To reveal the law governing V-Ti precipitation behavior in warm-rolled transformation-induced plasticity (TRIP) steel, two steel samples including 0.072V-0.051Ti steel (Bear-V-Ti steel) and 0.001V-0.001Ti steel (Free-V-Ti steel) are designed. Based on a comparative analysis, the former has an excellent combination of mechanical properties including a total elongation (TE) of 37%, ultimate tensile strength (UTS) of 935 MPa, and UTS × TE of 34 GPa•% after annealing at a temperature of 650°C. The superior mechanical properties are attributable to particles that precipitate in a composite form of (V-Ti)C/N at 650°C. These particles can refine the grains and improve the tensile strength of Bear-V-Ti steel. However, it should be noted that the two roles of precipitates in steel are size dependent. For sizes between 10-20 nm, the role mainly entails pinning the dislocation. This accounts for the precipitation strength. As the size increases to 20-60 nm, the role mainly involves pinning of the grain boundary, which leads to fine crystal reinforcement. These results provide useful data for the production of medium manganese steel using the warmrolled process.
To efficiently extract nickel from low grade limonitic laterite ore, a separation method of iron-nickel alloy nugget by selfreduction of coal composite limonitic laterite ore briquette was investigated. In this investigation, in order to decrease the separation temperature of iron-nickel alloy nugget, the selective reduction by control of C/O ratio was introduced and reductant added in the briquette was inadequate for the reduction of nickel and iron. Nickel was preferentially reduced in the reduction process, while iron was partially reduced due to the lack of reductant. After reduction, a certain amount of FeO existed in the reduced product. This residual FeO had a great role in the formation of low melting point slag, which could promote the formation and the separation of iron-nickel alloy nugget at relatively low temperature. In this investigation, the reduction experiments were all conducted at 1300°C. To evaluate the formation and the separation of iron-nickel alloy nugget in the reduction process, we observed the patterns of reduced products under different C/O ratio, CaO addition ratio and holding time conditions. And then the effect of C/O ratio and CaO addition ratio on nickel content of nugget and nickel recovery ratio were investigated. The results showed that 0.7 of C/O ratio, 8% of CaO addition ratio and 40min of holding time were suitable for the separation of iron-nickel alloy nugget from limonitic laterite ore. Nickel and iron content of the nugget and the nickel recovery ratio were 4.75%, 89.51% and 85%, respectively. Nuggets were easily separated from slag by crushing and screening. This separation method could be applied to any limonitic laterite ore by adjusting C/O ratio and CaO addition ratio.
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