The growing demand for clean and more efficient electric power creates a need for new gas and steam turbines with components manufactured in more high-alloyed and difficult-to-machine materials. Making a steam turbine requires hundreds of different tools, and one of the most common and challenging operations is grooving. Here are some of the tools used.
Months of difficult work
Compounding the dual challenges of time and precision in the manufacturing process is the sheer size of giant steam turbine components such as the casing, discs and shaft. For the shaft alone, it can take months of difficult work to machine away 22 tons of material for a 77-ton, 33-foot-long, 6.6-foot-diameter final product.
Grooving represents a large part of the machining process in steam turbine manufacturing. Streamlining this operation can potentially save several weeks in the overall machining operation.
Taking the heat. Ceramics are becoming more and more popular as a tool material when machining components in heat-resistant alloys, for example gas turbine discs. Grade CC6060 is the first choice and can be used at five to six times higher cutting data compared with the traditionally used cemented carbide tools.
Vibration free. When performing the final finishing operation on a steam turbine shaft, casing or discs it is paramount that no vibrations occur, otherwise months of work can be wasted. That is why Sandvik Coromant developed the patented dampening mechanism for vibration-sensitive grooving operations.
Reliable. The new chip breaker geometry — GM, available for R-size inserts with 0.59-inch widths, gives perfect chip control. It enables machining of deep wide slots in a single in-feed without time-consuming stops and back-outs, which improves productivity and process security when grooving on the huge (33-foot-long) turbine shaft.
CoroTurn SL and HP
Customized solution. Many types of grooves in a turbine shaft normally require special grooving tools. Thanks to the modular tooling system, CoroTurn SL, you can build a tool made of standard cutting units. The SL cutting units can be ordered with HP (high-pressure) coolant supply technology. Build your own customized system at www.tool-builder.com.
To learn more about grooving solutions from Sandvik Coromant, CLICK HERE.
Originally published in Metalworking World 2.2011, a business magazine published by Sandvik Coromant.
Text: Geoff Mortimore
Illustration: Kjell Thorsson