JPH04721B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a hot finish rolling method for hot strip. [Prior Art] In conventional hot finishing rolling equipment, finishing rolling is performed in which the bar thickness (thickness of the hot strip) is sequentially reduced by passing the hot strip through a number of finishing stands. Since only horizontal rolling is performed, the width of the strip is not constant and edge drops occur. For this reason, JP-A-51-103059, JP-A-54-
117355 and Japanese Patent Application Laid-Open No. 55-75802, it has been proposed to install width rolling equipment on the entry or exit side of the finishing rolling equipment or between the finishing rolling stands to perform width rolling to eliminate the above-mentioned problems. Therefore, Japanese Patent Application Laid-Open No. 51-103059 relates to an edge drop straightening device that prevents edge drops by installing a pair of vertical rolls close to the exit side of the final stand of a finishing rolling facility and performing a slight width reduction of 1 to 10 mm. It is. JP-A-55-75802 is equipped with a pair of vertical rolls on the entrance side of the rolling stand, and in order to prevent buckling due to width reduction, width reduction is applied to within 1/2 of the plate thickness on the entrance side of the vertical rolls to reduce edge drop. It is something that makes you However, when these techniques were actually tested, it was found that because the hot strip was thin (bar thickness was small), it buckled even under a slight width reduction, making it difficult to implement industrially. The technology disclosed in JP-A-54-117355 is aimed at reducing the temperature drop when the width of the bar is varied, and the bar thickness is increased and the width is reduced at the entry side of the finishing rolling equipment or at the front stage of the finishing rolling equipment to achieve the above purpose. It is something to do. However, this technology aims to prevent buckling due to width reduction by increasing the bar thickness, and to reduce temperature drop by reducing the surface area, so increasing the bar thickness is an essential requirement. Therefore, the finishing rolling equipment is required to have a large thickness reduction capability, which cannot be used with existing equipment. As mentioned above, in the method of reducing the width without applying tension, the limit is to reduce the width by 1/2 of the plate thickness, that is, the bar thickness, and therefore it is difficult to expect a sufficient improvement in edge drop. I couldn't do it. Further, in JP-A No. 57-160509, a vertical roll with a flange for edging a rolled material is arranged between the stands of a hot finishing rolling mill, and the opening degree of the vertical roll with a flange is controlled while controlling the tension of the rolled material. This has been shown to reduce the constraints of buckling phenomena and provide the necessary amount of width control. [Problems to be Solved by the Invention] However, the above-mentioned Japanese Patent Application Laid-Open No. 57-160509 only performs etching by arranging a pair of vertical rolls with flanges for width reduction between the hot finishing mill stands. Therefore, if the above width reduction is performed on the front side of the hot finishing mill, a large width reduction can be obtained due to the thick bar thickness and the application of tension, but the subsequent horizontal rolling There is a problem that edge drops occur and the width accuracy decreases, and even if the width reduction is performed at the later stage of the hot finishing mill, the bar thickness is thin, so even if tension is applied, the amount of width reduction is larger than a certain level. Therefore, there are problems in that it is not possible to obtain a sufficient width control amount, and it is not possible to control the plate crown. SUMMARY OF THE INVENTION The present invention aims to provide a hot finish rolling method that effectively reduces edge drops occurring in hot strips, enables sheet crown control, and prevents sheet width non-uniformity. [Means for Solving the Problems] The inventors of the present invention have conducted various experiments to reduce edge drops and improve strip width accuracy with low investment in equipment, and as a result, they have developed a state in which tension is applied to the hot strip during rolling. We obtained the knowledge that the buckling strength of the hot strip can be greatly improved by width reduction, and the amount of width reduction can be increased up to 2 to 3 times compared to the case without tension. Between the pre-finishing stands in the early stage of rolling, width reduction is performed mainly by final width adjustment and plate crown control, and between the finishing stands where the plate is thinner, width reduction is performed mainly by improving the edge drop at the ends of the hot strip in the width direction. He perfected the hot finish rolling method. That is, in the present invention, at least one edger is arranged between the front-stage stands and between the rear-stage stands of a hot finishing rolling line, and both are under tension, and the front-stage edger is 50 to 250% of the bar thickness between the stands. Hot finish rolling is characterized by performing final width adjustment and plate crown control by performing a width reduction of It depends on the method. [Function] The edger installed between the stands on the front stage of the hot finishing rolling line performs sheet crown control for final width adjustment by reducing the width by 50 to 250% of the bar thickness between the stands under tension. In addition, in the edger installed between the stands on the latter side of the hot finishing rolling line, when tension is applied, the bar thickness between the stands is 50~
Edge drop is improved by performing a 150% slight width reduction. The degree of tension applied is preferably 0.02 to 0.4 times the yield stress of the rolled material. As a method for applying tension to the hot strip, a known method may be applied depending on the characteristics of the hot finishing mill used. [Example] Hereinafter, an example of the present invention will be described with reference to the drawings. FIGS. 1 and 2 show an example of rolling equipment for carrying out the rolling method of the present invention, in which hot finishing stands 11 to 17 are arranged in the running direction of the hot strip s, and the first stand 11 and 2nd stand 12
and between the 6th stand 16 and the final stand 17
A vertical rolling stand (edzier) 21 is installed between the
22 are arranged respectively. Here, the hot finishing rolling stands 11 to 17 can be used not only in a four-high rolling mill as long as they can perform horizontal rolling. When hot finishing rolling the hot strip s in the hot finishing rolling line configured as described above, the rolling stands 1 before and after the vertical rolling stand 21 on the front stage side are used.
By changing the circumferential speed of work rolls 31 and 32 of No. 1 and 12 (for example, work roll 3 of No. 1 stand 11)
), the first stand 11 and the second stand
The width of the hot strip s1 between the stands 12 is reduced by the vertical rolling stand 21 while the tension of the hot strip _s1 is increased. In this case, since the hot strip _s1 is under tension, its buckling strength is increased, so that the amount of width reduction can be increased up to two to three times that of the conventional method. Therefore, plate crown control becomes easy and the final width adjustment amount can be increased. Further, in the rear vertical rolling stand 22, the rolling stands 16, 1 before and after the vertical rolling stand 22 are
By changing the circumferential speed of the work rolls 36 and 37 of No. 7 (for example, making the circumferential speed of the work roll 37 of the final stand 17 faster than the circumferential speed of the work roll 36 of the sixth stand 16), the circumference between the rolling stands 16 and 17 is changed. The tension of the hot strip _s2 is increased, and the width is rolled down by the vertical rolling stand 22. In this case, the hot strip _s2 becomes even thinner toward the latter stage, and its buckling strength drops significantly, but by applying tension, the buckling strength improves and a slight reduction in width becomes possible. Therefore, the accuracy of the final product width can be improved and edge drop can be improved. Here, it is preferable that the width reduction amount of the first stage vertical rolling stand 21 has a maximum width reduction capacity of approximately 250% with respect to the bar thickness in order to sufficiently adjust the width of the final product and control the plate crown. Further, the width reduction of the rear vertical rolling stand 22 is carried out for the purpose of improving edge drops at the ends of the hot strip in the width direction, and it is preferable to have a width reduction capacity of about 150% at maximum with respect to the bar thickness. Figure 4 shows the results obtained in a model experiment (model ratio 1/10) for actual hot-working steel using hard lead (material hardness K _f = 2.6 Kg/mm ² ) with edger entry width W ₀ = 100 mm (constant). This shows the relationship between the plate width ratio (edger entry width W ₀ / edger entry width bar thickness t ₀ ) and width reduction ratio (width reduction amount ΔW / edger entry width W ₀ ).
The maximum rolling reduction (buckling limit) in conventional width rolling without applying tension between stands is small as shown by the solid line, whereas in the case of the present invention with a tension of 0.3 kg/ ^mm2 , the maximum rolling reduction ( The buckling limit) increased as shown by the broken line, and the width reduction area was expanded by the shaded area. In Fig. 4, when no tension is applied, there is also a limit due to the bite limit for the roll diameter (30φ, 60φ), but when tension is applied as in the present invention, the influence of the roll diameter is not clearly seen. Nakatsuta. Figure 5 shows the results of the model experiment shown in Figure 4 above.
Converted to 1000mm (constant), relationship between plate thickness (mm) and possible width reduction (mm), and plate thickness (mm) and possible width reduction when applying tension/plate thickness (bar thickness) ×100
%, and the solid lines are for the entrance bar thickness, which has been conventionally used.
The case where width reduction of 50% is performed is shown, and the broken line shows the case where tension is applied to each case and width reduction of the present invention is performed. In the present invention, as shown in Fig. 5, width reduction is performed by 50 to 250% with respect to the entrance bar thickness on the front stage side of the hot finishing rolling line, and on the rear stage side with respect to the entrance bar thickness.
Set the width reduction range to perform width reduction of 50 to 150%. In other words, the bar thickness on the front stage side of a hot finishing rolling line is usually about 50 mm at maximum, so the value when the bar thickness is 60 mm with a little margin,
In other words, the upper limit is a width reduction of 250% of the entry bar thickness, and sufficient final width adjustment and plate crown control (especially concave plate crown) can be achieved with a width reduction of 50% relative to the entry bar thickness. Therefore, by setting this 50% as the lower limit and performing a width reduction of 50 to 250% with respect to the entrance bar thickness, final width adjustment and plate crown control can be performed favorably. Also, as shown in the figure, a large width reduction can be taken for the thin bar thickness on the rear stage side, but the main purpose of the rear stage side is to improve edge drop, and in contrast, the width reduction is 150% of the bar thickness on the entrance side. If the width is reduced more than this, there is a problem that the edge part will have an ear.
% width reduction is the upper limit, and since it is not possible to sufficiently prevent edge drop with a width reduction of 50% compared to the conventional entrance bar thickness, this 50% is set as the lower limit, and the width reduction is 50 to 150% relative to the entrance side bar thickness. The edge drop can be effectively improved by performing a width reduction of 50%. Note that the hot finish rolling method of the present invention is not limited to the above-mentioned example; the vertical rolling stand may be installed anywhere on the line as long as it is between the hot finish rolling stands; It goes without saying that various modifications can be made without departing from the gist of the present invention, such as being able to install more than just a stand. Specific examples of the present invention will be listed together with comparative examples. Table 1 shows the rolling conditions, and other rolling conditions are as follows. Rolling material specification steel Type: Low carbon aluminum killed steel Rough rolling dimensions: 40mm x 1320mm Finished dimensions: Invention: 3.5mm x 1300mm Comparative example: 3.5mm x 1320mm Rolling pass schedule (bar thickness when passing through each pass)

[Table] The rolling mill used is the one shown in Figure 1, and Comparative Example 1 was a conventional rolling mill without vertical rolls. The tension was generated by controlling the rotation speeds of the horizontal rolls 11, 12 and 16, 17.

[Table] The edge drop, plate crown, and width accuracy of the hot strips obtained by rolling were measured, and the results shown in Table 2 were obtained.

[Table] As shown in Table 2 above, the method of the present invention was able to significantly reduce edge drop and plate crown as compared to the comparative example, and was also able to further improve width accuracy. Note that the edge drop and plate crown referred to in the present invention are defined as follows. In other words, the strip profile SP is shown in Figure 3.
However, the edge drop Ed approximates the center curve of the strip profile SP to a quartic curve, and deviates from this curve with the thickness t ₂ of the starting point A and 5 from the edge.
mm Defined as the difference between the inner point B and the thickness _t1 . In addition, the plate crown Cr is defined as the difference between the thickness t ₃ at the center position in the width direction and the thickness t ₁ at a point 5 mm inside from the edge. Width accuracy is determined by measuring actual rolling width and target width. [Effects of the Invention] As described above, the hot finish rolling method of the present invention exhibits various excellent effects as described below. () By placing edgers between stands on the front and rear sides of the hot finishing rolling line and reducing the width while applying tension to the hot strip, the possible width reduction amount is increased. By performing width reduction of 50 to 250%,
Even if the strip is rolled in the thickness direction on the next horizontal stand, traces of the dog bones at the edges in the strip width direction remain.In other words, the strip crown can be controlled by strongly reducing the width so as to change the body crown of the hot strip. At the same time, the amount of final width adjustment can be increased, and edge drop can be effectively improved by reducing the width by 50 to 150% of the entrance side bar thickness on the later stage side. () When carrying out the present invention, only a vertical rolling stand is provided between the hot finishing rolling stands, so the equipment is simple and a conventional hot finishing rolling line can be easily modified. () With relatively simple equipment, the board width is constant,
A strip with fewer edge drops can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic plan view of an example of equipment for implementing the method of the present invention, FIG. 2 is a schematic side view of an example of equipment for implementing the method of the present invention, FIG. 3 is an explanatory diagram explaining the definitions of edge drop and crown, Figure 4 shows the expansion area of width reduction due to the addition of tension in a model experiment for hot-worked steel with hard lead specification, and Figure 5 shows the relationship between plate thickness and possible width reduction, and the relationship between plate thickness and width reduction when tension is applied. It is a diagram showing the relationship between possible width reduction amount/bar thickness x 100%. 11 to 17 are hot finishing rolling stands; 21, 2;
2 is a vertical rolling stand, and s, s ₁ and s ₂ are hot strips.

Claims (1)

[Claims] 1 At least one edger is arranged between the stands on the front stage and between the stands on the rear stage of the hot finishing rolling line, and both are in a tensioned state, with the front stage having a thickness of 50 to 250% of the bar thickness between the stands.
The final width adjustment and plate crown control are performed by reducing the width of
A hot finish rolling method characterized by improving edge drop by performing a width reduction of 150%.