B Eghbali
,
M Shaban
钢铁研究学报(英文版)
Grain refinement in a plain carbon steel under intercritical warm deformation was studied by torsion testing. Based on the experimental results, the warm flow behaviour and microstructural evolution of ferrite were researched with particular emphasis on the effect of the strain rate in controlling the grain refinement mechanism of ferrite. The deformed microstructures were investigated at various strain rates using optical microscopy and electron back-scattered diffraction (EBSD). The EBSD observations indicate that an increase in the strain rate leads to the development of new fine ferrite grains with high angle boundaries. Furthermore, it shows that the annihilation of dislocations occurs more readily at lower strain rate. The elongated ferrite grains continuously dynamically recrystallize to form the equiaxed fine ferrite grains. Thereby, the aspect ratio of elongated grains decreases with increasing the strain rate. Furthermore, the peak stress and steady state stress of ferrite both increase with increasing strain rate. Based on the study, the effect of strain rate on the development of fine ferrite grains during continuous dynamic recrystallization of ferrite was analyzed in detail.
关键词:
grain refinement
,
steel
,
strain rate
,
torsion testing
,
EBSD
V Soleymani
,
B Eghbali
钢铁研究学报(英文版)
Grain refinement is one of the successful and low-cost methods to develop metals having excellent combination of strength and ductility. Low carbon steel was deformed by using multidirectional forging (MDF) technique at room temperature. The influence of strain amount and annealing process on the microstructure and mechanical properties of investigated steel was studied. The grain refinement mechanism was studied by the microstructure observation. The results showed that the grain refinement was attained by multidirectional forging technique. The initial coarser grains of average 38 μm size fragmented into very fine ferrite with grain sizes of about 1.2 μm. After MDF, the strength properties improved significantly, although uniform elongation and elongation decreased with increasing strain.
关键词:
multidirectional forging
,
grain refinement
,
annealing
,
steel
,
recrystallization
ZHAO Xin
,
YANG Xiao-ling
,
JING Tian-fu
钢铁研究学报(英文版)
In order to investigate the effect of initial microstructure on warm deformation behavior, some specimens of 45 steel were annealed and some quenched. Then the specimens were isothermally compressed on a Gleeble 3500 machine. The deformation temperature range was 550 to 700 ℃ and the strain rate range was 0.001 to 0.1 s-1. An optical microscope (OM) and a transmission electron microscope (TEM) were used to study the microstructures. The results show that the microstructure of annealed specimens is ferrite and pearlite and that of quenched specimens is martensite. The flow stress of quenched specimens is higher than that of annealed ones at 550 ℃ when strain rates are greater than 0.001 s-1. However, at 600 to 700 ℃ and strain rate of 0.001 s-1, the whole flow curves of quenched specimens are below that of annealed ones. Under the rest conditions, the flow stress of quenched specimens is higher at the beginning of compression and then the opposite is true after the strain is greater than a critical value. The microstructure examination proves that the tempering and dynamic recrystallization easily occur in the specimens with martensite during warm compression, which results in the above phenomena.
关键词:
warm deformation
,
flow stress
,
steel
,
microstructure
ZHOU Guo-ping
,
LIU Zhen-yu
,
YU Shi-chuan
,
CHEN Jun
,
QIU Yi-qing
,
WANG Guo-dong
钢铁研究学报(英文版)
The formation of phosphorous surface inverse segregation (SIS) in twin-roll cast strips of low-carbon steels was studied. High phosphorous strips were fabricated by using a pilot twin-roll strip caster and a melt/substrate contacting apparatus, respectively. Solidification structures of strips were observed and analyzed, and phosphorus distributions along longitudinal sections of strips were investigated and discussed. The results showed that solidification structures of all strips were columnar grains, either integrated or coarse in the strip made by the melt/substrate contacting apparatus or damaged in some degree in cast strips; and that during cast strip solidification, enrichment of phosphorus occurred between columnar grains, and the average phosphorus concentration near the surface in the strip with 015% of phosphorus was measured to be about 027% which was obviously higher than that in the bulk.
关键词:
strip casting
,
phosphorus enrichment
,
inverse segregation
,
steel
,
solidification
CHEN Bo
,
YANG Jian-xin
,
OUYANG Zhi-yun
钢铁研究学报(英文版)
The internal recycling process of BOF slag which is one of the huge solid wastes from iron and steel industry was emphasized. Based on the four scenarios of different internal recycling strategies for BOF slag, life cycle assessment (LCA) as a valuable tool for industrial solid waste management was applied to analyze the contribution to reducing environmental impacts and resources burdens for each scenario. The global warming potential (GWP) results of the four scenarios show that the scenario which performs best in carbon reduction cuts off 14.2% of GWP impacts of the worst scenario. The results of this study show that the optimized internal recycling process of BOF slag can improve the environmental performance of crude steel. It is important to assess and choose an appropriate strategy to recycle BOF slag from LCA perspective to reduce the environmental impacts and resource burdens as much as possible.
关键词:
life cycle assessment
,
sustainable development
,
close-loop recycling
,
steel
,
BOF slag
