Characterized 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.

416 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 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.

Material stocked generally in condition P up to and including 63.5 mm dia.

NB. Check the mill certificate if critical for end use.

*Note drop in impact properties. Tempering within the range 400 ^oC - 580 ^oC should be avoided.

NB. High temperature use is therefore not generally recommended.

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.
Finished parts should be passivated.

Do not soak but commence forging immediately.

Do not overheat as this can cause a loss of toughness and ductility.

Do not forge below 900 ^oC

Finished forgings should be cooled slowly in air, ashes or dry lime etc. to room temperature and annealed immediately.

NB. Severe upset forging of this grade is not recommended.

*Soak as required, cool in air.

Quench in oil or air cool. Temper immediately while still hand warm.

Nitriding is carried out at 500 ^oC - 550 ^oC followed by slow cooling (no quench) reducing the problem of distortion. Parts can therefore be machined to near final size, leaving a grinding tolerance only. Always ensure that the tempering temperature employed during the initial heat treatment was higher than the nitriding temperature otherwise the core strength will be affected.

416 can of course be tempered at much lower temperatures, producing much higher tensile strengths, but with subsequent lower impact properties.

NB. Tempering however within the range 400 ^o C - 580 ^o C should be avoided due to the brittleness, resulting in a considerable reduction in impact properties and loss of corrosion resistance.

*Heating temperatures, rate of heating, cooling and soaking times will vary due to factors such as work piece size/shape, also furnace type employed, quenching medium and work piece transfer facilities etc.

Please consult your heat treater for best results.

If it is really necessary to weld in either condition the following procedure may be taken as a guide only.

Pre-heat at 200 ^oC - 300 ^oC and keep heat input to a minimum to reduce dilution of sulphur and filler metal. On completion of welding cool slowly as possible until hand warm and as required:

Post-weld sub-critical anneal at 650 ^oC - 750 ^oC or full anneal and harden and temper as required.

*Please consult your welding consumables supplier.