System for heat-treating a light metal component and heat-treated light metal component

Abstract

System for heat-treating a light metal component, comprising: an oven (30) for heating a light metal component, a cooling device (50) for cooling the light metal component, wherein the cooling device (50) comprises at least one cooling unit (51) with a plurality of spray nozzles for spraying a liquid medium onto the light metal component under spray pressure (P), and a rotation unit (55) for generating a relative rotational movement between the light metal component and the cooling unit (51), wherein the cooling unit (51) is configured to generate a distance-pressure ratio (Vap) of the distance (a) between a spray nozzle and the light metal component in millimeters to the spray pressure (P) of the spray nozzle in bar of less than or equal to five, and a transfer unit (40) for transferring the light metal component from the furnace (30) to the cooling device (50), wherein the transfer unit (40) is designed to transfer the light metal component from the furnace (30) to the cooling device (50) within a period of less than 30 seconds.

Description

[0001] The invention relates to a system for heat-treating a light metal component, in particular a rotationally symmetrical component, and to a correspondingly heat-treated light metal component that is produced in a system or with a method for heat-treating.

[0002] It is known that light alloy wheels for motor vehicles can be manufactured by casting or forging. The requirements for the molds and the alloy used differ between forging and casting.

[0003] From WO 2020 / 212578 A1, a light alloy wheel is known comprising a hub section, a rim section, and a plurality of circumferentially distributed spokes extending between the hub section and the rim section. The outer rim flange exhibits circumferentially acting tensile residual stresses that are greater than the circumferentially acting residual stresses of the inner rim flange.

[0004] WO 2017 / 076801 A1 discloses a light metal casting component made of a hypoeutectic aluminium casting alloy containing 3.5 to 5.0 weight percent silicon and 0.2 to 0.7 weight percent magnesium.

[0005] From JP 2001 288547 A, an aluminum casting is known with a composition, based on weight, of 2.0 to 6.0% silicon, 0.15 to 0.34% magnesium, up to 0.2% iron, 0.0003 to 0.01% strontium, the remainder being aluminum and unavoidable impurities, and optionally with 0.01 to 0.25% titanium and 0.0001 to 0.001% boron. After casting, the component is subjected to solution annealing at 540°C to 570°C for 15 to 60 minutes and quenched.

[0006] The present invention is based on the objective of proposing a system and a method for heat-treating a lightweight metal component, with which a lightweight metal component with an improved microstructure or long service life can be produced. Furthermore, the objective is to propose a corresponding lightweight metal component with improved microstructure or material properties.

[0007] A proposed method for heat-treating a light metal component comprises: providing a light metal component that is at least partially rotationally symmetrical with respect to a longitudinal axis; solution annealing the light metal component in a furnace at a temperature (T) of less than 100 K below the melting temperature (TS) of the light metal for a period (t) of less than two hours; transferring the solution-annealed light metal component from the furnace to a cooling device within a period of less than 30 seconds;Cooling of the solution-annealed light metal component in the cooling device, wherein a liquid medium is sprayed onto the solution-annealed light metal component by means of spray nozzles at a spray pressure (P), wherein the spraying takes place under relative rotational movement between the light metal component and the spray nozzles, wherein the cooling is carried out with a distance-pressure ratio (Vap) of the distance (a) between a spray nozzle and the light metal component in millimeters to the spray pressure (P) of the spray nozzle in bar of less than or equal to five.

[0008] The process enables very rapid and efficient cooling, resulting in a significant improvement in the mechanical properties of the lightweight metal component compared to known solutions. This applies to both static material properties such as tensile strength and hardness, as well as to the component's cyclic material properties. Thus, with comparable material usage specifications, the service life is increased, or conversely, with comparable service life specifications, the material requirement for the component is reduced. Spraying coolant at the specified distance-pressure ratio, combined with simultaneous circular cooling through relative rotation, further promotes uniform cooling of the component. This minimizes thermally induced deformations, for example, achieving a shape deviation of less than one millimeter in a component such as a vehicle wheel.

[0009] The transfer of the solution-annealed light metal component from the furnace to the cooling device is carried out rapidly, preferably in less than 30 seconds, particularly in less than 20 seconds, or optionally even in less than 10 seconds. According to a preferred method, the solution-annealed light metal component can be cooled at a cooling rate of at least 250 K / s. The target temperature of the component after the cooling process is preferably less than 100°C, and no subsequent temperature increase should occur over time.

[0010] During quenching, the relative rotational movement can be achieved by having the cooling device or its nozzles stationary, and the component being driven to rotate relative to this about the axis of rotation. Alternatively or additionally, the relative rotational movement can be achieved by having the component stationary, and at least a subset of the nozzles being rotatable relative to it.

[0011] The quenching process is carried out such that a characteristic value (V), determined from the relative rotational speed (r), number of nozzles (n), and distance (a) of the nozzles to the axis of rotation, is preferably less than or equal to 500. The characteristic value is calculated as the ratio between the relative rotational speed in revolutions per minute (r [r / min]) to the number of nozzles (n) on a circumferential line, multiplied by the distance (a [mm]) of the nozzles to the axis of rotation, i.e.: V=(r / n)∗a≤500.

[0012] This preferred rotational speed-to-nozzle ratio V applies to at least one group of nozzles arranged along a circumferential line. "Along a circumferential line" means that the spray cones of the nozzles have a radial overlap with this circumferential line. It is understood that, depending on the shape of the component, one or more further groups of nozzles may be provided for which the aforementioned rotational speed-to-nozzle ratio V may, but does not necessarily, apply. Thus, further groups of nozzles may be located on other circumferential lines, that is, on different radii and / or in a different orientation with respect to the axis of rotation.

[0013] For example, quenching can be carried out using a group of nozzles at a relative rotational speed (r) between the component and the cooling unit of 200 rpm and a number (n) of 10 circumferentially distributed nozzles, spaced (a) 20 mm from the axis of rotation, with a rotational speed-nozzle ratio V of 400, V = (200 / 10)*20 = 400. It is understood that any other values ​​for relative rotational speed, number of nozzles, and distance to the axis of rotation can be used to achieve the preferred characteristic value V of less than or equal to 500 for at least one group of nozzles.

[0014] In one possible embodiment, the solution-annealed light metal component can be rotated about its longitudinal axis in the cooling device using, for example, four to eight nozzles distributed around its circumference, at a speed of at least 100 rpm, and in particular at least 200 rpm, while the liquid medium is sprayed onto it. Water is preferably used as the spray medium. The liquid medium can be sprayed onto the light metal component at a temperature of at least 5°C and less than 60°C, and in particular less than 40°C. The spray medium can be applied to the light metal component at a pressure of at least 130 bar. The cooling or spraying process preferably takes place over a period of less than 45 seconds, and in particular less than 30 seconds, and in particular less than 20 seconds. For example, the total cooling time can be between 5 and 15 seconds.

[0015] The starting part can be manufactured, for example, by casting, especially low-pressure casting, from a molten light metal. Alternatively or additionally, the starting part can also be manufactured by pressure forming processes such as forging, extrusion, or die casting.

[0016] Regardless of the nature of the starting part and the associated upstream process, such as casting or die forming, the light metal component is preferably subjected to solution annealing with residual heat from the upstream process of at least 250°C. For this purpose, the light metal component can be subjected to solution annealing, for example, within a time of less than five minutes after removal from the upstream tooling. The upstream tooling can be, for example, a casting or die forming tool. By utilizing the residual heat from the upstream process, annealing times during solution annealing can be reduced, thus improving the overall efficiency of the process.

[0017] For a casting process, particularly low-pressure casting, an aluminum alloy with an aluminum content of at least 85 wt.% can be used, wherein the solution annealing is carried out at a temperature (T) of preferably at least 530°C and at most 550°C. Alternatively, a magnesium alloy with a magnesium content of at least 85 wt.% can also be used as a light metal, wherein the solution annealing is carried out at a temperature (T) of preferably at least 350°C and at most 450°C.

[0018] When using an aluminum casting alloy, the light metal component is preferably subjected to stress-relief annealing after cooling. Stress-relief annealing can be carried out, for example, for a period of less than 2.5 hours at less than 200°C.

[0019] It has been shown that the process leads to improved microstructure and mechanical properties regardless of the starting material, such as a casting or molded part, and regardless of the alloy composition. Therefore, the alloy compositions mentioned below should be understood as examples only and not as limiting.

[0020] A lightweight metal component produced according to the inventive method can, according to a first possibility, be manufactured from an aluminum casting alloy containing between 6.5 and 7.5 wt. percent silicon (Si), 0.20 to 0.65 wt. percent magnesium (Mg), iron (Fe) with up to 0.55 wt. percent, optionally further alloying elements with a combined total of less than 1.3 wt. percent, the remainder being aluminum (Al) and unavoidable impurities, wherein the lightweight metal component has a microstructure with aluminum solid solutions and intermetallic compounds, wherein silicon-containing precipitates are formed in the aluminum solid solutions, and wherein the silicon-containing precipitates formed in the aluminum solid solutions have, at least in an edge shell region of the lightweight metal component with a depth of, in particular, up to 2 mm, an average diameter of less than 0.3 micrometers, in particular less than 0.2 micrometers.

[0021] The product manufactured by this process therefore has particularly fine and uniformly distributed silicon-containing precipitates in the aluminum solid solutions, which advantageously contributes to an increased service life and strength of the component. The number of coarse, inhomogeneously distributed silicon-containing precipitates in the aluminum solid solutions is also low in the products manufactured by this process. In particular, at least in an edge shell region of the light metal component, that is, especially at a depth of up to 1 mm, measured on a polished surface of 498 square micrometers, the number of silicon-containing precipitates with an average diameter of more than 0.03 micrometers contained in the aluminum solid solutions is less than 500, especially less than 400, and especially less than 200.Furthermore, silicon particles can be formed at the grain boundaries of the aluminum solid solutions, whereby the silicon particles formed at the grain boundaries have a maximum diameter of less than 40 micrometers, in particular less than 20 micrometers, and in particular less than 10 micrometers, at least in an edge shell region of the light metal component. These characteristics, i.e., the relatively small number of coarse silicon particles at the grain boundaries and the relatively fine precipitates, also contribute to an improvement in the mechanical properties of the component and / or an increased service life.

[0022] The magnesium (Mg) content can range between 0.25 and 0.45 percent by weight. The iron (Fe) content can be a maximum of 0.12 percent by weight.

[0023] The aluminum casting alloy may optionally contain further alloying elements or unavoidable impurities in addition to aluminum (Al), silicon (Si), magnesium (Mg), and iron (Fe). The proportion of optional alloying elements and unavoidable impurities is, in particular, less than 1.0 percent by weight of the total weight of the light metal casting component. Therefore, the aforementioned aluminum casting alloy, which can also be referred to as an aluminum-silicon casting alloy, contains at least 90.3 percent aluminum by weight.

[0024] In one embodiment, the aluminium casting alloy may optionally contain copper (Cu) in a proportion of less than 0.1 percent by weight, in particular a maximum of 0.05 percent by weight.

[0025] According to one embodiment, the aluminium casting alloy can optionally contain manganese (Mn) in a proportion of less than 0.2 percent by weight, in particular a maximum of 0.1 percent by weight.

[0026] In one embodiment, the aluminium casting alloy may optionally contain zinc (Zn) in a proportion of less than 0.15 percent by weight, in particular a maximum of 0.07 percent by weight.

[0027] In one embodiment, the aluminium casting alloy may optionally contain titanium (Ti) in a proportion of less than 0.3 percent by weight, in particular a maximum of 0.2 percent by weight.

[0028] In one embodiment, the aluminium casting alloy may optionally contain boron (B) in a proportion of less than 0.1 percent by weight, in particular of a maximum of 0.01 percent by weight.

[0029] Depending on the specific design, the aluminum casting alloy can optionally contain strontium (Sr) in a proportion of less than 150 ppm.

[0030] Depending on the specific formulation, the aluminum casting alloy can optionally contain tin (Sn) in a proportion of less than 300 ppm.

[0031] Depending on the specific design, the aluminum casting alloy can optionally contain nickel (Ni) in a proportion of less than 550 ppm.

[0032] According to one embodiment, the aluminium casting alloy can optionally contain chromium (Cr) in a proportion of less than 500 ppm, preferably less than 200 ppm.

[0033] It is understood that all the aforementioned alloying elements can be used individually or in combination with one or more other elements. This also includes the possibility that none or only some of the optional alloying elements are present in the aluminum casting alloy or in the component manufactured from it. The remainder of the aluminum casting alloy consists of aluminum, silicon, magnesium, and unavoidable impurities.

[0034] A product manufactured using the process, in particular a light metal component made from an aluminium casting alloy, has at least in an edge shell area a 0.2% yield strength of greater than 215 N / mm2, a tensile strength Rm of greater than 280 N / mm2, a cyclic yield strength Rp0,2' of greater than 275 MPa and / or a Brinell hardness of greater than 85 HB.

[0035] A lightweight metal component produced using the inventive method can, according to an exemplary second possibility, be manufactured from an aluminum forging alloy containing 0.4 to 0.8 wt. percent silicon, 0.8 to 1.2 wt. percent magnesium, up to 0.9 wt. percent iron, optionally further alloying elements with a combined weight of less than 1.5 wt. percent, the remainder being aluminum, and unavoidable impurities. The product manufactured from this is accordingly an aluminum forging. The optional alloying elements can, for example, be provided as described above in connection with the first possibility for the aluminum casting alloy.

[0036] A lightweight metal component produced using the inventive method can, according to an exemplary third embodiment, be manufactured from a magnesium forging alloy containing 7.8 to 9.2 wt. percent aluminum, 0.2 to 0.8 wt. percent zinc, up to 0.55 wt. percent manganese, optionally further alloying elements with a combined total of less than 1.0 wt. percent, the remainder being magnesium, and unavoidable impurities. The product manufactured from this alloy is accordingly a magnesium forging. The optional alloying elements can be provided in proportions, for example, as described above in connection with the first embodiment for the aluminum casting alloy.

[0037] The problem is further solved by means of a system for heat-treating a light metal component, comprising: a furnace for heating a light metal component; a cooling device for cooling the light metal component, wherein the cooling device has at least one cooling unit with a plurality of spray nozzles for spraying a liquid medium at spray pressure onto the light metal component; and a rotation unit for generating a relative rotary motion between the light metal component and the spray nozzles, wherein the cooling unit is configured to generate a distance-pressure ratio of the distance between a spray nozzle and the light metal component in millimeters to the spray pressure of the spray nozzle in bar of less than or equal to five;and a transfer unit for transferring the light metal component from the furnace to the cooling unit, wherein the transfer unit is designed to transfer the light metal component from the furnace to the cooling unit within a period of less than 30 seconds.

[0038] The system offers similar advantages to the process. In particular, it enables very rapid and efficient cooling, leading to a significant improvement in the mechanical properties of the lightweight metal component. The design of the cooling device for spraying coolant with the specified distance-pressure ratio, combined with the circulating cooling effect of the rotating unit, promotes uniform cooling of the component. Thermally induced deformations can thus be minimized.

[0039] Specifically, a subset of nozzles can be arranged on a circumferential line at a distance around the axis of rotation. The subset of nozzles and their distance from the axis of rotation are selected, and the rotation unit is adjustable, such that the rotational speed-to-nozzle ratio (ratio of the relative rotational speed (n) between the light metal component and the cooling unit in revolutions per minute to the subset of nozzles, multiplied by the distance of the nozzles from the axis of rotation in millimeters) is less than or equal to 500. The nozzles are preferably arranged and designed such that, viewed in longitudinal section, the spray cones produced by the nozzles completely cover the light metal component.

[0040] In one possible configuration, several groups of cooling units, each with multiple nozzles, can be provided, with the different groups of cooling units being controllable separately from one another by means of a control unit. However, it is also possible to provide only one group of cooling units whose nozzles are controlled collectively.

[0041] Preferred embodiments are explained below with reference to the figures in the drawing. It shows: Fig. 1 schematically a method according to the invention for heat-treating a light metal component; Fig. 2 schematically a system according to the invention for heat-treating a light metal component; Fig. 3 a cooling device as a detail of the system Fig. 2 with the lightweight metal component included in longitudinal section; Fig. 4 a light metal component in the form of a wheel, manufactured according to the method or by means of the system according to the Fig. 1 to 3 have been manufactured; Fig. 5. Investigation results regarding the distribution of precipitates within the aluminium mixed crystals based on two samples or measuring points each ( Fig. 5A first measuring point and Fig. 5B second measuring point), showing the distribution of a light metal component manufactured according to the invention on the right-hand side, and showing the distribution of a comparison component on the left-hand side; Fig. 6 SEM images of the microstructures of components made from aluminium-silicon casting alloys, showing the microstructure of a component manufactured according to the invention on the right, and showing the microstructure of a comparison component on the left; Fig. 7 a lightweight metal component in the form of a wheel produced according to the invention in perspective view, with measuring points for residual stress measurement shown therein; Fig. 8 the results of the residual stress measurement on the in Fig. 7 measuring points shown, with indication of the measurement results of the component manufactured according to the invention on the right-hand side, and indication of the measurement results of the comparison component on the left-hand side; Fig. 9 Results of an Incremental Step Test (IST), showing the stress curve for a component manufactured according to the invention with a dashed line, and the stress curve for a comparison component with a solid line; and Fig. 10 different exemplary geometries of components that can be manufactured using the method or system according to the invention.

[0042] The Fig. 1 and Fig. Figures 2, which are described together below, schematically show a method and a system according to the invention for heat-treating a light metal component.

[0043] In step S10, a lightweight metal component is provided that is at least partially rotationally symmetrical with respect to a longitudinal axis. This lightweight metal component 1 forms the intermediate product, which is processed into a heat-treated lightweight metal component in the subsequent steps.

[0044] The intermediate product can be manufactured, for example, by casting, in particular by low-pressure casting, or by pressure forming, in particular forging, extrusion, or die casting. In the embodiment according to Fig. 2. The intermediate product is a casting, so the preprocess tool 10 is accordingly a casting tool. The casting tool can, for example, comprise a lower part 11, side parts 12, and an upper part 13, which form a cavity into which the molten metal is poured.

[0045] For casting, for example, an aluminum casting alloy can be used that contains between 6.5 and 7.5 wt. silicon (Si), 0.20 and 0.65 wt. magnesium (Mg), iron (Fe) up to 0.55 wt., optionally other alloying elements with a combined total of less than 1.3 wt., the remainder being aluminum (Al) and unavoidable impurities. Accordingly, the aluminum casting alloy has at least 90.3 wt. percent aluminum as its main component.

[0046] As optional alloying elements, the aluminum casting alloy may contain up to 0.2 wt% copper (Cu), up to 0.35 wt% manganese (Mn), up to 0.15 wt% zinc (Zn), up to 0.25 wt% titanium (Ti), up to 0.15 wt% lead (Pb), and / or up to 0.05 wt% tin (Sn) with a proportion of less than 0.3 wt%. Other optional alloying elements that may be present in the aluminum casting alloy, each with a maximum of 0.05 wt% and a combined maximum of 0.15 wt%, include, for example, boron (B), strontium (Sr), nickel (Ni), chromium (Cr), or other alloying elements that may result from the addition of scrap and unavoidable impurities.For example, AlSi7Mg (EN AC-42000) according to DIN EN 1706, or AlSi7Mg0.3 (EN AC-42100) according to DIN EN 1706, or an aluminum alloy with the composition of EN AW-6061 according to DIN EN 573-3 (UNS A96061) can be used, without being limited to these. Depending on the requirements of the component to be manufactured, other light metal alloys can also be used, in particular magnesium alloys, such as AZ80 (EN 1753 MG-P-61).

[0047] After the melt has solidified, component 1 is removed from the tool 10 and transported to the furnace 30 by means of a suitable transport device 20. This is designated as step S20. Component 1 is preferably transported from the tool 10 to the furnace 30 by the transport device 20 so quickly that, at the start of the solution annealing process in the furnace, it still has a residual heat of at least 250°C from the preliminary process S10 in the tool 10. For this purpose, the light metal component 1 is, for example, subjected to the solution annealing process within a period of less than five minutes after removal from the preliminary process tool 10. By utilizing the residual heat from the preliminary process, annealing times can be reduced and efficiency improved.

[0048] In step S30, the component is heated in furnace 30 at a temperature (T30) of less than 100 K below the melting or solidification temperature (TS) of the light metal for a duration (t30) of less than two hours. The melting or solidification temperature of an aluminum casting alloy, for example AlSi7Mg, is between 550°C and 625°C. Accordingly, solution annealing could be carried out in this case at a temperature between 525°C and 550°C. The heating time can be, for example, up to one hour. The holding time for annealing an aluminum casting alloy is preferably less than one hour. When using a magnesium alloy, solution annealing can be carried out at a temperature between 350°C and 450°C. The holding time for annealing a magnesium alloy is preferably less than 1.5 hours.

[0049] In step S40, the component 1 is transferred very rapidly from the furnace 30 to a cooling device 50 after solution annealing. This transfer is carried out using a suitable transfer unit 40 within a period (t40) of less than 30 seconds, preferably less than 20 seconds, and particularly less than 10 seconds. During solution annealing, the light metal component 1 can be cooled at a cooling rate of 250 K / s or more. The target temperature (T2) of the component 2 after the cooling process is preferably less than 100°C, and no subsequent temperature increase should occur over time.

[0050] In step S50, the solution-annealed light metal component is quenched in the cooling device 50. A liquid medium is sprayed onto the solution-annealed light metal component 1 by means of cooling units 51 or nozzles at a spray pressure (P). The spraying takes place with a relative rotational movement between the light metal component 1 and the cooling units 51. At least for a subset of the spray nozzles 51, the light metal component is subjected to a distance-pressure ratio (Vap) of less than or equal to five, in particular less than four. The characteristic value for the distance-pressure ratio (Vap) is defined by the quotient of the distance (a) between the spray nozzle and the light metal component in millimeters and the spray pressure (P) of the spray nozzle in bar, i.e., Vap = a [mm] / P [bar]. For example, a distance-pressure ratio (Vap) of less than or equal to five can be used for at least half of the cooling units 51, preferably more than 70% of the nozzles.Further details of the quenching or cooling device 50 are given below in connection with . Fig. 3 explained.

[0051] When using an aluminum casting alloy, the light metal component 1 is subjected to stress-relief annealing after quenching. This is shown schematically as step S60. The stress-relief annealing takes place in a suitable aging facility 60 and can, for example, be carried out for a duration (t60) of less than 2.5 hours at a temperature (T60) of less than 200°C.

[0052] In Fig. Figure 3 shows the cooling device 50 as a single, enlarged view. The cooling device 50 is adapted to the shape of the component 2 to be quenched, in this case a wheel. The cooling device 50 comprises several cooling units 51a, 51b, 51c, 51d, 51e, 51f for quenching the wheel 2. In the present embodiment, at least one cooling unit 51a is provided for quenching the hub section 3; at least one cooling unit 51b for quenching the spokes 4; at least one cooling unit 51c for quenching the outer surfaces 5 of the wheel; at least one cooling unit 51d for quenching the inner rim flange 6; at least one cooling unit 51e for quenching the outer rim flange 7; and / or at least one cooling unit 51f for quenching the inner surface 8 of the wheel.

[0053] The cooling units 51a, 51b, 51c, 51d, 51e, and 51f are designed to spray a cooling medium onto the wheel. They can be controlled collectively or, in an alternative configuration, separately by a control unit (not shown) with regard to the start and duration of cooling, as well as optionally at least one other parameter influencing the quenching effect, such as the temperature or pressure of the cooling medium. For example, steam or a liquid-gas mixture, in particular water or a water-air mixture, is used as the cooling medium. The cooling units 51a, 51b, 51c, 51d, 51e, and 51f include corresponding nozzles through which the cooling medium is sprayed onto component 1 at high pressure.

[0054] The cooling device 50 comprises a first device part 52 on which the cooling units 51a, 51b, 51c, 51e are arranged, acting on the inner surface 8 of the wheel, and a second device part 53 on which the cooling units 51d, 51f are attached, acting on the outer surface 5 of the wheel 2. The device parts 52, 53 are movable relative to each other, so that a wheel can be inserted and removed. The device can be designed such that the upper part is movable relative to the lower part, or conversely, the lower part relative to the upper part, or both parts are movable relative to each other. The two device parts 52, 53 are designed as housings. The component 1 is attached to a support element 54, then the device parts 52, 53 are positioned relative to the component 1 until the desired distance is reached. Finally, the quenching process begins by spraying the cooling medium.It is provided that the support element 54 can be driven by means of a rotary unit 55 in order to rotate the wheel relative to the cooling units 51a, 51b, 51c, 51d, 51e, 51f during quenching.

[0055] A subset of cooling units or nozzles is arranged on a circumferential line at a specific distance a around the axis A. This is explained below using the example of cooling unit 51b for cooling the outer surface of the spokes 4. Several cooling units 51b are arranged around the circumference with at least approximately the same radius a around the axis of rotation A. For at least one group of cooling units 51 that lie on a circumferential line or have the same distance a to the axis of rotation A, their number n and their distance a to the axis of rotation A are selected, and the rotation unit 55 is set, such that a rotational speed-nozzle ratio Vrn, calculated from the relative rotational speed (r) between component 1 and cooling units 51 in revolutions per minute to the subset (n) of nozzles multiplied by the distance (a) of the nozzles 51 to the axis of rotation A in millimeters, is less than or equal to 500. Thus, preferably for at least one group of cooling units 51, the following formula applies: V=(r / n)∗a≤500.

[0056] For quenching using, for example, the group of cooling units 51d, which may have a distance a51d of 10 mm from the axis of rotation A, the characteristic value for the speed-nozzle ratio Vrn according to the formula above, assuming a relative speed (r) between component 1 and the cooling unit of 200 rpm, results in a number (n) of 8 or more circumferentially distributed nozzles. Expressed as a formula: n ≥ (r*a) / 500. It is understood that other technically suitable values ​​for relative speed r, number n, and distance a to the axis of rotation A can be used to achieve the preferred characteristic value Vrn.

[0057] Preferably, the cooling units 51a, 51b, 51c, 51d, 51e, 51f are arranged, configured, and / or oriented such that, viewed in longitudinal section, the spray cones generated by the nozzles completely cover the light metal component 1. It is understood that the number, orientation, and arrangement of the cooling units depend on the geometry of the component 2 to be quenched. The cooling units 51a, 51b, 51c, 51d, 51e, 51f can be combined in a single cooling circuit, or several cooling circuits can be provided, each supplying individual groups of cooling units with cooling medium. For example, the cooling units 51a, 51b, 51c, 51d, 51e, 51f, each lying on a common circle around axis A, can be assigned to a common cooling circuit. If several cooling circuits are provided, these can preferably be controlled separately from each other, so that the voltage distribution of component 1 can be influenced by appropriate control.

[0058] Fig. Figure 4 shows a light metal component 1 in the form of a wheel, which is manufactured according to the method or by means of the system according to the Fig. Components 1 to 3 were produced from a casting as a semi-finished product. Accordingly, the lightweight metal component 1 exhibits a microstructure with aluminum solid solutions and intermetallic compounds, with silicon-containing precipitates forming within the aluminum solid solutions.

[0059] The Fig. 5A and Fig. Figure 5B shows the results of investigations regarding the distribution of precipitates within the aluminum solid solutions, with the distribution of a lightweight metal component produced according to the invention shown on the right and the distribution of a comparable component shown on the left. It was found that in the lightweight metal component 2 according to the invention, the silicon-containing precipitates formed in the aluminum solid solutions, at least in an edge shell region of the component up to 2 mm deep, have a diameter or longest extent of less than 0.3 micrometers, in particular less than 0.2 micrometers, and in particular less than 0.1 micrometers (right side). In contrast, the size or longest extent of the silicon-containing precipitates formed in the aluminum solid solutions in the comparable component is significantly greater than 0.3 micrometers (left side).Furthermore, it has been shown that, at least in the marginal shell area, i.e., measured at a depth of up to 2 mm, the number of silicon-containing precipitates with an average diameter of more than 0.03 micrometers contained in the aluminum solid solutions on a polished area of ​​498 square micrometers is less than 500, in particular less than 400, and in particular less than 200. In contrast, the number of silicon-containing precipitates with an average diameter of more than 0.03 micrometers contained in the aluminum solid solutions, measured at a comparable depth with the same polished area, was significantly above 500 in the comparison component.

[0060] Fig. Figure 6 shows SEM images of the microstructures of components made from aluminium-silicon casting alloys, with the microstructure of a component 2 produced according to the invention shown on the right, and the microstructure of a comparison component shown on the left.

[0061] It has been shown that the inventive method leads to a finer distribution of silicon particles in the eutectic. Due to the rapid quenching, the silicon particles remain smaller and act as more effective barriers to deformation, thus increasing the strength of component 2. The silicon particles formed at the grain boundaries of the aluminum solid solutions have a maximum diameter of less than 40 micrometers, particularly less than 20 micrometers, and particularly less than 10 micrometers, at least in an edge shell region of the lightweight metal component 2 with a depth of up to 2 mm. In contrast, the size of the silicon particles contained between the aluminum solid solutions in the comparison component was significantly greater than 50 micrometers.

[0062] Fig. Figure 7 shows a lightweight metal component 1 in the form of a wheel produced according to the invention in a perspective view, with measuring points M1, M2, M3, M4, M5, M6 shown therein for residual stress measurement.

[0063] Fig. Figure 8 shows the corresponding results of the residual stress measurements on the components in Fig. The 7 measuring points M1, M2, M3, M4, M5, and M6 are shown. The measurement results of the component 2 manufactured according to the invention are shown on the right under "INV," and the measurement results of the comparison component are shown on the left under "COMP." The stresses are denoted as σ, where the values ​​σ1 indicate the first principal stresses and the values ​​σ2 indicate the second principal stresses. Tensile residual stresses are also given as positive values, and compressive residual stresses as negative values ​​in megapascals (MPa). It has been shown that in the component manufactured according to the invention, compressive residual stresses can be increased, for example, to 355 MPa at measuring point M6, and detrimental tensile residual stresses can be significantly reduced, for example, to a value of 327 MPa at measuring point M2. Overall, this results in a more homogeneous stress distribution and a longer service life.

[0064] Fig. Figure 9 shows the results of an Incremental Step Test (IST), with the stresses σ plotted on the Y-axis over a number of blocks B on the X-axis. Each block B represents one cycle of load cycles applied to the component. A cycle can comprise any defined number of load cycles. For a component 1 manufactured according to the invention, the stress curve is represented by a solid line (line "INV"), and for a comparison component, by a stress curve represented by a dashed line (line "COMP"). It was found that higher stresses σ are necessary for the component 1 manufactured according to the invention (solid line) to achieve the same strain. Furthermore, at the beginning, i.e., during the first load cycle blocks, the component 1 manufactured according to the invention (solid line) exhibits faster hardening behavior compared to the comparison component.This is evident in the depicted area a, where the INV line rises faster, or reaches its maximum stress value more quickly, than the COMP line. It is also evident that, according to the COMP line, a conventional component can only withstand approximately 125 load cycles (blocks B) with a relatively constant maximum stress of approximately 200 MPa. In contrast, as the INV line shows, a component according to the invention can withstand significantly more load cycles (blocks B) with a relatively constant maximum stress of approximately 210 MPa, approximately 150, before the stress drops. This means, as shown in the depicted area b, that the service life of a component 1 manufactured using the inventive method can be significantly increased compared to a conventional component.

[0065] It has been shown that a component 1 produced using the inventive method from an aluminium-silicon casting alloy has, at least in an edge shell area, i.e. at least in a depth of up to 2 mm, a 0.2% proof strength of greater than 215 N / mm2, a tensile strength Rm of greater than 280 N / mm2, a cyclic yield strength Rp0,2' of greater than 275 MPa and / or a Brinell hardness of greater than 85 HB.

[0066] In Fig. Figures 10A to 10E show various exemplary geometries of components 2 that can be produced using the method or system according to the invention. Solid components 2 can be processed, as shown in Fig. Figure 10A shows the outer shell areas 9 of the lateral surface, the top surface (upper), and the base surface (lower), as well as the inner core 2. Components 2 can be treated as closed hollow cylinders or pot-shaped components, as shown in Fig. Figure 10B shows pot-shaped components 2 with a bore, as shown in Fig. 10C shown, sleeve- or tube-shaped components 2, as in Fig. 10D shown, and / or conical components 2, as in Fig. 10E is shown, without being limited to these. It is advantageous for the quenching process if the components are rotationally symmetrical about axis A, so that they can be rotated relative to the cooling units 51.

[0067] Overall, the process and the system enable very rapid and efficient cooling. This leads to a significant improvement in the mechanical properties of the lightweight metal component compared to known components. Furthermore, thermally induced deformations can be minimized. Reference symbol list 1 component 2 Component core 3 Hub section 4 spokes 5 Outside 6 Inner rim flange 7 outer rim flange 8 Inside 9 Edge shell area 10 tools 11 Lower part 12 side panels 13 Top 20 means of transport 30 oven 40 transfer units 50 Cooling device 51a-51f Cooling units / nozzles 52 Device part 53 Device part 54 Support element 55 rotary unit 60 Outsourcing facility Axis a distance K Cooling medium M1-M6 measuring point n number P Spray pressure r rotational speed S10-S60 Procedure steps Temperature t time Vap distance-pressure ratio VRn speed-nozzle ratio QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] WO 2020 / 212578 A1

[0003] WO 2017 / 076801 A1

[0004] JP 2001 288547 A

[0005]

Images