JPH0575486B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for reheating a plate-shaped material, which reheats both widthwise ends of the plate-shaped material whose temperature has decreased during transportation.

[Prior art]

To roll a steel plate or the like, a slab heated in a heating furnace is first roughly rolled and then finished rolled. In such a rolling process, the temperature at the edge of the plate material increases to 100% due to heat radiation from rough rolling to finish rolling.
℃, but when rolling conventional steel types, there is no need to reheat it, or even if it is reheated, it can be heated simply by installing a pair of induction heating coils at both ends of the sheet material in the width direction. Reheating at this temperature was sufficient.

〔problem〕

However, recently, in order to improve the quality and tensile strength of steel sheets, Ni, Cr, Mo, etc. have been added to the steel sheets, and these ingredients increase the strength and cause scratches on the rolling rolls. This tendency is particularly high at both ends in the width direction of the steel plate where the temperature drop is significant because the deformation resistance is large. If a flaw occurs locally on both ends of the rolling roll, this flaw will be printed on the steel plate, resulting in a defective product. Furthermore, although the central portion of the rolling roll is sound, both ends are flawed, which significantly accelerates repairs due to deterioration of the roll, resulting in decreased productivity and increased maintenance costs.

In order to improve this problem, it is necessary to reheat both ends of the plate material in the width direction to perform strict temperature compensation according to the temperature difference in the width direction. The temperature distribution pattern (temperature distribution in the width direction) due to the temperature drop at both ends of the plate material differs depending on the thickness of the plate material, conveyance speed, etc., and strict temperature compensation for this can be achieved by using a pair of guides as in the past. If this was to be done using a heating coil, it would be difficult to simply move the coil in the width direction, and furthermore, various coils of different sizes would have to be prepared and replaced, which would be extremely difficult in practice.

Therefore, the present invention provides a method for reheating a plate-like material, in which both ends of the plate-like material are induction heated according to the temperature distribution pattern in the width direction of the plate-like material, and the temperature distribution in the width direction of the plate-like material is made uniform. The purpose is to provide.

[Means and actions for solving problems]

In order to achieve such an object, the present invention provides a method for reheating a plate material in which both ends in the width direction of the plate material being conveyed are reheated to a temperature suitable for rolling. Measure the temperature distribution in advance (for example, for different plate thicknesses and conveyance speeds).
A plurality of pairs of induction heating coils that heat both ends of the plate material in the width direction are arranged in the conveying direction, and each set of induction heating coils is arranged in the width direction so as to form a temperature compensation pattern for the temperature distribution. The plate-like material is reheated by combining the position and the magnitude of the current flowing through each set of the induction heating coils, and by reheating in this way, rolling with high commercial value can be achieved. The product was made available for purchase.

〔Example〕

Hereinafter, the present invention will be explained in detail based on examples.

First, an induction heating apparatus used for carrying out the present invention is shown in FIGS. 1 and 2. The figure shows an induction heating device placed at an intermediate position between a rough rolling mill and a finishing rolling mill. At both ends of a plate-shaped steel plate 1 placed on rollers 2 and conveyed in the direction of the arrow, there are orthogonal flux type coils (hereinafter simply referred to as coils) as induction heating coils for heating the ends of the steel plate 1. is located.
A pair of coils 3a and 3b are arranged on the upstream side with respect to the conveyance direction of the steel plate 1, and a pair of coils 3c and 3d are arranged on the downstream side. In other words, two pairs of coils are arranged in the conveyance direction. As shown in FIG. 6b, each coil consists of a hollow coil conductor 6 having a flow passage 5 for cooling water and a plurality of plate-shaped iron cores 7a and 7b fitted into each coil piece, which are placed above and below a steel plate 1. It is arranged. Each of these coils is movably moved in the width direction of the steel plate 1 on a support base 4.
The support base 4 is equipped with a control device 8 that changes the magnitude of the current i flowing to each coil.
is provided. Note that 9 is a lead wire that connects each coil to a power source.

Next, a method for reheating a plate material according to the present invention will be explained.

In Figure 3, for example, the width of the conveyor in the direction of the arrow is 1000.
mm steel plate 1, A is the position after rough rolling, B is the position to be reheated by induction heating, and C is the position to be finished rolled.The temperature distribution in the width direction of the steel plate 1 at position A is determined in advance (Measurement may be performed for each condition including at least plate thickness, conveyance speed, etc.). As shown in Figure 4a, the temperature suddenly decreases from the position 100 mm from both ends of the steel plate 1 to the ends, and the temperature at both ends is 100° lower than the temperature at the center (1100°C). Assume that there is a distribution pattern.

In order to reheat the steel plate 1 with such a temperature distribution pattern so that the temperature distribution in the width direction becomes uniform as shown in FIG. 4c, a temperature compensation pattern as shown in FIG. 4b is required. Temperature compensation may be performed.

In order to reheat the steel plate 1 in the temperature distribution pattern shown in FIG. 4b, the following procedure is performed. When a medium frequency current i of, for example, 300 to 1000 Hz is passed through each coil of the induction heating device, magnetic fluxes φ ₁ and φ ₂ are generated that penetrate the steel plate 1 as shown in FIG. 6b, and the portion sandwiched between the coils A steel plate 1 is heated by induction. The temperature compensation pattern due to reheating is determined by the position of each set of coils in the plate width direction and the magnitude of the current i, so it is possible to A temperature compensation pattern can be obtained. In this embodiment, coil 3
As shown in FIG. 5a, the temperature compensation pattern by coils 3a and 3b is as shown in FIG.
The center position of the iron core 7a of 3b is relative to the edge of the steel plate 1.
The coils 3c and 3d are set 13 mm outside, and a current _i1 is applied so that the temperature compensation pattern by the coils 3c and 3d becomes as shown in FIG. 5b (so that the steel plate 1 is heated slightly toward the center). As shown in FIG. 6b, the centers of the iron cores 7a of the coils 3c and 3d are set 15 mm inside the end of the steel plate 1, and a current _i2 is applied. Then, as a result, the fifth
As shown in FIG. 5C, a graph obtained by combining the graph in FIG. 5A and the graph in FIG. 5B, that is, the required temperature compensation pattern is obtained. Figure 5a,
In b and c, grapha is a combination of graphi and b, so T ₁ +T ₂ = 100 (degrees).

As described above, reheating of the temperature compensation pattern shown in FIG. 4b is performed at the position B in FIG. 3, so that the temperature compensation pattern shown in FIG. As shown in the graph shown, the temperature distribution in the width direction of the steel plate 1 is uniform at 1100°C, and proper finish rolling is performed.

In other words, by setting the heating area and heating temperature of the plate material for each set of coils so as to obtain the temperature distribution of the required temperature compensation pattern, the temperature compensation pattern of each set of coils can be adjusted. By heating using the synthesized temperature compensation pattern, the temperature distribution in the width direction of the plate material is made uniform.

In this example, the temperature of the steel plate after rough rolling is shown in Figure 4a.
Since the temperature distribution was as shown in Figure 4b, the positioning of each set of coils and the magnitude of the current were determined so that the temperature compensation pattern was as shown in the graph shown in Figure 4b. Since it varies depending on conditions such as plate thickness and conveyance speed, the temperature compensation pattern also differs each time. Therefore, the positioning of each set of coils and the magnitude of the current must be determined depending on the conditions such as plate thickness, conveyance speed, etc.

In addition, in this embodiment, the sixth induction heating coil is
As shown in the figure, orthogonal flux type coils are used in which the direction of the alternating current flowing through the coil conductors 6 located above and below the steel plate 1 is the same, and when such orthogonal flux type coils are used, as shown in Figure 6b, Orthogonal magnetic fluxes φ ₁ and φ ₂ are generated, and an induced current flows in the steel plate 1 in a direction parallel to its surface, generating heat. Therefore, the frequency of the current can be lowered to, for example, about 300 to 1000 Hz, and the steep temperature rise of the steel plate directly under the coil that occurs when high-frequency current is used can be avoided, making it easy to obtain an appropriate temperature compensation pattern. Furthermore,
Heating efficiency is 30-40% compared to using high frequency.
expensive.

[Effect] As explained above, according to the present invention, the position in the width direction of each set of induction heating coils provided in plural sets and the current flowing to each set of induction heating coils in reheating the end portion of a plate-shaped material are By combining the sizes, the heating temperature distribution pattern at the end of the plate material can be freely set for each set. Therefore, when the temperature distribution in the width direction of the plate material to be reheated is different, heating by each set of induction heating coils is performed so that a heating temperature compensation pattern corresponding to each pre-measured temperature distribution is obtained. The plate material can be reheated by setting each temperature distribution pattern, and rolling can be performed in a state where the temperature distribution in the width direction of the plate is uniform. Therefore, not only can rolling be carried out properly and the defective rate of rolled products is reduced, but also the incidence of roll defects is reduced and the need for roll repair etc. is reduced. In other words, the operating rate of the rolling mill is improved and maintenance costs are reduced.

[Brief explanation of the drawing]

Fig. 1 and Fig. 2 relate to the induction heating device, Fig. 1 is a plan view, Fig. 2 is a view taken along the arrow F-F in Fig. 1, and Fig. 3 is a plan view.
6 to 6 relate to an embodiment of the method for reheating a plate material according to the present invention, FIG. 3 is an explanatory diagram showing the conveyance state of the steel plate, and FIG. 4 a shows the temperature distribution of the steel plate after rough rolling. 4b is a graph showing the temperature compensation pattern for temperature compensation, FIG. 4c is a graph showing the temperature distribution of the steel plate during finish rolling, and FIG. 5a is the temperature compensation pattern by coils 3a and 3b. FIG. 5b is a graph showing the temperature compensation pattern by the coils 3c and 3d, and FIG. 5c is a graph showing the temperature compensation pattern of coils 3c and 3d.
A graph showing the temperature compensation pattern obtained by synthesizing the graphs of .
FIG. 6b is an explanatory diagram showing the positional relationship between the steel plate and the coils 3c and 3d. DESCRIPTION OF SYMBOLS 1... Steel plate, 3a, 3b, 3c, 3d... Orthogonal magnetic flux coil, 4... Support stand, 8... Control device.

Claims (1)

[Claims] 1. In a method of reheating a plate-like material in which both widthwise ends of the plate-like material being transported are reheated to a temperature suitable for rolling, the temperature distribution in the width direction of the plate-like material is measured in advance, and the temperature distribution of the plate-like material is measured in advance. A plurality of pairs of induction heating coils that heat both ends of the sheet material in the width direction are arranged along the conveying direction of the sheet material, and the positions of the induction heating coils in the width direction and the current flowing through the induction heating coils are determined. The size is set for each group, and the plate material is reheated so that a temperature compensation pattern is obtained for the temperature distribution measured by combining the temperature distribution patterns of the induction heating coils of each group. A method for reheating plate material, characterized by: