Electron microscopic investigation on low carbon steel strips produced by the CSP process has been carried out. Large number of oxide dispersive precipitates have been observed in the ferrite matrix of the steel strip...Electron microscopic investigation on low carbon steel strips produced by the CSP process has been carried out. Large number of oxide dispersive precipitates have been observed in the ferrite matrix of the steel strips. Dimension of them is about 10~20 nm. Electron diffraction study showed that the structure of these precipitates consists with cubic system spinel structure. Their lattice parameter is about 0.83 nm. The results implied that they should be complex oxides of Fe, Al et al. Small sulfide particles with 100-300 nm in size have also been observed. Remarkable strengthening and grain refinement effects can be obtained by the precipitations. The oxygen and sulfur in steels could play beneficial role under certain conditions.展开更多
The microstructures of low carbon steel before, during and after rollingdeformation of each stand were observed using optical microscope. The result showed that themicrostructures were very fine after six passes rolli...The microstructures of low carbon steel before, during and after rollingdeformation of each stand were observed using optical microscope. The result showed that themicrostructures were very fine after six passes rolling deformation. The effect of the first standreduction on microstructure refinement was very distinct. During the rolling process, with theincrease of the accumulated strain, the microstructures would further refine, and the density ofdislocation would increase at the same time. In continuous casting thin slabs and each finishingstand, lots of observed precipitates were mainly A1_2O_3 and MnS along the grain boundaries or ingrains, which played an important role in the mechanical properties of the hot strips of low carbonsteel produced by CSP (compact strip production) technology.展开更多
In comparison with conventional production for hot strips, compact strip production (CSP) brings about some new micro-structural phenomena. Investigations were carried out to clarify the grain refinement mechanism of ...In comparison with conventional production for hot strips, compact strip production (CSP) brings about some new micro-structural phenomena. Investigations were carried out to clarify the grain refinement mechanism of low carbon steel strips produced by the EAF-CSP process. Samples, obtained from the same rolling stock during continuous rolling, were examined through SEM, TEM and XEDS. Thin slabs have a dominant columnar structure and the spacing of the secondary dendrite arms ranges from 90 to -125 μm. The average grain sizes for the central area of the samples from the 1st to 6th pass are 41.6, 25.2, 21.4, 20.2, 13.1, 6.7 μm, respectively. Large number of nanometer oxide and sulfide have been found in the low carbon steel produced by the CSP process. The grain refinement mechanism can be summarized as follows: finer solidification structure of the thin slab; austenite recrystalliza-tion at higher temperature and stain accumulation at lower temperature caused by the great reduction of single rolling pass during continuous rolling; nano-scaled precipitates of sulfide and oxide which drag grain boundaries of austenite or ferrite to prevent the grain coarsening.展开更多
Electron microscopy and X-ray Energy Dispersive Spectroscopy (XEDS) study oninfluence of Cu on low carbon hot strips produced by CSP (Compact Strip Production) process has beencarried out. The results indicated that c...Electron microscopy and X-ray Energy Dispersive Spectroscopy (XEDS) study oninfluence of Cu on low carbon hot strips produced by CSP (Compact Strip Production) process has beencarried out. The results indicated that copper segregation and enrichment at interfacial layerbetween oxidized surface and steel matrix is the key factor, which results in microcracks and edgeflaws on the strips. The primary considerations to prevent detrimental effects from Cu includecontrolling copper content in proper level, higher soaking temperature and non-oxidizable atmosphereduring soaking. Copper sulfide precipitates with nanometers in size were observed, they may bebeneficial to the properties of CSP products, and influence of Cu on quality of CSP hot strips isdiscussed.展开更多
文摘Electron microscopic investigation on low carbon steel strips produced by the CSP process has been carried out. Large number of oxide dispersive precipitates have been observed in the ferrite matrix of the steel strips. Dimension of them is about 10~20 nm. Electron diffraction study showed that the structure of these precipitates consists with cubic system spinel structure. Their lattice parameter is about 0.83 nm. The results implied that they should be complex oxides of Fe, Al et al. Small sulfide particles with 100-300 nm in size have also been observed. Remarkable strengthening and grain refinement effects can be obtained by the precipitations. The oxygen and sulfur in steels could play beneficial role under certain conditions.
基金This work was financially supported by the "973" Key Foundation of China (No. GJ998061500)
文摘The microstructures of low carbon steel before, during and after rollingdeformation of each stand were observed using optical microscope. The result showed that themicrostructures were very fine after six passes rolling deformation. The effect of the first standreduction on microstructure refinement was very distinct. During the rolling process, with theincrease of the accumulated strain, the microstructures would further refine, and the density ofdislocation would increase at the same time. In continuous casting thin slabs and each finishingstand, lots of observed precipitates were mainly A1_2O_3 and MnS along the grain boundaries or ingrains, which played an important role in the mechanical properties of the hot strips of low carbonsteel produced by CSP (compact strip production) technology.
文摘In comparison with conventional production for hot strips, compact strip production (CSP) brings about some new micro-structural phenomena. Investigations were carried out to clarify the grain refinement mechanism of low carbon steel strips produced by the EAF-CSP process. Samples, obtained from the same rolling stock during continuous rolling, were examined through SEM, TEM and XEDS. Thin slabs have a dominant columnar structure and the spacing of the secondary dendrite arms ranges from 90 to -125 μm. The average grain sizes for the central area of the samples from the 1st to 6th pass are 41.6, 25.2, 21.4, 20.2, 13.1, 6.7 μm, respectively. Large number of nanometer oxide and sulfide have been found in the low carbon steel produced by the CSP process. The grain refinement mechanism can be summarized as follows: finer solidification structure of the thin slab; austenite recrystalliza-tion at higher temperature and stain accumulation at lower temperature caused by the great reduction of single rolling pass during continuous rolling; nano-scaled precipitates of sulfide and oxide which drag grain boundaries of austenite or ferrite to prevent the grain coarsening.
文摘Electron microscopy and X-ray Energy Dispersive Spectroscopy (XEDS) study oninfluence of Cu on low carbon hot strips produced by CSP (Compact Strip Production) process has beencarried out. The results indicated that copper segregation and enrichment at interfacial layerbetween oxidized surface and steel matrix is the key factor, which results in microcracks and edgeflaws on the strips. The primary considerations to prevent detrimental effects from Cu includecontrolling copper content in proper level, higher soaking temperature and non-oxidizable atmosphereduring soaking. Copper sulfide precipitates with nanometers in size were observed, they may bebeneficial to the properties of CSP products, and influence of Cu on quality of CSP hot strips isdiscussed.
