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Stainless steels austentic
Ferritic stainless steels
Martensitic stainless steels
Principal stainless steels, their characteristics and applications

The stainless steels are different due to their corrosion resistance and oxidation resistance. The essential element in the stainless steel is chromium. Their particular property is the formation of a chromium oxide shield.

There are three large stainless steel categories: steel austenitic, ferritic steel, martensitic steel.

Stainless steels austenitic
Chemical components:
Chromium: from 14 to 30%
Nickel: from 6 to 36%
Iron: the remaining

These stainless steels are ductile, resistant to shocks and non-magnetic. They cannot be soaked but can acquire some hardness by cold machining. The nickel content serves to give and maintain the structure of steel. Also the nickel gives a better corrosion resistance.

Principal types of stainless steels austenitic: 301 to 304, 308, 316 to 318, 321, 330, 347.

Principal applications: chemical industry, foodstuffs, medical products.

Ferritic stainless steels
The ferritic stainless steels have a weak carbon concentration (0,08 to 20%). Due to this rate and to a high chromium concentration, they do not express a hardening appreciable at a high temperature. Their distension coefficient is low and they are resistant to atmospherical oxidation and by the oxidizing solutions. Moreover, they are adaptable to the applications that necessitate a high temperature, in the chemical factories and in outdoor. They are magnetical and non-hardable.

Principal types of stainless steels ferritic: 405, 430, 430F, 430 Se, 442, 446.

Principal applications: chemical industry, automobile trimming.

Martensitic stainless steels
These stainless steels are ferritic steels which one reheated (only ferritic steels which has less than 27% of chromium and a maximum of carbon 0,15%). They become martensitic with the seizure in the air or in a liquid after a heating above critical temperature. They undergo then a hardening by heat treatment. They are magnetic, really hard and resistant but fragile to shocks.

Principal types of stainless steels martensitic: 410, 403, 416, 416 Se, 420, 431, 440C.

Principal applications: surgical instruments, cutlery, plane pieces, chemical industry, articles of cutlery.

Principal stainless steels, their characteristics and applications
301Good resistance to corrosion in ambient temperature, good resistance to oxidation at high temperature. High mechanical resistance just enough of mechanical resistance and ductility to resist rigorous methods of forming. This nuance is not used in hardening by heat treatment. Good compatibility of welding with all current methods.Structural pieces for fuselage of plane, structure elements for trailers and wagons, hub caps for wheels, frameworks for mosquito nets, etc.
304One of the most popular stainless steels. Forming and welding excellent. Can undergo rigorous conditions of stamping, easy machinability. Preserves its annealing after welding and possesses excellent corrosion resistance in slightly corrosive places. This nuance cannot be thermal hardening.Cold tanks for milk, machinery for food industry, extinguishers pieces, wire of winding.
310Combines excellent characteristics at high temperature, good ductility and good weldability. Possesses a low distension coefficient that reduces the possibility to harden when heating. Good resistance to thermal tiredness and with the cyclic times of heat.Heater pieces for heat exchanger, heat, baskets and gauges for heat treatments.
316Resists to corrosion in a wider number of chemical products than 304. This nuance is not compatible with thermal hardening. Good compatibility with all current modes of welding.Pulp and paper machinery, heater exchanger, material of dyeing, propeller, elements in contact with sea air and marine environment.
410Hardening by heat treatment. Resistant to corrosion that reaches a maximum after hardening and polishing. Easily weldable by all current process. Always magnetic.Bolts, screw, pieces of gas turbines and vapour, valves.
416Good resistance to corrosion, maximum resistance after quenched and tempered, easily machineableAxes for engine, bolts, screws, washing machine.
430Not thermal hardening but shows a good corrosion resistance, forms well, possesses good mechanical properties. Breakable at ambient temperature but an annealing eliminates the problems. Good ductility. Mouldings for cars, heating supports, fasteners.
440CCan be hardened by heat treatment, has the best corrosion resistance. Good wear resistance. This stainless steel is magnetic.Heater parts.
The cast iron is an alloy of iron and carbon, not malleable at any temperature. What is different between cast iron and steel, it is the carbon content (2% to 5%).