EP0081847B1 - Enameling process - Google Patents

Enameling process Download PDF

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Publication number
EP0081847B1
EP0081847B1 EP82111592A EP82111592A EP0081847B1 EP 0081847 B1 EP0081847 B1 EP 0081847B1 EP 82111592 A EP82111592 A EP 82111592A EP 82111592 A EP82111592 A EP 82111592A EP 0081847 B1 EP0081847 B1 EP 0081847B1
Authority
EP
European Patent Office
Prior art keywords
aluminum
layer
steel sheet
plated
annealing
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP82111592A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0081847A1 (en
Inventor
Yoshihiro Kusanagi
Jiro Tsuchida
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nippon Steel Nisshin Co Ltd
Original Assignee
Nisshin Steel Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nisshin Steel Co Ltd filed Critical Nisshin Steel Co Ltd
Publication of EP0081847A1 publication Critical patent/EP0081847A1/en
Application granted granted Critical
Publication of EP0081847B1 publication Critical patent/EP0081847B1/en
Expired legal-status Critical Current

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    • 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
    • C23C2/26—After-treatment
    • 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
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/26—After-treatment
    • C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
    • 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
    • C23D—ENAMELLING OF, OR APPLYING A VITREOUS LAYER TO, METALS
    • C23D3/00—Chemical treatment of the metal surfaces prior to coating

Definitions

  • This invention relates to an enameling process comprising aluminum-coating a steel sheet, rolling, heat-treating and enameling the coated steel sheet.
  • Steel sheets the surface of which is coated with aluminum, hot-dip aluminum-coated steel sheets for instance, have excellent heat resistance, corrosion resistance, etc., and are widely used for automobile exhaust gas treatment apparatuses, parts of driers and stoves which are exposed to high temperature, roofing, interior finish, etc.
  • Enamel-coating is effected by applying an enamel glaze on the surface of the substrate and firing it at a suitable temperature.
  • the blister defect is caused by microscopic pin-holes, non-plated portions and minute cracks generated when the plated sheets are worked for shaping, etc., which exist in the plated aluminum layer. That is, a plated aluminum layer as plated is of the cast structure so to speak, and therefore it is inevitably accompanied by incidental minute pinholes and non-plated portions, and is poor in ductility and elongation, easily developing cracking when worked. These defects are rather slight and harmless for the heat resistance and corrosion uses. However, when the sheet is enameled, these defects become initiation points of the above mentioned blister defect. Therefore, if these defects in the plated aluminum layer are eliminated, the blister defect is also eliminated.
  • an aluminum-coated steel sheet comprising a base steel sheet, a first aluminum coating obtained by dipping the steel sheet into a molten aluminum bath and a second aluminum coating obtained by rolling together the aluminized steel sheet and an aluminum alloy or aluminum sheet.
  • the rolling is carried out with a reduction percentage of from 10 to 40% and is followed by a finish rolling and/or a softening treatment effected at a temperature between 400 and 580°C.
  • the object underlying the invention is to provide an enameling process according to which an aluminum-coated steel sheet can be enameled such that the surface of the formed enamel layer on the aluminum-coated steel sheet is free of blisters and craters, and thus the corrosion resistance and appearance of the enameled sheet is satisfactory.
  • the invention provides an enameling process as mentioned above.
  • said enameling process is characterized in that there is used a steel sheet with a carbon content of about 0.2% by weight or less, the rolling of the aluminum-coated steel sheet is effected with a reduction of 10 to 70% and the heat-treating is achieved by two annealing steps, the first annealing step being carried out at a temperature of about 300 to 480°C during 3 to 10 hours, and the second annealing step being carried out at a temperature of about 500 to 600°C during 3 to 12 hours.
  • the substrate sheet for enameling in accordance with this invention has a coated aluminum layerwhich has been rolled and annealed for recrystallization, and thus is free from pinholes and is provided with good ductility. Therefore, generation of cracks in the coated aluminum layer when the sheet is worked for shaping is prevented, and thus development of the blister defect in the stage of enameling is substantially avoided.
  • the aluminum-coated steel sheet for enameling according to the invention is produced for instance by aluminum-plating a base steel sheet by the conventional process, rolling the sheet and annealing the rolled sheet for recrystallization.
  • a low carbon steel sheet with a carbon content of 0.2% by weight of C or less is used from the viewpoint of formability.
  • alloying of the coated aluminum layer in the course of the recrystallization annealing and the later firing is retarded and thus adhesion of the resulting enamel layer is improved.
  • the preferred C content is not more than about 0.02%.
  • Nitrogen (N) has an effect to raise the alloy formation temperature, too, and therefore it is preferred that base steel sheets contain about 0.001-0.02% by weight N.
  • the aluminum coating layer can be formed by hot-dip plating, vacuum evaporation, powder coating, cladding, etc.
  • the AI-Fe alloy is usually formed at the interface between the base steel sheet and the plated layer. If the alloy, which is hard and brittle, is produced in a large amount, it will cause cracking when the plated sheet is rolled. In order to prevent this, it is effective to use an AI-Si plating bath containing not less than about 1.0% by weight of silicon (Si) instead of a neat AI bath. By the use of this bath, the thickness of the alloy layer formed during plating can be restrained to about 2-5 um or less, and thus occurrence of cracking during rolling can be avoided. However, if the bath contains too much Si, hard and brittle plate-like crystals of Si appear spread throughout the plated layer and cause cracking during rolling. The Si content should preferably be not more than 15% by weight.
  • the plated sheet is subjected to rolling. Either of cold rolling or warm rolling (at about 10G-450°C, for instance) will do. About 10% reduction is required in order to fill up pinholes and unplated portions of the cast structure of the plated layer, although the degree of reduction can be suitably selected in consideration of the thickness of the starting sheet and that of the finished sheet. Especially, if a sheet is rolled down by more than 20%, not only the coated aluminum layer but also the base steel sheet is modified to rolled structure, and their recrystallization temperature is lowered. Thus recrystallization of base steel sheets is achieved at a lower temperature. This fact is also advantageous in that alloying of the coated aluminum layer in the course of annealing is inhibited.
  • the aluminum coating layer is formed by hot-dip plating
  • an alloy layer formed in the interface between the base steel sheet and the plated aluminum layer during plating is divided minutely. This fact contributes to prevention of separation of and/or cracking in the plated layer, which would be caused during the later shaping work.
  • too high reduction again causes cracking in the plated aluminum layer, which induces the blister defect in the finished enamel. So the reduction is limited to 70%.
  • the rolled aluminum-plated steel sheet is now subjected to recrystallization annealing, since the plated aluminum layer is of a work-hardened rolled structure and is poor in ductility.
  • Annealing is preferably carried out at about 250-480 0 C. The annealing will be required for about 10 min. to 3 hours, for instance. So, by this annealing the plated aluminum layer is provided with good ductility and the filled-in pinholes etc. are completely eliminated by recrystallization.
  • the structure of the plated aluminum layer of the thus obtained aluminum-plated steel sheet is similar to the forged structure rather than the initial cast structure.
  • the plated layer is entirely free from pinholes, and has good mechanical properties, especially ductility. So this material can be used as the substrate for enameling as is or after shaping as desired, and gives excellent enameled products free from the blister defect.
  • the temperature of alloy formation at the interface between the base steel sheet and the aluminum coating layer is high, and therefore the alloy is not easily formed when the substrate is subjected to high temperatures.
  • This rise in alloy formation temperature is markedly exhibited when the recrystallization annealing is carried out at a rather high temperature within the above-mentioned range (about 250-480°C), preferably in the range of about 300-480°C.
  • the fact that the alloy formation temperature is high is very significant in that a higher firing temperature can be employed in the step of enamel layer formation.
  • Aluminum-coated steel sheets develop an alloy between the base steel sheet and the coated aluminum layer because of mutual diffusion of Fe and AI when they are subjected to a high temperature of about 500°C or higher.
  • the aluminum layer is alloyed up to the surface and becomes grayish black. If such alloy formation occurs during the enamel forming firing, the resulting enamel coating layer is poor in adhesion to the substrate and easily scales off. Therefore, high firing temperatures cannot be employed, and selection of usable glazes is strictly restricted.
  • the substrate sheets for enameling in accordance with this invention have high alloy formation temperatures, especially those which have been annealed at a temperature of about 300°C or higher, do undergo practically no alloying even if they are subjected to a high firing temperature in excess of 500°C, about 550°C or higher.
  • glazes can be selected from a wide range of materials and enameling can be effected at higher temperatures without sacrificing the adhesion to the substrate.
  • enamel products with excellent enamel layer characteristics such as chemical resistance, hardness, luster etc. can be obtained.
  • the alloy formation temperature is remarkably raised when the C content of the base steel sheet is lower and the AI coating layer contains Si.
  • the annealing after the rolling should be carried out at a temperature higher than the recrystallization temperature of the base steel sheet.
  • the temperature is about 50G-600°C. It must not exceed about 600°C in order to avoid melting of the coated aluminum layer.
  • the annealing is carried out at a higher temperature in comparison with the annealing intended for recrystallization of the aluminum coating layer only (about 250-480°C).
  • employment of a low carbon content base sheet and a Si-containing aluminum coating layer is effective as mentioned above.
  • the first step annealing is carried out over a range of about 3-10 hours for instance, and the second step annealing is carried out over a range of about 3-12 hours.
  • substrate sheets for enameling which have good workability with the base steel sheet and the aluminum coating layer both recrystallized, are obtained without causing alloying at the interface.
  • substrate sheets obtained by this two step annealing can be fired for enameling at a temperature higher than about 500°C without suffering from alloying at the interface, since their alloying temperature is high. Therefore, the products are free from the problem of poor adhesion, and have far more excellent enamel coating than the conventional enamel products, and glazes can be selected from a wider range of sources.
  • the thickness of the base steel sheet and the aluminum coating layer there is essentially no restriction on the thickness of the base steel sheet and the aluminum coating layer.
  • the reduction in rolling can be suitably selected within the above-mentioned range in accordance with the thickness of the aluminum-coated steel sheet and the thickness of the finished enamel product.
  • rolling and recrystallization annealing can be repeated as many times as required.
  • An aluminum-plated sheets for enameling was obtained by hot-dip plating a 0.8 mm thick cold rolled low carbon plain steel sheets, the surfaces of which had been degreased and cleaned by heating in a reduction atmosphere furnace, by passing them through an AI-Si plating bath (Si content: 9% by weight; temperature: 670°C) in a Sendzimir apparatus.
  • the obtained aluminum-coated steel sheets were rolled with reductions of 5-80%, and annealed at temperatures of 250-500 0 C for 6 hours. Thus 20 aluminum coated steel sheet samples were obtained.
  • a commercially available enamel glaze for aluminum-coated steel sheets was made into a suitable slip and was applied by spraying onto the surfaces of the aluminum-coated steel sheets obtained as described above to a thickness of 80 ⁇ m, and were fired at 550°C for 7 minutes, to produce enameled products.
  • Adhesion was determined in accordance with the drop impact deformation test by measuring the amount of the residual enamel layer when a test piece was placed between a die with a 25.5 mm diameter hole and a punch 25 mm in diameter and a 1 kg weight was dropped thereupon so as to form a deformation recess 3 mm in maximum depth.
  • the results are summarized in the column "AD”.
  • Low carbon steel sheets 0.8 mm in thickness (C content: 0.15-0.01 % by weight) were degreased and heated in a reduction atmosphere furnace so as to clean the surfaces thereof, and then were passed through an Al-Si plating bath (Si content: 9% by weight; temperature; 670°C; dipping time: 5 seconds).
  • the thus obtained aluminum-plated steel sheets were cold-rolled by 10-80%. Thereafter, they were heated at 350°C for 8 hours as the first step, and heated at 450-600 0 for 10 hours as the second step.
  • a commercially available glaze for aluminum-coated steel sheets was made into a suitable slip and was applied onto the degreased surfaces of the substrate sheets obtained as described above to form a 80 ⁇ m thick glaze layer.
  • the substrate sheets with the glaze layer were fired at 550°C for 7 minutes and enameled products were obtained.
  • Enamel characteristics of the obtained enameled products are shown in Table 7.
  • the sample substrate sheets were rolled and annealed, whereby the second step annealing was carried out at 550°C. Enamel characteristics were judged with respect to the worked portions.
  • the method of evaluation was the same as above.
  • the aluminum-coated steel sheets have excellent characteristics as the substrate for enameling, from which enameled products with an enamel layer free from blister defect and having good adhesion to the substrate can be obtained.
  • the firing temperature can be raised without sacrificing adhesion of the enamel layer, and therefore the restriction on selection of glazes is eased and the resulting enamel layer can be improved in chemical resistance, and other properties of the enamel.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Thermal Sciences (AREA)
  • General Chemical & Material Sciences (AREA)
  • Coating With Molten Metal (AREA)
  • Heat Treatment Of Steel (AREA)
  • Preventing Corrosion Or Incrustation Of Metals (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
EP82111592A 1981-12-15 1982-12-14 Enameling process Expired EP0081847B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP201790/81 1981-12-15
JP56201790A JPS58104165A (ja) 1981-12-15 1981-12-15 ほうろう加工用アルミニウム被覆鋼板の製造方法

Publications (2)

Publication Number Publication Date
EP0081847A1 EP0081847A1 (en) 1983-06-22
EP0081847B1 true EP0081847B1 (en) 1987-04-08

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ID=16446970

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EP82111592A Expired EP0081847B1 (en) 1981-12-15 1982-12-14 Enameling process

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EP (1) EP0081847B1 (ja)
JP (1) JPS58104165A (ja)
DE (1) DE3276009D1 (ja)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60128270A (ja) * 1983-12-14 1985-07-09 Ngk Insulators Ltd 琺瑯引きアルミニウム被覆鋼板およびその製造法
JP4708801B2 (ja) * 2005-01-27 2011-06-22 日新製鋼株式会社 ほうろう用アルミめっき鋼板の製造方法
JP5873465B2 (ja) * 2013-08-14 2016-03-01 日新製鋼株式会社 全反射特性と耐食性に優れたＡｌ被覆鋼板およびその製造法

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0079620A2 (en) * 1981-11-17 1983-05-25 Nisshin Steel Co., Ltd. Aluminum-coated steel sheets for enameling

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3300838A (en) * 1965-04-30 1967-01-31 Clevite Corp Method of making bimetallic bearing material
PL94340B1 (ja) * 1974-11-30 1977-07-30
US4148942A (en) * 1975-01-18 1979-04-10 Politechmika Slaska Im. Wincentego Pstrowskiego Removal of excess molten aluminum or its alloys from articles coated by the hot-dip method
JPS5263123A (en) * 1975-11-19 1977-05-25 Toyo Kogyo Co Production method of reactor material having excellent deformation resistance
JPS53130239A (en) * 1977-04-20 1978-11-14 Toyo Kogyo Co Al diffusion osmosis method
JPS5912745B2 (ja) * 1977-05-24 1984-03-26 日新製鋼株式会社 溶融アルミめつき鋼板のホウロウ加工前処理方法
DE2909418C3 (de) * 1978-03-10 1982-04-08 Furukawa Aluminium Co., Ltd., Tokyo Verfahren zur Herstellung von mit Aluminium oder Aluminiumlegierungen plattiertem Stahlblech

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0079620A2 (en) * 1981-11-17 1983-05-25 Nisshin Steel Co., Ltd. Aluminum-coated steel sheets for enameling

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN, unexamined applications, C field, vol. 4, no. 151, October 23, 1980, THE PATENT OFFICE JAPANESE GOVERNMENT, page 96 C 28 *

Also Published As

Publication number Publication date
JPS648071B2 (ja) 1989-02-13
JPS58104165A (ja) 1983-06-21
DE3276009D1 (en) 1987-05-14
EP0081847A1 (en) 1983-06-22

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