Low-Pressure Mold and Production Process for Aluminum Alloy Integrated Brake Calipers

Abstract

The present invention discloses a low-pressure mold and production process for aluminum alloy integrated brake calipers, relating to the technical field of casting. The mold comprises a bottom plate, a right mold core and a left mold core are provided on the bottom plate, and the right mold core and the left mold core have the same internal structure and are each provided with a sprue assembly. The low-pressure casting process has higher production efficiency and yield than gravity casting. Castings produced by low-pressure casting have higher structural compactness and more excellent mechanical properties than those produced by gravity casting.

What is claimed is: 
     
         1 . A low-pressure mold for aluminum alloy integrated brake calipers, comprising a bottom plate ( 1 ), wherein a right mold core ( 5 ) and a left mold core ( 6 ) are provided on the bottom plate ( 1 ), and the right mold core ( 5 ) and the left mold core ( 6 ) have the same structure and are each provided with a sprue assembly; and
 further comprising an ejection rod pushing plate ( 4 ), wherein an ejection rod ( 10 ) is provided on the ejection rod pushing plate ( 4 ), the ejection rod pushing plate ( 4 ) drives the ejection rod ( 10 ) to rise and fall, and a casting ( 15 ) is released from the mold through the ejection rod ( 10 );   wherein the right mold core ( 5 ) comprises an upper mold core ( 12 ) and a lower mold core ( 16 ), the upper mold core ( 12 ) is fixedly mounted on a top plate ( 2 ), the lower mold core ( 16 ) is fixedly mounted on the bottom plate ( 1 ), the top plate ( 2 ) drives the upper mold core ( 12 ) to move up and down to open and close the mold, a sand core ( 20 ) is provided between the upper mold core ( 12 ) and the lower mold core ( 16 ) for forming a cavity structure of the casting ( 15 ), and the sand core ( 20 ) is connected to a negative pressure exhaust device ( 9 );   the sprue assembly comprises a sprue bush ( 22 ) and a sprue cup ( 23 ) fixed on the lower mold core ( 16 ) through a pressure plate ( 24 ); and   the sprue assembly further comprises a sprue spreader ( 18 ), the sprue spreader ( 18 ) is fixedly mounted on the upper mold core ( 12 ), and the sprue bush ( 22 ), the sprue cup ( 23 ) and the sprue spreader ( 18 ) are arranged coaxially.   
     
     
         2 . The low-pressure mold for aluminum alloy integrated brake calipers according to  claim 1 , wherein a filter screen ( 21 ) is placed on the sprue bush ( 22 ), and the filter screen ( 21 ) is made of fibers. 
     
     
         3 . The low-pressure mold for aluminum alloy integrated brake calipers according to  claim 1 , wherein a riser ( 26 ) is further provided on the right mold core ( 5 ), an insulation insert ( 11 ) is provided at an upper portion of the riser ( 26 ), and asbestos is placed inside the insulation insert ( 11 ). 
     
     
         4 . The low-pressure mold for aluminum alloy integrated brake calipers according to  claim 3 , wherein the insulation insert ( 11 ) has a thickness of 3-5 mm. 
     
     
         5 . The low-pressure mold for aluminum alloy integrated brake calipers according to  claim 1 , wherein a novel cooling insert is further provided on the right mold core ( 5 ), and the novel cooling insert on the right mold core ( 5 ) is located at a thick position of the casting ( 15 ); and
 the novel cooling insert consists of an insert I and an insert II, which are tightly matched and welded together; the insert I has a cavity structure with a wall thickness of 15-20 mm; the insert II has a water inlet pipeline and a water outlet pipeline, with diameters of 8 mm.   
     
     
         6 . The low-pressure mold for aluminum alloy integrated brake calipers according to  claim 1 , wherein an exhaust groove with a depth of 0.1-0.25 mm and a width of 20-35 mm is provided on a parting surface between the upper mold core ( 12 ) and the lower mold core ( 16 ). 
     
     
         7 . The low-pressure mold for aluminum alloy integrated brake calipers according to  claim 1 , wherein an aluminum stopper ( 13 ) with a height of 15-40 mm and a fit clearance of 2-4 mm is further provided between the upper mold core ( 12 ) and the lower mold core ( 16 ). 
     
     
         8 . The low-pressure mold for aluminum alloy integrated brake calipers according to  claim 1 , wherein the ejection rod ( 10 ) has a diameter of 8-16 mm and is used with an ejection rod sleeve ( 14 ), and the ejection rod sleeve ( 14 ) is provided with an exhaust groove. 
     
     
         9 . The low-pressure mold for aluminum alloy integrated brake calipers according to  claim 1 , wherein the sprue bush ( 22 ) and the sprue cup ( 23 ) are made of ceramic. 
     
     
         10 . A production process for aluminum alloy integrated brake calipers, comprising the following steps:
 S1. aluminum melting:   aluminum alloy is composed of the following raw materials in percentage by weight: Si, 6.5-7.5%; Mg, 0.4-0.6%; Ti, 0.05-0.2%; Sr, 0.02-0.03%; Fe≤0.13%; Gu≤0.02%; other individual elements (excluding Al)≤0.03%; the total quantity of the other elements (excluding Al) is ≤0.10%, with the remaining Al;   after aluminum is melted, the molten aluminum is refined with nitrogen for 15-25 minutes at a temperature of 700-720° C., and then the refined molten aluminum is kept warm and stood for 30-50 minutes before use; the refining and standing can improve the purity of the molten aluminum and reduce the gas content and slag inclusion of the molten aluminum;   S2. preparation of a sand core:   organic resin sand is used, and the required gas generation rate is ≤13 ml/g; particle size index AFS: 53-63; during preparation, the temperature of a sand core mold is 200-230° C., and the curing time is 180-200 seconds;   after the sand core ( 20 ) is made, its surface is uniformly coated with a composite coating, and then the sand core is thoroughly dried at 100° C. for later use;   wherein the composite coating is a uniformly mixed mixture of an alcohol-based coating and alcohol in a ratio of 1:1 for later use; the coating can prevent sand adhesion on the surface of the casting ( 15 ) and improve the surface quality of the casting ( 15 );   S3. low pressure casting:   the prepared sand core ( 20 ) is put into a mold cavity, the mold cavity is blown with an air gun, then a filter screen ( 21 ) is placed at each sprue position, and the mold is closed;   the temperature of the molten aluminum during the casting process is set at 700-720° C.;   rising stage: 5-15 seconds, the pressure rises from 0 to 100-160 mbar, and the molten aluminum rises from a holding furnace to the lower end of the sprue cup ( 23 ) under the action of pressure;   pressure stabilizing stage: 1-5 seconds, the pressure remains unchanged from the rising stage, ensuring that the molten aluminum maintains a stable liquid level during filling;   filling stage: 15-25 seconds, the pressure increases from 100-160 mbar to 200-280 mbar, and the molten aluminum slowly fills the entire mold cavity through the sprue bush ( 22 ) and the sprue cup ( 23 ) under continuous pressure;   increasing stage: 5-10 seconds, the pressure continues to rapidly increase from 200-280 mbar to 600-900 mbar after the molten aluminum fills the mold cavity;   pressure maintaining stage: 100-150 seconds, the pressure is maintained at 600-900 mbar, and the mold cavity is continuously fed and cooled;   cooling stage: 80-110 seconds, the casting ( 15 ) is continuously solidified and cooled inside the mold cavity after pressure relief;   an air duct connected to the negative pressure exhaust device ( 9 ) is open throughout;   S4. sand shaking:   after the casting ( 15 ) is cooled to room temperature, the sand core ( 20 ) in the casting ( 15 ) is shaken to break it up and remove the sand;   S5. rough machining:   runners of the casting ( 15 ) are removed according to drawing requirements; and   S6. heat treatment:   solid solution temperature 535-545° C., solid solution holding time 420-500 minutes, quenching water temperature 30-50° C., aging temperature 160-175° C., and aging holding time 300-380 minutes.