JP4810766B2 - Manufacturing method of ultra-thin high-strength steel sheet for lightweight 2-piece can - Google Patents

Description

【００４５】
【表２】

【００４６】
【表３】

【００４７】
本発明例は、ｒ値が1.0 以上と高く、Δｒが±0.3 の範囲内となり、ｒ値の異方性が小さく、加工性に優れ、かつ歪時効硬化特性も大きく、10％予成形−塗装焼付処理相当熱処理を施したのち、引張強さＴＳ：430MPa以上を十分に満足する鋼板となっている。本発明の範囲を外れる比較例では、Δｒが大きくなり、異方性が強いか、あるいは歪時効硬化特性が不足した鋼板となっている。本発明例は、製缶時の耳発生の問題もなく、缶底部の耐圧強度も高くなった。また、ネック・フランジ加工性についても、高強度薄肉材であるにもかかわらず、不良の発生は認められず、良好であった。
【００４８】
また、これら本発明例の鋼板を用いて電気錫めっき処理を施した後、１stカップ成形、ＤＩ成形、４段ネック成形を行ってフラット底形状の250gストレッチドロー・アイオニング成形缶とした。その結果、本発明例の鋼板はいずれも、カップ成形性、アイアニング性、ボトム成形性とも問題なく、多段ネック、フランジ加工を施しても、ネックしわやフランジ割れの発生もなく、しかも板厚が薄いにも関らず、缶強度が確保できる特性を有していることがわかった。
【００４９】
【発明の効果】
本発明によれば、軽量飲料缶用として好適な、耳発生も少なく、所望の缶体の耐圧強度を確保できる、２ピース缶用極薄鋼板を、安価に製造でき、産業上格段の効果を奏する。
【図面の簡単な説明】
【図１】冷延鋼板のΔｒと熱間仕上圧延終了温度ＦＤＴ、巻取温度ＣＴとの関係を示すグラフである。
【図２】冷延鋼板のΔｒにおよぼす一次圧延（冷間）の圧下率の影響を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light steel plate for two-piece cans, and particularly has a sheet thickness of 0.20 having a small in-plane anisotropy of r value and a tensile strength after processing-paint baking (210 ° C. × 20 min) equivalent to 430 MPa or more. The present invention relates to an ultra-thin cold-rolled steel sheet for high-strength cans of mm or less.
[0002]
[Prior art]
Soft drinks, beverage cans such as beer, and various can containers such as food cans are divided into two-piece cans consisting of a can body and top lid, and three-piece cans consisting of a can body, top lid, and bottom lid. Separated. In particular, the steel plate used for the can body of a two-piece can is a variety of harsh processes such as deep drawing (cup forming), subsequent ironing to obtain the can height, neck diameter reduction processing, flange processing, dome processing, etc. Characteristics that can withstand proper molding are required. Furthermore, recently, for the purpose of reducing the weight of the can, the demand for a steel plate having a thickness of 0.20 mm or less has been increasing due to the trend toward thinning of the steel plate.
[0003]
Even when the steel plate is made thinner, it is necessary to maintain a strength higher than the specified strength as the can strength, so it is assumed that the steel plate as the material has a higher strength. It is desirable that the contents are hardened when filling the contents.
In addition, when deep drawing a raw steel plate into a cup shape, if a thin steel plate is used, even if a high strength steel plate is used, the rigidity is insufficient and wrinkles are likely to occur. This tendency becomes more remarkable as the limit drawing ratio (LDR) increases, that is, as the blank diameter increases. In order to reduce the generation of wrinkles, it is conceivable to increase the wrinkle restraining force (BHF). However, when the BHF becomes large, the punch shoulders are likely to break during processing, and the larger ears that occur in the circumferential direction of the cup are stretched (ear standing) or torn (ear cuts). is there. In order to solve this problem, a steel sheet having a small in-plane anisotropy of r value, that is, a small Δr is desired.
[0004]
Furthermore, recently, it has been directed to apply a two-piece can for coffee drinks in addition to carbonated drinks. When it is used for coffee drinks, since the inspection inspection is performed for the purpose of alteration inspection of the contents of the can, it is required to change the shape of the bottom of the can from a dome shape to a flat (flat bottom) shape. When the bottom of the can has a flat shape, a steel plate for cans made of a material capable of obtaining further high strength is desired in order to maintain pressure resistance.
[0005]
In order to obtain a thin steel plate for cans,
(1) Increase the cold rolling reduction ratio,
(2) Decreasing the thickness of the cold-rolled mother plate, that is, the thickness of the hot-rolled plate,
Two means are conceivable. However, the increase in the cold rolling reduction increases the in-plane anisotropy of the r value, and increases the generation of ears during drawing. Further, when the thickness of the hot-rolled sheet is reduced, there is a problem that the variation in hot rolling temperature in the width direction and the length direction is increased and the productivity of hot rolling is also reduced.
[0006]
For example, JP-A-59-38336 discloses C: 0.10% or less, Si: 0.06% or less, Mn: 0.50% or less, P: 0.03% or less, S: 0.03% or less. A continuous cast steel slab containing Al: 0.15% or less and N: 0.008% or less is hot-rolled at a finishing temperature of Ar ₃ or higher, wound at 640 to 700 ° C, and cold-rolled at a reduction rate of 80 to 95%. And after continuous annealing at 650 ° C or higher for 20 seconds or longer, cooling to 500 ° C or lower at 10 to 500 ° C / s, holding at a temperature of 500 to 350 ° C for 20 seconds or longer, and excellent workability A method for producing an ultrathin steel sheet for cans with small in-plane anisotropy is disclosed.
[0007]
Japanese Patent Laid-Open No. 9-241756 discloses that a hot rolled steel sheet having an average crystal grain size before cold rolling of 30 μm or more is subjected to cold rolling at a cold rolling reduction ratio of 70 to 98%, and a recrystallization temperature of 800 or more. After annealing for 3 min or more at ℃ or lower, re-rolling is further performed with a cold rolling reduction ratio of 1 to 70% and the total cold rolling reduction ratio to the final product is 88 to 98%. Discloses a method for producing a steel plate for containers, which is extremely small.
[0008]
However, in the techniques described in JP-A-59-38336 and JP-A-9-241756, the generation of ears at the time of drawing is reduced, but with respect to the decrease in pressure resistance accompanying the thinning of the steel sheet. Had left the issue of not being considered.
JP-A-4-350146 discloses C: 0.02 to 0.08%, Si: 0.02% or less, Mn: 0.05 to 0.30%, P: 0.025% or less, S: 0.025% or less, Al: 0.02 to 0.15% , N: 0.003 to 0.02% of the component, and the balance is hot-rolled continuously cast slab composed of iron and inevitable impurities, wound up at 570 to 670 ° C., and the amount of (N _total −N _as AlN) is 0.003. A steel plate for a two-piece can with a content of ˜0.010% is disclosed. In the technique disclosed in Japanese Patent Laid-Open No. 4-350146, wrinkles do not occur even when multi-stage neck-in is performed, cracks do not occur when the lid is tightened, and the pressure-resistant strength of the bottom of the can decreases even if retort sterilization is performed. Not to do.
[0009]
Japanese Patent Application Laid-Open No. 10-110238 discloses that a continuous cast piece containing C: 0.005 to 0.05%, Al: 0.08% or less, N: 0.012% or less is hot-rolled and subjected to a continuous annealing method. A method of manufacturing a steel sheet for a welded can body has been proposed in which temper rolling is performed at a rolling reduction of 5% or more and less than 15%, and solute C + solid solution N ≧ 50 ppm.
However, the technique described in Japanese Patent Laid-Open No. 4-350146 has a problem that in-plane anisotropy of the r value may increase when the thickness is reduced to 0.20 mm or less. Further, the technique described in Japanese Patent Laid-Open No. 10-110238 also has a problem that the in-plane anisotropy of the r value increases.
[0010]
[Problems to be solved by the invention]
The present invention solves the above-mentioned problems of the prior art, has an excellent deep drawing processability suitable for a lightweight two-piece beverage can, has few ears, and further imparts 10% processing strain and further paints. The purpose is to propose a method for manufacturing a high strength ultra-thin steel plate with a thickness of 0.20 mm or less that can achieve high strength of the can body with high tensile strength of 430 MPa or higher after heat treatment equivalent to baking treatment. To do.
[0011]
[Means for Solving the Problems]
In order to achieve the above-mentioned problems, the present inventors diligently studied the influence of various factors on deep drawing processability, ear generation, and can strength after canning.
As a result, the present inventors have determined that the steel plate strength at the bottom of the can after the processing-baking coating is applied determines the pressure resistance of the two-piece can, and the steel plate is equivalent to a processing strain of 10% -baking coating. If the tensile strength after treatment (heat treatment at 210 ° C x 20min) is 430MPa or more, even if the bottom of the can is flat, during retort treatment (heat treatment at 120 ° C x 90min), or It has been found that the problem of buckling occurring when a positive pressure can filled with nitrogen and under pressure is dropped can be solved. It was found that it is important to optimize the N content to 0.0090 to 0.0140 mass% in the steel composition in order to provide such a steel sheet with such characteristics.
[0012]
Further, the present inventors set the r value to an appropriate value of 1.0 to 1.5 and improve the in-plane anisotropy Δr of the r value to 0 ± in order to improve the deep drawing workability and reduce the generation of ears. It was found that it was necessary to reduce it to 0.3. In order to reduce Δr, it has been found that it is important to optimize hot rolling conditions and cold rolling reduction.
Next, the results of experiments conducted by the inventors will be described.
[0013]
Hot-rolled sheet by hot rolling with 0.045% C-0.21% Mn-0.037% Al-0.0113% N steel material in mass%, heated to 1200 ° C and changing finish rolling exit temperature FDT and coiling temperature CT The hot-rolled sheet was subjected to primary rolling (cold) to form a cold-rolled sheet, and then annealed at 700 ° C. and cooled. Thereafter, 1.5% temper rolling was performed to obtain Δr.
[0014]
FIG. 1 shows the relationship between Δr, FDT, and CT. From FIG. 1, it can be seen that Δr can be in the range of 0 ± 0.3 by setting the FDT to 860 ° C. or higher and CT to 620 ° C. or higher.
FIG. 2 shows the influence of the rolling reduction of primary rolling (cold) on Δr. From FIG. 2, it can be seen that Δr is smaller than −0,3 and close to 0 by setting the rolling reduction of primary rolling (cold) to 90% or less.
[0015]
That is, from these results, the inventors have determined that in order to reduce the strength as much as possible, increase the r value to 1.0 or more, and set Δr to 0 ± 0.3, the finish rolling finish temperature of hot rolling They found that it is important to increase the coiling temperature and lower the rolling reduction of primary rolling.
The present invention has been completed based on the above findings and further studies.
[0016]
That is, the present invention includes a hot rolling process in which a steel material is heated and hot rolled into a hot rolled sheet by rough rolling and finish rolling, and a winding process in which the hot rolled sheet is wound, and the hot rolled sheet A cold rolling to produce a cold rolled sheet, an annealing process to anneal the cold rolled sheet to a cold rolled annealed sheet, and a temper rolling process to temper roll the cold rolled annealed sheet In the manufacturing method of the ultra-thin cold-rolled steel sheet for cans having a sheet thickness of 0.20 mm or less, the composition of the steel material is, by mass%, C: 0.1% or less, N: 0.0090-0.0140%, Si: 0.03% or less, Mn: 0.05 to 0.60%, P: 0.02% or less, S: 0.02% or less, Al: 0.02 to 0.20%, O: 0.01% or less, or further, Group A to Group C Group A: Cu: 0.001 to 0.5%, Ni: 0.01-0.5%, Cr: 0.01-0.5%, Mo: 0.001-
One or more selected from 0.5%,
Group B: Ca: 0.005% or less, Nb: 0.10% or less, Ti: 0.2% or less selected from one or more,
Group C: B: see contains more than one group or two groups of 0.005% or more, a composition comprising the balance Fe and unavoidable impurities, the finish rolling end temperature FDT of the hot rolling step was 860 ° C. or higher, the Continuous annealing in which the coiling temperature CT in the winding process is 620 ° C. to 710 ° C., the cold rolling reduction in the primary rolling process is 90% or less, and the annealing process is less than the Ac ₁ transformation point. A plate having an average r value of 1.0 to 1.5, an in-plane anisotropy Δr of r value as small as 0 ± 0.3, and a tensile strength after heat treatment equivalent to a paint baking process of 430 MPa or more This is a method for producing an ultra-thin cold-rolled steel sheet for a high-strength two-piece can with a thickness of 0.20 mm or less. In the present invention, it is preferable that the rolling reduction of the temper rolling is 2% or less.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
First, the reasons for limiting the steel material composition used in the present invention will be described.
The steel material of the present invention is a low carbon aluminum killed steel, and its composition is preferably as follows.
C: 0.1% or less C is an important element that refines the crystal grains and increases the strength of the steel by solid solution strengthening. On the other hand, it forms carbides and decreases the ductility of the steel sheet and, consequently, the workability. Let For this reason, C is limited to 0.1% or less. If the C content is too low, the in-plane anisotropy Δr of the r value becomes large, and it becomes difficult to ensure a tensile strength of 430 MPa or more after aging, so C is preferably 0.015% or more. In order to secure the r value and reduce the in-plane anisotropy Δr of the r value, C is preferably 0.015 to 0.05%. In addition, More preferably, it is 0.03-0.05%.
[0018]
N: 0.0090-0.0140%
N is present in the steel sheet as precipitates such as solute N or AlN, and after imparting 10% processing strain after baking processing equivalent treatment after securing r value and Δr without adversely affecting flange processing and neck processing. Has the effect of increasing the tensile strength. In the present invention, since the strength of the can after molding needs to be kept high, the N content is made 0.0090% or more in order to increase the tensile strength after strain aging. If the content exceeds 0.0140%, surface defects such as bulges due to Ar bubbles and N ₂ bubbles remaining in the slab frequently occur. For these reasons, N is set to 0.0090-0.0140%.
[0019]
Si: 0.03% or less
Si is an element that increases the strength of steel by solid solution strengthening, but addition of a large amount causes problems such as deterioration in workability, surface treatment property, and corrosion resistance. For this reason, it is desirable to reduce as much as possible in the present invention, but it is acceptable up to 0.03%.
Mn: 0.05-0.60%
Mn is an effective element for preventing hot cracking due to S, and in order to obtain this effect, it is necessary to contain 0.05% or more. On the other hand, a large amount is uneconomical and tends to deteriorate the corrosion resistance and increase the strength variation. For this reason, in this invention, Mn is limited to 0.05 to 0.60%. In addition, Preferably it is 0.15-0.40%.
[0020]
P: 0.02% or less P significantly hardens steel, deteriorates flange workability and neck workability, and remarkably deteriorates corrosion resistance. For this reason, in the present invention, P is preferably limited to 0.02% or less.
S: 0.02% or less S is an element that exists as an inclusion in steel and lowers the ductility of the steel sheet and further deteriorates the corrosion resistance. In the present invention, S is preferably reduced as much as possible, but is acceptable up to 0.02%. it can. In addition, Preferably it is 0.015% or less.
[0021]
Al: 0.02-0.20%
Al acts as a deoxidizer and is an element necessary for increasing the cleanliness of steel, and it needs to be contained in an amount of 0.02% or more. However, excessive content is not economically preferable, and it suppresses the growth of the recrystallized grain size and lowers the r value. Therefore, the content needs to be 0.20% or less. For this reason, in the present invention, Al is limited to 0.02 to 0.20%. In addition, Preferably, it is 0.03-0.10%.
[0022]
O: 0.01% or less O is present as an oxide in steel and causes reduction in ductility and deterioration in corrosion resistance. Therefore, it is preferable to reduce it as much as possible, but in the present invention, up to 0.01% is acceptable. In particular, in order to obtain a thin steel plate, the content is preferably 0.005% or less.
[0023]
In the present invention, in addition to the above-described composition, the following group A to group C, group A: Cu: 0.001 to 0.5%, Ni: 0.01 to 0.5%, Cr: 0.01 to 0.5%, Mo: 0.00
One or more selected from 1 to 0.5%,
Group B: Ca: 0.005% or less, Nb: 0.10% or less, Ti: 0.2% or less selected from one or more,
Group C: B: One or more of 0.005% or more may be contained.
[0024]
Group A: Cu: 0.001 to 0.5%, Ni: 0.01 to 0.5%, Cr: 0.01 to 0.5%, Mo: 0.001 to 0.5%, one or more selected from the group
Since Cu, Ni, Cr and Mo can increase the strength without deteriorating the ductility of the steel, they can be appropriately selected and contained for adjusting the strength. These elements also have the effect of improving the corrosion resistance of the steel sheet. In order to exert these effects, it is preferable to contain at least 0.001% for Cu and Mo and at least 0.01% for Ni and Cr. However, even if the content exceeds 0.5%, the effect is saturated and the cost is increased. Therefore, the upper limit of the content is preferably 0.5% for both elements. In addition, the effect of these elements is demonstrated similarly even if it adds individually or in combination.
[0025]
Group B: Ca: 0.005% or less, Nb: 0.10% or less, Ti: 0.2% or less selected from one or more,
Ca, Nb and Ti are all elements useful for improving the cleanliness of steel, and can be selected and contained as necessary. In order to obtain the above-described effects, it is preferable to contain 0.002% or more of Ca, 0.001% or more of Nb, and 0.001% or more of Ti. However, an excessive Ca content exceeding 0.005% is not only uneconomical, but the non-metallic inclusions produced have a low melting point and become soft, and are elongated in the rolling process, resulting in poor can manufacturing. Connected. Therefore, Ca is preferably 0.005% or less.
[0026]
If Nb exceeds 0.10%, the recrystallization temperature rises due to the pinning effect of the grain boundaries due to the Nb-based precipitates, the workability of the continuous annealing furnace becomes poor, and the fine grains are reduced. Become. For this reason, it is preferable that Nb content shall be 0.10% or less.
If Ti is contained excessively in excess of 0.20%, sharp and hard precipitates are generated, which deteriorates the corrosion resistance and also causes creases during canning. Therefore, the Ti content is preferably 0.2% or less.
[0027]
Group C: B: 0.005% or less B is an element effective for improving grain boundary embrittlement, and can be contained if necessary. For example, it is effective to contain B in order to obtain good quality even in applications where the can is stored at a low temperature and an embrittlement crack may occur. However, B segregates at the recrystallized grain boundary during the continuous annealing and delays the recrystallization. Therefore, the content is preferably 0.005% or less. In addition, it is preferable that the lower limit of the B content is 0.0001% necessary for exhibiting the effect.
[0028]
The balance other than the above components is Fe and inevitable impurities.
The steel material having the above composition is melted by a generally known melting method to obtain a steel material such as a slab having a high cleanliness by a known casting method such as a continuous casting method.
In the present invention, a steel material is heated and turned into a sheet bar by rough rolling, and a hot rolling process in which the sheet bar is hot rolled by finish rolling, and a winding process for winding the hot rolled sheet to form a coil. A hot-rolled sheet wound around
[0029]
In rough rolling, the heating temperature and rolling conditions are not particularly limited, and it is sufficient that the sheet bar can have a predetermined size and shape. In addition, it is preferable that the heating temperature of a steel raw material shall be 1100-1250 degreeC. When the heating temperature is less than 1100 ° C., the rolling load in the rough rolling increases and it becomes difficult to set the finish rolling end temperature within a predetermined temperature range. On the other hand, when the heating temperature exceeds 1250 ° C., the formation of surface scale becomes remarkable, resulting in large scale loss and economical disadvantage, and a scale that is difficult to remove by finish rolling remains and tends to cause surface defects. Further, the coarsening of crystal grains becomes remarkable.
[0030]
After forming a sheet bar by rough rolling, the sheet bar is finish-rolled to obtain a hot-rolled sheet. The finish rolling finish temperature FDT of finish rolling is set to 860 ° C or higher.
When the FDT is less than 860 ° C., the in-plane anisotropy of the r value increases, and the occurrence of ears becomes prominent during deep drawing. On the other hand, if the FDT is too high, the generation of scale becomes remarkable, and there is a concern that the subsequent steps such as scale removal may be hindered. Therefore, the FDT is preferably 940 ° C. or lower. More preferably, the temperature is 870 to 910 ° C. After the hot rolling process, there is no problem as long as it is adjusted to a predetermined coiling temperature regardless of whether it is ordinary air cooling or water cooling.
[0031]
Further, in the present invention, after being formed into a sheet bar in the rough rolling step, before the finish rolling step, the front end portion of the sheet bar and the rear end portion of the sheet bar preceding the sheet bar are joined, and then finish rolling. can do. By joining the sheet bars in this manner, it is possible to easily prevent the disturbance of the shape in the longitudinal direction, which is a problem particularly in the ultrathin hot-rolled steel sheet as in the present invention, and the yield of products can be improved.
[0032]
Moreover, it is preferable to heat and heat the longitudinal direction edge part of a sheet bar over the full width between rough rolling processes and finish rolling, or to heat and heat the width direction edge part over the full length. The end of the sheet bar in the longitudinal direction or the end in the width direction tends to decrease in temperature, and the yield is improved by heating the temperature of this part to equalize the temperature in the sheet bar. Note that the heating method is preferably an induction heating method.
[0033]
Next, the hot-rolled sheet is wound in a coil shape in the winding process, and the winding temperature CT is set to 620 ° C to 710 ° C.
When CT is less than 620 ° C., the r value decreases, Δr increases, the in-plane anisotropy of the r value increases, and the occurrence of ears during deep drawing becomes significant. On the other hand, when CT exceeds 710 ° C., the crystal grains of the hot-rolled sheet become coarse as the carbides become coarse and coarse, the tensile strength TS decreases, and the desired strength cannot be obtained. For this reason, CT was limited to 620 ° C to 710 ° C. In addition, Preferably it is 630-710 degreeC.
[0034]
The thickness of the hot-rolled plate is determined depending on the thickness of the cold-rolled plate (product plate) as the base plate of the cold-rolled plate, but to make a thin cold-rolled plate with a thickness of 0.20 mm or less, In consideration of reducing the in-plane anisotropy and improving the r value, it is preferably 2 mm or less.
Next, the hot-rolled sheet manufactured by the above-described process is descaled by a conventional method such as hydrochloric acid pickling, and then cold-rolled to form a cold-rolled sheet, and the cold-rolled sheet is annealed and cooled. An annealing process for making a fired annealed sheet and a temper rolling process for temper rolling the cold rolled annealed sheet are sequentially performed.
[0035]
In the primary rolling process, it is sufficient if the desired cold rolled sheet size and shape can be obtained, but in order to reduce Δr, the reduction ratio of primary rolling (cold) is 90% or less, preferably 80% or more. To do. In order to achieve such a cold rolling reduction, it is preferable to reduce the thickness of the hot rolled sheet. When the primary rolling reduction exceeds 90%, the in-plane anisotropy Δr of the r value increases as shown in FIG. On the other hand, if it is less than 80%, in order to make a steel sheet for an ultra-thin can with a thickness of 0.2 mm or less, it is necessary to extremely reduce the thickness of the hot-rolled sheet. % Or more is preferable.
[0036]
Next, the cold rolled sheet is annealed in an annealing process. The annealing process is preferably performed in a continuous annealing furnace. Annealing is performed for imparting formability to the steel sheet, and in the present invention, the annealing temperature is set to a continuous annealing with an Ac ₁ transformation point lower than the annealing temperature. If the annealing temperature is equal to or higher than the Ac ₁ transformation point, the crystal grains become coarse and the strength cannot be obtained. The annealing temperature is preferably 670 to 720 ° C. from the viewpoint of workability and ensuring strength. It is sufficient that the soaking time at the annealing temperature is 1 s or more in view of operational stability. In addition, the cooling after the annealing step is not particularly limited as the same level of cooling as in the normal continuous annealing.
[0037]
Cold-rolled annealed sheets having passed through the annealing step, temper rolling step Ru is temper rolled by cold rolling at. Temper rolling reduction rate: you 2% or less. In the temper rolling in the present invention, SR (single cold-reducing) with a rolling reduction of 2% or less is used for the purpose of adjusting the shape of a generally known steel sheet, introducing movable dislocations, adjusting the surface roughness, and the like. If the rolling reduction exceeds 2%, the steel sheet strength increases excessively due to work hardening, and the workability deteriorates.
[0038]
The cold-rolled annealed plate thus manufactured may be used as a product plate (coil) after the rust prevention treatment. Alternatively, pickling treatment may be performed, and surface treatment such as tin plating, chromium plating, nickel plating, or the like may be performed on at least one surface to form a product plate. The product plate is preferably further oiled. Further, as the oil coating agent, DOS (Di-octyl sebacate) and ATBC (Acetyl tri-butyl citrate) are preferable.
[0039]
The ultra-thin cold-rolled steel sheet for cans manufactured by the above-described manufacturing method is a steel sheet having a small in-plane anisotropy having an average r value: 1.0 to 1.5 and Δr: 0 ± 0.3. If the average r value is less than 1.0, there is a problem that the deep drawing processability deteriorates and it is difficult to obtain the required can height. On the other hand, if the average r value exceeds 1.5, the elongation in the can height direction is large. Become.
The average r value and Δr are the r value (r _L , r _D , r _C ) in the rolling direction (L direction), 45 ° from the rolling direction (D direction), and perpendicular to the rolling direction (C direction), respectively. And the average r value = (r _L + r _C + 2r _D ) / 4 and Δr = (r _L + r _C −2r _D ) / 4.
[0040]
Furthermore, the ultra-thin cold-rolled steel sheet for cans produced by the production method of the present invention has a tempering degree after production of about T3 to T4, and has an appropriate average r value and a small Δr as described above. Can-making ability is good. Further, the tensile strength after applying 10% processing strain and heat treatment at 210 ° C. for 20 minutes is 430 MPa or more. By having such properties, the can body has a high pressure resistance and can achieve a light weight steel sheet for cans.
[0041]
【Example】
Steel having the composition shown in Table 1 was melted in a converter and then used as a rolling material (slab) with a vertical bending type continuous casting machine. Subsequently, these rolled materials were hot rolled under the conditions shown in Table 2 to obtain hot rolled sheets. In addition, sheet bar joining and sheet bar heating were performed on one part of the steel plate. After that, these hot-rolled sheets were descaled by pickling, further cold-rolled under the conditions shown in Table 2, and then annealed or further temper-rolled under the conditions shown in Table 2 to obtain an ultra-thin cold-rolled steel sheet. It was.
[0042]
About the obtained ultra-thin cold-rolled steel sheet, the hardness test and the measurement of r value were implemented. In addition, for the evaluation of the pressure strength of the bottom of the can, it was rolled as described above to give a strain of 10%, and further subjected to an aging treatment of 210 ° C. × 20 minutes corresponding to a paint baking process, and the tensile strength was determined by a tensile test. evaluated.
(I) Hardness test Regarding these cold-rolled steel sheets, the tempering degree was determined from the HR30T hardness in accordance with the provisions of JIS G 3303.
(Ii) JIS No. 5 tensile test specimens were sampled in the rolling direction (L) from the central part in the measurement width direction of the r value, 45 ° direction (D) from the rolling direction, and perpendicular direction (C) from the rolling direction, A tensile test was performed at a strain rate of 40% / min, and an r value was obtained from the ratio of logarithmic strains in the width direction and the plate thickness direction by the plastic strain method (JIS G 3135-1986, 18p). The average r value was calculated as follows: average r value = (r _L + r _C + 2r _D ) / 4, and Δr was calculated by Δr = (r _L + r _C −2r _D ) / 2.
(Iii) Tensile property test after strain aging Samples were taken from the center in the width direction of these cold-rolled steel sheets in the rolling direction and in the direction perpendicular to the rolling direction, and after adding a strain with a rolling reduction of 10% by cold rolling, 210 A heat treatment equivalent to a baking process at 20 ° C. was performed, and then a tensile test was performed to measure the tensile strength TS to obtain an average value in two directions.
[0043]
These results are shown in Table 3.
[0044]
[Table 1]

[0045]
[Table 2]

[0046]
[Table 3]

[0047]
In the present invention example, the r value is as high as 1.0 or more, Δr is in the range of ± 0.3, the r value is small, the workability is excellent, and the strain age hardening property is large, and 10% preform-paint After the heat treatment equivalent to the baking treatment, the steel sheet sufficiently satisfies the tensile strength TS: 430 MPa or more. In a comparative example outside the scope of the present invention, Δr is large and the anisotropy is strong, or the steel sheet has insufficient strain age hardening characteristics. In the present invention example, there was no problem of the occurrence of ears during can making, and the pressure resistance at the bottom of the can was also increased. In addition, the workability of the neck and flange was good because no defects were observed despite the fact that it was a high-strength thin-walled material.
[0048]
In addition, after the electrotin plating process was performed using the steel plates of the present invention examples, 1st cup molding, DI molding, and four-stage neck molding were performed to obtain a 250 g stretch draw / ioning molded can having a flat bottom shape. As a result, all of the steel sheets of the present invention have no problems with cup formability, ironing ability, and bottom formability, and even when subjected to multi-stage neck and flange processing, neck wrinkles and flange cracks do not occur, and the plate thickness is Despite being thin, it was found that it has a characteristic that can strength can be secured.
[0049]
【The invention's effect】
According to the present invention, an ultrathin steel sheet for a two-piece can suitable for a lightweight beverage can, having few ears, and capable of securing the pressure resistance of a desired can body can be manufactured at a low cost, and has a remarkable industrial effect. Play.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between Δr of a cold-rolled steel sheet, hot finish rolling end temperature FDT, and coiling temperature CT.
FIG. 2 is a graph showing the effect of rolling reduction of primary rolling (cold) on Δr of cold-rolled steel sheet.

Claims (2)

The steel material has a hot rolling step in which the steel material is heated to obtain a hot rolled plate by rough rolling and finish rolling, and a winding step in which the hot rolled plate is wound, and the hot rolled plate is cold rolled and cooled. A sheet thickness of 0.20 mm or less, including a primary rolling process for forming a rolled sheet, an annealing process for annealing the cold rolled sheet to form a cold rolled annealed sheet, and a temper rolling process for temper rolling the cold rolled annealed sheet In the manufacturing method of ultra-thin cold-rolled steel sheet for cans,
The composition of the steel material in mass%,
C: 0.1% or less, N: 0.0090-0.0140%,
Si: 0.03% or less, Mn: 0.05 to 0.60%,
P: 0.02% or less, S: 0.02% or less,
Al: 0.02~0.20%, O: see contains 0.01% or less, a composition comprising the balance Fe and unavoidable impurities,
The finish rolling finish temperature FDT of the hot rolling process is set to 860 ° C. or more, the winding temperature CT of the winding process is set to 620 ° C. to 710 ° C., and the cold rolling reduction ratio of the primary rolling process is set to 90% or less. ,
The annealing step is continuous annealing with the annealing temperature less than the Ac ₁ transformation point ,
Ultra-thin cooling for high-strength two-piece cans with an average r value of 1.0 to 1.5 and Δr of 0 ± 0.3, with a sheet thickness of 0.20 mm or less, characterized in that the rolling reduction of the temper rolling is 2% or less. A method for producing rolled steel sheets. In addition to the said composition, it has 1 group or 2 groups or more of following A group-C group by mass%, The manufacture of the ultra-thin cold-rolled steel plate for 2 piece cans of Claim 1 characterized by the above-mentioned. Method.
Group A: Cu: 0.001 to 0.5%, Ni: 0.01 to 0.5%, Cr: 0.01 to 0.5%, Mo: 0.001 to
One or more selected from 0.5%,
Group B: Ca: 0.005% or less, Nb: 0.10% or less, Ti: 0.2% or less selected from one or more,
Group C: B: 0.005% or more

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