JP3548390B2 - Steel plate for hard two-piece container with remarkably small earring and method for producing the same - Google Patents

Description

表２は熱延、冷延、焼鈍の後、形状矯正のための軽圧下を含む種々の圧下率で２ＣＲを施した最終板厚０．１８ｍｍの鋼板で特性を評価した結果である。なお、トータル冷延率は８７〜９５％であった。ヒートバックルについては再結晶温度＋４０℃で連続焼鈍ラインを通板した際の、ヒートバックル発生の有無で判定した。
【００３３】
【表２】

図２はトータル冷延率とイヤリング率の関係を見たものである。ここでトータル冷延率とは（最終板厚）／（冷延前板厚）で定義され、１ＣＲおよび２ＣＲを含んだ冷延工程での圧延率である。図２に示すように、本発明鋼では９０％以上の高冷延率領域で比較鋼と比しイヤリング率が小さい。また比較鋼は、２ＣＲを適用すると１ＣＲよりもイヤリング率が大きくなるが、本発明鋼では、２ＣＲを適用した場合にも非常に低いイヤリング率となるため、低イヤリングと良好な耐ヒートバックル性の両立が可能となる。
【００３４】
図２で用いた鋼成分を表３に示す。
【００３５】
【表３】

図２および表２から明らかなように本発明の範囲内で製造されたものはイヤリング性、耐ヒートバックル性ともに良好な特性が得られている。
【００３６】
図３はスラブ加熱温度が異なるトータル冷延率９２〜９３％、２ＣＲ率２５〜３５％の発明鋼について、（ＡｌＮとして存在するＮ）／（ＢＮとして存在するＮ）の影響を見たものである。図３に示すように、同程度の（ＡｌＮとして存在するＮ）／（ＢＮとして存在するＮ）であっても、スラブ加熱温度が１１００℃以下の場合にはイヤリング性の向上が見られる。特に、（ＡｌＮとして存在するＮ）／（ＢＮとして存在するＮ）の比が、０．４を境として、０．４以下になると急激にイヤリング率が小さくなる。
【００３７】
【発明の効果】
以上述べたごとく本発明によれば、イヤリング率を小さくしつつ、焼鈍時のヒートバックル発生率を低減することができ、極薄容器材料の高効率な製造が可能となる。
【図面の簡単な説明】
【図１】イヤリング率を説明するための図である。
【図２】トータル冷延率とイヤリング率との関係を示す図である。
【図３】スラブ加熱温度と（ＡｌＮとして存在するＮ）／（ＢＮとして存在するＮ）とがイヤリング率に及ぼす影響を示す図である。
【図４】２ＣＲ率（％）とイヤリング率との関係を示す図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ultra-thin container material that can be manufactured with small earrings and high productivity in the steel sheet manufacturing field and can manufacturing field, and in particular, a material for a two-piece can manufactured through drawing, ironing, and stretching. And a method for producing the same.
[0002]
[Prior art]
2. Description of the Related Art In recent years, for beverage cans, food cans, and the like, thinner raw materials have been required to reduce can costs by reducing the amount of raw materials used. What is needed at the time of manufacturing an ultra-thin material manufactured against this background is to suppress the bending of the steel plate called a heat buckle in the annealing step and increase the production efficiency. For this purpose, it is effective to keep the annealing temperature of the steel sheet low, and a steel sheet having a low recrystallization temperature is required. As a countermeasure against heat buckle in a situation where the annealing temperature must be set high from the viewpoint of recrystallization, at the time of annealing, a steel sheet thicker than the target sheet thickness is passed, and then re-rolling (2CR) is performed. A method for obtaining a plate thickness has been put to practical use. This method is a convenient production method from the viewpoint of securing the strength of the can, because work hardening compensates for the decrease in strength due to the use of an extremely thin material.
[0003]
At the same time, in the field of can manufacturing, a two-piece can, called a two-piece can, has a bottom and body integrally formed, such as a DI can or DTR can with a can wall height raised by drawing or stretching after drawing. Is increasing. At the time of these formings, it is desired to suppress the occurrence of earrings that reduce the yield, ironing or stretch formability of the steel sheet. Earrings are caused by the texture of the steel sheet, and it is important to control the cold rolling reduction rate, which has a significant effect on the texture formation.
[0004]
From these viewpoints, steel sheets in which the rolling distribution of cold rolling (1CR) before annealing and 2CR are controlled are disclosed in JP-A-58-151426, JP-A-59-113123, and JP-A-7-228925. However, in these steel sheets, heat buckle resistance and low earring properties are not fully satisfied with ultra-thin materials of 0.2 mm or less, which are required in recent years.
[0005]
For B-added steel, Japanese Patent Application Laid-Open Nos. Hei 5-271755 and Hei 6-41683 are considering application to container materials, but the purpose of B addition is to adjust hardness, aging properties, and particle size. Nothing is used to control earrings.
[0006]
[Problems to be solved by the invention]
The present invention 1) a steel plate suitable for a two-piece can container manufactured through drawing, ironing or stretching, which avoids the occurrence of earrings in the forming process of the can body, which avoids the occurrence of earrings in the annealing process. And a method for producing the same.
[0007]
[Means for Solving the Problems]
The gist of the present invention is to limit the ratio of N present as Al nitride to N present as B nitride in a B-added ultra low carbon steel with respect to a nitride whose form changes greatly with the addition of B. The purpose is to obtain a steel sheet capable of controlling the texture and suppressing the occurrence of earring after 2CR.
[0008]
As specific means for this, (1) C: 0.004% or less by weight%,
N: Including 0.004% or less,
B / N: 0.6-1.4,
(N present as AlN) / (N present as BN) <0.4;
A two-piece container steel sheet having a small earring, having a tensile strength of 400 MPa or more.
[0009]
(2) The steel sheet for a two-piece container according to the above (1), wherein P: 0.01 to 0.05% is contained.
[0010]
(3) The method for producing a steel sheet for a two-piece container according to the above (1) or (2), wherein after the final annealing, a secondary cold rolling of 10 to 40% is performed.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail. First, the basic technical concept of the present invention will be described.
[0013]
Earrings occur due to the texture of the steel sheet. Although this texture changes throughout the steel plate manufacturing process, the influence of the cold rolling process that causes crystal rotation directly by processing is relatively large. We studied the distribution of cold-rolling ratios of 1CR and 2CR and the occurrence of earrings in the ultra-low carbon steel produced in the 2CR process, and found that the addition of B resulted in low earrings even if the distribution of cold-rolling ratios to 2CR was high. I learned. Generally, the texture of the {111} to {211} plane is increased by cold rolling, and ears are generated in the direction of the rolling direction and 45 ° as earrings. For this reason, it is considered that in order to achieve low earring by 2CR, it is preferable to control the ears so that the ears are generated in the directions of 0 ° and 90 ° before 2CR, that is, after annealing. Alternatively, it is also considered effective to form, after annealing, an orientation in which crystal rotation is difficult in the {111} to {211} orientation by 2CR, in order to achieve low earring with the 2CR material. Although the mechanism is not clear at present, it is certain that the combination of the texture after annealing and the crystal rotation by 2CR in the present invention will reduce the earring. Phenomenologically, we examined the relationship between various manufacturing factors and earring properties, found that among the factors, B, Al and N were particularly strong, and conducted a more detailed study to find out whether Al nitride The result that the earring property can be determined based on the ratio of N present as B to N present as B nitride was obtained. Generally, an interstitial solid-solution element such as N has a strong interaction with dislocations and diffusion in steel is fast, so that it greatly affects the material. Regarding precipitates, relatively fine precipitates in steel such as AlN and BN are considered to have a large effect on the material, and controlling the solute N or nitride may cause the texture change as described above. It seems to have been done.
[0014]
Hereinafter, the numerical limitation will be described in detail. First, the components will be described. All components are% by weight.
[0015]
C is preferably low in terms of drawability, ironing property, elongation property, neck wrinkle resistance at the time of diameter reduction, flange formability, and the like in the production process of the container, and the upper limit is made 0.004%. In particular, when a material having good ductility is required at the time of ironing, stretching and flange forming, if the material is reduced to 0.0015% or less, the characteristics can be greatly improved. However, excessive reduction not only leads to an increase in cost, but also causes the steel sheet to become soft and insufficient can strength, so the lower limit is made 0.0003%.
[0016]
N is an important element in controlling the formation of nitride, which is an important requirement in the present invention. If the content is large, nitrides are excessively generated and the object of the present invention cannot be achieved, so the upper limit is made 0.004%.
[0017]
B is added as an essential element in the present invention because it affects the form of the nitride and improves the earring properties. However, excessive addition degrades the earring properties and other can properties, raises the recrystallization temperature, necessitates a rise in the annealing temperature, and tends to cause heat buckles. The main point is the ratio to N, so B / N is set to 0.6 to 1.4.
[0018]
An important condition in the present invention is the control of the type and amount of nitride, and the ratio of N present as AlN to N present as BN in the B-added ultra-low carbon steel is 0.4 or less. is necessary. Here, N present as AlN refers to the analysis of the amount of Al in a solution obtained by dissolving a residue in a sodium hydroxide aqueous solution when a steel sheet is dissolved in an iodine alcohol solution, and converting the total amount to the N amount as AlN. Value. N, which is present as BN, refers to the amount of B in a solution obtained by dissolving a residue obtained by dissolving a steel sheet in a bromine alcohol solution in a mixed solution of phosphoric acid, nitric acid, perchloric acid, and sulfuric acid. This is a value converted into the N amount as the total amount BN.
[0019]
In order to control the nitride in this way, the addition amounts and ratios of Al and B, the oxide serving as a precipitation nucleus of the nitride, that is, the O content in steel, and the thermal history over the entire production process are important. By setting Al / B: 20 or less and Al: 0.045 % or less, when the solute N excessively present in the steel precipitates nitride, it is preferentially bonded to B over Al to nitride. Preferred control of the type and quantity of the object becomes possible. In addition, 0.001 to 0.008% of O is effective for controlling nitride. This is because O in steel exists as oxides of Si, Al, and Mn. However, it is thought that the presence of an appropriate amount effectively acts as a precipitation nucleus of nitride, thereby enabling preferable nitride control. However, since excessive O in steel coarsens oxides and becomes a crack starting point in ultra-thin processing such as a 2P can, which significantly deteriorates product quality, the upper limit is preferably made 0.007%.
[0020]
P is added as necessary in consideration of the required can strength. Excessive addition not only hardens the material and may not be able to form a can, but also degrades the earring properties, so the upper limit is made 0.05%. Further, by adding P in the range of 0.01 to 0.05%, the earring property after 2CR is also improved.
[0021]
In order to use an ultra-thin material as a container material, the material needs to be hard from the viewpoint of ensuring the strength of the can, particularly the pressure resistance. For this reason, in the present invention, the tensile strength of the steel sheet is limited to 400 MPa or more.
[0022]
2CR is one of the features of the steel of the present invention. The 2CR is performed to ensure annealing passability or to obtain necessary can strength. The steel of the present invention shows good earring properties equal to or higher than that of the conventional material even when the 2CR ratio is low. However, it is clear from the graph showing the relationship between the 2CR ratio and the earring ratio for steel type a in Table 2 and FIG. In addition, when the 2CR ratio is 10 to 40%, a good earring property not seen in the conventional material is exhibited.
[0023]
In addition, by setting the total cold rolling rate to 87 to 95%, a good earring rate is exhibited as shown in FIG.
[0024]
Further, as the heat history in the manufacturing process, the influence of the slab heating temperature during hot rolling is great. As shown in FIG. 3, by limiting this temperature to 1100 ° C. or less, not only the earring property but also the deep drawing property, The neck wrinkle resistance can also be improved.
[0025]
As mentioned above, various methods are used in the manufacture of containers to increase the strength of the container. However, not only addition of P and 2CR, but also addition of reinforcing elements such as Si and Mn, and improvement of various characteristics such as corrosion resistance. The effect of the present invention is not lost even when an element is added for the purpose.
[0026]
Normally, the steel sheet of the present invention is used as an original sheet for a surface-treated steel sheet, but the surface treatment does not impair the effects of the present invention at all. As the surface treatment for cans, tin, chromium (tin-free) or the like is usually applied. Further, it can be used as a base plate for a laminated steel sheet to which an organic film, which has been used in recent years, is attached without impairing the effects of the invention.
[0027]
【Example】
The present invention has been achieved by the following experiments.
[0028]
Steel of each component shown in Table 1 was made into a slab by continuous casting, and slab heating was performed at 1200 ° C. Then, it hot-rolled and wound up at 630 degreeC, performed primary cold rolling in the range of 86-94%, and performed continuous annealing at 670 degreeC. Further, cold rolling was performed in the range of 1 to 50% as 2CR.
[0029]
Each of the steel sheets manufactured by the above method was evaluated for the earring rate and the heat buckle resistance.
[0030]
FIG. 1 shows the relationship between the peripheral position of the cup and the height of the cup body wall when can processing is performed, that is, the state of occurrence of ears. In the evaluation of the earring, the earring rate represented by FIG. Ear generation becomes more remarkable as the earring rate increases. In addition, as a material for ordinary two-piece cans, those having an earring rate of about 4% or less according to the present formula are used.
[0031]
Earring rate = (hmax−hmin) / (can wall average height) Equation 1
[0032]
[Table 1]

Table 2 shows the results of evaluating the properties of a steel sheet having a final thickness of 0.18 mm, which was subjected to 2CR at various reduction rates including light reduction for shape correction after hot rolling, cold rolling, and annealing. The total cold rolling reduction was 87 to 95%. Regarding the heat buckle, it was determined by the presence or absence of heat buckle when a continuous annealing line was passed at a recrystallization temperature of + 40 ° C.
[0033]
[Table 2]

FIG. 2 shows the relationship between the total cold rolling rate and the earring rate. Here, the total cold rolling ratio is defined as (final sheet thickness) / (sheet thickness before cold rolling) and is a rolling rate in a cold rolling step including 1CR and 2CR. As shown in FIG. 2, in the steel of the present invention, the earring ratio is smaller than that of the comparative steel in a high cold rolling reduction region of 90% or more. Also, the comparative steel has a higher earring rate than 1CR when 2CR is applied, but the steel of the present invention has a very low earring rate even when 2CR is applied, so that the low earring and good heat buckle resistance are obtained. Both are possible.
[0034]
Table 3 shows the steel components used in FIG.
[0035]
[Table 3]

As is clear from FIG. 2 and Table 2, those manufactured within the scope of the present invention have good characteristics in both earring properties and heat buckle resistance.
[0036]
FIG. 3 shows the effect of (N existing as AlN) / (N existing as BN) on the inventive steels having different total slab heating temperatures of 92 to 93% and a 2CR ratio of 25 to 35%. is there. As shown in FIG. 3, even if the (N existing as AlN) / (N existing as BN) of the same degree, when the slab heating temperature is 1100 ° C. or lower, the earring property is improved. In particular, when the ratio of (N existing as AlN) / (N existing as BN) becomes 0.4 or less with respect to 0.4, the earring rate rapidly decreases.
[0037]
【The invention's effect】
As described above, according to the present invention, the rate of occurrence of heat buckles during annealing can be reduced while reducing the earring rate, and highly efficient production of ultra-thin container materials becomes possible.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining an earring rate.
FIG. 2 is a diagram showing a relationship between a total cold rolling rate and an earring rate.
FIG. 3 is a diagram showing the effect of the slab heating temperature and (N present as AlN) / (N present as BN) on the earring rate.
FIG. 4 is a diagram showing a relationship between a 2CR rate (%) and an earring rate.

Claims (3)

C: 0.004% or less by weight%
N: Including 0.004% or less,
B / N: 0.6 to 1.4, (N present as AlN) / (N present as BN) <0.4, tensile strength of 400 MPa or more, for a two-piece container with a small earring steel sheet. The steel sheet for a two-piece container according to claim 1, wherein P: 0.01 to 0.05% is contained. The method for producing a steel sheet for a two-piece container according to claim 1 or 2, wherein after the final annealing, a secondary cold rolling of 10 to 40% is performed.

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