WO2019201181A1 - 热力管线用球墨铸铁管、其制备工艺及应用 - Google Patents

热力管线用球墨铸铁管、其制备工艺及应用 Download PDF

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Publication number
WO2019201181A1
WO2019201181A1 PCT/CN2019/082502 CN2019082502W WO2019201181A1 WO 2019201181 A1 WO2019201181 A1 WO 2019201181A1 CN 2019082502 W CN2019082502 W CN 2019082502W WO 2019201181 A1 WO2019201181 A1 WO 2019201181A1
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WO
WIPO (PCT)
Prior art keywords
ductile iron
iron pipe
pipe
ductile
coating
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PCT/CN2019/082502
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English (en)
French (fr)
Inventor
王宇新
郑建平
顾永辉
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广东北晟益通实业有限公司
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Publication of WO2019201181A1 publication Critical patent/WO2019201181A1/zh

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L9/00—Rigid pipes
    • F16L9/02—Rigid pipes of metal
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D13/00—Centrifugal casting; Casting by using centrifugal force
    • B22D13/02—Centrifugal casting; Casting by using centrifugal force of elongated solid or hollow bodies, e.g. pipes, in moulds rotating around their longitudinal axis
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L23/00—Flanged joints
    • F16L23/16—Flanged joints characterised by the sealing means
    • F16L23/18—Flanged joints characterised by the sealing means the sealing means being rings
    • F16L23/22—Flanged joints characterised by the sealing means the sealing means being rings made exclusively of a material other than metal
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L58/00—Protection of pipes or pipe fittings against corrosion or incrustation
    • F16L58/02—Protection of pipes or pipe fittings against corrosion or incrustation by means of internal or external coatings
    • F16L58/04—Coatings characterised by the materials used
    • F16L58/08—Coatings characterised by the materials used by metal
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L58/00—Protection of pipes or pipe fittings against corrosion or incrustation
    • F16L58/02—Protection of pipes or pipe fittings against corrosion or incrustation by means of internal or external coatings
    • F16L58/04—Coatings characterised by the materials used
    • F16L58/14—Coatings characterised by the materials used by ceramic or vitreous materials
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L59/00—Thermal insulation in general
    • F16L59/02—Shape or form of insulating materials, with or without coverings integral with the insulating materials
    • F16L59/028—Composition or method of fixing a thermally insulating material
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L59/00—Thermal insulation in general
    • F16L59/02—Shape or form of insulating materials, with or without coverings integral with the insulating materials
    • F16L59/029—Shape or form of insulating materials, with or without coverings integral with the insulating materials layered

Definitions

  • the invention relates to a ductile iron pipe for a heat pipeline, a preparation process and application thereof.
  • the steel pipe of the heat pipeline does not have the ability to withstand strong earthquake damage, especially after several years of corrosion, the pipe wall is thinned, the strength and toughness of the pipe are reduced to different degrees. At this time, when the pipe is subjected to external force stretching and extrusion When twisted and heavy objects collide, it is easy to break or even break.
  • One of the objects of the present invention is to provide a ductile iron pipe for a heat pipe to solve at least one of the above technical problems.
  • Another object of the present invention is to provide the above-described use of a ductile iron pipe for a heat pipe in a heat pipe to solve at least one of the above technical problems.
  • Another object of the present invention is to provide a method of producing the above-described ductile iron pipe for a heat pipe to solve at least one of the above technical problems.
  • a ductile iron pipe for a heat pipeline comprising: a ductile iron pipe body having a socket at one end and a socket at the other end; and a microcrystalline insulation layer disposed on the outer wall of the ductile iron pipe .
  • the tube body of the ductile iron pipe for the heat pipeline of the invention is based on the high-toughness ferrite matrix ductile iron as the base material, has strong corrosion resistance and high toughness, and the outer wall is coated with the microcrystalline insulation layer made of the microcrystalline material, and the insulation layer is insulated.
  • the thermal performance is good, the strength and the hardness are high. Therefore, when the ductile iron pipe of the invention is used for the thermal pipeline laying, the service life of the thermal pipeline can be greatly prolonged and the safety is greatly improved.
  • the microcrystalline material has good thermal insulation performance and is used for conveying hot water and steam, which can significantly reduce heat loss during transportation, save energy and reduce consumption.
  • the thickness of the microcrystalline insulating layer is thinner than that of the conventional rock wool thermal insulation layer, a better thermal insulation effect can be achieved, for example, it can be set to 10 to 25 mm, so that the thickness of the coating is higher than that of the rock wool thermal insulation layer.
  • the thickness is reduced by about 90%, so that the outer diameter of the tube is significantly reduced, and the strength and hardness of the microcrystalline insulation layer are high, which is not easy to be damaged, and facilitates transportation and installation of the tube.
  • the ductile iron pipe for the heat pipeline of the invention has a socket and a socket, and two adjacent ductile iron pipe bodies are connected through a socket and a socket when connecting, a flexible mechanical sealing interface is adopted, and a joint of the socket and the socket is provided Sealing ring made of high temperature resistant material.
  • the interface form may be a T-type sealing interface, an S-type mechanical sealing interface, a N I type mechanical sealing interface, a K II type mechanical sealing interface or a S II type mechanical sealing. Interface; when connecting, no on-site welding is required, installation and construction are quick and easy, the speed of pipeline laying construction can be significantly improved, and the comprehensive cost of pipeline construction and daily maintenance can be significantly reduced.
  • the interface of the flexible socket connection has good sealing performance, which can make the ductile iron pipe of the heat pipeline have flexibility and good flexibility, so it can resist the external force such as stretching, extrusion and twist applied to the pipe by the earthquake, and enhance the heat.
  • the pipeline uses ductile iron pipes to withstand the ability of strong earthquake damage. Thereby, the service life of the heat pipe can be extended.
  • the high temperature resistant material for preparing the sealing apron used in the connection of the ductile iron pipe of the heat pipeline of the present invention is nitrile rubber, hydrogenated nitrile rubber, neoprene rubber, ethylene propylene diene monomer, silicone rubber, fluorine. Rubber, fluorosilicone rubber or polytetrafluoroethylene.
  • the material of the seal ring is preferably nitrile rubber, hydrogenated nitrile rubber, neoprene or EPDM rubber, when used for thermal pipelines.
  • the material of the sealing rubber ring is preferably silicone rubber, fluorine rubber, fluorosilicone rubber or polytetrafluoroethylene.
  • the microcrystalline material of the present invention also referred to as glass-ceramic or glass-ceramic, refers to a base glass to which a specific crystal nucleating agent (with or without addition) is added, which is prepared by controlling crystallization to have one or more microcrystalline phases.
  • the composite material with the residual glass phase has excellent properties such as anti-corrosion and heat resistance.
  • waste glass, fly ash, non-metal ore, etc. are mainly used as a main raw material, and a foaming agent, a nucleating agent and an additive are added.
  • a porous microcrystalline glass prepared by a process such as preheating, melting, foaming, crystallization, annealing, or the like, that is, a microcrystalline foam glass.
  • the ductile iron pipe for a heat pipe of the present invention may further comprise a lining coating disposed on the inner wall of the ductile iron pipe.
  • a lining coating disposed on the inner wall of the ductile iron pipe.
  • the coating material of the above liner coating may be an epoxy ceramic or an enamel, preferably having a thickness of 30 to 150 ⁇ m.
  • the coating material of the inner liner coating is preferably epoxy ceramic, and the ductile iron pipe for the heat pipeline is applied to the heat of conveying temperature greater than 120 °C.
  • the coating material of the inner liner coating is preferably enamel.
  • the ductile iron pipe for the heat pipe of the present invention may further comprise a zinc coating disposed on the outer wall of the ductile iron pipe body, and the microcrystalline insulation layer is disposed on the zinc coating of the ductile iron pipe body, and the zinc coating
  • the layer thickness is preferably not less than 40 ⁇ m.
  • the ductile iron pipe for a heat pipe of the present invention may further include an outer protective coating, and the outer protective coating may be coated on the zinc coating and located between the zinc coating and the microcrystalline insulating layer (ie, microcrystalline The insulating layer is applied to the outer protective coating or coated on the microcrystalline insulating layer (ie, outside the microcrystalline insulating layer).
  • the coating material of the outer protective coating may be asphalt paint, epoxy asphalt paint, polyurethane or polyurea.
  • the ductile iron pipe for the heat pipeline provided by the invention has the advantages of strong corrosion resistance, long service life, high toughness, quick construction and installation, good thermal insulation effect, etc. compared with the existing steel pipe for thermal pipeline, and can be applied to laying.
  • Thermal pipelines reduce the construction cost of thermal pipelines and resist the destruction of geological disasters such as strong earthquakes, ensure the quality of life of urban residents and improve the city's ability to resist earthquakes and reduce disasters.
  • S2 spheroidization treatment: spheroidizing the original iron liquid with adjusted chemical composition by spheroidizing agent, and injecting the spheroidized iron liquid into the special casting electric furnace of spheroidal graphite cast iron, using iron casting furnace for special casting of ductile iron The pouring temperature of the liquid is maintained not less than the critical temperature of the molten iron;
  • Airtightness test According to the pressure requirement of the ductile iron pipe to be laid by the heat pipeline, that is, the design pressure of the designed heat transfer pipeline to be laid, the airtightness test of the ductile iron pipe blank after finishing processing is performed. Wherein, the test pressure is not less than 1.20 times the designed conveying pressure of the heat pipeline to be laid;
  • microcrystalline thermal insulation layer The microcrystalline material is coated on the outer wall of the ductile iron pipe blank which is qualified for the airtightness test, and the microcrystalline thermal insulation layer is prepared, that is, the ductile iron pipe for the thermal pipeline is obtained.
  • the molten molten iron in the preparation process of the present invention, is superheated to 1500 ° C or higher, and the molten iron is superheated to a temperature of not less than 1500 ° C in the preparation stage of the molten iron, which may promote The carbon exerts a deoxidizing and purifying action on the molten iron to achieve a pre-spheroidizing treatment effect on the original molten iron, thereby facilitating spheroidization of the graphite; further, in the preparation process of the present invention, according to the set value of the chemical composition of the molten iron The chemical composition of the original iron liquid was adjusted.
  • the raw iron liquid having a temperature of 1500 ° C or higher and having a chemical composition adjusted is spheroidized, and the spheroidized molten iron is injected into a cast iron special cast electric furnace (Inventive Example)
  • the cast iron special casting electric furnace mentioned in the above is the casting electric furnace equipment disclosed in the patent CN101658901B), and the spheroidized molten iron is injected into the special casting electric furnace of the ductile cast iron, on the one hand, the molten iron can be further desulfurized and deoxidized, on the other hand
  • the amount of residual Mg in the molten iron can be stabilized, thereby avoiding the spheroidization of the molten iron, ensuring the spheroidization level of the produced ductile iron pipe, and stabilizing the mechanical properties such as toughness and strength; and simultaneously pouring the molten iron It is always kept at a temperature range not less than the critical temperature of molten iron (ie, 1420 ⁇ 1480
  • the ductile cast iron pipe blank is prepared by the hot die centrifugal casting process, and the centrifugal casting process is started when the centrifugal force of the pipe mold reaches the centrifugal force setting value, and the preparation process enables The casting process is started under suitable centrifugal force according to requirements, thereby controlling the shrinkage of the prepared ductile iron pipe blank.
  • the centrifugal casting process adopts a high-speed large centrifugal force casting process, which ensures that the high-temperature molten iron for casting is gradually solidified under the action of large centrifugal force (this In the embodiment of the invention, it is preferred to start pouring when the centrifugal force of the tube mold reaches 80 to 100 G, and the centrifugal force of the tube rotation of the Bid Lavo method is increased by about 1 time, so that the high temperature molten iron is always in a large centrifugal force in the tube mold.
  • the pressure self-feeding of the ductile iron liquid in the porridge solidification and graphitization expansion coincidence stage thereby ensuring the dense structure of the ductile iron tube
  • the thickness of the thick-walled part is uniform and there are no casting defects such as shrinkage holes and shrinkage.
  • the wall thickness is also very uniform and compact, and there is no inclusion. Therefore, the prepared ductile iron pipe has good airtightness.
  • the appropriate carbon equivalent of the molten iron is combined with the instantaneous incubation, so that the matrix structure of the as-cast as-cast ductile iron pipe blank has no free cementite.
  • the invention adopts the hot mold centrifugal casting process of the coating, and the preheating coating needs to preheat the tube mold to 200-220 ° C before spraying, which can ensure that the insulating coating can be quickly dried during spraying, and can be avoided when the molten iron is injected into the tube mold.
  • the tube mold is ablated and damaged by the molten iron due to the detonation of the heat insulating coating, thereby causing a production interruption accident.
  • the present invention is prepared.
  • the spheroidal graphite cast iron tube blank is removed from the tube mold to eliminate the pearlite annealing treatment, thereby obtaining a ductile iron tube whose matrix structure is mainly ferrite, the pearlite content is low, and the elongation is good.
  • the present invention In the preparation process, the airtightness test of the finished ductile iron pipe is performed before the preparation of the microcrystalline insulating layer, and the test pressure is set to be not less than 1.20 times of the conveying pressure of the heat pipe to be laid, thereby ensuring the ductile iron High reliability of pipe tightness.
  • the iron liquid having the S content of not more than 0.12% can be directly injected into the induction heat preservation furnace without the external desulfurization treatment, and the chemical composition of the original iron liquid is not required to be adjusted.
  • the S content because: 1) The desulfurization effect of the spheroidization treatment is very good, and the high temperature and high sulfur iron liquid with a sulfur content of not more than 0.2% and a temperature of 1500 °C can be processed into a qualified ductile iron liquid.
  • the sulfur content of the spheroidized iron liquid can be removed to a level less than 0.01%; 2) the cast iron special cast electric furnace allows the spheroidization treatment to be directly carried out without slag treatment, and directly spheroidizes the MgS slag in the package
  • the MgO slag is directly poured into the furnace, and the S2- and O2- anions in the slag are removed by the direct current electrolysis.
  • the Mg2+ cation in the slag is reduced to Mg and re-enters the molten iron when it contacts the molten iron as the cathode.
  • the dynamic balance of Mg from the escape loss in the molten iron stabilizes the residual amount of Mg in the molten iron, avoids the spheroidization decay, and makes the MgS slag and the MgO slag harm, thereby realizing the recycling of the metallic magnesium. This also simplifies the production process and improves the consistency of the mechanical properties and quality of the prepared ductile iron pipe.
  • one of pig iron, scrap steel, iron filings, carbon-free bricks and recycled materials (mainly the pouring riser of pipe fittings or other castings and a small amount of non-conforming products of ductile iron pipes and fittings) may be selected.
  • the possible loss of chemical composition during the smelting process and the set value of the chemical composition of the molten iron so that the composition of the chemical composition of the molten iron after smelting is close to its setting. Value, simplifying the process of chemical composition adjustment of molten iron.
  • the process of melting the furnace material into the original iron liquid may adopt a cupola-induction electric furnace double smelting process, or a blast furnace pig iron liquid into the frequency conversion coreless induction furnace to adjust the chemical composition of the "short process" smelting process.
  • the molten iron liquid is superheated to not less than 1500 ° C, and the furnace charge can be smelted by using a cupola furnace.
  • the temperature of the original molten iron directly reaches 1500 ° C and above (that is, the tapping temperature of the original molten iron is not If it is less than 1500 ° C), the molten iron may be superheated in an induction furnace by using other melting methods, so that the temperature of the original molten iron reaches 1500 ° C and above (that is, the induction furnace holding temperature is set at 1500 ° C and above).
  • the flow treatment of the molten iron can promote the graphitization, prevent the spheroidization of the molten iron during the pouring process, and avoid the generation of free cementite.
  • the inoculant used in the inoculation treatment is a conventional inoculant, which may be one of a ferrosilicon inoculant, a silicon germanium inoculant or a combination thereof, preferably a 75FeSi inoculant, and the amount is 0.2 to 0.4 of the weight of the molten iron. %.
  • the cooling treatment performed on the tube mold during the pouring process is preferably a shower water cooling treatment.
  • the solidified shaped ductile iron pipe blank can continue to cool the pipe mold during the cooling process; the large-diameter thick-walled ductile iron pipe with relatively slow cooling rate after solidification can accelerate the cooling speed and can also be used in the pipe mold.
  • the solidified ductile iron pipe blank is subjected to air blowing or water spray.
  • the spheroidizing treatment of the raw iron liquid having the adjusted chemical composition is preferably a feeding method or a subcontracting method which does not affect the iron carbon equivalent and has a remarkable desulfurization effect.
  • the finishing processing includes the inner grinding of the socket, the outer grinding of the socket, the inner wall grinding, the pipe cutting, the chamfering, and the flange drilling of the sealed interface ductile iron pipe of the S type and the N type.
  • the internal grinding of the socket and the external grinding of the socket are to improve the surface finish of these parts, so that the sealing pressure of the ductile iron pipe can be further improved when the sealing rubber ring is matched during the connection of the ductile iron pipe.
  • the test pressure of the airtightness test shall be not less than 5.0 MPa.
  • the airtightness test of the ductile iron pipe production line generally adopts a test method in which the test pressure is not less than 5.0 MPa and the dwell time is not less than 20 seconds, and the test is qualified ductile iron.
  • the tube can continue to complete the subsequent internal and external coating, final inspection, spray labeling and digital marking, and then bundle into the warehouse to become the finished ductile iron tube for the heat pipeline.
  • the centrifugal force setting is no less than 80G and no greater than 110G. Since pouring at a small centrifugal force causes shrinkage and shrinkage defects, and the centrifugal force is too large, the tube mold and the equipment are deteriorated due to excessively high rotational speed, and the safety of the device is deteriorated. Therefore, the centrifugal force is set.
  • the fixed rotation speed is set to 80G ⁇ 100G (the centrifugal force of different diameters of ductile iron pipe is different, among which, the value of small diameter pipe is close to the upper limit value, and the value of large diameter pipe is close to the lower limit value), which can avoid loosening and shrinking. At the same time of defects, the stability of the operation of the equipment and the tube mold is ensured, thereby ensuring the quality of the manufactured ductile iron pipe and ensuring production safety.
  • the set temperature of the ductile iron tube blank solidified in the tube mold can be cooled to a temperature of 760 to 830 °C.
  • the extubation temperature is higher than 850 °C, the strength of the ductile iron pipe is insufficient. At this temperature, the pipe drawing tends to deform the ductile iron pipe during the extubation process, and when the extubation temperature is lower than the temperature of the eutectoid point (about 730 ° C)
  • the ductile iron pipe will undergo eutectoid transformation, which leads to the lattice transition causing the volume transition, which makes the ductile iron pipe expansion cause difficulty in extubation. Therefore, controlling the extubation temperature at 760-830 °C can prevent the difficulty of extubation and avoid deformation of the ductile iron tube.
  • step S2 the pouring temperature of the molten iron is kept not less than the critical temperature of the molten iron by using a cast iron special casting electric furnace, and the holding temperature in the special casting electric furnace of the ductile iron can be set to 1430 to 1480. °C achieved.
  • the holding temperature in the cast iron special casting electric furnace is set to 1430 to 1480 ° C, so that when the molten iron in the cast iron special casting electric furnace is injected into the pipe mold, the molten iron is kept non-oxidizing clean iron liquid, thereby It can ensure that the molten iron has sufficient fluidity, and it can ensure that the molten iron in the tube mold can still maintain a liquid time under the action of high centrifugal force after the pouring, thereby avoiding the pouring of the ductile iron pipe, cold separation, shrinkage, Casting defects and waste products such as shrinkage cavities, blisters, slag eyes, pores, and uneven wall thickness, the prepared ductile iron pipe wall is dense, uniform, defect-free, and airtight, and can be used for laying hot pipelines.
  • the spheroidizing agent may be a magnesium ingot, and the set value of the chemical composition of the molten iron may be: C is 3.3 to 3.7%, and Si is 2.2 to 2.8%.
  • Adjusting the chemical composition of the original molten iron according to the set value of the chemical composition of the molten iron includes:
  • the mass fraction of carbon and silicon in the original molten iron based on the above set values, so that the mass fraction of carbon in the original molten iron is not higher than 3.7%, and the carbon equivalent reaches the eutectic composition (ie, the carbon equivalent is 4.26%). Or the carbon equivalent can reach 4.1% to 4.3%. Therefore, the spheroidal graphite cast iron tube forming and the obtaining of the free cementite spheroidal graphite cast iron blank in the matrix structure can be favored in the process of the hot-melt centrifugal casting process of the coating of the invention, and the quality of the spheroidal graphite tube blank can be ensured Simplify the subsequent annealing process.
  • the use of magnesium ingot as a spheroidizing agent can greatly reduce the cost of the spheroidizing agent on the one hand, and avoid the influence and interference of the elements such as Si in the rare earth ferrosilicon spheroidizing agent on the iron component on the other hand. Save a lot of valuable rare earth elements.
  • the raw iron liquid having the adjusted chemical composition may be spheroidized by a subcontracting method, wherein the amount of the magnesium ingot spheroidizing agent is 0.10 to 0.20% of the weight of the original molten iron. .
  • the subcontracting method With the subcontracting method, the spheroidization treatment effect is good, and the speed of vaporization of the spheroidizing agent in the reaction chamber of the subcontracting is controlled without explosion.
  • the amount of the spheroidizing agent is 0.10-0.15% of the weight of the original molten iron, which can ensure that the Mg content in the molten iron is not less than 0.04% after the spheroidizing treatment is completed, and the ideal spheroidizing effect is achieved, when the S content in the original molten iron is greater than 0.12.
  • the amount of the spheroidizing agent may be increased to 0.18 to 0.20% by weight of the original molten iron as needed.
  • the following steps may also be included before the annealing process:
  • Ultrasonic non-destructive testing of the ductile iron pipe blanks after cleaning and purging the outer wall is carried out to determine whether the spheroidizing grade of the ductile iron pipe blank is qualified and whether the ductile iron pipe blank body has casting defects and other damage defects.
  • the actual temperature of the molten iron injected into the tube mold during casting is sufficiently high (for example, not lower than 1400 ° C)
  • the insulating coating sprayed on the inner wall of the tube mold is almost entirely hung on the ductile iron.
  • the outer wall of the tube blank is taken out. Therefore, the outer wall of the spheroidal graphite tube blank needs to be cleaned and then purged to clean the residual heat-insulating paint on the outer wall of the spheroidal iron tube blank.
  • the purge preferably uses high pressure steam to purge the outer wall of the ductile iron pipe.
  • ultrasonic nondestructive testing of the ductile iron tube blank is required to determine whether the spheroidization level of the ductile iron tube blank is qualified, and whether the ductile iron tube blank body has slag eyes, subcutaneous pores, blisters, and cold.
  • Other damage defects such as casting defects, heavy skin, shrinkage holes, shrinkage and other casting defects and damage cracks.
  • Ductile iron pipe blanks with spheroidal grades and no casting defects and damage cracks are recorded as qualified, and unqualified ductile iron pipe blanks are recorded as unqualified and directly remelted as furnace charge.
  • Ultrasonic testing of ductile iron pipe blanks can quickly complete the non-destructive testing of ductile iron pipes, and comprehensively test whether ductile iron pipes have casting defects and internal damage defects without impairing or affecting the performance of ductile iron;
  • the ultrasonic wave is used to determine whether the spheroidizing grade of the ductile iron pipe is qualified.
  • the detection efficiency is much higher than the traditional metallographic detection method, and even the different components and content of the ductile iron pipe base can be quantitatively determined.
  • ultrasonic waves are used.
  • the detection of the ductile iron tube blank can realize the continuous on-line detection of a large-volume ductile iron pipe of a single specification, which is beneficial to the automation of the ductile iron pipe production line.
  • the annealing treatment may have an annealing temperature of 780 to 850 ° C and an annealing time of 20 to 40 min.
  • the invention has the following obvious advantages: 1) The spheroidal graphite cast iron tube blank prepared by the preparation process of the invention does not contain free cementite, but the tube body is Normalizing occurs in the air. The eutectoid transformation at this time will cause the pearlite to exceed the standard. Therefore, it is only necessary to eliminate the low temperature annealing of the pearlite cast iron tube to obtain the high elongation and high toughness of the ferrite content.
  • Ductile iron tube which can significantly reduce the annealing temperature (from the traditional 980 ⁇ 1050 ° C to 780 ⁇ 850 ° C); 2) the annealing process of the present invention eliminates the high temperature annealing phase of the removal of the Leysite and the middle of the annealing kiln
  • the fast water-cooled (or air-cooled) structure simplifies the equipment structure of the tunnel annealing kiln, shortens the annealing time, reduces the energy consumption of the annealing treatment, and prolongs the life of the refractory material in the annealing kiln; 3) avoids the ductile iron pipe due to The risk of burnt and deformation (ie, the ductile iron pipe becomes elliptical) and the loss of waste; 4) Because the wall thickness of the ductile iron pipe is uniform, the smoothing process of the annealing process is ensured, and the cause can be completely avoided. Do local thickness is too thin ductile iron pipe fracture occurs upon
  • the following steps are included after the annealing process and before the finishing process:
  • the outer surface of the annealed ductile iron tube blank is sprayed with zinc.
  • zinc spraying may be achieved by means of hot-spraying zinc, cold-zinc coating, etc., and the thickness of the zinc layer is preferably not less than 40 ⁇ m.
  • Spraying zinc on the outer surface of the annealed ductile iron pipe blank is beneficial to improve the ability of the ductile iron pipe surface to withstand electrical corrosion. At the same time, it can avoid the subsequent ductile iron pipe blank during the airtightness test due to the spheroidal ink.
  • the cast iron tube blank body is in contact with water and causes the surface of the tube to rust.
  • the method further includes the steps of: preparing a liner coating on the inner wall of the airtight qualified ductile iron pipe blank by coating the inner liner material;
  • step S7 a microcrystalline insulating layer prepared by coating a microcrystalline material is coated on the zinc coating of the spheroidal graphite tube blank after the inner liner is coated with the inner liner.
  • the resistance of fluid transportation can be reduced, the corrosion resistance of the ductile iron pipe can be improved, and the service life of the ductile iron pipe can be prolonged.
  • the coating material of the liner coating may be an epoxy ceramic or an enamel.
  • the coating material of the liner coating may be an epoxy ceramic or an enamel.
  • FIG. 1 is a structural view of a ductile iron pipe for a heat pipe according to an embodiment of the present invention
  • Figure 2 is a cross-sectional view of the ductile iron pipe body for the heat pipe shown in Figure 1;
  • FIG. 3 is a structural view of a S II type mechanical seal interface of a ductile iron pipe for a heat pipe shown in FIG. 1 .
  • the ductile iron pipe for the heat pipe includes a ductile iron pipe body 1 having a socket 11 at one end, a socket 12 at the other end, and a microcrystalline insulation layer 3 provided on the outer wall of the ductile iron pipe body 1.
  • the microcrystalline insulating layer 3 is made of a microcrystalline material.
  • the microcrystalline material is preferably microcrystalline foam glass, and the thickness of the microcrystalline insulating layer 3 is preferably 15 mm.
  • the ductile iron pipe for the heat pipeline further comprises a lining coating 2 and a zinc coating 4, wherein the lining coating 2 is applied to the inner wall of the ductile iron pipe body 1, and the conveying medium temperature is ⁇ 120 ° C,
  • the coating material is preferably an epoxy ceramic; when the temperature of the medium is >120° C., the coating material is preferably enamel, and the coating thickness is 100 ⁇ m; the zinc coating layer 4 is disposed on the outer wall of the ductile iron pipe body 1 and located in the ductile iron pipe body.
  • the zinc coating 4 is coated on the outer wall of the ductile cast iron pipe 1, the microcrystalline insulating layer 3 is coated on the zinc coating 4
  • the zinc coating 4 has a thickness of 40 ⁇ m.
  • the outer wall of the ductile iron pipe ductile iron pipe body 1 for the heat pipeline is sequentially coated with the zinc coating layer 4 and the microcrystalline insulation layer 3 from the inside to the outside, and the inner wall of the ductile iron pipe body 1 is coated.
  • Lined coating 2 As shown in FIG. 2, in the present embodiment, the outer wall of the ductile iron pipe ductile iron pipe body 1 for the heat pipeline is sequentially coated with the zinc coating layer 4 and the microcrystalline insulation layer 3 from the inside to the outside, and the inner wall of the ductile iron pipe body 1 is coated.
  • Lined coating 2 As shown in FIG. 2, in the present embodiment, the outer wall of the ductile iron pipe ductile iron pipe body 1 for the heat pipeline is sequentially coated with the zinc coating layer 4 and the microcrystalline insulation layer 3 from the inside to the outside, and the inner wall of the ductile iron pipe body 1 is coated. Lined coating 2.
  • the lining of the ductile iron pipe for the heat pipeline is not coated with the lining coating 2, and the microcrystalline insulation layer 3 is not coated at the socket.
  • the lining coating 2 and the microcrystalline insulation layer 3 between the adjacent ductile iron pipes of the thermal pipeline can be continuously transitioned, and the entire pipeline lining is ensured after the thermal pipeline is connected by the ductile iron pipe.
  • the S II type mechanical seal interface is preferably used when the thermal pipeline is connected with the ductile iron pipe.
  • the outer surface of the socket 12 of the ductile iron pipe for the heat pipeline is provided with a retaining groove 121.
  • the socket 12 is provided with a pressing flange 63.
  • the pressing flange 63 is fixedly connected to the edge of the socket 11 by bolts 61 and nuts 62.
  • the inner surface of the socket 11 is provided with an embedding groove, and the embedding groove is embedded inwardly from the embedding slot port.
  • the sealing rubber ring 64 There is a sealing rubber ring 64, a spacer ring 65 and a locking ring 66.
  • the bottom end of the pressing flange 63 presses against the sealing rubber ring 64.
  • the bottom end of the locking ring 66 is pressed against the retaining groove 121, and the sealing rubber ring 64 and the spacer ring 65 are
  • the locking ring 66 is close together and is located between the inner wall of the socket 11 and the outer wall of the socket 12, and the sealing rubber ring 64, the spacer ring 65 and the locking ring 66 are combined to form an interference with the inner wall of the socket 11 and the outer wall of the socket 12.
  • the use of the lock ring 66 and the retaining groove 121 allows the interface to have better anti-slip capability.
  • the material of the sealing rubber ring 64 may be nitrile rubber, hydrogenated nitrile rubber, neoprene rubber, ethylene propylene diene monomer, polyurethane, silicone rubber, fluororubber, fluorosilicone rubber or polytetrafluoroethylene.
  • the material of the sealing rubber ring 64 is preferably a polytetrafluoroethylene material.
  • the structure is as shown in Embodiment 1, and the preparation method of the ductile iron pipe for the heat pipeline of the specification DN300 ⁇ 6000 mm includes the following steps:
  • the set value of the chemical composition of molten iron is: C: 3.4 ⁇ 3.7%, Si: 2.4 ⁇ 2.5%, using pig iron, scrap steel and recycled material as the charge, after the batching is in the 40t / h large long furnace
  • the slag iron is separated by the siphon type slag iron separator, and the original iron liquid is injected into the 60t large-capacity core induction heat preservation electric furnace from the tap hole, and the set temperature of the induction heat preservation furnace is 1500 ° C and maintain a constant temperature, according to the set value of the chemical composition of the molten iron set cupola melting process, so that the iron output temperature of the molten iron is greater than 1500 ° C, while ensuring the chemical composition of the original molten iron within the set value range, if exceeded
  • the set value range will be adjusted by using a 10t variable frequency coreless induction furnace to melt the molten iron and inject it
  • S2 spheroidizing treatment: Put the magnesium ingot with the weight of 0.12% of the original molten iron into the reaction chamber of 1.5t subcontracting, inject the original molten iron of the induction holding electric furnace into the subcontract for spheroidization treatment, and spheroidize the molten iron.
  • the residual amount of Mg is ⁇ 0.04%, and the chemical composition of the molten iron includes: C: 3.2 to 3.6%, Si: 2.2 to 2.5%, Mn: ⁇ 0.3%, P: ⁇ 0.07%, S: ⁇ 0.01%; Operation, the spheroidized molten iron in the subcontract is directly injected into the 8t ductile iron special casting electric furnace by the 5t rotary forklift, in order to keep the pouring temperature of the molten iron not less than the critical temperature of the molten iron, the special casting electric furnace of the ductile iron is set.
  • the set holding temperature is 1440 ° C;
  • the pre-rotation station of the unit When the pre-rotation station of the unit is pre-rotated to 80-90% of the set speed and then moved to the centrifugal casting station, the time for the centrifugal casting station to increase the speed of the tube mold can be saved, and the production efficiency can be improved); after moving to the centrifugal casting station Quickly increase the speed of the tube mold to the maximum value (centrifugal force reaches 100G), and then start pouring.
  • the iron liquid with a temperature of 1440 °C in the cast iron special casting electric furnace is injected into the tube mold by the quantitative solution, and the weight of the molten iron is 0.3%.
  • the 75FeSi inoculant is incubated with the stream, and at the same time, the tube mold is sprayed and cooled; the iron liquid is solidified and formed, and the tube mold is cooled to the cooling station (the tube mold can be continuously cooled by water spray, and the water can be sprayed into the tube mold at the same time) Fog, speeding up red hot ductile iron pipe The temperature of the billet is lowered, and then the tube mold is moved to the extubation station.
  • the tube extruding machine extracts the ductile iron tube blank from the tube mold; and pulls out the ductile iron tube The empty tube mold of the blank, and then through the cleaning station, the spraying station, etc., clean the residual paint on the inner wall of the tube end of the tube mold, re-spray the insulating coating and dry, and then recycle again for the preparation of the ductile iron tube;
  • the thermal insulation coating is a water-based coating, which is mainly composed of diatomaceous earth and bentonite by weight ratio (18-20):1, and the coating thickness can be 0.4-0.8 mm.
  • the diatomaceous earth and the bentonite in the water-based diatomaceous earth paint are disposed at a weight ratio of 20:1, and the coating thickness is 0.5 mm.
  • the core of the socket adopts the cold box process and adopts the core of automatic and efficient core shooting mechanism.
  • the brushing machine is used to clean and heat the heat-insulating paint brought out from the outer wall of the ductile iron tube blank drawn from the tube mold, and completely remove the sticking on the outer wall of the ductile iron tube blank. Residual insulation coating;
  • Non-destructive testing After the brush tube and the purge are completed, the spheroidal graphite tube blanks that have been cleaned and purged on the outer wall are subjected to ultrasonic non-destructive testing to determine the spheroidization level of the cast tube blank, whether there are casting defects or other damage defects.
  • the qualified ductile iron pipe that has passed the inspection enters the next process, and the ductile iron pipe which is judged as waste is remelted as the charge of the charge (normally, the scrap rate here does not exceed 0.2%);
  • the qualified ductile iron pipe blank is transferred into the tunnel annealing kiln annealing, the annealing temperature is controlled at 780-850 ° C, the annealing time is 30 min, and the kiln temperature is 680 ° C;
  • finishing processing finishing the spheroidal graphite cast iron blank after the spraying of zinc, including: grinding socket and socket, grinding inner wall, cutting ring chamfering, flange drilling, etc.;
  • air tightness test airtightness test of the ductile iron pipe blank after finishing processing, the test pressure is 5.0MPa, the dwell time is >20s; the ductile iron pipe qualified by the airtightness test enters the next process, The ductile iron pipe judged as waste is remelted as a charge (normally, the scrap rate here does not exceed 0.1%);
  • lining coating is applied on the inner wall of ductile iron pipe blank which is qualified for air tightness test.
  • the coating material is epoxy ceramic; the conveying medium temperature is >120°C.
  • the coating thickness is 100 ⁇ m;
  • microcrystalline thermal insulation layer microcrystalline foam glass is coated on the zinc coating of the spheroidal graphite tube blank coated with the inner liner on the inner wall to prepare a microcrystalline thermal insulation layer with a coating thickness of 15 mm, and then the final Inspection, the trademark code and quality tracking digital code for qualified products, that is, the finished ductile iron pipe for thermal pipelines.
  • the ductile iron pipe for the thermal pipeline prepared in this embodiment has no casting defects such as blisters, slag eyes, pores, cold partitions, shrinkage, shrinkage holes, etc., and the metallographic and mechanical properties are tested by the body sampling, and the spheroidization level is high. It is very stable, the matrix structure is mainly ferrite, the amount of pearlite is between P15 and P5, the elongation is 16 to 24%, and the tensile strength is 420 to 470 MPa.
  • the production line of the ductile iron pipe for the heat pipeline of the present invention can be automated or semi-automatic, such as: (1) In the preparation process of the molten iron, the cupola can be intelligently controlled by the expert system to realize the furnace working condition and the melting parameter.
  • the whole process of automatic control (2) during the spheroidization process, the molten iron in the subcontract can be spheroidized on the rotary forklift, iron liquid transfer, dumping into a dedicated casting electric furnace, etc.; (3) Insulation coating preparation process In the process, the centrifugal coating unit can automatically process the mixing system to process the qualified coating to be ready for use; (4) The installation of the socket core can be carried out by robots or robots, thereby saving manpower and material and improving the ductile iron. Tube production efficiency.

Abstract

一种热力管线用球墨铸铁管，包括：一端设有插口（12）、另一端设有承口（11）的球墨铸铁管体（1）和涂覆于管体（1）外壁的微晶保温层（3）。该球墨铸铁管耐腐蚀能力强，寿命延长，安全性显著提高。微晶保温层（3）硬度高、厚度小，保温隔热性能好，既方便管子运输与安装，又降低了热力输送过程的热损失。还涉及一种该热力管线用球墨铸铁管的制备工艺，通过此工艺制备的热力管线用球墨铸铁管无渣眼、砂眼、气孔、缩孔、缩松等铸造缺陷，气密性好，承压能力高，耐腐蚀能力强，大大延长了热力管线的使用寿命，热力管线建设与维护成本明显降低，还能避免高温蒸汽或热水泄漏引发的市政工程设施损坏与人身伤害事故。

Description

热力管线用球墨铸铁管、其制备工艺及应用 技术领域
本发明涉及一种热力管线用球墨铸铁管、其制备工艺及应用。
背景技术
目前我国城市和大型工矿企业所用的供热及热力管线，均采用外敷岩棉保温层的钢管铺设，但是这些管线存在以下问题：
(1)由于钢管的耐腐蚀能力差，特别是耐电腐蚀能力很差，因此管线的设计寿命都不太长，实际使用寿命往往不到10年，甚至有的4～5年钢管就被腐蚀透，造成高温高压蒸汽外泄，浪费大量的原材料资源和维修维护费用，特别是埋入地下或马路下面的供热和热力管线，维修时需要挖开路面，严重影响城市交通，不及时抢修还很容易造成高温蒸气大量泄漏，引发人员伤亡事故；
(2)钢管外敷的岩棉保温层厚度大，使外径增大，运输成本成倍提高；岩棉保温层的强度很低，易造成运输和安装过程的破损，造成损失；
(3)热力管线的钢管需要运到现场后焊接、试压等，操作麻烦，施工周期长，施工费用高，加重了市政工程建设投资与日常维修的负担；
(4)热力管线的钢管不具备抵御强地震破坏的能力，特别是经过几年腐蚀，管壁变薄后，管子的强度韧性不同程度的降低，此时当管子受到外力的拉伸、挤压、扭曲和重物砸碰时，很容易破坏甚至断裂。
因此，目前仍急需一种耐腐蚀能力强、使用寿命长、安装简便快捷、保温隔热效果好、且能抵御强地震破坏的热力管线用球墨铸铁管。
发明内容
本发明的其中一个目的在于提供一种热力管线用球墨铸铁管，以解决上述技术问题中的至少一个。
本发明的另一个目的在于提供上述热力管线用球墨铸铁管在热力管线中的应用，以解决上述技术问题中的至少一个。
本发明的另一个目的在于提供上述热力管线用球墨铸铁管的制备方法，以解决上述技术问题中的至少一个。
根据本发明的一个方面，提供了一种热力管线用球墨铸铁管，包括：一端设有承口、另一端设有插口的球墨铸铁管体和设于球墨铸铁管体外壁上的微晶保温层。
本发明热力管线用球墨铸铁管的管体以高韧性的铁素体基体球墨铸铁 为基材，耐腐蚀能力强、韧性高，外壁涂覆微晶材料制成的微晶保温层，其保温隔热性能好、强度及硬度高，因此，本发明的球墨铸铁管替代钢管用于热力管线铺设时，可使热力管线使用寿命大幅度延长，安全性大幅度提高。而且，微晶材料保温隔热性能好，应用于输送热水和蒸汽，可显著降低输送过程中的热损失，节能降耗。另外，由于微晶保温层的厚度在设置的较传统岩棉保温层的薄时即可达到更好的保温效果，例如设置为10～25mm即可，使得该涂层厚度比岩棉保温层的厚度降低了90％左右，从而使管子的安装外径明显缩小，且微晶保温层的强度、硬度高，不易损坏，方便管子的运输与安装。
本发明热力管线用球墨铸铁管具有承口和插口，连接时两个相邻球墨铸铁管体之间通过承口和插口连接，采用柔性机械密封接口，且承口和插口的连接处均设有耐高温材料制成的密封胶圈。本发明热力管线用球墨铸铁管连接时，其接口形式可以是T型密封接口、S型机械式密封接口、N I型机械式密封接口、K II型机械式密封接口或S II型机械式密封接口；连接时，无需现场焊接，安装施工简便快捷，管线铺设施工的速度可显著提高，管线建设和日常维修的综合成本可显著降低。此外，柔性承插连接的接口密封性能良好，可以使热力管线用球墨铸铁管具有可挠性和良好的伸缩性，因此可以抵抗地震施加给管子的拉伸、挤压、扭曲等外力，增强热力管线用球墨铸铁管道抵御强地震破坏的能力。由此，可以延长热力管线的使用寿命。
在一些实施方式中，本发明热力管线用球墨铸铁管连接时所用的制备密封胶圈的耐高温材料为丁腈橡胶、氢化丁腈橡胶、氯丁橡胶、三元乙丙橡胶、硅橡胶、氟橡胶、氟硅橡胶或聚四氟乙烯。当热力管线用球墨铸铁管应用于输送温度小于120℃的热水或蒸汽时，密封胶圈的材料优选丁腈橡胶、氢化丁腈橡胶、氯丁橡胶或三元乙丙橡胶，当热力管线用球墨铸铁管应用于输送温度大于120℃的热水或蒸汽时，密封胶圈的材料优选硅橡胶、氟橡胶、氟硅橡胶或聚四氟乙烯。
本发明所述微晶材料又称微晶玻璃或玻璃陶瓷，是指将加有形晶核剂(个别可不加)的特定组成的基础玻璃，通过控制结晶制成具有一种或多种微晶相和残余玻璃相的复合材料，具有防腐、耐热等优异性能，本发明实施例中，优选以废玻璃、粉煤灰、非金属矿等为主要原料，加入发泡剂、成核剂和外加剂等，经预热、熔融、发泡、析晶、退火等工艺制成的多孔微晶玻璃，即微晶泡沫玻璃。
在一些实施方式中，本发明热力管线用球墨铸铁管还可以包括设于球墨铸铁管体内壁上的内衬涂层。由此，可以提高热力管线用球墨铸铁管内 壁的耐腐蚀能力。
在一些实施方式中，上述内衬涂层的涂覆材料可以是环氧陶瓷或搪瓷，厚度优选为30～150μm。由此，不仅可以提高热力管线用球墨铸铁管的耐腐蚀能力，还能提高热力管线用球墨铸铁管的保温隔热能力。当热力管线用球墨铸铁管应用于输送温度小于120℃的热水或蒸汽时，内衬涂层的涂覆材料优选环氧陶瓷，当热力管线用球墨铸铁管应用于输送温度大于120℃的热水或蒸汽时，内衬涂层的涂覆材料优选搪瓷。
在一些实施方式中，本发明热力管线用球墨铸铁管还可以包括设于球墨铸铁管体的外壁上的锌涂层，且微晶保温层设于球墨铸铁管体的锌涂层上，锌涂层厚度优选不小于40μm。由此，可以提高热力管线用球墨铸铁管的耐腐蚀能力。
在一些实施方式中，本发明热力管线用球墨铸铁管还可以包括外防护涂层，外防护涂层可以涂覆于锌涂层上且位于锌涂层和微晶保温层之间(即微晶保温层涂覆于外防护涂层上)或涂覆于微晶保温层上(即位于微晶保温层外)。外防护涂层的涂覆材料可以为沥青漆、环氧沥青漆、聚氨酯或聚脲。
根据本发明的另一个方面，提供了上述热力管线用球墨铸铁管在热力管线中的应用。
本发明提供的热力管线用球墨铸铁管与现有热力管线用钢管相比，具有耐腐蚀能力强、使用寿命大大延长、韧性高、施工安装快捷、保温隔热效果好等优点，可以应用于铺设热力管线，降低热力管线建设成本，以及抵御强地震等地质灾害的破坏，确保城市居民生活质量和提高城市抗震减灾能力。
根据本发明的另一个方面，提供了上述热力管线用球墨铸铁管的制备工艺，包括如下步骤：
S1、铁液的制备：将炉料熔炼成原铁液并过热至不小于1500℃，根据铁液化学成分的设定值调整原铁液的化学成分组成；
S2、球化处理：利用球化剂对已调整好化学成分组成的原铁液进行球化处理，并将球化处理后的铁液注入球墨铸铁专用浇注电炉，利用球墨铸铁专用浇注电炉将铁液的浇注温度保持不小于铁液的临界温度；
S3、涂料热模法离心铸造：对喷涂的绝热涂料已干燥的热管模完成上承口芯后，驱动管模转动，并在管模转动的离心力达到离心力设定值时，将球墨铸铁专用浇注电炉中的铁液经定量包注入管模中，并在浇注过程中对铁液进行随流孕育处理和对管模进行冷却处理，浇注完成后，待凝固成形的球墨铸铁管毛坯冷却到设定温度时，将球墨铸铁管毛坯从管模中拔出；
S4、退火：对球墨铸铁管毛坯进行退火处理；
S5、精整：对退火后的球墨铸铁管毛坯进行精整加工；
S6、气密性实验：根据待铺设热力管线对球墨铸铁管的压力要求，即待铺设热力管线的设计输送压力设定试验压力，对精整加工后的球墨铸铁管毛坯进行气密性试验，其中，试验压力不小于待铺设热力管线的设计输送压力的1.20倍；
S7、微晶保温层的制备：在气密性试验合格的球墨铸铁管毛坯的外壁涂覆微晶材料，制备微晶保温层，即得热力管线用球墨铸铁管。
首先，本发明的制备工艺中，在铁液制备时是将熔炼出的原铁液过热到了1500℃及以上，由于在铁液制备阶段将原铁液过热至不小于1500℃的温度，可以促使碳发挥对铁液的脱氧净化作用，达到对原铁液的预球化处理效果，从而有利于石墨的球化；此外，在本发明的制备工艺中，还根据铁液化学成分的设定值对原铁液进行了化学成分组成的调整，由于球墨铸铁管口径规格及相应壁厚的不同，使不同规格的球墨铸铁管浇注后在凝固时间与冷却速度上存在差别，为防止球墨铸铁管的铸态毛坯出现游离渗碳体，对铁液碳当量的控制会根据不同口径、壁厚的球墨铸铁管的要求加以区别，给出不同的化学成分和碳当量的设定值，并据此进行调整；加之内壁喷涂了绝热涂层的热管模可以避免铁液激冷，从而能够避免在离心浇注过程中球墨铸铁管的铸态毛坯出现游离渗碳体，形成白口组织。
其次，本发明中是对温度在1500℃及以上且调整了化学成分组成的原铁液进行球化处理，并且将球化处理后的铁液注入到了球墨铸铁专用浇注电炉中(本发明实施例中提及的球墨铸铁专用浇注电炉为专利CN101658901B公开的浇注电炉设备)，将球化处理后的铁液注入球墨铸铁专用浇注电炉中，一方面可以进一步对铁液进行脱硫、脱氧，另一方面可以稳定铁液中的残留Mg量，从而避免了铁液球化衰退，保证了制得的球墨铸铁管的球化级别，并稳定了其韧性、强度等机械性能；同时将铁液的浇注温度始终保持在不小于铁液的临界温度(即1420～1480℃)的温度范围，使铁液始终为非氧化性的洁净铁液，避免了球墨铸铁管在离心浇注过程中产生砂眼、渣眼等铸造缺陷，这保证了铁液的浇注温度始终维持在稳定的高温水平，有利于消除气孔、砂眼、渣眼等夹杂缺陷，高温还使铁液的流动性得以大幅度提高，避免了产生带有冷隔、浇不足等缺陷的球墨铸铁管废品。
再次，本发明制备工艺中，采用涂料热模法离心铸造工艺制备球墨铸铁管毛坯，并且是在管模转动的离心力达到离心力设定值时，再开始离心浇注过程，这样的制备工艺，使得能够根据需求在适合的离心力下启动浇 注过程，从而控制制备出的球墨铸铁管毛坯的缩松情况。例如为了克服球墨铸铁凝固时的缩松缩孔倾向产生的内部疏松，离心浇注过程采用高转速大离心力的浇注工艺，这保证了浇注用的高温铁液始终在巨大离心力的作用下逐渐凝固(本发明实施例中优选在管模转动离心力达到80～100G时开始浇注，比德·拉沃法的管模转动离心力40～50G提高1倍左右)，使得高温铁液在管模内始终在巨大离心力的作用下向管模内壁挤压，而不能向管模中心方向自由膨胀，实现了球墨铸铁铁液在粥状凝固及石墨化膨胀重合阶段的压力自补缩，从而保证了球墨铸铁管组织致密，厚壁部位厚度均匀且无缩孔、缩松等铸造缺陷，还保证了壁厚非常均匀与致密，无夹杂，因此制得的球墨铸铁管气密性好。此外，铁液合适的碳当量加上瞬时孕育，使制得的铸态球墨铸铁管毛坯的基体组织无游离渗碳体。
另外，本发明采用涂料热模法离心铸造工艺，绝热涂料喷涂前需先将管模预热至200～220℃，可保证喷涂时绝热涂料能迅速干透，在铁液注入管模时可避免由于绝热涂料起爆而导致管模被铁液烧蚀损坏，从而造成生产中断事故。
然后，因为球墨铸铁管毛坯从管模中拔出后，由于管体温度高，可能会在冷空气中发生正火而产生大量珠光体，造成球墨铸铁管毛坯的延伸率下降，所以本发明制备工艺中，球墨铸铁管毛坯从管模中拔出后即进行消除珠光体的退火处理，从而获得基体组织以铁素体为主，珠光体含量低，延伸率好的球墨铸铁管。
最后，在对退火后的球墨铸铁管进行精整加工后，为确保球墨铸铁管的气密性，同时避免管体上的涂层对球墨铸铁管气密性试验结果真实性的影响，本发明制备工艺中，在制备微晶保温层之前先对精整加工后的球墨铸铁管进行气密性试验，且试验压力设置为不小于待铺设热力管线的输送压力的1.20倍，从而确保了球墨铸铁管气密性的高可靠性。
本发明实施例的铁液制备过程中，对S含量不大于0.12％的铁液均可以不经炉外脱硫处理直接注入感应保温电炉中，在调节原铁液的化学成分组成时，也不需要刻意对S含量进行控制，这是因为：1)球化处理的脱硫效果很好，对硫含量不大于0.2％、温度为1500℃的高温、高硫铁液都能处理成合格球墨铸铁铁液，并且可将球化后铁液的硫含量脱至小于0.01％的水平；2)球墨铸铁专用浇注电炉允许在球化处理后不必扒渣处理，而直接将球化处理包内的MgS渣和MgO渣直接倾入炉内，在直流电解的作用下将渣中的S2-和O2-阴离子脱掉，渣中Mg2+阳离子在接触到作为阴极的铁液时被还原成Mg重新进入铁液，与Mg从铁液中的逃逸损失形成动态平衡，稳定了铁液中的Mg残留量，避免了球化衰退，并使MgS渣和MgO渣化 害为利，实现了金属镁的循环利用。而这也简化了生产工艺，提高了制备出的球墨铸铁管的机械性能和质量的一致性。
本发明实施例中，可以选用生铁、废钢、铁屑、含碳免烧砖和回炉料(主要为管件或其它铸件的浇冒口和少量球墨铸铁管与管件的不合格品)中的一种或多种作为炉料，根据不同炉料的化学成分组成、熔炼过程中化学成分可能存在的损耗和铁液化学成分的设定值进行配料，使熔炼后的原铁液化学成分的组成接近其设定值，简化铁液化学成分调整的工艺处理。
本发明实施例中，将炉料熔炼成原铁液的工艺可以采用冲天炉-感应电炉双联熔炼工艺，也可以采用高炉生铁铁液进入变频无芯感应电炉调整化学成分的“短流程”熔炼工艺。本发明实施例中将原铁液过热至不小于1500℃，可以是通过利用冲天炉对炉料进行熔炼，在熔炼后原铁液温度直接达到1500℃及以上(即原铁液的出铁温度不小于1500℃)实现的，也可以是通过采用其他熔炼方式，将熔炼后的原铁液在感应电炉中进行过热，使原铁液温度达到1500℃及以上(即，感应电炉保温温度设定在1500℃及以上)实现的。
本发明实施例浇注过程中对铁液进行随流孕育处理可以促进石墨化、防止浇注过程中铁液球化衰退，避免游离渗碳体的产生。本发明实施例中随流孕育处理所用孕育剂为常规孕育剂，可以是硅铁孕育剂、硅钡孕育剂中的一种或其组合，优选75FeSi孕育剂，用量为铁液重量的0.2～0.4％。
本发明实施例中，浇注过程中对管模进行的冷却处理优选为喷淋水冷却处理。凝固成形的球墨铸铁管毛坯在冷却过程中，可继续对管模进行冷却处理；对凝固后冷却速度相对较慢的大口径厚壁球墨铸铁管，为加速其冷却速度，也可以对管模内已凝固的球墨铸铁管毛坯采取吹风或喷水雾措施。
本发明实施例中对已调整好化学成分组成的原铁液进行球化处理的工艺优选是对铁液碳当量不发生影响且脱硫效果显著的喂丝法或转包法。其中，需通过调整球化剂用量，使球化处理后铁液中Mg的残留量不小于0.035％。
本发明实施例中，精整加工包括承口内磨、插口外磨、内壁修磨、切管、倒角，以及S型、N型等密封接口球墨铸铁管的法兰钻孔。承口内磨、插口外磨是为了提高这些部位的表面光洁度，从而使其在球墨铸铁管连接过程中与密封胶圈配合时可以进一步提高球墨铸铁管的密封压力。
当热力管线用球墨铸铁管的输送压力没有明确规定时，气密性试验的试验压力应不小于5.0MPa。为了确保产品的高可靠性，本发明实施例中，球墨铸铁管生产线上的气密性试验一般均采用试验压力不小于5.0MPa、保 压时间不小于20秒的检验方式，试验合格的球墨铸铁管可以根据需求继续完成后续的内外涂覆、终检验、喷商标和喷数字化标记等工序，然后打捆入库成为热力管线用球墨铸铁管成品。
在一些实施方式中，离心力设定值不小于80G，且不高于110G。由于在离心力较小时进行浇注会导致缩松、缩孔缺陷，而离心力过大时管模会因转速过高而使管模及设备的稳定性和设备安全性变差，因此，将离心力的设定转速设置为80G～100G(不同口径的球墨铸铁管离心力取值不同，其中，小口径管取值接近上限值，大口径管取值接近下限值)，可以在避免缩松、缩松缺陷的同时，也保证设备与管模运转的稳定性，进而保证生产出的球墨铸铁管的质量和保证生产安全。
在一些实施方式中，管模内凝固成形的球墨铸铁管毛坯冷却到的设定温度可以为760～830℃。拔管温度高于850℃时，球墨铸铁管强度不足，此温度下拔管易导致球墨铸铁管在拔管过程中变形，而当拔管温度低于共析点的温度(约730℃)时，球墨铸铁管会发生共析转变，导致晶格转变引发体积跃迁，使球墨铸铁管膨胀造成拔管困难。因此，拔管温度控制在760～830℃可以防止拔管困难和避免球墨铸铁管变形。
在一些实施方式中，步骤S2中，利用球墨铸铁专用浇注电炉将铁液的浇注温度保持不小于铁液的临界温度，可以是通过将球墨铸铁专用浇注电炉中的保温温度设定为1430～1480℃实现的。将球墨铸铁专用浇注电炉中的保温温度设定为1430～1480℃，可以使球墨铸铁专用浇注电炉中的铁液注入管模中时，保持铁液为非氧化性的洁净铁液，由此既可以保证铁液有足够的流动性，又能保证浇注结束后管模内的铁液还能在高离心力作用下仍保持一段液态时间，从而避免球墨铸铁管产生浇不足、冷隔、缩松、缩孔、砂眼、渣眼、气孔、壁厚不均等铸造缺陷和废品，制得的球墨铸铁管管壁致密、均匀、无缺陷、气密性好，可用于热力管线的铺设。
在一些实施方式中，球化剂可以为镁锭，铁液化学成分的设定值可以为：C为3.3～3.7％、Si为2.2～2.8％，
根据对铁液化学成分的设定值调整原铁液的化学成分组成包括：
基于上述设定值调整原铁液中的碳和硅的质量分数，以使原铁液中碳的质量分数不高于3.7％，且使碳当量达到共晶成分(即碳当量达4.26％)或使碳当量达到4.1％～4.3％。由此，有利于本发明涂料热模法离心浇铸工艺处理过程中球墨铸铁管成形和获得基体组织中不含游离渗碳体的球墨铸铁管毛坯，在保证球墨铸铁管毛坯质量的同时，还能简化后续的退火工艺。同时，采用镁锭作为球化剂，一方面可以大幅度降低球化剂成本，另一方面也避免了稀土硅铁镁球化剂中的Si等元素对铁液成分的影响和干扰，还 可以节约大量宝贵的稀土元素。
在一些实施方式中，步骤S2中，可以采用转包法对已调整好化学成分组成的原铁液进行球化处理，其中，镁锭球化剂的用量为原铁液重量的0.10～0.20％。采用转包法，球化处理效果好，且球化剂在转包的反应室中汽化的速度受控而不会发生爆炸。球化剂的用量为原铁液重量的0.10～0.15％，即可保证球化处理完成后铁液中Mg含量不小于0.04％，达到理想的球化效果，当原铁液中S含量大于0.12％时，球化剂的用量可根据需要增加到原铁液重量的0.18～0.20％。
在一些实施方式中，在退火处理之前还可以包括如下步骤：
对制备的球墨铸铁管毛坯的外壁进行清刷、吹洗；
对外壁清刷、吹洗干净后的球墨铸铁管毛坯进行超声波无损检测，确定球墨铸铁管毛坯的球化级别是否合格以及球墨铸铁管毛坯管体是否有铸造缺陷和其它损伤缺陷。
如果浇注时注入管模的铁液的实际温度足够高(例如不低于1400℃)，球墨铸铁管毛坯从管模中拔出时，喷涂在管模内壁的绝热涂料会几乎全部挂在球墨铸铁管毛坯的外壁被带出，因此，需要对球墨铸铁管毛坯外壁进行清刷，再进行吹洗，将球墨铸铁管毛坯外壁残留的绝热涂料清洗干净。吹洗优选采用高压蒸汽对球墨铸铁管外壁进行吹洗。
刷管与吹洗完成后，需要对球墨铸铁管毛坯进行超声波无损检测，确定球墨铸铁管毛坯的球化级别是否合格，以及确定球墨铸铁管毛坯管体是否有渣眼、皮下气孔、砂眼、冷隔、重皮、缩孔、缩松等铸造缺陷和损伤裂纹等其他损伤缺陷。球化级别合格且无铸造缺陷和损伤裂纹的球墨铸铁管毛坯记为检验合格，而不合格的球墨铸铁管毛坯记为检验不合格，直接作为炉料回炉重熔。采用超声波对球墨铸铁管毛坯进行检测，可快速完成球墨铸铁管的无损检测，在不损害或不影响球墨铸铁使用性能的前提下，全面检测球墨铸铁管是否存在铸造缺陷和内部损伤缺陷；并且，将超声波用于测定球墨铸铁管的球化级别是否合格，其检测效率远高于传统的金相检测等方法，甚至还可以定量判定球墨铸铁管基体的不同组份及其含量；此外，采用超声波对球墨铸铁管毛坯进行检测，可以实现单一规格的大批量球墨铸铁管的连续在线检测，有利于实现球墨铸铁管生产线的自动化。
在一些实施方式中，退火处理的退火温度可以为780～850℃，退火时间为20～40min。与传统德·拉沃法退火工艺相比，本发明具有以下明显优势：1)本发明制备工艺制得的球墨铸铁管毛坯的基体中不含游离渗碳体，只是拔管后由于管体在空气中发生正火，此时发生的共析转变会使珠光体超标，因此，只需要对球墨铸铁管进行消除珠光体的低温退火，即可获得铁素体 含量合格的高延伸率、高韧性的球墨铸铁管，这样可以明显降低退火处理的温度(从传统的980～1050℃降低到780～850℃)；2)本发明退火工艺取消了消除莱氏体的高温退火阶段和退火窑中间的快速水冷(或风冷)结构，简化了隧道式退火窑的设备结构，缩短了退火时间，降低了退火处理的能耗，延长了退火窑中耐火材料的寿命；3)避免了球墨铸铁管由于过烧而变形(即球墨铸铁管变椭圆)的风险和废品损失；4)由于球墨铸铁管壁厚高度均匀，保证了退火过程的平稳流畅，可完全避免因个别球墨铸铁管局部壁厚过薄在加热后发生断裂带来的严重后果(断裂的球墨铸铁管堵塞在退火窑中，会引发连续式隧道退火窑设备故障，甚至引发停产事故)。
在一些实施方式中，在退火处理之后、精整加工之前还包括如下步骤：
对退火后的球墨铸铁管毛坯的外表面进行喷锌。
本发明实施例中，喷锌可以是通过热喷锌、冷涂锌等方式实现，锌层厚度优选不小于40μm。对退火后的球墨铸铁管毛坯的外表面进行喷锌，有利于提高球墨铸铁管表面耐受电腐蚀的能力，同时，还可以避免后续球墨铸铁管毛坯在进行气密性试验过程中，由于球墨铸铁管毛坯管体与水接触而导致管体表面生锈。
在一些实施方式中，在步骤S6之后还可以包括如下步骤：在气密性合格的球墨铸铁管毛坯的内壁涂覆内衬材料制备内衬涂层；
在步骤S7中是在内壁涂覆内衬涂层后的球墨铸铁管毛坯的锌涂层上涂覆微晶材料制备的微晶保温层。
由此，可以减小流体输送的阻力，提高球墨铸铁管的耐腐蚀能力，延长球墨铸铁管的使用寿命。
在一些实施方式中，内衬涂层的涂覆材料可以是环氧陶瓷或搪瓷。由此，不仅可以提高热力管线用球墨铸铁管内壁的耐腐蚀能力，还可以提高热力管线用球墨铸铁管的保温隔热能力。根据输送的热水或蒸汽的温度的不同，可以选择不同的涂覆材料，喷涂方式和涂层厚度也可以根据不同的涂覆材料按需设置。
附图说明
图1为本发明一实施方式的热力管线用球墨铸铁管的结构图；
图2为图1所示热力管线用球墨铸铁管管体的剖面图；
图3为图1所示热力管线用球墨铸铁管S II型机械式密封接口的结构图。
具体实施方式
下面结合附图对本发明作进一步详细的说明。
实施例1
图1和图2示意性地显示了根据本发明的一种实施方式的热力管线用球墨铸铁管。如图1所示，该热力管线用球墨铸铁管包括一端设有承口11、另一端设有插口12的球墨铸铁管体1和设于球墨铸铁管体1外壁上的微晶保温层3。
微晶保温层3由微晶材料涂覆制成，本实施例中，微晶材料优选微晶泡沫玻璃，微晶保温层3的厚度优选为15mm。
本实施例中，热力管线用球墨铸铁管还包括内衬涂层2和锌涂层4，其中，内衬涂层2涂覆于球墨铸铁管体1内壁，输送介质温度在≯120℃时，涂覆材料优选为环氧陶瓷；输送介质温度＞120℃时，涂覆材料优选为搪瓷，涂层厚度为100μm；锌涂层4设于球墨铸铁管体1的外壁上且位于球墨铸铁管体1外壁和微晶保温层3之间(即锌涂层4涂覆于球墨铸铁管体1的外壁上，微晶保温层3涂覆于锌涂层4上)，锌涂层4厚度为40μm。
如图2所示，本实施例中，热力管线用球墨铸铁管球墨铸铁管体1外壁由里向外依次涂覆有锌涂层4和微晶保温层3，球墨铸铁管体1内壁涂覆有内衬涂层2。
本实施例中，热力管线用球墨铸铁管的承口处不涂覆内衬涂层2、插口处不涂覆微晶保温层3。热力管线用球墨铸铁管连接时，相邻的热力管线用球墨铸铁管之间内衬涂层2和微晶保温层3可以连续过渡，保证了热力管线用球墨铸铁管连接后，整个管道内衬涂层2和微晶保温层3的连续性。
本实施例中，热力管线用球墨铸铁管连接时优选采用S II型机械式密封接口。如图3所示，本实施例中，热力管线用球墨铸铁管的插口12外表面上设置有止退槽121，管子连接时，插口12插入待连接的热力管线用球墨铸铁管的承口11内，插口12上设有压兰63，压兰63通过螺栓61和螺母62与承口11边缘固定连接，承口11内表面上设有嵌入槽，嵌入槽内从嵌入槽端口往内依次嵌入有密封胶圈64、隔离圈65和锁环66，压兰63的底端压住密封胶圈64，锁环66的底端压在止退槽121上，密封胶圈64、隔离圈65与锁环66三者紧挨在一起并位于承口11内壁和插口12外壁之间，且密封胶圈64、隔离圈65与锁环66组合在一起与承口11内壁和插口12外壁形成过盈配合，达到密封的目的。锁环66和止退槽121的配合使用，使接口具有较好的防脱滑能力。
密封胶圈64的材料可以是丁腈橡胶、氢化丁腈橡胶、氯丁橡胶、三元乙丙橡胶、聚氨酯、硅橡胶、氟橡胶、氟硅橡胶或聚四氟乙烯。本实施例中，密封胶圈64的材料优选为聚四氟乙烯材料。
实施例2热力管线用球墨铸铁管的制备
结构如实施例1所示，规格为DN300×6000mm的热力管线用球墨铸铁管的制备方法，包括如下步骤：
S1、铁液制备：铁液化学成分的设定值为：C：3.4～3.7％、Si：2.4～2.5％，选用生铁、废钢和回炉料作为炉料，配料后炉料在40t/h大型长炉龄富氧冲天炉中熔炼成原铁液后经虹吸式渣铁分离器将渣铁分离，原铁液由出铁口注入60t大容量有芯感应保温电炉中，感应保温电炉的设定温度为1500℃并保持恒温，根据铁液化学成分的设定值设定冲天炉熔炼工艺，使铁液的出铁温度大于1500℃，同时保证原铁液的化学成分在设定值范围内，若超出设定值范围则将使用10t变频无芯感应电炉熔化铁液并注入60t大容量有芯感应保温电炉中进行调整，以确保上述铁液化学成分达到设定值，以使原铁液中碳的质量分数不高于3.7％，且通过调整硅的质量分数使铁液碳当量基本为共晶成分(即CE＝4.2～4.3％)；
S2、球化处理：将原铁液重量0.12％的镁锭放入1.5t转包的反应室，将感应保温电炉的原铁液注入转包中进行球化处理，球化处理后铁液中Mg残留量≥0.04％，铁液中化学成分组成包括：C：3.2～3.6％、Si：2.2～2.5％、Mn：＜0.3％、P：＜0.07％、S：＜0.01％；无需扒渣操作，将转包内球化处理后的铁液由5t旋转叉车运载直接注入8t球墨铸铁专用浇注电炉，为使铁液的浇注温度保持不小于铁液的临界温度，球墨铸铁专用浇注电炉中设定的保温温度为1440℃；
S3、涂料热模法离心铸造：在已经预热至200℃、且内壁清刷干净的热管模内壁喷涂绝热涂料，待绝热涂料彻底干燥后，将管模移至上芯工位，由机器人将承口芯安装在管模承口处；上芯完成后，将管模移至在离心机组预转工位，预转至设定转速的90％时，移至离心浇注工位(管模在离心机组预转工位预转至设定转速的80～90％时再移至离心浇注工位，可以节省离心浇注工位提升管模转速的时间，提高生产效率)；移至离心浇注工位后，迅速将管模转速提升到最大值(离心力达到100G)，随即开始浇注，将球墨铸铁专用浇注电炉中的温度为1440℃的铁液经定量包注入管模中，同时加铁液重量0.3％的75FeSi孕育剂进行随流孕育，并且同时对管模进行淋水冷却；铁液凝固成形，将管模至冷却工位(可继续对管模喷淋水冷却，同时可向管模内喷水雾，加快红热球墨铸铁管毛坯的降温)，随后管模移至拔管工位，待管模内球墨铸铁管毛坯冷却至830℃以下时，拔管机将球墨铸铁管毛坯从管模中拔出；拔出球墨铸铁管毛坯的空管模，再依次经过清刷工位、喷涂工位等，将管模承口端内壁残余涂料清刷干净，重新喷涂绝热涂料并干燥后，再次循环用于球墨铸铁管的制备；
其中，绝热涂料是水基涂料，主要由硅藻土和膨润土按重量比(18～20):1配置而成，涂层厚度可以是0.4～0.8mm。本实施例中，水基硅藻土涂料中硅藻土和膨润土按重量比20：1配置，涂层厚度0.5mm。
承口芯采用冷芯盒工艺，采用自动化高效射芯机制芯。
S4、刷管与吹洗：利用刷管机对从管模中拔出的球墨铸铁管毛坯外壁带出的绝热涂料进行清刷及高压蒸气吹洗，彻底清除粘在球墨铸铁管毛坯外壁上的残余绝热涂料；
S5、无损检测：刷管与吹洗完成后，对外壁清刷、吹洗干净后的球墨铸铁管毛坯进行超声波无损检测，判定铸管毛坯的球化级别、有无铸造缺陷或其他损伤缺陷，检验合格的球墨铸铁管进入下一工序，判断为废品的球墨铸铁管作为炉料回炉重熔(通常情况下此处废品率不超过0.2％)；
S6、低温退火：经检验合格的球墨铸铁管毛坯转入隧道式退火窑退火，退火温度控制在780～850℃，退火时间30min，出窑温度为680℃；
S7、喷锌：利用喷锌机对退火后的球墨铸铁管毛坯的外表面进行热喷锌，锌层厚度为40μm；
S8、精整加工：对喷锌完成后的球墨铸铁管毛坯进行精整加工，包括：磨承口与插口、磨内壁、切环倒角、法兰钻孔等；
S9、气密性试验：对精整加工后的球墨铸铁管毛坯进行气密性试验，试验压力为5.0MPa，保压时间＞20s；经气密性试验合格的球墨铸铁管进入下一工序，判断为废品的球墨铸铁管作为炉料回炉重熔(通常情况下此处废品率不超过0.1％)；
S10、内衬涂层制备：在气密性试验合格的球墨铸铁管毛坯内壁涂覆内衬涂层，输送介质温度在≯120℃时，涂覆材料为环氧陶瓷；输送介质温度＞120℃时，涂覆材料为搪瓷，涂层厚度为100μm；
S11、微晶保温层制备：在内壁涂覆内衬涂层后的球墨铸铁管毛坯的锌涂层上涂覆微晶泡沫玻璃，制备微晶保温层，涂层厚度为15mm，之后再进行终检验，对合格品喷商标和质量跟踪数字码，即得热力管线用球墨铸铁管成品。
经检测，本实施例制得的热力管线用球墨铸铁管无砂眼、渣眼、气孔、冷隔、缩松、缩孔等铸造缺陷，经本体取样进行金相和机械性能检验，球化级别高且非常稳定，基体组织以铁素体为主，珠光体量在P15～P5之间，延伸率为16～24％，抗拉强度为420～470MPa。
在一些实施例中，本发明热力管线用球墨铸铁管的生产线可以实现自动化或半自动化，如：(1)铁液制备过程中，冲天炉可以由专家系统智能 控制，实现炉子工况和熔炼参数的全程自动控制；(2)球化处理过程中，转包内的铁液可以在旋转叉车上完成球化处理、铁液转运、向专用浇注电炉内倾倒等动作；(3)绝热涂料制备过程中，可以由离心机组自带的涂料自动化配置搅拌系统加工成合格涂料随时备用；(4)承口砂芯的安装可以通过机器人或者机械手进行等，由此，有利于节省人力物力，提高球墨铸铁管的生产效率。
以上所述的仅是本发明的一些实施方式。对于本领域的普通技术人员来说，在不脱离本发明创造构思的前提下，还可以做出若干变形和改进，这些都属于本发明的保护范围。

Claims (18)

  1. 热力管线用球墨铸铁管，其特征在于，包括：一端设有承口(11)、另一端设有插口(12)的球墨铸铁管体(1)和设于所述球墨铸铁管体(1)外壁上的微晶保温层(3)。
  2. 根据权利要求1所述的热力管线用球墨铸铁管，其特征在于，还包括设于所述球墨铸铁管体(1)内壁上的内衬涂层(2)。
  3. 根据权利要求2所述的热力管线用球墨铸铁管，其特征在于，所述内衬涂层(2)的涂覆材料为环氧陶瓷或搪瓷。
  4. 根据权利要求2所述的热力管线用球墨铸铁管，其特征在于，还包括设于所述球墨铸铁管体(1)的外壁上的锌涂层(4)，且所述微晶保温层(3)设于所述球墨铸铁管体(1)的锌涂层(4)上。
  5. 根据权利要求2～4任一项所述的热力管线用球墨铸铁管，其特征在于，所述内衬涂层(2)的厚度为30～150μm。
  6. 根据权利要求5所述的热力管线用球墨铸铁管，其特征在于，包括多个所述球墨铸铁管体(1)，每两个相邻球墨铸铁管体(1)之间通过承口(11)和插口(12)连接，且承口(11)和插口(12)的连接处设有耐高温材料制成的密封胶圈。
  7. 根据权利要求6所述的热力管线用球墨铸铁管，其特征在于，所述耐高温材料为丁腈橡胶、氢化丁腈橡胶、氯丁橡胶、三元乙丙橡胶、硅橡胶、氟橡胶、氟硅橡胶或聚四氟乙烯。
  8. 根据权利要求1～7任一项所述的热力管线用球墨铸铁管在热力管线中的应用。
  9. 权利要求1所述的热力管线用球墨铸铁管的制备工艺，其特征在于，包括以下步骤：
    S1、铁液的制备：将炉料熔炼成原铁液并过热至不小于1500℃，根据铁液化学成分的设定值调整原铁液的化学成分组成；
    S2、球化处理：利用球化剂对已调整好化学成分组成的原铁液进行球化处理，并将球化处理后的铁液注入球墨铸铁专用浇注电炉，利用所述球墨铸铁专用浇注电炉将铁液的浇注温度保持不小于铁液的临界温度；
    S3、涂料热模法离心铸造：对喷涂的绝热涂料已干燥的热管模完成上承口芯后，驱动管模转动，并在管模转动的离心力达到离心力设定值时，将球墨铸铁专用浇注电炉中的铁液经定量包注入管模中，并在浇注过程中对铁液进行随流孕育处理和对管模进行冷却处理，浇注完成后，待凝固成形的球墨铸铁管毛坯冷却到设定温度时，将球墨铸铁管毛坯从管模中拔出；
    S4、退火：对所述球墨铸铁管毛坯进行退火处理；
    S5、精整加工：对退火后的球墨铸铁管毛坯进行精整加工；
    S6、气密性实验：根据待铺设热力管线的设计输送压力设定球墨铸铁管毛坯的试验压力，对精整加工后的球墨铸铁管毛坯进行气密性试验，其中，试验压力不小于待铺设热力管线的设计输送压力的1.20倍；
    S7、微晶保温层的制备：在气密性试验合格的球墨铸铁管毛坯的外壁涂覆微晶材料，制备微晶保温层，即得热力管线用球墨铸铁管。
  10. 根据权利要求9所述的热力管线用球墨铸铁管的制备工艺，其特征在于，离心力的所述设定转速不小于80G，且不高于110G。
  11. 根据权利要求10所述的热力管线用球墨铸铁管的制备工艺，其特征在于，成形的球墨铸铁管毛坯冷却到的所述设定温度为760～830℃。
  12. 根据权利要求9所述的热力管线用球墨铸铁管的制备工艺，其特征在于，步骤S2中，利用所述专用浇注电炉将浇注温度保持不小于铁液的临界温度，是通过将球墨铸铁专用浇注电炉中的保温温度设定为1430～1480℃实现的。
  13. 根据权利要求9～12任一项所述的热力管线用球墨铸铁管的制备工艺，其特征在于，所述球化剂为镁锭，所述铁液化学成分的设定值为：C为3.3～3.7％、Si为2.2～2.8％，
    所述根据对铁液化学成分的设定值调整原铁液的化学成分组成包括：
    基于上述设定值调整原铁液中的碳和硅的质量分数，以使原铁液中碳的质量分数不高于3.7％，且使碳当量达到共晶成分或使碳当量达到4.1％～4.3％。
  14. 根据权利要求13所述的热力管线用球墨铸铁管的制备工艺，其特征在于，步骤S2中，采用转包法对已调整好化学成分组成的原铁液进行球化处理，其中镁锭球化剂的用量为原铁液重量的0.10～0.20％。
  15. 根据权利要求14所述的热力管线用球墨铸铁管的制备工艺，其特征在于，在所述退火处理之前还包括如下步骤：
    对制备的球墨铸铁管毛坯的外壁进行清刷、吹洗；
    对外壁清刷、吹洗干净后的球墨铸铁管毛坯进行超声波无损检测，确定球墨铸铁管毛坯的球化级别是否合格以及球墨铸铁管毛坯管体是否有铸造缺陷和其它损伤缺陷。
  16. 根据权利要求15所述的热力管线用球墨铸铁管的制备工艺，其特征在于，所述退火处理的退火温度为780～850℃，退火时间为20～40min。
  17. 根据权利要求16所述的热力管线用球墨铸铁管的制备工艺，其特征在于，在所述退火处理之后、精整加工之前还包括如下步骤：
    对退火后的球墨铸铁管毛坯的外表面进行喷锌。
  18. 根据权利要求17所述的热力管线用球墨铸铁管的制备工艺，其特征在于，在步骤S6之后还包括如下步骤：在气密性合格的球墨铸铁管毛坯的内壁涂覆内衬材料制备内衬涂层；
    在步骤S7中是在内壁涂覆内衬涂层后的球墨铸铁管毛坯的锌涂层上涂覆微晶材料制备的微晶保温层。
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