EP3081658A1 - Transport vessel for molten metal and method of filling a transport container with molten metal - Google Patents

Abstract

The present invention relates to a method for filling a transport container (1) for liquid metal, in particular liquid aluminum. The method is characterized in that at least prior to the introduction of the liquid metal into the transport container (1), the transport container (1) is acted upon with inert gas. Furthermore, the invention relates to a transport container for liquid metal.

Description

The present invention relates to a method for filling a transport container with liquid metal and a transport container for liquid metal.

Most metals tend to oxidize in the liquid state. Particularly in the case of aluminum and aluminum alloys, a high affinity for oxygen and a high solubility of hydrogen are present in the liquid state. In the air atmosphere, an immediate reaction of the oxygen and the water vapor content with the molten aluminum melt takes place and an oxide layer forms on the surface.

Methods are already known in which melt cleaning of liquid aluminum is performed to reduce air and moisture contact of liquid aluminum intended for shipment. Such a method is for example in the DE 43 07 867 A1 described. In this case, an inert gas treatment is carried out after the transfer of the melt in a container provided for transport. The inert gas treatment is carried out under vacuum and the melt is stirred by means of an agitator. The inert gas is injected here and preferably blown under the melt surface, for example by a stirring head. In this case, impurities and reaction products are suspended and removed from the melt surface. Subsequently, the liquid aluminum is transported in the transport container. This method has the disadvantage that even when transferring the liquid aluminum in the transport container, the melt can come into contact with oxygen and moisture, and thus the amount of oxides is increased.

The object of the present invention is therefore to provide a solution by means of which the metal loss, in particular metal loss due to oxidation, can be reduced.

The invention is based on the finding that this object can be achieved by setting desired conditions in the transport container before the liquid metal is introduced.

According to the first aspect, the invention therefore relates to a method for filling a transport container for liquid metal, in particular liquid aluminum. The method is characterized in that at least prior to the introduction of the metal into the transport container, the transport container is charged with inert gas.

The liquid metal supplied to the transport container is preferably liquid aluminum or a liquid aluminum alloy. Hereinafter, the liquid metal is also referred to as liquid aluminum for the sake of simplicity, the statements correspondingly apply to aluminum alloys, without explicitly mentioning them become. The liquid metal is also referred to below as a melt. As a transport container, a container is preferably referred to, which can be transported on a vehicle, in particular a truck. In particular, the transport container preferably has a shape that allows a pivoting of the transport container for emptying the transport container. For this purpose, the transport container has a holding pipe and, on the other hand, an outlet opening, which preferably merges into a pouring spout. At the holding stubs, the transport container be raised for example by means of a crane and a chain provided thereon and pivoted about the axis of the holding pipe for emptying. The outlet opening of the transport container is in this case preferably provided in the upper region of the wall of the transport container. A spout, for example, having a tubular shape, extends outwardly from the wall of the shipping container from the discharge port. The transport container also preferably has on the top a releasably secured lid, which closes an opening in a Verschließhaube, which can also be referred to as Abkrätzöffnung. Alternatively, the transport container may have a lid which closes the spout of the transport container and is releasably secured thereto. The transport container may for example have a capacity of 5 t.

According to the invention, at least prior to introducing the liquid metal into the transport container, the transport container is charged with inert gas. By pressurizing with inert gas is meant according to the invention the at least partial filling of the interior of the transport container with inert gas. As an inert gas, which can also be referred to as inert gas, this is understood to mean a gas which is inert with respect to the liquid metal, that is to say in which no or only a few chemical reactions occur with the liquid metal. Also with respect to impurities or alloying elements in the liquid metal, the inert gas is preferably inert.

The inert gas is introduced at least before filling the transport container in this. However, the supply of inert gas can also be maintained during and optionally after the filling of the transport container. By introducing the inert gas before filling the transport container is flooded with the inert gas. This means that preferably the entire interior of the transport container is filled with inert gas before the start of filling. Through the liquid metal, a portion of the inert gas from the. During filling Transport container displaced. During filling and after filling, the space above the melt surface in the transport container is filled with inert gas.

By filling the transport container with inert gas prior to introducing the liquid metal, that is before filling the transport container, a number of advantages can be achieved. On the one hand, the metal stream, which flows into the transport container during filling, can be protected by the inert gas. Furthermore, however, the melt surface of the liquid metal already accumulated in the transport container in the transport container can also be protected from contact with oxygen and moisture.

The inert gas employed in the process of the invention may be any gas which is inert to the liquid metal. Thus, for example, noble gases such as argon can be used for liquid aluminum. Preferably, however, nitrogen is used as the inert gas. This gas is used as a protective gas for aluminum and is also less expensive than other possible inert gases.

According to a preferred embodiment, inert gas is also supplied to the transport container during the filling of the transport container. Although the transport container is already filled with inert gas before filling the transport container with liquid metal, it is advantageous to maintain the inert gas supply even during the filling process. In this way, the entry of oxygen or moisture into the transport container can be reliably prevented and the protection of the liquid metal, in particular of the Befüllstrahls be maintained against oxidation.

According to a preferred embodiment, the inert gas is introduced at a low operating pressure in the transport container. Preferably, the inert gas is at a pressure above ambient pressure and below the pressure used to move or affect the melt surface of the liquid metal in the Transport container is necessary, is located, introduced. The ambient pressure is the pressure of the surroundings of the transport container. Before introducing the inert gas, the ambient pressure is also present in the interior of the transport container. The ambient pressure is usually about 1 bar. The pressure necessary to move the melt surface of the liquid metal in the transport container is dependent upon the removal of the inlet port for the inert gas to the melt surface. Preferably, however, a pressure is assumed which does not lead to a movement of the melt surface at a minimum distance between the inlet opening and the melt surface. By choosing the pressure higher than the ambient pressure, the transport container can be reliably filled with inert gas, that is, flooded. However, by using a pressure which is less than the pressure at which the melt surface would be moved at a minimum distance to the inlet opening, mixing of the melt can be prevented. The pressure with which the inert gas is introduced into the transport container is preferably in the range from 2 to 6 bar, and particularly preferably at 4 bar.

Preferably, the protective gas is introduced during the filling of the transport container with liquid metal above the melt surface of the liquid metal. By this position of the gas supply, on the one hand, a lower pressure for the supply of the inert gas is sufficient than when feeding below the melt surface. In addition, the position of the gas supply above the melt surface caused by the gas supply at a suitable pressure, no movement of the melt. Finally, by this position, the metal beam, which enters the transport container and which is above a melt surface already formed, be protected by the inert gas.

According to a possible embodiment, the inert gas is introduced through an inlet opening in a detachable lid of the transport container. As a cover of the transport container, a component is preferably referred to, which closes an opening of the transport container. According to one embodiment the lid closes an opening in a Verschließhaube the transport container. The closure cap in turn represents the upper boundary of the interior of the transport container and is preferably detachably or pivotally connected to the body of the transport container. The opening in the cap, which is closed by the lid, is also referred to as Abkrätzöffnung the transport container. Thus, with a gas supply through an inlet opening in the lid, the inert gas is introduced at the highest point of the interior of the transport container. As the inlet opening for the inert gas in this case the opening is referred to, via the gas exits into the interior of the transport container. In particular, the inlet opening does not constitute a passage opening for a lance or another gas line but the actual outlet opening of the gas. By introducing the inert gas over the cover of the transport container, which is provided on the cover, a reliable complete filling, ie flooding of the transport container be ensured before filling. In addition, a reliable gas supply in the space above the melt surface is ensured even during filling. The filling of the transport container takes place in this embodiment preferably via the spout.

According to a further embodiment, however, it is also possible that the inert gas is introduced via the spout of the transport container in the transport container. The spout is provided on the transport container in the upper region and is connected via the outlet opening with the interior of the transport container. About the outlet usually the liquid metal is removed from the transport container. For the method according to the invention, the inert gas can be introduced into the transport container via this spout and its outlet opening. In this embodiment, the filling of the transport container with liquid metal then takes place via the scraping opening. For introducing the inert gas via the pouring spout, a lid is preferably placed on the spout, in which an inlet opening for the inert gas is provided.

According to a further aspect, the invention relates to a transport container for liquid metal, in particular for liquid aluminum. The transport container is characterized in that it has an inlet opening for the inlet of inert gas in the upper region.

Advantages and features which have been described with regard to the method according to the invention also apply, as far as applicable, to the transport container according to the invention and vice versa.

In this case, the opening is referred to as the inlet opening, via which gas emerges into the interior of the transport container. In particular, the inlet opening does not constitute a passage opening for a lance or another gas line but the actual outlet opening of the gas.

By having an inlet opening in the upper area on the transport container according to the invention, the advantages can be achieved in particular that a reliable complete filling, ie flooding of the transport container can be ensured before filling, and also during the filling a reliable gas supply into the room ensured above the melt surface.

The inlet opening may be provided in the wall of the transport container in the upper region of the transport container of the transport container. According to one embodiment, the inlet opening is provided on or in a cover of the transport container, which closes the Abkrätzöffnung. Alternatively, the inlet opening may also be provided on or in a lid which closes the pouring spout. As provided on the lid, an inlet opening is referred to, which is offset to the underside of the lid, for example via a pipe, down. As provided in the lid, an inlet opening is referred to, which lies in the underside of the lid. In this case, the inert gas occurs directly on the underside of the lid in the interior of the transport container or in the spout. The provision of the inlet opening on or in the lid of the transport container has a number of advantages. The lid which covers the scraping opening is provided at the highest position in the transport container, whereby the above-mentioned advantages of reliable flooding and protection of a filling jet can be achieved. Also, a lid which closes the spout is provided in the upper region of the transport container, so that the above-mentioned advantages can be achieved reliably even in this embodiment. On the other hand, both the lid, which closes the Abkrätzöffnung and the alternatively usable lid, which closes the spout, releasably provided on each opening of the transport container, which are already provided for other functions of the transport container. Thus, structural measures on existing transport containers, such as the introduction of a hole in the wall of the transport container is not required. Finally, at an inlet opening on or in the lid of the transport container, the gas line can be easily connected because the lid is easily accessible.

According to one embodiment, the inlet opening for the protective gas is spaced from the filling opening for filling the transport container with liquid metal. As filling opening, the outlet opening in the pouring spout is used according to an embodiment, via which the transport container can also be emptied. In the alternative embodiment, in which the inlet opening is provided in particular in a cover on the pouring spout, the scraping opening in the closing hood of the transport container is used as the filling opening. By the inlet opening is spaced from the filling, on the one hand no obstruction of the filling process is given, which would be present in a guide of a lance through the filling opening. In addition, it can be ensured by the distance between the filling opening and the inlet opening that inert gas, which enters via the inlet opening, first flows through the container, displaces the oxygen present there and does not exit directly via the filling opening.

Preferably, the transport container according to the invention is designed for carrying out the method according to the invention.

• Figur 1: eine schematische Seitenansicht einer Ausführungsform des erfindungsgemäßen Transportbehälters;
• Figur 2: eine schematische Frontansicht einer Ausführungsform des erfindungsgemäßen Transportbehälters; und
• Figur 3: eine schematische Perspektivansicht einer Ausführungsform eines Deckels des erfindungsgemäßen Transportbehälters.

The present invention will be further explained below with reference to the accompanying drawings. Show it:

• FIG. 1 a schematic side view of an embodiment of the transport container according to the invention;
• FIG. 2 a schematic front view of an embodiment of the transport container according to the invention; and
• FIG. 3 : A schematic perspective view of an embodiment of a lid of the transport container according to the invention.

In FIG. 1 an embodiment of a transport container 1 according to the invention is shown schematically. The transport container 1 has a body 10 which has a round or oval cross-section and which tapers in the upper region. In the body 10, the interior 100 of the transport container 1 is formed, which serves for receiving liquid metal, in particular liquid aluminum. The interior 100 of the body 10 of the transport container 1 is provided with a lining 101. On the outside of the transport container 1 holding stubs 12 are provided laterally. In the upper region of the body 10 of the transport container 1, a pouring spout 11 is provided. The pouring spout 11 has a tubular shape in the illustrated embodiment and passes over the outlet opening 110 of the transport container 1. On the body 10 of the transport container 1 a Verschließhaube 13 is placed. The closure cap 13 therefore closes the open body 10 upwards. In the middle of the closure cap 13, a lid 14 is introduced in the illustrated embodiment. The lid 14 closes an opening in the closure cap 13, which is also referred to as Abkrätzöffnung 130. The Closing hood 13 is preferably removably or pivotally attached to the body 10 of the transport container 1 and can thus be removed or unfolded relative to the body 10. The lid 14 is detachably connected to the closure cap 13 and can be inserted, screwed or otherwise connected, for example, in the Abkrätzöffnung 130.

As is clear from the FIGS. 2 and 3 results, a gas supply 141 is provided on the lid 14. The gas supply 141 is formed in the embodiment shown by a bent tube which projects into the surface of the lid 14. The end of the gas feed 141, which projects into the lid 14 and preferably lies on the underside of the lid 14, represents the inlet opening 140 for inert gas. The other end of the gas feed 141 is preferably provided with a connection 142, through which the gas feed 141 a gas line 143 can be connected, is passed via the inert gas to the gas supply 141 and above to the inlet port 140.

In the illustrated embodiment, a support 144 for supporting the gas supply 141 is provided on the cover 14. By this configuration, the gas supply 141 can be used together with the support 144 as a handle to the cover 14 on the transport container 1, in particular in the opening of the Verschließhaube 13, insert and remove.

An embodiment of the method according to the invention will now be described again with reference to the illustrated embodiment of the transport container 1.

Before liquid metal, in particular liquid aluminum, is filled into the transport container 1, the transport container 1 is preheated. In addition, a cover 14 is applied to the transport container 1, on which or in which an inlet opening 140 is provided for inert gas. The lid 14 may have a closed lid (not shown) to be used for transportation, also referred to as Abkrätzdeckel is called replace. The gas supply 141 of the cover 14 is then connected via the port 142, which may represent, for example, a ¾ inch hose connection, to the gas line 143 for inert gas. The gas line 143 may form part of a service network. The pressure with which the inert gas enters the gas supply 141 and above into the inner space 100 of the transport container 1 can be adjusted by a valve 145. For example, a usual operating pressure of 8 to 10 bar down to 2 to 6 bar. Nitrogen is preferably used as the inert gas. The nitrogen is preferably liquefied cryogenic and used in the quality of ≥99.99%.

The outlet opening 110 and in particular the casting spout 11 are preferably opened during the flooding of the transport container 1. After the inner space 100 of the transport container 1 is completely filled with the inert gas, which is the case for example for a transport container with a capacity of liquid aluminum of 5t after 2 minutes, the pouring spout 11 and the outlet opening 110, which in this case represents the filling opening , liquid metal, in particular liquid aluminum filled in the transport container 1. For this purpose, for example, a filling channel (not shown) is applied to the pouring spout 11.

During the filling of the transport container 1 with liquid metal, the supply of inert gas, which takes place via the inlet opening 140, is maintained.

As soon as the transport container 1 has been filled with liquid material, that is to say the quantity of liquid material to be transported has been filled into the transport container 1, the gas supply from the gas conduit 143 can be interrupted. As a result, no inert gas passes more to the gas supply 141 and thus also not into the transport container 1. The gas supply 141 can then be separated from the gas line 143 via the connection 142. However, the gas supply 141 may also remain connected to the gas line 143. In this state, the lid 14 can be removed from the transport container 1 and replaced by a closed lid for transport. Alternatively, it is also possible that the lid 14 the transport container 1 is left and only a closure piece (not shown) to the gas supply 141 or the terminal 142 is attached.

In an alternative embodiment of the method according to the invention, no lid is applied to the scraping opening 130. Instead, a cover 14 'is applied to the spout 11, which closes the spout 11 and thus the outlet opening 110. The lid 14 'is in FIG. 1 indicated by dashed lines. The lid 14 'may also be the in FIG. 3 have shown construction. The above remarks on the cover 14 are therefore also applicable to the cover 14 'which closes the pouring spout 11. In this embodiment, in which a cover 14 'is provided on the spout 11, the Abkrätzöffnung 130 serves as a filling while the inert gas is supplied via the spout 11.

A number of advantages can be achieved with the present invention. In particular, the metal losses can be reduced by oxidation and gas absorption.

When filling transport containers with a capacity of 5 tons, conventional methods, that is to say without nitrogen loading, generate considerable amounts of oxidized aluminum in the form of scabies. By nitrogen loading before and preferably also during the filling process, the amount of scratching can be reduced by 60%. Also, the oxide content of the melt itself is lowered in this way.

LIST OF REFERENCE NUMBERS

1

transport container

10

body

100

inner space

101

lining

11

spout

110

outlet

12

holding stubs

13

Verschließhaube

130

Abkrätzöffnung

14, 14 '

cover

140

inlet port

141

gas supply

142

connection

143

gas pipe

144

support

145

Valve

Claims (10)

Method for filling a transport container (1) for liquid metal, in particular liquid aluminum, characterized in that at least prior to the introduction of the liquid metal in the transport container (1), the transport container (1) is acted upon with inert gas. A method according to claim 1, characterized in that the inert gas is nitrogen. Method according to one of claims 1 or 2, characterized in that also during the filling of the transport container (1) inert gas in the transport container (1) is supplied. Method according to one of claims 1 to 3, characterized in that the inert gas with a pressure which is above the ambient pressure and below the pressure, which leads to moving the melt surface of the liquid metal in the transport container (1) is introduced. Method according to one of claims 1 to 4, characterized in that the inert gas is introduced during the filling of the transport container (1) with liquid metal above the melt surface of the liquid metal. Method according to one of claims 1 to 5, characterized in that the inert gas through an inlet opening (140) in a detachable lid (14) of a Abkrätzöffnung (130) of the transport container (1) or in a detachable lid (14 ') of a spout ( 11) of the transport container (1) is introduced. Transport container for liquid metal, in particular for liquid aluminum, characterized in that it has an inlet opening (140) for the inlet of inert gas in the upper region. Transport container according to claim 7, characterized in that the inlet opening (140) is provided in a detachable lid (14) of the scraping opening (130) of the transport container (1) or in a detachable lid (14 ') of the pouring spout of the transport container (1). Transport container according to one of claims 7 or 8, characterized in that the inlet opening (140) for the inert gas to the filling opening (110, 130) for filling the transport container (1) with liquid metal is spaced. Transport container according to one of claims 7 to 9, characterized in that it is designed for carrying out the method according to the invention.

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