Salvage Of Casting With Arc Welding And The Welding Quality Evaluation

A new process of controlling the heat input and adding C and Si was studied to avoid the scrap of cylinder liner because of casting defects. Also evaluation of welding quality was proposed, with a view to promote the application of the new process and a systematic quality control of repair welding.Considering of aberration, machinability and tissue, Tarkall-C was welded by TIG with the same material. The cooling time was controlled by reducing current. The machinability and tissue was judged by microhardness testing, and the tissue was researched by metalloscope. The results showed that there was no color difference, no high hardness zone and no high carbon martensite, the ability of graphitization became strong in welds, the graphite changed into sheets from globular shape; the cementite in welds and fusion zones lessen, there was no high-carbon martensite and no cold cracking HAZ. Fe3C was lesser and the graphite grew. Also Fe3C became pearlite and the graphite shape changed from dot to flake by adding some C and Si.To less the experiment, the process of slow cooling was researched and optimized with ANSYS by choosing mathematical model, element, and heat source. The thermal cycle curve was tested by thermocouple and recorder, and it agreed well with the simulation results. On the basis of the calculation of the temperature field, welding stress was simulated by indirect method, and the stress of new process much lesser was found. By studying the current and slow cooling time with stress, the best parameters were got.The casting defect of cylinder liner of marine diesel engine was simulated by the best parameters. Referring to industry standards, the aberration, machinability, tissue and the security were evaluated. The security was evaluated by comparing the combination of residual stress and working stress with tensile strength.New process of controlling slow cooling time and adding C and Si was carried for the repairing, a new technology for casting repairs quality evaluation was established by simulating, provided a more convenient, and more reliable new way to repair technology for castings.