JPH1030152A - Steel sheet suitable for use in thin deep-drawn can, and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel sheet excellent in surface roughing characteristic and corrosion resistance, free from can body breakage at the time of continuous high speed can manufacture, having superior workability, and suitable for thin deep-drawn can, and its production. SOLUTION: The steel sheet can be produced by subjecting a hot rolled steel plate, having a composition consisting of 0.01-0.15% C, <=0.05% Si, <=0.9% Mn, <=0.04% P, <=0.04% S, 0.015-0.10% Al, 0.0020-0.015% N, and the balance Fe with inevitable impurities, to cold rolling, continuous annealing by means of a heat cycle containing overaging treatment, and temper rolling at 0.5-2.0% elongation percentage in succession. Further, the average crystalline grain size of the steel sheet after temper rolling is regulated to <=6.0μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a container material for food cans, beverage cans and the like, and more particularly to a steel sheet suitable for use in a thin-walled deep-drawing can which is excellent in deep-drawing workability, has good surface roughness, and has excellent corrosion resistance. It concerns the manufacturing method.

[0002]

2. Description of the Related Art Conventionally, a side seam is seamless.
As a method of forming a can, a method of applying an organic paint to the inside and outside of the can after forming a surface-treated steel sheet, a method of coating a metal sheet before forming with a resin film in advance, using the resin film as a kind of forming lubricant, There is a so-called thinned draw can molding method for reducing the thickness of a metal plate in a portion to be formed. As an example of the latter,
The present inventors have previously proposed a metal plate for a thinned drawn can having excellent surface roughness and corrosion resistance after can making by specifying the average crystal grain size and the average surface roughness of the metal plate ( JP-A-4-314535).

[0003]

However, when a thinned drawn can is formed by using a conventional metal plate previously coated with a resin film, there is a problem that the completed can side wall is extremely rough. That is, since the clearance between the die and the punch is larger than the thickness of the can side wall, and the can side wall is not restricted by the punch and the die during processing, and has a so-called free surface, DI (Draw and I)
There is a problem that the side wall of the can is easily roughened as compared with the molding method. When this rough surface state occurs, the adhesion between the original plate and the film decreases, which also contributes to film peeling. In addition, there is also a problem that the roughened surface is triggered by an external impact such as contact between cans during transportation, which causes fine cracks on the film surface, and eventually causes deterioration of corrosion resistance. Normally, a thin-walled deep-drawing can is formed by punching a coated metal plate into a disk shape and performing a two-stage drawing process.
In the second-stage drawing (redrawing), the thickness of the can side wall is reduced by applying a high wrinkle holding force to the flange portion and performing the drawing-extending process of the can side wall. In the above-mentioned processing method, redrawing is an extremely severe forming method, so that there is a problem that a broken body is likely to occur during continuous forming. If such a fracture occurs, the productivity of high-speed can manufacturing is impaired.
In addition, there was an urgent need to develop a steel sheet that is excellent in workability and suitable for thinning deep drawing cans. The present invention aims to solve the above-mentioned problems, and is suitable for use in thin-walled deep-drawing cans having excellent surface roughness, excellent corrosion resistance, no breakage during continuous high-speed can-making, and excellent workability. An object of the present invention is to provide a steel sheet and a method for manufacturing the same.

[0004]

Means for Solving the Problems The steel sheet suitable for use in the thinned deep-drawing can of the present invention is as follows: C: 0.01-0.15%, Si
≦ 0.05%, Mn ≦ 0.9%, P ≦ 0.04%, S ≦
0.04%, Al: 0.015 to 0.10%, N: 0.
A hot-rolled steel sheet comprising 0020 to 0.015%, the balance being Fe and unavoidable impurities, is subjected to cold rolling, annealing in a heat cycle including overaging treatment, and temper rolling at an elongation of 0.5 to 2.0%. , And the average grain size of the steel sheet after temper rolling is 6.0 μm or less, which is a steel sheet suitable for thinning and deep drawing. Further, C: 0.01 to 0.15%, Si ≦
0.05%, Mn ≦ 0.9%, P ≦ 0.04%, S ≦
0.04%, Al: 0.015 to 0.10%, N: 0.
0020 to 0.015%, Nb: 0.001 to 0.02
A hot-rolled steel sheet comprising 0%, the balance of Fe and unavoidable impurities is sequentially subjected to cold rolling, annealing in a heat cycle including overaging treatment, and temper rolling at an elongation of 0.5 to 2.0%. It is also desirable that the average grain size of the steel sheet after temper rolling is 6.0 μm or less. Next, the method for producing a steel sheet suitable for use in a thinned deep-drawing can according to the present invention is as follows: C: 0.01 to 0.1
5%, Si ≦ 0.05%, Mn ≦ 0.9%, P ≦ 0.0
4%, S ≦ 0.04%, Al: 0.015 to 0.10
%, N: 0.0020 to 0.015%, a hot-rolled steel sheet comprising the balance of Fe and unavoidable impurities is annealed in a heat cycle including cold rolling and overaging, and has an elongation of 0.5 to 0.5%.
This is a method for producing a steel sheet suitable for deep drawing, in which temper rolling at 2.0% is sequentially performed, and C: 0.01 to 0.1.
15%, Si ≦ 0.05%, Mn ≦ 0.9%, P ≦ 0.
04%, S ≦ 0.04%, Al: 0.015 to 0.10
%, N: 0.0020 to 0.015%, Nb: 0.00
A hot-rolled steel sheet comprising 1 to 0.020%, balance Fe and unavoidable impurities, is subjected to cold rolling, annealing in a heat cycle including overaging treatment, and temper rolling at an elongation of 0.5 to 2.0%. , Are preferably performed sequentially.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The steel sheet of the present invention is coated with a resin film of polyester or the like, punched into a disc shape, and subjected to continuous high-speed can-making with two-stage drawing, without causing a broken body. Moreover, it is possible to form a thin-walled deep drawn can having excellent workability. In particular, in recent years, the thickness of the steel sheet has been significantly reduced, and also in the steel sheet for cans, which has been increased accordingly, having both workability and strength to prevent the occurrence of a broken body at the time of two-stage severe deep drawing, In addition, it can satisfy the conditions of rough surface and corrosion resistance as a molded product. In other words, in deep drawing, ultra-thin steel sheet is used as a material, and in the redrawing process, it is subjected to strong tensile bending at the die corner with a small radius of curvature under the load of strong back tension and punch force, and the thickness is reduced. Therefore, it is necessary to have high workability to meet the demand for the thinning and deep drawing as well as strength to prevent the occurrence of a broken body at that time, and therefore, a balance between the strength of the can and the workability is important. In the present invention, after the heat cycle including the overaging treatment after the cold rolling, the temper rolling so that the elongation becomes 0.5 to 2.0% is combined, so that the overaging treatment after the cold rolling is performed. The effect of reducing solid solution C and N, improving elongation characteristics and improving workability, and improving the sheet strength by temper rolling after overageing are combined, and it is sufficient for ultra-thin steel sheets for cans. It can provide excellent workability and strength that does not cause a broken body. It is known that the addition of Nb generally contributes to refinement of crystal grains and reduction of solid solution C and N. However, it is combined with the heat cycle of the present invention including overaging treatment after cold rolling. Thereby, the solid solution C and N can be reduced by the overaging treatment, and the workability including the elongation property can be improved.
Is significantly enhanced, and together with the effect of preventing the crystal grains from being coarsened, it is possible to prevent the surface from being roughened and to achieve the effect of preventing the body from being broken in the deep drawing work for thinning the wall. These actions and effects are exhibited based on the properties of the specific component composition.
The regulation of the amount and the inclusion of a small amount of Nb in combination with these treatment steps can achieve the refinement of crystal grains which contributes to the improvement of the surface roughness.

Composition of hot rolled steel sheet Steel composition: C: 0.01-0.15%, Si ≦ 0.05
%, Mn ≦ 0.9%, P ≦ 0.04%, S = 0.04
%, Al: 0.015 to 0.10%, N: 0.0020
-0.015%, with the balance being Fe and unavoidable impurities. Further, those obtained by adding 0.001 to 0.02% of Nb to the above components are also preferably used. The reasons for the regulation of steel components are described below. When C is less than 0.01%, crystal grains become coarse, and the lower limit is made 0.01%. On the other hand, 0.15
%, The drawability deteriorates, so the range was made 0.01 to 0.15%. Si is an element harmful to corrosion resistance as a material for cans, but is an element inevitably contained in Al-killed steel, and the upper limit is 0.05%. Mn is a component necessary for preventing red-hot brittleness during hot rolling due to S as an impurity. On the other hand, if it exceeds 0.9%, drawability deteriorates, so the upper limit was made 0.9%. P is an effective component for refining the crystal grains, and is added at a certain ratio in order to increase the strength of the original sheet, but on the other hand, inhibits the corrosion resistance. P can be used as a steel sheet for cans of the present invention.
Exceeds 0.04%, the corrosion resistance, particularly the pitting resistance, is significantly reduced, so the upper limit was made 0.04%. S is an impurity component that causes red hot embrittlement during hot rolling, and is desirably as small as possible. However, S is an element inevitably contained, and the upper limit is set to 0.04%. Al is added to the steel bath as a deoxidizing agent during steel making and is removed as slag. However, if the added amount is small, a stable deoxidizing effect cannot be obtained.
% Or more is required. Al reacts with the solid bath N to form AlN.
And contribute to refinement of crystal grains. On the other hand, 0.
An addition exceeding 10% has little technical effect and is not economically preferable, so the upper limit was made 0.10%. N forms a nitride with Al and Nb and is an effective component for refining fine grains. However, if it is less than 0.002%, precipitation of the nitride is small, and the effect of refining is lost. On the other hand, if it exceeds 0.015%, cracks tend to occur on the slab surface, resulting in structural defects, so the range was made 0.002 to 0.015%. Nb is effective in refining crystal grains, and contributes to reduction of solid solution C and N. If it is less than 0.001%, there is no effect of grain refinement, while if it exceeds 0.020%, the amount of solute Nb increases and consequently the drawability deteriorates, so the upper limit was made 0.020%.

Although the slab heating temperature and the hot rolling conditions are not specified in the present invention, the slab heating temperature is set to 1100 ° C. from the viewpoint of the active decomposition of N and the stable securing of the hot rolling temperature. It is desirable to make the above. If the hot rolling finish temperature is lower than the Ar3 point, the crystal structure of the hot-rolled sheet is mixed and coarsened, so the hot rolling finish temperature is higher than the Ar3 point. In addition, the lower limit of the winding temperature is set to 450 ° C. in consideration of the quality stability in the coil width direction and the longitudinal direction at the time of hot rolling.
Since the skin becomes rough, the winding temperature is preferably in the range of 450 to 650 ° C.

[0008] If the rolling reduction is less than 75%, the annealing step results in coarsening or mixing of the grains of the steel sheet, and the grains cannot be sufficiently refined. Is preferably set to 75% as the lower limit.

Annealing Step In the present invention, it has been found that the adoption of annealing in a heat cycle including overaging treatment has an effect on fracture. This is considered to be due to a decrease in solid solution C and N. Annealing may be carried out by any of the following methods: continuous aging followed by over-aging after continuous annealing, and case where the temperature is once lowered and box annealing is performed again. The treatment temperature of the continuous annealing in the preceding stage may be at least the recrystallization temperature,
If the temperature exceeds 0 ° C., the crystal grains become coarse, which is not preferable. Here, the overaging treatment means a heat treatment at a low temperature for a long time as compared with a general annealing treatment. When the overaging treatment is performed after the continuous annealing, the soaking is performed at 400 to 550 ° C for 1 to 3 minutes. If the temperature is lower than 400 ° C., solid solution C and N cannot be reduced. If the temperature exceeds 550 ° C., crystal grains become coarse. If the heating time is less than 1 minute, the solid solution C and N cannot be sufficiently reduced, and if the heating time exceeds 3 minutes, the furnace length becomes longer.
Minute range. The overaging treatment may be box annealing. In case of box annealing, lower the temperature once to 400 ~ 5.
The temperature is raised to 50 ° C., and the soaking is performed for 2 to 10 hours. 400 ° C
If it is less than 30, the quality as the overaging treatment is not stable, and the characteristics vary. If it exceeds 550 ° C., the crystal grains become coarse as in continuous annealing. If the time is less than 2 hours, the quality as the overaging treatment is not stable, and the characteristics vary. On the other hand, treatment exceeding 10 hours is not economically advantageous.

[0010] In general, the effect of overage treatment decreases the total elongation and the uniform elongation by increasing the amount of solid solution C and N. This is due to the constriction that occurs when stretching,
This is probably because solid solution C and N act on the connection mechanism of the voids. Overaging treatment reduces solid solution C and N in steel,
Effective for softening steel. It is considered that by performing the overaging treatment, the solid solution C and N in the steel are reduced, the occurrence of constriction and the connection of voids are suppressed, and as a result, the susceptibility to breakage and rupture is reduced. The steel component range of the present invention is necessary for exerting the action in these overaging treatments,
The action of each of the above components is achieved through this overaging treatment. The lower limit of the amount of C and the presence of Al, Nb, etc. prevent the roughening of the crystal grains by grain refinement. In particular, the addition of a small amount of Nb exhibits the effect of reducing the solute C and N in combination with the overaging treatment. By doing so, the workability is improved.

Temper Rolling Temper rolling (SR, Single Reduce Roll
(Ling is an abbreviation for ling), since the occurrence of stretcher strain is prevented if the elongation percentage is in the range of 0.5 to 2.0%. In the present invention, the over-aging treatment reduces the solid solution C and N in the steel, suppresses the occurrence of constriction and the connection of voids, improves the workability in deep drawing, and reduces the thickness of the thin object which is the object of the present invention. In addition to satisfying the processing conditions for deep drawing, the steel sheet of the present invention is given a strength by performing temper rolling in an elongation range of 0.5 to 2.0%. In addition to the high workability required for the steel sheet, it is possible to impart a plate strength that does not cause the occurrence of a broken body during processing. As described above, in the present invention, these two steps can be combined to achieve the respective conditions of workability and plate strength. The temper rolling also achieves the required can strength required for extremely thin cans.

DR Rolling DR rolling is sometimes performed particularly when the strength of the can is increased after forming. The rolling reduction is set to 20 to 50%. If it is less than 20%, sufficient can strength cannot be obtained, and if it exceeds 50%, the steel sheet has high strength, and it becomes difficult to form a can. Where D
R Rolling is Double Reduce Rolli
ng, which is a rolling method in which the sheet thickness is more positively reduced and the sheet strength is increased more than in temper rolling. In the present invention, secondary cold rolling is performed including the temper rolling and the DR rolling.

Next, examples of the steel sheet used in the present invention include sheet-shaped and coil-shaped steel sheets, steel foils, and those obtained by subjecting these steel sheets to surface treatment. Especially,
Electrolytic chromic acid-treated steel sheet or ultra-thin tin-plated steel sheet, nickel-plated steel sheet, zinc-plated steel sheet having a two-layer structure of chromium metal on the lower layer and hydrated chromium oxide on the upper layer Is a hydrated oxide of chromium, and a surface treatment having a two-layer structure of a metal chromium layer as the lower layer is excellent in contact with the polyester resin.

Average Grain Size The specification of the crystal grain size will be described with reference to FIGS. FIG. 1 shows the relationship between the average crystal grain size and the roughness of the side wall of the can after the can-making process. From FIG. 1, it can be seen that when the average crystal grain size is large, the surface roughness after the can-making process is deteriorated. When the average crystal grain size exceeds 6 μm, the surface roughness is deteriorated, and the appearance and characteristics as a can are impaired. For this reason, the average crystal grain size does not exceed 6 μm. FIG. 2 shows the relationship between the average crystal grain size and the corrosion resistance. FIG. 2 also shows that the corrosion resistance is good when the average crystal grain size does not exceed 6 μm. In addition, evaluation of corrosion resistance was performed as follows. After the can-making process, the can was heat-treated at 130 ° C. for 20 minutes, filled with water, and the degree of corrosion (blackening) of the inner surface of the can after 2 weeks at 37 ° C. was visually evaluated.

[0015]

【Example】

[0016]

[Table 1]

[0017]

[Table 2]

Evaluation Example No. of the present invention 1 to 6 are within the range of the component of the present invention,
Excellent workability due to overaging treatment. As shown in Table 2, the average crystal grain size was 6.0 μm or less, and it was found that both the surface roughness and the corrosion resistance were excellent. In addition, excellent results are obtained in workability, which is important for the use of the thinned deep drawn can of the present invention. In particular, it can be seen that Examples Nos. 5 and 6 are excellent in workability by adding a small amount of Nb. On the other hand, in Comparative Example No. 7, since the C content was less than the lower limit of the range of the present invention, the crystal grains were coarse, the surface roughness and corrosion resistance were poor, and the workability was poor despite the overaging treatment. It has become. Comparative Examples No. 8 to 10
Although it is within the range of the components of the invention, it has not been overaged and has poor processability. Here, the evaluation cans were as follows. The evaluation of the roughness was measured by measuring the surface roughness of the inner wall of the can after molding the thinned deep drawn can.
μm or less is marked as ◎ (best), and 1 to 1.5 μm is marked as ○
(Good), 1.5 to 2 μm was evaluated as Δ (Slightly poor), and 2 μm or more was evaluated as × (Defective). The corrosion resistance was evaluated at 130 ° C. × 20 after forming a thinned deep drawn can.
For 2 minutes, filled with water, and visually evaluated for the degree of corrosion (blackening) of the inner surface of the can after elapse of 2 weeks at 37 ° C. ◎ (best) when the surface was not blackened at all, ○ (good) when the degree of blackening was minute, and Δ (slightly poor) when the degree of blackening was small (diameter of 5 mm or less). , Large (diameter 5
mm or more) was evaluated as x (defective). The workability was evaluated by increasing the wrinkle holding pressure at the time of forming a thin-walled deep-drawing can, and evaluating the magnitude of the wrinkle holding pressure until breaking.も の (slightly poor) when the wrinkle pressing pressure was 5 tons or less, ○ (good) when 5 to 7 tons were broken, and ◎ (best) when 7 tons or more were broken did.

[0019]

According to the present invention, there is provided a steel sheet which is excellent in surface roughness and corrosion resistance, does not break even during continuous high-speed can-making, and is excellent in workability and is suitable for a thin-walled deep drawn can. Can be. In addition, the steel sheet provided by the present invention can be used as a can for a steel sheet alone,
This steel sheet can be surface-treated and used as tinplate, TFS, nickel-plated steel sheet and the like. Further, the surface-treated steel sheet may be covered with a resin film such as polyester. Further, a steel sheet coated with a paint such as epoxy can also be used for thinned deep drawing cans.

[Brief description of the drawings]

FIG. 1 is a graph showing the influence of an average crystal grain size on skin roughness.

FIG. 2 is a graph showing the effect of average crystal grain size on corrosion resistance.

Claims (4)

[Claims] 1. C: 0.01 to 0.15%, Si ≦ 0.
05%, Mn ≦ 0.9%, P ≦ 0.04%, S ≦ 0.0
4%, Al: 0.015 to 0.10%, N: 0.002
A hot-rolled steel sheet comprising 0 to 0.015%, the balance being Fe and unavoidable impurities, is subjected to cold rolling, annealing in a heat cycle including overaging treatment, and temper rolling at an elongation of 0.5 to 2.0%. , In order that the average grain size of the steel sheet after temper rolling is 6.0 μm or less, which is suitable for thinning deep drawing cans. 2. C: 0.01 to 0.15%, Si ≦ 0.
05%, Mn ≦ 0.9%, P ≦ 0.04%, S ≦ 0.0
4%, Al: 0.015 to 0.10%, N: 0.002
0 to 0.015%, Nb: 0.001 to 0.020%,
The hot-rolled steel sheet consisting of the balance of Fe and unavoidable impurities is sequentially subjected to cold rolling, annealing in a heat cycle including overaging treatment, and temper rolling at an elongation of 0.5 to 2.0%. A steel sheet suitable for use in a thin-walled deep-drawing can having an average crystal grain size of 6.0 μm or less after rolling. 3. C: 0.01 to 0.15%, Si ≦ 0.
05%, Mn ≦ 0.9%, P ≦ 0.04%, S ≦ 0.0
4%, Al: 0.015 to 0.10%, N: 0.002
Hot-rolled steel sheet consisting of 0 to 0.015%, balance Fe and unavoidable impurities, cold-rolled, continuously annealed in a heat cycle including overaging treatment, tempering at an elongation of 0.5 to 2.0% A method for producing a steel sheet suitable for thinning deep-drawing cans, in which rolling and rolling are sequentially performed. 4. C: 0.01 to 0.15%, Si ≦ 0.
05%, Mn ≦ 0.9%, P ≦ 0.04%, S ≦ 0.0
4%, Al: 0.015 to 0.10%, N: 0.002
0 to 0.015%, Nb: 0.001 to 0.020%,
A hot-rolled steel sheet comprising the balance of Fe and unavoidable impurities is subjected to cold rolling, annealing in a heat cycle including overaging treatment, and temper rolling at an elongation of 0.5 to 2.0%, in order. A method for producing steel sheets suitable for drawing cans.