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WO2020048599A1 - Produit plat laminé à chaud en acier et procédé de fabrication - Google Patents

Produit plat laminé à chaud en acier et procédé de fabrication Download PDF

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Publication number
WO2020048599A1
WO2020048599A1 PCT/EP2018/074005 EP2018074005W WO2020048599A1 WO 2020048599 A1 WO2020048599 A1 WO 2020048599A1 EP 2018074005 W EP2018074005 W EP 2018074005W WO 2020048599 A1 WO2020048599 A1 WO 2020048599A1
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WO
WIPO (PCT)
Prior art keywords
content
weight
flat steel
atomic
steel product
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.)
Ceased
Application number
PCT/EP2018/074005
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German (de)
English (en)
Inventor
Nicholas WINZER
Richard G. THIESSEN
Rainer FECHTE-HEINEN
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
Priority to EP18773945.3A priority Critical patent/EP3847284B1/fr
Priority to PCT/EP2018/074005 priority patent/WO2020048599A1/fr
Publication of WO2020048599A1 publication Critical patent/WO2020048599A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/004—Dispersions; Precipitations
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite

Definitions

  • the invention relates to a hot-rolled flat steel product with an optimized combination of high tensile strength Rm and high
  • the invention also relates to a method for producing such a hot-rolled flat steel product.
  • Alloy elements relate to weight (in% by weight or YGEW, where Y is the element symbol). Likewise, the sums or total concentrations formed from this salary information relate to the weight (stated in% by weight or YGEW), unless expressly stated otherwise. Information given in “atom%” or “YAT” (where Y is the element symbol) about contents of alloy elements or summands formed therefrom relate to the number of atoms.
  • m Y is the atomic mass of element Y
  • I G EW is the content (in% by weight)
  • m is the atomic mass of component i in the mixture with Z components.
  • Treated steels known from the prior art or according to the invention and steel flat products produced therefrom are in accordance with the ISO 16630: 2017 standard of the International Organization for Standardization (see
  • Sheet metal punched hole is expanded with a mandrel until the first cracking.
  • Materials with very anisotropic or inhomogeneous microstructures are characterized by a relatively high sensitivity to edge cracking.
  • These include dual-phase steels, which consist of hard (e.g. martensite) and soft (e.g. ferrite) phases and have a distinctive rolling texture.
  • flat steel products with an isotropic or homogeneous microstructure are characterized by a relatively low sensitivity to edge cracking.
  • These steels include steels with a ferritic structure, in which very fine precipitates can be embedded to increase strength.
  • EP 1 338 665 A1 An example of such a steel is known from EP 1 338 665 A1.
  • the steel described there has a tensile strength of at least 550 MPa when hot-rolled into a flat steel product, which should be in combination with a high elongation and excellent elongation flange capability. Due to this combination of properties, such a steel is particularly suitable for the production of complex shapes
  • EP 1 338 665 A1 mentions that a hot-rolled steel strip (in
  • Wt .-%) ⁇ 0.15% C, 0.02 - 0.35% Ti and 0.05 to 0.7% Mo and should have a structure that should essentially consist of ferrite with single-phase and fine precipitations which are dispersed in the ferrite matrix with a grain size smaller than 10 nm.
  • a hot-rolled steel sheet corresponding to this requirement should consist of (in% by weight) ⁇ 0.06% C, ⁇ 0.5% Si, 0.5 - 2.0% Mn, ⁇ 0.06% P, ⁇ 0.005 S, ⁇ 0.1% AI, ⁇ 0.006% N, 0.02 - 0.10% Ti, 0.05 - 0.6% Mo and the rest are Fe.
  • the steel sheet composed in this way should have precipitates in its single-phase structure consisting of ferrite, the grain size of which is ⁇ 10 nm and of which 5 ⁇ 10 4 / pm 3 are present in the structure per unit volume.
  • d ”and d denote the precipitation quantities at the time 0 and t
  • V m the molar volume of the precipitation
  • Xc and XD the concentration or diffusivity of the speed-limiting element (for example Ti in the case of TiC precipitations)
  • g the interfacial energy g is composed in part of the strain energy, which is due to the
  • JP 2013-133498 A discloses a high-strength hot-rolled steel sheet which (in% by weight) 0.035-0.12% C, ⁇ 0.1% Si, ⁇ 1.2% Mn, ⁇ 0.03% P, ⁇ 0.005% S,
  • the structure of the hot-rolled steel sheet composed in this way consists of at least 95 area% ferrite with an average grain diameter of ⁇ 7 pm, carbide precipitates with an average diameter of less than 8 nm are present in the structure and the structure less than 0.1 vol. -% Contains cementite.
  • the steel sheet obtained in this way should have a tensile strength of at least 780 MPa.
  • the invention was based on the object of producing an inexpensive one
  • hot-rolled steel flat product which has a high strength and at the same time is too complex shaped for forming
  • Chassis components are increasingly being used to cut sheet metal from steel with a tensile strength of 550 MPa and more.
  • the sheet metal blanks are often subjected to a particularly high degree of deformation at their cut edges, which can lie on the outer edge of the sheet metal blank and / or on holes and cutouts. These deformations can occur when using materials with heterogeneous microstructures, such as. B.
  • Chassis components is suitable and because of its low
  • Edge crack sensitivity makes it possible to design these components so that the load to be borne by them can be safely introduced via the strongly deformed edges.
  • the invention has achieved this object in that such a flat steel product has at least the features specified in claim 1.
  • a hot-rolled flat steel product according to the invention is therefore characterized in that it has a tensile strength Rm of at least 550 MPa and a hole expansion ratio l of at least 30%, its structure comprising at least 90 area% of ferrite and the remainder up to 10 area% consists of pearlite or cementite and in the structure of the
  • Diameters of at most 10 nm are embedded.
  • the flat steel product according to the invention consists of a steel which consists of (in% by weight)
  • V the sum of the contents TIQEW of Ti and Nbc E w of Nb is limited to a maximum of 0.01% by weight. - In the event that Ti and / or Nb are present, the V content V G EW is at most 0.01% by weight.
  • Verhl (XAT + OGAT) / (CAT + NAT),
  • Cr AT is Cr GEW converted into atomic%
  • CAT is C GEW converted to atomic%
  • NAT N GEW converted to atomic%
  • T ⁇ A t Ti GEW converted to
  • VAT is V GEW converted into atomic%
  • Nb AT is Nb GE w converted into atomic%.
  • Verh2 XAUS / Cr A us
  • Ti A us is the Ti content of the precipitations in atomic%
  • V A us is the V content of the precipitations in atomic%
  • Nb A us is the Nb content of the precipitations in atomic%
  • Cr A us is the Cr content of the precipitates in atomic%.
  • the contents Ti AU s > VAUS, Nb AU s and Cr AU s of the excretions given in atomic% can be determined, for example, by energy-dispersive
  • a flat steel product according to the invention has a high tensile strength Rm of at least 550 MPa, in particular at least 660 MPa, and it also regularly achieves tensile strengths of at least 780 MPa or even at least 960 MPa.
  • the hole expansion ratio l determined for a steel flat product according to the invention in accordance with ISO 16630: 2017 is in each case at least 30%, in particular at least 50%, wherein hole expansion ratios l of at least 60% can also be represented.
  • a flat steel product according to the invention has a particularly favorable ratio of hole expansion capacity to
  • completely ferritic structure with carbonitride precipitates is particularly advantageous.
  • cementite and pearlite can be formed in the structure, the proportions of which can be up to 10% by area. may be.
  • the average grain size of the structure is typically 3 to 10 pm, in particular 3 to 8 pm.
  • the crystalline carbonitride precipitates embedded in the structure of a flat steel product according to the invention based on the inventive
  • the alloy selected according to the invention lays the foundation for the optimized properties of a hot-rolled one according to the invention
  • the carbon (C) provided in the steel alloy according to the invention is mainly set in the precipitates.
  • the concentration of the C dissolved in the mixed crystal is minimized.
  • a C content of more than 0.02% by weight, in particular more than 0.05% by weight, is required in order to achieve a high precipitation density and thus to achieve the required tensile strength of at least 550 MPa. Too high a C content would in turn lead to the formation of larger pearlite contents in the structure, which would reduce the ductility and increase the sensitivity to edge cracks.
  • the C content is therefore limited to a maximum of 0.3% by weight, in particular a maximum of 0.15% by weight, negative influences of the presence of C being able to be avoided particularly reliably if the C content of the steel is at most Is 0.10% by weight.
  • the contents of the elements determining the quantitative ratio Verhl are set within the content ranges specified according to the invention for these elements in such a way that 0.5 Verhl ⁇ 2.0 applies to the quantitative ratio Verhl, with quantitative ratios Verhl of 0.7-1.5 or 0.8 - 1, 3 have been found to be particularly favorable with regard to the desired properties of a flat steel product according to the invention.
  • Manganese (Mn) is an element that contributes to the strength of steel through the formation of mixed crystals. Mn also suppresses the formation of pearlite and cementite and in this way promotes the formation of Cr-containing carbonitride precipitates based on the contents of Ti, Nb or V provided according to the invention. For this reason, the Mn content in the steel according to the invention is at least 0 , 2% by weight, in particular more than 0.3% by weight, preferably at least 0.5% by weight, particularly preferably 1.0% by weight or 1.3% by weight, is provided. Too high a concentration of Mn has a negative effect on weldability and increases the risk of occurrence more strongly
  • the upper limit of the Mn content is therefore set to at most 2.5% by weight, with lower Mn contents of at most 2.0% by weight, in particular at most 1.7% by weight, of the possible negative effects of the presence Avoid particularly safe from Mn.
  • Silicon (Si) can optionally be added in amounts to suppress the formation of pearlite in the structure of a flat steel product according to the invention.
  • a content of at least 0.05% by weight of Si is required. The Si levels would be too high
  • the Si content is max. 0.7% by weight, with Si contents of up to 0.25% by weight, in particular up to 0.1% by weight, have proven to be particularly favorable with regard to the avoidance of negative influences of the presence of Si and, moreover, enable the product according to the invention to be galvanized in pieces later. If there are special demands on the ability to galvanize bars, a Si alloy is particularly preferably dispensed with and a maximum Si content of 0.03% by weight is selected.
  • Si At levels of up to 0.7% by weight, Si also contributes to solid solution strengthening, so that higher levels of Si may well be expedient if less demands are made on the surface quality and / or the ability to galvanize the piece.
  • Si contents which are above 0.7% by weight the rollability of the steels according to the invention is, however, influenced too strongly negatively, and the rolls may grow up during the rolling process.
  • Aluminum (AI) can also be added as an optional element to suppress the formation of pearlite. Because Al is usually used to deoxidize the melt, an Al content of at least 0.01% by weight is unavoidable in the normal production of the steel from which a flat steel product according to the invention is made. A too high Ai content can have a negative impact on the castability. Therefore, the upper limit of the Al content is limited to at most 1.0% by weight, preferably at most 0.7% by weight, in particular at most 0.5% by weight.
  • Findings of the invention can be used to coarsen the
  • the detection limit for Cr in steels of the type according to the invention is in the range of 0.03% by weight, whereas Cr contents of at least 0.05% by weight in
  • Atomic ratio of Ti to the Mo or W present is at most 4. This shows that the fact that in a
  • the upper limit of the Cr content in a flat steel product according to the invention is set to at most 0.5% by weight, preferably at most 0.25% by weight or at most 0.15% by weight. It should be noted that the Cr contents of a flat steel product according to the invention are set such that no pure Cr carbides are present in the flat steel product according to the invention.
  • the temperature at which the precipitation-stabilizing effect occurs is also reduced. This increases the certainty that a sufficient number of excretions can first be formed before the obstruction of coarsening of the excretions begins.
  • microalloying elements titanium (Ti), niobium (Nb) and vanadium (V) are for the formation of the precipitates in the structure of the invention
  • XGEW [% by weight] - TIGEW + (VGEW / 1 > 06) + (NbGEw / 1 > 94) is at least 0.02% by weight, in particular at least 0.05% by weight, the required density distribution of excretions achieved.
  • the precipitates formed by Ti, Nb or V are in the
  • Ti or Nb are only used in total contents of at most 0 , 01% by weight, preferably at most 0.005% by weight, which are in the range of the unavoidable impurities in which neither Ti nor Nb have an effect on the properties of the steel.
  • Ti and Nb can be added alone or together, however, because the
  • V is therefore only tolerated as an unavoidable impurity, which can be present in contents of up to 0.01% by weight, preferably up to 0.005% by weight.
  • the XGEW value is limited to 0.5% by weight. In this way it is avoided that, for example, increased Nb contents lead to crack formation during continuous casting or during slab cooling or reheating. At the same time, only a certain content of microalloying elements is required for the desired strengths. If this is exceeded, there is only a slight further increase in strength. In addition, the average diffusion distances decrease, which increases the risk of undesired large precipitates. For these reasons, the Nb, Ti or V contents of the steel of a flat steel product according to the invention
  • Phosphorus (P) is unfavorable for the weldability of a flat steel product according to the invention.
  • the P contents of a flat steel product according to the invention are therefore limited to at most 0.02% by weight, in particular less than 0.02% by weight, with P contents of at most 0.010% by weight, in particular less than 0.005% by weight. -%, are particularly cheap.
  • S sulfur
  • MnS or (Mn, Fe) S which has a negative effect on the elongation.
  • the S content must therefore be limited to at most 0.005% by weight, in particular less than 0.003% by weight, preferably less than 0.0015% by weight.
  • N is present in the flat steel product according to the invention as an unavoidable impurity due to the production.
  • Precipitates embedded in the steel flat product according to the invention lie as carbonitrides in the form of (Ti, Cr) (C, N); (Nb, Cr) (C, N); (V, Cr) (C, N) or (Ti, Nb, Cr) (C, N). If nitrogen “N” is present, Ti, Nb and V preferably form nitrides or carbonitrides in the presence of C with N. That is why in practice it is technically and economically among them
  • the upper limit of the N content is therefore set at 0.01% by weight, preferably 0.005% by weight.
  • the upper limit of the Ca content according to the invention limited to 0.01 wt .-%, in particular at most 0.005 wt .-%, preferably at most 0.002 wt .-%.
  • the Mo and W contents are limited to at most 0.05% by weight, in particular at most 0.04% by weight, preferably 0.03% by weight, since these
  • B must not exceed 0.002% by weight, in particular 0.001% by weight, preferably 0.0005% by weight, in order to prevent the movement of the phase boundaries from being slowed down by B segregated on them and thereby the formation of Carbides and carbonitrides of Ti, Nb and V is hindered.
  • Cu can separate out as coarse particles, which have a negative effect on the mechanical properties. Cu also has a negative impact on castability. In order to avoid any influence of Cu, the permissible upper limit of the Cu content in the invention is
  • Flat steel product 0.1% by weight, in particular less than 0.04% by weight or less than 0.02% by weight.
  • Ni, Sn, As, Co, Zr, as well as rare earths, in particular La and / or Ce, are also not required as alloy elements in the flat steel product according to the invention and count in the event that they are nevertheless used in the invention
  • the Ni content is at most 0.1% by weight
  • the Sn content is at most 0.05% by weight
  • the As content is at most 0.02% by weight
  • the Co content is at most 0.02% by weight
  • the Zr content to a maximum of 0.002% by weight, in particular a maximum of 0.0002% by weight
  • the content of elements attributable to the rare earths, such as La and Ce to a maximum of 0.002% by weight in each case .-%, in particular a maximum of 0.0002 wt .-% limited.
  • O is the same
  • the maximum permissible O content is therefore set to 0.005% by weight, preferably 0.002% by weight.
  • H is very mobile in interstitial spaces in steel and, particularly in high-strength steels, can tear open the core when it is hot-rolled.
  • Flat steel products should therefore be as low as possible, but in any case at most 0.001% by weight, in particular at most 0.0006% by weight or at most 0.0004% by weight, with H contents of at most 0.0002 % By weight are particularly desirable.
  • the method according to the invention for producing a flat steel product according to the invention comprises the following steps: a) Melting a steel which consists of (in% by weight) 0.02-0.3% C, ⁇ 0.7% Si, ⁇
  • V content V G EW is at most 0.01% by weight.
  • XGEW [% by weight] TIQEW + (V GE w / 1, 06) + (Nb GE w / 1, 94) applies 0.02% ⁇ X GEW ⁇ 0.5%.
  • C A T is CGEW converted into atomic%
  • N A T is NQEW converted into atomic%
  • Ti AT is TIGEW converted into atomic%
  • V T is VGEW converted, in atomic%
  • NbAT is Nb G Ew converted into atomic%.
  • alloyed steel is cast into a preliminary product after it melts, which is the classic
  • Production route will be a standard size slab.
  • the steel can also be obtained by direct hot rolling of a continuous casting in a casting or rolling mill as a preliminary product a thin slab or in a
  • the preliminary product is heated to or at at least 1150 ° C
  • the heating temperature is max. Limited to 1350 ° C.
  • the hot rolling of the preliminary product takes place in a conventional manner, whereby the final temperature of the hot rolling must be at least 880 ° C. If the hot rolling end temperatures are too low, the rolling forces increase disproportionately and the desired isotropy of the material is lost due to the effects of thermomechanical rolling. Over 980 ° C
  • the hot-rolled steel strip leaving the hot rolling stack is cooled at a cooling rate of 20-400 ° C / s to a coiling temperature which is in the range of 560-690 ° C.
  • a cooling rate of at least 20 ° C / s is required to avoid the formation of pearlite and cementite as far as possible. Cooling speeds above 400 ° C / s are not technically feasible.
  • Coiler temperatures of 560 - 690 ° C cover the temperature range in which precipitates with an average size of less than 10 nm, in particular less than 5 nm, are formed. At higher
  • the average size of the carbonitrides is more than 10 nm, with which the target properties of the flat steel product according to the invention can no longer be achieved.
  • a targeted formation of small ones Excretions the size of which is less than 7 nm, in particular less than 5 nm, can be caused by reel temperatures of 580-670 ° C., in particular 590-650 ° C. At reel temperatures below 580 ° C, carbonitrides would no longer be excreted and their strength-increasing effect would not be achieved.
  • the atomic ratio Verh2 is of particular importance with regard to the precipitation processes during cooling in the coil.
  • a ratio of 2 - 20 in the precipitates is necessary in order to avoid a coarsening of the steel flat product according to the invention
  • precipitations with an average particle size of more than 5 nm (i.e.> 5 nm) but not more than 10 nm (i.e. ⁇ 10 nm) are to be produced, this can be done, as explained above, on the one hand by adjusting the reel temperature in the upper part of the reel temperature range specified according to the invention be effected, and on the other hand, be supported by the ratio Verh2 being set to 5-15, in particular 5-10.
  • Precipitates that have an average particle size of less than 5 nm present a homogeneous Cr distribution.
  • the edges of the precipitates have significantly higher Cr contents than the core of the precipitates.
  • the "core” is defined as the area of the excretions that makes up approx. 50% of the area of the excretions in microscopy and is closest to the area center. The remaining area of the excretion is defined as the border. With precipitates of more than 10 nm, the Cr content at the edge is significantly higher than in the core area and Cr has no effect in terms of avoiding coarsening of the precipitates.
  • melts A - S alloyed according to the compositions given in Table 1 were produced and cast into slabs.
  • the melts not according to the invention and their contents of certain alloying elements which deviate from the specifications of the invention are highlighted in Table 1 by underlining (steels B, D, E, F, N, O).
  • EWT Heating temperature
  • the tensile strength Rm, the upper yield strength ReH, the lower yield strength ReL and the elongation A50 were determined on the hot-rolled steel strips thus obtained in accordance with DIN EN ISO 6892-1: 2017.
  • the hole expansion l was determined in accordance with ISO 16630: 2017, the product Rm x l was formed and the average particle size of the excretions and the ratio Verh2 were determined.
  • Verh2 The ratio Verh2 of X A us (see Table 1) to Cr A us (in atomic%) in the precipitates is given in Table 2. Verh2 increases with increasing reel temperature and excretion size.
  • Example A is a reference composition which was used to investigate the influence of the reel temperature (see Examples A1 to A7). With this composition, the optimal mechanical-technological properties were achieved at reel temperatures in the range of 590 - 650 ° C.
  • Heating temperature EWT or finish rolling temperature ET leads to the formation of coarse deposits or an anisotropic structure and therefore poor mechanical-technological properties (see examples G13 and H16).
  • Steels I and J are Nb concepts and steels K and L are V concepts, from which steel strips were produced with different reel temperatures (see examples 119 to K28).
  • Examples I to L contain different levels of Si and Al. As with those on steel A
  • the steels M to O have a similar X GE w concentration as the steel A but different combinations of Ti, Nb and V.
  • the steel strip produced in the example M30 based on the steel M (Ti and Nb) has comparable ones
  • the steel P has a very high ratio.
  • the steel Q has a high Al content, but is otherwise relatively low alloyed. In contrast, the steel R is relatively high alloy. Steel strips were produced from steels Q and R under optimal conditions. These tests show that very different strengths can be achieved with high Rm ⁇ values, provided the ratio Verhl is in the target range.
  • the (Ti, Cr) (C, N) excretions are not recognizable at a magnification of 1000 times.
  • Example A1 contained no (Ti, Cr) (C, N) precipitates.

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  • Engineering & Computer Science (AREA)
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  • Heat Treatment Of Steel (AREA)

Abstract

L'invention concerne un produit plat en acier laminé à chaud ayant une résistance à la rupture Rm ≤ 550 MPa, un rapport d'élargissement de trou λ ≤ 30 % et une structure constituée à ≤ 90 % surfacique de ferrite, le reste ≤ 10 % surfacique étant de la perlite ou de la cémentite, ladite structure ayant des précipités de carbonitrure incorporés d'un diamètre moyen ≤ 10 nm. Le produit plat en acier est constitué d'un acier comprenant (en % en poids) 0,02 - 0,3 % de C, ≤ 0,7 % de Si, ≤ 1,0 % d'Al, 0,2 - 2,5 % de Mn, 0,05 - 0,5 % de Cr, ≤ 0,02 % de P, ≤ 0,005 % de S, ≤ 0,01 % de N, ≤ 0,1 % de Cu ainsi qu'au moins un élément, formant des précipités de carbonitrure, des groupes „Ti, Nb, V" et le reste étant constitué de Fe et des impuretés inévitables, sous réserve que : - en présence de V, la somme des teneurs TiGEW et NbGEW est ≤ 0,01 % en poids; - en présence de Ti ou Nb, VGEW est ≤ 0,01 % en poids; - pour XGEW [Gew.-%] = TiGEW+(VGEW/1,06)+(NbGEW/1,94), on a la relation 0,02 % ≤ XGEW ≤ 0,5 %; - pour Verh1 = (XAT+CrAT) / (CAT+NAT), on a la relation 0,5 ≤ Verhl ≤ 2,0, où XAT = TiAT+VAT+NbAT; ΤίΑT, VAT, NbAT, CrAT, CAT et NAT correspondant, respectivement convertie en % atomique, à la teneur en Ti TiGEW, à la teneur en V VGEW, à la teneur en Nb NbGEW, à la teneur en Cr CrGEW, à la teneur en C CGEW età la teneur en N NGEW, et les teneurs TiGEW, VGEW, NbGEW, CrGEW,CGEW et NGEW étant respectivement exprimées en % en poids. L'invention concerne également un procédé de fabrication d'un tel produit laminé plat en acier.
PCT/EP2018/074005 2018-09-06 2018-09-06 Produit plat laminé à chaud en acier et procédé de fabrication Ceased WO2020048599A1 (fr)

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EP18773945.3A EP3847284B1 (fr) 2018-09-06 2018-09-06 Produit plat laminé à chaud en acier et procédé de fabrication
PCT/EP2018/074005 WO2020048599A1 (fr) 2018-09-06 2018-09-06 Produit plat laminé à chaud en acier et procédé de fabrication

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PCT/EP2018/074005 WO2020048599A1 (fr) 2018-09-06 2018-09-06 Produit plat laminé à chaud en acier et procédé de fabrication

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102021105357A1 (de) 2021-03-05 2022-09-08 Thyssenkrupp Steel Europe Ag Kaltgewalztes Stahlflachprodukt und Verfahren zu seiner Herstellung
DE102022121780A1 (de) 2022-08-29 2024-02-29 Thyssenkrupp Steel Europe Ag Verfahren zur Herstellung eines kaltgewalzten Stahlflachprodukts

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH07197124A (ja) * 1993-12-30 1995-08-01 Kobe Steel Ltd 耐孔あき腐食性に優れた高強度強加工用鋼板の製造方法
EP1338665A1 (fr) 2000-10-31 2003-08-27 Nkk Corporation Tole d'acier laminee a chaud presentant une resistance elevee a la traction et procede de fabrication
JP2013133498A (ja) 2011-12-27 2013-07-08 Jfe Steel Corp 耐食性に優れためっき用高強度熱延薄鋼板とその製造方法

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH07197124A (ja) * 1993-12-30 1995-08-01 Kobe Steel Ltd 耐孔あき腐食性に優れた高強度強加工用鋼板の製造方法
EP1338665A1 (fr) 2000-10-31 2003-08-27 Nkk Corporation Tole d'acier laminee a chaud presentant une resistance elevee a la traction et procede de fabrication
JP2013133498A (ja) 2011-12-27 2013-07-08 Jfe Steel Corp 耐食性に優れためっき用高強度熱延薄鋼板とその製造方法

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102021105357A1 (de) 2021-03-05 2022-09-08 Thyssenkrupp Steel Europe Ag Kaltgewalztes Stahlflachprodukt und Verfahren zu seiner Herstellung
WO2022184580A1 (fr) 2021-03-05 2022-09-09 Thyssenkrupp Steel Europe Ag Produit plat en acier laminé à froid et son procédé de production
DE102022121780A1 (de) 2022-08-29 2024-02-29 Thyssenkrupp Steel Europe Ag Verfahren zur Herstellung eines kaltgewalzten Stahlflachprodukts
WO2024046913A1 (fr) 2022-08-29 2024-03-07 Thyssenkrupp Steel Europe Ag Procédé de fabrication d'un produit plat en acier laminé à froid

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EP3847284A1 (fr) 2021-07-14
EP3847284C0 (fr) 2023-08-16

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