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AU689632B2 - Casting surface of a moving-wall mould for the continuous casting of metals - Google Patents
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AU689632B2 - Casting surface of a moving-wall mould for the continuous casting of metals - Google Patents

Casting surface of a moving-wall mould for the continuous casting of metals Download PDF

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Publication number
AU689632B2
AU689632B2 AU33164/95A AU3316495A AU689632B2 AU 689632 B2 AU689632 B2 AU 689632B2 AU 33164/95 A AU33164/95 A AU 33164/95A AU 3316495 A AU3316495 A AU 3316495A AU 689632 B2 AU689632 B2 AU 689632B2
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AU
Australia
Prior art keywords
casting
dimples
moving
dimple
metals
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.)
Ceased
Application number
AU33164/95A
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AU3316495A (en
Inventor
Hugues Legrand
Christian Marchionni
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.)
Thyssen Stahl AG
USINOR SA
Original Assignee
Thyssen Stahl AG
USINOR Sacilor SA
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 Thyssen Stahl AG, USINOR Sacilor SA filed Critical Thyssen Stahl AG
Publication of AU3316495A publication Critical patent/AU3316495A/en
Application granted granted Critical
Publication of AU689632B2 publication Critical patent/AU689632B2/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/04Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
    • B22D11/05Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds into moulds having adjustable walls
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/06Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
    • B22D11/0637Accessories therefor
    • B22D11/0648Casting surfaces
    • B22D11/0651Casting wheels

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Continuous Casting (AREA)
  • Coating With Molten Metal (AREA)

Abstract

The ingot mould, e.g. for molten steel, consists of two cooled rollers (2) set with a gap between them forming the moulding surface. Each of the rollers has a series of circular or elliptical recesses (7-10) formed by surface lobes (3-6). The lobed surface has a perimeter which is 1.1-1.5 times greater than an equivalent roller with a cylindrical surface.

Description

AUSTRALIA
Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT o r c Applicant! 1) 2) Invention s: USINOR SACILOR (Societe Anonyme) and THYSSEN STAHL AKTIENGESELLSCHAFT Title:
CASTING
FOR THE SURFACE OF A MOVING-WALL MOULD CONTINUOUS CASTING OF METALS The following statement is a full description of this invention, including the best method of performing it known to me/us:
-IA-
CASTING SURFACE OF A MOVING-WALL MOULD FOR TBHE CONTINUOUS CASTING OF METALS The invention relates to the continuous casting of metals. More precisely, it relates to installations for the continuous casting of metals such as steel, by the solidification of the liquid metal on a moving wall or between two moving walls. These moving walls may, in particular, consist of the curved surfaces of one or two rolls having a horizontal axis and being vigorously internally cooled.
Recent years have seen substantial progress made in the development of processes for casting thin steel strips directly from liquid metal. Currently, the process which seems most likely to rapidly emerge in an s industrial application is twin-rolled casting, in which the internally cooled rolls rotate about their horizontal axes in opposite directions and are arranged facing each other, the gap between them having a width substantially equal to the thickness which it is desired to give the cast strip (for example a few mm). The casting space containing the liquid steel is defined by the curved surfaces of the rolls, on which solidification of the o o strip starts, and by refractory lateral containment plates applied against the ends of the rolls.
25 An important element in the success of the casting operation is to achieve a good surface quality of the strip immediately. The reason for this is that the major advantage of thin-strip casting directly from liquid metal is the possibility that it affords in eliminating or considerably reducing the extent of The operation of hot rolling of the thick semi-finished product usually cast. When the steel is cast in thick format, it is possible to eliminate the surface defects by grinding. However, this operation is not possible on thin strips. In thin-strip casting processes it is therefore necessary to obtain a substantially defect-free S surface straight from casting.
The microcracks just mentioned arise from thermal 2 gradients which are established in the skin of the product during its solidification against the cooled wall of the roll and which generate stresses therein. In order to reduce these stresses, the surface of the rolls is commonly given a degree of rugosity. Air (or an inerting gas blown in and confined above the casting space) is trapped in the hollow parts of the surface before the latter comes into contact with the liquid metal. It forms a gaseous "blanket" between the metal and the roll, and this blanket tends to decrease the rate of cooling of the skin, and therefore the thermal gradients. The rugosity also makes it possible to distribute the thermal stresses and strains on a scale such that they do not cause defects.
It is proposed in document EP 0,309,247 to produce this rugosity in the form of "dimples", that is to say hollowed etched regions isolated from one another and with a circular or oval opening having a diameter of the order of from 0.1 to 1.2 mm and having a depth of 20 from 5 to 100 pm. When the surface of the roll comes into contact with the liquid metal, the latter penetrates into the dimples, the dimensions of which are chosen so that, through the effect of surface tension forces, liquid go :metal can penetrate thereinto and form protuberances, 25 without however completely filling them. It is necessary, in particular, to prevent the liquid metal from coming oee0 into contact with the bottom of dimples which would be too wide and/or too shallow, since it would cool there at a normal rate. The desired effect of attenuating the 30 thermal gradients would no longer be obtained and, in eooo S"addition, the protuberances would solidify while their presence on the strip is undesirable. If the dimples are of suitable size, the metal which penetrates therein does not solidify therein immediately. The protuberances then form reserves of material which exhibit a more plastic behaviour than the neighbouring portions of the skin solidified on the smooth parts of the roll. During cooling of the skin, which is accompanied by contraction of the metal, these protuberances behave as expansion joints. They contract more quickly than their surroundings, while at the same time absorbing the tensile stresses internal to the skin resulting from its contraction, which could otherwise lead to cracking of the surface of the strip. This accentuated contraction also means that protuberances are no longer observed, or hardly ever, on the solidified and cooled strip. In order for these dimples to be able to fulfil their role completely, it is necessary for the distances separating them to be maintained between lower and upper bounds specified in this document, these depending on the diameter of the dimples.
Document EP 409,645 proposes the use of a gas, as a gas for inerting the casting space of the installation, 15 which is partially soluble in the steel in order to oee prevent the appearance of dentation on the surface of the strip, which would be due to exaggerated expansion of the gas during the start of solidification if this gas were completely insoluble. Conversely, an entirely soluble gas S. 20 would run the risk of no longer fulfilling its role of acting as a blanket between the roll and the strip. For
S.
this purpose, it is proposed to use, as the soluble gas, S: nitrogen, hydrogen, carbon dioxide or ammonia, this soluble gas being mixed with argon or helium. The amount of soluble gas recommended in this mixture is 30 to 55C": The object of the invention is to give the eeoc dimples a configuration which enables them to fulfil S" their role of preventing microcracks even more effectively compared to the practice in the Prior Art.
For this purpose, the subject of the invention is a casting surface of a moving-wall mould for the continuous casting of metals, of the type including dimples of circular or elliptical general shape, wherein the said dimples have lobes on their perimeter. The said casting surface may, especially, consist of the curved surface of one cooled rotating cylinder or two cooled rotating cylinders.
As will be understood, the invention involves giving the dimples no longer a circular or oval shape but 4 a lobed shape. By lobed shape it is meant that, starting from an at least approximately circular or elliptical general shape, the perimeter of the dimples includes portions where its radius of curvature is significantly smaller, in absolute value, than the average radius of curvature of the dimple. This perimeter may thus consist of an alternation of portions of small radius of curvature. the concavity of which successively faces the interior and then the exterior of the dimple.
The invention will be better understood on reading the following description, given with reference to the appended figures: Figure 1, which shows a dimple according to the Prior Art; Figure 2, which shows an example of a dimple according to the invention, intended to replace the previous one.
One of the essential parameters in the action of the dimples on the solidification of the skin is the intense cooling of the metal which occurs on their border. Compared to dimples with a circular or oval opening, the lobed dimples according to the invention provide an increase in the length of the borders, and therefore consequently an increase in the cooling, for a 25 dimple surface area which remains identical to the Prior Art. Under these conditions, the overall cooling rate of the strip is not altered since it depends, all other S"things being equal, on the percentage of the surface area of the rolls which is occupied by the dimple openings.
The increase in the cooling rate of the strip caused by S"the configuration of the dimples according to the invention is only felt at a microscopic level, more especially as, for an equal dimple surface area, the minimum distance separating the edges of two neighbouring dimples is shorter in the case of lobed dimples than in the case of circular dimples. Moreover, for a given dimple perimeter, the volume of gas trapped within the dimple is smaller in the case of a lobed dimple than in the case of a circular dimple. The problems associated with expansion of the 5 gas, mention of which was made above, are therefore reduced.
The circular dimple 1 according to the Prior Art shown in plan view in Figure 1 (the distortions due to the curvature of the surface of the roll, the radius of which is of the order of from 250 to 750 mm and is very large compared to the size of the dimples which are of the order of one mm or less, have been neglected) has a radius R, a surface area S (equal to tR 2 and a perimeter length P (equal to 2nR). Likewise, Figure 2 shows, on the same scale, an example (this being non-limiting of course) of a lobed dimple 2 according to the invention.
This lobed dimple 2 is inscribed in a circle of radius this radius R' being calculated :o that the lobed dimple 2 has a surface area S' equal to the surface area S of the previous circular dimple 1. The perimeter of this lobed dimple 2 is in the form of an alternation of semicircles 3, 4, 5, 6, the concavities of which face the interior of the dimple, and of quadrants 7, 8, 9, 10, the 20 concavities of which face the exterior of the dimple. The radius of curvature of the semicircles 3-6 and the radius of curvature of the quadrants 7-10 are both equal to The centres of curvature of the semicircles 3-6 are located at the mid-points of the 25 sides of a square centred on the circle of radius R' and the centres of curvature of the quadrants 7-10 are located at the corners of this same square. A simple S"calculation sb' that the surface area S' of this lobed dimple 2 according to the invention is equal to 30 R' 2 (7+16)/9 and that its perimeter P' is equal to 2iR'.
In order for S' S, it is therefore necessary that R' i.e. R' 1.22 R.
Under these conditions, for this type of lobed dimple, the ratio is equal to 2.95/R', i.e.
expressed as a function of the radius R of the circular dimple of equivalent surface area, equal to 2.43/R, whereas P/S for this circular dimple would only be equal to 2/R. A lobed dimple is therefore obtained which has a perimeter substantially greater than that of a circular -6dimple of equivalent surface area, something which makes it possible to increase the desired anti-microcracking effect during solidification of the strip. Likewise in the case where it is desired to keep a constant perimeter length for the perimeter of the dimples, but to decrease their surface area in order to limit the volume of trapped gas, the condition P' P is then imposed, i.e.
27R' 27R, hence R' R and S'/S 0.68. For the same perimeter length, this dimple configuration therefore makes it possible to decrease by approximately one third the surface area of the dimples, and hence the volume of trapped gas, compared to circular dimples.
For the same dimple surface area, the dimples according to the invention make it possible to decrease 15 the distance separating two dimples since, as has been oseen, R' 1.22R. This reduction is favourable where it is desired to cast steels such as austenitic stainless steels of the AISI 304 type. From document EP 309,247, it is known for this purpose to make distances between dimples very small (less than 0.35 mm) in order to obtain a favourable solidification structure. The use of dimples .e according to the invention provides an additional degree of freedom in achieving this result.
The.ae dimples may be formed on the copper shell which usually constitutes the external or curved surface of the rolls, for example by running thereon a knurled wheel *'"which has etching in relief reproducing their shape. This etching pushes in the material of the shell to the desired depth (which is of the order of from 5 to 100 pm usually) and therefore causes the appearance of reliefs on the edges of the dimples. It is then necessary to grind the surface of the shell in order to remove these reliefs.
Of course; the dimple example which has been described and shown is not limiting, and other types of lobed dimples, including lobes which are different in shape and/or in number, are conceivable. Instead of being exactly inscribed in a circle, the dimples may be so only 1\ approximately, or else they may be inscribed in an 7 ellipse. Optimally, it is recoimmended that the lobed dimples have a perimeter length P' lying between 1.1 and times the perimeter length P of the circular dimples which would have an identical unit surface area. If P' is less than 1.1 times P, the advantci'a obtained is too small and not detectable. If P' is greater than 1.5 times P, this means that the contour of the dimples has many deep circumvolutions, which means that the edges of a dimple which are facing each other are at a very short distance from one another. In this case, there is a risk that the metal cannot penetrate into the dimple which can then no longer fulfil its role. Finally, it is important that these dimples should not have shape angles which would create abnormal solidification conditions thereat, and which could generate defects in the strip.
The invention is not only applicable to rolls intended for equipping a twin-roll steel casting machine but also to any casting surface of a mould having a moving wall or moving walls, such as the surface of a 20 roll of a machine for casting very thin strips on a rotating roll or that of a strip of a machine for casting metal between two moving strips.
b 0 beQ
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I

Claims (4)

1. A casting surface of a moving-wall mould for the continuous casting of metals, of the type including dimples of circular or elliptical general shape, wherein the said dimples have lobes on their perimeter.
2. A casting surface according to Claim 1, wherein the said dimples have a perimeter length lying between 1.1 and 1.5 times the perimeter length that a circular dimple of equivalent surface area would have
3. A casting surface according to claim 1 or 2 consisting of the curved surface of a cooled rotating roll.
4. A casting surface according to Claim 1 or 2, consisting of the curved surface of two cooled rolls rotating in opposite directions and defining a casting space between them. A casting surface substantially as hereinbefore described with reference to Figure 2. S- DATED: 29 January, 1998 PHILLIPS ORMONDE FITZPATRICK Attorneys for: USINOR SACILOR (SOCIETE ANONYME) and THYSSEN STAHL AKTIENGESELLSCHAFT V T SSDocment14 I II CASTING SURFACE OF A MOVING-WALL MOULD FOR THE CONTINUOUS CASTING OF METALS Abstract The invention relates to a casting surface of a moving-wall mould for the continuous casting of metals, of the type including dimples of circular or elliptical general shape, characterized in that the said dimples have lobes on their perimeter. The said casting surface may, especially, consist of the lateral surface of a cooled rotating roll or of two cooled rotating rolls. Figure for the anstract: Figure 2 Q0*O 0 0 0 00 0# 0 0 0:96. as 9
AU33164/95A 1994-10-31 1995-10-10 Casting surface of a moving-wall mould for the continuous casting of metals Ceased AU689632B2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9413028A FR2726209B1 (en) 1994-10-31 1994-10-31 CASTING SURFACE OF A CONTINUOUS CASTING LINGOTIERE OF MOBILE WALL METALS
FR9413028 1994-10-31

Publications (2)

Publication Number Publication Date
AU3316495A AU3316495A (en) 1996-05-09
AU689632B2 true AU689632B2 (en) 1998-04-02

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ID=9468385

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Application Number Title Priority Date Filing Date
AU33164/95A Ceased AU689632B2 (en) 1994-10-31 1995-10-10 Casting surface of a moving-wall mould for the continuous casting of metals

Country Status (10)

Country Link
EP (1) EP0709151B1 (en)
JP (1) JPH08206791A (en)
KR (1) KR960013520A (en)
AT (1) ATE184226T1 (en)
AU (1) AU689632B2 (en)
DE (1) DE69511984T2 (en)
DK (1) DK0709151T3 (en)
ES (1) ES2137467T3 (en)
FR (1) FR2726209B1 (en)
GR (1) GR3032048T3 (en)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT1295859B1 (en) * 1997-11-12 1999-05-28 Acciai Speciali Terni Spa COOLING ROLLER FOR CONTINUOUS CASTING MACHINES
KR100668126B1 (en) 2000-05-12 2007-01-16 신닛뽄세이테쯔 카부시키카이샤 Processing apparatus for cooling drums for thin cast continuous casting
AU2008100847A4 (en) 2007-10-12 2008-10-09 Bluescope Steel Limited Method of forming textured casting rolls with diamond engraving

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0463177A1 (en) * 1990-01-12 1992-01-02 Nippon Steel Corporation Continuously cast thin piece and method of casting thereof
EP0481481A1 (en) * 1990-10-19 1992-04-22 Nippon Steel Corporation Process for production of austenitic stainless steel thin cast strip and strip obtained thereby
EP0577833A1 (en) * 1991-01-11 1994-01-12 Nippon Steel Corporation Cooling drum for casting thin cast piece; device for and method of forming dimples on peripheral surface of said drum

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4887662A (en) * 1987-09-24 1989-12-19 Shigenori Tanaka Cooling drum for continuous-casting machines for manufacturing thin metallic strip
US5103895A (en) 1989-07-20 1992-04-14 Nippon Steel Corporation Method and apparatus of continuously casting a metal sheet

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0463177A1 (en) * 1990-01-12 1992-01-02 Nippon Steel Corporation Continuously cast thin piece and method of casting thereof
EP0481481A1 (en) * 1990-10-19 1992-04-22 Nippon Steel Corporation Process for production of austenitic stainless steel thin cast strip and strip obtained thereby
EP0577833A1 (en) * 1991-01-11 1994-01-12 Nippon Steel Corporation Cooling drum for casting thin cast piece; device for and method of forming dimples on peripheral surface of said drum

Also Published As

Publication number Publication date
DE69511984T2 (en) 2000-05-18
FR2726209B1 (en) 1996-11-29
EP0709151B1 (en) 1999-09-08
ES2137467T3 (en) 1999-12-16
FR2726209A1 (en) 1996-05-03
DK0709151T3 (en) 2000-04-03
AU3316495A (en) 1996-05-09
KR960013520A (en) 1996-05-22
ATE184226T1 (en) 1999-09-15
GR3032048T3 (en) 2000-03-31
EP0709151A1 (en) 1996-05-01
DE69511984D1 (en) 1999-10-14
JPH08206791A (en) 1996-08-13

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MK14 Patent ceased section 143(a) (annual fees not paid) or expired