Milling Grades Resist Thermal Cracking

Sandvik Coromant has launched two insert grades for steel milling: GC4330 and GC4340. Superseding the previous generation of grades with a new substrate, Inveio coating and improved post-treatment technology, these two grades promote longer tool life and process security. 

The optimized Inveio coating increases wear resistance and tool life dramatically without jeopardizing security, says the company. 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.

The substrate provides well-controlled grain size distribution, which results in more reliable and predictable tool behavior. Additionally, higher narrow edge-rounding tolerance promotes consistent tool life. The company points out that increased tool life delivers reduced cost per component, while improved process security brings predictable performance and less downtime as well as higher component quality.

The medium-hard GC4330 grade is designed for roughing to semi-finish face milling, while the tough GC4340 grade is preferred for rough shoulder milling and groove milling. Wet and dry machining are supported, although dry machining is recommended.

Both grades 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. Although the grades are optimized for steel, they are also suitable for mixed production involving ISO K (cast iron) and ISO M (stainless steel) workpieces.