1. Characteristics (physical and chemical characteristics) of the silicon-molybdenum rod heating element;

1. The silicon molybdenum rod is somewhat softened at high temperature (above 1500 degrees), but hard and brittle at low temperature;

2. Silicon molybdenum rod resistance heating element is a high temperature oxidation resistance heating element based on molybdenum disilide, with unique high temperature oxidation resistance.

3. In oxidized environment, the maximum service temperature is 1800. The resistance of silicon molybdenum rod heating element increases rapidly with the increase of temperature, and the resistance value is stable when the temperature is constant. Under normal conditions, the resistance of the component does not change with the use of time. Therefore, old and new silicon molybdenum rod heating elements can be mixed. (Temperature coefficient of resistance)

Second, general silicon molybdenum rod electric heating system

1. The electrical components of silicon molybdenum rod electric heating system generally have transformers for voltage reduction.

The resistance temperature coefficient of silicon molybdenum rod is larger than that of ordinary heating element, and the resistance value is very small at room temperature. If high voltage is applied, high current will burn the silicon molybdenum rod. After the temperature increases, the resistance of the silicon molybdenum rod heating element increases rapidly with the increase of temperature, at which time the voltage can be increased. Therefore, the electric heating voltage of the silicon molybdenum rod is generally provided by the transformer to protect the silicon molybdenum rod from damage.

2. The control mode of silicon-molybdenum rod electric heating system should be triggered by phase shift.

The electric heating control mode of silicon molybdenum rod should adopt phase shift triggering mode. Because the on-off control mode triggered by zero-crossing will generate inverter voltage on the secondary side of the transformer connected with the load of the silicon molybdenum rod, this voltage will be superimposed on the output voltage, which will generate large voltage and load on the electric heating silicon molybdenum rod, and generate large current, leading to the damage of the silicon molybdenum rod.

Third, the heating step of silicon molybdenum rod electric heating furnace

1. After the end of the electric heating furnace, it can formally start heating.

In order to avoid excessive current impact damage to electrical equipment, it is recommended to start the electric furnace according to the following steps and parameters:

Note: The shift time should not be too long, and the temperature of general components should not drop by 300~ 400, otherwise it is easy to cause current impact and damage to electrical equipment.

2. Electric heating process of silicon molybdenum rod in high temperature electric furnace (actual usage parameters)

The electric heating process of silicon molybdenum rod in high temperature electric furnace is divided into two parts:

1, below 300 degrees according to manual output temperature control;

2, more than 300 degrees to switch to the time program temperature control.

(1) When the temperature is lower than 300 degrees, it is controlled by manual output temperature

Start power-on, switch to manual mode, adjust the output value to 5%, and observe the current in real time (this current is the actual current of the load, please note the difference with the current displayed on the KSY-P interface), 10% above 50 degrees, 25% above 100 degrees; The current in the first 20 minutes should not exceed 50A, that is, 1/3 of the operating voltage; 1 hour before the current does not exceed 100A, that is, 2/3 of the operating voltage. Note: Heat up to 300 degrees in this way. (2) over 300 degrees to switch to the time program temperature control.

Manually adjust the temperature to more than 300 degrees, switch to the time program mode, according to the time program control. The control parameters are set as follows:

Four, silicon molybdenum rod electric heating precautions

According to the structure, working atmosphere and temperature of the heating equipment, the correct selection of the surface load of the heating element is the key.

1. Silicon molybdenum rod heating element should not be used in the temperature range of 400~ 700, because in this unfavorable condition, the element will be oxidized at low temperature, leading to its destruction and powder;

2. Silicon molybdenum rod heating element is suitable for air and neutral environment. Hydrogen and other reducing atmosphere will destroy the protective layer, chlorine and sulfur vapor will directly damage the components;

3. The heating rate of silicon-molybdenum rod should not be too fast, which is 4/min in actual case;

4. Observe the load current when the silicon molybdenum rod is heated.