Defect repair of machine tool castings: The results of repair of several traditional welding repair processes at machine tool casting defects are analyzed to determine the reasons for the poor repair results of machine tool castings. By studying the repair results of casting defect repair machines in machine tool castings, a new technology and its process for repairing on machine tool castings is determined to be indeed feasible.
1、Spray welding
According to the execution of the spray welding process, the guide surface will be preheated to more than 150 ℃, after completing the initial spraying of welding powder, the spraying surface will be heated to more than 900 ℃ - 1200 ℃, so that the welding powder melted to form a flat surface. Because of the preheating and heating time is long, the workpiece is heated area is larger, the thermal stress is larger, more likely to produce cracks than arc welding, while the line shrinkage has a greater tendency to produce cracks. As the cracking tendency is affected by the spray welding time, spray layer thickness and other factors, the size of the defect is somewhat limited, and the defect needs to be cleaned up, due to the high proportion of fe in the spray powder, the formation of the spray layer is more similar to the color of the base material than arc welding. But because of a certain amount of ni, so can not be closer to the color of the parent material, welding can be machined after repair.
2、Arc welding
Weld with cast iron welding rod z248, welding process is divided into two kinds, the first: preheating to 550 ℃ -650 ℃ before welding, welding after the insulation 5-8 hours; the second: the workpiece is not preheated before welding, after welding insulation 3-4 hours. Both methods are prone to cracks, hard spots, welding repair after the mechanical processing is not easy. The welding rod is cheap. With nickel-based cast iron welding electrode z308 welding electrode welding, welding layer and welding layer should be paused between cooling to 60 ℃ or less, welding patch area less porosity, cracking, good machinability, high bond strength, no shedding phenomenon, due to the machine tool guide processing oil absorption and welding rod blowing force, easy to produce biting, the formation of "welding patch marks", welding patch area Color and the parent material is very different, and the price of welding rod is expensive.
From the analysis of the results can be derived: the traditional welding repair process can not completely solve the machine tool guide defects repair the fundamental reason is the unified spray welding, arc welding process, welding repair is easy to produce cracks, the workpiece is susceptible to heat deformation, easy to appear secondary porosity, welding repair at the metal color and the parent material difference is its common characteristics.
