Conventional cast iron smelting
The carbon content is usually controlled at 2.6%-3.6%, the silicon content of 1.0%-2.0% can promote graphitization, and the manganese content of 0.6%-1.2% helps to refine pearlite and improve mechanical properties.
Ductile iron smelting
Take QT450-10 as an example, the carbon content needs to be strictly controlled at 3.4%-3.9%, and it needs to be spheroidized with silicon (2.5%-3.0%), magnesium (0.04%-0.10%) and other elements.
Carbon equivalent calculation
The simplified formula is: carbon equivalent = carbon + (silicon + phosphorus)/3. This indicator is used to evaluate the degree of cast iron close to eutectic, which directly affects casting performance and weldability.
Of course, the carbon content in smelting needs to be adjusted according to specific process requirements. The specific method of adding in smelting is to use a carburizer.
Increasing the carbon content in smelting is mainly achieved by adding [recarburizers]. The specific methods are as follows:
Recarburizer types
Common recarburizers include artificial graphite, petroleum coke, natural graphite, etc. Among them, artificial graphite has the best quality, and petroleum coke is widely used due to its price advantage.
Addition method
Addition in the furnace
When smelting in a medium-frequency electric furnace, add it to the middle and lower part of the furnace according to the carbon equivalent requirements, and the recovery rate can reach more than 95%.
When the carbon content of the molten iron is insufficient, the slag must be cleaned first and then the recarburizer is added. The carbon dissolution is promoted by heating and stirring, and the recovery rate is about 90%.
Recarburization outside the furnace
Spraying graphite powder (40kg/t) in the ladle can increase the carbon content from 2% to 3%, but the recovery rate is low (about 50%).
Add recarburizer with the flow when tapping iron, and the absorption effect is better after stirring.
Precautions
The recarburizer type should be selected according to the smelting process (such as induction furnaces often use graphitized recarburizers), and the addition time and recovery rate should be controlled.
Of course, the whole process needs to be constantly monitored and analyzed. Only when the analysis is qualified can casting work be carried out. Professional and reliable casting manufacturers will do this, so don’t worry about it.
If you have a large-scale casting production demand, you can choose Mulan Metal to cooperate. Mulan Metal has 12 years of casting processing experience and has helped customers in more than 30 countries complete casting processing business and has received unanimous recognition. We look forward to your cooperation consultation.
Here is our Custom metal Castings Display：
