Materials Science Forum Vol. 946

Abstract: Three medium carbon Cr-Mn-Mo structural steels with different content of alloying elements were studied. The austenite transformation during continuous cooling was investigated using dilatometer and metallographic analysis. The CCT diagrams were plotted showing the effect of the increased alloying elements content and B and Nb micro-alloying on the hardenability of the studied steels. The hardness dependences on the cooling rate were obtained.

Abstract: The approach for coupled experimental and numerical estimation of the heat treated steel part microstructure and hardness is presented. The method is based on the investigation of the austenite transformation in a steel during continuous cooling, Jominy hardenability test and numerical modeling of a quenching process. The presented approach is verified by estimation of the 20CrMo5 steel gear shaft microstructure and hardness. The estimated results are in good agreement with the experimental ones.

Abstract: The present work deals with the investigation of the transformations of the solid and liquid phases at high energy planetary ball milling of toluene together with titanium powder. The sequence of structural toluene transformations using FT-IR spectroscopy was investigated. Phase constitutions and morphology of ball milled titanium powders were studied by X-ray diffraction and scanning electron microscopy. It is shown that mechanically induced destruction of toluene occurs by the mechanism of catalytic cracking. During ball milling, concentration of aromatic hydrocarbons in the liquid phase decreases, at the same time the content of alkenes, cycloalkanes, and isoalkanes increases. The main solid products of the mechanosynthesis were cubic and hexagonal titanium carbo-hydrides.Evolution of lattice parameters, crystallites sizes, and micro-stresses of the solid phases during ball milling as a function of the mechanical energy dose have been discussed.

Abstract: Different mesostructural elements of 16Cr-19Ni-2Mo-2Mn-Nb-Ti-B austenitic steel have been examined after neutron irradiation to damage dose up to 82 dpa by scanning electron microscopy using orientation microscopy (EBSD). Radiation porosity with maximum void size up to 200 nm was observed in austenitic steel structure after neutron irradiation. Nonuniformity, related to mesostructural elements, such as general grain boundaries, special CSL boundaries Σ3 (twins), areas with high density of low-angle boundaries, is typical for radiation porosity.

Abstract: A manufacturing process was developed using an electric through-type furnace for capillary tubes used for single-use injection syringes. The process flow diagram consisting of a number of sequential steps and tube heat treatment conditions in protective atmosphere of pure hydrogen providing also for the tube purging with inert gas were considered. The electric furnace installed capacity and heating element dimensions were found as a result of the thermotechnical calculations. Industry research was carried out with a view to optimize the annealing process of capillary tubes in the electric furnace. A choice of material for the muffle fabrication was justified. Temperature fields inside the muffles were evaluated. The optimal flow of protective gas and the maximum allowable flow of purging gas in the form of nitrogen and argon were determined. Mechanical properties were studied for tubes (stocks), welded at the medical goods fabrication plant in Tumen and fabricated at the Pervouralsky Novotrubny Plant. Test data were obtained for optimal rates of tube movement in the furnace, allowing production of capillary tubes, acceptable for medical needle fabrication after annealing. It was demonstrated that capillary tube heat treatment, ensuring the required condition of both outside and inside surfaces, as well as required mechanical properties, is possible with the use of nitrogen as protective (instead of hydrogen) and purging gases. At that probability of better tube surface condition significantly grows.

Abstract: Different types of carbide phases and regions of their precipitation in tempered martensite of austenitic steel have been investigated with orientation microscopy (EBSD) and electron microprobe analysis. The steel structure consisted of large grains of high-temperature ferrite (~ 15%), without visible mesostructured, and martensite packages with a great number of low-angle boundaries. High-angle boundary spectrum with the most prominent coincidence site lattice (CSL) boundaries, Σ3, Σ11, Σ25b, Σ33с Σ41с, is typical for martensite. This spectrum, resulted from austenite transformation by shear mechanism according to orientation relationships (OR), intermediate between Kurdjumov-Sachs (K-S) and Nishiyama-Wassermann (N-W). In the structure two types of carbide precipitates were observed: large MC [~ NbC] along the boundaries of former austenite grains, and dispersed M₂₃C₆ [~ (W,Mo)₂(Cr,Fe)₂₁C₆] predominantly along the boundaries in martensite packages. It has been shown that under martensite tempering M₂₃C₆ precipitation was mainly at high-angle intergranular boundaries. Carbide almost did not precipitate at low-angle and special CSL Σ3 boundaries. A few carbides were detected at special CSL boundaries, Σ11, Σ25b, Σ33с Σ41с.

Abstract: Effects of boron in low-carbon tube steel grade 17G1SU on nonmetallic inclusions, structure and mechanical properties were investigated. Experimental samples of rolled metal containing boron 0.006 and 0.011% are characterized by predominantly small, nonmetallic inclusions not more than 5 μm, which are represented by complex alumomagnesium spinels in the shell of manganese and calcium sulfides, and small silicate inclusions. Nonmetallic inclusions of comparative pipe steel sample, containing no boron characterized by the presence of larger inclusions presented complex oxysulfide and sulfide films. The main structural component of the comparative and experimental samples is ferrite. The introduction of boron is contributed by a decrease in the average size of ferritic grains from 8.7 μm (0% B) to 6.2 (0.006% B). Increasing the boron content to 0.011% leads to slight increase (up to 6.8 microns) of the size. The mechanical properties of 10 μm rolled metal pipe steel ensured the production of rolled products of strength class X80 without additional (thermal) treatment, as a result of the reduction in the size and shape of nonmetallic inclusions, and formation of dispersed structure.

Abstract: The strength of abrasive wheels is one of the key factors affecting the performance of abrasive machining. The paper discusses ways to improve the strength of abrasive wheels. The stress-state mathematical model presented herein is a generalization of the existing models. It is used herein to find for the first time that there are numerous optimal combinations of the elastic modulus and reinforcing material density, which result in the same minimum value of the objective function. It is found out that increasing the radius of the reinforcing component while also optimizing the mechanical properties of its material may increase the permissible breaking speed of the wheel several times. We herein present a regression equation and a nomogram for finding the optimal combination of control factors. Conventional methods for testing the mechanical properties of materials, which have been proven reliable for testing metals and alloys, are not as reliable for testing abrasive materials, as the test results they generate are not sufficiently stable or accurate. We therefore propose an alternative method that does not require any special equipment or special studies.

Abstract: The article outlines the main principles of granulation technology for fused welding flux using highly concentrated heat sources (e.g. plasma arc). Modern plasma equipment and methods of its use for producing new welding materials (plasma-granulated welding flux) from mineral raw materials and synthetic mineral alloys are described. The developed technology makes it possible to produce granulated flux in a wide range of fractional composition (from 0.2 to 3 mm). Studies have focused on the influence of granulation regimes (plasmatron moving speed, current, voltage, arc length) on formation process and the morphology of welding flux particles. Mineral raw materials used for granulation were igneous rocks (basalt, hornblendite) and synthetic mineral alloys. The results obtained during experiments on the use of highly concentrated heat sources for granulation of a fused welding flux confirm the feasibility and prospects of this technology. Typical equipment for air-plasma cutting is used, and no new complex technological equipment is required, therefore it eliminates large material and labor costs.

Abstract: The article is devoted to the study of the impact of technological features of the anode paste production on one of the technical-and-economic indices – its consumption. It is shown that the prior thermal preparation significantly affects the quality characteristics of pitch and petroleum cokes. The comparison of pitches of foreign and homeland producers revealed the advantage of the last because of their small ash content and the lowered content of sodium. Granulometric composition of the dry mix is determined on the basis of different coke brands. They are close to the concentrations of fractions regulated by the technology of production of the anode paste. The conducted semi-industrial tests were in accordance with the laboratory studies and confirmed the fact of reducing the consumption of the anode paste when using the petroleum coke as a filler.