US3850699A - Process for manufacturing hot-dip aluminized pearlitic malleable cast iron and black heart malleable cast iron products - Google Patents

Process for manufacturing hot-dip aluminized pearlitic malleable cast iron and black heart malleable cast iron products Download PDF

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US3850699A
US3850699A US00288161A US28816172A US3850699A US 3850699 A US3850699 A US 3850699A US 00288161 A US00288161 A US 00288161A US 28816172 A US28816172 A US 28816172A US 3850699 A US3850699 A US 3850699A
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cast iron
castings
malleable
temperature
pearlitic
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US00288161A
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English (en)
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A Gierek
L Bajka
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Politechnika Slaska im Wincentego Pstrowskiego
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Politechnika Slaska im Wincentego Pstrowskiego
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    • 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
    • C21D5/00—Heat treatments of cast-iron
    • C21D5/04—Heat treatments of cast-iron of white cast-iron
    • C21D5/06—Malleabilising
    • C21D5/14—Graphitising
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/12—Aluminium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/70—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using melts
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12736—Al-base component
    • Y10T428/1275—Next to Group VIII or IB metal-base component
    • Y10T428/12757—Fe

Definitions

  • ABSTRACT A process for manufacturing hot-dip aluminized pearlitic malleable iron castings with lamellar or coagulated cementite and also black heart malleable iron castings by carrying out the graphitizing annealing simulta' neously with the annealing giving a homogeneous coating on aluminized castings.
  • SHEET 2 BF 3 PROCESS FOR MANUFACTURING HOT-DIP ALUMINIZED PEARLITIC MALLEABLE CAST IRON AND BLACK HEART MALLEABLE CAST IRON PRODUCTS The invention relates to a process for manufacturing hot-dip aluminized pearlitic malleable iron castings with lamellar or coagulated cementite and also black heart malleable iron castings. These products are provided for working at elevated temperatures and in highly corrosive conditions.
  • the production of hot-dip aluminized iron castings comprises two separate technical processes, namely a process for producing iron castings and a process for hot-dip aluminizing these iron castings.
  • One of the known processes for producing pearlitic malleable iron castings with lamellar or spheroidal cementite is based on the successive operations of heat treatment of the previously produced white cast iron castings being as a rule hypo-eutectic.
  • the white cast iron castings are annealed at temperatures in the range of 900 1000C for 8 16 hours in an inert atmosphere in order to graphitize them, effecting thereby decomposition of free cemetite and isolation of the temper carbon.
  • the castings together with the furnace are cooled to the range of temperatures of the eutectoid transformation i.e. from 850 730C and subsequently fast cooled to the ambient temperature.
  • the graphitizing process at temperatures from 900 lOOC may be preceded by a preliminary quenching of the white cast iron castings or by preliminary quenching with tempering. Applying the operation of the preliminary quenching or quenching combined with tempering greatly increases the quantity of graphitization nuclei causing thereby the refinement of temper carbon in the structure of the matrix of the pearlitic malleable cast iron or malleable black heart cast iron which greatly increases the mechanical properties of these cast irons.
  • the obtained castings having a pearlitic structure with lamellar cementite are submitted to subsequent annealing at temperatures from 6507 80C for the period of 0.25 hours.
  • the said operation causes the coagulation of cementite which appears in pearlite in the form 'of lamellas.
  • the castings are slow cooled and taken out of the furnace.
  • a protective coating is produced on surfaces ofaluminized castings, consisting of several layers which comprise from outside: a layer of aluminum oxides, aluminium or aluminium alloys having a chemical composition the same as the composition of the bath, the mixture of aluminium and iron compounds with aluminium, inter-metallic phases of aluminium and cast iron and the solid solution of aluminium inthe alpha iron.
  • the multilayer coating as well as high brittleness of the layer of intermetallic phases have a bad effect on its mechanical properties. Therefore after hot-dip aluminizing, the castings should be annealed at high temperatures in the range of 700 1,200C for a period of 4-20 hours.
  • the multilayer coating is transformed partially or entirely into a solid solution of aluminium in the alpha iron, which is characterized by an outstanding higher plasticity and corrosion resistance increased and additionally by the formation of a thin layer of aluminium oxides on the surface of the annealed and previously aluminized castings.
  • the process for producing black heart and pearlitic malleable castings and the subsequent process of diphot aluminizing them are carried out separately i.e. the aluminizing operation is applied after complementing the graphitizing annealing, which according to the known method has to be carried out in an inert medium.
  • the inert medium can be obtained by using protective atmospheres or by placing the annealed castings in annealing pots and ridging them with an inert material, most frequently with quartz sand.
  • the annealing in protective atmospheres i.e.
  • the present invention aims at reducing and overcoming the disadvantages of the hitherto known processes for producing hot-dip aluminized pearlitic malleable and black heart malleable castings and also aims at obtaining products having a homogeneous structure, free from surface decarbonization and oxides and scorches, covered with a structurally homogeneous coating formed by hot-dip aluminizing thereby providing high mechanical properties of the produced cast irons as well as high heatand corrosion resistances, simultaneously with considerable shortening of annealing rates, which can proceed in a neutral, oxidizing or reducing medium.
  • This problem has been solved by carrying out the graphitizing annealing step simultaneously with the annealing step for providing a homogeneous coating on aluminized white cast iron castings, black heart malleable castings or pearlitic malleable castings in an optional atmosphere.
  • the said process consisting in annealing the castings with an aluminium protective coating, enables the elimination of oxidation of their sur faces as well as decarbonization of the surface layer, thereby providing homogeneity of the structure of the castings and also a homogeneous structure of the aluminized coating, avoiding moreover surface scorches of quartz sand, which is used as a filler in the hitherto known processes.
  • the additional advantages attained in this process of the invention for producing hot-dip aluminized black heart and pearlitic malleable castings are: shortening of the annealing rate by simultaneous annealing of the core and the coating, elimination of expensive and complicated annealing furnaces with protective atmospheres and also fast-wearing annealing pots, These improvements enable elimination of laborious operations such as dressing of the surfaces of annealed castings before aluminizing them, loading the castings into the annealing pots and ridging them with sand which as well as the inert gases is not used in the process of the invention.
  • a process of the invention for producing hot-dip aluminized castings from a malleable pearlitic cast iron with a lamellar cementite consists in heat treatment of castings from white cast iron/in order to obtain the pearlitic structure with a lamellar cementite and isolate the temper carbon or to obtain the pearlite-ferritic structure with a temper carbon/simultaneously with dip aluminizing these castings and subsequently annealing them in order to obtain the homogeneity of the multilayer aluminium coating formed directly after drawing them out from the bath.
  • the castings from white cast iron with accurately dressed surfaces are immersed in the bath containing aluminium or aluminium alloys at temperatures in the range of 680 950C at a rate from 0.5 5 m/min.
  • the castings are kept in the bath for the time period which is necessary for them to obtain the bath temperature.
  • the castings are taken out from the bath at a rate from 0,5 m/min and cooled on air or in water This operation enables the castings to obtain a protective aluminium coating on the their surfaces a simultaneous hardening by formation of graphitization seeds in great numbers thereby increasing the final mechanical properties of the aluminized products from a malleable pearlitic cast iron with a lamellar cementite.
  • graphitizing annealing is effected in a range of temperatures of 900 1,000C for the period of 8 l6 hours. This operation is performed in order to additionally increase the quantity of graphitization seeds and it may be preceded by tempering of previously hardened castings. Simultaneously with the graphitizing annealing of the aluminized castings the formed aluminium coating is also annealed in order to obtain improved structure. After the annealing stage, the aluminized castings together with the furnace are cooled to the critical range of temperatures from 880 730C and then fast cooled in air to the ambient temperature.
  • This course of the process ensures a high efficiency in the production of aluminized castings from a pearlitic malleable cast iron with a lamellar cementite.
  • This process is illustrated in the diagram presenting the process rate in dependence on the range of temperatures of successive heat treatments as is shown in FIG. 1.
  • Example 2 In order to produce hot-dip aluminized castings from a pearlitic malleable cast iron with a spheroidal cementite, the heat treatment of previously hot-dip aluminized castings from a white cast iron is carried out with the same parameters as in the process for producing hot-dip aluminized castings from a pearlitic malleable cast iron with a lamellar cementite, and after the stage of graphitizing annealing an additional annealing is effected in the temperature range from 650780C for a period of 0.25 10 hours. This operation enables obtaining a better pearlite structure with coagulated cementite and further annealing of formed coating. The process is shown in FIG. 2 which illustrates the rate of the process in dependence on the range of temperatures of the heat treatment.
  • Example 3 The hot-dip aluminized castings from a pearlitic malleable cast iron with a spheroidal cementite are also obtained from a pearlitic malleable cast iron with a lamellar cementite, having no protective coating but only a dressed surface. They are hot-dip aluminized with the same peremeters as in the process of hot-dip aluminizing described in Example I. The castings with a formed aluminium coating are annealed for a period of 0.25 10 hours in a temperature range of 650-780C, then cooled in water to the ambient temperature.
  • This operation of additional'annealing aims at providing coagulation of lamellar cementite present in pearlite as well as annealing the formed aluminium coating.
  • the process course is shown in FIG. 3 illustrating the dependence of the rate of the heat treatment on the range of temperatures used.
  • Example 4 As a starting material for producing hotdip aluminized castings from a pearlitic malleable cast iron with spheroidal cementite, the non-aluminized castings of a black heart malleable cast iron may also be used.
  • the said castings are surface dressed and aluminized with the same parameters as those the examples given above. Subsequently, they are annealed for a period of 0.25 10 hours at temperatures in the range of 650 800C. This process enables obtaining pearlite with spheroidal cementite and also formation of a homogeneous coating.
  • FIG. 4 illustrating the dependence of temperatures on the rate of the heat treatment.
  • Example 5 A process of the invention for producing hot-dip aluminized castings from a black heart malleable cast iron consists in a simultaneous heat treatment of castings from the starting white cast iron in order to obtain the ferriticor pearlite-ferritic structure with the isolated temper carbon and also to obtain an aluminium coating with the highest mechanical properties.
  • the aluminizing operation of the castings is carried out with the same parameters as the aluminizing shown in examples given above. Subsequently the aluminized castings are submitted to two-stage graphitizing annealing, where they are heated to the range of temperatures from 950 1 ,000C and maintained at this temperature for the period of 18 24 hours, resulting in decomposition of free cementite and bleaching of a temper carbon. Then the castings together with the furnace are cooled to a range of critical temperatures from 880 730C and at these temperatures they are maintained for the period of 30 60 hours, then cooled to the ambient temperature.
  • the eutectoid cementite contained in pearlite is decomposed what enables obtaining a pure ferritic or pearlite-ferritic structure of the matrix with the isolated temper carbon.
  • the previously formed aluminium coating is also annealed, which provides increase of its mechanical properties and particularly its plasticity.
  • FIG. 5 illustrates the dependence of the rate of the heat treatment on the temperature of this process.
  • a method-of producing aluminized iron castings selected from the group consisting of aluminized pearlitic malleable iron castings with lamellar or coagulated cementite, and black heart malleable iron castings comprising dipping into a hot bath containing aluminum or aluminum alloys, an iron casting which has not yet been subjected to graphitizing annealing, said iron casting being selected from the group consisting of white cast iron castings, black heart malleable cast iron castings, and pearlitic malleable cast iron castings, and heating the iron casting now provided with a protective aluminum coating from said bath to a temperature to effect graphitizing annealing of said iron casting and simultaneous annealing of the coating to provide homogeneity of the structure of the casting and the coating.
  • the target cast iron is a malleable pearlitic cast iron with lamellar cementite obtained from white cast iron, the bath temperature being 680950C, the graphitizing annealing temperature being 900-1,000C and being applied for 8-16 hours, after which the casting and furnace in which it is inserted are cooled to 730-8 80C and then fast cooled to ambient temperature.
  • the target cast iron is a malleable pearlitic cast iron with spheroidal cementite obtained from white cast iron, the bath temperature being 680950C, the graphitizing annealing temperature being 9001,000C and being applied for 8-16 hours, after which the casting and furnace in which it is inserted are cooled to 730-880C and then fast cooled to ambient temperature, and further comprising an additional annealing at a temperature of 650-780C for 0.25l0 hours.
  • the target cast iron is a malleable pearlitic cast iron with spheroidal cementite obtained from pearlitic malleable cast iron with a lamellar cementite, the bath temperature being 680950C, the graphitizing annealing temperature being 650750C and being applied for 0.25-10 hours, after which the casting is cooled in water to an ambient temperature.
  • the target cast iron is a malleable pearlitic cast iron with spheroidal cementite obtained from black heart malleable cast iron, the bath temperature being 680-950C, the graphitizing annealing temperature being 650-800C and being applied for 0.25-10 hours, after which the casting is cooled in water to ambient temperature.
  • the target cast iron is a ferritic or pearlite-ferritic cast iron obtained from black heart malleable cast iron, the bath temperature being 680950C, the graphitizing annealing temperature being 950l ,000C and being applied for l824 hours, after which the casting and furnace in which it is inserted are cooled to 730880C and maintained thereat for 30-60 hours and then cooled to ambient temperature.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
  • Coating With Molten Metal (AREA)
  • Manufacture Of Alloys Or Alloy Compounds (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
US00288161A 1971-09-15 1972-09-11 Process for manufacturing hot-dip aluminized pearlitic malleable cast iron and black heart malleable cast iron products Expired - Lifetime US3850699A (en)

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PL15051471A PL69244B1 (enrdf_load_stackoverflow) 1971-09-15 1971-09-15

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US (1) US3850699A (enrdf_load_stackoverflow)
JP (1) JPS4861321A (enrdf_load_stackoverflow)
BE (1) BE788040A (enrdf_load_stackoverflow)
CS (1) CS171736B2 (enrdf_load_stackoverflow)
DD (1) DD98953A5 (enrdf_load_stackoverflow)
FR (1) FR2152767B1 (enrdf_load_stackoverflow)
GB (1) GB1408634A (enrdf_load_stackoverflow)
IT (1) IT967441B (enrdf_load_stackoverflow)
PL (1) PL69244B1 (enrdf_load_stackoverflow)
SE (1) SE400311B (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4036670A (en) * 1975-04-03 1977-07-19 Continental Copper & Steel Industries, Inc. Tool steel
US4096002A (en) * 1974-09-25 1978-06-20 Riken Piston Ring Industrial Co. Ltd. High duty ductile cast iron with superplasticity and its heat treatment methods
US4158710A (en) * 1976-12-31 1979-06-19 Politechnika Slaska Im. Wincentego Pstrowskiego Method of preparation of the surfaces of products made of iron alloys, preceding the process of hot-dip aluminizing
CN113646459A (zh) * 2019-03-20 2021-11-12 日立金属株式会社 经镀覆形成的黑心可锻铸铁部件的制造方法、及经镀覆形成的黑心可锻铸铁部件

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2887421A (en) * 1955-01-05 1959-05-19 Renault Method of producing castings having high mechanical properties
US3268369A (en) * 1961-04-10 1966-08-23 Gen Motors Corp Process for hardening the aluminum alloy portion of an aluminum alloysteel bearing

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2887421A (en) * 1955-01-05 1959-05-19 Renault Method of producing castings having high mechanical properties
US3268369A (en) * 1961-04-10 1966-08-23 Gen Motors Corp Process for hardening the aluminum alloy portion of an aluminum alloysteel bearing

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4096002A (en) * 1974-09-25 1978-06-20 Riken Piston Ring Industrial Co. Ltd. High duty ductile cast iron with superplasticity and its heat treatment methods
US4036670A (en) * 1975-04-03 1977-07-19 Continental Copper & Steel Industries, Inc. Tool steel
US4158710A (en) * 1976-12-31 1979-06-19 Politechnika Slaska Im. Wincentego Pstrowskiego Method of preparation of the surfaces of products made of iron alloys, preceding the process of hot-dip aluminizing
CN113646459A (zh) * 2019-03-20 2021-11-12 日立金属株式会社 经镀覆形成的黑心可锻铸铁部件的制造方法、及经镀覆形成的黑心可锻铸铁部件
CN113646459B (zh) * 2019-03-20 2023-08-15 株式会社博迈立铖 经镀覆形成的黑心可锻铸铁部件的制造方法、及经镀覆形成的黑心可锻铸铁部件

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DE2245164A1 (de) 1973-04-05
IT967441B (it) 1974-02-28
FR2152767B1 (enrdf_load_stackoverflow) 1974-10-25
PL69244B1 (enrdf_load_stackoverflow) 1973-02-28
JPS4861321A (enrdf_load_stackoverflow) 1973-08-28
DE2245164B2 (de) 1976-10-07
GB1408634A (en) 1975-10-01
FR2152767A1 (enrdf_load_stackoverflow) 1973-04-27
SE400311B (sv) 1978-03-20
BE788040A (fr) 1972-12-18
DD98953A5 (enrdf_load_stackoverflow) 1973-07-12
CS171736B2 (enrdf_load_stackoverflow) 1976-10-29

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