There are five main factors affecting induction furnace electricity consumption.
1. Intermediate Frequency Power Supply
1) Power density configuration of induction furnace. High configuration, fast melting speed, and good energy-saving effect. Whether the electric furnace can maintain a high power factor and transmit power to the furnace is also the difference between high and low energy consumption.
2) The efficiency of the induction melting furnace and the electrical efficiency of the induction coil. (The total efficiency of foreign advanced induction furnaces is up to 75%, the induction coil is up to 85%, and the domestic ones are 73% and 80% respectively).
3) Induction furnace electricity consumption conversion efficiency is high or low. 97%~98% abroad and nearly 97% at home, mainly on the efficiency of reactance and capacitance.
4) Layout of electric furnace unit. The distance between the power supply and the furnace body, the length of the power transmission copper bar, the length of the water-cooled cable, and the distance between the power supply incoming voltage and the high-voltage transformer and the power supply point are all influencing factors.
2. Effect of Melt Affecting the Induction Furnace Electricity Consumption
1) The cleanness of the charged surface (if there are 5% impurities, 5% electric energy will melt these impurities) will also affect the life of the furnace lining.
2) The electric efficiency and melting quality of the electric furnace will be affected if the length of the charging block is appropriate. Generally, the block size of 200~300mm is appropriate.
3) Whether there is liquid metal in the furnace during melting. The residual liquid should account for 15% of the furnace capacity. If it is too little, the overheating of this part of molten iron will be aggravated. If it is too much, the effective use of molten iron will be reduced, and the unit energy consumption will also be increased. The molten iron emptying reduces the power factor and the melting speed during use.
3. Refractory Materials
1) Reasonable hot surface material thickness. Increasing the melting rate can reduce its thickness, but its service life is reduced, the cost of furnace building is increased, and the potential safety hazard is increased.
2) The correct bottom thickness also affects the electrical efficiency and lining life. When the height of the furnace bottom exceeds 100mm of the effective coil, the refractory at the bottom will strongly scour the bottom due to the effect of the inductive stirring force, which will sharply reduce the service life.
3) Use the correct backing material. The isolation material is called backing material (such as asbestos cloth).
The harm of using asbestos cloth as backing material: people will stay in the lungs and have a tendency to cause cancer if inhaled; Asbestos cloth generally has a high moisture content, which is easy to enter quartz sand with moisture after being used a period of time, causing hardening and cracking. The function of the backing material is insulation, waterproofing, and fire resistance of the inductor coil. The surface of the mastic acts as an isolation and is convenient for the replacement of the furnace lining. At the back of the quartz sand hot surface, we hope that there is a loose layer so that the hot metal will stop here in case of overheating. The cooling water temperature of the inductor is a necessary condition for the formation of a loose layer. If the asbestos cloth with good heat insulation is used and moisture is added, the trace boric acid in the quartz sand will harden it. Mica paper is the best choice. It is treated with high-grade coil daub, with a smooth surface. It is unnecessary to use backing materials, but they must have the properties of convenient processing, no cracks after drying, and no reaction with acid substances.
4. Energy Saving during the Operation of the Induction Furnace
Feeding time. The first addition of solid charge shall reach about 1/3 of the furnace capacity, otherwise, it will affect the power output, spark (discharge) arc and consume power, and may cause cracks on the surface of the furnace lining, causing great damage to the neutral materials of cast steel. When the first batch of material reaches the melting state, the solid furnace charge will sink, and at this time, the material shall be added immediately, which can melt the softened solid material under pressure, so that the melting can be carried out at the fastest speed. It is normal for charging to ensure that there is no violent liquid billowing in the furnace (violent liquid billowing means that the metal liquid is overheated, the furnace wall is washed, and furnace lining materials are consumed). This requires that the power input of the melting time should be less than 20% (the first feeding) → 50% (softening) → 65% (feeding) → 100% feeding – reaching the temperature required by the process. Then power off and discharge the liquid.
5. Avoid High Induction Furnace Electricity consumption Due to Improper Operation
1) The liquid metal is overheated.
2) The liquid is discharged without stopping the boiler. It is not only unsafe, but also wrong in terms of energy consumption and the melting process. Generally, the inductor of an electric furnace is divided into upper and lower parts. When the metal liquid level in the furnace is less than half of the upper inductor, the upper inductor will no longer have induced current due to the change of resistance, but will concentrate on the lower inductor, so that the lower metal liquid will overheat, wash the furnace wall, and the life of the furnace lining will drop sharply.
3) High-temperature insulation. The long-time high temperature will change the metallography, phase change of C and Si, serious white mouth tendency of castings, and poor machinability.