Method for determining structural transformations and / or structure types and / or characteristics of a material of a workpiece, and device for said method

Abstract

The invention relates to a method for determining at least one structural transformation and / or at least one structure type of a material of a workpiece (102) and / or for determining at least one characteristic of the material of the workpiece (102), having the following steps: - thermally treating the workpiece (102) by supplying the workpiece (102) with low-temperature heat and / or high-temperature heat; and / or - pressing an indentation element (110) into the surface (112) of the workpiece (102), preferably with a static press-in force (Fe), in order to plastically deform the workpiece (102) by means of the indentation element (110) in order to produce a plastically deformed workpiece indentation (116) prior to and / or during and / or after the step of thermally treating the workpiece (102). The invention also relates to a device (100, 200) for determining at least one structural transformation and / or at least one structure type of a material of a workpiece (102) and / or for determining at least one characteristic of the material of the workpiece (102).

Description

[0001] Method for determining structural transformations and / or structural types and / or material parameters of a material of a workpiece and device therefor

[0002] The present invention relates to a method and a device for determining at least one microstructural transformation and / or at least one microstructure type of a material of a workpiece and / or a method and a device for determining at least one material characteristic of the material of the workpiece.

[0003] The methods and devices disclosed in the prior art for determining microstructural transformations or microstructure types as a result of heat treatments of materials (e.g. dilatometers) and / or for determining at least one material characteristic of a material (e.g. so-called indentation devices) are still expensive, time-consuming and complex in sample production and process control.

[0004] Such devices and methods are already known from the state of the art.

[0005] For example, DE 102011115519 A1 discloses a generic method and a generic device for determining at least one material characteristic of a material using an indentation device or an associated indentation method. However, DE 102011115519 A1 does not disclose the determination of microstructural transformations or microstructure types of materials as a result of heat treatment.

[0006] The present invention is therefore based on the object of providing, in particular, a method and a device for determining at least one microstructural transformation and / or at least one microstructure type of a material of a workpiece and / or for determining at least one material characteristic of the material of the workpiece, which are preferably more cost-effective, faster and easier to handle.

[0007] This object is achieved according to the invention by the features of independent claim 1. Advantageous developments of the invention are described in the dependent claims.

[0008] A method according to the invention can be configured to determine at least one microstructural transformation of a material of a workpiece. Additionally or alternatively, this method can be configured to determine at least one microstructure type of the material of the workpiece.

[0009] Additionally or alternatively, this method can be configured to determine at least one material characteristic of the material of the workpiece.

[0010] In its most general form, this process includes the following steps:

[0011] First, the workpiece is preferably subjected to heat treatment by applying high-temperature heat to the workpiece.

[0012] Additionally or alternatively, the workpiece can also be exposed to low-temperature heat.

[0013] Additionally or alternatively, an indentation body may be pressed into a surface of the workpiece for plastically deforming the workpiece by means of the indentation body to produce a plastically deformed workpiece indentation during the step of heat treating the workpiece.

[0014] The pressing of the indenter into the surface of the workpiece can be carried out additionally or alternatively after the step of heat treatment of the workpiece.

[0015] Additionally or alternatively, it may also be conceivable that the indentation body is pressed into the surface of the workpiece before the step of heat treatment of the workpiece.

[0016] The pressing of the indentation body into the surface of the workpiece can preferably be carried out with a static pressing force.

[0017] In its most general form, the material of the workpiece can be a ductile, preferably metallic, material that allows reproducible and defined plastic deformation (for example, with several indentation processes at different positions on the surface of the workpiece).

[0018] A material can be considered ductile if it can undergo permanent plastic deformation under shear stress before fracture or macroscopic separation. A material parameter that characterizes ductility is the so-called elongation at break, which can preferably range from approximately 0.1% to approximately 30%.

[0019] Metals can preferably be aluminum, iron, titanium, or magnesium. Furthermore, it can be advantageous if the metals are not present in pure form, but rather in the form of metal alloys such as aluminum alloys, iron alloys such as steel or cast iron, titanium alloys, or magnesium alloys.

[0020] The following steel alloys should preferably be used: unalloyed steels, alloyed steels or stainless steels.

[0021] Steel alloys can be further divided according to their function into: structural steel, case-hardening steel, tempering steel, nitriding steel, tool steel, stainless steel or acid-resistant steel.

[0022] Metallic materials or metal-based alloys (which are the main focus of this invention) generally have a crystalline structure, whereby the microstructure, in other words, characterizes the microstructural crystalline structure.

[0023] A microstructure of a metallic material thus characterizes the nature of the sum of all delimited partial volumes (e.g. by a grain or phase boundary), of which each partial volume is approximately homogeneous in terms of its composition and spatial arrangement.

[0024] A microstructure can be characterized by the shape, size, distribution and orientation of the microstructure components (crystallites or grains, fillers and amorphous regions).

[0025] In metal alloys (i.e., a metallic material that is at least macroscopically homogeneous and composed of at least two mixed alloying elements), the partial volumes of the at least two structural components can also be referred to as so-called phases. In this case, these phases can comprise one or the other alloying element, or contain a mixture of both alloying elements.

[0026] Within the scope of this invention, a microstructure can therefore refer to the defined subvolumes of a material that are similar to each other in terms of composition and spatial arrangement. The microscopic state of a metallic microstructure depends significantly on its temperature (or on a temperature-time curve during heat treatment), so that, depending on the heat treatment, different microstructure types, microstructure components, or phases can be present during and after this treatment.

[0027] A structural transformation of a metallic material can generally be understood as the temperature- and / or time-dependent transformation of the sum of the partial volumes explained above, each of which is transformed into another partial volume that differs from the previous initial partial volume in terms of its composition and spatial arrangement.

[0028] Explained more specifically using the example of a metal alloy with at least two alloying elements, a microstructural transformation can be understood as a transformation of one or more phases or phase mixtures into another or several other phases or phase mixtures within the microstructure.

[0029] As a rule, metallic materials have individual or material-specific transformation temperatures at which a structural transformation takes place.

[0030] In steel, for example (defined as an iron alloy with a maximum carbon content of 2.06 wt.%), a microstructural transformation from the ferrite phase to the austenite phase occurs at a high temperature of over 723 °C (according to the iron-carbon diagram) under thermodynamic equilibrium conditions, or vice versa at temperatures below 723 °C.

[0031] Since the phases have very different mechanical properties and thus influence the macroscopic mechanical properties of the material, these can be specifically and deliberately adjusted by appropriate heat treatment.

[0032] Heat treatment can be understood in particular as a process for treating workpieces in which the workpiece is heated and cooled again in a controlled manner, or vice versa, in order to specifically change its material properties.

[0033] Based on the above explanations, heat treatments can be applied primarily to metals or metal alloys. The most common heat treatment processes for metals, especially steels, include tempering, baking, hardening, quenching and tempering, solution annealing, bainitizing, and pearlitizing.

[0034] A workpiece may comprise a ready-to-use component that may be set up and configured for immediate installation and use in a respective operational product.

[0035] Alternatively, the workpiece can also be a semi-finished product, which can be understood as a prefabricated raw material and starting workpiece or as a semi-finished product in its simplest form.

[0036] Optionally, the workpiece can also be a sample made of the respective material specifically for the process described above.

[0037] A material parameter can be understood as a physical parameter by which the material can be characterized and quantified. Preferably, the material parameter can be a mechanical material parameter.

[0038] Examples of a mechanical material property can be one or more of the following properties: Young's modulus, yield strength, proof strength, tensile strength, in particular hot tensile strength or cold tensile strength, fatigue strength, yield stress, elongation at break, uniform elongation or hardness.

[0039] High-temperature heat refers to the amount of heat added to and / or removed from the workpiece during heat treatment at a high temperature above or equal to 0°C. The high temperature can reach values ​​of up to 1500°C.

[0040] Accordingly, low-temperature heat can be understood as the amount of heat that is added to and / or removed from the workpiece during heat treatment at a low temperature below 0°C. The low temperature can reach values ​​as low as -270°C.

[0041] The indentation body can preferably be a component of an indentation element region of an indentation element, by means of which the indentation body can be pressed into a surface of the workpiece. The indentation element and indentation body can be formed as a one-piece indentation unit, so that at the macroscopic level there is no separating surface between the indentation element and the indentation body.

[0042] Alternatively, the pressing element and pressing body can be designed in two parts, so that both the pressing element can have a separate pressing element body and the pressing body itself can have a separate body.

[0043] In this case, the indentation body can be accommodated by the indentation element and secured to it. The securing can be detachable.

[0044] The indentation body is the portion of the indentation element that penetrates the surface of the workpiece and thus creates the workpiece indentation as described above. In other words, the indentation body can also be referred to as the indenter.

[0045] The indentation direction is preferably perpendicular to the surface of the workpiece.

[0046] The indentation body may preferably have a conical shape, wherein it is aligned such that its conical tip faces the workpiece surface in the indentation direction.

[0047] The tip of the indenter can advantageously be rounded. This minimizes mechanical stress peaks caused by a notch effect in the resulting base of the workpiece indentation, allowing the process described above to be performed more precisely and reliably.

[0048] Alternatively, the indenter may have a spherical shape, a pyramidal shape, or a tetrahedral shape.

[0049] The indenter is preferably made of diamond. Natural or synthetic diamonds are conceivable. Other suitable materials such as boron nitride can also be used.

[0050] The static indentation force can have a force magnitude and a force vector aligned in the indentation direction. The static indentation force is generated by a force generator and transferred to the indentation element, by means of which the indentation body is then pressed into the surface of the workpiece.

[0051] The force vector of the indentation force should be aligned orthogonally to the surface of the workpiece, as should the longitudinal axis of the indentation element and the indentation body.

[0052] When force is applied, a movement occurs along the longitudinal axis of the pressing element or the pressing body.

[0053] However, the movement is so slow that it can still be described as a quasi-static force application to generate the workpiece impression.

[0054] The above-mentioned determination of the at least one structural transformation of the material of the workpiece also comprises detecting at least one indentation parameter characterizing the indentation of the indentation body.

[0055] The above-mentioned determination of the at least one microstructure type may additionally or alternatively comprise the detection of this indentation parameter.

[0056] The indentation parameter may preferably comprise the static indentation force and / or an indentation depth within the workpiece indentation.

[0057] Additionally or alternatively, the detection of the at least one indentation parameter characterizing the indentation of the indentation body may also comprise a change in the at least one indentation parameter.

[0058] The indentation body is pressed into the surface of the workpiece according to at least one indentation parameter.

[0059] Additionally or alternatively, the indentation body is pressed into the surface of the workpiece using a heat treatment parameter that characterizes the heat treatment.

[0060] The indentation body is preferably pressed into the surface of the workpiece at several different positions on the surface. For this purpose, the indentation body can be movable relative to the surface of the workpiece in all three spatial directions and can move to different positions on the surface of the workpiece.

[0061] Additionally or alternatively, the workpiece can also be movable in all three spatial directions.

[0062] Both the indentation parameter (e.g. in the form of the indentation force) and the heat treatment parameter (e.g. in the form of the workpiece temperature) can preferably be constant.

[0063] This is particularly true when a defined series (e.g. over the number or within certain time intervals) of workpiece impressions is to be generated.

[0064] The workpiece temperature may preferably refer to a temperature on the surface of the workpiece and / or to the temperature to which the workpiece is subjected by a heat treatment device.

[0065] In addition to detecting the at least one indentation parameter or its change, the corresponding heat treatment parameter and an indentation time can be detected and linked to the at least one detected indentation parameter or its change.

[0066] This heat treatment parameter and the indentation time thus form a data pair that characterizes the temperature-time curve of the heat treatment and can be linked to each recorded indentation parameter.

[0067] However, the link to each of the at least one recorded indentation parameter only occurs if the indentation body has been pressed into the surface of the workpiece and the at least one indentation parameter can be recorded in the first place.

[0068] Finally, the heat treatment parameter and the time during the heat treatment are recorded continuously (or according to the sampling rate of the corresponding recording devices). The generation of two consecutive workpiece indentations is associated with a certain minimum transition time, which can be several seconds, several tens of seconds, or several minutes.

[0069] The determination method explained above therefore has its limitations in that it cannot be used for short-time heat treatments (for example for processes with heating or cooling rates of approximately 50 K / s to approximately 1000 K / s or even more).

[0070] As explained above, the method for determining at least one microstructural transformation or at least one microstructure type of a material of a workpiece is based in particular on the indentation of the indentation body into the surface of the workpiece.

[0071] However, other methods exist for determining at least one microstructural transformation or at least one microstructure type of the same material in a workpiece (such as the dilatometer method). However, the dilatometer method cannot be used to determine material parameters.

[0072] In practice, so-called time-temperature transformation diagrams (for cooling processes) or time-temperature austenitization diagrams (for heating processes) can be determined dilatometrically for each technically relevant metal material.

[0073] These contain a large number of data pairs: heat treatment parameters (in the form of the workpiece temperature) and correspondingly linked points in time, which are assigned as a reference to the respective microstructure types and microstructure transformations occurring or are additionally linked to them.

[0074] By means of such a reference method, which differs from the method explained above, at least one reference microstructural transformation of the same material is determined.

[0075] Additionally or alternatively, at least one reference microstructure type of the same material is determined.

[0076] This reference method is preferably carried out prior to the above-described method according to the invention, so that the data thus determined can be used for reference purposes. Consequently, a corresponding reference heat treatment parameter and reference time are recorded and linked to the at least one reference microstructural transformation of the same material and stored in a material database.

[0077] Additionally or alternatively, the recorded and corresponding reference heat treatment parameter and reference time can be linked to at least one reference microstructure type of the same material and stored in the material database.

[0078] The above-described sequence of the reference method (e.g. dilatometer method) was described only on the basis of at least one reference heat treatment parameter and a reference time and a corresponding reference microstructural transformation or a reference microstructure type of the same material.

[0079] Of course, using the reference method, several 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000 or 10000000000 reference heat treatment parameters and several 10, 100, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000 or 10000000000 corresponding reference times (depending on the sampling rate of the corresponding sensors) and the corresponding reference microstructure transformations or reference microstructure types of the same material can be determined.

[0080] The material database can preferably be part of a device for carrying out the method according to the invention explained above. Alternatively, the material database can also be provided in a cloud-based format, to which the device has access.

[0081] Since each indentation parameter (such as indentation force or indentation depth) is now linked to a corresponding heat treatment parameter and an indentation time, a comparison with the data pairs from the material database can now enable the determination of a microstructure transformation or a microstructure type.

[0082] The determination procedure is as follows:

[0083] By comparing the heat treatment parameter with the reference heat treatment parameter from the material database, at least one structural transformation of the material of the workpiece is determined by pressing the indenter into the surface of the workpiece.

[0084] In addition or alternatively to the previous comparison, by comparing the indentation time with the reference time from the material database, the at least one microstructure type of the material of the workpiece is determined in addition or alternatively to the at least one microstructure transformation by means of indentation of the indentation body into the surface of the workpiece.

[0085] In other words, by comparing the heat treatment parameter (preferably in the form of a temperature of the workpiece) associated with each recorded indentation parameter (preferably in the form of an indentation depth or indentation force) and the corresponding indentation time, conclusions can be drawn about microstructural transformations or microstructure types of the material.

[0086] This is due to the fact that structural transformations or different types of microstructure are noticeable through a change in hardness, which in turn has a direct influence on the indentation parameter.

[0087] In this respect, microstructural transformations or different microstructure types can be determined in real time with minimal damage during the heat treatment of the workpiece.

[0088] Preferably, this determination can be carried out in such a way that a first indentation parameter (indentation force) is kept constant and the microstructure transformation can be determined, for example, by changing a second indentation parameter (indentation depth).

[0089] In addition to determining at least one microstructural transformation or at least one microstructure type of a material of a workpiece, the method according to the invention can additionally or alternatively be configured to determine at least one material characteristic of the material of the workpiece.

[0090] The procedure is as follows:

[0091] First, the shape of the plastically deformed workpiece indentation is recorded after the step of pressing in the indentation body. The recorded shape can, in particular, be a three-dimensional shape. As explained above, the step of pressing in the indentation body can take place before, during, or after the heat treatment.

[0092] Since the determination of at least one material characteristic of the material of the workpiece at high temperature or low temperature is particularly relevant, the step of indenting the indenter can preferably be carried out during the heat treatment.

[0093] Furthermore, since the shape of the plastically deformed workpiece indentation is detected by means of an optical detection device, the shape of the workpiece indentation cannot be determined during the heat treatment, but afterward at room temperature.

[0094] Following the detection step, the detected shape of the plastically deformed workpiece indentation is compared with a simulated shape of a plastically deformed workpiece indentation according to a material deformation model of the workpiece. The simulated shape can, in particular, also be a simulated three-dimensional shape.

[0095] Following the comparison, at least one material characteristic of the material of the workpiece is preferably determined from the comparison.

[0096] The simulated shape of the plastically deformed workpiece indentation is based on a so-called flow curve of the material, whereby the flow curve is mathematically defined by several material input parameters (to characterize the plastic material behavior).

[0097] The flow curve is processed together with the real boundary conditions of the previous step of indenting the indenter (such as static indentation force, indentation depth as well as shape and geometry of the indenter, temperature-time curves during cooling or heating) in a finite element simulation (according to the material deformation model), from which the simulated shape of the plastically deformed workpiece indentation is calculated.

[0098] This finite element simulation can be stored as a corresponding software application on a storage unit of an evaluation device and executed by a processing unit of the evaluation device. By varying the material input parameters, the evaluation device can use an optimization algorithm to iteratively minimize the difference between the simulated shape of the plastically deformed workpiece indentation and the actually recorded shape of the plastically deformed workpiece indentation (objective function) using the sum of squares method.

[0099] The optimization algorithm ends when the objective function converges and falls below a defined limit.

[0100] This limit value can preferably be approximately 5% deviation for three-dimensional simulation and approximately 3% deviation for two-dimensional simulation.

[0101] The flow curve calculated by convergence (with the final calculated material input parameters) can be converted into a technical stress-strain curve and from this the following comparative parameters can be determined based on the tensile test:

[0102] - Comparative yield strength / ? P o,2 (also known as R e identifiable);

[0103] - Comparative tensile strength R m ;

[0104] - hardening behavior; and / or

[0105] - qualitative determination of ductility for specific materials.

[0106] The comparative proof stress / ? P o,2 can thus be determined at additional temperature values ​​(from - 270 °C up to 1500 °C) and linked to these to form a cold or hot comparative yield strength.

[0107] The same applies to the comparative tensile strength R m in the form of a linked cold or hot comparative tensile strength.

[0108] By determining the microstructural transformations and microstructure types of a respective material of a workpiece 102 and one or more material parameters of the material of the workpiece 102, faster materials research and development is enabled.

[0109] In addition, a comprehensive development of heat treatment strategies for high- and low-temperature heat, preferably on metallic materials, and improved process monitoring and control are enabled. Furthermore, the present invention relates to a device for determining at least one microstructural transformation and / or at least one microstructure type of a workpiece material and / or for determining at least one material characteristic of the workpiece material, preferably comprising:

[0110] - a workpiece holder for holding and / or securing the workpiece;

[0111] - an indentation element comprising an indentation element region having an indentation body for indentation into a surface of the workpiece;

[0112] - a force generator, which is mechanically coupled to the workpiece holder and / or the indentation element, for generating an indentation force for indenting the indentation body into a surface of the workpiece for plastically deforming the workpiece by means of the indentation body to produce a plastically deformed workpiece indentation; and

[0113] - a heat treatment device for performing a heat treatment of the workpiece by applying low-temperature heat and / or high-temperature heat to the workpiece.

[0114] All structural and functional features associated with the previously described method and embodiments thereof may also be included in the device, either alone or in combination, and the associated properties, configurations, and advantages may also be included and achieved accordingly.

[0115] In addition, the method described herein may be designed to be executable by means of the device described above.

[0116] The workpiece holder can be configured, in particular, for releasably receiving and / or securing the workpiece. For this purpose, the workpiece holder can have one or more positive and / or non-positive receiving and / or securing elements for receiving and securing the workpiece.

[0117] Furthermore, the workpiece holder can be made of a temperature-resistant material that is resistant to temperatures from approx. - 270 °C to approx. 1500 °C.

[0118] The pressing element and / or the pressing body can also be made of this temperature-resistant material. The pressing element and the pressing body can be designed as a one-piece pressing unit, so that at the macroscopic level there is no separating surface between the pressing element and the pressing body.

[0119] Alternatively, the pressing element and pressing body can be designed in two parts, so that both the pressing element can have a separate pressing element body and the pressing body itself can have a separate body.

[0120] In this case, the indentation body can be held and secured by the indentation element. The securing can be detachable.

[0121] The force generator may comprise one or more hydraulic cylinders and / or one or more electro-mechanical force generators (such as a spindle driven by an electric motor) for generating the preferably static indentation force.

[0122] The mechanical coupling of the force generator with the workpiece holder and / or the pressing element can be understood as a direct mechanical coupling.

[0123] In other words, there can be direct mechanical contact between the force generator and the workpiece holder and / or the pressing element for direct force transmission.

[0124] Alternatively, the mechanical coupling of the force generator with the workpiece holder and / or the indentation element can be understood as an indirect mechanical coupling.

[0125] In other words, an indirect mechanical coupling (e.g. via another intermediate component) can exist between the force generator and the workpiece holder and / or the pressing element for indirect force transmission.

[0126] Furthermore, it can be provided that the force generator is only mechanically coupled to the pressing element for transmitting the static pressing force to the pressing element.

[0127] The heat treatment device may comprise at least one heat treatment chamber, which encloses at least the indentation element region, the workpiece, and / or the workpiece holder during the heat treatment. This heat treatment chamber may preferably be constructed as a hollow-cylindrical chamber.

[0128] The heat treatment device can in particular have an insulating gate, wherein the insulating gate has a thermally insulated passage opening for the passage of the pressing element.

[0129] The insulating gate is preferably arranged at an end of the heat treatment device facing the pressing element.

[0130] The heat treatment device can be constructed by means of a combined high-temperature and low-temperature heat treatment unit.

[0131] This design allows in particular a compact design of the heat treatment device.

[0132] Furthermore, with such a design, the heat treatment times can be shortened, since after the application of high-temperature heat has been completed and completed, the workpiece can be cooled more quickly by applying low-temperature heat.

[0133] Consequently, the heat treatment times can also be shortened conversely, since after the application of low-temperature heat has been completed, the workpiece can be heated more quickly by applying high-temperature heat.

[0134] Alternatively, the heat treatment device may be constructed by means of a separate high-temperature heat treatment unit and a separate low-temperature heat treatment unit.

[0135] The separate design allows each unit to be optimized for its purpose without taking the needs of the other unit into account, resulting in an optimized high-temperature heat treatment unit and an optimized low-temperature heat treatment unit.

[0136] The combined high-temperature and low-temperature heat treatment unit may comprise a heating unit, preferably an electric one, for generating the high-temperature heat and a cooling unit, preferably comprising at least one cooling medium channel for flowing through a cooling medium, for generating the low-temperature heat.

[0137] The heating unit may preferably be an electrical heating unit, wherein an inductive heating unit or a resistance heating unit may be conceivable.

[0138] The resistance heating unit or the inductive heating unit can extend spirally around the heat treatment chamber and be in direct gas contact with it.

[0139] Alternatively, an intermediate heat transfer element can be arranged between the resistance heating unit and the heat treatment chamber.

[0140] The cooling unit may have at least one cooling medium channel for flowing through a cooling medium.

[0141] The cooling medium channel can also extend spirally around the heat treatment chamber and be in direct gas contact with it.

[0142] Alternatively, an intermediate heat transfer element can be arranged between the cooling medium channel and the heat treatment chamber.

[0143] Because the cooling medium channel is flowed through by a cooling medium, the heat transfer mechanism of forced convection can also be utilized, which further improves the transfer of low-temperature heat.

[0144] The alternative embodiment in the form of the separate high-temperature heat treatment unit may comprise a heating unit for generating the high-temperature heat.

[0145] This heating unit may preferably be an electrical heating unit, whereby an inductive heating unit or a resistance heating unit may be conceivable.

[0146] The resistance heating unit can extend spirally around the heat treatment chamber and be in direct gas contact with it. Alternatively, an intermediate heat transfer element can be arranged between the resistance heating unit and the heat treatment chamber.

[0147] Furthermore, the separate low-temperature heat treatment unit may comprise a cooling unit for generating the low-temperature heat.

[0148] The cooling unit may have at least one cooling medium channel for flowing through a cooling medium.

[0149] The cooling medium channel can extend spirally around the heat treatment chamber and be in direct gas contact with it.

[0150] Alternatively, an intermediate heat transfer element can be arranged between the cooling medium channel and the heat treatment chamber.

[0151] Because the cooling medium channel is flowed through by a cooling medium, the heat transfer mechanism of forced convection can also be utilized, which further improves the transfer of low-temperature heat.

[0152] The device may further comprise a control and / or regulating unit, which may be connected to the heating unit, for controlling and / or regulating the temporal generation of the high-temperature heat by means of the heating unit.

[0153] In both cases - i.e. in the case of the combined high-temperature and low-temperature heat treatment unit or the separate high-temperature heat treatment unit - the control and / or regulation unit can be connected to the heating unit.

[0154] Additionally or alternatively, the control and / or regulation unit can be connected to the cooling unit for controlling and / or regulating the temporal generation of the low-temperature heat.

[0155] Accordingly, the control and / or regulation unit can also be used in both cases - i.e. in the case of combined high-temperature and low-temperature

[0156] The heat treatment unit or the separate low-temperature heat treatment unit can be connected to the cooling unit. The heat treatment device can comprise a temperature detection device for detecting a temperature in the at least one heat treatment chamber and / or a temperature on a surface of the workpiece.

[0157] The temperature detection device can be provided in the combined high-temperature and low-temperature heat treatment unit as well as in the separate high-temperature heat treatment unit and the separate low-temperature heat treatment unit.

[0158] The temperature detection device may further comprise a first temperature sensor for detecting the temperature in the at least one heat treatment chamber and a second temperature sensor for detecting the temperature on the surface of the workpiece.

[0159] The first and second temperature sensors may also be provided in the combined high-temperature and low-temperature heat treatment unit as well as in the separate high-temperature heat treatment unit and the separate low-temperature heat treatment unit.

[0160] The first temperature sensor may be a contactless temperature sensor for detecting the temperature in the at least one or respective heat treatment chamber.

[0161] The second temperature sensor can be in direct contact with the surface of the workpiece and measure the surface temperature there.

[0162] The second temperature sensor can be designed as a thermocouple that can be spot-welded directly onto the surface of the workpiece.

[0163] The heat treatment device may further comprise a gas connection and a gas line connected to it, which opens into the at least one heat treatment chamber, for supplying the at least one heat treatment chamber with protective gas during the heat treatment.

[0164] The gas connection can be provided for both the combined high-temperature and low-temperature heat treatment unit and the separate high-temperature heat treatment unit and the separate low-temperature heat treatment unit. The protective gas can be used to prevent oxidation effects, particularly at high temperatures of the workpiece material.

[0165] Further preferred features and / or advantages of the present invention are the subject of the following description and the drawings of exemplary embodiments.

[0166] The drawings show:

[0167] Fig. 1 is a schematic representation of a device according to an exemplary embodiment of the present invention;

[0168] Fig. 2 is a further schematic representation of the device according to Fig. 1 for carrying out a method according to an exemplary embodiment of the present invention;

[0169] Fig. 3 is a schematic representation of an apparatus according to a further exemplary embodiment of the present invention for carrying out the method according to Fig. 2; and

[0170] Fig. 4 is a schematic representation of a temperature-time curve of a heat treatment while the method according to Figs. 2 and 3 is carried out by means of the device according to Figs. 2 and 3.

[0171] Identical or functionally equivalent elements or devices are provided with the same reference numerals in all figures.

[0172] Fig. 1 shows a schematic representation of a device 100 according to an exemplary embodiment of the present invention.

[0173] The device for determining at least one microstructural transformation and at least one microstructure type of a material of a workpiece 102 comprises a workpiece holder 104 for receiving and securing the workpiece 102.

[0174] The material of the workpiece 102 can be a ductile metallic material that allows reproducible and defined plastic deformation. A material can be considered ductile if it can undergo permanent plastic deformation under shear stress before fracture or macroscopic separation.

[0175] A material parameter that characterizes ductility is the elongation at break, which can preferably be in a range from approximately 0.1% to approximately 30%.

[0176] Metallic materials can preferably be aluminum, iron, titanium, or magnesium. Furthermore, it can advantageously be provided that metals are present in the form of metal alloys such as aluminum alloys, iron alloys such as steel or cast iron, titanium alloys, or magnesium alloys.

[0177] The following steel alloys should preferably be used: unalloyed steels, alloyed steels or stainless steels.

[0178] The steel alloys can be further divided functionally into: structural steel, case-hardening steel, tempering steel, nitriding steel, tool steel, stainless steel or acid-resistant steel.

[0179] The workpiece holder 104 is configured to releasably hold and secure the workpiece 104.

[0180] For this purpose, the workpiece holder 104 can have one or more positive and / or non-positive receiving and / or fixing elements for receiving or fixing the workpiece 102.

[0181] The workpiece 102 is shown only schematically in Fig. 1 and can be designed as a workpiece sample made of the respective material that is geometrically adapted for the workpiece holder 104.

[0182] The device 100 further comprises an indentation element 106 with an indentation element region 108, which has an indentation body 110 for indentation into a surface 112 of the workpiece 102.

[0183] An indentation direction of the indentation body 110 extends perpendicular to the surface 112 of the workpiece 102. According to Fig. 1, the indentation body 110 has a conical shape, which is oriented such that its conical tip faces the workpiece holder 104 in the indentation direction. The conical tip can preferably be rounded.

[0184] The pressing element 106 and the pressing body 110 can be formed as a one-piece pressing unit, so that at the macroscopic level there is no separating surface between the pressing element 106 and the pressing body 110. Consequently, the pressing element 106 and the pressing body 110 can be made of the same material.

[0185] Alternatively, the pressing element 106 and the pressing body 110 can be formed in two parts, so that both the pressing element 106 can have a separate pressing element body and the pressing body 110 itself can have a separate body.

[0186] In this case, the indentation body 110 can be received and secured by the indentation element 106. The securing can be detachable.

[0187] The indentation body 110 may preferably be made of diamond, although other suitable materials such as boron nitride may also be conceivable.

[0188] The device 100 further comprises a force generator 114, which is mechanically coupled to the indentation element 106, for generating an indentation force Fe for indenting the indentation body 110 into a surface 112 of the workpiece 102 for plastically deforming the workpiece 102 by means of the indentation body 110 to generate a plastically deformed workpiece indentation 116.

[0189] Additionally or alternatively, the force generator 114 may be mechanically coupled to the workpiece holder 104 (not shown in Fig. 1).

[0190] The force generator 114 is housed in a vertical support structure 152. The force generator 114 may include one or more hydraulic cylinders and / or one or more electromechanical force generators (such as a spindle driven by an electric motor) for generating the static indentation force Fe.

[0191] The vertical support structure 152 is laterally secured to a base plate 154 by four support feet F (only two shown in Fig. 1) and, in the assembled state, is vertically aligned as shown in Fig. 1. The mechanical coupling between the force generator 114 and the pressing element 106 is achieved via a cantilever arm 156 having a cantilever head 158 for transmitting the static pressing force Fe to the pressing element 106.

[0192] The pressing element 106 is received and secured in the boom head 158. The securing is detachable.

[0193] The boom head 158 is translationally movable relative to the workpiece holder 104 and the base plate 154 in all three spatial directions (indicated by the double arrows on the boom head 158).

[0194] Consequently, the boom head 158 is also translationally movable relative to the workpiece 102 in all three spatial directions (indicated by the double arrows on the boom head 158).

[0195] Furthermore, the workpiece holder 104 is secured to the base plate 154 via an intermediate plate 160. This securing can preferably be detachable.

[0196] The intermediate plate 160 may be made of a low-temperature and high-temperature heat-resistant material and may also have heat-insulating properties.

[0197] The apparatus 100 further comprises a heat treatment apparatus 118 for performing a heat treatment of the workpiece 102 by applying low-temperature heat and high-temperature heat to the workpiece 102.

[0198] The mechanical coupling between the heat treatment device 118 and the vertical support structure 152 is achieved via a further cantilever arm 162.

[0199] The further cantilever arm 162 is fixed to the vertical support structure 152 by means of a guide rail 164 and is vertically translationally displaceable relative thereto (indicated by the double arrow) and rotatable or pivotable about this vertical translational displacement direction.

[0200] The heat treatment device 118 has a heat treatment chamber 120, which encloses at least the indentation element region 108, the workpiece 102, and the workpiece holder 104 during the heat treatment (shown in more detail in Fig. 2). The heat treatment device 118 is constructed according to Fig. 1 using a combined high-temperature and low-temperature heat treatment unit 122.

[0201] Accordingly, the combined high-temperature and low-temperature heat treatment unit 122 comprises an electrical heating unit 128 (shown schematically) for generating the high-temperature heat and a cooling unit 130 (shown schematically) for generating the low-temperature heat.

[0202] The electrical heating unit 128 can be constructed as a resistance heating unit or as an inductive heating unit.

[0203] The resistance heating unit or the inductive heating unit can extend spirally around the heat treatment chamber 120 and be in direct gas contact with it.

[0204] Alternatively, an intermediate heat transfer element may be arranged between the heating unit 128 and the heat treatment chamber 120 (not shown in Fig. 1).

[0205] The cooling unit 130 has a cooling medium channel 132 for flowing through a cooling medium.

[0206] The cooling medium channel 132 can extend spirally around the heat treatment chamber 120 and be in direct gas contact with it.

[0207] Alternatively, the intermediate heat transfer element can be arranged between the cooling medium channel 132 and the heat treatment chamber.

[0208] The device 100 further comprises a control and / or regulation unit 140.

[0209] The control and / or regulation unit 140 is connected to the heating unit 128 by means of a signal line 166 for controlling and / or regulating the temporal generation of the high-temperature heat by means of the heating unit 128.

[0210] The control and / or regulation unit 140 is further connected to the cooling unit 130 via a signal line 166 for controlling and / or regulating the temporal generation of the low-temperature heat by means of the cooling unit 130. The necessary control elements such as throttles, valves and lines for controlling or regulating the cooling medium flow are not shown in Fig. 1.

[0211] The heat treatment device 118 includes a temperature detection device 142 for detecting a temperature in the one heat treatment chamber 120 and a temperature on a surface 112 of the workpiece 102.

[0212] The temperature detection device 142 includes a first temperature sensor 144 for detecting the temperature in the heat treatment chamber 120 and a second temperature sensor 146 for detecting the temperature on the surface 112 of the workpiece 102.

[0213] The first and second temperature sensors 144, 146 are also connected to the control and / or regulation unit 140 via signal lines 166, which also applies to the force generator 114.

[0214] The first temperature sensor 144 may be a contactless temperature sensor for detecting the temperature in the heat treatment chamber 120.

[0215] The second temperature sensor 146 is in direct contact with the surface 112 of the workpiece 102 for temperature detection (not shown in Fig. 1).

[0216] The second temperature sensor 146 may be designed as a thermocouple that can be spot-welded directly onto the surface of the workpiece.

[0217] The heat treatment device 118 also comprises a gas connection 148 and a gas line 150 connected thereto, which opens into the heat treatment chamber 120, for supplying the heat treatment chamber 120 with protective gas during the heat treatment.

[0218] The shielding gas can be supplied in the form of an inert gas or an inert gas mixture. Inert gases can be noble gases such as helium, neon, argon, krypton, or xenon, or nitrogen or carbon dioxide.

[0219] Fig. 2 shows a further schematic representation of the device according to Fig. 1 for carrying out a method according to an exemplary embodiment of the present invention. The device 100 according to Fig. 2 basically has the same, equivalent, or corresponding structural and / or functional features as the device 100 according to Fig. 1.

[0220] In contrast to Fig. 1, in which the combined heat treatment device 118 is arranged in a position (in the direction of gravity) above the workpiece 102, the heat treatment device 118 according to Fig. 2 is positioned in a position enclosing the workpiece 102 for carrying out a heat treatment of the workpiece 102.

[0221] It is in contact with the intermediate plate 160 on the bottom side so that a defined position can be reached.

[0222] To accommodate the workpiece holder 104, the workpiece 102 and the indentation element 106, the heat treatment device 118 may have two half modules (not shown in Fig. 2) that can be opened and closed by a pivot joint.

[0223] Alternatively, the combined heat treatment device 118 may have a cover element in a side 168 facing the pressing element 106, which can also be opened and closed with a rotary joint (not shown in Fig. 2).

[0224] In the side 168 facing the pressing element 106, an insulating guide 170 is also introduced, which has a thermally insulated passage opening for the pressing element 106.

[0225] The side 168 facing the indentation element 106 refers to the state of the heat treatment device 118 in which it performs the heat treatment of the workpiece 102 and is positioned on the intermediate plate 160.

[0226] To determine at least one microstructural transformation and at least one microstructure type of the material of the workpiece 102, the device 100 executing the method according to an exemplary embodiment of the present invention now proceeds as follows:

[0227] First, a heat treatment of the workpiece 102 is carried out by applying high-temperature heat to the workpiece 102 by means of the heat treatment device 118. Additionally or alternatively, the workpiece 102 can be applied with low-temperature heat.

[0228] For this purpose, the heating unit 128 or cooling unit 130 controlled and / or regulated by means of the control and / or regulation unit 140 can set a predetermined temperature-time curve by means of which the workpiece 102 is treated.

[0229] High-temperature heat refers to the amount of heat applied to the workpiece during heat treatment at high temperatures, i.e., above or equal to 0°C. The high temperature can reach values ​​of up to 1500°C.

[0230] Accordingly, low-temperature heat can be understood as the amount of heat applied to the workpiece during heat treatment at low temperatures, i.e., below 0°C. The low temperature can reach values ​​as low as -270°C.

[0231] During the step of heat treating the workpiece 102, the indentation body 110 is generally pressed into the surface 112 of the workpiece 102 with a static indentation force Fe to plastically deform the workpiece 102 by means of the indentation body 110 to produce a plastically deformed workpiece indentation 116.

[0232] Additionally or alternatively, the pressing in of the pressing body 110 can also take place before the heat treatment step.

[0233] Additionally or alternatively, the pressing in of the pressing body 110 can also take place after the heat treatment step.

[0234] The workpiece impression 116 produced by pressing in the indentation body 110 before or after the heat treatment step can serve, for example, as a reference workpiece impression 116.

[0235] Determining the at least one microstructural transformation and the at least one microstructure type of the material of the workpiece 102 also includes detecting an indentation parameter characterizing the indentation of the indentation body 110. Additionally or alternatively, this detection may include a change in the indentation parameter.

[0236] The at least one indentation parameter can be the static indentation force Fe in the form of a first indentation parameter.

[0237] As a second indentation parameter, an indentation depth of the indentation body 110 in the workpiece indentation 116 in the surface 112 of the workpiece 102 is recorded.

[0238] The indentation depth can be measured using a displacement sensor that is part of the force generator 114. Additionally or alternatively, the indentation depth can also be measured optically using the workpiece indentation 116.

[0239] The indentation of the indentation body 110 takes place at several different positions into the surface 112 of the workpiece 102 according to the first indentation parameter, which is constant.

[0240] The indentation at the different positions can be carried out according to a first series of indentation processes, all of which are carried out with the first, constant indentation parameter.

[0241] A second series of indentation processes can then be carried out using the first indentation parameter, which is also kept constant and differs from the first indentation parameter of the first series.

[0242] The time difference between two consecutive indentation processes can be several seconds, several tens of seconds or several minutes, depending on the heat treatment process being carried out.

[0243] By keeping the first indentation parameter constant in the form of the indentation force, the change in the indentation depth can be recorded particularly clearly.

[0244] In addition, the indentation takes place at a heat treatment parameter that characterizes the heat treatment and is preferably constant.

[0245] The heat treatment parameter characterizing the heat treatment is preferably the temperature on the workpiece surface 112. The temperature detected in the heat treatment chamber 120 can be returned as an actual control or regulated variable to the control and / or regulation unit 140 for temperature control or regulation in the heat treatment chamber 120.

[0246] Additionally, the time is recorded once the heat treatment has begun. Thus, each time the indenter 110 is pressed into the surface 112 of the workpiece 102, the corresponding indentation time can be recorded.

[0247] In other words, in addition to the recording of the first and / or second indentation parameter or its change, the corresponding heat treatment parameter and the indentation time are recorded and linked to the recorded indentation parameter(s) or its change.

[0248] The heat treatment parameter is then compared with a reference heat treatment parameter from a material database and the indentation time is compared with the reference time from the material database.

[0249] As explained above, several 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000 or 1000000000 reference heat treatment parameters and several 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000 or 10000000000 corresponding reference times (depending on the sampling rate of the corresponding sensors) and the corresponding reference microstructure transformations or reference microstructure types of the same material can be stored in the material database.

[0250] The basic prerequisite for the unambiguous determination of at least one microstructural transformation and / or at least one microstructure type is that the respective reference heat treatment parameters and the respective associated reference times refer to the same material.

[0251] Furthermore, it may be necessary for the respective reference heat treatment parameters and the respective corresponding reference times, as well as the respective recorded heat treatment parameters and the respective corresponding recorded reference times, to refer to the same temperature-time curve of a heat treatment. In the case of high-temperature heat, a temperature-time curve can be achieved through a sequence of time-defined heating and cooling processes.

[0252] Additionally or alternatively, a temperature-time curve for low-temperature heat can be achieved through a sequence of time-defined heating and cooling processes.

[0253] Due to the combined heat treatment device 118, such temperature-time curves can be implemented very time-efficiently and easily in one device.

[0254] In addition, the process times during heat treatment can be shortened because the workpiece 102 can be cooled by means of the cooling unit 130 after the high-temperature heat treatment and vice versa.

[0255] Extensive series of tests have been documented in the literature or now also in electronic form for microstructural transformations or microstructure types in a variety of metallic materials (in particular iron-based materials such as cast iron or

[0256] steel) under a wide range of temperature-time profiles.

[0257] The comparison of a heat treatment parameter with a reference heat treatment parameter is unambiguous if the heat treatment parameter and the reference heat treatment parameter from the material database are identical or within a certain tolerance range. The same applies to the comparison of the indentation time with the reference time from the material database.

[0258] The reference heat treatment parameter and the reference time in the material database are linked as a data pair with a reference microstructure transformation and / or with a reference microstructure type of the same material.

[0259] Consequently, by means of this referential comparison, the at least one microstructural transformation and / or the at least one microstructure type of the material of the workpiece 102 can only be determined by pressing the indentation body 110 into the surface 112 of the workpiece 102.

[0260] The basic prerequisite here is that a micromechanical property of one or more phases within the structure of the material of the workpiece 102 changes in such a way that they can be detected. Specifically related to the indentation process, this means that the hardness changes during a microstructure transformation and, as a result, the first indentation parameter, in the form of the indentation force, remains constant, while the second indentation parameter changes in the form of the detectable indentation depth.

[0261] Conversely, the indentation depth can also be kept constant by appropriate control and detection of the changing static indentation force Fe, which also allows the determination explained above.

[0262] Since this change in the second indentation parameter in the form of the indentation depth is always linked to a heat treatment parameter in the form of a temperature on the surface 112 of the workpiece 102 and an indentation time, the comparison with the material database explained above can then be carried out and, as a result of this change, a microstructural transformation can be concluded.

[0263] If the second indentation parameter in the form of the indentation depth does not change, a microstructure type can still be determined.

[0264] This indentation parameter is linked to the temperature on the surface 112 of the workpiece 102 and an indentation time and can thus be adjusted to the same reference temperature and reference time.

[0265] Consequently, the comparison with the material database explained above can also be carried out in this way and, as a result of this link, a microstructure type can be deduced.

[0266] The adjustment explained above can be repeated with any number of indentation processes, as long as the same reference heat treatment parameters and reference times can be assigned or adjusted in the material database.

[0267] The corresponding reference heat treatment parameters and / or the reference times are / are determined using a reference method that differs from the above method according to an embodiment of the present invention and was carried out prior to this method. A frequently used reference method in this regard is a dilatometer method, which exploits the property of a material, preferably a metallic material, that its microstructure volume changes during a microstructural transformation.

[0268] This volume change can be recorded or measured in the form of a change in length of a sample during a defined temperature-time curve, and based on this recording or measurement, the reference microstructure transformation or the reference microstructure type can then be determined.

[0269] The corresponding reference heat treatment parameters and reference times are also recorded and linked to the at least one reference microstructural transformation and / or the at least one reference microstructure type of the same material and stored in the material database.

[0270] The method according to the invention accesses these linked data in the material database and can thus infer the microstructure transformation or microstructure types on the basis of the one or more recorded indentation parameters as described above.

[0271] In addition, the device according to Fig. 2 is configured to determine at least one material characteristic of the material of the workpiece 102.

[0272] To determine the at least one material characteristic of the material of the workpiece 102, the device 100 carrying out the method according to an exemplary embodiment of the present invention proceeds as follows:

[0273] First, a three-dimensional shape of the plastically deformed workpiece indentation 116 is recorded after the step of indenting the indentation body 110.

[0274] Furthermore, the recording takes place after the heat treatment has been carried out, since recording the shape during the temperature exposure would be technically difficult or uneconomical to implement.

[0275] The three-dimensional shape of the workpiece indentation 116 can be detected optically or tactilely. Preferably, the detection is performed optically using a shape detection device (not shown in Fig. 1). The shape detection device is preferably a white light interferometer.

[0276] Since the determination of at least one material characteristic of the material of the workpiece is relevant as a function of a high temperature or low temperature, the step of indenting the indentation body 110 takes place during the corresponding heat treatment.

[0277] Subsequently, the recorded three-dimensional shape of the plastically deformed workpiece indentation 116 is compared with a simulated three-dimensional shape of a plastically deformed workpiece indentation according to a material deformation model of the workpiece.

[0278] Following the comparison, at least one material characteristic of the material of the workpiece 102 is determined from the comparison as follows:

[0279] The simulated shape of the plastically deformed workpiece indentation is based on a so-called flow curve of the material, whereby the flow curve is mathematically defined by several material input parameters (to characterize the plastic material behavior).

[0280] The flow curve is processed together with the real boundary conditions of the previous step of indenting the indenter (such as static indentation force, indentation depth as well as shape and geometry of the indenter or temperature-time curves during cooling or heating) in a finite element simulation (according to the material deformation model), from which the simulated shape of the plastically deformed workpiece indentation is calculated.

[0281] This finite element simulation can be stored as a corresponding software application on a storage unit of an evaluation device (not shown in Fig. 2) and executed by a processing unit of the evaluation device.

[0282] By varying the material input parameters, the evaluation device can use an optimization algorithm to iteratively minimize the difference between the simulated shape of the plastically deformed workpiece indentation and the actually measured shape of the plastically deformed workpiece indentation (objective function) using the sum of squares method. The optimization algorithm terminates when the objective function converges and falls below a defined limit.

[0283] This limit value can preferably be approximately 5% deviation for three-dimensional simulation and approximately 3% deviation for two-dimensional simulation.

[0284] The flow curve calculated by convergence (with the final calculated material input parameters) can be converted into a technical stress-strain curve and from this the following comparative parameters can be determined based on the tensile test:

[0285] - Comparative yield strength / ? P o,2 (also known as R e identifiable);

[0286] - Comparative tensile strength R m ;

[0287] - hardening behavior; and / or

[0288] - qualitative determination of ductility for specific materials.

[0289] The comparative proof stress / ? P o,2 can thus be determined at additional temperature values ​​(from - 270 °C up to 1500 °C) and linked to these to form a cold or hot comparative yield strength.

[0290] The same applies to the comparative tensile strength R m in the form of a linked cold or hot comparative tensile strength.

[0291] By determining the microstructural transformations and microstructure types of a respective material of a workpiece 102 and one or more material parameters of the material of the workpiece 102, faster materials research and development is enabled.

[0292] In addition, a comprehensive development of heat treatment strategies for high and low temperature heat, preferably on metallic materials, and improved process monitoring and control are enabled.

[0293] Fig. 3 shows a schematic representation of a device 200 according to a further exemplary embodiment of the present invention for carrying out the method according to Fig. 1. The device 200 according to Fig. 3 basically has the same or equivalent or corresponding structural and / or functional features as the device 100 according to Figs. 1 and 2.

[0294] However, the following structural and / or functional feature differences should be highlighted:

[0295] The heat treatment device 172 is constructed by means of a separate high-temperature heat treatment unit 124 and a separate low-temperature heat treatment unit 126.

[0296] The separate high-temperature heat treatment unit 124 and the separate low-temperature heat treatment unit 126 are structurally and functionally constructed essentially like the combined high-temperature and low-temperature heat treatment unit 122.

[0297] Accordingly, the separate high-temperature heat treatment unit 124 lacks the cooling unit 130 and the separate low-temperature heat treatment unit 126 lacks the heating unit 128.

[0298] However, each of these units 124, 126 has its own heat treatment chamber 120, 174.

[0299] The separate high-temperature heat treatment unit 124 includes an electrical heating unit 134 for generating the high-temperature heat.

[0300] This electrical heating unit 134 can be designed as an inductive heating unit or as a resistance heating unit.

[0301] The resistance heating unit or the inductive heating unit can extend spirally around the heat treatment chamber 120 and be in direct gas contact with it.

[0302] Alternatively, an intermediate heat transfer element (not shown in Fig. 1) can be arranged between the heating unit 134 and the heat treatment chamber 120. The separate low-temperature heat treatment unit 126, however, comprises a cooling unit 136 having a cooling medium channel 138 for the flow of a cooling medium to generate the low-temperature heat.

[0303] The cooling medium channel can extend spirally around the heat treatment chamber 174 and be in direct gas contact with it.

[0304] Alternatively, an intermediate heat transfer element may also be arranged between the cooling medium channel 138 and the heat treatment chamber 174 (not shown in Fig. 3).

[0305] The separate high-temperature heat treatment unit 124, like the combined high-temperature and low-temperature heat treatment unit 122, is also mechanically coupled to the vertical support structure 152.

[0306] The mechanical coupling of the separate low-temperature heat treatment unit 126 to another vertical support structure 176 corresponds to the mechanical coupling of the separate high-temperature heat treatment unit 124 to the vertical support structure 152.

[0307] The further vertical support structure 176 also corresponds functionally and structurally to the vertical support structure 152 and is fixed to the base plate 154 on an opposite side.

[0308] Alternatively, one of the two vertical support structures 152, 176 may be omitted and both separate heat treatment units 124, 126 may be coupled to one of the two non-omitted vertical support structures 152, 176 (corresponding to the mechanical coupling of the combined high-temperature and low-temperature heat treatment unit 122).

[0309] The execution of the method described above in connection with Fig. 2 by means of the device 200 does not change fundamentally, except that a heat treatment with high-temperature heat is carried out by means of the separate high-temperature heat treatment unit 124.

[0310] Accordingly, a low-temperature heat treatment is carried out by means of the separate low-temperature heat treatment unit 126. Fig. 4 shows a schematic representation of a temperature-time curve of a heat treatment, while the method according to Figs. 2 and 3 is carried out by means of the device according to Figs. 2 and 3.

[0311] The heat treatment of the temperature-time curve shown corresponds to a tempering heat treatment with the following steps I to VI:

[0312] - I: Heating the workpiece 102 above a material-dependent austenitizing temperature

[0313] - II: Maintaining the austenitizing temperature to heat the workpiece 102

[0314] - III: Quenching the workpiece 102 by rapid cooling (cooling rates of up to 1000 K / s) to a high temperature of below 200 °C

[0315] - IV: Reheating the workpiece 102 to a tempering temperature of up to approximately 550 °C (depending on the tempering stage)

[0316] - V Maintaining the tempering temperature

[0317] - VI: Slow cooling (e.g. in air) from the tempering temperature to room temperature.

[0318] Steps I to III are also called hardening, whereas steps IV to VI are called tempering.

[0319] The typical duration of tempering according to step V can range from minutes to hours (depending on the workpiece dimensions, material, desired mechanical properties, etc.).

[0320] As shown in Fig. 4, during step V, indentation into the surface 112 of the workpiece 102 may be performed to determine the microstructural transformations taking place during tempering and the microstructure types present in a particular material of the workpiece 102, which was explained in detail in connection with Fig. 2.

[0321] Based on the diagram, which illustrates a series of six workpiece indentations 116 (see also the enlarged view of the workpiece), the microstructure transformation can be clearly seen based on a changing indentation parameter (here in the form of the indentation depth for indentations 5 and 6) while maintaining a constant static indentation force Fe. In addition, after tempering, as also described in connection with Fig. 2, at least one material characteristic of the material of the workpiece 102 is determined.

[0322] List of reference symbols

[0323] device

[0324] workpiece

[0325] Workpiece holder

[0326] Indentation element

[0327] Indentation element area

[0328] Indentation body

[0329] Surface of the workpiece

[0330] power generator

[0331] Workpieces in reverse

[0332] Heat treatment device

[0333] Heat treatment chamber combined high-temperature and low-temperature heat treatment unit separate high-temperature heat treatment unit separate low-temperature heat treatment unit

[0334] Heating unit

[0335] Cooling unit

[0336] Cooling medium channel

[0337] Heating unit

[0338] Cooling unit

[0339] Cooling medium channel

[0340] Control and / or regulation unit

[0341] Temperature detection device first temperature sensor second temperature sensor

[0342] Gas connection

[0343] Gas pipeline vertical support structure

[0344] base plate

[0345] boom arm

[0346] boom head

[0347] Intermediate plate for additional boom arm

[0348] guide rail

[0349] Signal line side facing the pressing element 170 Insulating gate

[0350] 172 Heat treatment device

[0351] 174 Heat treatment chamber

[0352] 176 additional vertical support structures

[0353] 200 device

[0354] Fe indentation force

[0355] F Support foot

Claims

Patent claims 1. A method for determining at least one microstructural transformation and / or at least one microstructure type of a material of a workpiece (102) and / or for determining at least one material characteristic of the material of the workpiece (102), comprising the following steps: - performing a heat treatment of the workpiece (102) by applying low-temperature heat and / or high-temperature heat to the workpiece (102); and / or - pressing an indentation body (110) into a surface (112) of the workpiece (102), preferably with a static indentation force (Fe), for plastically deforming the workpiece (102) by means of the indentation body (110) to produce a plastically deformed workpiece indentation (116) before the step and / or during the step and / or after the step of heat treating the workpiece (102).

2. The method according to claim 1, characterized in that determining the at least one structural transformation and / or the at least one structural type of the material of the workpiece (102) comprises detecting at least one indentation parameter characterizing the indentation of the indentation body (110); preferably the static indentation force (Fe) and / or an indentation depth; and / or a change in the at least one indentation parameter.

3. Method according to claim 2, characterized in that the pressing of the pressing body (110), preferably at several different positions, into the surface (112) of the workpiece (102) takes place according to the at least one pressing parameter, which is preferably constant, and / or takes place at a heat treatment parameter characterizing the heat treatment, which is preferably constant.

4. Method according to claim 2 or claim 3, characterized in that in addition to the detection of the at least one indentation parameter or its change, the corresponding heat treatment parameter and an indentation time are detected and linked to the at least one detected indentation parameter or its change.

5. Method according to one of the preceding claims, characterized in that by means of a reference method which differs from the method according to one of the preceding claims: - at least one reference microstructural transformation and / or at least one reference microstructure type of the same material is determined, and - a corresponding reference heat treatment parameter and reference time are recorded and linked to the at least one reference microstructural transformation and / or the at least one reference microstructure type of the same material and stored in a material database; wherein this method was carried out prior to the method according to one of the preceding claims.

6. The method according to claim 4 or claim 5, characterized in that by comparing the heat treatment parameter with the reference heat treatment parameter from the material database and / or by comparing the indentation time with the reference time from the material database, the at least one microstructure transformation and / or the at least one microstructure type of the material of the workpiece (102) is determined by means of the indentation body (110) being indented into the surface (112) of the workpiece (102).

7. Method according to one of the preceding claims, characterized by the following further steps: - detecting a shape, in particular a three-dimensional shape, of the plastically deformed workpiece indentation (116) after the step of indenting the indentation body (110); - comparing the detected shape, in particular the detected three-dimensional shape, of the plastically deformed workpiece impression (116) with a simulated shape, in particular a simulated three-dimensional shape, of a plastically deformed workpiece impression (116) according to a material deformation model of the workpiece (102); and - Determining the at least one material characteristic of the material of the workpiece (102) from the comparison.

8. Device (100, 200) for determining at least one microstructural transformation and / or at least one microstructure type of a material of a workpiece (102) and / or for determining at least one material characteristic of the material of the workpiece (102), comprising: - a workpiece holder (104) for receiving and / or fixing the workpiece (102); - an indentation element (106) comprising an indentation element region (108) having an indentation body (110) for indentation into a surface (112) of the workpiece (102); - a force generator (114) which is mechanically coupled to the workpiece holder (104) and / or the indentation element (106) for generating an indentation force (Fe) for indenting the indentation body (110) into a surface (112) of the workpiece (102) for plastically deforming the workpiece (102) by means of the indentation body (110) to generate a plastically deformed workpiece indentation (116); and - a heat treatment device (118, 172) for performing a heat treatment of the workpiece (102) by applying low-temperature heat and / or high-temperature heat to the workpiece (102).

9. Device (100, 200) according to claim 8, characterized in that the heat treatment device (118, 172) has at least one heat treatment chamber (120, 174) which encloses at least the indentation element region (108), the workpiece (102) and / or the workpiece holder (104) during the heat treatment.

10. Device (100, 200) according to claim 8 or claim 9, characterized in that the heat treatment device (118, 172) - is constructed by means of a combined high-temperature and low-temperature heat treatment unit (122); or - is constructed by means of a separate high-temperature heat treatment unit (124) and a separate low-temperature heat treatment unit (126).

11. Device (100, 200) according to claim 10, characterized in that the - combined high-temperature and low-temperature heat treatment unit (122) comprises a, preferably electrical, heating unit (128) for generating the high-temperature heat and a cooling unit (130), preferably comprising at least one cooling medium channel (132) for flowing through by means of a cooling medium, for generating the low-temperature heat, or - the separate high-temperature heat treatment unit (124) comprises a, preferably electrical, heating unit (134) for generating the high-temperature heat and the separate low-temperature heat treatment unit (126) comprises a cooling unit (136), preferably having at least one cooling medium channel (138) for flowing through by means of a cooling medium, for generating the low-temperature heat.

12. Device (100, 200) according to claim 10 or claim 11, characterized in that the device comprises a control and / or regulating unit (140) which is connected or connectable to the heating unit (128, 134) for controlling and / or regulating the temporal generation of the high-temperature heat by means of the heating unit (128, 134) and / or is connected or connectable to the cooling unit (130, 136) for controlling and / or regulating the temporal generation of the low-temperature heat by means of the cooling unit (130, 136).

13. Device (100, 200) according to one of claims 8 to 12, characterized in that the heat treatment device (118, 172) comprises a temperature detection device (142) for detecting a temperature in the at least one heat treatment chamber (120, 174) and / or a temperature on a surface (112) of the workpiece (102).

14. Device (100, 200) according to claim 13, characterized in that the temperature detection device (142) comprises a first temperature sensor (144) for detecting the temperature in the at least one heat treatment chamber (120, 174) and a second temperature sensor (146) for detecting the temperature on the surface (112) of the workpiece (102), wherein the second temperature sensor (146) is in direct contact with the surface (112) of the workpiece (102) for this purpose.

15. Device (100, 200) according to one of claims 8 to 14, characterized in that the heat treatment device (118, 172) comprises a gas connection (148) and a gas line (150) fluidly connected thereto, which opens into the at least one heat treatment chamber (120, 174) for supplying the at least one heat treatment chamber (120) with protective gas during the heat treatment.

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