20th International Forgemasters Meeting - IFM 2017

The weight of ingots from Ni-Base alloys has steadily increased over the last years. One of the drivers was the development of advanced ultra supercritical fossil power plants requiring steam temperatures well above 630°C. Ni-Base alloys proved to have promising properties for steam temperatures of 700 °C and above. Whereas smaller parts are needed for the boiler side, some turbine designs requires forgings with weights at the limit of experience. Regarding cost and manufacturing challenges Ni-Base material is not used for the complete turbine shaft, but only for the hottest part. Therefore, the design for turbine shaft is a welded construction of a Ni-Base part combined with steel shaft parts. With a diameter of about 1100 mm, the weight of the Ni-Base forging is in the range of 10 t to 15 t. After developments in the past focused on Alloy 617 and modification TOS1-X as well as Alloy 625, Saarschmiede has manufactured a full scale forging from the precipitation hardening Alloy 263 using a triple melt ingot (VIM / ESR / VAR) of ~23 t, which is the largest ever produced worldwide. The paper reports on ingot making, forging and properties of the Alloy 263 part as well as on TOS1X manufacture. For mechanical engineering Saarschmiede has remelted ESR ingots in Alloy 600 from EAF electrodes. Using a crucible of 1300 mm diameter, weights of up to 70 t have been achieved, which is the biggest ingot ever remelted worldwide from that alloy. Beneath cost saving effects by using one ingot for several forgings, this ingot is a milestone for even larger ingots. The paper reports on remelting and forging challenges as well as on achieved basic properties.