Those who want to operate gas turbines cost-effectively for power generation need turbines that withstand high pressure and temperatures. The components used for this purpose are exposed to extreme thermal and mechanical loads. Temperatures as high as 1500 degrees Celsius in the combustion chamber can only be mastered with extremely robust materials, mostly stainless or super alloys. With steam or condensing turbines, there are also enormous physical forces acting on the components, e.g. 1.5 times the speed of sound at the tip of a turbine blade. Here, only highly durable martensitic steels or titanium alloys are used as materials. We have the right metal cutting tools for machining these extremely demanding materials, and we use them to develop the appropriate machining processes.
1. Walter back counterbore: machining the seating face and clearance diameter for securing mechanism
With this high-tech draw bar tool from the technology brand MODCO®, back counterboring is possible even under unfavourable conditions. The automatically controlled cutting edges in Z = 2 design are actuated using coolant or compressed-air.
2. Walter Steam-tight mill: Fine-finishing the interfaces
A precision tool for fine-finishing the interfaces in steam turbine housings. Surface qualities of Ra 0.25 to 1.6 are achieved with a planarity from 0.01 to 0.05, over a length of 1000 mm. Available in 80 to 400 mm diameter with a wiper indexable insert (wiper geometry) mounted in a cartridge.
3. Walter heavy-duty cutter F2265: Roughing the interfaces
The Walter heavy-duty cutter F2265 is the ideal roughing tool when it’s time to get down to business. This mighty cutting tool has large, open chip clearances for optimum chip removal and offers excellent cutting data combined with high cutting performance.
4. Walter PrecisionMAXI B3234 precision boring tool: Finishing the burner holes
A powerful, modular precision boring tool in a bridge design with cartridges (Ø 150-640 mm). The indexable inserts have three cutting edges and are available in all required sizes. The tool with Capto™ or NCT interface can be adjusted with fine precision (0.01 mm Vernier scale) and has internal coolant supply directly to the cutting edge.
In steam turbines, the thermal and kinetic energy of the water vapour is converted into the kinetic energy of the rotating thermal shaft that is then converted into electrical energy by the generator. In modern steam turbines, the thermal shafts rotate at a minimum of 3000 revolutions per minute during operation. These impressive components are quite often 10 metres long and weigh over 100 tonnes. Machining such a stainless-steel shaft is generally considered one of the most demanding asks in production and usually takes months. Up to 20 tonnes of chips are produced. For dimension- ally accurate and cost-efficient machining of shafts of this kind, we have developed a component-specific machining process for the user. This process is implemented in the production environment with our high-precision special tools for milling, drilling and turning.
1. Walter back counterbore: Back counterboring the coupling holes
The customer-specific, customised tool solution for back machining of shaft couplings is available as back counterbore or circular interpolation technology. Also available as a manual solution for unfavourable ratios, alternatively with ScrewFit, shell bayonet interface.
2. Walter shell-type milling cutter: Machining curved fir tree grooves
In combination with Walter cutting tool materials and coatings, this monoblock tool (single profile Ø) is one of the best on the market in terms of smooth operation and performance. Its strength is the cost-efficient pre-machining of curved fir tree grooves. Further developed as L/R version for semi-machining large batches or for the first time: as a modular multi profile Ø solution.
3. Walter indexable insert form mill: Semi-finishing and finishing of fir tree profiles
The indexable insert special solutions for cost-efficient semi-machining; without the regrinding costs for solid carbide and with possible shorter machining times. The indexable insert technology has been further developed for finishing profiles down to a profile tolerance of ± 10 μm.
4. Walter Prototyp solid carbide and HSS form mills: Semi-finishing and finishing of fir tree profiles
As a solid carbide or HSS mill, this tool is particularly well-suited for smaller fir tree profiles or tighter tolerances. With this addition to complete machining, Walter has covered all customer and workpiece requirements in this field.
A turbine blade at full load covers up to 500 metres per second. This corresponds to a centripetal acceleration of 160,000 m/s2 with centrifugal forces of around 550 tonnes. The machining of complex blade profiles made of difficult- to-cut materials is a real challenge. The goal is faultless components that are in line with market requirements. We achieve this with a precisely matched range of tools for roughing and finishing. The compressor blades and vanes are also exposed to the highest of thermal and physical loads. The difficult cutting properties of the materials, such as Inconel, are an additional problem alongside the complex blade profiles. With our special machining solutions for these tasks, our users reduce the in cut times to an absolute minimum whilst achieving the best possible dimensional accuracy of the components at the same time.
1. Walter button insert cutter F2334R: Roughing the blade root, turbine blade and blade head
The F2334R copy mill with positive round indexable inserts has a reinforced design specifically optimised for the machining of turbine blades. The first choice when precision and long tool life are required.
2. Walter Octagon finishing cutter: Finishing the blade root
The Walter Octagon finishing cutter with hard nickel-plated surface is perfect for finishing the head and root rhombi of the turbine blades. 16 sharp cutting edges per indexable insert and the wear-resistant substrate ensure a long tool life and reduced tooling costs. A tool for more process reliability and maximum ease of handling.