An Investigation in the Exothermic-insulating Riser of Spheroidal Graphite Cast Iron
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摘要: 球墨鑄鐵軋輥的補縮,一般是采用砂型明冒口和澆注后每隔20-25分鐘用過熱鐵水點冒口1-2次的辦法解決,這樣的工藝使冒口金屬消耗量占軋輥毛重的15%左右。為了節約金屬和提高軋輥上輥頸質量,本研究工作是采用鋁型膨脹發熱劑單獨使用或與絕熱套組合成的保溫冒口,以取代原工藝以稻草灰覆蓋的干砂型冒口。經過實驗室及現場對此實驗表明:采用保溫冒口以后,球墨鑄鐵共晶凝固時間延長了33-62%,縮孔形狀由倒錐形變為盆形,軋輥冒口的致密段高度增加,省去了用過熱鐵水點冒口的工序。冒口高度可以降低25~50%,節約冒口金屬量20~50%。研究工作表明:采用保溫冒口是解決球鐵軋輥補縮的最合理、經濟而簡便的措施。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.
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