Mechanical and Microstructural Effects on Medium Carbon Steel Weld Joints when a Gmaw Process is used to Repair Structur
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MECHANICAL AND MICROSTRUCTURAL EFFECTS ON MEDIUM CARBON STEEL WELD JOINTS WHEN A GMAW PROCESS IS USED TO REPAIR STRUCTURAL COMPONENTS USED IN THE MANUFACTURING OF HEAVY MINING EQUIPMENT 1-2
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Eduardo Valenzuela ,Víctor López 1
Equipos de Acuña S.A. de C.V. Carretera Presa a la Amistad Km. 8.5 .Parque Industrial Modelo, C.P. 26220, Cd. Acuña, Coahuila, México, (877) 7730606 Ext. 5470, Fax (877) 7731131, 2Corporación Mexicana de Investigación en Materiales S.A. de C.V., Ciencia y Tecnología #790. Fracc. Saltillo 400, C.P. 25290, Saltillo, Coahuila, México, (844) 4113200 Ext. 1215, Fax (844) 4113210, [email protected] Abstract Meet the technical specifications defined by the design engineering department is a critical factor to have of a good performance during the normal life cycle of heavy mining equipment. This study was done to determine how the repair process carried out in order to recover structural components that did not meet the proper quality criteria after the inspection process, can alter the microstructure and the mechanical properties of the product used in the construction of heavy mining equipment. As the repair process can be done not only once, but twice and until three times using a manual GMAW process, this study was carried out under controlled conditions and using similar process parameters as those used in the manufacturing process. A set of four specimens were prepared, one without any repair, and the other three with one, two and three repairs. In order to evaluate the sanity of the welded unions and also the materials behavior of each one of the specimens, tensile, microhardness, macroetch, charpy, and metallographic tests were carried out Key words:Microstructure, Welding, Hardness, Mechanical Test, Scanning electron microscopy ( SEM ) Introduction It is a common practice in the production environments to repair pieces when during the inspection process a parte is rejected because it does not meet the quality standard; however it is very important to assure that every repair process can be defined properly to avoid to put in jeopardy the quality of the final product. This analysis was carried out in a company dedicated to the production of heavy equipment for mining operations One of the products made in the factory uses as a primary fabrication process a submerged arc welding process (SAW), however sometimes a repair process is needed when an
ultrasonic test carried out during the quality inspection detects an indication that after the evaluation done by a certified UT level II inspector became considered as a defect. Each part is 100 % tested following an ultrasound technique (UT) to determine if the component is good or bad. Only until the UT shows no defects the component is released to be used in the final product. Due to the fact that the repair process can be done once, twice and even three times, the main goal for this study is to determine how the repair process affects both the mechanical and the microstructural properties. During the repair process a welder “open
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