Papers by Keyword: Vanadium

Abstract: The inter-critical heat affected zone (ICHAZ) appears to be one of the most brittle sections in the welding of high-strength micro-alloyed steels (HSLA). Following repeated heating cycles in in with temperature ranging Ac₁ /Ac₃, the ICHAZ will face with an evident toughness and fatigue behavior reduction especially due to martensite-austenite constituent (MA) formation. Microalloying in high strength steels causes the generation of some phases in the matrix able to increase the mechanical properties of the joint. In this paper we report an investigation related to 1000 ppm vanadium addition in the welded joint of a structural S355 steel. The inter-critical zone of ta double pass welded joint is here reproduced by dilatometer, with second peak temperature ranging 720°C-790°C. The residual austenite dependence on inter-critical temperature is analyzed and related to the hardness behavior.

Abstract: Back-annealing during the hot dip galvanising (HDG) process was applied to heavily cold-worked low C-microalloyed VN steels in an attempt to achieve a yield strength of 700 MPa and a minimum A₈₀ elongation of 10 percent. HDG simulations were performed to compare recovery and recrystallisation kinetics in VN steel with that experienced in plain low C and Nb-Ti grades. Based on these results, an industrial melt was subjected to conventional hot rolling, cold rolling and back-annealing cycles during HDG. Precipitation in both VN and Nb-Ti steels extended the recovery window by about 75 degrees Celsius when compared to that found in low CMn steel. A temperature-time parameter M was used to compare the rates of softening. The M_rs (recrystallisation start) in both VN and Nb-Ti steels was 20.1 compared to 18 in a low CMn grade. The above properties were achieved by subjecting low C-microalloyed VN steel to low finishing and low coiling temperatures followed by back-annealing heavily cold-worked strip to a maximum temperature to prevent full recrystallisation. The softening rate during annealing is higher in both microalloyed steels than the CMn grade, with recrystallisation being completed more rapidly in the VN steel. Laboratory results implied insensitivity of restoration behaviour to hot rolling parameters whilst industrial results suggest that they are effective.

Abstract: This work examines the feasibility of joining two dissimilar metals, vanadium (V) and wrought Nitronic 40 stainless steel, through electron beam additive manufacturing (EBAM). Depositing V on Nitronic 40 led to mixed results with some builds exhibiting microcracking and other builds exhibiting severe cracking resulting in delamination. These build failures are thought to be caused by a large coefficient of thermal expansion (CTE) mismatch and solubility issues, demonstrating the challenges associated with this material combination. The large melting temperature discrepancy between Nitronic 40 and V was thought to exacerbate the issues with CTE mismatch and solubility. Four strategies could be employed by EBAM to mitigate the observed issues to successfully deposit V on Nitronic 40: (1) adjust wire feed speed, (2) use dual wire feeders, (3) use different wire feedstocks to control composition, and (4) create a transition layer known as buttering to accommodate CTE mismatch.

Abstract: The present experimental study demonstrates the feasibility of Vanadium doping of 3CSiC hetero-epitaxial material. Some of Vanadium incorporation trends as well as the influence of Vanadium doping on 3C-SiC resistivity are observed.

Abstract: A systematic germanium (Ge) and vanadium (V) study on 4H-SiC epitaxial layers is presented. Electrical results of TLM structures which were fabricated on these layers revealed that highly-doped Ge and V-implanted layers showed extremely low specific contact resistivity, down to 2 x 10^-7 Ω.cm². Current flow in the conducting state of Schottky barrier diodes has been successfully suppressed in some implanted layers, with highly V doped samples showing current density values of approximately 1 x 10^-5 Acm^-2 at 10 V. DLTS spectra reveal the presence of germanium and vanadium centers in the respective samples as well as novel peaks which are likely related to the formation of a novel GeN center.

Abstract: The paper investigates the technology of refining primary aluminum from vanadium impurities, based on flux treatment with boron-containing fluxes. In the Pavlodar region of the Republic of Kazakhstan, on the basis of local enterprises, the production of primary aluminum and products based on local raw materials is developing. The main problem in the production of primary aluminum on the basis of JSC “Kazakhstan Electrolysis Plant” is the presence of undesirable vanadium impurities, which pass into metal during electrolysis from baked anodes based on calcined coke (vanadium content up to 800 ppm) of the local enterprise LLP UPNK-PV (Pavlodar, Kazakhstan). The authors investigated the process of ladle refining of aluminum from vanadium using the Al-B (3% B) alloy. Laboratory and industrial tests have shown a decrease in the vanadium content by an average of 78% in the bulk of the metal, with an increase in its content in volume up to 5-10% of the ladle capacity. It was found that mixing leads to a certain averaging of the vanadium content in the ladle volume.

Abstract: Crude petroleum filters were prepared from low-cost materials based on kaolin powder and combustible materials as palm fronds powder which acts as pore creating agent. The samples with different content (10, 20, 30,40) wt% of palm fronds powder (P.F) were fabricated using a dry pressing method and fired at 1100 °C. Crude petroleum filters were characterized by X-ray diffraction (XRD), energy dispersive analysis (EDS) and Scanning electron microscopy (SEM). Physical properties (linear shrinkage, apparent porosity, water absorption, apparent density), mechanical properties (compressive strength and diametrical strength ) and Metallic Content.

Abstract: The article presents a study of the possibility of controlling the emission activity of heavy metals from building materials and structures. It has been established that the most active emission processes from building materials obtained using industrial wastes placed in aqueous media occur in the first five days in a neutral medium, and in the first ten days in an acidic medium. After that, the concentration of heavy metals in the aquatic environment begins to decrease. The results obtained on particular examples made it possible to establish dependencies that determine the intensity of emission processes under various conditions of contact between building materials and an aqueous medium. These dependencies are of a general nature and can be used to predict and control the formation of anthropogenic load. It is shown that the control of emission processes from building structures is possible by forming the structure of the material in the direction of increasing its hydrophobicity, density, and the content of alkaline compounds.

Abstract: The metallurgical characteristics of pellets (reducibility, strength after reaction, softening start and end temperatures), phase composition (X-ray phase analysis), and porosity were studied. Blast furnace smelting parameters were calculated using laboratory pellets with different basicities and degrees of metallization. Pellets were obtained from complex titanium-magnetite ores. The vanadium extraction of this ore into metal did not exceed 10 % during smelting of metallized pellets in an arc steelmaking furnace, but special techniques could raise this to 85 %. According to calculations from the Institute of Metallurgy of the Ural Branch of the Russian Academy of Sciences (IMET UB RAS), vanadium extraction up to 80–90 % can be achieved by using high-base and partially metallized pellets. The influence of changes in the composition and metallurgical characteristics of titanomagnetite pellets with increasing basicity (especially relative to strength after reduction) should be taken into account.

Abstract: Recently, the frequency of earthquakes has been increasing worldwide. As a result, steel reinforced with seismic performance that can satisfy the social needs to strengthen the existing seismic performance of existing infrastructure facilities and new buildings has become important. In general, to secure the yield strength of reinforcing bars and to reduce the production cost, reinforcing bars are produced by rolling the surface through a facility such as a Tempcore. In Korea, most of them have adopted the Tempcore process to ensure the mechanical requirements of the product. However, the use of a small amount of alloying elements and the application of Tempcore have limitations in producing reinforcing bars that require seismic performance. In recent years, remarkable progress has been made in the production and application of high strength rebars. Microalloying and fine-grain strengthening are the most effective methods in developing high strength rebars. That is, the precipitation of V (C, N) is promoted by the addition of V to improve the strength by precipitation strengthening of V-carbonitride. However, in V-microalloyed reinforcing bars, it was confirmed that the required strength did not increase proportional to the amount of V added. In this study, the effects of vanadium and other alloying elements on the mechanical properties and yield ratio of steel bars were investigated by tensile test results and microstructural evaluation.