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Stainless Steel Alloys

There are many alloys of stainless steel. Below are some of the key properties of many of the popular ones.

Stainless Steel 305 has the maximum formability among austenitic stainless steels due to lowest work and strain hardening rates. Corrosion resistance is similar to 304. 305 is used in applications that need maximum formability such as spun or deep drawn eyelets, barrels, shells etc. It is most suitable for cold working processes like drawing, spinning, heading and blanking. 305 can also be hot worked using forging, heading etc. and is generally weldable but not heat treatable. It is also used in products like drawn housings, rivets, tank covers, kitchen utensils and writing instruments.

Stainless Steel 308 is used as a filler material when welding stainless 304.

Stainless Steel 309 is used for high temperature applications up to 1900°F. It has higher strength and superior corrosion resistance compared to 304. It can be cold worked but is not heat treatable. It is easily weldable and machinable. 309 is used in furnace parts (burner, door, fan, piping, recuperators, grids, wind boxes), paper mill equipment, petroleum refining equipment (catalytic recovery systems, recuperators), power generation equipment (pulverized coal burners, tube hangers), thermal processing equipment (annealing covers and boxes, burner grids, doors, fans, lead pans and neutral salt pots, muffles and retorts, recuperators, walking beams, radiant tubes), waste treatment equipment (incinerators, rotary kilns, calciners), carbon saggers, brazing fixtures, glass forming equipment, thermowells, power boiler tube hangers, anchor bolts, oven linings, refractory supports, auto exhaust parts.

Stainless Steel 310 can also be used at high temperatures. It maintains good strength and corrosion resistance up to 2100°F. It can also be used at cryogenic temperatures down to -450°F. It has superior corrosion resistance compared to 304 and 309. Machinability is similar to 304. It is weldable and can be cold worked even though it has a high work hardening rate. It can not be heat treated. Typical applications are furnace parts, oil burner parts, heat exchangers, welding rods and filler wires, annealing covers, combustion tubes, fire box sheets, flare tips, fluidized bed coal combustors, radiant tubes, tube hangers for petroleum refining and steam boilers, coal gasifier internal components, thermowells, refractory anchor bolts, combustion chambers, retorts, muffles, food processing equipment, cryogenic structures, kilns, saggers, conveyor belts, rollers and oven linings.

Stainless steel 314 is similar to 310 but has a higher level of silicon. This provides better heat resistant properties that 310. Applications and other properties are similar to 310 grade.

Stainless steel 317 exhibits better corrosion resistance (general and pitting/crevice corrosion) than 304 and 316 in highly corrosive environments. It is weldable and machinable. It is not heat treatable. It can be cold or hot worked. Typical applications are textile equipment, paper equipment, chemical equipment, food processing equipment, petrochemical equipment, pharmaceutical equipment, power generation equipment, absorber towers, boilers, condenser tubes, fittings, heat exchangers, outlet and inlet ductwork, pipes, pressure vessels, slurry tanks, stack liners, valves.

Stainless steel 321 is similar to 304 except it can be used in more elevated temperatures (800-1500°F) and in environments where intergranular corrosion can cause problems. It is also resistant to scaling and vibration fatigue. It is less prone to creep and rupture compared to 304. Typical applications are aircraft exhaust stacks and manifolds, jet engine parts, chemical processing equipment, weld equipment, boiler shells, expansion joints, cabin heaters, fire walls, flexible coupling, pressure vessels, wire cloth.

Stainless steel 347 also offers resistance to intergranular corrosion. It is similar to 321.

Stainless steel 348 is similar to 347 but has an additional cobalt content.

Stainless steel 405 is highly suitable for welding applications. It is easily machinable and formable. Corrosion resistance is similar to 410. Typical applications are annealing boxes, steam nozzles, quenching racks, partitions and other fabrications that cannot be annealed after welding.

Stainless Steel 409 is mostly used in the automobile exhaust industry. It has got good corrosion resistance at elevated temperature, medium strength and good formability. Corrosion resistance is similar to 410. It is weldable. It can be cold worked and hot worked. It is not heat treatable. Typical Applications are automotive exhaust systems applications such as manifolds, agricultural spreaders, exhaust pipes, catalytic converters, mufflers, tail pipes and non-automotive exhaust applications such as home heating systems, gas turbine exhaust silencers, automotive thermostats and fuel filters, electrical transformer cases, caskets and heat exchanger tubing. Other applications are farm equipment, structural support and hangers, transformer cases, diamond tread plate and shipping containers.

Stainless steel 434 is a modification of 430 with additional molybdenum. This provides better corrosion resistance and higher heat resistance (up to 1500°F). It is machinable, formable and weldable. It is used in automotive trim applications and molding, furnace combustion chambers, dishwashers, rangehoods, gas burners, steam iron bases, flatware, gutters, downspouts, nitric acid plant equipment, oil refinery equipment, roofing, restaurant equipment.

Stainless steel 436 is similar to 434 but with higher molybdenum content and additional titanium. This allows higher pitting corrosion resistance compared to 434. Other properties and typical applications are similar to that of 434 grade.

Stainless steel 442 offers higher corrosion resistance due to the presence of higher chromium. It is also heat resistant. It is difficult to fabricate and can not be heat treated. It is suitable for high heat applications. Typical applications are furnace and combustion components, zinc die casting machines, nitrogen fixation parts, storage tanks for nitric acid, decorative trim.

Stainless steel 446 exhibits excellent resistance to hot corrosion and oxidation. It can also tolerate molten copper and brass. It is used in high temperature applications from 1500°F to 2000°F. It is machinable and weldable. It is difficult to be cold worked and is not heat treatable. Typical applications are boiler baffles, thermocouple protectors, furnace parts, neutral salt pot electrodes, waste heat boilers, X-ray tube bases, furnace and kiln linings, oil burner components, incinerators, recuperators,  injector nozzles in molten compounds, stack dampers, glass molds, combustion chambers, annealing boxes and industrial mufflers, spouts for conveying molten copper alloys, soot blowers, molten lead, salt baths, cement kilns.

Stainless steel 414 is similar to 410 but with better corrosion resistance due to the addition of nickel. Typical applications are springs and cutlery.

Stainless steel 431 has the highest corrosion resistance among hardenable martensitic stainless steels. It can be hardened up to 40HRC. It can be hot worked or cold worked. Typical applications are valves, pumps, aircraft components, propeller shafts, marine equipment, chemical equipment.

Stainless steel UNS S32101 is a duplex stainless steel. It has better resistance against corrosion and  stress corrosion cracking than 304 and 316L. It also has higher strength than 304 and 316L. Typical applications are air pollution control (external absorbers, outlet duct reinforcements), biodiesel plants and tanks, chemical process equipment (pressure vessels, heat exchangers, tanks, piping systems, tanks), food and beverage processing equipment (palm oil and wine storage tanks), bridges, flood gates, sluice gates, pulp and paper industry equipment (hydrogen peroxide bleaching reactors, white liquor storage tanks, digesters, washers, paper machine parts), seawater treatment (desalination system chambers, evaporators), water and waste water treatment plants.

Stainless steel UNS S32304 is a duplex stainless steel with corrosion resistance properties similar to 316L grade. But, it’s mechanical strength is significantly higher than 304 and 316. It is machinable and weldable. It can be cold formed and hot formed. Typical applications are similar to 304L and 316L. It is used in pulp and paper industry (chip storage tanks, white and black liquor tanks), caustic solutions and organic acids environment (stress corrosion cracking resistance), food industry equipment, pressure vessels and mining equipment.

Stainless steel UNS S32003 is a nitrogen enhanced duplex steel. It is used when both high strength and good corrosion resistance are required. It is used in subsea oil and gas fields. It has significantly higher strength than 316L. Corrosion resistance is similar to 316L.

Stainless steel UNS S31803 is the most widely used duplex steel grade. It has excellent corrosion resistance, superior to 316 and higher strength compared to 316. But, it is not suitable for high temperature applications (above 500°F). It is machinable and weldable and can be cold formed and hot formed. Typical applications are pumps, valves, chokes, pipeworks, flanges, bolting, connectors, manifolds, oil & gas industry equipments, brewing equipment, power generation equipment, chemical equipment, marine equipment, pollution control equipment, pulp and paper manufacturing, desalination equipment, auger, cargo tanks, couplings, diaphragm seals, fans, fasteners, instrumentation tubes, press rolls, screw conveyors.

Stainless steel UNS S32205 is similar to stainless steel UNS S31803. But, it has higher nitrogen content which ensures slightly higher corrosion resistance. Other properties and applications are similar to UNS S31803.

Stainless steel UNS S32760 is a super duplex steel. It can be used in warm seawater with excellent corrosion resistance. It has superior corrosion resistance properties and higher strength compared to UNS S32205. It is weldable and machinable. Typical applications are marine equipment, mining equipment, pharmaceutical equipment, petrochemical equipment and chemical equipment.

Stainless steel UNS S32750 is similar to UNS S32760.

Stainless steel UNS S32550 is a super duplex steel with better corrosion resistance and higher strength. Typical applications are valve bodies, paper machine components, marine equipment, pumps, shafts, demineralized water production equipment, pressure vessel.

Stainless steelUNS S32707 is a hyper duplex stainless steel. It is used in severe chloride environments such as hot tropical waters. It offers higher corrosion resistance and higher strength compared to S32750. It also offers higher resistance to stress corrosion cracking. It is weldable. Typical applications are marine equipments, petroleum equipment, heat exchangers,

Stainless steel UNS S33207 is another hyper duplex stainless steel. It offers excellent resistance to corrosion and stress corrosion cracking. It has exceptionally high mechanical strength. Typical applications are marine equipment and oil & gas exploration equipment.

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