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Li G.-P.,Shanxi Taigang Stainless Steel Co. | Li G.-P.,Taiyuan Iron & Steel Group Co. | Pei H.-X.,Shanxi Taigang Stainless Steel Co. | Li J.-C.,Shanxi Taigang Stainless Steel Co. | Zhang S.-L.,Shanxi Taigang Stainless Steel Co.
Gongcheng Kexue Xuebao/Chinese Journal of Engineering | Year: 2016

The precipitation behavior of σ phases in W-containing S32760 super duplex stainless steel was studied by aging treatment experiments. The morphology and chemical composition of the σ phases were investigated by scanning electron microscopy and transmission electron microscopy. The effects of the σ phases on the mechanical properties and corrosion resistance of the stainless steel were analyzed additionally. The σ phases composed of Fe-Cr-Mo-W have a tetragonal structure and abundantly precipitate at 850-1000℃ in the stainless steel with quite high strength and hardness and extremely poor plasticity, for example, the elongation is lower than 4.0%. There are still a few of σ phases at 1050℃, though the elongation increases to 31.1%, the values of impact toughness are discrete, and the average impact energy is low. Until 1080℃, the σ phases completely dissolve to the matrix. The tensile strength and the elongation are 640 MPa and 35.5%, and the longitudinal and the transverse impact energies averagely reached to 217 J and 110 J, respectively. As the treatment temperature increasing, the pitting potential (Eb) improves, and the mass loss rate of pitting corrosion decreases. The pitting potential of the stainless steel treated at 1080℃ is up to 1246 mV, while the mass loss rate decreases only to 0.005-0.007 g·m-2·h-1 when being soaked in a 3.5% NaCl solution at 50℃. © All right reserved.

Hu S.,Taiyuan Iron & Steel Group Co. | Chen H.,University Of Science And Technology Liaoning | Li S.,University Of Science And Technology Liaoning | Tang G.,Beijing Institute of Technology
Jinshu Rechuli/Heat Treatment of Metals | Year: 2015

Hot deformation behaviors of high carbon alloy steel 75Cr1 were investigated on Gleeble-3800 simulator at the temperature range of 800-1100 ℃ and strain rate range of 1-30 s-1. Experimental results show that the deformation resistance increases with the increase of strain rate and decrease of temperature; By using the linear regression analysis, the calculated hot deformation activation energy Qd of the 75Cr1 steel is 264 kJ/mol. Based on the stored energy evolution, the critical strain point of 75Cr1 steel was found and the expressions of dynamic recrystallization fraction XD of 75Cr1 steel were calculated under the different deformation conditions. ©, 2015, Chinese Mechanical Engineering Society of Heat Treatment. All right reserved.

Sun W.,Taiyuan University of Technology | Xue Y.,Taiyuan University of Technology | Xue Y.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research | Ren X.,Taiyuan Iron & Steel Group Co.
Emerging Economies, Risk and Development, and Intelligent Technology - Proceedings of the 5th International Conference on Risk Analysis and Crisis Response, RACR 2015 | Year: 2015

With the rapid development of Coal-Bed Methane (CBM) industry, ecological environment has been seriously destroyed. The assessment of ecological risk becomes increasingly significant. Therefore, the paper firstly defines the concept of ecological risk based on the industrialization development of CBM from the perspective of disaster system theory. And then, it analyzes the influencing factors according to the logical frame of hazard-induced Environment (E), Caused-hazards (C), hazard-affected Bodies (B) and disaster Losses (L). Besides, the paper constructs the index system of ecological risk assessment. Most importantly, it lays the basis for further research to construct quantified models of ecological risk based on the industrialization development of CBM. © 2015 Taylor & Francis Group, London.

Zhang T.,Taiyuan University of Technology | Wang W.,Taiyuan University of Technology | Wang Z.,Taiyuan Iron & Steel Group Company Ltd | Yan Z.,Taiyuan University of Technology | And 2 more authors.
China Welding (English Edition) | Year: 2015

The microstructure, mechanical and corrosion resistance properties of 445J2 ultra pure ferritic stainless steel thin plate joints conducted by the pulsed current gas tungsten arc welding (PCGTAW) were discussed in this paper. In order to avoid weld defects, the appropriate welding process was adjusted. The joints were subjected to optical microscopy, transverse static tensile, plastic deformation, intergranular corrosion and electrochemistry corrosion tests. The results indicated that the weld zone (WZ) is characterized with columnar grains and equiaxed grains and the heat-affected zone (HAZ) shows coarse ferrite grains due to the rapid solidification of thin plate welding. The PCGTAW joint exhibited acceptable mechanical properties and equivalent corrosion resistance properties as the base metal. Copyright: © 2015 Editorial Board of CHINAWELDING.

Li D.,North University of China | Li D.,Taiyuan Iron & Steel Group Co. | Li D.,Tianjin University | Li X.,North University of China | And 4 more authors.
Chinese Journal of Mechanical Engineering (English Edition) | Year: 2015

There are few relevant researches on coils by tempering, and the variations of microstructure and properties of steel coil during the tempering process also remain unclear. By using thermo-mechanical control process (TMCP) technology, Mn-Ti typical HSLA steel coils with yield strength of 920 MPa are produced on the 2250 hot rolling production line. Then, the samples are taken from the coils and tempered at the temperatures of 220 ℃, 350 ℃, and 620 ℃ respectively. After tempering the strength, ductility and toughness of samples are tested, and meanwhile microstructures are investigated. Precipitates initially emerge inside the ferrite laths and the density of the dislocation drops. Then, the lath-shaped ferrites begin to gather, and the retained austenite films start to decompose. Finally, the retained austenite films are completely decomposed into coarse and short rod-shape precipitates composed of C and Ti compounds. The yield strength increases with increasing tempering temperature due to the pinning effect of the precipitates, and the dislocation density decreases. The yield strength is highest when the steel is tempered at 220 ℃ because of pinning of the precipitates to dislocations. The total elongation increases in all samples because of the development of ferrites during tempering. The tensile strength and impact absorbed energy decline because the effect of impeding crack propagation weakens as the retained austenite films completely decompose and the precipitates coarsen. This paper clarifies the influence of different tempering temperatures on phase transformation characteristics and process of Mn-Ti typical multiphase steels, as well as its resulting performance variation rules. © Chinese Mechanical Engineering Society and Springer-Verlag Berlin Heidelberg 2015

Zeng L.,Taiyuan Iron & Steel Group Co Ltd | Zhang W.,Taiyuan Iron & Steel Group Co Ltd | Wang Y.,Taiyuan Iron & Steel Group Co Ltd
Cailiao Rechuli Xuebao/Transactions of Materials and Heat Treatment | Year: 2015

Microsegregation behavior of Cr20Ni24Mo6N steel during solidification was studied by means of SEM, TEM and EDS analysis. Phase precipitation behavior of the steel was revealed by theoretrical analysis using Thermal-Calc software. Element diffusion was analyzed based on the calculation of residual segregation parameter formula. The influence of homogenizing parameters on element redistribution was discussed. The results show that Cr20Ni24Mo6N steel exhibits severe segregation of Mo. The main precipitation is σ-phase. Residual segregation parameter decreases by increasing temperature and holding time. The homogenizing parameters for the elemination of element segregation is annealing at 1250℃ for 24 h. ©, 2015, Editorial Office of Transactions of Materials and Heat Treatment. All right reserved.

Hao W.,Taiyuan Iron & Steel Group Co. | Xue S.,Taiyuan Iron & Steel Group Co.
Xiyou Jinshu Cailiao Yu Gongcheng/Rare Metal Materials and Engineering | Year: 2015

The high-temperature oxidation behaviors of GH4700 alloy were studied by means of XRD, SEM and EDS. The results indicate that the oxidation kinetics obey parabolic law in a temperature range of 800 to 900℃, and the growth of the oxide film is controlled by the diffusion of oxygen in the film; the oxidation scale formed for 100 h consists of three parts, and the addition of Nb can effectively improve the oxidation resistance properties. Copyright © 2015, Northwest Institute for Nonferrous Metal Research. Published by Elsevier BV. All rights reserved.

Shu W.,Taiyuan Iron & Steel Group Co. | Li J.,Taiyuan Iron & Steel Group Co. | Lian X.-J.,Taiyuan Iron & Steel Group Co. | Wang X.-M.,University of Science and Technology Beijing
Gongcheng Kexue Xuebao/Chinese Journal of Engineering | Year: 2015

The effect of heat treatment on the high temperature ductility of 00Cr24Ni13 austenitic stainless steel casting billets was investigated by heat treatment experiment, thermo-compression test and thermal tensile test. The result showed that δ ferrite morphology in the casting billet could be significantly changed through the heat treatment process. After air cooling from 1200 ℃ for 3 h, large area of continuous reticular δ ferrite in the casting billet completely changed into dispersed granular phases. Compared with the casting billet before heat treatment, heat-treated samples which are composed of granular δ ferrite had a higher value of deformation resistance at different compression temperatures, but there was no sharp deterioration in deformation resistance, the thermal simulation tensile strength remained almost the same and the reduction of area (Z) at the same temperature increased obviously. The temperature region of Z≥60% extended from 1150-1280 ℃ to 1050-1300 ℃, and the high plasticity (Z≥80%) range is about 150 ℃ (1150-1300 ℃). ©, 2015 All right reserved.

Li Y.,Taiyuan Iron & Steel Group Co. | Wang Y.,Taiyuan Iron & Steel Group Co. | Li S.,Taiyuan Iron & Steel Group Co.
Xiyou Jinshu Cailiao Yu Gongcheng/Rare Metal Materials and Engineering | Year: 2015

The effect of cold processing deformation, annealing temperature and annealing time on the microstructure and mechanical properties of 617B alloy was studied. The results show that with the increase of deformation, grains are elongated along the direction of maximum principal strain to form a deformed strip belt, the tensile strength and yield strength of the alloy at room temperature gradually increase, while the elongation decreases. When the annealing temperature increases from 1080℃ to 1160℃, the grains of the alloy gradually grow up, the tensile strength and yield strength are reduced, and the ductility is improved. When the annealing temperature of 1160℃ continues to increase, the grain growth velocity increases obviously, while the strength and plasticity changes little; grain growth activation energy (Q) of the alloy with different deformation amounts is much higher than that of pure Ni, and the Q value increases first s and then decreases with the amount of deformation increasing; the grain growth exponent η of the alloy increases first and then decreases with the increase of annealing temperature. Copyright © 2015, Northwest Institute for Nonferrous Metal Research. Published by Elsevier BV. All rights reserved.

Yu J.M.,North University of China | Li X.B.,North University of China | Zhang Z.M.,North University of China | Wang Q.,North University of China | And 2 more authors.
Materials Science Forum | Year: 2016

The multi-pass hot compression deformation behavior of the cast alloy with the composition of Mg-13Gd-4Y-2Zn-0.6Zr, was investigated, and the four-pass compression tests were conducted at the temperatures ranging from 350℃ to 500℃ and strain rate 0.01 s-1. The experimental results showed that the alloys incurred different degrees of softening by multipass deformation. The microstructure evolution for the deformed alloy was investigated, the influence of the microstructure on the hardness properties of the alloy discussed. The tests reveal that dynamic recrystallization is not the main softening mechanism for this alloy; rather, kink deformation refines the grains to achieve the observed softening effect. The hardness test curve showed that the hardness increased gradually with an increasing number of deformation passes. The improvement of the main mechanical properties related to the strengthening by the grain refinement. In multipass deformation, the misorientation of the kink belt gradually increased,and refined the grains. On the other hand, the grain size of the eutectic phase at the grain boundary decreased with increase of deformation passes. In addition, the mechanical properties were improved by the distribution dispersion of tiny cuboidal particles and acicular-like phases in the matrix. © 2016 Trans Tech Publications, Switzerland.

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