Casting, Powder Metallurgy, and Joining Processes Overview

Casting process

Melting material, pouring into a mold, solidifying.

Advantages of Casting

Allows complex shapes, hollow sections, large parts.

Parting line

Separates the cope and drag of a mold.

Draft

Angle on pattern for easy casting removal.

Casting

Process and product of solidified molten metal.

Solidification process

Molten material solidifies into final shape.

Casting defects

Issues like gas porosity and shrinkage during solidification.

Nucleation

Initial formation of crystals during solidification.

Growth

Expansion of crystals during the solidification process.

Chill zone

Rapid nucleation at mold's cold walls.

Columnar zone

Long, thin crystals growing perpendicular to surface.

Equiaxed zone

Spherical, randomly oriented crystals in casting's interior.

Fluidity

Metal's ability to flow and fill mold.

Pouring temperature

Crucial factor affecting metal fluidity and solidification.

Gating system

Delivers molten metal to mold cavity.

Risers

Reservoirs feeding extra metal to compensate for shrinkage.

Blind riser

Riser contained entirely within the mold cavity.

Live riser

Receives last hot metal entering the mold.

Solidification shrinkage

Volumetric contraction during cooling of metals.

Sand casting

Common casting method using sand, clay, and water.

Refractoriness

Sand's ability to withstand high temperatures.

Cohesiveness

Sand's ability to retain its shape.

Permeability

Ability of gases to escape through sand.

Collapsibility

Sand's ability to accommodate shrinkage and removal.

Cores

Used to create complex internal cavities in castings.

Core making

Process of creating cores for improved casting design.

Dump-box shell molding

Method using heated patterns and resin-coated sand.

Shell-mold pattern

Two halves forming a shell for casting.

Casting design

Involves considerations for shape, strength, and functionality.

Green Sand Cores

Not suitable for complex shapes in casting.

Dry-Sand Cores

Used in molds for complex castings.

Chaplets

Supports cores during the casting process.

Cheeks

Second parting lines for withdrawable patterns.

Inset Cores

Enhance productivity in mold casting.

Investment Casting

Casting method using a mold made from wax.

Lost Foam Process

Polystyrene patterns coated in ceramic slurry.

Expendable Mold Casting

Separate mold produced for each casting.

Permanent Mold Casting

Mold can be reused immediately after casting.

Tilt-Pour Casting

Mold assembly tilted for pouring metal.

Die Casting

Molten metal forced into a mold under pressure.

High Pressure in Die Casting

Maintained during solidification for fine details.

Centrifugal Casting

Inertial forces distribute molten metal in molds.

True Centrifugal Casting

Mold rotated to create cylindrical castings.

Continuous Casting

Solidifies basic shapes for long feedstock lengths.

Post-Casting Operations

Includes removing cores, gates, and defects.

Process Selection

Evaluates advantages and disadvantages of casting methods.

Powder Metallurgy

Process of blending and heating fine powders.

Basic Steps of Powder Metallurgy

Includes powder manufacture, mixing, compacting, sintering.

Powder Mixing

Combines powders with binders for desired properties.

Compaction Sequence

Process of compressing powders into shapes.

Sintering

Heating process to bond powder particles.

Unique Composites

Produced through specific powder mixing techniques.

Mold Life

Duration a mold can be used for casting.

Cleaning and Finishing

Post-casting processes to improve surface quality.

Defects in Casting

Caused by trapped air in molds.

Long Mold Life

Characteristic of die casting due to durability.

Complex Details

Achieved through high-pressure die casting.

Compaction

Process of densifying powder materials.

Nonuniform Density

Density variation across compacted material.

Green Density

Density after compaction, before sintering.

Isostatic Compaction

Encapsulation in flexible mold under pressure.

Warm Compaction

Heating powder before pressing to improve flow.

Burn-off Stage

Removes air and lubricants during sintering.

High-Temperature Stage

Solid-state diffusion occurs during sintering.

Cooling Period

Controlled temperature reduction after sintering.

Hot-Isostatic Pressing (HIP)

Combines compaction and sintering in one step.

Metal Injection Molding (MIM)

Process for producing intricate metal parts.

Consolidation Processes

Methods for joining materials together.

Welding

Joining materials using heat and/or pressure.

Solid State Welding

Fusing materials without melting them.

Fusion Welding

Melting materials to create a joint.

Weld Defects

Flaws that occur in welded joints.

Bead Welds

Limited penetration welds for thin materials.

Groove Welds

Welds for thick materials requiring preparation.

Fillet Welds

Used for tee, lap, and corner joints.

Plug Welds

Permanent replacements for rivets or bolts.

Heat Affected Zone

Area around weld affected by heat.

Thermal Induced Residual Stress

Stress from temperature changes during welding.

Deposition Materials

Materials added during welding process.

Solidification Zone

Area where molten material solidifies.

Microstructure Changes

Alterations in material structure from welding.

Residual Stress

Internal stress remaining after welding.

Mechanical Properties

Characteristics determined by material density.

Finishing Treatments

Post-processing to enhance material properties.

Distortion

Deformation caused by welding stresses.

Restraints

Supports used to minimize distortion during welding.

Reaction Stresses

Additional stresses from fully restrained parts.

Warpage

Deformation resulting from uneven heating during welding.

Weldability

Material's ability to be welded reliably.

Weldability Tables

Guidelines for materials and welding processes.

Oxyfuel-gas Welding

Welding using a flame from burning gas.

Flame Cutting

Cutting metal using a flame.

Arc Welding

Welding using an electric arc for heat.

Metal Transfer Modes

Methods of transferring metal in arc welding.

Shielded Metal Arc Welding

Welding process using a consumable electrode.

Flux-Cored Arc Welding

Welding using a tubular electrode filled with flux.

Gas Metal Arc Welding

MIG welding using a continuous wire feed.

Submerged Arc Welding

Welding under a blanket of granular flux.

Nonconsumable-Electrode Arc Welding

Welding where the electrode does not melt.

Gas Tungsten Arc Welding

TIG welding using a non-consumable tungsten electrode.