Effect
of Carbon
Increase of Carbon increases hardness and tensile
strength, reduces ductility, increases responsiveness to heat treatment
(surface hardening), reduces formability in either hot or cold.
High carbon is undesirable for SS due to carbide
precipitation, reduces corrosion resistance
Effect
of Silicon, Sulphur and Phosphorus
Silicon
Silicon is used as deoxidizer during process of
manufacture.
Silicon addition in the range of 1.5 to 2% improves
hardenability. Used in some tool steel.
Sulphur
Sulphur in large quantity improves machinability.
Sulphur is detrimental to hot forming properties
Sulphur has detrimental effect on corrosion
resistance and weldablity.
Phosphorus
Phosphorus addition increases yield strength and
reduces ductility at low temperature.
Believed to increase resistance to
atmospheric corrosion
Phosphorus has detrimental effect on corrosion
resistance and weldbility.
Effect
of Manganese
Manganese is used as deoxidizer and to impart
strength.
Manganese addition improves hot working properties.
Manganese like nickel is an austenite former. Has
been used as substitute for Nickel in 200 series SS
Effect
of Chromium, Nickel
Cr is ferrite former.
Cr increases resistance to oxidation
Cr increase
response to heat treatment.
Cr increases depth of hardness penetration.
Cr with the addition of nickel in large amount
increases the resistance to oxidation and corrosion
Nickel is austenite former
Nickel increases strength and toughness both at high
and low temperature
Effect
of Molybdenum and Nitrogen
Molybdenum increases penetration of hardness and
increases toughness.
Mo improves creep strength, resists softening at
high temperature.
Mo when added to austenitic SS improves resistance
to pitting and crevice corrosion especially in chloride and sulphur containing
environments.
Nitrogen like Nickel is an austenite former.
Nitrogen addition improves the yield strength of SS
Effect
of Copper
Copper in small amount improves resistance to
atmospheric corrosion
Copper addition increases yield and ultimate
strength with slight loss of ductility.
Copper addition is done to produce precipitation
hardening properties
Copper
addition enhances corrosion resistance in sea water environments and sulphuric
acid
Effect
of Titanium, Niobium/Columbium
Titanium is added to austenitic SS as a stabilizing
element to make the steel immune to harmful carbide precipitation leading to
inter granular corrosion.
Niobium/columbium is added to steel in order to
stabilize carbon, as such, performs in the same way as titanium.
Niobium also has the effect of strengthening steels
and alloys for high temperature service.
Effect
of Aluminum, Boron, Tungsten,
Aluminum is used as an active deoxidizer in
producing steel. It refines the grain size.
Boron is added in small quantity to improve
hardenability. Acts as an intensifier, increasing the depth of hardening during
quenching
Tungsten is used as an alloying element in tool
steel and tends to produce a fine, dense grain and clean cutting edge when use
in small quantity. Used in large quantity to produce high speed steel which
retains hardness even at high temperature developed in high speed cutting. Also
used in heat resisting steel where retention of strength at high temperature is
required, usually used in combination with Cr or other alloying elements.
Effect
of Vanadium, Cobalt
Vanadium usually in small quantity 0.15 to 0.20%
retards grain growth, even after hardening from high temperatures or after
periods of extended heating. Tool steel containing vanadium resists shock
better.
Cobalt becomes highly radioactive when exposed to
intense radiation of nuclear reactors. SS used in nuclear service will have a
Co restriction of 0.2%.nickel used in SS invariably have Co as residual
element.
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