1. Role of manganese in steel
Content and general role: Most manganese content is about 0.5%, added to the steel can be used as a deoxidizer or sulfur fixing agent, can prevent the thermal cracking of steel.
Effect on transformation temperature: When the carbon content of the steel is high, manganese significantly reduces the transformation temperature by about 50%, probably due to the high amount of pearlite rather than the distribution of carburite at the boundaries.
Effect on impact properties: If the carbon content of the steel is higher than 0.15%, the high manganese content is decisive for the impact properties of normalized steels. This is because the high hardenability of the steel causes the austenite to transform into brittle upper bainite rather than ferrite or pearlite.
2. The role of nickel in steel
Similar effect with manganese: added to steel has a similar effect to manganese in improving the toughness of iron-carbon alloys, with the magnitude of the effect depending on the carbon content and heat treatment.
Effect on steels with very low carbon content: In steels with very low carbon content (about 0.02%), the addition of 2% nickel prevents the formation of carburization at grain boundaries in hot rolled and normalized steels, while at the same time substantially lowering the onset transition temperature, TS, and increasing the peak value of the Charpy impact curve.
Change in effect of increasing nickel content: The effect of increasing impact toughness decreases with further increases in nickel content. If the carbon content is so low that no carbides appear after normalizing, the effect of nickel on the phase transition temperature becomes very limited.
Benefits for normalized steels with about 0.10% carbon: The greatest benefit of adding nickel to normalized steels with about 0.10% carbon is to refine the grain and reduce the free nitrogen content, but the mechanism for this is not clear, probably because nickel acts as an austenite stabilizer, thereby reducing the austenite decomposition temperature.
3.the role of silicon in steel
Deoxidation and improve impact resistance: silicon added to steel for deoxidation, but also to improve impact resistance.
Effect on ferrite: If both manganese and aluminum are present in the steel, most of the silicon dissolves in the ferrite and increases δi through solid solution hardening. this effect is combined with an improvement in the impact properties by the addition of silicon. the addition of silicon by weight to iron-carbon alloys with stabilized grain sizes raises the 50% transition temperature by about 44°C. the effect of silicon in steel is also beneficial in improving impact properties.
Effect on Ferrite: Silicon, like phosphorus, is a stabilizer of ferrite and promotes ferrite grain growth. By weight, the addition of silicon in normalized steel will increase the average energy conversion temperature by about 60°C. The addition of silicon will increase the average energy conversion temperature by about 60°C. The addition of silicon will also increase the average energy conversion temperature by about 60°C.
4. the role of aluminum in steel
As an alloy and deoxidizer reasons: aluminum as an alloy and deoxidizer added to the steel for two reasons, one is generated in the solution with nitrogen AlN to remove free nitrogen; the second is the formation of AlN refinement of the ferrite grain.
Effect on transformation temperature: An increase of 0.1% in aluminum reduces the transformation temperature by about 40°C. However, when more aluminum is added than required, the effect of "curing" the free nitrogen diminishes.
alloy steel tube
