JPH01210106A - Method for preheating rolling roll - Google Patents

Abstract

PURPOSE:To effectively restrain generation of an abnormal crown caused by a heat crown by using a work roll provided with a heat crown over the total roll barrel width. CONSTITUTION:A heat crown is previously imparted over the total roll barrel width of a work roll in a finishing stand of a continuous hot rolling mill. Sharp changes of a roll crown amount caused by a heat crown by an actual rolled stock is prevented and no inflection point is generated by mearly equalizing a heat crown amount in a part where the stock passes to an actual heat crown amount in the stock passing part. Therefore, a good profile without cat's ears is obtained.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a technology for controlling the profile of a hot-rolled steel sheet, and more particularly to a method for preheating a rolling roll in a method for controlling the profile of a steel sheet by preheating a finishing work roll to impart a heat crown. [Technical background] In hot rolling of steel plates, a heat crown equivalent to the width of the rolled material is applied to the work roll at the beginning of the rolling chance, and then a wide material is rolled or the subsequent rolled material is off-center. In many cases, the sharp inflection point of the heat crown on the steel plate is transferred to the steel plate due to the bending of the roll when it is inside the rolled material, resulting in an abnormal crown called "character tear". Figure 4 shows an example of the abnormal profile caused by the heat crown.
The same figure (A> is the profile of a 3 foot wide steel plate, the same figure (
8) is the profile of the steel plate when the width is changed from 3 feet to 4 feet, and the portion inside the dots is a character shape. The occurrence of such an abnormal profile not only causes trouble in the next process, but also becomes one of the factors that hinder the schedule-free hot rolling, so it is necessary to prevent it as much as possible. [Problems to be Solved by the Invention] Conventionally, as a steel plate profile control means for preventing the above-mentioned abnormal profile of a steel plate, work roll benders, variable crown rolls, various shape control mills (work roll shift, HC, etc.) have been used. mill, pair cross mill, etc.), but none of them have been found to be very effective in suppressing the above-mentioned abnormal crowns. To put it bluntly, it is relatively effective to increase the shift amount and amplitude per work roll shift with a large shift length to disperse the heat crown formed in the early stage of rolling in the direction of the roll barrel. In practice, this method tends to cause problems such as promoting bending of the material, and it is difficult to completely suppress abnormal crowns due to heat crowns. This invention was made in order to solve the above-mentioned conventional problems, and is a method for preheating a rolling roll that can effectively suppress the occurrence of abnormal crowns due to heat crowns without requiring a mechanism such as a work roll shift. This is what we would like to propose.

[Means to solve the problem]

The method for preheating a rolling roll according to the present invention includes applying a heat crown to a work roll of a finishing stand of a continuous hot rolling mill in advance over the entire width of a roll barrel, and
By giving the heat crown of the rolled material passage part almost the same value as the heat crown of the rolled material passage part in the presented state, a sharp change in the roll crown due to the heat crown in the actual rolled material is prevented, It is characterized by not producing curved points.

[For production]

Character shine due to heat crown in hot rolled steel sheet
As described above, the heat crown that occurs at the beginning of the hot rolling cycle creates a steep inflection point at the edge of the plate shown in FIG. 4 on the work roll, and this inflection point is transferred. As a means for suppressing the occurrence of such abnormal crowns, it is effective to apply a heat crown to the work roll in advance. In such a case, the heat crown formation pattern would theoretically be such that if the area corresponding to the width of the rolled material is applied by means such as heating to the amount generated by rolling, the heat crown will also grow during subsequent rolling. This method was a common preheating method. Figure 3 illustrates the effect of the preheating method.
A> is a diagram showing the transition of the heat crown without roll preheating, and FIG. 6(B) is a diagram showing the transition of the heat crown during roll preheating. As is clear from this figure, by heating the area corresponding to the rolled material in advance to form a heat crown, it is possible to suppress the subsequent growth of the heat crown. However, with the method of applying a heat crown to the work roll only in an area corresponding to the width of the rolled material, an abnormal profile occurs due to a sharp inflection point of the heat crown that is noticeable when the width changes from narrow to wide or when the material goes off-center. It has no effect at all against (Chara Tsuiya). Another option is to heat the roll part that touches the edge of the sheet online, or to control the heat crown using roll cooling water, but these methods basically make the crown of the entire roll smaller. , local control may create an inflection point in the roll crown. Therefore, in this invention, as a measure to suppress the abnormal profile,
It was discovered that by applying a heat crown over the entire width of the roll barrel of the work roll, a sharp inflection point due to the heat crown during rolling does not occur. When applying a heat crown over the entire width of the roll barrel of a work roll, the specific temperature distribution is to apply a heat pattern of approximately 100°C at the roll center and approximately 40°C at the roll edge at a temperature below the thermal stress of the roll. suitable. The amount of heat crown provided by such temperature distribution is about 0.2 to 0.3 mm at the center of the roll. It has also been confirmed that by applying this degree of heat crown, the roll profile does not change during subsequent actual rolling. Methods for applying a heat crown over the entire length of the roll barrel include: 1) heating the entire length of the barrel with a roll preheater; 2) heating a portion equivalent to the width of the rolled material with a roll preheater to approximately 100°C, and then opening it for a long time. Any method may be used in which the heat is conducted and dispersed over the entire width of the barrel while the temperature is lowered to around 80'C. However, method (2) requires high equipment costs, whereas method (2) has the advantage of lower equipment costs and the ability to provide a uniform heat crown over the entire width of the roll barrel. FIG. 1 is a diagram showing an example in which a heat crown is applied over the entire width of a roll barrel of a work roll using a roll preheater. Note that (C) in the figure also shows an example (conventional example) in which a heat crown is provided only within the width of the rolled material. That is, by applying a heat crown over the entire width of the roll barrel of the work roll as shown in (a) and (b), abnormal crowns such as character wear can be suppressed. Further, among these, the pattern (a) in which a heat crown of about 0.2 to 0.3 mm is provided at the center of the roll has the greatest suppressing effect. In other words, applying a heat crown so that the amount of heat crown at the center of the roll is approximately 0.15 mm from the intersection of the heat crown (C) and a straight line extending perpendicularly from the inflection point (plate end) is the abnormal crown. It is extremely effective in suppressing the occurrence of oxidation, and also reduces the crown. [Example 1 F4 of finishing stand (F+~Fs) of hot rapid rolling mill
Figure 2 shows the effect of suppressing chara-sear when the present invention is applied to the work roll of the F6 stand and the sheet width is changed from 3 feet to 4 feet and the steel sheet is rolled.
Shown below. In this example, the width is 0.2 to 0 over the entire width of the work roll.
．． A preheat roll with a gentle P1-crown approximately 3 mm in size was used. As a result, as is clear from Figure 2 (A > (B)), conventionally when changing the size from narrow to wide, character tear occurred, but when changing from 3 feet to 4 feet, Since there is no steep inflection point caused by the heat crown, we were able to obtain a good profile as shown in the figure.Furthermore, by using the preheat roll of the present invention, it was possible to obtain a good profile without using any other crown control actuator. [Effect of the invention 1] As explained above, according to the method of this invention, the size of the rolled material can be narrowed by using a work roll provided with pea 1 to crown over the entire width of the roll barrel. Even if the width is changed from wide to wide, or if the rolled material becomes off-center, a sharp inflection point due to heat crown can be prevented, so a good profile without character sharpness can be obtained. Since the crown reduction effect is also large, it is possible to significantly improve the round control ability and meet the recent needs for low crown.Furthermore, the provision of a heat crown over the entire width of the roll barrel requires the use of a preheater. Since this can be done relatively easily by adopting this method, it is possible to easily suppress the abnormal profile without sacrificing the need for lower crown without particularly requiring mechanical modifications such as shifting.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example in which a heat crown is provided over the entire width of the barrel of a work roll using the roll preheater of the present invention. FIG. 2 is a diagram showing the effect of suppressing character glare in an embodiment of the present invention, in which Figure (A) shows a profile with a width of 3 feet, and Figure (B) shows a profile with a width of 4 feet. The figure shows the effect of the preheating method, and figure (A> is the transition of heat crown without preheating, figure <8).
shows the transition of heat crown during preheating. Figure 4 is a diagram illustrating an abnormal profile due to heat crown, and Figure (A) is a profile of a 3 foot wide steel plate;
Figure (B) shows the profile of a four foot wide steel plate. (A) Distance from roll center (III) (A) 3 feet width (3) (B) Distance from roll center (1 m) Figure 4 (B) 4 feet + 1+

Claims (1)

[Claims] 1. When controlling the steel plate profile by adding a heat crown to the finishing work roll of a continuous hot rolling mill in advance, the heat crown of the part where the rolled material passes is approximately the same value as the heat crown of the part where the rolled material passes in a steady state. A method for preheating rolling rolls, which is characterized in that a heat crown is applied over the entire width of a roll barrel.