钢厂中频感应电炉的结构和分类Structure and classification of steel plant medium frequency induction furnace

一 1 感应电炉熔炼是利用交流电感应的作用，使内的金属炉料本身发出热量，将其融化并进一步使液态金属过热的一种熔炼方法。感应电炉根据构造分为无芯式和有芯式两种。

I  Induction furnace smelting is a smelting method that uses the effect of induction of alternating current to make the metal charge in the furnace generate heat, by melt it and further overheat the molten metal. Induction furnaces are divided into coreless and core type according to their construction. 

二 炼钢用的是无芯式感应电炉，其工作原理是在一个耐火材料筑成的坩埚外面，有螺旋形的感应器。在熔炼过程中，坩埚内的金属炉料犹如插在线圈中的铁芯。当线圈通交流电时，由于感应作用在炉料或钢液内部产生感应电动势，并因此感生感应电流(涡流)。由于炉料或钢液本身有电阻，故在涡流的作用下发出热量，以使得炉料融化或钢液过热。

II   The steel is refined in a coreless induction furnace, which consists of a crucible of refractory material surrounding a spiral induction coil. During the melting, the metal charge in the crucible acts as the core of the coil. When an alternating current is passed through the coil, electromotance is set in the charge or molten steel by induction, and therefore an induced current (eddy current) is produced. Since the charge or molten steel has a certain resistance, heat is under the action of the eddy current, which serves to melt the charge or superheat the molten steel. 

picture  the working principle of cordless induction furnace 

1  sensor, 2 crucible 3  material in the induction furnace 

① direction of the instant current of the sensor

② Direction of induced current  of the material in the  induction furnace 

Schematic diagram of the structure of the coreless induction furnace body

1 tapping spout  出铁槽   2  sensor 感应圈   3  -磁性轭铁  Magnetic yoke iron  4 坩埚 crucible

5 支架  support frame 6 倾转机构 tilting mechanism  7-炉盖 cover  8 坩埚铁模 Crucible iron mold  9-水电引入系统 Water and electricity introduction system

三  III  中频感应电炉熔炼特点
在炉料的内部，磁通的分布是不均匀的，越靠近外层炉内壁，磁通量密度越大，越靠近坩埚内部密度越小，因此外部的感应电动势和电流比内层的大，即“集肤效应”，使得炉料外层的发热量大于里层。电流频率越高，集肤效应越明显，为此，应使电流频率与坩埚直径相适应。

Inside the charged material , the distribution of the magnetic flux is not uniform, the closer to the outer wall of the furnace, the greater the density of the flux, the closer to the inside of the crucible, the smaller the density, so that the induced electromotive force and the current outside are greater than those inside, ie. the "skin effect", which makes the heat generated on the outside of the charge greater than that on the inside. The higher the current frequency, the more pronounced the effect, and for this reason the current frequency should be adapted to the diameter of the crucible.
感应电炉的特点:
1.加热速度快:热量在炉料或合金液内部产生，直接加热方式，速度较快。
2.氧化烧损较轻，吸收气体少:没有电弧的超高温作用，元素烧损率较低。没有电弧电子冲击作用，减少合金液中气体的来源。3.炉渣的化学活泼性较弱:炉渣是被合金液加热，上面与大气接触，温度较低，化学性质不活泼，不能充分发挥在冶炼过程中的作用。

Characteristics of induction electric furnace:
1.Fast heating speed: Heat is generated inside the charge or alloy liquid, which is a direct heating method, the speed is relatively fast.
2.Lighter oxidation loss, less gas absorption: Without the super high temperature of the arc, the element loss rate is lower. Without the arc electron impact effect, the source of gas in the alloy liquid is reduced.
3.The chemical activity of slag is weaker: The slag is heated by the alloy, the upper part is in contact with the atmosphere, the temperature is low, and the chemical properties are not active, which can not play a full role in the smel process.
四、中频感应电炉电气系统 
由于感应电炉的感应器是一个很大的电感，再加上磁通是经过空气闭合的，所以感应电炉的无功功率相当大，功率因数相当低，一般只有0.10~0.11，因此必须采用相应的电容器与感应器并联，以补偿无功功率提高功率因数。

IV  The electrical system of the medium frequency induction furnace
Since the inductor of the induction furnace is a very large inductance, and the magnetic flux is closed air, the reactive power of the induction furnace is very large and the power factor is very low, usually only 0.10~0.11, so it is to use a corresponding capacitor in parallel with the inductor to compensate the reactive power and improve the power factor.