JPH0549361B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) When using a metal plate as a structural member, there are many cases in which the required strength differs depending on the part, and in such cases, a plate whose thickness changes locally may be required. Specifically, such metal plate products with variable plate thickness include corrugated plate a whose plate thickness changes in a wavy manner, tapered plate b whose plate thickness changes in a sloping manner, and plate thickness as shown in Fig. 3 a to c. Different thickness plate c with a shape that connects flat plates with different
etc. The present invention relates to a method of rolling a plate whose thickness changes in an arbitrary pattern, including the above-mentioned various plates. (Prior art) In rolling a metal plate product with variable thickness (hereinafter simply referred to as a steel plate with different thickness), the rolling device is operated only in the final pass, as described in Japanese Patent Publication No. 46-37086, for example. A control method is adopted in which the gap between the rolls is sequentially changed from the rolling biting position. However, this method does not give any consideration to the effect on the flatness of the rolled material. (Problems to be Solved by the Invention) Normally, when a differential thickness steel plate is manufactured by rolling from a material having the same thickness in the longitudinal direction, distortion occurs in the rolled material during a pass that changes the thickness. When the occurrence of this distortion is significant, waves at the center of the rolled material called medium waves and waves at the edges of the rolled material called ear waves are formed, resulting in the difference in thickness of the rolled steel plate. This results in a lack of flatness. The present invention provides a rolling method that can maintain good flatness when rolling a differential thickness steel plate to be processed. (Means for Solving the Problems) The present invention provides (1) in manufacturing a metal plate product whose thickness changes in the longitudinal direction by rolling a material having the same thickness in the longitudinal direction, the metal plate Rolling of a flat plate whose maximum thickness is the flat plate product thickness and a flat plate whose minimum thickness among the metal plate products is the flat plate product thickness, starting from a material with the above-mentioned thickness and finishing with the same number of passes. A pass schedule is created, and when rolling the material of the metal plate product, the target pass thickness of the maximum thickness part in each pass is set to the target pass thickness of the pass schedule for the maximum thickness flat plate mentioned above, and the target pass thickness of the minimum thickness part is set. The target pass thickness of the pass schedule for the above minimum thickness flat plate is the target pass thickness, and the target pass thickness of the intermediate thickness section is the target pass thickness of the two types of flat plates. This is a rolling method characterized by rolling according to a rolling pass schedule in which values are internally divided by an internal division ratio. (2) In the rolling method described in (1) above, the rolling pass schedule for the minimum thickness flat plate is such that the rolling reduction amount per pass is increased to the limit that can maintain the flatness of the minimum thickness flat plate, and A rolling pass schedule is created in which the reduction amount per pass is reduced to the limit that can maintain the flatness of the maximum thickness flat plate, and between the passes in the same order in the reverse order from the last pass of the above two types of rolling pass schedules. Find the first pass in which the target pass thickness of the rolling pass schedule for the minimum thickness flat plate exceeds the target pass thickness of the rolling pass schedule for the maximum thickness flat plate, and calculate the target pass thickness of the rolling pass schedule for the maximum thickness flat plate in that pass in the same pass. The rolling pass schedule of the maximum thickness flat plate is modified to match the target pass thickness of the rolling pass schedule of the minimum thickness flat plate, and on the first pass side, the same rolling pass schedule as the rolling pass schedule of the minimum thickness flat plate is changed to the rolling pass schedule of the maximum thickness flat plate. (3) To be adopted as a rolling pass schedule.
In the rolling method described in (2) above, check whether the flatness of the flat plate can be maintained with respect to the rolling pass schedule for the maximum thickness flat plate, and if it is not possible, the first pass determined above is repeated one by one on the first pass side. (4) In the rolling method of (1), (2), and (3) above, , create a rolling pass schedule for a plurality of flat plates in which the thickness between the maximum thickness and the minimum thickness in the metal plate product is the thickness of the flat plate product, and create a rolling pass schedule for the intermediate thickness part of the metal plate product. It is preferable to use an internal division ratio to create the rolling pass schedule for two flat plates having the target thickness of the intermediate thickness portion and the target thickness sandwiching the intermediate thickness portion. (Function) There is a lot of knowledge regarding the rolling of so-called flat plates having the same thickness in the longitudinal direction, and it is easy to create a rolling pass schedule for rolling flat plates. In the present invention, the rolling pass schedule of a flat plate having the same thickness is applied to the maximum and minimum thickness parts of the differentially thick steel plate to be processed, thereby suppressing the distortion in each part to below the wave generation limit. In addition, for the intermediate thickness part between the maximum thickness part and the minimum thickness part, by giving the target pass thickness in each pass by internally dividing the maximum thickness part and the minimum thickness part, the amount of reduction in each pass can also be applied to the maximum thickness part. Since the amount of rolling is the internal division of the amount of rolling and the amount of rolling of the minimum thickness part, the rolling reaction force is also approximately the internal division of the reaction force of the maximum thickness part and the reaction force of the minimum thickness part. Furthermore, if there is a rolling pass schedule that can roll flat plates of the same width and different thickness with good flatness, it is possible to achieve flatness by using a rolling pass schedule in which both the exit side plate thickness and reaction force in each pass are divided in the same ratio. A flat plate with a good intermediate thickness can be obtained. Therefore, by the rolling pass schedule of the differentially thick steel plate to be processed in the method of the present invention, a plate with good flatness can be obtained while suppressing distortion even in the intermediate thickness portion. Furthermore, by using the method (2) above, it is possible to reduce the number of passes in which the roll gap is changed during rolling passes, thereby improving productivity. (Example) An example of the present invention will be described with reference to FIGS. 1 to 3. Flat plate rolling pass schedule proposed by Yokoi et al. (Yokoi and Misaka: Plasticity and Processing, 16-168, (1975),
10.). In this method, the rolling reaction force of each rolling pass is calculated as Fi=αHi+β...(1) Fi: i-pass rolling reaction force Hi: i-pass exit side plate thickness α: Coefficient that determines plate crown β: When performing constant crown ratio rolling is the coefficient of the equation that determines the rolling reaction force, and this β is
For each rolling pass, there is a range, that is, an upper limit value and a lower limit value, for suppressing the corrugation of the steel sheet within an allowable range. These values are determined by the thickness and width of the steel plate, the specific conditions of the rolling mill, etc., and are therefore determined empirically and used in practice. When creating a rolling pass schedule for a flat plate,
According to the above theory, depending on how the values of α and β are taken, there is a rolling pass schedule in which the rolling reaction force in the finishing pass is relatively large (hereinafter referred to as the heavy rolling pass schedule), and a rolling pass schedule in which the rolling reaction force in the finishing pass is relatively small (hereinafter referred to as the heavy rolling pass schedule). (hereinafter referred to as a low-pressure pass schedule) can be created separately. However, in actual rolling, if α is made extremely large, the rolling reaction force in the finishing pass of rolling becomes large, resulting in problems such as impairing plate thickness accuracy and exceeding the capacity limit of the rolling mill drive motor in the middle pass. Therefore, there is a practical upper limit to the value of α that can be selected. On the other hand, if α is made too small, not only will the number of rolling passes increase and rolling efficiency will decrease, but the temperature of the material to be rolled will drop, making it difficult to continue rolling, so there is no practical lower limit for α. be. Further, β has upper and lower limits to prevent waves from forming on the plate, and the width thereof generally increases as the plate thickness increases. The procedures in FIGS. 1a to 1c correspond to means (1) and (2) above. In creating a rolling pass schedule for a differential thickness steel plate to be machined, the upper limit value βa of β and the maximum value αa of α for βa are determined for a flat plate having the target minimum thickness Hmin of the target differential thickness steel plate in Fig. 1a. A strong reduction pass schedule to be used is created and is called A schedule, which is a rolling pass schedule corresponding to the minimum thickness of the differential thickness steel plate to be processed. Here, the exit side plate thickness at the finished pass, that is, the n-th pass counting from the final pass, is expressed as Han, and the reaction force is expressed as Fan.
The lower limit value βb of β for a flat plate with the machining target maximum thickness Hmax of the differential thickness steel plate to be machined and α for βb
A weak pressure pass schedule using the minimum value αb of is created and is called the B schedule. Here, the exit side plate thickness at the nth pass counted from the finished pass is
Hbn, reaction force is written as Fbn. In the A and B schedules obtained by the above method, find the first path where Han≧Hbn. In Figure 1b (4)B
By gradually increasing the schedule α, the exit plate thickness of each pass is increased and the B schedule is modified so that Hbn=Han. The final n-1 passes of the modified B schedule and the schedule from the rolled material to the plate thickness Han of the A schedule are connected and called the B schedule again. Since the flatness of the B schedule is not guaranteed in connection with the A schedule, it is determined whether the flatness can be maintained. If the flatness is acceptable, this is set as a pass schedule corresponding to the minimum thickness and maximum thickness of the differentially thick steel plate to be processed, that is, the minimum thickness schedule and maximum thickness schedule. For distortion, n
Increase by 1 and perform the following steps. There are various methods to check whether flatness can be maintained, but a simple method is to set the B schedule to the exit side plate thickness.
Stop at Hbn and calculate α and β from the plate thickness and rolling reaction force of the final two passes, and check whether the values are within the allowable value for maintaining flatness when Hbn is the product thickness. be able to. If more strict guarantee is required, for example, the relationship between sheet crown ratio change and flatness (edited by the Iron and Steel Institute of Japan, Special Report No. 36 Theory and Practice of Sheet Rolling, p. 96) may be used. In FIG. 1c, the rolling pass schedule is determined as follows for creating the schedule for the intermediate thickness portion of the differential thickness steel plate to be machined. The plate thickness at position I from the tip of the plate to be processed is H (I).
Then, the internal division ratio P(l) for the maximum thickness and minimum thickness of the differential thickness steel plate to be processed is P(l) = (Hmax-H(l))/(Hmax-Hmin)
... Find (2). The target thickness Hi (Li) at the position Li in the i pass corresponding to the position l of the differential thickness steel plate to be processed is the target thickness of the A schedule and B schedule P: (1-
The internally divided value Hi(Li)=PHai+(1-P)Hbi (3). Assuming that Li is a variable thickness material and the volume from the plate tip to Li is equal to the volume from the plate tip to l, ∫ ^l ₀ H (l) dl = ∫ ^Li ₀ Hi (Li) dLi ……(4) It can be determined using a mathematical formula. Also, the reduction amount corresponding to Hi (Li) is ΔHi (Li) = Hi (Li ₊ 1) - Hi (Li) = P (Hai ₊ 1 -
Hai) + (1-P) (Hbi ₊ 1-Hbi) = PΔHai + (1
-P) ΔHbi...(5) ΔH: Reduction amount. As can be seen from equations (3) and (5), both the exit plate thickness and the reduction amount are the values that correspond to the minimum and maximum thickness parts of the differential thickness steel plate to be processed, divided internally by P: 1 - P. There is. In such a case, it is known that the rolling reaction force in that pass also has a substantially similar internal division value Fi(Li)≈PFai+(1-P)Fbi (6). Furthermore, as in this case, when the exit side plate thickness and rolling reaction force of the i-pass are both given by the same internal division ratio of rolling schedules A and B, which have good flatness, rolling according to that schedule results in good flatness. You can get a good board. In the above method, in addition to the B schedule corresponding to the maximum thickness part of the differential thickness steel plate to be processed, a C schedule is created as a rolling pass schedule for a flat plate whose thickness is an arbitrary intermediate thickness Hm of the differential thickness steel plate to be processed, In the part where H(l)<Hm, A schedule and C
Internal division of schedule, C in the part where H(l)<Hm
It is also possible to create a rolling pass schedule for the intermediate thickness section by dividing the schedule and B schedule internally. Furthermore, if the number of rolling pass schedules for the flat plate to be created is increased and internal division with finer divisions is applied, accuracy can be expected to improve.
Note that it is also possible to apply only (1) without applying the means (2) of the present invention, and to adopt a rolling pass schedule in which the roll gap is changed during all the rolling passes as shown in FIG. 2. be. Table 1 shows examples in which corrugated plates were rolled by the conventional example and each method shown in the present invention. Case A is a conventional example in which a thickness difference in the longitudinal direction is provided only in the final pass. Case B is a case of manufacturing by the rolling method described in means (2) above. in this case,
The final three passes are used to provide a difference in plate thickness. Case C is a case where only the above-mentioned means (1) is applied, and the roll gap is changed during the rolling pass over all passes. Table 2 shows the pass schedule for the target finish thickness pattern a for each case. The subscript i represents the pass number, Ha and Fa represent the exit side plate thickness and reaction force of each pass at the minimum thickness section, respectively, and Hb and Fb represent the output side plate thickness and reaction force of each pass at the maximum thickness section, respectively. The units of Ha and Hb are mm,
The units of Fa and Fb are TON. In addition, the first pass,
The second pass is a tentering pass. The actual rolling results will be explained below according to Table 1. In case A, medium waves were generated in the large thickness area and significant ear waves were generated in the small thickness area in all plate pressure patterns, and re-correction was required. Particularly in the case of target finishing plate thickness pattern b, the waves are not corrected even after re-straightening, and they end up as scraps. On the other hand, in case B and case C,
For all target finishing plate thickness patterns, sufficient flatness was obtained at least after re-straightening.
Controlling the thickness difference over all passes reduces the rolling speed, which increases the rolling time, but in Case C, the flatness is already sufficient at the end of rolling. , no re-correction was necessary.

【table】

【table】

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to manufacture a differential thickness steel plate having extremely good flatness over the entire length.

[Brief explanation of drawings]

Figures 1 a to c are diagrams showing a specific example of the procedure of the present invention, Figure 2 is a diagram showing an example of a rolling pass schedule in which the roll gap is changed during all rolling passes, and Figure 3 a -c are diagrams showing examples of metal plates whose thickness changes in the longitudinal direction.

Claims (1)

[Claims] 1. In manufacturing a metal plate product whose thickness changes in the longitudinal direction by rolling a material having the same thickness in the longitudinal direction, the maximum thickness of the metal plate product is determined in advance as the thickness of the flat plate product. A rolling pass schedule is created in which rolling is started from a material with the same thickness and finished with the same number of passes for a flat plate whose thickness is the minimum thickness of the metal plate product, and a flat plate whose thickness is the minimum thickness of the metal plate product. When rolling a material of As the target pass thickness, the target pass thickness of the intermediate thickness portion is set as a value obtained by internally dividing the target pass thickness of the two types of flat plates by the internal division ratio of the intermediate thickness to the maximum target thickness and minimum target thickness in the metal plate product. A rolling method characterized by rolling according to a rolling pass schedule. 2. As the rolling pass schedule for the minimum thickness flat plate, a schedule in which the amount of reduction per pass is increased to the limit that can maintain the flatness of the minimum thickness flat plate is adopted, and as the rolling pass schedule for the maximum thickness flat plate, the flatness of the maximum thickness flat plate is adopted. Create a schedule in which the rolling reduction amount per pass is reduced to the limit that can maintain the rolling pass schedule, and calculate the target pass thickness of the rolling pass schedule for the minimum thickness flat plate between the passes in the same order in reverse order from the final pass of the above two types of rolling pass schedules. Find the first pass in which the target pass thickness of the rolling pass schedule for the maximum thickness flat plate exceeds the target pass thickness of the rolling pass schedule for the maximum thickness flat plate, and convert the target pass thickness of the rolling pass schedule for the maximum thickness flat plate in that pass to the target pass thickness for the rolling pass schedule for the minimum thickness flat plate in the same pass. The rolling pass schedule of the maximum thickness flat plate is modified to match the thickness, and on the first pass side, the same rolling pass schedule as the rolling pass schedule of the minimum thickness flat plate is adopted as the rolling pass schedule of the maximum thickness flat plate. The rolling method according to item 1. 3 Check whether the flatness of the flat plate can be maintained according to the rolling pass schedule of the maximum thickness flat plate, and if it is not possible, change the first pass calculated above to 1.
3. The rolling method according to claim 2, wherein the flatness is checked while changing the pass to the first pass side, and the rolling pass schedule of the maximum thickness flat plate is corrected until the pass becomes passable. 4 Create a rolling pass schedule for a plurality of flat plates in which the thickness between the maximum thickness and the minimum thickness in the metal plate product is the thickness of the flat plate product, and set the rolling pass schedule for the intermediate thickness part of the metal plate product to the rolling pass schedule of the metal plate product. The rolling according to claim 1, 2, or 3, which is created using an internal division ratio from a rolling pass schedule of two flat plates having a target thickness of the intermediate thickness portion and a target thickness sandwiching it. Method.