Many researchers have explored the inclusion modification mechanism to improve non-metallic inclusion modifications in steelmaking. In this study, two types of industrial trials on inclusion modifications in liquid st...Many researchers have explored the inclusion modification mechanism to improve non-metallic inclusion modifications in steelmaking. In this study, two types of industrial trials on inclusion modifications in liquid steel were conducted using ultra-low-carbon Al-killed steel with different Mg and Ca contents to verify the effects of Ca and Mg contents on the modification mechanism of Al_2O_3-based inclusions during secondary refining. The results showed that Al_2O_3-based inclusions can be modified into liquid calcium aluminate or a multi-component inclusion with the addition of a suitable amount of Ca. In addition, [Mg] in liquid steel can further reduce CaO in liquid calcium aluminate to drive its evolution into CaO–MgO–Al_2O_3 multi-component inclusions. Thermodynamic analysis confirmed that the reaction between [Mg] and CaO in liquid calcium aluminate occurs when the MgO content of liquid calcium aluminate is less than 3 wt% and the temperature is higher than 1843 K.展开更多
The coating microstructure of hot-dip aluminum (HDA) of deformed low-carbon steel containing RE was analyzed by metallography microscopy, TEM and XRD, and the forming mechanism was also discussed. The results show tha...The coating microstructure of hot-dip aluminum (HDA) of deformed low-carbon steel containing RE was analyzed by metallography microscopy, TEM and XRD, and the forming mechanism was also discussed. The results show that, the Fe_2Al_5 phase, on whose subcrystal boundaries, Al particles with the size of 7～30 μm existing on parallel linear are, grows a strong orientation. And the spread activation energy of Al is 155.22 kJ·mol -1. In addition, the effects of deformation on coating microstructure of hot-dip aluminum and the function of RE were preliminarily analyzed.展开更多
Subsurface macro-inclusions and hooks are detrimental to the surface quality of deep-drawing steel sheets. However, little is known about the relationship between macro-inclusions and hooks. Thus, in this work, two ul...Subsurface macro-inclusions and hooks are detrimental to the surface quality of deep-drawing steel sheets. However, little is known about the relationship between macro-inclusions and hooks. Thus, in this work, two ultralow carbon （ULC） steel slabs and two low carbon （LC） aluminum-killed steel slabs were sampled to study the relationship between hooks and subsurface macro-inclusions, which were detected on the cross-sections of steel samples with an area of 56058 mm2 using an automated scanning electron microscopy/energy-disper-sive X-ray spectroscopy system. Results show that subsurface inclusions larger than 200 μm were almost entrapped by hook structures, whereas the location of other inclusions smaller than 200μm had no obvious dependence on the location of solidified hooks. Furthermore, the number density （ND） of subsurface inclusions larger than 200μm decreased from 0.02 to 0 cm-2 in ULC steel as the mean hook depth decreased from 1.57 to 1.01 mm. Similar trends were also observed in LC steel. In addition, the detected inclusions larger than 200μm were concentrated in the region near the slab center （3/8 width-5/8 width）, where hook depths were also larger than those at any other locations. Therefore, minimizing the hook depth is an effective way to reduce inclusion-induced sliver defects in deep-drawing steels.展开更多
Effects of Al- Si addition on hot modulus of rup- ture ~ HMOR） . thermal shock resistance ~ TSR~ . phase composition and mierostructure of low-carbon MgO - C materials were investigated. The results show that： Al an...Effects of Al- Si addition on hot modulus of rup- ture ~ HMOR） . thermal shock resistance ~ TSR~ . phase composition and mierostructure of low-carbon MgO - C materials were investigated. The results show that： Al and Si addition to low-carbon MgO - C materials leads to dramatic increase in MOR at elevated temperatures; it increases from 4 MPa to 11 -21 MPa at 1 200 ℃ and from 2 MPa to 21 -29 MPa at 1 400 ℃. Al and Si addition to low-carbon MgO - C materials also improves TSR： residual strength ratio after thermal shock when △T = 1 200 ℃ is increased,from 44% to 73% - 77%. Al reacts with C and N2 to form, Al4C3 and AlN, Si reacts with C to form SiC. Ultimately. in-situ formed non- oxides increase appreciably with temperature rising and are well interlaced in periclase skeleton structure at 1 300 -1 400 ℃. which is beneficial to thermomechanical properties.展开更多
Titanium is the impurity in some special steel grades.The existence of titanium decreases the grain size,depresses the yield strength,and results in the low quality of these steels in various properties.Thus,titanium ...Titanium is the impurity in some special steel grades.The existence of titanium decreases the grain size,depresses the yield strength,and results in the low quality of these steels in various properties.Thus,titanium should be removed to the minimum.Based on the industrial production of ultra low carbon Al-Si killed steel,the physical-chemical behavior of titanium was investigated in vacuum degassing refining（RH）process with and without desulfurization.The influences of titanium content in hot metal,ladle slag composition,and ladle slag quantity,etc,on titanium content of refined liquid steel were discussed.The results showed that the partition ratio of titanium between ladle slag and liquid steel is in inverse proportion to the 4/3square of aluminum content.The maximum partition ratio of titanium between top slag and liquid steel can be obtained by adjusting an optimum slag composition including contents of FeOxand Al2O3and the slag basicity,and the suitable range of them should be controlled higher than 6%,less than 20%,and within 1.5to 3.0,respectively.Moreover,desulfurization refining by RH decreases the partition ratio of titanium between ladle slag and liquid steel significantly.To ensure the titanium content stably less than 15×10-6 in a 300tladle,the titanium content in hot metal must be less than 500×10-6 and the thickness of basic oxygen furnace（BOF）slag carrying over must be less than 50mm.展开更多
Aluminum killed low-carbon steel sheets were cold rolled at different reduction ratios and annealed using different temperatures and holding time.The Vickers hardness was examined.The results show that when cold rolli...Aluminum killed low-carbon steel sheets were cold rolled at different reduction ratios and annealed using different temperatures and holding time.The Vickers hardness was examined.The results show that when cold rolling reduction ratios increase from 40% to 81%,recrystallization temperatures decrease from 602℃ to 572℃ during 4hisochronal annealing,as well recrystallization holding time decreases from 117 min to 5min during isothermal annealing at 610℃.All recrystallization temperatures and holding time can be calculated using the annealing experiment results.Microstructure was examined through electron backscattered diffraction（EBSD）.The results show that as rolling direction preferentially grows,equiaxed grains grow into cake-type during recrystallization.Cake-type grains are more beneficial to obtaining ideal〈111〉//ND（normal direcrtion）orientation texture.{111}orientation grains nucleate and grow up preferentially.Deformation grains of{111}〈110〉orientations grow into new recrystallization grains of{111}〈123〉and{111}〈112〉during recrystallization.Texture formation can be explained by directional nucleation.展开更多
： Titanium is an impurity element in some special steel grades. The existence of titanium decreases the grain size and lowers the yield strength ,resulting in low quality of these steels with regard to various proper...： Titanium is an impurity element in some special steel grades. The existence of titanium decreases the grain size and lowers the yield strength ,resulting in low quality of these steels with regard to various properties. Thus, the titanium content should be reduced to the minimum. Based on the industrial production of ultra-low carbon A1-Si killed steel, this paper investigated the physical-chemical behaviors of titanium with and without desulfurization during RH refining. The influences of Ti content in hot metal, ladle slag composition, and ladle slag quantity, etc., on the Ti content in refined liquid steel were discussed. The results show that the partition ratio of titanium between ladle slag and liquid steel is inversely proportional to the AI content to the power of 4/3 ,and the empirical formula regressed from practical experience can be expressed as w（TiO2）/WTi=48/w[AI]4/3 Maximum partition ratio of titanium between top slag and liquid steel can be ensured W[Til WIAIIby an optimum slag composition including components of FeOx and A12 03 and an appropriate slag basicity. The contents of FetO and A1203 should be controlled above 6% and below 20% respectively and the slag basicity should be kept within 1.5 to 3.0. Moreover, desulfurization refining in the RH vacuum will decrease the partition ratio of titanium between ladle slag and liquid steel significantly. To keep the Ti content stably below 15 ×10 ^-4% in a 300 ton ladle ,the Ti content in hot metal must be lower than 500 × 10^-4% and the thickness of ladle slag carried over from BOF slag must be less than 50 ram.展开更多
基金financially supported by the Fundamental Research Funds for the Central Universities (No. FRF-TP-16-079A1)the National Science Foundation for Young Scientists of China (No. 51704021)+1 种基金the Joint Funds of National Natural Science Foundation of China (No. U1560203)supported by Beijing Key Laboratory of Special Melting and Preparation of High-end Metal Materials
文摘Many researchers have explored the inclusion modification mechanism to improve non-metallic inclusion modifications in steelmaking. In this study, two types of industrial trials on inclusion modifications in liquid steel were conducted using ultra-low-carbon Al-killed steel with different Mg and Ca contents to verify the effects of Ca and Mg contents on the modification mechanism of Al_2O_3-based inclusions during secondary refining. The results showed that Al_2O_3-based inclusions can be modified into liquid calcium aluminate or a multi-component inclusion with the addition of a suitable amount of Ca. In addition, [Mg] in liquid steel can further reduce CaO in liquid calcium aluminate to drive its evolution into CaO–MgO–Al_2O_3 multi-component inclusions. Thermodynamic analysis confirmed that the reaction between [Mg] and CaO in liquid calcium aluminate occurs when the MgO content of liquid calcium aluminate is less than 3 wt% and the temperature is higher than 1843 K.
文摘The coating microstructure of hot-dip aluminum (HDA) of deformed low-carbon steel containing RE was analyzed by metallography microscopy, TEM and XRD, and the forming mechanism was also discussed. The results show that, the Fe_2Al_5 phase, on whose subcrystal boundaries, Al particles with the size of 7～30 μm existing on parallel linear are, grows a strong orientation. And the spread activation energy of Al is 155.22 kJ·mol -1. In addition, the effects of deformation on coating microstructure of hot-dip aluminum and the function of RE were preliminarily analyzed.
文摘Subsurface macro-inclusions and hooks are detrimental to the surface quality of deep-drawing steel sheets. However, little is known about the relationship between macro-inclusions and hooks. Thus, in this work, two ultralow carbon （ULC） steel slabs and two low carbon （LC） aluminum-killed steel slabs were sampled to study the relationship between hooks and subsurface macro-inclusions, which were detected on the cross-sections of steel samples with an area of 56058 mm2 using an automated scanning electron microscopy/energy-disper-sive X-ray spectroscopy system. Results show that subsurface inclusions larger than 200 μm were almost entrapped by hook structures, whereas the location of other inclusions smaller than 200μm had no obvious dependence on the location of solidified hooks. Furthermore, the number density （ND） of subsurface inclusions larger than 200μm decreased from 0.02 to 0 cm-2 in ULC steel as the mean hook depth decreased from 1.57 to 1.01 mm. Similar trends were also observed in LC steel. In addition, the detected inclusions larger than 200μm were concentrated in the region near the slab center （3/8 width-5/8 width）, where hook depths were also larger than those at any other locations. Therefore, minimizing the hook depth is an effective way to reduce inclusion-induced sliver defects in deep-drawing steels.
文摘Effects of Al- Si addition on hot modulus of rup- ture ~ HMOR） . thermal shock resistance ~ TSR~ . phase composition and mierostructure of low-carbon MgO - C materials were investigated. The results show that： Al and Si addition to low-carbon MgO - C materials leads to dramatic increase in MOR at elevated temperatures; it increases from 4 MPa to 11 -21 MPa at 1 200 ℃ and from 2 MPa to 21 -29 MPa at 1 400 ℃. Al and Si addition to low-carbon MgO - C materials also improves TSR： residual strength ratio after thermal shock when △T = 1 200 ℃ is increased,from 44% to 73% - 77%. Al reacts with C and N2 to form, Al4C3 and AlN, Si reacts with C to form SiC. Ultimately. in-situ formed non- oxides increase appreciably with temperature rising and are well interlaced in periclase skeleton structure at 1 300 -1 400 ℃. which is beneficial to thermomechanical properties.
基金Sponsored by National Natural Science Foundation of China(51104109)
文摘Titanium is the impurity in some special steel grades.The existence of titanium decreases the grain size,depresses the yield strength,and results in the low quality of these steels in various properties.Thus,titanium should be removed to the minimum.Based on the industrial production of ultra low carbon Al-Si killed steel,the physical-chemical behavior of titanium was investigated in vacuum degassing refining（RH）process with and without desulfurization.The influences of titanium content in hot metal,ladle slag composition,and ladle slag quantity,etc,on titanium content of refined liquid steel were discussed.The results showed that the partition ratio of titanium between ladle slag and liquid steel is in inverse proportion to the 4/3square of aluminum content.The maximum partition ratio of titanium between top slag and liquid steel can be obtained by adjusting an optimum slag composition including contents of FeOxand Al2O3and the slag basicity,and the suitable range of them should be controlled higher than 6%,less than 20%,and within 1.5to 3.0,respectively.Moreover,desulfurization refining by RH decreases the partition ratio of titanium between ladle slag and liquid steel significantly.To ensure the titanium content stably less than 15×10-6 in a 300tladle,the titanium content in hot metal must be less than 500×10-6 and the thickness of basic oxygen furnace（BOF）slag carrying over must be less than 50mm.
基金funded by National Natural Science Foundation of China(51275216)Initial Funding for Advanced Talents of Jiangsu University(14JDG129)
文摘Aluminum killed low-carbon steel sheets were cold rolled at different reduction ratios and annealed using different temperatures and holding time.The Vickers hardness was examined.The results show that when cold rolling reduction ratios increase from 40% to 81%,recrystallization temperatures decrease from 602℃ to 572℃ during 4hisochronal annealing,as well recrystallization holding time decreases from 117 min to 5min during isothermal annealing at 610℃.All recrystallization temperatures and holding time can be calculated using the annealing experiment results.Microstructure was examined through electron backscattered diffraction（EBSD）.The results show that as rolling direction preferentially grows,equiaxed grains grow into cake-type during recrystallization.Cake-type grains are more beneficial to obtaining ideal〈111〉//ND（normal direcrtion）orientation texture.{111}orientation grains nucleate and grow up preferentially.Deformation grains of{111}〈110〉orientations grow into new recrystallization grains of{111}〈123〉and{111}〈112〉during recrystallization.Texture formation can be explained by directional nucleation.
文摘： Titanium is an impurity element in some special steel grades. The existence of titanium decreases the grain size and lowers the yield strength ,resulting in low quality of these steels with regard to various properties. Thus, the titanium content should be reduced to the minimum. Based on the industrial production of ultra-low carbon A1-Si killed steel, this paper investigated the physical-chemical behaviors of titanium with and without desulfurization during RH refining. The influences of Ti content in hot metal, ladle slag composition, and ladle slag quantity, etc., on the Ti content in refined liquid steel were discussed. The results show that the partition ratio of titanium between ladle slag and liquid steel is inversely proportional to the AI content to the power of 4/3 ,and the empirical formula regressed from practical experience can be expressed as w（TiO2）/WTi=48/w[AI]4/3 Maximum partition ratio of titanium between top slag and liquid steel can be ensured W[Til WIAIIby an optimum slag composition including components of FeOx and A12 03 and an appropriate slag basicity. The contents of FetO and A1203 should be controlled above 6% and below 20% respectively and the slag basicity should be kept within 1.5 to 3.0. Moreover, desulfurization refining in the RH vacuum will decrease the partition ratio of titanium between ladle slag and liquid steel significantly. To keep the Ti content stably below 15 ×10 ^-4% in a 300 ton ladle ,the Ti content in hot metal must be lower than 500 × 10^-4% and the thickness of ladle slag carried over from BOF slag must be less than 50 ram.
