scholarly journals Evaluation of the structural stability of welded joints in welding

2021 ◽  
Vol 2131 (4) ◽  
pp. 042063
Author(s):  
V Schepkin ◽  
Yu Poletaev
Keyword(s):  
Structural Stability ◽  
Heat Affected Zone ◽  
Welded Joints ◽  
Heat Input ◽  
Thermal Conditions ◽  
Fluctuation Analysis ◽  
Power Equipment ◽  
Chemical Homogeneity ◽  
Urgent Task ◽  
The Stability

Abstract Brittle (intergranular) destruction of the heat-affected zone metal (local failure) of welded joints of power equipment during welding and heat treatment (tempering) was an unexpected and serious problem. Its solution based on the development of progressive technological solutions is an urgent task of modern power engineering. The article considers an applied method of fluctuation analysis for assessing the stability of the structure and the probability of local destruction (LD) of the metal of the heat-affected zone (HAZ) of thick-walled welded structures of power equipment made of low-alloy steel 15Kh2NMFA. A computational - experimental method for calculating the range of optimal values of heat input is stated. The LD mechanism is stated and its connection with the technology and thermal conditions of welding and the structural stability of the HAZ metal is established. It was found that the growth of austenite grains of the HAZ metal stimulates the tendency to LD, if a dendrid-type carbide phase is precipitated at grain boundaries during welding. By optimizing the heat input during welding, it is possible to control the structural and chemical homogeneity of the HAZ metal and the associated tendency to form LD.

Evaluation of Influence of Thermal Methods of Metal Separation Cutting on Welding Quality

2017 ◽  
Vol 265 ◽  
pp. 755-761 ◽  
Author(s):  
A.K. Tingaev ◽  
M.A. Ivanov ◽  
A.M. Ulanov
Keyword(s):  
Heat Affected Zone ◽  
Welded Joints ◽  
Heat Input ◽  
Experimental Studies ◽  
Welding Process ◽  
Regulatory Requirements ◽  
High Quality ◽  
Thermal Methods ◽  
Welding Seam

We have investigated a possibility of obtaining high-quality welded joints after oxygen and plasma cutting of steel С355 without removing the heat-affected zone (HAZ), in which the changes in chemical, phase and structural compositions are observed. Numerical and experimental studies of the effect of heat input of MAG and Submerged Arc welding on the quality of welded joints are performed. In particular, it was found that when the heat input of welding is at least 6.5 kJ/cm, the metal of HAZ of the edges after cutting is heated during the welding to temperatures above Ас3, which leads to its full recrystallization. When the heat input of welding is at least 10 kJ/cm, the edges after cutting are completely melted and become a part of the welding seam metal. The presence of extensive areas of melting and recrystallization of the edges in the welding process contributes to obtaining high-quality welded joints without removing the HAZ of the edges after cutting. To verify the results of numerical studies, experimental tests of control welded joints were conducted, which showed that the values of bending angle and impact toughness of the welding seam metal and heat affected zone are significantly above the regulatory requirements to quality of welded joints, and not less than the same requirements for steel С355. The obtained results confirm the possibility of revising domestic regulatory requirements for the steel constructions production in terms of the preparation of edges for welding using technologies of thermal cutting without subsequent machining.

scholarly journals Corrosion Behavior of Welded Joints in Different Stainless Steels

2001 ◽  
Vol 71 (3) ◽  
pp. 440-449
Author(s):  
Eniko Reka Fabian ◽  
Janos Kuti ◽  
Jozsef Gati ◽  
Laszlo Toth
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Pitting Corrosion ◽  
Stainless Steels ◽  
Heat Affected Zone ◽  
Welding Speed ◽  
Welded Joints ◽  
Heat Input ◽  
Laser Power ◽  
Base Material

The welded metals characteristics produced by TIG welding or laser beam welding depend on heat input as a function of laser power and welding speed. High laser power and high welding speed have produced welded joint with a remarkable decrease in fusion zone size and an acceptable weld profile with high weld depth/width ratio. At duplex stainless steels the microstructure of welded metal, and heat affected zone is strongly influenced by cooling rate, which is depend on heat input as a function of laser power and/or welding speed. It was found that increasing welding speed the corrosion rate of welded joints decreased. In austenitic stainless steels appeared pitting corrosion in the base material as well as in the welding zone. In case of 2304 duplex stainless steel pitting corrosion appeared in welded metal and heat affected zone in case of autogenously welding, but at 2404 duplex stainless steel pitting appear more in the heat affected zone.

scholarly journals Welding Thermal Cycles of Joints Made of S1100QL Steel by Saw and Hybrid Plasma-Mag Processes

2020 ◽  
Vol 20 (4) ◽  
pp. 75-86
Author(s):  
A. Sajek
Keyword(s):  
Quality Assessment ◽  
Welded Joints ◽  
Heat Input ◽  
Thermal Effects ◽  
Arc Welding ◽  
Measurement Data ◽  
Welding Process ◽  
Thermal Conditions ◽  
Hybrid Plasma ◽  
Welding Processes

AbstractThe aim of this article is to validate the method of conducting a multipoint temperature measurement in the area of welded joints as a tool for quality assessment of the joints in question. In order to establish a relationship between temperature readout at a given point, the value of heat input and the distance of the point form the weld axis, preliminary tests have been conducted on a set of padding welds. Correlation of measurement data analysis showed the high 0.99 level. In the second stage of the study, temperatures of joints welded with two different methods have been measured: the HPAW (Hybrid Plasma – Arc Welding) and classic SAW (Submerged Arc Welding) method. The obtained temperature curves reflect the intensity of heat input in a given welding process. When compared to thermal effects on metallographic specimens, the shapes of the curves show a potential for quality assessment of joints in production conditions. Estimating thermal effects with classic analytical methods proves imprecise with respect to advanced high-power welding processes. Monitoring temperature will allow to assess the quality of joints in the course of welding, which may be a remarkable factor in terms of limiting the HAZ (heat affected zone) tempering of joints made from MART steels (advanced high strength martensitic steel) – a phenomenon that exceedingly decreases the strength of the joints. The method for quality assessment of welded joints presented in this paper allows to extend the analysis of welding thermal conditions.

scholarly journals A Study on the Fiber YAG Laser Welding of 304L Stainless Steel

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 2022
Author(s):  
Essam R. I. Mahmoud ◽  
Hamad Almohamadi ◽  
Abdulrahman Aljabri ◽  
Mohamed Abdelghany Elkotb
Keyword(s):  
Stainless Steel ◽  
Fracture Strength ◽  
Heat Affected Zone ◽  
Welded Joints ◽  
Heat Input ◽  
Laser Power ◽  
Processing Parameters ◽  
304L Stainless Steel ◽  
Delta Ferrite ◽  
Full Penetration

This work aims to optimize the main YAG fiber laser parameters to weld 304L stainless steel plates of 3 mm thick. Different laser powers (2500, 2000, and 1500 W) and speeds (60, 40, and 20 mm/s) were used and merged in heat input, maintaining the defocusing distance at –2 mm to get full penetration. The weld quality and the effect of the laser heat input on the microstructures of the weld and heat-affected zones were investigated. Besides, the fracture strength of the welded joints and hardness distribution through the cross-sections were evaluated. The weld width has a direct relationship with heat input. The laser power of 2800 W produced full penetration joints without any macro defects while reduction in laser power pronounced partial penetration defects. The size of the heat-affected zone in all the processing parameters was very small. The microstructure of the weld zone shows columnar dendrite austenite grains with small arm spacing in most of the welded zone. The size of the dendrites became finer at lower heat input. At a higher heat input, a reasonable amount of lathy equiaxed grains with some delta ferrite occurred. A small amount of delta ferrite was detected in the heat-affected zone, which prevented the crack formation. The hardness of the weld metal was much higher than that of the base metal in all processing parameters and it has a reverse relationship with the heat input. The fracture strength of the welded joints was very close to that of the base metal in the defect-free samples and it increased with decreasing the heat input.

Challenges for income generation methods in monopoly companies

2019 ◽  
Vol 2 (2) ◽  
pp. 54-64
Author(s):  
Ali Zurapov
Keyword(s):  
Market Competition ◽  
Social Needs ◽  
Income Generation ◽  
Working Capital ◽  
Technical Base ◽  
Fundamental Goal ◽  
Urgent Task ◽  
The Social ◽  
The Stability ◽  
Commercial Organization

In conditions of market competition, the fundamental goal of any commercial organization is to obtain the greatest profit, which directly depends on the amount of income received and expenses incurred. Current paper discuses  about main source of development of the material and technical base of the enterprise, replenishment of its own working capital, ensuring the social needs of the companies. Main objectivity is income factor in the stability of the existence and progress of the monopoly companies. In this regard, the management of the income of the organization is currently quite an urgent task for every giant entrepreneur. The article reveals the essence, purpose, objectives and measures in the field of enterprise revenue management. On the example of a particular enterprise, a dynamic and structural analysis of its revenues is carried out.

scholarly journals Hot-Wire Laser-Directed Energy Deposition: Process Characteristics and Benefits of Resistive Pre-Heating of the Feedstock Wire

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 634
Author(s):  
Agnieszka Kisielewicz ◽  
Karthikeyan Thalavai Pandian ◽  
Daniel Sthen ◽  
Petter Hagqvist ◽  
Maria Asuncion Valiente Bermejo ◽  
...  
Keyword(s):  
Heat Input ◽  
Energy Deposition ◽  
Fine Tuning ◽  
Hot Wire ◽  
Process Stability ◽  
Electrical Signals ◽  
Melt Pool ◽  
Directed Energy Deposition ◽  
Directed Energy ◽  
The Stability

This study investigates the influence of resistive pre-heating of the feedstock wire (here called hot-wire) on the stability of laser-directed energy deposition of Duplex stainless steel. Data acquired online during depositions as well as metallographic investigations revealed the process characteristic and its stability window. The online data, such as electrical signals in the pre-heating circuit and images captured from side-view of the process interaction zone gave insight on the metal transfer between the molten wire and the melt pool. The results show that the characteristics of the process, like laser-wire and wire-melt pool interaction, vary depending on the level of the wire pre-heating. In addition, application of two independent energy sources, laser beam and electrical power, allows fine-tuning of the heat input and increases penetration depth, with little influence on the height and width of the beads. This allows for better process stability as well as elimination of lack of fusion defects. Electrical signals measured in the hot-wire circuit indicate the process stability such that the resistive pre-heating can be used for in-process monitoring. The conclusion is that the resistive pre-heating gives additional means for controlling the stability and the heat input of the laser-directed energy deposition.

scholarly journals Ultrafast femtosecond pressure modulation of structure and exciton kinetics in 2D halide perovskites for enhanced light response and stability

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Chunpeng Song ◽  
Huanrui Yang ◽  
Feng Liu ◽  
Gary J. Cheng
Keyword(s):  
Femtosecond Laser ◽  
Density Functional ◽  
Thermal Conditions ◽  
Light Response ◽  
Shock Pressure ◽  
Laser Shock Processing ◽  
The Density Functional Theory ◽  
Pressure Modulation ◽  
The Stability ◽  
Inorganic Framework

AbstractThe carriers’ transportation between layers of two-dimensional (2D) perovskites is inhibited by dielectric confinement. Here, for the first time, we employ a femtosecond laser to introduce ultrafast shock pressure in the range of 0~15.45 GPa to reduce dielectric confinement by modulating the structure and exciton dynamics in a perovskite single crystal (PSCs), e.g. (F-PEA)2PbI4 (4-fluorophenethylammonium, F-PEA). The density functional theory (DFT) simulation and experimental results show that the inorganic framework distortion results in a bandgap reduction. It was found that the exciton-optical phonon coupling and free excitons (FEs) binding energy are minimized at 2.75 GPa shock pressure due to a reduction in dielectric confinement. The stability testing under various harsh light and humid thermal conditions shows that femtosecond laser shocking improves the stability of (F-PEA)2PbI4 PSCs. Femtosecond laser shock processing provides a new approach for regulating the structure and enhancing halide perovskite properties.

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