WO2005103316A1

WO2005103316A1 - Steel sheet for can and method for production thereof

Info

Publication number: WO2005103316A1
Application number: PCT/JP2005/008399
Authority: WO
Inventors: Yuka Nishihara; Katsumi Kojima; Hiroki Iwasa; Eisuke Hotta; Teruhiro Saito; Kazuhiro Matsumoto
Original assignee: Jfe Steel Corporation
Priority date: 2004-04-27
Filing date: 2005-04-26
Publication date: 2005-11-03
Also published as: EP1741800A1; MXPA06012304A; TW200540284A; CN1946866A

Abstract

A steel sheet for a can which has a chemical composition, in wt %, C: 0.04 to 0.1 %, N: 0.002 to 0.012 %, Mn: 0.5 to 1.5 %, P: 0.01 to 0.15 % Si: 0.01 to 0.5 %, Nb: more than 0.025% and not more than 0.1 %, Al: 0.01 % or less, S: 0.01 % or less, and the balance: Fe and inevitable impurities, and is substantially consisted of a ferrite single phase structure having an average crystal grain diameter of 7 μm or less; and a method for producing the above steel sheet which comprises hot-rolling a steel having the above composition with a finishing temperature of an Ar3 transformation temperature or higher, winding up the resultant sheet at a winding temperature of 560 to 600°C, followed by washing with an acid, and then cold-rolling the resultant sheet with a rolling reduction of 80 % or more, followed by soaking-annealing at a temperature of 700 to 820°C. The resulting steel sheet for a can is a product obtained by a composite combination of solid-solution strengthening, deposition strengthening and refining strengthening, and exhibits a strength being the same as that of the DR steel sheet and also an elongation being greater than that of the DR steel sheet.

Description

Steel plate for can and method for producing the same

Technical field

The present invention relates to a thin steel sheet (hereinafter, also referred to as a steel sheet for cans) suitable for a surface-treated steel sheet for cans such as tinplate steel sheets and electrochrome plated steel sheets, and a method for producing the same.

Background art

In recent years, in order to reduce the cost of making cans, we have been using thin steel sheets and cold-rolled steel sheets for can manufacturing as raw materials.

There is also a need for cost reduction. For this reason, the industry has been required to reduce the thickness of steel plates for cans, not only for two-piece cans that are drawn but also for three-piece cans that are mainly formed by simple cylindrical molding.

However, simply reducing the thickness of the existing steel sheet for cans only reduces the strength. Therefore, in places where strength is required, such as the body of a Draw and Redraw can (hereinafter also referred to as a DRD can) or the body of a welded can. The current steel plate for cans cannot be applied. Therefore, there is a demand for a steel sheet for cans that can maintain strength even when it is made thinner.

Currently, the most frequently used method for producing steel sheets that can maintain strength even when they are thinned is the Double Reduce method (hereinafter also referred to as DR method), in which secondary cold rolling is performed after annealing. However, in the DR method, the cost is increased by adding one step of secondary cold rolling in addition to the normal steps of hot rolling, cold rolling and annealing. Moreover, the obtained steel sheet has an elongation of only a few percent and its workability is not good. In addition, surface flaws and stains occur chronically, and it is extremely difficult to completely prevent them.

Therefore, various methods of strengthening thin steel plates have been proposed as an alternative to the DR method. For example, Japanese Patent Application Laid-Open No. 2001-107186 describes that by adding a large amount of (:, N and baking and hardening, a steel sheet for cans having a strength as high as that of a steel sheet by the DR method can be obtained. This steel sheet for cans has a high yield stress of 550 MPa or more after baking. It discloses that the hardness obtained can be adjusted by the amount of N added and the heat treatment conditions. Although this method is an effective method for increasing the strength, even after temper rolling, there is a concern that yield elongation due to strain aging may occur, and there is a possibility that strain-strain occurs during processing.

Also, in Japanese Patent Application Laid-Open No. 8-325670, strength and elongation were balanced by combining precipitation strengthening with Nb carbide and grain refinement strengthening with Nb, Ti, and B carbonitrides in a complex manner. A method for manufacturing a steel sheet has been proposed. However, according to this method, the inventors set the amount of Nb added to 0.025 wt. /. The tensile strength of the obtained steel sheet was as low as 510MPa, and did not reach the strength of the steel sheet manufactured by the current DR method.

In Japanese Patent Application Laid-Open No. 5-345926, Rockwell hardness (HR30T) (see JIS G 3303) is described using solid solution strength P by P and crystal grain refinement strengthening by Nb, Ti, and B carbonitrides. A method for producing a steel sheet reaching a strength level of 60 to 75 has been proposed. Also, Japanese Patent Application Laid-Open No. 2000-119802 proposes a method for producing a high-strength steel sheet having a tensile strength of 540 MPa or more due to precipitation strengthening by adding alloying elements such as Nb and Ti. However, in any of these methods, the temper rolling is performed at a high reduction rate of about 10% to 30%, and only high strength is obtained. It does not reach the strength of steel sheets manufactured by the method (hereinafter, also referred to as DR steel sheets).

Japanese Patent Application Laid-Open No. 2003-34825 proposes a method in which a low-carbon steel is hot-rolled in the + r region, cooled at a high speed, and regulates a heating rate of annealing. By this method, a steel sheet having a tensile strength of 600 MPa and a total elongation of 30% or more has been obtained. However, the increase in strength due to this high-speed cooling increases operating costs.

The present invention has been made to solve the above problems. An object of the present invention is to provide a steel sheet for cans having both the strength equivalent to that of a DR steel sheet and the elongation exceeding that of the DR steel sheet, and a method for producing the same. Disclosure of the invention In the present invention, at a weight of ⁰ / o, C: 0.04 to 0.1%, N: 0.002 to 0.012%, Mn: 0.5 to 1.5% P: 0.01 to 0. 15%, Si: 0.01 to 0.5%, Nb: more than 0.025 to 0.1%, A1: 0.01% or less, S: 0.01% or less, balance Fe and unavoidable This is a steel sheet for cans consisting of chemical impurities and consisting essentially of a ferrite single-phase structure with an average crystal grain size of 7 / m or less. Further, in the present invention, the weight ^{_{0/0, C:. 0.}} 04~0 1%, N:. 0. 002~0 012%, Mn: 0. 5~ 1. 5%, P: 0. 01 ~ 0.15%, Si: 0.01 ~ 0.5%, Nb: more than 0.025 ~ 0.1%, A1: 0.01% or less, S: 0.01% or less, with the balance being less Steel consisting of Fe and unavoidable impurities is hot-rolled at a finishing temperature above the Ar ₃ transformation point, wound at a winding temperature of 560 to 600 ° C, pickled, and then reduced by 80% or more. This is a method for manufacturing steel sheets for cans in which cold rolling is performed at a low rate and then isothermal annealing is performed at a temperature of 700 to 820 ° C.

Furthermore, in the present invention, the weight ^{_{0/0, C:. 0.}} 04~0 1%, N: 0. 002~0 012% Mn:.. 0. 5 ~1 5%, P: 0. 010~ 0.15%, Si: 0.01-0.5%, Nb: 0.025-0.1%, A1: 0.01% or less, S: 0.01% or less, with the balance Fe andなり Consisting of unavoidable impurities, has a substantially ferrite single-phase structure, ferrite average crystal grain size of 7 jum or less, sheet thickness

A high-strength, high-ductility steel sheet for cans, characterized in that it is 0.2 ram or less. Brief Description of Drawings

FIG. 1 is a diagram illustrating the relationship between the amount of Nb added and the strength of a steel sheet for cans when Nb is added simultaneously with the solid solution element being Mn. BEST MODE FOR CARRYING OUT THE INVENTION

The present inventors have paid attention to a composite combination of solid solution strengthening, precipitation strengthening, and micronization as a means for strengthening a steel sheet. As a result, by adding appropriate amounts of P and Mn as the solid solution strengthening elements and Nb as the precipitation strengthening element and the finely divided strengthening element, it is possible to reduce the crystal grain size and increase the strength without impairing the elongation. Was found. Furthermore, they found that the strength and elongation could be made compatible at a high level by defining the structure as a substantially ferrite single phase structure and defining the average ferrite grain size. In the present invention, a high-strength steel sheet for cans is a thin steel sheet suitable as a base sheet of a surface-treated steel sheet such as a tinned steel sheet (electroplated tin sheet) or an electrochromic plated steel sheet.

The high-strength and high-elongation steel sheet for cans of the present invention is defined by the following elements and their amounts as solid-solution strengthening elements, precipitation strengthening elements and Z or refinement strengthening elements. It consists essentially of a ferrite single phase structure with a diameter of 7 / m or less. These are the most important requirements in the present invention, and a steel sheet for cans having a tensile strength of 550 MPa or more and an elongation of more than 10% can be obtained. The high strength and large elongation steel sheet for cans is hot-rolled at a finishing temperature higher than the Ar ₃ transformation point, wound at a winding temperature of 560 to 600 ° C, pickled, After cold-rolling at a rolling reduction of not less than%, the production can be performed by performing soaking annealing at a temperature of 700 to 820 ° C.

Hereinafter, the present invention will be described in detail.

The reasons for limiting the chemical components of steel in the present invention are as follows. In the present application, all the percentages indicating the components of steel are percentages by weight.

C: 0.04 ~ 0.1%

In order for the steel sheet after annealing to achieve a tensile strength of 550 MPa or more and an elongation of more than 10%, the crystal grain size must be 粒径 m or less. In order to satisfy these characteristics, the amount of C added is important, and C is one of the main requirements for the present invention. In particular, since the amount and density of carbides greatly affect the strength and particle size, it is necessary to secure the amount of carbon used for precipitation. Also, considering the high strength due to solid solution C, C is 0.04% or more. On the other hand, when the content exceeds 0.1%, a pearlite phase precipitates in the second phase, and the elongation decreases. Based on the above, C should be from 0.04% to 0.1%.

Si: 0.01 to 0.5%

Si is an element that increases the strength of the steel sheet by solid solution strengthening, but if added in a large amount, the corrosion resistance is significantly impaired. Therefore, the Si content ranges from 0.01% or more to 0.5% or less. To do. In order to prevent the corrosion resistance 14 from being impaired, the content of Si is preferably 0.01% or more to 0.3% or less.

Mn: 0.5 ~: 1.5%

Mn is an element that increases the strength of the steel sheet by solid solution strengthening, reduces the crystal grain size, and also increases the strength as finer strengthening. This is one of the main requirements for the present invention. The above-mentioned effect is remarkably recognized by adding 0.5% or more. On the other hand, when a large amount of Mn is added, the corrosion resistance is poor. Based on the above, Mn should be between 0.5% and 1.5%. Note that Mn is preferably 0.5% or more to 1.0% or less so as not to significantly increase the recrystallization temperature.

Ρ: 0.01-0.15%

P, like Mn, is an element having a large solid solution strengthening ability, and is one of the main requirements for the present invention. The effect is remarkable at 0.01% or more. On the other hand, when added in large amounts, the corrosion resistance of the steel sheet deteriorates. Based on the above, P should be between 0.01% and 0.15%. It should be noted that P is preferably from 0.01% or more to 0.1% or less in order not to impair the corrosion resistance.

S: 0.01% or less

S is an element that exists as inclusions in the steel and is disadvantageous to the elongation and corrosion resistance of the steel sheet, so it is preferable to reduce it as much as possible. From the above, S is set to 0.01% or less. Usually, it is about 0.0001% or more and 0.01% or less.

A1: 0.01% or less

If the A1 content increases, the recrystallization temperature rises, so it is necessary to raise the annealing temperature. When the annealing temperature is increased, the amount of A1N formed increases, the amount of solute N decreases, and the strength of the steel sheet decreases. Further, in the present invention, the recrystallization temperature is increased by other elements added to increase the strength of the steel sheet, and the annealing temperature is increased. Therefore, it is preferable to avoid an increase in the recrystallization temperature due to A1 as much as possible, and A1 is set to 0.01% or less. Usually, it is about 0.003% or more and about 0.01% or less.

Ν: 0.002 to 0.0012% N is an element that has a high solid solution strengthening ability and increases the strength of the steel sheet. Therefore, N is actively added. In order to effectively act on the strength increase, 0.002% or more is required. On the other hand, if a large amount is added, a problem occurs due to strain aging of the steel sheet. From the above, N should be from 0.002% or more to 0.012% or less.

Nb: Over 0.025 to 0.1%

Nb is one of the main requirements in the present invention. b is an element having a high ability to form carbides, which precipitates fine carbides and increases the strength of the steel sheet. Further, the fineness increases the strength.

FIG. 1 is a diagram illustrating the relationship between the amount of Nb added and the strength of a steel sheet for cans when Nb is added simultaneously with the solid solution element being Mn. From Fig. 1, it can be seen that by adding Nb at the same time as Mn, which is a solid solution element, the strength increase is higher than the strength of the steel sheet, which originally increases by solid solution strengthening. This factor is considered as follows. In other words, by adding a solid solution element (Mn in the example) simultaneously with Nb, the precipitated b-C is more soluble than the solid solution element (Mn in the example) alone. Mn) is suppressed, and the growth of recrystallized grains during annealing is inhibited. In other words, it is considered that the solid solution element itself effectively acts on the grain refinement, and the effect of the grain refinement strengthening is added to the effect of the solid solution strengthening. Then, the above-mentioned effect starts to occur remarkably when the Nb addition amount exceeds 0.025%.

On the other hand, Nb raises the recrystallization temperature, and if it exceeds 0.1%, the steel sheet becomes extremely hard during hot rolling and the workability during cold rolling deteriorates.

From the above, Nb is set to be more than 0.025% to 0.1% or less. From the viewpoint of the workability during cold rolling, Nb is preferably from more than 0.025% to 0.05% or less. Next, the reasons for limiting the organization will be described.

Ferrite single phase structure with average grain size of 7〃m or less

First, in the present invention, a ferrite single phase structure is used. Even if it contains about 1% of cementite or the like, it is determined that the structure is substantially a ferrite single-phase structure as long as the effects of the present invention are achieved. The inventors investigated the balance between strength and elongation by changing the steel structure to a ferrite single phase and changing the average crystal grain size of the ferrite phase. As a result, it was found that when the average grain size of ferrite was 7 im or less, a high-strength steel was obtained without a decrease in elongation. It was also found that if the average crystal grain size exceeds 7 _ <m, the surface appearance after can making becomes unsatisfactory. This is thought to correspond to extreme changes in surface roughness such as skin roughness. These phenomena, although varying in extent and extent of occurrence, were observed especially in 2-piece cans. Based on the above, the average crystal grain size of ferrite is as follows. The ferrite grain size is measured according to, for example, the average ferrite grain size obtained by the ASTM cutting method.

The steel sheet for cans of the present invention preferably has a thickness of 0.2 mm or less. When the sheet thickness is 0.2 mm or less, the cold rolling ratio increases, and a steel sheet for cans having a tensile strength of 550 MPa or more can be easily obtained. Next, a method for producing a high-strength and large-extension steel plate for a can according to the present invention will be described. According to a usual method, a molten steel adjusted to the above chemical composition is prepared using a converter or the like, and the molten steel is formed into a rolled material by a continuous forming method or the like. Next, the obtained rolled material is hot-rolled. The finishing temperature must be at the Ar ₃ transformation point or higher because the steel sheet must be in the r single-phase region. The temperature of the rolled material before hot rolling is preferably low so that the crystal grain size tends to be fine. Therefore, the final rolling temperature must be within the r single-phase region.

1150-1300 ° C is desirable. In order to increase the strength of the steel sheet after annealing by reducing the crystal grain size to 7 μm or less, it is necessary to set the winding temperature from 560 ° C or higher to 600 ° C or lower. If the winding temperature exceeds 600 ° C, the crystal grain size becomes coarse. On the other hand, if the coiling temperature in hot rolling is lower than 560 ° C, solid solution N and C remain in the hot-rolled steel sheet and inhibit formation of a favorable texture during recrystallization annealing after cold rolling. .

Next, after pickling, cold rolling is performed at a rolling reduction of 80% or more. By this cold rolling, the texture after annealing can be developed and markedly refined, and at the same time, a more uniform Site organization is obtained. If the rolling reduction is less than 80%, it is difficult to achieve a tensile strength of 550MPa or more. In order to ensure a rolling reduction of 80% or more, it is desirable that the sheet thickness after cold rolling be 0.2 mm or less.

Next, isothermal annealing is performed in a temperature range from 700 ° C or more to 820 ° C or less. The soaking temperature must be equal to or higher than the recrystallization temperature of the steel sheet in order to ensure good workability, and soaking at a temperature of 700 ° C or more to make the structure more uniform. There is a need. On the other hand, if the soaking temperature is higher than 820 ° C, the annealing process may be affected.

Next, it is preferable to perform temper rolling in order to adjust the surface properties. The temper rolling reduction at this time is preferably 1.5% or less in order to prevent elongation from decreasing due to excessive work hardening. More preferably, it is from 0.5% or more to 1.5% or less.

The tensile strength can be controlled to a target value by the components, the coil winding temperature during hot rolling, the soaking temperature, and the cold rolling reduction. Example 1

The composition of the steel was varied as shown in Table 1. A steel containing each of these components, with the balance being Fe and unavoidable impurities, was prototyped in an actual converter to produce a steel slab. Hereinafter, steel plates for cans were prepared according to the conditions shown in Inventive Examples 1 to 9 and Comparative Examples 1 to 8 in Table 2.

That is, after each steel slab was reheated at 1200 ° C, hot rolling was performed at the finish rolling temperature and the winding temperature shown in Table 2. Next, after pickling, cold rolling was performed at the rolling reduction shown in Table 2 to obtain a 0.2 mm thin steel sheet. The obtained steel sheet was subjected to soaking in a continuous annealing furnace at the heating rate and soaking temperature shown in Table 2 for 30 seconds. Thereafter, the steel sheet was cooled at a cooling rate of about 10 to 5 LC / s by a conventional method to obtain a steel sheet for cans.

Subsequently, the steel sheet for cans was subjected to temper rolling at a rolling reduction of about 1.5%, and a normal chrome plating was continuously performed to obtain an electrochromic plated steel sheet. The soaking temperature was adjusted according to the amount of Nb added, but the values in Table 2 were maintained. After examining the crystal structure and average crystal grain size of the obtained electrochromic plated steel sheet, a tensile test was performed to evaluate strength and elongation. Table 3 shows the obtained results.

The tests and survey methods are as follows.

A tensile test was performed using a JIS No. 5 size tensile test piece, and the yield point, tensile strength, and elongation were measured. Rockwell hardness was also measured separately.

The crystal structure was observed by optical microscopy by polishing the sample, corroding the crystal grain boundaries with nital.

The average crystal grain size was measured using the ASTM cutting method for the crystal structure observed as described above.

Table 3 shows that the steels of Invention Examples 1 to 9 are ferrite single-phase structures having an average crystal grain size of 7 µm or less. Therefore, it can be seen that both strength and elongation are excellent. On the other hand, it is understood that the steel j of Comparative Example 1 and the steel n of Comparative Example 5 are inferior in strength, although the elongation is about the same as that of the invention example due to the low P content. It can be seen that the steel k of Comparative Example 2 had a small amount of Nb, so that the elongation was about the same as the invention example, but the strength was inferior. In addition, in Steel 1 of Comparative Example 3, since the steel structure has an average crystal grain size of more than 7 m and a mixed structure of ferrite and pearlite, it has high strength but inferior elongation. I understand. Comparative Examples 4 and 6 were subjected to temper rolling at high pressure reductions of 20% and 33%, respectively, and although they had high strength, they were just the same technology as the conventional DR method. . The tensile strength of Comparative Example 8 was only 500 MPa despite the value after baking at 210 ° C for 20 minutes. Example 2

The steel type was fixed to steel a shown in Inventive Example 1 in Table 1, and the influence of the difference in manufacturing conditions was examined.

That is, steel a was used, and the production conditions shown in Invention Examples 1, 10 and 11 in Table 2 and Comparative Example 9 were applied. Obtained. The same test as in Example 1 was performed on the obtained electrochrome plated steel sheet, and the results are shown in Table 3.

According to Table 3, according to the manufacturing conditions of Invention Examples 1, 10 and 11, a single-phase ferrite having a crystal grain size of 7 / m or less can be formed into a single phase, so that a steel plate having a tensile strength of 550 MPa or more without impairing elongation. Is obtained.

On the other hand, under the manufacturing conditions of Comparative Example 9, the average crystal grain size of the ferrite exceeds 10 μm, indicating that the elongation is excellent but the strength is inferior. In Comparative Example 7, although high in strength, rapid heating and rapid cooling before and after annealing are required, and it is difficult to manufacture with conventional equipment.

When these steel sheets are drawn, the steel sheets of the present invention have good surface properties and no rough surface. On the other hand, in Comparative Examples in which the average crystal grain size of ferrite exceeded 10 / m, rough skin was observed.

According to the example of the present invention, it can be seen that the target tensile strength can be reliably achieved when the reduction ratio of the temper rolling after the annealing step is 1.5% or less.

Steel type C Si Mn PSN Nb Al Invention example 1 a 0.05 0.01 0.5 0.04 0.01 0.006 0.03 0.01 Invention example 2 b 0.05 0.01 1.0 0.04 0.01 0.006 0.03.0.01 Invention example 3 c 0.05 0.01 0.5 0.075 0.01 0.006 0.03 0.01 Invention example 4 d 0.05 0.01 0.5 0.04 0.01 0.006 0.05 0.01 Inventive example 5.β 0.05 0.2 0.5 0.04 0.01 0.006 0.03 0.01 Inventive example 6 f 0.04 0.01 1.0 0.075 0.01 0.006 0.03 0,01 Inventive example 7 g 0.04 0.01 1.0 0.075 0.01 0.01 0.03 0.01 Inventive example 8 h 0.04 0.01 1.0 0.01 0.01 0.006 0.03 0.01 Invention 9 i 0.04 0.01 1.0 0.075 0.01 0.002 0.05 0.01 Comparative 1 j 0.05 0.01 0.5 0.008 0.01 0.006 0.03 0.01 Comparative 2 k 0.05 0.01 0.5 0.04 0.01 0.006 0 0.01 Comparative 3 1 0.15 0.01 0.5 0.01 0.01 0.002 0.03 0.01 Comparative example 4 m 0.005 1 0.5 0.01-0.006 0 0.002 Comparative example 5 n 0.1 1 0.01 0.55 0.005 0.005 0.0015 0.025 0.055 Comparative example 6 o 0.05 0.005 0.25 0.01 0.009 0.0035 1 0.001 Comparative example 7 P 0.1 0,01 0.5 0.01 0.01 0.003-0.03 Comparative Example 8 9 0.0095 0.02 0.25 0.009 0.007 0.0095 0.007 0.002

Table 2

*: 20% reduction in temper rolling

**: Temper rolling reduction of 33%

Cooling rate after annealing is 1 000 ° C / s

Table 3 Steel grade Yield point Tensile strength Rockwell hardness Elongation Average grain size

(MPa) (MPa) HR30T (%) (j! M) Invention example 1 a 510 550-23 F * 5 Invention example 2 b 500 570-20 F 5 Invention example 3 c 520 570-20 F 5 Invention example 4 d 500 550-21 F 4 Invention 5 'Θ 490 560-21 F 5 Invention 6 f 550 600-19 F 5 Invention 7 g 490 560-17 F 5.5 Invention 8 h 500 560 113 F 5 Invention 9 i 490 550-13 F-3.5 Invention example 10 a 500 570-20 F 4.0 Invention example 11 a 480 550-23 F 5.0 Comparative example 1 j 450 500-26 F 5.5 Comparative example 2 k 430 390-17 F 10 Comparative example 3 I 500 600-10 F + P * *, 10 Comparative example 4 m--73--Comparative example 5 n 480 510-32 F 3.5 Comparative example 6 o-590 73 1-1 7 Comparative example 7 P 360 610 -33 one-Comparative example 8 q-'500 * * * 70-One comparative example 9 a 420 500 one 32 F 12.0

*: Ferrite phase

**: Pearlite phase

***: Bow I tension strength after baking at 210 ° C for 20 minutes

Industrial applicability

According to the present invention, a steel sheet for cans having a tensile strength of 550 MPa or more and an elongation of more than 10% and a method for producing the same are provided. This steel sheet can also be applied to parts such as the trunk of DRD cans and welded cans. The steel sheet is solid-solution-strengthened by using a number of elements, and is further increased in strength by combining precipitation strengthening with Nb and fine-grained stiffening. Therefore, the temper rolling after the annealing step can achieve the target tensile strength reliably with a reduction of 1.5% or less. Also, since the contents of C and N are suppressed, there is no concern about yield elongation due to strain aging. Therefore, the steel sheet can widely contribute to society as a thin steel sheet suitable for a surface-treated steel sheet such as a tinned steel sheet or an electrochrome plated steel sheet.

Claims

1. In% by weight, C: 0.004 to 0.1%, N: 0.002 to 0.012%, Mn: 0.5 to 1.5%, P: 0.01 to 0.15%, Si: 0.01 to 0.5%, Nb: more than 0.025 to 0.1%, A1: 0.01% or less, S:

A steel sheet for cans containing 0.01% or less, the balance being Fe and unavoidable impurities, and substantially consisting of a ferrite single phase structure with an average crystal grain size of 7〃m or less.

2. Weight ⁰ /. C: 0.004 to 0.1%, N: 0.002 to 0.012%, Mn: 0.5 to: 1.5%, P: 0.01 to 0.15%, Si: 0 .01 ~ 0.5%, Nb: more than 0.025 ~ 0.1%, A1: 0.01% or less, S

A steel containing 0.01% or less and the balance consisting of Fe and inevitable impurities is hot-rolled at a finishing temperature above the Ar ₃ transformation point and wound at a winding temperature of 560 to 600 ° C. A method for producing a steel sheet for cans in which pickling is performed, then cold rolling is performed at a rolling reduction of 80% or more, and then isothermal annealing is performed at a temperature of 700 to 820 ° C. Enclosure

3. Weight ⁰ /. And C: 0.004 to 0.1%, N: 0.002 to 0.012%, Mn: 0.5 to 1.5%, P: 0.010 to 0.15%, Si: 0.1. 01-0.5%, Nb: 0.025-0.1%, A1: 0.01% or less, S: 0.01% or less, with the balance being essentially Fe and unavoidable impurities A high-strength, high-ductility steel sheet for cans, which has a ferrite single-phase structure, an average ferrite grain size of 7 µm or less, and a sheet thickness of 0.2 or less.