JPH0637688B2 - Steel plate for DI can - Google Patents

Description

TECHNICAL FIELD The present invention relates to a steel sheet for DI can which is excellent in ironing workability and flange workability and is suitable for reducing the weight of a container.

(Prior Art) The DI can for which the steel sheet of the present application is targeted is a steel plate (tin plate) plated with tin and then punched (Darwin).
g), ironing process (Ironing), and other processes, and the representative process, Darwing and Ironing, is called a DI can. The ironed can is trimmed at the top of the can, washed, painted, necked in, and flanged so that the lid can be tightened. In the ironing process, only the side wall of the container is thinned, and the thickness of the can bottom is kept substantially the same as the thickness of the tin plate before processing. The general thickness of the tin plate for a DI can, which is the subject of the present application, is 0.28 to 0.33 mm, and from this thickness, the upper part of the can (flange part) on which the lid is wound is fastened.
Is ironed to a thickness of about 0.16 mm, and is thinned to about 0.10 mm on the side wall portion excluding the can upper portion. In this way, the side wall thickness of the DI can is as thin as about 0.10 mm, so it is not used as a so-called depressurized can where the inside of the can has a negative pressure. The internal pressure is several kg / cm ^{2 to} 7 kg / c, such as when enclosed.
It is used with m ² . Here, when the internal pressure is applied, the problem is the pressure resistance of the bottom of the can. In consideration of the pressure resistance, the combination of the thickness of the tin plate and the temper (yield strength) is selected. Among various combinations, the plate thickness is currently 0.28 to 0.33 mm and the tempers T-1 to T-2.
A combination of 5 (yield strength 20 to 28 kg / mm ² ) is selected. Soft materials such as T-1 to T-2.5
Based on the idea that drawing workability and ironing workability are excellent, and flange workability after ironing is also excellent, the teper is first determined, and the plate thickness is determined because the necessary pressure resistance is secured by the temper. Further, as a steel for DI can, a continuous cast material of Al deoxidization is used, and according to a normal strip process, after hot rolling, cold rolling, recrystallization annealing by a box type, at a rolling rate of 1 to 2%. After the temper rolling of
It is used as a tin plate. This plank, primarily, to obtain a lubricating effect during ironing, the tin usually 2.8 g / m ² or 5.6 g / m ² is plating, there is a tinplate for DI cans. In recent years, where competition with Al-made DI cans has become fierce, efforts have been made to reduce the thickness of the tin plate, that is, to increase the yield strength, from the viewpoint of providing more economical DI cans. JP-A-57-5783
5 is disclosed.

The gist of the present invention is to achieve high yield strength by making recrystallization annealing after cold rolling continuous annealing, but a large ironing load, easy occurrence of flange cracking, and yield strength obtained Is also less than 40 kg / mm ^{2, which} is not so large, and is excellent in ironing formability and flange formability, which is the object of the present application, and can be sufficiently thinned to a plate thickness of 0.18 to 0.25 mm. It is impossible. In addition, as a general method for achieving high yield strength to achieve thinning, solid solution strengthening by addition of strengthening elements such as C, Mn, P, N, precipitation strengthening, age hardening, strengthening by crystal grain refinement Etc., and further, there is strain strengthening that adds strain such as rolling, but there is a problem such as an increase in ironing load, flange cracking, etc. by these methods, high yield strength as intended by the present application, The reality is that thinning has not progressed.

(Problems to be Solved by the Invention) An object of the present application is to provide a thin yielding plate with high yield strength in order to make a DI can lightweight, that is, economical. The increase in the ironing load and the increase in the flange cracks prevent the high yield strength of the brass plate. If a flange crack occurs, it cannot be used as a can, and an increase in ironing load causes a flaw on the outer surface of the can during ironing, a breakage of the can, and an increase in die wear. It is an object of the present application to obtain a tin plate having a high yield strength and excellent ironing formability and flange formability.

(Means for Solving the Problems) The present application has been made as a result of many studies from the viewpoint of the material properties of steel to achieve the above-mentioned problems, and as a result, while achieving high yield strength, reduction of the ironing load, and ironing It was discovered that the outer surface of the can can be scratched, die wear can be reduced, and flange formability can be improved. In describing the contents of the present application, the ironing load and the flange formability that are the subject of the present application will be described in order to facilitate the understanding thereof. The ironing process consists of three consecutively spaced irons.
It is carried out by combining four dies and punches, and is a process in which the clearance between the inner diameter of the die and the outer diameter of the punch, that is, the clearance, is gradually reduced and the side wall thickness of the can is gradually reduced. Here, the force applied to the punch during ironing is called the ironing load. The magnitude depends on the deformation resistance of the work material, the frictional force between the punch and the die and the work material, the thickness reduction rate of each die, etc. Dependent. In order to reduce the ironing load without changing the thickness reduction rate, it is necessary to reduce the deformation resistance and frictional force of the material. Here, the frictional force can be reduced by increasing the amount of plated tin, but the increase of the amount of plated tin cancels the economic effect due to the thinning and is inappropriate. Therefore, reduction of the ironing load should be considered from the viewpoint of reducing the deformation resistance. The deformation resistance increases due to work hardening as the drawing and ironing processes progress, and becomes maximum at the final die for ironing. In the final die, the amount of tin deposited per unit area of the side wall of the can is the smallest due to the ironing process performed by the previous die, and the processing conditions in the final die are the most severe. . Therefore, scratching, breaking, and die wear of the outer surface of the can during ironing are the most serious problems in the final die. As is clear from the above description, from the viewpoint of pressure resistance, a material having a high yield strength (deformation resistance) and being as small as possible so that it can be hardened by subsequent processing, that is, a material having a small increase in deformation resistance, It is a material suitable for the purpose. In addition, the flange workability, which is another characteristic of the present application, depends mainly on the ductility of the material, and if the ductility of the ironed flange portion is poor, flange cracking is likely to occur. In addition,
The strength and ductility of steel generally show an inverse correlation, and increasing the yield strength of a steel plate and work hardening make flange cracks more likely to occur. The ironing load and the flange formability have been described above, but research has been carried out to improve these two characteristics at the same time as increasing the yield strength, and the objects of the present application have been achieved by using the following steel materials. I found that I would get it.

That is, the composition is C: 0.008 to 0.03%, Mn:
0.05-0.25%, P: 0.02% or less, Al:
0.01 to 0.10%, the balance is iron and unavoidable impurities, the yield strength is 40 to 65 kg / mm ² , and 2
Increase in yield strength by heating at 00 ℃ for 1 hour is 1.5kg / mm
A tin plate of ² or less is excellent in ironing workability and flange formability, can secure a necessary pressure resistance even when the plate thickness is 0.18 to 0.25 mm, and is excellent as a tin plate for a lightweight DI can. Found out.

The reasons for limitation of the present invention will be described below.

The C amount is 0.13% or less in the JIS standard, and is usually 0.03 to 0.08 depending on the agreement between the manufacturer and the user.
% Is used as a material for cans. Although it is an element that should be added to achieve high yield strength, if the C content increases, the work hardening in drawing and ironing becomes large, and the flange formability also deteriorates significantly. It is indispensable to set the content to 0.03% or less, which is less than or equal to the lower limit of the steel sheet. As described above, from the viewpoint of work hardening, it is desirable that the amount of C is small, but the amount of C is 0.0
It is not preferable to reduce the amount to 08% or less, which is not only economically expensive and not only economical, but also the size of crystal grains is large, resulting in surface defects called orange peel.
The lower limit is 0.008%. The Mn amount is specified by JIS standard to be 0.6% or less, and is usually 0.2 to
0.5% is used. Mn is also an element to be added from the viewpoint of increasing the yield strength, but it significantly increases work hardening and is not preferable in terms of flange formability, so it is preferable to reduce it as much as possible, and thus The lower limit is set to 0.25%, and the lower limit is set to 0.05% in order to prevent the adverse effect of S inevitably present. P is also not preferable from the viewpoint of work hardening, and its upper limit was set to 0.02%.
The lower limit of Al required for deoxidation is 0.01%, and if it increases, the cost increases and the amount of inclusions increases, so the upper limit was made 0.1%. The increase in yield strength after heating at 200 ° C for 1 hour was set to 1.5 kg / mm ² or less because
The reason why the yield strength is increased by m ² or more is that even if C, Mn, and P are in the above ranges, the hardening by the subsequent working is extremely large, and the flange workability is not preferable.

The drawing shows the relationship between the increase in yield strength and work hardening. X in the figure
-1, X-2, C: 0.02%, Mn: 0.19%,
P: 0.017% is contained, and Y-1 and Y-2 are C:
It is a steel plate containing 0.045%, Mn: 0.35%, and P: 0.018%. X-1, X-2, Y-1, Y-2
In both cases, box-type recrystallization annealing was performed after cold rolling in a normal strip process, and X-2 and Y-2 were further subjected to rapid heating and rapid cooling corresponding to continuous annealing. After that, temper rolling was performed so that the yield strength was 40 kg / mm ² . And yield strength 40 kg / mm ²
As a starting point, the work hardening after 40 kg / mm ² was compared.
When the yield strength of 40 kg / mm ² is heated at 200 ° C for 1 hour, the yield strength increase value is X-1: 0.5 kg /
mm ² , Y-1: 1.2 kg / mm ² , X-2: 7.5 kg / m
m ² and Y-2: 9.0 kg / mm ² , and those having a large yield strength increase value have significantly large work hardening. The yield strength of the four types of steel sheets was 55 by temper rolling.
when a kg / mm ^2, and the yield strength increase value due to heating at the time, the relationship of subsequent work hardening, yield strength 40 kg / mm ²
The same tendency as in the case of. It is considered that the magnitude of the yield strength increase value due to heating is determined by the dislocation density, the solid solution C, and the amount of solid solution N, but the suppression of the absorbed N during annealing and the recrystallization by optimizing the recrystallization temperature and time. The increase in yield strength due to heating can be made low by reducing the solid solution C by making the cooling rate slow after annealing.
Next, the reasons for limiting the yield strength and the plate thickness will be described. Plate thickness,
The yield strength is related to the pressure resistance of the bottom of the can, and the thinner the plate thickness, the higher the yield strength is required. From the standpoint of producing a more economical DI can, it is better to have a thinner tin plate, but both thinning and higher yield strength result in breakage during drawing and wrinkling during can bottom molding. It leads to such a defective phenomenon. From this point of view, the lower limit of the plate thickness was set to 0.18 mm, and from the viewpoint of economic effect, the upper limit was set to 0.25 mm. The yield strength is determined in relation to the plate thickness, the draw strength at the lower limit of the plate thickness and the upper limit of the yield strength are set in consideration of the pressure resistance, and the yield strength of the upper limit of the plate thickness is taken into consideration. The lower limit was set. As described above, the present application is
The amount of C and Mn is low, which is less than the lower limit of the steel plate for cans. 2
Yield strength increase by heating at 00 ℃ for 1 hour is 1.5kg /
It is a steel sheet for lightweight DI cans, which has an essential requirement of being mm ² and at the same time has a high yield strength and a thin wall. Among the various strengthening methods, rolling is economical as a method for achieving high yield strength. Conventionally, strengthening by rolling, which has been considered unfavorable in terms of ironing formability and flange formability, also reduces work hardening factors, that is, reduction of strain accumulation factors, by ensuring the essential requirements of the present application. It can be applied without impairing the flange formability.

(Examples) Examples of the present invention will be described below.

Steel having the chemical composition shown in Table 1 was melted in a converter and continuously cast into a slab. The slab is hot-rolled to a plate thickness of 2.0 mm according to a normal stripping process, hot-rolled, pickled, and
Subsequent cold rolling, recrystallization annealing and secondary cold rolling were carried out to obtain a tin plate having the yield strength and plate thickness shown in Table 2. In Table 2, the symbol BAF indicating the recrystallization annealing method is a soaking temperature of 60.
Box-type annealing in which heating is performed at 0 ° C. for 8 hours and cooling is performed at a cooling rate of 15 ° C./hr, the symbol CAL indicates 1 at a soaking temperature of 700 ° C.
Continuous annealing is shown in which after heating for 1 minute, cooling is performed at a cooling rate of 20 ° C./sec. After recrystallization annealing, rolled at the rolling rate shown in Table 2 to finish the plate thickness in the table, and then 1.2g / m ^{2 on} both sides
Was tin-plated to obtain a tin plate.

The tin plate is a squeeze can with a diameter of 53 mm and a diameter of 5 mm.
2.7mm punch and 0.20mm clearance (No.
1 die), 0.15mm (No.2 die), 0.095m
Ironing was performed using a die that is m (No. 3 die), and the following evaluation test was performed. Evaluation of ironing load is N
o. 1, No. 2 and No. 3 dies are subjected to 3 steps of ironing in order and evaluated with the maximum value of the ironing load with No. 3 die. Similarly, the ironing process was performed in three steps, and the outer surface of the can after the No. 3 die was evaluated. For flange formability, spin flange after cutting the open end of the can after ironing The workability was evaluated, and the superiority and inferiority of the flange formability was evaluated with the maximum flange width that can be projected without cracking. The flange width required for winding and tightening was 2.4 mm, and a flange width of 2.5 mm or more was set as an excellent range. Further, the deformation resistance described above that affects the ironing load was compared by a tensile test piece cut out from the side wall of the can after three-step ironing.

(Effects of the Invention) The steel sheet of the present invention is a high yield strength thin steel sheet having a characteristic steel material and excellent in ironing workability and flange workability, and is suitable for producing an economical DI can.

[Brief description of drawings]

The drawing is a diagram showing the relationship between the yield strength increase value due to heating at 200 ° C. for 1 hour and work hardening.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kaichi Kondo 1 775, Sachimachi, Shimomatsu City, Yamaguchi Prefecture (56) References JP 61-69928 (JP, A) JP 62-294136 (JP, A)

Claims (1)

[Claims] 1. C: 0.008 to 0.03%, Mn: 0.
05-0.25%, P: 0.02% or less, Al: 0.0
From 1 to 0.10%, the balance being iron and unavoidable impurities, thickness yield strength increase yield strength by 1 hour heating at 40~65kg / mm ^2, 200 ° C is 1.5 kg / mm ² or less Steel plate for DI can of 0.18 to 0.25 mm.