Formation Mechanism of Inclusion Defects in Large Forged Pieces

• Published in: Journal of iron and steel research, international international, 2016-06, Vol.23 (6), p.531-538
• Main Authors: QI, Rong-sheng, JIN, Miao, LIU, Xin-gang, GUO, Bao-feng
• Format: Article
• Language: English
• Subjects: anvil type; Applied and Technical Physics; Engineering; finite element method; inclusion defect; large forging; Machines; Manufacturing; Materials Engineering; Materials Science; Metallic Materials; Metallurgy and Metal Working; MnS; Physical Chemistry; Processes; 塑性变形; 大型锻件; 夹杂缺陷; 对比实验; 应力-应变曲线; 形成机理; 最终产品; 非金属夹杂物
• ISSN: 1006-706X; 2210-3988
• DOI: 10.1016/S1006-706X(16)30084-X

Nonmetallic inclusions mixed into large forged metal objects destroy the continuity in the metal and affect the quality of the forged product. Research on how inclusions affect the plastic deformation of a matrix shows the significance of the formation mechanism of inclusion defects. For upset forging, the nonlinear finite element model was shown to be appropriate for the ingot hot-forging process by comparing the results with experiments involving plastic and hard inclusions inserted into the forged piece. The high-temperature stress-strain curves of MnS plastic inclusions were obtained experimentally. The results show how, during upsetting, the morphology of MnS plastic inclusions varies from spherical to ellipsoidal, until finally becoming flat in shape. The larger the inclusion is, the larger the degree of deformation of the inclusion is, and large inclusions enhance the risk of the final product failing to pass inspection for inclusion flaws. Strain significantly concentrates in the matrix near a hard inclusion. When the hard inclusion reaches a certain size, conical fractures form on both sides of the inclusion. To pass inclusion-flaw inspection and close hole defects to the extent possible, the flat-anvil upsetting is recommended. Finally, the inclusion-deformation state obtained by finite element simulation is verified experimentally.