Copper (Cu) is normally present in stainless steel as a residual element. However, it is added to a few alloys to produce precipitation hardening properties or to enhance corrosion resistance particularly in sea water environment and sulphuric acid.
Nickel (Ni) is added in large amounts, over about 8% to high Chromium stainless steels to form the most important class of corrosion and heat resisting steels. These are the Austenitic stainless steels, typified by 18-8 (304/1.4301), where the tendency of Nickel to form Austenite is responsible for a great toughness (impact strength) and high strength at both high and low temperatures. Nickel also greatly improves resistance to oxidation and corrosion.
Ferro Vanadium (V) has an influence on Austenite (Hardenability) in term of increasing hardenability very strongly as dissolved and on the Ferrite in term of harden moderately by solid solution. The principal functions is elevating coarsening temperature of austenite (promotes fine grain), increasing hardenbility when dissolved and resisting tempering and causes marked secondary hardening.
Pure Tin (Sn), has the influence on stability of pearlite, even though the cast iron has the carbon equivalent (C.E) at the level of 4.7%, which normally graphite will be surrounded by pearlite but if there is Tin around 0.15% then will obtain the prefect pearlite structure.
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