How to improve the quality of cast iron

The casting properties of cast iron is better, easier to cast a complex shape, thickness unevenness of the casting and with less casting defects. In addition, graphite cast iron has some inherited properties, such as friction reduction, cushioning, good machinability and better fatigue fracture.

In order to ensure the reliability and stability of Cast Iron, the molten iron must have good quality. The quality of molten iron includes iron temperature, chemical composition, content of harmful elements, the number of non-metallic inclusions and gas furnace melting capacity.

The quality of molten iron can be improved from the following aspects:

1. Improved cupola

Although the melting temperature of cast iron is not high, mostly 1260 ℃ ~ 1400 ℃. But in order to get high quality liquid iron, there should be a higher melting temperature.

2. Application of medium frequency induction furnace

Induction furnace can produce high quality molten iron, which is characterized by energy-saving stoves, melting fast, warming up rapidly, simple, reliable, no interference on the power grid, power factor is high.

3. Importance of trace elements in pig iron

In general, trace elements in pig iron of ordinary cast iron does not matter, but they are important for ductile iron and good gray iron.

4. Increasing carbon in induction furnace

If induction furnace take the scrap steel as the main material, then increasing carbon will be very important to get generally pure molten iron.

5. Application of desulfurization technology

Desulfurization can reduce the amount spheroidizing agent and the number of sulfide. In developed countries, almost all of ductile iron production use desulfurization process.

6. Spheroidization

Spheroidization can improve the physical properties of cast iron to obtain spheroidal graphite cast iron, or called ductile iron. Ductile iron is more expensive than gray iron, but it has better strength and ductility.

7. Cast iron inoculation
Inoculation is an important part of enhancing the quality of cast iron. Good inoculation can meet the requirements of microstructure and mechanical properties, to ensure the casting and machining properties.

8. Adding alloy
Alloy elements are commonly used in cast iron, such as Si, Mn, Cu, Cr, Mo, Ni, Sn, Sb, V, Ti, P and so on. Adding appropriate alloy can greatly improve the performance of cast iron.

9. Filtering

Metal filtration technology in the industrial countries are more generally used. Practice has proved that the failure of critical parts is not entirely level of mechanical properties of test bars, but the robustness of the internal cast. Therefore, the pure pursuit of the perfect microstructure is not comprehensive. General small pieces using fiber filters, too large or important pieces of traffic using cellular or ceramic filter.

Of course, high quality molten iron is just one aspect of cast iron quality, there are many works to do to improve the quality of cast iron such as design of casting process, casting equipments and skill level of cast workers etc.

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