Innovative casting defect prediction
There are too many of affecting factors in casting process. Foundryman should control and adjust many parameters to produce sound casting. To prevent defect we should know our processes, the influencing factors in processes, relation between mentioned items and how these item could cause defects.
We could summarize sand casting process in following processes:
2-Designing risering and gating system
3-Designing molding process
13-Shot or sand blast
It will be very complicated job to control all influencing parameters in steel foundry especially when products are various in shape and alloys. To save our quality control costs and help QC efforts be more effective in EMC we have invented a new way to develop quality plans.
More than 30 years experience in foundry helps us to have a database of possible casting and head treatment detects for casting parts. Also we know our processes limitation and capabilities to prevent casting defects. By relating this information we consider following procedure for developing quality plan:
1- Relating possible defects to part according to shape and alloy factors as thin walls and thickness difference, cores quantity, geometric modulus, core thickness, X,Y,T or L sections, long shapes, limitations for core print, casting tolerances limitation, special shapes that limit linear contraction, Alloy brittleness, gas absorption during melting and pouring, active elements such as Al and Ti, Special elements as Nitrogen in duplex stainless steel, alloying elements quantity, carbon equivalent as a important factor for cutting and welding preheating and some other parameters.
2- Some defects could be detected visually and some of them need special instruments to detect them. So as FMEA method we have considered a detection factor to each defect. If a defect would be detect very hard so we should more strict control to prevent its occurrence.
3- Finally the defect occurrence will be related to production processes. So that QC department will know in which process which kind of defects is more likely to occur and quality control department should confirm the process in witness or hold points that have extracted from former estimations.
to be continued