JPH0252561B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention provides a hot width rolling method in which a vertical rolling mill and a horizontal rolling mill are operated reversibly to roll a metal slab along a predetermined rolling pass schedule to obtain a target finished width. More specifically, the present invention relates to a hot width rolling method for preventing the growth of fishtails at the leading and trailing ends that occur during hot width rolling of metal slabs. (Conventional technology) The feature of the hot width rolling method for metal slabs is that, unlike the conventional blooming method for steel ingots, the hot width rolling method for metal slabs is for continuously cast slabs. The ratio of roll gap shape ratio is 0.1
It is small at ~0.2, and the width reduction amount of the vertical roll is large at 200 to 300 mm per roll. For this reason, deformed portions called fishtails are likely to occur at the leading and trailing ends of the metal slab, which is the material to be rolled, resulting in increased crop loss. In addition, at the tip and rear ends of the material to be rolled, the material is allowed to escape in the longitudinal direction, so the cross section does not have a so-called dogbone shape, and when it is rolled in a horizontal mill after width rolling, While the other parts have their width restored by dogbone rolling, the tip and rear ends each have a length of about 1 m without any width returned, resulting in a part with insufficient width. Combined with the loss, this causes a decrease in the yield of rolled products. Among these causes of deterioration of yield, many methods have been proposed to reduce crop loss, which increases with width reduction. For example, as proposed in Japanese Patent Publication No. 51-35383, the rolling material is not passed through a reciprocating pass schedule after being rolled, but the rolling reduction is reduced before it leaves the rolling rolls, without passing the rolling material with a predetermined rolling reduction. Another example is the single-pass reversible rolling method, which repeats forward and reverse passes. In addition, regarding the reduction in the insufficient width, Japanese Patent Publication No. 58-51767 proposes that when rolling the material to be rolled in the width direction, the amount of reduction in the leading and trailing ends of the material to be rolled does not become large. There is a method of controlling the rolling force by arranging an annular piston-cylinder device within the fixed housing of a vertical roll machine. (Problem to be solved by the invention) When manufacturing various slab widths from a fixed slab width in the width rolling process that directly connects the continuous casting process and the hot rolling process, it is necessary to adjust the rolling efficiency to the capacity of the preceding and following processes. It is necessary to reduce the crop loss at the leading and trailing ends of the rolled material without interfering with the rolling time. In contrast,
In the double-pass rolling method proposed in Japanese Patent No. 35383, the amount of reduction in one roll is usually reduced during rolling, so two rolling cycles are required, resulting in a significant reduction in rolling efficiency. In addition, the method proposed in Japanese Patent Publication No. 58-51767, in which the rolling force is controlled during rolling so that the amount of rolling at the leading and trailing ends of the material to be rolled does not become large, does not impede rolling efficiency, Even if it is possible to eliminate the above-mentioned crop loss caused by the fish tail, it will not reduce the crop loss caused by the fish tail. For this reason, in the width rolling process where the continuous casting process and the hot rolling process are conventionally directly connected, it is desirable to have a method of reducing crop loss at the leading and trailing ends of the rolled material without impeding rolling efficiency. It was rare. The present invention provides an effective method for hot width rolling of metal slabs that solves the above problems. (Means for Solving the Problems) The gist of the present invention is to roll a metal slab to a target finished width according to a predetermined rolling pass schedule by reversibly operating a vertical rolling mill and a horizontal rolling mill. In the hot width rolling method for obtaining width rolling of a predetermined pass excluding the final pass, the roll opening degree at the time of biting of the metal slab is determined by the distributed width reduction amount ΔH of the predetermined pass as shown in Fig. 1a. The width obtained by adding the width reduction amount ΔH _{O-1 corresponding} to the rolling load difference ΔP between the biting end and the steady part of the slab when width rolling is performed with the distributed width reduction amount ΔH _{M-1 to M-1} . Set the roll opening degree G ₂ to obtain the rolling reduction amount ΔH _F-1 , and set the rolling load setting value to the maximum rolling load predicted value P ₁ when width rolling the steady portion of the predetermined pass with the distributed width rolling amount. When this set value is exceeded, the hydraulic rolling down mechanism is operated until the roll opening is expanded and the engaged end of the metal slab is rolled to a width.
After the roll opening reaches the roll opening G ₁ to obtain the distribution width reduction amount ΔH _M-1 of the predetermined pass, the operation of the hydraulic reduction mechanism is stopped, and the roll opening is fixed by the mechanical reduction mechanism. A method for hot width rolling of a metal slab, characterized in that width rolling is carried out using a metal slab. (Function) Hereinafter, the function of the present invention will be explained with reference to the drawings. Figure 2a shows that when a metal slab 1 is rolled in the width direction by a vertical rolling mill roll whose roll opening degree is set and fixed at a predetermined target width dimension of the metal slab, tips called fish tails are formed at the biting and biting ends. FIG. 4 is a diagram showing a state in which irregularly shaped portions 2 and 3 are generated at the rear end portion and the rear end portion. The present inventors investigated the fishtails 2 and 3 at the biting end and the biting-through end of the metal slab 11 produced by the above-mentioned width rolling. First, when width rolling is performed with the same rolling direction without reversible rolling from the start pass to the end pass of width rolling, the bite-through end irregularly shaped portion 3 is approximately three times as large as the bite end irregularly shaped portion 2, as shown in Fig. 2b. In reversible rolling, the positions of the bite end and bite-through end are changed alternately in relation to the rolling direction for each pass, so the irregularly shaped parts at the tip and rear ends are approximately equal, and the position of the bite end and bite-through end during unidirectional rolling is approximately equal. It was found that the average crop of the deep end and the open end was 4. For this reason, in the case of reversible rolling, in each pass of reversible rolling, the amount of width reduction at the biting end, which will be the biting-through end in the next pass, is preformed to be larger than other parts, and the width at the biting-through in the next pass is preformed. It was confirmed that by reducing the amount of rolling reduction, the amount of fish tails was significantly improved without hindering the rolling time, such as by setting a preforming pass in which only the edges were width-rolled. The present inventors have discovered a means to perform the above preforming even if the distributed width reduction amount is arbitrarily set in each width rolling pass in which the distributed width reduction amount is set without increasing the number of passes. be. FIG. 3a shows an example of the stand configuration of a width reduction mill, in which a horizontal roll 6 (H) is disposed between two stands of vertical mill rolls 5 (V ₁ ) and 7 (V ₂ ). The metal slab 1 is reversibly rolled between each roll 5, 6, 7. Figures 3b and 3c illustrate the slab shape during the rolling process. That is, vertical rolls 5, 7
Therefore, when a metal slab is width-rolled with the roll opening constant as described above, fish tails occur at the leading and trailing ends of the slab in the rolling direction, as shown in Figure 3b, and a uniform slab is formed from the leading and trailing ends. long 8,9
Locally increased thickness 10 occurs at both ends of the slab width, which is called a doghorn. If this locally increased thickness increases, it will cause surface flaws on the slab and an increase in rolling power during rolling in the width direction. These factors restrict the amount of slab width that can be rolled, so the thickness of the thickened part is horizontally rolled down by the horizontal rolling mill 6 as shown in Figure 3c, and the thickened part is rolled to the same thickness as other parts, or Reduce the thickness to less than that,
Rolling in the width direction is performed again to reduce the width, and the so-called rolling process shown in FIGS. 3b and 3c is repeated. In this case, the metal slab has a cross-sectional shape where the width center portion is thinner than the width end portions, and as shown in FIG. In addition, the wide reduction rolling process shows complicated rolling behavior, such as the above phenomenon not being observed in the leading and trailing ends 8 and 9. FIG. 4 shows a rolling load curve 12 when a metal slab is width-rolled with a constant rolling reduction (constant roll opening). In the rolling load curve 12 of FIG. 4, first, the rolling load fluctuation amount ΔP _s due to the heating furnace skid marks appears conspicuously. That is, in the width rolling process in which the continuous casting process and the hot rolling process are directly connected, the rolling efficiency is required to match the capacity of the preceding and following processes, so the heating time is subject to time constraints and rapid heating is performed. In addition, the end effect area (numerals 8 and 9 in Fig. 3 b and c) is located at the leading and rear ends of the metal slab.
) appears over 1 to 2 m,
A phenomenon is observed in which the rolling load is lighter in that part than in other parts, and the load reduction amount ΔP _F at the biting end is larger than the load reduction amount ΔP _T at the biting end. Based on these width rolling load patterns, the present inventors believe that if width rolling is performed by fixing the roll opening to a predetermined roll opening to obtain the distributed width reduction amount, the biting end where the rolling load gradually changes from a low level to a higher level can be , the part excluding the biting end and the biting-out end (hereinafter referred to as the steady part) is width-rolled at the maximum rolling load value when width-rolling is performed at the predetermined roll opening degree, or a value close to the lower (one side) thereof, and the part is kept steady. By preforming the metal slab to a narrower width than the front end, fishtails that occur at the leading and trailing ends of the metal slab can be significantly improved. FIG. 1 is an explanatory diagram of a specific rolling method of the present invention. In Fig. 1a, reference numeral 12-1 represents the load curve applied to the width rolling roll when a metal slab is width rolled with a constant rolling reduction amount (constant roll opening).
Reference numeral 13 indicates the width of the metal slab before rolling, and reference numeral 14 indicates the width of the metal slab after width rolling by the method of the present invention. In the figure, a material to be rolled having a metal slab width of 13 is width-rolled as follows. First, the setup is performed by setting the roll opening of the width rolling roll to the distribution width reduction amount ΔH _M-1 of the relevant pass, and adjusting the rolling distance between the biting end and the steady part when the entire length of the metal slab is width rolled at ΔH _M-1. Load difference ΔP (P ₁ − P ₂ )
The width reduction amount ΔH _{F-1 (} ΔH _M-1 + ΔH _O-1 ) obtained by adding the width reduction amount ΔH O- ₁ corresponding to The load setting value is set to the maximum rolling load value P ₁ when the portion of the metal slab excluding the biting end and the biting-through end is width-rolled with a predetermined reduction amount ΔH _M-1 . With this, the roll opening degree is expanded only when the actual rolling load value after biting exceeds this set value, and when it becomes less than the set value, the previous opening degree is maintained, and the width reduction amount ΔH is distributed to the corresponding pass. Predetermined roll opening to obtain _M-1
If width rolling is carried out in stages until G ₁ is reached, and after reaching the predetermined roll opening G ₁ , this roll opening is fixed and width rolling is performed with the distributed width reduction amount ΔH _M-1 , the slab width pattern 14 is A metal slab is obtained. At this time, the rolling load curve at the biting end becomes 12a-1 because skid marks are also present as in the other cases. That is,
When width-rolling a metal slab, if the roll opening is constant and the reduction amount at the biting edge and other parts is distributed over the pass as in the past, the rolling load at the biting edge will be the curve shown in Figure 4. As shown in Fig. 12, it is smaller than that of other parts, so in the present invention, this difference ΔP _F is eliminated and the rolling load is set to be equal to that of other parts, and the reduction amount of the biting end is set to be a reduction corresponding to the difference ΔP _F. The amount ΔH _O-1 is set larger than the other parts, the roll opening is set up to obtain this value, and rolling is performed to the biting width as described above. The width of the slab rolled in this way is 1
4 is width-rolled in the next reverse pass in the same way as in the previous pass, as shown in Fig. 1b, the bite-through end is preliminarily reduced in width by a larger amount than other parts due to biting rolling in the width rolling of the previous pass. Therefore, only this width reduction amount difference is the light reduction amount (ΔH _M-2 − (ΔH _F-1 −
ΔH _M-1 )). At this time, the rolling load curve becomes 12a-2 (dotted line) at the biting end and the biting through end compared to the load curve 12-2 (dotted chain line) where the rolling reduction amount is constant. By repeating the reversible rolling passes in this way, in each pass after the second pass, the biting end is preformed by strong rolling for the next pass, and the slab is preformed in the rolling direction of the previous pass under strong rolling in the previous pass. Light reduction rolling of the bite-through end is possible within the same pass. Furthermore, as a result of the investigation by the present inventors regarding the width of the finished slab, heavy rolling at the biting edge and light rolling at the biting edge were performed in a pass other than the final pass, and conversely in the final pass.
It has been found that if the rolling is carried out so that the amount of reduction at the leading end and the trailing end does not become large, the insufficient width at the leading end can be resolved. According to the method of the present invention, even when rolling is carried out at the maximum rolling load for the purpose of improving rolling efficiency, the rolling load difference ΔP between the biting end of the metal slab and other parts is used as described above, so that the rolling time is hindered. Clothopulosis can be significantly reduced by improving the fishtail without any problems. Next, an example of a rolling mill apparatus for carrying out the rolling method of the present invention is shown in FIG. In the figure, the rolls 5 and 7 of the vertical rolling mill are supported by chock 16 and are driven in communication with a roll drive shaft. The yoke 16 is integrally connected by a yoke 17, and the yoke 17 exerts a pulling force to the right in the figure by a pullback cylinder device 15 provided in a fixed housing 18 at the center of the rear surface, and each of the mechanical lowering mechanisms It is pressed into contact with a pressure block 20 provided at the tip of the reduction screw 19. The pressure block 20 has a built-in load cell and the like for measuring rolling load. In the mechanical lowering mechanism, each of the aforementioned lowering screws 19 is screwed into a lowering nut 21 which is provided in the fixed housing 18 via a detent so as to be able to move back and forth by a certain distance, and is connected to a worm wheel gear 22 at the rear end. Slide key is engaged. Further, in the hydraulic pressure lowering mechanism, an annular piston 24 is provided surrounding the screw 19.
and an annular cylinder 25, the annular cylinder 25 being placed in the stationary housing 18, while the annular piston 24 is attached to the lowering nut 2.
It is in contact with the back of 1. Reference numeral 26 is a liquid chamber gap formed by the piston 24 and the cylinder 25. When the hydraulic oil in this gap 26 is discharged, the lowering nut 21 and the annular piston 24 are also moved back by the pulling force of the pullback cylinder device 15, and the gap is closed. The right end of the piston 24 comes into contact with the bottom of the cylinder 25. In the figure, IO is the liquid chamber gap 2 of the annular cylinder 25.
6 side, the piping connects hydraulic oil with a pressure higher than the pulling force of the pullback cylinder device 15 to a source and a discharge pit in a switchable manner, and supplies and discharges the hydraulic oil to and from the liquid chamber gap 26, and is connected to a control valve. B _V and oil pressure detector P _n are interposed. Control valve B _V has manual ON-OFF control,
It is possible to switch to automatic control in which an opening oil drain operation is performed when the working oil pressure in the liquid chamber gap 26 detected by the oil pressure detector P _n reaches a set pressure, and a closing operation is performed when the pressure is less than the set pressure. Next, the operation for carrying out the method of the present invention will be described. Setup just before starting the width reduction pass Manually turn control valve B _V fully open (ON).
With the piping IO connected to the discharge pit,
The setting of the roll opening degree to obtain the set rolling reduction amount excluding the biting end, that is, the rolling reduction amount ΔH _M shown in FIG. Rotate the reduction screw 19 and remove the yoke 17.
This is done by moving forward or backward. At the start of this operation, the hydraulic oil in the liquid chamber gap 26 is discharged from the pipe IO, and the gap disappears. After setting the roll opening degree, the piping IO is switched to the hydraulic oil source, and hydraulic oil with a pressure slightly higher than the traction hydraulic pressure of the pullback cylinder device 15 is supplied into the liquid chamber gap 26 for the forward stroke length of the piston 24. [In other words, 1/2 of the width reduction amount corresponding to the maximum rolling load difference between the biting end and the steady portion determined in advance] is supplied to the piston 24, the reduction nut 21, and the reduction screw 1.
9. Via the pressure block 20, yoke 17, and choke 16, move the vertical roll 5 to the left side, that is, forward, against the traction force of the predetermined hydraulic pressure of the pullback cylinder device 15, and stop it at the opening degree at the time of biting. Set and after this setting control valve B _V manually
OFF (closed), then switch to automatic control and set the oil pressure setting value for opening operation as the oil pressure corresponding to the predicted maximum rolling load value when width rolling the stationary part of the metal slab with the distributed width reduction amount. . Roll opening degree control after set-up 1 When the tip of the metal slab is caught between the vertical rolls 5 set up as described above, the hydraulic pressure in the liquid chamber gap 26 that rises due to this is detected by the hydraulic pressure detector P _n , When this reaches the set oil pressure corresponding to the maximum rolling load value, the control valve B _V opens and drains the oil, and closes when the rolling part becomes high temperature such as the non-skid mark area and the load is reduced and the oil pressure falls below the set oil pressure. The operation is automatically carried out by retracting the piston 24, retracting the vertical rolls 5, and performing width rolling while controlling the roll opening degree to be enlarged step by step. In this way, when the piston 24 approaches and abuts the bottom B of the cylinder 25, the roll opening matches the target roll opening for width rolling the steady portion by the distributed width reduction amount. At this time, the hydraulic oil in the liquid chamber gap 26 is exhausted, and the expansion control is automatically stopped. 2. Thereafter, width rolling is performed with the roll opening degree being fixed and set to match the target roll opening degree until the roll is cut through. The above-described width rolling operation per pass is repeated for each pass except at least the final pass to achieve width rolling to the target finished width. (Example) Next, an example of the present invention will be shown. The rolling conditions are as shown in Table ₁ , and a continuous cast slab of ₂₈₀ mm thickness and 1800
Target slab dimensions from mm width: 250mm thickness, 600mm, 970mm,
Various sizes were manufactured with widths of 1190mm, 1400mm, and 1585mm.

【table】

[Table] Table 2 shows the inventive method and conventional method for various slab widths.
That is, this is a comparison with the one-pass reversible rolling method disclosed in Japanese Patent Publication No. 51-35383 mentioned above. Incidentally, the crop loss reduction rate is the improvement rate when rolling is performed with a constant reduction amount without changing the reduction amount, and when the method of the present invention and the conventional single-pass reversible rolling method described above are adopted. 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 requiring back-rolling to reset the roll opening. This resulted in cases where rolling was impossible.

【table】

[Table] (Note) − indicates that rolling is not possible due to temperature drop (effect) The application of the conventional yield-improving rolling method to a width rolling mill in a process that directly connects the continuous casting process and hot rolling process is due to the rolling time This is not possible as it would greatly hinder the process. According to the method of the present invention, it is possible to take a larger amount of width reduction at the biting end than in other parts, and because the difference in load between the biting edge and other parts is utilized, when rolling with a rolling amount equivalent to the maximum rolling load, This method can also be carried out without interfering with the rolling time, and the amount of fish tails generated at the leading and trailing ends of the metal slab can be significantly reduced with good productivity, resulting in a very useful effect industrially. Ru.

[Brief explanation of the drawing]

Figures 1a and b are explanatory diagrams of a specific rolling method of the present invention, and Figure 2a is an explanatory diagram of the state of fish tails that occur when a metal slab is rolled in the width direction.
Figure 2b is a diagram showing the relationship between the weight of the fishtail and the total width reduction amount, Figure 3a is a diagram showing an example of the stand configuration of a width reduction mill, and Figures 3b and c are explanations of the slab shape during the rolling process. FIG. 4 is a rolling load curve diagram when a metal slab is rolled with a constant reduction amount in the width direction, and FIG. 5 is a diagram showing an example of a rolling mill apparatus for implementing the present invention.

Claims (1)

[Claims] 1 In a hot width rolling method in which a vertical rolling mill and a horizontal rolling mill are operated reversibly to roll a metal slab along a predetermined rolling pass schedule to obtain a target finished width, the width of a predetermined pass excluding the final pass is During rolling, the roll opening degree at the time of biting of the metal slab is set to the distributed width reduction amount of the predetermined pass, and the difference between the biting end and the steady portion of the slab when width rolling is performed with the distributed width reduction amount. Set the roll opening to obtain the width reduction amount by adding the width reduction amount corresponding to the rolling load difference, and set the rolling load setting value to the maximum rolling when width rolling the steady part of the predetermined pass with the distributed width reduction amount. A predicted load value is set and the metal slab is bitten, and when this set value is exceeded, the hydraulic rolling mechanism is operated until the roll opening is expanded until it becomes less than the set value, and the width is rolled, and the roll opening is changed to the corresponding predetermined path. The method of heating a metal slab is characterized in that the hydraulic rolling mechanism is stopped operating after the roll opening is reached to obtain a distributed width reduction of , and width rolling is carried out with the roll opening being fixed by a mechanical rolling mechanism. Width rolling method.