Fushun Special Steel Co., Ltd. (FSSS) is a Chinese steel maker based in Fushun, Liaoning Province. State enterprise Dongbei Special Steel was the largest shareholder of the company. The rest of the shares float in Shanghai Stock Exchange.According to the officials of the company, the steel maker supplied steel to the manufacturing of aircraft carrier of China., Ltd., Ltd.
The control of grain size in superalloys through thermomechanical treatment (TMT) proves crucial, as it directly impacts their mechanical properties and service life. Exploring the mechanisms governing abnormal grain growth (AGG) remains vital to maintaining the microstructural stability and performance of superalloys. A combination of thermomechanical simulation, finite element analysis (FEA), and quasi-in-situ EBSD was employed to examine the microstructural evolution of the GH2787 superalloy during TMT. The mechanisms of dynamic recrystallization (DRX) under hot deformation were analyzed. At 10 % strain, the sample exhibited three DRX mechanisms: discontinuous, continuous, and twinning-induced recrystallization (TIDX). Particular attention was paid to abnormal grain coarsening during subsequent solution heat treatment. FEA revealed an arc-shaped gradient in effective strain across the cross-section of the deformed specimen, extending from the edge toward the center. During post-deformation heat treatment, coarse-grained bands, enriched with twin boundaries (TBs), formed at the interface between low-energy (GOS<0.5 degrees) and high-energy (0.5 degrees
The rapid development in the aerospace industry requires the service performance of high-strength and heat-resistant bearing steel, especially in terms of strength and ductility synergy. A modified CSS-42L steel was obtained by multicomponent modulation, and an exceptional strength and ductility synergy of the alloy was attained through the adjusted tempering treatment. The tensile strength of 1986 MPa, the yield strength of 1622 MPa, and the uniform elongation of more than 17
The low frequency electromagnetic casting(LFEC)was used to prevent hot cracking during the solidification process of GH4742 superalloy ingot.The effects of LFEC on the solidification macrostructure of the ingot were investigated through experiments and simulation.The results show that the average grain size decreases after application of LFEC.At the same time,the fraction of equiaxed grains increases compared with the ingots that without LFEC.In addition,the average grain size decreases and the fraction of equiaxed grains increases with increasing the current frequency.When the current frequency increases from 5 Hz to 20 Hz,the average grain size decreases from 5.39 mm to 4.74 mm,and the fraction of equiaxed grains increases from 41.21%to 55.24%.The distribution of Lorentz force,melt flow field and temperature field in the melt was simulated using COMSOL Multiphysics software.It is found that the Lorentz force increases and the forced convection is enhanced with increasing the current frequency,thus the melt flow velocity and heat transfer in the melt are promoted.It can facilitate the heterogenous nucleation in the melt,resulting in grain refinement,and further preventing hot cracking of large size ingots.
Duplex stainless steels are indispensable in marine, energy, and chemical applications, yet their mechanical reliability remains constrained by phase balance and texture, with effective pathways for integrated microstructural optimization still elusive. This study proposed a novel approach for multiscale microstructural optimization in duplex stainless steel via the introduction of trace nanoceramics. The in-situ synthesized and incorporated nanoparticles orchestrated microstructural evolution during solidification by acting as heterogeneous nucleation sites while simultaneously restricting dendritic growth and suppressing secondary-phase coarsening though solute confinement and interface pinning. During hot deformation and solution treatment, nanoceramic-mediated austenite boundary generation promoted recrystallization nucleation, while simultaneous grain pinning ensured phase ratio equilibrium and texture randomization. Nanoparticle-induced local stress field modulation reduced stacking fault energy, thereby facilitating dislocation rearrangement and coordinating interphase recrystallization to mitigate residual stress. Compared to the matrix steel, the reinforced steel exhibited improvements of 16.6 %, 9.5 %, 2.2 %, and 4.64 % in yield strength, tensile strength, fracture strain, and impact toughness, respectively, at room temperature. The strength contributions from grain refinement, the Orowan mechanism, thermal mismatch strengthening, and load transfer strengthening. This study establishes a novel processing paradigm for microstructural harmonization in dual-phase alloys.
Hypo-peritectic steels are widely used in various industrial fields because of their high strength, high toughness, high processability, high weldability, and low material cost. However, surface defects are liable to occur during continuous casting, which includes depression, longitudinal cracks, deep oscillation marks, and severe level fluctuation with slag entrapment. The high-efficiency production of hypo-peritectic steels by continuous casting is still a great challenge due to the limited understanding of the mechanism of peritectic solidification. This work reviews the definition and classification of hypo-peritectic steels and introduces the formation tendency of common surface defects related to peritectic solidification. New achievements in the mechanism of peritectic reaction and transformation have been listed. Finally, countermeasures to avoiding surface defects of hypo-peritectic steels duiring continuous casting are summarized. Enlightening certain points in the continuous casting of hypo-peritectic steels and the development of new techniques to overcome the present problems will be a great aid to researchers.
