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The welding results and analysis of the traditional welding repair process are HT200, the area of the defect of the guide rail is S < 1000mm2, and the depth is h < 8mm. Heat treatment status: 3 parts have not been surface quenched and 1 part has been surface quenched. With nickel based welding powder F103, arc welding with cast iron electrode: Z308, Z248. 2.2 Spray welding equipment, arc welding equipment, nickel base welding powder F103 (C≤0.15 8.0 < Cr < 12 2.5 < Si < 4.5 0 < B < 7 Fe≤8 other Ni), cast iron electrode: Z308, Z248.
1 Spray welding
According to the spray welding process, the guide rail surface is preheated to more than 150℃, after the beginning of the spraying of welding powder, the spraying surface is heated to more than 900℃-1200℃, so that the welding powder is melted to form a flat surface. Because of the long preheating and heating time, the workpiece is heated in a larger area, and the thermal stress is larger, which is easier to crack than arc welding, and the crack tendency is larger when the line is shortened. Because the crack tendency is affected by factors such as spray welding time and thickness of spray layer, the size of defects is bound to be limited, and the defects repaired by welding need to be cleaned. Because the proportion of Fe content in spray powder is higher, the color of spray layer formed by arc welding is closer to that of base metal. But because it has a certain amount of Ni, it can not be closer to the color of the base metal, and it can be machined after welding.
2 Arc welding
Cast iron welding rod Z248 is used for welding repair. There are two kinds of welding repair process. The first one is preheating to 550℃-650℃ before welding and holding heat for 5-8 hours after welding repair. The second one: the workpiece is not preheated before welding, and the heat preservation is 3-4 hours after welding. Both methods are prone to crack and hard spot, and mechanical processing is not simple after welding repair. The electrode is cheap. With nickel-based cast iron welding rod Z308 welding rod welding, the welding layer between the welding layer should be stopped and cooled to below 60℃, welding zone less porosity, crack, good mechanical processing, high bonding strength, no drop phenomenon, because the machine tool guide after processing oil absorption and the influence of the welding rod blowing force, easy to produce edge bite, constitute "welding repair traces", welding repair zone color and base metal is very different, And the electrodes are expensive.
3 Analysis of results
Traditional spray welding and arc welding processes are prone to crack after welding repair, the workpiece is prone to heat deformation, simple secondary porosity, and the metal color at the welding repair is very different from the base metal. This is also the fundamental reason why the traditional welding repair process cannot completely solve the defect correction of machine tool guide rail.
