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Welding repair results and analysis of the traditional welding repair process HT200, rail defect area S "1000MM2, depth H" 8MM. Heat treatment conditions: 3 were not surface-quenched and 1 had been surface-quenched. Used nickel-based welding powder F103, cast iron electrode for arc welding: Z308, Z248.2. 1.2 spray welding equipment, arc welding equipment, nickel-based welding powder F103 (C ≤ 0.158.0 "CR "122.5 "SI "4.51.0 " B "1.7FE ≤ 8 remaining NI), cast iron electrodes: Z308, Z248.
Spray welding
According to the spray welding process, the surface of the rail is preheated to 150° C. or more, and after the preliminary solder powder is sprayed, the sprayed surface is heated to 900° C.-1200° C. or more so that the solder powder is melted to form a flat surface. Due to the long preheating and heating time, the workpiece has a large heated area and a large thermal stress. It is more prone to cracks than arc welding. At the same time, the line shrinkage tends to produce more cracks. Because the crack tends to be influenced by the spray welding time, the thickness of the sprayed layer and other factors, the size of the defect is limited, and the defects of the weld repair must be cleaned. Because the proportion of the FE content in the powder spray is relatively high, the spray layer formed is better than the arc welding and the mother. The color of the wood is more similar. However, due to a certain amount of NI, it is not possible to get closer to the base metal color, and it can be machined after welding.
Arc welding
Z248 welding with cast iron welding, welding repair process is divided into two types, the first one: preheating before welding to 550 °C -650 °C, 5-8 hours after welding insulation; second: no preheat before welding workpiece, 3-4 hours after welding. Both methods are prone to cracks, hard spots, and are not easily machined after welding. Welding rods are cheap. Welding with nickel-based cast iron electrode Z308, the gap between the welding layer and the welding layer should be cooled to below 60°C, less porosity, cracks in the welding area, good machinability, high bonding strength, no shedding phenomenon, due to machine tool guide After the processing, the influence of the oil absorption and the blowing force of the welding rod is easy to produce undercuts and “welding marksâ€. The color of the welding repair zone is very different from that of the base metal, and the welding rod is expensive.
Result analysis
Traditional spray welding and arc welding processes are prone to cracks after welding repair. The workpieces are easily deformed by heat, and secondary air holes are likely to occur. The difference between the metal color of the welding repair site and the base metal is a common feature. This is also not a traditional welding repair process. Thoroughly solve the root cause of machine rail defect repair.
Analysis of the causes of poor repair results for machine tool castings
Through the repair results of several traditional welding repair methods at the defects of machine tool castings, the reasons for the poor repair results of machine tool castings are analyzed. Through the research on the repair results of the casting defect repair machine in machine tool castings, a new and practical new technology and process for repairing machine tool castings is determined.