JP2010149156A - Method for predictive calculation of roll crown of work roll - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To establish a method for predicting a thermal crown of a re-used roll, to ensure a desired plate crown, and to provide a method for the predictive calculation of a roll crown of a work roll for consistently manufacturing a hot-rolled steel plate without any plate-passing trouble. <P>SOLUTION: In the method for the predictive calculation of the roll crown of the work roll with less roll wear in a hot and continuous finishing rolling mill train, when the work roll is again assembled to a finishing rolling mill for use without any roll grinding after the roll assembly change of the work roll, firstly the cooling history and the elapsed time immediately after the roll assembly change to the start of the next rolling operation are saved as the data for each work roll. Secondly, the distribution in the axial direction of the temperature in the work roll and the thermal expansion at the starting time of the next rolling operation is calculated by using the saved data. Thirdly, the work roll crown is predicted by adding the calculation value of the distribution in the axial direction of the work roll wear by the rolling work before the assembly change of the work roll. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is a predictive calculation method for work rolls with low roll wear in hot continuous finish rolling mills, that is, roll crowns of high-speed rolls. The present invention relates to a roll crown prediction calculation method.

  In recent years, it has become important to improve the plate shape accuracy along with the strictness of the required accuracy of the plate crown, which is the thickness distribution in the plate width direction of the rolled material, and the stabilization of the high-tensile plate that is positioned as a difficult-to-produce material. Yes.

ここで、Ｐは圧延荷重、Ｆはワークロールベンディング力、Ｃoはロールクラウンの影響項、Ａ_P、Ａ_Fはミル形式、ミルディメンジョン、圧延材板幅などの圧延条件の関数として求められるモデル係数である。 By the way, in order to achieve the target plate crown and plate shape after rolling by computer control of the plate crown and plate shape of the rolled material, at the time when rolling conditions are given, first, the plate crown and plate generated by the rolling A model that expresses the shape with practical accuracy, that is, a plate crown shape prediction model is required. As this model, for example, a “rolling control method” disclosed in Patent Document 1 is known as a physical model expressing a rolling phenomenon. In this method, as a representative parameter of roll deformation, a plate crown at a plate crown definition point position realized when the load distribution in the width direction between the rolled material and the work roll is uniform is defined as a mechanical plate crown C. Defined. The mechanical plate crown C calculated depending on the rolling conditions varies depending on the mill type, but is known to be calculated as in the following equation (1), for example.

Here, P is a rolling load, F is a work roll bending force, Co is an influence term of a roll crown, A _P and A _F are model coefficients obtained as a function of rolling conditions such as a mill type, a mill dimension, and a rolled sheet width. It is.

ここで、ηはクラウン比率遺伝係数、ｒは圧下率、Ｃ_Hは入側板クラウン，ｉは熱間圧延機列の上流からのスタンド数である。このとき、クラウン比率遺伝係数ηは、入側のクラウン比率変化が出側のそれに及ぼす影響係数として表され、板厚、板幅、ロール直径の関数で表現されている。また、各圧延スタンドにおける板形状Δεは、次式（３）で表されている。

ここで、ξは形状変化係数，Ｈ,ｈは入出側板厚である。このとき、形状変化係数ξはクラウン比率変化と板形状との関係を表現するための影響係数であり、板厚、板幅、ロール直径の関数で表現されている。上述した従来技術からも分かるように、板クラウンおよび板形状の高精度化にはロールクラウンが大きく影響することになる。 This mechanical sheet crown C is a deformation amount determined only by the deformation characteristics of the rolling mill, but the width direction load distribution in actual rolling varies depending on the material deformation characteristics caused by the width of the inlet side sheet crown and the width direction metal flow of the rolled material. since changes, each rolling stand delivery side crown C _h for a hot rolling mill train, does not match the mechanical strip crown is generally expressed by the following equation (2).

Here, η is the crown ratio genetic coefficient, r is the rolling reduction, C _H is the inlet plate crown, and i is the number of stands from the upstream side of the hot rolling mill row. At this time, the crown ratio genetic coefficient η is expressed as an influence coefficient that the change in the crown ratio on the input side exerts on the output side, and is expressed as a function of the plate thickness, the plate width, and the roll diameter. Moreover, plate shape (DELTA) epsilon in each rolling stand is represented by following Formula (3).

Here, ξ is a shape change coefficient, and H and h are input / output side plate thicknesses. At this time, the shape change coefficient ξ is an influence coefficient for expressing the relationship between the crown ratio change and the plate shape, and is expressed as a function of the plate thickness, the plate width, and the roll diameter. As can be seen from the above-described prior art, the roll crown greatly affects the accuracy of the plate crown and the plate shape.

ここで、Ｗ_ＷＲはワークロール摩耗量，ｐは線荷重(圧延荷重/板幅)，Ｄ_ｗｒはワークロール直径，Ｌは圧延長，α：チューニング定数である。このとき、チューニング定数αは実操業データと実際の摩耗量からロール種別、スタンド毎に決められている。 On the other hand, for example, as described in Non-Patent Document 2, a high-speed roll with little roll wear is used as a work roll in a rolling stand of a hot rolling mill row. It has been known that a work roll absorbs heat from a rolled material by thermal contact (hereinafter referred to as a thermal crown) and wears due to contact with the rolled material during a rolling operation. As a method for calculating the thermal crown, for example, prediction models described in Patent Document 2 and Non-Patent Document 1 are known. This predictive model calculates the temperature distribution in the radial direction of the roll when calculating the temperature distribution in the roll of a work roll composed of two layers having different physical properties in hot rolling, that is, a core material and an outer layer material, during the rolling operation. The work roll thermal crown is calculated by calculating the temperature distribution in the work roll. Regarding roll wear, for example, the following equation (4) is used as a commonly used equation, which is tuned using current operation data for each stand.

Here, W _WR is a work roll wear amount, p is a line load (rolling load / sheet width), D _wr is a work roll diameter, L is a rolling length, and α is a tuning constant. At this time, the tuning constant α is determined for each roll type and stand from the actual operation data and the actual wear amount.

  Further, at the time of starting the rolling operation, the work roll is ground to a desired crown (hereinafter referred to as an initial crown), and incorporated into each rolling stand of the hot rolling mill row. Here, in general, the work roll is sufficiently cooled and ground to a desired initial crown in consideration of the roll wear portion in a state where the thermal crown is eliminated. Further, for work rolls with large roll wear, for example, a method for grinding an initial crown by warm grinding described in Patent Document 3 and Patent Document 4 is disclosed. This is because roll rolling is performed in a state where roll cooling is not performed sufficiently from the viewpoint of productivity, and the amount of thermal crown reduction from the time of roll recombination and grinding is calculated and combined with the amount of grinding as the initial crown. The method of applying is known.

JP 59-130614 Japanese Unexamined Patent Publication No. 7-80517 JP-A-6-328347 JP-A-8-43039 P652-657, "The 7th International Conference onSteel Rolling '98, ISIJ" P76-83, Development of high-sroll application technology for hot strip rolling, 1995, Nippon Steel Engineering Report

  In the work roll recombination operation, a roll crown is set (initial crown is set) according to a unit in which the work roll is used next. At this time, in general, the work roll is sufficiently cooled, the thermal roll (the amount of thermal expansion) is not present, and the work roll is measured with the wear roll only, and the desired initial crown is measured. The amount of grinding in the work roll axial direction is determined so that When the roll grinding operation is performed as described above, the initial crown at the time when the work roll is incorporated into the rolling mill is given with almost no setting error, and the initial crown at the start of the rolling operation is fixed. The desired plate crown and shape could be obtained from the start of operation.

  In recent years, high-speed rolls with extremely low roll wear have been used as work rolls for rolling stands in hot rolling mill rows. Because roll wear is extremely low, from the viewpoint of productivity, reduction of roll grinding time and reduction of the number of rolls held, the work rolls can be reassembled after the end of the rolling schedule unit, and if there are no scratches or defects in the work rolls, it will be as early as possible. The operation used in the next unit of the rolling schedule unit is performed (hereinafter, the roll is referred to as a reuse roll). In this rolling operation mode, roll wear is extremely small, so that no large step is generated in the roll axis direction. For this reason, it has been adopted as an operation form because there is no occurrence of abnormal rolling shape due to the step (local elongation) and no step on the plate crown. Furthermore, the operation which implements such reuse in the same roll twice or more is also performed.

  When the rolling operation described above is carried out, the work roll is not sufficiently cooled, so that it is incorporated into the rolling mill with a thermal crown added thereto. Furthermore, even if a high-speed roll with extremely low roll wear is used, the roll may not be ground and may be used twice or more, so the influence on the roll crown cannot be ignored regarding roll wear. That is, when the rolling operation is performed by applying the reuse roll, the initial crown of the work roll incorporated in the rolling mill cannot be accurately predicted.

At present, even when the rolling operation described above is carried out, the initial crown at the start of the rolling operation is applied to the initially ground crown (the ground crown when the work roll is sufficiently cooled), so that the plate crown and the plate shape Since the calculation was performed and the rolling operation was performed, there was a problem that not only a desired plate crown could not be obtained but also a rolling trouble due to the plate shape was caused.

  Accordingly, the present invention aims to solve the above-mentioned problems of the prior art and to provide a roll crown prediction calculation method for a work roll for carrying out a rolling operation without rolling trouble while ensuring plate crown accuracy. And

In order to achieve the above object, the gist of the present invention is as follows.
(1) In the roll crown prediction calculation method for a work roll with less roll wear in a hot continuous finish rolling mill row, when the work roll is reassembled and used again in the finishing mill without roll grinding after roll recombination, one work roll is used. Each time, the cooling history and elapsed time from immediately after roll recombination until the start of the next rolling operation is stored as data, and the axis of the work roll internal temperature and thermal expansion amount at the time of starting the next rolling operation using the stored data. A roll crown prediction calculation method for a work roll characterized by calculating a direction distribution, and then predicting the work roll crown by adding a calculated value of the axial distribution of the work roll wear amount due to the rolling work before the work roll recombination. It is.
(2) The roll crown prediction calculation of the work roll according to (1), wherein the roll crown of the work roll at the time when the roll recombination is performed at least twice and the next rolling operation is started is predicted. Is the method.
(3) The work roll roll crown prediction calculation method according to (1) or (2), wherein the work roll with less roll wear is a high-speed roll.

  According to the present invention, for each work roll, the axial distribution of the work roll thermal expansion amount is calculated based on the cooling history and elapsed time from immediately after roll recombination until the next work roll incorporation, and the work roll thermal expansion is calculated. Since the axial distribution of the quantity is the initial crown, it is possible to ensure the plate crown accuracy in the rolling operation and to carry out operations without rolling trouble (drawing, semi-finishing, etc.).

In the rolling operation, the next work roll recombination was not scheduled to be applied to the reuse roll, but there was a case where a plate passing trouble occurred and the work roll recombination was required suddenly. In such a case, if the roll grinding is not in time, the rolling operation may be interrupted. When adopting the present invention, all work rolls to be reused (for example, all high-speed rolls) are targeted, so even if the above trouble occurs, an appropriate roll is selected from the stored data, If the roll crown prediction calculation of the work roll is performed, adverse effects on productivity can be minimized.

  Hereinafter, the background of the inventors to the present invention will be described.

Rolling operations using high-speed rolls with little roll wear are carried out in the hot continuous finish rolling mills. A rolling trouble (drawing) occurred in the F4 stand during wide (1800 mm) rolling in the rolling unit after work roll recombination, and work roll recombination of the stand was performed. At this time, after confirming that the high-speed roll used in the previous rolling unit had no scratches or defects, it was again incorporated into the rolling mill and the rolling operation was started. In the first rolling, a large stretched shape occurred on the exit side of the F4 stand, causing a serious trouble without being caught in the F5 stand.

In order to analyze the cause of this trouble, the inventors focused on the fact that the high-speed roll incorporated in the F4 stand had only passed 40 minutes from the end of the previous unit to the execution of the rolling. The thermal crown was calculated until rolling. FIG. 1 shows the thermal crown calculation result, FIG. 2 shows the plate shape calculation result (calculation shape when a serious trouble occurs) when the thermal crown calculation result is used as the initial crown, and there is no thermal crown in the stand. The plate shape calculation result (roll crown flat) in the state (initial crown during grinding) is shown. From FIG. 1, it was found that the thermal crown of the reuse roll at the time of occurrence of the trouble hardly decreased. Furthermore, in this state, since the work roll was incorporated and used in the rolling mill, it was found that a large middle stretch shape as shown in FIG. In other words, it was recognized that the calculation of the plate crown and shape as if there was no thermal crown despite the presence of the thermal crown was the biggest cause of trouble (the plate shape was almost flat when there was no initial crown. ). Further, since the stand is a stand having a pair cross, such a plate passing trouble has been avoided if the crown control amount of the pair cross is effectively used. It has been found that, when roll roll recombination without roll grinding after work roll roll recombination is used again in the finishing mill, the biggest trouble factor is that the thermal crown is not predicted.

Therefore, the inventors memorized the elapsed time from the end of rolling of the previous rolling unit until the next incorporation into the rolling mill and cooling conditions for each work roll when carrying out the rolling operation mode described above. It has been found that the rolling trouble as described above does not occur if the thermal crown is calculated in consideration of the history before rolling is started again.

In practicing the present invention, it is necessary to predict the work roll profile. For the work roll thermal crown prediction of the same prediction, a known prediction model (for example, Patent Document 2, Non-Patent Document 1) was used. Formula (4) was used as a calculation formula for the wear amount of the work roll. The tuning constant α in equation (4) may be determined from the actual operation data and the actual wear amount.

An embodiment in which the present invention is applied to a hot continuous finish rolling mill will be specifically described.

An example of the calculation procedure according to the prior art is shown in FIG. In the case of the prior art shown in FIG. 4, even if the roll is a reusable roll, when the work roll is incorporated into the rolling mill, the thermal crown and the roll shaft of the wear from the start of the rolling operation are assumed to have no thermal crown and roll wear. The directional distribution will be calculated.

  FIG. 5 shows the thermal expansion amount of the work roll center during the rolling operation using the thermal crown prediction model in the F4 stand of the hot continuous finish rolling mill. FIG. 5 shows that when the number of rolling exceeds about 90, the work roll center thermal expansion amount becomes 0.2 mm or more per radius during the rolling operation. Further, FIG. 6 shows the result of calculating the distribution behavior (cooling history) of the thermal expansion amount in the roll axial direction under the air cooling condition from the end of rolling using the thermal crown prediction model.

In the rolling operation on the premise of the reuse roll, since the roll may be incorporated again into the rolling mill within one hour after the work roll recombination, as can be seen from FIG. For example, it is clear that the prior art work roll roll crown prediction based on the assumption that there is no thermal crown has a large error from the initial crown. Therefore, in the present invention, for each work roll, the cooling history and the elapsed time from immediately after the roll recombination until the start of the next rolling operation are stored as data, and the stored data is used to start the next rolling operation at the time. Calculate the axial distribution of the work roll internal temperature and the amount of thermal expansion, and then add the calculated value of the axial distribution of the work roll wear amount due to the rolling work before recombination of the work roll to predict the work roll crown. .

  An example of the calculation procedure according to the present invention is shown in FIG. In the case of the present invention shown in FIG. 3, thermal crown data after the end of the rolling operation (FIG. 3 S4) (when Patent Document 2 is used: outer layer material average temperature, core material average temperature, surface temperature, core as roll temperature information) The temperature gradient at the interface between the material and the outer layer material, the axial data of the roll center temperature) and the roll wear direction distribution of the roll wear data are collected (FIG. 3S5) and stored in the database for each work roll (FIG. 3S6). . Next, for each of the work rolls, the elapsed time and cooling history from the end of rolling until the next roll roll is incorporated (S6 in FIG. 3) are stored. At this time, the elapsed time and the cooling history, for example, as shown in FIG. 7, when re-installed in the rolling mill after air cooling-water cooling-air cooling from the end of rolling, the respective elapsed time and cooling history (here, the air cooling And the order thereof are stored in the database (S6 in FIG. 3). Next, before incorporating the reuse roll into the rolling mill next time, considering the elapsed time and rolling history, the roll axial distribution of the amount of thermal expansion at the time of incorporation of the work roll is calculated, and the roll wear during the previous use is calculated. Together with the amount and the roll crown at the time of grinding, the roll crown at the time of incorporating the roll of the reuse roll is obtained (S7 in FIG. 3). Next, the axial distribution of the temperature inside the work roll and the amount of thermal expansion is calculated in consideration of the cooling history and elapsed time from when the work roll is incorporated into the rolling mill until the start of rolling. The initial crown of the reusable roll is predicted (S2 in FIG. 3). At this time, the air-cooling and water-cooling heat transfer coefficients shown in FIG. 7 may be determined from actual air-cooling and water-cooling experiments and changes in roll thermal expansion amount and in-roll temperature. Next, the thermal crown and roll wear during the rolling operation may be calculated in the same manner as in the conventional technique (S3 in FIG. 3).

  FIG. 8 shows the results of comparing the thermal crown calculation results and measured values 5 minutes and 90 minutes after the end of rolling. As can be seen from the figure, it was found that the initial crown of the reuse roll can be accurately predicted by applying the present invention.

Table 1 shows the accuracy of sheet crown accuracy and sheeting troubles (drawing and semi-finishing) according to the present invention and the prior art for about 2500 rolling materials in a continuous hot rolling mill for about 1 month. The result of having carried out is shown. In the case of the present invention, it can be seen that the plate crown prediction accuracy is significantly improved and the number of stops, which is a trouble caused by the plate shape, is reduced as compared with the prior art. In addition, when the present invention was applied, there was no Hansei, which was a serious trouble during the investigation period.

  In the rolling operation, the next work roll recombination did not have a plan to apply a reuse roll, but there was a case where a plate trouble (squeezing, semi-finishing, etc.) occurred and the work roll recombination was urgently required. is there. In such a case, if the roll grinding is not in time, the rolling operation may be interrupted. When the present invention is adopted, all work rolls to be reused (for example, all high-speed rolls) are targeted. Therefore, even if the above trouble occurs, the stored data shown in FIG. If an appropriate roll is selected and the roll crown prediction calculation of the work roll is performed, adverse effects on productivity can be minimized.

  In the present invention, Patent Document 2 is used for the thermal crown calculation. However, it is not always necessary, and calculation may be performed using a commonly used difference method or finite element method.

Diagram showing thermal crown calculation results when a serious trouble occurs due to plate shape The figure which shows the plate shape calculation result at the time of serious trouble occurrence due to plate shape The figure which shows the calculation flow of this invention Diagram showing the calculation flow of the prior art The figure which shows the thermal expansion amount calculation result during the rolling operation Diagram showing the calculation results of thermal crown behavior from the end of rolling operation The figure which shows an example of the cooling history and elapsed time by this invention Diagram showing the prediction accuracy of thermal crown prediction model

Claims (3)

In the roll crown prediction calculation method for work rolls with less roll wear in the hot continuous finishing mill series,
When roll roll recombination without roll grinding after work roll recombination, the cooling history and elapsed time from the start of the next roll operation to the start of the next rolling operation are saved as data for each work roll, Using the stored data, calculate the axial distribution of the temperature inside the work roll and the amount of thermal expansion at the start of the next rolling operation, and then the axial distribution of the work roll wear amount due to the rolling work before the work roll recombination. The roll crown prediction calculation method of a work roll characterized by adding the calculated value of and predicting a work roll crown.   The roll crown prediction calculation method for a work roll according to claim 1, wherein the roll recombination is performed at least twice and the roll crown of the work roll at the time of starting the next rolling operation is predicted. The roll roll prediction calculation method for a work roll according to claim 1 or 2, wherein the work roll with less roll wear is a high-speed roll.

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