US3512574A

US3512574A - Continuous casting process and apparatus

Info

Publication number: US3512574A
Application number: US598759A
Authority: US
Inventors: Harold L Taylor
Original assignee: Inland Steel Co
Current assignee: Inland Steel Co
Priority date: 1966-12-02
Filing date: 1966-12-02
Publication date: 1970-05-19
Anticipated expiration: 1987-05-19

Description

May 19, 1970 H. .'TAYL.OR

CONTINUOUS CASTING PROCSS AND APPARATUS Filed Dec. 2. 196e 2 Sheets-Sheet l Ei .i

llllllllllllll l May 19, 1970 H. 'rAYLoR CONTINUOUS CASTING PROCESS AND APPARATUS 2 Sheets-Sheet 2 Filed Deo Inventor j'lcnrold L. Tcxlor lrmfwa @SM Mor-new United States Patent O 3,512,574 CDNTINUOUS CASTING PROCESS AND APPARATUS Harold L. Taylor, Hammond, Ind., assignor to Inland Steel Company, Chicago, Ill., a corporation of Delaware Filed Dec. 2, 1966, Ser. No. 598,759 Int. Cl. B22d 11 /12 U.S. Cl. 164-89 5 Claims ABSTRACT F THE DISCLOSURE A method and apparatus for secondary cooling of a continuous casting as the casting is withdrawn from a continuous casting mold in which the entire surface of the casting is contacted within an enclosure with a narrow stream of cooling medium flowing in turbulent flow which withdraws heat from the casting at a flux density of at least 75 calories per square centimeter per second. The cooling medium for the secondary cooling can be provided by directly connecting the casting mold cooling chamber and the secondary cooling enclosure.

The present invention relates generally to continuous casting of ferrous metals and more particularly to an improved process and apparatus for cooling a ferrous metal continuous casting.

The general principles of producing a continuous casting of a ferrous metal are well known and include the steps of introducing molten metal into an open-ended mold the walls of which are cooled to form an outer shell or skin of solidified metal about a core of molten metal and permitting substantially continuous withdrawal of the casting from the mold. After leaving the mold, the continuous casting usually passes through a secondary coolng zone wherein cooling fluid is applied directly onto the surface of the casting to complete solidiiication of the molten metal in the interior of thecontinuous casting.

There have been numerous commercial applications of the continuous casting process for ferrous metals, but there still remain deterrents to greater commercial use, such as the limited rate of production due to the relatively slow rate of withdrawal of the casting from the mold and the occurrence of metallurgical variations and defects in both the surface and internal metallurgical structure of a ferrous metal continuous casting.

While a considerable amount of work has been done on the problem of removing heat from the continuous casting mold, relatively little study has been made of ways and means of removing heat from the incompletely solidified continuous casting after the casting has been withdrawn from the mold. The most common commercial practice in present day continuous casting installations is to spray water onto the surface of the casting to effect the required secondary cooling of the casting, although spraying the cooling fluid is an inefficient means of removing heat and tends to cause metallurgical defects in the casting.

Thus, one of the major problems remaining in the continuous casting of ferrous metals is the effective removal of heat from the incompletely solidified metal casting after it has been withdrawn from the continuous casting mold, since this has a substantial effect on the rate of casting and on the metallurgical structure of the casting.

It is therefore an object of the present invention to provide an improved process and apparatus for more 3,512,574 Patented May 19, 1970 ICC economically producing ferrous metal continuous castlngs.

It is a further object of the present invention to provide an improved method and apparatus for removing heat from a continuous casting after withdrawal of the casting from the continuous casting mold.

Other objects of the present invention will be apparent to one skilled in the art from the detailed description and claims to follow when read in conjunction with the accompanying drawing wherein:

FIG. l is a schematic vertical sectional diagram of an apparatus for performing the process of the present invention; and

FIG. 2 is a schematic vertical sectional diagram of a modified apparatus for performing the process of the present invention.

It has been discovered that the above specified objects and other objects of the present invention can be achieved by employing a process of cooling a ferrous metal continuous casting in a channel quenching secondary cooling zone to very substantially increase the heat withdrawal fiux density and effect more rapid complete solidiiication of the continuous casting. It has now been found desirable and possible with the channel cooling apparatus of the present invention, for example, to effect a uniform heat withdrawal ux density of at least cal./cm.2/sec. (1,000,000 B.t.u./hr./ft.2) in the secondary cooling zone.

The channel cooling apparatus and process of the present invention is principally concerned with effecting cooling of a continuous casting after the casting has been withdrawn from the open end casting mold and has as an essential feature thereof contacting the entire lateral surface of the continuous casting as it is withdrawn from the mold with a continuous film or stream of a cooling medium fiowing in turbulent ow. One apparatus for effecting the secondary cooling of a continuous casting in accordance with the present invention is shown schematically in FIG. l of the drawing, wherein molten ferrous metal is poured into the inlet end of a continuous casting mold 10 of any suitable design. A mold suitable for continuously casting a 200 mm. by 1500 mm. steel slab normally would have a length of about 600 mm. The mold 10 preferably has a plurality of cooling fluid inlets 11 and cooling fluid outlets 12 'to allow circulation of cooling fluid through the mold 10 to effect rapid solidification in the mold of an outer shell or skin portion 13 about a fiuid inner core of the molten metal 14. A secondary cooling channel quenching apparatus 20` extends downwardly from the lower end wall of the mold 10 and is disposed to receive in the axially extending passage thereof the partially solidified continuous casting as it is withdrawn from the lower end of the .mold 10. A plurality of pinch rolls 35 are mounted immediately below the lower end of the secondary cooling apparatus 20 for drawing the casting through the apparatus. The pinch rolls 35 also serve to deflect water away from the casting surface into an exhaust water receiver 36 which surrounds the lower end of the channel quenching apparatus 20 and the pinch rolls 35. A deiector apron 37 with air jets 38 are mounted below each of the pinch rolls 35 and direct the flow of cooling iiuid away from the surface of the pinch rolls 35.

The channel quenching secondary cooling apparatus 20 of the present invention comprises a tubular shaped cooling wall 21 having a depth and width larger than the depth and Width of the continuous casting and adapted to receive the continuous Casting in the axial passage extending therethrough and providing a relatively narrow cooling liquid fiow channel 22 about the entire perimeter of the continuous casting for conveying a continuous stream of a cooling fluid between the inner surface of the cooling wall 21 and the outer surface of the shell 13 of the continuous casting. The width of the ilow channel 22 can range between about 0.5 cm. and 5.0 cm., and preferably is about 1.0 cm. The cooling wall 21 can be made of any material, such as cooper or steel, which is suiliciently heat resistant to withstand the relatively high temperatures encountered in the continuous casting of a ferrous metal.

At the upper end of the cooling Wall 21 is a chamber which receives a supply of cooling lluid, such as water, and feeds the cooling iluid to the upper or inlet end of the flow channel 22 formed about the continuous casting by the cooling wall 21. The chamber 25 is formed of a lateral wall section 26 and a lower wall section 27 which is welded or otherwise sealably secured to the outer surface of the cooling wall 21 at a point spaced from the upper end thereof and an upper wall section 28 which preferably also serves as the lower wall of the casing mold 10. The upper wall section 28 is spaced above the upper end of the cooling wall 21. A baille member 29 extends downwardly from the inner surface of the upper wall section 28 and terminates short of the lower wall sections 27. One or more cooling fluid inlets 30 are provided in the lateral Wall sections 26 adjacent the upper edge thereof. The chamber 25 is also preferably provided with interior support means 31 which can be ribs, rods or tubes extending supportively between the cooling wall 21, the baille means 29, and the lateral wall 26 to provide lateral support for the upper end of the Wall 21 and to maintain the dimensional spacing of the vertically dispersed

members

21, 25 and 29 of the chamber 25. The support means 31 is designed to minimize any restriction of the llow of cooling water and avoid localized heat withdrawal from the wall 21.

In a modiiied form of the apparatus of FIG. l, the cooling fluid inlet of the ilow channel 22 of quenching apparatus is operatively combined with the cooling liquid outlet of continuous casting mold `10. Thus, as shown in FIG. 2, a continuous casting mold-channel quenching apparatus has a casting mold wall 41 which receives the molten ferrous metal and which shapes the molten metal into the desired form of continuous casting 32. A cooling chamber 42 is formed integrally with the upper end of the mold wall 41 by providing a top wall section 43 connected to the upper end of the mold wall 41, a lateral wall section 44 and a lower wall section 45 which is spaced from the lower end of the mold Wall 41. An outer baille member 46 extends downwardly from the upper wall section 43 intermediate the ends thereof with the lower edge of the outer baille member 46 being spaced from the lower wall section 4S to provide a lluid passage for cooling uid introduced by means of one or more iluid inlets 47 in the lateral wall section 44 adjacent the upper edge thereof. The inner edge of the lower wall section 45 is sealably joined with an upwardly extending inner baille member 48 which projects vertically into the interior of chamber 42 between the baille member 46 and the casting mold wall 41, terminating short of the upper wall section 43. The inner baille member 48 is spaced from the mold wall 41 to provide a relatively narrow channel for the ilow of cooling fluid over the outer surface of the mold wall 41 to eifect rapid heat withdrawal therefrom. The cooling chamber 42 iS also preferably provided with interior support means 49 which can be ribs, rods or tubes, extending supportively between the mold wall 41, the inner baille member 48, the outer baille member 46, and the lateral wall section 44 to provide lateral support and dimensional stability for the vertically disposed

members

41, 44, 46 and 48 of the cooling chamber 42. The support means 49 is designed to minimize any restriction of the flow of cooling water and avoid undue localized heat withdrawal from the mold wall 41.

The lower end of the baille member 48 is integrally connected, preferably by means of a short tapered section 50, with an elongated cooling channel-defining wall member 51 which extend axially beyond the lower end of the mold wall 41 and is adapted to receive in the axial passage thereof the continuous casting as it leaves contact with the mold wall 41. The dimensions of the wall member 51 are such as to form a relatively narrow but substantially uniform cooling or quenching channel 52 between the outer Surface of the continuous casting and the inner surface of the wall member 51 for the flow of cooling iluid. The width of the quenching channel 52 is preferably the same as the spacing between the outer surface of the mold channel wall 41 and the bafe member 48. While the uniform channel 52 width can be as narrow as 0.5 cm. or as large as about 5.0 cm., in the preferred form the width of the channel is maintained at about 1.0 centimeter.

A plurality of water reflecting pinch rolls 55 engage the outer surfaces of the continuous casting immediately below the lower end of the -wall member 51 to direct the ilow of cooling fluid away from the continuous casting 32 into the exhaust water receiver 56. An apron 57 and air jets 58 are mounted below the pinch rolls 55 to remove cooling fluid from the surface of the pinch rolls 55.

In the operation of the secondary cooling channel quenching apparatus 20 of FIG. l, cooling fluid, such as water, is introduced through the water inlets 30 of the cooling chamber 25 wherein the bailles 29 uniformly distribute the cooling lluid which passes downwardly through the passage deiined by the outer wall section 26 and baille 29 and then upwardly over the upper end wall of the cooling wall 21 into the cooling channel 22 where the cooling water flows directly into contact with the surface of the solidified shell of the continuous casting and passes downwardly in continuous turbulent ilow over the entire perimeter of the continuous casting and outwardly past the lower end of the cooling wall 21. The pinch rolls 35 which are in substantially sealing engagement with the surface of the continuous casting 32 deflect the cooling Water laterally into the exhaust water received 36. The apron 37 and air jets 38 which are directed against the periphery of the pinch rolls 35 assist in deilecting the cooling water into the exhaust Water receiver 36 and away from the surface of the continuous casting 32. If desired, the cooling water can be recycled for use in the secondary cooling channel quenching apparatus 20 or for cooling the casting mold In operating the modiiied form of apparatus shown in FIG. 2, cooling lluid, such as water, is introduced through fluid inlets 47 into the casting mold cooling chamber 42 wherein the baille member 46 evenly distributes the inllowing cooling water, directing the ilow downwardly through the passage formed between the lateral wall section 44 and baille 46 and then upwardly over the upper end of the baille member 48 into contact with the outer surface of the mold wall 41 and downwardly into and through the secondary cooling channel 52. The cooling water then leaves the lower end of the cooling channel 52 and is deilected laterally by the pinch rolls 5S into the exhaust water receiver 56. The apron 57 and air jets 58 assist in dellecting the water from the pinch rolls 55 and casting 32 into the receiver S6.

In the continuous casting of a ferrous metal in accordance with the present invention, a generally rectangular slab of a low carbon steel having a width of 1500 mm. (60 inches) and a thickness of 200 mm. (8 inches) can be cast at a production rate of about 1.42 metric tons per minute (equivalent to a slab withdrawal speed of about 60.4 cm./min. or approximately 24 inches per minute) using a water ilow rate of 10.3 m5 per minute through the cooling channel formed about the entire lateral surface of the continuous casting slab with the cooling water having a velocity of 500 cm./sec. (16.4 ft./sec.) through the secondary cooling channel which has a length of 100 cm. (3.28 ft.) and a channel width of 1.0 cm. (.393 inch). A heat withdrawal flux density in excess of 75 cal./cm.2/sec. (1,000,000 B.t.u./ hr./ft.2) is attained with the apparatus shown in FIGS. l and 2. The temperature of the cooling water is increased about 14.6 C. as it passes through the secondary channel cooling apparatus of FIG. l, and a temperature increase of about 19 C. is produced when the cooling water passes through the combined casting mold and secondary cooling apparatus of FIG. 2. When using the apparatus of FIG. 1 it is necessary to provide a second source of cooling water for the mold in addition to the cooling Water supplied for the secondary cooling channel quenching apparatus. Thus, in the above described continuous casting operation employing the apparatus of FIG. l, it is necessary to provide cooling water at a rate of about 8 m.3/min. for the mold in addition to the 10.3 m.3/min. required by the secondary cooling apparatus. With the apparatus of FIG. 2 only the 10.3 m/min. of cooling water is required, since the cooling water from the mold is used as the source of cooling water for the secondary cooling apparatus.

It will be evident that the method and apparatus of the present invention, by employing relatively small volumes of cooling water and sufficiently high water velocities, can effect a very rapid and uniform, uninterrupted cooling of a ferrous metal continuous casting, while at the same time reducing the likelihood of encountering operational difficulties, such as remelting of the casting skin after withdrawal from the mold and irregular cooling of the continuous casting due to stoppage of one or more cooling sprays.

It will also be evident that when the velocity of the cooling water in the secondary cooling channel is increased to higher values, such as 2000 cm./sec. or 12,500 cm./see., substantially higher heat withdrawal ux densities and casting rates can be achieved. For example, when the water velocity in the secondary cooling channel is 2000 cm./sec. through a channel 100 cm. long having a width of 1.0 cm. and a water ow rate of 41.2 m.3/min., a heat withdrawal flux density of 150 cal./ cm.2/sec. (2 l06 B.t.u./hr./ft.2) and a casting rate of approximately 2.84 metric tons per minute can be achieved. At a cooling water velocity of 2000 cm./sec. in the apparatus of FIG. l, the temperature of the cooling water in the secondary cooling channel is increased about 7.3 C. and in the apparatus of FIG. 2 the water temperature is increased approximately 10 C. With a water velocity of 12,500 cm./sec. in the secondary cooling channel of the present invention, a heat Withdrawal llux density of 375 cal./cm.2/sec. can be achieved.

The term ferrous metal as used in the foregoing specification and in the following claims designates any of the various carbon steels and ferrous alloys which are normally continuously cast. A typical continuous steel casting of the present invention which can be used for producing a fully killed commercial quality steel for plate application has the following analysis: .17-.24% carbon, .3U-60% manganese, .l5-30% silicon, .30% maximum phosphorous, and .035% maximum sulfur.

I claim:

1. In a ferrous metal continuous casting apparatus, a secondary channel cooling means comprising an elongated tubular member with an axial passage extending the length thereof and adapted to receive in spaced relation therewith a continuous casting having a solidified shell with a core of molten metal as said casting is withdrawn from a liquid cooled continuous casting mold, the inner surfaces of said tubular member forming with said continuous casting an elongated cooling channel which has a width of about 0.5 cm. to 5.0 cm. about the entire perimeter of said casting, and a cooling liquid supply means in uid-ow communication with the upper end of said tubular member adapted to provide within said channel and in direct contact with the surface of said continuous casting a continuous stream of cooling liquid in turbulent flow effecting by means of said cooling liquid a heat withdrawal flux density from said casting of at least about ca1./cm.2/second.

2. A continuous casting apparatus as in claim 1, wherein said cooling liquid for said cooling channel is comprised entirely of said liquid from said continuous casting mold.

3. In a method of continuously casting a molten ferrous metal in a fluid cooled open-ended continuous casting mold wherein molten metal is introduced into one end of said mold and continuously forming therein a casting having a solidified shell with a core of molten metal, continuously withdrawing said solidified shell from the opposite end of said mold and further cooling said casting in a secondary cooling zone to complete solidiiication of said molten metal, the improvement comprising; passing said casting as withdrawn from said mold directly into a cooling chamber defining said secondary cooling zone having an elongated cooling medium flow channel between the outer surface of said shell and the inner surface of said cooling chamber with said flow channel having a width of about 0.5 cm. to 5.0 cm., passing liquid cooling medium through said cooling medium ow channel as a confined stream in direct contact with said shell, and maintaining said stream of liquid cooling medium flowing at a velocity which maintains said stream in turbulent flow while in said channel and effecting withdrawal of heat from said continuous casting at a flux density of at least 75 calories per square centimeter per second.

4. A method as in claim 3, wherein said cooling medium flow channel has a width of about 1.0 centimeter.

5. A method as in claim 3, wherein said stream of liquid cooling medium in said secondary cooling zone is provided by direct fluid ow communication between said channel and a cooling chamber of said continuous casting mold, and said cooling medium within said cooling chamber contacting the entire lateral surface of said mold and being maintained in turbulent flow therein.

References Cited UNITED STATES PATENTS 3,324,932 6/ 1967 Ayers 164-89 3,354,941 11/1967 Halstead 164-283 3,358,744 12/1967 Rossi 164-283 X 3,391,725 7/1968 Rossi 164-283 X 3,399,716 9/1968 Rossi et al; 164-128 X 894,410 7/1908 Trotz 164-283 X FOREIGN PATENTS 144,447 12/ 1951 Australia.

595,254 3/1960 Canada. 1,280,293 11/1961 France.

746,027 12/ 1944 Germany.

173,322 11/ 1960 Sweden.

233 ,610 1 l 1944 Switzerland.

I. SPENCER OVERHOLSER, Primary Examiner R. S. ANNEAR, Assistant Examiner U.S. Cl. X.R. 164-283