Papers by Keyword: Weld Joint

Abstract: The paper presents a formation of residual stresses near the weld-affected zone. It is shown that the residual stress values depend on load application and the type of weld joints. The proprietary know-how is suggested for the analysis of stress and strain state using measurement of the ultrasound velocity in weld joints under load. A correlation between effective and residual stresses is shown when testing the bridge crossing over the river Tom (Tomsk, Russia). A method of reducing these stresses using the ultrasonic impact treatment is suggested herein.

Abstract: Welding and pad welding are widely used methods of repair and regeneration of defective magnesium alloys castings. AZ91 is one of the most popular magnesium alloys used at temperature up to 120°C. Therefore there is need to study the influence of welding and elevated temperature exposure on the microstructure and properties of AZ91 weld joints. This paper discusses microstructural stability of AZ91 gas tungsten arc weld joint in T6 condition (solution treated and aged). In order to examine the weld joints microstructural stability, the long-term annealing has been carried out at 120°C. Hardness of the base metal and fusion weld was measured after 250, 500, 750 and 1000h exposure respectively. Additionally, the base metals and the welds microstructure after 1000h annealing was investigated. Both in the base metal and in the weld, long-term annealing caused decrease in the intermetallic phases volume fraction. However, neither phase composition nor hardness of the weld joint were influenced by the heat treatment. Based on these results, it could be stated that the microstructure of investigated weld joint is stable at working temperature.

Abstract: In this paper the mechanical heterogeneity of welded joints was studied. The experimental results show that the mechanical properties and fracture toughness vary significantly in zones of welded joint. To estimate the fracture parameter J-integral a numerical finite-element model based on the random variation of yield strength was proposed.

Abstract: Welding is the most widely used technology of creating permanent joints in the engineering industry. Correct setting of welding parameters predisposes quality weld joint without unwanted defects. Article deals with the influence of fusion welding parameters on the final quality welds. Describes the thermal cycle of welding and its effects on the weld joint and theoretically describes used methods MIG / MAG. Core of the article is devoted to the description of the experiment and on the technological parameters of the welding process. Quality of weld is tested visually, metallographic and microhardness measurement of the weld joints.

Abstract: Primary loop recirculation (PLR) piping weld joints in light water reactor (LWR) environments are more susceptible to stress corrosion cracking (SCC). Limited experimental work also suggested the complicated material and mechanical property of the fusion zone and the heat affected zone (HAZ) especially in dissimilar weld joints might play an important role in promoting SCC growth. In our study, different from the former sandwich like weld joint, a model of continuous heterogeneity mechanical property was established, the effect of welded mechanical heterogeneity on the stress-strain field and J-integral along the crack fronts at different locations were simulated in an Alloy 182-A533B dissimilar weld joint by the elastic-plastic finite element method (EPFEM). The results indicate that the crack near the dividing line of base metal (BM) and HAZ has higher resistance to SCC. At the dividing line of HAZ and weld metal (WM), the crack is prone to propagate into the WM, and will present more complex crack morphology and behaviors.

Abstract: Welding experiments were made with δ=14mm, 16MnR steel by three welding methods, manual electric arc welding, automatic submerged arc welding and semi-auto solid-core CO2 shielded arc welding, and weld joint test with samples from every welding specimen. The properties of welding joint were analyzed by three welding methods and in every position of welding, concluded that brittlement problems in heat affected zone arise from the CO2 shielded arc welding, it is because of the heat damage of alloy elements of weld joint metal while using CO2 shielded arc welding, but the strength of the weld joint is high because of its high fusion ratio. So for improving the mechanical properties of weld joints.it had better accelerate the cooling rate of weld bead and decrease the heat input of welding.

Abstract: Weld parameter is an important factor affecting micrographic structure and mechanical properties of weld joints. It was investigated by metallographic experiments and mechanical property experiments for the influence of weld heat input on dissimilar steel weld joint of penstock using B610CF and 16MnR steel in water conservancy and hydropower engineering using shielded metal arc welding method and mixed active gas arc welding method. Metallographic experimental results show that in weld metal with the increase of weld heat input the quantity of bainite decreases and crystalline grain is larger when using the same welding method; but in both B610CF and 16MnR steel heat affected zone, there is no distinct difference in microstructure. Mechanical property experimental results show that in weld metal with the increase of weld heat input the impact toughness decreases when using the same welding method, but in both B610CF and 16MnR heat affected zone, there is less difference in impact toughness; and there is no distinct difference in tensile strength and plasticity of weld joint. So moderate weld heat input is recommended.

Abstract: To research the corrosion of clad pipe weld joint, commenting the welding processes of and analysis of the corrosion medium of clad pipe weld joint, using electrochemical impedance spectroscopy carried out the comparative analysis of Nyquist and bode diagram within the time limit of clad pipe weld joint. The results showed that: 316L/20G clad pipe weld joint in the sewage water up to two weeks, because of the passive film thickening, weld corrosion resistance up to the maximum, and then stabilized; Its resistance is slightly decreased, but still has a good corrosion resistance, therefore, 316L/20G clad pipe can be widely used in the sewage pipelines of oil and gas fields.

Abstract: A kind of white massive microstructure in weld joint of P91 steel was first discussed by OM, SEM and EDS analysis. Results indicated that it is a kind of substance with low melting temperature other than the conventional delta ferrite. It contains high content of Cr due to improper choice of weld electrode and weld heat treatment. The existance of the abnormal microstructure will result in cracking under large stress for poor toughness. Solutions are suggested to prevent the formation of the white massive microstructure.

Abstract: Almost 50% above parts in the car are weld jointed. Corrosion effects are main threats to all this welded part and commonly cause the mechanical failure. Corrosion effect can be more when the car or any transportation is exposed to sea environment or salt water. The objective of this study are determining the effect of corrosion and predict the degree of durability on welded joint under corrosion effect. In order to perform the corrosion, salt spray test are used to give the corrosion effect welded joint parts. 48 hours in Salt spray test can give corrosion effect equal to 5 years of industrial condition. To obtain the structural condition, the tensile test, Infinite Focus Microscope (IFM) and Metallographic test was performed to get the corrosion rate. From the experiments, it was found that the corrosion effects will increase by the times. The roughness of the surface corrosion on welded joint gives a lower durability due to failure in welded parts.