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Automotive steel grades for lightweight design
Steel is strong, stiff, formable, widely available, and cost-effective. For this reason, it continues to be the material of choice for the chassis systems in mainstream passenger cars and light commercial vehicles. Conventional micro-alloyed high-strength steel grades remain the most commonly used in chassis applications. This product family offers designers a cost-effective material with strength and excellent durability. However, there is increasing pressure on automotive designers to reduce the weight of new cars in order to deliver better performance, including better fuel economy. This focus extends to the chassis, but reducing chassis weight is difficult.
The system is often positioned within a heavily package-constrained area which means that the designer only has a very limited space in which to design an optimized assembly (see figure 'Package constraints in chassis'). The design must also meet critical performance requirements related to durability and stiffness. Reducing weight by replacing a panel with a thinner, higher-strength material will not necessarily work in the chassis system because stiffness performance will be negatively affected. Material solutions can help designers achieve lighter chassis designs. Stronger materials increase component durability or safety performance and more ductile materials allow the designer to develop more complexly shaped components that fit smaller package spaces. A car manufacturer has developed a suite of advanced high-strength steel grades that meet both needs by combining high strength with improved ductility. This paper describes a benchmark study to evaluate the optimal use of the car manufacturer's advanced high-strength steel grades to save chassis weight without any compromise to package or performance requirements.
In most cases, the steel grades that are used per type of steel, to achieve a lighter frame are:
ASTM A572,and ASTM A588 for HSLA steel.
DP600, DP800, and TRIP800 for AHSS steel.
1040 and 1040 for Carbon steel
Borron steel
The manufacturer's automotive engineers were able to achieve an impressive 20% weight saving for the combined front and rear chassis assemblies. In the chart below the size of the "bubble" represents the combined front and rear chassis mass. The optimized solution (green bubble) met all stiffness, strength, and durability targets for each of the major load cases.
Utilizing the superior combination of strength and ductility of the mill's advanced steel portfolio can yield significant light-weighting potential. Component shapes that were previously considered too challenging to make are now a possibility. This enables designers to integrate high-strength and durable materials into their designs to fully unlock the potential of steel. This suite of advanced steel grades will support our customers in reducing their TCO, by offering a product optimized for the challenges of manufacturing chassis components
