JPS6036692A - Tinned steel sheet and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of a tinned steel sheet by forming a Cu layer contg. a specified amount of a Cu-Sn alloy besides an Fe-Sn alloy when an electrolytically tinned steel sheet is manufactured using a continuously cast material. CONSTITUTION:This tinned steel sheet has a layer consisting of 0.001-0.2g/m<2> Cu >=50wt% of which is in the form of a Cu-Sn alloy and 0.001-1.5g/m<2> (expressed in terms of Sn) Fe-Sn alloy and an Sn layer as an upper layer on a steel sheet. For example, a steel sheet is plated with 0.001-0.2g/m<2> Cu, and it is tinned and heated at about 150-400 deg.C to convert >=50wt% of the Cu into a Cu-Sn alloy. At the same time, 0.001-1.5g/m<2> (expressed in terms of Sn) Fe-Sn alloy is formed. Thus, the desired tinned steel sheet with improved corrosion resistance can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electro-tin plated steel sheet that improves corrosion resistance and a method for manufacturing the same.

Electrotinned steel sheets are used for food and beverage containers. This tin-plated ha plate is degreased, pickled, then tin-plated, and then heated for a short time above the melting point of tin to brighten the tin surface and form an iron-tin alloy at the same time. This iron-tin alloy greatly affects corrosion resistance.

On the other hand, in recent years, continuous casting materials have been used instead of ingot materials for the base steel of electrically tinned steel sheets due to customer needs or economical reasons.

Unlike the rimmed steel of ingot materials, the surface layer of Mdi materials does not have a surface layer similar to that of pure iron, but tends to have a uniform composition, including 'Rm, and is free of additives up to the surface layer. Contains a large number of impurity elements, which poses a major obstacle to corrosion resistance.In this way, the corrosion resistance of the alloy layer of tin-plated steel sheets made using continuous casting materials without a rim layer is poor, which can cause various troubles. .

The ATC test is used as a method for evaluating the corrosion resistance of tin-plated steel sheets. The ATC test shows the coverage of Fe-8n alloy on steel. Tin-plated steel sheets made from continuous casting generally have higher A,
High T C value and poor corrosion resistance.

Furthermore, it has poor corrosion resistance in actual citric acid-based foods, often causing problems with corrosion inside the can. The reason for the poor corrosion resistance is thought to be not only the iron-tin alloy coverage formed during tin melting, but also the fact that impurities in the surface layer accelerate corrosion of the steel, causing expansion can or pitting corrosion.

The ATC value decreases as the amount of iron-tin alloy increases. Compared to rimmed steel, continuous casting materials generally exhibit higher values even with the same amount of iron-tin alloy. Therefore, simply increasing the amount of iron-tin alloy is not a measure to improve ATC (111).

JP-A-57-108291 describes a method for improving the corrosion resistance of a blind tin-plated steel sheet using continuous casting material. This method modifies the surface layer of the steel by rolling three pieces of iron plating before tin plating, making it similar to the surface layer of rimmed steel, which is close to pure iron, but the surface layer of rimmed steel is cold-rolled. , 20 to 43 Izm for annealed and temper-rolled tin-plated steel sheets
To improve corrosion resistance to the same extent as rimmed steel, iron plating is required up to the thickness of the rim shell of rimmed steel. Iron plating to this thickness requires a large amount of electricity in electrolytic iron plating 1-, and it also deteriorates the shape of the plate, which is unfavorable both economically and in terms of quality. . In JP-A No. 54-108291, a trace amount of iron plating is applied, but the iron plating hwk is
In case J), the steel on the surface of the base steel cannot be sufficiently coated with iron plating, so the surface layer of the continuously cast material containing impurity elements cannot be modified.

In this application, in addition to the iron-tin alloy, 50% or more of the layer is Cu-8n.
By providing a Cu layer with an alloy, the above-mentioned drawbacks are overcome and the corrosion resistance of tin-plated steel sheets using continuous casting materials is improved.

On the other hand, there is Japanese Patent Publication No. 54-20940 as a method for improving the ATC value of electric tin-plated steel sheets. In this 3- invention, N1. Pre-plating one type of Cu and Nj-8n alloy in the range of 0.005 to 05 μm,
This is a method in which the pre-plating metal or alloy is heated in a non-oxidizing atmosphere until the entire amount permeates and diffuses into the steel sheet, and then tin plating is performed.

In the electro-tin plating line, the above gold w is applied to the tin plating surface.
&Also, since we do not have a heating device that allows the alloy to permeate and diffuse into the steel sheet, this must be done in the annealing process. However, after annealing, tin-plated steel sheets (tin plate) are generally subjected to temper rolling in order to achieve hardness and surface roughness suitable for the intended use, as well as to improve the shape. During temper rolling, even if there is a small amount of Cu or Ni on the surface of the steel sheet, the life of the roll will be short (
There are drawbacks such as the inability to correct the shape and the inability to correct the shape, causing various obstacles to practical application.

In this application, in order to avoid penetration and diffusion of Cu into the steel, Cu is alloyed by heating 811 in a normal electro-tin plating line in one step with #811 in an ordinary electro-tin plating line, in order to prevent Cu from permeating and diffusing into the steel. At the same time, a Fe-8n alloy is formed by reacting with the tin layer on the exposed steel that is not sufficiently coated with Cu. Cu reacts with 8n in the upper layer to form a Cu-8n alloy, and Cu suppresses the reaction with steel. For this reason, if only the Cu-8n alloy is used, it may not adhere sufficiently to the base steel, and the intermediate layer Cu-8n alloy and unformed Cu of the Cu-8n alloy may be separated when light processing is performed. For example, since it is removed together with the tin layer at the exbansion ring processing part of a can lid, a drawn can, etc., the adhesion between the tin layer and the base steel is strengthened by forming an Fe-8n alloy.

On the other hand, in Japanese Patent Publication No. 54-20940, Nl, Cu or N
The i-8n alloy is immersed and diffused, and this diffusion layer acts as a barrier, making it difficult to form an iron-tin alloy in the reflow step after tin plating. Furthermore, Cu-8 is heated until the pre-plated metal disappears and is effective in corrosion resistance.
This results in the formation of n alloy or Nl-8n alloy, which not only fails to exhibit excellent corrosion resistance but also tends to cause problems during temper rolling. The present application overcomes the above-mentioned drawbacks and improves the corrosion resistance of continuous casting materials.

Next, the present application will be specifically explained.

50. on the steel plate. ijI electric% or more forms Cu-8n alloy and 0.001~0.2 ft/n-Cu and 5nll
as o, o o i~1.5 r/nl of Fe-8
This is a tin-plated steel sheet having a layer made of n-alloy and a tin layer on top.

Cu an alloy and Cu have an effect on the corrosion resistance of the base steel surface, and the corrosion resistance is further improved by using Cu-8n alloy containing 50% by weight or more of Cu. Cu, :C
U-8n metal-containing it is O, OO1f/rt? If it does not exist, corrosion resistance will not be improved, and if it is 0.2 fed or more, no further corrosion resistance can be obtained.

Fe-8n alloy is mainly composed of Fe5nl, but if this amount is excessive, cracks may occur in the alloy layer during processing in the can-making process, and tin-plated steel sheets have become thinner in recent years. In view of this, the limit is 1.5 f/nl from the economic point of view.

In addition, the Fe-8n alloy has a tin content of 0.00 on the surface of the steel.
If Fe-8 is not present at 1f/y+- or more, the adhesion between the base steel and the tin layer will be insufficient, making it unsuitable for processing purposes.
n alloy has a tin content of 0.0019/ff+1 to 1.5
f/n? is preferred. The amount of tin is determined depending on the application, and o
,oi~15? It is possible to go up to A.

Hereinafter, the method for manufacturing a tin-plated steel sheet of the present invention will be specifically explained.

(1) After degreasing and pickling a cold-rolled, annealed, and temper-rolled steel plate, it is plated with o, o o i~0.2 fA♂ copper. As the copper plating bath, a birophosphoric acid bath, a sulfuric acid bath, and a borofluoride bath are used. It can be easily performed by electroplating, and immersion plating may also be used. Copper plating amount 0, 2 f/rr? If it exceeds this, the steel surface will be coated with Cu and it will be difficult to produce the Fe-8n alloy, which is the constituent element of the present application, in the next step.
It is necessary to set it to 0.001-0.2 t/rrl. After copper plating, tin plating is performed. The amount of tin plating is determined depending on the application. Usually, the amount of tin plating on tin-plated steel sheet is 2
．． 8.5.6.8.4 and 11, 2 t/n? Tei
b Le is 2.8 f/rr? For example below 1 f/lr
? Or even less. As the tin plating bath, a sulfuric acid bath, an alkaline bath, a halogen bath, and a fluoroboration bath can be used. Tin-plated 7- After that, the tin is molten and brightened in one step of reflowing.
Heat at 0°C. As a heating method, electric resistance heating, high frequency heating, and a combination thereof can be applied.

Practically speaking, heating is carried out in seconds, so if heating is not done for a short time at 150°C or higher, Cu-8n alloy and Fe-an alloy
It becomes difficult to form an alloy, and if the temperature exceeds 400°C, I
'5-8n alloy grows excessively, so 150-400℃
is preferred. After rapid cooling, chemical treatment and anointing (
1.

(2) Cold-rolled, annealed, and temper-rolled steel sheets are also degreased and pickled. OO1~1.5 f/rr? Tin plating is carried out and continued with 0. OO1~0.2 f/n?
Performs copper plating. Is the tin plating amount 1.5 f/rr? At this point, the tin will cover the entire curve of the steel, so in the next process CLI-
Since it becomes difficult for the 8n alloy to form near the w4 surface, the initial tin metal hll is 1.5? At? The following are suitable. A copper plating layer is plated on the exposed steel and on the tin plating layer.

Subsequently, a predetermined tin plating is applied and heated at 150 to 400°C. By heating, a Fe-8n alloy is formed as well as a Cu-8n alloy. The initial tin 8-plating layer forms a Cu-8n alloy with the formation of a Fe-8n alloy, and the copper plating layer reacts with the underlying tin and overlying tin to form a Cu-8n alloy. The amount of unformed Cu in the Cu-8n alloy is influenced by the heating temperature and copper plating area, and increases as the heating temperature decreases and the amount of copper plating increases.

The minimum temperature for Cu-8n alloy to be 50% is 150°C.

Below, I will explain Moku 5 Kiaki in detail based on my skills and examples.

Example 1 A 0.22 m aluminum killed continuous T+II4 cold rolled steel plate was electrolytically degreased in a 7% sodium hydroxide solution, washed with water,
After cracking in a 3% sulfuric acid m solution and washing with water, the copper pyrophosphate plating bath composition and conditions are as follows: 0.03 f/l
T? After performing copper plating and washing with water, 5. (Tin plating of 3 fat♂ was performed and heated for 3 seconds to a maximum temperature of 280°C using a resistance heating method to melt the tin and form a Cu-8n alloy and a Fe-8n alloy. The resulting Cu-an alloy had a copper content of 0.03.
The total amount of CO on the fi back was 0.79/nl in the Cu-an alloy, and the Fe-an alloy as a tin layer.

As a result of X-ray diffraction, the produced Cu-an alloy is mainly CuaS.
It was n@.

Composition of the plating bath and treatment conditions Composition Copper birophosphate 80 f/1 Potassium birophosphate 350 'I/1 Ammonia water
3 td/1 Electrolytic condition current density 2 k/dry? Processing amount of electricity: 0.80/d Cold bath temperature: 55°C Example 2 A cold-rolled steel sheet similar to that of Example 1 was pretreated, and then a copper plating bath similar to that of Example 1 was used to reduce the current density. 0.
I A/(1?l/, processing electricity ffi O, I C/
After applying copper plating of 0.004 mm and 74♂ with d-, washing with water, tin plating at 5.6 t/rl in a tin sulfuric acid plating bath, and heating to a maximum temperature of 250°C for 3 seconds using the resistance heating method. It was heated to melt the tin and form a Cu-an alloy and a Fa-an alloy. This was followed by chemical treatment in a commonly used sodium dichromate solution and oiling. The produced Cu-an alloy is 0.004 ? /v? t'Cu all CuCu-an alloy, Fa-an alloy is 0.8 f/rr? Met.

As a result of X-ray diffraction, the produced Cu-an alloy is mainly Cu5S.
It was n5.

Example 3 A cold-rolled steel sheet similar to that in Example 1 was pretreated, then tin plated at 0.01 f/d in a tin sulfuric acid plating bath, and then copper plated in the same manner as in Example 1. using a current density of 2 A/dtr? , processing electricity amount 0.4 C/dnl and 0.015 f/lr? After washing with water, tin plating at 5.6 rAI in a tin sulfuric acid plating bath, heating for 5 seconds to a maximum temperature of 220°C using a resistance heating method to bond Fe-an alloy and Cu- An alloy was formed. This was followed by chemical treatment in a commonly used sodium dichromate solution and oiling. The produced Cu-an
The alloy is o, 01 r/m' and the Cu alloying rate is 67%1
1-, and the Fe-an alloy is 0.01'? Ar? Met.

As a result of X-ray diffraction, the Cu-an alloy was mainly Cu5Sn5.

Comparative Example A cold-rolled steel sheet similar to that used in Example 1 was pretreated and then placed in a tin sulfuric acid plating bath at a temperature of 5.6? /lT? Tin plating is carried out, and by resistance heating method, the tin is melted and Fe is
-an alloy was formed. This was followed by chemical treatment in a commonly used sodium dichromate solution and oiling. The produced Fe-an alloy is 0.91//rr? Met.

The tin-plated steel plates obtained in Examples 1 to 3 and Comparative Example were subjected to a human TC test and the following corrosion resistance test.

Corrosion resistance test A 50m x 20m specimen was coated with Fa-8n alloy layer and Cu-
An, which did not form an an alloy, was kept at 0.35 V in an IN sodium hydroxide solution at 40° C. and electrolytically removed. The ends of this test piece were sealed and immersed in IM citric acid solution at 25°C, and the iron corrosion rate was determined from the amount of hydrogen 12- generated. Iron corrosion rate mg/dff
// Shown in hr.

As shown in Table 1, the tin-plated steel sheet of the present invention exhibited excellent corrosion resistance and significantly improved the corrosion resistance of continuous casting materials by -2.

Claims (3)

[Claims] (1) Cuto, 001~0.2 between the steel plate and the tin layer
0.001 to 1.5 f/rr as 1 back and 8n amount? 1. A tin steel sheet made of a Fe-Sn alloy, characterized in that Cu-8n base metal is present in an amount of 50% by weight or more in Cu. (2) Copper plating on the back of the steel plate at o, o o i ~ 0.2 F, followed by tin plating, followed by heating at 150 ° C ~
Heating at 400℃, 50% by weight or more of Cu
At the same time as forming f3n4 gold, 0 as 8n 凰,
001~1.5 f/n? The tin metal hw! according to claim 1, characterized in that an Fe-Sn alloy is formed. Method of manufacturing the board. (3) After tin plating 0.001 to 1.5 f/m' on the steel plate, o, ooi to 0.2 t/n? 150~400 after copper plating and then tin plating.
Heating at ℃, 50% by weight or more of Cu-8r
+ At the same time as forming an alloy, the amount of Sn is o, oo
2. The method for manufacturing a tin-plated steel sheet according to claim 1, characterized in that an Fe-Sn alloy with a thickness of i to 1.5 r/y is formed.