JPH0754101A - Steel sheet for thinning/deep drawing - Google Patents

Abstract

PURPOSE:To obtain a steel sheet for processing small in the breakage of a can wall via a shock line, in thinning/deep drawing, by specifying the chemical components in steel and furthermore specifying the X-ray diffraction intensity ratios in crystal planes parallel to the surface of the steel sheet and the sheet thickness and its yield strength. CONSTITUTION:This steel is one contg., by weight, 0.006-0.15% C, 0.1-0.7% Mn and 0.02-0.12% Al, and in which yield strength is regulated to 500-800N/mm<2>, as for P (200), P (211) and P (222), i.e., the X-ray diffraction intensity in crystal planes parallel to the sheet surface, the value of P (211)/P (200) is regulated >=70%, the value of P (222)/P (200) is regulated to >=30% and the value of (P (211)+P (200))/P (200) is regulated to >=110% and the sheet thickness is regulated to 0.15-0.25mm. Thus, the steel sheet for thinning/deep drawing can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel sheet for thinning and deep drawing which reduces the can diameter and the can wall thickness by drawing and then redrawing one or more times. More specifically, the present invention relates to a steel sheet that has excellent resistance to collapsing of the wall portion of a can during thinning and deep drawing.

[0002]

2. Description of the Related Art A DRD can (Drawn and Redraw) can be used as a two-piece can in which a can body and a can bottom are integrated.
n Can), DI can (Draw and Iron)
edcan) is common, and in recent years DTR cans (Dra)
w-Thin / RedrawCan) has been put to practical use. Since these cans are processed differently, the properties required of the materials are also different. The DTR can targeted by the present invention is a can manufacturing method (DTR processing or DTR processing in which the diameter of the can is reduced and the can wall thickness is reduced by drawing a steel sheet coated with an organic film on both sides and then redrawing. Thinning and deep drawing)
It is manufactured by. The reduction rate of the can wall thickness is usually 10 to 30%, but the thickness reduction is performed by bending the shoulder dies of the drawing die and redrawing die to a small size and then bending them back. Is. The die shoulder arm size is determined by the relationship with the thickness of the steel sheet to be processed,
Currently, the thickness of the steel plate that is put to practical use is approximately 0.2 m.
The thickness of the organic coating on both sides is 10 m.
˜30 μm. Here, as for the die shoulder arm, the one having a dimension of 1.5 to 3 times the plate thickness of the steel plate is suitable for reducing the thickness, but the dimension of the die shoulder arm is about one tenth of the case of the DRD can. And small. JP-A-3-3621 proposes such a material for thinning and deep drawing.
5, JP-A-4-314535. JP-A-3-362
No. 15 discloses a steel sheet having excellent in-plane anisotropy by defining steel components and manufacturing conditions.
4535 is intended to limit the crystal grain size and surface roughness of the original plate and prevent poor adhesion between the coated organic film and the steel plate due to skin roughness and cracks generated in the coated organic film. It is not intended to improve the crush resistance as intended by the present application.

[0003]

In the drawing and redrawing processes, at the start of forming, that is, when the tip of the punch hits the part which becomes the bottom of the can, the impact causes the plate of the die shoulder arm to hit the plate. It causes bending and thickness reduction. This reduction in plate thickness is called a shock line and has a ring shape. The reduction of the plate thickness is inversely proportional to the size of the die shoulder arm, and the reduction of the die shoulder arm increases the reduction of the plate thickness. Therefore, normal drawing is not a problem,
This is a problem in thin-walled deep drawing (DTR) using a die with a small shoulder size. This shock line is associated with the breakage of the can wall at the time of the impact or in the subsequent molding process, and is strongly desired to be improved in terms of productivity and material yield improvement. It is an object of the present invention to provide a material that has a small shock line and is unlikely to cause breakage (crushing) of a can wall in thin-walled deep drawing using a die with a small shoulder arm.

[0004]

The present invention has been studied from the viewpoint of the steel material in order to prevent crushing (breakage) caused by such a shock line during thinning and deep drawing. As a result, the amount of C is 0.006-0.15%, the amount of Mn is 0.1-0.7%, the amount of Al is 0.02-0.12%,
The yield strength is 500 to 800 N / mm ^2, and the X-ray diffraction peak intensity values P (211), P (222) related to the crystal planes (211), (222), and (200) parallel to the plate surface,
The relationship of P (200), that is, P (211) / P (2
The value of (00) × 100 is 70 or more, and P (222) / P (2
The value of (00) × 100 is 30 or more, (P (211) + P
By setting the value of (222)) / (200) × 100 to 110 or more, it is possible to obtain a steel sheet that is less likely to be crushed through the shock line, that is, a steel sheet that is excellent in crush resistance. .

[0005]

The operation of the present invention will be described below with reference to the thinning deep drawing process which is the object of the present invention. The thinning deep drawing is performed on the drawn can before the organic film coating by drawing and redrawing. FIG. 1 shows a state before thinning and deep drawing the front drawing can, and FIG. 2 shows a state during thinning and deep drawing. In the state of FIG. 1, first, a part of the can wall 6 and the can bottom 7 is restrained by the guide ring 3, the redrawing die 2, and the wrinkle retainer 1. Then, punch 4
Moves at a high speed in the direction of arrow 11 and collides with the can bottom 7 to start molding. At the time of the collision, a shock line is formed, which the present invention regards as a cause of breakage. The shock line is formed on the can bottom 7 that collides with the die shoulder 5, but in FIG. 2 it remains as a shock line on the re-drawing can shoulder 10 connecting the can bottom 7 to the can body. Although a shock line has already been formed on the shoulder portion 8 of the front squeezing can in the previous step, it moves rearward from the tip position by the molding of FIG. 2 and remains as the front squeezing can shock line 9. The shock line 9 has a ring shape on the circumference of the can at the same height as the bottom of the can. Although the shock line is formed as described above, the thin-walled deep drawing process targeted by the present invention has an extremely small die shoulder arm size R1 to be used as compared with the normal deep drawing process, and the shock line plate thickness. This is a point to be solved by the present invention, because the necking is large and the body is easily broken. The feature of this thinning deep drawing is that the die shoulder arm size R1
Is extremely small. First, the relationship with the die shoulder arm size will be described. The forming load and the breaking load during the thinning and deep drawing process change due to the different die shoulder arm dimensions, and the relationship also changes depending on the yield strength of the material. The relationship will be described. Dice shoulder
As the load becomes smaller, the forming load increases and the breaking load decreases. The breaking load is a load at the time of breaking when a wrinkle pressing force far exceeding a range suitable for molding is applied to force the breaking. The larger the difference between the breaking load and the forming load (hereinafter referred to as the load margin), the larger the margin for breaking, and the stable continuous production can be achieved with little breaking in the actual continuous can manufacturing. This load margin is smaller as the die shoulder arm size is smaller. Therefore, it is preferable that the die wall thickness is small from the viewpoint of reducing the thickness of the can wall, but if it is made small, crushing is likely to occur, so the die shoulder arm cannot be made smaller than a certain size. The desired die shoulder arm size is selected in consideration of the thickness reduction and breakage of the can wall. Here, when the die shoulder arm size is constant, the higher the yield strength of the material, the larger the load margin, and the less likely the fracture will occur. From the viewpoint of this load margin, the lower limit of the yield strength was set to 500 N / mm ² . On the other hand, when the yield strength is 800 N / mm ² or more, wrinkles are likely to occur during shrinkage flange deformation during drawing and redrawing. The upper limit of yield strength was set in terms of wrinkling.

Next, the reason for determining the C content, Mn content, and Al content will be described. C is an element that hardens steel,
From the viewpoint of hardening, it is necessary to add a certain amount, but if the amount is increased, carbides increase, and voids are formed around the carbides due to processing, which causes fracture. Therefore, 0.
The upper limit was 15%. On the other hand, when the content is 0.006% or less, not only hardening cannot be achieved, but also crystal grains become extremely large, and during processing, it is likely to break through rough skin. Next, the reason for determining the Mn amount will be described. Mn is also an element that hardens steel, and is added at least 0.1% for hardening and for preventing hot brittleness due to S existing in steel. On the other hand, when it is 0.7% or more, the hardness becomes extremely large, which causes a problem of wrinkling during molding. From these points, the upper and lower limits were set. Al is added for deoxidation. 0.0 for minimum deoxidizing effect
2% or more is required. On the other hand, if it is 0.12% or more,
Not only is the effect saturated, the cost is increased, but also the number of surface layer inclusions is increased, which is not preferable.

Next, the reasons for limiting the X-ray diffraction peak intensity of the crystal plane will be described. It is indispensable to obtain the desired steel sheet not only by setting the chemical composition and the yield strength of the steel sheet in the above-mentioned ranges but also by making the relationship regarding the X-ray diffraction peak strength of the crystal planes described below appropriate. is there.
It is said that the crystal orientation of the steel sheet affects the plastic anisotropy. Here, the shock line targeted by the present invention is bending with a high shear deformation degree because the die shoulder arm is extremely small, and bending back deformation, and although it is a special plastic deformation,
It was inferred that the crystal orientation had a considerable influence, and the study was conducted focusing on the crystal orientation degree. Here, the X-ray diffraction peak intensity of the crystal plane parallel to the plate surface was used as an index of the crystal orientation degree. Here, the steel plate is irradiated with X-rays, and (110), (21
1), (200), (222), etc. The peak strengths of the respective crystal planes and the relationship between the peak strengths were investigated for various materials, and the research on the relationship with the crushing through the shock line was carried out in detail and many studies were conducted. . As a result, crystal planes (211), (20
0) and (222) X-ray diffraction peak intensity values are respectively P
When (211), P (200), and P (222), the intensity ratio P (211) / P (200) × 100 is 70 or more,
The intensity ratio P (222) / P (200) × 100 is 30 or more, and the intensity ratio (P (211) + P (222)) /
When P (200) × 100 was 110 or more, it was found that there was very little breaking through the shock line.
Here, the upper limit of each intensity ratio is not regulated, but 280 for P (211) / P (200) × 100, 150 for P (222) / P (200), and (P (211) + P (222)) / P (20
0) x100 was about 400, and no phenomenon that should be a problem was observed. The X-ray diffraction peak strength values are steel components, finish rolling temperature of hot rolling, winding temperature, primary and secondary cold rolling rates, recrystallization heat treatment conditions (heating rate, soaking temperature, soaking time). Etc.), etc., but these conditions are selected in consideration of the thinning deep drawing condition, the characteristics required for the thin deep drawing can, and the like.

Regarding the relationship between the carbon content and the strength ratio, the higher the carbon content, the higher the strength ratio.
On the other hand, when the amount of carbon is small, breaking does not occur easily even if the strength ratio is low. The relationship with the yield strength is as follows. The yield strength of the present invention is preferably 500 N
/ Mm ^{2 to} 800 N / mm ^2, which is higher in yield strength than general steel sheets for cans. However, the method of obtaining this high yield strength is mainly due to work hardening such as rolling, or steel composition The relationship with the intensity ratio differs depending on whether or not Here, in the case of mainly using work hardening, it is essential that the strength ratio is high. On the other hand, when the amount of hardening by processing is small, the strength ratio does not have to be particularly large, that is, P (211) / P (200) × 100 is 70 to 9
0, P (222) / P (200) × 100 is 30 to 40
And (P (211) + P (222)) / P (200)
Even at a level of x100 of 110 to 130, the steel sheet is suitable for the purpose. As described above, the larger the strength ratio, the wider the range of materials that can be selected.However, considering the economic efficiency and other properties required for the can, the steel composition, yield strength, strength ratio, etc. should be selected. Become. Also, the plate thickness is 0.15-0.25 m
The range is m. When the plate thickness is 0.15 mm or less, when a gas beverage such as a carbonated beverage is filled, the can bottom buckles and cannot be used as a container. On the other hand, the plate thickness is 0.25 mm
If the above is the case, it becomes difficult to reduce the weight of the can, and the upper limit was set from the economical point of view. The steel sheet of the present invention is applied to a surface treatment and an organic film and is applied to thinning and deep drawing, and electrolytic chromic acid treatment is suitable as the surface treatment from the viewpoint of adhesion. The organic film to be coated is made of polyethylene terephthalate resin, polybutylene terephthalate resin, copolymerized polyester resin, modified olefin resin, phenol-epoxy resin, or the like, and resins based on these. Select and add lubricants and pigments as needed.
Regarding the thickness, the thickness of one side of the organic coating is 0.005 to the thickness of the steel plate of 0.15 to 0.25 mm.
Range of 0.030 mm, 1/30 to 1 of steel plate thickness
When it is in the range of / 6, it is excellent in terms of thinning, deep drawing workability, corrosion resistance, and economical efficiency.

[0009]

EXAMPLES Examples will be described below. Steel having the components shown in Table 1 was melted in a converter and hot-rolled in accordance with a conventional method.
Finishing rolling was performed at 00 ° C, and then rolled at 600 ° C to obtain a hot rolled sheet. After pickling and cold rolling the hot rolled sheet, recrystallization annealing was performed under the heat treatment conditions and rolling rates shown in Table 2.
Next cold rolling was performed to a plate thickness of 0.2 mm. BA in Table 2 is a box-type annealing with a heating rate of 100 ° C / hour and a soaking temperature x time of 650 ° C x 8 hours. CA is a soaking temperature x soaking rate of about 50 ° C / sec. Time is 680 ° Cx
Means continuous annealing for 60 seconds, BA-CA, CA-BA
Carried out CA after BA and BA after CA, respectively. The yield strength after the secondary cold rolling shows the average value in the direction parallel to the rolling direction and the direction perpendicular to the rolling direction. After the secondary cold rolling, degreasing and electrolytic chromic acid treatment were performed, and thereafter, a polyethylene terephthalate film having a thickness of 20 μm was laminated on both sides of the steel sheet, and after applying wax, it was subjected to thinning deep drawing. For thinning deep drawing, a blank with a diameter of 170 mm is
A drawing process of drawing with a punch of 00 mm (drawing ratio 1.7), a first redrawing process of redrawing with a punch of 80 mm in diameter (redrawing ratio 1.25), and then a diameter of 65 m.
It was carried out according to the second redrawing step (drawing ratio 1.23) of redrawing with a punch of m. Here, the drawing die,
The shoulder arms of the first redrawing die and the second redrawing die were 1.3 mm, 0.5 mm, and 0.3 mm, respectively. The evaluation of the crush resistance was performed under the same conditions for the drawing process and the first redrawing process, and was evaluated by the easiness of the crushing in the second redrawing process. That is, in the second redrawing process,
Except for unusual cases when the wrinkle holding force is above a certain value, it collapses starting from the shock line of drawing or first redrawing, but it was evaluated by the minimum value of the wrinkle holding force when breaking. . This is because the minimum value of the wrinkle holding force that causes the crushing has a high correlation with the crushing occurrence rate in the actual can manufacturing line. When the wrinkle pressing force for breaking the cylinder is 10 tons or more, there is no problem in production, and the steel sheet targeted by the present invention is obtained. The wrinkle holding force was changed within the range of 1 to 15 tons.

[0010]

[Table 1] (% by weight)

[0011]

[Table 2]

[0012]

EFFECT OF THE INVENTION The thin-walled deep-drawing steel sheet according to the present invention has a steel composition, a yield strength, and a crystal plane (21) parallel to the steel sheet surface.
By determining the X-ray diffraction peak intensity ratio and plate thickness for 1), (200), and (222), it is a steel plate that is less likely to be crushed through the shock line in thinning deep drawing.

[Brief description of drawings]

FIG. 1 is a schematic view showing a state before thinning deep drawing.

FIG. 2 is a schematic view showing a state in the middle of thinning and deep drawing.

[Explanation of symbols] 1 Wrinkle retainer 2 Redraw die 3 Guide ring 4 Punch 5 Die shoulder 6 Front draw can can wall 7 Can bottom 8 Front draw can shoulder 9 Front draw can shock line 10 Redraw can shoulder 11 Arrow R1 die shoulder arm dimensions

Claims (1)

[Claims] 1. Amount of C; 0.006-0.15%, amount of Mn;
0.1 to 0.7%, Al content: 0.02 to 0.12%, yield strength is 500 to 800 N / mm ² , and crystal planes (200) and (211) parallel to the plate surface. , (222)
X-ray diffraction peak intensities P (200), P (211), P
Regarding (222), P (211) / P (200) × 10
The value of 0 is 70 or more, P (222) / P (200) x 1
The value of 00 is 30 or more, and (P (211) + P
The value of (222)) / P (200) × 100 is 110 or more, and the plate thickness is 0.15 to 0.25 mm.