JPS6272430A - Straightening equipment provided with induction heating device - Google Patents

Abstract

PURPOSE:To uniformize the straightening and to simplify the equipment by arranging the induction heating device over the full length of a steel plate at the inlet side of a straightening machine in the rolling line of a thick steel plate. CONSTITUTION:A high frequency or low frequency induction heating device 5 is arranged in the medium of a rolling mill 4 and straightening machine 6 in the rolling line composed by a billet heating furnace 1, transfer table 2, descaling device 3, rolling mill 4, etc. The billet heated by the heating furnace 1 is transferred by the table 2 and rolled by the rolling mill 4. The temp. of the rolling stock after rolling falls with the radiation, heat transfer and convection while it reaches to the straightening machine 6. In this case, the straightening temp. is uniformized by heating the rolling stock over the full length of the plate by the induction heating device 6. With this heating, the straightening force is reduced, so the rolling stock can be straightened uniformly and the straightening equipment is simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to straightening equipment equipped with an induction heating device.

(B) Prior Art In a thick steel plate manufacturing line, the thick steel plate rolled from a slab to a predetermined plate width and thickness has a poor flat shape, so it is flattened by a straightening machine.

The straightening force at this time is directly proportional to the width and thickness of the rolled material and inversely proportional to the temperature of the rolled material.

Since the temperature of the rolled material decreases from the time it leaves the heating furnace to the time it reaches the straightening machine, the straightening machine had to increase its straightening force by the amount of the temperature drop. However, with conventional straightening machines,
Ear waves etc. in rolled material cannot be eliminated. Therefore, it has been proposed that a heat treatment furnace equipped with one or more induction heating coils is installed on the entry side of the straightening machine to heat-treat the rolled material before straightening. (Unexamined Japanese Patent Publication No. 52-11104
Publication No. 2).

However, when this equipment is used for online processing of thick steel plates, the heat treatment furnace is always open, resulting in large energy loss during charging and unloading, and requires initial investment for furnace installation. growing. In addition, when straightening is performed by installing an induction heating device after a conventional offline heat treatment furnace, the temperature of the steel plate before it is delivered to the heat treatment furnace is approximately room temperature, and since this is reheated, the steel plate after rolling is retained. energy is wasted.

Recently, direct quenching, or A r
Processing heat treatment such as accelerated cooling in which controlled cooling is performed from a temperature of 1 or higher to 650°C or lower is carried out online.

Various apparatuses for carrying out such mechanical heat treatment have been proposed in the past. For example, following the hot rolling mill,
Accelerated cooling device, reheating furnace, straightening machine arranged in this order,
Alternatively, the arrangement of the reheating furnace and straightening machine is reversed (Japanese Patent Publication No. 59-34213), or the hot rolling mill is followed by the heating furnace and the rapid cooling device (Japanese Patent Publication No. 53-161).
No. 5), ■ Following the hot rolling mill, a heat insulating device for a heat insulating cover, a hot leveler, and a water cooling device are arranged in this order ← JP-A-57-116732), ■ Following the hot rolling mill, an induction device is installed. A heating device and a quenching device arranged in this order (Japanese Patent Application Laid-open No. 1983-
87216) etc.

However, with the processing heat treatment equipment (2), although it is possible to obtain a thick steel plate with good flatness, it is difficult to obtain a thick steel plate with good flatness.
Etsuji Wave)? In addition to straightening with a hot leveler, the steel plate must be reheated after accelerated cooling to eliminate the temperature difference and ensure flatness by reheating to 500~Ac+, tii or higher. , the retained heat after hot rolling is not utilized effectively, resulting in thermal energy loss.

■、■ processing heat treatment equipment uses thick steel plate 2 with good flatness.
It is both difficult and impractical to obtain. With these devices, temperature variations during hot rolling and ensuring the maximum quenching temperature can be resolved by reheating using a reheating furnace, induction heating device, etc., but flatness defects that occur during hot rolling can be resolved by reheating. If the flatness remains unresolved and the flatness is poor before cooling, uniform cooling will not be possible (this will cause the temperature parasocket to return to the thick steel plate after cooling), and the flatness will worsen (due to uneven cooling). (deteriorating flatness). For this reason.

After straightening the flatness of a thick steel plate after quenching, it is difficult to straighten with a general hot leveler, so a powerful cold leveler is required, which is disadvantageous in terms of equipment and energy, and the straightening itself is Hi4 difficult. .

In addition, in the processing heat treatment equipment (2), a hot leveler is installed before the reheating furnace, and after straightening the flatness, reheating and direct quenching are performed. In this way, by performing the light insertion after flatness correction, the flatness does not deteriorate, which is advantageous in terms of flatness accuracy pi.

However, not all thick steel plates after hot rolling are straightened with a hot repeller. For example, it is difficult to correct the flatness of steel plates with a low finishing temperature, or with a large yield load at that temperature depending on the material or plate thickness. Requires a bending load,
Hot levelers do not eliminate the problem and it remains, resulting in poor flatness of thick steel plates after direct quenching.

(3-) The heat retention device of the processing heat treatment equipment does not completely prevent the temperature from decreasing, and it is possible to prevent the temperature non-uniformity in the width direction of the sheet that occurs during rolling from becoming even thicker. However, temperature variations cannot be made uniform. Therefore, if there are variations in the temperature of the thick steel plate before cooling,
Even if the flatness is corrected with the next hot repeller, temperature variations remain and lead to deterioration of the flatness during cooling, which does not necessarily result in good flatness.

In this way, if there are temperature variations or poor flatness before cooling, not only will a thick steel plate with good flatness not be obtained after cooling, but residual stress and residual strain will occur in the subsequent thick steel plate. This residual stress and residual strain is released by -S when cutting the finished product, causing the finished product to bend sideways, ie, so-called camber.

As mentioned above, what are the advantages and disadvantages of conventional processing heat treatment equipment in obtaining heat treated thick steel plates with stable flatness? had.

(C) Problems to be Solved by the Invention The problems to be solved by the present invention are to reduce the number of straightening chips by reheating the rolled material before or during straightening, to simplify the straightening equipment, and to improve the heating device. Uniform heating and straightening using simple products! l! - There is something to be gained.

B) Means for Solving the Problems The straightening equipment of the present invention solves the above-mentioned problems by installing an induction heating device on the inlet side of the straightening machine during the on-line production of thick steel plates.

Further, the straightening equipment of the present invention solves the above-mentioned problems by arranging at least two straightening machines and arranging an induction heating device between the straightening machines in the online manufacturing of thick steel plates.

(e) Examples The straightening equipment of the present invention is characterized in that the rolled material is reheated to a predetermined temperature before or during straightening.

FIG. 1 shows an embodiment of the equipment of the present invention. In the figure,
Reference numeral 1 denotes a steel billet heating furnace before rolling, which may be a commonly used continuous heating furnace or batch heating furnace. Reference numeral 2 denotes a conveyance table for conveying steel pieces and steel plates in the direction of the arrow, and a roller type is usually used. 3 is a descaling device that removes oxidized scale from a steel billet after heating. Usually, high-pressure water is injected onto the surface of the steel billet, or mechanical pressure is applied and then high-pressure water is injected to remove the scale! Remove. Reference numeral 4 denotes a rolling mill. Usually, a reversible rolling mill with double or quadruple rolls is used for rolling thick steel plates, but a continuous rolling mill or a row of two or more rolling mills may be used.

The format of 1 to 4 above should be arbitrarily selected depending on the size, type, and quantity of the steel piece or steel plate to be manufactured, and the present invention does not require any particular limitation.

Reference numeral 5 denotes a reheating device for heating the rolled material after hot rolling, and the type of device used is a high frequency or low frequency induction heating device. The induction heating device 5 heats the rolled material at 1600°C.
- Heating to Ac1 point to facilitate straightening of rolled material.

The induction heating device 5 can raise the temperature to the optimum cooling start temperature for each type of product for direct quenching or accelerated cooling, and can also eliminate differences in board temperature.Furthermore, the induction heating device 5 can perform the following Such uses are also possible. For example, for difficult-to-process materials such as titanium alloys and stainless steel alloys whose deformation resistance increases rapidly as the temperature decreases, conventional two-heat rolling or two-heat rolling, in which a heated raw steel billet is rolled to an intermediate thickness and then heated and rolled again, is used. 3 heat rolling is performed to produce a product with a predetermined thickness. However, for such a material, if the rolling temperature decreases and rolling becomes difficult, the induction heating device 5 raises the temperature and rolling can be continued again. By performing this type of rolling, the manufacturing schedule is shortened compared to conventional methods, less energy is used only for heating, and the finishing temperature can be increased, making it easier to straighten the flatness afterwards. There are advantages such as:

Reference numeral 6 denotes a straightening machine, which is generally a hot leveler and corrects flatness defects caused during hot rolling, achieves uniform cooling during cooling, and prevents flatness from deteriorating due to cooling.

In the present invention, the induction heating device 5 and the straightening machine 6 are collectively referred to as straightening equipment 7.

FIG. 2 shows seven other straightening devices of the present invention. This straightening equipment 7 includes at least two straightening machines 6, and an induction heating device 5a is arranged between the straightening machines 6.

The reason for heating during straightening is that when straightening a thin steel plate, coarse straightening is performed in the first stage and fine straightening is performed in the second stage.In particular, with thin steel plates, the temperature decreases and the straightening strength decreases, so it is difficult to straighten the steel plate. Kyoto's accomplishments are great when he goes to λ. Generally, heating efficiency increases when the distance between the heating coil surface and the rolled material is narrow. By using two straightening machines, there is no vertical movement of the steel plate, and the distance between the heating coil surface and the rolled material surface is narrowed.
In addition, it is possible to maintain a constant value, thereby reducing energy loss. Furthermore, the leveling workability can be improved and the time required to produce one sheet of rolled material can also be shortened.

(f) Function In the equipment shown in Fig. 1, a steel billet heated in a heating furnace 1 is transferred by a conveyance table 2 and rolled into a predetermined size by a rolling mill 3 (finishing temperature is approximately 1000 to 700°C). . Next, the rolled material is heated to 6bo to ToC by the induction heating device 5.

From the completion of rolling by the rolling mill 4 until the rolled material reaches the straightening machine 6, the temperature of the rolled material decreases due to radiation, heat transfer, and convection. In particular, when the plate thickness is thin, the temperature drop is large, and the straightening temperature is different between the tip of the plate where straightening begins and the diameter end of the plate where straightening ends, so the quality is not uniform. Therefore, by heating with the induction heating device 5 and making the straightening temperature uniform over the entire length from the tip to the rear end of the two plates, a material of constant quality can be obtained.

The straightening machine 6 applies a bending stress exceeding the yield point to the rolled material to remove distortion and obtain a flat shape.In order to reduce deformation resistance, the straightening temperature is set to suppress shape changes during cooling. It is better to set it as high as possible without causing any problems. By heating to a predetermined temperature using the induction heating device 5, deformation resistance can be reduced and straightening force can be reduced.

The equipment shown in FIG. 2 is almost the same as the equipment shown in FIG. Straighten the rolled material.

(g) Specific examples ■ Rolled material thickness 6.00 + a x width 3100 wa x length 2500
0 mw (40 kg steel) Ear wave generation of up to 100 m A, conventional method Before leveling 3-pass leveling 2 was performed using a straightening machine with a nominal capacity of 300 T at an average temperature of 510°C 0 As a result, the rolled material had a maximum of 40 m of ear wave generation. An ear wave remained. The rolled material was reheated in a heat treatment furnace, leveled, and the ear waves were removed.

B1 Method of the Invention Before Leveling The plate was heated to an average temperature of 680° C. using an induction heating device and held for 3 minutes at an average temperature of 510° C., and 3-pass leveling was performed using a straightening machine. The ear waves of the rolled material were almost eliminated.0 ■Rolled material thickness: 560 w x width: 2560 ytaa x length: 13
500w (5t JS 304 steel) Maximum 201 in the longitudinal direction
+Ill wave generation A, conventional method Three-pass leveling was performed using the straightening machine at an average temperature of 560° C. before leveling, but the longitudinal waves could hardly be eliminated.

B1 Method of the Invention After heating the plate to an average temperature of 790° C. using an induction heating device, three-pass leveling was performed using a straightening machine. As a result, most of the waves in the longitudinal direction were eliminated, and some waves of about 2 m remained. ■Others: The average amount of waves generated in the plate after rolling in front of the induction heating device was 30 m.
Then, the induction heating efficiency (4
0 kg steel thickness 8. ow x width 2500 ws x length 180001111% temperature range 500°C raised to 680°C, frequency 1480Hz) was η = 57.6%.

When leveling was performed in front of the induction heating device, the average amount of waves generated on the plate was 8.5 m, and the induction heating efficiency at this time with the air gap set to 45 days (same material, same size, same temperature range) was η=69.3chi.

Therefore, it can be seen that leveling before induction heating improves the efficiency of induction heating.

(Force effect: The straightening possible range (temperature immediately before leveling) of 40 kg steel is shown by the shaded area below the curve in Figure 3. As is clear from the diagram, by using an induction heating device, it is possible to straighten the steel over time. In the case of 40kg steel, correction of flatness defects is now possible when the plate thickness is 50mm or less.

[Brief explanation of drawings]

FIG. 1 is a plan view of the correction equipment of the present invention. FIG. 2 is a plan view of another correction equipment of the present invention. Figure 3 is a graph showing the correction effect of thick plate. 1: Billet heating furnace 2: Transfer table 3: Descaling device 4: Rolling mill 5: Induction heating device
6: Straightening machine 7: Straightening equipment patent applicant Sumitomo Metal Industries, Ltd. (5 others)

Claims (2)

[Claims] (1) Straightening equipment in a thick steel plate rolling line, characterized in that an induction heating device capable of heating the entire width of the steel plate is disposed on the entry side of the straightening machine. (2) Straightening equipment in a rolling line for thick steel plates, characterized in that at least two straightening machines are disposed, and an induction heating device capable of heating the entire width of the steel plate is disposed between the straightening machines.