JPH05346000A - Chromium plated steel sheet for welded can - Google Patents

Abstract

PURPOSE:To provide the beautiful and firm steel sheet for can barrel free from the contamination in the manufacturing environment and contents in the can and high in film adhesion in a welding touch-up coated zone by specifying the carbon content, the coating weight of a Cr plated layer and the surface roughness at a small level. CONSTITUTION:In the steel sheet, the carbon content is regulated to, by weight, <=0.2%. In this way, the workability and product strength are made easy to be balanced. Furthermore, on the surface, a metallic Cr layer of <=300mg/m<2> is formed, and below it, a hydrated Cr oxide layer of <=30mg/m<2> expressed in terms of the metallic Cr content is formed. In this way, sufficient film adhesion and corrosion resistance can be obtd. Moreover, the center line average roughness Ra at 1mum cut-off wave length of the Cr hydrated oxide layer at least per face is regulated to >=5nm. By controlling the coating weight of the Cr plated layer and the extremely small surface roughness into the ranges, the beautiful and film weld zone in which sufficient weldability can be secured without requiring pretreatment such as grinding on the zone to be welded prior to the weld zone.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel plate for producing a can body of a metal can used as a container by welding. More specifically, when the can body is formed by welding Cr-plated steel plates, it causes metal powder contamination of the can contents and the can making environment, and also improves the adhesion of the organic film applied to the can body by welding repair coating. Which can be a hindrance
It does not require mechanical pre-treatment such as mechanical grinding or chemical treatment of the steel plate for welding, has sufficient and sufficient strength of the welded portion, excellent paint adhesion and corrosion resistance, and is highly productive and economical. The present invention relates to a steel plate that can obtain a highly excellent can body.

[0002]

2. Description of the Related Art Gallon cans used for containers of oils and fats are
Although it is made using a Cr-plated steel sheet, conventionally, the Cr-plated steel sheet could not be welded as it is by a commonly used mash seam type can body welding machine (hereinafter referred to as “welder”). This is "Materials and Processes," Volume 4, Volume 1.
As described by the inventors on page 616, since the surface of the Cr-plated steel sheet is covered with Cr hydrate oxide exhibiting high electrical resistance, continuous welding is difficult with an AC power source seam welding machine. Is.

Therefore, in the past, when welding a Cr-plated steel sheet, a method of grinding and removing the surface of the welded portion immediately before the welding operation has been generally used. However, according to this method, there is a concern that the working environment is deteriorated by the grinding powder and the contents of the can are damaged due to the mixing of the grinding powder into the product can. Further, in many cases, it has been necessary to cut and remove a part of the steel sheet by so-called edge cutting of the ground portion after grinding due to a problem in controlling the width of the ground portion. This not only increases the number of processes, but also has a great adverse effect on the material yield directly.

Further, the ground iron is exposed in the ground portion, or the ground iron is further partially oxidized, and the adhesion of the coating film in the subsequent repair coating is
Not as good as Cr-plated steel. Therefore, even when repair coating is performed, problems such as peeling of the coating film and corrosion under the coating film are always included. In addition, as a matter of course, when the repair coating was not performed, the ground portion was corroded extremely quickly.

As an attempt to impart weldability to a Cr-plated steel sheet, a method of depositing a Cr-plated layer in a granular form or a Sn-plated layer on a Cr-plated steel sheet is known.

A method of improving weldability using a granular Cr layer is as follows.
The proposal is made by the inventors, for example, Japanese Patent Laid-Open No. 3-229897, etc., and this proposal is excellent in cost because it is composed only of a Cr plating step, that is, it does not require a separate treatment with a dissimilar metal. There is. However, the color tone is
In order to make it the same as the plated steel sheet, there was a constraint that the electroplating conditions had to be controlled as shown in the above proposal.

When Sn is deposited on the Cr plating, a special treatment is required to remove the Cr hydrate oxide layer, and the adhesion of the coating film on the Sn plating layer is likely to deteriorate. In addition, because of problems in quality control, it is not widely used in gallon can applications, which are often used in clear coating.

[0008]

DISCLOSURE OF THE INVENTION The present invention has the problems of the method of forming a can body by welding using the above-described conventional Cr-plated steel sheet, and more specifically, a can-making environment and a can due to scattering of grinding powder. An object of the present invention is to solve the problems such as contamination of the contents, to provide a steel plate capable of producing a can body capable of obtaining a highly reliable can body having high coating film adhesion in a weld repair coating part.

[0009]

DISCLOSURE OF THE INVENTION The inventors of the present invention have solved the problems of the conventional welding method by pre-grinding of the welded portion in a method of manufacturing a can body in which a can body is formed by welding using a Cr-plated steel sheet as a material. Therefore, the present invention has been accomplished by studying the relationship between the surface roughness of the steel sheet and the mash seam weldability.

That is, by using a steel sheet in which the carbon content and the adhesion amount of the Cr plating layer as well as the surface roughness at a level smaller than 1 μm, which has not been conventionally controlled, are used, a sound welded part appearance and a sufficient welded part appearance can be obtained. It has been found that it is possible to obtain a can body having both welding strength, excellent coating film adhesion, and corrosion resistance after coating.

Thus, according to the present invention, the carbon content of the steel sheet is 0.2% by weight or less, and the surface of the steel sheet is 300 mg / m 2.
^It has a metal chrome layer of ² or less, and further has a hydrated chromium oxide layer of 30 mg / m ² or less in terms of the amount of metal chrome, and cutoff of the hydrated chromium oxide layer on at least one side of the steel sheet. Center line average roughness Ra at a wavelength of 1 μm
Is 5 nm or more, and a Cr-plated steel sheet for a welding can is provided to achieve the above object.

When a mash seam welding machine is used to perform can body welding similar to tin plating using a Cr-plated steel sheet, the minimum welding current value at which joining at the material interface begins and the welded portion is melted and scattered. It was extremely difficult to obtain a sound welded part because the welding upper limit current at which a welding defect of so-called whisker-like projections, which is caused by rapid cooling, was generated, so-called splash, was extremely close to or reversed. The difference between the maximum value and the minimum value of the welding current is the weldable current range (ACR).
In the conventional Cr-plated steel sheet in which the r-plated layer was not precipitated in a granular form, this was very small or could not be obtained at all, and it was very unstable, so that it was not practical. Also,
If the Cr plating layer is granularly deposited, its metal C
The amount of deposited r and Cr hydrated oxides, the numerical range of the granular precipitated metal Cr layer, and the manufacturing method thereof were extremely limited.

Mash seam welding utilizes Joule heat generation due to the electrical resistance of the material interface as a heat source for the welding. Therefore, if the ACR of a certain material is very narrow, it will be different for each lot received in the welding process. Since the welding current and other welding conditions have to be changed, and the production equipment must be stopped during that time, it cannot be practically used for commercial production. This is the reason why materials with wide ACR are required. Here, the ACR of the material changes depending on the interfacial contact resistance between the materials to be welded and the accuracy of the overlap width of the weld overlapping portion.

Splash, which is the most important welding defect in mash seam welding and serves as an index for the upper limit of welding current during ACR determination, causes excessive heat generation by the welding current, causing the material near the weld interface to melt, and at that time The molten metal is extruded to the outside by the electrode pressure, etc., and is generated by rapid solidification. Due to the characteristics of the plating reaction, a Cr hydrated oxide layer having a high electric resistance is always present on the surface of the Cr-plated steel sheet, so that the interfacial contact resistance is higher than that of tinplate, and the The amount of heat generated increases. This means that in the Cr-plated steel sheet, a large change in the amount of heat generated occurs with a small change in the current value as compared with tinplate. In addition to this, the surface of the Cr-plated steel plate has larger friction than tin-plated steel plate such as tinplate,
The slipperiness with the jig is poor. That is, during the tubular molding prior to welding, the accuracy of overlap tends to vary due to the effect of being caught with the jig.

The inventors diligently studied the change in contact resistance due to the microstructure of the steel sheet peculiar to this Cr-plated steel sheet and the instability of the overlap width, and the adhesion amount of the Cr-plated layer on the steel sheet surface and its extremely fine By controlling the surface roughness within a certain range, the contact resistance values of the interface between the materials and the interface between the material and the electrode are stabilized in a state suitable for continuous welding,
In addition, it was found that the stability of the overlap width can be significantly improved, and practically sufficient weldability is ensured.
We succeeded in limiting the range of those numbers.

[0016]

[Structure] The structure of the present invention will be described in detail below.

The carbon content of the steel sheet of the present invention is 0.20% by weight or less, preferably 0.05% by weight or less, or low carbon steel or ultra low carbon steel (C <0.01% by weight). This is because it is easy to balance the workability and the strength of the product in this region as a material for cans, and Ys, Yp, r, Δ
This is a region in which mechanical properties necessary for forming a welding can body such as r can be stably obtained.

In the present invention, if it is possible to apply a predetermined Cr plating as the plated steel sheet original plate, for example, Ni plating is applied to the outermost surface of the steel sheet and then a Ni diffusion layer is formed by thermal diffusion treatment. It is also possible to use such a surface adjustment original plate, and similarly, between the Cr plating layer and the original plate, a metal such as Ni, Zn, Sn, or Fe or an alloy plating of these metals or an alloy plating of the metal and P or the like is simply used. It is also possible to insert layers or multiple layers.

The surface of the steel sheet in the present invention 300 mg / m ² or less, preferably the basis weight of the metal Cr layer of 30 to 200 mg / m ^2,
Further 30 mg / m ² or less of metal Cr terms thereon, preferably for the provision of the Cr hydrated oxide layer deposition amount of 2 to 20 mg / m ² is conventionally Cr-plated steel cans have been used applications In order to obtain sufficient coating film adhesion and corrosion resistance.

In the present invention, regarding the surface roughness of the steel sheet outermost layer plated with Cr, the center line average roughness Ra at a cutoff wavelength of 1 μm is 5 nm or more, preferably 10 nm.
It is 100 nm. In this area, when forming a can body using Cr-plated steel as a material, there is no need for pretreatment such as grinding of the welded part prior to the welded part, the splash of the welded part is minimal, and a beautiful and strong weld A part can be formed and sufficient strength can be obtained.

It is presumed that this is because the sliding property of the Cr-plated steel sheet with the jig in the welding machine is stable in this region, and the contact resistance value falls within the range suitable for mash seam welding.

As described above, in the present invention, based on the discovery of the fact that the surface microstructure of Cr-plated steel sheet influences the stability of the overlap as an important factor that determines the ACR together with the contact resistance, the surface microstructure is determined. It is limited by general roughness parameters.

As a method of measuring the roughness parameter specified in the present invention, a scanning probe microscope system such as a scanning electron microscope for three-dimensional shape measurement, a scanning tunnel microscope (STM), an atomic force microscope (AFM) ( SP
The method according to M) can be used. Specifically, Ra may be measured at a cutoff wavelength of 1 μm at arbitrary 5 points on the surface of the steel sheet, and all the measured values may be 5 nm or more.

For the steel sheet having such a roughness, the surface roughness of the temper rolling roll after annealing the cold rolled steel sheet is controlled within a certain range by controlling the grain size of shot blast and the laser surface processing pattern. Can be easily manufactured by a method such as controlling the chromic acid concentration in the chrome plating solution and the concentration of an auxiliary agent such as sulfuric acid, controlling the current density in the electrolysis operation, the electrolytic current waveform, the cathode-anode electrolytic pattern, etc. ..

The Cr-plated steel sheet as the material in the present invention may be any metal or non-metal other than Cr between the Cr-plated layer and the base steel sheet layer as long as it satisfies the performance suitable for the use as the can. Simple substance of element, multiple layers, alloy,
A dispersed plating layer or a diffusion layer of the iron layer and the surface Cr layer may be formed.

Regarding the coating of the uppermost Cr plating layer of the present invention to the upper layer, any surface treatment may be applied to the portion where direct welding is not performed. The parts other than the welded part may be painted or unpainted. The nature of the paint and the means of painting or coating may be of any kind.

[0027]

EXAMPLES The present invention will be described more specifically below based on examples.

Manufacturing method of can body Plate thickness 0.12 to 0.70 mm, carbon content 0.25 to
0.002% by weight of aluminum-killed cold-rolled steel sheet is plated with various amounts of deposited metal Cr and hydrated Cr, and an epoxy phenolic resin is applied to the inner surface of the can and an epoxy ester resin is applied to the outer surface of the can. Using a Cr-plated steel sheet coated with 60 mg / m ^2, a can body was weld-molded using a wire seamless welder manufactured by Sudronic. Table 1 shows the properties and welding conditions of the steel sheet.

[0029]

[Table 1]

[Table 2]

Evaluation Method The above cans were evaluated by the following methods.

Weldable current range: At various welding current values, the occurrence of splash in the weld, the determination of weld strength by peel (Hine) test, and the presence of cracks in the vicinity of the weld during flange forming of the welding can barrel Welding current range (ACR) is calculated by visual inspection, and the ratio of ACR to the welding current absolute value of the median value is calculated and 3%
The above was rated as good (⊚) and less than 3% was rated as bad (x).

Contamination of metal powder in the can: A cellophane tape having a width of 15 mm was applied to the left and right 4 cm of the center of the welded part in the can body after welding, and immediately peeled off.
Fe and Cr in the leachate were measured by putting in 50 cc of Cl and boiling for 10 minutes, and by atomic absorption analysis. When Fe or Cr exceeding the measurement limit was detected, it was evaluated as ×, and when not detected, it was evaluated as ⊚.

Salt spray test: Using a 5% NaCl aqueous solution, salt water is continuously sprayed on the weld repair coating part with a salt spray tester, and the red rust generation area is measured after 20 days, ± 20% of the numerical value of the reference example. Within, ○, over 20% ×,-
Those with less than 20% were evaluated as ⊚.

The above results are shown in Table 2. From this result, it is clear that the steel sheet of the present invention achieves the intended purpose.

[0035]

[0036]

EFFECTS OF THE INVENTION According to the present invention, there is no contamination of the can making environment and the contents of the can due to the scattering of grinding powder, and the coating adhesion of the weld repair coating part is high, and a highly reliable welded can body is manufactured. A Cr-plated steel sheet that can be used is provided.

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[Procedure amendment]

[Submission date] April 15, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction content]

Manufacturing method of can body Plate thickness 0.12 to 0.70 mm, carbon content 0.25 to
0.002% by weight of aluminum-killed cold-rolled steel sheet is plated with various amounts of deposited metal Cr and hydrated Cr, and an epoxy phenolic resin is applied to the inner surface of the can and an epoxy ester resin is applied to the outer surface of the can. Using a Cr-plated steel sheet coated with 60 mg / dm ^2, a can body was weld-molded using a wire seamless welder manufactured by Sudronic. Table 1 shows the properties and welding conditions of the steel sheet.

Front page continuation (72) Inventor Mori Tono No. 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Inside the Technical Research Division, Kawasaki Steel Co., Ltd. Kawasaki Steel Co., Ltd.Chiba Works

Claims (1)

[Claims] 1. A steel sheet having a carbon content of 0.2% by weight or less, and having a metal chromium layer of 300 mg / m ² or less on the surface of the steel sheet, and further having a metal chromium content of 30 mg / m ² or less on it. And a cutoff wavelength of the Cr hydrated oxide layer of at least one surface of the steel sheet.
A centerline average roughness Ra in μm of 5 nm or more is a Cr-plated steel plate for a welding can.