Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B7/00—Blast furnaces
  • C21B7/10—Cooling; Devices therefor
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B1/00—Shaft or like vertical or substantially vertical furnaces
  • F27B1/10—Details, accessories, or equipment peculiar to furnaces of these types
  • F27B1/24—Cooling arrangements
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D1/00—Casings; Linings; Walls; Roofs
  • F27D1/12—Casings; Linings; Walls; Roofs incorporating cooling arrangements
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D9/00—Cooling of furnaces or of charges therein
  • F27D2009/0002—Cooling of furnaces
  • F27D2009/0045—Cooling of furnaces the cooling medium passing a block, e.g. metallic
  • F27D2009/0048—Cooling of furnaces the cooling medium passing a block, e.g. metallic incorporating conduits for the medium
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D9/00—Cooling of furnaces or of charges therein
  • F27D2009/0002—Cooling of furnaces
  • F27D2009/0051—Cooling of furnaces comprising use of studs to transfer heat or retain the liner
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D9/00—Cooling of furnaces or of charges therein
  • F27D2009/0002—Cooling of furnaces
  • F27D2009/0056—Use of high thermoconductive elements
  • F27D2009/0062—Use of high thermoconductive elements made from copper or copper alloy

Definitions

• the present invention generally relates to a cooling plate for a metallurgical furnace and to a method for manufacturing such a cooling plate.
• Cooling plates also called “staves” have been used in blast furnaces for over a hundred years. They are arranged on the inside of the furnace armour and have internal coolant ducts, which are connected to the cooling system of the furnace. Their surface facing the interior of the furnace can be lined with a refractory material.
• a mould for casting a cooling plate body is provided with one or more sand cores for forming the internal coolant ducts. Liquid cast iron is then poured into the mould.
• This method has the disadvantage that the mould sand is difficult to remove from the cooling ducts and/or that the cooling duct in the cast iron is often not properly formed and that the cooling ducts are often not tight enough.
• preformed steel pipes in the mould and to pour the liquid cast iron around the steel pipes.
• these cooling plates have not proved satisfactory. Indeed, due to carbon diffusion from the cast iron into the steel pipes, the latter become brittle and may crack. Contact between the cooling pipes and the cooling plate body may also be responsible for cracks in the cooling plate body, most probably because of a difference in the coefficient of thermal expansion of both materials.
• DE-A-2128827 suggests to provide the preformed steel pipes with a metallic oxide coating so as to prevent carbon diffusion and metallurgical bonding between the cast iron and the steel pipes.
• DE-A-2128827 intends to provide an alternative to the prior known cooling plates, in which the steel pipes were coated with graphite or aluminium or plated with copper or tin, since, as mentioned, such layers do not prevent carburising.
• the alternative proposal which consists in applying a metallic oxide coating to the steel pipe is also unsatisfactory. As a result of casting, the coating has disappeared and there is a small air gap between the steel pipes and the cooling plate body, whereby pipes and body can expand independently.
• these cooling plates have the disadvantage of a bad thermal transmission coefficient, because the small air gap has an insulating effect.
• US 4,150,818 relates to a cooling plate for a metallurgical furnace comprising a cast cooling plate body wherein the steel cooling pipes are coated with a combination of two layers: a metallic layer in contact with the steel tube and a stable metallic oxide layer thereon.
• the metallic layer is made from a metal selected from the group consisting of Ni, Co, Mn, and Ag, either individually or including two or more.
• the metallic layer has a thickness in the range of 40 to 100 ⁇ m and the metallic oxide layer has a thickness in the range of 30 to 100 ⁇ m, the maximum total thickness of both layers being 200 ⁇ m.
• the metallic layer does avoid carburisation of the steel pipe, such cooling staves are however still unsatisfactory i.a. because of the oxide layer, which has a detrimental effect with regard to heat conductivity.
• GB-A-1571789 suggests to replace the sand core by a pre-shaped metal pipe coil made from copper or high-grade steel when casting the cooling plates in moulds.
• the coil is integrally cast into the cooling plate body in the casting mould and forms a spiral coolant duct. This method has also not proved effective in practice, inter alia because cavities and porosities in the copper cannot be effectively prevented with this method.
• a cooling plate made from a forged or rolled copper ingot is known from DE-A-2907511.
• the coolant ducts are blind holes introduced by mechanical drilling in the rolled copper ingot.
• WO-98/30345 teaches to cast a preform of the cooling plate with the help of a continuous casting mould, wherein rod-shaped inserts in the casting duct produce ducts running in the continuous casting direction, which form coolant ducts in the finished cooling plate.
• copper cooling plates generally have a far better thermal conductivity than cast iron cooling plates, they however have a far lower wear resistance than the latter. Thus, furnace zones in which the cooling plates are exposed to severe mechanical stresses cannot be equipped with copper cooling plates. Furthermore, copper cooling plates are more expensive than cast iron cooling plates.
• the object of the present invention is to provide a cooling plate that can be easily manufactured and that nevertheless has a good wear resistance and a low heat transfer resistance. This object is achieved by a cooling plate as claimed in claim 1. Summary of the invention
• a cooling plate for a metallurgical furnace in accordance with the present invention comprises a cast cooling plate body made of a ferrous metal and at least one steel cooling pipe cast in the cooling plate body. It shall be appreciated that a metallic jacket is provided on the outer surface of the steel cooling pipe in the cooling plate body.
• the metallic jacket has a thickness in the millimetre range and is made from a metal selected from the group consisting of copper, copper alloys, nickel and nickel alloys.
• the steel pipes are protected by a thick metallic jacket, which is believed to act as a physical barrier to carbon diffusion.
• the thickness of the metallic jacket is such that it is very improbable that carbon from the liquid ferrous metal, generally cast iron, will reach the steel cooling pipe.
• the metallic jacket acts as an intermediate layer, which avoids welding between the steel cooling pipe and the cast iron body, and which can absorb strains and stresses.
• the metallic jacket is in tight contact with both the steel pipe and the cast iron body. This is extremely advantageous with regard to heat transfer, since copper, nickel and their alloys have a high thermal conductivity. The tight contact between the different materials and the high thermal conductivity of the metallic jacket ensure an intensive heat transfer from the cast iron body to the cooling pipe.
• a method for manufacturing a cooling plate for a metallurgical furnace It com- prises the following steps: - providing at least one steel cooling pipe with a metallic jacket thereon, the metallic jacket having a thickness in the millimeter range and being made from a metal selected from the group consisting of copper, copper alloys, nickel and nickel alloys; - providing a mould for casting a cooling plate body;
• the present method thus allows for the manufacturing of cooling plates having an improved thermal conductivity due to the metallic jacket, which ensures an intensive heat transfer from the body to the cooling pipe. Moreover, the obtained cooling plate with a ferrous based plate body has a good wear resistance and thus an increased lifetime, whereby maintenance costs of metallurgical furnaces can be reduced.
• copper and copper alloys are particularly preferred for the metallic jacket. Indeed, copper and copper alloys are highly compatible with the surrounding materials, i.e. steel and cast iron, and have a high thermal conductivity.
• copper has a lower melting temperature (1 083°C) than the casting temperature of the cast iron (typically between 1 200 and 1 300°C)
• the use of a thick copper jacket permits to avoid its dissolution in the liquid cast iron.
• the copper jacket due to its thick thickness, rapidly absorbs the heat of the liquid cast iron, which then solidifies, without causing the copper to be washed out (i.e. re-melted and dispersed in the cast iron).
• the metallic jacket can thus be made from a metal or alloy having a lower melting temperature than the surrounding materials.
• copper and copper alloys have a greater thermal expansion coefficient than steel and cast iron, which means that in operation, the copper jacket will really be squeezed between the steel pipe and the cast iron body. Therefore, a very good contact between the different materials in the cooling plate is ensured, which is in favour of good heat transfer.
• the metallic jacket should preferably have a thickness of at least 2 mm, and of no more than 20 mm. More preferably, the thickness should be in the range of 5 to 10 mm, most preferably about 7 mm.
• the metallic jacket may advantageously be provided about the steel pipe by casting, since it is economically the more interesting method for forming such a thick metallic layer.
• the optimal thickness for the metallic jacket depends on the metal or alloy it is made of, and on the casting conditions.
• the copper jacket has to be sufficiently thick to absorb the heat from the liquid cast iron so as not to be washed out.
• the copper jacket is too thick, there will be a gap between the copper jacket and the cast iron body, due to shrinkage of the copper jacket.
• the casting result may vary depending on the casting conditions, such as e.g. temperature, duration and flow of the liquid cast iron. These parameters should thus preferably be taken into account when determin- ing the optimal thickness for the metallic jacket.
• the cooling plate body can consist of a variety of ferrous metals.
• the ferrous metal is preferably chosen from the group consisting of cast iron, ductile cast iron, malleable iron and steel.
• the protection against carbon diffusion provided by the metallic jacket is particularly important when the cooling plate body is made from cast iron, which has a high carbon content.
• Fig.1 is a sectional view of a preferred embodiment of a cooling plate in accordance with the invention.
• a preferred embodiment of a cooling plate 10 in accordance with the invention is shown in cross-sectional view.
• the cooling plate 10 comprises a cooling plate body 12 made of a ferrous metal, preferably cast iron.
• the cooling plate body 12 has the general form of a parallelepiped, whose front side and back side are respectively indicated 14 and 16.
• the front side 14 of the cooling plate 10 is advantageously provided with a series of regularly spaced parallel ribs 18, so as to increase its heat exchange surface and thus improve the cooling efficiency of the cooling plate 10.
• Reference sign 20 indicates a steel cooling pipe cast in the cooling plate body 12.
• the cooling plate 10 comprises a plurality of such cooling pipes 20.
• the cooling pipe 20 has a straight portion 22 essentially parallel to the front side 14 of the cooling plate 10.
• the straight portion 20 terminates at both ends by a bent portion 24 protruding on the rear side 16 of the cooling plate body 12, for connecting the cooling pipe 20 to a cooling circuit of e.g. a blast furnace.
• the cooling pipe 20 has a metallic jacket 26 surrounding its outer surface in the cooling plate body 12.
• the metallic jacket 26 is advantageously made of copper or of a copper alloy, and has a thickness in the range of 5 to 10 mm. During casting of the cast iron body, such a thick copper jacket 26 acts as a physical barrier to the diffusion of carbon from the liquid cast iron into the steel cooling pipe 20.
• the copper jacket 26, which has a high thermal conductibility, is in tight contact with both the steel cooling pipe 20 and the cast iron body 12.
• the good thermal conductivity between the cast iron body 12 and the steel cooling pipe 20 as well as the intimate contact between the materials allows an intensive heat transfer from the cast iron body 12 to the cooling fluid flowing in the steel cooling pipe 20.
• the coefficient of thermal expansion of copper and copper alloys is higher than that of steel and cast iron, whereby the good contact between the cooling plate body and the steel pipe is further ensured by the dilatation of the copper jacket when the cooling plate is in operation, i.e. subjected to intense heat.
• the thick copper layer has the ability of absorbing the heat of the liquid cast iron, which then solidifies, without causing the copper to be washed out, i.e. re-melted and dispersed in the cast iron body.
• the present cooling plate 10 can be easily manufactured by casting. Accordingly, the manufacture of the cooling plate 10 is preferably carried out as follows. A mould having the dimensions of the cooling plate body 12 is provided and the cooling pipes 20 provided with their metallic jacket 26 are arranged in the mould. Next, molten cast iron is poured into the mould around the cooling pipes and allowed to solidify therein. The obtained cooling plate is then removed from the mould.
• the metallic jacket is preferably cast about the steel pipe, since casting is economically the more interesting method for forming a thick metallic layer.
• a cooling plate 10 in accordance with the present invention has a proved to have a "cooling effect" which is significantly greater ( about two to three times) that of a conventional cast iron stave with steel pipes coated with a metallic oxide.
• This "cooling effect” is determined by measuring the hottest point on the hot side of the cooling plate 10, resp. the conventional stave, when exposed to a same heat source.
• the front side of a conventional stave will be about 600 to 650°C
• the front side of a cooling plate 10 in accordance with the invention will be about 200 to 250°C.
• a cooling pipe having an external diameter of 75 mm and a wall thickness of 10 mm was used.
• the steel cooling pipe was provided with a 7 mm thick copper layer.
• the steel cooling pipe with its 7 mm thick copper layer was placed in the mould and cast iron was poured therein at a temperature of 1250°C. After solidification, a cooling plate of 200 mm in thickness was obtained, which means that the copper jacket was covered by about 55 mm of cast iron.
• a transversal cut of the cooling plate was effected to observe the internal structure of the stave. After cutting, a thick and homogeneous copper jacket was observed around the cooling pipe, without any air gap between the cast iron body and the copper jacket. At the pipe/jacket interface, there is always a tight connection due to copper shrinkage. Hence, there was a tight contact at both interfaces of the copper jacket, and the steel cooling pipe could not be moved relatively to the cast iron body.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Furnace Housings, Linings, Walls, And Ceilings (AREA)
• Blast Furnaces (AREA)
• Heat Treatments In General, Especially Conveying And Cooling (AREA)
• Carbon Steel Or Casting Steel Manufacturing (AREA)

Applications Claiming Priority (3)

Publications (2)

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ID=19732029

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• 2002
  • 2002-01-16 LU LU90878A patent/LU90878B1/en active
  • 2002-12-21 JP JP2003560249A patent/JP2005514522A/ja active Pending
  • 2002-12-21 AU AU2002358789A patent/AU2002358789A1/en not_active Abandoned
  • 2002-12-21 CN CNB028271300A patent/CN1317397C/zh not_active Expired - Fee Related
  • 2002-12-21 WO PCT/EP2002/014692 patent/WO2003060168A2/fr active Application Filing
  • 2002-12-21 EP EP02793108A patent/EP1466021B1/fr not_active Expired - Lifetime
  • 2002-12-21 DE DE60236963T patent/DE60236963D1/de not_active Expired - Lifetime
  • 2002-12-21 KR KR10-2004-7010876A patent/KR20040072726A/ko not_active Application Discontinuation
  • 2002-12-21 AT AT02793108T patent/ATE473301T1/de active

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