PETpla.net Insider 05 / 2011

BOTTLE MAKING 20 PET planet insider Vol. 12 No. 05/11 www.petpla.net New metal alloy intended for more efficient PET bottle production The rule of hard blocks Deutsche Edelstahlwerke GmbH recently launched Cor- roplast FM, a new alloy intended as a primary material for preform moulds.It is intended to meet the industry’s need for greater efficiency, including improved machinability and metal hardness, without loss of corrosion resistance. Deutsche Edelstahlwerke GmbH (DEW) supplies the PET bottle indus- try with primary material for injection moulds for production of preform bottle blanks. Demand for bottles continues to increase. In 2009, a year of little eco- nomic growth, approximately 480,000t of PET were processed in Germany alone, mainly for use in the packag- ing industry and including PET bottles. Business pressures, including the need to improve competitive performance in international markets, mean that plastic manufacturers need to produce more and more bottles in less and less time – but without any loss of qual- ity. Efficiency is the decisive factor. This also applies to the primary mould material made of specialty steel. In response to these demands, DEW has launched ‘Corroplast FM’. It presented this new material as its solution for increased requirements in process cost optimisation at Euromold in Frankfurt. “The trend for a few years now has been towards increasingly pro- cessed corrosion-resistant moulds, mould frames and superstructures,” said Michael Bauer, head of technical customer support for tool steel at DEW. “The PET bottle industry is a clear example. For reasons of efficiency, cavities for up to 192 preforms are now used in one single injection mould.” Increased numbers of cavities leads to increased machining complexity. DEW claims that Corroplast FM demonstrates significantly increased machinability, compared with other proven plastic mould steels, without reduction of corro- sion resistance, and a good balance of those two features and metal hardness. Analysis and structure Development of the new material has taken more than two years. “In order to achieve the desired properties, we had to determine the optimum ratio of the alloy components – chromium, nickel, manganese and sulphur,” said Jens-Sebastian Klung, member of the department for development / mate- rial and process simulation. A particular challenge was homogenisation of the structure and the correct proportion of sulphur. In the right quantity, sulphur has a positive effect on the machining properties of specialty steel but it also decreases performance characteristics, especially in transverse direction, if the quantity is too high. Melting and subse- quent secondary metallurgic treatment were adjusted in order to reduce this negative effect. The possible formation of embrittling delta ferrite was mini- mised through thermodynamic calcula- tions, which further improves homoge- neity of the structure and its resulting properties. The homogenous structure ensures not only that Corroplast FM remains corrosion-resistant – even in an environment marked by heat, conden- sation and coolant – but also provides stability for filigree components and limited cavity spacing. As well as PET bottle producers, the material is also claimed to offer advan- tages to the automotive industry (for the production of plastic and rubber parts); cosmetic and food industry packaging manufacturers; or any operation that needs complex, corrosion-resistant and easy-to-machine base and build up plates, mould frames or plastic moulds. Full service from scrap metal to preforms Following the successful comple- tion of a series of experiments and tests, customers can now purchase Corroplast FM plastic mould steel as rolled or forged plate with a width of 1,000mm and a thickness between With the new material the processing/ production costs of the PET industry can be optimized. In the electric arc furnace selected scrap and certain alloying elements are melted.