JPH01180966A - Surface treated steel sheet for two-piece can - Google Patents

Abstract

PURPOSE:To obtain a surface treated steel sheet for a two-piece can having superior corrosion resistance under a paint film by successively forming a plating layer by electroplating and a plating layer of Al, Cr, Ni, Sn, etc., by a dry process on both sides of a steel sheet and further forming a lubricative coating film on the upper plating layer on one side. CONSTITUTION:A plating layer composed of metallic Cr+Cr oxide hydrate, metallic Ni, etc., is formed on both sides of a steel sheet by electroplating in about 0.001-10mum thickness. A single plating layer of a metal such as Al, Cr, Ni or Sn or an alloy based on such metals is then formed on the plating layer by a dry process. The pref. thickness of the upper plating layer is about 0.001-10mum. A surface treated steel sheet maintaining superior corrosion resistance under a paint film even after DRD or DI forming, having satisfactory strippability and causing no galling is obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a surface-treated steel sheet used in cans for filling beverages, food, etc., and two-piece cans made integrally with can bodies and can bottoms. .

[Prior art] Food cans and beverage cans are made of tin-plated steel sheets or tin-free steel (
Depending on the structure of the can, there are three-piece cans and two-piece cans. Three-piece cans are made by processing and molding the can lid, can body, and can bottom separately, and then joining these together by soldering, welding, rolling, etc., and two-piece cans are made by molding the can lid, can body, and can bottom separately, and two-piece cans have the can body and can bottom assembled together. It is molded in one piece and has a can lid attached to it.

Two-piece cans have no joints on the can body, and the seal is better when a can lid is attached, so in recent years there has been a shift from three-piece cans to two-piece cans. For such two-piece cans, DRD (drawing and redra) is used, which uses a can body manufactured by drawing two or more times.
wing) Can and a circularly punched metal plate are squeezed with force Roe (
The method of ironing is to form a cup into a cup shape by cirawing, then pass the cup through ties, and iron the body between the outer tie and the inner punch to increase the body length without reducing the board thickness. DI (drawing industry) using can bodies manufactured by
There are also ronin g) cans. When integrally molding the can body of these two-piece cans, very severe workability is required, and particularly severe conditions are imposed on the plating coating of the surface-treated steel sheet. Further, as can be seen from the above explanation, the processability of DI cans is more severe, so DI cans will be explained below.

DI cans made by DI molding have no joints on the can body, and there are fewer joints than three-piece cans, so the manufacturing process is simplified, the possibility of leakage of can contents is extremely small, and the body wall is It is thin, durable, and lightweight. DI cans have the above-mentioned advantages, especially surface-treated steel sheets such as Aluminum 11
In addition to being cheaper than sheets, it is expected that its use will expand in the future. However, with tin-plated steel sheets and tin-free steel sheets that have been conventionally used as can materials and closures, DI forming inevitably reduces the anti-corrosion performance of the plating film. That is, the tin plating layer is made by electroplating using an aqueous solution, and since tin is expensive, in order to obtain a uniform coating with a small amount, this electrodeposited coating is melted once by heating (
reflow). At this time, the steel plate and tin react, forming a hard and strong tin-iron alloy layer at the boundary between the steel plate and the tin plating layer.

During DI molding, especially when using ironine, this alloy layer is damaged and cracks form in the plating film, resulting in a decrease in anticorrosion performance.

Even if the inner surface of the can is coated and used as is, the corrosion resistance of the coating will be poor, and Fe ions will be eluted into the beverages and foods contained within the can. For this reason, after DI forming, tin-plated steel sheets must not be subjected to sealing treatment, which uses a phosphate treatment solution to cover defective areas with a phosphate film; this process is performed after forming, so there is no loss due to this process. I can only ignore the increase from 1. Tin-free steel has a chromium hydrated oxide film on the chromium plating layer electrodeposited from an aqueous solution, but the plating layer is hard and, like tin-plated steel sheets, film defects occur during DI forming. . To compensate for this, attempts have been made to coat both sides with thermosetting paint to compensate for the lubricating effect and the decrease in corrosion resistance on the paint film (for example, see Japanese Patent Application Laid-Open No. 55-82797). However, the corrosion resistance on the paint film is not sufficient, and when ironing, the can body sticks to the punch due to the paint film, requiring a force greater than the strength of the can body to pull out the punch, and curling occurs at the mouth end of the can body. It also had drawbacks such as being prone to so-called roll hacks. In addition, during forming, the steel plate is pressed down to a predetermined thickness by a die, which causes jamming between the steel plate and the die, which not only causes defects but also shortens the life of the die. , tin-free steel has not yet been put into practical use.

[Problem to be Solved by the Invention J] As mentioned above, conventional surface-treated steel sheets by electroplating require DI forming (seal link treatment) or tinting, unlike tin-plated steel sheets. Even if painted like free steel, the corrosion resistance on the paint film is insufficient, and excessive force is required to pull out the punch (hereinafter, the ease with which the punch can be pulled out is referred to as stripping ability), resulting in roll hacking. The life of the die was shortened due to jamming during molding.

In order to solve these problems, this invention has been made to maintain corrosion resistance on the coating film even when D&I molding is performed as well as DRD molding, and has good stripping property and no clogging. The purpose is to provide a surface-treated steel sheet that does not generate

[Means for Solving the Problems] In order to achieve the above object, the surface-treated steel sheet of the present invention has an electroplating layer on the surface of the steel sheet, and a layer of AI, Cr, Ni, etc. on the surface of the steel sheet.
It has a plating film consisting of a single plating layer formed by a tri-process of a metal selected from Sn or an alloy whose main component is these metals, and one side has a lubricating coating on this plating film. So. In this case, it is preferable that the plating film satisfy the following conditions.

(a) The electroplating layer should be [metallic Cr+Cr hydrated oxide] (hereinafter referred to as Cr+Cr0X) or metallic Ni.

(The thickness of the electroplated layer on the target is 0001 μm to 10 μm.

(c) The plating layer is 0.001μ thick by the try process.
m to 10 μm.

(d) Additive metal or Mg in the alloy plating layer.

Consists of one or more metals selected from Mn, Zn, Fe, Cu, Cr, Ti, and Si.

An electroplated film cannot withstand DRD molding or DI molding. On the other hand, a plating film produced by a dry process has good workability. By forming a thin film on top of the electroplating layer using the trial process, it is possible to reduce the corrosion resistance of the electroplating layer, which is economical and has a well-established mass production technology.For two-piece cans that can withstand DRD and DI forming. It is possible to obtain surface-treated steel sheets. Electroplated coatings that can be used in such applications include tin-free steel and N1 plated steel sheets. If the thickness of the plating layer of these electroplated steel sheets is less than 0,001 μm, the corrosion resistance will be insufficient, and if it exceeds 10 μm, the corrosion resistance will not improve at the rate of increase in thickness, and on the contrary, it is not practical from an economic standpoint. . Therefore, the thickness range of the electroplated layer is preferably 0.001 .mu.n1 to 10 .mu.n1.

Further, the plating layer formed on the electroplating layer by the try process is as follows.

Metals such as Al, Cr, Ni, and Sn, or alloys containing these as main components, all exhibit excellent corrosion resistance in the environments inside and outside the can. Therefore, do these plating films have good corrosion resistance?Are there any differences in physical properties between films made by trial processes such as ion plate ink or vacuum evaporation and films obtained by other methods? comes to life.

For example, hot-dip plating may be considered as another plating method for A1 or Sn, but this method inevitably generates a hard and brittle alloy layer between the steel sheet and the plating layer formed on it. As mentioned above, it causes cracks to occur in the DI molding-plating film. In addition, Cr, Ni, etc. are generally electroplated using an aqueous solution, or in the case of electroplating,
The plating film becomes hard and brittle due to hydrogen generated at the cathode penetrating or adsorbing into the film. In the case of Cr, the hardness is measured to be as high as 500 on the Wickers scale, or around 70 for a coating made by the tri-process, and even in the case of N1, the tri-process plating coating has a hardness of 300 compared to the electroplating coating. It is around 40. The film formed by the try process is very soft. In the trial process, metals or alloys are precipitated in a vacuum, so unnecessary elements are not forced to be placed, and a film is formed with only the necessary elements in a stable position and arrangement of energy. . For this reason, not only single-component plating but also alloy plating, which is difficult with electroplating, can be easily performed, and a soft and malleable coating can be obtained. In addition, with electroplating, the film is grown epitaxially, and the roughness of the film surface is directly affected by the fineness of the substrate, but with dry process, it is not affected and a unique smooth surface can be obtained. It is also possible to obtain desired surface properties by controlling the growth and structure of the film. If a dry process plating layer with such characteristics is placed on top of the electroplating layer, it will not undergo severe I-forming due to its excellent mechanical properties and smooth, controlled surface texture. It is also possible to maintain the corrosion protection performance before processing without damaging the coating.

=9- In this case, the thickness of the plating film must be at least 0001 μm, and if it becomes thinner, there is a risk that the plating film will not cover adequately.

Further, the thicker the coating, the higher the anticorrosion properties, but if the coating exceeds 10 μm, the effect tends to be saturated, and making the coating too thick is not practical from an economic standpoint.

The purity of the coating is of little concern; AI, Cr, Ni, S
n, Mg, Mn, Zn, Fe, Cu, Cr, Ti, Si
An alloy plating layer containing a selected metal may also be used. These metals are selected primarily in consideration of the chemical behavior of the contents of the can and the properties of other surface-treated steel sheets and metal sheets used in combination. Therefore, there are an infinite number of target metals and their combinations, and the ones described here are just a few.

In the present invention, a coated steel sheet has a lubricating coating on one side, and DI forming is performed so that the surface with the lubricating coating becomes the outer surface of the can. This allows the coating surface to come into contact with the tie during molding, resulting in the following effects. Ironine 2 requires a large amount of energy, or due to the friction and deformation caused by the strain, the contact surface with the tie converts into heat, softening the coating film, and acting as a softened coating film or lubricating film. At this time, it is necessary to maintain the state of the coating film as a continuous and uniform thin film without being separated. For example, a lubricating coating film that meets this condition is disclosed in JP-A-62-275172. There is.

[Example of the invention] Electroplating was applied to both surfaces of a cold-rolled steel sheet, plating was applied by a try process on top of that, and a lubricating paint was further applied to one side, which was subjected to DI molding, and the conditions during molding and molding were performed. The corrosion resistance of the can bodies was investigated. At the same time, we compared bamboos with electroplating, those without paint, and conventional techniques.

These results are shown in Table 1, and the details of the test materials and tests are as follows.

(Electroplating conditions) After cleaning both surfaces of a low carbon cold rolled steel sheet with a thickness of 03 mm by ordinary electrolytic degreasing and electrolytic pickling, the steel sheet was used as a cathode and plated in an electrolytic chromate treatment solution [CrO2: 1
50g/l, Na2S○4Q, 3g/l
, N H4F: 5 g/1] to form a metallic Cr layer and a Cr hydrated oxide layer, thereby obtaining tin-free steel. In Example 1, 002 μn1 of Al was applied on tin-free steel with a coating thickness of 003 μm, and in Example 2, Al-Mg alloy (Mg2.4
%) to 0.02 μn1, and in Example 3, N1 was plated to a thickness of 0.02 μm on tin-free steel by ion plating. In each case, a lubricating coating was applied only to one side. The ion plate ink was prepared as follows.

(Conditions for ion plating) After preheating in air at 200° C. for 110 seconds, plating was immediately performed under the following conditions.

Degree of vacuum: 6×1 O−6 Torr Substrate temperature: 200° C. Evaporation method: Distance between electron beam heating substrate and melting point: 50 cm Bias voltage: 500 V Ionization voltage: 25 V In Example 4, a Ni electroplated steel plate was obtained under the electroplating conditions shown below.

(Electroplating conditions) Using a low carbon cold-rolled steel sheet with a thickness of 0.3 mm, after electrolytic degreasing and electrolytic pickling on both sides, the steel sheet was used as a cathode in a normal nickel plating bath [nickel sulfate, 240 g/l, Nickel chloride 450g/l, boric acid 30g/l, tartaric acid: 30g/l, ammonium fluoride 15g/l]
Inside, a metal nickel layer of 100 mg/m 2 was formed on both sides of the steel plate at a liquid temperature of 50° C. and a current density of 10 ASD.

Cr was vacuum-deposited to a thickness of 0.02 μm on the N1 electroplated steel sheet. A lubricating coating was applied to one side.

Vacuum deposition was performed under the following conditions.

(Conditions for vacuum evaporation treatment) Degree of vacuum: 6 x 10'-6 Torr Substrate temperature: 200'C = 13- Evaporation method: Electron beam heating substrate - distance W: 50 cm Comparative example 1 is made of tin-free steel (Cr+Cr0X) The electroplating layer is shown, and Comparative Example 2 is the same as Example 4, with a Ni and Cr plating film, or a lubricating film was not applied.

Prior art example 1 used a tin-plated steel plate. The conditions for tin plating are as follows.

(Conditions for tin plating) A low carbon cold rolled steel plate with a thickness of 0.3 mm was used, and after electrolytic degreasing and electrolytic pickling on both sides, the steel plate was used as a cathode in a normal ferrostane plating bath [Sn''-30g/l. , free acid 15 g/I (calculated as sulfuric acid, ENSA: 5 g/L), at a liquid temperature of 40°C and a current density of 10 A SD. Tin plating layers of 0.56 m g/m 2 were formed on both sides of the D-'C' steel plate. In Conventional Example 2, a lubricating coating film was applied to both sides of tin-free steel.

The lubricating coating film was prepared by baking at 205°C for 10 minutes using a chlorinated chloride orcanosol paint containing a Teflon-modified polyethylene wax as disclosed in JP-A No. 62-275172. Thickness 50um
It was made into a coating.

In DI molding, the sample material is punched into a disc with a diameter of 123 mm, which is then molded into a cup with an inner diameter of 72 mm and a height of 36 mm using a commercially available cupping press.
Insert it into the machine, circulate the coolant at 40℃, Bonchi Speed F 30 m/min, stroke 600mm
Then, retro-processing and three-stage iron nink processing were performed. The molded can body has an inner diameter of 52 mm and a height of 130 mm, and the thickness of the can body is about half of the original. The molded can body is degreased and cleaned, and the outside surface is coated with 250 mg of Hinyl modified alkyd resin per can.
A copolymer resin paint of hinyl chloride, hinyl acetate, and maleic acid was applied to the inner surface at an amount of >250 mg per can and subjected to the above test.

Formability was calculated by determining the energy required for forming from the forming load and displacement amount. The smaller the molding energy, the better the moldability. Stripping property was evaluated based on the force required to pull the punch out of the molded can body. The smaller the force, the better the stripping property.

Corrosion resistance evaluation was conducted using UCC for the purpose of controlling under-coating corrosion resistance.
The test was conducted by FFC test and IPV test.

The UCC test is a test that examines the corrosion resistance under the coating on the inside of the can.
Cut out the specimen with the above coating film to a size of 50 mm x 70 mm, cut a cross cut into the coating film that reaches the substrate, and seal the back side and edge portions that are not subject to the test. After immersing it in a corrosive solution for 96 hours, a tape was attached to the coating surface and removed, and the corrosion width and peeling status of the coating were observed. The corrosive liquid is citric acid 1
5% and 1.5% sodium chloride at 35°C.

The FFC test targets the outside surface of the can, and a specimen prepared in the same manner as the UCC test is exposed to salt water spray at 35°C for 1 hour, then washed lightly with running water, and then exposed to a temperature of 45°C at a relative humidity of 85%.
The specimens were exposed to a constant temperature environment at a high temperature of 10°C for 10 days, and the width and length of the filamentous corrosion that had occurred was observed.

The IPV test measures the amount of iron dissolved from the can material into the contents of the can, and the can is filled with Coke 250-3.
After being stored at 8°C for 6 months, the eluted Fe ions were quantified.

As shown in Table 1, the molding energy of the Examples was small, the stripping property was good, the plating film was not damaged because the molding was smooth, and the corrosion resistance was good on both the inner and outer surfaces. On the other hand, Comparative Example 1 of electroplating layer thickness is UCC
Test results and IPV test The corrosion resistance under the coating is poor in terms of the test results. In Comparative Example 2, which did not have a lubricating coating film, jamming occurred between the tiles and the molding energy. In a comparison between the conventional example and the example of the present invention, all test items are superior to either the example or the conventional example.

Table 1 In the above examples, the alloy plating layer was A I -Mg, Al
- Does the case of Ti or other Mn, Mn, F
It goes without saying that similar effects can be obtained in the case of an alloy plating layer made of a metal selected from E, Cu, Cr, and Si.

[Effects of the Invention] As described above, the surface-treated steel sheet of the present invention has a soft, malleable and smooth plating layer formed by the try process on the electroplating layer, and a lubricating coating layer on top of the electroplating layer. It has a membrane. For this reason, even if subjected to severe I-forming, the coating will be damaged.It maintains sufficient corrosion resistance even after molding, and also eliminates unnecessary force during molding, so it is stable and does not cause accidents such as chewing or roll hacking. You will get a high quality product.

Further, there is no need to treat phosphates or the like after molding, which, combined with stable molding operation, reduces can manufacturing costs. As described above, the effects of this invention are significant and contribute to can manufacturing technology.

Claims (1)

[Claims] (1) On the surface of the steel plate, there is an electroplating layer and Al and Cr on it.
, Ni, and Sn, or a plating layer formed by a dry process of an alloy mainly composed of these metals, and one side has a lubricating coating on this plating layer. A surface-treated steel sheet for two-piece cans, characterized by having the following.