Magnesium casting plant

Abstract

Magnesium casting plant (100) for the production of magnesium die-cast components, comprising: - a magnesium die-casting machine (140); and - a magnesium melting furnace (120) comprising a crucible (122), a housing (121) accommodating the crucible (122), and at least one porous burner (123) for heating the crucible (122), wherein the porous burner (123) is arranged in the housing (121) such that its hot exhaust gas (A) can enter a heating chamber (124) surrounding the crucible (122) inside the housing (121); and - a holding furnace (130) for the magnesium melt (M); and - a device (110) for preheating the mass; and - a duct system for the exhaust gas (A) discharged from the heating chamber (124); wherein the holding furnace (130) and the ingot preheating device (110) can be heated by an exhaust gas stream from the magnesium melting furnace (120), such that the hot exhaust gas (A) generated by the at least one porous burner (123) is supplied, after being discharged from the heating chamber (124), at least partially through the duct system to the ingot preheating device (110) and the holding furnace (130).

Description

[0001] The invention relates to a magnesium casting plant for the production of magnesium die-cast components.

[0002] The magnesium casting plant includes, among other things, a magnesium melting furnace for producing and providing molten magnesium, which can be used for die casting magnesium components, especially automotive components.

[0003] Magnesium melting furnaces and magnesium casting plants are known from the prior art, for example reference to DE 10 2004 062 620 A1 and DE 10 2012 107 865 A1.

[0004] The closest patent application, DE 12 63 995 A, describes a magnesium melting and charging system for a die-casting machine, with a crucible arranged in a box. Burners designed as annealing burners generate a temperature of over 1000 °C without a visible flame and are directed inside the box towards the side walls of the crucible. The exhaust gases from the burners are collected and used via pipes or lines to preheat the ingots fed into the crucible. In other words, the system features preheating of the ingots using the crucible heating exhaust gases.

[0005] DE 10 2008 042 540 B4 describes a device for holding molten metal, wherein the container for the molten metal is double-walled at least in one section, the heating device comprises at least one burner, and the burner is connected to a space formed in the double-walled section of the container for passing through the hot exhaust gases generated by the burner. Preferably, a gas burner is used in which combustion takes place in an open pore volume or in a porous body.

[0006] Regarding the state of the art, reference is also made to the casting plant described in DE 103 08 208 A1, the device for melting metal described in EP 0 571 731 A2 and the melting and holding furnace for aluminium blocks described in DE 699 22 698 T2.

[0007] The invention is based on the objective of providing a magnesium casting plant which does not have at least one disadvantage associated with the prior art, or at least only to a reduced extent.

[0008] This problem is solved by a magnesium casting plant or magnesium die-casting plant according to the invention, in accordance with the features of claim 1. Preferred further developments and embodiments are described both in the dependent claims and in the following explanations.

[0009] The magnesium melting furnace of the magnesium casting plant according to the invention comprises a crucible and a housing for the crucible. Furthermore, the magnesium melting furnace comprises at least one porous burner for heating the crucible.

[0010] Porous burners are known as such from the prior art, for example reference is made to DE 103 44 979 A1 and DE 43 22 109 A1.

[0011] The porous burner of the magnesium melting furnace is, in particular, a porous burner that can be operated using a gas-air mixture. The combustion of the continuously or, if applicable, discontinuously supplied and pre-treated gas-air mixture (e.g., by premixing) takes place flamelessly (i.e., without an open flame) within a porous structure (or possibly a honeycomb structure or the like), which is, in particular, a ceramic foam or the like. This flameless combustion of the gas-air mixture within the porous structure (also referred to as volumetric combustion) generates hot exhaust gas or a hot exhaust gas stream and, if applicable, thermal radiation, which is used inside the magnesium melting furnace to heat the crucible.

[0012] Compared to the conventional heating of magnesium melting furnaces using electricity or gas burners, numerous advantages arise, such as homogeneous heat generation and distribution (and the associated excellent temperature stability), dynamic and stepless heat control (power regulation with short response times), quiet, clean, and low-emission combustion, as well as short heating times. The high efficiency and consistently low emission levels result in significant cost and environmental benefits. Furthermore, productivity gains and improved furnace and plant availability are achieved. In addition, the formation of magnesium sludge can be avoided or at least reduced.

[0013] The porous burner is arranged in the housing in such a way that its hot exhaust gas (or exhaust gas stream) can enter a heating chamber inside the housing that surrounds the melting crucible. Advantageously, this heating chamber surrounding the melting crucible can have a small volume, which, among other things, promotes a homogeneous heat and temperature distribution (within the heating chamber) and enables a compact design of the melting furnace.

[0014] Particularly preferred are several porous burners distributed within the housing, which are preferably arranged in a heating chamber wall surrounding the crucible and defining the heating chamber, so that uniform exhaust gas supply to the heating chamber and a homogeneous temperature distribution within the heating chamber can be achieved. The position of the porous burners can preferably be varied. Preferably, the porous burners are arranged next to each other with a gap or, optionally, without a gap, forming, for example, a porous burner ring, particularly located below the crucible. Such a porous burner ring can also be formed by individual porous burner segments. It is particularly preferred that individual porous burners or segments can be switched on or off as required and / or controlled or regulated independently. The porous burners or segments can therefore be operated continuously or discontinuously, depending on the requirements.

[0015] At least one flow control element, in particular a motor-adjustable flow control element, can be arranged in the boiler room. This element allows the exhaust gas (or exhaust gas flow) introduced into the boiler room to be directed and, for example, redirected to achieve a homogeneous heat distribution in the boiler room or to achieve a locally higher heating output in certain areas. A flow control element could be, for example, a duct damper or similar device.

[0016] The magnesium melting furnace preferably also includes a control device or control unit, which is provided for the (automated) control or regulation of the combustion process in at least one porous burner and / or for the (automated) adjustment of at least one adjustable flow element. The control or regulation is preferably software-based.

[0017] One method for operating the magnesium melting furnace involves automatically increasing the temperature of the molten magnesium in the crucible to a target temperature (typically the casting temperature plus a temperature increase) shortly before each melt withdrawal (during continuous or standard operation). This is achieved by controlling or regulating the combustion process in the porous burner(s) and / or by activating additional porous burners or segments. The melt temperature can be maintained below the withdrawal temperature between withdrawals, especially since the addition of unmelted magnesium material (e.g., in the form of ingots, billets, or granules) naturally causes cooling. This results in energy savings, and the described method enables energy-optimized furnace operation.

[0018] Shortly before an intended molten metal withdrawal, the melting temperature can be automatically increased to ensure that the molten magnesium in the crucible reaches the precise target temperature at the exact moment of withdrawal, without any temperature overshoot. This procedure requires dynamic adjustment of the melting temperature, which is made possible by the magnesium melting furnace with porous burner technology. The control of the combustion process in the porous burner (where, as already explained, the magnesium melting furnace can also include several porous burners) as well as the activation and deactivation of additional porous burners (including the control of the activated porous burners) is preferably accomplished by the control unit described above.

[0019] Preferably, the heat or thermal energy to be supplied to the crucible until the intended molten metal is drawn off (i.e., the required energy or heat demand) is automatically predicted, taking into account, and in particular simultaneously considering, the state of the melt (especially the temperature), the thermal inertia of the system (which results, for example, from the currently available molten mass, the crucible mass, the burner technology, and the like), and other environmental conditions (e.g., the climate of the building). The required burner output is then determined, particularly considering the time available until the intended molten metal is drawn off. Subsequently, the combustion process in the porous burner can be automatically controlled or regulated accordingly, and / or additional porous burners can be activated and, in particular, also controlled or regulated.

[0020] The calculation of the heat or thermal energy to be supplied is preferably carried out using software based on a comprehensive system model represented by the software. The software is preferably an integral part of the control unit. Preferably, the software and / or the control unit also includes a learning module that enables autonomous optimization of all control and / or regulation functions during operation. In this respect, the control unit and / or the operating procedure executed by means of this control unit can also be referred to as an artificially intelligent furnace control system, and the overall system as an artificially intelligent system.

[0021] A magnesium casting plant according to the invention serves to produce magnesium die-cast components, in particular motor vehicle components, such as clutch or gearbox housings, wherein the magnesium casting plant according to the invention can also be used for so-called small part casting.

[0022] A magnesium casting or die-casting plant according to the invention comprises: - (at least) one magnesium die-casting machine; and - (at least) a magnesium melting furnace (like this); and - (at least) a holding furnace or metering furnace for molten magnesium, which is specifically assigned to the magnesium die-casting machine; and - (at least) a device for ingot preheating or a comparable preheating device, which is specifically assigned to the magnesium melting furnace; and - a duct system for the exhaust gas routed from the heating room of the magnesium smelting furnace.

[0023] It is provided that the holding furnace and the ingot preheating device can be heated by an exhaust gas stream from the magnesium melting furnace and, in particular, are heated only or exclusively by this exhaust gas stream, such that the hot exhaust gas generated by the at least one porous burner of the magnesium melting furnace, after being discharged from the heating chamber, is at least partially supplied to the ingot preheating device and the holding furnace via the duct system.

[0024] It is particularly preferred that the magnesium casting plant according to the invention also has an exhaust gas recirculation to the magnesium melting furnace.

[0025] During continuous plant operation or in standard operation, only minimal or no additional or separate energy requirements or expenditures are necessary for the holding furnace and / or for ingot preheating; i.e., the previously common independent operation of these systems is no longer required. The magnesium casting plant according to the invention is therefore characterized by high efficiency, high cost-effectiveness, and low emissions.

[0026] Furthermore, lower investment costs result because the holding furnace or dosing furnace and / or the ingot preheating system (preheater) can be designed without a heating element. However, it is possible to provide the holding furnace and / or the preheater with an electric or gas-powered emergency heating system.

[0027] Preferably, the magnesium casting plant according to the invention also includes a control device or control unit for controlling or regulating the entire plant. The control or regulation of the entire magnesium casting plant particularly includes the control or regulation of the magnesium melting furnace already described. A method for operating the magnesium casting plant according to the invention can therefore include the method for operating the magnesium melting furnace described above. Conversely, the method serves to operate the magnesium melting furnace within a magnesium casting plant according to the invention. In this context, the control device of the magnesium casting plant can communicate with the control device of the magnesium melting furnace. It is also possible for the control device of the magnesium melting furnace to be integrated into the control device of the magnesium casting plant.

[0028] The invention is explained in more detail below by way of example and in a non-limiting manner with reference to the drawing. The drawing shows Fig. 1 in schematic representation one embodiment of a magnesium casting plant according to the invention, comprising a magnesium melting furnace.

[0029] The magnesium die-casting plant 100 shown comprises a device 110 for ingot preheating (preheater), a magnesium melting furnace 120 for producing and supplying molten magnesium M (by melting ingots fed in sections), a holding furnace 130, and a magnesium die-casting machine 140. The molten magnesium M produced in the magnesium melting furnace 120 is pumped at intervals by means of a melt pump 150 into the holding furnace 130 and from there into the die-casting machine 140 for the primary forming of magnesium components or magnesium die-cast components, which is known in and of itself from the prior art.

[0030] The magnesium melting furnace 120 comprises a housing 121 (with thermal insulation) and a crucible 122. The crucible 122 has, for example, a capacity of approximately 2500 kg and can be covered by a lid belonging to the housing 121. The crucible 122 is heated by porous burners 123, which are operated with a gas-air mixture G+L. The porous burners 123 are arranged in the housing 121 such that the generated hot exhaust gases A enter a heating chamber 124 inside the housing 121, surrounding the crucible 122. The crucible 122 is thus heated by thermal convection heat at the bottom, with the heat input not being localized but uniform across the entire underside or rear surface of the crucible. Heating can also occur by means of radiant heat emitted from the porous burners 123.The number 125 designates motor-adjustable flow guide elements with which the exhaust gases A in the boiler room 124 can be directed.

[0031] In the illustrated embodiment, several porous burners or porous burner segments 123 are grouped together to form a porous burner ring and are arranged in the boiler chamber wall below and around the melting pot 122. The control or, if necessary, regulation of the porous burners 123 is carried out automatically by the control unit 126. The flow guide elements 125 can also be actuated by the control unit 126 as required.

[0032] Preferably, the temperature T of the molten magnesium M in the crucible 122 is automatically increased to a target temperature S for melt withdrawal shortly before a melt withdrawal E (by pumping into the holding furnace 130), as illustrated in the temperature-time diagram (T / t) shown. For this purpose, the control unit 126 calculates an optimal energy or heat requirement, taking into account the melt state, the thermal inertia of the system, and the ambient conditions, and determines the required burner output based on the available time. The combustion process in the porous burners 123 can then be controlled or regulated accordingly, and / or additional porous burners or segments can be activated and, in particular, also controlled or regulated.Preferably, the control unit 126 is designed to be self-learning and evaluates and optimizes itself during operation.

[0033] Furthermore, it is provided that the hot exhaust gases A generated by the porous burners 123, after exiting the boiler room 124 (where the exhaust gas A can still have a temperature of up to 800°C), are at least partially fed via a suitably designed duct system to the ingot preheating unit 110 and the holding furnace 130, where heat exchange occurs and these units are heated by the exhaust gas flow before the exhaust gases A, possibly after cleaning, are discharged via a chimney or similar. In standard operation, the enthalpy of the exhaust gas A is sufficient to fully heat the downstream holding furnace 130 and the upstream ingot preheating unit 110.

[0034] In contrast to the illustrated embodiment, in which the exhaust gases A are fed to devices 110 and 130 in parallel, they can also be fed to devices 110 and 130 sequentially or in series. Arrows R indicate a possible exhaust gas recirculation system, allowing a portion of the exhaust gases A to be returned to the combustion process in the porous burner 123.

[0035] The system 100 may include a control device (not shown in the figure) for controlling or regulating the entire system 100. The casting system 100 may also include valves or similar components (e.g., for steering, regulating, and / or shutting off exhaust gas flows, which can be done particularly within the framework of intelligent exhaust gas control) and / or sensors (e.g., for measuring temperature, pressure, flow, and the like), which are not shown in the figure. Reference symbol list 100 Magnesium casting plant 110 Device for mass preheating 120 Magnesium melting furnace 121 cases 122 crucibles 123 porous burners 124 Boiler room 125 Flow guide element 126 Control unit 130 Warming oven 140 Magnesium die casting machine 150 melt pump A Exhaust gas, exhaust flow E Melt extraction G Gas L air M Magnesium molten metal Exhaust gas recirculation Target temperature T Melting temperature t time

Claims

[1] Magnesium casting plant (100) for the production of magnesium die-cast components, comprising: - a magnesium die-casting machine (140); and - a magnesium melting furnace (120) comprising a crucible (122), a housing (121) accommodating the crucible (122), and at least one porous burner (123) for heating the crucible (122), wherein the porous burner (123) is arranged in the housing (121) such that its hot exhaust gas (A) can enter a heating chamber (124) surrounding the crucible (122) inside the housing (121); and - a holding furnace (130) for the magnesium melt (M); and - a device (110) for preheating the mass; and - a duct system for the exhaust gas (A) discharged from the heating chamber (124); wherein the holding furnace (130) and the ingot preheating device (110) can be heated by an exhaust gas stream from the magnesium melting furnace (120), such that the hot exhaust gas (A) generated by the at least one porous burner (123) is supplied, after being discharged from the heating chamber (124), at least partially through the duct system to the ingot preheating device (110) and the holding furnace (130). [2] Magnesium casting plant (100) according to claim 1, characterized by an exhaust gas recirculation (R) to the magnesium melting furnace (120). [3] Magnesium casting plant (100) according to claim 1 or 2, further comprising a control device for controlling or regulating the entire plant (100). [4] Magnesium casting plant (100) according to any one of the preceding claims, characterized by, that the magnesium melting furnace (120) has several distributed porous burners (123) to enable uniform exhaust gas supply to the heating chamber (124) and a homogeneous temperature distribution. [5] Magnesium casting plant (100) according to any one of the preceding claims, characterized by , that the magnesium melting furnace (120) has at least one motor-adjustable flow guide element (125) arranged in the heating chamber (124) with which the hot exhaust gas (A) can be directed in a targeted manner.

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