Casting-forging Integral Process For Mg Control Arm Manufacturing

This paper studied the casting-forging composite process for front wheel control arm of AZ81 magnesium alloy based on a patented technology. With a systematic study via a combination of numerical simulation, experimental production and theoretical analysis, the production condition of a Mg control arm was established for high quality at low cost.In the composite forming process of squeeze casting and close die forging, it is necessary to design a perform of squeeze casting in order to forge out a net-shape part in one-shot deformation. The design of the squeeze casting perform is done in an inverse route based on the part design and the necessary deformation requirement for quality and performance with DEFORM-3D plastic deformation simulation software. With the obtained perform design, the squeeze casting process was simulated to optimize the design of squeeze casting process and mould. Finally, the AZ81 control arm was produced in industrial conditions.Through the research, the conclusions are as follows:(1)The deformation technology process and the key parameter for control arm with high quality are as follows: melting the alloy melt to 680℃and hold for around 30 minutes, filling the die-cavity preheated to 250℃at 0.5m/s speed after quantitative pouring, finish the solidification under 80MPa pressure in 10s. Before forging the squeeze cast perform at a speed of 2mm/s to have the net-shape part, the forging die and perform should be preheated to 400℃.(2) The microstructure of squeeze cast perform of AZ81alloy consists ofα-Mg andβ-Mg17Al12. Before forging, the alloy is basically uniform and single phase because theβ-Mg17Al12 in the as-casting microstructure has been gradually broken and dissolved during the preheating treatment to have a uniform temperature in the preform. In the close-die forging, dynamic recrystallization appears in the heavily deformed region, leading to a refined grain size and remarkably enhanced tensile properties. The plastic deformation also closes the shrinkage voids of casting defect, thus, to raise the processing quality of the part.(3)The ultimate tensile strength, yield strength, hardness and elongation of the squeeze casting perform are 226.14MPa, 138.17MPa, 71.6HRE and 7.65%, respectively. After close-die forging, the ultimate tensile strength, yield strength, hardness and elongation of the forged part are 260.38MPa, 153.24MPa, 80.3HRE and 10.26%, giving an improvement of 15.1%, 10.85%, 34.1% and 12.15%, respectively, in comparison with those of casting, which ensure the performance requirements of the product.