US3358744A

US3358744A - Cooling and apron arrangement for continuous casting molds

Info

Publication number: US3358744A
Application number: US510625A
Authority: US
Inventors: Rossi Irving
Original assignee: Concast Inc
Current assignee: Concast Inc
Priority date: 1965-11-30
Filing date: 1965-11-30
Publication date: 1967-12-19
Anticipated expiration: 1984-12-19

Description

Dec. 19, 1967 ROSS] 3,358,744

COOLING AND APRON ARRANGEMENT FOR CONTINUOUS CASTING MOLDS Filed Nov. 30, 1965 INVENTOR. IRVING Rossl ATTORNEYS United States Patent 3,358,744 COOLING AND APRON ARRANGEMENT FOR CONTINUOUS CASTING MOLDS lrving Rossi, Morristown, N..l., assignor to Concast, Inc., New York, N.Y. Filed Nov. 30, 1965, Ser. No. 510,625 6 Claims. (Cl. 164-282) This invention relates to continuous casting and, more particularly, relates to an improved cooling and apron arrangement for continuous casting molds.

In continuous casting processes, molten metal is poured into an open ended mold. The mold walls are cooled to solidify the molten metal around the periphery thereof to define a strand which is withdrawn in continuous manner from the exit aperture of the mold shaft.

In recent years, the continuous casting process has been increasingly applied to casting of steel. In such casting, many of the problems of continuous casting have been accented or increased.

Among these problems is the problem caused by breakout of the molten metal through the thin peripheral skin formed by the mold. There are three primary causes of breakout. The first cause is slag or other inclusions imbedded in the peripheral wall of the strand. These inclusions insulate the molten steel from the water sprays, thus, creating a weak spot through which the molten core may find a path. Also, the inclusions often fall out of the surface when the strand is subjected to the water spray of the cooling arrangements, again causing a physical weakness. The second cause can be attributed to rupture of the thin peripheral skin. These two breakouts occur primarily immediately below the continuous casting mold. The third cause of breakout may occur anywhere throughout the continuous casting arrangement and is caused by pinching of the casting in the roller aprons now usually employed in such apparatus. Since the withdrawal rolls are applying high withdrawal forces to the strand, any pinching applies a tension force to the strand which may exceed the tensile strength of the thin peripheral skin.

When such breakouts occur, the molten metal in the core of the strand is poured over the portions of the apparatus situated below the mold. Thus, the molten metal such as molten steel is poured over the withdrawal aprons. Although this effect is present in casting of straight strands, the resultant damage is particularly pronounced in the case of the curved molds which cast the strand on an arc.

It is, therefore, an object of the present invention to provide an improved cooling and apron arrangement which overcomes many of the primary causes of breakouts and in which the damaging effect of breakouts on equipment and down time is substantially reduced.

In accordance with this object, there is provided, in a preferred embodiment of this invention, a continuous casting mold. The mold is water cooled and is oscillated in conventional manner. Suspended immediately below the mold is a cooling mold constructed of plates positioned so as to bear on the strand, urging the cooling water admitted between the plates and the strand into contact with the mold. The plates are positioned on the faces of the strand by straps so as to permit relatively easy removal of the plates as, for example, in changing the size of the strand.

Below the cooling mold, there is provided a receiving apron to receive the strand to supportably guide the strand in its path towards the withdrawal rollers. The apron is formed as an open ended chute. A plurality of rollers are positioned along the open end of the chute to engage the strand in guiding relationship thereto. The trough is provided with cooling water which is introduced as a steady stream of water running down the trough. In addition, sprays are provided along the length of the apron to spray cooling water upon the strand passing therethrough.

The rollers are V-shaped and are adjustably positioned within the chute so as to provide means for easy adjustment of the chute arrangement to the various sizes of the strand cast. The V-shape will serve to center the strand in addition to providing a bearing force upon the strand, urging it into the desired curvature.

Withdrawal rollers are provided at the end of the cooling apron.

With this arrangement, the strand is effectively cooled during traversement of the chute and the frictional forces applied to the strand are significantly reduced. Thus, the possibility of application of tensional stress to the strand is considerably diminished. Thus, one of the major causes of breakouts is significantly reduced in an apparatus which is simpler to construct and is easier to utilize in the accommodation of various strand sizes.

The effects of breakout are drastically reduced in this apron arrangement. Since there is a continuous stream of water flow down the chute, if a breakout occurs, the steel will coagulate and be purged from the system by the water stream before it has an opportunity to weld to the chute and/ or the rollers therein. A single chute can accommodate a multiplicity of casting sizes since the only required change for a change of size is a repositioning of the rollers therein. Thus, operation with this arrangement is far simpler and more economical than with a conventional roller apron in which rollers are provided around the entire periphery of the strand.

Having briefly described this invention, it will be described in greater detail in the following portions of the specification, which may best be understood by reference to the accompanying drawings, of which:

FIG. 1 is an elevation view of a continuous casting plant in accordance with the present invention;

FIG. 2 is an elevation view of a portion of the apparatus shown in FIG. 1 to enlarged scale;

FIG. 3 is a cross sectional view taken along lines 3-3 of FIG. 2-;

FIG. 4 is a cross sectional view taken along lines 44 of FIG. 1; and

FIG. 5 is a cross sectional View taken along lines 5-5 of FIG. 4.

In FIG. 1, there is shown a continuous casting plant utilizing the present invention which includes a mold 10. The mold is a conventional continuous casting mold having a mold shaft into which molten metal is poured and being water cooled so as to solidify the periphery of the molten metal into a skin which defines the strand cast thereby. In the embodiment illustrated, this mold is a curved mold to cast a curved strand. Normally, the mold will be oscillated as is conventional.

Immediately below the mold, there is provided a cooling mold or a submold 12, the purpose of which is to effectively cool the issuing strand to augment the solidifi- Patented Dec. 19, 1967 cation of the skin initiated in the mold 10. The submold 12 may be oscillated synchronously with the mold 10. The specific construction of the subrnold is set forth in FIGS. 2 and 3 and a more detailed explanation will be given in connection with those figures.

Immediately below the submold, there is provided in the form of an open ended chute, an apron 14. The chute extends along the desired curvature of the strand and is provided with constraining rollers so that the strand will be centered within and follow the curvature of the apron 14. The constructional details of the apron are more specifically set forth in FIGS. 45 to which more detailed attention will be given in subsequent portions of the specification.

The chute is provided with a source of cooling water 16 which is poured down the chute and received by the sump 18. Cooling spray heads 20 may be provided along the open end of the chute to spray water on the strand to further augment cooling thereof. Withdrawal rollers 22 are positioned at the end of the apron to serve the purpose both of withdrawing the strand from the continuous casting plant and to straighten the strand for further processing.

The cooling mold details may best be seen by reference to FIGS. 2 and 3 which show the cooling mold 12. The cooling mold consists of plates 24 positioned on each side of the strand and held in contact therewith by the straps 26. The plates may be copper plates and are provided with ports 28 extending therethrough through which cooling water is supplied to the cavities 30 and thus, applied over the face of the strand side walls. The plates may be solid or may be provided with cooling water passages therein.

The cooling effect of the cooling mold results primarily from the water introduced between the plates 24 and casting. Thus, the plates may be made with copper faces or may be constructed from other metals such as steel or stainless steel. It is quite important, however, that the water introduced through the ports 28 be introduced at a pressure which does not exceed the ferrostatic head of the mold core at the point of introduction. Otherwise, the water will pierce the peripheral skin of the casting, leading to explosive breakout as the water is forced into the molten steel.

As previously mentioned, the cooling mold may be reciprocated with the main mold or may be stationary.

After exiting from the cooling mold, the strand enters the apron, the details of which are better shown in FIGS. 4-5 to which reference will now be made.

In FIGS. 4-5, there is shown a cooling apron 14 which comprises an open ended chute having a bottom wall 32 and upstanding side walls 34. The bottom wall 32 is preferably formed of a series of plates removably coupled to the apron as, for example, by bolts 36. In this manner, removal of the bottom wall is facilitated in the event of damage and need for replacement. Rollers 38 are provided along the chute and the shafts 40 thereof are journalled in the side walls 34 of the chute. In order to facilitate adjustment of the apron to accommodate various sizes of strand cast, the side walls may be provided with a plurality of holes 42 to receive the shafts 40 of the rollers. The rollers are V-shaped as is best shown in FIG. to serve to center the strand 11 within the chute as well as to provide a force holding the strand to the curvature of the chute. Thus, it can be seen with the present arrangement, adjustment of the apron to various sizes of casting is simply and easily accomplished. The rollers 38 are merely moved to the apertures in the side walls 34 for the size of strand being cast. Protective tubing 44 may be applied over the shafts 40 for protection against heat.

In the chute, the strand is, of course, cooled by the water 46 flowing down the entire length of the chute. However, to further augment cooling and to reduce the frictional drag, inlet apertures 48 are provided along the chute and positioned at the center of the bottom wall 32. Water is injected through the apertures 48 under a pressure which should not exceed the ferrostatic pressure of the mold core of the strand. The water injected through the apertures 48 serve the function of cooling the strand and in addition serves the function of providing a lubricant permitting the billet to slide down the chute without significant frictional drag. In addition, sprays from the heads 20 and sprays through the side wall from nozzle 50 may be introduced for augmented cooling of the strand.

Since the strand is essentially sliding on water and/ or water vapor film, the frictional drag is very much less than that with a constraining roller apron in which the rotatably mounted rollers are provided to bear on each side wall of the strand. Thus, the withdrawal force applied by the withdrawal rollers 22 of FIG. 1 can be materially reduced, resulting in a great decrease in the dimensional forces applied to the strand.

The cooling mold, of course, provides greater protection against breakout and against slag inclusion than the conventional water spray arrangements because of the bearing forces of the side plates provided therein.

However, if there is a breakout, the damage to the apron of this invention will be significantly less than that of a roller apron. For example, any breakouts occurring near the entrance of the chute (the most prevalent point for breakout) the molten metal will pour into the chute. However, since the chute is provided with a water stream flowing on the bottom thereof, the molten metal will coagulate and be purged from the chute without damage. In case of a power failure which results in cessation of this water flow, the bottom plates can be changed relatively simply. Thus, the down time which has a crucial impact upon operating costs can be drastically reduced with the present invention.

This invention may be variously modified and embodied within the scope of the subjoined claims.

What is claimed is:

1. A continuous casting plant comprising a continuous casting mold, said mold being an open ended mold to solidify the periphery of molten metal poured therein to define a strand continuously issuing from the bottom of said mold, a cooling apron positioned to receive the strand issuing from said mold, said cooling apron being an open topped chute having a bottom wall extending along the desired curve of said strand for continuously supporting said strand and side walls extending upwardly from said bottom wall, and means at the receiving end of said chute to introduce a steady stream of water into said chute to flow down said chute substantially along the entire length thereof.

2. A continuous casting plant in accordance with claim 1 in which said chute is provided with a plurality of rollers spaced along the length of said chute.

3. A continuous casting plant in accordance with claim 2 in which said rollers are V-shaped rollers to simultaneously urged the strand against the bottom wall of said chute and to center strand within said chute.

4. A continuous casting plant in accordance with claim 1 in which said bottom wall is provided with a plurality of inlet apertures and which includes means for injecting water into said inlet apertures to inject water between the base of said chute and said strand contained therein.

5. A continuous casting plant in accordance with claim 1 which includes a plurality of spray nozzles positioned along the length of said chute to spray water upon the strand contained within said chute for cooling thereof.

6. A continuous casting plant in accordance with claim I which includes a cooling mold positioned immediately below said casting mold, said cooling mold comprising a plurality of plates extending along the axial length of said strand, each plate being positioned adjacent a respective face of said strand and being urged into contact therewith by strap means coupling said plurality of plates together, each of said plates being provided with at least one port, and means to introduce water flow through said 3,358,744 5 6 port to provide a film of water between said plate and the FOREIGN PATENTS respective face of said strand for cooling thereof. 528,868 5/1954 Belgium 1,280,393 11/1961 France. References Clted 222,820 8/1962 Austria.

UNITED STATES PATENTS 5 930,193 7/1963 Great Britain.

8 3:22:53? figgg et aL 164-2 2 J. SPENCER OVERHOLSER, Primary Examiner.

1 648'9 XR R. S. ANNEAR, Assistant Examiner. 3,128,513 4/1964 Charleton et a1. 164-89