JP6627812B2 - Hot rolling method and hot rolling device - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot rolling method and a hot rolling device capable of effectively preventing a threading defect in the entire hot rolling line by preventing a threading defect in a rough rolling mill.

  In the hot rolling line, a plurality of mills (rolling mills) are arranged in series, and slabs are continuously passed through the mills to perform tandem rolling in which rolling is performed. In tandem rolling, a finishing mill (finish rolling mill) that is arranged at the subsequent stage to create the final shape of the steel sheet, and a rough mill (roughing) that is arranged at the front stage to create the rough shape of the steel sheet Rolling mill).

  In the middle of the tandem rolling, threading defects such as wedges (asymmetrical thickness in the width direction), cambers (lateral bending), and meandering (lateral deviation and / or rotation of the steel sheet) may occur during the tandem rolling. It is known that these threading defects are particularly problematic in finishing mills. When the sheet passing defect is remarkable, the guide member or the like near the finishing mill may come into contact with the steel sheet, and the sheet passing may be stopped.

  BACKGROUND ART Conventionally, the following Patent Documents 1 to 3 are known as techniques for preventing a threading defect in a finishing mill. Patent Literature 1 relates to a hot tandem rolling mill (finishing rolling mill), and determines a load difference in a rolling mill of an i-stand between a time when a steel sheet passes through an (i-1) stand and a time when the steel sheet passes through an i-stand. A method is disclosed in which the rolling leveling control of a rolling mill is canceled out. Patent Literature 2 discloses a method in which a meandering amount at an outlet side of an arbitrary rolling mill is detected during rolling of a material to be rolled, and leveling control of the rolling mill is performed based on the meandering amount. Patent Literature 3 discloses a rolling method in which the meandering amount of a steel plate is detected by a meandering meter provided on the entry side of a rolling mill, and feedforward meandering control is performed based on the meandering amount.

JP 09-262615 A JP-A-10-265335 JP 2004-306125 A

  As in Patent Document 1, when performing leveling control so as to cancel the differential load generated in a tandem-type finishing rolling mill, a post-rolling defect such as a wedge that has already occurred in a previous rough rolling mill is performed ex post. Will be treated. Therefore, it is not possible to completely eliminate the faulty threading at the time of rolling in the finishing mill. Further, when the level difference control generated in the finishing rolling mill and the actual behavior of the plate are different from each other, if the leveling control is automatically performed as in Patent Literature 1, a plate passing trouble may be caused.

  As in Patent Documents 2 and 3, when performing leveling control of a finishing rolling mill based on a measured value of the meandering amount between stands, it is necessary to perform leveling control in a state in which a shape defect has already occurred in a previous rough rolling mill. Become. Therefore, by performing the leveling control, a shape defect is further amplified, and there is a possibility that a trouble in passing a plate such as a guide coming off may occur.

  As disclosed in Patent Literatures 1 to 3 above, by performing leveling control in a finishing rolling mill, it is not possible to eliminate a shape defect already occurring in a rough rolling mill, and to solve the problem of threading trouble. There is a problem that it is difficult to completely solve.

  The present invention has been conceived in view of the above-described problems, and reliably minimizes threading troubles in the entire hot rolling, particularly in the finish rolling mill by minimizing threading defects in a rough rolling mill. An object of the present invention is to provide a hot rolling method and a hot rolling apparatus that can prevent the hot rolling.

The means of the present invention are as follows.
[1] In a hot rolling method in which a slab is passed through a rough rolling mill and a finishing rolling mill in order to perform rolling, before opening of a material to be rolled, an opening difference between both ends of a work roll of the rough rolling mill in advance. Perform leveling control to adjust the work, compared with the actual opening difference of both ends of the work roll in the ideal state in the past in which the steel plate was passed straight in the past, the work when passing the scheduled rolling material It is performed by obtaining an appropriate opening difference between both ends of the roll, and the appropriate opening difference is a predicted rolling load at the time of threading of the material to be rolled, an actual rolling load at the ideal state, and a parallelism at the time of threading of the material to be rolled. A hot rolling method determined using the rigidity, the parallel rigidity in the ideal state, and the off-center amount of the material to be rolled.
[2] The parallel stiffness is determined based on the mill constant of a rough rolling mill, and the mill constant is determined in advance by measuring the external shape of two calibration slabs of the same steel type, and then the calibration slabs are removed one by one. The hot-rolling method according to [1], wherein the hot-rolling method is performed based on the amount of change in the external shape before and after rolling of two calibration slabs after passing through a rough rolling mill and a rolling load measured at the time of passing.
[3] A movable guide member that can be displaced outward in the width direction of the slab when a load is applied is provided on both ends in the width direction of the slab on the entry side of the rough rolling mill, and the slab is provided with the movable guide member. The hot rolling according to [1] or [2], wherein when the movable guide member is displaced to a predetermined threshold or more by pressing, it is determined that a threading failure has occurred and the leveling control is performed again. Method.
[4] The hot rolling method according to [3], wherein the threshold is 50 mm.
[5] A hot rolling apparatus including a rough rolling mill, a finishing rolling mill, and a computing device that performs leveling control for adjusting an opening difference between both ends of a work roll of the finishing rolling mill, wherein the computing device is In comparison with the actual opening difference between both ends of the work roll in the ideal state where the steel sheet was passed straight in the past before passing the rolling material, the predicted rolling load at the time of passing the rolling material, the ideal state Using the actual rolling load, the parallel rigidity of the material to be rolled at the time of passing, the parallel rigidity in the ideal state, and the off-center amount of the material to be rolled, the properness of both ends of the work roll when passing the material to be rolled A hot rolling device that determines the difference in opening.
[6] The arithmetic unit determines the parallel stiffness based on the mill constant of the rough rolling mill, preliminarily measures the external shape of two calibration slabs of the same steel type, and then removes the calibration slabs one by one from the rough slab. The hot rolling apparatus according to [5], wherein the mill is passed through a rolling mill, and the mill constant is obtained based on a change in appearance of the two calibration slabs before and after rolling and a rolling load measured during the passing. .
[7] A movable guide member that is displaced outward in the width direction of the slab when a load is applied is provided on both ends in the width direction of the slab on the entry side of the rough rolling mill, and the slab is provided with the movable guide member. The operation device according to [5] or [6], wherein when the movable guide member is displaced to a predetermined threshold value or more by the pressing, it is determined that a threading failure has occurred, and the arithmetic device performs the leveling control again. Hot rolling equipment.
[8] The hot rolling apparatus according to [7], wherein the threshold is 50 mm.

  In the present invention, by calculating the appropriate leveling amount of the rough rolling mill before the passing, the passing failure in the rough rolling stage is minimized, thereby reliably preventing the passing trouble in the entire hot rolling line. can do.

FIG. 1 is a schematic diagram of a hot rolling line to which the present invention is applied. FIG. 2 shows a model diagram when two milling slabs are passed through to obtain a mill constant. FIG. 3 is a schematic diagram illustrating a mode in which the movable guide member is displaced. FIG. 4 is a flowchart of a calculation process performed when determining occurrence of a sheet passing failure. FIG. 5 is a graph showing the relationship between the length of the slab in the longitudinal direction and the amount of displacement of the movable guide member when various slabs are passed through a rough rolling mill.

  First, a hot rolling line to which the present invention can be applied will be described with reference to FIG.

  In a hot rolling line, a plurality of rolling mills are provided from the entry side to the exit side of the line. The finishing mill 1 is arranged on the downstream side of the line, and the rough rolling mill 2 is arranged on the upstream side of the line. The steel sheet is rolled by passing the slab 3 through the rough rolling mill 2 and the finishing rolling mill 1 in order. The finish rolling mill 1 has a function of precisely forming the shape of the steel sheet and rolling the steel sheet until it reaches the final thickness, and the rough rolling mill 2 has a function of roughly forming the shape of the steel sheet. The rough rolling mill 2 and the finishing rolling mill 1 may be arranged in plurals.

  In the rolling process, various threading defects may occur. Specific examples include wedges, cambers, meanders, and the like of steel plates (or slabs). A wedge of a steel sheet refers to a deformation in which the thickness of the steel sheet becomes uneven in the width direction. The steel plate camber refers to a deformation in which the steel plate is bent in the width direction. The meandering of the steel plate means that the center position of the steel plate is shifted from the center position of the threading line (off center) due to rotation or parallel displacement of the steel plate.

  In the present invention, before starting the slab rolling (before the passing of the material to be rolled), by performing leveling control in the rough rolling mill in advance, it is possible to effectively prevent the occurrence of the passing trouble in the entire hot rolling line. it can. Specifically, the opening difference (gap amount) between one end (op side) and the other end (dr side) in the longitudinal direction of the work roll of the rough rolling mill is adjusted. When performing leveling control, it is desirable to first find a mill constant (also referred to as mill rigidity) specific to the rough rolling mill.

  The mill stiffness is preferably measured by passing two calibration slabs of the same steel type through a rough rolling mill before passing the slab to be actually rolled. Before passing the slab for calibration, parameters of the appearance shape of the slab for calibration, for example, a thickness and a width of the slab, are measured in advance. Next, the calibration slab is rolled by a rough rolling mill, and the rolling load during rolling is measured. Finally, the parameters of the appearance shape of the calibration slab after rolling are measured in the same manner. As described above, according to the present invention, it is possible to calculate the mill rigidity specific to the rolling mill based on the amount of change in the parameter indicating the appearance before and after the rolling and the rolling load measured during the threading. The mill stiffness refers to a stiffness in consideration of a roll spring constant, a housing mill constant, and the like measured in a rolling mill.

Specifically, description will be made with reference to the schematic diagram of FIG. As shown in the upper part of FIG. 2, before passing the first calibration slab, the (incoming side) plate thickness H ₁ ^{IN of} the calibration slab and the plate width W ₁ of the calibration slab are measured. At the time of threading, the rolling load (P ₁ ) in the rough rolling mill is measured. After the passing of the plate, the (outside) plate thickness H ₁ ^OUT of the slab is measured. As shown in the lower part of FIG. 2, H ₂ ^IN , W ₂ , rolling load (P ₂ ), and H ₂ ^OUT are measured similarly when a second calibration slab is passed.

  In the present invention, the difference between the rolling load at the time of passing the second calibration slab and the rolling load at the time of passing the first calibration slab, and the exit side plate thickness of the second calibration slab It is preferable to calculate the mill stiffness based on the difference between the thickness of the first calibration slab and the exit side plate thickness. As described above, by using the respective differences, it is possible to cancel the mechanical error inherent in the rolling mill and accurately calculate the mill rigidity.

  Specifically, the mill stiffness can be calculated using the following equation (1).

However, the meaning of each symbol is as follows.
Kh: Mill rigidity (mill constant) [tonf / mm]
H ₁ ^OUT : Thickness [mm] of the first calibration slab after rolling
H ₂ ^OUT : Thickness [mm] of the second calibration slab after rolling
W ₁ : Sheet width [mm] of the first calibration slab before rolling
W ₂ : Width [mm] of the second calibration slab before rolling
P ₁ : Rolling load [tonf] when rolling the first calibration slab
P ₂ : Rolling load [tonf] when rolling the second calibration slab
K _Roll-Strip : Housing mill constant [tonf / mm ² ]
δ: gap setting difference between rolls [mm]

  After the measurement of the mill stiffness is completed by the above-described method, leveling control of the rough mill is performed using the mill stiffness, and then a slab to be actually rolled is passed. Hereinafter, the leveling control of the finishing mill will be described in detail.

  First, the parallel stiffness of a rolling mill can be calculated using the mill stiffness. The method for calculating the parallel rigidity is not particularly limited, and a conventionally known method can be used. For example, the parallel rigidity can be calculated using the following equation (2) for a 2Hi type rolling mill and using the following equation (3) for a 4Hi type rolling mill.

However, the meaning of each symbol is as follows.
Kl _i: parallel rigidity of the roughing mill [tonf / mm]
Kh _i: Mill stiffness (mill modulus) of the roughing mill [tonf / mm]
_Wi: Board width [mm]
W _i ^CHOCK: chock between the distance [mm]
W _i ^RollB: backup roll barrel width [mm]
K _i ^Roll-Strip: roll flat unit width spring constant [tonf / mm ^2]
K _i ^RollB-RollW: inter-roll unit width spring constant [tonf / mm ^2]

  In the leveling control of the rough rolling mill, before passing the steel sheet (rolling material) to be rolled from now on, the work rolls on both ends of the work roll should be fixed so that a passing failure such as a camber does not occur on the exit side of the rough rolling mill. Adjust the opening difference (gap amount). Specifically, the rolling conditions in the ideal state where the slab is passed straight without camber during the past operation are recorded. More specifically, it is desirable to record the gap amount, rolling load, parallel rigidity, and the like in an ideal state. When performing the leveling control, an appropriate difference in the opening degree between both ends of the work roll that allows the material to be rolled to pass in a straight line is obtained by comparing the actual opening degree difference between both ends of the work roll in an ideal state. It is desirable that the steel type of the slab at the time of scheduled rolling and the ideal state be the same.

  More specifically, the predicted rolling load at the time of passing (planned rolling) of the material to be rolled, the actual rolling load in the ideal state, the parallel stiffness at the scheduled rolling, the parallel stiffness at the ideal state, and the off-center amount of the material to be rolled By using, the appropriate opening degree difference can be calculated. More specifically, the following expression 4 can be used to determine the appropriate opening difference between the ends of the work roll when rolling the material to be rolled, based on the actual opening difference between the ends of the work roll in an ideal state. Before passing the material to be rolled, the gap amount between the work rolls of the rough rolling mill is adjusted so as to have an appropriate opening difference in advance.

However, the meaning of each symbol is as follows.
ΔS _i : appropriate opening difference [mm]
Kl _i: parallel rigidity at the time of scheduled rolling [tonf / mm]
Kl _i ^*: parallel rigidity of the ideal state [tonf / mm]
M _i ^OP : Mill constant on OP side [tonf / mm]
M _i ^DR : Mill constant on DR side [tonf / mm]
W _i ^CHOCK: chock between the distance [mm]
y i ^_c: off-center amount of time scheduled rolling [mm]
P _i : Predicted rolling load at scheduled rolling [tonf]
P i ^_*: actual rolling load of the ideal state [tonf]
ΔS _i ^* : Actual opening difference in ideal state [mm]
The off-center amount refers to a shift amount in the axial direction of the work roll (the width direction of the steel sheet) between the center in the axial direction of the work roll of the rolling mill and the center in the width direction of the steel sheet at the time of passing.

  After performing the leveling control by the above method, the slab to be rolled is passed through, and hot rolling is performed. Even during hot rolling, the steel sheet may have poor sheet passing such as camber and meandering. When such a passing failure occurs, the steel plate may come into contact with guide members provided at both ends in the width direction on the delivery side of the rolling mill, and the passing of the rolling plate may have to be temporarily stopped. It may cause damage. Therefore, it is required to detect and eliminate a threading defect in a rolling mill at an early stage. In the following, a method of detecting a threading failure in a rolling mill after starting hot rolling will be described.

  A specific example of the slab passing failure will be described with reference to FIG. 3 which is a top view. Reference numeral 31 in the figure denotes a rough rolling mill, and a slab 32 is passed from the right side (inlet side) to the left side (outside side) in the figure. When the slab 32 is bitten by the rough rolling mill 31, various slab passing defects may occur in the slab 32. In the example of FIG. 3, the slab 32 meanders from (1) to (2) due to skew between the upper and lower rolls in the rough rolling mill 31. If the meandering of the slab 32 is remarkable, as shown in (3) of FIG. 3, the leading end of the slab 32 sent to the exit side of the rough rolling mill 31 is located at both ends in the width direction on the exit side of the rough rolling mill 31. It may come into contact with the guide member 33 provided in the section, and troubles such as breakage of equipment may occur. In addition, even when camber of the slab 32 occurs, a problem may occur that the tip of the slab 32 contacts the guide member 33 as in (3) of FIG.

  In the present invention, the movable guide member 34 is attached to the entry side of the rough rolling mill 31. The movable guide members 34 are provided at both ends in the width direction of the slab 32. When a load is applied to the movable guide member 34 from the inside in the width direction, the movable guide members 34 at both ends are displaced so as to expand toward the outside in the width direction. For example, when the slab 32 meanders or cambers as shown in FIG. 3C, the tail end of the slab 32 presses the movable guide member 34 from the inside. Thereby, the movable guide members 34 on both sides are respectively displaced outward in the width direction. In this case, the displacement amount of one movable guide member 34 and the displacement amount of the other movable guide member 34 may be substantially the same.

  When the meandering of the slab 32 is remarkable, the load at which the tail end of the slab 32 presses the movable guide member 34 also increases, and the displacement X of the movable guide member 34 also increases. In the present invention, when the movable guide member 34 is displaced above a predetermined threshold value (when the displacement amount X is equal to or more than the threshold value), it is determined that a slab passing failure has occurred, and a measure for eliminating the passing failure is provided. Take.

  More specifically, this will be described with reference to the flowchart of FIG. Rolling is started in the rough rolling mill, and after the slab comes into contact with the movable guide member on the entry side of the rough rolling mill, it is determined whether the displacement amount of the movable guide member is equal to or larger than a threshold value. If the amount of displacement of the movable guide member is equal to or greater than the threshold, it is determined that a rolling failure has occurred, and various measures are taken to eliminate the rolling failure. For example, an alarm (announcement) is issued to the driver's cab, and the operator who has received the alarm releases the rolling down of the mill and sets up the leveling amount and the like again.

  The threshold value of the displacement amount can be set to a value with a high possibility that when the movable guide member is further displaced, the leading end of the steel sheet comes into contact with the guide member on the rolling mill exit side. The value of the threshold can be appropriately determined according to the size of the slab to be passed, the type of steel, the rolling reduction of the mill, the distance between the guide members at both ends, the distance between the movable guide members, and the like. Note that, as the displacement amount of the movable guide member, the total value (2X) of the displacement amounts of the movable guide members on both sides can be adopted, or the displacement amount (X) of the movable guide member on only one of the sides can be adopted. You can also. Hereinafter, the displacement amount X of only one movable guide member will be described as the displacement amount of the movable guide member.

  An example of the above-described threshold value of the displacement amount is 50 mm. That is, when one of the movable guide members is spread by 50 mm or more, it is preferable to issue an alarm or the like, assuming that there is a high probability that a sheet passing failure will occur. As a specific experimental example, FIG. 5 shows the results of measuring the amount of displacement of the movable guide member on the rough rolling mill entry side when hot rolling slabs having various longitudinal lengths. In the group (A) in the figure, the displacement amount of the movable guide member was 50 mm or more, and contact between the slab and the guide member occurred on the exit side of the rolling mill. On the other hand, in the group (B) in the figure, the displacement amount of the movable guide member was small, and no contact between the slab and the guide member occurred on the exit side of the mill. From the results, it was confirmed that the threading abnormality can be reliably supplemented by setting the threshold value of the displacement amount to 50 mm. Depending on the rolling conditions of the rolled material and the like, setting the above-mentioned threshold value to more than 50 mm may make it possible to properly detect a threading failure.

  Although not shown, a measuring device for measuring the amount of displacement of the movable guide member, an arithmetic device for processing measurement data in the measuring device, and the like may be appropriately provided. For example, as shown in FIG. 1, a signal relating to the amount of displacement of the movable guide member 4 provided on the entry side of the rough rolling mill 2 is input to the arithmetic unit 5, and the rough rolling mill 2 and finish rolling are performed in accordance with the amount of displacement. It is also possible to adopt a configuration in which a control signal for controlling the rolling conditions is output from the arithmetic unit 5 to the mill 1.

  Finally, the operation of the present invention will be described.

  When restarting the hot rolling line after it has been temporarily stopped, such as immediately after periodic repair of the hot rolling line and immediately after the roll change of the rough rolling mill, check the threading condition and confirm that there are no problems. For example, leveling control of a rough rolling mill is performed. After performing the leveling control, the slab (rolling material) is actually passed through to start rolling.

  When performing leveling control, first, two calibration slabs of the same steel type are passed through a rough rolling mill. The mill stiffness is calculated using the outer shape of the calibration slab during rolling, the rolling load, and the like.

  Using the mill stiffness obtained above, an appropriate opening difference is calculated by comparing with the actual opening difference in an ideal state, and the gap amount between the OP side and the DR side of the work roll becomes the appropriate opening difference. Thus, the operating conditions of the rough rolling mill are adjusted. Then, rolling of the slab is actually started.

  During the rolling of the slab, there may be a case where the slab has poor sheet passing such as camber and meandering. Whether or not these threading defects are remarkable to a problem is evaluated by the displacement of a movable guide member provided on the entry side of the rough rolling mill. When the displacement amount becomes equal to or larger than a predetermined threshold value, it is determined that there is a high possibility that trouble such as equipment breakage will occur, and the rolling is temporarily stopped. Then, after the leveling control of the rough rolling mill is performed again by the same method as described above, the rolling is restarted.

  As described above, in the present invention, hot rolling is performed after performing optimal leveling control before the start of rolling. It is possible to prevent the problem of a thread passing through being amplified by a rolling mill. Furthermore, by using a movable guide member, even if a passing failure occurs in the rough rolling mill, the failure can be detected early and eliminated to prevent the occurrence of a passing trouble. can do.

DESCRIPTION OF SYMBOLS 1 Finish rolling mill 2, 31 Rough rolling mill 3, 32 Slab 5 Computing device 33 Guide member 4, 34 Movable guide member

Claims (6)

In a hot rolling method in which a slab is passed through a rough rolling mill and a finishing rolling mill in order to perform rolling,
Before the passing of the material to be rolled, perform leveling control to adjust the difference in opening between the work roll ends of the rough rolling machine in advance,
The leveling control is compared with the actual opening difference between both ends of the work roll in an ideal state where a steel sheet was passed straight in the past, and the appropriate opening difference between the two ends of the work roll when passing the rolled material. Done by asking,
The appropriate opening difference, the predicted rolling load at the time of passing the material to be rolled, the actual rolling load in the ideal state, the parallel rigidity at the time of passing the material to be rolled, the parallel rigidity at the ideal state, and the material to be rolled. Calculated using the off-center amount ,
The parallel rigidity is determined based on the mill constant of the rough rolling mill,
The mill constant is determined in advance by measuring the external shape of two calibration slabs of the same steel type, and then passing the calibration slabs one by one through the rough rolling mill. A hot rolling method obtained based on a difference between a rolling load at the time of passing the sheet and a difference between the exit side sheet thicknesses . On both ends in the width direction of the slab at the entry side of the rough rolling mill, a movable guide member that can be displaced outward in the width direction of the slab when a load is applied,
2. The leveling control according to claim 1 , wherein when the slab presses the movable guide member, when the movable guide member is displaced by a predetermined threshold or more, it is determined that a sheet passing failure has occurred and the leveling control is performed again. Hot rolling method. The hot rolling method according to claim 2 , wherein the threshold is 50 mm. Rough rolling mill, finishing rolling mill, and a computing device that performs leveling control to adjust the difference in opening between the work rolls of the rough rolling mill, and a hot rolling mill having
Before the passing of the material to be rolled, the arithmetic unit compares the actual opening difference between both ends of the work roll in an ideal state where the steel plate was passed straight in the past, and the predicted rolling load at the time of passing the material to be rolled. The actual rolling load in the ideal state, the parallel stiffness of the material to be rolled during passing, the parallel rigidity in the ideal state, and the off-center amount of the material to be rolled, and the work when passing the material to be rolled is used. Find the appropriate opening difference between both ends of the roll ,
The arithmetic unit determines the parallel stiffness based on the mill constant of the rough rolling mill, measures the appearance of two calibration slabs of the same steel type in advance, and then sends the calibration slabs one by one to the rough rolling mill. A hot rolling apparatus that passes the sheet and obtains the mill constant based on a difference between a rolling load at the time of passing the second sheet and a time at the time of passing the first sheet and a difference between the exit side sheet thicknesses . On both ends in the width direction of the slab on the entry side of the rough rolling mill, a movable guide member that is displaced outward in the width direction of the slab when a load is applied,
When the slab presses the movable guide member, when the movable guide member is displaced by a predetermined threshold or more, it is determined that a sheet passing failure has occurred, and the arithmetic device performs the leveling control again. hot rolling apparatus according to 4. The hot rolling apparatus according to claim 5 , wherein the threshold is 50 mm.