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Machine tool castings repair analysis

Machine tool castings defect fix: based on several kinds of traditional welding repair technology in machine tool castings defect repair as a result, the reasons for the analysis of machine tool castings repair results.Through to the casting defect repair machine repair results of research in machine tool castings, determine a really feasible on the machine tool castings to repair the new technology and process.
Traditional welding repair technology of weld material HT200 results and analysis, the guide rail defect area S < 1000 was, depth h < 8 mm.Heat treatment condition: three pieces of surface quenching, 1 piece has surface quenching.Powder F103 with nickel-based welding, arc welding with cast iron welding rod: Z308, Z248.2.1.2 spray welding equipment, welding equipment, nickel-based welding powder F103 (C 0.158.0 or less
1, spray welding
By spray welding process execution, will guide surface preheat to 150 ℃ above, completion of initial welding powder spraying, the spray surface heated to 900 ℃ to 1200 ℃ above, after melt welding powder form a smooth surface.Because of preheating and heating time is long, the workpiece is heated area is larger, the thermal stress is bigger, more easily than arc welding cracks, at the same time line contraction cracks tend to be larger.Because of the trend by spray welding crack influence factors such as time, spray layer thickness, defect is limited by a certain size, and weld defects need to be cleaned up, due to higher Fe content in the powder spraying, formation of shotcrete layer more similar than arc welding with the color of the parent metal.But it has a certain amount of Ni, so can't and closer to the parent metal color, can undertake machining after welding repair.
2, electric arc welding,
Cast iron welding rod Z248 for welding repair, welding repair process is divided into two kinds, the first: preheat to 550 ℃ to 650 ℃ before welding, welding repair 5-8 hours after heat preservation;The second: artifacts no preheating before welding, after welding heat preservation 3-4 hours.Two methods are easy to appear crack, hard point, after welding repair is not easy to do mechanical processing.Electrode is cheap.With nickel base cast iron welding rod Z308 welding rod welding, welding and welding layer should pause between cooling below 60 ℃, weld zone less porosity, crack, good machinability, high bonding strength, no fall off phenomenon, because of the machine tool guideway processed oil absorption and the influence of electrode blow force, are prone to bite edge, forming the weld mark, weld area color and material is very different, and the electrode is expensive.
3, from the analysis results can be concluded that:
Traditional welding repair technology cannot completely solve the root cause of the machine tool guide rail defect fix is a series of spray welding, arc welding process, welding cracks easily after repair, easy to heat deformation of workpiece, prone to secondary porosity, and parent metal in weld metal color difference is their common characteristic.