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.
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.
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.
Shen K.,Control Iron and Steel Research Institute, China |
Lu L.-H.,Jiangsu Shagang group Co. |
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.
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