Development And Production Of Extrusion Cast Aluminum Alloy Control Arms

As the demand for vehicle versatility rises, equipment such as electronic equipment and high-quality safety systems continue to increase, resulting in an increase in the weight of passenger vehicles. At the same time, requirements for improved fuel efficiency and regulations on emissions are becoming more stringent around the world. Both the downsizing of the body and the reduction of body mass can achieve the goal of improving fuel efficiency and reducing emissions. Reducing the mass of the vehicle to achieve fuel efficiency and emission goals is currently the easiest technical means to achieve. Therefore, how to reduce the quality of the vehicle has become one of the hot spots in current engineering development. Aluminum alloy has a series of characteristics such as light weight, high specific strength and good corrosion resistance, and has been widely used in the manufacture of front axle and beam components. Due to lightweight design considerations, the shape and size of parts are often changed in order to reduce mass, and these changes will lead to changes in the strength and toughness of the part and may lead to part failure. Therefore, as a newly designed light alloy suspension component, it is very important to endow the appropriate material with the appropriate function and undergo multiple rounds of structural topology optimization analysis and forming process simulation.

Taking the steel plate stamping and welding lower control arm of a mass-produced model as the lightweight target, based on aluminum alloy and casting technology, the lightweight control arm was developed through integrated design to meet the lightweight needs of the entire vehicle.
The stamped and welded lower control arm of a certain type of steel plate is shown in Figure 1. The main requirements for replacing the original components with aluminum alloy castings are as follows: ① The impact performance of the aluminum alloy control arm is equivalent to that of the reference component. Impact performance requirements; ②Compared with the replacement parts, after changing the material, the self-weight is reduced by more than 20%; ③Meet the corrosion resistance requirements of the OEM, which is equivalent to the corrosion resistance of the original steel parts; ④Meet the original installation conditions, can be Implement a direct replacement. In the process of local structure change, the part that has no assembly relationship with other components is involved. After the structural adjustment, the original assembly relationship of the components remains unchanged, and direct replacement assembly can be realized; ⑤The cost increase shall not exceed 20%.

Fig. 2 is the design scheme of the AlSi7Mg aluminum alloy control arm. Considering the characteristics of the squeeze casting process, it is impossible to use sand cores to form a cavity structure. It was decided to change the original steel plate stamping and welding control arm with cavity structure into an "H" type structure aluminum alloy casting, and increase the overall rigidity of the casting by adding ribs and reinforcing ribs, so as to realize one-time casting, and remove the unsuitable for casting structure changes. Figure 3 shows the design scheme of the aluminum alloy control arm. Based on the original stamping and welding parts design, the original surrounding assembly environment cannot be changed, and the structure and assembly of the original parts must be carefully considered. The overall design scheme is to replace the original upper plate, lower plate, connecting upper plate, connecting lower plate, bushing sleeve and shock absorber bracket with an integrated design "H" type aluminum alloy extruded control arm to form an integral control arm .

A vertical extruder is used for extrusion. The pouring system consists of a material cake and a "Y" shaped sprue, and an overflow tank is set above the casting. The mounting hole on the casting and the original structural axis are formed through the core pulling on the left side. By setting the connecting hole formed on the upper part of the casting by setting the core, it can be inserted before the mold is opened or inserted during the filling process by setting the action of the oil cylinder, and it can be used as an extrusion needle to eliminate casting defects. The mass of the control arm casting is 2.282kg, the mass of the control arm cake and gating system is 4.250kg, the mass of the overflow tank and the exhaust channel is 0.660kg, and the total mass is 7.192kg. The process yield rate is 31.7%, and the process yield rate is low . Considering that the components were developed for trial production and the process yield rate was not optimized, in actual production, one mold and two parts can be considered to improve the process yield rate.
(1) Through structural topology optimization design, a lightweight cast aluminum alloy control arm was developed based on the original steel control arm, achieving the set target of 25% weight reduction, and passing the OEM test, other performance was not reduced.

(2) The development of castings was completed using the squeeze casting process, and local extrusion technology was introduced, which effectively eliminated defects that could not be eliminated by increasing the holding time and boost pressure. The tensile strength was 293.2MPa and the yield strength was 226.48 MPa, elongation 9.01%.

(3) Design and testing show that the steel-aluminum hybrid structure control arm with aluminum alloy casting as the core can meet the use requirements of the lower control arm, significantly reduce its own weight, and meet the needs of lightweighting of the entire vehicle.