|Stainless Steel – Grade 416 (UNS S41600), SUS416|
|SUS416 is a free machining basic straight chromium high hardenability martensitic stainless steel with excellent machinability, reasonable strength and corrosion resistance. Generally supplied either hardened and tempered in the tensile range 550 – 700 Mpa (condition P) Brinell range 152 – 207, or in the annealed condition with a maximum Brinell hardness of 207.
Characterised by excellent machinability, non-galling and non-seizing properties due to its higher sulphur content which has the effect of lowering its corrosion resistance. It is however resistant to mild corrosive atmospheres, fresh water, steam, organic materials, many mild acids and petroleum products, coupled with reasonable strength in the hardened and tempered condition.
SS416 due to its excellent hardenability is capable of being through hardened up to Rc40 depending upon carbon content and section size. Small sections can be air cooled and larger sections oil quenched for maximum through hardness.
Pre hardened and tempered stainless steel 416 will also respond readily to nitriding achieving a typical surface hardness of over Rc65. The nitriding process however reduces the corrosion resistance and is therefore not generally recommended except for critical applications where the benefit outweighs all other considerations.
Material magnetic in all conditions.
|Chemical Composition||Min. %||Max. %|
|*Nickel & Molybdenum addition optional.||Carbon||0.09||0.15|
Grade Specification Comparison
Elevated Temperature Properties
|While sus416 displays a reasonable resistance to scaling in continuous service up to 650 oC, it does however experience a substantial drop in tensile strength, creep and stress rupture strength at relatively low working temperatures. It is also susceptible to hot cracking due to its high sulphur content.
NB. High temperature use is therefore not generally recommended.
|Low Temperature Properties|
|416SS is not recommended for use at sub-zero temperatures due to a substantial drop in impact properties consistent with most steels other than the austenitic steel types.|
|S41600 due to its higher sulphur content has lower resistance to all corrosion types than grade SUS410, and indeed all of the 400 series martensitic stainless steels.
Its selection therefore is generally based upon its excellent machinability coupled with its lower corrosion resistance capabilities.
NB. It has optimum corrosion resistance in the hardened and tempered condition and is not therefore recommended for use in the annealed condition.
It is most important that oxygen is always allowed to circulate freely on all stainless steel surfaces to ensure that a chrome oxide film is always present to protect it. If this is not the case, rusting will occur as with other types of non stainless steels.
For optimum corrosion resistance surfaces must be free of scale and foreign particles.