JP3915146B2 - Method for producing a steel plate for a two-piece can with excellent non-earring properties and rough skin resistance - Google Patents

Description

【００２８】
【表２】

【００２９】
【表３】

【００３０】
表３から、本発明により製造した缶用鋼板は、良好な成形性のほか、特にΔｒが０．２以下、引張後の表面粗度が０．６以下であり良好な特性を示していることがわかる。また、円筒加工テストにおいても、加工時の割れ、肌荒れ、イヤリングのいずれにおいても何ら問題のないことが明らかである。
また、図４より、本発明法で製造すれば、２次冷間圧下率が高い領域においてもｒ値は高く、また、従来法によって製造した鋼板に比べて、圧下率の増加に対する△ｒの低下が小さいために、２０％を超える高圧下率域においても△ｒは±０．２以内と小さく、プレス加工性、ノンイヤリング性ともに良好であることがわかった。また、このため、２次冷間圧延における圧下率のとりうる範囲が広くなり、調質度の対応範囲も広くなった。
【００３１】
【発明の効果】
以上、説明したように、本発明によれば、プレス加工性のほかに、耐肌荒れ性、ノンイヤリング性にもに優れた缶用鋼板が提供可能になる。したがって、本発明によれば、深絞り加工を施す食缶や飲料缶等における表面性状の改善、歩留りの向上に大きく寄与する。また、本発明による鋼板の適用範囲は、各種金属缶のみならず、乾電池内装缶、各種家電・電器部品、自動車部品等の幅広い範囲への活用も期待できる。
【図面の簡単な説明】
【図１】結晶粒の軸比と△ｒの絶対値との関係を示すグラフである。
【図２】結晶粒度番号と肌荒れとの関係を示すグラフである。
【図３】仕上げ圧延終了から水冷開始までの時間とｒおよび△ｒとの関係を示すグラフである。
【図４】２次冷間圧下率とｒおよび△ｒとの関係を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to materials for can containers such as food and beverage cans, and in particular, manufacture of steel plates for two-piece cans that are excellent in non-earring property (low occurrence of ears) and skin resistance after press working in addition to deep drawability. It is about the method.
[0002]
[Prior art]
Cold-rolled steel sheets used for two-piece cans such as deep-drawn cans, DRD (Drawn and Redrawn) cans and DI (Drawn and Ironined) cans manufactured by press forming such as deep drawing are mainly Such characteristics are required.
1) It should be possible to mold without defects such as cracks during processing.
2) The surface roughness of the steel sheet after press working is small, and the finished appearance is good.
3) The anisotropy of the material is small and the generation of ears (earrings) after deep drawing is small.
In particular, it is necessary to cut off the portion where the earring is generated after the deep drawing of the can. For this reason, when the earrings are large, not only the yield of the material is deteriorated, but also the necessary molding height cannot be obtained in some cases, and the entire molded product must be discarded. Therefore, it is desirable that earrings generated during deep drawing are as small as possible.
By the way, the height of the earring has a good correlation with the in-plane anisotropy Δr of the r value (Rankford value) of the cold rolled sheet metal, and it is known that the earring height becomes 0 when Δr = 0. It has been.
Here, Δr = (r ₀ + r ₉₀ −r ₄₅ ) / 2 (where r ₀ , r ₉₀ , and r ₄₅ are r values in directions of 0 °, 90 °, and 45 ° in the rolling direction, respectively).
[0003]
By the way, several proposals have been made so far regarding manufacturing technology of cold-rolled steel sheets for deep drawing with small earrings.
For example, JP-A-58-151426 discloses that a low carbon Al killed steel is finish-rolled at a high temperature above the Ar ₃ transformation point, hot-rolled at a high temperature and cold-rolled at a reduction rate of 80 to 95%. Discloses a technique for improving the average r value and improving Δr. According to this technique, an appropriate effect is observed, and the in-plane anisotropy is reduced to some extent.
[0004]
[Problems to be solved by the invention]
However, it is still difficult to say that the suppression of earrings is sufficient, and particularly when the secondary cold rolling reduction ratio is high, the earring resistance is insufficient. Such a phenomenon has been an obstacle to the can manufacturing process when trying to increase the secondary cold rolling reduction ratio in order to cope with the thinning of the raw material for the purpose of reducing the can manufacturing cost. In particular, in the case of ultra-low carbon steel, the steel sheet strength after annealing is low, so in order to achieve thinning of the can, secondary cold rolling is performed at a high rolling reduction of about several to 40% after annealing. Therefore, Δr after secondary cold rolling increases in the negative direction, which is a factor that makes it easy to generate earrings.
[0005]
Therefore, the main object of the present invention is to provide a deep drawability sufficient for forming a two-piece can even when manufacturing by secondary cold rolling at a high pressure reduction rate, and the occurrence of earrings is small, and the resistance to resistance after press forming is reduced. The object is to produce a steel plate for a two-piece can with excellent skin roughness.
Another object of the present invention is to provide a steel plate for the above two-piece can having an r value of 1.5 or more and Δr within ± 0.2 even when it is produced by secondary cold rolling at a high pressure reduction rate of 20% or more. There is to manufacture.
[0006]
[Means for Solving the Problems]
As a basic experiment for achieving the above object, the inventors first investigated the relationship between the crystal grain size of the cold-rolled steel sheet, the form of the crystal grains, press workability, earring property, and skin roughness. The results are shown in FIG. 1 and FIG. FIG. 1 shows the relationship between the axial ratio of crystal grains (= length in the major axis direction / length in the minor axis direction) and Δr. From this, Δr of the equiaxed grain structure is compared with that of the stretched grain structure. It was found to be small and excellent in non-earring properties. Moreover, FIG. 2 shows the relationship between the rough skin resistance and the crystal grain size. The larger the crystal grain size, the better. Based on the results of these investigations, the inventors conducted further detailed research on hot rolling conditions such as cooling after finish rolling, and as a result of appropriately controlling these conditions, the crystals after hot rolling Grain becomes equiaxed and fine grained uniform structure, the effect is inherited even after cold rolling and annealing, the crystal grain after annealing becomes uniform and fine equiaxed grain, excellent in non-earring property, and press working The inventor found that a steel sheet having excellent surface roughness resistance later can be produced, and has completed the present invention.
[0007]
That is, the gist configuration of the present invention is as follows.
(1) C: 0.0005 to 0.0090 wt%, Si: 0.10 wt% or less, Mn: 0.1 to 0.6 wt%, P: 0.02 wt% or less, S: 0.02 wt% or less, Al : 0.015 to 0.15 wt%, N: 0.02 wt% or less, Nb: 0.020 wt% or less, Ti: 0.020 wt% or less B: Any selected from 0.0001 to 0.0030 wt% A steel slab containing one or two kinds, the balance being Fe and inevitable impurities, hot-rolled, cold-rolled with a reduction rate of 80 to 95%, and annealed at 750 ° C. or lower to obtain an ASTM crystal Re-crystallized grains having a grain size number of 10 or more and a crystal grain axis ratio of 1.2 or less, and then subjected to secondary cold rolling with a rolling reduction of 20 to 40%. Manufacture of excellent steel plates for 2-piece cans Law.
[0008]
(2) C: 0.0005 to 0.0090 wt%, Si: 0.10 wt% or less, Mn: 0.1 to 0.6 wt%, P: 0.02 wt% or less, S: 0.02 wt% or less, Al : 0.015 to 0.15 wt%, N: 0.02 wt% or less, Nb: 0.020 wt% or less, Ti: 0.020 wt% or less, B: 0.0001 to 0.0030 wt% A steel slab containing any one or two of them, the balance being Fe and inevitable impurities, is heated to an average temperature Ac of ₃ points or higher, and the end temperature (Ar ₃ points + 150 ° C.) to (Ar ₃ points + 50 ° C.) ), Followed by finish rolling at an end temperature Ar of ₃ points or higher, starting quenching within 0.5 seconds after finishing rolling, winding at 750 to 550 ° C., then pickling and rolling reduction 80-95% cold rolling and 75 An annealing at 0 ° C. or lower is performed to form a recrystallized grain having an ASTM grain size number of 10 or more and a grain axis ratio of 1.2 or less, and further, secondary cold rolling at a rolling reduction of 20 to 40% is performed. A method for producing a steel plate for a two-piece can having excellent non-earring characteristics and rough skin resistance.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described.
(1) About steel components;
C: 0.0005 to 0.0090 wt%
C is less advantageous for elongation and press workability. On the other hand, if it is too small, the steel sheet becomes excessively soft and it becomes impossible to ensure the strength as a can body, so it is necessary to contain 0.0005 wt% or more. On the other hand, if the content exceeds 0.0090 wt%, the steel sheet becomes hard and the elongation decreases and the press workability deteriorates, so the range is 0.0005 to 0.0090 wt% .
[0010]
Si: 0.10wt% or less
Since Si is an element harmful to corrosion resistance for cans and an element that extremely hardens the material, its upper limit is set to 0.10 wt%.
[0011]
Mn: 0.1 to 0.6 wt%
Mn is an element useful for preventing red hot brittleness during hot rolling due to S, and addition of 0.1 wt% or more is necessary, but if added over 0.6 wt%, cracks occur during hot rolling. Or harden the steel sheet excessively. Therefore, the amount of Mn added is in the range of 0.1 to 0.6 wt%.
[0012]
P: 0.02 wt% or less P is a harmful element that lowers corrosion resistance. In particular, when P exceeds 0.02 wt%, the effect becomes significant. Therefore, the upper limit is 0.02 wt%.
[0013]
S: 0.02 wt% or less S is a harmful element that causes red hot brittleness during hot rolling, and is desirably as small as possible, but is acceptable up to 0.02 wt%.
[0014]
Al: 0.015-0.15wt%
Al is an element necessary as a deoxidizing material in steelmaking. If the addition amount is small, a stable deoxidation effect cannot be obtained, so it is necessary to add 0.015 wt% or more. On the other hand, even if it exceeds 0.15 wt%, there is no further effect and it is economically undesirable, so the upper limit is made 0.15 wt%.
[0015]
N: 0.02 wt% or less When N exceeds 0.02 wt%, the upper limit is set to 0.02 wt% in order to cause hardening of the steel sheet and a decrease in elongation and to deteriorate press workability.
[0016]
Nb: 0.020 wt% or less
Nb is an element that forms carbonitrides and is useful for improving the elongation and r-value by reducing the solid solution C and N. However, if the addition amount exceeds 0.020 wt%, the recrystallization end temperature is raised, and recrystallization is insufficient due to continuous annealing, resulting in deterioration of workability. Therefore, 0.020 wt% is the upper limit.
[0017]
Ti: 0.020 wt% or less
Ti is an element that forms carbonitrides similarly to Nb, and is an element useful for improving the elongation and the r-value by reducing the solid solution C and N. However, if the amount of addition exceeds 0.020 wt%, the recrystallization end temperature is raised, resulting in insufficient recrystallization due to continuous annealing, resulting in deterioration of workability and deterioration of the surface properties of the steel sheet. The upper limit.
[0018]
B: 0.0001-0.0030wt%
Since B fixes N even if the coiling temperature in hot rolling is low, it is possible to prevent material defects at the front and rear end portions of the hot-rolled steel strip that have a large temperature drop after coiling. In order to obtain this effect, at least 0.0001 wt% is necessary. However, if it exceeds 0.0030 wt%, the in-plane anisotropy of mechanical properties increases. For this reason, B addition amount shall be the range of 0.0001-0.0030 wt%.
[0019]
(2) Manufacturing conditions;
-The slab used as the slab rolling material is preferably manufactured by a continuous casting method in order to minimize macro segregation of components.
- hot heating rolling hot-rolled before the steel slab may be made heated above ₃ points Ac. Specifically, the range of 1050 to 1350 ° C is suitable.
Rough rolling ends in a temperature range of (Ar ₃ point + 150 ° C.) to (Ar ₃ point + 50 ° C.). In the case of rough rolling at a low temperature of less than (Ar ₃ point + 50 ° C.), the finish rolling is necessarily rolling in the α region, and the annealed plate has a mixed grain structure of coarse crystal grains and relatively fine grains. Therefore, sufficient workability after secondary cold rolling and rough skin resistance after processing cannot be obtained. On the other hand, if rough rolling is performed at a high temperature exceeding (Ar ₃ points + 150 ° C.), the life of the rolling roll is shortened. Accordingly, the rough rolling is finished in a temperature range of (Ar ₃ point + 150 ° C.) to (Ar ₃ point + 50 ° C.).
[0020]
In finish rolling, it is necessary to finish rolling at a temperature equal to or higher than the Ar ₃ transformation point, start water cooling of the hot-rolled steel strip within 0.5 seconds after the end of rolling, cool to at least 750 ° C, and then wind up at 750 to 550 ° C. is there.
This is because, in the finish rolling process, when rolled below the Ar ₃ transformation point, it becomes a coarse processed structure extending in the rolling direction, and this structure is inherited after cold rolling and annealing. This is because the generation of earrings is increased rather than equiaxed grains having an axial ratio of 1.2 or less.
In addition, when cooling is started within 0.5 seconds after finishing rolling, uniform equiaxed and fine grains are obtained. When water cooling is performed after exceeding 0.5 seconds, the austenite grains grow and do not become fine grains, and the temperature difference in the plate width direction of the steel strip becomes large. Since the growth rate is high, the grains become coarse, and the vicinity of the width end portion where the temperature is low, on the contrary, becomes relatively fine crystal grains, resulting in a more uneven structure.
FIG. 2 shows the relationship between the time from the end of finish rolling to the start of water cooling, the r value, and Δr. It can be seen from FIG. 2 that both of these characteristics are remarkably improved by starting water cooling within 0.5 seconds after finishing rolling.
In the above rapid cooling, it is preferable that the cooling rate is 70 ° C./sec or more and the Ar ₃ transformation point or less is cooled within 1 second. When this cooling is removed, the crystal stays at a high temperature for a long time, so that recrystallization, grain growth or recovery, grain growth proceeds, resulting in a coarse hot-rolled structure. This is because the grains are easier to expand, so that after annealing, the grains have a large axial ratio and the occurrence of earrings increases.
[0021]
Further, when the coiling temperature is as low as 550 ° C. or less, precipitation of AlN and NbC does not occur sufficiently, which inhibits recrystallization and grain growth during annealing, and deteriorates the r value and Δr. In addition, when the temperature exceeds 750 ° C., the scale growth after winding is remarkably reduced, and the pickling property is deteriorated, the crystal grains are abnormally coarsened, the material is deteriorated, and the skin resistance is deteriorated. A malfunction occurs. Therefore, the coiling temperature is set to a temperature range of 750 to 550 ° C.
[0022]
-Cold rolling process The hot-rolled sheet obtained in this way 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. The rolling reduction in cold rolling is more desirable at higher pressures in order to reduce the thickness in order to reduce costs. If the rolling reduction is less than 80%, such a purpose cannot be met, the crystal grains are abnormally coarsened or mixed in the annealing process, the material deteriorates, and a texture effective for deep drawability is developed. I can't. However, when the rolling reduction rate exceeds 95%, the r value decreases, Δr increases, and the earring becomes larger. Therefore, the rolling reduction shall be the range of 80% to 95%.
[0023]
-Annealing process The annealing should be performed by continuous annealing in terms of productivity and cost. The annealing temperature needs to be higher than the recrystallization end temperature, but if it is too high, the crystal grains will become abnormally coarse, resulting in increased surface roughness after processing, as well as the risk of in-furnace breakage and buckling that are characteristic of thin materials. . Therefore, the annealing temperature shall be the upper limit of 750 ° C..
[0024]
The annealed steel sheet produced by the above method is ASTM grain size no. The structure can be made of fine grains of 10 or more and equiaxed grains having an axial ratio of 1.2 or less. The crystal grain axial ratio needs to be 1.2 or less in order to reduce Δr and improve non-earring properties, and in order to improve the rough skin resistance after processing, the grain size no. It must be 10 or more. Note that Δr needs to be within ± 0.2 in order to be a non-earring steel plate.
[0025]
-Secondary cold rolling After annealing, secondary cold rolling is performed in order to increase the strength of the material by strengthening the work and to adjust the surface roughness. The rolling reduction of secondary cold rolling is determined at any time according to the tempering degree of the steel sheet, but it is necessary to perform rolling at a rolling reduction of 20 % or more. On the other hand, when rolling at a rolling reduction exceeding 40%, the steel sheet is excessively hardened, the workability is lowered, and the r value is decreased and Δr is increased. Therefore, the rolling reduction of the secondary cold rolling is in the range of 20 to 40%.
[0026]
【Example】
Using a slab obtained by continuously casting steels having the components shown in Table 1, hot rolling, cold rolling, annealing and secondary cold rolling were performed under the conditions shown in Table 2 to produce steel plates for cans. Further, this steel sheet was tin-plated with the 25th mark, and various properties were investigated. These survey methods are as follows.
(A) The cross section of the steel sheet after the metal structure annealing was polished and etched, and then examined by observation with an optical microscope. The investigation items were crystal grain axial ratio and ASTM grain size No., both of which were obtained from the average in the plate thickness direction from the outermost surface to the plate thickness 1/2 position.
(B) Mechanical properties A tensile test was carried out using JIS No. 5 test pieces. Further, the r value and the in-plane anisotropy Δr of the r value were determined by the following equations, respectively.
r = (r ₀ + r ₉₀ + 2r ₄₅ ) / 4
Δr = (r ₀ + r ₉₀ −r ₄₅ ) / 2
However, r ₀ , r ₉₀ , and r ₄₅ represent r values in directions of 0 degrees, 90 degrees, and 45 degrees in the rolling direction, respectively.
(C) Skin roughness After imparting 20% tensile strain to a test piece of JIS No. 5, the surface roughness of the steel sheet was measured with a roughness meter. In addition, the product surface roughness Ra before pulling was all the same and was 0.21 μm. In addition, it has been confirmed by the inventors' experiments that a problem due to rough skin after press working does not occur if the surface roughness Ra after the 20% tensile test is 0.60 μm or less.
(D) Cylindrical processing test A cylindrical processing test was conducted in order to comprehensively investigate the workability, rough skin property, and earring property during deep drawing. A circular plank having a diameter of 100 mm is molded into a cup shape with a drawing ratio of 2.2, and cracking, rough skin and earrings are not generated during processing, ○: no generation or minute, Δ: light to moderate, ×: impractical Evaluation was made in three stages.
These measurement results are summarized in Table 3. FIG. 4 shows the results of investigating the r value and Δr by changing the rolling reduction in the secondary cold rolling over a wide range, in comparison with the conventional method.
[0027]
[Table 1]

[0028]
[Table 2]

[0029]
[Table 3]

[0030]
From Table 3, the steel sheet for cans produced according to the present invention has good formability, and in particular, Δr is 0.2 or less, and the surface roughness after tension is 0.6 or less, showing good characteristics. I understand. Also, in the cylindrical machining test, it is clear that there are no problems in any of cracks during processing, rough skin, and earrings.
Further, from FIG. 4, when manufactured by the method of the present invention, the r value is high even in a region where the secondary cold rolling reduction is high, and the Δr with respect to the increase in rolling reduction compared to the steel plate manufactured by the conventional method. Since the decrease was small, Δr was small within ± 0.2 even in a high pressure under-rate region exceeding 20%, indicating that both press workability and non-earring properties were good. For this reason, the range that the rolling reduction in the secondary cold rolling can take is widened, and the corresponding range of the tempering degree is also widened.
[0031]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a steel plate for a can that is excellent in not only press workability but also in rough skin resistance and non-earring properties. Therefore, according to the present invention, it greatly contributes to improvement of surface properties and yield of food cans and beverage cans subjected to deep drawing. In addition, the application range of the steel sheet according to the present invention can be expected to be utilized not only for various metal cans but also for a wide range of dry battery interior cans, various home appliances / electrical parts, automobile parts, and the like.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the axial ratio of crystal grains and the absolute value of Δr.
FIG. 2 is a graph showing the relationship between crystal grain size number and rough skin.
FIG. 3 is a graph showing the relationship between the time from the end of finish rolling to the start of water cooling and r and Δr.
FIG. 4 is a graph showing the relationship between secondary cold rolling reduction and r and Δr.

Claims (2)

C: 0.0005 to 0.0090 wt%, Si: 0.10 wt% or less, Mn: 0.1 to 0.6 wt%, P: 0.02 wt% or less, S: 0.02 wt% or less, Al: 0.0. Any one selected from 015 to 0.15 wt%, N: 0.02 wt% or less, Nb: 0.020 wt% or less, Ti: 0.020 wt% or less, B: 0.0001 to 0.0030 wt% A steel slab containing one or two kinds, the balance being Fe and unavoidable impurities, is subjected to hot rolling, cold rolling with a rolling reduction of 80 to 95%, and annealing at 750 ° C. or less , and ASTM grain size It is excellent in non-earring property and rough skin resistance, characterized by forming recrystallized grains having a number of 10 or more and a crystal grain axis ratio of 1.2 or less, and then performing secondary cold rolling at a rolling reduction of 20 to 40%. How to make steel plates for 2-piece cans . C: 0.0005 to 0.0090 wt%, Si: 0.10 wt% or less, Mn: 0.1 to 0.6 wt%, P: 0.02 wt% or less, S: 0.02 wt% or less, Al: 0.0. Any one selected from 015 to 0.15 wt%, N: 0.02 wt% or less, Nb: 0.020 wt% or less, Ti: 0.020 wt% or less, B: 0.0001 to 0.0030 wt% A steel slab containing seeds or two kinds, the balance being Fe and unavoidable impurities is heated to an average temperature Ac of ₃ points or higher, and rough at the end temperature (Ar ₃ points + 150 ° C.) to (Ar ₃ points + 50 ° C.). Rolled, and then finish-rolled at an end temperature Ar of ₃ points or higher, rapidly cooled within 0.5 seconds after finishing the finish rolling, wound up at 750 to 550 ° C., and then pickled and rolled at a reduction rate of 80 to 95 % Cold rolling and above 750 ° C And annealed under, ASTM grain size number 10 or more and the crystal grain axial ratio of 1.2 or less of the recrystallized grains and without further and characterized by performing a rolling reduction 20% to 40% of the secondary cold rolling The manufacturing method of the steel plate for 2 piece cans which is excellent in the non-earring property and the rough skin-resistance which do.

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