Major Applications of Nichrome heating wire - Heanjia Super-metals Co., Ltd.

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Major Applications of Nichrome heating wire

Thermocouple is one of the most common instruments in which nichrome heating wire is used. For this a combination named as chromel-alumel is prepared in which 90/10 nickel alloy is used in conjunction with 95/5 Ni/Al alloy that behaves as a heating element having maximum operating temperature 1100 degree C. By using this combination the couple turns into susceptible to drift in area of 1000 degreeC because of favored oxidation after an extended use. When silicon is mixed, it is observed that the above effect is no more in use. In industrial status Nicrosil (containing 14% Cr and 1.5% Si) and Nisil containing 4.5% Si and 0.1% Mg) is also used.

Since 80/20 nichrome heating wire has superior oxidation and hot resist to corrosion than inexpensive iron-nickel-chromium alloys, hence it is used for wrought and cast parts in high temperature uses. Senior chromium material alloys are more preferred in the uses where fuel ashes and deposits like alkali metal salts for example sulphates, are meet. The reason behind this is the reactive behavior of fuel ashes towards oxide scale.

Ashes with vanadium is mainly violent that have a fluxing effect on the scale which increase the susceptibility of the alloy when oxidation attacks. Formation of chromium sulphide (Cr2S3) having melting point 1550°C is preferred to nickel sulphide in sulphur containing surroundings. Nickel sulphide is preferentially formed because it obstructs the formation of nickel/nickel-sulphide eutectic that has low melting point. Limited chromium equipments may be pooped, leaving sulphur to react with nickel that forms eutectic compound having low melting point that leads to liquid phase attack. Alloys which experience liquid phase attack, they have wart-like developments on in their regions. Senior chromium including nickel chromium alloys is better resistant to liquid phase attack because of preferential formation of chromium sulphides.

Nichrome heating wire including more than 30% chromium have a two phase structure. This structure contains chromium and nickel. Because of the brittleness of chromium, this alloy reduces the ductility by raising the chromium material. If 1.5% niobium is mixed then strength and ductility is increased but embrittlement is decreased following temperature exposure offered contamination like carbon, nitrogen and silicon are restricted.

Tensile and ductility properties for some nickel chromium alloy at room temperature.

Cr Content (%)	Tensile Str (MPa)	Elong. (%)
35	480	62
50	540-680	7-24
60	800-1000	1-2

In the environment of hot working, alloys having chromium materials up to about 35% are appropriate. More than this value, these are mainly used for casting. By mixing zirconium or titanium, increase in ductility may be accomplished.

Inconel 671 alloy having 48% Cr and 0.35% Ti is mainly used in uses consisting of duplex tubing for coal-fired superheating tubing.

Environmental Properties
Resistance Factors
1=Poor 5=Excellent
Flammability	5
Fresh Water	5
Organic Solvents	5
Oxidation at 500C	5
Sea Water	5
Strong Acid	5
Strong Alkalis	5
UV	5
Wear	5
Weak Acid	5
Weak Alkalis	5

Wear machinery is complicated but excessive hardness and fine resist to corrosion helps to achieve a better wear resistance. Nichrome heating wire supplies a financial substitute to contents like weld deposited cobalt-chrome alloys by adding carbon and tungsten that are mainly used wear resistant uses. 8-12% Cr, 0.3-1.0% C, 3-4% Si, 1.5-2.5% B, 1-4% Fe and the rest is Ni is a common example of nickel chromium alloy for the above type of use.

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