Relation between Structure and Creep Rupture Strength of Centrifugally Cast HK40 Steel

COllsiderable variations ill as-cast structures oj centrifugally cast H K 40 tubes were obtained by controlling the cooling rate during Ihe solidification.The cooling rate was controlled by emjlloying three t)'pes oj moulds and two rotating speeds .The higher cooling ra te Inomoted an as-cast structure with a larger size oj columllar and dendrite cell structures as compared with thatlJlwnoled by Ihelow cooling rate.Also, th e tube with the higher cooling rate had a smaller volume Jraction ~r carbides eutectic and resulted in a larger amount oj dissolved carbon in the as-cast condition than the tube with the low cooling rate.I t was Jound that the initial structure was a Ilersistellt facial' Jar the creell ntllture strengthening ~r the centrifugally cast HK40 tubes.Ilarticularly at higher tempera tures or after prolonged times.when Ihe effect oj secondary Il recipilated carbides all the strellglhelling dimini rhed .The creep rupture strength , a, was inversely proportional to the reciprocal 1'001 oj the dendrile cell structure, d, or acc -I/ v'd. Introdu ction