KR200272350Y1 - Cooling Roll for Double Roll Type Sheet Casting Machine - Google Patents

Abstract

The present invention relates to a cooling roll for laminating molten steel by the cooling effect of the cooling water introduced into the roll of the twin roll type sheet casting apparatus for producing a thin sheet directly from the molten metal, and the cooling water to cool the cooling roll for manufacturing the thin sheet. In forming a plurality of cooling water holes at equal intervals along the circumferential direction so as to flow, the diameters of the entrance and exit sides of the cooling water holes are different, but the cooling water holes at the entrance side are large and the cooling water holes at the exit side are small. The cooling roll for sheet metal casting apparatus is a summary.

Description

Cooling roll for twin roll sheet casting machine

The present invention relates to a cooling roll for forming molten steel by the cooling effect of the cooling water introduced into the roll of the twin roll type sheet casting apparatus for producing a thin sheet directly from the molten metal. By uniformizing the cooling capacity of the roll between both ends of the roll width direction to stabilize the operation during casting and to improve the quality of the thin plate.

As shown in FIG. 1, the twin roll type sheet casting apparatus manufactures a thin plate 5 directly through a rotating cooling roll 3 having a cooling water hole 4 through which cooling water flows through the molten steel 2 supplied from the nozzle 1. The cooling characteristics of the cooling roll 3 are greatly dependent on the cooling water holes 4 for cooling the cooling roll 3.

FIG. 2 shows a conventional cooling water passage inside the cooling roll 3. The cooling water introduced through the center of the cooling roll 3 has a one-way flow from the roll width direction both ends 7 toward the other roll width direction both ends 7. This is usually the case.

However, a problem in casting the thin plate 5 using the cooling roll 3 having such a one-way cooling water flow is that the cooling water passes from both ends of the cooling roll width direction 7 to the other ends of the cooling roll width direction 7. Due to the amount of heat absorbed from the molten steel, the cooling water temperature rises, and the thermal expansion amount in the radial direction of the cooling roll 3 due to the coagulation capacity gradient between the roll width direction both ends 7 of the cooling roll and the temperature gradient in the cooling roll 3 width direction. Due to the difference, the shape of the cast slab (6) ultimately cast is not uniform in the width direction of the cooling roll (3), as well as affects the difference in roll repulsion force between the ends of the roll width direction (7) to require extreme precision Process control of the twin roll casting method also causes many problems.

In general, the heat transfer phenomenon in the coolant hole 4 depends on the heat transfer coefficient at the coolant hole 4 which is determined by the flow rate, the geometric size and the shape at the coolant hole 4, and the thermoelectric coefficient values are the same shape ( In the conventional cooling water hole 4 having the shape of the cooling water hole 4 having the contact area and having the same heat transfer coefficient value in the width direction, it is difficult to eliminate the thermal expansion difference in the cooling roll 3 widthwise. Remains.

Therefore, as one way to solve this problem, inserts 6 and 6a having different diameters in the width direction of the cooling roll 3 are mounted in the cooling water holes 4 as shown in FIG. Cooling Roll (3) The cooling roll (3) has been devised that can reduce the thickness variation and the roll repulsion difference due to the difference in thermal expansion amount.

This conventional design has a heat transfer at the inlet side 4 of the cooling water hole and the cooling water hole exit 8 when the cooling water hole flow rate adjusting insert 6 is inserted into the cooling water hole 4 of the cooling roll 3 as shown in FIG. The coefficient can be changed by the cooling water speed and the change in the effective diameter of the cooling water hole 4 to offset the heat transfer difference of the cooling roll 3, thereby offsetting the effect of increasing the cooling water temperature.

However, the conventional method of adjusting the heat transfer of the roll end portions 7 by mounting the inserts 6 having different diameters in the width direction of the cooling roll 3 in the cooling water hole 4 is equivalent to fabrication because the shape of the insert is not simple. Not only is there a problem that a separate expense of the liquid is required, but above all, in order to mount the inserts 6 and 6a in the coolant hole 4, the coolant hole 4 is limited to a certain size or more.

In other words, commercial rolls usually have a roll width of more than 1000mm, and if the size of the cooling water hole 4 becomes smaller than about 10mm, the diameter of the inserts 6 and 6a is too small, resulting in an effective heat transfer difference. The processing of (6) (6a) is almost impossible, and there are also many difficulties in mounting. For effective processing and mounting of inserts (6) (6a), the roll width should be at least 20mm for wider rolls over 1000mm.

Therefore, in the present invention, in order to solve this problem of the roll using the conventional insert, the thickness variation due to the difference in the amount of thermal expansion of the roll between the ends of the roll by making the size of the coolant hole different from the inlet and outlet of the coolant even without a separate insert. And providing a cooling roll capable of reducing the difference in roll repulsion.

The present invention having the purpose as described above causes a difference in heat transfer effect in the cooling water holes at both ends of the roll width direction among the cooling rolls used in the twin roll-type thin plate manufacturing apparatus, and at the same time, reduces the size of the cooling water holes to improve the overall cooling performance of the rolls. It is characterized by a dual roll type sheet casting device cooling roll having a structure that uniformly cools the cooling roll by varying the ratio of the heat transfer coefficient value aimed at the diameter of the inlet and the outlet side of the cooling water hole for the purpose.

Figure 1 is a schematic diagram for showing the side of the cooling roll for producing a thin plate in a typical double roll type sheet casting apparatus

Figure 2 is a schematic cross-sectional view showing the flow of coolant inside the cooling roll for a conventional twin-roll thin plate casting apparatus

3A and 3B are perspective views of an insert used in a cooling water hole inside a cooling roll for a conventional twin roll sheet casting device.

Figure 4a, b is a cross-sectional view of the insert inserted in the cooling roll for a twin-roll type sheet casting apparatus equipped with a conventional insert

5 is a cross-sectional view showing a cooling water hole of the cooling roll for a twin roll thin plate casting device of the present invention.

Figure 6 is a front view showing the cooling water holes of the cooling roll for the twin-roll thin plate casting apparatus of the present invention

<Code Description of Main Parts of Drawing>

1: nozzle 2: molten steel

3: cooling roll 4: cooling water hole

5: sheet 6,6a: insert

7: both ends

5 and 6 show side cross-sectional views and front views of cooling rolls 3 having different sizes of cooling water holes 4 at the cooling water inlet and outlet sides of the present invention, and the difference between the sizes of cooling water holes 4 is the cooling roll 3. The effect on the cooling ability of both ends 7 is shown as compared with the case where the conventional inserts 6 and 6a are used.

When there is an insert in a coolant hole having a predetermined shape, the thermoelectric coefficient value at the coolant hole 4 is obtained by an empirical formula, and the following Dittus-Boelter equation is widely used.

Nu = (h × D ') / k = 0.023 × Re ^0.8 × Pr ^0.4

Re = (U × D) / ν

Pr = (C _p × ν × ρ) / k

Where h is the heat transfer coefficient

D ': Representative length (D-d, D: Coolant hole diameter, d: Insert diameter)

k: cooling water thermal conductivity,

U: coolant average flow rate,

ν: cooling water kinematic viscosity,

C _P : Coolant Specific Heat

ρ: coolant density

From this equation, h is expressed as

h = Constant × U ^0.8 × D ^-0.2

U = Constant '/ (D ² -d ² )

Finally

h = Constant "× (1 / CD-d) ^0.2 × (1 / (D ² -d ² )) ^0.8

<Example 1>

When using conventional inserts 6 and 6a in cooling water holes 4

As an example, if the inserts 6 and 6a of FIGS. 3A and 3 are diameters of 5 mm and 15 mm, respectively, in the coolant hole 4 having a diameter of 20 mm, the heat transfer coefficient values for the diameters of the inserts 6 and 6 a are as follows. As follows.

5mm insert: h = constant ”× (1/15) ^0.2 × (1/375) ^0.8 = constant” × 5.1 × 10 ^-3

15mm Insert: h = constant "× (1/5) ^0.2 × (1/175) ^0.8 = constant" × 11.6 × 10 ^-3

Therefore, the heat transfer coefficient values at both ends of the roll width 7 may be about twice as large, and may have an effect of canceling the effect of increasing the cooling water temperature.

<Example 2>

In the case of the present invention, when the hole diameter on the cooling water inlet side is 20 mm, the same effect as in Example 1 can be obtained if the hole diameter on the cooling water outlet side is about 13.5 mm.

20 mm hole: h = constant "x (1/20) ^0.2 x (1/400) ^0.8 = constant" x 4.6 x 10 ^-3

13.5mm hole: h = constant "x (1 / 13.5) ^0.2 x (1 / 182.25) ^0.8 = constant" x 9.2 x 10 ^-3

In addition, even if the size of the cooling water hole is small in the case of the present invention can obtain the same effect as in Example 1, for example, even if the entrance hole diameter is 10mm and the exit diameter is 7mm as follows: The heat transfer coefficient of) can be seen that the difference of about 2 times.

10 mm hole: h = constant "x (1/10) ^0.2 x (1/100) ^0.8 = constant" x 15.8 x 10 ^-3

7 mm hole: h = constant "x (1/7) ^0.2 x (1/49) ^0.8 = constant" x 30.1 x 10 ^-3

In particular, when the size of the cooling water hole 4 is small, not only can a difference in the heat transfer coefficient values at both ends of the width 7 be obtained, but the overall heat transfer coefficient value is increased, resulting in increased productivity of the double roll 3 itself. It also has the side effect of simultaneously improving and increasing durability.

Cooling water hole for the purpose of improving the overall cooling capacity of the roll by reducing the size of the cooling water hole and making the difference in the heat transfer effect in the cooling water hole at both ends of the cooling roll in the cooling roll used in the twin roll type sheet manufacturing apparatus. There is an effect of uniformly cooling the cooling rolls by differing by the ratio of the heat transfer coefficient values aimed at the diameter of the inlet and outlet sides.

Claims (1)

In forming the plurality of cooling water holes 4 at equal intervals along the circumferential direction so that the cooling water flows to cool the cooling roll 3 for manufacturing the thin plate 5, the diameters of the inlet and outlet sides of the cooling water holes are different. Cooling roll for twin roll type sheet casting device, characterized in that the cooling water hole on the inlet side is large and the cooling water hole on the outlet side is small.