Preparation of long large forgings (長 尺 大型 鍛造 品)

摘要

Method comprises (a) preparing an alloy steel melt of composition (by wt.%) 0.08-0.25%C, 0.02-0.15%Nb, 9.12%Cr and more than 80% Fe, (b) pouring the melt into a metal mould having a H:D ratio of max. 1 (where H is the mould height neglecting the hot top portion and D is the diameter at height 0.5H), and (c) forging the resulting ingot in the radial direction unitl the length of the forging is greater than its diameter. The method is esp. useful in the prodn. of a steam turbine rotor shaft. The ingot casting conditions provide a greater solidification rate at the ingot and the ingot body is free from Nb carbides and non metallic inclusions.