Based on experimental data of positron annihilation technology, electrolyticdissolution technique, electron back-scattered pattern, etc. and by analysis the strengtheningfactors, the strengthening mechanism of ultra-t...Based on experimental data of positron annihilation technology, electrolyticdissolution technique, electron back-scattered pattern, etc. and by analysis the strengtheningfactors, the strengthening mechanism of ultra-thin hot strip of low carbon steel produced by CSP(Compact Strip Production) technique was investigated. The value of each strengthening mechanism andits contribution percentage to yield strength were achieved. The results show that refinementstrengthening is the predominant strengthening mode; precipitation strengthening and dislocationstrengthening are second to it, their contributions to yield strength are almost equal.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
The casting structure, chemical composition segregation, dendrite arm space,inclusiona and during the CSP (compact strip production) rolling process were investigated. Theresults show that the CSP thin slab has a feat...The casting structure, chemical composition segregation, dendrite arm space,inclusiona and during the CSP (compact strip production) rolling process were investigated. Theresults show that the CSP thin slab has a feature of uniform fine grains, more columnar crystals,less central porosity and segregation etc. There is no great difference in macrostructure betweenthe CSP thin slab and conventional slab; however, the fine dendrite structure of the CSP slab ismore uniform. Moreover, the central porosity and segregation are obviously improved after the firstpass; and the dendrite is bent along the rolling direction rather than broken into pieces. Smallinclusions with the diameter less than 10 mum in the CSP slab are dominantly consisted of aluminatesformed by Al deoxidation and Ca treatment and not floating out of the melt. The large sizeinclusions found in the continuous casting slab are very few.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
基金This work was financially supported by the state foundation for key projects: Fundamental Research on New Generation of Steels (No: G1998061500).
文摘Based on experimental data of positron annihilation technology, electrolyticdissolution technique, electron back-scattered pattern, etc. and by analysis the strengtheningfactors, the strengthening mechanism of ultra-thin hot strip of low carbon steel produced by CSP(Compact Strip Production) technique was investigated. The value of each strengthening mechanism andits contribution percentage to yield strength were achieved. The results show that refinementstrengthening is the predominant strengthening mode; precipitation strengthening and dislocationstrengthening are second to it, their contributions to yield strength are almost equal.
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.
基金This work was financially supported by the National Natural Science Foundation of China (No. 50334010)
文摘The casting structure, chemical composition segregation, dendrite arm space,inclusiona and during the CSP (compact strip production) rolling process were investigated. Theresults show that the CSP thin slab has a feature of uniform fine grains, more columnar crystals,less central porosity and segregation etc. There is no great difference in macrostructure betweenthe CSP thin slab and conventional slab; however, the fine dendrite structure of the CSP slab ismore uniform. Moreover, the central porosity and segregation are obviously improved after the firstpass; and the dendrite is bent along the rolling direction rather than broken into pieces. Smallinclusions with the diameter less than 10 mum in the CSP slab are dominantly consisted of aluminatesformed by Al deoxidation and Ca treatment and not floating out of the melt. The large sizeinclusions found in the continuous casting slab are very few.
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.
