JPS59153843A - Cooling method of strip - Google Patents

Abstract

PURPOSE:To prevent the deterioration in shape owing to uneven cooling in the transverse direction of a strip and to decrease driving force for a pump by disposing the headers of nozzles in the dipping water for cooling the heated strip apart from each other respectively, independent of the advance direction of the strip. CONSTITUTION:Nozzles (b) for ejecting cooling water are provided at a prescribed pitch, for example, in seven steps, in dipping water for cooling a strip 1, and respective nozzle headers (a) are disposed, independently at spaces D from each other in the advance direction of the strip 1. When cooling water is introduced through a water feed pipe (c) at the center of each header (a) and is sprayed toward the strip 1 from the nozzles (b) the jets of the cooling water colliding against the surface to be cooled of the strip flows out through the spaces D between the headers to the part behind the headers. The cross flows generated with the conventional multi-step slit nozzles is thus prevented and the uniformity in the transverse cooling of the strip is provided. The cooling capacity per unit flow rate of the cooling water is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a strip cooling method in which a heated strip is rapidly cooled by water cooling in order to harden the strip.

[Prior art and its problems]

Figures 1 and 2 are inventions of the present applicant (Japanese Patent Publication No. 56-520
This shows a strip quenching device according to No. 94),
1 is strip, 2 is cooling tank, 3 is su) IJ7″1
A pair of cooling water injection devices placed in symmetrical positions on both sides, 4 is a zinc roll.

5 is a cooling water supply pipe for supplying fresh water to the cooling tank 2, 6
7 is a drain pipe that connects the cooling tank 2 and the water storage phase 7, 7 is a water level adjustment weir, 7 is a partition plate, and 8 is a conduit.

9 is a pump, 10 is a roll in contact with both sides of the strip 1, 1 is a rear wall with a semicircular cross section, 12 is a screen such as a wire mesh, and 13 is a nozzle plate in which a plurality of slit nozzles 16 and 17 are bored. It is.

3(A) and 3(B) show the flow of cooling water generated by the apparatus shown in FIGS. The accompanying flow tends to flow downward, resulting in a vortex as shown in Fig. 3 (A), and since the flow does not escape between the slit nozzles 16, the vortex shown in Fig. 3 (B) is generated. ), which causes cross-flow. Therefore, the cooling capacity on the surface of the strip 1 tends to be larger at both ends of the strip width (edge portions) than at the center of the strip width, and cooling at both ends of the strip width is performed more quickly than at the center. Since the central part of the plate width shrinks more slowly than the edges, the plate shape of the strip f1 will have ear waves and compound elongation, which will cause operational problems such as poor running stability of the strip f1. was often the case. This tendency for cooling in the center of the strip 1 to be inferior to that at the edges is due to the fact that multi-stage slits and nozzles 1
Escape of water discharged from the center of the multi-stage slit nozzle 16: Since the duck only exists at the periphery of the multi-stage slit nozzle 16, the static pressure near the center of the multi-stage slit nozzle is high, and the amount of cooling water discharged near the center is limited to the periphery. It will be less than the amount of cooling water to be discharged. In addition, the cooling water discharged near the center flows sideways, so the area around the center is not effectively cooled. For this reason, in order to ensure the cooling rate necessary for product quality and metallurgy at the center of the plate width, where the cooling rate tends to be slow, a considerably large amount of cooling water has to be flowed.

Therefore, the cooling water discharge cylinder f9 needs to have a high pressure and a large flow rate, and the pump power is large, leading to an increase in running costs.

[Purpose of the invention]

This invention eliminates the conventional problems of stripping, shape deterioration due to non-uniform cooling in the board width direction, and the negative effects on the running stability of IJgs. It is an object of the present invention to provide a method for cooling a strip that can reduce running costs such as power reduction.

[Summary of the invention]

The inventor conducted theoretical flow analysis, heat transfer
In addition to simulations, we conducted many experiments and devised the following cooling method. That is, the present invention provides cooling water injection nozzles in multiple stages in immersion water for cooling the heated strip, and the headers of each nozzle are arranged independently and spaced apart from each other in the direction in which the strip travels. Instead, a gap is created between each nozzle header, and the jet of cooling water that collides with the cooled surface of the strip is directed toward the header and flows out to the rear of the header through the gap between the nozzle headers. This prevents the lateral flow that occurs in the slit nozzle and provides uniformity in cooling in the width direction of the plate. In addition, the cooling capacity per unit flow rate of the cooling water supplied to the nozzle is improved, making it possible to significantly reduce the amount of cooling water required to obtain the current cooling capacity, reducing equipment costs and running costs. be able to.

[Embodiments of the invention]

Immersion water to cool IJ tube 1 (heated bath)
Cooling water injection nozzles b are provided in 7 stages at a pitch of 80 mm (the part where the cooling water injection device 3 in the figure is arranged), and each nozzle header a is made independent from the other so that 19 They were spaced apart with a gap of .5 mm+ as shown in Figure 5. Figure 4 shows a cross-sectional view of one of the cooling water injection nozzles.The nozzle header a and the slit-shaped nozzle b are connected by bolts, and the cooling water is introduced from the water supply pipe C in the center of the header. However, the nozzle structure is such that cooling water is sprayed from the nozzle b toward the strip f1.

The distance between the nozzle b and the strip 1 was set to be the slit nozzle distance A, that is, 40+mn. Also,
The details are shown below, and the details of the conventional cooling device are also shown. (Figure 2 shows the concept of a conventional nozzle, and the number of slit nozzle stages is different from the actual one.) Cooling device according to the present invention> Slit width (long side length) 125 (Lmm) Number of stages: 7-stage slit opening, short side length: 3-adjustment discharge pressure
Cooling water amount for 1000 hours
650 m/h strip width 900-12
00kaku <Conventional cooling system> (See Figures 2 and 3)
Slit width (long side length) 1250 Kasumi slit nozzle number of stages 14 stages slit opening, short side length 2.5 adjustment discharge pressure
1000 throat cooling water amount
1100m/h strip width 900-120
FIG. 6 shows a comparison of the cooling effects of the cooling device of the present invention and the conventional cooling device. It can be seen that the difference in heat transfer coefficient between the esso part of the board and the central part of the board is significantly improved compared to the current cooling system, and the heat transfer coefficient obtained with the cooling system of the present invention is also higher than that of the conventional cooling system. Despite the fact that the amount of cooling water obtained was decreasing, it was confirmed that the amount of cooling water was increasing.

Since the required power of the pump is approximately proportional to the product of flow rate and pressure, the cooling device according to the present invention has a lower power consumption than the conventional cooling device.
Both the amount of cooling water and the required power for the pump are reduced by approximately 40%.
This shows that it is possible to significantly reduce equipment costs and running costs.

As described above, the present invention significantly alleviates the non-uniform cooling that occurs when the IJ76t is continuously rapidly cooled, and also greatly improves the cooling capacity. The value is extremely large.

Examples of the second aspect of the invention will now be described.

In the first embodiment shown in FIGS. 4 to 6,
Depending on the running speed of Juzzo 1, it is discharged from each slit nozzle b, collides vertically with the steel plate, and then splits into two (
The flow pattern of the water jet that separates (up and down) changes slightly, and the flow tends to be unstable, which in turn causes instability in the cooling rate, resulting in uneven cooling rate on the string surface in the line traveling direction. However, the average cooling rate tends to be slightly slower. This is due to the accompanying flow (in the field of fluid mechanics,
This is because the degree of the jet flow (called QuetFlow) naturally changes depending on the line speed, and as a result of various studies, as shown in Figs. 7 and 8,
Through some ingenuity, it is possible to reliably and stably divide the flow into two parts (up and down) (regardless of line speed), and keep the surface heat transfer coefficient constant regardless of line speed. Now I can do it.

The feature of this embodiment is that the member E in FIG. 7 is provided. A member E having such a rectifying effect is provided at the center of each nozzle b in Fig. 5 so that its tip is aligned on the same straight line as the nozzle outlet, and its rear end is aligned with the rear end of the nozzle header a. , the length was such that they were on the same straight line. In this example, a SUS steel plate with a fin thickness of 2.0 is used, and reinforcing members (f, g in Fig. 7), which are round bars with a diameter of 3 to 0, are installed at a pitch of 100+ mn in the width direction of the strip. The main body and
Constructed as one.

Note that the length of the rear end of the member E (the length in the flow direction of the discharged water after colliding with the steel plate) needs to be long to a certain extent in order to have a sufficient rectifying effect. So,
It was necessary to extend the nozzle header a to the rear of the line connecting the centers of the nozzle header a (S in FIG. 7).

In this example, 8.75
mm (D/ in Fig. 8).

In this manner, the entire apparatus was constructed as shown in FIG. FIG. 8 is the same as FIG. 4 and FIG. 5 except that member E shown in FIG. 7 is added. In this example, as shown by the arrows in FIG. 8, a flow pattern in which the impinging jets from each nozzle are divided into two impinging jets was reliably and stably obtained. Although the running speed of the strip 1 may be varied up to 3 U Ompm and the vibration condition of the strip 1 varies depending on the shape of the strip 1, the flow pattern is extremely stable and the result is (Japanese) It was confirmed that the cooling rate of IJzzo 1 will be kept extremely stable.

Note that the above-described cooling water injection nozzle b of the present invention is not limited to the slit-shaped one shown in FIG. ) etc. are attached to one header a at intervals, it goes without saying that similar effects can be obtained. In Figure 9, a is a nozzle header, and b is a nozzle, which is a circular tube nozzle or a nozzle tip such as a flat spray.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration of a conventional strip cooling method, Fig. 2 is an enlarged sectional view of the cooling water injection device, and Fig. 3 is a diagram showing the structure of a conventional strip cooling method. An explanatory diagram showing the flow of cooling water, Figure 4 is a sectional view showing the structure of the cooling water injection nozzle and header used in the invention, and Figure 5 shows the nozzle and header placed in immersion water. Fig. 6 is an explanatory diagram of the method of the present invention showing the state, Fig. 6 is an explanatory diagram of the operation and effect comparing the cooling effect of the method of the present invention and the conventional method, Fig. 7
8 are a sectional view corresponding to FIG. 4 showing a second embodiment of the present invention and an explanatory view corresponding to FIG. 5, and FIG. 9 is a perspective view showing an example of a modification of the cooling water injection nozzle. 1... Strip, a... Nozzle header, b...
・Cooling water injection nozzle. Applicant's representative Patent attorney Takehiko Suzue Figure 3 (A) (B) Figure 4 Figure 5 Figure 8 Figure 9

Claims (1)

[Claims] Cooling water injection nozzles are provided in multiple stages in the immersion water that cools the heated strips, and the headers of each nozzle are spaced apart from each other in the direction in which the strips travel, so that a jet of cooling water collides with the cooled surface of the strips. A method for cooling a strip, characterized in that the strip is uniformly cooled in the width direction by letting the goo flow out from the gap between each header to the rear of the header.