GB2027374A - Method of Sequential Continuous-casting of Different Grades of Steel - Google Patents
Method of Sequential Continuous-casting of Different Grades of Steel Download PDFInfo
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- GB2027374A GB2027374A GB7920857A GB7920857A GB2027374A GB 2027374 A GB2027374 A GB 2027374A GB 7920857 A GB7920857 A GB 7920857A GB 7920857 A GB7920857 A GB 7920857A GB 2027374 A GB2027374 A GB 2027374A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/08—Accessories for starting the casting procedure
- B22D11/086—Means for connecting cast ingots of different sizes or compositions
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Abstract
Sequential continuous-casting of different grades of molten steel comprises stopping the pouring of a first grade of molten steel 14 into a mold 12; immersing a cooling material consisting of steel stock or a steel structure 18 slightly smaller than the inner cross-sectional area of the mold by way of guiding jigs fastened to said cooling material; forming a solidified phase 22 around said cooling material and merging said solidified phase into a solidified shell 16 developed from the wall of the mold to form a solidified layer shutting off the lower portion of the first grade of molten steel. Pouring of the second grade steel 20 is started before the surface of the first grade steel is completely solidified, and at the same time, drawing of the cast slab is started again and the change-over to normal continuous casting of the second grade steel is effected. <IMAGE>
Description
SPECIFICATION
Method of Sequential Continuous-casting of Different Grades of Steel
The present invention relates to method of sequential continuous-casting of different grades of steel, and particularly to method of sequential continuous-casting of different grades of steel wherein cutting loss at the joint portion is very low and the workability of the process is excellent.
In the case of casting different grades of molten steel by continuous process, heretofore, in general, there has been adopted such a procedure that, upon completion of continuous casting of one grade of molten stee, continuous casting of another grade of molten steel cannot be started until the preparatory working for continuous casting has been performed all over again. However, the period of time required for the preparatory working for continuous casting usually amounts to 60 to 90 minutes, it has not been avoidable that the casting efficiency is reduced to a considerable extent in the case of conventional working process for the different grades of molten steel.
In the case of changing over from the continuous casting of a first grade of molten steel to a second grade of molten steel that are different in constituent from each other, if the second grade of molten steel which is different in constituent from the first grade is successively poured into the mold by the conventional method without resorting to any appropriate measure, it has been known the fact that the mixing between the different grades of molten steel reaches a depth as deep as five to eight meters from the liquid level in a mold due to the mixing occurred between the different grades of molten steel, suction caused by solidification shrinkage and bulging, and diffusion of the molten steel and convection caused by the difference in temperature.As the result of said mixing action, such a cast slab in which different grades of molten steel are mixed together is formed in the boundary area between two grades of cast slab which cannot be used as either grade of steel and therefore should be scrapped, thus significantly decreasing the yield of molten steel. Heretofore, there have been proposed various processes for minimizing production of such mixed cast slab.
According to the invention described in the publication of Japanese Patent Application Laid-Open
No. 57921/75 representing one of the typical processes, it is intended that the connecting function to connect the different grades of cast slab to each other is performed by a connecting material such as
H-steel, and the mixing occurring between the different grades of cast slab is completely shut off by charging a coolant material such as nail scrap. However, according to this process, although there are slight differences depending on the types of continuous casting machines used, the tensile load imposed on the connecting material can reach 30 to 100 tons.And, to draw the second grade of cast slab which is continuously cast later, the drawing force is imparted to said cast slab through the connecting material connected to the lower portion of said cast slab and the first grade of cast slab connected to said connecting material. Consequently, it becomes necessary to make the end portions of the respective grades of cast slabs be solidified completely.To attain such solidification, there are presented such disadvantages that the period of time required for treatment should be extended by three to ten minutes, and moreover, such a possibility is very high that, due to notch effect breakdown occurs in a solidified shell caused to the joint portion of the connecting material interposed between the different grades of cast slab to which said drawing force is imparted, and in turn the joint portion is broken, to thereby allow the molten steel cast to flow downwardly from the water-cooled mold.
Other examples of the prior art are disclosed in the pubiications of Japanese Patent Application
Laid-Open Nos. 112431/76 and 30723/77, for example. These conventional techniques contemplate that one or more stages of partition plates, the center portion of which is open are arranged on the upper surface of the first grade of molten steel, and the second grade of molten steel is poured onto said partition plate or plates to thereby partition the second grade of molten steel off the first grade of molten steel. By this, the purpose has been attained to a certain extent and the cast slab in which the different grades of steel are mixed could be reduced to as short as about one meter.However, in these conventional techniques, as the partition plate or plates have the open center portions, partial mixing between the different grades of molten steel cannot be prevented from occurring, and the best result obtainable by this technique is to shorten the scope of the mixed cast slab to one meter. Further, according to these conventional techniques, there is presented such a disadvantage that, since the partition plate or plates are mounted on the upper surface of the first grade of molten steel, a solidified shell produced in the mold may be broken at a portion of said partition plate or plates, thus resulting in the so-called breakout, i.e. the molten steel leaking out of said portion when the cast slab is drawn.
The object of the present invention is to obviate the disadvantages of the prior art and provide a continuous casting process of different grades of molten steel wherein cutting loss at joint portions is very low and the workability of the process is excellent.
The above described object of the present invention can be achieved by the present invention, the technical gist of which resides in the following.
Namely, in a continuous casting process wherein the continuous casting of the first grade of molten steel is changed over to the continuous casting process of the second grade of molten steel, and former and the latter being different in constituent, said continuous casting process comprises the steps of:
stopping the pouring the first grade of molten steel into the mold;
immersing a cooling material into the first grade of molten steel at the substantially center portion of said mold;
forming a solidified layer merging in a solidified shell developed from the wall of said mold and around said cooling material; and
pouring the second grade of molten steel into said mold before the upper surface of the first grade of molten steel on the top of said cooling material is solidified.
Other objects and features of the present invention will become apparent more fully from the description of the following embodiment given by way of example only and with reference to the accompanying drawings.
Figure 1 is a schematic longitudinal sectional view showing the solidifed conditions of the first and second grades of molten steel in the mold when the lattice-shaped cooling material embodying the present invention is used;
Figure 2 is an oblique view showing the main body of a lattice-shaped cooling material embodying the present invention;
Figures 3A, 3B, 3C and 3D are schematic plan views showing the embodiments of cooling materials according to the present invention;
Figure 4 is an oblique view showing the cooling material equipped with guiding jibs according to the present invention;
Figure 5 is an oblique view showing another embodiment of the cooling material equipped with guiding jigs according to the present invention;;
Figure 6 is a schematic longitudinal section view showing the process of immersing the cooling material shown in Figure 5 into the mold;
Figure 7 is a schematic longitudinal, sectional view showing the solidified layer in the cast slab when the drawing of the cast slab is started after the second grade of molten steel has been poured in the use of the cooling material shown in Figure 5;
Figure 8 is a schematic sectional view showing the descending conditions of the joint portion between the different grades of molten steel after the time shown in Figure 7;
Figure 9 is a correlational diagram showing the change in concentration of manganese and soluble aluminum at the portions above and below the cooling materials as in an embodiment of the mixed conditions of the different grades of steel according to the present invention;;
Figure 1 OA is a longitudinal sectional view showing an embodiment of cast slab at a portion adjacent the joint portion according to the present invention;
Figure 1 OB is a correlational diagram showing the changes in manganese content included in the changes in constituent corresponding to the respective portions of the cast slab adjacent the joint portion thereof as shown in Figure 1 OA;
Description will hereunder be given of the details of the present invention and one embodiment thereof with reference to the accompanying drawings. Firstly, description will hereunder be given of a first specific form of the present invention with reference to Figure 1.
The pouring of the first grade of molten steel 14 being continuously cast previously from the tundish into the mold 12 is stopped and simultaneously the drawing of the first grade of cast slab is also stopped. At this time, in the first grade of molten steel 14 in the mold 12, a solidified shell 1 6 of the first grade of cast slab is formed at the wall of mold 12.
Upon stopping the pouring of the first grade of molten steel 14, a cooling material 18 is
immersed and embedded in the first grade of molten steel 14 in the mold 12. Then, the first grade of
molten steel around the cooling material 1 8 is partially and quickly cooled, forms a solidified phase at
the spot, and is connected to a previously formed solidified shell 16, thus forming a provisional bottom.
After this condition takes place, the pouring of the second grade of molten steel 20 is started, which is
followed by the drawing work.
. As the cooling materials used in accordance with the present invention, a steel structure having a
plurality of vacant spaces allowing the molten steel in the mold to pass vertically therethrough is
effective.
A A lattice-eye-shaped structure as an example of the abovedescribed steel structure will be shown in Figure 2. In addition, as for the cooling materials used in accordance with the present invention,
there may be preferably used the cooling material having a plurality of vacant spaces of one or more
types selected from among the vacant spaces of net-eye shape, rectangular-eye shape, triangular-eye
shape, polygonal-eye shape, circular-eye shape, elliptic-eye shape, star-eye shape and others in addition to the lattice-eye shape. These cooling materials are each disposed in a planar fashion in the
molten steel contained in the mold. It is preferable to select the height of the cooling material from the
top surface to the bottom surface to be 40 mm and more so as to allow the molten steel poured into
the mold to pass through the vacant spaces of the cooling material as substantially vertical and
unidirectional current. Furthermore, it is necessary that the thickness of the wall between one vacant
space and the adjacent vacant space, i.e., the wall thickness of the cooling material has such a value
that the cooling material is not melted by the molten steel, and it is preferable to have a thickness of 2
to 20 mm practically.
Figures 3A, 3B, 3C and 3D illustrate several types of cooling materials according to the present invention. The cooling materials shown in Figures 3A and 3B have lattice-shaped vacant spaces, both of which can be integrated or superposed on each other in use. The cooling material shown in Figure 3C has net-eye shaped vacant spaces which may be superposed on a metal lath in cooling use. Shown in Figure 3D is a cooling material in which steel plates penetratingly provided therein with cylindrical holes and spaced apart from each other at a predetermined interval are connected to each other by means of webs. In passing, polygonal, elliptic and star-shaped vacant spaces can formed except for the cylindrical holes.
In addition, it is convenient to install cooling material guiding jigs 1 9 as shown in Figure 4 on the cooling materials 18 so as to facilitate the immersion of the cooling material 18 into the mold 12 and to stably hold the position of the cooling material 1 8 in the horizontal direction during immersion.
Additionally, according to the present invention, the depth of the cooling material being immersed and embedded in the molten steel contained in the mold is preferably large so as to secure the connecting strength by the use of the cooling material between the solidified cast slab of the first grade of molten steel previously poured in and the solidified cast slab of the second grade of molten steel poured in later. However, in the case the depth is excessively large, if the closing of the vacant spaces by the solidified phase is incomplete, the different grades of molten steel are mixed with each other, whereby the zone of the mixed and solidified cast slab is increased in size, which portion must be cut off later, thus decreasing the yield. Consequently, as viewed from the connecting strength, it is desirable to immerse the cooling material at least 50 mm in depth.
Description will hereunder be given of the timing of starting pouring of the second grade of molten steel 20. Namely, pouring of the second grade of molten steel 20 should be started before the outer surface of the first grade of molten steel 1 4 is not solidified which remains on the top of the shutoff layer consisting of a solidified phase having said cooling member 1 8 as the core material thereof.
The reason for this is that the joint portion between the first grade of molten steel 14 and the second grade of molten steel 20, thereby enabling to stand the drawing resistance. It is only two to three minutes from the completion of pouring the first grade of molten steel to the start of pouring the second grade of molten steel 20.
Even if the pouring of the second grade of molten steel 20 is started before the vacant spaces of the cooling material 1 8 are not clogged or part of the solidified phase 22 is broken which is clogging the vacant spaces of the cooling material 1 8 through the action of attracting force caused by the shrinkage of the first grade of molten steel 14 due to the solidification, the vacant spaces of the cooling material 1 8 are only vertically penetratingly provided, whereby the second grade of molten steel 20 passes through the vacant spaces as downwardly parallely dispersed currents, so that the mixing with the first grade of molten steel 14 can be restricted to the minimum.
Even if the pouring of the second grade of molten steel 20 is started as described above, the mixing with the first grade of molten steel 14 can be restricted to the minimum extent, a solidified phase 24 in which the first grade of molten steel 14 and the second grade of molten steel 20 are mixed to the minimum extent is formed on the solidified phase 22 of the first grade of molten steel 14, and thereafter, drawing is started again.
When the drawing is started again after the second grade of molten steel 20 is poured, the connection at the lowest limit can be maintained by the connecting strength of the boundary portion between said level L-L and the upper end line of the cooling material 1 8, i.e., between the solidified phases 22 and 24 disposed in a zone ranging from the level L-L to the depth H. According to the present invention, all of the solidified phases surrounding the cooling material 18 are integrated, and the solidified phases of the first and second grades of molten steel are integrated to be firmly connected together. As the time further lapses, still higher connecting mechanism becomes obtainable in the whole cross section of the mold.
Description will hereunder be given of a second specific form of the present invention with reference to Figures 5 through 8. In this case, as the cooling material a steel stock being circular or polygonal in cross section is used. With this method, the objects of the present invention can be effectively achieved as well. Namely, upon stopping pouring of the first grade of molten steel 14, a cooling material 28 comprising a steel stock having a circular or polygonal shape in cross section as shown in Figure 5 is put in. It is desirable that the cooling material 28 have such a configuration that guiding jigs 28B are welded to the steel stock 28A of a circular or polygonal shape in cross section as shown in the oblique view of Figure 5.As shown in Figure 5, said guiding jigs 28B are constructed such that a small steel bar 32 is welded to a small steel bar 30 to form a letter 'T' shape, the bottom end of the 'T' shape is welded to a steel stock 28A, and further the opposite ends of the 'T' shape are connected to the bottom end thereof by wires 34 or the like to form an inverted triangular shape. When put into the mold 12, the cooling material 28 is guided by said guiding jigs 28B, so that said steel stock 28A can be readily and accurately introduced into the center position of the mold 12. Except for the shape shown in Figure 5, the guiding jig 28B can be modified into an inverted triangular place or the like.
In addition, as for the configuration of the cooling material 28, it is necessary to use one which is large enough in volume to bring the molten steel 14 surrounding it to be cooled and solidified after it is immersed and sunk in the molten steel 14, and therefore, it is desirable to use one capable of satisfying the condition of the following formula.
V/S > 1 cm (1) where
V: Apparent cooling volume (cm3)
S: Apparent cooling outer surface (cm2)
The condition of the formula (1) is obtained from experiments. Such a cooling material is preferable that which is infusible to some extent and tends to form a solidified layer therearound because the larger the outer surface of the cooling material contracting the molten steel as compared with the volume, the more easily fusible the cooling material is.Since the cooling material 28 is put into the substantially center portion of the mold 12, and therefore, if the width and thickness of said cooling material are excessively small as compared those of the mold 12, then quick formation of the partition wall may not be reaiized, and if the width and thickness of said cooling material are excessively large as compared those of the mold 12, then the connection with the solidified shell in the joint portion cannot be secured. Accordingly, the following dimensions in length I and thickness d of the cooling material may be preferable for a mold having width of about 1 500 mm and thickness of about 220 mm.
Mold width200 mm < l < Mold width100 mm
Mold thickness100 mm > d > Mold thickness--20 mm
Figure 6 is an enlarged sectional view showing the condition of the cooling material 28 upon being put in after the pouring of the first grade of molten steel 14 is stopped. In general, the cooling material 28 is larger in specific gravity than the molten steel 14. Then, when put into, the cooling material 28 slowly descends, is set at the predecided portion of the mold 12 as shown in Figure 7, then quickly forms a solidified layer 30 therearound.Said solidified layer is connected to a solidified shell 1 6 of the first grade of molten steel 14, and the cooling material 28, the solidified layer 36 surrounding the cooling material 28 and the solidified shell 1 6 are integrally formed into a shut-off layer 38.
After the replacement of tundish due to the change in the grade of steel, if the pouring of the second grade of molten steel 20 different in constituent onto said shut-off layer 38 is started, then as shown in Figure 8, in the mold 12, a cast slab 1 4A of the first grade of molten steel 14 is formed at the lowermost portion, a provisional bottom composed of the shut-off layer 38 is formed thereon, and the second grade of molten steel 20 is poured still thereonto, whereby a solidified shell 40 of the second grade of molten steel 20 is formed from the portions thereof contacting the shut-off layer 38 and the mold 12, said solidified shell being drawn downwardly. During this process, the guiding jigs 28B used for the put-in which are provided on the steel stock of the cooling material 28 is melted by the first grade of molten steel 14 after the put-in.Although the surface layer of the steel stock 28A is hardly melted, the steel stock 28A together with the solidified shell formed therearound integrally form the shut-off layer 38 to constitute a joint portion between the first and second grades of molten steel 14 and 20 which will be drawn off as shown in Figure 8. Then, only said joint portion is cut off, so that a good product of the second grade of molten steel 20 different in constituent from the first grade of molten steel 14 from the first grade of cast slab 1 4A as shown in Figure 1 OA and 1 OB.
As described above, the solidified shell produced in the upper portion of the cast slab formed of the first grade of molten steel is utilized as the joint portion between the different grades of steel, the cooling material comprising the steel stock having the guiding jigs and being circular or polygonal in cross section is put in and sunk in the unsolidified portion of said first grade of molten steel in the mold, whereby the upper and lower portions of the unsolidified portion is shut off from each other, the solidified layer formed around the steel stock of the cooling material is connected to the existing solidified shell, whereby the upper and lower portions of the unsolidified portion is shut off from each other by the cooling material and the solidified phase, both of which constitute the partition wall, and the second grade of molten steel is poured thereon, whereby the mixing can be reliably prevented which would otherwise occur between the first and second grades of molten steel.
Description will hereunder be given of the embodiments of the present invention.
Example 1
Two grades of molten metal including A-grade of molten steel and B-grade of molten steel, the chemical compositions of which are shown in Table 1 , were continuously cast by use of a continuous casting machine having a first and a second strands in accordance with the present invention. In addition, for the cooling material, one illustrated in an oblique view of Figure 2 was used. Table 2 shows the results. Furthermore, the symbols indicating the data of the cooling material as shown in
Table 2 correspond to those shown in Figure 2.
Table 1
Chemical composition (wt. %J Grade of steel C Si Mn totalAl
A 0.14 0.18 0.76 0.006
B 0.12 0.18 0.93 0.039
Table 2
First strand Second strand
Size of slab 200 mmx 1570 mm 200 mmx 1570 mm
Shut-off cooling material As shown in Fig. 2 As shown in Fig. 2
W2xW, 140 mmx1490 mm 140 mmx1490 mm Thickness 4.5 mm 4.5 mm
Height D 90 mm 100 mm
Total weight 39 Kg 30 Kg
Work procedure and required time
Completion of casting grade-A
steel (stop of draw) Immersing cooling material 20 sec 20 sec
Stop of draw~Start of
pouring grade-B Steel 120 sec 120 sec
Stop of draw~Strand draw
restart 140 sec 135 sec
Additionally, since the cooling material shown in Table 2 weighs over 30 Kg, it was divided into two parts in use.Further, to hold the cooling material at the embedded depth H (corresponding to H in
Figure 1) which is about 1 50 mm and to align the cooling material with the center portion of the shell in the mold, guiding jigs 19 as shown in Figure 4 were fastened to the cooling material 1 8.
To study the mixing conditions of molten steel in this embodiment, a sample of the slab was cut out which extends 1000 mm in length in the drawing direction, i.e., on the side of grade-A steel and aiso extends 600 mm in length in the direction opposite to the drawing direction, i.e., on the side of grade-B steel as referenced from the boundary where the different grade of steel are connected to each other, divided into two at the center line of the width of the slab, and further, a drill sample is picked up at the center line of the thickness of the slab. One example of the results is shown in Figure 9. From the drawing, it was found that, in the first strand, the mixing was shut off 300 mm below the undersurface of the cooling material, and in the second strand, the mixing was shut off 700 mm below the undersurface of the cooling material.As compared with the natural mixing which is 5 to 8 m, the mixing according to the present invention was reduced by substantially one tenth. Furthermore, as for the strength of the joint portion, there was encountered no problem, and no cracking was seen in the joint portion.
Example 2
Using a mold having width of 1275 mm and thickness of 220 mm, the process according to the present invention was applied in changing over from continuous casting of the first grade of molten steel having the chemical composition shown in Table 3 to continuous casting of the second grade of molten steel.
Table 3
Chemical composition (wt. /0) Grade of steel C Si Mn ~ P S Al
First Grade of molten steel 0.46 1.9 0.36 0.012 0.009 0.050 Second grade of molten steel 0.14 4.9 1.14 0.017 0.009 0.025
Firstly, upon stopping the pouring of the first grade of molten steel 14, the cooling material 28 as shown in Figure 5 is put into the mold 12. The steel stock 28A has diameter of 100 mm and length of 1175 mm, and satisfies the condition of V/S=2.5 according to the aforesaid formula (1). The tundish was replaced simultaneously with the put-in of the cooling material. Upon stopping the pouring of the second grade of molten steel 20, casting was interrupted for three minutes and then, the pouring of the second grade of molten steel 20 is started.The cast slab drawing speed after the pouring of the second grade of molten steel was set at 0.4 m/min. However, it was restored to the normal drawing speed of 1.0 m/min in five minutes. Figures 1 OA and 1 OB show the condition of the joint portion in cross section between the first and second grades of molten steel and the change in the concentration of manganese corresponding to the respective positions, wherein 0 indicates the center of the joint portion.Namely, studies were made on the cast slab 1 4A produced from the first grade of molten steel 14, the cast slab
20A produced from the second grade of molten steel 20 and the shut-off layer 38 constituting the joint
portion between said two grades of molten steel in their cross sections, and as the result, it was found
a shrinkage cavity 42 immediately beneath the position to which the cooling material 28 was sunk due
to the formation of the shut-off layer as shown in Figure 1 OA. The mixing zone 44 where the first and
second grade of molten steel were mixed was about 10 cm in length. Study conducted on a sample
picked up from a portion of the slab at the center of the width and at the depth of one half thereof
made it clear that the mixing was completely prevented in portions forwardly and rearwardly of said
mixing zone as shown in Figure lOB.In addition, the shut-off layer 38 thus formed draws a parabolic
line in cross section as shown in Figure 8, the portion of the slab to be cut off was about 50 cm in length.
As apparent from the above embodiment, according to the present invention, in continuously
casting the different grades of molten steel, upon stopping the pouring of the first grade of molten steel at first, the cooling material having the guiding jigs slightly smaller in cross section than the mold is immersed in the center portion of the mold so as to form a solidified phase around said cooling
material, whereby said solidified phase is integrally connected to a solidified shell of the first grade of
molten steel formed on the inner wall of the mold, thereby forming a shut-off layer for shutting the upper portion off the lower portion in the intermediate portion of the first grade of molten steel in the
mold.Thereafter, the second grade of molten steel different in constituent from the first grade of
molten steel is poured in before the upper surface of the first grade of molten steel disposed on the top of shut-off layer is solidified completely. As the result, the second grade of molten steel forms a solidified phase on the top of a solidified phase of the first grade of molten steel formed around said cooling material, and at the same time, forms newly a solidified shell thereof on the top of a solidified shell of the first grade of molten steel on the inner surface of the mold, which integrally connected to the solidified phase of the second grade of molten steel formed around the cooling material, whereby the mixing with the first grade of molten steel is restricted to the minimum, thus enabling to restart the drawing.
Even if the drawing of the cast slab is started again, the solidified phase of the first grade of
molten steel surrounding the cooling material, the solidified phase integrally connected to the top of
said solidified phase and the solidified shell of the second grade of molten steel laminated on the top of the solidified shell of the first grade of molten steel formed on the inner wall of the mold are all
integrally, firmly connected and descend, so that such a trouble can be avoided that the molten steel
leaks out due to the break in the joint portion, which is called break-out, thus allowing the different
grades of cast slab jointed with the second grade of steel to be smoothly drawn off and descend.
Furthermore, in the case such a cooling material is used which has a plurality of vacant spaces through which the molten steel as described in the example 1 can pass only in the vertical direction,
even if the timing of pouring the second grade of molten steel is too early, said vacant spaces are not yet clogged due to the suction caused by shrinkage when the first grade of molten steel is solidified or the pouring is started again when the solidified shell is broken, the mixing with the first grade of molten steel can be avoided to the minimum because the flow of the second grade of molten steel is only 'downwardly directed and parallelly divided.
Further, in the process of continuously casting the different grades of molten steel according to the present invention, only three minutes of interruption in pouring molten steel is required, the
workability in the change-over work is excellent. In addition to the above, since the mixing portion of the different grades of molten steel is as short as about 10 cm in the joint portion between the different
grades of molten steel, the cast slab cut-off portion at the joint is as short as about 50 to 70 cm, thus
presenting such an advantage that the yields of molten steel and cast slab can be significantly
improved.
Furthermore, according to the present invention, the time during which continuous casting of the first grade of molten steel is changed over to that of the second grade of molten steel may be utilized for moving the shorter side plates of the mold, so that the change in width of the cast slab can be very
easily carried out simultaneously with the change-over between the different grades of molten steel.
Claims (13)
1. A method of sequential continuous-casting wherein continuous casting of a first grade of molten steel is changed over to continuous casting of a second grade of molten steel different in constituent from the first grade of molten steel, characterized in that said process comprises the steps of:
stopping the pouring of the first grade of molten steel into a mold;
immersing a cooling material in the substantially center portion of the first grade of molten steel in said mold;
forming around said cooling material a solidified layer merging in a solidified shell developed from the wall of said mold; and
pouring the second grade of molten steel into said mold before the surface of the first grade of molten steel above said cooling material is solidified.
2. A method of sequential continuous-casting of the different grades of molten steel as set forth in claim 1, characterized in that said cooling material is a steel structure having a plurality of vacant spaces allowing the molten steel in said mold to pass vertically therethrough.
3. A method of sequential continuous-casting of the different grade of molten steel as set forth in claim 1 or 2, characterized in that said cooling material is a steel structure having lattice-eye-shaped vacant spaces.
4. A method of sequential continuous-casting of the fifferent grades of molten steel as set forth in claim 1 or 2, characterized in that said cooling material is a steel structure having triangular-eyeshaped vacant spaces.
5. A method of sequential continuous-casting of the different grades of molten steel as set forth in claim 1 or 2, characterized in that said cooling material is a steel structure having polygonal-eyeshaped vacant spaces.
6. A method of sequential continuous-casting of the different grades of molten steel as set forth in claim 1 or 2, characterized in that said cooling material is a steel structure having circular-eyeshaped vacant spaces.
7. A method of sequential continuous-casting of the different grades of molten steel as set forth in claim 1 or 2, characterized in that said cooling material is a steel structure having elliptic-eye-shaped vacant spaces.
8. A method of sequential continuous-casting of the different grades of molten steel as set forth in claim 1,2, 3, 4, 5, 6 or 7, characterized in that the wall thickness of said cooling material is 2 to 20 mm.
9. A method of sequential continuous-casting of the different grades of molten steel as set forth in claim 1, characterized in that said cooling material is a columnar steel stock.
10. A method of sequential continuous-casting of the different grades of molten steel as set forth in claim 1, characterized in that said cooling material is a steel stock having polygonal shape is cross section.
11. A method of sequential continuous-casting different grades of molten steel as set forth in claim 1, 9, or 10, characterized in that the length I and thickness d of said cooling material satisfy the conditions of the following two formulae for the mold having the width of 1 500 mm and thickness of 220 mm.
Mold width 300 mm < l < Mold width-100 mm
Mold thickness--100 mmEd < Mold thickness-20 mm
12. A method of sequential continuous-casting of different grades of molten steel as set forth in claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11 , characterized in that the depth of immersing and embedding said cooling material in the first grade of molten steel in said mold is at least 50 mm as measured from the top of said cooling material.
13. A method of sequential continuous-casting of different grades of molten steel substantially as hereinbefore described with reference to the accompanyinq drawings.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP53075031A JPS5942587B2 (en) | 1978-06-20 | 1978-06-20 | Continuous casting method for molten steel of different steel types |
| JP8224678A JPS558376A (en) | 1978-07-05 | 1978-07-05 | Continuous casting method of different kind of steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2027374A true GB2027374A (en) | 1980-02-20 |
| GB2027374B GB2027374B (en) | 1982-09-08 |
Family
ID=26416187
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7920857A Expired GB2027374B (en) | 1978-06-20 | 1979-06-15 | Method of sequential continuous-casting of different grades of steel |
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| Country | Link |
|---|---|
| CA (1) | CA1144735A (en) |
| DE (1) | DE2924925C2 (en) |
| FR (1) | FR2429055A1 (en) |
| GB (1) | GB2027374B (en) |
| SE (1) | SE444522B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3673379D1 (en) * | 1986-01-03 | 1990-09-13 | Dislich Geb Hoyer Margrit Dr | METHOD AND ARRANGEMENT FOR CONNECTING A NEW CASTING STRAND IN A CONTINUOUS CASTING SYSTEM. |
| CN102380595A (en) * | 2011-10-27 | 2012-03-21 | 内蒙古包钢钢联股份有限公司 | Continuous casting method for easily drawable steel wires |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3534804A (en) * | 1968-03-26 | 1970-10-20 | Gulf & Western Ind Prod Co | Continuous casting apparatus |
| AT323916B (en) * | 1970-12-02 | 1975-08-11 | Voest Ag | PROCESS FOR FULLY CONTINUOUS CONTINUOUS CASTING OF MELT LIQUID METALS |
| JPH0557921A (en) * | 1991-09-05 | 1993-03-09 | Tokyo Electric Co Ltd | Line printer |
-
1979
- 1979-06-15 GB GB7920857A patent/GB2027374B/en not_active Expired
- 1979-06-18 CA CA000330005A patent/CA1144735A/en not_active Expired
- 1979-06-19 SE SE7905393A patent/SE444522B/en not_active IP Right Cessation
- 1979-06-20 DE DE19792924925 patent/DE2924925C2/en not_active Expired
- 1979-06-20 FR FR7915823A patent/FR2429055A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| FR2429055A1 (en) | 1980-01-18 |
| DE2924925C2 (en) | 1983-04-28 |
| DE2924925A1 (en) | 1980-01-17 |
| SE444522B (en) | 1986-04-21 |
| GB2027374B (en) | 1982-09-08 |
| CA1144735A (en) | 1983-04-19 |
| FR2429055B1 (en) | 1983-07-22 |
| SE7905393L (en) | 1979-12-21 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19980615 |