Metallurgy: Mechanical Properties & Testing of Steel

Introduce the basics of crystal lattice, atomic radii, and lattice dimensions; examine how atoms occupy volume in unit cells and calculate void volumes in FCC structures.

Explore how simple cubic, fcc, and bcc lattices pack atoms, determine atoms per unit cell, and relate lattice dimensions to atomic radii in steel.

Explore how atomic packing factor is calculated for simple cubic, BCC, and FCC unit cells by counting atoms and using 4/3 pi r^3, noting FCC ~74%, BCC ~68%, SC ~52%.

Learn how the FCC unit cell in austenite contains eight tetrahedral voids and four octahedral voids, with two tetrahedral and one octahedral void per atom, shaping alloying occupancy.

Calculate the interstitial radius and the space inside the FCC octahedral void, and derive the lattice atom radius relation with a 0.414 ratio to determine fitting atoms.

Apply the Pythagoras theorem to FCC geometry to calculate the tetrahedral void radius and the space available within one tetrahedral void, deriving the interstitial radius X/r = 0.25.

Explore tetrahedral and octahedral voids in a body-centered lattice, deriving 12 tetrahedral voids and 6 octahedral voids per unit cell.

Calculate tetrahedral and octahedral voids in bcc structures and determine their radii from lattice parameters, linking distorted bcc voids to fcc voids.

Compare voids in fcc and bcc structures by analyzing unit cells, atom counts, and void volumes, and relate these spaces to solubility and mechanical properties.

Examine the solubility of carbon in steel and its effect on mechanical properties, including calculating carbon equivalent, carbon behavior, and how carbon atoms influence alloy structures and hardness.

Examine how carbon solubility in steel is high in fcc (austenite) due to fit into octahedral voids, drops in btc, and how rapid cooling traps carbon to form martensite.

Understand how carbon's atomic structure enables strong bonds and high hardness, from diamond to martensite formation in iron when carbon is introduced and cooled rapidly.

Explore how carbon content controls steel hardness, strength, and brittleness, and use carbon equivalent values to predict hardness and welding compatibility across low, medium, and high carbon steels.

Explore how hardness and reliability interrelate, identify elements that improve hardness, and learn how chromium and nickel equivalents relate to welding, at atomic and structure levels.

Explore how chromium and nickel stabilize weld metal phases and form a self-healing passive film, enabling stainless steel properties and filler selection via chromium and nickel equivalents and Kepler diagram.

Explore how atomic behavior, slip planes, and grain boundaries in fcc and btc structures, along with cold working, determine steel properties under stress.

Explore how slip bands and slip planes govern ductility under shear in FCC and other crystal structures, producing surface steps and, with multiple slip planes, a more uniform surface.

Dislocations enable slip under shear stress, moving along densely packed planes in fcc and bcc metals; fcc requires less force to move dislocations, with multiple slip directions (12) guiding motion.

Explore how grain boundaries and dislocations govern ductility and yield strength in steel, showing how dislocations move under shear and are halted by grain boundaries, with finer grains enhancing strength.

Explore how cold working and grain boundaries influence ductility and strength in steel, with dislocation forests, elongated grains, and the role of annealing in relieving residual stresses.

Assess piping material integrity through metallurgical, destructive, and non-destructive testing, guided by codes and standards, including visual inspection and marking, to ensure safe performance across process conditions.

Discover metallurgical testing for pipe materials, covering five test categories to detect corrosion and defects and verify chemical composition against standards.

Explore grain size testing and its role in balancing mechanical properties, showing how finer grains increase strength and how automated measurements apply standard grain size scales.

Identify intergranular corrosion in stainless steel, chromium carbide depletion at grain boundaries during sensitization, and summarize ASTM A262 five test methods for screening and mitigation.

Ferrite testing uses a probe with a magnetic circuit to non-destructively measure ferrite content in stainless and duplex steels, with 4–8% ferrite deemed acceptable for balance of properties.

Explore hydrogen induced cracking (HIC) and how atomic hydrogen forms internal cracks and blisters in steel, with testing methods like magnetic particle inspection and phased array ultrasonic testing.

Explore sulfide stress corrosion cracking under tensile stress in hydrogen sulfide environments, especially in high-strength iron alloys with hard zones and heat-affected areas, and potential prevention strategies.

Explore destructive testing methods used to verify steel properties, including tensile, bend, threatening, impact, and grip tests, under various temperatures, ensuring compliance with material standards.