5 major factors in the power consumption of induction melting furnaces

1In terms of intermediate frequency power supply

a. The power density configuration of the induction furnace. The configuration is high, the melting speed is fast, and the energy saving effect is good. Whether the electric furnace can maintain a high power factor and send electricity to the furnace is also the difference between the level of energy consumption. To

b. The efficiency of the induction melting furnace and the electrical efficiency of the induction coil. (The total efficiency of foreign advanced induction electric furnaces is as high as 75%, the induction coil is as high as 85%, and domestically, it is 73% and 80%). To

c. The conversion efficiency of the intermediate frequency power supply is high or low. It is 97%～98% abroad, and close to 97% in China, mainly in the efficiency of reactance and capacitance.

d. The layout of the 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, the power supply voltage and the distance between the high-voltage transformer and the power supply point are all influencing factors. To

2 The influence of the melt

1) The cleanliness of the surface of the furnace charge (if there are 5% impurities, 5% electric energy to melt these impurities), it will also affect the life of the furnace lining. To

2) Whether the length of the charge block is appropriate will affect the electric efficiency and melting quality of the electric furnace. Generally, the block size of 200～300mm is appropriate. To

3) Whether there is liquid metal in the furnace when melting starts. The residual liquid should account for 15% of the furnace volume. If it is too small, the overheating of this part of the molten iron will be aggravated, and if it is too much, it will reduce the effective use of the molten iron and increase the unit energy consumption. When molten iron is emptied, the power factor and the melting speed decrease during use. To

3 Refractory materials

1) Reasonable thickness of hot surface material. Increasing the melting rate can reduce its thickness, but the service life will be reduced, the cost of building the furnace will increase, and the potential safety hazards will increase. To

2) The correct bottom thickness also affects the electrical efficiency and the life of the furnace lining. When the height of the furnace bottom exceeds the effective coil 100mm, the refractory material at the bottom will strongly wash the bottom due to the induction stirring force, which will drastically reduce the service life. To

3) Correct use of backing material. The isolation material is called the backing material (such as asbestos cloth, etc.).

Using asbestos cloth as a backing material harms: human inhalation will stay in the lungs and have a carcinogenic tendency; asbestos cloth generally has a high moisture content, and it is easy to cause hardening and cracking after the quartz sand is used for a period of time with water entering the quartz sand. The function of the backing material is insulation, waterproofing, and fire resistance of the inductor coil. The surface of the cement is used for isolation and facilitates the replacement of the furnace lining. On the back of the quartz sand hot surface, we hope that there is a loose layer so that if the molten iron drills over the hot surface, it will stop here. The cooling water temperature of the sensor is a necessary condition for creating a loose layer. If you use asbestos cloth with better heat insulation and add moisture, the trace boric acid in the quartz sand will make it harden, and mica paper is the best choice. Treated with high-grade coil cement, the surface is smooth, no backing material is needed, but it must be easy to process, crack-free after drying, and not react with acidic substances.

4 Energy saving in the operation of induction melting furnace

Timing of feeding. The amount of solid charge added for the first time should reach about 1/3 of the furnace capacity, otherwise it will affect the power output, will also ignite (discharge) and draw the arc, consume electricity, and may cause cracks on the surface of the furnace lining, which will damage the neutral material of the cast steel. Great damage. When the first batch of material reaches the molten state, the solid charge sinks, and the material should be refilled immediately at this time. This can press down the softened solid material to melt, so that the melting can proceed at the fastest speed. It is normal for the feeding to take no liquid violent churn in the furnace (the liquid violent churn means that the molten metal is overheated and washes the furnace wall and consumes the lining material). This requires the power input of the melting time to be less than 20% (first feeding) → 50% (softening) → 65% (feeding) → 100% feeding-the regular change of the temperature required by the process. Then power out the liquid. To

5 Avoid improper operation causing high energy consumption

a. The molten metal is overheated. To

b. The liquid is discharged continuously from the furnace. Not only is it unsafe, it is also wrong in terms of energy consumption and melting process. Generally, electric furnace inductors are divided into upper and lower parts. When the molten metal level in the furnace is lower than half of the upper inductor, due to the change of resistance, the upper inductor no longer has induced current to pass, and all are concentrated in the lower inductor, so that the lower molten metal Overheating, scouring the furnace wall, the life of the furnace lining drops sharply. To

c. High temperature insulation. Long-term high temperature will change the metallographic phase, C and Si phase change, the white mouth tendency of the casting is serious, and the machining performance is deteriorated.