which various residual stresses were applied, the material was sheared to the dimensions of a blank for a welding can, and the actual roll forming was performed in the coil width direction to measure the winding width. Here, the roll former was adjusted so that the winding width was 0 mm when the residual stress was about 0 MPa. FIG. 2 shows the relationship between the difference (Δ) in residual stress between the surface and the center of the sheet thickness and the winding width. Here, as shown in FIG. 3, the winding width was defined as the interval between one end and the other end of the blank that was rounded by roll forming. When the ends of the blanks overlap, the overlap width is represented by a negative value as the winding width. In FIG. 2, the tensile residual stress is a positive value, the compressive residual stress is a negative value, and the absolute value of the difference obtained by subtracting the residual stress at the center of the sheet thickness from the residual stress on the surface is the residual stress difference ( Δ).
[0023]
As shown in FIG. 2, as the difference in residual stress increases, the winding width gradually decreases. At 80 MPa, the winding width is reduced by about 4 mm, and the roll forming effect is obtained. In addition, the difference in winding width of 4 mm is almost equal to the difference in winding width caused by the difference in thickness of 0.005 mm. For example, in the actual can making process, when two types of steel plates having different thicknesses of 0.005 mm are roll formed. If a residual stress of 80 MPa is applied to the thinner steel sheet, the two types of steel sheets exhibit the same winding width. Therefore, it is possible to continuously perform roll forming without adjusting the roll former device. On the other hand, when the difference in the applied residual stress is less than 80 MPa, the roll width reduction amount is less than 4 mm, so that the roll forming effect is small. As described above, the difference in residual stress between the surface of the steel sheet and the center of the thickness is limited to 80 MPa or more.
[0024]
In the present invention, the maximum value of the residual stress in a range from the position of 0.005 mm from the surface of the steel sheet to a position of 1/4 of the thickness of the steel sheet is defined as the residual stress of the surface of the steel sheet. The reason for removing the outermost layer 0.005 mm is that the outermost layer may exhibit a singular point residual stress.
[0025]
In addition, the residual stress at a depth of １ ／ of the steel sheet thickness from the steel sheet surface is defined as the residual stress at the center of the steel sheet.
[0026]
Next, the reasons for limiting the steel components will be described.
If the amount of C is less than 0.001%, it becomes extremely soft and it is difficult to secure the strength. On the other hand, if the content exceeds 0.08%, coarse cementite precipitates and the workability of flanging deteriorates, so that it is not suitable as a steel sheet for cans. Therefore, the C content is preferably 0.001 to 0.08%.
[0027]
Si is desirably as small as possible to degrade corrosion resistance, but is inevitably mixed, so the upper limit is preferably made 0.04%.
[0028]
Mn is an element necessary to prevent cracking of the hot-rolled coil, and the lower limit is preferably set to 0.05% in order to exhibit the effect. However, if the content is large, the workability during can making is deteriorated, so the upper limit is preferably set to 0.5%.
[0029]
P deteriorates corrosion resistance. Since the effect becomes remarkable when it exceeds 0.05%, the upper limit is made 0.05%.
[0030]
Since S causes ear cracks of the hot-rolled coil and also causes inclusions to cause a reduction in flange workability, the upper limit is preferably set to 0.03%.
[0031]
sol. Al is added for the purpose of deoxidizing molten steel. If the Al content is less than 0.01%, a sufficient effect cannot be obtained, while if it exceeds 0.1%, the effect is saturated and nonmetallic inclusions increase. As described above, the content is preferably set to 0.01 to 0.1%.
[0032]
N has the effect of increasing the strength of the steel sheet, but if it exceeds 0.02%, the ductility is reduced, which is not preferable in terms of flange workability. On the other hand, if it is less than 0.002, it is not preferable because it becomes soft and it becomes difficult to secure necessary strength. Therefore, the N amount is preferably set to 0.002 to 0.02%.
[0033]
In the present invention, Nb, Ti, and B may be further included.
Nb has the effect of reducing the aging effect by fixing carbon, but if it is less than 0.002%, the effect is too small. On the other hand, if it exceeds 0.06%, the uniformity of the structure is adversely affected. As described above, the content is preferably set to 0.002 to 0.06%.
[0034]
Ti has the same effect as Nb, but if it is less than 0.002%, the effect is too small, and if it exceeds 0.06%, the effect is saturated.
[0035]
B has the effect of improving the uniformity of the structure, but if it is less than 0.0005%, the effect is insufficient, and if it exceeds 0.005%, the workability is deteriorated. Is preferred.
[0036]
When the sheet thickness exceeds 0.3 mm, a problem of roll forming property rarely occurs. Considering the recent tendency of gauge down of steel sheets for cans, the sheet thickness is preferably 0.3 mm or less.
[0037]
In addition, the method for producing a steel sheet for a three-piece can excellent in roll forming properties of the present invention is not particularly limited as long as the residual stress is within the range of the present invention.
[0038]
Since the residual stress is hardly affected by the surface treatment, the effects of the present invention can be obtained regardless of whether the surface treatment is performed on the cold-rolled steel sheet. It does not matter whether or not it is a surface-treated steel sheet (plated steel sheet) that has been subjected to plating or the like. That is, the present invention also includes a plated steel sheet in which a cold-rolled steel sheet is usually subjected to tin plating or the like, and a surface-treated steel sheet in which coating or lamination is performed after plating. Also, regardless of the type of plating, plating such as metal chromium or chromic acid treatment may be used.
[0039]
Furthermore, in the present invention, the residual stress in the coil width direction is limited, but the residual stress in the coil longitudinal direction is not limited.
[0040]
【Example】
After performing hot rolling and cold rolling on the aluminum-killed steel slabs shown in Table 1, continuous annealing is performed, and the cooling rate after annealing is made different between the front surface and the back surface, so that the internal residual stress is larger than usual. Was given. Next, after normal temper rolling or secondary cold rolling is performed, only internal residual stress in the rolling direction is reduced by roller leveling, and SR and DR having internal residual stress greater than normal only in the coil width direction are reduced. A plating base plate was obtained. The plating base plate obtained above was subsequently subjected to normal plating, painting and baking to prepare Examples 1 to 4.
[0041]
In addition, using the same aluminum killed steel slab as the test material, hot rolling and cold rolling are performed, and then, without giving a larger internal residual stress than usual, continuous annealing, temper rolling, and further plating, Painted and baked steel sheets were produced as Comparative Examples 1 to 4.
[0042]
YP was measured by performing a tensile test after temper rolling. The residual stress was defined as the residual stress after temper rolling, and was determined in the same manner as in FIG.
[0043]
The steel sheet obtained as described above is sheared to the dimensions of a blank for a welding can, and in the coil width direction, the roll former is adjusted so that the winding width of the comparative example becomes 0 for each No, and roll forming is performed. The width was measured. Here, the method of measuring the winding width is the same as in FIG.
[0044]
Table 2 shows the obtained results together with the steel sheet components and the like.
[0045]
[Table 2]

[0046]
From Table 2, it can be seen that in Examples, since the difference in residual stress was within the range of the present invention, the winding width was small and the roll forming property was excellent.
[0047]
On the other hand, in the comparative example, since the difference in the residual stress is out of the range of the present invention, the winding width is larger than that in the example.
[0048]
In each case of the four types of steel plates having different plate thicknesses and strengths, it can be seen that the example has a smaller winding width than the comparative example and is excellent in roll forming properties without being affected by springback.
[0049]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a three-piece steel sheet having excellent roll forming properties. Further, since the roll forming property is improved without lowering the YP, even if the steel sheet is hardened by gauge down or from the viewpoint of securing the strength of the can at the same time as the gauge down, the roll forming property is not adversely affected, and the roll forming property is not adversely affected. It is suitable as a three-piece steel plate for which a reduction in can cost is required. Further, since adjustment and remodeling of the apparatus are not required in the roll forming process, the production can be performed efficiently.
[Brief description of the drawings]
FIG. 1 is a diagram showing a relationship between a depth position and a residual stress.
FIG. 2 is a diagram showing a relationship between a difference (Δ) in residual stress between a surface and a center portion of a sheet thickness and a winding width.
FIG. 3 is a diagram illustrating a method of measuring a winding width.

Claims (3)

By weight%, C : 0.001 to 0.08 %, Si : 0.04 % or less, Mn : 0.05 to 0.5 %, P : 0.05 % or less, S : 0.03 % or less, sol.Al : 0.01 to 0.1 %, N : 0.002 to 0.02 %, And the balance consists of Fe and inevitable impurities, and in the coil width direction, the difference between the tensile or compressive residual stress near the steel sheet surface and the tensile or compressive residual stress at the steel sheet thickness center: Δ ≧ 80 MPa Excellent three-piece steel sheet with excellent roll forming characteristics. Claim One Further, in the steel sheet described in Nb : 0.002 ~ 0.06 %, Ti : 0.002 ~ 0.06 % Of either One Seed or Two Claims characterized by containing a seed One Excellent roll forming property described in Three Steel plate for piece cans. In addition, in weight percent, B : 0.0005 ~ 0.005 %. One Or Two Excellent roll forming property described in Three Steel plate for piece cans.

Images