EP2239350A2 - Method for producing thermally treated sheet metal moulded parts from sheet metal material with an anti-corrosion coating and sheet metal moulded part - Google Patents

Abstract

The method comprises deforming a printed circuit board made of a heat-treatable steel sheet metal material (1) to a sheet metal molded part, where the printed circuit board has a corrosion-protective coating (12) applied on one side, and carrying out a heat treatment on the sheet metal molded part for changing the material properties of the steel sheet metal material. An oxide layer (13) forms on the corrosion-protective coating in an area-wise manner and defines itself during the heat treatment. The process is carried out, so that sufficient layer quality of the oxide layer is achieved. The method comprises deforming a printed circuit board made of a heat-treatable steel sheet metal material (1) to a sheet metal molded part, where the printed circuit board has a corrosion-protective coating (12) applied on one side, and carrying out a heat treatment on the sheet metal molded part for changing the material properties of the steel sheet metal material. An oxide layer (13) forms on the corrosion-protective coating in an area-wise manner and defines itself during the heat treatment. The process is carried out in such a way that a sufficient layer quality of the oxide layer is achieved with respect to subsequent coating and/or joining of the sheet metal molded part, so that the oxide layer remains onto the sheet metal molded part. The heat treatment step is a press hardening process. The sufficient layer quality of the oxide layer is achieved by selecting the steel sheet metal material, by selecting a deformation process and/or accompanying deformation-technical measures and by adjusting the process variables of the heat treatment, where the process variable is insertion temperature, furnace temperature, processing time, removal temperature, cooling time, pressing pressure and/or tool temperature. A further step such as chemical treatment, oiling, further heat treatment and/or removal of the sheet metal molded part follows the heat treatment step to achieve the sufficient layer quality of the oxide layer. The layer quality of the oxide layer is quantified based on a parameter, which gives the information about the layer quality of the oxide layer if the sheet metal molded part is subsequently coatable and/or joinable. The parameter is an electrical resistance value, conductive value, heat-conductive value, layer-thickness value of the oxide layer, roughness value of the oxide layer, adhesion value of the oxide layer, hardness value of the oxide layer, color value of the oxide layer and/or spectral value. One of the process steps is carried out and is optionally adapted, so that the parameter of the produced sheet metal molded part or the sheet metal molded part to be produced is present within a defined range to ensure that a defined mechanical material property of the sheet metal molded part is present within a defined range. The individual steps are defaultly carried out to obtain the sheet metal molded part with the sufficient layer quality of the oxide layer. The execution of one step is adapted during the process flow to obtain the sheet metal molded part with the sufficient layer quality of the oxide layer. The steps of the process flow are repeatedly carried out to produce the sheet metal molded parts, where the layer quality of the oxide layer of the produced sheet metal molded parts is determined and is optionally adapted based on the execution of one step of the process flow to obtain the sheet metal molded part with the sufficient layer quality. The produced sheet metal molded part is classified based on the layer quality of its oxide layer to release the sheet metal molded part for subsequent coating and/or joining and to bring post-processing or other use purpose. An independent claim is included for a sheet metal molded part.

Description

The invention relates to a method for the optimized production of heat-treated sheet metal parts from a steel sheet material, wherein the steel sheet material is provided with a corrosion protection coating, in particular with a metallic corrosion protection coating. The invention further relates to a sheet-metal shaped part made of a steel sheet material with a corrosion protection coating applied on at least one side, in particular with a substantially metallic corrosion protection coating, according to the preamble of the independent claim.

A sheet metal part in the sense of the invention is a three-dimensional component made from a flat sheet metal blank (blank) of a sheet steel material by deformation. This is preferably a component for a motor vehicle.

In particular, in the automotive industry increasingly heat-treatable steel sheet materials are used whose material properties and in particular mechanical material properties, such. the strength and / or hardness, are selectively changed by means of a heat treatment.

In order to prevent corrosion of sheet steel materials and / or the sheet metal parts produced therefrom, various corrosion protection coatings are known from the prior art. A common corrosion protection coating is e.g. formed by a metallic coating. The choice of an effective metallic corrosion protection coating requires the knowledge of the corrosion-chemical relationships.

Sheet steel materials with corrosion protection coating are typically not suitable for a heat treatment, since in this case the corrosion protection coating, for example can be damaged by evaporation, oxidation and / or scaling, especially if the heat treatment is carried out in high temperature ranges, for example above 400 ° C and sometimes even above 900 ° C.

From the DE 20 2004 021 264 U1 is a novel sheet steel material with a metallic anticorrosive coating or a metallic coating is known in which during heat treatment forms a protective protective layer on the metallic anti-corrosion coating, so that this steel sheet material is suitable for a heat treatment. This protective layer is essentially formed of oxides. The layer thickness of such a protective layer is, for example, 150 nm to 200 nm, and in some cases smaller layer thicknesses of approximately 100 nm were also measured.

Prior to further processing of a sheet-metal molded part produced and heat-treated from such a steel sheet material, this protective layer must be removed or removed at least in regions according to the current state of the art, in particular in those areas in which a coating and / or joining of the sheet metal part is intended below.

The DE 10 2007 022 174 B3 suggests for this purpose a cleaning of the sheet metal part with dry ice particles. Dry ice is carbon dioxide (CO ₂ ) in the solid state. The disadvantage of this is the high cost and high costs. Furthermore, it has been shown in practice that the removal of the protective layer by means of dry ice particles often does not achieve the quality required for subsequent production steps. In addition, depending on the ambient conditions, such as in particular humidity and temperature (dew point), come to the condensate on the sheet metal part, which is a corrosion problem. In addition, the use of dry ice from an environmental point of view seems increasingly questionable.

The Applicant has recognized that the protective layer can be removed in other ways from a manufactured and heat-treated sheet metal part, which is the subject of another invention. However, these measures are associated with effort and costs.

The object of the invention is to reduce the overall effort in the production of heat-treated sheet metal parts made of a steel sheet material with a corrosion protection coating, in particular with regard to a subsequent coating and / or joining these sheet metal parts.

This object is achieved by the method according to the invention with the features of claim 1. This object is further achieved by the sheet metal part according to the invention having the features of the independent claim. Advantageous and preferred developments and / or possible embodiments are the subject of the respective dependent claims.

To understand the invention is expressly to the documents mentioned DE 20 2004 021 264 U1 and DE 10 2007 022 174 B3 directed.

• Bereitstellen einer Platine aus einem wärmebehandelbaren Stahlblechmaterial, mit der wenigstens einseitig aufgebrachten Korrosionsschutzbeschichtung;
• Umformen dieser Platine zu einem Blechformteil;
• Ausführen einer Wärmebehandlung am Blechformteil, zur Veränderung der Werkstoffeigenschaften des Stahlblechmaterials, wobei sich während der Wärmebehandlung definiert und zumindest bereichsweise eine Schutzschicht auf der Korrosionsschutzbeschichtung ausbildet.

The inventive method according to claim 1 is used to produce heat-treated sheet metal parts with a corrosion protection coating. It includes (at least) the following steps:

• Providing a board made of a heat-treatable steel sheet material, with the at least one side applied corrosion protection coating;
• Forming this board to a sheet metal part;
• Performing a heat treatment on the sheet metal part, for changing the material properties of the steel sheet material, wherein defined during the heat treatment and at least partially forms a protective layer on the anti-corrosion coating.

According to the invention, it is provided that the method is carried out in such a way that a sufficient layer quality of the protective layer is achieved or achieved with regard to a subsequent coating and / or joining of the sheet metal part, so that the protective layer can remain on the sheet metal shaped part.

According to the invention, this can be done by setting the entire process sequence or process run (chronological execution of the individual steps) or individual steps and / or individual substeps in such a way that in the Result sufficient layer quality of the protective layer is achieved. "Adjustment" is understood to be a manual or automatic selection, modification and / or adaptation of at least one relevant influencing variable.

The individual steps and / or sub-steps of a method sequence can be executed immediately following one another or intermittently. An interruption is e.g. then given when the sheet metal part to be produced is stored temporarily after forming or transported to another processing location.

The inventive method is used to produce at least one heat-treated sheet metal part and preferably a plurality of heat-treated sheet metal parts, which are produced in particular by a repetitive execution of the procedure.

For the definition of a sheet metal part and the function of a corrosion protection coating, reference is made to the introductory explanations.

According to the method of the invention, it is provided that the anticorrosive coating is already formed on at least one side and preferably on both sides already on the provided steel sheet material or the blank cut therefrom. It is preferably provided that it is a substantially metallic corrosion protection coating in the form of a coating, which is formed in particular substantially of aluminum and / or zinc and / or their compounds. Such a metallic corrosion protection coating is applied, for example, by the manufacturer by means of a continuous hot-dip coating. Also in this regard is on the DE 20 2004 021 264 U1 and DE 10 2007 022 174 B3 directed. The thickness of the anticorrosive coating is preferably not more than 400 g / m ² , more preferably not more than 300 g / m ² and especially not more than 200 g / m ² . In particular, it is provided that the corrosion protection coating has a layer thickness of 7 to 14 microns.

A board is understood to mean a blank made from a steel sheet material provided. In the context of the method according to the invention, the blank can according to different specifications. Preferably, the finish cutting of the board is provided before forming, so that subsequently no further cutting operations are required. In contrast, it is possible to first produce a precut from the steel sheet material provided and to trim the sheet metal part after the forming and / or after the heat treatment.

The steel material of the sheet steel material from which the board is formed, is heat-treatable and curable in particular by a heat treatment. It is preferably provided that it is a 22MnB5 steel material or that the steel material is at least based thereon. This heat treatable steel material is particularly suitable for automotive body parts, with the term "22MnB5" being a group name of similar steel materials. Alternatively, a comparable steel material or a steel material group can be used, such. a 19MnB5.

The forming of the provided board to a sheet metal part is preferably carried out by deep drawing. For this purpose, a single drawing stage or several drawing stages may be provided. Alternatively, other forming methods are possible, such as e.g. a bending in the die, a folding and the like more.

A heat treatment is understood to mean measures for the defined setting of technological material properties and in particular the mechanical material properties of the steel sheet material (more precisely the steel material included herein) at elevated temperatures. Such mechanical material properties are e.g. elastic modulus, strength (tensile strength, shear strength, etc.), hardness, and the like. From the prior art, a variety of heat treatment measures for steel materials are known, such. Stress relieving, soft annealing, normalizing, annealing, recrystallization annealing, tempering, annealing, and the like.

The execution of the heat treatment on the sheet metal part takes place essentially after the forming. By "substantially" it is meant that carrying out the heat treatment also involves forming, in particular one final forming step such as a Kalibrierpressen, at least partially combined. Furthermore, it can be provided according to the inventive method to subject the already finished formed and heat-treated sheet metal part of a further heat treatment in order to selectively set other material properties, in particular mechanical material properties.

When carrying out the heat treatment and / or a further heat treatment (as explained above), a protective layer is formed on the anticorrosive coating of the steel sheet material and at least partially formed. This is in particular an oxide layer. This protective layer serves to protect the anticorrosive coating in order to protect it during the heat treatment, e.g. before evaporation, excessive oxidation and / or scaling, and optionally also a mechanical abrasion in the forming tool to protect.

Under a defined design of the protective layer is to be understood that it does not occur accidentally or as a by-product during the heat treatment and in particular during heating, but that provided with the anti-corrosion coating steel sheet material is designed specifically for this purpose, such as in the DE 10 2004 021 U1 or the DE 10 2007 022 174 B3 described. This protective layer consists, for example, substantially of oxides (eg, alumina, magnesia, calcia, titania, silica, boron trioxide, manganese oxide and / or the like), including any impurities resulting, for example, from the atmosphere and / or oiling of the board for forming ,

In order to be able to coat and / or add the heat-treated sheet-metal shaped part on which a protective layer has been formed in a subsequent production step, it is provided according to the invention that the method, ie at least one step or partial step, is carried out such that one sufficient layer quality of the protective layer with respect to this subsequent coating and / or joining of the sheet metal part is achieved or achieved, so that as a result the protective layer may remain on the sheet metal part.

A coating is understood to mean the application of a firmly adhering coating material to the sheet metal part. Coating is understood, in particular, as painting of the sheet-metal shaped part, wherein the applied lacquer layer may comprise a plurality of individual layers. Joining is understood to mean the materially bonded connection of the sheet metal part to another component. A cohesive Fügverbindung is in particular a welded joint, possibly also a solder joint or an adhesive bond. This does not exclude that the sheet metal moldings produced by the process according to the invention, at least in addition also by Fungemente elements, such as. Screws, rivets and the like, can be joined.

While it is indispensable in the prior art to remove the protective layer in order to coat and / or paste the produced and heat-treated sheet metal part, an essential idea of the invention is to dispense with removal of the protective layer and instead to permanently remove it leave the sheet metal part. For this, however, the protective layer must have a sufficient layer quality. The term "layer quality" summarizes various aspects (but at least one aspect), which may be relevant for a subsequent coating and / or joining. Such aspects are not exclusive to the protective layer alone, but may include other aspects such as e.g. Include the steel material of the steel sheet material, any intermediate layers, an adhesive effect and the like. By "sufficient" is meant that the layer quality of the protective layer satisfies at least a minimum requirement, whereby such a minimum requirement may also be a minimum requirement range.

This may well be the case that there are different requirements with respect to the subsequent manufacturing steps to the remaining on the sheet metal part protective layer and / or their protective layer quality. For example. could be the requirement that the protective layer must be relatively thin to allow welding and / or painting of the sheet metal part. On the other hand, there may be the requirement that the protective layer must be relatively thick, for. B. to improve a resulting corrosion protection effect. In such cases a compromise may have to be found.

The solution according to the invention has many advantages. An advantage is e.g. in the effort and cost savings achieved by eliminating the removal of the protective layer. The elimination of the removal of the protective layer may also have a positive effect on a subsequent manufacturing step, e.g. also simplify the linking of the production steps. Another advantage is e.g. to be seen in that it is possible to dispense with the environmentally hazardous dry ice, which has hitherto been used for removing the protective layer. Another advantage is the fact that the protective layer can have an additional corrosion protection effect for the sheet metal part. Furthermore, the sheet metal parts can be provided with a higher dimensional accuracy or component quality, since the removal of the protective layer can have an adverse effect on the dimensional stability. This list is not exhaustive.

According to a preferred embodiment, it is provided that the heat treatment is a hardening process in order to bring about a hardening and possibly also an increase in the strength of the steel sheet material. A hardening process comprises at least the substeps of heating and cooling, optionally quenching, the steel sheet material, whereby hardening and / or strength increase occurs according to the known mechanisms.

It is preferably provided that the heat treatment is a press hardening process in which the steel sheet material is converted and cured quasi in a combined step. This can be done, for example, by heating the steel sheet material to a temperature above the austenitizing temperature, usually at 870 ° C. or above 900 ° C., and then shaping it in a cold forming tool. The forming tool deforms the hot steel sheet material, which cools very quickly due to the surface contact with the forming tool, whereby a hardening and / or strength increase occurs. Alternatively, the steel sheet material may first be cold formed and the sheet metal preform already preformed in this manner may finally be subjected to a press hardening process in which it is calibrated for dimensional accuracy, for example. As already explained above, a further heat treatment can be provided below. Such a further heat treatment is for example an annealing.

The protective layer and the layer quality which occur during the heat treatment and in particular during hardening or press-hardening can be influenced by adjusting and, in particular, adjusting the method sequence, a single step and / or a partial step of the method according to the invention. This can e.g. take place according to the measures explained in more detail below, which are also the subject of preferred developments.

According to a preferred development, it is provided that the sufficient layer quality of the protective layer (with regard to a subsequent coating and / or joining) is achieved by selecting a steel sheet material. This can e.g. by selecting a steel material including its alloying elements and / or the sheet thickness, as well as by selecting the corrosion protection coating and / or their layer thickness. This has an influence on the layer quality of the protective layer obtained.

According to a preferred embodiment, it is provided that the sufficient layer quality of the protective layer (with regard to a subsequent coating and / or joining) is achieved by selecting a forming process and / or at least one accompanying forming-technical measure. Thus, e.g. between cold working or hot working, where influence on the protective layer formation and the layer quality during the subsequent heat treatment can be taken. Accompanying forming measures are e.g. the application and optionally the removal of a lubricant, which may be e.g. the selection of the lubricant and / or the amount of lubricant can influence the protective layer formation and layer quality during the subsequent heat treatment.

According to a preferred development, it is provided that the sufficient layer quality of the protective layer (with regard to a subsequent coating and / or joining) is achieved by setting at least one process variable of the heat treatment, which is in particular a hardening process. A process variable is any factor that can be used to influence the protective layer formation and the layer quality during the heat treatment. Under "Setting" becomes a manual or automatic Changing and especially adapting these process variables with regard to an optimal protective layer formation and layer quality understood.

It is preferably provided that this process variable is an insertion temperature, the furnace temperature, the furnace atmosphere, the passage time, a removal temperature, a cooling time (possibly also a special atmosphere during cooling), the pressure and / or the tool temperature. This is to be understood in detail: the insertion temperature of the sheet metal part and / or the board in the furnace, the furnace temperature of the furnace, the particular chemical composition of the furnace atmosphere (eg inert gas atmosphere), the transit time of the sheet metal part and / or the board through the heater, the Withdrawal temperature of the sheet metal part and / or the board from the heating furnace, the free cooling time and / or the guided cooling time after removal of the sheet metal part from the forming tool, the pressing pressure during press hardening, the mold temperature of the forming tool during press hardening, the removal temperature of the sheet metal part after press hardening and / or a free cooling time between two steps of the heat treatment. Of course, this is not an exhaustive list. Thus, e.g. also by selecting a cooling medium, e.g. of a gas or oil, and whose temperature is influenced by the protective layer formation and the layer quality.

Furthermore, e.g. by cleaning and, in particular, washing of the sheet-metal part prior to the heat treatment, which in particular results in the removal of dirt and oil residues, e.g. from the forming process, influence on the layer quality of the protective layer can be taken. Optionally, at this point, by an opposite measure, i. the application of a specific lubricant or the like, influence on the layer quality are taken. Likewise, it is possible first to clean and then apply a coating, in particular oiling, to the sheet metal part.

Furthermore, an intermediate storage of the steel sheet material and / or the sheet metal part between the individual steps of the method according to the invention and / or individual partial steps can influence the layer quality of the Protective layer are taken. During a temporary storage, for example, relevant aging processes can take place.

According to a preferred embodiment, it is provided that the heat treatment is followed by at least one further step in order to achieve a sufficient layer quality of the protective layer (with regard to a subsequent coating and / or joining of the sheet metal part).

It is preferably provided that this further step is a chemical treatment, a precoating, a further heat treatment and / or an aging of the sheet metal part. A chemical treatment is e.g. a leaching or etching of the sheet metal part. A precoating can be carried out with one or more different coating materials, which are to be selected according to the subsequent coating and / or joining of the sheet metal part. Such a precoating can in particular also be oiling or back-oiling of the heat-treated sheet metal part. This may well be the case that a pre-coating before coating and / or joining is to be removed again. Another heat treatment is e.g. a tempering of the heat-treated sheet metal part. An outsourcing is understood as an intermediate storage of the sheet metal part before coating and / or joining. Aging processes can occur during the storage period, which can influence the coating quality of the protective layer. Swapping may also be done under altered atmospheric conditions, e.g. in an active or inert atmosphere, which may also affect the coating quality of the protective layer. Such a further step may e.g. also be a cleaning and washing of the sheet metal part in particular, which serves in particular the removal of dirt and oil residues. These measures can also be combined with each other.

According to a preferred development, it is provided that the layer quality of the protective layer is quantified on the basis of at least one parameter which provides information as to whether the sheet metal part is subsequently coated and / or joined. In this case, it may be the case that different parameters for coating and joining are to be determined. Such a quantified parameter should be reliable and can be determined by measurement or determined and / or also be determined by estimation. The layer quality of the protective layer is preferably determined on the basis of several parameters. Such a parameter is preferably determined at the end of the manufacturing process and / or on the finished sheet metal part and before the subsequent coating and / or joining. Alternatively and / or additionally, it is possible to predict such a parameter during the course of the process for the sheet metal part to be produced and, based thereon, to intervene in the method sequence, eg according to one of the above-explained measures, in order to obtain a sheet metal part with a sufficient layer quality of the protective layer. This will be explained in more detail below.

It is preferably provided that this parameter is an electrical resistance value, a sound conduction value, a heat conduction value, a layer thickness value of the protective layer, a rough value of the protective layer, a adhesion value of the protective layer, a hardness value of the protective layer, a color value of the protective layer and / or a spectral value. This is not an exhaustive list. Each of these values can be determined manually or automatically. In the following, possibilities for determining these values are shown.

An electrical resistance value, a sound conduction value and a heat conduction value can be determined, for example, by placing measuring sensors, wherein the determined or determined value need not relate exclusively to the protective layer. A layer thickness value of the protective layer can be determined, for example, by contactless means of X-ray or ultrasound measurement. A rough value of the protective layer can be determined tactilely and / or without contact by appropriate measuring devices. An adhesion value of the protective layer may be determined, for example, by means of an adhesive tape peeling test. A hardness value of the protective layer can be determined, for example, by means of a scratch test. A color value of the protective layer can be evidently determined eg by comparison with color charts. A color value can also be determined, for example, by means of incident light measurement. The determined or determined color value can also be influenced by the anti-corrosion coating underneath the protective layer. A spectral value can be determined by spectral analysis, which need not be limited to the protective layer.

It is preferably provided that at least one of the above-mentioned steps of the method according to the invention is carried out and optionally adjusted such that the parameter for the layer quality of the protective layer of the produced or produced sheet metal part is at least within a defined range, wherein it must be ensured at least one defined mechanical material property of the sheet metal part is at least within a defined range. A defined area can be closed or open on one side. By "at least" is meant that instead of a defined area, a single value may be given, which is to be corresponded.

This is to be understood as meaning that the setting and, in particular, adaptation of individual steps and / or sub-steps of the method according to the invention, e.g. by means of the above-described measures, not to the detriment of the obtained mechanical material properties of the produced or manufactured sheet metal part may take place. In particular, the mechanical material properties to be set by means of the heat treatment, such as e.g. hardness and / or strength, meant. This is based on the idea that one or more process windows can be defined for the entire process sequence, individual steps and / or individual substeps, within which only adjustments and in particular adjustments can be made, with respect to the mechanical material properties and the layer quality of the protective layer To get good part.

According to a preferred development, it is provided that the individual steps of the method according to the invention are carried out in a preset manner, in order to obtain a sheet-metal shaped part with a sufficient layer quality of the protective layer. This also includes all sub-steps of a step. The setting is preferably carried out within predetermined limits (process window), for which reference is made to the explanations in the preceding paragraph. The presettings are made once, for example when the sheet steel material is supplied, and remain without intervention and / or regulation. This presetting can be based, for example, on empirical values or on estimates or forecasts and is based, for example, on the steel sheet material provided (eg the thickness of the Steel sheet material, the steel material, the material and the thickness of the anticorrosive coating) and / or its Grundöölung (eg the amount and / or the type of lubricant), as well as other information and / or values, which can be detected manually and / or automatically. The desired or to be obtained layer quality is preferably measured using a parameter that must be at least within a defined range, as explained above.

According to another preferred embodiment, it is provided that the execution of at least one step (or a substep) during the process sequence of the method according to the invention is adapted to obtain a sheet metal part having a sufficient layer quality of the protective layer. This adjustment can e.g. take place in a direct control loop, for which purpose at least one actual variable is detected during the course of the method, on the basis of which an automatic adaptation of individual steps or even individual partial steps takes place. This adaptation preferably takes place within predetermined limits (process window), for which reference is made to the preceding explanations in this regard. The actual quantity can be any meaningful statement and / or any meaningful value that is suitable for being automatically recorded and evaluated and that has some correlation with the quality of the shift. The desired or to be obtained layer quality is preferably measured using a parameter that must be at least in a defined range, as explained above.

According to another preferred embodiment, it is provided that the steps of a process sequence are carried out repeatedly to produce a plurality of sheet metal parts, wherein at least randomly the layer quality of the protective layer of a manufactured sheet metal part is determined and optionally based on the execution of at least one step (or substep) of a subsequent procedure is adapted to subsequently obtain a sheet metal part having a sufficient layer quality of the protective layer (good part). The layer quality of the produced sheet metal part is preferably based on a parameter (possibly also several parameters) sized, which must be within a defined range, as explained above. The parameter is preferably determined automatically, whereby a manual determination is possible. The on the Determining the layer quality of the sheet metal part produced based adjustment of a subsequent process flow, which is preferably the immediately following process flow, takes place in particular in a control loop, in contrast to the control circuit explained in the preceding paragraph, the actual size is determined by the process flow and thus only can be used to customize a subsequent procedure.

According to a preferred development, it is provided that a produced sheet-metal part is classified on the basis of the layer quality of its protective layer in order to release it for subsequent coating and / or joining, to supply it to a post-processing or to supply it to another intended use. Depending on the classification, a separation of a manufactured sheet metal part may also be required. The classification with respect to the layer quality is preferably carried out manually or automatically, e.g. on the basis of at least one parameter, for which reference is made to the above explanations. One possible post-processing is e.g. in it, individual steps and / or sub-steps of the method according to the invention with the sheet metal part concerned, if necessary, manually re-execute.

According to a preferred development it is provided that a computer-based and / or PLC-based process control takes place.

The shaped sheet metal part according to the invention is formed from a steel sheet material having a corrosion protection coating applied at least on one side, wherein a defined protective layer is formed on this corrosion protection coating at least in regions as a result of a heat treatment. According to the invention it is provided that this protective layer remains permanently on the sheet metal part.

The anticorrosive coating is formed in particular of a metallic material, for which reference is made to the above explanations. The protective layer is in particular an oxide layer, to which reference is likewise made to the above explanations. The sheet metal part according to the invention is produced in particular by the process according to the invention.

According to a preferred embodiment, it is provided that this sheet metal part is coated with the protective layer and / or joined. In particular, this sheet metal part is joined to at least one other component, in particular sheet metal part, to form a composite part and, for. involved in a bodywork for a motor vehicle. A joining of the sheet metal part is preferably cohesively, as explained above. Alternatively and / or additionally, the sheet metal part may also be provided by means of friction elements, such as e.g. Screws, rivets and the like be joined.

According to a preferred embodiment, it is provided that this sheet metal part is a body component or a body component for a motor vehicle. A body component is in particular a structural component. A body attachment is e.g. a bumper beam or the like.

The shaped sheet metal part according to the invention can be developed analogously according to the features explained above in connection with the method according to the invention.

Fig. 1

einen Schnitt durch das Stahlblechmaterial eines nach dem erfindungsgemäßen Verfahren hergestellten und wärmebehandelten Blechformteils;

Fig. 2

das erfindungsgemäße Verfahren in einer bevorzugten Ausführungsmöglichkeit, in einer schematischen Übersicht; und

Fig. 3

die anschauliche Darstellung eines Prozessfensters zur Herstellung von Gutteilen nach dem erfindungsgemäßen Verfahren.

The invention will be explained in more detail by way of example with reference to the figures. Show it:

Fig. 1

a section through the steel sheet of a produced and heat treated sheet metal molding according to the inventive method;

Fig. 2

the inventive method in a preferred embodiment, in a schematic overview; and

Fig. 3

the graphic representation of a process window for the production of good parts by the method according to the invention.

Fig. 1 shows a section through the steel sheet 1 of a sheet metal molding produced according to the inventive method after a heat treatment and in particular after a press hardening process, as in the following in connection with Fig. 2 explained. The steel sheet material 1 comprises a heat-treatable or hardenable steel material (substrate) 10, the manufacturer with a one-sided applied corrosion protection coating 12th is provided. This corrosion protection coating 12 may also be applied to the steel material 10 on two sides. It is particularly preferred that the steel material 10 is a 22MnB5. The anticorrosive coating 12 is particularly preferably formed essentially of zinc or a zinc compound, possibly plus an iron and / or aluminum content and further constituents. Between the anticorrosive coating 12 and the sheet steel material 10, a non-illustrated inhibiting layer 11 or an inhibiting layer mechanism may be formed, as in DE 10 2007 022 174 B3 described.

During the heat treatment, a protective layer 13 has been formed on the anticorrosion coating 12 in a defined manner. This protective layer 13 consists of oxides, such as aluminum oxide, which has formed during the heat treatment essentially of a minor aluminum content in the anti-corrosion coating 12, as for example in the DE 20 2004 021 264 U1 is described. In addition, the protective layer 13 also comprises other constituents, in particular impurities.

Both the anticorrosion coating 12 and the protective layer 13 have cracks 14 and 15 due to the heat treatment. In addition, 13 cavities 16 may be formed between the anti-corrosion coating 12 and the protective layer. This may, inter alia, cause a poor adhesion of the protective layer 13 to the anti-corrosion coating 12, which is why the protective layer 13 according to the prior art, in particular with regard to a subsequent coating and / or joining of the sheet metal part, to remove, but this is associated with various disadvantages , as explained above. As a remedy, the method according to the invention is proposed.

Fig. 2 gives an overview of the inventive method according to a preferred embodiment. The overview comprises six process steps I to VI, wherein the first process step I and the last process step VI essentially serve to illustrate, and are not relevant components of the inventive method. The inventive method can also not shown and not further explained below intermediate and sub-steps include.

The method begins in step II with the provision of a cut-to-size board 2 made of a heat-treatable sheet steel material 1 with a corrosion protection coating 12 applied at least on one side. The steel sheet material 1 is removed in step I, e.g. provided in the coil or in the stack.

To form a sheet metal part 3, the board 2 is subjected to cold forming in step III in a deep drawing process. This cold working can take place in several drawing stages. The final geometry of the sheet metal part 3 to be produced is in this case e.g. formed with a dimensional accuracy of about 95% or greater. Alternatively, this forming of the board 2 to a sheet metal part 3 can also be done differently.

The forming is followed in step IV by a press hardening process in which the steel sheet material 1 is hardened and the sheet metal shaped part 3 is quasi calibrated simultaneously to 100% dimensional accuracy. Here, a protective layer 13 is formed on the anticorrosive coating 12 of the sheet steel material 1, as in FIG Fig. 1 shown. The formation of this protective layer 13 is material already predisposed in the delivered steel sheet material 1.

The press hardening process in step IV comprises various sub-steps, which are not explained in detail here. Such a sub-step is, for example, the heating of the sheet metal part 3 in a continuous furnace. Alternatively, steps III and IV can also be summarized, which is represented by a binding clip. Thus, for example, the board 2 can first be heated and then formed in a cool forming tool and simultaneously cooled or even quenched, whereby a hardening and possibly also increasing the strength of the steel sheet material 1 (strictly speaking, the steel material 10) occurs. Instead of a press hardening process, the sheet metal part 3 may also be subjected to another heat treatment. Furthermore, the press hardening process can optionally be followed by a further heat treatment of the sheet metal part 3, such as tempering.

According to the invention, it is provided that the method, and in particular at least one of the steps II, III or IV, is carried out in such a way that a sufficient layer quality of the protective layer 13 is achieved with respect to a subsequent coating and / or joining of the sheet metal part 3, so that the protective layer 13 can remain on the sheet metal part 3. This is to be seen against the background that according to the prior art, the mandatory removal of such a protective layer 13 is provided to coat the sheet metal part 3 and / or add.

A protective layer 13 having a sufficient layer quality in this sense is e.g. from, by low cracking, good adhesion to the anticorrosive coating 12, proper thickness and / or density, beneficial surface roughness, composition and the like. (Thus, for example, a "rough" surface of the protective layer 13 may be advantageous for subsequent bonding.) A small thickness of the protective layer 13 may be advantageous, for example, for subsequent painting and / or welding.)

This sufficient layer quality of the protective layer 13 is preferably achieved by adjusting and, in particular, adjusting the method sequence, individual steps and / or substeps. Thus, e.g. in the steps I and / or II by the selection of a steel sheet material 1, which includes the selection of a steel material 10 and / or the selection of a corrosion protection coating 12, influence on the layer quality of the protective layer 13. In step III, it is possible to influence the layer quality of the protective layer 13 by selecting a forming process and / or at least one accompanying shaping-technical measure. In step IV, by adjusting at least one process variable of the press hardening process, or an accompanying measure such as e.g. a previous washing, influence on the layer quality of the protective layer 13 are taken. In this regard, reference is made in detail to the above detailed explanations.

In order to obtain a sufficient layer quality of the protective layer 13, a further optional step V may be required. This further step V can be, for example, a chemical treatment, a precoating, another Heat treatment and / or aging of the heat-treated sheet metal part 3, as explained above.

If a finished sheet metal part 3 does not have sufficient layer quality, a post-processing of the relevant sheet metal part 3 is optionally provided or optionally also the supply to another use or a separation. A corresponding assignment may e.g. by classifying the layer quality. The layer quality of the protective layer 13 of a sheet metal molding 3 may be e.g. be quantified by at least one determinable parameter, e.g. Information about whether the sheet metal part 3 is subsequently coated and / or available. Also in this regard, reference is made to the above detailed explanations.

Thereafter, the finished and heat treated sheet metal part 3 'may be coated (e.g., painted) and / or joined (e.g., welded) in step VI without removing the protective layer 13, thereby saving effort, energy and cost. This coating and / or joining of the produced sheet metal part 3 'is not a relevant part of the method according to the invention. Nevertheless, the method according to the invention serves to enable this subsequent coating and / or joining of the sheet metal shaped part 3. Furthermore, within the scope of the invention, it can definitely be provided that a parameter (or several parameters) representing the layer quality and / or a classification of the layer quality of a produced sheet metal part 3 'is used in a subsequent coating and / or joining in order to achieve this subsequent production step to be able to optimally design the protective layer that has not been removed. This can optionally be done individually for each sheet metal part or for a group or series of sheet metal parts.

The inventive method can be carried out once for the production of a heat-treated sheet metal part 3 or repetitive to produce a plurality of such sheet metal parts 3. In this case, there is the possibility that the individual steps, in particular the steps II to V, are carried out as a preset in order to obtain a sheet-metal shaped part 3 with a sufficient layer quality. It is also possible that the execution of at least one step is adjusted during the process flow to obtain a sheet metal part 3 with a sufficient layer quality. This can be done eg in a control loop. Furthermore, there is the possibility that the layer quality of a manufactured sheet metal part 3 'is determined at least randomly and, if appropriate, based on this, the execution of at least one step of a subsequent process sequence is adapted to subsequently obtain a sheet metal part 3 with a sufficient layer quality (good parts). This can also be done in a control loop, for example. The setting or presetting and in particular adjustment can be made manually or automatically. With regard to preferred measures for adjusting the procedure, individual steps and / or sub-steps, reference is made to the preceding explanations.

If necessary, it may be considered that setting and in particular adjusting the method sequence, individual steps and / or partial steps in order to achieve a sufficient layer quality of the protective layer 13 must take place within one or more process windows, so that at least one defined mechanical material property of the Sheet metal part 3 is located within a defined range. This is schematically in the Fig. 3 shown. The rectangular frame represents a manufactured sheet metal part 3, which is produced by the process according to the invention. This sheet metal part 3 is determined inter alia by its mechanical material properties, such as hardness, modulus of elasticity, strength and the like, and by the layer quality of the protective layer 13. The left ellipse A represents a set of adjustment and adaptation possibilities in the process sequence with regard to the mechanical material properties of the sheet metal part 3 to be produced. The right ellipse B represents a set of adjustment possibilities in the process sequence with regard to the layer quality of the protective layer 13 to be achieved Production of a good part, with regard to the mechanical material properties and the layer quality of the protective layer 13, however, only those adjustment and adjustment options can be used that are within the intersection C.

LIST OF REFERENCE NUMBERS Process for the preparation of heat-treated sheet metal parts from a steel sheet material with a corrosion protection coating and such sheet metal part

1

Sheet steel material (with corrosion protection coating)

10

Steel material (substrate)

11

baffle

12

Anticorrosion coating

13

protective layer

14

Crack

15

Crack

16

cavity

2

Board (cut)

3, 3 '

Sheet metal part

A

Adjustment and adjustment options (material properties)

B

Adjustment and adjustment options (shift quality)

C

intersection

I

first step - providing sheet steel material

II

second step - crop board / deploy circuit board

III

third step - reshape

IV

fourth step - press hardening

V

fifth step - optional step

VI

sixth step - coating and / or joining

Claims (18)

Process for producing heat-treated shaped sheet metal parts (3) with a corrosion protection coating (12), in particular a substantially metallic corrosion protection coating, comprising the steps: - Providing a board (2) made of a heat-treatable steel sheet material (1), with the at least one side applied corrosion protection coating (12); - Forming this board (2) to a sheet metal part (3); - Performing a heat treatment on the sheet metal part (3), for changing the material properties of the steel sheet material (1), wherein defined during the heat treatment and at least partially a protective layer (13), in particular an oxide layer, on the corrosion protection coating (12) is formed; characterized in that
the method is carried out such that a sufficient layer quality of the protective layer (13) with respect to a subsequent coating and / or joining of the sheet metal part (3) is achieved, so that the protective layer (13) can remain on the sheet metal part (3). Method according to claim 1,
characterized in that
the heat treatment is a hardening process and in particular a press hardening process. Method according to claim 1 or 2,
characterized in that
the sufficient layer quality of the protective layer (13) is achieved by selecting a sheet steel material (1). Method according to one of the preceding claims,
characterized in that
the sufficient layer quality of the protective layer (13) is achieved by selecting a forming process and / or at least one accompanying shaping measure. Method according to one of the preceding claims,
characterized in that
the sufficient layer quality of the protective layer (13) is achieved by adjusting at least one process variable of the heat treatment. Method according to claim 5,
characterized in that
this process variable is an insertion temperature, the furnace temperature, the furnace atmosphere, the lead time, a bleed temperature, a cool down time, the press pressure, and / or the tool temperature. Method according to one of the preceding claims,
characterized in that
the heat treatment is followed by at least one further step in order to achieve a sufficient layer quality of the protective layer (13). Method according to claim 7,
characterized in that
the further step is a chemical treatment, a precoating, in particular oiling, a further heat treatment and / or an aging of the sheet metal part (3). Method according to one of the preceding claims,
characterized in that
the layer quality of the protective layer (13) is quantified on the basis of at least one parameter, which provides information as to whether the shaped sheet metal part (3) is subsequently coated and / or joined. Method according to claim 9,
characterized in that
the parameter is an electric resistance value, a sound conduction value, a heat conduction value, a layer thickness value of the protection layer (13), a rough value of the protection layer (13), a adhesion value of the protection layer (13), a hardness value of the protection layer (13), a color value of the protection layer (13 ) and / or a spectral value. Method according to claim 9 or 10,
characterized in that
at least one of the above-mentioned steps is carried out and optionally adapted such that the parameter of the produced or manufactured sheet metal part (3) is at least within a defined range, it being ensured that at least one defined mechanical material property of the sheet metal part (3) at least within a defined range. Method according to one of the preceding claims,
characterized in that
the individual steps are carried out as a preset in order to obtain a sheet-metal shaped part (3) with a sufficient layer quality of the protective layer (13). Method according to one of the preceding claims 1 to 11,
characterized in that
the execution of at least one step during the process is adapted to obtain a sheet metal part (3) with a sufficient layer quality of the protective layer (13). Method according to one of the preceding claims 1 to 11,
characterized in that
the steps of a process sequence are repeated to produce a plurality of sheet metal parts (3), wherein the layer quality of the protective layer (13) of a produced sheet metal part (3) is determined at least randomly and, if appropriate, the execution of at least one step of a subsequent process sequence is adjusted based on this to obtain below a sheet metal part (3) with a sufficient layer quality. Method according to one of the preceding claims,
characterized in that
a manufactured sheet metal part (3) is classified on the basis of the layer quality of its protective layer (13) in order to release it for subsequent coating and / or joining, to feed it to a post-processing or to feed it to another intended use. Sheet metal part (3) made of a steel sheet material (1) with a corrosion protection coating (12) applied on at least one side, in particular with a substantially metallic corrosion protection coating, in particular produced by a process according to one of the preceding claims, wherein at least on this corrosion protection coating (12) as a result of a heat treatment in regions a defined protective layer (13), in particular an oxide layer, is formed,
characterized in that
this protective layer (13) permanently on the sheet metal part (3) remains. Sheet metal part (3) according to claim 16,
characterized in that
this is coated and / or joined to the protective layer (13). Sheet metal part (3) according to claim 16 or 17,
characterized in that
this is a body component or a body attachment for a motor vehicle.

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