Compact industrial process for hot stamping of quenchable steels – PRICECAT
In order to reduce the CO2 emission of their cars from currently 130 g/km to 95 g/km before 2020, car makers are looking for new innovative lightening solutions.
A wide use of boron quenchable steels is seen as a very attractive one. Thanks to their very high mechanical properties, they offer opportunities for reducing thicknesses for structural parts by improving the cars’ safety and crash behaviour. The use of quenchable boron steels is therefore today in expansion and the huge majority of car makers are already implementing them on their new vehicles and body in white concepts. Nevertheless the use of these quenchable steels is limited because of process capabilities limits. The corresponding thermo-mechanical forming process, named hot stamping, is based on a fast quenching of the blank in the forming tool right after a forming step at high temperature. This fast quenching induces a metallurgical transformation of the steel which confers very high mechanical characteristics to the formed part. So hot stamping combines good formability properties of steel at high temperature and very high in-use properties of the final part.
Nevertheless, parts produced with this process have limited geometrical complexity because no further forming step is possible after quenching. So all the forming has to be done in one and only one operation.
Hot stamping costs are also a limiting parameter for car makers because of the high amount of investment needed and because of a production rate limited to a very few parts per minute (3 in average), which means that the amortization of the equipments has a strong impact on the part’s cost.
This project aims at permitting the hot stamping of complex shape parts by the development of the scientific and technological knowledge to deserve the design of an integrated progressive die for hot stamping. Progressive stamping, widely used in cold stamping, combines high productivity and the possibility to make very complex shape parts. Its development for hot stamping will open new lightening opportunities and part integration possibilities for car designers thanks to the enlargement of high strength part designs. Thanks to this tool, a whole production line (blanking press, furnace, press, laser cutting) which is currently needed will be replaced by a unique tool under a unique press. This innovative tool will decrease the cost of quenched parts thanks to a reduction of the amount of investment and an increase of productivity up to 10 parts per minute (today’s productivity : 3 parts per minute) .
Progressive stamping consists in forming a part with several successive cutting and forming operations done with the same tool. Its development for hot stamping will necessitate the integration of some very attractive and innovative technologies (fast heating, hot cutting) to be able to hang together several operations in adapted thermo-mechanical conditions. More, due to the specificity of this process, the quenching step will have to be managed in a particular way in comparison with the standard one. The behaviour of existing quenchable steels and of their coatings will have to be checked in such conditions.
To successfully achieve this project, cooperation between a steelmaker (ArcelorMittal), a stamping tool maker (SMP), a specialist of electrical generators and heating devices (SREM Technologies), a laboratory working on tool wear (ICA) and a laboratory specialised in forming and multiphysics modelling (LIMATB-Université de Bretagne-Sud (UBS)) will take place. Its success is insured by previous and on-going collaborations between these partners.
The main force of this project is to be at the heart of today’s automotive world challenges and to give a pragmatic answer to two of the most key issues: the production cost reduction and the lightening of bodies in white, by developing a practical process solution.
Monsieur Hubert Salmon-Legagneur (ArcelorMittal Atlantique et Lorraine)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
SMP Société Mécanique de Précision
AM MTT ArcelorMittal Atlantique et Lorraine
ARMINES ICA ARMINES Institut Clément Ader de l'Ecole des Mines d'Albi Carmaux
LIMATB Laboratoire d'Ingénierie des MATériaux de Bretagne
SREM SREM Technologies
AM MTT ArcelorMittal Atlantique et Lorraine
Help of the ANR 1,245,571 euros
Beginning and duration of the scientific project: December 2013 - 48 Months