Last class MAR transformation Austenitization tempering Stainless steels

Last class MAR transformation Austenitization & tempering Stainless steels Today More stainless steels Tool steels Cast irons Case hardening

Types of steels Plain carbon steels Low carbon steels Stainless steels alloy steels high carbon steels 420 440 A 440 C 13 Cr-0. 15 C 230 ksi(ht cutlery treated) 17 Cr-0. 5 Ni-0. 7 C 260 ksi(ht cutlery treated) 17 Cr-0. 5 Ni-1. 2 C 285 ksi(ht ball bearings treated) 405 430 13 Cr-0. 5 Ni-0. 08 C 60 ksi(annealed) machine parts 16 Cr-0. 5 Ni-0. 12 C 65 ksi(annealed) acid tanks 304 L 316 19 Cr-10 Ni-0. 08 C 85 ksi(annealed) food equipment 19 Cr-10 Ni-0. 03 C 80 ksi(annealed) food equipment 17 Cr-12 Ni-0. 08 C 85 ksi(annealed) chemical tanks

Types of steels Stainless steels

Stainless steels 420 440 A 440 C 13 Cr-0. 15 C 230 ksi(ht treated) 17 Cr-0. 5 Ni-0. 7 C 260 ksi(ht treated) 17 Cr-0. 5 Ni-1. 2 C 285 ksi(ht treated) 405 430 13 Cr-0. 5 Ni-0. 08 C 60 ksi(annealed) 16 Cr-0. 5 Ni-0. 12 C 65 ksi(annealed) 304 L 316 19 Cr-10 Ni-0. 08 C 85 ksi(annealed) 19 Cr-10 Ni-0. 03 C 80 ksi(annealed) 17 Cr-12 Ni-0. 08 C 85 ksi(annealed)

Stainless steels hardenable! not hardenable!

Stainless steels sufficient amt of Ni ––> AUS at rm temp austenitic SSs ----- ≥ 18% Cr & ≥ 8% Ni not hardenable

Types of steels Plain carbon steels Low carbon steels Stainless steels Tool steels alloy steels high carbon steels

Some types of tool steels W 1, W 2. . . water hardening 0. 60 -1. 40 C S 2, S 2. . . shock resisting 0. 5 C-Cr, W, Mo O 1, O 2. . . oil hardening 0. 9 C-Mn, Ni, W A 2, A 3. . . air hardening 1. 25 C-5 Cr, V, Mo H 10, H 11. . . hot work 0. 4 C-0. 4 V-3 -5 Cr T 1, T 2. . . high-speed 0. 8 C-4 Cr-18 W-1 -2 V Compositions not exact - higher grades have different compositions

Speaking of tools…. . What about "carbide" tools? Most are WC fragments imbedded in Co matrix phase the "glue" angular WC fragments

Speaking of tools…. . OK, then, what about "ceramic" tools? Most from Al 2 O 3 - pressed to near-net shape & sintered at 1600 -1700° C - ground on diamond wheels At high temps, high hardness, wear resistance Can use for mat'ls w/ up to RC 66 Very brittle Cost ≈ 2 X that of carbide tools

Cast irons Types White - C is all in CM Grey - C as graphite flakes Ductile (nodular) - C as graphite nodules

Cast irons

Cast irons White - C is all in CM very brittle, wear resistant, not machinable, limited use Grey - C as graphite ("corn") flakes Si added to graphitize, brittle cuz of flake stress raisers - cheap, widely used, vibration damping Ductile (nodular) - C as graphite nodules "inoculated" w/ Mg or Ce to get nodules - up to 40% EL

Case hardening Gear tooth Carburizing - pack & gas - add C from CO gas