JP3700280B2 - Manufacturing method of steel plate for cans - Google Patents

Description

【００４１】
【表２】

【００４２】
【表３】

【００４３】
表３から明らかなように、本発明に従い、粗圧延工程で総圧下率：80％以上、その内最終パス圧下率：20％以上の圧延を施し、ついで仕上げ圧延工程において、950℃以上の温度域で総圧下率：70％以上の圧延を施し、さらにＡr₃〜950℃の温度域で総圧下率：55％以上の圧延を施して、最終仕上げ温度がＡr₃−50℃以上となるように熱間圧延を終了し、ついで 550〜750℃の温度範囲で巻き取ることにより、均一で微細な、加工性と強度バランスに優れ、しかも極薄で広幅（900〜1200mm、板幅／板厚＜ 20000）の鋼板を製造することができた。なお、本発明による鋼板では、幅端から20mm以内の幅縁部を除く領域における、HR30Tの変動値が５％以下にあり均一な材質を示した。
【００４４】
また、図１には、仕上げ圧延工程における 950℃以上での圧下率と最終製品の粒度番号との関係を示す。
用いた素材は鋼No.11 で、製造条件は表２，３の条件Ｄと同じである。
同図に示したとおり、950 ℃以上の温度域で総圧下量：70％以上の圧延を行うことにより、最終段階における組織が微細となるため、その段階での再結晶を効果的に行わせることが可能となり、結果的に最終製品の粒径を微細化することができる。
【００４５】
また、図２には、仕上げ圧延工程におけるＡr₃〜950 ℃の温度域での圧下率と最終製品の粒度番号との関係を示す。
用いた素材は鋼No.11 で、製造条件は表２，３の条件Ｄと同じである。
同図に示したとおり、Ａr₃〜950 ℃の温度域で55％以上の圧延を行うことにより、再結晶しにくいこの領域でも微細化が実現されることが判る。
【００４６】
実施例２
前掲表１に示した鋼No.1〜19を用い、表４および表５に示す条件で缶用鋼板を製造した。
かくして得られた各鋼板の結晶粒径、板厚方向での組織の均一性、ロックウェル硬さ、ｒ値、Δｒ値およびフランジ成形性について調べた結果を表５に併記する。
【００４７】
【表４】

【００４８】
【表５】

【００４９】
比較鋼のうち、鋼No.7, ９はいづれも、ｒ値が低く、深絞り性に劣っていた。また鋼No.7, 8, 9, 17, 18, 19はいずれも、Δｒが負で大きな値となり、絞り変形した際に耳が大きく不良となることが判る。さらに、鋼No.10, 17, 18 については、混粒組織が残り、肌あれ判定が×となった。
これに対し、本発明の要件を全て満足する鋼No.1〜６、11〜16はいずれも、全ての特性に優れた極薄・広幅鋼板とすることができた。
【００５０】
【発明の効果】
かくして、本発明によれば、極低炭素鋼板であっても、微細かつ均一な組織を持ち、強度と加工性の両者を兼ね備え、しかもフランジ成形性にも優れた缶用鋼板を得ることができ、しかも本発明によれば、従来望み得なかったほどの極薄で広幅の鋼板の製造も可能となる。
【図面の簡単な説明】
【図１】仕上げ圧延工程における 950℃以上での圧下率と最終製品の粒度番号との関係を示したグラフである。
【図２】仕上げ圧延工程におけるＡr₃〜950 ℃の温度域での圧下率と最終製品の粒度番号との関係を示したグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a steel plate for cans such as an ultrathin tin plate and tin-free steel, and particularly has excellent workability and strength property balance, as well as excellent properties for cans such as skin roughness, and the like. Compared to, it is possible to produce ultra-thin and wide steel plates.
[0002]
[Prior art]
Container cans such as beverage cans, 18 liter cans, and pail cans can be roughly classified into two-piece cans and three-piece cans from the manufacturing method (process).
Two-piece cans are processed by deep drawing, DWI, DRD, etc. on surface-treated steel sheets that have undergone tin plating, chrome plating, chemical conversion treatment, oiling, etc., and the bottom and can body are integrated. It is a can made of two parts which is molded and has a lid attached thereto.
A three-piece can is a three-piece can that is formed by bending a surface-treated steel sheet into a cylindrical shape or a rectangular tube shape, joining ends together to form a can body, and then attaching a canopy and a bottom lid to the can body. is there.
[0003]
Since all of these cans have a high ratio of material costs to can costs, there is a strong demand for cost reduction of the steel sheets. Therefore, it is desirable to produce steel plates for cans by continuous annealing with high production efficiency and excellent yield and surface quality, rather than inefficient and box annealing with poor material yield and surface quality. .
As such a continuous annealing technique, for example, there is a technique disclosed in Japanese Examined Patent Publication No. 63-102113, and a technique with further improvements has been developed and expressed by the value of Rockwell hardness (HR30T). A soft steel plate for cans having a refining degree of about T2 (50-56) can be obtained.
Furthermore, technology for producing soft steel sheets by continuous annealing has also been developed. For example, as disclosed in Japanese Patent Publication No. 1-52452, an extremely low carbon steel sheet is applied, and various hardened materials are combined with work hardening after annealing. Technology for manufacturing steel plates for cans has also been developed.
[0004]
However, even this type of steel sheet for cans is required to further reduce costs, and in order to meet this demand, it is necessary to develop a new manufacturing process and a new material.
As one method for reducing the cost, it is conceivable to reduce the thickness of the steel sheet to be used and to strengthen the neck diameter reduction of the upper lid. However, even if the plate thickness decreases, the strength of the can must be maintained. To that end, the material must be high-strength, so the required material properties are becoming increasingly severe. There is a need for a technique for producing steel plates for cans that have good workability (for example, deep drawability) that can be tolerated.
[0005]
For example, Japanese Patent Application Laid-Open No. 6-306536 proposes a technique that achieves both strength and formability using an ultra-low carbon steel sheet.
However, the ultra-low carbon steel sheet, which is advantageous for workability, tends to have a larger particle size than the low-carbon steel sheet, and causes problems such as rough skin after can molding. Therefore, the structure of the ultra-low carbon steel sheet is uniform and fine. In addition, development of a manufacturing technique for a very thin and wide surface treatment original plate is desired.
[0006]
[Problems to be solved by the invention]
The object of the present invention is to achieve better strength by a more rational manufacturing method different from the conventional one while maintaining good characteristics as a steel plate for cans even under severe processing conditions. It is intended to improve workability and make it possible to produce ultra-thin and wide steel sheets.
[0007]
[Means for Solving the Problems]
Now, in order to achieve the above object, the inventors conducted a thorough examination on the steel composition and production conditions, and also conducted a metallurgical examination on the factors governing the necessary characteristics of the steel sheet for cans, The following findings were obtained.
(1) In conventional steel plates for cans, unlike deep drawing steel plates used in automobiles and the like, a high r value is not necessarily an essential condition. However, recently, as the thickness of the material plate decreases, the uniform ductility is inevitably lowered because the strength is increased in order to satisfy the can body strength. Therefore, in order to compensate for ductility, a high r value has been required particularly for a steel plate for a two-piece can. In order to obtain a high r value, reduction of the carbon content is indispensable, and a high r value that cannot be obtained with a low carbon steel plate can be expected with an extremely low carbon steel plate.
[0008]
(2) It is desirable that the in-plane anisotropy (Δr) of the r value is small. This is because it not only leads to an improvement in the yield of the steel sheet for drawing, but can also cause distortion in printing if the anisotropy is large in a can type that is drawn after coating and printing, such as a DRD can. It is. Further, when the neck-in workability was examined, it was found that if the anisotropy is large, a residual stress is generated, which causes a neck wrinkle. The recent reduction in sheet thickness and increase in strength must increase the primary cold rolling reduction and secondary rolling reduction after sinter, and inevitably tend to increase Δr with negative values. There is a need for a steel sheet with low anisotropy even under such conditions. In order to improve the anisotropy, it is necessary to control the crystal grain size and texture during rolling, and it is necessary to control the change in material properties particularly in the γ region.
[0009]
(3) A fine structure is desirable in terms of uniform deformation. This involves skin roughness and the like, and in particular, a technique for reducing the crystal grain size is required. However, in the ultra-low carbon steel sheet that can achieve the high r value as described above, the particle size tends to increase.
The crystal grain size of hot-rolled sheets is not only the grain growth property by steel composition, but also the control of grain growth by optimizing hot rolling conditions and the control of grain growth property by controlling the presence of precipitates. It becomes.
[0010]
Although this invention is an important hot rolling process that has a great influence on the properties of products in the manufacturing process, the reduction conditions in the transformation and recrystallization processes of steel, which has not been much attention in the past, were examined in detail. As a result, it was developed.
[0011]
That is, the gist configuration of the present invention is as follows.
1) C: 0.0005 to 0.0150 wt%,
Si: 0.2 wt% or less,
Mn: 0.05-0.6 wt%
P: 0.02 wt% or less,
S: 0.02 wt% or less,
A steel containing Al: 0.15 wt% or less and N: 0.020 wt% or less, with the balance being Fe and inevitable impurities, is made into a slab after melting, and then in the hot rough rolling process after slab heating, Rolling ratio: 80% or more and final pass rolling ratio: 20% or more rolling, then joining the preceding sheet bar with the preceding sheet bar before finish rolling, in the hot finish rolling process, Rolling at a total reduction ratio of 70% or more at a temperature range of 950 ° C. or higher, followed by rolling at a total reduction ratio of 55% or higher at a temperature range of Ar _{3 to} 950 ° C., and a final finishing temperature: Ar ₃ −50 Finishes hot rolling above ℃, then winds in the temperature range of 550-750 ℃, removes scale, and after cold rolling and recrystallization annealing, reduction rate: 30% or less skin pass or secondary rolling The manufacturing method of the steel plate for cans characterized by giving.
[0012]
2) In 1 above, the steel composition is further
Nb: 0.003 to 0.020 wt%,
Ti: 0.003 to 0.020 wt% and B: 0.0002 to 0.0020 wt%
The manufacturing method of the steel plate for cans characterized by becoming the composition containing 1 type or 2 or more selected from among.
[0013]
3) In the above 1 or 2, the steel composition is further
Cu: 0.5 wt% or less,
Ni: 0.5 wt% or less,
Cr: 0.5 wt% or less and
Mo: A method for producing a steel plate for cans, characterized in that the composition contains one or more selected from 0.2 wt% or less.
[0014]
4) In 1, 2 or 3 above, the obtained steel plate satisfies the requirements of plate thickness: 0.25 to 0.05 mm, plate width: 1200 to 900 mm, plate width / plate thickness <20000 A method for producing a steel plate for cans, characterized in that it is a wide material. Here, “the material is uniform” is defined as that the variation value of HR30T is within 5% in a region from a position 20 mm from the width end to a position 20 mm from the opposite width end.
5) In 1, 2, 3 or 4 above, before finish rolling the sheet bar obtained by hot rough rolling, the sheet bar is joined to the preceding sheet bar, and at the width edge and the length end of the sheet bar. It is desirable to apply a treatment for making the temperature uniform.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
In order to improve the balance between strength and workability, it is necessary to make the structure of the final plating original plate uniform and fine. For this purpose, it is essential to obtain a uniform and fine structure in the hot rolling stage. This is because, in the hot rolling stage, if it is a coarse or mixed grain structure, no matter how much the cold rolling conditions (for example, the increase in the cold rolling reduction) and the annealing conditions (decreasing the annealing temperature) are added, Even if the strength is high, only a steel sheet having poor workability can be obtained.
In addition, the ultra-low carbon steel sheet, which is the component system of the present invention, has a grain size that is larger than that of the low carbon steel sheet in the conventional hot rolling method, or a texture after annealing due to the remaining processed structure. It was not uncommon to have an adverse effect.
This can be attributed to the high transformation point and the difference in grain growth.
[0016]
The present invention makes it possible to uniformly refine the structure after cold rolling and smelting by optimizing the heat treatment conditions in the hot rolling process at the same time as using steel with properly controlled components. Is.
In particular, the present invention is a control that has not been attracting much attention in the past to optimize the amount of processing strain in the high temperature γ region (recrystallization region) and the low temperature γ region (non-recrystallized region) even under hot rolling conditions. By using the law, the above goal has been achieved.
[0017]
Hereinafter, the reason why the composition of the steel sheet and the production conditions in the present invention are limited to the above ranges will be described.
First, the reasons for limiting the hot rolling conditions, which are the main conditions of the present invention, will be described.
(1) Slab heating temperature If the slab heating temperature is too high, the precipitates become fine, and the grain size of the hot-rolled sheet is made fine, so that it is not only difficult to harden but also undesirably reduces local deformability. Therefore, it is desirable that the precipitate be coarsened at 1250 ° C. or lower to achieve both moldability and softening.
[0018]
(2) Allocation of reduction ratio in hot rolling This condition is a particularly important parameter in the present invention, and it becomes possible to obtain a uniform and fine structure by controlling this condition.
In the rough rolling process, the total rolling reduction is 80% or more, and the final pass rolling reduction is 20% or more. Furthermore, in the subsequent finish rolling process, rolling at a total reduction ratio of 70% or more is performed at a temperature range of 950 ° C. or higher, and then a total reduction ratio of 55% or higher is applied at a temperature range of Ar _{3 to} 950 ° C. There is a need.
[0019]
Hereinafter, the operation and reason for limitation will be described.
(a) In the rough rolling process, the particularly important process of performing the reduction of the total reduction ratio: 80% or more and the final pass reduction ratio: 20% or more is (b) and (c) described later. In order to keep the grain sizes to some extent before the finish rolling, a processing strain amount in rough rolling and a certain processing strain amount accompanying recrystallization are required. Moreover, since this steel plate is applied to the steel plate for cans, it is characterized in that the final product is very thin compared to automobiles and home appliances. For this reason, unless it is made thin to some extent at the stage of rough rolling, there is a possibility that the allowable amount of the finish rolling mill will be exceeded. Considering these, the lower limit of the total amount of reduction was set to 80%.
In addition, if the reduction amount of the final pass is less than 20%, it will not be sufficiently sized at the stage of entering the finishing mill (non-uniform structure of the structure from the surface layer to the center). The amount of reduction was 20% or more.
[0020]
(b) In the finish rolling process, the total rolling reduction in a temperature range of 950 ° C. or higher should be 70% or higher. This temperature range is a γ range and can be sufficiently recrystallized by rolling strain. ->Recrystallization-> Rolling strain-> Recrystallization can be said to be a temperature range in which the grain size becomes fine. Nonetheless, if the rolling reduction is less than 70%, not only such fine graining does not proceed sufficiently, but also due to insufficient rolling strain, it does not recrystallize uniformly and is a partly large grain size region. Therefore, it is important that the total rolling reduction in the temperature range of 950 ° C or higher is 70% or higher.
[0021]
(c) The total rolling reduction in the temperature range of Ar _{3 to} 950 ° C. should be 55% or more. This temperature range is the same γ range as (b) described above.
1) Delay of element diffusion due to lower temperature
2) Pinning effect by precipitates
3) Furthermore, the effect of inhibiting recrystallization by solid solution elements overlaps, making it difficult to recrystallize sufficiently.
In the conventional method, this region has not been distinguished from other temperature regions, particularly the above-mentioned recrystallization γ region. Therefore, depending on the component, it becomes a texture that is undesirable for workability or a mixed grain, resulting in a uniform structure. It was very difficult to control.
In fact, if the rolling ratio in this region is less than 55% in total, it does not recrystallize at all, leaving a texture that adversely affects workability, or only partially recrystallizing and avoiding mixed grains. There wasn't.
In this respect, if the rolling reduction is 55% or more, even if Nb or the like enters and recrystallization is very delayed, the transformation nuclei can be uniformly and finely precipitated by the introduced strain.
For the above reasons, the total rolling reduction in the temperature range of Ar _{3 to} 950 ° C. is limited to a range of 55% or more.
[0022]
(3) Final finishing temperature Hot finishing rolling must be completed at a temperature of Ar ₃ -50 ° C or higher. By satisfying this requirement, the structure and grain size of the hot-rolled sheet can be made uniform and fine. it can.
If the hot rolling end temperature is less than Ar ₃ -50 ° C, the processed structure remains depending on the coiling temperature, which not only deteriorates the cold rolling property but also becomes a recrystallized texture that adversely affects the workability. In addition, even if there is no processing strain, the structure becomes coarse and the strength-workability balance deteriorates, which is not preferable.
[0023]
(4) Winding temperature When the coiling temperature exceeds 750 ° C, the scale thickness increases significantly, and the descaling property during pickling decreases. Without this, the recrystallization texture was adversely affected, so the coiling temperature was limited to the range of 550 to 750 ° C.
[0024]
(5) Continuous rolling (endless rolling)
Conventionally, in order to manufacture an ultrathin and wide steel plate that has been difficult to manufacture, it is necessary to manufacture a thin and wide hot-rolled steel strip. For this purpose, after rough rolling, the sheet bar is wound up prior to finish rolling, and joined to the preceding sheet bar, and preferably the temperature at the width edge and the length edge of the sheet bar is made uniform with an edge heater or the like. Since it is extremely useful to do so, the present invention performs such continuous rolling.
[0025]
Next, the reason for limitation about the component composition of a steel plate is described.
C: 0.0005 to 0.0150 wt%
When the C content increases, the crystal grain size becomes finer and a high tempering degree can be obtained, but when it exceeds 0.0150 wt%, the workability is reduced. In view of aging deterioration, the C content should be 0.0150 wt% or less (preferably less than 0.0100 wt%).
On the other hand, from the viewpoint of formability, a lower C content is desirable, but the lower limit of C is set to 0.0005 wt% based on the fact that the crystal grain size becomes coarse and the current steelmaking technology level.
[0026]
Si: 0.2 wt% or less
Si is an element that degrades the surface properties of steel sheets, and if added in a large amount, it is not only desirable as a surface-treated steel sheet, but also hardens the steel, making hot rolling difficult, and hardening the steel as the final product. Let From this point of view, Si needs to be 0.2wt% or less. In addition, it is desirable to make it 0.050 wt% or less especially in applications where the requirement of surface properties is strict.
[0027]
Mn: 0.05-0.6 wt%
If the Mn content is less than 0.05 wt%, even when the S content is reduced, it is difficult to avoid so-called hot brittleness, causing problems such as surface cracks, while if it exceeds 0.6 wt%, Since the transformation point is too low and it is difficult to obtain a preferable hot rolled sheet, the Mn content is limited to a range of 0.05 to 0.6 wt%.
[0028]
P: 0.02 wt% or less Although the corrosion resistance can be improved by reducing the P content, excessive reduction leads to an increase in manufacturing cost. Therefore, P should be contained at 0.02 wt% or less because of these factors. did. In order to significantly improve the workability, it is preferably 0.010 wt% or less.
[0029]
S: 0.02wt% or less Increasing the S content increases inclusions such as MnS, which causes a decrease in local ductility typified by stretch flangeability, and further reduces the content compared to conventional steel sheets. Significantly improves the total elongation. Therefore, the S content is limited to 0.02 wt% or less. In order to significantly improve the workability, it is preferably 0.010 wt% or less.
[0030]
sol.Al: 0.15wt% or less
sol.Al is an element necessary for deoxidation, but if it exceeds 0.15 wt%, not only the deoxidation effect is saturated but also inclusions are generated, which adversely affects the moldability. For this reason, sol.Al content was limited to 0.15 wt% or less. In order to secure stable production conditions, a range of 0.030 to 0.10 wt% is preferable.
[0031]
N: 0.020 wt% or less N forms precipitates and causes a decrease in elongation. On the other hand, when left in a solid solution state, it is possible to harden the steel appropriately and improve the balance between strength and workability. However, if it exceeds 0.020 wt%, not only the elongation is remarkably lowered but also it causes slab cracking, so it is limited to 0.020 wt% or less. When workability is more important than strength, it is preferably 0.010 wt% or less.
[0032]
Although the essential components have been described above, the present invention can further contain the following elements as appropriate.
Nb: 0.003 to 0.020 wt%
Nb not only contributes to the reduction of aging and softening of steel by carbon fixation, but is also useful in that it has a fine structure by moderately suppressing recrystallization in the γ region during hot rolling. Element. However, if the content exceeds 0.020 wt%, not only a non-uniform structure is caused in the hot-rolled sheet, but also an increase in the load during hot-rolling is caused. Was added in the range of 0.003 to 0.020 wt%. In addition, when emphasizing workability, it is desirable to set it as the range of 0.003-0.015 wt%.
[0033]
Ti: 0.003 to 0.020 wt%
Ti has the same effect as Nb, and the formability can be improved by the combined addition with Nb. However, even if added over 0.020 wt%, the effect reaches saturation and only increases the cost. On the other hand, if less than 0.003 wt%, the addition effect is poor, so Ti is 0.003 to 0.020 wt%. In this range, it was added.
[0034]
B: 0.0002-0.0020wt%
B is an element useful for refining the structure of a hot-rolled sheet in combination with hot-rolling conditions. It also serves to prevent secondary processing brittleness. However, excessive addition not only delays the recrystallization of austenite during hot rolling and increases the load during rolling, but also degrades the material of the annealed material, particularly the elongation, so B is in the range of 0.0002 to 0.0020 wt%. It was supposed to be added.
[0035]
Cu: 0.5 wt% or less, Ni: 0.5 wt% or less, Cr: 0.5 wt% or less, Mo: 0.2 wt% or less
Cu, Ni, Cr and Mo are all solid solution strengthening elements like Mn, and are useful elements for refining the structure because they lower the transformation point. However, if it is added too much, not only the cost of the steel is increased, but also the load of cold rolling due to the hardened hot rolled sheet is increased, so the upper limit is 0.5 wt%, especially for Mo, considering the cost, 0.2 wt% %.
[0036]
Next, manufacturing conditions other than the hot rolling process will be described.
(a) Cold rolling conditions after pickling Cold rolling is preferably performed at a rolling reduction of 70 to 90%. This is because, although the steel according to the present invention has been reduced, the grain size of the hot-rolled sheet is still quite large, so if the rolling reduction is less than 70%, the driving force for recrystallization decreases, and after annealing, This is because the grains tend to be coarse, and if over 90%, anisotropy is deteriorated.
[0037]
(b) Annealing and skin pass after cold rolling, and annealing after secondary rolling cold rolling are preferably performed at a temperature higher than recrystallization by continuous annealing from the viewpoint of productivity.
Then, in order to adjust to the target tempering degree and from the viewpoint of stretcher strain resistance, it is necessary to perform skin pass or secondary rolling. At that time, the rolling reduction should be 30% or less. This is because, if the rolling reduction is higher than this, the strength becomes too high and the balance between workability and strength cannot be maintained, and the in-plane anisotropy deteriorates.
[0038]
By using the above-described component composition and manufacturing conditions, not only the strength and workability are excellent, but also satisfies the relationship of plate thickness : 0.25 to 0.05 mm, plate width : 1200 to 900 mm, plate width / plate thickness <20000. An ultra-thin and wide steel plate can be obtained stably. Such a steel plate is an extremely thin and wide steel plate that could not be expected by a conventional manufacturing method.
[0039]
[Real deer example]
Example 1
Steels having the composition shown in Table 1 were melted to prepare test materials.
First, using steel Nos. 1 and 11 in Table 1, hot rolling was performed under the conditions shown in Table 2, and after pickling, cold rolling and recrystallization annealing were performed at the rolling reduction shown in the same table. Secondary rolling was performed under the conditions shown in Table 3. Each specimen was joined to the rear end portion of the preceding sheet bar prior to finish rolling, endless rolling was performed, and the width edge portion was soaked with an edge heater.
Table 3 shows the results of the examination of the crystal grain size (GSN), the structure uniformity in the thickness direction, the Rockwell hardness, the r value, the Δr value, and the flange formability of each steel plate thus obtained.
The scale of Rockwell hardness was HR30T. The r value was evaluated by the anisotropy of the elastic modulus as defined in JIS. Furthermore, the flange formability is tin plating equivalent to # 25 under normal conditions, this is formed into the can body of a 3P can by roll forming and high-speed seam welding, and subjected to necking and stretch flange processing. Evaluation was made based on the presence or absence of skin roughness and cracking.
[0040]
[Table 1]

[0041]
[Table 2]

[0042]
[Table 3]

[0043]
As apparent from Table 3, in accordance with the present invention, rolling is performed at a total rolling reduction ratio of 80% or more in the rough rolling process, of which the final pass rolling reduction ratio is 20% or more, and then at a temperature of 950 ° C. or higher in the finish rolling process. Rolling at a total rolling reduction of 70% or more in the region, and rolling at a rolling reduction of 55% or more in the temperature range of Ar _{3 to} 950 ° C so that the final finishing temperature becomes Ar ₃ -50 ° C or more. After finishing the hot rolling, and then winding up in the temperature range of 550-750 ° C, it is uniform and fine, excellent in workability and strength balance, and extremely thin and wide (900-1200mm, width / thickness) < 20000 ) steel sheet could be produced. In the steel sheet according to the present invention, the variation value of HR30T was 5% or less in the region excluding the width edge portion within 20 mm from the width end, indicating a uniform material.
[0044]
FIG. 1 shows the relationship between the rolling reduction at 950 ° C. or higher and the grain number of the final product in the finish rolling process.
The material used was steel No. 11, and the production conditions were the same as the conditions D in Tables 2 and 3.
As shown in the figure, by rolling at a total reduction of 70% or more in a temperature range of 950 ° C or higher, the microstructure in the final stage becomes finer, so that recrystallization at that stage is effectively performed. As a result, the particle size of the final product can be reduced.
[0045]
Also, FIG. 2 shows the relationship between the grain size number of rolling reduction and final product in the temperature range of Ar ₃ to 950 ° C. in the finish rolling process.
The material used was steel No. 11, and the production conditions were the same as the conditions D in Tables 2 and 3.
As shown in the figure, it can be seen that by performing rolling of 55% or more in the temperature range of Ar _{3 to} 950 ° C., miniaturization is realized even in this region where recrystallization is difficult.
[0046]
Example 2
Steel plates for cans were produced under the conditions shown in Tables 4 and 5 using Steel Nos. 1 to 19 shown in Table 1 above.
Table 5 shows the results of examination of the crystal grain size, the structure uniformity in the thickness direction, the Rockwell hardness, the r value, the Δr value, and the flange formability of each steel plate thus obtained.
[0047]
[Table 4]

[0048]
[Table 5]

[0049]
Among the comparative steels, steels Nos. 7 and 9 had low r values and poor deep drawability. Further, in each of Steel Nos. 7, 8, 9, 17, 18, and 19, Δr is negative and becomes a large value, and it is understood that the ear becomes large and defective when the diaphragm is deformed. Further, for steel Nos. 10, 17 and 18, the mixed grain structure remained and the skin roughness judgment was x.
On the other hand, all of the steel Nos. 1 to 6 and 11 to 16 satisfying all the requirements of the present invention were able to be ultra-thin and wide steel plates excellent in all properties.
[0050]
【The invention's effect】
Thus, according to the present invention, it is possible to obtain a steel plate for a can that has a fine and uniform structure, has both strength and workability, and is excellent in flange formability even with an extremely low carbon steel plate. Moreover, according to the present invention, it is possible to manufacture a steel sheet that is as thin and wide as could not be expected.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the rolling reduction at 950 ° C. or higher and the grain number of the final product in the finish rolling process.
FIG. 2 is a graph showing the relationship between the rolling reduction in the temperature range of Ar _{3 to} 950 ° C. and the grain number of the final product in the finish rolling process.

Claims (4)

C: 0.0005 to 0.0150 wt%,
Si: 0.2 wt% or less,
Mn: 0.05-0.6 wt%
P: 0.02 wt% or less,
S: 0.02 wt% or less,
A steel containing Al: 0.15 wt% or less and N: 0.020 wt% or less, with the balance being Fe and inevitable impurities, is made into a slab after melting, and then in the hot rough rolling process after slab heating, Rolling ratio: 80% or more and final pass rolling ratio: 20% or more rolling, then joining the preceding sheet bar with the preceding sheet bar before finish rolling, in the hot finish rolling process, Rolling at a total reduction ratio of 70% or more at a temperature range of 950 ° C. or higher, followed by rolling at a total reduction ratio of 55% or higher at a temperature range of Ar _{3 to} 950 ° C., and a final finishing temperature: Ar ₃ −50 Finishes hot rolling above ℃, then winds in the temperature range of 550-750 ℃, removes scale, and after cold rolling and recrystallization annealing, reduction rate: 30% or less skin pass or secondary rolling The manufacturing method of the steel plate for cans characterized by giving. In Claim 1, the steel composition further comprises
Nb: 0.003 to 0.020 wt%,
Ti: 0.003 to 0.020 wt% and B: 0.0002 to 0.0020 wt%
A method for producing a steel plate for cans, characterized by having a composition containing one or more selected from the above. The steel composition according to claim 1 or 2, further comprising:
Cu: 0.5 wt% or less,
Ni: 0.5 wt% or less,
Cr: 0.5 wt% or less and
Mo: A method for producing a steel plate for cans, characterized in that the composition contains one or more selected from 0.2 wt% or less. The obtained steel sheet according to claim 1, 2 or 3, the sheet thickness: 0.25 to 0.05 mm, the sheet width : 1200 to 900 mm, the sheet width / thickness < 20 000, satisfying the requirements of ultra-thin, uniform material A method for producing a steel plate for cans, characterized in that it is a wide material.

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