Stainless Steel

• Stainless Steel pada dasarnya adalah baja paduan dengan kadar chrom tinggi.

• Cr larut dalam baja, bila terekspos pada ling-kungan yang bersifat oksidising maka Cr akan bereaksi membentuk lapisan pelindung di permukaan benda tsb.

• Menurut strukturmikronya, group Stainless Steel:– Ferritik, Cr tinggi C rendah, magnetik, non hardenable– Martensitik, Cr rendah C tinggi, magnetik, non

hardenable.– Austenitik, Cr + Ni (+Mn), non magnetik, non

hardenable

Diagram Fase Fe-18Cr – C

Dengan Cr 18 % dan kadar C rendah struktur tetap ferritik

Diagram Fase Fe-12Cr – C

Dengan 12 % Cr dan kadar C agak tinggi, bila dipanaskan dapat terjadi austenit, bila didinginkan akan mudah menjadi martensit

Diagram Fase Fe-18Cr-8Ni – C

Dengan Cr 18%, Ni 8% pada kadar C rendah strukturmikro pada temperatur kamar terdiri dari austenit

403Turbine quality grade, similar to 410, used for steam turbine blading and other highly stressed parts

410Base alloy for this group, general purpose, heat-treatable type, used for machine parts, pump shaft

414Higher Ni content increases hardenabi-lity and corrosion resistance, used for springs, tempered rolls, machine parts

416Free-machining modification of 410 (contains S), for heavy cuts

420High-carbon modi-fication of 410, has higher hardness and wear resistance, used for cutlery, surgical instruments, valves

440CHighest carbon con-tent (0.95 to 1.20%) of the stainless steels, used for balls, bearings, races

431Higher chromium content improves corrosion resistance, has high mechanical properties, used for air-craft fittings, heater bar, paper machinery parts bolt

416SeFree-machining modification of 410 (contains Se), for light cuts and where hot working or cold heading is involved

440ASlightly lower carboncontent than 440B for greater toughness, can have higher hardness than 420, good corrosion resistance, used for cutlery, valve parts

440BSlightly lower carbon content than 440C improves toughness, used for foine cutlery, valve parts

Martensitic Stainless Steels

430FFree-machining modifi-cation of 430 (contains S), for heavy cuts and screw-machined parts

430Basic alloy for this group, a nonhardening chromium type, used for decorative trim, nitric acid tank, annealing basket

430SeFree-machining modifi-cation of 430 (contains Se), for light cuts and where hot working or cold heading may be involved

405Addition of Al improves weldability of this other-wise martensitic alloy, making it a nonharden-able, used where air-hardenig types (410 or 403) are objectionable

446Higher chromium content than 442 increases corrosion and scaling resistance at high temperatures, used espcially for intermittant service often in sulfur-bearing atmosphere

442High chromium content for increased corrosion and scaling resistance, used for furnace parts, nozzles, combustion chambers

Ferritic Stainless Steels

302Basic alloy for this group, used for trim, food handling equipment, aircraft cowling, antennas, springs, archi-tectural products, cookware

302BMore resistant to scaling than 302 because of Si content, used for furnace parts, still liners, heating elements

202General purpose low-nickel equivalentof 302, Ni partially replaced by Mn

347Similar to 321 except Cb or Ta is added to stabilze for welded application

304Low-carbon modification of 302 for restriction of carbide precipitation during welding, used for chemical and food-processing equipment, recording wire

304LExtra low-carbon modification of 304 for further restrictio of carbide precipitation during welding

308High-alloy (Ni and Cr) con-tent increases corrosion and heat resistance, principally used for welding filler metals to compensate alloy lost in welding

305High-nickel content to lower work- hardening rate, used for spinforming and severe drawing operations

321Ti content prevents Chrom-um carbide precipitation during welding, for severe corrosive conditions and service from 800 to 1600 oF, used for air-craft exhaust manifold, boiler shells, process equipments

309Similar to 308, except alloy content (Ni and Cr) is higher has excellent corrosion and scaling resistance, used for aircraft, heaters, heat-treating equipment, furnace parts

348Similar to 347 except for a maximum limit on Ta, used for nuclear energy applications

309SLow-carbon modificationof 309 for improved weldability

303Free-machining modification (contains S) of 302, for heavy cuts, used for screw machine products, shafts, valves

303SeFree-machining modification (contains Se) of 302, for light cuts and where hot working or cold heading maybe involved

314Similar to 310, except higher silicon content increases scaling resistance at high temperature

310Similar to 309, except alloy content (Ni and Cr) is higher used for heat exchangers, fur-nace parts, combustion cham-bers, welding filler metals

310SLow-carbon modification of 310 for improved weldability

316Higher corrosion resistance than 302 or 304 because of Mo content, has high creep resistance, used for chemical , pulp-handling, photo-graphic and food equipment

316LLow-carbon modification of 316, for welded construction

317Higher Mo content than 316 improves resistance to corro-sion and creep

201Low-nickel equivalent of 301, Ni partially replaced by Mn, has high work-hardening rate

301Work-hardening rate increased by lower Cr and Ni content, used for high-strength high-duc-tility applications such as rail-road cars, trailer bodies, aircraft structural member

Austenitic Stainless Steels

Austenitc Stainless Steel: Chemical analysis

Type Nmr

Analysis201 202 301 302 309 316

Chromium 16.0 -18.0 17.0 - 19.0 16.0 – 18.0 17.0 – 19.0 22.0 – 24.0 16.0 – 18.0

Nickel 3.5 – 5.5 4.0 – 6.0 6.0 – 8.0 8.0 – 10.0 12.0 - 15.0 10.0 - 14.0

Other ElemntsN2 0.25

maxN2 0.25

max- - - Mo 2.0-3.0

Carbon 0.15 max 0.15 max 0.15 max 0.15 max 0.20 max 0.08 max

Manganese 5.5 – 7.5 7.5 – 10.0 2.0 max 2.0 max 2.0 max 2.0 max

Silicon 1.00 max 1.00 max 1.00 max 1.00 max 1.00 max 1.00 max

Martensitic Stainless Steel: Chemical Analysis

Type Nmr

Analysis410 416 420 440A 501 502

Chromium 11.5 – 13.5 12.0 – 14.0 12.0 – 14.0 16.0 -18.0 4.0 – 6.0 4.0 -6.0

Nickel 0.50 max - - 0.50 max - -

Other Elemnts - - -Mo 0.75

maxMo 0.4 –

0.65Mo 0.40 –

0.65

Carbon 0.15 max 0.15 max 0.15 max 0.60 – 0.75 0.10 min 0.10 max

Manganese 1.0 max 1.0 max 1.0 max 1.0 max 1.0 max 1.0 max

Silicon 1.0 max 1.0 max 1.0 max 1.0 max 1.0 max 1.0 max

Ferritic Stainless Steel: Chemical Analysis Type Nmr

Analysis405 430 446

Chromium 11.5 – 14.5 14.0 – 18.0 23.0 – 27.0

Nickel 0.50 max 0.5 max 0.5 max

Other Elemnts Al 0.1-0.3 -N2 0.25

max

Carbon 0.06 max 0.12 max 0.20 max

Manganese 1.0 max 1.0 max 1.5 max

Silicon 1.0 max 1.0 max 1.0 max