JPS6129110B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control method in a hot strip mill line for controlling the heating temperature of a material to be rolled (hereinafter referred to as a hot bar) within a predetermined range.

Generally, in order to ensure the uniformity of the quality of hot-rolled products in the longitudinal and width directions in a hot strip mill, it is necessary to keep the temperature of the rolled material on the exit side of the finishing rolling mill at or above the Ar ₃ transformation point. The smaller the temperature variation over the entire area of the material (longitudinal and width directions), the more desirable.

However, at present, skid marks on the slab that occur in the heating furnace are not removed during the rolling process as they result in temperature unevenness in the longitudinal direction. Furthermore, the temperature of the hot bar at the time of passing through the finishing side rolling mill entrance is about 100° C. between the leading end and the trailing end due to natural cooling. For this reason, the thickness of the product plate at the finish rolling mill delivery section becomes non-uniform, and the temperature of the rolled material also becomes non-uniform. Further, since the heat dissipation area is large at both ends in the width direction, the temperature drop becomes more significant than at the center part in the width direction. This leads to quality deterioration and, in some cases, both ends cannot be used as a product and must be cut and removed.

The present invention provides an induction heating coil at the entrance of the finishing rolling mill and controls the temperature at the exit of the finishing rolling mill to be within a predetermined temperature range, thereby uniformly heating the hot bar and controlling the temperature at which the slab is extracted from the heating furnace. To provide a temperature control method in a hot strip mill line, which can lower the temperature and aim at energy saving of a heating furnace. Figure 1 is a layout diagram showing the line configuration of a hot strip mill.
1 is a slab heating furnace using a pusher type or walking beam type combustion method; 2, 3, and 4 are first-stage rough rolling mills; 5 is a final set rolling mill; 6 is a finishing mill consisting of multiple stages; 7 is a coiler; 8 1 is a table for transferring the slab 9, 10 is a day table, 11 is a hot line table, 12 is a hot bar, 20
is an induction heating coil.

Next, the operation will be explained. In FIG. 1, a slab 9 is heated to a predetermined temperature in a heating furnace 1, extracted, sent by a transfer table 8, processed in rough rolling mills 2 to 4, and then processed in a final rough rolling mill 5. The finishing mill 6 processes the hot bar 12 into the required thickness and width, and then the day table 1.
sent out to 0. The tip of the hot bar 12 is cut off by a crop shear (not shown) on the entry side of the finishing rolling mill 6, and then rolled in the finishing rolling mill 6 to be finished into a product with a predetermined thickness, and transported on the hot run table 11. The coiler 7 then winds up the film.

FIG. 2 is a diagram showing the change in temperature of the material in the arrangement shown in FIG. 1, where the change in the conventional method is shown as characteristic A, and the temperature change when the induction heating coil 20 of the present invention is installed is shown in characteristic B. show. Although this figure shows the change in average temperature across the entire slab, by installing an induction heating coil 20 at the entrance of the finishing rolling mill to raise the temperature, the extraction temperature of the slab 9 at the exit of the heating furnace 1 can be lowered. This suggests that.

FIG. 3 shows the temperature change in the longitudinal direction of one piece of the hot bar 12, and _T1 is the temperature of the hot bar 12 from the tip to the tail end when viewed from the inlet point of the induction heating coil 20 on the delay table 10. Show change. The wavy temperature changes are caused by skid marks. Since the position of the skid mark is determined by the configuration of the heating furnace 10,
correspond to the distance from the tip of the hot bar 1
By detecting the temperature of 2 and controlling the power of the induction heating coil 20 as shown by the curve P, the heating coil outlet temperature can be made almost uniform over the entire length of the hot bar as shown by the curve of To. Alternatively, the temperature can be controlled to the required minimum temperature according to the rolling speed in the finishing mill 6. Finish rolling is carried out based on the minimum required temperature on the discharge side of the finishing mill 6, and corresponds to changing factors such as the plate thickness at the inlet side and the plate thickness at the outlet side (product plate thickness) of the finishing mill 6, rolling speed, etc. By calculating the necessary temperature on the inlet side of the machine 6 using a computer and controlling the power to be applied to the induction heating coil 20 using this value as a target value, it is possible to equalize quality and reduce power consumption in induction heating. It is possible to reduce the amount to the necessary minimum.

FIG. 4 shows an embodiment of a heating method for an induction heating coil to achieve the above-mentioned object.

FIG. 4 shows a heating method using a solenoid induction heating coil surrounding the hot bar. In FIGS. 1 and 4, the hot bar 12 transferred by the conveyance roller 13 of the day table section is heated by a solenoid-type induction heating coil 21 supplied with AC power. It is well known that by controlling the power supplied to the coil 21, the temperature of the hot bar at the outlet of the induction heating coil 21 can be controlled since the amount of heating is varied.

Figures 5a and 5b show a heating method in which transverse induction heating coils are arranged above and below the hot bar. It is heated by 22a and 22b and taken out. Induction heating coils 22a, 22
By controlling the power of the hot bar 12
Needless to say, the outlet temperature can be controlled.

The difference between FIG. 4 and FIG. 5 is that the temperature increase distribution in the width direction of the hot bar 12 in FIG. 4 is different from that in FIG. 6.
While Ts tends to be almost flat over the entire width, in the case of Fig. 5, Tt shown in Fig. 7
This means that the amount of temperature increase at the widthwise end portions of the hot bar 12 can be increased by 50° C. to 100° C. (this value can be arbitrarily selected depending on the coil structure) compared to the central portion.

In general, the temperature at the ends in the width direction of the hot bar tends to be 50°C to 100°C lower than the center, so it can be said that the heating method shown in Figure 5 is desirable; Depending on the temperature, the fourth
A combination of the figure and FIG. 5 is also conceivable.

By configuring a system that combines the heating method and control method described above, the following effects can be obtained.

(a) Sketch marks can be removed.

(b) Energy saving of heating furnace can be achieved.

(c) Energy saving of induction heating can be achieved.

(d) Uniform quality can be achieved.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram showing the configuration of a hot strip mill line, Figure 2 is an explanatory diagram showing temperature changes in materials, and Figure 3 is an explanatory diagram showing longitudinal temperature changes within a single hot bar. , FIG. 4 is a perspective view of a main part of a heating method using a solenoid induction heating coil, which is an embodiment of the present invention, and FIG. 5a is a perspective view of a heating method using a transverse induction heating coil, which is another embodiment of the invention. A plan view of the main parts of the system, Fig. 5b is similar to Fig. 5a.
FIG. 6 is an explanatory diagram showing the temperature increase distribution in the width direction of the plate according to FIG. 4, and FIG. 7 is an explanatory diagram showing the temperature increase distribution in the width direction of the plate according to FIGS. 5a and 5b. In the figure, 1 is a heating furnace, 5 is a rough rolling mill, 6 is a finishing mill, 12 is a heated material (hot bar), and 20 is an induction heating coil. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In a temperature control method in a hot strip mill line equipped with a roughing mill and a finishing mill for rolling a material to be rolled heated in a heating furnace to a predetermined thickness, the roughing mill and the finishing mill In the heating furnace, the temperature of the rolled material at the exit of the finishing rolling mill is set to be lower than the temperature at the exit of the heating furnace, which is set so that the temperature of the material to be rolled at the exit of the finishing rolling mill when the material to be rolled is rolled is the final exit temperature. The material to be rolled is heated, and an induction heating coil is disposed between the rough rolling mill and the finishing rolling mill, so that the temperature of the material to be rolled at the exit of the finishing rolling mill becomes the final exit temperature. A method for controlling temperature in a hot strip mill line, characterized in that the power supplied to the induction heating coil is controlled as follows.