Pushing limits together
The voestalpine way of optimally coating tools used in the forming of ultra-high strength steels
Tool life increased by 460%, excellent adhesion and wear reduction. With its Duplex-VARIANTIC®-1400 tool coating, voestalpine eifeler sets a milestone in the economical cold forming of ahss steels.
If you suspect that there is probably more to this outstanding accomplishment in terms of competence and (wo)man power, you are certainly right. Dr. Farwah Nahif, Head of Research and Development at voestalpine eifeler, and Christian Walch, Head of Application Technologies at voestalpine Steel Division, provide some insights here.
Based on industry requirements
Automotive Notes: Under the motto of "Taming the Steel," voestalpine has developed optimally tuned high-strength steels and tool coatings. What was the impetus for this project?
F. Nahif: Customer requirements. Higher strength, less weight and continuous increases in production efficiency are decisive factors in lightweight automotive design.
Automotive Notes: High strengths and easily formable steels are the basic requirements here, and voestalpine can supply them?
C. Walch: Yes, the ultra-light high-ductility steels we have developed exceed strengths of 1,000 MPa, combine high strength with good formability and make it possible to cold-form high-strength components of demanding complexity.
Cooperation as a success factor
Automotive Notes: The strongest develops most strongly alone. Does this not apply to voestalpine?
F. Nahif: Right. The voestalpine Steel Division has a great deal of expertise in ultra-lights, is a leading developer of high-strength and ultra-high-strength steels for lightweight automotive designs. At voestalpine eifeler, we are experts in tool and component surface coatings in the voestalpine Group. We also have companies within the Group who specialize in tool steel and the forming process itself. In close collaboration during development, we have shared expertise pertaining to each parameter relevant to the success of our customers.
Automotive Notes: Ausgangspunkt ist der zu verarbeitende Stahl. Which steel grades did you focus on?
C. Walch: We focused most heavily on the development of dual-phase high-ductility steels in two families of strength classes ranging between 1,200 and 1,400 MPa: Dual phase high ductility (drawing type) and complex phase high ductility (bending type). Our main focus in the development process itself was on process-safe manufacturability and balancing property profiles in terms of mechanical, joining and forming properties.
Automotive Notes: Were targets defined for the coating developers?
F. Nahif: The objective of the cross-divisional and cross-divisional Group project, as far as we were concerned, was to develop a coating for tools used in the forming of steels in strength classes of 1,200 MPa and above.
Automotive Notes: Which factors contributed most prominently to your success?
F. Nahif: We belong to the same corporate group, and so the exchange of information was uncomplicated. It was like we all belonged to the same family. The atmosphere was very creative, and everyone was so ambitious that you would have thought we were a start-up company. We benefited greatly from the input from our steel developers.
C. Walch: And we steel developers have profited from insights into related topics. We were all sitting at a virtual table, as it were, and as experts in our field we looked beyond our own horizons.
World's first system solution
Automotive Notes: Can you outline the project and give an example of one of the benefits of your collaboration?
F. Nahif: At voestalpine eifeler, we have a great deal of experience in developing coating solutions for presses and punching machines as well as products for forming tools. We were able to build on our experience. The use of special alloys and the modification of parameters such as pressure and temperature down to hundredths of a unit made it possible for us to develop several solutions that were tested in the laboratory. Here is a concrete example of our cooperation: The project began in 2015. At the time, hardly anyone besides voestalpine Steel Division was in a position to offer market-ready ultra-high-strength steels of 1,200 MPa and higher.
C. Walch: We supplied forming materials that met practical requirements, including for subsequent test runs under real conditions. The test runs were conducted at voestalpine forming companies. The many different possibilities under one corporate roof accelerated and simplified the development process.
Automotive Notes: A final question. What was the best part of the project for you personally?
C. Walch: For me as a steel developer, it was the first pressing of a B pillar in DP1200HD steel when the sample component proved the workability of high-ductility steels for the entire process chain from production planning, press shop, toolmaking and pressing to optimization of the joining process.
F. Nahif: It is always nice for a coating developer to see things perform just the way it was planned. This was the general rule in the development of Duplex-VARIANTIC®-1400. It was even nicer to see that our expectations were even exceeded in the practical application. The optimally tuned system and interaction between the material, the tool steel and tool coating have taken us a step further in the cost-effective production of high-strength components for automotive lightweight designs.
- Tool coating for cold forming
- For steel strengths of up to 1,400 MPa and more
- Al (Cr, Ti) N-based PVD coating with adhesive and top layer
- Hardness: 3.000 +/- 200HV
- Up to 460% longer tool life
- Excellent resistance to abrasive and adhesive wear
- Very good adhesion to the forming tool resulting from plasma-based pretreatment in the coating process
- Improved workpiece quality
Dr. Farwah Nahif
Head of Research and Development
voestalpine eifeler Vacotec GmbH
Head of Application Technologies
voestalpine Steel Division