JPS5953127B2 - Manufacturing method of ultra-thin steel sheet for can making - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an ultra-thin steel plate for can making, and more particularly to an improved method for producing an ultra-thin steel plate for can making that has excellent shape and flatness.

Here, a steel plate with excellent shape refers to a steel plate that is medium elongated and has no local shape defects such as waves, and a steel plate with excellent flatness refers to a steel plate with right angle warpage (warpage in the horizontal direction of the strip) and parallel warpage (warp in the horizontal direction of the strip). A steel plate with no warpage in the length direction of the strip. In today's metal container manufacturing, the method of printing multicolor directly onto steel sheet material is commonly used, but if the shape of the steel sheet used as the material is poor, printing misalignment may occur, making it difficult for the product to be used as a metal container. This results in a significant loss of value.

In addition, from the perspective of the production process, if the shape or flatness of the plate is poor, problems such as the inability to continuously supply blanks during the barrel forming process will occur, hindering productivity, and reducing mass production. It is an important branch for the basic can manufacturing industry.
For the above reasons, the shape standards required for steel plates for can making are extremely strict, and it is desirable that the height and thickness deviations of waviness and elongation within a single cut plate be substantially zero.

In response to such strict shape standards, with conventional manufacturing methods, the lower limit of the thickness of can-making steel plates that can be supplied in large quantities and with sufficient profitability is about 0.16 mm. When producing ultra-thin steel sheets for can manufacturing, conventional manufacturing methods fail to obtain a satisfactory sheet shape, and due to the strict shape standards for can manufacturing steel sheets, yields drop significantly and the cost of the product increases. This results in an inviting result. Due to such manufacturing difficulties, the lower limit of the thickness of conventional steel plates for can making on a mass production scale has been limited to about 0.16 mm. According to the present invention, it is possible to solve the above-mentioned manufacturing difficulties and commercially produce ultra-thin steel sheets for can making, mainly with a thickness of less than 0.16 mm, with high productivity and good yield. becomes. Levelers such as roller levelers and tension levelers are usually used to improve the shape of steel plates, but when the thickness of the steel plate is 0. .16
For hard steel plates that are thin (less than mm), have a high cold rolling rate of usually 20 to 70%, and have a tensile strength of approximately 50 to 100 kg/1d, conventional levelers use work rolls that are usually used. Since the minimum diameter is about 20 mm, almost no correction effect can be obtained.

A device for bending and tightening a steel strip with an extremely small radius of curvature to correct its shape is proposed by the present inventors in U.S. Pat. No. 3,812,697 and U.S. Pat.
, 812,701.

The former method corrects the shape by supporting and bending the steel strip through fluid pressure formed by a film of fluid uniformly ejected across the width of the steel strip under tension. The latter is a device that corrects the shape of the steel strip by bending it in contact with an extremely small diameter roll supported on the fluid film, but these devices alone do not correct warpage, i.e., flatness. I can't correct my gender. Further, US Pat. No. 3,834,202 proposed by the present inventors discloses an apparatus for improving flatness using a small diameter roll based on the latter principle.
is disclosed.

However, the small diameter roll of this device is considered to be unsuitable for high-speed continuous operation because it is easily worn and damaged and may damage the strip. Moreover, to the best of the inventors' knowledge, none of the previously known devices and methods for straightening the shape and flatness of steel strips is capable of obtaining the elongation necessary for straightening under high speed conditions. Since it is difficult due to seizure etc., the feed rate of the steel strip is set at 2.
This is possible only in the relatively slow range of 0.00 to 300 m/min, and the steel strip is
It is clearly unsuitable for use in which the shape and flatness are straightened immediately following a cold rolling process in which the sheet is discharged at a high speed of 1,000 m/min.

The present inventors have discovered that the shape straightening of a steel strip produced by cold rolling is not determined only by the ratio of the bending radius of the straightening tool to the thickness of the steel strip; The contact between the tool surface and the steel strip, as well as the tension applied to the strip, are also significantly influenced by the contact between the tool surface and the steel strip. At the same time, the tension applied to the steel strip is constant depending on the thickness, width, tensile strength, modulus of longitudinal elasticity (Young's modulus) of the steel strip, and the bending radius of the straightening tool. It has been found that by selecting a range within the range, the shape of the steel strip can be effectively corrected while running the steel strip at high speed.

Further, according to the present invention, the bending process of the steel strip is performed in multiple stages, and the ratio of the two bending radii of the steel strip in the first stage to the plate thickness of the steel strip, and the bending radius of the first stage and It has been found that shape correction and flatness correction can be performed simultaneously by selecting the ratio of the bending radii of the second and third stages to a certain range. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for effectively correcting the shape of a rolled steel plate for can manufacturing while running the rolled steel plate at high speed.

Another object of the present invention is to provide a method for correcting the shape and flatness of cold-rolled steel sheets for can making at high speed.

Still another object of the present invention is to provide a method for correcting the shape and flatness of a cold-rolled steel plate for can manufacturing without damaging the steel plate during high-speed operation.

Another object of the present invention is to provide a method for cold rolling and correcting the shape and flatness of a cold rolled steel sheet for can making in the same process. According to the present invention, a steel strip manufactured by cold rolling is forcibly bent on a stationary tool curved surface through a fluid film uniformly supplied to the tool curved surface. , when the steel strip is in tension, the ratio (γJT) of the bending radius (γ1 mm) to the plate thickness (Tmm) of the steel strip is in the range of 10 to 50, and the following formula and T σYtb...・・・・・・・・・・・・・・・
......In formula (2), β is a coefficient in the range of 0.2 to 1.0, and T is the tension (K
g), and σy is the tensile strength of the steel strip (Kg/7n
it), and E is the longitudinal elastic modulus of the steel strip (Kg/
Mit), b is the plate width (Mm) of the steel strip, and γ1 and t have the meanings described above. The process of correcting shape defects in the steel strip, and the bending radius (γ
1) A step of bending the steel strip at least once with a bending radius (γ2) that is 1 to 2 times that of 1) to straighten the right angle warp in the steel strip; It consists of a combination of the process of applying at least one bend with a bending radius (γ3) of 6 times to correct the parallel warpage of the steel strip, and the order of bending in each process is set so that the bending directions are opposite to each other. Provided is a method of manufacturing an ultra-thin steel sheet for can making, which is characterized by carrying out the following steps.

According to the present invention, in the above method, a straightening tool is formed between the tool curved surface and the steel strip in the following formula, where γ1 represents the bending radius (Mm) of the straightening tool, and b represents the plate width (Mm) of the steel strip. The fluid is supplied at a pressure (PO, kg/M7i gauge pressure) that satisfies the following: Mm), T represents the tension (Kg) applied to the steel strip, and α is a coefficient of 0.5 to 2.0. There is provided a method for manufacturing an ultra-thin steel plate for can making, which is characterized by the following.

In FIG. 1 for explaining the process of the invention, a steel strip 1 is fed from the coil of an unwinding reel 2, passes through a driven inlet bridle 3, and then passes through a shape straightening tool 4 and a warpage straightening tool 4. After the bends are applied by the tools 5, 6 in such a way that the directions of the bends are successively opposite,
Passing through the driven outlet side bridle 7, the take-up reel 8
It is wound into a coil by.

The shape correction tool 4 is used to correct shape defects such as waves and middle elongation, and the warpage correction tool 5 is mainly used to correct right angle warpage.
The warpage correction tool 6 is provided for the purpose of correcting parallel warpage. In this example, two bends by the shape straightening tool 4 and one bend each by the warpage straightening tools 5 and 6 are performed on the steel strip 1 in such a way that the direction of the bending is sequential. It is given in opposite directions to obtain excellent shape and flatness.

The steel strip 1 is placed under constant tension by a driven inlet bridle 3 and a driven outlet bridle 7. In the present invention, any steel strip produced by cold rolling once or multiple times can be used as the steel strip to be subjected to the treatment, but from the viewpoint of producing 11] U plates for can manufacturing, , thickness 0.18 to 0.0
8mm, especially 0.16 to 0.11mm, tensile strength is 50
It is preferable to use a cold-rolled steel plate having a weight in the range of 100 kg/ml to 100 kg/ml, especially 56 to 90 kg/Ud.

Such cold-rolled steel sheets generally have shape defects such as significant elongation or waving, and non-flatness such as right angle or parallel warping, but by applying the treatment of the present invention, these defects can be improved. It becomes possible to completely correct defects.
The cold-rolled steel sheet can be wound onto a reel and then subjected to the treatment of the present invention, but as described below,
Cold-rolled steel strip can be immediately subjected to the process of the invention without winding. In the present invention, first, the steel strip is bent on a stationary tool curved surface through a fluid film uniformly supplied to the tool curved surface, while the steel strip is running at high speed. , is extremely important for effective shape correction.

For example; U.S. Patent Nos. 3,812,701 and 3,8
As described in No. 24,202, when bending a steel strip by forcibly bringing it into contact with a rotating tool curved surface, the feeding speed of the steel strip is less than 600 m/min. Even if satisfactory shape correction is achieved in some cases, the 600
At a supply rate of m/Min or more, shape correction becomes difficult due to causes such as whirling of the mouth. In contrast, in the present invention, a stationary tool surface is used, and the tool surface is forcibly bent through a fluid film that is uniformly supplied onto the tool surface, thereby achieving extremely high speed bending. Shape correction becomes possible. The principle of forced bending of a steel strip fluid film and a stationary tool curved surface used in the present invention and the structure of the tool used therein have already been disclosed in U.S. Pat. No. 3,812,699.
It is known from the specification No. 7.

FIG. 2 is an enlarged cross-sectional view of the shape correction tool 4 used in the process shown in FIG. However, a large number of depressions 12 are provided at small intervals in the width direction of the strip in the center of the tip portions 13, 13, and a pore 11 passing through the depressions 12 is provided.

A pressurized fluid (not shown), such as water or rolling oil emulsion, is ejected outwardly from the depression 12 through the pores 11 and is interposed as a fluid film between the steel strip 1 and the stationary tool curved surface 13. do. The steel strip 1 is tensioned by the two bridle pairs 3,3 and 7,7 described above, and a fluid is applied onto the tool curved surface 13. The steel strip 1 is forcibly bent while floating through the membrane. In the present invention,
The ratio (YlA) of the bending radius of the steel strip (γ1, Wi1A) and the plate thickness (T, mm) of the steel strip is 10 to 5.
0, especially 25 to 40, is extremely important to effectively prevent shape defects.
If γ1/t is larger than the above range, it will be difficult to correct the ridge-like defects in the steel strip to the extent that it can be used for can manufacturing, and the ratio to J1 (γ1/t) will be larger than the above range. If it is too small, there is a greater tendency for the surface of the steel strip to become rough or scratched, which is undesirable.

The bending radius (γ1) of the steel strip is determined by the shape and dimensions of the tip curved surface 13 of the tool 4 shown in FIG. There is nothing wrong with thinking about it.

In the present invention, the tension (T, kg) applied to the steel strip in this bending process is defined as the tensile strength of the steel strip,
It is extremely important to determine the longitudinal elastic modulus, plate width, plate thickness, and bending radius (γ1) of the steel strip so as to satisfy the experimental formulas (1) and (2).

That is, if ε9 is smaller than 0.002, even when the above two conditions are satisfied,
It becomes difficult to correct the shape so that the middle elongation and wave height become substantially zero, and on the other hand, if the value of ε9 is set to 0.
If it is larger than 0.002, the properties of the steel strip, that is, its mechanical properties, will change drastically, making it unsuitable for use as a thin sheet for canning.

In the present invention, the value of ε9 mentioned above is 0.01 to 0.
．． It is particularly desirable to set the tension (T) to 003.

The above (1) and (3) have the following meanings.

When bending the strip while applying tension, the ratio of the bending radius γ1 of the strip to the plate thickness t (γJ) is 10 to 50.
In the range of , the tensile strain occurring at the center of the plate is .

When the strip is made of high tensile strength steel plate, the effect of elastic elongation that occurs until the five plates yield cannot be ignored, and when the tension of the strip is removed and the subsequent can making process is started, the elastic recovery of the plate is required. The tensile strain at the center of is reduced by βq/E. That is, when the strip is bent under tension with a bending radius γ1, the effective tensile strain for correcting the strip j shape defect is as follows. Here, β is related to R1/t, and γ1/t is 1
0 place. The coefficient is given as 0.2 in the case of 50, and 1.0 in the case of 50. A similar tensile strain occurs when the plate is bent back (straight) from bending radius γ1 to 1 under tension, and in the end, with one bending and unbending, (
becomes.

When bending and unbending twice in opposite directions as in the present invention, a slight tensile strain occurs even at the bending radius γ2 for correcting right-angled warpage, so in the end, the correction is impossible. The resulting tensile strain at the center of the plate is

There is also an optimum value for the pressure of the fluid supplied between the stationary curved surface 13 of the tool and the steel strip 1, and generally, in the following empirical formula,
γ1 represents the bending radius of the tool (Mm), b represents the width of the steel strip (Mm), T represents the tension (Kg) applied to the steel strip, α is 0.5 to 2.0, particularly preferred It is desirable to supply fluid at a pressure (PO, kg/m!t gauge) that satisfies a coefficient of 1.0 to 1.8.

That is, if the pressure of the fluid is lower than the pressure given by the above-mentioned empirical formula (4), there is a greater tendency for the steel strip to be damaged during bending, making shape correction particularly difficult at high speeds. Furthermore, when the pressure of the fluid exceeds the pressure expressed by the above empirical formula (4), the pressure at each recess 12 of the tool 4 and the pressure between the recesses tend to fluctuate, which causes the steel strip to have a vertical shape. There may be wrinkles. In addition, in the above empirical formula (4), the reason why the coefficient α has a certain range is as follows.
This is because the optimum fluid pressure changes depending on the wrapping area (wrapping angle) of the steel strip around the stationary curved surface of the tool. The above formula (4) has the following meaning.

Assuming that the strip is uniformly bent on the tool with a bending radius of .gamma.1 and that the fluid pressure distribution on the tool surface and the strip surface is a constant value, the pressure of the supplied fluid is uniquely expressed by.

In reality, the strip is a part of the tool with a minimum bending radius γ1
In addition, the pressure distribution of the fluid on the tool surface and the strip surface varies in the range from supply pressure to atmospheric pressure. That is, the angle at which the steel strip is wrapped around the stationary curved surface of the tool and the tension vary from the idealized state described above. For this reason, it is actually desirable to optimize the fluid supply pressure by introducing a coefficient α.

During shape correction, the winding angle (θ) of the steel strip around the stationary curved surface of the tool is generally 10° to 60°, particularly 20°.
A range of 35° to 35° is desirable in order to achieve the various objectives of the present invention mentioned above.

In the empirical formula (4), if the winding angle (θ) is relatively large, the coefficient (α) and 2; τ7! :?
, :ko:j, and vice versa.The shape straightening process in the present invention uses a pair of straightening tools 4, 4 whose bending directions are sequentially opposite, as shown in FIG. Although this is desirable, it is of course also possible to use a single straightening tool. According to the present invention, a steel strip that has undergone shape correction is bent once at a bending semi-radius (γ,) 2,'5 of 1 to 2 times the bending radius (γ1), which is less than 4≦. The steel strip is then bent at least once with a bending radius (γ,) that is 2 to 6 times the bending radius (γ1) described above. to correct the parallel warpage of the steel strip.

The tools used to correct these flatness defects are the same as those used to correct shape defects, except that the bending radius of the stationary surface is within the range described above, and , through a fluid film! *It is also used to correct shape defects even at the point where it can be bent during machining. 1 insect, 2.

. 1,46. ．． When bending a steel strip, it is difficult to completely remove these warps.

According to the invention, the steel strip is thus
While feeding at a high speed of 000 m/Mm, all shape defects and flatness defects can be corrected, making it possible to provide thin steel sheets for can manufacturing at high production speed and high yield.

Furthermore, it should be understood that the apparatus used for the straightening process of the present invention has a low equipment cost, and especially when combined with a cold rolling mill, can produce ultra-thin steel sheets for can manufacturing at low running costs. The excellent effects of this are explained in the following example. Example 1 A 2.0 mm hot rolled steel strip was cold rolled to 0.20 mm in a 5 stand dandem cold strip mill, degreased by electrolytic cleaning, intermediate annealed, and then 2 stand cold rolled. Passed through a strip mill once
．． Cold rolling was carried out to 14 mm.

The tensile strength after rolling is 60 kg/Md, and the longitudinal elastic modulus is 21.
000. kg/1 d, and the plate width was 900 mm (steel strip A). The average height of this thing is 3.2m
The steel plate had a poor shape and large warpage, and was unsuitable as a steel plate for can manufacturing. 0.1 by lowering the rolling reduction rate and passing twice with the same 2-stand mill.
When cold rolled to 4mm, the tensile strength is 62kgnom.
l, longitudinal elastic modulus is 21000kg/ml, board width is 900
ws (steel strip B).

Although the shape of this product was slightly improved, with an average height of 2.2 mm, it was still unsuitable for use as a steel plate for can manufacturing. This steel plate strip A was fed to the strip straightening apparatus shown in FIG. 1 at a speed of 1000 m/min under the conditions shown below.

Type of fluid to tools 4, 5, 6 10% aqueous emulsion of rolling oil Fluid pressure (PO) = 90kg/I! i In this case, the conditions defined in the present invention are as follows.

γ1/t=28.6 ε, =0.0023 T/b =1.9kg/Mm<8.4kg/Mmno/γ
1=1y3/γ1=4.

In this way, the amount of mid-elongation and warpage of the steel plate was substantially O, and a product suitable for use as a steel plate for can making could be obtained.

Therefore, it was possible to salvage steel strips that were conventionally unsuitable for use as steel sheets for can manufacturing, and it was possible to achieve a significant improvement in yield. Example 2 The steel strip was straightened under the same conditions as Example 1, except that the type of steel strip 1 and the bending radius (γ1) of the tool 4 were changed as shown in Table 1 below, and the results shown in Table 1 were obtained. Obtained.

From the results in Table 1, the value of γ1/t is 50 or less, especially 40.
It can be seen that shape defects such as middle elongation can be effectively corrected by the following conditions.

Although it is not shown in Table 1, the bending radius (γ1) is set to 1.
mm, γ1/t=7.1, numerous wrinkles and scratches were observed on the surface of the steel strip.
Ajiken Example 3 The steel strip was straightened under the same conditions as in Example 1, except that the type of steel strip and the tension (T) applied to it were changed as shown in Table 2 below, and the results are shown in Table 2 below. Obtained.

The results in Table 1 show that when the value of ε9 is smaller than 0.002, it is difficult to correct the shape such as elongation, whereas
It is shown that by setting the value of 2 to 0.002 or more, the middle elongation height can be corrected to substantially zero.

Next, by changing the type of steel strip and varying the tension (T), the relationship between the value of ε9 and the mechanical properties of the steel strip was investigated, and the results shown in Table 3 were obtained.

According to the results in Table 3, it is clear that when the value of ε9 exceeds 0.002, the mechanical properties of the steel strip change significantly from those before treatment, which deviates from the purpose of shape correction.

Example 4 The results shown in Table 4 below were obtained in the same manner as in Example 1 except that the pressure (PO) of the fluid supplied to tool 4 was set to the value shown in Table 3 below.

In the results shown in Table 4, Experimental Examples 2 to 5 satisfy the above general formula (4), and at a pressure that satisfies this general formula (4), the occurrence of scratches on the steel strip surface is eliminated. It is clear that

Example 5 The results shown in Table 5 below were obtained in the same manner as in Example 1 except that the bending radius ratio (Y2/γ1) of tool 4 and tool 5 was set to the value shown in Table 5 below.

The results in Table 5 show that when the ratio of Y2/γ1 exceeds 2.0,
This indicates that it is difficult to correct right angle warps.

Example 6 Ratio of bending radius between tool 4 and tool 6 (Y3/γ
The results shown in Table 6 below were obtained in the same manner as in Example 1 except that 1) was set to the values shown in Table 6 below. .

The results in Table 6 above show that when the ratio of Y3/γ1 is smaller than 2, right-angle sagging remains, and the ratio of Y3/γ1 is 6.
If the value exceeds the value, it is difficult to correct parallel curvature, but it is clear that by setting this value in the range of 2 to 6, both right angle curvature and parallel curvature can be corrected. According to the above results, by processing the steel strip so as to satisfy the various conditions stipulated in the present invention, shape defects and flatness defects can be completely eliminated, and the steel strip can be manufactured without roughness or scratches on the surface. It will be appreciated that thin steel sheets can be obtained at high production rates.

As shown in Figure 3, if a shape straightening tool and a warpage straightening tool are provided on the exit side of the cold rolling mill and rolling and straightening are performed in the same process, the shape and warpage straightening effect can be achieved more economically. be able to.

In FIG. 3, the steel strip 14 rolled by the work roll 15 is bent twice by the shape straightening tool 16, and by the warpage straightening tool 17, which mainly corrects right angle warping, and the parallel warping. One bend is applied in each case by the straightening tool 18 so that the bending directions are successively opposite, and then the coil is wound up as a coil by the take-up reel 20 through the exit bridle 19. It should be noted that the above description and drawings have been shown to enable a thorough understanding of the principles of the invention, and do not limit the invention in any way, and the invention is subject to many modifications and changes within the scope of the claims. It is possible to make modifications.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing an embodiment of the present invention. FIG. 2 is a side sectional view of the straightening tool used in the embodiment of FIG. 1. FIG. 3 is a schematic side view showing an embodiment of the present invention in which cold rolling and straightening are performed in the same process. 1,
14 is a steel strip, 4, 16 is a shape correction tool, 5,
Reference numeral 17 indicates a tool for correcting a right angle warp, numerals 6 and 18 indicate tools for correcting a parallel warp, and 3, 7, and 19 indicate a bridle, respectively.

Claims (1)

[Claims] 1. A steel strip manufactured by cold rolling is forcibly bent on a stationary tool curved surface through a fluid film uniformly supplied to the tool curved surface, so that the steel strip is bent. , in the tensile state, the ratio (γ_1/t) of the bending radius (γ_1 mm) to the plate thickness (tmm) of the steel strip is in the range of 10 to 50, and the following formula 0.02≧4.35 {(T/ 2
γ_1σ_yb)−(β・σ_y/E)}≧0.002
and T<σ_ytb, where β is a coefficient ranging from 0.2 to 1.0, T is the tension (kg) applied to the steel strip, and σ_y is the tensile strength (kg/mm^2) of the steel strip. , E is the longitudinal elastic modulus of the steel strip (kg/mm^2), and b
is the plate width (mm) of the steel strip, and γ_1 and t have the meanings described above.The steel strip is bent twice in opposite directions under the condition that γ_1 and t have the meanings described above. 1 to 2 of the bending radius (γ_1) for the steel strip that has undergone the above process.
A step of straightening the right angle warp of the steel strip by applying at least one bend with double the bending radius (γ_2), and a bending radius of 2 to 6 times the bending radius (γ_1) for the steel strip that has undergone the above process. It consists of a combination of the step of applying bending at least once in step (γ_3) to straighten the parallel warpage of the steel strip, and is characterized in that the order of bending in each step is performed so that the bending directions are opposite to each other. A method for manufacturing ultra-thin steel sheets for can manufacturing. 2. The method according to claim 1, wherein the steel strip is a steel strip having a thickness of 0.18 to 0.08 mm and a tensile strength of 50 to 100 kg/mm^2. 3 Cold rolled steel strip 500 to 3000
2. A method according to claim 1, wherein said process is fed at a feed rate of m/min. 4. The method according to claim 1, wherein the bending in each step is carried out immediately thereafter without winding up the steel strip subjected to cold rolling. 5. A steel strip manufactured by cold rolling is forcibly bent on a stationary tool curved surface through a fluid film uniformly supplied to the tool curved surface, and the steel strip is in a tensile state, The ratio (γ_1/t) of the bending radius (γ_1 mm) and the plate thickness (tmm) of the steel strip is in the range of 10 to 50, and the following formula 0.02≧4.35 {(T/2
γ_1σ_yb)−(β・σ_y/E)}≧0.002
and T<σ_ytb, where β is a coefficient ranging from 0.2 to 1.0, T is the tension (kg) applied to the steel strip, and σ_y is the tensile strength (kg/mm^2) of the steel strip. , E is the longitudinal elastic modulus of the steel strip (kg/mm^2), and b
is the plate width (mm) of the steel strip, and γ_1 and t have the meanings described above.The steel strip is bent twice in opposite directions under conditions that satisfy the above-mentioned meanings. 1 to 2 of the bending radius (γ_1) for the steel strip that has undergone the above process.
A step of straightening the right angle warp of the steel strip by applying at least one bend with double the bending radius (γ_2), and a bending radius of 2 to 6 times the bending radius (γ_1) for the steel strip that has undergone the above process. (γ_3) in which the steel strip is bent at least once to straighten the parallel warpage, and the bending order in each step is so that the bending directions are opposite to each other, and and the steel strip, the following formula P_o=(T/γ_
1・b)×α In the formula, γ_1 represents the bending radius (mm) of the straightening tool, b represents the plate width (mm) of the steel strip, T represents the tension (kg) applied to the steel strip, and α is a coefficient of 0.5 to 2.0.
A method for producing an ultra-thin steel plate for can manufacturing, characterized by supplying a fluid at a pressure of 2 gauge/mm^2 gauge pressure.