JPH0247048A - Sn-plated very thin steel plate excellent in flange workability and weldability - Google Patents

Abstract

PURPOSE:To improve flange workability and weldability inexpensively by limiting the components of a steel plate, performing Sn-plating on both sides of the plate, and making the Sn-loading on one side thicker than the one on the other side. CONSTITUTION:A steel plate contains by weight % 0.004% of less of C, 0.04% or less of Si, 0.05-0.3% of Mn, 0.02% or less of S, 0.02% or less of P, 0.02-0.15% of Al, 0.004% or less of N, 0.01% or less of Nb, and the balance of substantially Fe, as well as 0.12-0.18mm of thickness. Sn-plated layers having different loading amounts are provided on both side faces of the plate in such a manner that the Sn loading amount of one side face is 1.0-5.5g/m<2> and that of the other side face is 0.5-2.8g/m<2>.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention mainly relates to Sea 1. This is a Sn-plated ultra-thin steel plate with a thickness of 0.12 to 0.18 mm for food cans and beverage cans that are joined together by welding, and has improved flange workability and weldability.

<Prior Art> In recent years, seam welding has become widely used as a method for joining can holes, replacing the conventional solder joining method. The seam welding method is
5I because the lamp part is thinner than conventional soldered or adhesive cans.
It has advantages such as good liability and strong side seams.

The material for such welded cans has so far been the so-called Sn method, in which a low C material with a C content of 0.03 to 0.06% is continuously annealed and finished with a skin bath with a reduction rate of 2% or less. Steel plates with a thickness of 0.20 mm or more are used.

However, in the field of cans, especially beverage cans, there are many low-priced competing materials such as aluminum, plastic, and paper, and S
N-plated steel sheets are in a difficult position in terms of cost. Therefore, recently, attempts have been made to weld cans using ultrathin steel plates with a temporary P of 10.12 to 0.18+m, which are subjected to secondary rolling at a rolling reduction of 5 to 30% after annealing (DCR method).

However, these ultra-thin steel plates also have the problem that the heat-affected zone during welding of the side seam tends to crack when processing flanges to attach the top or bottom cover to the can body after the side seam. Therefore, a problem arose in that the appropriate welding current range (ACR) became narrow.

Flange cracking occurs because, in addition to the hardening of the material due to secondary cold rolling, the hardness of the side seam increases further due to the effects of heat during welding.

So far, welded cans using DCR materials have used box-annealed materials, which have less flange cracking than continuous-wire annealed materials. Since the hardness increase is small, it is thought that flange cracking is less likely to occur. However, compared to continuous annealing, box annealing requires a much longer annealing time and is not only less productive, but also has poorer uniformity in temporary material quality and flatness.

In addition, the seam welding method utilizes the heat generated by the electrical resistance of the steel plates to melt and join the steel plates, so if the plates are thin, the inside of the steel plates will melt from the time the steel plates begin to join, causing a splash. The current range up to this point becomes narrower. In other words, the appropriate welding current range becomes narrower, making welding difficult.

On the other hand, up until now, as an ultra-thin soft steel sheet for cans, C was 0.0
An aluminum-killed steel sheet with a trace amount of Nb added to less than 0.04% was proposed in Japanese Patent Application Laid-Open No. 197224/1982, but as welding machines have become faster and more diverse, it still has insufficient flange workability. Sn-plated steel sheets with weldability have not been obtained.

<Problems to be Solved by the Invention> The present invention is directed to S, which is low cost and can compete with other can materials such as aluminum, and which has excellent flange workability and weldability.
The present invention provides n-plated ultra-thin steel sheets.

Means for Solving the Problems> The present invention provides C: 0.004% or less, Si:
0.04% or less, Mn: 0.05-0.3%, S
: 0.02% or less.

P: 0.02% or less, AlO, 02-0.15%,
Contains N: 0.004% or less, Nb: 0.01% or less, and the remainder is substantially Fe.
Sn with different basis weights on both sides of a 0.1h+* steel plate
It has a plating layer, preferably the Sn basis weight on one side is 1.
．． 0 to 5.5 g/po, and the Sn basis weight on the other side is 0.
5 to 2.88/m2. This is a Sn-plated ultra-thin steel sheet with excellent flange workability and weldability.

<For production> First, the reasons for limiting the components of the steel sheet of the present invention will be discussed.

The reason why the CI is set to 0.004% or less is to improve the elongation of the steel plate and improve the flange workability.

The inventors of the present invention found that compared to c:o, o3~0.06%, which has been used for steel sheets for cans up to now, the 0.0.
It has been found that by setting the amount in the range of 0.004% or less, even an extremely thin steel plate can have good flange workability.

Regarding Si, Mn, S, N, and P, if these elements are present in large amounts, grain growth during continuous annealing is suppressed, which not only makes the plate hard but also inhibits the corrosion resistance of tinplate. . Therefore, it is better to have less < , Si
: 0.04% or less, Mn: 0.3% or less, S: 0
．． 0.02% or less, N: 0.004% or less, p:o
, oz% or less. However, Mn is zero in order to fix S, which causes embrittlement during hot rolling, as MnS.
．． It is necessary to contain 0.05% or more.

An appropriate amount of ^l is required to fix N as 8 lN and reduce solid solution N, but adding a large amount will increase the cost, so A should be 1.02% or more and 0.15% or less. .

Furthermore, the addition of a small amount of Nb completely fixes the solid solution C and N, reduces the in-plane anisotropy of the r value, and improves workability. However, adding a large amount increases manufacturing costs, so 0.01
% or less.

Now, in the present invention, Sn plating is applied to both sides of a steel plate, and the Sn basis weight on one side is made thicker than on the other side.
The so-called differential thickness is applied. The reason for doing this is that when the can body is constructed with the thicker side as the inner surface of the can, flange workability and weldability are very improved.

Of the two electrodes that sandwich the welded area during seam welding, the electrode on the inner side of the can has a smaller electrode ring diameter than the one on the outside of the can, and its ability to cool heat generated by resistance is smaller, so the inner side of the lap part is less affected by heat. The inventors have discovered that this difference in thermal influence causes a difference in hardness between the inner and outer surfaces of the lap part, which causes distortion during flange processing, which is a cause of flange cracking. did. Therefore, by increasing the Sn density on the inner surface of the can, which is in contact with the small-diameter electrode, than on the outer surface, and by reducing the resistance heat generation that occurs between the electrode and the inner surface of the can, it is possible to Since the difference is smaller, it is now possible to manufacture cans without cracking the flange.

In addition, when the plate thickness becomes extremely thin (about 0.12 to 0.18 mm), splash is likely to occur as mentioned above.Although welding was difficult, this splash often occurs on the inside of the can, so By increasing the Sn weight, it is possible to reduce the resistance heat generation between the temporary electrode and the inner surface, suppress the occurrence of splash, and widen the appropriate welding current range.
Commercial production became possible.

Further, the amount of Sn plating is preferably 0.5 to 5.5 g/%. If it is less than 0.5 g 10 r, not only will the corrosion resistance be poor, but the amount of metal Sn remaining after painting and *ing will be small, and weldability will also be poor. Also 5,5 B/n? This is because, if it exceeds this, the manufacturing cost will increase and the cost reduction which is the aim of the present invention will be hampered.

Furthermore, does making the Sn weight on the inside of the can twice or more than on the outside mean flange workability? It is more preferable from the point of view of 8-contact property.

Preferably, the amount of Sn on the inner surface of the can is 1.0 to 5.5 H/nr, and the amount of Sn crushed on the outer surface of the can is 0.5 to 2.8 g/r+? It is.

As described above, according to the present invention, it is possible to obtain a Sn-plated ultra-thin steel sheet that is very advantageous in terms of manufacturing cost and has excellent corrosion resistance, weldability, and flange workability.

<Examples> Next, the present invention will be specifically described based on Examples and Comparative Examples.

Other than C and Nb shown in Table 1, the components of aluminum-killed steel that is used as a steel plate for cans, namely Si:
0.04% or less 9Mn: 0.05-0.3%, S:
0.02% or less, p: 0.02% or less, 8f: o, 0
2 to 0.15%, N: Using a continuously annealed DCR material with a plate thickness of 0.12 to 0.1 hm adjusted to 0.004% or less,
After degreasing and pickling, Sn plating is carried out in a halogen bath.
Furthermore, reflow treatment was performed, followed by chromate treatment.
Examples 1 to 4゜Sn-plated ultra-thin steel sheets corresponding to Comparative Examples 1 to 5 were further coated with 0.07 g/bo N1 plating before continuous annealing, which is currently widely used as a thin coating. Other than that, Examples 5 to 7 were manufactured by the above method. Comparative Examples 6 to 7 Sn-plated thin steel sheets for cough guards were obtained.

The weldability, flange workability, and corrosion resistance of this Sn-plated ultra-thin steel plate were tested in the following manner.

Weldability welding? Using a copper wire of about 1.5m+aφ as the T-pole, the test material pieces were overlapped under constant pressure while moving the wire, and electric resistance welding was performed at a welding speed of 55m/min to ensure that the welded area was sufficient. The appropriate welding current range was determined based on the conditions that the welding strength is as high as 1, and no splash occurs.

Flange workability The can bodies subjected to the above welding were flanged, and the flanging workability was evaluated as follows based on the incidence of flange cracking.

Flange cracking incidence (ppm) evaluation: 1 to 100 △ 100 or more × Corrosion resistance (IEV) This indicates the degree of iron exposure. The larger the 6 values obtained by measuring the Tt flow value at that time, the larger the amount of iron exposure.

(ΔTC) The ATC value after baking at 210'CX for 20 minutes was measured on the inner surface of the can.

(Rust Resistance Test) The appearance of rust on the outer surface of the can after one week was observed using a dry-wet cycle tester, and the results were determined as follows.

Number of pieces requested (in 100c) 1 to 10 11 to 50 51 or more Comparative Example 1 has less 5nil on the inner surface, so there is no appropriate welding current range and the flange workability is not good.

Comparative Example 2 had poor flange workability because the steel contained a large amount of C and no Nb was added.

Comparative Example 3 has poor flange workability because Nb is not added to the steel.

Comparative Example 4 has poor flange workability due to a large amount of C in the steel.

Comparative Example 5 has good flange workability, but because the amount of Sn plating is small, there is no suitable welding current range and the corrosion resistance is poor.

Comparative Example 6 has a large amount of Cl in the steel and a small amount of Snl inside the can, so there is no suitable welding current range and the flange workability is poor.

In Comparative Example 7, the amount of Sn deposited on the inner surface of the can was small, so there was no suitable welding current range, and the flange workability was also slightly inferior.

In Examples 1 to 7, which satisfied the conditions of the present invention, there was a sufficient appropriate welding current range and no flange cracking occurred.

In particular, the amount of Sn plating on the inside of the can is 2 times the amount of Sn plating on the outside of the can.
In Examples 1 to 3.5 to 7, which were doubled or more, a wide appropriate welding current range was obtained even if the total amount of Sn on both sides was the same. In particular, in Examples 5 to 7, since the Ni diffusion plating treatment is performed, the appropriate welding current range is wider, and further savings of 5 nil can be achieved. By Ni diffusion treatment, free metal S
This is thought to be due to the increase in nl.

Further, in Examples 1 to 7, since C■ in the steel is small,
There are fewer pinholes in the plating, and Sn
It also has superior corrosion resistance compared to plated steel sheets.

<Effects of the Invention> According to the present invention, an ultra-thin steel plate with a thickness of 0.12 to 0.18 rrn is used for welded cans, which has excellent flange workability and weldability.
Plated ultra-thin steel sheets can be obtained at low cost, and they also greatly contribute to resource and energy conservation, so they have extremely high economic value.

Patent applicant: Kawasaki Steel Corporation

Claims (2)

[Claims] (1) C: 0.004% or less, Si: 0.04% by weight
% or less, Mn: 0.05-0.3%, S: 0.02% or less, P: 0.02% or less, Al: 0.02-0.15%
, N: 0.004% or less, Nb: 0.01% or less, and the remainder is substantially Fe, and has a thickness of 0.12 to 0.
An ultra-thin Sn-plated steel sheet with excellent flange workability and weldability, characterized by having Sn-plated layers with different basis weights on both sides of an 18 mm steel sheet. (2) Sn basis weight on one side is 1.0 to 5.5 g/m^
2. Sn basis weight on the other side is 0.5 to 2.8 g/m^2
The Sn-plated ultra-thin steel sheet according to claim 1, which has excellent flange workability and weldability.