Selection of the heating element resistance furnace

A. Select the basic elements of heating elements
1. According to the temperature: (heating element temperature = furnace temperature +100- -200 degrees)
General furnace temperature is less than 1000 degrees, the choice of NiCr, FeCrAl
Furnace at 1000-1200 degrees, use FeCrAl (Cr27Al7Mo2)
Furnace temperature greater than 1200 degrees, the choice of pure metal or nonmetal
2. According to structural characteristics of the furnace
3. Treatment of the workpiece according to the situation
4. High radiation efficiency
5. Convenient source
Two. Select the heating element should have the following properties
High resistance, cross-sectional area, good mechanical strength, thermal expansion coefficient some chemical stability
III. Heating element surface load (W) select
1. W greater the shorter the life
2. High resistance furnace temperature, corrosive atmosphere, W is to take a small
3. Heating element with shield (such as car heaters, heating elements in the furnace under the floor), W is to take a small
4. Furnace can be ventilated, W whichever is greater (can be increased 30-50 percent)
5. Ribbon elements, W whichever is greater (can be increased 30-50 percent)
6. Replace difficult element, W to take a small
Four. Alloy element surface load Recommend
Material heating element temperature (unit: ° C)
Less than 1000 less than 1,100 less than 1200
OCr25Al5 1.6 - 1.8 1.2 - 1.5 0.81
Cr20Ni80 1.1 0.5 - 0.8
Cr15Ni60 0.8
CrAl7Mo2 at 1200-1300 degrees, W is taken 1.6-1.8
Five. Pure metal surface load
W, Mo, Ta less than 1800 °, W is taken 10-20W/cm2
Graphite W Less than 15-20W/cm2