WO2023121241A1 - Tôle d'acier plaquée ayant une excellente adhérence de placage et une excellente résistance à la corrosion après formage à la presse à chaud, procédé de préparation de tôle d'acier plaquée, et élément de formage pressé à chaud - Google Patents

Tôle d'acier plaquée ayant une excellente adhérence de placage et une excellente résistance à la corrosion après formage à la presse à chaud, procédé de préparation de tôle d'acier plaquée, et élément de formage pressé à chaud Download PDF

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WO2023121241A1
WO2023121241A1 PCT/KR2022/020870 KR2022020870W WO2023121241A1 WO 2023121241 A1 WO2023121241 A1 WO 2023121241A1 KR 2022020870 W KR2022020870 W KR 2022020870W WO 2023121241 A1 WO2023121241 A1 WO 2023121241A1
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Prior art keywords
steel sheet
less
plating layer
content
hot press
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PCT/KR2022/020870
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English (en)
Korean (ko)
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오진근
김성우
이세웅
김상헌
박재성
이루리
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주식회사 포스코
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Publication of WO2023121241A1 publication Critical patent/WO2023121241A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/12—Aluminium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • 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
    • 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
    • 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
    • C23C28/04—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 of inorganic non-metallic material
    • 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
    • C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
    • C23C28/34—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates
    • C23C28/345—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates with at least one oxide layer
    • 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
    • C23C28/40—Coatings including alternating layers following a pattern, a periodic or defined repetition
    • C23C28/44—Coatings including alternating layers following a pattern, a periodic or defined repetition characterized by a measurable physical property of the alternating layer or system, e.g. thickness, density, hardness

Definitions

  • the present invention relates to a coated steel sheet for hot press forming, a method for manufacturing the coated steel sheet, and a hot press formed member.
  • the hot press forming method is a method of forming a low-temperature structure such as martensite in a steel sheet by processing the steel sheet at a high temperature suitable for processing and then rapidly cooling it to a low temperature to increase the strength of the final product.
  • a high temperature suitable for processing
  • a low temperature suitable for processing
  • a low temperature to increase the strength of the final product.
  • Patent Document 1 has been proposed as a method for solving this problem.
  • a steel sheet subjected to aluminum plating is used in a process of heating and rapidly cooling after hot press forming or room temperature forming (briefly, 'post heat treatment'), and since the aluminum plating layer exists on the surface of the steel sheet, the steel sheet is oxidized during heating. It doesn't work.
  • Patent Document 1 US Patent Publication No. 6,296,805
  • a coated steel sheet for hot press forming capable of improving coating adhesion of a hot press formed member and ensuring corrosion resistance, and a method of manufacturing the coated steel sheet.
  • a hot press-formed member excellent in paint adhesion and corrosion resistance is provided.
  • a plated steel sheet includes a base steel plate and a plating layer made of an Al-Fe alloy formed on the base steel plate, and the total content of Al and Fe in the plated layer is 80% or more by weight, wherein the The average content of Fe in the plating layer may be 20% or more by weight, and the product of Ra and RPc of the surface of the plating layer may be 60 to 150 ⁇ m/cm.
  • Ra means arithmetic average roughness and its unit is ⁇ m
  • RPc means the number of peaks per unit length and its unit is /cm.
  • a coated steel sheet includes a base steel sheet and a plating layer made of an Al-Fe alloy formed on the base steel sheet, wherein the total content of Al and Fe in the plating layer is 80% or more by weight, The average content of Fe in the plating layer is 20% or more by weight, and the number of cracks existing in each region obtained by dividing the surface of the plating layer into 10 equal parts horizontally and vertically when observing the surface of the plating layer at a magnification of 100 times with a scanning electron microscope. is 10 to 200 per 1 mm 2 , and the ratio of the area occupied by the indentation portion on the surface of the plating layer may be 5 to 50%.
  • the indentation means a region having a brightness of 70% or more compared to the highest brightness measured in an area observed at a magnification of 100 times with an optical microscope.
  • a method for manufacturing a plated steel sheet according to another aspect of the present invention includes obtaining an Al-Fe alloy plated steel sheet having a plating layer made of an alloy of Al and Fe formed on a base steel sheet; and performing skin pass rolling on the Al-Fe alloy coated steel sheet under the condition that the SPMI expressed by the following relational expression 1 is 5000 to 8500.
  • P is the rolling force during skin pass rolling (unit: ton)
  • the Ra roll is the arithmetic average roughness of the surface of the skin pass rolling roll (unit: ⁇ m)
  • the RPc roll is the number of peaks per unit length of the skin pass rolling roll (unit: /cm).
  • the unit of the SPMI is ⁇ Ton ⁇ m/cm.
  • a hot press-formed member includes a base steel plate and a plating layer made of an Al-Fe alloy formed on the base steel plate, and the total content of Al and Fe in the plated layer is 70% by weight.
  • the content of Fe in the plating layer may be 30% or more by weight, and the product of Ra and RPc of the surface of the plating layer may be 60 to 150 ⁇ m/cm.
  • Ra means arithmetic average roughness and its unit is ⁇ m
  • RPc means the number of peaks per unit length and its unit is /cm.
  • a hot press-formed member includes a base steel plate and a plating layer made of an Al-Fe alloy formed on the base steel plate, and the total content of Al and Fe in the plated layer is 70% by weight.
  • the average content of Fe in the plating layer is 30% or more by weight, and present in each region obtained by dividing the field of view obtained when the surface of the plating layer is observed at a magnification of 100 times with a scanning electron microscope into 10 horizontally and vertically.
  • the number of cracks may be 15 to 220 per 1 mm 2 , and the ratio of the area occupied by the indentation portion on the surface of the plating layer may be 5 to 50%.
  • the indentation means a region having a brightness of 70% or more compared to the highest brightness measured in an area observed at a magnification of 100 times with an optical microscope.
  • the Ra and RPc of the surface of the coated steel sheet of the present invention are controlled to appropriate levels, it is possible to secure sufficient paint adhesion of the member even if a large increase in roughness does not occur during the hot press forming process.
  • Example 1 is a photograph of the surfaces of aluminum-iron-based coated steel sheets prepared by Comparative Example 1 (a) and Inventive Example 2 (b) observed with a scanning electron microscope (SEM).
  • Figure 2 is a photograph of the image processing result of observing the surface of the aluminum-iron-based coated steel sheet prepared by Comparative Example 1 (a) and Inventive Example 2 (b) with an optical microscope.
  • 3 is a graph showing the relationship between the number of cracks generated on the surface of an aluminum-iron-based coated steel sheet according to skin pass rolling conditions.
  • the steel sheet refers to a coil or sheet state before being processed into a specific shape
  • a member refers to a steel sheet processed into a non-plate shape by a molding process
  • the plating layer referred to in the present invention means a layer of metal, alloy or intermetallic compound formed in contact with the base steel sheet.
  • a pre-alloyed plated steel sheet it may have an alloy layer having a structure in which hydrogen is easily discharged on the surface, thereby reducing the possibility of hydrogen delayed fracture.
  • the plating layer formed on the surface of the hot press-formed member is formed by an alloying reaction between aluminum and iron and is relatively chemically stable. As such, since the surface of the hot press-formed member is chemically stable, it is difficult to improve the roughness any longer even with phosphate treatment.
  • the surface roughness increases in the process of heating the aluminum-coated steel sheet, sufficient roughness can be secured without phosphate treatment, so there may be no major problem in paint adhesion.
  • the aluminum alloy plating layer is not superior in sacrificial corrosion protection performance compared to the zinc-based plating layer, there is a problem in that corrosion occurs along with blisters when the steel sheet is exposed due to cracks or the like.
  • Ra ⁇ RPc of the surface of the plated layer of the coated steel sheet may be 60 ⁇ m / cm or more.
  • Ra is the arithmetic mean roughness and has a unit of ⁇ m
  • RPc is the peak count (Peak Count) and has a unit of the reciprocal of cm (/cm).
  • the lower limit of the Ra ⁇ RPc may be set at 60 ⁇ m/cm.
  • the lower limit of Ra ⁇ RPc may be set to 70 ⁇ m/cm.
  • the higher the value of Ra ⁇ RPc the better.
  • the upper limit of the Ra ⁇ RPc may be set to 150 ⁇ m/cm, and in some cases, the upper limit of the Ra ⁇ RPc may be set to 140 ⁇ m/cm.
  • the coated steel sheet according to another embodiment of the present invention by appropriately adjusting the ratio of the number of cracks formed on the surface and the area ratio of the indentation portion, the coating adhesion and corrosion resistance of the member obtained by the subsequent hot press forming process can be improved.
  • the plated steel sheet according to one embodiment of the present invention may have 10 to 200 cracks per 1 mm 2 of the surface area of the plated layer, and the ratio of the area occupied by the indentation portion on the surface of the plated layer may be 5 to 50%.
  • the cracks can serve as a fixing part in which the coating layer is anchored on the surface of the hot press-formed member, in one embodiment of the present invention, 10 or more cracks per unit area of 1 mm 2 of the plating layer, in some cases There may be more than 15 cracks.
  • the number of cracks is measured by converting the number of cracks observed in 100 areas obtained by dividing the field of view of a microscope (magnification: 100 times) into 10 equal parts horizontally and vertically, respectively, to those observed in an observation area of 1 mm 2 .
  • the microscope may be a ZEISS SUPRA 55VP model scanning electron microscope.
  • the number of cracks may be equal to the number of regions where the cracks are observed.
  • the number of cracks is equal to that number. This is a concept considering the total length of cracks within the observation area, and this is because the total length of cracks affects the fixing effect of the coating layer.
  • the aluminum-based coated steel sheet does not have a sacrificial corrosion protection function unlike the zinc-based coated steel sheet, corrosion may occur through the crack when a crack exists. Therefore, since an excessive number of cracks may impair the corrosion resistance of the steel sheet, the upper limit of the number of cracks per 1 mm 2 calculated in the above-described manner may be limited to 200, and in some cases may be limited to 180.
  • a large number of indentations may be formed on the surface of the coating layer to increase the contact area of the coating layer.
  • Ra and RPc of the surface of the plating layer may increase.
  • the ratio of the indentation portion on the surface of the plating layer may be 5% or more, and in some cases may be 8% or more.
  • the indentation may mean an area having a brightness of 70% or more compared to the highest brightness measured in an area observed at a magnification of 100 times with an optical microscope.
  • the result of observing the surface image at 100 times magnification with a Leica DM6000M model optical microscope was divided into 256 color brightness using Clemex Vision PE software.
  • the area ratio can be obtained by specifying a portion having a brightness equal to or higher than 70% of the highest brightness value as the indentation portion. If the ratio of the indentation part is too high, the load applied to the steel sheet to form the indentation part is excessive and surface cracks may increase, so the upper limit of the ratio of the indentation part may be set to 50% or 45%.
  • the indentation portion may be formed by skin pass rolling, but is not necessarily limited thereto.
  • the object of the present invention is an alloy plated steel sheet of aluminum and iron
  • the total content of Al and Fe needs to be 80% or more by weight.
  • the upper limit of the sum of the contents of these elements does not need to be particularly determined, and a plating layer made of only 100% Al and Fe may also correspond.
  • the average content of Fe has a value of 20% or more based on weight. If the content of Fe in the plating layer is less than 20%, it may not be very helpful in solving problems such as melting of the aluminum plating layer or hydrogen embrittlement during heating, so in the present invention, Al-Fe containing 20% or more of Fe by weight Applies to alloy coated steel sheets. In some cases, the Fe content may be 30% or more, and may be 40% or more.
  • the upper limit of the Fe content is not particularly limited, but when considering the Fe content in a conventional alloy coated steel sheet, the upper limit of the Fe content may be set to 90%, and in some cases may be set to 80% or less.
  • the average content of Fe means the average of the Fe content in the entire plating layer, and there may be various measurement methods. After integrating the Fe content curve according to the depth (thickness) that appears when the interface is analyzed, it can be used as a value divided by the thickness of the plating layer (ie, the distance from the surface to the interface of the steel sheet).
  • the point where the Al and Fe content curves intersect is defined as the interface between the coating layer and the steel sheet from the GDS results.
  • the plating layer may further include general elements included in the plating layer in addition to the above-described Al and Fe.
  • these elements include one or two or more selected from among Mg, Zn, Mn, Cr, Mo, Si, and Ti, and they may be included in the plating layer up to 20% by weight or less in total.
  • the Fe content in the surface portion of the aluminum iron alloy plated steel sheet for hot press forming may be 50% or more compared to the average content of Fe in the plating layer. That is, by setting the Fe content on the surface to 50% or more of the average Fe content in the plating layer, a plated steel sheet sufficiently alloyed to the surface of the plating layer can be obtained.
  • the Fe content on the surface may be 15% or more by weight.
  • the surface portion may mean a point having a depth of 1 ⁇ m from the outermost surface.
  • the Fe content of the surface portion can be measured through EDS surface analysis at a site magnified 100 times with a scanning electron microscope.
  • the steel sheet of the present invention is a steel sheet for hot press forming, and the composition is not particularly limited as long as it is used for hot press forming.
  • weight% by weight% (hereinafter, it is necessary to note that the composition of the steel sheet and the plating layer of the present invention is based on weight unless otherwise specifically expressed), C: 0.01 to 0.5%, Si: 2.0% or less (excluding 0%), Mn: 0.1 to 4.0%, P: 0.05% or less, S: 0.02% or less, Al: 0.001 to 1%, Cr: 5.0% or less (excluding 0%), N: 0.02% or less, Ti: 0.1% or less (excluding 0%), B: 0.0001 to 0.01%, the balance may have a composition including Fe and unavoidable impurities.
  • the C is an essential element to increase the strength of the heat treated member and may be added in an appropriate amount. That is, in order to sufficiently secure the strength of the heat treated member, the C may be added in an amount of 0.01% or more. In one embodiment, the lower limit of the C content may be 0.05%. However, if the content is too high, the strength of the hot-rolled material is too high when the hot-rolled material is cold-rolled in the case of producing cold-rolled material, so that not only the cold-rollability is greatly inferior, but also the spot weldability is greatly reduced. It may be added in an amount of 0.5% or less to secure weldability. In addition, the C content may be limited to 0.45% or less and 0.4% or less.
  • Si 2.0% or less (excluding 0%)
  • Si not only needs to be added as a deoxidizer in steelmaking, but also suppresses the formation of carbides, which have the greatest effect on the strength of hot-press-formed parts, and also converts to martensite lath grain boundaries after martensite is formed in hot-press forming. It can be added in steel to enrich the carbon to obtain retained austenite.
  • the upper limit of the Si content may be set at 2% (excluding 0%) in order to secure sufficient plating properties when aluminum plating is performed on the steel sheet.
  • the Si content may be limited to 1.5% or less.
  • the lower limit of the Si content may be set to 0.01%.
  • the Mn may be added in an amount of 0.1% or more to secure a solid solution strengthening effect and to lower a critical cooling rate for securing martensite in a hot press molded member.
  • the Mn content may be 4% or less in terms of securing workability in the hot press forming process by properly maintaining the strength of the steel sheet, reducing manufacturing cost, and improving spot weldability, and one embodiment of the present invention In , it can be 3.5% or less, or 2.5% or less.
  • the P exists as an impurity in steel, and the smaller the content, the more advantageous it is. Accordingly, in one embodiment of the present invention, P may be included in an amount of 0.05% or less. In another embodiment of the present invention, P may be limited to 0.03% or less. Since P is an impurity element that is advantageous the smaller it is, there is no need to specifically set an upper limit on its content. However, in order to excessively lower the P content, there is a concern that the manufacturing cost will increase. In this case, the lower limit may be set to 0.001%.
  • the maximum content is set to 0.02% (preferably 0.01% or less).
  • the lower limit of the content may be 0.0001%.
  • the Al, together with Si, can be added in an amount of 0.001% or more because it can increase the cleanliness of the steel by deoxidizing in steelmaking.
  • the Al content may be 1% or less in order to prevent the temperature of Ac3 from becoming too high so that the heating required during hot press molding can be performed in an appropriate temperature range.
  • the Cr serves to improve the strength of the hot press formed part by improving the hardenability of the steel, it is necessary to add Cr.
  • the lower limit of the Cr content may be set to 0.001%.
  • the upper limit of the Cr content may be set at 5.0%.
  • N is an element included as an impurity in steel, and the lower the content is, the more advantageous it is to reduce the sensitivity to crack generation during continuous casting of slabs and secure impact characteristics, and therefore may be included at 0.02% or less. Although it is necessary to specifically set the lower limit, the N content may be set to 0.001% or more in one embodiment in consideration of the increase in manufacturing cost.
  • the Ti By reacting with nitrogen, the Ti may contribute to improving hardenability by B.
  • fine precipitates are formed to improve the strength of the hot press molded member and refine crystal grains, it is effective in improving impact toughness, so it may be added in an amount of 0.1% or less (excluding 0%).
  • the lower limit of the Ti content may be set to 0.0005%.
  • B is an element capable of improving hardenability even with a small amount of addition and suppressing brittleness of hot press formed parts due to segregation of grain boundaries of P and/or S by being segregated at old austenite grain boundaries. Accordingly, B may be added in an amount of 0.0001% or more. However, if it exceeds 0.01%, the effect is not only saturated, but also causes brittleness in hot rolling, so the upper limit may be 0.01%, and in one embodiment, the B content may be 0.005% or less.
  • one or two or more elements selected from Nb: 0.1% or less, Mo: 0.5% or less, Ni: 1% or less, Cu: 1% or less, and V: 0.5% or less, if necessary. can include more.
  • Nb is effective in improving the steel sheet of heat treated members by forming fine precipitates, stabilizing retained austenite and improving impact toughness by refining crystal grains, it can be added to steel. However, if the added amount exceeds 0.1%, the effect is saturated and the cost may increase due to the excessive addition of ferroalloy. In one embodiment of the present invention, 0.001% or more of Nb may be added.
  • Mo is an element capable of securing strength and crystal grain refinement through enhancement of hardenability and precipitation strengthening effect. However, when added excessively, weldability may be deteriorated, so it may be added in an amount of 0.5% or less in consideration of this. In one embodiment of the present invention, when the Mo is added, the lower limit of the amount added may be set to 0.001%.
  • the Ni is an element that improves strength by forming fine precipitates. However, if the value exceeds 1.0%, excessive cost increases, so the upper limit is set at 1%. In one embodiment of the present invention, the addition amount of Ni may be 0.005% or more in order to surely obtain the above-mentioned effect.
  • Cu is an element that improves strength by forming fine precipitates. However, if the value exceeds 1.0%, excessive cost increases, so the upper limit is set at 1%. In order to reliably obtain the above-mentioned effect, the addition amount of Cu may be 0.005% or more.
  • the V may be added to steel because it is effective in improving the steel sheet of the heat treated member by forming fine precipitates, stabilizing retained austenite and improving impact toughness by refining crystal grains. However, if the added amount exceeds 0.5%, the effect is saturated and the cost may increase due to excessive addition of ferroalloy. In one embodiment of the present invention, 0.001% or more of V may be added in order to ensure the effect of adding V described above.
  • Iron and unavoidable impurities may be mentioned as the remainder other than the above-mentioned components, and any component that can be included in the steel sheet for hot forming is not particularly limited.
  • the manufacturing method of the steel sheet for hot press forming described below is an example, and the steel sheet for hot press forming of the present invention does not necessarily have to be manufactured by the present manufacturing method, and any manufacturing method is a method that satisfies the scope of the present invention. It should be noted that if it is, there is no problem in using it to implement each implementation example of the present invention.
  • the steel sheet is obtained by obtaining an aluminum-iron (Al-Fe) alloy plated steel sheet having an aluminum-iron alloy plating layer formed on the steel sheet; And it can be manufactured by performing skin pass rolling with respect to the aluminum-iron (Al-Fe) alloy plated steel sheet.
  • the aluminum-iron alloy-coated steel sheet is obtained by obtaining an aluminum-coated steel sheet coated with aluminum or an aluminum alloy; And it can be obtained by a process comprising the step of alloying by heating the aluminum-coated steel sheet.
  • any aluminum-coated steel sheet may be used as long as it is industrially referred to as aluminum-based, and in one embodiment of the present invention, one having an Al content of 70% or more by weight may be used.
  • the remaining elements other than Al in the plating layer one or more components selected from Si, Mg, Zn, Mn, Cr, Mo, Ti, Fe, and/or other impurity elements that may be normally added to the aluminum-based plating layer are selected.
  • Si may be included in an amount of 0.01 to 20%.
  • the Si content included in the plating bath may be limited to 0.01 to 20%.
  • One or two or more elements selected from Mg, Zn, Mn, Cr, Mo, and Ti may be included in the plating layer by 20% by weight or less in total.
  • the above-described aluminum-based plating layer may be formed by a hot-dip aluminum plating method in which a hot-rolled or cold-rolled and annealed steel sheet is immersed in a molten aluminum plating bath.
  • the plating amount during the aluminum plating may be 10 to 100 g / m 2 on a single side basis. If the plating amount is less than 10 g/m 2 , corrosion resistance is reduced, whereas if the plating amount exceeds 100 g/m 2 , a problem of deteriorating weldability occurs. Therefore, in the present invention, it is preferable to limit the coating amount to 10 to 100 g / m 2 on a single side basis during aluminum plating. On the other hand, in another embodiment of the present invention, the plating amount during the aluminum plating may be 20 to 90 g / m 2 on a single side basis.
  • the step of heating and alloying the aluminum-coated steel sheet is directly connected to a line for plating the steel sheet with aluminum or aluminum alloy, and is performed by online heating in which the coated steel sheet is heated while running.
  • the heating temperature range during the alloying may be 670 to 900 ° C, and the holding time may be 1 to 20 seconds.
  • the heating temperature range may be 680 to 880 ° C, and the holding time may be 1 to 10 seconds.
  • the step of heating and alloying the aluminum-coated steel sheet may be performed by upper annealing of heating the coiled coated steel sheet in a box-shaped annealing furnace.
  • the coil cooled to room temperature after aluminum plating may be heated for 0.1 to 100 hours at a temperature in the range of 600 to 800 ° C in an upper annealing furnace in a hydrogen or hydrogen and nitrogen atmosphere having a dew point temperature of less than -10 ° C (the present invention In the above temperature range, the highest temperature at which the furnace atmosphere temperature reaches is set as the heating temperature).
  • the holding time means the time from when the ambient temperature reaches the target temperature until cooling is initiated.
  • the skin pass rolling may be performed under the condition that the SPMI represented by the following relational expression 1 is 5000 to 8500.
  • P is the rolling force during skin pass rolling (unit: ton)
  • the Ra roll is the arithmetic average roughness of the surface of the skin pass rolling roll (unit: ⁇ m)
  • the RPc roll is the number of peaks per unit length of the skin pass rolling roll (unit: /cm).
  • the unit of the SPMI is ⁇ Ton ⁇ m/cm.
  • the SPMI is a condition that can control the surface state of the steel sheet devised by the present inventors, and the Ra and RPc of the steel sheet surface are affected not only by the Ra and RPc of the roll surface but also by the rolling force applied by the roll, and their influence
  • the relationship represented by the above relational expression 1 was shown.
  • the SPMI value needs to be 5000 or more, and in some cases, the SPMI value may be limited to 5500 or more.
  • the value may be limited to 8500 or less, and in some cases may be limited to 8000 or less.
  • a hot press-formed member according to one aspect of the present invention will be described.
  • the method for manufacturing a hot press-formed member is not particularly limited in the present invention because it consists of a process of heating and maintaining a steel sheet at a temperature equal to or higher than the austenitizing temperature, followed by rapid cooling and forming at the same time as is well known in the prior art.
  • a hot press-formed member includes a base steel plate and a plating layer made of an Al-Fe alloy formed on the base steel plate, and the product of Ra and RPc of the surface of the plated layer is controlled to combine paint adhesion and corrosion resistance.
  • Ra ⁇ RPc of the surface of the plating layer of the member obtained by hot press molding may be 60 ⁇ m/cm or more in order to secure high paint adhesion.
  • Ra is the arithmetic mean roughness and has a unit of ⁇ m
  • RPc is the peak count (Peak Count) and has a unit of the reciprocal of cm (/cm).
  • the lower limit of the Ra ⁇ RPc may be set at 60 ⁇ m/cm. In some cases, the lower limit of Ra ⁇ RPc may be set to 70 ⁇ m/cm.
  • the upper limit of Ra ⁇ RPc may be set to 150 ⁇ m/cm, and in some cases, the upper limit of Ra ⁇ RPc may be set to 140 ⁇ m/cm. there is.
  • the number of cracks formed on the surface of the Al-Fe alloy plating layer and the area ratio of the indentation portion are appropriately adjusted to paint the member obtained by the subsequent hot press forming process. Adhesion and corrosion resistance can be improved.
  • the plated steel sheet according to one embodiment of the present invention may have 15 to 220 cracks per 1 mm 2 of the surface area of the plated layer, and the ratio of the area occupied by the indentation portion on the surface of the plated layer may be 5 to 50%.
  • the cracks can serve as a fixing part in which the coating layer is anchored on the surface of the hot press-formed member, in one embodiment of the present invention, 15 or more cracks per unit area of 1 mm 2 of the plating layer, in some cases More than 20 cracks may be present.
  • the number of cracks is measured by converting the number of cracks observed in 100 areas obtained by dividing the field of view of a microscope (magnification 100 times) into 10 equal parts horizontally and vertically, respectively, to those observed in an observation area of 1 mm 2 .
  • the microscope may be a ZEISS SUPRA 55VP model scanning electron microscope.
  • the number of cracks may be equal to the number of areas in which the cracks are observed.
  • the number of cracks is equal to that number. This is a concept considering the total length of cracks within the observation area, and this is because the total length of cracks affects the fixing effect of the coating layer.
  • the aluminum-based coated steel sheet (member) does not have a sacrificial corrosion protection function unlike the zinc-based coated steel sheet, corrosion may occur through the crack when a crack exists. Therefore, since an excessive number of cracks may impair the corrosion resistance of the member, the upper limit of the number of cracks per 1 mm 2 may be limited to 220, and in some cases may be limited to 200.
  • a large number of indentations may be formed on the surface of the coating layer of the steel sheet in order to increase the contact area of the coating layer, and these indentations may remain on the member to improve paint adhesion.
  • Ra and RPc of the surface of the plating layer may increase.
  • the ratio of the indentation portion on the surface of the plating layer may be 5% or more, and in some cases may be 8% or more.
  • the result of observing the surface image at 100 times magnification with a Leica DM6000M model optical microscope is the highest after classifying the color brightness into 256 using Clemex Vision PE software.
  • a portion of the brightness value corresponding to 70% of the brightness value or more was specified as the indentation portion, and the area ratio thereof was obtained. If the ratio of the indentation part is too high, the load applied to the plating layer to form the indentation part is excessive and surface cracks may increase. Therefore, the upper limit of the ratio of the indentation part may be set to 50% or 45%.
  • the aluminum-iron (Al-Fe) alloy plating layer may include a total of 70% or more of Al and Fe by weight. Since the plating layer may be made of only these elements, there is no need to specifically set an upper limit on the sum of the contents, and the sum of the contents of these elements may be 100%.
  • Fe in the plating layer may diffuse into the plating layer during hot press molding, Fe may be included in an amount of 30% or more by weight. If the content of Fe in the plating layer is less than 30%, it may not be very helpful in solving problems such as hydrogen embrittlement during storage. In some cases, the Fe content may be 35% or more, and may be 40% or more.
  • the upper limit of the Fe content there is no particular limitation on the upper limit of the Fe content, but when considering the Fe content in the plating layer of a conventional hot press-formed member, the upper limit of the Fe content may be set to 90%, and in some cases set to 80% or less.
  • the average content of Fe means the average of the Fe content in the entire plating layer, and there may be various measurement methods. After integrating the Fe content curve according to the depth (thickness) that appears when the interface of is analyzed, it can be used as a value divided by the thickness of the plating layer.
  • the point where the Al and Fe content curves intersect is defined as the interface between the coating layer and the steel sheet.
  • the plating layer of the hot press-formed member may further include common elements included in the plating layer in addition to the above-described Al and Fe.
  • these elements include one or two or more selected from among Mg, Zn, Mn, Cr, Mo, Si, and Ti, and they may be included in the plating layer up to 20% by weight or less in total.
  • the holding steel sheet of the hot press-formed member of the present invention may have various structures for each strength. If the tensile strength is 400 to 800 MPa, it may have a microstructure consisting of one or two or more phases selected from 5 to 50% of martensite and the remaining ferrite, pearlite, bainite, and austenite based on area, and tensile strength When is 800 to 1300 MPa, it may have a microstructure consisting of 90% or more of martensite and one or more phases selected from the remaining ferrite, pearlite, bainite and austenite based on area, and the tensile strength is 1300 MPa or more may have a microstructure consisting of one or more phases selected from 95% or more of martensite and the remaining ferrite, pearlite, bainite, and austenite on an area basis.
  • a cold-rolled steel sheet for hot press forming having a composition shown in Table 1 was prepared as a base steel sheet. After annealing heat treatment of the base steel sheet in a conventional manner, molten aluminum plating was performed.
  • the plating bath was set to have a composition substantially consisting of 9.5% Si and balance Al by weight%, and the plating bath temperature was set to 660°C. After plating, the coating weight was adjusted to 40 g/m 2 based on one side using an air knife.
  • alloying was performed by on-line or phase annealing for each invention example and comparative example to obtain an Al-Fe alloy plated steel sheet.
  • Online alloying was performed by reheating the steel sheet to 720 ° C, holding it for 5 seconds and cooling it to room temperature, and alloying by normal annealing was performed by maintaining the coil in an ordinary annealing furnace at 650 ° C for 10 hours.
  • the coated steel sheet was skin-pass rolled with a rolling force shown in Table 2 using a roll having surface roughness (Ra) and peak number (RPc) shown in Table 2, thereby adjusting the surface state of the alloyed plating layer of the steel sheet.
  • the sum of the contents of Al and Fe in the alloy plating layer obtained by each alloying method and skin pass rolling and the Fe content were 90% and 43%, respectively, and there was no particular difference between examples.
  • the Fe content on the surface of the plating layer was 77% of the average Fe content in the plating layer, and did not show a large difference.
  • the surface of the plating layer means a point having a depth of 1 ⁇ m from the outermost surface of the plating layer.
  • the skin pass-rolled plated steel sheet was heated at 930° C. for 6 minutes in an air atmosphere, and hot press forming and rapid cooling were performed to obtain a hot press formed part. It was confirmed that the internal structure of the obtained hot-press-formed part consisted of substantially 100% martensite, and that the strength was 1500 MPa. However, the structure and strength of the steel material can be changed as needed, and a person skilled in the art will have no difficulty in manufacturing a member having a target structure and strength by changing the manufacturing conditions including the composition of the steel material or cooling conditions. .
  • the sum of Al and Fe contents in the alloy plating layer and the Fe content were 83% and 44%, respectively, and no particular difference was confirmed for each example.
  • the surface roughness (Ra), the number of peaks (RPc), the number of cracks per unit area, and the ratio of indentations were measured for the skin pass-rolled plated steel sheet and the hot press formed member.
  • the surface roughness and number of peaks were obtained by measuring five areas according to the JIS B 0601 (2013) standard and averaging the values.
  • the number of cracks was measured by converting the total number of cracks observed in each of 100 areas obtained by dividing the field of view of a microscope (magnification: 100 times) into 10 equal parts horizontally and vertically, respectively, to those observed in an observation area of 1 mm 2 .
  • a ZEISS SUPRA 55VP model scanning electron microscope was used for the measurement, and the average value of the measurements for five sites was obtained and used for analysis.
  • the ratio of the indentation was 70% of the highest brightness value after observing the surface image at 100 times magnification with a Leica DM6000M model optical microscope and classifying the color brightness into 256 using Clemex Vision PE software. A portion having a brightness corresponding to or greater than that was specified as the indentation portion, and the area ratio thereof was obtained. The area ratio was also set as the average value of the results of observing five locations.
  • those for coated steel sheets are shown in Table 3, and those for hot press formed parts are shown in Table 4.
  • the coating adhesion rating was determined by coating the member obtained according to the GMW14829 method, forming grid scratches at 1 mm intervals, and evaluating the peeling of the tape. If the rating is 1 or less, it can be regarded as good.
  • the Ra ⁇ RPc of the plating layer, the indentation ratio, and the number of cracks may be sufficient to secure the paint adhesion of the member, but the corrosion resistance of the member deteriorates as shown in Table 4 as damage occurs to the plating layer.
  • the plating layer is damaged, corrosion may occur due to exposure of the base steel sheet through the damaged gap in the aluminum alloy-based plating layer that does not provide the anticorrosive performance of the sacrificial anode method. can be bigger
  • Example 1 shows a coated steel sheet (a) manufactured by Comparative Example 1 and a coated steel sheet (b) manufactured by Inventive Example 2.
  • the plated steel sheet manufactured by Comparative Example 1 does not have sufficient surface irregularities, whereas the plated steel sheet manufactured according to Inventive Example 2 has sufficiently formed irregularities on the surface, followed by hot press forming.
  • the surface of the member produced by this can be made suitable for fixing the paint layer.
  • FIG. 2 the surface of the steel sheet manufactured by Comparative Example 1 and Inventive Example 2 was observed with a microscope (DM6000M) at 100 magnification, processed using Clemex Vision PE software, and then the area (indentation part) of 70% or more of the highest brightness was white.
  • Inventive Example 2 in which skin pass rolling was performed by controlling the SPMI to an appropriate range according to the present invention, a much higher indentation was formed than in Comparative Example 1, in which skin pass rolling was performed under low SPMI conditions.
  • the graph of FIG. 3 shows the relationship between the SPMI value and the number of cracks. From the figure, it can be seen that when the SPMI value has a value between 5000 and 8000 ⁇ Ton ⁇ m/cm, the number of cracks can be maintained within an appropriate range.

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
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  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Inorganic Chemistry (AREA)
  • Coating With Molten Metal (AREA)

Abstract

La présente invention concerne : une tôle d'acier plaquée pour formage à la presse à chaud, ayant une excellente adhérence de placage et une excellente résistance à la corrosion après formage à la presse à chaud ; un procédé de préparation de la tôle d'acier plaquée ; et un élément de formage pressé à chaud. La tôle d'acier plaquée selon un aspect de la présente invention comprend une tôle d'acier de base et une couche de placage constituée d'un alliage Al-Fe formé sur la tôle d'acier de base, la quantité totale d'Al et de Fe dans la couche de placage étant supérieure ou égale à 80 % en poids, la quantité moyenne de Fe dans la couche de placage étant supérieure ou égale à 20 % en poids, et le produit de Ra et RPC de la surface de la couche de placage pouvant être de 60 à 150 µm/cm. Ici, Ra représente une rugosité moyenne arithmétique et son unité est µm, et RPC représente le nombre de pics par unité de longueur et son unité est /cm.
PCT/KR2022/020870 2021-12-23 2022-12-20 Tôle d'acier plaquée ayant une excellente adhérence de placage et une excellente résistance à la corrosion après formage à la presse à chaud, procédé de préparation de tôle d'acier plaquée, et élément de formage pressé à chaud WO2023121241A1 (fr)

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KR1020210185822A KR20230096381A (ko) 2021-12-23 2021-12-23 열간 프레스 성형 후 우수한 도장 밀착성과 내식성을 나타내는 도금강판, 도금강판의 제조방법 및 열간 프레스 성형 부재

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6296805B1 (en) 1998-07-09 2001-10-02 Sollac Coated hot- and cold-rolled steel sheet comprising a very high resistance after thermal treatment
JP2002317258A (ja) * 2001-04-19 2002-10-31 Nippon Steel Corp 加工後の耐食性に優れた溶融アルミめっき鋼板とその製造方法
JP2011137210A (ja) * 2009-12-28 2011-07-14 Nippon Steel Corp ホットスタンプ用鋼板及びその製造方法
KR20130110532A (ko) * 2012-03-29 2013-10-10 현대제철 주식회사 용융 도금 강판의 제조 방법 및 이를 사용하여 제조된 용융 도금 강판
KR20190078013A (ko) * 2017-12-26 2019-07-04 주식회사 포스코 수소지연파괴특성이 우수한 철-알루미늄 합금 도금강판, 그 제조방법 및 그로부터 제조된 열간 프레스 성형 부재
CN112877592A (zh) * 2019-11-29 2021-06-01 宝山钢铁股份有限公司 具有优异漆膜附着力的热成形部件及其制造方法

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6296805B1 (en) 1998-07-09 2001-10-02 Sollac Coated hot- and cold-rolled steel sheet comprising a very high resistance after thermal treatment
JP2002317258A (ja) * 2001-04-19 2002-10-31 Nippon Steel Corp 加工後の耐食性に優れた溶融アルミめっき鋼板とその製造方法
JP2011137210A (ja) * 2009-12-28 2011-07-14 Nippon Steel Corp ホットスタンプ用鋼板及びその製造方法
KR20130110532A (ko) * 2012-03-29 2013-10-10 현대제철 주식회사 용융 도금 강판의 제조 방법 및 이를 사용하여 제조된 용융 도금 강판
KR20190078013A (ko) * 2017-12-26 2019-07-04 주식회사 포스코 수소지연파괴특성이 우수한 철-알루미늄 합금 도금강판, 그 제조방법 및 그로부터 제조된 열간 프레스 성형 부재
CN112877592A (zh) * 2019-11-29 2021-06-01 宝山钢铁股份有限公司 具有优异漆膜附着力的热成形部件及其制造方法

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