Mechanical Manufacturing Processes - Casting & Foundry Technology Vocabulary

Vocabulary flashcards reviewing core terms, casting methods, mould properties, gating components, and defects for Midterm 1 in Mechanical Manufacturing Processes.

Grey Cast Iron

A type of cast iron featuring good compressive strength, good machinability, self-lubricating properties, and excellent vibration damping; commonly chosen for machine beds and slides.

Cylindrical Sprue

A vertical channel in a mould with a constant cross-sectional area where metal velocity increases as it flows downward, causing the liquid stream to separate from the sprue wall and produce the aspiration effect.

Tapered Sprue

A sprue designed with a decreasing cross-sectional area toward the bottom, preferred over cylindrical sprues because it keeps the channel filled and prevents air aspiration into the molten metal.

Aspiration Effect

The drawing of atmospheric gases into the molten metal stream within the sprue, which occurs when fluid velocity increases while the channel cross-sectional area remains constant.

Riser

A reservoir of molten metal integrated into the mould that feeds liquid shrinkage as the main casting solidifies; it must remain liquid longer than the main casting and freeze last.

Chill

A metallic element inserted into the mould cavity to increase or equalize the local cooling rate of molten metal, helping control directional solidification and reduce shrinkage defects in thick sections.

Core Print

An extension added to a pattern that creates a supporting recess in the mould to position and hold a core in place without inserting an extra metallic element into the casting cavity.

Chaplet

A metallic support element placed inside the mould cavity to support a core; it becomes part of the final casting and can produce local chilling or defect locations if fusion is incomplete.

True Centrifugal Casting

A casting method that forces molten metal against the inner wall of a rotating mould using centrifugal force, producing hollow cylindrical components without using a core.

Slush Casting

A hollow casting process in which molten material solidifies against the mould wall to form a outer shell, after which the remaining unsolidified liquid center is poured out.

Investment Casting

A lost-pattern precision casting process that uses wax, plastic, or frozen mercury patterns surrounded by a ceramic mould to produce intricate geometries, high dimensional accuracy, and smooth surface finishes.

Gating Ratio

The proportion of the sprue-bottom area to the runner area to the ingate area, expressed as $A_s : A_r : A_g$, which controls fluid velocity, pressure, filling behavior, turbulence, and aspiration.

Hot Tears

Casting defects consisting of cracks or fractures formed during solidification when the thermal contraction of the cooling casting is restricted by rigid mould components or non-collapsible cores.

Misrun

A casting defect resulting from incomplete filling of the mould cavity, caused by premature solidification when molten metal is poured too slowly or at insufficient temperatures.

Cold Shut

A surface defect formed when two streams of liquid metal meet in the mould cavity but fail to fuse completely due to premature cooling.

Pattern Allowances

Dimensional adjustments incorporated into pattern design to account for physical phenomena, including shrinkage allowance, draft allowance, machining allowance, rapping allowance, and distortion allowance.

Rapping Allowance

A negative pattern allowance subtracted from pattern dimensions because tapping or rapping the pattern to loosen it from the sand enlarges the mould cavity.

Sand Moulding

A widely used casting process relying on sand mixtures to form moulds; it is simple and versatile but yields lower dimensional accuracy and rougher surface finishes than shell moulding.

Shell Moulding

A moulding technique that uses a thin sand-resin shell formed around a reusable metallic pattern heated to $175 - 370\,^\circ\text{C}$, delivering high accuracy, smooth surface finish, and fast production.

Fettling

The stage of post-casting operations in which the mould is broken after sufficient cooling, and the casting is removed, cleaned, and separated from gating elements and risers.

Metallostatic Force

The upward hydraulic pressure generated by liquid metal filling the mould cavity that tends to lift the cope away from the drag, requiring external clamping or top weights.

Types of Cast Iron

The primary classifications of cast irons based on carbon form, alloying, and heat treatment: Grey Cast Iron, White Cast Iron, Malleable Cast Iron, Nodular Cast Iron, and Alloy Cast Iron.

Mould-Material Defects

Casting imperfections caused by mould material failures or improper sand preparation, including cuts and washes, fusion, swells, run out, drops, metal penetration, rat tails, buckles, and veins.

Gating System Elements

The complete network of passage components directing molten metal from the ladle to the mould cavity, including the pouring basin, sprue, sprue base well, runner, runner extension, ingate, and riser.

X-Ray Inspection

A non-destructive testing method that penetrates a casting with X-radiation to reveal internal density differences and defects such as gas porosity and internal voids.

Computed Tomography Scanning

An advanced non-destructive inspection technique combining multiple X-ray images to generate a three-dimensional view of a casting and its internal structural flaws.

Machine Moulding Methods

Mechanical sand-compacting techniques—including jolting, squeezing, jolt-and-squeeze, and sand slinging—used to increase moulding speed and mould density consistency over hand moulding.

Refractoriness

The thermal property of moulding sand or core material that enables it to resist high molten metal temperatures without melting, fusing, or breaking down.

Permeability

The capacity of a sand mould to permit air, gases, and steam created during pouring to escape through its porous structure.

Collapsibility

The ability of a mould or core to yield and disintegrate as the solidifying metal contracts, preventing internal stresses and cracking in the casting.

Core

A preformed insert placed within a mould cavity to form internal features such as holes, undercuts, recesses, or hollow passages.

Die Casting

A permanent mould process where liquid metal is forced into reusable metal dies, delivering high dimensional accuracy, thin walls, and fast output, but incurring high tooling costs and potential internal porosity.