Simulated coarse-grained heat-affected-zone microstructures in DIN 22NiMoCr37 steel

Summary s of DIN 22NiMoCr37 nuclear reactor pressure vessel steel have been heat treated for 1 h in the temperature range 1373–1473 K to obtain different prior austenite grain sizes. Excessive coarsening of prior austenite grains has been observed. This is attributed to the absence in this sample of steel of ‘microalloying’ elements such as Ti, Nb or V, which can combine with C and/or N and precipitate as carbides, nitrides and/or carbonitrides. These particles are able to pin grain boundaries at high temperatures, and hence prevent excessive grain growth.