PEC EPE Metallurgical flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Ellingham diagram

A plot of standard Gibbs free energy of oxide formation versus temperature. A metal can reduce any oxide whose line lies above its own at the operating temperature.

Shrinking-core model

A kinetic model for leaching a solid particle through a product layer. Diffusion control gives 1-3(1-x)^(2/3)+2(1-x)=kt; chemical control gives 1-(1-x)^(1/3)=kt.

Separation factor in solvent extraction

The ratio of distribution coefficients of two metals, β = D1/D2. Values near 1 require many stages, while large values allow separation in few stages.

Gibbs phase rule

F = C - P + 2 relates degrees of freedom, components, and phases. At constant pressure it becomes F = C - P + 1, useful for binary phase diagrams.

Hall-Petch relationship

Yield strength rises as σy = σ0 + k d^(-1/2), where d is grain diameter. Finer grains increase strength and improve toughness by blocking slip.

Jominy end-quench test

A hardenability test in which a standard bar is quenched at one end and hardness is measured along its length. Alloying elements increase hardness at greater distances.

Van't Hoff equation

d(lnK)/dT = ΔH°/(RT²). It shows that endothermic reactions are favored by raising temperature and exothermic reactions by lowering it.

Arrhenius rate equation

k = A exp(-Q/RT). Plotting ln k against 1/T gives a straight line whose slope equals -Q/R, allowing activation energy determination.

Boudouard reaction

C + CO2 → 2CO. It is strongly endothermic and produces gas volume, so it becomes favorable at high temperature and drives carbothermic reduction in furnaces.

Slag basicity

The ratio CaO/SiO2 in slag. Higher basicity improves phosphorus and sulfur removal but increases slag volume and lime consumption in steelmaking.

BOF steelmaking

Basic oxygen furnace process blowing pure oxygen onto hot metal. Carbon, silicon, and manganese oxidize while lime flux forms a basic slag removing phosphorus and sulfur.

Continuous casting

Molten steel is poured through a water-cooled mold, forming a shell that is spray-cooled and withdrawn as a strand, improving yield and consistency over ingot casting.

Bragg's law

nλ = 2d sinθ describes constructive diffraction from crystal planes. It is the basis of X-ray diffraction phase identification and lattice parameter measurement.

Atomic packing factor

The fraction of unit cell volume occupied by atoms: 0.74 for FCC and HCP, 0.68 for BCC. Higher packing correlates with denser slip planes in FCC metals.

Considère criterion

Necking begins when dσt/dεt = σt in true stress-strain terms. For Hollomon behavior σt = K εt^n, this occurs at true strain equal to n.

Fracture toughness KIc

A material property describing resistance to crack propagation. Failure occurs when KI = Y σ √(πa) reaches KIc, linking stress, flaw size, and geometry factor.

Ductile-to-brittle transition

The temperature range where fracture mode changes from ductile to brittle in Charpy testing. It is indexed by 27 J absorbed energy or 50% shear appearance.

Bond's comminution law

W = 10 Wi (1/√P80 - 1/√F80) gives specific grinding energy in kWh/t, where Wi is the work index and sizes are in micrometers.

Froth flotation reagents

Collectors adsorb on target minerals to make them hydrophobic, frothers stabilize bubbles, and activators or depressants modify selectivity. Lime and cyanide are common depressants.

Tromp curve

A partition curve plotting the fraction of feed reporting to concentrate against particle density or size. Its probable error Ep = (d75 - d25)/2 measures separation sharpness.

Faraday's law of corrosion

Mass loss m = (M I t)/(n F). It converts measured corrosion current into metal loss, enabling corrosion rate calculation in mm per year.

Pourbaix diagram

A potential versus pH diagram showing immunity, corrosion, and passivation regions for a metal in water. It predicts thermodynamic tendency, not corrosion rate.

Sensitization of stainless steel

Chromium carbide precipitation at grain boundaries in the 425-815 °C range depletes chromium locally, making the steel susceptible to intergranular corrosion in aggressive environments.

Chvorinov's rule

Solidification time t = B (V/A)^2, where V/A is the casting modulus. Risers must have a larger modulus than the section they feed to prevent shrinkage porosity.

Carbon equivalent

CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15 estimates weldability. Values above about 0.4 increase cold-cracking risk and require preheat.

Welding heat input

H = ηVI/v in joules per millimeter, where η is arc efficiency, V voltage, I current, and v travel speed. Higher heat input widens the heat-affected zone.

Hierarchy of controls

Risk controls ranked by effectiveness: elimination, substitution, engineering controls, administrative controls, and personal protective equipment. PPE is the last line of defense.

Confidentiality obligation

Engineers must protect client and employer information learned during work, including after leaving the organization, except where law or public safety requires disclosure.

Net present value

The sum of discounted cash flows at the minimum attractive rate of return. A positive NPV means the project adds value and should be accepted.

Break-even quantity

Q = FC/(p - vc), where FC is fixed cost, p unit price, and vc variable cost per unit. Output above Q yields profit.

Critical path method

A scheduling technique identifying the longest path through a network. Activities on it have zero total float, so any delay there delays project completion.

Process capability index Cpk

Cpk = min(USL-μ, μ-LSL)/(3σ) measures how well a centered or off-center process fits specification limits. Values of 1.33 or more are commonly targeted.