The lining used in induction melting furnace should be selected according to the smelting steel or smelting non-ferrous metal varieties
Choose, for example, for some steel grades only suitable for smelting in an alkaline furnace, smelting high manganese steel grades in the acid furnace
When gold, (Mn0) will combine with Si0: in the furnace lining to form low melting point silicate, which will rapidly damage the furnace lining.molten
Smelting steel with higher aluminum and titanium Si0, inclusions than the alkaline furnace steel, so the best is also in the alkaline
Smelting in a furnace; Graphite crucible is selected for smelting silver and its alloys.
Intermediate frequency furnace smelting is basically a melting process, rarely using oxidation smelting, usually do not have
Decarbonization function and the slag temperature is low, the ability to remove sulfur and phosphorus is poor, therefore, the requirement of the charge is not
Figure: Production of intermediate frequency furnace lining
Sulfur and phosphorus content in the charge should be as low as possible, at least 0.005% lower than the lower limit of specification.010%. will
All charges, including the weight and chemical composition of various ferroalloys, must be accurately known in order to facilitate the smelting process
After calculating the composition of the steel, the charge shall be clean, dry, and rust-free, especially for gas-sensitive steel and alloy
Such as nickel-based gold should be more so, charge and slag before use must be fully preheated baking.
It should also be pointed out that scrap should not be mixed with non-ferrous metals, not to mix airtight containers and explosive items, to
Avoid explosion accidents. In addition, the bulk of the charge should be appropriate
Charge and melt
Medium frequency furnace should be cleared before loading the residue in the furnace, check the lining damage, serious local damage due to cooling
Fast and black, should be repaired. The particle size of furnace repairing material should be
Slightly smaller than the knotting material, the binder should be slightly more. loss
A serious bad large furnace can be suspended to fill the furnace iron mold
Due to the medium frequency furnace steel after the rapid cooling, it should be installed quickly
Material, as far as possible should be packed in barrels. In order to accelerate melting, should
The reasonable distribution according to the temperature distribution in the furnace.Medium frequency furnace temperature
Figure 4-25 shows the distribution. Due to the skin effect of the current, the
The surface around the material column near the crucible wall (zone I) is the high-temperature zone,
Basic points of induction smelting of steel
The heat dissipation in the bottom and middle (zone ⅱ and ⅲ) is poor and the upper (zone ⅳ) has less magnetic flux and heat loss
Large is the low-temperature region.
In order to slag in advance, before loading can be added on the bottom of the furnace accounted for material weight 1 T;: Lo slag, alkaline furnace with lime
And fluorite, acid furnace with broken glass.
When melting begins, the current is unstable because the inductors and capacitors on the line do not match up quickly enough. Therefore, in
It can only be supplied at low power for a short time. Once the current is stable, it should be converted to full load during the melting of the outlet
Capacitance should be constantly adjusted to maintain a high power factor for electrical equipment. The molten steel will overheat after the fusion of the charge barrier
To a certain extent, the input power is reduced according to smelting requirements.
Proper melting time should be controlled. Melting time is too short, will be in the voltage, capacitor selection
Difficult, too long will increase the unhelpful heat loss. Improper cloth or too much rust in the charge can occur
The phenomenon of “building Bridges” should be dealt with in time.”Bridge the upper bundle of molten material can not fall into the molten steel
Liquid, so that the melting stagnation, and the bottom of the molten steel overheating easy to damage the furnace lining, but also make a large number of liquid steel absorption gas
Due to the electromagnetic stirring, the molten steel is uplifted in the middle, and the slag often flows to the edge of the crucible and becomes consolidated on the furnace wall.
Therefore, the melting process should continue to add material according to the furnace condition.
Refining and defluorination
Decarburization boiling is generally not carried out after full melting of charge. It can be decarbonized by adding ore powder or blowing oxygen, but the problem is
More, furnace lining life is difficult to guarantee. As for dephosphorization and desulfurization, the furnace can not dephosphorization; Under certain conditions
Some of the sulfur is removed, but it’s expensive. Therefore, the most appropriate way is to mix carbon, sulfur, phosphorus to reach the steel
Deoxidation is the most important task of intermediate frequency furnace smelting. In order to get a good deoxidation effect, the first choice should be made
Slag of moderate composition. Medium frequency furnace slag temperature is low, so should choose a low melting point and good flow furnace
Slag. Generally, 70% lime and 30% fluorite are used as alkaline slag. Because fluorite is constantly in the smelting process
Volatile, so it should be added at any time, but considering the erosion and infiltration of fluorite on the crucible, the amount of addition is not
To be too much.
When smelting the steel with strict inclusion content requirements, the early slag should be removed and made into new slag
It is about 3% of the material amount. In smelting certain alloys containing higher readily oxidized elements such as aluminum
When salt and potassium chloride mixture or crystal stone can be used as slagging material. They will be in metal
Thin slag can be rapidly formed on the liquid surface, thus isolating the metal from the air and reducing the oxidation of alloying elements
An intermediate frequency furnace can adopt the precipitation deoxidation method. Diffusion deoxidation may also be used. Precipitation deoxidation is best
Use compound deoxidizer; Diffused deoxidizer for carbon powder, aluminum powder, silicon calcium powder, and aluminum lime. To promote diffusion off
Oxygen reaction, smelting process should often be pounded slag shell operation, but in order to prevent a large number of diffusion deoxidizer infiltration
Molten steel should be melted before slag tamping operation.