Car chassis components in AHSS steel

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.

Lower control arms get performance upgrade

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.

UHSS complex phase steel boosts lower control arm’s capabilities

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.

13% weight reduction for trailing arm in complex phase UHSS

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.

Getting the required AHSS ductility for innovative chassis spring links

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.