Immaculate surfaces at the highest possible performance capacity – in the last decade the manufacturing requirements for plastic injection moulding die casting have become significantly more strict. Thus the demand for pre-hardened plastic mould steels with uniform hardness has increased, to be combined with excellent burnishing qualities and high wear resistance. In order to comply with increasing market expectations, Deutsche Edelstahlwerke continually works on the development of these steel solutions. The editors spoke with Daniel Frie, Technical Customer Service representative at Deutsche Edelstahlwerke, about the technological challenges faced when developing steel solutions.
The editors: How have customers’ plastic injection moulding requirements changed in the past few years?
Daniel Frie: When producing for high-tech sectors such as the automotive industry, the requirements are plastic injection processes that produce faultless products with the highest possible manufacturing efficiency. In the last few years, there has been a trend towards ever-higher injection pressures that are required to optimize the cycle times. At the same time, the surface finish of the plastic product must be high-grade and consistently repeatable. A prerequisite for the manufacturing of the required plastic moulds are tool steels that can be forged with the greatest accuracy grade and are robust in use. In application areas where large-sized, complex plastic moulds are used, the demands made on the material are disproportionately higher. Few steel manufacturers have the technological resources and material grade know-how to produce mould steel that meets these requirements.
The editors: Which steel grade solutions does Deutsche Edelstahlwerke offer and what is innovative about them?
Daniel Frie: We had already initiated the development of the pre-hardened plastic mould steel Formadur 320 approximately ten years ago in order to fulfill increasing demands on improved burnishing qualities and resistance to wear and tear. The basis for this are standard steel grades 1.2311 und 1.2738, that are standard solutions for frames and moulds for plastic injection moulding. We significantly increased the hardness of the steel and optimized its machinability. In order to guarantee a consistently perfect surface finish, the hardness of the steel must be uniform from surface to the core of the block. Even at that point we had reached a milestone in the area of plastic mould steel by achieving delivery hardness of up to 355 HB with Formadur 320. However, continuously setting new standards is the key point for being an innovation leader – and that is a guiding principle for the entire SCHMOLZ + BICKENBACH Group, to which Deutsche Edelstahlwerke belongs. In cooperation with our customers, we now have the new product Formadur 400 ready for serial production. With a hardness of up to 410 HB this high-grade steel provides an excellent hardness level for mould steels, which results in great burnishing qualities.
The editors: What are the biggest technical challenges in developing specifically requested steel, and how do you accomplish this?
Daniel Frie: One of the biggest challenges is to ensure the homogeneous hardness of large steel blocks. Thes must be guaranteed even at the core of the block in order to ensure uniform and repeatable surface qualities of the plastic product. The minimal differences in the hardness profiles of Formadur 320 and Formadur 400 show the advancement we have made in this area. Our technological competitive advantage includes heat treatment furnaces and quenching tanks suitable for heat treatment of largest steel blocks. For end-users who require even higher steel standards, we also offer our Formadur steels in Superclean condition. By using the electro-slag-remelting process we achieve the highest possible degree of purity and an extraordinarily homogeneous structure. This becomes noticeable with the excellent results in terms of polishing, texturing and durability. As a result, the quality, resistance and lifetime of the plastic mould are increased. The bottom line is that the production of high standard plastic mould steels in the end is dependent on experience and technological resources.