Metal Chemical Composition Research Articles

Improving the Desulphurization in COREX Process by Adjusting the Hot Metal Chemical Composition

The COREX process, which has many advantages, still has high and fluctuating sulfur levels in the hot metal. To overcome the desulfurization problems, several measures were proposed, and the adjustments of chemical compositions of hot metal were explained in the current study. Theoretical calculations and experimental results showed that increments in either of or both silicon and manganese levels were beneficial to the desulfurization from the thermodynamic viewpoint. However, high silicon content would increase the costs of the coal of COREX process and did not meet the requirements of dephosphorization and low slag content in steelmaking. Besides, superfluous manganese was also unnecessary as it would increase the costs of COREX. Therefore, the existing silicon content should be decreased (< 1.5 pct), and the manganese content should be increased in a suitable range (from 0.6 to 0.8 pct) for COREX-3000 in China.

Evaluation of microstructure and mechanical properties of P91 steel weldment due to addition of boron trioxide into flux during submerged arc welding

The present investigation studied the effect of boron trioxide (B2O3) addition into flux on the microstructure and mechanical properties of modified 9Cr-1Mo (P91) steel in submerged arc welding (SAW) process. Boron trioxide powder was mixed with commercial flux in different ratios to change the weld metal chemical composition. Optical emission spectroscopy results showed that weight percentage of boron varies from 0.00 to 0.0068 with the addition of boron trioxide into welding flux. Weld metal microstructure without the addition of boron reveals the presence of tempered martensite and ferrite phase, whereas boron-added microstructures highlighted the dominating nature of tempered martensite. Scanning electron microscope analysis also showed that the dispersed carbides especially M23C6 were increased with the addition of boron. Weld metal macrohardness profile reveals that boron has the significant effect on the weld metals. The maximum hardness of 342 HV was found for the 12.5% B2O3, whereas weld of without boron shows the hardness of 240.8 HV. Boron addition has a positive effect on the tensile strength of weld joints except for the 12.5% B2O3. But the toughness of weld zone decreases with the addition of boron.

Applicability of low transformation temperature welding consumables to increase fatigue strength of welded high strength steels

Application of Low Transformation Temperature (LTT) consumables in welding is a recent approach to increase the fatigue strength of welds. In this paper high strength steels with yield strengths ranging from 650 to 1021MPa were fillet and butt welded using different LTT and conventional consumables. The effects of weld metal chemical composition on phase transformation temperatures, residual stresses and fatigue strength were investigated. Lower transformation start temperatures and hence lower tensile or even compressive residual stresses were obtained close to the weld toe for LTT welds. Fatigue testing showed very good results for all combinations of LTT consumables and high strength steels with varying strength levels. For butt welds, the characteristic fatigue strength (FAT) of LTT welds at 2million cycles was up to 46% higher when compared to corresponding welds made with conventional filler materials. In fillet welds, a minimum FAT improvement of 34% and a maximum improvement of 132% was achieved when using LTT wires. It is concluded that different LTT consumables can successfully be employed to increase fatigue strength of welds in high strength steels with yield strength up to 1021MPa. Weld metals with martensite transformation start temperatures close to 200°C result in the highest fatigue strengths.

The Influence of Shielding Gas Flow Rate on the Transfer Frequency of Electrode Metals Drops

Chemical composition of weld metal and properties of a joint weld are dominated by the processes occurring in the drop of molten electrode metal and in metal of the weld pool. Under certain conditions in consumable electrode welding with jet gas shielding the drop of electrode metal is influenced significantly both by main forces and the force of gas-dynamic impact of the shielding gas jet. The results of research have revealed that changing rate of shielding gas flow on the nozzle section influences the processes taking place in the welding area. There are changes in the transfer frequency of electrode metal drops and chemical composition of weld metal.

Weldability assessment and high-temperature properties of advanced creep resisting austenitic steel X6CrNiNbN25-20 (DMV310N/HR3C)

The modern Ultra Super Critical Power Plants (USC PP) applying the 600 °C technology require advanced stainless steels in superheater/reheater systems in order to cope with the increased steam parameters. Different grades of stainless steels have been developed by increasing Cr-contents, alloying with stabilizing and precipitating elements as well as thermomechanical heat treatments resulting in high creep rupture strengths and improved oxidation/corrosion resistance. In the context of a collaborative research project, X6CrNiNbN25-20 (DMV310N/HR3C) has been investigated. The main focus of the research project was on characterization and weldability assessment. As a result, the base metal under investigation was compared with governing code cases and specifications. Base metal chemical composition, microstructures, mechanical properties, reheat cracking sensitivity, and hot ductility as well as creep rupture strengths have been investigated. A weldability assessment, including thermal simulation and welding procedure qualifications, has been performed to establish parameter windows for similar and dissimilar welding. Dissimilar welding between grade 92 and austenitic steel tubes has been performed. The project also took the opportunity to investigate the behavior of a recently developed gas tungsten arc welding (GTAW) P87 consumable for dissimilar welding. Cross-weld creep rupture tests have been conducted for both similar and dissimilar welding, while aging tests addressed microstructural stability.

Influence of Filler Metals in Welding Wires on the Phase and Chemical Composition of Weld Metal

The influence of filler metals used in welding wires on the phase and chemical composition of the metal, which is surfaced to mining equipment exposed to abrasive wear, has been investigated. Under a laboratory environment, samples of Mo-V-B and Cr-Mn-Mo-V wires were made. The performed experiments have revealed that fillers of the Cr-Mn-Mo-V system used in powder wire show better wear resistance of the weld metal than that of the Mn-Mo-V-B system; the absence of boron, which promotes grain refinement in the Mn-Mo-V-B system, significantly reduces wear resistance; the Mn-Mo-V-B weld metal has a finer structure than the Cr-Mn-Mo-V weld metal.

Morphology, chemical composition, and electrical characteristics of hybrid (Ni-C) nanocomposite structures grown on the van der Waals GaSe(0001) surface

The morphology and chemical composition of metal (Ni), carbon, and composite (Ni-C) nanostructures grown on oxidized and unoxidized (0001) surfaces of a layered GaSe crystal by electron beam vacuum evaporation of the material from a liquid ion source in an electric field have been investigated using atomic force microscopy and X-ray photoelectron spectroscopy. It has been demonstrated that this technology makes it possible to grow nanostructures with different morphologies depending on the growth mode and substrate surface state. Dense homogeneous arrays of nickel nanoparticles (Ni@C) (with geometrical sizes of ∼1–15 nm and a lateral density of higher than 1010 cm−2) encapsulated into carbon shells, as well as carbon layers (with a thickness of the order of several nanometers), are grown on the unoxidized van der Waals GaSe(0001) surface, whereas Ni-C composite nanostructures are grown on the oxidized surface. The formation of oxide nanostructures on the van der Waals surface and their chemical composition have been examined. Vertical hybrid Au/Ni/(Ni-C)/n-Ga2O3(Ni@C)/p-GaSe structures grown on the GaSe(0001) surface contain Ni@C nanoparticles embedded in the wide-band-gap n-Ga2O3 oxide. The current-voltage characteristics of these structures at temperatures close to T = 300 K exhibit specific features of the Coulomb blockade effect.

Electromagnetic shielding wood-based composite from electroless plating corrosion-resistant Ni–Cu–P coatings on Fraxinus mandshurica veneer

A novel and simple electroless Ni–Cu–P plating process was used for preparing corrosion-resistant and electromagnetic interference shielding wood-based composite. The effects of CuSO4·5H2O concentration, pH value in the plating solution and operation temperature on the metal deposition, surface resistivity, chemical composition, corrosion resistance and surface morphology of the composite were investigated. The surface morphologies were observed by using scanning electron microscopy and the chemical compositions were analyzed by X-ray energy dispersive spectrometer. The electromagnetic shielding effectiveness (ESE) was measured by spectrum analyzer. The corrosion resistance was evaluated by potentiodynamic corrosion measurement. The results show that metal deposition increases with pH value and temperature increase; however, it decreases with CuSO4·5H2O concentration increase. The corrosion resistance of the plated Ni–Cu–P coatings obviously depends on the total content of Cu and P in the coating. Higher total content of Cu and P leads to higher corrosion resistance. The optimum conditions are as follows: CuSO4·5H2O concentration of 1.0 g/L, pH value of 9.5, and operation temperature of 90 °C. The obtained coating contains 77.41 % Ni, 8.96 % Cu, and 13.63 % P. The wood-based composite exhibits higher corrosion resistance and ESE of around 60 dB in frequencies ranging from 9 kHz to 1.5 GHz. In this paper, a promising process for corrosion-resistant and electromagnetic shielding wood-based composites was developed.

Weldability assessment and high temperature properties of advanced creep resisting austenitic steel DMV304HCu

The modern (USC PP) applying the 600 °C technology require advanced austenitic stainless steels in superheater/reheater systems in order to cope with the increased steam parameters. Different grades of austenitic stainless steels have been developed by increasing Cr contents, alloying with stabilizing and precipitating elements as well as thermomechanical heat treatments resulting in high creep rupture strengths and improved oxidation/corrosion resistance. In the context of a collaborative research project, DMV304HCu (X10CrNiCuNb18-9-3) has been selected. The main focus of the research project was on characterization and weldability assessment. As a result, the base metal under investigation was compared with governing code cases and specifications. Base metal chemical composition, microstructures, mechanical properties, reheat cracking sensitivity, hot ductility as well as creep rupture strengths have been investigated. A weldability assessment, including thermal simulation and welding procedure qualifications, has been performed to establish parameter windows for similar and dissimilar welding. Dissimilar welding between Grade 92 and austenitic stainless steel tubes has been performed. The project also took the opportunity to investigate the behavior of a recently developed gas tungsten arc welding (GTAW) P87 consumable for dissimilar welding. Cross-weld creep rupture testing has been conducted for both similar and dissimilar welding, and aging tests addressed microstructural stability.

Preparation of EMI Shielding and Corrosion-Resistant Composite Based on Electroless Ni-Cu-P Coated Wood

A simple electroless Ni-Cu-P plating process for preparing an EMI-shielding and corrosion-resistant wood-based composite has been developed. The effects of solution pH value on the metal deposition, surface resistivity, chemical composition, anti-corrosion properties, and crystal structure of the coatings were studied. The coatings were characterized using X-ray photoelectron spectroscopy, X-ray diffraction, and scanning electron microscopy. When the solution pH was increased from 8.5 to 10.0, the metal deposition increased and the surface resistivity decreased. Chemical composition indicated that the nickel deposition increased, whereas the opposite effect was obtained on copper and phosphorus elements with a pH increase from 9.0 to 10.0, and the crystal structure of the Ni-Cu-P coatings changed from an amorphous state to a microcrystalline one. Tafel curves of the Ni-Cu-P coatings prepared at pH 9.0 or 9.5 showed that they had excellent anti-corrosion properties in a 3.5 wt% NaCl solution. The morphology of the coating containing 69.86% Ni - 7.65% Cu - 22.49% P is superior to that with 75.99% Ni - 6.60% Cu - 17.41% P after corrosion tests. The plated birch veneers exhibited electromagnetic shielding effectiveness higher than 58 dB in frequencies ranging from 9 KHz to 1.5 GHz, and the coating firmly adhered to the wood surface.

A química da formação do cordão na soldagem TIG

A soldagem TIG apresenta elevados níveis de estabilidade e permite um controle mais apurado do que a maioria dos demais processos de soldagem a arco. É bem conhecido, contudo, que pequenas variações de composição química do metal base ou da região de operação do arco podem ter um efeito pronunciado no formato do cordão de solda, o que reduz a capacidade de controlar e a previsibilidade do processo. Este trabalho apresenta uma revisão da variabilidade do cordão de solda obtido no processo TIG com pequenas alterações na composição química do metal base e das soldagens A-TIG e TIG com gás ativo. Aspectos comuns e particulares de cada caso são realçados e discutidos e os mecanismos propostos na literatura em cada caso são apresentados e comparados.

Preventing inadmissible erosion-corrosion thinning from occurring in the diffuser segments of feedwater supply control systems of power units at nuclear power stations equipped with RBMK-1000 reactors

Results obtained from investigations of erosion-corrosion processes that occur during operation of the feedwater supply control systems used in power units of nuclear power stations equipped with RBMK-1000 reactors and the sensitivity of these processes to variations in the chemical composition of metal and in the flow path geometry are presented. It is found that local erosion-corrosion thinning of the walls in the diffuser segments of feedwater supply control systems occur mainly due to intense mass transfer in the near-wall region taken in combination with a low content of chromium. Hydrodynamic simulation was carried out, and it was shown based on its results that local erosion-corrosion thinning of the walls of pipeline segments downstream of the valves controlling the supply of feedwater to power units of nuclear power stations equipped with RBMK-1000 reactors can be prevented by subjecting them to appropriate modernization. It is found that the above mentioned diffuser parts can be made more resistant to erosion-corrosion wear by keeping the content of chromium in the main metal and weld joints at a level of no less than 0.25% and concurrently reducing the hydrodynamic effect in the zones of weld connections.

Low-Temperature Cu-Cu Wafer Bonding

Metal thermo-compression bonding is a process suitable for 3D interconnects applications at wafer level. The process requires typically bonding temperatures of ~400{degree sign}C and high contact pressure applied during bonding. Temperature reduction below such values is required in order to solve some issues regarding wafer-to-wafer misalignment after bonding and to minimize thermo-mechanical stresses. Low-temperature (LT) Cu-Cu wafer bonding was successfully demonstrated at 175{degree sign}C. The bond quality, bond strength, metal interface layers microstructure and chemical composition of Cu-Cu wafer pairs bonded under different process conditions were investigated. Experimental results on various Cu native oxide methods evaluation as well as results obtained for various bonding and annealing temperatures are presented.

Geochemical Assessment of a Subtropical Reservoir: A Case Study in Curitiba, Southern Brazil

AbstractSuspended particles and dissolved substances in water provide reactive surfaces, influence metabolic activity and contribute to the net sediment deposition. It therefore plays an important part in the ecology and quality of the water mass. The water quality in reservoirs is crucial and it is naturally maintained by flushing and sedimentation, which continuously remove phosphorus from the water. In some reservoirs, however, these removal processes are countered by recycling of ions which could play a key role to start and/or maintain the eutrophic state. The combination of macro‐, trace‐ and microanalysis techniques can be useful to trace pollution sources through a chemical fingerprint, whether be during an acute environmental disaster or a long‐term release of pollutants. The water quality and total metal content of reservoir sediments were assessed in a reservoir, situated in the capital of the Paraná State, in the South‐Eastern part of Brazil. The goal of this paper was to determine the metal presence in the sediment and metal and ionic speciation in the Green River reservoir water. Water and bed sediment samples, collected from various sites during 2008 and 2009, were investigated using XRF, ICP‐OES, ICP‐MS, XRD and zeta potential measurements. Based on the results, the heavy metal concentration and chemical composition of the suspended matter in the water samples, as well as the sediment's chemical composition will be discussed.

Study on Changes of Metal Chemical Composition by Abrasive Wear of Alfalfa Powder

The abrasive wear of 45 steel and HT200 iron which are usually used on agriculture machine was tested by alfalfa powder on a grinding abrasion testing machine. The chemical composition on both wear metal surface and original surface were analysed with energy dispersive spectroscopy (EDS). The results indicated that metal element contents on the metal wear surface were decreased, while the nonmetallic element contents were increased.

Estudo comparativo de eletrodos comerciais para soldagem subaquática molhada

Com o objetivo de fornecer subsídios para a seleção de consumíveis para a soldagem molhada foram determinadas algumas propriedades do metal de solda a partir de juntas soldadas em água doce com eletrodos revestidos comerciais específicos para este fim. As soldas foram realizadas em tanque a 0,5m de profundidade por dispositivo de soldagem por gravidade. Foram levantados dados que auxiliem a eleger os consumíveis de melhor desempenho para serem testados em maiores profundidades. Foram realizados os seguintes testes e avaliações: caracterização microestrutural, análise e quantificação das inclusões, composição química do metal de solda, dureza Vickers, hidrogênio difusível e avaliação da soldabilidade. Os resultados obtidos permitem classificar os consumíveis testados em dois grupos com características bem distintas. No primeiro grupo está o único eletrodo do tipo oxidante e no segundo grupo estão os quatro eletrodos do tipo rutílico testados. Quanto às propriedades mecânicas e às características operacionais, os eletrodos do tipo rutílico apresentaram os melhores resultados. Por outro lado, o eletrodo oxidante testado produziu soldas com mais baixo teor de hidrogênio difusível e, portanto, menor risco potencial de provocar trincas a frio. As diferenças de propriedades entre os eletrodos testados são evidenciadas e discutidas no presente trabalho.

Estudo da soldagem de tubos de aço inoxidável duplex e superduplex na posição 5G

Os aços inoxidáveis duplex e superduplex possuem uma microestrutura austeno-ferrítica com fração média de cada fase de cerca 50%. A microestrutura duplex é responsável pelas excelentes propriedades mecânicas, especialmente o limite de escoamento e a tenacidade, e pela elevada resistência a corrosão por pites e sob tensão em meios contendo cloretos. A soldagem destes aços é frequentemente uma operação crítica. Neste trabalho, um tubo de superduplex SAF 2207 foi soldado pelo processo TIG (GTAW) no passe de raiz e eletrodo revestido (SMAW) nos passes de enchimento, e um tubo de duplex SAF 2205 foi todo soldado pelo processo GTAW. A microestrutura do metal base, zona afetada termicamente (ZTA) e metal de solda foi caracterizada e quantificada. As propriedades de tenacidade, resistência a corrosão e composição química foram avaliadas e correlacionadas. Os valores de tenacidade ao impacto Charpy-V foram considerados adequados. Não foi observada a precipitação de intermetálicos, carbonetos e nitretos. O melhor resultado no teste de corrosão da junta soldada de aço inox superduplex, comparado ao duplex, foi atribuído ao baixo teor de ferrita delta na solda e ZTA, e composição química da solda enriquecida em Cr, Mo, W e N.

Influence of the precrystallization flow of copper and aluminum melts on the mechanical properties of ingots

The influence of the precrystallization flow of copper and aluminum melts on the hardness and abradability of ingots is investigated. The flow was organized via passing the melts through the round-section tubes. The hardness of metals was determined by the Brinell method, and abradability was evaluated on a setup for investigating the friction properties of materials. The stability of the chemical composition of metals was monitored by spectral chemical analysis. It is established that there is an 8–17 and 7–10% increase in hardness and a 11–15 and 10–11% decrease in abradability, respectively, in the samples of copper and aluminum subjected to the flow in the molten state. It is noted that, taking into account the results of a spectral chemical analysis, the variation in the properties of metals is most likely caused primarily by the directed precrystallization flow of corresponding melts rather than by variations in the chemical composition.

Neutron diffraction analysis of residual strain/stress distribution in the vicinity of high strength welds

Residual stresses resulting from non homogeneous heat distribution during welding process belong to most significant factor influencing behavior of welded structures. These stresses are responsible for defect occurrence during welding and they are also responsible for crack initiation and propagation at the either static or dynamic load. The significant effect of weld metal chemical composition as well as the effect of fatigue load and local plastic deformation on residual stress distribution and fatigue life have been recognized for high strength steels welds. The changes in residual stress distribution have then positive effect on cold cracking behavior and also on fatigue properties of the welds [1-3]. Several experimental methods, both destructive and non-destructive, such as hole drilling method, X-ray diffraction, neutron diffraction and others, have been used to examine residual stress distribution in all three significant orientations in the vicinity of the welds. The present contribution summarizes the results of neutron diffraction measurements of residual stress distribution in the vicinity of single-pass high-strength-steel welds having different chemical composition as well as the influence of fatigue load and local plastic deformation. It has been observed that the chemical composition of the weld metal has a significant influence on the stress distribution around the weld. Similarly, by aplying both cyclic load or pre-stress load on the specimens, stress relaxation was observed even in the region of approximately 40 mm far from the weld toe.

Immunological parameters of dental alloy corrosion; A study of gingival inflammation after placement of stainless steel crown

The dental alloy is widely used in many fields of dentistry as a restoration material, orthodontic, prosthodontic, oral surgery and endodontic treatments. Naturally, most of the metallic materials without exception to stainless steel alloy will experience a process of corrosion in a form of electrochemical reaction to achieve thermodynamic equilibrium. The corrosion process in the oral cavity is due to the reaction of metal with saliva as an oral cavity electrolyte fluid. SSC has preformed restoration material conform with dental anatomy, manufactured from stainless steel alloy which is formable and adaptable to the teeth. Stainless Steel Crown generally made of austenitic stainless steel 18/8 of AISI 304 group contain chrome 18% and Nickel 8%, can be used as a restoration for teeth with excessive caries, crown fracture, email hypoplasia, or restoration after endodontic treatment. The toxic effect of Ni+2 released due to corrosion process may cause an inflammation of the gingiva and periodontal tissue. Laboratorically this condition indicated by the expression of pro-inflammation cytokines as immunological parameters such as IL-6, IL-8, TNF and IL-1β whose main role is to initiate and enhance any inflammation responses. The presence of pro-inflammation cytokines can be detected as soon as 1 hour after placement of SSC by examination of gingival crevicular fluid (GCF) by ELISA technique. The magnitude of the toxic effect depends on corrosion rate and ions release which is influenced by metal chemical composition, environment temperature and pH, metal wear due to abrasion and friction, soldering if any, and elongation of the metal. Conclusion: The release of Ni+2 during corrosion process after placement of SSC cause gingival inflammation which is indicated by the change of the immunological parameters.