i am working in a company as a metallurgical engineer.
in copper casting ( slab forms), we observed cracks on the slab surface. how to can eliminate the surface cracks?
Thank you
Cracks or Misruns? A misrun can sometimes look like a crack. It’s basically when two converging fronts come together but the are cooling to quickly and form what can resemble a line or crack. A crack can then propergate from the misrun given certain conditions. How do you remove them? There’s lots of things you can try - redesign the risers, runners so that you don’t get converging fronts. Increase the temperature of the molten material. Just bare in mind that every time you change something, you’ll likely affect something else. It’s best to do small trials with single changes to understand the effect on dimension quality and mechanical properties.
What is the casting process? the only cracks I’ve seen in castings I think are referred to as cold tears In die casting. It’s when the part is ejected from the mould to fast and it hasnt had enough time to properly solidify. It’s also down to the amount of draft you have in the mould and often other design features, or the casting machine and die itself I.e in terms of how the act when ejecting the componen.
Hope that helps. Let me know if you have any more detail or want to discuss further. All the best Saeed.
Controlling the moisture content in the molding sand.
Proper gating system.
Eliminate entrainment of surface oxide films. Easier said than done though. Requires a new level of thinking about your production system.
Cracks should be eliminated by careful control of melt quality (especially the elimination of entrainment defects (bifilms)) and proper design of gating system (avoid any turbulence during casting).
Another important factor is the temperature of the melt, and the mold. If the surface cracks are in fact cold lap defects, an increased melt and mold temperature can solve the problem.
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