JP7128127B2 - Straightening method of steel plate by roller leveler - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for straightening a steel plate using a roller leveler used for straightening the shape of a metal plate such as a steel plate or a metal strip.

In recent years, with the spread of automatic cutting and automatic welding of thick steel plates, demands for flatness of thick steel plates are increasing. On the other hand, the manufacturing process of thick steel plates incorporates technologies such as controlled rolling and accelerated cooling to improve material properties, and is prone to poor flatness and shape defects after cutting due to residual stress. Hot straightening by a roller leveler arranged downstream of a hot rolling mill or an accelerated cooling device is generally applied to such poor flatness and residual stress.

Rolls of the roller leveler, particularly leveling rolls that come into direct contact with the steel sheet, wear as the amount of straightening increases, so the roll opening of the roller leveler also changes over time. Specifically, as the wear of the rolls progresses, the actual roll opening becomes large, that is, the amount of roll reduction of the steel sheet becomes small, and it gradually becomes impossible to impart a sufficient amount of bending necessary for straightening, so insufficient straightening tends to occur. .

In order to solve the above problems, in the prior art, it is common to reduce the effects of uneven wear by providing a crowning mechanism that bends the leveling rolls in the axial direction (the trunk length direction of the leveling rolls) (Japanese Patent Application Laid-Open No. 2015). -123460).

JP 2015-123460 A

However, in plate mills, there are many facilities that have been in operation for a long time, and some of the old facilities are not equipped with a crowning mechanism, so it is not easy to apply the conventional technology.

The present invention has been made in view of such circumstances, and even in an old-type roller leveler that is not equipped with a roll crowning mechanism, it is possible to suppress insufficient straightening of the steel plate due to uneven wear of the leveling roll, and the straightening effect on the steel plate. To provide a method for straightening a steel plate by a roller leveler capable of improving

One aspect of the present invention, which has been made to solve the above problems, is a method for straightening a steel plate by a roller leveler having a plurality of leveling rolls arranged in a zigzag pattern along a pass line, wherein the axis of the leveling roll A step of adjusting the zero point of the leveling roll opening based on the non-worn portion of the direction end, and setting the reduction amount of the leveling roll based on the average wear amount of the leveling roll in the steel plate width of the steel plate to be passed. A steel plate straightening method using a roller leveler comprising the steps of:

In the steel plate straightening method using a roller leveler used to straighten the shape of a metal plate such as a steel plate or a metal strip, the steel plate straightening method using the roller leveler is provided with these steps, so that it can be used as an old model that does not have a roll crowning mechanism. Also in the roller leveler of (1), insufficient straightening of the steel plate due to uneven wear of the leveling rolls can be suppressed, and the straightening effect on the steel plate can be improved. According to the step of adjusting the zero point of the leveling roll opening, the zero point of the leveling roll opening is adjusted based on the non-worn portion of the axial end of the leveling roll. The zero point can be precisely adjusted. Furthermore, according to the step of setting the reduction amount of the leveling roll, even in an old-type roller leveler without a roll crowning mechanism, an appropriate reduction amount considering the degree of wear of the roll and the width of the steel plate to be corrected. It can be set to a set value, and the lack of straightening of a particularly narrow steel plate caused by uneven wear of the leveling rolls in the axial direction can be corrected to the same level as that of the leveling rolls before wear. As a result, in the steel plate straightening method using the roller leveler, even in the old type roller leveler without a roll crowning mechanism, it is necessary to set an appropriate reduction amount setting value considering the degree of wear of the roll and the width of the steel plate to be straightened. can be done.

It is preferable that the average amount of wear is estimated for each steel sheet width based on the accumulated sheet threading amount of the roller leveler. By estimating the average wear amount of the leveling rolls used in the reduction amount setting step of the steel sheet straightening method by the roller leveler for each steel sheet width based on the accumulated sheet passing amount of the roller leveler, the reduction amount can be easily set. and can be implemented accurately.

As the zero point adjustment step, a leveling roll when an upper leveling roll arranged above the pass line is pressed down on a steel plate placed on a lower leveling roll arranged below along the pass line. A step of obtaining the relationship between the opening degree and the load applied to the upper leveling roll, the relationship between the leveling roll opening degree and the load obtained in the obtaining step, and the leveling roll opening degree and the load obtained in advance from the steel plate. and calculating a zero-point adjustment amount of the leveling roll opening by comparing with the relationship. By performing the zero-point adjustment of the leveling roll opening degree using the relationship between the leveling roll opening degree and the load in this way, it is possible to improve the efficiency of the zero-point adjustment process. In addition, in the steel plate straightening method using the roller leveler, the same steel plate can be used repeatedly, so the generation of waste materials can be suppressed, and resource saving can be achieved.

Here, the "load applied to the upper leveling roll" refers to the rolling force required to keep the upper leveling roll at a constant leveling roll opening. When the upper leveling roll is pushed down on the steel plate, the upper leveling roll receives a reaction force from the steel plate, and the upper leveling roll must roll down against this reaction force, but the above load is equal to this reaction force.

The steel plate straightening method by the roller leveler of the present invention can suppress insufficient straightening of the steel plate due to uneven wear of the leveling rolls and improve the straightening effect on the steel plate even in the old-type roller leveler that is not equipped with a roll crowning mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view schematically showing a roller leveler used in a steel plate straightening method using a roller leveler according to an embodiment of the present invention; It is a figure which shows the non-worn part of a leveling roll. It is a figure which shows the zero point of a leveling roll opening. 4 is a graph showing an example of progress of wear by position from an axial end of a leveling roll; It is a graph showing the state of wear of a used leveling roll in the past. FIG. 2 is a side view schematically showing a roller leveler used in a zero-point adjustment step of a steel plate straightening method using a roller leveler, which is different from the steel plate straightening method using the roller leveler of FIG. 1 ; FIG. 7 is a plan view schematically showing the roller leveler of FIG. 6; It is a graph which shows the relationship between a leveling roll opening degree and a load. It is a graph which shows the relationship between the leveling roll opening degree and load for demonstrating a calculation process. 4 is a graph showing the average amount of wear of leveling rolls in the width of a steel plate that is passed in Examples. It is a graph which shows the relationship between the leveling roll opening degree and load in the zero point adjustment process in an Example.

[First embodiment]
A first embodiment of a method for straightening a steel plate by a roller leveler according to the present invention will be described in detail below.

<Straightening method of steel plate by roller leveler>
A method of straightening a steel plate by a roller leveler according to an embodiment of the present invention is a method of straightening a steel plate by a roller leveler having a plurality of leveling rolls arranged in a zigzag pattern along a pass line. The steel sheet straightening method using the roller leveler includes a step of adjusting the zero point of the opening degree of the leveling rolls, and a step of setting the reduction amount of the leveling rolls. By including these steps in the steel plate straightening method using the roller leveler, the old roller leveler, which does not have a roll crowning mechanism, can cope with insufficient straightening of a particularly narrow steel plate caused by uneven wear of the leveling rolls in the axial direction. It is possible to improve the straightening effect on the steel plate.

In general, thick steel plates are subjected to shape correction by a roller leveler or the like arranged downstream of a hot rolling mill. Specifically, a thick steel plate is passed between the upper and lower leveling roll groups, and a load exceeding the yield stress is applied to the thick steel plate to repeatedly bend it, thereby removing the strain of the thick steel plate and reducing the residual stress. I'm trying to make it as small as possible. FIG. 1 is a side view schematically showing a general roller leveler used in a steel plate straightening method using the roller leveler. The roller leveler has a plurality of upper leveling rolls 2a and lower leveling rolls 2b arranged in a zigzag pattern along the pass line. A steel plate 1 is passed while being sandwiched between a plurality of upper leveling rolls 2a and lower leveling rolls 2b. The upper leveling rolls 2a apply a rolling force P transmitted from a rolling device (not shown) across the width of the steel plate 1, thereby deforming the steel plate 1 and improving the flatness of the steel plate 1. As shown in FIG.

Each step of the steel plate straightening method using the roller leveler will be described below.

[Zero point adjustment process]
In the zero point adjustment step, the zero point of the leveling roll opening degree is adjusted based on the non-worn portion of the axial end of the leveling roll (hereinafter also referred to as "roll"). In this process, the zero point of the roll opening is adjusted based on the non-worn parts of the upper and lower leveling rolls of the roller leveler that do not contact the steel plate, so the reference is always constant and the zero point of the roll opening can be adjusted accurately. Here, the "roll opening degree" refers to the distance between a plane connecting the lower ends of the upper roll group and a plane connecting the upper ends of the lower roll group.

(Zero point of leveling roll opening)
Unlike a rolling mill which basically consists of a pair of upper and lower work rolls, a roller leveler has a plurality of integrated roll groups on each of the upper and lower sides. Further, when the strip is threaded, the roll positions are different between the entrance side and the exit side of the roller leveler, and the roll reduction amount with respect to the steel sheet is usually the entry side > the exit side. Therefore, in the steel plate straightening method using the roller leveler, the lower end of each upper roll and the upper end of each lower roll are at the same height as the "zero point of the roll opening" when the upper and lower roll groups are horizontal. Define the position as "zero".

(Adjustment of zero point of leveling roll opening)
In general, among the rolls used for straightening the steel sheet, the leveling rolls that directly contact the steel sheet in particular are worn only at the portion corresponding to the steel sheet passing portion. Therefore, at both ends of the leveling roll in the axial direction, there are portions that do not come into contact with the steel plate and are not worn at all. In other words, as the wear of the rolls progresses, the aforementioned "lower end of the upper roll group" and "upper end of the lower roll" are no longer constant in the axial direction of the rolls.

FIG. 2 is a diagram showing non-wearing portions of the upper and lower leveling rolls. FIG. 3 is a diagram showing the zero point of the leveling roll opening in the method of straightening a steel plate using the roller leveler. A dashed line in FIG. 2 indicates the upper leveling roll 2a, the lower leveling roll 2b, and the center line 4 of the steel plate 1. As shown in FIG. The arrow W in FIGS. 2 and 3 represents the axial direction (body length direction) of the leveling rolls. The dashed line in FIG. 3 indicates the zero point 6 of the leveling roll opening. As shown by the worn portion 5 in FIG. 3, the wear of the leveling rolls is also affected by the width of the steel plate to be straightened. The wear of the rolls in the central portion in the axial direction tends to progress, and the leveling rolls wear unevenly in the axial direction. In other words, the more the leveling roll wear progresses, the more likely it is that a narrow steel plate will be insufficiently straightened. Further, as shown in FIG. 3, non-wear portions 3, which are portions that do not contact the steel plate and do not progress in wear, are formed at both ends of the leveling roll in the axial direction. In other words, the non-wear portion 3 corresponds to a non-contact portion with the steel plate.

The roll opening of the roller leveler changes over time due to roll wear associated with an increase in the amount of straightening processing. Therefore, even if the roll opening is set to a predetermined value, it gradually changes with the passage of time, so the roll reduction amount (hereinafter also referred to as "roll reduction amount") with respect to the steel sheet also gradually changes. Therefore, it is necessary to check the deviation between the display value of the roll opening and the actual roll opening and adjust the zero point for each strip. Here, the "roll reduction amount" refers to the difference between the roll opening and the plate thickness when the roll opening is made equal to or less than the plate thickness of the steel plate, and the above "adjustment of the zero point of the leveling roll opening" , to match the actual roll opening with the displayed roll opening.

In the steel plate straightening method using the roller leveler, the zero point of the roll opening is based on the non-worn portions of the axial ends of the leveling roll regardless of the progress of roll wear, and the zero point of the roll opening is based on the non-worn portions. to adjust.

A specific procedure for adjusting the zero point of the leveling roll opening is as follows.
(1) A space between upper and lower rolls is opened, and a metal plate is placed on the lower roll group. This metal plate must be wide enough to contact the non-worn portions of the axial ends of the leveling rolls. In addition, the plate thickness should be sufficiently thick so that the upper roll group is not plastically deformed when the upper roll group is rolled down in parallel, and the amount of elastic deformation remains minute.
(2) A metal that plastically deforms when the upper roll group is parallel-rolled down onto the metal plate at the positions where the non-wearing portions at both ends in the axial direction of the leveling rolls contact the metal plate, that is, near both ends in the width direction of the metal plate. Install the material. Specifically, for example, a pure aluminum bar or the like generally used for measuring the gap between rolls of a rolling mill or roller leveler may be prepared and installed along the sheet threading direction.
(3) After the upper roll group is rolled down in parallel until it touches the metal plate, that is, by the thickness of the metal plate, the roll opening is widened and the metal material is taken out. Since impressions remain on the metal material at each contact portion with the upper roll group, if the rolling balance of the upper and lower leveling roll groups is lost, the remaining thickness of the impressions will also be different, so that it can be determined. The front and rear (entry side and exit side) and left and right (driving side and operating side) positions of the upper and lower leveling roll groups are adjusted so that the residual thicknesses of these impressions are uniform. Further, after adjusting the remaining thickness of these impressions to be the same regardless of the wear of the leveling rolls, the thickness of the impressions remaining on the metal material is checked again to complete the zero point adjustment.

[Rotation amount setting process]
In the reduction amount setting step, the reduction amount of the leveling rolls is set based on the average wear amount of the leveling rolls in the width of the steel sheet to be passed. Specifically, after adjusting the zero point of the roll opening based on the non-worn parts of the upper and lower leveling rolls of the roller leveler, when each steel plate is passed, the reduction amount of the leveling rolls (initial value) determined in advance In addition, by adding the average wear amount of the leveling rolls corresponding to the width of the steel sheet, the reduction amount of the leveling rolls during the main threading is set. Then, the steel sheet is threaded under this set reduction amount. Here, the predetermined reduction amount (initial value) of the leveling roll refers to an appropriate reduction amount for the roll immediately after normal grinding, that is, before the roll is worn. A predetermined reduction amount (initial value) of the leveling rolls, for example, on the entry side generally imparts a large amount of bending to the steel sheet, and gradually decreases as it progresses toward the exit side. Inclined draft to zero. More specifically, for the entry side, the value should be set so that the "plasticity rate (percentage of the plastic bending deformation rate in the plate thickness direction of the steel sheet) necessary for flatness correction" is empirically said to be 80% or more for the roller leveler. set. This plasticity ratio is calculated by a straightening theoretical formula based on the material properties such as the yield strength of the steel sheet, and the work curvature obtained from the roll diameter, roll pitch, reduction amount, etc. on the leveler side. Further, on the delivery side, the rolling reduction, which is the value at which the roll opening is equal to the thickness of the steel sheet, is generally set to zero.

If the reduction amount (initial value) of the leveling rolls is determined in advance, the flattening of the steel sheet becomes insufficient as the rolls wear. The reduction amount is set by adding the amount of wear.

The reduction amount setting value of the leveling roll refers to an appropriate reduction amount setting value in the state of "before roll wear", which generally refers to a roll immediately after grinding. Since the width of the steel plate to be threaded varies, the axial central portion of the leveling roll, which is in contact with a high frequency of contact, that is, the portion of the roll that is always in contact with narrow to wide steel is prone to wear. is generally unevenly worn in the axial direction. Therefore, if the reduction amount is set as it is, the correction becomes insufficient as the roll wears, so the reduction amount setting value is increased to compensate for the wear of the roll. However, the wear of the rolls at the center in the axial direction of the rolls with high contact frequency progresses easily, and the leveling rolls wear unevenly in the axial direction. Therefore, insufficient straightening tends to occur especially for a steel plate having a narrow width. As described above, since the degree of influence of roll wear differs depending on the width of the steel plate to be leveled, by adding the average wear amount of the leveling rolls for the width of the steel plate to be leveled, An appropriate reduction amount setting value can be set in consideration of the width and the degree of wear of the rolls. As a result, the steel plate can be corrected in the same manner as the leveling roll before wear.

In addition, regardless of the width of the steel plate to be passed, if the wear amount of the axial center portion of the leveling roll that wears the most is uniformly added to the reduction amount setting value, the roll wear will decrease as the steel plate width increases. There is a risk that contact with parts will increase, resulting in excessive roll-down as a whole. As the width of the steel plate increases, the equipment load such as the straightening load also increases. Therefore, according to the steel plate straightening method using the roller leveler, excessive reduction can be suppressed and the equipment can be protected.

As the average amount of wear, it is preferable to estimate an average amount of wear per one threaded steel sheet for each width of the steel sheet to be threaded based on the cumulative number of threaded sheets of the roller leveler. Specifically, the amount of wear of the leveling roll can be predicted from the accumulated amount of the steel sheets passed starting from the state of the roll immediately after normal grinding, that is, before the roll wears. By estimating the average wear amount per threaded steel sheet for each width of the steel sheet to be threaded based on the accumulated threaded amount of the roller leveler, it is possible to easily and accurately set the reduction amount.

Here, the cumulative threading amount can be predicted based on the cumulative number of steel sheets threaded, the cumulative threading distance, the cumulative mail order weight, and the like.

For example, when predicting the average wear amount based on the cumulative number of steel sheets passed, the prediction method is, for example, first, in the applicable steel plate straightening device, the wear amount of all used rolls taken out for roll replacement to measure. In this embodiment, the roll wear amount is measured by measuring the diameter of an unused roll and the diameter of a used roll at each position from the end of the leveling roll in the longitudinal direction from the end of the leveling roll in the axial direction. Next, let the difference between the diameter of the unused roll and the diameter of the used roll be the amount of wear. FIG. 4 is a diagram showing an example of progress of wear for each position from the axial end from the end of the leveling roll. In FIG. 4, the horizontal axis indicates the position (mm) from the end of the leveling roll in the axial direction, and the vertical axis indicates the difference between the diameter of the unused roll and the diameter of the used roll. Shown as quantity. Then, based on the number of strips threaded during the period of use of the roll, the average wear amount per threaded strip (mm/roll or μm/roll) is calculated, and the cumulative threading of the roll after replacement is calculated. The amount of roll wear can be estimated from the number of rolls. FIG. 5 is a graph showing the state of wear of each leveling roll obtained by measuring the wear amount of past used rolls of the roller leveler. The horizontal axis of the graph in FIG. 5 indicates the position of the leveling roll in the axial direction with the central portion of the leveling roll being zero. 5 corresponds to the position on the center line 4 of the upper leveling roll 2a and the lower leveling roll 2b of the leveling rolls shown in FIG. The vertical axis of the graph in FIG. 5 indicates the measurement results of the amount of wear when the number of strips passed during the period of use of the roll is 20,000, 40,000, and 50,000 as an estimated amount of wear. As described above, FIG. 5 shows that the wear of the rolls in the axial center of the rolls with high contact frequency progresses easily, and the leveling rolls wear unevenly in the axial direction.

In the steel plate straightening method using the roller leveler, even when the simplest accumulated number of steel plates passed (number of sheets) is used as the accumulated plate passing amount, the prediction accuracy of the average wear amount is 0.1 mm, which is necessary and sufficient. accuracy can be obtained. In addition, by using the cumulative number of steel sheets passed as the cumulative threaded amount, it is possible to accurately cope with situations in which steel sheets of various widths are passed by the roller leveler. Specifically, for example, in the cumulative wear amount data of the used rolls described above, if the width of the steel sheet to be passed is 3000 mm, all the rolls of the straightening device are at positions within ±1500 mm from the axial center of the rolls. If the width of the steel sheet to be passed next is 4000 mm, all the rolls of the straightening device are uniformly worn at positions within ±2000 mm from the axial center of the rolls. Combining the wear amount data for these two rolls, the wear amount data for two strips is obtained at the position within ±1500 mm of the center in the axial direction of the roll, and at the position within ±1500 to 2000 mm of the center in the axial direction of the roll This is the wear amount data for one strip.

In measuring the amount of wear, it is preferable to use vernier calipers as a method of measuring the roll diameter from the viewpoint of compatibility between workability and accuracy. Even if it is assumed that the roll is uniformly worn in the circumferential direction, there is no problem in terms of accuracy, and the measurement position in the roll circumferential direction is not particularly limited. In addition, with respect to the measurement points of the roll diameter in the axial direction, it is necessary to measure at intervals of at least 200 mm in order to ensure accuracy, and it is preferable to measure at intervals of 100 mm.

In order to obtain the straightening effect of the steel plate by the roller leveler, the distance between the surface connecting the lower end of the upper roll group and the surface connecting the upper end of the lower roll group should be less than the plate thickness of the steel plate to be processed. However, the above roll reduction imparts a large amount of bending to the steel sheet on the entry side, and gradually decreases as it progresses to the exit side, and the amount of distortion is reduced on the exit side. It is common to apply a gradient reduction to almost zero. In other words, the contact surface pressure, which is the load that the leveling rolls receive from the steel plate, is not uniform from the entry side to the exit side, and wear of the entry side rolls progresses more easily. Therefore, in a roller leveler in which the sheet passing direction is always constant, it is necessary to estimate the average amount of wear per sheet passing by using different amounts of wear between the entry-side roll and the exit-side roll. However, in the case of roller levelers for thick steel plates, the threading direction is not always the same, and there are many things that reverse the threading direction. It is possible to adjust the amount of wear of leveling rolls on the entry side and the exit side according to the situation.

In addition, the steel plate straightening method using the roller leveler makes it possible to suppress insufficient straightening due to the progress of wear of the leveling rolls. The deviation of the reduction amount in the width direction of the steel plate to be plated also increases. If the reduction amount deviation becomes excessive, the strain distribution in the steel sheet may be expanded by passing the steel sheet through the roller leveler, and the flatness and residual stress may be deteriorated. Therefore, the steel plate straightening method using the roller leveler can exhibit a more excellent effect within the wear range of the leveling rolls in which the reduction amount deviation does not become excessive.

According to the method for straightening a steel plate by the roller leveler, even an old-type roller leveler without a roll crowning mechanism can improve the straightening effect on the steel plate against insufficient straightening of the steel plate caused by uneven wear of the leveling rolls in the axial direction.

<Advantages>
The steel plate straightening method using the roller leveler can easily and accurately correct insufficient straightening caused by uneven wear of the leveling rolls in the axial direction, so it can be suitably used in the manufacturing process of thick steel plates.

[Second embodiment]
A second embodiment of the method for straightening a steel plate using a roller leveler according to the present invention will be described in detail below.

<Straightening method of steel plate by roller leveler>
A steel plate straightening method by a roller leveler according to another embodiment of the present invention is a steel plate straightening method by a roller leveler having a plurality of leveling rolls arranged in a zigzag pattern along a pass line. The steel plate straightening method using the roller leveler includes a step of adjusting the zero point of the leveling roll opening based on the non-worn portion of the axial end of the leveling roll, and the average of the leveling roll in the steel plate width of the steel plate to be passed. and setting the reduction amount of the leveling rolls based on the amount of wear.

[Zero point adjustment process]
The zero point adjustment step includes an acquisition step and a calculation step.

<Acquisition process>
In the obtaining step, as shown in FIGS. 6 and 7, the steel plate 7 placed on the lower leveling rolls 2b arranged below along the pass line is coated with an upper leveling roll arranged above along the pass line. The relationship between the opening degree of the leveling rolls and the load applied to the upper leveling rolls 2a when the rolls 2a are rolled down is acquired.

(Reduction device)
The load is applied by transmitting a rolling force P from a rolling device 8 to the upper leveling roll 2a, as shown in FIGS. Normally, there are a plurality of upper leveling rolls 2a, but the screw down device 8 is preferably configured so that the rolling force P from the screw down device 8 is transmitted to all the upper leveling rolls 2a.

It is preferable that the roll-down devices 8 are arranged at the non-wearing portions at both ends of the upper leveling roll 2a in the axial direction. Zero-point adjustment is performed based on the non-worn portion, and the non-worn portion comes into contact with the upper leveling roll 2a more reliably than the worn portion. Zero adjustment can be performed. In addition to the non-worn portion, the position of the screw down device 8 is preferably a position where the screw down force P can be transmitted relatively evenly to the upper roll group (the plurality of upper leveling rolls 2a). Preferably, for example, as shown in FIG. 7, four screw down devices 8 are used and arranged at the four corners of the upper roll group.

In the following, a case where the screw-down device 8 is arranged at the position shown in FIG. 7 will be described as an example. There is no particular limitation, and other arrangement positions may be used.

The magnitude of the load applied to the upper leveling roll 2a can be measured by a load meter (not shown) arranged in each of the four screw down devices 8. As shown in FIG. The magnitude of the load applied to the upper leveling roll 2a is obtained by summing the measured values of these four load meters.

(steel plate)
The steel plate 7 is placed on the lower leveling rolls 2b. As the steel plate 7, one having high rigidity and being difficult to deform is preferable. Specifically, the steel plate 7 is preferably thick. By making the steel plate 7 thick, deformation of the steel plate 7 due to the load can be suppressed, so that the relationship between the opening degree of the leveling rolls and the load can be obtained with high accuracy.

The lower limit of the average thickness of the steel plate 7 is preferably 50 mm, more preferably 60 mm. If the average thickness of the steel plate 7 is less than the above lower limit, it may be difficult to accurately obtain the relationship between the leveling roll opening and the load. On the other hand, the upper limit of the average thickness of the steel plate 7 is not particularly limited as long as it can be inserted between the upper leveling roll 2a and the lower leveling roll 2b. In addition, it is preferable that the thickness of the steel plate 7 is uniform.

As for the size of the steel plate 7 in plan view, it has a width that can cover the non-worn portions at both ends in the axial direction of the upper leveling rolls 2a and the lower leveling rolls 2b. The size is such that it is long enough to cover everything.

Further, when performing the obtaining step, the temperature of the steel sheet 7, that is, the ambient temperature when performing the obtaining step is preferably normal temperature. In other words, the lower limit of the temperature of the steel plate 7 is preferably 10°C, more preferably 20°C. On the other hand, the upper limit of the temperature of the steel plate 7 is preferably 50°C, more preferably 40°C. If the temperature of the steel plate 7 is below the above lower limit, equipment such as a cooling device is required, which may increase the cost for zero point adjustment. Conversely, if the temperature of the steel plate 7 exceeds the above upper limit, the rigidity of the steel plate 7 decreases, and it may become difficult to accurately obtain the relationship between the leveling roll opening and the load.

(load)
The load is applied by pressing the upper roll group by the screw down device 8 against the steel plate 7 placed on the lower leveling roll 2b.

As for the pressing method of the upper roll group (orientation of the upper roll group), it is preferable that the upper roll group is rolled down in parallel with the lower roll group. Such a parallel rolling makes it easy to uniformly apply the rolling force P to the non-worn portion regardless of the roll positions of the upper roll group. Alternatively, the upper roll group may be pressed against the steel plate 7 so that the loads of the four load cells are equal. In the case where the deviation of the zero points between the upper roll group and the lower roll group depends on the roll position, it is possible to adjust the zero point in consideration of the position dependence. The attitude of the upper roll group can be controlled, for example, by independently adjusting the relative heights of the contact points of the four screw-down devices 8 with the upper roll group. More specifically, as shown in FIG. 6, when the screw down device 8 is arm-shaped, the length of the arm can be adjusted independently for each screw down device 8 . As the leveling roll opening degree when the relative heights are individually adjusted in this way, the average leveling roll opening degree of the upper roll group may be used, or the leveling at one specific point (for example, one point of the screw down device 8) A roll opening may be used as a representative value.

By pressing the upper roll group against the steel plate 7 as described above, the relationship between the leveling roll opening when the upper leveling roll 2b is lowered and the load applied to the upper leveling roll 2b is obtained. At this time, when the opening degree of the leveling rolls is sufficiently larger than the thickness of the steel plate 7, the upper roll group does not contact the steel plate 7, so the load becomes zero. When the upper roll group is rolled down and the upper roll group comes into contact with the steel plate 7, the load shows a positive value. Here, even if the steel plate 7 is thick and has high rigidity, when the upper roll group is strongly pressed against the steel plate 7, the leveling roll itself elastically deforms due to the load. It becomes a numerical value below the thickness of 7, and the load increases. Accordingly, when the relationship between the leveling roll opening degree and the load is acquired when the upper leveling roll 2b is lowered, the relationship shown in FIG. 8 is obtained.

In addition, when acquiring the relationship between the leveling roll opening and the load, starting from the side where the leveling roll opening is large, the pressing of the upper roll group is strengthened (pressing downward against the steel plate 7), Although the relationship between the leveling roll opening and the load may be acquired, after pressing the upper roll group downward until the leveling roll opening reaches a predetermined amount, while raising the upper roll group The relationship between the leveling roll opening degree and the load may be acquired.

<Calculation process>
In the calculation step, the zero point adjustment amount of the leveling roll opening is calculated by comparing the relationship between the leveling roll opening and the load obtained in the obtaining step and the relationship between the leveling roll opening and the load previously obtained from the steel plate 7. Calculate

The relationship between the leveling roll opening degree and the load obtained in the above obtaining step shows unique characteristics for each roller leveler, but has reproducibility as long as the object to be rolled down (that is, the steel plate 7) does not change. On the other hand, if the zero point of the leveling roll opening deviates due to aging due to use, etc., as shown in FIG. The relationship is shifted in the positive direction (A in FIG. 9) or in the negative direction (B in FIG. 9).

Since this shift amount is the zero point adjustment amount of the leveling roll opening, the relationship between the leveling roll opening and the load obtained in the above acquisition step, and the relationship between the leveling roll opening and the load obtained in advance from the steel plate. A zero point adjustment amount can be calculated by comparing .

As the relationship between the leveling roll opening degree and the load previously obtained from the steel plate, it is preferable to use the relationship between the leveling roll opening degree and the load obtained at the start of use of the roller leveler. When the roller leveler starts to be used, the leveling roll is not worn over the entire width, so adjustment can be easily made so that the zero point does not deviate. Therefore, the relationship between the degree of opening of the leveling rolls and the load in this state can serve as an absolute reference for the zero point. In addition, when the roller leveler itself is used, when the leveling roll is replaced, the time when the leveling roll is not worn immediately after the replacement.

Alternatively, as the relationship between the leveling roll opening degree and the load obtained from the steel plate 7 in advance, the relationship between the leveling roll opening degree and the load in the above-mentioned zero point adjustment process when the steel plate was straightened by the roller leveler performed last time may be used. can. By comparing the relationship between the leveling roll opening and the load between the previous time and this time, the relative zero point adjustment amount (difference) with respect to the previous zero point adjustment amount can be found, so this difference can be added to the previous zero point adjustment amount. can calculate the necessary zero point adjustment amount.

The steel plate used for the relationship between the degree of opening of the leveling rolls and the load obtained in advance and the steel plate used in the obtaining step are the same steel plate. The term "same steel sheet" includes not only physically identical steel sheets but also different steel sheets of the same type, shape, and size. However, from the viewpoint of the accuracy of zero point adjustment, it is preferable that the steel plates are physically the same.

Various methods can be used to calculate the shift amount that is the amount of zero point adjustment of the leveling roll opening. Using the case of calculating the shift amount of R and A in FIG. 9, the method of calculating the shift amount will be specifically described. and the difference (X in FIG. 9) can be used as the shift amount.

Alternatively, since the relationship between the leveling roll opening and the load generally exhibits linearity in a region where the leveling roll opening is small, the relationship between the leveling roll opening and the load in this linear region is represented by R and A in FIG. is approximated by a linear approximation formula (RL and AL in FIG. 9), and the difference (Y in FIG. 9) of the leveling roll opening at the intersection with the leveling roll opening axis (the position where the load is 0) is the shift amount may be In this method, a linear approximation formula should be determined so that the slopes of the linear regions of R and A in FIG. 9 are equal. Since R and A in FIG. 9 usually have a shifted relationship with respect to the leveling roll opening, the slopes in the linear region are essentially the same. Therefore, the approximation error can be reduced by determining the linear approximation formula so that the slopes of the linear regions of R and A in FIG. 9 are equal. When the slopes of the linear regions of R and A in FIG. position), the same shift amount is always obtained.

The zero point adjustment can be completed by performing the adjustment according to the zero point adjustment amount calculated in this calculation step.

[Rotation amount setting step]
The reduction amount setting process is the same as the reduction amount setting process in the first embodiment, so detailed description thereof will be omitted.

<Advantages>
In the steel plate straightening method using the roller leveler, the efficiency of the zero point adjustment process can be improved by performing the zero point adjustment of the leveling roll opening using the relationship between the leveling roll opening and the load. In addition, in the zero-point adjustment method described in the first embodiment, the metal plate with the indentation is difficult to reuse and becomes a waste material. Therefore, it is possible to suppress the generation of waste materials and save resources.

It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is not limited to the configuration of the above-described embodiment, but is indicated by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims. be.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples.

[Example 1]
(1) Material to be straightened Steel plates shown in Table 1 below were used as materials to be straightened.
(2) Facility overview As shown in Table 1, a hot straightening roller leveler, which is located downstream of the cooling equipment of the hot strip mill and in front of the cooling bed, is used to straighten the steel sheet to be straightened. A method of straightening a steel plate using the roller leveler was implemented. The number of strips passed through the roller leveler was about 20,000. As the roller leveler, a quadruple type in which the load of the leveling rolls is received by backup rolls was adopted. In addition, the sheet passing direction can be reversed, and 3-pass to 5-pass straightening was performed mainly for thin materials with poor flatness and accelerated cooling materials.

A group of 5 upper rolls and a group of 6 lower rolls are integrated, respectively. is integrally moved up and down to control the roll opening (reduction amount), and the structure is such that the steel sheet being passed is bent and straightened. not prepared.

Table 1 below shows the main specifications of the hot straightening roller leveler.

(3) Zero-point adjustment of roll opening of roller leveler After setting the positional roll opening constant, the upper and lower rolls were opened while maintaining the above state, and a thick steel plate (material SS400, plate thickness 70 mm, plate width 4800 mm) at room temperature was placed on the lower roll group. Further, a pure aluminum rod (diameter 10 mm) was placed on each of the top surfaces of the thick steel plate in the width direction (operating side and driving side) one by one in the sheet passing direction, and the upper roll group was rolled down in parallel to a roll opening of 70 mm. , the upper roll group was lifted and the aluminum rod was taken out.

About the indentations of five upper rolls left on each aluminum bar, the remaining thickness was measured at a total of four locations on the entry side, the exit side, the operation side, and the drive side. Comparing the entry side and exit side, the operation side and the drive side, and the pair on the diagonal line, the deviation of each remaining thickness is within 0.2 mm, and the deviation from the remaining thickness in the state before wear of the roll is After confirming that it was within ±0.1 mm, the zero point adjustment was completed.

(4) Estimation of Average Amount of Wear of Leveling Rolls FIG. 10 is a graph showing accumulated data of the amount of wear of used rolls as an average amount of wear of the leveling rolls in the width of the passed steel plate. Then, from the data of the graph in FIG. 10, based on the number of strips passed by the roller leveler (approximately 20,000) and the steel plate width of Example 1, the average wear amount of each leveling roll during strip threading in Example 1 was estimated. . The average wear amount was 0.0064 μm/piece. Since the roller leveler used in this embodiment also performs reverse pass threading in the opposite direction, there is little difference in the load on the leveling rolls among all 11 leveling rolls, and the average wear amount difference per steel plate threaded is within ± Since it was within 5%, it can be judged that the average wear amount of each leveling roll of the roller leveler is the same value.

(5) Setting of reduction amount At the stage after approximately 20,000 strips have been passed cumulatively from the point before wear of the leveling rolls, the average amount of wear of the leveling rolls is added to the predetermined reduction amount, and the material to be straightened is A steel plate was passed through.

[Comparative Example 1]
Comparative Example 1 was obtained by performing straightening under the same conditions except that the steel plate was straightened with the predetermined reduction amount.

[evaluation]
(flatness defect rate)
The flatness of the steel sheet straightened by the roller leveler was checked after air cooling, and the flatness defect rate (%) was determined. The flatness defect rate is the number of flatness exceeding the acceptable standard/the number of hot straightening. Specifically, the number of steel sheets whose flatness exceeds the acceptance criteria is the number of waves ("medium waves" in which the center of the width of the steel sheet undulates and "end waves" in which the edges of the width of the steel sheet undulate) after hot straightening and air cooling. It is the number of steel sheets whose warpage (warpage in the width direction and warpage in the longitudinal direction of the plate) exceeds the acceptable standard range.

As a result of calculating the flatness defect rate of Example 1 and Comparative Example 1, the flatness defect rate of the steel plate of Comparative Example 1 in which the steel plate was straightened without performing the steel plate straightening method by the roller leveler was set to 100%. The flatness defect rate of Example 1 was 49%, and the flatness defect rate of Example 1 was greatly improved.

Based on the above results, the steel plate straightening method using the roller leveler improves the steel plate straightening effect even with the old roller leveler, which does not have a roll crowning mechanism, against insufficient straightening of the steel plate caused by uneven wear of the leveling rolls in the axial direction. shown that it can be done.

[Zero point adjustment using the relationship between leveling roll opening and load]
Zero point adjustment using the relationship between the leveling roll opening degree and the load described in the second embodiment was performed in the following procedure.

(1) Steel plate A steel plate made of SS400 and having a width of 4000 mm, a length of 2000 mm and an average thickness of 70 mm was prepared as a steel plate used in the zero point adjustment step.
(2) Outline of Equipment As the roller leveler, the same equipment as in Example 1 was used.

<Zero point adjustment process>
(Acquisition process)
The steel plate was placed on the lower roll group. Next, after the upper roll group was rolled down in parallel until the leveling roll opening was 67.0 mm, the relationship between the leveling roll opening and the load was obtained while raising the upper roll group (A in FIG. 11). The load was measured at intervals of 0.1 mm from 67.0 mm to 67.8 mm of the leveling roll opening. Of these, FIG. 11 shows a range of loads from 350 tons to 700 tons.

(Calculation process)
The relationship between the leveling roll opening and the load obtained in the acquisition step (A in FIG. 11) was compared with the relationship between the leveling roll opening and the load previously obtained from the steel plate (R in FIG. 11). Note that R in FIG. 11 represents the relationship between the leveling roll opening degree and the load obtained at the start of use of the roller leveler, and was obtained in the same manner as in the obtaining process described above.

A and R in FIG. 11 show linearity in the range of 350 tons or more and 700 tons or less. In this linear region, a linear approximation formula was determined so that the slopes of A and R in FIG. 11 are equal (solid line and broken line in FIG. 11).

From this result, it was found that the shift amount was 0.2 mm. Therefore, the zero point of the leveling roll opening was corrected by 0.2 mm in the direction of decreasing the leveling roll opening, and the zero point adjustment was completed.

As described above, the leveling roll opening and the A step of acquiring the relationship between the load applied to the upper leveling roll, the relationship between the leveling roll opening and the load acquired in the acquiring step, and the relationship between the leveling roll opening and the load acquired in advance from the steel plate. By comparison, it was confirmed that the zero point adjustment process including the process of calculating the zero point adjustment amount of the leveling roll opening functioned.

INDUSTRIAL APPLICABILITY The steel plate straightening method using the roller leveler of the present invention can easily and accurately correct insufficient straightening caused by uneven wear of the leveling rolls in the axial direction. can.

1 Steel plate 2a Upper leveling roll 2b Lower leveling roll 3 Non-worn part 4 Center line 5 Worn part 6 Leveling roll opening zero point 7 Steel plate 8 Rolling down device P Rolling force

Claims (3)

A method of straightening a steel plate by a roller leveler having a plurality of leveling rolls arranged in a zigzag pattern along a pass line,
A step of adjusting the zero point of the opening degree of the leveling roll based on the non-worn portion of the axial end of the leveling roll;
A method of straightening a steel plate by a roller leveler, comprising: setting the reduction amount of the leveling roll based on the average wear amount of the leveling roll in the width of the steel plate to be passed. 2. The method of straightening a steel sheet by a roller leveler according to claim 1, wherein the average amount of wear is estimated for each width of the steel sheet based on the accumulated amount of sheet threading of the roller leveler. As the zero point adjustment process,
A leveling roll opening and an upper leveling roll when an upper leveling roll arranged above along the pass line is pressed down on a steel plate placed on a lower leveling roll arranged below along the pass line. obtaining a relationship with the load applied to
A step of calculating the zero point adjustment amount of the leveling roll opening by comparing the relationship between the leveling roll opening and the load obtained in the obtaining step and the relationship between the leveling roll opening and the load previously obtained from the steel plate. The method of straightening a steel plate by a roller leveler according to claim 1 or 2, comprising:

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