May be accidentally will appear in the process of precision casting
precision casting crack, what method can prevent?
1 should fully consider when casting, casting structure casting structure, shape, large, wall thickness and transition effects such as factors of liquid and solid state contraction of castings, select the appropriate process parameters, to prevent the shrinkage of casting defects such as shrinkage.
Castings poured riser system design is reasonable, if you want to use cold iron process measures, such as the site of setting to reasonable, both to ensure the density of the casting internal organization, and try to avoid stress concentration occurs.
2, smelting smelting process, try to reduce the content of harmful elements such as P, S, lower N, H, O gas and inclusion content, etc.
Through the adoption of low phosphorus steel intermediate alloy, can have very good effect.
3, heat preservation heat preservation time of the casting sand mold by extended appropriately, mainly control box temperature below 70 ℃, ensure full completion of liquid and solid in the sand mould castings contraction, avoid the external force factors cause the stress concentration, the precision casting.
4, shakeout in the process of casting sand cleaning, do not play the box when watering the sand mould and casting, it is forbidden to use the strong external forces such as hit box shakeout impact way, avoid interaction force and the internal stress of the casting crack.
5, cutting riser under casting condition choose proper thermal poured riser cutting process, ensure hot cut starting temperature is not lower than 300 ℃.
Operation, gas cutting and blowing oxygen tube using vibration cutting.
Important thing in a timely manner after gas cutting with asbestos cloth cover every mouth or into the furnace heat treatment.
For the champions league and the axial flow blades on a class of complex structure, process take special measures of castings, adopting secondary hot cut.
6, in the precision casting defect processing, to insist on the principle of preheating.
When blowing process, welding process, the workpiece to preheat to 108 ℃ or more before operation.
If discover the larger crack defects, should be conducted to stress relieving, again for processing.
7, increasing annealing on major precision casting a eventually eliminate stress annealing process, strictly control the heat preservation time and melt temperature.
Its purpose is to reduce the production process of new stress concentration, the more thoroughly eliminate the internal stress of castings, to prevent the crack.
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