1. GENERAL DEFECT
1.1. Misrun & Cold Shut
1.1.1. A casting that has solidified before completely filling mold cavity.
1.1.2. Causes
1.1.2.1. Incomplete fusion where to streams of metal meat.
1.1.2.2. Metal freezes before mold is filled.
1.1.2.3. Die too cold.
1.1.3. Remedies
1.1.3.1. Increase pouring temperature
1.1.3.2. Increase die temperature
1.1.3.3. Increase permeability of sand.
1.2. Cold Shot
1.2.1. Causes
1.2.1.1. When small droplets of metal fall into a metalcasting mold,solidify and fail to remelt when the remaining metal is introduced
1.2.1.2. The defect is caused primarily by faulty pouring practices, but it also can be influenced by misplaced runners and risers
1.2.2. Remedies
1.2.2.1. Metal casters can stop the defect from occurring by improving pouring conditions and protecting the mold openings against metal splashing.
1.3. General Shrinkage Cavity
1.3.1. Depression in surface or internal void caused by solidification shrinkage that restricts amount of molten metal available in last region to freeze
1.3.2. Causes
1.3.2.1. Failure to supply liquid feed metal
1.3.2.2. Pouring temperature is too high causing liquid to shrinkage.
1.3.2.3. Pre mature solidification
1.3.3. Remidies
1.3.3.1. Apply principles of casting, reduce the pouring temperature and provide adequate risers, feeders, which supply the molten metal to compensate the shrinkage.
2. METAL CASTING PROESS
2.1. Design Considerations in Casting
2.1.1. Geometric Complexity
2.1.2. Corner on the casting
2.1.3. Machining allowances.
2.1.4. Dimension tolerance and surface finished.
2.1.5. Draft
2.2. Metals for Casting
2.2.1. Ferrous
2.2.1.1. Mostly contain iron
2.2.1.2. Have small amounts of other metals or elements added to give the required properties.
2.2.1.3. Ferrous are magnetic.
2.2.1.4. Steel,Cast Iron
2.2.2. Non-Ferrous
2.2.2.1. Do not contain iron
2.2.2.2. Not magnetic
2.2.2.3. Zinc Alloys,Copper Alloys.Aluminum
3. Sand Casting Defect
3.1. Sand Blow
3.1.1. Balloon‑shaped gas cavity caused by release of mold gases during pouring
3.1.2. Balloon‑shaped gas cavity caused by release of mold gases during pouring
3.2. Pin Holes
3.2.1. Formation of many small gas cavities at or slightly below surface of casting
3.2.2. Causes
3.2.2.1. Low pouring temperature
3.2.2.2. Gases blowing from mold
3.2.2.3. Excessive turbulence during molding
3.2.2.4. Moisture condensed on densors and chills
3.2.3. Remidies
3.2.3.1. Use correct pouring temperature and check with pyrometer
3.3. Penetration
3.3.1. When fluidity of liquid metal is high, it may penetrate into sand mold or core, causing casting surface to consist of a mixture of sand grains and metal.
3.3.2. Causes
3.3.2.1. This occurs because the sand is coarse or no mold wash was applied on the surface of the mold. The coarser the sand grains more the metal penetration.
3.4. Mold Shift
3.4.1. A step in the cast product at parting line caused by sidewise relative displacement of cope and drag.
3.4.2. Causes
3.4.2.1. The mold shift defect occurs when cope and drag or molding boxes have not been properly aligned.
4. Foundry Inspection Methods
4.1. Visual inspection.
4.1.1. To detect obvious defects such as misruns, cold shuts, and severe surface flaws
4.2. Dimensional measurements.
4.2.1. To insure that tolerances have been met.
4.3. Coin Testing.
4.3.1. By hitting with a coin on to the component and by hearing the sound coming from the casing, the presence of the defect can be estimated.