Semi-solid slurry generator and high pressure die casting method

Abstract

Disclosed are a semi-solid slurry generator and a die casting method which can obtain a dense structure in the entire cross section of a molded product by uniformly dispersing and stirring an inert gas in a slurry compared to a conventional one. The die casting method comprises: a step of immersing a rotating diffuser in a molten metal contained in a ladle to rotate and stir the molten metal while being supplied with an inert gas, or rotating and stirring the molten metal and the inert gas, which are sucked into a pumping impeller, while being ejected through a hole provided on a side surface of the impeller by stirring the same, such that the molten metal is cooled while gas bubbles caused by the inert gas are uniformly dispersed in the molten metal, thereby forming a semi-solid slurry; and a step of pressurizing and injecting the semi-solid slurry into a mold of a molding machine.

1 . A semi-solid slurry generator for generating a semi-solid slurry by supplying an inert gas to a molten metal contained in a ladle, the semi-solid slurry generator comprising:
 a diffuser for supplying the inert gas into the molten metal in a state of being immersed in the molten metal contained in the ladle;   an inert gas supply unit for supplying the inert gas to the diffuser;   a rotation support to rotatably support the diffuser;   a rotation unit configured to rotate the diffuser;   a slide guide to guide upward and downward movements of the rotation support;   a lifting unit configured to move the rotation support up and down along the slide guide; and   a guide support unit to support the slide guide.   
     
     
         2 . The semi-solid slurry generator of  claim 1 , wherein the diffuser includes a porous impeller having an empty space configured to accommodate the inert gas supplied from the inert gas supply unit and a plurality of pores so as to disperse and supply the inert gas supplied into the empty space. 
     
     
         3 . The semi-solid slurry generator of  claim 1 , wherein the diffuser includes a pumping impeller including a hollow portion communicating with the inert gas supply unit and having an open lower portion and a lateral hole formed in a side surface and communicating with the hollow portion inside, and
 wherein the pumping impeller has a pumping function of rotationally stirring the molten metal while rotating stirring the inert gas supplied from the inert gas supply unit and the molten metal sucked into the hollow portion from the opened lower portion of the hollow portion and ejecting the molten metal through the lateral hole by a centrifugal force.   
     
     
         4 . The semi-solid slurry generator of  claim 1 , wherein the guide support unit includes a post and a horizontal support unit connected to the slide guide and supported by the post, and the horizontal support unit is configured to be horizontally movable on the post, and the horizontal support unit is provided with a horizontal movement unit to horizontally move the horizontal support unit. 
     
     
         5 . The semi-solid slurry generator of  claim 1 , further comprising:
 a control unit to control operations of the rotation unit and the lifting unit.   
     
     
         6 . The semi-solid slurry generator of  claim 1 , wherein the diffuser includes grooves or protrusions, which are formed to be spaced apart from each other along an outer circumferential surface thereof so as to function as an impeller, or the diffuser is formed to have a polygonal cross section or is provided with an actual impeller so that the molten metal can be stirred and flowed well when the diffuser rotates (the impeller includes a diffuser-integrated impeller, a detachable impeller, and an impeller capable of pumping). 
     
     
         7 . The semi-solid slurry generator of  claim 1 , wherein the diffuser is made of ceramic or graphite and is detachably attached to the head. 
     
     
         8 . The semi-solid slurry generator of  claim 4 , the semi-solid slurry generator comprising:
 a control unit to control operations of the inert gas supply unit, the rotation unit, the lifting unit, and the horizontal movement unit,   wherein the rotation support is provided with a temperature measuring unit to measure a temperature of the molten metal and to input an information of the measured temperature to the control unit.   
     
     
         9 . The semi-solid slurry generator of  claim 2 , wherein the impeller diffuser has a cross section having a polygonal shape or a groove, a curved surface or a concavo-convex shape as a whole or in part such that the molten metal can be flowed and stirred well when the diffuser rotates. 
     
     
         10 . The semi-solid slurry generator of  claim 1 , wherein the rotation support is provided with a baffle plate disposed apart from the diffuser so as to disturb rotation of the molten metal. 
     
     
         11 . A die casting method comprising:
 a step of immersing a diffuser in a molten metal contained in a ladle and rotating the diffuser while supplying an inert gas so as to cause gas bubbles, which are formed by the inert gas, to be evenly dispersed and stirred in the molten metal, so that the molten metal is cooled to generate a semi-solid slurry; and   a step of performing molding by pressurizing and injecting the semi-solid slurry into a mold of a molding machine.   
     
     
         12 . The die casting method of  claim 11 , wherein the molten metal is a molten metal of an Al-alloy or Mg-alloy, and the inert gas is argon gas or nitrogen gas. 
     
     
         13 . The die casting method of  claim 11 , wherein the semi-solid slurry is supplied to a plunger of the molding machine at a temperature, which is equal to or lower than a melting point of the metal. 
     
     
         14 . The die casting method of  claim 11 , the die casting method comprising:
 a step of disturbing rotation of the molten metal by disposing a baffle plate in the ladle to be spaced apart from the diffuser.   
     
     
         15 . The die casting method of  claim 11 , wherein a step of enhancing a rotational bubbling and stirring effect by disposing a baffle plate inside the ladle to be spaced apart from the diffuser. 
     
     
         16 . The die casting method of  claim 11 , wherein the step of generating the semi-solid slurry is performed using a semi-solid slurry generator comprising:
 a diffuser for supplying the inert gas into the molten metal in a state of being immersed in the molten metal contained in the ladle;   an inert gas supply unit for supplying the inert gas to the diffuser;   a rotation support to rotatably support the diffuser;   a rotation unit configured to rotate the diffuser;   a slide guide to guide upward and downward movements of the rotation support;   a lifting unit configured to move the rotation support up and down along the slide guide; and   a guide support unit to support the slide guide.   
     
     
         17 . The die casting method of  claim 16 , wherein the diffuser of the semi-solid slurry generator includes a porous impeller having an empty space configured to accommodate the inert gas supplied from the inert gas supply unit and a plurality of pores so as to disperse and supply the inert gas supplied into the empty space. 
     
     
         18 . The die casting method of  claim 16 , wherein the diffuser of the semi-solid slurry generator includes a pumping impeller including a hollow portion communicating with the inert gas supply unit and having an open lower portion and a lateral hole formed in a side surface and communicating with the hollow portion inside, and
 wherein the pumping impeller has a pumping function of rotationally stirring the molten metal while rotating stirring the inert gas supplied from the inert gas supply unit and the molten metal sucked into the hollow portion from the opened lower portion of the hollow portion and ejecting the molten metal through the lateral hole by a centrifugal force.   
     
     
         19 . The die casting method of  claim 16 , wherein the guide support unit of the semi-solid slurry generator includes a post and a horizontal support unit connected to the slide guide and supported by the post, and the horizontal support unit is configured to be horizontally movable on the post, and the horizontal support unit is provided with a horizontal movement unit to horizontally move the horizontal support unit. 
     
     
         20 . The die casting method of  claim 16 , wherein the semi-solid slurry generator further comprises a control unit to control operations of the rotation unit and the lifting unit.