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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 co.sumables 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

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 co.fficient,and fuel gas co.position,were modified to study their effects on NO_(x) emissions under varying working *** results were co.pared 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 co.e oven gas in the fuel gas raises the co.bustion temperature as well as the NO_(x) *** the thermal efficiency and NO_(x) emissions should be ***,the reco.mended values based on the simulation results are as follows:the air preheating temperature should not exceed 400℃,the excess air co.fficient should be between 1.1 and 1.2,and the volume fraction of the co.e oven gas should not exceed 30%.

关键词： W-type radiant tube NO_(x) co.bustion numerical simulation

Investigation and improvement of tiny spot defects on hot-dip galvanized automotive steel sheets

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Baosteel technical Research 2024年第2期18卷 32-38页

作者： GE Zhiyong YANG Bo YANG Jiwu Baosteel Zhanjiang Iron&steel co. Ltd.Zhanjiang 524072GuandongChina

The causes of tiny spot defects on the surface of hot-dip galvanized automotive steel sheets were studied using scanning electron microsco.y(SEM)and energy dispersive spectrometer(EDS),and effective co.trol measures were *** results show that rubbing against the top roller after galvanizing is easy due to the local thickness of tiny spot defect location co.ting;therefore,the surface morphology is different from the normal *** kinds of defects,namely zinc slag,small slivers,and pitting,are likely to cause local thickening of the co.ting after galvanizing,leading to the formation of tiny ***,resolving the three types of defects can effectively co.trol the generation of tiny spot *** them,due to the hereditary nature of the small sliver defect,focusing on its co.trol and supervision is necessary.

关键词： hot-dip galvanizing tiny spot zinc slag pitting small sliver

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

co.trolling 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 co.tinuous-casting billets and hot-rolled or tempered pipes were analyzed using a metallographic microsco.e 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

Geometrical transition properties of vortex cavitation and associated flow-choking characteristics in poppet valves

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第6期25卷 455-469页

作者： Liang LU Zhongdong LIANG Yuming LIU Zhipeng WANG Shohei RYU School of Mechanical Engineering Tongji UniversityShanghai 201804China Frontiers Science center for Intelligent Autonomous Systems Tongji UniversityShanghai 201210China technical Research Laboratory Hitachi Construction Machinery Co.Ltd.Tsuchiura 300-0013Japan

Poppet valves have beco.e increasingly significant in ensuring precise digital flow rate and pressure co.trol in hydraulic systems,necessitating a more profound understanding of the geometrical properties of cavitation in them,as well as associated flow-choking *** a co.parative analysis with experimentally observed cavity images,we found that large eddy simulation(LES)turbulence modeling effectively replicates the geometrical properties of cavitation in these *** analysis demonstrated that cavitation is generated from vortices that result from the interaction between the notch co.tracta flow and the surrounding fluid *** in the internal or external vena co.tracta co.ditions result in fixed or discrete cavities,and the length-to-diameter ratio serves as a measure of the transition between internal and external vena co.tracta flow *** study establishes a threshold length-to-diameter ratio of approximately 2 for the tested poppet *** specifically,in notch structures with a smaller valve opening,longer sealing length,and smaller throttling angle(co.responding to a larger length-to-diameter ratio),the liquid-to-vapor transfer process is more evident than that in the reverse direction.A long-standing vapor cavity beco.es fixed inside the notch,leading to a more pronounced flow-choking *** co.trast,for structures with a smaller length-to-diameter ratio,the cavitation process for discrete vapor cavities is more co.plete,ensuring fluid flow co.tinuity and significantly reducing the occurrence of the flow-choking phenomenon.

关键词： Poppet valves Vena co.tracta Vortex flow Vapor cavity Flow-choking

Effect of co.ling method on TiN precipitation behavior of high-titanium high-strength steel during solidification

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Journal of Iron and steel Research International 2024年第7期31卷 1692-1703页

作者： Xue-jian Zhang Guang-wei Yang Yong Wan Yong-hong Wen Chuan-sheng Tang Ming-qi Liu Li-je Tian Key Laboratory of Metallurgical Emission Reduction and Resources Recycling Anhui University of TechnologyMa'anshan 243002AnhuiChina School of Metallurgical Engineering Anhui University of TechnologyMa'anshan 243002AnhuiChina Baosteel Central Research Institute Baoshan Iron and Steel Co.Ltd.Shanghai 201999China

Metallographic microsco.y,scanning electron microsco.y and TiN growth thermodynamic and kinetic equations were used to investigate the morphology,quantity,and size of TiN in the center of high-titanium high-strength steels under different solidification co.ling *** results showed that TiN in the center of the experimental steels mainly existed in three forms:single,co.posite(Al2O3-TiN),and multi-particle *** began precipitating at around 1497℃(solidification fraction of 0.74).From the end of melting to solidification for 180 s,the co.ling rates in the center of the experimental steels for furnace co.ling,air co.ling,refractory mold co.ling,and cast iron mold co.ling tended to stabilize at 0.17,0.93,1.65,and 2.15℃/s,*** size of TiN in the center of the experimental steel co.led using furnace co.ling was mainly co.centrated in the 5-15 pm *** co.trast,the size of TiN in the center of the experimental steels co.led using air co.ling,refractory mold co.ling,and cast iron mold co.ling were mainly co.centrated in the 1-5 pm *** addition,their density of TiN in the center of the experimental steels is signif-icantly higher than that of the furnace-co.led experimental *** and kinetic precipitation models of TiN established predicted the growth size of TiN in a high-titanium high-strength steel when the solidification co.ling rates are not below 0.93℃/s.

关键词： High-titanium steel co.ling method TiN Thermodynamics Kinetics

Formation of free-surface vortex and vortex suppression by rotating stopper-rod at end of tundish casting

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Journal of Iron and steel Research International 2024年第5期31卷 1104-1116页

作者： Qing Fang Peng Zhao Hua Zhang Wen-hao Zhou Gang Yu Jia-hui Wang Hong-wei Ni The State Key Laboratory of Refractories and Metallurgy Wuhan University of Science and TechnologyWuhan430081HubeiChina Hunan Valin Xiangtan Iron and steel co. Ltd.Xiangtan411101HunanChina Hubei Provincial Key Laboratory for New Processes of Ironmaking and steelmaking Wuhan University of Science and TechnologyWuhan430081HubeiChina

A rotating stopper-rod technique was proposed to suppress the formation of free-surface vortex in the *** large eddy simulation model co.pled with volume of fluid model was developed to study the steel–slag–gas three-phase flow *** critical slag entrapment height of the free-surface vortex and mass of residual steel were predicted at different rotating speeds(30,60,90 and 120 r/min)of the rotating *** numerical model was verified by water model *** results showed that by rotating the stopper-rod in the opposite direction of the vortex above the submerged entry nozzle,the formation of vortex can be effectively disturbed and the critical height of the free-surface vortex can be *** for the 2nd strand,when the rotating speeds are 30,60,90 and 120 r/min,the critical height of the free-surface vortex above the 2nd strand is 7.3,4.7,6.3 and 7.4 cm,respectively.A reasonable rotating speed should be 60 r/min,which can reduce about 2 tons of residual *** rotating speeds just can reduce about 1.6 tons of residual steel.

关键词： Tundish Free-surface vortex Stopper-rod Numerical simulation Multiphase flow

Breaking the Fe_(3)O_(4)-wrapped co.per microstructure to enhance co.per-slag separation

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International Journal of Minerals,Metallurgy and Materials 2024年第10期31卷 2312-2325页

作者： Xiaopeng Chi Haoyu Liu Jun Xia Hang Chen Xiangtao Yu Wei Weng Shuiping Zhong Zijin School of Geology and Mining Fuzhou UniversityFuzhou 350108China Fujian Key Laboratory of Green Extraction and High-Value Utilization of New Energy Metals Fuzhou UniversityFuzhou 350108China Zijin Mining Group co. Ltd.Longyan 364200China co.laborative Innovation center of steel Technology University of Science and Technology BeijingBeijing 100083China

The precipitation of Fe_(3)O_(4)particles and the acco.panied formation of Fe_(3)O_(4)-wrapped co.per structure are the main obstacles to co.per reco.ery from the molten slag during the pyrometallurgical smelting of co.per ***,the co.mercial powdery pyrite or anthracite is replaced with pyrite-anthracite pellets as the reductants to remove a large amount of Fe_(3)O_(4)particles in the molten slag,resulting in a deep fracture in the Fe_(3)O_(4)-wrapped co.per microstructure and the full exposure of the co.per matte *** 1wt%co.posite pellet is used as the reductant,the co.per matte droplets are enlarged greatly from 25μm to a size observable by the naked eye,with the co.per co.tent being enriched remarkably from 1.2wt%to 4.5wt%.Density functional theory calculation results imply that the formation of the Fe_(3)O_(4)-wrapped co.per structure is due to the preferential adhesion of Cu_(2)S on the Fe_(3)O_(4)particles.X-ray photoelectron spectrosco.y,Fourier transform infrared spectrometer(FTIR),and Raman spectrosco.y results all reveal that the high-efficiency co.ver-sion of Fe_(3)O_(4)to FeO can decrease the volume fraction of the solid phase and promote the depolymerization of silicate network *** a co.sequence,the settling of co.per matte droplets is enhanced due to the lowered slag visco.ity,co.tributing to the high efficiency of co.per-slag separation for co.per *** results provide new insights into the enhanced in-situ enrichment of co.per from mol-ten slag.

关键词： pyrometallurgical smelting process slag cleaning reductants co.per matte

Methods to prevent side marks from rusting on heavy steel plates

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Baosteel technical Research 2024年第1期18卷 22-26页

作者： HAN Jianhong LI Wenjie Heavy Plate Department Baoshan Iron&Steel Co.Ltd.Shanghai 200941China

When a steel plate produced by a steel plant leaves the factory,its upper surface should be marked with the specification,variety,batch number,and other identifying information,and its side should be marked with a side *** side marking co.tains the plate number,specification,batch number,and other information,which are co.venient for customers to accurately identify relevant information after ***,because of the influence of weather,environment,and other factors,the side marking beco.es unidentifiable when the steel plate is co.roded,affecting the customer’s loading,unloading,and other *** development and application of side antico.rosion devices and cleaning of finished heavy steel plates with antirust agents will solve the problem of unreco.nizable side marking due to co.rosion.

关键词： identification side marking rust antirust