High Speed Turning in Steel from Sumitomo

The need for improved wear resistance, surface finish and size control when performing challenging high speed continuous turning cycles on all types of steel has led Sumitomo to develop its latest ACE Coat AC810P range of high performance grades. The new s are capable of providing up to 50 per cent increases in feed rates while maintaining 1.5 times the in-cut life at speeds between 200 and 500 m/min and can be used over a wide range of applications from high speed machining to interrupted cutting cycles.

AC810P s have an ultra-hard CVD applied Super FF titanium carbonitride (TiCN) coating of thickened and toughened Aluminia giving a 30 per cent increase in hardness. The s also incorporate Sumitomo’s latest NME chip breaker development in addition to well-proven NSE, NSEW and NGE styles used with the company’s other turnings.

Available through Sumitomo Electric Hardmetal of Princes Risborough the Super FF coating uses ultra-fine crystals to provide an homogenous structure with extreme levels of density that enables an ultra-smooth surface finish to be created on the with the added advantage of high orders of coating strength and adhesion. As a result, the coating with its 50 per cent reduction in surface roughness, provides improved resistance to peeling, cracking, chipping and wear when applied at cutting speeds over 300 m/min on carbon, alloyed and stainless steels as well as cast iron.

According to Sumitomo, from data collected from customers involved with high speed turning, it was concluded that more than half of damaged or failed s were due to crater wear. Crater wear is a consequence of chip flow eroding the rake face of the which reduces the toughness of the cutting edge, as well as lowering the hardness of the carbide substrate and ceramic coating.

Explains Sumitomo’s development team, control of crater wear is not only influenced by the grade of the turning but also by the geometry of the chip breaker. Sumitomo now offer four ‘E’-type chip breaker styles on AC810P s, the latest NME for roughing which creates a very smooth chip flow, NSE for finishing, NSEW for high efficiency finishing and NGE for more general purpose turning.

NME has the advantage created by a dimpled surface which helps control thermal elevation, a 4 deg primary ridge with a wide yet shallow breaker geometry that improves control of the chip and its ejection from the cutting zone. NSE has a wave shaped cutting edge with a 5 deg primary ridge on the top rake to help control chip flow giving stable chip management in a wide range of processes and a side ridge to reduce any stress concentration and rake face damage.

The new NSEW profile improves a ‘wiper’ effect and enables high feed conditions without any compromise to surface finish. Meanwhile, NGE has a 3 deg primary ridge and smooth curved rake face which reduces stress when roughing at high speed and using a heavier depth of cut.

ACE Coat AC810P s with the latest ‘E’-type chipbreakers can be applied with between 1 mm and 6 mm depth of cut and run at feed rates between 0.1 mm and 0.7 mm/rev. Inserts are available in 55 and 80 deg diamond, square and triangular styles as well as 80 deg Trigon. All s are coloured gold for easy identification of cutting edge wear.