Microstructure Evolution and Surface Cracking Behavior of Superheavy Forgings during Hot Forging. (30th January 2018)

• Record Type: Journal Article
• Authors: Wang, Zhenhua; Xue, Hongpeng; Zhao, Deli
• Other Names: Ruffino Francesco Academic Editor.
• Is Part Of: Advances in materials science and engineering. Volume 2018(2018)
• Publication Date: 2018-01-30
• Subjects: Materials science -- Periodicals; Materials science; Periodicals; 620.11
• DOI: 10.1155/2018/4780638
• Languages: English
• ISSNs: 1687-8434

Abstract

Abstract : In recent years, superheavy forgings that are manufactured from 600 t grade ingots have been applied in the latest generation of nuclear power plants to provide good safety. However, component production is pushing the limits of the current free-forging industry. Large initial grain sizes and a low strain rate are the main factors that contribute to the deformation of superheavy forgings during forging. In this study, 18Mn18Cr0.6N steel with a coarse grain structure was selected as a model material. Hot compression and hot tension tests were conducted at a strain rate of 10 −4 ·s −1 . The essential nucleation mechanism of the dynamic recrystallization involved low-angle grain boundary formation and subgrain rotation, which was independent of the original high-angle grain boundary bulging and the presence of twins. Twins were formed during the growth of dynamic recrystallization grains. The grain refinement was not obvious at 1150°C. A lowering of the deformation temperature to 1050°C resulted in a fine grain structure; however, the stress increased significantly. Crack-propagation paths included high-angle grain boundaries, twin boundaries, and the insides of grains, in that order. For superheavy forging, the ingot should have a larger height and a smaller diameter.