JPS6223937A - Method and apparatus for cooling steel strip in continuous annealing treatment - Google Patents

Abstract

PURPOSE:To develop a cooler which is small in size and has excellent cooling capacity by providing flow regulating plates for cooling water on both sides of a steel strip and forcibly flowing the cooling water at a high speed in the direction opposite from the traveling direction of the steel strip thereby improving the efficiency of cooling the steel strip in the stage of cooling the steel strip in a continuous annealing line. CONSTITUTION:The long-sized steel strip S subjected to continuous annealing is run in the flow regulating plates 1a, 1b for the cooling water having outlets 6a, 6b and inlets 5a, 5b for the cooling water at the top and bottom and having sealing rolls 2a, 2b, 3a, 3b and 4a, 4b for preventing the leakage of the cooling water to the upper and lower parts as well as the side parts in the stage of cooling the strip S. On the other hand, the cooling water is pressurized by pumps 7a, 7b and is put through the inlets 5a, 5b into the plates 1a, 1b where the water is forcibly flowed in the direction opposite from the traveling direction of the steel strip and is discharged from the outlets 6a, 6b. The strip S is uniformly and quickly cooled in the transverse direction thereof. The steel strip is thus cooled with the excellent treating capacity by the small-sized cooler.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method and a cooling device for cooling a steel strip in a continuous annealing rye.

In general, original plates for surface treatment, ifa plates for deep drawing, etc. are -□
After cold rolling, so-called continuous annealing is performed in which heat treatments such as heating, soaking, and cooling are sequentially performed in order to impart predetermined mechanical properties.

Recently, there has been an increase in demand for ultra-thin materials with a thickness of about 0.3 or less, and therefore the continuous annealing parline has been increasing its threading speed and throughput. Therefore, the furnace equipment inevitably becomes long, and there are problems in terms of equipment construction such as construction costs and installation space, as well as operational problems as described below.

In other words, as the furnace becomes longer, the thermal inertia of the furnace increases, and in addition to requiring a longer time to change the heat treatment conditions, various problems arise, such as meandering of the steel strip and heat buckling, compared to conventional furnaces. It was.

The present invention is intended to advantageously solve the problems related to final cooling, among the various problems that arise as a result of the above-described high-speed furnace operation.

(Prior Art) Cooling methods C employed in continuous annealing include gas jet cooling, roll cooling, and immersion cooling.

Of these, gas jet cooling involves spraying cooled atmospheric gas onto the steel strip, and roll cooling involves wrapping the steel strip around a roll through which a refrigerant is passed.
Furthermore, immersion cooling involves cooling the steel strip by immersing it in a cooling water tank, and the cooling rate increases in the order of gas jet cooling, roll cooling, and immersion cooling. Therefore, in the cooling zone of a continuous annealing line, When cooling from the recrystallization temperature to a temperature that does not oxidize in the atmosphere, it is considered most efficient to use gas jet and/or roll cooling on the high temperature side, while immersion cooling on the low temperature side. .

Regarding such immersion cooling, various methods have been proposed so far.For example, ITr457'-
The methods disclosed in Publications No. 11981 and No. 57-11938 efficiently cool steel strips by using multiple cooling water tanks and controlling water injection into each tank, and by combining spray cooling and mist cooling. In addition to cooling the water, the temperature of the water after cooling is raised as much as possible so that it can be effectively used as hot water.

(Problems to be Solved by the Invention) Immersion cooling is usually performed at a temperature of about 250 to 300'C, at which the amount of change in saturated solid solute carbon fIt in the steel strip is small, but at a temperature at which temper color does not occur in the atmosphere. Applicable for cooling up to. In the past, if the cooling rate by dipping treatment was too fast, there was a concern about aging problems due to solid solution carbon, but recently, non-aging materials 1' have been developed, such as Nb-added ultra-low carbon steel. Materials in which solid solution carbon is fixed with the 8th element have come to be used.Therefore, from a metallurgical perspective, no matter how high the cooling rate is, it is no longer a problem, but rather, it is necessary to increase the cooling speed and increase production efficiency. Final appearance, final □
``It is desired to further improve the cooling rate in cooling.''However, in response to the above-mentioned demands, conventional immersion cooling still leaves the following problems.

(1) In order to suppress the temperature rise of the cooling water,
It is essential to replenish cooling water into the tank, but in this case, the flow of water in the tank stops at the top and there is almost no water movement at the bottom, so the hot steel strip is immersed in the cooling water. At this time, a vapor film is generated on the surface of the steel strip, and since it is difficult to remove or destroy this vapor film, there is a limit to the cooling efficiency. Therefore, in order to increase the speed and efficiency of the cooling process, it is necessary to increase the size of the immersion cooling equipment, which increases construction costs and
There were major disadvantages in terms of installation space, etc. Furthermore, it was almost impossible to increase speed by improving existing equipment.

(2) As mentioned above, the uneven movement of water in the immersion water tank causes temperature unevenness, which adversely affects the steel strip.

(8) When reusing the cooling water discharged from the immersion cooling water tank as hot water, it is necessary to use at least two immersion tanks 2" and perform cascade control, which not only increases the size of the I device but also , complex flit control is also required.

The present invention advantageously solves the above-mentioned problems and aims at proposing an efficient cooling method for final cooling, together with a suitable cooling device for its implementation.

That is, in this invention, when the steel strip that has passed through the cooling zone of the continuous sintering line is finally cooled using a cooling liquid,
This method of cooling an m-band in continuous annealing treatment is characterized in that the cooling liquid is forced to flow in the opposite direction to the cooling direction of the steel strip and in a rectified flow along the front and back surfaces of the steel strip.

The present invention also provides a cooling device that performs final cooling using a cooling liquid on a steel strip that has passed through a cooling zone of a continuous annealing line. A plate is provided oppositely from the front and back surfaces of the steel strip across a coolant flow path, and the flow straightening plate has a coolant supply port on the downstream side in the running direction of the steel strip and a discharge port on the other upstream side. This is a cooling device for a steel strip in a patented continuous annealing furnace, which is characterized in that it is provided with the following features: □This invention will be explained in detail below.

(Function) FIG. 1 schematically shows the cooling procedure according to the present invention. In the figure, the symbol S is moving upward on the steel strip. In addition, W is rectified cooling water, which is supplied from the side of the steel strip S and changes its direction downward at the position where it contacts nz#i*s. The mechanism is to make it flow.

As mentioned above, by forcing the entire cooling water to flow 1 inch opposite to the running surface of the steel strip, the cooling water does not stagnate unlike the conventional immersion method, and it also prevents steam from forming on the surface of the steel strip. Even if a film is formed, it can be quickly removed or destroyed, so efficient cooling can be achieved.

Here, if the speed of the steel strip S is vs (m/s) and the speed of the cooling water is vW (m/s), and the downward direction is positive, then the relative speed of the cooling water W with respect to the steel strip S is Vr (m/s). /S)
is expressed by the following equation.

V-V-V River・・・・・・・・・・・・・・・
...(1) "r W S The relative velocity Vr and the heat transfer coefficient α (1 (cal/
Figure 2 shows the results of investigating the relationship between h and 6c). As shown in the figure, the heat transfer coefficient α increases in proportion to the relative velocity vr, and the relationship between the two is expressed by the following equation: It turns out that it can be approximated.

α-5600V ・ ・・・・・・・・・・・・・
...(2) For example, if we consider the case where the relative velocity Vr is 10 m/s, then the heat transfer coefficient α is 268
00 koal/m'-h・'c.

In this regard, the heat transfer coefficient in conventional immersion cooling is high k 5000 koal/m''-h- as shown in Figure 8.
”C, which is a fraction of that of the cooling method of this invention.
No more than the following.

(Example) First, the cooling device of this invention will be explained.

FIG. 4 shows a cross section of a preferred embodiment of the present invention, and FIG. 5 shows a main part thereof in a perspective view, numbered 1a in the figure.

1b is a rectifying plate for guiding the cooling liquid along the front and back surfaces of the steel strip S, that is, as a rectifier, and is installed parallel to one both surfaces of the steel strip S. Pa! b, 8a and 78b are seal rolls that prevent the coolant from flowing out at the front and rear ends of the steel strip S in the running direction. 4b is a seal part provided on both sides of the rectifier plate 1b, and the same seal part is provided on both sides of the rectifier plate 1b.
They are also provided on both sides of the rectifying plates 1a, 1a, and 1b, and by joining them, they prevent leakage of the coolant from the sides, and also have the function of positioning the rectifying plates 1a, 1b, and 1b.

5a and 5b are installed on the rectifier plates 1a and 1b, respectively.

6a and 6a are the supply ports for the cooled coolant, and 6a and 6a are the discharge ports.

Note that F a and 7b are pressurizing pumps for supplying cooling liquid, and 8
, 9 are deflector rolls O. Now, the cooling liquid introduced into the rectifying plate from the supply ports 5a and 5b passes through the gap or flow path formed between the steel strip S and the rectifying plates 1a and 1b. It flows in the opposite direction to the traveling direction of the steel strip S and is discharged from the discharge ports ea and Qb provided at the other end of the current plate 1atlb. Effective cooling is achieved by forcing flow through the relatively narrow gap between the two.

Other embodiments of the cooling device are shown in FIGS. 6-8. Figure 6 shows
The example shown in Fig. 4 is an example in which the rectifying plate is attached to the inside where the steel strip S runs, and the ones shown in Figs. 7 and 8 are examples in which the rectifying plate is U-shaped and W-shaped, respectively. .

The final cooling of the steel strip was performed using the cooling device illustrated in FIG. 4 under the following conditions.

・Steel strip dimensions Thickness: Q, 8m, width +9001m
- Processing amount: 60 t/h - Cooling start temperature: 150°C - Supply cooling water temperature: 80°C - Temperature after steel strip cooling: 60°C - Cooling water channel thickness: approx. 40 t/h, and the cooling water outlet temperature was about 70''C.

Through this cooling treatment, the steel plate is cooled uniformly in the width direction.
This is caused by uneven cooling and the formation of a vapor film.

No adverse effects were observed.

The amount of cooling water required to process the above amount of rope using the conventional immersion method is about 60 t/h, and in this respect, the cooling method according to the present invention achieves a significant reduction in the amount of cooling water.

(Effects of the Invention) Thus, according to the present invention, it is possible to cool the steel strip with much higher efficiency than in the past, and it is therefore very effective in improving the throughput in continuous annealing treatment.

Furthermore, the cooling device can also be made smaller than before.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the cooling procedure according to the present inventionζ FIG.
Relative velocity of cooling water to steel strip vrl- and heat transfer coefficient α
FIG. 8 is a graph showing the relationship between steel strip temperature-cooling water temperature and heat transfer coefficient in conventional immersion cooling. FIG. 4 is a cross-sectional view of the cooling device according to the present invention. , Figure 5 is its perspective view, ゛□
6 to 8 are schematic diagrams of other embodiments. 1a, xb... Rectifying plate 2a, 2b, 3a, 8b-&-/l/0-le 4b
...Seal parts 5a, 5b...Cooling liquid supply ports 6a, 6b...Cooling liquid discharge ports a, 7b...Pressure pump 8.9...Deflector roll

Claims (1)

[Claims] 1. A steel strip passed through a cooling zone of a continuous annealing line,
Steel in a continuous annealing process characterized in that during final cooling using a cooling liquid, the cooling liquid is forced to flow in a direction opposite to the running direction of the steel strip and as a rectified flow along the front and back surfaces of the steel strip. Method of cooling the strip. 2. The steel strip passed through the cooling zone of the continuous annealing line,
A cooling device that performs final cooling with a cooling liquid, in which a rectifying plate that guides a forced flow of the cooling liquid along the front and back surfaces of the steel strip is provided oppositely from the front and back surfaces of the steel strip, with a flow path of the cooling liquid being separated from the front and back surfaces of the steel strip, A cooling device for a steel strip in continuous annealing treatment, characterized in that the current plate is provided with a cooling liquid supply port on the downstream side in the running direction of the steel strip, and a discharge port on the other upstream side.