EP0887129A1 - Améliorations dans ou relatives à la coulée - Google Patents

Améliorations dans ou relatives à la coulée Download PDF

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Publication number
EP0887129A1
EP0887129A1 EP98304885A EP98304885A EP0887129A1 EP 0887129 A1 EP0887129 A1 EP 0887129A1 EP 98304885 A EP98304885 A EP 98304885A EP 98304885 A EP98304885 A EP 98304885A EP 0887129 A1 EP0887129 A1 EP 0887129A1
Authority
EP
European Patent Office
Prior art keywords
vessel
casting
molten material
tundish
ladle
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.)
Withdrawn
Application number
EP98304885A
Other languages
German (de)
English (en)
Inventor
Leslie Charles c/o Kvaerner Metals CC Ltd Wright
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.)
Kvaerner Clecim Continuous Casting Ltd
Kvaerner Metals Continuous Casting Ltd
Original Assignee
Kvaerner Clecim Continuous Casting Ltd
Kvaerner Metals Continuous Casting Ltd
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 Kvaerner Clecim Continuous Casting Ltd, Kvaerner Metals Continuous Casting Ltd filed Critical Kvaerner Clecim Continuous Casting Ltd
Publication of EP0887129A1 publication Critical patent/EP0887129A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • B22D11/10—Supplying or treating molten metal
    • 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
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/18—Controlling or regulating processes or operations for pouring
    • B22D11/181—Controlling or regulating processes or operations for pouring responsive to molten metal level or slag level

Definitions

  • This invention concerns improvements in and relating to casting of molten materials, particularly molten metal being cast into strips, slabs or other forms.
  • Strip and slab casting typical involves feeding molten steel through a casting nozzle and then between rollers to give the desired strip/slab thickness.
  • the molten metal feed to the nozzle comes from a tundish which is fed from a delivery ladle.
  • the level of molten material within the tundish is kept constant throughout the majority of the casting stage by balancing the pouring rate from the ladle into the tundish against the extraction rate from the tundish via the casting nozzle.
  • the ladle represents a batch delivery system to the tundish it must periodically be replaced by another full ladle. To ensure a sufficient level of material in the tundish during change over, the level can be increased slightly before hand. The tundish level depletes during change over until the level can be topped up once more by the replacement ladle.
  • the present invention aims to provide greater versatility and control in the casting system.
  • a method of casting comprising feeding molten material to a vessel from a source of molten material, the vessel feeding molten material to a casting location through an outlet passage, the volume of molten material in the vessel being variable, the head of molten material over the outlet passage being substantially constant independent of the volume of molten material in the vessel.
  • the vessel is a tundish.
  • the tundish may be heated.
  • the tundish may be heated by induction heating and/or plasma heating.
  • the tundish has a capacity of between 20 and 120 tonnes.
  • the ratio of maximum to minimum working volume of the vessel is greater than 1.5:1 and more preferably greater than 1.75:1 or even greater than 2:1.
  • the vessel is provided with an enclosed head space above the inlet from the vessel to the outlet passage.
  • the enclosed head space may be provided with a controlled or inert atmosphere.
  • the surface of the material in the vessel may be provided with oxidation inhibitors, such as tundish powders. Preferably such materials are excluded from any enclosed head space.
  • the source of molten material is a ladle.
  • the ladle is used to transfer molten material from a melting location to the casting location.
  • the ladle is unheated.
  • the ladle preferably has a capacity of between 10 and 100 tonnes of molten material.
  • the material is preferably fed from the ladle to vessel under gravity. Control valves may be used to regulate the flow.
  • the flow rate of material from ladle to vessel is preferably at least 1.5 times greater than the casting flow rate, more preferably at least 3 times and may be as high as 5 times the rate.
  • the molten material is a metal, including alloys. Most preferably the material is steel.
  • the casting location comprises a casting nozzle.
  • the casting nozzle may feed molten material direct to casting rollers.
  • the casting nozzle may feed material to a pool in proximity to casting rollers.
  • the casting location may be fed with material via a fixed or flexible link.
  • the feed may be direct from the vessel or via intervening means.
  • the feed is preferably affected by gravity.
  • Control means such as valves, may be provided to regulate the flow.
  • the vessel can be adjusted to accommodate varying volumes of material whilst maintaining a constant head.
  • the variation in volume may be provided by varying the volume of material accommodated within the vessel away from the outlet.
  • the variation is accommodated on a continuous basis during casting.
  • the variation may be accommodated by altering the position of the vessel.
  • the variation in the positioning may occur through tilting the vessel or pivoting it.
  • the pivoting or tilting may occur about one, preferably fixed, axis.
  • the vessel has a volume portion adjacent to the outlet passage and a volume portion distal to the outlet passage.
  • the volume accommodated in the vessel is increased by lowering the level of the distal portion relative to the level of the portion adjacent the outlet passage.
  • the volume is decreased by raising the level of the distal portion relative to the level of the portion adjacent to the outlet passage.
  • the tilt or pivot may occur about a fixed location.
  • the fixed location is about the outlet passage.
  • the fixed location may be at the outlet from the outlet passage into an intervening vessel.
  • the adjustment of the vessel to maintain a constant head may be based on level measurements in the vessel and/or based on mass of material in the vessel.
  • the head is maintained at a value related to the casting rate. In this way casting quality can be maintained.
  • the head is preferably measured in the vertical direction.
  • the head measured may be measured in terms of the projected head based on the vertical separation of the molten material level in the vessel and the outlet level to which it is feed.
  • a head of greater than 300mm may be provided.
  • Preferably the head is maintained at a minimum without causing vortexing of the metal.
  • the outlet level may be the casting location where material is fed direct from the vessel to that location.
  • the outlet level may be the level in an intervening vessel between the vessel and casting location where the material is fed to such a vessel prior to feeding to the casting location.
  • the intervening vessel may comprise a headbox. The exit of material from the headbox to the casting location may be controlled by a weir or dam.
  • the method is used for casting strips, slabs, blooms and billets. Its use for casting strips of thickness less than 10mm is particularly preferred.
  • the material is cast at a rate of between 5 and 150 tonnes per hour and more preferably between 10 and 100 tonnes per hour.
  • casting apparatus comprising a source of molten material, a vessel to which the molten material is fed, the vessel feeding material to a casting location via an outlet passage, the vessel being adjustable to present a constant head of material independent of the volume of material accommodated within the vessel.
  • the vessel is a tundish.
  • Induction heating and/or plasma heating means may be provided for the tundish.
  • the vessel is provided with an enclosed head space above the inlet from the vessel to the outlet passage.
  • the enclosed head space may be defined by portions of the vessel which dip below the surface of the molten material in the vessel to separate enclosed and unenclosed portions.
  • the source of molten material is a ladle.
  • the ladle is unheated.
  • the ladle may be provided with control valves to regulate the flow of material from the ladle to the vessel.
  • the casting location may comprise a casting nozzle.
  • the casting nozzle may be provided with a flexible link or fixed link from the vessel or from an intervening vessel fed from the vessel.
  • the feeder material from the vessel to casting location may be regulated by control means as valves.
  • the vessel is pivotally mounted.
  • the vessel is pivotally mounted about one, preferably fixed, axis.
  • the pivot location is about the outlet passage, and most preferably about the outlet from the outlet passage into an intervening vessel.
  • the apparatus may be provided with mass and/or level monitoring means for the vessel and/or for the intervening vessel.
  • the intervening vessel may comprise a head box.
  • the head box may be provided with weirs, dams or other flow regulating means.
  • a method of casting comprising feeding molten material to a vessel from a source of molten material, the vessel feeding molten material to a casting location, the molten material being fed to the casting location substantially continuously during casting, the molten material being fed to the vessel from the source for less than 90% of the time during casting.
  • the molten material is fed from the source to the vessel for less than 75% of the time during casting, more preferably less than 50% of the time and still more preferably less than 33% of the time.
  • Steel strips and slabs are generally produced by feeding molten metal through a nozzle into a casting machine and then rolling the material in a series of stages to the desired thickness and width.
  • the cast material sizes prior to rolling vary from 2 to 6mm thicknesses and widths upto 2000mm for strips through thin slab (50 to 120mm thick, 700 to 2000mm wide), midi slab (120 to 185mm thick, 700 to 3200mm wide) to thick slab (185 to 300mm, 700 to 3200mm wide).
  • a typical strip casting operation may employ flow rates of between 10 and 100 tonnes/hour.
  • FIG. 1a to 1d A series of such nozzle 1 and casting roller 3 arrangements are illustrated in Figure 1a to 1d for a strip casting operation. As shown casting can occur at a variety of orientations. Equally the casting can occur direct from the nozzle 1 to rollers 3, as in Figures 1a, 1b and 1d, or via a localised pool 5 of molten metal in proximity to the rollers 3, as in Figure 1c.
  • molten metal is delivered to the casting apparatus in unheated ladles 10. It is desirable to keep the ladle size as large as practically possible to minimise scrap losses.
  • the ladle 10 is gradually emptied into tundish 12 which in turn feeds the casting nozzle 14. Metal leaving the nozzle 14 passes between rollers 16 and onto subsequent rolling and processing.
  • a depth of around 400mm is typical for slab casting with lower depths for the lower flow rates of strip casting. The necessary depth increases with increasing flow rate.
  • the flow is balanced by pouring from the ladle to the tundish.
  • the ladle approaches empty another is readied.
  • the last part of the ladle volume can be emptied at a higher rate into the tundish to give a slight increase in level for a very limited portion of the cycle of the casting.
  • the empty ladle is then withdrawn and replaced by another. This further ladle can then be emptied into the tundish in a similar manner to the first to initially restore the tundish level and then to balance the flow from the nozzle.
  • a constant supply of ladles in this way presents a severe constraint to the operation of the melt shop. Whilst in certain slab casting applications the casting speed can be reduced to reduce the rate at which material is drawn from the tundish and thus allow further time in which to obtain an additional ladle this process is prone to problems. Thicknesses below 50mm cannot successfully be achieved using such techniques and even above this size performance is impaired. Problems stem from the increased cooling which occurs with slower pouring. The ladle 10 is unheated and thus loses heat during use. The slower the pour, the greater the time to dispense its volume and hence the lower the temperature of the metal dispensed as the pour progresses. The variation in temperature causes problems. Furthermore by the end of the pour the temperature may have decreased to such an extent that the metal solidifies within the system. Freezing is particularly prone to occur in the tundish and nozzle control valves.
  • the present invention provides a system with a synchronous metal feed.
  • the molten metal is obtained and transferred to the system in the standard way using a ladle 20.
  • the ladle 20 is discharged into a heated tundish 22.
  • Plasma, induction and other heating systems may be provided.
  • the tundish 22 in turn feeds a headbox 24 and hence to the casting nozzle 26. Casting from the nozzle 26 through rollers 28 follows the general principals of the prior art. Unlike the prior art the tundish is fed from the ladle at a far higher rate than it discharges, in this case approximately 5 times. For significant periods of the casting cycle therefore no metal is being fed to the tundish.
  • the tundish contains 15 tonnes it contains sufficient material to allow effective casting and material is fed to the nozzle at the rate of 0.2 tonne/min.
  • the ladle is emptied long before casting has finished from the tundish. In this way the system allows a substantial time period in which another ladle can be readied. A new ladle is thus always available without having to vary casting speed and without having to risk casting problems. Feed form the new ladle to the tundish is generally initiated once the minimum tolerable level in the tundish is approached.
  • the rate of feed to the casting nozzle is determined by the head in the headbox and as a consequence it is important to maintain it at the desired level throughout.
  • the tundish is mounted in such a way that the melt level over the flow route from it to the headbox is kept constant whatever the volume of the tundish. This is achieved in this particular example by using a tilting tundish. This assists in minimising turbulence in the head box and allows the minimal volume possible to be provided in the headbox.
  • the described embodiment is pivotally mounted at the delivery passage into the head box.
  • the tundish reaches its maximum content value as the ladle finishes discharging, Figure 4c. In this state the tundish is tilted down to the left such that the majority of the melt is away form the passage to the head box.
  • the head 50 is, however, maintained constant.
  • the control of the tundish can be effected by the use of mass sensing and/or level sensing in the tundish or head box.
  • the tundish 22 is illustrated with an enclosed head portion 30 over the delivery outlet 32 to the casting nozzle 26 to allow an inert atmosphere to be employed to protect the steel. Outside this area 30 the steel can be treated with tundish powders to protect the steel from oxidation and to assist in the removal of inclusions. The separation of the areas reduced the risks of tundish powders being carried down and into the casting material.
  • the tundish can also be used in conjunction with a variety of existing techniques to promote inclusion floating, control mould powder layers and maintain steel quality without effecting the applicability of the present invention.
  • the ladle to tundish passage is then opened and during the first passage of time the ladle volume decreases and the tundish volume increases. Once the tundish level reaches the desired level (10 tonnes) the tundish to casting passage is opened and casting begins. Shortly after this the ladle completes its discharge and the tundish is at its maximum value (32 tonnes) for this first cycle.
  • tundish contents now decline as casting continues but no new material is feed to the tundish.
  • level approaches the minimum tolerable (10 tonnes) a fresh ladle is introduced and the tundish contents are replenished. This sequence is then repeated over and over.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Continuous Casting (AREA)
EP98304885A 1997-06-25 1998-06-22 Améliorations dans ou relatives à la coulée Withdrawn EP0887129A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9713265.8A GB9713265D0 (en) 1997-06-25 1997-06-25 Improvements in and relating to casting
GB9713265 1997-06-25

Publications (1)

Publication Number Publication Date
EP0887129A1 true EP0887129A1 (fr) 1998-12-30

Family

ID=10814811

Family Applications (1)

Application Number Title Priority Date Filing Date
EP98304885A Withdrawn EP0887129A1 (fr) 1997-06-25 1998-06-22 Améliorations dans ou relatives à la coulée

Country Status (3)

Country Link
EP (1) EP0887129A1 (fr)
JP (1) JPH1177255A (fr)
GB (1) GB9713265D0 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005053877A2 (fr) * 2003-12-02 2005-06-16 Voest-Alpine Industrieanlagenbau Gmbh & Co Procede de coulee sequentielle pour produire un boyau de coulee metallique de purete elevee

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
LU45127A1 (fr) * 1963-01-25 1964-02-28
DE2141835A1 (de) * 1970-08-20 1972-02-24 Societe Nouvelle Spidern, Pans Unter Luftabdichtung arbeitende Vorrichtung zum kontinuierlichen dessen mit hoher Geschwindigkeit
JPS6056449A (ja) * 1983-09-08 1985-04-02 Nippon Steel Corp 容器等への液体供給流量を一定化する方法
JPH08294752A (ja) * 1995-03-02 1996-11-12 Nippon Steel Corp 溶融金属および合金の少量供給制御方法および装置

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
LU45127A1 (fr) * 1963-01-25 1964-02-28
DE2141835A1 (de) * 1970-08-20 1972-02-24 Societe Nouvelle Spidern, Pans Unter Luftabdichtung arbeitende Vorrichtung zum kontinuierlichen dessen mit hoher Geschwindigkeit
JPS6056449A (ja) * 1983-09-08 1985-04-02 Nippon Steel Corp 容器等への液体供給流量を一定化する方法
JPH08294752A (ja) * 1995-03-02 1996-11-12 Nippon Steel Corp 溶融金属および合金の少量供給制御方法および装置

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 009, no. 191 (M - 402) 7 August 1985 (1985-08-07) *
PATENT ABSTRACTS OF JAPAN vol. 097, no. 003 31 March 1997 (1997-03-31) *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005053877A2 (fr) * 2003-12-02 2005-06-16 Voest-Alpine Industrieanlagenbau Gmbh & Co Procede de coulee sequentielle pour produire un boyau de coulee metallique de purete elevee
WO2005053877A3 (fr) * 2003-12-02 2005-11-10 Voest Alpine Ind Anlagen Procede de coulee sequentielle pour produire un boyau de coulee metallique de purete elevee
AU2004295039B2 (en) * 2003-12-02 2009-10-29 Siemens Vai Metals Technologies Gmbh & Co Sequential casting method for the production of a high-purity cast metal billet
US7789123B2 (en) 2003-12-02 2010-09-07 Voest-Alpine Industrieanlagenbau Gmbh & Co. Sequence casting process for producing a high-purity cast metal strand
KR101165478B1 (ko) * 2003-12-02 2012-07-13 지멘스 브이에이아이 메탈스 테크놀로지스 게엠베하 고순도 주물 금속 빌릿을 형성하기 위한 순차적 주조 방법

Also Published As

Publication number Publication date
JPH1177255A (ja) 1999-03-23
GB9713265D0 (en) 1997-08-27

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