JPH01170567A - Direct rolling method - Google Patents

Abstract

PURPOSE:To improve the productivity of a cast slab by setting rolling conditions on each rolling mill so that the cast slab length after rolling becomes shorter than the distance up to the rolling mill in the next order and controlling the rolling reduction amt. of each rolling mill and the cast slab cut length. CONSTITUTION:Rolling is executed in order on a slab 2 by installing 1st, 2nd rough rolling mills 3, 4 at the downstream of the cutting machine of a continuous casting machine. In this case, a oil pressure control device 30 is connected to the rolling reduction device of each backup roll 5, 8 and a microcomputer 10 is arranged at the input side thereof. The slab length inputted to the memory of the microcomputer 10 and the various data of the rolling mills are called in order by a CPU to respectively operate the roll opening of each rolling mill and the cast slab length B1, B2 of after casting. At this time, the rolling conditions of a rolling reduction amt., etc., are controlled so that the cast slab length of after rolling becomes shorter than the gap L of the rolling mills at all times. The productivity of the cast slab is improved because the weight per coil is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a direct rolling method in which a continuously cast slab is directly sent to a rolling mill and continuously rolled into a thin plate coil.

[Prior Art] Recently, from the viewpoint of energy saving, a so-called direct rolling method has been developed in which a continuous casting process and a rolling process are directly connected to produce an integrated product from slab to rolled coil. In the direct rolling method,
The completely solidified continuously cast slab is passed through an insulation zone to raise the surface temperature of the slab due to the heat retained inside the slab, and then cut into a predetermined length by a cutting machine.Then, the cut slab is passed through a heating furnace. The cast slab is sent directly from the continuous casting machine to the hot strip mill without any intervention, and is continuously hot rolled into strip before the temperature drops, and this is wound into a coil.

In the conventional direct rolling method, the cutting length of the slab is not limited by the size of the heating furnace charging inlet, so when rolling the billet (
The slab is cut into longer lengths than in the conventional rolling method (hereinafter referred to as the normal rolling method), sequentially and continuously rolled using a rough rolling mill and a finishing rolling mill, and then the elongated strips are wound up to near the winding limit of the coiler. In other words, the direct rolling method makes it possible to increase the weight per fill (hereinafter referred to as coil weight) compared to the normal rolling method.
When the total weight of the product is the same, the number of coils is reduced, loss due to cutting off of the leading end is reduced, and yield is improved.

[Problems to be solved by the invention] However, in the conventional direct rolling method, since the initial length of the slab is long, when the slab is elongated by rough rolling,
The length of the slab becomes longer than the distance between the stands, and the slabs are simultaneously caught in the independently operating rough rolling mills at the front and rear, making rolling impossible. Therefore, the cutting length of the slab cannot be increased indefinitely.

By the way, in order to increase the unit weight of the coil, it is possible to increase the cross section (thickness and width) of the slab, but in order to realize this, it is necessary to modify the continuous casting machine, and
The rolling load of the rough rolling mill increases. In other words, since there are limits to the rolling capacity (rolling load, biting thickness, etc.) of each roughing mill in hot strip mill equipment, these conditions should also be taken into account when setting the rolling amount of each roughing mill. There is a need. For this reason, there is a problem in that the size of the slab that can actually be directly rolled is limited, and the weight per rolled coil cannot be sufficiently increased.

This invention was made in view of the above circumstances, and therefore it is possible to maximize the cutting length of the slab without causing simultaneous jamming accidents in the rough rolling mill, and it is possible to increase the unit weight of the coil. The purpose of the present invention is to provide a direct rolling method that enables direct rolling.

[Means for Solving the Problems] The direct rolling method according to the present invention is a direct rolling method in which continuously cast slabs are cut into predetermined lengths, and the cut slabs are directly conveyed to a series of rolling mills for continuous rolling. In this step, the various factors that influence the length of the rolling mill for the cut slab are ascertained, and based on the grasped factors, the length of the rolled slab is determined from the distance from the rolling mill to the garment rolling machine. Find the rolling reduction m that will shorten the length for each rolling mill, control the rolling amount of each rolling mill, and change the cutting length if the rolling conditions (rolling load, biting thickness) are not satisfied. It is characterized by

[Function] In the direct rolling method according to the present invention, various factors that affect the length of the slab after rolling, such as the thickness, width, cutting length, temperature, and steel type of the cut slab, are understood, and these factors are adjusted accordingly. Based on this, the maximum rolling amount is set for each rolling mill so that the length of the slab after rolling is shorter than the distance from the rolling mill to the clothing rolling mill, and the rolling reduction l of each rolling mill is controlled. In setting this rolling reduction amount, the rolling capacity of each rolling mill is also taken into account. Therefore, while making full use of the capacity of existing equipment, it is possible to effectively prevent the slabs from being caught simultaneously by the front and rear rolling mills, and to carry out continuous rolling.

[Embodiments] Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.

Fig. 1 is a block diagram showing the calculation flow of the computer used in the direct rolling method according to the embodiment of the present invention, and Fig. 2 is a part of a rolling mill group in which the direct rolling method according to the embodiment of the present invention is used. FIG. A rolling line of a hot strip mill is provided continuously as an extension of the horizontal line of a vertical pultrusion continuous caster (not shown). A cutting machine equipped with a control device is installed on the horizontal line of the continuous casting machine, and the continuously cast slab is cut into a predetermined length. A hot strip mill is equipped with a number of rough rolling mills and finishing mills, and a winding machine in that order. An induction heating device is installed in a continuous section of the insulation zone from the continuous casting machine to the most upstream rough rolling mill, so that the ends of the slab in the width direction are heated by induction. The rough rolling mills are arranged upstream of the rolling line and separated from each other by a predetermined interval. A reduction blade is applied to the slab in the thickness direction by a rolling roll.

As shown in FIG. 2, a first rough rolling mill 3 and a second rough rolling mill 6 are installed downstream of a cutting machine (not shown) of the continuous casting machine, respectively, to cut the material into a predetermined length. Slabs 2 are successively rolled. Note that third and fourth rough rolling mills (not shown) are installed downstream of the rough rolling mill 3.6, and a number of finishing rolling mills (not shown) are further installed downstream of the third and fourth rough rolling mills (not shown). . Of the pair of upper and lower work rolls 4.4 and 7.7 of each rough rolling mill 3.6, the upper roll is provided so as to be movable up and down. That is, rough rolling mill 3
．． 6 is a high-lift mill that can significantly change its roll gap, and is capable of rolling thick slabs.

The hydraulic control device 30 is connected to the rolling devices (not shown) of the backup rolls 5.5 and 8, 8 of each roughing mill 3.6 via a hydraulic circuit, and furthermore, the microcomputer 10 is connected to the hydraulic control device 30. The hydraulic control device 30 is operated in response to a command signal from the microcomputer 10, and the rolling blades in the thickness direction applied to the slab 2 from the rough rolling mills 3 and 6 are respectively controlled. It has become so.

Next, the operation of the embodiment will be explained.

Molten steel is poured into a water-cooled mold of a continuous casting machine to form a thin solidified shell around the outer periphery of the slab, and this unsolidified slab is guided by a group of support guide rolls and pulled out by pinch rolls to create a slab with a predetermined curvature. Bend approximately 90° with
During these drawing and bending processes, the slab is sprayed with water,
is injected to promote solidification inside the slab (secondary cooling).
Next, the completely solidified slab is passed through an insulation zone to increase the surface temperature of the slab due to the heat retained inside the slab, and is then cut into a predetermined length using a cutting machine.The cut slab 2 is passed through a first rough rolling mill 3. Ship directly. Then, the slab 2 is continuously rolled while controlling the reduction amount of each of the rough rolling mill groups by the hydraulic control device 30 based on the calculation result of the microcomputer 10.

Next, referring to FIG. 1, the microcomputer 10
The operation will be explained. When the power switch of the microcomputer 10 is turned on (step 12), the slab length before rolling and each rough rolling mill data are input from the host computer to its memory (step 1).
4). For example, various elements such as the cutting length, thickness, width, surface temperature, and linear expansion coefficient of the steel type of the slab 2 are stored in the memory. The stored input data is sequentially recalled from the memory by the CPLJ (Central Processing Unit) before cutting the slab, and using a predetermined mathematical model, first the roll opening of the first roughing mill 3 is calculated, and then the roll opening of the first rough rolling mill 3 is calculated. The slab length when rolled with the roll opening is calculated (step 16).

If the calculated value of the roll opening exceeds the rolling load and biting limit of the first rough rolling mill 3, the mathematical model is changed and the calculation is performed again (step 18). Incidentally, the rolling reduction ratio in rough rolling is limited to a range of 30%±10%, and the precision of the rolling amount in each rough rolling mill is 0.111 Iffi. If the calculated value of the roll opening clears the rolling capacity of the first rough rolling mill 3, then whether or not the length B1 of the slab 2 after rolling exceeds the distance between the rolling mills 3 and 6 is determined. (Step 20). If the length B1 is smaller than the distance, the calculation ends (step 26). length B
If 1 exceeds the distance 11L, the calculation is performed again. That is, the minimum plate thickness for which the length B1 is smaller than the distance 11L is calculated, and the number of buses is increased from the initial one according to this minimum plate thickness (step 24), and the calculation is ended (step 26). In this case, if the minimum plate thickness already exceeds the plate thickness before rolling, return to step 14, change the initial setting conditions (shorten the slab cutting length, etc.), and execute the above calculation again to find the optimum plate thickness. The calculation is repeated until the roll opening degree is determined. When the calculation of the first rough rolling mill 3 is completed, the calculation of the second rough rolling mill 6 is similarly executed based on the performance result of the first rough rolling mill ta3. In the calculation for the second rough rolling mill 6, in step 20, the slab length B2 exceeds the distance between the second rough rolling mill 6 and the third rough rolling mill (not shown), and If the minimum plate thickness cannot be calculated in step 22, the initial setting conditions (such as shortening the slab cutting length) in step 14 are changed.

Then, the calculation is performed again starting from the first rough rolling mill 3. In this way, calculations are performed sequentially from the first rough rolling mill to the second rough rolling mill from the most downstream, and the rolling reduction amount and slab cutting length are determined for each rough rolling mill.

According to the above example, the maximum length of the slab in the conventional heating furnace method was 9200 m+n, but this was changed to 14500 mm.
The coil unit weight (or PIW) can be increased by about 58%. In addition, in the past, if a simultaneous jamming accident occurred, the equipment would be stopped for about 2 to 3 hours due to yield loss and processing due to material scrap, but this type of simultaneous jamming problem has been completely eliminated. I was able to do it.

[Effects of the Invention] According to the present invention, the cutting length of the slab can be maximized without causing simultaneous jamming accidents in the rough rolling mill, and the unit weight of the coil can be increased.

Therefore, productivity can be improved, and accidents such as damage to the rolling equipment and abnormalities in sheet threading can be effectively prevented from occurring.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the calculation flow of the computer used in the direct rolling method according to the embodiment of the present invention, and Fig. 2 is a part of a rolling mill group in which the direct rolling method according to the embodiment of the present invention is used. FIG. 2; Slab, 3, 6; Roughing mill, 10: Microcomputer, 30: Hydraulic control device applicant patent attorney Takehiko Suzue

Claims (1)

[Claims] Understand the various factors that affect the length of the cut slab after rolling in a direct rolling method in which continuously cast slabs are cut into predetermined lengths and the cut slabs are directly sent to a group of rolling mills lined up in series for continuous rolling. Then, based on the various factors identified, the amount of reduction that will make the length of the rolled slab shorter than the distance from the relevant rolling mill to the next rolling mill is determined for each rolling mill, taking into consideration the rolling conditions. A direct rolling method characterized in that the rolling reduction amount of each rolling mill and the cutting length of the slab are controlled respectively.