WO2019186891A1 - Tôle d'acier zinguée et matériau en acier traité thermiquement - Google Patents

Tôle d'acier zinguée et matériau en acier traité thermiquement Download PDF

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WO2019186891A1
WO2019186891A1 PCT/JP2018/013233 JP2018013233W WO2019186891A1 WO 2019186891 A1 WO2019186891 A1 WO 2019186891A1 JP 2018013233 W JP2018013233 W JP 2018013233W WO 2019186891 A1 WO2019186891 A1 WO 2019186891A1
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granular
zinc
oxide
steel sheet
zinc oxide
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PCT/JP2018/013233
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English (en)
Japanese (ja)
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保明 河村
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日本製鉄株式会社
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Priority to PCT/JP2018/013233 priority Critical patent/WO2019186891A1/fr
Priority to JP2018540873A priority patent/JP6443599B1/ja
Publication of WO2019186891A1 publication Critical patent/WO2019186891A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
    • B21D22/20—Deep-drawing
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D201/00—Coating compositions based on unspecified macromolecular compounds
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
    • C09D7/40—Additives
    • 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

Definitions

  • the present invention relates to a zinc-based plated steel sheet and a heat-treated steel material.
  • a material having high mechanical strength tends to have a reduced shape freezing property in a forming process such as a bending process, and it is difficult to form a complicated shape.
  • a so-called hot press method also called a hot stamp method, a hot press method, or a die quench method
  • the hot pressing method a material to be formed is once heated to a high temperature, and the steel sheet softened by heating is pressed and formed and cooled.
  • the hot press method since the material is once heated to a high temperature and softened, the target material can be easily press-formed into a desired shape. Furthermore, the mechanical strength of the material can be increased by quenching by cooling after press molding. Therefore, according to the hot press method, a molded product (heat treated steel) having high dimensional accuracy and mechanical strength can be manufactured.
  • oxide scale compound
  • oxide scale compound
  • a descaling process for removing the oxide scale after hot pressing is required, which increases the manufacturing cost.
  • a steel sheet to be hot pressed is previously coated.
  • various materials such as organic materials or inorganic materials are used for coating the steel plate.
  • zinc (Zn) -based plated steel sheets that have a sacrificial anticorrosive action on steel sheets are widely used for automotive steel sheets.
  • Patent Documents 1 to 4 disclose hot-pressed plated steel sheets in which a steel sheet having a predetermined chemical composition is coated with a zinc-based metal coating.
  • a hot dip galvanized steel sheet or an alloyed hot dip galvanized steel sheet is used as the hot press steel sheet.
  • the structural member can be hot press formed without forming oxide scale (iron oxide) on the surface.
  • Patent Document 4 when a zinc oxide layer is formed thick on the surface of a steel material obtained by hot pressing a zinc-based plated steel sheet, the coating film adhesion of the steel material and the corrosion resistance after coating are adversely affected.
  • An invention is disclosed in which the zinc oxide layer is removed to perform or the thickness of the zinc oxide layer is reduced before coating.
  • Patent Documents 5 and 6 disclose inventions that improve coating film adhesion and corrosion resistance after coating of a steel material obtained by hot pressing a zinc-based plated steel sheet.
  • Patent Document 5 discloses an invention using a hot-dip galvanized steel sheet whose surface is coated with a silicone resin film
  • Patent Document 6 discloses a barrier layer (P) containing phosphorus (P) and silicon (Si).
  • An invention is disclosed in which a hot-dip galvanized steel sheet coated with a phosphate is exemplified as Si and colloidal silica is exemplified as Si as a steel sheet for hot pressing.
  • Patent Document 7 an element that is easier to oxidize than zinc (easily oxidizable element) is added to the galvanized layer, and the oxide layer of these easily oxidizable element is added to the zinc layer during temperature increase during hot pressing.
  • An invention is disclosed in which volatilization of zinc is prevented by forming it on the surface layer of the plating layer.
  • Patent Document 8 discloses a surface-treated steel sheet for heat treatment having a surface treatment layer formed from a treatment liquid containing granular silica on a zinc-based plating layer and having good corrosion resistance. Furthermore, Patent Document 9 is provided with a surface treatment layer containing at least one selected from titanium oxide, nickel oxide and tin (IV) oxide on the surface of the base material, and for coating film adhesion after hot pressing. An excellent galvanized steel sheet is disclosed.
  • the zinc-plated steel sheet When the hot pressing method is applied to a zinc-plated steel sheet, the zinc-plated steel sheet is heated to a high temperature of 800 ° C or higher, and the zinc in the plating film evaporates and oxidizes on the plating surface, forming a zinc oxide film. Is done. For this reason, since the effective zinc amount which contributes to corrosion resistance reduces, corrosion resistance falls, and since a zinc oxide film
  • the present inventor performs hot pressing on a hot-dip galvanized steel sheet whose surface is covered with a silicone resin film, disclosed in Patent Document 5, and A supplementary test was conducted to manufacture. As a result, as will be described later, it was found that although the corrosion resistance after coating of the hot pressed steel material in the cyclic corrosion test in which the wet and dry environment is repeated is good, the coating adhesion of the hot pressed steel material is not necessarily good.
  • the hot-pressed steel material obtained by the invention disclosed in Patent Document 5 is, for example, a part or member where water tends to accumulate due to its structure (for example, a bag-like structure part under the door, a closed cross-section member in the engine compartment, etc. ) Is not suitable for use.
  • the surface-treated steel sheet for heat treatment disclosed in Patent Document 8 is slightly inferior in terms of corrosion resistance in a more severe corrosive environment.
  • deletion part is provided in Si containing film and the adhesiveness of an electrodeposition coating film is improved with the zinc oxide which appears on the surface through there, it cannot necessarily be said to be sufficient, but the room for improvement is left.
  • the zinc-based plated steel sheet disclosed in Patent Document 9 is excellent in coating film adhesion after hot pressing, there remains room for improvement in terms of chemical conversion treatment.
  • the present invention has been made to solve the above problems, and provides a galvanized steel sheet and a heat-treated steel material that are excellent in spot weldability in addition to corrosion resistance after hot pressing, adhesion after coating, and chemical conversion treatment.
  • the purpose is to do.
  • the present invention is as listed below.
  • a base material having a zinc-based plating layer on the surface of the steel sheet A surface treatment layer formed on at least one side of the base material, The surface treatment layer is a content per one side, Granular carbon black: 0.15 to 1.0 g / m 2 , Granular silica: 0.5-2.0 g / m 2 , and Containing granular zinc oxide: 0.20 to 2.0 g / m 2 ; Galvanized steel sheet.
  • the surface treatment layer is a content per side, Granular carbon black: 0.15 to 1.0 g / m 2 , Granular silica: 0.5 to 1.5 g / m 2 , and Containing granular zinc oxide: 0.50 to 2.0 g / m 2 ;
  • the galvanized steel sheet according to (1) or (2) above.
  • the surface treatment layer is a content per one side, Granular carbon black: 0.15 to 1.0 g / m 2 , Granular silica: 1.0-2.0 g / m 2 , and Containing granular zinc oxide: 0.20 to 1.0 g / m 2 ;
  • the galvanized steel sheet according to (1) or (2) above.
  • the granular zinc oxide particles are granular doped zinc oxide particles.
  • the galvanized steel sheet according to any one of (1) to (4) above.
  • the surface treatment layer is a content per one side, and Titanium-containing compound: containing 0.2 to 2.0 g / m 2
  • Titanium-containing compound containing 0.2 to 2.0 g / m 2
  • the titanium-containing compound is a titanium oxide having an average particle diameter of 1 to 200 nm and / or a titanium-containing non-oxide ceramic having an average particle diameter of 0.2 to 5 ⁇ m.
  • the surface treatment layer has a total content of at least one selected from zirconia, lanthanum oxide, cerium oxide and neodymium oxide having a content per one side and an average particle size of 5 to 500 nm. Containing 2 to 2.0 g / m 2 , The galvanized steel sheet according to any one of (1) to (7) above.
  • the surface forming layer is a content per one side, Silica: 0.5-2.0 g / m 2 , and Containing zinc oxide: 0.20 to 2.0 g / m 2 , and
  • the area ratio occupied by zinc oxide having a particle diameter of 0.01 to 1 ⁇ m in the cross section perpendicular to the surface of the surface forming layer and from the surface to the center in the thickness direction is 10 to 50%.
  • a galvanized steel sheet and a heat-treated steel material that are excellent in spot weldability in addition to corrosion resistance after hot pressing, adhesion after coating, and chemical conversion treatment can be obtained.
  • FIG. 1 is a diagram schematically showing a cross section of a heat-treated steel material according to an embodiment of the present invention.
  • FIG. 2 is an SEM photograph of the surface of the heat-treated steel sheet according to the present invention after the phosphate treatment.
  • FIG. 3 is a SEM photograph of the surface after the phosphate treatment of the heat-treated steel sheet according to the comparative example.
  • FIG. 4 is a diagram schematically showing a cross section of the heat-treated steel material of the comparative example.
  • FIG. 5 is a diagram schematically showing a cross section of a heat-treated steel material of a comparative example.
  • % related to chemical composition or concentration means “% by mass” unless otherwise specified.
  • the zinc-based plated steel sheet according to the present invention includes a base material and a surface treatment layer formed on at least one side of the base material.
  • the surface treatment layer contains the following amounts of granular carbon black, granular silica, and granular zinc oxide per side.
  • the galvanized steel sheet according to the present invention is suitably used for the hot pressing method.
  • Granular carbon black 0.15 to 1.0 g / m 2
  • Granular silica 0.5 to 2.0 g / m 2
  • Granular zinc oxide 0.20 to 2.0 g / m 2
  • Base material of the zinc-based plated steel sheet according to the present invention has a zinc-based plating layer on the surface of a steel sheet (base steel sheet).
  • the base steel sheet is not limited to a specific steel sheet, and various steel sheets having known characteristics and chemical compositions can be used.
  • the chemical composition of a base steel plate is not specifically limited, It is preferable that it is a chemical composition which can obtain high intensity
  • the base steel plate has C: 0.05 to 0.4%, Si: 0.5% or less, and Mn: 0.5-2. 5%, P: 0.03% or less, S: 0.01% or less, sol. Al: 0.1% or less, N: 0.01% or less, B: 0 to 0.005%, Ti: 0 to 0.1%, Cr: 0 to 0.5%, Nb: 0 to 0.1 %, Ni: 0 to 1.0%, and Mo: 0 to 0.5%, with the balance being made of quenching steel having a chemical composition consisting of Fe and impurities.
  • the chemical composition of the base steel sheet may not be the above chemical composition.
  • the total content of Mn and Cr is preferably 0.5 to 3.0% from the hardenability during quenching and the formability of Mn oxide and Cr oxide contained in the zinc oxide layer after heating. More preferably 0.7 to 2.5%.
  • the total content of Mn and Cr is less than 0.5%, the amount of complex oxide formed on the surface layer after hot pressing becomes insufficient, and better coating adhesion may not be obtained.
  • the total content of Mn and Cr exceeds 3.0%, the coating adhesion is not a problem, but the cost is increased, and the toughness of the spot welded portion is significantly reduced, or the wettability of plating. Deterioration may be significant.
  • the zinc-based plating layer of the base material is not particularly limited, and generally known zinc-based plating can be used.
  • Examples of zinc-based plating layers include hot-dip Zn plating, alloyed hot-dip Zn plating, hot-dip Zn-55% Al-1.6% Si plating, hot-melt Zn-11% Al plating, hot-melt Zn-11% Al-3% Mg plating, hot-melt Zn-6% Al-3% Mg plating, hot-melt Zn-11% Al-3% Mg-0.2% Si plating, electric Zn plating, electric Zn-Ni plating, electric Zn-Co plating, etc. Illustrated.
  • a specific hot dip plating process is to immerse the steel plate in a plating bath in which Zn or Zn alloy in a molten state is held, and to lift the steel plate from the plating bath.
  • the amount of plating attached to the steel sheet is controlled by adjusting the pulling speed of the steel sheet or adjusting the flow rate or flow rate of the wiping gas ejected from the wiping nozzle provided above the plating bath.
  • the alloying treatment after plating is performed by additionally heating the steel plate after plating in a gas furnace, an induction heating furnace, or a heating furnace using a combination thereof after the hot dipping treatment.
  • the hot dipping may be performed by either a continuous coil plating method or a single plate cutting method.
  • a specific electroplating process is to perform an electrolytic process between a counter electrode and a steel sheet as a negative electrode in an electrolytic solution containing Zn ions. Moreover, the amount of plating attached to the steel sheet is controlled by adjusting the composition of the electrolytic solution, the current density, or the electrolysis time.
  • the thickness of the zinc-based plating layer that is, the adhesion amount of the zinc-based plating layer is preferably 10 to 100 g / m 2 per side. If the thickness of the zinc-based plating layer is less than 10 g / m 2 per side, the amount of effective zinc after hot pressing cannot be ensured, and the corrosion resistance of the heat-treated steel after hot pressing may be insufficient. On the other hand, if the thickness of the zinc-based plating layer exceeds 100 g / m 2 per side, the workability and adhesion of the zinc-based plating layer may be reduced.
  • the thickness of the zinc-based plating layer is more preferably 20 to 80 g / m 2 per side.
  • the zinc Zn-plated Ni, the alloyed hot-dip Zn plating, or the alloyed hot-dip Zn plating on which the melting point of the zinc-based plating is improved during hot pressing is preferred.
  • Granular Carbon Black means carbon black that exists in the form of particles in the surface treatment layer. By using granular carbon black, it is possible to suppress the oxidation of zinc on the surface of the zinc-based plating by sacrificial oxidation of the granular carbon black during the heating of the hot press, and to improve the emissivity of the surface treatment layer, thereby improving the atmosphere. It is possible to increase the rate of temperature increase in heating in the atmosphere or furnace heating.
  • the granular carbon black contained in the surface treatment layer has a content per side of 0.15 to 1.0 g / m 2 . If the granular carbon black content is less than 0.15 g / m 2 , the effect of suppressing the oxidation of zinc cannot be obtained because the absolute amount of carbon black is small. On the other hand, when the content of the granular carbon black exceeds 1.0 g / m 2 , the effect of suppressing the oxidation of zinc is saturated and the corrosion resistance before hot pressing is lowered.
  • the average particle size of the granular carbon black is preferably 10 to 100 nm. In order to suppress the oxidation of zinc, it is advantageous that the particle size of the granular carbon black is small, but carbon black having an average particle size of less than 10 nm is difficult to obtain, leading to an increase in cost. On the other hand, when the average particle diameter of the granular carbon black exceeds 100 nm, the contact area between the granular carbon black and the galvanized steel sheet is reduced, and the sacrificial oxidation of the granular carbon black during hot pressing is reduced.
  • the average particle diameter of the granular carbon black is more preferably 20 to 50 nm.
  • the average particle diameter (primary particle diameter) of granular carbon black can be measured by a known method. For example, it can be measured by preparing a cross-section embedded sample after coating, measuring several particle sizes of granular carbon black in the film, and averaging the obtained measurement results to obtain an average particle size.
  • Examples of the granular carbon black include carbon black used as a coloring pigment and the like, or a carbon black dispersion liquid obtained by previously dispersing carbon black in a solvent.
  • Specific commercial products include carbon black manufactured by Mitsubishi Chemical Corporation and high-concentration carbon black dispersion manufactured by Toyo Color Co., Ltd.
  • Granular silica does not exist in a state of being dissolved in the treatment liquid, such as a silane coupling agent, but in a state of particles having a primary particle diameter of several nm or more. It means a substance mainly composed of Si oxide. By using granular silica, it is possible to suppress the evaporation of zinc from the zinc-based plating layer by forming a glassy film during the hot press heating.
  • the granular silica contained in the surface treatment layer has a content per side of 0.5 to 2.0 g / m 2 .
  • the content of the granular silica is less than 0.5 g / m 2 , a glassy film is not uniformly formed on the surface of the zinc-based plating layer, and zinc evaporation cannot be sufficiently suppressed.
  • the content of the granular silica is more than 2.0 g / m 2 , the thickness of the glassy silica coating layer increases, so that the electrical resistance value of the coating surface increases and good spot weldability is obtained. I can't.
  • the average particle diameter of the granular silica is preferably 2 to 100 nm. From the viewpoint of promptly forming a glassy film that suppresses the evaporation of zinc, it is advantageous that the particle size of the granular silica is smaller, but those having a particle size of less than 2 nm are difficult to obtain and cost increases. . On the other hand, when the particle size of the granular silica exceeds 100 nm, it is difficult to form a uniform film, and local evaporation of zinc is likely to occur.
  • the particle size of the granular silica is preferably 7 to 40 nm.
  • the average particle diameter (primary particle diameter) of granular silica can be measured by a known method. For example, it can be measured by preparing a cross-sectional embedded sample after coating, measuring several particle sizes of granular silica in the film, and averaging the obtained measurement results to obtain an average particle size.
  • colloidal silica dispersed in an aqueous solution in advance is exemplified.
  • Specific examples of commercially available products include the Snowtex (registered trademark) series manufactured by Nissan Chemical Co., Ltd.
  • Granular Zinc Oxide means zinc oxide present in the form of particles in the surface treatment layer. Due to the granular zinc oxide, the granular zinc oxide is present on the surface of the film after hot press heating, so that zinc phosphate crystals are easily formed during the phosphate treatment, which is a chemical conversion treatment for automobiles. The coating film adhesion after coating is improved.
  • the mechanism of the formation of phosphate crystals due to the presence of zinc oxide is that when the chemical conversion treatment is performed with an acidic chemical conversion treatment solution, the zinc oxide exposed on the surface of the resin coating film is dissolved by the acidic chemical conversion treatment solution. Since the pH in the vicinity increases, components of the chemical conversion treatment liquid (for example, acid chlorides such as phosphates) precipitate and grow.
  • the chemical conversion treatment liquid for example, acid chlorides such as phosphates
  • the granular zinc oxide contained in the surface treatment layer has a content per side of 0.20 to 2.0 g / m 2 . If the content of granular zinc oxide is less than 0.20 g / m 2 , the amount of zinc oxide present on the surface of the coating after heating in the hot press is not sufficient, resulting in a slaked chemical conversion crystal. The coating film adhesion after painting is poor.
  • the content of granular zinc oxide is more than 2.0 g / m 2 , the thickness of the coating layer containing zinc oxide increases, so that the cohesive strength of the coating is reduced. As a result, the adhesion of the coating film decreases and the electrical resistance value on the surface of the coating increases, and good spot weldability cannot be obtained.
  • the average particle diameter of the granular zinc oxide is preferably 0.01 to 1 ⁇ m.
  • the particle size of the granular zinc oxide is smaller, but those having a particle size of less than 0.01 ⁇ m are difficult to obtain, Cost increases.
  • the average particle diameter of the granular zinc oxide is preferably 0.05 to 0.5 ⁇ m.
  • the average particle diameter (primary particle diameter) of zinc oxide can be measured by a known method. For example, it can be measured by preparing a cross-sectional embedded sample after coating, measuring the particle size of granular zinc oxide in the film, and averaging the obtained measurement results to obtain the average particle size.
  • zinc oxide powder which is a commercially available chemical, is exemplified.
  • Each of the above-described effects can be obtained by containing the above-described predetermined amounts of the above-described granular carbon black, granular silica, and granular zinc oxide.
  • granular carbon black undergoes sacrificial oxidation during hot press heating to suppress zinc oxidation
  • granular silica forms a glassy film to suppress zinc evaporation.
  • excellent corrosion resistance and spot weldability and (c) the presence of zinc oxide on the coating surface after hot pressing to form a uniform zinc phosphate coating during phosphating, Good coating film adhesion after electrodeposition can be obtained.
  • Resin and cross-linking agent for the formation of the surface treatment layer, granular carbon black, granular silica and granular zinc oxide may be applied as they are on the zinc-based plated steel sheet, but the stability of the treatment liquid In order to improve the adhesion of the surface treatment layer, it is preferable to apply it to a galvanized steel sheet as a treatment liquid in which a resin and a crosslinking agent are mixed.
  • the resin when a carbon black dispersion is used as the granular carbon black and colloidal silica is used as the granular silica, it is preferable to use a water-soluble or water-dispersible resin.
  • the resin include polyurethane resin, polyester resin, epoxy resin, (meth) acrylic resin, polyolefin resin, phenol resin, and modified products of these resins.
  • solvent-based resins using various solvents as solvents may be used.
  • crosslinking agent examples include silane coupling agents, zirconium carbonate compounds, organic titanium compounds, oxazoline polymers, water-soluble epoxy compounds, water-soluble melamine resins, water-dispersed blocked isocyanates, and water-based aziridine compounds.
  • the content of granular carbon black, granular silica and granular zinc oxide preferably satisfies the following formula (i).
  • the granular zinc oxide occupies the film formed during the heating of the hot press uniformly, and this does not hinder the effects of the above-described granular carbon black and granular silica.
  • a uniform zinc phosphate coating can be formed during the phosphate treatment.
  • coating film adhesion after electrodeposition coating is improved.
  • C Granular carbon black content (g / m 2 )
  • S Content of granular silica oxide (g / m 2 )
  • Z Content of granular zinc oxide (g / m 2 )
  • the granular zinc oxide is preferably a granular doped zinc oxide because spot weldability after hot pressing is more excellent.
  • the granular doped zinc oxide for example, at least one element selected from the group consisting of Group 13 elements of Periodic Table and Group 15 elements of Periodic Table (hereinafter also referred to as “doping elements”) is used. And particles that are doped to develop conductivity.
  • Examples of group 13 elements of the periodic table include B, Al, Ga, In and the like.
  • Examples of group 15 elements of the periodic table include P and As.
  • Al and Ga are preferable as doping elements for improving conductivity, and Al is more preferable from the viewpoint of cost.
  • the content of the doping element is preferably 0.05 to 5 atm% and more preferably 0.1 to 5 atm% with respect to the undoped zinc oxide particles in order to improve conductivity.
  • granular dope-type zinc oxide is dissolved in a chemical conversion treatment solution, and then promotes the growth of crystals of the chemical conversion treatment film (for example, crystals of acid chlorides such as phosphates).
  • crystals of the chemical conversion treatment film for example, crystals of acid chlorides such as phosphates.
  • the adhesion between the resin coating film and the coating film can be further improved by the crystal anchor effect of the chemical conversion film.
  • the dope-type zinc oxide particles are dissolved in the chemical conversion treatment solution and then taken into the chemical conversion treatment film.
  • the dope-type zinc oxide particles not only improve the adhesion of the coating film after electrodeposition coating, but also have conductivity, so that they also act as a conductive pigment to improve conductivity and provide excellent spot weldability. It is done.
  • the granular dope-type zinc oxide contained in the surface treatment layer has a content per side of 0.20 to 2.0 g / m 2 like the granular zinc oxide. If the content of granular dope-type zinc oxide is less than 0.20 g / m 2 , the amount of zinc oxide present on the surface of the coating after heating in the hot press is not sufficient, resulting in a slaked chemical crystal.
  • the film adhesion after electrodeposition coating may be inferior.
  • the content of the granular zinc oxide is more than 2.0 g / m 2 , the thickness of the coating layer containing the dope-type zinc oxide is increased, so that the cohesive strength of the coating is reduced, and after electrodeposition coating There is a risk that the adhesion of the coating film will be reduced.
  • the average particle diameter of the granular dope-type zinc oxide is preferably 0.1 to 1 ⁇ m.
  • the average particle diameter of the granular zinc oxide is preferably 0.2 to 0.5 ⁇ m.
  • Titanium-containing compound As another component that is preferably further contained in the surface treatment layer, a titanium-containing compound is exemplified.
  • the presence of titanium oxide, which is oxidized after hot pressing, on the surface of the steel sheet has some influence on the agglomeration and precipitation of the electrodeposition coating during electrodeposition coating. Further, by firmly adhering the oxide and the electrodeposition coating film, even if the chemical conversion treatment is not sufficient, strong coating film adhesion can be obtained.
  • the emissivity of a surface treatment layer improves like a carbon black mentioned above by containing a titanium containing compound
  • the temperature increase rate by the heating in an air atmosphere or a furnace heating can be raised.
  • the content of the titanium-containing compound is preferably 0.2 to 2.0 g / m 2 .
  • titanium-containing non-oxide ceramics having an average particle size of 0.2 to 5 ⁇ m are preferably used.
  • titanium-containing non-oxide ceramics having an average particle size of 0.2 to 5 ⁇ m have zinc oxide at the time of hot pressing because the surface or a part thereof becomes titanium oxide when heated by hot pressing. Inhibits oxidation and evaporation. Moreover, since the titanium-containing non-oxide ceramic remaining without being oxidized exhibits excellent conductivity, conductivity is improved and spot weldability is improved.
  • non-oxide ceramics means ceramics composed of a compound not containing oxygen as an element.
  • examples of non-oxide ceramics include boride ceramics, nitride ceramics, silicide ceramics, and the like.
  • Boride ceramics, nitride ceramics and silicide ceramics are non-oxide ceramic particles containing titanium having boron (B), nitrogen (N) and silicon (Si) as the main non-metallic constituent elements, respectively. It is.
  • titanium-containing non-oxide ceramics examples include TiB (electric resistivity at 25 ° C .: 40 ⁇ 10 ⁇ 6 ⁇ cm), TiB 2 (electric resistivity at 28 ° C .: 10 ⁇ 6 ⁇ cm), TiC (180 electrical resistivity 10 -6 [Omega] cm) at ° C., TiN (22 electrical resistivity 10 -6 [Omega] cm at °C), TiSi (63 electrical resistivity 10 -6 [Omega] cm at ° C.), electricity at TiSi 2 (123 ° C. Examples thereof include at least one kind of particles selected from the group consisting of particles having a resistivity of 10 ⁇ 6 ⁇ cm. Specific examples of commercially available products include titanium-containing non-oxide ceramics manufactured by Nippon Shin Metal Co., Ltd.
  • titanium-containing compound titanium oxide having an average particle diameter of 1 to 200 nm may be used, or a mixture of the above titanium-containing non-oxide ceramic and titanium oxide may be used.
  • titanium oxide having an average particle size of 1 to 200 nm suppresses oxidation and evaporation of zinc during hot pressing, and in addition to coating film adhesion after hot pressing, corrosion resistance after hot pressing. Can be increased.
  • Titanium oxide usually exists stably in the form of a metal oxide, but it reacts with zinc oxide present in the film to form a complex oxide with zinc oxide, thereby further suppressing zinc oxidation and evaporation. It is estimated that. In order to obtain this effect more efficiently, the average particle diameter of titanium oxide is preferably 2 to 100 nm.
  • titanium oxide has a high emissivity, and unlike carbon black, which has the same emissivity, it exists as titanium oxide even in a heated state near 900 ° C., so that it is heated for a long time as described later during hot pressing.
  • the titanium oxide content is preferably less than 0.2 g / m 2, and more preferably 0.1 g / m 2 or less.
  • titanium oxide is a titanium oxide dispersion previously dispersed in an aqueous solution.
  • Specific examples of commercially available products include the Snowtex (registered trademark) series manufactured by Nissan Chemical Co., Ltd.
  • Zirconia Lanthanum Oxide, Cerium Oxide, and Neodymium Oxide
  • Other components that are preferably added to the surface treatment layer include zirconia (zirconium oxide), lanthanum oxide, cerium oxide, and neodymium oxide.
  • the surface treatment layer contains one or more selected from the above-mentioned zirconia, lanthanum oxide, cerium oxide and neodymium oxide, Al oxide which exists before hot pressing and is formed during hot pressing.
  • zirconia, lanthanum oxide, cerium oxide, and neodymium oxide present in the surface treatment layer during heating are rendered harmless.
  • the average particle size of the above oxide is 5 It is preferable that the thickness is ⁇ 500 nm.
  • the surface treatment layer contains one or more of a P-containing compound, a V-containing compound, and a Cu-containing compound at a predetermined content. Also good.
  • the P-containing compound is a compound containing phosphorus as a constituent element.
  • Examples of the P-containing compound include phosphoric acid, phosphorous acid, phosphonic acid, phosphonous acid, phosphinic acid, phosphinic acid, phosphine oxide, and phosphine, or ionic compounds having these compounds as anions. Illustrated.
  • All P-containing compounds are commercially available as reagents or products and can be easily obtained.
  • the P-containing compound exists in a state of being dissolved in the treatment liquid or dispersed as a powder in the treatment liquid, and is present in a state of being dispersed as a solid in the surface treatment layer.
  • V-containing compound is a compound containing vanadium as a constituent element.
  • V-containing compounds include vanadium oxides containing vanadium pentoxide, metavanadate compounds containing ammonium metavanadate, vanadium compounds containing sodium vanadate, and other V-containing compounds.
  • V-containing compounds are all commercially available as reagents or products and can be easily obtained.
  • the V-containing compound exists in a state dissolved in the treatment liquid or dispersed as a powder in the treatment liquid, and exists in a state dispersed as a solid in the surface treatment layer.
  • the surface treatment layer preferably contains one or more compounds selected from P-containing compounds and V-containing compounds in an amount of 0.0 to 0.01 g / m 2 per side in terms of P and V, respectively.
  • One or more kinds of compounds selected from P-containing compounds and V-containing compounds are oxidized during hot pressing to become oxides, unevenly distributed at the interface between the zinc-based plating layer and the surface treatment layer, and at least either P or V An oxide layer having a weak cohesive force is formed.
  • the content of one or more selected from the P-containing compound and the V-containing compound in the surface treatment layer exceeds 0.01 g / m 2 per side, the thickness of the oxide layer having a weak cohesive force formed during hot pressing The adhesion between the zinc-based plating layer and the surface treatment layer decreases, thereby decreasing the adhesion of the coating film after electrodeposition coating.
  • the content of one or more compounds selected from the P-containing compound and the V-containing compound in the surface treatment layer is P and V converted. And more preferably 0.0 to 0.003 g / m 2 per side.
  • the Cu-containing compound is a compound containing copper as a constituent element.
  • Examples of the Cu-containing compound include metal Cu, copper oxide, various organic copper compounds, various inorganic copper compounds, various copper complexes, and the like.
  • Cu-containing compounds are all commercially available as reagents or products and can be easily obtained. These Cu-containing compounds are present in a state dissolved in the treatment liquid or dispersed as a powder in the treatment liquid, and are present in a state dispersed as a solid in the surface treatment layer.
  • the surface treatment layer preferably contains one or more compounds selected from Cu-containing compounds in an amount of 0.0 to 0.02 g / m 2 per side in terms of Cu.
  • One or more compounds selected from Cu-containing compounds are oxidized during hot pressing to become oxides, unevenly distributed at the interface between the zinc-based plating layer and the surface treatment layer, and containing Cu with weak cohesive force Form a layer.
  • Oxide with weak cohesive force formed during hot pressing because the content of one or more compounds selected from Cu-containing compounds is 0.0 to 0.02 g / m 2 per side in terms of Cu The thickness of the layer is reduced, and the adhesion between the hot-pressed zinc-based plating layer and the surface treatment layer is further improved.
  • the content of one or more selected from Cu-containing compounds in the surface treatment layer exceeds 0.02 g / m 2 per side, the thickness of the oxide layer with weak cohesive force formed during hot pressing increases. Moreover, the adhesiveness of the interface of a zinc-type plating layer and a surface treatment layer falls, and the coating-film adhesiveness after electrodeposition coating also falls. In addition, since Cu is an element more noble than Fe, which is the main component of the base steel sheet, the corrosion resistance is also reduced.
  • the content of one or more compounds selected from Cu-containing compounds in the surface treatment layer is 0. More preferably, it is 0 to 0.005 g / m 2 .
  • Nickel oxide and tin (IV) oxide are contained in the surface treatment layer to improve the durability of the coating.
  • nickel oxide and tin (IV) oxide like titanium oxide, have a relatively high emissivity, and unlike carbon black having the same emissivity, nickel oxide and tin oxide are also heated in the vicinity of 900 ° C. Since it exists as (IV), when performing heating for a long time as will be described later at the time of hot pressing, corrosion resistance may be impaired because Zn during plating diffuses through the base steel plate. Therefore, titanium oxide, the total content of nickel oxide and tin (IV) oxide is preferably less than 0.2 g / m 2, and more preferably 0.1 g / m 2 or less.
  • the heat-treated steel material according to the present invention includes a base material and a surface forming layer formed on at least one side of the base material.
  • the surface forming layer contains the following amounts of silica and zinc oxide per side.
  • the area ratio occupied by zinc oxide having a particle diameter of 0.01 to 1 ⁇ m in the cross section perpendicular to the surface of the surface forming layer and from the surface to the center in the thickness direction is 10 to 50%.
  • Silica 0.5 to 2.0 g / m 2
  • Zinc oxide 0.20 to 2.0 g / m 2
  • the heat-treated steel material refers to a steel material that can be hot-pressed on a predetermined steel plate.
  • the type of the base material is not particularly limited, but in the following description, a heat-treated steel material obtained by subjecting the above-described zinc-based plated steel sheet to hot pressing will be described as an example.
  • FIG. 1 is a view schematically showing a cross section of a heat-treated steel material according to an embodiment of the present invention.
  • the base material 10 of the heat-treated steel material 100 has, for example, a zinc-based plating layer 12 on the surface of a steel plate (base steel plate) 11.
  • a zinc-based plating layer 12 on the surface of a steel plate (base steel plate) 11.
  • base steel plate 11 and the zinc-type plating layer 12 since it is the same as the above-mentioned zinc-type plating steel plate, description is abbreviate
  • a boundary layer (not shown) is formed at the boundary between the base steel plate 11 and the zinc-based plating layer 12 by heating before hot pressing. As described later, there are two types of heating methods before hot pressing, short-time heating and long-time heating, and the configuration of the boundary layer varies depending on the heating method.
  • a solid solution layer and an intermetallic compound layer are formed sequentially from the base steel material 11 side toward the zinc-based plating layer 12 side.
  • the solid solution layer is formed by diffusing zinc in the plating layer into the base steel plate 11, and is a layer composed of an iron zinc solid solution phase containing 50 to 80% by mass of Fe.
  • the intermetallic compound layer is a layer composed of a zinc-based ⁇ phase containing 9 to 30% by mass of Fe.
  • a solid solution layer is formed between the base steel material 11 and the zinc-based plating layer 12.
  • the above iron-zinc solid solution phase contains Zn, it exhibits excellent corrosion resistance by having a solid solution layer mainly composed of Zn.
  • the ⁇ phase is a zinc-based intermetallic compound, it has a higher sacrificial anticorrosive ability than the iron zinc solid solution phase. Therefore, the sacrificial anticorrosive ability which was excellent by having an intermetallic compound layer is exhibited.
  • the iron-zinc solid solution phase has the same crystal structure (body-centered cubic lattice) as that of the base steel plate, but since Zn is dissolved, the lattice constant is larger than that of the base steel plate and can be distinguished. .
  • a surface formation layer 20 in which zinc oxide 22 is dispersed in a matrix 21 mainly composed of silica is provided on the substrate 10.
  • silica contained in the matrix 21 in the surface forming layer 20 is obtained by changing the granular silica contained in the surface treatment layer into a glassy state during hot press heating. By containing silica in the surface forming layer 20, evaporation of zinc from the zinc-based plating layer can be suppressed.
  • the content of silica contained in the surface forming layer 20 depends on the content of granular silica contained in the surface treatment layer. Therefore, the silica content is 0.5 to 2.0 g / m 2 as the content per one side.
  • the zinc oxide 22 in the surface forming layer 20 is obtained by dispersing granular zinc oxide contained in the surface treatment layer. As described above, the zinc oxide 22 dispersed in the surface forming layer 20 is included and is present on the surface of the surface forming layer 20, so that zinc phosphate crystals are formed during the phosphate treatment that is a chemical conversion treatment for automobiles. It becomes easy to produce
  • the silica content is 0.20 to 2.0 g / m 2 as the content per one side.
  • the area ratio occupied by zinc oxide having a particle size of 0.01 to 1 ⁇ m in the cross section from the surface 20a to the center 20b in the thickness direction perpendicular to the surface 20a of the surface forming layer 20 is 10 to 50. % Is desirable.
  • the area occupied by the zinc oxide can be measured by a known method. For example, first, a cross-section embedded sample of a heat-treated steel material is prepared, and a cross section perpendicular to the surface of the surface forming layer and from the surface to the center in the thickness direction is observed with a scanning microscope. Subsequently, it is possible to identify zinc oxide having a particle diameter of 0.01 to 1 ⁇ m in the cross-sectional field of view and obtain the area ratio of zinc oxide by image processing.
  • the zinc oxide in the surface forming layer may be a doped zinc oxide.
  • a titanium containing compound etc. may be contained. The preferred content is as described above.
  • the manufacturing method of the zinc-based plated steel sheet and the heat-treated steel material according to the present invention is not particularly limited.
  • a galvanized steel sheet can be produced by forming a surface treatment layer on the surface of the substrate by the method described below.
  • a heat-treated steel material can be produced by subjecting the zinc-based plated steel sheet to hot pressing under the following conditions.
  • the method for forming the surface treatment layer is as follows: a treatment liquid containing granular carbon black, granular silica and granular zinc oxide is applied to the surface of the substrate, followed by drying and baking. Good.
  • the coating method is not limited to a specific method, and the substrate is immersed in the treatment liquid, or the treatment liquid is sprayed on the surface of the substrate, and then a roll or a gas spray is applied so that a predetermined adhesion amount is obtained. Examples of the method for controlling the adhesion amount by the coating method, or the method of applying with a roll coater, curtain coater or bar coater.
  • the drying method and baking method may be any method that can volatilize the dispersion medium (mainly water), and are not limited to a specific method.
  • the dispersion medium mainly water
  • the surface treatment layer is formed in-line in the production line of the plated steel sheet, but it may be formed in a separate line or after blanking for forming. It may be.
  • a treatment liquid containing granular carbon black and granular silica is applied to the surface of a zinc-based plated steel sheet, and then a treatment liquid containing granular zinc oxide is applied to the upper layer to form a film. It is more preferable to form In this case, the resin layer may be applied and formed before applying zinc oxide.
  • the coating may be dried and baked each time the coating is applied, or two or three layers may be applied simultaneously using a multilayer curtain coater and baked at once.
  • the contents of granular carbon black, granular silica and granular zinc oxide in the surface treatment layer can be measured by a known method. For example, after confirming that the various compounds are silica or zinc oxide by means of cross-sectional energy dispersive X-ray (EDX) analysis, etc., the film is dissolved and ICP (Inductively Coupled Plasma) It can be measured by using a coupled plasma emission spectroscopy. Further, the contents of the P-containing compound, the V-containing compound, and the Cu-containing compound in the surface treatment layer can be measured by the same method.
  • ICP Inductively Coupled Plasma
  • Hot press working method In the hot working method shown below, after the zinc-based plated steel sheet is heated to a predetermined temperature, press forming and cooling are performed simultaneously. Each will be described in detail.
  • the galvanized steel sheet according to the present invention is subjected to hot press forming, it is usually heated to 700 to 1000 ° C., but after rapid cooling, it becomes a martensite single phase, or the martensite is 90% by volume. % Or higher, the heating temperature is Ac 3 points or higher. In the present invention, the case of a two-phase region of martensite and ferrite after rapid cooling is also included, so that the heating temperature is preferably 700 to 1000 ° C.
  • the heating method before hot pressing can be roughly divided into two types, short-time heating and long-time heating, after reaching a predetermined temperature (around 900 ° C.) and depending on the standing time in the heating furnace (in-furnace time). .
  • short-time heating after reaching a predetermined temperature, it is quickly removed from the furnace and pressed.
  • long-time heating after reaching a predetermined temperature, the zinc in the plating is kept in the heating furnace until the iron zinc solid solution phase formed by diffusing into the base steel sheet is sufficiently formed, Remove from the furnace and press.
  • examples of the heating method used include an electric furnace, a gas furnace, flame heating, energization heating, high-frequency heating, induction heating, and the like. Also, the atmosphere during heating is not particularly limited.
  • press molding is preferably performed in a temperature range of 730 to 500 ° C.
  • the galvanized steel sheet is held for a certain period of time and then press-molded, and then rapidly cooled by contact with the mold.
  • the product characteristics after hot pressing may be controlled by heating the press die and changing the quenching temperature or the cooling rate.
  • the zinc-based plated steel sheet according to the present invention is cold-formed to form a cold press-formed body, and this cold press-formed body is subjected to Ac 3 points by gentle heating. It is good also as heating-processing steel materials by heating above and cooling using a metal mold
  • the heat-treated steel manufactured using the zinc-based plated steel sheet according to the present invention has excellent corrosion resistance, adhesion after electrodeposition coating, chemical conversion treatment, and spot weldability.
  • the galvanized steel sheet according to the present invention has a long holding time so that the molten zinc in the galvanized layer is bonded to Fe and becomes a solid phase (iron zinc solid solution phase) by hot pressing by gentle heating. By making time, the effect is remarkably produced.
  • Base steel plate The molten steel which has the chemical composition shown in Table 1 was manufactured, and the slab was manufactured by the continuous casting method using each manufactured molten steel. The obtained slab was hot rolled to produce a hot rolled steel sheet. Subsequently, the hot-rolled steel sheets were pickled and then cold-rolled to produce cold-rolled steel sheets, and cold-rolled steel sheets # 1 to # 8 having chemical compositions shown in Table 1 were produced. Each of the cold-rolled steel plates # 1 to # 8 has a thickness of 1.6 mm.
  • cold-rolled steel plate # 1 was subjected to hot dip galvanizing treatment, and a hot-dip galvanized steel plate GI (containing 0.4% Al) was produced without performing alloying treatment.
  • various types of zinc plating such as electric Zn plating and electric Zn—Ni plating were performed on the cold-rolled steel plate # 1.
  • electrolytic treatment was performed between a counter electrode and a steel plate as a negative electrode in an electrolytic solution containing Zn ions.
  • the amount of plating attached to the steel sheet was controlled by the composition of the electrolytic solution, current density, and electrolysis time.
  • the adhesion amount of the zinc-based plating layer was 45 g / m 2 per side.
  • A6 and 7 which electroplated Ni on the GA mentioned above and performed Ni plating were also produced.
  • A6 GA + Ni plating (attachment amount per side 2 g / m 2 )
  • A7 GA + Ni plating (adhesion amount per side 8 g / m 2 )
  • medical solution which becomes the composition of Table 2 on the above-mentioned conditions further A plated steel sheet was produced.
  • the adhesion amount of the treatment liquid was adjusted by dilution of the liquid and the number of the bar coater so that the total adhesion amount of the nonvolatile content in the treatment liquid became the values shown in Tables 4 to 8.
  • the solid content concentration of each component is described as the ratio (unit: mass%) of the nonvolatile content of each component such as “granular carbon black” to the nonvolatile content of the entire treatment liquid.
  • Powdered carbon black C1: Carbon black powder (Mitsubishi Chemical Corporation # 2650), particle size 13 nm (catalog value)
  • C2 carbon black powder (Mitsubishi Chemical Corporation MA100), particle size 24 nm (catalog value)
  • C4 carbon black powder (carbon powder of high purity chemical), particle size 5 ⁇ m (catalog value)
  • Powdered silica S1 Colloidal silica (Nissan Chemical Co., Ltd. Snowtex (registered trademark) OXS), particle size of about 4 nm to 6 nm (catalog value)
  • S2 Colloidal silica (Nissan Chemical Co., Ltd. Snowtex (registered trademark) O), particle size of about 10 nm to 15 nm (catalog value)
  • S3 Colloidal silica (Nissan Chemical Co., Ltd. Snowtex (registered trademark) OYL), particle size of about 50 nm to 80 nm (catalog value)
  • S4 Porous silica (Fuji Silysia Chemical Co., Ltd. silo mask 02), particle size 2 ⁇ m
  • S5 Silicone resin (Shin-Etsu Chemical Co., Ltd. KR-300)
  • Powdered zinc oxide Z1 Zinc oxide powder (Huxitec Co., Ltd. fine particle zinc oxide F-1), particle size 0.1 ⁇ m (catalog value)
  • Z2 Zinc oxide powder (Zinc oxide, high purity chemical), particle size 1 ⁇ m (catalog value)
  • Z3 Conductive zinc oxide powder (Huxitec Co., Ltd. conductive zinc oxide 23-k), particle size 0.12 ⁇ m to 0.25 ⁇ m (catalog value)
  • Z4 Conductive zinc oxide powder (Huxitec Co., Ltd., conductive zinc oxide Pazet CK), particle size 0.02 ⁇ m to 0.04 ⁇ m (catalog value)
  • Resin A Urethane resin emulsion (Daiichi Kogyo Seiyaku Co., Ltd. Superflex (registered trademark) 150)
  • B Urethane resin emulsion (Daiichi Kogyo Seiyaku Co., Ltd. Superflex (registered trademark) E-2000)
  • C Polyester resin emulsion (Toyobo Co., Ltd. Vylonal (registered trademark) MD1480)
  • V Crosslinking agent M: Melamine resin (Mitsui Cytec Co., Ltd. Cymel (registered trademark) 325) Z: Ammonium zirconium carbonate (Kishida Chemical Co., Ltd. Zirconium ammonium carbonate solution) CP: Silane coupling agent (Nimi Shoji Co., Ltd. Sila Ace S510) (Si-containing compound)
  • Titanium-containing compound T1 Titania sol (Taika Co., Ltd. Titania sol TKS-203), particle size 6 nm (catalog value)
  • T2 Titania powder (Ioritech Co., Ltd.), particle size 10-30nm (catalog value)
  • T3 Titanium oxide (Ishihara Sangyo Co., Ltd. titanium oxide R-930), particle size 250nm (catalog value)
  • T4 Titanium nitride (Nippon Shin Metals Co., Ltd. TiN), particle size 700-1190nm (catalog value)
  • Zr Zirconia (Nissan Chemical Co., Ltd. Nanouse ZR40BL)
  • P Calcium phosphite (general reagent) (P-containing compound)
  • V Potassium vanadate (general reagent) (V-containing compound)
  • Cu Copper (II) oxide (general reagent) (Cu-containing compound)
  • chemical solution No. 45 had a small amount of silica and an excessive amount of titanium oxide, so that it could not be uniformly applied to the surface of the substrate without being dispersed. Therefore, it is not used for subsequent tests.
  • the hot-pressed steel sheet of each number was hot-pressed by one of the following two methods to produce a heat-treated steel material.
  • Method 1 Heating for a short time Hot pressing was performed by a furnace heating method, and hot pressing was performed.
  • the atmosphere in the furnace was 910 ° C.
  • the air-fuel ratio was 1.1
  • the steel sheet was quickly taken out of the furnace after reaching 890 ° C. and air-cooled until it reached 700 ° C.
  • a plate-shaped heat-treated steel material was produced by sandwiching the steel plate using a flat plate mold equipped with a water cooling jacket. Even in a portion where the cooling rate during hot pressing was slow, the steel was cooled and quenched to a cooling rate of 50 ° C./second or more to about 360 ° C., which was the martensite transformation start point.
  • Method 2 Long-time heating The hot press was heated by the furnace heating method, and the hot press was performed. In the furnace heating, the furnace atmosphere: 910 ° C., the air-fuel ratio: 1.1, the steel sheet temperature reached 890 ° C. and left in the furnace for 5 minutes, and then quickly removed from the furnace.
  • a plate-shaped heat-treated steel material was produced by sandwiching the steel plate using a flat plate mold equipped with a water-cooled jacket. Even in a portion where the cooling rate during hot pressing was slow, the steel was cooled and quenched to a cooling rate of 50 ° C./second or more to about 360 ° C., which was the martensite transformation start point.
  • a cross-section embedded sample was prepared, and an area occupied by zinc oxide having a particle diameter of 0.01 to 1 ⁇ m was obtained for the cross section perpendicular to the surface of the surface forming layer and from the surface to the center in the thickness direction. It was measured. Specifically, a cross-section embedded sample of each heat-treated steel material is prepared, and included in a cross-section from the surface to the center in the thickness direction perpendicular to the surface of the surface forming layer at a field of view of 5000 times with a scanning microscope. Zinc oxide having a particle diameter of ⁇ 1 ⁇ m was identified, and the area ratio of zinc oxide was determined by image processing. This measurement was performed in 10 fields of view, and the average value was defined as the occupation area ratio of each sample.
  • “D” in the “occupied area” column in the table means an area ratio of less than 5%
  • “C” means an area ratio of 5% or more and less than 10%
  • “B” means an area ratio of 10%. More than 25%
  • “A” means an area ratio of 25% or more and 50% or less
  • “E” means an area ratio of more than 50%.
  • “B” or “A” was used as a surface forming layer of a good heat-treated steel material.
  • Tables 9 to 12 show the composition of the surface forming layer of the heat-treated steel material of each test number and the area occupied by zinc oxide.
  • the phosphate treatment was performed using a zinc phosphate treatment liquid Palbond 3020 (trade name) manufactured by Nippon Parkerizing Co., Ltd.
  • the temperature of the treatment liquid was 43 ° C., and the heat-treated steel was immersed in the treatment liquid for 120 seconds, and then washed and dried.
  • A0 is the total area of the visual field (11250 ⁇ m 2 ).
  • the average of the see-through area ratio TR (%) of the five visual fields was defined as the see-through area ratio (%) of the heat-treated steel material having the test number.
  • Coating film peeling rate (A2 / A10) ⁇ 100 (2)
  • “F” in the column “Coating adhesion” in Tables 9 to 12 means a coating film peeling rate: 30.0% or more
  • “E” means a coating film peeling rate: 20% or more and less than 30%
  • “D” means coating film peeling rate: 10% or more and less than 20%
  • “C” means coating film peeling rate: 5% or more and less than 10%
  • “B” means coating film peeling rate: 2.5. % Means less than 5%
  • “A” means coating film peeling rate: less than 2.5%.
  • “C”, “B” or “A” was considered excellent in paint adhesion.
  • FIG. 2 is a SEM photograph of the surface after the phosphate treatment of the heat-treated steel sheet according to the example of the present invention.
  • the zinc oxide is uniformly dispersed in the surface forming layer. A zinc film is formed.
  • FIG. 3 is an SEM photograph of the surface after the phosphate treatment of the heat-treated steel sheet according to the comparative example.
  • the amount of carbon black in the surface treatment layer of the used zinc-based plated steel sheet is small, and granular zinc oxide is not included. Therefore, as shown in a schematic cross section in FIG. 4, the coating 41 was cracked and the zinc oxide 42 derived from the plating layer 32 appeared on the surface.
  • coat was formed only slightly and became a result in which a phosphate processability is inferior.
  • a silicone resin was contained in the surface treatment layer of the used galvanized steel sheet instead of granular silica.
  • zinc oxide was not dispersed in the vicinity of the surface layer of the surface forming layer, and a phosphate film was hardly formed, resulting in extremely poor phosphate treatment properties.
  • heat treated steel plate No. L121 is a plated steel plate No. in which no surface treatment layer is formed. It is a comparative example using 130.
  • the zinc in the plating layer 32 becomes zinc oxide 50 by hot pressing, as schematically shown in cross section in FIG. As schematically shown in FIG. 5, the adhesion of the zinc oxide 50 was poor, causing peeling, resulting in poor adhesion after coating and poor corrosion resistance.
  • Base material 11. Steel plate (base steel plate) 12 Zinc-based plating layer 20. Surface forming layer 20a. Surface 20b. Center in thickness direction 21. Matrix 22. Zinc oxide

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Abstract

L'invention concerne une tôle d'acier zinguée qui est pourvue de : un matériau de base qui porte une couche de zingage sur la surface d'une tôle d'acier ; et une couche de traitement de surface qui est formée sur au moins une surface du matériau de base. Cette tôle d'acier zinguée est conçue de façon telle que la couche de traitement de surface contient, pour une surface, 0,15 à 1,0 g/m2 de noir de carbone granulaire, 0,5 à 2,0 g/m2 de silice granulaire et 0,20 à 2,0 g/m2 d'oxyde de zinc granulaire.
PCT/JP2018/013233 2018-03-29 2018-03-29 Tôle d'acier zinguée et matériau en acier traité thermiquement WO2019186891A1 (fr)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4239098A4 (fr) * 2020-10-30 2023-12-06 Nippon Steel Corporation Article moulé estampé à chaud plaqué de zn
EP4268989A4 (fr) * 2021-04-08 2024-01-31 Nippon Steel Corp Feuille d'acier pour estampage à chaud et élément estampé à chaud

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011149084A (ja) * 2010-01-25 2011-08-04 Nippon Steel Corp 昇温特性に優れた熱間プレス用Ａｌめっき鋼板及びその製造方法
WO2016159306A1 (fr) * 2015-03-31 2016-10-06 新日鐵住金株式会社 Tôle en acier galvanisé

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011149084A (ja) * 2010-01-25 2011-08-04 Nippon Steel Corp 昇温特性に優れた熱間プレス用Ａｌめっき鋼板及びその製造方法
WO2016159306A1 (fr) * 2015-03-31 2016-10-06 新日鐵住金株式会社 Tôle en acier galvanisé

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4239098A4 (fr) * 2020-10-30 2023-12-06 Nippon Steel Corporation Article moulé estampé à chaud plaqué de zn
EP4268989A4 (fr) * 2021-04-08 2024-01-31 Nippon Steel Corp Feuille d'acier pour estampage à chaud et élément estampé à chaud

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