Material for Die Plates
The core of an underwater pelletizer is the die plate, a perforated plate. It contains numerous holes through which the plastic melt is pushed and cut to the desired length on the blades rotating on the plate. Together with its clients Coperion and Gala Industries, Deutsche Edelstahlwerke (DEW), a member of Schmolz + Bickenbach Group, have developed a material for the die plates that has more than doubled the service life of the systems: the new Nikrodur.
The joint development work on a material which, from the start, was designed and optimised on a customer-specific basis, especially for the underwater pelletizing application, began as early as 2008. “Together with our customers Coperion and Gala Industries, we have created a quite specific requirements profile for the material, for example with regard to optimal wear and corrosion characteristics and the thermal conductivity of the material. The objective was to increase the service life of the systems by approximately 50%”, says Dr Horst Hill.
From Development Phase...
The specialists at DEW carried out numerous material simulations in the laboratory. “Based on the Ferro-Titanit materials, we are working on significantly improving all three core characteristics of the material for this type of die plate – i.e. to achieve the highest possible wear and corrosion resistance and to achieve a reduction in thermal conductivity”, says DEW specialist Dr Hill. Only if these properties interact optimally does the service life of the die plates, which are used under extreme conditions, also increase. “In fact, our material simulations and laboratory tests confirm that we have been able to produce a material that, compared to standard Ferro-Titanit, has 50% better wear resistance, about one-third higher corrosion resistance and one-fifth lower thermal conductivity for this application”, says Dr Hill. The materials experts carried out selected trial melts on a laboratory scale, and finally manufactured the material on an industrial scale. Until then, the material had fulfilled its promise – now it was also to prove itself in practice. “We deliberately offered the material for testing to two development partners who manufacture underwater pelletizing systems or die plates in different dimensions”, explains Dr Hill.
... to Series Production
The test phase for the new material began for Coperion in 2013, when it used its own customers to carry out additional corrosion tests under realistic operating conditions, as well as various production tests. “The tests confirmed that the new material was as impressive in the processing as the proven material types. There was therefore nothing to prevent production of a prototype”, explains Product Manager Jürgen Bartl. This was especially adjusted to the needs of one of Coperion’s customers and has been in use there since 2014. Both the customer and Coperion itself carried out regular prototype performance checks for about a year. In 2016, there was nothing to prevent series production with material made of Nikrodur. Like Coperion, Gala Industries also receives Nikrodur exclusively for die plate manufacture. This American company made a successful start to series production in 2015.
Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG
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