JPH054300A - Steel sheet for can superior in di processability - Google Patents

Abstract

PURPOSE:To obtain a steel sheet for a can superior in DI processability. CONSTITUTION:The surface of a steel sheet where undulation Wca of the surface of the steel sheet is not exceeding 0.5mum and at least 10.5 in by crystalline' grain number is coated with one kind out of Sn, Sn-Cr alloy and Sn-Ni alloy. Then the same can be made into such constitution also that the surface of the steel sheet is coated with an Sn-Fe alloy plated layer and its top layer is plated with Sn. Then it can be made into such constitution that the surface of the foregoing steel sheet is plated with an Sn-Cr alloy or an Sn-Ni alloy and its top layer is plated with the Sn. With this construction, corrosion resistance can be improved by one time coating, which can contribute to improvement in productivity and reduction of cost.

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 cans having excellent DI processability.

[0002]

2. Description of the Related Art As a method for improving the workability of a tin-plated steel sheet for DI processing, a technique has already been disclosed for improving the flange workability of the end portion of the DI processed product by reducing the amount of inclusions in the steel. There is. Further, a technique for improving the separability of a DI processed product from a tool by roughening the surface of a tin-plated steel plate, a tin-plated steel plate having no Fe-Sn alloy layer in the tin-plated layer, is used for DI processing. Techniques with improved lubricity are disclosed.

In the midst of such technological progress, the quality of tin-plated steel sheets for DI processing has been improved. However, compared to aluminum, there is a problem with the quality of DI processed products, and there is a strong demand for improvement. The biggest problem is that the outer surface is inferior in paint clarity and the inner surface is inferior in coating quality due to the low tin coverage of the inner and outer surfaces of the DI processed can,
There is a problem of elution of Fe into the contents. In the case of aluminum cans, since there is no such problem, the coating on the inside and outside of the can is done only once, whereas in the case of DI cans made of tin-plated steel plate, in order to solve this problem. , It is premised that the inner and outer surfaces of the can are painted twice. Such a difference is a major cause of the high cost of DI cans made of tin-plated steel sheets, and there is a strong demand for improvement in this respect.

[0004]

DISCLOSURE OF THE INVENTION The present invention is intended to provide a steel sheet for cans which is excellent in DI processability and which satisfies such requirements.

[0005]

The subject matter of the present invention is as follows. (1) The steel plate surface waviness Wca is 0.5 μm or less, and the grain size is 10.5 or more on the steel plate surface, S
A steel sheet for cans having excellent DI workability, which is coated with any one of n, Sn—Cr alloy, and Sn—Ni alloy.

(2) Steel plate surface waviness Wca is 0.5 μ
A steel sheet for a can having excellent DI workability, characterized in that the surface of a steel sheet having a grain size of 10.5 or more and a grain size of 10.5 or more is coated with a Sn-Fe alloy, and Sn is coated on the upper layer thereof. (3) The steel sheet for a can having excellent DI processability according to the above item 1, which is obtained by coating any one of Sn—Cr alloy and Sn—Ni alloy and coating Sn on the upper layer.

(4) A steel sheet for cans having excellent DI processability as described in any one of the above items 1, 2 and 3, characterized by being coated with 0.1 g / m ² or more of Sn. (5) 0.0% Sn-Cr alloy or Sn-Ni alloy
The can steel sheet excellent in DI processability according to any one of the above items 1, 3 and 4, characterized in that it is coated with 2 to 1.0 μm.

(6) The steel sheet for a can having excellent DI processability according to any one of the above items 1, 2, 3, 4 and 5, wherein a lubricating oxide film is formed on the uppermost layer. (7) The steel sheet for a can having excellent DI processability according to any one of the above items 1, 2, 3, 4, 5 and 6, which is subjected to a single coating process. Generally, the surface of tin-plated steel sheet has a mountain-to-mountain pitch of 10
The peak-to-peak pitch is 1 to 10 μm on the top of the undulation (Wca) of the order of 0 μm and the height of 0.1 to 1 μm.
It has a form in which fine peaks having a height on the order of 0.1 to 1 μm overlap. On the other hand, at the time of DI processing, such a steel plate is cut out into a circular shape, and a material to be processed is drawn into a relatively shallow cylindrical container, and then ironed to form a deep container by reducing the thickness of the side wall of the cylindrical container. . During this process, the surface of the work material undergoes complicated changes. That is,
During the drawing-ironing process, the ridges of the undulations existing on the surface of the work material before processing become higher during the drawing process, and are gradually smoothed during the ironing process, and the entire surface becomes a mirror surface. In this process, since the ridges of the undulations are in direct contact with the tool surface, large deformation is locally applied in a high surface pressure state. for that reason,
The soft tin layer on the surface of the undulations is destroyed, exposing the base metal. Regarding the degree of exposure of the ground iron, the higher the undulations, the higher the surface pressure generated by the tool contact, and therefore the exposure of the ground iron becomes more remarkable. Therefore, the lower the peak height of the surface waviness, the more effective.

Therefore, in order to secure a tin coverage of 100% after DI processing under the processing degree of an industrially manufactured DI can, Wca is 0.5 μm or less and the grain size number is 10. It was found to be difficult unless it was 0.5 or more.
That is, a mountain with a high swell with a Wca of more than 0.5 μm is D
When the mountain is crushed during the I machining, the deformation resistance is high (the surface pressure is also high), the deformation amount is large, and the plated metal may be cut off, which is not preferable.

If the grain size number is less than 10.5 and the grain size is large, the surface roughness (Ra) after DI processing becomes large, which adversely affects the surface gloss and the like. As for the upper limit of the grain size, in the production on an industrial scale, the grain size number of 13 is advantageous in terms of productivity and the like. Next, the aspect of the metal with which the surface of the steel sheet is coated will be described. Sn, Sn-Cr, Sn-Ni
The DI processability can be improved by plating any one of the above. In the case of Sn, the thickness is 0.1 g / m
² or more (upper limit may be in a general range, for example, 5.6 g
/ M ² ), in the case of the Sn alloy plating, the thickness is 0.02
.About.1.0 .mu.m is sufficient, and Sn is more than 5% as an alloy.
The rest may be other metals.

In the Sn-plated steel sheet, since the waviness (Wca) is as low as 0.5 μm or less as described above, there is no local ridge deformation, and the solid lubricating action of Sn effectively acts, and the ground by DI processing is effective. It is possible to reliably prevent the exposure of iron. In addition, in Sn-Cr or Sn-Ni alloy-plated steel sheets, the relatively hard alloy plating layer suppresses local peak deformation, and barely exposes the base steel at the ridge of the undulation, and solid lubrication is possible. It also works effectively.

Further, Sn--Fe alloy plating is applied, and Sn plating is generated on the upper layer thereof, whereby the upper Sn layer is formed.
Due to the solid lubricating action of and the hard Sn-Fe alloy layer of the lower layer, Sn destroyed in DI processing is replaced with Sn-F of the lower layer.
The presence of the e-layer suppresses the exposure of the ground iron. Further, the hard Sn-Fe layer can surely prevent defects caused by foreign matter during processing.

Also, when Sn plating is applied to the upper layer of the Sn-Cr or Sn-Ni plating layer, the same effect as above can be obtained. In addition, by applying Sn—Cr or Sn—Ni alloy plating to the upper layer of the Sn plating layer, hard Sn—Ni and Sn—C with high deformation resistance of the upper layer are formed.
The r layer suppresses local deformation of high swell mountains,
When the hard plating breaks, the underlying steel can be reliably prevented from being exposed by the solid lubricating action of Sn in the lower layer.

As a lubricating oxide film on the uppermost layer of the plating layer as described above, for example, a chromium oxide film, a tin oxide film, a phosphoric oxide film or the like is 0.01 to 1000 mg / m ² (converted to the amount of metal in the oxide film). By generating the DI, the DI processability can be further improved. The plated (surface-treated) steel sheet of the present invention having such a structure does not expose the base metal due to DI processing, and the conventional double-coating coating can ensure sufficient corrosion resistance by the single-coating coating. And contributes to cost reduction.

[0015]

EXAMPLES Next, examples of the present invention will be given together with comparative examples.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3]

[0019]

[Table 4]

[0020]

[Table 5]

[0021]

[Table 6]

[0022]

[Table 7]

[0023]

[Table 8]

Note 1) Tin-plated steel plate: plate thickness 0.240 m
m, original plate before plating is normal Al-k steel T4CA material. Note 2) The Sn-Fe alloy layer in the plating layer is processed by heat treatment after Sn plating. The Sn-Cr and Sn-Ni alloy layers were formed by electroplating. Note 3) The processing conditions for DI cans are as follows.

(1) Blank diameter of molding material: 140φ (2) 1 drawing ratio (blank diameter / punch diameter): 1.6 (3) 2 drawing ratio (punch diameter ratio of 1 and 2 drawing): 1.3 (4) 1 Ironing amount (sheet thickness reduction rate): 20 (%) (5) 2 Ironing amount (sheet thickness reduction rate): 30 (%) (6) 3 Ironing amount (sheet thickness reduction rate): 40 (% ) Note 4) Definition of Sn coverage on the side wall of the DI can (1) Measurement site: A part corresponding to 1/2 of the can height (2) Measurement method: EPMA line analysis measurement distance: 1.0 mm Measurement conditions: Acc. V = 15 KV, S.I. C. = 0.0
15 μmA, 100 μm / min, Lα = F. S5kcp
s (3) Evaluation method: Ratio (%) of the portion where the analysis intensity of Sn is 1500 CPS or more in all the measurement distances Note 5) Evaluation of mold biting: After DI processing, the outer wall of the can is visually observed, The case where linear flaws were observed was defined as scoring. Note 6) Surface waviness (Wca): What is defined in JIS-B0610. Note 7) Crystal grain size number of plating original plate: JIS G 055
2 (cutting method). Note 8) Can coating conditions (1) Single coating External coating: White ink normally used for 2-piece cans (30 mg / dm ² ) Internal coating: Epoxy phenol resin (180 mg coating)
/ Dm ² ) The baking condition was 200 ° C. × 10 minutes.

(2) Two-time coating outer surface coating: The lower layer was a white coat (adhesion amount: 30 mg / dm ² ) usually used for two-piece cans, and white ink was coated thereon. Inner surface coating: lower layer is epoxy phenolic resin (adhesion amount is 120 mg / dm ² ), and baking condition is 200 ° C. × 10 minutes.

The upper layer was also the same. Note 9) Evaluation method of image clarity on the outer surface of the can: L value measurement on the coated surface. The conditions equivalent to the two-time coating conditions were marked with ◯, those exceeding them were marked with ⊚, and those less than them were marked with x. Note 10) Evaluation method of corrosion resistance on the inner surface of can: 1.5% NaCl +
Immerse in a 1.5% citric acid aqueous solution and measure the amount of eluted Fe. The conditions equivalent to the two-time coating conditions were marked with ◯, those exceeding them were marked with ⊚, and those less than them were marked with x.

[0028]

According to the constitution of the present invention, in a DI can made of a tin-plated steel sheet as a raw material, the tin coverage after DI processing is greatly improved, which has been impossible in the past with a tin-plated steel sheet. A coating method can be applied. As a result, the tin-plated steel plate can be coated once, like the aluminum plate, to ensure the painting clarity of the can appearance and the corrosion resistance quality of the inner surface of the can. Further, when the steel sheet having the constitution of the present invention is used for the current two-time coating, the effect of improving the corrosion resistance on the inner surface and improving the clarity of the outer coating was confirmed. Further, the present invention has excellent effects such as effectively functioning as a countermeasure against die galling, thinning of tin plating, or countermeasures against wear of DI molding tools due to increased can production speed.

Claims (7)

[Claims] 1. A steel plate surface having a steel plate surface waviness Wca of 0.5 μm or less and a crystal grain size of 10.5 or more is coated with any one of Sn, Sn—Cr alloy and Sn—Ni alloy. Steel sheet for cans with excellent DI processability, which is characterized by 2. A steel sheet having a surface waviness Wca of 0.5 μm or less and a grain size of 10.5 or more in grain size is coated with an Sn—Fe alloy, and an upper layer thereof is coated with Sn. Steel sheet for cans with excellent DI processability. 3. The steel sheet for a can having excellent DI workability according to claim 1, wherein any one of Sn—Cr alloy and Sn—Ni alloy is coated, and Sn is coated on the upper layer thereof. 4. The steel sheet for a can having excellent DI processability according to claim 1, wherein Sn is coated in an amount of 0.1 g / m ² or more. 5. A can having excellent DI processability according to claim 1, wherein the Sn-Cr alloy or the Sn-Ni alloy is coated with 0.02 to 1.0 μm. steel sheet. 6. The steel sheet for a can having excellent DI processability according to claim 1, wherein a lubricating oxide film is formed on the uppermost layer. 7. The can steel sheet excellent in DI processability according to any one of claims 1, 2, 3, 4, 5 and 6, characterized by being applied once.