Pre-treatment of a thixotropic metal bolt

Abstract

The invention relates to a pre-treatment device and method for production of a thixotropic metal bolt ( 10 ), in a casting chamber ( 30 ) of a thixo-moulding unit. The pre-treatment device comprises a container ( 14 ), for accommodating a metal bolt ( 10 ), an oven ( 20 ), for converting the metal bolt ( 10 ) in the container ( 14 ) into a partly fluid thixotropic state and a transport unit for transporting and feeding the thixotropic metal bolt ( 10 ), into the casting chamber ( 30 ). The container ( 14 ) is a cylinder-shape heating tube ( 14 ), with closable sides. Furthermore, the pre-treatment device is so arranged that, during the entire pre-treatment, namely the heating process in the oven ( 20 ), the transport into the casting chamber ( 30 ) and the period in the casting chamber ( 30 ), the metal bolt ( 10 ) remains in the heating tube ( 14 ).

1 . Pretreatment device for provision of a thixotropic metal bolt ( 10 ) in a casting chamber ( 30 ) of a thixoforming device, containing a container to hold a metal bolt ( 10 ), an oven ( 20 ) to transfer the metal bolt ( 10 ) in the container into a part-liquid thixotropic state, and a transport device for transporting and introducing the thixotropic metal bolt ( 10 ) into the casting chamber ( 30 ), characterised in that 
 the container is a cylindrical heating tube ( 14 ) which can be closed at the sides, and the pretreatment device is formed such that the metal bolt ( 10 ) can remain in the heating tube ( 14 ) throughout the entire pretreatment, namely the heating process in the oven ( 20 ) and transport to the casting chamber ( 30 ) and its stay in the casting chamber ( 30 ) until the start of the thixoforming process.    
     
     
         2 . Pretreatment device according to  claim 1 , characterised in that the internal diameter d R  of the heating tube ( 14 ) as a function of the bolt diameter d B  is selected such that the metal bolt ( 10 ) at its solidus temperature T solid  substantially has the same diameter d B  as the internal diameter d R  of the heating tube ( 14 ).  
     
     
         3 . Pretreatment device according to  claim 1  or  2 , characterised in that the heating tube ( 14 ) consists of metal, preferably steel, in particular stainless steel or tool steel.  
     
     
         4 . Pretreatment device according to  claim 1  or  2 , characterised in that the heating tube ( 14 ) consists of ceramic material.  
     
     
         5 . Pretreatment device according to any of  claims 1  to  4 , characterised in that when the metal bolt ( 10 ) is in a substantially horizontal position during the heating process, the heating tube ( 14 ) is tightly closed on both sides by sealing elements ( 16 ,  18 ), where the sealing elements ( 16 ,  18 ) are designed with regard to material choice and form such that their friction properties in the heating tube ( 14 ) firstly allow a shift due to thermal expansion of the metal bolt ( 10 ) during the heating process in the direction of the longitudinal axis l of the heating tube ( 14 ), and secondly prevent a shift due to the pressure exerted by the metal bolt ( 10 ) on the sealing elements ( 16 ,  18 ) after reaching the temperature necessary for the desired thixotropic state.  
     
     
         6 . Pretreatment device according to any of  claims 1  to  4 , characterised in that for a substantially vertical metal bolt position during the heating process, the heating tube ( 14 ) is closed on one side at the lower tube end ( 15 ), where on use of a sealing element ( 16 ) the sealing element ( 16 ) is designed with regard to material choice and form such that firstly during the heating process in the oven ( 20 ) no liquid metal ( 24 ) can emerge from the heating tube ( 14 ) and secondly the friction of the sealing element ( 16 ) in the heating tube ( 14 ) is less than 10 N.  
     
     
         7 . Pretreatment device according to  claim 5  or  6 , characterised in that the sealing elements ( 16 ,  18 ) consist of ceramic material.  
     
     
         8 . Pretreatment device according to any of  claims 1  to  7 , characterised in that the oven ( 20 ) is an induction oven.  
     
     
         9 . Pretreatment device according to any of  claims 1  to  8 , characterised in that the transport device is a robot where the clamping device of the robot to hold the heating tube at least on the surface directed towards the heating tube consists of ceramic material.  
     
     
         10 . Use of the pretreatment device according to any of  claims 1  to  9 , for provision of a thixotropic metal bolt ( 10 ) in a casting chamber ( 30 ) of a horizontal thixoforming device.  
     
     
         11 . Use of a pretreatment device according to any of  claims 1  to  9 , for provision of a thixotropic metal bolt ( 10 ) from an aluminium alloy.  
     
     
         12 . Process for provision of a thixotropic metal bolt ( 10 ) in a casting chamber ( 30 ) of a thixoforming device, where a metal bolt ( 10 ) in a solid state of aggregation is placed in a container, and the metal bolt ( 10 ) in the container is heated in an oven ( 20 ) until the metal bolt ( 10 ) is in a thixotropic state, and the thixotropic metal bolt ( 10 ) is transported by means of a transport device into the casting chamber ( 30 ) of a thixoforming device, characterised in that 
 the container is a cylindrical heating tube ( 14 ), the metal bolt ( 10 ) remains in the heating tube ( 14 ) throughout the heating process and subsequent transport into the casting chamber ( 30 ), and the heating tube ( 14 ) containing the metal bolt ( 10 ) is positioned in the casting chamber ( 30 ) such that during the subsequent thixoforming process the plunger ( 34 ) of the thixoforming device can push the thixotropic metal bolt ( 10 ) out of the heating tube ( 14 ).    
     
     
         13 . Process according to  claim 12 , characterised in that the internal diameter d R  of the heating tube ( 14 ) as a function of the bolt diameter d B  is selected such that at room temperature the internal diameter d R  is greater than the bolt diameter d B  and at the solidus temperature T solidus  of the metal bolt ( 10 ) the bolt diameter d B  substantially corresponds to the internal diameter d R  of the heating tube ( 14 ).  
     
     
         14 . Process according to  claim 12  or  13 , characterised in that after the heating process but before insertion of the heating tube ( 14 ) containing the thixotropic metal bolt ( 10 ) into the casting chamber ( 30 ), the liquid metal ( 24 ) which emerged during the heating process from the metal bolt ( 10 ) is at least partly removed from the heating tube ( 14 ).  
     
     
         15 . Process according to any of  claims 12  to  14 , characterised in that the heating tube ( 14 ) is sealed on at least one side during the heating process of the metal bolt ( 10 ).  
     
     
         16 . Process according to any of  claims 12  to  15 , characterised in that a heating tube ( 14 ) which is tightly closed at one end, at the lower tube end ( 15 ), with a sealing element ( 16 ) and containing the metal bolt ( 10 ), is placed in a vertical position vertically onto the table plate ( 26 ), preferably onto a table plate ( 26 ) of ceramic material, and the table plate ( 26 ) is introduced vertically, preferably from below, into the oven ( 20 ), and the heating tube ( 14 ) containing the metal bolt ( 10 ) is heated until the metal bolt ( 10 ) is a thixotropic state, and subsequently the heating tube ( 14 ) containing the thixotropic metal bolt ( 10 ) is removed vertically, preferably by lowering the table plate ( 26 ), from the oven ( 20 ) and separated from the sealing element ( 16 ).  
     
     
         17 . Process according to any of  claims 12  to  15 , characterised in that the heating tube ( 14 ) containing the metal bolt ( 10 ) is tightly sealed on both sides with a sealing element ( 16 ,  18 ) which can be moved in the direction of the concentric longitudinal axis l of the heating tube ( 14 ) and with preset friction properties between the heating tube ( 14 ) and the sealing element ( 16 ,  18 ), and is introduced into the oven ( 20 ) in a substantially horizontal position, where during the heating process the two sealing elements ( 16 ,  18 ) due to thermal expansion of the bolt material ( 10 ) are pushed apart and after reaching the thixotropic state the sealing elements ( 16 ,  18 ) are held in their position due to friction, and after removal of the heating tube ( 14 ) containing the metal bolt ( 10 ) from the oven ( 20 ) the two sealing elements ( 16 ,  18 ) are removed from the heating tube ( 14 ).  
     
     
         18 . Use of the process according to any of  claims 12  to  17  to provide a thixotropic metal bolt ( 10 ) in a horizontal thixoforming device.  
     
     
         19 . Use of the process according to any of  claims 12  to  17  to provide a thixotropic metal bolt ( 10 ) from an aluminium alloy.