With their compositions, properties and applications.

NUTS AND BOLTSSCREWS GEARS AIRCRAFT FITTINGS BUSHINGS SHAFTS HEAT TREATMENT : Solution Treatment (Annealing) - Heat to °C and cool rapidly. This grade cannot be hardened by thermal treatment

GENERAL CHARACTERISTICS:  Grade 304 is the standard "18/8" stainless.  It is the most versatile and most widely used stainless steel.  Available in a wider range of products, forms and finishes than any other.  It has excellent forming and welding characteristics.  The balanced austenitic structure of Grade 304 enables it to be severely deep drawn without intermediate annealing, which has made this grade dominant in the manufacture of drawn stainless parts such as sinks, hollow-ware and saucepans. HEAT TREATMENT : Solution Treatment (Annealing) - Heat to °C and cool rapidly. These grades cannot be hardened by thermal treatment. GENERAL CHARACTERISTICS:  Grade 304 is the standard "18/8" stainless.  It is the most versatile and most widely used stainless steel.  Available in a wider range of products, forms and finishes than any other.  It has excellent forming and welding characteristics.  The balanced austenitic structure of Grade 304 enables it to be severely deep drawn without intermediate annealing, which has made this grade dominant in the manufacture of drawn stainless parts such as sinks, hollow-ware and saucepans. HEAT TREATMENT : Solution Treatment (Annealing) - Heat to °C and cool rapidly. These grades cannot be hardened by thermal treatment.

EXCELLENT CORROSION RESISTANCE GOOD OXIDATION RESISTANCE UPTO 870 C – INTERMITTANT SERVICE UPTO 925 C – CONTINOUS SERVICE EXCELLENT WELDABILITY OF ALL STANDARD FUSION METHODSHAVE HIGHER MACHINING RATESLOWER TOOL WEAR

GRADEWHY IT MIGHT BE CHOSEN INSTEAD OF 304? 301L A higher work hardening rate grade is required for certain roll formed or stretch formed components. 302HQ Lower work hardening rate is needed for cold forging of screws, bolts and rivets. 303 Higher machinability needed, and the lower corrosion resistance, formability and weldability are acceptable. 316 Higher resistance to pitting and crevice corrosion is required, in chloride environments 321 Better resistance to temperatures of around °C is needed…321 has higher hot strength. 3CR12 A lower cost is required, and the reduced corrosion resistance and resulting discolouration are acceptable. 430 A lower cost is required, and the reduced corrosion resistance and fabrication characteristics are acceptable.

 SS 316 is an improved version of SS 304, with the addition of molybdenum and a slightly higher nickel content.  The molybdenum makes the steel more resistant to pitting and crevice corrosion in chloride-contaminated media, sea water and acetic acid vapours.  The lower rate of general corrosion in mildly corrosive environments gives the steel good atmospheric corrosion resistance in polluted marine atmospheres.  Subject to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above about 60°C. Considered resistant to potable water with up to about 1000mg/L chlorides at ambient temperatures, reducing to about 500mg/L at 60°C.  SS 316 is an improved version of SS 304, with the addition of molybdenum and a slightly higher nickel content.  The molybdenum makes the steel more resistant to pitting and crevice corrosion in chloride-contaminated media, sea water and acetic acid vapours.  The lower rate of general corrosion in mildly corrosive environments gives the steel good atmospheric corrosion resistance in polluted marine atmospheres.  Subject to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above about 60°C. Considered resistant to potable water with up to about 1000mg/L chlorides at ambient temperatures, reducing to about 500mg/L at 60°C.

Food Preparation Equipment Particularly In Chloride Environments. Laboratory BenchesBoat FittingsChemical ContainersHeat Exchangers Woven or welded screens for mining, quarrying & water filtration. Threaded Fasteners And Springs

GREAT RESISTANCE TO CHEMICAL ATTACK AND CORROSION (> SS 304) DURABLE AND EASY TO FABRICATE GOOD WELDING PROPERTIES

PROPERTYREASON CORROSION RESISTANCE It has excellent corrosion resistance when exposed to a range of corrosive environments and media. It is not resistant to warm sea water. Warm chloride environments can cause pitting and crevice corrosion. It is also subject to stress corrosion cracking above around 60°C. HEAT RESISTANCE It has good resistance to oxidation in intermittent service to 870°C and in continuous service to 925°C. However, continuous use at °C is not recommended if corrosion resistance in water is required. In this instance 316L is recommended due to its resistance to carbide precipitation. COLD WORKINGIt is readily brake or roll formed into a variety of parts. It is also suited to stamping, heading and drawing but post work annealing is recommended to relieve internal stresses. Cold working will increase both strength and hardness of 316 stainless steel. HOT WORKINGAll common hot working processes can be performed on 316 stainless steel. Hot working should be avoided below 927°C. The ideal temperature range for hot working is °C. Post-work annealing is recommended to ensure optimum corrosion resistance.

ALTERNATIVES OF SS 316

BOLTS AND NUTSSCREWSBUSHINGSPUMPS AND VALVE PARTSSTREAM AND GAS TURBINE PARTSPETROLEUM FRACTIONING TOWERSMINE LADDER RUNGS

PROPERTIESREASONS CORROSION RESISTANCE  It resists dry atmosphere, fresh water, mild alkalies and acids, food, steam and hot gases.  Must be hardened for maximum heat and corrosion resistance.  Performance is best with a smooth surface finish.  Less corrosion resistant than the austenitic grades and also less than 17% chromium ferritic alloys such as Grade 430. HEAT RESISTANCE  Good resistance to scaling up to approximately 650°C, but generally not recommended for use in temperatures between 400 and 580°C, because of the reduction in mechanical properties. MACHINING  In the annealed or highly tempered conditions grade 410 is relatively easily machined, but if hardened to above 30HRC machining becomes more difficult.  Free machining grade 416 is a very readily machined alternative.

 Grade 416 has the highest machinability of any stainless steel, at about 85% of that of a free-machining carbon steel.  It is sometimes used in the unhardened or hardened and highly tempered condition because of its low cost and ready machinability.  These martensitic stainless steels are optimised for high hardness, and other properties are to some degree compromised.  Fabrication must be by methods that allow for poor weldability and usually also allow for a final harden and temper heat treatment.  Corrosion resistance is lower than the common austenitic grades, and their useful operating temperature range is limited by their loss of ductility at sub-zero temperatures and loss of strength by over-tempering at elevated temperatures  Grade 416 has the highest machinability of any stainless steel, at about 85% of that of a free-machining carbon steel.  It is sometimes used in the unhardened or hardened and highly tempered condition because of its low cost and ready machinability.  These martensitic stainless steels are optimised for high hardness, and other properties are to some degree compromised.  Fabrication must be by methods that allow for poor weldability and usually also allow for a final harden and temper heat treatment.  Corrosion resistance is lower than the common austenitic grades, and their useful operating temperature range is limited by their loss of ductility at sub-zero temperatures and loss of strength by over-tempering at elevated temperatures

GOOD CHIP BREAKAGEEXCEPTIONALLY GOOD MACHINABILITY WELDING OF ALL SORT IS NOT ADVISABLE ( SULPHUR CAUSES POROSITY) LOW FRICTIONAL PROPERTIES – REDUCING GALLIND AND SEIZINGUNSUITABLE FOR MARINE AVERAGE HEAT RESISTANCE: UPTO 760 C – INTERMITTANT USE UPTO 675 C – CONTINOUS USE POOR WELDABILITY

410  The high machinability of 416 can be sacrificed to gain better corrosion resistance and formability. 303  A slight drop in machinability to gain better availability. Grade 303 is non-hardenable. 182  A free-machining ferritic grade with better "soft magnetic" performance for solenoid shafts. Grade 182 is non-hardenable.