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Three-stage niobium mineralization at Bayan Obo, China

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National Science Review 2024年第4期11卷 102-110页

作者： Yan Yu Yang Li Yu Liu Xiao-Xiao Ling Li-Guang Wu Li Yang Lan Yang Bo Yang Yong-Gang Zhao Xian-Hua Li State Key Laboratory of Lithospheric Evolution Institute of Geology and Geophysics Chinese Academy of Sciences College of Earth and Planetary Science University of Chinese Academy of Sciences Ministry of Education Key Laboratory of Orogenic Belts and Crustal Evolution School of Earth and Space SciencesPeking University Mining research institute Baotou Iron and Steel(Group) Co.LTD State Key Laboratory of Baiyunobo Rare Earth Resource research and Comprehensive Utilization

The Chinese Bayan Obo deposit is a world-class rare earth element(REE) deposit with considerable niobium(Nb) and iron(Fe) resources. A complete genetic understanding on all metals is fundamental for establishing genetic models at Bayan Obo. With extensive research being focused on REE enrichment, the timing and controls of Nb enrichment remain unresolved at Bayan Obo, which is mainly due to the challenges in dating, i.e. multistage thermal events, fine-grained minerals with complex textures and the rare occurrence of uranium-enriched minerals with mature dating methods. Based on robust geological and petrographic frameworks, here we conducted ion probe uranium-lead(U-Pb) dating of ferrocolumbite to unravel the timing, hence the genesis of Nb mineralization. Three types of hydrothermal ferrocolumbites—key Nb-bearing minerals—are identified based on their textures and mineral assemblages. They yield U-Pb ages of 1312.± 47 Ma(n = 99), 438 ± 7 Ma(n = 93), and 2.8 ± 5 Ma(n = 19), respectively. In line with deposit geology, we tentatively link the first, second and third stage Nb mineralization to Mesoproterozoic carbonatite magmatism, ubiquitous early Paleozoic hydrothermal activity, and Permian granitic magmatism, respectively. While quantifying the contribution of metal endowment from each stage requires further investigation, our new dates highlight that multi-stage mineralization is critical for Nb enrichment at Bayan Obo, which may also have implications for the enrichment mechanism of Nb in REE deposits in general.

关键词： niobium mineralization U-Pb dating ferrocolumbite Bayan Obo

Instrumented oscillographic study on impact toughness of an axle steel DZ2.with different tempering temperatures

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International Journal of Minerals,Metallurgy and Materials 2024年第7期31卷 1590-1598页

作者： Shuo Liu Peng Zhang Bin Wang Kaizhong Wang Zikuan Xu Fangzhong Hu Xin Bai Qiqiang Duan Zhefeng Zhang Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China Technology Center Ma'anshan Iron and Steel Co.Ltd.Ma'anshan 243000China

Compared with the conventional Charpy impact test method,the oscillographic impact test can help in the behavioral analysis of materials during the fracture *** this study,the trade-off relationship between the strength and toughness of a DZ2.axle steel at various tempering temperatures and the cause of the improvement in impact toughness was *** tempering process dramatically influenced carbide precipitation behavior,which resulted in different aspect ratios of *** toughness improved along with the rise in tempering temperature mainly due to the increase in energy required in impact crack *** characteristics of the impact crack propagation process were studied through a comprehensive analysis of stress distribution,oscilloscopic impact statistics,fracture morphology,and carbide *** poor impact toughness of low-tempering-temperature specimens was attributed to the increased number of stress concentration points caused by carbide morphology in the small plastic zone during the propagation process,which resulted in a mixed distribution of brittle and ductile fractures on the fracture surface.

关键词： axle steel DZ2 tempering process impact toughness oscillographic impact test impact crack propagation carbides

Influence of heat input on microhardness and microstructure across the welding interface between stainless steel and low alloy steel

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Baosteel Technical research 2024年第1期18卷 14-21页

作者： ZHU Min research institute Baoshan Iron&Steel Co.Ltd.Shanghai201999China

The welding interface is crucial to the service safety of dissimilar metal weld(DMW)joints between stainless steel(SS)and low alloy(LA)*** status of welding interfaces was prepared by cladding SS consumables to LA steel substrates with different heat inputs via tungsten inert gas arc welding(TIG),followed by a series of microstructural characterizations and hardness *** showed that a hardening and transition layer(TL)would be generated along the welding interface,and the width and hardening degree of the TL would increase with the heat ***,heavy load hardness tests showed that highly severe inhomogeneous plastic deformation and the microcrack would be generated in the interfacial region and the welding interface respectively in the highest heat input sample(1.03 kJ/mm).These results indicate that the increase in heat input would deteriorate the bonding performance of DMW *** microstructural observations showed that the higher hardening degree of the highest heat input sample was mainly attributed to the stronger grain boundary,solution,and dislocation strengthening effects.

关键词： welding interface transition layer heat input microstructure hardness

research and development of 3PP coating steel pipes

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Baosteel Technical research 2024年第2期18卷 1-11页

作者： FANG Wenqi MA Yuan HUI Linlin research institute Baoshan Iron&Steel Co.Ltd.Shanghai 201999China

The industrial application of an exterior three-layer anticorrosive polypropylene coating system(3PP)on large-diameter(larger than Φ600 mm)steel pipes was developed using an experimental process simulation study and the optimization of raw materials inspection,steel pipe surface pretreatments,and water cooling control on a coating application *** coating properties meet ISO standard 2.809 on buried or submerged 3PP pipelines used in the petroleum and natural gas *** scanning calorimetry and X-ray diffraction were used to analyze the crystallinities and grain sizes of polypropylene(PP)top coats with different cooling *** the melt cooling rate reduces the crystallinity and grain size of the PP top coat and enhances its strength and toughness.

关键词： 3PP steel pipe oil and gas pipelines cathodic disbondment polypropylene coatings exterior anticorrosive system

Influence of heat input on the microhardness and microstructure of the welding interface between nickel-based alloy and low-alloy steel

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Baosteel Technical research 2024年第3期18卷 33-38页

作者： ZHU Min research institute Baoshan Iron&Steel Co.Ltd.Shanghai 201999China

The evolution of microstructure and local properties near the welding interface is essential for the service safety of dissimilar metal welded joints between nickel-based alloy(NA) and low-alloy steel(LA).In this work,NA filler metal was deposited on LA substrate under different heat inputs by tungsten inert gas(TIG) *** characterization and microhardness tests were carried out near the prepared cladding *** and scanning electron microscopes show the lack of evident hardening transition layer along the welding *** the heat input increases,the mean hardness of the deposited layer also increases remarkably due to the rising dilution *** characterization shows a significant composition gradient across the cladding interface,but the diffusion gradient is limited to a small *** high heat input,a planar grain zone is generated along the interface due to the large temperature gradient across the interface region.

关键词： welding interface heat input microstructure microhardness

Creep property research of new martensite heat-resistant steel G115

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Baosteel Technical research 2024年第3期18卷 23-28页

作者： ZHAI Guoli research institute Baoshan Iron&Steel Co.Ltd.Shanghai 201999China

G115 steel was jointly developed by China iron & steel research institute Group Co.,*** Baosteel for usage in 600-650 ℃ ultrasupercritical boiler *** a hot extruded G115 tube,creep tests were conducted under a constant stress of 130 MPa and temperatures of 62.,650 and 675 ℃.Comparing creep curves under different temperatures,it is observed that the creep performance of a G115 tube is more sensitive to temperature than ***-state creep rates of creep specimens are significantly increased by enhancing the temperature.A micro-structural analysis of ruptured creep specimens under a stress of 130 MPa and temperatures of 650 ℃ and 675 ℃ was performed;the fracture mechanism of creep specimens under these two temperatures mainly included the appearance of creep holes on the grain boundary and a decrease in the martensite lath density.

关键词： G115 steel creep property steady-state creep rate

Effect of casting process on the inner-wall band segregation of high-strength antisulfur pipes

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Baosteel Technical research 2024年第1期18卷 27-36页

作者： LUO Ming ZHANG Zhonghua research institute Baoshan Iron&Steel Co.Ltd.Shanghai 201999China

Controlling inner-wall band segregation is one of the difficulties in the production of high-strength antisulfur *** tests were carried out on different casting processes(superheat,mold electromagnetic stirring,end electromagnetic stirring,casting speed and soft reduction)for the smelting of high-strength antisulfur *** microstructures of continuous-casting billets and hot-rolled or tempered pipes were analyzed using a metallographic microscope and scanning electron *** mechanism and evolution law regarding the inner-wall band segregation of high-strength antisulfur pipes were studied,and the influence of different casting processes was explored.

关键词： high strength antisulfur pipe casting process spot segregation band segregation

Study on the high-temperature properties of heat-resistant steel 309S

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Baosteel Technical research 2024年第3期18卷 16-22页

作者： HUANG Junxia BI Hongyun LI Shi research institute Baoshan Iron&Steel Co.Ltd.Shanghai 201999China

The properties of heat-resistant steel 309S at elevated properties were *** results revealed a rapid decrease in the short-time tensile strength at elevated *** 1 000 ℃,the yield strength and tensile strength are 14% and 7% of their respective values at room temperature,*** creep rupture strength was inferred in terms of the relationship between stress and duration time at high *** 1 000 h,the creep rupture strength is 37.98 MPa at 800 ℃,12.63 MPa at 900 ℃,and 7.2. MPa at 1 000 ℃.The fractures occurring at these high temperatures were intergranular in *** the experimental condition,the fatigue limit stress is 2. *** number of fatigue cycles and crack growth time decrease with increasing *** morphology analysis shows that the fatigue cracks initiate on the surface of the sample and propagate through transgranular expansion.

关键词： strength at elevated temperature creep rupture strength fatigue limit stress

Numerical simulation of the influence factors of NO_(x) emission on a W-type radiant tube

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Baosteel Technical research 2024年第1期18卷 1-7页

作者： LIU Yanyan research institute Baoshan Iron&Steel Co.Ltd.Shanghai 201999China

The radiant tube burner was modeled and analyzed by the numerical simulation method to investigate the influence factors and rules of NO_(x) emissions in a W-type radiant *** factors,which include air preheating temperature,excess air coefficient,and fuel gas composition,were modified to study their effects on NO_(x) emissions under varying working *** results were compared with the theoretical calculation value based on chemical reaction equilibrium theory and the onsite experimental value to verify the simulation *** results show that NO_(x) emissions rise with increasing air preheating ***_(x) production increases to an extreme value and then decreases during the oxygen-poor to oxygen-enriched process with the rise of the excess air *** the proportion of coke oven gas in the fuel gas raises the combustion temperature as well as the NO_(x) *** the thermal efficiency and NO_(x) emissions should be ***,the recommended values based on the simulation results are as follows:the air preheating temperature should not exceed 400℃,the excess air coefficient should be between 1.1 and 1.2.and the volume fraction of the coke oven gas should not exceed 30%.

关键词： W-type radiant tube NO_(x) combustion numerical simulation