JP2001321801A - Method and device for completely continuous hot-rolling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve joining strength between a preceding and succeeding bars without making large equipment investment to an existing hot strip mill. SOLUTION: In the method for completely continuous hot-rolling by which the tail end of the preceding bar and the tip of the succeeding bar which are materials in rolling between rough rolling and finish rolling are overlapped along the longitudinal direction and joined with a rolling mill, the length of the overlapped part in the longitudinal direction of both the bars is set to be <1/2 of the width of the bar.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a completely continuous hot rolling method and a rolling apparatus.

[0002]

2. Description of the Related Art First, a hot strip mill process will be described. A typical layout is shown in FIG. As shown in FIG. 1, this layout includes, in order from the upstream side to the downstream side, a heating furnace 1, a rough rolling mill group 2, a delay table 3, a crop shear 4, a finishing descaling device (FS
B) 5, a continuous finishing mill group 6, a run-out table 7, and a coiler group 8 are arranged.

First, a high-temperature slab extracted from the heating furnace 1 (for example, having a thickness of about 250 mm and a width of about 700 to 2000
mm, the length is about 10 m), the thickness is reduced to about 30 mm in the rough rolling mill group 2 having a plurality of rough rolling mills, the width is almost the same as the slab width, the length is about 80 m, and the temperature is About 1100 ° C
Semi-finished product. This is called a bar. This bar is conveyed on a delay table 3 to a continuous finishing mill (hereinafter referred to as a finishing mill) group 6 side. The tip is cut into a rectangular cross section substantially perpendicular to the bar longitudinal direction.

[0004] Thereafter, the tip of the bar passes through a finishing mill group 6 through a finishing descaling device 5 to form a strip of about 850 ° C with a product thickness of several mm. Here, the rear end of the bar has a temperature drop during that time, but is cut into a rectangular cross section by the crop shear 4 like the front end, and the finishing mill group 6 is cut.
Pass through (extract tail end). The strip leaving the finishing mill group 6 travels on the run-out table 7 at a speed of about 50 km / hr, receives water cooling, and is wound on a coiler. The strip length can be as long as 1 km or more.
This rolling method is also called batch continuous hot rolling.

On the other hand, in recent years, equipment for realizing a so-called perfect continuous hot rolling, in which bars are joined and subjected to rolling and the strip is cut while running in front of a coiler, is practically used for the batch continuous hot rolling. It is becoming.

Conventionally, for joining bars, a method of welding a leading bar and a trailing bar after a final rough rolling mill of a hot strip mill and before a finishing rolling mill has been generally used (Japanese Patent Laid-Open No. 11-1999). 123453). Here, a rectangular end face obtained by cutting the tail end of the preceding bar vertically in the longitudinal direction and a rectangular end face obtained by cutting the tip end of the following bar vertically in the longitudinal direction are induction-heated or energized, and each end face is divided into the two. In general, a method of pressing horizontally in contact with the center of the cross section so that the centers of the cross sections coincide with each other. However, this method has the following problems.

A. Heating both end surfaces to a temperature at which mild steel can be pressed in about 5 seconds requires a large power supply and control equipment. b. A precise alignment device is required to make the gap between both ends of the leading bar and the trailing bar nearly zero mm. c. It requires a device that clamps the ends of the leading and trailing bars over 10 meters and runs parallel to the bars. d. Finally, a device for removing burrs generated due to the horizontal pressing force is required.

[0008] It is difficult to realize each of the above-mentioned devices with an existing hot strip mill in terms of space. Also,
Even if possible, the equipment costs would be enormous.

On the other hand, Japanese Patent Application Laid-Open No. Sho 51-112449 has proposed a simple and complete continuous hot rolling method. As shown in FIG. 2, this technology uses a half of the width W of the leading bar 11 (or the trailing bar 12) in a finishing continuous rolling mill.
The preceding bar 11 and the following bars 11, 12 are overlapped over the above-mentioned overlapping length Lov, rolled and pressed. As is clear from Table 1 of the above publication, for example, 122
In the case of a bar having a width of 5 mm, it is necessary to overlap the bar over a length of 620 mm. However, this method has a drawback that the crimp strength is weak for the following reasons.

In general, when rolling a steel sheet using upper and lower working rolls having substantially the same diameter, a rolling phenomenon that is vertically symmetrical in a roll bite is generated. In the rolling in which the leading bar 11 and the trailing bar 12 are overlapped as shown in FIG.
The scale (iron oxide) 13 plane between 1 and 12 becomes the plane of symmetry. In the rolling tool during rolling, the material (bar) naturally moves in the traveling direction, but the material (bar) is moved toward the symmetry plane by receiving the rolling force by the upper work roll 14 and the lower work roll 15. However, the scale surface is thinned by being vertically pushed from the upper and lower preceding bars 11 and the following bar 12, but does not completely contact the upper and lower materials.

That is, the leading bar 11 and the trailing bar 12 are separated by the scale 13 and do not adhere to each other. Leading bar 1
1. Although some shearing deformation due to free deformation occurs at the end of the trailing bar 12, additional shearing deformation at the end is limited to a small extent because the mating material undergoes steady deformation with its front and rear restrained. Here, increasing the overlap length Lov of the leading bar 11 and the trailing bar 12 only increases the plane-symmetric rolling portion, but increases the area of the joining surface, so that the entire area of the leading bar 11 and the trailing bar 12 above and below is increased. The purpose is to increase the bonding strength and does not contribute to the increase in the bonding strength per unit area of the bonding surface.

In other words, according to the above-mentioned complete continuous hot rolling method, the scale of the joint surface is not sufficiently broken or the shear deformation is insufficient, so that the joint strength per unit area of the joint surface is low.
Therefore, in order to increase the overall bonding strength, the overlapping length must be unnecessarily larger than 1/2 of the bar width W. Also, if the overlapping length Lov of the upper and lower leading bars 11 and the following bar 12 is large, the length of the joint is increased, and the amount of joint removal in the final product is increased. There was a problem that the advantage of rolling could not be obtained.

Further, in the completely continuous hot rolling method disclosed in Japanese Patent Application Laid-Open No. 51-112449, the side surface of the overlapping portion of the material must be removed beforehand in order to prevent the material from warping in the direction of winding around the roll. Plate welding was required, and a welding device for that purpose was also required.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above circumstances, and is intended to reduce the length of the longitudinally overlapping portion of the preceding bar and the following bar to less than 1/2 of the bar width. To provide a completely continuous hot rolling method capable of dramatically improving the joining strength per unit area of a joining surface and realizing a reliable joining without requiring a special welding device as in the past. Aim.

Further, the present invention includes a heating furnace, a rough rolling mill group, a crop shear, a finishing descaling device, a finishing rolling mill, and a control system electrically connected to each of these components. It has a controller for rolling joining and a measuring roll arranged on the upstream side of the finishing mill, and the control system sets the tail end of the preceding bar and the tip of the following bar as long as possible in the longitudinal direction. By having a function of rolling and joining bars in a roll bite by rolling by entering into a finishing mill and shortening it vertically and vertically, without making a large capital investment for existing hot strip mills It is another object of the present invention to provide a complete continuous hot rolling apparatus capable of easily and stably joining a bar by mainly using only a control system.

[0016]

SUMMARY OF THE INVENTION A completely continuous hot rolling method according to the first invention of the present application comprises a tail end of a preceding bar and a tip of a following bar which are materials being rolled between rough rolling and finish rolling. And in a complete continuous hot rolling method in which the two bars are overlapped in the longitudinal direction and joined by a rolling mill, the length of the overlapping portion in the longitudinal direction of both bars is set to less than 1/2 of the bar width. I do.

A completely continuous hot rolling apparatus according to a second aspect of the present invention includes a heating furnace for heating a plate-like leading bar and a following bar, and a bar disposed downstream of the heating furnace to reduce the thickness of the bar. A rough rolling mill group, and a crop shear that is disposed downstream of the rough rolling mill group and cuts the bar vertically in the longitudinal direction;
A finishing descaling device disposed downstream of the crop shear to remove iron oxide formed on the bar;
A finishing rolling mill arranged downstream of the finishing descaling device, and a control system electrically connected to each of the constituent members, wherein the control system includes a rolling joining controller and an upstream side of the finishing rolling mill. And the control system superimposes the tail end of the preceding bar and the tip of the following bar on top of each other with the length of overlap in the longitudinal direction as short as possible, and the finish rolling mill It is characterized by having a function of rolling and joining bars in a roll bite by entering and rolling.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

The present invention relates to a hot strip mill,
An upstream rolling mill in the finishing mill that achieves product thickness.
The purpose of the present invention is to provide an apparatus and a method for reliably rolling and joining the tail end of the leading bar and the tip of the following bar, and to perform the threading work of the material tip and the extraction work of the bar tail end at least after the intermediate stand of the finishing rolling mill. It is intended to realize a completely continuous hot rolling mill capable of realizing rolling without the rolling. As a result, it is possible to prevent the generation of scratches on the surface of the finish rolling roll caused by the adhesion of the debris material to the roll and the biting due to the threading and tail end punching work (hereinafter referred to as unsteady portion rolling). Prevents fluctuations in thickness and width caused by fluctuations in material tension during rolling, reduces misrolling caused by poor control during unsteady rolling, enhances hot lubrication effect, and runs out at the leading and trailing ends of the strip. This brings effects such as a reduction in yield loss caused by poor table running.

In other words, the present invention solves the above-mentioned problem relating to the joining of the leading and trailing bars, and realizes the joining of the sheet bars without making a large capital investment for the existing hot strip mill. Further, a thin sheet perfect continuous hot finish rolling is provided by providing a flying shear before the coiler. That is, as shown in FIG.
Rather than making _ov longer than １ ／ of the bar width W, the lap length L _ov is less than _の of the bar width W, preferably a length equivalent to the (rolled) contact arc equivalent length. By adopting such a short length, the bonding strength per unit area of the bonding surface is remarkably improved, and reliable bonding is realized.

The "contact arc equivalent length" is substantially equal to the contact arc length where the trailing bar 12 and the upper work roll 14 contact each other in FIG. Here, “substantially equal to the contact arc length” means an overlap portion length at which a joining strength equivalent to the joining strength when the overlapping portion length is rolled at the contact arc length is obtained, and is slightly smaller than the contact arc length. If the effect obtained is substantially the same regardless of whether the length is longer or shorter, the "contact arc equivalent length" is substantially equal to the "contact arc length". In other words, the contact arc equivalent length means the length of the overlapping portion having substantially the same effect as the contact arc length, and specifically, the overlapping length that achieves the bonding strength ratio of 0.7 or more shown in FIG. Is preferred. Further, most preferably, it is advantageous to shorten the bonding strength ratio to 0.9 or more, and in terms of the bar width to 1/10 or less of the bar width.

Referring to FIG. 4, when the overlapping length L _ov is shortened, the end A of the leading bar 11 and the end B of the following bar 12 come close to each other and the unsteady portions at both ends in the roll bite. Influence each other. As a result, a vertically asymmetric rolling state occurs, and very large free deformation occurs at the ends of the upper and lower materials. This generates shear flow not only parallel to the scale surface of the material but also perpendicular to the scale surface of the material, and the upper and lower materials enter each other. And, since the material is greatly deformed at the interface, the scale is significantly destroyed, and a strong joining between the upper and lower materials can be secured.

FIG. 5 shows a roll having a roll radius of 400 mm, a thickness of 25 mm, a width of 1225 mm, and a temperature of 850 ° C.
2 shows the results of examining the bonding strength of the material after rolling two low carbon steel sheets. However, the length of the overlapping portion was changed, and the rolling reduction was in the range of 20 to 40%. Also,
A tensile test piece having a width of 30 mm was cut out in the rolling direction from the material after rolling so as to include the joining surface, and the tensile strength at break was defined as the joining strength. In FIG. 5, the joining strength ratio on the vertical axis is obtained by dividing the joining strength by the tensile strength of the base material.

From FIG. 5, it is apparent that when the length of the overlapping portion is 1/2 of the bar (plate) width W, the bonding strength ratio is about 0.5, and the bonding strength ratio does not change much as the number of overlapping portions increases. It is. This is because, in the pressure welding method with a long overlapping portion as described above, the steady rolling is symmetrical in the vertical direction in most cases, and the fracture state and shearing deformation are small. Due to low bonding strength.

On the other hand, when the length of the overlapping portion is small, that is, when the length is equivalent to the contact arc, a very large bonding strength ratio is obtained. This is because, as described above, the upper and lower materials simultaneously undergo an unsteady deformation accompanied by a large additional shear deformation in the roll bite, and the scale is significantly destroyed and the material is completely fixed at the joint surface due to the large material deformation.

As described above, since all of the overlapping portions are accommodated in the roll bite at the moment, the upper and lower materials undergo extremely large deformation accompanied by additional shearing deformation, and the joining strength per unit area is dramatically improved. It is intended.
Therefore, it is desirable that the overlapping portion has a length substantially equal to the contact arc equivalent length. Even if the length of the overlapping portion between the preceding bar and the following bar is about the length corresponding to the contact arc, a bonding strength ratio larger than that in FIG. 5 can be obtained.

When roughly calculated, for example, the upper and lower bar thicknesses H
Is 25 mm each, and the outlet thickness h of the overlapping portion is 30 mm,
When the working roll radius R is 400 mm, the contact arc length L is the square root of the product of the roll radius R and the reduction amount Δh, and is about 90 m.
m. This value is determined as follows. L = (R · Δh) ^1/2 = {R · (H−h)} ^1/2 = (400 × 20) ^1/2 ≒ 90 mm This is the overlap length on the entry side from the calculation of the area of the roll bite shape. L _ov is equivalent to 72 mm. That is, 72
By performing the above-mentioned rolling in the state of the overlap length of not more than mm, the overlapping portion of the upper and lower materials is rolled in the contact arc, and a large joining strength can be secured. As can be seen from the above, in order to increase the bonding strength, a length one digit smaller than the overlapping length disclosed in Japanese Patent Application Laid-Open No. Sho 51-112449 is required. According to this method, since the overlapping portion is short, the material does not wrap around the roll, and plate welding is unnecessary in advance. In addition, since the overlapping portion is small, the loss of removing the joint in the final product can be minimized, and the advantage of the original complete continuous hot rolling can be enjoyed.

[0028]

Embodiments of the present invention will be described below in detail with reference to the drawings. (Embodiment 1) First, a control system which is one configuration of a complete continuous hot rolling apparatus according to the present invention will be described with reference to FIG. However, the same members as those in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof will be omitted.

In FIG. 6, reference numeral 21 indicates a rough final rolling mill (RL) arranged at the end of the rough rolling mill group 2. Also,
Reference numeral 22 indicates a first finishing mill located at the beginning of the continuous finishing mill 6. Each of the rough and final rolling mills 21 and the finishing rolling mills 6 and 22 are provided with a motor for driving a rolling mill and a control device (including a speed instruction / actual result) 23. Each of the tables, crop shears 4, and FSBs 5 of the delay table group 3 are provided with a table driving motor and a control device (including speed command / actual) 24, respectively. Just before the first finishing mill (F1) 22 and the last table of the delay table group 3, measuring rolls 2 are provided.
5 and 26 are respectively arranged. Immediately before the crop shear 4, a detector 27 for detecting the tip of the bar is arranged.

Reference numeral 28 in FIG. 6 denotes a rolling joining controller (hereinafter, referred to as a controller). The controllers 28 and 24 are connected to the controller 28. The controller 28 has a tracking function, a prediction function, and a control function described below.

Tracking function: That is, the tracking function means a function of performing “tail tracking of the leading bar” and “tracking of the leading edge of the following bar”. Prediction function: That is, the prediction function is F1 at the tail end of the preceding bar.
"Previous bar tail end transport prediction chart" that predicts the distance to and transport time and displays each on the horizontal axis (X axis) and vertical axis (Y axis)
This shows the function of producing. In the present embodiment, the origin of the X axis is set to F1
RL corresponding to the distance (Xr1) between F1 and RL
Suppose that exists. The Y-axis origin is associated with the current time.

Control function: That is, the control function is a function of correcting the rolling speed command value of the preceding bar, RL rolling of the following bar, and operating the speed command value of the transfer table. The control function has a function of creating a trailing bar leading edge conveyance prediction chart, which will be described later, and performing follow-up bar follow-up control based on the information.

A hot strip mill process computer 29, an F1 pressure reduction control device 30, an RL pressure reduction control device 31, and a tracking sensor group 32 are electrically connected to the rolling joining controller 28.

As described above, the complete continuous hot rolling apparatus according to the above embodiment has a heating furnace 1 for heating a plate-shaped leading bar and a following bar, and the heating furnace 1 disposed downstream of the heating furnace 1 and A rough rolling mill group 1 having a rough final rolling mill 21 for reducing the thickness of the bar, a crop shear 4 disposed downstream of the rough rolling mill group 1 and cutting the bar vertically in a longitudinal direction; 4, a finishing descaling device (FS) for removing iron oxide formed on the bar.
B) 5, a finishing rolling mill group 6 having a first finishing rolling mill 22 disposed downstream of the FSB 5, and electrical components to the rough final rolling mill 21, the first finishing rolling mill 22, and the like. The control system includes a controller 28 for rolling joining and measuring rolls 25 and 26 arranged on the upstream side of the first finishing mill, and the control system includes The tail end of the bar and the tip of the following bar are overlapped up and down with the overlap in the longitudinal direction as short as possible,
It is configured to have a function of entering a finishing mill and rolling and joining bars in a roll bite by rolling.

In this embodiment, the leading end of the following bar 12 is caused to follow the rear end of the preceding bar 11 being rolled by the finishing mill just before the first finishing mill 22, and the tail end of the clean preceding bar immediately after the FSB is removed. The surface of the bar is dried, and the front end of the clean following bar 12 immediately after the FSB is dried on the back surface and is placed on top of the bar, passed through the first finishing mill 22. That is,
Since the surfaces of both bars are active and the degree of mixing of the materials of both bars is large, it is possible to realize a good joint that does not break in subsequent rolling. In order to reliably realize the above-mentioned superposition between the final roll of FSB and F1, the final roll of FSB is picked up by about 10 mm, and a nitrogen gas purge is applied to the front and back surfaces of the material before F1. The overlapping length Lov is set to 50 mm in consideration of the positioning accuracy of the control system in the bar longitudinal direction.

Next, the operation of the rolling device will be described. 1. Tracking method: 1) “Tracking of tail end of preceding bar” is based on the tracking (bar tail end and F
(Calculation of the distance to 1). This can be performed, for example, by collecting the signal of the tachometer of the motor that drives the delay table as the actual speed and, for example, performing integral calculation every 0.1 seconds. Further, from the time when the tail end of the preceding bar has passed through the crop shear control bar front end rear end detection device, F1
The trailing end of the preceding bar is tracked using the distance signal of the immediately preceding major link roll 25. When the tail end reaches F1 in calculation, the main tracking ends.

2) “Tracking of the leading end of the following bar”
Tracking starts from the load relay signal when the following bar 12 loads on the RL 21. The material speed on the RL exit side can be grasped from the work roll diameter of the RL21, the tachometer, and the predicted advance rate. For example, by integrating and calculating every 0.1 seconds, the tracking of the leading end of the following bar (the distance between the leading end and F1) is performed. Calculation) is possible. After the leading end of the following bar has passed the bar leading edge detector 27 for crop shear control, tracking of the leading end is performed using a measuring roll for crop shear controlling. This tracking ends when the tip reaches F1 in calculation.

2. “Preceding bar tail end transport prediction chart”:
This chart is created and updated after the bar bites into F1 until the bar loads off F1. The future material speed on the F1 entry side of the preceding bar tail end can be predicted from the F1 roll speed of the current preceding bar, the predicted reverse speed, and the acceleration and deceleration rates determined in advance by the pass schedule. Therefore, the function Y = ftail (X), 0 ≦ X ≦ Xtail, which is the “tail end conveyance prediction chart”, is determined based on the tail end position (X tail) obtained from the “tail end tracking of the preceding bar”. This chart will be described later, for example, the "post-bar leading edge conveyance prediction chart" calculated every 0.1 second.

3. Assuming the above function, the transport speed control of the trailing bar 12 so that the leading end of the trailing bar follows the preceding material in a state of overlapping length L _ov mm at F1 will be considered below. First, the basic movement of the controller with respect to the following bar 12 after the preceding bar 11 has entered F1 will be described with respect to a position combination (case) of each bar. Here, RL2
It is noted that between 1 and F1, the bar speed at the time of cutting the crop shear at the tip of the bar is the slowest due to equipment restrictions. In the following cases 1, 2 and 3, it is assumed that the following bar 12 is in a state of being engaged with the RL 21 or in a state where the rolling at the RL 21 has been completed. The main speed of the following bar 12 in the state of biting into the RL 21 is the RL speed, and the table before and after the following bar 12 rides is synchronized with the RL in consideration of the advanced rate and the reverse rate of the material. Therefore, RL is linked. On the other hand, the succeeding bar 12 that has completed rolling at the RL 21 is set to be linked to the table by setting the speed master for the table group on which the following bar 12 rides.

Case 1. Crop shear 4 at tail end of preceding bar
If it is further upstream, it is a “supplying bar leading end conveyance prediction chart” up to the crop shear 4 at the leading end of the succeeding bar, assuming that the following bar 12 is rolled or conveyed at the maximum possible speed as a first approximation. Y = ftop (X) and Xcrop ≦ X ≦ Xtop are created in consideration of deceleration before crop shearing. Where X
crop is the distance between F1 and crop shear 4, Xtop
Is the distance of the leading end of the following bar from F1.

This Y = ftop (X) and Y = ftail (X)
The current master speed of the succeeding bar is determined so that the time between bars becomes Tsup seconds between Xcrop ≦ X ≦ Xtop (FIG. 4). That is, the master speed of the following bar 12 is tried numerically, and Y = ftop
(X) is created, and the current master speed that satisfies the above-mentioned bar-to-bar time condition is obtained by an iterative method. This iterative method may be a linear search method or a secant method referred to in the numerical analysis method. Then, the master speed of the succeeding bar determined in this way is set in the equipment.

Case 2. Crop shear 4 at the tip of the following bar
, Y = fta in the “tail end conveyance prediction chart”
At the time il (0), the leading end of the following bar advances a distance of (Xtop + Lov), that is, (Xtop + Lov) / ftail
The speed (0) is set as the speed master of the following bar 12.
However, in this case, when the preceding bar 11 and the following bar 12 collide upstream of the last roller in the FSB table, the speed of the following bar 12 is saturated so that the preceding bar 11 and the following bar 12 collide immediately above the same roller. .

Case 3. When the leading end of the following bar is in the deceleration control area for cutting the leading end before crop shearing, the table speed on which the following bar 12 rides is controlled according to the deceleration control sequence.

For states other than the above three cases,
It is assumed that the speed control state at the previous time is held. Actually, there is another function of separating the interlocking range between the preceding bar 11 and the following bar 12, but the details are omitted because they are not essential.
Thus, the tracking function for the leading and trailing ends of the bar, the transport prediction function, and the leading bar 11 of the trailing bar 12
The basics of the superimposition control function to follow up on are explained.

The F1 load relay signal during rolling joining is collected by increasing the differential weight of the F1 load signal. Also, in actual operation, the tip of the following bar is reduced in thickness by about 10% in order to realize reliable biting of the overlapped portion in F1. This is realized by setting the value to about 0.5 second smaller than that at the time of the preset calculation. Further, immediately before the overlapping portion bites into F1, the F1 roll gap command value is increased by about 10% of the rolling reduction over one second to prevent overloading of F1, but more precisely, the overlapping portion of the overlapping portion is prevented. It is desirable that schedule calculation be performed to satisfy the material bite angle, load, and torque constraints in F1, and the roll gap be increased within a range that satisfies each constraint.

Also, when the trailing bar 12 is too far from the preceding bar 11 and it is difficult to follow up, it has a function of realizing the catching-up by lowering the master speed of the finishing rolling mill. Further, in the present example, the temperature of the rear end is increased by using a bar heater on the delay table to ensure the bonding.

(Embodiment 2) In the embodiment 1, the rolling joining is realized by F1, but it is also possible to realize the rolling joining by a second finishing mill (hereinafter, referred to as F2). In the second embodiment, in accordance with the first embodiment, control is performed on the following bar speed so that the leading end of the following bar reaches F1 immediately after the tail end of the preceding bar passes F1, and the following bar is moved to F1. After biting, F1 is accelerated, F2 achieves the same overlap as in the previous example, and is bitten into F2 to realize rolling joining. In this case, by dynamically moving the looper height between F1 and F2, it is possible to realize that the succeeding material rides on top of the preceding material.

(Embodiment 3) In recent years, a hot strip mill has been installed which realizes energy saving and finishing high pressure reduction by installing a sheet bar coiler (also called a coil box) on a delay table. The third embodiment aims at a synergistic effect in combination with the sheet bar coiler. That is, in the third embodiment, the leading end of the bar sent out from the sheet bar coiler is added to the tail end of the bar sent out from the sheet bar coiler in front of F1 and roll-joined at F1. According to the third embodiment, the same effect as that of the first embodiment can be realized.

[0049]

As described above in detail, according to the completely continuous hot rolling method of the present invention, the length of the longitudinally overlapping portion of the preceding bar and the following bar is less than 1/2 of the bar width. Accordingly, the joining strength per unit area of the joining surface can be remarkably improved without requiring a special welding device as in the related art, and reliable joining can be realized.

Further, according to the completely continuous hot rolling apparatus of the present invention, the heating furnace, the rough rolling mill group, the crop shear, the finishing descaling apparatus, the finishing rolling mill, and the control for electrically connecting these components. The control system has a controller for rolling joining and a measuring roll arranged on the upstream side of the finishing mill, and the control system has a tail end of a preceding bar and a tip of a following bar. The existing hot strip mill has a function to overlap the bar up and down by shortening the overlap margin in the longitudinal direction as much as possible, enter the finishing mill, and roll-join the bars in the roll bite by rolling. Therefore, stable bar joining can be easily and simply realized mainly with only the control system without making a large capital investment.

[Brief description of the drawings]

FIG. 1 is a hot strip layout diagram.

FIG. 2 is a diagram showing a superimposition state of a preceding bar and a following bar.

FIG. 3 is a diagram showing a rolled state in a case where an overlapping portion of a leading bar and a following bar is long.

FIG. 4 is a diagram showing a rolled state in a case where an overlapping portion of a leading bar and a trailing bar is short.

FIG. 5 is a characteristic diagram showing the relationship between the length of the overlapping portion of the leading and trailing bars and the bonding strength ratio.

FIG. 6 is an explanatory diagram of a control system which is one configuration of the complete continuous hot rolling apparatus according to the present invention.

FIG. 7 is a characteristic diagram showing how to use a “leading bar rear end conveyance prediction chart” and a “backing bar front end conveyance prediction chart”.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Heating furnace, 2 ... Rough rolling mill group, 3 ... Delay table, 4 ... Crop shear, 5 ... Finishing descaling apparatus (FSB), 6 ... Continuous finishing rolling mill group, 7 ... Run-out table, 8 ... Coiler group, 11: Leading bar, 12: Trailing bar, 14: Lower working roll, 15: Upper working roll, 21: Rough final rolling mill (RL), 22: First finishing rolling mill (F1), 23: Rolling mill drive Motor and control device, 24: table driving motor and control device, 25, 26: measuring roll, 27: detector, 28: rolling joining controller.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuhiro Soya 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Inside the Kokan Co., Ltd. (72) Inventor Tsuneo Ikeda 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Sun (72) Inventor Hiroshi Sekine 1-1-2 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) 4E002 AD04 BC07 BD05 BD08 BD10 CB08

Claims (3)

[Claims] 1. A completely continuous hot working method in which the tail end of a preceding bar, which is a material being rolled between a rough rolling and a finish rolling, and the tip of a following bar are overlapped in the longitudinal direction and joined by a rolling mill. A completely continuous hot rolling method, wherein a length of an overlapping portion in a longitudinal direction of both bars is less than 1/2 of a bar width. 2. The continuous continuation according to claim 1, wherein the length of the overlapping portion of the preceding bar and the following bar in the longitudinal direction is set to a length corresponding to the contact arc of the roll bite when the rolling bar is engaged. Hot rolling method. 3. A heating furnace for heating a plate-like leading bar and a following bar, a rough rolling mill group arranged downstream of the heating furnace to reduce the thickness of the bar, and a downstream of the rough rolling mill group. A crop shear that is disposed on the side and cuts the bar vertically in the longitudinal direction; a finishing descaling device that is disposed downstream of the crop shear and removes iron oxide formed on the bar; A finishing rolling mill arranged downstream, and a control system electrically connected to each of the constituent members, wherein the control system is a controller for rolling joining and a measuring arranged upstream of the finishing rolling mill. With a roll,
The control system overlaps the tail end of the preceding bar and the tip of the following bar with the length of overlap in the longitudinal direction shortened to the length corresponding to the contact arc of the roll bite when biting into the rolling mill, and superimposes them vertically. A completely continuous hot rolling apparatus having a function of rolling and joining bars in a roll bite by rolling by entering the rolling bar.