CA1234673A - Cooling pad for use in a continuous casting apparatus for the production of cast sheets - Google Patents

Cooling pad for use in a continuous casting apparatus for the production of cast sheets

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Publication number
CA1234673A
CA1234673A CA000488157A CA488157A CA1234673A CA 1234673 A CA1234673 A CA 1234673A CA 000488157 A CA000488157 A CA 000488157A CA 488157 A CA488157 A CA 488157A CA 1234673 A CA1234673 A CA 1234673A
Authority
CA
Canada
Prior art keywords
water supply
water
cooling pad
cooling
holes
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA000488157A
Other languages
French (fr)
Inventor
Nagayasu Bessho
Tomoaki Kimura
Yasuhiro Habu
Hakaru Nakato
Tsutomu Nozaki
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
JFE Steel Corp
Hitachi Ltd
Original Assignee
Hitachi Ltd
Kawasaki Steel Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hitachi Ltd, Kawasaki Steel Corp filed Critical Hitachi Ltd
Priority to CA000488157A priority Critical patent/CA1234673A/en
Application granted granted Critical
Publication of CA1234673A publication Critical patent/CA1234673A/en
Expired legal-status Critical Current

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  • Continuous Casting (AREA)

Abstract

A COOLING PAD FOR USE IN A CONTINUOUS
CASTING APPARATUS FOR THE PRODUCTION OF CAST SHEETS

Abstract A cooling pad for use in a continuous casting apparatus for the production of cast sheets is disclosed, which is provided with plural water supply and discharge holes satisfying the particular relations on the arrange-ment thereof. By using such a cooling pad, a filmy cooling water flow is uniformly and stably formed in the casting.

Description

3 ~3 58-203,609 ~ COOLING PAD FOR USE IN A CONTINUOUS
CASTING APPARATUS FOR THE PRODUCTION OF CAST S~IEETS

This invention relates to a filmy fluid (water) flow-forming pad ~hereinafter referred to as a cooling pad) in a continuous casting apparatus for the direct production of cast sheets having a thickness of 05 not more than 30 mm (e.g. sheet bar or the like) from molten metal, particularly molten steel (hereinafter referred to as a belt caster). More particularly, it relates to an improvement in the cooling pad which properly selects the size and arrangement of supply hole and discharge hole for cooling water so as to form a desired filmy water flow.
As a continuous casting apparatus for directly producing steel sheets such as sheet bar or the like from molten steel, there is a belt caster as disclosed in Japanese Patent laid open No. 57-100,851. In such a disclosed synchronous type belt caster~ there are many systems, a typical example of which is shown in Fig. 1.
This belt caster has usually such a structure that a casting space is defined by a pair of endlessly circulat-ing metal belts 4, 5 oppositely arranged to each otherat a given interval for retaining molten steel 2 over a predetermined distance, each of which being guided and supported through plural guide rolls 6a, 6b, 6c or 6'a, 6'b, 6'c and cooled by a filmy cooling water flow from ~23~73 4881-233 the back face, and a pair of side plates disposed between the metal belts 4, 5 and positioned near the side edge portions of these metal belts.
Moreover, numeral 1 is a tundish, numeral 3 a pouring nozzle, numerals 7, 8 cooling pads arranged behind the metal belts 4, 5 for cooling these belts and forming a filmy water flow capable of supporting the static pressure of the poured molten steel, numerals 9/ 10 springs for tensioning the belts, and numeral 11 a cast sheet.
Since the static pressure of molten steel or semi-solidified cast sheet changes from the molten steel surface level toward the cast sheet-drawing direction, the cooling pads 7, 8 act to balance the static pressure of molten steel at various stages of the cast sheet (various positions in the cast sheet-drawing direction) by the pressure of the filmy cooling water flow. To this end, each cooling pad is provided at a side facing the respec-tive metal belt with plural supply holes for the cooling water, each of which is provided at its top with a storing recess having a size enough to adjust the flow amount of the cooling water supplied.
In Figures 2 and 3 is shown a structure adopted in the conventional cooling pads 7 and 8, wherein each of plural oblong recesses 12 is disposed on the top portion of the corresponding water supply hole 15 for injecting the cooling water, which hole is formed in each of the cooling pads at its side facing the metal belt 4, 5, whereby a film flow of the cooling water is formed between the metal belt 4 or 5 and the cooling pad 7 or 8 to counter-1~3~3 4881-233 act the static pressure of the molten steel and to uniformly cool the metal belt. Moreover, the oblong recesses 12 have usually a minor axis a of 50-150 mm and a major axis b of 100-200 mm and are so arranged that a transverse distance (~1) between centers of minor axes of mutual recesses is 200-400 mm and a longitudinal distance (~2) between centers of major axes of mutual recesses is 200-600 mm.
In the conventional cooling pad of such a structure, if it is intended to continuously cast thin slabs and sheets bars, the flow rate of the cooling water is considerably different between the water flowing portion 14 formed in the recess 12 and the filmy water portion 13 formed in an area other than the recess, causing a difference in the cooling strength, resulting in a wavy deforma-tion of the metal belt. As a result, the liquid-tight contact between the metal belt 4, 5 and the fixed side plate is weakened to produce a gap therebetween, which causes the leakage of molten steel, casting troubles, and production of cast sheet having a poor shape such as fin and the like. Also, the surface of the cast sheet is not smooth, which affects the surface properties of thin steel sheet after the rolling and causes deterioration in quality.
It is, therefore, an object of the invention to overcome the drawback of the conventional cooling pad, wherein the rear sur-face of the metal belt is cooled by the filmy water portion 13 and the water flowing portion 14, by an arrangement of water supply hole and water discharge hole for forming a filmy cooling water flow so as to match static pressure of molten steel as mentioned later and to prevent the occurrence of accidents in the casting .~
.;

~:3~3 ~ 81-233 operation and the deterioration of qualities in the cast produc-ts.
According to the invention, there is provided in a con-tinuous casting apparatus for the production of cast sheets com-prising a pair of endlessly circulating metal belts oppositely arranged at such a gap to hold molten metal and its cast sheet a-t both long sides of the cast sheet, a pair of side plates each located at one side near the side edge portions of both belts and brought into intimate contact therewith, and a cooling pad for supplying and discharging cooling water to the rear surface of the metal belt, the improvement wherein said cooling pad is provided with plural water supply holes and water discharge holes each open-ing to said metal belt so as to satisfy the following relations:
0.5< Ai < 7 Ai/Ao > 1.1 n lc < 20, wherein Ai is a sectional area (cm2) of the water supply hole, Ao is a sectional area (cm2) of the water discharge hole, n is a parameter depending on the arrangement of the water supply and dis-charge holes, and lc is a distance (cm) between the centers of the water supply hole and the water discharge hole, said water discharge holes being disposed around said water supply hole in said cooling pad into a triangular shape at n=0.5, a square shape at n=l or a hexagonal shape at n=2.
For a better understanding of the invention, reference is made to the accompanying drawings, in which:
Figure 1 is a schematic view of an embodiment of the continuous casting apparatus for the direct production of cas-t ~3~73 4881-233 thin sheets;
Figure 2 is a partial sectional view of the conventional cooling pad as mentioned above;
Figure 3 is a parti.al plan view of the conventional cool-ing pad viewed from the metal belt;
Figures 4 to 6 are schematic views of embodiments on the arrangement of water supply and discharge holes in the cooling pad according to the invention, respectively; and Figure 7 is a graph showing the influence of the correc-tion factor in sectional area ratio of water supply hole to waterdischarge hole upon the index of cast sheet form.

4a -~3~67~
~ ccording to the invention, plural water supply holes 15 and plural water discharge holes 16 opening to the metal belt 4 or 5 are simultaneously disposed on each of the cooling pads 7 and 8 in the 05 contin~lous casting apparatus, and the size ànd arrange-ment thereof are characterized by satisfying the following requirements as a result of the observation of flow velocity distribution of filmy cooling water flow and the measurement of the heat transfer coefficient in model experiments and actual operation:
(l) The water supply holes 15 are uniformly dispersed ~s far as possible facing the rear surface of the metal belt 4 or 5;
(~) The water discharge holes 16 are symmetrically disposed around each water supply hole 15;
(3) The cross sectional area of the water supply hole Ai (cm2) and the cross sectional area of the water discharge hole Ao (cm2) satisfy the following equation:
Ai/Ao > ~n ................ (l) , wherein n is a parameter depending upon the arrangement of the water supply and discharge holes. That is, when the arranging shape of the water discharge holes is triangular, n is 0.5. Further, n is l in case of the square shape and 2 in case of the hexagonal shape.
Such arranging shapes are shown in Figs. 4-6.
And also, ~ is a correction factor in a sectional area ratio of water supply hole to water discharge hole. If ~<1, the uniform formation of the ~23~673 filmy water flow is difficult and there is occasionally caused -the melting loss of the metal belt during the casting. In order to uniformly and stably form the filmy water flow having a -thickness of about 300 to 2,000 ~m, ~ is necessary to be not less than 1.1, preferably not less than 1.2 as shown in Figure 7, in which ~
represents triangular arrangement, ~ represents square arrangement and o represents hexagonal arrangement;
(4) When the sectional area Ai (cm2) of the water supply hole 15 is less than 0.5, the clogging of the hole is apt to be caused due to the adhesion of scale, while when it exceeds 7, stagnation is produced in the water flow. Therefore, the sectional area Ai is necessary to satisfy the following relation:
0.5 < Ai < 7; and (5) The distance ec between the centers of the water supply hole and the water discharge hole is necessary to be ,ec< 20 cm, preferably ~c< 17.5 cm because it is difficult to ensure the uniform formation of the filmy water flow distribution as the value of ec becomes large.
Although the symmetry is lost or some of the above requirements are not satisfied in the marginal portion of the cooling pad, it is not of importance because the metal belt corre-sponding to the marginal portion of the cooling pad does not directly cool the cast sheet. Further, the arrangement of the water discharge holes determining the value of n need not necessarily be exactly held at the triangular shape or the like, and can be changed to the extent that a large change of heat flow distribution is not caused. Moreover, the invention is applicable :A~

~23~16~3 to not only belt caster comprising a pair of fixed side pla-tes but also belt caster comprising a pair of side plates moving synchron-ously with the metal belts.
The following examples are given in illustration of the invention and are not intended as limitations thereof.
Example 1 A continuously cast sheet of low-carbon aluminum killed steel having a thickness of 100 mm and a width of 500 mm was pro-duced through the belt caster shown in Figure 1, wherein each of the cooling pads 7, 8 used was provided with plural water supply and discharge holes 15, 16 having a sectional area of water supply hole Ai=l.l cm2 (hole diameter di=12 mm), a sectional area of water discharge hole Ao=0.38 cm2 (hole diameter do=7 mm), a distance between water supply and discharge holes ec=12 cm and n=2 ~hexagonal shape shown in Figure 6). In this operation, the temper-ature of molten steel 2 in the tundish 1 was 1,560C and the maximum drawing speed was 3.0 m/min. As the metal belt 4 or 5 was used a thin steel having a thickness of 1.2 mm.
The resulting cast sheet, after the cooling from the back surface of the metal belt using the above cooling pad was even and smooth at its surface as compared with the cast sheet obtained by using the conventional cooling pad shown in Figures 2 and 3, from which was obtained a rolled thin steel sheet having a beauty surface. Even after the casting of about 30 tons, the metal belt was normal and did not produce deformation and the formation of fin accompanied therewith.
Example 2 The same procedure as described in Figure 1 was repea-ted, ~4~;73 except that the arrangement of water supply and discharge holes in the cooling pad had Ai=0.79 cm2 (di=10 mm), Ao=0.79 cm2 (do=10 mm), ~c=10 cm and n=0.5 (triangular shape), to produce a cast sheet, which was subjected to the usual rolling treatment to obtain a thin steel sheet of 1.2 mm in thickness. In this case, the surface of the cast sheet was smooth, and the surface properties of the thin steel sheet were excellent.
Example 3 A continuously cast sheet of aluminum killed steel having a thickness of 30 mm and a width of 1,000 mm was produced through a belt caster comprising a converged-type side face tapering toward the casting direction and a cooling pad having that arrangement of water supply and discharge holes which has Ai=3.1 cm2 (di=20 mm), Ao=0.79 cm2 (do=10 mm), ~c=17.5 cm and n=l (square shape). The maximum drawing speed was 5.3 m/min. As a result, the sheet bar obtained was good in shape and in surface properties as in the cases of Examples 1 and 2.
Comparative Example 1 A continuously cast sheet oE aluminum killed steel having a thickness of 30 mm and a width of 1,000 mm was produced at a drawing speed of 4.7 m/min through a converged-type belt caster, wherein the arrangement of water supply and discharge holes in the cooling pad had Ai=3.1 cm2 (di=20 mm), Ao=0.79 cm2 (do=10 mm), ~c=23 cm and n=l (square shape). In this case, only the distance between holes ~c was outside the range defined in the invention (ec S 20 cm). When the inner surface of the steel belt (having a thickness of 1.2 mm) was observed after the casting of about 5 tons, unevenness was locally produced, so that it was necessary to replace the steel belt with a new one.
As mentioned above, according to the invention, the filmy cooling water flow can be uniformly and stably formed on the rear surface of the metal belt, whereby cooling unevenness in the belt can be avoided and hence wavy deformation of the belt is pre-vented. As a result, contact between the metal belt and the fixed side plate is improved, whereby not only are accidents in the cast-ing avoided, but also the qualities of the cast sheet and finished sheet are improved.

Claims (2)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a continuous casting apparatus for the production of cast sheets comprising a pair of endlessly circulating metal belts oppositely arranged at such a gap to hold molten metal and its cast sheet at both long sides of the cast sheet, a pair of side plates each located at one side near the side edge portions of both belts and brought into intimate contact therewith, and a cooling pad for supplying and discharging cooling water to the rear surface of the metal belt, the improvement wherein said cooling pad is pro-vided with plural water supply holes and water discharge holes each opening to said metal belt so as to satisfy the following relations:
0.5 ? Ai ? 7 Ai/Ao ? 1.1 n 1c ? 20, wherein Ai is a sectional area (cm2) of the water supply hole, Ao is a sectional area (cm2) of the water discharge hole, n is a parameter depending on the arrangement of the water supply and dis-charge holes, and 1c is a distance (cm) between the centers of the water supply hole and the water discharge hole, said water dis-charge holes being disposed around said water supply hole in said cooling pad into a triangular shape at n=0.5, a square shape at n=1 or a hexagonal shape at n=2.
2. The continuous casting apparatus according to claim 1, wherein said distance between the centers of the water supply and discharge holes is 1c<17.5.
CA000488157A 1985-08-06 1985-08-06 Cooling pad for use in a continuous casting apparatus for the production of cast sheets Expired CA1234673A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CA000488157A CA1234673A (en) 1985-08-06 1985-08-06 Cooling pad for use in a continuous casting apparatus for the production of cast sheets

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CA000488157A CA1234673A (en) 1985-08-06 1985-08-06 Cooling pad for use in a continuous casting apparatus for the production of cast sheets

Publications (1)

Publication Number Publication Date
CA1234673A true CA1234673A (en) 1988-04-05

Family

ID=4131122

Family Applications (1)

Application Number Title Priority Date Filing Date
CA000488157A Expired CA1234673A (en) 1985-08-06 1985-08-06 Cooling pad for use in a continuous casting apparatus for the production of cast sheets

Country Status (1)

Country Link
CA (1) CA1234673A (en)

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