1. Fixed carbon and ash content
Fixed carbon and ash are two opposing parameters in the recarburizer, and they are important parameters that affect the effect of recarburization. If the recarburizer has high fixed carbon content and low ash content, the carbon increase efficiency is high, and vice versa, the carbon increase efficiency is low. Since there are many factors that affect the production conditions, it is difficult to strictly evaluate the impact of the two parameters on the efficiency of carbon increase. The ash content is high, which has an inhibitory effect on carbon increase, and will increase the amount of slag, thereby prolonging the working time, increasing power consumption and human consumption.
2. The influence of joining method
The way the recarburizer is added also has a great influence on the recarburization efficiency.
When charging, the recarburizer is mixed with the charge and placed on the bottom and middle of the induction furnace, which has a higher recarburization efficiency. When smelting gray cast iron in a coreless induction electric furnace, the target composition of the cast iron, the ratio of various charges, and various other process factors will all affect the recarburization efficiency of the recarburizer. Adding a recarburizer in the ladle when tapping iron, and then flushing into the molten iron, the recarburization efficiency is much lower than the one added in the furnace
3. The sulfur content in the recarburizer
When smelting ductile iron, recarburizers with low sulfur content should be used. Although low-sulfur recarburizers are expensive, they are necessary. When smelting gray cast iron, it is advisable to use a recarburizer with a higher sulfur content. In this way, not only can the production cost be reduced, but also the sulfur contained in it can be used to enhance the response ability of the molten iron to the inoculation treatment, and to obtain castings with high metallurgical quality. Under these conditions, the one-sided pursuit of "high quality" recarburizers and the selection of low-sulfur brands will not only increase production costs, but also have negative effects.
4. Nitrogen content in recarburizer
Gray cast iron contains a small amount of nitrogen, which has the effect of promoting pearlite and helps to improve the mechanical properties of cast iron. If the nitrogen content (mass fraction) is above 0.01%, the casting is prone to "nitrogen-induced pores".
The nitrogen content in scrap steel is higher than cast iron. When smelting cast iron with an induction electric furnace, the nitrogen content in the cast iron produced will be correspondingly higher due to less cast iron ingots and more scrap steel used in the charge.
In addition, due to the large amount of scrap steel used in the charge, recarburizers must be used, and most of the recarburizers have relatively high nitrogen content, which is another factor that causes the nitrogen content in cast iron to increase.
5. The influence of other process factors on the efficiency of carbon increase
In addition to the fixed carbon content and ash content in the recarburizer have an important impact on its recarburization efficiency in cast iron, process factors such as the particle size of the recarburizer, the method of adding, the temperature of the molten iron, and the stirring effect in the furnace All have a significant impact on the efficiency of carbon increase.
When iron is tapped, the recarburizer is added into the ladle and then flushed into the molten iron. The recarburization efficiency is related to the temperature of the molten iron. Under normal production conditions, if the temperature of the molten iron is higher, the carbon is easier to dissolve in the molten iron, and the carbon increase efficiency is higher.