JPH0413043B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a rolling method for rolling a metal slab in the width direction using a vertical rolling mill. Specifically, the present invention relates to a rolling method for rolling a metal slab in the width direction using a vertical rolling mill. The present invention relates to a rolling method for preventing formation. (Prior art) The characteristics of the width reduction rolling method when producing narrow width slabs from wide slabs, compared to conventional rolling, are the ratio of the roll contact arc length to the average plate width during rolling, that is, the shape ratio between the rolls. is as small as 0.1 to 0.2, and the amount of repeated vertical roll width reduction per roll is as large as 200 to 300 mm. As a result, irregularly shaped parts called fishtails occur at the leading and trailing ends of the rolled material, resulting in crop loss. Many methods have been proposed to reduce crop loss, which increases with width reduction.
These methods apply the methods and knowledge that have been put into practical use in blooming. For example, the double-pass rolling method is characterized in that the material to be rolled is not passed through a reciprocating scheduler with a predetermined reduction amount, but the reduction amount is reduced before it leaves the rolling rolls ( Japanese Patent Publication No. 51-35383 (Japanese Patent Publication No. 51-35383) and a press forming method (Japanese Patent Publication No. 35383/1983) in which at least one longitudinal end of the material to be rolled is press-formed into a narrow width and then rolled by a subsequent rolling mill.
57-81902). (Problems to be Solved by the Invention) In all of these conventional methods, rolling efficiency is significantly reduced. In other words, the double-pass rolling method normally requires two rolling cycles to reduce the amount of reduction during rolling, and the press forming method requires stop time for positioning the material to be rolled and for the press operation process. is necessary. Therefore, these methods cannot be applied to a width-reducing vertical rolling mill designed to realize a process that combines a continuous casting process and a rolling process that can utilize the sensible heat possessed by continuously cast slabs. When manufacturing narrow width slabs from wide slabs in the width rolling process, which directly connects the continuous casting process and the hot product rolling process, it is necessary to have rolling efficiency that matches the capacity of the preceding and following processes, and it is necessary to ensure that the rolling process does not impede the rolling time. It is required to reduce crop loss at both ends of the material. The present invention provides an effective width reduction rolling method for metal slabs that solves the above problems. (Means for Solving the Problems) The gist of the present invention is as follows. When hot rolling slabs of various widths using a vertical rolling mill, repeating a forward pass from one metal slab supply side to the other delivery side and a reverse pass from the delivery side to the supply side. , Immediately before starting width rolling, divide the target full width reduction of the metal slab by the maximum permissible width reduction per pass of the vertical rolling mill (hereinafter referred to as "maximum width reduction") to obtain the maximum allowable width. The number of passes (n+1), which is the number of passes resulting in the rolling reduction amount plus a single pass that is less than the allowable maximum width reduction amount, is once determined as the number of passes for the rolling with the maximum allowable width reduction amount, and then Calculate the width reduction allowance according to the following formula, and perform width rolling according to a rolling schedule that distributes this width reduction allowance to arbitrary passes. Maximum allowable width reduction amount x (n+1) - Target full width reduction amount = Width reduction allowance amount. At that time, in the pass to which the width reduction allowance is allocated, the engagement end of the metal slab is rolled with the maximum allowable width reduction, and thereafter, the reduction allowance allocated from the allowable large reduction amount is rolled. A method for hot width rolling of a metal slab, characterized in that the biting end is made thin (narrow in width) by rolling with a reduced rolling reduction amount. (Function) Hereinafter, the function of the present invention will be explained with reference to the drawings. In FIG. 2a, when the metal slab 1 is rolled in the width direction, irregularly shaped parts called fish tails are generated at the biting ends 2 and the biting edges 3. The mechanism of occurrence of this deformed part is the combination of the end deformations 2', 3' caused by steady section rolling shown in Fig. 2b and the end deformations 2'', 3'' shown in Fig. 2c during wide reduction rolling. This is thought to be caused by Therefore, the amount of fish tails at the biting end and the biting-through end of the metal slab are different, and as a result of investigation by the present inventors, as shown in FIG. It turned out to be about 3 times as large. For this reason, in reversible rolling, in each pass except the final pass, the width reduction amount of the biting edge, which will become the biting edge in the next pass, is set larger than the biting edge of the relevant pass, that is, the biting edge of the relevant pass. It was confirmed that by making the width narrower than the width of , the amount of metal flow toward the rear of the bite edge in the next pass can be reduced, and the amount of feed tail can be significantly improved. FIG. 1A shows an example of the stand configuration of a width reduction rolling mill, in which a horizontal roll 5 is disposed between two stands of vertical rolling mills 4 and 6. The metal slab is fed in the direction of arrow a, reversibly rolled between stands 4, 5, and 6, and finished in the direction of arrow b. In this rolling process, just before the metal slab is supplied to the rolling mill, a rolling pass schedule is calculated to obtain the target slab dimensions, and is used to set the roll opening degree in subsequent rolling. In this calculation process, when the number of passes is calculated from the calculated width reduction amount that can be rolled with the maximum permissible rolling load of the vertical rolling mill, that is, the maximum permissible width reduction amount, a line diagram 7 shown in FIG. 1b is obtained. The number of passes in actual rolling is an integer number as shown in the diagram 8, and is an odd number of passes in the finishing direction.
Therefore, while the number of passes is 7, which is calculated based on the maximum allowable width reduction amount, a single pass that is less than the allowable maximum width reduction amount occurs. That is, in this single pass, a reduction margin is generated with respect to the maximum permissible width reduction amount. In FIG. 1b, a rolling margin 9 is generated for the finished slab width W _i . This rolling margin is distributed to each pass. FIG. 1c shows the thus calculated rolling margin per vertical roll for each width of the finished slab. Here, the maximum width reduction amount is the same as the conventionally generally known definition, that is, the width reduction amount when the metal slab is width rolled at the maximum allowable rolling load of the vertical rolling mill, The thickness, width, temperature, rolling speed, etc. before rolling change between passes. FIG. 4 shows a rolling method according to the present invention. As shown in FIG. 4a, when rolling the biting end 2 of a metal slab with the vertical rolling rolls 4 or 6, rolling is performed with the maximum width reduction ΔH _nax , and the center part other than the biting edge and the biting edge As shown in FIGS. 4a and 4b, No. 1 is rolled with a rolling reduction amount ΔH obtained by subtracting the allocated rolling allowance amount Δh from the maximum width reduction amount ΔH _nax . At the bite-through end 3 in the subsequent reverse pass schedule, the reduction amount Δh preformed in the previous pass becomes a light reduction amount, and the reduction amount ΔH of the center portion 1 other than the bite end and bite-through end becomes ΔH - Δh. . That is, according to the method of the present invention, there is a heavy reduction at the biting end and a weak reduction at the biting end, and since the margin of reduction is utilized with respect to the maximum permissible width reduction, it can be carried out without interfering with the rolling time, and the cropping can be reduced.・Loss can be significantly improved. Therefore, the method of the present invention can be applied to a width reduction mill in a process that directly connects a continuous casting process and a hot rolling process, and can enjoy a great effect of improving yield. Next, FIG. 5 shows a row of rolling mill equipment for carrying out rolling according to the present invention. When rolling the width of the metal slab 1, the opening degree of the hard roll VR is controlled by a screw-type rolling down mechanism (a rotation transmission shaft 1 directly connected to a drive motor and a speed reducer (not shown) with an umbrella-shaped gear 10c interposed therebetween).
0a, 10b, a wheel 10d that partially screws into the shaft 10b, and a spline shaft 10e that engages with the axis of the wheel 10d. ) is set by In other words, vertical rolls for steady width rolling of slabs.
The opening degree of VR is adjusted and set in advance with the screw type reduction mechanism so that it is obtained when the piston 13c position of the hydraulic cylinder type reduction mechanism is set to the forward start starting position 13'c, and the amount of heavy reduction at the biting end is set. The opening degree of the vertical roll VR is adjusted according to the stroke by adjusting the stroke of the piston 13c of the hydraulic cylinder type lowering mechanism to 13''.
Choke 14-Reduction rod 13b-Cylinder 1
3a - Piston 13c - Spline shaft 10
This is a pullback cylinder that prevents backlash of the e-wheel 10d. If you have a stand configuration in which two vertical rolling mills are installed, it is better to install the roll opening hydraulic control device on both stands as shown in Fig. 6, which will reduce the number of times of heavy rolling at the biting end and light rolling at the biting end. This increases the amount of space available for reduction of the front stand, and makes effective use of the front stand reduction margin, resulting in a significant yield effect. Note that, in the final pass, heavy reduction at the biting end is not performed in order to control the width reduction at both ends caused by width reduction rolling. (Example) Next, an example of the method of the present invention will be shown. The rolling conditions are as shown in Table 1, and a continuous cast slab of 250 x 1800 mm was made using the 3-stand reverse rolling method of V ₁ - H - V ₃ .
A finished slab with dimensions 250 x (700-1800) mm was manufactured from.

[Table] Table 2 compares and contrasts the method of the present invention and the conventional method for various slab widths. Incidentally, the crop loss reduction rate is the improvement rate when rolling is performed at a constant reduction amount without changing the reduction amount, and when the method of the present invention and the conventional method are adopted. In the conventional method, the rolling device of the vertical rolling mill is only a screw-type rolling mechanism (lacking a roll opening hydraulic control device). Then, the rolling opening of the steady section, that is, the roll opening that obtains the maximum allowable width reduction amount, is changed to the roll opening that is equal to the rolling margin, and the rolling opening is changed to the rolling opening of the steady section that follows the biting end. The so-called bite-back width rolling method was adopted. The number of passes of each embodiment of the present invention shown in Table 2 is as shown in FIG. As is clear from the examples in Table 2, in the conventional method, the number of passes increases and the rolling temperature drops significantly, making it impossible to control the screw opening, and it is necessary to perform back-rolling to reset the roll opening. There were cases where rolling was impossible.

【table】

[Table] (Note) - indicates that rolling is not possible due to temperature drop (effect of the invention) The adoption of the conventional rolling method for the width reduction mill in a process that directly connects the continuous casting process and hot rolling process reduces the rolling time. This is not possible as it would greatly hinder the process. According to the method of the present invention, crop loss is improved without interfering with rolling time, and furthermore, in the stand arrangement comprising two vertical rolling mills, the yield is significantly improved by installing a roll opening hydraulic control device for each. This makes it possible to bring about very useful effects industrially.

[Brief explanation of drawings]

Figure 1 a, b, and c are explanatory diagrams of the margin of reduction that occurs during reversible rolling in a stand configuration with two vertical rolling mills, and Figure 2 a, b, and c are illustrations of the margin of reduction that occurs during width reduction rolling. An explanatory diagram of the mechanism by which fish tails occur. Figure 3 is a diagram showing the relationship between the amount of fish tail and the amount of width reduction at the biting end and the biting-out end. Figures 4 a and b are under heavy pressure at the biting end and under light pressure at the biting-through end. FIG. 5A is a detailed view of the roll opening hydraulic control device, FIG. 5B is a detailed view of the hydraulic cylinder, and FIG. 6 is an explanatory diagram of the number of passes and the number of rolling times according to the method of the present invention. 1... Metal slab, 2, 2', 2''... Engagement end fish tail, 3, 3'3"... Engagement end fish tail, 4... Vertical rolling mill (V ₁ mil), 5......
Horizontal rolling mill, 6... Vertical rolling mill (V ₂ mill), 7...
... Number of passes based on the maximum allowable width reduction amount, 8... Number of passes, 9... Allowance for reduction amount, 10... Screw roll opening device, 11... Pullback device, 12...
...Roll opening hydraulic control device, 13, 13', 1
3″...Roll opening hydraulic cylinder.

Claims (1)

[Claims] 1. Slabs of various widths are produced using a vertical rolling mill by repeating a forward pass from one metal slab supply side to the other delivery side and a reverse pass from the delivery side to the supply side. When performing hot width rolling, immediately before the start of width rolling, the target full width reduction amount of the metal slab is set at the permissible maximum width reduction amount per pass of the vertical rolling mill (hereinafter referred to as "allowable maximum width reduction amount"). The number of passes (n+1), which is the number of passes resulting in the maximum permissible width reduction amount (n) plus a single pass that is less than the maximum permissible width reduction amount, is calculated by dividing the number of passes (n+1) that results in the maximum permissible width reduction amount. The width reduction margin was determined according to the following formula, and the allowable maximum width reduction amount x (n+1) - target full width reduction amount = width reduction margin amount This width reduction margin amount was distributed to arbitrary passes. Width rolling is carried out according to the rolling schedule, and in the pass where width reduction margin is allocated, the biting end of the metal slab is rolled with the maximum allowable width reduction, and after that, the width reduction is rolled with the maximum allowable width reduction. 1. A method for hot width rolling of a metal slab, characterized in that the biting end is made thinner (narrower) by rolling with a reduction amount that is less than an allocated reduction margin amount.