Indirect Squeeze Casting Zalsi7mg Alloy Partitions For Mine Shells

【research Highlights】

In This Project, the Self-developed Shp34-500a Multifunctional Liquid Forming Machine Was Used to Trial-produce Zalsi7mg Aluminum Alloy Partitions for Mine Shells, and the Influence of Indirect Extrusion Casting Process on the Structure and Properties of Aluminum Alloy Castings Was Studied. the Main Purpose is to Establish Indirect Squeeze Casting Process-structure-performance Relationship, Research on Indirect Squeeze Casting Preparation Process, Casting Structure and Performance, and Realize the Controllable Preparation of High-performance Extrusion Aluminum Alloy Castings.

【research Proposal】

The Test Material is Zalsi7mg Aluminum Alloy, and the Composition Analysis Results of Direct Reading Spectrometer Are Shown in Table 1.

Aluminum Alloy Separator Castings Were Trial-produced by Shp34-500a Multifunctional Liquid Forming Machine. the Mold Material is H13 Steel. After Material Preparation, Smelting, Mold Preheating, Pouring, Indirect Extrusion and Other Processes, the Aluminum Alloy Partition Casting is Finally Produced. the Process Route Diagram is Shown in Figure 2.
 

The Structure of the Extrusion Die is Shown in Figure 2. Preheat the Die with a Mold Temperature Controller and Set the Temperature at 260 °c; Put the Zalsi7mg Aluminum Ingot into the Preheated Crucible; After the Zalsi7mg Aluminum Alloy is Melted, Use Hexachloroethane to Refine and Degas , Stand Still, Remove Slag. Use a Thermocouple to Measure the Temperature of the Melt and Prepare for Pouring; Start the Multi-functional Liquid Molding Machine to Test Whether the Slider and the Top Cylinder Are Running Normally, and Open the Mold to Prepare for Pouring; After the Melt Reaches the Predetermined Temperature, Take out the Crucible and Start Pouring; After Closing the Mold and Maintaining Pressure After That, Open the Mold to Pick Up the Parts, and Start the Next Pouring.


1 Support Column, 2 Thimble Back Plate, 3 Mold Base, 4 Thimble, 5 Punch Mold Set, 6 Punch 7 Bearing Block, 8 Die Set, 9 Material Cylinder, 10 Push Rod, 11 Pressure Head, 12 Gate Set, 13 Die, 14 Casting, 15 Guide Post, 16 Guide Sleeve, 17 Fixing Bolt, 18 Thimble Fixing Plate, 19 Return Guide Post

The Extrusion Casting Process Parameters Are Shown in Table 1. by Controlling the Variable Method, It is Divided into Three Times, and the Variables Are Pouring Temperature, Specific Pressure and Pressure Holding Time in Turn, and the Mold Temperature is Set at 260 °c.

The Samples Prepared Under Different Processes Were Processed into Regular Shapes by Wire Cutting, and the As-cast Microstructure Was Observed, and the Samples Corresponding to the Best Microstructure Were Selected for Solution Treatment at 535 ℃ × 6 H (t6). Quenching is Carried Out, and the Quenching Time Does Not Exceed 10 S, and then Aging Treatment is Carried out at 185 ℃ × 6 H, and then Air-cooled.

Samples Were Taken from the Casting Body, and the As-cast and T6 Samples Were Turned into Standard Tensile Samples, and the Average Value of 3 Samples Was Taken for the Samples Under Each Process Parameter. the Tensile Samples Are Shown in Figure 3. Tensile Tests at Room Temperature Were Carried out on a Cmt5105 Microcomputer-controlled Electronic Universal Testing Machine with a Loading Rate of 1.0 Mm/min. the Vickers Hardness Test Was Carried out with a Tmhvs-1000 Automatic Digital Microhardness Tester Under a Load of 500 N for 15 S. the Scanning Electron Microscope is Used to Scan the Fracture Morphology of the Samples in Different States, and the Metallographic Structure, Microscopic Appearance and Mechanical Properties of the Samples in Different Processing States Are Analyzed.


 

Figure 4 Shows the Microstructure of Extrusion Casting Zalsi7mg Aluminum Alloys at Pouring Temperatures of 700, 720 and 740 °c, Respectively. It Can Be Seen That the Gray Phase is the -al Primary Phase, Which is Distributed in a Dendritic Shape, and the Eutectic Si is Distributed in the Grain Boundaries of the Dendrites and is Black. As the Pouring Temperature Increases, the Average Grain Size (gs) Increases Gradually.
 

(a) 700°c (b) 720°c (c) 740°c

Fig.4 Microstructure of Zalsi7mg Aluminum Alloy at Different Pouring Temperatures

Figure 5 Shows the Microstructure of Zalsi7mg Aluminum Alloy Castings when the Specific Pressure is 110, 120, and 130 Mpa. It Can Be Seen That the Average Grain Size is 39.1 µm at 110 Mpa, and the -al Phase Mainly Exists in the Form of Equiaxed Crystals. As the Pressure Increases, the Rosette Grains Increase Significantly at 130 Mpa, As Shown in Figure 5b, and the Average Grain Size Decreases to 34.2 µm.
 

(a) 110 Mpa (b) 120 Mpa (c) 130 Mpa

Fig.5 Microstructure of Zalsi7mg Aluminum Alloy Under Different Extrusion Pressure

Figure 6 Shows the Microstructure of Z