JP2018140400A - Rolling workpiece treatment method on hot-finished rolling abnormal time - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling workpiece treatment method which stabilizes rolling by preventing a fracture or a cornice of a rolling workpiece on hot-finished rolling abnormal time.SOLUTION: In a hot-finished rolling machine consisting of a plurality of stands, before rolling a rolling workpiece, after presetting a load allowable range in each stand and a target plate thickness on the last stand outlet side, when the load of a specific stand, during rolling the rolling workpiece in a specific stand except the last stand, exceeds the allowable range to come into an abnormal state to come into an abnormal state, a rolling draft of a specific stand is changed to return the load of the specific stand to an allowable range, and a mass flow (plate thickness×plate speed) is calculated from the plate thickness and the plate speed of the rolling workpiece on the specific stand outlet side after returning the load to an allowable range, thereby, regardless of the target plate thickness on the last stand outlet side, setting, in each stand from a specific stand to the last stand, a rolling draft within the load of each stand, and with a constant calculated mass flow (plate thickness×plate speed) to perform rolling, and to take the workpiece up in a coil form.SELECTED DRAWING: Figure 1

Description

  TECHNICAL FIELD The present invention relates to a method for treating a material to be rolled when hot rolling is performed by a hot finish rolling mill composed of a plurality of stands and the load of a specific stand exceeds an allowable range and becomes an abnormal state. When a sudden increase in load is detected, the plate thickness is automatically changed at the final stand after a specific rolling stand, preventing overload and breakage of the rolled material, and stably and efficiently. Relates to a method of processing.

  In the hot rolling process for producing a metal strip, a metal slab (hereinafter also referred to as a slab) is heated and then rolled with a roughing mill to produce a rough bar. Rolled to a target range of plate thickness by a finish rolling mill and wound as a metal strip. In each stand of the hot finish rolling mill, the rolling conditions are determined so that the sheet thickness, sheet width, etc. of the material to be rolled on the final stand exit side satisfy the target range. The rolling condition of each stand is called a draft schedule (or pass schedule), and greatly affects the quality and productivity of the metal strip. Therefore, it is required to determine an appropriate draft schedule according to the quality of the metal strip.

  The draft schedule of a hot finish rolling mill is usually rolled as much as the latter stage stand closer to the final stand in order to reduce the rough surface due to wear on the surface of the work roll during rolling and to keep the surface property of the metal strip by the transfer good. It is set to lighten the load. Therefore, in the normal draft schedule, the rolling reduction is made smaller as the latter stage stand.

  Moreover, in order to control the thickness of the metal strip, automatic thickness control (AGC) is applied. In this AGC, the absolute load AGC (Absolute Gage-AGC) that detects changes in rolling load and compensates for changes in the upper and lower deformations (mill stretch) of the rolling mill by the rolling position control, and the rolling stand output to be controlled There is a monitoring AGC (Monitoring-AGC) that measures the thickness with a thickness gauge installed on the side and returns it to the rolling stand to control the reduction position.

  However, when the thickness setting (setup) value before rolling differs from the thickness of the material to be rolled, and the error is large, unexpected cooling water splashes in the rolling mill, When the thickness of the material to be rolled becomes excessively thicker than the target value, such as when the temperature of the material to be rolled is abnormally lowered at the local part of the metal band due to the occurrence of a waiting time, etc. AGC excessively tightens the gap between the work rolls in an attempt to achieve the target thickness in the thickness control during hot finish rolling. As a result, when the deviation from the set roll position of the work roll exceeds the threshold value, the AGC function is automatically stopped, the plate thickness control does not work, and the roll position of the work roll is fixed. As a result, the exit side plate thickness of each stand does not become the target value, and it becomes impossible to control, the mass flow between each stand (plate thickness x plate speed) is disturbed, the over-tension acts between the stands, and the material to be rolled becomes Problems such as breakage, and the material to be rolled overlap between the stands and become bellows and become clogged.

  When the material to be rolled breaks between the stands or becomes bellows, the work roll and, depending on the case, the back-up roll may be taken out and broken to remove the material to be rolled and its broken pieces and return to the normal rolling state. It is necessary to remove the hot-rolled material having a bellows shape. Further, the roll may be wrinkled due to breakage or overlap of the material to be rolled, and the wrinkle is transferred to the surface of the next material to be rolled as it is and becomes defective, so it is necessary to replace it with a new roll. Many of these operations had to be performed manually, and it took a lot of time and was a factor that significantly hindered production.

  Therefore, the inventors of the present invention, when the load of the specific stand increases during hot rolling and the deviation from the set roll position of the work roll exceeds the threshold value and becomes an abnormal state, the rolling is performed at a high speed. In order to remove the material to be rolled without causing breakage and bellows, despite the increase in the load of the specific stand, the material to be rolled is stably rolled and processed in the same manner as a normal material to be rolled, Attempts were made to wind up and remove at the exit of the finishing mill.

  For this purpose, if the sticking to the target finish plate thickness on the exit side of the finish rolling mill is concerned, the AGC acts and the overload state cannot be avoided. Therefore, if the thickness target of each stand by AGC can be reset regardless of the target finish thickness and the disturbance of mass flow between each stand can be prevented, the material to be rolled is taken up and removed at the finishing mill exit side. I figured out that I could do it.

  As a means for keeping the mass flow constant, Patent Document 1 discloses a continuous rolling mill including a running plate thickness change control device, an automatic plate thickness control device, and a dynamic speed control device.

  Patent Document 2 discloses a technique for determining a change rate from a plate thickness change amount and a change time when changing the Nth stand target thickness during tandem finish rolling.

  However, the means disclosed in Patent Document 1 and Patent Document 2 are an apparatus and a method for rolling to a target plate thickness, and do not consider an abnormal state in which an unexpected load fluctuation has occurred. Since the thickness is the target plate thickness, when the load on the specific stand increases, AGC acts to accelerate an abnormal state of overload. In addition, since the thickness of each stand is not newly set, nothing is described about the thickness control for a specific stand that has caused a load fluctuation or a subsequent stand.

JP 2004-255421 A JP 2011-206780 A

  TECHNICAL FIELD The present invention relates to a method for treating a material to be rolled in a hot finish rolling consisting of a plurality of stands, when the load on a specific stand exceeds an allowable range, and the load suddenly increases at a specific rolling stand while rolling the material to be rolled. When an abnormal state of rolling is detected, the thickness is automatically changed regardless of the target finishing plate thickness at the final stand after the specific rolling stand, and the mass flow at each stand is kept constant. Thus, it is an object of the present invention to prevent rolling of the rolled material and bellows due to overloading, to perform stable rolling and to perform a winding process.

In order to solve the above problems, the present invention has the following configuration.
[1]
In rolling the material to be rolled by a hot finish rolling mill consisting of multiple stands,
Before rolling the material to be rolled, after setting in advance the allowable range of load in each stand of the rolling mill and the target plate thickness on the final stand exit side,
While rolling the material to be rolled,
In a specific stand excluding the final stand, when the load of the specific stand exceeds the allowable range and becomes abnormal,
The amount of rolling of the specific stand is changed to return the load of the specific stand to an allowable range, and the mass flow (plate thickness) from the thickness and the plate speed of the rolled material on the exit side of the specific stand after the load is returned to the allowable range. X plate speed)
Regardless of the target plate thickness on the final stand exit side, the reduction amount within the allowable range of the load of each stand and the calculated mass flow is constant in each stand from the specific stand to the final stand. A method for treating a material to be rolled when an abnormal hot finish rolling is performed, wherein the material is rolled by setting and rolling.
[2]
When the load of the specific stand exceeds the allowable range and becomes abnormal, the difference between the load and the allowable load is obtained, the difference of the reduction amount is calculated from the difference of the load, The method for treating a material to be rolled at the time of abnormal hot finish rolling according to the above [1], wherein the reduction amount of the specific stand is corrected by the difference to make the load within an allowable range.
[3]
When the load of the specific stand exceeds the allowable range and becomes an abnormal state, the reduction rate from the specific stand to the final stand is made to coincide with the value of the reduction rate after the reduction amount change in the specific stand. The method for treating a material to be rolled at the time of abnormal hot finish rolling according to [1] or [2].
[4]
When the load of the specific stand exceeds the allowable range and becomes an abnormal state, the thickness change position of the material to be rolled by the change of the reduction amount reaches each rolling stand from the specific stand to the final stand. The rolled material treatment method at the time of abnormal hot finish rolling according to any one of the above [1] to [3], wherein the amount of reduction of the rolling stand is sequentially changed at the time of completion.

  The present invention automatically detects an abnormal load increase at a specific stand in hot finish rolling, and the target plate of each stand after the specific stand regardless of the initially set target plate thickness on the exit side of the finishing mill. Since the thickness was reset and the mass flow was constant and stable rolling was possible, even when the plate thickness setup error is large or when the rolling position deviation due to the increase in deformation resistance due to local temperature reduction of the material to be rolled is large, By preventing breakage and bellows of the material to be rolled, the material to be rolled can be processed with high efficiency without impairing productivity.

FIG. 1 is a diagram showing a hot finish rolling mill as an example of the present invention and rolling means in an abnormal state. FIG. 2 is a diagram showing a flow of the method for processing a material to be rolled at the time of abnormality of the present invention.

  In order to solve the above problems, the present invention is a hot finish rolling mill composed of a plurality of stands. During rolling of a single material to be rolled, in a specific stand excluding the final stand, a load deviation or a workpiece from a target value is achieved. When the roll roll position deviation exceeds a certain amount, the final stand outlet thickness is reset regardless of the target outlet thickness, and the target thickness values for each stand outlet are changed from the specified stand to the final stand. Then, the operation of the hot finish rolling mill is controlled so that the mass flow (sheet thickness × sheet speed) is constant.

  Here, in the present invention, although not particularly limited, the plurality of stands are six stands or seven stands.

  FIG. 1 is a diagram showing a hot finish rolling mill as an example of the present invention and rolling means in an abnormal state.

  In the example of FIG. 1, the hot finish rolling mill has a series of rolling stands from the first stand to the seventh stand so that one rolled material can be tandem-rolled by a series of a plurality of rolling stands. It is configured. These seven rolling stands have a pair of work rolls 1, a pair of backup rolls 2, a load detector 3, and a plate thickness meter 4 on the exit side of the rolling stand, if necessary, for each stand, A reduction position control device, an automatic plate thickness control device, and a speed control device are provided.

  The reduction position control device is, for example, a device that sets and controls a reduction position that is a gap between a pair of work rolls 1 by hydraulic reduction, and is a reduction applied from an automatic plate thickness control device (for example, absolute value AGC, monitor AGC). It operates so as to match the rolling position of each rolling stand with respect to the command value of the position, thereby adjusting the gap between the pair of work rolls 1 and controlling the thickness of the material to be rolled.

  Normally, a draft schedule such as a thickness target at each rolling stand for each material to be rolled is set before finishing rolling of the material to be rolled is started.

  FIG. 2 shows a flow of the method for treating a material to be rolled at the time of abnormality of the present invention.

  As shown in FIG. 2, in rolling a material to be rolled by a hot finish rolling mill composed of a plurality of stands, before rolling the material to be rolled, the allowable range (upper limit) of the load in each stand and the final stand outlet side A target plate thickness is set. Subsequently, the rolling of the material to be rolled is started, and the material to be rolled is rolled while being automatically controlled so as to have a target plate thickness on the outlet side of each stand. Further, until the rolling of the material to be rolled is completed, the load of each rolling stand is measured at any time or every predetermined time, and it is determined whether or not it exceeds the preset allowable load range.

  During rolling of the material to be rolled, if the load of the specific stand exceeds the allowable range and becomes overloaded in the specific stand excluding the final stand, the reduction amount Δh of the specific stand is changed to allow the load of the specific stand Return to range.

  At that time, the outlet side plate thickness of the specific stand is a value deviating from the target plate thickness, and the final stand outlet side is also a value deviating from the target plate thickness. However, regardless of this, the mass flow (plate thickness x plate speed) is calculated from the plate thickness and plate speed of the material to be rolled on the specific stand exit side, and the value of the mass flow is kept constant until the final stand. Then, reset the reduction amount within the allowable range of the load on each stand.

  The rolling of the material to be rolled is continued with the reduced amount of each stand set again, wound as a metal band in a coil shape, and processed in a subsequent process.

  By taking the above flow, even if the load of a specific stand exceeds its allowable range and becomes overloaded, the mass flow collapses, abnormal tension acts between the stands, and the material to be rolled breaks or is rolled The material will not clog and become bellows.

  In addition, the material to be rolled or the bellows to be rolled get caught between the work rolls, and the surface of the work roll is wrinkled. Or serious problems such as work roll spalling (damage).

  However, according to the present invention, such a problem can be avoided. As a result, by stably rolling and winding up, not only can the material to be rolled be efficiently processed as a defective product, but the work roll is kept healthy without generating wrinkles on its surface, so that The material to be rolled can be rolled with high quality and stability.

  When the load of a specific stand exceeds the allowable range, the difference between the load exceeding the allowable range and the target load within the allowable range is obtained, and the plastic constant of the material to be rolled is calculated from the difference between the loads. It is preferable to convert it into a difference in the amount of reduction by using it, correct the amount of reduction in the specific stand using this difference in amount of reduction, and make the load on the specific stand within the allowable range.

  For example, if the load difference between the load Pfbk exceeding the allowable range and the target load Pset within the allowable range is ΔP and the plastic constant is K, the reduction amount Δhi is expressed by the following equations (1) and (1): Calculated from (2).

ΔP = Pfbk−Pset (1)
Δhi = −ΔP / K (2)
Using this Δhi, the amount of reduction of the specific stand may be corrected.

  In addition, when the load of the specific stand exceeds the allowable range, the reduction ratio after the reduction of the reduction amount from the specific stand to the final stand may be constant.

  In other words, as described above, in the present invention, the mass flow from the specific stand to the final stand is constant, but when setting the mass flow (plate thickness x plate speed), either the plate thickness or the plate speed is a uniform reference. If it can be given, it can be quickly controlled.

  At that time, by setting the reduction ratio of each stand to be constant, as shown below, the reduction amount after the specific stand can be easily set, and quick control becomes possible.

First, when the entrance side plate thickness in each stand after the specific stand is hi and the exit side plate thickness is hi + 1, the rolling reduction ratio ri + 1 of each stand is expressed as shown in Expression (3).
ri + 1 = 1-hi + 1 / hi (3)
Further, if the difference in the amount of reduction of each stand after the specific stand is Δhi, the inlet side plate thickness of the next stand following each stand is equal to the plate thickness on the outlet side of each stand, and is expressed as hi + Δhi.

  Further, if the difference in the amount of reduction of the next stand following each stand is Δhi + 1, the outlet side plate thickness of the next stand is represented as hi + 1 + Δhi + 1.

  Therefore, assuming that the reduction ratio of each stand after the specific stand is constant, the relationship of the following formula (4) is established.

1-hi + 1 / hi = 1- (hi + 1 + .DELTA.hi + 1) / (hi + .DELTA.hi) (4)
Therefore, if equation (4) is modified, Δhi + 1 is obtained by equation (5) below.

Δhi + 1 = (hi + 1 / hi) × Δhi (5)
That is, if the difference Δhi of the reduction amount of the specific stand is obtained by the above equation (2), the reduction amount of each stand after the specific stand is obtained by the above equation (5) by making the reduction rate of each stand constant. It is only necessary to obtain Δhi + 1 sequentially from the next stand following the specific stand.

  Furthermore, when the load of a specific stand exceeds the allowable range, when the plate thickness change position of the material to be rolled by changing the reduction amount reaches each rolling stand from the specific stand to the final stand, the rolling It is preferable to sequentially change the amount of reduction of the stand.

  That is, if the change position of the rolling amount at a specific stand in the material to be rolled changes, for example, the amount of rolling down of the corresponding stand before reaching the corresponding stand, a difference in the plate thickness of the material to be rolled will result in a gap between the stands. If the mass flow is disturbed and breaks, or if the amount of reduction of the corresponding stand is changed after a certain time has elapsed after reaching the corresponding stand, the load on the corresponding stand may increase and rolling may become impossible. Therefore, in order to perform stable rolling without causing these problems, when the change position of the reduction amount at the specific stand in the material to be rolled reaches each rolling stand from the specific stand to the final stand, the rolling stand It is preferable to sequentially change the amount of reduction.

  In addition, in order to prevent the shape of the material to be rolled from becoming defective due to the change of the plate thickness, the shape control function of the material to be rolled may be utilized, for example, the vendor compensation control utilizing the above-described reduction amount Δh. It is good to do.

  As an example of the present invention, a plurality of steel slabs having a thickness of 230 mm and a width of 1600 mm to 780 mm are heated and rolled into a rough bar having a thickness of 20 mm to 40 mm by a hot roughing mill, and then the hot bar is subjected to 7 hot finishes. When finishing a steel strip with a thickness of 1.8 mm to 4 mm in a rolling mill, the allowable range of the load in each stand of the hot finish rolling mill and the target plate thickness on the final stand exit side are set in advance, and the above rough bar is 200 This was rolled.

  At that time, as a method of the present invention, for a specific stand excluding the final stand for 100, when the load of the specific stand exceeds the allowable range, the difference between the load and the allowable range is obtained, Based on the difference in load, the difference in rolling amount is calculated using the plastic constant of the material to be rolled, the rolling amount of the specific stand is corrected by the difference in the rolling amount, and the load is returned to the allowable range. Regardless of the target plate thickness, the mass flow (plate thickness x plate speed) is calculated from the plate thickness and plate speed of the material to be rolled on the specific stand delivery side, and within the allowable load range for each stand from the specific stand to the final stand. And setting the amount of reduction to make the mass flow constant, and matching the value of the reduction rate of the specific stand from the next stand to the final stand of the specific stand, and When the plate thickness change position of the material to be rolled due to the change in the lower amount reaches each rolling stand from the specified stand to the final stand, the rolling amount of the rolling stand is sequentially changed and rolled, and the steel strip is wound. And processed in subsequent steps.

  As a conventional example, the remaining 100 steel slabs of the same size and the same steel type are heated and rough-rolled to form a rough bar of the same size as above, and then the rough bar is converted into the 7-stand hot finish rolling mill. When finishing and rolling to a steel strip of the same size as above, rolling was performed with the plate thickness on the final stand exit side being the target plate thickness only without using the method of the present invention.

  Meanwhile, in the intermediate stand excluding the first stand and the final stand of the hot finish rolling mill, a large amount of cooling water is scattered between the stands and the local part of the material to be rolled is rapidly cooled, and the load of the specific stand exceeds the allowable range. Things happened.

  In the conventional example, the material to be rolled broke between the stands, the broken material to be rolled was removed from the hot finish rolling mill, and the work roll and backup roll with wrinkles were replaced with rolls without wrinkles. Therefore, it took a lot of time, and during that time, production had to be stopped for a long time.

  On the other hand, when the method of the present invention is used, the material to be rolled does not break between the stands, can be rolled stably and can be wound up as a steel strip, and the steel strip is a defective product in a later process. Could be processed as Moreover, since no wrinkles were formed on the work roll and the backup roll, the subsequent material to be rolled could be stably rolled to the target plate thickness as it was.

1 Work roll 2 Backup roll 3 Load cell 4 Thickness gauge

Claims (4)

In rolling the material to be rolled by a hot finish rolling mill consisting of multiple stands,
Before rolling the material to be rolled, after setting in advance the allowable range of load in each stand of the rolling mill and the target plate thickness on the final stand exit side,
While rolling the material to be rolled,
In a specific stand excluding the final stand, when the load of the specific stand exceeds the allowable range and becomes abnormal,
While changing the amount of reduction of the specific stand to return the load of the specific stand to an allowable range,
Calculate the mass flow (plate thickness x plate speed) from the plate thickness and plate speed of the rolled material on the specified stand exit side after returning the load to the allowable range,
Regardless of the target plate thickness on the final stand exit side, the reduction amount within the allowable range of the load of each stand and the calculated mass flow is constant in each stand from the specific stand to the final stand. A method for treating a material to be rolled when an abnormal hot finish rolling is performed, wherein the material is rolled by setting and rolling.   When the load of the specific stand exceeds the allowable range and becomes abnormal, the difference between the load and the allowable load is obtained, the difference of the reduction amount is calculated from the difference of the load, 2. The method for treating a material to be rolled at the time of abnormal hot finish rolling according to claim 1, wherein the rolling amount of the specific stand is corrected by the difference to make the load within an allowable range.   When the load of the specific stand exceeds the allowable range and becomes an abnormal state, the reduction rate from the specific stand to the final stand is made to coincide with the value of the reduction rate after the reduction amount change in the specific stand. The method for treating a material to be rolled at the time of abnormal hot finish rolling according to claim 1 or 2.   When the load of the specific stand exceeds the allowable range and becomes an abnormal state, the thickness change position of the material to be rolled by the change of the reduction amount reaches each rolling stand from the specific stand to the final stand. The rolling material processing method at the time of abnormal hot finish rolling according to any one of claims 1 to 3, wherein the amount of rolling reduction of the rolling stand is sequentially changed at the time of completion.

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