JPS6218609B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for cooling metal strips in a continuous processing line for metal strips without causing inconveniences such as poor shape, and by utilizing the exhaust heat of the continuous processing line, and a cooling roll used in the method. It is related to. Conventionally, continuous annealing of ordinary steel strips has been mainly used for annealing blanks for tin plating. An example of the strip temperature diagram in the annealing furnace in this case is shown in FIG. In this case, the cooling of the strip is
In the slow cooling zone, indirect radiation cooling using low-temperature cooling tubes was mainly used, and in the rapid cooling zone, cooling was mainly used by blowing low-temperature reducing atmosphere gas directly onto the strip. In addition, in recent years, a technology has been developed to obtain cooled steel sheets with excellent drawability and workability by continuous annealing instead of the conventional batch annealing, resulting in higher productivity and lower costs than conventional batch annealing. Because it is possible to
There is a tendency for continuous annealing equipment to be used more frequently in the future. The temperature diagram of the strip in this case is shown in FIG. Furthermore, the continuous annealing technique described above has recently come to be applied to high-strength steel plates, and the temperature diagram of the strip in this case is shown in FIG. As shown in the temperature diagrams in Figures 1 to 3, in continuous annealing, the strip is rapidly cooled at a rate higher than the metallurgically required minimum cooling rate (for example, in the quenching zone in Figures 2 and 3). , cooling is required in the shortest possible time using inexpensive equipment and at low cost (for example, the rapid cooling zone in FIG. 1 and the cooling zone in FIG. 2). However, the above-mentioned cooling method using direct blowing of low-temperature gas has difficulty in achieving a high cooling rate and requires high equipment costs, and cannot meet such demands. In order to meet these demands, a method of rapid cooling by bringing a so-called water-cooled roll, which circulates cooling water inside the roll, into contact with the strip has been proposed and has come into practical use. Although this water-cooled roll does not have any problem with its rapid cooling ability, it has the disadvantage that it tends to have poor shape such as wrinkles and creases in the strip after cooling. The reason for this is that cold-rolled strips usually have a side elongation of around 0.1% (edge elongation where the edge part of the strip stretches, or medium elongation where the center part of the strip stretches), which allows the strip to make good contact with the rolls. There are parts that are not quenched due to insufficient contact with the quenched parts, and as a result of non-uniform cooling, thermal stress is generated, which causes shape defects such as wrinkles and creases. As a result of researching the relationship between the strip cooling method and the shape defects that occur in the strip, the present inventors first determined that the strip temperature and the cooling Patent application No. 55-97482 describes a method for cooling a strip, the gist of which is that by keeping the difference △T from the roll temperature within the temperature difference shown below, defects in shape can be suppressed to a level that does not pose a practical problem.
No. 55-97483. Strip temperature (contact start temperature) Temperature difference △T 300℃ 225℃ 400℃ 205℃ 500℃ 197℃ 600℃ 184℃ 700℃ 160℃ 800℃ 115℃ However, in the above prior method, the cooling roll is the water-cooled roll. In this case, the temperature of the cooling water flowing inside the roll is at most 100°C, but normally it is below 80°C, and if the strip temperature is high, △T exceeds the above allowable limit, causing shape defects. It was hot. The present invention eliminates these drawbacks of water-cooled rolls, and makes effective use of the heat held in exhaust gas from heating zones, soaking zones, overaging zones, etc. (hereinafter referred to as heating zones, etc.), which were previously discarded. It was created for use in That is, the present invention provides (1) a method for cooling a high-temperature metal strip running at a predetermined speed in a continuous metal strip processing line by bringing it into contact with the outer peripheral surface of a cooling roll, in which the inside of the cooling roll is made hollow; A method for cooling a metal strip, characterized in that exhaust gas discharged from a heating zone or the like of the continuous processing line or a mixed gas of the exhaust gas and air is caused to flow through the hollow part. (2) The interior used in the method (1) above is hollow, and the exhaust gas discharged from the heating zone of the continuous processing line or a mixed gas of the exhaust gas and air is circulated through the hollow space. (3) A heat pipe used in the method (1) above, which has the configuration described in (2) above and is filled with a heat medium that evaporates at high temperatures and condenses and liquefies at low temperatures. The invention relates to a cooling roll in which a part of the metal strip is disposed in an internal hollow part of the cooling roll so as to be in close contact with the inner circumferential surface of the cooling roll. The metal strip can be rapidly cooled while keeping the temperature difference within the tolerance limits mentioned above. Hereinafter, the method and roll of the present invention will be described in detail with reference to the accompanying drawings. FIG. 4 is a diagram for explaining one embodiment of the present invention. In FIG. 4, 1 is a metal strip to be cooled, 2 is a cooling roll according to the invention, and 3 is a roll bearing. 4 is an inlet for exhaust gas from a heating zone or the like or a mixture of the exhaust gas and air; 5 is an outlet for the gas;
Reference numeral 6 designates heat transfer promoting fins provided on the inner wall of the cooling roll 2, 7 an inner cylinder for causing the gas to flow near the inner wall of the cooling roll 2, and 8 a support for the inner cylinder 7. The above-mentioned exhaust gas is used by recovering the exhaust gas discharged from the heating zone, soaking zone, or overaging treatment zone in the continuous metal strip processing line, such as the exhaust gas from the radiant tube heater used in the heating zone. However, since the exhaust gas from the radiant tube heater is normally 500 to 600°C, it is mixed with air to the required temperature and then flowed into the cooling roll 2 through the inlet 4 mentioned above. Of course, if the exhaust gas from the radiant tube is not very high temperature and there is no need for temperature control, there is no need to mix air, and the same applies when exhaust gas from the overaging treatment zone is recovered and used. I can say that. (Hereinafter, these exhaust gases are referred to as cooling gases.) The metal strip 1 is wrapped around one or more of the cooling rolls 2 provided in the cooling area of the heat treatment line, and is not in contact with the cooling rolls 2. Heat is removed from the surface and cooled. Using the cooling rolls shown in Fig. 4 above, when performing cooling treatment under the following conditions, for example, the temperature of the metal strip at the entrance of the cooling zone is 650°C, the temperature of the metal strip at the exit of the cooling zone is 400°C, and four cooling rolls are used, each cooling roll is For example, the temperature relationship is as shown in the table below.

[Table] In addition, in the cooling roll of the present invention, in order to increase the heat transfer capacity between the cooling gas and the cooling roll, reduce the amount of cooling gas, and reduce the required power, FIG. A heat pipe 10 can be provided as shown in the figure. For example, as shown in FIGS. 5 and 6, a plurality of heat pipes 10 are provided in the axial direction and the circumferential direction, and one end thereof is brought into close contact with the inner circumferential surface of the cooling roll 2, and the heat pipes 10 are evaporated at a high temperature and cooled at a low temperature. A heating medium that condenses and liquefies is enclosed. Note that, like the fins 6 in FIG. 4, the heat pipe 10 also has fins 1.
1 can be installed. The heat medium enclosed in the heat pipe 10 is
At the temperature of the cooling gas, it condenses and becomes a liquid 12', and at the temperature of the roll 2, it evaporates and becomes a gas body 12.
The droplets 12' condensed on the central portion 13 of the roll 2 through which the cooling gas flows fall onto the inner wall of the roll 2 due to the centrifugal force and gravity caused by the rotation of the roll 2, where they fall onto the metal strip 1. Kara roll 2
It evaporates immediately due to the heat taken away, and reaches the part indicated by the reference numeral 13 above. During this evaporation, a large amount of latent heat is taken away from the roll, increasing its heat transfer ability. As the above-mentioned heat medium, one whose evaporation temperature can be adjusted according to the temperature conditions of the cooling roll 2 is desirable, and for example, the following ones can be used. Biphenyl (boiling point 254℃, critical temperature 528℃, critical pressure 41.4 atm) Decalin (boiling point 185-195℃, critical temperature 408-419
) Quinoline (boiling point 238°C, critical temperature 509°C) Terphenyl (boiling point 220°C, critical temperature 652.8°C) Sulfur (boiling point 444.6°C, critical temperature 1040°C) By the way, the cooling gas flowing through the cooling roll is
(1) It may be necessary to preheat the cooling gas in order to keep the temperature difference between the cooling roll and the metal strip within the permissible limits described above. (2) To make the axial temperature distribution of the cooling roll uniform ( In the case of non-uniformity, it goes without saying that non-uniform cooling of the metal strip will occur.)
In order to achieve this, it is necessary to avoid local temperature increases in the cooling gas due to heat input from the rolls, and for this purpose, preheating is required due to the need to raise the cooling gas to a certain temperature level. If exhaust gas discharged from a heating zone or the like is used as the cooling gas as in the invention, the heat held by the exhaust gas can be effectively utilized, which is extremely advantageous in terms of energy saving.

[Brief explanation of the drawing]

Figures 1 to 3 show temperature diagrams during continuous annealing of various types of steel. Figure 3 relates to high-tensile steel plates. FIG. 4 is a diagram for explaining one embodiment of the present invention, FIG. 5 is a diagram for explaining another embodiment of the present invention, and FIG. 6 is a partially detailed diagram of FIG. be.

Claims (1)

[Scope of Claims] 1. A method for cooling a high-temperature metal strip running at a predetermined speed in a continuous metal strip processing line by bringing it into contact with the outer peripheral surface of a cooling roll, wherein the inside of the cooling roll is made hollow, and the inside of the cooling roll is made hollow. A method for cooling a metal strip, characterized in that exhaust gas discharged from a heating zone or the like of the continuous processing line or a mixed gas of the exhaust gas and air is passed through the heating zone. 2. A cooling roll that cools a high-temperature metal strip running at a predetermined speed in a continuous processing line for metal strip by bringing it into contact with its outer circumferential surface. A cooling roll for a metal strip, characterized in that exhaust gas discharged from a heating zone or the like or a mixed gas of the exhaust gas and air is passed through the roll. 3. In a cooling roll that cools a high-temperature metal strip running at a predetermined speed in a continuous metal strip processing line by bringing it into contact with its outer peripheral surface, the inside of the roll is hollow, and the hollow part is filled with:
The exhaust gas discharged from the heating zone of the continuous processing line or a mixed gas of the exhaust gas and air is circulated, and one of the heat pipes is filled with a heat medium that evaporates at a high temperature and condenses and liquefies at a low temperature. 1. A metal strip cooling roll, characterized in that the metal strip cooling roll is disposed in close contact with the inner circumferential surface of the cooling roll.