Why is Stainless Steel Incredible?

Why is STAINLESS STEEL INCREDIBLE? STAINLESS STEEL IS INCREDIBLE! WHY? BECAUSE IT HAS A NATURALLY OCCURRING PROTECTIVE LAYER ON ITS SURFACE THAT PROTECTS IT FROM CORROSION. THIS IS DUE TO THE CHROMIUM IT CONTAINS – ANY STEEL ALLOY THAT CONTAINS A MINIMUM OF 10.5% CHROMIUM IS CONSIDERED TO BE STAINLESS STEEL. IRON Fe CHROMIUM STAINLESS Cr STEEL NICKEL Ni THE PROPERTIES OF STAINLESS STEEL CHANGE IF DIFFERENT ALLOY MATERIALS ARE ADDED (SEE BELOW). E.G. MOLYBDENUM IS ADDED TO IMPROVE CORROSION RESISTANCE. WHY IS STAINLESS STEEL CORROSION RESISTANT? STAINLESS STEEL IS A SOLID METAL AND NOT JUST A COAT- ING APPLIED TO STEEL. THE CHROMIUM IN THE STAINLESS STEEL COMBINES WITH OXYGEN IN THE NORMAL ENVIRON- MENT TO FORM A 'CHROMIUM OXIDE' OR A 'PASSIVE FILM' LAYER ON THE SURFACE. THIS PROTECTS THE IRON IN THE STEEL FROM BEING ATTACKED BY CORROSIVE AGENTS (E.G. SALT) AND CREATING RUST. WHEN THE CHROMIUM OXIDE LAYER IS DAMAGED MECHANICALLY OR CHEMICALLY... IT REPAIRS ITSELF - ASSUMING OXYGEN (EVEN IN VERY SMALL AMOUNTS) IS PRESENT. NB: THAT'S WHY MOST STAINLESS STEELS (EXCEPT SUPER DUPLEX 2507) DON'T PERFORM WHEN SUBMERSED IN SALT WATER BECAUSE THERE ISN'T ENOUGH OXYGEN TO GENERATE THE CHROMIUM OXIDE LAYER. QUALITIES OF STAINLESS STEEL RUST/STAIN RESISTANT IF THE CHROMIUM OXIDE LAYER IS RELATIVELY STRONG MAINTAINED AND NOT UNDER REGULAR MECHANICAL VIBRATION, IN TERMS OF TENSILE STRENGTH, IT 50 1000 'IT SHOULD PROBABLY LAST FOREVER Mpa CAN RANGE FROM 500 TO 1000 MPA. MAINTAINS LOOKS OVER TIME RECYCLABLE DEPENDING ON A RANGE OF FACTORS (FINISH, GRADE, ENVIRONMENT, STAINLESS STEEL IS 100% RECYCLABLE CLEANING) STAINLESS SHOULD AND NON-TOXIC. MAINTAIN ITS APPEARANCE OVER TIME. DELIVERS VALUE FOR MONEY OOH LA LA. IN GENERAL, IT OUTLASTS STEEL COATINGS (E.G. ZINC OR GALVANIZ- STAINLESS STEEL IS ALSO KNOWN AS INOX STEEL'OR 'INOX' FROM FRENCH ING), SO OVERALL DELIVERS A LOWER COST OVER THE ENTIRE LIFE-CYCLE. "INOXYDABLE" HOW IS THE PERFORMANCE OF STAINLESS STEEL IMPROVED? NICKEL IMPROVES FORMABILITY ADD - USED IN 304 & 316 & WELDABILITY INCREASED MOLYBDENUM ADD - USED IN 316 CORROSION RESISTANCE INCREASED ADD ELECTRO-POLISHING CORROSION RESISTANCE CARBON CORROSION RESISTANCE REDUCE %3D E.G. 316L IMPROVED IF WELDED INCREASED ADD SHINY SMOOTH SURFACE CORROSION RESISTANCE HEAT TREATMENT INCREASED %3D ADD (FOR MARTENSITIC GRADES) HARDNESS TYPES OF STAINLESS STEEL THERE ARE MORE THAN 60 GRADES OF STAINLESS STEEL. HOWEVER ALL STAINLESS STEELS CAN BE DIVIDED INTO ONE OF FIVE TYPES IDENTIFIED BY THEIR MAIN CRYSTAL STRUCTURES: AUSTENITIC THE MOST COMMONLY USED STAINLESS STEELS (E.G. 304 AND 316 ) ACCOUNTING FOR MORE THAN 70% OF STAINLESS FASTENER PRODUCTION. IT HAS EXCELLENT CORROSION RESISTANCE, WELD-ABILITY AND FORMABILITY. FERRITIC THESE ARE PLAIN CHROMIUM STAINLESS STEELS (E.G. 430) WITH VERY LITTLE OR NO NICKEL AND THEREFORE HAVE A LOWER COST. HOWEVER THEY HAVE LOW CORROSION RESISTANCE AND ARE NOT OFTEN USED TO MAKE STAINLESS STEEL FASTENERS. DUPLEX HIGH CHROMIUM AND NICKEL CONTENT IN DUPLEX STAINLESS STEELS (E.G. 2205) PROVIDE GREATER CORROSION RESISTANCE PARTICULARLY FROM STRESS CORROSION CRACKING. THEY ARE ALSO HIGH STRENGTH LEADING TO WEIGHT SAVING. MARTENSITIC USED IN THE FIRST STAINLESS STEELS COMMERCIALLY DEVEL- OPED (SUCH AS CUTLERY) AND HAVE RELATIVELY HIGH CARBON CONTENT. THEY HAVE MODERATE CORROSION RESISTANCE WITH THE BENEFIT THAT THEY CAN BE HARDENED BY HEAT TREATMENT. EXAMPLES INCLUDE 410 AND 420. PRECIPITATION HARDENING (PH) SUPPLIED INA SOLUTION TREATED CONDITION (IN WHICH THEY ARE MACHINEABLE). THEY ARE THEN HARDENED AFTER FABRICATION TO ACHIEVE VERY HIGH STRENGTH. A COMMON GRADE IS 17-4PH. lanzor specialists in stainless fasteners THIS INFORMATION IS PROVIDED AS A GUIDE ONLY AND ANZOR DOES NOT ACCEPT LIABILITY FOR THE APPLICATION OF THIS INFORMATION. SPECIFIC ADVICE ON GRADE SELECTION FOR CRITICAL APPLICATIONS SHOULD BE SOUGHT FROM wwW.ASSDA.ASN.AU OR www.CORROSIONCONTROL.CO.NZ REFERENCES HTTP://www.ASSDA.ASNAU/TYPES-OF-STAINLESS-STEEL HTTP://www.BSSA.ORG.UK/TOPICS.PHP?ARTICLE-668&FEATURED-1 HTTP://Www.CDACR.COMANDEX.PHP?OPTION=COM_CONTENT&VIEW-ARTICLE&ID=137&ITEMID=343&LANG-EN HTTP://Www.SSINA.COM/OVERVIEW/FEATURES.HTML HTTP://www.WORLDSTAINLESS. ORG/WHAT_IS_STAINLESS_STEEL/INTRODUCTION_TO_STAINLESS_STEEL