JPH03106510A - Scale removing method for hot rolled steel sheet - Google Patents

Abstract

PURPOSE:To improve the quality of a rolled steel sheet by removing a primary scale by a high pressure water descaling after floating the scale with the execution of edging on the steel sheet, flattening the surface with its cooling and grinding the residual secondary scale by a brush roll. CONSTITUTION:Edgers (vertical scale breakers) 3 for floating the primary scale of the surface are arranged in opposition to the right and left, a high pressure water descaling device 4 is then arranged, a rough rolling mill 5 moreover and a wire brush roll device 6 at the final step are respectively arranged in opposition vertically. The grinding removal of the primary scale by the brush roll is enabled by executing edging. A steel plate becomes in the dog bone shape that the both ends thereof are deformed but it is straightened by the rough rolling mill and the brush roll is acted after making it flat, so the secondary scale is completely removed. The generation of a scale flaw is thus prevented and the quality of the steel plate can be improved.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for removing scale from hot-rolled steel sheets, and in particular, in high-Si steel sheets (Si-containing hot-rolled steel sheets), the present invention relates to a method for removing scale from hot-rolled steel sheets, and in particular, to remove scales remaining on uneven portions at the interface between base material and base metal in high-Si steel sheets (Si-containing hot-rolled steel sheets). The present invention relates to a method for removing scale and low melting point oxides.

(Prior Art) Several methods have already been proposed as methods for removing scale from the surface of steel sheets in hot rolling lines.

For example, as a method for removing primary scale generated in a heating furnace, a method is generally adopted in which the scale is first lifted by esodizing and then removed by a high-pressure water descaling device. Alternatively, there is a method of cracking the scale using a brush roll device and then removing it using a high-pressure water descaling device, or a method of rapidly cooling the surface with a pressure water jet as shown in Japanese Patent Application Laid-Open No. 59-82110 to remove scale growth. A method is known in which the process is accelerated and then peeled off using a mechanical brush.

(Problem to be Solved by the Invention) By the way, the water pressure of high-pressure water descaling equipment currently commonly used in hot rolling mills is 100 to 170 kg/CI1.
1, and in the case of ordinary steel, almost all scale removal is achieved by this, but the primary scale generated in the heating furnace may stay in the furnace for a long time of 2 to 4 hours, and its thickness is 1 to 3.
5 1IIffl. In particular, in the case of high-Si steel sheets (Si-containing hot-rolled steel sheets), when primary scale is generated in the heating furnace, the interface between the primary scale and the base metal is markedly uneven, and the invasion of scale into grain boundaries is noticeable. , it is impossible to remove this with a high-pressure water descaler. In addition, low melting point oxide 2 is added to the adhered scale on the uneven parts and the scale invaded parts.
FeO・Sing (eutectic temperature 170°C) is sticky and cannot be easily removed if it is under thick primary scale, and as it is rolled and stretched, it becomes a kind of scale flaw. This causes surface defects called red scale.

The present invention has been made to solve this problem, and provides a scale removal method that can completely remove primary scale and secondary scale remaining on the uneven parts of the steel plate interface. With the goal.

(Means for Solving the Problems) In order to achieve the above object, the method for removing scale from a hot rolled steel plate according to the present invention is to first perform engineing on #1 plate extracted from a heating furnace to remove scale. After floating, the primary scale is removed by high-pressure water descaling, and the surface of the steel plate after the primary scale has been removed is cooled.Then, the cooled surface is flattened by a rough rolling mill, and the remaining secondary scale is ground by brush rolls. The idea is to scrape it off.

(Function) In the present invention, primary scale is removed by edging and high-pressure water descaling, and residual scale (containing low melting point oxides) that has taken root and strongly adheres to the base steel is rapidly cooled and The surface portion is brought to a temperature below the melting point (1170'C) and solidified. This allows for abrasive removal with a brush roll. By edging, the steel plate becomes deformed at both edges, creating a so-called dogbone shape, but this is corrected and flattened using a rough rolling mill, and then a brush roll is applied to the steel plate surface, resulting in a uniform grinding effect on the steel plate surface. and secondary scales are completely removed.

(Example) Hereinafter, embodiments of the present invention will be described based on illustrative drawings.

In the figure, edgers (vertical scale breakers) 3 are placed on the left and right sides of a steel plate A extracted from a heating furnace 1 and transported along a rolling line 2 in the direction of the arrow. Installed oppositely,
Next, a high-pressure water descaling device 4, a rough rolling mill 5, and a wire brush roll device 6 at the final stage are installed vertically facing each other.

In other words, the edger 3 presses the autopsy plate A from both edges thereof, and this action causes the primary scale on the surface to rise.

Next, the floating primary scale is peeled off and removed by high-pressure water of, for example, 150 kg/a+1, which is injected from the nozzle of the high-pressure water descaling device 4. The residual scale (secondary scale) containing substances cools rapidly, loses its stickiness, and solidifies.

Next, the steel plate A, which has been pressurized and deformed by an edger 3 and has a dogbone shape, is straightened by a rough rolling mill 5 and made flat, and then the secondary scale is ground and scraped off by a wire brush roll 6. Therefore, this grinding affects the entire surface of the steel plate equally.

Incidentally, as a result of applying the method of the present invention to the St-containing hot rolled steel plate (width 1300 mm x thickness 2.3 mm) shown in Table 1 below under the conditions shown in Table 2 below, scale could be effectively removed.

Table 1 Unit double weight % Table 2 (Effects of the invention) As explained above, the present invention floats the primary scale by edging, removes it by high-pressure water descaling, and at the same time removes the low melting point oxidation existing at the interface of the base metal. This method applies a rapid cooling action to the secondary scale containing particles to solidify it, straightens the deformed steel plate, and applies a grinding and scraping action to the entire surface of the steel plate. Since the residual scale containing low melting point oxides at the interface is effectively removed, the occurrence of scale defects called red scale is prevented, and the quality of the rolled steel sheet is significantly improved.

[Brief explanation of drawings]

The drawings are perspective views illustrating embodiments of the invention. 2 is a heating furnace, 2 is a rolling line, 3 is an edger, 4 is a high-pressure water descaling device, 5 is a rough rolling mill, and 6 is a wire brush roll device. ,t-. ,fffi material

Claims (1)

[Claims] (1) First, the steel plate extracted from the heating furnace is edged to lift the scale, then the primary scale is removed by high-pressure water descaling, and the surface of the steel plate after the primary scale has been removed is cooled, and then the rough rolling mill is used. A method for removing scale from a hot-rolled steel sheet, comprising flattening the cooled surface and scraping off residual secondary scale by grinding with a brush roll.