JPS5930798B2 - Steel plate for welded can containers and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steel plate for a welded container, which is a material for can manufacturing, and which has excellent corrosion resistance particularly at welded parts and after painting, and a method for manufacturing the same.

In recent years, along with advances in electric resistance welding, welding methods (
For example, can manufacturing methods using Sudronik welding have made remarkable progress.

In order to meet these demands, we have developed excellent welding areas and
There is a need for a steel sheet for containers with a low COSI and excellent performance, corrosion resistance, painting performance (paint adhesion ratio, corrosion resistance after painting), and workability required as a material for can manufacturing (steel sheet for containers). Traditionally, Sn-plated steel plates (tinplate) have been used as ore plates for containers.
It has a beautiful appearance, excellent corrosion resistance, corrosion resistance, coating performance, and solder resistance, making it extremely suitable as a steel sheet for containers.

However, its biggest drawback is that its price is extremely high due to the soaring price of Sn metal. Therefore, attempts have been made to reduce Cos by reducing the amount of Sn attached, but in this case, a problem arises in that the corrosion resistance deteriorates. In particular, as a material for welded cans, the amount of Sn coating is low, especially the amount of Sn plating is 2000 per side.
In the case of ~/a or below, the weld zone and the heat-affected zone near the weld zone during welding are formed by a Fe-Sn alloy layer (mainly FeSn,
layer), the alloy layer grows to the surface of the plating layer,
The surface becomes blackish gray due to oxidation due to high heat, and the appearance of the welded area deteriorates, and the coating performance (paint adhesion ratio,
There are also problems such as significantly inferior corrosion resistance after painting.

The purpose of the present invention is to solve these problems and provide a steel plate for containers that has a low Sn plating amount, has excellent welded areas, is free from defects in the welded areas, and has excellent corrosion resistance. Ni plating is applied to the surface of the steel plate, and then Sn
The objective is to be achieved by performing chromate treatment immediately after plating, or by performing heat melting treatment (Melt treatment) after Sn plating and then performing chromate treatment.

That is, one aspect of the present invention is to apply a coating of 30 to 30% per side on the steel plate surface.
1000mfi1/Tl (:!) Ni Metsugo Formation and 10
This is a steel plate for a welded container, which has a Sn oxide layer of 0 to 2000 η/d and a chromate coating layer of 2 to 20 w/y in terms of Cr on the surface.

The second aspect of the present invention is to apply 30 to 1000 W per surface on the steel plate surface.
19/d (17) Ni Metsugo and 100-2000Tn
9/d(7) Apply Sn Metsugo, temperature 240-350
This is a method for manufacturing a steel plate for a welded container, in which a chromate coating layer having a chromium equivalent amount of 2 to 20/d is formed after heating and melting at a temperature of 250 to 300°C.

Next, the present invention will be explained in more detail.

First, Ni metal coating is applied to the surface of the steel plate at a rate of 30 to 1,000 W/Trll, preferably 100 to 500 Tf19/I, and further 100 to 2,000 T/I, preferably 300
~1000~/TI Sn plating is applied.

In other words, by applying Ni undercoat treatment, even if the amount of Sn metal is reduced, the amount of pinholes generated due to the additive effect due to overlapping plating will be reduced, and the corrosion resistance will be improved.
The presence of the base plating layer suppresses the growth of the Fe-Sn alloy layer (mainly Fesn2 alloy layer) in the heat-affected zone (weld zone, near the weld zone) during electric resistance welding. Even in this case, there is no deterioration in appearance and bendability due to the occurrence of welding defects as described above. As is conventionally known, the Fesn2 alloy layer produced by heating is a columnar crystal, and the growth in the thickness direction of the Metsu layer is remarkable.When the Sn amount is low, the growth surface grows in the direction of the Metsu layer surface. Easy to reach the layers. On the other hand, the Ni-Sn alloy layer (mainly the NiSn alloy layer) is a granular fine crystal, and it grows less in the thickness direction of the Metsugi layer and grows in the plane direction, so the Metsuki layer extends to the surface of the Metsugi layer as described above. At the very least, it will never reach the weld and will not cause defects in the weld. In addition, even if the i part of the Ni metal layer diffuses to the surface layer by welding, Ni metal has excellent heat resistance and oxidation resistance, so Ni
-Sn alloys are less prone to the above drawbacks. The thickness of the Ni metal layer ranges from 30 to 1000 W/I per side.

If it is less than 30 to /d, the effect of improving corrosion resistance due to the pinhole prevention effect and the effect of suppressing the growth of the Fesn2 alloy layer during welding cannot be obtained.

If it exceeds 1000η/go, the effect will be saturated and the price will be high, so it will not be economical.
η/I or less is preferable.

Therefore, the optimum range is 100 to 500 η/a. Sn
The thickness of the Metsugo layer is in the range of 100 to 2000 mm per side.

If it is less than 100 η/d, the formation of uniform weld nuggets in a wide range of welding conditions (pressure force, current, etc.) due to the effect of the low melting point Sn metal during welding is inhibited.

Further, the Sn plating layer itself has many pinholes, which is undesirable because the anodic corrosion protection effect of Sn metal against steel sheets or Ni in the corrosive environment inside the can manufacturing container, for example, in an oxygen-free citric acid aqueous solution, is significantly reduced. 2000～/
If the temperature exceeds m'', the effect becomes saturated and becomes uneconomical, and the Ni metal substrate treatment of the present invention becomes meaningless.

Therefore, it is preferably in the range of 300 to 1000 η/d. Ni-metsuki is performed using the normal Ni-mettsu method.

There are no particular regulations regarding the method or conditions. for example, 1L-1UJjyυ ν IvvSn Metsugo is held using the normal Sn Metsugo method.

No particular conditions or methods are specified.

(Example) After washing with water in Ferrostan bath, perform chromate treatment using the same method as before, or apply flux and heat melt treatment (Melt treatment) 2
It is constructed by carrying out a chromate treatment after carrying out a temperature of 40 to 350°C.

A chromate film is formed simultaneously with the removal of oxides on the Sn surface after the melt treatment or melt treatment, suppressing the growth of Sn oxides during storage, and improving coating performance in the same way as with conventional tinplate. By performing Ni plating and Sn plating and then heating and melting treatment (Melt treatment), Sn
Improved appearance due to increased metallic luster of plating layer and Ni-Sn
Aiming to further improve the corrosion resistance by forming a system alloy layer 4.
Heat melting treatment (Melt treatment) is performed by washing with water after Sn plating, and then applying it as it is or applying an aqueous solution flux for 2 hours in air or in a non-acidic atmosphere (for example, N2 atmosphere).
Sn at 41-350°C, preferably 250°C-300°C
The Metsugo layer is melted. The flux is melted by dipping or spraying, for example, in the case of a ferrostane bath, by applying phenolsulfonic acid 2 to 109/t (in terms of sulfuric acid) SnSO42 to 109/.t.

The amount of chromate coating applied in the method of the present invention is extremely important from the viewpoint of welding conditions, and the thickness of the chromate coating is in the range of 2 to 20ヮ/m'' in terms of Cr.

When the ratio is less than 2 to 1, the effect of suppressing the oxide film of the Sn layer is small, and the effect of improving coating curvature cannot be obtained.

If it exceeds 20W9/d, the above effect is good, but it inhibits the formation of uniform nuggets during welding, so 20η/7T
It is necessary that it is less than I, preferably 5 to 15η
/d (talom equivalent amount).

A normal chromate treatment method may be used as the chromate treatment method, and SO4-2, ct contained as an unavoidable impurity can be used.
Chromic acid, chromate (ammonium chromate, sodium chromate, potassium chromate, etc.) containing first class impurities,
Immersion or cathodic electrolysis treatment in an aqueous solution of dichromate (ammonium dichromate, sodium dichromate, potassium dichromate, etc.).

For example, the concentration is 10-1209/t1, preferably 20-6
09/t aqueous solution is used, and in the immersion treatment method, the temperature is normal temperature to 70 °C, preferably 30 to 50 °C, and treatment time 0.5
~5 seconds, preferably 1-3 seconds.

Claims (1)

[Claims] 1. Ni plating layer of 30 to 1000 mg/m^2 per side, Sn plating layer of 100 to 2000 mg/m^2, and further chromate of 2 to 20 mg/m^2 in terms of Cr on the surface of the steel plate. A steel plate for welded can containers, characterized by being formed of a coating layer. 2. After applying Ni plating of 30 to 1000 mg/m^2 and Sn plating of 100 to 2000 mg/m^2 per side on the steel plate surface and performing heat melting treatment at a temperature of 240 to 350 °C, the amount of Cr converted to 2 A method for manufacturing a steel plate for welded can containers, characterized in that a chromate coating layer of ~20 mg/m^2 is formed.