Austria - The right material and grade for the right job can save time and money - keeping mould makers competitive. Standard parts manufacturer Meusburger in Austria gives an overview of what to consider when choosing the right material grades.
Mould manufacturers serving various end markets with their mould design, build and repair specialties are always searching for ways to improve their moulds. The appropriate selection of mould material proves to have a dramatic impact. The right material and grade for the right job can save time and money - keeping mould makers competitive.
The classification in hot-work steel and cold-work steel provides information about which temperatures can be used for different types of steel. The prerequisite is that the characteristics which they obtain through the heat treatment can also be exhibited after the treatment. Hot-work steels are suitable for operating temperatures of up to approx. 600°C and are for example suited for zinc or die-cast aluminium. Cold-work steels, on the other hand, can be used for operating temperatures of up to approx. 200°C. These are preferably applied in injection moulding.
Unalloyed structural steels, for example 1.0577, provide very good weldability due to their low carbon content and are suited for making simple dies, moulds, jigs and fixtures. If the weldability is not relevant, it is advisable to select an unalloyed tool steel (for example 1.1730). This not only offers high strength, but also a better machinability. Unalloyed tool steel is mainly used for unhardened components in mould, die, and jig construction as well as plates and frames for mould bases.
Steel for case-hardening is characterised by a high surface hardness and a tough core and is ideal for materials with fillers, like for example optical fibres or carbon fibres. Other applications are synthetic resin press moulds for the processing of thermoplastics and thermosetting plastics or guiding elements and cores. As for material structuring (polishing, graining...) very good results can be achieved through the hardened and tempered steel 1.2311, due to its low sulphur content. The alloyed, hardened and tempered tool steel 1.2312 has a strength of 1080 N/mm² and through the sulphur additive receives the best machining characteristics. Nitriding is recommended to increase the wear resistance of these steels and a prior stress-relieving heat treatment at about 580°C is advisable.
Stress relieving heat treatment reduces warping during machining
During the production of steel plates tension grows in the material from various machining processes – caused, for example, by irregular temperature. With stress-relieving heat treatment, the tension in the material is minimised without major changes to the microstructure or strength. This is a great advantage during subsequent machining. If there was still tension in the material, it would, for example, cause distortion during sawing or milling. If they are cooled more quickly, tension - and even the formation of cracks - could once more occur in the material.
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