KR20000040930A - Cooling roll for twin roll type thin film casting machine - Google Patents

Abstract

PURPOSE: A cooling roll for a twin roll type casting machine is provided to manufacture cast pieces with a certain thickness by forming the equal solidified shells over the entire width of a roll contacted with a ladle. CONSTITUTION: A solidified shell starts to be cooled by contacting a ladle with a couple of rolls(3a,3b). The solidification is delayed by widening a gas gap between the solidified shell and the rolls. A solidification delay part is formed over the entire width of the rolls and the solidified shell widthwise the rolls is equalized. At the same time, cast pieces have the equal thickness when passing through the rolls.

Description

Cooling roll for twin roll sheet casting machine

The present invention relates to a cooling roll employed in a twin-roll type sheet casting machine, and more particularly, by providing a fine curved surface on the outer peripheral surface of the roll to prevent abnormal solidification phenomenon (coagulation delay) occurring on both edges of the casting during casting, and thus the edge portion is good. The present invention relates to a cooling roll for a twin-roll type sheet casting machine capable of manufacturing a cast having a shape, which can stabilize the operation and improve the quality of the sheet during casting.

In general, the twin-roll type sheet caster 10 rotates the molten steel 2 supplied from the nozzle 1 as a driving motor (not shown) while cooling the molten steel 2 supplied from the nozzle 1 with cooling water. It is a device for directly manufacturing the slab (5), the quality and shape of the cast (5) to be cast is appropriate compensation method of the thermal expansion amount of the roll (3a) (3b) and solidification in the width direction of the roll (3a) (3b) Depends heavily on ability

Figure 2 shows the initial state in which the molten steel (2) is in contact with the roll (3a) (3a) to form the solidified shell (4) in a general twin roll type sheet casting machine, when the solidified shell (4) begins to form As shown in the S direction, the solidification shell 4 at both ends of the roll is contracted to the center portion 7 of each of the rolls 3a and 3b. As shown in FIG. The gas gap 6 between 3b becomes larger than the roll center part 7. The difference in the size of the gas gap 6 between the two edge portions 8 and the center portion 7 is only a few microns so that it is difficult to visually observe, but the slab 5 and the roll 3a (a) affecting the coagulation ability ( There is a big difference in the heat transfer coefficient values between 3b), and as a result, the solidification of the cast 5 is delayed at both edge portions 8 of each roll 3a, 3b.

The solidification delay at both edge portions 18 of the cast piece 5 generated during the initial contact is continuously affected by the increase in the contact time between the cast piece 5 and the rolls 3a and 3b. The solidification shell 4 at both edge portions 18 when the slab 5 exits the roll nip, because it causes a relative decrease in the thickness of the solidification shell 4 at both edge portions 18. The thickness and the thickness of the solidification shell (4) in the central portion 17 will be a big difference.

Therefore, both edge portions 18 having a small thickness of the solidified shell 4 are separated from both edge portions 18 due to molten steel (non-solidified shell) or the like in the central portion 17 of the cast steel 5, or Swelling bulging occurs. That is, generally, the shape of the rolls 3a and 3b is the center of the rolls 3a and 3b, as shown in Fig. 3 (a) to compensate for the thermal expansion of the rolls 3a and 3b during casting. Both edge portions 18 of the cast piece 5 cast while passing between the rolls 3a and 3b even when the crowns are formed such that the recesses 7 are concave and both edge portions 8 are convex. As a result of the bulging phenomenon of the unsolidified molten steel in the center, as shown in FIG. 3 (b), the center portion 17 is flat and both edge portions 13 have a rather thick shape.

If the bulging phenomenon occurs on both edge portions 18 of the slab 5, not only will the quality of the sheet be lowered and the real error rate will be lowered, but also the diameter of the slab edge portion 18 will continue to increase during winding. This can cause various problems, such as the occurrence of wave in time. Therefore, it is essential to uniformly cool the width direction of the rolls (3a) and (3b) in terms of stable operation and improvement of cast error rate, and various methods have been devised for this purpose.

As a countermeasure for preventing the lowering of the solidification ability of the cast piece 18 as described above, the method of greatly varying the width solidification ability of the rolls 3a and 3b and the deformation of the initial crown shape of the rolls 3a and 3b. Two methods have been mainly devised to improve the solidification performance at the edge portion 8 of both rolls 3 and 3b by varying the roll spacing in the rolls.

First, one method of changing the widthwise cooling ability of the rolls 3a and 3b is to reduce the roughness distribution on the surfaces of the rolls 3a and 3b so that both edge portions 8 of the rolls 3a and 3b are made smaller. On the other hand, the center portion 7 of the rolls 3a and 3b is made larger so that the cooling ability at the edge portion 8 of the rolls 3a and 3b is larger than the center portion 7 of the rolls 3a and 3b. This is to prevent the bulging phenomenon on both edges 18 of the cast piece 5 to be cast (Japanese Patent Laid-Open No. 9-327753).

In addition, there is another method of arbitrarily adjusting the initial roll crown shape applied to offset the thermal expansion amount in the same state so that the solid phase rate of the slab edge portion 18 in the roll fin becomes higher than or equal to a certain value (Japanese Patent). 9-103845).

However, as described above, the method of canceling the difference in cooling ability between the two edge portions 18 and the central portion 17 of the cast piece 5 by varying the surface treatment in the width direction of the rolls 3a and 3b is a coagulation ability. There is a limit to the roll surface roughness difference applied to make a difference. That is, in order to improve the relative cooling ability of both edge portions 18 of the cast piece 5, roughness is reduced to both edge portions 8 of the rolls 3a and 3b, while the center portion of the rolls 3a and 3b is reduced. (7) should be large, but since the surface roughness of a certain level is required to generate cracks on the surface of the cast slab 5 to be cast, the roughness of the center portion 7 of the rolls 3a and 3b must be made very large. . Therefore, in this case, since the surface shape of the rolls 3a and 3b is transferred to the surface of the cast piece 5, the glossiness of the central portion 17 of the cast piece 5 is at both edge portions of the cast piece 5. It differs from (18), causing many problems in post-treatment such as post-cast cold rolling.

In addition, the method of adjusting the crown amount formed in the both ends of the roll 3a (3b) so that the solid-state rate value of the two edge parts 10 of a slab may become fixed or more in the roll is the edge part 18 of the cast piece 5 Although the bulging phenomenon can be prevented, the resulting slab 5 has a crown shape in which the thickness of the center portion 17 is considerably larger than that of the edge portion 18. There has been a problem that the real rate of the cast slab 5 is lowered, such as having to slit a substantial portion.

In addition, in both of these methods, when the casting thickness and the cast steel type are different, the cooling ability difference between the center portion 17 and the edge portion 18 of the cast steel 5 is generated, and thus edge bulging phenomenon occurs as in the prior art, or as a roll 3a. There is a problem that undesirable phenomena such as excessive roll repulsion force acting on both edge portions 8 of 3b) may occur.

Accordingly, the present invention is to solve this conventional problem, the object is to form a bent portion in the center of the roll, the shrinkage phenomenon of the cast when contacting the molten steel and the roll not only at the edge of the roll but also at the center of the cast The present invention is to provide a cooling roll for a twin-roll sheet caster that can cast a cast of a certain thickness by forming a uniform solidification ability over the entire width of the roll in contact with the molten steel.

1 is a schematic view showing a typical double roll type sheet casting machine,

Figure 2 is a schematic diagram showing the solidification state of the initial molten steel in a general twin roll sheet casting machine,

Figure 3 (a) (b) is a schematic diagram showing the shape of the cast having a non-solidified roll and the roll having a crown of the general twin-roll sheet caster,

Figure 4 is a schematic diagram showing the shape of the cooling roll for a twin roll thin caster according to the present invention,

Figure 5 is a schematic diagram showing the cast slag solidification during the initial molten steel contact in the cooling roll for the twin-roll sheet caster according to the present invention.

Explanation of symbols on the main parts of the drawings

1 ..... Nozzle 2 ..... Molten Steel

3a, 3b ..... roll 4 ..... solidified shell

5 ..... Cast 6 ..... Gas gap

7 ..... Center of roll 8 ..... Edge of roll

17 ..... Center of cast steel 18 .... Edge of cast steel

20 ..... Bend C ...... Crown

22, 25 .... Height 23, 24 .... Bottom length

The present invention as a technical configuration for achieving the above object,

In the sheet casting machine for manufacturing a cast steel by injecting molten steel supplied from the nozzle between a pair of rolls flowing the cooling water,

The roll is formed in the center of the roll with a base length equal to the bottom length of the crown, and formed of a plurality of bent portions having a height twice as large as the crown height and having a slope twice as large as that of the crown. By providing a cooling roll for a twin-roll sheet caster characterized in that the solidification ability in the width direction of the uniform.

Figure 4 is a schematic diagram showing the shape of the cooling roll for the twin-roll sheet caster according to the present invention, Figure 5 is a schematic diagram showing the cast steel solidification during initial steel contact in the cooling roll for a twin-roll sheet caster according to the present invention. .

As shown in FIGS. 4 to 5, the twin roll-type sheet casting machine cooling roll 30 according to the present invention has roll edges during initial solidification of the rolls 3a and 3a through which cooling water flows and the molten steel 2 contained in the molten metal pool. The plurality of bent portions 20 are formed to protrude on the outer circumferential surface of the roll center portion 7 so as to eliminate the coagulation delay occurring in the portion 8.

As shown in FIG. 4, the bent portion 20 formed on the outer circumferential surface of the center portion 7 of the rolls 3a and 3b has a crown formed on both edge portions 8 of the rolls 3a and 3b. It is appropriate that the average inclination of C) is about twice, and the bottom length 24 corresponding to 1/2 of the bottom face length L of the bent part 20 is rolled from both ends of the edge part 8. It is the same as the bottom length 23 of the crown C, which starts in the width direction of 3a) and 3b and ends at the center portion 7 of the roll, on the outer peripheral surface of the center portion 7 of the rolls 3a and 3b. The height 25 of the radially protruding portion 20 is twice as long as the height 22 of the crown C protruding in the radial direction and is continuously arranged on the central outer circumferential surface of the rolls 3a and 3b. Is formed.

Accordingly, the inclination of the bent portion 20 formed at the uppermost part of the bent portion 20 to the left and right sides thereof has a base length 24 having the same size as the bottom length 23 of the crown C, and Since the height 25 having a size twice as large as the radial height 22 of the crown C is formed as the bend height 25 / bend bottom length 24, the inclination of the bend 20 is a radius. As the crown height 22 / crown bottom length 23 in the direction, it protrudes approximately twice as large as the inclination of the crown C formed on both edge portions 8 of the rolls 3a and 3b.

In addition, in the general cooling roll of the commercial thin sheet casting machine, the radial crown height 22 is usually 100-300 microns, whereas the base length 23 of the crown C of the rolls 3a and 3b of the present invention is 50. As formed to a large length of from 100 mm to 100 mm, the bent portion 20 formed in the central portion 7 of the rolls 3a and 3b is generally roll 3a or 3b for the purpose of preventing surface defects of the slab 5. Dimples (approximately 50 microns in depth and 500 microns in diameter) and their roles are fundamentally different from those applied to the outer surface of the), and there is no difficulty in processing the rolls 3a and 3b. Have

The function of the curved part 20 formed in the center part 7 of these rolls 3a and 3b is as follows. That is, as described above, the solidification at both edge portions 10 of the cast piece 5 cast in the sheet casting machine having only the crown C at the left and right edge portions 8 is relatively smaller than the central portion 9. In the process of solidifying and contracting the molten steel 2, the cast steel 5 and the rolls 3a and 3b are formed on both sides of the roll 8 by the shape of the rolls 3a and 3b in contact with the molten steel 2. Since the gap between the gaps 6 is larger than that of the other parts, the phenomenon that the molten steel 2 shrinks as it solidifies into the slab 5 passes between the rolls 3a and 3b, is a natural phenomenon.

At this time, in the place where the inclination is severe, such as both edge portion 8 in which the crown (C) is formed, the additional generation of the gas gap (6) during shrinkage becomes large, the heat transfer is particularly delayed, as shown in Figures 4 and 5 Likewise, when the bent portion 20 having a size twice as large as the inclination of the crown C is also provided to the center portion 7 of the rolls 3a and 3b corresponding to the center portion 17 of the cast piece 5, Shrinkage of the solidification shell 4 generated during initial contact between the molten steel 2 and the rolls 3a and 3b is not only at both edges 8 of the rolls 3a and 3b but also in the rolls 3a ( Since it occurs evenly over the entire width of 3b), uniform solidification can be obtained.

That is, when the molten steel 2 starts to contact with the rolls 3a and 3b and starts to cool after the solidified shell 4 is formed, the solidified shells are formed at both edge portions 8 of the rolls 3a and 3b. In the upper part of the bent part 20 formed in the center part 7 which corresponds to the roll part 3a (3b) which corresponds to the center part 17 of the cast piece 5 cast for the same reason as (4) lifts, the solidification shell 4 As the gas gap 6 increases between the roll and the rolls 3a and 3b and the solidification is delayed, when the unevenness of the bent portion 20 is in the center portion 7 of the rolls 3a and 3b, the roll 3a The solidification delay portion is formed over the entire width of the (3b), and as a result, the solidification ability in the roll width direction becomes uniform, and the thickness of the cast slab cast through the rolls 3a and 3b becomes uniform.

Further, the inclination of the bend 20 is adjusted depending on whether the shape of the cast piece 5 is to be the same thickness over the entire width or the center 17 of the cast piece 5 is somewhat convex in consideration of post-processing. do. That is, when it is desired to obtain the slab 5 in which the central portion 17 is slightly convex, it is preferable that the cooling ability at the edge portion 8 of the rolls 3a and 3b is slightly smaller than the cooling ability at the central portion 7. The inclination of the bend 20 is formed to be slightly less than twice the inclination of the edges 8 of the rolls 3a and 3b. This is because the degree of inclination of the bent portion 20 is a major factor for adjusting the solidification ability of the slab solidified in both rolls 3a and 3b.

In addition, as shown in FIG. 4, both the rolls are formed by the curved portions 20 so as to offset the difference in the solidification ability in the upper and lower surfaces of the cast pieces 5 which are in contact with the curved portions 20 and cast. It is preferable to process so that the uneven part formed in the outer peripheral surface of 3a) (3b) cancels each other.

According to the present invention as described above, when the molten steel 2 for sheet casting is in contact with the rolls 3a and 3b, the shrinkage of the slab 5 is reduced by the edges 8 of the rolls 3a and 3b. By forming the bent portion 20, which is twice the size of the inclination of the crown C, in the central portion 7 of the rolls 3a and 3b, as well as in the central portion 7, the initial stage of the molten steel 2 Since the solidification delay phenomenon which occurred only at the roll edge 8 during solidification can be eliminated, the uniform solidification performance occurs over the entire width of the rolls 3a and 3b in contact with the molten steel 2 so as to have excellent quality with a constant thickness. The effect of producing cast (5) of is obtained.

Claims (3)

In the sheet casting machine for manufacturing the slab 5 by injecting the molten steel (2) supplied from the nozzle (1) between a pair of rolls (3a) (3b) through which cooling water flows, The center portion 7 of the rolls 3a and 3b has a base length 24 equal to the bottom length 23 of the crown C, which is twice the radial height 22 of the crown C. Comprising a height of 15 to form a plurality of bent portion 20 made of the inclination twice the slope of the crown (C) to uniform the solidification ability in the width direction of the roll (3a) (3b) Cooling roll for a twin-roll sheet caster, characterized in that. The cooling roll for a twin roll thin caster according to claim 1, wherein the bottom length (23) of the crown (C) is formed in a length of 50 to 100 mm. According to claim 1, wherein the bent portion (20) of the two rolls (3a) (3b) by the bent portion 20 so as to cancel the difference in the solidification ability in the upper and lower surfaces of the slab (5) in contact with this Cooling roll for a twin-roll sheet caster, characterized in that the irregularities formed on the outer peripheral surface is formed to cancel each other.