JPH0375397A - Production of surface treated steel sheet for welded can - Google Patents

Abstract

PURPOSE:To provide a steel sheet for cans capable of high speed resistance seam welding and excellent in corrosion resistance by continuously subjecting a sheet metal to nickel plating, to annealing, and to temper rolling and immediately carrying out electrolytic chromic acid treatment at specific electrolytic current density. CONSTITUTION:A sheet metal is continuously subjected to degreasing, nickel plating, and continuous annealing. Successively, temper rolling is applied to the above in a dry state. Then, without pickling, electrolytic chromic acid treatment is immediately performed at 200-600A/dm<2> electrolytic current density. Temper rolling is exerted in a wet state. Nickel plating layer is formed on the steel sheet surface by 10-500mg/m<2> nickel coating weight by means of electroplating, and then, continuous annealing is carried out in a reducing atmosphere containing hydrogen gas at 600-900 deg.C for 10-90sec. Further, metallic chromium and chromium hydrated oxide are formed by 20-150mg/m<2> and 3-20mg/m<2>, respectively. By this method, this steel sheet can contribute to can cost reduction.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for producing an inexpensive surface-treated steel sheet for cans that can be welded at high speed without grinding. The present invention relates to a method for manufacturing an inexpensive surface-treated steel sheet for cans, which has a chromium hydrated oxide layer and can be welded at high speed without grinding.

<Conventional technology> Currently, general cold-rolled steel sheets are used as steel sheets for cans only in some applications, but for applications that require corrosion resistance, such as food cans and beverage cans, tinplate and electrolytic chromic acid treated steel sheets are mainly used. It is used.

In recent years, so-called welded cans, in which the can body is formed by copper wire seam welding, have rapidly become popular. Conventionally, from the viewpoint of soldering properties, the minimum amount of tin deposited was 2.8 g/m2, but with the spread of welding methods, the amount of tin deposited has decreased to 1.
．． It became possible to use tinplate with a thin coating of 0 g/m' or less, and a significant reduction in can cost was achieved.

In order to further reduce the cost of welded cans, it is desirable to use electrolytic chromate-treated steel sheets with a thin metallic chromium layer and a chromium hydrated oxide layer, without using expensive tin. Sufficient welding could not be achieved due to the presence of hydrated chromium oxide, which is a conductor.

Methods for solving this problem can be divided into two types: those that improve the welding method and those that improve the weldability of materials.

Examples of the former type include, for example, Japanese Patent Application Laid-Open No.
There is a method using tin-plated copper wire as shown in No. 23389, but the use of such expensive wire is economically disadvantageous.

Examples of the latter category include JP-A-61-2
No. 13399 and Japanese Patent Publication No. 63-26200, the weldability was considerably improved by forming minute protrusions on the metal chromium layer, but stable high-speed weldability could not be obtained.

Further, for example, Japanese Patent Publication No. 57-19752 proposes a method of forming a porous metal chromium layer by reducing the amount of metal chromium, but this method not only has poor corrosion resistance but also fails to provide sufficient weldability.

JP-A No. 63-238299 discloses that a metal chromium layer and a hydrated chromium oxide layer are formed in the form of a flat plate having no granular or angular protrusions by electrolytic chromic acid treatment after a trace amount of nickel plating. However, due to the presence of a metallic nickel layer, pitting corrosion was likely to occur.

Further, JP-A No. 62-297491 discloses a method in which electrolytic chromic acid treatment is performed after nickel diffusion treatment, but the weldability is only comparable to that obtained when tin-plated copper wire is used.

<Problem to be solved by the invention> An inexpensive surface treatment that maintains high corrosion resistance and also satisfies sufficient high-speed weldability even when using copper-plated wire that does not undergo expensive special treatments such as tin plating. There is no example of successful development of steel plate yet.

As a result of a detailed study of the welding phenomena of electrolytic chromic acid-treated steel sheets, it was found that improving the coverage of the base steel by a metallic chromium layer and chromium hydrated oxide is important for achieving high-speed weldability, but increasing the amount of them It was found that high-speed weldability deteriorates again when the steel passes through the steel.

When the amount of metallic chromium exceeds 20 tng/rn2, the coating of the base iron becomes quite good, but minute micropores remain, and the exposed iron sometimes oxidizes during paint baking, impairing weldability.

On the other hand, if the amount of chromium hydrated oxide is increased, the micropores can be covered, but if the amount of chromium hydrated oxide, which is a poor electrical conductor, exceeds 20 mg/m2, welding becomes extremely difficult. Although it is possible to improve weldability to some extent by covering the base iron with metallic chromium and chromium hydrated oxide and by limiting the amount, it is currently not possible to stably perform high-speed welding at speeds exceeding 40 m/min. .

An object of the present invention is to provide an inexpensive method for manufacturing a surface-treated steel sheet for cans that can be welded at high speed without grinding.

As a result of research, we have found that the following requirements are essential in order to solve the above problems.

■To reduce the number of micropores in the metal chromium layer,
The electrolytic current density of electrolytic chromic acid treatment is 200 to 600 A/
Let it be dm2.

■In order to control the oxidation of the bare steel exposed through the micropores of the metallic chromium layer and chromium hydrated oxide layer, a nickel diffusion layer is provided on the surface of the bare steel.

■In order to obtain a good appearance, no pickling treatment is performed when applying electrolytic chromic acid treatment to steel sheets that have been treated with nickel diffusion.

That is, according to the present invention, in order to achieve the above object,
Thin steel plates are continuously degreased, nickel plated, and continuously annealed.
After subsequent temper rolling in a dry state, electrolytic chromic acid treatment was performed immediately without pickling at an electrolytic current density of 200 to 600.
Provided is a method for manufacturing a surface-treated steel sheet for welded cans, which is characterized in that the manufacturing method is carried out at a temperature of \^/dm''.

Further, according to the present invention, a thin steel sheet is continuously degreased, nickel plated, continuously annealed, and then temper-rolled in a wet state, and then degreased and immediately subjected to electrolytic chromic acid treatment without pickling. A method for manufacturing a surface-treated steel sheet for welding cans is provided, which is characterized in that the process is carried out at a current density of 200 to 600^/dm''.

It is preferable that the nickel plating is performed by electroplating to form a nickel deposition amount of 10 to 500 mg/m'' on the surface of the steel sheet.

The continuous annealing is performed at a temperature of 600 to 900°C and a time of 10 to 9
It is preferable to carry out the reaction for 0 seconds in a reducing atmosphere containing hydrogen gas.

The electrolytic chromic acid treatment removes 20 to 150 m of metallic chromium.
g/m" and 3 to 20 H7 m2 of chromium hydrated oxide.

The present invention will be explained in more detail below.

Cold-rolled thin steel sheets must undergo degreasing, nickel plating, continuous annealing, temper rolling, and electrolytic chromic acid treatment continuously on the same line.

When applying electrolytic chromic acid treatment to a thin steel sheet with a nickel diffusion layer formed by nickel plating and continuous annealing,
If pickling is performed in advance, poor appearance may occur, which is thought to be caused by uneven dissolution on the surface of the steel sheet. This is not a big problem when the current density of electrolytic chromic acid treatment is as low as 100 to 150 A/dm2, but it becomes noticeable when the current density is as high as 200 to 600 A/dm' as in the present invention. No washing is done. Furthermore, if the nickel diffusion treatment and the electrolytic chromium e treatment are performed on separate lines, pickling cannot be omitted, so they must be performed on the same line. Therefore, temper rolling for tempering thin steel sheets is naturally performed on the same line. Temper rolling must be performed in a wet state when the rolling reduction is a few percent or more, and in that case, it is necessary to perform degreasing before electrolytic chromic acid treatment. Unlike pickling, degreasing does not affect the appearance or quality of the plating.

In addition, washing with water, drying, etc. shall be performed as appropriate between each main process. For example, water washing between degreasing before nickel plating and nickel plating, water washing and drying between nickel plating and continuous annealing, and degreasing and electrolytic chromic acid treatment in the case of wet temper rolling. These include washing with water, washing with water after electrolytic chromic acid treatment, and drying.

Degreasing before nickel plating and degreasing before electrolytic chromic acid treatment may be carried out by conventional methods such as electrolytic degreasing in an aqueous solution containing sodium hydroxide as a main ingredient, and are not limited in any way.

A preferred method for forming the nickel diffusion layer is a combination of nickel plating and continuous annealing. For example, as shown in Japanese Patent Publication No. 54-25896, there is a method in which nickel salt is applied and then annealed to reduce and diffuse nickel, but there is a possibility that undiffused metallic nickel remains on the surface of the steel sheet, and nickel is removed from the steel sheet. It is not used in the present invention because it is extremely electrically sensitive compared to the metal base metal, so if a scratch that reaches the base metal is formed, pitting corrosion is likely to occur. Therefore, it is not used in the present invention.

There is no need to particularly limit the bath conditions for nickel plating, but the amount of nickel deposited is 10 to 500 mg/I.
n2 range, preferably within the range of 20 to 200 H7m''.Nickel deposition amount is 10 vag/ln2
If the amount is less, the paint baking in some micropores of metallic chromium and chromium hydrated oxide will not have a sufficient effect of suppressing oxidation of iron, and the desired high-speed weldability will not be obtained. Also,
If it exceeds 500 tsg/m', not only will undiffused metallic nickel remain on the surface, causing pitting corrosion, but even if it exceeds 500 mg/m', it is not expected to be effective in suppressing further oxidation of iron. This is not possible and is economically disadvantageous.

Continuous annealing is preferably carried out at a temperature of 600 to 900°C and a time of 10 to 90 seconds depending on the degree of tempering, and in a reducing atmosphere containing hydrogen gas. Patch annealing is also considered as an annealing method, but annealing Because the time exceeds 10 hours,
As nickel diffuses too much and the nickel concentration on the surface of the steel sheet decreases too much, paint baking becomes insufficiently effective in suppressing oxidation of the base steel. If the continuous annealing time is shorter than 10 seconds, metallic nickel remains on the surface, and if the continuous annealing time is longer than 90 seconds, nickel will diffuse too much.

In addition, since electrolytic chromic acid treatment is required for pickling after nickel diffusion treatment, continuous annealing should be performed in a reducing atmosphere containing hydrogen gas. It may be carried out at a rate of 0.1 to 60%. Since dry temper rolling is possible when the rolling reduction is several percent or less, the subsequent degreasing process (including water washing) can be omitted, which is advantageous because the equipment becomes compact. However, depending on the degree of tempering, it is necessary to perform wet temper rolling with a rolling reduction of several percent or more, and in that case, a degreasing step is required. Furthermore, the presence or absence of degreasing does not affect the subsequent electrolytic chromic acid treatment.

Electrolytic chromic acid treatment uses an electrolytic current density of 200 to 600 A.
/dm". Current density is 200
If it is lower than A/dm2, the number of pores in the metal chromium layer increases and sufficient high-speed weldability cannot be obtained. Furthermore, even if the current density is made higher than 600^/dm, the bore of the metal chromium layer cannot be further reduced, and the power consumption increases due to the rise in bath voltage. Electroplated steel sheets for containers that form metallic chromium and chromium hydrated oxide through acid treatment are disclosed in JP-A-62-2.
No. 97491, but in this method, the current density of electrolytic chromic acid treatment is 40 to 150^/d+*'', which is lower than that of the present invention, so the coating of the base steel sheet with metallic chromium is insufficient, and it is not possible to 40m for steel wire seam welding
It is difficult to weld at a speed of more than 1 minute. Therefore, in the present invention, the electrolytic chromic acid treatment is carried out at 200 to 600 A/d.
What you do in i2 is extremely important.

The bath composition for electrolytic chromic acid treatment does not need to be particularly limited; it uses hexavalent chromium such as anhydrous chromic acid or dichromic acid as the main ingredient, sulfuric acid or sodium silicofluoride as an auxiliary agent, and contains some trivalent chromium. A normal treatment bath will suffice.

Further, although either a one-liquid method or a two-liquid method may be used, the one-liquid method is more advantageous in order to make equipment compact. In the one-component method, the entire electrolytic chromic acid treatment may be performed at Zoo to 600 A/d-, but in order to adjust the amount of hydrated chromium oxide, the treatment may be performed at a low current density only in the final stage. 2
In the case of the liquid method, the chromium plating process that forms the metal chromium layer may be performed at 200 to 600 A/dm, and the subsequent chemical treatment process that forms the chromium hydrated oxide layer is performed within this current density range. No need, just 5-100 ^/
There is no problem in using DM2.

Metallic chromium formed by electrolytic chromic acid treatment is 20
~150mg/m2 preferably 30-100 tsg
/l chromium hydrated oxide is 3 to 20 mg/+'
Preferably, it is 5 to 15 mg/m''. If the metallic chromium content is less than 20 mg/m'', the coating of the base steel will be insufficient, which will not only be disadvantageous to weldability but also reduce the corrosion resistance after painting. Inferior. In addition, the amount of metallic chromium was increased to 150 t.
If the amount of chromium hydrated oxide is less than 3 mg/m2, no further improvement in both weldability and corrosion resistance after painting can be expected.
If it is more than 20 mg/m2, weldability will be poor.

Washing with water and drying after the electrolytic chromic acid treatment are necessary, but there is no need to specifically limit them. Water washing may be by dipping, spraying or a combination thereof. In order to remove hexavalent chromium remaining on the surface, it is desirable to perform water washing at least once at a temperature of 60° C. or higher.

<Example> The present invention will be specifically explained below based on Examples.

[Example 1] After electrolytically degreasing a low carbon cold-rolled steel sheet in an aqueous sodium hydroxide solution and washing with water, NiSO4.77H2O240/It
, N1CfL4・6 H2045g/IL,
Hs B O < 30 g/fL, temperature 50°C, current density 15^/dm' with steel plate as cathode, electrolysis time 0
．． After 6 seconds of electrolytic nickel plating, washing and drying,
Immediately, it was annealed in a reducing atmosphere (10% H2% dew point -25°C, balance N2) at a temperature of 700°C for 30 seconds, followed by dry temper rolling at a rolling reduction of 1%. Immediately without degreasing or pickling, Cr0380g/l, Na25i
F, 1.4D/11, sulfuric acid 0.4 gill, CS”
The steel plate was subjected to electrolytic chromic acid treatment at a temperature of 45° C. using a steel plate as the # electrode at a current density of 400 A/dm 2 and an electrolysis time of 0.08 seconds, washed with hot water at 70° C., and then dried to obtain a test material. The amount of nickel deposited is 0. At 1 g/m2, no undiffused metallic nickel was present. The amount of metallic chromium is 100 mg7m2 The amount of chromium hydrated oxide is 1
It was 10ll1/l112.

[Example 2] After electrolytically degreasing a low carbon cold rolled steel sheet in an aqueous sodium hydroxide solution and washing with water, NNi5044H2024G/It,
NiCf 4'66H2O45/Jl, H3BO4
30gIn.

At a temperature of 50°C and a steel plate as a cathode, the current density is 3°A/dm'.
Electrolytic nickel plating with an electrolytic time of 0.6 seconds is applied,
After washing and drying, it was immediately annealed in a reducing atmosphere (10% H2, dew point -25°C, remainder N2) at a temperature of 800°C for 60 seconds, and then wet temper rolled at a reduction rate of 15%.

Subsequently, it was electrolytically degreased in an aqueous sodium hydroxide solution.
After washing with water, CCrO38D/
11, Na25iF61.4g/J2, sulfuric acid 0.4g
ill, (:r"1 gIn,, temperature 45°C, current density 500 A/dm' with steel plate as cathode, electrolysis time 0.
The sample was subjected to electrolytic chromic acid treatment for 0.8 seconds, washed with warm water at 70°C, and then dried to obtain a test material. The amount of nickel deposited is 0
．． At 2 g/m', no undiffused metallic nickel was present. The amount of metallic chromium was 120 mg/m' and the amount of hydrated chromium oxide was 12 mg/m2.

[Example 3] After electrolytically degreasing a low carbon cold rolled steel sheet in an aqueous sodium hydroxide solution and washing with water, NiSO4.7H20240g/fL
, N1Cj! ,・61(2045g/j2, 83B
Electrolytic nickel plating was applied at 0430g/11 at a temperature of 50°C using a steel plate as a cathode at a current density of 45A/dm2 and an electrolysis time of 0.6 seconds. After washing and drying, the plate was immediately placed in a reducing atmosphere (10% H2% dew point -25°C, remainder N2), temperature 850
C. for 60 seconds, followed by dry temper rolling at a rolling reduction of 1%. Subsequently, after electrolytic degreasing in an aqueous sodium hydroxide solution and washing with water, C
r0380g/f11Na, SiF, 1.4D/11,
Sulfuric acid 0.4g/jZ, Cr3”1g/fl, temperature 45
Current density 200 A/dm' with steel plate as cathode at ℃
Electrolytic chromic acid treatment with electrolysis time of 0.10 seconds and 70℃
After washing with warm water, the sample was dried. The amount of nickel deposited was 0.3 g/m", and there was no undiffused metallic nickel. The amount of metallic chromium was f 20 mg/m
``The amount of hydrated chromium oxide was 12 mg/m2.

[Example 4] After electrolytically degreasing a low carbon cold rolled steel sheet in an aqueous sodium hydroxide solution and washing with water, NlSO4'7H207H2O240
, N1CJ! 4”6) 12045g/jl, 83B0
Electrolytic nickel plating was performed at 430 g/jZ, at a temperature of 50°C, with a current density of 3°A/d[11', and an electrolysis time of 0.6 seconds, using a steel plate as a cathode.After washing and drying, the plate was immediately placed in a reducing atmosphere ( 10% H2, dew point -25℃, balance N2), temperature 8
Annealing was performed at 50° C. for 40 seconds, followed by wet temper rolling at a rolling reduction of 40%. Subsequently, after electrolytic degreasing in an aqueous sodium hydroxide solution and washing with water, Cr (1+80g/jZ, Na, SiF, 1.4
g/l, sulfuric acid a, 4g/x, Cr"Ig/fL, current density 600^/dm2 using a steel plate as a cathode at a temperature of 45℃
Electrolytic chromic acid treatment with an electrolysis time of 0.04 seconds was performed, and 7
After washing with warm water at 0° C., the material was dried to obtain a test material. The amount of nickel deposited was 0.3 g/m2, and no undiffused metallic nickel was present. The amount of metallic chromium is 120mg/m
2 The amount of chromium hydrated oxide was 12 B/m''.

[Example 5] After electrolytically degreasing a low carbon cold-rolled steel sheet in an aqueous sodium hydroxide solution and washing with water, NiSO4.77H2O240/I1
．． , N1CJ1.・6Hz045g/u, H3BO4
30g/i, temperature 50℃, current density 6 with steel plate as cathode
Electrolytic nickel plating with 0A/dm2 electrolysis time of 0.6 seconds is applied, and after washing and drying, it is immediately placed in a reducing atmosphere (10
% H2, dew point -25°C, remainder N2), temperature 650°C, and time 60 seconds, followed by wet temper rolling at a reduction rate of 40%. Subsequently, after electrolytic degreasing in an aqueous sodium hydroxide solution and washing with water, Cr was immediately removed without pickling.
(h80g, AQ, Na2SiF61.4g/fL, sulfuric acid 0.4g/11, Or"Ig/42, temperature 45℃
Electrolytic chromic acid treatment was performed using the steel plate as a cathode at a current density of 300 A/dm2 for an electrolysis time of 0.10 seconds, followed by washing with warm water at 70°C and drying to obtain a test material. The amount of nickel deposited was 0.4 g/m2, and no undiffused metallic nickel was present. The amount of metallic chromium was 30 mg/ln, and the amount of hydrated chromium oxide was 4 Barn.

[Example 6] After electrolytically degreasing a low carbon cold rolled steel sheet in an aqueous sodium hydroxide solution and washing with water, NiSO41) 120240 g/u,
N1CIL4・6Hz045g/J2, l(3
Electrolytic nickel plating was performed at BOdOg/u at a temperature of 50°C with a current density of 15A/dm2 and an electrolysis time of 0.6 seconds using a steel plate as the cathode. After washing and drying, the plate was immediately placed in a reducing atmosphere (
10% H275 point -25℃, balance N2) Temperature 700
C. for 30 seconds, followed by dry temper rolling at a rolling reduction of 1%. Subsequently, without degreasing or pickling, (: rOa180 gill, Na25iFe2g
/x, sulfuric acid 0.8gait, Cr"2g/IL,
Current density 400 A/d with steel plate as cathode at temperature 50℃
m2 After chrome plating with an electrolysis time of 0.08 seconds, Cr (h80g/J2) was washed with water.

Na25iFe2.4g/A, sulfuric acid 0.1g/f, C
After applying electrolytic chromic acid treatment using r'''''0.05 gel and a steel plate as a cathode at a temperature of 40°C and a current density of 20 A/dm' and an electrolysis time of 0.30 seconds, and washing with hot water at 70°C,
It was dried and used as a test material. The amount of nickel deposited is 0.1g/
m2, no undiffused metallic nickel was present. The amount of metallic chromium was 100 mg/m, and the amount of hydrated chromium oxide was 13II1g/IQ2.

[Example 7] After electrolytically degreasing a low carbon cold-rolled steel sheet in an aqueous sodium hydroxide solution and washing with water, NiSO4.77H2O240/I1
．． , N1Cj14・an2o4sg#, )I3BO
dOg/vertical, temperature 50℃, current density 1 with steel plate as cathode
5A/da" electrolytic nickel plating with an electrolytic time of 0.6 seconds, washing with water and drying, and immediately placing it in a reducing atmosphere (10
%H2, dew point -25°C, remainder N2), temperature 700°C, time 30 seconds, and then dry temper rolling with a rolling reduction ratio of 1%. Subsequently, C immediately without degreasing or pickling.
rO380g/11, NazSiFel, 4g/-12
, 0.4 g/u of sulfuric acid, 1 g/J2 of Cr, a current density of 400 A/dm' with a steel plate as a cathode at a temperature of 45°C, and an electrolytic chromic acid treatment with an electrolysis time of 0.08 seconds, followed by an electric current in the same bath. Density 100 A/dm' Electrolysis time 0.08
The sample was subjected to electrolytic chromic acid treatment for a second, washed with warm water at 70°C, and then dried to obtain a test material. The amount of nickel deposited is 0.1
g/m' and no undiffused metallic nickel was present.

The amount of metallic chromium was 120 mg/m2, and the amount of hydrated chromium oxide was 13 mg/m2.

[Comparative Example 1] A low carbon cold rolled steel sheet was electrolytically degreased in an aqueous sodium hydroxide solution, washed with water, dried, and then exposed to a reducing atmosphere (10% H2 dew point -2
It was annealed at 5° C., balance N2) at a temperature of 700° C. for 30 seconds, followed by dry temper rolling at a rolling reduction of 1%. next,
After electrolytic degreasing in aqueous sodium hydroxide solution and washing with water, 5%
After pickling by immersion in sulfuric acid, Cr0580g/IL, Na
25iF, 1.4g/IL, sulfuric acid a, 4g/x, temperature 45℃, current density 50 A/dm2' with steel plate as cathode
! It was subjected to electrolytic chromic acid treatment with a dissolution time of 1.2 seconds, washed with warm water at 70°C, and then dried to obtain a test material. The amount of metallic chromium is 100 B/m2 The amount of chromium hydrated oxide is 10
It was mg/m2.

[Comparative Example 2] A low carbon cold rolled steel sheet was electrolytically degreased in an aqueous sodium hydroxide solution, washed with water, dried, and then exposed to a reducing atmosphere (10% H2% dew point -
It was annealed at 25° C. (remainder N2) at a temperature of 700° C. for 30 seconds, and then dry skin-pass rolled at a rolling reduction of 1%. Next, electrolytic degreasing was performed in an aqueous sodium hydroxide solution, and after washing with water,
After pickling in sulfuric acid, Cr0580g/11,N
a25JF, 1.4g/41, sulfuric acid 0.4g/Jl,
Electrolytic chromic acid treatment was performed at a temperature of 45°C, a current density of 400A/dm2, and an electrolysis time of 0.08 seconds using a steel plate as a cathode, washed with hot water of 70°C, and dried to obtain a test material.Metal The amount of chromium is 100mg/rn”
The amount of chromium hydrated oxide was 10 mg/aa2.

[Comparative Example 3] A low carbon cold rolled steel sheet was electrolytically degreased in an aqueous sodium hydroxide solution and washed with water, then N15O,.71 (,0240g/x
, NiCl14.6) 12045 g/It%H
880430g/12.

Current density 15A/dm2 with steel plate as cathode at temperature 50℃
Electrolytic nickel plating with an electrolytic time of 0.6 seconds is applied,
After washing and drying, it was immediately annealed in a reducing atmosphere (10% H2s dew point -25°C, remainder N2) at a temperature of 700°C for 30 seconds, and then dry temper rolling was performed at a reduction rate of 1%. Next, electrolytically degreased in an aqueous sodium hydroxide solution, washed with water,
After pickling by immersion in 5% sulfuric acid, Cr0380g/fl,
Na25IFa1.4g/JZ, sulfuric acid 0.4g/n,
(:S"1g/41, electrolytic chromic acid treatment with a current density of 100A/dm' and an electrolysis time of 0.6 seconds using a steel plate as a cathode at a temperature of 45℃, washing with hot water at 70℃, drying, and testing. The amount of nickel deposited was Oll g/ra.
2, no undiffused metallic nickel was present. The amount of metallic chromium was 100 mg/ra2 and the amount of hydrated chromium oxide was 10 mg/ra2.

(Comparative Example 4) After electrolytically degreasing a low carbon cold rolled steel sheet in an aqueous sodium hydroxide solution and washing with water, NiSO4.7H20240g/u,
N1CA 4・6H2045g/fL%H3BO430
g/interchange, current density 15^ with steel plate as cathode at temperature 50℃
/dm' Electrolytic nickel plating with an electrolytic time of 0.6 seconds was applied, and after washing and drying, it was immediately placed in a reducing atmosphere (10% H
2% dew point -25℃, balance N2), temperature 700℃, time 3
It was annealed for 0 seconds and then dry temper rolled at a rolling reduction of 1%. Next, electrolytically degreased in a sodium hydroxide aqueous solution,
After washing with water, immersing in 5% sulfuric acid and pickling, Cry380g
/fL, NazSiFal, 4g/jZ, sulfuric acid 0.4
g/42, Cr"1g/fl, temperature 45℃, current density 400 A/dm2, electrolysis time 0.0 with steel plate as cathode
It was subjected to electrolytic chromic acid treatment for 8 seconds, washed with warm water at 70°C, and then dried to obtain a test material. The amount of nickel deposited is 0.
1g/a+'', and no undiffused metallic nickel was present.The amount of metallic chromium was 100 mg/m2, and the amount of hydrated chromium oxide was 10 mg/m''.

[Comparative Example 5] A low carbon cold rolled steel sheet was electrolytically degreased in an aqueous sodium hydroxide solution, washed with water, and then treated with NiSO4.7Hz0240g/It.
, N1CfL4・6) 12045 gN), , H3BO
430g/IL.

Current density 15A/dm2 with steel plate as cathode at temperature 50℃
Electrolytic nickel plating with an electrolytic time of 0.6 seconds is applied,
After washing and drying, it was immediately annealed in a reducing atmosphere (10% H2% dew point -25°C, remainder N2) at a temperature of 700°C for 30 seconds, and then dry temper rolling was performed at a reduction rate of 1%. Immediately thereafter, 1. After electrolytic degreasing in an aqueous sodium hydroxide solution and washing with water, Cr0380g/f was obtained without pickling!
,,Na2SiF61.4g/IL, sulfuric acid 0.4g/j
Z, Cr3Jg/u, temperature 45°C, current density io with steel plate as cathode.

A/dm2 It was subjected to electrolytic chromic acid treatment for an electrolysis time of 0.6 seconds, washed with warm water at 70°C, and then dried to obtain a test material. The amount of nickel deposited was 0.1 g/m', and no undiffused metallic nickel was present. The amount of metallic chromium is 100
Barn2 The amount of chromium hydrated oxide is 10 mg/m
"Met.

[Comparative Example 6] A low carbon cold rolled steel sheet was electrolytically degreased in an aqueous sodium hydroxide solution, washed with water, and then treated with NiSO4.7H20240g/vertical.
N1Cj24・6) 12045 g/II, 83B04
30g/Il.

Current density 15A/dm' with steel plate as cathode at temperature 50℃
Electrolytic nickel plating with an electrolytic time of 0.6 seconds is applied,
After washing with water and drying, it was immediately annealed in a reducing atmosphere (io% H2, dew point -25°C, balance N2) at a temperature of 700°C for 30 seconds, and then dry temper rolled at a rolling reduction of 1%. Subsequently, immediately after electrolytic degreasing in an aqueous sodium hydroxide solution and washing with water, Cr0580g/IL was obtained without pickling.
Na25iFs1.4g/f, sulfuric acid 0.4g/jZ, C
r"Ig/u, electrolytic chromic acid treatment was performed at a temperature of 45°C using a steel plate as a cathode at a current density of 500A/dm2 for an electrolysis time of 0.01 seconds, and after washing with hot water at 70°C, it was dried and used as a test material. The amount of nickel deposited is 0.1g/m2,
There was no undiffused metallic nickel present. The amount of metallic chromium is 10 mg/m2 The amount of chromium hydrated oxide is 8 m
g/m2.

[Comparative Example 7] A low carbon cold rolled steel sheet was electrolytically degreased in an aqueous sodium hydroxide solution, washed with water, and then treated with NlSO4.7H20240g/42
, N1CJ24・6H2045g/It, H3BO43
0g/l, temperature 50℃, current density 15 using steel plate as cathode
A/dm2 Electrolytic nickel plating with an electrolytic time of 0.6 seconds is applied, and after washing and drying, it is immediately placed in a reducing atmosphere (10%
H2, dew point -25°C, balance N2), annealing at 700°C for 30 seconds, followed by dry temper rolling at a rolling reduction of 1%. Immediately thereafter, electrolytic degreasing was performed in a sodium hydroxide rum aqueous solution, and after washing with water, Cr038 was removed without pickling.
0g/l, Na25iFa1.4g/Il, sulfuric acid 0.4
g/u, Cr3Jg/J! , current density 400A/dm' with steel plate as cathode at temperature 55℃, electrolysis time 0.08
The sample was subjected to electrolytic chromic acid treatment for a second, washed with warm water at 70°C, and then dried to obtain a test material. The amount of nickel deposited is 0.
At 1 g/m2, no undiffused metallic nickel was present. The amount of metallic chromium was 1100III/l112 and the amount of hydrated chromium oxide was 2 mg/m2.

[Comparative Example 8] After electrolytically degreasing a low carbon cold rolled steel sheet in an aqueous sodium hydroxide solution and washing with water, NiSO4.7H, 0240 g/IL
, Ni(:n 4・6H, 04s g#, H3B
Electrolytic nickel plating was performed using O430g/42 at a temperature of 50°C and a current density of 15A/dm2 using a steel plate as a cathode for an electrolysis time of 4.6 seconds. After washing and drying, the plate was immediately placed in a reducing atmosphere (10% H2% dew point -25°C, remainder N2), temperature 700
C. for 30 seconds, followed by dry temper rolling at a rolling reduction of 1%. Subsequently, immediately after electrolytic degreasing in an aqueous sodium hydroxide solution and washing with water, Cr was removed without pickling.
0380g/l, Na2SiF61.4g/u, sulfuric acid 0
．． 4g/jl! , Cr"1g/u, temperature 45℃, current density 400A/dm' with steel plate as cathode, electrolysis time 0
．． The sample was subjected to electrolytic chromic acid treatment for 0.8 seconds, washed with warm water at 70°C, and then dried to obtain a test material. The amount of metallic chromium is 1
100rn/m2 The amount of chromium hydrated oxide is 10mg/
There were 112 days. The amount of nickel deposited is 0.8g/m'
Therefore, undiffused metallic nickel was present.

[Comparative Example 9] A low carbon cold rolled steel sheet was electrolytically degreased in a sodium hydroxide aqueous solution, washed with water, and then Ni was degreased with a 10% nickel acetate aqueous solution.
Immediately after coating and drying 80 mg/m2, annealing was performed in a reducing atmosphere (10% H2, dew point -25°C, balance N2) at a temperature of 680 t, for 30 seconds, and then the rolling reduction was 1%.
Dry temper rolled. Subsequently, immediately without degreasing or pickling, Cr0.80g/I1%Na, 5iFs1
．． 4g/u, sulfuric acid 0.4g/11, Cr”Ig
/Jl, current density 400 with steel plate as cathode at temperature 45℃
A/d+n' It was subjected to electrolytic chromic acid treatment for an electrolysis time of 0.05 seconds, washed with 70 tons of warm water, and then dried to obtain a test material. The amount of metallic chromium is 100 mg/va2
The amount of chromium hydrated oxide was 10 B/m2. The amount of nickel deposited was 0.08 g/m2, and undiffused metallic nickel was present.

[Comparative Example 10] A low carbon cold rolled steel sheet was electrolytically degreased in a sodium hydroxide aqueous solution, washed with water, and then Ni was degreased with a 10% nickel acetate aqueous solution.
Immediately after coating and drying 80 mg of 7 m'', it was annealed in a reducing atmosphere (10% H2% dew point -25°C, remainder N2) at a temperature of 880°C for 30 seconds, and then dry temper rolling was performed at a reduction rate of 1%. , immediately without degreasing or pickling, CrO360g/fL, NH4F4g/
fL%CS"2g1ll, a current density of 100 A/d+n" using a steel plate as a cathode at a temperature of 50°C, electrolytic chromic acid treatment with an electrolysis time of 0.5 seconds, washing with hot water at 70°C, and drying to obtain the test material. And so. The amount of metallic chromium is 100mg
/m2 The amount of chromium hydrated oxide was 10 rsg/m2. The amount of nickel deposited was 0.08 g10+', and undiffused metallic nickel was present.

(Comparative Example 11) After electrolytically degreasing a low carbon cold rolled steel sheet in an aqueous sodium hydroxide solution and washing with water, NiSO4.7H20240g/x,
N1CJ24・6H2045gHL, H3BO430g
/u, current density 15A/u with steel plate as cathode at temperature 50℃
Electrolytic nickel plating was applied with an opening time of 0 seconds upon dissolution of ilE, and after washing and drying, immediately annealing was performed in a non-reducing atmosphere (dew point -25℃) at a temperature of 700℃ for 30 seconds, followed by annealing at a reduction rate of 1%. Dry temper rolling was carried out. Immediately thereafter, electrolytic degreasing was carried out in an aqueous sodium hydroxide solution, and after washing with water, Cr0380g/u, Na25iF was applied without pickling.
, 1.4g/j! , sulfuric acid a, +g/i, , Cr”Ig/
j2, current density 500^ with steel plate as cathode at temperature 45℃
/dm2 It was subjected to electrolytic chromic acid treatment for an electrolysis time of 0.01 seconds, washed with warm water at 70°C, and then dried to obtain a test material. The amount of nickel deposited was 0.1 g/m2, and no undiffused metallic nickel was present. The amount of metallic chromium is 10
mg/m2 The amount of chromium hydrated oxide is 81g/l112
Met.

[Comparative Example 12] A low carbon cold rolled steel sheet was electrolytically degreased in an aqueous sodium hydroxide solution, washed with water, dried, and then subjected to a reducing atmosphere (10% H2, dew point -
It was annealed at 25° C. (remainder N2) at a temperature of 700° C. for 30 seconds, and then dry skin-pass rolled at a rolling reduction of 1%. Next, electrolytic degreasing was performed in an aqueous sodium hydroxide solution, and after washing with water, Cr (h80g/J!, Na25iFa) was removed without pickling.
1.4g/i, sulfuric acid 0.4g/Il, CS”1g/
JZ, current density 400 with steel plate as # pole at temperature 45℃
A/dm" Electrolytic chromic acid treatment was applied for an electrolysis time of 0.08 seconds, and the sample was washed with hot water at 70°C and dried to obtain a test material. The amount of metallic chromium was 100 mg7m2, and the amount of hydrated chromium oxide was 2 mg. /m'.

Evaluation of each sample material obtained as described above was carried out as follows.

(1) Appearance: Appearance was evaluated in three stages.

O: Good, Δ: Slightly defective, X: Clear uneven appearance (2) Weldability: Using a copper wire resistance seam welder (pressure force 50 kg, welding speed 50 m7 minutes) Weldability was evaluated with an overlap of 0.4 mm. Weldability was evaluated based on the size of the appropriate welding current range in which the number of splashes with a length of 1 mm or more was 2 or less per can and sufficient welding strength was obtained.

◎... 300 A or more O... 100 A or more and less than 300 A △... -10 A or more and less than 100 A was carried out as follows. Apply 50 mg/dm2 of epoxy phenol paint and bake.
The ends and back side were sealed, the lower half was immersed in tomato juice at 55°C, and evaluation was made based on the occurrence of blisters in the area above the liquid level after 2 weeks.

O...Almost no blisters Δ...Small blisters occur After applying the same coating as above and sealing the end and back surfaces, a cross cut was made in the center and immersed in an aqueous solution of 7.5 g/11 citric acid and 7.5 g/11 common salt.
Evaluation was made based on the maximum corrosion width and maximum corrosion depth after 6 hours.

Maximum corrosion width O...0.2mm or less △・-0.2mm more than 0.4mm or less ×...More than 0.4mm maximum corrosion depth ○...0.1mm or less △-More than 0.1mm and less than 0.15m ×...-0.15mm or more The weldability is improved because However, the appearance is poor due to pickling. The extent of this is due to the electrolytic chromic acid treatment. It is worse than Comparative Example 3, which has a low flow density. ing.

Comparative Example 5 has a good appearance because it is not pickled before the electrolytic chromic acid treatment, but the high-speed weldability is insufficient because the current density of the electrolytic chromic acid treatment is as low as 100 A/da+'.

In Comparative Example 6, nickel diffusion treatment and electrolytic chromic acid treatment were performed at a high current density of 500 A/dm'', but the amount of metallic chromium was too small at 10 mg/m2, resulting in poor weldability.

Comparative Example 7 also underwent nickel diffusion treatment and electrolytic chromic acid treatment at a high current density of 400 A/dm', but the weldability was poor because the amount of chromium hydrated oxide was too small at 2 mg/+n''. The manufacturing methods and quality evaluation results of Examples 1 to 7 and Comparative Examples 1 to 12 are shown in Table 1.

Examples 1 to 7 all meet the requirements of the present invention It satisfies not only the appearance but also high-speed welding. It satisfies both durability and corrosion resistance.

Comparative Examples 1 and 2 have poor weldability because they do not have nickel diffusion treatment. However, since Comparative Example 2 uses electrolytic chromic acid treatment at a high current density of 400 A/dII+', Comparative Example 1 has a low current density of 50 A/da'.
Better weldability.

In Comparative Example 3, nickel diffusion treatment was performed, but the current density of the electrolytic chromic acid treatment was as low as 10 OA/dI112, resulting in poor high-speed weldability and, moreover, the appearance was poor due to pickling.

Comparative Example 4 has a lower electric power compared to Comparative Example 3. The dechromic acid treatment is as high as 400 A/dm2 and has poor performance.

In Comparative Example 8, since the amount of nickel deposited was too large at 800 mg/-, metallic nickel remained after annealing, and therefore pitting corrosion was likely to occur.

Since both Comparative Examples 9 and 10 are coated with nickel salt, metallic nickel remains after annealing and pitting corrosion is likely to occur. Further, in Comparative Example 10, the current density of the electrolytic chromic acid treatment was as low as 100 A/dm2, so high-speed weldability was poor.

In Comparative Example 11, annealing was performed using hydrogen gas. It was not carried out in a reducing atmosphere. A small amount of rust remains on the surface, resulting in poor appearance. In addition, weldability and corrosion resistance are poor. Ru.

In Comparative Example 12, there was no nickel diffusion treatment and the amount of hydrated chromium oxide was too small at 2 B7 m2, resulting in poor high-speed weldability and poor corrosion resistance.

<Effects of the Invention> Since the present invention is configured as described above, according to the present invention, seam resistance welding can be performed at high speed without using expensive copper wire such as tin-plated copper wire. It is now possible to provide an inexpensive steel sheet for cans with excellent corrosion resistance. The manufacturing method of the present invention may include nickel plating,
Continuous annealing, tempering X-rolling, and electrolytic chromic acid treatment are performed in one continuous line, which has the additional advantage of significantly reducing costs.

Therefore, it is expected that the present invention can greatly contribute to reducing the excessively high domestic can costs, which have been a problem recently.

649-

Claims (4)

[Claims] (1) After a thin steel plate is continuously degreased, nickel plated, continuously annealed, and then temper rolled in a dry state, it is immediately subjected to electrolytic chromic acid treatment without pickling at an electrolytic current density of 200~
A method for producing a surface-treated steel sheet for welded cans, characterized in that the process is carried out at 600 A/dm^2. (2) Thin steel sheets are continuously degreased, nickel-plated, continuously annealed, and then temper-rolled in a wet state, followed by degreasing and immediately electrolytic chromic acid treatment without pickling at an electrolytic current density of 200 to 600 A. 1. A method for manufacturing a surface-treated steel sheet for welded cans, characterized in that the manufacturing method is carried out at /dm^2. (3) The method for manufacturing a surface-treated steel sheet for welded cans according to claim 1 or 2, wherein the nickel plating is performed by electroplating to form a nickel deposition amount of 10 to 500 mg/m^2 on the surface of the steel sheet. (4) The continuous annealing is performed at a temperature of 600 to 900°C for 1 time.
The method for producing a surface-treated steel sheet for welded cans according to any one of claims 1 to 3, wherein the process is carried out for 0 to 90 seconds in a reducing atmosphere containing hydrogen gas. (5) The electrolytic chromic acid treatment contains 20 to 150 mg/m^2 of metallic chromium and 3 to 150 mg/m^2 of chromium hydrated oxide.
The method for producing a surface-treated steel sheet for welded cans according to any one of claims 1 to 4, wherein the surface-treated steel sheet for welded cans is formed at 20 mg/m^2.