JPH02137608A - Hot rolling process - Google Patents

Abstract

PURPOSE:To stabilize a travelling of the head area at a pass by cooling the longitudinal head area of stock to be rolled after a hot rolling by reducing the density of cooling quantity per unit area in cooling zones and increasing relatively cooling zones to be used. CONSTITUTION:As a strip 1 passed out from the last stand 2 in a finishing mill is travelling at a high speed on a run-out table 3, it is coiled in a coiler 4 after cooling to a specified temperature through banks 5 connected to branch pipes 6 with flow regulating valves. in this hot rolling method which the above hot rolling, cooling and coiling are repeated intermittently, the above banks 5 are divided into plural zones in where on-off is possible and the cooling density at each zone is adjustable. Using this cooling method, the longitudinal head area of the strip 1 is cooled to the specified temperature by decreasing the cooling density per unit area and increasing relatively cooling zones to be used. Thus, the travelling of the head area of the strip 1 is maintained stably and can be coiled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for hot rolling a strip.

[Prior Art] In a method of hot rolling a strip, the strip is cooled with water to obtain a desired material quality while being wound up in a coiler after rolling. That is, after the strip leaves the finishing mill, it travels at high speed on a runout table and is wound up by a coiler, during which time cooling water flows out from above and below the strip to cool it.

In the conventional technology, the cooling water is discharged by laminar flow from the upper part and spray from the lower part,
Each is organized into laminar flow or spray zones (hereinafter referred to as banks) with a specific length. The cooling zone in the runout table is composed of multiple banks. The cooling of the strip is determined by its dimensions, material This is done by selecting the number of banks based on conditions such as rolling speed.

In order to reliably cool the tip of the strip, water injection by the bank is started 1 to 2 seconds before the tip reaches the bank, taking into account delays in the control system.

[Problems to be Solved by the Invention] Conventional strip cooling in runout tables is performed by controlling the number of banks. There are the following problems with this.

This type of strip is rolled at high speed in order to maintain the finish rolling temperature, so it is run at high speed on a runout table.
Furthermore, because the winding is performed at a low temperature, a large number of banks are required for cooling, and since the strip is thin and has low rigidity, the running properties of the strip tip are extremely poor, resulting in poor threading (the strip tip gets stuck and loops are formed). This is likely to occur, and may result in poor winding.

The present invention has been made to solve the above-mentioned problems, and aims to provide a hot rolling method with good running stability during strip passing.

[Means for Solving the Problems] A hot rolling method according to the present invention is a hot rolling method in which hot rolling, cooling, and winding are intermittently repeated. The cooling density of the zone can be adjusted, and while the cooling amount density per unit area of the cooling zone is reduced at the front end of the rolled material in the longitudinal direction, the coiling temperature of the rolled material can be adjusted by relatively increasing the cooling density used. This is a hot rolling method that stabilizes the running of the leading end of the material to be rolled while maintaining it at a predetermined value.

[Function] Since the hot rolling method of the present invention performs cooling control by the method described above, running stability of the strip on the runout table can be obtained.

[Example] FIG. 1 is an explanatory diagram showing an example of the present invention. After the strip 1 has been rolled by a final stand 2 of a finishing mill, it travels on a runout table 3 and is wound up by a coiler 4. During this time, the strip 1 is cooled by the bank 5. Cooling water is supplied to the bank 5 from a branch pipe 6 via an on/off valve 7 and a flow control valve 8. Flow rate adjustment is 5.7 J per strip unit area per bank.
/ sec, m” ~ 16, O(1/ sec, m
” will be carried out within the range.

For thick materials, cooling is performed by bank control, but for thin materials, running stability is achieved by increasing the number of banks and reducing the flow rate per bank so that the flow density per unit area of the strip remains constant. . 1st
Table 2 shows the experimental results regarding the runnability of the conventional method and the method of the present invention. This will be explained below using these tables. A soft material with a thickness of 2.0 mm and a width of 950 mm was used as the test material. The cooling conditions for the conventional method include a total of 9 banks (upper and lower banks), and a flow rate of 1.0 n(
/see was selected. In addition, as the cooling conditions for the method of the present invention, a total of 12 banks, a flow rate of 6.0 (1/sec, m") per bank, and a flow rate of 1.1rd/see for the entire cooling zone were selected. Rolling The speed is 640-700m/win, the winding temperature is 56
Temperatures of 0 to 640°C were taken, and the running stability of the test materials in these combinations was investigated. Table 1 shows the test results using the conventional method. As shown in Table 1, the lower the coiling temperature and the higher the rolling speed, the worse the running stability of the strip. Table 2 shows the test results according to the method of the present invention. Although the same trends as in Table 1 are shown, the running stability of the strip is significantly improved as the rolling speed is lower and the coiling temperature is higher.

Table 1 The examples described above are hot rolling methods that are repeated intermittently, including hot rolling, but as another example, after hot rolling, cutting is carried out during running, cooling, and winding. It can also be applied when carrying out complete or incomplete continuous rolling up to hot rolling, followed by running cutting, cooling, and winding.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing one embodiment of the present invention. 1... Strip, 2... Finishing mill final stand, 3... Runout table, 4... Coiler 5...
・Bank, 6... Branch pipe, 7... On/off valve, 8...
・Flow control valve.

Claims (1)

[Claims] In a hot rolling method in which hot rolling, cooling, and winding are repeated intermittently, the cooling can be turned on and off in multiple zones, and the cooling density of each zone can be adjusted, and the leading end in the longitudinal direction of the rolled material is cooled. While reducing the cooling amount density per unit area of the zone and relatively increasing the number of cooling zones used, it is possible to maintain the winding temperature of the rolled material at a predetermined value and stabilize the running of the leading end of the rolled material. Characteristic hot rolling method.