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Effects of Mn, P, S, Si & V on the Mechanical Properties of Steel

The general symbol of a chemical element is represented by:AZN

where A is the atomic number indicating the number of protons exist in the nucleus of the atom; N is the atomic m

nit, defined as the ratio of the average mass per atom to1/12of the atomic mass of carbon-12 in its nuclear and

lectronic ground state; and Z is the chemical symbol of the element.

Manganese, 25Mn54.938049

Manganese increases hardenability and tensile strength of steel, but to a lesser extent than carbon. It is also able toecrease the critical cooling rate during hardening, thus increasing the steels hardenability much more efficient thanny other alloying elements. Manganese also tends to increase the rate of carbon penetration during carburizing andcts as a mild deoxidizing agent. However when too high carbon and too high manganese accompany each other,mbrittlement sets in. Manganese is capable to form Manganese Sulphide (MnS) with sulphur, which is beneficial

machining. At the same time, it counters the brittleness from sulphur and is beneficial to the surface finish of carboteel.

or welding purposes, the ratio of manganese to sulphur should be at least 10 to 1. Manganese content of less than.30% may promote internal porosity and cracking in the weld bead, cracking can also result if the content is over.80%. Steel with low Manganese Sulphide ratio may contain sulphur in the form of iron Sulphide (FeS), which caause cracking (a "hot-short" condition) in the weld

hosphorus, 15P30.973761

hosphorus increases strength and hardness, but at the expense of ductility and impact to toughness, especially inigher carbon steels that are quenched and tempered. As such its content in most steel is limited to a maximum of.05%. Phosphorus prevents the sticking of light-gage sheets when it is used as an alloy in steel. It strengthens low

arbon steel to a degree, increases resistance to corrosion and improves machinability in free-cutting steels. In termwelding, phosphorus content of over 0.04% makes weld brittle and increases the tendency to crack. The surfaceension of the molten weld metal is lowered, making it difficult to control.

ulphur, 16S32.065

ulphur improves machinability but lowers transverse ductility and notched impact toughness and has little effects he longitudinal mechanical properties. Its content is limited to 0.05% in steels but is added to freecutting steels inmount up to 0.35% with the manganese content increased to counter any detrimental effects since sulphur iseneficial to machining. For welding, weldability decreases with increasing sulphur content. Sulphur is detrimentalurface quality in low carbon and low manganese steels and it promotes hot shortness in welding with the tendency

ncreasing with increased sulphur.

ilicon, 14Si28.0855

ilicon increases strength and hardness but to a lesser extent than manganese. It is one of the principal deoxidizerssed in the making of steels to improve soundness, i.e. to be free from defects, decays or damages. Silicon is presell steels to a certain extent. Its content can be up to 4% for electric sheets that are widely used in alternating curre

magnetic circuits.

n welding, silicon is detrimental to surface quality, especially in the low carbon, resulphurized grades. It aggravate

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racking tendencies when the carbon content is fairly high. For best welding condition, silicon content should notxceed 0.10%. However, amounts up to 0.30% are not as serious as high sulphur or phosphorus content.

or galvanizing purposes, steels containing more than 0.04% silicon can greatly affect the thickness and appearancehe galvanized coating. This will result in thick coatings consisting mainly zinc-iron alloys and the surface has a dand dull finish. But it provides as much corrosion protection as a shiny galvanized coating where the outer layer isure zinc.

Vanadium, 23V50.9415s

Vanadium is used to refine grain size. Steels containing vanadium have a much finer grain structure than steels ofmilar compositions without vanadium. It decreases the rate of grain growth during heat treating processes and rai

he temperature at which grain coarsening sets in thus improving the strength and toughness of hardened and tempeteels. Contents up to 0.05% increases hardenability while larger amounts tend to reduce hardenability due to theormation of carbide. Vanadium lessens softening on tempering and induces secondary hardness on high speed stee

Vanadium is used in nitriding, heat resisting, tool and spring steels together with other alloying elements. It is alsoeing utilized in ferrite/pearlite microalloy steels to increase hardness through carbonitride precipitation strengthenf the matrix.

References

. Automotive Handbook, Bosch, 1st English Edition, 1978, p 154-158

. Lawrence H. Van Vlack, Elements of Material Science and Engineering, 4th Edition, Addison-Wesley, 1980, p 32

. http://www.webelements.com

. http://www.macsteel.com/mdb/general_information/glossary_of_metallurgical_terms.htm

. http://www.weldind.com/wl4.html

. http://www.summitsteel.com/term.htm

. http://www.metals.about.com/library/bl-glossary-m.htm

. http://www.mesteel.com/dictionary

. http://www.metal-mart.com/Dictionary/dictlist.htm0.http://www.steelforge.com/infoservices/steellog/pdoc.htm1.http://www.witt.com/galvanizing-process.htm