Industrial electric heater MoSi2 Heating Elements

 

Molybdenum disilicide mosi2 heating element for electronics

 

MoSi2 heating elements is a kind of resistance heatingelement made from Molybdenum Disilicide.

It can be used in air and various gases environments. Working temperature of MoSi2 heating element is 1300C to 1800C. It has the characteristics of high temperature resistance, oxidation resistance, corrosion resistance, heating fast, long service life, high temperature low distortion, easy installation and maintenance, excellent chemical stability, which has been widely used as heaters in high temperature furnaces and kilns of metallurgy, glass, ceramic refractory, crystal electronic device, industrial furnace manufacture and chemical industry field.

 

Types of MoSi2 Heating Elements

1. According to temperature: 1700C and 1800C

2. According to Shape: U, W, I, UL, WL, Spiral types.

 

MoSi2 heating elements standard size

(Hot zone dia / Cold zone dia)

3/6mm, 4/9mm, 6/12mm, 9/18mm, 12/24mm.

 

Chemical property

High temperature oxidation resistance:

When MoSi2 elements are usedat high temperature and under oxidation circumstance, a dense layer of quartz (SiO2) is generated on the surface of the element to prevent it from further oxidation.

When the temperature of element is over 1700℃, the SiO2 protecting film whose melting point is 1710℃ will be melted. Due to its surface tension, SiO2 agglomerate into drops and lose protection. The SiO2 protecting film is formed again when the element continues to be used under the oxidation circumstance.

It must be pointed out is that the MoSi2 heating element cannot be used in the temperature between 400℃ to 700 ℃ for long time. Otherwise, the element will be pulverized because of the strong low-temperature oxidation.

 

Resistance characters

 

MoSi2 elements have good resistance characteristic, so it is an ideal heating material to replace traditional heating elements.

 

At room temperature, its resistivity is very low, with the increase of temperature, the resistance increases sharply. The advantages of heating up fast and low power consumption are obvious. 

 

In normal operating circumstances, the resistance of the element is constant, so the old and new components can be mixed.

 

Physics characters

Bulk density	Bending strength	Hardness	Apparent porosity	Drawing water rate	Thermal elongation rate
5.6~5.8g/cm3	20MPa(20℃)	(hv)570kg/mm²	0.5~2.0%	0.5%	4%

 

Recommend surface load:

Furnace Temp(°c)	1400	1500	1600	1650	1700
Surface load of hot zone(W/cm²)	<18	<15	<12	<10	<8

 

 

Atmosphere influence on the MoSi2 heater’s operating temperature

 

Atmosphere	The max element temperature(℃)
	1700type	1800type
Air	1700	1800
N2	1600	1700
He  Ar  Ne  Argon, Helium	1600	1700
Dry Hydrogen(dew point) -80℃	1150	1150
Wet Hydrogen(Dew point) -20℃	1450	1450
mixed gas(e . g . 10%CO2, 50%CO, 15% H2)	1600	1700
mixed gas(e . g . 40%CO2 , 20%CO)	1400	1450
Cracked and partly burnt ammonia	1400	1450

 

Installation of heating element for electronics

 

1) Vertically hanging

Under normal temperature, MoSi2 element is very brittleness, while under high temperature, it is plasticity, so the better way to install U Shape element is to hang it vertically from the furnace top through the support clamping chuck. The aim of such way is to avoid putting the mechanical stress directly to the element heat-generating end; otherwise the element will easily be broken.

 

2) Support clamp

Support clamp are applied to 9/18 and 6/12 two kinds of elements respectively. The support clamp supports the whole weight of the element and the position of the element is also determined by it, therefore, it must be installed carefully to assure the element vertically hung. In order to prevent the element from being over heated locally, the taper part of the element lower end must put into the furnace chamber. 

 

Application:

Item	name	distinction criterion	specification	Using range
Heating elements	1700  type	Element operating temperature 1700℃ is acceptable	Le Φ 6-12W type/U type/L type/all kinds of hetero type / stripe shape	high temperature electric resistance furnace
	1800  type	Element operating temperature 1800℃ is acceptable
	1800J type	Element operating temperature≥1800℃	Le Φ 3-12W type	Special,high temperature and high-power electric resistance furnace
	1800T type	Element operating  temperature≤1800℃	Le Φ 3-12W type U type	Not oxidized special air high temperature electric resistance furnace

 

Product use and maintenance

 

1. MoSi2 heating elements belong to Metal ceramic material. They are hard, crisp and low impact strength at room temperature .Therefore to be careful to avoid damage during transport and installation.

 

2. When MoSi2 elements continuously operate in an oxidation atmosphere, the surface temperature of 1700 type should not exceed 1700 ° C,1800-type should not over 1800 ℃ and for intermittent use,1700 type-element should not over 1650 ° C,1800type-element cannot exceed 1750 ℃.

 

 

Furnace dryness

New or old furnace not used for a long time needs to be dried before using. Generally, the drying temperature is 100-200℃.

 

However, if the element is used for a long time under the low temperature, it will cause the low-temperature oxidation.

 

For little furnace, the drying time is short, the influence of several drying hours is little, but for large furnace, which need to be dried for a long time, you had better open the furnace door to ventilate well. you can open the furnace door ajar with the temperature increment and completely close until the temperature reach 1000℃ above.

 

Furnace start

If the furnace dry out has been completed or does not need drying, it has to rise its temperature. In order to avoid the over sized electric current impact and cause the electrical equipment overload;

Please go up the furnace temperature according to the following table.

 

Small furnace (power100KW)		Large furnace(Power 100-500KW)
Furnace temperature	Voltage	furnace temperature℃	Voltage
20-150	1/3Operating Voltage	200-300	1/3Operating Voltage
150-500	2/3Operating Voltage	300-700	2/3Operating Voltage
500-operating temperature	The Whole-Operating Voltage	700-Operating temperature	The whole-Operating Voltage

 

It should not take a long time when shifting gears. Otherwise it easily causes the electric current shocking to break the electrical equipment.

 

Element Replacement

If there is a damaged part found in the process of operation, the first thing you should do is determine its location and get all the combination elements ready. After that, you should separate the wire the damaged element clipped to from the screw which is connected to the generatrix. Then remove the remained refractory wool and pull out the refractory stoppers. Insert the new combination elements into the furnace from its roof. Connect all the wires and get the refractory wool filled, and finally raise the temperature.