EP1537251A1 - Alliage de zinc et procede de trempage apres zingage par immersion a chaud d'acier - Google Patents

Alliage de zinc et procede de trempage apres zingage par immersion a chaud d'acier

Info

Publication number
EP1537251A1
EP1537251A1 EP03790958A EP03790958A EP1537251A1 EP 1537251 A1 EP1537251 A1 EP 1537251A1 EP 03790958 A EP03790958 A EP 03790958A EP 03790958 A EP03790958 A EP 03790958A EP 1537251 A1 EP1537251 A1 EP 1537251A1
Authority
EP
European Patent Office
Prior art keywords
hot
steel
alloy
bath
galvannealing
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.)
Withdrawn
Application number
EP03790958A
Other languages
German (de)
English (en)
Inventor
Bruno Gay
Serge Claessens
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Umicore NV SA
Original Assignee
Umicore NV SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Umicore NV SA filed Critical Umicore NV SA
Priority to EP03790958A priority Critical patent/EP1537251A1/fr
Publication of EP1537251A1 publication Critical patent/EP1537251A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • 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
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/06—Zinc or cadmium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C18/00—Alloys based on zinc
    • C22C18/04—Alloys based on zinc with aluminium as the next major constituent
    • 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

Definitions

  • the present invention relates to a hot-dip coating alloy composition suitable for galvannealing steel sheet.
  • Galvannealed coated products are well known to the automotive industry as product with excellent properties . Weldability and paint adhesion are particularly good. Nevertheless, market needs require most coating lines to produce galvanised and galvannealed products alternatively.
  • a bath of molten zinc Prior to entering the bath, the sheet typically undergoes a preparatory heat treatment in a furnace with a reducing atmosphere. A so-called snout makes the connection between this preparatory furnace and the coating bath. After passing through the bath, the desired coating thickness is obtained by means of air knives.
  • the steel sheet undergoes an additional heat treatment in an annealing furnace so as to perform the diffusion of Fe into the Zn coating. This heat treatment is applied immediately after the hot-dip step and the operation of the air knives .
  • At least some Al is typically added to the molten zinc bath for controlling Fe-Zn alloy growth during the passage of the steel sheet through the bath.
  • a relatively high Al concentration of more than 0.13 wt . % is normally used.
  • the main advantage of a high concentration of Al is that the formation of intermetallic Fe-Zn compounds in the bulk of the bath is avoided. These compounds, called bottom dross, have a tendency to slowly sink to the bottom of the bath. They also tend to form a deposit on the surface of the galvanised products, thereby jeopardising their surface quality.
  • the high Al concentration results in the formation of some Fe-Zn-Al intermetallic compounds, called top dross, because of their tendency to float on the bath surface. This type of dross is however easy to deal with as it can readily be skimmed off from the surface.
  • This high Al bath moreover produces a dense and impermeable Fe 2 Al 5 Zn x inhibition layer on the steel/zinc interface.
  • the object of the subsequent annealing step is precisely the formation of a Fe-Zn alloy, a process whereby Fe has to migrate freely through the steel/zinc interface.
  • the permeability of the interface is normally achieved by using a Zn alloy bath with a relatively low Al content of less than 0.13 wt.%.
  • JP08-291379 and JP04-254530 describe the use of the so-called pre-oxidation and subsequent reduction, during which a reactive metallic surface layer is created.
  • a Zn-alloy for hot-dip galvannealing steel, characterised in that it contains 0.12 to 0.35 wt.% Al and 0.02 to 0.11 wt . % Cr.
  • the alloy contains 0.135 to 0.29 wt.% Al and 0.05 to 0.10 wt.% Cr.
  • the alloy only contains Zn and unavoidable impurities.
  • the invention also encompasses a process for coating steel on an individual hot-dip line, comprising, in either order, the steps of:
  • a further embodiment concerns a process for galvannealing dual- phase steel by hot-dipping in a Zn alloy bath, characterised in that the Zn alloy contains 0.12 to 0.35 wt.% Al and 0.02 to 0.11 wt.% Cr
  • the invention also realises a lowering the specific energy consumption of a furnace used for annealing a product after hot-dipping in a Zn alloy bath, by performing either one or both steps of:
  • concentrations correspond to the bulk analysis of the bath, i.e. including undissolved floating compounds .
  • the enhanced Fe migration through the inhibition layer allows for an increase in the Al content of the alloy used for galvannealing.
  • This effect is particularly useful for galvannealing high-strength Si and P rich steels, which, as a rule, show low Fe diffusivity into the coating during annealing.
  • very low Al amounts down to 0.10 wt.%, are classically called for.
  • a considerable quantity of bottom dross is unavoidable in these conditions.
  • the Al content can be raised to 0.12 wt.% or event to 0.135 wt.% or more. The formation of bottom dross is thus considerably reduced.
  • top dross may be formed, the formation of bottom dross, which is as explained above a serious inconvenient, is considerably reduced or even totally avoided.
  • the enhanced Fe migration through the inhibition layer allows for a decrease in the annealing temperature.
  • This possibility is particularly useful for heath sensitive steels such as dual- phase steels. Indeed, such steels rapidly lose their useful properties when subject to high temperatures.
  • dual-phase steels are meant steels containing e.g. 0.35 Cr, 0.15 Si, 0.20 Mo; X: 0.70 Cr, 0.40 Si, 0.20 Mo.
  • the enhanced Fe migration through the inhibition layer allows for a decrease in the annealing time.
  • a specific energy input is needed during the annealing step to obtain the desired Fe-Zn alloying degree.
  • the annealing furnace may have become the limiting factor.
  • the invention then permits to increase the line throughput.
  • the above advantages can be combined, e.g. by decreasing the residence time in the annealing furnace and by lowering the annealing temperature.
  • Cr is an ecologically acceptable element, in particular when present in its elemental form such as in an alloy.
  • Al level of at least 0.12 wt.% The reasons for maintaining an Al level of at least 0.12 wt.% are explained above.
  • An Al level of more than 0.35 wt.% is undesirable, as the solubility, and hence the activity of Cr, decreases sharply at higher Al contents .
  • a minimum of 0.02 wt.% of preferably soluble Cr is needed to render the intermetallic crystals formed at the interface between the steel sheet and the zinc overlay sufficiently permeable to Fe diffusion.
  • the amount of Fe diffused into the coating is a measure for the annealing reactivity. Typical values are in the range between 9 and 11 % of Fe, corresponding to an Fe content in the coating of 4.5 to 5.5 g/m 2 for an assumed coating thickness of 7 ⁇ m.
  • annealing reactivity data is produced for a typical cold-rolled multi-phase steel with, in wt.%, 0.12 C, 0.12 Si, 1.5 Mn, 0.25 Cr and 0.20 Mo.
  • the Fe content in the coating was determined for a classical galvannealing bath and for a bath according to the invention.
  • Table 1 shows that a significantly higher reactivity is obtained with the Cr-bearing bath according to the invention: the reactivity increases with about 60 %, even thought a significantly lower annealing temperature was used.
  • Table 1 Annealing reactivity vs. bath composition
  • annealing reactivity data is shown for a classical Ti-IF steel with approximately 0.002 wt.% C, 0.17 wt.% Mn and 0.04 wt.% Ti, the other elements being the normal impurities in steel.
  • the annealing conditions were 30 sec. at 480 °C, which are typical for industrial lines.
  • Figure 1 gives the Fe-content in the coating vs . the Cr-content in the coating bath. It appears that an increase of approximately 3 g/m 2 of Fe is obtained for each 0.10 wt.% Cr added to the bath, both for 0.135 wt.% Al (a conventional galvannealing bath) and for a 0.20 wt.% Al (a conventional galvanising bath).

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Thermal Sciences (AREA)
  • Coating With Molten Metal (AREA)

Abstract

La présente invention concerne une composition d'alliage de revêtement par immersion à chaud, adaptée pour le trempage après zingage d'une feuille d'acier. L'ajout de 0,02 à 0,11% en poids de Cr à l'alliage permet d'obtenir dans le bain un contenu en Al plus élevé, tout en garantissant une diffusion suffisante de Fe dans le revêtement de Zn au cours du recuit. Ceci est particulièrement avantageux dans les lignes de revêtement dans lesquelles les produits galvanisés et trempés après zingage sont fabriqués en alternance. L'ajout de Cr permet d'abaisser la température de recuit et de réduire le temps de séjour de l'acier dans le four de recuit. Le processus de trempage après zingage d'aciers à deux phases, qui doivent être traités à des températures relativement basses, est ainsi sensiblement facilité.
EP03790958A 2002-08-28 2003-08-28 Alliage de zinc et procede de trempage apres zingage par immersion a chaud d'acier Withdrawn EP1537251A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP03790958A EP1537251A1 (fr) 2002-08-28 2003-08-28 Alliage de zinc et procede de trempage apres zingage par immersion a chaud d'acier

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
EP02078543 2002-08-28
EP02078543 2002-08-28
US40724402P 2002-09-03 2002-09-03
US407244P 2002-09-03
EP03790958A EP1537251A1 (fr) 2002-08-28 2003-08-28 Alliage de zinc et procede de trempage apres zingage par immersion a chaud d'acier
PCT/EP2003/009730 WO2004020684A1 (fr) 2002-08-28 2003-08-28 Alliage de zinc et procede de trempage apres zingage par immersion a chaud d'acier

Publications (1)

Publication Number Publication Date
EP1537251A1 true EP1537251A1 (fr) 2005-06-08

Family

ID=36459859

Family Applications (1)

Application Number Title Priority Date Filing Date
EP03790958A Withdrawn EP1537251A1 (fr) 2002-08-28 2003-08-28 Alliage de zinc et procede de trempage apres zingage par immersion a chaud d'acier

Country Status (6)

Country Link
US (1) US20060108032A1 (fr)
EP (1) EP1537251A1 (fr)
JP (1) JP2005537395A (fr)
KR (1) KR20050048621A (fr)
AU (1) AU2003264148A1 (fr)
WO (1) WO2004020684A1 (fr)

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60155660A (ja) * 1984-01-24 1985-08-15 Kawasaki Steel Corp 塗膜の２次密着性が優れたガルバニ−ルド鋼板およびその製造方法
JPH0413856A (ja) * 1990-05-02 1992-01-17 Nippon Steel Corp 耐食性にすぐれた合金化溶融亜鉛メッキ鋼板の製造法
JPH0688192A (ja) * 1991-08-28 1994-03-29 Nisshin Steel Co Ltd 加工性に優れた合金化溶融亜鉛めっき鋼板及びその製造方法
EP0852264A1 (fr) * 1997-01-02 1998-07-08 Industrial Galvanizadora S.A. Alliages de zinc donnant des revêtements anticorrosifs sur matériaux ferreux

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2004020684A1 *

Also Published As

Publication number Publication date
WO2004020684A9 (fr) 2004-05-27
AU2003264148A1 (en) 2004-03-19
JP2005537395A (ja) 2005-12-08
AU2003264148A8 (en) 2004-03-19
US20060108032A1 (en) 2006-05-25
WO2004020684A1 (fr) 2004-03-11
KR20050048621A (ko) 2005-05-24

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