Production Of Welded Joints Research Articles

STRUCTURAL-PHASE STATE AND METAL FRACTURE SURFACE OF WELDS MADE WITH THE USE OF NEW MATERIALS BASED ON TECHNOGENIC RAW MATERIALS

The structural-phase state and the metal fracture surface of 09G2S steel welds made using new welding materials based on technogenic raw materials of metallurgical production (silica manganese slag and aluminum electrofilter dust) were studied by scanning and transmission electron microscopy methods. The production of welded joints was carried out in laboratory conditions using welding wire of the Sv-08GA brand on the equipment of the scientific and production center "Welding Processes and Technologies" of SibSIU. Quantitative analysis of the parameters of the structure and dislocation substructure of the weld metal was performed, using the equipment of the Institute of High-current Electronics SB RAS (Tomsk). The contributions of scalar and excessive dislocation density to the strength of the weld metal are estimated. It is established that the main metal phase of the studied welds (regardless of the introduction of the additive) is a solid solution based on α-iron (ferrite, BCC crystal lattice, α-phase). In addition to α-iron, particles of iron carbide (cementite) and (mainly in the sample without additives) iron silicide of the composition Fe3S are present in the weld metal. Analyzing electron microscopic images of the structure of the weld metal, it was noticed that the narrowest contours are formed at the interfacial boundaries of the inclusion – matrix. Such inclusions detected by transmission electron microscopy methods may be cementite particles located in the volume and at the boundaries of ferrite grains, and iron silicide particles of rounded (spherical) shape located in the volume of ferrite grains. It is revealed that the inclusions of the second phase present in the weld metal are stress concentrators and can be centers of microcrack nucleation under mechanical action on the material.

Determination of Parameters of Electrode Metal Transported Drops by Simulation and Visualization

The nature of the molten electrode metal melting and transfer is the main process parameter of manual metal arc welding (MMA) with coated electrodes. It significantly affects the efficiency of the welding process. For this reason the relevant task is to identify the parameters of the transferred molten electrode metal drops and their further transfer into the weld pool with maximum accuracy. The aim of the given paper is to develop a method and visual representation of the form and the geometrics (volume, area, mass) of a molten electrode metal drop.We have developed the method of simulation modeling and visualization for molten electrode metal drops transfer and their parameters. It allows obtaining highly reliable input data to be used for developing and verification of mathematical models for the thermal fields distribution along the welded item surface. The algorithm is realized as the calculation programs for specifying the molten metal drop parameters and means of its geometrics and space form visualization.We used this method to specify a number of molten electrode metal drop parameters: volume, mass, center-of-gravity position, surface area.We have established that it is possible to conduct the measurements with maximumThe suggested method significantly decreases the labor intensity of experimental studies aimed at specifying the size of electrode metal drops in comparison to the standard methods. When we know the size of the drops under certain welding conditions we can control the drop transfer process, i. e. reduce the heat input into the welded item and produce weld joints with the tailored performance characteristics.

Analysis of the Formation of Welded Joints from Non-Ferrous Alloy

The features of the production of welded joints from non-ferrous alloys are considered. The disadvantages of the used capacitor welding methods are described. To reduce the possibility of intermetallic compounds, it is proposed to use high-voltage capacitor welding with induction-dynamic drive (HVCW with IDD) on super-rigid modes of action. The technological scheme methods of HVCW with IDD are given, the physical nature of the impulse process is described. The results of comparative analysis of the waste of thermal energy depending on the technological method and roughness of the welded surfaces, as well as the ratio of thermal and mechanical energies for each method of HVCW with IDD are given.

Features of electron-beam welding of Ti-TiB alloy with 12Х18Н10Т steel

The basic regularities and ways of optimizing the production of welded joints of Ti – TiB alloy plates and 12Х18Н10Т steel were studied. The ways to achieve the necessary mechanical characteristics of welded structures from elements with a thickness of 10 mm obtained by electron beam welding were found out. It was determined that electron beam welding of Ti – TiB alloy compounds with 12Х18Н10Т steel is effective when using a double strip of niobium and 10Г2 steel. It was found that in order to obtain welded joints of the Ti – TiB alloy with Nb electron beam welding, it is necessary to ensure the melting of the Ti – TiB alloy, conditions for wetting niobium with the obtained melt, and to prevent the formation of an intermetallic layer in the weld. It is shown that the welded joint Ті-TiB - Nb - 10Г2 - 12Х18Н10Т obtained by electron beam welding allows to achieve a strength level of at least σв = 260 MPa.

Effect of laser mode on microstructure and corrosion resistance of 316L stainless steel weld joint

The different welding methods can produce weld joints with different microstructure, mechanical properties and corrosion resistance. The purpose of this paper is to investigate differences of two kinds of weld joints that prepared by the Nd:YAG and the Slab CO2 lasers welding 316L stainless steel. The macroscopic, microscopic structure and corrosion resistance of the weld joints are characterized by optical microscope, scanning electron microscope (SEM) and electrochemical workstation. The results show that compare with the weld joint of the Slab CO2 laser, the Nd:YAG laser with the larger dimension of weld metal zone and heat affected zone, and the dendrite arm spacing (DAS) and secondary dendritic arm spacing (SDAS) are larger on both sides of the weld metal under the heat input is the same. More ferrite and carbide precipitate in the heat affected zone of the Nd:YAG laser, which contributes to the corrosion resistance of the entire welded joint is worse. The grain size in the center of the Slab CO2 laser weld metal is coarser results in the corrosion resistance of its weld metal inferior to the Nd:YAG laser.

Influence of Aluminum Coatings on the Quality of Weld Joints

The application of a longitudinal magnetic field in welding aluminum coated sheet is considered. A special welding head is used to produce weld joints of satisfactory quality. Findings are obtained regarding the formation and metallographic structure of the metal in the seam, with the segregation of aluminum over its cross section. The formation of composite structure is noted.

Experimental Investigation on Mechanical and Distortion Characteristics of Titanium/Aluminium Dissimilar Metal Joint Using Laser Beam Welding

Laser beam welding (LBW) is based on interaction between the laser source and base metals. Different methods have been developed recently to produce weld joints of light metals. This produces good weld bead to simplify the structure and reduce the weight and cost to meet the important concerns of aerospace industry. To achieve these, Ti (Ti6Al4V) and Al (AA2024) dissimilar alloy sheets are welded with butt joint configuration using Nd: YAG pulsed laser welding unit. The weldment is subjected to tests to evaluate mechanical and distortion characteristics. From the test results, it is found that LBW is very much suitable for joining Titanium/Aluminium (Ti/Al) alloy sheets.

Comparison of the mechanical properties and microstructural evolution in the HAZ of HSLA DOMEX 700MC welded by gas metal arc welding and electron beam welding

High strength low alloyed steels are nowadays an important group of engineering materials, with numerous industrial applications. Properly chosen chemical composition together with the thermomechanical processing allow to reach high mechanical properties, while the carbon content is maintained low. Resulting microstructure is therefore sensitive to the amount of the heat introduced to the metal during welding. During welding procedure, softening phenomenon can occur in the heat affected zones and it could lead to the degradation of the mechanical properties of the final joint. Nowadays, welding technologies based on the high energy electron beam are able to produce weld joints with very narrow heat affected zone. In this study, authors compare mechanical properties and the microstructural evolution in the heat affected zone of the GMAW and EB welded joint of the DOMEX 700MC HSLA steel. The carried out experiments showed that both evaluated technologies are able to produce joints with appropriate mechanical properties. Welded joints made by the EBW technique showed slightly better mechanical properties of the whole joint, as a result of the narrower HAZ.

Optimization of Current, Voltage and Powder Feed Rate on Mechanical Properties of Plasma Transferred Arc Welded SS 316 Joints

Abstract Plasma Transferred Arc Welding (PTAW) process parameters were optimized for joining 316 stainless-steel plates to produce weld joints with maximum tensile strength, impact strength and hardness. Taguchi technique was applied for optimizing the selected welding parameters such as welding current (I), welding voltage (V) and powder feed rate (PFR). L9 orthogonal array was selected according to the aforementioned factors with three levels and experimental tests were performed. Signal-to-noise (SN) ratio was used to evaluate the experimental results. The results indicate that the welding voltage has the greatest infiuence on tensile & impact strength and welding current is the significant factor for hardness.

Investigation on TIG welding parameters of 2205 duplex stainless steel

TIG welding process parameters were analysed for joining duplex stainless-steel plates. Signal to noise (SN) ratio and Analysis of Variance (ANOVA) analyses were applied for investigating the selected welding parameters. The selected parameters were current (A), gas flow rate (L/min) and speed (mm/min). The purpose of this work is to produce weld joints with maximum impact of strength and hardness. L9 orthogonal array was selected according to the aforementioned factors with three levels. The impact strength of the joints was found using the Izord impact testing machine and hardness of all joints was measured using the Brinell Hardness machine. From the SN ratio analysis, it was observed that for the high impact strength, the required welding current was 150 A, gas flow rate was 14 L/min and the welding speed was 210 mm/min while for high hardness, the welding current was 190 A, gas flow rate was 12 L/min and the welding speed was 175 mm/min. ANOVA analysis indicated that the gas flow rate was the most significant one for both impact strength and hardness of the joints.

Optimization of weld bonding process parameters of austenitic stainless steel 304L and low carbon steel sheet dissimilar joints

Weld bonding is a hybrid joining process used to produce weld joints between similar or dissimilar metallic materials. In this work, a systematic study has been undertaken to investigate the effect of the input process parameters on the weld joint quality of dissimilar materials i.e. austenitic stainless steel 304L and low carbon steel sheet, in terms of joint strength. Experiments were planned on the basis of response surface methodology technique with three control factor and their three levels of process parameters. Experimental results were used to develop a mathematical model to predict the tensile shear strength and peel strength of the weld joint. A mathematical model, correlating the process parameters and their interaction on responses, was also established. The developed model was validated with the confirmation test case experiment, and it has been observed that the developed model is capable to evaluate weld joint strength within the range of process parameters being used. Numerical optimization technique was applied to find out the optimal set of input parameters.

Avaliação da Influência de Tratamentos Térmicos Pós-Soldagem Sobre a Microestrutura e Propriedades Mecânicas de Juntas de um Aço API 5L X70Q

ResumoAços que atendem à norma API 5L são aplicados na construção de dutos e há grande interesse naqueles de maior resistência, como o grau API 5L X70Q. Ainda são escassos os estudos relacionados a tubos sem costura. Durante a montagem, os tubos podem ser soldados por eletrodos revestidos (SMAW) e eventualmente sofrer aquecimento indutivo para adequação à topografia do terreno, processos que podem alterar a microestrutura das juntas. Neste trabalho foram obtidas juntas soldadas pelo processo SMAW, a partir de tubo sem costura grau API 5L X70Q. As juntas foram submetidas a tratamentos térmicos pós-soldagem nas temperaturas 920 °C e 600 °C. Foram realizados ensaios de tração, impacto Charpy e microdureza, além de caracterização metalográfica nas amostras de metal base e nas juntas como soldadas e após os tratamentos térmicos. O tratamento térmico a 920 °C promoveu a formação de estrutura ferrita/perlita, com consequente redução na resistência mecânica das juntas a valores inferiores aos especificados para o grau X70Q. Porém, o tratamento térmico a 600 °C mostrou-se benéfico devido à redução da fração volumétrica dos constituintes martensita/austenita e martensita-austenita-bainita, sem reduzir de forma significativa a resistência mecânica e com relativo ganho na tenacidade ao impacto na ZTA e na ZF.

Mechanical properties of duplex steel welded joints in large-size constructions

Thick panels measuring 9.5, 14.5, and 18.5 mm made of UNS S31803 duplex steel were tested for welding with the use of powder wire. The target task consisted in determination of the impact of the welding process with an increased root gap on the mechanical properties of joints, as compared with the properties achieved by welding with a 6-mm threshold distance in compliance with the provisions set out in the DNV regulations. The results demonstrated that the root gap tolerance could be extended; furthermore, they proved that wide-clearance welding – production of welded joints through double cordon welding with a single operator in the vertical position (PF) – is possible without the need to apply border hardening in the case of duplex steel, provided that the weld groove geometry has a root gap within 6–10 mm, from the point of view of compliance of welded joints with requirements concerning mechanical properties.

Metallurgical special features of the production of welded joints in dispersion‐filled metallic composite materials

Metallurgical special features of the production of welded joints in dispersion‐filled metallic composite materials

Technology of production of welded joints in high‐hardness steels resistant in hydrogen sulphide media

Technology of production of welded joints in high‐hardness steels resistant in hydrogen sulphide media

Laser welding of gold alloys.

A neodymium glass laser was used to produce weld joints between test pieces of four different casting gold alloys. The mechanical properties of the welds were determined and their microstructures were evaluated. The results of this study indicate that laser welding of dental casting gold alloys is metallurgically feasible.