JPH093547A - Production of high strength steel sheet for can - Google Patents

Abstract

PURPOSE: To increase the strength of a steel sheet while satisfying the formability necessary for use in can material and to reduce the thickness of the steel sheet by specially combining the composition of an extra low carbon steel slab as a stock with manufacturing conditions. CONSTITUTION: A slab of a steel, which has a composition consisting of, by weight, <=0.0050% C, <=0.020% Si, 0.050-1.50% Mn, <=0.010% S, <=0.0200% N, <=0.100% Al, and the balance Fe and containing, if necessary, 0.002-0.020% Nb and/or 0.005-0.020% Ti, is used as a stock. Hot rolling, where finish rolling is finished at a temp. exceeding the Ar3 transformation point, is applied to the stock to <1.8mm plate thickness. The resulting plate is subjected to water cooling, which is started within 0.2sec from the completion of finish rolling, at >=50 deg.C/sec average cooling rate, followed by coiling at <=450 deg.C. After ordinary acid pickling, cold rolling is performed at 80-98% draft. The resulting sheet is subjected to short time annealing at a temp. not lower than the recrystallization temp. and then to temper rolling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a steel sheet for a can which is excellent in deep-drawing formability and is excellent in strength characteristics. Specifically, the present invention intends to propose a method for producing a steel sheet suitable for applications that require a certain drawability, for example, those intended for containers that are usually called two-piece cans.

[0002]

Beverage cans, which have been consumed in large quantities these days, 18
2 liter cans, pail cans, etc., depending on the manufacturing method (construction method)
It can be roughly divided into a piece can and a three piece can. The former two-piece can is a tin-plated, chrome-plated, surface-treated steel sheet that has been subjected to chemical conversion treatment, oil coating, etc., shallow drawing, and DWI.
(Drawn & Wall Ironed) processing, DRD (Drawn & Redr
It is a can made of two parts, one that has been subjected to processing such as awn) processing and the lid. The latter three-piece can is a can consisting of three parts, a can body formed by bending the above-mentioned surface-treated steel plate into a cylindrical shape or a rectangular tube shape and joining the abutting ends, a canopy, and a bottom lid.

These two-piece cans and three-piece cans have a high material cost ratio to the can manufacturing cost.
There is a strong demand for cost reduction for steel sheets. Therefore,
In producing such a steel sheet for cans, the conventional box annealing method is inefficient and the material yield is inferior to the surface quality, so that the production efficiency is high, the yield is high, and the surface quality of the continuous annealing method is excellent. Application is mandatory. Regarding the manufacturing method of the steel plate for a can to which such a continuous annealing method is applied,
For example, in addition to the proposal in Japanese Patent Publication No. 63-10213,
Techniques with further improvements have been developed, and soft steel plates for containers having a temper of up to about T2 have been manufactured. Further, in recent years, technological development for producing a softer steel plate by a continuous annealing method has been advanced, and for example, by using ultra-low carbon steel as disclosed in JP-A-1-52452 and combining work hardening after annealing. Technology has been developed for making steel plates for cans of various hardness.

On the other hand, there is an ever-present demand for cost reduction of steel sheets for cans. Therefore, it is demanded to improve the strength of the steel sheets to reduce the thickness of the steel sheets to be used in order to meet the demand. It became so. However, as is well known, improving the strength of a steel sheet generally leads to deterioration of workability or formability, and therefore simple enhancement of strength cannot withstand actual use. Moreover,
Generally, even if the strength is the same, as the thickness of the steel sheet decreases, the formability represented by elongation tends to deteriorate, so achieving thinning by increasing the strength of the steel sheet is a difficult task in a double sense. It was Therefore, in order to achieve thinning without any adverse effect in the use of the steel sheet for cans, it has been necessary to apply a new method for strengthening, which has never existed before.

[0005]

As described above, in the conventional method for manufacturing a steel sheet for cans, it is possible to achieve thinning while satisfying the specification of the workability of the steel sheet for containers, which requires severe workability. High strength of steel sheet could not be realized.

Therefore, the present invention provides roll forming,
High strength of steel sheet while satisfying not only the formability for a three-piece can for forming such as flanging but also the formability as a steel sheet for a container for so-called two-piece can for performing deep drawing. It is an object of the present invention to propose a method for manufacturing a steel sheet for a high-strength can, which makes it possible to reduce the thickness of the steel sheet.

[0007]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the inventors have studied the components and hot rolling conditions, and have a metallurgical method that governs the usage characteristics of steel sheets for containers. After conducting various studies, the following findings were obtained.

First, thinning the two-piece can that is deep-drawn
The important points regarding the properties required for the steel sheet when strengthening are as follows. (1) A high r value is not a requirement. (2) It is desirable that the in-plane anisotropy (Δr value) of the r value is small. (3) Uneven deformation such as ridging cannot occur. (4) A fine structure is desirable in terms of uniform deformation. Further, if the structure is fine, it is possible to prevent appearance defects such as rough skin after can making. (5) Aging does not necessarily have to be completely non-aged as in box annealed material (low carbon aluminum killed steel), but with normal continuous annealed material (low carbon aluminum killed steel), the can manufacturing process and the subsequent secondary, There is a high risk of inconvenience occurring in the third processing step. (6) The local ductility at the high processing speed equivalent to the actual forming process, which is one to two orders of magnitude faster than those, is important, not the ductility at the low processing speed condition obtained by the normal tensile test.

Based on such knowledge, various studies have been conducted on the combination of steel components and manufacturing conditions in order to satisfy the above-mentioned characteristics, and as a result, the present invention has been obtained. The gist of the present invention is as follows.

C: 0.0050 wt% (hereinafter, simply expressed as%)
Below, Si: 0.020% or less, Mn: 0.050 to 1.50%, P: 0.
020% or less, S: 0.010% or less, N: 0.0200% or less and
Al: A steel slab containing 0.100% or less and the balance Fe and unavoidable impurities is used as a material, and this material is hot-rolled to finish rolling at a temperature above the Ar ₃ transformation point
Water cooling was started at less than 1.8 mm and started within 0.2 s from the end of the finish rolling at an average cooling rate of 50 ° C / s or more, and after winding at 450 ° C or less, ordinary pickling was performed and the reduction rate was 80 to 98%. Cold rolling, followed by short-time annealing at a recrystallization temperature or higher, followed by temper rolling (first invention).

Invention in which Nb and / or Ti is further added as a selective addition component, that is, C: 0.0050% or less, Si:
0.020% or less, Mn: 0.050 to 1.50%, P: 0.020% or less, S: 0.010% or less, N: 0.0200% or less and Al: 0.10.
Including 0% or less, and Nb: 0.002 to 0.020% and Ti: 0.
A steel slab containing one or two selected from 005 to 0.020% and the balance being Fe and unavoidable impurities is used as the material, and the heat for finishing rolling at a temperature exceeding the Ar ₃ transformation point is applied to this material. Cold rolling to a plate thickness of less than 1.8 mm, water cooling that started within 0.2 s after the finish rolling was completed at an average cooling rate of 50 ° C / s or more, and after winding at 450 ° C or less, normal pickling was performed. After that, cold rolling with a reduction rate of 80 to 98% is performed, then short-time annealing at a recrystallization temperature or higher is performed, and then temper rolling is performed, followed by temper rolling (second invention). .

In order to further increase the strength of the steel sheet from the as-annealed state, in the first invention or the second invention,
A method for producing a steel sheet for high-strength cans, which is characterized by performing secondary cold rolling with a reduction rate of 30% or less instead of temper rolling (third invention).

[0013]

In this invention, in addition to limiting the compositional range of the steel composition, the main requirement is to combine hot rolling conditions, particularly rapid cooling immediately after hot rolling with extremely low hot rolling temperature conditions. Of these requirements, the steel composition range is
Ultra-low carbon steel (C content: 0.00
(50% or less), N is positively added to improve the strength, and the presence state of such components in the steel is optimized to achieve both strength and formability of the steel sheet. The mechanism of high strength in the present invention is the uniform miniaturization of the structure and the strengthening by solid solution N. By applying such a mechanism, it is possible to utilize the unprecedented characteristic of being soft and easy to mold at the molding stage and having a high final can strength.

Regarding the cooling conditions after hot rolling according to the present invention, it is not possible to increase the cooling rate and to quench immediately after rolling due to the arrangement of the cooling equipment and the remarkable deterioration of the shape of the steel sheet in the conventional equipment. Although it was made possible, it has become possible to achieve this by using the latest quenching facility described later and continuous hot rolling that has not been performed until now. Further, as described above, it has been found that extremely high r-values are not necessary for steel plates for cans, unlike steel plates for general use and automobiles, so it is possible to select such extreme hot rolling conditions. It has become.

Further, in the case of the low carbon steel which has been mainly used as a steel sheet for cans in the related art, when the above cooling conditions after hot rolling are applied, the strength can be secured but the ductility is remarkably deteriorated. Therefore, the inconvenience that the applicable range is limited to an extremely narrow range is unavoidable. However, in this invention, it became clear that deterioration of this material can be avoided by using ultra low carbon steel as the material. That is, the r value of the steel sheet for cans of the present invention is not higher than the so-called high r value steel sheet applied to conventional steel sheets for automobiles and the like, but the balance between strength and ductility is extremely good. It can be sufficiently applied to processing involving deep drawing.

The reasons for limiting the numerical values of the respective constituents will be described below. C: 0.0050% or less If the C content exceeds 0.0050%, the variation ratio of the final material increases, so the C content needs to be approximately 0.0050% or less. If workability is important, 0.0040% or less is more desirable. The lower limit of the amount of C is not particularly limited, but C
If the amount is reduced, the tendency of coarsening of crystal grains appears.
It is desirable that the amount be 0.0010% or more. Regarding the upper limit, 0.0030% is more desirable from the viewpoint of workability improvement.
It is the following.

Si: 0.020% or less If the Si content exceeds 0.020%, the surface properties of the steel sheet deteriorate, which is not desirable as a surface-treated steel sheet, and the steel hardens to make the hot rolling process difficult. Is 0.020%
I made it.

Mn: 0.050 to 1.50% If 0.050% or more of Mn is not added, it is difficult to avoid so-called hot embrittlement even when S is lowered, and problems such as surface cracking may occur. Further, Mn is a component that has the effect of solid solution strengthening the steel sheet and also lowers the transformation point of the steel sheet, so it is effective for relaxing the hot rolling finish temperature condition of the steel sheet. However, when Mn is added in an amount of more than 1.50%, although the detailed mechanism is unknown, the uniformity of the structure deteriorates and a layered structure is easily formed. When workability is particularly important, the Mn content is preferably 0.80% or less.

P: 0.020% or less By reducing P, the effect of improving workability and corrosion resistance can be obtained.
Even if it is excessively reduced, the effect is saturated, and the manufacturing cost is increased, which is not desirable. Therefore,
The amount of P was set to 0.020% or less.

S: 0.010% or less S must be reduced in order to improve workability. About 0.
When the content is 010% or less, the workability (especially the stretch flange characteristic) is remarkably improved, but a smooth reduction does not result in a great improvement effect, but also leads to an increase in manufacturing cost. If a high degree of local ductility is required, it is desirable to reduce the S content to 0.007% or less.

N: 0.0200% or less N is one of the characteristic components in the present invention, and when it is added up to about 0.0200%, a remarkable strengthening effect is obtained. On the other hand, N is added in this range. If so, the deterioration of aging is relatively small. Further, N lowers the transformation point of steel during hot rolling, and is therefore effective in relaxing restrictions on hot rolling conditions. Further, if the content exceeds 0.0200%, the steel is significantly hardened, which hinders the cold rolling process and increases the risk of producing blowholes in the steel during the steel making process, which is not preferable. Therefore, the upper limit of N is set to 0.0200%. The lower limit is not particularly limited, but is generally 0.0030%
By adding the above, the production of the steel of the present invention is significantly facilitated. From the balance of strength and ductility, the range of 0.0050 to 0.0150% is more preferable.

Al: 0.100% or less Al must be added as a deoxidizing agent in order to improve cleanliness. It is not necessary to determine the minimum amount of addition from the viewpoint of material quality, but from the viewpoint of improving cleanliness, it is desirable to add approximately 0.005% or more. However, if it is added in excess of 0.100%, not only the cleanliness improving effect is saturated, but also problems such as an increase in manufacturing cost and an increase in the tendency to generate surface defects occur. Further, it becomes difficult to utilize the solid solution N as a strengthening component. Taking these into consideration, the upper limit of Al was set to 0.100%. A more desirable range is 0.020 to 0.080%.

The above-mentioned components are essential components. In the present invention, Nb and Ti can be added alone or in combination in addition to these components, which is effective for improving the material quality. Nb: 0.002 to 0.020% Nb is effective for refining the structure of steel, preventing ridging, and reducing aging. In order to exert such desirable effects, 0.0020% or more must be added. . Also, 0.
Addition in excess of 020% increases the non-uniformity of the structure after hot rolling, not only makes the material unsuitable as a can material, but also raises the manufacturing cost. From the viewpoint of material stability, the range is more preferably 0.0050 to 0.0150%.

Ti: 0.005 to 0.020% Ti is an effective component for refining the structure of the steel sheet.
Since there is an action of adjusting the aging property by fixing a part of C, it is possible to improve the material quality by addition, so it is desirable to add selectively. The desirable effect described above is exhibited from an addition amount of approximately 0.0050% or more. However, if the addition amount exceeds 0.0200%, there is a high possibility that the structure after hot rolling becomes non-uniform, and there is a concern that the corrosion resistance may deteriorate. Therefore, 0.0050 to 0.0200% is set, but 0.0080 to 0.0200% is more preferable when considering the balance between strength and ductility.

Next, the reasons for limiting the hot rolling conditions will be described. Finishing rolling temperature: a temperature exceeding the Ar ₃ transformation point The limiting of the finishing rolling temperature is to make the structure of the steel sheet uniform and fine. That is, when the finish rolling temperature falls below the Ar ₃ transformation point and reaches the temperature range where the ferrite phase appears, the generated ferrite undergoes processing and is rapidly cooled without being able to completely release strain, resulting in extremely uneven heat. It becomes a rolled sheet structure. This nonuniformity of the structure is not completely removed even after cold rolling and annealing, and the suitability as a steel sheet for cans deteriorates. Therefore, the finish rolling temperature is set to a temperature exceeding the Ar ₃ transformation point. The upper limit of finish rolling temperature is not particularly limited. A higher finish rolling temperature is preferable in that the in-plane anisotropy of the steel sheet material can also be improved.

The thickness of the hot-rolled mother plate obtained by such finish rolling needs to be less than 1.8 mm. The reason for this is that the subsequent cooling is performed more rapidly, but 1.8
By making it less than mm, the material of the material after cold rolling and annealing,
This is because it is effective in remarkably improving the in-plane anisotropy. The lower limit is determined by the constraint of ensuring the finish rolling temperature, and there is no particular constraint on the material. Furthermore, it is desirable that the material is less than 1.6 mm.

Cooling after finishing rolling is one of the extremely important requirements. That is, the steel sheet after finish rolling needs to start water cooling within 0.2 s after the completion of rolling. Although the detailed mechanism is unknown, by starting water cooling immediately after rolling in this way, remarkable micronization of the structure of the hot-rolled base metal occurs, which is even after cold-rolling and annealing of the hot-rolled base metal. Since it is inherited, the structure of the final steel sheet is made uniform and fine, and a remarkable effect is exhibited in improving the strength-ductility balance.
It is desirable to start this water cooling in a shorter time, and this lower limit value is derived from equipment problems.

The water cooling equipment for starting water cooling in a short time after finishing rolling is basically the same as the conventional hot line cooling equipment, but the installation position of the equipment is the same as that of the rolling mill. Must be close to the side. For this reason, it becomes necessary to remove a thermometer, a thickness gauge, etc., which are usually installed on the outlet side, so that a higher rolling control capability is required. Further, in general, the heat transfer efficiency due to water cooling is lowered in a high temperature region, so it is desirable to apply a cooling device having a water amount density higher than usual.

Next, the average cooling rate after the start of cooling is
It should be 50 ℃ / s or more. If the cooling rate is lower than 50 ° C / s, the target uniform and fine steel sheet structure cannot be obtained. More desirably, by setting the cooling rate to 70 ° C./s or more, the strength is further improved while maintaining the ductility. Water cooling at such an average cooling rate of 50 ° C / s or more is performed within a temperature range from the start of cooling to at least about 700 ° C. Since this temperature range is a region where ferrite grain growth and AlN precipitation rapidly proceed, rapid cooling is required.

The coiling temperature should be 450 ° C. or lower.
By controlling the coiling temperature to 450 ° C. or lower, the precipitation of N and C in the steel sheet is suppressed and the micronization of the structure is achieved uniformly, and this state is maintained even after cooling and annealing. The characteristics are desirable for the ultra-thin high-strength steel sheet targeted in. In addition, in order to completely suppress the precipitation of AlN, 45
A winding temperature condition of 0 ° C. or lower is essential. Up to now, the hot-rolled base plate of steel sheet used for cans is generally thinner than the base plate of ordinary cold-rolled steel sheet, so when such rapid cooling / low-temperature winding is performed, the shape of the steel sheet is disturbed. Becomes remarkable,
This was the cause of various problems in the cold rolling process of the lower process. However, in the steel of the present invention, the shape defect is relatively slight even when such cooling is performed. Also,
In order to further improve this inconvenience, the rear end portion of the preceding sheet bar and the leading end portion of the succeeding sheet bar are joined on the entry side of the finishing rolling mill to continuously hot-roll a plurality of sheet bars. It is effective to keep the steel sheet under tension always and to prevent the edge portion of the steel sheet from being overcooled to perform uniform cooling in the width direction.

In addition, regarding the coiling temperature, in the case of conventional general cold-rolled steel sheets (particularly continuous annealed materials), it is necessary to carry out high temperature coiling at about 680 ° C. from the necessity of increasing the r value of the steel sheet. The same manufacturing method was also applied to. However, as a result of various studies, in the steel of the present invention, even if rapid cooling and low temperature winding are applied after finish rolling as described above, the deterioration of r value is relatively small, and the remarkable strength-
It was clarified that the ductility balance could be improved. The reason for limiting the hot rolling coiling temperature is as described above. However, the coiling temperature is preferably 300 ° C or lower in order to obtain higher strength.

The hot rolled coil thus obtained is subjected to cold rolling by removing the scale on the surface by a usual method. Under the hot rolling conditions of the present invention, one of the major characteristics is that a hot rolled mother plate having extremely good descaling property can be obtained.

The cold rolling reduction is 80 to 98%. If the cold rolling reduction rate is less than 80%, the steel sheet structure cannot be sufficiently and uniformly refined,
The r-value level is also low. The higher the cold rolling reduction, the better the r-value, but at a reduction of more than 98%, the steel will be significantly hardened, making rolling difficult and in addition, the Δr value will show a large negative value. This is not desirable. Therefore, the cold rolling reduction is set to 80 to 98%, but more preferably 83 to 92% in view of the balance between the average r value and the Δr value.

Annealing after cold rolling is performed by a continuous annealing method in a short time (for example, soaking time: 10 to 40 s), and the annealing temperature is not less than the recrystallization temperature. For special applications, it is possible to obtain a so-called partial recrystallization structure by applying annealing at a recrystallization temperature or lower, but this is not desirable from the viewpoint of material stability. Therefore, the annealing temperature is set to the recrystallization temperature or higher. The upper limit of the annealing temperature is the Ac ₃ transformation point, but it is also determined from the process limit of continuous annealing.

The annealed steel sheet is temper-rolled at 5% or less in order to adjust the surface roughness and eliminate the elongation at yield. Further, in order to further increase the strength of the steel sheet from the as-annealed state, it is also effective to apply secondary cold rolling with a reduction ratio of more than 5% and 30% or less instead of temper rolling. The use of work hardening by imparting secondary cold rolling is an advantageous method because it can be applied to a considerably wide range of applications because it does not cause a significant increase in cost and uniform elongation deteriorates but local elongation does not deteriorate. . However, when the steel is strengthened by secondary cold rolling with a rolling reduction of more than 30%, the in-plane anisotropy of yield strength becomes remarkable, and the occurrence of earrings becomes conspicuous. . Therefore, the secondary cold rolling reduction rate after annealing should be 30% or less. More preferably, by setting the content to 20% or less, better workability can be secured.

The steel of the present invention obtained from the steel composition range and the manufacturing process described above is hot-rolled and then rapidly cooled,
Further, since winding is performed at a low temperature, a large amount of solid solution N remains, so that the so-called aging property is high. However, although the detailed mechanism is not clear in the intended use for cans of the present invention, the molding speed is remarkably higher than that of normal press molding, or the shape of the molded body is compared with the axial object. Because of its simplicity, there are no problems such as the occurrence of so-called stretcher strain due to its large aging effect. This allows the application of N enhancements for this application. In addition, probably because the strain aging effect due to N is sufficiently exerted when used after being formed as a can body, a larger strengthening effect than that simply explained by conventional solid solution strengthening can be obtained.

[0037]

【Example】

Example 1 Various steels shown in Table 1 were melted, the hot rolling conditions and the cold rolling conditions were variously changed, and the characteristics of the obtained cold rolled steel sheet were investigated. The results are shown in Table 2. Among them, the ridging property was evaluated by squeezing a steel plate into a shallow cylindrical shape and observing its surface texture. The r value and the Δr value were determined by JIS, which is a method for evaluating the anisotropy of elastic modulus. The slab heating temperature during hot rolling was in the range of 1100 to 1250 ° C. Although the annealing temperature was changed as shown in the table, the soaking time of annealing was kept constant at 20 s. After annealing, temper rolling was performed at a reduction rate of 1.5 to 2.0%. In this example, a soft ultrathin material is assumed, and is manufactured under a relatively high primary cold reduction condition.

[0038]

[Table 1]

[0039]

[Table 2]

As is apparent from these tables, in the conformity example according to the present invention, the effect of increasing the strength of the steel sheet can be obtained by adding N, and the ductility is high despite the high TS (tensile strength) and the high strength. It can be seen that this is a surface-treated original plate which is good and has a small in-plane anisotropy of mechanical properties of the steel plate. Also,
A conforming example shows a much higher r-value than the average r-value of 1.0 or less for high-strength steel sheets manufactured by the conventional method (continuous annealing of low-carbon aluminum killed steel). It is clear that they have. Furthermore, all the conforming examples use solid solution strengthening of N, and since the work strengthening is minimized, the yield stress (YS) is low and the yield ratio (YS / TS) value is 0.65. Since it is in the range of to 0.75, it can be seen that the press moldability is good. Also, the Δr is as large as about -0.6 in the conventional method (continuous annealing of low carbon aluminum killed steel), but the present invention has a small Δr, which is good.

Example 2 A cold-rolled steel sheet was produced under the conditions shown in Table 3 using the steel having the chemical composition shown in Table 1. At the time of this production, at the annealing temperature shown in the table, secondary cold rolling was performed at a rolling reduction of 18% after annealing for a soaking time of 15 seconds. Then, tin plating equivalent to # 25 was performed under normal conditions, and ordinary coating / baking treatment was performed. The product thickness is fixed at 0.180 mm. This was formed into a can body portion of a three-piece can by roll forming and high-speed seam welding, and the roll forming property was judged by the variation in shape after forming. Next, this molded body was subjected to stretch flange processing, and the presence or absence of flange cracking was investigated. This flange crack was judged by the presence or absence of HAZ (Heat Affected Zone) crack of 3% or more in the flange forming test conducted under the conditions assuming a normal 350 ml size can. Table 3 also shows these results. Also, for reference, | Δr | of the present invention is about 0.2,
Conventional low carbon aluminum killed steel sheet double cold rolled material | Δr |
It was good compared to = 0.6.

[0042]

[Table 3]

From Table 3, it is clear that the products manufactured under the conditions according to the present invention satisfy the required characteristics. Also, the strength characteristics of the can body were the same as those of the low-carbon steel double cold rolling method shown in the comparative example.
The reason is not clear in detail, but it is considered that N existing in a solid solution state greatly contributes to the increase in the strength of the can body. In addition, the roll forming property is YS of the material.
Does not correspond to. The detailed mechanism is unknown, but it is presumed to be due to the peculiarities of the actual roll forming process.

Example 3 Using the steel having the components shown in Table 1, a cold rolled steel sheet was produced under the production conditions shown in Table 4. After annealing at the annealing temperature shown in the table for a soaking time of 30 seconds, secondary cold rolling with a reduction rate of 10% was performed. The surface of the steel sheet is then plated with normal Cr, then coated to give a lubricating effect, then drawn once and redrawn twice to form a so-called DRD can. The surface condition and others were investigated. The results are shown in Table 4.

[0045]

[Table 4]

From Table 4 it can be seen that the adaptations according to the invention fulfill the required properties. Further, the corrosion resistance was also investigated according to the usual method, but there was no problem in the conformity example. This is probably because the soundness of the painting contributed.

[0047]

The method for producing a steel sheet for a high-strength can of the present invention has the above-described structure, and therefore, the obtained steel sheet is used as a base sheet for a container (in some cases, when no special surface treatment is performed). However, it has a better strength-ductility balance than the one produced by the conventional process, and has a higher average r value and good (small) Since it has in-plane anisotropy, it has a wider formable range at the time of various press forming than the case where conventional steel is used, and the risk of causing press work defects is small. Further, the press formability of the steel sheet generally tends to deteriorate only when the thickness of the steel sheet becomes thin, but by using the steel sheet according to the present invention having good press formability, the formability of the steel sheet due to the reduction of the plate thickness is improved. Since deterioration can be compensated for, rationalization of thin steel plate can be achieved. Furthermore, since the steel sheet obtained by the present invention positively uses solid solution N as a strengthening component, it is relatively soft during press forming and has excellent formability, and the strength due to subsequent natural aging (or accelerated aging). Is increased and the strength characteristics as a can can be sufficiently satisfied.

Claims (3)

[Claims] 1. C: 0.0050 wt% or less, Si: 0.020 wt% or less, Mn: 0.050 to 1.50 wt%, P: 0.020 wt% or less, S: 0.010 wt% or less, N: 0.0200 wt% or less and Al: A steel slab containing 0.100 wt% or less and the balance Fe and unavoidable impurities is used as a material, and this material is hot-rolled to finish rolling at a temperature above the Ar ₃ transformation point to a plate thickness of less than 1.8 mm. , The average cooling rate of water cooling started within 0.2 s after the finish rolling was 50 ℃ / s
After performing the above, after winding at 450 ℃ or less, through ordinary pickling, cold rolling with a reduction rate of 80 to 98%, followed by short-time annealing above the recrystallization temperature, and then temper rolling. A method of manufacturing a steel sheet for high-strength cans, which is characterized by the above. 2. C: 0.0050 wt% or less, Si: 0.020 wt% or less, Mn: 0.050 to 1.50 wt%, P: 0.020 wt% or less, S: 0.010 wt% or less, N: 0.0200 wt% or less and Al: Including 0.100 wt% or less, and Nb: 0.002-0.020 wt% and Ti: 0.005-0.020 wt%
The steel slab containing 1 or 2 selected from the above, the balance being Fe and unavoidable impurities is used as the material, and this material is subjected to hot rolling to finish the finish rolling at a temperature exceeding the Ar ₃ transformation point. With a sheet thickness of less than 1.8 mm, water cooling started within 0.2 s after the finish rolling was completed, and the average cooling rate was 50 ° C / s.
After performing the above, after winding at 450 ℃ or less, through ordinary pickling, cold rolling with a reduction rate of 80 to 98%, followed by short-time annealing above the recrystallization temperature, and then temper rolling. A method of manufacturing a steel sheet for high-strength cans, which is characterized by the above. 3. The method for producing a steel plate for a high-strength can according to claim 1 or 2, wherein secondary cold rolling with a reduction rate of 30% or less is performed instead of temper rolling. Steel plate manufacturing method.