Analysis of Welding Technology about Bimetallic Clad Pipelines

Butt girth welding was a knotty problem for future application of bimetallic clad pipelines. At present, there were two kinds of problems: 1) To decide whether to use a variety of alloy welding procedure or to use corrosion resistant alloy full welding procedure; 2) After selecting the procedure, what kind of welding material should be equipped. In view of the above problems, taking 316L SS or 2205 DSS clad pipe as an example, welding process design and experimental analysis were conduted in this paper. Analysis of welding process from theory, standard and practice pointed out the control of welding hardness under different welding materials and procedure and directional suggestions of welding for bimetallic clad pipelines were provided. Futher the hardness distribution and CVN absorbed Energy test results of different welding processes showed welding quality could be guaranteed only when ENiCrMo-3 welding material was chosen for the whole weld.

Technological features of repair cracks in ship plates by comb cutting method

Ремонт трещин в судовых пластинах является наиболее ответственной и сложной операцией Задача получения заданных размеров проплава с обратной стороны свариваемого металла резко усложняется в тех случаях, когда доступ к обратной стороне шва затруднен или вообще невозможен, выполнение двухсторонних сварных швов на наружной обшивке корпуса судна, в большинстве случаев для доступа к поврежденным районам, приводит к увеличению числа сопутствующих работ по демонтажу (монтажу) оборудования и влияет на нормативные сроки ремонта судов, в том числе и при стоянке судов в доке. В данной работе излагаются результаты исследования эффективности технологии ремонта трещин, в судовых пластинах, путем ориентации сварочной ванны вдоль плоскости повреждения, за счет гребенчатой разделки поврежденного района с различной геометрией кромок. Представлены результаты аналитического исследования и факторных экспериментов оценки прочности сварных соединений с различной геометрией гребенчатой разделки, при односторонней сварке, с использованием различных сварочных материалов и варьировании режимов сварки. Приведены результаты металлографического исследования (на макрошлифах) полученных сварных соединений. Предложены технологически эффективные, для практического применения в судоремонте, параметры гребенчатой разделки трещин в судовых пластинах. Repair of cracks in the ship plates is the most responsible and complex operation The task of obtaining the specified dimensions of the melt on the reverse side of the welded metal is sharply complicated in cases where access to the reverse side of the seam is difficult or even impossible, the implementation of double-sided welds on the outer skin of the hull of the vessel, in most cases for access to damaged areas, leads to an increase in the number of related works on the dismantling (installation) of equipment and affects the normative terms of repair of vessels, including when ships are parked in the dock. This paper presents the results of the study of the effectiveness of the technology of repair of cracks in the ship plates, by orienting the welding bath along the damage plane, due to the comb cutting of the damaged area with different geometry of the edges. The results of analytical research and factor experiments assessment of the strength of welded joints with different geometry of comb cutting, with one-sided welding, using different welding materials and varying welding modes. The results of metallographic research (on macro-grinds) of the obtained welded joints are given. Technologically effective parameters of comb cutting of cracks in ship plates are proposed for practical application in ship repair.

About the threshold concentration of nickel oxide nanoparticles in long-term inhalation exposure of rats

Introduction. Nickel oxide nanoparticles are of interest for toxicological science, not only as engineered nanoparticles, producing for industrial and scientific needs, but also as spontaneous pollutants of the atmosphere and the working area in industrial processes related to metallurgy and welding. Materials and methods. Rats were exposed to nickel-oxide aerosol at a concentration of 2.4 ± 0.4 µg/m3 in a “nose only” inhalation setup for 4 hours at a time, 5 times a week, during an overall period of 2 weeks to 6 months. Results. Of the several dozen examined parameters, only a few statistically significant manifestations associated with the reaction of the deep airways to inhaled nanoparticles were noted. However, in the biochemical and morphometric parameters of the lungs, even at the longest periods of exposure, the intergroup differences were insignificant. At the same time, even from the first weeks of the exposure period, genotoxic and allergic indices shifts are detected. Conclusion. For most of the evaluated effects, this level of exposure to nickel oxide nanoparticles may be considered as close to LOAEL, or even to NOAEL. However, according to some indicators, there are effects that suggest a non-threshold nature.

Erratum: Čapek et al. On the Weldability of Thick P355NL1 Pressure Vessel Steel Plates Using Laser Welding. Materials 2021, 14, 131

The authors would like to correct the sentence in the “Materials and Methods” section of their article [...]

METHODICAL APPROACHES TO COMPLEX SANITARY AND HYGIENIC EVALUATION OF WELDING TECHNOLOGIES AND MATERIALS BASED ON MATHEMATICAL MODELING

The purpose of this article is to develop methodological approaches to a complex sanitary and hygienic assessment of welding materials based on modern methods of mathematical modeling. An ideological structure of a computerized database is proposed, which would allow to collect and edit data on welding materials and welding modes, to systematize them, as well as to display the necessary user information on the screen by processing various requests. The complex of harmful and dangerous factors accompanying welding processes is analyzed. The method of mathematical modeling of the dependence of the intensity of welding aerosol release on the set of technological factors is given and the necessity of its improvement is argued. The urgency of creating an information-analytical system of complex sanitary assessment of welding materials for the selection of optimal, from a hygienic point of view, welding technologies is substantiated. The advantages and disadvantages of the existing developments of information-analytical systems of managerial decision-making in the welded production are given. The structure and conceptual aspects of creating a new database for the computer system of information support of complex sanitary and hygienic assessment of welding technologies and materials, in accordance with modern requirements of the standard DSTU ISO 15011- 4: 2008.

Investigation of friction stir spot welding of high density polyethylene and polypropylene sheets

In this study, two different polymer materials were used. In the joints made with friction stir spot welding, firstly (PP/PP and HDPE/HDPE) and then different materials (PP/HDPE, HDPE/PP) joining processes were carried. The influence of the tool rotational speed and the stirring time on joint formation and weld strength were determined. The temperature of the liquid welding materials varies according to the materials to be combined. High weld strengths were obtained at the friction stir spot welding of similar plastic sheets. The highest weld strengths were obtained in PP-PP welds. Low weld strengths were obtained at the friction stir spot welding of dissimilar plastic sheets because of immiscible and incompatible blends formed during the welding operation. The lowest weld strengths were obtained in PP-HDPE welds. The chemical composition and the phase morphology of the blends, the mechanical scission occurrence and the welding residual stresses determine the strength of the welds.

Investigation of the Residual Stress in a Multi-Pass T-Welded Joint Using Low Transformation Temperature Welding Wire

We investigated whether low transformation temperature (LTT) welding materials are beneficial to the generation of compressive residual stress around a weld zone, thus enhancing the fatigue performance of the welded joint. An experimental and numerical study were conducted in order to analyze the residual stress in multi-pass T-welded joints using LTT welding wire. It was found that, compared to the conventional welded joint, greater tensile residual stress was induced in the flange plate of the LTT welded joints. This was attributed to the reheat temperature of the LTT weld pass during the multi-pass welding. The formerly-formed LTT weld pass with a reheat temperature lower than the austenite finish temperature converted the compressive residual stress into tensile stress. The compressive residual stress was generated in the regions with a reheat temperature higher than the austenite finish temperature, indicating that LTT welding materials are more suitable for single-pass welding.

Welding of pipes in fixed position with internal anti-corrosion protection of joints

The article reviews the weldability of clad steel used for protection of inner surface of oil-and-gas pipelines from corrosion by different welding materials. It is indicated that during welding of the root pass by stainless electrodes in one pass the transition structures appear on the interface of two dissimelar metals. This process leads to the formaion of cracks. To reduce negative impact of the transition structures on the characteristics of welded joints it is recommended to weld the first two passes with strainless electrodes.