Stainless Steels for Plastic Mold Frames Featuring Enhanced Machinability

Steels for the production of frames for plastic molds frequently need to exhibit resistance to corrosion while at the same time requiring large amounts of machining. Machinability as a crucial property can be enhanced by the addition of sulfur, resulting in the formation of favorable sulfides, which in turn can deteriorate mechanical properties and corrosion resistance. The detrimental effect on mechanical properties is caused, among others, by the elongation of sulfides during rolling or forging. In a novel approach, a special wire treatment of the melt is performed, which results in improved spherical morphology and chemical composition of the inclusions, yet leading to even enhanced machinability (tested, among others, by means of milling). Milling tests reveal increased productivity compared to conventionally manufactured material, which means an improved lifetime of milling inserts even at the highest cutting speeds. In addition, orthogonal cutting trials are performed aiming at understanding differences in machinability. At the same time, mechanical properties, in particular toughness, are slightly improved, while corrosion resistance is not severely affected.