CA2030812A1 - High corrosion resistant multi-layer coated steel sheets having excellent paintability by enabling the prevention of occurrence of bubble-like ed paint defects, and producing method thereof - Google Patents
High corrosion resistant multi-layer coated steel sheets having excellent paintability by enabling the prevention of occurrence of bubble-like ed paint defects, and producing method thereofInfo
- Publication number
- CA2030812A1 CA2030812A1 CA002030812A CA2030812A CA2030812A1 CA 2030812 A1 CA2030812 A1 CA 2030812A1 CA 002030812 A CA002030812 A CA 002030812A CA 2030812 A CA2030812 A CA 2030812A CA 2030812 A1 CA2030812 A1 CA 2030812A1
- Authority
- CA
- Canada
- Prior art keywords
- alloys
- coating
- layer
- coated
- steel sheet
- 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.)
- Abandoned
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 105
- 239000010959 steel Substances 0.000 title claims abstract description 105
- 239000003973 paint Substances 0.000 title claims abstract description 46
- 230000007547 defect Effects 0.000 title claims abstract description 36
- 238000000034 method Methods 0.000 title claims abstract description 33
- 238000005260 corrosion Methods 0.000 title claims abstract description 28
- 230000007797 corrosion Effects 0.000 title claims abstract description 27
- 230000002265 prevention Effects 0.000 title claims description 4
- 238000000576 coating method Methods 0.000 claims abstract description 156
- 239000011248 coating agent Substances 0.000 claims abstract description 103
- 229910001297 Zn alloy Inorganic materials 0.000 claims abstract description 65
- 238000010438 heat treatment Methods 0.000 claims abstract description 53
- 239000001257 hydrogen Substances 0.000 claims abstract description 51
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 51
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 50
- 229910052725 zinc Inorganic materials 0.000 claims abstract description 38
- 229910000640 Fe alloy Inorganic materials 0.000 claims abstract description 26
- 238000011282 treatment Methods 0.000 claims abstract description 22
- 239000002131 composite material Substances 0.000 claims abstract description 19
- 229910052742 iron Inorganic materials 0.000 claims abstract description 18
- 239000010410 layer Substances 0.000 claims description 110
- 230000001590 oxidative effect Effects 0.000 claims description 10
- 239000002356 single layer Substances 0.000 claims description 8
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- 229910052804 chromium Inorganic materials 0.000 claims description 6
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical compound O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 claims description 6
- 229910052748 manganese Inorganic materials 0.000 claims description 5
- 229910052750 molybdenum Inorganic materials 0.000 claims description 5
- 229910052721 tungsten Inorganic materials 0.000 claims description 5
- 229910007567 Zn-Ni Inorganic materials 0.000 claims description 4
- 229910007614 Zn—Ni Inorganic materials 0.000 claims description 4
- 229910007564 Zn—Co Inorganic materials 0.000 claims description 3
- 229910052796 boron Inorganic materials 0.000 claims description 3
- 229910052681 coesite Inorganic materials 0.000 claims description 3
- 229910052906 cristobalite Inorganic materials 0.000 claims description 3
- 229910052759 nickel Inorganic materials 0.000 claims description 3
- 229910052698 phosphorus Inorganic materials 0.000 claims description 3
- 239000000377 silicon dioxide Substances 0.000 claims description 3
- 235000012239 silicon dioxide Nutrition 0.000 claims description 3
- 229910052682 stishovite Inorganic materials 0.000 claims description 3
- 229910052719 titanium Inorganic materials 0.000 claims description 3
- 229910052905 tridymite Inorganic materials 0.000 claims description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims 2
- 229910052593 corundum Inorganic materials 0.000 claims 2
- 229910001845 yogo sapphire Inorganic materials 0.000 claims 2
- 238000010521 absorption reaction Methods 0.000 abstract description 11
- 239000010935 stainless steel Substances 0.000 abstract 1
- 239000011701 zinc Substances 0.000 description 50
- 239000010408 film Substances 0.000 description 35
- 238000007747 plating Methods 0.000 description 15
- 238000004070 electrodeposition Methods 0.000 description 11
- 238000009713 electroplating Methods 0.000 description 11
- 239000000203 mixture Substances 0.000 description 9
- 238000005275 alloying Methods 0.000 description 8
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 7
- 238000005096 rolling process Methods 0.000 description 7
- 238000007598 dipping method Methods 0.000 description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 5
- 125000002091 cationic group Chemical group 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 4
- 238000011156 evaluation Methods 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 238000007654 immersion Methods 0.000 description 4
- 230000006698 induction Effects 0.000 description 4
- 238000010422 painting Methods 0.000 description 4
- 229910019142 PO4 Inorganic materials 0.000 description 3
- 238000000137 annealing Methods 0.000 description 3
- 238000000151 deposition Methods 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 3
- 239000010452 phosphate Substances 0.000 description 3
- 238000006873 Coates reaction Methods 0.000 description 2
- 150000001768 cations Chemical class 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000005238 degreasing Methods 0.000 description 2
- 230000032798 delamination Effects 0.000 description 2
- 150000002431 hydrogen Chemical class 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 238000005554 pickling Methods 0.000 description 2
- 238000004445 quantitative analysis Methods 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- NJXPYZHXZZCTNI-UHFFFAOYSA-N 3-aminobenzonitrile Chemical compound NC1=CC=CC(C#N)=C1 NJXPYZHXZZCTNI-UHFFFAOYSA-N 0.000 description 1
- 101150067539 AMBP gene Proteins 0.000 description 1
- 241000892681 Erigenia bulbosa Species 0.000 description 1
- 208000010201 Exanthema Diseases 0.000 description 1
- 239000007832 Na2SO4 Substances 0.000 description 1
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- -1 Zn-~ln Inorganic materials 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 230000000994 depressogenic effect Effects 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000005485 electric heating Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 201000005884 exanthem Diseases 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- ZZUFCTLCJUWOSV-UHFFFAOYSA-N furosemide Chemical compound C1=C(Cl)C(S(=O)(=O)N)=CC(C(O)=O)=C1NCC1=CC=CO1 ZZUFCTLCJUWOSV-UHFFFAOYSA-N 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 238000007733 ion plating Methods 0.000 description 1
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 206010037844 rash Diseases 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
- C25D5/10—Electroplating with more than one layer of the same or of different metals
-
- 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
- C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
- C23C28/02—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material
- C23C28/023—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material only coatings of metal elements only
-
- 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
- C23C2/261—After-treatment in a gas atmosphere, e.g. inert or reducing atmosphere
-
- 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
- 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
- C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
- C23C2/36—Elongated material
- C23C2/40—Plates; Strips
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D3/00—Electroplating: Baths therefor
- C25D3/02—Electroplating: Baths therefor from solutions
- C25D3/56—Electroplating: Baths therefor from solutions of alloys
- C25D3/562—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of iron or nickel or cobalt
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D3/00—Electroplating: Baths therefor
- C25D3/02—Electroplating: Baths therefor from solutions
- C25D3/56—Electroplating: Baths therefor from solutions of alloys
- C25D3/565—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of zinc
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
- C25D5/48—After-treatment of electroplated surfaces
- C25D5/50—After-treatment of electroplated surfaces by heat-treatment
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D7/00—Electroplating characterised by the article coated
- C25D7/06—Wires; Strips; Foils
- C25D7/0614—Strips or foils
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Mechanical Engineering (AREA)
- Electrochemistry (AREA)
- Physics & Mathematics (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Thermal Sciences (AREA)
- Other Surface Treatments For Metallic Materials (AREA)
- Laminated Bodies (AREA)
Abstract
ABSTRACT
The present invention relates to high corrosion resistant multi-layer coated steel sheets having excellent paintability, as corrosion resistant steel sheets especially suitable to automobiles, and relates to a producing method thereof. The inventive steel sheet is a multi-layer coated steel plate having, on the surface thereof, a coated film based on Zn or Zn alloys of coating weight being not less than 25 g/m2 including at least coatings based on Zn alloys or composite coatings based on Zn or Zn alloys, and on said coated film, a coated film based on Fe' or Fe alloys of coating weight being 1 to 10 g/m' including at least Fe coating or the coatings based on Fe alloys of not less than 50% Fe, and wherein a hydrogen absorption amount in total in the coated film and in the steel is limited to be not more than 300 m /m2 (per one surface).
Such a multi-layer coated steel plates has excellent paintability because they can prevent the generation of craters during electropainting and the occurrence of bubble-like paint defects concurrently, and have also corrosion resistance of high degree.
Further a producing method of the present invention forms said multi-layer coatings on the steel sheets ! and carries out heating-treatment of the multi-layer coated steel sheets at a temperature of 100 to 400°C so as to produce the coated steel sheets of the above mentioned properties.
The present invention relates to high corrosion resistant multi-layer coated steel sheets having excellent paintability, as corrosion resistant steel sheets especially suitable to automobiles, and relates to a producing method thereof. The inventive steel sheet is a multi-layer coated steel plate having, on the surface thereof, a coated film based on Zn or Zn alloys of coating weight being not less than 25 g/m2 including at least coatings based on Zn alloys or composite coatings based on Zn or Zn alloys, and on said coated film, a coated film based on Fe' or Fe alloys of coating weight being 1 to 10 g/m' including at least Fe coating or the coatings based on Fe alloys of not less than 50% Fe, and wherein a hydrogen absorption amount in total in the coated film and in the steel is limited to be not more than 300 m /m2 (per one surface).
Such a multi-layer coated steel plates has excellent paintability because they can prevent the generation of craters during electropainting and the occurrence of bubble-like paint defects concurrently, and have also corrosion resistance of high degree.
Further a producing method of the present invention forms said multi-layer coatings on the steel sheets ! and carries out heating-treatment of the multi-layer coated steel sheets at a temperature of 100 to 400°C so as to produce the coated steel sheets of the above mentioned properties.
Description
3~ 2 13igh corrosion resistant multi-layer coated steel sheets having excellent paintability by enahling the prevention of occurrence of bubble-like ED paint defects, and producing method thereof TECIINICAL FIELD
The present invention relates to multi-layer coated stéel sheets having high corrosion resistance excellent in paintability particularly coated steel sheets suitable to rust proof steel sheets for automobiles, and relates to a producing metllod thereof.
BACKGROUND OF TIIE T~CI~NIQUE
Aùtomobile bodies are mainly composed of thin steel sheets.
For keeping, therefore, body appearances and safety thereof due to maintenance of mechanical strength for a long term of time~ it is indispensable to provide excellent corrosion resist-ance and paintability for the steel sheets themselves to be used. To improve the corrosion resistance of the steel sheet, alloy-electroplated steel sheet such as Zn-Fe, Zn-Ni and otilers have been conventionally developed. I!ith respect to the paint-ability, on the other hand, since crater shaped paint defects appear when zinc or zinc alloy coated steel sheets are subjected 20 to cationic electrodeposition paint, arts for avoiding such defects are required. As a technique therefor, two-layer coated steel sheets, which have lower layers of zinc or zinc alloy coating and upper layers of Fe-Zn alloy coating having compositions containing not less than 50% Fe thereon, have been developed (Japanese Patent Publication No.58-15554, same No.57-28754, and Plating and Surface Finishing, i2 (1985~ No.8, P52). Accordingly, by using said two-layer coated steel sheets, the high corrosion ~ ~ 3 ~
resistance and the e~cellent paintability may be made compatible.
Ilowever, going with prologation of using terms of the auto-moiles, :nore excellent corrosion resistance than heretofore has become necessary. ~s a method of imparting the corrosion resistance to the steel sheets, it is most preEerable to apply Zn or Zn alloy coatings having sacrifice protection, talcing damages at the coated parts into consideration. There are improvements in the compositions and coating thiclcness as methods of obtaining tl-e high corrosion resistance in the coatings based on Zn or Zn alloys. Ilowever, the improvements in the composi-tions have conventionally been fully investigated, there will not be many chances of finding out new origins or chemical compositions exhibiting more excellent properties than the present ones. Therefore the coating thickening has actually become the most powerful technique for high corrosion resist-ance. Since heavily coated materials of course require the paint-ability, it is necessary to provide, as the upper coated layer, Fe-Zn alloy coatings or other coatings based on Fe or Fe alloys containing not less than 50% Fe. However according to the invent 20 ors' investigations, thougll multi-layer thick-coated rust proof steel sheets which were formed, via the electroplating method, with the upper layers of Fe-Zn alloy coatings or other coatings based on Fe or Fe alloys containing not less than 50-~ Fe, might avoid the crator appearances during the electrodeposition paint, it was found that the finished outer appearances of the electro-deposited paint films were considerably de~eriora~ed. Such coating defects depend upon the electrodepositing or baking J
conditions, and were observed as protrudent or depressed rashes or pepper-and-salt like non-uniformities. Viewin~ through a scanning type electron microscope, it was found as seen in photographs of rig.l, that these defects were bubble-like defects caused in electrodeposited paint. They are quite tlifferent sorts of paint defects from the crators reported hitherto, and as later mentioned, when balcing the electrotleposited paint, absorbed hydrogen is released from the coated layer or the interior of the steel, and such absorbed hydrogen becomes the bubbleg in tlle paints. The bubble-lilce paint defects do not appear in the conventional multi-layer lightly coated steel shcets performe(l by the electrodeposition paint under the same condit-ions. Accordingly, the bubble-lilce paint defects may be said as the defects particular to the multi-layer heavily coated steel sheets~ The above stated paint defect is not only a pro~lem from the standpoint of the appearances but also harmful in view of the corrosion resistance, and is therefore a vital issue to be solved for putting the multi-layer heavily coated steel sheets :into practice.
DISCLOSURE OF TIIE INVE,NTION
The inventors made studies on tlle above mentioned paint defects, and conse(luently cleared up that the cause of the defect occurrence was a hydrogen absorbed in the multi-layer thick-coated steel sheets dtlring producing processes, and found that said paint defects could be avoided by limiting an amount of the llydrogen absorption to be not more than 300 m~lm~.
~ ~ 3 ~
The present invention is based upon such findings, and is charactrizetl by a multi-layer coated steel sl-eet having, on the surface thereof, a coated film based on Zn or Zn alloys of a coating adheslon amount being not less than 25 g/m', wllich is a single layer or multi-layer coated film being composed of one or more than one Icind selected from plated coatillgs based on Zn alloys or/and composite plated coatings based on Zn or Zn alloys; or whicll is a multi-layer coated film being composed of Zn plated coating, and one or more than one kind 10 selected from plated coatings based on Zn alloys or/and comyosite plated coatings based on Zn or Zn alloys, F'urther on said coated film basetl on Zn or Zn alloys, a coated film based on Fe or Fe alloys of a coating adhesion amount being 1 to 10 g/ml, which is composed of one or more than one kind selected from Fe plated coating or/and plated coatings based on Fe alloys containing not less than 50~ Fe, and wherein a total amount of the absorbed hydrogen in the coated film and the steel is not more than 300 m~/m~ (per one side).
Such multi-layer coated steel plates have the excellent paintabilities and the high degree corrosion resistance, because of avoiding concurrently occurrences of the craters and the bubble-lilce paint defects caused by the electrodeposition paint.
~ producing metllod of the present invention may produce efficiently such coate~ steel sheets. and is characteized by forming, on the surface t~ereof, a coated film based on Zn or Zn ?, ~ ~
alloys of a coating adhesion amount bei~g not less than 25 g/m', which is a single layer or multi-layer coated film being composed of one or more than one kind selected from plated coatings based on Zn alloys or/and composite plated coatings based on Zn or Zn alloys; or wl~ich is a multi-layer coated film being composed of Zn plated coating, and one or more than one Icind selected from plated coatings based on Zn alloys or/and composite plated coatings based on Zn or Zn alloys, and subsequently forming, on saitl coated film based cn 10 Zn or ~Zn alloys, a coated film based on Fe or Fe alloys of a coating- adhesion amount being 1 to 10 g/m', whicll is composed of one or more than one Icind selected from Fe plated coating or/andi plated coatings based on Fe alloys containing not less than 50~ Fe, and heat-treating said rnulti-layered steel plates at a temperature between 100 and 400C.
In the producing method of the present invention, it is preferable to carry out the heating treatment of tlle steel plate after the coating in a continuous line for heightening product~
20 ivity, and in this case, the coated steel sheet is heated at a temperature of the steel surface between 100 an~ ~iOOC for not less than one second. In addition, for obtaining a press formability of high degree, the coated steel plate in an open coil is heated in a non-oxidizing atmosphere to a temperature between 100 and 250C.
BRIE~ DESCRIPTION 0~ T}IE DR~INGS
Fig.l is a magnifying microphotograph showing bubble~ e defects occurring in a cationic electrodeposited paint film;
Figs.2 and 3 show, with respect to an as-coated multi-layer steel sheets and the multi-layer steel sheets of multi-layers having removed the absorbed hydrogen by heating after coating, the results of the quantitative analysis of the concentrations of the al)sorbed hydrogen therein by an ion micro mass analyzer;
Fie.4 shows the degrees of the relation between the amounts of the~hydrogen absorption and the bubble-like ED paint defects;
Fig.5 sho~/s the relation betlleen the releasing o the absorbed hydrogen and the temperature; ~ig.6 sho~s, with respect to the as-coated multi-layer steel plate and the multi-layer steel plate having been heat-treated after coating, the results of the measurement of the hydrogen absorbed therein by a gas chromatography.
DET~ILED DESCRIPTION OF TIIE I~IVEr~TION
The present invention will be explained in detail.
Tlle multi-layer coated steel sheets of this invention have the inner layer plated coating, and the outer layer plated coating, said inner layer coating being composed of coated films based on Zn or Zn a]loys having at least the plated coatings based on Zn alloys or the composite plated coatings based on Zn or Zn alloys, and said outer layer plated coa~ing being composed of
The present invention relates to multi-layer coated stéel sheets having high corrosion resistance excellent in paintability particularly coated steel sheets suitable to rust proof steel sheets for automobiles, and relates to a producing metllod thereof.
BACKGROUND OF TIIE T~CI~NIQUE
Aùtomobile bodies are mainly composed of thin steel sheets.
For keeping, therefore, body appearances and safety thereof due to maintenance of mechanical strength for a long term of time~ it is indispensable to provide excellent corrosion resist-ance and paintability for the steel sheets themselves to be used. To improve the corrosion resistance of the steel sheet, alloy-electroplated steel sheet such as Zn-Fe, Zn-Ni and otilers have been conventionally developed. I!ith respect to the paint-ability, on the other hand, since crater shaped paint defects appear when zinc or zinc alloy coated steel sheets are subjected 20 to cationic electrodeposition paint, arts for avoiding such defects are required. As a technique therefor, two-layer coated steel sheets, which have lower layers of zinc or zinc alloy coating and upper layers of Fe-Zn alloy coating having compositions containing not less than 50% Fe thereon, have been developed (Japanese Patent Publication No.58-15554, same No.57-28754, and Plating and Surface Finishing, i2 (1985~ No.8, P52). Accordingly, by using said two-layer coated steel sheets, the high corrosion ~ ~ 3 ~
resistance and the e~cellent paintability may be made compatible.
Ilowever, going with prologation of using terms of the auto-moiles, :nore excellent corrosion resistance than heretofore has become necessary. ~s a method of imparting the corrosion resistance to the steel sheets, it is most preEerable to apply Zn or Zn alloy coatings having sacrifice protection, talcing damages at the coated parts into consideration. There are improvements in the compositions and coating thiclcness as methods of obtaining tl-e high corrosion resistance in the coatings based on Zn or Zn alloys. Ilowever, the improvements in the composi-tions have conventionally been fully investigated, there will not be many chances of finding out new origins or chemical compositions exhibiting more excellent properties than the present ones. Therefore the coating thickening has actually become the most powerful technique for high corrosion resist-ance. Since heavily coated materials of course require the paint-ability, it is necessary to provide, as the upper coated layer, Fe-Zn alloy coatings or other coatings based on Fe or Fe alloys containing not less than 50% Fe. However according to the invent 20 ors' investigations, thougll multi-layer thick-coated rust proof steel sheets which were formed, via the electroplating method, with the upper layers of Fe-Zn alloy coatings or other coatings based on Fe or Fe alloys containing not less than 50-~ Fe, might avoid the crator appearances during the electrodeposition paint, it was found that the finished outer appearances of the electro-deposited paint films were considerably de~eriora~ed. Such coating defects depend upon the electrodepositing or baking J
conditions, and were observed as protrudent or depressed rashes or pepper-and-salt like non-uniformities. Viewin~ through a scanning type electron microscope, it was found as seen in photographs of rig.l, that these defects were bubble-like defects caused in electrodeposited paint. They are quite tlifferent sorts of paint defects from the crators reported hitherto, and as later mentioned, when balcing the electrotleposited paint, absorbed hydrogen is released from the coated layer or the interior of the steel, and such absorbed hydrogen becomes the bubbleg in tlle paints. The bubble-lilce paint defects do not appear in the conventional multi-layer lightly coated steel shcets performe(l by the electrodeposition paint under the same condit-ions. Accordingly, the bubble-lilce paint defects may be said as the defects particular to the multi-layer heavily coated steel sheets~ The above stated paint defect is not only a pro~lem from the standpoint of the appearances but also harmful in view of the corrosion resistance, and is therefore a vital issue to be solved for putting the multi-layer heavily coated steel sheets :into practice.
DISCLOSURE OF TIIE INVE,NTION
The inventors made studies on tlle above mentioned paint defects, and conse(luently cleared up that the cause of the defect occurrence was a hydrogen absorbed in the multi-layer thick-coated steel sheets dtlring producing processes, and found that said paint defects could be avoided by limiting an amount of the llydrogen absorption to be not more than 300 m~lm~.
~ ~ 3 ~
The present invention is based upon such findings, and is charactrizetl by a multi-layer coated steel sl-eet having, on the surface thereof, a coated film based on Zn or Zn alloys of a coating adheslon amount being not less than 25 g/m', wllich is a single layer or multi-layer coated film being composed of one or more than one Icind selected from plated coatillgs based on Zn alloys or/and composite plated coatings based on Zn or Zn alloys; or whicll is a multi-layer coated film being composed of Zn plated coating, and one or more than one kind 10 selected from plated coatings based on Zn alloys or/and comyosite plated coatings based on Zn or Zn alloys, F'urther on said coated film basetl on Zn or Zn alloys, a coated film based on Fe or Fe alloys of a coating adhesion amount being 1 to 10 g/ml, which is composed of one or more than one kind selected from Fe plated coating or/and plated coatings based on Fe alloys containing not less than 50~ Fe, and wherein a total amount of the absorbed hydrogen in the coated film and the steel is not more than 300 m~/m~ (per one side).
Such multi-layer coated steel plates have the excellent paintabilities and the high degree corrosion resistance, because of avoiding concurrently occurrences of the craters and the bubble-lilce paint defects caused by the electrodeposition paint.
~ producing metllod of the present invention may produce efficiently such coate~ steel sheets. and is characteized by forming, on the surface t~ereof, a coated film based on Zn or Zn ?, ~ ~
alloys of a coating adhesion amount bei~g not less than 25 g/m', which is a single layer or multi-layer coated film being composed of one or more than one kind selected from plated coatings based on Zn alloys or/and composite plated coatings based on Zn or Zn alloys; or wl~ich is a multi-layer coated film being composed of Zn plated coating, and one or more than one Icind selected from plated coatings based on Zn alloys or/and composite plated coatings based on Zn or Zn alloys, and subsequently forming, on saitl coated film based cn 10 Zn or ~Zn alloys, a coated film based on Fe or Fe alloys of a coating- adhesion amount being 1 to 10 g/m', whicll is composed of one or more than one Icind selected from Fe plated coating or/andi plated coatings based on Fe alloys containing not less than 50~ Fe, and heat-treating said rnulti-layered steel plates at a temperature between 100 and 400C.
In the producing method of the present invention, it is preferable to carry out the heating treatment of tlle steel plate after the coating in a continuous line for heightening product~
20 ivity, and in this case, the coated steel sheet is heated at a temperature of the steel surface between 100 an~ ~iOOC for not less than one second. In addition, for obtaining a press formability of high degree, the coated steel plate in an open coil is heated in a non-oxidizing atmosphere to a temperature between 100 and 250C.
BRIE~ DESCRIPTION 0~ T}IE DR~INGS
Fig.l is a magnifying microphotograph showing bubble~ e defects occurring in a cationic electrodeposited paint film;
Figs.2 and 3 show, with respect to an as-coated multi-layer steel sheets and the multi-layer steel sheets of multi-layers having removed the absorbed hydrogen by heating after coating, the results of the quantitative analysis of the concentrations of the al)sorbed hydrogen therein by an ion micro mass analyzer;
Fie.4 shows the degrees of the relation between the amounts of the~hydrogen absorption and the bubble-like ED paint defects;
Fig.5 sho~/s the relation betlleen the releasing o the absorbed hydrogen and the temperature; ~ig.6 sho~s, with respect to the as-coated multi-layer steel plate and the multi-layer steel plate having been heat-treated after coating, the results of the measurement of the hydrogen absorbed therein by a gas chromatography.
DET~ILED DESCRIPTION OF TIIE I~IVEr~TION
The present invention will be explained in detail.
Tlle multi-layer coated steel sheets of this invention have the inner layer plated coating, and the outer layer plated coating, said inner layer coating being composed of coated films based on Zn or Zn a]loys having at least the plated coatings based on Zn alloys or the composite plated coatings based on Zn or Zn alloys, and said outer layer plated coa~ing being composed of
2~3~
coated films based on Fe or Fe alloys. The inner layer coating is to impart the corrosion resistance to the multi-layer coated steel sheet. The coating adhesion amount of the coated layer is necessarily not less than 25 g/m2 for securing a desired corrosion resistance specially in the bodies of automobiles and the like.
As the coated films based on Zn or Zn alloys as an inner layer coating, there are, for example, coated films of single layer or multi-layer structure composed of coatings based on Zn alloys or composite coatings based on Zn or Zn alloys, or coating films of multi-layer structure composed of coating based on Zn alloys and composite coating based on Zn or Zn alloys. Actually, usually assumed are (i) single layer structure of coating based on Zn alloys, (ii) multilayer structure composed of the coatings based on Zn alloys of different kinds (including such a case that contents of alloying compositions are different. The same will be applied to the followings), (iii) single layer structure of the composi.te coating based on Zn or Zn alloys, (iv) multi-layer structure composed of the composite coatings based on Zn or Zn alloys of the different kinds, and (v) multi-layer structure composed of the coatings based on Zn alloys of one or more than one kind, and composite coatings based on Zn or Zn alloys of one or more than one kind The inner layer coating may be structured by mixing the coating based on Zn alloys or the composite coating based on Zn or Zn alloys, or the both, with Zn coating respectively.
Also in this case, as the coating based on Zn alloys and the ~3~3~ ~ ~
composite coating based on Zn or Zn alloys, the coatings of one or more than one kind being different may be mixed.
Tlle coatings based on Zn alloys are Zn-Fe, Zn-Ni, Zn-~ln, Zn-Co alloyed coatings, or said alloyed coatings thereof, each of ~hich is contained with one or more than one kind of elements as Ti, Cr, ~to, 1~, etc.
~ s a means for producing these coatings based on Zn alloys, there are a metllod of thermally alloying the hot dipping Zn platings,or electrogalvanized platings, an electroplating method, 10 a vacuum evaporating method, and an ion plating method.
~ s the composite coating based on Zn or Zn alloys, one or more than one kind of A1203, Cr2O3, SiO2, BaCrO4, etc. are Co deposited in the Zn coating or the above mentioned coatings based on Zn alloys.
The coating based on Fe or Fe alloys as the outer layer coatings are composed of an Fe coating or the coating ~ased on Fe alloys containing not less than 50~ Fe, or the multi-layer coatings of these coatings, and have a coating adhesion amount of 1 to lO g/m~. ~or preventing the occurrences of the craters 20 during the electrodeposition paint, it is necessary to form the coating based on Fe or Fe alloys in the uppermost layer.
In the case of the coating based on Fe alloys, the Fe content of less than 50% is not sufficient to prevent the crater occurr-ence.
The coated film based on Fe or Fe alloys is usually composed of the single layer structure of Fe alloyed coating or Fe coating but, as the case may be, this film may be, for example, composed c~
of tlle multi-layer structure of Fe coating and Fe alloyed coating, or the multi-layer structure, etc. of more than one Icind of the coatin~s based on Fe alloys containing different ~e contents.
Ilerein, if the coating weight of the outer layer coating is less than lg/m~, the surface coverage is low, and the crater occurrence cannot be exactly prevented. On the other hand, i~ the coating amount is more than 10 g/m , the adhering property of the coated layer is lowered.
Tlle outer layer coating is formed by an electro-plating.
At the present, as an industrial method ~or forming closely and uniformly a thin coated layer over a strip of lar~e width, the electro-plating method is the only way.
The coatings based on Fe alloys are coatings containin~, in Fe, one or more than one kind of, e.g., Zn, Ni, Co, Mn, Cr, Mo, W, P and B.
In the present invention, the total amount of the absorbed hydrogen in the coated film and in the steel sheet is limited to be not more than 300 m~/m per one side of the steel sheet 20 (which is the absor~ed amount under the normal conditions of 1 atm and 25C) in producing the above mentioned multi-layer coated structures.
If the coated film based on Fe alloys or the Fe coated film is formed as the outer layer by means of the electro-plating the hydrogen is generated on surface of the inner layer in great volume, and a part thereof is absorbed in ~he coated layers and the steel.
_ 10 -?J !~J ~ J
With respect to the multi-layer coated steel sheets formed with the coating of Fe-Zn alloy containing 80% ~e on the hot dipping alloyed Zn coating, and the multi-layer steel sheets wllere said coate~d steel sheets are heated after coating to remove the absorbed hydrogen, Figs.2 and 3 sho~Y the results of the quantitative analysis oE the ccncentration of tl1e absorbed hydro-gen therein by an ion micro mass analyzer (I~IA). If a comparison is made between the case having removed the absorbed hydrogen by heating and the case not having done, it is found that the hydrogt~n is considerably absorbed in as-coated steel sheets.
The hydrogen was released by heating in an Ar atmosphere the multi-layer coated steel plates as mentioned above, and the hydrogen amount was measured with a gas chromatograpl1 method, and the amount of the absorbed hydrogen in the coated steel sheets was measured. Then the relation between the amount of the absorbed l~ydrogen and an occurring degree of bubble-lilce paint defects ~Yas obtained. Fip,.4 shows the results. A test sample used herein was the multi-layer coated steel sheet with the inner layer being the hot dipping alloyed zinc coating of the coating amount of 38 g/ml and the outer layer being the 80~ Fe-Zn alloyed electro-plated coating of the coating amount of 5 g/m2. The amount of the absorbed hydrogen in the coated steel sheet was adjusted by a preheating treatment prior to the electro-painting. As seen from Fig.4t it is a necessary condition that the amount of the absorbed hydrogen is to be not more than 300 mQ/ml for preventing the occurrence of the bubble-lilce defects.
It is apparent from the above mentioned result that the hydrogen absorbed in the coated layers and in the steel sheet apparently has a close relation with the bubble~ e paint defect. 'lhe bubble-lilce paint defect is assumed to be generated due to a mechanism as follo~s. Namely, if the electrodeposition paint is performed on the steel sheet where the llydrogen of more than a determined amount is absorbed in the coated layer and in the steel, the surface of the electrodeposited paint film is solidified before the hydrogen is fully released in a baking process, and a thin film is formed on the outside thereof. Since the hydrogen wllich is not rele~sed at the beginning of tlle baking process and remains therein, is enclosed within the coated film, the llydrogen gathers, and further is expanded by the heating and turns out the bubbles to cause the defects in the electrodeposited paint film. The bal~ing tempera-ture of the electrodeposited paint is generally 170 to 1~0C, and this is a temperature range ~here the absorbed hy(lrogen is released at a high transmisson rate, as seen in Fig.5, that is, a temperature condition ~here the absorbed hydro~en is easily released, and accordingly the bubble is easily generated.
~ or controlling the amount of the absorbed llydrogen, there are methods of ~1) heating, after coating the outer layer, the coated steel sheet; (2) selecting conditions diEficult to cause the hydrogen absorption, as the condition of coating the outer layer; (3) employing steel kinds which are low in the hydrogen absorption, or difficlllt to release the hydrogen if absorbing it, or methods of combining them.
~ J~r~) A furtl1er reEerence will be made to a producing method of the invention, a subject of wllich is to release the absorl7ed hydrogen by heating.
The producing method of the invention, as said above, comprises forming, on the steel surface, the inner layer coating composed of the coated filrn based on Zn or Zn alloys having at least the coating based on Zn alloys or the composite coating based on Zn or Zn alloys, and lurther forming, on said inner layer coating, the outer layer coating composed of the coated film ~ased on Fe or Fe alloys, and heating the steel sheet at a temperature oE lO0 to 400C after having formed said f~lms.
If the heating temperature is less than 100C, the bubble-lilce paint defects cannot be sufficiently avoided, and if it exceeds 400C, the inner layer coating and the steel plate malce a thermal diffusion, and an alloyed layer is formed where the coating adhesion is deteriorated. For these reasons, the heating temperature is set to be lO0 to 400C.
The heating procedure is performed in a continuous line, aiming at a hlgh productivity for not less than one second at said 20 temperature ~steel surface temperature). If the heating tempera-ture is less tl1al1 one second, it is diffuclt to avoid the bubble-like paint defects even at said temperature range. A maximum heating time is not especially limited, as far as the inner layer coating and the steel sheet do not create an ailoying reaction. Ileatil1g manners are a high frequency induction heating system, and electric heating system and others, not especially limiting. ~ heating atmosphere is sufficient with the atmosphere 2~3 ~
containing no hydrogen or hydrogen of a degree actually not causing the hydrogen absorption, such as a nitrogen, or an air atmosphere, not yet especially limiting. If heating for a long period of time in the atmosphere, the outer layer coating is oxidized, and consequently a modifying treatment is hindered.
Therefore, a time is limited to the heating in the at~osphere.
~ or imparting a press formability of lligh degree to the steel sheet, the heating treatment is carried out in the open coil heating. In this open coil heating, the steel sheet is 10 heated' at the temperature between 100 and 25aoc in the non-oxidizing atmosphere. The lower limit thereof is as referred to above. In SUCII heating system taking a long time from the heating to the cooling as the open coil heating, if heating at ~he temperature range exceeding 250C, the inner layer coating and the steel plate are effected with a thermal diffusion to form an alloyed layer of the coating adhesion being deteriorated.
Therefore, the upper limit of tlle heating temperature is set at 250C. Further, the heating atmosphere is determine(l to be non-oxidizing for the following reasons. If heating in the 20 oxidizing atmosphere, the coating based on ~e or Fe alloys of the outer layer is oxidized on the surface during heating and cooling, and subsequently a phospllate film is not normally formed which is required as an undercoated treatment for painting.
Ilowever, if using a gas bearing the hydrogen, though the non-oxidizing atmosphere, the hydrogen concentration thereof should be made to an extent that the hydrogen is not absorbed in the coated layer and in the steel sheet while performing _ 14 -
coated films based on Fe or Fe alloys. The inner layer coating is to impart the corrosion resistance to the multi-layer coated steel sheet. The coating adhesion amount of the coated layer is necessarily not less than 25 g/m2 for securing a desired corrosion resistance specially in the bodies of automobiles and the like.
As the coated films based on Zn or Zn alloys as an inner layer coating, there are, for example, coated films of single layer or multi-layer structure composed of coatings based on Zn alloys or composite coatings based on Zn or Zn alloys, or coating films of multi-layer structure composed of coating based on Zn alloys and composite coating based on Zn or Zn alloys. Actually, usually assumed are (i) single layer structure of coating based on Zn alloys, (ii) multilayer structure composed of the coatings based on Zn alloys of different kinds (including such a case that contents of alloying compositions are different. The same will be applied to the followings), (iii) single layer structure of the composi.te coating based on Zn or Zn alloys, (iv) multi-layer structure composed of the composite coatings based on Zn or Zn alloys of the different kinds, and (v) multi-layer structure composed of the coatings based on Zn alloys of one or more than one kind, and composite coatings based on Zn or Zn alloys of one or more than one kind The inner layer coating may be structured by mixing the coating based on Zn alloys or the composite coating based on Zn or Zn alloys, or the both, with Zn coating respectively.
Also in this case, as the coating based on Zn alloys and the ~3~3~ ~ ~
composite coating based on Zn or Zn alloys, the coatings of one or more than one kind being different may be mixed.
Tlle coatings based on Zn alloys are Zn-Fe, Zn-Ni, Zn-~ln, Zn-Co alloyed coatings, or said alloyed coatings thereof, each of ~hich is contained with one or more than one kind of elements as Ti, Cr, ~to, 1~, etc.
~ s a means for producing these coatings based on Zn alloys, there are a metllod of thermally alloying the hot dipping Zn platings,or electrogalvanized platings, an electroplating method, 10 a vacuum evaporating method, and an ion plating method.
~ s the composite coating based on Zn or Zn alloys, one or more than one kind of A1203, Cr2O3, SiO2, BaCrO4, etc. are Co deposited in the Zn coating or the above mentioned coatings based on Zn alloys.
The coating based on Fe or Fe alloys as the outer layer coatings are composed of an Fe coating or the coating ~ased on Fe alloys containing not less than 50~ Fe, or the multi-layer coatings of these coatings, and have a coating adhesion amount of 1 to lO g/m~. ~or preventing the occurrences of the craters 20 during the electrodeposition paint, it is necessary to form the coating based on Fe or Fe alloys in the uppermost layer.
In the case of the coating based on Fe alloys, the Fe content of less than 50% is not sufficient to prevent the crater occurr-ence.
The coated film based on Fe or Fe alloys is usually composed of the single layer structure of Fe alloyed coating or Fe coating but, as the case may be, this film may be, for example, composed c~
of tlle multi-layer structure of Fe coating and Fe alloyed coating, or the multi-layer structure, etc. of more than one Icind of the coatin~s based on Fe alloys containing different ~e contents.
Ilerein, if the coating weight of the outer layer coating is less than lg/m~, the surface coverage is low, and the crater occurrence cannot be exactly prevented. On the other hand, i~ the coating amount is more than 10 g/m , the adhering property of the coated layer is lowered.
Tlle outer layer coating is formed by an electro-plating.
At the present, as an industrial method ~or forming closely and uniformly a thin coated layer over a strip of lar~e width, the electro-plating method is the only way.
The coatings based on Fe alloys are coatings containin~, in Fe, one or more than one kind of, e.g., Zn, Ni, Co, Mn, Cr, Mo, W, P and B.
In the present invention, the total amount of the absorbed hydrogen in the coated film and in the steel sheet is limited to be not more than 300 m~/m per one side of the steel sheet 20 (which is the absor~ed amount under the normal conditions of 1 atm and 25C) in producing the above mentioned multi-layer coated structures.
If the coated film based on Fe alloys or the Fe coated film is formed as the outer layer by means of the electro-plating the hydrogen is generated on surface of the inner layer in great volume, and a part thereof is absorbed in ~he coated layers and the steel.
_ 10 -?J !~J ~ J
With respect to the multi-layer coated steel sheets formed with the coating of Fe-Zn alloy containing 80% ~e on the hot dipping alloyed Zn coating, and the multi-layer steel sheets wllere said coate~d steel sheets are heated after coating to remove the absorbed hydrogen, Figs.2 and 3 sho~Y the results of the quantitative analysis oE the ccncentration of tl1e absorbed hydro-gen therein by an ion micro mass analyzer (I~IA). If a comparison is made between the case having removed the absorbed hydrogen by heating and the case not having done, it is found that the hydrogt~n is considerably absorbed in as-coated steel sheets.
The hydrogen was released by heating in an Ar atmosphere the multi-layer coated steel plates as mentioned above, and the hydrogen amount was measured with a gas chromatograpl1 method, and the amount of the absorbed hydrogen in the coated steel sheets was measured. Then the relation between the amount of the absorbed l~ydrogen and an occurring degree of bubble-lilce paint defects ~Yas obtained. Fip,.4 shows the results. A test sample used herein was the multi-layer coated steel sheet with the inner layer being the hot dipping alloyed zinc coating of the coating amount of 38 g/ml and the outer layer being the 80~ Fe-Zn alloyed electro-plated coating of the coating amount of 5 g/m2. The amount of the absorbed hydrogen in the coated steel sheet was adjusted by a preheating treatment prior to the electro-painting. As seen from Fig.4t it is a necessary condition that the amount of the absorbed hydrogen is to be not more than 300 mQ/ml for preventing the occurrence of the bubble-lilce defects.
It is apparent from the above mentioned result that the hydrogen absorbed in the coated layers and in the steel sheet apparently has a close relation with the bubble~ e paint defect. 'lhe bubble-lilce paint defect is assumed to be generated due to a mechanism as follo~s. Namely, if the electrodeposition paint is performed on the steel sheet where the llydrogen of more than a determined amount is absorbed in the coated layer and in the steel, the surface of the electrodeposited paint film is solidified before the hydrogen is fully released in a baking process, and a thin film is formed on the outside thereof. Since the hydrogen wllich is not rele~sed at the beginning of tlle baking process and remains therein, is enclosed within the coated film, the llydrogen gathers, and further is expanded by the heating and turns out the bubbles to cause the defects in the electrodeposited paint film. The bal~ing tempera-ture of the electrodeposited paint is generally 170 to 1~0C, and this is a temperature range ~here the absorbed hy(lrogen is released at a high transmisson rate, as seen in Fig.5, that is, a temperature condition ~here the absorbed hydro~en is easily released, and accordingly the bubble is easily generated.
~ or controlling the amount of the absorbed llydrogen, there are methods of ~1) heating, after coating the outer layer, the coated steel sheet; (2) selecting conditions diEficult to cause the hydrogen absorption, as the condition of coating the outer layer; (3) employing steel kinds which are low in the hydrogen absorption, or difficlllt to release the hydrogen if absorbing it, or methods of combining them.
~ J~r~) A furtl1er reEerence will be made to a producing method of the invention, a subject of wllich is to release the absorl7ed hydrogen by heating.
The producing method of the invention, as said above, comprises forming, on the steel surface, the inner layer coating composed of the coated filrn based on Zn or Zn alloys having at least the coating based on Zn alloys or the composite coating based on Zn or Zn alloys, and lurther forming, on said inner layer coating, the outer layer coating composed of the coated film ~ased on Fe or Fe alloys, and heating the steel sheet at a temperature oE lO0 to 400C after having formed said f~lms.
If the heating temperature is less than 100C, the bubble-lilce paint defects cannot be sufficiently avoided, and if it exceeds 400C, the inner layer coating and the steel plate malce a thermal diffusion, and an alloyed layer is formed where the coating adhesion is deteriorated. For these reasons, the heating temperature is set to be lO0 to 400C.
The heating procedure is performed in a continuous line, aiming at a hlgh productivity for not less than one second at said 20 temperature ~steel surface temperature). If the heating tempera-ture is less tl1al1 one second, it is diffuclt to avoid the bubble-like paint defects even at said temperature range. A maximum heating time is not especially limited, as far as the inner layer coating and the steel sheet do not create an ailoying reaction. Ileatil1g manners are a high frequency induction heating system, and electric heating system and others, not especially limiting. ~ heating atmosphere is sufficient with the atmosphere 2~3 ~
containing no hydrogen or hydrogen of a degree actually not causing the hydrogen absorption, such as a nitrogen, or an air atmosphere, not yet especially limiting. If heating for a long period of time in the atmosphere, the outer layer coating is oxidized, and consequently a modifying treatment is hindered.
Therefore, a time is limited to the heating in the at~osphere.
~ or imparting a press formability of lligh degree to the steel sheet, the heating treatment is carried out in the open coil heating. In this open coil heating, the steel sheet is 10 heated' at the temperature between 100 and 25aoc in the non-oxidizing atmosphere. The lower limit thereof is as referred to above. In SUCII heating system taking a long time from the heating to the cooling as the open coil heating, if heating at ~he temperature range exceeding 250C, the inner layer coating and the steel plate are effected with a thermal diffusion to form an alloyed layer of the coating adhesion being deteriorated.
Therefore, the upper limit of tlle heating temperature is set at 250C. Further, the heating atmosphere is determine(l to be non-oxidizing for the following reasons. If heating in the 20 oxidizing atmosphere, the coating based on ~e or Fe alloys of the outer layer is oxidized on the surface during heating and cooling, and subsequently a phospllate film is not normally formed which is required as an undercoated treatment for painting.
Ilowever, if using a gas bearing the hydrogen, though the non-oxidizing atmosphere, the hydrogen concentration thereof should be made to an extent that the hydrogen is not absorbed in the coated layer and in the steel sheet while performing _ 14 -
3 $ ~ ~3 the heating. The heating time is suf~iclent with not less thall one second in total at the steel temperature of not less than 100C. If tlle heating time is less than one secon~, it is not possible to prevent the occurrence of the bubble-lilce ED paint defects even in said temperature range. The upper limit of the heating time in said temperature range is not especially limited, and is enough with about 30 minutes, talcing the productivity into consideration.
With respect to the multi-layer coated steel sheet ~ormed 10 ~itil Fç-Zn alloy coating of 80% Fe on the hot dippin~ alloyed zinc c`oating, and the multi-layer coated steel plate heated after having coated said steel sheet, Fig.6 shows the results that the hydrogen absorption amount in the coated steel sheet was measured with the gas chromato~raph in the both cases.
Ilhen the hydrogen absorption amounts are compared between the cases heated and non-heated, it is found that the hydrogen is considerably absorbed in an as-coated steel sheet, and tlle hydrogen concentratioll is lowered after heating.
Tlle bubble-like paint (lefects generated in the electro-20 deposition paint can be prevented by the heating as abovementioned, because the hydrogen which has been absorbed while coating the outer layer, is removed by said heating, and in addition to such a factor, there is a possibility that it also influences thereto that Fe enriched contents of tlle outer layer are diffused, so that a closer outer coated layer is forrned.
In other words, as another reason why the bubble-lilce paint defect is generated other than the reason of the hydrogen _ 15 -absorption caused at coating of the outer layer, the following consideration may be talcen. That is, an electric current is concentrated at the inner layer coatin~ exposed microscopic-ally when depositing the outer layer, and as a result, the hydrogen gas bubl)les are locally concentrated. These gas bubbles are not completely released from the coated layer during the baking process but remain therein, and it is assumed that such bubbles expanded become the bubble-lilce paint defects. By heating them at the higl1 temperature, the coated state of the outer layer which is, if heing as-coated, incomplete microscop-ically, is improved due to the thermal diffusion thereby, and it is also assumed that the microscopic defects of the outer layer are repaired consequently. Therefore, the above mentioned matters will possibly contribute to the prevention oE the occurrence of the bubble-like paint defects.
If the producing object of this invention is Bll steel sheets, it is preferable to perform the heating treatment at a temperature as low as practicahle. A temper rolling can be performed after coating the inner layer, coating the outer layer or the heating treatment, but it is desirable to carry out the temper rolling after the heating treatment for providing the high degree press formability or in a case of outer panels of the automobiles.
Depending upon the present invention, it is possible to supply the multi~layer coated steel sheets having the high corro-sion resistance and without causing the crators and the bubble-like paint defects at the cation electrodepositing paint and 2 ~ 3 ~ 2 accordingly with the excellent paintability. Thus, the high corrosion resistance and the beautification of the automobile bodies and others are compatible.
EXA~IPL~S
Example I
The cold rolled coils of the compositions of Table l were successively subjected, as blank coils, to the hot dipping zinc plating in the continuous plating line of the non-oxidiæing furnace system, the alloying treatment, the temper rolling, and Fe~Zn electric plating, whereby the multi-layer coated steel sheets were produced. The hy~rogen absorption amounts were adjusted by changing the Fe-Zn coating amounts, continuously l1eat-treating the multi-layer coated steel sheets at the tempera-ture of not less than lOO C in the induction heating sys-tem~ or heat-treating the open coils. The Fe-Zn electric platings for the outer layers were practised under following conditions:-(l) Plating bath Composition FeSO~.7~1,0 ~
~ - 350 - 500 g/~, ZnSO4.7ll20 -CH,COOt~la.3fl~0 20 g/~
Na2SO4 30 ~/e pll 1.8 to 2.0 (2) Plating conditions Bath temperature 50C
Flowing rate 2 m/s .
~urrent density 30 to 120 A/dm~ 2 The Fe contents in the films of the Fe-Zn by electric platings adjusted by mainly changing Fe salt ratio ( = FeS04.
7H,0/[FeS04.7H20+ZnS04.7H~0]) and the current density, and the adhesion amounts were adjusted by changing the coating time and the current density. Table 2 shows the appreciating results of the outer appearances of the coated films and the corrosion resistances after the electrodeposition paint and the process-abilities. It is seen from the same that the multi-layer coated 10 steel plates where the releasing amounts of the absorbed hydrogen were not more than 300 m /m , are superior in all properties.
Example II
The multi-layer coated steel sheets were produced from the cold rolled coils shown in the Table 1 which have passed the annealings and temper rollings, by alkaline degreasing, sulfuric acid picklings, Zn-Fe alloy electroplating and Fe-Zn alloying electroplatings in the electrogalvanizing line. The hydrogen absorption amounts were adjusted by the amounts of the outer layer coatings and by the continuous heating treat-20 men-t or batch-heating treatment at the temperature of no-t less than 100C after having been coated. The inner and outer layer coatings of this Example were practised under the same conditions as the outer layer Fe-Zn electric platings of Example Io The Fe contents and the coating weight of Fe-Zn and Zn-Fe electro-plated films were also adjusted under the same manners as Example I. The results of the evaluation of the properties are shwon .
- 1 0 - 2 ~
n Table 3. It is seen from the same that the multi-layer coated steel sheets where the releasing amounts of the absorbed hydrogen were not more th~n 300 m /m2, are superior in all properties.
Example III
The cold rolled coils of the compositions of Table 1 were successively subjected, as blank coils, to the hot dipping zinc plating in the continuous plating line of the non-oxidizing furnace system, the alloying treatment, the temper rolling, and Fe-Zn electroplating, and were successively subjected to the heating treatment under the atmospheric conditions via the induction heating system. With respect to the thus produced multi-layer coated steel sheets, Table 4 the shows results of the evaluation of the outer appearances of the coated ~ilms and the corrosion resistances after the electro-deposition paint and the coating adhesion together with the producing conditions.
According to the above table, the multi-layer coated sceel sheets heat-treated at the temperature from 100 to 400C are superior in all properties.
Example IV
The multi-layer coated steel plates were produced from the cold rolled coils shown in the Table 1 which have passed the annealings and temper rollings, by alkaline degreasing, sulfuric acid picklings, Zn-Fe alloying electroplating and Fe-Zn alloying electroplatings, and were successively subjected to the heating treatmetns under the nitrogen at~osphere via 2~3 ~.2 ~he induction heating system. With respect to the thus produced multi-layer c`oated steel sheets, Table 5 shows the results of the evaluation of the outer appearances of the coated films and the corrosion resistances after the electro-deposition paint and the coating adhesion together with the producing conditions, It is seen from the sarne that the multi-layer coated steel sheets which have been heat-treated at the temperature between 100 and 400C, are superior in all properties.
Example V
The cold rolled coils of the compositions of Table 1 ~ere successively subjected, as blank coils, to the hot dipping zinc plating in the continuous plating line of the non-oxidizing furnace system, the alloying treatment, the temper rolling, and Fe-Zn electroplating, whereby the multi-layer coated steel sheets were produced. Thereafter, these coated steel plates were subjected to the open coil heating with a cover type annealing furnace under the nitrogen gas bearing atmosphere.
~ith respect to the thus produced multi-layer coated steel sheets, Table 6 shows the results of the evaluation of the outer appearances of the coated films and the corrosion resistances after the electro-deposition paints and the coating adhesion together with the producing conditions. It is seen from the same that the multi-layer coated steel plates of open coils which have been heat-treated at the temperature between 100 and 250C, are superior in all properties.
:, . : .
INDUSTRIAL APPLICABILITY
The present invention is especially useEul as the coated steel plates to be painted witll a cationic electrodeposition for bodies of automol)iles, and as a pro~ucing method thereof.
Table 1 (~t~) . _ Cbils C Si Mn P S Sol.Al N Others _ _ I
. A 0.0028 0.01 0.17 0.0090.008 0.032 0,0035 Ti:0,072 I I I
U 0.0024 0.17 0.58 0.0250.006 0.05~ 0.0025 Nb:0.013 C 0.0012 0.01 0,023 1 0.010 0.011 0.0~5 0.0042 D 0.0~2 0.01 0.023 ¦ 0.010 0.011 0.0~5 0.00~2 E 0.020 0.01 0.015 0.012 ~0.010 0.0~0 0.0025 ~ c ~
~ ~ 9 o 3 ~ . ~ 2 ~c~5 ~G~
e'~
~ ~ ~ ~ ~ ~ ~ ~ T ~ ~
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i Z * ¢ r r L ¢ i ¢ ¢ L l ¢ ¢ ¢ r ¢ ¢ ¢ ¢ l ¢ ¢ ¢ ¢ ~ E C P- E ..
~ ~ ~ ~ ~ ~ ~ a O ~ c i r r ~ ~ r r r r r O z ~ ~ h ~ E a ~ ~ ~ L~ L~ U~ U~ ~:1 Il~ C~l O U~ Lr~ cr ~r ~ c~ c~ ,~ n u~ t~ c~ u~ O ~ : E ~ ~a ~`
~ O f O L O r--r r--l O I o r~ O O O O O O O l ~ v ~ ~ c H X ~ oo oO oO oo oo o0 cO j~a L LL L ~ L L Lq~ ~ L L ~ ~ ~ O j~ O H h ~: V
~* ~ 1- ~ 1 1 ~ ~ ~ ._ ~ c~ L~ L~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
- ~ I¢ I¢ - _ L¢ _ L¢ L~ _ _ L ¢ ~ i ~ 1~ ~ ~ ¢ ¢ 1~ ¢ ~ 1l o ~ c _ ~ L~ 1~ L~ ~ 1~ ~ L~ 1~ ~ ~ ~ ~ ~ r 0l ~ ~ Ln I ~c ~ . . Examples I I 1 ~_ . ...... - - ~'J
e~
K '`~,~' O
O ¢ ¢ ¢ ¢ ¢ L ¢ ¢ ¢ ¢ ¢ ¢ ¢ ¢ ¢ r ¢ ¢ ¢ ¢ _ ¢ ~ a o z * ¢ ¢ ~ ~ ¢ ~ ¢ ¢ r ¢ ¢ ¢ r ¢ ¢ r ~ ¢ ¢ ¢ ¢ a 7. ,~ Vl 1~ 1~ ~ ~ v L o L ~ ~ O ~ r O L~ O r ~ r ~` ~ o E
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o ~ L~ ~ ~ L ~ ~ i~ ~ ~ c~ ~ ~ ~ r- Oo l~ ~ C~ ~ m ,~
~Z Exampl e s I I Comp .
_ -- 23 ~
,, . , _ ~, 1, ~ ~ ~3 ~.3 ~o~ .~, C~, P~ f~5 ~Ga ~,e~ ~ , ~ ~ . ~ u ~ ~ ~a~ 1 ~
~ ~T ;~ ~ E O ~ ~
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H E ~ ~ ~ ~ ~ ~ ; ~ ~ ~ ~ i i O ;~ r ~ ~ O ~ i C ~ ~ E E - ~
_ ~æ ~ ~ ~ ~ ~ ¦~ ~ ~ - ~ - ~ ~ o ~ - ~ ~ ~ :~ ~ ~ v v t~ --r ~1~ ~L E~ll P :5 I I e~ E E
~T ;- ~ r j~:
,_ ~ c3 ~ ¢ ~ :~ :~ ~ ~ :~ ~ ~ _ :~ ~ :~ ~ _ :~ r~ r ~ ~ ~ ¢ ~ ;~ ¢ ~ a: ¢
~ ~ I¢ ~ ` 1 ~ ` i ~ ` ~ ~
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E ~_ O ~ ~ ~ ~ _ r O O rr~ _ i _ ~ ~ ~ ~ :~ E ~ o o ~ ~ h v o~ I
C~ ~,r~ U~O 1~ r,~ O ,r~1 ~ O ~ O ~ ~ ~ ~ ~ ~ ~ ~ :C 1 O~0 r~l r~l ~ ~
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~ ~ ~ _ I I ~ I I I ~ ? U) a Q) (I~ r~ ¦ ~ ~ ~--~ _ _ ~_ ~ ~ ~D O 0 ~L~1 ` _ ~ _ ~ U 0~ 00 Q~ E
: ~ L~L ~L ; ~ L o ~L~ ~ 2 ~ _; H ~ ~ Q~ ?
u~ I ¦ ¦ ¦ ¦ ¦ ~ ~ ~ ~ ~ ~ ~ ~ ~ o ~L- ~1~ ~ ~ Q H ~ I ~a a a) I I ~1~ ~ l c ~ ~ ~ ~ ~ ¦m¦~ ~1¢1~ 1~--i ~ ~ 3 E~
n~ c~ ~1~ _ _ o _ c~ r~ ~1~ _ _ ~ --~ C~l ¦~------.~ ~ Q~
~ I Ex~mple IV ¦ Comp.
'~ ~ 3)~2 - 1~ 1~ 1~ 1~ ~ 1 ~ I 1~
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ V~ ¢ _ :~ ~ _ :: ::: r. :~ _ :: :~ ::: :~ :~ : 2 :~ ¢ 2 _ _ _ ~q * ¢ :~ :~ ~ ~ _ ~ ~ ~ ~; ¦ ~ ~ _ ~ ¢ ~ C 5~:
* e ¢ __ ~ O ~ ~ _ ~ _ ~ __ ~ O ~ O __ m ~ _ _ ~ C~
O O O O O O O O O O O O O O O O O O O OI O O ~ C
~: ~ ~D Il~ c~l ~ _ oo C~ ~ tD r~l Ll~ Il~ Il ~ I_ _ Ir~ u~ Il~ Il~ ~ ~ ~ ¦ ~ O ~ Q ~J r u _. E O t o o o o _ + o ~ ~ o V ~; 1 ~ ~ l 2 ~ ~
~ a ~I r ~ ~1 ~ ~ ~ r ~ --~ I L ~ I z I . . z h ~ r-l 0 ~ r~ ~~
_I_ I I _ _ _ I I _ Tr __ ~ O ~ cn _ ~ ~ ::: ¦ ~ ~; ~ ~: ~ cr~ O ~ ~ :: ~: U ) ::~ ~ t~) a.) ~ rl (~ _ + ¦ + ¦ +1 + _ ~1-- a) rl ~ S~ r-l I c~ ~ I - - I ~ ~ - ~ - I ~ ~ u~ 10~ 1 - I - I - ~ ~ ~ I ~ ? I ~ I ~ o ~ ~ o t ~ ~ T--_ _ t I I _I I I I _ _ ~ t~ _ ~ ~ r-l 1: ~ r~
.` H ¦oo I - ~ I ~ ~ ~ ~ I :c ~ ~ 1 1 l co I - ~ ~ o O ~ a) h ~ O O
II t _ _ _ ~ I II I I I I I I I I _ u~ o ~D I ~ ~ ~ ::: -- --~ ~¦~ C ~ -- ~ :::~ .
c~ ~ ¢ I ~ ~ I ~ ~ ~ I ~ c I ~ I - ~ I ~ I - I m I O ~1~1 ¢ I ~ ~ I ~ I - ~ ~ o ~ c~
r-l I t _ _ _ t --I t +l I I_ I I I I I _ ~ z ~1~ ~ _ _ _ ~1~ ~1~ ~ I ~r I ~ ~ ~ C~ o Exampl~s V ¦ Comp.
~ ~ 3 ~
Table 7 Test method and evaluating references Testing items Testing methods Evafluating re erences _ Immersion type phosphate treatment . (PAL BOND 3080) . l Cationic electro B : Occurrence of Bubble-like painting defects paint defects (ELECTRON 9410) A : No occurrence of . l defects , ~ .
After baking, observing outer appearance Immersion type .
phosphate A: The number of treatment crators, not more . (PAL BOND 3080) than 10/40 mm~
~ . .
Cation electro- B: The number of depositing crators, more than Crators (ELECTRON 9410 10 - less than 50/
Distance between 40 mm~
cathode and anode, 1:1 Momentary conduc-tivity, 280V, 3min) l' C: The number of Evaluating outer crators, not less appearance than 50/40 mm~
.
Immersion type phosphate .
treatment (PAL BOND 3080) Cationic electro-Corrosion painting A: Not more than 0.1 mm resistance (ELECTRON 9410) s,,,,~
Scribing . 1~
Cyclic corrosion .
tests .
Corrosion (Combination of resistance SST, HCTj Salt B: Not less than water immersion 0.3 mm and drying) 3 months After removing coating paint films and corrosion product s measuring maximum corrosion depth _ . Draw bead test A: No delamination . I of plated films Coating ~' Adhesion Taping B: P~emarkable delamination of .
plated f.ilms
With respect to the multi-layer coated steel sheet ~ormed 10 ~itil Fç-Zn alloy coating of 80% Fe on the hot dippin~ alloyed zinc c`oating, and the multi-layer coated steel plate heated after having coated said steel sheet, Fig.6 shows the results that the hydrogen absorption amount in the coated steel sheet was measured with the gas chromato~raph in the both cases.
Ilhen the hydrogen absorption amounts are compared between the cases heated and non-heated, it is found that the hydrogen is considerably absorbed in an as-coated steel sheet, and tlle hydrogen concentratioll is lowered after heating.
Tlle bubble-like paint (lefects generated in the electro-20 deposition paint can be prevented by the heating as abovementioned, because the hydrogen which has been absorbed while coating the outer layer, is removed by said heating, and in addition to such a factor, there is a possibility that it also influences thereto that Fe enriched contents of tlle outer layer are diffused, so that a closer outer coated layer is forrned.
In other words, as another reason why the bubble-lilce paint defect is generated other than the reason of the hydrogen _ 15 -absorption caused at coating of the outer layer, the following consideration may be talcen. That is, an electric current is concentrated at the inner layer coatin~ exposed microscopic-ally when depositing the outer layer, and as a result, the hydrogen gas bubl)les are locally concentrated. These gas bubbles are not completely released from the coated layer during the baking process but remain therein, and it is assumed that such bubbles expanded become the bubble-lilce paint defects. By heating them at the higl1 temperature, the coated state of the outer layer which is, if heing as-coated, incomplete microscop-ically, is improved due to the thermal diffusion thereby, and it is also assumed that the microscopic defects of the outer layer are repaired consequently. Therefore, the above mentioned matters will possibly contribute to the prevention oE the occurrence of the bubble-like paint defects.
If the producing object of this invention is Bll steel sheets, it is preferable to perform the heating treatment at a temperature as low as practicahle. A temper rolling can be performed after coating the inner layer, coating the outer layer or the heating treatment, but it is desirable to carry out the temper rolling after the heating treatment for providing the high degree press formability or in a case of outer panels of the automobiles.
Depending upon the present invention, it is possible to supply the multi~layer coated steel sheets having the high corro-sion resistance and without causing the crators and the bubble-like paint defects at the cation electrodepositing paint and 2 ~ 3 ~ 2 accordingly with the excellent paintability. Thus, the high corrosion resistance and the beautification of the automobile bodies and others are compatible.
EXA~IPL~S
Example I
The cold rolled coils of the compositions of Table l were successively subjected, as blank coils, to the hot dipping zinc plating in the continuous plating line of the non-oxidiæing furnace system, the alloying treatment, the temper rolling, and Fe~Zn electric plating, whereby the multi-layer coated steel sheets were produced. The hy~rogen absorption amounts were adjusted by changing the Fe-Zn coating amounts, continuously l1eat-treating the multi-layer coated steel sheets at the tempera-ture of not less than lOO C in the induction heating sys-tem~ or heat-treating the open coils. The Fe-Zn electric platings for the outer layers were practised under following conditions:-(l) Plating bath Composition FeSO~.7~1,0 ~
~ - 350 - 500 g/~, ZnSO4.7ll20 -CH,COOt~la.3fl~0 20 g/~
Na2SO4 30 ~/e pll 1.8 to 2.0 (2) Plating conditions Bath temperature 50C
Flowing rate 2 m/s .
~urrent density 30 to 120 A/dm~ 2 The Fe contents in the films of the Fe-Zn by electric platings adjusted by mainly changing Fe salt ratio ( = FeS04.
7H,0/[FeS04.7H20+ZnS04.7H~0]) and the current density, and the adhesion amounts were adjusted by changing the coating time and the current density. Table 2 shows the appreciating results of the outer appearances of the coated films and the corrosion resistances after the electrodeposition paint and the process-abilities. It is seen from the same that the multi-layer coated 10 steel plates where the releasing amounts of the absorbed hydrogen were not more than 300 m /m , are superior in all properties.
Example II
The multi-layer coated steel sheets were produced from the cold rolled coils shown in the Table 1 which have passed the annealings and temper rollings, by alkaline degreasing, sulfuric acid picklings, Zn-Fe alloy electroplating and Fe-Zn alloying electroplatings in the electrogalvanizing line. The hydrogen absorption amounts were adjusted by the amounts of the outer layer coatings and by the continuous heating treat-20 men-t or batch-heating treatment at the temperature of no-t less than 100C after having been coated. The inner and outer layer coatings of this Example were practised under the same conditions as the outer layer Fe-Zn electric platings of Example Io The Fe contents and the coating weight of Fe-Zn and Zn-Fe electro-plated films were also adjusted under the same manners as Example I. The results of the evaluation of the properties are shwon .
- 1 0 - 2 ~
n Table 3. It is seen from the same that the multi-layer coated steel sheets where the releasing amounts of the absorbed hydrogen were not more th~n 300 m /m2, are superior in all properties.
Example III
The cold rolled coils of the compositions of Table 1 were successively subjected, as blank coils, to the hot dipping zinc plating in the continuous plating line of the non-oxidizing furnace system, the alloying treatment, the temper rolling, and Fe-Zn electroplating, and were successively subjected to the heating treatment under the atmospheric conditions via the induction heating system. With respect to the thus produced multi-layer coated steel sheets, Table 4 the shows results of the evaluation of the outer appearances of the coated ~ilms and the corrosion resistances after the electro-deposition paint and the coating adhesion together with the producing conditions.
According to the above table, the multi-layer coated sceel sheets heat-treated at the temperature from 100 to 400C are superior in all properties.
Example IV
The multi-layer coated steel plates were produced from the cold rolled coils shown in the Table 1 which have passed the annealings and temper rollings, by alkaline degreasing, sulfuric acid picklings, Zn-Fe alloying electroplating and Fe-Zn alloying electroplatings, and were successively subjected to the heating treatmetns under the nitrogen at~osphere via 2~3 ~.2 ~he induction heating system. With respect to the thus produced multi-layer c`oated steel sheets, Table 5 shows the results of the evaluation of the outer appearances of the coated films and the corrosion resistances after the electro-deposition paint and the coating adhesion together with the producing conditions, It is seen from the sarne that the multi-layer coated steel sheets which have been heat-treated at the temperature between 100 and 400C, are superior in all properties.
Example V
The cold rolled coils of the compositions of Table 1 ~ere successively subjected, as blank coils, to the hot dipping zinc plating in the continuous plating line of the non-oxidizing furnace system, the alloying treatment, the temper rolling, and Fe-Zn electroplating, whereby the multi-layer coated steel sheets were produced. Thereafter, these coated steel plates were subjected to the open coil heating with a cover type annealing furnace under the nitrogen gas bearing atmosphere.
~ith respect to the thus produced multi-layer coated steel sheets, Table 6 shows the results of the evaluation of the outer appearances of the coated films and the corrosion resistances after the electro-deposition paints and the coating adhesion together with the producing conditions. It is seen from the same that the multi-layer coated steel plates of open coils which have been heat-treated at the temperature between 100 and 250C, are superior in all properties.
:, . : .
INDUSTRIAL APPLICABILITY
The present invention is especially useEul as the coated steel plates to be painted witll a cationic electrodeposition for bodies of automol)iles, and as a pro~ucing method thereof.
Table 1 (~t~) . _ Cbils C Si Mn P S Sol.Al N Others _ _ I
. A 0.0028 0.01 0.17 0.0090.008 0.032 0,0035 Ti:0,072 I I I
U 0.0024 0.17 0.58 0.0250.006 0.05~ 0.0025 Nb:0.013 C 0.0012 0.01 0,023 1 0.010 0.011 0.0~5 0.0042 D 0.0~2 0.01 0.023 ¦ 0.010 0.011 0.0~5 0.00~2 E 0.020 0.01 0.015 0.012 ~0.010 0.0~0 0.0025 ~ c ~
~ ~ 9 o 3 ~ . ~ 2 ~c~5 ~G~
e'~
~ ~ ~ ~ ~ ~ ~ ~ T ~ ~
* ¢ ¢ ¢ ~ ¢ ¢ ¢ r ¢ ¢ ¢ ¢ ¢ ¢ ¢ ¢ ¢ ¢ ¢ ¢ ¢ ¢ ¢ : : E - O x O ¢ ¢ ¢ ¢ ¢ ¢ ¢ ¢ ¢ ¢ r ¢ r ¢ ¢ ¢ r ¢ ¢ ¢ ¢ ~ ~ ¢ E E ~, E
i Z * ¢ r r L ¢ i ¢ ¢ L l ¢ ¢ ¢ r ¢ ¢ ¢ ¢ l ¢ ¢ ¢ ¢ ~ E C P- E ..
~ ~ ~ ~ ~ ~ ~ a O ~ c i r r ~ ~ r r r r r O z ~ ~ h ~ E a ~ ~ ~ L~ L~ U~ U~ ~:1 Il~ C~l O U~ Lr~ cr ~r ~ c~ c~ ,~ n u~ t~ c~ u~ O ~ : E ~ ~a ~`
~ O f O L O r--r r--l O I o r~ O O O O O O O l ~ v ~ ~ c H X ~ oo oO oO oo oo o0 cO j~a L LL L ~ L L Lq~ ~ L L ~ ~ ~ O j~ O H h ~: V
~* ~ 1- ~ 1 1 ~ ~ ~ ._ ~ c~ L~ L~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
- ~ I¢ I¢ - _ L¢ _ L¢ L~ _ _ L ¢ ~ i ~ 1~ ~ ~ ¢ ¢ 1~ ¢ ~ 1l o ~ c _ ~ L~ 1~ L~ ~ 1~ ~ L~ 1~ ~ ~ ~ ~ ~ r 0l ~ ~ Ln I ~c ~ . . Examples I I 1 ~_ . ...... - - ~'J
e~
K '`~,~' O
O ¢ ¢ ¢ ¢ ¢ L ¢ ¢ ¢ ¢ ¢ ¢ ¢ ¢ ¢ r ¢ ¢ ¢ ¢ _ ¢ ~ a o z * ¢ ¢ ~ ~ ¢ ~ ¢ ¢ r ¢ ¢ ¢ r ¢ ¢ r ~ ¢ ¢ ¢ ¢ a 7. ,~ Vl 1~ 1~ ~ ~ v L o L ~ ~ O ~ r O L~ O r ~ r ~` ~ o E
, :~ o o u : : : æ C ~ ~ o o o z ~7 7 ~ o r ~ l :~~
~ol~ 3 W L ~L
~ i~ ~ i~ ~ ~ f~ 7~r~'`
_ ,_ ,_ _ ~ _ ~ l ~ ~ ~ c~l _ _ ~ ~ ~r ~ _ ~r ~ ~r _ , O ^ ~ ~ ~ . .
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o ~ L~ ~ ~ L ~ ~ i~ ~ ~ c~ ~ ~ ~ r- Oo l~ ~ C~ ~ m ,~
~Z Exampl e s I I Comp .
_ -- 23 ~
,, . , _ ~, 1, ~ ~ ~3 ~.3 ~o~ .~, C~, P~ f~5 ~Ga ~,e~ ~ , ~ ~ . ~ u ~ ~ ~a~ 1 ~
~ ~T ;~ ~ E O ~ ~
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H E ~ ~ ~ ~ ~ ~ ; ~ ~ ~ ~ i i O ;~ r ~ ~ O ~ i C ~ ~ E E - ~
_ ~æ ~ ~ ~ ~ ~ ¦~ ~ ~ - ~ - ~ ~ o ~ - ~ ~ ~ :~ ~ ~ v v t~ --r ~1~ ~L E~ll P :5 I I e~ E E
~T ;- ~ r j~:
,_ ~ c3 ~ ¢ ~ :~ :~ ~ ~ :~ ~ ~ _ :~ ~ :~ ~ _ :~ r~ r ~ ~ ~ ¢ ~ ;~ ¢ ~ a: ¢
~ ~ I¢ ~ ` 1 ~ ` i ~ ` ~ ~
Y o ¢ ~ ~ t ~ ~ ~ ~ ~ ~ ~ ~ 1~ ~ ¢ ~ ~ ¢ l) ¢ ~ c * æ ¢~ ~ r 1 ~ :~ :: :~ : :~ - ::: :~ - ::: ~ m ~ I¢ ~ ¢ ~ ~ ~ fi o o s ~ o~c tc I o ¦o ~ ~ o o o o o o o o o o o ~ c o ~i~ o o o ~a rl fi I t t t--t~ ~ a ~
E ~_ O ~ ~ ~ ~ _ r O O rr~ _ i _ ~ ~ ~ ~ :~ E ~ o o ~ ~ h v o~ I
C~ ~,r~ U~O 1~ r,~ O ,r~1 ~ O ~ O ~ ~ ~ ~ ~ ~ ~ ~ :C 1 O~0 r~l r~l ~ ~
~ ~ ~ _~__ _ _ _ ~ _ _ ~_;__ ~ ~ _ _ _ ~ ~`1 h a v ~ 1 ~ ~
~ c ¦ ~ ~ ~: r. ~ ~ cr) o ~ ~ :~ ~ ` ~ 1 ` ~ ¦ ` ¦ ` ~ --~ ¦ - Q
~ ~ ~ _ I I ~ I I I ~ ? U) a Q) (I~ r~ ¦ ~ ~ ~--~ _ _ ~_ ~ ~ ~D O 0 ~L~1 ` _ ~ _ ~ U 0~ 00 Q~ E
: ~ L~L ~L ; ~ L o ~L~ ~ 2 ~ _; H ~ ~ Q~ ?
u~ I ¦ ¦ ¦ ¦ ¦ ~ ~ ~ ~ ~ ~ ~ ~ ~ o ~L- ~1~ ~ ~ Q H ~ I ~a a a) I I ~1~ ~ l c ~ ~ ~ ~ ~ ¦m¦~ ~1¢1~ 1~--i ~ ~ 3 E~
n~ c~ ~1~ _ _ o _ c~ r~ ~1~ _ _ ~ --~ C~l ¦~------.~ ~ Q~
~ I Ex~mple IV ¦ Comp.
'~ ~ 3)~2 - 1~ 1~ 1~ 1~ ~ 1 ~ I 1~
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ V~ ¢ _ :~ ~ _ :: ::: r. :~ _ :: :~ ::: :~ :~ : 2 :~ ¢ 2 _ _ _ ~q * ¢ :~ :~ ~ ~ _ ~ ~ ~ ~; ¦ ~ ~ _ ~ ¢ ~ C 5~:
* e ¢ __ ~ O ~ ~ _ ~ _ ~ __ ~ O ~ O __ m ~ _ _ ~ C~
O O O O O O O O O O O O O O O O O O O OI O O ~ C
~: ~ ~D Il~ c~l ~ _ oo C~ ~ tD r~l Ll~ Il~ Il ~ I_ _ Ir~ u~ Il~ Il~ ~ ~ ~ ¦ ~ O ~ Q ~J r u _. E O t o o o o _ + o ~ ~ o V ~; 1 ~ ~ l 2 ~ ~
~ a ~I r ~ ~1 ~ ~ ~ r ~ --~ I L ~ I z I . . z h ~ r-l 0 ~ r~ ~~
_I_ I I _ _ _ I I _ Tr __ ~ O ~ cn _ ~ ~ ::: ¦ ~ ~; ~ ~: ~ cr~ O ~ ~ :: ~: U ) ::~ ~ t~) a.) ~ rl (~ _ + ¦ + ¦ +1 + _ ~1-- a) rl ~ S~ r-l I c~ ~ I - - I ~ ~ - ~ - I ~ ~ u~ 10~ 1 - I - I - ~ ~ ~ I ~ ? I ~ I ~ o ~ ~ o t ~ ~ T--_ _ t I I _I I I I _ _ ~ t~ _ ~ ~ r-l 1: ~ r~
.` H ¦oo I - ~ I ~ ~ ~ ~ I :c ~ ~ 1 1 l co I - ~ ~ o O ~ a) h ~ O O
II t _ _ _ ~ I II I I I I I I I I _ u~ o ~D I ~ ~ ~ ::: -- --~ ~¦~ C ~ -- ~ :::~ .
c~ ~ ¢ I ~ ~ I ~ ~ ~ I ~ c I ~ I - ~ I ~ I - I m I O ~1~1 ¢ I ~ ~ I ~ I - ~ ~ o ~ c~
r-l I t _ _ _ t --I t +l I I_ I I I I I _ ~ z ~1~ ~ _ _ _ ~1~ ~1~ ~ I ~r I ~ ~ ~ C~ o Exampl~s V ¦ Comp.
~ ~ 3 ~
Table 7 Test method and evaluating references Testing items Testing methods Evafluating re erences _ Immersion type phosphate treatment . (PAL BOND 3080) . l Cationic electro B : Occurrence of Bubble-like painting defects paint defects (ELECTRON 9410) A : No occurrence of . l defects , ~ .
After baking, observing outer appearance Immersion type .
phosphate A: The number of treatment crators, not more . (PAL BOND 3080) than 10/40 mm~
~ . .
Cation electro- B: The number of depositing crators, more than Crators (ELECTRON 9410 10 - less than 50/
Distance between 40 mm~
cathode and anode, 1:1 Momentary conduc-tivity, 280V, 3min) l' C: The number of Evaluating outer crators, not less appearance than 50/40 mm~
.
Immersion type phosphate .
treatment (PAL BOND 3080) Cationic electro-Corrosion painting A: Not more than 0.1 mm resistance (ELECTRON 9410) s,,,,~
Scribing . 1~
Cyclic corrosion .
tests .
Corrosion (Combination of resistance SST, HCTj Salt B: Not less than water immersion 0.3 mm and drying) 3 months After removing coating paint films and corrosion product s measuring maximum corrosion depth _ . Draw bead test A: No delamination . I of plated films Coating ~' Adhesion Taping B: P~emarkable delamination of .
plated f.ilms
Claims (13)
1. High corrosion resistant multi-layer coated steel sheet having excellent paintability, enabling the prevention of occur-ence of bubble-like ED paint defects, having, on the surface thereof, a coated film based on Zn or Zn alloys of a coating weight being not less -than 25 g/m2, which is a single layer or multi-layer coated film being composed of one or more than one kind selected from plated coatings based on Zn alloys or/and composite plated coatings based on Zn or Zn alloys; or which is a multi-layer coated film being composed of Zn plated coating, and one or more than one kind; selected from plated coatings based on Zn alloys or/and composite plated coatings based on Zn or Zn alloys, on said coated film based on Zn or Zn alloys, a coated film based on Fe or Fe alloys of a coating weight being 1 to 10 g/m', which is composed of one or more than one kind selected from Fe plated coating or/and plated coatings based on Fe alloys containing not less than 50% Fe, and wherein a total amount of the absorbed bydrogen in the coated film and the steel is not more than 300 m /m2 (per one side).
2. The steel sheet as claimed in claim 1, wherein the coating based on Zn alloys is Zn-Fe, Zn-Ni, Zn-Mn or Zn-Co alloyed coat-ings, or said alloyed coatings, each of which is contained with one or more than one kind of elements as Ti, Cr, Mo, W, etc.
The steel sheet as claimed in claim 1, wherein the composite coating based on Zn or Zn alloys is that one or more than one kind of Al2O3, Cr2O3, SiO2, and BaCrO4 are Co deposited in the Zn coating or the coating based on Zn alloys.
4. The steel sheet as claimed in claim 1, wherein the coating based on Fe alloys contains one or more than one kind of the elements as Zn, Ni, Co, Mn, Cr, Mo, W, P and B.
5. A method of producing the multi-layer coated steel sheet as claimed in claim 1, characterized by forming, on the surface thereof, a coated film based on Zn or Zn alloys of a coating weight being not less than 25 g/m2, which is a single layer or multilayer coated film being composed of one of more than one kind selected from of plated coatings based on Zn alloys or/and composite plated coatings based on Zn or Zn alloys; or which is a multi-layer coated film being composed of Zn plated coating, and one or more than one kind selected from plated coatings based on Zn alloys or/and composite plated coatings based on Zn or Zn alloys, and subsequently forming, on said coated film based on Zn or Zn alloys, a coated film based on Fe or Fe alloys of a coating weight being 1 to 10 g/m2, which is composed of one or more than one kind selected from Fe plated coating or/and plated coatings based on Fe alloys containing not less than 50% Fe, and heat-treating said multi-layer steel plates at a temper-ature between 100 and 400°C.
6. The method as claimed in claim 5, wherein th heating treat-ment is carried out in a continuous line, and the coated steel sheet is heated for not less than one second at a steel surface temperature of 100 to 400°C.
7. The method as claimed in claim 5, wherein the heating treat-ment is carried out in an open coil in a non-oxidizing atmosphere and the coated steel sheet is heated to a temperature of 100 to 250°C.
8. The method as claimed in claim 5, wherein the heating treat-ment is carried out in an atmosphere containing no hydrogen or in an atmosphere of such a hydrogen concentration to an extent that the hydrogen is not absorbed in the steel sheet practically.
9. The method as claimed in claim 5, wherein the heating treat-ment is carried out in an atmosphere containing no hydrogen or an atmosphere of such a hydrogen concentration that the hydrogen is not absorbed in the steel sheet practically, and the coated steel sheet is heated for not less than one second at a steel surface temperature of 100 to 400°C.
10. The method as claimed in claim 5 wherein the heating treat-ment is carried out in an open coil in a non-oxidizing atmosphere containing no hydrogen or in a non-oxidizing atmosphere of such a hydrogen concentration that the hydrogen is not absorbed in the steel sheet practically, and the coated steel sheet is heated for more than one second at a steel surface temperature of 100 to 250°C.
11. The method as claimed in claim 5, wherein the coating based on Zn alloys is Zn-Fe, Zn-Ni, Zn-Mn or Zn-Co alloyed coatings, or said alloyed coatings, each of which is contained with one or more than one kind of elements as Ti, Cr, Mo, W, etc.
12. The method as claimed in claim 5, wherein the composite coating based on Zn or Zn alloys is that one or more than one kind of Al2O3, Cr2O3, SiO2, and BaCrO4 are Co deposited in the Zn coating or the coating based on Zn alloys.
13. The method as claimed in claim 5, wherein the coating based on Fe alloys contains one or more than one kind the elements as of Zn, Ni, Co, Mn, Cr, Mo, W, P and B.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8927189A JPH02267251A (en) | 1989-04-07 | 1989-04-07 | Highly corrosion resistant double layer plated steel sheet capable of preventing occurrence of bubble-like electrodeposition coated film defect and excellent in coating suitability |
| JP89271 | 1989-04-07 | ||
| JP192527 | 1989-07-27 | ||
| JP19252789A JPH0361396A (en) | 1989-07-27 | 1989-07-27 | Production of double-layer plated steel sheet excellent in electrodeposition coating property capable of preventing generation of bubbly defect in electrodeposition coating film |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2030812A1 true CA2030812A1 (en) | 1990-10-08 |
Family
ID=26430700
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002030812A Abandoned CA2030812A1 (en) | 1989-04-07 | 1990-04-06 | High corrosion resistant multi-layer coated steel sheets having excellent paintability by enabling the prevention of occurrence of bubble-like ed paint defects, and producing method thereof |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0419678A4 (en) |
| KR (1) | KR920700310A (en) |
| CA (1) | CA2030812A1 (en) |
| WO (1) | WO1990012128A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ES2324273B1 (en) | 2008-02-01 | 2010-05-24 | Clear Glass Curtains, S.L. | SPACE CLOSURE SYSTEM. |
| DE102009053368A1 (en) * | 2009-11-14 | 2011-05-19 | Bayerische Motoren Werke Aktiengesellschaft | Process and manufacturing plant for producing a sheet metal part with a corrosion protection coating |
| EP3040440B1 (en) | 2013-08-26 | 2019-03-06 | JFE Steel Corporation | High-strength hot-dip galvanized steel sheet and method for manufacturing same |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5573888A (en) * | 1978-11-22 | 1980-06-03 | Nippon Kokan Kk <Nkk> | High corrosion resistant zinc-electroplated steel sheet with coating and non-coating |
| JPS5751283A (en) * | 1980-09-12 | 1982-03-26 | Nippon Steel Corp | Electroplating method for zinc-iron alloy |
| JPS5923893A (en) * | 1982-07-29 | 1984-02-07 | Sumitomo Metal Ind Ltd | Plated steel sheet with superior corrosion resistance and its manufacture |
| JPH0610358B2 (en) * | 1986-12-06 | 1994-02-09 | 日新製鋼株式会社 | Multi-layer electric plated steel sheet |
-
1990
- 1990-04-06 EP EP19900905670 patent/EP0419678A4/en not_active Withdrawn
- 1990-04-06 CA CA002030812A patent/CA2030812A1/en not_active Abandoned
- 1990-04-06 WO PCT/JP1990/000471 patent/WO1990012128A1/en not_active Application Discontinuation
- 1990-12-06 KR KR1019900702571A patent/KR920700310A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| KR920700310A (en) | 1992-02-19 |
| EP0419678A4 (en) | 1993-12-01 |
| EP0419678A1 (en) | 1991-04-03 |
| WO1990012128A1 (en) | 1990-10-18 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |