Casting and Forging Processes MANF1000 Casting and Forging Processes MANF1000 Casting and Forging Processes MANF1000 Casting and Forging Processes MANF1000 Note the post-machining completed on these parts! Casting and Forging Processes MANF1000 Casting and Forging Processes MANF1000 Hot Chamber Die Casting Casting and Forging Processes MANF1000 Hot Chamber Furnace Casting and Forging Processes MANF1000 Cold Chamber Die Casting Casting and Forging Processes MANF1000 Two forms of mold: (a) open mold and (b) closed mold for more complex mold geometry with gating system leading into the cavity Types of sand: green sand, water “binder”, Petro-Bond sand: petroleum binder. Casting and Forging Processes MANF1000 The gating system comprises of the sprue, runners, risers, and gate, and has specific design requirements dependent on the size and shape of the mold. The sprue is tapered to mitigate aspiration, the process by which air mixes with the liquid as it falls down the sprue. The riser is a large cylindrical cavity with minimal surface area contact to surrounding walls per unit volume. This causes the riser to solidify last, which guarantees it can supply molten metal to the mold as it shrinks The gating system is often designed with runners that during solidification. change direction, ensuring the molten metal travels through it at the proper flow rate. Casting and Forging Processes MANF1000 Casting and Forging Processes MANF1000 Investment Casting http://youtu.be/BX8w-GUPz1w Casting and Forging Processes MANF1000 Casting and Forging Processes MANF1000 Centrifugal Casting http://www.metaltek.com/productapplications/castings/centrifugalcastings.html Casting and Forging Processes MANF1000 Prediction of Solidification Time • Important for strength properties • Cast part should solidify before the risers • Most efficient design of risers minimizes surface area with required volume. Casting and Forging Processes MANF1000 A pure metal solidifies at a constant temperature equal to its freezing point (same as melting point) Most alloys freeze over a temperature range Phase diagram for a copper-nickel alloy system and cooling curve for a 50%Ni-50%Cu composition Casting and Forging Processes MANF1000 TL “Slush” Liquid+solid “Slush” solid TS Casting and Forging Processes MANF1000 Grain structure of a pure metal Characteristic grain structure in a casting of a pure metal, showing randomly oriented grains of small size near the mold wall, and large columnar grains oriented toward the center of the casting. Casting and Forging Processes MANF1000 Grain structure in an alloy Characteristic grain structure in an alloy casting, showing segregation of alloying components in center of casting Casting and Forging Processes MANF1000 Dendrite – A crystalline mass with a branching tree-like structure. Casting and Forging Processes MANF1000 Casting and Forging Processes MANF1000 Casting and Forging Processes MANF1000 Prediction of Solidification Time n • Chvorinov’s rule: V 3 V = volume: in T = C TS m 2 A = surface area: in A n=2 C = constant for metal cast, mold material and casting conditions: min/ in2 Casting and Forging Processes MANF1000 Prediction of Solidification Time Casting and Forging Processes MANF1000 Metal Shrinkage (0) starting level of molten metal immediately after pouring; (1) reduction in level caused by liquid contraction during cooling Casting and Forging Processes MANF1000 Metal Shrinkage (2) reduction in height and formation of shrinkage cavity caused by solidification; (3) further reduction in volume due to thermal contraction during cooling of solid metal Casting and Forging Processes MANF1000 Common Casting Defects (a) (b) (c) (d) (e) (f) (g) metallic projections – fins, flash, swells, rough surfaces cavities discontinuities – cracks, hot/cold tearing defective surface – surface folds, laps, scars, adhering sand layers, oxide scale wash – sand carried away by molten metal during the pouring process misrun – premature solidification Cold shut – an interference in a casting that lacks complete fusion, because of the meeting of two streams of liquid metal from different gates Casting and Forging Processes MANF1000 Mold Flow Analysis Casting and Forging Processes MANF1000 Casting and Forging Processes MANF1000 Casting and Forging Processes MANF1000 Casting and Forging Processes MANF1000 Forging A process in which the workpiece is shaped by compressive forces applied through various dies and tooling Casting and Forging Processes MANF1000 Casting and Forging Processes MANF1000 Impression-die Forging Casting and Forging Processes MANF1000 Casting and Forging Processes MANF1000 Closed-die Forging Casting and Forging Processes MANF1000 Forging Defects Casting and Forging Processes MANF1000 Forging
