JPS58213833A - Continuous annealing furnace - Google Patents

Abstract

PURPOSE:To provide a continuous annealing furnace for a steel plate which is reduced of initial and running costs and cools the steel plate uniformly by combining a gas cooler, a small-diameter cooling roll group and a large-diameter cooling roll group, and providing tension devices on the upstream and downstream sides of the cooling roll groups. CONSTITUTION:A heated strip X enters the 1st cooling chamber 5 through a holding zone 1 in a continuous annealing furnace and is cooled in a gas cooler 10. The strip is slowly cooled with a small-diameter roll group 11 and is cooled down to a set temp. with a large-diameter roll group 12. Tension devices 13, 14 are provided respectively on the upstream side and downstream side of the groups 11, 12 to apply moderate tension on the strip so that the contact between the groups 11, 12 and the strip X is made uniform to make the cooling uniform. The strip X after the cooling is fed to an overaging zone 3. There is no need for increasing the length of the overaging zone, the need for any pickling device, etc. is eliminated and the cooling is accomplished uniformly with the above-mentioned annealing furnace.

Description

[Detailed Description of the Invention] The present invention relates to a continuous annealing furnace◎ In recent years, it has become a worldwide trend to use continuous annealing furnaces to produce cold-rolled steel sheets and high-strength steel sheets for drawing. When manufacturing cold-rolled steel sheets or high-strength steel by continuous annealing, an important point is the cooling method after soaking.

The main cooling methods currently available industrially include:

Cooling gas jet, cooling roll, water or hot water.

Examples include immersion in hot water or cooling with mist or spray. The cooling rate is 1000-20011 E/sec for water immersion, 60-20011 E/sec for cooling four-wheel, and 5-200 E/sec for cooling gas jet. In the case of water cooling, the time is the shortest in general, about 3 minutes for cooling rolls, and about 5 minutes for gas jet cooling.
In minutes, this is the longest. Therefore, the slower the cooling rate, the longer the over-aging zone, which requires excessive equipment costs.

On the other hand, in water cooling, mist or spray cooling, an oxide film is generated on the surface of the steel plate during the cooling process, so excessive equipment such as pickling equipment is required to remove this film in a subsequent process.

In contrast to these cooling methods, cooling using a cooling roll does not require a very long overaging zone and does not generate an oxide film.

This cooling method can be said to be very superior in terms of both equipment costs and operating costs. However, in the case of cooling using a cooling roll, the cooling mechanism is based on solid contact between the steel plate and the surface of the cooling roll, so uniform cooling in the width direction of the plate cannot be achieved. It is difficult to obtain, and thermal deformation occurs due to the shape of the steel plate and the difference in plate temperature.

It is necessary to eliminate factors that inhibit uniform contact cooling, such as the thermal crown of the rolls.

The invention was made in view of the above-mentioned nine points, and employs a combination of a gas cooling device, a small diameter cooling roll group, and a large diameter cooling roll group, and also provides tension on the upstream and downstream sides of the cooling roll group, respectively. The basic feature is that it is equipped with a device.

An embodiment of the present invention will be described below based on the drawings. @ Fig. 1 is a partial diagram showing the cooling equipment of a continuous annealing furnace. It is set up following this. Ma fc (3) is an overaging treatment zone O. The cooling equipment (2) includes, in order from the upstream side, a gas cooling device αQ, a small diameter cooling roll group 0th, and a large diameter cooling roll group <12. Gas cooling device (g) and small diameter cooling roll group (1)
1 is arranged almost vertically and installed in the first cooling chamber (5). Further, the large diameter cooling roll group (b) is installed in a second cooling chamber (6) arranged in the horizontal direction.

The gas cooling device ← consists of a plurality of gas jet injection pipes (101) provided oppositely on the front and back sides of the strip flash,
Strip the cooling gas from the air supply (101) (
3) The shape and size of the nozzle of the injection pipe (101) configured to inject water into the air are determined as appropriate to ensure uniform cooling. The temperature of the strip at the exit side of the necked injection pipe (101) is controlled to the set temperature at the inlet side of the roll cooling. Each of the rolls is configured to be able to move in the horizontal direction while holding the strip (3), like a leveler, and to adjust the contact length between each roll and the strip (3).

This roll group αη may be provided with reinforcing rolls, a bender mechanism, etc. to enable control of the roll crown. Further, although water is usually used as a refrigerant for the cooling roll, other materials may be used.

The large-diameter cooling roll group (b) is also arranged so as to sandwich the strip (3) and face each other alternately, and each roll can move up and down to adjust the length of contact with the strip (3). It has become.

In this embodiment, three large diameter rolls are used.

- This large diameter roll can also be left open to form a pass line (7) as shown by the imaginary line.

, Small diameter cooling roll group a■ and large diameter cooling roll group (6)
A forward tensioning device α→' and a rear tensioning device α are provided on the upstream and downstream sides of the forward tensioning device 0. It is installed in front of αO and consists of three rolls.

The position of this front tensioning device 0 may be just before the small diameter cooling roll group αC. The rear tension device 04 has a second cooling chamber (
6) is provided behind the large-diameter cooling roll group (6), and similarly consists of three rolls. These tensioning devices (to) 04 should normally be operated with a unit tension of 2 to 3 Ky/l, 1, but the tension should be adjusted as appropriate depending on the plate thickness, plate width, and plate temperature. It is a deflector roll.

In the above configuration, the strip flash is heated in the heating equipment and then held in the soaking zone (1) for about 45 seconds at just below the Al transformation point, that is, at 700 to 730°C. Then, it first enters the first cooling chamber (5) and is cooled to the roll cooling inlet temperature by the gas cooling device α0, and then the small diameter cooling roll group U
cooled down. Since the body is relatively cooled here, it is possible to effectively prevent the plate from squeezing, which tends to occur during the high-temperature cooling process.In addition, since an appropriate tension is applied to the tensioning device (b) q◆, the rolls and strips are ) Contact with the IJ tube is uniform, and cooling is uniform.

The strip (3) is then finally cooled to a set temperature by a group of large diameter cooling rolls (6). At this time, adjust the vertical position of each large diameter cooling roll according to the set temperature.
Adjust the contact length with J knob (3). In the large-diameter cooling roll group (6), since the IJ tube (a) enters in a state cooled to a certain temperature, deformation of the strip due to cooling is effectively prevented.
(Kumesaki is under tension due to 1104)
is cooled to

After cooling, the strip (3) is subjected to an overaging treatment in an overaging treatment zone (3) and then sent to the next step.

FIG. 2 shows an example of a thermal cycle when the continuous annealing furnace described above is used.

As explained above, according to the annealing furnace of the present invention, there is no need to lengthen the overaging zone, and no pickling equipment or the like is required, so that equipment costs and operating costs can be reduced. In addition, uniform cooling can be performed and high quality products with a long lifespan can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a partial view showing one embodiment of the annealing furnace of the present invention;
The figure is a graph showing thermal cycles. (1) Soaking area, (2) Cooling equipment, (3)
... Overaging treatment zone, (5) ... First cooling chamber, (6)
...Second cooling chamber, (7)...Pass line, (8)
... deflation crawl, α0... gas cooling device,
(101)...Injection pipe, H...Small diameter cooling pole group,
(6)... Large diameter cooling roll group, (g)... Front tension device, a4... Back tension device Patent applicant Nippon Kokan Co., Ltd.

Claims (1)

[Claims] In a continuous annealing furnace for producing cold-rolled steel sheets for drawing or high-strength steel sheets, which includes heating, soaking, cooling, and over-aging treatment equipment, a gas cooling device, a group of small diameter cooling rolls following the gas cooling equipment, and A group of large diameter cooling rolls following the group of cooling rolls, and an IJ knob front tension device located upstream of the group of cooling rolls of a small diameter, and an IJ knob located downstream of the group of cooling rolls of a large diameter. A continuous annealing furnace characterized by being equipped with a cooling facility having a rear tensioning device.