Analysis of machine tool casting repair

Defect repair of machine tool castings: Through the repair results of several traditional welding repair processes 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 repairing machine on the machine tool castings, a new technology and process for repairing the machine tool castings is determined.

　　The welding repair results and analysis of the traditional welding repair process. Material is HT200, the area of u200bu200bthe guide rail defect is S<1000mm2, and the depth h<8mm. Heat treatment status: 3 pieces have not been surface quenched, and 1 piece has been surface quenched. Use nickel-based solder powder F103, cast iron electrodes for arc welding: Z308, Z248. 2.1.2 Spray welding equipment, arc welding equipment, nickel-based solder powder F103 (C≤0.158.0

　　1, spray welding

　　 According to the spray welding process, the guide rail surface is preheated to above 150℃. After the initial spraying of the solder powder, the sprayed surface is heated to above 900℃-1200℃ to melt the solder powder and form a flat surface. Due to the long preheating and heating time, the workpiece has a larger heated area and larger thermal stress, which is more likely to produce cracks than arc welding, and at the same time, the tendency of linear shrinkage to produce cracks is greater. Since the crack tendency is affected by spray welding time, spray coating thickness and other factors, the size of the defect is limited, and the welding defects need to be cleaned up. Due to the higher proportion of Fe in the spray powder, the spray layer formed is more The color of the wood is more similar. However, due to a certain amount of Ni, it cannot be closer to the color of the base metal, and can be machined after welding. (Guide: Failure and Prevention of Cold Work Mold)

　　2, arc welding

　　 Use cast iron electrode Z248 for welding repair. There are two repair welding processes. The first one: preheat to 550℃-650℃ before welding, and keep it for 5-8 hours after welding; the second one: not before welding. Preheat, keep warm for 3-4 hours after welding. Both methods are prone to cracks and hard spots, and it is not easy to perform mechanical processing after welding. Welding rods are cheap. Welding repair with nickel-based cast iron electrode Z308 electrode, the welding layer and the welding layer should be cooled to below 60 ℃, there are few pores and cracks in the welding repair area, the machinability is good, the bonding strength is high, and there is no dropout phenomenon, due to the machine tool guide rail The influence of oil absorption and welding rod blowing force after processing is prone to undercut and weld repair marks. The color of weld repair area is very different from the base metal, and the welding rod is expensive.

　　3. From the results of the analysis, we can get:

　　The basic reason why the traditional welding repair technology can not completely solve the defect repair of the machine tool rail is the unified spray welding and arc welding technology, which is prone to cracks after welding, the workpiece is easy to be deformed by heat, and secondary air holes are prone to appear. The metal color of the welding repair The big difference from the base metal is its common feature.

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