US20130248056A1 - Method for enhancing the self-feeding ability of a heavy section casting blank - Google Patents

Method for enhancing the self-feeding ability of a heavy section casting blank Download PDF

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Publication number
US20130248056A1
US20130248056A1 US13/991,564 US201113991564A US2013248056A1 US 20130248056 A1 US20130248056 A1 US 20130248056A1 US 201113991564 A US201113991564 A US 201113991564A US 2013248056 A1 US2013248056 A1 US 2013248056A1
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United States
Prior art keywords
casting blank
self
heavy section
enhancing
temperature
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Abandoned
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US13/991,564
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English (en)
Inventor
Dianzhong Li
Yikun Luan
Paixian Fu
Lijun Xia
Yiyi Li
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Institute of Metal Research of CAS
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Institute of Metal Research of CAS
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Assigned to INSTITUTE OF METAL RESEARCH CHINESE ACADEMY OF SCIENCES reassignment INSTITUTE OF METAL RESEARCH CHINESE ACADEMY OF SCIENCES ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: LI, Dianzhong, FU, Paixian, LI, Yiyi, LUAN, Yikun, XIA, LIJUN
Publication of US20130248056A1 publication Critical patent/US20130248056A1/en
Abandoned legal-status Critical Current

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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
    • B22D25/00—Special casting characterised by the nature of the product
    • B22D25/06—Special casting characterised by the nature of the product by its physical properties
    • 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
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
    • B22D27/04—Influencing the temperature of the metal, e.g. by heating or cooling the mould
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D30/00—Cooling castings, not restricted to casting processes covered by a single main group

Definitions

  • the present invention relates to the fields of manufacturing of casting blanks, such as wide and thick metal slabs, round/square/rectangular heavy section casting blanks, and in particular to a method for enhancing the self-feeding ability of a heavy section casting blank, and eliminating the shrinkage voids and the surface cracks of the casting blank.
  • Wide and thick slabs have been widely applied in economic construction.
  • a great amount of wide and thick slabs are used in large-sized ships, ocean platforms, hydroelectric generating sets, thermal power generating units, pressure containers, dies, and long-distance pipelines. Therefore, there are huge demands on thick-large section wide and thick slabs for rolling the wide and thick plates.
  • the maximum thicknesses of the continuous casting slabs all are smaller than 400 mm. If the continuous casting slabs are adopted to roll the wide and thick plates with a thickness of 200 mm, it is difficult to ensure the performance of the core due to a small reduction ratio.
  • the mold casting method or electroslag remelting method for producing the wide and thick slabs has the disadvantages of low productivity, low success ratio, and high cost.
  • the heavy section round continuous casting blank is used for replacing the common molded steel ingots, which shows a good development trend due to high production efficiency and high material utilization ratio.
  • the heavy section casting blank can be used for producing nuclear torches, wind-power rings, and bond axis type of parts related to vehicles, ships and machines.
  • the continuous casting technology has been more and more applied in production of the heavy section casting blanks. This technology is as follows: continuously pour the liquid metal into a water cooling crystallizer, solidify the liquid steel in the water cooling crystallizer, and continuously cast the solidified part out from the lower end through a dummy bar to realize continuous casting of the blanks.
  • This technology also has defects: the height-diameter ratio of the casting blank produced by this technology is large, so realization of axis feeding of the casting blanks is difficult, and it is easy to cause shrinkage and porosity of the centre of the cast blanks;
  • the outer surface of the blank is usually processed with a forced-cooling process, which causes an extremely low temperature to the outer surface and results in cracks. Those defects limit the development of the round continuous casting blanks to the bigger section size ( ⁇ 800 mm).
  • the square and rectangular heavy section continuous casting blanks with a thickness of over 400 mm also have the macro defects of inner shrinkage, porosity, and surface cracks.
  • a larger feeder head or a thermal-insulating (heating) feeder head is adopted to realize sequential solidification of the blanks along the gravity direction.
  • the feeder head ratio of the heavy section continuous casting blank is very small, and the height-diameter ratio thereof is bigger than 4, so the axial gravity feeding of the casting blank cannot be realized.
  • the inner shrinkage, porosity, and surface cracks of the heavy section casting blanks are technical bottlenecks that limit the development of the casting blanks towards the bigger section sizes.
  • enhancing the feeding ability of the heavy section casting blanks in the solidification process is of key importance for overcoming the defects of the inner shrinkage and porosity and surface crack of the heavy section casting blanks.
  • the aim of the present invention is to provide a method for eliminating the centre shrinkage, porosity, and surface cracks of heavy section molded wide and thick slabs and round and rectangular continuous casting blanks through enhancing the self-feeding ability of the heavy section casting blank. Therefore, it is beneficial to develop technologies for manufacturing round casting blanks with a diameter of over 500 mm and square or rectangular casting blanks with a thickness of over 400 mm.
  • a method for enhancing the self-feeding ability of a heavy section casting blank comprises these steps: after pouring the liquid metal, immediately forced-cooling the outer surface of a casting blank by means of molded water cooling, direct water spraying, fog spraying or blowing to rapidly solidify it; when the temperature of the outer surface of the casting blank is reduced to 800 ⁇ 1000° C. and the thickness of the solidified layer reaches 5-30% of the thickness or diameter of the blank section, stop forced-cooling the outer surface.
  • control the cooling conditions of the outer surface of the casting blank to keep the outer surface of the casting blank at a temperature of 200 ⁇ 400° C. below solidus, which makes the solidified layer of the outer surface of the casting blank stay in the plastic deformation region with a low deformation resistance.
  • a thermal insulating material or a heat cover to insulate the outer surface of the casting blank to reduce the intensity of heat exchange between the outer surface of the casting blank and the environment; then the temperature of the outer surface of the casting blank rises because of the latent heat in the casting blank core which reducing the radial temperature gradient of the casting blank, and then the core of the casting blank forms the mushy region and is solidified synchronously.
  • the casting blank surface and the casting blank core are still in the high temperature state; at this time, de-mold at the high temperature, wherein the de-molding temperature required by the casting blank is higher than 800° C.
  • the de-molding temperature required by the casting blank is preferably 850-1,200° C.
  • the method for enhancing the self-feeding ability of a heavy section casting blank is applicable to square or rectangular casting blanks with a thickness of over 400 mm, round casting blanks with a diameter of over 500 mm, and molded wide and thick slabs with a thickness of over 600 mm.
  • the casting blanks usually perform axial feeding along the gravity direction; the present invention realizes the radial self-feeding in a direction vertical to the gravity direction during the solidification of the casting blanks by controlling the outer cooling conditions of the casting blanks.
  • the present invention adopts a water cooling, fog cooling or air cooling means to enhance the coefficient of heat exchange between the casting blank and the outside to rapidly solidify blank surface, thus fast increasing the casting blank surface strength and preventing thermal cracks generated because of thin solidified layer of the casting blank surface and low strength in the initial stage of solidification.
  • the thickness of the solidified layer of the casting blank reaches 5-30% (usually 5-300 mm) of the diameter or thickness of the section, stop forced-cooling the outer surface of the casting blank; at this time, the solidified outer layer is at a low temperature, which provides a low-temperature external environment for the region of the casting blank core that is not solidified, guarantees the solidification speed of the liquid metal of the core, and avoids excessively big crystal particles of the core.
  • the present invention performs thermal insulation on the casting blank surface such that the temperature of the casting blank surface rises to stay in the plastic region, which is good for preventing the casting blank surface from cracking due to relatively thermal stress.
  • the present invention performs thermal insulation on the casting blank surface, which can reduce the temperature gradient of the heavy section casting blank from the inside to the outside, enables the large area of the blank centre to form the mushy region synchronously, realizes synchronous solidification of the blank centre, and avoids generation of the centralized defects of the shrinkage voids.
  • the radial tensile stress generated by solidification and shrinkage drives the high-temperature solid metal which has been solidified on the outer surface of the casting blank to plastically move from the casting blank surface to the centre, thus realizing the radial self-feeding during the solidification of the casting blank, and eliminating the defect of inner shrinkage and porosity of the casting blank.
  • the method provided by the present invention fully maximizes the radial self-feeding ability of the heavy section casting blank, which can reduce the feeder heat size of the casting blank and further improve the material utilization ratio of the heavy section casting blank.
  • the present invention can be applied in a large scope and can be used for producing round, square or rectangular heavy section casting blanks, molded wide and thick slabs, and other heavy section castings.
  • the method provided by the present invention also can realize blank high-temperature de-molding and hot charging, improve the production efficiency, and saves energies.
  • the present invention quickly solidify and crust the outer surface of the casting blank to increase the strength and prevent surface crack at first, and then perform thermal insulation on the casting blank surface such that large area of the core forms the mushy region and that the solidified layer of the casting blank surface is maintained at a relatively high temperature to facilitate realization of the plastic deformation, thus realizing synchronous solidification and solid-phase movement in the subsequent solidification and shrinkage processes of the casting blank, fulfilling the aim of radial self-feeding of the high-temperature deformable metal, eliminating the inner shrinkage and surface crack of the casting blank, obviously eliminating the inner shrinkage of the casting blank.
  • the present invention is applicable to the heavy section metal castings, in particular to the round and square heavy section casting blanks which have a large height-diameter ratio and cannot eliminate axis shrinkage pipe through the feeder head.
  • FIG. 1 shows a water-cooling molded wide and thick slab produced by the present invention.
  • FIG. 2 shows a round heavy section casting blank produced by the present invention, wherein, FIG. 2( a ) shows a real round heavy section casting blank, and FIG. 2( b ) shows the cross section of the round casting blank.
  • FIG. 3 shows a round casting blank which is not produced by the prevent invention and has shrinkage voids in the centre, wherein, FIG. 3( a ) shows a real round heavy section casting blank, and FIG. 3( b ) shows the cross section of the round casting blank.
  • the present invention provides a method for eliminating inner shrinkage, porosity and surface cracks by enhancing the self-feeding ability of a heavy section casting blank, comprising the following steps:
  • Adopt melting equipment such as the electric induction furnace or electric arc furnace to melt liquid steel, and then perform deoxidization and degassing.
  • the temperature gradient between the blank centre and the outer surface gradually decreases, and the large area of the blank centre forms the mushy region.
  • the blank centre is solidified synchronously; a tensile stress is generated because of the solidification and shrinkage, which promotes the solidified solid-state metal on the outer surface of the casting blank to generate plastic deformation and plastically move from the casting blank surface to the centre, thus realizing the radial self-feeding during the solidification of the casting blank.
  • the method provided by the present invention is adopted to produce the molded wide and thick slab; the material of the wide and thick slab is Q345; the thickness of the wide and thick slab is 1,000 mm, and the total mass is 60 tons.
  • An electric arc furnace is used to melt the liquid steel; then the liquid steel is refined in an LF furnace and next poured into the VD furnace for deoxidization and degassing.
  • the liquid steel is poured into a separated water-cooling mold in a total time period of 30 min.
  • the thickness of the solidified layer of the surface of the wide and thick slab is 90 mm 40 min after pouring. At this time, reduce the water flow of the water-cooling mold and increase the gap between the mold and the width and thick slab to reduce the speed of heat dissipation on the surface of the width and thick slab.
  • the surface temperature of the wide and thick slab rises from 920° C. to 1,100° C.-1,250° C. and then the casting blank is gradually cooled until totally solidified. After the casting blank is completely solidified, de-mold at a high temperature of 900° C., and slowly cool after de-molding with a speed controlled to be 30-40° C./h.
  • FIG. 1 shows a wide and thick slab produced in this embodiment. Through non-destructive inspection, it is found that the slab has no defect of inner shrinkage avoid and surface cracks.
  • the method provided by the present invention is adopted to produce the heavy section round continuous casting blank; the material of the round blank is 20 CrNi 2 Mo; the diameter is 1,000 mm; the length is 8 m; and the total mass of the round blank is 45 tons.
  • FIG. 2( a ) shows the heavy section round casting blank produced by the technology of the present invention in this embodiment. Through non-destructive inspection, it is found that the blank has no inner shrinkage void and the casting blank surface has no cracking defect.
  • FIG. 2( b ) shows the cross section of the round blank without centralized shrinkage voids in centre and with a porosity level of below 2.
  • FIG. 3( a ) shows the round casting blank which is not produced by the technology provided by the present invention and has the same size and specification.
  • the centre of the round blank has shrinkage voids in a large area and the porosity defect, as shown in FIG. 3 b ).
  • the present invention enables a large area of the blank centre to form the mushy region and meanwhile maintains the solidified layer of the casting blank surface at a relatively high temperature, thus realizing the plastic movement of the solid phase in the subsequent solidification processes, fulfilling the aim of radial self-feeding of the high-temperature deformable metal, eliminating the inner shrinkage and porosity of the casting blank, and preventing surface crack.
  • defect levels before and after the ⁇ 800-1,200 mm round blank processed in the above embodiment is subject to the detection processing in accordance with YB/T 4149-2006 can be seen in table 1.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Continuous Casting (AREA)
US13/991,564 2010-12-23 2011-06-30 Method for enhancing the self-feeding ability of a heavy section casting blank Abandoned US20130248056A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
CN201010604260.1 2010-12-23
CN2010106042601A CN102161090B (zh) 2010-12-23 2010-12-23 一种提高厚大断面铸坯自补缩能力的方法
PCT/CN2011/076640 WO2012083671A1 (fr) 2010-12-23 2011-06-30 Procédé d'amélioration de la capacité d'auto-alimentation d'ébauche de coulée à profil épais

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US (1) US20130248056A1 (fr)
EP (1) EP2656946A4 (fr)
JP (1) JP5852126B2 (fr)
KR (1) KR101588677B1 (fr)
CN (1) CN102161090B (fr)
WO (1) WO2012083671A1 (fr)

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CN102806330B (zh) * 2012-08-08 2015-02-04 中国科学院金属研究所 一种提高厚大断面连铸坯内部质量的方法
CN103008577B (zh) * 2012-12-07 2014-06-11 中国科学院金属研究所 微缺陷高利用率优质模铸钢锭的制备方法和模具
CN103128268B (zh) * 2013-01-17 2015-10-14 中国科学院金属研究所 用于大型特厚板坯的中低温打箱的方法
CN103008626B (zh) * 2013-01-17 2015-08-12 中国科学院金属研究所 用于大型特厚板坯的高温带液芯打箱的方法
CN112974730B (zh) * 2021-02-05 2022-02-11 燕山大学 用于大断面铸件的铸造装置及其铸造方法

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US20090044926A1 (en) * 2007-08-17 2009-02-19 Michio Kida Silicon casting apparatus
US7516775B2 (en) * 2005-10-28 2009-04-14 Novelis Inc. Homogenization and heat-treatment of cast metals

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Publication number Priority date Publication date Assignee Title
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US20040020632A1 (en) * 2000-08-10 2004-02-05 Zajber Adolf Gustav Method and strand guide for supporting, guiding and cooling casting strands made of steel, especially preliminary sections for girders
US7516775B2 (en) * 2005-10-28 2009-04-14 Novelis Inc. Homogenization and heat-treatment of cast metals
US20090044926A1 (en) * 2007-08-17 2009-02-19 Michio Kida Silicon casting apparatus

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JP5852126B2 (ja) 2016-02-03
CN102161090A (zh) 2011-08-24
KR101588677B1 (ko) 2016-01-27
KR20130094330A (ko) 2013-08-23
WO2012083671A1 (fr) 2012-06-28
JP2014500801A (ja) 2014-01-16
CN102161090B (zh) 2012-11-07
EP2656946A4 (fr) 2017-10-25
EP2656946A1 (fr) 2013-10-30

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