JP5811686B2 - Steel plate for high-strength can and manufacturing method thereof - Google Patents

Description

  The present invention relates to a steel plate for cans which is a three-piece can body material and a top cover material used as a container material for beverages and foods, and a method for producing the same.

  In recent years, in order to expand the demand for steel cans as steel plates for cans, reduction of can manufacturing costs has been taken. As a measure to reduce can manufacturing costs, the cost of materials can be reduced, and not only two-piece cans that are drawn, but also three-piece cans mainly made of simple cylindrical molding, the use of thinner steel sheets can be achieved. It is being advanced.

  However, simply reducing the thickness of the steel sheet reduces the strength of the can body, so that the thinned steel sheet cannot be used in places where a high-strength material such as the can body of a welded can is used. Therefore, high strength and extremely thin steel plates for cans are desired for can bodies of welded cans.

  In addition to YP and TS, the mechanical properties that affect the strength of the can body are greatly influenced by the stiffness of the welded cylinder, that is, the Young's modulus. In other words, steel plates for cans with high YP, high TS, and high Young's modulus are required for thinning.

  There is a strong correlation between the Young's modulus of iron and the crystal orientation. When <111> increases the accumulation of texture (γ fibers) perpendicular to the rolling surface, the Young's modulus in all directions increases, ideally about 220 GPa. I know that In addition, the texture (α fiber) in which <110> is parallel to the rolling direction increases the Young's modulus in the 90 ° direction from the rolling direction, especially by increasing the accumulation of the {112} <110> orientation. A Young's modulus of 280 GPa can be achieved. When the crystal orientation of the steel material does not have an orientation in a specific orientation, that is, the Young's modulus of the steel plate having a random texture is about 205 GPa. However, there is actually no technology aimed at high Young's modulus in steel plates for cans.

  Currently, steel plates for cans that are ultrathin, high YP and high TS are manufactured by the Double Reduce method (hereinafter sometimes referred to as DR method) in which secondary cold rolling is performed after annealing. However, since the DR method has one more process than the processes up to normal rolling, such as hot rolling, cold rolling, annealing, and secondary cold rolling, the cost increases accordingly. Therefore, the steel sheet for cans manufactured by the DR method is demanded to reduce the cost, and a method of adding various strengthening elements to the recrystallization annealing process in order to omit the DR process has been proposed.

  For example, Patent Document 1 and Patent Document 2 provide a steel sheet characterized by a high r value and small anisotropy by performing recrystallization annealing. Such a steel plate having a small anisotropy is suitable for a drawn can or the like that should suppress the occurrence of ears as much as possible.

However, a steel sheet that does not require a small amount of anisotropy does not necessarily need to be recrystallized after cold rolling.
In the past, studies have been made on an as-rolled steel sheet that is not subjected to any heat treatment until cold rolling, or a steel sheet that has recovered its ductility by a heat treatment at a temperature lower than the recrystallization completion temperature. Since these do not contain reinforcing elements, there is no need to worry about the effect on corrosion resistance, and they can be used with confidence as beverage cans and food cans.
Therefore, when trying to produce a high strength steel sheet that does not require small anisotropy, a method of performing recovery annealing below the recrystallization completion temperature is effective, and the following techniques have been proposed. .

  In Patent Document 3, finish rolling is performed at an Ar3 transformation point or less, high-temperature winding is performed, the crystal grain size after hot rolling is set to 50 μm or more, cold rolling is performed at a rolling reduction of 85 to 90%, and 450 A technique is disclosed in which a steel sheet having TS of 530 to 570 MPa and El of 6 to 8% is obtained by performing continuous annealing at ˜580 ° C.

  In Patent Document 4, YS is obtained by performing finish rolling below the Ar3 transformation point at the time of hot rolling, performing cold rolling at a reduction rate of 85% or less, and then heat-treating at 200 to 500 ° C. for 10 minutes. A technique for obtaining a 640 MPa steel sheet is disclosed.

  Patent Document 5 discloses a technique for obtaining a Rockwell hardness (HR30T) of about 70 by performing cold rolling and annealing at 400 ° C. or higher and a recrystallization temperature or lower.

  In Patent Document 6, the steel having the same composition as Patent Document 5 is hot-rolled at least 50% at a temperature below the Ar3 transformation point, cold-rolled at a reduction ratio of 50% or more, and then 400 ° C or more. A technique for obtaining steel having a Rockwell hardness of about 65 by annealing at a recrystallization temperature or lower is disclosed. The recrystallization temperature here refers to the temperature at which the recrystallization rate becomes 10%.

  In Patent Document 7, finish rolling is performed at 40% or more of the total rolling reduction below the Ar3 transformation point during hot rolling, and cold rolling is performed at a rolling reduction of 50% or more, and then annealing is performed in a short time of 350 to 650 ° C. By doing so, YS discloses a technology for obtaining steel of 540 MPa to 700 MPa.

On the other hand, as for the steel sheet aiming at high Young's modulus, various manufacturing methods are provided for the purpose of increasing impact absorption energy in a thick plate (Patent Document 8) and an automotive steel sheet (Patent Document 9).
In Patent Document 8, in addition to rolling from one direction, the texture is controlled by rolling from a right angle direction, and a technique for obtaining a thick steel plate with an increased Young's modulus in the 90 ° direction from the rolling direction and the rolling direction is disclosed. ing.
Patent Document 9 optimizes the component and temperature during hot rolling and the difference between different peripheral speeds of the upper and lower rolls, effectively introduces strain into the shear layer, has a Young's modulus in the rolling direction of 220 GPa or more, and expandability Discloses a technology for obtaining an automotive steel plate excellent in the above.

JP 2001-107186 JP 2005-336610 A Japanese Patent Laid-Open No. 48-92221 JP-A-8-269568 JP-A-6-248338 JP-A-6-248339 JP-A-8-41549 Japanese Patent Laid-Open No. 4-147917 JP2009-19265

  However, all of the above conventional techniques have problems.

  For example, in Patent Document 3, Patent Document 4, Patent Document 6, and Patent Document 7, it is necessary to perform finish rolling below the Ar3 transformation point during hot rolling. Certainly, when finish rolling below the Ar3 transformation point, the ferrite grain size of the hot-rolled material increases, and the strength of the steel after hot rolling decreases as shown in Fig. 3 shown in Patent Document 3, It is effective as a method for reducing the strength of steel itself. However, the edge part, which has a faster cooling rate than the center part, tends to have a lower temperature during finish rolling, and the strain introduced during finish rolling tends to increase the strength of the edge part without being released by recrystallization or recovery. is there. For this reason, the difference in strength between the center portion and the edge portion becomes large, and it is difficult to obtain a uniform hot-rolled sheet in the width direction, so it is difficult to obtain a uniform one in the current operation.

  In Patent Document 4, steel having a YS of 640 to 680 MPa is obtained by annealing at 200 to 500 ° C. for 10 minutes or more after cold rolling and taking strain. However, if annealing is performed for 10 minutes or longer in a continuous annealing furnace, the line speed must be lowered, and the productivity is significantly reduced.

  Patent Document 5 and Patent Document 6 are characterized by annealing at 400 ° C. or more and a recrystallization temperature or less, but the strength of the steel obtained is about 65 to 70 in Rockwell hardness, which is the intended strength in the present invention. In order to obtain the steel of the level, it is necessary to lower the annealing temperature. Therefore, since it cannot obtain at the annealing temperature manufactured with the normal can material, it is necessary to provide an annealing cycle separately, and productivity falls.

  In Patent Document 8, the rolling direction is changed to a right angle in the middle, but for thin steel plates, a steel strip is rolled in one direction to form a steel strip, and then a continuous annealing line or plating line is generally used. It is. Therefore, the manufacturing method which changes the direction of rolling in the middle is not realistic.

  In Patent Document 9, the texture is controlled by introducing strain to the shear layer by utilizing the control of the rolling temperature during hot rolling and the peripheral speed difference between the upper and lower rolls. Problems occur.

  The present invention has been made in view of such circumstances, and is applied to, for example, welded cans, and is particularly suitable for steel plates for cans that require high strength and high Young's modulus in one direction. An object of the present invention is to propose a high-strength steel plate for cans that can keep the pressure strength of the weld can high and a method for manufacturing the steel plate.

  As shown above, in the DR method, although the strength is increased, the elongation is remarkably deteriorated, and the balance between the strength and the elongation is deteriorated. For this reason, there is a problem that a breakage due to insufficient elongation occurs in the flange processing in the can manufacturing process as the strength is increased. In addition, methods such as solid solution strengthening and precipitation strengthening have a problem that the production efficiency is significantly reduced because the energy for thinning is used greatly during cold rolling.

Therefore, the present inventors have intensively studied to solve the above problems. As a result, the following knowledge was obtained.
On the premise that the target strength is obtained by reducing the strength by recovery annealing, optimization of the component composition and manufacturing conditions was studied. As a result, by performing finish rolling at a temperature equal to or higher than the Ar3 transformation point, it is possible to obtain a uniform hot-rolled steel sheet with no difference in strength between the central part and the edge part in the steel strip width direction, and annealing at a temperature of 520 to 700 ° C. By doing so, it has a high Young's modulus in the 0 ° and 90 ° directions from the rolling direction by lowering it to the target strength level in the recovery stage, and further increasing the accumulation of α fibers by leaving the rolled structure to form a textured structure. It has been found that a steel plate can be obtained. These are features of the present invention and are major requirements.

The present invention has been made based on the above findings, and the gist thereof is as follows.
[1] By mass%, C: 0.003% or less, Si: 0.02% or less, Mn: 0.05 to 0.60%, P: 0.02% or less, S: 0.02% or less, Al: 0.01 to 0.10%, N: 0.0010 to 0.0050 %, Nb: 0.001 to 0.05%, B: 0.0005 to 0.002%, the balance is made of Fe and inevitable impurities, and ({112} <110> orientation accumulated strength) / ({ 111} <112> orientation strength) ≧ 1.0, tensile strength in the 90 ° direction from the rolling direction is 550 to 800 MPa, and Young's modulus in the 90 ° direction from the rolling direction is 230 GPa or more. Steel plate for cans.
[2] By mass%, C: 0.003% or less, Si: 0.02% or less, Mn: 0.05 to 0.60%, P: 0.02% or less, S: 0.02% or less, Al: 0.01 to 0.10%, N: 0.0010 to 0.0050 %, Nb: 0.001 to 0.05%, B: 0.0005 to 0.002%, the balance is made of Fe and inevitable impurities, and ({112} <110> orientation accumulated strength) / ({ 111} <112> orientation strength) ≧ 1.0, the tensile strength in the rolling direction is 550 to 750 MPa, the tensile strength in the 90 ° direction from the rolling direction is 550 to 800 MPa, and the Young's modulus in the rolling direction is 210 GPa or more, A steel plate for high-strength cans having a Young's modulus in the 90 ° direction from the rolling direction of 230 GPa or more.
[3] For high-strength cans according to [1] or [2], wherein the total elongation in the rolling direction is 5% or more and the total elongation in the 90 ° direction from the rolling direction is 2% or more. steel sheet.
[4] Any one of [1] to [3] above, wherein a bending radius ratio r / t ≧ 0.5 (r: bending radius [mm], t: steel plate thickness [mm]) is satisfied. The steel plate for high strength cans described in 1.
[5] The steel having the chemical composition described in [1] or [2] is formed into a slab by continuous casting, rough-rolled, hot-rolled at a hot finish rolling temperature of 850 to 960 ° C, and then 550 Winding at a temperature of ~ 750 ° C, pickling, cold rolling at a rolling rate of 80% or more, followed by annealing at a temperature of 520-700 ° C and temper rolling Manufacturing method of steel plate for strength can.
In addition, in this specification,% which shows the component of steel is mass% altogether.

  According to the present invention, it has a tensile strength of 550 to 750 MPa in the rolling direction, 550 to 800 MPa in the 90 ° direction from the rolling direction, and has a high Young's modulus of 210 GPa in the rolling direction and 230 GPa or more in the 90 ° direction from the rolling direction. Furthermore, a steel plate for cans having a total elongation in the rolling direction of 5% or more and a total elongation in the 90 ° direction of 90 ° from the rolling direction of 2% or more is obtained.

  Furthermore, since the recrystallization start temperature is increased by adding Nb and B to the ultra-low carbon steel, the production method of the present invention allows recovery annealing in the same temperature range as a normal steel plate for low carbon cans. Thus, the energy cost can be reduced. As a result, the steel sheet for cans can be produced without impeding productivity.

  Furthermore, in the present invention, since annealing is performed in a temperature range in which the strength change due to the annealing temperature is small, a steel plate for cans having a uniform strength level in the width direction can be obtained even if the annealing temperature varies.

  And the steel plate for cans of this invention can be used for the welding can which can ensure pressure-resistant strength, even if it thins, and the further thinning is attained by high Young's modulus. Furthermore, as an effect of increasing the Young's modulus, the spring back is reduced and the roll forming property is excellent. The ductility is superior to that of conventional DR materials, and it is particularly excellent in formability in flange forming and bending of welded cans.

Hereinafter, the present invention will be described in detail.
The steel plate for cans of the present invention has a tensile strength (hereinafter sometimes referred to as TS) of 550 to 750 MPa in the rolling direction, 550 to 800 MPa in the 90 ° direction from the rolling direction, and ({112} <110> orientation By controlling the texture with a value of (accumulation strength) / (accumulation strength of {111} <112> orientation) of 1.0 or more, the Young's modulus is 210 GPa in the rolling direction and 230 GPa or more in the 90 ° direction from the rolling direction. It is a steel plate for cans. And such steel plates for cans are hot finish rolled at a hot finish rolling temperature of 850 to 960 ° C., wound at a temperature of 550 to 750 ° C., pickled, and a rolling rate of 80% or more. It can be manufactured by performing cold rolling at 520 and annealing at a temperature of 520 to 700 ° C. These are the most important requirements of the present invention.

The component composition of the steel plate for cans of this invention is demonstrated.
C: 0.003% or less The steel plate for cans of the present invention is strengthened by the strain introduced by cold rolling, and the annealing temperature is kept below the recrystallization start temperature, and the rolled structure remains after annealing to ensure the same strength as DR material. It is characterized by doing. In order to produce more efficiently, it is necessary to raise the recrystallization temperature and reduce the C content. Regarding the ductility, too much C cannot provide sufficient local ductility required during can molding. In addition, if the amount of residual solute carbon increases, cracks will occur during stretch flange molding of the tightened part, which is the final process of can manufacturing, and wrinkles will occur when performing neck processing and flange processing because the amount of work hardening will also increase. There is a risk of doing. Therefore, the C content is 0.003% or less.

Si: 0.02% or less
Si is an element that increases the strength of steel by solid solution strengthening, but if added in a large amount, the plating property is impaired and the corrosion resistance is remarkably lowered. Therefore, the Si content is 0.02% or less.

Mn: 0.05% to 0.60%
If the Mn content is less than 0.05%, it becomes difficult to avoid hot brittleness even when the S content is reduced, and problems such as surface cracks occur during hot rolling. Therefore, the lower limit of Mn is set to 0.05%. On the other hand, Mn increases the strength of steel by solid solution strengthening and reduces the crystal grain size. However, in the ladle analysis value specified in JIS G 3303 and the ladle analysis value of the American Society for Testing and Materials (ASTM), the upper limit of Mn content for tin plate used for ordinary food containers is defined as 0.60% or less. ing. If it exceeds 0.60%, it concentrates on the surface and produces Mn oxide, which adversely affects the corrosion resistance. For this reason, the upper limit of the Mn content is 0.60%.

P: 0.02% or less
When P is added in a large amount, it causes hardening of the steel and deterioration of corrosion resistance. Moreover, even if it reduces too much, in addition to the effect being saturated, it leads to an increase in manufacturing cost, which is not desirable. Therefore, the upper limit of the P content is 0.02%.

S: 0.02% or less
S combines with Mn in steel to form MnS and precipitates in large quantities, thereby reducing the hot ductility of the steel. Therefore, the upper limit of S is 0.02%.

Al: 0.01-0.10%
Al is an element added as a deoxidizer. Moreover, by forming N and AlN, it has the effect of reducing the solute N in the steel. However, if the Al content is less than 0.01%, a sufficient deoxidizing effect or solute N reducing effect cannot be obtained. On the other hand, if it exceeds 0.10%, not only the above effects are saturated, but also problems such as an increase in manufacturing cost and an increase in the occurrence rate of surface defects occur. Therefore, the Al content is 0.01% or more and 0.10% or less.

N: 0.0010-0.0050%
N is preferably as small as possible because it combines with Al, Nb or the like to form nitrides or carbonitrides and impairs hot ductility. N is one of the solidity strengthening elements, and if added in a large amount, it leads to hardening of the steel, and the elongation is remarkably lowered to deteriorate the formability. Therefore, the upper limit of N amount is 0.0050%. On the other hand, it is difficult to stably make N less than 0.0010%, and the manufacturing cost also increases. Therefore, the N content is set to be 0.0010% or more and 0.0050% or less.

Nb: 0.001 ~ 0.05%
Nb is an element having a high carbide-forming ability, and the recrystallization temperature rises due to pinning of grain boundaries by the generated carbide. Therefore, by changing the amount of Nb added, it is possible to change the recrystallization temperature of the steel and perform annealing at the target temperature as needed. Also, by changing the annealing temperature as needed, it is possible to match the chance of annealing with other steel plates of different steel types, which is very efficient from the viewpoint of productivity. However, if the content exceeds 0.05%, the recrystallization temperature becomes too high and the CAL threadability is lowered. Moreover, it becomes higher than a target intensity | strength by precipitation strengthening of a carbide | carbonized_material. Therefore, the Nb content is 0.05% or less. Basically, in the present invention, an element that increases the strength of the steel sheet is not added, but Nb needs to be added from the viewpoint of the annealing temperature, and if it is 0.05% or less, the precipitation of Nb is rather adjusted by adjusting the addition amount. It is possible to use reinforcement to achieve the desired strength. Further, the addition of Nb is also effective in preventing a decrease in welding strength by suppressing recrystallization during welding. On the other hand, if the Nb content is less than 0.001%, the above effect cannot be exhibited, so 0.001% is made the lower limit.

B: 0.0005-0.002%
B is an element that raises the recrystallization temperature. Therefore, B is added for the same reason as Nb addition. However, if added in excess, recrystallization in the austenite region must be inhibited during hot rolling and the rolling load must be increased, so the upper limit is made 0.002%. Further, if it is less than 0.0005%, the recrystallization temperature cannot be increased, so 0.0005% is made the lower limit.

  The balance is Fe and inevitable impurities.

  Next, the mechanical properties of the steel plate for cans of the present invention will be described.

Texture: ({112} <110> orientation accumulation strength) / ({111} <112> orientation accumulation strength) ≧ 1.0 at the center of the plate thickness
In the present invention, in order to obtain a rolled structure in which recrystallized grains are not generated, <110> is a texture that is parallel to the rolling direction, that is, a structure in which a so-called α fiber is developed. In particular, when the accumulation of {112} <110> orientation increases, the Young's modulus in the 90 ° direction from the rolling direction and the rolling direction increases. This {112} <110> orientation is a rolling texture that develops remarkably when the rolling rate during cold rolling is around 90%.
On the other hand, at the time of recrystallization, the accumulation of {112} <110> orientation decreases, and the {554} <225> orientation and the {111} <112> orientation which is a γ fiber develop.
Therefore, by increasing the rolling rate during cold rolling to increase the accumulation of {112} <110> orientation, and then annealing in a temperature range that does not cause the recrystallization phenomenon that the {111} <112> orientation increases, A steel sheet having a high Young's modulus in the 90 ° direction from the direction and the rolling direction can be obtained.

  As described above, in the present invention, in the central portion of the plate thickness, the texture is controlled so that ({112} <110> orientation accumulated strength) / ({111} <112> orientation accumulated strength) ≧ 1.0. A steel sheet having a Young's modulus in the direction of 210 GPa or more and a Young's modulus in the 90 ° direction from the rolling direction of 230 GPa or more is obtained.

  The above ({112} <110> orientation accumulation strength) / ({111} <112> orientation accumulation strength) is performed by chemical polishing (oxalic acid etching) for the purpose of thickness reduction and strain removal, Next, the texture can be measured and evaluated using an X-ray diffractometer at the position of the polished plate thickness 1/2. Details will be described later in Examples.

Tensile strength Tensile strength is necessary to ensure the pressure resistance of the lid, the piercing strength of the can and the strength of the can body. In addition, the present invention enables the omission of the DR process as a cost reduction of the steel plate for cans produced by the DR method. And in the present invention, the strength is controlled by softening the rolled structure by recovery in the temperature range where the recrystallization phenomenon does not occur, and mechanical properties equivalent to conventional DR materials can be obtained, so it is used as the current DR8-9. Substitution is possible for the application. Therefore, as the strength corresponding to DR8-9, the tensile strength is 550-750 MPa in the rolling direction and 550-800 MPa in the 90 ° direction from the rolling direction.
The tensile strength can be measured by a metal material tensile test method shown in “JIS Z 2241”.

The steel sheet for cans of the present invention having a Young's modulus in the rolling direction of 210 GPa or more and a Young's modulus in the 90 ° direction of 230 GPa or more from the rolling direction is suitably used for the can body of a welded can. Thinning is achieved by applying the Young's modulus in the rolling direction to 210 GPa or more, the Young's modulus in the 90 ° direction from the rolling direction to 230 GPa or more, and the circumferential direction of the welded can body to be 0 ° and 90 ° from the rolling direction. The can body strength can be secured even with the steel plate made. Conventional steel plates for cans are less than 210GPa, so that the can body rigidity can be improved and the can body strength can be improved by applying the welding can body to either the 0 ° or 90 ° direction from the rolling direction. Can do. From the above, the Young's modulus in the rolling direction is 210 GPa or more, and the Young's modulus in the 90 ° direction from the rolling direction is 230 GPa or more.

Total elongation: Rolling direction: 5% or more, 90 ° direction from rolling direction: 2% or more (preferred conditions)
For bend forming applications such as the flange formability of welded cans, total elongation is required more than before. In particular, there is a correlation between the incidence of flange cracking and total elongation. In the present invention, the rolled structure is freed from strain by the recovery phenomenon to obtain ductility higher than that of the conventional DR material, and considering that the total elongation of the conventional DR material is less than 2%, the total elongation is at least 2 % Or more. By setting the total elongation in the rolling direction to 5% or more and the total elongation in the 90 ° direction from the rolling direction to 2% or more, the incidence of flange cracking can be reduced to a conventional level.

Bending radius ratio r / t ≧ 0.5 (r: bending radius [mm], t: steel plate thickness [mm]) (preferred condition)
The bending workability is generally evaluated by the ratio between the bending radius and the steel plate thickness. By setting r / t ≧ 0.5, cracking does not occur even when bending by 180 °, and the bending characteristics are excellent. The pull tab used for the lid is required not to be deformed until the score (cut) is broken when the can is opened, and high rigidity is ensured by bending the end face of the steel plate. In addition, chassis used inside PCs, game machines, home appliances, etc. are bent by molding or fixing screws. By applying the present invention, which has excellent bending properties, to pull tabs and chassis of electronic components, the crack generation rate can be reduced as compared with conventional DR materials.

Next, the manufacturing method of the steel plate for cans of this invention is demonstrated.
The steel plate for cans according to the present invention is a slab formed by continuous casting of steel having the above composition, roughly rolled, hot rolled at a hot finish rolling temperature of 850 to 960 ° C, and then at a temperature of 550 to 750 ° C. It is manufactured by winding, pickling, performing cold rolling at a rolling rate of 80% or more, subsequently annealing at a temperature of 520 to 700 ° C., and performing temper rolling.

  It can be melted by a generally known melting method using a converter or the like. Moreover, it is set as a rolling raw material by the casting methods used normally, such as a continuous casting method. At this time, the slab reheating temperature is preferably 1050 to 1300 ° C. The slab reheating temperature before hot rolling is not particularly limited, but if the heating temperature is too high, problems such as product surface defects and increased energy costs may occur. On the other hand, if it is too low, it will be difficult to ensure the final finish rolling temperature.

A hot-rolled sheet is obtained by hot rolling. At the start of rolling, the rolled material is preferably 1250 ° C. or higher.
Hot finish rolling temperature: 850-960 ° C
The hot finish rolling temperature is set to be equal to or higher than the Ar3 transformation point from the viewpoint of grain refinement of the hot rolled steel sheet and uniformity of precipitate distribution. On the other hand, even if the finish rolling temperature is too high, γ grain growth after rolling occurs more vigorously, and the accompanying coarse γ grains cause coarsening of the α grains after transformation. Specifically, the finish rolling temperature is in the range of 850 to 960 ° C. When the temperature is lower than 850 ° C., the rolling becomes below the Ar3 transformation point, which leads to coarsening of α grains. Therefore, the finish rolling temperature is 850 ° C. or higher and 960 ° C. or lower, preferably 870 ° C. or higher and 930 ° C. or lower.
Winding temperature 550 ~ 750 ℃
In the temperature range where the coiling temperature is lower than 550 ° C., although hardened, coarse and fine ferrite grains are mixed and the material becomes non-uniform. On the other hand, when the temperature is higher than 750 ° C., the scale thickness of the steel sheet is remarkably increased, and the descaling property at the time of pickling in the next process may be deteriorated. Therefore, it is set to 550 ° C. or higher and 750 ° C. or lower. Further, the total elongation in the rolling direction is 5% or more and the total elongation in the 90 ° direction from the rolling direction is 2% or more, or the bending radius ratio r / t ≧ 0.5 (r: bending radius [mm], t: steel plate thickness [Mm]), it is necessary to make the crystal grains of the hot-rolled sheet coarse, and the winding temperature is preferably 580 ° C. or higher and 750 ° C. or lower. The subsequent pickling process is not particularly limited as long as the surface scale can be removed.

Next, cold rolling, annealing, and temper rolling are performed.
Rolling ratio: 80% or more When the rolling ratio of cold rolling is less than 80%, the desired strength is not reached after annealing. Furthermore, the deterioration in the material surface considered to be caused by the non-uniformity of the structure in the plate thickness direction becomes remarkable. Further, the rolling rate is 80% or more from the viewpoint of forming a texture of {112} <110> orientation. Preferably, it is 85% or more.
Annealing temperature: 520-700 ° C
Annealing is performed in a temperature range of 520 to 700 ° C. The purpose of annealing in the present invention is to reduce the strength of the steel sheet to the target strength by performing strain relief annealing from the state where the strength of the steel sheet is increased by the strain introduced by cold rolling. If it is less than 520 ° C., the strain is not released sufficiently and becomes higher than the target strength, so 520 ° C. is the lower limit. On the other hand, if the temperature is too high, recrystallization will start and the target strength will not be obtained due to softening too much, or the accumulation of {112} <110> orientation will decrease and the {111} <112> orientation will accumulate. Therefore, the upper limit is 700 ° C. As described above, the annealing temperature is an important factor in that the texture is accumulated in the {112} <110> orientation, and the material strength and Young's modulus are ensured within a specified range, preferably 520 ° C. or more and 700 ° C. or less. It is. Further, the total elongation in the rolling direction is 5% or more and the total elongation in the 90 ° direction from the rolling direction is 2% or more, or the bending radius ratio r / t ≧ 0.5 (r: bending radius [mm], t: steel plate thickness [Mm]), it is necessary to release a large amount of distortion of the steel sheet, and it is preferably 550 ° C. or higher and 700 ° C. or lower. From the viewpoint of obtaining the characteristics that the total elongation in the rolling direction is 5% or more and the total elongation in the 90 ° direction from the rolling direction is 2% or more, it is more preferably 570 ° C. or more and 700 ° C. or less. From the point of obtaining the characteristics of the bending radius ratio r / t ≧ 0.5 (r: bending radius [mm], t: steel plate thickness [mm]), it is more preferably 590 ° C. or more and 700 ° C. or less. The annealing method is preferably a continuous annealing method from the viewpoint of material uniformity and high productivity. The soaking time during annealing is preferably 10 seconds or more and 90 seconds or less from the viewpoint of productivity.
In the temper rolling, the rolling conditions are not particularly defined as long as the target surface finish can be achieved.

A steel slab was obtained by melting steel containing the composition shown in Table 1 and the balance being Fe and inevitable impurities. The obtained steel slab was reheated at 1250 ° C., and then hot rolled at a finish rolling temperature of 870 to 890 ° C. and a winding temperature of 560 to 680 ° C. Next, after pickling, the steel sheet was cold-rolled at a rolling rate of 82.6% to 91.3% to produce a steel plate having a thickness of 0.20 to 0.30 mm.
The obtained steel sheet was subjected to (recovery) annealing at an annealing temperature of 500 to 750 ° C. and an annealing time of 30 s in a continuous annealing furnace, and temper rolling was performed so that the elongation ratio of No1 to 13 was 1.5% or less. . For No. 14 to 15, secondary rolling was performed at a rolling rate of 25%. Detailed production conditions are shown in Table 2.

A tensile test was performed on the steel sheet obtained as described above. The tensile test was performed using a JIS5 size tensile test piece and the tensile strength was evaluated. The Young's modulus was calculated from the resonance frequency by the natural vibration method specified in JIS Z2254.
The texture was measured at the position of 1/2 the thickness of the polished plate by chemical polishing (oxalic acid etching) for the purpose of thickness reduction and strain removal. An X-ray diffractometer was used for the measurement, and (110), (200), (211), and (222) pole figures were created by the Schulz reflection method. A crystal orientation distribution function (ODF) was calculated from these pole figures, and a Ψ2 = 45 ° section of Euler space (Bunge method) was drawn. At this time, in order to remove the influence of the ghost, the odd term was also calculated.
In addition, a test was conducted in which a steel plate was adjusted to a length of 100 mm × width of 20 mm and bent 180 °. The test was carried out while changing the bending radius, and the minimum bending radius at which no cracks occurred in the cross section of the steel plate at the bending portion was clarified. The bending radius ratio r / t (r: bending radius [mm], t: steel plate thickness [mm] ]). The bending radius ratio r / t was 0.5 or more, and less than 0.5 was x.

  The results obtained as described above are shown in Table 3.

From Table 3, the present invention examples (No 2 to 5, No 11 to 13) have a tensile strength in the rolling direction (hereinafter referred to as RD (Rolling Direction)) of 550 to 750 MPa and a 90 ° direction from the rolling direction (hereinafter referred to as TD ( (Transverse Direction)) is tensile strength of 550 to 800 MPa, and (integrated strength of {112} <110> orientation) / (integrated strength of {111} <112> orientation) is 1.0 or more, Young's modulus of RD is 210 GPa or more and Young's modulus of TD is 230 GPa or more. Further, the bending radius ratio r / t can be secured to 0.5 or more, and it can be seen that when bending by 180 °, cracking does not occur and bending characteristics are excellent.
On the other hand, in the comparative example (No. 1), the annealing temperature is below the range of the present invention, the recovery does not progress, and the tensile strength of TD is excessive. In the comparative examples (Nos. 6, 8 and 9), the annealing temperature exceeds the range of the present invention and exceeds the recrystallization start temperature, so that recrystallized grains are generated and the tensile strength is insufficient. In Comparative Example (No10), Nb is not added and the amount of C exceeds the range of the present invention, and in Comparative Example (No7), B is not added, so the recrystallization temperature does not increase. . Therefore, the tensile strength within the range of the present invention is not reached despite the annealing temperature range of the present invention. Nos. 14 and 15 are DR materials manufactured by the DR method, which is an existing technology, but the tensile strength is within the range of the present invention, but the ductility is deteriorated by performing secondary rolling. Further, since the recrystallization is completely completed, the α fiber texture is not accumulated, and the Young's modulus is outside the scope of the present invention for both RD and TD.

Claims (5)

In mass%, C: 0.003% or less, Si: 0.02% or less, Mn: 0.05 to 0.60%, P: 0.02% or less, S: 0.02% or less, Al: 0.01 to 0.10%, N: 0.0010 to 0.0050%, Nb : 0.001 to 0.05%, B: 0.0005 to 0.002%, the balance consists of Fe and inevitable impurities,
In the central portion of the plate thickness, ({112} <110> orientation accumulated strength) / ({111} <112> orientation accumulated strength) ≧ 1.0,
A steel plate for high-strength cans having a tensile strength in the 90 ° direction from the rolling direction of 550 to 800 MPa and a Young's modulus in the 90 ° direction from the rolling direction of 230 GPa or more. In mass%, C: 0.003% or less, Si: 0.02% or less, Mn: 0.05 to 0.60%, P: 0.02% or less, S: 0.02% or less, Al: 0.01 to 0.10%, N: 0.0010 to 0.0050%, Nb : 0.001 to 0.05%, B: 0.0005 to 0.002%, the balance consists of Fe and inevitable impurities,
In the central portion of the plate thickness, ({112} <110> orientation accumulated strength) / ({111} <112> orientation accumulated strength) ≧ 1.0,
The tensile strength in the rolling direction is 550 to 750 MPa, the tensile strength in the 90 ° direction from the rolling direction is 550 to 800 MPa,
A steel plate for high-strength cans having a Young's modulus in the rolling direction of 210 GPa or more and a Young's modulus in the 90 ° direction from the rolling direction of 230 GPa or more.   The steel sheet for high-strength cans according to claim 1 or 2, wherein the total elongation in the rolling direction is 5% or more and the total elongation in the 90 ° direction from the rolling direction is 2% or more.   The high-strength can according to any one of claims 1 to 3, wherein a bending radius ratio r / t ≧ 0.5 (r: bending radius [mm], t: steel plate thickness [mm]) is satisfied. Steel plate. It is a manufacturing method of the steel plate for high intensity | strength cans as described in any one of Claims 1-4 , Comprising : Steel is made into a slab by continuous casting, rough rolling, and it is hot at the hot finishing rolling temperature of 850-960 degreeC. After rolling, it is wound at a temperature of 550 to 750 ° C., pickled, cold rolled at a rolling rate of 80% or more, and subsequently annealed at a temperature of 520 to 700 ° C. A method for producing a steel plate for a high-strength can characterized by being performed.