Selection of heating elements for furnace

- Apr 29, 2020-

  1. Basic points of selecting electric heating elements 

           

    1. According to the temperature: (heating element temperature = furnace temperature + 100-200 ℃).  Generally, the furnace temperature is less than 1000 ℃, NiCr and FeCrAl are selected.            The furnace temperature is between 1000-1200 ℃, FeCrAl (cr27al7mo2) is selected. If the furnace temperature is more than 1200 ℃, select pure metal or non-metal    

            

    2.  According to the structural characteristics of the furnace            1.3. According to the condition of heat treatment workpiece            1.4. High radiation efficiency           

      1.5. Convenient source           

       

  2. The selection of heating elements shall have the following properties           


    High resistance, large cross-sectional area, good mechanical strength, small coefficient of thermal expansion, stable chemical performance           

     

  3. Heating element surface load (W) selection           

    3.1. The larger the W, the shorter the life           

    3.2. When the temperature in the furnace is high and there is corrosive atmosphere, W is smaller           

    3.3. When the heating element has shield (such as trolley furnace, the heating element is under the furnace bottom plate), W is smaller            3.4. The furnace can be ventilated, W is larger (can increase by 30-50%)            3.5. Take the largest w (30-50% increase)           

    3.6. Replace difficult components, W is smaller           

     

  4. Recommended surface loads for alloy components            Material heating element temperature (unit: Celsius)          

    Less than 1000 less than 1100 less than 1200        

    OCr25Al5 1.6--1.8 1.2--1.5 0.81           

    Cr20Ni80 1.1 0.5--0.8            

    Cr15Ni60 0.8            

    When Cral7mo2 is between 1200-1300 degrees, W is 1.6-1.8           

     

    5、 Pure metal surface load           

    When W, Mo and TA are less than 1800 degrees, W is 10-20w / cm2            Graphite W is less than 15-20w / cm2