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Zhou F.,Wuhan University of Science and Technology | Zhou F.,Lianyuan Iron and Steel Co. | Wu K.,Wuhan University of Science and Technology | Zhou W.,Wuhan University of Science and Technology | And 2 more authors.
Journal of Coastal Research | Year: 2015

The relationship between microstructure and the mechanical properties of the X80 pipeline steels produced by an ultra fast cooling process was investigated using scanning and transmission electron microscopy and an energy dispersive spectrometer. Predominantly fine-grained acicular ferrite microstructure was obtained from the ultra fast cooling process. The developed X80 pipeline steel had low yield ratio and low temperature impact toughness. The ultra-fast cooling resulted in work hardened austenite before the phase transformation and also pushed the transformation to a lower temperature. Also, the Nb-Ti carbonitride precipitation was inhibited during ultra fast cooling. Therefore, the fine-grained microstructure and superior mechanical properties were attributed to grain refinement and the inhibiting of Nb-Ti carbontride precipitation, which was caused by ultra fast cooling. © 2015 Coastal Education and Research Foundation, Inc.

Luo Q.,Lianyuan Iron and Steel Co. | Lu D.,Zhangjiajie Institute of Aeronautical Engineering | Luo J.,Chongqing University
Advanced Materials Research | Year: 2010

In this paper, a new welding experiment is studied by applying an additional longitudinal electromagnetic field to CO2 welding process (abbr. LEM-CO2 welding).The characteristics of droplet transfer, macrostructure and microstructure are compared between LEM- CO2 welding and general CO2 welding on Q235 low carbon steel thick plate joint. The research results shows that, an additional longitudinal magnetic field can have a significant effect on properties of the droplet transfer in CO2 welding, the frequency and stability of the droplet transfer in LEM-CO2 welding are improved. The grains of welding seam are refined and welding joints has a higher quality. So the additional longitudinal magnetic field is a very simple and effective method to improve the properties of CO2 welding thick plate joint. © (2010) Trans Tech Publications.

Zhao G.,Chongqing University | Luo Q.,Lianyuan Iron and Steel Co. | Wang X.,Chongqing University | Luo J.,Chongqing University
Advanced Materials Research | Year: 2010

Numerical simulation and deposited experiment of MAG welding are carried out on the conditions of Electro-Magnetic Stirring (EMS) in this paper. Based on the research of EMS welding arc action, a simple EMS-MAG welding Gaussian distribution model using whole heat flux density is established, which MAG welding arc and droplet transfer are regarded as one integrated system. The important additional magnetic field parameter in EMS-MAG surfacing deposited welding is considered in this model. The computer-aided arc measurement system is used to analyze the effects of additional magnetic field in MAG welding. Effects of excitation current on welding penetration and width are analyzed by deposited experiments. Many deposited experiments are used to adjust model parameters and verify the simulation results. By defining key parameter and optimizing the model on the basis of experimental data, it can improve the simulation accuracy effectively. The results show that the established Gaussian distribution model can be used to simulate EMS-MAG welding process. © (2010) Trans Tech Publications.

Huang G.,Wuhan University of Science and Technology | Jiao G.,Lianyuan Iron and Steel Co. | Wen D.,Lianyuan Iron and Steel Co. | Zhou C.,Lianyuan Iron and Steel Co. | Wu K.,Wuhan University of Science and Technology
Advanced Materials Research | Year: 2011

The mechanical properties of the heat treated 65Mn steel that produced by CSP (Compact Strip Production) and conventional continuous casting process were investigated. Measured results showed that 65Mn steel produced by CSP exhibits higher hardness than that produced by conventional continuous casting process. The better mechanical property was attributed to fine-grained microstructures in the as-rolled CSP strips.

Zhu D.-Q.,Central South University | Xiao Y.-Z.,Central South University | Xiao Y.-Z.,Lianyuan Iron and Steel Company | Chun T.-J.,Central South University | Pan J.,Central South University
Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals | Year: 2013

The size of metal iron grain of low grade hematite during coal based direct reduction was tested using optical microscope and Leica image analysis software. The growth behavior of metal iron grain was investigated using Hillert grain growth dynamic model. The results show that the growth rate constant of metal iron grain is 1.155 μm2/minwhen reduced at 1200°C for 5-120 min. The relationship between the average size of metal iron grain D(μm) and reduction time t(min) is D=exp(0.565ln T+0.072) at reduction temperature of 1200°C. The relationship between the average size of metal iron grain D(μm) and reduction temperature T(K) is D=exp(-8995845ln T+8.899) when reduced for 120 min. The apparent activation energy of metal ferrous grain growth is 132.53 kJ/mol in a reduction temperature range from 1000°C to 1200°C.

Zhou F.,Wuhan University of Science and Technology | Zhou F.,Lianyuan Iron and Steel Co. | Wu K.-M.,Wuhan University of Science and Technology
Cailiao Gongcheng/Journal of Materials Engineering | Year: 2015

According to the NACE standard, the corrosion resistance of the new type ultra fast cooling process produced X80 pipeline steel to sulfide stress corrosion cracking (SSCC), hydrogen induced cracking (HIC) and CO2 was investigated. SSCC corrosion experiments show that critical cracking stress value is about 65%σs(390MPa), over the critical value, corrosion sensitivity of the test specimen becomes higher, and the corrosion resistance becomes poor. Under the 95% σs loading level, the stress sensitivity is extremely high. HIC corrosion experiments show that the crack sensitive percentage, the crack length percentage and the crack thickness percentage is all zero, CO2 corrosion resistance experiments show that when the pressure of CO2 is 0.1MPa, the average corrosion rate is 0.6843mm/a. The research shows that the X80 pipeline steel produced by the ultra fast cooling process have superior resistance to SSCC, HIC and CO2. ©, 2015, Beijing Institute of Aeronautical Materials (BIAM). All right reserved.

Qiao R.,Lianyuan Iron and Steel Co. | Guo G.,Lianyuan Iron and Steel Co.
Yejin Fenxi/Metallurgical Analysis | Year: 2014

Certified reference material of dolomite and limestone underwent direct compression, and the contents of calcium oxide, magnesium oxide and silicon dioxide were corrected by loss on ignition, so the calibration curve was plotted based on the correspondence between its content and intensity, and thus the method for the determination of three main components of dolomite and limestone by X-ray fluorescence spectrometry (XRF) was established. One portion of the sample could be determined after direct compression while another portion could be analyzed with the loss on ignition test, so the dosage of the certified reference materials could be significantly reduced. The tests on ignition time showed that when the analyte was burned for 0.5 h at 1100°C, its weight could become constant; and the tests on granularity showed that when the sample size surpassed 200 mesh, the granularity effect could be eliminated. Matrix correction with the CaO and MgO contents could eliminate its influence on low-content SiO2; and the adoption of experiential coefficient method can eliminate the absorption-enhancement effect among the elements. Precision test results indicated that calcium oxide, magnesium oxide and silicon dioxide measurement results had relative standard deviations (n=8) in the range of 0.03 8%-3.5%; certified reference materials of limestone and dolomite as well as actual samples were tested to determine the accuracy of the method, and it was found that the measured values were consistent with the certified values or those obtained by titration method.

Li G.,Wuhan University of Science and Technology | Xiao A.,Wuhan University of Science and Technology | Xiao A.,Lianyuan Iron and Steel Co. | Wen D.,Lianyuan Iron and Steel Co. | And 3 more authors.
Materials Science Forum | Year: 2010

Ti micro-alloyed high strength hot rolled steel was developed in Valin Lianyuan Steel in the CSP line. The cleanliness of liquid steel was good enough for thin slab casting after LF refining. The mould powder was adjusted for stabilizing the heat flux of thin slab continuous casting mould. Homogeneous microstructure consisting of ferrite and pearlite was obtained in the hot rolled steel plates by the improving of rolling process. The nano-scale precipitates of Ti(C, N) and Nb(C, N) is the main strengthening mechanism. The yield strength of developed hot rolled plate is higher than 660 MPa and the tension strength is 760 MPa. The ductile-brittle transition temperature is below -60 degree Celsius. The developed Ti alloyed steel with designed composition fulfils the requirements of 600 MPa grade steel for engineering machinery. © (2010) Trans Tech Publications.

Zeng B.,Lianyuan Iron and Steel Co. | Zeng B.,Control Iron and Steel Research Institute, China | Li Z.-D.,Control Iron and Steel Research Institute, China | Sun X.-J.,Control Iron and Steel Research Institute, China | And 2 more authors.
Journal of Iron and Steel Research International | Year: 2015

A novel hot rolled steel LG600A with the tensile strength exceeding 700 MPa was developed for automatic teller machine application. The low-cost C-Mn steel was microalloyed with 0.08 mass% - 0.12 mass% Ti rather than noble alloying elements, such as Nb, V, Mo, and Cu, etc. The novel steel had a good surface quality and welding property. After the hot rolled steel coils were leveled, the steel plates, the length of which was even down to 1500 mm, had an excellent flatness. The effects of hot rolling parameters on mechanical performance, microstructure and recrystallization behavior were studied. The metallurgical concept for the steel production was also discussed. The result shows that decreasing the finish rolling temperature, increasing cooling rate in the first cooling stage and decreasing the cooling rate in the last cooling stage, together with coiling at a modestly high coiling temperature all resulted in the refined grains and TiC precipitates, thereby improving the strength and toughness of this new steel greatly. © 2015 Central Iron and Steel Research Institute.

Zeng B.,Lianyuan Iron and Steel Co. | Zeng B.,Control Iron and Steel Research Institute, China | Li Z.-D.,Control Iron and Steel Research Institute, China | Sun X.-J.,Control Iron and Steel Research Institute, China | And 2 more authors.
Kang T'ieh/Iron and Steel | Year: 2016

51CrV4 steel has excellent heat treatment performance and mechanical properties, thus it has been widely used as high-grade spring steel. To improve the properties of the existing saw blade steel, 51CrV4 steel was innovatively developed for manufacturing diamond welded saw blade matrix in this paper based on its unique chemical composition. By studying the dynamic CCT diagram, the effect of coiling temperature on the microstructure and the second phase precipitates, and the effect of quenching and tempering processes on carbide particle size, grain size and mechanical properties, the feasibility of 51CrV4 steel used for welded saw blade was discussed. The results show that, with the increase of coiling temperature, the size of proeutectoid ferrite grain and the lamellar spacing of pearlite become large, and the proportion of the (V, Cr) C particles whose size is below 10 nm reduces in the total amount of MC precipitate; Quenching temperature increases from 800 to 900℃, the austenite grain size changes slowly at first and then quickly grows up, and more and more carbide particles dissolve in the steel, the hardness of the saw blade after tempering also is enhanced, while tempering temperature increases from 450 to 550℃, the lamellar cementite locating at the boundary of martensite lath is gradually spheroidized, and the strength decreases obviously while the plasticity was slightly improved; By an optimized coiling temperature to control the size of second phase carbides together with quenching at 850-900℃ and tempering at about 450℃, the 51CrV4 weld diamond saw blade with high hardness and high toughness can be prepared. © 2016, Chinese Society for Metals. All right reserved.

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