Manufacturing Processes (Casting, Forming, PM, Ceramics) - Lecture Notes Review

These flashcards cover key concepts from the provided lecture notes on casting, forming, powder metallurgy, ceramics, and related inspection and processing topics.

What is manufacturing?

The creation of finished goods through tools, machines, labour, chemical processing, etc., by transforming raw materials into finished products.

What are primary and secondary manufacturing processes?

Primary processes transform raw materials into basic shapes; secondary processes refine, assemble, and finish into finished products.

What is casting as a manufacturing process?

A primary process where molten metal is poured into a mold cavity and allowed to solidify into a desired shape.

Name the common casting processes discussed in the notes.

Sand casting, Die casting, Investment casting, Centrifugal casting, Shell molding.

What are the basic steps in the sand casting process?

Pattern making, Mold making, Melting, Pouring, Solidification, Shakeout, Finishing.

What is pattern making in casting?

Creating a replica of the part (from wood, plastic, or metal) to form the mold cavity.

What is mold making in sand casting?

Preparing a mold using sand, metal, or ceramic materials; molds can be expendable or permanent.

What is shakeout in sand casting?

Breaking the mold and removing the solidified casting.

What is finishing in casting?

Removing excess metal, cleaning surfaces, and performing quality checks.

What percentage and role of sand casting in metal casting?

Sand casting accounts for over 90% of metal castings and uses granular refractory sand with clays and water.

What are the key features of sand casting?

Simple and low tooling costs, wide material compatibility, versatile shapes, rough surface finish, slow production rate, and environmentally friendly.

What are the disadvantages of sand casting?

Lower dimensional accuracy, rough surface finish, need for post-processing, and slower production than some alternatives.

Name typical applications of sand casting.

Engine blocks, pump/valve bodies, large machine components, pipes, railway components, agricultural equipment parts, wind/hydro power components, manhole covers.

What is die casting?

A process that injects molten non-ferrous alloys into a mold under high pressure to produce complex parts with high precision and smooth surfaces.

What are the key features of die casting?

Uses non-ferrous metals (Al, Zn, Mg); high-pressure injection; reusable steel dies; high dimensional accuracy and smooth surface; suitable for mass production.

What are the advantages of die casting?

High precision and dimensional accuracy, high production speed, good surface finish, ability to form complex geometries, reduced secondary machining.

What are the disadvantages of die casting?

High initial tooling costs, size/weight limitations, potential porosity, design constraints, and potential for defects.

What is investment casting?

A wax pattern is coated with refractory ceramic material to form a mold; wax is melted out and molten metal is poured to form the final component.

What are the advantages of investment casting?

Highly accurate, complex shapes; excellent surface finish; near-net shape; minimal machining; can cast high-melting-point alloys.

What are the disadvantages of investment casting?

High cost and long lead times; limited size; fragile shells; not ideal for very high-volume production.

Where are investment castings commonly used?

Turbine blades, biomedical implants, precision military components, valves and pump parts, industrial components, art and jewelry.

What is centrifugal casting?

A process where molten metal is poured into a rotating mold; centrifugal force distributes the metal to the inner surface, producing dense, high-integrity castings (good for cylindrical shapes).

What is shell molding?

A resin-coated sand is formed into a shell around a heated pattern to create a precise mold for casting; shells are thin and high-precision.

What are the advantages of shell molding?

Excellent surface finish and dimensional control, high accuracy, repeatability, and reduced machining compared to full sand molds.

What are the disadvantages of shell molding?

Higher tooling costs due to metal patterns, not ideal for very large parts, resin-coated sand cost, shells can crack during handling.

What are casting defects broadly categorized as?

Gaseous defects (blowholes, porosity, pinholes), shrinkage cavities, defects due to poor molding material, poor molten metal quality, and metallurgical defects.

What is porosity in casting defects?

Small cavities or pinholes caused by trapped gases within the solidifying metal.

What are blowholes and pinholes in casting defects?

Blowholes are larger gas bubbles creating cavities near or at the surface; pinholes are very small gas pockets often subsurface.

What is a shrinkage cavity defect?

Void created when metal contracts during solidification and there is not enough metal to fill the space.

What are common defects due to poor molding material?

Cuts, washes, swells, drops, fusion and penetration of sand into casting.

What is a cold shut defect?

Two streams of molten metal fail to fuse properly before solidifying, creating a weak seam.

What is a misrun defect?

Molten metal fails to completely fill the mold cavity.

What are slag inclusions?

Non-metallic pockets or ribbons of slag trapped in the casting during melting.

What is hot tearing (hot cracking)?

Cracking that occurs as the casting cools and the metal is weak while hot, due to residual stresses.

What is a hot spot (hard spot)?

An area that cools more rapidly than surrounding metal, becoming harder than its neighbors.

What are non-destructive testing (NDT) methods used for casting?

Visual inspection, dimensional inspection, radiographic testing, ultrasonic testing, magnetic particle inspection, dye penetrant testing, eddy current testing, infrared/thermal testing, acoustic emission, CT scanning, etc.

What are destructive testing methods used for casting?

Mechanical tests (tensile, hardness, impact), chemical analysis, metallurgical analysis.

What is powder metallurgy (PM)?

A manufacturing technology where metal powders are compacted into shapes and sintered to bond particles, enabling near-net-shape parts and mass production.

What are the four basic steps in powder metallurgy?

Powder production, mixing/blending, compacting (forming a green compact), and sintering (bonding particles in a controlled atmosphere).

What are the main categories of powder production methods?

Mechanical (crushing, milling, mechanical alloying), physical (atomization, centrifugal, gas or water), chemical (oxide reduction, precipitation), and electrochemical/electrolytic deposition.

What is near-net shape in PM?

Producing parts that require little or no finishing after sintering, closely matching final dimensions.

What is compaction in PM and its purpose?

Compressing metal powder in a die to form a green compact with sufficient strength, reduced porosity, and dimensional accuracy before sintering.

What is sintering in PM?

A thermal treatment below melting point where particles bond by diffusion in a controlled atmosphere, increasing strength and reducing porosity.

What are typical sintering temperatures for metals?

Generally 70–80% of a metal’s melting point (e.g., iron ~1100–1200°C; copper 750–1000°C; aluminum ~590–620°C; cemented carbides 1350–1450°C).

What is the purpose of sintering?

To increase strength and hardness, improve electrical/thermal conductivity, reduce porosity, and ensure dimensional stability.

What are traditional ceramics?

Ceramics made from naturally occurring raw materials like clay, silica, feldspar, and kaolinite; low-cost, brittle but versatile for construction and insulation.

What are new (advanced) ceramics?

Ceramics made from synthetically refined powders (Al2O3, ZrO2, SiC, Si3N4, TiO2) designed for high performance, high strength, wear resistance, and thermal stability.

What are glasses in ceramics?

Amorphous inorganic solids formed by rapid cooling of molten materials; typically insulating and can be transparent.

What are the typical processing steps for traditional ceramics?

Mining/beneficiation, crushing and mixing with water, forming, drying, firing (sintering).

What are typical processing steps for glasses?

Mixing/melting raw materials, forming (blowing, floating, pressing), annealing, cutting/finishing.

What are bulk deformation processes?

Processing methods that deform work material significantly: rolling, forging, extrusion, drawing.

What is rolling in metal forming?

A process where material thickness is reduced by passing between two rotating rolls; used to produce sheets, plates, and other shapes.

What are common stock shapes in rolling (bloom, billet, slab)?

Bloom: large square/rectangular cross-section; billet: small square or circular cross-section; slab: wide, thick plate.

What are typical rolling mill configurations?

Two-high, three-high, four-high, cluster, and tandem mills; reversing or non-reversing setups.

What are the advantages of rolling?

High production rate, uniform thickness, good surface finish (cold rolling), refined grain structure, low waste, automation potential, scalability.

What are the disadvantages of rolling?

High equipment cost, high power requirements, limited shape complexity, potential for springback, surface scale in hot rolling, possible defects.

What is draft in rolling?

Draft d = to − tf, the thickness reduction from entry to exit.

What is reduction in rolling?

Reduction r = d / to, the relative thickness reduction.

What is the no-slip (neutral) point in rolling?

The point along the roll-work contact arc where work velocity equals roll velocity; slip occurs on either side.

What is the rolling force formula?

F = Yf wL, where Yf is the average flow stress, w is work width, and L is contact length.

What is the rolling torque and power formulas?

Torque T ≈ 0.5 F L; Power P = 2π N F L, with N the roll speed and L the contact length.

What is the role of friction in rolling?

Friction drives the sheet through the rolls; the maximum draft is limited by μ, R, dmax = μ^2 R.

What is forging as a manufacturing process?

A deformation process where the workpiece is compressed between two dies, using impact or gradual pressure to impart die shapes.

What are open-die, impression-die, and flash-less forging?

Open-die forging uses two flat dies; impression-die forging uses shaped dies to form the part; flash-less forging confines the work fully within the die with no flash.

What are advantages of open-die forging?

Can produce very large parts, simple shapes, improved grain structure, less waste, lower tooling costs, suitable for small batches.

What are disadvantages of open-die forging?

Less dimensional accuracy, poorer surface finish, limited to simple shapes, requires skilled labor, more machining.

What are advantages of impression-die forging?

Near-net-shape parts, high precision, strong grain flow, good surface finish, reduced waste, suitable for high production and automation.

What are disadvantages of impression-die forging?

High die/tooling costs, limited shape changes, flash removal needed, die wear, longer lead times for new dies.

What are advantages of flash-less forging?

No flash, higher material utilization, better dimensional accuracy, improved surface finish, reduced post-processing, shorter production times.

What are typical applications of open-die forging?

Turbine shafts, propeller shafts, heavy machinery rolls, discs, rings, and large structural components.

What are typical applications of impression-die forging?

Automotive connecting rods/crankshafts, gears, tools, aerospace brackets, and other high-volume precision parts.

What is shell molding process and its key features?

A resin-coated sand shell is formed around a heated pattern to create a thin, precise mold; yields high accuracy and good surface finish.

What are the applications of shell molding?

Gear housings, cylinder heads, valve bodies, camshafts, crankshafts, impellers, and other small-to-medium automotive and machine parts.

What is the purpose of gating in casting?

Directs and controls the flow of molten metal into the mold cavity to ensure proper fill and quality.

Define cope and drag in sand molds.

Cope is the top half of the mold; drag is the bottom half; together they enclose the pattern and form the mold cavity.

What is a riser in casting?

A reservoir of molten metal that feeds the casting as it solidifies to prevent shrinkage defects.

What is a sprue, gate, and runner in gating systems?

Sprue is the vertical channel from the pouring cup to the runners; gates are the openings into the mold cavity; runners are channels that feed the cavity.

What is the difference between a mold and a pattern?

A pattern shapes the mold cavity; the mold is the actual cavity formed in sand, metal, or ceramic materials.

What is a ‘mushy zone’ in solidification of alloys?

A region where both solid and liquid coexist during solidification, due to a temperature range between liquidus and solidus, affecting microstructure.

What is nucleation and crystal growth in solidification?

Nucleation is the formation of tiny solid particles; crystal growth enlarges these grains as solidification proceeds.

What are the four basic ceramic categories mentioned?

Traditional ceramics, New (advanced) ceramics, and Glasses (amorphous ceramics) are covered (Traditional/New/Glasses as three main types).

What are typical raw materials for traditional ceramics?

Clay minerals (kaolinite), silica, feldspar, bauxite, quartz.

What are typical raw materials for new (advanced) ceramics?

Alumina (Al2O3), Zirconia (ZrO2), Silicon carbide (SiC), Silicon nitride (Si3N4), Titania (TiO2).

What are typical processing steps for glasses?

Mixing/melting raw materials, forming (blowing, floating, pressing), annealing, cutting/finishing.