JP3726371B2 - Steel plate for cans with high age-hardening properties and excellent material stability and method for producing the same - Google Patents

Description

【００３７】
【表２】

【００３８】
【表３】

【００３９】
表３から、本発明材は、十分な伸びと時効硬化量を有し、成形直前の強度は従来材とほぼ同等であるが、その後の実際の缶体として使用される段階では従来材に比して格段に高い強度を示すことがわかる。
【００４０】
次に、これら鋼板を塗装、焼き付け処理後、３ピース溶接缶に適用した場合の相違点を明らかにすべく、表１の鋼１に、表４に示す各製造条件を適用して板厚0.18ｍｍの鋼板を製造し、材質を調査すると共に曲げ成形による円筒成形試験を実施した。
降伏応力については製品コイルの長手方向１０ケ所で試験片を採取し、降伏応力（平均値）のほか標準偏差を調査した。なお、円筒成形試験では成形直前に、レベリング加工をおこない、直ちに円筒に成形する方法によった。この方法を用いた理由は、実際の製缶装置においては、円筒成形がおこなわれる直前にフレクサーと呼ばれる一種のレベリング機構が設置してあることを考慮し、より実製缶に近い成形条件を実現しようとするためである。成形後の缶の真円度の評価のため、缶断面の長軸と単軸を測定し、（長軸径一短軸径）／（長軸径）により偏平度を求めた。これらの試験結果を表５にまとめて示す。
【００４１】
【表４】

【００４２】
【表５】

【００４３】
表５から、発明例では、高い降伏応力を有しているにもかかわらず、そのばらつきは小さく、安定した材質制御が可能なこと、また、成形前の降伏応力が高いにもかかわらず、円筒の曲率半径が極めて安定することが明らかである。
なお、上記円筒成形の後、溶接を行い、フランジ成形性を調査したが、発明例の鋼板は、板厚精度が良好で、材質のばらつきが小さいことによると推定されるが、フランジ割れ発生率は従来例に比しておおむね３０％程度改善された。
【００４４】
図１、図２は、0.02wt％Ｃ−0.01wt％Si−0.25Mnwt％−0.01wt％Ｐ−0.008 wt％Ｓ−0.055 wt％Al−0.0045wt％Ｎ鋼を素材とし、加熱条件を変化させて固溶Ｎ量を変化させ、二次冷延圧下率を変化させた場合について降伏応力を比較したものである。
本発明に従って、固溶Ｎを利用することにより、より高い降伏応力が得られこと、しかもこれは高い２次冷延率の範囲でも、また、時効を行った後でも発揮されることがわかる。このとき、延性の劣化は伴うことがないため、固溶Ｎを利用する本発明鋼板は強度と延性のバランスに優れたものといえる。
【００４５】
【発明の効果】
以上説明したように、本発明では、熱延鋼板を製造するにあたり、化学組成、スラブの熱片挿入条件、熱延条件さらには冷延後の焼鈍条件などを適正化して、最終の製品段階で固溶状態のＮを十分な量、確保することによって、強度の高い、均一な微細組織が得られ、加工性を犠牲にすることなく、塗装、焼き付け後の硬化現象を利用した十分な缶体強度が確保可能となる。
したがって、このような成形性に優れた高強度缶用鋼板の出現は、３ピース缶、２ピース缶などの缶体の薄肉化による製缶コストの低減化に大きく寄与するものである。
【図面の簡単な説明】
【図１】時効処理による降伏応力の増加に及ぼす固溶Ｎ量の影響を示す図である。
【図２】焼鈍後の２次冷延圧下率と降伏応力との関係に及ぼす固溶Ｎ量の影響を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steel plate for cans that is suitable for use as a raw material for three-piece cans and two-piece cans by applying tin plating, chromium plating, and the like, and particularly relates to a thin steel plate for cans and a method for producing the same.
[0002]
[Prior art]
With the increase in consumption of various cans such as beverage cans, 18 liter cans, and pail cans, recently there has been an increasing demand for reduction in can manufacturing costs. Lowering the cost of can materials as well, the material thickness tends to decrease.
Despite such thinning of the plate thickness, the strength of the can as a can body must be maintained, and thus proposals for techniques for increasing the strength of the material itself have been attempted.
For example, the method disclosed in Japanese Patent Laid-Open No. 51-131413 uses a secondary cold rolling after annealing, so-called double reduction (hereinafter simply abbreviated as DR) to ensure the hardness of the steel sheet and reduce the thickness. It measures. In this method, the coiling temperature after hot rolling is controlled so that the steel sheet does not become excessively hard after DR, and solid solution N in the steel is fixed as AlN.
[0003]
[Problems to be solved by the invention]
However, as in this technique, using only the so-called work strengthening to increase the strength of the steel sheet has a drawback that the ductility is greatly lowered and the yield stress is increased, so that the formability is lowered. As a decrease in formability, for example, when shape freezeability is compared as an evaluation of workability, the amount of springback increases due to an increase in yield stress, which increases the risk of shape failure. .
[0004]
On the other hand, as another strengthening mechanism, there is a technique that uses a solid solution strengthening action by N or the like. For example, Japanese Patent Laid-Open No. 58-27930 proposes a technique for producing a hard tin plate that uses solute N as a strengthening element. This technology regulates the content of C and N as components, the coiling temperature during hot rolling, and the recrystallization annealing conditions after cold rolling, and if the surface hardness simply falls within the specified range, as in the past. It is an economical manufacturing method that does not have any problem for good applications.
However, this technique cannot control the variation in mechanical properties in the steel strip and cannot meet the high demands of recent users. This is because with the recent further expansion of can applications and the sophistication of the forming level, it is no longer possible to satisfy the usage characteristics required by users with the conventional regulation of only surface hardness. And it seems that the yield stress (YS), tensile strength (TS), and elongation (El), which are more general strength characteristics, are required to be uniform in the steel strip both before and after aging. It became.
[0005]
In addition, as an example in which solute N is actively used, there is a method proposed in Japanese Patent Publication No. 7-107117. This technique controls the hardness level by controlling the ingredients and hot rolling conditions, particularly the slab reheat temperature.
However, even with this technology, material uniformity is not sufficient for can applications, and the biggest problem is that this technology is a direct hot charge rolling, a new hot rolling process. It is difficult to apply to Rolling (hereinafter simply abbreviated as DHCR).
Note that DHCR is a process in which a continuously cast slab is inserted into a heating furnace as it is without being cooled to room temperature as in the prior art, and is extended and has a great effect on energy saving. It is.
[0006]
Then, the objective of this invention is providing the steel plate for cans which has large age-hardening property, has favorable ductility, and outstanding material stability, and its manufacturing method.
Another object of the present invention is a steel plate for cans having a stable age-hardening property with an increase in yield stress after forming of 10 MPa or more, an elongation of 20% or more, and excellent material stability even in a steel strip. And providing a manufacturing method thereof.
Here, as material stability, in addition to a stable increase in strength due to age hardening, a standard deviation of yield stress in the steel strip is 15 MPa or less.
Still another object of the present invention is to provide an advantageous production method by the DHCR process for producing the above steel plate for cans.
[0007]
[Means for Solving the Problems]
The inventors first conducted experiments and researches to solve the above-mentioned problems. As a result, in addition to the steel components, among the DHCR conditions, the insertion temperature into the heating furnace, the finish rolling finish temperature, the cooling after finish rolling, etc. By optimizing conditions such as coiling temperature and annealing conditions after cold rolling, control of ferrite structure and control of solid solution C and N, especially stable control of solid solution N in DHCR process As a result, the present invention has been completed.
[0009]
  That is, the gist configuration of the present invention is as follows.
(1) C: 0.0010 to 0.04 wt%, Si: 0.10 wt% or less, Mn: 0.1 to 1.5 wt%, P: 0.04 wt% or less, S: 0.01 wt% or less, Al: 0.005 to 0.060 wt%, N: 0.0020 to 0.0150 containing wt%, 25% or more of the above N amount, and containing 0.001 to 0.01 wt% of solid solution N, Nb: 0.003 to 0.020 wt%, Ti: 0.003 to 0.020 wt%, B: 0.0005 to 0.0020 A steel plate for cans having high age-hardening properties and excellent material stability, characterized in that it contains any one or more selected from wt%, and the balance consists of Fe and inevitable impurities.
[0010]
(2) C: 0.0010 to 0.04 wt%, Si: 0.10 wt% or less, Mn: 0.1 to 1.5 wt%, P: 0.04 wt% or less, S: 0.01 wt% or less, Al: 0.005 to 0.060 wt%, N: 0.0020 to 0.0150 including wt%, 25% or more of the above N amount, and 0.001 to 0.01 wt% of solid solution N, Cu: 0.5 wt% or less, Ni: 0.5 wt% or less, Cr: 0.5 wt% or less, Mo: Steel plate for cans having high age-hardening properties and excellent material stability, characterized by containing one or more selected from 0.5 wt% or less, the balance being Fe and inevitable impurities.
[0011]
(3) C: 0.0010 to 0.04 wt%, Si: 0.10 wt% or less, Mn: 0.1 to 1.5 wt%, P: 0.04 wt% or less, S: 0.01 wt% or less, Al: 0.005 to 0.060 wt%, N: 0.0020 to 0.0150 containing wt%, 25% or more of the above N amount, and containing 0.001 to 0.01 wt% of solid solution N, Nb: 0.003 to 0.020 wt%, Ti: 0.003 to 0.020 wt%, B: 0.0005 to 0.0020 Contains one or more selected from wt%, and further selected from Cu: 0.5 wt% or less, Ni: 0.5 wt% or less, Cr: 0.5 wt% or less, Mo: 0.5 wt% or less A steel plate for cans having high age-hardening properties and excellent material stability, characterized in that it contains any one or more of them, and the balance is Fe and inevitable impurities.
[0012]
(Four) C: 0.0010 to 0.04 wt%, Si: 0.10 wt% or less, Mn: 0.1 to 1.5 wt%, P: 0.04 wt% or less, S: 0.01 wt% or less, Al: 0.005 to 0.060 wt%, N: 0.0020 to 0.0150 wt%Contains Nb : 0.003 ~ 0.020wt %, Ti : 0.003 ~ 0.020wt %, B: 0.0005 ~ 0.0020wt %, Any one or more selected from%, with the balance being Fe And inevitable impuritiesSteel is continuously cast and the resulting slab is heated and held at 1050-1300 ° C for 10-240 minutes without cooling to an average cross-section temperature of 850 ° C or lower, and then the finish rolling finish temperature is set to 850-1000 ° C. Hot-rolled, wound up at 400-600 ° C, then pickled and cold-rolled, heated at 500 ° C or higher at 10 ° C / sec or higher, soaking at recrystallization temperature-850 ° C It is characterized by performing continuous annealing for 60 seconds or less and further performing secondary cold rolling at a reduction rate of 20% or less.High age hardening and excellent material stabilityManufacturing method of steel plate for cans.
[0013]
(Five) C: 0.0010 to 0.04 wt%, Si: 0.10 wt% or less, Mn: 0.1 to 1.5 wt%, P: 0.04 wt% or less, S: 0.01 wt% or less, Al: 0.005 to 0.060 wt%, N: 0.0020 to 0.0150 wt%Contains Nb : 0.003 ~ 0.020wt %, Ti : 0.003 ~ 0.020wt %, B: 0.0005 ~ 0.0020wt %, Any one or more selected from%, with the balance being Fe And inevitable impuritiesSteel is continuously cast and the resulting slab is heated and held at 1050-1300 ° C for 10-240 minutes without cooling to an average cross-section temperature of 850 ° C or lower, and then the finish rolling finish temperature is set to 850-1000 ° C. Perform hot rolling, start forced cooling within 0.5 seconds, wind up at 400-600 ° C, then go through pickling and cold rolling processes, heating rate at 500 ° C or higher to 10 ° C / sec or higher , Continuous annealing at a recrystallization temperature of 850 ° C. within 60 seconds, and secondary cold rolling at a reduction rate of 20% or less.High age hardening and excellent material stabilityManufacturing method of steel plate for cans.
(6) C: 0.0010 ~ 0.04wt %, Si : 0.10wt %Less than, Mn : 0.1 ~ 1.5wt %, P: 0.04wt %, S: 0.01wt %Less than, Al : 0.005 ~ 0.060wt %, N: 0.0020 ~ 0.0150wt % And further Cu : 0.5wt %Less than, Ni : 0.5wt %Less than, Cr : 0.5wt %Less than, Mo : 0.5wt % Or any one or more selected from below, with the balance being Fe And steel made of inevitable impurities is continuously cast, and the resulting slab is cross-sectional average temperature 850 Without cooling below ℃ 1050 ~ 1300 ℃ Ten ~ 240 After heating and holding for a minute, the finish rolling finish temperature 850 ~ 1000 Perform hot rolling to ℃, 400 ~ 600 Winding at ℃, then through the steps of pickling and cold rolling, 500 Heating rate above ℃ Ten ° C / s ec With the above, soaking is the recrystallization temperature ~ 850 At ℃ 60 Continuous annealing is performed within a second, and rolling reduction 20 A method for producing a steel plate for cans having a high age-hardening property and excellent material stability, characterized by secondary cold rolling at a% or less.
(7) C: 0.0010 ~ 0.04wt %, Si : 0.10wt %Less than, Mn : 0.1 ~ 1.5wt %, P: 0.04wt %, S: 0.01wt %Less than, Al : 0.005 ~ 0.060wt %, N: 0.0020 ~ 0.0150wt % And further Cu : 0.5wt %Less than, Ni : 0.5wt %Less than, Cr : 0.5wt %Less than, Mo : 0.5wt % Or any one or more selected from below, with the balance being Fe And steel made of inevitable impurities is continuously cast, and the resulting slab is cross-sectional average temperature 850 Without cooling below ℃ 1050 ~ 1300 ℃ Ten ~ 240 After heating and holding for a minute, the finish rolling finish temperature 850 ~ 1000 Perform hot rolling to ℃, 0.5 Start forced cooling within seconds, 400 ~ 600 Winding at ℃, then through the steps of pickling and cold rolling, 500 Heating rate above ℃ Ten ℃ / sec With the above, soaking is the recrystallization temperature ~ 850 At ℃ 60 Continuous annealing is performed within a second, and rolling reduction 20 A method for producing a steel plate for cans having a high age-hardening property and excellent material stability, characterized by secondary cold rolling at a% or less.
(8) C: 0.0010 ~ 0.04wt %, Si : 0.10wt %Less than, Mn : 0.1 ~ 1.5wt %, P: 0.04wt %, S: 0.01wt %Less than, Al : 0.005 ~ 0.060wt %, N: 0.0020 ~ 0.0150wt % And further Nb : 0.003 ~ 0.020wt %, Ti : 0.003 ~ 0.020wt %, B: 0.0005 ~ 0.0020wt Any one or more selected from%, and Cu : 0.5wt %Less than, Ni : 0.5wt %Less than, Cr : 0.5wt %Less than, Mo : 0.5wt % Or any one or more selected from below, with the balance being Fe And steel made of inevitable impurities is continuously cast, and the resulting slab is cross-sectional average temperature 850 Without cooling below ℃ 1050 ~ 1300 ℃ Ten ~ 240 After heating and holding for a minute, the finish rolling finish temperature 850 ~ 1000 Perform hot rolling to ℃, 400 ~ 600 Winding at ℃, then through the steps of pickling and cold rolling, 500 Heating rate above ℃ Ten ° C / s ec With the above, soaking is the recrystallization temperature ~ 850 At ℃ 60 Continuous annealing is performed within a second, and rolling reduction 20 A method for producing a steel plate for cans having a high age-hardening property and excellent material stability, characterized by secondary cold rolling at a% or less.
(9) C: 0.0010 ~ 0.04wt %, Si : 0.10wt %Less than, Mn : 0.1 ~ 1.5wt %, P: 0.04wt %, S: 0.01wt %Less than, Al : 0.005 ~ 0.060wt %, N: 0.0020 ~ 0.0150wt % And further Nb : 0.003 ~ 0.020wt %, Ti : 0.003 ~ 0.020wt %, B: 0.0005 ~ 0.0020wt Any one or more selected from%, and Cu : 0.5wt %Less than, Ni : 0.5wt %Less than, Cr : 0.5wt %Less than, Mo : 0.5wt % Or any one or more selected from below, with the balance being Fe And steel made of inevitable impurities is continuously cast, and the resulting slab is cross-sectional average temperature 850 Without cooling below ℃ 1050 ~ 1300 ℃ Ten ~ 240 After heating and holding for a minute, the finish rolling finish temperature 850 ~ 1000 Perform hot rolling to ℃, 0.5 Start forced cooling within seconds, 400 ~ 600 Rolled at ℃ Through the steps of pickling and then pickling and cold rolling, 500 Heating rate above ℃ Ten ℃ / sec With the above, soaking is the recrystallization temperature ~ 850 At ℃ 60 Continuous annealing is performed within a second, and rolling reduction 20 A method for producing a steel plate for cans having a high age-hardening property and excellent material stability, characterized by secondary cold rolling at a% or less.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described.
(1) About steel components;
C: 0.0010 to 0.04 wt%
If the amount of C exceeds 0.04 wt%, the ductility deteriorates, so that the tendency of deterioration of workability due to the thinning of the steel sheet is further increased, which is not preferable. In addition, the cold rollability also decreases. For this reason, the amount of C is made into 0.04 wt% or less. On the other hand, when the amount of C is less than 0.0010 wt%, the crystal grains become prominent, and the risk of causing rough skin defects similar to the orange peel phenomenon increases. Therefore, the C amount is 0.0010 to 0.04 wt%. When a higher level of material stability and excellent ductility are required, the range of 0.0020 to 0.020 wt% is desirable.
[0015]
Si: 0.10wt% or less
If the amount of Si exceeds 0.10 wt%, it causes problems such as deterioration of surface treatment properties and deterioration of corrosion resistance, so the upper limit is set to 0.10 wt%. In addition, when particularly excellent corrosion resistance is required, the content is preferably 0.02 wt% or less.
[0016]
Mn: 0.1 to 1.5 wt%
Mn is an element that is effective in making crystal grains fine and preventing hot cracking due to S, and it is desirable to add Mn according to the amount of S contained. In order to exert these effects, it is necessary to add at least 0.1 wt%. However, excessive addition deteriorates the corrosion resistance and deteriorates the cold rolling property due to hardening of the steel sheet, so the upper limit is made 1.5 wt%. In addition, when better corrosion resistance and moldability are required, it is desirable to add in the range of 0.60 wt% or less.
[0017]
P: 0.04wt% or less
P is a harmful element that hardens the steel and deteriorates the flange workability and the neck workability, and at the same time, deteriorates the corrosion resistance. Therefore, the upper limit is set to 0.04 wt%. In addition, when these characteristics are regarded as particularly important, the content is preferably 0.01 wt% or less.
[0018]
S: 0.01wt% or less
S is an element present in the steel as inclusions, reduces ductility, and causes deterioration of corrosion resistance. Therefore, the upper limit is made 0.01 wt%. In applications where particularly good workability is required, 0.005 wt% or less is desirable.
[0019]
Al: 0.005 to 0.060 wt%
  When Al is less than 0.005 wt%, deoxidation is insufficient, and a steel sheet with a lot of inclusions is formed, and flange workability and neck formability are lowered. Therefore, the lower limit is set to 0.005 wt%. On the other hand, when the content is too large, the surface properties are deteriorated and lead to an excessive decrease of the solid solution N, so the upper limit is made 0.060 wt%. In addition, from the viewpoint of the stability of the material, 0.008 to 0.040 wt% is desirable.
[0020]
N: 0.0020 to 0.0150 wt%
N is an element necessary for increasing the strength of the steel sheet due to the solid solution strengthening effect. This hardening can be stably obtained by addition of 0.0020 wt% or more, but if added over 0.015 wt%, the occurrence of internal defects in the steel sheet will be increased, and the occurrence of slab cracking during continuous casting will also occur. Is set to 0.0150 wt%. In view of the stability of the material in consideration of the whole manufacturing process and the improvement of the yield, it is preferable to contain in the range of 0.0030 to 0.0090 wt%.
[0021]
Solid N: 0.001 to 0.01wt% and over 25% of total N
The solid solution N is obtained by subtracting the precipitation N (measured by a bromine ester dissolution method) from the total N amount in the steel. If this value is not 0.001 wt% or more, a sufficient amount of solid solution strengthening cannot be secured, and there is a risk that the strength of the can after the can can be insufficient. On the other hand, if the content exceeds 0.01 wt%, the ductility deteriorates when aging progresses, which is not preferable. Accordingly, the amount of solute N is preferably in the range of 0.001 to 0.01 wt%, and preferably in the range of 0.0015 to 0.0050 wt% from the viewpoint of the stability of the material.
Further, the solute N needs to be present in an amount of 25% or more of the total N amount. If a large amount of N is added, the solid solution N present in the product stage tends to increase. However, as a result of detailed studies, the remaining solid solution N is small relative to the total N amount. In such a case, the crystal grains are remarkably mixed, the ductility tends to deteriorate, and it is not suitable when the surface is required to be beautiful. In addition, it has been clarified that in such a structure, the material, particularly the bake hardenability, fluctuates due to slight variations in manufacturing conditions. In order to avoid such a phenomenon, it has become clear that the solid solution N remaining in the solid solution state in the product state with respect to the total N contained may be 25% or more of the total N amount. Various methods for analyzing the precipitation N were examined. However, the dissolution method using bromine ester employed in the present invention was best applied, which corresponded to the change in material.
[0022]
  Nb: 0.003 to 0.020 wt%
Nb is an element that is effective in making the steel structure finer, improving stretch flangeability, and preventing rough skin. Such an effect is exerted by the addition of 0.003 wt% or more, and if added over 0.020 wt%, the strengthening due to solute N is drastically reduced. Therefore, the amount of Nb added is 0.003 to 0.020 wt%. In addition, the range of 0.012 wt% or less is more preferable in terms of material.
[0023]
  Ti: 0.003 to 0.020 wt%
  Ti also has the effect of refining the structure, just like Nb. In order to obtain this effect, addition of 0.003 wt% or more is necessary. However, if it is added in excess of 0.020 wt%, the occurrence of surface defects that can be considered fatal becomes significant in steel sheets for cans. Accordingly, Ti is in the range of 0.003 to 0.020 wt%, preferably 0.015 to 0.020 wt%.
[0024]
B: 0.0005-0.0020wt%
B is an element effective for refinement of structure and adjustment control of aging. Such an effect is exhibited by addition of 0.0005 wt% or more. However, addition exceeding 0.0020 wt% is not preferable because the in-plane anisotropy of the steel sheet increases. Therefore, B is added in the range of 0.0005 to 0.0020 wt%, preferably 0.0005 to 0.0010.
[0025]
  Cu: 0.5 wt% or less, Ni: 0.5 wt% or less,
  Cr: 0.5 wt% or less, Mo: 0.5 wt% or less
Any of these elements has an effect of increasing the strength of the steel sheet, and is added as necessary. However, if added over 0.5 wt%, the cold rolling property is deteriorated, so add in the range of 0.5 wt% or less.
Each of the elements belonging to the group of Nb, Ti and B, Cu, Ni, Cr and Mo, which are the above selective additive elements, may be added individually in each group, or elements of both groups May be added in combination.
[0026]
(2) Manufacturing conditions;
The slab to be rolled material is preferably produced by a continuous casting method in order to minimize macro segregation of components.
This continuous cast slab must be inserted into a heating furnace without being cooled excessively and at least with an average cross-sectional temperature of 850 ° C. or lower. When it is cooled below this level, the detailed mechanism is not necessarily clear, but the solid solution N significantly decreases at the hot-rolled plate stage, and the solid solution N also decreases at the final product stage. The amount of dissolved N cannot be secured. By inserting the slab temperature into the heating furnace without lowering the average cross-sectional temperature to 850 ° C. or lower, the sensitivity of the material to fluctuations in manufacturing conditions in the next process and below can be reduced.
[0027]
In the heating furnace, the slab needs to be held at a temperature of 1050-1300 ° C for 10-240 minutes. When the holding temperature is lower than 1050 ° C., the risk of causing wrinkles in the steel plate edge portion during subsequent rolling increases. If the holding temperature exceeds 1300 ° C, it will cause an increase in the structure non-uniformity (abnormal grain growth), and the benefits of energy saving (decrease in heating intensity) by the DHCR process will be lost. . The minimum holding time is 10 minutes. Below this range, rolling problems such as sheet bar warping and bending occur frequently due to uneven temperature in the slab. In addition, if it is held for more than 240 minutes, it becomes difficult to make the structure uniform and refined in the final product, and the risk of forming a mixed grain structure increases, and in addition, the scale loss due to the increase in scale thickness is remarkable. Therefore, the upper limit of the holding time is 240 minutes.
[0028]
Next, in the hot rolling consisting of rough rolling and finish rolling, the finish rolling finish temperature is set to 850 ° C. or higher so that a uniform and fine hot-rolled base metal structure can be obtained. Can be realized. Moreover, the amount of solute N can be stably secured at the stage of the hot-rolled mother board, and the mechanical properties in the final product are also stabilized.
However, if the finish rolling finish temperature exceeds 1000 ° C., the generation of wrinkles due to the scale becomes severe, making it unsuitable for steel sheets for cans that strongly require surface integrity. Therefore, the hot finish rolling finish temperature is set to 850 to 1000 ° C. In addition, the range of 880-920 degreeC is more preferable from the uniformity of a material.
[0029]
Forced cooling (usually water cooling) is performed after finish rolling. In the present invention, since it is necessary to leave a large amount of solute N at the stage of the hot-rolled base plate, it is very effective to start forced cooling within 0.5 seconds after the finish rolling. This treatment also makes it possible to refine the structure, which is effective in improving the balance between strength and ductility.
[0030]
The temperature of winding after hot rolling is important in securing the amount of solute N in the hot-rolled mother plate and ensuring a sufficient amount of solute N in the final product. In order to secure a sufficient amount of solid solution N, it is necessary to wind up at a temperature of 600 ° C. or lower. However, when the coiling temperature is below 400 ° C., the shape of the steel sheet deteriorates, and the hardness difference in the width direction of the steel sheet becomes remarkable, which causes deterioration of the steel sheet shape after cold rolling. Therefore, the coiling temperature is 400 to 600 ° C, preferably 500 to 580 ° C.
[0031]
The hot-rolled sheet thus obtained is pickled (descaled) and cold-rolled. The pickling conditions may be carried out according to a conventional method by removing the surface scale with an acid such as hydrochloric acid or sulfuric acid. Although the rolling reduction of cold rolling follows a conventional method, the sheet rolling is slightly higher because of the thin plate thickness, and it is preferable that the rolling reduction is generally in the range of 65 to 95%.
[0032]
Furthermore, annealing (continuous annealing) is required after cold rolling in order to ensure the formability of the product. In this continuous annealing, it is necessary to pay attention to the heating rate and the annealing temperature.
Although the continuous annealing method can anneal the steel sheet in a short time, the present inventors have conducted many investigations and studies, and in the annealing of a cold-rolled steel sheet that has undergone processing and thermal history as in the present invention method, the heating rate during annealing In particular, it was revealed that a uniform and fine recrystallized structure can be obtained when the heating rate from 500 ° C. to the maximum heating temperature is 10 ° C./sec or more. When the heating rate is lower than this value, the tendency to become a mixed grain structure becomes remarkable.
The annealing temperature is higher than the recrystallization temperature. However, if the annealing temperature exceeds 850 ° C., partial abnormal grain growth occurs after the completion of the recrystallization, and conversely increases the material variation.
Therefore, the annealing temperature is in the range of the recrystallization temperature to 850 ° C., and the heating rate from 500 ° C. to the maximum heating temperature is 10 ° C./sec or more. In order to stabilize the operation of the continuous annealing process, it is preferable to set the temperature range to 800 ° C. or less. The recrystallization temperature is about 660 ° C.
Further, regarding the annealing time (soaking time), if this exceeds 60 sec, the material variation becomes significant when annealing in a high temperature region. Although the lower limit of the time is not particularly defined, there is no problem even if the soaking time is substantially 0 sec as long as the recrystallization is completed. Therefore, the annealing temperature is 60 sec or less, preferably within 20 sec.
[0033]
Secondary annealing is performed after annealing. The purpose of secondary cold rolling is to increase the strength of the material by strengthening the work, and to reduce the plate thickness and adjust the surface roughness and the like. When the rolling reduction of secondary cold rolling exceeds 20%, ductility deteriorates and applicable applications are extremely limited. Therefore, the rolling reduction of secondary cold rolling is 20% or less, preferably 15% or less, and it is desirable to make it 10% or less for applications where press formability is required. The lower limit of the rolling reduction is determined from the aspect of surface roughness management other than the material, but it is desirable to give 1% or more.
[0034]
The final product is obtained through the steps described above. Although the final thickness of the steel sheet is not particularly defined, the advantage of positively using solute N is more effectively exhibited in the range of 0.30 mm or less.
As the surface treatment on the steel plate, any of those applied to normal steel plates for cans is applicable. That is, tin plating, chrome plating, nickel plating, nickel / chrome plating, and the like. In addition, the present invention can be applied to any special purpose such as painting or applying an organic resin film after plating to make a can.
[0035]
【Example】
Steel containing the composition shown in Table 1 and the balance being substantially Fe was melted in a converter and made into a slab by a continuous casting method. This steel slab was subjected to hot rolling, cold rolling, continuous annealing, and secondary cold rolling under the conditions shown in Table 2 to obtain a steel plate having a final finished sheet thickness of 0.20 mm.
Thereafter, the steel plate was continuously subjected to tin plating corresponding to No. 25 in a halogen type electric tin plating line to finish it with a tinplate. For comparison, the same tin plating was applied to a steel plate with the same finished thickness (adjusted the secondary cold rolling reduction after annealing so as to have almost the same hardness) manufactured by the conventional method. did.
The tensile property of the obtained tin-plated steel sheet was investigated. The results are shown in Table 3. The normal tensile test is conducted within one day after commercialization. To investigate the bake-hardening characteristics, the material is first subjected to aging treatment equivalent to baking and baking at 210 ° C. for 20 minutes, then 5% elongation strain is applied, and the deformation stress after aging for 1 hour at room temperature after unloading. Evaluation was based on an increase in (yield stress).
[0036]
[Table 1]

[0037]
[Table 2]

[0038]
[Table 3]

[0039]
From Table 3, the material of the present invention has sufficient elongation and age-hardening amount, and the strength just before molding is almost the same as that of the conventional material, but compared with the conventional material at the stage where it is used as the actual can body thereafter. Thus, it can be seen that the strength is remarkably high.
[0040]
Next, in order to clarify the difference when these steel plates are applied to a three-piece welded can after painting and baking treatment, the manufacturing conditions shown in Table 4 are applied to steel 1 in Table 1 to obtain a thickness of 0.18. A steel sheet of mm was manufactured, the material was investigated, and a cylindrical forming test by bending was performed.
For yield stress, specimens were collected at 10 locations in the longitudinal direction of the product coil, and the standard deviation was investigated in addition to the yield stress (average value). In the cylindrical molding test, a leveling process was performed immediately before molding, and the cylinder was immediately molded into a cylinder. The reason for using this method is that in actual can manufacturing equipment, a kind of leveling mechanism called a flexor is installed just before cylindrical molding is performed, realizing molding conditions closer to that of actual cans. This is to try. In order to evaluate the roundness of the can after molding, the major axis and the uniaxial axis of the can cross section were measured, and the flatness was obtained by (major axis diameter minus minor axis diameter) / (major axis diameter). These test results are summarized in Table 5.
[0041]
[Table 4]

[0042]
[Table 5]

[0043]
Table 5 shows that in the invention examples, although the yield stress is high, the variation is small, stable material control is possible, and the cylinder is obtained despite the high yield stress before forming. It is clear that the radius of curvature of is extremely stable.
In addition, after the above-mentioned cylindrical forming, welding was performed and the flange formability was investigated. The steel sheet of the invention example is estimated to have good plate thickness accuracy and small variations in material, but the flange crack occurrence rate Was improved by about 30% compared with the conventional example.
[0044]
Fig. 1 and Fig. 2 show 0.02wt% C-0.01wt% Si-0.25Mnwt% -0.01wt% P-0.008wt% S-0.055wt% Al-0.0045wt% N steel as the raw material, changing the heating conditions. The yield stress is compared for the case where the amount of dissolved N is changed and the secondary cold rolling reduction ratio is changed.
According to the present invention, it can be seen that by using solute N, a higher yield stress can be obtained, and this can be exhibited even in the range of a high secondary cold rolling rate and after aging. At this time, since there is no deterioration of ductility, it can be said that the steel sheet of the present invention using solute N has an excellent balance between strength and ductility.
[0045]
【The invention's effect】
As described above, in the present invention, in manufacturing a hot-rolled steel sheet, the chemical composition, the slab hot piece insertion conditions, the hot-rolling conditions, and the annealing conditions after cold rolling are optimized, so that the final product stage. By securing a sufficient amount of N in a solid solution state, a strong and uniform microstructure can be obtained, and a sufficient can body utilizing the hardening phenomenon after painting and baking without sacrificing workability Strength can be secured.
Therefore, the appearance of such high-strength can steel plates excellent in formability greatly contributes to the reduction of can manufacturing cost by thinning cans such as 3-piece cans and 2-piece cans.
[Brief description of the drawings]
FIG. 1 is a diagram showing the effect of the amount of solute N on the increase in yield stress by aging treatment.
FIG. 2 is a graph showing the effect of the amount of solute N on the relationship between the secondary cold rolling reduction ratio and the yield stress after annealing.

Claims (9)

C: 0.0010 to 0.04 wt%, Si: 0.10 wt% or less, Mn: 0.1 to 1.5 wt%, P: 0.04 wt% or less, S: 0.01 wt% or less, Al: 0.005 to 0.060 wt%, N: 0.0020 to 0.0150 containing wt%, 25% or more of the above N amount, and containing 0.001 to 0.01 wt% of solid solution N, Nb: 0.003 to 0.020 wt%, Ti: 0.003 to 0.020 wt%, B: 0.0005 to 0.0020 A steel plate for cans having high age-hardening properties and excellent material stability, characterized in that it contains any one or more selected from wt%, and the balance consists of Fe and inevitable impurities. C: 0.0010 to 0.04 wt%, Si: 0.10 wt% or less, Mn: 0.1 to 1.5 wt%, P: 0.04 wt% or less, S: 0.01 wt% or less, Al: 0.005 to 0.060 wt%, N: 0.0020 to 0.0150 including wt%, 25% or more of the above N amount, and 0.001 to 0.01 wt% of solid solution N, Cu: 0.5 wt% or less, Ni: 0.5 wt% or less, Cr: 0.5 wt% or less, Mo: Steel plate for cans having high age-hardening properties and excellent material stability, characterized by containing one or more selected from 0.5 wt% or less, the balance being Fe and inevitable impurities. C: 0.0010 to 0.04 wt%, Si: 0.10 wt% or less, Mn: 0.1 to 1.5 wt%, P: 0.04 wt% or less, S: 0.01 wt% or less, Al: 0.005 to 0.060 wt%, N: 0.0020 to 0.0150 containing wt%, 25% or more of the above N amount, and containing 0.001 to 0.01 wt% of solid solution N, Nb: 0.003 to 0.020 wt%, Ti: 0.003 to 0.020 wt%, B: 0.0005 to 0.0020 Contains one or more selected from wt%, and further selected from Cu: 0.5 wt% or less, Ni: 0.5 wt% or less, Cr: 0.5 wt% or less, Mo: 0.5 wt% or less A steel plate for cans having high age-hardening properties and excellent material stability, characterized in that it contains any one or more of them, and the balance is Fe and inevitable impurities. C: 0.0010 to 0.04 wt%, Si: 0.10 wt% or less, Mn: 0.1 to 1.5 wt%, P: 0.04 wt% or less, S: 0.01 wt% or less, Al: 0.005 to 0.060 wt%, N: 0.0020 to 0.0150 Contains wt% , Nb : 0.003 to 0.020 wt %, Ti : 0.003 to 0.020 wt %, B: 0.0005 to 0.0020 wt %, one or more selected from the rest, Fe and inevitable After continuous casting of steel made of mechanical impurities , the obtained slab was heated and held at 1050 to 1300 ° C for 10 to 240 minutes without cooling to an average cross-section temperature of 850 ° C or lower, and the finish rolling finish temperature was 850 to Performs hot rolling to 1000 ° C, winds up at 400-600 ° C, then pickles and cold-rolls, heats at 500 ° C or higher to 10 ° C / sec or higher, and recrystallizes soaking Age-hardening is characterized by performing continuous annealing at a temperature of 850 ° C. for 60 seconds or less and further performing secondary cold rolling at a rolling reduction of 20% or less. A method for manufacturing steel plates for cans that are large and have excellent material stability . C: 0.0010 to 0.04 wt%, Si: 0.10 wt% or less, Mn: 0.1 to 1.5 wt%, P: 0.04 wt% or less, S: 0.01 wt% or less, Al: 0.005 to 0.060 wt%, N: 0.0020 to 0.0150 Contains wt% , Nb : 0.003 to 0.020 wt %, Ti : 0.003 to 0.020 wt %, B: 0.0005 to 0.0020 wt %, one or more selected from the rest, Fe and inevitable After continuous casting of steel made of mechanical impurities , the obtained slab was heated and held at 1050 to 1300 ° C for 10 to 240 minutes without cooling to an average cross-section temperature of 850 ° C or lower, and the finish rolling finish temperature was 850 to Performs hot rolling to 1000 ° C, starts forced cooling within 0.5 seconds, winds up at 400-600 ° C, then passes through pickling and cold rolling, and heats at 500 ° C or higher at 10 ° C / Sec., Continuous annealing at a recrystallization temperature of 850 ° C. within 60 seconds, and secondary cold rolling at a reduction rate of 20% or less. DOO large age hardenable characterized by method of steel sheet for cans having excellent material stability. C: 0.0010 ~ 0.04wt %, Si : 0.10wt %Less than, Mn : 0.1 ~ 1.5wt %, P: 0.04wt %, S: 0.01wt %Less than, Al : 0.005 ~ 0.060wt %, N: 0.0020 ~ 0.0150wt % And further Cu : 0.5wt %Less than, Ni : 0.5wt %Less than, Cr : 0.5wt %Less than, Mo : 0.5wt % Or any one or more selected from below, with the balance being Fe And continuously casting steel consisting of inevitable impurities, The obtained slab is cross-sectional average temperature 850 Without cooling below ℃ 1050 ~ 1300 ℃ Ten ~ 240 After heating and holding for a minute, the finish rolling finish temperature 850 ~ 1000 Perform hot rolling to ℃, 400 ~ 600 Winding at ℃, then through the steps of pickling and cold rolling, 500 Heating rate above ℃ Ten ° C / s ec With the above, soaking is the recrystallization temperature ~ 850 At ℃ 60 Continuous annealing is performed within seconds, and rolling reduction 20 A method for producing a steel plate for cans having a high age-hardening property and excellent material stability, characterized by secondary cold rolling at a% or less. C: 0.0010 ~ 0.04wt %, Si : 0.10wt %Less than, Mn : 0.1 ~ 1.5wt %, P: 0.04wt %, S: 0.01wt %Less than, Al : 0.005 ~ 0.060wt %, N: 0.0020 ~ 0.0150wt % And further Cu : 0.5wt %Less than, Ni : 0.5wt %Less than, Cr : 0.5wt %Less than, Mo : 0.5wt % Or any one or more selected from below, with the balance being Fe And steel made of inevitable impurities is continuously cast, and the resulting slab is cross-sectional average temperature 850 Without cooling below ℃ 1050 ~ 1300 ℃ Ten ~ 240 After heating and holding for a minute, the finish rolling finish temperature 850 ~ 1000 Perform hot rolling to ℃, 0.5 Start forced cooling within seconds, 400 ~ 600 Winding at ℃, then through the steps of pickling and cold rolling, 500 Heating rate above ℃ Ten ℃ / sec With the above, soaking is the recrystallization temperature ~ 850 At ℃ 60 Continuous annealing is performed within seconds, and rolling reduction 20 A method for producing a steel plate for cans having a high age-hardening property and excellent material stability, characterized by secondary cold rolling at a% or less. C: 0.0010 ~ 0.04wt %, Si : 0.10wt %Less than, Mn : 0.1 ~ 1.5wt %, P: 0.04wt %, S: 0.01wt %Less than, Al : 0.005 ~ 0.060wt %, N: 0.0020 ~ 0.0150wt % And further Nb : 0.003 ~ 0.020wt %, Ti : 0.003 ~ 0.020wt %, B: 0.0005 ~ 0.0020wt Any one or more selected from%, and Cu : 0.5wt %Less than, Ni : 0.5wt %Less than, Cr : 0.5wt %Less than, Mo : 0.5wt % Or any one or more selected from below, with the balance being Fe And steel made of inevitable impurities is continuously cast, and the resulting slab is cross-sectional average temperature 850 Without cooling below ℃ 1050 ~ 1300 ℃ Ten ~ 240 After heating and holding for a minute, the finish rolling finish temperature 850 ~ 1000 Perform hot rolling to ℃, 400 ~ 600 Winding at ℃, then through the steps of pickling and cold rolling, 500 Heating rate above ℃ Ten ° C / s ec With the above, soaking is the recrystallization temperature ~ 850 At ℃ 60 Continuous annealing is performed within seconds, and rolling reduction 20 A method for producing a steel plate for cans having a high age-hardening property and excellent material stability, characterized by secondary cold rolling at a% or less. C: 0.0010 ~ 0.04wt %, Si : 0.10wt %Less than, Mn : 0.1 ~ 1.5wt %, P: 0.04wt %, S: 0.01wt %Less than, Al : 0.005 ~ 0.060wt %, N: 0.0020 ~ 0.0150wt % And further Nb : 0.003 ~ 0.020wt %, Ti : 0.003 ~ 0.020wt %, B: 0.0005 ~ 0.0020wt Any one or more selected from%, and Cu : 0.5wt %Less than, Ni : 0.5wt %Less than, Cr : 0.5wt %Less than, Mo : 0.5wt % Or any one or more selected from below, with the balance being Fe And steel made of inevitable impurities is continuously cast, and the resulting slab is cross-sectional average temperature 850 Without cooling below ℃ 1050 ~ 1300 ℃ Ten ~ 240 After heating and holding for a minute, the finish rolling finish temperature 850 ~ 1000 Perform hot rolling to ℃, 0.5 Start forced cooling within seconds, 400 ~ 600 Winding at ℃, then through the steps of pickling and cold rolling, 500 Heating rate above ℃ Ten ℃ / sec With the above, soaking is the recrystallization temperature ~ 850 At ℃ 60 Continuous annealing is performed within seconds, and rolling reduction 20 A method for producing a steel plate for cans having a high age-hardening property and excellent material stability, characterized by secondary cold rolling at a% or less.

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