JPH08257602A - Continuous hot rolling method - Google Patents

Abstract

PURPOSE: To improve material by promoting precipitated particle such as inclusions in steel of a rolled stock by retaining the temp. of a rolled stock with buffers and also to improve the capacity of temp. process by making rolling continuous. CONSTITUTION: In a continuous rolling line having buffering function and bar joining machine between a roughing mill and a finishing mill and having splitting function in the inlet side of coiling, while a preceding rolled stock is made to stay with a device having buffering function, after the next rolled stock is made to bite into the finishing mill preceding to the rolled stock in the buffering function, bar joining of the preceding rolled stock is executed and continuous rolling is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot continuous rolling method for producing hot strip by perfect continuous rolling.

[0002]

2. Description of the Related Art In a conventional hot rolling line, slabs are extracted from a heating furnace one by one and rolled by a rough rolling mill group into a sheet bar having a predetermined thickness. After being rolled into a strip, it is wound into a coil by a coiler. This conventional hot rolling line has the following problems because the rolled material is subjected to rough rolling and finish rolling one by one.

That is, since it is necessary to smoothly engage each rolled material with the upper and lower rolling rolls of the rough rolling mill group and the finish rolling mill group, the shape of the tip portion and the plate thickness can be adjusted for each rolled material. It is necessary, and uniform quality cannot be obtained from the front end to the rear end. In addition, the difference in temperature between the front and rear ends of the rolled material causes uneven product quality. Especially in thin strip rolling, the strip speed cannot be increased until the tip of the strip reaches the coiler, resulting in poor productivity. Furthermore, rolling between the tip rolled material and the trailing rolled material Since there is a space that is not involved in the work at all, there is a problem that the utilization efficiency of the equipment is low and the production efficiency is poor.

In order to solve these problems of the conventional hot rolling line, in recent years, in order to continuously hot roll the sheet bar, the trailing end portion of the running rolled material and the leading end portion of the trailing rolled material are being rolled. As a method of butt-welding a sheet with a sheared cut surface and continuously rolling the welded sheet bar, a method of winding the sheet bar into a coil to provide a buffer function has been proposed. However, this continuous rolling method involves rolling a sheet bar of a predetermined thickness by means of a group of rough rolling machines in the order of extraction from the heating furnace, winding the sheet bar once into a coil shape, then imparting a buffer function, then joining and continuing. In addition, it is a method of rolling into a strip having a required thickness by a finishing rolling mill group. That is, as shown in FIG. 4, the N-th sheet bar from the rough rolling final stand is once wound into a coil and then unwound, and its rear end is joined to the tip of the N + 1-th coiled sheet bar by bar joining. Is the way to do it.

[0005]

In the conventional continuous rolling method having a buffer function as shown in FIG. 4, the buffer function improves the temperature process capability for simply preventing the temperature decrease before bar joining. However, there is a problem that the buffer time is short and the function improvement by the buffer cannot be fully enjoyed.

[0006]

[Means for Solving the Problems] In order to solve the above-mentioned problems, as a result of intensive development by the inventors, as a result of providing a buffer function with a function for passing the next rolled material through, the rolled material in the buffer is provided. The object of the present invention is to provide a continuous hot rolling method in which the temperature retention is performed to improve the material quality by promoting precipitates such as inclusions in the steel as a rolled material and improve the temperature process capability by continuation. The gist of the invention is that in a continuous rolling line having a buffer function and a bar joining machine between a rough rolling machine and a finishing rolling machine, and having a dividing function on the winding side, a device having a buffer function for a preceding rolled material. Hot rolling, characterized in that the following rolled material is bite into the finish prior to the rolled material in the buffer function, and the preceding rolled material is bar-joined and continuously rolled while being retained at On the way.

[0007]

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a configuration diagram showing a continuous hot rolling line according to the present invention. As shown in this figure, after the slab heated in the heating furnace is roughly rolled by the group of rough rolling mills, the rolled material is retained by the device having the buffer function and retained in the buffer to remove the steel in the rolled material. After controlling the inclusions, the bar joining machine joins the trailing end of the preceding rolled material and the leading end of the trailing rolled material, and finish rolling is performed by the finishing rolling mill group, and the trailing end is continued by the high speed shear. After cutting, it is carried out in a series of steps in which it is wound into a coil by a winding machine.

FIG. 2 is a diagram showing a continuous hot rolling process according to the present invention. As shown in FIG. 2, the N-th sheet bar rolled by the final stand of rough rolling is wound into a coil by a winding machine and then temporarily stored in the buffer function. Then, the next N + 1th rolled material precedes the preceding rolled material in the buffer function, bites into the finishing rolling mill group to start finish rolling, and the preceding rolled material is in the middle of the finish rolling of the N + 1th rolled material. The Nth rolled material is extracted from the buffer equipment, the Nth leading end is bar-joined to the trailing end rolled from the N + 1th rough rolling final stand, and the Nth trailing end and N + 2nd The bar is joined to the tip of the rough rolling final stand to achieve continuity.

In this way, the N-th rolled material is temporarily stored in the buffer function, then bar-joined with the preceding next material and continuously rolled to finish rolling with high-speed threading, and the head temperature is secured. In addition, the buffer function compensates for the temperature drop due to thermal rundown from the center to the tail. Therefore, the N-th rolled material can secure the residence time in the buffer while overcoming the problem of securing the finishing temperature, and can significantly improve the material quality by controlling the precipitates.

[0010]

Example A 30 mm thick rolled material of Ti-SULC material shown in Table 1 as a test steel was heated at 1300 ° C. for 1 hour, and then 9
It was finish rolled to mm. Then, by grinding 9 mm to 5.3 m
m, and 0.8 mm (reduction rate of 85%) was used instead of 5.3 mm by cold rolling, and then continuous annealing was performed at 850 ° C. for 40 seconds. At that time, 5 to 60 m between passes during hot rolling
FIG. 3 shows the results of comparing the degree of material improvement by controlling the precipitates while maintaining the temperature at 1000 ° C. or 1100 ° C. for in.

[0011]

[Table 1]

FIG. 3 shows the relationship between the holding time and the average r value when deposit control of the rolled material according to the present invention is performed. By introducing a coil box having a buffer function from FIG. 3, it is possible to secure a holding time by applying the rolling method described above, and it is possible to significantly improve the r value by controlling inclusion precipitation in steel. I can.

[0013]

As described above, the retention in the buffer according to the present invention promotes the precipitation in the steel, improves the quality of the steel material, and improves the temperature process capability by continuation. It is possible to obtain a hot-rolled material of good quality in which the finishing outlet temperature is secured. Such a rolling method has an extremely excellent effect of improving productivity and rolling quality.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a continuous hot rolling line according to the present invention,

FIG. 2 is a diagram showing a continuous hot rolling process according to the present invention,

FIG. 3 is a diagram showing the relationship between the retention time and the average r value when deposit control of rolled material according to the present invention is performed;

FIG. 4 is a diagram showing a conventional continuous hot rolling process.

Claims (1)

[Claims] 1. A continuous rolling line having a buffer function and a bar joining machine between a rough rolling mill and a finish rolling machine, and having a dividing function on the winding side, while retaining the preceding rolled material by a device having a buffer function. In the hot continuous rolling method, the following rolled material is bite into the finish prior to the rolled material in the buffer function, and then the preceding rolled material is bar-joined and continuously rolled.