Study Regarding Process of the Electrical Discharge Machining with Magnetic Activation of the Welded Joints of some Materials High Alloy Steel

The scientific paper presents an extensive research on modeling and optimizing the technological parameters of the process for processing by processing electric discharges with massive electrode with and without magnetic activation. Scientific research is based on real data collected from the process of electrical discharges performed on various samples extracted from areas of welded joints of metal components made of high alloy steel. The processing of experimental data was performed both classically and actively, especially the method of the central factorial experiment composed of orthogonal and rotary. The process parameters that were initially modeled and subsequently optimized were based on a series of independent variables characteristic of dimensional processing by copying the shape of the electrical discharge processing. Subsequent research conclusions and directions, as well as original contributions, are an experimentally validated point of view and worthy of consideration. All these fundamental ideas highlighted above find their explanations and the corresponding explicit treatment in the content of this scientific paper that addresses both managers at all levels and researchers.

Increasing the reliability of refrigerators used to produce green paste

The work is aimed at the oxidative processes occurring in the metallic structures of the universal refrigerators “UKHB 3/30” used to transport and cool calcined coke. The temperature of the coke entering the device reaches 1320 oC. As it moves along the device, chemical and thermal effects occur on unprotected metallic structures with the formation of erosion centers and through damage to the shells. The service life of refrigerators hot-cut metallic structures made of A284 Grade B (ASTM) is 1 year, which determines its repairs frequency. Experiments on the oxidative processes in real conditions of operation of refrigerators were conducted for samples made of carbon steel of the A284 Grade B (ASTM) brand and heat-resistant high-alloy steel AISI 301. Changes in the chemical composition and physical parameters were determined in the samples. The thermogravimetric method for estimating the corrosion kinetics based on the sample mass loss, spectrometric study of metal samples, and classical chemical “wet” analysis were used. According to the results, the degree of corrosion damage of samples after 1,5 hours is estimated. The kinetics of corrosion has been studied. The mechanism of decarburization of the surface layer in A284 Grade B (ASTM) steel and the accompanying deterioration of the metal mechanical properties are described. An economic analysis of the feasibility of using AISI 301 steel to increase the service life of refrigerators was carried out.

Development of Universal Mould Geometry for the Teeming of Cylindrical Iron-Base Alloy Ingots

The presented work is aimed at developing a mould geometry suitable for casting both low- and high-alloy steel grades into 500 kg experimental ingots. The high Height-to-Diameter (H/D)-ratio mould currently used in COMTES FHT Inc. served as a reference and for finite element method simulations (FEM) of the filling and solidification process. The optimized mould geometry, balancing the porosity and segregations, was determined using MAGMA software. Four different steel grades were defined for the simulation. Case studies were carried out for 34CrNiMo6 (W.Nr. 1.6582), DHQ8, CB2 and borated stainless steel grades ranging from low-alloy steel to high-alloy steel. Extended user-defined criteria and verified boundary conditions were used to predict the formation of A-segregations in cast steel. Both primary (PDAS) and secondary (SDAS) arm spacings were modelled as well. The optimized mould shape and the casting assembly were designed based on the simulation results.

Investigation of the accumulation of alloying elements (Mn, Ni, Mo) on the surface of high-alloy steel in acid medium

The formation of corrosion products in the surface layers of steel 15KH12VNMF brand was investigated in solutions of hydrochloric, sulfuric, phosphoric, and nitric acids. Comparative data were obtained on the accumulation of impurity alloying elements in surface layers of high-alloy steel 15KH12VNMF brand. The content of alloying elements was defined in the surface layer of steel and corrosion products when holding samples in solutions with a certain concentration for 1 hour. The obtained data indicate that the accumulation of manganese, molybdenum and nickel in the surface layer does not occur in the sulfuric acid solution. The surface layers in the solution of phosphoric acid accumulate intensively alloying impurities, whereas in nitric and hydrochloric acids there is a selective accumulation. The surface films on the steel 15KH12VNMF brand in solutions of hydrochloric, sulfuric, phosphoric, nitric acids were Identified at high concentrations and times of incubation. It was established that the rate of manganese accumulation in hydrochloric acid is constant, regardless of the acid concentration. For nickel and molybdenum, the rate of accumulation increases at initial concentrations, and tends to its constant value at high concentrations. In sulfuric acid solutions, the amount of manganese on the surface depends not only on the concentration, but also on the holding time. The accumulation of nickel and molybdenum on the surface of the plate depends as on the concentration and the time. It was determined that in solutions of phosphoric acid the accumulation of manganese occurs only at the primary time, in the future remains constant. The accumulation of nickel and molybdenum on the surface depends as on the concentration and the time and has a similar character. The data are obtained that the accumulation of manganese, nickel, molybdenum on the surface of the sample in solutions of nitric acid with increasing concentration occurs regardless of the holding time of the sample.

Wear and Corrosion Resistance of Hardened Fe-Al-Mn Grinding Ball

Objective: This study aimed to determine the effect of hardening temperature on microstructure, wear and corrosion resistance of Fe-Al-Mn alloy grinding ball. Methods: Hardening process was carried out at 900oC, 950oC, 1000oC, 1050oC and 1100oC, held for 60 minutes and cooled using SAE 20 oil. Tests included chemical composition, SEM-EDS, wear and corrosion resistance test. Results: Chemical composition test results show that this alloy is high alloy steel because it contains 3.6% aluminum (Al), 13.6% manganese (Mn) and 1.1% carbon (C). Microstructures found are austenite, ferrite and kappa. EDS test results show that in the austenite phase, C decreased when hardening temperature increased. Ferrite phase contains Mn which increased when hardening temperature increased while C was the other way around. Mn is relatively stable in the kappa phase. The best wear and corrosion resistance (4.3 x 10-7 mm2/kg and 0.00026 mm/yr) of hardened Fe-Al-Mn grinding ball occurred at 900oC. The corrosion rate is extraordinary. Conclusion: Microstructures of the Fe-Al-Mn alloy grinding ball after the hardening process are austenite, ferrite and kappa.

Occupational Dermatitis in Welding: Does Nickel Exposure Account for Higher Rates in Women? Analysis of a Canadian Cohort

Objectives Women are reported to have higher rates of nickel sensitization than men, but there have been few studies of sex-related differences in dermatitis associated with occupational nickel exposure. This analysis examines dermatitis in a large cohort of women and men in welding and electrical occupations and considers how far differences in rates of dermatitis may be accounted for by nickel exposure. Methods Women and men were recruited to cohorts of workers who had entered welding and electrical apprenticeships (the WHAT-ME and WHAT-MEN studies). Participants completed questionnaires at baseline and every 6 months for up to 5 years. At each contact, cohort members were asked about current dermatitis and whether it was made worse by work. From the first follow-up after recruitment, those working in their trade completed detailed subroutines about tasks in their trade including, for welders, the process, base metal, and consumables. Exposures were considered by trade and, within welding, by stainless or high alloy steel (SOHAS) as the base metal. Urinary nickel concentration was also examined. Using only report of dermatitis that began after entry to the trade, new-onset dermatitis, all episodes of dermatitis, and dermatitis made worse by work were examined against exposure by multilevel, multivariable logistic regression, allowing for potential confounding. Results Among 1885 participants (welders; 447 women, 554 men: electrical trades; 438 women, 446 men), 200 reported dermatitis that started before they entered the trade, leaving 1685 for analysis. Women, but not men, who had entered the welding trades were more at risk of new onset [odds ratio (OR) = 1.54; 95% confidence interval (CI) 1.02–2.32] or dermatitis episodes (OR = 1.75; 95% CI 1.10–2.77) than those entering the electrical trades. Within welding, women were more at risk than men of new-onset dermatitis (OR = 1.85; 95% CI 1.15–2.96) and dermatitis episodes (2.14; 95% CI 1.24–3.68) but were not more likely to report these were made worse by work. Use of SOHAS as the base metal was associated with reports that dermatitis was made worse by work (3.54; 95% CI 1.04–12.03), but having adjusted for SOHAS use, women still remained at greater risk. A final analysis considered the effect on risk estimates of removing those welding SOHAS from the analysis. The risk for women of episodes of dermatitis was essentially unchanged, whether the comparison group was male welders or women in the electrical trades. Conclusions Welding is associated with risk of dermatitis in women. Although welding of SOHAS was associated with dermatitis that was made worse by work, it does not importantly explain the higher female rates in welding and other causes must be examined to support preventive measures.