球墨铸铁轧辊保温冒口研究
An Investigation in the Exothermic-insulating Riser of Spheroidal Graphite Cast Iron
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摘要: 球墨铸铁轧辊的补缩,一般是采用砂型明冒口和浇注后每隔20-25分钟用过热铁水点冒口1-2次的办法解决,这样的工艺使冒口金属消耗量占轧辊毛重的15%左右。为了节约金属和提高轧辊上辊颈质量,本研究工作是采用铝型膨胀发热剂单独使用或与绝热套组合成的保温冒口,以取代原工艺以稻草灰覆盖的干砂型冒口。经过实验室及现场对此实验表明:采用保温冒口以后,球墨铸铁共晶凝固时间延长了33-62%,缩孔形状由倒锥形变为盆形,轧辊冒口的致密段高度增加,省去了用过热铁水点冒口的工序。冒口高度可以降低25~50%,节约冒口金属量20~50%。研究工作表明:采用保温冒口是解决球铁轧辊补缩的最合理、经济而简便的措施。Abstract: In practice using sand open risers and pouring hot molten metal into it once or twice every 20~25 minutes after pouring to compensate the volume contraction of spheroidal graphite cast iron rolls is very common.This method consumes a large quantity of metal for riser which is about 15% of the gross weight of the rolls.In order to save metal and to improve the quality of the upper edge of the roll barrel, we make use of the riser covered with Al-exothermic compound, in combination with insulating sleeve instead of previous procedure in which straw-ash heat insulator was used to cover the dry-sand open riser.The results of experiment show;that the eutectic transformation time of spheroidal graphite cast iron elongates by 33~62%;shrinkage cavity transformas from conical-shape to basin-shape.The hight of denser part increases, and the riser hight may be decreased by about 25~50%. As a result, the riser metal can be saved up to 20~50%. It can be coucluded that using the exothermic-insulating riser is most efficient and advantageous for the production of spheroidal graphite cast iron rolls.