Solidification microstructure evolution and inclusion analysis of Ce-containing 7Mo super-austenitic stainless steel

WANG Qi; DU Yue; WANG Lijun; ZHANG Wei; ZHENG Yaxu; LU Suling; ZHU Liguang

doi:10.7513/j.issn.1004-7638.2025.01.018

Volume 46 Issue 1

Feb. 2025

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WANG Qi, DU Yue, WANG Lijun, ZHANG Wei, ZHENG Yaxu, LU Suling, ZHU Liguang. Solidification microstructure evolution and inclusion analysis of Ce-containing 7Mo super-austenitic stainless steel[J]. IRON STEEL VANADIUM TITANIUM, 2025, 46(1): 124-132. doi: 10.7513/j.issn.1004-7638.2025.01.018

Citation:

WANG Qi, DU Yue, WANG Lijun, ZHANG Wei, ZHENG Yaxu, LU Suling, ZHU Liguang. Solidification microstructure evolution and inclusion analysis of Ce-containing 7Mo super-austenitic stainless steel[J]. IRON STEEL VANADIUM TITANIUM, 2025, 46(1): 124-132. doi: 10.7513/j.issn.1004-7638.2025.01.018

Citation:

WANG Qi, DU Yue, WANG Lijun, ZHANG Wei, ZHENG Yaxu, LU Suling, ZHU Liguang. Solidification microstructure evolution and inclusion analysis of Ce-containing 7Mo super-austenitic stainless steel[J]. IRON STEEL VANADIUM TITANIUM, 2025, 46(1): 124-132. doi: 10.7513/j.issn.1004-7638.2025.01.018

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Solidification microstructure evolution and inclusion analysis of Ce-containing 7Mo super-austenitic stainless steel

doi: 10.7513/j.issn.1004-7638.2025.01.018

1.
College of Materials Science and Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, Hebei, China
2.
University of Science and Technology Beijing, Beijing 100083, China
3.
Baowu Group, Taiyuan 030003, Shanxi, China

Received Date: 2024-05-17
Publish Date: 2025-02-27

Abstract

Abstract

Rare earth Ce treatment is a hot topic in the modification of solidification microstructure for super austenitic stainless steel. In this study, the solidification phase structure, evolution of inclusions, and element segregation behavior of a 500 kg scale Ce-treated 7Mo super austenitic stainless steel were systematically analyzed, for the purpose of providing theoretical basis for Ce treatment of 7Mo super austenitic stainless steel. The results show that the non-equilibrium solidification path of 7Mo super austenitic stainless steel is L→L+γ→L+γ+δ→L+γ+δ+σ→L+γ+σ→L+γ+σ+Cr₂N. During cooling and solidification process, an intermediate phase δ phase exists, and the δ phase decomposes into σ phase and γ₂ phase at the end of solidification. The main second phase precipitated in the steel is the σ phase rich in Cr and Mo, resulting in a cast solidification structure composed of austenite and σ phase. After Ce treatment in super austenitic stainless steel, the inclusions in the ingot are mainly composite inclusions composed of AlCeO₃ and Al₁₁O₁₈Ce, with a low mismatch AlCeO₃ structure, which can serve as heterogeneous nucleation cores. During cooling and solidification process, the deoxidation ability of Al is enhanced, and the equilibrium of deoxidation reaction is broken, resulting in the generation of inclusions with Al₁₁O₁₈Ce encapsulating AlCeO₃ morphology. The microstructure of the ingot core is coarse, with severe microsegregation between dendrites. The size of micro grains is the key factor affecting the microsegregation between dendrites, and reducing the size of micro solidification structure grains can effectively improve the degree of element segregation inside the grains and then reduce Mo and Cr content in the σ phase between dendrites.
- 7Mo super austenitic stainless steel,
- solidification segregation,
- thermodynamic calculation,
- inclusion

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References(21)

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