Livarski vestnik 57 / 2010 Nr. 1
A. Bührig-Polaczek; M. Mathes; E. Schaberger-Zimmermann
MODERN ANALYSIS METHODS FOR PROCESS CONTROL AND DEVELOPMENT OF CAST COMPONENTS
R. Hanus
A NEW CAST STEEL GRADE OF ADVENCED 9-10% CR STEEL IS BORN. REPORT FROM IDEA - VIA RESEARCH - TO PILOT COMPONENTS - AND TO THE COMMERCIAL PRODUCTION OF HEAVY STEEL CASTINGS
J. Stachańczyk, S. Pysz, P. Wieliczko, A. Ościłowski, L. Ościłowski
CAST STEEL FILTRATION - THE PARAMETERS AND PROCESS EFFECTIVENESS
A. Bührig-Polaczek; M. Mathes; E. Schaberger-Zimmermann
Modern Analysis Methods for Process Control and Development of Cast Components
Abstract
Microscopy, X-ray analysis, tensile tests, and the measurement of dimensional accuracy are standard methods for the quality control of casting processes and cast products. The further development of these methods and the use of new methods in the daily work in a foundry and in R&D projects give new opportunities for an improved process and product optimisation. In addition a new quality level can be achieved by combining these methods with simulation programmes of casting processes and microstructure.
A New Cast Steel Grade of Advanced 9-10% Cr Steel Is Born. Report from the idea - via research - to pilot components - and to the commercial production of heavy steel castings
Abstract
Steel castings of creep resistant steels play a key role in fossil fuel fired power plants for highly loaded components in the high and intermediate pressure section of the turbines. Inner and outer casings, valve casings, inlet connections and elbows are examples of such critical components. Figure 1 shows the section through a steam turbine, where all cast components can be found. Herein HP means High Pressure Part, IP Intermediate Pressure Part and LP Low Pressure Part.
The most important characteristic in a power plant is the efficiency, which mainly drives the CO2-emission. In Figure 2 the CO2-emission is plotted over the efficiency and one can realize the significant reduction of CO2-emission through increase of efficiency.
As a consequence of steadily improving power plant efficiencies and ever stricter emission standards, steam parameters become more critical and the creep resistance of the materials must be constantly improved.
The most important characteristic in a power plant is the efficiency, which mainly drives the CO2-emission. In Figure 2 the CO2-emission is plotted over the efficiency and one can realize the significant reduction of CO2-emission through increase of efficiency.
As a consequence of steadily improving power plant efficiencies and ever stricter emission standards, steam parameters become more critical and the creep resistance of the materials must be constantly improved.
Figure 1: Section through a Steam Turbine
Needless to say, the cast steel grades must also be adapted to the more demanding specifications for material properties. A steel foundry alone cannot carry on the necessary material development on the appropriate scale; all suppliers of power plant components therefore cooperate in defining optimum chemical compositions, in performing test melts, creep tests and microstructure investigations, and in testing pilot components, etc.
This paper illustrates the role of a steel foundry within the COST program, where the new materials are being developed; in addition, it describes how these new 9-10%Cr cast steel grades are transferred from research into the commercial production of heavy cast components. The problems incurred are pointed out, cycles of process development are outlined and comparisons are made with the usual low-alloy steels.
After selecting the most promising alloy from the laboratory melts, welding tests were performed - mostly with matching electrodes also produced within COST. Base material and welds were investigated in respect of microstructure, creep resistance, mechanical properties and weldability. Heat treatment investigations were also necessary for optimization of the mechanical properties.
This paper illustrates the role of a steel foundry within the COST program, where the new materials are being developed; in addition, it describes how these new 9-10%Cr cast steel grades are transferred from research into the commercial production of heavy cast components. The problems incurred are pointed out, cycles of process development are outlined and comparisons are made with the usual low-alloy steels.
After selecting the most promising alloy from the laboratory melts, welding tests were performed - mostly with matching electrodes also produced within COST. Base material and welds were investigated in respect of microstructure, creep resistance, mechanical properties and weldability. Heat treatment investigations were also necessary for optimization of the mechanical properties.
Figure 2: Reduction of CO2 emission through advanced technologies [2]
Based on the results of these studies, pilot components and plates for testing welding processes were cast in order to verify the castability and weldability of larger parts and to make any necessary adjustments to chemical composition, heat treatment or welding parameters.
Parallel to the ongoing creep tests within COST, the steel grades were introduced into the commercial production of large components. This involved finding solutions to process related problems such as deoxidation, solidification behaviour, heat treatment with long holding times, welding on the casting, stresses, etc.
In the meantime a total of more than 500 parts with a maximum individual weight of 60 tonnes have been successfully manufactured. The ongoing developments within COST will, of course, present further challenges - also for the foundrymen.
Parallel to the ongoing creep tests within COST, the steel grades were introduced into the commercial production of large components. This involved finding solutions to process related problems such as deoxidation, solidification behaviour, heat treatment with long holding times, welding on the casting, stresses, etc.
In the meantime a total of more than 500 parts with a maximum individual weight of 60 tonnes have been successfully manufactured. The ongoing developments within COST will, of course, present further challenges - also for the foundrymen.
J. Stachańczyk, S. Pysz, P. Wieliczko, A. Ościłowski, L. Ościłowski
Cast Steel Filtration – The Parameters and Process Effectiveness
Abstract
The paper describes the selected range of research and technological work regarding filtration of cast steel and special alloys. The methods of filter control were presented with special emphasis put on the technological tests performed with the use of cast metallic materials. On an example of the selected casting of a bracket, computer simulation was made for the process of mould cavity filling through a gating system in which a foamed ceramic filter has been placed. To conclude the conducted tests and research, pilot series of the steel castings were made and examined to evaluate the effectiveness of the filtration process.
In summing up of the paper, further trends in the development of filtration techniques applied to cast steel and special alloys were defined, using the filters manufactured in Poland.
In summing up of the paper, further trends in the development of filtration techniques applied to cast steel and special alloys were defined, using the filters manufactured in Poland.