Speed, safety and long tool life – these are the three main advantages of the Tiger·tec Silver® high-performance cutting material for cast iron machining, which is now available in two new geometries: A regular flat top geometry with a stepped plateau, as well as a particularly robust variant for maximum process reliability, even for extreme interrupted cuts. In addition, Tiger·tec Silver® has been available for cast iron with the MK5 universal geometry since June.
A key feature of the new ISO K geometries is their plateau step between the location face and the cutting edge. This step enables the location face to be ground after coating. This is not possible to grind the location faces of standard CNMA, DNMA,… inserts without a chipbreaker groove. While the uneven location face on standard inserts can lead to micro-vibrations and chipping at the cutting edge, the evenness of the face on the new ISO K geometry from Walter ensures that the indexable insert is seated with the utmost stability. As a result, cutting-edge wear is reduced, particularly in the event of high dynamic loads.
The MK5, RK5 and RK7 geometries – universal, classic and robust – were specifically designed for cast iron machining. The ISO K MK5 geometry for medium machining is universally suitable for all cast iron workpieces. It has an open chip breaker groove for a soft cutting action, and should be used, above all, for ductile cast iron (GJS), unstable components or internal machining with low cutting pressure. The RK5 and RK7 geometries are new for roughing operations. RK5 is a classic flat top insert without chipgroove for cast iron workpieces. A stepped plateau guarantees more process reliability for cast iron machining. A ground contact surface on a CNMA, DNMA,… indexable insert ensures long tool lives and maximum safety, in the event of dynamic loads from interrupted cuts, for example. RK5 is the first choice for grey cast iron. RK7 is an extremely robust insert for very heavy interrupted cuts, tolerance variations, very uneven material removal and hard cast skin. The geometry is designed similarly to the RK5 geometry, but it also has a protective chamfer on the cutting edge. It is also suitable for the hard/soft machining of hardened steels with hardnesses from 40-61 HRC, for which CBN inserts are not suitable in most cases.
The Tiger·tec Silver® cutting tool material offers Walter customers three main advantages: Speed, reliability and longer tool life. The increased cutting speed is a result of the Tiger·tec Silver® CVD coating using aluminium oxide with an optimised microstructure. Thanks to the optimised alignment of the structure, it takes longer for crater-wear recesses to form, which detrimentally alter the geometry of the cutting edge. Machining is faster and more flexible as a result. Increased process reliability and toughness – the second main advantage – are achieved thanks to mechanical post-treatment. To do this, compressive stresses are introduced into the coating, which prevent fractures to the cutting edge. As a result, the cutting tool material can be introduced into mass production without any problems, and without leading to insert breakages or problems. The third important feature of the Tiger·tec Silver® coating relates to the longer tool life and resulting performance, particularly when machining cast iron workpieces. A 75 percent increase in tool life is attainable– in individual cases, even higher values can be achieved.
The Tiger·tec Silver® WKK10S and WKK20S cutting materials are used on grey cast iron, ductile cast iron and vermicular cast iron. WKK10S is the harder cutting tool material and stands out thanks to its maximum wear resistance and high cutting speed. It is primarily used for grey cast iron and is suitable for continuous cuts through to light interrupted cuts. WKK10S is particularly recommended for use in dry machining. In contrast, WKK20S is suitable for wet and dry machining. As a universal cutting material, WKK20S is suitable for around 50 percent of all tasks, and offers high process reliability particularly for workpieces with interrupted cuts, cast skin or cross holes.
Ductile cast iron is the primary application for this cutting material. Field tests were carried out, among others, on a brake disc (GJL250 material) at the premises of a supplier to the automotive industry and on a crankshaft (GJS600 material) used in the automotive industry.
The result was that the tool life increased by 50 to 100 percent, the insert worked for both internal and external machining and stood out thanks to increased process reliability, particularly when web machining the crankshaft.Source Walter Tools