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Fabrication of high nitrogen austenitic stainless steels with excellent mechanical and pitting corrosion properties

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International Journal of Minerals,Metallurgy and Materials 2009年第4期16卷 387-392页

作者： hua-bing li Zhou-hua jiang Yang Cao Zu-rui Zhang School of Materials and Metallurgy Northeastern University Shenyang 110004 China

A series of high nitrogen austenitic stainless steels were successfully developed with a pressurized electroslag remelting furnace. Nitride additives and deoxidizer were packed into the stainless steel pipes, and then the stainless steel pipes were welded on the surface of an electrode with low nitrogen content to prepare a compound electrode. Using Si3N4 as a nitrogen alloying source, the silicon contents in the ingots were prone to be out of the specification range, the electric current fluctuated greatly and the surface qualities of the ingots were poor. The surface qualities of the ingots were improved with FeCrN as a nitrogen alloying source. The sound and compact macrostructure ingot with the maximum nitrogen content of 1.21wt% can be obtained. The 18Cr18Mn2Mo0.9N high nitrogen austenitic stainless steel exhibits high strength and good ductility at room temperature. The steel shows typical ductile-brittle transition behavior and excellent pitting corrosion resistance properties.

关键词： high nitrogen austenitic stainless steels electroslag remelting nitrogen alloying ductile-brittle transition pitting corrosion resistance

Pitting corrosion and crevice corrosion behaviors of high nitrogen austenitic stainless steels

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International Journal of Minerals,Metallurgy and Materials 2009年第5期16卷 517-524页

作者： hua-bing li Zhou-hua jiang Yan Yang Yang Cao Zu-rui Zhang School of Materials and Metallurgy Northeastern University Shenyang 110004 China

Pitting corrosion and crevice corrosion behaviors of high nitrogen austenitic stainless steels （HNSS） were investigated by electrochemical and immersion testing methods in chloride solution, respectively. The chemical constitution and composition in the depth of passive films formed on HNSS were analyzed by X-ray photoelectron spectrum （XPS）. HNSS has excellent pitting and crevice corrosion resistance compared to 316L stainless steel. With increasing the nitrogen content in steels, pitting potentials and critical pitting temperature （CPT） increase, and the maximum, average pit depths and average weight loss decrease. The CPT of HNSS is correlated with the alloying element content through the measure of alloying for resistance to corrosion （MARC）. The MARC can be expressed as an equation of CPT=2.55MARC-29. XPS results show that HNSS exhibiting excellent corrosion resistance is attributed to the enrichment of nitrogen on the surface of passive films, which forms ammonium ions increasing the local pH value and facilitating repassivation, and the synergistic effects of molybdenum and nitrogen.

关键词： high nitrogen austenitic stainless steel pitting corrosion crevice corrosion nitrogen critical pitting temperature syner-gistic effect

Intergranular corrosion behavior of high nitrogen austenitic stainless steel

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International Journal of Minerals,Metallurgy and Materials 2009年第6期16卷 654-660页

作者： hua-bing li Zhou-hua jiang Zu-rui Zhang Yang Cao Yan Yang School of Materials and Metallurgy Northeastern University Shenyang 110004 China

The intergranular corrosion （IGC） behavior of high nitrogen austenitic stainless steel （HNSS） sensitization treated at 650-950℃ was investigated by the double loop electrochemical potentiodynamic reactivation （DL-EPR） method. The effects of the electrolytes, scan rate, sensitizing temperature on the susceptibility to IGC of HNSS were examined. The results show that the addi-tion of NaCl is an effective way to improve the formation of the cracking of a passive film in chromium-depleted zones during the reactivation scan. Decreasing the scan rate exhibits an obvious effect on the breakdown of the passive film. A solution with 2 mol/L H2SO4＋1 mol/L NaCl＋0.01 mol/L KSCN is suitable to check the susceptibility to IGC of HNSS at a sensitizing temperature of 650-950℃ at a suitable scan rate of 1.667 mV/s. Chromium depletion of HNSS is attributed to the precipitation of Cr2N which results in the susceptibility to IGC. The synergistic effect of Mo and N is suggested to play an important role in stabilizing the passive film to prevent the attack of IGC.

关键词： intergranular corrosion high nitrogen austenitic stainless steel sensitization passive film chromium depletion

High Nitrogen Austenitic Stainless Steels Manufactured by Nitrogen Gas Alloying and Adding Nitrided Ferroalloys

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Journal of Iron and Steel Research International 2007年第3期14卷 63-68页

作者： li hua-bing jiang Zhou-hua SHEN Ming-hui YOU Xiang-mi School of Materials and Metalllargy Northeastern University Shenyang 110004 Liaoning China

A simple and feasible method for the production of high nitrogen austenitic stainless steels involves nitrogen gas alloying and adding nitrided ferroalloys under normal atmospheric conditions. Alloying by nitrogen gas bubbling in Fe-Cr-Mn-Mo series alloys was carried out in MoSi2 resistance furnace and air induction furnace under normal atmospheric conditions. The results showed that nitrogen alloying could be accelerated by increasing nitrogen gas flow rate, prolonging residence time of bubbles, increasing gas/molten steel interfaces, and decreasing the sulphur and oxygen contents in molten steel. Nitrogen content of 0.69% in 18Crl8Mn was obtained using air induction furnace by bubbling of nitrogen gas from porous plug. In addition, the nickel-free, high nitrogen austenitic stainless steels with sound and compact macrostructure had been produced in the laboratory using vacuum induction furnace and electroslag remelting furnace under nitrogen atmosphere by the addition of nitrided alloy with the maximum nitrogen content of 0.81%. Pores were observed in the ingots obtained by melting and casting in vacuum induction furnace with the addition of nitrided ferroalloys and under nitrogen atmosphere. After electroslag remelting of the cast ingots, they were all sound and were free of pores. The yield of nitrogen increased with the decrease of melting rate in the ESR process. Due to electroslag remelting under nitrogen atmosphere and the consequential addition of aluminum as deoxidizer to the slag, the loss of manganese decreased obviously. There existed mainly irregular Al2O3 inclusions and MnS inclusions in ESR ingots, and the size of most of the inclusions was less than 5 um. After homogenization of the hot rolled plate at 1 150℃ × 1 h followed by water quenching, the microstructure consisted of homogeneous austenite.

关键词： nitrogen gas alloying nitrided ferroalloy high nitrogen austenitic stainless steel vacuum induction melting electroslag remelting

Effect of Grain Size on Mechanical Properties of Nickel-Free High Nitrogen Austenitic Stainless Steel

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Journal of Iron and Steel Research International 2009年第1期16卷 58-61页

作者： li hua-bing jiang Zhou-hua ZHANG Zu-rui YANG Yan School of Materials and Metallurgy Northeastern University Shenyang 110004 Liaoning China

The fine grained structures of nickel-free high nitrogen austenitic stainless steels had been obtained by means of cold rolling and subsequent annealing. The relationship between microstructure and mechanical properties and gain size of nickel-free high nitrogen austenitic stainless steels was examined. High strength and good ductility of the steel were found. In the grain size range, the Hall-Petch dependency for yield stress, tensile strength, and hardness was valid for grain size ranges for the nickel-free high nitrogen austenitic stainless steel. In the present study, the ductility of cold rolled nickel-free high nitrogen austenitic stainless steel decreased with annealing time when the grain size was refined. The fracture surfaces of the tensile specimens in the grain size range were covered with dimples as usually seen in a ductile fracture mode.

关键词： grain refinement strengthening nitrogen nickel-free high nitrogen austenitic stainless steel Hall-Petch equation

MIMO-OFDM channel estimation method utilizing correlation in time domain for B3G-TDD uplink

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The Journal of China Universities of Posts and Telecommunications 2007年第2期14卷 23-27页

作者： ZHOU Ming-yu li li-hua jiang Jun ZHONG Ming-hua TAO Xiao-feng Wireless Technologies Innovation Institute Beijing University of Posts and Telecommunications Beijing 100876 China

This article proposes a simple pilot-aided channel estimation method based on correlation in time domain for multiple-input and multiple-output olthogonal frequency division multiplexing （MIMO-OFDM） systems. Pilot symbols in all transmit antennas are generated from different circular shifting of a certain sequence. Through once correlation, the receiver can obtain time-domain pulse responses for channel fading from all transmit antennas to a certain receive antenna, from which channel estimation in frequency domain can be obtained. Beyond 3G time-division duplex （B3G-TDD） uplink is introduced, and the channel estimation method is used in it. Theoretical analysis and simulation are both carried out. Mean square error （MSE） performance shows that the method can exhibit precise estimation. Complexity analysis proves it requires very low complexity. System simulation result shows that it guarantees the performance of B3G-TDD uplink very well.

关键词： multiple-input and multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) channel estimation time-domain pulse response

Generation of Vibrational Entangled Coherent States of Two Trapped Ions

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Communications in Theoretical Physics 2005年第4X期44卷 712-714页

作者： liN li-hua jiang Yun-Kun YANG Zhen-Biao YE Sai-Yun Department of Electronic Science and Applied Physics Fuzhou University Fuzhou 350002 China

We propose a scheme for the generation of entangled coherent states for the center-of-mass and relative vibrational modes of two trapped ions. In the scheme the ions are simultaneously illuminated by a single standing-wave laser tuned to the carrier. The scheme allows the production of an entangled coherent states with a considerably high speed as long as a laser field of sufficiently high intensity is available.

关键词： entangled coherent state vibrational mode trapped ion

Aging Precipitation Behavior of 18Cr-16Mn-2Mo-1.1N High Nitrogen Austenitic Stainless Steel and Its Influences on Mechanical Properties

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Journal of Iron and Steel Research International 2012年第8期19卷 43-51页

作者： li hua-bing, jiang Zhou-hua, FENG Hao, MA Qi-feng, ZHAN Dong-ping (School of Materials and Metallurgy, Northeastern University, Shenyang 110819, liaoning, China) School of Materials and Metallurgy Northeastern University Shenyang 110819 Liaoning China

The solution-treated (ST) condition and aging precipitation behavior of 18Cr-16Mn-2Mo-1.1N high nitrogen austenitic stainless steel (HNS) were investigated by optical microscope (OM), scanning electron microscope (SEM), and transmission electron microscope (TEM). The results show that the ST condition of 18Cr-16Mn-2Mo-1.1N HNS with wN above 1% is identified as 1100 ℃ for 90 min, followed by water quenching to make sure the secondary phases completely dissolve into austenitic matrix and prevent the grains coarsening too much. Initial time-temperature-precipitation (TTP) curve of aged 18Cr-16Mn-2Mo-1.1N HNS which starts with precipitation of 0.05% in volume fraction is defined and the 'nose' temperature of precipitation is found to be 850 ℃ with an incubation period of 1 min. Hexagonal intergranular and cellular Cr2N with a=0.478 nm and c=0.444 nm precipitates gradually increase in the isothermal aging treatment. The matrix nitrogen depletion due to the intergranular and a few cellular Cr2N precipitates induces the decay of Vickers hardness, and the increment of cellular Cr2N causes the increase in the values. Impact toughness presents a monotonic decrease and SEM morphologies show the leading brittle intergranular fracture. The ultimate tensile strength (UTS), yield strength (YS) and elongation (El) deteriorate obviously. Stress concentration occurs when the matrix dislocations pile up at the interfaces of precipitation and matrix, and the interfacial dislocations may become precursors to the misfit dislocations, which can form small cleavage facets and accelerate the formation of cracks.

关键词： solution-treated condition aging precipitation behavior time-temperature-precipitation curve high nitrogen austenitic stainless steel mechanical property

Peakon Excitations and Fractal Dromions for General (2+1)-Dimensional Korteweg de Vries System

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Communications in Theoretical Physics 2007年第12期48卷 1063-1066页

作者： MA Song-hua li jiang-Bo FANG Jian-Ping College of Mathematics and Physics,lishui University,lishui 323000,China College of Mathematics and Physics Lishui University

By means of an extended mapping approach and a linear variable separation approach,a new family ofexact solutions of the general (2+1)-dimensional Korteweg de Vries system (GKdV) are *** on the derivedsolitary wave ex... 详细信息

关键词： extended mapping approach GKdV system peakon excitation fractal dromion