Chassis components need to meet several performance requirements, including crash worthiness, durability, peak loads, and noise/vibration/harshness (NVH) comfort needs. Advanced high strength steels — combining superior strength, formability, and fatigue resistance — enable chassis part designers to deliver high-performance parts with lower weight and in a cost-efficient way.
The chassis’ lower control arm helps keep the car’s wheels aligned and maintain proper tire contact with the road, while helping to absorb shocks on rough terrain. Given its critical role, upgrading from low-alloy steel to Docol® HR800HER75-GI can deliver increased performance and fatigue resistance – all at reduced weights.
A supplier of lower control arms was looking to improve its product performance from the existing HR420LA steel. The Docol® HR800HER75-GI material was compelling for multiple reasons:
It significantly increased the strength of the lower control arm – enhancing its fatigue resistance – but can be used in either 3.0 mm or 4.0 mm thicknesses, reducing its weight. The new hot-rolled steel also has a guaranteed hole expansion rate of 65% (with typical values closer to 75%), providing excellent edge ductility for the control arm’s complex geometry. Docol® HR800HER75-GI also provides hot-dip galvanizing for corrosion resistance, further improving its durability.
With excellent cold-forming properties for punched and stretched edges, Docol® complex phase steels – including this HR1000CP – can be a real problem solver for the complex geometries of lower control arms found in automotive chassis.
Car chassis designers are finding significant performance improvements by continuing to increase the strength level of their steel parts. For example, this control arm was already made from an AHSS steel: HR800 complex phase steel. But by upgrading to Docol® HR1000CP, the lower control arm improved its fatigue resistance. It also meant the complex phase steel could be made thinner – down to 2.9 mm thickness – for weight reduction.
A formula for chassis lightweighting success: increase steel strength to reduce component wall thicknesses, such as this trailing arm in Docol® HR1000 complex phase steel.
Connecting the rear axle of a car to its body, trailing arms are responsible for maintaining proper alignment of the axle. Given this crucial function, an auto OEM wanted to improve the fatigue resistance of its trailing arms while saving weight. Going from HR800CP in 4.0 mm thickness to Docol® HR1000CP in 3.5 mm and 3.8 mm thicknesses delivered a 13% weight reduction with improved fatigue resistance.
Car spring links featuring stretched punched flanges and deep drawing: a good application for Docol® 800HER 75-GI.
Deep drawn shapes with punched flanges: these new designs for chassis spring links could be a serious edge-cracking challenge for forming operations trying to use steel grades with high yield strengths, e.g., 660 to 820 MPa. But these new designs found a ductile solution in Docol® HR800HER 75-GI: an AHSS steel with a guaranteed hole expansion ratio of 45% and typical values of 75%.
With a tensile strength of 760 to 960 MPa, Docol® hot-rolled 800HER 75-GI allowed the chassis spring links to have a wall thickness of 3.15 mm, reducing weight while achieving good fatigue resistance.
Spring link: HR800CP – HR1000CP
Anti roll bar / Stabilizer tube: 34MNB5
Front Subframe / Engine cradle: HR420LA – HR600FB – HR1000CP
Upper Control arm: HR700LA – HR1000CP
Lower Control arm: HR800CP – HR1000CP
Trailing arm: HR800CP – HR1000CP
Toe link: HR800CP – HR1000CP
Rear Control arm: HR800CP – HR1000CP
Rear Subframe / Rear Twist Beam Axle: HR420LA – HR600FB – HR1000CP
In just one to two weeks, you can get trial samples of most of our commercially available AHSS/UHSS steel grades – plus some of our newest, not-yet-released steels.
Our steel grades serve specific design purposes and are chosen by designers for a wide range of automotive applications.
In 2014, Gestamp launched a joint project with its customer Toyota. The objective was to develop a front lower control arm for use in the production of the Toyota Yaris in Europe. However, it soon became clear the steel grade required to develop this part did not yet exist. This was when Gestamp approached SSAB.
To form or stretch cut edges that are crack-free can be a major challenge when working with advanced-high strength steels (AHSS). To reduce the risk of cracked raised edges, SSAB has introduced two new hot-rolled 800 megapascal steels with extremely high edge ductility.
Complex phase steels have the highest — up to 100% — hole expansion ratios available from advanced high strength steels. Their high HER values provide excellent cold-forming properties for punched and stretched edges/flanges, as well as deep-drawn shapes. CP steels’ superior yield strengths are used for high crash-energy absorption, while their elevated UTS levels enable thinner walls for significant automobile weight reductions.