The roles of Ce and Mn on solidification behaviors and mechanical properties of 7Mo super austenitic stainless steel

He, Jinshan; Xu, Shiguang; Zhang, Fucheng; Wang, Xitao

doi:10.1016/j.jmrt.2022.11.148

Cited by 13 publications

(8 citation statements)

References 32 publications

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“…Rare earth inclusion is generally not the cause of crack growth, but sulfide is the direct cause of fatigue crack growth. This is because when the crack extends to the inclusion, the rare earth inclusion slows down the stress concentration, thereby preventing the crack growth [28,35]. Rare-earth inclusions have better fusion with the steel matrix than MnS inclusions and MnS-Ti-V complex inclusions.…”

Section: Tensile Propertiesmentioning

confidence: 99%

Study on Influence of Rare Earth Ce on Micro and Macro Properties of U75V Steel

Feng,

Ren,

Yang

2024

Materials

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Non-metallic inclusions in steel have great influence on the continuity of the steel matrix and the mechanical properties of steel. The precipitation sequence of Ce inclusions in molten steel is predicted by thermodynamic calculations. The results show that Ce content will affect the precipitation sequence of rare earth inclusions in molten steel, and the formation of CeO2, Ce2O3 and CeAlO3 will be inhibited with the increase in Ce content. Our laboratory smelted the test steel without rare earth additive and the test steel with rare earth Ce additive (0.0008%, 0.0013%, 0.0032%, 0.0042%). It was found that the MnS inclusions and inclusions containing Al, Ca, Mg and Si oxides or sulfides in the steel after rare earth addition were modified into complex inclusions containing CeAlO3 and Ce2O2S. The size of inclusion in steel was reduced and the aspect ratio of inclusion was improved. The addition of Ce also improved the grain size of U75V steel and significantly refined the pearlite lamellar spacing. After mechanical property testing of the test steel, it was found that when Ce is increased within 0.0042%, the tensile and impact properties of U75V steel are also improved.

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Section: Tensile Propertiesmentioning

confidence: 99%

Study on Influence of Rare Earth Ce on Micro and Macro Properties of U75V Steel

Feng,

Ren,

Yang

2024

Materials

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“…An excessive σ phase will cause cracking during processing [4,5] and reduce corrosion resistance [6]. In order to reduce the influence of the σ phase on hot processing and application, the σ phase can be reduced by regulating the alloy composition [3,[7][8][9] or by adopting homogenization treatment [10]. However, the dissolution temperature of the σ phase increases with the increasing alloying contents in steels, to pose a challenge in the homogenization process [11].…”

Section: Introductionmentioning

confidence: 99%

“…For example, alloying modifier can increase crystal defects to accelerate the atomic diffusion, while the addition of refractory elements with a slow diffusion rate will greatly increase the homogenization time [17]. Typical refiners in steels are rare earth elements, which have been confirmed as helpful elements in reducing the second phase [7,[20][21][22]. The austenite-forming element Mn has also been studied in high-alloyed steels for reducing the element segregation tendency [7,23].…”

Section: Introductionmentioning

confidence: 99%

“…Typical refiners in steels are rare earth elements, which have been confirmed as helpful elements in reducing the second phase [7,[20][21][22]. The austenite-forming element Mn has also been studied in high-alloyed steels for reducing the element segregation tendency [7,23]. However, the Mn content in SASSs is controlled below 3 wt.% mostly, and the application of rare earth elements in SASSs is still in the initial stage.…”

Section: Introductionmentioning

confidence: 99%

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The Optimized Homogenization Process of Cast 7Mo Super Austenitic Stainless Steel

Zhang

et al. 2023

Materials

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Super austenitic stainless steels are expected to replace expensive alloys in harsh environments due to their superior corrosion resistance and mechanical properties. However, the ultra-high alloy contents drive serious segregation in cast steels, where the σ phase is difficult to eliminate. In this study, the microstructural evolution of 7Mo super austenitic stainless steels under different homogenization methods was investigated. The results showed that after isothermal treatment for 30 h at 1250 °C, the σ phase in steels dissolved, while the remelting morphologies appeared at the phase boundaries. Therefore, the stepped solution heat treatment was further conducted to optimize the homogenized microstructure. The samples were heated up to 1220 °C, 1235 °C and 1250 °C with a slow heating rate, and held at these temperatures for 2 h, respectively. The elemental segregation was greatly reduced without incipient remelting and the σ phase was eventually reduced to less than 0.6%. A prolonged incubation below the dissolution temperature will lead to a spontaneous compositional adjustment of the eutectic σ phase, resulting in uphill diffusion of Cr and Mn, and reducing the homogenization efficiency of ISHT, which is avoided by SSHT. The hardness reduced from 228~236 Hv to 220~232 Hv by adopting the cooling process of “furnace cooling + water quench”. In addition, the study noticed that increasing the Ce content or decreasing the Mn content can both refine the homogenized grain size and accelerate diffusion processes. This study provides a theoretical and experimental basis for the process and composition optimization of super austenitic stainless steels.

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“…It has been reported that a high content of Mo enhances the formation of Mo-rich intermetallics, such as sigma and chi phases, degrading mechanical properties and encouraging hot cracking [13,14]. Therefore, homogenization heat treatment of the cast 316L billet is necessary before hot forging the cast billet [13,[15][16][17][18]. The distribution and morphology of δ-ferrite and sigma phases in the austenite matrix of the 316L cast billet are strongly related to following hot/cold forging of the cast billet.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Homogenization Heat Treatment on 316 Stainless Steel Cast Billet

Chu,

Shiue,

Cheng

2023

Preprint

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The investigation aims to analyze the effect of homogenization heat treatment on the quantity, distribution, morphology, and chemical composition of δ ferrite and sigma phase in the 316L austenitic stainless steel cast billet. Microstructures of the cast billet at different locations, center, 0.5 R, R, and the subsequent 2/6-hour homogenization heat treatment at 1240 oC were examined. The microstructure at the radius R was much more uniform and expected a better performance in the following hot/cold forging processes due to the highest cooling rate compared with those at 0.5R and center. The δ ferrite often accompanies the generation of the sigma phase, and the transformation of δ ferrite into the sigma/(austenite) and retained δ ferrite is strongly related to the cooling rate after homogenization heat treatment. The sigma phase is hard and detrimental to the subsequent hot/cold forgings. It must be removed from the homogenization heat treatment before forging. Fast air cooling from 850 oC to room temperature after homogenization heat treatment cannot prohibit the sigma phase formation. Rapid cooling between 850 and 1240 oC after homogenization treatment is required to avoid the sigma phase formation in the 316L stainless steel cast billet.

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The roles of Ce and Mn on solidification behaviors and mechanical properties of 7Mo super austenitic stainless steel

Cited by 13 publications

References 32 publications

Study on Influence of Rare Earth Ce on Micro and Macro Properties of U75V Steel

Study on Influence of Rare Earth Ce on Micro and Macro Properties of U75V Steel

The Optimized Homogenization Process of Cast 7Mo Super Austenitic Stainless Steel

The Effect of Homogenization Heat Treatment on 316 Stainless Steel Cast Billet

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