Abstract
Microstructural non-uniformity in the wrought material of Alloy 690 is investigated in this study by analyzing the dissolution behavior of intergranular carbides, performing laboratorial forgings to explore the microstructural evolution rules and conduct industrial forgings to verify the laboratorial results. The intergranular carbides in Alloy 690 ESR ingots cannot be fully dissolved at a temperature < 1473 K (1200 °C), and undissolved carbides cause the appearance of carbide strips in the forged microstructure. Carbide strips are confirmed to be responsible for the formation of fine-grain bands in the wrought material by restricting the growth of nearby grains during annealing treatment. Industrial forgings agree well with the laboratorial tests, and it is recommended that in industrial practice the soaking temperature of large ESR ingots should be set between 1473 K and 1493 K (1200 °C and 1220 °C) for better carbide dissolution, and an evident ingot temperature drop prior to deformation should be avoided.
Published Version
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