JPH04284914A - Flow rate setting method for flange water-cooling device - Google Patents

Abstract

PURPOSE:To provide a flow rate setting method a flange cooling device to prevent a shape defect such as bending or buckling, etc., after cooling when shapes having flanges of H-shape steel or I-shape steel, etc., are manufactured by rolling. CONSTITUTION:By processing a controlling range of cooling capacity of a spray nozzle 2 at each step of a water cooling device 4 for a flange as a parallelogram formed of an injection-collision area S and a water flowing area F, the amount of water of the nozzle at each step is set.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate setting method for a flange water cooling device.

0002

[Prior Art] Generally, when hot rolling steel sections with complex cross-sectional shapes, such as H-section steel and I-section steel, the temperature difference within the cross section caused by the difference in wall thickness at various parts of the cross section causes bending and bending after cooling. It is known that shape defects such as buckling occur.

[0003] Therefore, in order to prevent this shape defect,
A method is used in which the thick-walled flange is forcibly cooled with water during or after hot rolling to uniformize the temperature distribution within the cross section of the steel section.

FIG. 8 shows an example of an H-shaped steel rolling line, in which the rolled material is heated and soaked in a heating furnace 5, then roughly rolled in a breakdown mill 6, and then final rolled in an intermediate universal mill 7 and an edging mill 8. After being rolled to a size and shape close to the product, it is shaped using a finishing universal mill 9. After that, flange water cooling devices 4 are installed on both sides of the H-beam conveyance line.
By forcibly cooling both sides of the flange with water, the temperature difference within the cross section is reduced, and in the next step, the flange is cut to a predetermined length and then left to cool.

As shown in FIG. 9, the flange water cooling device 4 uses a multistage nozzle header 3 in which a large number of spray nozzles are arranged.

Regarding the method of setting the flow rate in this multi-stage nozzle header, as disclosed in Japanese Patent Laid-Open No. 2-92413, the entire surface to be cooled is evaluated by the cooling capacity of the surface on which the cooling water jets from each stage nozzle collide. A method has been adopted to do so.

That is, based on the cooling rate when a constant water density is injected from the nozzles of each stage, the effective water density is calculated for each injection area of each stage nozzle, and this effective water density is calculated when the flowing water is 0. This is a method of setting the water volume of each stage nozzle by expressing the ratio of the effective water volume density of the top stage as a function of the water volume density flowing downward from above and the actual water volume density.

[0008]

[Problems to be Solved by the Invention] However, the method disclosed in JP-A-2-92413 is effective when the number of nozzle stages is large and the mounting angles of the nozzles are the same; It has been found that this method is unsuitable for a small number of cooling stages, for example, two to three stages, because the mounting angle of the nozzle is different for each stage.

That is, in two- to three-stage cooling, the influence of the flow of water jetted from each nozzle itself is large within the jetting area of each nozzle, and the entire cooling surface cannot be evaluated as the jetting surface.

[0010] Therefore, the main object of the present invention is to prevent the occurrence of shape defects such as bending and buckling when manufacturing a section steel having a flange such as an H section steel or an I section steel by rolling, and to prevent the formation of a nozzle. The present invention provides a flow rate setting method for a flange cooling device that can be applied to cooling with a small number of stages, for example, 2 to 3 stages. The present invention provides a flow rate setting method for a flange water cooling device in which the amount of water for each nozzle can be set using a cooling capacity evaluation formula.

[0011]

[Means for solving the problem] The above problem is solved by a flange water cooling system in which a large number of cooling water injection nozzles are arranged in multiple stages in the height direction facing a section steel whose flange surface is placed almost perpendicular to a horizontal surface. A flow rate setting method for forcibly cooling the flange surface of the section steel during or after hot rolling using a device, the flow rate being determined in advance by determining the amount of water in each stage nozzle and the flange of the cooling water when injected from each stage nozzle. By determining the relationship between the heat transfer coefficient in the running water area considering the surface collision area and flowing water, and evaluating the heat transfer coefficient of each stage nozzle as a function of the collision area and the running water area, This can be solved by sequentially setting the amount of water for each stage.

0012

[Function] As shown in FIG. 1(B), the present inventor developed a flange water cooling system in which cooling water injection nozzles 2 are arranged in three stages in the height direction with respect to the flange 1f of the H-section steel 1 after hot rolling. Cooling water is injected onto the flange 1f surface of the H-shaped steel 1 by the device 4,
When forced cooling was performed, the following was found.

(1) The jetted water that collides with the vertical flange surface becomes flowing water along the surface and flows downward, but it does not flow under the injection area S of the lower nozzle, but flows into the lower drainage area F.
flows to (2) In multi-stage spray cooling, as shown in Figure 2,
The heat transfer coefficient, which is an index of the cooling capacity, can be divided into a jet impingement area S where the jet water hits directly and a flow area F where the water flows downstream. (3) The cooling capacity control range of each stage nozzle is shown in Figure 1 (
As shown in A), it can be treated as a parallelogram formed by the jet collision area S and the flowing area F. From the above experimental results, in the present invention, the heat transfer coefficients αS, αF (
kcal/m2h℃) as shown in Figures 3 and 4.
It can be organized as a function of water quantity Qi (l/min · book). αS = f(Qi)...(1) αF = g(Qi)...(2) On the other hand, the influence of flowing sewage water (ΣQ) from above increases the heat transfer coefficient multiple of the flowing water area, as shown in Figure 5. Regarding k, it can be summarized by the ratio of flowing sewage water to the amount of water (ΣQ/Qi). k=h(ΣQ/Qi)...(3) where h: heat transfer coefficient. Therefore, from each of the above equations, the cooling capacity αi of each stage nozzle
(kcal/m2h°C) can be expressed by the following equation, assuming that the length ratio of the collision area and flowing area of each stage nozzle in the conveyance direction is lS and lF. αi = lS f (Qi ) + lF g (Qi )
×h(ΣQ/Qi)...(4) =F(Q
i)...(4)', Qi =F-1(αi)...
...(5) That is, if each heat transfer coefficient αi is given as the target cooling capacity of each stage nozzle, the water amount of each stage nozzle can be set sequentially from the upper stage using equation (5).

[0014] Then, based on the set water volume of each stage nozzle, cooling water is injected from each stage nozzle to water-cool the flange of the H-section steel, thereby making the temperature distribution within the cross section of the H-section steel uniform. Therefore, it is possible to prevent shape defects such as bending and buckling after cooling.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in more detail below with reference to embodiments shown in the drawings. As a rolling line for carrying out the present invention, the rolling line shown in FIG. 8 described above was applied as is, and forced water cooling of the flange of an H-section steel was carried out under the following conditions.

As shown in FIGS. 1A and 1B, the flange water cooling device 4 according to the present invention has spray nozzles arranged in three stages in the height direction with respect to the flange 1f, which is substantially perpendicular to the horizontal plane. The spray nozzle 2 was arranged with a twist angle δ, and the spray angle of the upper stage of the spray nozzle 2 was 40°, and the spray angle of the middle and lower stages were 80°. Moreover, the mounting pitch of the water cooling device 4 was a staggered arrangement every 250 mm in the transport direction of the H-section steel, and the mounting pitch was every 75 mm in the height direction. Table 1 shows the mounting angle of each stage nozzle. Further, the horizontal distance between the nozzle 2 group and the flange 1f surface was 200 mm.

[0017]

[Table 1]

Next, prior to water cooling the flange of the H-section steel,
A flow rate setting method for a flange water cooling device according to the present invention will be explained. In addition, in Table 2, the target stop temperature in this example is 725° C., and the target heat transfer coefficient at each stage is set by calculation in advance.

[0019]

[Table 2]

First, the flow rate setting of the flange water cooling device is as follows.
It was determined from the water volume of the upper nozzle. αi = lS f (Qi ) + lF g (Qi )
×h(ΣQ/Qi)...(4) Here, from the nozzle conditions in Table 1, the length ratio of the collision area of the upper stage nozzle lS = 0.34 The length ratio of the flowing area of the upper stage nozzle lF = 0.66 Also, since it is in the upper stage, since the flowing water ΣQ = 0, the heat transfer coefficient multiple k = h (ΣQ/Qi) = 1.0 of the flowing water area. Also, from the relationship between the water volume of the upper stage nozzle and the heat transfer coefficient, the impact area Heat transfer coefficient αS =
f (Qi ) = 15.4Q12.52 Heat transfer coefficient of flowing water area αF = g (Qi ) = 145Q10.81 Therefore, the cooling capacity of the upper nozzle is α1 = 5.24Q1
2.52 +95.7Q10.81 ...(6)(6)
From the formula, the diagram shown in Figure 6 can be expressed, and as a result, α1 = 1500 kcal/m2h ℃ The water amount is Q1
=8l/min ・Books are obtained.

Next, the amount of water in the middle nozzle is determined in the same manner as above.

[0022] Length ratio of the collision area of the middle nozzle lS = 0
．． 6 Length ratio of middle nozzle flow area lF = 0.4 Heat transfer coefficient of collision area αS = f (Qi ) = 2.0Q22.52
Heat transfer coefficient of flowing water area αF = g (Qi) = 875Q20
．． 27 Therefore, the cooling capacity of the middle nozzle is α
2 = 1.2Q22.52 +350Q20.27 ×
h(8/Q2)...(7) From equation (7), the diagram shown in Figure 6 can be expressed, so as a result, α2 = 2500kcal/m2h The amount of water at ℃ is Q2
=18l/min ・Books are obtained.

Incidentally, from FIG. 5, the heat transfer coefficient multiple k=h(8/18)=1.04 of the flowing water area can be found.

Finally, the amount of water in the lower nozzle is determined in the same manner as above.

[0025] Length ratio lS of the collision area of the lower nozzle = 0
．． 43 Length ratio of lower nozzle flow area lF = 0.57 Heat transfer coefficient of collision area αS = f (Qi ) = 1.1Q32.52
Heat transfer coefficient αF = g (Qi ) = 746Q3
0.27 Therefore, the cooling capacity of the lower nozzle is
α3 =0.47Q32.52 +425Q30.27
×h(26/Q3)...(8) From equation (8), Figure 6
As a result, α3 =
The amount of water at 1500kcal/m2h ℃ is Q3 = 16l
/min ・You can get a book.

Incidentally, from FIG. 5, the heat transfer coefficient multiple k=h(26/16)=1.14 of the flowing water area can be found.

Table 2 shows the target heat transfer coefficients for each stage nozzle described above, as well as the flow rate set values according to the present invention method and the flow rate set values according to the conventional method, which were determined by the above method.

[0028] Note that the inclination angle (γ) and twist angle (δ
), the angle is determined to prevent cooling water from getting on the web surface and to prevent insufficient cooling or overcooling.
If both angles are 30 degrees or less, the purpose can be achieved without any problem. Further, the arrangement of the nozzles is determined by the spray angle and distance, but a staggered arrangement is preferable. Furthermore, although this embodiment has shown an example in which the determination is made from the top, it is not necessarily necessary to determine the determination sequentially from the top.

Based on the flow rate setting values set by the method of the present invention and the conventional method, 850 The flange surface was forcibly cooled while being transported for about 12 seconds. As a result, as shown in Fig. 7, in the conventional method, there is considerable variation in temperature distribution, whereas in the method of the present invention, it is possible to achieve almost the target stop temperature within ±10°C. can.

[0030]

As described above, according to the present invention, the water volume of each nozzle can be set using a highly accurate and simple cooling capacity evaluation formula, and as a result, the temperature distribution within the cross section of the H-section steel after cooling is uniform. Therefore, occurrence of shape defects such as bending and buckling can be prevented.

[Brief explanation of the drawing]

FIG. 1 (A) is a diagram showing a cooling control mechanism according to the present invention. (B) is a side view showing the arrangement of spray nozzles according to the method of the present invention.

FIG. 2 is a diagram showing the relationship between the temperature and heat transfer coefficient of the collision area and the flowing water area.

FIG. 3 is a diagram showing the relationship between the amount of water in the collision zone and the heat transfer coefficient.

FIG. 4 is a diagram showing the relationship between the amount of water and the heat transfer coefficient in a flowing water area without running water.

FIG. 5 is a diagram showing the influence of flowing sewage.

FIG. 6 is a diagram showing the relationship between heat transfer coefficient and water amount.

FIG. 7 is a diagram showing temperature measurement results before and after flange water cooling after rolling.

FIG. 8 is a schematic diagram showing a rolling line for H-section steel.

FIG. 9 is a side view showing the arrangement of spray nozzles according to a conventional method.

[Explanation of symbols]

1 H-beam steel 1f flange 2 Spray nozzle 3 Cooling header 4 Flange water cooling device 5 Heating furnace 6 Breakdown mill 7 Intermediate universal mill 8 Edging mill 9 Finishing universal mill

Claims (1)

[Claims] [Claim 1] A flange water cooling device in which a large number of cooling water injection nozzles are arranged in multiple stages in the height direction facing a section steel whose flange surface is placed substantially perpendicular to a horizontal plane.
A flow rate setting method for forcibly cooling the flange surface of the section steel during or after hot rolling, in which the amount of water in each stage nozzle and the flange surface collision area of the cooling water when injected from the each stage nozzle are determined in advance. By determining the relationship between the heat transfer coefficient in the flowing water area considering flowing water, and evaluating the heat transfer coefficient of each stage nozzle as a function of the collision area and the flowing water area, the water volume of each stage nozzle can be determined. A flow rate setting method for a flange water cooling device characterized by setting the flow rate sequentially for each stage.