JP2849274B2 - Method for removing oxide film from cold-rolled steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of removing an oxide film from a continuously annealed high-tensile cold-rolled steel sheet.

[0002]

2. Description of the Related Art Conventionally, in continuous annealing, oxidation of a steel strip is prevented by using an inert gas in a furnace. In addition, Japanese Unexamined Patent Publication No.
In the case of performing overaging treatment in an air atmosphere as in Japanese Patent Application Laid-Open No. 4-29821, a method of removing an oxide film formed on the surface of a steel strip by a mechanical method such as pickling or shot blast is known. .

[0003]

However, in recent years, due to global environmental problems, low pollution and high fuel efficiency of automobiles have been called for, and reduction of automobile weight has become a major theme. Under these circumstances, the need for high-strength steel sheets is increasing,
Automotive steel sheets are becoming mainstream. However, in the high-strength steel sheet, when Si is contained in an amount of 0.2% by weight or more, even if the inside of the furnace is an inert gas, Si is combined with a small amount of 0 to form an oxide film. Has a problem that it is very strong and cannot be completely removed only by ordinary pickling or a mechanical method.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides continuous annealing in an inert gas atmosphere.
A high-strength cold-rolled steel sheet containing 0.2% by weight or more of i is subjected to brush grinding as a first step, followed by hydrochloric acid pickling as a second step to remove a surface oxide film. And a method for removing an oxide film from a cold-rolled steel sheet.

[0005]

FIG. 1 is an explanatory cross-sectional view of a steel sheet in a thickness direction showing an oxide film removing mechanism according to the present invention. In FIG.
(A) is an explanatory view showing a state of formation of an oxide film, and (b) is a first view.
Explanatory drawing showing a state in which brush grinding is performed in a second stage, (c) is an explanatory diagram showing a state in which hydrochloric acid pickling is performed in a second stage, and 1 is a continuously annealed high-tensile cold-rolled steel sheet and 2 is a continuous annealing. The oxide film 3 formed by the above is hydrochloric acid.

According to the present invention, as shown in FIG. 1, the Si oxide film is firstly brush-ground as a first step, and a part of the Si oxide film is removed to expose the Fe layer (FIG. 1).
(B)) Subsequently, by performing hydrochloric acid pickling as the second step, the oxide film is hardly dissolved in hydrochloric acid, but the Fe layer at the interface between the oxide film and the Fe layer can be dissolved from the exposed Fe layer. Therefore, by proceeding the pickling, the Si oxide film can be efficiently peeled off and removed from the Fe layer (FIG. 1C).

When hydrochloric acid is used as an acid for pickling, an oxide film can be removed more quickly than when, for example, sulfuric acid is used. The concentration of hydrochloric acid for pickling is 5 to 10% by weight and the temperature is 50%. Those having a temperature of -70 ° C are preferably used. As the brush used in the first step, a nylon brush containing abrasive grains is preferably used.

[0008] The present invention can be implemented with or without overaging.

[0009]

FIG. 2 is a schematic diagram showing an arrangement of the apparatus according to an embodiment of the present invention. The annealed high-strength cold-rolled steel sheet 1 having a Si content of 0.2% by weight or more is conveyed by a roll 4 after leaving an annealing furnace 5 in an atmosphere of an inert gas. Then, a part of the surface oxide film was cut off with a grinding brush 7. Subsequently, as a second step, the solution was put into the pickling apparatus 8, and the concentration was 10 g / liter and the temperature was 60 ° C.
Was pickled with hydrochloric acid for 10 seconds. The oxide film could be quickly and safely removed from any of the steel sheets.

[0010]

According to the present invention, it has become possible to efficiently remove an oxide film due to Si of a continuous-annealed high-tensile cold-rolled steel sheet. Further, the improvement of the pickling efficiency not only improves the coating property and the chemical treatment property, but also improves the production efficiency and is inexpensive.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view of a steel sheet in a thickness direction showing an oxide film removing mechanism according to the present invention.

FIG. 2 is a schematic diagram showing an arrangement of devices according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Steel plate 2 Oxide film 3 Hydrochloric acid 4 Roll 5 Annealing furnace 6 Brush grinding device 7 Grinding brush 8 Pickling device

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeo Kurokawa 1 Kawasaki-cho, Chuo-ku, Chiba-shi Kawasaki Steel Works Co., Ltd. (72) Inventor Shigeki Taniguchi 1 Kawasaki-cho, Chuo-ku, Chiba-shi Kawasaki Steel Corporation Inside Chiba Works (58) Field surveyed (Int. Cl. ⁶ , DB name) B21B 45/06 B08B 7/04 C22C 38/00 C23G 1/08

Claims (1)

(57) [Claims] (1) continuous annealing in an inert gas atmosphere;
A high-strength cold-rolled steel sheet containing 0.2% by weight or more of Si is subjected to brush grinding as a first step, followed by hydrochloric acid pickling as a second step to remove a surface oxide film. Method for removing oxide film from cold rolled steel sheet.