Papers by Keyword: Arc Welding

Abstract: Welding processes are commonly used in the industry for the manufacture of large parts or due to their complex geometry that does not allow the part to be manufactured as a whole. Nevertheless, the union can show worst mechanical properties than the rest of the piece, affecting negatively its service behavior, so it is necessary evaluate weald seam to ensure the correct process application. Electrical welding operations are commonly used due to the reduced equipment size or their possibilities application in numerous metallic materials. Notwithstanding, different variables have to be taken into account during the metal deposition, as intensity or speed deposition, among others. Weald seam geometrical evaluation is usually utilized to validate the union surface conditions. Despite this, surface irregularities caused during the process make its difficult to measure correctly with conventional equipment. However, laser profilometry is a non-contact technique that can be used to generate 3D profile of weald seam, facilitating its measurement with high accuracy. Therefore, in this work an initial analysis of the influence of material deposition speed and arc welding intensity on the weald seam geometry will be carried out using a laser profilometry equipment. In addition, to ensure a correct information acquisition, the laser profilometer requires a constant speed movement in relation with the weald seam analyzed, so new equipment has been manufactured, using additive manufacturing techniques, to support the profilometer throughout the information acquisition process.

Abstract: This paper provides a complete overview of the entire process of designing a welding head moving device and its implementation as a semi-automatic welding machine. The mechanical structure of the device is designed based on the size of the material pipe and the accompanying technical requirements. The system is equipped with an arc generator set and a rotary speed control unit allowing its use as an orbital welder.

Abstract: The statistical model is created for predicting penetration depth in an alternating current-based additional axial magnetic field controlled shielded metal arc welding of ASTM A 516 Gr.70 steel. The design for the trials is developed using the Placket-Burman design and response surface methodology. The created model determines the optimum process variables for getting excellent penetration depth. The input variables (current, magnetic field density, and magnetic frequency) are chosen for a response like penetration depth. This model can predict the main effects and the interacting effects of three process variables. The findings reveal that a higher current value with a low magnetic field density leads to deeper penetration and vice versa. Furthermore, a greater penetration depth is achieved at lower magnetic field density and higher magnetic frequency. With a desirability of 98.8%, the optimum process variables are 110 A, 0 mT, and 60 Hz. The predicted response values produced from the regression equation based upon process variables are extremely similar to the observed output, demonstrating the usefulness of second-order regression equations. For improved joint efficiency, a high level of penetration is needed.

Abstract: In orbital welding technology, it is difficult and time-consuming to make a standard weld by manual welding. This requires a skilled weld. Therefore, a more optimal welding method than automatic rotary welding has been created to replace the conventional manual welding method. This significantly improves weld quality and reduces welding time. In this explanation, we have experimented with an automatic orbital welding device that integrates a filler wire-feeder device into the welding process. We refer to the American National Standard AWS D18.1/D18.1M: 2009 documents to review the weld results. We then analyze the advantages and disadvantages of the weld and propose solutions.

Abstract: Current aspects of the developing of modern self-shielding flux-cored wires composition for arc welding of low-alloyed steels are considered. Advantages and disadvantages of flux-cored wires of carbonate-fluorite, oxide and oxide-fluoride types of are shown in comparison. The effectiveness of gas shielding of molten metal at welding with self-shielding flux-cored wires of carbonate-fluorite type is analyzed considering the thermal properties of their cores. It is shown that to improve reliability of gas shielding at welding using the wires of this type it is important not only to ensure generation of sufficiently large volume of shielding gases at thermal destruction of the wire core, but also to control this process, providing gas evolution at all stages of heating and melting of the wire. The results of complex thermal analysis of the wire core mixtures containing, for example, lithium carbonate show substantially large heat losses for heating and melting of the wire core, which are accompanied by the development of energy-intensive processes of thermal destruction of core components. It is shown that the limitation of lithium carbonate content in the wire at the level of not more than 2 wt. % allows not only to preserve welding arc burning stability at the acceptable level but also to provide effective gas shielding of molten metal and easy separation of slag crust. The control of thermochemical reactions in the core is achieved by selection of its proper composition to ensure favorable melting of flux-cored wire and electrode metal transfer to the welding pool. Results of metallographic examinations of distribution and composition of non-metallic inclusions in metal of the welds made with wires of the oxide and oxide-fluoride types are presented. Main properties of the developed self-shielding flux-cored wires and recommendations on welding are given in conjunction with prospective fields of their application.

Abstract: A review of publications on metallurgical and foundry production showed that many authors, when analyzing the properties of liquid metals and alloys, proceed from the concept of their cluster structure. The cluster structure of a liquid is a hypothesis, but it is confirmed by studies of diffraction of X-rays, electrons and neutrons reflected from its surface. This paper considers the existing concept that a cluster is a crystal-like concentration of atoms. Around the clusters there is a weakened zone, which consists of disordered atoms, the volume of which does not exceed 3 ... 5%, and this provides the fluidity of many melts. The authors of the publications have achieved success in explaining the forming structure of ingots, proceeding from the cluster mechanism of the crystallization of liquid metals and alloys. The authors of this work suggested that the superheated liquid metal in the head of the bath, which has smaller clusters, moves under the action of magnetic fields to its tail, and provides refinement of the weld metal structure during welding with the action of a control transverse magnetic field.

Abstract: The article describes the results of experiments on the use of silicon production waste as an additive that improves the structure and properties of materials and the efficiency of welding process. The flotation technology can be used to separate gas cleaning dust, which is a silicon production waste product, into commercial products. The chamber product, containing ultrafine silica, was used as a modifying additive in concrete. It improved its structure and increased its strength compared to the samples without additives. The modifier made from chamber products introduced into gray cast iron made it possible to obtain graphite of a more favorable shape as compared to the lamellar form of graphite in traditional gray cast iron. Its strength increased. The experimental results on the welding process with an activating flux, which includes ultrafine silica isolated from the metallurgical waste, are presented. The activating flux improved the penetrating ability of the welding arc by 1.5-3 times, the energy consumption decreased by 30-50%.

Abstract: The paper presents data of experimental research into the importance of protective surface coatings in welded products for MMA stability; heat field distribution patterns on their surfaces, and structure and phase composition of the welded metal. The study has revealed that a protective surface coating in a welded item in MMA has a positive effect on shortcut duration, increasing it by 5-11 %, raising its formation and transformation time by 10-12 %; 15% dimensional increase of a welded metal grain is registered as well, and a heat impact zone expands by 25%.

Abstract: The paper addresses mathematical models of element transition into overlaying metal and weld metal in different methods of arc welding: stir welding, welding taking account the transition coefficients, empirical, kinetic, and thermodynamic welding. Their comparative analysis is made, their advantages, disadvantages, as well as various applications, are demonstrated. The approach to creation of mathematical models of manual arc welding with coated electrodes and flux cored wire, based on the method of complete material balance, is grounded.

Abstract: The possibility of making welded steel joints using arc welding in a reducing medium of carbon monoxide was studied. A method was proposed to eliminate its negative biological effect by heating the feed gas above its flash point, followed by oxidation till carbon dioxide was obtained. Welding modes have been selected to ensure the formation of a quality welded joint. Comparative studies of welded joints obtained using an oxidizing atmosphere of carbon dioxide and a reducing atmosphere of carbon monoxide were carried out. A chemical and metallographic analysis of welded joints was performed. The thermodynamic substantiation of chemical reactions in which carbon and microalloying additives can participate was presented. It was established that the main difference between the proposed welding method and those used at present was the suppression of oxidative processes in liquid metal due to the presence of a reducing atmosphere.