Combining with the study of analogue experiments and test analysis, the kinetics of precipitation and growth of AlN and MnS in non-oriented electrical steel produced by the CSP process is calculated. The results show ...Combining with the study of analogue experiments and test analysis, the kinetics of precipitation and growth of AlN and MnS in non-oriented electrical steel produced by the CSP process is calculated. The results show that the precipitate phase particles of AlN and MnS in typical non-oriented electrical steel grades produced by the CSP process have grown to some extent in the soaking stage, but the precipitation contents are less than 20% of the total contents of nitride and sulfide. The precipitate phase particles of AlN and MnS have precipitated almost after the hot rolling process. The precipitation contents are more than 80% of the total contents of nitride and sulfide, but it is very late for the precipitate phase particles to grow at the end of the hot rolling process.展开更多
借助SEM、EDS及Image-Pro Plus 6.0图像分析软件,对不同热装温度下无取向硅钢铸坯中夹杂物的析出行为进行研究。结果表明,铸坯中MgS、AlN容易以硅酸铝、硅酸镁、硅酸铝镁氧化物为核心析出,且复合夹杂物的形状与其中MgS和AlN的含量有关,...借助SEM、EDS及Image-Pro Plus 6.0图像分析软件,对不同热装温度下无取向硅钢铸坯中夹杂物的析出行为进行研究。结果表明,铸坯中MgS、AlN容易以硅酸铝、硅酸镁、硅酸铝镁氧化物为核心析出,且复合夹杂物的形状与其中MgS和AlN的含量有关,当AlN含量较高时,复合夹杂呈六棱柱状,当MgS含量较高时,复合夹杂一般呈球形。铸坯中硫化物主要以MgS的形式存在,少量以CaS形式存在,但试验钢中未检测到MnS。随着铸坯热装温度的降低,复合夹杂中MgS组分的含量增加,夹杂物平均尺寸也会随之增加,但CaS析出会对MgS的析出起抑制作用,热装温度可通过影响复合夹杂中AlN、MgS的析出来调控夹杂物尺寸。本试验条件下,最合适的铸坯热装温度为700℃,此时钢中尺寸小于0.5μm的微细夹杂物的数量最少。展开更多
The existing forms of N and Al in HSLC (high strength low carbon) steel produced by TSCR (thin slab casting and rolling process), the precipitation thermodynamics and kinetics of AlN, and its effects on structure and ...The existing forms of N and Al in HSLC (high strength low carbon) steel produced by TSCR (thin slab casting and rolling process), the precipitation thermodynamics and kinetics of AlN, and its effects on structure and mechanical property are studied. The experimental results show that only a small quantity of nitrogen is com- bined into AlN in HSLC steel produced by TSCR and most of the nitrogen in steel is still free nitrogen. Aluminum-nitride is mainly precipitated during the period of slow air cooling after coiling, but not during rolling and water cooling. The acid-soluble aluminum has no obvious effect on the grain size and mechanical property of HSLC steel produced by TSCR whose acid-soluble aluminum content is 0.005%―0.043%. The precipitation of AlN is not the main cause of grain refinement of HSLC steel produced by TSCR, nor is AlN the dominating precipitate that has precipitation strengthening effect. The nano nitrides are not pure AlN, but have complex compositions.展开更多
In low carbon steels, dissolution and precipitation of the second phases such as carbides and nitrides during annealing cycles can affect the final structure and properties of the materials. The interaction of above p...In low carbon steels, dissolution and precipitation of the second phases such as carbides and nitrides during annealing cycles can affect the final structure and properties of the materials. The interaction of above processes depends on parameters such as reheating temperature, heating rate, annealing temperature, soaking time and finishing temperature in hot rolling stage before cold rolling. The effects of heating rate and annealing temperature on the microstructure and hardness were investigated. Two heating rates for annealing temperatures of 550, 610 and 720℃ were applied on cold-rolled specimens and St-14 low carbon steel, which were immediately quenched after isothermal annealing. The intercept method was used tO measure average grain sizes. However, resulted microstructures are dif- ferent for the two heating rates. While pancaked structures were observed in specimens annealed with low heating rate, in samples annealed with high heating rate, equiaxed microstructures were observed. Vickers micro-hardness values decreased at all temperatures, which were more significant at higher temperatures. At longer annealing time, signs of increase of hardness values were detected. All results and observations consistently suggest that a precipitati- on process has occurred concurrently with restoration processes during annealing. In addition, the energy dispersive spectroscopy analysis resulted from transmission electron microscopic micrographs have proved that the nano particles precipitated in grain boundaries are AlN.展开更多
The composition,morphology,size,and number of inclusions in Fe-22Mn-xAl-0.7C(x=0.5%,5.2%,and 10.5%)lightweight steels after smelting and heat treatment experiments are characterized by scanning electron microscopy and...The composition,morphology,size,and number of inclusions in Fe-22Mn-xAl-0.7C(x=0.5%,5.2%,and 10.5%)lightweight steels after smelting and heat treatment experiments are characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy from both 2D and 3D perspectives.The inclusions are classified into eight categories according to chemistry and morphology.For the steel sample with a low Al content(0.5%),the inclusions are MnS,AlN-MnS,and Al_(2)O_(3)-MnS,among which Al_(2)O_(3)-MnS is the primary type.With the increase in Al content in the steel sample(to 5.2%),the populations of AlN and AlN-MnS inclusions of 1-3μm in diameter increase.A further increase in Al content(to 10.5%)leads to a significant decrease in the amount of AlN inclusions of 1-3μm in diameter,and an increase in the amount of AlN-MnS inclusions.The precipitation behavior during the phase transformation is also studied by FactSage 8.0 thermodynamic software,and a precipitation mechanism is proposed based on the calculation results.During the heat treatment,AlN inclusions re-precipitate out,due to the interactions between Al and dissolved N in the steel matrix.However,AlN inclusions cannot grow large because of unfavorable kinetic conditions.The re-precipitation phenomenon of AlN is predominant under low Al and high N conditions but not at high Al cases.展开更多
基金Mega-Projects of Science Research for the 10th Five-Year Plan (2004BA318B)
文摘Combining with the study of analogue experiments and test analysis, the kinetics of precipitation and growth of AlN and MnS in non-oriented electrical steel produced by the CSP process is calculated. The results show that the precipitate phase particles of AlN and MnS in typical non-oriented electrical steel grades produced by the CSP process have grown to some extent in the soaking stage, but the precipitation contents are less than 20% of the total contents of nitride and sulfide. The precipitate phase particles of AlN and MnS have precipitated almost after the hot rolling process. The precipitation contents are more than 80% of the total contents of nitride and sulfide, but it is very late for the precipitate phase particles to grow at the end of the hot rolling process.
文摘借助SEM、EDS及Image-Pro Plus 6.0图像分析软件,对不同热装温度下无取向硅钢铸坯中夹杂物的析出行为进行研究。结果表明,铸坯中MgS、AlN容易以硅酸铝、硅酸镁、硅酸铝镁氧化物为核心析出,且复合夹杂物的形状与其中MgS和AlN的含量有关,当AlN含量较高时,复合夹杂呈六棱柱状,当MgS含量较高时,复合夹杂一般呈球形。铸坯中硫化物主要以MgS的形式存在,少量以CaS形式存在,但试验钢中未检测到MnS。随着铸坯热装温度的降低,复合夹杂中MgS组分的含量增加,夹杂物平均尺寸也会随之增加,但CaS析出会对MgS的析出起抑制作用,热装温度可通过影响复合夹杂中AlN、MgS的析出来调控夹杂物尺寸。本试验条件下,最合适的铸坯热装温度为700℃,此时钢中尺寸小于0.5μm的微细夹杂物的数量最少。
基金the National Natural Science Foundation of China (Grant No. 50334010)the State Foundation for Key Projects: New Generation of Steels (Grant No. G1998061500)
文摘The existing forms of N and Al in HSLC (high strength low carbon) steel produced by TSCR (thin slab casting and rolling process), the precipitation thermodynamics and kinetics of AlN, and its effects on structure and mechanical property are studied. The experimental results show that only a small quantity of nitrogen is com- bined into AlN in HSLC steel produced by TSCR and most of the nitrogen in steel is still free nitrogen. Aluminum-nitride is mainly precipitated during the period of slow air cooling after coiling, but not during rolling and water cooling. The acid-soluble aluminum has no obvious effect on the grain size and mechanical property of HSLC steel produced by TSCR whose acid-soluble aluminum content is 0.005%―0.043%. The precipitation of AlN is not the main cause of grain refinement of HSLC steel produced by TSCR, nor is AlN the dominating precipitate that has precipitation strengthening effect. The nano nitrides are not pure AlN, but have complex compositions.
文摘In low carbon steels, dissolution and precipitation of the second phases such as carbides and nitrides during annealing cycles can affect the final structure and properties of the materials. The interaction of above processes depends on parameters such as reheating temperature, heating rate, annealing temperature, soaking time and finishing temperature in hot rolling stage before cold rolling. The effects of heating rate and annealing temperature on the microstructure and hardness were investigated. Two heating rates for annealing temperatures of 550, 610 and 720℃ were applied on cold-rolled specimens and St-14 low carbon steel, which were immediately quenched after isothermal annealing. The intercept method was used tO measure average grain sizes. However, resulted microstructures are dif- ferent for the two heating rates. While pancaked structures were observed in specimens annealed with low heating rate, in samples annealed with high heating rate, equiaxed microstructures were observed. Vickers micro-hardness values decreased at all temperatures, which were more significant at higher temperatures. At longer annealing time, signs of increase of hardness values were detected. All results and observations consistently suggest that a precipitati- on process has occurred concurrently with restoration processes during annealing. In addition, the energy dispersive spectroscopy analysis resulted from transmission electron microscopic micrographs have proved that the nano particles precipitated in grain boundaries are AlN.
基金This work was supported by the National Natural Science Foundation of China(Grant No.U20A20270).
文摘The composition,morphology,size,and number of inclusions in Fe-22Mn-xAl-0.7C(x=0.5%,5.2%,and 10.5%)lightweight steels after smelting and heat treatment experiments are characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy from both 2D and 3D perspectives.The inclusions are classified into eight categories according to chemistry and morphology.For the steel sample with a low Al content(0.5%),the inclusions are MnS,AlN-MnS,and Al_(2)O_(3)-MnS,among which Al_(2)O_(3)-MnS is the primary type.With the increase in Al content in the steel sample(to 5.2%),the populations of AlN and AlN-MnS inclusions of 1-3μm in diameter increase.A further increase in Al content(to 10.5%)leads to a significant decrease in the amount of AlN inclusions of 1-3μm in diameter,and an increase in the amount of AlN-MnS inclusions.The precipitation behavior during the phase transformation is also studied by FactSage 8.0 thermodynamic software,and a precipitation mechanism is proposed based on the calculation results.During the heat treatment,AlN inclusions re-precipitate out,due to the interactions between Al and dissolved N in the steel matrix.However,AlN inclusions cannot grow large because of unfavorable kinetic conditions.The re-precipitation phenomenon of AlN is predominant under low Al and high N conditions but not at high Al cases.
