JPS60244401A - Method and device for continuous hot rolling of strip - Google Patents

Abstract

PURPOSE:To join strips in short time and to hot roll continuously the strips by cutting the rear end of the preceding strip and the front end of the succeeding strip and heating both cut parts then joining the cut faces with pressure and hot rolling the strips. CONSTITUTION:A carriage 20 is moved to follow up the material speed so as to set the rear end of the preceding strip 8 and the front end of the succeeding strip 9 to the cutting position. The ends are then clamped by strip holders 21, 22. The rear end of the strip 8 and the front end of the strip 9 are cut by lower tool rests 23, 24 and upper tool rests 25, 26 at the same instant. The cut blocks 28, 29 are extruded by an extruder in the horizontal direction perpendicular to the advancing direction of the strips. The clamps 22 of the strip 8 are opened and the speed of the carriage 20 is so controlled that the rear end comes to the position of a high-frequency heater 63. The clamps 21 of the strip 9 are opened to bring the front end of the strip 9 into light contact with the rear end of the strip 8 by a pressing device 35. The strips are heated by the heater 63 and after the strip 8 is clamped by the clamp 65, the strips are pressed and joined by the device 35 and are continuously rolled.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention completely changes the hot rolling method for steel billets (slabs, blooms, billets and bars at the product stage thereof),
Concerning rolling methods that improve quality, yield, and save energy.

[Background of the invention]

FIG. 1 shows the layout of a typical conventional hot strip mill.

1 is the Nα1 rough rolling mill, which is usually a reversible type. 2 is an Nα2 rough rolling mill, which is often a unidirectional rolling mill. Reference numeral 3 denotes a crop shear for cutting the front end or rear end of the strip 8 or 9 provided on the entry side of the finishing mill group 4. Reference numeral 5 indicates a louver provided between the finishing rolling mills, and reference numeral 6 indicates a pinch roller provided on the inlet side of the down coil rough. 10, 11, 12
．． 13 are roller tapes, respectively. The finishing mill group 4 is usually composed of 5 to 7 finishing mills, and the strip is rolled across all the finishing mills at the same time. However, the rolling is carried out intermittently, one slab at a time, and on the exit side, one coil at a time. Therefore, the leading end threading and the trailing end ash removal work are performed for each slab, causing a lot of damage. This problem disappears if many slabs are combined into one long slab. The reason why this is not currently realized is as follows. In other words, when slabs are manufactured using a blooming mill, the size of the slab is limited to the size of the steel ingot, so in order to join them together to make a long slab, a thickness of around 200 blocks is required. There is a need for a quick and economical way to join things together, but this is difficult and has not yet been achieved.

On the other hand, continuous casting can practically obtain infinitely long slabs, but the production volume of continuous casting strands is 1/3 to 1/4 of that of hot strip mills, and therefore, the production volume of continuous casting strands is 1/3 to 1/4 of that of hot strip mills. ~ Slabs would have to be alternately supplied from a four-strand continuous casting facility,
There is no choice but to cut the continuous slab into appropriate lengths and feed them to the hot strip mill.

By the way, if the slabs are made continuous, the following effects can be expected.6 (1) Downsizing of equipment and energy saving a) Continuous slabs eliminate the need for biting and tail removal, so work is easier due to biting performance. There is no need to increase the roll diameter for this reason. (Reduction amount limit th-=μ2-D7: work roll diameter, μ: roll-to-material mass coefficient) b) Since the impact torque generated during biting and ash removal is eliminated, the drive system, and therefore the diameter of one work roll, can be made smaller.

C) Recently, in hot rolling, oil lubrication has been used to extend the life of the rolls and reduce the rolling load and rolling power. Refueling must be interrupted during this period, and
A complicated oil draining device must be provided. When the slab becomes a continuous slab, these are no longer necessary, and the scales do not need sufficient oil lubrication at all times.

Therefore, the rolling mill can be made smaller.

Due to reasons a), b), and c), the work roll diameter can be made significantly smaller, and the reinforcing roll diameter can also be made smaller due to the reduction in rolling load due to its own reduction and the effect of reducing the rolling load due to oil lubrication. can be made smaller. In addition, without trying to downsize - by increasing the reduction per stand,
It is also possible to reduce equipment costs by reducing the number of stands.

Also, since the rolling power is approximately proportional to the square root of the work roll diameter, for example, the diameter of one work roll can be increased from the conventional 800 m to 64 m.
%51211I11, rolling power is 20%
This saves 200 kW drive motors per stand.
0 kW can be saved.

Generally, when the diameter of the work roll is reduced in this way, the lateral rigidity of the work roll decreases, and the axial deflection of the work roll due to changes in rolling load and sheet width increases, and the crown shape (flatness) of the product strip increases. ), but this problem can be solved by applying roll bending (work roll or intermediate roll), which is effective in known killing rolling mills with a movable intermediate roll axis and four-high rolling mills with a movable work roll axis. I can deal with it.

(2) Improved quality and yield In conventional rolling methods, tension is not applied to the strip during the threading process in the finishing mill, but tension is applied at other times.
Changes occur in plate thickness and width, and since there is no tension at the leading and trailing ends, plate bending is likely to occur, which reduces yield quality. This can be resolved by making it continuous. Furthermore, in order to minimize the difference between the tension and the zero tension during threading and ash removal, the tension had to be as low as possible during normal rolling.

Continuing eliminates the need for this, and by applying appropriate tension, it is possible to reduce the rolling load, reduce pressure, and roll thinner products.If necessary, it is also possible to consciously control the tension and use control of the plate width. You can also do it.

As described above, although continuous production has a great economic effect, it has been extremely difficult to realize it. Continuous rolling of cold strip steel has already been achieved.

This is achieved by joining the tail end of the preceding coil and the tip of the following coil by welding to achieve continuity, but since the plate is thin and at room temperature, a strip looper is installed between the rolling machine and the welding machine. .

The strip is supplied to the rolling mill from this looper and welding can be performed while the welding machine is stopped while rolling continues. On the other hand, in hot rolling equipment, the slab thickness is around 200 ma+, and the thickness at the entry side of the finishing rolling mill is 30 to 50 Iff11, making it difficult to make a loop, and even if it is possible, the rolling time is short. However, there is a problem that the time required for welding the slabs together is very short. Incidentally, in cold rolling, the rolling time for one coil is 3 to 5 minutes and the welding time is 1 to 2 minutes, whereas in hot rolling, the rolling time for one slab is at most 1 minute or less. Therefore, if continuous welding is to be achieved, welding cannot be achieved unless welding is completed in several seconds using an inter-travel welding machine.

However, as a conventional continuous hot rolling method, JP-A-48-6
In the "Method for joining and continuous rolling of heated materials" proposed in No. 7159, the head of the subsequent unit material is brought into contact with the head of the subsequent unit material while approaching the inlet of the rough rolling mill and following the progress of the tail of the heated material during rough rolling. The periphery of the contact surface is joined by electrowelding or pressure welding, and this joining method is successively continued to perform continuous rolling.

However, electrolysis requires time on the order of minutes, and for example,
Even if the material advances at a speed of 30 m/an and the welding time is 1 minute, the welding machine itself needs to move with the material about 30 m, which poses various problems in terms of space and mechanical structure.

On the other hand, even if the ends are simply pressed together, it takes a long time to join depending on the cross-sectional shape and scale adhesion, and the reliability of the joint is low. There is a high possibility that they will be separated.

On the other hand, according to the ``method for hot rolling steel billets'' proposed in JP-A No. 51-59748, when continuously hot rolling -m pieces, the front and rear ends in the longitudinal direction are preliminarily rolled. When shearing a steel billet in the width direction, the angle at which the sheared end face intersects the steel billet is sheared at a constant angle (20" to 85@), this sheared surface is descaled, and the sheared end face is sheared at the same angle. Both steel pieces are pressed against each other by rolling while pressing against the rear end face of the preceding steel piece, and are successively joined.

However, in this method, it is necessary to shear so that the angle at which the sheared end surface intersects the steel slab is 20 to 85'', but it is difficult to perform this kind of work during rolling, and it is difficult to do this during rolling. This is offline work before insertion into the furnace.Also, shearing at an angle itself is difficult to shear with high precision.Furthermore, with this method,
Both sheared end surfaces of a steel piece are pressed and forced into rolling rolls, but it is difficult to set the pushing force and rolling reduction rate.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and apparatus for continuous hot rolling of steel billets, which enable joining of steel billets in a short time and continuous hot rolling of steel billets.

[Summary of the invention]

A feature of the present invention is that on the entry side of the rolling mill of a hot rolling equipment, the rear end of the preceding steel billet and the tip end of the following steel billet are aligned in the traveling direction of the steel billet. After cutting the rear end and the tip of the steel piece that are close to each other or in contact with each other, and immediately after cutting, the cut surfaces of both ends are rapidly heated to raise the temperature.
A series of steel billets in which the trailing end cut surface of the preceding steel billet is pressed against the leading end cut surface of the succeeding billet, and then the joined steel billets are continuously rolled. In the hot rolling method.

Further, other features of the present invention include a steel billet clamping device that fixes the rear end of the preceding steel billet and the tip end of the following steel billet, and A cutting device that cuts both ends of a steel billet, and after cutting, a cutting device that cuts both ends of a steel billet, and after cutting, rapidly heats and raises the temperature while keeping both ends of the billet in contact with each other for a certain period of time. A suppression device is installed to clamp the succeeding billet and to transfer the succeeding billet in the traveling direction so as to pressure-join the tip end cut surface of the billet. A continuous hot rolling apparatus for steel billets is provided with each device on a movable truck, and this truck is placed on the entry side of the rolling mill so that the rolling process can be carried out at a speed substantially equal to the speed in the advancing direction of the rolling mill.

[Embodiments of the invention]

FIG. 2 shows an embodiment according to the invention. FIG. 2 shows the case where the strip is made continuous on the entry side of the finishing mill.

To make the strip continuous, a device capable of joining the preceding and succeeding strips in a short time is placed at the entry side of the finishing mill, and the strip is moved a certain short distance by following the advancing speed of the strip.

(2.5 m if 5 seconds including cutting, joining, etc.) Next, a short time strip joining method will be described. There are methods to join the strips, such as welding brazing, forge welding, pressure welding, and mechanical joining, but (1) joining must be done in a short time (within a few seconds). (Problem of scale generation) (2) The joint strength must be strong enough to prevent the joint from coming apart during rolling in the finishing mill in the subsequent process.

Considering these conditions, ■ flash butt welding, ■
The methods are narrowed down to high-frequency induction heating + pressing and (1) pressure welding, but for (2) the welding time is on the order of several tens of seconds to minutes, and (2) has the following various problems.

That is, since the hot rolled strip itself has a temperature of about 1000 to 1100° C. at the joining position, if pressure welding can be performed at this temperature level, joining can be performed without consuming energy.

Therefore, the inventor conducted a test using a small model (material size: 9 mm thick, 60 mm wide).

However, it was found that bonding was impossible in tests with a pressing force of up to 3 kg/ya''.It is possible to increase the pressing force to 5 to 10 kg/mm2, but piece, for example, 50nwn thick x 15
In the case of a material with a width of 00+am, the suppression load is (5o x 150
0) X (5~10) = 375ton~
750.70n, which is extremely large and requires large equipment, and the hot steel billet itself is bent, making it impossible to implement.

Furthermore, in order to pursue the possibility of method (2), the inventor conducted various tests and studies using the above-mentioned model, and determined that the range of combinations of heating temperature and pressing force (hatching part) as shown in Fig. 6 was obtained. It was confirmed that it was a bondable area. That is, the heating temperature is in the range of 1250'C to 1450°C,
Of these, it is clear that the pressing force must be large on the low temperature side, while on the other hand, the pressing force may be small on the high temperature side.

In short, as a condition for welding, it is necessary to heat the hot billet to near the melting point of the material and press it.

Also, if the high frequency power supply capacity is selected appropriately (io00'c~11
The heating time from 00°C to 1250°C to 1450°C can be set to 5 to 20 seconds.

Furthermore, in the post-process hot rolling process, good bonding conditions are: ■ Completely bonded, ■ Only peripherally bonded, ■ Only internally bonded. (2) is effective when considering power consumption) and short-time bonding. Meanwhile, another test (100
There is an example in which an actual slab (nn thickness x 1400 nyn width) could be rolled to a sheet bar without any problem at #J circumference joining ratio (welding) of 30%. As for item (2), it breaks during hot rolling due to the surface notch effect.

As described above, peripheral bonding is advantageous both economically and from the viewpoint of short bonding time, and high-frequency heating can be said to be optimal from this point of view as well.

According to this method, it is possible to join in a short time of 5 to 20 seconds in the atmosphere, and continuous hot rolling of steel slabs is possible.

FIGS. 3 and 4 show an embodiment of a device that makes this joining possible.

In FIG. 3, the trolley 20 can run on rails 41 so as to match the moving speed of the steel pieces. The trolley 20 is configured to fix and hold the vicinity of the rear end of the preceding steel piece 8 and the vicinity of the tip of the following steel piece 9, respectively.
A strip restraint device 22.21 is provided. These strip suppressing devices 22 and 21 include a detection device 62 that detects the position of the rear end of the preceding steel strip 8 and a subsequent strip suppressing device 62 that detects the position of the rear end of the preceding steel strip 8.
The built-in hydraulic cylinder devices 22a, 2 are operated by a detection signal from a detection device 61 that detects the position of the tip of the
1a so that the ends of each steel piece can be clamped. In addition, the strip suppressing device 21
．． A shearing device is arranged between the lower tool rests 23 and 24 with the cutter 42 and the upper tool rest 25 and 26 with the cutter 43, and the upper tool rests 25 and 213 are each equipped with a hydraulic cylinder device. 25a and 26a are operated, and the rear end of the leading steel piece 8 and the tip end of the trailing steel piece 9 are vertically cut by a predetermined dimension. Moreover, the upper turret 2
5. Below the 26, that is, below the steel piece, there is an upper tool rest 2s.
, 26 are lowered, the hydraulic cylinder device 2 is operated in synchronization with the lowering of the hydraulic cylinder device 2.
7a is installed, and this mount 27
When cutting the end of the steel piece 8°9, the mount 27 is lowered together with the lowering of the upper tool rest 25 and 26 while applying a certain force to the steel piece to ensure that the steel piece is cut reliably and at a high height. It can be done with precision.

Furthermore, as shown in FIG. 4, a motor 31, a rack 32, and a pinion 33 are provided between the lower tool rests 23 and 24.
A crop extrusion device 30 is installed which moves in a horizontal direction perpendicular to the running direction of the billet as a rack 32 engaged with a pinion 33 moves by driving a motor 31. Then, the rear end portion of the steel billet 8 and the tip portion of the steel billet 9 cut by the shearing device are removed to the outside from the traveling line of the steel billet so as not to interfere with the next joining operation.

Further, in the first cart 20, the ends of the steel slabs 8 and 9 are cut by a shearing device, and then the cut steel slabs are removed by a crop extrusion device 30, and then the rear end of the leading steel billet 8 and the trailing steel billet 9 are cut. The tip position is advanced to the position of the high-frequency heating device 63 (in this figure, a high-frequency induction heating device is shown), and the temperature is raised to 1 of the temperature of the heated part steel billet.
Dokei sensor 64 indicates that the temperature has reached 250℃~1450℃.
After the detection, a pressing device W35 is installed to press and join the trailing steel billet 9 to the leading billet while the leading billet 8 is clamped by the clamp cylinder 65, as shown in FIGS. 4 and 5. There is. This suppression device 35 includes upper and lower pressure plates 51.52 that pressurize the following steel billet 9 from above and below, a hydraulic cylinder 36 that adjusts the gap between these pressure plates 51.52, and a hydraulic cylinder 36 that moves in the traveling direction of the steel billet and It is composed of a hydraulic cylinder device 37 and a rail 47 that can press the cut surface of the tip end of the steel piece 9 against the cut surface of the rear end of the piece 8.

Next, the operation of the continuous hot rolling apparatus will be explained.

In FIG. 3, the cart 20 is made to follow the material speed so that the rear end of the leading strip 8 and the leading end of the trailing strip 9 are set at the cutting position, and are clamped by the strip holding device 21.22, and at the same time, the lower tool rest 23.24 and upper turret 25
．． A shearing device constituted by 26 cuts the trailing end of the leading strip and the leading end of the trailing strip simultaneously or within a short time difference. At this time, the strips 8 and 9 are sandwiched between them and under the upper cutter 25.26. When cutting, while holding the strips 8 and 9 with a certain force in the vertical direction, as the upper cutter 25.26 descends, Lowering platform 27
is the provision.

The cut crops 28 and 29 shown by the two-dot chain line are the fourth
For example, motor 31. A crop extrusion device 30 composed of a rack 32, a pinion 33, etc. extrudes the rolled strip in a horizontal direction perpendicular to the traveling direction.

After the rear end of the leading strip 8 and the leading end of the trailing strip 9 are cut, and the crops 28 and 29 are extruded, the holding clamp 22 of the leading strip 9 is opened, and the rear end position is the position of the high frequency heating bag N63. Traveling trolley 2
Control the speed of the trailing strip 9 and hold down the clamp 2
1 is opened, and the strip 9 is set by the pressing device 35 so that the leading end of the preceding strip 8 touches the rear end of the strip 9 lightly or at a certain distance, also at the position of the high-frequency heating device 63. After setting, the temperature is increased by the high frequency heating device 63, and when the temperature of the rear end of the strip 8 and the tip of the strip 9 reaches 1250°C1 to 1450°C, the strip 8 is held down and clamped with the clamp 65. , pressure bonding is performed using a suppressing device 35. Pressure force is 3kg
/+nm2 or less is desirable.

Thereafter, as shown in FIG. 2, the joined steel pieces are led to a finishing mill group 4 and continuously rolled.

FIG. 7 is a schematic diagram of the high frequency heating device.

This embodiment includes all functions having the following functions.

Namely, (1) a detector 61.62 for detecting the position of the trailing end of the leading strip and the leading end of the trailing strip; (2) a strip clamping device 21.22 for fixing both ends before cutting and joining them; 3) A cutting device 23 for cutting both ends in a clamped state.
24, 25. 26 (4) Crop processing device 30 for processing the cut crop after cutting (5) Pressing device M for pressing the vertical section of the leading end of the succeeding strip against the vertical cut surface of the trailing end of the preceding strip
35 (6) High frequency heating device that heats both cross sections (7) Cutting,
A movable device 20 performs joining and associated operations while following the progress of the strip.The strip thus joined must be cut before the winder. In this case, if a flying shear 14 is provided on the exit side of the pinch roller 6 as shown in Fig. 2, a constant tension is always applied to the exit of the finishing stand, and changes in board width due to bending of the board or changes in tension can be prevented. It becomes less. Incidentally, due to the continuity, the operating magnifying glass 5 between the finishing stands shown in FIG. 1 can be replaced with a fixed tension meter I6 as shown in FIG. 2, thereby reducing equipment costs and improving maintainability.

〔Effect of the invention〕

According to the present invention, steel billets can be joined in a short time, and hot rolling of steel billets can be realized continuously.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the arrangement of a conventional hot strip mill, Fig. 2 is a schematic diagram showing the arrangement of a hot strip mill that enables continuous rolling to which the present invention is applied, and Fig. 3 is an embodiment of the present invention. General view of the example continuous strip joining device, No. 4
The figure is a plan view of Figure 3, Figure 5 is a view from ■-■ arrow in Figure 4,
Figure 6 shows the heating temperature ("C) and pressing force (kg) for good bonding.
/+nn”) is shown in Figure 4, Figure S.

Claims (1)

[Scope of Claims] 1. The rear end of the steel billet that runs in advance on the entry side of the rolling mill of the steel billet hot rolling equipment and the tip end of the steel billet that runs following the said steel billet. In a state of being close to each other along the direction of travel,
After cutting the rear end portion and the tip end portion of the steel piece, and heating both cut portions immediately after cutting, the following steel piece is cut against the cut surface of the rear end portion of the preceding steel piece. A method for continuous hot rolling of steel billets, characterized in that the cut surfaces of the tips of the steel billets are joined by pressing, and then the joined steel billets are hot rolled. 2. In claim 1, when pressing the cut surface of the tip end of the succeeding steel piece against the cut surface of the rear end of the preceding steel piece, both cut surfaces are brought into contact or non-contact. 1. A continuous hot rolling method for a steel billet, characterized in that the temperature is raised by high-frequency heating, and then both cut surfaces are joined by pressing. 3. In claim 2, the temperature raised by the high-frequency heating is 1250°C to 1450°C.
A continuous hot rolling method for a steel billet, characterized in that both cut surfaces are joined by pressing after the temperature is reduced to .degree. 4. In claim 1, when the rear end portion of the preceding steel piece and the tip end portion of the succeeding steel piece are cut and press-joined, the cutting, heating, temperature raising, pressing, and joining are performed. A continuous hot rolling method for a steel billet, characterized in that the operation is carried out while following the traveling of the steel billet so as to substantially match the speed in the traveling direction of the steel billet. 5. In a continuous hot rolling machine for #1 pieces, a steel piece clamp device that fixes the rear end of the preceding steel piece and the front end of the following steel piece, and clamps the steel piece. a cutting device that cuts each end of the steel billet in a state in which the steel billet is cut, a high frequency heating device that simultaneously heats the end of the steel billet, and a cutting surface of the rear end of the preceding billet; a pressing device that clamps the succeeding steel piece in order to pressure-join the cut surfaces of the tip portion and transports the succeeding steel piece in the running direction; 1. A continuous hot rolling apparatus for steel billets, comprising a cart on which all of the above-mentioned apparatuses are mounted so that the continuous hot rolling can be carried out at almost the same speed. 6. The continuous heating of steel billets according to claim 4, characterized in that the cart is provided with a transfer device for removing the steel billets cut by the cutting device out of the traveling path of the steel billets. Inter-rolling equipment.