Environmental legislation to control emissions and reduce pollution continues to tighten across the globe. To meet these mandated challenges in the automotive sector, faith is increasingly being put in the use of battery electric vehicles, hybrids and more efficient internal combustion engine vehicles.
A key concern for developers in all of these technologies is a simple one: the weight (mass) of each vehicle contributes to the amount of energy needed to move it. Therefore, the race is on to reduce the weight of every type of vehicle and increase their efficiency, leading to reduced emissions, increased range and improved performance. Lightweighting, as it has come to be known, has never been more important for designers and manufacturers. This has, in turn, led to a sustained increase in the use of aluminum as the material of choice when manufacturing components, or even entire vehicle structures.
The use of aluminum to keep weight down is nothing new, but industry is on a constant mission to improve its structural strength, integrity, consistency, durability, and safety while reducing its cost. Moreover, manufacturers are always looking to make the material easier to work with, meaning improved, lower cost production processes that can use standard, widely available alloys are a major focus of research. Any new process must balance all of these factors and operate increasingly efficiently, as well as affording a greater range of possibilities to a designer’s imagination.
One highly innovative solution which meets all of these challenges and offers a step-change in lightweighting potential, to automotive, aerospace, rail, industrial and many other sectors, is Hot Form Quench (HFQ) technology, a patented hot forming process and matching simulation capability.
This pioneering, unique and easy-to-adopt manufacturing process and forming simulation package allows automotive OEMs to form deep-drawn and complex shapes from high and ultra-high strength aluminum, replacing the use of steel or cold formed aluminum grades. The process is rapid and meets the cycle times required for low-cost, high-volume manufacturing.
Encompassing the simulation, design and manufacturing of high-strength aluminum parts for the automotive industry. HFQ aims to advance global standards of aluminum processing, and, as a common solution for the entire supply ecosystem, facilitate cooperation and best practice sharing among OEMs, Tier 1 suppliers, aluminum producers, and design software and equipment vendors.
Manufacturing With Aluminum
Aluminum has already gained a foothold in the construction of vehicles, particularly with premium brands such as Rolls-Royce, Jaguar, Land Rover, Audi, Aston Martin and Tesla. Ford pioneered the use of high-volume aluminum-bodied vehicles with its F-150 pickup truck. According to the research agency Ducker Worldwide, aluminum content in cars is set to increase by up to 30 percent over the coming decade, driven by lightweighting in auto manufacturing.
Aluminum is increasingly being used in closures, bumpers, sub-frames and—in the premium segment—the entire body-in-white construction. Other aluminum products such as wheels, engine blocks and suspension components are now commonplace within the sector. However, using aluminum for sheet product in body-in-white construction, within budgets, is highly desirable and will generate additional significant advantages for volume car manufacturers.
By using HFQ designed parts, manufacturers in the automotive sector can take advantage of the engineering flexibility to use a variety of grades of aluminum, namely: 6xxx and ultra-high-strength 7xxx series aluminum. In the future, alloys with high recycled content, offering lower cost and major carbon-saving benefits, will be compatible with the HFQ process. This is because the characteristics of the process can maintain formability even with high levels of impurities, which would otherwise render the alloy unsuitable.
Linked to its inherent recycling benefits, HFQ also enables the creation of a closed-loop cycle of aluminum, as up to 90 percent of this metal could be recycled at the end of the product life cycle.
The HFQ Process
The first stage is to heat a standard heat-treatable grade of aluminum sheet in a furnace until it reaches its solutionizing temperature, about 550°C, depending on the grade.
From the furnace the blank is automatically transferred to a press and formed between a cold punch and die tool. The tools remain closed for five to 10 seconds to allow rapid cooling of the formed part, until the pressing is quenched. For all aluminum grades, quenching freezes the microstructure of the alloy in a supersaturated solid solution state. During the forming process, there is, in effect, virtually no cold-working of the aluminum alloy, thereby eliminating the need for complicated springback compensation in the part design.
Subsequently, should a heat treatable aluminum alloy be used, the part can be artificially aged to further increase the strength of the pressing, thanks to the prior quenching method—taking a little over two hours for aluminum grade AA6082 to achieve peak strength.
Partial artificial aging may also be carried out, followed by full aging after the part has been assembled into the vehicle structure. Full aging in this scenario means that HFQ pressing can take advantage of the heat generated during the paint bake process to achieve the highest strength.
HFQ’s ability to improve formability widens the scope for automotive applications in terms of design freedom, process optimization and achieving high levels of structural strength and stiffness within component Bill of Materials (BOM) cost budgets.
Case Study: Aston Martin DB11 A-Pillar
A vehicle’s A-pillars are integral structural members running both sides of the windscreen and typically extend from below dash level upwards into the roof structure. The A-pillar must support roof crush loads under crash conditions, which impose substantial bending moments on the pillar. These pillars must withstand major loads without excessive collapse.
Aston Martin is one of the first OEMs to realize the benefits of designing A-pillars and other parts using HFQ. The desire to reduce overall weight and part complexity, but enhance torsional rigidity and structural integrity, allowed designers and engineers to work with HFQ from the earliest phase of design to manufacture an A-pillar pressing without compromise.
Aston Martin was able to maintain the desired design language of the DB11 as HFQ was able to achieve tight radii (R/T 0.8), which reduced the width of the A-pillar for better driver visibility. In addition, HFQ enabled a complex and deep drawn pillar to be formed in a single draw operation, while achieving high levels of strength in roof-crush performance.
The single-draw operation also reduced tooling investment cost, as existing presses were adapted to produce high formability in deep sections of the A-pillar—a result previously not achievable using conventional cold production methods.
The commercialization of HFQ Technology signifies the start of a new international standard and provides a collaborative roadmap for future light-weighting in the automotive industry.
A full range of significant advantages can be delivered when HFQ forming is adopted at the outset of a design program. As illustrated by Aston Martin’s DB11 use case, HFQ is already validated on premium vehicles. Complex parts for world-renowned manufacturers are already under evaluation as candidates for HFQ adoption, as this unique process has the potential to deliver simpler, stronger structures on budget.
Through HFQ, there is an opportunity to catalyze the greater adoption of high-strength aluminum alloys. It allows manufacturers to refine existing structures while giving them greater freedom in creating new body and chassis concepts.
John Sellors is director of applications engineering
at Impression Technologies Ltd.