JP2676581B2 - Steel sheet suitable for thinned deep-drawing can and its manufacturing method - Google Patents

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 plate suitable for use in a thin-walled deep-drawing can having excellent deep-drawing workability, good surface roughness and 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]

A steel sheet suitable for use in a thin-walled deep-drawn can of the present invention is 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.
Hot-rolled steel sheet consisting of 002 to 0.015%, balance Fe and unavoidable impurities, cold rolling, annealing in a heat cycle including overaging treatment, DR rolling with a reduction rate of 20 to 50%,
And the average crystal grain size of the steel sheet after DR rolling is 6.0μ.
A steel sheet having a thickness of m or less, which is suitable for thin-walled deep drawing can applications .
Further, C: 0.01 to 0.15%, Si ≦ 0.05%,
Mn ≦ 0.9%, P ≦ 0.04%, S ≦ 0.04%, A
1: 0.015-0.10%, N: 0.002-0.0
15%, Nb: 0.001 to 0.020%, a hot-rolled steel sheet consisting of balance Fe and unavoidable impurities, cold-rolled, annealed in a heat cycle including overaging treatment, a reduction ratio of 20 to 5
It is also preferable that the average grain size of the steel sheet after DR rolling is sequentially performed by 0% DR rolling to be 6.0 μm or less. Next, the manufacturing method of the steel sheet suitable for use in the thin-walled deep drawing can of the present invention is as follows: C: 0.01 to 0.15%, Si ≦ 0.05%, M
n ≦ 0.9%, P ≦ 0.04%, S ≦ 0.04%, A
1: 0.015-0.10%, N: 0.002-0.0
A thin-walled deep-drawn can in which a hot-rolled steel sheet consisting of 15%, balance Fe and unavoidable impurities is sequentially subjected to cold rolling, annealing in a heat cycle including overaging treatment, and DR rolling at a reduction rate of 20 to 50%. a method of producing steel sheets suitable for use, also,
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: 0.002 to 0.015
%, Nb: 0.001 to 0.020%, the balance of Fe and unavoidable impurities in a hot rolled steel sheet is annealed in a heat cycle including cold rolling and overaging, and a reduction rate of 20 to 50%.
It is also desirable to sequentially perform the DR rolling in.

[0005]

The steel sheet of the present invention is coated with a resin film such as polyester and punched into a disk shape, and even if it is subjected to continuous high-speed can-making processing by two-step drawing, no crushing occurs and the workability is improved. Can form excellent thin-walled deep-drawn cans. Especially in recent years
The thickness was significantly reduced and the strength was increased accordingly.
Even for steel sheets for cans, it can be used for deep deep drawing in two stages.
Combines workability and strength to prevent breakage, and
As a molded product, it can meet the conditions of rough skin and corrosion resistance.
You . That is, ultra-thin steel sheet is used
And, in the redrawing process, strong back tension and punch force
Strength at a die corner with a small radius of curvature under the load of
These thin films are thinned by the tensile bending process of
Highly workable to meet the demands of deep drawing
It is necessary to have enough strength to prevent the formation of a barrel.
The balance between strength and workability is important. In the present invention
DR after heat cycle including overaging treatment after cold rolling
By combining rolling, it is possible to use over-effect treatment after cold rolling.
The solid solution C and N are reduced, the elongation characteristics are improved, and the workability is improved.
DR with a large reduction rate after overaging
Combined with the improvement of plate strength by rolling, it becomes an ultra-thin steel plate for cans.
Gives sufficient workability and strength that does not cause crushing
be able to. Also, the addition of Nb generally refines the crystal grains.
And that it is known to contribute to the reduction of solute C and N
However, the heat treatment of the present invention including overaging treatment after cold rolling is performed.
By combining with the cycle,
Resolved C and N are reduced, and workability including elongation characteristics is improved.
Combined with improvement, solid solution during overaging treatment
The effect of reducing C and N is remarkably enhanced.
Combined with the effect of preventing coarsening of crystal grains, it also prevents rough skin.
Achievement of collapsing prevention effect in thinning deep drawing
Can be . And these actions and effects are
It is exerted based on the properties of the component composition,
Especially, the amount of C and the small amount of Nb are contained in these treatment steps.
Combined with the refinement of crystal grains that contribute to the improvement of rough skin
Can be achieved.

[0006]

[Examples] Components of hot-rolled steel sheet The steel components are 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: 0.002 to
0.015%, balance 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. If C is less than 0.01%, the crystal grains are coarsened, and the lower limit is made 0.01%. On the other hand, 0.15%
If it exceeds 1.0 , the drawability deteriorates, so the range is set to 0.
It was set to 01 to 0.15%. Si is an element harmful to corrosion resistance as a material for cans, but is an unavoidable element in Al-killed steel, and the upper limit is 0.05%.
Mn is a component necessary to prevent red hot embrittlement due to impurities S during hot rolling. 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 to increase the strength of the original sheet, but impairs corrosion resistance. As a steel sheet for cans for use in the present invention, if P exceeds 0.04%, corrosion resistance, particularly puncture resistance remarkably decreases, 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 as a deoxidizing agent in the steel bath during steelmaking and is removed as slag. However, if the added amount is too small, a stable deoxidizing effect cannot be obtained.
5% or more is required. Also, Al reacts with solid solution N to form Al
Precipitates as N and contributes to grain refinement. On the other hand, addition of more than 0.10% has little technical effect and is economically unfavorable, so the upper limit was made 0.10%. N is Al
It is a component that forms nitrides with Nb and N, and is an effective component for grain refinement, but if it is less than 0.002%, the precipitation of nitrides is small and the grain refinement effect disappears, while 0.015% If it exceeds 0.1%, cracks are likely to occur on the slab surface, causing 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 refining, while if it exceeds 0.020%, the amount of solid solution Nb increases and conversely deteriorates drawability, 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 it is less than 1 minute, the solid solution C and N cannot be sufficiently reduced, and if it exceeds 3 minutes, the furnace length becomes long, so
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
When the amount is less than the above, the quality as 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,
It is considered that solid solution C and N act on the void connection mechanism. Overaging treatment reduces solid solution C and N in steel,
By overaging, which has the effect of softening the steel, the solid solution C and N in the steel is reduced, the occurrence of necking and the connection of voids are suppressed, and as a result, the susceptibility to fracture and shattering is reduced. it is conceivable that. The range of steel composition of the present invention is
It is necessary to exert the action in aging treatment,
The action of each of the above components is achieved through this overaging treatment.
Things. The lower limit of C content and the presence of Al, Nb, etc.
It prevents rough skin by making the crystal grains fine, but
Addition of Nb has the effect of reducing the solute C and N by overaging treatment.
Workability is improved by taking advantage of this .

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%.

DR rolling DR rolling is necessary to give can strength after forming, but the rolling reduction is 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. Here, the DR rolling is an abbreviation for Double Reduce Rolling, and is a rolling method that more positively reduces the sheet thickness and increases the sheet strength than the temper rolling. In the present invention, the secondary cold rolling includes the above temper rolling and DR rolling. In the present invention
Reduces the solute C and N in the steel by overaging.
It suppresses the necking and void connection and allows deep drawing.
Which is the target of this invention
By performing the DR rolling while satisfying the processing conditions of
To impart strength, which makes the steel sheet of the present invention thin
During processing in accordance with the high workability required for deep drawing
It is possible to provide a plate strength that does not cause breakage of the plate.
Thus, in the present invention, these two steps are combined.
Achieved the conditions of workability and plate strength
Can be In addition, this DR rolling enables ultra-thin plate thickness
Achieving the required can strength required for other cans
It is.

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]

[Table 1]

[0016]

[Table 2]

Evaluation Example No. 1 of the present invention. Nos. 1 to 6 were overaged within the range of the components of the invention, and were excellent in workability. In Table 2
As shown, the average crystal grain size is 6.0 μm or less, and the skin is rough.
It can be seen that both the corrosion resistance and the corrosion resistance are excellent. In addition, the present invention
It has excellent workability, which is important for thin-walled deep-drawing can applications.
The result has been. In particular, Example No. 5 and 6 are slight
It can be seen that the workability is excellent by adding a certain amount of Nb . one
If, Comparative Example No. 7 is small when the amount of C is below the lower limit of the range of the present invention.
Since it is not present, the crystal grains become coarse and the surface roughness and corrosion resistance are poor.
Therefore, even though overaged, it is easy to process.
The result is inferior. Comparative Example No. 8-10
Is within the range of the components of the invention, but has not been overaged and is inferior in workability. Here, the evaluation cans were as follows. The roughness of the skin is evaluated by measuring the surface roughness of the can side wall on the inner surface of the can after forming the thin-walled deep-drawing can and measuring Ra.
Was evaluated as ⊚ (best), 1 to 1.5 μm as ◯ (good), 1.5 to 2 μm as Δ (slightly bad), and 2 μm or more as x (bad). In addition, the corrosion resistance was evaluated at 130 ° C after forming a thin-walled deep-drawing can.
It was heat treated for 20 minutes, filled with water, and visually evaluated for corrosion (blackening) of the inner surface of the can after 2 weeks at 37 ° C.
If the surface is not blackened at all, it is ◎ (best), if the degree of blackening is minute, it is ○ (good), and if the range of blackening is small (diameter 5 mm or less) is Δ (somewhat bad). , Large (diameter of 5 mm or more) was evaluated as x (poor). 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. Crumpled with a wrinkle holding pressure of 5 tons or less △
(Slightly bad), crushed with 5 to 7 tons ○
(Good), crushed at 7 tons or more was rated as ◎ (best).

[0018]

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)

(57) [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
˜0.015%, balance Fe and unavoidable impurities, hot-rolled steel sheet is sequentially cold-rolled, annealed in a heat cycle including overaging treatment, and DR-rolled at a reduction rate of 20-50%, and then DR-rolled. A steel sheet suitable for thin-walled deep-drawing can applications, in which the subsequent steel sheet has an average crystal grain size of 6.0 μm or less. 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
To 0.015%, Nb: 0.001 to 0.020%, the balance of Fe and unavoidable impurities, hot-rolled steel sheet is annealed in a heat cycle including cold rolling and overaging, and a reduction ratio of 20 to 50. %, Which is suitable for thin-walled deep-drawing can applications, in which the average grain size of the steel sheet after DR rolling is 6.0 μm or less. 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
˜0.015%, balance Fe and unavoidable impurities, hot-rolled steel sheet is sequentially subjected to cold rolling, annealing in a heat cycle including overaging treatment, and DR rolling at a reduction rate of 20 to 50% to reduce the wall thickness. Steel plate manufacturing method suitable for deep drawing can applications. 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
To 0.015%, Nb: 0.001 to 0.020%, the balance of Fe and unavoidable impurities, hot-rolled steel sheet is annealed in a heat cycle including cold rolling and overaging, and a reduction ratio of 20 to 50. % Steel production method suitable for thin-walled deep-drawing can applications in which DR rolling in sequence is performed sequentially.