In some engineering machinery factories who produce, when the rough castingsare mechanical processed, there will be large areas of “spotted” deficiency on the cast irons.
Through inspection, it can be found that the color of large areas of “spotted” defects on the cast irons is apparently dark and gray, compared with the normal color of other parts on the cast irons. And the defects are in the upper part.
When the “spotted” areas are processing, it is obviously that the the hardness of the parts is low and the cutting tool is tacky. Sometimes because the surface hardness is inequality which will damage the cutting tools and equipment, the surface of cast irons can not meet the technical requirements. The result is that the chemical composition of the casting is unqualified. The content of carbon, silicon and manganese are on high levels.
If carbon equivalent is higher than normal level, it is easy to generate too much of graphite. And the decaying spheroidization and inoculation fading is likely to cause the “flower” graphite. Graphite floating is more found in the upper part of the final cooling cast irons, the lower part of core and the cast irons blind angle.