EP2883967B1 - Method and device for post-treatment of a hardened metallic moulded part by means of electrical resistance heating - Google Patents

Description

The invention relates to a method and a device for the aftertreatment of a hardened metallic molded part. Such hardened metallic moldings can be produced, for example, from sheet metal blanks, which are then hot-formed, or press-hardened.

From the DE 197 43 802 A1 For example, methods for producing a metallic mold component are known that have regions with higher ductility than the rest of the component. After a first procedure, it is provided that first partial areas of the board in a time of less than 30 seconds are brought to a temperature between 600 ° C and 900 ° C, whereupon the heat-treated board formed in a press tool to form the mold component, and the mold component in Pressing tool is tempered. According to an alternative process control it is provided that the board is first heated homogeneously to a temperature between 900 ° C and 950 ° C and then formed in a press tool to form the mold, and then the mold component is still tempered in the press tool. Subsequently, partial areas of the molded component are brought to a temperature between 600 ° C and 900 ° C in a time of less than 30 seconds. The partial heat treatment can be carried out by inductive heating in both methods.

From the DE 10 2012 110 649 B3 A hot-forming line and a method for producing a hot-formed and press-hardened motor vehicle component are known. The thermoforming line has a heating device and a tempering station with an upper tool and a lower tool for cooling or heating up. Replaceable temperature control plates for conductive temperature control are arranged on the upper tool and / or the lower tool. With the tempering plates first areas and second areas of the component can be tempered with different temperatures. In this case, the first areas of the component have a direct contact with the temperature control with closed temperature control, while in the second areas between the component surface and the temperature control a distance is formed.

From the DE 10 2010 004 823 B4 For example, a method of manufacturing a metal mold component for automotive components having higher ductility zones is known. For this purpose, a board made of a steel alloy is heated to a temperature between 900 ° C and 950 ° C, then formed in a press tool to form the molded part and tempered. After tempering, the mold component is partially annealed, wherein the heating process is carried out conductively in soft annealing within a period of less than 30 seconds.

From the DE 102 12 819 A1 For example, a method for producing a metallic component by heating followed by curing by rapid cooling is known. The heating takes place by means of resistance heating, areas being cooled or electrically and / or thermally bridged during the resistance heating so that these areas remain below the austenitizing temperature. For electrical bridging, the component is subjected to a separate solid from the electrodes, which has a higher conductivity compared to the component. In this case, the solids influence the current flow introduced by the electrodes into the component and thus act indirectly on the temperature in these regions of the solids.

From the DE 10 2011 078 075 A1 there is known a method of forming a product comprising the steps of: performing a heat-treating and press-hardening process to form a product having a uniform first tensile strength; Performing a post heat treatment by selectively heating a first region above a defined temperature between 400 ° C and 700 ° C while maintaining a second range below the defined temperature; and then cooling the first region to obtain a tensile strength that is less than the first tensile strength of the press-hardened product. For heat treatment post-processing of the first region, conduction heating is suggested.

From the DE 197 23 655 A1 is a method for producing a steel sheet product by heating a cut steel sheet, hot working the steel sheet in a pair of tools, and hardening the formed product by rapidly cooling from the austenitic temperature in the pair of tools. When hardening the product, subregions remain uncured so that rapid cooling is avoided in these subareas.

The present invention has for its object to propose a method for the aftertreatment of a metallic molding, with the parts on the molding with different material properties such as ductility or strength can be easily generated. The object is also to propose a corresponding device which enables a partial adjustment of different material properties on a metallic molded part with high accuracy.

A solution consists of a method of after-treatment of a deformed and hardened metallic material component by means of an electric resistance heating apparatus comprising at least a first pair of mold contact pieces and a second pair of mold contact pieces, comprising the steps of: contacting a first portion to be heated the component with the mold contact pieces of the first pair such that the first portion to be heated is arranged between the mold contact pieces of the first pair; Contacting a second portion of the component with the mold contact pieces of the second pair such that the second portion is disposed between the mold contact pieces of the second pair; Heating the first portion of the component to a first temperature (T1) of at most 900 ° C in that electrical current through the first pair of mold contact pieces through the Component is passed; Tempering the second portion of the component by means of the second pair of mold contact pieces to a second temperature (T2), wherein the second temperature (T2) is set independently of the first temperature (T1) or is adjustable.

One advantage is that the hardened component can be selectively softened in partial areas, in order to achieve a higher ductility here, whereby, for example, subsequent machining processes can be simplified. By using multiple pairs of mold contact pieces, the ductility of the component can be adjusted in different areas targeted to the individual requirements. For example, it is possible to heat the first portion by heating To soften a higher first temperature while an adjacent second portion is cooled simultaneously to a second temperature and thus maintains a higher hardness. But it is also possible by appropriate adjustment of the first and second temperatures in both partial areas to achieve a hardening compared to the cured state, but to varying degrees. According to a preferred embodiment, the first pair of mold contact pieces and the second pair of mold contact pieces can be individually controlled with respect to at least one parameter influencing the degree of heating. For example, in the first pair, the electric current can be controlled, while in the second pair, the temperature of a cooling medium can be controlled.

In the present case, the term hardened metallic component is understood to be any metallic component which has been formed as part of a forming process and at the same time or subsequently has been completely hardened, at least in partial regions. In this case, the component can have partial regions with different sheet thicknesses, which can be produced, for example, by flexible rolling of strip material or by joining a plurality of components of different sheet thickness. By flexible rolling produced boards with different sheet thicknesses are also referred to as Tailor Rolled Blanks. Boards, which are composed of several sub-boards with different sheet thickness and welded, are also called Tailor Welded Blanks. In principle, the component can also be composed of different materials; It is crucial that it has at least one metallic portion, which is formed into a particular three-dimensional shape. The component can also be referred to as a molded part.

Preferably, the first pair of mold contact pieces and the second pair of mold contact pieces are disposed immediately adjacent to each other, or are brought into contact with the component immediately adjacent to each other. This advantageously achieves that transition areas between the softened first partial area and the adjacent second partial area with optionally different material properties are small. The component is safe held between the contact pieces and it can be selectively heat treated defined portions. A softened partial area can be limited to a defined area by cooling an immediately adjacent partial area. The mold contact pieces used for cooling have a thermally insulating effect, so that the component properties are changed only in the first part. Depending on the design or function, the molded contact pieces may also be referred to as shaping electrodes or as shaped jaws.

The at least one first pair of mold contact pieces is designed for post-treatment of the component by means of conductive heating. It is meant by at least a first pair, that also a plurality of first pairs of mold contact pieces may be provided for conductive heating of portions of the component. In conductive heating, the metallic component forms part of the electrical circuit. In this case, a standing in contact with the mold contact pieces area of the component is traversed by electric current. Due to the electrical resistance occurs in the area traversed by electrical energy heating of the component, which is why this method is also referred to as resistance heating.

According to a preferred method, the first portion is heated to a first temperature which is at least 200 ° C, preferably at least 500 ° C, in particular at least 700 ° C, and / or at most 900 ° C. The higher the temperature is selected for heating the first portion, the shorter can be holding time with which the component must be heated in order to achieve the desired softening. According to a preferred embodiment, the first portion is heated for a period of at least 30 seconds. Hereby, the formation of hardness distortions can be reduced or avoided altogether in an advantageous manner. With regard to the ratios between temperatures for the respective duration of the heating to soften the first portions, the following preferred embodiments are given: at up to 700 ° C at least 5 minutes holding time; at least 2.5 minutes holding time at up to 750 ° C; at least 1.25 minutes holding time at up to 800 ° C; and at over 850 ° C at least 30 seconds holding time.

The at least one second pair of mold contact pieces serves to temper an associated second partial region of the component to a different or second temperature than that of the first partial region, wherein the temperature control of the second partial region to the second temperature can be heating or cooling.

According to a first possibility, the step of tempering the second portion of the component is heating, which is carried out by passing electrical current from one of the mold contact pieces through the component to the other of the molded contact pieces. In this case, the current flow for the second pair can be controlled individually, that is to say independently of the first pair. For example, a lower or higher electrical energy can be entered into the component in the second subregion so that the geometric features such as a smaller or larger sheet thickness of the second subregion can be taken into account.

Preferably, at least one of the following applies to the step of heating: the first portion and the second portion of the component are heated by passing electrical current through the first pair of molded contact pieces on the one hand and the second pair of molded contact pieces on the other; and / or electrical current is passed through the component with at least partial temporal overlap from the first pair of mold contact pieces and from the second pair of mold contact pieces; and / or the first partial area and the second partial area of the component are heated by passing electrical current of different current strengths through the first pair of molded contact pieces on the one hand and through the second pair of molded contact pieces on the other hand. The shaped contact pieces of the first, second and optionally another pair designed as shaping electrodes can also be designed as segments of a single electrode, with the individual segments being individually controllable.

In a second possibility, the step of tempering the second portion of the component is cooling, which is done by cooling the mold contact pieces of the second pair. For this purpose, the mold contact pieces of the second pair, for example be designed as a heat sink, which are cooled by suitable means such as an integrated cooling circuit. By contacting the heat sink with the second portion of the component of this is cooled, so that there is no or only a small softening.

For the arrangement of the first and second pairs of mold contact pieces on the component fundamentally different alternatives are conceivable. The hardened component is preferably a shaped part made of sheet steel whose thickness is only a fraction of the extension in the longitudinal or transverse direction of the component, or whose length and width in each case is a multiple of the thickness. As a steel material, for example, 22MnB5 can be used, with any other hardenable steel material is also conceivable.

According to a first possibility, the component is arranged between the mold contact pieces such that the mold contact pieces of a pair lie opposite one another in the thickness direction of the component. This may apply to the first pair and / or the second pair of mold contact pieces. A first mold contact of a pair is brought into contact with a bottom of the component while the second mold contact is brought into contact with the top of the component. In this way, the component is held or clamped between the mold contact pieces. This has the particular advantage that undesired distortion of the component during aftertreatment is avoided. The functional surfaces of the mold contact pieces, which are in contact with the component during heating, are preferably adapted in terms of their geometry to the shape of the component. The mold contact pieces of the first pair, which are used for conductive heating, thus assume two functions, namely on the one hand, the introduction of electrical current into the component and on the other a fixing of the component between the contact surfaces. The mold contact pieces of the second pair can, depending on the design, perform one or two functions, depending on whether they serve only for cooling, or for conductive heating.

For contacting the mold contact pieces of the first and / or second pairs, preferably at least one of the following applies in the arrangement in the thickness direction: an upper mold contact piece of the first pair and an upper contact piece of the second pair are brought into contact with the component at the same time; and / or a lower mold contact piece of the first pair and a lower contact piece of the second pair are simultaneously brought into contact with the component.

According to a second possibility, the component is arranged between the mold contact pieces such that the mold contact pieces of a pair lie opposite one another in a transverse direction of the component. This in turn may apply to the first pair and / or the second pair of mold contact pieces. In the case of components made of flexibly rolled strip material, it is particularly advantageous if both of the formula electrodes of a pair, that is to say the positively poled electrode and the negatively poled electrode, are arranged in a thickness region with a uniform thickness in the transverse direction. In this way, a uniform heating of this section is achieved. A first mold contact piece of the pair is brought into contact with a first edge portion of the component, while the second mold contact piece is brought into contact with an opposite second edge portion of the component. By introducing electrical current of the extending in the transverse direction between the two edge portions first portion is heated. The mold contact pieces can be designed in this second possibility as gripping jaws or gripper tongs, which are clamped to the respective edge portion.

Before the post-treatment at least one of the following steps can be provided: flexible rolling of strip material; Working out a board of flexibly rolled strip material, the board having a variable thickness over the length; Hot forming a board to the component; complete hardening of the component; Cleaning the component; and / or descaling the component. It is understood that further process steps are conceivable, previous, subsequent or further intermediate steps.

The solution of the above-mentioned object is further in a device for post-treatment of a formed and hardened component made of a metallic material, comprising: at least a first pair of mold contact pieces, which are used as shaping electrodes for passing electrical current through a first Partial region of the component are designed, wherein the contact surfaces of the mold contact pieces of the first pair are adapted to outer surfaces of the first portion, wherein the first portion of the component is heated when passing electrical current to a first temperature; at least a second pair of mold contact pieces for tempering a second portion of the component, wherein the contact surfaces of the mold contact pieces of the second pair are adapted to outer surfaces of the second portion; wherein means are provided with which the second pair of mold contact pieces is adjustable to a second temperature, which is different from the first temperature.

By this device, the same advantages as they have been described in connection with the method according to the invention, so that in brief the above description reference is made. It is understood that all mentioned embodiments of the method are transferable to the device, and vice versa. According to a possible development, the second partial region of the component is arranged adjacent to the first partial region and, correspondingly, the second pair of molded contact elements is arranged adjacent to the first pair of molded contact pieces. It is understood that in addition to the first and second pair of mold contact pieces, the apparatus can also have further pairs of mold contact pieces in order to specifically soften or to produce a higher ductility thereon of other portions of the component. The device thus offers a high degree of flexibility in order to set different zones of the component as required to defined material properties. This is especially true for those zones that are later treated further manufacturing technology, for example, welded or drilled for tying to other components.

As stated above, the mold contact pieces of the second pair are, in a first possibility, shaped as shaping electrodes for passing electrical current through the second portion of the component. In this case, an electronic control unit is preferably provided, with which the passage of electric current through the shape of the electrodes of the first pair on the one hand and the shape of the electrodes of the second pair is individually controllable with respect to at least one parameter influencing the heating of the component.

According to a second possibility, the mold contact pieces of the second pair are designed as cooling contact pieces, with which the second portion is adjustable to the temperature below the temperature. For this purpose, the cooling contact pieces may have integrated Kühlkreiskäufe through which flows through a cooling medium such as water or steam.

According to a preferred embodiment, means are provided with which at least the mold contact pieces of the first pair are movable towards each other to come into contact with an upper and a lower outer surface of the component. These means may be designed in the form of a feed or drive, with which the mold contact pieces of a respective pair are movable relative to each other. This includes as options that a contact piece is arranged stationary and another is moved relative thereto, or that both contacts are moved towards each other at the same time.

Alternatively or in addition, means may further be provided with which a plurality of adjacent mold contact pieces are movable together to come into contact with an outer surface of the component. For example, contact pieces of a first pair and a second pair may be arranged immediately adjacent to one another and accommodated in a common tool. By moving the tool, the contact pieces received therein are also moved together, which has the advantage that they come into contact with the component at the same time and unfold their tempering or shape-retaining function here.

In particular, it can be provided that lower mold contact pieces are provided in a lower tool part, on which the component is placed. In a relative to the lower tool part movable upper tool part corresponding upper mold contact pieces can be arranged, which cooperate with the lower contact pieces. By moving the upper tool part to the lower, the component is clamped between the lower and upper mold contact pieces so that it retains its shape when heated.

In a preferred embodiment, the first mold contact of the first pair has a mold surface adapted to a first surface of the component and the opposed second mold contact has a second mold surface adapted to the opposite second surface of the component. Of course, this also applies equally to the mold contact pieces of the second and optionally each further pair. As a result of the aforementioned configuration, a secure fixing of the component between the contact pieces is achieved even with any component geometry. In particular, with variable sheet thickness over the length or width of the component, the mold contact pieces can be adjusted accordingly, so that a uniform heating or cooling of the respective sections is guaranteed.

The shape contact pieces of the first and / or second pair designed as shaping electrodes preferably each have a contact area which is smaller than 400 mm ² . This achieves a good current introduction into the component and a good adaptation to the component geometry.

Figur 1

ein umgeformten und gehärteten Bauteil zur Nachbearbeitung von Teilbereichen in Draufsicht;

Figur 2

eine erfindungsgemäße Vorrichtung in einer ersten Ausführungsform zur Nachbehandlung des Bauteils aus Figur 1, im Querschnitt;

Figur 3

ein umgeformten und gehärteten Bauteil zur Nachbearbeitung von Teilbereichen in Draufsicht;

Figur 4

eine erfindungsgemäße Vorrichtung in einer zweiten Ausführungsform zur Nachbehandlung des Bauteils aus Figur 3, schematisch in perspektivischer Darstellung;

Figur 5

ein umgeformtes und gehärtetes Bauteil zur Nachbearbeitung von Teilbereichen in Draufsicht;

Figur 6

eine erfindungsgemäße Vorrichtung in einer weiteren Ausführungsform zur Nachbehandlung des Bauteils aus Figur 5, im Querschnitt;

Figur 7

eine erfindungsgemäße Vorrichtung zum Nachbearbeiten von Teilbereichen eines umgeformten und gehärteten Bauteils in einer weiteren Ausführungsform in Draufsicht;

Figur 8

die Vorrichtung aus Figur 7 im Querschnitt durch ein erstes Paar von Formkontaktstücken;

Figur 9

die Vorrichtung aus Figur 7 im Querschnitt durch ein zweites Paar von Formkontaktstücken; und

Figur 10

das Bauteil aus Figur 7 mit nachbehandelten Teilbereichen in Draufsicht.

Preferred embodiments will be explained below with reference to the drawing figures. Hereby shows:

FIG. 1

a formed and hardened component for post-processing of partial areas in plan view;

FIG. 2

a device according to the invention in a first embodiment for the aftertreatment of the component FIG. 1 , in cross section;

FIG. 3

a formed and hardened component for post-processing of partial areas in plan view;

FIG. 4

a device according to the invention in a second embodiment for the aftertreatment of the component FIG. 3 schematically in perspective view;

FIG. 5

a deformed and hardened component for post-processing partial areas in plan view;

FIG. 6

a device according to the invention in a further embodiment for the aftertreatment of the component FIG. 5 , in cross section;

FIG. 7

a device according to the invention for reworking portions of a deformed and hardened component in a further embodiment in plan view;

FIG. 8

the device off FIG. 7 in cross-section through a first pair of mold contact pieces;

FIG. 9

the device off FIG. 7 in cross section through a second pair of mold contact pieces; and

FIG. 10

the component off FIG. 7 with post-treated parts in plan view.

The Figures 1 and 2 , which will be described below together, show a device 2 according to the invention for the post-treatment of a formed and hardened component 3, which is made of a metallic material, in a first embodiment.

The device 2 comprises a first pair of mold contact pieces 4, 5, which are designed as shaping electrodes for passing electrical current through a first portion 6 of the component 3. The contact surfaces 7, 8 of the mold contact pieces 4, 5, which may also be referred to as functional surfaces, are adapted to outer surfaces 9, 10 of the first portion 6. By this is meant that the geometry of the contact surfaces 7, 8 is designed opposite to the geometry of the first portion 6, in particular, different sheet thicknesses of the component can be considered by appropriate design of the mold contact pieces. The shaped electrodes 4, 5 are brought into surface contact with the component 3, which is clamped between an upper and a lower shaped electrode 4, 5. By closing the electrical circuit between the two formula electrodes 4, 5 electrical current is passed through the first portion 6, so that this portion 6 is heated due to the electrical resistance to a first temperature T1. The first portion 6 is in FIG. 1 hatched shown. The mold contact pieces 4, 5 have in plan view a corresponding to the contour of the first area designed contact surface.

A special feature of the present embodiment is that the component 3 is arranged in its thickness direction between the two mold contact pieces 4, 5. A lower mold contact piece 5 is brought into contact with the underside of the component 3, while an upper mold contact piece 4 is brought into contact with the upper side of the component. Thus, the component 3 is held or clamped between the mold contact pieces 4, 5. An undesirable delay due to the heating of the component can thus be avoided. The contact surfaces 7, 8 of the mold contact pieces 4, 5 of the first pair is preferably smaller than 400 mm ² for a good current introduction, wherein in principle even larger surfaces are conceivable. In the present embodiment, the electric current flows substantially perpendicular to the contact surface 7, 8, that is substantially in the thickness direction of the component 3. This results in a rapid heating.

Preferably, the first portion 6 is heated to a first temperature T1, which is at least 500 ° C, preferably at least 700 ° C. A maximum limit for the first temperature T1 may in particular be 900 ° C. The higher the temperature T1 is selected for heating the first portion 6, the shorter the exposure time can be selected, with which the component must be heated in order to achieve the desired softening. Preferably, the first portion 6 is heated over a period of at least 30 seconds, so that the formation of undesired hardness distortions is reduced. With regard to the relationships between temperatures for the respective duration of the heating to soften the first portions, preferred embodiments are given below without being limited thereto: at least 5 minutes holding time at up to 700 ° C; at least 2.5 minutes holding time at up to 750 ° C; at least 1.25 at up to 800 ° C Minutes of holding time; and at over 850 ° C at least 30 seconds holding time.

The device 2 further comprises a second pair of mold contact pieces 44, 45 for tempering a second portion 46 of the component 3 to a second temperature T2. Even with the second pair, the contact surfaces 17, 18 of the mold contact pieces 44, 45 are adapted to the outer surfaces 19, 20 of the second portion 46 accordingly. The mold contact pieces 44, 45 of the second pair are designed here as cooling contact pieces, with which the second portion 46 is adjustable to the temperature T2 below the temperature T1. For this purpose, the cooling contact pieces 44, 45 temperature adjusting, in particular with integrated Kühlkreiskäufen 22, 23 (shown in phantom) through which a cooling medium such as water or steam can be passed. The configuration as cooling contact pieces 44, 45 ensures that the heat introduced into the component 3 by means of the shaping electrodes 4, 3 remains spatially limited to the first portion 6 and only here leads to a softening, while the second portion 46 due to the cooling its Maintains initial strength. For cooling, the mold contact pieces 44, 45 of the second pair are preferably set to a temperature T2 of less than 300 ° C, more preferably of less than 200 ° C or even less than 100 ° C.

The mold contact pieces of the first pair (4, 5) and the second pair (44, 45) are made of a high-strength temperature-resistant material. In shape and size they are, as explained above, designed to be heated or to be cooled portions of the component. By the adjoining first mold contact pieces 4, 5 for heating and second mold contact pieces 44, 45 for cooling, a short transition region is advantageously realized between the softened first portion and the untreated second portion. The acted upon by electric current form contact pieces 4, 5 can be cooled to increase the service life.

The device may be constructed in two parts, and comprise a lower tool part, in each of which a first mold contact piece 5, 45 of the first and second pair are arranged, and an upper tool part, in each of which the corresponding second mold contact piece 4, 44 of the first and second pair are arranged. By moving the upper tool part in the direction of the lower tool part, or vice versa, the component 3 between the lower and upper mold contact pieces 5, 45; 4, 44 pinched. For moving the tool part, a suitable mechanism may be provided.

The FIGS. 3 and 4 , which will be described together below, show a device according to the invention in a second embodiment. This corresponds in terms of their design and operation in large parts of those according to the Figures 1 and 2 , so that reference is made to the above description in terms of similarities. The same or corresponding details are provided with the same reference numerals, as in the Figures 1 and 2 ,

A special feature of the present embodiment according to the FIGS. 3 and 4 is that four pairs of mold contact pieces are provided, it being understood that also a different number of two, three, five or more pairs can be used. The mold contact pieces of each pair 4, 5; 14, 15; 24, 25; 34, 35 are designed as shaping electrodes with which electrical current can be passed through the component 3. In this case, a first partial area 6 is heated by the first pair 4, 5, a second partial area 16 by the second pair 14, 15, a third partial area 26 by the third pair 24, 25 and a fourth partial area 36 by the fourth pair 34, 35 ,

The pairs of mold contact pieces can be individually controlled with regard to one or more parameters influencing the degree of heating, for example with regard to the current intensity or the energization duration. In this way, the various subregions 6, 16, 26, 36 can be heated individually. In this case, it is also possible in particular to take account of any existing differences in sheet thickness of the subregions, so that overall targeted heating and thus also defined defrosting is achieved.

The first pair of shaping electrodes 4, 5 may be heated to a first temperature T1 while the second pair of shaping electrodes 14, 15 may be heated to a different one second temperature T2 can be heated. Also, the third and fourth pairs of shaping electrodes 24, 25; 34, 35 can be individually controlled with respect to the desired temperature, and can be set to one of the temperatures T1 or T2, or deviating temperatures.

Incidentally, for each of the four pairs of the present embodiment, according to FIGS FIGS. 3 and 4 alike that in connection with the embodiment according to the Figures 1 and 2 For the first couple said. In this respect, reference is made in this regard to the above description.

The FIGS. 5 and 6 , which will be described together below, show a device according to the invention in a third embodiment. This corresponds in terms of their design and operation of a combination of embodiments according to the Figures 1 and 2 with the one according to the FIGS. 3 and 4 , so that reference is made to the above description in terms of similarities. The same or corresponding details are provided with the same reference numerals, as in the FIGS. 1 to 4 ,

A special feature of the present embodiment is according to the FIGS. 5 and 6 is that these four pairs of mold contact pieces 4, 5; 14, 15; 24, 25; 34, 35 which are designed as shaping electrodes and designed for heating or defrosting of the subregions 6, 16, 26, 36. It applies that in connection with the FIGS. 3 and 4 Said alike. In addition, a pair of mold contact pieces 44, 45 are provided, which are designed as cooling contact pieces, corresponding to the cooling contact pieces 44, 45 according to the Figures 1 and 2 , In this respect applies with respect to the cooling contact pieces in connection with the Figures 1 and 2 Said alike. Reference is made in this regard to the above description.

One advantage of the present embodiment is that only a small transition region is formed between the heated or softened partial regions 6, 16, 26, 36 and the cooled partial region 46. This is achieved in that the shaping electrodes 4, 5; 14, 15; 24, 25; 35, 36 on the one hand and the cooling contact pieces 44, 45 on the other hand spatially adjacent to each other.

The FIGS. 7 to 10 , which will be described together below, show a device according to the invention in a further embodiment. This corresponds in its design and operation in large parts of those according to the Figures 1 and 2 , so that reference is made to the above description in terms of similarities. The same or corresponding details are provided with the same reference numerals, as in the Figures 1 and 2 ,

A peculiarity of the present embodiment is that the mold contact pieces 4, 5 of the first pair are arranged opposite to each other in a transverse direction of the component 3 only in peripheral areas of the component 3. A between the negative shape electrodes 4, 4 'and the positive shape electrodes 5, 5 'flowing stream heats the component 3 across its width between the negative and positive electrodes. It results in total in FIG. 10 shown unbonded first portion 6, which is shown hatched.

Laterally adjacent to the mold contact pieces 4, 4 ', 5, 5' of the first pair, second pairs of mold contact pieces 44, 45; 54, 55 are arranged, one of which (44, 45) in cross section in FIG. 9 is shown. The mold contact pieces of the second pairs are each designed as cooling contact pieces. The cooling contact pieces 44, 45; 54, 55 are schematically in FIG. 7 shown. The cooling zones 46, 56, which of the cooling contact pieces 44, 45; 54, 55 are generated schematically in FIG FIG. 10 shown. Between the cooling zones 46, 56 is located in the transverse direction of the component 3 extending soft zone 6, which is also referred to as a deconsolidated portion.

In FIG. 9 It can be seen that the second pairs each have a lower mold contact piece 45 and an upper mold contact piece 44, which are each adapted to the geometry of the component 3 with regard to their shape. The second pairs of mold contact pieces 44, 45; 54, 55 correspond in terms of structure and operation in the Figures 1 and 2 shown embodiment, so that in this respect short-term reference is made to the above description. The second pair is arranged in the post-processing immediately adjacent to the first pair, so that the in FIG. 10 shown cooling zones 46, 56 with intermediate soft zone 6 of the component 3. Between the cooling zones 46, 56 and the soft zone 6 only small transition areas are formed.

The component 3, which is the lower part of a B-pillar for a motor vehicle, may have a uniform sheet thickness over the length and width, or it may have a variable sheet thickness over the length and / or width. This can be achieved for example by flexible rolling of the strip material used as the starting material. For a uniform heating or uniform softening, it is favorable if the first pair of molded contact pieces 4, 4 ', 5, 5' are arranged in a region of uniform sheet thickness. In the present case this would be the subarea 6.

A method according to the invention for the aftertreatment of a formed and hardened component from a metallic material may comprise the following steps.

In a first method step, a first partial region of the hardened component to be heated is brought into contact with the molded contact pieces of the first pair. At the same time or with a time delay, the mold contact pieces of a second pair are brought into contact with a second portion of the component. Subsequently, the first subregion of the component is heated to a first temperature T1 by passing electrical current through the component by means of the first pair of molded contact pieces. Preferably, the first portion is heated to a first temperature of at least 500 ° C, in particular at least 700 ° C, with a preferred heating time of at least 30 seconds.

Upon heating of the first portion, a second portion, which is in particular adjacent to the first portion, tempered by means of one or more second pairs of mold contact pieces to a second temperature T2, that is, heated or cooled. In this case, the tempering of the second partial region of the component takes place with regard to at least one parameter influencing the degree of heating, independently of the heating of the first partial region. In one embodiment, in which the second pair of mold contact pieces are designed as shape electrodes for resistance heating, the tempering (heating) can be done by selecting a different energizing time or other current than the first pair. In an embodiment in which mold contact pieces of the second pair are designed as cooling elements, the tempering (cooling) can take place by controlling the flow or the temperature of the cooling medium.

The described method can be combined with one of the devices for electrical resistance heating according to one of the FIGS. 1 to 10 having at least a first pair of mold contact pieces 4, 5 and a second pair of mold contact pieces 44, 45.

The above-described method for reworking the hardened component for producing softened partial areas or soft zones may be preceded, for example, by the following method steps: Flexible rolling of strip material; Working out a board from the flexibly rolled strip material, the board having a variable thickness over the length; Hot forming a board to the component; complete hardening of the component; Cleaning the component; and / or descaling the component.

An advantage of a device or method according to the invention is that the previously hardened component 3 can be specifically softened in partial regions 6, 16, 26, 36 in order to achieve a higher ductility here. By using a plurality of pairs of mold contact pieces, the ductility of the component can be adapted to the individual requirements in different partial areas, or the molded contact pieces themselves can be adapted to different requirements with regard to the geometry of the component.

LIST OF REFERENCE NUMBERS

2

contraption

3

component

4

Form contact piece

5

Form contact piece

6

first subarea

7

contact area

8th

contact area

9

surface

10

surface

14

Form contact piece

15

Form contact piece

16

second subarea

17

contact area

18

contact area

19

surface

20

surface

22

cooling channel

23

cooling channel

34

Form contact piece

35

Form contact piece

36

subregion

44

Form contact piece

45

Form contact piece

46

subregion

54

Form contact piece

55

Form contact piece

56

subregion

Claims (15)

1. Method for post-treating a formed and hardened component made of a metallic material by means of a device for electric resistance heating, which has at least one first pair of contact pieces (4, 5) and at least one second pair of contact pieces (14, 15; 24, 25; 34, 35; 44, 45; 54, 55), the method comprising the steps of:

   contacting the contact pieces (4, 5) of the first pair with a to be heated first partial region (6) of the component (3) such, that the to be heated first partial region (6) is arranged between the first pair of contact pieces (4, 5),

   contacting the contact pieces (14, 15; 24, 25; 34, 35; 44, 45; 54, 55) of the second pair with a second partial region (16, 26, 36, 46, 56) of the component (3) such, that the second partial region (16, 46, 56) is arranged between the second pair of contact pieces,

   heating the first partial region (6) of the component (3) to a first temperature (T1) of maximal 900°C by conducting electric current through the component (3) by the first pair of contact pieces (4, 5);

   setting the second partial region (16, 26, 36, 46, 56) of the component (3) to a second temperature (T2) by the second pair of contact pieces (14, 15; 24, 25; 34, 35; 44, 45; 54, 55), wherein the second temperature (T2) is set independently of the first temperature (T1).
2. Method according to claim 1,
   characterised in
   that the step of heating the first partial region (6) of the component (3) comprises at least one of the following:

   the first partial region (6) is heated to a first temperature (T1) of at least 500°C;

   the first partial region (6) is heated for a period of at least 30 seconds.
3. Method according to claim 1 or 2,
   characterised in
   that for the step of contacting at least one of the following applies:

   that an upper contact piece (4) of the first pair and an upper contact piece (14, 24, 34, 44, 54) of the second pair are brought into contact with the component (3) at the same time,

   that a lower contact piece (5) of the first pair and a lower contact piece (15, 25, 35, 45, 55) of the second pair are brought into contact with the component (3) at the same time.
4. Method according to any one of claims 1 to 3,
   characterised in
   that the first pair of contact pieces (4, 5) and the second pair of contact pieces (14, 15; 24, 25; 34, 35; 44, 45; 54, 55) are individually controlled concerning at least one parameter influencing the degree of heating.
5. Method according to any one of claims 1 to 4,
   characterised in
   that the step of setting the second partial region (16, 26, 36) of the component (3) to the second temperature (T2) is a heating process, which is achieved by conducting electric current from one of the second pair of contact pieces (14, 15; 24, 25; 34, 35) through the component (3) to another one of the second pair of contact pieces (15, 14; 25, 24; 35, 34).
6. Method according to claim 5,
   characterised in
   that for the step of heating the first partial region (6) and the second partial region (16, 26, 36) at least one of the following applies:

   electric current is conducted between the first pair of contact pieces (4, 5) and the second pair of contact pieces (14, 15; 24, 25; 34, 35) through the component (3) with a timely offset,

   electric current is conducted between the first pair of contact pieces (4, 5) and the second pair of contact pieces (14, 15; 24, 25; 34, 35) through the component (3) with at least a partial timely overlap,

   electric current is conducted between the first pair of contact pieces (4, 5) on the one hand and the second pair of contact pieces (14, 15; 24, 35; 34, 35) on the other hand through the component (3) with different electric currents.
7. Method according to any one of claims 1 to 4,
   characterised in
   that the step of setting the second partial region (46, 56) of the component (3) to a second temperature (T2) is a cooling process, which is achieved by cooling the contact pieces (44, 45; 54, 55) of the second pair.
8. Method according to any one of claims 1 to 7,
   characterised in
   that the first pair of contact pieces (4, 5) and the second pair of contact pieces (14, 15; 24, 25; 34, 35; 44, 45; 54, 65) are arranged directly next to each other respectively that they are brought into contact directly next to each other with the component (3).
9. Method according to any one of claims 1 to 8,
   characterised in
   that at least one of the following steps is provided before the post-treating:

   flexible rolling of strip material;

   cutting a blank from the flexible rolled strip material, wherein the blank has a varying thickness across the length;

   hot-forming of a blank to the component (3);

   complete hardening of the component (3);

   cleaning of the component (3),

   scaling the component (3).
10. Device for post-treating a formed and hardened component made from a metallic material, comprising:

    at least one first pair of contact pieces (4, 5), which are configured as form electrodes for passing electric current through a first partial region (6) of the component (3), wherein the contact faces (7, 8) of the contact pieces (4, 5) are adapted to the outer faces (9, 10) of the first partial region (6), wherein the first partial region (6) of the component (3) is heatable up to a first temperature (T1) by conducting electric current through the first partial region (6),

    at least one second pair of contact pieces (14, 15; 24, 25; 34, 35; 44, 45; 54, 55) for setting a second partial region (16, 26, 36, 46, 56) of the component (3) to a temperature, wherein the contact faces of the second pair of contact pieces are adapted to the outer faces of the second partial region (16, 26, 36, 46, 56), wherein a temperature setting mechanism is provided that is configured such that the second pair of contact pieces (14, 15; 24, 25; 34, 35; 44, 45; 54, 55) are adjustable to a second temperature (T2) different from the first temperature (T1).
11. Device according to claim 10,
    characterised in
    that the contact pieces (14, 15; 24, 25; 34, 35) of the second pair are configured as form electrodes for conducting electric current through the second partial region (16, 26, 36) of the component (3).
12. Device according to claim 10 or 11,
    characterised in
    that an electronic control unit is provided, that is configured to individually control the electric current through the form electrodes (4, 5) of the first pair on the one hand and through the form electrodes (14, 15; 24, 25; 34, 35) of the second pair on the other at least with respect to one parameter influencing the heating of the component (3).
13. Device according to any one of claims 10 to 12,
    characterised in
    that the form contact pieces (44, 45; 54, 55) of the second pair are formed as cooling contact pieces, that are configured to cool the second partial region (46, 56) to a second temperature (T2) below the first temperature (T1).
14. Device according to any one of claims 10 to 13,
    characterised in
    that means are provided with which at least the contact pieces (4, 5) of the first pair are movable towards each other, to contact an upper and a lower outer face (19, 20) of the component (3), and/or
    that means are provided with which at least the form contact pieces (4, 5) of the first pair are movable jointly, to contact an outer face (19, 20) of the component (3).
15. Device according to any one of claims 10 to 14,
    characterised in
    that the second partial region (16, 26, 36, 46, 56) of the component (3) is arranged next to the first partial region (6) and
    that the second pair of contact pieces (14, 15; 24, 25; 34, 35; 44, 45; 54, 55) is arranged next to the first pair of contact pieces (4, 5).

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