EP3775299A1 - Procédé destiné à fabriquer un module en acier pourvu d'une housse à partir d'un produit plat en acier, produit plat en acier et module en acier - Google Patents

Procédé destiné à fabriquer un module en acier pourvu d'une housse à partir d'un produit plat en acier, produit plat en acier et module en acier

Info

Publication number
EP3775299A1
EP3775299A1 EP18726728.1A EP18726728A EP3775299A1 EP 3775299 A1 EP3775299 A1 EP 3775299A1 EP 18726728 A EP18726728 A EP 18726728A EP 3775299 A1 EP3775299 A1 EP 3775299A1
Authority
EP
European Patent Office
Prior art keywords
steel
forming
oxide layer
flat
furnace
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP18726728.1A
Other languages
German (de)
English (en)
Inventor
Bernd Linke
Maria KÖYER
Manuela Ruthenberg
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ThyssenKrupp Steel Europe AG
ThyssenKrupp AG
Original Assignee
ThyssenKrupp Steel Europe AG
ThyssenKrupp AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by ThyssenKrupp Steel Europe AG, ThyssenKrupp AG filed Critical ThyssenKrupp Steel Europe AG
Publication of EP3775299A1 publication Critical patent/EP3775299A1/fr
Pending legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C21D1/76—Adjusting the composition of the atmosphere
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/56—Continuous furnaces for strip or wire
    • C21D9/561—Continuous furnaces for strip or wire with a controlled atmosphere or vacuum
    • 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
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/62—Quenching devices
    • C21D1/673—Quenching devices for die quenching

Definitions

  • the invention relates to a method for producing a steel component by hot forming a steel flat product coated with an aluminum-based corrosion protection coating. Furthermore, the invention relates to a steel component produced by hot forming a flat steel product coated with an aluminum-based corrosion protection coating and to a flat steel product for the production of such a steel component.
  • Such coatings consist for example of aluminum or aluminum alloys or of zinc or zinc alloys and protect the underlying steel substrate from corrosion on the one hand because of their effect as a mechanical barrier and on the other hand because of their cathodic protection.
  • a coated flat steel product consists of a steel substrate, which may be, for example, a steel strip or a steel sheet or a blank produced from a steel sheet, such as a printed circuit board, and a corrosion protection coating present on at least one side of the steel substrate.
  • flat steel products are heated and cooled in a mold.
  • two types of hot forming are distinguished.
  • direct hot forming the flat steel product to be formed is first heated and placed immediately after the heating in a forming tool, in which it is formed and at the same time is cooled tig.
  • indirect hot forming the steel flat product to be formed is first cold formed in a first forming tool, then heated and cooled after heating in a second mold, in which, however, it is little or no longer reshaped.
  • Indirect hot forming offers the advantage of less tool wear compared to direct warp forming when using uncoated flat steel products.
  • the scale formed on uncoated flat steel products during heating rubs against the surfaces of the forming tool, which thereby wears faster.
  • the scale formation and thus the tool wear can be reduced by coating the flat steel product with a corrosion protection coating.
  • WO 2008/053273 A1 discloses a method for producing a steel component provided with an aluminum-based corrosion protection coating.
  • the aluminum or aluminum alloy coated board is heated at a rate of 4 to 12 ° C / s, held for 3 to 13 minutes at temperatures of 880 - 940 ° C, then transferred to a forming tool, formed and cooled at a rate of at least 30 ° C / s.
  • the coating of the component has a multilayered layer structure with an interdiffusion layer, an intermediate layer, an intermetallic layer and a surface layer.
  • the interdiffusion layer consists of 86-95% Fe, 4-10% Al and up to 5% Si.
  • the intermediate layer consists of 39-47% Fe, 53-61% Al and up to 2% Si.
  • the intermetallic layer consists of 62-67% Fe, 30-34% Al and 2-6% Si.
  • the surface layer consists of 39-47% Fe, 53-61% Al and up to 2% Si.
  • the component should have a good wel
  • the invention is based on the object of providing a coating with an aluminum-based corrosion protection coating and a low hot-forming tool wear. chendes steel flat product for the production of a steel component and a steel component produced therefrom to provide.
  • this object is achieved by a method having the features specified in claim 1.
  • Advantageous and preferred embodiments of the method according to the invention are specified in the claims referring back to claim 1.
  • the object is achieved by a flat steel product with the features mentioned in claim 8.
  • Advantageous and preferred embodiments of the flat steel product according to the invention are specified in the claims appended to claim 8.
  • the steel component the object is achieved by a steel component having the features mentioned in claim 12.
  • Advantageous and preferred embodiments of the steel component according to the invention are specified in the claims back to claim 12.
  • a process according to the invention for the production of a steel component provided with an aluminum-based corrosion protection coating comprises at least the following process steps:
  • a flat steel product is provided in method step a), which is provided with an aluminum-based corrosion protection coating.
  • the steel used for the steel substrate of the flat steel product is preferably a steel consisting of 0, 1 - 0.4 wt .-% C, preferably 0, 15 - 0.3 wt .-% C, particularly preferred 0.19 to 0.25 wt.% C, 0.5 to 3.0 wt.% Mn, preferably 0.9 to 1.6 wt.% Mn, 0.05 to 0.5 wt.
  • % Si preferably 0, 15-0.4 wt.% Si, 0.01-0.2 wt.% Al, preferably 0.01-0.1 wt.% Al, 0.005-1.0 wt % Cr, preferably 0, 1 to 0.4% by weight Cr, 0.0005 to 0.01% by weight B, 0.001 to 0.2% by weight V, preferably 0.001 to 0.010% by weight % V, more preferably 0.002 - 0.006 %
  • V 0.001-0.1% by weight of Ti, 0.001-0.1% by weight of Nb, optionally 0.01-0.4% by weight of Ni, optionally 0.01-0, 8% by weight of Cu, optionally 0.002-1.0% by weight of Mo, optionally 0.001-1.0% by weight of W, up to 0.01% by weight of N, and the remainder being iron and unavoidable impurities is up to 0, 1 wt .-% P and up to 0.05 wt .-% S attributable to the unavoidable impurities.
  • particularly suitable steel substrates for the present invention have a thickness of 0.4 to 3 mm.
  • alloy contents and compositions of liquid or solid phases refer to weight or mass unless otherwise specified. If information on atmospheric compositions is provided in the present case, these refer to the volume unless expressly stated otherwise.
  • the corrosion protection coating on the steel substrate is made of pure aluminum or an aluminum alloy.
  • Suitable aluminum alloys typically consist of 3-15% by weight of Si, preferably 7-12% by weight of Si, particularly preferably 9-10% by weight of Si and optionally one or more elements selected from the group consisting of in the following contents: 2 to 3.5% by weight of Fe, 0.05 to 2% by weight of transition metals other than Fe, preferably 0, 1 to 0, 5 wt .-% of other transition metals than Fe, particularly preferably 0, 15 to 0.4 wt .-% of other transition metals as Fe, 0.05 to 2 wt .-% alkaline earth metals, preferably 0, 1 to 0.5 wt.
  • Alkaline earth metals more preferably 0, 15 to 0.4 wt .-% alkaline earth metals, and the balance of aluminum and unavoidable impurities.
  • transition metals a distinction is made here between iron and other transition metals, because iron may be present in higher contents than other transition metals. Iron, other transition metals and also elements of the group of alkaline earth metals lead to a dense, thin and opaque oxide layer, which reduces the penetration of diffusible hydrogen.
  • the following alkaline earth metals or transition metals have proved to be particularly suitable: Mg, Ca, Sr, Ba, Zr and Ti.
  • the anticorrosive coating may be applied to the steel substrate in a conventional manner, for example, by a hot dip coating process. Other application methods that enable the application of a corrosion protection layer are also possible conceivable.
  • a suitable anticorrosive coating is typically at most 30 microns thick per side, more preferably 10 to 30 microns thick per side.
  • the coated steel flat product for hot forming which is carried out in process step e), is heated.
  • the invention is based on the finding that the wear of the forming tool is influenced by the composition of the atmosphere of the heating furnace.
  • the heating furnace is also referred to as a hot forming furnace because it heats the coated steel substrate prior to the hot forming process and for the heat forming process.
  • a preferred example of a hot forming furnace is a roller hearth furnace. From an oxygen content of 6% by volume in the furnace atmosphere, an aluminum oxide layer is formed on the aluminum-based corrosion protection coating. When nitrogen is present, in addition to the aluminum oxide layer, aluminum nitride particles (AIN) are formed in the form of a rod or needle on the surface of the coated flat steel product.
  • AIN aluminum nitride particles
  • AIN generally has a very high hardness.
  • the hardness of AIN is typically about 1230 HV1. If these AIN rods or needles grow beyond the aluminum oxide layer, they will damage the surface of the forming tool during the forming process and cause increased wear of the forming tool. Particularly high wear can be observed at levels of up to 13% oxygen by volume. As the oxygen content increases, tool wear decreases.
  • the invention is based on the finding that, starting from oxygen contents in the hot-working atmosphere of at least 16% by volume, the formation of AIN rods is so hindered that there are significantly less AIN rods grown beyond the aluminum oxide coating than at contents of less than 16 vol.% Oxygen.
  • the heating of the coated steel flat product in process step b) therefore takes place in a hot-forming furnace whose atmosphere contains at least 16% by volume, preferably at least 18% by volume, particularly preferably at least 19% by volume of oxygen.
  • Aluminum oxide layers with an average thickness of at least 50 nm have been found to be favorable proven to reduce tool wear. It is believed that aluminum oxide layers having an average thickness of at least 50 nm have a smoothing effect. That is, AIN rods do not grow beyond this layer thickness.
  • Aluminum oxide layers of at least 50 nm average thickness have proved favorable for preventing caking of the tool on the molded part and for reducing scoring on the tool, since the aluminum oxide layer acts as a release agent between the forming tool and the surface of the flat steel product to be formed acts and separates the liquid phase components from the tool surface in the case of insufficiently annealed flat steel products.
  • Aluminum-based anticorrosive coatings on which alumina layers of at least 50 nm mean thickness have been formed typically contain Fe (All-xSix), t ⁇ Fe3 (Al, Si) 5, Fe2Al5 and Fe3 (All-xSix).
  • Opaque aluminum oxide layers have proved to be particularly effective for reducing tool wear.
  • opaque aluminum oxide layers are understood as meaning aluminum oxide layers which completely cover the surface of the anticorrosive coating.
  • oxide layers having an average thickness of less than 50 nm are formed. These are often not opaque, which has a negative effect on tool wear.
  • a furnace atmosphere of up to 100% by volume of oxygen would be possible to reduce the AIN formation.
  • pure oxygen is very explosive.
  • the oxygen content of the furnace atmosphere is preferably less than 50% by volume and more preferably not more than 30% by volume.
  • the oxygen content of the furnace atmosphere can be limited to at most 25 vol .-%, preferably to at most 20 vol .-%.
  • the atmosphere of the hot forming furnace contains at least 50% nitrogen by volume in addition to oxygen to reduce the explosiveness of the furnace atmosphere.
  • the nitrogen content of the furnace atmosphere is preferably less than 84% by volume, more preferably less than 82% by volume, most preferably less than 81% by volume.
  • the atmosphere of the hot forming furnace consists of at least 16% by volume of oxygen, more preferably at least 18% by volume of oxygen, most preferably at least 19% by volume of oxygen, and the remainder each of nitrogen and unavoidable impurities.
  • one or more noble gases in proportions of up to 1.5% by volume may also be added to the atmosphere of the hot-forming furnace, in addition to oxygen and nitrogen, so that the atmosphere of the hot-forming furnace consists of at least 16% by volume of oxygen, especially preferably at least 18% by volume of oxygen, very particularly preferably at least 19% by volume of oxygen, up to 1.5% by volume of one or more noble gases, and the remainder being nitrogen and unavoidable impurities.
  • one or more noble gases may be added to the atmosphere of the hot-forming furnace without significant amounts of nitrogen being added so that the atmosphere of the hot-forming furnace comprises at least 16% by volume of oxygen, particularly preferably at least 18% by volume of oxygen. most preferably at least 19 vol .-% oxygen, and the remainder each consists of noble gases and unavoidable impurities.
  • impurities in the furnace atmosphere may occur with other gases in proportions of up to 1.1% by volume.
  • the atmosphere of the hot forming furnace may also contain water vapor with a water content of 0.5 to 15 g / m 3 .
  • furnace atmospheres are preferred whose composition is not explosive and not harmful to health.
  • the dew point TP of the furnace atmosphere is set to values between -20 ° C and +15 ° C, preferably to values between -15 ° C and +15 ° C.
  • a dew point less than -20 ° C will lower the oxygen content in the hot forging furnace, whereas higher than +15 ° C may lead to increased hydrogen uptake.
  • the ratio of the volume fraction of nitrogen, V (N 2), to the volume fraction of oxygen V (O 2) is from 3.80 to 5.30:
  • V (N2) volume of nitrogen in the hot-forming furnace in% by volume
  • V (02) volume of oxygen in the hot-forming furnace in% by volume. Nitrogen-to-oxygen ratios of 4.0 to 5.2 have proved to be particularly effective.
  • the steel flat product is heated in step b) in a hot-forming furnace with furnace temperatures of 830 to 950 ° C. to a temperature TI which is between 830 and 950 ° C., preferably between 900 and 950 ° C.
  • the heating is preferably carried out in a continuous furnace, particularly preferably in a roller hearth furnace.
  • the furnace temperature corresponds to the temperature to which the flat steel product is to be heated.
  • the steel flat product is introduced into the hot-forming furnace at room temperature. Residence times of the flat steel product in the heat forging furnace of 2 to 15 minutes have proved to be particularly favorable.
  • the steel flat product can be kept at this temperature in a working step c) in the hot-forming furnace after reaching the temperature TI.
  • the residence time of the flat steel product in the hot forging oven is also 2 to 15 minutes in this case, including the time for heating to oven temperature and the time for optionally holding the flat steel product to oven temperature.
  • the furnace atmosphere is the same during holding as in step b) during heating.
  • the steel flat product obtained in step b) after heating or optionally in process step c) after optional holding has an aluminum oxide layer with an average thickness of at least 50 nm, preferably at least 100 nm, on the surface of the anticorrosive coating .
  • Lower average thicknesses are often not opaque, which has a negative effect on tool wear.
  • the average thickness of the alumina layer is not limited to the top. For operational reasons, typically average thicknesses of at most 2300 nm are achieved. On average, the oxide layer thicknesses are on average only up to 1500 nm. However, if flat steel products with an improved weldability and an improved coating and adhesive suitability are to be produced in a targeted manner As a result, thinner aluminum oxide layers having an average thickness of at most 150 nm have proved favorable.
  • AIN rods may be present on the aluminum oxide layer.
  • at most 10 AIN rods are present on the aluminum oxide layer present on the surface of a flat steel product according to the invention per 1000 pm 2 .
  • a larger number of AIN rods per 1000 pm 2 has a negative effect on the overhaul and cleaning intervals within a forming campaign.
  • a forming campaign is understood to mean the entirety of all the blanks to be formed in a row under the same hot forming conditions.
  • a forming campaign typically involves up to 1500 boards. Forming a circuit board in the forming tool is also referred to as a stroke.
  • a reworking and cleaning of the hot forming tools must take place after 40-60% of the applied component surface of a forming campaign, at a density of at most 10 AIN rods per 1000 pm 2 surface a revision and cleaning of hot forming tools, however, only after more than 60% enforced component surface of a forming campaign, especially after 70 - 80% enforced component surface of a forming campaign done.
  • the tool wear can be further reduced to a revision and cleaning of the hot forming tools after more than 80% of enforced component surface of a forming campaign, when the density of AlN rods per 1000 pm 2 surface is limited to a maximum of 5.
  • a particularly low wear can be achieved with a rod density of at most 2, in particular zero AIN rods per 1000 pm 2 surface.
  • a reworking and cleaning of the hot forming tools is only required after 100% of the component surface has been inserted.
  • the term "penetrated component surface of a forming campaign” is understood to mean the surface of the sinkers which were hot-formed in the tool as a whole within a forming campaign.
  • the flat steel product obtained in process step b) after heating or optionally in process step c) after the optional holding has a corrosion protection coating whose thickness is typically 30 to 130 g / m 2 or 12-60 pm per side.
  • the anticorrosive coating typically contains four intermetallic phases: Fe (All-xSix), t ⁇ Fe3 (Al, Si) 5, Fe2AI5 and Fe3 (All-xSix).
  • the tool wear can be further reduced if the AlN rods grow out of the aluminum oxide layer by at most 6 pm, preferably by at most 2 pm, that is to say not more than 6 pm, preferably not more than 2 pm, in particular preferably not more than 1.0 pm protrude from the aluminum oxide layer.
  • AIN rods come up, then their height h or the length with which the AIN rods protrude from the aluminum oxide layer is typically 0.5-6 ⁇ m.
  • the height h of the AIN rods refers to their protruding from the aluminum oxide layer length. In this case, the vertical perpendicular of the tip of the AIN rod on the Oberflä surface of the aluminum oxide layer is understood by the height of an AIN-rod.
  • the AIN rods have a diameter D of at most 2 pm, preferably of at most 1.1 pm, which likewise has a favorable effect on the tool wear. Typically, their diameter is 1 - 2 pm.
  • the diameter of an AIN rod is understood to mean the width of the AIN rod that is halfway up the AIN rod and parallel to the surface of the aluminum oxide layer.
  • the negative effects on tool wear can be reduced particularly effectively if the AIN rods after heating both by at most 6 pm, preferably by at most 2 pm, protrude from the aluminum oxide layer, as well as at most 2 pm thick.
  • the steel flat product obtained in process step b) after heating or optionally in process step c) after the optional holding, provided with a corrosion protection coating, is transported from the hot-forming furnace to a forming tool in process step d) and placed in this.
  • the transport from the hot forming furnace to the forming tool and the insertion of the flat steel product in the tool takes place in a conventional manner. Transfer times of 3 to 15 s have proven to be particularly favorable. Under the transfer time will be in the present case, the time span between the discharge of the furnace until it closes the tool.
  • the flat steel product in the forming tool is converted to a component in a conventional manner and simultaneously cooled.
  • the cooling also takes place in a conventional manner.
  • the forming is preferably carried out immediately after inserting the flat steel product in the tool. Cooling speeds of from 20 to 1000 K / s, preferably from 25 to 500 K / s, have proved to be particularly favorable. In particular, for a hardening of the flat steel product, these cooling rates have proven to be suitable.
  • the process for producing a steel component provided with an aluminum-based corrosion protection coating consists only of process steps a) to e), that is, it does not include any further process steps beyond process steps a) to e).
  • the steel component obtained by the method according to the invention after carrying out step e) is provided with an aluminum-based corrosion protection coating, in particular it has an aluminum-based corrosion protection coating.
  • an aluminum-based corrosion protection coating in particular it has an aluminum-based corrosion protection coating.
  • diffusion of iron atoms from the steel substrate into the anticorrosive coating may occur, whereby the thickness of the anticorrosive coating may increase.
  • the thickness of the corrosion protection coating of the steel component after hot working is typically 30 to 130 g / m 2 or 12 to 60 ⁇ m per side.
  • the steel component On the surface of the anticorrosion coating, the steel component has an aluminum oxide layer with an average thickness of at least 50 nm, preferably at least 100 nm.
  • the average thickness of the aluminum oxide layer is at most 2300 nm, preferably at most 1500 nm, particularly preferably at most 150 nm. From the aluminum oxide layer project per 1000 pm 2 area at most 10, preferably at most 5, more preferably at most 2, most preferably no AIN-sticks out. In particular, at most 10 AIN rods per 1000 pm 2 , preferably at most 5, particularly preferably at most 2, very particularly preferably no AIN rods are present on the aluminum oxide layer.
  • the AlN rods projecting from the aluminum oxide layer of the steel component are at most 6 ⁇ m, preferably at most 2 ⁇ m, especially preferably at most 1.0 mih high and have a diameter of at most 2 gm, preferably of at most 1, 1 gm.
  • the anticorrosive coating typically has four intermetallic phases: Fe (All-xSix), t ⁇ Fe3 (Al, Si) 5, Fe2AI5 and Fe3 (All-xSix).
  • a steel component according to the invention can be produced by a method according to one of claims 1 to 7.
  • a steel component according to the invention can be produced using a flat steel product according to one of claims 8 to 11.
  • Fig. 1 Schematic representation of the growth of AIN rods and the alumina layer
  • Fig. 2 Schematic representation of the aluminum oxide layer and the AlN rods to Erläute tion of the abbreviations used
  • FIG. 1 the growth of AIN rods is shown schematically.
  • an aluminum-based corrosion protection coating 2 is applied on a steel substrate 1.
  • a thin aluminum oxide layer 3 forms on the aluminum-based corrosion protection coating 2 (FIG. 1 a)).
  • the aluminum oxide layer is very brittle.
  • the anticorrosive coating extends underneath the aluminum oxide layer and at least partially melts. Due to the volume expansion, the brittle aluminum oxide layer 3 ruptures at some points.
  • AIN nitrides can grow in the gaps of the aluminum oxide layer 3, which initially grow to small AIN rods 4 (FIG. 1b)). Because of their elongated shape, the rods can also be called AIN needles.
  • the AIN rods 4 typically have a round cross section with a diameter D which is almost constant over the length (FIG. 2).
  • the AIN rods continue to grow in length and width as the heating process progresses, and at the same time the thickness of the aluminum oxide layer increases (FIG. 1c) and FIG. 1d)).
  • the AIN rods project out of the alumina layer with a flea h ( Figure 2).
  • four forming campaigns were carried out with 1000 boards each.
  • steel strips having the compositions shown in Table 1 were made available and coated on both sides with aluminum-based anticorrosive coatings having the compositions given in Table 2 in a conventional manner by hot-dip coating. From the coated steel strips each boards were punched out in a conventional manner and used in a roller hearth furnace for heating.
  • the blanks were heat treated at the conditions given in Table 3.
  • the blanks were heat treated in hot working ovens with furnace atmospheres having oxygen contents of 15 to 20% by volume and dew points of -15 ° C to + 10 ° C.
  • the furnace atmospheres can in principle be adjusted in various ways. One possibility is to allow the hot-forming furnace to cool first before introducing the furnace atmosphere according to the invention, which typically can take up to 20 hours, and to heat it up again after the furnace atmosphere has been introduced. Another possibility is to introduce the furnace atmosphere according to the invention into a warm hot-forming furnace, which can have a favorable effect on a reduction of the heating time. Another possibility, which contributes to further shortening of the heating times, is to heat the furnace atmosphere according to the invention before it is introduced into the warm hot forming furnace. In Experiments 1 to 4, the furnace atmospheres were respectively adjusted by feeding the respective gases into the furnace by means of a gas line.
  • the 1.5 mm thick boards were each heated to steel flat product temperatures TI of 925 ° C (experiment 1), 910 ° C (experiment 2, 4) and 930 ° C (experiment 3).
  • the residence times t of the platens in the hot-forming furnace which comprise the time from heating up to leaving the furnace, were between 4 and 6 minutes.
  • the heated blanks were each removed from the hot forging furnace, sampled and a part of the blanks was placed in a press for forming within 3 to 10 seconds, formed into a component and then re-sampled. For each test condition, multiple blanks were fabricated until wear on the tool required demolition for cleaning and, if necessary, tool maintenance.
  • a board or a formed component was sampled before and after the forming.
  • the sampling of the formed blanks was carried out in flat areas of the components in which the blanks were exposed to little or no deformation.
  • the thickness of the oxide layer per board was determined on 3 samples by X-ray photoelectron spectroscopy (XPS).
  • the samples were degreased with n-heptane, rinsed with propanol and blown off in air.
  • the samples were each mounted on a sample carrier, introduced into the measuring chamber of the X-ray photoelectron spectroscope and examined in a high vacuum.
  • the boiler pressure was ⁇ 5xlO A 8 mbar.
  • the bombardment gas used was argon.
  • the radiation was excited as AI K a with a shelling voltage of 2 or 4 kV.
  • At least one thickness measurement of the alumina layer was performed on each sample.
  • the results of the thickness measurements of all samples of a board were arithmetically averaged each time and are referred to herein as mean alumina layer thickness or as average thickness.
  • a height was determined for each AIN rod.
  • the vertical perpendicular of the AIN rod tip was measured on the surface as height h.
  • a width value was measured in each case, which is referred to as the diameter of the AIN rod.
  • the width was measured along a section running parallel to the surface.
  • the state of the forming tools was visually inspected by expert personnel on site. Visual inspection of the forming tools was performed after every 100 strokes.
  • the furnace atmosphere not according to the invention contained only 15 vol .-% oxygen.
  • 13 AIN rods per 1000 pm 2 were measured on average before and after hot forming.
  • the height of the AIN rods was between 3 and 5.5 pm, the diameter was between 1.5 pm and 2 pm.
  • the oxide layer had an average thickness of 45 nm after hot working.
  • massive dust formation in the tool and abrasive damage to the radii occurred, so the tool had to be cleaned after 500 strokes and the radii had to be reworked after only 1000 strokes.
  • the furnace atmosphere contained 21% by volume of oxygen, 78% of nitrogen, the remainder noble gases and unavoidable impurities.
  • a maximum of 1 AIN rods per 1000 pm 2 with a maximum height of 0.6 ⁇ m and a maximum diameter of 1.1 ⁇ m were determined on the samples taken before and after warping.
  • the oxide layer had an average thickness of 2100 nm.
  • 800 strokes could be performed until it was necessary to clean the forming tool.
  • the forming tool had minimal scratches, so no premature overhaul was required.
  • the increased oxide layer formation led to a deterioration of the weldability, painting and adhesive suitability.

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  • Coating With Molten Metal (AREA)

Abstract

La présente invention concerne un procédé destiné à fabriquer un module en acier par déformation à chaud d'un produit plat en acier recouvert d'une housse de protection contre la corrosion à base d'aluminium, un module en acier produit par déformation à chaud d'un produit plat en acier recouvert d'une housse de protection contre la corrosion à base d'aluminium ainsi qu'un produit plat en acier pour la fabrication d'un tel module en acier. Les étapes du procédé consistent au moins : a) à produire un produit plat en acier pourvu d'une housse de protection contre la corrosion à base d'aluminium ; b) à chauffer le produit plat en acier recouvert dans un four de déformation à chaud dont l'atmosphère de four contient au moins 16 % en volume d'oxygène et comporte un point de rosée compris entre −20 °C et +15 °C ; c) éventuellement, à maintenir le produit plat en acier recouvert dans le four de déformation à chaud ; d) à transporter le produit plat en acier chauffé du four de chauffage à un outil de déformation et à introduire le produit plat en acier dans l'outil de déformation ; e) à déformer et à refroidir simultanément le produit plat en acier dans l'outil de déformation. Le produit plat en acier pourvu d'une housse de protection contre la corrosion à base d'aluminium comporte, après avoir été chauffé ou le cas échéant après avoir été éventuellement maintenu, une couche d'oxyde d'aluminium dont l'épaisseur moyenne est d'au moins 50 nm sur la surface de la housse de protection contre la corrosion, au maximum 10 bâtonnets d'AlN étant présents pour 1000 µm² sur la couche d'oxyde d'aluminium. Le module en acier obtenu après avoir été déformé comporte une couche d'oxyde d'aluminium dont l'épaisseur moyenne est d'au moins 50 nm sur la surface de la housse de protection contre la corrosion, au maximum 10 bâtonnets d'AlN étant présents pour 1000 µm² sur la couche d'oxyde d'aluminium.
EP18726728.1A 2018-04-05 2018-04-05 Procédé destiné à fabriquer un module en acier pourvu d'une housse à partir d'un produit plat en acier, produit plat en acier et module en acier Pending EP3775299A1 (fr)

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PCT/EP2018/058717 WO2019192703A1 (fr) 2018-04-05 2018-04-05 Procédé destiné à fabriquer un module en acier pourvu d'une housse à partir d'un produit plat en acier, produit plat en acier et module en acier

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EP3775299A1 true EP3775299A1 (fr) 2021-02-17

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EP18726728.1A Pending EP3775299A1 (fr) 2018-04-05 2018-04-05 Procédé destiné à fabriquer un module en acier pourvu d'une housse à partir d'un produit plat en acier, produit plat en acier et module en acier

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EP (1) EP3775299A1 (fr)
CN (1) CN112041467A (fr)
WO (1) WO2019192703A1 (fr)

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DE102020114053B4 (de) 2020-05-26 2022-07-14 Audi Aktiengesellschaft Prozessanordnung zur Herstellung eines warmumgeformten und pressgehärteten Stahlblechbauteils
DE102020124488A1 (de) * 2020-09-21 2022-03-24 Thyssenkrupp Steel Europe Ag Blechbauteil und Verfahren zu seiner Herstellung
EP4283003A1 (fr) * 2022-05-24 2023-11-29 ThyssenKrupp Steel Europe AG Procédé de fabrication d'une pièce moulée en tôle

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Publication number Priority date Publication date Assignee Title
JP2006051543A (ja) * 2004-07-15 2006-02-23 Nippon Steel Corp 冷延、熱延鋼板もしくはＡｌ系、Ｚｎ系めっき鋼板を使用した高強度自動車部材の熱間プレス方法および熱間プレス部品
US8307680B2 (en) 2006-10-30 2012-11-13 Arcelormittal France Coated steel strips, methods of making the same, methods of using the same, stamping blanks prepared from the same, stamped products prepared from the same, and articles of manufacture which contain such a stamped product
BRPI0915898B1 (pt) * 2008-07-11 2017-07-18 Nippon Steel & Sumitomo Metal Corporation Coated aluminum steel sheet for quick heating pressure heating method, same production method and hot stemping method with quick heating using that steel plate
BR112013025401B1 (pt) * 2011-04-01 2020-05-12 Nippon Steel Corporation Peça estampada a quente de alta resistência e método de produção da mesma
EP2848709B1 (fr) * 2013-09-13 2020-03-04 ThyssenKrupp Steel Europe AG Procédé de fabrication d'un composant en acier revêtu d'une coiffe métallique protégeant de la corrosion et composant en acier
EP2993248B1 (fr) * 2014-09-05 2020-06-24 ThyssenKrupp Steel Europe AG Produit plat en acier doté d'un revêtement Al, son procédé de fabrication, et procédé de fabrication d'un composant en acier formé à chaud

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WO2019192703A1 (fr) 2019-10-10

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