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Mn-Series Low-Carbon Air-Cooled Bainitic Steel Containing Niobium of 0.02%

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Journal of Iron and Steel Research International 2010年第4期17卷 53-58页

作者： FENG Chun fang hong-sheng ZHENG Yan-kang BAI Bing-zhe Department of Materials Science and Engineering Tsinghua University Beijing 100084 China

A new hot rolled low-carbon air-cooled bainitic steel containing Nb of 0.02% has been developed based on alloying design of the grain boundary allotriomorphic ferrite （FGBA）/granular bainite （BG） duplex steel. The as-rolled microstructure and mechanical properties of bainitie steel containing Nb of 0. 02% were investigated by tensile test, optical microscopy （OM）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. The results show that adding 0.02 % of Nb obviously improves the strength without sacrificing toughness of the FGBA/BG steel. Adding 0.02% of Nb not only refines the grain boundary allotriomorphic ferrite grains but also promotes the refinement of granular bainite including its bainitic ferrite and M/A island. Any Nb（C,N） has been hardly observed in the steel containing Nb of 0.02%. It is suggested that the strengthening mechanism of Nb of 0.02% can be mainly attributed to the effect of Nb in solution （solute drag-like effect） on the phase transformation rather than the precipitation strengthening of Nb（C, N） particles.

关键词： low-carbon air-cooled bainitic steel niobium microstructure mechanical property

Effect of Chromium on CCT Diagrams of Novel Air-Cooled Bainite Steels Analyzed by Neural Network

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Journal of Iron and Steel Research International 2007年第4期14卷 39-42页

作者： YOU Wei XU Wei-hong LIU Ya-xiu BAI Bing-zhe fang hong-sheng Department of Mechanical and Electrical Engineering North China Institute of Science and Technology Beijing 101601 China Department of Electronics and Information Engineering North China Institute of Science and Technology Beijing 101601 China Department of Materials Science and Engineering Tsinghua University Beijing 100084 China

The quantitative effects of chromium content on continuous cooling transformation （CCT） diagrams of novel air-cooled bainite steels were analyzed using artificial neural network models. The results showed that the c... 详细信息

关键词： novel air-cooled bainite steel CCT diagram artificial neural network chromium content quantitative effect

A new development of Al-Ti-C grain refining master alloys

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中国有色金属学会会刊：英文版 2000年第3期10卷 298-303页

作者： ZHANG Bai qing(张柏清) LI Jian guo(李建国) MA hong tao(马洪涛) fang hong sheng(方鸿生) Tsing Hua Univ Dept Mat Sci & Engn Beijing 100084 Peoples R China

Al Ti C master alloys have been prepared with a novel production method. A combination of X ray phase analysis, SEM and EDS was used to examine the phases and microstructures of the master alloys. The master alloys have block like Al 3Ti particles and submicron size TiC X with X ranging from 0.49 to 0.78 and show excellent grain refining performance for commercially pure aluminum. Titanium carbides were observed at the crystallization centers in refined castings.

关键词： Al Ti C master alloy microstructure grain refinement

RBF-Type Artificial Neural Network Model Applied in Alloy Design of Steels

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Journal of Iron and Steel Research International 2008年第2期15卷 87-90页

作者： YOU Wei LIU Ya-xiu BAI Bing-zhe fang hong-sheng Department of Mechanical and Electrical Engineering North China Institute of Science and Technology Beijing 101601 China Department of Electronics and Information Engineering North China Institute of Science and Technology Beijing 101601 China Department of Materials Science and Engineering Tsinghua University Beijing 100084 China

RBF model,a new type of artificial neural network model was developed to design the content of carbon in low-alloy engineering *** errors of the ANN model are：MSE 0.052 1,MSRE 17.85%,and VOF 1.932 *** results obtaine... 详细信息

关键词： radial-basis-function, artificial neural network, carbon alloy design neurobalance

CCT Curves of Low-Carbon Mn-Si Steels and Development of Water-Cooled Bainitic Steels

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Journal of Iron and Steel Research International 2010年第3期17卷 46-50页

作者： XU Feng-yun WANG Yong-wei BAI Bing-zhe fang hong-sheng Key Laboratory for Advanced Materials of Ministry of Education Department of Materials Science and Engineering Tsinghua University Beijing 100084 China

CCT curves of Mn-Si steels with different manganese contents or carbon contents were determined. The results show that the transformation range of bainite can be separated from that of ferrite when the manganese content approaches a certain content, and the incubation period of ferrite increases more significantly than that of bainite transformation with the increase of carbon content in Mn-Si steels. Furthermore, water-cooled bainitic steels without adding expensive alloying element were developed. Granular bainite was obtained when a bar with diameter of 300 mm was cooled by water, and a mixed microstructure of granular bainite and martensite was obtained in watercooled plate with thickness of 40 mm. The developed water-cooled bainitic Steels containing no expensive alloying element showed a good combination of strength and toughness. The tensile strength, yield strength, and toughness （AKU at --20℃ ） of bar with diameter of 300 mm after water cooling were higher than 850 MPa, 620 MPa, and 65 J, respectively, and those of plate with thickness of 40mm after water cooling were higher than 1000 MPa, 800 MPa, and 50J, respectively.

关键词： bainitic steel water cooling granular bainite CCT curve Mn-Si steel

Creation of Air-Cooled Mn Series Bainitic Steels

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Journal of Iron and Steel Research International 2008年第6期15卷 1-9页

作者： fang hong-sheng FENG Chun ZHENG Yan-kang YANG Zhi-gang BAI Bing-zhe Department of Materials Science and Engineering Tsinghua University Beijing 100084 China

The development and mechanical performances of new type air-cooled Mn series bainitic steels including granular bainitic steels, FGBA/BG duplex steels, CFB/M duplex steels, medium carbon bainite/martensite steels, cast bainitic steels invented by the authors are summarized. The novel series of bainitic steels are alloyed with Mn, and several series bainitic duplex microstructures can be easily obtained under the condition of air cooling through unique composition design. The invented idea, the principle of alloying design, the strengthening mechanism, and the evolution of the microstructure of new type air cooled Mn series bainitic steels are presented. Furthermore, the applications in different fields of these Mn series air cooled bainitic steels with different strength level are also introduced. It is suggested that the significance of the development of the air cooled Mn series bainitic steel can be summarized as follows： reducing costs of both raw materials and production; good combination of strength and toughness; self-hardening with high bainitic hardenahility by air cooling from hot working without additional quenching-tempering treatment or quenching procedure; large savings in energy resources; and reduced environmental pollution.

关键词： bainite bainitic steel microstructure mechanical property air cooling

Influence of Nb on Microstructure and Property of Low-Carbon Mn-Series Air-Cooled Bainitic Steel

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Journal of Iron and Steel Research International 2010年第1期17卷 49-53页

作者： WANG Yong-wei FENG Chun XU Feng-yun BAI Bing-zhe fang hong-sheng Department of Materials Science and Engineering Tsinghua University Beijing 100084 China

The effect of Nb on the microstructure evolution of low-carbon Mn-series air cooled bainitic steels has been studied by using thermomeehanical simulation machine, SEM, and TEM observation. The results show that the amount of ferrites is relatively higher in the steel without Nb than that of Nb-bearing steel under same deformation conditions, and the ferrites in Nb-bearing steel are more finer. The mechanical properties of the Nb-bearing steel are higher than those of the steel without Nb at the same finishing rolling temperature （FRT）, and the toughness of the Nb- bearing steel is about 100J higher than that of the steel without Nh at the finishing rolling temperature 750℃. The toughness of Nb microalloyed steel will be improved more effectively than that of the steel without Nb with the decrease of FRT.

关键词： Mn-series bainitic steel grain boundary allotriomorphic ferrite finishing rolling temperature Nb microalloyed steel toughness

New Duplex Microstructure of Grain Boundary Allotriomorphic Ferrite/Granular Bainite

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Journal of Iron and Steel Research International 2002年第2期9卷 33-38页

作者： XU Ping-guang fang hong-sheng BAI Bing-zhe WANG Zhen-jia YANG Zhi-gang HUANG Jin-feng Tsinghua University Central Iron&Steel Research Institute

This was a feasibility study for a modified 304 steel resistant to stress corrosion cracking (SCC) in aqueous environment containing chloride. SCC tests were conducted potentiostaticaly with spot welded specimens, which had both crevice and residual stress, mainly in 3 % NaCl solution at various temperatures to determine the critical temperature for SCC at and below which the steel would not suffer from SCC. The effects of individual alloying element of silicon, manganese and copper on SCC of 18Cr 14Ni steels which phosphor content is 0.002 % and molybdenum content is 0.01 % were examined. Addition of 1 or 2 % of copper has beneficial effect on resistance to SCC, while increasing silicon or manganese content has no significant effect. Critical temperature of the steel with 0.002 % of phosphor and 2 % of copper is 150 ℃, which is markedly higher than 50 ℃ of 304L steel. However, the beneficial effect of copper is reduced with increasing phosphor content. From practical viewpoint, the modified steel with good SCC resistance should have 0.01 %-0.015 % of phosphor and 0.3 % or more of molybdenum, because it is very difficult to reduce phosphor content below 0 008 % industrially and such molybdenum content is inevitably introduced through cost saving melting process using return steel. Aluminium is to be added as another alloying element and 3 % of aluminium combined with 2 % of copper has been found to negate the deleterious effects of increased phosphor and molybdenum content. As a candidate steel at this stage, 14Cr 16Ni 0.013P 2Cu 1Al (0.3 1)Mo steel has critical temperature of 110 ℃.

关键词： austenitic stainless steel NaCl solution stress corrosion cracking

Effect of Tempering Temperature on Strength and Toughness of Novel Carbide-Free Bainite/Martensite Duplex Phase Steel

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Journal of Iron and Steel Research International 2002年第1期9卷 46-49页

作者： LIU Dong-yu BAI Bing-zhe fang hong-sheng YANG Zhi-gang ZHANG Chi YAN Wen-yan Tsinghua University

The microstructure in the weld metals for HQ130+QJ63 high strength steels, which are welded by Ar CO 2 gas shielded metal arc welding, was analyzed by means of microscope and scan electron microscope (SEM). The relative content of different microstructure was evaluated with XQF 2000 micro image analyzer. The effect of acicular ferrite content on the impact toughness was also studied. The test results indicated that the main microstructure in the weld metals of HQ130+QJ63 high strength steels is acicular ferrite and a few pro eutectic ferrite on the boundary of original austenite grain. Near the fusion zone there are columnar grains whose direction coefficient (X) is 3 22, but the microstructure in the center of the weld metal is isometric grain, whose direction coefficient X=1 In order to avoid welding crack and improve welding technology the weld heat input should be strictly controlled in 10-16 kJ/cm. Thus, the main microstructure in the weld metals is fine acicular ferrite and the content of pro eutectic ferrite is limited. The impact toughness in the weld metals of HQ130+QJ63 steels can be ensured and can meet the requirements for application in engineering and machinery.

关键词： high strength steel gas shielded metal arc welding weld metal micro image