JPH0525601A - Reflow treatment of tinned steel plate - Google Patents

Abstract

PURPOSE:To prevent the generation of wood grain patterns while retaining the island-shaped distribution of tin by accelerating the formation of an oxide film after melting of tin in an atmosphere where an oxygen concn. is high. CONSTITUTION:The steel plate is enclosed by sealing rolls 3 and a sealing box 4 at the time of executing a reflow treatment at a high speed. Pure gaseous oxygen is charged therein and the oxygen concn. is controlled to >=30%. The temp. of the steel plate of this time is set at about the m. p. of the tin and the tin is distributed uniformly to the island shape on the surface of the steel plate by the balance of the surface tension of the molten tin and the interfacial tension of the base iron.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflow processing method which does not generate a wood grain pattern.

[0002]

2. Description of the Related Art In a conventional tin-plated steel sheet, tin is distributed smoothly in a reflow process for melting tin, and tin is partially distributed in a streak pattern, which causes an appearance defect called a wood grain pattern. To do. As a means to solve the wood grain pattern, a chemical called flux such as ammonium chloride or phenol sulfonic acid is applied before the reflow treatment to accelerate the fluidization of tin in the reflow process and to distribute the tin evenly. It has prevented the occurrence.

However, in recent years, as a tin-plated steel sheet having a thin weight for welding cans, a steel sheet in which tin of the entire steel sheet is distributed in an island shape has been developed. Even in this steel sheet in which tin is distributed in an island shape, tin is partially distributed evenly, so that a wood grain pattern is generated in the smoothed portion, which lowers the product value. Further, the conventional wood grain pattern preventing method by applying flux like the tin-plated steel sheet cannot be used because it eliminates the island-shaped distribution of tin required as a product.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to produce a grain pattern in a smooth tin distribution area even in a tin-plated steel sheet in which tin is distributed in an island shape or when reflowing at a high speed. There is an object of the present invention to provide a reflow processing method capable of preventing the above.

[0005]

[Means for Solving the Problems] Island tin is formed by the balance of the surface tension of molten tin, the interfacial tension between molten tin and base iron and the surface tension of base iron when tin is melted, and especially the surface tension of molten tin. Is decreased by the temperature rise of the molten tin and is increased by the tin oxide film formed on the surface of the molten tin.

In order to uniformly distribute tin on the surface of the steel sheet in an island shape and prevent the smooth distribution of tin, the formation of an oxide film after melting of tin is promoted and the surface tension of the tin layer is lowered with the temperature rise. It is effective to suppress Further, in order to accelerate the formation of the oxide film, it is effective to melt tin in an atmosphere having a high oxygen concentration. The present invention has been made based on the above findings.

That is, according to the present invention, in the reflow treatment of the tin-plated steel sheet, the oxygen concentration around the steel sheet at the time of tin melting is 30%.
The present invention provides a reflow treatment method for tin-plated steel sheets, which is characterized by controlling the atmosphere to be at least 0.1%.
Further, according to the present invention, when performing the reflow treatment of the first item at a high speed, a steel plate in the vicinity of the melting point of tin is surrounded by a seal box, and pure oxygen gas is charged therein to adjust the oxygen concentration around the steel plate to 30%. %, And a reflow treatment method for tin-plated steel sheet.

The present invention will be described in more detail below. The present invention relates to conditions for a reflow treatment after tin plating in a tin-plated steel sheet manufacturing method. As described above, the grain pattern is generated during the reflow process, which is a problem. Even when tin was distributed in an island shape, a smooth tin-plated portion was formed, and a grain pattern was also generated there. The production line for tin-plated steel sheets is becoming faster, and it is desired to develop operating conditions that do not generate a wood grain pattern even at high speeds and with a light weight.

In order to uniformly distribute tin in the form of islands, the flux that impedes the contact between the tin layer and air is removed from the surface of the steel sheet, and the tin is subjected to a melting treatment (reflow treatment) with an oxygen concentration of 30%.
It is performed in an atmosphere controlled as described above.

In the atmosphere, the oxygen concentration is about 20%, and in order to increase the oxygen concentration to 30% or more, the tin-plated steel sheet portion reaching the vicinity of the melting point of tin during the reflow treatment after tin plating is surrounded by a seal box and the It is effective to add pure oxygen gas to the. As a result, the formation of an oxide film on the surface of the island-shaped tin is promoted, and the shape of the island-shaped tin is fixed by the oxide film before the surface tension of the island-shaped tin is lowered to form a uniform island-shaped tin. As described above, by enclosing the portion to be reflow-treated with the seal boss and setting the oxygen concentration in the atmosphere to 30% or more, the reflow treatment can be performed at a high speed without generating a wood grain pattern.

[0011]

EXAMPLES The present invention will be specifically described below based on examples. In order to carry out the present invention, the oxygen concentration in the atmosphere in the vicinity of the melting point of tin was changed by using an apparatus as shown in FIG. Condition Steel plate T4CA 0.22mm x 850mm Before annealing N
i-plating is applied at 80 mg / m ² . Tin deposit 0.8g / m ² , 1.4g / m ² , 2.0g / m ² Alloy amount 0.3g / m ² Line speed 100mpm, 200mpm, 300m
Oxygen concentration in pm atmosphere 20%, 25%, 30% Table 1 shows the results. From this, the oxygen concentration is 3 under each condition.
It was revealed that the grain pattern does not occur when the content is 0% or more.

[0012]

[0013]

According to the present invention, the wood grain pattern can be eliminated even in the operating range where the wood grain pattern has been conventionally generated.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of an apparatus for carrying out the present invention used in an embodiment.

[Explanation of symbols]

1 Inlet conductor roll 2 muffle furnace 3 seal roll 4 seal box 5 Quench 6 Delivery side conductor roll

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Koji Koji             1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd.             Company Chiba Steel Works (72) Inventor Shinichiro Muto             1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd.             Company Chiba Steel Works (72) Inventor Makoto Tanaka             1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd.             Company Chiba Steel Works

Claims (2)

[Claims] 1. In the reflow treatment of a tin-plated steel sheet,
A reflow treatment method for a tin-plated steel sheet, characterized in that the atmosphere around the steel sheet during tin melting is controlled to have an oxygen concentration of 30% or more. 2. When performing the reflow treatment of the first aspect at a high speed, a steel plate near the melting point of tin is surrounded by a seal box, and pure oxygen gas is introduced into the seal box so that the oxygen concentration around the steel plate is 30%. A reflow treatment method for a tin-plated steel sheet, which is controlled as described above.