A perfect fit: Tailored portfolio for cost-effective lightweight steel seat structures
A perfect fit: Tailored portfolio for cost-effective lightweight steel seat structures
Front and rear seats must meet the highest demands in terms of economy, installation space, lightweight design, safety, and comfort.
thyssenkrupp Steel offers a tailored portfolio with best forming properties for cost-effective lightweight steel seat structures: From highly ductile hot-rolled strip and medium-wide strip to micro-alloyed cold-forming steels and cold-rolled high-strength multiphase steels – with best forming and joining properties.
Modern car seat has to be a true all-rounder: it has to be lightweight yet crash-proof, take up very little installation space, be inexpensive to produce – and all of this, of course, without compromising comfort. The use of high-strength steel helps to meet these diverse requirements.
Take the issue of weight, for example: Today, each seat weighs on average around 12.5 kilograms – and that’s just the load-bearing steel seat structures. Together, then, the front and rear seat structures of a car can easily weigh in at around 50 kilos. A tailored portfolio of steel grades to meet to the specific seating requirements have a noticeable positive impact here and help reduce weight by up to 15 percent – at no extra cost.
Overview front seat structure
Seat rails, standard thickness 1.5 to 2.0 mm
precidur® HSM 700 HD
perform® 550 HD
CP-K® 780Y980T2
Transverse tubes, standard thickness 2.0 to 2.5 mm
perform® 355
DP-K® 440Y780T HHE
CP-K® 570Y780T
Seat shell, standard thickness 0.8 mm
MHZ® 340
MHZ® 380
DP-K® 290Y490T
Cushion side member, standard thickness 1.6 mm
perform® 500 HD
CP-W® 660Y760T
DP-K® 700Y980T
Upper seatback crossbar, standard thickness 0.8 to 1.1 mm
MHZ® 420
Lower seatback crossbar, standard thickness 0.8 to 1.0 mm
DP-K® 440Y780T HHE
MHZ® 420
Backrest side member, standard thickness 0.8 to 1.1 mm
DP-K® 440Y780T HHE
DP-K® 590Y980T
DP-K® 700Y980T
Adapter unit, standard thickness 3.0 to 5.0 mm
precidur® HLB 22
precidur® HSM 700 HD
precidur® HSM 650 HD
scalur® S600MC
Seat height adjuster, standard thickness 3.0 to 5.0 mm
precidur® HLB 37
Articulated lever, standard thickness 3.0 to 5.0 mm
precidur® HSM 700 HD
Backrest side member
Seat structures are a complex system in which every single structural component is important. Take safety: The front seatback is stressed by the passenger in the event of a rear-end crash and by whatever’s on the rear seat or possibly in the trunk in a frontal collision. Accordingly, different crash load cases must be considered for the backrest side member, cushion side member, and seat shell.
A task made for our robust high strength dual-phase steel DP-K® 440Y780T HHE. With a rating of 800 MPa, this cold-rolled dual-phase steel is not only extremely strong but also easy to form, making it perfect for difficult-to-form structural components that are exposed in the event of a crash, such as the backrest side member.
Material recommendation:
DP-K® 440Y780T HHE DP-K® 590Y980T DP-K® 700Y980T Benefit: High strength with good formability for maximum weight savings
Cushion side member
Depending on the shape of the component in question, dual-phase steel DP-K® 700Y980T or highly ductile micro-alloyed steel perform® 500 HD can be used, e.g., for the cushion side member (the new HD steel grade is particularly easy to form).
Material recommendation:
perform® 500 HD Benefit: High strength and good formability
CP-W® 660Y760T Benefit: High yield and tensile strength as well as good bending and edge formability
DP-K® 700Y980T Benefit: High strength with good formability for maximum weight savings
Seat rails
Highly ductile micro-alloyed, high-strength perform® steels (hot wide strip) as well as precidur® steel grades made from Hohenlimburg precision steel in particular are ideal for classic cold-rolling processes and seat rail applications. Finally, the cold-rolled uncoated complex-phase steel CP-K® 780Y980T is another high-performance material in the 1,000 MPa strength class that features excellent forming properties and meets the highest thickness tolerance requirements – and not only for seat rails.
Material recommendation:
perform® 550 HD Benefit: High strength and good formability
precidur® HSM 700 HD Benefit: Especially suited to complex forming processes
CP-K® 780Y980T Benfit: High lightweight potential
Adapter unit, seat height adjuster and articulated lever
The case-hardening and tempered steels and the highly ductile micro-alloyed fine-grain structural steels of the precidur® family, for example, offer hot-rolled precision strip with extremely tight thickness and profile tolerances that is ideally suited to making functional components such as adapter units, seat height adjusters and articulated levers.
Material recommendation adapter unit:
precidur® HLB 22 Benefit: Good processing and forming properties in hot-rolled and annealed condition
precidur® HSM 650 HD precidur® HSM 700 HD Benefit: Especially suited to complex forming processes
scalur® S600MC Benefit: High lightweight potential and best processing properties
Material recommendation seat height adjuster:
precidur® HLB 37 Benefit: Good processing and forming properties in hot rolled and annealed condition
Material recommendation articulated lever:
precidur® HSM 650 HD precidur® HSM 700 HD Benfit: Especially suited to complex forming processes
Overview rear seat structure
Rear seat panel, standard thickness 0.5 to 0.6 mm
DP-K® 290Y490T (tolerances ±0.05 mm, tighter tolerances on request)
MHZ® 420, standard thickness approx. 0.6 mm
HC460LA, standard thickness approx. 0.5 mm
Reinforcement brackets, standard thickness 2.0 to 2.5 mm
scalur® S420MC
Profiles, standard thickness 0.8 to 1.2 mm
DP-K® 700Y980T, ideal for roll forming
CP-K® 570Y780T
DP-K® 440Y780T
HC460LA
Rear seat panels and reinforcement brackets
While seat structures for front seats have the same or comparable structure depending on the car model, rear seat structures vary greatly depending on the vehicle, e.g. adjustable individual seats, divisible or non-divisible rear seat benches with profiles or tubes.
Micro-alloyed steels MHZ® 420 and HC460LA are predestined for forming operations such as flanging and beading and therefore ideally suited for the production of rear seat panels. Profiles and reinforcement brackets are used to meet the high crash requirements of the rear bench seat (e.g. load case: protection against load). Our steel grade scalur® S420MC, pickled micro-alloyed hot-rolled strip with extremely narrow thickness tolerances of up to ±0.05 mm and a very flat profile, offers not only the best processing properties but also high lightweighting potential.
MHZ® 420, usual thickness approx. 0.6 mm HC460LA, usual thickness approx. 0.5 mm Benefit: Excellent forming properties for operations such as flanging and beading
Material recommendation reinforcement brackets:
scalur® S420MC Benefits: - High lightweight potential and best processing properties - Excellent suitability for MIG, MAG and laser welding
Profiles
Dual-phase steel DP-K® 700Y980T (ideally suited for roll forming) and complex-phase steel CP-K® 570Y780T are both suitable for rear seat structures in tubular design. Both steel grades combine high strength with good formability and offer high lightweighting potential.
Material recommendation:
DP-K® 700Y980T CP-K® 570Y780T HC460LA Benefits: - High strength with good formability and high lightweight potential - Ideal for structural components with high crash performance (load scenario: protection against cargo)
Highly ductile micro-alloyed steel grades for better forming performance in automotive engineering
Highly ductile micro-alloyed steels are the go-to material when significantly improved formability for complex component geometries in seat structures, like cushion side members and seat rails, is required. They offer better formability and higher hole expansion values. The special microstructure of the HD grades ensures stable mechanical properties (low scatter), the best prerequisite for high production reliability.
1. Not all thickness and width combinations possible.
Perfect fit, even at the collar – thanks to Brose and thyssenkrupp Steel
Cooperation between Brose and thyssenkrupp Steel: Investigation of the forming behavior of high-strength complex-phase steels during collar drawing.
Automotive supplier Brose has teamed up with thyssenkrupp Steel to investigate the forming behavior of high-strength complex-phase steels during collar drawing. The aim was to optimize the process using a numerical simulation - based on a new material card.
When it comes to further developing processes in the automotive industry, practical cooperation is required. Such as between thyssenkrupp Steel and automotive supplier Brose.
In collar drawing, a hole is punched into a steel blank, the edge of which is then raised to form a flange. This raised zone – the so-called collar – serves as a functional connecting element in the subsequent component and thus, for example, as a bearing point or preliminary stage for thread forming. The particular challenge is that the cut edge of the material is subjected to high stresses. Depending on the degree of deformation and the interaction with the materials used, different boundary conditions arise until the material reaches the load limit. The exact prediction of this behavior is crucial for the process design – especially for high-strength materials.
High-strength complex-phase steel for seat structures
The project focused on the cold-rolled complex-phase steel CP-K® 780Y980T from thyssenkrupp Steel. With a tensile strength of at least 1,000 megapascals and its fine-grained microstructure, it combines high strength, good hole expansion and reliable formability – all properties that predestine it for crash and safety-relevant applications in lightweight automotive construction. "Our customers are increasingly demanding reliable data for new materials - not only on mechanical properties, but also on overall process behavior," explains Sarah Abraham, Product Manager at thyssenkrupp Steel. The behavior is particularly complex at the cutting edge, as it is strongly influenced by the microstructure and the forming process."
"CP-K® grades allow us to rethink geometric freedoms, for example at bearing points. Although these can still be implemented afterwards, this involves additional work steps," says Gerald Erdmann from Brose's Materials Development and Sustainability department. “Our CP-K® 780Y980T is characterized not only by its excellent local but also by a comparatively high global forming behavior,” adds Sarah Abraham.
Practical collar pulling tests at thyssenkrupp Steel's Dortmund technical center.
In order to provide valid information, thyssenkrupp Steel conducted extensive tests to create a validated material card for its high-strength, cold-rolled CP-K® 780Y980T, which also takes fracture mechanical parameters and cutting edge properties into account. "With our testing equipment, we are able to create material cards that can be used for both forming and crash applications. The focus here is on our customers' requirements, which can be requested from us at any time on a customer-specific basis," explains Hartwig Rösen, from the materials modeling department at thyssenkrupp Steel. At the same time, practical collar pulling tests were carried out in the Dortmund technical center of the steel manufacturer Dortmund in order to demonstrate real load and failure mechanisms on the material.
Simulation meets practice: thyssenkrupp Steel and Brose work together
In the next step, Brose took over the numerical modeling: detailed simulations of the collar pulling process were created using the data provided by thyssenkrupp Steel. The focus was particularly on sensitivity analyses, i.e. the question of how strongly changes in friction, cutting force or edge radius affect the result. “The data provided gave us a very good foundation for the digital mapping of the process,” says Alexander Kulikov, Project Engineer Simulation at Brose. “This not only allowed us to systematically compare variants, but also to supplement the physical tests in a targeted manner.” The results show: The real and simulative observations match – particularly with regard to the geometry of the formed collars and the influence of cut edge quality. There are still slight deviations with regard to the exact fracture behavior, which can now be used to further refine the models.
The material data provided was used to simulate the collar pulling process at Brose. The Brose project team: Alexander Kulikov, Development Standards & Digitalization Engineer, Gerald Erdmann, Materials Development & Sustainability Engineer and Thomas Kreissl, Metal Technology & Forming Engineer (from right to left).
“Our detailed material cards are key to the digitalization of forming processes,” emphasizes Sarah Abraham. “They enable realistic simulations – and therefore save valuable time and resources.” From thyssenkrupp Steel's perspective, the project is a successful example of a successful development partnership. “When materials knowledge, application technology and customer requirements come together, resilient solutions for real challenges are created,” says Stefan Woestmann, application engineer at thyssenkrupp Steel. “This is not only helpful in specific cases – it also provides a valuable basis for future developments.”
“The collaboration with thyssenkrupp Steel enables us to incorporate our experience into both the design of the stamping processes and the subsequent forming,” says Thomas Kreissl, forming technology technologist at Brose, summing up the successful project.
Brose – Mechatronic systems for vehicle doors and seats as well as electric motors and drives
Brose is one of the five largest family-owned automotive suppliers in the world. Every third new car is equipped with at least one Brose product. The mechatronics specialist develops and manufactures systems for vehicle doors, flaps and seats. Brose also produces electric motors from 200 watts to 14 kilowatts for various applications such as steering, thermal management or e-scooters. More than 80 automotive manufacturers and 40 suppliers rely on Brose's system expertise.
Multiphase steels for safe and light vehicle seats
Complex-phase steel CP-K® 780Y980T with best forming properties for use in seat rails.
With two new high-strength, cold-rolled multiphase steels with special forming properties, thyssenkrupp Steel is supplying the automotive industry with ideal materials for weight-reduced seat structures.
Application Vehicle seats consist of complex safety and crash-relevant structural components. As is the case throughout vehicle construction, saving weight in these components is also a key issue. thyssenkrupp Steel offers two new steel solutions for this. Specifically, we are talking about uncoated dual- and complex-phase steels with strengths of 800 and 1,000 megapascals for lightweightstructural components with high crash relevance and forming complexity. Firstly, the dual-phase steel DP-K® 440Y780T HHE for components in the seat frame with good deep-drawing and elongation properties. The grade offers impressively high work hardening properties, and absorbs significantly more energy in the event of a crash than conventional microalloyed steels. This is complemented by the complex-phase steel CP-K® 780Y980T, which increases the functional reliability of seat rails thanks to its maximum strength. Both materials allow a reduction in material thickness without limiting function and safety.
Processing In addition to the possibility of weight optimization and good crash performance, both steels offer very good forming properties – the best prerequisite for efficient production of complex seat components. With its property profile, the robust DP-K® 440Y780T HHE is suitable for deep-drawn, flanged, complex structural elements such as the backrest side section. Its special analysis makes the grade more resistant to edge cracking in complex forming geometries. The CP-K® 780Y980T has an even higher hole expansion capacity, can be optimally processed by roll forming, bending and edging and is ideal for seat rails.
Sustainable lightweight construction Thanks to high-strength multiphase steels, seat components can be designed thinner, thus reducing weight – and also saving CO2. With bluemint® Steel, the high-quality flat steel with reduced carbon footprint, maximum CO2 savings are achieved – with the same excellent material and processing properties as the existing grades.
Lightweight construction, crash safety and forming complexity – these are the hallmarks of our new multiphase steels.
Sarah Abraham, Product Management Industry
Your request
Whether strip, sheet or slit strip – use our form for your flat steel inquiry.
In addition to a customized portfolio for steel seat structures, thyssenkrupp Steel provides its automotive customers with extensive material characteristics on request. Both variants with a standard scope and complex material cards with implemented damage and failure models are available.
