JPH1081919A - Production of steel sheet for two-piece can, excellent in non-earing characteristic and surface roughing resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel sheet for two-piece can, having sufficient deep drawability for two-piece can forming even in the case of secondary cold rolling at high draft, minimal in the occurrence of earing, and excellent in surface roughing resistance after press forming. SOLUTION: A slab of a steel, having a composition consisting of, by weight, 0.0005-0.0150% C, <=0.10% Si, 0.1-0.6% Mn, <=0.02% P, <=0.02% S, 0.015-0.15% Al, <=0.02% N, one or two kinds selected from <=0.020% Nb, <=0.020% Ti, and 0.0001-0.0030% B, and the balance Fe with inevitable impurities, is hot-rolled, cold-rolled, and annealed, by which recrystallized grains of ASTM crystalline grain size number 10 or above, having <=1.2 crystalline grain axial ratio, are formed. Subsequently, secondary cold rolling is performed at 0.5-40% draft.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material for cans such as food and beverage cans, and in particular, has excellent non-earring properties (less occurrence of ears) and excellent skin roughness after press working in addition to deep drawing properties. The present invention relates to a method for manufacturing a steel sheet for two-piece cans.

[0002]

2. Description of the Related Art Deep drawing cans, DRD (Drawn and Redrawn) cans, and D.D.
The following characteristics are mainly required for cold-rolled steel sheets used for two-piece cans such as I (Drawn and Ironined) cans. 1) Formability without generating defects such as cracks during processing. 2) The surface roughness of the steel sheet after pressing is small and the finished appearance is good. 3) The anisotropy of the material is small and ear generation (earring) after deep drawing is small. Above all, the portion where the earring has occurred must be cut off after deep drawing of the can. For this reason, if the earring is large, not only does the material yield deteriorate, but in some cases, a required molding height cannot be obtained, and the entire molded product must be discarded. Therefore, it is desirable that the earring generated during deep drawing is 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 board, and it is known that if Δr = 0, the earring height becomes zero. Have 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 for the technology of manufacturing cold-rolled steel sheets for deep drawing with small earrings. For example, Japanese Patent Application Laid-Open No. 58-151426 discloses that low-carbon Al-killed steel is finish-rolled at a temperature higher than the Ar ₃ transformation point, and hot-rolled at a high temperature and cold-rolled at a rolling reduction of 80 to 95%. Discloses a technique for improving the average r value and improving Δr. According to this technique, a certain effect is observed, and the in-plane anisotropy is reduced to some extent.

[0004]

However, it is still difficult to say that the suppression of the earring is sufficient, especially when the secondary cold rolling reduction is high, the earring resistance is insufficient. Such a phenomenon has been an obstacle to the can making process when trying to increase the secondary cold rolling reduction in order to cope with the material thinning for the purpose of reducing the cost of can making. In particular, in the case of ultra-low carbon steel, since the strength of the steel sheet after annealing is low, in order to achieve a thinner can, several% to 4% after annealing.
Since it is necessary to perform the secondary cold rolling at a high rolling reduction of about 0%, Δr after the secondary cold rolling increases in the negative direction,
This was a factor that easily caused earrings.

Accordingly, a main object of the present invention is to provide a two-piece can with sufficient deep drawability, small earring generation, and press forming even in the case of secondary cold rolling at high pressure. An object of the present invention is to manufacture a steel sheet for a two-piece can having excellent resistance to rough skin. Another object of the present invention is to provide a steel sheet for a two-piece can having an r value of 1.5 or more and a Δr of ± 0.2 or less even when the secondary cold rolling is performed at a high pressure reduction of 20% or more. To manufacture.

[0006]

Means for Solving the Problems The inventors of the present invention conducted basic experiments to achieve the above-mentioned objects. First, the crystal grain size of the cold-rolled steel sheet, the morphology and press workability of the crystal grain, the earring property,
The relationship with skin roughness was investigated. The results are shown in FIGS. FIG. 1 shows the relationship between the axial ratio of crystal grains (= length in the long axis direction / length in the short axis direction) and Δr. From this, it can be seen that Δr of the equiaxed grain structure is equal to that of the elongated grain structure. It was found to be smaller and excellent in non-earring properties. FIG. 2 shows the relationship between the rough surface resistance and the crystal grain size. The smaller the crystal grain size, the better. The present inventors have conducted detailed studies on hot rolling conditions such as cooling after finish rolling based on the results of these investigations.As a result, if these conditions are appropriately controlled, the crystal after hot rolling can be obtained. The grains have an equiaxed, fine-grained uniform structure, and the effect is inherited even after cold rolling and annealing, and the crystal grains after annealing also become uniform and fine equiaxed grains, and have excellent non-earring properties, and press working. The present inventor has found that a steel sheet excellent in later resistance to surface roughening can be manufactured, and has completed the present invention.

That is, the gist of the present invention is as follows. (1) C: 0.0005 to 0.0150 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%
Hot rolling on steel slab consisting of Fe and unavoidable impurities,
Cold rolled and annealed, ASTM grain size number 1
A two-piece can having excellent non-earling properties and surface roughening resistance, wherein recrystallized grains having a grain size ratio of 0 or more and 1.2 or less are formed, and then subjected to secondary cold rolling at a rolling reduction of 0.5 to 40%. Manufacturing method for steel sheet.

(2) C: 0.0005 to 0.0150 wt%, Si: 0.10 wt%
%, 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, and Nb: 0.020 wt% or less, Ti: 0.020 wt% or less B: Contains one or two selected from 0.0001 to 0.0030 wt%, with the balance being
The steel slab consisting of Fe and inevitable impurities was
c Heat to ₃ points or more and finish temperature (Ar ₃ points + 150 ° C) ~ (A
r ₃ points + 50 ° C), followed by finish rolling at an end temperature Ar of ₃ points or more, rapid cooling is started within 0.5 seconds after finishing rolling, winding is performed at 750 to 550 ° C, and then pickling is performed.
Cold rolled and annealed, ASTM grain size number 1
A two-piece can excellent in non-earling property and surface roughening resistance, characterized in that recrystallized grains having a crystal grain axis ratio of 0 or more and 1.2 or less and further subjected to secondary cold rolling at a rolling reduction of 0.5 to 40%. Manufacturing method for steel sheet.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. (1) Regarding steel components; C: 0.0005 to 0.0150 wt% C is less advantageous for elongation and press workability. On the other hand, if the amount is too small, the steel sheet becomes excessively soft and secures strength as a can. Since it is no longer possible, it is necessary to contain 0.0005 wt% or more. On the other hand, if the content exceeds 0.0150 wt%, the elongation decreases due to the hardening of the steel sheet, and the press workability deteriorates, so that 0.0005 to 0.0150 wt%, preferably 0.0005 to 0.01 wt%.
The range is 0.0090.

Si: 0.10 wt% or less Si is an element which is harmful to the corrosion resistance for cans and is also an element which extremely hardens the material.
%.

Mn: 0.1 to 0.6 wt% Mn is a useful element for preventing red hot embrittlement during hot rolling by S, and it is necessary to add 0.1 wt% or more of Mn.
If added in excess of 6 wt%, cracks occur during hot rolling and the steel sheet becomes excessively hard. Therefore, the addition amount of Mn is set in the range of 0.1 to 0.6 wt%.

P: not more than 0.02 wt% P is a harmful element that lowers the corrosion resistance.
If it exceeds 02 wt%, the effect becomes remarkable. Therefore,
The upper limit is set to 0.02 wt%.

S: 0.02 wt% or less S is a harmful element that causes red hot embrittlement during hot rolling, and is desirably as small as possible, but is acceptable up to 0.02 wt%.

Al: 0.015 to 0.15 wt% Al is an element necessary as a deoxidizer in steelmaking. If the addition amount is small, a stable deoxidation effect cannot be obtained,
It is necessary to add 015 wt% or more. On the other hand, if it exceeds 0.15 wt%, there is no further effect and it is not economically preferable, so the upper limit is made 0.15 wt%.

N: not more than 0.02 wt% If N exceeds 0.02 wt%, the hardness of the steel sheet is reduced and the elongation is reduced, so that the press workability is deteriorated, so the upper limit is made 0.02 wt%.

Nb: 0.020 wt% or less Nb is an element which forms carbonitrides and is useful for improving elongation and r-value by reducing solid solution C and N. However, if the addition amount exceeds 0.020 wt%, the recrystallization end temperature increases,
Since continuous annealing causes insufficient recrystallization and deteriorates workability, the upper limit is set to 0.020 wt%.

Ti: 0.020 wt% or less Ti is an element that forms a carbonitride similarly to Nb, and is an element useful for improving elongation and r value by reducing solid solution C and N. However, if the amount exceeds 0.020 wt%, the recrystallization end temperature is raised, and recrystallization becomes insufficient due to continuous annealing, resulting in deterioration of workability and deterioration of the surface properties of the steel sheet. Upper limit.

B: 0.0001 to 0.0030 wt% B is used to fix N even if the winding temperature in hot rolling is low, so that the tip of the hot-rolled steel strip, whose temperature decreases greatly after winding,
Material defects at the rear end can be prevented. To obtain this effect, at least 0.0001 wt% is necessary,
If added in excess of 30 wt%, the in-plane anisotropy of the mechanical properties will increase. For this reason, the amount of B added is set in the range of 0.0001 to 0.0030 wt%.

(2) Regarding Manufacturing Conditions; Slab The slab to be rolled is desirably manufactured by a continuous casting method in order to minimize macro segregation of components. -Hot rolling process The heating of the steel slab before hot rolling may be performed by heating it to _three or more Ac points. Specifically, the range of 1050 to 1350 ° C is suitable. The rough rolling is completed in a temperature range of (Ar ₃ points + 150 ° C.) to (Ar ₃ points + 50 ° C.). When rough rolling is performed at a low temperature of less than (Ar ₃ points + 50 ° C.), the finish rolling is necessarily performed in the α range, and the annealed sheet has a mixed grain structure of coarse crystal grains and relatively fine grains. Therefore, sufficient workability after the second cold rolling and rough surface resistance after the working cannot be obtained. On the other hand, (Ar ₃ points + 1
When rough rolling is performed at a high temperature exceeding 50 ° C.), the life of the rolling roll is shortened. Therefore, rough rolling is (Ar ₃
The process ends in a temperature range of (point + 150 ° C.) to (Ar ₃ points + 50 ° C.).

In the finish rolling, the rolling is completed at a temperature equal to or higher than the Ar ₃ transformation point, and water-cooling of the hot-rolled steel strip is started within 0.5 seconds after the completion of the rolling, and the strip is cooled to at least 750 ° C.
It needs to be wound at 550 ° C. That is, in the finish rolling step, when rolling is performed at a temperature lower than the Ar ₃ transformation point, a coarse work structure extending in the rolling direction is obtained.
This is because, since it is inherited even after annealing, the crystal grains do not become equiaxed grains having an axial ratio of 1.2 or less, and the occurrence of earring increases. Also, if cooling is started within 0.5 seconds after the finish rolling, uniform equiaxed and fine grains are formed. If water cooling is performed after more than 0.5 seconds, austenite grain growth proceeds,
Fine grains are not formed, and the temperature difference in the strip width direction of the steel strip increases.The grain growth rate is high at the center of the high-temperature width, so the grains become coarse because the grain growth rate is high. The crystal grains become extremely fine, resulting in a more non-uniform structure. FIG.
Is the time and r value from the end of finish rolling to the start of water cooling, Δ
This shows the relationship with r. From FIG. 2, it can be seen that by starting water cooling within 0.5 seconds after the finish rolling, both these characteristics are significantly improved. In the rapid cooling, it is preferable that the cooling be performed at a cooling rate of 70 ° C./sec or more and within 1 second to the Ar ₃ transformation point or less. When deviating from such cooling, the crystal grains stay for a long time at a high temperature, so that recrystallization / grain growth or recovery / grain growth progresses, resulting in a coarse hot-rolled structure, and further coarsening in the cold rolling step. This is because the grains are more likely to spread and become grains having a large axial ratio after annealing, and the occurrence of earrings increases.

When the winding temperature is as low as 550 ° C. or less, precipitation of AlN and NbC does not sufficiently occur, which hinders recrystallization and grain growth during annealing and deteriorates the r value and Δr. . On the other hand, when the temperature exceeds 750 ° C., the scale growth after winding is remarkable, and the pickling property is reduced. In addition, the crystal grains are abnormally coarsened, the material is deteriorated, and the skin roughening resistance is deteriorated. Failure occurs. Therefore, the winding temperature is in a temperature range of 750 to 550 ° C.

Cold Rolling Step The hot rolled sheet thus obtained is pickled (descaled) and cold rolled. The pickling may be carried out in a conventional manner by removing the surface scale with an acid such as hydrochloric acid or sulfuric acid. The rolling reduction of the cold rolling is preferably higher at a higher pressure in order to reduce the thickness for cost reduction. If the rolling reduction is less than 80%, such a purpose cannot be met. In addition, the crystal grains are abnormally coarsened or mixed in the annealing step, the material is deteriorated, and a texture effective for deep drawing is developed. Can not do.
However, when the rolling reduction becomes higher than 95%, r
The value decreases, Δr increases, and the earring increases.
Therefore, it is desirable that the rolling reduction is in the range of 80 to 95%.

Annealing step Annealing is preferably performed by continuous annealing in terms of productivity and cost. The annealing temperature must be equal to or higher than the recrystallization end temperature, but if it is too high, the crystal grains become abnormally coarse, the surface roughness after processing becomes large, and the risk of in-furnace breakage and buckling occurring specific to thin materials increases. . Therefore, the annealing temperature is 750
It is desirable to set the upper limit to ° C.

The annealed steel sheet manufactured by the above method is
ASTM particle size No. The structure can be made up of 10 or more fine grains and equiaxed crystal grains having an axial ratio of 1.2 or less. The axial ratio of the crystal grains needs to be 1.2 or less in order to reduce Δr and improve the non-earring property. Must be 10 or more. In addition, in order to be a non-earring steel sheet, △ r
Must be within ± 0.2.

Secondary Cold Rolling After annealing, secondary cold rolling is performed in order to increase the strength of the material by work strengthening and to adjust the surface roughness. The rolling reduction in the secondary cold rolling is determined as needed depending on the tempering degree of the steel sheet, but it is necessary to roll at a rolling reduction of 0.5% or more in order to prevent the occurrence of stretch yard strain. on the other hand,
Rolling at a rolling reduction of more than 40% excessively hardens the steel sheet, lowers workability, lowers the r value, and increases Δr. Therefore, the rolling reduction of secondary cold rolling is 0.
The range is 5 to 40%.

[0026]

EXAMPLE A slab obtained by continuously casting steel having the components shown in Table 1 was subjected to hot rolling, cold rolling, annealing and secondary cold rolling under the conditions shown in Table 2 to obtain a steel sheet for cans. Manufactured. further,
The steel sheet was tin-plated with a 25th and various properties were investigated. These survey methods are as follows. (A) Metallographic structure The cross section of the steel sheet after annealing was polished and etched, and then observed by an optical microscope. The items to be investigated were the crystal grain axial ratio and AS.
TM grain size No.
The average in the thickness direction up to two positions was determined. (B) Mechanical properties A tensile test was performed using a JIS No. 5 test piece. Also,
The r value and the in-plane anisotropy Δr of the r value were determined by the following equations. r = (r ₀ + r ₉₀ + 2r ₄₅ ) / 4 Δr = (r ₀ + r ₉₀ −r ₄₅ ) / 2 where r ₀ , r ₉₀ , and r ₄₅ are each 0 in the rolling direction.
Represents the r value in the directions of degrees, 90 degrees and 45 degrees. (C) Roughness After applying 20% tensile strain to a JIS No. 5 test piece, the surface roughness of the steel sheet was measured with a roughness meter. In addition, the product surface roughness Ra before tension was all the same and was 0.21 μm. In addition,
According to experiments by the inventors, it has been confirmed that if the surface roughness Ra after the 20% tensile test is 0.60 μm or less, no problem occurs due to the surface roughness after the press working. (D) Cylindrical processing test A cylindrical processing test was performed in order to comprehensively investigate the workability, surface roughness, and earring properties during deep drawing. Diameter 1
A round plank of 00 mm is formed into a cup with a drawing ratio of 2.2, and the occurrence of cracks, rough skin, and the occurrence of earrings during processing are as follows: o: no occurrence or minute, Δ: light to moderate, ×: impractical 3 It was evaluated on a scale. Table 3 summarizes the measurement results. 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]

From Table 3, it can be seen that the steel sheet for cans produced according to the present invention has good formability and, in particular, Δr of 0.2 or less and surface roughness after tension of 0.6 or less, showing good properties. You can see that it is. Also, in the cylindrical processing test, it is clear that there is no problem with any of cracks, rough surfaces, and earrings during processing. From FIG. 4, it can be seen from FIG. 4 that the r value is high even in the region where the secondary cold rolling reduction is high when manufactured by the method of the present invention, and that Δr with respect to the increase of the rolling reduction is higher than that of the steel plate manufactured by the conventional method. Since the decrease is small, Δr is ± 0.2 even in a high pressure reduction range exceeding 20%.
It was found to be as small as 2 or less, and both press workability and non-earring properties were good. Further, for this reason, the range in which the rolling reduction in the secondary cold rolling can be widened, and the range in which the degree of tempering can be widened.

[0031]

As described above, according to the present invention, it is possible to provide a steel sheet for cans which is excellent not only in press workability but also in rough surface resistance and non-earring properties. Therefore, according to the present invention, it greatly contributes to the improvement of the surface properties and the yield of food cans and beverage cans subjected to deep drawing. Further, the application range of the steel sheet according to the present invention is expected to be applicable not only to various metal cans but also to a wide range of dry battery interior cans, various home electric appliances / electric 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 a relationship between a crystal grain size number and skin roughness.

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 a relationship between a secondary cold reduction ratio and r and Δr.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Osamu Furukun 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel Co., Ltd. Kawasaki Steel Corporation Chiba Works

Claims (2)

[Claims] C: 0.0005 to 0.0150 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%
Hot rolling on steel slab consisting of Fe and unavoidable impurities,
Cold rolled and annealed, ASTM grain size number 1
A two-piece can having excellent non-earling properties and surface roughening resistance, wherein recrystallized grains having a grain size ratio of 0 or more and 1.2 or less are formed, and then subjected to secondary cold rolling at a rolling reduction of 0.5 to 40%. Manufacturing method for steel sheet. 2. C: 0.0005 to 0.0150 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%
The steel slab consisting of Fe and inevitable impurities was
c Heat to ₃ points or more and finish temperature (Ar ₃ points + 150 ° C) ~ (A
r ₃ points + 50 ° C), followed by finish rolling at an end temperature Ar of ₃ points or more, rapid cooling is started within 0.5 seconds after finishing rolling, winding is performed at 750 to 550 ° C, and then pickling is performed.
Cold rolled and annealed, ASTM grain size number 1
A two-piece can excellent in non-earling property and surface roughening resistance, characterized in that recrystallized grains having a crystal grain axis ratio of 0 or more and 1.2 or less and further subjected to secondary cold rolling at a rolling reduction of 0.5 to 40%. Manufacturing method for steel sheet.