Classifications

• • 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 invention relates to the field of metal mold casting wide slab, thick section continuous casting round billet, billet and rectangular billet, etc., in particular to improving the self-reduction ability of thick and thick section billet, improving and eliminating casting A method for loosening pores and surface cracks in a blank. Background technique
• Wide and thick plates are widely used in China's economic construction. Heavy plates are used extensively on large ships, offshore platforms, hydropower units, thermal power units, pressure vessels, mold making, and long-haul pipelines. In China, we have recently built dozens of wide and thick plate rolling production lines, including Angang 5000mm, 5500mm rolling mill, Baosteel 5000mm rolling mill, etc., with a new capacity of more than 20 million tons. Therefore, the demand for thick and thick slabs for rolling wide and thick plates is enormous. At present, the maximum thickness of the continuous casting slab is less than 400 mm, and the continuous casting slab is used to roll a thick plate having a thickness of 200 mm. Since the reduction ratio is small, it is difficult to ensure the core performance.
• the large-section continuous casting round billet is used to replace the general die-cast steel ingot, which has high production efficiency and high material utilization rate, showing a good development momentum.
• Large-section continuous casting round billet can be used to produce nuclear torch parts, wind power ring parts and key shaft parts for automobiles, ships and machinery.
• the annual output of the target products of thick and large round billets exceeds 30 million tons.
• the technique is to continuously cast a molten metal into a water-cooled crystallizer, and the molten steel is solidified in a water-cooled crystallizer, and the solidified portion is continuously pulled out from the lower end by a starter device to realize continuous casting of the cast strand.
• the slab is produced by the process, and the height-to-diameter ratio is large, and it is difficult to realize the axial packing of the slab, which is easy to cause shrinkage and looseness in the center of the steel ingot; and because the outer surface of the steel ingot adopts a forced cooling process, the outer surface temperature is too low, resulting in crack.
• the size of the riser is increased, or the riser is heated to achieve the sequential solidification of the slab in the direction of gravity.
• the proportion of the riser of the thick section continuous casting billet is very small, and the aspect ratio is greater than 4, and the axial gravity feeding of the billet cannot be achieved.
• the object of the present invention is to provide a method for improving the shrinkage and surface cracks of the thick and large slab, the continuous casting round billet and the rectangular billet at the center by increasing the self-retracting capacity of the thick and large section casting blank, and solving the existing method.
• the center of the casting blank is of poor quality, the surface is cracked, and the scrap rate is high.
• a method for improving the self-retracting capacity of a thick section casting blank after the pouring of the molten metal, the outer surface of the casting blank is forcedly cooled by means of water cooling, direct water spraying, spraying or blowing, so that the outer surface of the casting blank is fast Coagulating crust;
• the outer surface temperature of the billet is lowered to 800 ⁇ 1000 °C, when the thickness of the solidified layer reaches 5-30% of the thickness or diameter of the billet section, the external surface is forced to cool.
• the method for improving the self-retracting capacity of the thick and large section casting blank when the thickness of the solidified layer reaches 50-300 mm, stops the forced cooling of the outer surface of the outer casting blank.
• the method for improving the self-retracting capacity of the thick and large section casting blank controls the cooling condition of the outer surface of the casting blank, so that the temperature of the outer surface of the casting blank is maintained between 200 and 400 ° C below the solidus line, and the outer surface of the casting blank is solidified.
• the layer is in a plastic deformation zone with low deformation resistance.
• the method for improving the self-retracting capacity of the thick and large section casting blank after the outer surface of the casting blank is stopped for forced cooling, the outer surface of the casting blank is insulated by the heat insulating material or the heat insulating cover, and the heat exchange between the outer surface of the casting blank and the outside is reduced.
• Strength using the core heat of the slab to increase the temperature of the outer surface of the slab, reducing the radial temperature gradient of the slab, so that the core of the slab enters the mushy zone at the same time, and the core of the slab is simultaneously solidified.
• the method for improving the self-shrinking ability of a thick and large section casting blank when the core metal liquid is simultaneously solidified, the solidification shrinkage generates a radial tensile stress, and the tensile stress acts on the outer surface high temperature solidified layer to plastically deform the solidified metal. Plastic movement occurs from the outer surface to the center of the slab to achieve radial self-feeding of the slab.
• the method for improving the self-retracting capacity of the thick and large section casting blank, the core of the casting blank is simultaneously solidified, and after the radial self-feeding, the surface of the casting blank and the core are still in a high temperature state;
• the casting mold release temperature is greater than 800 °C.
• the method for improving the self-shrinking ability of the thick and large section casting blank is preferably 850-1200 ° C.
• the method for improving the self-retracting capacity of a thick and large section casting blank is suitable for a continuous casting billet or a rectangular blank having a thickness of more than 400 mm, a continuous casting round blank having a diameter of more than 500 mm, and a molded wide and thick slab having a thickness of more than 600 mm. .
• the castings are supplemented by the axis in the direction of gravity.
• the invention achieves the radial self-feeding perpendicular to the direction of gravity during the solidification of the slab by controlling the external cooling conditions of the slab.
• the forced cooling outside the slab is stopped, and the temperature of the solidified outer layer is low. It is used to provide a low temperature external environment for the unsolidified area of the core of the slab, to ensure the solidification speed of the core metal liquid, and to avoid the core grain being too coarse.
• the invention heats the surface of the slab to heat the surface of the slab to the plastic zone, which is beneficial to prevent the surface of the slab from being subjected to large thermal stress and causing cracks.
• the invention keeps the surface of the slab in the middle and late stage of solidification of the slab, and can reduce the temperature gradient from the inside to the outside of the slab of the thick section, so that the large area of the slab at the same time enters the mushy area at the same time, and realizes the center of the slab simultaneously Solidification, to avoid the occurrence of concentrated shrinkage defects.
• the diameter is solidified and contracted.
• the tensile stress drives the high-temperature solid phase metal which has solidified outside the slab to move from the surface of the slab to the center, and achieves the radial self-feeding of the slab solidification process, improving or even eliminating the shrinkage porosity of the slab.
• the radial self-retracting capacity of the thick and thick section slab can be fully utilized, the size of the slab riser can be reduced, and the material utilization rate of the thick section slab can be further improved.
• the invention has wide application range and can be used for producing round-shaped continuous billet, billet or rectangular billet, and can also be used for producing moulded wide and thick slab, and can also be used for producing other thick and large section castings.
• the slab can be subjected to high temperature demolding and heat transfer, thereby improving production efficiency and saving energy consumption.
• the present invention firstly controls the external cooling condition of the slab in different solidification stages, firstly rapidly solidifies the outer surface of the slab, and establishes strength to prevent surface cracking; then, the surface of the slab is insulated and slowly cooled to make the core large area.
• the solidified layer on the outer surface of the slab is maintained at a higher temperature to facilitate plastic deformation; thereby achieving simultaneous solidification and solid phase movement in the subsequent solidification and shrinkage of the slab, and achieving high-temperature deformable metal radial self-feeding
• the purpose of this is to eliminate internal shrinkage cavities and surface cracks in the slab and significantly improve until the internal looseness of the slab is eliminated.
• the method can realize high-temperature heat transfer of the slab, improve production efficiency, and achieve energy saving.
• the invention is suitable for thick and large section metal casting blanks, and is especially suitable for thick and large section continuous casting round billets and billets which have large height to diameter ratio and can not be improved by feeder feeding.
• Figure 1 shows a water-cooled die cast wide slab produced by the present invention.
• Figure 2 shows a thick section continuous casting round billet produced by the present invention.
• Fig. 2(a) is a solid view of a thick section continuous casting round billet
• Fig. 2(b) is a cross section of a continuous casting round billet.
• Figure 3 is a continuous casting billet having a shrinkage cavity defect in the center produced by the present invention.
• Fig. 3(a) is a solid view of a thick and continuous continuous casting round blank
• Fig. 3(b) is a cross section of a continuous casting round blank. detailed description
• the invention improves the self-retracting ability of the thick and thick section casting blank, eliminates the internal shrinkage cavity and surface crack, and improves the looseness.
• the implementation steps and methods are as follows:
• the molten steel is smelted by a melting furnace such as an induction furnace or an electric arc furnace, and then deoxidized and degassed.
• a melting furnace such as an induction furnace or an electric arc furnace
• the outer surface of the slab is forcibly cooled by water-cooled mold and crystallizer, so that the outer surface of the slab can be quickly solidified and crusted.
• the water can be sprayed, sprayed or blown to enhance the external heat exchange of the slab.
• the surface temperature of the slab is monitored by contact or non-contact temperature measuring equipment, and the surface temperature of the slab is controlled as much as possible at 800 ⁇ 1000 °C.
• the solidified phase of the solidified metal undergoes a solid phase transformation to induce tissue stress and induce cracks; also avoid the temperature is too high, the thickness of the solidified layer is thinner, the strength is lower, and the surface of the slab is "bulk belly" under the static pressure of the metal liquid. A crack is formed.
• the surface of the slab is stopped for forced cooling, and the surface of the slab is kept warm.
• the surface temperature of the slab is continuously increased, the temperature of the outer surface of the slab is monitored, and the interfacial heat exchange intensity between the slab and the outside is adjusted by heat preservation or cooling, so that the surface temperature of the slab is maintained below 200 ⁇ 400 ° C of the solid phase of the material.
• Plastic deformation zone
• the temperature gradient between the center and the outer surface of the slab is gradually reduced, and the central area of the slab enters the mushy area in a large area.
• the center of the slab is simultaneously solidified; the solidification shrinkage generates tensile stress, and the solid metal which has solidified on the outer surface of the slab is plastically deformed, and the surface of the slab is plastically moved toward the center to realize the radial self-solidification process of the slab. Feeding.
• This embodiment produces a molded wide and thick slab by the method of the present invention.
• the wide and thick slab material is Q345, the thick and thick slab has a thickness of 1000 mm, and the total mass is 60 tons.
• the electric arc furnace is used for molten steel smelting, and then refined by the LF furnace, and then the molten steel is transferred to the VD furnace for deoxidation and degassing.
• the molten steel is poured into the split water-cooling mold at 1560 Torr, and the total pouring time is 30 min.
• the thickness of the solidified layer on the surface of the wide and thick slab is 90 mm 40 minutes after the pouring.
• the water flow rate of the water-cooling mold is reduced, and the gap between the mold and the wide and thick slab is increased, and the heat dissipation speed of the surface of the wide and thick slab is reduced.
• Fig. 1 shows a wide and thick slab produced in the present embodiment. It is found by nondestructive testing that there is no loose and shrinkage hole defect in the continuous casting steel ingot, and the surface quality of the slab is intact, and no surface crack is found.
• This embodiment uses the method of the present invention to produce a thick section continuous casting round billet, the round billet material is 20CrNi2Mo, the diameter is 1000 mm, the length is 8 m, and the total weight of the round billet is 45 tons.
• the pouring temperature is 1540 ⁇ , slab casting speed of 0.1m / mi n.
• the surface solidified layer has a thickness of about 50 mm and a surface temperature of about 850 °C.
• the surface of the slab is insulated with an insulating material such as asbestos cloth, and the surface temperature of the slab is raised to 1200-1260 ° C, which is in the plastic zone.
• the temperature gradient of the slab from the inside to the outside is small, and the central region is simultaneously solidified.
• the outer surface of the slab is plastically deformed, and the solid phase undergoes contraction and movement from the outside to the inside, realizing radial self-feeding.
• this is a thick-section continuous casting round blank produced by the technique of the present invention. After non-destructive testing, there is no shrinkage hole defect inside the slab, and there is no crack defect on the surface of the slab. As shown in Fig. 2(b), the round billet cross section has no concentrated shrinkage hole defects in the center, and the looseness level is less than 2 grades.
• the invention can control the external cooling condition of different solidification stages of the slab, so that the center of the slab enters the mushy area in a large area, and at the same time, the solidification layer on the outer surface of the slab is maintained at a higher temperature, thereby realizing the subsequent solidification and shrinkage process of the slab.
• the solid phase plastic movement in the medium achieves the purpose of radial entanglement of the deformable metal at high temperature, improves the shrinkage of the internal shrinkage of the slab, and prevents the occurrence of cracks on the outer surface.
• the defect grade of the &800-1200 mm round billet treated in the above embodiment was measured according to YB/T 4149-2006 (see Table 1).

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• Mechanical Engineering (AREA)
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• 2010
  • 2010-12-23 CN CN2010106042601A patent/CN102161090B/zh active Active
• 2011
  • 2011-06-30 EP EP11851813.3A patent/EP2656946A4/de not_active Withdrawn
  • 2011-06-30 WO PCT/CN2011/076640 patent/WO2012083671A1/zh active Application Filing
  • 2011-06-30 JP JP2013539120A patent/JP5852126B2/ja active Active
  • 2011-06-30 KR KR1020137011195A patent/KR101588677B1/ko active IP Right Grant
  • 2011-06-30 US US13/991,564 patent/US20130248056A1/en not_active Abandoned

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