HOME ASSIGNMENT PART II

SAND CASTING

Sunil SutarMTech (Design Engineering)

M P GururajanAssistant Professor

Applied Mechanics Department

Presented to-

Prepared By-

Different Components…Different Aspects

SmallSimple

Big Complex

Courtesy: Google images

23 feet,6 tonnes ,99.72% iron,No rust since 5th century AD

Iron pillar

Casting Casting =Pattern making + Mold making + Pouring Molten Metal + Cooling + Removal + Inspection

Types of Casting :Expendable Mold, Multiple Use Mold

Sand Casting :Expendable Mold casting process uses sand as molding material

Casting Terminology

Parting line

Courtesy: efunda

Pattern Making

What is pattern?Approximate duplicate of product

Pattern material: Wood, Metals, Urethanes etc.

Types of Patterns:One Piece or solid pattern, Split Pattern, Match-plate pattern, Drag & Cope Pattern

Allowances:Shrinkage, Machining, Draft, Distortion

Pattern Making

One piece or Solid Pattern

Cope & Drag PatternMatch Plate Pattern

Split Pattern

Mold Making

Consists : Sand Preparation and Mold Making

Sand Properties : Refractoriness, Cohesiveness, Permeability, Collapsibility

How to get these properties?

Mold Making Methods: Hand Ramming, Sand Slinger, Jolting, Squeezing,

Combination

Pouring

Pouring System:

Pouring cup/Basin: Rectangular Shape-No vortex-No suction of Gases

Sprue: Short-Less KE –Less turbulence-Tapered shape

Sprue Well : Dissipate KE-Prevent splashing –less turbulence

Pouring

Need :Directional SolidificationFeeding molten metal to compensate for solidification shrinkage

Criteria: Riser should solidify after the casting.

Types:

Riser

Image Courtesy: wiki

Cooling/SolidificationCooling Curve for a Pure Metal:

Pouring Temp.: Temp of first liquid entering Mold cavity

Start of Solidification

End of Solidification

Alloy-Distinct M.P.-freezing range

High Cooling Rate-fine structures-good mechanical properties

Chvorino’s rule : ts=B(V/A)n

B=Mold constantn=1.5 to 2

Effect of Cooling rate:

Process Yield Strength(MPa)

Tensile strength(MPa) Elongation(%)

Sand Casting 55 131 8Permanent Mold 62 158 10

Die Cast 110 227 9

Cast Structure:

Image Courtesy: wiki

Solidification

Removal of Casting:Shake out-vibrating machineShot blasting-Removal of internal surface sand

Trimming:Excess material-manual cutting, sawing-Trimming Press

Inspection:Nobody is perfect…Sand Casting too…Defects…

Image Courtesy: IITM, Manufacturing Processes, Lecture notes

Casting Defects:

Different Sand Casting Processes:

Green Sand Casting:88% silica sand, 9% clay,3% water

CO2 Molding:Sodium Silicate(3-6%)-CO2 flow- Strength Gain

Shell Molding:Silica Sand + Thermo setting phenolic resin+ heat sensitive liquid catalyst-shot on preheated metal pattern-shell formation

Includes :Casting=PMPCRI

Sand Casting -versatile process -produce almost all size & shape of components -poor surface finish and dimensional accuracy.

Sand Casting Methods : Green Sand, CO2 sand , Shell

Summary:

1. Materials and Processes in Manufacturing, J T Black and Ronald A Cohser, 10 th edition.

2. Assistant Professor M P Gururajan http://mogadalai.wordpress.com/2006/01/14/some-

thoughts-on-making-presentations/

Acknowledgements:

Thank you…