In aluminum killed steels, the size, shape, quantity and formation of non-metallic inclusions in ladle steel (before and after RH vacuum treatment) and in tundish as well as in slabs were studied by EPMA (Electron Pro...In aluminum killed steels, the size, shape, quantity and formation of non-metallic inclusions in ladle steel (before and after RH vacuum treatment) and in tundish as well as in slabs were studied by EPMA (Electron Probe Microanalysis) and by analyzing the total oxygen. The results showed that in the slabs the total oxygen was quite low and the inclusions discovered were mainly small-sized angular alumina inclusions. This indicates that most inclusions have been removed by floating out during the continuous casting process. In addition, the countermeasures were discussed to decrease the alumina inclusions in the slabs further.展开更多
The effects of an electric field on AIN precipitation and recrystallization texture were investigated. Cold-rolled 08Al killed steel sheets were annealed at 550℃ according to the two-step processes, for various maint...The effects of an electric field on AIN precipitation and recrystallization texture were investigated. Cold-rolled 08Al killed steel sheets were annealed at 550℃ according to the two-step processes, for various maintaining times, with and without applying an electric field. It was found that the electric field promotes the precipitation of the second phase （AlN particles）, strengthens the γ-fiber and weakens the α-fiber texture component in the recrystallized specimens. A possible explanation for the reinforcement of γ-fiber texture by the electric field is that the second phase AIN particle promotes the growth of γ-fiber at the expense of differently oriented grains.展开更多
Aluminum killed cold rolled steel used for automobiles was welded in this paper by using CO 2 laser with wavelength 10.6μm.The experiment shows that high quality of welding can be realized at welding speed of 4 500m...Aluminum killed cold rolled steel used for automobiles was welded in this paper by using CO 2 laser with wavelength 10.6μm.The experiment shows that high quality of welding can be realized at welding speed of 4 500mm/min by optimizing the parameters.The strength and hardness of laser welded joints for aluminum killed cold rolled steel increased compared to those of the base metal while the formability decreased.Forming limit diagram of joint material indicated that the laser weld seam should avoid the maximum deformation area of automobile parts during the designing period for the position of weld seam.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
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
In this study, the intercritical annealing process for a typical low-carbon aluminum killed steel is investigated. A cold-rolled sheet was annealed at intercfitical temperatures ranging from 730 ℃ to 770 ℃ and then ...In this study, the intercritical annealing process for a typical low-carbon aluminum killed steel is investigated. A cold-rolled sheet was annealed at intercfitical temperatures ranging from 730 ℃ to 770 ℃ and then cooled in air or water. The annealed steel was then baked at 210 ℃, and its mechanical properties and microstructures were analyzed in detail. It is shown that after the air-cooling process,the strength of steel decreased and ductility increased with an increase in the annealing temperature. However, after water-cooling, the strength and ductility both increased with the increase of annealing temperature. These results are attributed to the property- optimization of the steel.展开更多
The continuous annealing process of a typical aluminum killed steel was investigated. A cold rolled sheet was annealed continuously at holding temperature ranging from 580 to 760 ℃. The microstructures were analyzed ...The continuous annealing process of a typical aluminum killed steel was investigated. A cold rolled sheet was annealed continuously at holding temperature ranging from 580 to 760 ℃. The microstructures were analyzed in detail based on contiuous cooling transformation（ CCT） curves that were simulated with JM artP ro softw are. The results show ed that recrystallization and perlitic transformations caused a diversity of microstructures and mechanical properties. In comparison with annealed steel that was produced from insufficient recrystallization,annealed steel produced from sufficient recrystallization had more isometric grains and exhibited low er strength and higher ductility. Higher annealing temperatures than A_1 provided steel with lamellar pearlite zones,large ferrite grains,low strength,and high ductility. The results are attributed to the property optimization of the steel.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
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
By using a Gleeble 350013 thermo-mechanical simulator, the nucleation behavior of intragranular acicular ferrites （IAF） was studied in a Ti-killed C-Mn steel. During continuous cooling transformation, the allotriomo...By using a Gleeble 350013 thermo-mechanical simulator, the nucleation behavior of intragranular acicular ferrites （IAF） was studied in a Ti-killed C-Mn steel. During continuous cooling transformation, the allotriomorphic ferrite （AF） and ferrite side plate （FSP） microstructures grew more rapidly with the temperature decreasing from 800 to 650 ℃, and the IAF microstructure was dominant within austenite grain with further cooling to 600 ℃. The diffusion bonding experiment and the effect of C, Mn and Si concentrations on the Ao3 temperature by thermodynam- ic calculation confirm that Ti2O3 itself absorbs neighboring Mn atoms to form Mn-depleted zone （MDZ）, which pro- motes the nucleation of IAF microstructure effectively. High temperature holding tests indicate that the nucleation potential of IAF microstructure was lowered in the Ti-killed C-Mn steel when it was treated at high temperature （1250 ℃ ） for a longer time, which is attributed to the saturated absorption degree of Mn atoms by titanium oxide.展开更多
文摘In aluminum killed steels, the size, shape, quantity and formation of non-metallic inclusions in ladle steel (before and after RH vacuum treatment) and in tundish as well as in slabs were studied by EPMA (Electron Probe Microanalysis) and by analyzing the total oxygen. The results showed that in the slabs the total oxygen was quite low and the inclusions discovered were mainly small-sized angular alumina inclusions. This indicates that most inclusions have been removed by floating out during the continuous casting process. In addition, the countermeasures were discussed to decrease the alumina inclusions in the slabs further.
基金This work was supported by the National Natural Science FoundationShanghai Bao Steel Group of China under Grant No.50374028Doctor Foundation.
文摘The effects of an electric field on AIN precipitation and recrystallization texture were investigated. Cold-rolled 08Al killed steel sheets were annealed at 550℃ according to the two-step processes, for various maintaining times, with and without applying an electric field. It was found that the electric field promotes the precipitation of the second phase （AlN particles）, strengthens the γ-fiber and weakens the α-fiber texture component in the recrystallized specimens. A possible explanation for the reinforcement of γ-fiber texture by the electric field is that the second phase AIN particle promotes the growth of γ-fiber at the expense of differently oriented grains.
文摘Aluminum killed cold rolled steel used for automobiles was welded in this paper by using CO 2 laser with wavelength 10.6μm.The experiment shows that high quality of welding can be realized at welding speed of 4 500mm/min by optimizing the parameters.The strength and hardness of laser welded joints for aluminum killed cold rolled steel increased compared to those of the base metal while the formability decreased.Forming limit diagram of joint material indicated that the laser weld seam should avoid the maximum deformation area of automobile parts during the designing period for the position of weld seam.
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.
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In this study, the intercritical annealing process for a typical low-carbon aluminum killed steel is investigated. A cold-rolled sheet was annealed at intercfitical temperatures ranging from 730 ℃ to 770 ℃ and then cooled in air or water. The annealed steel was then baked at 210 ℃, and its mechanical properties and microstructures were analyzed in detail. It is shown that after the air-cooling process,the strength of steel decreased and ductility increased with an increase in the annealing temperature. However, after water-cooling, the strength and ductility both increased with the increase of annealing temperature. These results are attributed to the property- optimization of the steel.
文摘The continuous annealing process of a typical aluminum killed steel was investigated. A cold rolled sheet was annealed continuously at holding temperature ranging from 580 to 760 ℃. The microstructures were analyzed in detail based on contiuous cooling transformation（ CCT） curves that were simulated with JM artP ro softw are. The results show ed that recrystallization and perlitic transformations caused a diversity of microstructures and mechanical properties. In comparison with annealed steel that was produced from insufficient recrystallization,annealed steel produced from sufficient recrystallization had more isometric grains and exhibited low er strength and higher ductility. Higher annealing temperatures than A_1 provided steel with lamellar pearlite zones,large ferrite grains,low strength,and high ductility. The results are attributed to the property optimization of the steel.
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.
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.
文摘By using a Gleeble 350013 thermo-mechanical simulator, the nucleation behavior of intragranular acicular ferrites （IAF） was studied in a Ti-killed C-Mn steel. During continuous cooling transformation, the allotriomorphic ferrite （AF） and ferrite side plate （FSP） microstructures grew more rapidly with the temperature decreasing from 800 to 650 ℃, and the IAF microstructure was dominant within austenite grain with further cooling to 600 ℃. The diffusion bonding experiment and the effect of C, Mn and Si concentrations on the Ao3 temperature by thermodynam- ic calculation confirm that Ti2O3 itself absorbs neighboring Mn atoms to form Mn-depleted zone （MDZ）, which pro- motes the nucleation of IAF microstructure effectively. High temperature holding tests indicate that the nucleation potential of IAF microstructure was lowered in the Ti-killed C-Mn steel when it was treated at high temperature （1250 ℃ ） for a longer time, which is attributed to the saturated absorption degree of Mn atoms by titanium oxide.
