CN110662850A - Plate-shaped molded part and method for producing plate-shaped molded part - Google Patents
Plate-shaped molded part and method for producing plate-shaped molded part Download PDFInfo
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- CN110662850A CN110662850A CN201880034322.4A CN201880034322A CN110662850A CN 110662850 A CN110662850 A CN 110662850A CN 201880034322 A CN201880034322 A CN 201880034322A CN 110662850 A CN110662850 A CN 110662850A
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- 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
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
- C21D9/48—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals deep-drawing sheets
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- 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
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D28/00—Shaping by press-cutting; Perforating
- B21D28/24—Perforating, i.e. punching holes
- B21D28/26—Perforating, i.e. punching holes in sheets or flat parts
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- 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
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- 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
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0257—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment with diffusion of elements, e.g. decarburising, nitriding
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- 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
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
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- 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
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
- C21D8/0405—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing of ferrous alloys
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- 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
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
- C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
- C21D8/0426—Hot rolling
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- 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
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- 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
- C21D2211/008—Martensite
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- 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
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- 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
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Sheet Steel (AREA)
- Heat Treatment Of Articles (AREA)
- Shaping Metal By Deep-Drawing, Or The Like (AREA)
Abstract
The invention relates to a sheet-shaped profiled section produced by hot forming and press hardening from a hardenable, one-piece and single-material steel alloy, wherein the sheet-shaped profiled section 1 has a tensile strength of more than 1200MPa, in particular more than 1350MPa, and a bending angle of more than 60 DEG at a wall thickness of 0.5 to 1.5mm or a bending angle of more than 45 DEG at a wall thickness of 1.5 to 2.5mm, characterized in that a plurality of martensite layers are formed in the sheet-shaped profiled section, which martensite layers lie on top of one another, wherein the martensite layers lying on the outside in each case at the sheet-shaped profiled section have a higher toughness than the martensite layers lying therebelow.
Description
The invention relates to a sheet-shaped profiled part produced by thermoforming and press hardening according to the features of the preamble of claim 1.
The invention further relates to a method for producing a sheet-shaped profiled part according to the features of claim 7 and a method for producing a semi-finished metal product according to the features of claim 8.
It is known from the prior art to manufacture plate-shaped profiled parts. For this purpose, the sheet metal is formed into a three-dimensionally shaped part by means of customary forming methods (for example deep drawing). Such sheet-shaped molded parts are used primarily in the motor vehicle industry and are used therein as motor vehicle parts. In the sense of the present invention, therefore, a plate-shaped profiled part is understood to be a motor vehicle part.
In motor vehicles, a particular difference is the motor vehicle structural parts, from which in particular self-supporting motor vehicle bodies are produced. These include the known motor vehicle pillars, i.e. a-pillars or B-pillars, longitudinal beams, transverse beams, roof rails, rocker panels or the like. It is also possible to manufacture exterior body skin parts of motor vehicles, such as the engine hood, the roof skin or also the door skin. It is likewise possible to produce add-on or crash-proof components, such as crash boxes, bumper beams, etc.
However, the motor vehicle industry requires that lightweight construction of the components and improved rigidity or crash resistance are thus achieved. Thermoforming and press hardening techniques have been developed for this purpose. A sheet (Platine) or a preform blank made of a hardenable steel alloy can thereby be heated to a temperature above the austenitizing temperature (AC 3). The sheet is shaped in this heated state. This aspect provides the following advantages: the possible degree of deformation to be produced of the sheet is increased by heating above the austenitizing temperature. The still warm sheet-shaped formed part is rapidly cooled during and/or after forming, so that an austenite-to-martensite structure transformation takes place and a high strength is set thereby.
The parts which are hot-formed and press-hardened have high strength. However, the high strength may cause brittleness or reduced toughness of the thus-produced plate-shaped molded member.
However, this is undesirable in most cases, since it can lead to brittle fracture and, in the event of a crash, to tearing of the sheet-like profiled element at the connecting point.
Conventional furnace heaters are generally used, for example having a heating section of 30 to 40m length. Correspondingly, heating times in relation to this are required to exceed the austenitizing temperature.
Sheet-shaped formed parts, for example made of steel of the 22MnB5 type by hot forming and press hardening, have good properties with respect to strength and at the same time toughness.
However, contactor heating has been known in recent years just in the heating field required for hot forming and hot forming to exceed the austenitizing temperature. It is possible here to heat the sheet at a much faster rate with a low space requirement in the production plant and at the same time with a high heating rate of more than 30K/s, in particular more than 50K/s, for the thermoforming and subsequent press hardening. However, it has been found that, when using the known hardenable steel alloys, although high strength is achieved on the finished product, the product has a reduced toughness (and thus a reduced bending angle) due to the shorter heating time. It is precisely the parts associated with the impact that cannot or cannot be produced in a process-safe manner with rapid heating.
It is therefore an object of the present invention, starting from the prior art, to provide a component and a method for producing the component, which overcome the above-mentioned disadvantages.
According to the invention, the previously stated object is achieved by a sheet-shaped profiled part which is produced by thermoforming and press hardening having the features of claim 1.
The method of this object is achieved, in part, by a method of manufacturing a plate-shaped profiled part according to the features of claim 7.
A further method technique of this object is achieved in part by a method of manufacturing a metal semi-finished product according to the features of claim 8.
Advantageous embodiment variants of the invention are the subject matter of the dependent claims.
The plate-like formed member of the present invention is manufactured by thermoforming and press hardening. The plate-shaped profiled part is produced from a hardenable, one-piece and single-material steel alloy. The platen material is not involved, but is a material that is integrated in cross section and is formed unitarily. The sheet-shaped profiled part here has a tensile strength Rm of more than 1200MPa, in particular more than 1350 MPa. The sheet-shaped profiled part furthermore has a bending angle of more than 60 ° at a wall thickness of 0.5 to 1.5 mm. At larger wall thicknesses of 1.5 to 2.5mm, the plate-shaped profiled section has a bending angle of more than 45 °. The tensile strength should not exceed 2500 MPa.
The bending angle was determined in a platelet bending experiment according to VDA 238-100:2010 at an elongation limit Rp0.2 of more than 900 MPa.
According to the invention, the sheet-shaped profiled part is now distinguished in that, starting from both surfaces, a layered martensitic sub-layer or layer is formed. Therefore, adjacent martensite layers having different properties are formed in the plate thickness or wall thickness from the upper and lower sides of the three-dimensionally formed plate-like formed member. To alternating tough and hard martensitic layers. The tough martensitic layer is always on the surface or outside.
According to the present invention, the plate-like formed member is manufactured from a hot rolled product (hereinafter also referred to as a semi-finished product). The hot rolled product is one piece and is made of a single material. However, after the rolling process is completed, there are different layers in the material structure. These layers may also be referred to as sublayers or rows (Zeilen). These layers are formed in particular planar and preferably extend over the entire surface of the provided semifinished product, but at least over the entire strip width. The semifinished product is preferably provided in the form of a sheet.
According to the invention, in the semifinished product, the outer layers respectively form a ferrite layer. The ferrite layer further preferably has a thickness of 4 to 140 μm. Thus, ferrite layers located outside are formed on the upper and lower sides of the semi-finished product. A pearlite layer is formed below this ferrite layer, preferably having a thickness of 4 to 25 μm. Additional ferrite and pearlite layers are then alternately bonded across the thickness of the ribbon or the thickness of the wall, respectively. These layers always extend over the entire width of the strip.
After rapid heating, hot forming and subsequent cooling during press hardening, an outer low-carbon martensite layer and an underlying carbon-rich martensite layer can be produced from the semifinished product thus laminated, since diffusion equilibrium cannot occur between the ferrite layer and the pearlite layer by rapid heating. The outer ferrite layer is thus transformed into a martensitic layer with less strength but at the same time with high toughness. The underlying pearlite layer transforms into a martensitic layer with comparatively higher strength but reduced toughness.
Preferably at least three, in particular at least five and particularly preferably at least seven martensite layers are formed in the wall thickness.
Preferably the delta or difference in strength between the layer of martensite having higher strength but reduced toughness and the layer of martensite having lower strength but higher toughness is between 100 and 300 MPa. This means that the martensitic layer with the higher strength is at least 100 to 300MPa stronger than the martensitic layer with the greater toughness but lower strength. However, the Δ between separate martensite layers having different strengths should not exceed about 1000 MPa.
It can further be provided that the outermost layer is formed as an edge-decarburized layer by an additional targeted edge decarburization of the semifinished product, which has a very low carbon content.
In this edge-decarburized layer, the very low-carbon ferritic material structure present is not or only to a small extent transformed into martensite during press hardening, so that this edge-decarburized layer has a significantly lower strength. The edge decarburized layer has a substantially ferritic material structure. The strength difference may be up to 1000MPa compared to a martensitic layer with higher strength and reduced toughness.
These layers of different strength and different toughness extend alternately one after the other over the thickness of the strip. However, the plate-shaped molded component, which is thermoformed and press-hardened as a whole, has high toughness while having high strength, so that the above-described bending angle can be achieved even when the semi-finished product is rapidly heated.
Simultaneously or additionally, edge decarburization may be performed. In the produced sheet-shaped profiled part, the toughness in the edge region is thereby increased again, preferably with a constant strength. The edge decarburization is preferably carried out after the hot rolling of the strip.
The outer layers (i.e. the outer martensitic layers) at the sheet-shaped profiled section in particular each have a layer thickness of 4 to 140 μm, preferably 10 to 140 μm, in particular 14 to 140 μm.
If the sheet-shaped profiled part has an optional edge decarburization, this edge decarburization extends from outside the surface into the sheet-shaped profiled part and is therefore contained in the abovementioned layer thickness of the outer layer, respectively, or the edge-decarburized layer can for example also form the outer layer. For example, the edge decarburization can extend from the surface into the sheet-shaped part, in particular into the outer martensitic layer, in a layer of 10 to 140 μm, preferably 20 to 100 μm.
For the production of the sheet-shaped profiled part according to the invention, a hardenable steel alloy can be used, for example 22MnB5 or also MBW1900 or MBW 1500. This is manganese boron steel. The manganese boron steel preferably has the following variants. It has proven advantageous for the production of semifinished products of hardenable manganese-boron steels to have a manganese (Mn) content of 0.5 to 1.7% and a boron (B) content of 0.0008 to 0.005%, in wt.%. The manganese content delays the incubation period for bainite and ferrite formation. Ferrite and pearlite formation is retarded by the boron content. By means of this combination of the alloying elements, isolated ferrite-pearlite transformation zones starting from the surface can be produced, so that the structure/structure layer in the semifinished product can be formed specifically by the cooling treatment connected downstream of the rolling. The targeted cooling in the cooling section after the last rolling stand makes it possible to achieve a stratified structure of ferrite and pearlite starting from the surface in the strip thickness. By rapid heating, thermoforming and press hardening connected downstream, the layered structure is transformed into corresponding martensitic layers with strength properties different from each other. In particular in the ferrite and pearlite layers, a fine martensitic structure with locally different carbon contents is produced.
As sheet-shaped molded parts, in particular motor vehicle parts are produced, whereby further preferred are vehicle body parts, very particularly preferred are vehicle body structural parts which meet in particular crash-related requirements.
Rapid heating from room temperature to a temperature above AC3 temperature at a heating rate of more than 30K/s, in particular more than 50K/s, in less than 1 minute, preferably less than 30s, very particularly preferably less than 20s, is preferably carried out within the scope of the invention by heating with a contactor. For this purpose, the contact plate is applied to the semi-finished product (i.e. to the sheet) on one or both sides. The contact plate has a higher temperature, which is output to the semifinished product to be heated due to heat conduction. Induction heating, heating by means of burner flame or infrared are also possible.
The use of contactor heating technology makes it possible to likewise deliberately control the temperature in only a local region. In this way, only partial planar regions of the semifinished product can be heated to above the austenitizing temperature, which then also achieves partial hardening only in these planar regions in the subsequent hot forming and press hardening. Tempering and hardening take place in these partially planar regions over the entire wall thickness. In the case of hardening, different martensitic sub-layers are produced.
It is also possible to manufacture semi-finished products in which the planar regions have different wall thicknesses from one another.
The invention further relates to a method for producing a sheet-shaped molded part, comprising the following method steps:
-hot rolling the hardenable steel alloy,
-producing a ferrite-pearlite layer structure with a ferrite layer of the hot rolled product at the surface over the whole strip width,
-cutting into a sheet,
rapid heating of the sheet from ambient temperature to above the austenitizing temperature at a heating rate of more than 30K/s, preferably more than 50K/s, in particular more than 60K/s, particularly preferably more than 80K/s, in a time of less than 60s,
-hot forming and press hardening the sheet-like formed part.
In the above method, in particular, a hot rolled product is used as the metal semi-finished product, which is manufactured by the following method:
-hot rolling the hardenable steel alloy,
-producing a ferrite-pearlite layer structure with a ferrite layer of the hot rolled product at the surface over the whole strip width,
-breaking into sheets.
The hot rolling can be carried out in particular with the following process parameters:
-providing a slab and heating to a core temperature of more than 1200 ℃ for a time of more than 60s,
rolling to a prefabricated strip thickness of between 45 and 55mm,
medium rolling to a strip thickness of 13 to 25mm,
-the rolling temperature of the rolled steel strip is between 860 and 920 ℃,
the rolling speed is 3-12m/s,
cooling at 15 to 30K/s after the last rolling stand, preferably over a section of 65 to 80m,
-a winding temperature of 650 to 800 ℃ is reached,
-rolling the manufactured steel strip.
The steel sheet strip thus hot-rolled and cooled has a ferritic and pearlitic structure according to the invention, in particular in the outer layer, which provides improved toughness of the produced sheet-shaped component in the downstream hot-forming and press-hardening process (compared to conventionally hot-formed and press-hardened steel with rapid heating in the past).
It is also possible to coat the steel strip, for example, with an AlSi coating or a zinc coating.
Other advantages, features, properties and aspects of the invention are the subject of the following description. Preferred design variants are depicted in the schematic drawings. These design variations serve to make the invention easier to understand. In the drawings:
figure 1 shows a manufacturing sequence in which a semifinished product according to the invention is first manufactured and further processed into a plate-shaped profiled part manufactured according to the invention,
FIG. 2 shows a partial cross-sectional view through a semi-finished product of the invention, an
Figures 3a to c each show a partial cross-sectional view through a plate-like profiled part produced according to the invention,
FIG. 4 shows a plate-shaped profiled part produced according to the invention with faces which differ locally in strength from one another, an
Fig. 5 shows a partial cross-sectional view through a plate-like profiled part according to the invention with wall thicknesses differing from one another.
In the drawings, the same reference numerals are used for the same or similar components even if duplicate explanations are omitted for the sake of simplicity.
Fig. 1 illustrates the manufacturing method of the present invention. The slab 2 is first manufactured from a hardenable steel alloy, heated in a furnace 14 and then guided through the rolling section 3. The furnace 14 has a temperature T greater than 1200 deg.C1. After the pressing of the last rolling stand 4, the steel strip 5 thus rolled has a rolling temperature. Then introduce itLeading through the cooling section 6. At the end of the cooling section 6, the cooled steel strip 7 has a coiling temperature in order to be subsequently coiled on a coiling device 8. Thereby providing a hot rolled product in the form of a coil of steel. The strip width B extends in the plane of the figure.
However, according to a next method step, the hot-rolled product can also be a correspondingly sectioned sheet 9. In an unwinding process, not shown, the steel plate strip 7 is fed to a cutting apparatus 10. The individual sheets 9 are then subjected to rapid heating in accordance with the invention in a tempering station 11 and heated to above the austenitizing temperature. For this purpose, a contact plate 12 is arranged in the tempering station 11, which contact plate makes contact with the sheet 9 to be heated.
The heated sheet 9 is transferred into a thermoforming and press hardening mould 13 and thermoformed and press hardened there. After the press hardening process is finished, the plate-like shaped component 1 manufactured according to the invention is obtained.
In fig. 2 a partial cross section of the semi-finished or divided sheet 9 is shown before heating, i.e. before austenitization. The sheet 9 has a total wall thickness (hereinafter wall thickness W) of preferably 0.5 to 2.5 mm. From the respectively outer surfaces 15, 16, a plurality of ferrite layers and pearlite layers are arranged alternately one above the other in the wall thickness W. The ferrite layer and the pearlite layer are arranged directly adjacent to each other here. Through the wall thickness W, the web 9 or the semifinished product is formed in one piece and material-individually.
The ferrite layers 17 which are respectively located on the outside preferably have a thickness D17 of 4 μm to 140 μm. The outer ferrite layer 17 then also forms the surfaces 15, 16 of the sheet 9, respectively. Proceeding from the surface 15 or 16, a respective pearlite layer 18 is arranged below the ferrite layer 17. The pearlite layer 18 preferably has a thickness D18 of 4 to 25 μm. Then alternately follows further ferrite layers 19 and consequently the corresponding pearlite layers 20. These layers may also have a thickness of 4 μm to 25 μm, respectively.
Shown here are thirteen layers formed over the wall thickness W. According to the invention, at least three ferrite and pearlite layers, preferably more than five ferrite and pearlite layers, in particular more than seven ferrite and pearlite layers, are formed over the wall thickness W. The individual layers are not shown to scale relative to each other in their respective wall thickness ratios.
Fig. 3a shows a detail from fig. 2 of an already produced sheet-shaped profiled part 1, i.e. having been heated, thermoformed and press-hardened. In addition, a separate layer is formed over the wall thickness W. However, the structure has transformed into martensite. The previous ferrite layer has been transformed into a martensitic layer 21 having a lower strength and a higher toughness than the martensitic layer 22 described later. The lower pearlite layer 18 and also the more internal pearlite layer 20 proceeding from the surfaces 15, 16 have already been transformed into a martensite layer 22 with higher strength and lower toughness. Further inside are then layers 21 of martensite with lower strength and higher toughness and layers 22 of martensite with higher strength and lower toughness, respectively, arranged alternately one after the other.
Fig. 3b shows a detail similar to fig. 3a, wherein the layers 26, which are formed in each case by edge decarburization, are present in each case on the outside. The layers have a substantially ferritic material structure, or the layer 26 can also consist entirely of ferrite. The edge decarburized layer 26 then transitions to the outer martensitic layer 21 which has low strength but higher toughness. Optionally, the edge decarburized layer 26 may also form the entire outer layer. Directly followed by a martensitic layer 22 of higher strength. This is shown in fig. 3 c.
Fig. 4 shows a plate-shaped profiled part 1 produced according to the invention as a motor vehicle part and here in particular as a motor vehicle pillar. Such a plate-shaped profile part 1 has, for example, a foot region 23 at the bottom, a top connecting region 24 at the top and a middle section 25 between them. The intermediate section 25 may have a smaller wall thickness W25 than, for example, the leg regions 23.
In fig. 5 a partial longitudinal section is shown according to section line a-a. It can be discerned that the wall thickness W23 in the foot region 23 is less than the wall thickness W25 in the middle section 25. A separate martensitic layer is also formed in the region with the smaller wall thickness. The individual layers are produced, for example, by soft cold rolling of the sheet 9 or the cooled steel strip 7. Thus, the ferrite and pearlite layers are upset and have a smaller thickness, but the same amount throughout the entire wall thickness W. After austenitization, hot forming and press hardening are completed, separate martensite layers of the same number but of smaller thickness are also formed within a smaller wall thickness.
List of reference numerals:
1-plate-shaped formed part
2-thick plate
3-rolling section
4-Rolling Mill Stand
5-Steel plate strip
6-Cooling stage
7-cooled steel strip
8-winding apparatus
9-sheet
10-breaking apparatus
11-temperature regulating station
12-contact plate
13-thermoforming and press hardening mould
14-furnace
15-surface of
16-surface
17-ferrite layer located on the outside
18-pearlite layer
19-ferrite layer
20-pearlite layer
21-Martensitic layer with lower strength, higher toughness
22-Martensitic layer with higher strength, less toughness
23-lower foot region
24-Top connection area located at the top
25-middle section
26-edge decarburized layer
W-wall thickness
Wall thickness of W23-to 23
Wall thickness of W25-to 25
Thickness of D17-to 17
Thickness of D18-to 18
Width of the B-belt
Claims (10)
1. Sheet-shaped profiled part (1) produced by hot forming and press hardening from a hardenable one-piece and material-specific steel alloy, wherein the sheet-shaped profiled part (1) has a tensile strength of more than 1200MPa, in particular more than 1350MPa, and a bending angle of more than 60 ° at a wall thickness (w) of 0.5 to 1.5mm or a bending angle of more than 45 ° at a wall thickness (w) of 1.5 to 2.5mm, characterized in that a plurality of martensite layers (21, 22) are formed in the sheet-shaped profiled part (1) overlapping one another, wherein the martensite layer (21) lying respectively on the outside at the sheet-shaped profiled part (1) has a higher toughness than the martensite layer (22) lying thereunder.
2. Plate-shaped profiled element (1) according to claim 1, characterized in that starting from two mutually opposite surfaces (15, 16), at least three, preferably at least five, preferably at least seven martensite layers (21, 22) are formed over the wall thickness (w), and/or the outer martensite layer (21) respectively has a thickness of 4 μm to 140 μm.
3. Plate-shaped profiled part (1) according to one of the preceding claims, characterized in that both surfaces (15, 16) have an edge decarburization and/or are arranged on the outside with an edge decarburized layer (26) having a substantially ferritic material structure.
4. Plate-shaped profiled element (1) according to one of claims 1 to 3, characterised in that the martensitic layers (21, 22) are produced from a semifinished product having a ferrite layer (17) respectively on the outside and a pearlite layer (18) underneath and preferably having further ferrite layers (19) and pearlite layers (20) alternately underneath.
5. Plate-shaped profiled element (1) according to one of claims 1 to 4, characterized in that the hardenable steel alloy is a manganese boron steel with a manganese content of 0.5 to 1.7 wt. -% and a boron content of 0.0008 to 0.005 wt. -%.
6. Plate-shaped profiled element (1) according to one of claims 1 to 5, characterized in that the plate-shaped profiled element (1) has different strength from each other and/or different wall thickness (W23, W25) from each other per surface area.
7. Method for manufacturing a plate-shaped profiled part (1) according to claim 1, characterized by the following method steps:
-hot rolling the hardenable steel alloy,
-producing a ferrite-pearlite layer structure with a ferrite layer (17) of the hot rolled product at the surface (15, 16) over the entire strip width (B),
-cutting into sheets (9),
-rapidly heating the sheet (9) from ambient temperature to above the austenitizing temperature at a heating rate of more than 30K/s, preferably more than 50K/s,
-hot forming and press hardening the sheet-like formed part (1).
8. Method for producing a semi-finished metal product from a hardenable steel alloy, in particular for further processing into a sheet-shaped profiled part (1) according to claim 1, characterized by the following method steps:
-hot rolling the hardenable steel alloy,
-producing an outer ferrite layer (17) and an underlying pearlite layer (18) at both surfaces (15, 16) of the hot rolled product over the entire strip width (B),
-cutting into sheets (9).
9. Method according to claim 7 or 8, characterized in that the hot rolling is carried out with the following parameters:
-providing a slab (2) and heating to a core temperature of more than 1200 ℃ for a time of more than 60s,
rolling to a prefabricated strip thickness of between 45 and 55mm,
medium rolling to a strip thickness of 13 to 25mm,
-the rolling temperature of the rolled steel strip (5) is between 860 and 920 ℃,
the rolling speed is 3-12m/s,
-cooling at 15 to 30K/s after the last rolling stand (4), preferably over a section of 65 to 80m,
-a winding temperature of 650 to 800 ℃ is reached.
10. Method according to claim 7, characterized in that the rapid heating is carried out by contactor heating, in particular at a heating rate of more than 50K/s, preferably more than 80K/s.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE102017112164.1 | 2017-06-01 | ||
| DE102017112164.1A DE102017112164A1 (en) | 2017-06-01 | 2017-06-01 | Sheet metal forming component and method for producing the Blechumformbauteils |
| PCT/DE2018/100530 WO2018219412A1 (en) | 2017-06-01 | 2018-06-01 | Formed sheet-metal component and method for producing the formed sheet-metal component |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN110662850A true CN110662850A (en) | 2020-01-07 |
Family
ID=62791467
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201880034322.4A Pending CN110662850A (en) | 2017-06-01 | 2018-06-01 | Plate-shaped molded part and method for producing plate-shaped molded part |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US20210156000A1 (en) |
| EP (1) | EP3612652A1 (en) |
| CN (1) | CN110662850A (en) |
| DE (1) | DE102017112164A1 (en) |
| WO (1) | WO2018219412A1 (en) |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DD135917A1 (en) * | 1978-04-26 | 1979-06-06 | Wolfgang Schmitt | METHOD FOR PRODUCING ROLLING MOLECULAR PRODUCTS WITH MULTILAYER FUEL ASSEMBLY |
| JP2001140041A (en) * | 1999-11-15 | 2001-05-22 | Sumitomo Metal Ind Ltd | Chromium stainless steel with double layer structure for spring and producing method therefor |
| CN101505906A (en) * | 2006-07-27 | 2009-08-12 | 国立大学法人东京大学 | Multilayer steel and method for producing multilayer steel |
| CN103827325A (en) * | 2011-09-16 | 2014-05-28 | 本特勒尔汽车技术有限公司 | Method for producing structural components and chassis components by hot forming, and heating station |
| CN104769138A (en) * | 2012-09-06 | 2015-07-08 | 安赛乐米塔尔研发有限公司 | Method for the production of press-hardened, coated steel parts and pre-coated steel sheets that can be used for the production of said parts |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015088523A1 (en) * | 2013-12-11 | 2015-06-18 | ArcelorMittal Investigación y Desarrollo, S.L. | Cold rolled and annealed steel sheet |
| US10273555B2 (en) * | 2013-12-27 | 2019-04-30 | Nippon Steel & Sumitomo Metal Corporation | Hot-pressed steel sheet member |
-
2017
- 2017-06-01 DE DE102017112164.1A patent/DE102017112164A1/en not_active Withdrawn
-
2018
- 2018-06-01 EP EP18735493.1A patent/EP3612652A1/en not_active Withdrawn
- 2018-06-01 US US16/618,293 patent/US20210156000A1/en not_active Abandoned
- 2018-06-01 CN CN201880034322.4A patent/CN110662850A/en active Pending
- 2018-06-01 WO PCT/DE2018/100530 patent/WO2018219412A1/en unknown
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DD135917A1 (en) * | 1978-04-26 | 1979-06-06 | Wolfgang Schmitt | METHOD FOR PRODUCING ROLLING MOLECULAR PRODUCTS WITH MULTILAYER FUEL ASSEMBLY |
| JP2001140041A (en) * | 1999-11-15 | 2001-05-22 | Sumitomo Metal Ind Ltd | Chromium stainless steel with double layer structure for spring and producing method therefor |
| CN101505906A (en) * | 2006-07-27 | 2009-08-12 | 国立大学法人东京大学 | Multilayer steel and method for producing multilayer steel |
| CN103827325A (en) * | 2011-09-16 | 2014-05-28 | 本特勒尔汽车技术有限公司 | Method for producing structural components and chassis components by hot forming, and heating station |
| CN104769138A (en) * | 2012-09-06 | 2015-07-08 | 安赛乐米塔尔研发有限公司 | Method for the production of press-hardened, coated steel parts and pre-coated steel sheets that can be used for the production of said parts |
Also Published As
| Publication number | Publication date |
|---|---|
| DE102017112164A1 (en) | 2018-12-06 |
| WO2018219412A1 (en) | 2018-12-06 |
| US20210156000A1 (en) | 2021-05-27 |
| EP3612652A1 (en) | 2020-02-26 |
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