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Properties of Cr-Mo and Cr-Mo-V steel castings for elevated temperature service

Relations between chemical composition, microstructure and mechanical properties of low- alloy Cr-Mo steel, of the WC 9, and high-alloy Cr-Mo-V steel, of the C12A quality (according to ASTM SA-217/SA-217M) for the production of valve housings for elevated temperatures service has been analyzed in this paper. Applied heat treatment process, that consisted of normalization and tempering on high temperatures (above 700°C) resulted the formation of ferrite regions and regions of proeutectiod ferrite with fine dispersed carbides inside ferrite grains and on the boundaries of original austenite grains in the case of low-alloy WC9 steel. Microstructure of high-alloy C12A steel consisted after the heat treatment process (normalization and tempering at high temperatures) of ferrite and bainite with finely dispersed carbides. This microstructures resulted in achieving values of mechanical properties and of retention of the attained mechanical properties at elevated temperatures, i.e. high creepresistance. The obtained results of examinations revealed that performed production process with the heat treatment of steel that followed gave satisfactory microstructures and mechanical properties as demanded by standards.

low-alloyed Cr-Mo cast steel ; high-alloyed Cr-Mo-V cast steel ; normalization ; high-temperature tempering ; elevated temperature service

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