JPH0734194A - Steel sheet suitable for application to thinned deep-drawn can and its production - Google Patents

Abstract

PURPOSE:To produce a steel sheet for a thinned deep-drawn can with a specified grain size excellent in workability, surface roughening properties and corrosion resistance by subjecting a hot rolled steel sheet having a specified compsn. constituted of C, Si, Mn, P, S, Al, N, Nb and Fe to cold rolling, continuous annealing and specified skinpass rolling. CONSTITUTION:A steel slab constituted of 0.01 to 0.08% C, <=0.05% Si, <=0.9% Mn, <=0.04% P, <=0.04% S, 0.015 to 0.10% Al, 0.0020 to 0.015% N and 0.001 to 0.02% Nb, and the balance Fe with inevitable impurities is subjected to hot rolling at the Ar3 point or above. This hot rolled steel sheet is subjected to cold rolling at >=75% draft and is thereafter subjected to continuous annealing at about <=750 deg.C. After that, the steel sheet is subjected to skinpass rolling at 0.5 to 2.0% elongation percentage and DR rolling at 20 to 50% draft. Thus, the grain size of the steel sheet is regulated to <=6.0mum. In this way, the steel sheet free from the generation of the breakage of the barrel at the time of continuous high speed can producing, furthermore excellent in workability and suitable for the application to a thinned deep-drawn 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 container material for food cans, beverage cans, etc., and particularly to a steel sheet suitable for use in thin-walled deep-drawing cans, which has excellent deep-drawing workability, good skin roughness, and excellent corrosion resistance. It relates to the manufacturing method.

[0002]

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

[0003]

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

[0004]

However, when a conventional thin metal can is formed using a metal plate coated with a resin film in advance, there is a problem that the side wall of the can after completion is extremely rough. That is, the clearance between the die and the punch is larger than the thickness of the side wall of the can, and the side wall of the can is not restricted by the punch and the die at the time of processing and is a so-called free surface.
There is a problem that the side wall of the can is liable to be rough compared to the molding method. When this rough skin condition occurs, the adhesive force between the original plate and the film is reduced, which also contributes to film peeling. In addition, rough skin is also triggered by an external impact such as contact between cans during transportation, which causes minute cracks on the film surface, and eventually leads to deterioration of corrosion resistance. In general, a thin-walled deep-drawing can is formed by punching a coated metal plate into a disc shape and then drawing this in two steps.
At the time of this second-stage drawing (redrawing), a high wrinkle holding force is applied to the flange portion to draw and project the side wall of the can to reduce the thickness of the side wall of the can. In the above-mentioned processing method, redrawing is an extremely severe forming method, so that there has been a problem that breakage easily occurs during continuous forming. When such crushing occurs, the productivity of high-speed can manufacturing is impaired, so crushing is less likely to occur,
Moreover, there was an urgent need to develop a steel sheet that has excellent workability and is suitable for thin-walled deep-drawing can applications. The present invention is intended to solve the above problems, and is suitable for use in thin-walled deep-drawing cans that have excellent skin roughness and corrosion resistance, do not break during continuous high-speed can manufacturing, and have excellent processability. An object is to provide a steel sheet and a manufacturing method thereof.

[0005]

A steel sheet suitable for use in a thin-walled deep-drawing can of the present invention is C: 0.01 to 0.08%, 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
%, The balance Fe, and unavoidable impurities, a hot-rolled steel sheet is sequentially cold-rolled, continuously annealed, and temper-rolled with an elongation of 0.5 to 2.0%. Is 6.
It is characterized by being 0 μm or less. Also, C: 0.0
1 to 0.08%, Si ≦ 0.05%, Mn ≦ 0.9%,
P ≦ 0.04%, S ≦ 0.04%, Al: 0.015
0.10%, N: 0.0020 to 0.015%, Nb:
A hot-rolled steel sheet consisting of 0.001 to 0.02%, the balance Fe and unavoidable impurities is sequentially subjected to cold rolling, continuous annealing, and DR rolling with a rolling reduction of 20 to 50%, and the crystal grains after the DR rolling. A steel plate having a diameter of 6.0 μm or less is also suitably used. Furthermore, the manufacturing method of the steel sheet suitable for use in the thin-walled deep-drawing can of the present invention is C: 0.01 to 0.08%, Si ≦ 0.0.
5%, 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%, balance Fe and unavoidable impurities are used for cold rolling, continuous annealing, and elongation of 0.5 to 2.0%. Quality rolling,
Is sequentially performed. Also, C: 0.01-
0.08%, 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.
001-0.02%, the balance of Fe and inevitable impurities are hot-rolled steel sheets, cold-rolled, continuously annealed, with a reduction ratio of 20.
A manufacturing method in which DR rolling of ˜50% is sequentially performed is also suitably used.

[0006]

The steel sheet of the present invention is coated with a resin film such as polyester, punched into a disk shape, and subjected to a high-speed can-making process with a two-stage drawing. It is possible to mold thin-walled deep-drawn cans with excellent skin roughness and corrosion resistance.

[0007]

【Example】

Components of hot-rolled steel sheet Steel components are C: 0.01 to 0.08%, Si ≦ 0.05
%, Mn ≦ 0.8%, P ≦ 0.04%, S ≦ 0.04
%, Al: 0.015 to 0.10%, N: 0.0020
.About.0.015%, Nb: 0.001 to 0.015%, balance Fe and unavoidable impurities. The reasons for restrictions on steel components are described below. The smaller the amount of C, the better the extensibility, which is advantageous for the deep drawability. However, when the amount of C is too small, the effect of refining the crystal grains becomes insufficient. If it is less than 0.01%, the crystal grains become coarse, and if it exceeds 0.08%, the workability is impaired in continuous annealing.
Was made 0.08%. Si is an element harmful to corrosion resistance as a can material, but is an element inevitably contained in Al-killed steel, and the upper limit was 0.04%.
Mn is a component necessary for preventing red hot embrittlement due to impurities S during hot rolling. On the other hand, if it exceeds 0.9%, cracking occurs during slab rolling, so the upper limit was made 0.9%. . P is a crystal refining component and is added in a fixed ratio because it increases the strength of the original plate, but on the other hand it impairs corrosion resistance. As a steel sheet for cans used in the present invention, P is 0.00
If it exceeds 4%, the corrosion resistance, in particular, the perforation resistance is markedly deteriorated, so the limit value was made 0.04%. S is an impurity component that causes red hot brittleness during hot rolling, and it is desirable that S is as small as possible, but S is inevitably contained, and the upper limit is 0.04.
%. Al is added as a deoxidizing agent in the steel bath during steelmaking and removed as slag. If the added amount is too small, a stable deoxidizing effect cannot be obtained, so 0.015% was made the lower limit. The addition of 0.10% or more has little technical effect and is economically unfavorable, so the upper limit was made 0.10%. If N is less than 0.002%, the effect of crystallization disappears, and if it exceeds 0.015%, the yield of the ferronitride added during steelmaking is remarkably lowered, and the stability is lacking. Further, the upper limit was set to 0.015% because cracks are likely to occur on the surface during continuous casting, resulting in casting defects. Nb is added for refining crystal grains and forming NbC, so if it is less than 0.001%, the effect of refining cannot be obtained, while if it exceeds 0.020%, the amount of solid solution Nb increases. On the contrary, the workability is deteriorated, so the content is made 0.001 to 0.020%.

The hot rolling slab heating temperature and hot rolling conditions are not specified in the present invention, but the slab heating temperature is 1100 ° C. from the viewpoint of positive decomposition of N and solid solution and stable securing of the hot rolling temperature. It is desirable to set it as above. When the hot rolling finishing temperature is set to Ar3 point or lower, the structure of the hot rolled steel sheet is mixed and coarsened. Therefore, the hot rolling finishing temperature is set to Ar3 point or higher.
The coiling temperature is 450 ° C as a lower limit in consideration of quality stability in the width direction and longitudinal direction of the coil during hot rolling, and the coiling temperature is 650 ° C.
If the temperature exceeds the range, crystal grains become large during hot rolling and during continuous annealing and rough skin occurs. Therefore, the upper limit of the coiling temperature was 650 ° C.

Cold rolling process In the cold rolling, if the reduction ratio is less than 75%, the crystal grains cannot be sufficiently refined because they become coarse or mixed grains in the annealing process. It is desirable that the ratio be 75% as the lower limit.

Continuous Annealing Step Continuous annealing requires an annealing temperature higher than the recrystallization temperature.
If the annealing temperature is too high, the crystal grains become coarse and the surface roughness after processing becomes large, so it is preferable to set the upper limit to 750 ° C.

Conditioned rolling Conditioned rolling (SR, Single Reduce Roll)
(abbreviation of "ring") is suitable in the range where the elongation is in the range of 0.5 to 2.0% because the occurrence of stretcher strain is prevented.

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 becomes high in strength, which causes difficulty in can forming. 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 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 foil, and those obtained by subjecting these steel sheets to surface treatment. In particular, an electrolytic chromic acid-treated steel sheet or ultra-thin tin-plated steel sheet having a two-layer structure in which the lower layer is metallic chromium and the upper layer is chromium hydrated oxide,
A nickel-plated steel sheet, a zinc-plated steel sheet, and a steel sheet obtained by subjecting these plated steel sheets to a surface treatment having a two-layer structure of chromium hydrate oxide or an upper layer of chromium hydrate oxide and a lower layer of a metal chromium layer Excellent contact.

Average Crystal Grain Size Identification of the crystal grain size will be described with reference to FIGS. 1 and 2. FIG. 1 shows the relationship between the average crystal grain size and the surface roughness of the can side wall after the can manufacturing process. It can be seen from FIG. 1 that when the average crystal grain size becomes large, the surface roughness of the surface after the can manufacturing process deteriorates. When the average crystal grain size exceeds 6 μm, the surface roughness is deteriorated, and the appearance and properties of the can are impaired. Therefore, the average crystal grain size should not exceed 6 μm. Further, FIG. 2 shows the relationship between the average crystal grain size and the corrosion resistance. It can be seen from FIG. 2 that the corrosion resistance is good in the range where the average crystal grain size does not exceed 6 μm. The corrosion resistance was evaluated as follows. After the can-making process, the can was heat-treated at 130 ° C. for 20 minutes, filled with water, and visually evaluated for the degree of corrosion (blackening) of the inner surface of the can after 37 ° C. and 2 weeks.

[0015]

[Table 1]

[0016]

[Table 2]

Evaluation Examples Nos. 1 to 7 of the present invention are within the ranges of the components of the present invention.
It has been subjected to continuous annealing, has a crystal grain size of 6.0 μm or less, and has excellent surface roughening properties, corrosion resistance, and workability. Comparative Examples Nos. 8, 8 and 9 are inferior in surface roughening and corrosion resistance because the crystal grains are large because box annealing is performed. Comparative Examples Nos. 10 and 10 have a small amount of C and large crystal grains, and thus have poor surface roughness and corrosion resistance. Comparative examples No. 11, 12, 1
In No. 4, Nb was not added, so that the particles were not made fine and the surface roughness and corrosion resistance were poor. Comparative Example 13 has a large amount of C and is inferior in workability. The surface roughness 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. Ra of 1 μm or less is ◎ (best), 1 to 1.5 μm is ○ (good), 1.
5 to 2 μm was evaluated as Δ (slightly defective), and 2 μm or more was evaluated as × (defective). The corrosion resistance was evaluated by visually inspecting the degree of corrosion (blackening) on the inner surface of the can after heat treatment at 130 ° C. for 20 minutes, filling with water after forming for 2 weeks at 37 ° C. after forming a thin-walled deep-drawn can. . ◎ If the surface is not blackened at all
(Best), the degree of blackening is minute (good), the degree of blackening is small (diameter 5 mm or less) is Δ (somewhat bad), and large (diameter 5 mm or more) is x ( It was evaluated as (defective). The workability was evaluated by increasing the wrinkle holding pressure during the forming of the thin-walled deep-drawing can and evaluating the size of the wrinkle holding pressure before breaking. A crushed product with a wrinkle holding pressure of 5 tons or less was rated as Δ (somewhat poor), a crushed product with 5 to 7 tons was rated as ◯ (good), and a product crushed with 7 tons or more was rated as ◎ (best). did.

[0018]

EFFECTS OF THE INVENTION According to the production method of the present invention, a steel plate suitable for use in thin-walled deep-drawing cans, which has excellent surface roughness and corrosion resistance, does not cause crushing during continuous high-speed can manufacturing, and has excellent processability Can be provided. The steel sheet provided by the production method of the present invention can be used alone as a steel sheet for use in a can.
It can also be used as FS, nickel-plated steel plate, etc. Further, these surface-treated steel plates may be coated with a resin film such as polyester. Also, a steel sheet coated with a paint such as epoxy can be applied to a thin-walled deep drawing can application.

[Brief description of drawings]

FIG. 1 shows the relationship between the average crystal grain size and the surface roughness of a can side wall after can manufacturing.

FIG. 2 shows a relationship between average crystal grain size and corrosion resistance.

Claims (4)

[Claims] 1. C: 0.01 to 0.08%, 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 0.02%, the hot rolled steel sheet consisting of balance Fe and unavoidable impurities is cold rolled, continuously annealed, and has an elongation of 0.5 to 2.0%. A steel sheet suitable for use in a thin-walled deep-drawing can, which is subjected to temper rolling in order and the crystal grain size after the temper rolling is 6.0 μm or less. 2. C: 0.01 to 0.08%, 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 0.02%, the hot-rolled steel sheet consisting of balance Fe and unavoidable impurities is sequentially subjected to cold rolling, continuous annealing, and DR rolling with a reduction rate of 20 to 50%. A steel sheet suitable for use in thin-walled deep-drawing cans, which has a crystal grain size of 6.0 μm or less after the DR rolling. 3. C: 0.01 to 0.08%, 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 0.02%, the hot rolled steel sheet consisting of balance Fe and unavoidable impurities is cold rolled, continuously annealed, and has an elongation of 0.5 to 2.0%. A method for manufacturing steel sheets suitable for thin-walled deep-drawing can applications, in which temper rolling is performed sequentially. 4. C: 0.01 to 0.08%, 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 0.02%, the hot rolled steel sheet consisting of the balance Fe and unavoidable impurities, cold rolling, continuous annealing, DR rolling with a reduction ratio of 20 to 50%,
A steel plate manufacturing method suitable for thin-walled deep-drawing can applications that is performed sequentially.