EP3245307A1 - Method and system for selective heat treatment of a sheet metal - Google Patents

Method and system for selective heat treatment of a sheet metal

Info

Publication number
EP3245307A1
EP3245307A1 EP16700815.0A EP16700815A EP3245307A1 EP 3245307 A1 EP3245307 A1 EP 3245307A1 EP 16700815 A EP16700815 A EP 16700815A EP 3245307 A1 EP3245307 A1 EP 3245307A1
Authority
EP
European Patent Office
Prior art keywords
grid pattern
sheet metal
metal material
heated
forming
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.)
Withdrawn
Application number
EP16700815.0A
Other languages
German (de)
French (fr)
Inventor
Christer Svensson
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.)
Hardmesch AB
Original Assignee
Hardmesch AB
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 Hardmesch AB filed Critical Hardmesch AB
Publication of EP3245307A1 publication Critical patent/EP3245307A1/en
Withdrawn legal-status Critical Current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
    • C21D1/62—Quenching devices
    • C21D1/673—Quenching devices for die quenching
    • 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
    • C21D1/34—Methods of heating
    • 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
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • 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
    • C21D8/0294—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a localised treatment
    • 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
    • C21D1/34—Methods of heating
    • C21D1/38—Heating by cathodic discharges
    • 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
    • C21D1/34—Methods of heating
    • C21D1/42—Induction heating
    • 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
    • C21D11/00—Process control or regulation for heat treatments
    • 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
    • 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
    • C21D2221/00—Treating localised areas of an article
    • 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
    • C21D2261/00—Machining or cutting being involved
    • 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
    • C21D8/0494—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 involving a localised treatment
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Definitions

  • the present invention relates to a method for improving the formability and/or component properties of a sheet metal material by selective heat treatment.
  • Press hardening processes allow for the production of light weight, high strength sheet metal components. Press hardened materials are highly deformation resistant.
  • Press hardening techniques have played an increasingly important role with the vehicle industry during recent years, as the press hardened materials are suitable for absorbing great deformation energies such as in a vehicle collision.
  • the sheet metal used in press hardening techniques are boron steel with a ferrous or pearlitic base structure being characterized by a tensile strength of 600MPa and extension degree of about 26% for uncoated sheets and about 10% for sheets coated with AISi (Aluminum Silicon).
  • the sheet metal In current press hardening processes the sheet metal is transported through a furnace and thus heated up to its austenization temperature of about 900 to 950 °C whereby it is transformed into 100% austenite. In the austenitic state the material has a tensile strength of about 200MPa and an extension degree of about 40%. After the heat treatment the austenite material is rapidly moved into a processing tool for shaping the material before it starts to oxidize. Usually the duration of the shaping stage is about 8 to 10 seconds. During the shaping the shaped material is subject to cooling during which the austenite is transformed to marteniste. In other words a phase transformation occurs during the cooling. When the shaped material leaves the shaping tool, its temperature is about 150 to 200 °C. Normally the shaping tools are provided with a cooling system to cool the shaped material down to the desired temperature.
  • Press hardening parts therefore currently represent one of the most advanced lightweight solutions for the car body structure.
  • a drawback of current press hardening techniques is that it is a relatively slow process. Moreover, the final product has far higher/larger tensile strength than the original sheet material which may not always be desired due to desired deformability characteristics of the sheet metal in us.
  • An object of the present invention is to eliminate or alleviate at least one of the drawbacks mentioned above, in accordance with the appended claims.
  • An advantage of the present invention is that the thickness of the sheet metal material may be reduced while providing reinforcement at desired locations of the sheet metal material.
  • a further advantage is that the formability of the sheet metal material is improved.
  • the deformation capability of the resulting component may be tailor made.
  • a method for providing a sheet metal material with a certain component property comprises providing a sheet metal material in a non- formed state, said sheet metal material comprising boron steel.
  • the method comprises conducting a selective heat treatment on the sheet metal material when in its non- formed state.
  • the selective heat treatment comprises selectively heating the sheet metal material according to a grid pattern designed based on the certain component property, thereby forming a heated grid pattern in the sheet metal material, said heated grid pattern having a first material characteristic being different than that of the non-heated areas of the sheet metal material, wherein the first material characteristic relates to the boron steel of the selectively heated sheet metal material forming into a grid pattern of austenite.
  • the method further comprises cooling the locally heated grid pattern, thereby forming a locally cooled grid pattern having a second material characteristic being different from the first material characteristic and the material characteristic of the non-heated areas, and wherein second material characteristic relates to the austenite grid pattern forming into a martensite grid pattern.
  • a component comprising a reinforced sheet metal material being produced by the method is provided.
  • a system for providing a sheet metal material comprising boron steel with a certain component property comprising boron steel with a certain component property.
  • the sheet metal material is provided in a non-press formed state.
  • the system comprises a heating unit selectively heating the sheet metal material, when in its non-press formed state, according to a grid pattern designed based on the certain component property, thereby producing a heated grid pattern in the sheet metal material, said heated grid pattern having a first material characteristic being different than that of the non-heated areas of the sheet metal material wherein the first material characteristic relates to the boron steel of the selectively heated sheet metal material forming into a grid pattern of austenite.
  • Fig. 1 is a flow chart of a method according to an embodiment
  • Fig. 2 is a flow chart of a method according to an embodiment
  • Fig. 3 shows a system for reinforcing a sheet metal material according to an embodiment
  • Fig. 4 shows a system for reinforcing a sheet metal material according to an embodiment
  • Figs 5 to 8 illustrate exemplary grid patterns according to an embodiment, respectively
  • Figs 9a to 9c illustrate exemplary grid patterns applied to a sheet metal material according to an embodiment, respectively;
  • Fig. 10 illustrates a press forming tool according to an embodiment
  • Figs 1 la to l id illustrates a component being provided with a grid pattern according to an embodiment.
  • An idea of the present invention is to conduct selective heat treatment to the sheet metal material based on required sheet material formability/trimability or required component properties.
  • the selective heat treatment includes heating the sheet metal material according to a specific heat pattern, e.g. grid pattern, followed by cooling of the grid pattern thereby forming a grid pattern of local reinforcements in the sheet metal material.
  • a specific heat pattern e.g. grid pattern
  • the sheet metal material is made of boron steel
  • the boron steel at the position of the grid i.e. along the grid lines of the grid pattern, converts into austenite while heating, and during the cooling the austenite converts into martensite along the grid lines of the grid pattern, and the martensite then acts as the reinforcing structure of the processed sheet metal material.
  • the sheet metal material may be considered being a ready-use-component.
  • press forming and/or cutting is required before the selective heat treated sheet metal material is considered being a ready -to -use component or product.
  • the grid pattern may be said to form a skeleton structure in the sheet metal material.
  • the grid structure may improve or facilitate subsequent forming of the sheet metal material.
  • the grid pattern provided sheet metal may be designed to allow for tailor made deformation capabilities of the resulting sheet metal component.
  • the grid pattern, its shape and position in view of the sheet metal material is designed and carried out based on the identified needs/requirements concerning forming, trimming or/and component performance/properties. Hence, the design of the grid pattern may be derived by reverse engineering.
  • the grid pattern is applied either before or after sheet material shaping process depending on economic feasibility.
  • a method 10 for improving the formability or the reinforcement of a sheet metal material arranged to absorb deformation energies in use comprises supplying a sheet metal material optionally comprising boron steel. Moreover, the method comprises conducting 12 a selective heat treatment on the sheet metal material when in its non-press formed state.
  • the selective heat treatment comprises selectively heating 121 the sheet metal material according to a grid pattern designed based on desired or required component properties, thereby forming a heated grid pattern in the sheet metal material.
  • the sheet metal material comprises boron steel the sheet metal material along the lines of the grid pattern will convert into austenite during the heating process.
  • the selective heat treatment comprises cooling (either passive or active) 122 the selectively heated sheet metal material, whereby the austenite along the lines of the grid pattern is converted into martensite.
  • An advantage of conducting the selective heat treatment onto the sheet metal material, when in its non-press formed state, i.e. when it is still flat or essentially flat, is that the heat treatment process and equipment assembly is less complex. Moreover, by providing ready-to-form/trim/cut heat treated metal sheets, the bulkiness during shipping of the treated metal sheets may be kept to a minimum as the heat treated metal sheets can be stacked very efficiently. This leads to reduced environmental impact. Furthermore, the ready -to-form/trim/cut heat treated metal sheets may be used in the same assembly processing lines as conventionally used for press forming, trimming and cutting. Hence, the heat treated metal sheets of the present invention may be used for subsequent processing in existing equipment used e.g. in the vehicle industry for the processing of vehicle components such as car components.
  • the method may comprise press forming 13 the sheet metal material being provided with the martensite grid pattern in a press forming tool into a single component having a desired shape.
  • the press forming step may be executed immediately after the selective heat treatment, such that parts of the sheet metal material, in particular the martensite grid pattern, has a higher temperature than the ambient temperature.
  • the sheet of metal material is first press formed and/or trimmed in press forming tools, e.g. dies, at room temperature.
  • press forming tools e.g. dies
  • reinforcement is provided by conducting selective heat treatment, according to a grid pattern designed in accordance with desired component properties, of the sheet metal material.
  • a method 20 for reinforcing a sheet metal material comprises supplying 21 a sheet metal material, e.g. comprising grid boron steel. Moreover, the method comprises press forming 22 the sheet metal material in a press forming tool into a desired shape. Furthermore, the method 20 comprises conducting 23 a selective heat treatment on the sheet metal material.
  • the selective heat treatment comprises selectively heating 231 the shaped sheet metal material according to a grid pattern designed based on desired or required component properties, thereby converting the boron steel into austenite along the lines of the grid pattern of the shaped sheet metal material. Moreover, the selective heat treatment comprises cooling 232 the selectively heat treated sheet metal material, whereby the austenite along the lines of the grid pattern is converted into martensite.
  • the selective heat treatment changes the material characteristics of the sheet metal material at the position of the grid pattern, e.g. going from boron steel to austenite during heating and then to martensite during cooling.
  • the grid pattern may be designed based on desired or required formability and/or component properties of the end product comprising the grid pattern provided sheet metal material.
  • information relating to the grid pattern may be derived from component performance or property analysis. Accordingly, a specific grid pattern may be designed based on input data comprising information of the required behavior of the resulting ready-to-use component and its intended location and use. It should be appreciated that in some situations only some portions of the sheet metal material may require selective heat treatment.
  • the component performance or property analysis may identify those areas in which selective heat treatment is required to meet the required performance or properties of the ready-to-use component comprising the grid pattern applied sheet metal material.
  • the input data may relate to certain deformability properties of the component, the location of the component in the vehicle in use, the design of the ready -to use component (shape, holes, fittings, supports, etc), as well as information relating to details of the sheet metal material (alignment, width, thickness, material composition) and the press forming process (details regarding the dimensions and geometrical shapes created by the press forming tool, etc).
  • the martenisite grid pattern By knowing the position in which the vehicle component is to be positioned in the vehicle in use, it is possible to create a martenisite grid pattern on at least part of the sheet metal material of the component, which will deform in a desirable manner in the event of collision with a foreign object in use. It should be noted that the parts of the sheet metal material not constituting the martensite grid pattern will deform more easily than the martensite grid pattern. Hence, the martensite grid pattern will in effect form a skeleton structure or a number of deformation zones being designed to have improved deformability in certain contemplated deformation directions.
  • the resulting deformation zones allow for a predefined and controlled deformation of the component upon impact with a foreign object.
  • the design of the grid pattern may therefore be created based on a desired deformation direction in the event of the component being subjected to a deformation force in use.
  • a reinforced component for use in a vehicle Such a component may be arranged in the engine compartment at the front end of the vehicle, and essentially extending in a lateral direction in view of the longitudinal axis of the vehicle and at an outer boundary of the vehicle, e.g. close to the grill of the vehicle.
  • a frontal collision it is important to protect the occupants in the vehicle.
  • it may be desired to as far as possible preventing damage to vital engine components in the vehicle engine compartment.
  • a grid pattern designed according to the intended placement of the grid pattern provided component in the vehicle in use is selectively heated in the sheet metal material of the component, whereby it is possible to allow deformation of the component at a higher extent in certain more preferred directions to avoid injuries to the occupants of the vehicle and at the same time minimize the damage to the vehicle vital components.
  • Figs 3 to 4 show non-limiting examples of a grid pattern P being selectively heat treated into a sheet metal material, thereby forming a martensite grid pattern.
  • the remaining parts of the sheet metal material are denoted with reference numeral C.
  • the martensite grid pattern in conjunction with non-heat treated parts C of the sheet metal material together form a number of well defined energy absorbing deformation zones.
  • Figs 5 to 8 show further non-limiting examples of components being provided with grid pattern according to some embodiments.
  • the applied grid pattern may be arranged to allow for a first degree of deformation when a deformation force acting on the pattern in a first direction, and a second degree of deformation when a deformation force acting on the pattern in a second direction.
  • the applied grid pattern is a honeycomb pattern with comparably low density and relatively high out-of-plane compression properties and out-of-plane shear properties.
  • the applied grid pattern comprises at least one rhomboid shaped section, wherein each rhomboid section is attached or integral with at least another rhomboid section of the grid pattern.
  • the applied grid pattern comprises at least one rectangular shaped section, wherein each rectangular section is attached or integral with at least another rectangular section of the grid pattern.
  • the applied grid pattern comprises at least one ring shaped section, wherein each ring section is attached or integral with at least another ring section of the grid pattern.
  • the design of the grid pattern could also be a combination of the different designs as presented in Figs 5 to 8.
  • Figs 9a to c illustrate three non-limiting examples of different applied grid patterns 91 being provided on a press formed sheet metal material 92.
  • the grid pattern is applied before forming/trimming.
  • the grid pattern is provided onto the sheet metal material such as to provide local reinforcements of the sheet metal material, thereby facilitating the subsequent press forming of the sheet metal material.
  • a grid pattern comprising a single line of reinforcing austenite may be used as a folding support structure, along which the sheet metal material may be folded into the final desired shape.
  • the grid pattern is applied to the sheet metal material by means of a heating unit 31, 32 of a laser system.
  • a system 30 for reinforcing a sheet metal material comprising boron steel is provided.
  • the system 30 comprises a laser system 30 used to provide an austenized grid pattern 33, 34 in the sheet metal material 39.
  • the sheet metal material 39 is moved in the direction of the arrow in relation to two laser units 31, 32.
  • the first laser unit 31 irradiates the sheet metal material intermittently along a grid line 33 (lateral) extending over the width of the sheet metal material.
  • the expression “intermittently” is here meant to be understood as occurring at regular intervals.
  • the grid line 33 may e.g.
  • a second laser unit may be configured to provide at least one austenized grid line 34 in the longitudinal (i.e. parallel to the direction of movement indicated by the arrow) direction of the sheet metal material 39.
  • Such a second laser unit may be provided to irradiate the sheet metal material such as to provide at least one austenized grid line 34 when the sheet metal material is moved in the direction as indicated by the arrow.
  • the two austenized grid lines 33, 34 together form the austenized grid pattern in the sheet metal material.
  • Fig. 4 illustrates a system 40 for reinforcing a sheet metal material comprising boron steel.
  • the system 40 comprises a single laser unit 41 providing the locally austenized grid pattern by locally heating the sheet metal material by means of laser irradiation.
  • the single laser unit 41 continuously, or at least more frequent than for the lateral lines of austenization, irradiates at least one position of the sheet metal material by means of laser arrays 32a, 32b such as to provide a longitudinal line of austenization 34.
  • a second set of laser arrays 31a intermittently heats a lateral line of the sheet metal material to austenization temperature.
  • the resulting locally austenized grid pattern of Fig. 4 is the same as that of Fig. 3.
  • the laser system uses a pattern generator for providing the desired austenized grid pattern.
  • a control unit (not shown) may be used to control the operation of each laser unit, in conjunction with controlling of the movement of sheet metal material, such as to provide a desired grid pattern in the sheet metal material.
  • the control unit may comprise a processor and a memory.
  • control unit is configured to receive grid pattern design data, and based on the received grid pattern data control the operation of the selective heat treatment unit such as to selectively heat parts of the sheet metal material according to the grid pattern data.
  • the grid pattern of the sheet metal material is provided by means of an induction hardening system.
  • coils arranged in accordance with the grid lines of the grid pattern are lowered over the sheet metal, and due to the interaction between the coils and the sheet metal material, the grid lines of the sheet metal material are locally heated.
  • the coils may be embedded, e.g. in cavities, in an induction unit in accordance with the grid lines of a predetermined grid pattern. Cooling
  • the cooling may be conducted by means on passive cooling by the relatively cooler ambient or still air, such that a passive cooling at a sufficient rate of the defined heat treated pattern is achieved.
  • the sufficient rate may be around 27°C per second up to around 50°C per second, since this is the known cooling rate required for the austenite to convert into martensite.
  • the passive cooling i.e. not using any cooling device, has shown to meet the sufficient cooling rate of 27 °C per second, since the selective heat treatment is local, meaning that the adjacent areas to the grid pattern are very cool, i.e. close to room temperature, in relation to the temperature of the grid pattern, thereby cooling the heated grid lines sufficiently rapid for the austenite to convert into martensite.
  • Passive cooling is advantageous since it does not require any complex cooling system.
  • the cooling may be induced by a cooling unit actively cooling the metal sheet, e.g. by an air cooling device or air fan.
  • the protective gas e.g. argon
  • some lasers e.g. fiber lasers
  • the protective gas e.g. argon
  • some lasers e.g. fiber lasers
  • the cooling unit may e.g. be an air cooling device supplying a cool stream of air around the grid pattern provided sheet metal material.
  • the cooling unit may be a heat exchanging unit optionally included in a press forming tool by means of heat exchanging channels provided therein.
  • the channels may be filled with a refrigerant fluid flowing there through.
  • the refrigerant may either be a gas or a liquid.
  • the cooling is preferably conducted rapidly in order for the austenite to convert to martensite.
  • the heating temperature of the grid pattern of the sheet metal material may attain temperatures of up to 950°C thereby converting the boron steel into austenite along the grid lines of the grid pattern. Cooling down the grid lines of the grid pattern to a temperature of around 450°C ensures that the austenite converts into martensite.
  • the method further may further comprise a step of cutting the formed single component to form ready-to-use component.
  • a step of cutting the formed single component to form ready-to-use component.
  • it may be required to cut away certain parts of the reinforced component after the two materials have been welded together in the heating step.
  • Both the subsequent cutting and optional forming of the selectively heat treated sheet metal may be conducted in ambient air temperature, e.g. room temperature, Press hardening/forming
  • Fig. 10 illustrates a side view of a press hardening tool 100 according to an embodiment.
  • the press hardening tool 100 comprises a first press part 101, and a corresponding second pressing part 102.
  • the press hardening tool further comprises a heating device 103 being provided in the first press part.
  • An austenized pattern 104 is provided in the sheet metal material between the first 101 and second 102 press parts.
  • Figs 1 la to l id show a ready-to-use component 1 11 being provided with a grid pattern P.
  • Figs 1 la and 1 lb is a 3D view of the component, whereas Figs 1 lc to l id show the component in a top view.
  • Figs 1 lb and l id respectively show an enlarged section of the component.
  • the grid pattern is comprises different shapes at different portions of the component.
  • a generally square sized the grid pattern covers a majority of the component (as is best seen in Figs 1 lc and l id).
  • This square shaped grid pattern ends some distance from each of the edges formed by cut outs or holes 1 12 of the component and the component exterior edges.
  • a contour line grid pattern follows each of the edges, thereby reinforcing the sheet metal material round the holes 1 12 and the outer edges of the component.
  • the contour lines of the grid pattern may be provided by the selective heat treatment before the holes are cut out of the sheet metal material. In this sense, the contour lines of the grid pattern being located around the intended holes or cut outs reinforces the sheet metal material in these parts of the component, thereby facilitating for the subsequent cutting process.
  • Figs 1 la to l id could e.g. be regarded as a typical component used in a vehicle.
  • the non-heat treated parts i.e. the parts not being subject to the selective heat treatment, are denoted C.
  • the method according to the embodiments of the invention is not limited to processing only boron steel sheet metal materials.
  • Other metal materials, not necessarily converting into austenite and martensite could also be advantageously in order to provide the sheet metal material with a grid pattern using selective heat treatment, wherein the sheet metal material after the selective treatment has an advantageous different material characteristics than the non-treated parts, i.e. the original material characteristics, of the sheet metal material.
  • Such a metal could be aluminum.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Articles (AREA)
  • Shaping Metal By Deep-Drawing, Or The Like (AREA)

Abstract

A method and system for selective heat treatment of a sheet metal is provided.

Description

METHOD AND SYSTEM FOR SELECTIVE HEAT TREATMENT OF A SHEET METAL
TECHNICAL FIELD
The present invention relates to a method for improving the formability and/or component properties of a sheet metal material by selective heat treatment.
BACKGROUND
Press hardening processes allow for the production of light weight, high strength sheet metal components. Press hardened materials are highly deformation resistant.
Press hardening techniques have played an increasingly important role with the vehicle industry during recent years, as the press hardened materials are suitable for absorbing great deformation energies such as in a vehicle collision.
The alternatives to press hardening techniques are few. Perhaps the only alternative solution suitable for the vehicle industry is using a cold press process, however, although this technique produces high strength steel components, the cons are lower tolerances and the increased resiliency in the material.
The sheet metal used in press hardening techniques are boron steel with a ferrous or pearlitic base structure being characterized by a tensile strength of 600MPa and extension degree of about 26% for uncoated sheets and about 10% for sheets coated with AISi (Aluminum Silicon).
In current press hardening processes the sheet metal is transported through a furnace and thus heated up to its austenization temperature of about 900 to 950 °C whereby it is transformed into 100% austenite. In the austenitic state the material has a tensile strength of about 200MPa and an extension degree of about 40%. After the heat treatment the austenite material is rapidly moved into a processing tool for shaping the material before it starts to oxidize. Usually the duration of the shaping stage is about 8 to 10 seconds. During the shaping the shaped material is subject to cooling during which the austenite is transformed to marteniste. In other words a phase transformation occurs during the cooling. When the shaped material leaves the shaping tool, its temperature is about 150 to 200 °C. Normally the shaping tools are provided with a cooling system to cool the shaped material down to the desired temperature.
Subsequently, the shaped material is cut or processed further e.g. by means of laser treatment. Press hardening parts therefore currently represent one of the most advanced lightweight solutions for the car body structure.
A drawback of current press hardening techniques is that it is a relatively slow process. Moreover, the final product has far higher/larger tensile strength than the original sheet material which may not always be desired due to desired deformability characteristics of the sheet metal in us.
SUMMARY
An object of the present invention is to eliminate or alleviate at least one of the drawbacks mentioned above, in accordance with the appended claims.
An advantage of the present invention is that the thickness of the sheet metal material may be reduced while providing reinforcement at desired locations of the sheet metal material.
A further advantage is that the formability of the sheet metal material is improved.
Moreover, by the provision of a grid pattern in the sheet metal material the deformation capability of the resulting component may be tailor made.
According to a first aspect a method for providing a sheet metal material with a certain component property is provided. The method comprises providing a sheet metal material in a non- formed state, said sheet metal material comprising boron steel.
Moreover, the method comprises conducting a selective heat treatment on the sheet metal material when in its non- formed state. The selective heat treatment comprises selectively heating the sheet metal material according to a grid pattern designed based on the certain component property, thereby forming a heated grid pattern in the sheet metal material, said heated grid pattern having a first material characteristic being different than that of the non-heated areas of the sheet metal material, wherein the first material characteristic relates to the boron steel of the selectively heated sheet metal material forming into a grid pattern of austenite. The method further comprises cooling the locally heated grid pattern, thereby forming a locally cooled grid pattern having a second material characteristic being different from the first material characteristic and the material characteristic of the non-heated areas, and wherein second material characteristic relates to the austenite grid pattern forming into a martensite grid pattern. According to another aspect a component comprising a reinforced sheet metal material being produced by the method is provided.
According to yet another aspect a system for providing a sheet metal material comprising boron steel with a certain component property is provided. The sheet metal material is provided in a non-press formed state. The system comprises a heating unit selectively heating the sheet metal material, when in its non-press formed state, according to a grid pattern designed based on the certain component property, thereby producing a heated grid pattern in the sheet metal material, said heated grid pattern having a first material characteristic being different than that of the non-heated areas of the sheet metal material wherein the first material characteristic relates to the boron steel of the selectively heated sheet metal material forming into a grid pattern of austenite.
In yet another aspect a press forming tool comprising the system is provided. BREIF DESCRIPTION OF THE DRAWINGS
In order to explain the invention, a number of embodiments of the invention will be described below with reference to the drawings, in which:
Fig. 1 is a flow chart of a method according to an embodiment;
Fig. 2 is a flow chart of a method according to an embodiment;
Fig. 3 shows a system for reinforcing a sheet metal material according to an embodiment;
Fig. 4 shows a system for reinforcing a sheet metal material according to an embodiment;
Figs 5 to 8 illustrate exemplary grid patterns according to an embodiment, respectively;
Figs 9a to 9c illustrate exemplary grid patterns applied to a sheet metal material according to an embodiment, respectively;
Fig. 10 illustrates a press forming tool according to an embodiment; and Figs 1 la to l id illustrates a component being provided with a grid pattern according to an embodiment.
DESCRIPTION
An idea of the present invention is to conduct selective heat treatment to the sheet metal material based on required sheet material formability/trimability or required component properties. The selective heat treatment includes heating the sheet metal material according to a specific heat pattern, e.g. grid pattern, followed by cooling of the grid pattern thereby forming a grid pattern of local reinforcements in the sheet metal material. If the sheet metal material is made of boron steel, during the selective heat treatment the boron steel at the position of the grid, i.e. along the grid lines of the grid pattern, converts into austenite while heating, and during the cooling the austenite converts into martensite along the grid lines of the grid pattern, and the martensite then acts as the reinforcing structure of the processed sheet metal material.
In some applications, after the selective heat treatment the sheet metal material may be considered being a ready-use-component. In other cases press forming and/or cutting is required before the selective heat treated sheet metal material is considered being a ready -to -use component or product.
The grid pattern may be said to form a skeleton structure in the sheet metal material. The grid structure may improve or facilitate subsequent forming of the sheet metal material. Also, the grid pattern provided sheet metal may be designed to allow for tailor made deformation capabilities of the resulting sheet metal component.
The grid pattern, its shape and position in view of the sheet metal material is designed and carried out based on the identified needs/requirements concerning forming, trimming or/and component performance/properties. Hence, the design of the grid pattern may be derived by reverse engineering.
Selective heat treatment before trimming or forming, i.e. in a non-press formed state
In case the purpose of the selective heat treatment is to improve the component properties or performance by reinforcement, the grid pattern is applied either before or after sheet material shaping process depending on economic feasibility.
In an embodiment according to Fig. 1, a method 10 for improving the formability or the reinforcement of a sheet metal material arranged to absorb deformation energies in use is provided. The method comprises supplying a sheet metal material optionally comprising boron steel. Moreover, the method comprises conducting 12 a selective heat treatment on the sheet metal material when in its non-press formed state. The selective heat treatment comprises selectively heating 121 the sheet metal material according to a grid pattern designed based on desired or required component properties, thereby forming a heated grid pattern in the sheet metal material. When the sheet metal material comprises boron steel the sheet metal material along the lines of the grid pattern will convert into austenite during the heating process. Moreover, the selective heat treatment comprises cooling (either passive or active) 122 the selectively heated sheet metal material, whereby the austenite along the lines of the grid pattern is converted into martensite.
An advantage of conducting the selective heat treatment onto the sheet metal material, when in its non-press formed state, i.e. when it is still flat or essentially flat, is that the heat treatment process and equipment assembly is less complex. Moreover, by providing ready-to-form/trim/cut heat treated metal sheets, the bulkiness during shipping of the treated metal sheets may be kept to a minimum as the heat treated metal sheets can be stacked very efficiently. This leads to reduced environmental impact. Furthermore, the ready -to-form/trim/cut heat treated metal sheets may be used in the same assembly processing lines as conventionally used for press forming, trimming and cutting. Hence, the heat treated metal sheets of the present invention may be used for subsequent processing in existing equipment used e.g. in the vehicle industry for the processing of vehicle components such as car components.
Furthermore, the method may comprise press forming 13 the sheet metal material being provided with the martensite grid pattern in a press forming tool into a single component having a desired shape. Here, the press forming step may be executed immediately after the selective heat treatment, such that parts of the sheet metal material, in particular the martensite grid pattern, has a higher temperature than the ambient temperature.
Selective heat treatment after forming, i.e. in a press-formed state
Alternatively, the sheet of metal material is first press formed and/or trimmed in press forming tools, e.g. dies, at room temperature. After forming and trimming, reinforcement is provided by conducting selective heat treatment, according to a grid pattern designed in accordance with desired component properties, of the sheet metal material.
Hence, according to an alternative embodiment in view of Fig. 2, a method 20 for reinforcing a sheet metal material is provided. The method comprises supplying 21 a sheet metal material, e.g. comprising grid boron steel. Moreover, the method comprises press forming 22 the sheet metal material in a press forming tool into a desired shape. Furthermore, the method 20 comprises conducting 23 a selective heat treatment on the sheet metal material. The selective heat treatment comprises selectively heating 231 the shaped sheet metal material according to a grid pattern designed based on desired or required component properties, thereby converting the boron steel into austenite along the lines of the grid pattern of the shaped sheet metal material. Moreover, the selective heat treatment comprises cooling 232 the selectively heat treated sheet metal material, whereby the austenite along the lines of the grid pattern is converted into martensite.
The selective heat treatment changes the material characteristics of the sheet metal material at the position of the grid pattern, e.g. going from boron steel to austenite during heating and then to martensite during cooling.
The grid pattern
The grid pattern may be designed based on desired or required formability and/or component properties of the end product comprising the grid pattern provided sheet metal material.
In an embodiment, information relating to the grid pattern, such as size, shape, placement in relation to the sheet metal material may be derived from component performance or property analysis. Accordingly, a specific grid pattern may be designed based on input data comprising information of the required behavior of the resulting ready-to-use component and its intended location and use. It should be appreciated that in some situations only some portions of the sheet metal material may require selective heat treatment. The component performance or property analysis may identify those areas in which selective heat treatment is required to meet the required performance or properties of the ready-to-use component comprising the grid pattern applied sheet metal material.
Within the vehicle industry, much effort is directed to increasing the safety of occupants as well as non-occupants in the unlikely event of an accident. Here, the input data may relate to certain deformability properties of the component, the location of the component in the vehicle in use, the design of the ready -to use component (shape, holes, fittings, supports, etc), as well as information relating to details of the sheet metal material (alignment, width, thickness, material composition) and the press forming process (details regarding the dimensions and geometrical shapes created by the press forming tool, etc).
By knowing the position in which the vehicle component is to be positioned in the vehicle in use, it is possible to create a martenisite grid pattern on at least part of the sheet metal material of the component, which will deform in a desirable manner in the event of collision with a foreign object in use. It should be noted that the parts of the sheet metal material not constituting the martensite grid pattern will deform more easily than the martensite grid pattern. Hence, the martensite grid pattern will in effect form a skeleton structure or a number of deformation zones being designed to have improved deformability in certain contemplated deformation directions.
Thanks to the provided grid pattern the resulting deformation zones allow for a predefined and controlled deformation of the component upon impact with a foreign object.
The design of the grid pattern may therefore be created based on a desired deformation direction in the event of the component being subjected to a deformation force in use. For example, imagine a reinforced component for use in a vehicle. Such a component may be arranged in the engine compartment at the front end of the vehicle, and essentially extending in a lateral direction in view of the longitudinal axis of the vehicle and at an outer boundary of the vehicle, e.g. close to the grill of the vehicle. In the event of a frontal collision it is important to protect the occupants in the vehicle. Moreover, it may be desired to as far as possible preventing damage to vital engine components in the vehicle engine compartment. A grid pattern designed according to the intended placement of the grid pattern provided component in the vehicle in use is selectively heated in the sheet metal material of the component, whereby it is possible to allow deformation of the component at a higher extent in certain more preferred directions to avoid injuries to the occupants of the vehicle and at the same time minimize the damage to the vehicle vital components.
Figs 3 to 4 show non-limiting examples of a grid pattern P being selectively heat treated into a sheet metal material, thereby forming a martensite grid pattern. The remaining parts of the sheet metal material are denoted with reference numeral C. The martensite grid pattern in conjunction with non-heat treated parts C of the sheet metal material together form a number of well defined energy absorbing deformation zones.
Figs 5 to 8 show further non-limiting examples of components being provided with grid pattern according to some embodiments.
In accordance with the embodiment of Fig. 5 to 7, the applied grid pattern may be arranged to allow for a first degree of deformation when a deformation force acting on the pattern in a first direction, and a second degree of deformation when a deformation force acting on the pattern in a second direction.
In Fig. 5 the applied grid pattern is a honeycomb pattern with comparably low density and relatively high out-of-plane compression properties and out-of-plane shear properties. In Fig. 6, the applied grid pattern comprises at least one rhomboid shaped section, wherein each rhomboid section is attached or integral with at least another rhomboid section of the grid pattern.
In Fig. 7, the applied grid pattern comprises at least one rectangular shaped section, wherein each rectangular section is attached or integral with at least another rectangular section of the grid pattern.
In Fig. 8, the applied grid pattern comprises at least one ring shaped section, wherein each ring section is attached or integral with at least another ring section of the grid pattern.
The design of the grid pattern could also be a combination of the different designs as presented in Figs 5 to 8.
Figs 9a to c illustrate three non-limiting examples of different applied grid patterns 91 being provided on a press formed sheet metal material 92.
Formability
In cases the purpose of the treatment is to improve the formability/trimability, the grid pattern is applied before forming/trimming.
In an embodiment, the grid pattern is provided onto the sheet metal material such as to provide local reinforcements of the sheet metal material, thereby facilitating the subsequent press forming of the sheet metal material. As a very simple example, a grid pattern comprising a single line of reinforcing austenite may be used as a folding support structure, along which the sheet metal material may be folded into the final desired shape.
Unitfs for conducting the selective heat treatment
In an embodiment, the grid pattern is applied to the sheet metal material by means of a heating unit 31, 32 of a laser system. In accordance with Fig. 3 a system 30 for reinforcing a sheet metal material comprising boron steel is provided. The system 30 comprises a laser system 30 used to provide an austenized grid pattern 33, 34 in the sheet metal material 39. In this embodiment, the sheet metal material 39 is moved in the direction of the arrow in relation to two laser units 31, 32. The first laser unit 31 irradiates the sheet metal material intermittently along a grid line 33 (lateral) extending over the width of the sheet metal material. The expression "intermittently" is here meant to be understood as occurring at regular intervals. The grid line 33 may e.g. be created when the sheet metal material is brought to a stop, as it takes some time for the sheet metal material along the line 33 to reach the required austenization temperature. The result of the first laser unit is that discrete austenized grid lines 33 are created at regular intervals along the sheet metal material 39. A second laser unit may be configured to provide at least one austenized grid line 34 in the longitudinal (i.e. parallel to the direction of movement indicated by the arrow) direction of the sheet metal material 39. Such a second laser unit may be provided to irradiate the sheet metal material such as to provide at least one austenized grid line 34 when the sheet metal material is moved in the direction as indicated by the arrow. The two austenized grid lines 33, 34 together form the austenized grid pattern in the sheet metal material.
Fig. 4, illustrates a system 40 for reinforcing a sheet metal material comprising boron steel. The system 40 comprises a single laser unit 41 providing the locally austenized grid pattern by locally heating the sheet metal material by means of laser irradiation. Here, the single laser unit 41 continuously, or at least more frequent than for the lateral lines of austenization, irradiates at least one position of the sheet metal material by means of laser arrays 32a, 32b such as to provide a longitudinal line of austenization 34. A second set of laser arrays 31a intermittently heats a lateral line of the sheet metal material to austenization temperature. Hence, the resulting locally austenized grid pattern of Fig. 4 is the same as that of Fig. 3.
In an embodiment, the laser system uses a pattern generator for providing the desired austenized grid pattern.
A control unit (not shown) may be used to control the operation of each laser unit, in conjunction with controlling of the movement of sheet metal material, such as to provide a desired grid pattern in the sheet metal material. The control unit may comprise a processor and a memory.
In an embodiment, the control unit is configured to receive grid pattern design data, and based on the received grid pattern data control the operation of the selective heat treatment unit such as to selectively heat parts of the sheet metal material according to the grid pattern data.
In an embodiment, the grid pattern of the sheet metal material is provided by means of an induction hardening system. In one alternative, coils arranged in accordance with the grid lines of the grid pattern are lowered over the sheet metal, and due to the interaction between the coils and the sheet metal material, the grid lines of the sheet metal material are locally heated.
In another embodiment, the coils may be embedded, e.g. in cavities, in an induction unit in accordance with the grid lines of a predetermined grid pattern. Cooling
The cooling may be conducted by means on passive cooling by the relatively cooler ambient or still air, such that a passive cooling at a sufficient rate of the defined heat treated pattern is achieved. The sufficient rate may be around 27°C per second up to around 50°C per second, since this is the known cooling rate required for the austenite to convert into martensite. In fact, the passive cooling, i.e. not using any cooling device, has shown to meet the sufficient cooling rate of 27 °C per second, since the selective heat treatment is local, meaning that the adjacent areas to the grid pattern are very cool, i.e. close to room temperature, in relation to the temperature of the grid pattern, thereby cooling the heated grid lines sufficiently rapid for the austenite to convert into martensite. Passive cooling is advantageous since it does not require any complex cooling system.
Alternatively, the cooling may be induced by a cooling unit actively cooling the metal sheet, e.g. by an air cooling device or air fan.
Moreover, also the protective gas, e.g. argon, associated with some lasers, e.g. fiber lasers, may be used to provide cooling of the heat treated pattern.
The cooling unit may e.g. be an air cooling device supplying a cool stream of air around the grid pattern provided sheet metal material.
In an alternative embodiment, the cooling unit may be a heat exchanging unit optionally included in a press forming tool by means of heat exchanging channels provided therein. The channels may be filled with a refrigerant fluid flowing there through. The refrigerant may either be a gas or a liquid.
It is also possible to cool the heat treated metal sheet using by allowing the metal sheet to engage in relatively cooler objects, such as tools, dies and jigs/fixtures or cooled tools & dies, wherein the tools e.g. have heat exchanging channels filled with a refrigerant fluid flowing there through, and jigs/fixtures.
In some situations, such as for heat treating a boron steel sheet metal material, the cooling is preferably conducted rapidly in order for the austenite to convert to martensite. For example, during the heating temperature of the grid pattern of the sheet metal material may attain temperatures of up to 950°C thereby converting the boron steel into austenite along the grid lines of the grid pattern. Cooling down the grid lines of the grid pattern to a temperature of around 450°C ensures that the austenite converts into martensite. Although not always required, at very dense grid patterns it would be advantageous to increase the cooling such as to convert the austenite to martensite when the sheet metal material comprises boron steel, and also for preparing the selectively heat treated sheet metal material for the further processing steps optionally required to provide a ready-to-use-product.
Post-processing of the component
In an embodiment, the method further may further comprise a step of cutting the formed single component to form ready-to-use component. Depending on the sheet metal material at hand, it may be required to cut away certain parts of the reinforced component after the two materials have been welded together in the heating step.
Both the subsequent cutting and optional forming of the selectively heat treated sheet metal may be conducted in ambient air temperature, e.g. room temperature, Press hardening/forming
Fig. 10 illustrates a side view of a press hardening tool 100 according to an embodiment. The press hardening tool 100 comprises a first press part 101, and a corresponding second pressing part 102. The press hardening tool further comprises a heating device 103 being provided in the first press part. An austenized pattern 104 is provided in the sheet metal material between the first 101 and second 102 press parts.
Figs 1 la to l id show a ready-to-use component 1 11 being provided with a grid pattern P. Figs 1 la and 1 lb is a 3D view of the component, whereas Figs 1 lc to l id show the component in a top view. Figs 1 lb and l id respectively show an enlarged section of the component. As may be seen in Figs 11a and 1 lb the component is press- formed and hence it is no longer a flat sheet metal material. It may also from Figs 11c and l id that the grid pattern is comprises different shapes at different portions of the component. In this example, a generally square sized the grid pattern covers a majority of the component (as is best seen in Figs 1 lc and l id). This square shaped grid pattern ends some distance from each of the edges formed by cut outs or holes 1 12 of the component and the component exterior edges. At this position a contour line grid pattern follows each of the edges, thereby reinforcing the sheet metal material round the holes 1 12 and the outer edges of the component. It should be noted that the contour lines of the grid pattern may be provided by the selective heat treatment before the holes are cut out of the sheet metal material. In this sense, the contour lines of the grid pattern being located around the intended holes or cut outs reinforces the sheet metal material in these parts of the component, thereby facilitating for the subsequent cutting process. The component of Figs 1 la to l id could e.g. be regarded as a typical component used in a vehicle. In Figs 1 la to 1 Id the non-heat treated parts, i.e. the parts not being subject to the selective heat treatment, are denoted C.
It should be appreciated that although the sheet metal material according to some embodiments have been described to comprise boron steel, the method according to the embodiments of the invention is not limited to processing only boron steel sheet metal materials. Other metal materials, not necessarily converting into austenite and martensite could also be advantageously in order to provide the sheet metal material with a grid pattern using selective heat treatment, wherein the sheet metal material after the selective treatment has an advantageous different material characteristics than the non-treated parts, i.e. the original material characteristics, of the sheet metal material. Such a metal could be aluminum.

Claims

1. A method (10) for providing a sheet metal material with a certain component property, comprising:
providing (1 1) a sheet metal material in a non- formed state, said sheet metal material comprising boron steel;
conducting (12) a selective heat treatment on the sheet metal material when in its non- formed state, the selective heat treatment comprising
selectively heating (121) the sheet metal material according to a grid pattern designed based on the certain component property, thereby forming a heated grid pattern in the sheet metal material, said heated grid pattern having a first material characteristic being different than that of the non-heated areas of the sheet metal material, wherein the first material characteristic relates to the boron steel of the selectively heated sheet metal material forming into a grid pattern of austenite,
cooling (122) the locally heated grid pattern, thereby forming a locally cooled grid pattern having a second material characteristic being different from the first material characteristic and the material characteristic of the non-heated areas, and wherein second material characteristic relates to the austenite grid pattern forming into a martensite grid pattern.
2. The method (10) according to claim 1, further comprising
press forming (13) the selectively heated sheet metal material in a press forming tool into a desired shape.
3. The method (10, 20) according to any of the previous claims, wherein the heated grid pattern encompasses a number of non-heated parts, thereby forming a number of energy absorbing deformation zones.
4. The method (10, 20) according to any of the preceding claims, wherein the cooled grid pattern is arranged to provide a first degree of deformation when a deformation force acting on the pattern in a first direction, and a second degree of deformation when a deformation force acting on the pattern in a second direction.
5. The method (10, 20) according to any of the preceding claims, wherein the certain component property pertains to a deformability property.
6. The method (10, 20) according to any of the preceding claims, wherein the grid pattern comprises a honeycomb pattern with comparably low density and relatively high out-of-plane compression properties and out-of-plane shear properties.
7. The method (10, 20) according to any of the preceding claims, wherein the grid pattern comprises at least one ring shaped section, wherein each ring section is attached or integral with at least another ring section of the grid pattern.
8. The method (10, 20) according to any of the preceding claims, wherein the grid pattern comprises at least one rhomboid shaped section, wherein each rhomboid section is attached or integral with at least another rhomboid section of the grid pattern.
9. The method (10, 20) according to any of the preceding claims, wherein the grid pattern comprises at least one rectangular shaped section, wherein each rectangular section is attached or integral with at least another rectangular section of the grid pattern.
10. The method (10, 20) according to claim 2 or any one of claims 3 to 9 being dependent thereon, further comprising the step of cutting (14) the heat treated and press formed sheet metal material such as to form ready-to-use component.
1 1. The method (10, 20) according to any of the previous claims, wherein the cooling is conducted by means of an air cooling device.
12. The method (10, 20) according to any of the previous claims, wherein the cooling is conducted by means of a cool brush.
13. The method (10, 20) according to any of the previous claims, wherein the cooling is conducted by the press forming tool by means of heat exchanging channels provided therein.
14. The method (10, 20) according to any of the previous claims, wherein the grid pattern heating of the sheet metal material is conducted by an induction unit.
15. The method (10, 20) according to any of the previous claims, wherein the grid pattern heating of the sheet metal material is conducted by a laser unit.
16. A component comprising a reinforced sheet metal material according to any of the claims 1 to 15.
17. A system (30, 40) for providing a sheet metal material with a certain component property, wherein the sheet metal material comprises boron steel and is provided in a non-press formed state, comprising
a heating unit (31, 32, 41) selectively heating (121) the sheet metal material, when in its non-press formed state, according to a grid pattern designed based on the certain component property, thereby producing a heated grid pattern in the sheet metal material, said heated grid pattern having a first material characteristic being different than that of the non-heated areas of the sheet metal material wherein the first material characteristic relates to the boron steel of the selectively heated sheet metal material forming into a grid pattern of austenite.
18. The system (30, 40) according to claim 17, further comprising a cooling unit for cooling (122) the heated grid pattern, thereby forming a locally cooled grid pattern having a second material characteristic being different from the first material characteristic and the material characteristic of the non-heated areas, and wherein second material characteristic relates to the austenite grid pattern forming into a martensite grid pattern.
19. A press forming tool (100) comprising the system of claim 17 or 18.
EP16700815.0A 2015-01-15 2016-01-15 Method and system for selective heat treatment of a sheet metal Withdrawn EP3245307A1 (en)

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