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Jian‑bo Xie,Bei‑bei Liu,Xiang‑yu Wu,Jian‑xun Fu 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.5
This work aims to comprehensively summarize the types and distribution of the isolated Bi particles and MnS inclusions inthe Bi-bearing steels, to study the precipitated behavior of sulfide, and to study the effect of Bi particles on grain sizes andthe volume thermal expansion coefficients of the steels. Results show that the average percentage of the isolated Bi particles,semi-encapsulation, complete encapsulation, back-bridge, tiny encapsulation, cavity bridge Bi–MnS inclusions in the Bibearingsteels was 16.89%, 20.49%, 3.44%, 16.89%, 31.63%, 10.66%, respectively. The average equivalent diameters of thegrains in the 0 ppm, 130 ppm, 240 ppm, 760 ppm, 1200 ppm and 2300 ppm Bi content steels were 20.88, 20.17, 19.54, 18.13,13.98 and 13.25 μm, respectively. The precipitated equilibrium mass concentration product of the MnS (w[Mn]·w[S]) wascalculated to be 1.07, and the solid fraction fS value was 0.61. At 950 °C, the volume thermal expansion coefficient change(ΔVE) in 760 ppm Bi content steel was minimum 4 × 10–10%, while at 461.6 °C the ΔVE was maximum, 0.09%, which meansthat Bi affected the volume thermal expansion of the steel strongest in this temperature range.
Enhancement of Impurity, Machinability and Mechanical Properties in Te-Treated 0Cr18Ni9 Steel
Jian‑bo Xie,Tian Fan,Han Sun,Zhi‑qi Zeng,Jian‑xun Fu 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.6
To enhance the machinability and mechanical properties of 0Cr18Ni9 steel, free-machining element Te was introduced inthis work. By adding various quantities of Te to steel, several machining and tensile tests were carried out. Results show thatwith Te addition of 530 ppm, the number of inclusion sizes below 1 μm disappeared. With raising Te from 360 to 530 ppm,more MnTe–MnS inclusions of 10–40 μm were in spherical shape; above 50 μm2, the ratio of inclusion area at 530 ppmwas greatest among all, and the large-sized inclusions occupied a larger share. Te addition contributed to the surfaces ofmachining steels more smooth. The ultimate tensile strength of steel increased from 399 to 435 MPa. Te resulted in growthof sulfides and improved the machinability of steel.
Austenite Grain Growth Behavior of 30BF Steel Before Rough Rolling
Yong‑feng Chen,Jian‑bo Xie,Yan‑xin Wu,Jian‑xun Fu 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.4
To investigate the eff ect of heat treatment on the grain size of austenite in 30BF steel, the comparisons of the morphologiesand sizes of austenite grains between heating samples were made with a high-temperature electric resistance furnace, andthe austenite growth models were built with method of mathematics. The results show that most grains in original specimenwith the sizes below 70 μm uniformly distributed. At a heating rate ( v ) of 10 °C/s, the grain size ( d ) value under a certain time( t ) increased by 60–100 μm with raising temperature ( T ) from 850 to 1100 °C, whereas the d value under a certain T merelyincreased by 70–120 μm with raising time to 60 min. Under v = 0.1 °C/s, T = 850 °C, and t = 0 s, the occupied ratio of grainswith sizes of 40–50 μm was 0.165, whereas at 900 °C, the occupied ratio was 0.125. The evolutions of ln (d5.8− d5.80 ) with1/ T were in negative linear correlations, whereas the ln (d5.8− d5.80 ) with ln t were in positive linear correlations. To sum up,the grain growth behavior of steel was elucidated.