JPH05345998A - Chromium plated steel sheet for welded can - Google Patents

Abstract

PURPOSE:To provide the steel sheet for can barrel capable of obtaining a beautiful and firm welded can free from the contamination in the can manufacturing environment and can contents and high in film adhesion on the welding touch-up coated zone by specifying the carbon content in the steel sheet, the coating weight of a Cr plated layer and the surface roughness of the steel sheet. 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 an uppermost surface, a hydrated Cr oxide layer of <=30mg/m<2> expressed in terms of the metallic Cr content is formed, and below it, a metallic Cr layer of <=300mg/m<2> is formed. In this way, sufficient film adhesion and corrosion resistance can be obtd. Furthermore, the center line average roughness Ra in the case of 0.8mm cut-off wave length on the uppermost surface layer is regulated to 0.05 to 1.5mum, and in the case of 1mum cut-off wave length at least per face, Ra is regulated to >=5nm. By controlling the coating weight of the Cr plated layer and extremely fine surface roughness into the ranges, the objective beautiful and firm weld zone can be obtd. 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 of the inventors, for example, the one represented by JP-A-3-229897, etc., is that the proposal can produce a product only by the Cr plating step, that is, it does not require a separate treatment with a different metal other than Cr. Excellent in cost. But,
In order to make the color tone the same as that of a normal Cr-plated steel sheet, there was a constraint that the electroplating conditions had to be controlled as shown in the above proposal.

Further, when Sn is deposited on the Cr plating, a special treatment is required to remove the Cr hydrated oxide layer, and the adhesion of the coating film on the Sn plating layer is likely to deteriorate. Due to operational and quality control problems, 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 proposed a method for manufacturing a can body in which a can body is formed by welding using a Cr-plated steel sheet as a material, in order to solve the problems of the welding method by the usual pre-grinding of the weld portion. The present invention has been accomplished by studying the relationship between the surface roughness of steel sheets and mash seam weldability.

That is, the surface roughness of the steel sheet which has not been conventionally controlled from the viewpoint of the relationship between the carbon content, the amount of the Cr plating layer and the weldability is relatively macroscopic range and ultrafine range. It was found that a steel body having a sound welded part appearance, sufficient weld strength, and excellent coating film adhesion and post-coating corrosion resistance can be obtained by using the steel sheets which are controlled at the same time.

Thus, according to the present invention, the carbon content is 0.2% by weight or less, and the outermost surface layer has a metal Cr content of 3%.
Cr hydrate oxide layer of 0 mg / m ² or less, 300 mg / m underneath
^It has a metallic Cr layer of ² or less, and the center line average roughness Ra at the cutoff wavelength (Lc) 0.8 mm of the outermost layer is 0.05.
Provided is a Cr-plated steel sheet for welding cans, wherein Ra is 5 nm or more when Lc is 1 μm on at least one side of the steel sheet, in the range of up to 1.5 μm,
The above object is achieved.

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 electric resistance of the material interface as a heat source for the welding. Therefore, when the ACR of a certain material is very narrow, it is received in the welding process. Since the welding current and other welding conditions must be changed for each lot and the production must be stopped during that period, 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 overlap 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 sheet has a larger friction than the tin-plated steel sheet such as tin plate, and the sliding property 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 of low carbon steel or ultra low carbon steel (C <0.0
1% by weight). This is because the workability and the strength of the product can be easily balanced in this region as a material for cans, and the mechanical properties required for welding can body molding such as Ys, Yp, r, and Δr can be stabilized. This is the area that can be obtained.

Further, in the present invention, if it is possible to apply a predetermined Cr plating as the plated steel plate original plate, for example, the Ni diffusion layer is formed by thermal diffusion treatment after Ni plating is applied to the outermost surface of the steel plate. It is also possible to use such a surface adjustment original plate, and similarly, a single layer of a metal such as Ni, Zn, Sn, or Fe, or an alloy plating of these metals, or an alloy plating of a metal and P or the like is provided between the Cr plating layer and the original plate. Alternatively, a plurality of layers can be inserted.

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 cutoff wavelength (Lc)
The center line average roughness Ra at 1 μm is 5 nm or more, preferably 10 to 100 nm, and the cutoff wavelength (L
c) The center line average roughness Ra at 0.8 mm is 0.05 to
It is in the range of 1.5 μm, preferably 0.1 to 1.0 nm. In this area, when forming a can body using a Cr-plated steel sheet as a material, pretreatment such as grinding of the welded portion preceding the welded portion is not required, and the generation of splash in the welded portion is minimal, resulting in a beautiful and strong weld. A part can be formed and sufficient strength can be obtained.

This is because the formability of a Cr-plated steel sheet in a welding machine and the slipperiness with a jig are stable mainly by controlling the surface roughness in a large order, and the surface roughness is controlled for an ultrafine structure. It is estimated from this that the contact resistance value falls within a range suitable for mash seam welding.

Among the surface roughness regions of the present invention, particularly the surface roughness of the cutoff wavelength of 0.8 mm is described in known documents,
For example, a study by SALA HADIN ANIK et al. (DOC.No.:III-563-77, 1
977MEETING OF INTERNATIONAL INSTITUTE OF WELDING I
According to N COPENHAGEN), etc., it is in the region where the contact resistance increases conversely, but these studies are for spot welding in which there is no horizontal movement of the material during welding. According to the above-mentioned findings found by the person, the relationship between the contact resistance value and the weldability in spot welding does not necessarily match the case in mash seam welding.

Regarding the surface roughness at a cut-off wavelength (LC) of 1 μm, Cr having a conventional granular precipitated Cr layer is used.
In the publicly known technology regarding plated steel sheets, only the contact resistance reducing effect of the metal Cr deposited in the form of particles or horns was focused, while the effect of the surface microstructure of the underlying iron layer was taken into consideration. It is based on the discovery that by setting the surface roughness within a certain range, it is possible to obtain the contact resistance reduction effect between the steel sheets, which is considered to be due to the destruction effect of the Cr hydrated oxide film having high electric resistance.

As a method of measuring the ultrafine roughness parameter defined in the present invention, a scanning probe microscope such as a scanning electron microscope for three-dimensional shape measurement, a scanning tunneling microscope (STM) or an atomic force microscope (AFM) is used. System (S
PM) method 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.

The same applies to the control of the surface roughness at the cutoff wavelength of 0.8 mm, and the measurement result by a commonly used roughness measuring machine may be within the range of the present invention at any 5 points on the steel sheet. ..

The steel sheet having such a roughness is used for cold rolling and temper rolling after annealing, and the roughness of the rolling roll surface is controlled by shot blast grain size distribution control and roughness pattern control in laser surface processing. It can be easily produced by a method of controlling the electrolytic current density during chrome plating, the chromic acid concentration of the chrome plating solution, and the concentration of the auxiliary agent after controlling the temperature within a predetermined range by.

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 body. 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.

As for the coating of the uppermost Cr plating layer of the present invention on the upper layer, any surface treatment may be applied to the portion which is not directly welded. 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.

[0028]

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.

[0030]

[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 can body Welded 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.
% Or more is good (◎), 3% or more and less than 5% is acceptable (△), 3%
Less than was designated as unacceptable (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.
It was put in 50 cc of Cl and boiled for 10 minutes, and Fe and Cr in the leachate were measured by atomic absorption spectrometry. 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 was continuously sprayed on the welded and repaired coating part by a salt spray tester, and the area of red rust generation after 20 days was measured, ± 20% of the numerical value of the reference example. ○ within, × over + 20%,
Those with less than −20% were marked with ⊚.

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.

[0036]

[0037]

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.

[Procedure amendment]

[Submission date] April 15, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0029

[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.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Nobuyuki Morito, Inventor 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba, Kawasaki Steel Corporation Technical Research Division (72) Inventor Hideo Kugaminato Kawasaki, Chuo-ku, Chiba, Chiba No. 1 town Kawasaki Steel Co., Ltd. Chiba Works

Claims (1)

[Claims] 1. A Cr hydrated oxide layer having a carbon content of 0.2% by weight or less and having a metal Cr content of 30 mg / m ² or less in the outermost layer, and below 300 mg / m ² of metal Cr. Have layers,
The centerline average roughness Ra of the outermost layer at a cutoff wavelength (Lc) of 0.8 mm is in the range of 0.05 to 1.5 μm, and Ra is 5 nm when the cutoff wavelength is 1 μm on at least one surface of the steel sheet. The above is the Cr-plated steel sheet for welding cans.