Stainless Steel

Stainless steel

An alloy containing iron, relatively low carbon, a minimum of 11% chromium and up to 30% nickel. For increased corrosion resistance or for manufacturing requirements in specific applications, chromium may be increased and other elements such as manganese, aluminium, titanium and/or molybdenum may be added as required. The key element in stainless steel is chromium which forms a tenacious, refractory oxide, protective film on any exposed layer, i.e. a corrosion barrier. This relatively impervious film is considered to be self-healing or self-restoring. It will, if broken, repair itself spontaneously upon re-exposure to an oxidising agent such as air or nitric acid. Resistance to corrosive attack under specific conditions is enhanced by progressively increasing chromium and/or by the addition of other elements.

Austenitic stainless steel

A stainless steel with a metallurgical content that includes 17-25% chromium and 7-20% nickel. It includes grades 201, 301, 304, 304L, 316, 316L, 321 and 310.

Essentially Austenitic stainless steel is non-magnetic in its softened condition but shows varying degrees of magnetism when cold worked. It cannot be hardened by heat treatment.

Typical uses -

201 - Railcars; buses; general roll formed sections; rainwater goods; sinks and drainers; commercial refrigeration cabinets; conveyor belts.

301 - Railcars; commercial fabricated items; sink drainers.

304 - Sinks; tubs; architectural finishes; food handling, processing and serving equipment; rainwater goods; hospital, brewing and dairy equipment.

304L - Chemical plant; food processing equipment; coal and petroleum industry.

310 - Furnace parts over 900^oC; baffles; heat treatment boxes; heat exchangers.

316 - Exterior applications subject to severe industrial or marine atmosphere; chemical, textile, photographic and paper making equipment; wine vats.

316L - Chemical plant and food processing equipment.

321 - Chemical plant and food processing equipment; heavy welded items and furnace parts.

Ferritic stainless steel

A stainless steel that includes 12-17% chromium. Includes grades 409, 430 and 3CR12. Its name is derived from the ferritic metallurgical structure which is stable at room temperature.

Ferritic stainless steel is magnetic and cannot be hardened by heat treatment.

Typical uses -

409 - Auto exhausts.

430 - Architectural; auto trim; domestic appliances; restaurant equipment; stove and heater components.

3CR12 - Coal wagons, coal wash plants, sugar processing plants, sewage treatment plants.

Martensitic stainless steel

A stainless steel with 12-18% chromium and up to 1% carbon which can be hardened by heat treatment, making it useful where high mechanical strength is required eg knives.

Finishes

A number of polished finishes are available for stainless steel -

MF (Mill Finish) - an off-the-mill finish; roll forming marks are retained and an indication of the weld may be visible.

BP (Buff Polish) - a pleasing bright finish with medium lustre. Traces of external welding and roll marks cab be visible.

SL (Surfline Polish) - A bright and reflective finish, just short of a mirror finish, which may have traces of welding markings.

GP (Grit Polish) - produced by centreless belt polishing to the grit size specified by the customer i.e. 60, 120, 180, 240, 320, 400. There are no roll or weld-line markings.

SP (Satin Polish) - Standard grit finish produced by polishing with 120-150 grit abrasive, and matches No. 4 finish. On square or rectangular tube the polishing pattern runs longitudinally.

IP (Internal Polish) - internally grit polished tube in lengths of up to 6 metres for diameters of 38.1 to 101.6mm available.

GENTUBE - similar to SL but confined mainly to small diameter light wall tube.

Grade	Modulus of Elasticity Annealed Conditions MPa	Density 0^oC kg/m³	Specific Heat 0^o-100^okJ/kg.K	Electrical Resistivity 20^oC µΩm	Thermal Conductivity		Mean Co-efficient of Thermal Expansion per degree C
Grade	Modulus of Elasticity Annealed Conditions MPa	Density 0^oC kg/m³	Specific Heat 0^o-100^okJ/kg.K	Electrical Resistivity 20^oC µΩm	100^oC W/m.K	500^oC W/m.K	0-100^o	0-650^o
301	193 x 10³	80 x 10²	0.50	0.72	16.3	21.5	16.9 x 10^-6	18.7 x 10^-6
304	193 x 10³	80 x 10²	0.50	0.72	16.3	21.5	17.3 x 10^-6	18.7 x 10^-6
304L	193 x 10³	80 x 10²	0.50	0.72	16.3	21.5	17.3 x 10^-6	18.7 x 10^-6
310	193 x 10³	80 x 10²	0.50	0.78	13.0	17.3	14.4 x 10^-6	17.4 x 10^-6
316	193 x 10³	80 x 10²	0.50	0.74	15.6	21.0	16.0 x 10^-6	18.5 x 10^-6
316L	193 x 10³	80 x 10²	0.50	0.74	15.6	21.0	16.0 x 10^-6	18.5 x 10^-6
321	193 x 10³	80 x 10²	0.50	0.72	16.1	22.2	16.7 x 10^-6	19.3 x 10^-6
409	200 x 10³	77 x 10²	0.46	0.60	24.9	28.6	9.9 x 10^-6	11.7 x 10^-6
430	199 x 10³	77 x 10²	0.46	0.60	24.9	28.8	10.4 x 10^-6	11.9 x 10^-6

Typically available range of sizes

Other sizes are probably available by arrangement. Coils typically have an internal diameter of 508mm.

Finish	Form	Thickness mm	Width mm	Length mm
2B/2D	Coil	0.30 to 0.40	13 to 750	-
		0.45 to 0.60	13 to 1000
		0.70 to 0.80	13 to 2000
		0.90 to 1.60	20 to 1500
		1.80 to 3.25	50 to 1500
		3.50 to 5.00	150 to 1500
	Sheet	0.30 to 0.40	450 to 750	900 to 1800
		0.45 to 0.60	450 to 1000	900 to 3600
		0.70 to 0.80	450 to 1200	900 to 3600
		0.90 to 5.00	450 to 1500	900 to 3600
Bright Annealed	Coil	0.30 to 0.40	13 to 750
		0.45 to 0.60	13 to 900
		0.70 to 0.80	13 to 1000
		0.90 to 1.60	20 to 1200
		1.80 to 2.00	50 to 1200
	Sheet	0.30 to 0.40	450 to 750	900 to 1800
		0.45 to 0.60	450 to 900	900 to 3600
		0.70 to 0.80	450 to 1000	900 to 3600
		0.90 to 2.00	450 to 1200	900 to 3600
No. 4 Polish	Coil	0.70 to 0.80	13 to 1200
		0.90 to 1.60	20 to 1500
		1.80 to 3.25	50 to 1500
		3.50 to 5.00	150 to 1500
	Sheet	00.45 to 0.60	450 to 1000	900 to 2400
		0.70 to 1.00	450 to 1200	900 to 3600
		1.20 to 5.00	450 to 1500	900 to 3600

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