Cutting tool and tooling systems specialist Sandvik Coromant (www.sandvik.coromant.com) has launched two new insert grades for steel milling — GC4330 and GC4340.

These feature a new substrate, the company’s Inveio coating and an improved “post-treatment technology”, allowing the new grades to offer substantially increased tool life and process security when compared with the previous-generation grades GC4230 and GC4240, which have now been superseded.

Sandvik says manufacturers face many challenges when milling ISO P workpieces, including the fact that some hard and abrasive steels can generate wear along the flank face of the insert, especially at higher speeds and with a longer time in cut.

In addition, machining in unstable conditions due to compromised clamping or long overhang increases the risk of insert chipping, while thermal fluctuation during machining — especially under wet conditions — can cause crack formation and subsequent sudden breakages.

Magnus Engdahl, product application manager at Sandvik Coromant, says the new grades overcome these issues in a number of ways. “For instance, the Inveio coating increases wear-resistance and tool life dramatically, without jeopardising security.

"With its uni-directional crystal orientation, the coating has a high resistance to thermal cracks, which in turn promotes long and reliable tool life — a factor further supported by a new post-treatment process that strengthens the insert by modifying its mechanical properties.

"Furthermore, a newly developed substrate provides well-controlled grain size distribution, which provides more-reliable and predictable tool behaviour, while a more-narrow edge-rounding tolerance ensures consistent tool life.”

GC4330 is a medium-hard grade and is the first choice for roughing to semi-finish face milling, with the tough GC4340 grade preferred for rough shoulder milling and groove milling; and while both wet and dry machining are accommodated, dry machining is recommended.

Both GC4330 and GC4340 are available in the following product families: CoroMill 390 and CoroMill 490 for shoulder milling; CoroMill 345 and CoroMill 745 for face milling; CoroMill 210 for high-feed milling; CoroMill 200 for profile milling; and CoroMill 331 for grooving and parting off.

Moreover, Sandvik says that while the grades are optimised for steel, they can also be used for mixed production involving ISO K (cast iron) and ISO M (stainless steel) workpieces.