Feeding of Hollow Cylindrical Castings
Feeding of Hollow Cylindrical Castings
P.K.Sandell
Chief Executive, Sandell Associates, Kolkata, India and Vienna, Virginia, U.S.A
OP-37
internal centerline shrinkage, which was unacceptable. A major factor is the blockage of feed metal flow which result in micro-porosity or voids in the solid casting. These voids add up to produce a centerline shrinkage.
FEEDING
Feeding covers methods adopted to produce castings without shrinkage defects. In the case of solid solution alloys like steel, this is achieved by ensuring that the feeders solidify later than the castings. Simply stated, a feeder must contain enough liquid metal to compensate for the volume contraction occurring while the casting cools from the liquidus to the solidus temperatures.
Computerised methods for deriving riser sizes based on relative solidification times are readily available .One of the earliest attempt at mathematical riser sizing was derived from
Chvorinov’s equation, which established a relationship between the solidification time of a casting to its volume-tosurface area ratio .This ratio was called the modulus of solidification. Wlodawer 2 developed extensive data based on this modulus concept, for determination of riser sizes, with a twenty percent safety factor. Empirically, Caine 3, using his FreezingRatioand Bishop et al 4, using the
ShapeFactorratiodeveloped formulae and curves prescribing riser diameters for various casting volumes, shapes and sizes.
The Steel Founders’ Society of America (SFSA) has
ABSTRACT
The paper deals with the methodology and the manufacturing process used to successfully develop a long cylindrical casting, called the Hollow Shaft. Both experience as well as a rough estimate of the Niyama Criterion indicated strong possibilities of a centerline shrinkage The methodology was based on (1 )
The Shape Factor and Feeding Distance formulae specified in the SFSA Feeding and Risering Guidelines for Steel Castings1,
(2) Use of a
P.K.Sandell
Chief Executive, Sandell Associates, Kolkata, India and Vienna, Virginia, U.S.A
OP-37
internal centerline shrinkage, which was unacceptable. A major factor is the blockage of feed metal flow which result in micro-porosity or voids in the solid casting. These voids add up to produce a centerline shrinkage.
FEEDING
Feeding covers methods adopted to produce castings without shrinkage defects. In the case of solid solution alloys like steel, this is achieved by ensuring that the feeders solidify later than the castings. Simply stated, a feeder must contain enough liquid metal to compensate for the volume contraction occurring while the casting cools from the liquidus to the solidus temperatures.
Computerised methods for deriving riser sizes based on relative solidification times are readily available .One of the earliest attempt at mathematical riser sizing was derived from
Chvorinov’s equation, which established a relationship between the solidification time of a casting to its volume-tosurface area ratio .This ratio was called the modulus of solidification. Wlodawer 2 developed extensive data based on this modulus concept, for determination of riser sizes, with a twenty percent safety factor. Empirically, Caine 3, using his FreezingRatioand Bishop et al 4, using the
ShapeFactorratiodeveloped formulae and curves prescribing riser diameters for various casting volumes, shapes and sizes.
The Steel Founders’ Society of America (SFSA) has
ABSTRACT
The paper deals with the methodology and the manufacturing process used to successfully develop a long cylindrical casting, called the Hollow Shaft. Both experience as well as a rough estimate of the Niyama Criterion indicated strong possibilities of a centerline shrinkage The methodology was based on (1 )
The Shape Factor and Feeding Distance formulae specified in the SFSA Feeding and Risering Guidelines for Steel Castings1,
(2) Use of a
References: 1. Steel Founders’ Society of America : Feeding & Risering Guidelines for Steel Castings , 2001 2. Wlodawer R: Directional Solidification of Steel Castings, Pergamon Press, First English Edition pp40 -70, 1966 Vol 56, pp492 – 501.1948 and Vol 57p66, 1949 4 Simulation Metallurgical and Material s Transaction Vol 33 B, pp 731-39, 2002 Pressure Casting American Foundry Society Transactions, paper N0 01-026, 2001