The 10 Rules of Good Casting
ďƒ˜The last few years have seen an extraordinary increase in the understanding of the casting process. ďƒ˜Now, to produce reliable castings by incorporating the latest technology, manufacturers follow 10 rules. Here is a summary of them.
Rule 1: Provide a Good Quality Melt ďƒ˜ The melt is prepared and treated
using the best current practice prior to casting. ďƒ˜ The melt is provided at the
correct temperature, with low residual levels of dissolved inclusions and gas.
Rule 2: Avoid Liquid Front Damage ďƒ˜ To prevent this, the meniscus
should not go too quickly. ďƒ˜ However, even at higher
speeds such exterior turbulence break can be prevented if the casting filling system is adequately thin to hold back the meniscus.
Rule 3: Avoid Arrest of the Liquid Front ďƒ˜ To prevent this from
happening, the meniscus should not set out too slowly and stop at any point on the front. Make sure that the liquid front only advances uphill. ďƒ˜ The advancing liquid metal
meniscus must not contain any thick oxide film.
Rule 4: Avoid Bubble Damage ďƒ˜ To prevent this common defect in
castings the running system should be free from air bubbles. ďƒ˜ They should not be allowed to pass
through the liquid metal in the mould cavity if they are entrained. Or else a mixture of oxide bubble trails as well as residual misshapen bubbles will be present in the casting.
Rule 5: Avoid Core Blows ďƒ˜Gases from cores should not be allowed to enter the liquid metal.
Rule 6: Avoid Shrinkage Damage ďƒ˜Because of unreliable pressure gradient there should be no feeding uphill. Control the level of flash at mould and core joints.
Rule 7: Avoid Convection Damage Convection problems can be automatically avoided by thick or thin section castings.
Rule 8: Plan Segregation Distribution If the casting is out of chemical specification it could be due to the change in distribution of alloying elements in the casting, which happens during the change of section If properties are threatened such problems will have to be addressed and may need prior negotiation with the customer.
Rule 9: Control Residual Stress ďƒ˜
By forbidding quenching of low ductility, following high temperature solution treatment you can avoid unidentified or accidental residual stress.
Rule 10: Provide Location Points ďƒ˜
For dimensional reference and for pickup for machining, all castings will be provided with fixed location points.
For more details visit VR Foundries, www.vrfoundries.com is an established producer of Grey and SG iron castings. It caters to the automobile, textile, pump manufacturers, General engineering, tractors and hydraulic industries.