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Hu Z.,Nanjing Iron and Steel United Co. | Yang C.,Research Institute of Wuhan Iron and Steel Group Co.
Steel Research International | Year: 2015

The influences of Ti-Al complex deoxidation inclusions on nucleation of intragranular acicular ferrite (IAF) in C-Mn steel have been investigated based on four specimens with different Ti and Al contents. The inclusions of Steel 1 and Steel 2 both containing high Al are detected as Al2O3 and Ti3O5·Al2O3, respectively. Owing to the low concentration of Mn in these inclusions, the manganese depletion zones (MDZs) which act as predominant driving force of IAF nucleation could not form easily. In Steel 3, Ti3O5-MnS is found as the main inclusion, which could be considered as potent nucleus. However, the excessive Ti leads to the aggregation of numerous inclusions less than 1μm at grain boundaries, consequently restraining the nucleation of IAF. The main inclusions of Steel 4 containing low Al and medium Ti are found as Ti3O5·Al2O3·MnO, which effectively facilitate IAF nucleation. The size of inclusions mainly distributes in optimum zone corresponding to the maximum possibility of IAF nucleation. Therefore, the Al should be controlled as low as possible to ensure the nucleating effectivity of inclusion. While Ti should be appropriately controlled at medium level to distribute the inclusion size in the optimum zone to obtain well-developed microstructures of IAF in C-Mn steel. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Jin X.,Chongqing University | Jin X.,Nanjing Iron and Steel United Co. | Chen D.,Chongqing University | Xie X.,Chongqing University | And 2 more authors.
Steel Research International | Year: 2013

This study aims to propose suitable simulation methods, which enable to reduce the major differences between water model and real caster, such as the gradually decreased flow space, flow mass in the casting direction, and the momentum decay in the mushy zone. With consideration of solidified process, the method is concerned with the change of flow space and flow mass at the casting direction in water model. The level fluctuations, stimulus-response curves, velocities of liquid surface, and distributions of liquid slag have been changed in the water model to study the differences of flow character and the variation of fluid flow in molds. The mold with a solidified shell leads to significant differences in flow behaviors, such as higher level fluctuations, higher surface velocities, and worse liquid slag distributions. Neglecting the solidified shell causes unrealistic lower surface velocities and level fluctuations in water model. The mold with consideration of flow mass balance has higher level fluctuations and surface velocities than the mold without shell, and has lower level fluctuations and surface velocities than that of mold with a shell. The results indicate that it is necessary for water model to take the solidified process into account to acquire more accurate and reliable experiment results, especially for thinner slab. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Duan Z.-T.,Northeastern University China | Li Y.-M.,Northeastern University China | Zhu F.-X.,Northeastern University China | Zhang H.-Y.,Northeastern University China | Cheng K.-R.,Nanjing Iron and Steel United Co.
Jinshu Rechuli/Heat Treatment of Metals | Year: 2012

The microstructure and mechanical properties of a Q690D high strength steel quenched at different temperatures were investigated. The results show that when the quenching temperature is between 890°C and 970°C, with increasing quenching temperature, the strength of the tested steel increases firstly then decreases and the maximum value reaches at 930°C, and variation of the impact toughness and elongation are inverse compared with the strength. When the quenching temperature is in the range from 890°C to 970°C, the mechanical properties of the tested steel could meet requirement of Q690D steel. The grain size of prior austenite is in range from 13.2 μm to 35.3 μm with increasing quenching temperature. The coarse lath-like microstructure can be obtained from coarse austenite grain after quenching.

Lu Z.-A.,Tongji University | Wu L.-J.,Tongji University | Zhou W.-G.,Tongji University | Sun G.-P.,Tongji University | Xiong L.-Y.,Nanjing Iron and Steel United Co.
Kang T'ieh/Iron and Steel (Peking) | Year: 2010

According to the actual situation of No.2 blast furnace in Nanjing Iron and Steel United Co., LTD., the thermal analysis and intelligent monitor of new type cast copper stave located in the furnace belly and bosh were carried out. With the help of the measuring point temperature of cooling stave body and its rib, simultaneously, artificial neural network was introduced into the numerical simulation of blast furnace. The simulation software which has the define intelligence to acknowledge and simulate the characteristics of the actual object makes the prediction to the maximum temperature and slag thickness of cooling stave hot surface come true by the combination of the heat transfer analysis and artificial neural network. Consequently, the blast furnace shape and trend are clear at a glance for the BF operators.

Qing G.-L.,Shougang Institute of Technology | Qing G.-L.,University of Science and Technology Beijing | Wang C.-D.,Nanjing Iron and Steel United Co. | Hou E.-J.,Anshan Iron and Steel Group Corporation | And 3 more authors.
Journal of Iron and Steel Research | Year: 2014

Increasing iron grade, lowering silicon content and improving metallurgical property was the main direction of blast furnace beneficiated burden. The reduction swelling index and effect of MgO content on compressive strength and metallurgical performance of low silicon pellet were studied. The results show that, low silicon pellet has high iron grade and low gangue, however the reduction swelling index will deteriorate with decrease of silicon content which influence blast furnace operation. The reduction swelling index of low silicon pellet can be improved by increasing of MgO content, and reducibility and smelting performance also can be improved at the same time. While SiO 2 content is lower than 2%, the reduction swelling index is higher than 60% and it can be lowered to less than 20% after MgO content is increased to 2. 15%. The compressive strength of low silicon pellet will decrease with increase of MgO content, however higher firing temperature can form stable and uniform magnesium ferrite which is useful to increase the compressive strength of low silicon magnesium pellet. The firing temperature should be increased to 1270 °C , while MgO content is 2.15% , and 1300 °C of temperature is needed for pellet contains 2. 8% MgO.

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