Zhangjiagang, China
Zhangjiagang, China

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Shen K.,Control Iron and Steel Research Institute, China | Lu L.-H.,Jiangsu Shagang Group Co Ltd | Liao S.-L.,Control Iron and Steel Research Institute, China | Ma H.,Control Iron and Steel Research Institute, China
Cailiao Rechuli Xuebao/Transactions of Materials and Heat Treatment | Year: 2014

The austenitic grain size, CCT curve and TTT curve of Nb-V microalloyed high carbon steel were investigated. The effect of heating temperature, cooling rate and isothermal transformation temperature on microstructure and properties of the steel was studied. The results show that the furnace temperature must be controlled below 1100℃ to avoid the austenite grain coarsening, and the homogeneous sorbite and good properties can be obtained for the rolled steel under cooling rate from 1.0 to 2.5 K/s between 620 to 650℃ with initial cooling rate higher than 8 K/s before transformation. ©, 2014, Editorial Office of Transactions of Materials and Heat Treatment. All right reserved.

Jiang S.,Tsinghua University | Liu M.,Tsinghua University | Hao J.,Tsinghua University | Qian W.,Jiangsu Shagang Group Co.
Computers and Industrial Engineering | Year: 2015

Abstract A steelmaking-continuous casting (SCC) scheduling problem is an example of complex hybrid flow shop scheduling problem (HFSSP) with a strong industrial background. This paper investigates the SCC scheduling problem that involves controllable processing times (CPT) with multiple objectives concerning the total waiting time, earliness/tardiness and adjusting cost. The SCC scheduling problem with CPT is seldom discussed in the existing literature. This study is motivated by the practical situation of a large integrated steel company in which the just-in-time (JIT) and cost-cutting production strategy have become a significant concern. To address this complex HFSSP, the scheduling problem is decomposed into two subproblems: a parallel machine scheduling problem (PMSP) in the last stage and an HFSSP in the upstream stages. First, a hybrid differential evolution (HDE) algorithm combined with a variable neighborhood decomposition search (VNDS) is proposed for the former subproblem. Second, an iterative backward list scheduling (IBLS) algorithm is presented to solve the latter subproblem. The effectiveness of this bi-layer optimization approach is verified by computational experiments on well-designed and real-world scheduling instances. This study provides a new perspective on modeling and solving practical SCC scheduling problems. © 2015 Elsevier Ltd.

Ding M.,Control Iron and Steel Research Institute, China | Yu B.,Control Iron and Steel Research Institute, China | Sun L.,Control Iron and Steel Research Institute, China | Yu X.,Jiangsu Shagang Group Co.
Jinshu Rechuli/Heat Treatment of Metals | Year: 2014

Dilatometry was used to determine the phase transformation temperature of a high Ni-Cr centrifugal composite ductile cast iron rolls. Based on the critical transformation temperature, the ductile cast iron rolls were quenched and tempered, and effects of normalizing temperature and tempering temperature on microstructure and mechanical properties were investigated. The results show that hardness of the ductile cast iron roll is higher when normalized at 860-890℃. The amount of retained austenite increases when the normalizing temperature is above 890℃, which leads to obvious decrement of the hardness. When normalized at 830℃, pearlite with lower hardness forms. When normalized at 860℃ and tempered at 400℃, residual stress in the ductile cast iron roll was fully removed, and the fine carbides uniformly and dispersedly distribute in martensite and the hardness is relatively higher which is of benefit to restrain crack propagation. ©, 2014, Chinese Mechanical Engineering Society of Heat Treatment. All right reserved.

Guo H.,University of Science and Technology Beijing | Cheng J.,Jiangsu Shagang Group Co. | Yang S.,University of Science and Technology Beijing | He X.,University of Science and Technology Beijing
Journal of Alloys and Compounds | Year: 2013

Three ultra-low carbon steels with different additions of Cu and Nb are studied to figure out the influence of combined addition of Cu and Nb on the microstructure, hardness and precipitation behavior during tempering. TEM observation shows that the Cu and NbCN particles are distributed separately. The increase of Nb content significantly promotes the Cu precipitation and also accelerates coarsening. The addition of Cu slightly delays the coarsening of NbCN precipitates. The calculation shows that the strength increment due to the precipitation of NbCN is significantly higher than the strength reduction caused by the accelerated coarsening of Cu particles due to the combined addition of two elements. © 2012 Elsevier B.V.

Qian Y.,Jiangsu Shagang group Co. | Li X.,Jiangsu Shagang group Co.
Jinshu Rechuli/Heat Treatment of Metals | Year: 2012

The causes of furnace sow of Shagang roller hearth furnace were analyzed. That is because the tamping, accumulating and stacking of the hot rolled scale on the surface of steel plate and the slag on the edge of the steel plate after flame cutting on the surface of the roller under high temperature. Some countermeasures were put forward, such as replacing the furnace roller, checking the heavy plate carefully before heat treatment, improving shot blasting technology and charging schedule, controlling the furnace atmosphere and using the method of scrubbing the roller surface nodular, ect.

Song D.,Nanjing Southeast University | Song D.,Hohai University | Sun W.,Nanjing Southeast University | Jiang J.-Y.,Nanjing Southeast University | And 3 more authors.
Journal of Iron and Steel Research International | Year: 2016

A new low-cost corrosion-resistant rebar (HRB400R) was designed and fabricated by Cr micro-alloying. The HRB400R rebar had uniform distribution of Cr element in ferrite grains. The corrosion behavior of the rebar in the neutral Cl--containing environment was studied systematically, and the improved corrosion resistance of the HRB400R rebar was revealed. According to the corrosion-morphology observation and electrochemical monitoring during the constant immersion corrosion in the 3.5 mass% NaCl solution, the HRB400R rebar presented alleviated corrosion damage, nobler Ecorr, lower Icorr, and larger Rt values, and these phenomena were more remarkable in the initial corrosion period. The elevated electrode potential of the rebar, caused by the solid-solution of Cr micro-alloying in the ferrite grains, was the key to the corrosion-resistance improvement. The HRB400R rebar also presented much lower mass-loss rate in the salt spray corrosion test. Besides the elevated corrosion resistance of the matrix, the doping and enrichment of Cr element in the rust layer was another factor for the higher corrosion resistance, which retarded the penetration of aggressive medium through the rust layer. © 2016 Central Iron and Steel Research Institute.

Wang X.,Dalian University of Technology | Kong L.,Dalian University of Technology | Du F.,Dalian University of Technology | Yao M.,Dalian University of Technology | And 3 more authors.
ISIJ International | Year: 2016

The thermal resistances of the slag films and the air gap between the slab and the mold are important factors in heat transfer and lubrication control inside a continuous casting mold. The formation, evolution, composition and distribution of the slag film and air gap have significant influences on the initial solidification of the strand shell and slab quality. In this paper, based on experimentally measured thermocouple data and casting conditions, an inverse problem model of mold heat transfer is developed, with the purpose of accurately predicting the mold heat transfer states and slab solidification processes of actual casting conditions. Furthermore, a numerical model of the heat transfer between the air gap and the liquid/solid slag films is developed, based on analysis of the formation mechanism, distribution and heat transfer characteristics of the air gap and slag films. The non-uniform distribution of the thermal resistance of the air gap and the liquid/solid slag films, and the heat conduction and heat radiation inside them are simulated, which provide a theoretical foundation for exploring the complicated heat transfer behavior and surface crack prediction during the continuous casting process. © 2016 ISIJ.

Wang X.,Dalian University of Technology | Xiao P.,Dalian University of Technology | Yin S.,Dalian University of Technology | Yao M.,Dalian University of Technology | Zhang X.,Jiangsu Shagang Group Co.
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2014

Heat transfer and distortion of mould plates have a great impact on surface defects and cracks. Based on the measured data of online monitoring system for wide and thick continuous casting mould, the inverse mathematical model for mould heat transfer is built, in which the distribution of heat flux and temperature of mould plates is calculated from the measured temperatures. Through applying the inverse simulation results on the thermo-elastic-plastic model, the thermal behavior and distortion of mould plates are further investigated. The results indicate the distribution of mould temperature takes on a notably non-uniform characteristic and has an inherited tendency along the casting direction. Maximal distortion appears at the center area in wide faces, and decreases gradually towards slab corners. Along the width direction, plate distortion has the same trend with the profiles and fluctuations of mould temperatures. The analysis methods through combination of online measurement data with numerical simulation can reflect the non-uniform characteristics of mould process, and provide reliable basis for prediction of surface defects and process optimization. ©2014 Journal of Mechanical Engineering

Liu Y.,Dalian University of Technology | Wang X.-D.,Dalian University of Technology | Wang X.-D.,Jiangsu Shagang Group Co. | Yao M.,Dalian University of Technology | Zhang X.-B.,Jiangsu Shagang Group Co.
Journal of Iron and Steel Research | Year: 2015

Based on the measured temperature of thermocouple, the two-dimensional temperature and its change velocity at copper plate of mold during continuous casting process were visualized. The propagation behaviors of the temperature at copper plate of mold in time and space were considered synthetically during the formation and development of sticker breakout. The temperature, position and time at abnormal zone were extracted by virtue of 8 connected component labeling and boundary tracking algorithm in computer image processing. The average and maximum change velocities of the temperature as well as area, width, height, characteristics of vertical and horizontal propagation velocities of the zone were also calculated. The common features of samples of sticker breakout were analyzed by statistical induction during continuous casting process. The results show that the change velocity of the temperature, geometry characteristic and propagation velocity can be used as main criterions for online prediction of sticker breakout and are helpful to enhance the accuracy of prediction system of sticker breakout which can be used to decrease sticker breakout. Meanwhile, they offer the method and basis to develop a visual and intelligent monitoring technology for mold.

Xiao F.-R.,Yanshan University | Cao Y.-B.,Yanshan University | Qiao G.-Y.,Yanshan University | Zhang X.-B.,Jiangsu Shagang Group Co Ltd | Liao B.,Yanshan University
Journal of Iron and Steel Research International | Year: 2012

Nb is often considered to be a powerful alloying element for controlling the recrystallization process in microalloyed high strength steels. However, Nb can be presented either as solute in solution, where it is thought to exhibit a strong solute drag effect, or as NbC precipitates, which are thought to be effective at pinning grain boundaries. Therefore, it is very important to quantitatively measure Nb in solution or in NbC precipitates. A quantitative analysis method of Nb in solution and in precipitates was proposed. The test procedure involved chemical dissolution, filtration and inductively coupled plasma atomic emission spectroscopic (ICP-AES) analysis. The amount of Nb in solution in Nb-microallyed steels under different treatment conditions was evaluated. The results show that the niobium and carbon contents in steels have a great effect on niobium dissolution kinetics. The solute Nb is more effective to retard dynamic recrystallization, while the NbC precipitates are more effective to inhibit static recrystallization. The results may help to comprehend effect of Nb in steels, and provide some guides in the design of new high strength Nb-bearing steels. © 2012 Central Iron and Steel Research Institute.

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