For the alloy steel casting, the pouring temperature is generally above 1380 ℃, at this temperature, the appearance will quickly heat pyrolysis of gas and liquid, through the secondary decomposition, there will be a large number of pyrolysis products pyrolytic carbon precipitation. However, since the cast iron itself has a high carbon content, so the cast iron surface does not appear to increase carbon defects, but the performance is easy to form corrugated or drop-like wrinkles defects.
When the metal liquid filling speed is higher than the alloy steel casting pyrolysis product vaporization rate, the metal liquid flow front gathered a layer of liquid polystyrene, so that contact with the surface layer of metal to form a layer of hard crust. When the layer of crust is advanced by the metal liquid in the break, that is pressed to the casting on both sides of the casting surface in the formation of corrugated or drop-like wrinkles defects. Open the box after the sand, you can find wrinkled skin surface accumulation of toner, pyrolysis products is the second reaction after the production of pyrolysis elemental carbon. When the mold density is too high, the adhesive surface with too much glue, casting filling is not smooth caused by turbulence, the casting of carbon defects more serious.
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