JPS6250017A - Straightening device for hot steel sheet - Google Patents

Abstract

PURPOSE:To perform the straightening of a steel sheet effectively and to increase the quality of product by performing an optimum cooling by using the cooling means provided by dividing in the width direction according to the temp. on the front and back face of the steel sheet and the shape of the steel sheet. CONSTITUTION:The shape measurement is performed by a shape measuring means 7 and the temp. on the surface and back face of a steel sheet 4 are measured by thermometers 6a, 6b as well in case of straightening a hot steel sheet 4 by passing it between the upper and lower straightening rolls 1-3 arranged the upper and lower in zigzags. By performing the flow adjustment of cooling sprays 5a, 5b so that the differential temp. between the surface and back face of the steel sheet 4 becomes in the necessary temp. difference, the steel sheet is effectively straightened by overlapping the deflection due to bending and the deflection due to thermal gradient. The straightening is thus performed effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a hot steel plate straightening device for correcting defective shapes of a steel plate by passing the plate between straightening rolls, and in particular, the present invention utilizes a thermal gradient, The present invention relates to a hot steel plate straightening device that effectively corrects poor flatness of a steel plate.

(Prior Art) Conventionally, in order to correct the warpage of a steel plate, as shown in Fig. 1, a plurality of upper straightening rolls L and a plurality of lower straightening rolls are arranged in a staggered manner. The steel plate 4 is threaded using a straightening device having a straightening device, and the internal stress is reduced by repeatedly bending the steel plate.

The flatness defects of rolled steel plates can be roughly divided into shape defects and warpage defects. Shape defects are caused by differences in elongation of the material in the longitudinal direction, and this results in ear waves and back waves, and these shape defects are particularly common in thin steel plates.

Conventional straightening devices are designed to correct warpage (particularly warpage in the longitudinal direction) of steel sheets by reducing residual stress. Therefore, it is suitable for straightening thick steel plates with few shape defects, but for thin steel plates with many shape defects, plastic elongation (in the case of ear waves, abdominal stretch, return wave In this case, it is not possible to provide for the elongation of the ears), and the correction ability is low.

As a method for correcting partial distortions such as ear waves and return waves, Japanese Patent Application Laid-open No. 1983-
No. 148414 is disclosed. This method optically measures the surface shape of a steel plate, converts the measurement result into a pattern, detects it, and then uses a roller leveler equipped with a roll bending device to change the shape of the steel plate in accordance with the detected patterns. This is a method of correction.

(Problem to be solved by the invention) However, with the above-mentioned method, it is impossible to provide a free bending shape according to the shape of the distortion (quarter buckle, etc.). It is insufficient as a corrective method for.

(Means for Solving the Problems) The purpose of the present invention is to provide a straightening device for straightening steel plates that can eliminate and improve the drawbacks and problems of conventional devices. The above object can be achieved by providing a hot steel sheet straightening device according to the claims. That is, the present invention provides a straightening device for straightening a hot steel sheet by passing the sheet between upper and lower straightening rolls arranged in a staggered manner, including a shape measuring means for measuring the shape of a rolled steel sheet, and a shape measuring means for measuring the shape of a rolled steel sheet; A means for measuring the temperature of the front and back surfaces of the steel plate during threading, and a cooling pattern corresponding to the temperature difference based on the shape measurement by the shape measuring means are set in the longitudinal direction between the straightening rolls. The present invention relates to a hot steel plate straightening device including cooling means installed in a staggered manner.

First, the principle of straightening a steel plate using the apparatus of the present invention will be explained with reference to FIG. The radius of curvature between the roll l and the thickness center line is P
1. The thickness of the steel plate 4 is 6t, the distance from the center line in the thickness direction to the skin is h, and the bending stress at an arbitrary point is σh.

The strain 6h at an arbitrary point is expressed as in equation (1).

Further, if Young's modulus is IE, the stress σh will be expressed by equation (2).

εh = h/ρ ・・・・・・・・・
...(1) σh=Eεh= Eh/P ...
...(2) If this stress σh becomes larger than the yield stress σh, the steel plate will yield in the range from the skin to h''! This range is the plastic yield region, and the larger this yield region, the greater the yield stress. The straightening effect becomes higher.However, conventional straightening devices can only apply a uniform longitudinal stress in the width direction.As mentioned above, in order to correct partial strain, it is possible to apply uneven stress (strain) in the width direction of the steel plate. It is necessary to apply a larger stress (larger stress) to the part where there is no strain than to the part where there is strain.One way to apply this stress was to use a thermal gradient.

As an example, the explanatory diagram of the heat distribution in Figure 3 (fa), Figure 3 (
As can be seen from the explanatory diagram of the thermal strain distribution in b), if there is a linear thermal gradient on the steel plate, the thermal strain εT at any point on the steel plate is expressed as in equation (3).

Here, TU is the temperature of the upper surface of the plate, TL is the temperature of the lower surface of the plate (TU < TL), α: coefficient of linear expansion, and t: thickness of the plate.

First, if an attempt is made to keep the steel plate 4, whose upper surface is lower in temperature, flat, tensile strain will occur on the upper surface of the steel plate 4, as shown in FIG. 3(b). The relationship shown in Figure 3(b) can be expressed as
As shown in FIG. 4, by superimposing the state shown in FIG. 4, the region of high stress, that is, the yield region, where thermal stress 4b is added to bending stress 4a, increases, and the straightening effect becomes high.

The present invention is based on the above-mentioned findings, and is a straightening device for straightening a hot steel plate, which applies a thermal gradient to the front and back sides of the hot voice plate to increase the yield area and perform the straightening.

Hereinafter, the present invention will be explained with reference to the drawings.

FIG. 1 is an explanatory diagram of the arrangement of the correction apparatus of the present invention, in which several leveling rolls are arranged in a staggered manner. 1 is an upper leveling roll, 2 is a lower leveling roll, 3 is a backup roll, and 4 is a steel plate passed between the upper leveling roll 1 and the lower leveling roll 2 to undergo straightening. A cooling spray nozzle 5b is installed below the upper leveling roll l via the steel plate 4, and a cooling spray nozzle 5b is installed below the lower leveling roll 2.
Cooling spray nozzles 5a are also installed above the steel plate 4, respectively. These spray nozzles 5a,
A plurality of nozzles 5b are installed in the width direction, and the flow rate of each nozzle can be adjusted by a flow rate adjustment valve (not shown in the drawing).

Further, in front of each nozzle, a plurality of thermometers 6a for measuring the steel plate temperature on the front side of the steel plate and a plurality of thermometers 6b for measuring the steel plate temperature on the back side of the steel plate are installed in the width direction of the steel plate.

In addition, a shape measuring device 7 for measuring the distorted shape of the steel plate is installed in front of the straightening device.

Next, a method for straightening a hot steel plate using the apparatus of the present invention will be explained.

The steel plate 4 is straightened based on the strain measured by the shape measuring device 7, but as shown in FIG. Due to the limitation, only a strain of ε1 can be applied, but if a temperature difference Δto can be applied between the front and back surfaces of the steel plate 40, the amount of strain ε0 necessary for straightening the steel plate can be reached.

Measure the temperature difference Δtl between the front and back surfaces of the steel plate 4 with a thermometer 6a.

6b, and by adjusting the flow rates of the cooling sprays 5a and 5b so that the required temperature difference ΔtO as shown in FIG. It improves effectiveness. The same applies when there is a partial strain on the steel plate 4, and the strain on the rolled steel plate is measured using a shape measuring device @7 (for example, a shaver that projects a slit-shaped light beam onto the object to be measured and calculates the strain from the reflected light). Then, a target temperature difference according to the strain shape is determined by calculation as shown in FIG.

In order to obtain this target temperature difference, first, the temperature of the front and back surfaces of the steel plate 4 on the entrance side of the straightening device is measured using thermometers 6a and 6b, and the longitudinal direction is adjusted to obtain the target humidity difference Δto according to this temperature difference Δt1. Adjust the cooling pattern in the two width directions. In addition, in order to suppress cooling errors caused by each cooling device as much as possible, the steel plate 4
A cooling pattern is determined to obtain a temperature difference by installing a thermometer on the front of each cooling device in the longitudinal direction of the cooling device.

For example, the humidity difference Δt1 measured by the hygrometers 6a and 6b,
The steel plate is corrected according to the distorted shape measured by the shape measuring device ε7. For example, in the case of a return wave, the cooling pattern is adjusted so that the flow rate at the abdomen is lower than at the ear. For example, the steepness of the entrance side is adjusted. 2%, and when the steel plate temperature is 350 C, if a temperature difference of 100 C is applied to the steel plate by adjusting the flow rate of the cooling spray, the steepness Vi will be 0.8% at the exit side of the straightening device. In this way, the partial distortion of the steel plate is reduced to the shape i! By measuring with an fjJ constant device, each roll is corrected with a temperature difference one after another, and the steepness can be set to 0%.

(Effects of the Invention) As explained above, a shape measuring device and a cooling device are provided in a hot steel sheet straightening device, and humidity differences according to the strained shape of the steel sheet are treated as gI. The steel plate could be corrected very effectively against partial distortions such as waves.

Therefore, the effect of the present invention that contributes to improving the quality of steel sheets is extremely large.

[Brief explanation of the drawing]

Fig. 1 is an explanation of the arrangement of the orthodontic device of the present invention, Fig. 2 is an explanatory diagram of the correction principle, Fig. 3(a) is an explanatory diagram of an example of temperature distribution, and Fig. 3 is an explanatory diagram of the correction principle.
Figure (b) is an explanatory diagram of the strain distribution in the furniture distribution of Figure 3 (a), Figure 4 is an explanatory diagram showing when the stress due to the roll and the stress due to the temperature difference are superimposed, and Figure 5 is an explanatory diagram showing the stress due to the roll and the stress due to the temperature difference. Figure 6 is a diagram showing the relationship between the steepness on the entry side and the steepness on the exit side when the copper plate is corrected by applying a temperature difference.
The figure is an explanatory diagram of a conventional steel plate straightening device.

Claims (1)

[Claims] 1. In a straightening device for straightening a hot steel plate by passing the sheet between upper and lower straightening rolls arranged in a staggered manner: a shape measuring means for measuring the shape of a rolled steel plate; means for measuring the humidity on the front and back surfaces of a steel sheet being passed between the straightening rolls; and a means for measuring the humidity on the front and back surfaces of a steel sheet being passed between the straightening rolls; A hot steel plate straightening device comprising cooling means installed in a staggered manner on the front and back sides of a steel plate. 2. The cooling means is provided in large numbers divided in the width direction, and a cooling pattern can be arbitrarily set in the longitudinal direction and the width direction according to the temperature of the front and back surfaces of the steel plate and the shape of the steel plate.
A straightening device for hot steel sheets as described in Section 1.