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
  • B22D11/009—Continuous casting of metals, i.e. casting in indefinite lengths of work of special cross-section, e.g. I-beams, U-profiles
• • 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
  • B22D11/12—Accessories for subsequent treating or working cast stock in situ
  • B22D11/124—Accessories for subsequent treating or working cast stock in situ for cooling
• • 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
  • B22D11/12—Accessories for subsequent treating or working cast stock in situ
  • B22D11/128—Accessories for subsequent treating or working cast stock in situ for removing
  • B22D11/1287—Rolls; Lubricating, cooling or heating rolls while in use

Definitions

• the present invention relates to a method and a device for cooling and guiding a beam blank in a curved secondary cooling zone of a beam blank caster.
• a typical beam blank caster comprises a continuous casting mould with a heavily cooled copper mould that forms a steel strand having a solidified outer shell surrounding a still molten core. Solidification of this strand is completed by spray cooling in a secondary cooling zone, in which the beam blank is guided along a curved path in a vertical plane, so that its flanges are vertical. It will be noted that the beam blank presents along this curved path a so called intrados channel, which is delimited between its vertical flanges at the side of the intrados face (i.e. the concave face) of the curved web, and an extrados channel, which is delimited between its vertical flanges at the side of the extrados face (i.e.
• a device for guiding a beam blank in a curved secondary cooling zone of a beam blank caster typically comprises a set of guiding and support rollers co- operating to define the curved path for the beam blank and to avoid a bulging of the shell by the ferrostatic pressure of the liquid steel it contains.
• a plurality of intrados web support rollers bear in the intrados channel on the intrados web face, whereas a plurality of extrados web support rollers bear in the extrados channel on the extrados web face. Further guiding rollers bear on the tip and lateral surfaces of the flanges.
• Spray cooling of the strand in the secondary cooling zone is achieved by means of a plurality of cooling water spray nozzles, which may be either standard spray nozzles or so called air mist nozzles. These spray nozzles are arranged around the strand so as to spray the cooling water (respectively a water-air mist) mainly on the perimeter surfaces of the most massive zones of the beam blank, i.e. the intrados and extrados connections surfaces between the flanges and the web and the outer faces of the flanges. Part of the cooling water evaporates in contact with the hot surfaces of the beam blank. The cooling water that does not evaporate drops down at the extrados side, whereas at the intrados face it flows axially through the intrados channel of the beam blank.
• the cooling water that does not evaporate drops down at the extrados side, whereas at the intrados face it flows axially through the intrados channel of the beam blank.
• Such a major drawback is e.g. the formation of transverse cracks in the intrados flange tips when the beam blank is straight- ened in the straightening unit. These transverse cracks are observed in particular, but not exclusively, in large section and high strength beam blanks. Although it is very likely that the transverse defects are due to an undesired quench of the tips of the flanges, it has not yet been possible to reliably avoid these cracks by a more selective control of the cooling water sprays.
• U.S. patent N° 3,923,093 discloses an apparatus for continuously casting metal in various cross-sectional shapes, such as blooms, billets and "dog- bones" of various proportions.
• the guiding rolls are disposed in tiers along the path of the continuously cast metal.
• the position of the guiding rolls in each tier is adjustable so as to be able to configure different cross-sections between the guiding rolls. It will be appreciated that this patent contains no specific teaching relating to the prevention of transverse cracks in the intrados flange tips of beam blanks.
• the object of the present invention is to provide a solution for reliably avoiding the aforementioned transverse cracks in the intrados flange tips.
• this solution consists in an improved method, respectively an improved device, for cooling and guiding a beam blank in a curved secondary cooling zone of a beam blank caster, such as defined in claim 1 , respectively claim 6.
• the present invention has the merit to have discovered that the intrados tips of the flanges are subjected to an excessive cooling due essentially to the fact that the intrados web support rollers (which are generally made as large as possible to provide the best support for the web) dam up the cooling water in the intrados channel to such an extent that an important part of this intrados cooling water flows over the tips of the flanges instead of being evacuated axially through the intrados channel of the beam blank.
• the intrados tips of the flanges are subjected to an undesired quench by a cooling water overflow, which is due to a dam-effect of the intrados web support rollers.
• the present invention also has the merit to propose a solution for efficiently avoiding an undesired quench of the intrados tips of the flanges by an overflow of cooling water dammed up behind an intrados web support roller, which is designed as large as possible to provide the best possible support for the web.
• This solution consists in that the intrados web support roller is provided with a cylindrical bearing surface that includes groove means designed so as to avoid an overflow generating cooling water dam up behind the intrados web support roller by channelling sufficient cooling water underneath the intrados web support roller axially through the intrados channel, thereby avoiding a quench of the intrados tips of the flanges by overflow water.
• an advantageous side effect of the groove means is an improvement of the cooling of the intrados web support roller, which has of course a positive effect on its lifetime.
• the groove means comprises for example a plurality of axially spaced ring-shaped grooves or a helical groove.
• the groove means advantageously has chamfered or rounded edge surfaces as transition surfaces to the cylindrical bearing surface. These chamfered or rounded edge surfaces help to avoid surface marks on the intrados web face of the beam blank when the grooved intrados web support roller is pressed against the intrados web face.
• FIG. 1 is a section through a beam blank caster with a curved secondary cooling zone
• FIG. 2 is a section through a beam blank in the curved secondary cooling zone of the beam blank caster of FIG. 1 , wherein an intrados web support roller is shown; and FIG. 3: is an enlarged detail of the intrados web support roller of FIG. 2.
• FIG. 1 shows a caster 10 for continuously casting "near-net-shape" sections for rolling I-beams or H-beams, which are generally called beam blanks.
• a beam blank 12 has a dog-bone-like cross-section with a web 14 and two flanges 16', 16".
• reference number 18 refers to a tundish, i.e. a refractory-lined liquid steel distributor, which receives molten steel from a furnace ladle (not shown) to discharge it in a controlled manner into a vertical continuous casting mould 20.
• the latter includes a heavily cooled copper mould (not shown) that forms the beam blank 12 as a steel strand having a solidified outer shell sur- rounding a still molten core.
• a heavily cooled copper mould (not shown) that forms the beam blank 12 as a steel strand having a solidified outer shell sur- rounding a still molten core.
• the partially solidified beam blank 12 is guided by a foot roller segment 22 into a curved secondary cooling zone 24, where its solidification is completed by spray cooling.
• spray cooling covers classical spray cooling and the so called “air mist cooling”.
• the secondary cooling zone 24 comprises several guiding and spray cooling segments 30.,, 30 2 , 30 3 and 30 4 .
• Each of these guiding and cooling seg- ments 30 1 to 30 4 comprises a frame 32 supporting a plurality of guiding and support rollers 34, 36.
• These guiding and support rollers 34, 36 co-operate to define in a vertical plane (i.e. the plane of Fig. 1) a curved path for the beam blank 12.
• a further object of the guiding and support rollers 34, 36 is to support the solidified shell of the beam blank 12 in such a way as to avoid its bulging by the ferrostatic pressure of the liquid steel it contains.
• FIG. 2 shows a cross-section through the beam blank 12 in such a guiding and cooling segment 30,.
• the bent beam blank 12 has its flanges 16', 6" vertical and that its curved web 14 has an intrados face 38 (i.e. a concave face) and an extrados face 40 (i.e. a convex face).
• the bent beam blank 12 consequently presents a so called intrados channel 42, which is delimited between its vertical flanges 16', 16" at the side of the intrados face 38 of the curved web 14, and an extrados channel 44, which is delimited between its vertical flanges 16', 16" at the side of the extrados face 40 of the curved web 14.
• Reference number 46 identifies an intrados web support roller, which bears on the intrados web face 38 in the intrados channel 42.
• An extrados web support roller 48 which bears on the extrados web face 40 in the extrados channel 44, is schematically represented in FIG. 2 by doted lines.
• some or all of the guiding and spray cooling segments 30 1 to 30 4 may further include intrados flange support rollers 50', 50" bearing on the intrados tips 52', 52" of the flanges 16', 16", extrados flange support rollers 54', 54” bearing on the extrados tips 56', 56" of the flanges 16', 16", and lateral guide rollers 58', 58" bearing on the lateral outer faces 60', 60" of the flanges 16', 16".
• Spray cooling of the beam blank 12 in the secondary cooling zone 24 is achieved by means of a plurality of cooling water spray nozzles 62 (or spray ramps).
• These spray nozzles 62 are arranged over the whole length of the secondary cooling zone 24 around the beam blank 12 so as to spray the cooling water or the air mist mainly on the perimeter surfaces of the most massive zones of the beam blank 12, i.e. the intrados and extrados connections surfaces between the flanges 16', 16" and the web 14 and the lateral outer faces 60', 60" of the flanges 16', 16".
• spray nozzles is used to cover standard spray nozzles as well as so called “air mist nozzles”, which form an air-water mist.
• Part of the cooling water sprayed onto the beam blank 12 evaporates in contact with the hot surfaces of the latter.
• the cooling water that does not evaporate drops down at the extrados side, whereas at the intrados side it flows into the intrados channel 42 of the beam blank 12.
• the intra- dos web support roller 46 includes a cylindrical bearing surface (globally identified by reference number 64) that is regularly interrupted by ring-shaped grooves 66. These axially spaced grooves 66 are designed as groove means for channelling sufficient cooling water between the rotating intrados web support roller 46 and the intrados face 38 of the web 14, so as to prevent an excessive dam up of cooling water behind the intrados web support roller 46.
• a ring-shaped groove 66 has two ring-shaped side walls 68', 68" and two chamfered and rounded ring- shaped edge surfaces 70', 70" as transition surfaces between the side walls 68', 68" and the cylindrical bearing surface 64. These chamfered and rounded transition surfaces 70', 70" help to avoid surface marks on the intrados web face 38 of the beam blank 12.
• the intrados web support roller 46 also has chamfered edge surfaces 72', 72" at both of its ends. It will be appreciated that these chamfered edge surfaces 72', 72" allow to work with a web support roller 46 being in contact with a flat central portion of the web face 38 over the whole width of the latter, without risking to produce surface marks in the rounded web-flange connections 76', 76", when the beam blank 12 or the web support roller 46 is subjected to lateral movements.
• the dimensions of the cooling water channelling grooves 66 will be fixed in function of the cooling water flow that has to be channelled between the rotating intrados web support roller 46 and the intrados face 38 of the web 14, so as to prevent an excessive dam up of cooling water behind the intrados web support roller 46.
• Typical dimensions of the grooves are for example as follows: width 10-20 mm; depth 3-12 mm.
• the width of the ring-shaped cylindrical bearing surface 64 subsisting between two successive grooves 66 is typically in the range of 10-20 mm. This ring-shaped cylindrical bearing surface 64 can however be broader if fewer grooves are needed to avoid a quench producing cooling water overflow.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Continuous Casting (AREA)
• Heat Treatments In General, Especially Conveying And Cooling (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=19731978

Family Applications (1)

Country Status (7)

Families Citing this family (6)

Family Cites Families (5)

• 2001
  • 2001-04-03 LU LU90751A patent/LU90751B1/en active
• 2002
  • 2002-04-02 PL PL02363030A patent/PL363030A1/xx unknown
  • 2002-04-02 KR KR10-2003-7012913A patent/KR20030090705A/ko not_active Application Discontinuation
  • 2002-04-02 WO PCT/EP2002/003603 patent/WO2002081124A1/en not_active Application Discontinuation
  • 2002-04-02 JP JP2002579152A patent/JP2004534655A/ja not_active Withdrawn
  • 2002-04-02 US US10/473,937 patent/US20050028962A1/en not_active Abandoned
  • 2002-04-02 EP EP02726234A patent/EP1390170A1/en not_active Withdrawn

Non-Patent Citations (1)

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