JPS6036693A - Tinned steel sheet and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of a tinned sheel sheet by forming a Cu-Ni layer contg. specified amounts of a Cu-Sn alloy and an Ni-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 <=0.2g/m<2> in total of >=0.001g/m<2> Cu >=50wt% of which is in the form of a Cu-Sn alloy and >=0.001g/m<2> Ni >=50wt% of which is in the form of an Ni-Sn alloy and 0.001- 1.5g/m<2> (expressed in terms of Sn) Fe-Sn alloy between a steel sheet and an Sn layer. For example, a steel sheet is plated with 0.001-0.199g/m<2> Cu, and it is plated with >=0.001g/m<2> Ni. The total amount of Cu and Ni is adjusted to <=0.2 g/m<2>. The plated steel sheet is tinned and heated at about 150-400 deg.C to convert >=50wt% of the Cu into a Cu-Sn alloy and >=50wt% of the Ni into an Ni-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 is 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 steel sheet is degreased and pickled, then tin-plated, and then heated for a short time above the melting point of tin to make the tin surface bright and at the same time form an iron-tin alloy. This iron-tin alloy greatly affects resistance and k resistance.

On the other hand, due to the needs of customers and economical reasons, in recent years, lotus-cast steel has been used instead of ingot steel for electrolytic tin-plated steel sheets.

Continuous casting shrines do not have a surface rim layer that is close to pure iron like ingot rimmed steel, but they tend to have a uniform composition including the surface layer, and contain many impurity elements added to the surface layer. This is a major obstacle to corrosion resistance. As described above, the corrosion resistance of the alloy layer of a tin-plated steel sheet using a continuous casting material without a rim layer is poor, which may 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 coating properties of the Fe-an alloy on the steel. Tin-plated steel sheets made from continuous cast materials have a higher AT than when using general rimmed steel.
High C value (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 coverage of the iron-tin alloy formed when tin is melted, 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 the ATC value.

JP-A-57-108291 discloses a method for improving the corrosion resistance of electro-tinned copper plates using continuous casting materials. In this method, iron plating is applied before tin plating to modify the steel surface layer so that the surface layer is similar to the surface layer of rimmed steel, which is close to pure iron. However, the surface layer of rimmed steel is cold rolled, annealed, The temper-rolled original plate for tin-plated steel sheet is thick at 20 to 40 μm, and in order to improve the corrosion resistance to the same level as rimmed steel, iron plating is required to the thickness of the rim layer of rimmed steel. If iron plating is carried out at this rate of 1 = 3, a large amount of electricity will be required for iron plating, and the deterioration of the shape of the plate due to electrodeposition stress will be avoided, both economically and in terms of quality. It's not good to be in a coma. In JP-A No. 54-108291, a small amount of iron plating is applied, but if the iron plating l is too small, the steel on the surface of the base steel cannot be sufficiently coated with iron plating, so continuous casting is required. The surface layer of the material containing impure elements cannot be modified.

In this application, in addition to the iron-tin alloy, 50% by weight or more is Cu-Sn.
By providing a Cu layer having an alloy and an N1 layer having 50% by weight or more of an Nl-Sn alloy, the above-mentioned drawbacks are overcome and the corrosion resistance of a tin-plated steel sheet using a continuously cast material is improved.

On the other hand, there is Japanese Patent Publication No. 54-20940 as a method for improving the A and T C values of electrolytic tin-plated steel sheets. This invention involves pre-plating the surface of a steel plate with one of Nl, Cu and N1-Sn alloy to a thickness of 0.005 to 05 μm, and all of the pre-plating metal or alloy permeates and diffuses into the steel plate in a non-oxidizing atmosphere. This method involves heating the material until it reaches 100%, and then tin-plating it.

4- Since the electro-tin plating line does not have a heating device for permeating and diffusing the upper IT4 metal or alloy into the steel sheet before tin plating, it is naturally carried out 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. Even if a small amount of Cu or Nl is present on the surface of a steel sheet during temper rolling, there are drawbacks such as shortened roll life and difficulty in shape correction, which poses various obstacles to practical application.

In order to prevent Cu and N1 from penetrating and diffusing into the steel, Cu and N1 are alloyed with Sn, which is subsequently plated, and Sn in a normal electro-tin plating line by heating in a single step of melting and brightening the tin. At the same time as C
The Fe-Sn alloy is formed by reacting with the tin layer on the exposed steel which is not sufficiently coated with u and N1. C
u and N1 react with sn in the upper layer to form a Cu-Sn alloy and a Ni-Sn alloy, and Cu and Nl suppress the reaction with steel. For this reason, Cu-Sn alloy and N1-Sn alloy alone do not adhere well to the base steel, and when the eaves are processed, the intermediate layer Cu-Sn alloy and N1
-Sn alloys as well as unalloyed Cu and N1 may spall. The Fe-
The formation of the Sn alloy strengthens the adhesion between the tin layer and the base steel.

On the other hand, in Japanese Patent Publication No. 54-20940, prior to tin plating, N1°Cu or N1-Sn alloy was heated at a high temperature of approximately 700°C in an annealing process to diffuse the diffusion layer. acts as a barrier, making it difficult to form an iron-tin alloy in the single glue flow step after tin plating. Furthermore, it is heated until the pre-plated metal disappears, and Cu is effective for corrosion resistance.
-The formation of Sn alloy or N1-Sn alloy occurs (
(However, it has the drawback that it not only cannot exhibit good corrosion resistance, but also tends to cause trouble 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.

Cu content between the steel plate and the tin layer is 0.001 f/lt?
That's all, N11it O,001f/n? above and Sn
It is made of a Fe-Sn alloy with 0001-1.5 f/d as i, the sum of Cu and Nil is 02 or less, and the Cu-8n alloy in Cu is more than 50% fA%-1-1Nl in Nl.
This is a tin-plated steel sheet in which l-Sn alloy is present in an amount of 50% or more.

The Cu-Sn alloy and Cu have a positive effect on the corrosion resistance of the base steel surface, and the presence of Ni and the N1-Sn alloy further improves the corrosion resistance. 0, 0 as Cu@
01 r? 17. Corrosion resistance has been improved above 0,001? At? The presence of N1 further improves corrosion resistance. Is the sum of N1 and Cu 0.2? /l
r? No higher corrosion resistance of 11 can be obtained with the above. Cu
Corrosion resistance is improved by alloying 50% or more of Nl with Sn.

Fe-Sn alloys mainly consist of FeSn2, but if this amount becomes too large, cracks may occur in the alloy layer during processing in the can manufacturing process, and tin-plated steel sheets have become thinner in recent years. Considering this, 1.5?
/rr? is the limit. In addition, Fe-Sn alloy is applied to the surface of the steel as tin. OO1t/lr? If E does not exist, the adhesion between the base steel and the tin layer will not be sufficient, and the Fe-Sn alloy will not be suitable for processing purposes.
Toshite O,OO1~1.5? /rr? is suitable.

Hereinafter, two methods for producing a tin-plated steel sheet according to the present invention will be specifically explained.

(1) Is it 0.001 to 0.19 f/rr when cold rolled, annealed, and temper rolled steel sheets are degreased and pickled? Perform copper plating or nickel plating. As the copper plating bath, a birophosphoric acid bath, a sulfuric acid bath, and a borofluoride bath are used.

Copper plating can be performed by electroplating, and immersion plating may also be used.

Electroplating is suitable for nickel plating, and any of nickel sulfate plating baths, nickel chloride plating baths, sulfuric acid baths and MIN1 ammonium baths can be used as nickel plating baths. . After copper plating (or nickel plating), continue with nickel (or copper plating). Nickel (or copper) plating is performed so that the total amount of Cu and N1 is 0.2 or less. In the next step, copper plating reacts with tin, resulting in C
Part or all of u = 8 part forms Cu, -Sn alloy. Cu and Cu-S
Is the total amount of n alloy 0.0019an as Cu? Corrosion resistance will not be improved unless more than 0.001 W/n? The above is necessary. Nl, N
i-Sn alloy is 0.001 V/rr as N1 condition? Although the above is effective in further improving corrosion resistance, CuJ
If the sum with ii exceeds 0.2/-, it will be difficult to form a Pc-Sn alloy, so the sum of the amounts of copper plating (1) and Nitsuno1 plating is preferably 022242 or less. Copper plating and nickel plating may be performed in any order. After copper plating and nickel plating, tin plating is performed.

The amount of tin plating is determined depending on the application, and the amount of tin plating on tin-plated steel sheets is usually 28.5, 6.84 and 11.2.

? ,/ly? However, a tin plating bath of 287/silence or less, for example 17 or less, can be used.3 As the tin plating bath, a sulfuric acid bath, an alkaline bath, a halogen bath, and a borofluoride bath can be used. After tin plating, the tin is heated at 150 to 400°C in a reflow step to melt and brighten the tin.

As the heating method, electric resistance heating, high frequency heating, and fJt use thereof can be applied. In an actual continuous line, heating is performed in seconds, so the heating temperature can be controlled from the maximum temperature reached. This heating causes the formation of Cu-8n alloy, i"Ji-8n alloy, and Fe-8n alloy. More than 50 mk% of the plated Cu and Nl is alloyed with 8n, that is, Cu-8n alloy, Since N1-8n alloy must be formed,
Heating to 150°C or higher is required. At the same time, the formation of Fe-8n alloy occurs, but when heated above 400℃, re-8n
The temperature is preferably 150 to 400°C since alloy formation becomes excessive. When the melting point of tin is 231.9°C or higher, Cu-8n alloy, N
Since the formation rate of i-8n alloy and Fe-8n alloy is high, the alloying rate of Cu and Ni is high. After heating, it is rapidly cooled, a prescribed chemical treatment is performed, and oil is applied.

(2) In the method (1) above, Cu and Ni
Instead of plating, the tin-plated steel sheet of the present invention can also be produced by eutectoid plating of Cu and Ni on a steel sheet. A birophosphoric acid bath can be used as the eutectoid plating bath. The eutectoid plating amount is 0. OO1? More than yen, Ni amount 0, 0
019/n? Is the total amount 0.21/n? It is as follows. After eutectoid plating, metal plating is performed in the same manner as in (1) above, and heated at 150 to 400°C. After heating, chemical treatment and oiling are applied.

Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 Annealed, I & I quality rolled 0,22 piece aluminum killed series N
A cold-rolled steel plate was electrolytically degreased in a 79'6 sodium hydroxide solution and washed with water. /, After electrolyzing in a 3% sulfuric acid solution and washing with water, 0032h? with the following pyrophosphoric acid phase plating bath composition and conditions. After performing copper plating and washing with water, nickel sulfate plating bath composition and conditions shown below were used for 0. O
I W//n? After applying nickel plating and washing with water, it was placed in a tin sulfate plating bath at 6.6 t/lr? was plated with tin, and heated for 3 seconds to a maximum temperature of 270° C. using a resistance heating method to melt Sn and form a Cu-811 alloy, a Ni-8n alloy, and an Fa-8n alloy. This was followed by a chemical treatment in a commonly used sodium dichromate solution, dried and oiled.

The produced it Cu-So alloy is 0.0 as CuM
3? /lr? , 1l-Ni-8n alloy has a Ni content of 0. An alloy was formed with both Cu and Nl in a total amount of 8n in OIV and Yen. Fe-
8n alloy has Sn content of 0.8 f/rr? Met.

X-ray diffraction results show that the Cu-8n alloy is Cu5Snb, Ni
-8n alloy was Ni1sn4.

Composition of copper plating bath and processing conditions Composition Pyrophosphate phase 80 W/1 Potassium pyrophosphate 350 f/1 Ammonia water 3αshi'l Processing conditions Current density 2 A/drr? Processing amount: 0.8 C/d bath Temperature: 55°C Nickel plating bath composition and processing conditions: Nickel sulfate: 200 f/1 Boric acid: 10 f/1 Processing conditions: Current density: I A/dTr? Processed electric fish 0.40/dze12- Bath temperature 45°C Example 2 A cold-rolled steel plate similar to that used in Example 1 was pretreated, and then a nickel plating bath similar to that used in Example 1 was used to conduct electric current treatment. Density I A/dze, processing electricity I C/d door 0.025
After applying nickel plating of f/d and washing with water, using the same copper plating bath as in Example 1, a current density of 0.1 k/d was applied.
tr? , processing electricity 1jt 0. IC/drr? Copper plating is applied to 0.004 f//m'', washed with water, and then plated at 5.61/W in a tin sulfuric acid plating bath, and heated to a maximum temperature of 240°C for 3 seconds using the resistance heating method. Heating to melt Sn, Cu-8n alloy, N
An i-8n alloy and a Fe-8n alloy were formed. This was followed by chemical treatment in a commonly used sodium dichromate solution and oiling. The produced Cu-8n alloy has a Cu content of 0.004 f! /d, Ni-8n alloy has an Nl content of 0.025? /W? Therefore, both Cu and Ni became a total [Sn and (D alloy).The Fe-an alloy was 0.7
It was VArl. The X-ray diffraction results show that the Cu-an alloy is C
The u58ru+, N1-an alloy was N15Sn4.

Example 3 A cold-rolled steel sheet similar to that of Example 1 was pretreated, and then eutectoid plating with Cu and Nl was performed using the following pyrophosphoric acid bath, resulting in a plating of 0.02 f/m''. Cu and 0.039/d
Ni was precipitated. After rinsing with water, tin plating was performed at 5°6 f/nt" in a sulfur and acid tin plating system, and the highest temperature was heated for 10 seconds to the melting point of Sn (220°C below the surface), and Cu- 8n4 gold, N1-Sn alloy and Fe-8o alloy were formed, followed by chemical treatment in commonly used sodium dichromate solution.
I anointed it with oil.

The produced Cu-Sn alloy is 01014ri/n? , Ni-
The Sn alloy is 002 and the alloying rate of Cu is 57%, Ni
The alloying ratio of is 67%, and the Fe Sn alloy is 0.029/
lt? De-) It is. As a result of X-ray inspection, the Cu-Sn alloy was CueSo6, and the Ni-Sn alloy was N15Sn4.

Composition and processing conditions for eutectoid plating of Cu and N1 Composition Nickel birophosphate 300 ? /1 Copper pyrophosphate 15 t/1 Potassium pyrophosphate 350 ? /10 Tushiel Junior
25v/ρ Processing conditions Current density IA,/(Jrr? Processing electricity amount 3C/dn? Bath temperature 60°C Comparative example Using the same cold rolled steel sheet as in Example 1, pretreatment was performed and then tin sulfuric acid plating was performed. Tin plating is carried out at 5.6 ?/n? in a bath, and the tin is melted in the heat by resistance heating method
'e-Sn alloy was formed. It was then chemically treated in a sodium dichromate solution, which is commonly used in criminal cases, and then anointed with oil. The produced Fe-Sn alloy had a density of 0.9P/silence.

The tin-plated steel sheets obtained in Examples 1 to 3 and Comparative Example were subjected to human 't' c i< tests and the following corrosion resistance test.

Corrosion resistance test A 50w+X20m specimen was coated with Fe-Sn alloy layer and CI
Sn that did not form a J-Sn alloy was electrolytically removed in an IN water 15-sodium oxide solution at 40° C. while maintaining the voltage at 0.35 V. The end face of the second specimen was sealed and soaked in IM citric acid solution at 25°C, and the iron corrosion rate was estimated from the amount of hydrogen generated. The iron corrosion rate was expressed as ■/dWhr.

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

16 one

Claims (1)

[Claims] (1) Between the steel plate and the tin layer, Cu11O,001f/n
? Above, Nl amount 0.001 f/r1 or above and 8ni
0,001 to 1.5 tA as l? ? F'e-Sn
Made of alloy, the total amount of Cu and N1 is 0.2 f/rr
? Below, Cu-8n alloy in Cu is 50% or more,
A tin-plated copper plate characterized in that Ni-8n base metal is present in an amount of 50% by weight or more in Nl. (21w4 board 0.001~0.199 ?/rr?
(After D copper plating, nickel plating is performed at 0.001 f/lr? or more and the total amount with Cu is 0.2 f/yrl or less, followed by tin plating,
Heating at 00℃, 50% by weight of Cu-8n alloy in Cu
As described above, at the same time as forming 50% by weight or more of a Ni-Sn alloy in Ni, the process is performed. (3) 0001~0.199 rk on steel plate? After nickel plating, 0.001t/n? Therefore, the sum of -E and N1h↓ is 0.2? /n? The following copper plating is carried out, followed by tin plating, heated at 150 to 400°C, and Cu-8n alloy is added to Cu in an amount of 50% by weight or more, Ni
At the same time, when the Ni-3nO gold is made into an E shape by 50 layers and 1% or more, the process is performed simultaneously. (4) On steel plate +: 0.001 t/rr? Above C
u and 0.001? N1 over 7 arms, the sum of which is 0.2
After eutectoid plating with Cu and Ni at f/lr/ or less, tin plating is performed, followed by heating at 150 to 400°C to form a Cu-Sn alloy of not less than 50% by weight in Cu.
At the same time, at the same time as 50% by weight or more of Ni-8n alloy is formed in