Although it is said that alloy steel casting is only a very common casting, a casting often contains many details. If you do not pay attention and do not operate according to the correct method, it is easy to cause looseness. How to avoid loose castings in daily life? To avoid this problem, we should do the following:
1. Improve the process design of large-scale ductile iron processing parts, and reasonably set up the gating and riser system, cold iron and subsidies to ensure that the castings are fed during the solidification process.
2. Use insulation risers, heating risers, pressure risers and electric heating risers with high feeding efficiency instead.
3. Improve the structural design of alloy steel castings, reduce the difference in wall thickness of the castings, make the transition between the wall thickness and the thin-walled parts of the castings smooth, and try to avoid the formation of isolated hot spots. In the parts where the feeder feeding distance cannot be reached, such as the isolated hot joints of the casting, inner and outer cold irons are used to speed up the solidification speed of this part.
4. For important large-scale ductile iron castings, computer-aided design can be carried out on the basis of computer numerical simulation to optimize the casting structure and casting process.
5. Strengthen alloy refining, purify molten metal, and reduce the content of dissolved gas and low melting point impurities in the alloy to facilitate solidification and feeding.
6. Using suspension casting technology, grain refiner or slightly chilled iron is added to the molten metal during the casting process to speed up the solidification of the alloy and refine the grains.
7. Enhance the rigidity and strength of the casting mold, and avoid the displacement and lifting of the mold wall.
8. Adjust the alloy composition, perform good modification or inoculation treatment, reduce the solidification temperature interval of the alloy, and enhance the casting performance of alloy steel castings, so as to facilitate the sequential solidification of the molten metal in the mold in the direction of the runner and riser, and enhance the pouring and riser system. the packing effect.
9. Alloy castings and ductile iron castings with a wide solidification temperature interval should adopt a balanced solidification process, and make full use of the graphitization expansion during solidification to compensate for the liquid shrinkage and solidification shrinkage of cast iron.
10. Reduce the sulfur, phosphorus content and residual magnesium content of large-scale ductile iron processing. When processing with rare earth magnesium alloy, the carbon and silicon content should be appropriately increased; the pouring temperature and pouring speed should be reduced, and the pouring time should be extended; point riser. For a period of time after pouring, refill high-temperature molten metal into the open riser to increase the amount of molten metal fed in the riser, prolong the time that the amount of molten metal in the riser maintains high temperature, and increase the feeding efficiency of the riser; mouth. Stir the molten metal in the open riser with a rod to prevent premature condensation on its surface, so as to increase the feeding efficiency of the open riser.
How to avoid loose alloy steel castings, we can increase the casting strength and reduce the impurity content to avoid the occurrence of loose castings, and also improve the strength of the castings and reduce the occurrence of some defects.
