JPH05287591A - Tin-free steel sheet for welded can with one-surface brightness enhanced - Google Patents

Abstract

PURPOSE:To produce a tin-free steel sheet for the welded can excellent in weldability and with the brightness of the formed can improved by forming a granular metallic Cr layer on one surface of the sheet and forming a flat metallic Cr layer on the opposite surface. CONSTITUTION:A cold rolled steel sheet is cathodized in a Cr2O3-contg. electrolyte to plate both surfaces with Cr. Only one surface is anodized in the same electrolyte to dissolve off the deposited Cr while leaving >=10mg/m<2> of Cr, and the amt. of Cr to be dissolved on the opposite surface is controlled to < 10%. The plated steel sheet is then electrolyzed in an aq. Cr2O3 contg. soln. with the sheet as a cathode, hence 40-150mg/m<2> of Cr layer is formed on the unanodized surface, 5-25mg/m<2> of hydrous Cr oxide layer, expressed in terms of Cr, is formed thereon, and a protrusion with the maximum diameter of a part of the Cr layer controlled to 20-250nm, the height from the base to >10nm and the abundance to 1X10<12> to 1X10<15> units/m<2> is formed. The unanodized surface has 40-150mg/m<2> of Cr layer and 2.5-25mg/m<2> of hydrous Cr oxide layer, expressed in terms of Cr, thereon, the height of the protrusion is controlled to <100nm, and the protrusions of >=10nm are controlled to <=1X10<14>units/m<2>.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tin-free steel plate for a welding can having a high surface brightness on one side of a steel plate and a method for producing the same.

[0002]

2. Description of the Related Art Welded cans, which are three-piece cans that use a can body manufactured by the welding method and a top and bottom can lid, have been evaluated for their high productivity and reliability. ing. As a material for this welding can, tinplate is initially used, and more recently, so-called light weight tinplate (LTS) is used. The tinted tint plate has a higher market share than the tint plate because it has a higher evaluation in terms of weldability. There is a difference in production cost, but tinplate is also LT
S is also a tin-plated steel plate. The reason why steel plates for welding cans were limited to tin-plated steel plates is not only due to the fact that such steel plates have a long track record as materials for cans since the age of solder-bonded cans. It has excellent characteristics above. Weldable current range (ACR) in mash seam welding
Is due to the fact that it is inversely proportional to the magnitude of the surface contact resistance of the material to be welded, and the tin-plated steel sheet is
This is because it was a material for cans that exactly met that demand.

However, as is clear from the fact that the mainstream of materials for welding cans is changing from tinplate to LTS, supply insecurity and price instability due to uneven distribution of tin resources reduce the cost of making cans. The pressure on the material for cans is clearly towards non-tin based, cheaper plated steel.

One of the answers to that preference is the use of electrochromic steel sheets (ECCS, TFS or tin-free steel sheets). With the development of a high-speed can body forming method using an organic adhesive, this steel sheet has come to be used in a wide range, mainly for beverage cans and food cans, and the production amount has greatly increased. This material is also used in the can body forming method by welding,
Although its application was tried, the contact resistance between the materials is high because it has a chromium hydrate oxide layer with high electrical resistance on the surface, and in the normal state, a good welding state cannot be obtained by mash seam welding. It was As an attempt to apply a tin-free steel plate to a welding can body, a Cono Weld method or the like has been developed to remove the surface plating layer of the weld immediately before welding, but due to problems such as removal of grinding powder, generally It didn't spread. Further, as an improvement on the plated steel sheet side, a patent relating to a porous chrome plating layer (Japanese Patent Publication No. 57-19752).
No.) was published, but it was not practical because the corrosion resistance could not be maintained in an unhealthy plating layer.

The first tin-free steel sheet for welding cans to achieve both the corrosion resistance and the weldability was that an anodic electrolytic treatment was inserted between the cathodic electrolysis for chromium plating, that is, by a method such as reverse electrolytic treatment. The chrome-tin-free steel plate was a granular chrome-tin steel plate that formed a granular raised structure on the chrome plating layer. This is because the electrode pressure force during welding is concentrated on the granular metallic chromium of the plating layer, and the chromium hydrated oxide layer with high electrical resistance, which is above it, is destroyed from the contact portion of the metallic chromium particles, resulting in a material It is intended to reduce the contact resistance between the two, and as is apparent from Japanese Patent Publication No. 63-26200, it is recognized that the contact resistance is greatly reduced and good weldability is obtained.
In addition, in this type of tin-free steel sheet, the chromium plating layer covers the entire surface of the steel sheet, and therefore has good corrosion resistance. The performance of a tin-free steel sheet having a granular metallic chromium layer for a welding can is determined by the amount of metallic chromium deposited and the amount of hydrated chromium oxide, the particle size of metallic chromium particles, and the distribution density and distribution state.

The present inventors have previously reported that the Japanese Patent Publication No. 63-262.
In No. 00, as a tin-free steel plate for a welding can, the practical range of the above numerical values was limited. That is, it is
"40-150 mg / m ² metal chrome layer on the steel plate surface and 5
It has a non-metallic chrome layer of -25 mg / m ² , and a part of metallic chrome is projected, and the diameter of the projection base is 5 to 1000.
nm, 1 × 10 ¹¹ to 1 × 10 ¹⁴ per 1 m ² of uniformly distributed protrusions. “Tin-free steel plate for welding cans”.

Further, as a manufacturing method thereof, "cold rolled steel sheet is plated with 40 to 140 mg / m ² of metallic chromium in an aqueous solution containing Cr ^6+, and then the steel sheet is used as an anode to 0.1 to 10 C / dm ²
And then perform cathodic electrolysis so that a metal chromium layer of 10 to 60 mg / m ² is deposited in an aqueous solution containing a chromium plating aid and Cr ⁶⁺ . "

The tin-free steel sheet produced by the above method and having the properties in the above range is an excellent material having both good weldability and corrosion resistance. However, it has long been known that a chrome-plated steel sheet having granular projections on the surface is likely to develop a unique surface color tone (for example, a study by Katsushi Yoshida et al. (Iron and Steel, Vol. 66 (1980) No. 7). No. 2
Page 18) etc.). Color tone abnormality may occur in a part of the range of particle diameter and density of metallic chromium particles defined in Japanese Patent Publication No. 63-26200, and the plated steel sheet in such a state has weldability and safety as a container. Although there is no problem with the above, it is necessary to increase the thickness of the base coating more than usual in the type of can that is shipped to the market after painting and printing, and it takes extra time for color matching in the printing process. There was the inconvenience of raising the total can manufacturing cost.

In order to solve the above-mentioned problem of the color tone of the tin-free steel sheet, the inventors of the present invention have previously disclosed JP-A-3-22.
In No. 9897, a metal layer of chromium 40~150mg / m ² in the plating film properties of the granular tin-free steel "steel sheet surface has a non-metallic chromium layer of 5 to 25 mg / m ^2, and a part of the metallic chromium Is protruding, and the diameter of the base of the protrusion is 20
-200 nm, the density of protrusions is 1 × 10 ¹² to 1 × 10 ¹⁴
A tin-free steel sheet "for welded cans, which is a number, also, as a manufacturing method thereof, the" cold-rolled steel sheet Cr ⁶⁺
After plating in an aqueous solution containing, in the same solution, using a steel plate as an anode, the current density is 5 to 20 A / dm ² , and the electricity density is 1 to 1.
Reverse electrolytic treatment at 0 C / dm ² to reduce surface metal chromium adhesion to 10
A tin-free steel sheet having a high surface brightness, which is characterized in that it is dissolved by leaving more than mg / m ² and is further subjected to electrolytic treatment with a current density of 20 to 80 A / dm ² in a solution containing Cr ⁶⁺ as a cathode. The invention identified as "manufacturing method" is disclosed.

With the above invention, it becomes possible to manufacture a granular tin-free steel sheet having a high surface brightness. However, from the viewpoint of operating efficiency, there is an upper limit on the current density, which means that there is an upper limit on the strip running speed of the steel strip that is the object to be plated. On the contrary, in order to increase the production speed without violating the current density regulation range, it is often necessary to add plating cells or modify the equipment, which is a factor of increasing the production cost in any case. was there. Also, from the viewpoint of constructing a production system, the fact that three types of current density control ranges must be provided in one plating operation leads to a complicated control system, equipment cost, production yield, and maintenance of equipment. There were also management issues.

[0011]

DISCLOSURE OF THE INVENTION The present invention alleviates the above-mentioned restrictions on manufacturing conditions when manufacturing a tin-free steel plate for a welding can having a high surface brightness, and is a welding can excellent in weldability and corrosion resistance. It is an object of the present invention to provide a tin-free steel sheet for use and a method for producing it stably and at low cost.

The surface color tone of the can is usually a problem on the surface thereof, that is, the outer surface of the can. Regarding the inner surface of the can, the color tone is not a particular problem except for a special purpose can.
From this, the surface color of tin-free steel plate for welding can is
In particular, paying attention only to the surface that becomes the outer surface during can making, the surface on one side of the steel plate is treated in the same way as a normal tin-free steel plate to give a bright surface tone, while the surface on the opposite side of the steel plate is made of granular chromium. Although it is naturally conceivable to use a tin-free steel plate, it is difficult to secure stable weldability even if a chrome-plated steel plate in which only one side is a granular tin-free steel plate is actually manufactured. It was

In a can manufacturing process in which high-speed mass production is a top priority, such instability of production is extremely unacceptable, and therefore the granular precipitation C on one side as described above.
The production of can bodies made of tin-free steel plates having an r layer and a common flat metal Cr layer on the opposite surface has not been actually carried out. In other words, it was not known what kind of plating layer a steel sheet that achieved the surface appearance with the granular metal Cr layer on one side of the tin-free steel sheet should have an industrial property. The method for stable production was completely unknown.

[0014]

DISCLOSURE OF THE INVENTION The present inventors have investigated the properties of granular precipitated metal Cr and its role in the welding phenomenon,
A wide ACR that guarantees stable production in high-speed mass production of can bodies, and at least one side of the steel plate has the exact same color tone as the conventional flat tin-free steel plate,
The inventors invented a tin-free steel sheet having Cr-plated layers with different properties on the front and back sides, and a method for producing the same.

As described above, in a chrome-plated steel sheet whose one side is simply a granular tin-free steel sheet,
It was difficult to form a stable can body by welding. The weldability of the granular tin-free steel sheet is due to the effect that the metallic chrome grains penetrate the chromium hydrate oxide layer having high electrical resistance by the pressing force applied from the welding electrode, thereby lowering the electrical resistance in the initial stage of welding. , The oxide layer on the surface of a normal tin-free steel plate is 20 mg / m in terms of the amount of metal chromium converted, in terms of the amount of metallic chromium.
^{2. It has} a thickness of about 20 to 30 nm, and has a plate-like Cr layer having such a property on one side and a conventionally known granular Cr plating layer with a base diameter of 100 nm of Cr grains on the other side. A can-body welding is carried out using the steel plate that it has, and even if it is attempted to destroy the oxide film by the granular metal chrome layer existing only on one side of the steel plate, a practical ACR
Can hardly be obtained. This is because the oxide film thickness is too large compared to the size of the metal chromium particles, so the oxide film destruction due to the metal Cr particles is incomplete, and as a result the initial welding resistance does not decrease and continuous weldability is ensured. It is thought that it depends on what is not done. If the oxide film becomes thicker, granular metal C
It is self-evident that the height of the granular protrusions of the r layer must also be high.

However, according to the results of the observation of the plating layer surface by the inventors of the present invention using a scanning tunneling microscope and an atomic force microscope, the height of the granular metal Cr is usually less than about half the diameter of the base portion thereof. Base diameter 50-100 nm
The average particle size of metal Cr is 25 to 50 nm or less, and an oxide film layer of about 10 nm or more is present on the surface of the granular metal Cr, and the Cr hydrated oxide layer crushed in the valleys of the particles is Considering that they are swept away, the oxide film destruction by the metal Cr grains and the mechanical and electrical contact between the metal Cr particles are not enough to make continuous welding possible.

Based on the above findings, the inventors of the present invention have provided a granular metal Cr layer and a layer thereof on which a corrosion resistance sufficient for normal use as a tin-free steel sheet and a weldability sufficient to guarantee high-speed mass production are satisfied. The properties of the oxide film were determined. That is, with respect to the surface Cr plating layer of the tin-free steel plate, the surface which becomes the inner surface of the can after the formation of the can body by welding is formed with a granular metal Cr plating layer, and the shape of the metal Cr particles is welded by oxide film destruction. 40 to 150 mg / m ² of metal Cr with a part protruding in order to secure the current-carrying effect
The properties of the metal Cr protrusions are as follows: the maximum diameter of the protrusions is 20 to 200 nm, and the existence density of protrusions having a height from the base of 10 nm or more is 1 × 10 ¹² to 1 × 10 ¹⁵ pieces / m ^2.
And regarding the Cr hydrated oxide layer existing thereon,
The amount of metal chromium is 5 to 25 mg / m ^2, and the other surface of the steel sheet, which is the outer surface during can body forming, is 40 to 150
It has a metal chromium layer of mg / m ^2, was found that good to have a hydrated chromium oxide layer of 2.5~25mg / m ² by metal chromium amount in terms thereon.

The metal Cr layer on the outer surface of the can body is, of course, desired to have a completely smooth surface if importance is attached to the metallic luster of the appearance. Large-scale plating equipment for steel strip, such as equipment for producing tin-free steel sheets, cannot be obtained by electrolysis, and usually a certain degree of roughness is artificially imparted by transfer from rolling rolls. It is not practical to give a completely smooth plating layer to the steel sheet for cans. If the surface appearance is to be approximated to that of a general tin-free steel plate, it is sufficient if metal Cr particles having a size that interferes with visible light to affect the appearance are not formed. Regarding the plating layer on the side corresponding to the outer surface of the can, the inventors may project a part of the surface chromium metal layer or chromium oxide layer. In that case, the protrusion height of the metal chromium layer surface may be increased. Is 100 nm or less and the height of the protrusion is 10 n
It was discovered that the density of protrusions of m or more should be 1 × 10 ¹⁴ / m ² or less. In that case, in the plating process, in the anodizing of the steel sheet following the first cathodic electrolysis,
The amount of metallic chromium dissolved on the non-anodized surface of the steel sheet is calculated as
It may be 0% or less, or separately, anodizing one side of the steel sheet in an aqueous solution containing Cr ⁶⁺ , and then C
It was discovered that the same effect can be obtained by electrolytically treating both sides of the steel sheet as cathodes in a solution containing r ⁶⁺ . Then, they have found that a cathodic electrolysis treatment for forming a hydrated chromium oxide may be performed if necessary.

The present invention will be described in more detail below. The tin-free steel sheet according to the present invention has a metal chromium layer of 40 to 150 mg / m ^{2 on} one surface of the steel sheet (the surface which becomes the inner surface of the can after the can making), and has a metal chromium amount of 5 to 25 mg / m ² on it. m ²
Has a hydrated chromium oxide layer, and a part of the metal chromium layer is protruding, and the maximum diameter of the protruding portion is 20 to 200 n.
m, the existence density of the protrusions having a height of 10 nm or more from the base is 1 × 10 ¹² to 1 × 10 ¹⁵ pieces / m ² , and the other surface of the steel sheet (the surface which becomes the outer surface of the can after can making) 40 ~
It has a metal chromium layer of 150 mg / m ^2, thereon having a hydrated chromium oxide layer of 2.5~25mg / m ² by metal chromium amount in terms, and projection part of the metallic chromium layer or chromium oxide layer And the height of the protrusions on the surface of the metal chrome layer is 100n.
A chromium-plated steel sheet for welding cans, wherein the density of protrusions having a height of 10 nm or more and a height of 10 nm or more is 1 × 10 ¹⁴ pieces / m ² or less.

[0020] One aspect of the present invention steel sheet (surface to be the can manufacturing after the can inner surface) is hydrated chromium of 5 to 25 mg / m ² in 40~150mg / m ² of metallic chromium layer and a metal chromium terms of steel sheet surface It has an oxide layer.

The reason for limiting the amount of metallic chromium to the range of 40 to 150 mg / m ² is as follows. The amount of metallic chrome is 40
If it is less than mg / m ² , the metallic chromium layer has a porous structure and cannot sufficiently cover the surface of the steel sheet, resulting in deterioration of corrosion resistance and paint adhesion. Further, even if the amount of metallic chromium exceeds 150 mg / m ² , further improvement in corrosion resistance and paint adhesion cannot be expected.

Next, the reason why the amount of hydrated chromium oxide is limited to the range of 5 to 25 mg / m ^{2 in} terms of metallic chromium will be described.
If the amount of hydrated chromium oxide is less than 5 mg / m ² , a porous structure cannot be obtained and the surface cannot be sufficiently covered, resulting in a decrease in paint adhesion. Further, when the amount of hydrated chromium oxide exceeds 25 mg / m ² , the weldability sharply decreases. This is because when the chromium hydrated oxide layer becomes too thick, the protruding metal chromium portion does not break through the thick non-conductive chromium hydrated oxide tank, and the contact resistance increases.

A part of the metal chrome layer on this surface is projected, the maximum diameter of the projection is 20 to 200 nm, and the existence density of the projections with a height of 10 nm or more from the base is 1 × 1.
It is 0 ¹² to 1 × 10 ¹⁵ pieces / m ² .

These numerical ranges were limited for the following reasons. That is, when the maximum diameter of the protrusion is less than 20 nm, the metal chromium protrusion is not high enough to break through the chromium hydrate oxide layer during welding, and when the maximum diameter of the protrusion exceeds 200 nm, the metal chromium is not formed. This is because the protrusions are united with each other and it is difficult to contribute to the weldability.

FIG. 1 shows the relationship between the contact resistance and the density of protrusions having a height of 10 nm or more from the base. If the existence density of protrusions of 10 nm or more is less than 1 × 10 ¹² pieces / m ² , the number of metal chromium protrusions that contribute to weldability is too small, and 1 × 10 2
^If it exceeds ¹⁵ pieces / m ² , the metal chrome protrusions are united with each other, and it becomes difficult to contribute to the weldability. The requirement for the metal chromium projections that contribute to such weldability is determined by the interaction with the properties of the other surface which will be the outer surface of the can after the can-making described below.

Next, the other surface of the steel sheet (the surface which becomes the outer surface of the can after the can is made) has a metal chromium layer of 40 to 150 mg / m ² and a metal chromium conversion of 2.5 to 25 mg / m ² . It has a hydrated chromium oxide layer.

The reason for limiting the amount of metallic chromium to the range of 40 to 150 mg / m ² is as follows. The amount of metallic chrome is 40
If it is less than mg / m ² , the metallic chromium layer has a porous structure and cannot sufficiently cover the surface of the steel sheet, resulting in deterioration of corrosion resistance and paint adhesion. Further, even if the amount of metallic chromium exceeds 150 mg / m ² , further improvement in corrosion resistance and paint adhesion cannot be expected.

Next, the reason why the amount of hydrated chromium oxide is limited to the range of 2.5 to 25 mg / m ^{2 in} terms of metallic chromium will be described. As will be described later, this surface has a small height and density of metal chromium protrusions, and is closer to a flat plate tin-free steel plate than the side that is the inner surface of the can after the above-mentioned can making. Therefore, the lower limit of the chromium hydrated oxide layer is 2.5 because the covering property of the hydrated chromium oxide layer is good.
mg / m ² is sufficient. If the amount of hydrated chromium oxide is less than 2.5 mg / m ² , a porous structure is formed and the surface cannot be sufficiently covered, resulting in a decrease in paint adhesion. Further, when the amount of hydrated chromium oxide exceeds 25 mg / m ² , the weldability sharply decreases. This is because if the chromium hydrated oxide layer becomes too thick, the protruding metal chromium portion will not break through the thick non-conductive chromium hydrated oxide layer and the contact resistance will increase.

On the other hand, if the amount of hydrated chromium oxide exceeds 25 mg / m ² , the color tone of the steel sheet becomes dark, and even if the height and density of metal chromium projections are reduced as described above, satisfactory brightness cannot be obtained.

On this surface, a part of the metal chromium layer or the chromium oxide layer is further projected, the projection height on the surface of the metal chromium layer is 100 nm or less, and the projection height is 10 n.
The density of protrusions of m or more is 1 × 10 ¹⁴ protrusions / m ² or less.

The height of the protrusions on the surface of the metallic chromium layer is 100 n.
If it exceeds m, the surface brightness as that of the flat metal chrome tin-free steel plate cannot be obtained. Even if the existence density of the projections with a projection height of 10 nm or more exceeds 1 × 10 ¹⁴ pieces / m ² , the surface brightness is Spoil. It is preferably 1 × 10 ¹³ pieces / m ² or less,
The surface brightness becomes bright enough. FIG. 2 shows the relationship between the surface brightness of the steel sheet and the density of protrusions having a protrusion height of 10 nm or more. From this figure, the above description is clear.

From the necessity of the manufacturing process or the working process, it is not necessary to form a so-called dull that is usually provided on the surface of the steel plate for cans on the steel plate by a roll having an arbitrary roughness. It does not impair the effects of the present invention. Further, even if a substance other than Cr oxide and hydrated oxide is mixed in the oxide film, the effect of the present invention is sufficiently exhibited as long as the oxide film amount is within the above range.

Next, a method of manufacturing the tin-free steel plate of the present invention will be described. In producing the above tin-free steel sheet, after cold-rolled steel sheet is subjected to cathodic electrolytic treatment in an aqueous solution containing Cr ⁶⁺ and plated, one side of the steel sheet is anodized in the same solution to subject the steel sheet to anodization. The amount of metal chromium deposited on the side is 10 mg / m ² or more, and is dissolved, and the amount of metal chromium dissolved on the non-anodized surface of the steel sheet at that time is within 10% of the amount deposited, and subsequently Cr ⁶⁺ is included. Electrolytic treatment is performed in a solution using a steel sheet as a cathode. As a result, a tin-free steel plate for a welding can having a surface with high surface brightness can be manufactured.

In producing the tin-free steel sheet, one surface of the steel sheet is anodized in an aqueous solution containing Cr ⁶⁺ , and then electrolytically treated in a solution containing Cr ⁶⁺ using both sides of the steel sheet as cathodes. .. As a result, a tin-free steel plate for a welding can having a surface with a high surface brightness can be manufactured.

Further, in producing a tin-free steel sheet by any of the above-mentioned methods, after subjecting the cold-rolled steel sheet to the series of electrolytic treatments described above, a chromium hydrate oxide film is further formed on the plating layer upper layer. For this purpose, electrolytic treatment is ^{carried out} in an aqueous solution containing Cr ⁶⁺ . As a result, a tin-free steel plate for a welding can having a surface with a high surface brightness can be manufactured.

In these methods, the plating equipment used for producing the tin-free steel plate is such that it can form a metal Cr and Cr hydrate oxide / chromium hydrate oxide film on an iron plate by electrolytic plating. , Its format does not matter. The composition of the plating bath is not particularly limited as long as it is a Cr plating bath. Immediately after anodic electrolysis,
The amount of adherence on both sides of the steel sheet differs greatly,
In the flat plate-like plating layer and the granular precipitation-plating layer, metal C is used.
Since the deposition efficiency of r is also different, in the cathodic electrolysis process after anodizing, changing the electrolysis conditions of the anodized surface and the non-anodized surface, that is, the amount of electricity and the electrolytic current density, controls the plating layer properties of the product. It is naturally necessary to do so, and it is in accordance with the gist of the present invention to do this appropriately. In this case, on the anodizing side, it is possible to set the amount of electricity for cathodic treatment to zero. Also, a plurality of types of plating baths can be used in stages during a series of plating steps.

[0037]

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

Example 1 A cold rolled steel sheet was subjected to an ordinary degreasing and pickling treatment.
After the treatment, the electrolytic treatment of the present invention was performed. Chromic acid
(CrO₃) 150 g / l, sodium fluorosilicate (Na₂S
iF₆) 5 g / l and sulfuric acid (H₂SO_Four) 0.6 g / l
100A / dm in the aqueous solution containing 50 ℃²0.20
Second cathodic electrolysis treatment, and then continuously in the same bath, one side of the steel plate
5A / dm on the side²Anodic electrolysis for 0.20 seconds.
6) on the anodized surface of the steel plate in the same bath.
0 A / dm²Electrolysis for 0.3 seconds at the same time
50A / dm on the surface not subjected to pole treatment²In 0.3 second shadow
After the electrodeposition treatment and washing with water, CrO₃60g / l and
Na₂SiF₆40 ° C aqueous solution containing 0.15 g / l
Among them, 1.4A / dm²Cathodic electrolysis for 0.8 seconds (oxide film
Treatment electrolysis) was performed to obtain a tin-free steel plate. Plating
The amount of Cr deposited after the first cathodic treatment that was discontinued and investigated
100g / m²And the anodized surface is anodized
The amount of metal Cr deposited afterwards is 18 g / m²Met. On the anodized surface
The amount of metal Cr is 91.5 g / m², The amount of oxidized Cr is changed to the amount of metallic
8.8g / m in total²And the maximum diameter of the protrusion is 20 to 2
Existence of protrusions with a height of 00 nm or more than 10 nm from the base
Density 1.0 × 10¹⁴Pieces / m ²Recognized, non-anodized surface
The amount of deposited metal Cr is 73.3 mg / m², The amount of Cr oxide is metal
8.3g / m in terms of Cr amount²And the height of the protrusion is 10
Protrusions that are 0 nm or less and the height of the protrusions is 10 nm or more
Existence density of 1 × 10¹²Pieces / m²Met.

[Examples 2 to 5 and Comparative Examples 1 to 10] By the same method as in Example 1, the electrolysis conditions were changed.
The list is shown in Table 1. The electrolytic treatment described in Table 1 as oxide film treatment electrolysis is the same as in Example 1 except that CrO _{3 is used.}
It corresponds to a cathodic electrolysis treatment carried out for 0.8 seconds at 1.4 A / dm ² in an aqueous solution containing 60 g / l and 0.15 g / l Na ₂ SiF ₆ at 40 ° C. The conditions except the electrolysis time are the same as in Example 1. The results of contact resistance measurement, corrosion resistance test and surface color tone measurement are also shown for these examples. Examples 1-5 all exhibit excellent corrosion resistance, bright surface tones, and low contact resistance ensuring a wide ACR. The test conditions are as follows.

(Contact Resistance Test) Two pieces of plates were lap-welded by a spot welding machine so that the front and back faces each other, and the initial resistance between the plates was measured 0.5 msec after energization. Electrode: Cu-Cr alloy CF type electrode with a diameter of 1.2 mm Pressing force: 60 daN Current: 3 kA

(Corrosion resistance test) After ungreasing the unpainted test piece with steam, 90% humidity, 90 ° C for 30 minutes and 50 ° C pure water spray for 3 times
The appearance of rust on the outer surface was visually judged after standing for 3 days in an environment of 0 minutes. ◎ No rust ○ Spot rust (diameter 1 mm or less), rust area ratio 0.1%
Less than. △ Spot rust (diameter 1 mm or less), rust area ratio 1% or less. × Surface rust (diameter 1 mm or more) occurred.

(Surface color tone) Using an integrating sphere type color difference meter,
The L value of the Hunter color difference was measured.

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

[Table 3]

[0046]

[Table 4]

[0047]

According to the present invention, the weldability is ensured by the granular metal Cr layer formed on one surface of the tin-free steel plate (the surface which becomes the inner surface of the can after can making), and the opposite surface (the outer surface of the can after making the can). A flat metal Cr layer is formed on the surface of the steel sheet, and a steel sheet that has both a high-brightness surface and an outer surface similar to those of a conventional tin-free steel sheet during can making, and a stable manufacturing method thereof can be obtained.

[Brief description of drawings]

FIG. 1 Metal C in the chromate layer of a tin-free steel plate
It is a figure which shows the relationship between r protrusion density and contact resistance.

FIG. 2 Metal C in the chromate layer of tin-free steel plate
It is a figure which shows the relationship between r grain presence density and surface brightness.

Claims (5)

[Claims] 1. A steel plate having a metal chromium layer of 40 to 150 mg / m ² on one surface thereof, and having a metal chromium amount of 5 to 2 on it.
It has a hydrated chromium oxide layer of 5 mg / m ² , and part of the metallic chromium layer is protruding, and the maximum diameter of the protruding portion is 20 ~
The existence density of protrusions having a height of 200 nm or more from the base of 10 nm or more is 1 × 10 ¹² to 1 × 10 ¹⁵ pieces / m ² , and 40 to 150 mg / m ² of metal on the other surface of the steel sheet. It has a chrome layer, and the amount of metal chrome on it is 2.5-
It has a hydrated chromium oxide layer of 25 mg / m ² and part of the metal chromium layer or chromium oxide layer is protruding, and the height of the protrusion on the surface of the metal chromium layer is 100 nm or less and the height of the protrusion is 100 nm or less. Is a tin-free steel plate for a welding can having a high surface brightness on one side, which has a density of protrusions of 10 nm or more of 1 × 10 ¹⁴ pieces / m ² or less. 2. A cold rolled steel sheet is subjected to cathodic electrolytic treatment in an aqueous solution containing Cr ⁶⁺ to be plated, and then one side of the steel sheet is anodized in the same solution to obtain metallic chromium on the anodized side of the steel sheet. dissolved leaving coating weight 10 mg / m ² or more, a metallic chromium amount of dissolution of the non-anodized surface of the steel plate at that time was within 10% of the amount of deposited cathode steel sheet in a solution containing a further followed by Cr ⁶⁺ 40 to 1 on the surface of the steel sheet to be anodized by electrolytic treatment
50 mg / m ² metal chrome layer and 5-25 mg / m ² chrome hydrated chrome oxide layer on it, part of metal chrome layer is protruding, and the maximum diameter of protrusion is Is 20
To 200 nm, the existence density of the protrusions having a height of 10 nm or more from the base is 1 × 10 ¹² to 1 × 10 ¹⁵ pieces / m ² , and further, on the surface of the steel sheet on the non-anodized side, Four
And 0~150mg / m ² of metallic chromium layer, the hydrated chromium oxide layer of 2.5~25mg / m ² by metal chromium amount in terms thereon, a portion of the metallic chromium layer or chromium oxide layer is projecting The protrusions on the surface of the metal chromium layer have a height of 100 nm or less, and the protrusions having a height of 10 nm or more are present at a density of 1 × 10 ¹⁴ pieces / m ² or less. A method for producing a tin-free steel plate for a welding can having a high surface brightness on one side. 3. A cold-rolled steel sheet is anodized by subjecting one side of the steel sheet to an anodization in an aqueous solution containing Cr ⁶⁺ , and then electrolytically treating both sides of the steel sheet as a cathode in a solution containing Cr ^6+. 40 to 150 mg / m ² of metallic chrome layer on the surface of the coated side, and 5 to 25 mg / m ² of chromium hydrate oxide layer in terms of the amount of metallic chromium on it, part of the metallic chromium layer is projected. The maximum diameter of the protrusion is 20 to 200 nm, and the height from the base is 1
Presence density of protrusions of 0 nm or more is 1 × 10 ¹² to 1 × 10 ¹⁵
Pieces / m formed such that ^2, further to a surface of the non-anodized side of the steel plate, and 40～150Mg / m ² of metallic chromium layer, a metal chromium amount in terms thereon 2.5～25Mg / The chromium hydrated oxide layer of m ² has a part of the metal chromium layer or the chromium oxide layer protruding, and the height of the protrusion on the surface of the metal chromium layer is 100 nm or less and the height of the protrusion is 10 nm or more. A method for producing a tin-free steel plate for a welding can having a high surface brightness on one side, characterized in that the density of protrusions is formed to be 1 × 10 ¹⁴ pieces / m ² or less. 4. A cold-rolled steel sheet is subjected to cathodic electrolytic treatment in an aqueous solution containing Cr ⁶⁺ to be plated, and then one surface of the steel sheet is anodized in the same solution, so that the surface of the steel sheet on the anodized side is anodized. The amount of metallic chromium deposited is 10 mg / m ² or more and is dissolved, and the amount of metallic chromium dissolved on the non-anodized side of the steel sheet at that time is within 10% of the amount of deposited chromium, and subsequently Cr ⁶⁺ is included. The steel sheet is subjected to electrolytic treatment in the solution as a cathode, and subsequently both surfaces of the steel sheet are subjected to cathodic electrolysis treatment in an aqueous solution containing Cr ⁶⁺ to form chromium hydrate oxide, and the surface of the steel sheet on the anodized side is subjected to 40%. ~
A metallic chromium layer of 150 mg / m ^2, a hydrated chromium oxide layer of 5 to 25 mg / m ² in metal chromium amount in terms thereon, which protrudes a part of the metallic chromium layer, the maximum diameter of the protruding portion Is 2
The protrusions having a height of 0 to 200 nm and a height from the base of 10 nm or more are formed so as to have a density of 1 × 10 ¹² to 1 × 10 ¹⁵ protrusions / m ² , and further formed on the surface of the steel sheet on the non-anodized side. ,
And 40~150mg / m ² of metallic chromium layer, the hydrated chromium oxide layer of 2.5~25mg / m ² by metal chromium amount in terms thereon, a portion of the metallic chromium layer or chromium oxide layer is projecting The protrusions on the surface of the metal chromium layer have a height of 100 nm or less, and the protrusions having a height of 10 nm or more are present at a density of 1 × 10 ¹⁴ pieces / m ² or less. A method for producing a tin-free steel plate for a welding can having a high surface brightness on one side. 5. A cold-rolled steel sheet is anodized on one side of a steel sheet in an aqueous solution containing Cr ⁶⁺ , and then electrolytically treated in a solution containing Cr ⁶⁺ using both sides of the steel sheet as cathodes. In order to form a hydrated chromium oxide, a metal chromium layer of 40 to 150 mg / m ² is formed on the surface anodized by cathodic electrolysis in an aqueous solution containing Cr ^6+, and a metal is formed thereon. A hydrated chromium oxide layer of 5 to 25 mg / m ^{2 in} terms of chromium amount,
A part of the metal chrome layer is protruding, the maximum diameter of the protruding portion is 20 to 200 nm, and the existence density of the protruding portions having a height from the base portion of 10 nm or more is 1 × 10 ¹² to 1 × 10 ¹⁵ pieces / m ² . And a metallic chromium layer of 40 to 150 mg / m ² on the surface of the steel sheet on the non-anodized side, and a chromium water of 2.5 to 25 mg / m ^{2 in} terms of the metallic chromium amount thereon. A part of the chromium metal oxide layer or the chromium oxide layer is protruding from the hydrated oxide layer, and the height of the protrusion on the surface of the metal chromium layer is 100 n.
A tin-free steel plate for a welding can having a high surface brightness on one side, characterized in that the density of protrusions having a protrusion height of 10 nm or more is 1 × 10 ¹⁴ pieces / m ² or less. Manufacturing method.