TW201632636A - Steel sheet for two-piece can and manufacturing method therefor - Google Patents

Abstract

Provided are: a steel sheet for two-piece cans that is suitable not only for drawing and ironing but also for molding of beads or geometric shapes on the can barrel and that can be favorably used for molding specially shaped cans, particularly two-piece specially shaped cans; and a manufacturing method therefor. The present invention is a steel sheet for two-piece cans, wherein: the steel sheet contains, in mass%, C: 0.020%-0.080%, Si: not more than 0.04%, Mn: 0.10%-0.60%, P: not more than 0.02%, S: not more than 0.015%, Al: 0.010%-0.100%, and N: 0.0005%-0.0030%, the remainder being obtained from Fe and unavoidable impurities; tensile strength is at least 480 MPa; elongation is at least 7%; yield elongation is not more than 3%; and ferrite particle diameter is less than 6 [mu]m.

Description

Two-piece steel plate for cans and manufacturing method thereof

The present invention relates to a steel sheet for cans suitable as a material for can containers used in food and beverage cans, and a method for producing the same. In particular, the present invention relates to a two-piece high-strength steel sheet for cans having excellent moldability and a method for producing the same, and the two-piece high-strength steel sheet for a can is particularly suitable for use in a two-piece shaped shape processed in a can body portion. tank.

In recent years, in order to reduce the load on the environment and reduce the cost, the amount of steel sheets used in food cans and beverage cans has been continuously reduced. Therefore, whether it is a two-piece can or a three-piece can, the steel plate as a material is thinned.

Recently, in order to compensate for the decrease in the strength of the can body due to the reduction in the thickness of the steel sheet, it has been conventionally produced as a shaped can having a convex corrugation process or a geometric shape formed on the can body portion. When manufacturing a two-piece can of a shaped can (sometimes called a two-piece shaped can), it is first processed by punching or shrinking to form a higher degree of processing. Processing. Therefore, the steel plate used for the production of the shaped can of the two-piece can is required to have higher formability. On the other hand, the degree of processing is lower At the bottom of the tank, the strength derived from work hardening is less increased. Therefore, when the steel sheet is made thinner, the strength of the steel sheet tends to be insufficient at the bottom of the can. In particular, in the case where the shape of the bottom of the can is a flat concave can, the strength thereof must be higher than that of the conventional primary cold rolled steel sheet (hereinafter referred to as "Sinle Reduce Steel plate"). Therefore, it is effective to use a secondary cold-rolled steel sheet (hereinafter referred to as a double-reduced steel plate) which can easily achieve high strength even if the bottom of the can is made thinner.

Since the DR steel sheet is mainly a hardened steel sheet by work hardening, generally, the formability is low. When the formability is lowered, as described above, it is not suitable for the can body portion. Therefore, it is a review of how to improve the formability of DR steel sheets.

For example, the resin-coated steel sheet for dry-drawing and shrinking processing cans disclosed in Patent Document 1 has a composition of C: 0.001 to 0.10%, Mn: 0.05 to 0.50%, and Al: 0.015 to 0.13% in terms of mass%. , Si: 0.05% or less, P: 0.03% or less, S: 0.03% or less, and the rest is composed of Fe and unavoidable impurities, the crystal grain size is 6 to 30 μm, and the center line average roughness is 0.05 to 0.6 μm. An electrolytic chromic acid-treated steel sheet having a thickness of 0.15 to 0.30 mm is coated with a thermoplastic resin having a thickness of 10 to 50 μm on both sides thereof, and a high-temperature volatile lubricant is applied to the surface thereof.

Patent Document 2 discloses a method for producing a resin-coated steel sheet for a dry-drawing and shrinking processing can, characterized in that it is a steel sheet. The composition of the component is C: 0.001 to 0.06%, Mn: 0.05 to 0.50%, Al: 0.015 to 0.13%, Si: 0.05% or less, P: 0.03% or less, and S: 0.03% or less, and the remainder is A hot-rolled steel sheet composed of Fe and unavoidable impurities is subjected to pickling, cold rolling, continuous annealing, and then rolled at a rolling reduction ratio of 5 to 25% to produce a center line average roughness of 0.05 to 0.6. A steel plate having a thickness of 0.15 mm to 0.30 mm is immediately subjected to electrolytic chromic acid treatment, and then a thermoplastic resin having a thickness of 10 to 50 μm is coated on both sides thereof, and a high-temperature volatile lubricant is applied to the surface thereof.

Patent Document 3 discloses a steel sheet for a profiled can, characterized in that its composition is C% by weight: 0.02 to 0.07%, Si: 0.005 to 0.05%, Mn: 0.1 to 1.5%, and P: 0.04. % or less, S: 0.02% or less, Al: 0.005 to 0.1%, N: more than 0.003 to 0.007%, B: 0.001 to 0.01%, and the relationship of B/N is 0.3 to 1.5, and the rest is Fe and inevitably The composition of the impurities is such that the plastic strain ratio (r value) of at least one of the rolling direction and the sheet width direction of the steel sheet is 0.8 or less.

[Previous Technical Literature] [Patent Document]

Patent Document 1: Japanese Patent No. 3140929

Patent Document 2: Japanese Patent No. 2937788

Patent Document 3: Japanese Patent No. 4630268

However, in the above-mentioned conventional techniques, the following problems can be cited.

The technique described in Patent Document 1 can ensure the formability required when forming into a straight smooth can. However, in the technique described in Patent Document 1, it is not possible to ensure the formability required when the can body portion is subjected to a processed canned shape such as a convex corrugation process.

The technique described in Patent Document 2 is similar to the technique described in Patent Document 1, and it is possible to ensure the formability required when molding into a straight smooth can. However, in the technique described in Patent Document 2, similarly, the formability required for molding into a can-shaped can is not ensured.

The technique described in Patent Document 3 is a steel sheet suitable for a three-piece can. In the steel sheet described in Patent Document 3, since the r value of at least one of the rolling direction and the sheet width direction is 0.8 or less, the anisotropy is large. Such a steel sheet having a large anisotropy does not have the formability required for forming a two-piece can including a punching process.

The present invention has been developed in view of such circumstances, and its object is to solve the above problems of the prior art, and to provide a two-piece high-strength steel sheet for cans which can be particularly suitably used for forming a two-piece shaped can. Its manufacturing method.

The inventors of the present invention have been continually striving to solve the above problems. Specifically, in order to find a method that can combine the excellent strength required for the bottom of the can and the excellent formability required for the can body, and continually study hard, the result finally finds a kind of originality, namely: by The above problems can be solved by adjusting the composition, tensile strength, elongation, elongation at break, and ferrite iron particle size within a specific range, and the present invention has finally been completed in accordance with such a concept.

The present invention has been completed in accordance with the above-mentioned novelty, and the gist of the invention is as follows.

(1) A high-strength steel sheet for a two-piece can, characterized in that the composition thereof contains, by mass%, C: 0.020% or more and 0.080% or less, Si: 0.04% or less, and Mn: 0.10% or more and 0.60% or less. P: 0.02% or less, S: 0.015% or less, Al: 0.010% or more and 0.100% or less, N: 0.0005% or more and 0.0030% or less, and the balance is composed of Fe and unavoidable impurities, and the tensile strength is 480 MPa or more and elongation. The rate is 7% or more, the elongation at break is 3% or less, and the particle size of the ferrite is less than 6 μm.

(2) The two-piece high-strength steel sheet for cans according to the above (1), which is characterized by further containing B: 0.0001% or more and 0.0030% or less by mass%.

(3) A method for producing a two-piece high-strength steel sheet for cans, which is a method for producing a two-piece high-strength steel sheet for cans according to (1) or (2), which is characterized in that: Heating the heating to a heating temperature of 1130 ° C or higher, The hot-rolled hot rolling step of the billet after the heating step is performed at a hot-rolling refining temperature of 820 to 930 ° C, and the hot-rolled steel sheet obtained by the hot-rolling step is wound at 640 ° C or lower. The winding step of winding the temperature, the pickling step of pickling the hot-rolled steel sheet after the winding step, and the hot-rolled steel sheet after the pickling are performed under conditions of a rolling reduction ratio of 85% or more a cold rolling step of primary cold rolling, a cold-rolled steel sheet obtained by the primary cold rolling step, a continuous annealing step of continuous annealing at an annealing temperature of 620 ° C to 690 ° C, and a continuous annealing step The obtained annealed steel sheet is subjected to a secondary cold rolling step of secondary cold rolling under conditions of a rolling reduction ratio of 6 to 20%.

The two-piece high-strength steel sheet for cans of the present invention is adjusted to have a specific composition and is adjusted to have a tensile strength of 480 MPa or more, an elongation of 7% or more, and an elongation at break of 3% or less. The iron particle size is less than 6.0 μm. As a result, the high-strength steel sheet for a two-piece can of the present invention has excellent strength required for the bottom of the can, and has excellent formability required for the can body. Therefore, it is easy to manufacture a two-piece shaped can as long as the high-strength steel sheet for a two-piece can of the present invention is used.

As described above, according to the present invention, it is possible to reduce the thickness of the steel sheet used for the production of food cans, beverage cans, and the like, and to achieve resource saving and cost reduction, and to have industrial applicability.

Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments.

<Two-piece high-strength steel plate for cans>

The high-strength steel sheet for a two-piece can of the present invention contains C: 0.020% or more and 0.080% or less, Si: 0.04% or less, Mn: 0.10% or more and 0.60% or less, and P: 0.02%. Hereinafter, S: 0.015% or less, Al: 0.010% or more and 0.100% or less, and N: 0.0005% or more and 0.0030% or less, and the balance is composed of Fe and unavoidable impurities.

Moreover, the physical properties of the two-piece high-strength steel sheet for cans of the present invention have a tensile strength of 480 MPa or more, an elongation of 7% or more, and a creep elongation of 3% or less.

Further, the structure of the high-strength steel sheet for a two-piece can of the present invention is a structure in which the particle size of the ferrite iron is less than 6 μm.

Hereinafter, the composition, physical properties, and structure of the high-strength steel sheet for a two-piece can of the present invention will be described in order.

As described above, the high-strength steel sheet for a two-piece can of the present invention contains C: 0.020% or more and 0.080% or less, Si: 0.04% or less, and Mn: 0.10% or more and 0.60% or less in terms of mass%. P: 0.02% or less, S: 0.015% or less, Al: 0.010% or more and 0.100% or less, N: 0.0005% or more and 0.0030% or less, and the rest is Fe and It is composed of inevitable impurities. The reason for using this component is as follows. In the following description, "%" indicating the content of each component means "% by mass".

C: 0.020% or more and 0.080% or less

C is an important element for improving strength. By controlling the C content to 0.020% or more, the tensile strength can be made 480 MPa or more. Further, if the C content exceeds 0.080%, the elongation will be reduced to less than 7%, and the potability will be deteriorated. Therefore, the upper limit of the C content must be set to 0.080%. Further, the more the C content is, the finer the particle size of the ferrite iron is, and the higher the strength is. Therefore, it is preferred that the C content be set to 0.030% or more. Moreover, it is preferable to set the C content to 0.060% or less based on the viewpoint of ensuring the potability.

Si: 0.04% or less

When the Si content is too large, the surface treatment property is deteriorated due to the concentration of the surface, and the corrosion resistance is deteriorated. Therefore, the Si content must be set to 0.04% or less. More preferably, it is below 0.03%.

Mn: 0.10% or more and 0.60% or less

Mn has an effect of increasing the hardness of the steel sheet by solid solution strengthening. Further, the Mn system can prevent the deterioration of the thermal ductility due to S contained in the steel by forming MnS. In order to obtain such an effect, the Mn content must be set to 0.10% or more. Especially want to use solid solution of Mn Intensification is obtained: even if the reduction of the rolling reduction rate during the DR rolling can ensure the effect of the tensile strength, it is preferable to set the Mn content to 0.30% or more. If the Mn content exceeds 0.60%, the elongation will be remarkably lowered, and the potability will be deteriorated, so the Mn content must be set to 0.60% or less.

P: 0.02% or less

If the P content is too large, it will be too hard or the formability will be deteriorated due to the occurrence of central segregation. Further, when the P content is too large, the corrosion resistance is deteriorated. Therefore, the upper limit of the P content is set to 0.02%.

S: 0.015% or less

The S system forms sulfides in the steel, thereby reducing the thermal ductility. Therefore, the upper limit of the S content is set to be 0.015% or less.

Al: 0.010% or more and 0.100% or less

The Al system forms AlN with N, whereby the solid solution N in the steel can be reduced, the elongation at break can be lowered, and the tensile deformation can be suppressed. Therefore, it is necessary to set the Al content to 0.010% or more. It is preferable to set the Al content to be 0.050% or more based on the viewpoint of lowering the elongation at break to improve the potability, and it is more preferable to set it at 0.060% or more. Further, when the Al content is excessive, a large amount of alumina is generated, and the alumina remains in the steel sheet to deteriorate the potability. Therefore, the Al content must be set to 0.100% or less. More preferably, it is 0.080% or less.

N: 0.0005% or more and 0.0030% or less

If N is present as solid solution N, the elongation at break will increase, and tensile deformation will occur, the appearance of the surface will become poor, and the potability will be deteriorated. Therefore, the N content must be set to 0.0030% or less. More preferably, it is 0.0025% or less. On the other hand, it is also difficult to stably control the N content to less than 0.0005%, and if it is desired to control the N content to less than 0.0005%, the manufacturing cost also rises. Therefore, the lower limit of the N content is set to 0.0005%.

In the high-strength steel sheet for a two-piece can of the present invention, in addition to the above-mentioned essential components, B may be regarded as a component which can be optionally added, and B is contained in a range of 0.0030% or less.

B: 0.0001~0.0030%

The B system can form BN with N to reduce the solid solution N, thereby lowering the elongation at break. Therefore, B is preferably contained, and in order to obtain the effect of adding B, the B content is preferably 0.0001% or more, more preferably 0.0003% or more. However, if B is excessively contained, not only the above effect tends to be saturated, but also the elongation is lowered, and the anisotropy is deteriorated, resulting in deterioration of the potability. Therefore, it is preferable to set the upper limit of the B content to 0.0030%.

Further, in addition to the above-mentioned essential components and the components which can be optionally added, Fe and unavoidable impurities are contained. Examples of unavoidable impurities include Cr: 0.08% or less, Cu: 0.02% or less, Ni: 0.02% or less, and O: 0.006% or less.

Next, the physical properties of the high-strength steel sheet for a two-piece can of the present invention will be described. As described above, the high-strength steel sheet for a two-piece can of the present invention has a tensile strength of 480 MPa or more, an elongation of 7% or more, and an elongation at break of 3% or less. The technical significance of each physical property is as follows. However, the present invention combines these physical properties, the above-described components, and the structures described later, so that it can have both the excellent strength required for the bottom of the can and the can body. This is also an important technical significance in terms of the excellent formability required.

Tensile strength: 480MPa or more

In order to ensure the strength of the bottom of the can, the tensile strength of the steel plate must be adjusted to 480 MPa or more. More preferably, it is 490 MPa or more. Further, the tensile strength of the steel sheet was measured by the method described in the examples. Further, in the present invention, the usual tensile strength is 580 MPa or less.

Elongation: 7% or more

In addition to the punching and shrinking processing, in order to ensure the workability of the can body such as the convex corrugations, the elongation must be adjusted to 7% or more. Better is 9% or more. By adjusting the steel component content to a predetermined range and making the ferrite iron particle diameter finer according to the production conditions described later, it is possible to obtain a high strength of 480 MPa or more and an elongation of 7% or more, thereby ensuring Good canning properties. Further, the elongation of the steel sheet was measured by the method described in the examples. Also, the usual elongation in the present invention It is 25% or less.

Elongation at break: 3% or less

In order to prevent tensile deformation during canning, it is necessary to adjust the elongation at break to 3% or less. Better is below 2%. Further, the elongation at break of the steel sheet was measured by the method described in the examples.

Next, the structure of the two-piece high-strength steel sheet for cans of the present invention will be described. The particle size of the ferrite iron in the structure of the high-strength steel sheet for a two-piece can of the present invention is less than 6 μm.

Fermented iron particle size: less than 6μm

In addition to adjusting the composition of the steel sheet in the above-described content range, the balance between the high strength and the elongation can be improved by making the grain size of the ferrite iron fine. Therefore, it is necessary to control the particle size of the ferrite iron to be less than 6.0 μm. In addition, by miniaturizing the particle size of the ferrite iron to less than 6.0 μm to lower the elongation at break to less than 3%, it also improves the adhesion between the resin coated on the steel sheet and the surface of the steel sheet. Effect. Based on this point of view, it is preferable to set the particle size of the ferrite iron to be 5.5 μm or less. Further, as described in the examples, the particle diameter means an average crystal grain size.

The present invention is based on the consideration of the reason for increasing the elongation, and it is preferable to adjust the content of the ferrite-grain iron phase in the structure to 95 vol% or more. More preferably, it is 98 vol% or more. As for the other phases other than the iron phase of the ferrite, it is exemplified by: snow, iron, ferritic, and toughened iron.

<Method for Producing High Strength Steel Sheet for Two-Piece Cans>

An example of the method for producing a two-piece high-strength steel sheet for a can according to the present invention includes a heating step, a hot rolling step, a coiling step, a pickling step, a primary cold rolling step, a continuous annealing step, and a secondary cooling. Manufacturing method of the rolling process. Hereinafter, each step will be described.

Heating process

The heating step refers to a step of heating the billet to a heating temperature of 1130 ° C or higher. When the heating temperature before hot rolling is too low, a part of AlN has not been melted. This unmelting is the main cause of the coarse AlN which deteriorates the potability. Therefore, the heating temperature in the heating step is set to 1130 ° C or higher. More preferably, it is above 1150 °C. Although the upper limit of the heating temperature is not particularly specified, if the heating temperature is too high, too much scale will be generated, which may become a defect on the surface of the product. Therefore, it is preferred to set the upper limit of the heating temperature to 1,260 °C.

Further, the composition of the billet becomes a component of the high-strength steel sheet for the two-piece can, and therefore, the composition of the billet must be adjusted to conform to the above-described two-piece high-strength steel sheet of the present invention. Group ingredients.

Hot rolling process

The hot rolling step is a step of hot rolling the billet after the heating step under the conditions of a hot rolling refining temperature of 820 to 930 °C. If the hot rolling refining temperature is higher than 930 ° C, the particle size of the ferrite iron in the hot rolled steel sheet will become coarse, and the particle size of the ferrite iron in the annealed steel sheet will become coarse. When the tensile strength is lowered, the balance between the tensile strength and the elongation is also deteriorated. Therefore, the upper limit of the hot rolling refining temperature is set at 930 °C. Moreover, if the hot rolling refining temperature is less than 820 ° C, the anisotropy of the tensile properties will become large, and the potability will be deteriorated. Therefore, the lower limit of the hot rolling refining temperature is set at 820 °C. A better lower limit is 860 °C.

Coiling process

The coiling step refers to a step of winding up the hot-rolled steel sheet obtained in the hot rolling step at a coiling temperature of 640 ° C or lower. If the coiling temperature exceeds 640 ° C, the particle size of the ferrite iron in the hot-rolled steel sheet will become coarse, the grain size of the ferrite iron in the annealed steel sheet will become coarse, the tensile strength will decrease, and the tensile strength will be lowered. The balance between the two and the elongation also deteriorates. Therefore, the upper limit of the coiling temperature is set at 640 °C. Although the lower limit of the coiling temperature is not particularly specified, it is considered that the amount of solid solution N is reduced in order to reduce the elongation at break in order to reduce the elongation at break, and the coiling temperature is set to 570 ° C or higher. should.

Pickling process

The pickling step refers to a step of pickling the hot-rolled steel sheet after the coiling step. The pickling conditions are as long as the surface scale can be removed, and the conditions are not particularly specified. The pickling can be carried out by a commonly used method.

One cold rolling process

The primary cold rolling step is a step of subjecting the hot-rolled steel sheet after the pickling to a cold rolling at a rolling reduction ratio of 85% or more. The rolling reduction ratio of the primary cold rolling is required to be 85% or more in order to make the grain size of the ferrite iron after annealing finer and to improve the balance between the tensile strength and the formability. When the rolling reduction ratio at the time of cold rolling is too large, the anisotropy of the tensile property may become large, and the potability may be deteriorated. Therefore, the rolling reduction rate of one cold rolling is preferably 90% or less.

Continuous annealing process

The continuous annealing step is a step of continuously annealing the cold-rolled steel sheet obtained in the primary cold rolling step under the conditions of an annealing temperature of 620 ° C to 690 ° C. In order to ensure formability, it is necessary to sufficiently recrystallize it during annealing, and therefore it is necessary to set the annealing temperature to 620 ° C or higher. Further, if the annealing temperature is too high, the grain size of the ferrite iron becomes coarse, and therefore the annealing temperature must be set to 690 ° C or lower. Although the annealing method is not limited, it is preferable to use a continuous annealing method based on the viewpoint of material uniformity.

Secondary cold rolling process

The secondary cold rolling step is a step of performing secondary cold rolling on the annealed steel sheet obtained in the continuous annealing step under the conditions of a rolling reduction ratio of 6 to 20%. The annealed steel sheet is further strengthened by secondary cold rolling and is made thinner. In order to achieve sufficient strength, it is necessary to set the rolling reduction ratio to 6% or more. In addition, because of the implementation of secondary cold rolling, the relief The long rate will be reduced. Further, if the rolling reduction ratio at the time of secondary cold rolling is too high, the formability will deteriorate. Therefore, it is necessary to set the rolling reduction ratio to 20% or less. When there is a special requirement for moldability, it is preferable to set the rolling reduction ratio to 15% or less.

According to the above process, the two-piece high-strength steel sheet for cans of the present invention can be obtained. It is also possible to perform a plating treatment such as tin plating, nickel plating, or chrome plating as a surface treatment of the steel sheet, and an organic film such as a chemical conversion treatment or a coating film may be further applied.

[Examples]

The steel billet was obtained by melting the steel containing the components A to K shown in Table 1 and the remainder of the steel consisting of Fe and unavoidable impurities. The obtained steel billet is heated according to the conditions shown in Table 2, hot-rolled, coiled, and pickled to remove the scale, and then subjected to cold rolling once, in the continuous annealing furnace, according to the respective annealing temperatures. Annealing for 15 seconds, and performing DR rolling (secondary cold rolling) according to the secondary reduction ratio shown in Table 2, and obtaining a steel plate having a thickness of 0.17 to 0.19 mm (steel plate No. 1 to 18) ). The above-mentioned steel sheet was subjected to chrome plating (without tin) treatment to prepare a surface-treated steel sheet which was coated with an organic film.

Tensile strength, elongation, elongation at break

After the organic film was removed from the above-mentioned coated steel sheet by concentrated sulfuric acid, a tensile test piece of Japanese Industrial Standard JIS No. 5 was taken from the rolling direction, and according to the Japanese Industrial Standard JIS Z 2241, Strength, elongation (total elongation), and elongation at break were evaluated.

Fertilizer iron particle size

After being embedded in the cross section in the rolling direction, after polishing, the grain boundary of the ferrite-grain crystal grains is formed by etching with a nitric acid etching solution, and then the average is measured by the cutting method according to the Japanese Industrial Standard JIS G 0551. The crystal grain size was evaluated for the grain size of the ferrite.

Canning rating

In order to evaluate the can-making property, the above-mentioned coated steel sheet is punched into a circular shape, and then deep drawing processing, shrinking processing, and the like are performed, and after the can is formed into a cylindrical shape, the center of the height of the can body portion and In a total of 15 mm of the upper and lower sides, a convex corrugation process was performed in the circumferential direction of the can to form the same can body as the two-piece can used for the beverage can. The sample which was not broken when the can was produced and the tensile deformation was almost invisible was evaluated as "◎". Although no holes were formed, it was found that the sample with slight tensile deformation was evaluated as "○", a sample with a hole or a stretched deformation pattern was rated as "X".

The results are shown in Table 3. Each of the examples of the present invention is pulled The tensile strength is 480 MPa or more, the elongation is 7% or more, the elongation at break is 3% or less, and the particle size of the ferrite iron is less than 6.0 μm, and has excellent formability and strength. On the other hand, the comparative example is inferior in one or more of the above characteristics. For example, in the case of the steel plate marks No. 9, 11, 13, and 17, the potability evaluation is "○", but the tensile strength of the steel sheet is low, and sufficient strength cannot be obtained for the bottom of the can.

Claims (3)

A steel sheet for a two-piece can, characterized in that the composition thereof contains C: 0.020% or more and 0.080% or less, Si: 0.04% or less, Mn: 0.10% or more and 0.60% or less, and P: 0.02%. Hereinafter, S: 0.015% or less, Al: 0.010% or more and 0.100% or less, N: 0.0005% or more and 0.0030% or less, and the balance is composed of Fe and unavoidable impurities, and the tensile strength is 480 MPa or more and the elongation is 7%. Above, the elongation at break is 3% or less, and the particle size of the ferrite is less than 6 μm. The steel sheet for a two-piece can according to claim 1 further contains, by mass%, B: 0.0001% or more and 0.0030% or less. A method for producing a two-piece steel sheet for cans, which is a method for producing a two-piece steel sheet for cans according to claim 1 or 2, which is characterized in that it has heating for heating the billet to 1130 ° C or higher. The heating step of the temperature, the hot rolling step of hot rolling at a hot rolling purification temperature of 820 to 930 ° C, and the hot-rolled steel sheet obtained by the hot rolling step at 640 a winding step of winding up at a coiling temperature of ° C or less, a pickling step of pickling the hot-rolled steel sheet after the winding step, and a hot-rolled steel sheet after pickling, at a rolling reduction ratio of 85% or more Article a primary cold rolling step of cold rolling, a cold-rolled steel sheet obtained by the primary cold rolling step, a continuous annealing step of continuous annealing under conditions of an annealing temperature of 620 ° C to 690 ° C, and The annealed steel sheet obtained in the continuous annealing step is subjected to a secondary cold rolling step of secondary cold rolling under conditions of a rolling reduction ratio of 6 to 20%.