Weldability Evaluation of Martensitic Heat Resisting Chromium Steels with Tungsten Additions and Properties of Welded Joints

Short characteristics of the out-of-date Polish power generation system are given, which shows that in the near future there will be a shortage of electrical energy and the necessity to build supercritical power units. A lignite-fired boiler will be build at the RAFAKO Boiler Plant. Supercritical operating parameters require new creep resisting steels to be applied for the boiler and pipe systems. Therefore at the Institute of Welding weldability examinations have been performed on selected Cr-W heat resisting steels. Welding thermal cycles have been simulated on steels: HCM2S (T23/P23), T92/P92, E911 and HCM12A. The influence of t_8/5 cooling times on Charpy V notch toughness, HV10 hardness and microstructure of simulated HAZ's is presented in the form of graphs and prints of microstructures. By means of simulation technique the susceptibility to reheat cracking of those steels has been evaluated. At REMAK- Opole (Enterprise for the Modernisation of Power Installations) and RAFAKO tube and pipe test joints were welded, to select proper fabrication conditions. Mechanical properties of the welded test joints, KV notch toughness of weld metals and HAZ’s and microstructures were examined and are presented.