JP2018109228A - Steel plate for can and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel sheet for cans capable of making the axial cross section of a can body nearly a perfect circle after welding and a method of manufacturing the same.SOLUTION: In the steel sheet for cans according to the present invention, an elastic limit (σ) in the case that yielding occurs continuously or an upper yield point (U-YP) in the case that yielding occurs discontinuously is 300 MPa or more and 600 MPa or less, a stress-strain curve satisfies the following equation (1) in the case of continuous yielding and the following equation (2) in the case of discontinuous yielding respectively, and the lower yield point (L-YP) does not exist or the lower yield point is positioned at a strain lower than σ. σ≤0.98×σ(1), U-YP≤0.98×σ(2). Here, σis the elastic limit, U-YP is the upper yield point, σis a stress corresponding to an intersection of the stress-strain curve with a straight line parallel to a slope of the stress-strain curve in the elastic region, that passes through a point represented by a stress of 0 MPa and a plastic strain (%) given to the steel sheet for cans when formed into the can body by roll forming.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a steel plate for a can suitable for a three-piece can used as a container material for beverages and foods, and a method for producing the same. More specifically, the steel sheet for cans that can form a can body portion having a small roundness in the axial direction cross section, that is, the axial section of the can body portion after roll forming and welding is close to a perfect circle, that is, a manufacturing method thereof It is about.

  In recent years, thinning of steel plates for cans has been promoted from the viewpoint of reducing manufacturing costs of steel cans. However, as the thickness of the steel sheet is reduced, that is, as the thickness of the steel sheet is reduced, the can body easily deforms when welding after roll forming. As a result, the roundness of the axial cross section of the can body increases, and the strength of the can may be reduced.

  Many studies have been conducted to solve the above problems. For example, Patent Document 1 discloses a technique for improving the deformation and roundness of a can body portion. This method contains C: 0.01 to 0.10% by mass, Mn: 0.1 to 1.0% by mass, and has a Young's modulus of 170 GPa or less. Cold rolling is disclosed. In the invention described in Patent Literature 1, the roundness of the can body portion is hardly changed, and a steel plate for cans excellent in shape maintenance is obtained.

  In Patent Document 2, C: 0.020 to 0.100 mass%, N: 0.0130 to 0.0200 mass%, and other components are also limited. The yield strength is 440 MPa or more and the total elongation is 12% or more. A technique is disclosed in which the roundness of the can body after forming a three-piece can is 0.34 mm or less.

  Patent Document 3 discloses a technique for thinning a steel sheet. Specifically, C: 0.001 to 0.080 mass%, N: more than 0.0150 and 0.0200 mass% or less, and others A high-strength, high-workability steel sheet for cans having a limited component and a tensile strength of 550 MPa or more and a breaking elongation of 7% or more is disclosed, and it is described that secondary cold rolling is performed.

JP 2000-17387 A International Publication No. 2013/183274 JP 2013-119655 A

  However, there is room for improvement in any of the conventional techniques as described below.

  The Young's modulus corresponds to the slope of the straight line portion of the stress-strain curve with stress on the vertical axis and strain on the horizontal axis. In the technique of Patent Document 1, the Young's modulus is decreased. However, as the Young's modulus decreases, the distortion increases and the shape of the material becomes difficult to return. In addition, it is necessary to perform rolling below the transformation point in finish rolling during hot rolling, and manufacturing is not easy. Furthermore, there is a problem that cost increase is unavoidable in secondary cold rolling.

  Since the steel sheet obtained by the technique of Patent Document 2 contains a large amount of N, there is a problem that excessive nitride is generated and workability is deteriorated.

  In the technique of Patent Document 3, since a large amount of N is contained, excessive nitride is generated, workability is deteriorated, and can manufacturing ability may be lowered. Moreover, roll foam workability falls with the raise in hardness in secondary cold rolling. Furthermore, there is a problem that an increase in cost is inevitable.

  The present invention has been made in view of such circumstances, and provides a steel plate for a can that can solve the above-described problems of the prior art and can make the axial cross section of the can body portion after welding close to a perfect circle, and a method for manufacturing the same. With the goal.

  The inventors of the present invention have intensively studied to solve the above problems. As a result, we obtained knowledge to solve the problem based on the following facts.

  First, since the can body of the can is a rectangular flat plate rolled into a cylindrical shape and joined at the end, roundness is an important form factor of the product after molding and has a significant effect on can strength. doing.

  Second, in order to maintain the can strength accompanying the reduction of the steel plate thickness, it is desirable that the roundness of the axial cross section of the can body portion be as small as possible. As YP increases, roll foam processability (ease of roll foam processing) is improved, and the can body is less likely to be deformed even when the can body is restrained during welding, and the roundness is reduced. Therefore, increasing YP is an effective means for controlling the roundness.

Thirdly, when the stress up to the strain applied by the roll foam processing is equal to or higher than the elastic limit (σ ₀ ) or upper yield point (U-YP) of the steel plate for cans, the strain during processing can be dispersed, The deformation of the can body due to bending can be prevented, and the shape of the can body can be maintained well.

Based on the above, as a result of further studies, while defined elastic limit (sigma ₀₎ or upper yield point (U-YP) to a specific range, and an elastic limit (sigma ₀₎ or upper yield point (U- YP) and the relationship between the stress up to the strain imparted to the steel sheet during roll forming, and it has been found that it is important to reduce the roundness of the can body after welding. .

  Moreover, in order to obtain the steel plate for cans which satisfy | fills the said relationship, it discovered that optimization of manufacturing conditions including temper rolling conditions was effective.

  The present invention has been made based on the above findings, and the gist thereof is as follows.

[1] Steel plate for cans, elastic limit (σ ₀ ) when continuously yielding, and upper yield point (U-YP) when not yielding continuously is 300 MPa or more and 600 MPa or less, and the stress-strain curve is continuous. When yielding, the following formula (1) is satisfied, and when not yielding continuously, the following formula (2) is satisfied, and the falling yield point (L-YP) does not exist or the falling yield point exists on the lower strain side than σ ₁ A steel plate for cans characterized by that.
σ ₀ ≦ 0.98 × σ ₁ (1)
U-YP ≦ 0.98 × σ ₁ (2)
Where σ _{0 is the} elastic limit, U-YP is the upper yield point, σ ₁ is a straight line parallel to the slope of the elastic region of the stress-strain curve, stress = 0 (MPa), and strain = roll foam. The stress at the intersection of the straight line passing through the point of the plastic strain amount (%) given to the steel plate for cans when the can body part is formed by processing, and the stress-strain curve.

  [2] By mass%, C: 0.0010 to 0.0100%, Si: 0.01 to 0.10%, Mn: 0.10 to 1.00%, P: 0.020% or less, N: For cans according to [1], containing 0.0050% or less, S: 0.03% or less, Al: 0.02 to 0.10%, the balance being Fe and inevitable impurities steel sheet.

  [3] The composition according to [2], further comprising at least one of Nb: 0.10% or less, Ti: 0.10% or less, and B: 0.008% or less in mass%. Steel plate for cans.

[4] A method for producing a steel plate for cans according to any one of [1] to [3], wherein the steel slab is rolled at a finish rolling temperature of 850 ° C. or higher and wound at a winding temperature of 550 ° C. or higher. A hot rolling step to be taken, a cold rolling step for rolling the steel plate after the hot rolling step at a reduction rate of 80% or more, and an annealing for annealing the steel plate after the cold rolling step at an annealing temperature of 700 to 900 ° C. And a temper rolling step of performing temper rolling under conditions of the following temper rolling elongation ratio and tension: 10 to 26 kg / mm ² after the annealing step. Method.
(Temper rolling elongation)
(I) When Nb and / or Ti are less than 0.01% in total: When the C content is 0.0050% or less, the temper rolling elongation is set to 2 to 5%, and the C content is 0.00. When it is more than 0050% to 0.0100%, the temper rolling elongation is made more than 5% to 10%.
(II) When Nb and / or Ti is 0.01% or more in total: When the C content, Nb content and Ti content satisfy the following formula (A), the temper rolling elongation is set to 2 to 5 %, And when the C content, the Nb content, and the Ti content satisfy the following formula (B), the temper rolling elongation is set to more than 5% to 10%.
1.0 <(Nb / C) × (12/93) + ((Ti / C) × (12/48) ≦ 4.5 (A)
0.1 ≦ (Nb / C) × (12/93) + ((Ti / C) × (12/48) ≦ 1.0 (B)
The element symbols in the formulas (A) and (B) mean the content (% by mass) of each element.

  ADVANTAGE OF THE INVENTION According to this invention, the steel plate for cans which can make the axial direction cross section of the can body part after welding approximate a perfect circle is obtained.

It is a figure for explaining σ ₁ and σ ₀ . It is a figure for demonstrating (sigma) ₁ , U-YP, and L-YP.

  Hereinafter, embodiments of the present invention will be described. In addition, this invention is not limited to the following embodiment.

The steel plate for cans of the present invention (hereinafter sometimes referred to as “the steel plate of the present invention”) has an elastic limit (σ ₀ ) when yielding continuously, and an upper yield point (U-YP) when not yielding continuously. It is 300 MPa or more and 600 MPa or less. Moreover, when the stress-strain curve of the steel plate of this invention yields continuously, following (1) Formula is satisfy | filled. Moreover, when the continuous yield does not occur in the stress-strain curve of the steel sheet of the present invention, the following equation (2) is satisfied, and the lower yield point (L-YP) does not exist or the lower yield point is on the lower strain side than σ _1. Exists.
σ ₀ ≦ 0.98 × σ ₁ (1)
U-YP ≦ 0.98 × σ ₁ (2)
In the case of continuous yielding, the elastic limit (σ ₀ ), in the case of no continuous yielding, the upper yield point (U-YP): 300 MPa to 600 MPa, the steel plate for cans of the present invention has an elastic limit (σ ₀ ) for continuous yielding. When not yielding continuously, the upper yield point (U-YP) is set to 300 MPa or more and 600 MPa or less. The elastic limit (σ ₀ ) is set for continuous yielding, and the upper yield point (U-YP) is set to 300 MPa or more for non-continuous yielding, so that the can body deforms even when the can is restrained during welding. The roundness of the axial cross section of the can body portion is reduced, the can strength can be maintained, and the can shape can be maintained well. Preferably, in the case of continuous yielding, the elastic limit (σ ₀ ) is 380 MPa or more, and in the case of no continuous yielding, the upper yield point (U-YP) is 380 MPa or more. On the other hand, if the yield limit is (σ ₀ ) in the case of continuous yielding and the upper yield point (U-YP) exceeds 600 MPa in the case of no continuous yielding, the roll form workability deteriorates as the plate thickness decreases. Here, YP can be measured by a tensile test based on JIS Z 2241 by cutting out a JIS No. 5 tensile test piece in the rolling direction.

σ ₀ ≦ 0.98 × σ ₁ (1)
U-YP ≦ 0.98 × σ ₁ (2)
As described above, the elastic limit (σ ₀ ) is increased in the case of continuous yielding, and the upper yield point (U-YP) is increased in the case of no continuous yielding. Thus, while the can strength can be maintained, the roll foam processability deteriorates if the elastic limit (σ ₀ ) is continuous yielding and the upper yield point (U-YP) is too high when continuous yielding is not achieved. In the present invention, the elastic limit (σ ₀ ) is set for continuous yielding, and the upper yield point (U-YP) is set to 600 MPa or less and 0.98 × σ ₁ or less is satisfied if no continuous yielding occurs. Is one of the features.

σ ₁ is a plastic strain applied to the steel plate for can when parallel to the slope L1 of the elastic region of the stress-strain curve L, when stress = 0 (MPa) and strain = roll foam processing to form the can body The stress at the intersection of the straight line L2 passing through the point of the quantity x1 and the stress-strain curve L. The inclination of the elastic region is specified according to the description of JIS Z 2241. FIG. 1 and FIG. 2 show the relationship among L, L1, and L2. FIG. 1 shows the case of continuous yielding, and FIG. 2 shows the case of no continuous yielding.

  The plastic strain amount x1 can be defined by [can thickness] / [2 × can diameter (diameter of the cross section in the axial direction of the can body)] × 100 (%) in manufacturing the can.

σ ₁ corresponds to the stress at the maximum strain applied to the steel plate for cans during roll forming, and is a stress with respect to the strain amount obtained by adding the plastic strain amount x1 to the elastic strain amount. During roll forming, the behavior of the stress-strain curve up to this stress σ ₁ is important. Therefore, the σ ₀ ≦ 0.98 × σ ₁ If continuous yielding, if not continuous yielding it to meet the _{U-YP ≦ 0.98 × σ 1} , strain in the roll form process is distributed Thus, local deformation of the can body due to buckling can be prevented, and the can body can hardly be deformed during welding, and a good shape can be maintained.

If the lower yield point (L-YP) is on the higher strain side than σ ₁ , the deformation of the can body becomes non-uniform at the time of roll forming, that is, the strain is concentrated without being dispersed. The shape of the part deteriorates. Therefore, in the stress-strain curve of the steel sheet for cans of the present invention, there is no need for a lower yield point or a lower yield point on the lower strain side than σ ₁ (see FIG. 2).

Component composition The component composition of the steel sheet of the present invention will be described. In the following description, “%” representing the content of a component means “mass%”.

C: 0.0010 to 0.0100%
C has the effect of forming fine carbides and increasing the YP of the steel sheet. In order to make the elastic limit (σ ₀ ) in the case of continuous yielding and the upper yield point (U-YP) in the case of no continuous yielding of 300 MPa or more, the C content is preferably made 0.0010% or more. On the other hand, when the C content exceeds 0.0100%, the stress (σ ₁ ) up to the strain given by roll forming may be lower than YP, the stress is concentrated at one point, and the axial section of the can body part The roundness of may increase. For this reason, the C content is preferably in the range of 0.0010 to 0.0100%. A more preferable C content is 0.0020 to 0.0060%.

Si: 0.01-0.10%
Si is an element having an effect of increasing YP of a steel sheet by solid solution strengthening. In order to ensure YP stably, the Si content is preferably 0.01% or more. On the other hand, since Si is an element harmful to corrosion resistance for cans, the upper limit is preferably set to 0.10%.

Mn: 0.10 to 1.00%
Mn is an element having an effect of increasing YP of a steel sheet by solid solution strengthening. In order to ensure YP stably, the Mn content is preferably 0.10% or more. On the other hand, when the Mn content increases, the strength of the steel sheet becomes excessively high, and the relationship between the appropriate elastic limit (σ ₀ ) or upper yield point (U-YP) and σ ₁ cannot be obtained. In addition, since the cost of the raw material increases, the upper limit of the Mn content is preferably 1.00%. However, since the upper limit of the Mn content of the tin plate used for the food container is defined as 0.6% or less, it is preferably 0.6% or less when used as a food container.

P: 0.020% or less P is an element having an effect of increasing YP of a steel sheet by solid solution strengthening. P segregates at the grain boundaries and lowers the ductility and toughness of the steel sheet. P is also a harmful element that lowers corrosion resistance, and the upper limit of its content is preferably 0.020%. In addition, More preferably, it is 0.010% or less.

N: 0.0050% or less When N is contained in a large amount, excess nitride is generated, and the ductility and toughness of the steel sheet are lowered. Moreover, since N deteriorates workability, the upper limit of the N content is preferably set to 0.0050%.

S: 0.03% or less S preferably contains Mn and Ti. In the present invention, Ti combines with Ti to form TiS and Mn to form MnS. Since these sulfides deteriorate surface properties and reduce ductility in hot rolling, the upper limit of the S content is preferably 0.03%. More preferably, it is 0.01% or less.

Al: 0.02-0.10%
Al is a useful element that acts as a deoxidizer. In order to obtain the effect, the Al content is preferably 0.02% or more. On the other hand, if the Al content exceeds 0.10%, surface defects of the steel sheet are induced, so the upper limit is preferably 0.10%.

Nb: 0.10% or less, Ti: 0.10% or less, B: 0.008% or less Any one or more of Nb combines with C to form a fine carbide of Nb. This carbide has the effect of increasing YP. In order to obtain this effect, when Nb is contained, the content is preferably 0.01% or more. On the other hand, if the Nb content exceeds 0.10%, YP exceeds 600 MPa, the strength increases, and the desired roll foam processability may not be obtained. Moreover, since the rolling load is increased, it may be difficult to produce a stable steel sheet. Therefore, when Nb is contained, the Nb content is preferably limited to a range of 0.01 to 0.10%.

  Ti, like Nb, combines with C to form fine carbides of Ti. This carbide has the effect of increasing YP. In order to obtain this effect, when Ti is contained, the content is preferably 0.01% or more. On the other hand, if the Ti content exceeds 0.10%, YP increases and the desired roll foam processability may not be obtained. Further, the increase in Ti content not only increases the cost of the alloy, but also increases the recrystallization end temperature. Furthermore, when the Ti content increases, it is necessary to increase the rolling load, which makes it difficult to produce a stable steel sheet. Therefore, when Ti is contained, the Ti content is preferably limited to a range of 0.01 to 0.10%.

  B combines with N and has the effect of fixing N, which impairs hot ductility, as BN. Further, since the solid solution B segregates at the crystal grain boundaries and exhibits the effect of refining the crystal grains and is effective in increasing YP, the content is preferably 0.0005% or more. On the other hand, when the B content exceeds 0.008%, the recrystallization completion temperature in the continuous annealing process is excessively increased due to an increase in the solid solution B, and there is a risk that the in-furnace fracture occurs. Therefore, when it contains B, it is preferable to limit B content to 0.0005 to 0.008% of range.

  The balance is Fe and inevitable impurities. Inevitable impurities include Cu, Ni, Cr, Co, Mo, Sb, W, As, Pb, Mg, Ca, Sn, Ta, V, REM, Cs, Zr, and Hf. 2% or less is mentioned.

Thickness Although the thickness of the steel plate for cans of the present invention is not particularly limited, one feature of the present invention is that the thickness is 0.1 to 0.3 mm and the axial cross section of the can body portion after welding can be made close to a perfect circle. One.

  The steel plate for cans of the present invention can be preferably used as a steel plate for 3-piece cans. In addition, since it will have the effect of this invention if it uses for manufacture of the can shape | molded by roll-form processing, it is not necessarily limited to 3 piece cans.

Manufacturing method Next, an example of the manufacturing method of the steel plate for cans of this invention is demonstrated. The manufacturing method of the steel plate for cans of this invention has a hot rolling process, a cold rolling process, an annealing process, and a temper rolling process.

Hot rolling process As a hot rolling process, a steel slab is rolled at a finish rolling temperature of 850 ° C or higher and wound at a winding temperature of 550 ° C or higher.

When the finish rolling temperature is lower than 850 ° C., the number of uncrystallized grains increases, the steel plate becomes hard, and an appropriate elastic limit (σ ₀ ) or upper yield point (U-YP) and σ ₁ relationship cannot be obtained. Moreover, when it is set as the steel plate for cans with thin plate | board thickness, since the temperature of the edge side of a coil tends to fall, finish rolling temperature shall be 850 degreeC or more. In addition, if the finish rolling temperature is too high, 950 ° C. or lower is preferable because the grain growth becomes excessive and the steel sheet strength decreases.

  When the coiling temperature is lower than 550 ° C, the steel sheet becomes hard due to the generation of a hard low-temperature transformation phase such as bainite and martensite, and the load at the time of cold rolling thereafter becomes high, which may make operation difficult. is there. Therefore, the winding temperature is set to 550 ° C. or higher. On the other hand, when the coiling temperature exceeds 700 ° C., the ferrite grains in the hot-rolled sheet stage become coarse, and YP decreases. Therefore, the winding temperature is preferably 700 ° C. or lower.

Cold rolling process As a cold rolling process, the steel sheet after the hot rolling process is rolled at a rolling reduction of 80% or more. In addition, an oxide film is removed as needed after a hot rolling process. Examples of the method for removing the oxide film include pickling and mechanical removal.

  A desired yield strength can be obtained by setting the rolling reduction in the cold rolling step to 80% or more. If the rolling reduction in cold rolling is less than 80%, the crystal grains are coarsened and the material is softened. Therefore, the rolling reduction in cold rolling is 80% or more.

Annealing Step As the annealing step, the steel sheet after the cold rolling step is annealed.

  The annealing temperature is not particularly limited. However, when the annealing temperature is lower than the recrystallization temperature, the ductility is greatly reduced and the steel sheet may be broken. Therefore, the annealing temperature is preferably equal to or higher than the temperature at which recrystallization is completed. On the other hand, if the annealing temperature is too high, the crystal grains become coarse and YP decreases. It is preferable that the soaking temperature (annealing temperature) is 700 ° C. or more and 900 ° C. or less from the viewpoint of preventing breakage during annealing of the thin steel plate and strengthening the fine grains.

Temper rolling step As the temper rolling step, after the annealing step, temper rolling is performed under the following conditions of temper rolling elongation and tension: 10 to 26 kg / mm ² .

  The condition of temper rolling is an important condition in the production method of the present invention. Depending on the carbon content of the steel sheet, temper rolling is performed under appropriate conditions.

First, when the tension during temper rolling is less than 10 kg / mm ² , defects on the steel sheet surface tend to occur. Particularly in steel sheets for cans with a small plate thickness, even if the surface defects are small, the subsequent formability of the can deteriorates and the roundness of the axial cross section of the cylindrical portion increases, so the temper rolling tension is 10 kg / mm ² or more. To. On the other hand, if the tension during temper rolling is too high and exceeds the fracture stress of the material, the material may break during rolling. Therefore, the tension during temper rolling is set to 26 kg / mm ² or less.

In addition, the temper rolling conditions are adjusted according to the carbon content in order to suppress the occurrence of stretcher strain, suppress the decrease in stress until the roll foam processing is completed, and avoid deformation due to buckling. When the carbon content is small, rolling at a high elongation rate causes deterioration in workability and elongation due to hardening of the steel sheet. On the other hand, when the carbon content is large, when rolling at a low elongation rate, yield elongation remains, the stress of strain given by roll forming decreases, deformation due to buckling is inevitable, and roundness increases. . From the above, from the results of various tests conducted by the inventors,
(I) When Nb and / or Ti are less than 0.01% in total: When the C content is 0.0050% or less, the temper rolling elongation is set to 2 to 5%, and the C content is 0.00. When it is more than 0050% to 0.0100%, the temper rolling elongation is made more than 5% to 10%.
(II) When Nb and / or Ti is 0.01% or more in total: When the C content, Nb content and Ti content satisfy the following formula (A), the temper rolling elongation is set to 2 to 5 %, And when the C content, the Nb content, and the Ti content satisfy the following formula (B), the temper rolling elongation is set to more than 5% to 10%.
1.0 <(Nb / C) × (12/93) + ((Ti / C) × (12/48) ≦ 4.5 (A)
0.1 ≦ (Nb / C) × (12/93) + ((Ti / C) × (12/48) ≦ 1.0 (B)
The element symbols in the formulas (A) and (B) mean the content (% by mass) of each element.

  The steel plate obtained as described above is then subjected to surface treatment such as electroplating, such as tin plating, chromium plating, nickel plating, or a resin coating, if necessary. To make a steel plate for cans. In addition, since the film thickness of surface treatments, such as plating and a resin film, is sufficiently small with respect to plate | board thickness, the influence on the mechanical characteristic of the steel plate for cans is a level which can be disregarded.

  Hot rolling, pickling, cold rolling, annealing and temper rolling were performed on the slab having the composition shown in Table 1 under the conditions shown in Table 2 to produce a steel plate for cans having a plate thickness of 0.15 mm. In addition, these steel plates for cans were manufactured on the assumption that the diameter of the can was 52.5 mm. No. The following evaluation was performed on the steel plates for cans 1 to 28. The evaluation method is as follows, and the evaluation results are shown in Table 3.

Tensile test JIS No. 5 tensile test piece (JIS Z 2201) having a tensile direction parallel to the rolling direction was taken from the obtained steel plate for cans and subjected to a tensile test in accordance with the provisions of JIS Z 2241. The elastic limit (σ ₀ ) was measured when continuous yielding occurred, and the upper yield point (U-YP) was measured when continuous yielding did not occur (when yield point drop was indicated). Also, the relationship between σ ₁ and σ ₀ or U-YP is
0.97 × σ ₁ <(σ ₀ or U-YP) ≦ 0.98 × σ ₁ (◯),
(Σ ₀ or U-YP) ≦ 0.97 × σ ₁ is (◎),
The case of σ ₀ > σ ₁ or U-YP> σ ₁ was expressed as (×).

Measurement of roundness In order to measure the roundness, a three-piece can roll form was formed on a steel plate and then welded. Specifically, the steel plate plated with tin on the surface of the steel plate was sheared into a rectangular flat plate blank (length: 160 mm, width: 140 mm). With the rolling direction as the bending direction, the roll former was adjusted so that the winding width was 5 to 10 mm, and roll forming was performed with a strain of 0.3%. Both ends of the formed cylindrical shape were joined by seam welding of electric resistance welding, and the roundness of the central portion in the can height direction was measured using a roundness measuring device defined in “JIS B 7451”. The roundness of the can body in the present invention is, as shown by “JIS B 0621”, when the circular shape is sandwiched between two concentric geometric circles, the interval between the two parallel circles is minimized. Expressed by the difference in radius between two circles. The case where the roundness is 0.20 mm or less is considered to be even better (◎), the case where the roundness is 0.21 mm or more to less than 0.30 mm is passed (O), and the case where the roundness is 0.30 mm or more is not acceptable. It was set as a pass (x).

Claims (4)

A steel plate for cans,
In the case of continuous yielding, the elastic limit (σ ₀ ) is, and in the case of no continuous yielding, the upper yield point (U-YP) is 300 MPa or more and 600 MPa or less,
When the stress-strain curve yields continuously, the following equation (1) is satisfied. When the stress-strain curve does not yield continuously, the following equation (2) is satisfied, and there is no lower yield point (L-YP) or the lower yield point is σ ₁ Steel plate for cans characterized by being present on the low strain side.
σ ₀ ≦ 0.98 × σ ₁ (1)
U-YP ≦ 0.98 × σ ₁ (2)
Where σ _{0 is the} elastic limit, U-YP is the upper yield point, σ ₁ is a straight line parallel to the slope of the elastic region of the stress-strain curve, stress = 0 (MPa), and strain = roll foam. The stress at the intersection of the straight line passing through the point of the plastic strain amount (%) given to the steel plate for cans when the can body part is formed by processing, and the stress-strain curve.   In mass%, C: 0.0010 to 0.0100%, Si: 0.01 to 0.10%, Mn: 0.10 to 1.00%, P: 0.020% or less, N: 0.0050 2 or less, S: 0.03% or less, Al: 0.02 to 0.10%, the balance is made of Fe and inevitable impurities, The steel plate for cans according to claim 1, characterized in that.   3. The can according to claim 2, further comprising at least one of Nb: 0.10% or less, Ti: 0.10% or less, and B: 0.008% or less in mass%. steel sheet. It is a manufacturing method of the steel plate for cans in any one of Claims 1-3,
Rolling a steel slab at a finish rolling temperature of 850 ° C. or higher and winding at a winding temperature of 550 ° C. or higher;
A cold rolling step of rolling the steel sheet after the hot rolling step at a reduction rate of 80% or more;
An annealing step of annealing the steel sheet after the cold rolling step at an annealing temperature of 700 to 900 ° C;
A temper rolling step of performing temper rolling under the following conditions of temper rolling elongation and tension: 10 to 26 kg / mm ² after the annealing step, a method for producing a steel plate for cans.
(Temper rolling elongation)
(I) When Nb and / or Ti are less than 0.01% in total: When the C content is 0.0050% or less, the temper rolling elongation is set to 2 to 5%, and the C content is 0.00. When it is more than 0050% to 0.0100%, the temper rolling elongation is made more than 5% to 10%.
(II) When Nb and / or Ti is 0.01% or more in total: When the C content, Nb content and Ti content satisfy the following formula (A), the temper rolling elongation is set to 2 to 5 %, And when the C content, the Nb content, and the Ti content satisfy the following formula (B), the temper rolling elongation is set to more than 5% to 10%.
1.0 <(Nb / C) × (12/93) + ((Ti / C) × (12/48) ≦ 4.5 (A)
0.1 ≦ (Nb / C) × (12/93) + ((Ti / C) × (12/48) ≦ 1.0 (B)
The element symbols in the formulas (A) and (B) mean the content (% by mass) of each element.

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