Introduction to Special Casting Process
Now a day’s special Casting process has been developed to effect a saving time and expense to produce a better quality casts. In comparing to Sand Casting the main difference is, in this process do not in all cases require drying or Baking of moulds or cores or rapid hardening action takes place due to chemical reactions in them.
Classification of Special Casting Process:
Need for special casting process
· Sand mould casting process gives satisfactory results at low cost.
· All metals may be cast in sand moulds and there is no limitations as regards the size of the casting which can be made.
· Sand casting enjoys wide applications and a very large quantity of castings even today is produced through sand casting only.
· However, sand moulds are single purpose moulds as they are completely destroyed
after the casting has been removed from the moulding box.
· It becomes therefore obvious that the use of a permanent mould do a considerable saving in labour cost of mould making.
· There are certain other limitations also possessed by conventional sand casting technique which necessitated the developments of Special casting processes.
Advantages of special casting process over sand casting
· Greater dimensional accuracy.
· Higher metallurgical quality.
· Lower production cost (in certain cases).
· Ability to cast extremely thin sections.
· High production rates.
· Better surface finish on the castings; therefore low labour and finishing costs.
· Minimum need for further machining of castings.
· Castings may possess a denser and finer grain structure.
· Castings are slightly stronger and more ductile than solid mould castings.