STAINLESS STEEL OVERVIEW: TUTORIAL

How is it made?

Stainless steel is produced in an electric arc furnace where carbon electrodes contact recycled stainless scrap and various alloys of chromium (and nickel, molybdenum etc. depending on the stainless type). A current is passed through the electrode and the temperature increases to a point where the scrap and alloys melt. The molten material from the electric furnace is then transferred into an AOD (Argon Oxygen Decarbonization) vessel, where the carbon levels are reduced (remember stainless has a much lower carbon level than mild steel) and the final alloy additions are made to make the exact chemistry. Exhibit 1 shows the process from melting and casting either into ingots or continually cast into a slab or billet form. Then the material is hot rolled or forged into its final form. Some material receives cold rolling to further reduce the thickness as in sheets or drawn into smaller diameters as in rods and wire.

Most stainless steels receive a final annealing (a heat treatment that softens the structure) and pickling (an acid wash that removes furnace scale from annealing and helps promote the passive surface film that naturally occurs).

LIFE CYCLE
The fact that stainless steel has a great resistance to corrosion means that using stainless will result in a very long life compared to mild steel. Structures made from stainless steel will last many times the normal life (well over 100 years in most cases). So, while stainless steel is probably more expensive to buy in the beginning -- because it lasts a long time, it is usually cheaper in the long run because there is little or no maintenance and repair costs. AND, once the useful life is over, stainless steel is 100% RECYCLABLE. Scrap stainless steel is recharged into the electric furnaces for re-melting back into stainless steel. Stainless steel is a true "full life cycle" material.

Mechanical Properties

(Annealed condition)

 

Tensile Strength

Yield Strength

Elongation

Hardness

Stainless

ksi

MPa

ksi

MPa

 

 

410

70

483

45

310

25

B80

430

75

517

50

345

25

B85

304

84

579

42

290

55

B80

316

84

579

42

290

50

B79

Elongation in 2" (50.80 mm)

Hardness in Rockwell B

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