Papers by Keyword: Weld

Abstract: The ends of the welding beads are the site of certain non-conformities due to the transitory regime used for welding. In these start and end areas of the welding beads, the thermal field is propagated in non-stationary regime, as opposed to the portions from the middle of the welding bead where the heat is propagated in quasistationary regime.This paper proposes to present the influence of non-stationary thermal field from the welding ends on the hardness values performed in such critical areas, by comparing these values with the values of hardness performed on the middle portions of welding beads. A similarity comparison is made with the situation of the welding works performed within the reconditioning process by welding, when the welding works are of short length executed with multiple rows, were the thermal field is also propagated in non-stationary regime.

Abstract: Petrochemical equipment and installations are vital components of a National energy system. Age and their wear, uncertainty related to their technical status, lack of automation and monitoring systems slows the implementation process of the risk management system in the context of the new regulations on safety in operation and environmental protection requirements. The paper presents an inspection, related to structural integrity of a petrochemical plant component. As a complementary technique, of the classical mechanical tests, an advanced method of examination SEM was used. Combining the results led to highlighting and a comprehensive understanding of the failure mechanisms of the tested materials, impacting on the confidence of the risk level and the safety in operation of inspected components.

Abstract: The influence of the welding current and method of gas shielding in MAG welding on the content of silicon and manganese is considered. Results of study of the welded specimens of steels 45 and 30HGSA when applying welding wire of different formulas and different types of gas shielding (traditional shielding and two-jet shielding) are given. It is established that in MAG welding the value of the welding current and the speed of the gas flow from the welding nozzle have a considerable impact on the chemical composition of the weld metal. The consumable electrode welding under double-jet gas shielding provides the directed gas-dynamics in the welding area and enables controlling the electrode metal transfer and the chemical composition of a weld.

Abstract: Due to the difficulty of manufacturing complex small pieces ofthe new bearing steel0.30C-Cr-W with high-performance in the aviation industry, the electron beam welding process are usually used for preparing the complex parts.Thewelding performance of 0.30C-Cr-W steelwas calculated by theory and confirmedby actual experiments.The base metal was preheated,then welded and heattreated for weldments.The purpose of this work is to study the properties and the microstructure changes of base metal after heat treatment, weldments before heat treatment and weldments after heat treatment.The results show that the base metalafter heat treatment is sorbitic,weldzone of weldments after heat treatmentismartensite and austenite, theprecipitated M₂₃C₆ and M₆C in latter (the weld zoneof weldmentsafter heat treatment) were more thanthe former (the base metalafter heat treatment), and the strengthof the latter is 23.4%lower than the former, theroom temperature impact absorbing energy and hardness of the latter increased 13.5% and 6.6%. It may be considered that0.30-C-Cr-W steel is not suitablefor welding by the theoretical calculations, but after reasonable preheat and post-weld heat treatment, the mechanical properties of the weld afterheat treatment can satisfy the requirements.

Abstract: Mechanical tests of alloyed TiNi compounds with shape memory effect were performed. Low-cycle tests of alloyed compounds showed that an increase in the number of cycles to failure doubled. Studies conducted using the indentation showed shape recovery of print on material of alloyed weld within 0.7-1.2%.

Abstract: To research the failure mode of solid-web type telescopic jib typical weld, extract and quantify failure characteristics, obtain failure regularity of jib performance and solve the problem that welds do not be established by conventional finite element analysis. The weld strength is replaced by the maximum stress of the corresponding section, which may cause the simulation results low and distortion, and cannot simulate weld defects. A new modeling method is used by this article, which establishes and simplifies the weld physical shape, simulate and analyze weld strength. The Life and Death element technology which is based on the ANSYS software is used to simulate weld defects. The weld strength that is obtained by conventional analysis simulation is 110MPa, after processing, stress of weld model without defects is 395MPa, the theoretical value be calculated is 437MPa, stress of weld model with defect 1, 2, 3 respectively is 586MPa, 402MPa and 475MPa. Through comparing the simulation value and the theoretical value and the comparison between the simulation values, the simplified model that is proved is reasonable, the technical route which is used to simulate weld defect by Life and death element technology is feasible. It can be used to predict failure critical value under typical working condition, assess whether the weld failure. The working condition of jib can be simulated, and the main factors can be retrospect.

Abstract: In this paper are presented the results of experimental studies determining the dependence of the impact of an innovative welding micro-jet method on the intensity of abrasive wear of chrome-manganese 20MnCr5. The presented method is generally used for the constructions work items matrix for the production of silicate. The results confirm that the micro-jet welding method reduces the abrasive wear intensity of about 20% compared to the steel after thermo-chemical treatment. Other parameters such as the friction coefficient and power friction show comparable value, and therefore do not have a significant impact on working conditions.

Abstract: Attenuation coefficient is frequently-used for ultrasonic creep inspection in metals. However, in practical inspecting, e.g. thick wall weldment in high temperature pipings, it is usually difficult to measure the accurate propagating distance of ultrasound, which results in an inaccuracy of attenuation coefficient calculation. Therefore, a modified method for attenuation coefficient calculating was proposed here, in which the flight-time of ultrasound was substituted for propagating distance. The new calculated attenuation coefficient was named as flight-time-attenuation parameter, and had a unit as dB/us. A uniaxial tension creep experiment with pure lead was conducted to verify the detecting ability of this new parameter. Two piezoelectric wafers were pasted on the pure lead specimen, and ultrasonic testing was carried out simultaneously without interrupting the tension procedure. Attenuation coefficient and flight-time-attenuation parameter were calculated with inspecting signal acquired from creep specimen, and compared with each other. The results showed that two ultrasonic parameters had the same variation tendency along with creep procedure, and flight-time-attenuation parameter had a better sensitivity. Accordingly, the flight-time-attenuation parameter could be used for ultrasonic creep inspection in metals, and worked as a replacement of attenuation coefficient calculated with propagating distance. Another creep inspecting experiment with P91 steel weldments was conducted to verify the practicability of the new parameter, in which the new flight-time-attenuation parameter showed a good distinguishing ability for different creep status.

Abstract: Weld cladding was investigated using a nickel alloy clad on a high strength low alloy carbon steel substrate. The effects of pre-heat temperature, clad material and post-weld heat-treatment are examined, along with the potential for thinner clad layers using laser cladding. Experimental residual stress measurements show good correlation with the simulation model. Metallurgical studies illustrate good fusion between clad and substrate materials. The potential for a fatigue-resistant cladding was demonstrated in a stainless steel clad with the possible use of post-cladding operations to enhance the outcomes for the nickel alloy clad.

Abstract: Industrial Radiography is the most widely accepted NDT technique for weld quality in industries. As it is an indirect method, defect type and nature must be obtained by analyzing the radiographs. Manual interpretation of radiographs is subjective in nature. So the paradigm shifted to automated weld defect detection system. Though considerable research is done in automated weld defect detection, an accurate domain specific technique has not yet been evolved due to noise, artifacts in radiographs, low contrast between the defect region and the background and difficulty in isolating the defect. The proposed work aims at developing an automated weld defect detection system that enhances the contrast between the object and the background and isolates the weld defect. In this work, real time weld radiographs are acquired and contrast enhancement is performed with DWT. Slag and Porosity are isolated and dimensionally characterized.