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We are excited to share with you a summary of an article, written for our AHSS Application Guidelines database, by Eren Billur, Billur Makine and Billur Metal Form, Turkey. It is one of the most detailed, comprehensive, and interesting reads on the progression of Press Hardened Steels in vehicle applications that we have seen to date. The big problem was, how to summarize the original 15-page article for this blog! With Dr. Billur’s help, we provide a snapshot here. But please accept this as just a taste of what you can expect to see when our new online AHSS Guidelines is released later this year.

The Beginnings of PHS Use

Press hardening, as we know it today, was developed in Luleå, Sweden, by Norrbottens Järnverks AB (abbreviated as NJA, translated as Norrbotten Iron Works). The first patent application was completed in 1973 and awarded in 1977.N-23 The technology was first commercialized in agriculture components, where the high strength of Press Hardened Steels (PHS) was favored for wear resistance.B-45

In 1984, automotive applications of PHS started with the Saab 9000 side impact door beams, as seen in Figure 1. A total of 4 parts were used in this car.A-66 The uncoated blanks were almost half the thickness of a cold stamped beam.T-26

Figure 1: Door beams of the Saab 9000 (1984-1998): (a) A see-through car in Saab MuseumS-82, (b) the hot stamped part.L-42

 

The majority of the PHS parts were door beams through the mid-1990s, with approximately 6 million beams produced in 1996. By this time, the demand for bumper beams was also increasing.F-31 By the end of 1996, the European New Car Assessment Program (EuroNCAP) was formed, which increased the pressure on the OEMs for improved crashworthiness.T-26 In 1998, both the new Volvo S80L-44 and Ford Focus5 were equipped with Press Hardened bumper beams.

The year 1998 saw the development of one of the most important breakthroughs in Press Hardening technology. French steel maker Usinor developed an aluminum-silicon (AlSi) pre-coated steel, commercialized as Usibor 1500 (indicating the typical tensile strength, 1500 MPa.C-24, L-39 In 2000, BMW rolled out its new 3 series convertible. In this vehicle, the A-pillar is made from 3 mm thick uncoated, PHS sheet. This was BMW’s first PHS application, and one of the first PHS A-pillar reinforcement.S-83, S-84 Accra started delivering roll formed PHS components for the Volvo V70, initially an optional 3rd row seating support. Approximately 10,000 parts/year were supplied.G-28

AlSi coated steel was first hot stamped at a French Tier 1 supplier, Sofedit.V-15 This grade was first used in the front bumper beam of the 2nd Generation Renault Laguna (2000-2007). Laguna 2 was the first car to receive a 5-star safety rating from Euro NCAP.V-10 AlSi coated blanks were also used in PSA Group’s Citroën C5 (1st Gen: 2001-2007) in the front bumper beam, and the A-pillars. These three parts weighed a total of 4.5 kg, approximately 1% of the total BIW weight, Figure 2a. About one month later, PSA Group started production of the compact hatchback Peugeot 307, which had five hot stamped components (A- and B-pillars and rear bumper beam). Unlike the Citroën C5, these parts were uncoated. The total weight was 12 kg, corresponding to 3.4% of the BIW weight.R-17, P-27

Figure 2: Increase in press hardened component usage: (a) 2001 Citroën C5P-27, (b) 2002 Volvo XC90L-29 and (c) 2005 VW Passat.H-50

Figure 2: Increase in press hardened component usage: (a) 2001 Citroën C5P-27, (b) 2002 Volvo XC90L-29 and (c) 2005 VW Passat.H-50

 

Volvo started producing the XC90 SUV in 2002. The body-in-white with doors and closures weighed 531 kg.B-44 A total of 10 parts, weighing 37 kg are either roll formed or direct stamped PHS. This accounts for approximately 7% of the BIW weight.L-43 During its time, this was the highest use of PHS in car bodies. In Figure 2b, the Press Hardened components other than the 2nd row seat frame, which is a load bearing body part, are shown.

Accelerated Use and Globalization

The use of press hardened parts increased rapidly after the introduction of the VW Passat in 2005. This car had approximately 19% of its BIW (by weight) made from press hardened steels, Figure 2c. Some parts in this car saw the first use of varnish coated blanks in a two-step hybrid process. Three parts were produced using either an indirect or hybrid process, including the transmission tunnel.H-50

Following are a few highlights of PHS use in vehicle applications during this time period :

  • In 2006, the Dodge CaliberK-37 and BMW X5P-28 were among the first cars to have tailor-rolled and Press Hardened components in their bodies (Figure 3).
Figure 3: (a) Tailor Rolling ProcessZ-5, (b) B-pillar of BMW X5 (2nd Gen: 2006-2013)P-28

Figure 3: (a) Tailor Rolling ProcessZ-5, (b) B-pillar of BMW X5 (2nd Gen: 2006-2013)P-28

 

  • BMW 7 Series (5th Gen: 2008-2015) became the first car to have Zn-coated Press Hardened components in its body-in-white. The car also contained uncoated parts, as shown in Figure 4 (next page). The total PHS usage in this car was approximately 16%.P-20

Figure 4: PHS usage in BMW 7 Series (5th Gen: 2008-2015) (re-created using P-20).

 

  • Press hardening also allowed car makers to create unconventional cars. In 2011, Hyundai rolled out the 1st generation Veloster, a 3-door coupé (also known as 2+1, with one door on the driver side and 2 doors on the passenger side), and as such containing axisymmetric front doors. Thus, the car could not have a full B-ring, as illustrated in Figure 5a.B-14, R-19 Another unconventional design was the Ford B-Max subcompact MPV sold in Europe between 2012 and 2017. The car had conventional swing doors in the front and two sliding rear doors. A PHS B-pillar was integrated in the doors, providing ease of ingress. Its PHS components (integrated B-pillar in front and rear doors, door beams and cantrail) are shown with blue color in Figure 5b.B-14, L-45
Figure 5: Unconventional car designs with PHS: (a) Hyundai Veloster, asymmetric 2+1 doors coupé (re-created after Citation R-19), and (b) Ford B-Max, sub-compact MPV with integrated B-pillars in the doors.L-45

Figure 5: Unconventional car designs with PHS: (a) Hyundai Veloster, asymmetric 2+1 doors coupé (re-created after Citation R-19), and (b) Ford B-Max, sub-compact MPV with integrated B-pillars in the doors.L-45

 

In 2013, the Acura MDX (3rd Gen: 2013-2020) became the first car to have a Hot Stamped door ring. The part was a tailor welded blank comprised of two sub-blanks, as shown in Figure 6a. The design saved about 6.2 kg weight per car and had high material utilization ratio thanks to sub-blank nesting optimization.A-67, M-46  One of the most recent PHS applications was in 2017 Chrysler Pacifica with 5 sub-blanks, as shown in Figure 6b. This car also has a PQS550 sub-blank at the lower B-pillar region.D-28

Figure 6: Hot stamped door rings: (a) First application in 2013 Acura MDX had 2 sub-blanks, (b) a more recent application in 2017 Chrysler Pacifica has 5 sub-blanks with PQS550 at the lower B-pillar (re-created after Citations B-14, A-67, D-28).

Figure 6: Hot stamped door rings: (a) First application in 2013 Acura MDX had 2 sub-blanks, (b) a more recent application in 2017 Chrysler Pacifica has 5 sub-blanks with PQS550 at the lower B-pillar (re-created after Citations B-14, A-67, D-28).

 

  • Tubular hardened steels have been long used in car bodies, with minimal forming. Since 2013, a special 3-D hot bending and quenching (3DQ) process has been employed. One of the earliest uses of this technology was Mazda Premacy (known as Mazda 5 in some markets). The same process was also used in making the A-pillars of the Acura NSX (Honda NSX in some markets, 2016-present), as seen in Figure 7a.H-29 Since 2018, tubular parts formed with internal pressure, called form blow hardened parts, are used in the Ford Focus (4th Generation) (Figure 7b) and Jeep Wrangler (4th Generation).B-16, B-17

    Figure 7: Tubular hardened steel usage in A-pillars of: (a) 2015 Acura NSXH-29, (b) 2018 Ford Focus.B-16

    Figure 7: Tubular hardened steel usage in A-pillars of: (a) 2015 Acura NSXH-29, (b) 2018 Ford Focus.B-16

 

PHS Use in xEVs: Hybrid Electric, Battery Electric,

Plug-in Hybrid Electric & Fuel Cell Electric Vehicles

The first commercially available Hybrid Electric Vehicle (HEV) was the Toyota Prius (1st Gen: 1997-2003). The second-generation Prius (2003-2009) had very few Press Hardened components, as shown with red color in Figure 8a. This was the first time Toyota used hot stamped components.M-47 The third generation Prius (2009-2015) had approximately 3% of its BIW Press Hardened. In the 4th generation Prius released in 2015, the share of >980 MPa steels has risen to 19%.U-10 Figure 8b shows the Press Hardened parts in this latest Prius.K-38

Figure 8: PHS usage in Toyota Prius: (a) 2nd generation (2003-2009) and (b) 4th generation (2015-present) (re-created after Citations M-47 and K-38)

Figure 8: PHS usage in Toyota Prius: (a) 2nd generation (2003-2009) and (b) 4th generation (2015-present) (re-created after Citations M-47 and K-38)

 

The 2012 Tesla Model S and Model X launched using aluminium bodies, with PHS reinforcements in the pillars and the bumpers. Model S is known to have a roll-formed PHS bumper beam. High volume Model 3 and Model Y have a significant amount of press hardened components in their bodies.T-35

In 2011, General Motors started production of its first Plug-in Hybrid Electric Vehicle (PHEV), the Chevrolet Volt (known as Opel Ampera in EU and Vauxhall Ampera in the UK). This car had six Hot Stamped components, including A and B pillars, accounting for slightly over 5% of the BIW mass.P-29

The smaller BEV Chevrolet Bolt, launched in 2017, had aluminum closures, but a steel-intensive BIW that is 80% steel, 44% of which is Advanced High-Strength Steels including 11.8% PHS. Figure 9.A-69

Figure 9: Chevrolet Bolt Body Structure and Steel ContentA-69

Figure 9: Chevrolet Bolt Body Structure and Steel Content.A-69

 

In December 2020, Hyundai announced their new electric platform, E-GMP. The platform will utilize Press Hardened steel components to secure the batteries.H-52

Automakers have turned to PHS to manage the extra load of Fuel Cell powertrains as well. The first-generation Toyota Mirai had only Press Hardened B-pillars, cantrails and lateral floor members.T-38 The second generation has a number of parts with PHS in its under body as well.T-39

In 2018, Hyundai Nexo became the first fuel-cell car to be tested by EuroNCAP, achieving a 5-Star rating. The car has PHS A- and B-pillars, rocker reinforcements, and several under body components, as seen in Figure 10.H-53

Figure 10: Press hardened steel usage in Hyundai Nexo Fuel Cell vehicle: (a) side view and (b) top view (re-created after Citation H-53).

Figure 10: Press hardened steel usage in Hyundai Nexo Fuel Cell vehicle: (a) side view and (b) top view (re-created after Citation H-53).

 

There will be more on the history and detailed information about some of the technical terms used in this article (such as form blow hardening or 3DQ) in the AHSS Guidelines which will be available by mid-2021. PHS technology, both in terms of steel making and automotive use, is still evolving and is expected to have a higher share in the near future.

 

Author: Dr. Eren Billur, Technical Manager
Billur Makine and Billur Metal Form
Dr. Billur, is a mechanical engineer, automotive enthusiast, and a second-generation business owner on metal forming, located in Ankara, Turkey. He has completed his doctoral studies on press hardening technology, with Prof. Taylan Altan at The Ohio State University in 2013. Dr. Billur is continuing to work on advanced material characterization, new generation press hardening steels, 3rd generation AHSS and servo-press technologies. He has authored/co-authored more than 20 scientific papers (including proceedings) and contributed to four books, including “Hot Stamping of Ultra High Strength Steels” published in late 2018. Since 2015, he is acting as technical manager of Billur Makine and Billur Metal Form companies, both located in Ankara, Turkey.

 

Citations:

  • A-66.  J. Aspacher, “Hot Stamping Market Overview & Process Review,” Presented at Schuler Hot Stamping Workshop, May 14, Dearborn, MI, USA, 2013.
  • A-67.  Altair Engineering, “Industry First Hot Stamped Door Ring,” Altair Enlighten Award Nominee, 2013,
  • A-69.  Courtesy of the American Iron and Steel Institute.
  • B-14.  E. Billur, Ed., “Hot stamping of ultra high-strength steels: From a Technological and Business Perspective,” Springer, 2019.
  • B-16.  J. Büchner, T. Oberlander and B. Benneker, “Ford Focus,” Presented at EuroCarBody 2018, October 16-18, Bad Nauheim, Germany, 2018.
  • B-17.  A. Bagley and T. Rybicki, “Jeep Wrangler,” Presented at EuroCarBody 2018, October 16-18, Bad Nauheim, Germany, 2018.
  • B-44.  J. Bernquist, “Safety cage design in the VOLVO XC90,” Great Design in Steel – 2004, Sponsored by American Iron and Steel Institute.
  • B-45.  E. Billur, G. Berglund and T. Gustafsson, “History and Future Outlook of Hot Stamping,” Chapter 3 in Hot stamping of ultra high-strength steels: From a Technological and Business Perspective, Edited by E. Billur, Springer, 2019, pages 31-44.
  • C-24. D. Cornette, T. Hourman, O. Hudin, J.P. Laurent and A. Reynaert, “High Strength Steels for Automotive Safety Parts,” in SAE Technical Paper 2001-01-0078, 2001, doi.org/10.4271/2001-01-0078.
  • C-25.  Ö. M. Çeteci, “The New Ford Transit Connect,” Presented in Aachen Karoserietage 2014, September 23, Aachen, Germany, 2014.
  • D-28.  L. Decker and J. Truskin, “The All-New 2017 Chrysler Pacifica,” Presented at Strategies in Car Body Engineering 2017, March 22-23, Bad Nauheim, Germany, 2017.
  • F-31.  P. Fahlblöm, “Analys för val av emballagesystem : en studie gjord för att underlätta valet av emballagesystem (Analysis for choice of packaging: a study done on choosing of packaging methods, in Swedish),” Master’s Thesis, Luleå University of Technology, Sweden, 1997.
  • G-28.  A. Gier, “Hot Forming and Hardening of Rollformed Sections,” Aluminum and Steel Forming in Automotive Engineering, pp. 172-237, 2005.
  • H-29.  K. Horner, “Strategic Steel Application in the Acura NSX Space Frame,” Great Design in Steel – 2018, Sponsored by American Iron and Steel Institute.
  • H-50.  D. Holzkamp, “Recent Developments on UHSS Welding and Its Simulation for Prevention of Heat Distortion,” Presented at Insight Edition Conference, September 20-21, Gothenburg, Sweden, 2011.
  • H-52.  Hyundai Motor Group, “Hyundai Motor Group to Lead Charge into Electric Era,” Press Release, 2020.
  • H-53.  Hyundai Motor Company, “NEXO: Emergency Response Guide”, 2018.
  • K-37.  A. Kröning, “Lightweight solutions for body applications,” Presented at Insight Edition Conference, September 20-21, Gothenburg, Sweden, 2011.
  • K-38.  N. Koreishi and T. Hioki, “Vehicle Development for the Application of Laser Screw Welding,” Presented at Joining in Car Body Engineering, April 5, Bad Nauheim, Germany, 2017.
  • L-29.  H. Lindberg, “Advanced high strength steel technologies in the 2016 Volvo XC90,” Presented at Great Designs in Steel 2016, Sponsored by American Iron and Steel Institute.
  • L-39.  J.-P. Laurent, J.-P. Hennechart, D. Spehner and J. Devroc, “Coated hot-and cold-rolled steel sheet comprising a very high resistance after thermal treatment,” US Patent 6,296,805, 2001.
  • L-43.  H. Lanzerath, A. Bach, G. Oberhofer and H. Gese, “Failure Prediction of Boron Steels in Crash,” in SAE Technical Paper 2007-01-0989, 2007.
  • L-44.  .K. Larsson and L. Hanicke, “Multi-material Approach with Integrated Joining Technologies in the New Volvo S80,” SAE Technical Paper 1999-01-3147, 1999, doi.org/10.4271/1999-01-3147.
  • L-45.  D. Ludlow, “Ford B-Max preview,” posted on February 23, 2012.
  • M-46.  R. Zum Mallen and J. Riggsby, “Development of a Global First SUV Body Construction,” Presented at Automotive Engineering Expo, June 4-6, Nürnberg, Germany, 2013.
  • M-47.  N. Matsuyama and S. Morimatsu, “The New Toyota PRIUS Car Body,” Presented at EuroCarBody 2005, October 25-27, Bad Nauheim, Germany, 2005.
  • N-23.  Norrbottens Jaernverk, A. B., “Manufacturing a hardened steel article,” Great Britain Patent, GB1490535, 1977.
  • P-20.  M. Pfestorf, “Multimaterial lightweight design for the body in white of the new BMW 7 series,” in International Conference of Innovative Developments for Lightweight Vehicle Structures, May 26-27, Wolfsburg, Germany, 2009.
  • P-27.  G. Plassart and G. Philip, “Materials Criteria Selection and Certification Process for the Body in White in PSA Peugeot Citroën,” SAE Technical Paper 2002-01-2051, 2002, doi.org/10.4271/2002-01-2051.
  • P-28.  M. Pfestorf and J. Rensburg, “Functional Properties of High Strength Steel in Body in White,” Great Design in Steel – 2006, Sponsored by American Iron and Steel Institute.
  • P-29.  W. Parsons and A. DeZess, “The New Opel Ampera,” Presented at Strategies in Car Body Engineering 2012, March 21-22, Bad Nauheim, Germany, 2012.
  • R-17.  A. Reinhardt, “Development of hot stamped Ultra High Strength Steel parts on the Peugeot 307 and the Citroën C5,” Presented at EuroCarBody 2001 – 3rd Global Car Body Benchmarking Conference, Bad Nauheim, Germany (2001).
  • R-19.  B. Ramirez, “Media Launch: 2013 Veloster Turbo,” Hyundai Motor North America Newsroom, 2012.
  • S-82.  Saab 9000 Cross Section.
  • S-83.  J. Staeves, “Höherfeste Stähle für den Automobil-Leichtbau (High strength steels for automobile lightweight – in German),” Presented at Fachhochschule München, June 6th, Munich, Germany, 2002.
  • S-84.  J. Staeves, “Höherfeste Stähle für die Karosserie (High strength steels for car body – in German),” Presented at Technical University of Munich, June 28th, Munich, Germany, 2004.
  • T-26.  T. Taylor and A. Clough, “Critical review of automotive hot-stamped sheet steel from an industrial perspective,” Materials Science and Technology, vol. 34, pp. 809-861, 2018, doi.org/10.1080/02670836.2018.1425239.
  • T-35.  Tesla, “Emergency Response Guides,” Accessed January 3, 2021.
  • T-38.  Thatcham Research, “Toyota Mirai,” 2015.
  • T-39.  Toyota, “New Mirai Press Information,” 2020.
  • U-10.  “Under the Hood of the All-new Toyota Prius,” 2015.
  • V-10.  L. Vaissiere, J.P. Laurent and A. Reinhardt, “Development of Pre-Coated Boron Steel for Applications on PSA Peugeot Citroën and Renault Bodies in White,” SAE Technical Paper 2002-01-2048, 2002, doi.org/10.4271/2002-01-2048.
  • V-15.  T. Vietoris, “Hot Stamping with USIBOR1500®,” Presented at AP&T Press Hardening, Next Step Seminar, Novi, MI, September 15th, 2010.
  • Z-5.  M. Zoernack, “Competitive Designs With Tailor Rolled Products,” Great Design in Steel – 2018, Sponsored by American Iron and Steel Institute.